Editorial Comment Hugh S

THE PRACTICAL RADIO JOURNAL 27th Year of Publication

No. 931. FRIDAY, JULY 2ND, 1937. VOL. XLI. No. 1.

Proprietors : ILIFFE & SONS LTD.

Editor : EDITORIAL COMMENT HUGH S. POCOCK. Editorial, Even for those who may not con- Advertising and Publishing Offices : Television template building a television receiver DORSET HOUSE, STAMFORD STREET, Our Receiver Design themselves, the articles will neverthe- LONDON, S.E.I. less be found a source of complete Telephone : Waterloo 3333 (so lines). information of a practical nature such Telegrams : "Ethaworld, Sedist, London." N this week's issue we begin a series of articles describing the as it has not hitherto been possible to COVENTRY : Hertford Street. obtain from any other source. These Telegrams: Telephone: practical design and construction "Autocar, Coventry." saxo Coventry. of a complete sound and vision practical articles, studied in conjunc- receiver for the B.B.C. television trans- tion with general articles on television BIRMINGHAM : Guildhall Buildings, Navigation Street, 2. missions. We make no excuse for the which have been appearing for some Telegrams : Telephone apparent complexity of the apparatus time in The Wireless World, may be "Autopress, Birmingham." 2971 Midland (4 lines). -this is inevitable at present, and is, regarded as a complete course of MANCHESTER : 260, Deansgate, 3. of course, common to all television re- instruction in the subject. Telegrams : Telephone : "Riffe, Manchester." Blackfriars 4452 (4 lines). ceivers, but the complexity can be The design is one which is particu- said to resolve itself into only a larly suited to the requirements of the GLASGOW : 26s, Renfield Street, C.2. question of quantity when the equip- student and experimenter, because of Telegrams : "Iliffe, Glasgow." Telephone: Central 4857. ment is dissected into its component the accessibility of every párt, whilst PUBLISHED WEEKLY. ENTERED AS SECOND - taken as for instruction and demonstration re- CLASS MATTER AT NEW YORK, N.Y. units. The construction, units stage by stage, offers no greater quirements this feature is invaluable. Subscription Rates : difficulty than an ordinary receiver and, Home, Ls Is. 8d. ; Canada, £i is. 8d. ; other countries, ¡I 3s. sod. per annum. in fact, may be considered to be less exacting in many respects. Radio Propaganda As many of eke circuits and apparatus described in these Very special attention has been given pages are covered by patents, readers are advised, before Probable Official making use of them, to satisfy themselves that they would adjustment Attitude not be infringing patents. in the design to make initial simple and to render the operation of WHILST we know that the controls as little critical as possible, so Government deplores the that, when constructed, no technical policy of some foreign CONTENTS knowledge or special skill will be governments of broadcasting, particu- in order to work it. Page necessary larly on short waves, anti-British propaganda, yet we believe that there Editorial Comment .. 1 High Quality Throughout is no evidence at present to justify the The Wireless World Television Re- The different units have been made rumours that action is to be taken to

ceiver -1. The Vision Receiver easily . accessible by the particular compete in this sphere. It can be and Power Unit .. 2 design adopted for the cabinet frame- regarded as certain that any move Delayed Switching 7 work. No attempt has been made to which it is decided to make will not be cheapen construction by the use of com- in the nature of reprisals, but will take Current Topics .. 9 ponents with a bare margin of safety, the form of seeing fhat, wherever Periodic Variations of the Iono- but every component is chosen to anti -British propaganda reaches, there sphere ...... 10 have ample voltage and power rating also would the influence of accurate Listeners' Guide for the Week .. 12 to guard against risk of breakdowns. British news be extended with at least All high voltage sections are pro- equal radio power. Principal Broadcasting Stations of vided with proper protection so that the On the question of language, any Europe ...... 14 constructor who undertakes building broadcast to counteract the effect of Random Radiations .. .. 16 the equipment should be involved in no propaganda would, no doubt, be put Broadcast Brevities . 18 risks, provided the ordinary pre- out in the same languages as were cautions, such as his experience in being used by the of#ending foreign Practical Hints and Tips.. 19 .. building other mains -operated appa- stations. This use of languages was Letters to the Editor . 20 ratus will already have taught him, foreshadowed in the Broadcasting Recent Inventions...... 22 are observed. Report.

www.americanradiohistory.com Wireless World, July 2;id, 19S7 The wireless World Television

I. FULL DETAILS OF THE VISIOZ

FOLLOWING upon the theoretical articles which have been appearing in " The Wireless World," complete constructional details of a television receiver are being given in a new series of whiéh this is the first: The vision receiver and its power unit, which also supplies LT for tube and time -base, 'is described here in detail.

A front view of the complete equipment. The time -base will be seen that three RF stages for the first, second and third stages. controls can be seen on the are used with a diode detector Single tuned circuits are used for the left of the tube. and one VF stage ; the remaining intervalve couplings and are suitably two valves are a diode for restor- damped so that the requisite band -width ing the DC component to the out- can be secured. No artificial damping is put signal and an RF pentode for employed in the case of the first three cir- sync separation. cuits, for the low input impedance of the ASTRAIGHT set has been selected' For the RF stages pentodes of high pentodes at ultra -high frequencies is as the most sùitable type of mutual conductance have been selected, chiefly relied upon for damping. In the vision receiver fér reasons which and they operate with the screens at the case of the first circuit L2 Ci, damping is have been given In recent articles' same steady potentials as the anodes. It also imposed by the aerial circuit. in The Wireless World.' These reasons ire is consequently possible to use common The second and third couplings are of briefly that it requires fewer valves, is decoupling for screen and anode and so the tuned anode type, the tuning coils simpler to construct and adjust, and, most effect a saving in the number of com- being L3 and L4 tuned by the condensers important, is free from The serious inter- ponents required. This decoupling is C5 and Cg. Because the input imped- ference problems of the superheterodyne. effected by the resistances and condensers ance of the diode detector is much higher The circuit diagram of the receiver, R3 and C3, R5 and C7, and R8 and CI' than that of an RF pentode at very high which has been based upon many months of theoretical and practical research with Fig. i. -The 'complete circuit diagram of the vision receiver and amplitude filter is shown here. many types of set, is shown in Fig. 1. It Three RF stages are used with a diode detector and one VF stage ; the remaining valves are the DC restorer and the sync separator.

JO/ 5000 soo n 200 n R3 R5 RS

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R2 10,00011 C R TUBE MODULATION OUTPUT SOCKET

www.americanradiohistory.com Wireless World. hu!y 2nd, 1937 3

RECEIVER AND ITS CONSTRUCTION

frequencies the fourth and last tuned circuit must be artificially damped by the resistance Rio. This last RF coupling differs from the others in being of the tuned grid type ; this is necessary because the detector must have an external path of low DC resistance apart from its load resistance Rir. A choke feed with Chu and Cie is adopted for this circuit, therefore, and this last RF valve is operated with fixed bias provided by Rq. The two early valves have initial bias provided by RI and R4, but can be further biased for gain control by the variable resistance R2. The Vision -Frequency Stage The detector is a low impedance diode with a 5,00o-ohm load resistance RI', and a ioµµF by-pass condenser Cr4. The A rear view of the output is applied directly to the grid equipment wi.h the of the VF amplifier, which is another RF back removed. pentode. Bias is obtained from the roo- ohm resistance Ria which is shunted by the 500 -,uF condenser Cry. The full HT voltage is applied to the screen, no decoupling either of this or the anode cir- A view of the upper cuit being necessary. The output shelf showing the coupling vision receiver and consists of the resistance Rie time-base to the left and right o: the

tube .

z .le and the coil L6, and enables a response are also applied through R15 to the grid Iaa v 14 characteristic to be obtained which is fiat of the RF pentode, which functions as a within some 3 db. up to the extremely sync separator. This valve is operated high frequency of 2.o Mc /s, and this with with some 40 volts screen, 140 volts a stage gain of about 20 times. anode, and -4 volts grid potentials. The vision signals developed across the These voltages are obtained from the coupling impedance are applied through voltage divider comprising R17, Ri8. R19, Cr6 to the CR tube, the DC restorer, and and R2o, and decoupling is effected by the sync separator. The DC restoration, Cr7, Ci8, and C19. The resistance R2o is which is only rendered necessary by our actually an adjustable potentiometer vary- having to include Cr6, is effected by the ing grid bias and anode voltage simul- low impedance diode shunting Ru4. This taneously in order to permit compensa- resistance has a value of 2.0 Mi2, but it tion being obtained for variations in com- is shunted externally to the receiver by ponents and valves. It is a pre -set, and another resistance of the same value. not a panel, control. This is done in order to safeguard the CR Since there is only a single television tube and prevent its being damaged transmitter variable tuning is unnecessary, SYNC should it be accidentally disconnected and the four tuning condensers OUTPUT are SOCKET from the receiver. The effective load cir- accordingly regarded as- pre -set controls, cuit of this diode thus has a value of and are not brought out to the panel. I.o M4, not 2.0 MS.2. The only panel control for the vision re- The volts developed across this circuit ceiver is the gain control R2.

www.americanradiohistory.com WIIp®hoo .¢ 'My JULY 2nd, 1937

HOW THE COILS ARE MADE, DETAILS OF THE CHASSIS CONSTRUCTION, AND THE WIRING CONNECTIONS

2/16 -moi

6 " L3 &L4 6TURNS N? 22 DS C WIRE 6 B A ROD 2 LONG / SPACED 8 TURNS PER INCH 22 D L 5 8 TURNS N? S C WIRE L4 MOUNTED REVERSE WAY TO L3 SPACED 8 TURNS PER INCH

2 3 I /16 I L2 11.1110Wi ::Ir 4 Ll

21%6 L6 105 TURNS NS 34 D S C WIRE CLOSE WOUND

Ll 2 TURNS N2 34 D 8 C WIRE INTERWOUND AT EARTH ENE

L2 6 TURNS N? 22 D 8 C WIRE SPACED 8 TURNS PER INCH

12 7i

N? 18 GAUGE ALUMINIUM

CONTROL GRID

C R TUBE MODULATION OUTPUT SOCKET

CONTROL GRID

VISION RECEIVER PLUG

Complete constructional details of the receiver, together with wiring, are given in these drawings as well as coil winding data.

www.americanradiohistory.com JULY znd, 1937 WATSIl@OO Mp110 S in conjunction with two 8 -µF. electrolytic condensers suffices for smoothing, and the output is about 250 volts at 75 mA. Returning to the vision receiver, the components are in most cases standard in spite of the high

k.w..»t < operating frequency, for there is no point in using special low- loss types when it is essential for the circuits to be heavily damped in order to.secure the necessary band -width. The tuning condensers are of the air - dielectric type, however, but this choice has been made not on the score of efficiency but in order to secure stability of tuning. From the point of view of efficiency the ordinary mica -dielectric type would be quite satisfactory and somewhat cheaper. Mica condensers, however, suffer from some inconstancy of capacity, for they are appreciably affected by temperature, vibration and humidity. Again for constancy, the coils are former wound.

A plan view of the vision receiver.

The power unit is built as a separate unit, and its circuit diagram appears in Fig. 2. Not only does it supply HT and The VF amplifier LT for the vision receiver, but it also can be seen on the left with the supplies LT for the tube and time -base, sync separator on and it also includes the delay-switch for the right and the the high -voltage unit. The mains trans- DC restorer be- former has windings rated at 2.o volts tween them. 1.5 amps. for the CR tube heater, 4.0 volts 8.o amps. for the vision receiver valve heaters, 4.0 volts 8.o amps. for the time -base valve heaters; and 4.0 volts 2.3 amps. for the rectifier filament. This rectifier is a Ur2, and its anodes are supplied. from the 350 -o -350 volts winding. A single high- inductance smoothing choke

A side view of the RF amplifier ; short connections are obtained by in- verting alternate valves.

The method of construction adopted is somewhat unorthodox, but combines a maximum of screening with a minimum of stray circuit capacity, and maintains the overall dimensions within reasonable limits. It is unnecessary to explain this in detail, for it will be abundantly clear from the photographs and drawings ; it may be as well to say, however, that the chassis is in two pieces. One consists of the four compartments for the RF valves and detector, and the other of the side chassis carrying the VF stage and sync separator. This latter chassis has an extension which forms the base of the compartments. The compartments should consequently be completely wired before the two sections are screwed together. In most cases the wiring can be carried out with wire such as No. 22 tinned copper run in insulating sleeving. For the heater connections, however, No. 16 must be used on account of the heavy

www.americanradiohistory.com 6 WRT,SIM JULY 2nd, 7937 WoHfld condensers. Their optimum settings will be towards their minimum capacities. No difficulty should be experienced in finding the signal, for it is on a lower wavelength than the sound, and the characteristic signal of a vision transmitter is easily recognised, consisting chiefly of the frame synchronising pulses. If the phones are unusually good it may also be possible to hear the very high pitched note of the line synchronising pulses.

Testing the Receiver TIME - BASE LT PLUG It should readily be possible to obtain very loud phone signals, and such signals are about the strength necessary for operation of the CR tube. Provided that strong signals are obtained it is unnecessary to make any attempt at adjusting the circuits accurately, for this must be done for the best picture quality. In general, the circuits should not be all MAINS INPUT tuned accurately to the signal, but some 5 f TO Hy UNIT OVERALL HEIGHT OF CHASSIS i 8 N418 GAUGE ALUMINIUM of them staggered, notably the coupling to the detector. Naturally this can only be done with the tube connected and working so that the effect of the tuning on the picture quality can be observed. At this stage, therefore, one should be that the receiver VISION content with determining RECEIVER SOCKET works properly in producing loud phone signals. Before pictures can be obtained it is, of have a time -base and COI MAINS course, necessary to INPUT PLUG other associated equipment. Construe- KJ oJ Ó-O 210 V tional details of the time base will be given next week, while the high -voltage ft-0 2 30 V unit, tube assembly and sound equipment a later in this series of `-O 250 V will be dealt with TIME - PASE articles. The operation and adjustment of L T PLUG the apparatus will be fully treated in the concluding instalment. C P TUBE HEATER O SOCKET O"

MAINS INPUT TO H N UNIT

Fig. 2. -These drawings show the theoretical circuit, constructional details and practical wiring plan of the vision receiver power unit. current, and this gauge is also convenient for a few other cases where especial rigidity is desirable. When receiver and power unit have been completed they can with advantage be tested independently of the remainder of the equipment with the aid of a pair of phones or even a loud speaker. The phones or speaker transformer primary should be connected across R14, a condenser of o.iµF. or more being inter- posed to prevent the DC load resistance of the diode becoming too low for safety. The complete list of the components em- Choose a time when the vision trans- ployed will be found on page 17 ; in vision receiver power mitter is working, and with the gain con- The many cases the use of suitable alternatives unit contains the delay is permissible. trol set somewhere near maximum tune switch controlling the high - in this signal by means of the four tuning voltage unit.

www.americanradiohistory.com Wireless World, July and, 1937 7' Delayed Switching VALVE -ACTUATED RELAY FOR PROTECTING THE heating element of a gas -filled valve must be raised GAS - FILLED RECTIFIERS to full working temperature before HT voltage is applied to its By PAUL D. TI ERS anode. A new method of introducing the necessary delay automatically is described in this THE properties of a gas rectifier and the inside of the equi- potential article. are such that the full load must cathode than usual. Certain valves, how- not be taken until the cathode ever, can be given a heating period of has reached the necessary oper- sufficient duration to be suitable for use ating temperature. Accordingly, it is with existing gas rectifiers. A modifica- tube, then there is a chance of the high - usual to provide some form of time delay tion of the circuit is shown dotted, in tension load circuit being applied before switch. Many arrangements have been which the delay period is increased by the gas rectifier cathode is sufficiently suggested and used, one of the most reducing the heater temperature by added hot. This difficulty can be overcome if familiar being a pair of contacts rendered series resistance Rz. This means that the it is thought worth considering, by so operative by the displacement of a bi- full emission of the cathode is not neces- constructing the cathode of the delay tube metal strip associated with a heater coil sarily obtained, but as relays will operate that there is more radiation than usual. connected in parallel with the filament of on comparatively low currents, this is of This can be achieved, for example, by the rectifier: A thermal delay is intro- no importance. The table shows the heat- adding radiating fins to the cathode. The duced, and the contacts are arranged to ing time of various representative valves. cathode can be extended well beyond operate the HT or load circuit after an From this it is quite easy to choose a suit- the end of the anode. As the tube does has elapsed. Arrange- appreciable period able combination of valves, relay and not have to function as an efficient therm - ments of this type are sometimes mounted operating conditions which give a delay ionic device, the radiation surface can in a vacuum, the bi -metal strip being of a suitable period. The delay valve be made large by using an appreciable heated by direct radiation from a fila- can be energised either from the AC mains anode distance so as to accommodate the ment. Alternatively, use is made of a or from the supply for an early amplifier. necessary radiating fins. simple heating coil wound round a bi- metal strip which actuates the high - Practical tension contacts. Points Thermally actuated contacts sometimes Further protection can be introduced give trouble, since the operating force is by circuit arrangements. In this case the not very great whether of the open or heater of the delay tube can be connected vacuum type. Such arrangements have in series with the heater of the gas recti- also proved microphonic and are liable fier valve so that should either fail the to be upset by vibration. In an endeavour high- tension circuit is opened. Providing to overcome these difficulties the follow- the delay tube has a far quicker cooling ing arrangement was devised by . the time than the cathode of the gas rectifier, writer and was found to be highly suc- is no TO H T then there possibility of damage cessful in practice. CIRCUIT occurring. This scheme, outlined above, is being utilised in commercial design and Device Described is actually covered by pending patents, but it is one which should prove useful to The contact device constitutes an the experimenter. ordinary relay, which is a very rigid and If use is made of a mains rectifier for mechanically sound piece of apparatus. the delay valve, quite heavy currents (of Its reliability is proved by the multiplicity the order of 6o to ioo milliamps) are of such devices employed in ordinary tele- available. This means that a fairly circuits which are phone communication Fig. Theoretical heavy power relay can be employed if day. Moreover, the device 1.- circuit of the valve -oper- in use every ated relay ; the resistance shown dotted is cheap. It is actuated by the anode enables the delay to be increased by reducing r current of a hard valve fitted with an in- the cathode temperature. Delay Introduced by Different directly heated cathode with an appre- Valves ciable thermal delay. The theoretical cir- It is easy to elaborate the fundamental cuit is shown in Fig. i. idea so as to ensure even greater protec- UR3c .. .. 75 seconds It is obvious that if an appreciable time tion. While a long thermal delay may 1W4 at 3 volts .. .. 90 seconds elapses before the cathode emission is be introduced by increasing the quantity obtained after switching on the heater of insulated material between the heater 1W4 at 2 volts .. .. 240 seconds current, there will be a delay in opera- and the inside of the cathode, it is obvious (Reduced output) tion of the relay, and the scheme pro- that one has a greater mass of material vides a very effective and reliable delay at a high temperature, and accordingly device. the cooling period is equally lengthened. desired, and this is advantageous if it is When a very long delay period is re- This means that should the amplifier be very robust, and it can be used to operate quired, it is preferable to construct a temporarily switched off and should the comparatively heavy contacts with appre- valve in which there is rather more cathode of the gas rectifier cool far more ciable pressure. On the other hand, a thermal insulation between the heater rapidly than the cathode in the delay small relay operating with a current of

www.americanradiohistory.com ,g Vgp @ll® w JULY 2nd, 1937 w© ll of Delayed Switching- most cautious body, which never grants any a few milliamps can also be employed. DISTANT such application until possible problems that a have been considered in all their aspects. It will be noticed in the diagram WLW, however, the Cincinnati station, has series resistance is shown in the relay RECEPTION NOTES proved so completely successful as a 50o- circuit. The function of this is really kilowatt plant that others are bound to fol- two -fold. The High power Mysteries low. Possibly the Commission doesn't want In the first place, it acts as a safety to issue its decisions until it has received all and prevents too heavy a load the applications that are likely to come in, resistance SOME of the giant stations which ought being placed on the rectifier if the relay into operation by now so that the problem can be considered as a to be coming whole. Would that in Europe we had some- winding is of quite low resistance. It can seem to have been delayed in their with of F.C.C. ! also be used to regulate the current at construction by one cause or another. thing the powers the which the relay will operate. It may be Labour troubles probably give the reason I don't know about you, but I always find whether it is yester- shunt the relay why France's Radio National is still some it difficult to remember found convenient to day or to-morrow in places such as New either with a fixed or variable resistance. way from being ready. But what of the new Deutsthlandsender? This station is Zealand, Australia and the South Sea It will be appreciated that as the valve Islands. Working out the local time in warms up, so the current begins to in- still largely wropt in mystery. There have of the countries whose shortwave transmissions- you low of the order of been all kinds rumours about power crease, and currents going to possess when it comes into pick up can be, in fact, quite a puzzling the that it's D. a few milliamps will pass through action, but I think we can discount those business. EXER. relay circuit before the final cathode tem- which credit it with more than 200 kilowatts perature is reached. It is obvious, there- at the outside. It will most likely- fall into fore, that if use is made of a low current line with most of the other big stations on relay, the relay must be heavily shunted the long waves by adopting a 150-kilowatt Television to ensure that it does not operate too soon. rating for general working purposes, though It is best to aim at using a relay which possibly there will be a good deal in hand Programmes will operate at a heavy current for the for special occasions. reasons mentioned above, but if such a And then there are the expected Italian an easy high -powered stations, including two of Izo Transmissions are from 3 -4 and 9 -10 type is not available it is quite for Rome. Work on these also daily. with shunt and kilowatts matter to experiment seems to have gone forward more slowly Vision 45 Mc /s. Sound 41.5 Mc /s. series resistances until a current value is than was anticipated, but I hear that a big found that will càuse the relay to operate speed-up is taking place now. FRIDAY, JULY znd. at the end of the heating period. Amongst other high-powered transmitters 3, Animals from the Zoo, presented by G. M. it should not be Vevers. 3.15, Gaumont -British News. 3.25, On the other hand, " From West -End Cabarets " -a variety with assumed that the adjustment is very music by the Television Orchestra ; presenta- critical, and, once the experiments have tion by D. H. Munro ; compère, Paul Gerrits. been made with the actual relay, the re- 9, Repetition of 3 programme. 9.15, British sistances can be substituted by ordinary Movietonews. 9.25, Repetition of 3.25 pro- fixed carbon types. Some consideration, gramme. however, must be given to the total power SATURDAY, JULY 3rd. seen in the circuit, and it will readily be 3, " Thrust and Parry " : a demonstration of that this is of the order of several watts, the Art of the Foil, by Gwendoline Neligan and and accordingly a resistance with an Maestro Leon Bertrand, in Alexandra Park. 3.20, The Hogarth Puppet Cabaret. 3.35, ample rating should be employed. British Movietonews. 3.45, Operetta. 9, Maria Luth in Period Songs. 9.10, " Coffee Stall." 9.25, Gaumont- British News. 9.35, National Physical Laboratory Les Allen and his pianists in " Queue for Song." ON CE a year the National Physical MONDAY, JULY 5th. vv Laboratory opens its gates to visitors 3, Anona Winn in Songs. 3.10, More Marine and shows them something of the work Models : a review of prototype power boats on throughout the year. This work the lake in Alexandra Park. 3.35, " Ad Lib " : carried on a revue by Herbert Farjeon, with all branches of physics, and wireless music by covers Michael Sayer ;, production by Stephen Thomas. forms a comparatively small proportion of the activities. 9, Music- Makers : Maria Korchinska, harp. in the 9.10, Artists and Their Work -talk by Miss Little new was to be seen this year Rhodes Dawson. 9.25, Gaumont -British News. sections devoted to radio and allied matters. The origin of the well -known nightingale 9.35, Repetition of 3.35 programme. Doubtless, the time has not yet come to interval signal from Trieste is disclosed when reveal the secrets of the year's research. we see Miss Paola Guastalla of the station TUESDAY, JULY 6th. A portable ultra- short -wave direction staff winding up the clockwork unit that 3, Naunton Wayne. 3.10, Gaumont -British finding receiver was demonstrated in the supplies the distinctive call. News. 3.20, " Derby Day," an operetta by grounds on signals from the Alexandra A. P. Herbert, produced by Stephen Thomas. are Palace and also from a small local trans- that have not yet materialised the two 9, Men's Dress Reform : masculine fashion mitter about a hundred yards away. Sharp Brussels stations, which long ago announced parade. 9.10, British Movietonews. 9.20, null points were obtained with the result their intention of going up from 15 to 75 Repetition of 3.2o programme. that the apparatus was easy to handle. kilowatts. Probably there will be a spate The receiver is a superheterodyne with a of newcomers as autumn draws near. WEDNESDAY, JULY 7th. push -pull frequency- changer operating, from Meantime I have news from America that 3, The Charlot Starlets, with John Byron, This WBZ, of Boston, Massachusetts, has ap- Patricia Leonard and Patricia Russell. 3.30, a single -turn screened frame aerial. Picture Page, 69th edition. portion of the apparatus is mounted with plied for permission to increase its power in a screening box on a tripod from 5o to 50o kilowatts. It is prophesied 9, Repetition of 3 programme. 9.20, Gaumont - its batteries British News. 9.30, Picture Page, loth and is connected by a screened cable to the that the application will be granted fairly edition. IF amplifier on the ground. soon, and when it is the plant will be moved THURSDAY, JULY 8th. apparatus mention to that queer- shaped piece of land, Cape Among the precision 3, Relache. 3.20, Gaumont - British News. must be made of the direct reading Cod. 3.30, " How She Lied to her Husband," a frequency -measuring equipment, which is I mentioned some time ago that several play by George Bernard Shaw, with Greer designed for frequencies ranging from I Mc / s other U.S.A. stations had put in applica- Garson and D. A. Clarke- Smith. Produced by to as high as 75 Mc /s ; it is self- checking. tions to increase their power to Soo kilowatts, George More O'Ferrall. Radio- frequency bridges and apparatus for but so far no news has come that any of 9, Repetition of 3 programme. 9.20, British the measurement of current at radio - them has been successful. The Federal Movietonews. 9.30, Repetition of 3.3o pro- frequencies were also shown. Communications Commission is rightly a gramme.

www.americanradiohistory.com Wireless World, July 2nd, 1937 9

EVENTS OF THE WEEK IN Current BRIEF REVIEW New Station for West Africa is proposed to erect a broad- IT casting station at Dakar, to be used in conjunction with a opics special receiving station. The intention is to pick up pro- system of communication be- grammes from France and re- tween headquarters and a num- broadcast them for the benefit ber of mobile units. Several of the French- speaking inhabi- constables are being trained as tants of Senegal. telegraphists. It is proposed at wire- WORDS NOT a later date to extend the BULLETS less network to the surrounding American Plans A new country so that the police sta- type of ACONSIDERABLE exten- "O.B." van is now tioned there can co- operate more being used by the sion of activities is being closely with their city col- contemplated by the N.B.C., broadcasting leagues. organisation i n and plans are being made for France. The design the erection of new studios and Gramophone War favours the offices in different parts of THE dispute between the contours of an the country. Headquarters, Danish State Broadcasting armoured car. modelled on those at Radio Corporation and the gramo- higher -priced sets, this being City, New York, are to be phone industry which has been i accounted for partly by the erected in several important dragging on for years desire for better quality of re- several production and cities at a total cost of over in a desultory manner, is now Popularity of Wireless partly by the 3 million dollars. fact that more expensive cabi- likely to be brought to a head TEN thousand families in by of nets of the console type are the decision the broad- Chicago were recently asked being demanded. Interference in France casting authorities to encourage what they planned to buy next AREPORT issued by the a new company which was regis- as soon as funds permitted. Radio Romance French P.M.G. announces tered at Copenhagen the other New automobiles came an easy LAST summer well - that, so far, anti- interference day to manufacture gramo- first with fresh insurance policies the phone records. known Swedish opera measures have only been taken ; second wireless sets were, how- singer, Sigurd in twenty-seven towns. As a ever, a good third. Björling, visited result of numerous requests More New Stations Iceland to give a special broadcast from the Reykjavik station. from various parts of the ACCORDING to an Italian New Use for Car Radio country it is hoped, however, As a result of this visit he was report a very powerful MANY recently that before long the organisa- short-wave broadcasting station screen and stage direc- married to the lady tion of the anti -interference tors, always on the look- announcer of that station. is to be built at Prato Smeraldo, out for new talent, make section of the French post is the a point near Rome. It said that of listening assiduously the office will be improved. power will be not' less than to Australian SW broadcasting programmes in the Transmissions 10o kW. Turkey has just hope of for July Trouble in Norway medium -wave a " find." Mr. Leslie ordered a 120 kW Cardew, of the Pinewood Film SYDNEY, VKzME, 9,59a recent strike of Nor- transmitter for Ankara and a kc /s, THE Studios, carries on policy to 31.28 metres. Sun- wegian ships' officers was 20 kW short-wave one. These such an extent that he has had days, o5oo to 0700, 0930 to partly concerned with a dispute are to be ready in August, 1938. his car fitted with radio solely 1330, 1630 to 1830. Mondays, regarding the remuneration of for the purpose of enabling him 1630 to 1830. mates who also operate the Tristan da Cunha to keep his ears open for likely Melbourne, VK3ME, 9,510 wireless installation in addition kc /s, 31.50 metres. of what is talent when on the road. All week- to their other duties. The new THE inhabitants days, 0900 to 1200. provides this often referred to as " the agreement that island in the world," A Famous Radiophobe Perth, VK6ME, 9,590 kc /s, extra work shall be paid for at loneliest 31.28 metres. All weekdays namely, Tristan da Cunha in M. EDOUARD BRANLY, of the rate of L3 per month. 11o° to 1300. the South Atlantic, have been coherer fame, has, it is presented with a wireless set said, always had an aversion to Japan Prefers Talks with which it is hoped they will broadcasting as a means of en- News from Panama to recent statis- be able to enjoy broadcasting tertainment. He recently de- the ACCORDING concerning establishment of tics published all the year round. The set, livered a talk before the micro- SINCEbroadcasting in Panama in broadcasting in Japan, it ap- which has been given by the phone in which he frankly con- 1935 there has been a tremen- pears that, on the whole, lis- Ekco Co. of Southend, was re- fessed that although he listened dous increase in imports talks of some kind of re- teners prefer cently handed over to the Rev. to certain transmissions on his ceiving sets. Nearly all the or another. No less than 51 H. Wilde, of Tristan da Cunha, grandchildren's receiver he was receivers come from the United per cent. of the total pro- who is at present visiting this by no means an enthusiastic States. gramme time during 1936 was country . listener. devoted to a combination of Hitherto, the battery prob- news and topical talks, music lem has prevented the success- America Wants Better Holidays Guide for occupying less than 10 per ful running of a set in the island Quality Motorists cent. of the time. as the mailboat, with a supply THE sale of wireless sets is each copy of The of fresh batteries, only visits booming in the U.S.A., WITHWITHMotor Cycle, dated July Bombay Police Wireless Tristan da Cunha once a year. figures for the first four months 1st, a 32 -page Holidays Guide VERY exhaustive wireless ex- To overcome the HT part of of the year being from 20 to 40 will be presented free. The

. periments are being the problem, the all -wave set per cent. greater than for the Guide contains a wealth of de- carried out by the Commissioner supplied is of the " no HT '' corresponding period of 1936. tail about many of England's of Police in Bombay, who has type exhibited at Olympia It is estimated that during the finest beauty spots and clearly received a grant of 5,000 rupees last year, while the LT problem present year over ro million marked maps of all the country from the Government with a is being solved by means of a sets will be sold. There is now between Land's End and John view to establishing an effective wind -driven generator. a much greater demand for the O'Groats are included.

www.americanradiohistory.com ro Wireless World, July lud, 1937 Periodic Variations of the quency will lie just below the penetration frequency, for that is the frequency which, THEIR PRACTICAL. EFFECT ON while it is adequately refracted by the F layer, suffers least attenuation in both the SHORT -WAVE RECEPTION E and F regions. In this connection it is as well to remember that the penetration OUR conception of the ionosphere and positive ions. The agents producing frequencies in the case of a short-wave and of the part it plays in radio this ionisation are of two kinds, viz., a broadcast station will be far higher than wave propagation is continually solar wave radiation of a frequency in the those given by scientific experiments made changing, and from time to time ultra -visible part of the spectrum (ultra- to determine the penetration frequency of some new discovery causes us materially violet light), and a stream of corpuscles the layers, because in the former case the to alter our ideas on the subject. The which are shot off from the sun so as to wave is projected at a relatively small recent announcement by Watson Watt of bombard the molecules of gas and thus angle to the ground, so as to have a glanc- the presence of a number of ionised layers liberate electrons by direct collision. Both ing incidence at the layer, whereas in the at comparatively low altitudes is a case in these agents appear to play a part in the latter case the wave is sent vertically up- point, and although this particular dis- ionisation of both the layers, so that the wards. It is easy to see that a wave reach- covery may not directly affect ordinary ionising influence exerted at the E layer ing the layer at glancing incidence would short-wave reception, it brings home to us, depends to some extent on the amount of be completely refracted at an ionisation in a startling way, the fact that we have solar radiation absorbed at the F, and thus level which would allow a vertically inci- yet a great deal to learn about the upper on the amount of filtration to the lower dent wave of the same frequency to pene- atmospheric regions. Perhaps the most layer. While the radiation is much more trate. clearly evident thing about the iono- intense at the F than at the E, and the sphere, from the viewpoint of short -wave level of ionisation produced is thus much The Diurnal Variation reception, is that it is in a constantly higher, yet the intensity of the radiation As is well known, the ion content of the changing state, and it is interesting to try at the F is not the major factor which de- layers is not constant, but undergoes pro- and correlate the periodic changes in short- termines the ionisation level reached there. nounced periodic changes of three kinds wave réception conditions with coincident For, since much of the ionising energy is -diurnal, seasonal, and an eleven -year changes in the medium which alone makes not absorbed, owing to the comparative variation due to the sunspot cycle. There such reception possible. rarity of the air molecules, it is evident are also sharp day-to -day variations of an that the density of the molecules or gas erratic nature. Structure of the Ionosphere pressure is the main determining factor. Considering first the diurnal change, we On the other hand, the gas pressure at the see that soon after dawn the ionisation The atmospheric region popularly E layer is high, but the amount of ionis- levels of both layers commence to rise with known as the ionosphere is mainly coming agent reaching this layer is limited, the increasing intensity of the solar radia- prised of the two layers of ionised air, and thus the ionisation level reached is tion, and continue to increase towards which surround the earth in the form of very much lower than at the F layer, and noon. At the E layer, where the gas.pres- concentric shells, the inner or E layer at is determined mainly by the intensity of sure and consequently the recombination a distance of about 6o miles, and the outer the radiation, and not by the gas pressure. rate are high, the ionisation level follows or F layer about i8o miles from the earth, Ions and electrons in a dissociated state closely the intensity of the radiation, so together with a belt of much less highly have a strong tendency to combine, and that at noon it commences to fall, and at ionised air in between them. At certain in the ionosphere they can do this at a rate dark the fall becomes much accelerated, times of the day subsidiary layers are depending on the gas pressure. As this is so that by midnight the attenuating effect formed, namely, the E2 region, situated very much higher in the lower layer than of the layer upon the frequencies we are just above the E layer, and the F2 region in the higher, the E layer recombination considering is very small. just above the F layer, looking upward rate will greatly exceed that of the F layer. The recombination rate at the F layer from the earth. In addition to these is so low that the rate of ion production regions of the ionosphere proper, there Refracting and Attenuating Layers about midday exceeds it to such an extent appear to be the two bunches of layers in that a time lag is introduced, with the the lower atmosphere' announced by Radio waves higher in frequency than result that the maximum level is not Watson Watt, called the C and .D regions, about 3 Mc / s pass through the E layer and reached till late in the afternoon. Then and far out into space beyond the F layer undergo refraction or " bending " in the the level falls slowly and continues to do (according to Alway and Philips) there F. The degree of bending and also the so throughout the night, though it remains appears at certain times a belt of air ion- attenuation suffered will vary directly as at a relatively high level until past mid- ised to a degree comparable to that of the the density of the free electrons and in- night. Remembering what has been said F layer and named the G region. versely as the square of the frequency, about limiting frequencies, we see that the As, however, these latter regions do not and, while the ion content of the E layer effect of these changes on 'long- distance play a regular part in the propagation of will rarely be sufficient to cause complete short-wave receptions will be as indicated the frequencies we are considering, we will bending, yet it will cause the wave to be in Fig. r. During the morning rise in ion- henceforward confine our attention to the attenuated. And, since the wave will ex- isation level the band of frequencies for ionosphere proper, viz., that part of the pend more energy in passing twice through good reception is moved toward the higher atmosphere from the lower boundary of the E than it will during its excursion into frequency end of the spectrum, but at the E layer to the upper boundary of the the F, we may regard the E layer as the noon the band begins to broaden, since F. main source of attenuation, and the F the higher limiting frequency continues to When the molecules of gas comprising layer as the bending layer. rise, while the lower limit commet ces to the air in the layers are subjected to the Thus we see that the upper limit for fall. Even when the ion content of the sun's influence they become split up by goòd reception is set by the penetration F layer starts falling, the broadening effect the action of solar radiation, so that elec- frequency of the F layer, and the lower by of the good reception band continues, be- trons are liberated, and the layers contain, the frequency which suffers complete cause the lower limit falls more rapidly to a greater or less degree, free electrons attenuation in the E. The optimum fre- than the higher. Nevertheless, the opti-

www.americanradiohistory.com Wireless World, July and, 1937

AT certain distances above the earth are well- defined layers of ionised air which play a very important part in short -wave reception. Though the ionisation of these layers is continually Ionosphere changing it is explained in this article that the variations are mainly aperiodic, and by applying such knowledge that is available mum frequency now begins to fall, and it is possible to reach a decision regarding the frequencies to use while it continues to do so throughout the for best reception at different times of the day and at different comes night there a time (usually near seasons. midnight) when the good reception band is at its broadest, since then the ion content of the E layer is so low that the layer layer, where gas pressure is not the con- ionisation level of the F layer is much has very small attenuating effect on fre- trolling factor. In winter the ion content higher than at the minimum period, and of the layer is low because the amount of provides adequate bending for the high solar radiation affecting the layer is small, frequencies, while the normal recombina- but, as the season advances, although the tion process in the E layer after dark re- density of the air decreases, the molecules moves its attenuating effect on the lower REFRACTION CURVE are still sufficiently numerous to absorb the frequencies. maximum amount of the radiation, and From this we may deduce that,the best this is increased for two reasons : (a) the possible conditions for short -wave recep- amount of radiation from the sun is tion would exist after darkness in the greater, and (b) less of this is absorbed winter of a sunspot maximum year, for F at the F layer and so reaches the.E. Thus then it appears that we might have the the ion content of the E layer rises, so that highest possible F layer ionisation with ABSO PT ON is reached at midsummer. The very little E, permitting us to receive a CURVE a peak result of these variations is as indicated in very large range of frequencies in the Fig. 2. In winter the frequency band for short -wave band. 2 4 6 0 10 z 2 4 8 10 good reception will be at its broadest, both There remain those erratic day -to -day o 2 AM o high and low frequencies being well re- variations that play such havoc with con- DAWN z PISU M SET ceived. In summer the penetration fre- sistent short-wave broadcast reception, the quency of the F layer is lowered, and the attenuating effect of the E layer is raised. Fig. t. The characteristics of both E and F so that the very high frequencies heard in layers determine the highest frequency for winter will no longer be received. Never- good short -wave reception. Attenuation takes theless, the best received signals will be place mainly in the E region and refraction R FRACTION in the F region. The changes in these two at towards the higher frequencies, as a large CURVE different times of the day are shown by these band of the lower frequencies will suffer curves. heavy E layer attenuation, and the good quencies in the S/W band, while the F reception band is considerably narrowed. layer level is still high enough to refract If one observes the U.S.A. stations, one frequencies as high as 20 Mc /s, or even can already observe these effects, the very higher. Of course, when considering di- high frequencies no longer being heard, ABSORPTION urnal' changes in short-wave reception we with conditions generally worse than in -CURVE must consider the daylight conditions over winter. Wcc z the whole transmission path, remembering Eleven -Year Cycle î 7î that stations in the opposite hemisphere î 7 will have winter conditions when we have Lastly we must take into account the Ñ summer, so that, even if they are on the effect of the eleven -year sunspot cycle. same meridian as ourselves, conditions will Sunspots are the main cause of the erratic Fig. 2. These curves show the variation in day -to -day variations in short-wave recep- the ion content of the E and F layers at often vary from daylight to darkness over different seasons of the year. the path. Nevertheless, the broadening tion, for when they are prevalent there is effect of the good reception band can easily an increased amount of solar radiation, so be observed on a transmission path such that higher ionisation levels are reached cause of which is undoubtedly a fluctua as that from the U.S.A. to this country in both layers. But, although they in- tion of the solar radiation, possibly due to in the evening hours. crease in numbers and in size so as to sunspots. Could these be minimised and reach a peak every eleven years, they are a reliable service maintained at all times? Seasonal and Long Period not obliging enough to do so in a regular It seems that their effect might be reduced Variations manner, and consequently we get all sorts to a considerable extent if the transmission of irregular variations in the ion content engineer were able to forecast the sunspot In winter the solar radiation is at its of the layers. However, if we ignore conditions a day ahead (and this he wel; lowest ebb, but is. nevertheless, sufficient these and consider only the average values, might do in co- operation with an Astro- tq raise the ion content of the F layer to we see that there is a gradual rise in the nomical Observatory), and so change his a high value. As the season advances and ionisation levels towards the sunspot maxi- frequencies from day to day to suit con- the sun's effect becomes more powerful mum period. According to Professor ditions. But this no listener would toler- the air heats up and consequently becomes Appleton, the F layer level is now 30o per ate, even if it were possible from the point much less dense, so that, although there cent. and the E layer level 5o per cent. of view of the international authorities. is now a greater amount of ionising radia- above its minimum sunspot level. Conse- And so he is limited in the scope of his tion reaching the F layer, it is largely in- quently the optimum frequency for any attack. However he does (in the case of effective, owing to the increasing rarity of transmission path, whether in daylight or the larger broadcast organisations), from the gas molecules. Although the solar darkness, is now much higher than it was time to time, so consider the frequencies at radiation has increased, the gas pressure during the sunspot minimum period, and his disposal, the transmission paths to be has fallen, and the net result is that the will possibly be higher still before the sun- traversed, and the prevailing seasonal and F layer ionisation level falls towards mid- spot maximum is reached. Also, the fre- sunspot conditions, as to give the best summer and then rises towards the winter quency band for good reception after dark- service with the power at his disposal and again. A different effect occurs at the E ness is particularly broad, for the residual within the limits he is obliged to work.

www.americanradiohistory.com 12 Wireless World, July. 2nd, 1937 Listeners' Guide for proposed to take listeners to Outstanding Broadcasts the Festival of Youth at Wembley. This is the first at Home and Abroad assembly of its kind in this country. In aid of King George's Jubilee Trust, there at the end of which, incidentally, is corn- young cooper will be thousand when he is posed entirely of wood and tell per- apprenticeship, formers, and Their Majesties' rolled in a large barrel that has string instruments. Dorothy arrival will be announced by been built around him for the Careless will sing. fanfares followed . by the occasion. Z fore- POT -POURRI OF SPORT National Anthem played by Mr. C. L. Homer, a the in a Black THE O.B. Department will massed bands of the Bri- man enameller gade of Guards. ALAN PAUL, who wrote hard toy factory, has be especially active tomorrow Country The vivid description by the musical' comedy for a wager- been learning the tricks of his between- 2 and 5.15, when music is to commentator, now his chamber he will National listeners will hear the stirring be broadcast Nationally on trade for 21 years, and strains of listeners. commentaries on three out- the bands, and the Thursday evening. describe them to voices of the eager thousands of toys, standing events. Still on the subject' of youth assembled on this N recent years, during the Miss M. Guest will talk about John Snagge, who has made months of July, August in recent years such a great occasion should make an in- dresses that she designs for spiring outside broadcast. and September, the lis- dolls. The whole programme success of his boat -race broad- tener has had to accept H. casts (he is himself an enthu- In the evening, at 8.45, on will be compèred by F. the Regional programme, Ber- the radiation of a single pro- Grisewood-thus is success siastic oarsman and got his trial unpleasant in- eights at Oxford) will be nard Grey, one of the North's gramme as an ensured ! evitability. This year alter- 0 0 stationed in a special stand sports commentators, . will describe native programmes on the IS ENDED erected by the Regatta autho- the Speedway Test THE SONG Match between National and Regional wave- " THE Melody Lingers On " rities at the finishing post at England and Australia lengths respectively will be is the title of a reminiscent pro- Henley. One of the typically at Belle Vue, ,Man- broadcast, and so it is natural chester. that new week -by -week fea- TO- MORROW . 0 0 be presented. AFTERNOON tures should some of the events STARS FOR " MUSIC HALL " July seems to associate itself at Henley Regatta GooD news for "Music with blue skies, a warm sun, will be described Hall " listeners : John Shar- the seaside with its gay colours' to listeners by man has arranged John Snagge. for Flanagan and, of course, the pier. The and Allen to appear in his B.B.C. have tracked just such show tomorrow at 8 in the a train of associations as this National programme. This is to its logical conclusion, so their fourth recent appearance, next Thursday at 7.25 on the and in the same show the ever - National wavelength we get popular Bebe Daniels and Ben Shows from the Seaside, the Lyon will be making their last first of a series of concert party broadcast in this country broadcasts, arranged by Harry before going on a tour of South Pepper. Instalment No. I Africa. Phyllis Robins makes comes from the Pier Pavilion, a welcome return to music to English scenes which Britons in the Harry Pepper with gramme of dance be Music Worthing. National exile remember when languish- " Hall," and Rupert Davy Burnaby will introduce heard on the wave- Hazell and Elsie Day take length Tuesday at 8. Ben ing beneath the torrid sun is the Richard Jerome's " Gay on their part in what they call Parade." Frankel, the well -known tableau which the Henley Re- " Harmonylariety." 4, O 4, arranger of film and radio gatta presents. The river is a ANOTHER SERIES music, impressed with the great jewel, glittering in a ver- from dant setting glorious foliage THE first of the series called number of requests of IN PRAISE OF QUIET '. " Tricks of the Trade," which listeners asking band leaders to while the water's edge is AN escape from the clatter was referred to in The Wireless play popular melodies of recent fringed with punts filled with and busy hum of city streets, World some weeks ago, is to be years, conceived the idea of a youth, gaily dressed- in sum- the maddening hubbub . of heard Nationally at 6.2o on musical presentation consisting mer attire. modern existence, an escape Monday. This will bring to of popular tunes of the past, It is from this scene that the from it all -just for forty the microphone a journeyman orchestrated in modern -day commentator will describe the minutes. That is what Alan cooper from Burton-on- Trent, manner. Many favourite num- progress of the boats, and it is Paul has planned for those who a woman who makes dresses bers of the past twenty years hoped to include the finals of care to listen to his programme, for dolls, and a man who for are dated as regards their the Grand Challenge Cup and " In Praise of Quiet Things," many years has been making tempo and orchestration, but the Diamond Sculls. to be broadcast in the National toys. are capable of rivalling the On this day, in all probability, programme at 10.20 on Thurs- The cooper, Mr. R. P. modern rhythm melodies if the finals of the All- England day evening. Those taking Stanesby, was chairman only given modern treatment. Hence Lawn Tennis Championship part include Jean Pougnet, a few weeks ago at a typical the title of the programme will be fought at Wimbledon. violin ; David Martin, violin ; ceremony, and this should which has been arranged by Colonel Brand and Captain Anthony Pini, 'cello ; with brighten that part of his story Jack Davies, Jr. Ben Frankel Wakelam will describe the Alan Paul himself at the piano. which describes the ancient has scored the music and will final contest of the struggle. Garda Hall, soprano, will be custom of " initiating " a be conducting the orchestra In the afternoon it is also the vocalist. Appropriate verse

www.americanradiohistory.com Wireless World, July 2t td, 1937

German Opera House by Ber -. lin at 8 p.m. on Saturday, should find many listeners in this country for it was made extremely popular by Jenny the Lind with her Wcek vivacious singing in the title rôle. Of all and prose selected by Anne acquired considerable experi- the composer's will be works, this can Barker spoken between ence, the former when he was be the items, and the programme truly described as the most programme director of a radio brilliant. The glorious finale, is presented by William station abroad, and the latter " Salute to France," has few Maeburg. he when was conducting at equals in operatic music. To those who are prejudiced, Austrian and German opera Not unnaturally Verdi is the perhaps not without reason, houses. choice on the 9 Rome pro against chamber music of all -' " Bluebeard " will be broad- gramme when his Force of varieties, let it be known " that cast on Wednesday between 8 Destiny " will be relayed from Alan Paul has written a suc- and 9 in the pro- National Cremona. The music is fine, cessful musical comedy, com- gramme ; be the Group will but the theme is indubitably a plete with dance music, as the assisted by the Revue Chorus " gory " one ; all the princi- result of a remark made to him and the Theatre Orchestra. pals come to a violent end, by a friend : " I don't expect o and the opera eventually EFFORT. " Bunny " Austin in you could write a dance tune peters out for lack of charac- attitude symbolical of cham- if you tried "; -therefore this ROYAL AGRICULTURAL pionship tennis. Commentaries SHOW ters to carry on ! The singing programme in- will be heard from Wimbledon should have an VIEWPOINTS and personali- could not be in better terest for hands- at various times during the after- even the rhythm sec- ties will be broadcast from the both Gina Cigna and Borgioli, noons of to -day and tomorrow tion of the listening public. 0 Royal Show, held this year at so recently heard at Covent (National). 0 Wrottesley Park, Wolver- MUSIC Garden, are in the cast. at 8 by an O.B. from Silke- hampton. idea is WITH the B.B.C. Symphony The to bring 0 0 0 borg, Jutland, in the shape of Orchestra away on annual to the microphone several FROM DENMARK a concert by the Silkeborg leave, there will be fewer speakers who are attending the A number of English Koncertorkester, a popular studio broadcasts of orchestral show and have interesting and American rhythm songs provincial orchestra, the mem- music during the month of points of view to express about will be presented by " The bers of which have earned the as seen July until the Proms. begin on new developments at Five Kentucky Singers," who reputation as specialised ex- August 7th. The B.B.C. the show or about agriculture are broadcasting from Den- ponents of Scandinavian Empire Orchestra, however, generally. The transmission mark at 9.25 on Monday. This music. will broadcast Mendelssohn's will be heard Nationally at transmission will be preceded THE AUDITOR. First Symphony on Tuesday at 6.2o on Wednesday. c 9 (Regional), when they will 0 o HIGHLIGHTS OF THE WEEK be conducted by Clifton Helli- CRICKET FRIDAY, JULY 2nd. THE Abroad. well. annual 'Varsity cricket Nat., 7.30, Peter Yorke and his Radio -Paris, 8.40, Casino Concert On Thursday, at 8 match is, as a rule, a fast - Orchestra. ¶B.B.C. Scottish from Vichy -also relayed by most (National), Julius Harrison moving game, played on the Orchestra. 9.20, Caf' Chant'- other French stations. another little show. will conduct the London Sym- "` get on or get out " principle. TUESDAY, JULY 6th. Reg., 7.25, Recital by Susan Nat.. 6.25, B.B.C. phony Orchestra in a broad- This adds to its value from the Metcalfe Casals (mezzo -soprano). Theatre Organ. ¶Storm in a 9.20, cast performance of Dvorak's commentary point of view, and 8, Stanelli's Batchelor Party, Tea Cup. America. To-day talk on No. 13. Produced by Max - First Symphony and Sibelius' it should give Howard Marshall economic problems Kester and Stanelli. by Geoffrey "` Tapiola. " plenty to talk about during his Abroad. Crowther. Reg., 7.30, Alfredo Campoli and his Breslau, 8.10, German Folk Songs Salon Orchestra. B.B.C. Singers and Music in old and new settings. (A). 'Pleas for Pleasure. 9.40. SATURDAY, JULY 3rd. Is it the Law? Nat., 7.30. A.B.C. 8, Music Hall. Abroad. 10, My Own Poetry. 10.20, Konigsberg, 8.10, " A Dance Chamber Music. Medley." Erich B irschel Dance Reg., 6, Dance Music. From the Band. London 8, B.B.C. Theatre. 7th. Northern Orchestra. ¶King's WEDNESDAY, JULY Nat., 5.15, Ambrose and his Muster : George IV Visits Orchestra the Paris Ex- Scotland. from Abroad. hibition. 9.20, " I Protest " : a talk on common nuisances. Rome, 9, " The Force of Destiny " Reg., 7.30, Kaleidoscope. ¶Piano- -act opera (Verdi). -Four forte Recital by Leopold SUNDAY, JULY 4th. Muenger. 9.45, Robb Wiltt'n as Nat., 6.45, Fred Hartley and his Mr. Muddlecombe, J.P. Sextet. 7.30, Bransby Williams. Abroad. 7.55, Service from the City Leipzig, 8, Concert from the SONGS FROM THE SEASIDE. No. 1 comes from the Pier Pavilion, Temple. Belvedere Open -Air Theatre, Worthing, on Thursday at 7.25 (National). Reg., 6.45, Eugene Pini and his Weimar. Tango Orchestra. You 9.5, As THURSDAY, JULY 8th. T!-9 Opera Group, a corn- descriptions, which last for Like It. ¶Epilogue. Nat., 6.20, Book Talk by Allen pany of young English singers, fifteen minutes and which are Abroad. Ferguson. ¶BB.C. Military Hamburg 8, " A Century of Garden founded about two years ago to be radiated in the National Band. 8, London Symphony Music "-a romantic serenade. by Dr. Ernst Schoen and programme at 1.15 and at 5.o Orchestra. George Knepler, on Monday, Tuesday, and MONDAY, JULY 5th. Reg., 6, B.B.C. Northern Orchestra. presents Nat., 7, B.B.C. Scottish Orchestra. ¶Beatrice Harrison, 'cello. 8, Offenbach's comic opera, Wednesday. ¶Tricks of the Trade. 9.35, Melody Out of the Sky-Jay " Bluebeard." The group, Dove Days. gr the Derbyshire Wilbur and his Band. which will be broadcasting for OPERA ABROAD Angler. Abroad. Reg., 6.35, Pianoforte Recita' by Luxembourg, 9.30, Symphony Con- time, specialises in DONIZETTI'S c l s s i c the third a Claud Biggs. 9.45 Melody and cert with Lazare Lévy (piano- smaller opera, in which both ' ` Daughter of the Regiment," Rhythm. forte). Schoen and Knepler have which is to be relayed from the

www.americanradiohistory.com T.1 Wireless World, July and, 1937. PRINCIPAL BROADCASTING STATIONS OF EUROPE Arranged in Order of Frequency and Wavelength (This list is included in the first issue of each month. Stations with an Aerial Power of 50 kW. and above in heavy type) Tuning Ting Mettes. Station. to. Positions. Metres. kW. Station. ka/s. Positions. kW. 785 382.2 120 Ankara (Turkey) .. . . 152 1973.5 5 Leipzig (Germany) ...... Kaunas (Lithuania) ...... 153 1961 7 Barcelona, EAJ1 (Spain) ...... 795 377.4 7.5 Radio Romania (Brasov) Romania .. 160 1875 150 Lwow (Poland) ...... 795 377.4 50 Hilversum, No. i (Holland) (10 kW. till 1840) 160 1875 150 North Welsh Regional (Penmon) .. .. 804 373.1 5 Lahti (Finland) 166 1807 150 Welsh Regional (Washford Cross) .. .. 804 373.1 70 Moscow, No. 1, RW1 (Komintern) (U.S.S.R.) 172 1744 500 Milan, No. 1 (Italy) ...... 814 368.6 50 Paris (Radio Paris) (France) .. 182 1648 SO Bucharest (Romania) .. .. 823 364.5 12 Istanbul (Turkey) .. .. 185 1622 5 Kiev, No. 2, RW9 (U.S.S.R.) .. .. 832 360.6 35 Irkutsk (U.S.S.R.) 187.5 1600 20 Agen (France) ...... 832 360.6 1.5 Deutschlandsender (Germany) 191 1571 60 Berlin (Germany) ...... 841 356.7 100 Droitwich . . 200 1500 150 Sofia (Bulgaria) ...... 847.5 354 1 850 352.9 Minsk, RW10 ( U.S.S.R.) .. 208 1442 35 Norwegian Relay Stations ...... - Reykjavik (Iceland) .. .. 208 1442 16 Valencia (Spain) .. .. 850 352.9 3 Motala (Sweden) 216 1389 150 Simferopol, RW52 (U.S.S.R.) .. .. 859 349.2 10 Novosibirsk, RW76 (U.S.S.R.) 217.5 1379 100 Strasbourg (France) ...... 859 349.2 100 Warsaw, No. i (Poland) .. 224 1339 120 Poznan (Poland) .. 868 345.6 16 Luxembourg 232 1293 150 London Regional (Brookmans Park) .. 877 342.1 70 Leningrad, No. i RW53 (Kolpíno) (U.S.S.R.) 232 1293 100 Linz (Austria) ...... 886 338.6 15 Kalundborg (Denmark) .. 240 1250 60 Graz (Austria) ...... 886 338.6 15 Vienna, No. 2 (Austria) .. 240 1250 0.5 Helsinki (Finland) ...... 895 335.2 10 895 335.2 1.5 Kiev, No. 1 (U.S.S.R.)...... 248 1209.6 100 Limoges, P.T.T. (France) ...... Vigra (Aalesund) (Norway) .. 253 1186 10 Hamburg (Germany) ...... 904 331.9 100 Tashkent, RW11 (U.S.S.R.) .. 256.4 1170 25 Dniepropetrovsk (U.S.S.R.) .. .. 913 328.6 10 Oslo (Norway) .. 260 1153.8 60 Toulouse (Radio Toulouse) (France) .. 913 328.6 60 Moscow, No. 2, RW49 (Stchelkovo) (U.S.S.R..) 271 1107 100 Brno (Czechoslovakia) ...... 922 325.4 32 Tromsö (Norway) .. 282 1065 10 Brussels, No. 2 (Belgium) ...... 932 , .. 321.9 15 Tiflis, RW7 (U.S.S.R.) .. 283 1060 35 Algiers (Algeria) ...... 941 318.8 12 Saratov (U.S.S.R.) .. . 340 882.3 20 Göteborg (Sweden) ...... 941 318.8 10 Finmark (Norway) .. .. 347 864 10 Breslau (Germany) .. .. 950 315.8 100 959 312.8 60 Archangel ( U.S.S.R.) .. 350 857.1 10 Paris (Poste Parisien) (France) .. .. Rostov-on -Don, RW12 (U.S.S.R.) .. 355 845.1 25 Bordeaux-Sud -Ouest (France) .. .. 968 309.9 30 Budapest, No. 2 (Hungary) .. . . 359.5 834.5 18 Odessa (U.S.S.R.) .. 968 309.9 10 Sverdlovsk, RW5 (U.S.S.R.) .. 375 800 40 Northern Ireland Regional (Lisburn) .. 977 307.1 100 Voroneje, RW25 (U.S.S.R.) .. .. 390 769 10 Genoa (Italy) ...... 986 304.3 10 Boden (Sweden) 392 765 0.6 Torun (Poland) 986 304.3 24 Banka- Bystrica (Czechoslovakia) (15 klV. 392 765 30 Hilversum No. 2 (Holland) (15 kW. till 1840) 995 301.5 60 after 1700) Bratislava (Czechoslovakia) ...... 1004 298.8 13.5 Geneva (Switzerland) 401 748 2 Midland Regional (Droitwich) .. .. 1013 296.2 70 Moscow, No. 3 (RCZ) ( U.S.S.R.) 413.5 726 100 Chemigov (U.S.S.R.) ...... 1013 296.2 4 3 Ostersund (Sweden) .. . . 413.5 726 0.6 Barcelona, EAJ15 (Spain) ...... 1022 293.5 Oulu (Finland).. .. 431 696 10 Cracow (Poland) ...... 1022 293.5 2 1022 293.5 0.7 Tartu (Estonia) .. . . 511 587.1 0.5 Oviedo (Spain).. .. Hamar (Norway) .. 519 578 0.7 Königsberg, No. 1 (Heilsberg) (Germany) .. 1031 291 100 Innsbruck (Austria) 519 578 1 Parede (Portugal) .. 1031 291 5 Ljubljana (Yugoslavia) 527 569.3 6.3 Leningrad, No. 2, RW70 (U.S.S.R.) .. 1040 288.5 10 Viipuri (Finland) .. 527 569.3 10 Rennes -Bretagne (France) .. ..' 1040 288.5 120 20 Bolzano (Italy) . . 536 559.7 10 West Regional (Washford Cross) .. .. 1050 255.7 Wilno (Poland) .. .. 536 559.7 50 Bari No. 1 (Italy) ...... 1059 283.3 20 Budapest, No. 1 (Hungary) .. M6 549.5 120 Paris (Radio Cité) (France) ...... 1068 280.9 0.8 Beromünster (Switzerland) .. 556 539.6 100 Tiraspol, RW57 (U.S.S.R.) .. .. 1068 280.9 10 Athlone (Irish Free State) .. 565 531 100 Bordeaux -Lafayette (France) .. 1077 278.6 35 1086 276.2 0.7 Klaipeda (Lithuania) .. . . 565 531 10 Zagreb (Yugoslavia) ...... Palermo (Italy) .. 565 531 3 Falun (Sweden) ...... 1086 276.2 2 Stuttgart (Germany) .. 574 522.6 100 Madrid, EAJ7 (Spain) ...... 1095 274 5 Alpes -Grenoble, P.T.T. (France) 583 514.6 20 Vinnitsa (U.S.S.R.) ...... 1095 274 10 Madona (Latvia) .. 583 514.6 50 Kuldiga (Latvia) ...... 1104 271.7 10 Vienna, No. 1 (Austria) .. 592 506.8 100 Naples (Italy) ...... 1104 271.7 1.5 Rabat (Morocco) .. . . 601 499.2 25 Morayska- Ostrava (Czechoslovakia) .. 1113 269.5 11.2 Sundsvall. (Sweden) .. 601 499.2 10 Radio Normandie (Fécamp) (France) .. 1113 269.5 10 Florence (Italy) .. 610 491.8 20 Alexandria, No. 1 (Egypt) ...... 1122 267.4 0.5 Cairo, No. 1 (Egypt) .. 620 483.9 20 Newcastle ...... 1122 267.4 1 Brussels, No. 1 (Belgium) 620 483.9 15 Nyiregyhaza (Hungary) ...... 1122 267.4 8.25 Lisbon (Portugal) .. .. 629 476.9 15 Hörby (Sweden) ...... 1131 265.3 10 Tröndelag (Norway) . .. 629 476.9 20 Turin, No. 1 (Italy) ...... 1140 263.2 7 Christiansand (Norway) 629 476.9 20 Trieste (Italy) ...... 1140 263.2 10 Prague, No. 1 (Czechoslovakia) 638 470.2 120 London National (Brookmans Park) .. 1149 261.1 20 Lyons, P.T.T. (France) .. 648 463 100 North National (Slaithwaite) .. .. 1149 261.1 20 Petrozavodsk (U.S.S.R.) .. 648 463 10 Scottish National (Falkirk) ...... 1149 261.1 50 Cologne (Germany) . . 658 455.9 100 Kosice (Czechoslovakia) ...... 1158 ' 259.1 10 North Regional (Slaithwaite) 668 449.1 70 Monte Ceneri (Switzerland) ...... 1167 257.1 . 15 1176 255.1 10 Jerusalem (Palestine) .. . . 668 449.1 20 Copenhagen (Denmark) ...... 60 Sottens (Switzerland) .. .. 677 443.1 100 Nice -Corse (France) .. .. 1185 253.2 Belgrade (Yugoslavia) .. 686 437.3 2.5 Frankfurt (and Relays) (Germany) .. .. 1195 251 25 Paris, P.T.T. (France) 695 431.7 120 Prague, No. 2 (Czechoslovakia) .. .. 1204 249.2 5 Stockholm (Sweden) .. 704 426.1 55 Lille, P.T.T. (France) .. .. 1213 247.3 60 Rome, No. 1 (Italy) .. .. 713 420.8 50 Bologna (Radio Marconi) (Italy) .. .. 1222 245.5 50 Klnarkov, No. 1, RW20 (U.S.S.R.) .. 722 415.4 10 Gleiwitz (Germany) ...... 1231 243.7 5 1235 242.9 1 Fredrikstad (Norway) .. . . 722 415.4 1 Cork (Irish Free State) ...... Tallinn (Estonia) .. 731 410.4 20 Saarbrücken (Germany) ...... 1249 240.2 17 Madrid, EAJ2 (Spain) 731 410.4 3 Riga (Latvia) ...... 1258 238.5 15 1258 238.5 1 Seville (Spain) .. .. 731 410.4 5.5 Rome, No. 3 (Italy) ...... 1258 238.5 1 Munich (Geri any) . 740 405.4 100 Bilbao, EAJ8 (Spain) ...... 236.8 2 Marseilles, P.T.T. (France) 749 400.5 100 Nürnberg (Germany) ...... 1267 1276 235.1 27 Pori (Finland) .. .. 749 400.5 i Radio Mediterranée (Juan -les -Pins) (France) 1285 233.5 0.25 Katowice (Poland) . . 758 395.8 12 Dresden (Germany) ...... 1285 233.5 1 Scottish Regional (Falkirk) . 787 391.1 70' Aberdeen ...... North Scottish Regional (Burghead) 767 391.1 60 Klagenfurt (Austria) ...... 1294 231.8 5 1294 231.8 5 . . 776 386.6 10 Vorarlberg (Austria) ...... Stalino (U.S.S.R.) .. 0.5 Toulouse, P.T.T. (France) .. 776 386.8 120 nnwio 1303 230.2

www.americanradiohistory.com JULY 2nd, 1937 WñpsUgo 'ThpIld

Timing Station. kc/s. Positions. Metres. kW. Station ko/a. Positions. Metres. kW. Swedish Relay Stations ...... 1312 228.7 - Vaasa -Vasa (Finland) ...... 1420 211.3 10 Magyarovar (Hungary) ...... 1321 227.1 1.25 Alexandria, No. 2 (Egypt) .. .. 1429 209.9 0.5

German Relay Stations .. 1330 225.6 . .. .. - Turku (Finland) .. .. , .. 1429 209.9 0.5 Montpellier, P.T.T. (France) .. .. 1339 224 1.5 Miskolc (Hungary) ...... 1438 208.6 1.25 Lodz (Poland) ...... 1339 224 2 Paris (Eiffel Tower) (France) , . .. 1456 206 7 Dublin (Irish Free State) ...... 1348 222.6 0.5 Pecs (Hungary) .. .. 1465 204.8 1.25 Rjukan (Norway) ...... 1348 222.6 0.15 Belgian Relay Stations .. , . .. 1465 204.8 0.1 Salzburg (Austria) ...... 1348 222.6 2 Bournemouth ...... 1474 203.5 1 Tampere (Finland) ...... 1348 222.6 0.7 Plymouth .. , ...... 1474 203.5 0.3 2 Cairo No. (Egypt) ...... 1348 222.6 0.5 Binche (Belgium) ...... , . 1487 201.7 0.1 Königsberg (Germany) ...... 1348 222.6 2 Belgian Relay Stations , . .. .. 1492 201.1 0.1 Nottoden (Norway) ...... 1357 221.1 0.15 Nimes (France) ...... 1492 201.1 0.7 Italian Relay Stations ...... 1357 221.1 - Albacete (Spain) ,...... 1492 201.1 0.2 L'Ile de France (France) ...... 1366 219.6 2 Santiago (Spain) ...... 1492 201.1 0.5 Basle (Switzerland) ...... 1375 218.2 0.5 Belgian Relay Stations .. 1500 200 0.1 Berne (Switzerland) ...... 1375 218.2 0.5 Pietarsaari (Finland) ...... 1500 200 0.25 Warsaw, No. 2 (Poland) . .. .. 1384 216.8 10 Radio Alcalá (Spain) ...... 1500 200 0.2 Lyons (Radio Lyons) (France) .. .. 1393 215.4 25 Karlskrona (Sweden) ...... 1530 196 0.2 Stara -Zagora (Bulgaria) ...... 1402 214 2 Liepàja (Latvia) .. .. 1734 173 0.1 SHORT -WAVE STATIONS OF THE WORLD Call Toning Station. Sign. kc /s. Positions. Metres. kW. Station. Sign. ke/s. Positions. Metres, kW. Batavia (Java) .. .. YDA 3,040 98.68 5 Lisbon (Portugal) ...... CT1CT 9,680 31.00 0.5 Kharbarovsk (Russia) .. .. RV15 4,273 70.20 20 Madrid (Spain) ...... EAQ 9,860 30.43 20 Caracas (Venezuela) ...... YV5RH 5,800 51.72 1 Lisbon (Portugal) ...... CSW 9,940 30.18 5 San Jose (Costa Rica) .. TIGPH 5,820 51.52 0.5 Bandoeng (Java) .. .. PMN 10,260 29.24 8 Vatican City (Vatican State) .. HVJ 5,970 50.26 10 Ruvsselede (Belgium) .. .. ORK 10,330 29.04 9 Mexico City (Mexico) .. .. XEBT 6,000 50.00 1 Buenos Aires (Argentina) .. .. LSX 10,350 28.99 12 Moscow (Russia) ...... RW59 6,000 50.00 20 Teneriffe (Canary Isles) .. .. EAJ43 10,360 28.94 4 Montreal (Canada) ...... CFCX 6,005 49.96 - Tokio (Japan) ...... JVM 10,740 27.93 20 Havana (Cuba) COCO 6,010 49.92 0.5 Bandoeng (Java) ...... PLP 11.010 27.25 3 Prague (Podebrady) (Czechoslovakia) OLR 6,010 49.92 30 Lisbon (Portugal) , . .. CSW 11,040 27.17 5 Bogota (Colombia) ...... HJ3ABH 6,018 49.90 1 Motala (Sweden) ...... SBG 11,700 25.63 1 Zeesen (Germany) ...... DJC 6,020 48.83 50 Winnipeg (Canada) ...... CJRX 11,720 25.60 2 Boston(U.S.A.) ...... W1XAL 6,040 49.67 10 Paris (Radio -Colonial) (France) .. TPA4 11,720 25.60 12 Miami (U.S.A.) ...... W4XB 6;040 49.67 2.5 Daventry (Gt. Britain) .. .. GSD 11,750 25.53 10-50 Daventry (Gt. Britain) .. .. GSA 6,050 49.59 10-50 Zeesen (Germany) ...... DJD 11,770 25.49 50 Cincinnati (U.S.A.) .. .. WIXAL 6,060 49.50 10 Boston (U.S.A.) ...... W1XAL 11,790 25.45 20 Philadelphia (U.S.A.) .. .. W3XAU 6,060 49.50 10 Tokio (Japan) ...... JZJ 11,800 25.42 20 Skamlebaek (Denmark) .. .. OXY 6,060 49.50 0.5 Vienna (Austria) ...... OE112 11,800 25.42 1.5 Motala (Sweden) ...... SBG 6,060 49.50 1 Rome (Italy) ...... 12RO4 11,810 25.40 25 Chicago (U.S.A.) ...... W9XAA 6,080 49.34 0.5 Daventry (Gt. Britain) .. .. GSN 11,820 25.38 10-50 Nairobi (Kenya) ..- VQ7L0 6,083 49.31 0.5 Wayne (U.S.A.) ...... W2XE 11,830 25.86 10 Toronto (Bowmanville) (Canada) .. CRCX 6,090 49.26 0.5 Lisbon (Portugal) CT1AA 11.830 25.36 2 Hong Kong (China) .. .. ZBW2 6,090 49.26 2 Prague (Podebrady)(Czechoslovakia) OLR 11,840 25.34 30 Johannesburg (South Africa) .. ZTJ 6,100 49.20 5 Zeesen (Germany) ...... DJP 11,850 25.31 50 Bound Brook (U.S.A.) .. .. W3XAL 6,100 49.18 35 Daventry (Gt. Britain) .. .. GSE 11,860 25.29 10-50 Chicago (U.S.A.) .. .. W9XF 6,100 49.18 10 Pittsburgh (U.S.A.) ...... W8XK 11,870 25.27 40 Belgrade (Yugoslavia) .. .. 6,100 49.18 1 Paris (Radio -Colonial) (France) .. TPA3 11,880 25.23 15 Manizales (Colombia) .. .. HJ4ABB 6,105 49.12 1 Moscow (Russia) ...... RNE 12,000 25.00 20 Daventry (Gt. Britain) .. .. GSL 6,110 49.10 10-50 Lisbon (Portugal) .. .. CT1CT 12,082 24.83 0.5 Calcutta (India) ...... VUC 6,110 49.10 0.5 Reykjavik (Iceland) ...... TFJ 12,235 24.52 7.5 Wayne (U.S.A.) ...... W2XE 6,120 49.02 10 Parede (Portugal) ...... CT1G0 12,400 24.20 0.35 Pittsburgh (U.S.A.) ...... W8XK 6,140 48.86 40 Warsaw (Poland) ...... SPW 13,635 22.00 10 Winnipeg (Canada) ...... CJRO 6,150 48.78 2 Amateurs ...... 14,000 21.42 0.01 Lisbon (Portugal) . .. .. CSL 6,150 48.78 0.5 to to Caracas (Venezuela) ...... YVSRD 6,150 48.78 1 14,400 20.84 Parede (Portugal) .. .. GT1GO 6,200 48.40 5 Sofia (Bulgaria) .. , , .. LZA 14,970 20.04 1.5 San Jose ( Cossta Rica) .. .. TIPG 6,410 46.80 0.5 Zeesen (Germany) .. DIL 15,111 19.85 50 Valencia (Colombia) ...... YV4RV 6,520 46.00 0.5 Vatican City (Vatican State) .. HVJ 15.123 19.84 10 Riobamba (Ecuador) .. .. PRADO 6,620 45.31 2 Daventry (Gt. Britain) .. .. GSF 15,140 19.82 10-50 Amateurs ...... 7,000 ...... 42.86 0.01 Bandoeng (Java) .. .. YDC 15,160 19.80 8 to to Daventry (Gt. Britain) .. .. GSO 15,180 19.78 10 7,300 41.10 Hongkong (China) ...... ZBW4 15,190 19.75 2 Moscow (U.S.S.R.) RW96 7,520 38.89 25 Zeesen (Germany) ...... DJB 15,200 19.74 50 Prangins (Radio -Nations) (Switz'l'd) HBP 7,780 38.48 20 Pittsburgh (U.S.A.) ...... W8XK 15,210 19.72 40 Budapest (Hungary)...... HAT4 9,125 32.88 5 Huizen (Holland) PCJ 15,220 19.71 20 Bangkok (Siam) ...... HS8PJ 9,350 32.09 20 Prague (Podebrady)(Czechoslovakia) OLR 15,230 19.70 30 Madrid (Spain) .. .. EAQ2 9,480 31.65 20 Paris (Radio -Colonial) (France) .. TPA2 15,243 19.68 12 Rio de Janeiro (Brazil) .. .. PRF5 9,500 31.58 5 Boston (U.S.A.) .. .. WIXAL 15,250 19.67 20 Daventry (Gt. Britain) .. .. GSB 9,510 31.55 10-50 Daventry (Gt. Britain) .. .. GSI 15,260 19.66 10-50 Melbourne (Australia) .. .. VK3ME 9,510 31.55 1.5 Wayne (U.S.A.) ...... W2XE 15,270 19.65 10 Hongkong (China) ...... ZBW3 9,520 31.49 2 Zeesen (Germany) ...... DJQ 15,280 19.63 50 Jelöy (Norway) .. .. LK.I1 9,520 31.49 1.5 Buenos Aires (Argentina) .. .. LRU 15,290 19.62 5 Schenectady (U.S.A.) .. .. W2XAF 9,530 31.48 35 Daventry (Gt. Britain) .. .. GSP 15,310 19.60 10 -50 Zeesen (Germany) ...... DJN 9,540 31.45 50 Schenectady (U.S.A.) .. .. W2XAD 15,330 19.57 18 Suva (Fiji) ...... VPD2 9,540 31.45 3 Zeesen (Germany) DJR 15,340 19.56 50 Prague (Podebrady)(Czechoslovakia) OLR 9,550 31.41 30 Budapest (Szekesfehervar) (Hungary) HAS3 15,370 19.52 25 Zeesen (Germany) ...... DJA 9,560 31.38 50 Hongkong (China) ...... ZBWS 17,750 16.90 2 Bombay (India) ...... VUB 9,565 31.36 4.5 Zeesen (Germany) ...... DJE 17,760 16.89 50 Millis (U.S.A.) ...... WIXK 9,570 31.35 10 Wayne (U.S.A.) ...... W2XE 17,760 16.89 10 Daventry (Gt. Britain) .. .. GSC 9,580 31.32 10-50 Huizen (Holland)1 .. .. PHI 17,770 16.88 23 Lyndhurst (Australia) .. .. VK3LR 9,580 31.32 1 Bound Brook (U.S.A.) .. .. W3XAL 17,780 16.87 35 Philadelphia (U.S.A.) .. .. W3XAU 9,590 31.28 10 Daventry (Gt. Britain) .. .. GSG 17,790 16.86 10 -50 Sydney (Australia) ...... VK2ME 9,590 31.28 20 Bandoeng (Java) ...... PLE 18,830 15.93 60 Huizen (Holland) PCJ 9,590 31.28 20 Bangkok (Siam) ...... HS8PJ .19,020 15.77 20 Frangins (Radio -Nations) (Switz'l'd) HBL 9,595 31.27 20 Bandoeng (Java) .. .. PMA 19,350 15.50 60 Moscow (Russia) ...... RW96 9,600 31.25 20 Daventry (Gt. Britain) .. .. GSH 21,470 13.97 10-50 Rome (Italy) ...... I2R03 9,635 31.13 25 Wayne (U.S.A.) ...... W2XE 21,520 13.94 10 Sourabaya (Java) ...... YDB 9,640 31.11 1 Daventry (Gt. Britain) .. .. GSJ 21,530 13.93 10-50 Lisbon (Portugal) .. .. CT1AA 9,655 31.09 2 Pittsburgh (U.S.A.) ...... WSXK 21,540 13.93 40 Daventry (Gt. Britain) .. .. GST 21,550 13.92 10-50

www.americanradiohistory.com Wireless World, July 2nd, 1937.

By Random Radiations "DIALLIST "

Frequencies or Wavelengths ? Since then I have been able to " do " the Comparative Viewing and here are pities we ever adopted exhibition more thoroughly It's extremely interesting to make your IT'S a thousand that like you and wavelengths for the tuning of our wire- some impressions. To those, way down the line of viewing booths when the positions of me, who are interested in the history and a demonstration is in progress and to com- less sets and for indicating the whole stations in the radio scale. Wavelengths are the technicalities of television, pare the reproduction of the various re- thing is of the greatest interest; but I don't an instance of those unhappy legacies from ceivers at work. All of them are pretty a new department of think that quite enough is being done to good, but there are distinct differences in the early days of his wife which often cause so much em- show the man in the street and the results, as you may see to the best advan- science I may have later on. They came into use and family what it all means. tage if you place yourself rather far back barrassment but I didn't see anyone because of the old methods of " explain- been unfortunate, and opposite the partition between any pair waves there acting as an official guide or prepared of booths so that you can turn your gaze ing " wireless by analogies with the take ripples moving in widening to give explanations to the puzzled. To instantly from one screen to the other and of the sea, the the Emitron camera, over the surface of a pond after the just one example, back again. I confess I am disappointed circles which most people have read some- impact of a stone, and so on. They were about with the Scophony results. The definition long as all wireless trans- thing in their newspapers as one of the won- is distinctly good for 240 -line television, and all very well so was the way of the man in ders of modern scientific development, the big flat screen is a wonderful achieve- missions that came with no one of the " long-wave " or just standing forlornly by itself ment. Flicker there probably must be with the street were or how it worked. " medium -wave " types; but with the coming to answer questions show a system using only 25 frames a second; but of " short- wave " and " ultra- short-wave ' in the Scophony reproduction there are two broadcasting, wavelengths have become just Worth Trying ? other points which call for friendly criticism. a clumsy absurdity. There are, for ex- Here's a suggestion which the authorities The first is that the illumination appears to ample, twenty -two stations listed on wave- might well consider. In many departments be much less good near the edges of the lengths between 19.52 and 19.95 metres- of the British Museum, including the main screen than in the middle; the second, that twenty -two stations with a total wavelength - building in Bloomsbury, and, I believe, the you are very, very conscious of the whirling difference of a little under seventeen inches! Natural History Museum and the Science scanner right in the centre of the picture. Museum itself, there are officials known as So much so that the effect, on me at any rate, Is It Too Late ? guide -lecturers who conduct parties at given is that, willy -nilly, attention is apt to be Is it, I wonder, too late now to try to get times each day. Their services are very concentrated on that small spiralling area in the man in the street to think and tune in much appreciated by the public, as is shown the middle of the image. B.B.C. made kilocycles or. megacycles? The by the size of the parties that collect at the % % the attempt a good while ago, with marked times billed for tours. Wouldn't it be a L lack of success; but that, I think, was first -rate plan for those who are running the The Valve Question largely due to their endeavour to introduce Television Exhibition to give the guide -lec- FROM an Enfield correspondent I have a yet a third term to the already perplexed turer system at any rate a trial? I am sure letter criticising my recent remarks average listener. They tried to make him it would catch on at once with the public, about the large numbers of valves and adopt the kilohertz, which, if more academic- and it might do a great deal for television valve parts that we import each month from ally correct, was likely to be forbidding as just at the time when its greatest need is America and from the Continent. He's in- being a new thing to him. America aban- to establish a firmer hold on public interest. clined to take me to task for suggesting that doned wavelengths years ago, but in that such avast importation is a bad thing. " On country the transition from wavelengths was the contrary," he writes, " it is in my easy. The authorities adopted a io-kilocycle opinion the only thing that will wake up basis for their broadcasting distributing the British valve makers and set makers." scheme, and as the frequencies were all My correspondent has rather missed the multiples of ten they at once appealed to the point of my note. I have always contended listener as being far more straightforward that prices of British valves were far too than bits and pieces of metres denoted by high, and my feeling is that we should be decimal places. Unfortunately we've noth- able to make our own valves at prices which ing like that to help us, but now that so will bear direct comparison with those that many ordinary listeners have swallowed the come in from America. And then valve kilocycle and the megacycle on the short- parts : It does seem to me perfectly absurd wave ranges of their receivers it probably that we should have to pay the foreigner would not be very difficult to extend the thousands of pounds each month for parts reform to other ranges. And there's another which are presumably turned eventually thing that has removed some of the diffi- into " British -made " valves. If we are culties in the way. In the years before going to keep valve prices at their present tuning dials marked with the names of sta- ridiculous level there is no excuse whatever tions became pretty well universal most lis- for buying their components abroad. teners knew by heart the wavelengths of a good many stations. Enthusiasts could Why Shouldn't We ? probably have told you those of most stations within their ken without many mis- lf, on the other hand, the big reduction takes. But nowadays the majority of lis- in prices that is so long overdue is at last teners neither know nor need to know the going to take place, surely our proper course wavelengths of any of the medium -wave or is to install the machinery which will enable long -wave broadcasting stations that they use us to make our own parts as cheaply as any- in the ordinary way. There thus wouldn't one can make them for us. It can't be a be anything like so much opposition to the question of wages, for the labour which introduction of the kilocycle and megacycle makes American valves is, I believe, more as the only units of measurement; already a highly paid than our own in actual money,' good many sets have scales calibrated in though what the workman pockets over both frequencies and metres. there may not go so far when he comes to spend it as the smaller pay of his British ti ti L counterpart. The secret of low costs in South Ken. Revisited America appears to be mass production on CAR RADIO AERIAL. Fitted just forward WHEN I wrote my recent note on the the grand scale by means of the most modern of the front door this Philco aerial is only for American Television Show at the Science Museum 20 inches long when closed up but can be machinery. The market I had had time for only the briefest of visits. extended to over five feet when required. valves is admittedly bigger than that for

www.americanradiohistory.com JULY 2nd, 1937 '17 WW©ii lld Random Radiations - The Wireless ours, but we could increase our own both World at home and abroad enormously if prices TELEVISION RECEIVER were more reasonable. We could, for example, make and sell at home the greater (See description on pp. 2 -6 of this issue) of millions of valves part the that America THE LIST OF PARTS USED. sends us each year. Certain components of other makes % but of similar characteristics may be Mc CA IR If IH - Flimsy Condensers used as alternatives to those given in , THERE'S nothing much wrong with the the following list. fixed condensers used in our receiving VISION RECEIVER OUTSTANDING 9 -VALVE sets if they are of first -rate make and well 4 Air Condensers, 15 mmfds., Cl, C5, C9, C13 up to the strains that are likely to be im- Raymart VCISX ALL -WAVE SUPERHET 5 Shaft Couplings, tin. Bulgin posed upon them. But you do need a con- 4 Knobs Bulgin K16 siderable margin of safety in the wireless For all- wave reception 1 RF choke, ultra -short wave type, Ch 1 set of to -day, and, unluckily, condensers Eddystone 1011 at its very best which possess it are more expensive than 4 Coils B.T.S. To the all -wave enthusiast, this exceptional receiver those that don't. The problem of the set 1 VF Coupling Coil B.T.S. offers a number of interesting features, with'quite unusual designer nowadays must be a very difficult 1 Potentiometer wire'wound, ro,000 ohms, R2 range, and power output. Few receivers at present on one. The prices of receiving sets have come Reliance " TW " the market can claim so high a standard of design and down and down and down in recent years I Potentiometer wire-wound, r,000 ohms, R20 performance. and there still seems to be no end- in sight Reliance " TW " of manu- Fixed Condensers: to this kind competition between 6 o.or mfd., mica, C2, C3, C6, C7, C10, is facturers. The wretched designer told that Cll T.C.C. " M " he must produce a set at a figure which not 3 0,0005 mfd., mica, C4, C8, C12 so long ago would have seemed fantastically T.C.C. " M " small, and all that he can do is to pare 3 0.5 mid., tubular, C16, C18, C19 down costs of materials and manufacture to Dubilier 4428 the uttermost fraction of a penny. Can you I 50 mfds., 12 volts, electrolytic, C17 blame him, then, if he gives way to the Dubilier 3016 temptation to save something by using here 1 500 mfds., 12 volts, electrolytic, C15 which are just, T.C.C. 501 and there fixed condensers r ro mmfds., ceramic, C14 Dubilier CDS3 and only just, up to the work imposed upon Resistances: them in the ordinary way? Can you wonder 4 100 ohms, watt, R1, R4, R9, R13 if in the very cheap set the margin of safety Erie is insufficient or that one of the commonest I 200 ohms, á watt, R8 Erie causes of breakdowns nowadays is the 2 500 ohms, ,) watt, R3, R5 Erie failure of a fixed condenser to carry on with r 5,000 ohms, # watt, R11 Erie its job? 1 10,000 ohms, watt, RIO Erie 3 100,000 ohms, watt, R6, R7, R16 Erie I 0.5 meghom, 1 watt, R15 Erie Coursey Slide Rule I 2 meghoms, watt, R 14 Erie 2 3,500 ohms, z watts, R12, R 19 Erie ASLIDE rule designed especially for the 2 10,000 ohms, 2 watts, R17, RIS Erie solution of electrical problems is ob- 5 Valve holders, 7 -pin (without terminals) tginable from the Dubilier Condenser Co., Clix Chassis Mounting Standard Type 173 2 Valve holders, 4 -pin (without terminals) 4 wavebands : 12.8-33, 29.80, 190- 550, 800 -2000 Ltd., of Ducon Works, Victoria Road, North Clix Chassis Mounting Standard Type VI metres. Illuminated dial with principal station Acton, London, W.3. It consists essentially 2 Plugs and ,sockets, 3 -pin Belling -Lee 1119 coloured lights for each wave-wave - of a combination of two slide rules. One is 1 Socket strip, Al, A2, and E Clix ". C" band. of the normal type with the A, B, C and D 4 Plug-top valve connectors Belling-Lee 1175 Controls, -A feature of the receiver is the number scales, and carrying on the back the usual 1 Screened top connector Bulgin P64 of independent controls fitted, making it extremely log, sine, and tangent scales. The other has 1 Cable, 5 -way, with twin 7o/36 leads and interesting to operate. These include : sensitivity fixed scales for voltage, frequency and wave- 5 -pin plug Goltone control (varying bias on R/F stage). Q.A.V.C. with 1 Connector, 4 -way Bryce 5C2 manual muting control, and switch for inter -station length and moving scales for capacity and noise suppression. Separate potentiometer current. Chassis B.T.S. bias controls Miscellaneous : Peto =Scott for output valves. 5- position wave- change and gramo- X111 scales can, of course, be used in con- Wire, systoflex, brackets, screws, etc. phone switch. Progressive variable tone control junction with one another, and many prob- Valves : operative on radio and gram. lems which are constantly arising in elec- 4 TSP4 Mullard Circuit in Brief. -Aerial input to pre -selector circuit, radio solved. The rule 2 D4z, I MSP4 frequency amplifier, latest type triode- hexode frequency trical work can rapidly be Osram changer, 2 band -pass I.F.T. coupled I.F. amplifiers, double is obtainable at the price of 39s. 6d. diode detector, L.F. amplifier. parafeed transformer- coupled VISION RECEIVER POWER PACK push -pull triode output giving 6 watts. Heavy cadmium -plated steel chassis. Finest components and 1 Mains transformer, Primary: zoo -25o volts, workmanship throughout. 5o c /s; Secondaries: volts 350-o-350 A.C. models ready for immediately delivery. New Cossor Frequency - 75 In/ A., 4 =volts 2.5 amps., 4 volts 8 A.C/D.C. models also in production, and will be available amps., 4 volts 8 amps., 2 volts 1.5 amps., for delivery shortly. C.T. Viand Sales TEL /350 DE LUXE MODEL 14 GNS. Changer Several additional refinements full particulars on 1 Smoothing choke Varley Dual DPII application. - 1 Condenser, electrolytic, 8 -8 mfds., Cl, C2 ANEW frequency- changer of the triode - Dubilier 9203EW IMPORTANT hexode type, the 2o2STH, is announced 2 The prices at wsich McCarthy Chassis are advertised Valve holders, 4 -pin (without terminals) include Marconi Royalties. " Wireless World " readers by Cossor. It is an addition to the AC /DC Clix Chassis Mounting Standard Type VI should. for their own protection, make sure before range, and has a heater consuming 0.2 am- 1 Valve holder, 5 -pin (without terminals) purchasing any receiver that the quoted price includes pere at 20 volts. The hexode section is Clix Chassis Mounting Standard Type VI the Royalty payment. rated for anode and screen supplies of 25o 1 Fused mains input connector with 2 amp. fuses Belling-Lee 1114 All McCarthy receivers supplied complete with volts and too volts respectively, while the valves, knobs, pilot lamps, leads, mains cable and minimum grid bias is -1.5 volts ; for 1 Twin safety-fuse holder with 1 amp. fuses plug. 12 months' guarantee. medium and long waves a bias resistance Belling-Lee 1033 Deterred terms on application, or through London of 175 ohms is recommended, but for short I Plug and socket, 3 -pin Belling -Lee 1119 Radio Supply Co., 11, Oat Lane, E.C.2. waves it should be increased to 400 ohms. I Mains connector, 2 -way Bulgin P76 Cash with order on 7 days' approval. Also write Chassis B.T.S. for illustrated catalogue of complete range of all Under normal conditions the conversion Miscellaneous: Peto -Scott McCarthy receivers. conductance is o.6 mA /V, and an oscillator Wire, systoflex, screws, etc. voltage of 8 volts RMS is required. The Valves: MDCAIRTIli' VATIC ILTD, valve is fitted with the standard 7 -pin base r Ux2 Osram 44a, Westbourne Grove, London, W.2 is and priced at 15s. 1 DLS /10 Mazda Tdeahone t Bamruoater 3201/2.

www.americanradiohistory.com r,4 Wireless World, July 2nd, 1937.

in that it will represent the most motley group of people that could be imagined. Its members will include some of the Broadcast revities leading musicians in the country, ex- actors, at least two NEWS FROM Daventry to Tell the Long- haired Intellectuals clergymen, office boys, steno- PORTLAND PLACE World? The first bulletin of the series graphers, advertisement can- Indications from reliable shows that the B.B.C. does, to vassers, journalists, trained sources are that Daventry will a large extent, see itself as nurses and representatives of " D.G." : The Truth eventually be used for world others see it. fifty other vocations and pro- RY has been made of propaganda. The service would " The staff," says the bul- fessions. MYSTEMYSTERYSir John Reith's recent come under the general surveil- letin, " must, in the interests of To draw up rules which will flying visit to Gibraltar, the lance of the B.B.E. Empire efficiency, be shut away in suit all these varied interests will suggestion being that the D.G. Director, but a sub -department transmitting stations or studios, call for the wisdom of Solomon, was taking the first steps to in- would be formed under a Direc- and cannot be seen by the pub- whose own domestic troubles augurate a system of propa- tor of Propaganda who would lic at their work. Hence, per- were not dissimilar. ganda stations. arrange multi -lingual transmis- haps, some of the legends . . . The real motive of the visit sions at hours which would not " Sometimes their chiefs are It Cured the Rajah was to watch an inspection of conflict with the existing Em- depicted as rigid disciplinarians That certain people have the Mediterranean fleet. Sir pire service. on the quarter -deck. . . . At supreme faith in the B.B.C. is John had been present a few VA <01 co, other times the staff are repre- evidenced by the correspond- days earlier at Spithead during Hearsay About Portland sented as t bunch of long- ence files. A butler wrote to the celebrated illuminations, Place haired intellectuals. . . ask what was the correct way and, being in nautical mood, " Anyone who really knows to address an Italian duchess. readily accepted an invitation THE iron hand of Portland the B.B.C. from the inside is Place was once supposed to A Serbo-Macedonian asked the to see how they do these things aware that the staff is a ' happy the name weigh heavily on the provincial B.B.C. to broadcast at ' Gib.' ship ' . . . we have heard less of the drug which had cured the stations, but Rajah Bahedar Ramdidla of in- A Propaganda Service of this of late. Actually, de- man is so nearly B.B.C. Staff Association somnia. Another -an Talking of propaganda, even centralisation Englishman this time -desired odds are now being laid that a achieved that there seem to be THE B.B.C. staff will soon employees in the North the Corporation to indicate a British radio propaganda service B.B.C. have its own " Union." spot where he could live at least West who have " heard - will come into existence within and Following the special investiga ten miles from any woman. the next twelve months. tell " of headquarters only at tion of the Director of Staff second hand from Regional Administration, Mr. J. The B.B.C., of course, can St. Pym, The Anngler take no decisions in the matter, Directors and other officials who a Committee has been formed to Largo which is the responsibility of the occasionally make the long and make recommendations as to the In fact, the present year has Foreign Office. But there is a perilous journey to London. constitution of this unique staff been a good one in the corre- feeling of discontent in association, the members being spondence department. A growing " What is Broadcasting ? " Parliament and elsewhere that Sir James Ray, representing the " lover of music " wrote : certain Continental stations To counteract this aloofness, Treasury, Mr. Bowen, joint " Please thank the young mart should broadcast inaccuracies in Portland Place is now issuing general secretary of the Union of that played the B.B.C. organ English without fear of radio bright little bulletins so that the Post Office Workers, and Mr. for playing the Anngler Largo- contradiction. country cousins can tell the in- Darbyshire, establishment officer it is very nice, that is my sort One European station pro- quiring public just what it's all of the L.M. & S. Railway. of music." Another writer of " about. They are designed to asked : " What form of salute duces a daily spate "news Musicians and Office Boys in sixteen languages, English in- answer the judicial question : would a guardsman at the cluded. " What is Broadcasting? " The association will be unique Tower give to a lady in 152o? "

LISTENING

IN COMFORT

Although the unhandiness of the typical are housed in a cabinet fitted with ball - broadcast receiver -and more particularly bearing castors so that it can be turned that of the typical radio-gramophone -is round easily for either radio or gramophone generally admitted, external design has operation at armchair level, all dimensions become so conventionalised that few are being arranged for effortless control. Note bold enough to introduce radical changes the record storage space, the shelf (which making for greater convenience in operation. fits flush when not in use) and the cupboard One of the exceptions to this rule is illustrated for programme journals, etc., under the in these photographs, sent to us by Mr. W. tuning panel. As the loud speaker is ex- Ewart Puddicombe. His " Wireless World" ternal it can, of course, be mounted in an Single -Span Receiver and Quality Amplifier acoustically satisfactory position.

www.americanradiohistory.com Wireless World, July 2nd, í937.

c PRACTICAL AIDS TO liltt s gnuand 1S BETTER RECEPTION

THE greatest disadvantage of the the very last ounce is desired is still pos- simple regenerative detector circuit is sible. the fact that, whatever form of reaction In practice, R, which is intended to be control is used, the feed -back effect always mounted as a pre -set control, is adjusted increascs with frequency, necessitating, until the set oscillates and is then br.adly speaking, a readjustment of the slackened off gradually until there is no reaction knob for oscillation at any wavelength ; once set, it Constant every station. Ingen- should not require further attention. CI Reaction ious mechanical de- should normally be set at zero during this vices, which aimed at process, but it must be realised that ad- keeping the reaction justment is largely a matter of trial and condenser in step with the tuning con- error ; the values of C and Cz, for in- denser, have from time to time appeared stance, depend largely upon the charac- in patent specifications, but as meanwhile teristics of the tuning coil and reaction the " straight " circuit was rapidly dis- coil, the degree of coupling and even the appearing in favour of the superhetero- detector anode voltage ; CI should be dyne they apparently aroused little small, but must be large enough to pro- enthusiasm. duce oscillation at any wavelength, while However, since the TRF type of set still C may be between o.0005 and o.00r has certain advantages, particularly to the mfd. A convenient value for R, which quality enthusiast, possibly a method of should be wire -wound, is 5,000 ohms. obtaining more or less constant reaction by purely electrical means may be of THOSE having experience in winding sufficient interest to warrant description. their own low -loss coils with litzen- The circuit arrangement is shown in draht may remember that the diffi- Fig. z ; a conventional regenerative circuit culty of baring each and every strand of is modified by shunting a variable resist- the terminating wires without breaking ance R across the reaction condenser CI, any of them is apt to be rather a laborious the extra condenser C being necessary to business. Now that prevent short- circuiting the HT. the use of litz wire is Soldering becoming more and Litz more general, both for Wires RF and IF coils, even in the cheaper factory-built sets, it must have occurred to many that the original method of carefully sand-papering off the silk covering from each separate strand before attempting to apply solder would WHATEVER YOUR hardly be compatible with mass- produc- tion processes, and that there must surely NEED THERE'S A be a quicker way of dealing with the enamel-covered wire that is almost always " used nowadays. The method actually adopted is the C C essence of speed and simplicity. It consists of holding the end of the wire for a second which means or two in the flame of a spirit lamp and then dipping it, red hot, straight into a A PRODUCT BACKED bath of methylated spirits. The insulation is completely removed by the opera- BY OVER 28 YEARS' tion, leaving the wires so clean that they may now be wrapped round their fixing SPECIALISED tags and soldered without difficulty. Incidentally, it CONDENSER Fig. x.-The semi -fixed reaction circuit may be of interest to discussed in the text. note that in the case of litz -wound IF transformers, where the frequency is EXPERIENCE usually The underlying principle about 465 kc /s, the effect of is that, where- breaking one or two of as the reactance of a condenset increases the strands is not nearly so serious as might be with wavelength, the impedance of a pure supposed - the drop in sensitivity is not, in fact, ap- resistance is constant. The function of R preciable therefore is to the ear, although measurable to provide an alternative low - with suitable T.C.C. apparatus. impedance path to RF currents above a ALL-BRITISH certain wavelength (usually about 300 metres) and so produce regeneration in- Regent's Park Theatre dependently of CI. It is not claimed that CONDENSERS THE Open Air Theatre in Regent's Park has absolutely constant reaction at all wave- been installed for the third year in succes- The Telegraph Condenser Co. Ltd., Wales lengths is possible by this modification, sion with Trix sound equipment. This instal- Farm Road, N. Acton, W.3. but rather that a much more uniform sen- lation comprises more than fifteen microphones, with multiple mixing panel and double sitivity throughout the tuning range is channel :,43,, 2138. amplifiers. Improvements have been made obtained ; the use of critical reaction when this year in a number of details.

www.americanradiohistory.com 2Ö Wireless World, July 2nd, 1937.

The Editor does not hold himself Letters to the Editor responsible for the opinions of his correspondents ionisation may remain the same or even be and on the following ,days since the increased, but signals do not reach it, even beginning of May this has been over of very high frequency, because they have 40 Mc /s : May 17th (morning). -IBE 48 all been returned to earth by the E layer. Mc /s rough AC carriers up to 52 Mc /s. May Superhets v. Straight Receivers Until your issue of June lrth appeared 18th (morning). -SPW 41 Mc /s. May 27th THE views expressed by " Nauticus " in I had previously not had any definite in- (morning). -SPW 41 Mc /s. June and your issue of May 28th are interesting, stance of the above taking place, but your (morning). -IEM 40 Mc /s, (evening) (19.35 more so when one considers that manufac- contributor in " On the Short Waves " G.M.T.), IBT 49 Mc /s. June 3rd (morn- turers are now designing sets for the forth- states : " There have been a number of ing).-IBE 48 Mc /s. June 4th (evening). - coming season. Dillinger fade -outs during the past week - IEM 40 Mc / s. June 8th (morning). -IBT Whilst agreeing with " Nauticus " under there was a very severe one on June 3rd 49 Mc / s (evening), unidentified commercial his section (a), the points in section (b) war- from` o6.10 -o7.00 G.M.T." " Now, this is C W signals on 5o Mc /s. rant comment. extremely interesting, because on June 3rd On June 3rd, having observed that condi- (1) Given a reasonable locality, what at 06.45 G.M.T. I was hearing short -distance tions were good in the early morning on the superhet on medium waves gives a clear signals up to 5o Mc /s (harmonics mostly), UHF, I asked YL2CD, in my 14 Mc /s channel either side of Hilversum between including IBE on 48 Mc / s, and at 08.05 schedule at o7.00 G.M.T. with him, to Midland Regional and Northern Ireland; G.M.T. I succeeded in transmitting 56 Mc /s change to 28 Mc /s. At o7.5o G.M.T. we and on long waves a clear channel either signals to YL2CD in Riga, Latvia. (See contacted on 28 Mc /s. I then asked him side of Berlin, between Droitwich and Radio note later.) This leaves little doubt that the to listen on 56.1 Mc /s, and called him from. Paris? A TRF set of these capabilities is failure of longer- distance signals on June 3rd 08.05 to 08.15 G.M.T. He came hack on one of our standard range. was due to unusually intense ionisation, pre- 28 Mc /s and reported my 56 Mc /s signals (2) The overall amplification of a good sumably by ultra -violet radiation. To say R5 with some fading. Unfortunately, YL2CD TRF set is both uniform and sufficient for that the signals were completely attenuated did not have a 56 Mc /s transmitter working. practical purposes. in the E layer is rather misleading, rather or otherwise we could have made a two -way (3) The superhet has more, but not they were bent back to the earth by the E 56 Mc /s contact. Soon after 08.20 these un- easier, facilities for variable selectivity. On layer, and thus did not reach the F layer. usual conditions deteriorated, and the upper our TRF sets we keep the band width as In a letter in your issue of June 11th Mr. frequency limit soon dropped to around constant as any superhet. I. Campbell -Bruce records the reception of 35 Mc /s. (4) This is a question of multiple -purpose a signal on May 18th in the region of The 56 Mc /s transmitter used here was a valves versus others. The characteristics 56 Mc /s. There is little doubt that this was simple oscillator of the " long -lines " type of TRF sets are more constant than super - a semi -long distance station, and probably with a Mazda ESW5oi valve and an input hets with the interchanging of valves. a harmonic, as on the morning of May 18th of a little over 5o watts. A long wire aerial In summarising, mention must be made at 08.50 G.M.T. the harmonic of SPW on 8 /2 waves long and end fed was used as a of sensitivity. Whilst the superhet has a 41 Mc / s approximately was R6, showing that radiator. higher sensitivity, a good TRF set has a conditions were suitable for intense E D. W. HEIGHTMAN (G6DH). sensitivity to three microvolts; this is suffi- refraction. Gt. Clacton, Essex. cient under present conditions. Between the months of May and August " Reproduction as faithful as can be on certain days signals can be heard up to achieved should be the starting point in 6o Mc /s, and contacts would be possible Horn - loaded MC Speakers been in our minds. on the amateur 56 Mc /s band if only ama- design." This has always AM afraid on mass production, teurs would forsake, to some extent, the I I must chip in again, though We could provide, I don't be the demand, a TRF set with overcrowded 7 and 14 Mc /s bands and work want to. First, in reply to Mr. should there J. K. Todd. I think he is all-round performance and value - consistently on 28 and 56 Mc /s. confused. a better Both of Fourier's for-money for the same price as any super - Already this year, on May 14th and 15th, theorems are proposi- market. our American amateur friends made 6o Mc /s tions in pure mathematics. Hence they are het in a particular " rigorously applicable " to loud Until the public realise the meaning of contacts from East coast to Middle West. speakers as as applied to Daily I record the upper frequency limit, to anything else if the data are " rigor- efficiency, value and quality ously " accurate. theirs will be the lot of " Superhet " radio Perhaps my first letter was too com- and its various evils. pressed. What I O. B. PINHORN, intended by " other things Dynatron Radio, Ltd. being equal " was that if in any given device we extend the frequency range without making other changes, such as change of efficiency or power handling capacity, we Observation on S-W Reception shall improve the transient response. REFERRING to Mr. L. Hipsman's letter His examples to the contrary are singu- in your issue of June 4th and my own in larly unfortunate. In the case of the RC the issue of May 7th, the following may be coupling the addition of a suitable choke of interest:- not only increases the " top " when calcu- Occasionally at this time of year we hear lated for sustained notes, but also gives a signals of very high frequencies (over 4o shortened time -constant from the transient Mc /s) refracted at short distances of, say, point of view -hence its use in television 500 -1,000 miles. These signals, we are told, receivers, which are (or at any rate should are bent in the E layer when the ionisation be) designed entirely on a time -constant is unusually intense. How, therefore, can basis. one differentiate between the intense E I can neither agree nor disagree with his causing fade -outs by attenuation and the statement that headphones, etc., " are intense E causing ultra high frequencies to really quite good on transients," because be reflected? If, simultaneously with the this last phrase is meaningless to me. But failure of longer-distance signals, usually my experience is that " headphones, loud - bent by the F layer, high- frequency signals speaking telephones, and the older pick- of short distance appeared, we could then ups " have a most inferior transient response say that the failure of the longer - distance compared with that of a wide -range device E layer MUSEUM PIECE ? The dramatic producer such as a good MC speaker, and I think circuit was due to unusually strong at Milan uses an ordinary speaking tube in ionisation causing signals to be refracted that most of your readers will agree. preference to its modern electrical counter- is back to earth at short distances before they part for the purpose of communicating Secondly, Mr. Brierley convinced that had a chance of reaching the F layer. In instructions from the control room to his to use with a horn a speaker designed for this case it will be seen that the F layer actors in the studios during rehearsals. a baffle must give bad results. Has he tried ?.

www.americanradiohistory.com JULY 2nd 1937 nl psUm íi WopIld It is sad to have to put on record the fact better than that of any other known method, that in loud-speaker work an ounce of prac- and is less dependent on the instruments tice is worth a ton of such theory as we used. The bridge' method of calibration is have, and various customers of my firm essential for precise results, and to avoid one have found, beyond any doubt at all, that small source of error I prefer to connect the moir&LLa these speakers at any rate work most ex- bridge permanently in series with the tuned cellently in a good horn, though they were circuit, switching it out by shunting a large designed for the baffie. condenser across it rather than a change- YELAVRES P. K. TURNER, over, as shown by Mr. Pettifor. Incident- Hartley Turner Radio, Ltd. ally, the formula for the type of bridge of the em) Isleworth. described be R' not as should - R, -R,' ; ROLA F IF interest in horns and baffles has not given and, of course, in his Fig. r the 90 v. 742-PM should like and 3o v. should be interchanged. become too attenuated, I It may be of interest to note that the to suggest an amalgamation. I like Mr. AC/SG valve walls and mentioned may not be effec- Maggs' idea of using two adjacent tive at the higher frequencies now in general the ceiling to form the open end of a horn, eliminate his acute -angle use; if any difficulty is experienced the but would rather AC / Sz valve should be tried. I have had bend. Of course, the acoustically ideal solu- would be to knock a big one oscillating at 6o Mc / s, but the practical tion of the problem limit for factory tests is probably more like hole in the corner and to build out behind it zo Mc / s. Even is for present - of section, the three sides that enough a horn triangular day ordinary needs. merging into the walls and ceiling, and the centre line passing through the - Another suggestion is that the relay straight method of controlling the dynatron bias, centre of the room. But that is not the architectural ideal -at any rate in Europe. shown in Figs. z and 3, might be replaced However, if we choose a corner next to a by the automatic amplitude control (de- neighbouring room we may bend our centre scribed in my article mentioned above) as it tine in a gentle curve through about 50 so could be arranged to give an instant and that two sides of the horn become flat sur- continuous reading without the need for a faces, continuations of one wall and the mechanical relay. M. G. SCROGGIE. NEW ' ALNICO' ceiling. To do this it is only necessary to Bromley, Kent. knock a few bricks out of a partition wall, MAGNET MATERIAL horn in the adjoining room, which build the GIVES IMPROVED may be a pantry or other uninhabited The New Marconiphone Sets region, and redecorate. It may be more PERFORMANCE convenient to use the floor instead of the IN the Model 562 battery transportable we ceiling or to perforate the ceiling instead of find an entirely new chassis designed to New magnet material . . . new a wall ; but in any case it is possible to have give the highest possible refinement of per- moisture proof metal and com- a horn, more than good enough to suit Mr. formance from batteries. The price is 15;} pound shielded transformer ... Voigt, which is at the same time an no guineas and there has been attempt to new standards of sensitivity " infinite " bailie to please Mr. Barden, compete with the cheaper battery portables, without occupying any space in the listening though the receiver is entirely self -con- with a 9r diameter speaker - room; tained. There is a stage of RF amplifica- these are some of the special No, I am not connected with a firm of tion preceding the triode hexode frequency features which distinguish the builders and decorators. changer and the single IF stage works at Rola F742 -PM. This remark- DAVID W. ASHWORTH. [24 kc /s. A double -diode -triode occupies able unit has the same flux Cam, Glos. the second detector stage, and it is interesting to find that separate pentode valves are density as the giant G.12 -PM, employed in the QPP output stage. Bias 11,500 lines per square centi- Measuring RF Resistance is automatic and the set may be used for meter and is particularly TN reply to Mr. D. R. Parsons, I must gramophone reproduction, the volume con- suitable for battery set or agree that my statement that a bifilar trol being operative on both radio and extension speaker use and for grid winding in the Hartley circuit gets over gramophone. all replacement purposes where the resistance difficulty is perhaps subject The second receiver (Model 559) in the to qualification. The DC resistance must present issue is a de luxe version of the extreme sensitivity is required. certainly be studied on the long -wave band; Model 557 and is a 3- waveband superhetero- Write to -day for details. but I am not at all sure that the bifilar dyne for AC mains. A new type of tuning method is altogether impracticable in Mr. scale of the rectangular pattern is uni- Parsons' case. He has to provide a good formly illuminated by a long filament lamp, oscillator valve conductance for the highest and a cathode -ray tuning indicator occupies frequencies, and would probably be able to the top left-hand comer. The loud speaker sacrifice more than o. r volt LT on the much is of the latest elliptical type and the price easier 150 -300 kc / s band. Alternatively, of the Model 559 is 14 guineas. the grid portion of the coil, if tightly coupled, F 742- could be made very small; or an iron-cored oscillator coil used, for the same reasons as PM those given by Mr. Parsons in favour of an Club News iron -cored feed choke. Kentish Town and District Radio Society WITHOUT TRANSFORMER 42;- Referring now to the article by Mr. Petti- Headquarters: Holmes Road School, Kentish Town, for, also in the June r8th issue on the dynatron London, N.W.5. OVER 8 MILLION IN USE Hon. Sea.: Mr. R. Pidsley, 27, Herbert Street, Queen's method of measuring RF resistance, I would Crescent, N.W.5. confirm that this is capable of excellent On July 3rd and 4th the Society, in con- accuracy as well as being the easiest to junction with the R.S.G.B., are holding a carry out. Mr. Pettifor stresses the latter 5 -metre field week -end. The transmitter advantage, as he is dealing with rapid test- will be situated at the highest point of Dun- ing of factory products. Looking from the stable Downs and will work continuously for hours, laboratory standpoint, I called attention in twenty -four commencing at 8 p.m. on (Pre 11iot/t6 ltoducetS an article, " Applications of the Dynatron," July, 3rd. Readers who pick up the trans- irteát in The Wireless Engineer, October, to missions are asked to send in reports, which 1933, will be acknowledged. Those who care to THE BRITISH ROLA CO.. LTD. the accuracy that is obtainable when suit- visit the transmitter will find much to interest MINERVA ROAD, PARK ROYAL,N.W.10. able precautions are taken. now I venture them. The site may be reached by any of PHONE WILLESDEN 4322 -3- 4 -5 -6. the opinion that the possible accuracy is the various services to Whipsnade.

www.americanradiohistory.com 22 Wireless World, July end, 1937 r-- signal input circuit Lr, CI and the local- oscillator circuit L2, C2 are Brief descriptions both connected to other grids of B the more in- the same valve, so that they are electronically coupled. The three teresting radio Inventions circuits are ganged together thus devices and improve- the present wide variety of valves partly as a rejector circuit for making the rejector equally effec- ments issued as patents by a so- called " universal " valve. interference. The upper and lower tive at all settings of the tuning This will have, say, a nine -pin limbs A, Ar of the dipole aerial control. will be included in this base and be capable, when suit- are connected to the tube T and Marconi's Wireless Telegraph section. ably connected, of performing all to the extension E, respectively, at Co., Ltd. and A. T. Witts. Ap- the functions required in wireless intermediate points, which are plication date September 21st, reception. The possession of one selected so as to give the required 1935. No. 463070. " spare" is then sufficient to impedance match. n o on CATHODE-RAY TUBES allow a listener to replace any E. C. Cook and J. L. Pawsey. TELEVISION SYSTEMS TO reduce the risk of " implo- disabled valve, no matter at what .Application date September 57M, TO avoid the necessity of scan- particular stage in the receiver. 1935. No. 462951: -1- ning, and the difficulties sion "-or collapse due to ex- o U O ternal air -pressure-the body cf a With this object in view, all O associated with synchronisation, cathode -ray tube is made of the valve -holders in the chassis of SUPPRESSING "IMAGE " the whole of the picture is radi- with end -pieces of glass. a set are designed to take a nine- FREQUENCIES ated simultaneously as a complex metal, pin valve of As shown in half-section in the the " universal " IN a superhet set, any given sta- band of frequencies. A wedge - drawing, the body D of the tube is type, though the external circuit tion can, in theory, be received shaped piezo -electric crystal is tubular connections are limited to the par- at two different settings ort the used at the transmitter to gener- welded to an intermediate ticular electrodes required from section S of metal having the tuning scale, one being as far ate the frequencies required. It same coefficient of expansion as stage to stage. For instance, all above the local -oscillator fre- is placed between the two plates glass. This in turn, is fused to a the electrodes will be connected quency as the other is below. In of a polariser, and, when energ- the up if the valve is to be used as a practice, of course, it is highly ised by a thermionic valve, gener- piece of glass G, which forms frequency -changer, bulb end of the tube and carries whilst if it is fluorescent screen. to be used as a detector one or the more of the electrodes will simply be " dummies." E. K. Cole, Ltd., and G. Brad- field. Application date October 8th, 1935. No. 462991. o o o o CATHODE RAY RECEIVERS THE Half- section drawing of CR tube ordinary method of electrostatic scanning is which is made of metal with found to pro- glass end pieces. duce a trapezium- shaped picture, instead of a strictly rectilinear one. This is due to the fact that the The smaller end of the metal lines of force tend to spread out- part D is welded or soldered to wards at the edges of the deflect- another section Sr, similar to the ing plates, instead of keeping section S, which is fused to a glass strictly perpendicular to the axis strip Gr, through which the leads of the electron with re- of the beam, the to the internal electrodes sult that the scanning spdt is tube are taken. A breakable accelerated or retarded to a greater joint may be provided near this or less extent from the normal. section to allow a new cathode to As a remedy it is proposed to fit be inserted, or the tube to be a guard -ring around each pair of repaired at a fraction of the cost. deflecting plates, at the ends near of a new one. the anode. The rings may be con- The British Thomson- Houston nected to the accelerator anode, Co., Ltd., H. W. H. Warren; and or they may be otherwise biased W. J. Scott. Application date according to the geometry of the September 11th, 1935. No. system as a whole. 462600. electrode o o o o Marconi's Wireless Telegraph Co., Ltd., and A. J. Young. Ap- LIGHT -SENSITIVE plication date August 3ist, 1935. AMPLIFIERS No. 461907. TWO light- sensitive electrodes o o o o are set at opposite ends cf a Superheterodyne frequency- changer embodying a tuned image- signal discharge tube, with a ring -shaped SHORT -WAVE AERIALS rejector circuit " collector" or anode between IN order to ensure an efficient them. They are connected across transfer of energy between a desirable to cut out one of these ates a wide band of frequencies, an external circuit which is fed short -wave aerial and a transmis- " image " signals. This object which vary from point to point from a high- frequency source, so sion or feed line, it is usual to can be achieved by using a high over the surface of the crystal. that their polarity rapidly match the respective impedances intermediate frequency, say, 450 Light from a projected image changes. by some form of transformer kilocycles, which automatically will then be modulated by the One has a central aperture to coupling. throws the higher " image " fre- crystal-and -polariser combination The feed -line, which consists of admit light, . which falls upon the quency outside the tuning range so as to produce a complex band opposite electrode, where it proof the set. of picture signals, which are duces secondary electrons. These Since this particular remedy has handled, at the receiving. end, by are, in turn, projected towards the certain disadvantages the alter- a similar arrangement. Here the opposite electrode, as the latter native course of providing a re- crystal is placed between a pair of becomes positive, and so liberate jector circuit for the undesired polarising plates, as before, and more secondary electrons. Mean- signal is sometimes adopted, and serves to modulate the light re- while a low- frequency potential is the invention consists in ganging ceived from an arc lamp so as to applied to the " collector " anode such a rejector circuit both to the throw the reconstituted picture to cause it periodically to draw off input circuit and to the local os- upon a viewing screen. from the electron stream a current Impedance matching section for cillator. Standard Telephones and proportional to the intensity of a short-wave aerial. As shown in the figure the Cables, Ltd. (assignees of Le Ma- the light first entering the device. " image- rejecting " circuit L, C is teriel Telephonique Soc. Anon.). Baird Television, Ltd., and an outer tube T and an inner con- connected to one of the grids of Convention date (France) June J. R. H. Forman. Application ductor C, is provided for this pur- the mixing valve V, whilst the 8th, 1935. No. 462877. date September loth, 1935. No. pose with an extension -piece E of 463061. the same shape and cross -section o o o o as the tube T, and lying parallel The British abstracts published here are prepared with the permission WIRELESS SETS to it. Its outer end is connected of the Controller of H.M. Stationery Office, from Specifications FROM the point of view of to the centre conductor C of the obtainable at the Patent Office, 25, Southampton Buildings, London, mass- production, as well as feeder by a lead L, as shown. The W.C.2, price I - each. A selection of patents Issued in U.S.A. is of subsequent " servicing," there extension acts partly as an imped- also included. is much to be said for replacing ance- matching transformer, and

www.americanradiohistory.com THE PRACTICAL RADIO JOURNAL $i,. ' 27th Year of Publication i. + 111:h

No. 932. FRIDAY, JULY 9TH, 1937. VOL. XLI. No. 2.

Proprietors : ILIFFE & SONS LTD. Editor : EDI TOR IAL COMMENT HUGH S. POCOCK. Editorial, aggressive, however, there is every Advertising and Publishing Offices : DORSET HOUSE, STAMFORD STREET, Radio Propaganda justification for adopting a defensive LONDON, S.E.i. attitude. The best means of defence Telephone: Waterloo 3333 (5o lines). Justification for Jamming would appear to be to make it im- Telegrams : "Ethaworld, Sedist, Loudon." possible' for foreign transmitters to

COVENTRY : Hertford Street. WE referred briefly last week invade British territory with unfriendly Telegrams: Telephone: growing concern of broadcasts. To do this would necessi- "Autocar, Coventry." 5210 Coventry. to the the Government over the tate setting up a jamming station in BIRMINGHAM : anti - British propaganda those territories affected. These jam- Guildhall Buildings, Navigation Street, 2. which has for so long been the subject ming stations would not be monopolis- Telegrams : Telephone: "Autopress, Birmingham." 2971 Midland (4 lines). of broadcasts from certain Continental ing additional wavelengths ; they stations. would be so designed as to maintain MANCHESTER : 260, Deansgate, 3.

Telegrams : Telephone : These broadcasts, as readers are their frequencies on the transmission "Ilifle, Manchester." Blackfriars 4412 (4 lines). aware, are not confined to the language frequencies of the foreign stations,

GLAscow : 26B, Renfield Street, C.2. of the country of origin but are fre- whose transmissions in any case Telegrams : "IIiSe,Glasgow." Telephòne: Central 4357 quently made in languages of the monopolise these wavelengths and make PUBLISHED WEEKLY. ENTERED AS SECOND - countries to whom the propaganda is them unserviceable for other purposes CLASS MATTER AT NEW YORK, N.Y. being directed. Official representa- in these territories.

Subscription Rates : tions to the governments concerned Home, £r as. 8d. ; Canada, £r is. 8d. ; other may have some effect, but do not seem A Matter for the Government countries, £i 3s. sod. per annum. to produce a satisfactory cessation of

As many of the circuits and apparatus described in these the offending transmissions. It cannot We -recommended this alternative pages are covered by patents, readers are advised, before making use of them, to satisfy themset,es that they would be supposed that this country will last year and said that this action not be infringing patents. much longer remain passive in the could only be regarded as defensive matter, and whilst we do not for one and would surely be legitimate in the moment believe that the Government peculiar circumstances. On that occa- would stoop to indulge in similar sion, too, we emphasised that in our CONTENTS offensive propaganda by way of retali- view the matter was not one in which Page ation, we believe that active measures it would be fair to ask the B.B.C. to . . . . . 23 Editorial Comment. are being taken to provide for accurate participate, and we questioned whether, The Wireless World Television Re- news bulletins to reach British terri- in order not to disturb B.B.C. im- ceiver-Il. Constructing the tories with a strength at least equal partiality, it would not be proper for Time Base ...... 24 to that of the foreign propaganda, such efforts to be conducted by stations The Case for Class " B " Restated 28 with the object of counteracting its wholly unconnected with the B.B.C. Unbiased .. 30 effect. organisation. Current Topics - .. 31 That any action of this nature should The Evolution of the Phon.. 32 Defence, Not Aggression have to be contemplated is truly offérs such Listeners' Guide for the Week 34 deplorable. Broadcasting If we do not retaliate with reprisals wonderful opportunities for contri- Practical Hints and Tips . . 36 in the form of aggressive propaganda of buting to a better understanding Letters to the Editor .. 37 our own it is simply because it has between nations that to find it being Listening in Europe 39 always been the policy of this country employed as a means of provoking Broadcast Brevities...... 40 to avoid the use of broadcasting for unrest and mistrust is all the more only hope it is On the Short Waves...... 41 such purposes and to do all that has regrettable, and we can been in our power by peaceful per- but a passing phase and that inter- Random Radiations 42 suasion to encourage others to follow national broadcasting is destined in the Television Programmes .. .. 43 this example. future to perform a nobler service to Recent Inventions .. 44 Whilst we may not desire to be mankind.

www.americanradiohistory.com 24 Wireless World, July 9th, 1937

The Wireless World

FULL details were given last week of the vision receiver and its power unit and in Televisior this article the time -base is described. It is designed for a tube with electrostatic deflection characteristic. The frame scanning am- and has balanced outputs, the aw- tooth oscillators plifier must thus deal with frequencies of being gas filled triodes some 5o c,'s to 500/1,000 c /s, and the line scanning amplifier with frequencies of about 1o,000 c/s to 100,000 /200,000 cos. Not only must the amplifier give a large output and handle a wide range of fre- THE DOUBLE quencies, but the output must be balanced II.- CONSTRUCTING to earth. With electrostatic deflection severe distortion of the shape of the pic- TIME - BASE ture occurs if this condition is not .com- plied with ; instead of a rectangular raster being obtained, unbalanced outputs. re- SECOND in importance only to the of waveform resistance coupled stages are sult in a raster shaped like a trapezium. receiver is the time -base which practically essential. In spite of the saw - An unbalanced output is obtained when must provide suitable voltages for tooth wave of each scan being of constant one of the two output terminals is main- deflecting the beam in the " frequency," the amplifier must be tained at earth potential, and the potential cathode -ray tube and so permit the con- capable of dealing with a wide band of of the other varies above and below earth. struction of the raster. The CR tube re- frequencies if distortion is not to be intro- With a balanced output neither output quires about Loop volts between its duced. Actually, to handle a perfect terminal is earthed, and at any instant the deflection plates to move the spot from saw-tooth wave with an instantaneous fall two output terminals are at equal and one side of the screen to the other, and from maximum to zero voltage, or " fly- opposite potentials -with respect to earth. the wave form of the time -base output back," the frequency response curve of The familiar push -pull amplifier is an must rise steadily and linearly with time the amplifier would have to be flat from example of a balanced amplifier, and a from zero to its maximum in nearly 1/5o the frequency of repetition of the wave to form of push -pull is actually employed in second for frame scanning and 1/1o,125th infinity, and there would also have to be the time -base output circuits. second for line scanning, and having zero phase distortion over this range. The complete time -base circuit appears reached its maximum value it must fall in Fig. 2, and V4 is the frame scanning back to zero in as short a time as possible. Balanced Output oscillator and is a gas -filled triode. The The total time of each rise of voltage and valve is initially non -conductive and the its subsequent fall back to zero must be In practice, the fly-back time is finite capacity formed by Cir and C12 in series 1 /50th second and 1/10,125th second for and of the order of 5 per cent. of the scan charges through R17 and R18. The the frame and line scans respectively. time. When this is so the amplifier need voltage across these condensers and In general it is not possible to generate be capable of dealing with frequencies hence the anode voltage of V4, conse- a true saw -tooth waveform with a voltage from the fundamental time -base frequently rises at a rate dependent upon the as great as 1,000 volts p -p directly: It is qu. ncy to about ten or twenty times this HT voltage and the value of R17. When necessary to generate a lower voltage, and value only. Since phase shift is impor- the voltage rises to a certain value, de- then to amplify it and in view of the type tant this implies a good frequency pendent upon the grid bias of V4 and

.wwwv .0 + Riß 1.000 V R3 R9 10,0000 R17 R23 10,0000 zm0 2M0 20,0000 R1 R26 100,0000 2000000 o LT R10 R18 0.6Ml1 0.5111 n R4 R24 20.000 0 160,0000 LCANINE FRAME fi 6018 R19 o 1,0000 1C11 lo C3 R°0.6 mfJ C2 0.002 miJ 07 CR 014 .002 ila 0.001 m1J 0.1 AIM 0.1 r,111 V1 V2 V3 V4 V5 V6 41N) R11 10,0000 R6 R15 1,000 n R13 6018 R14 20,0000 R2 R5 60 000 0 60,0000 N- R20 R25 1010 1010 C12 MA 0.201J 6Mn

R12 C4 L1 p 09 0.0006 ila 2,s00n 0.001 nlrA

) R8 C5 C101 R21 1.000 n 25 AIN* 25011,15 2,0000 C13 R7 R22 SO mm 5,000!) 6,0000

Fig. 2. -The complete circuit diagram of the time -bases is shown here. Each of the two consists of a gas -filled triode oscillator and one triode amplifier with a triode phase- reverser for balanced operation.

www.americanradiohistory.com Wireless World, July glh, x937 25 -

HT supply of some 1,000 volts is needed. The two amplifier valves are biased by a common cathode resistance comprising R21 and R22. The cathode of the gas - filled triode V4 is returned to the slider on R2r, and a portion of the bias of V5 and V6 is used also for V4. The Filter Circuit

The line time -base is similar and corn - prises the gas -filled triode V3, the amplifier V2 and the phase- reverser Vi. The resistance R6 is included in series with C4 to accelerate the fly -back speed, and a filter circuit is included in the grid cir- A view of the complete time - cuit of V3. This assists in the sync base. The gas-filled triodes separation and appreciably improves the are provided with insulated top -caps. line synchronising, especially when interference is present. The filter comprises the resistances R11 determined by the setting of R21, V4 be- the other vertical deflecting plate of the and R12, and the tuned circuit Li, C6, comes conductive and rapidly discharges tube. Owing to the phase- reversal in and it is in reality a crude form of band - the condensers. The resistance Rig is this valve, its output is in opposite phase pass filter. The main filtering is accom- included merely to limit the discharge to that of V5, and so the balanced out- plished by Li and C6, the circuit being current to a safe value for the valve. put is secured. The use of this additional tuned to the line frequency of 10,125 c /s. This is . the action without synchro- valve V6 not only enables balanced oper- The resistance R11 is included in order to nising. In practice, however, synchronisation to be obtained, but it also permits ensure a fairly high resistance grid circuit ing is essential, and the output of the the required output being obtained with for thé gas -filled triode V3, since experi- sync separator in the vision receiver is about one -half the HT voltage which ence shows that if the DC resistance of the applied to the terminals shown. The would otherwise be necessary. Even so, an grid circuit is too low V3 operates irregu- mixture of line and frame sync pulses flows through the two parallel circuits C8, R14 and C7, R13, and the desired amplitudes are taken off these potentiometers. A simple filter circuit comprising R15 and C9 is connected between R14 and the grid of V4, so that only the frame sync pulses are applied in any amplitude to the valve.

The Effect of the Sync Pulses When in normal operation, the -action is now as described above, but while the anode voltage of V4 is still rising, and before it has reached a high enough value to initiate the discharge in V4, the frame sync pulse arrives and drives the grid of V4 positive. This starts the discharge at a definite time. The net result is that the time of each discharge is determined by the frame sync pulses and the oscillator is maintained at the correct frequency. The varying voltage across C12 is applied to the triode amplifier V5 and about 500 volts p -p is developed across its anode resistances R23 and R24, and is applied to one deflecting plate of the CR tube. One - tenth of this voltage, that developed across R23 is applied to the grid of V6 through C14 with the result that a further 500 volts p -p is developed across the coupling resistance R26 and applied to The time -base is shown here to the right of the tube.

www.americanradiohistory.com 26 Mutt JULY 9th, 1937 The Wireless World Television Receiver- THE LIST OF PARTS FOR THE TIME -BASE larly. If the grid circuit resistance is not high enough there is an appreciable vari- Certain components of other makes but of similar ation in the starting times of the lines, and characteristics may be used as alternatives to those a consequent reduction of the picture de- given in the following list. finition. Fixed Condensers: I 10,000 ohms, 3 watts, R16 Erie A very important point lies in the I 0.0005 mfd., mica C4 Dubilier 690W 90,000 ohms, 3 watts, R4 Erie shunting resistance R12 to the tuned cir- 2 0.001 mfd., mica C7, C9 Dubilier 690W 1 500,000 ohms, 3 watts, R 1 Erie cuit. This must be of quite low value for 2 0.002 mfd., 5,000 volts DC test, C2, C3 z8o,000 ohms, 3 watts, R24 Erie a low Dubilier 680 I 200,000 ohms, 3 watts, R26 Erie satisfactory performance, enough, 1 0.1 mfd., 1,5oo volts working, C14 Potentiometers, nongraded : in fact, to make the tuned circuit non- Dubilier 950A 1,000 ohms, wire -wound, RS oscillatory. If this resistance has too I 0.5 mfd., 1,500 volts working, C11 Reliance " TW " high a value the tuned circuit is oscilla- Dubilier 950A I 2,00o ohms, wire- wound, R21 1 I mfd., r,000 volts working, CI Reliance " TW " tory, which means that any sudden Dubilier 950A change in the voltage applied to it makes 2 50,000 ohms, R13, R14 Reliance " SG " I 0.1 mfd., tubular, C8 Dubilier 4523 2 2 megohms, R9, R17 Reliance " SG " the circuit oscillate for a few cycles at its I 0.2 mfd., tubular, C12 Dubilier 4425/S 6 Valve holders, 5 -pin (7 -pin type fixing) natural frequency. This natural fre- 2 25 mfds., 25 volts, electrolytic, C5, C10 Clix Chassis Mounting Type. Dubilier 3016 2 Extension control outfits Eddystone 1008 quency is slightly different from the nor- I 5o mfds., 5o volts, electrolytic, C13 mal resonance frequency determined by 4 Shaft couplings, lin. Bulgin Dubilier 3004 2 Plugs and sockets, 3 -pin Belling =Lee 1119 the inductance and capacity, for it is 1 Pre -set double o.0009 mfds. C6 2 Insulated valve top connectors Bulgin P92 3288 affected also by the circuit resistance. Hunt's 1 Connector, 5-way Bryce 5C4 also the grid Resistances : 1 Choke 0.25 H B.T.S. Now the sync pulses and I 2,500 ohms, watt, R12 Erie current of V3 are of an ideal form for 2 Terminals, ebonite shrouded, Syn, E. 2 10,000 ohms, watt, R3, Ru 1 Erie BeliingLee " B " kicking Li, C6 into oscillation and such 2 20,000 ohms, watt, R15, R23 Erie Chassis Sound Sales oscillation has a very detrimental effect 2 I megohm, watt, R2, R5 Erie Miscellaneous: Peto =Scott upán the operation of the time -base. 2 5 megohms, watt, R20, R25 Erie r 5,000 ohms, 1 watt, R7 Erie Paxolin bracket and strip, wire, systoflex, Actually, Li has an inductance of the r 8,00q ohms, 1 watt, R22 Erie screws, etc. order of 0.25 H and C6 is about o.00i,uF. 2 T.5 megohm, r watt, R10, R 18 Erie Valves: - In order to make the circuit non- oscilla- 2 1,000 ohms, 2 watts, R6, R19 Erie 4 AC /P, 2 T31 Mazda tory, R12 must not be greater than 2,500 ohms. With these values the filter func- being merely in the values of components voltage unit which will be described later, tions very well indeed, and materially im- necessitated by the much higher operat- but the LT comes from the vision re- proves the stability of synchronisation. ing frequency. The unit as a whole con- ceiver power pack described last week. This time -base does not need detailed sumes about 15 /2omA. at i,000 volts for Constructionally there is little to say explanation since it is essentially the same HT and some 8 amperes at 4 volts for LT. about the time -base, for all components as the frame time -base, the differences The HT supply is taken from the high-. are assembled on the underside of the

R21 R8 R12 C9

3,150 TURNS N. 40 D S C WIRE 0.25 H

R18 I \,`I .0- Ilm, rat.:. `110=111M o _ t . ..401airi.1 R4 .. ,

- I - 11R20 I; II , n!_ R23 R3 !"+ C13 o., 02 -- 0 M- iied N LINE SCAN ¡¡ SOCKET FRAME ` R16 CO © SCAN : SOCKET Iì', lO1 R1 13/4" 1%; HT FROM OH VOLTAGE UNIT 4%

N4 18 GAUGE ALUMINIUM

LT FROM VISION POWER UNIT

Full constructional and wiring details of the time -base are given here.

www.americanradiohistory.com JULY 9th, 1937 iq W©deal The Wireless World Television Receiver - picture in the horizontal and vertical direc- nising pulses to be varied ; only very chassis and everything is quite straight- tions respectively while R9 and R17 con- occasional adjustment is needed, and if it forward. Owing to the high voltage em- trol the time -base frequencies. The re- were desired to reduce the number of ployed, however, care must be taken to maining controls Ria and R14 enable the panel controls they could be arranged is see that good insulation is obtained and amplitudes of the line and frame synchro- pre -set controls adjustable internally. [In the next instalment the design and construction of the high- voltage unit will be described in detail.]

An underview of the chassis showing the insulating strips which carry R9 and Riz AN UNUSUAL METER FAULT and form convenient anchorage points for wiring and resistances. Beware of Steel Filings ANEW tester, combining milliammeter, hair. Attempts to move it failed at first, voltmeter and ohmmeter, was as great care was needed to avoid damage that the clearances between the valve legs received from the makers about three to the coil. Acting on the assumption that and chassis, and output sockets and months ago. The meter was of the i,000 the obstruction might be a metal filing, a chassis are adequate. If insufficient ohms per volt type, its readings on the steel pin was inserted in an attempt to clearance is allowed a flash -over may ioo -volt, 250 -volt and i,000 -volt ranges attract it. This experiment was success- occur. In order to avoid this, the valve being on the low side, but just about ful and the filing, as it turned out to be, holders specified are of a type permitting within the tolerance given in a trade test came out on the point of the pin. an unusually large clearance. In the report. It gave good service until The pointer was now quite free to move, wiring, too, care must be taken in insu- recently, when the indicator began to stick but on test the readings were now lower lation, and it is unwise to rely upon in- at one particular spot on the dial and even- than before. Testing with a two -volt sulating sleeving for the high- voltage cir- tually would not move past this point. accumulator, the reading was now low on cuits. While it may be convenient to use The instrument was removed from its case the ro -volt range, showing only 1.8 volts. this, it should be as an extra precaution, and an inspection made. The pointer It would appear that this meter had been and not be relied upon for insulation. itself appeared to meet no obstruction, and calibrated with the filing, causing an error Run each high -potential wire so that bare at first no apparent reason could be dis- but no actual obstruction to cause sticking. wire could be used. covered for the trouble. A few experiments were then made to There are six controls on the time -base A light was then projected through the correct the calibration, and eventually and they are brought out to the panel by gap between coil and magnet. On looking correct readings were obtained on the io- means of extension rods. The potentio- very closely, an obstruction could be seen volt range and a greater degree of meters R8 and R21 control the size of the which had the appearance of a minute accuracy on the higher ranges. W. G. G.

www.americanradiohistory.com Wireless World, July 9th, 1937. The Case for Class "B"

REFINEMENTS APPLICABLE TO THE NEGATIVELY BIASED SYSTEM Restated

By RICHARD H. McCUE N the second of two articles dealing a low- resistance potentiometer across the with different aspects of push -pull filament battery for fine adjustment of grid amplification' " Cathode Ray " re- bias on the driver and Class " B " valves. ferred to the disadvantages of posi- several advantages over the double -pen- This will allow a continuous variation tive -grid Class " B " amplification, which tode system. over a range of two volts -more than at one time seemed likely to oust all_ In the simple circuit shown in the sufficient to overlap the tappings on the other systems for giving high output with accompanying diagram there, are a num- grid-bias battery. The reason why a low - economy in battery- operated receivers, ber of details-all of them important- resistance potentiometer is specified is that but which is now almost completely which perhaps have not been stressed it is necessary to keep the ohmic resist- eclipsed by the type of QPP employing sufficiently in the past. The triode de- ance of the Class " B " input circuit as two balanced pentodes in a single glass tector valve, besides being adequately de- low as possible. A 40- or 5o -ohm poten- envelope. coupled, must be parallel-fed to the driver tiometer is suitable, and will impose but a Although the present writer agrees that stage. This may seem a dogmatic state- light drain on the filament battery. with the earlier types of zero -bias Class ment, but it is made as the result of ex- Driver stages in battery- operated Class " B " valve it was exceedingly difficult to perience. A grid stopper is included to " B " systems are usually rather over- avoid that unpleasant form of distortion keep any trace of RF from the driver biased for reasons of economy, and it which became known as " Class ' B' valve. Secondly, it seems that the LP2- might be thought that when an LP2 type of driver is used with only as much grid bias as the O+H T output valve its anode cur- 20,000, 0,0000 rent would be rather high. 4 mfds 4 mfds This is not the case, how- I I ever, since the decoupling resistance in the driver stage to a great extent regulates the voltage on its anode. It should not now be necessary to use the relatively enormous fixed condensers sometimes shown connected across each half of the Class " B " output trans - f ormer - apparently in a last desperate attempt to avoid parasitic oscillation and other .. distortion. In- stead, a simple tone - corrector consisting of a io,000 -ohm resistance in +LT series with a o.002 or 0.003 - mfd. condenser may be connected from each anode to -LT earth. As a final precaution, a io-mfd. condenser is connected across the HT battery. The various details that affect quality of reproduction in a Class "B" circuit are shown in this diagram. Neglecting any RF stages which might be included, edge " (particularly evident in the repro- type of small power valve under any of its such an arrangement of three valves in duction of piano music, and of transients equivalent type- numbers (i.e., the type itself forms a " local station " receiver generally), in his opinion the later type of of small power triode with a short grid- capable of giving a very satisfying quality double- triode, operating with a bias of base, low impedance and high mutual- of reproduction. It is very flexible and several volts, undeservedly inherited this conductance) is always preferable in the will work well with a low HT voltage- slur, and, in fact, has not attained the driver stage. This valve is also decoupled in which case a fine adjustment of grid popularity which it merits. This nega- with a io,000 -ohm resistance and a 4-mfd bias can be obtained with the potentio- tively biased type of Class " B " valve is condenser. It is .generally emphasised that meter ; this is also used to compensate for capable of a high standard of reproduc- the driver transformer is the crux of the the HT voltage falling as the battery ages, tion, provided a few simple pre- whole system. This may be so, but no thus avoiding , the " over -bias " distortion cautions are taken. To the home con- difficulty has been experienced with any so often tolerated by battery-set users structor, at least, it would appear to offer of several good makes ; a i to x ratio is when the first bloom of their HT supply i " About Push -push," The Wireless World, generally satisfactory. has faded. More overall amplification is April 23rd, 1937. Notice next an important refinement- available than with a QPP pentode stage,

www.americanradiohistory.com JULY 9th, 1937 whCgIlsgg 29-

The Case for Class " B " Restated - of Holmer Works, Dalefield, Bridge Street, with the situatictr to -day and concludes with and much higher maximum output. Manchester, 3, and it is priced at 5s. a chapter on television. One last fact, rather beside the point, In the third part broadcasting conditions perhaps, but, nevertheless, in the chief countries throughout the world of interest tb La Radiodiffusion Puissance Mondiale. By are discussed. In the fourth broadcasting battery-set users. The output of the Arno Huth. Pp. 508. Published by is looked at from the point of view of a " Wireless World " or any similar trans- Librairie Gallimard, 43, rue de Beaune, public service and its influence from econo- verse- current microphone, when applied Paris. mic and social standpoints investigated. through its appropriate transformer to the book is in five parts, of which the The book concludes with much useful infor- first of the three valves shown in the dia- THISfirst is devoted to the birth and develop- mation in tabular form and chapters on tele- gram (the grid condenser being discon- ment of broadcasting, while the second deals vision and facsimile. nected, of course, and the ends of the transformer secondary connected to the grid and to a suitable tapping on the bias battery), is just right for loading the Class Telephone Dial Tuning " B " valve to full capacity. A similar outfit was used by the writer last summer for " PA " work at a good -sized garden By G. E. CLATWORTHY fête. This may sound rather ambitious for a battery- operated amplifier, but with contacts are wired to light the appropriate an anode voltage of 16o and a really indicator on the control panel which serves efficient loud speaker with directional as a pilot light to show when the set is baffle the results were perfectly satisfac- " on ' besides indicating the station to tory-so much so that the use of the which the circuits are tuned. has for The relay supplies current to an electric apparatus been asked again this motor through a system of metal strips in year. contact with a common busbar. A station is dialled and the relay supplies current to the motor through BOOKS the selected strip contact. As the motor runs it moves a " carriage " The Superheterodyne Receiver. By Alfred The dialling unit may along the busbar, lifting each con- T. Witts. Pp. 182 +vii. Third edition. be plugged into a socket mounted at any point remote from the receiver. tact strip from the busbar until it Published by Sir Isaac Pitman and comes to the one supplying the cur- Sons, Ltd., London, W.C.2. Price' THE writer ventures to think that the rent. When this is lifted the motor stops, 3s. 6d. following brief account of a system and as the strips are adjusted to coincide THE nets edition of this book contains the whereby an automatic telephone dial with the selected stations, the receiver is material of its predecessors with extra is used to control a receiver may be of inter- thus tuned through a chain of gears to the matter bringing it up to date. The early est to some readers of The Wireless World. desired programme. chapters are devoted to the history of the The system is the subject of a provisional Dialling an " off " position results in the superheterodyne, and a large section of the patent. motor being reversed, book describes, in an accurate and intelli- The dial is used to operate a the tuning condenser gible manner, the mode of operation of this relay consisting of seven banks of returned to zero, and type of receiver. twenty -five contacts. The action the receiver switched A number of modern commercial receivers of the relay is a continuous rotary off. are described in detail and the book con- one, and in this case the contacts The receiver in use at cludes with a chapter on the television are wired in groups of four, mak- present is a two -HF superheterodyne. This is necessarily some- ing every fifth posi- what sketchy, for it is almost a subject in tion an " off " itself, and in this chapter one of the few position. This allows errors occurs. The frequency of the sound for the selection of transmitter is given as 46.5 Mc /s instead of four stations. 41.5 Mc / s. As a result the subsequent re- Another bank of marks, although correct in themselves, are not directly applicable to present conditions. W. T. C. Below is shown the receiver with the THE third edition of Servicing Super - remotely controlled heterodynes, by John F. Rider, is now mechanism whereby available. An additional chapter has been in- the tuning condenser cluded giving data on recent developments, shaft is rotated ; on and the list of intermediate frequencies has the right is another been brought up to date. The book is ob- view of the actuating tainable from Holiday and Hemmerdinger, mechanism.

" quality " set, and is " dialled " from any room provided with a socket for the control panel. From the point of view of convenience, it would appear to be difficult to improve upon this system ; by a spin of the dial the desired station may be tuned -in in comfort from one's favourite armchair.

www.americanradiohistory.com Wireless World, July 9th, 1937.

It was soon clear to me that there must be some unexpected_ factor at work which I had failed to take into my calculations, and I at once began an ardent search for UNBIASED it. Immediately one very strange and sig- nificant fact forced itself on my attention and that was the altogether uncannily ac- By FREE GRID curate fashion with which certain jockeys Wireless and the Police were timing their " effort." I suppose that even those of you whose IN all probability most people turn offensively at me, but there was nothing knowledge of racing is confined to the daily automatically, as I do, to the police very out of the ordinary in this, and so sprint for the City train do not imagine news as soon as they have finished I took no particular notice of it. that the horses keep going at top speed all perusing the racing page of their favourite I had, I suppose, been proceeding along the time irrespective of the length of the daily. If so, they cannot help having for some ten minutes, during which the course. It is one of the secrets of good noticed, from time to time, the apparent music, and myself in sympathy with it, jockeyship to know when to start going backwardness in the education of our legal had passed from waltz to foxtrot, and " all out " and it is just as fatal to a'o this luminaries who are constantly expressing from foxtrot to one of those eccentric, ignorance of facts known to the ordinary new-fangled dances which are all the rage man for years. Only recently a learned nowadays. Suddenly, without the slight - judge, who has been married for years, t:t warning, I was accosted by two police demanded to know, " What is a loud constables, and before I had time to col- speaker? " lect my wits I found myself being hustled I believe that this strange state of affairs along to the nearest police station. In is due to the fact that, as the legal lumin- spite of my protests, I was subjected to aries say, the Law " takes no cognisance all the indignities of a test for inebriation of a happening until it is officially in- by a sorely puzzled police surgeon, who formed of it." Until lately, however, I was eventually compelled to give me a must confess that I never realised that this clean bill of health in this respect, attitude of mind extended right through although he rather offensively suggested our judicial system down to the humblest to the station -sergeant that I be detained At the conclusion police constáble, but that it does do so I for mental observation. of the meeting. have recently had very convincing and The strangest part of the whole busi- personal proof. ness, however, was that my explanations too soon as to leave it until it is too late, It so happened that a few weeks ago I were completely discounted, even though A jockey has to vary 'the timing of his had occasion to visit a London theatre, I persuaded the station- sergeant to don the effort in accordance with many factors, not few and, as is my custom, took along a small earphones and listen for himself for a the least of which is the position of the pocket headphone set with me in order to minutes, the reason he . gave being that other horses in the race. keep my usual watchful eye-or rather no official mention of pocket wireless sets Unfortunately he is, more often than ear the doings of the B.B.C. while the was to be found in the Police Regulations. not, in the worst possible position to ob- -on regu- 'play was in progress. The evening was It was indeed fortunate for me that serve what the others are doing and it has mention pocket wireless exceedingly oppressive, and after the show lations did not frequently been said that if it were only done so, I learned, I over a stroll in one of the sets, as, had they possible for the trainer from his coign of was I took Lon- the Sedi- for Needless should have been charged under vantage to convey telepathetically to the don parks a breather. to say, to the fact when the my earphones which, being tion Act, owing that jockey his " reading " of the race, it would I still wore station- sergeant listened to it the set hap- of the acorn -sized deaf-aid type, be as good as won, and this, I discovered, actually pened to be tuned to one of the Continental " stations. was exactly what was happening except "propaganda that a far more reliable method than tele- pathy was being employed. Two to One Bar One. It did not take me long to prove my theory at the meeting following Ascot, and ISUPPOSE that like myself a good many with very little searching about among the of you have still got the post -Ascot feel- ultra -short waves I soon picked up the ing even though a week or two has elapsed particular wavelength being employed, since the meeting. I, personally, have with the result that I have since been reap- not had such a disastrous time for many ing a golden harvest at the bookmakers' a long year but it was comforting to ob- expense. serve that I was far from being the Even now, however, I haven't fully only person of note queuing up, watch and solved the mystery for although a flea - chain in hand, at the entrance to the little power ultra -short wave transmitter and a portable mont -de -piété near the railway lapel microphone is easily concealed about station, at the conclusion of the meeting. the ample clothing of the average trainer Hustled along to the nearest police station. Now I don't know about you, but when- and a receiver can easily be distributed ever anything goes seriously amiss with my about the person of a jockey, some sort of are very inconspicuous, and as I strolled plans, it is my invariable custom to sit headphones are absolutely essential and along I put my hand in my trousers quietly down and find out exactly where I have so far failed to locate through my pocket and tuned in the National pro- I've gone wrong. It is an invaluable habit binoculars the faintest suggestion of even gramme. which I learned in my early set-construct- a miniature earpiece. At that time in the evening, of course, ing days when I was frequently rewarded The only thing I can think of at the dance music was being served up from the by silence from the loudspeaker after many moment is that some sort of bone- conduc- London studio, and, carried away by the weary hours of toil. Consequently, when tion reproducer is being employed, but rhythm of the waltz, I suppose I must all my investments at Ascot, concerning surely, even so, it would have to be ap- have subconsciously permitted my body to which I had received information from un- plied to the skull? Perhaps one of you can sway and gyrate in time with the melody. impeachable sources, started to go up in get to work and solve the problem in return noticed one or two people staring rather smoke, I began to put on my thinking cap. for my divulging the wavelength.

www.americanradiohistory.com Wireless World, July 9th, /937 rgi

ators and oscillators as stan= dards of frequency. The presentation will take place at the next meeting of the Physical Society, which will be held at Current Topics 5.15 p.m. this evening (July 9th) at the Imperial College of Science and Technology, South NEWS OF THE WEEK IN BRIEF REVIEW One Kensington. Hundred per Cent. The Duddell Medal is awarded Berlin Exhibition that each section contains at THE Polish village of Helmi- to " persons who have con- least one item which does not camala boasts that it is the tributed to the advancement of THE German National Radio depend on sound. only place in the world where all knowledge by the invention or Exhibition will be held the inhabitants are radio design of scientific instruments, this year between July 3oth Late Concerts from Poland listeners. There are forty -five or by the discovery of materials and August 8th. houses and forty -five wireless used in their construction." DURING July and August the licences. Broadcasting from a Train Lwow station is to try the experiment of broadcasting until Folkemottager Influences African Chief's Voice THE famous Philadelphia r a.m. every morning. Recorded Symphony Orchestra has Licence Figures DURING a visit to the just completed a broadcasting Luxemburg's Programmes THE Norwegian People's Re- H.M.V. factory, the Alake tour of the U.S.A. It has ceiver is proving very popu- of in ACCORDING to a statement Abeokuta, a well-known travelled all over the country lar and is having a very marked African potentate, recorded a a specially equipped ten -car made recently in the House by the Assistant P.M.G., influence on the number of new speech for the benefit of his sub- Pullman train. On one occasion licences taken out. There has jects. Copies of this record are it broadcast a programme while further representations have recently been made to the Luxem- been a very great increase since being sent out to Abeokuta. the train was in motion, a speci- this receiver was first marketed. ally fitted coach being used as burg Government against the a studio. broadcasting of advertisements Belgian Ship -to -Shore in English on a wavelength not Danish Midget Telephony allotted to the Luxemburg TWO companies are being New Lithuanian Station issue of station by international agree- floated to handle the large - IN our June 25th we PLANS have been afoot for ment. scale production "of a midget re- reported the inauguration of some time to erect a a telephony service via the national high -power broadcast- Blaavandshuk station between ing station in Lithuania, but ships crossing the North Sea and financial difficulties have hither- Denmark. La Société Inter- to stood in the way. The nationale de TSF, of Brussels, Minister of Communications has reminds us that similar facilities now announced, however, that have been provided on the Bel- at last these difficulties have gian Dover -Ostend lines for been disposed of, and tenders some time. are to be invited for the erection of the station. It will prob- Institute of Public Address ably have a power of roo kW. Engineers AT a recent meeting of the Car Radio in the U.S.A. Technical Committee it was ALTHOUGH there is a popu- decided to examine the various lar belief that a very large means employed for the deter- proportion of the cars in mination of the audio -frequency America is fitted with wireless, output of amplifiers and the this is far from being the case. harmonic content therein in Of the 23 million cars on the order to determine the most road in the U.S.A., rather less satisfactory method with a view than 4 million are equipped to its adoption by the Institute with wireless receivers. There as a standard. are strong rumours, however, The syllabus of the examina- that the Chrysler combine are tion paper for associate mem- intending to go in seriously for bers was approved. Eight ques- car radio, and to that end are tions (six of which have to be taking over a well -known radio The winners of a recent 40-metre DF contest held by the Southall answered) will be set, covering manufacturing concern. Radio Society, Mr. H. G. Swann (right) captained the team Ohm's Law, Technical Terms, Fault Finding, Application of Television for the Deaf Radio Doctoring ceiver produced by Mr. A. Kiel - Valves, Impedance Matching, sen, a well -knòwn Danish engi- Lay -outs, Description of Typical ASERIES of practical tests FREE medical advice is now Testing. from broad- neer. One company, which has Apparatus, and It is is being carried out by the given Italian a capital of roo,000 proposed to hold examinations casting stations. is kroner, will G.E.C. to determine the interest The scheme handle the home market, while four times a year. Full particu- value which television possesses being operated in much the lars entry forms avail- as a further company, with a capi. and are for the totally deaf. A set has same manner that adopted by tal of 150,000 kroner, will deal able on application. been installed at the Tower certain newspapers over here, in with House Home for deaf and dumb which the sufferer writes to the foreign interests. The Kielsen set is a three -valve bat- Technical Catalogues men at Erith, and the results paper concerning his symptoms, tery- operated receiver i The question and answer being w h c h Wanted have been very promising. the will sell at about 5s. tests are being continued in published for the benefit of THE librarian of the All -Union order to find out, among other readers at large. In the case of Arctic Institute, 34, Fon- things, whether television will the Italian broadcasting service, Duddell Medal Award tanka, Leningrad, 14, U.S.S.R., still exercise an appeal after the however, either the post or the THE Council of the Physical asks us to invite British manu- novelty has worn off, and what telephone can be used to Society has decided to give facturers of receivers and trans- type of programme is most describe the symptoms, the the fourteenth Duddell Medal mitters to send technical cata- suitable for deaf persons. It is treatment being broadcast at a award to Walter G. Cady, Pro- logues and other literature for probable that a complete report certain hour of the day which fessor of Physics at the Wes- the Institute's library, where will be sent to the B.B.C. in the is devoted to this service. leyan University, Middletown, they will be studied by engineers hope that they will be able to Presumably, the identities of Connecticut, U.S.A., for his engaged in developing the arrange their programmes so patients are not disclosed. work on piezo -electric reson- Arctic communication systems.

www.americanradiohistory.com 32 Wirs'ess World, July gth, 1937. The Evolution of the Phon A SUCCESSOR TO THE DECIBEL NOTATION FOR SOUND

OUDNESS is the magnitude which the MEASUREMENT sound intensity, zero decibels, to corre- brain assigns to that quality of spond to the threshold of audibility at a J a sound corresponding to its frequency of i,000 c /s. physical intensity. By Now, if one tries to reconcile the decibel Until quite recently the graduations of as a loudness unit with the data in Fig. i, loudness according to popular conception D. B. FOSTER, M.Sc., Ph.D. one finds the following anomalies : Loud- were represented by about five coarse ness varies with frequency for constant steps -very loud, loud, medium loud, soft sound intensity in decibels ; for example, and very soft, corresponding to the musi- So decibels would appear to be twice as a sound of 3o decibels at i,000 c/s is cal notations ff, f, mf, p and pp. Recent loud as a sound of 4o decibels. This linear louder than a sound of 3o decibels at research has established that there are relationship between loudness and its 200 c/ s, and a sound of 3o decibels at more like zoo minimum perceptible incre- scale of measurement is, of course, a very zoo c/s is something less than inaudible ! ments of loudness between the softest and desirable requirement. In a further attempt to overcome this the loudest sounds which the drawback the zero decibels ear can perceive at the datum was deprived of its middle of the frequency THE author discusses the shortcomings of the decibel constant sound intensity cri- range. terion, and was made to In early experiments on for the numerical evaluation of loudness, and correspond to the threshold loudness it was customary describes the nature of its derivative, the " phon," which of audibility curve over the to make loudness variations has recently been defined by the British Standards whole frequency range in- in the sound produced by a stead Institution and accepted as the unit of loudness of only at r,000 c /s. telephone receiver held to This distorted decibel was the ear by varying the elec- sometimes given the title of trical power supplied to the Sensation Unit, but was receiver from an oscillator. These elec- (c) It had been found by experience clearly unsuitable, since, due to the con- trical power changes were expressed in that one decibel represented about the vergence of the equal loudness contours terms of decibels, and so it became cus- minimum loudness change with which one towards the low frequencies, N decibels tomary to express the corresponding loud- was normally concerned, another emi- (above threshold) at 5o c/s corresponded ness changes from the receiver in terms nently desirable requirement. to a greater loudness than ' N decibels of the same number of decibels, assuming The first doubts as to the suitability of (above threshold) at i,000 c /s. that the receiver had a linear input- output the decibel as a loudness unit came when The next attempt to reconcile the decibel characteristic. comprehensive data became available on as a loudness unit was to give each equal A natural development of the above the relationship between loudness and loudness contour the same number of association was to assign a value of zero sound intensity over the whole audible fre- decibels independent of frequency, and the decibels to the sound from the receiver quency range. Such a plot of aural number of decibels for each contour was which was just audible -that is, to the characteristics is given in Fig. i. The made numerically equal to the sound in- "threshold of audibility." An increased horizontal scale represents frequency, the tensity of the contour in decibels at loudness from this point corresponding to 1,000 c /s. In order to differentiate be- a further electrical power increase through Da tween the sound intensity decibels at 14 111111=18l111lII I III the receiver of N decibels was therefore IIIIII11111111IIIII 1,000 c/s and the equal loudness contour known as a loudness of N decibels. 11114iC!!!!111111A11111111C.' decibels, the latter were sometimes given This original association of the decibel I111111111m1111\1ii1!!%l the title of " decibels (1,000 c/s equiva- and loudness was therefore purely circum- 1111111111111111OICGI:Ii'/JI lent loudness)." stantial, due to the ease of control of loud- I11mm11111111I!1'/,i iiA The original desire to associate the deci- Wi::1iM.M11111111 -.',. I!!/11UMI ness from a headphone by means of elec- [51:ii\111111CI11111 bel with loudness had therefore produced trical attenuation or amplification. There `1i:11\\`:111111E!1!i1111iCw three successive types of decibels each were, however, three further good reasons li:éM\1111111111\i/,i111121 more closely fitting the loudness data. for the popularity of the association, and l11111\\CIIIIi1111)Ilili\.`\CIIIIIW?IIIli111111C% This co-existence of three types of loud- these were as follows :- IIIIII II/JJ ness decibels corresponding to (a) sound (a) The ear can perceive a maximum 111111r:1_111..11:ú1/Jíli intensity, (b) sound intensity above loudness change corresponding to a sound threshold, and (c) i,000 c/s equivalent intensity of io,000,000,000,000: i. The loudness, was the chaotic state of affairs IIIIIIÌÌIÌIil!;iii. . .. . :Ilill decibel is a logarithmic unit of power ratio, when the British Standards Institution and its use converts the above unwieldy FREQUENCY IN C/S met about two years ago to standardise on ratio to the more practicable figure of 13o Zero db. at 1,000 c/s= 0.0002 dynes /sq. cm. (RMS.) a loudness unit. They decided, in effect, decibels by the formula :- Fig. r. -Aural characteristics : the relation- that, whatever the name to be given to Decibels= io Log10 Sound Intensity ship between loudness (in phons) and sound the loudness unit. it should have the same Ratio. intensity above threshold (in decibels) over value along any equal loudness contour, (b) The Weber -Fechner law suggests the entire audible frequency scale. and it was agreed that the third type of that physiological reaction magnitudes decibel given above, namely, decibels such as loudness, brightness or pain are vertical scale represents sound intensity, (1,000 e / s equivalent loudness) repre- related logarithmically to the associated and the curves are equal loudness contours sented the type of unit they required. physical stimulus. This suggested, in other commencing with the threshold of audi- Unless given this full cumbersome title this words, that the loudness of a sound was bility at the bottom and finishing with the unit was liable to be confused with sound directly proportional to its magnitude in threshold of pain or feeling at the top. intensity and electrical power ratio deci- decibels, so that, for example, a sound of It is customary to assume the datum of bels, so the unit was given the new short

www.americanradiohistory.com .1

JULY 9th. 1937 Wilpd,@gaWatt 33 The Evolution of the Phon- Method of noise measurement, it is found 5o per cent. (" half as loud ") represents title of " phon," and the term decibel was in practice that in order to obtain reliable a redùction of 8 phons from zoo phons to retained for the magnitude of sound in- results it is necessary to employ a large 92 phons. It would be difficult to memor- tensity above a constant datum. This number of observers and average their ise all the data represented by this family datum was in the region of threshold of results. Under ideal conditions it is pos- of curves, but the following values are audibility at 1,000 c /s, and was standard- sible to achieve results which are accurate worth remembering for use with radio re- ised as corresponding to a RMS pressure within the limits of plus or minus 5 phons. production round about a normal loudness of 0.0002 dynes per sq. cm. The phon has provided us with a loud- of 70 -8o phons. The loudness of a sound in phons is ness unit which is trustworthy, but it has Reduction Estimated Loudness therefore numerically equal to the sound two drawbacks. In the first place, as men- in phons. Reduction intensity in decibels of an equally loud tioned in the preceding paragraph, it is 1 -2 Just perceptible. 1,000 c/s pure tone. The phon is there- practically impossible to obtain precision 3 -5 Marked or 25 ",,. 8 -10 50 " (" halt as loud. ") fore called a Unit of Equivalent Loudness. results to the nearest phon, and in the 16 -20 75% (" quarter u loud. ") Reference to Fig. z will show that the second place the phon scale of loudness equal loudness contours represent equal does not linearly represent intuitive judg- The precise loudness of a radio set is, numbers of phons, and that these contours ments of loudness. That is to say, if an as is well known, a major factor in deter- coincide with the same numbers of sound observer listening to a radio set producing mining how closely the quality of the re- intensity in decibels at i,000 c /s. q0: production follows the original sound. Consider that a programme is being Noise Meters broadcast with the loudness following the 70 -phon contour in Fig. i over the whole It will thus be seen that it is simple to frequency range. If no distortion is intro- make a loudness-measuring meter which duced in any part of the transmission or will give true results in terms of phons. reproduction the sound will appear iden- Such a meter consists of a z,000 c/s tone tical with the original if reproduced at the from an oscillator fed to a headphone and same loudness of 7o phons. If, however, controlled by an attenuator in decibel II I the volume control is set io decibels above steps, the attenuator being engraved zero the correct value, the loudness will go up when the intensity of the tone corresponds to 8o phons at ',boo c/s to 83 phons at to the datum pressure of o.0002 dynes per INNIEMPFMAII 200 c/s and to 92 phons at 5o c/s. The sq. cm. In order to measure the loudness original loudness balance will therefore be PANION- OX of a noise in phons the headphone is held ,M lost, and the reproduction will become to one ear and the intensity of the refer- _re,marop- " boomy," due to relative increase of loud- 0 IO 20 30 40 50 e0 70 SO 90 ao ence tone is increased by adjusting the ness at the lower frequencies. In the attenuator until the loudness from the PHONS Fig. 2. -Showing the relationship between same way, if the reproduction is carried on headphone at the one ear is judged to be aurally estimated loudness and the phon lower than the original loudness, the lower equally loud as the noise entering the un- scale. frequencies will be excessively depressed covered ear. The loudness of the noise in a loudness of 8o is to and the quality will lack bass. is to numerically equal phons asked turn phons then said be down the volume With regard to the permanence of the to the intensity of the reference tone in control until it is " half as loud," he will not phon as a loudness unit, it is conceivable decibels. Thus, if the attenuator had to reduce it to 40 phons but probably to something between 65 and that as the data on the relationship bebe turned up 5o decibels from the zero This is tween intensity and loudness, as given in datum to equal the loudness of the noise, 75 phons. effect contrary to the statement of the Weber -Fechner law Fig. 2, becomes more comprehensive it will then the noise would have a loudness of stated earlier. Consequently, an untrained ob- be replaced by a unit whose magnitude is 5o This type of loudness measure- phons. server has little conception of loudness a direct indication of loudness. Attempts ment is known as the Subjective Equality the change represented by any specified have already been made in this direction Method, and is the only one by which change in the number of phons, nor has in the U.S.A., where a scale of loudness be obtained which are, loudness values can he an accurate Conception of numbers having direct loudness interpre- by definition, accurate in terms of phons. the absolute loudness represented by any part of the tations has been tentatively approved by is a common belief that loudness in There phon scale. the Acoustical Society of America. be measured by a device, com- phons can The following table based on practical The tendency of feeling in the respons- monly called a " noise meter," consisting ible body in this country is that, while a indicating measurements will give an idea of phon of a microphone, amplifier and magnitudes direct loudness scale has advantages, the meter. Such is not the case, although :- collection and checking of accurate data results can be No. of phons. under certain circumstances 130 Threshold of feeling or pain. on which such a scale might be founded obtained which are close to the true loud- 110 -120 .. Vicinity of aeroplane engine. have not achieved finality, and it is there- ness in phons. This type of objective 105 -110 .. Vicinity of pneumatic drill. fore as well to continue using a unit which, meter is properly termed a " sound level 100 -105 .. Vicinity of loud motor horn. if more difficult to interpret, is quite stable. referred 90 -95 .. Interior of tube train, windows meter." and the results should be open. to as " sound level in decibels." Such 90 Interior of noisy motor vehicle ; meters may have incorporated a frequency loud radio set. Pilot Model B344 80 Interior main -line train, windows weighting characteristic corresponding to THIS new battery receiver at ii} guineas of the equal loudness contours shown open. one 70 Interior of quiet motor car ; has been produced to meet the demand in Fig. I, but the results obtained are of medium radio set. for a sensitive all -wave set suitable for use an arbitrary nature. It is not infrequently 60 -75 Conversation (average to loud) at week -end bungalows, on motor cruisers, found that the results from these meters 40 -50 Suburban residential district. etc. Its cabinet is conventional in ap- decibels lower than 20-30 Quiet country residence. pearance, however, so that it is equally are of the order of 3o o.. Threshold of audibility. the numerically correct loudness in phons suitable as a permanent domestic receiver obtained by the Subjective Equality A number of research workers have in country districts. as A double -pentode output stage gives a Method. These errors are based on the recently investigated the relationship between scale and intuitive or rated output of 2 watts, and the 4 -valve inability of a sound level meter to integrate the phon superheterodyne circuit is designed for the components of a complex noise accord- " man -in- the -street " loudness judgments, reception on 16 -52 metres in addition to the ing to the manner of aural integration and and a typical result of such work is shown usual medium- and long -wave ranges. The also on the inability to provide masking in Fig. 2. For example, if the extreme standard Pilot circular dial is fitted and allowances. right-hand curve is examined it will be there is a tone control as well as provision Returning to the Subjective Equality seen that a reduction from zoo per cent. to for a gramophone pick -up.

www.americanradiohistory.com 34 Wireless World, July 9t11, 1937 Listeners' Guíde for CAERNARVON CASTLE, PERSIAN PICNIC duced as a potpourri on Sun- magnificent creation of THE Persian desert was, un- day at 9.5 (Nat.) and again on Edward L birthplace of the til last year, practically unex- Monday at 6.o (Reg.). The first Prince of Wales, scene of ploited by the tourist, but in programme will, no doubt, ap- blood, folly and wisdom, will the summer holidays of 1936 peal to many listeners not receive the King and Queen on Mr. Everet Barger and a party only for its intrinsic interest. Thursday at the end of their of twenty British students but because the songs will be busy two -days' visit to Wales. crossed the Dasht -i -Kavir by given in the language of their There will be a ceremonial car. The 5,000 -mile tour origin. The B.B.C. Chorus procession through the Inner through Persia was organised (Section C) and the B.B.C. for of and Outer Bailey to the dais, the National Union Theatre Orchestra will be Yvonne Arnaud in a " still " from a several presentations will be Students of England and conducted by Stanford Robin- recent television production. She is to made and Their Majesties will Wales. son, who is also responsible for give a pianoforte recital on Sunday at hear an address by the Right A description of the careful the production. 6 (Reg.) Honourable D. Lloyd George, preparations necessary before ' m .1> the party could make the member of the family has Keeper of the Castle. A B.B.C. NEW STARS asked someone down for the observer will describe the journey in comfort and " CAFÉ COLETTE," the mythi- security will be broadcast by week -end, but, by breakfast scene from the Queen's Gate, cal rendezvous created by time on Sunday, the guests, before the arrival of the King Mr. Barger, a 26- year-old lec- A. W. Hanson, the B.B.C. turer on Mediæval History at dazed and exhausted by their and Queen,' and another -will producer, will again be the hosts' efforts at entertainment, take up the story as the Royal Bristol University. He will re- scene of a broadcast at 8.2o on call many of the thrilling ad- have departed. party reaches the Water Gate. Tuesday on the National wave- The whole play is a master- Later, as the procession ventures of the party during makes length. piece of satire and wit. There its way from the Eagle's their eight weeks' tour and give Nicolina, singer of inter- is not a dull moment in the Tower, an observer on the some account of the country national repute, is coming speci- side -splitting " chain of mis- King's Gate will continue the they passed through, and of " ally from Paris to take part in adventures which comprise one story and will describe the the efforts of an Eastern people the programme, which will also of the finest comedies written scene on the dais. to profit from their knowledge bring to the microphone for his in modern English. , " Hay Listeners will also hear a of the West. The talk will be first broadcast here Charles given on Monday at 12.3o (Reg.) Fever " will be heard at 7.45 massed choir of 800 voices Vadja, the Hungarian singer and singing a traditional Welsh air m m m on Monday (Nat.) again who sang with Gitta Alpar in on Wednesday at 8.45 (Reg.). in the broadcast which begins FOLK MUSIC OF ELEVEN C. B. Cochran's " Home and COUNTRIES at 4.5 in the National pro- Beauty " revue. MAJOR AND MINOR" gramme. A COUNTRY'S history is often C. Denier Warren, well BECAUSE they were so good To -day the King will unveil reflected in its traditional known for his work with Harry when they made their first a block of Aberdeen granite music. Dr. Julius Buerger has Pepper's " White Coons " and microphone appearance to- marking the site of the Empire collected the folk music of " Kentucky Minstrels," will be gether not long ago, John Exhibition at Bellahouston eleven countries - England, heard for the first time as Sharman has again booked Park, Glasgow, and listeners Russia, Germany, France, " chef d'orchestre." He played " Major and Minor " to take to the National programme at Italy, Czechoslovakia; Poland, in the Café Colette film. part in the Music Hall broad- will a Austria, 11.50 a.m. hear com- Norway, Spain and m cast tomorrow at 8. mentary from the scene of Hungary. Entitled " Festival HAY FEVER The men behind the name action. of Folk Music," it is to be pro- THE cast of Noel Coward's of the act are Alec McGill and satirical comedy of week-end Fred Yule, and as entertainers manners is now complete. at the piano they have a tech- Marie Tempest, who will have nique which makes them par- her first full- length rôle in a ticularly suitable for radio. broadcast play, heads a dis- During the same programme tinguished cast as Judith listeners will hear Anona Wynn Bliss. making her first appearance in Frank Cellier, who made a Music Hall since the panto- brilliant Quince in the Corona- mime season, and Billy Russell tion week production of " Mid- (" on behalf of the working summer Night's Dream," will classes "). be heard as David Bliss, the m m part created on the stage by BAGPIPES AND ORGAN Marie Tempest's husband, the PIPE -MAJOR LAIN MACDONALD late W. Graham Browne. MURRAY (of Scottish extrac- Other members of the company tion) taught the Duke of include Lawrence Hardman, Windsor (when he was Prince Norman Shelley and Ann of Wales) to play the bagpipes, Trevor, who will be heard in and he is to broadcast with her original part of Jackie Reginald Foort, who arranged Coryton. the programme after a recent The action of the play is set audition at the B.B.C. in the riverside home of Judith Theatre Organ. In comment- Bliss, famous actress, who has ing on the broadcast, Reginald A scene from the stage production of " Hay Fever," showing Marie recently retired from the stage, Foort remarked that, to him, Tempest, who will take part in the broadcast version of the play on her husband, David, and their Scottish music had just been Monday and Wednesday son and daughter. Each Scottish music until he , met

www.americanradiohistory.com Wireless World, July 9th, 1937 35

Orchestra, conducted by Clifton Helliwell, Eda Kersey will be Outstanding Broadcasts the soloist on Wednesday in Mario Castelnuovo- Tedesco's he Week at Home and Abroad violin concerto, at 3.15 (Reg.). At 8.2o on the same day Alex- Pipe -Major Macdonald Mur- ray ; then he discovered to his surprise that it is divided into CaernarvonCastle, which is the scene three distinct types - the of a National Border ballad, Gaelic music transmission on and Highland pipers' music. Thursday, when " Originally," he said, " the the King and Queen will be re- pipes were to be accompanied ceived there. by the Theatre Organ because I can easily get it to imitate bagpipes, but the scale of the two instruments is quite different. That of the pipes is the courtesy of definitely Arabic, proving, I the National think, that they were of Broadcasting Eastern origin. We shall, there- Corporation of fore, play just one tune to- America, on gether to let listeners hear the Saturday after- strange effect." noons, a typi- During . the programme cal light pro- which will be radiated Nation- gramme such ally at 9.35 on Saturday, re- as was being presentative pieces of the three radiated in types of music will be played. America. The First a medley of Border programme was given under MUSIC ander Moskovsky will give a ballads, then James McPhee the title of " Five Hours ON Sunday at 9.5 (Reg.) the violin recital, also in the will sing a selection of Gaelic Back," which is the difference B.B.C. Midland Orchestra with Regional programme. songs, and the pipes will after- between New York and Green- the B.B.C. Midland Singers, Eileen Joyce will play the wards have a few minutes to wich time. conducted by Eric Warr, will solo piano part in a " French themselves. Listeners who like to com- broadcast a programme of Mountain Song " by Vincent m pare the broadcasting systems music by Vaughan Williams, d'Indy, with the British will including the Overture, The Women's Symphony Orchestra, MICAH CLARKE of England and America be interested to hear the first of Wasps. Arnold Matthews will conducted by Boyd Neel at 8 THE late Sir Arthur Conan sing Five Mystical Songs. on Tuesday (Reg.). Doyle, though famous for his another series of trans -atlantic broadcasts to -night (Friday) at Accompanied by the Empire THE AUDITOR. creations of imagination, wrote ` several historical stories which 7.30, when ' Five Hours adhere very closely to fact. Back " re- HIGHLIGHTS OF THE WEEK enters British FRIDAY, JULY 9th. ¶Hay programmes. Fever. 9.35, Haigh Mar- Nat., 7.15, In Other Gardens : talk. shall String Orchestra. The new 7.30, " Five Hours Back." 8, Reg.. 6, Folk Music. 8, Geraldo series will be Music from the Movies. ¶London and his Gaucho Tango Orchestra. Traffic-reminiscences. ¶B.B.C. Scottish Orchestra. Reg., 6, B.B.C. Theatre Organ. Abroad. 8, Orchestral Concert. ¶Blue- Stuttgart, 9.15, Songs of the German beard. 9.45, Three in Waltz Mountains. Levy Louis Time. TUESDAY, JULY 13th pres e nts Abroad. Nat., 6.25, Theatre 8, " Music from Paris PTT. 830 Symphony Con- Organ. British Diarists. the Movies " cert from the Casino Vichy. ¶Café Colette. to -day at 8. He 9.40, Chamber Music. is seen here SATURDAY, JULY 10th. Reg., 6, Eugene Pini and his Tango with Robert Nat., 730, A.B.C. 8, Music Hall. Orchestra. 9, Swift Serenade. Ashley, one of 9.20, Monthly Affairs (from Abroad. his vocalists. America). ¶Orchestre Ray- Munich, 8, " The Dardanelles - monde. Gallipoli " -pages from history. Reg., 6, The Luton Band. 730, WEDNESDAY, JULY 14th. was one of these, broadcast every Friday from Frank Merrick (pianoforte). Micah Clarke ¶B.B.C. Midland Orchestra Nat., 6.20, Peter Yorkc and his and a broadcast version of it 7.30 -8 p.m., the last pro- Abroad. Orchestra. 7.40, Background to Sport. 8.20. Radio will be heard on the Regional gramme being on October 1st. Milan I, 9, " The Force of Destiny ": Rodeo. Reg., 6, B.B.C. Scottish Orchestra. wavelength at 9 on Thursday. The National Broadcasting opera (Verdi). 7.30, Stop Dencing ! -light music. The play reconstructs the Corporation proposes to intro- SUNDAY, JULY 11th. ¶Hay Fever. Battle of Sedgemoor and al- duce as much variety as pos- Nat., 6, Talk by H. de Vere Stac- Abroad. though it will not be broadcast sible in this series, but it poole. 7.55, Service from St. Berlin, 8.10, Military Band Concert. should be borne in mind that Martin -in- the -Fields ; the address THURSDAY, JULY 15th. on the actual anniversary of by Lord Halifax. the battle, it is being presented it is the ordinary sustaining Reg., 6, Yvonne Arnaud (piano- Nat.. 6.20, They Came to see only ten days afterwards. The programme which is being forte). ¶Commodore Grand England : talk by Roger Falford. Orchestra. 10.5, Fred Hartley Piano recital by Susan Slioko. production is by Cyril Wood radiated from their own aerials. 7.25, Shows from the Seaside, 2. It is by radio link that the and his Sextet. and the play has been adapted Abroad. Reg., 6, B.B.C. Military Band. by John Hollaway. programme comes to us, it Kalundborg. 8.50, " The Elusive 8, Radiovue. 9, Micah Clarke: play. m being picked up at Tatsfield Melody " : musical comedy. Abroad. FROM AMERICA and thence relayed by land MONDAY, JULY I2th. Cologne, 8.10. " The Dance " : LAST year the experiment line to London and the trans- Nat., 6.20, Tricks of the Trade. four centuries of dancing. was made of relaying through mitters.

www.americanradiohistory.com J6 Wireless World, July gth, 1937. HINTS and TIPS APART from a rather high -pitched hum being that either a high or low reading Practical Aids to which is often experienced where instrument may be used. mains input filtering is inadequate, uni- Referring to Fig. I, if we connect a volt- versal AC / DC sets are usually fairly free meter between point A and chassis, and Better Reception from mains hum when connected to a DC proceed to short- circuit the oscillator supply. It sometimes happens, however, tuning condenser, the resulting cessation that when the supply of oscillations should cause a change in is changed over to AC, voltage to be shown. If there is no move- punity. Actually, nothing could be in Hum or the owner moves to ment of the meter needle, it is fairly safe farther from the truth, and opportunity AC;'DC Sets another district where to assume that the valve is not oscillating. is taken here to warn readers that a the supply is AC, Actually the test may be made rather ' ` live " battery set needs to be handled there is found to be an unpleasant back- more convincingly by applying the volt- with discretion. ground of hum which was not present meter to point B or C, as the total anode before. Reversing the mains plug in its current (and consequently both the screen Fragile Battery Valves socket sometimes effects an improvement, and automatic bias voltage) will be but if the set has been in use for some con- affected by the change. In practice it is To begin with, the battery type valve is siderable time it is more probable that the advisable always to use one or other of notoriously delicate, and, because its fila- cause of the trouble is imperfect insula- these two positions, as in some cases the ment can be destroyed by even the briefest tion between heater and cathode.of one or connection of a voltmeter across the short- circuit of HT through it, needs very more valves. This is a fault which is apt cautious treatment when compared with to develop gradually in use, and although the much more robust mains types. Valve a valve may work quite blamelessly on burn -outs, however, are less common DC, it may nevertheless be useless on AC nowadays, due to the use of practically on account of hum. This trouble has fool -proof on -off switches and to the more been particularly common amongst widespread knowledge that accidents of American midget sets, which seems to this kind can never occur so long as the suggest that heat dissipation may have LT accumulator remains directly con- some connection with it. The valves nected to the valves ; but it is probably likely to be affected are detector and AF not so widely realised that, in spite of this types in general, and particularly diodes. precaution, it is still possible to do other damage, just as serious and irrevocable, by carelessly short- circuiting points at HT potential to the chassis. T N seeking for the cause of " no signals " In this case the responsible factor is the A in any superheterodyne, the logical particular nature of the power obtained trouble- tracer, having satisfied himself from primary batteries. In a mains set first that the AF amplifier is functioning the resistance of the rectifier and smooth- normally, will then try to find out whether ing circuits is always large enough to limit the frequency-changer valve is oscillating. the current that can flow in the event of Unfortunately it is a short- circuit to a fairly low value; for not possible to Is it make this reason, almost any amount of prod- certain of this with- ding can be indulged in with a mains set Oscillating? it out some kind of Fig. 1. -Is oscillating ? without serious risk of trouble. An HT meter ; the usual itself is sufficient steip battery, on the other hand, has only its a milliammeter in the oscillator coil to method is to connect to own internal resistance -a few ohms. anode circuit, and then to oscillations and so nullify the test. oscillator Both points are conveniently accessible by Consequently, a direct short may allow a effect of short -circuiting either observe the raising the valve just sufficiently to allow current of several amperes to flow or reaction coil. If the valve is the grid a thin prod to make contact with its pins. momentarily- enough to do considerable oscillating there will be a change in the damage, quite apart from its bad effect anode current, and, if not, no change. on the battery itself. An obvious disadvantage of this method THERE seems to be a general impres- One of the commonest examples of the is that it is usually far from convenient to sion that if, either carelessly or in- more serious accidents that can occur is break any connections for the purpose of tentionally, an attempt is made to a burning -out of an IF transformer, connecting a milliammeter in circuit, par- investigate the inside of a mains set with- caused by an uninsulated anode thimble - ticularly when it becomes necessary to out first switching off the risk incurred clip being allowed to touch any part of the remove the set from'its cabinet in order to in doing so is far greater than in the case chassis ; a very few moments is usually do so. What is wanted is a method of of a humble battery sufficient to burn out the primary com- obtaining the vital information without set. This idea is Battery pletely. Similarly, of course, an HF going farther than removing the back of somewhat misleading, Power -a choke, any anode -circuit RF or IF coil, the set. because, although the Warning or even an output transformer, is liable rather obvious risk of to be damaged in the same way, and, even Detecting Voltage Changes shock is undoubtedly more serious though it should be removed before the with the all- electric set, there is damage is obvious, will usually have its The following method, which is used by another and more material risk to be efficiency seriously impaired by the over- the majority of busy servicemen and considered -that of damage to com- heating. applies to any type of frequency -changing ponents -and it would be unfortunate if It should be added that these remarks valve, is probably hard to improve upon. by comparison the battery set should come apply with even greater force to HT It is based on the foregoing method, but to be regarded as not requiring the same accumulators, Of which the internal re- makes use of a voltmeter instead of a respect, and, therefore, as something with sistance is extremely low. The moral, of milliammeter, an additional advantage which liberties may be taken with im- course, is " Disconnect the HT First ! "

www.americanradiohistory.com Wireless World, July 91l1, 1937. '37 LETTERS to the EDITOR The Editor does not hold himself DF Experiment listening 3 to 4 watts output is surely responsible for the opinions with a will avoid AM in process of developing a direction - enough speaker that boom of his correspondents finding instrument based on a novel prin- and provide a reasonably bright " top." ciple, but find to my regret that my prac- Could we not have a constructional article tical knowledge of construction is too limited on such an outfit, please? to cope with the layout of such things as Manchester DONALD H. SMITH. photo -electric cells, etc. If any one of your Some valve makers give their ratings at readers who is interested in this kind of con- 5 per cent. total harmonic content, others struction would care to co- operate, I should at 9 per cent., while still others give ratings be very glad to hear from him. Long - distance Television Reception for z per cent. and io per cent. These last two are C. G. WILLSON- PEPPER. enclosing, in holy they will called the undistorted and maximum IAM the that outputs. This method " Harbourne," Hawks Hill, Leatherhead. be of interest, some snaps of television seems to me the pictures recently received at Ipswich. fairest, but few set makers are likely to ; if Straight u. Superhet On some the heavy interference experi- adopt it the valve will give 6 watts out- enced here plainly shows. I am using an put they will claim this, even if the 6 watts LIKE many other people I was interested is for 3o per cent. distortion. in wireless in a casual way from the arrangement for filtering the synchronising pulses that Mr. Tyers kindly sent to me and The audible effect of distortion, however, end of the Great War, and I listened (on is not as simple as it seems. very elementary apparatus) to the earliest synchronism is maintained at all times. Acoustic com- These snaps were taken with a Leica parison has been made with various valves, " broadcasts " from Chelmsford. My elec- triode, pentode and beam power valves, trical knowledge is not deep, and I suppose caitera, f2 lens, } to sec. exposure, Kodak Super X panchromatic film. singly and in push -pull, with and without I was a " constructor " rather than a negative feed -back. It has been found that i genuine experimenter. I built crystal, 5 per cent. second harmonic has no harm- crystal -valve, reflex, and various other cir- ful effect, and ro per cent. is tolerable for cuits that promised great things if only re- reasonable quality. When the even har- action could be controlled. After several monics are balanced out, as by using push - I a neutralised. HF affairs went back to pull, 5 per cent. of third harmonic mean- is annoy- det. 2LF set for quite a long time, ing and io per cent. is really serious. Har- while realising that the superhet was beyond monics of higher order, especially uneven, my knowledge, and anyway could be cannot be tolerated when they exceed r per bought more cheaply than it could be cent. one " constructed." Eventually I bought I would suggest, therefore, the rating of a some- of most reputable breed, standing valve be based upon the audible effect of what between the production jobs and the distortion by using a distortion factor which individually built regardless -of -cost outfits. can be evaluated from a formula which And what a life I have had ! suitably combines the actual amplitudes of Quality, for domestic requirements, was the harmonics. For example, the formula its quite nice at first. Then one of speakers might be P =a when P is the distortion occa- +3b evidently couldn't take the punch it factor and a and b are the amounts of sionally got and started a whole lot of TELEVISION AT 65 MILES. Allowing for second and third harmonics respectively. was rattles. The wave -change switch a the loss of clarity incidental to the process The factor 3 by which the third harmonic curse. So was an extension speaker jack. of rep -oduction, these untouched photographs is multiplied is the amount by which the The IF trimmers appear to unscrew them- give an excellent idea of the high standard harmonic is of reproduction attained by Mr. West at third more objectionable than selves at intervals, and several expensive the same amount of second. Thus, a valve valves have gone Ipswich. and amazingly complex giving a certain output with 3 per cent. most of these are west. Granted second harmonic and 2 per cent. third, mechanical faults, but the superhet layout would be given a distortion factor of 6, doesn't help one to get at them for easy whereas one giving r per cent. second and repair. Now what of the superhet part 3 per cent. third harmonic would have itself ? P =ro. On the normal method of rating It will " get " about 35 to 4o medium - each valve would be given the same dis- wave stations but only about five pro- tortion of 3.16 per cent. grammes, and I should say that of its time P. WINKELER, Radio Engineer. in use, it is tuned thus : North Regional, Antwerp, Belgium. 85 per cent., North National 24 per cent., Midland Regional 0.95 per cent., " listening to Eufope " 0.05 per cent. Now, why should I, have a superhet? I don't want Horn - loaded MC Loud Speakers distance, I don't want short wave, I don't IWAS very interested to read the letter want long wave. Isn't my radio history of Mr. Wykes in your issue of June 28th. that of thousands of others? I am fond of The information that he gives is most in- good music, but my taste is catholic ; Bach, structive, but, while I do not wish to dissent Wagner or Gershwin all have a place. I from his conclusions, there are several criti- would rather hear them well from the local Although not quite as good as the original cisms to be made. than badly from Schenectady, Prague or picture received they indicate pretty well The " well -balanced " jury contained two Peru. I want the news of the day, and I the type of results obtainable here. people " without knowledge or special in- wish to keep pace with the trend of human Ipswich. S. WEST. terest in wireless or music." Such people progress and endeavour -it is part of my are notoriously unreliable critics. job to do so. Valve A zft. 6in. baffle is not large enough for Speech and music of good quality, there- Ratings the Goodman unit. Of what material was fore, from the local B.B.C. transmitters are IN a letter appearing in The Wireless the baffle made? My Goodman's roin. what I need, and the straight set will do all World for May 21st, J. B. rightly draws High Fidelity Auditorium Speaker is that is necessary'. But who makes one at our attention to the fact that certain valves mounted on a baffle made of two thicknesses a reasonable price to give good quality of are rated at 3-1- watts, while another set of Celotex. Its area is about 28 sq. ft. and reproduction? maker claims for the same valve an output it is secured to a very rigid wooden frame. Must I turn constructor again? The of only 24 watts. This naturally raises the When the speaker is mounted on a plywood negative feed -back amplifier in The Wireless question of what the output of a valve really baffle, eft: square, the reproduction is de- World, June 28th, fed by a simple detector is and when it can truly be called undis- cidedly inferior. should answer my needs. For domestic torted. I cannot see why gramophone records

www.americanradiohistory.com "Vp®Ilsoo . 38 JULY 9th, 1937 Wcp11cl

were used for the test. The B.B.C. at its make such disturbance illegal, both for the a " bust in the lug " from MSU's 5 kW best surely gives superior quality. manufacturer and also for the user of elec- spark, I should like it to be known that the In view of the great difference in the price trical apparatus who fails to maintain his enormous improvement of the past twelve of the units under discussion, it is remark- purchases in good, silent condition. years is still adding unto itself. Here, at able that they are comparable at all. Fed My set employs a self -contained frame the river gate of London, it is obvious. Only by a local- station receiver coupled to a modi- aerial, but I can see no reason why, as a one of every twenty -five ships passing in- fied version of the " W.W." Push -pull listener. I should be compelled to change or wards is audible as she gives GNF her QTP. Quality Amplifier, the Goodman unit gives adapt my set. That is putting the cart Outward TR's are scarcer. superior fidelity to many of the efforts of the before the horse, and is as absurd in its own However, seeing that the dogs of war have B.B.C. The inferior quality of outside way as it would be to inform the victim of been suitably unleashed on the real culprits broadcast (e.g., the recent broadcast of the an assault that he shouldn't have been and offenders, the shipowners, I will leave Aldershot Tattoo) is unpleasantly apparent, there the matter to the public -spirited few to fur- and the distortion in some of the gramo- I would suggest that people responsible ther without even saying anything a bit phone record programmes is shown to be for broadcasting static should at least be unkind regarding the " little higher tech- simply appalling. made to take out a transmitting licence ! nical qualifications " of the poor operator. I think that Mr. Barden was unwise to ' T` . J. E. WARBURTON. I will not dispute that strange and fearful challenge the superiority of the Voigt com- things happen to those who go down to the bination, but his firm has certainly made a A Devonian P r oblem sea in ships (I remember the weird behaviour reproducer of considerable value to many RECEPTION in the County of Devon is of an "1r F " DF under calibration due people who cannot afford to buy the more to three diligent lascars inside the frame), expensive horn- loaded equipment. not too glorious at the present, and with the new transmitter to be erected at Start but, for the love of Pete, what kind of ships I have no connection with either firm. shift stays and derricks once they are at sea? Isleworth, Middlesex. D. ROGERS. Point we should get better conditions. But will we? Maybe we shall hear something more First, we have a very powerful station, about it all. GRANDPA. PA Systems Rennes -Bretagne, Ito kW. at 1,040 kc /s. Gravesend. 1912 -1930. IWAS interested to read the remarks of This is liable to cause side -band splash, and " Diallist " recently regarding the low in- is certainly going to ruin the hopes of any telligibility of the majority of PA systems local " quality enthusiasts. and the improvement that can be obtained Secondly, what of West Regional or the by a low- frequency cut-off. Welsh, as it will then be? It is 246 kc /s This is a matter which does not appear lower than the proposed new transmitter, The New Philips to be generally realised, and as a result i.e., twice 123 kc /s. This is a popular much money is wasted on microphones intermediate frequency amongst certain which are wholly unsuited to the high -level manufacturers, and it seems that the Welsh Car Radio radiation of speech. The confusion appears programme is going to suffer from whistles to arise from failure to distinguish clearly due to second -channel interference. IN general principle the latest Philips between the frequency characteristic and the Some sets have come to my notice that " Motoradio " follows its, predecessor, but non-linear distortion of microphones. There give whistles on " West Regional " due to radical changes have been made in the lay- can be no doubt that high speech intelli- " Rennes-Bretagne." The outlook for the out and mechanical design. The six -valve gibility is best secured by a rising frequency quality enthusiast and the layman looks for- superheterodyne circuit has been produced characteristic and a sharp low- frequency midable. The majority of listeners will still specially for the conditions of road recep- cut -off, but, in addition, non -linearity must have their sets tuned to their favourite tion, with special attention to sensitivity be reduced to a minimum. In practice, in " Fécamp " or " Luxembourg " during most order to obtain a low value of non -linear of the day, and will not notice the distortion, microphones of the so-called changes so quickly. They've been inoculated "high- quality " type (i.e., moving coil or already ! transverse current carbon) are used, and Here's to July 1st and hoping- their relatively flat frequency characteristic Exeter. A. G. P. MOWER, B.Sc. gives rise to the low intelligibility of which " Diallist " complains. This flat frequency characteristic, which is not required for PA Marine Wireless Gear working, is obtained at the expense of NOW I am an old, old man. Indeed, I output. was an old chap when they dis- Surely, in the case of those PA systems entangled my barnacle -laden beard from the which are required to radiate speech and key contacts, assured me that MPD was music from a pick-up, the reasonable solu- dead, that Ushant Radio was no longer tion is a straight, high -quality amplifier and FFF, that nobody used " gravel cracker " a microphone which, so far as non-linearity fixed gaps; and that the bulbs blossoming is concerned, is in the high -quality class at my elbow were " short-wave onions," and yet has a frequency characteristic of the after which they gently put me ashore in a shape required. J. R. HUGHES. baggage sling. London, S.E.7. Sitting in my chimney corner I do sometimes mutter about ten -inch coils, and recall Interference Reports the fiendish gurgles, glugs and chuckles of ICANNOT allow the comments of Mr. MRA trying to strike his " modern " io kW arc -and I am glad they are gone Philip W. Crouch, in your issue of Mas' -but Completely self- contained in a cabinet 91 X 21st, to pass without a reply, which I hope True, I can corroborate " Operator's " 8 x 7 in. the new Philips " Motoradio " you can find space to print. remarks on antiquated gear (I know of receiver can be fixed in any position by a I am not sure of the exact date when .l several passenger ship stations still function- single bolt. made my complaint and received my visit ing on gear at least seventeen years old), and from the engineers, but it was some time In some respects, too, I can offer the sym- and efficient AVC. New miniature valves during 1935. For all I knew to the con- pathy he seems to need. We who fought are employed, and a low -pass aerial filter in trary when I wrote on the subject to Wire- and bled with early S / W gear and DF had conjunction with a tuned U- shaped aerial less World, Post Office engineers may drive our soul - searing experiences. gives effective elimination of ignition inter- about in Rolls -Royce saloons nowadays! Still, I can't remember anyone trying to ference without resorting to the use of sup- The fact remains that two years ago they calibrate his transmitter by his own receiver. pressor resistances in the plug leads. arrived more humbly, and during a'thunder- That would have been asking a lot of both The set is now entirely self-contained with storm, and departed without requesting me sides of the installation (or am I old - its PM speaker, designed to take into to fill in any forms whatever. I still con- fashioned? ). There were other ways, even account the acoustics of the average saloon sider that the present method of dealing without a wavemeter. But that was long car. A single bolt fixes the complete set with interference is too long -winded and ago; the art may have died. to any part of the car and flexible leads clumsy, especially when the interference is And because my aged ears (phone cal- from the steering -column control panel are intermittent The only effective cure is to loused though they be) still echo at times to attached to a swivelling junction box, so

www.americanradiohistory.com JULY 9th, 1937 WhosgIl@oo 39 WOpIld that sharp bends are avoided. The colour- Power consumption is rated at 33 watts illuminated dial for the medium and long from a 12 -volt system, and the set will work wavebands and the electrical locking device either with a positive or negative earth. are retained, but a new departure is to be HT is derived from a vibratory unit. The ep found in the wave- change switching, which price is 14 guineas and there is a de luxe is now effected by a magnetic relay instead model with separate loud speaker at 16,E of mechanically as in the earlier model. guineas. McCAIR1f IF1/ Listening In Europe OUTSTANDING 9 -VALVE SOME INTERESTING STATISTICS ALL -WAVE SUPERHET For all - wave reception By A. R. BURROWS at its very best THE year 1936 was notable for the the million mark, while, judging from the To the all -wave enthusiast, this exceptional receiver large increase in the number of increase shown since January, Belgium and offers a number of interesting features, with'quite unusual broadcast listeners in Europe and in Czechslovakia will probably reach seven range, and power output. Few receivers at present on the non- European countries bordering the figures before December 31st. Among the the market can claim so high a standard of design and Mediterranean. This increase, which is smaller nations the biggest progress is being performance. based on the number of licences issued in made by the Irish Free State, Jugoslavia and the various countries concerned, was 12.8 Latvia. per cent. over the 1935 figures. The total In the case of all countries. the biggest 12 number of licences in force at the end of GNS. 1935 was 24,575,000. By the end of 1936 this had risen to 27,719,925. F o r obvious reasons the figures for Spain during the past year in- o 7 have not been z cluded. Statistics for 6 the U.S.S.R. are not oD given for either F year. Allowing an aver- ó age of four listeners ó4 r to each licence, the cc ¢ o á z z total wireless Z 3 z 5 a z audience in Europe x O (Complete ¢ with 9 B. V.A. and the Mediter- 2 valves.) ranean countries on 5 rz December 31st, 1936, W o w was well over 110 O. o 4 wavebands : 12.8 -33, 29 -80, 190 -550, 800-200) metres. Illuminated dial with principal station millions. It is note- names. Separate coloured lights for each wave- worthy that . Bul- band. garia alone among Controls. -A feature of the receiver is the number European countries of independent controls fitted, making it extremely showed a decrease interesting to operate. These include : sensitivity in the number of control (varying bias on R/F stage). Q.A.V.C. with listeners. At the manual muting control, and switch for inter- station end of the noise suppression. Separate potentiometer bias controls other for output valves. 5- position wave-change and gramo- comes e r- scale G phone switch. Progressive variable tone control many where a 11 operative on radio and gram. records were broken, Circuit in Brief. -Aerial input to pre -selector circuit radio with an increase of frequency amplifier, latest type triode- hexode frequency changer, 2 band -pass I.F.T. coupled I.F. amplifiers, double diode detector, L.F. amplifier, parafeed transformer- coupled push-pall triode output giving 6 watts. Heavy cadmium -plated steel chassis. Fines: compon_nts and This diagram enables workmanship throughout. a mental picture to be A.C. models ready for immediately delivery. A.C.'D.C. models also in production, and will be available formed of the distri- for delivery shortly. bution of listeners DE LUXE MODEL 14 GNS. among the various Several additional refinements - full particulars on European countries. application. T h e shaded portion IMPORTANT indicates the position The prices at which McCarthy Chassis are advertised at the end of 5935, include Marconi Royalties. " Wireless World " readers should for their own protection, make sure before the white part purchasing any receiver that the quoted price includes representing the the Royalty payment increase during 1936. Al! McCarthy receivers supplied complete with valves, knobs, pilot lamps, leads, mains cable and plug. 12 months' guarantee. increase in the number of licences takes Deferred terms on application, or through London 975,000. In the matter of percentage in- place, as one would expect, during the winter Radio Supply Co.. 11, Oat Lane, E.C.2. crease, however, the palm must be awarded months, but even in the summer relatively Cash with order on 7 days' approval. Also write for illustrated catalogue of complete range of all to Palestine, the actual figure being 67.11 per good progress is shown so far as the majority McCarthy receivers. cent. Luxembourg was not very far behind are concerned, there being comparatively few with a 66.67 per cent. increase. instances where a decrease is shown during MCCAIL1FIFI'Y lRÀIL110 ILri, Since the beginning of the present year the proverbially slack season for broadcast 44a, Westbourne Grove, London, ßi'.2 and Holland Switzerland have both passed listening. Telephone : Bau,water 3201/2

www.americanradiohistory.com Wireless World, July geh, 1937. Broadcast Brevities Since then the programmes have NEWS FROM PORTLAND PLACE been vicariously so -so, good, and marvellous. This is mere his- Wales and the West the dailies would print the facts; tory ; but alas, the fame of all ALTERATIONS entailed in as, for example, when a shut- the activities of Mr. Gerald. Cock the separation of Wales and down is due to the grid blocking and his staff at Alexandra the West have involved the re- condenser on a particular unit Palace seems not yet to have arrangement of certain wave- failing, or owing to a blown fuse penetrated to America. They -in lengths which can be seen at a the EHT circuit in a modu- are now in the throes of inaugur- glance in the table below. lator panel. What would the ating a television in con- Ordinary service Plymouth and Bournemouth reader make of the nection with the 1939 New York low -power transmitters, oper- " overheating of a right -hand World's Fair, and in announcing ating on 203.5 metres (1,474 anode closed circuit tuning con- the fact the National Broad- kc /s), will transmit the same denser," or of a " lead- covered casting Company of America programme as the West of Eng- grid circuit wire sagging on to affirms that demonstrations of land Regional transmitter, ex- HF bus bar in final RF ampli- the " marvels of sound and sight cept at those times when this fier "? Here is a typical entry broadcasting " will be brought transmitter is silent or is radiat- in the engineers' log -book : to visitors " for the first time in ing the National programme, " Array 19 shut down to replace radio history " in a building when they will radiate the Lon- stand -off insulators on array. being constructed on the fair- don Regional programme. 18.27.30 power on after tempor- ground in New York City. Lord ary repair. 18.27.50 temporary Selsdon, Sir Noel Ashbridge and Area That Start Point repair effected. Changed to array their colleagues of the Television Will Serve 1 (294 deg.). Power on 18.32.0o. Sub- Committee and the B.B.C. 18.46.30 power off The new arrangement for the to change may or may not be delighted at SKY SCRAPER. The tele- West of England is temporary, back to array 19 (16o deg.). the news that America is about vision aerial on the top of the and when the high -power sta- After further attempt at repair, to make television history in Empire State Tower in New tion near Start Point, in South repair successful." If that this way. York. The range of the trans- Devon, is completed (the con- wasn't a technical hitch, what mission is stated by the N.B.C. struction will begin shortly), it was it? to be nearly fifty miles. will take over the West of Eng- A Family Muirk land Regional programme from Television's Extra Hour WELSH Wales is still in the New Radio Drama the Washford transmitter, using THE extra hour's television broadcasting limelight. AS a pendant to the details of the wavelength of 285.7 metres. transmission announced by The B.B.C. announces fre- the next ,three months' The station is intended to serve the B.B.C. in May last has now quently new appointments to its variety programmes given re- the whole of Dorset and most of been fixed to start on August Welsh staff -it is becoming the cently in this page, here is news Devon and Cornwall, but it will 23rd, that is, a week most hefty of all regional staffs of the B.B.C.'s second " big after the pull," as radio not serve Bristol and certain service is resumed following the -and too often the officer ap- drama has been pointed is described as " the son called. Nine new productions areas in North Devon and three weeks' suspension of all Somerset. For that purpose a transmissions from Alexandra of an eminent Welshman." One will be heard by listeners during medium -power relay station is Palace. Instead, however, of these days listeners may ex- July, August and September. of pect to hear of Marie Tempest will to be erected on a site which has the extra period being from 12.30 the appointment play the lead of an eminent in Noel ; not yet been chosen. It will to 1.3o p.m., as originally ar- Welshman him- Coward's " Hay Fever " self. another play will be `' The take over the 203.5 metres wave- ranged, it will be from 11.30 te, 4,1 4,1s Lunatic at Large," adapted by length from Bournemouth and a.m. to 12.30 p.m., which, for Plymouth, whose -service areas Lance Sieveking from the well- some reason or other, is con- Transmitter known novel by Storer Clouston. will be covered by the high - sidered to be more suitable for Synchronisation power station at Start Point. " Taffrail's trade purposes. Perhaps the IF the feeling of the Summer " Thriller earlier period is regarded as Meeting at Lausanne of the Marianne Helweg, one of A Technical Hitch causing less interference with International Broadcasting Sieveking's colleagues on the TEMPORARY suspensions of the trade's luncheon period. The Union is any guide to the inten- staff of the Drama Department, transmissions are generally afternoon transmissions, which tions of the Cairo Conference of has adapted that charming fairy stated in the popular Press to normally take place between next spring, it is a foregone story, " The Little Mermaid," be due to " a technical hitch." 3 and 4 p.m., will be from 4 to conclusion that the future of by Hans Andersen, and it will So much easier on the layman's 5 p.m. during the period of the broadcasting will be concen- be produced by Val Gielgud, eye and mind than a full -blown exhibition at Olympia only. trated to an increasing degree on B.B.C. Drama Director. " Taff - technical explanation, but a 1.,1 Cs, GO the synchronisation of trans- rail," whose identity was dis- cause of amusement to the radio ';For the First Time ..." mitters for national systems, covered some time ago as that journalist, who assumes that BRITISH television is gener- while the sharing of wave- of Capt. Tapprell Dorling, R.N. the simpler statement is due to ally considered to be ten lengths between different coun- (retired), has written a new play annoying reticence on the part months ahead of other countries. tries will assume less importance. entitled " S.O.S.," which proof the B.B.C. It was demonstrated at The Summer Meeting indicated vides bim with a theme from which he can wring the last Radiolympia in August last ; a its belief in this development. Supper Table Problems regular service was inaugurated ounce of drama without destroy- ing the probabilities. If, however, Broadcasting by the British Postmaster - Long -wave Problem , House were to go more closely General in November, 1936, As to the long waves, no solu- From the Regions into detail, it is unlikely that with a flourish of trumpets. tion could be found under the The regions will have their Lucerne Plan of the serious cases share of the limelight. " Storm of interference between Programme Transmitter. Location. Wavelength. Frequency. several in a Teacup," James Bridie's stations ; this matter will prob- brilliant adaptation of a German Welsh .. West Regional Wachford .. . ably have to be dealt with at comedy, will come from the Penmon .. .. Penmon.. } 373.1 metres 804 kc /e. Cairo ; but another meeting of Scottish Region. George Eliot's West of West of England Washford .. 285.7 metres 1,05010/s. the U.I.R. will be held before " Mill on the Floss " is Midland England Regional then -at Nice in November or Region's offering, while " The December next ; and the final Playboy of the Western World," National .. Droitwich National Droitwich 1,500 metres 200 kc /s. London National.. Brookman's Park plans for the big International by J. M. Synge, and " Bird in North National .. Moorside Edge.. }. 261.1 metres 1,149 kc /s. Radiocommunications C o n f e r- Hand," by John Drinkwater, Scottish National .. Westerglen ence at Cairo will then be will be contributed by Northern drawn up. Ireland and Western regions.

www.americanradiohistory.com Wireless World, July 9th, 1937 On The Short Waves

DO sunspots give rise to good or bad I NOTES FROM A conditions? I must apologise to ! LISTENER'S LOG readers for once more returning to 1 this question, but so much is now being written generally about sunspots and their two transmitters working isochronously associated on electromagnetic manifestation GSG 17.79 Mc / s, one for the Far East and that one would like again to set forth what the other for India, Ceylon and is believed Malaya. to be informed English opinion One of the 17.79 Mc / s transmitters remains on this subject. There are two schools of in,use until midnight B.S.T. thought on the subject. The Americans who Yet some of the British manufacturers believe that sunspots presage poor condi- recently advertised in Eastern journals re- tions, and whose opinions are probably fol- ceivers which only tuned down ! lowed to 19 metres rather too slavishly by a number of I think the conclusion is that if amateurs in you are this country who illogically prepared to make full use of the 19 Mc / s assume everything from the U.S.A. to be band, changing to somewhat lower fre- good, and rarely give a thought to the quencies at night if necessary, " prophets " but rarely in their own country. Some of below 10 Mc / s, then on a 24 -hour basis the British scientific research group have short-wave conditions in the sunspot also inclined maxi- to the American view. mum years are much superior to those of the A careful study of the situation, however, minimum years. If you confine your con- based on over twelve years' detailed listen- sideration to certain parts of the day (the ing below loo metres and the practical ex- transatlantic telephone service may provide perience of operating world -wide short-wave an example), then you may be able to dis- circuits, leads one to the definite conclusion count the very poor night conditions of the that sunspots are much more useful to the minimum years, those blank nights when short-wave engineer than he is prepared to only 4 Mc / s (7o metres) or long-wave opera- admit. tion is possible. I/ \® \11 The average transmission engineer and Finally, it was rather amusing to note writer in the popular Press pays far too much rather poor conditions prevailing during the attention to occasional or transitory dis- past week-end (June 27th), which on investi- turbed conditions andfade -outs which natur- SPECIFIED gation proved most probably to be due to a ally occur more frequently during the sun- noticeable fall in solar activity, since in place for the spot maximum years than during the in- of the now usual moderate to high activity terim periods between the maximum and " Wireless " only one or two sunspots were visible ! World minimum epochs. With the transatlantic radio -telephone service using WKN and WKF in the 19 Mc / s " Five Hours Back " Relays band, and WLA in the 18 Mc /s band almost TELE V ISION exclusively, it is easy to see that 14 Mc /s A bare two years ago, however, when amateur signals will be poor at present. only a single sunspot was to be seen every Owing to the sunny days ( ?) little detailed RECE three or four weeks, transmission conditions listening has been done during the past fort- IVER from the U.S.A. were so poor that the night, but it is thought that a few notes on B.B.C. could not continue its " Five Hours new transmitters and new frequencies for V I S I O N Back " relays later than 5 p.m., and even old ones would be helpful. then one or two of the relays were quite The station causing the heterodyne on 6 0.01 mfd. mica. "M" poor in spite of all the efforts of the modern JZK on 15.16 Mc / s is believed to be Stock- Price each 21- JUST as in the very beam diversity holm SBG 15.155 Mc /s, but the Mexican equipment at Tatsfield and 3 0.0005 mfd. mica. "M" first days of Radio - the numerous transmitters in operation on transmitter XEWW has also been heard Price each 9d. and before-T.C.C. operating on 15.16 Mc / s. The Javanese sta- the other side. 1 500 mfds. 12 volts, Condensers always This year it is proposed to conduct an- tion YDC at Soerabaja is now working on Electrolytic. 501. Price 6/- featured in outstand- other series of " Five Hours Back " relays 9.548 Mc /s, and COBC, a new Cuban trans- ing Receivers, so round about 11 p.m.! mitter, on 9.34 Mc / s. again in Television, The point seems to be that the changing Lastly, the Midwest Company in London S O U N D where accuracy and ionisation conditions due to the solar cycle report good reception of the Berlin tele- reliability are even vision sound transmissions / 2 0.01 mfd. mica. "M" demand changes in transmitter technique, on 42.3 Mc s more vital, do you between 2.20 Price each 2 in particular the more careful use of the and 2.46 p.m. on Thursday find the designer afternoon, June 17th; peak signal was 1 0.0001 mfd. mica "M" higher frequencies; in daylight during the the specifying T.C.C. summer months the optimum at 2.35 p.m. B.S.T. and the station finally Price 8d. So band this again has t F.C.C. year ranges from 17 to 21 Mc /s (17 to 14 faded out rapidly. Did any other reader 2 0.0005 mfd. mica. "M" metres), whilst in the coming winter it will hear this? ETHACOMBER. Price each 9d. dependability prompted the de- range from 54 to 35 Mc /s (zo to 8 metres), 1 mfds., 50 12 volts, signers' choice. and these figures show only too clearly why electrolytic. " FT " the average listener finds conditions poor, at The Radio Industry Price 2;'3 least during the summer. 2 8 mfds., 460 volts M.R. Supplies, of xi, New Oxford Street, peak, Most all -wave receivers do not tune above London, W.C.i, has electrolytic. 802. just issued a new list of Price each 6/. 18 Mc /s (below 16.5 m.) and quite a few microphones, amplifiers and associated PA above 15 Mc /s (below 19 m.), so that the equipment. An entirely new model of the only distant transmitter which is likely to M.R. Transverse Current Microphone has been give a good service until late in the evening introduced at the price of 37s. 6d. now is W3XAL on 17.78 Mc / s. Very unfor-

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www.americanradiohistory.com .17 Wireless World, July 911i, 1937 Random Radiations By Impropaganda the matter will be taken up by the U.I.R. TT S good that the subject of the violent and that at a conference in the near future "DIALLIST" anti -British propaganda which has been it may be possible to induce all countries going out from the broadcasting stations of to agree not to indulge in external propa- y certain countries has been raised in Parlia- ganda. There isn't, of course, the slightest ment after an extensive ventilation in the cor- reason why they shouldn't ' ` propagand " as ceivers which will work in some kind of respondence columns of The Sunday, Times. much as ever they like in their own lan- way with a high- tension battery that regis- Though not the only offender, Italy has guages for the benefit of people within their ters a voltage of about i zo when new and frontiers. But when been the worst. Highly coloured news bul- it comes to sending perhaps 70 or 8o after it has been used for a letins have been sent out from her stations out this embittered stuff in languages which few weeks. Most British battery valves are in no fewer than sixteen languages, and, so aren't spoken in any of their own dominions at their best when the plate voltage is in it is rather too much of a bad thing. far as I can make out, the transmissions the neighbourhood of 15o ; hence their per- continue, though their tone does appear to % formances are a long way below what they be modified to some extent. Possibly you Z Z should be when the battery voltage is izo, may have heard some of those in English Good Commenting and become very poor indeed when it drops which emanate from medium -wave stations DID you go to the Air Force display at from 40 to 5o volts below that. I do blame such as Milan and Bari and from the short- Hendon? If so, you must have been both set manufacturers and battery manu- wave station IzRO4. If you haven't, it is struck by the excellent commentaries wire - facturers for failing to instil into the great worth while tuning them in, the medium - lessed from plane to ground by the airmen body of listeners that the battery set of wave stations between seven and eight themselves whilst they did their stuff. It to -day can be very nearly as good as the o'clock in the evening or at about a quarter - struck me that they were very much mains set if only they will use an adequate past eleven at night, and the short-wave superior to the bulk of B.B.C. commen- source of high -tension supply, and, secondly, station at 3 p.m. or just after midnight. taries ; they were fresh, they were alive, that batteries which seem very cheap on ac- Those who know Oriental languages such as they were graphic and they were intimate. count of their low initial cost are often a Arabic may get even bigger surprises than One particularly successful commentator very poor investment owing to their short listeners who know English only. The was the leader of the Flight Aerobatics, who life. Arabic programme is given each weekday made you feel almost as if you were taking L ti % at 6.3o p.m. on 25.4 metres. part yourself in the wonderful show put up Facts and Figures by his planes. " Now then, over we go," Not Good Enough he cried-and over they went. B.B.C. IT happens to me quite often to hear from some user of small cheap batteries that he Wireless commentators tend to be just a little too could be and should be one of aloof, a little has a set which draws, say, ten milliamperes the greatest factors in world for too dry. I hope many of them the pro- were at Hendon and realised from what when the HTB is up to its nominal rzo moting international understanding and they heard volts, that he uses it not less than six hours peace, but, used in this way, it might easily the airmen do how very good the rather less formal type of commentary a day, and that he obtains fine performance become just the opposite. One hopes that can be. and perfect reproduction for six or seven .- '. ._ months from each new HTB. It's no good telling such a fellow that the thing is A Television Problem theoretically impossible. Even will he close SPEAKING of commentaries brings to his eyes and his ears to hard, cold practical mind one rather queer effect which ac- facts. He is so anxious to believe in his companied the B.B.C.'s first attempt to own cleverness in securing a bargain that he televise Wimbledon tennis. When the first will put up with almost incredible distortion trial was made they " married " the com- and thoroughly bad performance in every mentary intended for National broadcasting way rather than admit that his cheap bat- to the television transmission. If you hap- tery is no longer doing its job. Laboratory pened to be looking -in, the result was rather tests show the real facts and figures, but if extraordinary. The commentator seemed to you quote them to him or show him test lag always nearly a stroke behind the actual records in graph form they no more sink in does play as you saw it. It doesn't, of course, than water poured upon a duck's back ! matter a bit for sound broadcasting alone if % % _. his remarks are made a second or two after Better Tuning Dials the event described has taken place ; but it emphatically does matter for a television oNE of the outstanding features of many running commentary, and it seems that a vv of the new season's wireless sets that I. different technique altogether is going to be have seen is the big all -round improvement needed when sporting broadcasts by tele- that has been made in tuning dials. In these vision become more general. columns I have long waged war against the small tuning dial with station names on the m. L medium- and long -wave bands that are difficult to read, a cramped and not too well A Battery Tragedy marked scale of metres or megacycles on the THOUGH many battery receiving sets are short-wave range and the pointer about as designed for use with special HTBs, thick as a poker. An idea firmly fixed in tha there's no question that the r2o -volt minds of the big men of some firms was that standard capacity battery is the one that any kind of large dial must be unsightly and the man in the street has come to regard that the ordinary user much preferred a as the normal and proper source of plate small dial to one that was open and easily LOW - TENSION AND HIGH - TENSION current for his receiving set. He is offered legible. That obsession seems now to hava FROM THE WIND. -As announced last everywhere batteries of this kind priced at been removed, for one finds semicircular week, the Rev. Harold Wilde, chaplain of five or six shillings and he buys them, dials six or seven inches in diameter and Tristan da Cunha, has been presented with though the proper replacement unit for his rectangular ones of similar goodly dimen an Ekco all -wave receiver for the use set may cost two or three times as much - sions. of the islanders. This photograph shows or I should say because it costs two Sometimes, think, there is a Mr. Wilde with the windmill generator, perhaps I tendency to which will be used to charge a 4 -volt accu- or three times as much. The saddest part crowd in rather too many station names, mulator feeding the filaments directly and of the whole business is that not a few which may mean that small type has to be also providing HT through the intermediary makers of battery sets are finding themselves used for them. Those who design dials of a vibratory generator. forced by popular demand to turn out re- should remember that not everybody has

www.americanradiohistory.com JULY 9th, 1937 Wilp4@go 'MpH 43 first -rate eyesight, and that it can be a bit gramme transmission. I am inclined to of a bore to have to put on glasses whenever wonder, though, whether it is wise to try to you want to change from one station to get so large an audience into a viewing another. booth. It is rather important to give audi- POINTS 0V L S ti ences the best possible impression of what Co- Axials and Valves television can do. I find that some apology is due to the ERYCJO:' WHAT a big difference the co -axial cable Museum authorities for my last week's is going to make to communications in remarks concerning the lack of information this country ! Quite close to my home there at the Television Exhibition. I must have if/ the ii?ola was until recently a huge array of overhead been unlucky at my earlier visit ; the facts wires borne on the Siamese -twin type of are that one of the official Guide -Lecturers telegraph post. These were the main Lon- makes frequent tours of the Exhibition and (Log don- Birmingham lines. Now they have all also those in charge of the demonstration come down. The posts remain for the receivers are able and willing to answer any moment, gaunt and hideous in their naked- technical enquiry. ness (it's amazing how naked a line of telegraph poles can look without any wires ! ) and the underground co -axial cable lies snugly tucked away, safe from gales and Television snowstorms. The co -axial cable could never . have been made to serve any useful purpose if it hadn't been for the wireless valve. Now Programmes it carries in its slim self telegraphy and tele- Transmissions are from 3 -4 and 9 -10 phony and before long it will be carrying daily. television, too. Only those who remember the telephone in its earlier days can realise Vision : 45 Mc!s. Sound : 41.5 Mcfs. what a change the valve has made. It used to take hours to put through a trunk call for FRIDAY, JULY 9th. which now you're bidden to hold the line. 3, The Raft : an interlude by Stephen Leacock. And if the distance was more than 40 or 5o Scene -Lost in the Caribbean Sea. 3.15, miles you shouted at your correspondent and Sculpture ; making a plaster cast. 3.25, British heard a muzzy whispering from him. Movietonews. 3.35, Douanes, with Valerie Hobson, Ernst and Lotte Berk and Eric Wild % 1 1 and his Tea -Timers. 9, Pyramus and Thisbe : Shakespeare comedy, THE SPEAKER Television at Radiolympia produced by Jan Bussell. 9.15, Gaumont - TT is good to see television is to have a British News. 9.25, Repetition of 3.15 pro- SELLS THE SET that gramme. 9.35, Ad Lib. Revue. real chance at this year's Radiolympia, So widely has the phenomenal per- the B.B.C. co- operating with the organisers SATURDAY, JULY Toth. formance of the Rola G.i2 become to make it a real success. The programmes 3, In Our Garden, by C. H. Middleton. 3.15, recognised that it is true to say that are to be altered during the run of the The Hogarth Puppet Cabaret. 3.30, Gaumont - it is a speaker that sells the set. Exhibition so as to make it possible for a British News. 3.40, Plus la Change -light Once you have heard the remarkable very large number of people to see com- entertainment. fidelity of this unit you will be content plete items. With this end in view they 9, Repetition of 3.4o p.m. programme. with no receiver that is not G.I2 9.20, equipped. You will discover too, will be divided into three fifteen -minute Summer Gardening : C. H. Middleton. 9.30, British Movietonews. 9.40, Variety, with that the mere presence of a G.12 in a periods, each complete in itself, with in- the radio receiver affords proof of its tervals of five minutes between items to give Hobart Trio, Collinson and Dean and the B.B.C. Television Orchestra. quality,for it would pay no manufac- time for one audience to leave the booth and turer to install this unit in a set that another to come in. There are going to be MONDAY, JULY 1zth. was not able to do full justice to such at least fifteen or sixteen booths, and I see 3, Recital by Lisa Minghetti (violin) and a reproducer. Ask your dealer to it is suggested that each of them will ac- Manta Farell (soprano) accompanied by Cyril demonstrate a Rola G.I2 and let your own ear confirm our claims. commodate about thirty people. If that is Belcher. 3.15, Film : Building a Building. so it will be possible to let between T,300 3.25, Two Diminutive Dramas. 3.50, Gaumont - and 1,400 people look -in " during each pro- British News. G.12 P.M. (as illustrated) lass Trans- " former ...... £4 18 0 Repetition of 3 p.m. : 9, programme. 9.5, Film with Transformer ...... £5 5 0 Deep Sea Thrills. 9.15, Discussion on Salads G.12 P.M. 0.12 D.C. Complete with 7mnsformer, between M. Marcel Boulestin and C. H. Mounting Stand, Handle Ferranti "1137" Middleton. 9.30, British Movietonews. 9.40, and Base ...... £5 6 0 Television Follies. G.12 D.C. with Mounting Stand, Handle and Base, but without TUESDAY, JULY 13th. Transformer ... £4 16 o 3, An O.B. 3.10, Fashion Parade, arranged G.12 D.C. Stripped, but with Trans- by £4 4 o H. E. Plaister and G. R. Kenward -Eggar. G.12 D.C. Stripped and without Trans- 3.25, British Movietonews. 3.35, Mizzen Cross ... £3 15 o Trees. former (When ordering please stets Field Resistance and of Transformer required.) 9, Repetition of 3 p.m. programme. 9.15, Film : Impedance Building a Building. 9.25, Damon and Phyllida. For Public Address work iaoth the P.M. and Ener- a one -act opera. 9..50, Gaumont- British News. gised Models can be supplied with a 15 ohm Voice Coil at an additional charge of 3/ -. WEDNESDAY, JULY r4th. Folder A. 3, Pyramus and Thisbe : Shakespeare comedy, Write for produced by Jan Bussell. 3.15, Film : Deep Sea Thrills. 3.25, Revue. 3.50, Gaumont - USE British News. OVER 8 MILLION IN 9, Recital by Marita Farell (soprano) accompanied by Cyril Belcher. 9.10, Excavations at Maiden Castle in Dorset. 9.25, British Movie - tonews. 9.35, Two Diminutive Dramas. THURSDAY, JULY 15th. 3, Dancer. 3.15, Waxworks demonstration by BASED on the Model 837, recently re- Bernard Tussaud. 3.25, British Movietonews. viewed in these pages, this set is housed 3.35, Revue. lt ótha

www.americanradiohistory.com .(f lCirrlasc ll"nrld, brie 9th, 1937 Recent Inventions Brief descriptions of former so that it generates con- capacity K, Kr, K2 mounted at tinuous oscillations and feeds the base. The Unit A may, for the more interesting them into the primary winding. instance, be inserted in the plate radio devices and im- The higher voltage induced in the circuit of an intermediate-fre- secondary winding is then fed to quency valve, and the unit C in provements issued as a rectifier valve and smoothing the grid circuit of the following patents will be included circuit. The auxiliary valve is, of valve, the unit B then serving as course, switched out of operation a coupling link between the other in this section when the device is coupled to an two. The coils of the units A and AC supply. C are set at right angles to each FLUORESCENT SCREENS The British Thomson -Houston other and at a definite distance apart. The coupling is varied by FLUORESCENT material is Co., Ltd. Convention date (Bel- 5934. swinging the coil of the unit B sprinkled upon a 5o per cent. gium) August 25th, No. 463410. about the pivot P by means of a solution of caustic soda which has 0 0 0 0 handle (not shown) embracing the been spread over a backing -plate yoke Y. of soda- glass. The matrix is then " DIELECTRIC GUIDES" ULTRA -SHORT waves, of the Johnson Laboratories Inc. (As- baked. This is stated to prevent signees of A. Crossley and H. E. the fluorescent crystals from being order of 2,000 megacycles from Meinema). Convention date dislodged from their setting by are transmitted point to (U.S.A.) August loth, 5935. No. mechanical vibration, and also point through a "dielectric guide" 463202. avoids any loss in sensitivity due consisting of a cylindrical body of Method of increasing gain and to the screening action of the air or other dielectric, enclosed by selectivity in an amplifier with usual water -glass binding. a metallic sheath sin. in diameter. a band -pass input circuit. Ferranti, Ltd. and M. K. Tay- The wave travels through this lor. Application date October 3rd. guide in much the same way as it would space, cuits, and so increases both the 1935. Nu. 463642. travel through open gain and selectivity of the set. except that it is strictly localised o 0 0 0 Without this resistance, when inside the metallic sheath. both -pass CATHODE.RAY TUBES The invention is concerned with band circuits are exactly various ways means im- in resonance, the phase conditions AIVANTAGE is taken of the and of are such that no regeneration peaked impulses applied to pressing telephonic or other sig- occurs. the deflecting coils of a cathode - nals upon such a carrier wave, and or rectifying The output from the amplifier ray television receiver to obtain of demodulating the can also be rectified and used to " free" DC voltage for biasing signals at the distant end. provide automatic volume control. the second anode of the tube. Standard Telephones and Cables, Automatic selectivity control is The deflecting coils are shunted Ltd. (Assignees of G. C. South - similarly obtained by varying the by a circuit including a variable worth and A. P. King). Conven- bias on the grid of the valve, and, resistance, in series with a recti- tion date (U.S.A.). October therefore, the amount of feed- fier valve and a condenser. The 12th, 1935. No. 463238. back. rectifier is inoperative during the 0 0 0 0 Marconi's Wireless Telegraph forward stroke of each scanning RF COUPLINGS Co., Ltd. (Assignees of J. Pleban- line, but comes into action during THE " selectivity " response of ski). Convention date (Poland) the " flyback " period, to charge the ordinary two -tuned cir- October 7th, 1935. No. up the series condenser. This is 463233. cuit varies from the peaked curve 0 0 0 0 from Fig. 2. Method of mounting shunted by a potentiometer A, Fig. 5, which corresponds to which a supply of DC voltage is the roils and condensers in the MICROPHONES tapped off to the second anode of three -circuit coupling unit. THE carbon -granule type of the tube. microphone, when used for Marconi's Wireless Telegraph TUNING COILS public address systems or for Co., Ltd. (Assignees of A. W. tIHIGH -FREQUENCY coil is broadcasting. has a pronounced Vance). Convention date (U.S.A.) designed so that the inherent directional effect, which makes it September 29th, 5934. No. 463253. t.tpacity between its windings is necessary to set several instru- o o 0 0 sufficient to tune it over an ex- ments at different angles in order WHEN external magnetic coils tended range of frequencies. A to secure a correctly balanced are used for deflecting the small variable condenser may he pick -up. say, from a large orches- stream inside a cathode -ray tube, added for trimming purposes, but tra or choir. there is a tendency for part of th, the selective action of the coil de- According to the invention the field to stray out of its proper pends mainly on the fixed capacity microphone is fitted with a curved path, and, by affecting the eh-u between its windings plus the vari- diaphragm, circular in cross -sec- tron stream, to produce distortion ation in inductance due to a mov- tion, and a number of carbon of the picture. able powdered -iron core. " cells " are mounted around the According to the invention th, The coils are preferably wound periphery over, say, an angle of in a single layer. A separate 18o The cells may all be con- ferro- magnetic core of the deflect - deg. ing coil is provided with extra movable core may be provided at nected in parallel, or certain of pole- pieces, which are adjustable each end to allow of tuning over them may be coupled to a separate relatively to each other so as to two different wavelength ranges. amplifier. A single instrument of offset or prevent the passage of S. G. Brown. Application date this type will receive equally stray fields into any part of the Fig. Typical response curves August 3oth, 1935. No. 463724. sound -waves coming either from a I.- of or tube where they may produce of a two -circuit coupling are o o o o point directly in front it at results. wide angles of divergence, and will undesirable shown by curves A and B with FEEDBACK AMPLIFIERS A. H. Gilbert; L. R. Merdier; loose and tight coupling re- give a correctly balanced output. V Instead of being circular in and Baird Television, Ltd. Ap- spectively. Curve C is that of THE output from an amplifier plication date September 12th, the three -circuit coupling unit is fed back through a con- cross- section, the diaphragm may 1935. No. 462684. described. denser C and a coil L connected, be curved at one part of its peri- as shown, to a hand -pass input phery and flat at another. O 0 O o Houston loose coupling to the double - circuit. A resistance R in the in- Tke British Thomson- MAINSSUPPLY UNIT humped curve B produced by put circuit to the grid introduces Co., Ltd.. and L. B. Ault. Appli- AHIGH- TENSION unit is de- tight coupling. The object of the a 90 deg. phase- shift, which pro- cation date October 3rd, 1935. signed for use with either invention is to vary the selectivity duces regeneration in both cir- No. 463649. 110 or 220 volts on either AC or of a set from curve A to curve C, DC mains, and to deliver a higher which has a broad and sub- with the permission voltage than that sup- stantially flat top and steep sides. The British abstracts published here are prepared rectified of the Controller of 11.51. Stationery Office, from Specifications even in Fig. 2 shows a three- circuit plied by the mains, the obtainable at the Patent Office, 25, Southampton Buildings, London, case of a DC supply. The step- coupling designed for this purpose. W.C.2, prier I - each. A selection of patents issued in U.S.A. is means of an of units A, B. C up is secured by Each the consists also included auxiliary valve, which is con- of a coil fitted with a powdered - nected across the supply trans- iron core, and a small variable

www.americanradiohistory.com d _ .:_;.

The THE PRACTICAL RADIO JOURNAL ¡OWN*, 2711' Year of Publication .. -4*ji(r!'

No. 933. FRIDAY, JULY 16TH, 1937. VOL. XLI. No. 3.

Proprietors : ILIFFE & SONS LTD. Editor : EDITORIAL COMMENT HUGH S. POCOCK. Editorial, after making allowances for different Advertising and Publishing Offices : Transatlantic circumstances. Too often the wireless DORSET HOUSE, STAMFORD STREET, apparatus is put on board as a mere LONDON, S.E.I. Experiment afterthought, and, worst of all, none Telephone: Waterloo 3333 (3o lines). Telegrams : " Ethaworld, Sedist, London." Wireless and Air Navigation of the personnel of the aircraft is sufficiently skilled in its operation. COVENTRY : Hertford Street. T is gratifying to learn that the Telegrams: Telephone: Things happen quickly in the air "Autocar, Coventry." 52 to Coventry. carefully organised wireless where operating and technical standards services contributed so much to : should, if anything, be higher,. rather BIRMINGHAM the successful outcome of the Guildhall Buildings, Navigation Street, 2. than lower, than in the marine service. Telegrams : Telephone: transatlantic test flights recently carried The wild "Autopress, Birmingham." 2971 Midland (4 lines). rumours current about Mrs. out by the Caledonia and the American Putnam's fate would almost certainly MANCHESTER : 260, Deansgate, 3. flying boat. Though there has un- never have been circulated had her Telegrams: Telephone: doubtedly been some exaggerated talk " Iliffe, Manchester." Blackfriars 4452 (4 lines). machine been even half as elaborately as to the navigators' dependence on equipped and well manned wirelessly GLASGOW : 26s, Renfield Street, C.2. radio bearings, it is certain that the as was the Caledonia. Telegrams : " Bide, Glasgow." Telephone: Central 4857. normal direction- finding technique and, PUBLISHED WEEKLY. ENTERED AS SECOND - above all, the successful application of CLASS MATTER AT NEW YORK, N.Y. the Marconi -Adcock principle to the National "Quality" Subscription Rates : obtaining of reliable bearings on short Home, £I Is. 8d. ; Canada, Li is. 8d. ; other waves at great distances have together countries, £I 3s. iod. per annum. been more than valuable, and helped Listening As many of the circuits and apparatus described in these the navigators to maintain such good pages are covered by patents, readers are advised, before Effect of the New B.B.C. making use of them, to satisfy themselves that they would courses that fast times could be made. not be infringing patents. The topography of the Northern Arrangements transatlantic route is unfortunately SURPRISINGLY little comment such that existing D.F. stations (in- and, so far as can be judged at cluding those specially established at present, few complaints have CONTENTS each of the terminal points) do not been made on the B.B.C.'s decision to Page give good wide -angle bearings for the close down the London and North

Editorial Comment ...... 45 exact determination of position of an National medium -wave transmitters in -ocean. if the is The Wireless World Television Re- aircraft mid However, during daytime. This change ceiver -III. Constructing the the long -distance short -wave system incidental to the provision of a separate Mains Units 46 of direction-finding has indeed come up Regional programme for Wales. to expectation as fully as we believe, As a result, those who are accustomed Television in the Making 50 it may be thought worth while to to listen during the daytime to the Unbiased .. .. 52 make a serious attempt to overcome National programmes through the Broadcast Brevities 53 the many and obvious difficulties in stations in question have now no the way of erecting a third installation alternative to the long -wave trans- Random Radiations 54 in Greenland. A station in the neigh- mitter at Droitwich. Good as is the Frequency Modulation 55 bourhood of Cape Farewell should, in quality of that station, there are in- Current Topics .. 57 conjunction with the existing terminal herent reasons why it cannot reach the stations, provide right -angle " fixes " general standard of the now-silent Listeners' Guide for the Week .. 58 over the crucial part of the route. medium -wave Nationals. Here is a Letters to the Editor .. 60 In any case, Imperial Airways is to strong additional argument for the be congratulated on having taken early inauguration of the ultra- short- An Ideal Valve Voltmeter . . .. 62 wireless so seriously ; would that the wave service for which " quality " Imperial Model ADIS Receiver .. 64 same could be said of all others re- enthusiasts have so long been waiting Recent Inventions ...... 66 sponsible for long- distance flights, even and for which we have so long pleaded.

www.americanradiohistory.com 46 Wireless World, July 16th, 1937. The Wireless World Television Receiver III. -CONSTRUCTING THE HIGH- VOLTAGE SUPPLY

UNIT AND THE SOUND POWER STAGE DESIGNED BY W. T. COCKING

N the preceding articles the vision Owing to . the high voltages, special care sheet of aluminium so that all com- receiver time -base, and the vision re- has been taken in the design of this part of ponents can be earthed by their contact ceiver power pack have been described, the equipment, not only to provide ade- with it. Before screwing down the con- and the high -voltage unit, which sup- densers it is wise to scrape off the paint plies HT for both tube and time -base, must beneath the fixing flanges so that a good now be dealt with. The circuit diagram ap- ACATHODE-RAY tube de- contact is ensured. Incidentally, in the pears in Fig. 3 and the mains input voltage mands an HT supply of several case of the condensers C5, C6, C7, C8 and is derived from the vision receiver power thousand volts, but quite a small C9, which are all in a single container, pack in which the delay switch is included. current is needed. Components must the case is actually the connection to one The mains transformer has two second- consequently be built to withstand side of C9 and it is accordingly fitted with for the aries rated at 4 volts I ampere, much greater voltages than is usual an earthing screw. filaments of the two U17 valves, and a in receiving equipment and the ap- The two valveholders are carried on a winding rated at 3o mA. at 1,75o volts. paratus must be adequately protected. Paxolin strip supported above the base by The two rectifiers are connected in the wooden blocks in order that The peak voltages are reduced adequate in- voltage -doubler circuit with condensers Cr by sulation may be obtained. Similarly the and C2 of o.i F. and z.o hF. respec- using the voltage- doubler rectifier, and fixed and variable resistances and the out- tively. A current of some 20 mA. at 2,000 this is economical in permitting the put terminals are mounted on another volts is withdrawn from the junction of time -base HT supply to be derived Paxolin panel. All this will be clear from these condensers and is used for operating .from the same equipment. the drawings, as also will be the wiring. the time -base. It is dropped to r,000 volts by means of R2 and R3 which also provide smoothing in conjunction with C3 and C4. The voltage across Cr and C2 is about 4,50o volts and is used for the cathode - ray tube HT supply. The tube current consumption is very small, and the total current is substantially that consumed by the voltage divider -about i mA. Smoothing. is effected by the resistance Ri and the following condensers. These condensers are connected across the tapping points of the voltage- divider, and so also tend to maintain the tube electrodes at cathode potential for alternating currents. The two potentiometers .R4 and R5 are termed the horizontal and vertical shift controls respectively, since they permit the picture to be moved sideways or up and down on the screen of the tube and so to be centred accurately. The potentiometer R9 enables the second anode vol- spot can tage to be varied so that the light A rear view be focused on the screen. These three con- of the HV unit trols are brought out to the panel for with the pro- convenience, but as they only require oc- tecting cover casional adjustment it would be quite removed. permissible to make them internally ad- quate insulation but also to guard against justable. The fourth control on this unit accidental contact with any part at high is the brilliancy control ; it is R13 and potential. Plywood has been selected varies the grid bias of the tube. for the base and is faced with a thin

www.americanradiohistory.com cell JULY 16th, 1937 47

CONSTRUCTIONAL DETAILS OF THE HIGH- VOLTAGE UNIT

24 23 >'< 2

1 4,...... 41 R8 LAI, R8 °RB R102 R4 X1 I: C Í.:J ,. w--- A1 - ¡ ¡: j.î. 5 2 R7 Y1 PATE' C 0 é R5 , gl -in e e+HT 1 I R5 9 111 ;RII 4 1 1¡ 1 ° 8/2" % /a li G 1 ' i i s 4 1' 1 R1 2

1IIIINL1111#IUsm, .llll'I#IIINIIIIIIIIILob '® 1 1Will

VALVE PLATFORM

7/ LONG X 2% WIDE

g UV MAINS INPUT PLUG FROM VISION RECEIVER 2 POWER UNIT 4V 1A 1 I --- /8 ., . OVERALL HEIGHT 14 I T U1 B .70 33/15/0 o 4 %2

Y ANODE 9" i/8 "4 o f/ Ut7 05 o 0 ANODE 0

1% o \4V 18 1,7508 30 mA

-4- 31/4" >< 41/ 53/8 5Y., 4 2d

NVvVs.o. o.25M 0 R6 iR1 V.' 1TICAL sMn SHIFT 110 R7 0.5M n HORIZONTAL C1 .. SHIFT 0.1 mfd.. X10 R8 Io V 1.75 M A30 R9 A20 0.5M0 MAINS INPUT PLUG R3 R2 FROM VISION RECEIVER 30,0000 30,0000 POWER UNIT C7 1 mfd R10 0.25 M0 Al

F111 o M 0 H T + 0 C A TIME - BASE .. C4 - 03 ._O2 Id 2 nlIdo 1 mid H T - R12 5,000 n C9 4 mid*

R13 0.15M 0 HT-0

Fig. 3. -The theoretical circuit diagram is shown here as well as the practical wiring diagram.

www.americanradiohistory.com WipisIlisoo 48 MpIlt JULY 26th, 1937 " The Wireless World " Television Receiver - No reliance can be placed on insulating sleeving at high voltages, of course, and every high -voltage wire should be spaced by half an inch or so from other wires or components. No. 18 or even 16 gauge wire stretched straight is the most convenient on account of its rigidity. Especial care must be taken in the construction and wiring of this unit. Although the variable resistances have "dead " spindles, no reliance is placed in their insulation, MAINS0 INPUT and insulating couplers are provided for the PLUG couplings to the extension control shafts. of 350-0-350V These couplers are the type used in 75mA short -wave apparatus for the avoidance of hand- capacity effects and consist of a length of insulating tubing with a set -screw at each end. When connecting up remember to insert the extension shaft only far enough for the set -screw to grip properly. The couplers are hollow and it would be possible to push a shaft through so far that it could butt up against the end of 5 " the potentiometer spindle. To do this OVERALL HEIGHT OF CHASSIS 1/ N9 18 GAUGE ALUMINIUM would completely defeat the end in view arid would be asking for trouble.

SPEAKER Enclosing the HV Unit 0 PLUG

SPEAKER! of perforated zinc covers the SOCKET A screen 1,6R0ó n L in it is im- unit, and when it is position A--I WO SOUND SMOOTHING possible to come into contact with any RECEIVER CHOKE 4 V 2.5 A it is not SOCKET high -voltage part. Although R1 essential to the working of the apparatus, O 100 0 04 is device the use of which is 0.1 mkt FUSE it a safety 891.a. SÇ tá.T strongly recommended. INPUT 0-11 Suitably insulated wire must be used 360 - 0 350 V MAINS for the external connections to this unit. 75 m A INPUT Ordinary good quality lighting flex can be EO 0.2R513YIU PLUG 210 V used for the - HT and cathode leads ; 50 mtds heavily insulated cable similar to motor- 230 V ignition cable is adopted for the high - car FUSE 250 V voltage connections. 4 V 1 A Before passing on to the tube connections, inter -unit connections and cabinet, 4 V 4 AO it may be as well to deal with the sound equipment. The receiver has already been dealt with in The Wireless World' under the title of The Ultra -Short -Wave Quality Fig. 4. -Full details are given here of a L The Wireless World, April 23rd, 1939. simple power unit for the sound receiver.

in possession of this amplifier, however, will need an output stage and mains equipment, and a small unit has been designed for this purpose. The circuit diagram appears in Fig. 4, and it will be seen that a single PX4 output valve is employed with resistance coupling, while the mains equipment is of the simplest type. The output of such a valve is entirely adequate for television purposes, for experience shows that appreciably lower volume is needed than for ordinary broadcast reproduction. This is undoubtedly partly be- The sound receiver cause one listens more attentively when power unit contains a one has vision as well as sound, but it is single triode output also due to the size of the picture. For valve. optimum results, the picture size and sound volume must be correctly balanced. Receiver. i t can be used with the Push - The construction of the sound power Pull Quality Amplifier if desired, and unit is entirely straightforward and calls space has been left in the cabinet to ac- for no comment. When it is used, how- commodate it. Those who are not already ever, the Ultra -Short -Wave Quality Re-

www.americanradiohistory.com Wfip@hog JULY 16th, x937 opIlAI 49 ". The Wireless World " Television Receiver - ceiver must be altered in one particular -the resistance Rio in the receiver must be short- circuited and only the " + Out- put " terminal employed. It is also important to use a metallised detector valve or to fit a valve screen over a plain detector ; if this is not done the valve will pick up the scanning voltages by electrostatic induction from the tube since it is mounted immediately alongside its end. A single 5 -way cable in which four wires only are employed serves to convey power to the sound receiver, and a single screened lead carries the AF output to the power unit. A permanent- magnet type loud speaker having very good characteristics has been selected and has proved very satisfactory. In this connection it must not be forgotten that the stray field of the magnet is important and may distort the picture. Excessive field will distort the rectangular picture into a trapezium. In order to avoid this effect the speaker has been carefully chosen and has been mounted as far as possible from the tube. The assembly of the various units will be described next week. A side view of the lower deck of the apparatus ; from left to right the units are the HV supply equipment, the vision receiver power pack, and the sound receiver power pack. THE LIST OF PARTS USED 2 30,000 ohms, 4o watts, R2, R3 I Io mfds. (multiple block), C5, CG, C7, Certain components of other makes Bulgin PR39 C8, C9 Dubilier BE526 but of similar characteristics may be (R8 =2 X 0.75M0, + I X0.25MQ) 2 Valve holders 4 -pin (without terminals) used as alternatives to those given in Resistances Variable, non -tapered. Clix Chassis Mounting Standard Type VI 1 150,000 ohms, R13 " SG " Reliance 2 Plug.top valve connectors, Belling =Lee 1175 the following list. 3 0.5 megohm, R4, R5, R9 Reliance " SG " 1 Mains connector, 2 -way Bulgin P33 HIGH =VOLTAGE UNIT Fixed Condensers: 9 Terminals, ebonite shrouded, HT+, HT- (2). Ar, Az, A3, C, X, Y Belling =Lee " B " 1 Mains transformer, Primary: 200 -250 volts, I o.1 mfd., 7,000 volts, oil- immersed, CI 5o c /s; Secondaries: 1,750 volts 3o m /A., Dubilier 951 4 Extension control outfits Eddystone 1008 4 volts I amp., 4 volts I amp. I I mfd., 2,000 volts, oil- immersed, C3 Miscellaneous: Peto.Scott Sound Sales TEL /EHT Dubilier 951B Paxolin sheet, baseboard, perforated zinc, Resistances: I I mfd., 3,000 volts, oil- immersed, C2 wire, sistoflex, screws, etc. 15,00o ohms, I watt,R12 Erie Dubilier 951C Valves: Erie Loofa volts, C4 3 250,000 ohms, I watt, Rl, R8, RIO I mfds., oil- immersed, 2 U17 Osram 1400,00o ohms, 1 watt, Rit Erie Dubilier 950A 2 0.5 megohm, I watt, R6. R7 Erie Erie 2 0.75 megohm, 2 watts, R8 SOUND RECEIVER POWER PACK I Mains transformer, Primary: 200/250 volts, 5o c/ s ; Secondaries : 350-o -350 volts 75 m /A., 4 volts 2.5 amps., 4 volts 4 amps., 4 volts r amp., C.T. Bryce 5VT28 1 Smoothing Choke Varley Dual DPII Fixed Condensers: 10.1 mfd., 35o volts, tubular, C4 T.C.C. 250 18 +8 mfds., 45o volts, electrolytic, Cl, C2 T.C.C. 70211/3c 15o mfds., 5o volts, electrolytic, C3 Dubilier 3004 Resistances: I 100 ohms, watt, RI Erie 1 250,000 ohms, f watt, R3 Erie 1 750 ohms, 3 watts, R4 Erie 1 1,500 ohms, 3 watts, R2 Erie 2 Valve holders, 4 -pin (without terminals), Clix Chassis Mounting Standard Type VI I Valve holder, 5 -pin (without terminals) Clix Chassis Mounting Standard Type VI I Fused mains input connector with I amp. fuses BellingLee 1114 I Plug and socket, 3 -pin Belling.Lee 1119 2 Terminals, ebonite shrouded, E, Input Belling =Lee " B " 1 Loud speaker with transformer Goodman's WWT Auditorium Chassis Sound Sales Miscellaneous: Peto.Scott The two rectifiers in the HV unit are clearly Vire, sistoflex, screws, etc. shown in this illustration. Valves: I Uiz, I PX4 Osram

www.americanradiohistory.com Wireless World, July 16th, 1937 Television in

The televising of the Coronation proces- BEHIND THE SCENES sion at Apsley Gate, Hyde Park Corner, was undoubtedly television's greatest fillip. presided over by D. H. Munro. It is the Photo by courtesy of British Productions Department that " pulls the Pictorial Productions, Ltd. strings," attending to studio management and contriving that, as far as is humanly possible, the producer's ideas are trans- the idea is placed lated into reality. on the knees of the Meanwhile, the producer has found time gods at the next to consult with Peter Bax, the scenery programme meet- expert, and already he is designing the ing. If the gods dummy revolving door of the " Hotel," smile, the pro- and it is now taking shape in the car- ducer may or may penter's shop. The scene painters are at not be, a happy work in their rather flat medium of black, m a n, depending grey and white, to supply the background upon how many of the " Hotel " lounge. But " Hotel Cos- AKE an oblong of frosted glass other programmes are absorbing all his mopolitan " only becomes really interest- loin. x 8in. and a loud speaker. waking hours. ing when the artistes are assembled and To fill the one with a living Let us assume that " Hotel Cosmopoli- rehearsals have begun, so we may pass picture, the other with concord- tan " -a brisk singing and dancing show over such severely practical details as ant sound, for 120 minutes a day for six -has been duly tabled for presentation a booking the artistes, reducing the script to days a week, and let it be a good picture month hence. Cecil Madden, the Pro- continuity form, and cutting it to fill, say, and good sound." This, briefly, is the gramme Organiser, must find the right thirty minutes. task entrusted to Mr. Gerald Cock, niche for this super production, his task B.B.C. Director of Television. Is it easy? being to achieve programme balance and Rehearsal Problems If you have doubts ask a stage pro- avoid awkward clashes. The guiding prin- ducer whether he would choose to turn ciple is to please as many viewers as pos- If a genius could invent a means , to out " something new " every day ; sible in sixty minutes of varied entertain- obviate the learning of lines, television. re- whether, instead of rehearsing for three ment. The Television Orchestra, con- hearsal time could be cut down consider- weeks and then settling down for a steady ducted by the indefatigable Hyam Green- ably. In the case of a production with run, he would prefer the deliciously varied baum, will be required, so " Hotel Cos- speaking parts a good deal of dogged job of putting on fresh material every mopolitan " will come up for discussion rehearsing must be gone through before it night. If he deigns to reply, and if you at the music meeting, which follows on can be tried out before the cameras. Often - still have lingering doubts, put the ques- after the programme discussion. the preliminary rehearsals are carried out tion to a film director who works fever- When, a date has been found for at Broadcasting House. Once in the tele ishly all day, rehearses his artistes line by " Hotel Cosmopolitan," the programme is vision studio the show is treated as if it line and shot by shot, is mortified a dozen allotted a space in the elaborate time -table were actually on the air ; the producer, times in as many hours by having to of the Productions Department, which is after a brief period on the floor wall the " cut " and start again, and whose daily output of screen time is ... perhaps two minutes. His reply is a foregone conclusion. Achievement And still television lives. Animated images have been thrown on the opalescent screen for more than 450 hours since November 2nd last year. Drama, variety, ballet, musical comedy, talks, outside broadcasts, orchestral works, recitals -=all these have been presented, and although the programmes are, of course, open to all the winds of criticism, it is generally conceded that production has reached a stage of finesse which justifies the serious consideration of entertainment lovers. How does a programme evolve from an idea to a finished production? The story of any particular production begins just about five weeks before it springs to life on the screen. Someone on the programme side is visited by an idea -Dallas Bower thinks of " Pasquinade," The stage is set. By the judicious use of scenery Peter Bax creates atmosphere in the studio. George More O'Ferrall of " Hassan," This photograph was taken during Harry Pringle's show " Music Hall Cavalcade," which Stephen Thomas of " Derby Day " -and was produced in May.

www.americanradiohistory.com Wirelesss World, July i6th, 1937 5r the Making By ALEXANDRA PALACE T E. C. THOMSON

Instruction in golf artistes, leaves that side of the business to in Alexandra Park the studio manager, and takes his seat at was one of the first O.B.s attempted by the producer's window high up at the back the television staff. of the studio. There, so far as his own Here Miss Poppy show is concerned, he is monarch of all Wingate is seen he surveys. Facing him are two monitor demonstrating a shot before the camera tubes, one showing the picture which, if in June. transmission were on, would actually be radiated, and the other giving a choice of pictures from the other cameras in the mopolitan." After three hours' rehearsal with " Revolving Door," the opening studio. At the " word of command " the on the morning of the day itself, includ- chorus. sound and vision control engineers supply ing a final run -through timed by the studio Meanwhile, the producer has his hands any combination of picture and sound that manager's stop- watch, all is ready for full. Following continuity " he has transmission at, say, 3.25. As the time faded from the caption card to the tele- draws near the producer gives a last cine circuit for a film loop showing the anxious look round the studio and then bustle and excitement outside a large ascends to his uneasy chair to watch the hotel, and is now bringing down the gain closing shot in the preceding news reel, control on orchestra for- the announcer's which, incidentally, has been timed to the opening sentences. Back to full volume split second in the Film Viewing Room. on orchestra, he fades out the film loop " Two minutes to go " he signals to his and brings in Camera I on the Cosmopoli- studio manager, who blows the warning tan Choristers gyrating around the revolv- whistle. People in the studio talk in whis- ing door. ers. A make -up assistant dashes on to the The show is on. set to powder a nasal high light . . . an O.B. Technique In the first of Outside broadcasts are controlled in just these three photo- the same way, the only difference being graphs the camera man is seen that the producer is denied a direct view focusing on the of what is happening, and must rely on players on the what he sees in the monitor and on mes- Centre Court at sages received by field telephone from his Wimbledon during the tennis " studio " manager. He is, of course, in champions h i p s. constant touch with camera and micro- He is kept in phone squads by means of headphones. touch with the Starting cues are usually given by the the producer may require. control van by man instructions from During rehearsals the producer means of the camera on the con- ` headphones he is trol desk. uses a ' talk back " speaker, wearing. The " And that, ladies and gentlemen, con- but this, of course, cannot be middle picture cludes our television transmission for to- employed during actual trans- shows the tele- day " says the announcer at the end of the mission; but he can still communicate with the studio by visual signals, through headphones worn by the camera and microphone operators, and by telephone to the studio manager. Cue lights are also used, and are invaluable to

the announcers and the conductor of the vision cable , orchestra. among a number of others, leaving the commenta- Improved lighting and make -up tor's box to be carried, as shown Although make -up is rarely required for in the third pic- rehearsal, Miss Mary Allen, in charge of ture, to the Evan which was sta- make -up and wardrobe, or one of her tioned a quarter assistants, is present to observe whether of a mile away. certain faces are likely to need special attention, and each artiste is watched on the announcer does smiling practice before day's programme. Staff and artistes go floor and on the studio monitoring re- camera 3 . . . the senior studio engineer home. Hotel Cosmopolitan " and all ceiver. Nowadays, since improved light- moves a lamp a few degrees. Then another the effort it involved will soon be for- ing has been made possible, a very light whistle, and the red indicator registers gotten, for tomorrow a fresh band of make -up is required. " Sound on, Vision on." A green cue artistes will arrive to give the public The stage is set, then, for " Hotel Cos- light flashes and the orchestra strikes up " something new."

www.americanradiohistory.com 52 Wireless World, July 16th, 1937

spoil the enjoyment of the book by giving the dénouement aiiaS7. .y During the past few days my attention , has ,been devoted to an enthralling work on " Occupational Diseases," and I have been learning all about such things is Naturally, when the move had taken Housemaid's Knee, Writer's Cramp, and By place and the set went off colour all sorts Commercial Traveller's Conscience. The of things such as local screening was sus- best part of the book, however, is that FREE GRID pected, but these were discounted by the which tells of the curious psychological fact that the performance of an old bat- symptoms brought about by certain tery receiver which my friend possessed activities: Who_ would have thought, for instance, that persistent working in the Another well -known and was quite as good in the new house as in the old. Lost Property Office would result in the ar respected figure. development The AC set was thoroughly over- of absent- mindedness and hauled without improvement, finally memory weakness. The most interesting and of all Inferior Electricity it occurred to my, friend to make these curious psychological effects, the however, AGOOD many of you will no doubt acquaintance of the tenant of his is that which has been noticed old in connection recollect the great howl of indigna- dwelling and arrange for the mains con- with wireless servicemen. tion which went up throughout the land nections from his set to be passed over According to the report they invariably, some years ago when the various gas the garden wall to one the appear to develop habits of unpunctuality of lighting after they companies started to charge by the therm sockets of his old house. At once the set have been in this occupation instead of by the good old cubic foot. behaved normally, and, naturally, this for some little time. Strangely enough Everybody started to moan that they was immediately taken to indicate that the this curious " disease " has also been observed were being cheated and couldn't under- fault was in the mains. Accordingly, the to be prevalent among whaf the stand why one company gave more cubic voltage was tested by means of a borrowed report terms " Amateur Wireless Service- men " by which, feet to the inch than others ; in fact, those AC voltmeter and the periodicity checked I take it, is meant companies whose gas was so good that it with a stroboscope on the gramophone people who repair their friends' sets, and, possibly, required less feet to make a therm than turntable, the stroboscope being one home constructors also. others were accused of swindling, just as which he had used in his old residence. In Apparently medical science is completely though they had been trying to supply, both cases all was found in order. baffled by this strange effect, and can suggest cubic feet containing fewer than twelve The net results of all this is that my neither the cause nor the cure. cubic inches. friend is quite satisfied that his indifferent To my mind this attitude on the part Although Mr. Therm is now quite a reception is solely due to what he alleges well -known and respected figure in the to be the " poor quality " of the current community, I do not think that the supplied to him, and unless I can find`a average man really understands his better explanation very quickly he is relationship to the cubic foot even now, going to the expense of having a per- as only last week, when paying a visit manent cable laid from his old house, he to an old acquaintance who has recently, having come to the necessary financial moved to a new abode, the indifferent arrangement with the tenant. If, there- performance of his mains radiogram was fore, any of you power station wallahs excused on account of the " poor quality can give me a helping hand in the matter of the current supplied." When I asked I shall be very grateful indeed, as my the reason for this astounding statement technical reputation is at stake. my friend justified it on the grounds that it was obvious that it must be so as all other explanations of the set's poor performance had been exhausted, and, Debunking Psychology furthermore, the cost per unit was IKE myself I suppose that you fellows cheaper than in the .last district in which often get tired of the sentimental Hints and Tips -Simple de- magnetisation he lived, this being " similar to the case slush offered for our mental recreation by of one's time-piece. of gas, the cost of a cubic foot of which the bookstalls, and yearn for some more is also less when the quality is inferior." ennobling literature. Whenever this sort of the medical men is merely another in- I naturally laughed his explanation to of feeling comes over me more strongly stance of the objectionable habit of scorn, and after trying my best to make than usual I almost invariably repair to scientific men generally of seeking long- him understand that the cost of gas didn't H.M. Stationery Office and seek to winded and elaborate explanations of depend on its quality, I pointed out that elevate my mind by some of the soul - quite simple and straightforward effects in any case the " quality " in the case of stirring works which they publish. and overlooking the obvious and simple electricity could not possibly vary. I I always find that, among other things, causes which lie right under their noses. must confess, however, that after hearing the termination of the stories published It seems quite clear to me, for instance, all the evidence I am not feeling quite so by the Stationery Office is totally unex- that the cause of unpunctuality among cocksure about the matter as I am at a pected which is so unlike the case of the wireless servicemen is merely that their complete loss for an explanation of the average cheap novelette where anybody, watches are slow due to the gradually set's wretched performance. with any gumption at all can detect right increasing retarding effect brought about My friend's new house is in the next from the very first chapter who it was by the magnetising of their " innards, street to his old one, and the two gardens that murdered the old squire and stuffed which is inevitable among people who actually back on to each other. The two his body into the refrigerator. As an are constantly messing about in the houses are, however, in different boroughs instance of what I mean I may mention vicinity of powerful loud speaker and receive their electricity supply from that quite recently I finished an exciting magnets. The cure is as simple as the different undertakings, although the volume entitled " Causes of Mortality in cause, namely, to hold the watch for a voltage and periodicity is the same in the Mercantile Marine," and found that few moments each day in the vicinity of both cases. The set is a conventional the principal cause is not, as I should a powerful AC dynamo. Any power AC model which has given perfectly good have thought, fire or tempest, nor is it station engineer will be only too happy results in my friend's old house. what you think either-but I will not to oblige if approached in the right way.

www.americanradiohistory.com Wireless World, July 16th, 1937 53

Creating Authentic Atmosphere This is a knock at the farm- yard school which thinks that you have only to bring an BROADCAST BREVITIES honest -to-goodness countryman to the " mike " in order to pro- Propaganda NEWS FROM PORTLAND PLACE vide the authentic atmosphere WHILE one marks a growing of the locality. There has been restlessness in many quar- cashiers, control room engineers To Be Seen, but . . . a little too much of this sort of ters over the amount of propa- and announcers. In the Talks BALANCE and control engi- thing in the past. The man -in- ganda which is being put on Department Mr. Roger Wilson neers in St. George's Hall the- street is a good fellow, but the air in various languages by was translated from London to have been wearing a worried ... well, let us leave it at that. German and Italian broadcast- Manchester, while Mr. I. Cox expression of late, the reason Mr. Beadle's aim, and it might ing stations, the Government performed the journey in the to well be copied in some of the being that their little cubicle regions, and the B.B.C. preserve an un- opposite direction. Mr. T. Dor- the right of the stage is not other will be to employ ruffled serenity. The most mer, the Chief Cashier, resigned local talent at all times, so long that soundproof. All sorts of canny as can be drawn from Government on attaining the age limit, his attempts to keep out the sounds it is talent. spokesmen in reply to questions place being taken by Mr. J. S. from the stage and auditorium in the House of Commons is Dawbarn, who was originally a failed, until the other day a A Cairo Canard receptionist. that the matter is receiving con- genius suggested the use of IT is time to nip in the bud sideration. Mr. G. C. Beadle, chief of the special sound -excluding 'phones. certain rumours anent the Staff Training College, applied Several pairs of these, which meeting of the international tele- Other Methods for the post of West of England are of the moving-coil type, graph and telephone delegates Regional Director, and got it. The delay in announcing what have now been provided, and it at Cairo in 1938. Suggestions He takes up his duties in Octo- is one steps, if any, are to be taken to understood that could have been made that the agenda ber. Mr. H. M: Fitch, who was drop a Mills bomb counter foreign propaganda is within six includes discussion on questions Assistant Regional Director in feet of the engineers and they of broadcast propaganda and due to several causes ; the most Manchester, is now Acting would still maintain their jamming reprisals. Actually, important being that while the Regional Director in place of balance and control. B.B.C. is fully aware that its the conference will be concerned Mr. E. G. D. Liveing, resigned. tOt Gal CO, machinery is available and may WI exclusively with the technical Mr. Beadle Speaks aspects of electrical communica- some day be commandeered for Transferred to Television engaging in the game of vocal JUST what do the Regions tion, of which broadcasting is a pyrotechnics, other propaganda To television came Mr. R. A. want that the National pro- part, but only a part. methods are at Great Britain's Rendall, after organising the gramme cannot give them? This ¡o, <4,1 tc, command. For Palestine Broadcasting Com- question is not easily answered, Murder in Television example, and some of the doughtiest through the ruling princes, pany ; Mr. Jan Bussell, trans- champions of local in Studio whose lightest word is law in ferred from a Producership at talent become - TELEVISION pro- their own domain, she can in- Manchester ; and Mrs. Mary broadcasting tongue Adams, from the Talks Depart- tied when pressed to explain. grammes from Alexandra fluence India's millions ; through Palace in the autumn are to races ment at B.H. But Mr. G. C. Beadle, who the leaders of native them- has just been appointed West of include more original material selves, living beneath the British Restless Occupation England Regional Director, has than at present, and script flag in other Dominions, colo- definite views on the point. writers are now getting busy on nies and protectorates, she can Paul Askew, formerly Dance plays specially suited to the reach those to whom she desires Bands executive, is off to Bris- Where the Artiste Comes In television medium. that the facts shall be known. tol as Studio Executive there. " It is easy enough," he says, One play in preparation deals Foreign Office wireless, or B. Walton O'Donnell, conductor " to broadcast -concerts, dance with a murder in the studio ; " British Official," is also avail- of the B.B.C. Military Band, able for disseminating news. becomes Music Director at Bel- Thus Portland Place does not fast. " Freddie " Grisewood has expect to be asked, at present at left the announcing staff at all events, to give up programme headquarters for the wider field time to foreign language broad- of O.Bs. -and so the tale goes casts whose effectiveness is on. doubtful. Broadcasting is a restless occupation, and rightly so. To in Round " settle down " would mean Round Pegs stagnation. Holes t, WI dl d LIKE an ever -rolling stream, Bouquets for Empire life in Broadcasting House Station is constantly on the move, al- SINCE the new Empire trans- ways changing. Since the be- INTEREST IN TELEVISION. Over 48,000 persons visited the ginning of the year considerably mitters at Daventry took of -boiled Television Exhibition at the Science Museum, South Kensington, more than two hundred altera- the air some the hard during the first three weeks. This flashlight photograph shows tions in staff have taken place, critics in the Antipodes have a part of the crowd watching demonstrations of two of the eight consisting of new appointments, paid handsome tribute to the commercial receivers that are being shown in operation. changed conditions. Says Wire- transfers and cessations ; and in less Weekly (Australia) : " It bands and all forms of ready - another centres round the dis- general the object has been to made entertainment, but these covery of chloroform in 1847 and get the round pegs into round would be difficult to imagine broadcasts of a better type than by themselves are not enough. the dramatic moment when half holes and to prevent them from The important side of regional a dozen doctors, led by James being kept too long in square can now be heard from . . . on broadcasting is not to be found Simpson, nearly killed them- holes. In many cases transfers Daventry. The stations the 19 -metre band provide a ready made ; it has to be created selves while experimenting with are asked for by members of afresh every time." the new anaesthetic. the staff themselves, and one wonderful entertainment. On rg metres GSO is the most con- Mr. Beadle considers that real But perhaps the most vivid may assume that these are sistent transmitter." regional entertainment consists programme in store for viewers anxious to avoid stagnating in South Africa is just as of creating sound pictures in will be that built around all the one job year in, year out. pleased. Says the Cape Argus: speech or music of regional ceremony of the arrival and de- "Reception has never been affairs, present or past, and pre- parture of an Atlantic liner. General Post better from the B.B.C. studios. senting these pictures to the Some of the scenes will be The list of transfers is an im- If any listener is dissatisfied let audience with a degree of finesse filmed in advance at Southamp- posing one, for it includes him speak now, or for ever hold which is only found in the ton, and the film interspersed Station Directors and junior his tongue." artiste. appropriately in the programme.

www.americanradiohistory.com 54 Wireless World, July 16th, 1937

noise -to- signal ratio. Just how bad this can be, with a small superhet, at any rate, has RANDOM RADIATIONS been brought home to me rather strikingly of Iate. Wanting (partly out of sheer curi- osity, and partly because I had a man stay- The Welsh Regionals By "DIALLIST" ing with me who knows several oriental NOW that Wales has achieved not just languages) to hear what the Italian pro- one, but two Regional transmitters of grammes for the Far East were like, I tried its very own, its long -standing grouse Plywood and Boom several times to tune -in the Rome transmissions against the B.B.C. should be removed once IN the old days when wireless sets were ex- on 25.4 metres at intervals between and for all. The old arrangement of trying 3 o'clock and 4.30 in the afternoons. The pensive, the cabinets that contained station to satisfy both Welshmen and West their works were often made of good thick apparently uses some kind of direc- Countrymen with the same Regional pro- wood, cut from the solid tional aerial for these, for signal strength plank. Nowa- here is gramme obviously couldn't work. What- days, when the aim of so many manufac- considerably below normal. If any ever happened, the Welshmen complained turers seems to be to turn out something reader cares to try for himself, he will find that there wasn't half enough Welsh in the rather that he has to turn the wicks right up, with cheaper than the next man's, the ply- the programmes, whilst the men of Devon and wood cabinet -and, it may be, not very result that background noises make Somerset and Cornwall were equally certain thick plywood at much of the programmes exceedingly hard that -seems to have come to follow. that there was far too much. And you can't to stay. Plywood has, of course, much to Some of the noise is undoubtedly be surprised. Welsh folk love their own recommend it, for it due to mush, which any kind of set would can be obtained with bring in, language, which is as unintelligible as all kinds of beautiful veneers and it lends but the greater part of it seems to Swahili to the great majority of people liv- itself to original and striking designs. But me to be peculiar to the superhet. ing south of the Bristol Channel. In fact, I can't help thinking that a good deal of Queer Languages you can't really imagine two more dissimi- the boominess, about which many listeners lar regions in language, music, thought and complain, is due Still, there are times when these trans- to the use of plywood. I missions to the Far outlook than Wales and West. They are far wonder if any maker of moderately priced East come in pretty more unlike in many respects than London receivers will be bold enough well, and when you happen to strike respect- to try the ex- able conditions you and North Scottish ; for one thing, the Scots periment of offering can spend some interest- the same chassis in a ing moments in have no desire for the bulk of their pro- de luxe cabinet of solid wood at a somewhat discovering how queer some grammes to be transmitted in Gaelic. higher price? languages can sound. One of the strangest I have an idea that the ex- that I have periment might be rather successful if come across so far is Chinese, Will Wales Respond ? the which gives you cabinet were particularly designed to avoid the impression that it con- The next question is whether, now that boominess. sists entirely of questions, owing to its Anyhow, it might be worth try- peculiar rhythm the B.B.C. has done its bit by giving Wales ing. I don't mean that the more expensive and the way in which the all the Welsh programmes pos- speaker's voice runs up and down the musi- that it can set should be the only one offered ; my idea cal scale ! There sibly want, Welsh folk will play up by be- is that it should be there as an alternative is no difficulty about tell- coming more interested in radio? At the to the standard model. ing which language is being used, for the end of last year Wales showed announcer always gives out in English that the poorest ti % % figure but one for the ratio of licences to Superhets and the talk will be in such and such a tongue. Sensitivity The talks in Eastern languages always " estimated number of households." That TOUCHING seem estimate was made by taking average recently on the much vexed to come on at about 4 o'clock, after the the question of number of persons in a family for the whole the superhet versus the news and the musical programme. Try it of Great Britain. In Wales, though, large straight set, I mentioned that one of the for yourself and you will get some idea of families are not uncommon and I'd he in- drawbacks of the former was that if you the extraordinary variety of noises that the clined to think on made use of anything like the full sensitivity human animal makes in different parts of that this account the real in number of households is possibly less than available order to hear a weak signal you the world in order to communicate its the 659,660 shown in the B.B.C. report. It were apt to obtain a_ most unsatisfactory thoughts to its fellows. is, . perhaps, rather remarkable that though even last year the Washford Cross Regional programmes were so largely in Welsh, West Television Programmes Region showed a percentage of 66 of licences to households, as against 53 for Wales. So Transmissions are from 3 -4 and 9 -10 daily far, increase the produced by the opening Vision 49 Mc of Penmon has been distinctly disappoint- /s. Sound 41.5 Mc /s ing. One hopes that now that Wales has FRIDAY, JULY 16th. TUESDAY, JULY zoth. 3, Freddie Dosh -Comedy also a 70- kilowatt Regional on the very Impressions. 3.5, 3, " The Man with a Flower in His Mouth "- favourable Friends from the Zoo -first Zoo O.B. 3.20, a Dialogue by Luigi Pirandello. wavelength of 373.1 metres Film Casting Animals." 3.30, 3.15, Film- there may be a rapid and continuous rise in -" Television " Ladybirds." 3.25, Eric Coates conducts Follies, presented by Gordon Crier. 3.50, the B.B.C. Television the licence figures. Gaumont Orchestra -solo saxo- -British News. phone, Ken Gray. 3.50, Gaumont -British 9, Friends from the Zoo, by Alan Best. 9.15, News. National Reception Film Wayward Canary." -" 9.25, " A Review 9, The John Carr Jacquard Puppets. 9.15, I can't help wondering how some parts of of Revues," presented by Dallas Bower. 9.50, Film Lobsters." British Movietonews. -" 9.25, Cabaret, with Eric the West Country will fare during the time Wild and his Tea -Timers. 9.50, British that they are deprived of a " local National " SATURDAY, JULY 17th. Movietonews. station (what a queer contradiction in terms 3, " Swings and Roundabouts " -an O.B from WEDNESDAY, those words are !) until the Start Point the Fair in Alexandra Park. 3.15, Film- JULY 21st. transmitter gets to work and the non -Welsh " Wayward Canary." 3.25, " Have You For- 3, Ernest Mills, Cartoonist. 3.10, " Boys and station at Washford Cross resumes its gotten ? "- Remembered by Jean Colin, Monti Girls Come Out to Play. " -O.B. from Alexandra National status. I know the Ryan, Richard Murdock and Percival Mackey Park. 3.25, British Movietonews. 3.35, Ad that " Luxem- Lib.-Revue by Herbert Farjeon. burg effect " is pretty pronounced in some and his Band. 3.50, British Movietonews. places, whilst in others Droitwich fades very 9, Reine Paulet, in French Songs. 9.5, Film- 9, Marie Eve in Continental Songs. 9.10, " Casting Animals." 9.15, Freddie Dosh- Repetition of p.m. programme. 9.25, Gau- badly. However, I hope to be able to -write mont British 3 ere long from first -hand knowledge, Comedy Impressions. 9.25, Gaumont -British News. 9.35, " Mizzen Cross for I am News. 9.35, Repetition of 3.25 p.m. programme. Trees " -Revue of Nautical Songs and Dances. expecting to take the holiday that I feel is so richly deserved -curious how difficult it MONDAY, JULY 19th. THURSDAY, JULY 22nd. is to convince others that you're overworked 3, Film -" Lobsters." 3.10, Derby Day. Comic 3, " Starlight " -Elsie Carlisle, accompanied a place in Mount's Opera by A. P. Herbert. 3.50, British Movie - by Ronald Aldrich and Freddie Aspinall. -at Bay, -which is re- tonews. puted to be exceedingly bad from the Home 3.10, Talk by Myfanwy Evans -" Expedition broadcasting point of view. The programme will be interrupted during this on a Bicycle." 3.25, Gaumont- British News. Naturally, it'll afternoon and tomorrow be a busman's holiday, for I shall afternoon for short relays 3.35, Repetition of Tuesday's 9.25 p.m. pro- take at from the Inter -Zone Final of the Davis Cup at gramme. least one wireless set with me. I am won- Wimbledon. dering just how much it will 9, Repetition of Tuesday's 3.0 p.m. programme be possible to 9, Film -" Ladybirds." 9.10, Repetition of 9.15, hear of the home programmes, particularly Film-" Mickey's Pal Pluto." 9.25, 3.10 p.m. programme. 9.35, Gaumont -British Repetition of 3.35 p.m. programme. 9.50, the National. News. British Movietonews.

www.americanradiohistory.com Wireless World, July 16th, 1937 55 Frequency Modulation By A POSSIBLE SOLUTION OF "CATHODE RAY" SOME DIFFICULTIES the receiver being capable of selecting either of them without interference from But this spreading is really quite THERE are two serious obstruc- the other. Assuming it is technically from modulation. tions in the way of radio com- different frequency practicable, it is thus possible either to little while ago I When a single audible programme fre- munication. A double the number of programmes in a of them quency, such as a r -kc tuning note, is wrote about one - /s given waveband or (preferably) to double the limiting factor in the impressed on a wave of 500 kc / s, Noise*-as carrier the band -width of each, and so to improve before the limit the carrier remains there, but is supple- range of reception. Long the quality and ease of separation. modern tech- mented by frequencies of 500 of amplification possible with side ± i Although I have no definite information is reached noise steps in and makes kc / s, which are also of fixed frequency nique on the point it does appear that an useless to go any farther. so long as that note is being transmitted it ordinary broadcasting station with narrow The other obstruction -crowding of (Fig. 2). The strength of the tuning note, wavelengths -limits the number and or depth of modulation, is represented by quality of transmissions that can be put the strength of the side frequencies rela- out. If half the stations in Europe were tive to the carrier wave. Of course, in a eliminated, the other half could be re- musical or speech programme these side - ceived much better. frequencies are very numerous, and In the article on noise I referred occupy a more or less continuous band rather sketchily to the Armstrong fre- each side of the carrier wave (Fig. 3). If quency- modulation system which has been the tuning note were being transmitted by iI u IIII VIII I I 500 kc /s proved by practical experiment to be a frequency-modulated transmitter the tokc/s >< 10kc /s capable of things that were thought im- carrier wave itself would shift up and FREQUENCY possible ; such, for instance, as better re- down at a frequency of i kc / s, and the of ception under severe conditions atmo- width of the frequency band covered by Fig. 3.-Or a complex programme like this, spherics, etc. , from a 2- kilowatt trans- it in this process would have nothing to where the single side frequencies spread out mitter 85 miles away than from the regular do with the frequency of the programme into sidebands. 50-kilowatt broadcaster at only 20 miles. but would be a measure of its strength. Unhappily, the system is very complex In the Armstrong system ioo kc / s might. frequency modulation superimposed would continue and inapplicable to the ordinary broadcast be taken to correspond to no per cent. to give the same service as at waveband because the superiority as represent to owners of ordinary receiving gards signal/ noise ratio depends on sets, and listeners who cared to use special using a wide frequency band such as zoo receivers would be able in addition to kilocycles, which occupies the room of switch over to the alternative programme. eleven ordinary stations, and so must be Such a scheme would make it absolutely relegated to the ultra -short waveband. essential that the two sorts of modulation Thus, if the Armstrong system success- should not be mixed up at all. In the fully presses back one of our two obstruc- type of transmitter in which the modu- tions, it does so only by yielding ground 499 k c/s 500 kc /s 501 k C/S lator acts directly on the oscillator valve, to the other. FREQUENCY still used in many amateur stations, ampli- Frequency modulation means that the tude modulation is accompanied by fre- programme is impressed on the carrier Fig. 2. -The simplest possible programme- quency modulation, and the same pro- wave by causing its frequency to oscillate a note of one constant frequency -would gramme would be heard however the then be represented like this on the ordinary receiver were arranged. Of course, modern around the normal instead of by varying amplitude- modulation system. its amplitude as in the ordinary system. broadcasting stations set a very high modulation. But if the anti -noise proper- standard, and the chief burden falls on ties are sacrificed it is quite possible to the receiver. It is not at all easy to obtain full modulation by a frequency design a reasonably simple receiver shift of perhaps only o. z kc / s. No doubt Capable of separating two programmes from even a perfect transmitter. you will say, " Oh yes ! This means that broadcast stations could be packed olìly o.2 kc / s or so apart if they were frequency - modulated, instead of the present 9 kc / s 500 kc /s k so is inadequate)." Well, as FREQUENCY (which even a matter of fact it doesn't ; for even a frequency - modulated carrier Fig. 1. -An unmodulated carrier wave narrowly might be represented like this. covers a frequency band just as wide as any other, though this may not be obvious Some readers may not be quite clear about proof. But there is 600 k c/s without mathematical FREQUENCY this distinction, because they know per- one way in which it might be possible fectly well that the ordinary or amplitude - to attack the problem of overcrowding. modulation system causes the frequency It consists in modulating the transmitter Fig. 4. -A frequency -modulated trans- of a transmitter to spread out by the for- so impressing two mission consists of a carrier wave vibrating both ways at once and in frequency over a range dependent not on mation of sidebands. programmes on it simultaneously. The the frequency but the strength of the s Noise, Jan. 15th, 1937. success of this idea obviously depends on programme.

www.americanradiohistory.com 56 Wfipg@go JULY 16th, 1937 WopIld1 Frequency Modulation- in practice be established at the second come some simple contrivance that was easy . J. R. Woodyard, in the Proceedings of detector of a superhet. So I started on to use and easy to read. the I.R.E. (May, 1937), has given some those lines, loosely coupling the IF valve One idea put up by a reader is so in idea of how it might be done. Anybody to the diode detector, and coupling both genious that I feel an urge to make it up if who has possessed a receiver with reaction to a local I can find the time to do so. Briefly, it oscillator. These couplings had consists control, and who has even been so un- to be of a fixed disc surrounded by one rather carefully adjusted to get the that is movable. scrupulous as to allow it to oscillate when Fig. 5 type of result at all, but when at The movable disc is marked off into receiving a station, knows that the beat - last it was obtained there was a very hours ; the fixed one into degrees of longi- note or howl obtained in this way falls in marked suppression of the programme tude and the names of key stations. The pitch the more closely the receiver is outer disc carries a metal arm, which, over tuned to the carrier wave. The fre- certain parts of its travel makes contact quency of the note is, in fact, equal to with one or other of two pairs of copper the difference in frequency between the strips. There is also a fixed pointer. The receiver oscillation and the carrier wave, whole arrangement is mounted on a shallow and so it ought to be possible to make it box containing a flash -lamp battery and two bulbs behind a red and as low as one likes. In practice it falls green window respectively. As you turn the disc, all times quite steadily to a certain pitch and then shown with neither bulb alight are " to- disappears completely, and there is a day." When the pointer, by making con- small tuning range over which no beat tact with one pair of strips, causes a green note is heard, before it reappears the light to appear, the hour reading is " to- other side of exact tuning. The cause of morrow." Similarly this result is that the carrier wave pulls the appearance of a the receiver into step with itself, and the red light indicates stronger it is that the hour is the wider is the silent space. " yesterday." Under certain conditions of coupling It would take a between signal, local oscillation, and de- bit of working out, tection the detector response is unaffected but it might prove by the strength of the incoming signal, a very useful gadget but is affected by the frequency within f o r long - distance the silent space. In other words, it work. responds to frequency modulation but not Another most handy adjunct for to amplitude modulation. Fig. 5 illus- Fig. 6.--Circuit diagram (due to J. R. Woodyard, Proc. I.ß.E., the D.X.'ers table is trates the type of result described by Mr. May, 5937) illustrating the method of getting the result shown in the great circle pro- Woodyard ; the diagonal line shows how Fig. 5. jection map of the the detector response depends uniformly world published by on the signal frequency within the silent over the middle portion of the silent space. The Wireless World. It enables you to space, which usually covers only a few I never managed to get anything ap- obtain the distance and the true bearing of any hundred cycles at most. IIf the signal is proaching complete suppression, but the station that you may pick up in a brace of shakes experiment was rather rough and the cir- with the aid of an ordinary foot rule marked off into tenths of an inch -one- cuits unscreened.. It was very noticeable tenth equals ioo miles. that the lower audible frequencies were I've had mine mounted in linen and sec- suppressed much more completely than tioned so that it folds up compactly. The the higher. Mr. Woodyard claims to sectioning, of course, very slightly impairs have achieved separation of two pro- its accuracy, but not so much as to make grammes complete enough for listening any enormous difference. And, in any case, purposes. if you want measurements or bearings of precision it's easy enough to allow for the ÑSILENT, Apart from the objection that broad- gaps caused by the sectioning. SPACE" casters would risk causing interference by There have been reports that Moscow trying it, the receiver would be very tricky No. r, on 1744 metres, SIGNAL FREQUENCY has been deliberately to adjust, and, of course, to -day's trend is interfered with of late. I've tuned in to all in the direction of making things very this station several times lately when pro- Fig. 5.- Showing the curious sort of res- simple for the listener. Still, a receiver to grammes in various foreign languages have ponse given by a receiver detector to a do all the things a very up-to -date model been going on and so far I have not come signal on which a local oscillation is super- now does would have seemed to a 1927 across any sign of attempts to jam the trans- imposed when conditions missions, except are suitably engineer to have to be excessively tricky.' the German tall:. adjusted. - Japanese medium -wave stations have But in 1937 it is the manufacturer who has been heard, and heard strongly, in this country ; made stronger the silent space is widened performed all the tricks and the listener but has any one ever succeeded in picking out, as shown by the dotted line, but the has practically nothing to think about- up any of the stations in Australia, New original diagonal part is entirely un- or that is the intention, anyway.. Zealand, Hawaii, China and other places in affected. Theoretically, therefore, an the Far East and in the region of the amplitude-modulated programme would Antipodes ? Many of these stations are pretty well be inaudible, and a frequency -modulated heard in America, but they don't seem to reach us. The most favourable time programme heard ; and by . switching off DISTANT for trying for them is a little before daybreak the local oscillator the situation would be -perhaps that's why we don't have more reversed (assuming the recei'*r tuning to RECEPTION NOTES success with them. D. EXER. be flat -topped within the limits of frequency modulation). Y best thanks to those readers who HARTLEY TURNER M12 RECEIVER This sounds so remarkable that I did a have been kind enough to send me IN the circuit diagram of this receiver which little investigating on my own. The suggestions for overcoming the diffi- appeared in our issue of June 25th, con- elementary circuit given by Woodyard is culty of ascertaining the local time in distant densers were omitted from the leads from the countries and for remembering, diodes to the IF output filter and from shown in Fig. 6, in which A, B, and C once you've the found the hour, lead joining the " Earthing " end of the first indicate the couplings on which the whether it's yesterday, to -day or tomorrow. Actually, I have a tuned circuit in the aerial, input filter to the proper action depends ; coupling coils. A complete but he points out time -chart and use it to some extent but it circuit, including that to avoid separate adjustment of these the output and rectifier stages, is available isn't a very satisfactory one. I feel sure from Hartley Turner Radio, Ltd., Thornbury circuits for each station this process would that, like myself, fellow D.X.'ers would wel- Road, Isleworth, Middlesex.

www.americanradiohistory.com Wireless World, July 16th, 1937 57

Wireless and Whales MANY experts are prophesy- ing the rapid extermination of the whale, owing to the fact that now the New Zealand whale Current Topics fishing companies are reported to have equipped their fleets and listeners should not be radiated tions of any important matches depots with wireless telephony EVENTS OF during normal broadcasting they choose. A similar arrange- in order that rapid information hours, but should be sent only ment has been made in the can be transmitted concerning THE WEEK at a special time of the day. An neighbouring country of Fin- the movements of whales. It is alternative suggestion is that land. thought that it will not be long IN BRIEF special " talks " stations should before most whaling fleets ;n be provided, working on an ex- Scandinavia Encourages other parts of the world are REVIEW clusive wavelength. Tourists similarly equipped. IN future, foreign visitors to An Interesting Russian Denmark are to be permitted Chinese School Television at Ninety Experiment to use wireless receivers for two Broadcasting Miles A TRIANGULAR conversa- weeks without being called upon THE Minister of Education in ACOMPLETE programme tion has recently taken to pay for a licence. After this China has decided to equip from the Alexandra Palace place between people travelling they must pay the equivalent of a further 5,000 schools with re- has been successfully received at by land, water, and air. It was 9s. for an ordinary annual ceiving sets. There are at the G.E.C. works at Coventry. arranged for experimental pur- licence. In Norway visitors are present 2,000 provided with Although brief extracts have poses by the Soviet Army to be allowed to use sets for sets. All schools receivers are been received on previous occa- authorities, and very successful eight weeks free of charge. made in the State factory in sions, it has not hitherto been results were obtained. The Shanghai. possible to " hold " the transmis- travellers by water were in a Radio Rowdies sion through the entire period submarine, the land travellers THE increasing degree of Sponsored Programmes of the programme. A standard being in a fast - moving annoyance caused to neigh- . is well known, American receiver was employed in con- car. bours in certain quarters of Paris AS broadcasting programmes junction with a special high - by the habit indulged in by are not paid for out of licence efficiency valve in one part of Swedish Broadcasting many thoughtless listeners of fees as is the case in this the circuit. Dispute Settled operating loud speakers at full country, but by various com- THE recent difference of volume all day and far into the mercial concerns who sponsor Indian Wireless Trade opinion between the night is having some unforeseen programmes for the purpose of Figures Swedish broadcasting authorities consequences. Certain sufferers, interlarding them with advertis- THE imports of wireless ap- and the leading football clubs exasperated at having been un- ing announcements. Drug firms paratus into India show a concerning the question of pay- able to obtain relief by legal are by far the largest users of steady yearly rise. In 1934-35 ment for broadcast running means, have been deliberately radio advertising, they being the value of the imports was commentaries on important causing etheric interference by responsible for no less than 33 1,600 000 rupees. This increased to 2,600,000 rupees in 1935-36, and to 3,500,000 in 1936 -37. A further large increase is expected for the year 1937 -38. The largest share of the trade was taken by the U.S.A., which exported wireless goods to the value of 1,602,354 rupees to India during the past year. The United Kingdom exported 1,262,625 rupees' worth. Hol - land despatched to India radio goods valued at 438,660 rupees, the share of the trade captured by other countries being 236,432 rupees. European Listeners THERE are now over three - quarters of a million licences issued in Poland, the actual figure being 773,470. A large increase is expected when the various new transmitters which are projected are put into service. On May 1st there were 922,814 listeners in Belgium, and 972,694 in C zechoslovakia. On June 1st France had 3,926,902, a n d Germany 8,372,848 listeners COMPREHENSIVE CARGO BOAT INSTALLATION. The S.S. Malancha, which ran her trials last week, has, in addition to a 600f800 -metre ICW/CW installation, by Gambrell Radio Communications, a short -wave France Decries Uplift transmitter, auto alarm and direction finder by the same firm. The capacity of the independent emergency Programmes gear greatly exceeds B.O.T. and international requirements. ARESOLUTION has been matches has now been settled the use of various pieces of ap- per cent. of the income of one passed by the Congress of in a satisfactory manner. In paratus such as violet -ray leading broadcasting company. the French National Federation future the broadcasting authori- generators. The operation of Foodstuff firms come second, of Broadcasting demanding that ties will pay a fixed amount such devices makes reception im- they accounting for 27 per cent. programmes of an educative and annually to the association of possible over a wide area and of the income. Motor manufac- informative character appealing clubs, and this will give them causes the innocent to suffer turers, who contribute io per only to a limited section of the right to broadcast descrip- with the guilty. cent., occupy third place,

www.americanradiohistory.com S8 Wireless World, July 161h, 1937

ONDON is featured twice in this week's pro- I grammes. On Satur- day, at 9.20 (Nat.), will be presented the first of a weekly series of seven enter- Listeners' Guide for taining and topical broadcasts, " Summer over the British years a point of attraction to Grisewood will give running Isles." The series, to which emigrants from all over the commentaries from Wimbledon HIGHLIGHTS.OF C each of the Regions will contri- world. The contrasting rea- on the first day's play in the THE WEEK bute, will portray, by means sons why people from other Inter -zone final for the Davis FRIDAY, JULY 16th. of recorded shots and studio lands have made London their Cup between Nat., 7.30, " Five Hours Back "-II. a America and Ger- 8.30, The Rocky Mountaineers. scenes, the work and pleasure home will be brought out. many. On Monday and Tues- Reg., 8.30, Jelly D'Aranyi (violin) of the peoples in different parts Typical " squatters " will tell day afternoons, also, he will and Myra Hess (piano). 9.20, of the British Isles. In the pro - how London has affected their give commentaries from Wim- Ladies and Gentlemen of the gramme on Saturday, Laurence life stories. Chorus." bledon. The motor cycling Abroad. Munich, 6.35, Mozart s ' Don Giovanni " from the Residenz- theater. SATURDAY, JULY 17th. Nat., 3.15 -5.15, Saturday's Sport. 8, " Palace of Varieties." 9.20, " Summer in London." Reg., 6, British Legion Band. 8 and 8.40, Bruckner Festival Con- cert from the Festival Hall, Linz (Upper Austria). Abroad. Budapest, 8, " Soldiers on the Stage " : dances from old and new operettas. SUNDAY, JULY 18th. Nat., 2.50, Service for the Merchant Navy and Fishing Fleet in South- ampton Docks. 9.5, Stanford Robinson conducts the Theatre Orchestra. 9.50, The London Mozart Orchestra. Reg., 6.30, B.B.C. Military Band and Dennis Noble. 9.5 " Why - London ? " Abroad. Rome, 9, Gigli in Donizetti's " L'elisir d'amore.' MONDAY, JULY 19th. Nat., The Song is Ended -1. A reminiscent programme of dance musk. 935, Almonds and Raisins : a Jewish Review. Reg., 8, " The Lunatic at Large " : an exhilarating farce of the '90's. r Abroad. l Bordeaux, 8.30, Messager's operetta " Véronique." TUESDAY, JULY 20th. Nat., 6.50, " The Lunatic at Large." 9.40, " Follow -on " : a revue in TYPICALLY LONDON. This aerial view of part of the great metropolis with St. Paul's, which is symbolic of miniature. 10, Ina Souez and the London, in the foreground shows the Thames winding towards Westminster. Twice this week London is Theatre Orchestra. featured in the programmes. Reg., 730, Tzigane music from Budapest. 8. Variety from the Hippodrome, Boscombe. 9.40, Gilliam will present " Sum- SATURDAY SPORT broadcasts on Saturday come Pianoforte recital, Angus Morrison. mer in London." The second EACH succeeding Saturday from Donington Park, where at Abroad. of this series of broadcasts seems to surpass the last in the Radio Paris, 9, " La Vivandière " : 4.15 and 4.45 C. R. Hodgson operetta (Godard). will be given on Wednes- matter of abundance and and George A. Allan will de- day at 10.3o (Nat.) and will variety of sporting broadcasts. WEDNESDAY. JULY 21st. scribe the closing stages in the : Stay -at -home Nat., 8, " Nikki Makes News " be " Summer in Scotland." sportsmen will International Six Days Motor a new radio burlesque. 10.30, This will emphasise the plea- have a good afternoon of listen- Cycle Trial. " Summer in Scotland." sures and beauties of long ing this Saturday, for from . O O Reg., 330, Polo commentary from summer days in the remote (Nat.) athletics, rifle Hurlingham. 7.30, Music from 3.15 -5.15 MOVIE MUSIC the Moves. 9, Commentary on highlands of the outer islands. shooting, tennis, and motor Louis LEVY and his Sym- Speedway racing. The second occasion on cycling will be described for phony come to the end of the Abroad. which London will be the their benefit. At 3.15 and 4.20 Warsaw. 9, Recita' of Chopin s present series of " Music from polonaises. theme of a programme is on H. M. Abrahams will tell lis- the Movies " with the fifteenth Sunday at 9.5 (Reg.) when teners of the progress of events THURSDAY, JULY 22nd. programme on Wednesday at Nat., 8 Entertainment tour of ' listeners will hear " Why Lcn- at the A.A.A. championships 7.30 (Reg.), their penultimate Blackpool. 9.20, A Saint -Saëns don? " The idea behind this at the White City. From 3.3o broadcast will be given to -night programme, by the B.B.C. Orch- programme, which has been to 4 Capt. J. V. Jackson and (Friday) at 8 (Reg.). estra (C). For his Reg., 8, " Why August ? " : dis- prepared by Berthe Grossbard Capt. E. H. Robinson, the choice of numbers for the final cussion on spread -over holidays. I and will be produced by Felix well-known wireless correspon- programme, Louis Levy is 9, " Nikki Makes News." Felton, is to present London as dent, will be at Bisley to de- being guided entirely by the Abroad. Cosmopolis and to show that scribe the shooting for the letters Munich, 7, Operetta melodies 'rom received from listeners Strauss to Lehár. it has been for many, many King's Cup. At 4 and 5 F. H. requesting repetitions.

www.americanradiohistory.com Wireless World, July 16th, 1937 59 eek ,nding Broadcasts Mme and Abroad

GOING, GOING . HENRY HALL will direct the B.B.C. Dance Orchestra for the last time in a broadcast on Saturday night. It is fitting that this programme should be the popular Henry Hall's HENRY HALL with members of the B.B.C. Dance Orchestra, which is being disbanded and will be heard for the last time Saturday. Hour followed by Midnight on Music. As announced in May, Canada as " The Melody THE CHORUS Wayne, the comedian, will the orchestra is to be dis- Girl." LISTENERS' memories will, play the part of the lunatic. banded as from August 7th. She will play the piano, by the new production " Ladies 0 ó From Saturday until that date accompanied by Reginald and Gentlemen of the the members be Chorus," OPERA will on their Foort at the B.B.C. Theatre be whisked back LORTZING'S annual holiday. Although Organ. over the years to the days "Waffen- virtually it is the end of the o 0 when chorus girls did little else schmied," from Berlin at 8.10, B.B.C. Dance Orchestra as " PALACE OF VARIETIES " on the stage than put one foot is the least familiar of Friday such, Saturday will not, in BERTHA RICARDO, Who re- gracefully before the other and evening's opera. First pro- fact, be the last time its mem- cently made her first radio smile sweetly. This produced in Vienna in 1846, it is bers and director will be heard. appearance in an Ernest Long - gramme is dedicated to both among the less popular of the For on their return from holi- staffe production, is to accom- the old and new style of composer's dozen or so operas. daying, Henry Hall will pany Ralph Truman -as his chorus. Broadcasts have al- Saturday's least familiar work assemble a band of his own fiancée -to radio's mythical ready been written in honour is the Zandonai opera, "I which will be employed by the music hall, the "` Palace of of stars o_ f the stage, and now cavalieri di Ekelaft," which is B.B.C. in a full time capacity Varieties." for the seventh it is the turn of the chorus based on a story of the veteran until September 25th, when broadcast which comes in the which is often called the back- Swedish writer, Selma Lager- Henry Hall's resignation from National programme on Satur- bone of the stage. It will re- 16f. Zandonai is one of the the B.B.C. takes effect. This day at 8. mind listeners of artistes who most esteemed of living Italian orchestra, which will include Sitting in the stalls, their started in the chorus and who composers. Born in 1883, he the greater part of the per- conversation between the acts, later found stardom. would seem to be at the height sonnel of the B.B.C. Dance picked up by an eavesdropping Bryan Michie, who is proof his powers. Orchestra plus five or six new- microphone, will serve as a ducing the show, has per- Athlone is making a new comers, will be known to lis- commentary on thé turns suaded George Graves, of departure in spreading Verdi's teners as Henry Hall and his which they are seeing. " Merry Widow " fame, to act " Aida " over four evenings. Dance Orchestra. Artistes booked for the pro- as compère. The show, which Acts I -IV being given on Sun- c o gramme include Charles Pen- has been written by Gale Ped- day at 5.30, Monday at 7.15, THE MELODY GIRL rose, in one of his " laughing " rick, will include scenes typical Tuesday at 7.o, and Wednes- DURING her first visit to songs ; Suzette Tarri -one of of the stage door. day at 7.0 respectively. Three England since she was six Ernest Longstaffe's " dis- 0 0 0 hours of Verdi's " big guns " years old, Vera Guilaroff, coveries°' ; G. H. Elliott, the would be rather a stiff dose for daughter of a former English original Chocolate Coloured AT LARGE a listening public not yet diplomat, is to broadcast from Coon, singing some of his older A NEW radio play by Lance inured to opera. numbers; Sieveking, based on J. Storer The big thing on the French Monsewer Clouston's celebrated novel, stations on Wednesday is the Eddie Gray - " The Lunatic at Large," Radio Paris 8.3o performance "fugitive which has been selling regu- of " La reine Fiammette " by from the larly since its appearance in Xavier Leroux, a composer Crazy Gang," 1900, will be broadcast twice who, though born in the Papal this week -on Monday at 8 States, was French of the (Reg.) and on WITH THE Tuesday at 6.5o French. MICROPHONE (Nat.). Thursday's big event is the in hand Harold The adaptation was a happy production at the Salle Gaveau Abrahams con- thought, for this exhilarating of Félix Raugel's new arrange- gratulates a farce lends itself winner at a re- admirably ment of Handel's " The Mes- cent A.A.A. to microphone treatment. The siah," which Radio Paris re- meeting. He two principal characters, Man- lays at 8.3o. This supreme will be com- dell Essington, the aristocratic masterpiece was written in 24 mentating at the is White City on lunatic, who wandering days, in the autumn of 1741, Saturday. through England in the '90's and received its première, not having any idea as to who strangely enough, in Dublin. he is, and the Baron Rudolph The programme of "` The her native London on Thurs- who, introduced by Eddie von Blitzenberg, jolly, old - Messiah," by " Mr." Handel, is day at 7.3o (Reg.) in a pro- Windsor, will be making his fashioned German tourist, still to be seen in the Library gramme of the kind that has first broadcast in this country ; make excellent comedy in all of Trinity College, Dublin. made her known throughout and Bransby Williams. their encounters. Naunton THE AUDITOR.

www.americanradiohistory.com 60 Wireless World, July 16th, 5937

lative grounds. Perhaps the veriest tyro of the public might do likewise. I would like to draw the attention of Letters to the Editor readers to the new IF system employing Rochelle Salt Crystals and a steel bar as a The Editor does not hold himself responsible for the opinions of his correspondents controlling element (and which savours somewhat of magnetostriction principles), Components five connections, two are connected to the developed by the Brush Development Co., positive and negative terminals, and two go and described in Q.S.T. for April and June, AS my company has been specialising in 1937, by J. J. Lamb. The idea is not new, for to the " Delay " section, wlîile the last plug the needs of home constructors allows for necessary adjustment at various and cannot truly be compared with wide - something like eighteen years, your editorial band quartz crystal filters as mentioned in the unsatisfactory position of periods during the life of the HTB. I don't comments on see how any of these can be sacrificed with- my letter of June 18, 1937. It is better than is without interest component supplies not out some loss in adaptability to voltage de- normal LC circuits, though. to us. cline. Thanks to all these very plainly Until crystal filters are obtainable at a For ourselves, we are unable to agree that reasonable price, I still plump for TRF. components is not marked connections I am enabled to obtain an adequate range of the very last usable volt from my HTBs. Portsmouth. " NAUTICUS." available to experimenters. Whilst we pay Backs to sets, particular attention to " Author kits," we all battery as well as mains, odd components for are absolutely necessary in my opinion. are also able to offer Prevention is far better than cure, and far IHAVE read with much interest the com- constructor sets which have been described ments concerning the respective merits of in during the last five better is it to exclude dust in the first place the technical papers than to try dangerously to remove it later superhet and straight set. I notice that not years ; and the wide range of every sort and one on. My ' ` Pye " set has a back which is of your correspondents has mentioned condition of component is sometimes, if we easily opened, and which, being nearly all the straight set using untuned RF trans- may confess it, the despair of the manage- dust -proof (but not soundproof) fabric, formers. Much of the difficulty of design- ment and storekeeper alike. does not cause " boom." ing a really high -gain straight set lies in the We do not think that any mass- produc- fact that stable amplification with over three would T. J. E. WARBURTON. tion set or component manufacturer East Molesey, Surrey. tuned RF stages is practically impossible, to entertain the idea of reopening the com- say nothing of the wide variation of band ponent market for one moment, for the very width over each waveband which would good reason that they have not got the occur with such an arrangement. It is not organisation for the supply and distribution Straight v. Superhet Receivers realised that a well -designed untuned trans- of such lines. The average radio dealer to this present time of writing six former. will give constant band width and can hardly be expected to stock a neces- UPletters, excluding my nearly constant amplification over the whole sarily widely varied range of small articles own, have appeared in The Wireless World, and since of the MW band, and could be switched for against a problematical market ; and the the various dual -wave use. With a band-pass aerial cir- manufacturer, with his trade distribution writers are apparently fairly representative of the manufacturer, wireless cuit, a band -pass filter between first and and specialised production planning, would repairer and second RF stages, and two or three find it much more bother and expense than interested amateur classes, an stages analysis of their remarks is of untuned RF amplification using low - was worth while to sell these components indicated. Mr. Pinhorn, of Dyratron Radio, makes impedance pentodes, followed by a negative direct to the public. some very definite statements, feedback anode -bend detector, a gain as In spite of the fact that we ourselves are and I agree with him entirely. It is interesting to high as, and a consistency of band width as singularly well placed to cater for the needs observe his firm have specialised good as, the best superhet could be of the experimenter, we sometimes wonder in straight obtained, receivers for many years. The fact that it with none of the disadvantages of the super - if it is worth while developing this side of het. While the selectivity business. continues to do so seems to indicate a select would not be so our We would be prepared to market provides their customers. good as the equivalent superhet, extend our activities if we could be reason- Mr. H. J. this does Dix represents the second class, and to this not matter so much in a high- fidelity set, ably sure of fair support ; we but have a gentleman I would quote a which, incidentally, would be able feeling the market is not large humorous story to make that enough as an analogy to his creed. full use of the wider band width present to justify the extra effort required. A with lower selectivity. has be realised " certain man was lecturing a class of It to that, for every keen first -year engineering Smethwick. B. J. and knowledgeable reader The students, and in BRETTELL. of Wireless describing an ordinary engineer's steel. World, there probably exist 400 or 500 12ín. rule, said : ' The longest listeners who are not in the least interested vertical marks are in home construction. The temptation to the inch divisions, the next longest are the The Radio Industry larger half -inch divisions, and the shorter ones cater for the market is obvious. you need not trouble " PHILCO RADIO announces that the Philco- Your readers' comments on foregoing about.' the This same attitude seems to be the creed phone, an audio- frequency inter -room would be of real interest and value. of most repairers I have communication system, will be on the market London, E.C.I. H. A. HARTLEY, met. Perhaps I towards the end of August. have been unlucky. Section 3 is in two Peto Scott Co., Ltd. 0 parts, and perhaps Mr. Foley is best repre- Important extensions have been made to the sentative of the real keen amateur class. Great Eastern Street premises of Brown Bros., However, my letter published in your issue Ltd., the well -known distributors. HT Battery Connections of June 18th, 1937, should show the fallacy O 6 O IREALLY must comment upon a few of believing pre -HF amplification in super - The address of the Philips' Liverpool branch things which " Diallist " has said in his hets. tó be the absolute cure for all the is now 47a -49, Tithebarn Street, Liverpool, 2. interesting notes recently, and will do so evils of this type. Also, this is what I 0 as briefly as possible. manage to do very successfully with a TRF " Sound Engineering " is the title of a use- With regard to battery connections, it set. Single tuned circuit preceding first ful publication (price is.) just issued by R. A. seems to me that simplicity, while an admir- RF followed by band -pass to second RF Rothermel, Ltd., Canterbury Road, London, followed N.W.6. It deals at length with-the problems able goal to aim for, can be carried to too by a second band -pass stage to of commercial PA, and contains much informa- great extremes. With only two connections third RF, then a single -tuned circuit before tion on piezo -electric appliances. to the HTB there is thereby abolished flexi- a diode detector, one AF stage feeding a O O O bility in adjustment, which, as the battery push -pull pair of triodes. Rectifier, sub- Telsen Electric Co. (5935), Ltd., have re- runs down, becomes more and more desir- sidiary circuit. A triode operating as a cently taken over the manufacture and sale able. I am not talking about grid bias, quartz crystal oscillator at 5o kc /s, har- of the instruments and appliances formerly which should be automatic in every case monics of which are used for gauging pur- made by Lystan Products, Ltd., of Lytham. where it is possible, but about those other poses. The 3oth harmonic is weak and is An extensive range of instruments will be intermediate connections which enable one very useful for tuning up the tuned circuits. added to the present Lystan series, which now AVC is not employed, includes valve testers, suppressor safety plugs to obtain a variety of results. Regarding as I believe in ade- and adaptors. my own set, there are seven connections. quate metering at all crucial positions. . 0 0 However, here are 10 valves. Messrs. - While two of these are to the GB section of Hew A scheme for the insurance of cathode -ray the HTB, once they are plugged in no son, Curtis, and " J. W. B." are obviously tubes has been put into operation by Arthurs, further adjustment is needed during the keen listeners with some constructive ability Gray House, 150, Charing Cross Road, London, whole life of the battery. Of the remaining and favour the TRF, principally on manipu- W.C.2.

www.americanradiohistory.com Wireless World, July 76th, 7937 6r NEW VALVES-Marconi and Osram Output Tetrodes and the International Series THE pentode was originally developed as an output valve and grew out of the n1cCA 111f IH earlier screen -grid tetrode. At that time the Octalvalve base as r used for the Inter- tetrode was unsatisfactory when called upon national series. The to deal with any large amount of power locating key, which OUTSTANDING 9 -VALVE OCATING KEY is slightly longer because the presence of the negative-resist- KEY than the pins, pre- ance bends in its characteristics prevented WAY v e n t s accidental ALL -WAVE SUPERHET contact being madç the attainment of large power output with- until the valve is out severe distortion. A suppressor grid was correctly inserted. For all - wave reception consequently introduced between the screen The International Series also contains at its very best grid and anode to remove the effects of tetrodes, the KT63 and KT66. The valves To the all-wave enthusiast, this exceptional receiver secondary emission and the valve became in this series are fitted with the American offers a number of interesting features, with:quite unusual the well -known pentode. Octal bases, and are the equivalent in range, and power output. Few receivers at present on Means have now been found of obtaining characteristics of American types. With the the market can claim so high a standard of design and pentode -type characteristics with a tetrode exception of the rectifier, the heaters are all performance. construction; in other words, it is now pos- rated at 6.3 volts, and, apart from the two sible to remove the bad effects of secondary output tetrodes, consume o.3 ampere. The emission from a tetrode without having to X63, W63, and Z63 are equivalents of the introduce a suppressor grid. This leads 6A8G, 6K7G, and 6J7G, and no alteration 12 to a simpler electrode assembly and often to other than the readjustment of trimming is some improvement in performance. needed ; the H63, D63, DH63, KT63, and Several methods of preventing the nega- KT66 are equivalents of the 6F5G, 6H6G, tive -resistance bends in the valve curves are 6Q7G, and 6L6, and may be substituted for known, and in the new Marconi and Osram them without alteration. types earthed metal plates are fitted near the The rectifier is the U5o, and is the anode. These assist in the formation of a equivalent of the 5Y3; it is of the full -wave, cloud of electrons between screen and anode, 500 volt, 120 mA. type, and its filament is and this cloud repels secondary electrons rated at 5 volts 2 amperes. The range is which may be emitted from the anode. completed by the Y63 cathode -ray tuning The first of the new valves is the KT2, indicator. which has characteristics similar to those of For use in AC -DC sets, the N3o /G, N31, the well -known PT2, with which it is inter- and U3o are recommended for the output changeable. In the AC range the KT42 is the stage and rectifier. These valves consume equivalent of the N42 which it replaces. 0.3 ampere at 13/26 volts, according to type.

(Complete AIRCRAFT WIRELESS with 9B.V.A. valves.) Equipment of the "Caledonia" 4 wavebands : 12.8 -33, 29.80, 190 -550. 800 -2009 THE radio installation which has been metres, Illuminated dial with principal station fitted in the " Caledonia " and her names. Separate coloured lights for each waveband. sister ship, the ' ` Cambria," was carried out by the Marconi Co. There are Controls. -A feature of the receiver is the number two trans- of independent mitters, the first of which is for CW only controls fitted, making it extremely interesting to operate. These include : sensitivity and is intended for long- distance work. It control (varying bias on R/F stage). Q.A.V.C. with covers the 16.5 to 75 -metre waveband. manual muting control, and switch for inter -station The second transmitter operates on CW, noise suppression. Separate potentiometer bias controls ICW, or telephony, and is used on the 95- for output valves. 5- position wave- change and gramo- 185 -metre band for long -distance and ap- phone switch. Progressive variable tone control proach work on the American side. When operative on radio and gram. nearing the European is Circuit in Brief. -Aerial input to pre -selector circuit radio side it operated frequency amplifier, latest type triode- heaode frequency on the 500 -7,000 -metre band. Both trans- changer. 2 band -pass I.F.T. coupled I.F. amplifiers, double mitters are independent of each diode detector, L.F. amplifier, parafeed transformer- coupled other, but push -pull triode output giving 6 watts. operate from a common source of supply, Heavy cadmium - plated steel chassis. Finest components and consisting of a motor-generator driven by workmanship throughout the aircraft accumulators. A A.C. models ready for immediately delivery. light- weight A.C./D.C. models also in production, and will be available petrol engine is carried for use if the accu- for delivery shortly. mulators are out of commission. DE LUXE MODEL 14 GNS. Several additional refinements - full particulars on The main receiver works on 15 -loo application. metres, 183 metres, and 600 -2,000 metres, IMPORTANT DF circuits being incorporated in the latter Tee prices at which McCarthy Chassis are advertised band. There is a second receiver provided include Marconi Royalties. " Wireless World" readers should, for their own protection, make sure before for use as a standby, and it covers the 180- hasing ann receiver that the quoted price includes 2,000-metre band. It can be used for ordi- ty nary reception or for both aural and visual DF work. All McCarthy receivers supplied complete with valves, knobs, pilot lamps, leads, mains cable and There are three aerials -a trailing one for plug. 12 months' guarantee. long -distance work, a fixed aerial running Deferred terms on application, or through London along the length of the niachine, and a Radio Supply Co., 11, Oat Lane, E.C.2. rotatable frame. The Cash with order on 7 days' approval. Also write latter enables the for illustrated catalogue of complete range of all operator to take cross bearings on various McCarthy receivers. The Marconi retractable loop aerial as fitted land and ship stations, and can be with- to the " Caledonia " and similar flying boats. drawn into the hull of the machine when AAc1CAUR11-1 -IY IRASIDIIIC ILTD. When not in use it is withdrawn into the not in use, in order to reduce drag and so 44a, Westbourne Grove, London, W.2 hull to reduce drag. increase the speed of the boat. Telephone : Bauswoter 3201/2.

www.americanradiohistory.com 62 Wireless World, July i6lh, 1937 An Ideal Valve Voltmeter METER WHICH AVOIDS MANY SHORTCOMINGS OF THE CONVENTIONAL INSTRUMENT

WHILE the valve voltmeter AT all but audio frequencies the between cathode and earth, while the should be one of the most use- measurement of AC voltage second is between anode and earth ful of laboratory instruments, (the second filter condenser). These two the limited range, the necessity demands the use of a valve voltmeter, condensers are essential in providing for expensive and fragile microammeters, and in many cases this instrument is paths of low impedance across the anode and the fact that most instruments of this also the best at quite low frequencies. and cathode resistors at low frequencies, type have been designed for battery opera- while the ioo-m-mfd. mica condensers In this article simple voltmeter is tion greatly limit their usefulness to ex- a mounted at the 6F5 socket (in parallel perimenters and servicemen. The high- described which has a wide range to the 8 -mfd. electrolytic units) prove tension batteries used with such an instru- and does not necessitate the use of equally effective at high frequencies. ment have a definite life, shelf and when any meter. Thorough test of this instrument in used occasionally it will be found that the the Application Laboratories of the batteries may have run down just when Hygrade Sylvania Corporation indicated most needed! Also, the use of delicate ence and short leads in high- frequency that a calibration made at 6o c/s held for indicating instruments with the valve volt- measurements. In most cases it should meter places a great strain on the average be possible to make, the " hot " lead less experimenter. A single lapse of memory than min. in length, as it is usually con- 4.5 or attention with regard to the backing off venient to " hang " the valve by its grid voltage, or an " open " grid circuit, may clip. Between the grid and earth is result in a damaged instrument. This not connected a resistance of 5 to Io megohms. only postpones the experiment but also The latter value will result in the absorp- hurts the pocket -book severely. tion of less power by the voltmeter input A recent innovation in American volt- circuit, but can only be used with gas - meters is one in which all the shortcomings free valves. However, of 15 valves of the conventional instrument have been checked for this purpose none was eliminated : no batteries; wide range-o.i affected by the use of the high resistance, to 200 volts, AC and DC; and no indicat- proving that it should be possible to ing instruments (microammeters or milli - obtain satisfactory valves. Of course, it is ammeters), greatly reducing cost of com- permissible to use the voltmeter without

ponents, and upkeep ! an input resistance when no DC appears As shown in Fig. I, this perfect valve across the source of AC which it is desired Fig. 2. -A sample calibration scale for the voltmeter employs a metal 6F5 valve (t = to check. variable resistance R2 is shown here. loo ; Ra = 65,000 ohms -at Ea = 25o Supply Circuits volts and Eg = -2 volts) which operates as a linear automatic -biased rectifier of the Proceeding to the power unit, a trans- frequencies from 3o c/s to above 6o Mc /s. anode bend type. (This method of opera- former and rectifier supply 300 to 35o The high- frequency calibration was checked against a tion was named "reflex" by early English volts at Io to 15 milliamperes ; a single - Ferris signal generator, experimenters in this field.) This valve, section resistance -capacity filter as shown and held to the high- frequency limit of the generator. In addition to assuring calibration free from frequency errors, the two mica by -pass condensers serve to keep high-frequency currents out of the cable, thus giving stability without resorting to a shielded cable. At this point it may be well to state that the shell of the 6F5 is also earthed. After discussing the prod and power supplies, the calibrated resistor, Rz, and the 6E5 cathode -ray indicator must be treated. Direct Calibration R2 is a wire-wound potentiometer of 50,000 -ohms resistance which serves as the bias resistor for the 6F5. The 6E5 grid is connected to the slider on this resistor, having applied to it a sufficient voltage to close its shadow. In operation the 6F5 input is connected across the unknown voltage. The slider on Rz is then Fig. i.-The circuit of the voltmeter is shown here. It is completely mains -operated and an the 6E5 shadow just closes, inexpensive cathode -ray tuning indicator is employed instead of a milliammeter. varied until or perhaps it may be more accurate with two mica by -pass condensers of loo is satisfactory. It will be seen that to adjust for a " hair line " separation m -mfd. capacity, is mounted on the end of in this unit are two additional by -pass between the two shadow edges. R2 is a cable 18in. to eft. in length for conveni- condensers of 8 mfd. One is connected equipped with a dial or scale of at least

www.americanradiohistory.com JULY rbth, 1937 Wfip@Ilsm 63 WOpIlcI An Ideal Valve Voltmeter- 6m. diameter, and is calibrated directly in voltage. Two scales are necessary-one for AC of any frequency, and one for DC. A sample scale (actual) is shown in Fig. 2. After setting R2 all that remains is the reading of the voltage impressed on the 6F5. It will be realised that the operation of this instrument leaves little to desire in simplicity or dependability. In some cases it may be worth while to decrease the 6E5 target and plate voltage from 25o to approximately 150 volts (above earth), as this valve is more sensitive to small changes in grid voltage (greater deflection of shadow for a given grid voltage) under this condition- although the target does not flow so bril- liantly at the lower voltage. When first setting up the voltmeter for calibration, R1 is adjusted so that the 6E5 shadow just closes with no signal, and with the arm of R2 at its cathode or positive end. This control will seldom require adjustment- unless the mains voltage undergoes a marked change. After calibration, the operation requires only the adjustment of R2 until the shadow nearly closes -an adjustment which will be found very definite and easy of duplication -at which point the voltage is read directly from the scale. It may be ,..QoatkeNIGNER VOLTAGES advisable to point out that the accuracy Television and ' Output' gear call voltages much of the voltmeter depends in large measure LONGER LIFE Quality for on the size of the scale. Both calibration NO " CREEPING " in excess of those previously encountered .... Again T.C.C. and reading are much more difficult with provide the right condensers for these exacting demands, with a small dial. Valves have little effect on the accuracy of calibration, as 15 6F5s were substituted SAFER AGAINST for the one for which the instrument was BREAKDOWN PETROLEUM JELLY- calibrated, with no readable error. NO FREE LIQUID IMPREGNATED PAPER Stability In a preliminary model of this volt- NO LEAKAGE CONDENSERS in meter three neon lamp's series were SMALL SIZE connected (with the proper series resist- Built on entirely new principles they are specially designed for ance) across the high -voltage anode e Television, etc. They work up fo 2,500 V.D.C. Jelly- imprzg- supply. This was done to minimise the nated, there is NO FREE LIQUID thus having all the change in calibration with shifts in mains - TEMPERATURES advantages of oil but without risk of leakage or " creeping." voltage, but it was later decided to eliminate this feature in the interest of economy UP TO 140 F. Wherever high voltages and high temperatures are involved and simplicity. However, in locations PERMISSIBLE -play for safety -and use these "specialist- built" condensers. where the mains voltage varies over a wide range, and in cases where the maximum Type 111 Type 12113 Type 131 Type 141B accuracy is desired, it will be advisable to Capacity 1,000 V.D.C. 1,500 V.D.C. 2,000V.D.C. 2,500V.D.C. FOR STILL HIGHER employ a neon bank, Stabilovolt, or a Working Working Working Working VOLTAGES variable resistance in series with the trans- s. d. s. d. s. d. s. d. 0.1 3 6 4 3 5 0 ' IO 0 the following types are avail - former primary. An AC voltmeter may 0.25 4 0 6 3 7 6 II 6 in all capacities, pricesrites be connected across the transformer 0.5 4 6 6 9 8 0 14 0 P 1 6 0 8 6 10 0 20 0 on application. primary, or a low- voltage meter may be 2 8 3 12 0 15 0 35 0 4 I4 6 18 6 21 0 60 0 Type 161/C 3,000 v. D.C.working used by connecting it across a filament or 5 18 0 24 0 171 4,000v. heater winding. 6 21 0 29 6 33 0 94 0 191 5,000v. 8 32 0 39 0 43 0 115 0 201 C 6,000v. Where a DC voltage is superimposed 10 40 0 48 0 54 0 150 0 221.0 7,500v. on the unknown AC voltage, a blocking condenser of o.or mfd. may be connected between the 6F5 grid and the high side of the voltage to be measured. This meter was developed by Mr. George C. Connor, New York sales engineer for the Hygrade Sylvania Corpora- tion, makers of Sylvania valves. In addi- The Telegraph Condenser Co., Ltd., T.C.C. tion to checks by the Sylvania labora- Wales Farm Road, N. Acton, W.3. tories, a number of these instruments were ALL-BRITISH built by servicemen, and are giving satisfactory performance. CONDENSERS VE;_284

www.americanradiohistory.com 64 Wireless World, July i6th, 1937

rnperialMODEL AD45

A SELF -CONTAINED FIRESIDE RECEIVER FOR AC OR DC MAINS

FEATURES. Type. -Self- contained transportable for AC or DC mains. Circuit. -Var. -mu pentode RF /AF amplifier -heptode frequency -changer - triode second detector with reaction pentode output valve. Half-wave valve rectifier. Controls. -(1) Tuning. (2) Waverange. (3) Volume and on-off switch. (4) Tone. (5) Sensitivity (IF reaction). Price. -124- guineas. "Stand 31s. 6d. extra. Makers. - Betterset Radio Ltd., Clarendon Works, Montague Street, Worthing. THE sets made by this firm are notable alike is passed to the grid of the pentode output for their neatness of valve through a resistance -capacity coup- cabinet design and for ling circuit. Beyond this point the circuit the originality of their circuits. follows conventional practice with a In many ways the AD45 may variable tone control across the primary be regarded as a grown -up mains version of the output transformer and the usual of the Model P23 " Baby " battery trans- diode anode. The plate of the valve is diode rectifier and smoothing circuit for portable reviewed in our issue of Decem- supplied with HT from a potentiometer the HT supply. ber 18th, 1936. It has the same style of through a decoupling resistance, and is tied As in the case of the " Baby " battery cabinet, with louvred loud speaker fret, to earth as far as RF currents are con- portable, the chassis unit carries also the and the circuit is reflexed. cerned by a suitable by-pass condenser. loud speaker and the frame aerials. These Separate frame aerials are used for An electron coupling circuit is thus formed, are mounted parallel to the sides of the medium and long waves, and the signal giving regeneration additional to that pro- cabinet and at right angles to their more is first amplified at radio frequency by a vided by the cathode coupling coil and usual position so that with the mass of pentode amplifier with tuned grid coup- providing a sensitive control. In the earth the loud speaker further removed from the ling to the octode frequency changer return circuit of the IF transformer field of the coils an appreciable improve- which follows. The usual IF transformer secondary there is the usual diode load ment in circuit efficiency is to be expected. is connected in the anode circuit of this resistance across which are developed the The set is entirely self -contained, and valve, both primary and secondary being AVC and rectified AF volts. measures 15in. x I9in. x Thin. When used tuned. No IF amplifier valve is, however, AVC is supplied to both the frequency - in conjunction with the special stand which employed, but increased sensitivity is changer and the RF amplifier, but the has been designed for it, it makes ,,an obtained by reaction from the second de- constants of the filtering circuits differ so admirable fireside receiver for easy opera- tector stage. that the AF output is applied only to the tion from the comfort of an armchair. The The valve employed for this purpose is grid of the first valve in the circuit. After three principal controls of tuning, wave - a triode in which the grid functions as a amplification by this stage the AF voltage range, and volume are the only ones

SPEAKER FIELD

AEC 1 w UP

.-.-i ..,_..-do_.

A reflexed input stage and a triode second detector arranged to give diode rectification with reaction, are unusual features of the superheterodyne circuit.

www.americanradiohistory.com JULY ióth, 1937 f'5 -

Imperial Model AD45- useful programme value in daylight. On accessible from the front of the cabinet. the South Coast, of course, all these A neat rectangular tuning scale carries stations would rank automatically as first station names arranged on diagonal lines, selection stations. and the shadow of the tuning point is The directional properties of the frame

R F AND A F AMPLIFIER VALVE

H P 1 3 OUTPUT VALVE PP36 FREQUENCY CHANGER VALVE VO13 RECTIFIER VALVE V30

FLUX DENSITY EQUALS THE

Comparison between this 91' diameter speaker selling at 49(6 and the giant Rola G.12 -PM may at first sight appear rather preposterous. Yet when space and price are REACTION serious considerations this CONTROL new Rola unit is the ideal CONTROL 2nd DETECTOR VALVETONE substitute for its famous com- T W reless World COPYRIGHT HL13 panion. Like the G.12 -PM it possesses a flux density of t 5,Soo lines per square centi- Loud speaker, frame aerials and chassis form a self- contained unit easily removed metre. It is super sensitive from the cabinet. and therefore ideal for Battery set and Extension speaker thrown on to the scale by a pilot light aerial, due to the efficient AVC, are not use. Special features include which travels with the pointer. very marked, so that help from this pro- the use of a new magnet material ' Alnico ' and a At the back of the set there are two perty cannot be relied upon as an aid to moisture proof transformer, controls, one for reaction on the IF trans- selectivity. On the other hand, it is grati- metal and compound shielded. former, which need only be used when fying tO know that one need not neces- No better value in reproducers is obtainable to -day. Please pushing the set to its limits on distant sarily orientate the set every time a fresh write for full particulars. stations, and the other a tone control, station is received, although a turntable which, when adjusted to the taste of is provided for this purpose. On long the listener's requirements, needs no waves comfortable separation was possible further attention. between Radio -Paris and Droitwich, and IN Excellent results as regards quality of on the medium waveband between two L' reproduction were obtained with the tone and three channels were lost on either side control anywhere from the half -way mark of the London Regional transmitter when to the position of greatest high-note re- using the set in Central London. sponse. There is plenty of real bass re- Without the advantage of the high sponse unmarred by cabinet resonances, signal -to -noise ratio which an outdoor and tone in general is of a type which in aerial gives one generally expects to find a violin would be described as free play- a comparatively high level of background WITHOUT TRANSFORMER 421- ing. The volume can be increased well noise and switch clicks entering through OVER" 8 MILLION IN USE % above the level normally required from a the mains leads ; but it will be seen from set of this type without any suggestion of the circuit that filtering chokes have been overloading, and the input to the last included in both mains leads, and it is safe stage from the principal continental broad- to say that the set is as quiet as this type casts such as Fécamp, Luxembourg, and of receiver can be made. Radio -Paris is more than adequate to give Provision is made for the attachment the full output of which the set is capable. of a gramophone pick -up, but as the input L!/otJ4 ?lima e' gllacet4 Stations such as Hilversum on the long is made directly to the grid of the output waves and Cologne on the medium waves stage the high voltage output from a THE BRITISH ROLA CO.. LTD. required some help from the sensitivity crystal type pick -up would seem to be MINERVA ROAD, PARK ROYAL,N.W.10. control before they could be regarded as of called for. PHONE WILLESDEN 4322 -3-4 -S -6.

www.americanradiohistory.com 64 Wireless World, July 16th, 1937 Recent Inventions Briefdescriptions of ELECTRON MULTIPLIERS coated with a metallic layer de- the more interesting TWO photo -sensitive cathodes posited, say, from a colloidal sus- C. Ci are set opposite each pension of gold in lavender oil, radio devices and im- other, rather like the two halves upon which a sensitive layer of of an open cylinder. They are zinc selenide is applied by spray- provements issued as both perforated and coated with ing or by being allowed to settle patents will be included a layer of caesium on silver. from a suspension in liquid. Outside them are mounted two When the tube is in operation in this section. " collector " electrodes B, Bi conan electrode which collects the nected to leads L, Li, whilst in electrons emitted from the screen Method of generating saw - SCREENING POTS the centre of the bulb is a spiral - is given a positive bias of from 5 wire anode A carrying a high posi- to to volts. This is stated to in- toothed oscillations for scanning THE action of the ordinary in television apparatus. metal case, used to screen, tive voltage. crease the sensitivity of the screen say, a high -frequency coil. is due When light strikes against one and to reduce any lag in response. to the fact that primary currents or other of the sensitised cathodes. It also avoids the so- called " tilt- during the so- called " tly -back " in the coil induce eddy currents in the electrons set free are acceler- ing " effect, which is usually mani- period of scanning. the metal screen. The eddy cur- ated towards the central anode. fested in the picture by a Marconï s Wireless Telegraph rents, by the laws of induction, Some of them pass through to the gradually increasing brightness Co., Ltd. and G. B. Banks. Ap- have such a direction that they opposite cathode, where they pro- along a scanning line which should plication date August 2nd, 1935 oppose the passage of those lines duce other electrons by secondary be of uniform illumination. No. 463625. of force which tend to spread out- emission. If we suppose the H. Miller. Application date, o o o o cathodes to he solid plates, instead September 24th, 1935. No. 463297. wards from the coil. " DIELECTRIC GUIDE coil in- " LINES But, in addition, the CENTIMETRE waves are fed duces other Foucault currents in into a " dielectric guide " the screen which tend to flow in a which may consist of a rod of circular path around the metal in fused quartz, or of a rod of some a plane at right -angles to the axis other dielectric sheathed in cop- of the HF coil. These have an per, or of a hollow conductor en- undesirable damping effect, and closing a core of air. The waves tend to increase the inherent travel through the dielectric as capacity of the coil. " displacement " currents, there In order to suppress them, the being no return circuit in the screening pot is divided longitu- ordinary sense of slit, edges of the term. The dinally by a the energy is strictly localised inside which are "seamed'' together the guide line and does not set up around a suitable insulating any external the path field, providing the material so that circular diameter of the " guide " is proof the undesired currents is perly related to the wavelength it broken. is called upon to handle. G. Fodor; J. Toutain; and M. The invention is particularly Bloch. Convention date (France) concerned with a guide line of this October 17th, 1935. No. 463676 o o o o character in which one or more partitions are provided to keep SHORTWAVE OSCILLATORS each of a number of separate fre- INSTEAD of using ordinary quencies distinct from the rest, so 1 Lecher -wires to take the out- that the line can be used for multi- put from a short-wave valve of the plex working. magnetron type, the tuned cir- Standard Telephones and Cables, cuit consists of an outer tube R Ltd. (assignees of S. A. Schel- and an inner conductor C form- Arrangement of the elements in the electron multiplier described in Patent No. 463514. kunoff). Convention date (U.S.A.) ing a concentric " transmission December 31st, 1935. (Addition line." The two ends of the outer to Patent No. 420447). No. tube R are cut away as shown, of being perforated, the electrons TIMEBASE CIRCUITS AGENERATOR of saw- toothed 464185. and enclosed inside a glass vessel would surge to and fro between O 00 o V to form the usual "split " them. But because of the perfora- oscillations, used for scan- anode of this type of oscillator. tions, a certain proportion of the ning in television, consists of a WIRELESS FOR MOTOR CARS The filament F is mounted be- electrons pass through on to the screen -grid valve with its anode - prevent radiation from the tween the two inner conductors C. collectors B, B1. If the latter are cathode circuit back- coupled to ro ignition system of a motor the grid. A condenser C in the car, such as is likely to cause in- grid circuit is connected through a terference to wireless reception, D1 resistance R to a source of say 240 it has already been proposed to volts. The grid current first insert suppressor resistances of the charges up the condenser to Spaghetti type between the spark- " block " the valve, and then the ing plugs and their leads. charge leaks away through the According to the invention resistance R. This creates a rec- these are replaced by a flexible tilinear or saw- toothed voltage core of pure silk which has been across the condenser plates, which coated or impregnated with is drawn off at the terminals T graphite to the degree necessary and used for scanning. Synchro- to provide a resistance of the re- Constructional details of ultra -short wave magnetron valve. nising impulses are applied at S to quired value. The prepared core " trigger " the valve, and are is then enclosed in an outer rub- The arrangement allows the im- connected to an external tuned effective even though of very ber covering. The result is a pedance of the resonant circuit to circuit, a steady state is arrived small amplitude. stable " suppressor " of constant be more accurately matched with at, in which the two cathodes are Another series of square- topped resistance, having considerable that of the valve, whilst the uni- kept in phase -opposition and the negative pulses are simultaneously flexibility and tensile strength. formly distributed capacity of the device acts as a generator of sus- produced in the screen -grid circuit, F. R. F. Ramsay. Application concentric arrangement is not dis- tained oscillations. and are tapped off at S and used date October loth, 1935. No. turbed by the valve electrodes. Farnsworth Television Inc. to suppress the cathode -ray beam 464278. Discs D, Di collect the electrons, Convention date (U.S.A.) May as they move axially under the 71k. 1935. No. 463514. external magnetic field applied to o o O O The British abstracts published here are prepared with the permission the valve. of the Controller of H.M. Stationery Office, from Specifications Telefunken Ges. fur drahtlose PNOTOSENSITIVE SCREENS obtainable at the Patent Office, 25, Southampton Buildings, London, Telegraphie M.b.h. Convention TILE photo -electric screen of a W.C.2, price 1 - each. A selection of patents issued in l'. S.A. is date (Germany) August 15th, cathode -ray television trans- also Included. 1935. No. 463236. mitter consists of a sheet of mica

www.americanradiohistory.com THE PRACTICAL RADIO JOURNAL 27 tit Year of Publication

No. 934. FRIDAY, JULY 23RD, 1937. VOL. XLI. No. 4.

Proprietors : ILIFFE & SONS LTD. Editor : EDITORIAL CONNT,NT HUGH S. POCOCK.

Editorial, good aerials for reception, but that is Advertising and Publishing Offices : Aerials no longer the case to -day. STREET, DORSET HOUSE, STAMFORD A LONDON, S.E.I. The Penalty of Neglect campaign for better aerials would, we beliève, do much to improve the Telephone: Waterloo 3333 (5o lines). N discussing the effect of the Telegrams : "Ethaworld, Seelist, London." general standard of reception and station changes in the West of reduce complaints of local interference. COVENTRY : Hertford Street. England and South Wales which Telegrams : Telephone: `Autocar, Coventry." 5210 Coventry. . took place recently the B.B.C. Absurd Prejudice specially directs the attention of listén- BIRMINGHAM : It is not easy to determine whether Guildhall Buildings, Navigation Street, 2. ers to the question of aerials. the small number of effective aerials to Telegrams : Telephone It is well that from time to time be seen during a "Autopress, Birmingham." 2971 Midland (4 lines). day's journey through the matter of aerials should be made the countryside is due to public in- MANCHESTER : 260, Deansgate, 3. a subject for discussion because far difference or some stronger feeling Telegrams : Telephone: " Iliffe, Manchester." Blackfriars 4412 (4 lines). too little attention is paid to this amounting almost to antipathy. It is important aspect of reception to -day. certain, however, that many people GLASGOW : 26e, Renfield Street. C.2. Because receivers have improved in regard a prominent aerial as Telegrams : "Iliffe, Glasgow." Telephone : Central 4857. an eyesore efficiency there is a steadily growing -and it must be freely admitted that PUBLISHED WEEKLY. ENTERED AS SECOND- tendency to minimise the importance CLASS MATTER AT NEW YORK, N.Y. far too many of the crazy erections that of the aerial and be content with a very are seen leave much to be desired on Subscription Rates : small one or an indoor aerial trailing aesthetic grounds. Home, LI rs. 8d. ; Canada, £r is. 8d. ; other around the house. The direct result countries, £r 3s. rod. per annum. As to whether it is possible to instal of a poor aerial is that the receiver is a good aerial on a picturesque old As many of the circuits and apparatus described in these pages are covered by patents, readers are advised, before operated at a more sensitive position, house without spoiling its appearance making use of them, to satisfy themselves that they would thereby making it responsive to inter- not be infringing patents. we will not hazard an opinion, but it ference which is also picked up easily should be easy enough for the architect on the small aerial because of its of a modernistic type of building to proximity to buildings or to the house make proper provision for an aerial wiring. CONTENTS without in any way detracting from the Few Exceptions appearance. One or two serious at- Page tempts have apparently been made to Editorial Comment.. 67 Only when using an unselective set in do so, but we should like to see more of The Wireless World Television Re- close proximity to a powerful trans- them. ceiver-IV. Framework and mitter is there a good reason for Unit Assembly .. 68 reducing the size of the aerial. In all Good SetsBad Aerials other cases the aerial should be high, The indifference of the listening Broadcast Brevities.. 73 placed as far as possible away from public to the aerial question is reflected 40 -Metre Working .. 74 likely sources of interference -the down - in the fact that there are few firms Current Topics .. 75 lead should be direct and, if necessary, to -day to whom one can turn for of the anti -interference type. the erection of an efficient mast Model and Belmont 700 Reviewed 76 The service area of transmitters aerial. For a local radio salesman to On the Short Waves .. 77 does not, from experience, appear to suggest a good aerial would often be New Apparatus Reviewed.. 79 increase with power as much as theory taken to-day as a reflection on the would predict. Is not this probably capabilities of the set merely because, Listeners' Guide for the Week 80 due to the present tendency to neglect for some unaccountable reason, the Decoupling .. .. 82 the aerial and to expect satisfactory public have been permitted to come to The Modern Noise Meter.. 84 reception from the very poorest forms the conclusion that the efficiency of of collector ? In the early days of a receiver can be measured in terms Random Radiations 86 broadcasting transmitting authorities of its ability to dispense with aerial Recent Inventions .. .. 88 could base their estimates on reasonably efficiency.

www.americanradiohistory.com 68 Wireless World, July 23vd, 1937 wireless The World Television IV. THE FRAMEWORK AND THE ASSEMBLY OF UNITS

THE construction of the various units -which comprise the sound LS are given in this article of the method of assembly of the and vision receivers has been dealt DETAIDETAILS units which comprise the television receiver, and the frame- with in the preceding articles, and, before going on to discuss the operation work which houses them is described. The sound receiver is also and adjustment, their inter -connection and briefly redescribed. housing must be dealt with. Unless the equipment is operated in darkness some form of container is necessary in order to keep light from the back of the tube ; it The sound and vision receiver chassis necessarily made outside the box and the is, however, inconvenient to fit the units are screwed on the right -hand side of the joins should consequently be carefully into a cabinet of normal design, for they upper shelf and the time -base on the lef t- wrapped with rubber insulating tape, would be inaccessible. hand side at the rear. Between these and many layers being used. The method of housing adopted is one immediately beneath the tube base are which enables all units to be got at readily mounted the two o.oi mfd. high- voltage The Connections to the Tube and it consists really of a special form of condensers for the line deflecting plates. cabinet construction. It consists of a The two o.i µF. condensers for the frame The theoretical circuit of the tube and framework made of the four corner posts deflecting plates and the four 5- megohm its immediately associated equipment, suitably braced and carrying two shelves resistances are contained in a small wood- which must be considered a part of the for the gear. These posts are grooved and en box and screwed underneath the shelf framework, is given in Fig. 5 and the prac- sliding panels are used for the sides and under the ;tune -base. These components tical wiring plan will be found' among the front. The latter must be considered a fix - are fitted in ä box to guard against acci- other drawings which also show the way tine since: the various control shafts .pass dental contact with any, of the connections in which the various units are interconnec- through it, but the two sides and back can for many of these are at high voltage. The ted. There are many, connections and be slid out at a moment's notice: The de- connections to the o.oi µF. condensers are great care should be taken to see that no tails of the construction will be clear from the drawings and it will be noticed that small wheels in a swivel mounting are fitted to the legs. Naturally it is a matter of individual preference whether these are adopted or not, but they are recommended in view of the . weight of the apparatus since they enable it. to lie readily moved. À sheet Of i-in. plate glass is fitted in the viewing window to protect': the tube fróm accidental damage. In this connection, it must be remembered thât ' a large cathode -ray tube is somewhat fragile and must be handled with care; it is electrically robust, but mechanically deli - cate and care must be taken to see that it is never knocked. Remember, that the external air pressure is several tons ; the glass is built to withstand this, but it is folly to increase the strain on it by rough handling. The Tube Mounting

Th e tube is supported at the front end on two small blocks of sponge rubber and at the other by a cradle, rubber cushioning again being adopted. The tube base fits on the end and is supported entirely by the tube. A side view of the lower shelf showing the power units.

www.americanradiohistory.com Wireless World, July 23rd, 1937 69

DESIGNED BY W. T. COCKING

This box, mounted under the time - base, contains the condensers C3 Receiver and C4 and four resistances.

mistakes are made. The deflection plate RF valve is employed with a reacting grid connections may be a little confusing but detector. The two tuned circuits provide no damage will result if an error is made. adequate selectivity to avoid interference If the connections to the Y-plates are re- from the vision signals and these tuning distance from the Alexandra Palace. In versed the picture will appear upside condensers are ganged together and oper- the writer's experience the best results are secured from a centre -fed half -wave dipole mounted vertically and with a reflector behind it. Details regarding various types of aerial were given in a recent issue of The Wireless World,' and from the data given there it is easy to obtain the dimensions and method of construction of a suitable type.

The Aerial System Within two or three miles of the transmitter good results can be secured with almost any aerial, even the ordinary broadcast aerial. At greater distances a dipole is to be recommended, and at eight miles or more the addition of a reflector is strongly to be advised since ' it doubles the signal strength as well as greatly reducing interference which origi- nates to the rear of the array.

Tke receivers, time -base, and tube are clearly shown in this illustration.

down, while a reversal of the leads to the This photograph shows the con- X- plates will reverse the picture from left densers Cs and C2 beneath the to right. The remedy is obvious, but it tube base. should be pointed out that should such a misconnection occur, it can be put right ated by a single control knob. either by reversing the leads on the tube Following the detector, for which socket or on the appropriate time -base a metallised valve must be used, plug. comes another triode. When the Push -Pull Quality Amplifier is The Sound Receiver employed this valve acts as a phase -splitter and gives little gain. The power units are all mounted on the When the smaller amplifier de- lower shelf and the connections pass scribed last week is employed, through holes in the upper shelf. Except however, the resistance Rio is in the case of the high -voltage unit, plug short-circuited and the valve acts and socket connectors are used through- as an amplifier giving good gain

out. The AF connection between the and . an output adequate to load sound receiver and its power unit is a PXS, type valve. Whatever aerial system is used it should screened, as is also the lead between the It will be seen from the drawings that be erected as high as possible and away vision receiver and time -base. the two aerial coils of the sound and vision from metalwork such as drain pipes and Although the sound receiver has been receivers are connected in series and joined gutters. In particular, it should be kept already described, the circuit diagram is to the aerial. The type of aerial used is of away from any metalwork which is a repeated here for convenience of reference. considerable importance, especially when multiple of a half -wave in length. A drain It will be seen from Fig. 7 that a single the equipment is used at any great 1 The Wireless World, May 28th, 1937.

www.americanradiohistory.com 7, JULY 23rd, 1937 Worl'lli

c1E 0.01 rnfd HIGH VOLTAGE UNIT 12H

o a02=- fd -- I A30 L NE SCAN SOCKETS PLUG C3 ON 0.11 mfd TIME BASE

zRin5o FRAME SCAN C4 PI IIG 0.1 mfd

1W ` A2

CS TUBE HEATERN FLUG MODULATION I HT SOCKET ON VISION PLUG, RECEIVER POWER UNIT 1W SOCk ET ON VISION RECEIVER

STANDARD FLEX

TIME BASE VISION RECEIVER

COUPLING UNIT HOLE 1 VISION POWER UNIT

C4 TIME BASE L T

VIS ON RECEIVER

C R TUBE HEATER

TERMINAL STRIP ON HIGH VOLTAGE UNIT

-HT

A2 Al

Fig. 5. Circuit diagram and practical wiring plan of the cathode -ray tube and connections to its associated units. The coupling unit should be wired before the high -voltage unit is inserted in the cabinet. On the opposite page, Fig. 6 shows suggested cabinet and layout ; also wiring of terminal strips and inter -unit connectors.

www.americanradiohistory.com JULY 23rd, 1937 Wh'SRIlc0 7t S1 t1, \'ñ%(ji Jllç

j ,-- o - ,

VFEW ING CATHODE RAY TUBE 12 H I WINDOW . l O 0 ^ 1 O O 63/4'

O 0 0 O P, ,l i >t i

COUPLING UNIT I l

4:1.. I

SECTION Ca OF LEG I

LEGS 13% SQUARE X 4Ft LONG MATCHING l TRANSFORMER I SLOTTED 38 DEEP ' TO TAKE PAN°_LS 197/8 4-

I #

i 61/4 LOUD \ SPEAKER ` y

L 0 t 251/4 - PLYWOOD PANELS a 1 3/s FRONT & BACK 243/4 x 3,3"x 1/4

Ial.l 1 I 1 I I I I I I I I , SIDES 1 2 3 4 5 6 7 8 8 10 11 12 26 x 36"x 1/4 SCALE OF INCHES

COUPLING UNIT HOLES FOR UNDER TOP BASEBOARD P4SSINO WIRE 24"

TO DIPOLE

H13í1 VOLTAGE UNIT AERIAL V 1S1O5 MAINS INPUT RECEIVER EARTH ro PLUG HIGH VOLTAGE UNIT

EARTH VISION POWER UNIT SYN OUTPUT+ SYNC OUTPUT A &E SOCKET SOCKET MAINS INPUT PLUGS AC SUPPLY MAINS INPUT

EARTH

SOUND RECEIVER PLUG & SOCKET TO SPEAKER MATCHING Fir;. 6. TRANSFORMER

www.americanradiohistory.com 72 WAp@11MO JULY 23rd, 1937 WOpIlO) The Wireless World Television Receiver IV- jects and so does not need pipe of lift., 22ft., 33ft. in length will any special attention in the resonate at the wavelength of the vision way of spacing from walls. signal and if it is close to the aerial, within It should, however, be run lift. or so, it is likely greatly to reduce tidily and in such a way that the efficiency. it is not subjected to Whether a reflector is used or not, the mechanical strain, other- dipole must be joined to the receiver by wise a broken conductor a feeder of definite impedance (some 72 will sooner or later ohms). Special feeder cable in 6oft. interfere with reception. LIST OF PARTS FOR The operation of th e equipment and the ne- FRAMEWORK AND cessary initial adjust- ASSEMBLY OF UNITS ments will be described

1 Cathode Ray tube Ediswan 12H in next week's instal- 1 Tube base (G.E.C. type) Bulgin CR10 ment. Fixed Condensers: 2 0.1 mfd., 5,000 volts, tubular, C3, C4 Dubilier The RF valve and 2 0.01 mfd., 5,000 volts, tubular, Cl, C2 Dubilier tuning system of the sound receiver are clearly shown here. Resistances : 1 2 megohms, ¡ watt, R Erie 4 5 megohms, z watts RI, R2, R3, R4 Erie LIST OF PARTS USED FOR THE SOUND RECEIVER 11 Extension rods, }in., two 15kin., live rgin., four i8fin. Bulgin Certain components of other makes but of similar Miscellaneous : Peto -Scott characteristics may be used as alternatives to those Wood, glass, screws, sistoflex, wire, etc. given in the following list.

2 Variable condensers, mmfds., Cl, C5 1 Trimmer, is 40 C2 Bulgin SW95 lengths available from Belling and Lee " Apex Economy " Webb's Radio Z Coils and is to be recommended. The loss in the 14, Soho St., W.I. 3 Extension control outfits Eddystone 1008 feeder naturally increases with length but I Variable condenser, 15 mmfds., C6 1 Valve holder, 7 -pin (without terminals) in any reasonable quantity is negligible. " Apex Economy " Webb's Radio Clix Chassis Mounting SW Type V5 1 Dial, dual ratio Eddystone 1070 1 Valve holder, 5 -pin (without terminals) There is, consequently, no need to choose Condensers: Clix Chassis Mounting SW Type VS 2 0.01 mfd., mica, C3, CIO T.C.C. " M " 1 Valve holder, 7 -pin (without terminals) r 0.0001 mfd., mica, C7 T.C.C. " M " Clix Chassis Mounting SW Type V5 2 o.0005 mfd., mica, C4, CS T.C.C. " M " Socket strip Clix " C " I. 5o mfds., 12 volts, electrolytic, C11 2 Terminals, ebonite shrouded, output +, - T.C.C. " FT " Belling -Lee " B " 2 8 mfds., 46o volts peak, electrolytic, C9, 1 Group board, to -way Bulgin C32 C12 T.C.C. 802 I Plug top valve connector Belling-Lee 1175

+H T

R6 R7 R8 100,000. RECEIVER R3 R4S500^ PL c C6 Rá0300.

R12 X 25.000.t

0-0001Lmid mfd 0'01 OUTPUT C7 010 R5 03 -O-- The sound receiver, showing ó C1S ;C2 150,0000 2M! the detector and O0005 mfd AF valves. Al sifl o R11 0 .- 2,0030 A2 o 5 "CB ! R2 R1 00005 n,fd (Right) Fig. 7. -The com- 1Qo000 plete circuit of the sound 1000 receiver is 510 shown here for C3C001 mra 25,000 n the Push -Pull Quality Am- plifier. When used with the smaller power unit Rio should be short -circuited. the aerial position for a short lead -in and Resistances : 1 Connector, 5 -way Bryce it can be selected solely on its merits for 1 loo ohms, - watt, R1 Dubilier Ff I Cable, 5 -way, with twin 70/36 leads and reception. If the attainment of an extra 1 500 ohms, ¡ watt, R4 Dubilier Ff 5 -pin plug Goltone 1 2,000 ohms, ï watt, R11 five feet in aerial height involves in- Dubilier Ff Chassis B.T.S. an 1 10,000 ohms, watt, R6 Dubilier Ff ¡ Miscellaneous : Peto -Scott crease in feeder length of twenty feet or 3 25,000 ohms, ¡ watt, RIO, R12, R13 more by virtue of a different Dubilier 2 Lengths Systoflex, r oz. No. i8 tinned aerial posi- Ff copper wire, aluminium for brackets, 1 50,000 ohms, watt, R7 Dubilier Ff tion, the change will probably be well - etc. Screws: 48 6BA ¡in. R x 75,000 ohms, watt, R8 Dubilier Ff /hd.; worth while. ¡ 2 4BA ¡in. R /hd. ; z 6BA tin. 1 150,000 ohms, R/hd.; ¡ watt, R5 Dubilier Ff all with nuts and washers. The feeder itself consists of two wires 12 megohms, ¡ watt, R9 Dubilier Ff embedded in insulating material and it is 1 100,000 ohms, z watts, R3 Dubilier F2 Valves: I TSP4, metallised Mullard unlikely to pick up interference to any seri- 1 Potentiometer, xo,000 ohms, wire-wound, R2 I MH4, plain Osram ous degree. It is " dead " to external ob- Haynes Radio i MII4, metallised Osram

www.americanradiohistory.com Wireless World, July 23rd, 1937 73

record (Big Ben is now relayed direct). At the close of the evening television transmission Broadcast Brevities the man at control placed the needle in the wrong groove. NEWS FROM able valve unit which had been that the occupants sink into Viewers were surprised by the inserted at 03.12.00. them, and, although only the yapping of a terrier. PORTLAND PLACE " GSO.S.3 shut down from select few get a seat at the 07.01.00 to 07.07.30 to array " Proms," it is Human Wants of the due quite likely that Truth About the Sync. selector switch ` C ' parted on their characteristic curves in Signal Empire hook." the new seats may set up unex: NO drastic overhaul of the WHILE Portland Place is The Daventry . log -book is a pected resonances. Anyhow, we apparatus spending sleepless masterpiece re- shall hear. at Alexandra nights - of literary Palace will and days puzzling straint. And, of course, a new take place during -in out what ventila- the " shut down," one excellent mental pabulum to provide for tea CGI tea ta tion system may play the deuce reason being the heterogeneous masses who with the sound waves. that the trans- Victoria Regina mitters will be functioning on go to make the Empire what it PEOPLE have been wondering most is, those same days during that period. masses have whether the B.B.C. has Sir Henry's Forty -third But the gear will their own idea be " tidied of their broad- overlooked the splendid broad- The " Proms " programmes up," to use the engineers' own casting wants. And very human casting material in Mr. Laurence for 1937 follow the well -tried expression, are their needs. and during the pro- Housman's now famous series of model. Mondays will, as always, cess special attention will be plays, Victoria Regina. Actu- be dedicated to Wagner; given to the synchronisation Big Ben Make3 the ally, the Corporation is now Wednesdays will oscillate be- pulses, but they will not be Running considering a series of broad- tween Bach, Brahms, and increased in power. In writing to the B.B.C. casts incorporating not only the Handel ; Fridays will be sacred Empire listeners still put Big Victoria Regina plays but to Beethoven ; and Saturdays Resumption Ben at the top of the list of what several original plays by Mr. will be " popular " nights. After the " shut -down " they want to hear, with news Housman on the same theme. E very night,' however, will be period transmissions fro m bulletins a close second. 'talks Look out for an interesting Sir Henry Wood's night. The August 16th to 21st will be at must have an Empire flavour, announcement. G.O.M. of British music will be the normal hours, 3 -4 and 9 -10. e.g., the " Responsibilities of CG1 tea WI Cea Empire " series, or must be High .links on the South about the English countryside. Coast " In Town To- night," with its characteristic CAR radio will perform a new London atmo- role on August Iz, when sphere, is another favourite feature. Harry Pepper produces his " Round the Fol -de -Rols " programme, in which different com- Technical Hitches : Some panies at Eastbourné, Llandud- Inner History no, Sandown and Hastings will THE " technical hitches " broadcast in quick succession in which cause shut -downs in- order to provide National lis- volve a multitude of major and teners with one continuous minor mishaps difficult to ex- seventy- minute show. plain to the public at large. Harry Pepper will make his Many radio amateurs, how- opening announcement at East- ever, . would often be grateful bourne ; then, when the show is for more information, and if under way, he will dash off by some of the transmission logs car to Hastings to give the clos- were published the B.B.C. en- ing announcement there. While gineers might win a good deal en route he will listen to the of from DURING THE U.S.A. FLOODS last March, Walter Stiles, jun., after sympathy the people show on his car radio. spending all night handling emergency who understand something of messages, received a desperate call for help from a township 70 miles distant. Stiles, who is the difficulties involved. Cues by Radio here seen with his apparatus, set out on an all -nigh: journey with Nightmare at Daventry To guard against breakdown the relief party, taking with him his portable transmitting gear with a second car will follow, also which he handled traffic continuously for 24 hours, until relieved by Here is the cold -blooded fitted with radio. two other operators. For a total of 160 hours his station formed the record of a real nightmare at sole link between the stricken town and the outside world. For his Incidentally, the Fol -de -Rois work in this emergency Stiles received Daventry a fortnight ago : the first annual William S. - at the different seaside towns Paley award, and the presentation ceremony was broadcast on the ' ` GSF.S.6 shut down from will listen to each other's per- Columbia Network, 23.21.30 to the end of the trans- formances and will take their mission (41 minutes 3o seconds) cues by radio. Harry Pepper conducting his forty -third On August 23rd and 24th, the and from 00.17.00 to 00.24.00 will have one assistant and two Promenade season. two days prior to the opening of due to (a) suspected rocky point OB engineers at each point. At C the Radio Show at Olympia, on gap 5 with CAM 4 and 5 grid least twelve microphones will be Syncopating Big Ben there will be three hours' trans- meters and grid resistances used. mission of film, with sound burnt out, (b) failure of drive NO listener seems to have announcements, the additional noticed Big Ben due to unreliable plate coil con- that ap- period being from 11.30 a.m. - nections in amplifier No. 1, (c) Queen's Hall Alterations peared to strike two at teatime 12.30 p.m. one day last week. The engi- fault on control circuit prevent- WILLWILL the new decorations During the show, from ing closing of A.C.B." and seating arrangements neer controlling the National August 25th to September 4th, in the Queen's Hall be notice- transmission inadver- there will be three one -hour When the Hook Parted able by listeners to the tently switched out the West- transmissions daily. The3e minster chime the will Next day there were three " Proms " ? Such a thing is after first be given from 11.30 a.m. to stroke of five ; more spots of bother :- just possible, for the alterations then, realising 12.30 p.m. (film) and from 4 -5 " GSI.S.3 shut down from have included new seating the mistake, he plugged back and 9 -r) (actuality). 03.00.0o to 03.12.00 due to fail- arrangements and an improved again, but only in time to get After the exhibition normal ure of right -hand anode tuning system of ventilation. Every- the last stroke. programme times will be re- condenser in demountable valve one knows that the size of an sumed, with an additional unit. audience affects the acoustics of A Dog Barked morning period for trade pur- " GSI.S.3 shut down from a building, but perhaps atten- A worse mistake occurred at poses, made up as follows : 04.50.00 for the last ro minutes tion has not been given to the Alexandra Palace a few weeks 10.30 -II a.m., cruciform pat- of transmission 6. Overheating effect of an audience's shape. ago, when clock chimes were tern with tone, and II a.m. -rz of anode condenser in demount- Th, new seats are so luxurious taken from a gramophone noon, magazine sound films.

www.americanradiohistory.com 7-1 Wireless World, July 23rd, 1937. 40 -Metre Working By MODIFYING THE SIMPLE TWOS AUSTIN FORSYTH VALVE TRANSMITTER FOR 7 MC ;S OPERATION G6FO

ANY readers have enquired if the in the original article he has found the 1.7 Mc/ s transmitter described answer to every amateur's prayer-the crystal "1 At all events, in The Wireless World dated perfect " rubber varying the coupling by can be modified for two otherwise normal specimens give direct to LI- June nth moving the clip up or down the coil on 40 metres altering the between them varying depths of control on -but working by this method, though simple, is not advis- a 7 Mc / s upwards of thirty points in the 1.7 Mc /s values and substituting crystal. able. The loose- coupled arrangement is it it ! band. Several on different The answer is that can and can't other crystals better in every way, and tuning is per- In anticipation of such enquiries, tests bands behave in the same way when fectly simple : with the tank circuit Li -Cr have been made to check performance on directly excited, and the phenomenon is at resonance (minimum plate current) the in- investigated ; it was first 7 Mc / s- though the set was originally now being coupling between and L3 is set at as seven years Li tended only for 16o metres, explained observed by the writer about several inches and, with the aerial con- in article it has been found that ago, was then put down as being due the -and but nected, C3 is till circuit tunes, the manufacture. rotated that in the- hands of a competent operator to poor indicated by a slight rise in plate current. will actually give results on transmitter The coupling is then increased and both any band. The Circuit condensers CI and C3 brought to reson- The difficulties are not so much with ance circuits Li-Ci and L3 -C3 as in the -the react CW telephony working, due to Reverting to Fig. i, it is evident that the on one another more and more as the fact that with such a simple arrangement - circuit is actually a tuned- plate- and-grid coupling is tightened, process controlled oscillator this being a directly power -fre- with crystal lock, and the performance de- continued till the valve is drawing the quency modulation is almost inevitable pends entirely upon the efficiency of the required plate current. If the no -load speech is being used. With proper when current is about 10-15 m /A the best adjustment this is not evident on 1.7 Mc /s, transfer will usually be when the coupling but, it becomes so the much higher fre- on is adjusted to produce about 3o m/A quency of 7 Mc / s. Further, as implied in " draw." the article, ordinary crystals will not gener- While the modified circuit will give ally stand such hard treatment, direct ex- satisfactory CW performance on 7 Mc/ s, citation and keying, as they will on i.7 some trouble may be experienced on or 3.5 Mc/ s, hence the fact that this point 'phone for the reason already mentioned, also introduces a difficulty. and therefore when modulating on this interest However, in view of the shown band the depth of control must be kept in this question of 40 m. working, the cir Iow, not more than 5o per cent. or so on suit has been modified slightly, as given peaks. 'With values, in Fig. Z. is now The crystal To sum up, then, it can be said that the loose- coupled to the grid circuit, thus re- transmitter will work well when modified dùcirig the crystal load while retaining the and carefully adjusted, but those who are essential feature of frequency control by unfamiliar with this type of circuit would are the crystal. Tuning and adjustment be well advised to carry out some prelimi- the same as before. nary tests with an " artificial aerial " before going on the air with the set. Checking Frequency Fig. 1.-Modification to oscillator circuit for 7 Mc/s operation. A power -type crystal It should be noted that the transmitter should be used, loose- coupled as shown. is much more tricky on 7 than on 1.7 Values for 7 Mc /s are: LI, L3, twelve turns Mc /s, and it will be very necessary when No. I2 enamelled, Sin. dia. spaced about lin. AMERICAN THREE - tuning on to the crystal frequency for the between turns. Lz, thirteen turns No. 18 enamelled, slightly spaced on valve -base or CIRCUIT first time to have a monitor available so similar former (Ihn. diameter approximately). INTER - that after the grid and plate circuits have L4, three or four turns closely coupled to MEDIATE - been resonated the crystal frequency can and on same former as Lz. All other FREQUENCY be found correctly. Though the point at values as given in the issue dated June i th. TRANSFORMER. The latest type of which the crystal takes control can be seen 465 -kc /s IF coup- by a double -dip on the plate milliammeter, lock. If it is made too great, the crystal ling developed by a monitor on which the right frequency can is over -loaded, as it would be when direct- Aladdin Radio In- be located is almost essential for correct coupled ; if it is too loose, there is not dustries, Inc., of and the Chicago. Primary, adjustment. An additional reason for this enough control transmitter output secondary and in- is that crystals, when directly excited in is unstable. A 7 Me /s power crystal termediate cir- circuits of this type, exhibit curious pro- should be used, and as the degree of cuits are all tuned perties. They appear to have a number of coupling required varies with different by trimmers removed crystals, some alteration of the turns of mounted at the resonant frequencies, far from the top of the assem- fundamental, on any of which some degree L4 may be necessary. bly. The reson- of control is possible. This in spite of the A further point is with regard to the ance curve has fact that when used in the ordinary way aerial circuit ; on 40 metres a half -wave a broad flat top wire is usually possible (66ft. long approxi- about 8 kc /s wide, only one resonant point occurs -the funda- with steep sides. mental. The writer believes that through mately), and this should be coupled as the medium of the transmitter described shown. The same aerial can be tapped

www.americanradiohistory.com Wireless World, July 23rd, 1937 75

Television Expenditure are put out by French sponsored- programme stations. They IN reply to a question in the House, are demanding that, if these the P.M.G. has stated stations are to their his Department is continue, that consider- programmes will have to be ing question of the whether the raised to a much greater artistic B.B.C.'s income is adequate for Current level, the name of the sponsor- it to conduct efficiently the ser- ing firm being announced once vices entrusted to it. The ques- NEWS OF THE only tion of at the beginning and again the expenditure on tele- at the ending of the programme. vision is the subject of special WEEK IN consideration. Italy and Radio BRIEF REVIEW opics Advertising Russian Television ALTHOUGH the Italian Minis- A TELEVISION exhibition is of the Japanese people, they are Each pair of headphones is ter of Popular Culture is to be held in Moscow dur- actually more popular. Educa- provided with a separate said to have come to a decision ing the autumn in connection tional broadcasts are now volume control which the to suppress radio advertising, it with the celebrations attending divided into three categories, patient can adjust to suit his does not necessarily mean the the twentieth anniversary of there being a special Kinder- particular needs. The patients disappearance of the sponsored the Soviet régime. garten hour and a " Higher can not only be supplied with programme. Provided that a Education " hour, in addition broadcasting programmes or complete programme of real Brussels Rejects Relays to the ordinary transmissions with gramophone recitals and artistic merit is prepared it will view for schools. Over 3,000 schools concerts originated within the not be illegal for a firm to make IN of the strong protests it known they which have been made are now provided with wireless hospital, but they can be con- that are respon- by sets. nected by landline with any of sible for it. Apparently, how- Belgian manufacturers and traders, the various the Paris theatres by means of ever, advertising of the coarse Communes N.R.E.A. the Theatrophone service. and blatant type, likely to offend forming Greater Brussels have THE 1937 Western Area decided against refined taste, will no to abandon their project examinations f or the tolerated. of instituting an inter- communal American Trade Figures longer be Fellowship of the National to the latest wireless relaying system for dis- Radio Engineers' Association ACCORDING tributing programmes. figures available, there are French High -power Station will take place at Bristol next approximately 6o firms solely THE two transmitters at the Wednesday (July 28th). The devoted to the manufacture of French national station Pirate Transmissions chief examiner will be Mr. A. R. wireless sets, and 4o valve - now being built Allouis will Twiss, at short -wave enthusi- F.R.E.A., M.I.E.E. makers. The manufacturers of each be capable of transmitting MANYasts are reporting recep- Applications should be made PA systems are said to number with a power of 500 kW. The not later than tomorrow (July tion of signals on the 7 Mc /s 40- metre) band from G6SL. This 24th) to Mr. G. E. Palmer, call -sign is allotted to the Western Area secretary, 3, Two - experimental station at the Mile Hill, Kingswood, Bristol. Eddystone works of Stratton Tel. : Kingswood 73218. - and Co., Ltd. This station is at present in the process of An Important Legal reconstruction, and in any case Decision INSTANTLY confines its activities to the THE French Court of Cassa- SEE 56 Mc /s (5- metre) band. The tion has upheld the decision transmissions must therefore be of the Court of Appeal and the coming from an unlicensed Lower Court in an action station which is illicitly using brought by a wireless trader this call -sign. against a doctor. The action was in respect of the grave pre- Lazy Man's Tuning judice caused to the business of the w ireless trader by the doc- SPASMODIC attempts have tor's electro- therapeutic appara- been made from time to tus. The trader alleged that the time in this country to produce doctor's apparatus caused seri- sets of the so- called " auto- ous interference with the listen- matic " type in which any given ing of his customers, this hav- station can be tuned in by using ing, indirectly, an adverse effect a dialling arrangement similar to on his business. The two Lower that used in the case of the auto- Courts decided in favour of the matic telephone system. Simi- trader, and the Court of Cassa- AMPLIFIER FOR WATCH REPAIRERS. The watch is placed on lar arrangements have also ap- tion has agreed with them. the microphone to the right, and is compared with a standard clock peared in the U.S.A., but it now in the instrument so rapidly that it can be regulated in three or seems that the Americans are New Ceylon Station four minutes. In addition, provision is made for using the amplifier as an aid to the location of defects ; it is stated that a cracked jewel, taking these automatic tuning THE new 5 kW. Colombo really seriously, a bent balance wheel or a worn pinion each produces a distinctive systems as a station was designed by the sound in the headphones large number of receivers em- Ceylon Radio Department and, bodying these arrangements in to a large extent, was con- no fewer than 15o, but it must work of installing the appa- some form or other are being structed on the island. The be remembered in America this ratus is expected to commence produced for the coming season. relatively few parts of the trans- includes many firms who make almost immediately. These and similar systems are mitter which are of external nothing but loud- speaking inter- known in America by the some- origin were ordered from Eng- office communication systems. Miscellaneous Advertise- what appropriate description of land. An entirely new studio There are no reliable figures Lazy Man's Tuning. ments for August 6th Issue has also been built. available concerning radio com- WITH the approach of the ponent manufacturers. August Bank Holiday The Oriental Mind The Theatrophone slight alterations are necessary Japan, talks and educa- THE new Beaujon Hospital in Boring Programmes in our printing arrangements. IN tional programmes are far Paris claims to have the is stated the French listeners Miscellaneous advertisements more numerous than those in- most up -to -date wireless instal- IT are becoming rather satiated intended for the issue of tended for entertainment, and lation in existence. There are with the indifferent programmes, August 6th must be received not it is reported that, owing to the forty loud speakers and nine interlarded with false facetious- later than first post on Friday, peculiar psychological make -up hundred pairs of headphones. ness and cheap witticisms, which July 30th.

www.americanradiohistory.com Wireless World, Judy 23rd, 1937

Belmont MODEL 700 High Sensitivity and Good Quality in a Compact Table Model

S the result of arrangements which have recently been completed, sets FEATURES.- Table model super- of this make are now being manu- heterodyne for AC mains. (190 -280 factured in this country. The volts, 50 cycles). Waveranges. -(1) 16.5- Model 700 is a worthy representative of 56.5 metres. (2) 187-588 metres. (3) 860 -2,150 metres. the range and has many points, both in Circuit.- Heptode mixing valve -triode oscillator- var. -mu pentode cabinet design and performance, which IF amplifier-double -diode triode second detector -pentode output valve. Full-wave wove rectifier. cannot fail to earn for it a good reputation. Controls. (1) Tuning. (2) Volume and on -off switch. (3) Tone. (4) Waverange. (.5) Radio - The large oval dial is distinctive, and gramo. switch. Price. 13 guineas. Makers. -British Belmont Radio Ltd., Belmont House, if we may disagree with the arrangement 4/5, Ridgmottnt Street, London; W.C.1. of scales in which the greatest length goes to the long-wave range, which needs it least, there is no denying the lucidity of which is not shared by one waveband cerned. This precaution has been taken the station calibrations and the conveni- alone, nor is there any obvious falling -off in the Model 700, and there is nothing ence of the indicator showing the setting at the ends of each range. In daylight to complain of in the set's behaviour while of the waverange switch. the medium-wave range is crowded with the pointer is traversing the short gaps Immediately above the tuning scale is stations, and the majority of the long- between useful stations. The high inter- the cathode -ray tuning indicator. This wave transmissions are fully loading the mediate frequency (465 kc /s) compen- is provided with a shade so that the glow loud speaker before the volume control sates to some extent for the fact that there is still easily distinguishable in bright reaches the half -way mark. The short- is only one stage of preselection on short light. Tuning controls are four in number wave performance is no less convincing, waves, and second -channel repetition and are arranged in a row immediately and so far as sensitivity is concerned the points for stations have to be carefully below the oval dial. They are not identi- reception of American transmissions will searched for to be found. . fied by any form of lettering, but one soon be effortless whenever conditions in the On the medium-wave range, for which learns to memorise the order which, from ionosphere permit a signal to get across. a band -pass filter is provided, the selec- left to right, is as follows : Volume control There is room for improvement, however, tivity is sufficient to give clear reception and on -off switch, tone, tuning, wave - in the ratio of the slow motion control for outside i channels on either side of the range switch. A separate switch at the this range, and a certain delicacy of touch power local stations and on long waves, back of the chassis is used to change over is necessary when making the final ad- where there is a single tuned circuit in- from radio to gramophone, and it should justment of tuning. stead of the band -pass filter, station be noted that the volume control operates separation though adequate is not quite only for radio reception, and that a pick- Signal -to -Noise Ratio sufficient to give Deutschlandsender clear up incorporating a separate volume control of Droitwich and Radio -Paris in London. will be required. High sensitivity brings its own special No less impressive than the high sensi- From the moment of switching on there problems, and before it can be allowed full tivity is the quality of reproduction which can be no doubts of the outstanding sensi- rein a set must be cleaned up so far as provides ample justification for those who tivity of this receiver. This is a property background noise and whistles are con- maintain that an off-set speaker in a

A band -pass filter is used on medium waves and single tuned circuits on the short- and long -wave ranges. Separate valves are used for the oscillator and mixing functions of the frequency- changer.

www.americanradiohistory.com JULY 23rd, 1937 Eoollogo 77. WopIlCI Belmont Model 700 - using a separate oscillator in conjunction reception of W2XE on 21.52 Mc /s seems to cabinet of a horizontal type is an effective with a heptode mixing valve has been have been strongest on the second (typical) method of steering clear of cabinet reson- adopted. Apart from this and the fact day, a result which bears out the evening ances and the peaks and troughs which a that band -pass tuning is used only on the performance. symmetrical arrangement gives. Cer- medium waveband, the circuit follows the These results, of course, quite definitely point to a fall in F layer ionisation on polar tainly there is in this set a wide and usual layout with a var. -mu. pentode IF routes mobile bass response, reg;ster when the sunspot activity is excessive and the top amplifier, double- diode -triode second de- or of .a particular kind, but to a steady in- is crystal clear with no trace of the 2,5oo- tector and pentode output valve. crease in the F layer levels on equatorial or cycle peaks which so often set a limit to The chassis as a whole is neat and corn- non -polar routes. the volume which can be tolerated. pact, and a good feature is the protection The important point, to which I have pre- At all events, no reduction of high -note of the mains voltage adjustment by an viously drawn attention in these notes, is response seems to be called for under any easily detachable cover plate. The that the agent responsible for the fall in ionisation is able to distinguish between polar and TUNING non -polar routes. This is a INDICATOR well -known property of OSCILLATOR VALVE I F AMPLIFIER VALVE 6 G 5 charged particles. 6 C 5 6 K 7 During the second Polar Year observations at Tromso in 1932 -31, the Radio Research 2nd DETECTOR Board reported that a com- VALVE plete cessation of echoes was RECTIFIER 6Q7 often noted on their layer - VALVE height measuring equipment, 5 Y 3 the fade -out being complete on all available frequencies FREQUENCY for vertical incidence pulses. CHANGER The explanation advanced VALVE to account for these phen- 6 L 7 omena was that they were OUTPUT VALVE due to severe attenuation of 6F6 the signals caused by an increase in E (or lower layer) ionisation. During the sunspot minimum years we often experi- AERIAL enced magnetic storm activ- AND ity when the F layer levels EARTH LEADS fell, following a decline' in GRAMO. SWITCH sunspot activity to zero. An MAINS VOLTAGE ADJUSTMENT analysis of the Polar year magnetic records also shows this effect, i.e., a magnetic m°W reless World COPYR IGHT storm accompanied the fade- outs, which also seems to be The change -over from radio to gramophone is effected by a separate switch at the back of the chassis. due to a fall in F layer ionisa- Extension loud speaker connections must be made directly to the terminal panel of the internal loud speaker tion. unit. It is not safe to draw hard - and -fast conclusions, but the conditions of operation, so that the fact cathode-ray tuning indicator, generally the inference is obvious. that the range of the tone control is rather least accessible of valves, is in this case not This idea of a neutralising radiation from crowded towards the lower end does not only the easiest to replace, but is mounted the sun seems to be quite recent, but is amount to a serious criticism. in a special clip with a detachable socket obviously worth further consideration. image can be Incidentally, it should not be implied In the arrangement of the frequency- on flexible leads so that the from the foregoing that I retreat from the changing circuits the American practice of easily adjusted for angle. contention that on the whole sunspots are beneficial to short -wave propagation ! There was an error in my last notes. The " Five Hours Back " series is, of course, run- On The Short raves ning from 7.30-8.0 p.m. on Fridays. It is the " America Dances " broadcasts, taken NOTES FROM A LISTENER'S LOG at Tatsfield, via W2XE, of the Columbia system, which occur at 11.30 p.111. THE past week has fortunately given cuits, coupled with a general improvement Turning to more definite things one hears one a' further opportunity to study in signal strengths. rumours of intended or actual increases in the effect of a high degree of solar The same effect was noted on the second power of many of the Western stations. The activity in some detail. day, although the hoped -for further im- Mexican transmitter XEWW on 15.16 and From July loth there has been an amaz- provement did not seem to materialise in 9.5 Mc /s, for example, has a 10 kW (output) ing increase in the number of spots, a total case of the U.S. and Japanese signals. transmitter similar to W2XE, and TGW of forty or so having been counted on On the third. day, when an additional in- Guatemala City will also have one of this July 14th, crease in activity was noted, a general de- power shortly. Power increases are also During this period careful observations terioration took place in the high -frequency rumoured for W2XAD and W2XAF. were made during the late evening, when signals, about 16 Mc /s and higher, from Judging by the signal strength of GSG the effect of daylight, at least on the E layer, the U.S. and Japan, the optimum frequency 17.79 Mc / s in London in the early evening, had largely worn off, on the U.S. and :the decreasing to between 13 and 15 Mc /s or the Daventry Empire station is now pump- easterly circuits, taking care to select signals o, but in the case of the Eastern (non - ing out some useful power. in pairs, one of the pair having travelled polar) signals the optimum frequency, as far On July 2nd sunspot activity was quite via the poles (to a greater or lesser degree), as it was possible to judge, again increased low, only one small group being visible, and and the other over a sensibly equatorial or and very high signal strengths were encoun- in the late evening, at 10.50 p.m., W3XAL non-polar path. tered on 18 Mc /s, and higher even over com- was fairly good, but W2XAD was very A most remarkable effect was noted on pletely night paths. I Appleton, Naismith and Ingram (Miss), the first day of the increased activity : the No reliable comparisons are available in Trans. Royal Society, Series A, 764, Vol. 236, optimum frequency increased on all the cir- respect of daylight reception except that 1937.

www.americanradiohistory.com 78 WIp®11,sm JULY 23rd, 1937 `'1000Ild On the Short Waves- the evening from those stations received good indeed, and, as would be expected, regularly. Television excellent reception was also obtained on this An interesting record was played at PCJ occasion from WIXAL on 11.79 Mc /s. 9.59 Mc /s at 7.40 p.m. on Tuesday, July Programmes The Japanese beam telegraph transmitters 13th. This record was composed of eight JNG -C -B, ranging 19 13 Mc were from to /s, or nine separate recordings of the reception Vision 45 Mc;'s Sound 41.5 Mc¡s. all good on Saturday afternoon, July 3rd, of various short -wave stations on a well - JNG on the highest frequency being easily known commercial receiver. FRIDAY, JULY 23rd. the strongest. Excerpts from the programmes of the fol- 3, " Pyramus and Thisbe." A most lamentable comedy by William Shakespeare. 3.15, Film A rather surprising round -the -world echo lowing stations were heard : (I) W 1XAZ was heard on GSG at 10.3o p.m. on Sunday, Boston, (2) -Mickey's Pal PIuto. 3.25, Mizzen Cross RNE Moscow, (3) LRX Buenos Trees. 3.50, British Movietonews. and good conditions seemed prevalent. Aires, (4) W2XAD /F Schenectady, (5) Strong signals were intercepted from PRF5 Rio, (6) I2R0 Rome, (7) HVJ Vati- 9, ,' The Raft " -an Interlude by Stephen Leacock. Film " SPW, Warsaw, at 6.45 p.m. on Friday, can, and (8) VK3LR 9.15, - Bugle from Blue Melbourne. Grass." 9.25, " Ad Lib " -Revue by Herbert July 9th, and good results were obtained in Quite a bag ! ETHACOMBER. Farjeon. 9.50, Gaumont- British News. SATURDAY, JULY 24th. 2.30, Relays from Wimbledon. Ig addition, programmes will be interrupted between 3 and 4 p.m. for short relays from the Challenge Scophony Television System Round of the Davis Cup at Wimbledon. 3, In Our Garden-Another practical talk by C. H. Middleton from the garden in Alexandra Park. High- definition Pictures Projected on Large Screens 3.15, The John Carr Jacquard Puppets. 3.25, Gaumont- British News. 3.35, " Review of Re- pERHAPS the most interesting feature Two sets were demonstrated on this occa- vues" : cast includes Adèle Dixon, Valerie of the Scophony system of television, sion ; one was a home model and the other Hobson and Cyril Pritchard ; production by of which a special demonstration was a public hall receiver having a screen 5ft. by Dallas Bower. given to us recently, is that the picture is Oft. When viewed from appropriate dis- 9, Starlight : Elsie Carlisle in Comedy Songs. projected by means of a special optical sys- tances there was no appreciable difference 9.10, Summer Gardening VII -by C. H. tem on to an external screen. The problem in the brightness of the picture on these sets Middleton. 9.25, British Movietonews. 9.35, of adequately illuminating comparatively despite the great difference in size. Defini- Repetition of 3.35 p.m. programme. large been # r screens has also overcome by a tion was perhaps a shade better with the DURING new development known as Supersonic smaller the television " close-down period " the picture. from Monday, July 26 to Saturday, Light Control. This August 14 inclusive, there will be two test differs from the transmissions daily, with the exception of usual method of Saturdays, when the morning transmission scanning in that one alone will be given. These will be solely for whole line contain- the benefit of the radio industry. There will be ing all the picture no transmission on Sundays or on Saturday, elements July 31, or Monday, August 2. The trans- in that line missions is thrown on will be radiated from 11.o a.m. to the 12.0 noon and from 2.0 to 3.o p.m., and will screen at a time. It consist of the television demonstration film, is claimed that by short magazine films and news reels, accom- this means far panied by sound, and exterior shots from the brighter illumination balcony with gramophone records, all of which is obtained than if will be interspersed with periods of cruciform pattern with the picture ' were tone on the sound transmitter. In addition, the Davis Cup Challenge Round scanted by a spot of match light only. is will be relayed from Wimbledon be- It tween 3.o and 4.0 p.m. on Monday and Tuesday largely due to this next, July 26 and 27. development that screens of some 20 square feet in area can be employed The Radio Industry and adequately illu- CELESTION loud speakers will be found minated with a stan- this yeàr at Radiolympia on Stand 26, and dard cinema arc the new season's models will include extension lamp. speakers and " Auditorium " chassis models ranging in price from 225. 6d. to £22 Is. As in previous years the retail distributing side of the business will be in the liànds of Cyril The scanning por- French, 29, High Street, Hampton Wick, tion of the Scophony Kingston -on- Thames: high- definition home O . receiver is very com- Mr. I. T. Watkins has been appointed as pact and can be Midlands area representative of the Westing- accommodated in ,a house Brake and Signal Co., Ltd. His . ad- space approximately dress is, 26, Featherstone Road, King's Heath, Soin. cube. Birmingham. 0 Batwin Electrical Appliances, Ltd., 138, In a home model, for which a screen The subjects demonstrated (films in this Southwark Street, London, S.E.r, have sent us eft. by ift. loin. is employed, the light case) were chosen for the vast amount of a pamphlet describing the Cetron photo -cell, source is a specially developed mercury detail they contained, and were admittedly for which the firm holds an agency. The lamp consuming amperes 7o DC, difficult associated firm of U.S. Radio, Ltd., of the A at volts subjects to televise. Nevertheless, same address, has also or 25o watts approximately. the reproduced pictures were issued catalogues and very good, leaflets giving particulars of American Arcturus Needless to say, it is a high- definition both in definition and steadiness, the syn- valves. system, and although at the demonstration chronising holding perfectly throughout. O O O at their Campden Hill laboratories only the Apart from the 25- picture flicker the results The Alma Grove (London, N.1) factory of 240 -line 25 -frame apparatus was shown compared very favourably in all respects Sinclair Speakers will be closed for the annual working, we were told sets for use on the with contemporary systems. holidays from Saturday, July 31st, until Mon- preseát 405 -line B.B.C. transmissions, with A point of interest regarding the Sco- day, August 9th. scanning had is the highest a 0 interlaced been developed and phony apparatus that voltage on instructions of Acting received from H.M. would be available as soon as the B.B.C. used in any the receivers, home or public Office of Works, the British Thomson-Houston have made a promised improvement in the hall models, is 35o, and it is understood that Co., installed the sound amplifying equipment regularity of the synchronising signal from the former can even be operated successfully for use during the recent visit of the King to Alexandra Palace. on 25o volts or so. Caernarvon Castle.

www.americanradiohistory.com Wireless World, July 23rd, 1937 79 New Apparatus Reviewed

Recent Products of the Manufacturers BERCO POWER POTENTIOMETERS nr HE BRITISH ELECTRICAL RESIST- -A- Pon- WEARITE CONDENSER ANALYSER The accuracy of this test set is far better ANCE CO., LTD., Queensway, ders End, Middlesex, have for long special- THIS test set has been developed by than the ordinary tolerance of condensers and resistances, so that it will adequately ised in the manufacture of high -grade Wright and Weaire, Ltd., 740, High variable and fixed resistances. Road, Tottenham, London, N.17, mainly meet the requirements of service engineers and radio dealers. It is simple to handle Among their products is a range of for the use of service engineers and radio toroidal -wound potentiometers designed to dealers requiring a compact, self -contained and is operated entirely from the AC mains. instrument for the measurement of capacity The price complete with testing leads is and for generally testing condensers of all 9 95. kinds. Though this is its primary function, it also provides the means for measuring re- WARD CAR -RADIO AERIAL sistances, since a bridge circuit that func- AMONG the various problems that arise tions on the principle of balancing one im- in installing radio in a motor car is pedance against another can with very that of arranging for an efficient aerial little change be made to serve equally well system. For in the restricted space avail- for resistance only. able only very short aerials can be em- The two functions, viz., capacity and re- ployed, added to which they are usually sistance measurement, are, therefore, em- required to be inconspicuous, must not in- bodied in this one instrument. terfere with the entry and egress of driver Berco heavy -duty potentiometers; the large In addition, a test circuit is included for and passengers, yet be required to effect model is a Soo -ohm loo -watt type. ascertaining the condition of a condenser. good reception under all conditions. Leakage and short- circuits are determined From the technician's point of view the handle comparatively high power, and they by applying voltages of from zoo to 500 obvious place for an aerial is on the roof are consequently particularly well suited for across the condenser and observing the of the car, and if properly mounted and use in public address equipment and relay effect on a neon lamp. shaped to conform with the lines of the installations. Though not provided with a scale or a cars' body, it should not impair the ap- The Type T, as these power resistances calibration for insulation resistance, an appearance. are described, are made in 5o and zoo -watt proximate idea of the state of the con- That an outside aerial can combine the sizes. In order to provide adequate venti- denser, or other component tested on this attributes of efficiency and attractiveness is lation the resistance wire is wound on a circuit, can be had by noting the period of exemplified by the recently introduced large porcelain former which allows free flashing in the neon lamp. Ward Car Aerial, obtainable_ from Wireless access of air to all parts of the winding. The method of ascertaining the approxi- The laminated con- mate leakage resistance is dealt with fully tact arm is construc- in the operating instructions. ted of nickel and Three capacity and two resistance scales phosphor -bronze, and calibrated directly in microfarads and ohms to it is fitted a con- respectively are provided. They are marked tact brush of a copper C1, C2, C3, Ri, and R2. Range C1 takes and graphite mixture. in capacities of from o.0000z to 0.004 mfd. ; An extension of the C2 covers o.001 to 0.4 mfd., and C3 o.z mfd. contact arm bears to 40 mfds. The two resistance ranges against a collector cover zoo to 40,000 ohms and zo,000 ohms ring. to 4 megohms respectively. The spindle, con- All kinds of condensers, including the tact arm and collec- electrolytic variety, can be tested and tor ring are insulated measured on this bridge, which will give from the spindle, the insulation being adequate to withstand Ward Streamline aerial for fitting on the roof of a car. 3,000 volts. The resistances can therefore Supplies Unlimited, 278 -282, High Street, be mounted on n.etal panels even though Stratford, London, E.15. they be used in high -voltage circuits. It consists of two chromium- plated rods These resistances are delightfully smooth, each aft. Tin. long and mounted on black and they are quite silent in use. Some stand -off insulators which raise the aerial tests were made with a zoo-watt model Sin. above the roof. If assembled in line having a resistance of 300 ohms, its rated an aerial just over 7ft. 6M. long can be maximum current being 58o mA. Though obtained, for a few inches has to be allowed not tested with the full load a sufficient lead for overlap at the centre. was employed to enable an opinion to be Alternatively, the two rods can he reached regarding its ability to handle the mounted in the form of a V with the diverg- rated power. No trace of loosening of the ing arms towards the back of the car. winding was observed, while the good ven- It is quite unnecessary to drill holes in tilation allowed for rapid dissipation of the the roof for mounting the aerial as the insu- heat generated. lators are securely fixed in position by a The former on this model measured special cement in conjunction with a suc- Ain. in diameter, 'kin. deep and tin. wide. tion cup which is on the base of each insu- Considering the fine workmanship ex- lator. The only hole needed is in the wind- hibited and the power rating the prices of screen pillar to bring the downlead into the these potentiometers are very reasonable. car and so to the receiver. As the insula- The 30o -ohm zoo -watt type costs 22s. In Wearite capacity and resistance measuring a long leakage path the effi- this size the resistance values range from set. tors provide ciency of the aerial will not be impaired in 3 to 17,000 ohms and prices from 21s. to also a measurement of power factor. A wet weather. 24s. visual indication of balance is employed, This model costs 22s. 6d. There are In the 5o -watt series resistances of from the indicator being a miniature cathode -ray various other types available for fitting to 3 to 7,800 ohms are made and their prices tube. sports cars, tourers and open two -seaters. range from 15s. to 17s. 6d.

www.americanradiohistory.com So Wireless World, July 23rd, 1937' Lísteners' Guide chester, will provide many, Outstanding Broadcasts commentaries' for National listeners on Saturday, Monday, and Tuesday. P. G. H_, at Home and Abroad Fender will be the commentator, and the times of trans- TEW KESBURY Drama Festival is being held mission will vary from day to ABBEY, fro m in aid of the fund for the repair be day. which will ,. of the Norman Abbey of heard part of Between 2.30 and 5 on Eliot's " Murder Tewkesbury. Listeners will Saturday, National listeners in the Cathe- hear excerpts from the final will be lookers -on, through the dral," to -night scenes of E. Martin Browne's at 9.40. eyes of B.B.C. commenta- production of "` Murder in the tors, at the Davis Cup Chal- Cathedral," by T. S. Eliot, lenge Round 'matches at Wim- published will which is one of the plays being bledon and the Ireland v. take part in performed in the open air Hurlingham polo match for this pro- against the west front of the the Empire Cup at Hurling- g r am me, Abbey. If it is wet it will be ham. No times of individual among them produced inside the Abbey. relays are given, as they will being Violet This will be broadcast at 9.40 largely depend upon the pro- MORE and more use Lorraine, singing " Dear Old in the Regional programme gress of each event. Listeners is being made by Saturday Night " ; G. H. to -night (Friday). will, however, be kept in the B.B.C. of re- Elliott, singing " I Used to touch with each match by cordings of special Sigh for the Silvery Moon," SUMMER short running commentaries. events which take place early and Ellaline Terriss, who will LISTENERS are to have im- The play at Wimbledon on in the day for inclusion in the sing the first song Darewski pressions in the third of the Monday will also be com- evening's programme. This wrote, namely, " Au Revoir, series, " Summer Over the mented upon at intervals allows for a greater number of My Little Hyacinth." Lola British Isles," of a tour of during the afternoon, as will listeners to hear the broadcast Shari and Morgan Davies the romantic coast -line and also the third day's play-that than would be the case if the will be heard _ in this pro- quiet rivers of Devon and is, if the match does not finish transmission took place at the gramme, and so will Captain Cornwall, where thousands of in two days. actual time of the event. A Bruce Bairnsfather, for visitors from all over the 0 0 0 case in point is the occasion of whose wartime show, " The British Isles are spending their Their Majesties' visit to Better '01e," Herman Darew- summer holiday. This will be DANCING. Northern Ireland on Wednes- ski wrote the music. broadcast Regionally on Sun- WITH the departure of the day. Throughout the day the day at 9.45, and should prove B.B.C. Dance Orchestra B.B.C. Mobile Recording van WATERMEN interesting and enjoyable for listeners are to hear a variety and its crew of engineers will THE annual race for " hog - the thousands of listeners who of dance bands during the be present at various cere- gett's Coat and Badge " along have been awestruck as they coming weeks. Among those monies which are to take t h e four- and -a- quarter -mile have gazed on the rugged rocks broadcasting during the even- place. Records will be made Thames course from London and relentless lashing of the ing programmes this week are of the actual ceremonies, to- Bridge to Chelsea will provide Atlantic breakers. Al Collins and his Dance gether with descriptions, and a 15- minute broadcast for - O Orchestra (Friday, 8.3o, these will be broadcast in the Regional listeners this morning SEASIDE SHOWS Nat.) ; Dave Frost and his National programme at 6.20. (Friday) at 11.15. Those THE third and fourth broad- Band, who are presenting A similar instance occurs on competing are young water - casts in the series, " Shows the following day (Thursday) men who are still within the from the Seaside," will be when King Farouk is crowned first year after their admit- heard this week. To -night King of Egypt. It is hoped to tance into the Watermen's (Friday) at 6.25, Harry Pepper record a description of the Company. The prize, a red and Davy Burnaby will intro- actual ceremony as it takes coat with a large silver badge duce " Dazzle," from Pierrot place at 8.3o a.m., and to in- on the arm bearing the white Land, Bognor. On Thursday, clude this in the evening's horse of Hanover, was first 6.25 (Reg.), listeners will National programme at 9.20. rowed for in 1715, when it was be taken over to the Band- presented by Thomas Doggett, stand Pavilion, Littlehampton, " THE MAN BEHIND THE a celebrated comic actor, " in for an excerpt from " Summer MELODIES " commemoration of H.M. King Revellers." THIS is the apt title given to George's happy accession to Another broadcast from a a programme to be broadcast the British throne." holiday resort comes from the by the National transmitter on John Snagge will, from the West on Monday, relayed in Tuesday at 8, when Herman top of a tall building on the Regional programme at 8, Darewski recalls many of his Chelsea Embankment, de- when " Show of Shows, 1937 musical memories. The pro- scribe the approach of the Edition," will be broadcast gramme will be produced by competitors (probably six) from Knightstone Pavilion, an old friend of his, Max and the final scenes of excite- Weston- super -Mare. Kester, of the B.B.C. Variety ment and enthusiasm at the LARRY ADLER, the American Department. Many of the well - finishing point. CRICKET, TENNIS AND POLO wizard of the harmonica, will known people who were the THE second Test Match bebe heard during Saturday's CATHEDRAL "Music Hall," as will also first to sing Herman Darew- MURDER IN THE tween England and New Turner Layton and Gus ski's songs when they were FOR the second year a Zealand at Old Trafford, Man- Chevalier.

www.americanradiohistory.com Wireless World, July 23rd, 1937 81

Colonel " is an opera-bouffe, like his own " Esther de HIGHLIGHTS OF THE WEEK Carpentras," but has a mili- FRIDAY, JULY 23rd. tary background. Both of Nat., 7.30, Five Hours Back. these will be heard in this 9.40. Robb Wilton as Mr. the Week transmission. Muddlecombe, J.P. r Reg., I I.I5 a.m., Commentary on " When You and I Were Bayreuth Festivals are in pro- Those who wish to hear the whole the race for " Doggett s Coat and Dancing -Tunes of Yester- gress, and relays from these of " Falstaff," and not Badge." 6.25, Shows from the day " at 8 (Reg.) to -night two great musical events will Acts II and III Only, should Seaside. 9.40, Tewkesbury in to Lyons at 7 on Mon- Drama Festival. (Friday) ; Nat Gonella and be given on three occasions. tune day. Abroad. his Georgians (Saturday, 5.15, On Saturday at 8.45 (Reg.) Brussels 1, On Tuesday at 7, Radio 8.30, Gala Benefit Con- Reg.) ; Victor Silvester and the third Act of Wagner's cert for the War Disabled. his Ballroom Orchestra (Tues- " Lohengrin " will be relayed Paris is relaying Richard Strauss' "Der Rosenkavalier," SATURDAY, JULY 24th. day, 7.30, Reg.) ; Jack Payne from the Festspielhaus, Bay- Nat., 2.30 -5, Commentaries from and his Band, who will present reuth, the capital of Fran- of which G. Bernard Shaw is Wimbledon and Hurlingham. " Favourites of the Famous" conia. the librettist, from the Salz- 8, Act II "Lohengrin" 9.20, Description of the Paris at 6.5o (Nat.) on Wednesday From Salzburg, on Monday, burg Festival. It will, by the an- Exhibition by M. Stéphan; from and Carroll Gibbons and the come two relays of Verdi's way, be the 81st birthday Paris. Savoy Hotel Orpheans, who " Falstaff," which is being niversary of G.B.S. on this Reg., 6, Callender's senior band and will be heard on Thursday at conducted by the great Tos- day. the St. David's Singers. 8.45, - Act III " Lohengrin." 8 (Nat.). canini. At 8 (Nat.) will be o 0 Abroad. O O O heard Act II, followed at 9.30 MILITARY BANDS GALORE. Munich, and all German stations, HERO WORSHIP (Reg.) by Act III. FOR those who like military 4-I0, " Lohengrin " from Bay- THE inescapable penalty of For next week, arrangements band music, there is a treat in reuth. fame in any walk of life is.that have been made to relay from store if they will tune in to the SUNDAY, JULY 25th. of having ardent fans besieg- Salzburg the second Acts of wavelength of Brussels I at Nat., 7.55, Service from the Temple Church. 9.5, Victorian Melo- ing the hero or dies -16. 9.45, Margate Muni- heroine wherever cipal Orchestra. they are getatable. Reg., 5, Light Concert from Berlin. Gladiators a n d 6.30, Recital : Oda Slobodskaya. 9.45, Summer Over the British Olympian athletes Isles-3. doubtless had their Abroad. fans, but they Vienna, 8.35, Salzburg festival were harmless relay of Cathedral Concert. compared with MONDAY, JULY 26th. thou of to -day, Nat., 7, Monday at Seven. 9.35, Hachem Khan (baritone) and the when autograph Theatre Orchestra. hunting is the Reg., 8, " Show of Shows-1937 mildest form of edition," from Weston-Super- fan -worship. It Mare. 8.45, Billy Thorburn and his music. 9.30, Act Ill view " Falstaff " from Salzburg. SAL2 BURG. A Abroad. of the city the Festi- Radio Paris, 8.45, Symphony Con- val of which will frequently feature in cert from the Casino, Vichy. the programmes dur- TUESDAY, JULY 27th. ing the next week or Nat., 8, Darewski -the man behind two. the melodies. 9.20, America To- day -talk on literature. Reg., 6.30, Recital-Guelda Waller was left to Lewis Waller to " The Magic Flute," " Don 8.3o to -night (Friday). This and Vera Maconochie (songs and inspire the first organised band Giovanni " and " Die Meister- station is relaying, from the duets) and William Busch (piano). of fans ; these were known as singers." Grand Palais du Centenaire, a 9, Walter Widdop and the Mili- the " K.O.W.s," or " Keen In the programmes from gala benefit concert for War tary Band. Abroad. Order of Wallerites." abroad there is little opera Disabled, which includes a Radio Paris, 7, "Der Rosenkavalier" Since those days, with the other than the relays from the French military band, Band of (Richard Strauss) from Salz- coming of films and radio, fan - two festivals referred to above. the 2nd Batt. Somerset Light burg. worship has become more and Munich and all German sta- Infantry, Band of the Royal WEDNESDAY, JULY 28th. more popular. tions are taking from Bay- Carabineers of Italy, Band of Nat., 6.20, Recorded impressions The idea of the broadcast reuth Wagner's " Lohen- the Royal Romanian Guard of Their Majesties' visit to which will grin " in its from 4 a Belgian military band. Northern Ireland. 6.50, Jack " Fan," be heard entirely -Io. and Payne and his band. 10, " Rhythm on Thursday at 8.3o (Reg.), is During the interval from 7.45 0 . 0 on the Roof," American cabaret. to show that fan -worship can -8.45 a visit will be made to Reg., 8, Variety from the Argyle be sincere as well as sinister, Wagner's House, Villa Wahn- MISCELLANY Theatre, Birkenhead. 8.45, " The SOME of the best known of Romantic Young Lady "- and that in its most genuine fried, where solos will be Spanish Play. form it affords relief in drab played on the great composer's Carl Michael Bellman's songs Abroad. lives by bringing a star into own piano. will be heard in a special com- Breslau, 8.10, Dances old and new. memorative programme to be close contact with the admirer. Admirers of the ultra- THURSDAY, JULY 29th. It will conjure up a scene in modern in French music will given by Swedish stations on Nat., 6.40, " The Romantic Young a gallery at a first night and doubtless be pleased by the Monday at 9.5. Lady." 9.20, Recital : Lisa deal with the phenomenon of Milhaud and Sauguet operas An all- Norwegian pro- Minghetti (violin) and Adolph fan -mail. gramme of old and new church Hallis (piano). which form Saturday's emis- Reg., 6, Medvedeff's Balalaika or- 0 o v sion commune from Paris music will be given by aug- chestra. 6.25, Shows from the OPERA RELAYS. PTT, Marseilles and Alpes- mented choirs in the ancient Seaside-4 ; 8.30, " Fan . " 9, WE are to have a fair sprink- Grenoble at 8. Recently cathedral of Trondheim, on " Dorothy ": comedy opera. Thursday at 8, which will be Abroad. ling of opera in the home pro- Milhaud referred in the most Radio Paris, 8, " The Master - grammes this week, the reason complimentary terms to relayed by Oslo. singers " (Wagner) from Vichy. being that the Salzburg and Sauguet whose " Plume du THE AUDITOR.

www.americanradiohistory.com Wireless World, July 23rd, 1937 Decoupling By Separating the Various Kinds of Current "CATHODE RAY"

HE problems of the radio circuit is needed ; for 5o-cycle current large iron- cheaper, more compact, and incapable of designer are very similar to those cored coils are required. inductive coupling with other components. that confront the Minister of It is sound psychology not to control Fig. 2 looks like an exception. A re- Transport. Both are obliged to people only by restrictions, but for each sistance is often connected as shown with legislate for routes that carry different barrier to provide also a legitimate outlet the object of stopping RF. Here the valve classes of traffic at the same time, and for energy. It is also sound radio en- itself is the discriminating component, for are expected to arrange things so that, as gineering. For straining out one sort of between grid and cathode it is, in effect, far as possible, each can move without in- current from a circuit it is wise to provide a small condenser, probably about io µµF. juring or interfering with the others. The at least two components -one to bar and Suppose the resistance is half a megohm. radio designer has the advantage that his the other to by -pass. This seems quite high, but to DC the valve electric traffic obeys known laws, and he VI in Fig. I is a de- is virtually infinity, and by comparison can measure very accurately the resistance tector valve, and the resistance in the grid lead is negligible, of each path to current of any frequency. therefore has in its and whatever bias is applied to the re- The Minister of Transport has to rely on anode circuit three sistance finds its way to the grid. At even very imperfect machinery for ascertaining the highest audio -frequencies the valve is in advance the resistance of, say, a cer- 2. -This works several megohms, and receives the greater tain cycle track, and may consequently be as a separator only part of any signal that is applied ; but at quite a lot out in his results. He may find because the valve 47o kc /s (for example) the valve is only acts as a condenser. an unexpectedly strong current of cyclists a little over 30;000 S2, and most of a flowing in part of a route supposed to be sorts of current original radio signal of that frequency is lost in the confined to faster traffic. -the -fre- resistance. quency signal in amplified form, the low In the same way, certain paths in a re- frequency from The decouplers normally included in ceiver are intended for steady currents, resulting the detection pro- anode cess, and the DC necessary to feed the circuits require a relatively large some for low frequencies and some for capacity in order to valve. The first of these is a sort of waste be effective for two high ; and if they are allowed to run riot reasons : (i) Such a by- product, and unless it is utilised high resistance as along a single route there is likely to be for reaction, it should be short- circuited away Mfg would waste a large part of the HT trouble. So we have chokes, " stoppers," because the anode -to- from other paths by means of the con- cathode path is cer- blocking and by -pass condensers, and so tainly not an infinité resistance, denser CI. The capacity of CI must be and (2) it forth. It is easy enough to keep DC out normally chosen to be as attractive as possible to is designed to stop not only of a path intended for AC condenser is radio -frequencies but also -a the radio -frequency currents, but not so the very low a complete block to DC, and if of sufficient frequencies of large as to waste an appreciable propor- " motor- boating." Fig. 3 capacity offers negligible obstruction to is an example. Although - tion of the low frequencies. These are DC does not par ticularly like" going wanted at the grid of the next valve, through resistance it is obliged to pass through RI, R2, and whither they are led by a condenser C2 ; R3, simply because there is no alternative. and to keep them from finding a short - frequency circuit through the battery the high- induct- Radio- currents from the valve go straight back again through ; ance choke L2 is inserted. A direct con- Ci audio - frequencies find Ci too small, nection to the grid of V2 would let the but go through C2 to the next valve, HT battery voltage get there, whereas so while circuits of any frequencies at all far as DC is concerned the grid needs to that may try to work be negative, and is supplied from the grid back from battery through a resistance high enough the next valve + (where to cause very little leakage of audio -fre- the currents quency signals. are very much stronger) are by- Resistance -capacity Filtering passed safely by C3, and are unable A resistance, if it is nothing more, looks to get via C2 to the the same to DC and AC of all frequen- grid of the next valve. Suppose the Fig. i. -- Example of how the different cies ; and a correspondent is not clear how currents present in a single circuit are it can be useful for separating. By itself voltage between the separated out. it certainly is completely ineffective. If points A and E is there is only a single railway carriage on varying, due to AC. Taking advantage of the fact that the train it must be used by passengers of currents in later the obstruction proportionately grows less all sorts. But if another marked " Non- C3 stages of the ampli- as the frequency increases, a condenser is smoking " is available, the first imme- fier, the proportion often used to separate low- from high -fre- diately becomes less attractive to some of such voltages quency AC, but, of course, the separation people and more attractive to others, Fig. 3.-Example of is never complete. although it has undergone no change, and the usual type of There is no component that can be used thus it exercises a discriminating influence. decoupling. to pass DC freely and block AC com- As a resistance discriminates between pletely, but a suitable choke coil comes different sorts of current only in this in- appearing at the point B depends on the near to this specification. The lower the direct manner, it is not so effective as a proportion . of the total impedance that frequency the greater the inductance that choke coil, but it has the merits of being exists from B to E. That proportion can

www.americanradiohistory.com JULY 23rd, 1937 WATA®m 83 W©i lcal Decoupling- The existence of more than ioo per cent. be reduced either by increasing R3 or re- across the condenser alone may appear to ducing the impedance of C3 (done by contradict the rule : "The part cannot be increasing its capacity) . The latter is to be greater than the whole," but it is one of preferred, because R3 wastes the HT bat- the paradoxical results of the phenomenon tery voltage ; but whereas a resistance costs of resonance (see " The Tuned Circuit," no more for a greater number of ohms, a February 26th, 1937). It just shows how McCAIIRIf II-i

Fig. 4. - Curves 11a..=IMIIla0' .. NW . i AG /IEM showing the effec- , IMNíllN L OUTSTANDING 9 -VALVE tiveness of re- MIE /61 /ll/Ii/ G411. ALL-WAVE sistance capacity IIIIiMI^ aIns SUPERHET decouplers or 11111/1s IIRS.ai IJM separators. R is For all - wave reception in ohms, C in !:g1i/IiiÍ1í5i/i1I.iliii a.. microfarads, and at its very best L in henrys. If To the all -wave enthusiast, this exceptional receiver loo s''iiiÍÍI.011D.iÌ11sa.alrlaaG ataI-a'iSattat:at]I-sI an alternating MN AMa IMIIMMrAMIIIMIr :aum s11M7f/R_I a ñi offers a number of interesting features, with' quite unusual p E7 IN WI M If I IitJJIIL M EMP2 M1111C71. 11 I17s voltage exists ni.r.M.MWAsIMPWMrr,liM=MMIKIMnMP://iiI / range, and power output. Few receivers at present on across capacity I4IMIPJ:iWAMPlíGINIMPT%MIrS:E /Gi/,/, the market can claim so high a standard of design and and resistance (or li SS/IIIGUIIS performance. inductance) in Ifi1IMM- IIIRDIII3112 III11SI/ series, the percentage appear- u'II1I/% ÍiI.iIÇIIIiI1 ing across the 12 condenser only MINIENNIMPI111111111 can be read off o 10 01 o the vertical scale. GNS. PERCENTAGE OF ALTERNATING VOLTAGE LEFT condenser increases in price almost in pro- careful one must be with inductive de- portion to its capacity, and an economic couplers. limit is soon reached. When it is necessary to reduce an AC It may be suggested : Why not use a ripple to a very small residue it is more choke instead of R3 and avoid HT loss economical to do it in several stages, as almost entirely ? The objection is that to in Fig. 5. The RC curves give an approxi- stop very low frequencies, such as ten per mate idea of the effectiveness of such an seconfl or even less, a choke would have arrangement; two stages, each of which is to be of enormous inductance to be more found by the curve to reduce to I per effective than the 50,00o-ohm resistance cent. , when combined can be expected to that might be allowable for R3, and the reduce to about o.oi per cent. But the stray capacity across it might then be results of LC systems are not always even (Complete fre- with 9 B. V. A. enough to cause trouble with very high approximately found in this way. valves.) quencies. Every case must be judged on Methods of calculation were given in a its merits. ' . series of issues (June 19th and 26th, July 3rd, loth, and 17th, 1936), 4 wavebands : 12.8-33, 29-80, 190 -550, 500 -2008 and at the best metres, Illuminated dial with principal station are a good deal more complicated to work names. Separate coloured lights for each wave- odt than the single -stage systems. band. For decoupling purposes it is seldom Controls. -A feature of the receiver is the number necessary to use more than one stage. of independent controls fitted, making it extremely interesting to operate. These include : sensitivity control (varying bias on R/F stage). Q.A.V.C. with The Metal Valve Situation manual muting control, and switch for inter- station noise suppression. Separate potentiometer bias controls INTERVIEWS with four of America's for output valves. 5- position wave-change and gramo- largest valve manufacturers, states our phone switch. Progressive variable tone control Fig. 5.-Two-stage filter. The result given correspondent, indicate that less than 25 operative on radio and gram. may be quite different from that.indicated per cent. of the total production this year Circuit in Brief. -Aerial input to pre -selector circuit radio by multiplying the percentages ascertained frequency amplifier, latest type triode- bexode frequency from Fig. 4. will be metal valves. It seems that of these changer, 2 band -pass I.F.T. coupled I.F. amplifiers, double nearly 90 per cent. will be used by RCA and. diode detector. L.F. amplifier, parafeed transformer -coupled be helpful in giving some push -pull triode output giving 6 watts. Fig. 4 may General Electric of America, the two manu- Heavy cadmium -plated steel chassis. Fines: components cud idea of how effective a given combination facturers who sponsored this development. workmanship throughout. models ready for be. There are two sets of curves ; On the other hand, as many manufac- A.C. immediately delivery. will A.C. /D.C. models also in production, and will be available the full lines are for resistance/ capacity turers turn away from the metal valve, they for delivery shortly. and show the percentage of turn to the glass valve in a new form -the DE LUXE MODEL 14 GNS. combinations, Several additional refinements - full particulars on a voltage, applied to both in series, that octal base or " G " type. So popular is this application. type of construction that 90 per cent. of the appears across the condenser. A combina- IMPORTAMT valves used in new receivers this season will The prices at which McCarthy Chassis are advertised tion of 50,000 SZ and 2µF (or any that be of this type, with the exception of RCA include Marconi Royalties. " Wireless World " readers multiplies up to 100,000) can be seen to should, for their own protection, make sure before and General Electric. ppuerc tyanny receiver that the quoted price includes reduce a 5o -cycle signal to a little over While all new valves were introduced in 3 per cent. The inductance /capacity their metal overcoats up to a few months combination to give the same result would ago, several have lately been placed on the All McCarthy receivers supplied complete with valves, knobs, pilot lamps, leads, mains cable and need an LC (judged from the graph) of market only in their octal -base glass form, plug. 12 months' guarantee. about 300 (150 H- and µF, or 3o H and with no metal counterparts, showing a Deferred terms on application, or through London decided trend away from metal construction. Radio Supply Co., 11, Oat Lane, E.C.2. Io ,uF, for example) . But whereas the RC Although the G type of valve is little dif- Cash with order on 7 days' approval. Also write reduces a, io -cycle voltage to Io per cent., for illustrated catalogue of complete range of all ferent internally from the older glass form, McCarthy receivers. the LC actually produces more than loo it is a great step forward as far as the ser- per cent. across the condenser-in short, vicing of receivers is concerned, and it is AAICIRIf-lam IRÀIDIIC ILTE. it would be no good. At higher frequen- therefore likely that this base will long 44a, Westbourne Grove, London, W.2 cies, of course, the situation is reversed. remain standard in America. Telephone: Bayswater 3201/2.

www.americanradiohistory.com Wireless World, July 23rd, 1937 The Modern Noise Meter A Versatile Instrument with Many Applications

trate on the maximum readings more easily. As a matter of interest, a sound of roo milliseconds duration gives a deflection which is only 2 db. less than that given by a continuous note of the same frequency and intensity, and for a duration of 25 milliseconds the reduction is not more than 4 db. Another useful feature of the Tannoy meter is that it has right -hand zero, and the biasing arrangements are such that a sudden increase of sound while giving a left to right deflection actually reduces the current in the meter. There is thus no possibility of damage from mishandling of the apparatus. The standard instrument is housed in two teak cases measuring approximately 20 X 14 x 81-in. One of these is devoted ECENT proposed regulations of curve chosen is that of the average ear at to the power supply with suitable adjust- the Ministry of Transport regard - a level of 75 phons. This falls approxi- ments and monitoring meter, and contains ing the maximum noise which will mately in the middle of the range of levels in the case of the battery -operated model be tolerated from motor vehicles generally met with in practice. Volume a rotary converter designed to run off a have refocused attention upon instruments controls are included in the grid .circuits r2 -volt car battery. There are also models which can be relied upon to give scienti- of the second and third stages and are for AC mains only and for AC mains or fically accurate meter readings as a basis calibrated directly in phons as coarse and battery operation. It is understood that for comparison. The equipment adopted fine adjustments. The third stage also a more compact edition is in course of for preliminary investigations is the Tan- includes a correction network for the preparation, and that when completed this noy Noise Meter manufactured in colla- microphone, and one of the first steps in will be available for operation from a boration with the National Physical testing the instrument is to adjust this 2 -volt LT battery supply. Laboratory. correction with the " weighting " networks Apart from its application to the legal Like other instruments of its type, it out of circuit until a flat response is aspect of motor car noise, the noise meter consists essentially of a microphone am- obtained. is finding innumerable applications in in- plifier suitably "` weighted " to reproduce It is in the rectifier and its associate$ dustry. The motor car manufacturers, for the characteristics of the ear, and an indi- meter that the chief interest is to be found. instance, are using these instruments to cating meter in association with an attenu- The meter is of the high -speed type, but investigate body resonances and panel ator. Every instrument is issued with an even so, it is not quick enough in action drumming, while the tyre manufacturers N.P.L. certificate and is calibrated directly to give an accurate reading on the short - have found them invaluable in their search to read in phons. On steady tones it gives impulse sounds which constitute the sub- results which agree closely with other ject of most of the measurements which recognised standard instruments, but on have to be made. Accordingly, a time - 55 MILLISECONDS short impulse sounds, which, after all, are constant circuit is introduced which stores those generally described as noise, there the energy during the impulse and feeds it is a fundamental difference. Whereas to the meter after the impulse has passed. 80 most noise meters tend to average the The values are so adjusted that the steady sound energy of a discontinuous noise, the reading of the meter falls very little short Tannoy meter gives a peak reading which of the peak value of the sound impulse, 40 is very close to the level of any individual and the important thing to note is that impulse, and is not seriously affected by for impulses of equal strength the meter the frequency with which those impulses reading is not increased, even though the occur. As a result the Tannoy meter gives time interval between the pulses may be o 250 500 750 a more accurate assessment of noises, such considerably reduced. MILLISECONDS as a motor cycle exhaust, and one which In Fig. I the action of the metering cir- is closer to the truth as far as the noise is shown The Fig. I.- Diagram showing rise and fall of cuits diagrammatically. meter needle for a sound impulse of short value of the sound is concerned. shaded portion represents an impulse of duration. Up to the rectifier stage the circuit is short duration and the curve shows the straightforward. Three stages of resist- deflection of the meter pointer. It will be for a silent tread. Manufacturers of ance- coupled LF amplification using H3o seen that by the time the impulse has domestic appliances, such as refrigerators, non -microphonic valves are used to am- ceased the meter has only reached about sewing machines and electric fans are find- plify the output from the non -directional 45 per cent. of its final deflection, which ing that exact information regarding the piezo -electric microphone. The charac- occurs some time after the impulse has amount of noise emitted is being de- teristics of the ear are simulated by two ceased. Nevertheless, the full reading is manded by buyers. Gas burners, particu- tone -correction circuits, one in each of the reached very quickly, but the return is larly those of the high -pressure type, are intervalve couplings, and the frequency slower, so that the eye is able to concen- being redesigned with the aid of the noise

www.americanradiohistory.com JULY 23rd, 1937 Wlpdem - 85 Wcm 11c1 The Modern Noise Meter - the loud speakers required to cover any meter to reduce the amount of hiss, and event if they are provided with a plan of in the electrical engineering industry the the ground beforehand. Experience has instrument is being used to investigate shown very little discrepancy between the transformer lamination hum and the run- estimates and the results. ning noise of rotary machinery. The industrial psycho-. logist regards it as one of his most important aids, for noise level in factories is one of the most prominent factors determining fatigue. In banks and other offices where counting machines and type- writers are in use the question of noise is also important. To return nearer home, the manufacturers of the meter have found it useful in another branch of their activity, namely, PA work, and it has been the means of obtaining useful data regarding the distribution and covering power of loud speaker units of different types. With this exact information at their disposal the PA engineers have been able to predict the layout of

Many applications have been found for the noise meter in industry. Here it is seen in use for measuring the STAMP noise emitted by ventilating of fans and domestic refrige- rating apparatus. A NAME - that stands for recognised "TELEVISOR -Name Now Decontrolled DEPENDABILITY

BAIRD TELEVISION, LTD., desires to way affect the rights of the company in inform the public and their friends respect of its other registered trade -marks, FOR over 28 years T.C.C. have in the trade that in future all their which it will continue to use and defend if specialised in the design and manu- goods will be marketed under the trade- occasion arises. facture of the one product mark " Baird," which has already been - largely used by the company. condensers and condensers alone. As a result T.C.C. have brought As is generally known, the company is the registered proprietor of the trade -mark Valve Price Reductions in first to the world of cables, second " Televisor," but this word, which was Germany to Radio and now to Television a originally invented by Mr. Baird in 1925 standard of dependability which and registered by him as a trade -mark, has BY restricting the number of types to be only specialisation can give. Look now become in the United States the gener- manufactured and by restricting the back over the years, almost invari- ally recognised word for describing tele- number of new types for this season to one, ably wherever a vital step forward vision apparatus, and although the com- the German valve industry have been able in condenser design has been made, pany has taken the necessary steps to pro- to reduce prices of radio valves generally by that step has been made by T.C.C. tect its rights in this country it has become 25-30 per cent. The reductions take effect . Little wonder "T.C.C." means apparent to them that to continue doing so from July 15th. Notably the prices of new DEPENDABILITY. would be likely to result in the necessity valves now employed in modern receivers for unfriendly action on their part against have been reduced, whereas the reduction on The illustration shows two T.C.C. Piper competitors and others without any coun- older types is only about 10 per cent. These Condensers. Left a Type 5o non -inductive 4 mfd. tested ro goo V.D.C. for 200 v. work- terbalancing advantage. Television appa- older types now only account for about one- ing, and right a Type 8o non- inductive 8 mfd. ratus is still, comparatively speaking, in its fifth of the total German valve sales. tested to 80o V.D.C. for goo v. working infancy, and the company considers that it As the cost of the valves for a medium - would be right to use as its trade -marks sized receiver was about L5 in Germany, a words which will be regarded by all as dis- reduction of 25 per cent. means a consider- tinctive of its goods rather than a word able saving. Roughly speaking, no German which many contend should be available for valve now costs more than Rm. 15 (15/ - at the use of all as a descriptive word for any par or 25 /- at present rate of exchange). kind of television apparatus. Accordingly, Here are some examples : ACH1, formerly T.C.C. Baird Television, Ltd., announces that it is Rm. 17.5o, now Rm. 13 ; BCHr from Rm. 19 abandoning its registration of the word to Rm. 15; CHI from Rm. 14 to Rm. 12.5o; ALL - BRIT /SH " Televisor " as a trade -mark, and that this CLz from Rm. 18 to Rm. 15. Of fourteen word will in future be free, so far as they types of 4 -volt A.C. valves eleven types CONDENSERS are concerned, for all to use as a word de- have been brought down in price. Whereas scriptive of television apparatus generally. of forty -one old- fashioned types only eleven The Telegraph Condenser Co. Ltd., Wales Farm Rd., N. Acton, W.3 The above announcement does not in any have come down. rilg 2333

www.americanradiohistory.com S6 Wifeless World, July 23rd, 1939

How Many Controls ? IT'S curious to notice how often th4 Random Radiations pendulum swings in matters wireless. Fifteen or more years ago, when the bulk " of those who held receiving licences knew By "DIALLIST something about the technical side and wanted to get the very utmost from their sets, control knobs and switches increased A Big Improvement inside out, so to speak, for the aforemen- in number and variety, sprouting on the ITALY'S friendly gesture in toning down tioned ordinary listener would then kick at panels like mushrooms in an autumn field. the news bulletins and the propaganda having to tune higher in order to obtain a Cast your mind back and you'll remember talks sent out by her medium -wave and station of a lower place in the published lists. that we often had three RF circuits tuned short-wave stations should not go unnoticed The reform would have to be a double one : by separate condensers, as well as the amongst wireless folk. Let's hope that she it would be necessary to reverse the order of reaction coupling control. There was will keep it up and that other countries will the list of stations so as to make them show usually a rheostat for each valve, and many follow her excellent lead. Personally, I am the stations with the highest frequencies at of us went in for such things as variable more than glad that we have not succumbed the top. That would be a terrific upheaval, grid leaks and variable anode resistances in to the temptation to use the Empire trans- when you come to think of it, and I very resistance -coupled circuits. Then there were mitters for counter -propaganda. So far we much doubt whether it will ever come to switches doing a multiplicity of jobs. As have kept the party clean, and I trust we pass. popular interest in broadcasting increased shall go on doing so. Probably our best way makers strove hard to reduce the number of of showing the world how to keep external controls, putting the one -knob set before politics and propaganda out of wireless is Is It a Possibility ? themselves as the ideal. Now there are to develop first -rate broadcasting systems in All difficulties would, of course, be swept distinct signs of a breakaway from the mini- every part of the Empire. Give people good away were it possible for the International mum possible number of controls, and it propaganda -free programmes from their local Broadcasting Union to adopt a ten -kilocycle will be interesting to see what developments stations and they won't worry very much basis for its next European Plan. We should there are in this direction this season. about those that come in from outside. then be in the same happy position as our cousins in the United States, who number their broadcasting channels (they use the Simplicity and Performance Not from Daventry medium waves only) from 53, which is 53o You can't very well reduce the number of controls below four -main tuning, on-off In any event, it would be an almost im- kilocycles, to 155, which is 1,55o. On the face of it, the adoption of a ten -kilocycle switch, volume control, wave- change- possible task for the Daventry short-wave though this number can be brought down once basis on this side of the Atlantic seems station to endeavour to broadcast even to three by combining the on -off switch with a week in their own languages or dialects to utterly impossible, since so many stations have to be fitted in. The long waveband the volume control. In the better -class all the inhabitants of this Empire of ours. receiver most people nowadays probably Comparatively few people realise the magni- we needn't bother about, for it seems to insist upon tone control in the audio - problem. Were you to transmit be already past praying for ; but is a ten - tude of the kilocycle plan for the medium waveband frequency circuits, and there's no question to India alone in Urdu, Punjabi, Eastern of the advantage of having selectivity con- Hindi, Western Hindi, Pushtu, Baluchi, quite out Of the question? At the I.B.U.'s meeting in. June the Technical Committee trol as well. Many will go further and ask Gujerati, Marathi, Sindhi, Bengali, Oriya, for means Malayalam stressed strongly the advantages shown in other of adjusting the various Telugu, Kanarese, Tamil and circuits of a set from the panel. I observe there would still be millions of inhabitants practical working of synchronised transmissions in national systems. It is just on that some of the big American sets are going of the Indian sub -continent who wouldn't in for large was said. To cover the cards that in view of the big gains in quite numbers of knobs. One understand a word that many directions with thirty valves has seven manual con- the whole Empire thoroughly from Daventry that would result if there trols ; another, with eleven valves, a -wave station we should require broad- were a ten -kilocycle basis British and Con- has short dozen. I don't think we'll go as in hundreds of different languages, and tinental authorities might be persuaded to quite far casts facilitate its as but I have an idea in the bigger any thing is clearly quite outside the adoption by increasing the that, that such number of sets that we shall see this year makers won't bounds of possibility. That's why I synchronised stations and thus think making fewer channels necessary be afraid of adding a knob or two we'd best stick to English in our broadcasts to provide to the and leave it to the local authorities to supply for Europe's requirements. conventional number if their presence really programmes intelligible by their local aids performance. One receiver that has just appeared has an aerial trimmer for use on people. Short -wave Crowding the short wavebands. I handled that set Anyone who listens to short -wave trans- a month or two ago whilst it was still in missions, and that means pretty well every laboratory form, and the aerial trimmer Kilocycles or Metres ? owner of a wireless set nowadays, must certainly made a world of different to short- SOME time ago I asked in these notes realise how badly overcrowded the more im- wave results. whether it was now too late to induce portant broadcasting belts have become. the man in the street to think in kilocycles The situation is growing worse and worse rather than in metres. An East Barnet as time goes on. The Technical Committee The Bathroom Again reader sends a very interesting comment. of the I.B.U. is hard at work now trying ANOTHER case of a fatal electric shock You will never induce the man in the street to find some solution, and the matter will received in a bathroom was reported to think in kilocycles, he suggests, so long be fully thrashed out at next year's con- recently. The victim this time was found as a clockwise movement of his tuning dial ference at Cairo. The main trouble is that dead in her bath with a small mains portable decreases the number of cycles. He has what we loosely call the short waveband resting on her body. Part of the mains become accustomed to a steady increase in isn't one band at all ; it consists of at least leads were burnt out, showing that a very, metres as he tunes " higher." If you want six -the 13- metre, the 16- metre, the 19- heavy current must have passed through to educate him to think in terms of fre- metre, the 25- metre, the 31-metre, and the them. Presumably, the insulation of the quencies all that you have to do is to per- 49- metre -each of which has its own special flex leads was defective, and the victim suade manufacturers to supply tuning con- characteristics, which vary from hour to touched them with a wet hand. Though densers whose capacity decreases as the hour, from season to season, and from year well- designed mains sets and other elec- knob is turned clockwise. Low- frequency to year. Any country which hopes to con- trical apparatus are completely safe in the signals will then be received at low conduct a satisfactory world- broadcasting ser- ordinary way, there is one room in the house denser settings and high -frequency signals vice, therefore, needs a considerable number which is emphatically not suitable for them, at high dial readings -which is, after all, of different wavelengths for its transmitters. and that's the bathroom. The wise course the logical arrangement. It isn't going to be easy to obtain inter- is not to take your wireless set in your bath There is a good deal in that, for with the national agreement for any plan put for- with you and to put the light switch-which usual type of tuning condenser the ordinary ward, and the longer such a plan is delayed should certainly not be of the metal type - listener cannot see why, when it comes to the more difficult will it be to obtain its in a place where it cannot be reached by frequencies, it should be a case of the higher acceptance. Stations which have dug them- anyone who is actually in the bath. The you go the fewer. But it wouldn't be selves firmly in on this wavelength or that best and safest of all positions for the set is enough just to turn the tuning.arrangements don't give it up very readily. outside the bathroom.

www.americanradiohistory.com Wireless World, July 23rd, 1937 87 First of the New G.E.C. Sets TWO BATTERY MODELS AND AN AC MAINS RECEIVER

A COMPLETE list of G.E.C. receivers for metres, in addition to the two normal broad- the 1937-38 season has been prepared, cast bands, is employed' in the " Battery and three of the sets, an AC and two battery All -Wave 4 " at ro 1os. This receiver is models, are now ready for release. equipped with the new G.E.C. " Chromo- scopic " dial, automatic two -speed tuning and a " touch -lighting " control for dial illumination while the set is being tuned. The " Chromoscopic " dial in which the coloured station names are edge illuminated against a black background, is a feature of the new " All -Wave 5 " for AC mains which in common with all the new G.E.C. mains receivers is fitted with a noise shield to guard against power line interference. This set, which costs :9 19s. 6d., includes a 16 -5o metre range, and is housed in a polished walnut cabinet with sloping tuning panel.

FLUX DENSITY EQUALS THE G.E.C. " Battery SP3 " in new cellulosed cabinet. ROLA G.12 -PM In the " Battery SP3 "-a two -waveband, Comparison between this 9l' three -valve straight set -special attention diameter speaker selling at 49/6 and the giant Rola has been given to economy in maintenance G.i2 -PM may at first sight as well as in first cost. The station -cali- appear rather preposterous. brated dial carries a visual switching indi- Yet when space and price are cator, and the set is housed in a distinctive serious considerations this brown cellulosed cabinet. Including valves A sloping tuning dial with indirect lighting new Rola unit is the ideal substitute for its famous corn - batteries the price is ¡6 15s. of All 5 and is a feature the " -Wave " and other Like the -PM it 16 -5o G.E.C. models. panion. G.12 A superheterodyne circuit covering table possesses a flux density of 11,500 lines per square centimetre. It is super sensitive and therefore ideal for Battery set and Extension speaker News from the Clubs use. Special features include the use of a new magnet Wirral Amateur Transmitting and Southend and District Radio and material ' Alnico ' and a Short -wave Club Scientific Society moisture proof transformer, Headquarters: King's Square Café, Birkenhead. Hon. Sec.: Mr. F. S. Adams, " Chippenham," 27, Eastern metal and compound shielded. Meetings: Last Wednesday evening in each month. Avenue, Southend -on -Sea. No better value in reproducers Hon. Sec.: Mr. J. R. Williamson, 40, Neville Road, The society recently held a very successful is obtainable to -day. Please Bromborough, Birkenhead. DF contest when twenty -three members write for full particulars. At the last monthly meeting Mr. W. Rogers scoured Essex with portable receivers in an (G8OC) gave a talk on the application of the oper- re- endeavour to trace a hidden transmitter electronic oscillator to detection in SW ating on a wavelength of 155.8 metres. Only of a successful 3 -valve ceivers. A description one competitor, Mr. M. Tapson, GGIF, suc- receiver embodying this principle was given, with diagrams and coil specifications. ceeded in finding it. together A series of similar events will be held throughout the summer as well as many indoor Bradford Short -wave Club meetings. The full programme of lectures will Headquarters: Bradford Moor Council School, Leeds be resumed in September. Rrr.id, Bradford. Meetings: Fridays at 7.30 p.m. Hon. Sec.: Mr. G. Walker, 33, Napier Road, Thornburg, Leicester Amateur Radio Society Bradford, Yorks. Headquarters: Winn', Café, Granby Street, Leicester. The Morse practice' classes will be resumed Hon. Sec.: Mr. T. Cribb, 53, Knighton Drive, Leicester. evening (Jul yy 23rd) as Mr. K. Abbott, At the recently -held annual general meeting, this WITHOUT TRANSFORMER 42/- the instructor, is returning to the club. after the election of officers and committee, there was a discussion on the question of re- OVER' 8 MILLION, iN USE 111i ducing the amount of the subscription for mem- Newcastle Radio Society bers under 20 years of age, and it was finally Headquarters: 2, Duke Street, Newcastle -on -Tyne. decided to do so. The following items were Meetings: Sundays at 6 p.m. and Thursdays at 7 p.m. for Hon. Sec.: Mr. G. C. Castle, 10, Henry Street, Gosforth, arranged the summer: Newcastle-on-Tyne, 3. July 24th or 25th. -Visit to the Borough A programme has been got together for new- Hill Transmitting Station. comers to radio which is so arranged that it August 2211d. -Social outing for members also forms a refresher course for the experi- and their womenfolk. enced. Practical constructional work is fol- September 5th. -Visit to the South Kensing- ?lie GtWat14 7-üieáf Itoducei4 lowed by a talk on theory and design. Morse ton Science Museum. instruction is given in the final half -hour of September 7th.-Meeting at H.Q. to check THE BRITISH ROLA CO., LTD. every meeting. apparatus and arrange for field day. MINERVA ROAD, PARK ROYAL,N.W.10. A visit to the Newcastle station and trans- September 12th. -16o -metre DF field day, PHONE WILLESDEN 4322-3-4 -5 -6. mitter is shortly to be arranged. using a portable station..

www.americanradiohistory.com 88 Wireless World, July 23rd, 1937

The British abstracts published here are prepared with the permission of the Controller of H.M. Stationery Office, from Specifications obtainable at the Patent Office, 25, Inventions Southampton Buildings, London, W.C.2, price 1;- each. Recent A selection of patents Issued in U.S.A. is also included.

TUNING UNITS of allow the two carriers to have a THE drawing shows a self -con- Brief descriptions the more interesting radio minimum " guard band " or safety tained tuning unit for mounting devices and improvements issued as patents gap between them, so as to on a wireless receiver. An air -cored will be included in this section. economise ether space. long -wave coil L and an iron - Both sets or signals are received cored medium -wave coil Li arc on a broadly alternative, is open to enlarged tuned input circuit both carried by a two -part the objec- by lenses which can be and are passed to a common local former F, the upper portion of tion that it contains substances, directed on to the positive or which, oscillator and a common fre- which contains the powdered -iron during the subsequent " impact " side of the screen, quency- changer. From the latter core K. A trimming condenser C, baking and pumping processes, where the resulting fluorescence is may contaminate brightest. the intermediate amplifiers for the fluorescent the sound and picture signals material of the screen. The difficulty of keeping the s-an- are To branched off as separate channels overcome these difficulties, ning stream always in focus, as it across a common the anode is formed moves to and fro coupling. The upon the glass over the inclined latter is so arranged that the wall of the tube by applying a surface of the screen, is overcome channel input which "accepts" dilute aqueous solution of lead salt. by using an auxiliary Control field. the picture signals which is This acts as a re- then converted into the is derived from the current jector circuit for sound black lead -sulphide by the action passing through the ordinary de- the flecting signals, and vice versa: of an alkaline solution of thio- coils, so that its intensity Marconi's Wireless carbamide or thiourea. varies in proportion to the angle Telegraph Co., Ltd. (assignees of C. D. Kent - S. T. Henderson. Application of deflection. Alternatively, the ner). Convention date October 9th, 1935. deflecting coils may date (U.S.A.) No. be inclined to October 31st, 1934. No. 464286. 464105. the main axis of the cathode -ray o o o o 0 0 0 0 Medium- and long-wave tube so as to ensure the required coil correction. AMPLIFIERS unit for use in broadcast LOUD SPEAKERS. TO improve the fidelity and THE - P. T. Farnsworth. receivers. tone quality of a high Application power of a push -pull amplifier, powered speaker, suitable for date February 28th, 1936. No. a part of the output use in a cinema or for public 463896. circuit is de- fixed underneath the panel, con- signed to produce even harmonics, address purposes, is improved by which are then combined with sists of two metal plates separated inserting a rotating vane or screw the THE same source of current is fundamental and odd harmonics by a mica spacer, one of the plates ' nside As the main diaphragm. used to (a) in such a way as being bent or dished outwards, so shown ill the figure, a small supply the anode to diminish dis- that the effective capacity can be of a valve used to amplify the tortion. altered by turning the screw S. received picture signals, (b) the Standard Telephones and Cables, The various leads are taken out modulating electrode of the Ltd. (assignees of V. M. Cousins). to tags T, as shown, and the tun- cathode-ray tube, and (c) an ex- Convention date (U.S.A.) May ternal focusing coil for the elec- Ist, 5935. No. 464231. ing coils are covered by a screen- o o o o ing pot P. The condenser C is tron stream flowing through the connected across the coils L, Li tube. . MUTING CIRCUITS. and is adjusted to compensate for The anode of the amplifier valve THE intermediate- frequency inherent and other " stray " is connected directly to the grid L amplifier V of a superhet re -. capacities. of the cathode-ray tube through a ceiver is coupled through the The General Electric Co., Ltd., series resistance, whilst the anode second detector (shown diagram- and R. W. Speirs. Application of the CR tube is connected matically at D) to the control grid date November 26111, 1936. No. directly to the common source of of a low- frequency amplifying supply. The external focusing 463393. valve VI. The cathode of VI is o 0 0 0 coil is connected across the com- tapped to a point I' in the anode - mon source of supply in series with cathode circuit of the valve V, TELEVISION SYSTEMS variable BOTH the picture and synchro- a resistance. One advan- whilst the suppressor grid is nising signals are derived tage of the arrangement is that tapped to a point Q on a potentio- should the source of supply fail, meter shunting the valve V. from a single photo - electric cell, leaving the synchronising impulses being the CR tube with no bias, The valve V is subject to auto- the electron stream is simul- matic volume control. Therefore, of such amplitude as to reduce the taneously carrier -wave to zero. The adjust- defocused or scattered so at a certain predetermined level of that it does not burn the fluores- signal strength, the potential of ment of the transmission level then cent becomes purely optical, with the screen. the point P becomes equal to, or following advantages Baird Television, Ltd., and L. lower than, the point Q, and the :- Rotating helical screw mounted R. Merdler, Application date pentode VI will then pass (a) The intensity of the syn- inside signals diaphragm of loud October 8th, 1935. No. 463973. through to the loud speaker. For chronising impulses remains con- speaker to improve quality of stant. reproduction. (b) The amplitude remains constant, in spite of other fluctua- driving cone is energised from an tions, because it is definitely de- electromagnetic movement M, termined by the " vanishing " of and, in turn, drives a larger cone the current from the final output B, which fits inside a ring R. The stage of the amplifier. large end of the cone B is rigidly (c) The amplifier can be set to held by the arms K. Inside is a strict linearity, so that the half- shaft carrying a helical screw S, tones of the picture are accurately which is rotated at a speed of from reproduced irrespective of any 1,200 -2,200 revolutions per minute automatic regulation that may be by an induction motor P. necessary. The useful effect of the screw Radio -Akt. D. S. Loewe. Con- S is due to the fact that it varies vention date (Germany) October the air pressure in the vicinity of 25t /t. 1934. No. 464483. the vibrating surface of the cone o 0 0 0 B, causing the latter to approxi- TUBES mate more closely to the ideal CATHODE.RAY " piston -like " action. ONE of the anodes of a cathode - ray tube usually censists R. R. Glen. Application rate of October 5935. No. a metallic surface of silver 'de- 4th, 463734. Muting circuit for a superheterodyne receiver. posited on the inside surface of the o o o o glass. A disadvantage is that the TELEVISION RECEIVERS SOUND AND PICTURE signals below this " threshold " silver, being highly reflecting. THE fluorescent screen of a RECEIVERS value the pentode is " blocked " throws light on to the fluorescent cathode -ray receiver is set ASET designed to receive tele- and the set automatically muted. screen, and this may affect the obliquely to the main axis of the vision signals on one carrier E. K. Cole, Ltd., and A. W. tone contrasts of the received pic- tube instead of at right -angles to frequency, and sound signals on an Martin. Application date Decem- ture. The use of graphite, as an it. This allows the image to be adjacent carrier, is designed to ber 12th, 2935. No. 463748.

www.americanradiohistory.com THE PRACTICAL RADIO JOURNAL 27 th Year of Publication

No. 935. FRIDAY, JULY 30TH, 1937. VOL. XLI.

Proprietors : ILIFFE & SONS LTD. EDITORIAL COMMENT Editor : HUGH S. POCOCK. Television Television transmissions, on the other Editorial, hand, started on a very high level ; the Advertising and Publishing Offices : What Is the Public Waiting For? receivers were designed to do them DORSET HOUSE, STAMFORD STREET, full justice and so far as one can see LONDON, S.E.I. THE Television Exhibition is those made at present will continue to Telephone: Waterloo 3333 (5o lines). proving to be one of do so for a long time tocome. The second Telegrams : "Ethaworld, Sedist, London." the biggest draws that the Science Museum big difference is that in " sound " COVENTRY : Hertford Street. at South Kensington has ever broadcasting, increases in output power Telegrams : Telephone: "Autocar, Coventry." 52ío Coventry. had in the way of a special show. and in the numbers of stations made a A daily attendance of over 2,000 is higher and higher degree of selectivity BIRMINGHAM : essential. Receiving Guildhall Buildings, Navigation Street, 2. reported. There is no question that sets, in other Telegrams : Telephone: the public in general is eager to know as words, became out of date because "Autopress, Birmingham." 2971 Midland (4 lines). much as possible abolit television, wants their selectivity was insufficient. On

MANCHESTER : 260, Deansgate, 3. to see demonstrations of reception, the television waves there is no likeli- Telegrams : Telephone: hood of such "Ilitfe, Manchester." Blacldriars 4412 (4 lines). and having seen them, is loud in its any happening to an praises of the clearness and the steadi- extent where mutual interference GLASGOW : 26s, Renfield Street, C.2. ness of the images. Why then is it would occur. Telegrams : " Mlle, Glasgow." Telephone: Central 4857. that television sets are not selling more PUBLISHED WEEKLY. ENTERED AS SECOND - rapidly ? At Olympia last year many CLASS MATTER AT NEW YORK, N.Y. people estimated that within six months Stealing Electricity Subscription Rates : some ten -thousand television receivers Problem for the German P.O. Home, {I Is. 8d. ; Canada, SI Is. 8d. ; other would be in use, yet to -day countries, Lr 3s. rod. per annum. probably less than half that number have been OUR correspondent in Germany As many of the circuits and apparatus described in these use of wireless pages. are covered by patents, readers are advised, before sold. reports that the making use of them, to satisfy themselves that they would Actually the service area of the energy radiated from the Ham- not be infringing patents. Alexandra Palace transmitter has burg station to provide light for turned out to be very much greater their bungalows has brought a group than was originally anticipated, thereby of local dwellers before the Hamburg CONTENTS increasing the number of potential court. Their bungalows, it seems, are purchasers of television receivers. Many in the immediate vicinity of Hamburg's Page people who could well afford to buy roo kW aerial. By fixing electric bulbs Editorial Comment 89 receivers and would like to have them to a simple circuit these people have Transient Response 90 are waiting, it would seem, to see enjoyed free electric light supplied whether there will be any big new by the energy radiated from the trans- Straight Set versus Superheterodyne 93 development at this year's Exhibition. mitter. Unbiased .. 96 Such an attitude seems entirely un- The owners of the station, the Current Topics 97 justified by the facts. German- Post Office, sued them for The early story of " sound " broad- stealing wireless energy which would The Wireless World Television casting is quite different from that of otherwise go to listeners. The accused Receiver V- Adjustment and television, for two main reasons. The contended that they were using energy Operation .. 98 original " sound " transmitters were floating in the air which would other- Broadcast Brevities 101 very crude in their lack of fidelity and wise go to waste. The judge has re- Listeners' Guide for the Week 102 old receiving sets were perhaps cruder quested the Post Office to supply still. As improvements were made in definite proof of the weakening of Letters . . to the Editor 104 transmission,. receiving sets became Hamburg's signals caused by the New Apparatus Reviewed 105 out of date because their performance house owners " sucking off " the Little Princess Portable .. 106 was not sufficiently good to keep energy for lighting purposes. It will pace with them ; the receiver could be interesting to learn how the P.O. Random Radiations .. .. 108 not reproduce what the transmitter authorities succeed in demonstrating Recent Inventions.. 110 was sending out unless it was up to date. this to the satisfaction of the judge.

www.americanradiohistory.com Wireless World, July 3oth, 1937 Transient Response REAL AND FICTITIOUS TRANSIENTS IN RELATION TO

LOUD SPEAKER DESIGN By P. G. A. H. VOIGT, B.Sc., A.M.I.E.E.

IN this article the author challenges the prevailing idea that wideness of frequency response is the sole factor of importance in the The fact that infinite forces can never reproduction of transients. He gives reasons for his belief that a be available in a natural sound limits the considerable proportion of transients normally encountered do not contain acceleration force. This limitation causes both a extremes of frequency. Later he describes an imaginary loud speaker rounding of the corners and a time period for the duration of the having an infinitely wide frequency response, and shows that it transient. The fact that infinite velocities night, nevertheless, be incapable of reproducing even the simplest of are also impossible is likewise taken care transients satisfactorily of by the existence of the duration time, since with finite time, the velocity is also finite. Fig. 2 shows matician so the modification pro- ONCE upon a time, there were obvious, that everybody (even duced by these factors. clever mathematicians who the writer !) believes it. If we consider our air particle as being realised that vibrations, etc., did Now humans resemble sheep in a most located on the envelope of an imaginary not consist only of unmodulated extraordinary manner, and because the balloon with the source of the transient combinations of sine waves, but might clever mathematicians analysed this most impulse at the centre, section 4 implies also involve changes. Any such change difficult transient and proved that it con- that the " balloon " is now of different can be described by that general word, a tained all frequencies, a lot of not quite diameter. The air pressure within it con- As is the way with mathe- so clever technicians ask no ques- " transient." further sidered as a whole has therefore changed, maticians, they examined the subject tions and assume that this result neces- and although this gives us the correct mathematically and found that to study sarily applies to all transients regardless complementary square- topped pressure the multitude of different possible tran- of their waveform. Tut, tut ! Truly a sients would have been a superhuman little learning is a dangerous thing 1 task. The task was, therefore, simplified Thus has grown up an accepted idea that by deciding to study one transient only, to reproduce transients (presumably any and this simplification was justified by transient), an infinitely wide frequency picking such a nasty transient that, in _response is desirable. p ROUNDED solving its problems, the general process CORNERS for solving all others would have been Practical Considerations >' AVERAGE mapped out. VELOCITY

! I The transient selected happens, on STOP Let us consider whether the 1 paper, to look particularly inneceht, and very special transient selected by the to--14 DURATION is by now very famous. It is in fact our mathematicians ever occurs in nature. TIME old friend the square- topped pressure Does it ? Its electrical counterpart is wave (only the rising front of it), together easily produced, but I can think of only with its complementary pressure wave one way of making an actual sound which ROUNDED - CORNERS WAVE FRONT NO which comprises a single impulse in one gets even remotely near it-and for that LONGER VERTICAL direction only. According to the analysis I require an electric spark -so this sound this simple-looking wave includes all fre- is hardly to be expected from the average TIME quencies from zero to infinity, a conclu- orchestral broadcast, Actually, natural sion so easy, and even to the non- mathe- sounds are not nearly so complex, and it should be interesting to examine a Fig. 2.--In practice the infinitely high transient of the kind more likely to be velocity and acceleration implied by the ideal square- topped transient cannot be generated naturally. attained and the nearest approach is that Let us begin by considering what is depicted above. It should be noted that wrong with the mathematicians' transient only in the case of a sine (or cosine) wave from a practical point of view. For in- are the pressure curve and complementary velocity curve of similar shape. vestigation this can be considered in the four sections marked respectively r, 2, 3, and 4 in Fig. i. What do these sections wave, Nature, objecting to unbalanced involve? pressures, will promptly push (or pull) (I) Air particle at rest. (No difficulty the " balloon " back to its correct dia- 1 4 here.) meter, thus restoring atmospheric pressure. (2) Air particle accelerated instan- In the practical case, therefore, this taneously to an infinitely high velocity. transient is not self- supporting, and (This involves infinitely high acceleration cannot end with section 4. It must be forces, and is therefore impossible in followed by a restoration period whose practice.) waveform depends upon circumstances. TIME (3) Air particle instantly decelerated Whatever these are the average velocity and brought to rest. ( Just as impossible must be in the reverse direction, and in as 2.) order the finishing point shall coincide Fig. 1. -The mathematicians' ideal transient that -a square- topped pressure wave with (4) Air particle remains at rest in its with the starting point, the area above the vertical rising front. new position. zero line of the velocity/ time curve must

www.americanradiohistory.com JULY 3oth, 1937 .gyp ®ll® 91 World. - Transient Response - and it would be interesting to know early days when I was searching for simple equal the area below it. The necessity whether the sound of Fig. 5 can be dis- ways of augmenting the ends of the scale for this recovery period adds a further tinguished by ear from that of Fig. 4, and with reference to the middle. I knew modification to the original transient, and if not, how far can the waves A and B be from the impedance curves of the horn one of many possible shapes for the re- separated before the ear does- perceive speaker with which I was experimenting covery period can be seen in the complete the difference. I fancy that altering the that at the top the impedance rose owing curve of Fig. 3. to the inductance of the speech coil, while Having shown in the bass it rose in the horn cut -off region that natural con- owing to reduction of loading which per- ditions tend to re- mitted increased diaphragm velocity. A move the Violent ex- fixed resistance in series with the speech tremes from the coil, while reducing the magnetic damp- mathematicians' ing, should reduce the two ends of the transient, let us in- scale only a little and the main part con- vent one for our- siderably. This was therefore tried, the selves which shall be the volume control being readjusted to as simple as possible, make good the general loss of volume. and at the same time RECOVERY As expected, the frequency response was be practical. PERIOD wider, and with this improvement the Such a one is " quality " (which includes transients) shown in Fig. 4, and should have been better. But was it? consists of a com- For a moment, yes. It seemed that there bination o f t w o had been an improvement, but on listen- curves. One is one TIME ing for a while doubts cropped up. The cycle only of a 300 - bass seemed to have lost its incisiveness cycle cosine curve Fig. 3. -The waveform of the transient of Fig. 2 is quite practicable in and become " flabby," the string, drum wave amplitude +I the movement of a sound emitting surface, but the sustained increase and brass bass no longer having their with centre line dis- of pressure cannot exist in free air and a recovery period will follow. clear-cut differences of character. Also placed downwards by the top was peaky, and other detail defects I, and the other is one cycle only of a relative position of waves A and B as too small to be singled out caused the 600-cycle cosine curve amplitude 2 with above immediately brings into the Fourier definite decision that the overall result as centre line displaced upwards by 2, the analysis additional terms depending upon heard by ear was better without the series two curves being phased so that the crest the amount of displacement between the resistance, i.e., with reduced frequency of one occurs simultaneously with the waves. response but improved magnetic damping. trough of the other. By making one It will be seen from the above that for curve of shorter time interval, but bigger the majority of possible kinds of tran- Reverberation amplitude numerically than the other, it sients, i.e., all the ones without sharp is possible to make their areas equal. By corners (which includes most speech From considerations and experiments displacing the curves on opposite sides of transients except sibilants) , damping is such as these I am convinced that, the centre line they can be made to likely to be more important than fre- although very sharp transients un- balance, and by using the cosine curve quency range. doubtedly require reproduction of high instead of the sine curve sharp corners frequencies, there' are many simple are avoided. Experimental Verification transients in which this is not the case. This transient, by avoiding sharp There is no doubt that perfect reproduc- corners, avoids high accelerating forces. Of this I have had experimental verifi- tion of the mathematicians' transient in- The areas above and below the zero line cation in two different ways. First, with volves all frequencies from zero to infinity. are equal ; the final position of the air a commercial baffle speaker mounted in According to the common idea, therefore, particle is therefore the same as the start- an infinite baffle, the result was good as it is only a matter of designing a speaker ing position. The transient is conse- regards response, and no serious reson- capable of this range of frequencies, and quently complete and self-supporting and ances or other faults could be identified ; -hey presto! -the transient in question could easily occur in practice. the result, however, sounded " loud - can be perfectly reproduced. I wonder ! speakerish." A short horn (mouth and Is this necessarily right? Damping taper suitable for 200 cycles upwards) For example, I can visualise an was then held in front of the diaphragm. imaginary speaker with a perfectly even I am no mathematician, and cannot ex- Immediately the press this curve in its correct Fourier response seemed re- analysis formula without looking up stricted, especially as maths. I have forgotten long ago. I regards the lower would be very surprised, however, if the end of the scale. CURVES A AND B analysis contains any frequencies other The actual sound COMBINED than 30o and 600 cycles. Also, for that heard, however, be- reason, I do not expect the reproduction came more lifelike, of that transient to be affected in the and the choir and slightest degree by the addition of either orchestra seemed to a " tweeter " or a " woofer " speaker. I sort itself out, and do, however, expect that critical damping instead of coming Fig. 4.- Synthesis of a self- supporting transient which might easily at both 30o and 600 cycles is essential if through as a con- occur in practice. the waveshape is to be retained. Also, I fused mass of sound, anticipate that if there is a time delay in each section stood out separately. This response from zero to infinity which will the loud speaker, i.e., as the wave is test has often been repeated, always with deal perfectly with any sustained note, propagated along the diaphragm or horn the same result, i.e., greater separa- and spoil every transient so completely (if any), this time delay should be tion in spite of the slight reduction in as to be quite useless for any practical identical at both frequencies. " apparent " frequency range, The more listening. It is believed that the ear has large complex the sound, the more marked is Has blind acceptance of specialised tolerances in connection with such time the effect. mathematical analysis caused the over- delay differences (usually called phase), The second verification occurred in the looking of something outside that analysis,

www.americanradiohistory.com T@l® 92 MTH JULY 3oth, 1937 Transient Response- No, perhaps not, but more than 99.99 per BOOK REVIEW but, nevertheless, vital to the reproduction cent. of the loud speakers ever made have Alternating Current Measurements. By of transients? moving parts which, in relation to their David Owen, B.A., D.Sc., F.Inst.P. I will now describe this extraordinary damping, are much too heavy not to store I20 pages, 8o diagrams. Methuen and imaginary speaker. Immediately it is energy . and do something of this kind at Co., Ltd., 36, Essex Street, London, described you will say -" But no one in one or more points in the scale. W.C.2. Price 3s. 6d. his senses would dream of constructing Under such conditions can a level fre- THIS is one of an extensive series of mono- such a speaker," and no doubt you will quency response be a guarantee of perfect graphs within the field of physics, and transient performance? I doubt it. " is intended to supply readers of average Now you theoreticians, get busy and scientific attainment with a compact state- prove me wrong. Show us that the ment of the modern position in each sub- (UrvE Ap simple transient invented for Fig. 3 con- ject." tains all frequencies from zero to Estimates of the level of scientific attain- infinity. ment that Show us that the fantastic speaker just constitutes an average may differ, I but anybody who is likely to be interested in described can, for example, deal with the the subject of AC measurements at all need " transient " produced when the player have no fear of being unable without mathe- of a tin whistle one CURVE B covers of its holes matical ability to make good use of the little so as to change the pitch of the note being volume by Dr. Owen. Neither need Wireless emitted. But please translate the results World readers suppose that it is likely to of your work into intelligible word waste their time with such problems as the Fig. Synthesised transient phase pic- 5.- with a measurement of power in three - phase difference between the 300- and 600 -cycle tures. I have forgotten my maths., and components. The family likeness with the no doubt many " W.W." readers are in a systems. The book is limited to the mea- curve of Fig. 3 should be noted. similar position. surements of inductance, capacitance, resistance and frequency; and they are tackled Show us that transient response as dis- be from a conspicuously " wireless " aspect. perfectly correct, but it is often useful tinct from frequency response is a myth! The first chapter runs through essential to examine in imagination something AC theory, from fundamentals to the prin- hopelessly fantastic in order to realise ciples underlying bridge networks, finishing something very obvious. with two examples of deriving the conditions Let us imagine first an echo room with Guglielmo Marconi of balance in bridges. The remaining chap- walls of ioo per cent. reflection efficiency, ters are devoted to practical methods of and of such irregular construction that it measurements; the last, on radio frequency has no natural frequencies of its own. World -wide Tributes work, comprises two- thirds of the book. Let this room have an opening of such One chapter deals with the conditions of size that substantially all the sound accuracy in low-frequency bridge measurements, energy is passed in a fixed and another draws attention to the out time, say rather neglected merits of the AC potentio- I sec., into the open air where the listener meter. is situated. Providing that none of the The low-frequency bridge chapters can be energy re- enters the " echo -room " loud highly recommended to those want a speaker, this gives the sound in effect a much briefer treatment thán tht of Hague's reverberation of i sec. at all frequencies. standard textbook. The great practical im- Now assume that a perfectly portance of conditions for balance being " aperiodic " loud speaker had been in- independent of one another is fully empha- vented of infinite frequency range which sised, and illustrative examples give the responded instantly and without dis- reader some idea of the magnitude of the standards used and the accuracy to be ex- tortion to any wave fed into it (such a pected. The formula for working out the masterpiece of course would reproduce results are expressed clearly, with the adjust- any and every transient perfectly), and able quantities distinguished by an " arrow " that this loud speaker was situated inside notation. the echo chamber. The " mouth " of my The index might with advantage be fantastic loud speaker would be the open- fuller; one expects such an item as " induct- ing of the echo chamber. ance " to be included. The radio- frequency chapter is of particular interest, though the reviewer considers Frequency Calibration that the use of a valve voltmeter shown in so many diagrams for the adjustment of a Let us hang a calibrating microphone circuit to resonance is generally less con- near the mouth and consider what venient than one or other of the beat -note happens. We feed to our loud speaker a methods, and introduces complications due low note. The sound in the echo room to its shunt impedance. Such complications builds up for i sec. to its steady value are needlessly aggravated in Fig. 61, where which is measured by the microphone and the voltmeter ought to be across the coil. plotted. Switch off, the sound dies away The possible sources of error seem also to THROUGHOUT the world warm tributes be less clearly pointed out than in the audio - for i sec., and we go on to the next note, frequency chapters. For example, the cir- and so on. In each case, since the have been paid to the meinory of the Marchese Marconi. The initiative which cuit diagram of a wavemeter (or frequency originating loud speaker is perfect, the he showed in the early days, w hen at first meter) shows terminals for an indefinite response builds up to the same value from his ideas were by no means enthusiastically coupling coil right in the calibrated tuned the lowest to the highest frequency. In received, enabled him to achieve successes circuit, and a variable by -pass condenser other words, this arrangement has a per- which eventually paved the way for the across 'phones in series with it. The use of fectly smooth response from zero to development of radio communication as the term " first harmonic " for that double infinity. But what happens to a we know it to -day. the frequency of the fundamental is, we had transient? Will the change it represents In much of the subsequent progress he supposed, obsolete and liable to cause con- not be stretched out for one whole second, took an active part, his enthusiasm stimu- fusion. lating the work of those he gathered round Nevertheless, in the limited space avail- no matter how sudden it may have been him as collaborators, whilst throughout his able the chapter gives a useful indication of to start with? life his interest in everything connected radio -frequency measurement technique. You may well claim that no one in his with wireless development never tired. His The book, as a whole, is concise, clear and senses will ever have an echo chamber life's work will remain a permanent practical, and can be recommended. like this connected to his loud speaker. monument to his genius. M. G. S.

www.americanradiohistory.com Wireless World, July 30th, 1937 9?

Straight Set versus Superheterodyne odyne scores, for there is no doubt whatever that it is much easier to secure high selectivity with it than with the straight set. It is difficult to use more than four quency, more thorough screening is needed tuned circuits in a straight set, because to maintain stability. Moreover, the condensers with more than four sections mechanical difficulties of screening are are not available. Of course, one can somewhat more difficult than in the super- go up to eight circuits if one does not ETTERS . which have recently ap- object to two tuning. peared heterodyne because of the need for vari- controls. The in the correspondence mechanical linking of two columns able condensers and wave- change switches separate con- of The Wireless World densers to obtain the equivalent of a six- J have revealed in each stage. These difficulties are by that in spite of the or eight-gang condenser has certain diffi- popularity of the no means insuperable, however, especially superheterodyne there culties connected with the matching of the are still many who remain faithful to the if several RF stages are used. This may seem rather surprising, but it is neverthe- sections. In the superheterodyne, how- straight set. The number who favour ever, it this less a fact that it is easier to obtain a is possible to use any number of type of receiver is indeed rather sur- tuned circuits at the intermediate fre- prising given amplification with stability from when it is remembered that for quency, and up to three at signal fre- several years few such sets have been several low gain stages than from one or two each giving a high gain. Moreover, quency. available. Various reasons have been It appears, however, that the full advanced in support of individual prefer- possibilities of the straight set in the ences and at first sight some of these ap- matter of selectivity have not been ex- pear contradictory ; a closer investigation, Factors Which ploited. Development in these receivers however, often reveals that the conflict- almost ceased with the reintroduction of ing arguments are conflicting only because the superheterodyne some five years ago, they are based on different premises. Affect Design but recent work has shown it to be cap- It should be self- evident that there is able of giving surprisingly high selectivity no such thing as the best receiver, there the apparatus is then much less critical in spite of the limitation of four tuned is only the best receiver for a particular and a greater tolerance for variations in circuits only. It is not, of course, as good purpose. One man wants a set which will values of components can be allowed. as a large superheterodyne with eight or tune from 5 metres to 2,000 metres, and Turning now to the question of back- more tuned circuits, but on the medium give him extreme sensitivity and selec- ground noise, most advocates of the waveband there is little to choose be- tivity, and he is right in saying that the straight set bring against the superheter- tween it and the smaller superheterodynes, superheterodyne is better than the straight odyne the charge of noise. Actually, this and on the long waveband it is better. set -for his particular requirements in the is unjustified, for it is not in accordance This brings us to another point on which matter of performance. Another only with the facts. If a comparison be made the straight set is at a disadvantage as wants to be able to receive his two local between the two types it will be found stations and naturally prefers the straight that there is nothing to choose in the set. Neither type of set can truly be said matter of the signal /noise ratio, provided to be better than the other without taking that the two sets have the same sensi- HE controversy on the relative into account the conditions under which tivity, the same overall modulation fre- merits of the straight set and it will be used and the performance ex- quency response, and the same degree of the superheterodyne,' which raged pected. internal regeneration, and provided that some years ago, appeared to have In view of this it is a matter of some the superheterodyne includes an effective been settled in favour of the super- importance to examine impartially the RF amplifier. When considering signal /, heterodyne, but it has been revived merits and defects of the two types of re- noise ratio, one must be careful to dis- in recent months and the issue now ceiver. With a clear idea of their respec- tinguish between two different types of appears somewhat doubtful. Modern tive characteristics it naturally becomes superheterodyne. Sets in which the first design technique has greatly improved easier to make a choice between them, valve is the frequency- changer are almost the performance of the straight set always bearing in mind that the choice invariably noisier than straight sets of the does not depend on the receiver's charac- same sensitivity, but they are also noisier and there is now much to be said teristics alone, but on those characteristics than the better class of superheterodyne for it. The characteristics of both in relation to individual conditions and rein which the frequency- changer is pre- types of receiver are discussed in quirements. ceded by an RF amplifier. this article and the pros and cons Much of the criticism of the superheter- of each are carefully weighed up. Sensitivity odyne in the matter of noise is really due to an unfair comparison. Most super - In the matter of sensitivity there is no heterodynes give the impression of being compared with the superheterodyne. With difference between the two receivers, for noisy because they are much more sensi- the latter the selectivity is nearly inde- it is possible to build a straight set which tive than the average straight set. If pendent of the wavelength to which the is as sensitive as the most sensitive super- the comparison be made fairly, however, set is tuned, but the selectivity of the heterodyne. It is not quite so easy to do by tuning each set to the same signal, straight set varies very considerably over so, however, for as the amplification is all then there is very little to choose between the waverange, increasing with wave- obtained at signal frequency, instead of them. length. Moreover, it is much more diffi- being split and obtained partly at signal The next point to be considered is selec- cult to devise a good variable selectivity frequency and partly at intermediate fre- tivity, and it is here that the superheter- system with such sets.

www.americanradiohistory.com 94 WpsilQgg JULY 3oth, 1937

Straight Set versus Superheterodyne - valve or the frequency- changer is over- correctly designed. The conventional These remarks apply to the normal loaded. Experience shows that under aerial coupling gives neither the best broadcast bands. On short waves very average conditions a receiver including an efficiency nor the best ganging. high selectivity is necessary and it can- RF stage usually develops a greater The adjustment of ganging demands not be obtained with the straight set, al- number of whistles than one which does merely the setting of trimmers for maxi- though this type of receiver is quite suit- not. Unless an RF stage is included, mum response and can be carried out able, perhaps more so than the super- however, the signal /noise ratio is lower without any source of known frequency. heterodyne, for the ultra -short waves than it can be. The reason why an RF A test oscillator is naturally convenient, where high selectivity is at present un- stage increases whistle production is that but the ganging can be performed just as necessary. For good short-wave recep- by its amplification it so increases the in- easily and just as accurately on a signal. tion the superheterodyne has no rival. put to the frequency- changer from a local Now in the superheterodyne the IF In spite of the high selectivity of the station that this valve is overloaded, and amplifier must be aligned by means of its superheterodyne this receiver suffers from this in spite of the fact that the signal - trimmers, and while it is easy enough to a liability to certain types of interference frequency circuits may be appreciably make all circuits tune to the same fre- from which the straight set is quite free. mistuned from the local station. The quency it is by no means easy to make The best known of these special forms of remedy is, of course, better preselection. sure that this frequency is the correct interference is second channel or image one unless an accurately calibrated test interference, but there are many other Ganging oscillator is available. It is very import- kinds which have similar audible results, ant that the intermediate frequency used and which normally manifest themselves In view of these points the early stages should be the one for which the receiver as whistles, the pitch of which varies with of a superheterodyne call for very careful is designed, for if it is not large errors in the setting of the tuning control. In a design. In general an RF stage should the ganging of signal and oscillator badly designed or badly adjusted receiver be used, but for the best performance its circuits are inevitable. it is quite possible for a whistle to appear gain should be no higher than is necessary In the ganging pioper, the signal -fre- on every station in the medium waveband; to attain the maximum signal/noise quency circuits follow the same rules as on the other hand, in a well- designed and ratio, and the preselection should be as those of a straight set, but the oscillator properly adjusted receiver it is normally high as possible. In this connection, it is must always be tuned to a frequency possible to keep the whistles down to two worthy of notice that the results are higher than the signal by the intermediate or three or even to eliminate them en- greatly affected by the aerial. Any in- frequency. With the usual " padding " tirely. Much depends on local conditions, crease in the aerial efficiency will be re- system of ganging it is only possible to however, and upon whether the receiver flected in an improved signal /noise ratio secure correct ganging at three points in is used in close proximity to a powerful and with a good aerial it is quite possible the tuning range. Two of these points broadcasting station. for a superheterodyne without an RF are normally 1,400 kc /s and 600 kc /s The Characteristics of Straight Set and Superheterodyne

ATTRIBUTE. STRAIGHT SET. SUPERHETERODYNE. Sensitivity ...... No limit No limit.

Signal/Noise Ratio Set by thermal agitation in first tuned circuit ... Set by thermal agitation in first tuned circuit if the receiver includes an RF stage. Adjacent Channel Selectivity In practice limited, because it is rarely possible to No limit. use more than four tuned circuits. Whistles ... The avoidance of whistles demands careful design and precise adjustment of the receiver. Modulation Frequency Response... Liable to vary over the waveband. A good com- Substantially independent of wavelength. A good compromise between selectivity and quality is not promise between selectivity and quality can readily be easy. A form of variable selectivity is necessary secured. Continuously variable selectivity can be in a selective set. arranged fairly easily. General Distortion... Can be kept very small ... Can be kept very small.

Adjustments Ganging can readily and accurately be carried out Correct ganging necessitatez the use of an accurately without instruments. Defects which cause gang- calibrated oscillator. Defects which cause ganging errors ing errors are easily traced. are not always easy to locate.

There are two main causes of whistles. stage to be quieter than a set with such a and adjustments , must be carried out at Many can be produced by the feed -back stage, or a straight set, used with a poor these frequencies, so that a test oscillator of harmonics of the intermediate fre- aerial. Within the service area of a trans- again becomes necessary. The third quency to the early circuits and their mitter, however, any increase in aerial correct point is settled in the design of the avoidance demands very thorough screen- efficiency increases the liability to receiver and if everything is in order its ing. In fact, as much screening is needed whistles, so that for any given superhet- position falls automatically at about goo in a superheterodyne for the avoidance of erodyne in any given locality there is kc / s, the frequencies of maximum error whistles as in a straight set for the main- actually an optimum figure for the aerial in ganging being about 1,50o kc / s, 1,120 tenance of stability. The other chief cause efficiency which gives the best com- kc /s, 730 kc /s and 55o kc /s. of whistles is a lack of selectivity at signal' promise between the conflicting factors. The magnitude of the errors is not very frequency. It is necessary to provide We have now to consider the questions large, but is greater with a high inter- quite a high degree of selectivity before of ganging and its adjustment. In the mediate frequency than with a low. It is the frequency-changer for the avoidance straight set all tuned circuits are similar especially important to note, however, of second -channel and kindred forms of and except for the aerial circuit it is only that if the IF circuits are adjusted to a interference, especially when the set is necessary to use tuning coils of identical frequency differing only slightly from the used 'within a few miles of a broadcasting inductance and a gang condenser with correct one the ganging errors are greatly station. identical sections for perfect ganging to be increased. It will still be possible to ad- The question of an RF stage also in- secured. Perfect ganging of the aerial just the early circuits so that correct troduces difficulties because the liability circuit is theoretically impossible, but in ganging is secured at 1,40o kc / s and 600 of a receiver to produce whistles is practice the errors can be made ex- kc / s, but the third point will no longer enormousry increased if either the RF tremely small provided that the circuit is be goo kc /s. It may shift to Boo kc /s

www.americanradiohistory.com JULY 39th, 1937 WIpSUM 95 WOrs'Ild Straight Set versus Superheterodyne - erodyne and some form of variable low wavelength station and adjusting and this will reduce the errors at lower selectivity becomes essential. each trimmer on the gang condenser for frequencies but increase them at higher, The main attributes of the two types maximum response ; then tuning in a and the errors in tuning at I,o6o kc /s of receiver are listed in the table for station at the other end of the waveband may become very large. ready comparison and it will be clear that and repeating the process, this time using As the selectivity is determined chiefly the straight set has two points very the inductance trimmers. For the most by the IF amplifier, the dial settings definitely in its favour- namely, the accurate results this should be followed depend on the oscillator circuit, and the absence of whistles and the much greater by a check on the settings of the capacity result of the ganging errors is to make the ease of ganging. This latter point is one trimmers at a low wavelength, but there signal- frequency circuits the ones which which will carry great weight with is nothing at all difficult about the process are mistuned. The result is that the errors amateurs who as a rule have little in the and no test oscillator is needed. are effective in reducing the preselection way of test apparatus. It is, in fact, clear The arrangement of the circuits is a and consequently increase the liability of that the only way in which the super- matter of importance. With four tuned the receiver to whistles and reduce the heterodyne is unquestionably superior is circuits it has become conventional to signal/ noise ratio. It is probably true to in the ease of obtaining very high ad- use two RF stages so that the circuits are say that 8ó per cent. of the whistles jacent channel selectivity. If it is arranged as two single -tuned circuits and present in modern superheterodynes are possible to obtain, not necessarily as high one coupled pair. This entails an ap- caused by ganging errors and that of selectivity as that of the superheterodyne, preciable reduction in selectivity, how- these errors half are due to the use of the but adequate selectivity for present -day ever, unless the coupling is made so loose wrong intermediate frequency and half to broadcasting conditions with the straight that the sensitivity is seriously impaired. insufficiently accurate matching of coils set, it is obvious that it has much in its The maximum selectivity is secured with and condensers. favour and many will be justified in pre- three RF stages and it is then easy to The matter of quality has yet to receive ferring it. secure high gain. It is necessary to limit consideration and here there is theoreti- Since the number of tuned circuits is the gain per stage in the interests of both cally nothing to choose between the limited to four, it is clear that the maxi- stability and selectivity and this is best straight set and the superheterodyne. mum of selectivity must be obtained done by a combination of two ways. The There is little doubt, however, that it is from each.. Efficient coils must be used, grid bias of the valves is increased above easier to obtain freedom from amplitude therefore, and must be so connected in the normal minimum, thus reducing the 3istortion with the straight set, although circuit that a minimum of damping is im- mutual conductance and increasing the the reason for this is not very clear. As posed upon them. Furthermore, every AC resistance, and the circuits are regards frequency distortion, however, ,effort must be made to secure accurate coupled very loosely to the valves so that the superheterodyne is likely to be the ganging if the inherent selectivity of the a minimum of damping is imposed. better, especially if the selectivity is fixed. individual circuits is to be combined In this way it is easy to secure good Because the selectivity is obtained at a properly to realise its theoretical amplification and a degree of selectivity fixed frequency it is possible to use many maximum. which is in practice adequate for most re- tuned circuits in coupled pairs and so ob- In practice, the greatest ganging errors quirements. The selectivity is, in fact, so tain an approach to the ideal square - occur through mismatching of the coils. high that a very considerable degree of topped resonance curve. This course is It is not difficult, however, completely to sideband cutting occurs and means for not practicable in a straight set with its eliminate this source of error by employ- reducing it for high quality reception of limited number of circuits, for it is neces- ing coils of adjustable inductance so that powerful signals must be included. On sary to make the most of each circuit if they can be matched by the user while the long waveband, for instance, it is reasonable selectivity is to be secured. In they are in the set. This does not in- readily possible to receive Deutschland - consequence it is not so easy to obtain a crease the difficulty of ganging, it only sender with no more than a certain good compromise between selectivity and makes the process a little longer. amount of sideband splash from Droit- quality in a straight set as in superhet- Actually, ganging involves tuning in a wich and Radio Paris.

Bass Reflex Baffle IN this cabinet baffle developed for use with the American Jensen r8 -inch loud speaker, the apertures in the back panel are designed to bring the output from the back in phase with the front wave. A response uniform down to 30 cycles is claimed.

Jensen " Bass Reflex " baffle incorporated in a McMurdo Silver receiver installation.

www.americanradiohistory.com Wireless World, July 3oth, 1937 UNBIASED A Ginevision By FREE GRID IN nearly all of us there is a strong vein 11 of avariciousness which is apt to cause when I was suddenly conscious of a us to cast about for any and every means radiantly beautiful nurse bending over me whereby we can save money and, like the and asking me if I felt better. It was, I man who, to save the railway fare, walked suppose, the result of the pickled cabbage. from London to Scotland and later had to I have been warned about it before. Íoot a heavy doctor's bill, we are usually so blinded by some obvious saving that Radio Rowdies . . . noisy loud speakers .. . we are apt to overlook the fact that in many cases our so- called economy may WE wireless people seem to be so busy mean far greater expenditure later on. denouncing those who interfere notorious disturbers of the peace in a well- One of the most striking instances of this with our reception by means of " unsup- known London suburb and arranging tem- sort of thing that has ever been brought pressed " electrical apparatus, and in de- porarily to fit their dwellings with a loud to my notice came my way the other day. manding that laws be passed to suppress speaker in every room. In each case so I happened to be enjoying a peaceful both them and their wretched apparatus, far, the complaints from the neighbours half -hour at home, as Mrs. Free Grid had that we are apt to overlook the rising tide have ceased instantly, and, what is more been unexpectedly called to the bedside of indignation at the interference with the to the point, the inhabitants of the erst- of a sick friend, when I was disturbed ordinary amenities of life caused by many while noisy households, have themselves from my rest by a seedy -looking indivi- wireless listeners. I refer, of course, to appreciated the comfort of the arrange- dual whom I at first took to be a wireless the ever -increasing menace of the over- ment to such an extent that they have at manufacturer who, poor souls, are always loud speaker next door which bellows un- once bought a set of loud speakers for hard put to it to stave off the wolf which ceasingly day and night. themselves. ever menaces the. door of their humble At one time a complaint of such inter- cottages. I was soon enlightened as to ference only arose during the summer the reason of his visit as he sought to when people took the loud speaker into the Inferior Electricity interest me financially in a new company garden or placed it near an open window. IGREATLY fear that some of the re- which, he informed. me, was being floated Nowadays, however, the volume at which marks which I made under the above for the purpose of building a chain of loud speakers are operated has risen to title the other week have been twisted, cinemas in the suburbs. such a pitch that in many cases they can turned and torn out of their context by many people Now, as I pointed out to him, in my be heard two or three houses away. Now to make it appear as though opinion this sort of thing is already over- to my mind the only way to remove this I were ignorant of the elementary fact that done, and there does not seem much room menace of noisy loud speakers is to take there are 1,728 cubic inches to a cubic for a new venture of this kind. He at away the cause of it. The question is, foot. I feel now that I can at last under- once informed me that the proposed corn - of course, what is the cause, and I flatter stand what Kipling was driving at when pany would be able to offer the same com- myself that I have unearthed both the he wrote his famous lines fort as an ordinary cinema but at far cause and the cure as the result of my very "If you can bear to hear the truth you've spoken, Twisted by knaves to make a trap for fools." cheaper rates, since it was intended to diligent application to the problem. I effect a drastic cut in costs by using only The whole trouble is, I find, due to the have been overwhelmed by letters one projector for the whole chain of fact that nowadays people are getting so purporting to show that I stated that cinemas. used to the wireless set as a background to there were only 12 cubic inches to a cubic their daily activities, that they cannot do foot. Needless to say, I said no such without it. Now most people have only thing as anybody who cares to read my one wireless set, while extension loud remarks carefully can prove for them- speakers are still a comparative rarity in selves. What I said was, " just as the average family. Consequently, when though they had been trying to supply any member of the household is in a part cubic feet containing fewer than 12 cubic of the house other than the room in which inches," which is quite a different thing. the loud speaker is installed, he or she de- Undoubtedly it was, and is, perfectly cor- mands that it be run at excessive volume rect for me to imply that it would be in order to be able to follow the pro- swindling to supply cubic feet containing gramme. fewer than 12 cubic inches, so I cannot In the case of households where the see that my remarks constituted an error. fort is held all day by a woman, you will It is true that it would be equally as much swindling to supply a cubic foot . asking if I felt better. nearly always notice that the set is run contain- at very great volume when she is potter- ing 13 cubic inches, but I quite fail to see In response to my request as to how ing about the different parts of the house where I have said it would not. So that's it was proposed to carry out this apparent doing what she dignifies by the name of that. impossibility he explained that there work. The remedy is an obvious one, With regard to the actual question of would be one central cinema equipped namely, to have all houses permanently the inferior performance of the set, the with a first -class projector and the pictures wired for loud speakers and to have an ex- most likely explanation that I have re- would be transmitted to all the satellite tension instrument fitted to every room. ceived is to the effect that it is due to a cinemas by means of a low- powered tele- I have long used this arrangement at poor power factor associated with the par- vision transmitter, the afore-mentioned home, and consequently nobody in my ticular mains concerned, although one satellites each being fitted with a number household, no matter even if they be in reader states that he came across a similar of television receivers dotted about the the coal cellar, has to call for the family trouble in a house where the electric light auditorium, one receiver to each half - set to be run at excessive volume. wiring consisted of unsheathed rubber - dozen members of the audience. I was I have actually proved my theory to covered cable, the usual metal conduit or just about to reach for my cheque -book be correct by approaching one or two lead covering being absent.

www.americanradiohistory.com . , ^ f.Ji ¡¿=i: .

Wireless World, July 301, 1937 97 Current Topics

Mr. Montague M. EVENTS OF THE WEEK IN BRIEF REVIEW MacQueen who, as chairman of the 729 -line Television this country the B.B.C. will R a d i o Manufac- turers' Association, by the make frequent relays of the IT has been announced N.B.C. commentaries. will influence the Fernseh Company that at the policy of the industry Berlin Radio Show, which opens Danish Radio Chief Dies this season and direct to-day (July 3oth) they will be the organisation of MR. en- demonstrating 729 -line television. Kay Christiansen, the the Radio Show. Mr. gineer - in - chief of the MacQueen is man- Wireless Booming Danish Post Office and technical ager of the wireless head of Danish broadcasting, section of the G.E.C. SO great has been the demand has died at the early age of for the Norwegian was All About France of American stations, which will forty -six. Mr. Christiansen take place " People's Receiver " that for two years assistant to Pro- ON Mondays, Wednesdays during the next few . months, manufacturers are finding it ex- fessor and later spent and Saturdays from 6.45 so that the results keep Pedersen obtained may be used tremely difficult to abreast some time in America. In 1931 p.m. until 7 p.m. listeners who by the of orders. So far, 18,2oo have tune in 1938 Cairo Conference in the he presided over the Inter - Rennes or Lille will be preparation been sold, 14,600 of these being Radio Convention at able to pick up special talks of a world plan for A further natioual the allocation of short waves. of the AC type. Copenhagen, and in 1932 -3 was broadcast in English giving are on order. 5,800 sets the official advisor in tele- official information concerning Foreign Broadcasting Bergen Exhibition graphic and telephonic matters conditions in France. On Mon- Policy to the League of Nations. days these talks will be devoted A WIRELESS exhibition will to setting forth what France is WHEN discussing the ques- be opened in Bergen on GW Calling trying to do in the social do- tion of " propaganda " and will remain in broadcasting we August 7th GM carne main, extracts being given con- are apt to think being until September 5th. A WHEN the prefix that it is confined to just a few into use for Scottish ama- cerning town planning, housing studio with glass walls is being conditions, education reform, countries. It is somewhat sur- in teur transmitting stations a few prising erected inside the exhibition mentioned etc. Wednesday's talks will to learn, therefore, that people some idea months ago it was according to a statement made order to give was the only coun- deal more with the events of the of how broadcasting is carried that Wales while, the other day no fewer than try of the United Kingdom not day on Saturdays, out. Special " amateur nights " descriptive travel talks will be twenty -one countries are broad- possessing its own prefix. This casting special programmes are being arranged in which the reme- given and points such as hotel for to broad- deficiency has now been listeners outside their borders public will be invited died, the G.P.O. having re- prices, which would interest the cast from the studio. intending visitor, will be given. and are using foreign languages cently sanctioned the use of the for the purpose. Amateur Movement prefix, GW, by Welsh amateur B.E.R.U. Trophy Contest stations. Spreading AN Australian amateur, Mr. Smith, Jones or Jensen AN amateur radio society Wireless Operators Wanted Ivan Millar, VK3EG, has AMONG the unusual items Experimen- succeeded in obtaining first planned by the Programme known as the " THE R.A.F. will be requiring tal Radio Society of Egypt " has place in the high-power section Department of the Danish Broad- four hundred boy entrants casting Service for the near been founded in the Land of the for training in the of the amateur transmitting con- Pharaohs. The first President in September test organised by the British future is a special " Jensen owner of trades of Armourer, Photo- Empire Day." On this day it is hoped is Mr. W. E. Marsh, Wireless Operator. Radio Union. In the amateur station, grapher and low -power section, which is that every item broadcast will the Egyptian Candidates must be not less than SUxWM. limited to amateurs employing either be written or performed by 15jä more than 171 years and not not more than 25 watts, first somebody bearing the name of Amateur Award of age on September 1st, 1937. place has been gained by a Jensen, which is fully as com- THE annual Maxim award for The initial period of engagement Londoner, Mr. R. Holmes, mon as is Johnson in this the most outstanding record is for nine years after attaining G6RH. Actually this contest, country. The day will be the age of 18. Full particulars of amateur radio achievements which is an annual event, was opened by the new . chief of during the year has been won by are contained in Air Ministry broadcasting who bears may be held last February, and the lapse this Victor Clark, owner of station Pamphlet No. 54, which of a few months in announcing name. e. W6KFC, for his work during had free of charge from the Royal the results is inevitable, as en- Spoken Letters 1936. The award was estab- Inspector of Recruiting, tries are received from the re- lished as a memorial to their Air Force, Victory House, THE latest application of the W.C.2. motest parts of the Empire, father by the children of the late Kingsway, London, every one of which has to be thermionic valve appears to Hiram Percy Maxim, founder carefully checked. be in connection with the and president of the American Mid -Ocean Concerts " spoken letter " service in- Radio Relay League, and is IT is reported that at the re- U.I.R. Meeting augurated by the Dutch Post given annually to the amateur quest of the owners of the AT the conclusion of its Office. Outside the G.P.O. who, in the opinion of the judges, French liner Normandie the summer meeting the Inter- in Amsterdam, The Hague, and has the most noteworthy record N.B.C. has been carrying out national Broadcasting Union other large towns, are installed of work and achievement. an inspection of the ship's presented an electric clock to special automatic recording v ireless facilities with a view to Vice -Admiral Sir Charles Car - machines. The user inserts a The America's Cup relaying concerts from the liner pendale, Deputy- Director of the coin into the slot and then pro- Commentary over the U.S. radio network on B.B.C., in recognition of his ceeds to speak about 15o words EVERY possible means, in- these occasions when prominent services as President of the into a microphone mounted on cluding the use of aero- radio artists are among the pas- Union during its first ten years. the instrument. By means of a planes and blimps, will be em- sengers. Considerable atten- The chief business of the valve amplifier and other ployed by the N.B.C. commen- tion, it is said, has been devoted meeting was in connection with apparatus . his words are duly tators in their endeavour to to the question of a suitable the ever- growing problems of recorded on a disc, which is then convey to listeners a vivid word - room for a studio. If the broad- waveband congestion, more delivered by the machine, com- picture of the various races for casts are successful it is pro- especially on the short waves. plete with a special envelope the America's Cup, which com- bable that the Cunard -White The technical committee has ready for despatch to a friend. mence tomorrow (July 31st). Star liner Queen Mary will be prepared a programme of tests, The reverse side of the disc is For the benefit of listeners in similarly equipped. involving the close collaboration available for spoken advertising.

www.americanradiohistory.com q,4 Wireless World, July 3oth, 1937

The Wireless world Television

VISION CAIN CONTROL LINE SYNC

FRAME SYNC .

É. H.2. PICAI U R E HEIGHT --- -- ^'` SOUND TUNING PICTURE WIDTH SOUND REACTION FRAME SCAN FREQUENCY SOUND VOLUME LINE SCAN FREQUENC

HORIZONTAL SHIFT FOCUS VERTICAL BRILLIANCY SHIFT

V.- Adjustment DESIGNED BY and W. T. COCKING

Operation voltage unit and the tube modulation plug from the vision receiver. To the latter socket connect a pair of WHEN the apparatus has been In this view of the apparatus phones or speaker, interposing completed, no difficulty should the controls are labelled for easy reference. a fixed condenser ; the capacity be experienced in obtaining good is not important, anything results if the necessary initial ad- larger than 0.05 µF will do. justments are properly carried out. These Now tune are in the vision actually much easier than may at first signal, adjusting each of the appear, four trimmers and any apparent complexity is mains plug on the vision receiver power for maximum response. In general the due largely to their unfamiliarity. The pack. For precise details regarding first three trimmers will adjustments in- be near their will consequently be des- itial adjustments to the sound receiver, minimum capacity, and the last about cribed in some considerable detail. the constructor is referred to the article one -third in. It should be possible to Except at the shortest distances from in which this set appeared.' The tuning obtain very loud phone signals, Alexandra or rather Palace a resonant aerial should control, reaction and sound volume con- weak load speaker signals, from the sync be used and at any considerable distance trol are the only controls which affect it, pulses, and. until these are obtained there a centre -fed half -wave aerial with reflec- and it should readily be possible to tune is little use in proceeding further. tor is strongly recommended. Not only in the sound transmissions at good There should be no difficulty in does this obtain- type give greater signal strength, volume. In the original receiver the dial ing such signals, and the HV unit can but it is directional and will in conse- setting was about 14 and the vision signal now be switched on. Before quence doing so, often reduce interference. could be heard near zero. make sure that the tube and all valves A good earth is essential, not for recep- in the time -base are alight. The tion, but for heaters safety. If the equipment is Tuning the Vision Receiver can all be clearly seen except in the case not properly earthed, the screens and of the 131 valves. With these it may metal work be generally can become charged Turning now to the vision side, all ad- necessary to remove the top -caps for in- to quite a high voltage. It is wise, there- justments can be carried out by watch- spection. fore, not only to install a good earth, but ing the effect on the tube, but it is Before switching on, make sure that the to arrange it so that it cannot easily be- generally more convenient to tune the re- brilliancy control is turned fully anti- come disconnected. ceiver first with the aid of a pair of phones clockwise, the focusing control The and the sound and vision receivers are en- or even a loud speaker. To do this re- six controls on the left -hand side of the tirely separate and can consequently be move the mains plug from the high- window are set about half -way round tested separately. Test the sound receiver their travels. first ; this may be done by pulling out the The Wireless World, April 23rd, 1937 Then push the mains plug on the HV

www.americanradiohistory.com . 4: Tlß{ äk ...' l . i . . ; Vt.! r.

Wireless World, July 30th, '931 99

FULL constructional details of the television equipment have appeared in the earlier articles_ in this series and it now remains to describe the adjustments necessary for the attainment of a good performance. It will be seen that these adjustments are by no means complex Receiver and are, in fact; easier than thole needed by many modern broadcast sets.

unit. This will function immediately for is best done by turning the line sync am- set at zero, and the last with somewhat the delay switch in the vision receiver plitude control fully clockwise and turning more capacity than the optimum for power unit will have been closed for some the line frequency control. As this is ro- signal strength. As these circuits are time since it has been in operation during tated the various black marks on the pic- varied the gain control should be altered the testing of the vision receiver. ture will change and at some points simultaneously so that the picture bril- Turn the gain control right down and become lines which swing round through liancy remains constant. then slowly turn up the brilliancy con- the vertical. At one point, the picture At certain settings of the controls it will trol. An illuminated rectangle should will suddenly appear with a black edge on be found that on the right -hand edge appear on the end of the tube. Leave the right -hand side which will lock in on (viewing the tube from the front) of a the control set at moderate brilliancy so the extreme right. The setting of the line black object there appears a band of white that the rectangle is clearly visible. Then frequency control is more critical than or on the edge of a white object a band of centre the raster with the panel opening that of the frame, but is not unduly so. black. This indicates that the circuits by the two shift controls on the right of In fact, the setting of no control is nearly are so tuned that frequency distortion is the speaker fret. as critical as the tuning of an ordinary occurring. broadcast set ! During the adjustment of the circuits, settings will probably The Time -base Controls The picture should now be steady and be found at which recognisable, but will probably be of the interference from the sound occurs, and wrong shape, for the size of the picture these must naturally be avoided. The The next step is to adjust the raster to depends not only on the settings of the interference manifests itself as a horizon- approximately the right size. This is height and width controls, but also upon tal dark shadow across the picture which done by the centre pair of knobs to the the frequency controls. If the picture is varies with the sound modulation ; it may left of the window ; the left -hand knob not wide enough, turn the picture width also affect the sync. On the tuning signal controls the picture height and the right control clockwise, at the same time turn- a regular wobble of the lines, so that while hand the picture width. These should ing the line frequency control in the same " B.B.C. " is moving sideways to the left, be so is adjusted that the raster about the direction so that the sync is not upset. " Tuning Signal " is moving to the right, size of the window. Now focus the spot Then adjust the height by simultaneously is a definite indication of interference from on the screen by means of the upper of turning the height and frame frequency the sound signal. When such interference the two knobs on the left of the speaker controls in the same direction. is not due to the vision receiver being in- fret. Adjust this slowly for maximum correctly tuned, it will be found that the sharpness of the horizontal lines which Final Adjustments cause is misadjustment of the aerial circuit build up the raster. It is essential to turn trimmer on the sound receiver. this knob slowly for there is a small time When satisfied with the picture defini- lag between its movement and a change Now inspect the picture closely. It tion it is only necessary to adjust con- are the on the tube. At this stage the lines are will probably be found that the lines trast. This is done by varying the bril- unlikely to be steady for there is as yet wandering slightly up'and down, and this liancy and vision gain controls for the best be careful setting no sync being applied. can corrected by more results. In general, an increase in bril- The next step is to apply the signal by of the frame frequency control. The next liancy will give better detail in dark parts turning up the vision gain control until step is to adjust the focus precisely for of the picture, but may be accompanied black and white marks appear on the pic- maximum sharpness of the lines and this by a loss of detail in light parts. The two ture. Then turn the sync separator bias is now easily done for the lines are per- controls should thus be adjusted for the control (R2o on the vision receiver) fully fectly steady and not wandering. best effect. anti -clockwise and then back about one - Turn down the gain control so that the quarter of its travel. picture disappears and turn down the Set the frame sync amplitude control brilliancy so that the raster just dis- Precautions (top left -hand knob) fully anti -clockwise, appears. Then turn up the gain control and slowly turn the frame frequency con- so that a very faint picture appears. This These adjustments are, of course, car- trol. A horizontal black line will be ob- will probably be unsteady, so adjust the ried out when initially setting up the reserved moving vertically across the tube, sync separator control for maximum ceiver, and in normal use only the gain but as the frame frequency control is stability. On turning up the gain control controls and brilliancy need attention. turned its speed of movement will vary. farther a good steady picture should be Before switching off always turn the bril- If it increases, turn the knob the other obtained, but it may be a bit fuzzy for the liancy control fully anti -clockwise and be- way. The speed will then slow down and tuning has not yet been properly adjusted. fore switching on always make sure that a point will be found at which the black This is the next step and should be carried it is in this position. If this is not done line stops. When it does, turn up the out with a fairly bright picture. there is a risk of the screen being burnt, frame sync amplitude control about half- The tuned circuits should, after the pre- for the time -base HT voltage falls more way. The black line will now probably liminary tuning, be all in resonance with rapidly than the tube voltage when switch- be moving across the screen in a jumpy one another, and although this condition ing off. If the brilliancy control is not manner ; readjust the frame frequency gives the greater sensitivity it does not turned down, therefore, the raster col- control, and a point will be found at which give the best picture. The circuits must lapses and leaves a bright spot in the it will lock in at the top of the raster and be mistuned slightly for the best results, centre of the tube. become invisible. The setting of the and this condition must be found experi- When switching on, do not turn up the frame frequency control is not critical mentally, since the precise settings will brilliancy control until the delay switch with a good amplitude of sync pulse, and vary with different receivers. In the closes. This will usually be audible as a may be varied appreciably without visible original model the best results were clatter in the speaker ; if it is not heard, effect. obtained with the first and third circuits allow two minutes before turning up the The line must now be adjusted and this tuned to resonance, the second trimmer control. After switching off, do not

www.americanradiohistory.com . . .: rfp..,w.$,.g: 1.11+. > :; jw4P1?lPl,".Ff

I00 71p,4@oo 'JULY 3oth, 1937 WOOyild. The Wireless World Television Receiver -V- therefore, occasional readjustment of the switch on again within five minutes, other- REFERENCE TO EARLIER line frequency control may prove neces- wise the delay switch may not have INSTALMENTS sary. opened, and will not afford any protection July 2nd The Vision Units to the condensers. July 9th The Time Base The best results are naturally secured Radio Amateur Call Book when the equipment is operated in a dark July 16th The Mains Units THE summer edition, 1937, of the Radio room, complete is no July 23rd Framework and Assembly but darkness by - Amateur Call Book Magazine is now means essential. At night good results The Sound Receiver A model of the complete receiver will be available and can be obtained from F. L. are obtainable with ordinary room light- shown on " The Wireless World" stand Postlethwaite, 41, Kinfauns Road, Good - ing, an.I in the afternoon it is normally during the Olympia Radio Show. mayes, Ilford, Essex. The price is 6s. post necessary only to draw the curtains in the free. room. The most important point is to In addition to the call signs of amateur prevent so far as possible light from fall- It will normally be found that the syn- stations throughout the world, there is much ing on the end of the tube, and in general chronising holds the time -bases in step information of value to the short -wave the receiver is consequently best placed over long periods without adjustment. listener. For example, there is a list of with its back to the window. The stability of operation, however, is commercial stations that transmit weather In darkness, the brilliancy obtainable is affected in some degree and press news on the short waves, and by temperature, another of indeed, it is usually stations operating regularly in amply sufficient, and, and there may be a slight drift during the proximity to the amateur bands which can necessary to work with less than full bril- first quarter of an hour or so after the be used for the purpose of frequency liancy to avoid dazzle. Some people gear is switched on. For a short time, calibration. "Haus des Rundfunks" THE HEADQUARTERS OF GERMAN BROADCASTING

UNLIKE Broadcasting House in London, the headquarters of German broadcasting in Berlin form the focal point of a complete entertainment centre, where are held various fairs and exhibitions, and in particular the Radio Exhibition. Adjacent also to the actual broadcasting house is the five- hundred -foot " Funk- turm," which, somewhat like the much older Eiffel Tower, supports a restaurant in addition to wireless aerials. The actual broadcasting house itself is of unusual design, the outer buildings resembling the letter D, the vertical portion of the letter forming the front, which is about 45oft. long. Inside the outer ring of buildings are three wings radiating from a common point, where there is a The light well of the large Berlin Broadcasting light well passing through all four House passes through floors, and from which entrance is gained all four floors and to all studios. Apart from a large number from it access is of studios and apparatus rooms, the entire gained to the various administrative machinery of the State studios. The view broadcasting company, as well as that below, taken from the of the two companies Funkturm, shows which operate tyre clearly the three inner Deutschlandsender and the Berlin national wings surrounded by transmitter, is contained inside the the D- shaped outer building. E. K. building.

prefer subdued room lighting while viewing the pictures, and the brilliancy obtainable is entirely adequate. When working with a large amount of room light, however, it will be found that there is a limit to the brilliancy and this is set by defocusing of the spot in white parts of the picture. Such defocusing causes a loss of detail, and the best results are consequently secured when the room is dark enough to permit the attainment of a bright picture without excessively high settings of either the brilliancy control or the vision gain control.

www.americanradiohistory.com Wireless World, July 3oth, 1937. IOI BROADCAST BREVITIES Clearing Up the Dance Band Muddle NEWS FROM PORTLAND PLACE LIKE the poor, the " dance band situation " is always each week entitled " An Hour to Homage to Wireless . . . with us, but John Watt has gone Play, specialising in the in- staff are hoping that a long way towards alleviating dividual presentation methods of BB.C.the Corporation w i l l certain asperities by outlining the various dance band leaders. emulate the example of Sbuth the clearest-cut scheme the America in ordaining that B.B.C. has yet evolved for B.B.C. at Radiolympia September 21 shall be regarded pleasing everybody concerned. as " Wireless Day." The occa- EMPIRE broadcasting is to be Self- expression the main feature of the B.B.C. display at Radiolympia. NEARING COMPLETION. Every type of dance band fan A considerable advance has resident Most people have a hazy should be pleased, every notion of when and how the been made on the construc- in Tin Pan Alley should be grati- various tion of the North - east parts of the Empire pick Regional Station at Stag - fied, and even the dance band up programmes from the leaders themselves should find their shaw, near Newcastle. It Mother Country, so whole scope for that self- expression the is expected that the station intricate process is be be over which look upon as their to made will ready to take they clear by flashing signs (well the 267.4 metre trans- birthright. shielded, one hopes) showing missions early in October. the areas covered by the six John Watt's Plans transmissions. In a heart -to -heart talk with three representatives of the Six- colour Scheme dance band fraternity, namely, Mr. Jack Payne, Mr. Jay Wil- Three large circular displays bur, and Mr. Lou Preager, the are being arranged. The first new Variety Director has ex- will deal with the transmission's plained that three types of dance Lumber and the countries served programmes are to be featured. by that transmission ; a second The first, appealing to the display will show the time at largest class, will be devoted which a transmission takes purely to entertainment, and place ; and the third will show, will consist of comedy songs, by means of a giant map on a concert arrangements, novel- special projection of the world, ties and symphonic effects. the areas covered by the trans- " Vocals " will not be restricted missions. The various sections in any way so long as they are will be illuminated by neon good. Eight programmes of this lights in six colours, each trans- kind will be given each week. mission being outlined separately by a time -switch system. For People Who Dance te:;" ta, The second type of dance Hands Across the Sea band programme will be in- THE B.B.C. may broadcast tended for people who actually greetings to a new neigh- want to dance. In spite of the bour when the projected short- ceaseless outpouring of rhythm wave station at the Irish Free firm offering to sub- it is strange, but true, that com- sion will be observed in curious enterprising State begins radiating to Irish- fashion ; instead of proclaiming mit the artists' clothing to a paratively few listeners do dance men abroad before the end of to radio. Therefore, only four the fact from the mast tops, the special process which would next year. Constructional work stations will remain in " com- make the water trickle off in of these programmes will be is to be started almost imme- weekly. No vocalists plete silence in homage to little 'globules in " duck's back " radiated diately. wireless." fashion. will be tolerated, the intention The staff of Portland Place Oddly enough, the umbrella being to provide strict rhythm. have such a deep veneration for manufacturers have not troubled Those B.B.C. Vowels wireless that they feel one day to write. For Connoisseurs THE limelight has been turned would hardly be enough. A The third type of programme on last week's agony ad- week at least is recommended. -twice a week-will be reserved vertisement for a young man Neck to Neck dance connoisseurs. The fare for with a command of B.B.C. ... And to Television TS Germany leading Great will be carefully selected not vowels. they are Britain in the matter of only from the British bands but At Alexandra Palace Actually, a large number of paying three weeks' homage to wireless licences? . The B.B.C. from some of the best Conti- people seem anxious to talk television. denies it, although the June nentals relayed direct, and B.B.C. English, to judge from figures-Germany, 8,511,000 ; gramophone records. the applications for copies of the Britain, 8,234,000- suggest that booklet issued by the Advisory Duck's Back Effect for An to the Fatherland leads by a short " Hour Play " Committee on Spoken English. Television ? head. The dancing week will follow The Committee's recommenda- HARRY PRINGLE, whose In point of fact, practically a well- ordered rhythm. Tues- tions are primarily for the " Cabaret Cruises " bave half a million German licences days will be notable for " B.B.C. enlightenment of B.B.C. an- got nearer to realism than most are issued free to war veterans, Ballroom," Wednesdays f o r nouncers, who must necessarily other television shows, has been bringing the total of paid licence " Siesta " and " Hill -Billy " follow a regulation standard, wondering whether the good fees down to eight million. In programmes in alternate weeks, and the Corporation is anxious ;hip " Sunshine " could weather this country free licences are and Thursdays for " Thé Dan - not to foist its own rules on the a storm. Word got around that issued only to blind persons, of sant " in the afternoon and general public. he was considering how to pro- whom there are 47,000 on the comedy numbers at night. Fri- Nevertheless, the man with a duce a real deluge without soak- licence registers. Thus it will. days will be devoted to " sym- copy of the " recommenda- ing the artists. As a result, a be seen that in paid licences phonic " dance music, while tions " in his pocket is a formid- letter arrived at Alexapdra Britain leads by approximately Saturdays will offer a full hour able conversationalist. Palace a few days ago from an 150,000.

www.americanradiohistory.com 102 Wireless World, July 3oth, 1937

LTHOUGH the week under review includes Bank Holiday Monday the programmes are not outstanding, the reason Listeners' fo being, no doubt, that the pro- Guíde gramme planners realise that TIDWORTH TATTOO as many people as possible get FROM the Southern Com- Outstanding Broadcasts at I- out into the wide open spaces mand Tattoo at Tidworth COUNTY CRICKET He will relate in this series during this, the last holiday cornes two relays in the EARLIER this year I stated of talks the misery and week -end of the summer, and National programme on Satur- that Mr. S. J. de Lotbinière adventures that befell him on are therefore not likely to be day. At 9.45 the massed was hoping this season to the road. He feels too listening in. bands of the Southern Com- make cricket broadcasts as strongly about it all to try to For those, however, who by mand will be heard for fifteen popular here as in Australia. turn it into an exciting desire or necessity are at minutes. Then from 11.5 to He is certainly making a good narrative, and too grateful to home on Monday, there is one 11.45 will be heard the effort to do so. This week- those who helped him during highlight, namely a broadcast Musical Drive of the 2nd end he has arranged for com- that period to belittle their from Plymouth during the Brigade of the Royal Horse mentaries on two matches efforts by pretending that he enjoyed his adventures. His story will, therefore, be absolutely authentic, and should prove truly enthralling to all listeners. The first talk will be given at 12.45 (Reg.) on Saturday. 0 0 WEST COUNTRY THE late John Drink - water's three -act, West Coun- try comedy, " Bird in Hand," has been adapted for broadcasting by Cyril Wood and will be heard by National listeners on Tuesday at 7 and Region- ally on Thursday at 8.45. The scenes for each of the three acts are set in the Gloucester- shire inn, " The Bird in PLYMOUTH HOE with Smeaton Tower to the left of the picture from which, during the broadcast on Bank Holiday Monday at 6.35 (Nat.), the commentator will describe the scenes of merriment. In the distance Hand." Although not a dia- behind the tower can be seen Drake's Island. lect play in the strict sense, for there are several contrasted types of visitors to the country- Navy Week celebrations which Artillery accompanied by four which will be in progress ; open tomorrow (Saturday, Cavalry and two Infantry Yorkshire v. Lancashire at side, authentic dialect will be spoken by the actors taking July 31st). The broadcast, bands. This will be followed Bramall Lane, Sheffield, and which begins at 6.35, will pro- by the finale, which will con- Kent v Hampshire at St. Law- Gloucestershire parts. vide National listeners with an clude with the singing of the rence Ground, . Canterbury. O impression of the gaiety at this National Anthem by all The first will be commented HIGH SPEED naval port. It will commence present. During the Tattoo no upon by P. G. H. Fender and ERNEST LONGSTAFFE, who with a description of the scenes fewer than nineteen bands the second by Howard always manages to introduce a on the Hoe from Smeaton with one thousand performers Marshall. It is proposed to novel twist in his variety pro- Tower, next comes a bird's will be taking part. An ob- broadcast from both of these grammes, will produce " Next, eye view from an aeroplane, server will set the scene be- matches during each of the Please," a high -speed variety given by J. Best. For this a fore each broadcast, thereby three days' play ; on Satur- show for National listeners on short-wave link will be used. helping listeners to visualise day at 1. io and 5, on Monday Wednesday at 8. The pro- Following this comes a the splendour of this military between 4 and 5.2o, and again gramme, which can be truly commentary on the ancient pageant. on Tuesday at 1.10 and 5. All termed " lightning variety," the commentaries will be given ceremony of " crossing the O O will form a mosaic, each item line," which will take place in in the National programme. blending into the next, and for the Royal Naval Dockyard. SALZBURG RELAYS t> O O this reason there will be no And finally, listeners will be As mentioned last week, we "I WAS A TRAMP" studio audience present, so switched over to the Alham- are to hear three relays from A SERIES of talks under this that applause will not interfere bra, Devonport, when they the great musical festival at heading will be given during with the maintaining of speed. will hear the harmonica band Salzburg this week. Toscanini the next few weeks by a young Among those taking part are of H.M.S. Rodney. will be the conductor to -night journalist who will, however, Haig and Escoe, who will be In the afternoon commen- (Friday), when at 8.35 (Reg.) remain anonymous. At the broadcasting for the first time; taries on the International comes the second act of age of twenty -two he found Cecil Johnson, giving a bur- Athletic Meeting at the White Mozart's " The Magic Flute," himself without a job, or any lesque talk on physical train- City will be given by H. M. and again on Thursday at 7 immediate prospect of obtaining ; Tollefsen, the wizard of Abrahams and Jack Love- (Nat.), when Act 2 of Wagner's ing one, and with only a few the accordion; Scott and lock between 4 and 5.2o " Die Meistersinger " is re- shillings between him and Whaley, the celebrated Kol- (Nat.). During this period layed. On Monday Bruno starvation. He decided to oured Komedy Kings; and also, the second day's play in Walter will be conductor when tramp the country, not be- Chick Endor and Charlie Far- the two county cricket the second act of Mozart's cause of any romantic notion, rell, America's popular song- matches, referred to later, will " Don Giovanni " is heard at but that there seemed at the sters. provide commentaries 8.55 (Reg.). moment nothing else to do. Wilfrid Parry will be at the

www.americanradiohistory.com Wireless World, July 3oth, 1937 .103

HIGHLIGHTS OF THE WEEK

FRIDAY, JULY 30th. Nat., 7.35, Five Hours Back. 8, the Week " Dorothy " : comedy opera. Reg., 8, Recital : Frederick Sharp and Abroad WALTER GIESE- (baritone) and Thelma Reiss KING, the celebrated ('cello). 8.35, Salzburg relay. piano, and Bram Martin and German pianist who Abroad. his dance orchestra will play will be heard from Vienna, etc., 7.5, " The Magic Deutschlands ender Flute," from Salzburg. several interpolated features on Monday at 9.55, and a concluding number. photographed with SATURDAY, JULY 31st. Bram Martin, who was asso- the composer, Pro- Nat., 8, " Past, Present and Future": fessor Pfitzner (left) Eddie Pola and Jack Hylton. ciated for some time with the 9.45 and 11.5, Tidworth Tattoo. Holborn Restaurant, has now EXCHANGE monly known as Ladies' Day, 10, Jan van der Gucht and the taken to the stage with a new ON Monday at 10.3o (Nat.) will be the occasion of another Theatre Orchestra. combination, and this will be the B.B.C. Symphony Orches- broadcast at 5.30, when the Reg., 7.30, Old Swedish Dance tra will be conducted by Hans Music from Stockholm. 9, " Four its first radio appearance. judges of the hunter and pony Meetings " from the short story G O n Adolf Winter, premier conduc- classes will be interviewed. by Henry James. " PAST, PRESENT AND tor of the Munich broadcasting 0 0 0 Abroad. FUTURE " station. An exchange visit AMERICAN MEMORIAL Radio Mediterannee, 9.10, Sym- JACK Hylton and Eddie will be paid to Munich by FROM 3-4.15 on Sunday phony Concert from the Casino, Monte Carlo. Pola are to present the first of Clarence Raybould, a B.B.C. Radio Paris will relay the their programmes under this staff Conductor, who has been ceremony of the unveiling SUNDAY, AUGUST 1st. heading on 8 of the American Memorial Nat.. 6.45, Robert Easton and the Saturday at invited by the German broad- War Theatre Orchestra. 7.55, Scottish (Nat.). In this series they will casting authorities to conduct at Montfauçon- d'Argonne. The Service from Dunblane Cathedral. introduce stars and events of a concert for them. broadcast will include ad- 9.50, Concert from the Knocke yesterday and to -day, and o dresses by President Lebrun, Casino. of tomorrow. BERLIN RADIO SHOW Reg., 6.35, Tatiana Makushina stars possibly General Pershing, Marshal (soprano) and the Modern Wind FROM Sunday until Satur- Among those who will be heard Pétain and the American Am- Quartet. 9.5, " Hereward " : this week include Vesta day, August 7th, the evening bassador. President Roose- adaptation of Jefferson Farjeon's Victoria, Marriott Edgar, programmes from the German velt's address, broadcast from stage play. Elrick and Frances stations are almost entirely de- Abroad. George Washington, will also be re- Kalundborg, 4, Open Air Band Con- Day. The music will be voted to relays from the Berlin layed by Radio Paris. cert (seventy performers). An played by Jack Hylton and Radio Show. arrangement 0 o n MONDAY, AUGUST 2nd. his band with Eddie Pola act- has been made whereby each OPERA Nat., 4 -5.20, Athletics and County ing as compère. regional station will be respon- THE idea of giving an act Cricket. 635, Relays from Ply- o sible for the entertainment on per evening from Athlone mouth. 8.30, Summer Over the FROM THE NORTH the great stage of the show for seems to have become a settled British Isles : IV -The North. of Reg., 6.35, Dale Smith and Stem - AN interesting cross -section one evening. policy that station, for this dale Bennett in songs for two. of the North at play may be o evening at 8.15 and tomorrow 730, " The Song is Ended " : anticipated when the fourth DUBLIN HORSE SHOW (Saturday) at 8.25 comes the reminiscent programme of popu- programme in the series, THIS horse show, which is third and fourth acts of Verdi's lar songs. 8.55, Salzburg relay. Abroad. ' Summer Over the British reckoned to be the biggest in " Othello." Radio Toulouse 9.10, Selections Isles," is broadcast on Mon- the world, takes place this year There is no mention of the from Lèhar's " Frasquita." day at 8.3o (Nat.). A com- from August 3rd to the 7th. Salzburg festival in the Ger- TUESDAY, AUGUST 3rd.

. prehensive impression of On Wednesday, at 5.30, Ath- man programmes. Listeners Nat., 7, " Bird in Hand " : West summer in such a vast area as lone broadcasts interviews with must tune -in to Vienna, Radio Country comedy. 9.40, " Late the North of England means officers of the various foreign Paris or Sottens if they Night Final "-a news revue. Reg., 7.30, Sullivan-German pro- only a few moments of music jumping teams and also an in- wish to hear the operas in full. gramme : the Military Band. or speech from each place or terview with the judge of the These stations will be relaying 9, Variety from the Theatre Royal, at 7.5 to - night Worcester. (Friday) "The Abroad. Brussels I, 8.30, French version of Magic Flute," and two plays from Laurence Hous- " Don Giovanni " man's " Victoria Regina." on Monday at 7. WEDNESDAY, AUGUST 4th.

From the Resid- Nat., 8, " Next Please " : high -speed ence Theatre, variety. 9.20, " Tonight, Twenty - Munich, will be three Years Ago ": Harold Nicol - son, M.P. Reg., 8.20, 'Cello and pianoforte duets : Nikolai Graudan and CROWDS gather Hansi Fraudberg. 9, " Murder nightly about the en- in the Embassy " : thriller by trance to the great Francis Durbridge. Festspielhaus, Salz- Abroad. burg, to get a glimpse Vienna, 8, Richard Strauss Concert of some of the great from the Salzburg Festival. opera singers arriving for the festival. THURSDAY, AUGUST 5th. Three relays from Nat., 7, Salzburg relay. 8, " Murder Salzburg come into in the Embassy." 9.30, The the English pro- Richard Crean Orchestra. grammes this week. Reg., 625, Shows from the Sea- side : 5-Brighton Follies. 8.45, " Bird in Hand." person, listeners -hunt During relayed Mozart's " Figaro " Abroad. but will hear inter competition. Munich, 8.10, The Magic of the something of the entertain- this broadcast army bands will by Munich at 7.5 to -night Voice : a concert with famous ments to which Northern holi- provide music in the show (Friday). soloists. day- makers are flocking. grounds. Thursday, corn- THE AUDITOR.

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Wireless World, July 3oth, 1937

Replying in particular to the letter of " Nauticus " in the issue of June 25th I do not think his detailed comparison is sound. Letters to she Editor I have always taken it as an axiom that in The Editor does not hold himself a supersonic receiver the IF amplifier should Disc for provide all the selectivity against " neigh- Synchronising Film and responsible the opinions bouring " stations in the wave -band, while IT is generally accepted that high- quality of his correspondents the RF side looks after " distant " inter- sound recording on direct play -back ference such as second -channel, break- blanks is now being obtained regularly by through of extremely near stations, etc. amateur and professional recordists possess- " lead " or " lag " to be corrected instantly. Consequently, in spite of what I have said ing good -class apparatus and sufficient It may be observed that almost all above, band -pass circuits may be used in operating experience, and so the experi- methods of synchronising consist of flexible the RF side provided the band is always -to- that menter naturally turns his attention to other shafts (although the projector turntable quite wide -say 20 -25 kc /s overall. In related unsolved problems, for, like many coupling can with advantage be rigid), i.e., practice there is no serious difficulty in scientists, the true experimenter tends to mechanical connections, which, of course, keeping the band -width reasonably constant lose interest when all the difficulties have have the disadvantage that free movement over the working range. been overcome. of the camera over a large area is restricted, His point of " drift" in the tuned circuits as more six feet of is One of the remaining problems of great much than shafting of the IF amplifier is not one that has given importance is that of synchronising amateur not permissible. The professional method us any serious difficulty at all, though a set sub -standard films, i.e., 16 mm. or 9.5 mm., is to employ what is known as " electrical using " single -peaked " tuning might be interlock," which expected to be extra- sensitive to this. provides exact In fact, though I respect the serious synchronism and thought that " Nauticus " has given to the does not necessitate matter, I am forced by practical experience the camera being of designing and selling sets designed for real very near to the faithfulness, to disagree with nearly all the recording apparatus. points of his design. P. K. TURNER. (There is no space Isleworth. Hartley Turner Radio, available to explain Ltd. what " electrical interlock " is, and Numerical Condenser Symbols those desiring in- IHAVE not seen any suggestion regarding formation should the graphical indication of condenser refer to a good tech- values on circuit diagrams, but feel that nical film book, e.g., your readers would welcome such an NUMBER innovation. My A successful method suggestion is that of coupling the home t h e conventional cine projector to sound -on -disc re- symbol representing corder is described a condenser of any value should be in the accompanying replaced by one drawn in accordance with letter. the system shown in the sketch. Short lines added to the left -hand element with sound -on -disc recording. (The prob- Lester Cowan's Recording Sound for Motion of the conventional symbol indicate the lems and expense of recording sound on Pictures.) decimal point, while further lines give the sub- standard film cannot usually be faced Here, then, is an opportunity for experi- number of ciphers. Similar lines added to by the average amateur, and so will not be menters to display their ingenuity in de- the right -hand element indicate the numb °r. discussed, although it may be worth while veloping (1) a simple system of " electrical --- - 1 mid --- 0'001 mid to mention that RCA has recently released interlock " for use on time- (frequency) a 16 mm. sound -on -film camera for ama- controlled AC mains, or (2) some mechanical ---I = 2 mfds -- = 0'004 mid teur use at L95, which price compares very method of synchronising. - - favourably with the cost of a professional This letter has been written in the hope 35 mm. sound-recording camera, namely, that it will stimulate experimenters to make ---11-- = 0'1 mid -IF-- = 0'0001 mfd £1,5O0!) public their efforts in synchronised SOD by in- Many attempts have been made films, and I feel sure that you will be gener- --E - - 0'2 mid -- - = 0'0005 mid eta dividual workers and by members of ous enough to open these columns to short amateur. cine societies to produce a cheap letters giving details of various methods of --f E-- = 001 mfd Condenser values by and effective synchronising mechanism for synchronism. DONALD W. ALDOUS. graphical symbols. recording and play -back on discs, but Ilford, Essex. apparently few have been really successful -- -- - 0'03 mid information has been published on for little The of system will be made the subject. Straight Set v. Superhet. application the of the Eltham I HAVE read with interest the various clear by the accompanying examples. However, two members Kidderminster. F, J. CLARKE. Cine Society, Messrs. D. C. Pruden and letters in your recent issues on the J. F. Shore, have succeeded in devising a above subject, but it seems to me that in suitable picture- camera-to -sound recorder many cases the writers have not really Are Cheaper Valves Coming ? coupling and synchronising mechanism be- grasped the design problem. ARE we going to see at long last a really tween projector and play -back turntable. First of all, so far as. I can see, none of big reduction in British -made valve They have very kindly given me permis- them has referred to the complete difference prices this year? There are, I think, cer- sion to state some particulars of their in design called for in (a) a set designed for tain signs that something of the sort may device. The camera -to- recorder coupling home construction and use by the intelligent happen. One of them is the announcement is not the major difficulty, as is often amateur and (b) one for factory construction of one firm that its new receivers are to be thought, provided a common drive is em- and adjustment with elaborate apparatus, fitted with valves and valve -sockets of the ployed ; a powerful recording motor but for use by the unskilled. international range. This must mean that coupled by a 3 : z ratio gear box and an old Second, the crux of the whole design of unless our own valves are to be substantially car speedometer drive to the camera are a quality set at present is to get " top " cheaper, the replacement market for them used in this instance. The outstanding diffi- without interference, and so long as stations will be very considerably narrowed. One culty is the synchronising mechanism be- are spaced only 9 kc /s apart and we want would require a very special brand of tween projector and turn -table, and this has úp to 9 kc / s of audio response this must be patriotism to resist the temptation of buy- been overcome by a special gear box design the first consideration ; as you know, my ing a replacement valve of overseas origin (epicyclic gears), with a novel feature of own opinion is that for this requirement all rather than its British counterpart at, per- " adjustable coupling " which enables, " band- pass " circuits are fundamentally haps, three times the price. whilst the film is actually running, sound unsatisfactory. Barnet. GEOFFREY McNEIL.

www.americanradiohistory.com Wireless World, July 3oth, 5937 Ios

New Apparatus Reviewed Recent Products of the Manufacturers

WAVEMASTER MICA TRIMMING venient source of HT for a mobile trans- CONDENSERS mitter or receiver might well consider its merits, for it will provide 25o volts at 6o mA THE Webb Condenser Co., Ltd., 32, after smoothing, and it takes its power from Hatton Garden, London, E.C.1, have a 6 -volt battery. IR1f IH introduced mica nWcCA a new range of miniature One of these units was used on a recent dielectric trimming condensers with a occasion for this purpose, and it proved nominal maximum capacity of 35 m -mfds. very satisfactory indeed. of 9 Some are assembled on bakelite platEs From tests made, the overall efficiency is SPECIAL -VALVE very good quality, and the Type too, as this of the order of 5o per cent. when delivering style is described, is available as single con- between 40 and 5o mA of DC after smooth- FOUR -WAVE SUPERHET densers measuring and in only lin.xjfin., ing and at a voltage of just over 25o. It banks of two, three, and four separate con- thus compares very favourably indeed with DE LUXE densers assembled on a strip of bakelite tin. wide. The De Luxe Model of this exceptional receiver includes The single models are intended to be many interesting features, and combines unusual sensitiv- suspended in the wiring or joined across the ity with great flexibility of control. Only receivers now soldering lugs on coil formers, and in view on the market at very much higher prices can claim so of of their very small size this method high a standard of design and performance. fixing is very convenient. Holes are pro - vided in the end tags, however, to allow for alternative methods of fixing. In the case of the multi -bank models there are fixing holes at each end of the bakelite strips. The majority of the samples tested were actually slightly larger in capacity than the figure quoted, the values obtained varying from 43 m -mfds. to 48 m -mfds. at maximum. Their minimum capacities are very low indeed, being of the order of 1.5 to 2 m -mfds. Bulgin " Electronic " HT vibrator generator Not only are these condensers very well rectifier Type HTV. i, and the MT.5 trans- made but high quality material is used former. throughout, and their prices are most reasonable. most other forms of HT supply devices that (Complete series with 9 B.V.A In the bakelite (Type too) the single operate from a low- voltage accumulator. valves.) condenser costs only 4d. For the multi -bank On light loads the voltage is inclined to types the price is 4d. for each condenser ; rise to high levels ; for example, with but thus a two -bank costs 8d., a three -bank is., 20 mA flowing, goo volts were obtained ; 4 wavebands : 12.8-33, 29 -80, ISO -550, 500 -2000 and a four -bank is. 4d. with 40 mA there were 325 volts, and with metres. illuminated dial with principal station There. is also another style available, in 6o mA the voltage was 240. names. Separate coloured lights for each wave- which the condenser is assembled on a fre- The Bulgin vibrator generator is a self - band. quentite base. These are described as the rectifying device, and the only additional Type tot Postage Stamp Trimmer con- parts needed are the transformer, smooth- Controls. -A feature of the receiver is the number of independent controls fitted, making it extremely densers. In this style, apparently, only ing choke, and several condensers. A low - size resistance interesting to operate. These include : sensitivity single condensers are available, the and smoothing choke was used in control (varying bias on RIF stage). Q.A.V.C. with the method of construction being the same order to obtain the high output voltages manual muting control, and switch for inter -station given, that used noise suppression. 5- position wave -change and gramo- being the Bulgin phone switch. Progressive variable tone control No. F185 of 320 operative on radio and gram. ohms resistance. Circuit in Brief- Aerial input to pre -selector circuit, radio This is a to -henry frequency amplifier, latest type triode -hexode frequency changer, 2 band -pass I.F.T. coupled I.F. amplifiers, double choke, but for a diode detector, L.F. amplifier and special push -pull pentode sensitive re- output stage. Heavy cadmium- plated steel chassis. Finest ceiver more smooth- components and workmanship throughout. ing will be required. A C. models ready for immediate delivery. A.0 D.C. models also in production, and will be available However, there are for delivery shortly. ample volts avail- STANDARD MODEL 12 GNS. able, so that a larger as above, but with triode push -pull output, and fewer inductance can be controls fitted. used even though IIVII ORTAMT The prices at which McCarthy Chassis are advertised Wavemaster miniature include Marconi Royalties. ' Wireless World " readers trimming condensers; should, for their own protection, make sure before purchasing any receiver that the quoted price includes single- and multi -type the Royalty payment. are shown.

All McCarthy receivers supplied complete with as that of the single model in the tot series. this may require a choke of higher DC valves, knobs, pilot lamps, leads, mains cable and One sample was tested, its minimum and resistance. plug. 12 months' guarantee. maximum capacities being z and 34.5 When taking measurements the Bulgin Deferred terms on applicatioi, or through London m -mfds. respectively. It costs 6d. MT. 5 transformer giving an output of 25o Radio Supply Co., 11., Oat Lane, E.C.2. volts was employed, but when lower volt- Cash with order on 7 days' approval. Also write BULGIN VIBRATOR FIT SUPPLY ages will suffice, the MT. z model for illustrated catalogue of complete range of all can be McCarthy receivers. EQUIPMENT used, its output being 15o volts 'THOUGH this vibrator unit was (smoothed) at 6o mA. The combined HT developed primarily to provide the HT vibrator generator and rectifier is described AtcCAI ?111 Y ILTD. for operating car radio receivers, its useful- as the Type HTV. s, and it costs 23s. 4d. 44a, Westbourne Grove, London, W.2 5 ness is not necessarily restricted to this one The price of the Type MT. transformer is Telephone : Bayswater 3201/2. function. Experimenters requiring a con- 14s. 7d., and of MT. 2 model its. 9d.

www.americanradiohistory.com zoG Wireless World, July 3o/h, 1937 "Little Princess Portable

HIGH UNDISTORTED OUTPUT FROM A PORTABLE OF SMALL DIMENSIONS

on Luxembourg to avoid overloading on coupled to the grid detector valve by a the output valve, and all the usual long- tuned anode circuit to which reaction is wave transmissions are capable of work- applied by the usual capacity -controlled ing the set at or very near full volume. circuit. An intermediate bias between +, Careful screening of the set as a whole, and - LT is provided by the well -known and in particular of the RF coupling cgils, expedient of using two grid leaks, one leaves a very clean minimum in the pick- returned to each of the LT leads. The up from the frame aerial, so that its direc- detector is followed by a first stage of AF tional properties are of real value as an aid amplification using a triode valve. This to selectivity when an appreciable angle is resistance- coupled to the detector and exists between the directions of the wanted transformer -coupled to the output valve, and unwanted stations. Using this a volume control being provided by a method, the Deutschlandsender was suc- variable resistance across the primary. cessfully received clear of Droitwich, LTHOUGH in general specification though the effort required in tuning is not Combined Volume the circuit will be familiar to one which, in the ordinary way of listen- Control those who have made a compara- ing, one would have the necessary energy tive study of the various receivers The AF volume control and the reaction to indulge in. control are combined in a single compo- comprising the small portable class, there A sharp minimum, of course, is not are one or two differences which ensure nent of rather interesting design. It con- that this receiver will not be treated as sists of a solid -dielectric variable condenser " just another portable." in which the fixed vanes occupy a quad- FEATURES. Type. -Self - contained rant of 90 degrees. At the back of the con- Most important of these, in our opinion, battery portable. Circuit.Pentode RF is the choice of a Hivac- Harries output denser and operated by the same spindle is amplifier -triode grid detector with reaction a carbon track resistance with a triple con- tetrode valve in place of the usual battery -triode first AF amplifier- letrode output output tact brush arm. For nearly three -quarters pentode. Although the anode cur- valve. Controls. -(1) Tuning. (2) Volume. is of the range of the control the reaction rent consumption of this valve appreci- (3) Waverange and on -off switch. Price. ably higher than that of the so- called - condenser is at its minimum, and only the 7 guineas. Makers.-Peto Scott Electrical " economy " pentode, there can be little AF volume control is in action. In the Instruments (Holdings) Ltd., Pilot House, last quarter, reaction and AF amplifi- doubt in the mind of anyone who has Church Street, Stoke Newington N.16. listened to this set that the increased cur- cation are increased simultaneously, and rent results in more than a proportional the point at which oscillation starts is ad- increase in volume and reduction in har- justed to be near the end of the control so monic distortion. As the volume control without its disadvantages, and when in that useful gain at low frequency shall not is turned up and the limits of the ordinary search of distant stations one must keep in be lost. portable are passed and left well behind mind the approximate bearing of the sta- The anode circuit of the output valve it is difficult to believe that one is not tion to avoid trying to time it on its mini- is provided with a telephone jack and handling a first-class table model battery mum. Also, a few degrees of rotation special high- sensitivity headphones are receiver or even a small mains set. Not near the position of maximum pick -up available from the manufacturers for those only does the reproduction carry may make all the difference between suc- who may be tempted by the performance " punch," but it has the correct balance cess and failure in receiving a station near of the set to go in for really ambitious for conditions in the open air, and there the limits of the range of the set. Ter- long -distance reception. need be no excuse for breaking up a picnic minals are provided for the addition of an The cabinet design is neat with the party to crowd round the loud speaker aerial or earth, but ample variety of fare controls fitted on a sunk panel which when an item calling for attentive listening is provided without calling in their aid. brings them practically flush with the out - crops up. The pentode RF amplifier which takes side of the case. The long, narrow the output from the frame aerial is receiver chassis is mounted close to the Sensitivity Guaranteed reception of twenty -five stations is mentioned in the maker's literature, and, judging from the sensitivity, they should have no difficulty in substan- tiating this claim, though a little care may be required in tuning, say, the last half a dozen required to complete the list. In Central London good programmes were tuned -in without difficulty from Fécamp, Cologne, Paris PTT and Brussels No. r. The excellent strength of the latter station confirms the impression that the sensitivity is well maintained at the top end of the medium waveband. The same applies to the long-wave range and the volume from Huizen is well above the average. The volume control requires to be turned down Complete circuit diagram. A Hivac- Harries tetrode is used in the output stage.

www.americanradiohistory.com JULY 3oth, 1937 WAp@NOg '10¡ WopM "Little Princess " Portable - they apply to the Corporation for the neces- top of the cabinet, leaving ample space sary facilities, which are readily granted. for the 90 -volt HT battery and the i7- In the case Of the Little Bardfield event amp: -hour jelly electrolyte 2 -volt accumu- Mrs Nurrow, C.B,S. representative in yng- lator. A total HT current consumption land, seeing in this little village the pos- of 6I mA is mentioned as an average sibilities for a broadcast to America, asked the B.B,C. to arrange matters for him. value in the maker's literature, but in the This necessitates the rental of a Post Office case of the receiver tested the consumption line and the supplying of B.B.C. engineers, at 90 v. with -3 v. bias was 10.5 mA. microphones and transmitting gear at the At 6o v. with the same bias the current scene of the broadcast. The transmission is fell to 4.5 mA, but there was a consider- then sent by line to Broadcasting House able falling-off in the liveliness of the set. and thence by line to Rugby, where it is On special occasions, when greater volume transmitted to America.

1st A F AMPLIFIER VALVE DETECTOR VALVE H210 D 2 1 0 OUTPUT VALVE Y 220 RF sdprupols ,;!1 AMPLIFIER VALVE

V P 2 1 5 OBSTACLES ARE OVERCOME - THE Cif HEIGHrs ATTAINED - ONLY THROUGH TELEPHONE HIGH INTENT, TENACITY OF PURPOSE JACK AERIAL AND A STEADFAST WILL TO ACHIEVE AND EARTH SOCKETS THROUGH more than 28 years 1 T.C.C. have always had but a single goal -the attainment of perfection in the manufacture of GB condensers. From that original BATTERY intent-to concentrate on the one product alone, T.C.C. have never deviated. Passing time has brought it problem, demands have varied and T.C.C. have in- 'Wireless World variably been the first to solve the COPYR IGHT difficulty. A case in point is the T.C.C. Wet Electrolytics. Intro- duced to this country by T.C.C. these voltage regulators have A 7 -inch permanent- magnet ir.oving coil loud speaker makes good use of the output from played the biggest possible part the tetrode valve in the final stage of the circuit. The grid bias battery is a separate unit in making the A.C. Receiver a and should not be overlooked when making replacements. DEPENDABLE instrument. The inherent SURGE VOLT danger is required and extra expenditure of HT Not only was the fact that the item was to components has been elimi- the bias may be reduced not heard by British listeners criticised, but nated. For safety sake - use seems justified, these T.C.C. Wets in your A.C. to v., when a per cent. increase many must have asked who pays for all the -1.5 40 arrangements. It is difficult to say why the Receiver. of current may be expected. Incidentally, Programme Department did not avail them- the measured LT current for the set as a selves of the material at hand, but, as to whole was 0.53 amp. the cost, this is borne entirely by the B.B.C. The set is of convenient size, and In the same way, when the B.B.C.'s FOUR STANDARD TYPES measures only 94ín. high, irtin. wide American representative, Felix Greene, asks Working Volts and Ain. deep. The weight is 18 lb., the N.B.C. or C.B.S. for facilities to broad- Type Capacity Continuous and the collapsible carrying handle is well cast a special item to England, they are 802 16 mfds. 440 volts Peak immediately forthcoming with no charge placed from the point of view of balance. 602 8 mfds. 440 volts Peak whatever to the B.B.C. It is, however, true that we do not include American items in EOS 8 mfds. 500 volts Peak our programmes to anything like the degree 809 32 mfds. 320 volts Peak that the Americans do those from the English- American Special types are available to meet the stringent conditions found English side, but the arrangement remains, in A.C.ID.C. Receivers. Write for full details. and it may well be that the balance will one Broadcasts day swing over on our side of the scale. A Reciprocal Arrangement The Radio Industry fact that the B.B.C. arranged a THEbroadcast from the Essex village of W. Andrew Bryce and Co., Ltd., of North Road, Burnt Oak, Edgware, Middx, sends us T.C.C. Little Bardfield for the Columbia Broadcast- a leaflet cotitaining a reprint of an N.P.L. re- ing System of America and yet did not in- port on the Bryce multiple connector blocks. SURGEdPROOF clude the item in their own programmes The connectors withstood voltages up to 5,900 caused a certain amount of adverse criticism applied between adjacent " ways," while the WET ELECTROLYTICS at the time. Upon enquiry at Broadcasting inserts carried a current of zo amperes for four House, it was learned that this broadcast hours with a mean temperature rise of only ro deg. C. was only one of a number of such trans- THE TELEGRAPH CONDENSER CO., LTD., missions, the arrangement being if the z O O that During the annual Philco holidays' (July 3rst WALES FARM ROAD, NORTH ACTON, W.3. C.B.S. or N.B.C. wish to broadcast an to August 9th) the works will be closed down event taking place in this country, whether so far as production is concerned, but new it is being broadcast by the B.B.C. or not, machinery and assembly lines will be installed. ig.) =35

www.americanradiohistory.com Wireless World, July 3oth, 1937

By Random Radiations " DIALLIST"

Tuning Made Difficult HT Battery Connections It follows that with its 33} per cent. greater just one or two of the new season's re- IWAS rather surprised at some criticisms load the section between HT- and HT +1 IN ceiving sets that I have handled I notice of my remarks about simplifying the HT wears out a good deal more rapidly than a defect which calls for immediate remedy. connections in battery sets which appeared that between HT + r and HT + 2. The GB The tuning knob is distinctly stiff and heavy in a recent letter in the correspondence section, on the other hand, remains un- to move, particularly when the " fast " drive columns of The Wireless World. One remark affected, save by the effects of " shelf life." is in use. There is nothing that makes tun- of the writer's about his own set I cannot With a well- designed voltage divider all ing more difficult or more unpleasant than follow at all. He mentions that by using parts of the battery run down equally fast, a stiff drive. It becomes real hard work to five HT connections, plus two for GB, he is and something like a proper balance between spend half an hour or so with the set in able to obtain the very last usable volt from plate, screening -grid and control -grid volt- search of foreign stations, and if, as is some- his HTB. That's all very well, but he ages is maintained automatically. You thus times the case, the knob itself is small, your also says that the grid-bias leads are get the " last usable volt " without any fingers can be made quite sore. You should plugged into the GB section of the HTB, trouble. be able to move without effort from one end and " once they are plugged -in no further ti to the other of any tuning range, and it is adjustment is needed during the whole life Marconi especially important for short-wave work of the battery." As it is, or should be, THE writer of practically every obituary that the slow- motion drive should be as light under no load, the GB section of a battery notice which has appeared about Mar- as a feather. If it isn't, you'll keep on may show almost its full nominal voltage coni has dwelt at length upon the famous jumping past the exact resonance point, and when the rest of the battery, having sup- " S " signals by which wireless first spanned it's the dickins and all to tune -in any rather plied current for a more or less lengthy the Atlantic on December izth, t9or, but feeble transmission. period, makes no very good showing on the none of them seems to be aware of the reason voltmeter. In other words, the writer is why Marconi chose this particular letter in- ti ti 1. apparently using approximately the same stead of the more customary " V " which was PA Woomphs negative biasing voltage on the grids of his in almost universal use for test purposes by low- frequency valves when his HT battery land -line telegraphists and was later adopted FROM a reader who is interested in the has run down to, say, 8o volts as he was for the same purpose by wireless operators. making of public- address apparatus I when its EMF was 15o in its first youth. Indeed, the choice of ' S " must seem, on have a letter referring to my recent para- the face of it, to be a singularly unwise graphs on the poor intelligibility of many one, Treating 'em all Alike. since a letter consisting solely of dots is far of the outfits that one hears. After much One great point about having automatic harder to distinguish through atmospherics experimenting he is in complete agreement grid -bias and only two and background noises realises HT connections is generally than one with me that not every manufacturer that every part of the battery is always containing dashes, irrespective of is whether the very real need that there for PA under an exactly equal load. To see headphones or a morse inker are a bass what employed. equipment to be provided with cut- this means, take the simple case of a set The reason is a simple one but of con- off control. He is also of opinion that a using a battery with a GB section and hav- siderable technical interest. In the great good deal of trouble arises from the use of ing leads for HT - cum GB , HT + r, HT effort to span the Atlantic the Poldhu unsuitable microphones. Of course it + + 2 and GB - . Suppose that HT + 1 serves transmitter was being worked " all out," isn't a bit of good designing a first -rate various screening or priming grids and and there was a very great likelihood use it with a that of the amplifier if you're going to their circuits require a current of 3 milli- dielectric of the main condenser breaking whose response is poor to the microphone amperes. while HT + 2 supplies the plate cir- down under the strain, thus short- circuit- most important parts of the scale of fre- cuits, which draw between them 9 milli- ing and burning out the power transformer. of quencies from the intelligibility point amperes. Then the total load on the section Test signals had to be kept up over a period view. My correspondent makes another of the battery between HT- and HT +1 is of many days, and it was considered that point which is of very great importance. 12 milliamperes, that on the section between a series of short signals be -or, in other words, The human element, he says, cannot HT +r and HT +2, 9 milliamperes, and that dots -would impose far less strain on the people take it for overlooked. Many on the section between GB + and GB - , nil. condenser than even a few signals of greater granted that their microphone voices are everything that they should be and will endeavour to use PA apparatus without any preliminary instruction. The Acid Test This I can bear out from personal experience. Not long ago I was running a gym- khana and a very good PA outfit was hired for the day so that announcements could be made. One man insisted on taking on the job of announcer and airily brushed aside all suggestions that he should have a trial run on the morning before the show started. When he got to work he gabbled so fast and pitched his voice so low that literally only a word here and there could be understood by anyone. He was quite indignant when, as a result of protests, the committee had to substitute a more satisfactory speaker. I had just written the above when a PA van went slowly past my house. A good deal of noise was coming from the loud speakers on its roof but, honestly, I couldn't make out a word. I gathered that it was advertising some meeting or other, a following the van was for car displaying The winner of the 4o metre field -day contest held by the Thames Valley Amateur Radio a selection of posters. But what came from and Television Society, Mr. A. F. E. Bott (G5VB), is here shown operating his transmitter. the loud speakers was just noise and nothing On the left, adjusting the receiver, is Mr. L. Cooper (G5LC). Power was limited to 5 watts, more. supplied from batteries. Scoring was based on points awarded according to the distance covered.

www.americanradiohistory.com JULY 30th, 1937 WfipAseo Pi WOgIld length ; hence the choice of a letter contain- telegraphy came into being and the founda- ing no dashes. tions were laid for broadcasting, which is Comparatively few newspapers seemed to undoubtedly one of the most important de- have called to mind the fact that one of the velopments in the history'of mankind. earliest occasions on which the superiority DX enthusiasts must look upon him as of wireless over the land -line, under adverse the founder of their craft, for he was the meteorological conditions, was dramatically earliest of all long- distance men. That proved occurred as early as 1898. In the simple signal received across the Atlantic winter of that year, when Press telegrams thirty -six years ago was the first piece of were' on the point of being dispatched DX work. We who have experienced the announcing the arrival of Mr. Gladstone at thrills of capturing some almost absurdly Bournemouth -a visit paid just before his tiny and distant station can realise some- death -an exceptionally heavy snowstorm thing of what he felt when those groups of brought down all the telegraph and tele- dots were received ; but only something, for phone wires in the neighbourhood. The to him they meant the triumphant vindica- town would have been completely isolated tion of the inventions upon which he had from a telegraphic point of view had it not worked so long and so patiently. been for the fact that Marconi was there at For those who are fond of the more diffi- the time conducting experiments across the cult feats of reception, quite a number of Solent to Totland Bay, and when he got out -of-the -way little stations are waiting on into touch with his colleagues there he found the medium -wave band. I don't mean mem- comparatively good weather prevailing, so bers of big common -wave groups ; those that that the telegraph lines in the Isle of Wight I have in mind are the small fry which either were undamaged possess individual wavelengths or are to be By a curious coincidence, the death of found working on their own if you try for Marconi occurred on the fortieth anniver- them at the right times. sary of the founding of the firm which bore At the very top of the band, on 587.1 his name. When it came into being on metres, there is the Estonian Tartu, rated at July 20th, 1897, it was called the " Wireless 0.5 kilowatt. As it has no other station Telegraph and Signal Company," the name within 8 kilocycles of it, the station should being changed to Marconi's Wireless Tele- be receivable when conditions are good. I graph Company in 190o. have never yet logged it, but that is possibly due to the fact that there is a good deal of interference in my neighbourhood on wavelengths above about 56o metres. Television A tempting little station is the loo -watt New German Standard Egyptian- Assiout. Nominally it shares a wavelength with Madrid EAJ2 and Seville THE BEST (410.4 m), but the Spanish stations RECEIVERS me seem to work very irregularly just now. for the future the international tele- Assiout has, I know, been recorded by ARE G.12 EQUIPPED vision standard for all public television work several enthusiasts. Glance inside the cabinet of any receiver in Germany. The standard, which has Zagreb (0.7 kilowatt, 276.2 metres) used in the " de Luxe " class and nine times already been accepted in America, is 441 not to be difficult to receive, but I have not out of ten you will find a Rola G.12. lines, 25 frames, interlaced scanning. It heard it for a long time now. It has a wave- Any manufacturer could tell you the is thought that this tandard will soon be length partner in Falun, so that one's only reason. The fact is that the Rola G.12 followed by France and Britain. The ques- real chance is when the Swedish station has achieved such a unique reputation tion of mains frequency would, however, closes down early. for supreme quality that it pays them to have to be taken into consideration. Down towards the bottom of the band pay the little more that a G.12 costs, The new standard of television definition there are two smallish Hungarian stations, and secure the thousands of additional is considered, in Germany, to be Magyaróver and Miskole, each of which has sales that its installation ensures. the For reason in its own wavelength. Both are rated at 1.25 this the G.12 is itself present optimum, and that it will remain a guarantee of the quality of the set in works 227.1 so for a long period of years. To further kilowatts. The former on which it is found. Make sure that your increase the number of lines would bring metres, the latter on 208.6. Miskole I have set is G.12 equipped and enjoy radio new .and difficult technical problems with- heard, though Magyaróvar has so far escaped entertainment in its most perfect form. out. much gain in picture quality. At the my net -at any rate, I have not identified it. moment the Berlin television service is still Binche, the Belgian 0.1- kilowatt station G.12 D.C. (as illustrated) Stripped and without Transformer f!3 15 0 on 201.7 metres, is . oftên not difficult to operating on the previous German standard, G.12 D.C. Complete with Transformer, 180 lines, 25 frames. This will be discon- pick up, and the 0.2- kilowatt Karlskrona Mounting Stand, Handle (Sweden) may be heard on 196 metres if and Base ... £5 5 0 tinued shortly after the close of the forth- G.12 D.C. with Mounting Stand, Handle coming Radio Exhibition. New studio your set will tune down low enough. I am and Base, but without using one just now goes down to little Transformer £4 16 0 premises for television have already been that a 0.12 D.C. Stripped, but with Trans- completed. below 170 metres, but so far I. have not former £4 4 0 works (When ordering please state Field Resistance and It will be remembered that last year found the Latvian Liepaja, which on Impedance of Transformer required.) Germany seemed to favour the adoption of 173 metres and is rated at roo watts. G.12 P.M. less Transformer ...... £4 16 0 a, 375 -line standard. It is thought better, There are two much bigger stations which 0.12 P.M. with Transformer ...... £5 5 0 is Belgrade, 2.5 For Public Address work both the P.M. and Ener- however, to follow the international trend are teasers. One rated at gised Models can be supplied with a 15 ohm Voice and to increase the number of lines for kilowatts, which, working on 437.3 metres, Coil at an additional charge of 3, -. scanning to the present technical optimum. is sandwiched between the 1oó -kilowatt Write for Folder A. 441-line pictures by wire and wireless will Sottens' and the 120-kilowatt Paris P.T.T. be a feature of the German Radio Exhibi- The other is Stara-Zagora, the Bulgarian OVER 8 MILLION IN USE tion which opens to -day. (July 3oth). The station on 214 metres, whose rating is 2 kW. new transmitters on the Brocken and on the Two wavelength changes are announced Feldberg will open with the new number of from Italy. It has been found that Radio lines in. autumn. Sets are expected to be Marconi's 5o kilowatts cannot do themselves available at 6o -65 Rm. justice on 245.5 metres, and the station is to replace Genoa on 304.3. Genoa, which,

like Trieste, . relays the Turin. No. 1 pro- Distant Reception Notes grammes, is to go to 263.2 metres. Turin No. r, Trieste and Genoa will be synchron- THE whole civilised world was shocked ised. It is rather interesting that two syn- P IvOtka -Final if? ltDlà4ó(CPJt4 to hear of the death of the Marchese chronised groups of three stations apiece will THE BRITISH Marconi at the comparatively early age be working on adjacent channels, for the ROLA CO:. LTD. of sixty- three. It was through his genius, British Nationals on 261.1 metres are next MINERVA, ROAD, PARK ROYAL,N.W.10. his energy and his persistence that wireless door to the Italians. D. EXER. *PHONE < WILLESDEN 4322-3-4-.5-6.

www.americanradiohistory.com ITO Wireless World, July 3oth, 1937 Recent Inventions SHORTWAVE AERIALS Brief descriptions of the more interesting radio IT is desirable to keep the total impedance of a short-wave devices and improvements issued as patents transmitting aerial, over a range will be included in this section. of frequencies, substantially equal to the resistance of the aerial ar the carrier frequency to which it down to the so- called zero fre- way as to shorten the fly -back is tuned. quency, which represents the period. With this object the main leed- " average illumination " of the Ferranti, Ltd. and J. C. Wilson. line C, O is coupled to the aerial transmitted picture. Application date October 29th, A, A5 through a " dummy " line To do this the incoming sig- 1935. No. 464541. consisting of a centre conductor nals are first passed through a pair o o o o D and an outer sheath Di. The of valves in order to suppress the DIRECTION FINDING Method of applying regenera- centre conductor C of the feed line DC or zero- frequency component. THE so- called " night effect " in tion to a CR tube. is connected to the outer sheath At the same time a modulating direction -finding is due to a frequency is applied so as to pro- rotation of the plane of polaris- sistance Ri in the anode circuit of duce pulses of recurrent peaks and ation of the transmitted wave, as that valve, from which they are crests in the output. The DC it is reflected from the Heaviside fed back by a tapping T to the component is afterwards restored layer, and tends to mask the true control grid of the CR tube. by rectifying the pulses, and the direction of the transmitting The degree of feed -back is con- A effect of the deliberately-intro- beacon. trolled by a suitable choice of the duced modulation is removed by According to the invention, the resistance R and the tapping point suitable filter - circuits. Alter- disturbing effect, as manifested in T. Because of the resistance natively, the pulses may be ar- the frame aerial F, is offset by the coupling the feed -back voltage is ranged to occur at relatively unim- pick -up voltage from a horizontal kept in phase with the original portant times, e.g., when the mar- dipole aerial D, both voltages be- signals. The method is applicable gins of the picture are being ing combined in a circuit C, which over a wide range of frequencies, scanned. is coupled to the receiver. The and requires no special or auxil- Baird Television, Ltd. and currents in the two aerials are ary electrode in the cathode -ray P. W. Willans. Application date brought into correct relation, be- tube. October 23rd, 1935. No. 464979. fore being combined, by means of E. Michaelis. Convention date. o o o o à phasing resistance R inserted (Germany) June 22nd, 1935. No. either in the frame aerial, as 464064. TINE =BASE CIRCUITS SAW - TOOTHED oscillations, suitable for scanning in tele- Feeder and coupling system vision, are derived from a screen - to broaden response of a dipole grid or pentode valve in which aerial. back -coupling between the screening grid and the anode is Utilised Di of the " dummy," and vice to improve the shape of the wave- versa, whilst reciprocal connec- form, and in particular to shorten tions are made at R and Ri. The the " fly -back " or idle stroke. upper and lower limbs A, Ax of Oscillations from a previous the aerial are directly joined to the hack -coupled valve are applied to two outer sheaths. The arrange- the grid of a triode V, and are

Combination of frame and dipole aerials to counteract " night effect." shown, or in the dipole. When AERIALS FOR AIRCRAFT the arrangement is used for waves AN aerial suitable for use on an of loo metres or more, both aerials aeroplane consists of a length should be located at least one- of wire which is normally wound third times the square root of the up on a spring reel enclosed in a working wavelength above ground. suitable housing. To bring the Telefunken ges fur drahtlose aerial into use, the wire is pulled Telegraphie m.b.h. Convention out against the spring of the date (Germany) August 7th, 1935. roller, until a button near the end No. 464075. of the wire can be slipped into a o o o o bayonet slot. This locks it in the APPLYING REACTION TO A extended position. When no CR TUBE longer required, the button is with- THE sensitivity of a cathode - drawn from the slots, and the ex- ray tube is increased by means tended wire is then automatically of the regenerative circuit shown rewound by the spring of the Method of shortening the fly -back stroke in a saw -toothed in the Figure. Picture signals roller. A second wire, similarly ar- oscillation generator. applied at P to the control elec- ranged, can be used as a counter- trode C produce voltages across poise. ment is particularly suitable for used to time the discharge of a the cathode resistance R. These Convention the transmission of television sig- condenser C, which- is recharged K. Schuchter. date nals. a suitable are fed to the grid of an auxiliary (Austria) September 12th, 1935. through resistance R, valve V, and reappear across a re- No. 464769. A. D. Blumlein ; E. C. Cork ; such as a saturated diode. and J. L. Patvsey. Application The resulting imperfect impulses dates October 19th, 1935 and July are fed to the grid of the pentode The British abstracts published here are prepared with the permission loth, 1936. No. 464443. P and produce scanning voltages o o o o across the coils S. The anode is of the Controller of H.Si. Stationery Office, from Specifications TELEVISION AMPLIFIERS back- coupled to the screening grid obtainable at the Patent Office, 25, Southampton Buildings, London, TN a television receiver it is ne- through a condenser Cx, whereby W.C.2, price 1 - each. A selection of patents issued in U.S.A. is t cessary to amplify a wide the impulses are made to react on also included. band of frequencies, extending their own generation in such a

www.americanradiohistory.com THE PRACTICAL RADIO JOURNAL 27 rh Year of Publication

FRIDAY, AUGUST 6TH, 1937. VOL. XLI. No. 6.

Proprietors : ILIFFE & SONS LTD. Editor : EDITORIAL COMMENT HUGH S. POCOCK.

Editorial, the value of sound broadcasts, excellent Advertising and Publishing Offices : Television DORSET HOUSE, STAMFORD STREET, propaganda for television would be LONDON, S.E.I. Programme Problems provided by letting the listening public know Telephone: Waterloo 3333 (5o lines). that certain items they were Telegrams: "Ethaworld, Sedist, London." T was quite natural that because listening to were at the same time being of technical as well as general COVENTRY : Hertford Street. seen by those who had television Telegrams: Telephone: considerations the studios for receivers. " Autocar, Coventry." 52ro Coventry. television were established in the We do not suggest that the time is closest possible proximity to the BIRMINGHAM : trans- yet ripe for a complete change -over Guildhall Buildings, Navigation Street, 2. mitter itself. There was not much which would bring the whole of the Telegrams : Telephone: choice in the selection of a site for the "Autopress, Birmingham." 297í Midland (4 lines). television programme arrangements transmitter to serve the London area into the same fold as sound broad- MANCHESTER : 260, Deansgate, 3. and experience seems to prove that the Telegrams: Telephone: casting, but we do strongly recommend "Rife, Manchester." Blackfriars 4412 (4 lines). present site of the Alexandra Palace that this arrangement for the future was a most happy, one. When ance, : should not be lost sight of, and the GLASGOW 26a, Renfield Street, C.2. then, it was settled that the studios had Telegrams : " Iliffe, Glasgow." Telephone: Central 4857. longer an independent television organi- to be located with the transmitter, PUBLISHED WEEKLY. ENTERED AS SECOND - sation continues without close linking CLASS MATTER AT NEW YORK, N.Y. it was natural that an independent with the sound side, the more difficult television programme organisation will it be to bring them together when Subscription Rates : should be set up. Home, Li is. 8d. ; Canada, LI Is. 8d. ; other the proper time arrives. If arrange- countries, LI 3s. rod. per annum. It is common knowledge that it is ments were made now for occasional proving very costly to find the material As n,anv of the circuits and apparatus described in these sound broadcasts to be televised at pages are covered by patents, readers are advised, before for the television programmes, and the same time, experience would be making use of them, to satisfy themselves that they would a not be infringing patents. unless great deal more money be- gained without risk of disorganising comes available for expenditure in this either arrangement and the way would direction, it seems doubtful whether it be prepared for a combination in the will be possible to effect any substantial future which it seems certain would CONTENTS improvement in the programme stan- effect substantial economies, whilst at dard. Page the same time giving to viewers a very much better service than they can Editorial Comment 111 Location No Longer Fixed Studio expect so long as television is left Oscillators . . for Circuit Alignment 112 We suggest that now that television alone to stand on its own feet Television- Scanning and Syn- cables have been devised and television chronising .. 115 is no longer tied to a local studio a Notes and News .. 118 serious effort should be made to see German Radio of the material, AVC in PA Equipment.. 119 how far some especially Television Progress Listeners' Guide for the Week 120 of the variety type, at present used in the sound studios of ordinary broad- THE, annual Radio Show in Berlin Unbiased 122 casting, could be made available at is now open and is, perhaps, Peto -Scott Television Receiver 123 the same time for television. For more than ever a National affair Principal Broadcasting Stations. . 124 television to make ' progress on the this year. Television occupies an Ratings 126 programme side it would seem that it important section, and the progress more linked in Cossor Cathode -Ray Oscilloscope .. . 127 ought to be closely the made brings German television into Broadcast Brevities 128 future with the widely experienced and close competition with our own for first organised programme departments of place in the world. On the Short Waves 129 the sound side. There is much of the Arrangements have been made for Random Radiations 130 present sound broadcasting material our readers to have a full report on Letters to the Editor 131 which could be well illustrated by the new features of technical interest Recent Inventions 132 television and, without detracting from exhibited in a forthcoming issue.

www.americanradiohistory.com 112 Wireless World, August 6th, 1937. Oscillators for Circuit

Frequency Modulated APPARATUS for use in the adjustment of tuned circuits is becoming increasingly important as receivers grow in complexity. Test Equipment In this article, oscillator circuits are described which are suitable for use with the cathode -ray tube for the visual depiction of resonance Employing the CR curves. of real use the frequency f must be band of frequencies approaches the value Tube capable of adjustment over a large range. of f, while the other band recedes from Further consideration will make it clear it. The separation between the bands in that a Liven change of capacity or induct- Fig. i remains constant at 40 Mc /s, so ance Nkill provide a value of m which is that filtering of the unwanted band does THE rise of popularity of the dependent upon the adjustment of f; hence not become more difficult for other values superheterodyne receiver during it is necessary to use a beat -frequency of f ". the last five years has brought oscillator and to modulate the fixed fre- The filtering out of the frequency f from to the fore the question of accu- quency circuit. the output of the oscillator is rendered rate alignment of the tuned circuits. A If f is the mean frequency of the fixed relatively easy if f is made considerably frequency modulated oscillator in con- oscillator, f -m and f + m the limits of higher than the highest required value of junction with a cathode-ray oscillograph frequency excursion, and f' the frequency f". Thus, for a maximum value of enables the accuracy and rapidity ad- of of the variable oscillator, the output of f" equal to 15 Mc /s f might be chosen justment of to be these circuits greatly in- the mixer will contain, amongst other fre- to be 3o Mc /s. In this case f' must be creased. quencies, the bands of frequencies ex- variable between the limits 45 and 30.15 If an oscillator having a constant tending from f' +(f -m) to f' +(f +m) Mc / s to provide values of f" over the amplitude over a small frequency range and f'- (f -m) to f'- (f +m). Fig. 1 range of 0.15 Mc /s (2,000 metres) and is adapted so that the output frequency shows these frequencies in diagrammatic 15 Mc / s (2o metres). may be continuously varied over this form. In order to make the diagram more range, it provides a suitable source of easy to understand actual frequency Frequency Modulated Oscillator potential for aligning, or testing the align- values have been given in the diagram, ment of, radio receivers. Such an oscil- and the wanted carrier frequency has Several methods of modulating the fre- lator will supply an output frequency f ". The relatively great been designated quency of the fixed, _varying continuously from f -m to f + m, between these frequency oscillator portion of separation a beat-frequency where f is any selected carrier frequency easy to separate out the oscillator have been bands makes it designed. The earliest method and m has a predetermined value, usually lower band which is required for use. It was a mechanical one, in which the tuning 15 kc / s per second. The output fre- will be noticed that as f' is varied one con- quency is made to vary from f -m to denser was arranged to be of such a value f + m in a linear manner with respect to as to produce the required frequency time, and the cathode -ray tube, which is change when the capacity was varied used as an indicating device, is arranged from the minimum to the maximum value. to have the spot deflected linearly in a 41'015 This condenser was coupled to an electric UPPER horizontal direction and in synchronism 41 SIDEBAND motor so that it was rotated a few times with the change of frequency. In this 40'985 a second. On the same shaft was way the instantaneous horizontal position mounted the contact arm of a robust of the cathode -ray spot indicates the in- potentiometer. A DC potential was con- stantaneous value of the frequency of the nected across the potentiometer, and as oscillator. the arm rotated the potential between it and one end of the potentiometer in- Beat- frequency Oscillator creased in a linear manner. This varying potential was connected to the horizontal If the output of the oscillator is fed, deflectors of a cathode-ray tube, while via the receiver to be tested, on to the the resonant output of the oscillator was 21 vertical deflecting system of the cathode - fed, via the receiver to be tested, on to ray tube the spot will move vertically in 20 the vertical deflectors of he cathode-ray proportion to the receiver output, which tube. Such a system is fundamentally depends upon the receiver characteristic satisfactory, but suffers from all the in- and upon the instantaneous value of the herent disadvantages of most mechanical frequency. A visual response curve will devices in that it is noisy, bulky, and re- therefore appear upon the screen. Since quires frequent attention in the way of the response curve is visible as a whole, oiling and cleaning if it is to give con- and since it is repeated several times a sistently good results during a long period of service. second, it becomes an easy matter to f'-(f-m) 1'015 of the circuits until the A later development in which the adjust the tuning f"= f'- 10 LOWER most favourable curve is depicted on the SIDE BA ND mechanical method of frequency modula- fluorescent screen of the cathode -ray tube. f'-(f + 'TO 0'985 tion is replaced by an electrical method Moreover, such an adjustment may be employs a magnetic means of controlling made much more rapidly and with the modulation. The tuned circuit of greater accuracy than is possible with an Fig. 1. -The fixed -frequency oscillator has the fixed- frequency oscillator has a fixed ordinary signal generator. the frequency f and is modulated so that it capacity and a variable inductance. The varies between f -{- m and f - m. When It will at once be obvious that if such mixed with the frequency f' the groups of inductance is wound on an iron core and a frequency modulated oscillator is to be frequencies shown occur. includes ah additional winding; by vary-

www.americanradiohistory.com Wireless World, August 61h, 1937. 113

RF and IF circuits are usually aligned in conjunction with the rectifier with By which they are to be used, since in this way the tuning of the circuits is not modi- O. S. PUCKLE fied by the testing apparatus. In the case Alignment of receivers having a large audio output the use of the amplifier V6 is unnecessary, in; the current through the extra winding which deflects the cathode -ray beam in and the receiver may be coupled directly the magnetic flux is altered, with a re- a horizontal direction. The variations in to the vertical deflector of the cathode - sultant change in the value cf the tuning the DC current in the transformer cause ray tube. inductance. The method employed is changes in the value of the inductance of A more recent method of modulating shown in Fig. 2. the secondary winding and hence produce the frequency of an oscillator valve makes The valve VI is a gas -discharge triode a variation in the frequency generated by use of the Miller effect. The capacity arranged to discharge the condenser Cr the valve V3. between grid and earth of a valve is equal after it has been charged via the resist- The valve V4 is the variable oscillator, to mC , where m is the gain of the ance Ri. The condensers C2 and C3 form and the outputs of both oscillators are fed stage, and C is the total anode -grid a potentiometer and are arranged to apply to the mixer valve V5, the anode of which capacity of a valve having a resistive

+ 1,000V

240V

m.C2

TO RECEIVER UNDER TEST

FROM RECEIVER UNDER TEST

CRO

Fig. 2. ---The complete circuit of a frequency -modulated oscillator is shown here. The oscillator frequency is varied by means of the iron - cored coil T.

a portion of the time -base sweep voltage is tuned to the beat frequency. The out- anode load. By causing the mutual con- on to the grid of the modulating valve put of the mixer is .fed to the receiver ductance or slope of the valve to vary in V2 so that the primary winding of the under test, and the output of the receiver accordance with the time -base deflection, transformer Ti has a direct current flow- is normally fed, via an amplifying valve the capacity as measured between grid ing through it proportional to, and in V6, to a vertical deflector of the cathode - and earth will be caused to vary in the synchronism with, the time -base potential ray oscillograph. same way. Fig. 3 shows the circuit

www.americanradiohistory.com 174 WpYdsog `AUGUST 6th, 1937. Wald. Oscillators for Circuit Alignment - receivers has been greatly improved in arrangements adopted in this case. recent years, largely due to the use of With this circuit VI behaves exactly as efficient ganging oscillators. in Fig. 2, but the potentiometer C2 C3 is . Another form of ganging oscillator in arranged to alter the bias and hence the which the carrier frequency is modulated slope of the valve V2. As a result of from zero to maximum amplitude in an this the capacity across the coil Li, which extremely short period of time has been is equal to m[C,o +C4], is varied, result- employed for aligning the circuits of tele- ing in modulation of the frequency gener- vision receivers. This form of oscillator ated by the valve V3. The remainder of generates the wave form shown in Fig. 4, the circuit is exactly as shown in Fig. 2. but is not a frequency modulated gener- A test signal consisting of a varying fre- ator, so that it does not come within the quency as generated by the apparatus scope of this article. It is mentioned as described in this article is only satisfac- being of great interest in that it is another tory provided the rate of change of fre- form of apparatus intended for circuit quency is extremely slow; that this is so alignment.

1000 V

A chef tells listeners of the means adopted by a leading restaurant to prevent waste in 240 V the kitchens. at theatres, are kept for the next day. A certain stock of topical recordings is always available to fill in gaps on uneventful days. For instance, a record dealing with the deed- =C1 W. C2 ing of the swans can be easily broadcast on any day of the week, whereas, of course, the important visitor must " go over " as TO V1 V3 MIXER soon as possible. Use of Tape Recordings These Echo broadcasts do not deal with political events. They are intended to de- 3 scribe happenings in the region which C would not normally appear in the actual news bulletins, but which, when actually picked up on the spot, gain radio interest. From a technical point of view, quality is good. The records are made on pliable *TO DEFLECTOR OF C R discs of a particular material manufactured specially for the German broadcasting corn - Fig. 3. -In this circuit the oscillator frequency is variable by means of the input capacity of the pany. Records of very important happen- valve V2. ings are made on wax as well. Recent recordings on 16 mm. film and, in certain will be appreciated when it is remembered cases, on steel tape have also been employed. The steel -tape method enables re- that an increase in the rate of frequency Berlin's Daily Echoes cordings to be made in trains and motor modulation increases the band -width cars while actually in motion. occupied by the signal. The permissible Broadcasts of Recorded Reports rate of modulation is dependent upon the THE " Echo of the Day " is a twice - Q value of the circuits under test; the daily feature of the Berlin station's higher the value of Q the lower must be programmes. Echo at noon and the rate of modulation employed. Under Echo at night, two brief 15 -20- minute normal conditions twenty -five sweeps per programmes, each contain equally brief second is not unduly high, but this value accounts of the day's more important hap- should never be exceeded, and where penings, which range from the arrival of especially good coils are being tested the some famous visitor at the station to the repetition rate should be reduced to ten fact that the town of Berlin has decided to or twelve times per second. feed starving swans on the frozen stretches of canal which run through the town. A staff of trained reporters, all free- lances, is at the disposal of the station. Procedure is simple. A recording car sets out in the morning and works round the town and outlying districts according to a prearranged schedule. The car and its en- '--EXTREMELY SHORT TIME gineers meet a different reporter at each point. It returns at noon with the finished Fig. 4. -A type of modulation used in tele- records, which are edited and then broad- vision test oscillators. cast in the midday news bulletin. Then, according to a schedule which has been These ganging oscillators are, of course, drawn up in the morning, as news of events arrives the car sets out on the afternoon equally suitable for ordinary tuned cir- tour, which often lasts until late at night. cuits, whether staggered or not, and also Records which are required for the evening for band -pass circuits. They may also " Echo " are sent to the broadcasting head- be used for testing filters. quarters by a special messenger, and the The wandering microphone ascertaining the The performance of superheterodyne late evening records, mostly of first nights views of an important visitor.

www.americanradiohistory.com Wireless World, August 6th, 1937

Television SCANNING AND

SYNCHRON 151 NG THE attainment of good synchronising has been lone of the major obstacles which has had to be overcome in the development of television. Finality of design has DETAILS OF A SYNC SEPARATOR not yet been reached, and in this article a system AND PULSE =SHAPING CIRCUIT is described for which unusually good stability of synchronisation is claimed. By PAUL D. TYERS

TELEVISION receiver can operate slow or too fast. Strong electrical interfer- distinct advantages, since variation in con- . with either a driven or self -run- ence was found in many cases to upset the stants in the set itself which might change ning time -base. A driven time - synchronising adjustment, whilst variation the output, such as line voltage variation, base is one in which the saw - in carrier strength or sensitivity of the ageing of valves, day-to -day or hour -to- tooth generators are entirely controlled by receiver would have a similar effect. hour carrier change, would have no effect the transmitter. In a self- running time - An attempt was therefore made to pro- upon the synchronising impulse. More - base the voltages are generated at approxi- duce a scanning and synchronising ever, it was obvious that if the impulse mately the correct frequencies and a fine system, which had a very high inherent were of constant magnitude, it would be degree of control is imparted by the syn- degree of stability in so far as changes of far easier to bring about constant or stable chronising impulse derived from the trans- constants in the time -base circuits, varia- operating conditions in the time -base itself. mitter. It is generally held that the tion in output, and peak voltages due to The first requirement, therefore, appeared driven time -base is not so satisfactory as electrical interference were concerned. An to be some form of synchronising separa- a self- running unit, although the writer attempt was also made to develop a system tor which would give an output entirely cannot recall having seen any direct proof in which the inherent stability was so great free from picture content and be reason- that there was no need to provide manual ably insensible of carrier variation. The adjustments for the line and frame speed. advisability of maintaining as nearly per- } M T Moreover, an attempt was made to obtain fect as possible the wave front of the syn- these results by utilising a single gas -triode chronising impulse was also borne in mind. as the time -base relay. It was realised, too, that the synchronis- The problem appeared to divide itself ing separator had to operate from the line into two distinct issues. In the first place impulse, which always starts at constant it seemed necessary to provide in some way level, and also the frame impulse, which or other a reasonably constant synchronis- may commence from any level. An ing impulse or, rather, a constant voltage arrangement which, therefore, appeared applied to the time -base derived from the suitable was a DC coupled biased diode.

Fig. 1. The circuit of the sync separator is shown here. of this assertion. In the case- of a self - running time -base it is also generally held that the most satisfactory conditions of operation are those in which a very weak synchronising voltage is applied to the control element of the saw -tooth generators. After experimenting with most known types of synchronising circuits and self - running time -bases, it was thought that considerable room for improvement still existed. The normal time -base under a weak controlling impulse needs critical adjustment. If the natural frequency is wrong, the picture breaks up into small in the line direction, and it is Fig. 2. The connections of the sync separator to the vision- frequency amplifier are best mada elements across the coupling resistance only. almost impossible to see whether it is too fast or too slow. When the frame speed is synchronising pulse, which was not wholly The basic connection is shown in Fig. i, in wrong a roller-blind effect is obtained, and dependent upon the absolute output of the which it will be noted that the diode -anode it is not easy to determine whether it is too receiver. It appeared that this would have circuit contains a load resistance which is

www.americanradiohistory.com WilTe® AUGUST 6th, 1937. W©i ll al Television Scanning and Synchronising - diode itself has a certain capacity, of the put from the separating diode if the cath- returned to the slider of a potentiometer order of a few micro -microfarads, and the ode is taken to a low enough value on the connected across the HT line. The cathode effect of this capacity will be determined voltage gradient. It should be very ob- is taken to the anode of a VF stage. By by the load resistance in the diode -anode vious that this arrangement alone is not varying the slider on the potentiometer it circuit. It would seem advisable, there- satisfying one of the essential conditions - is possible to make the diode conduct at fore, to use a very high load so that the that is, a synchronising impulse of con- effective capacity is reduced to a mini -. stant magnitude. This difficulty is there- mum. Unfortunately, however, liberties fore overcome in the following manner : cannot be taken with the coupling circuit A gas -relay time -base requires a positive from the diode separator, as there is a voltage to trip the relay, and it is obvious great risk of losing the straight front of the that the synchronising impulse derived synchronising impulse, and a compromise from the diode separator is the wrong direc- value is necessary. Fig. 3 shows schematic- tion, and, accordingly, phase -reversal ally the conductive conditions of the means must be included. One can use a separating diode with the voltage gradient transformer or a phase -reversal valve. marked against the cathode and anode load of the diode. It is very easy to see The Pulse- shaping Circuit that a constant output will not be obtained from this arrangement if certain changes Instead of amplifying the pulse with a occur. In the first place, if the line volt- phase-reversal valve in the normal manner, age varies, the voltage applied to the diode the valve is arranged so that it functions as anode will v4ry, which means that the a limiter. It is obvious that the output from diode will not conduct at the same in- the separating diode is not likely to vary stant as it did before the variation over a very wide range, and, accordingly, occurred. Similarly, if the output of the it is only necessary to amplify a portion receiver varies, similar trouble will occur. of the impulse. For example, if four volts This means that the arrangement does not were normally delivered from the diode it necessarily give a synchronising impulse could be arranged to use only two volts of constant value. Provided the cathode by applying the output to an amplifying connection to the diode is taken low valve with a short grid-base and a sharp enough on the voltage gradient, there can cut -off. Whatever variation occurred from be no possible chance of its conducting in the diode output the phase -reversal am- Fig. 3. The action of the sync separator is the picture zone, unless tremendous varia- plifying valve would then deliver a sub- easily understood from this diagram which tion in output occurs of such shows the voltages on the anode of the VF magnitude stantially constant voltage. valve for black, white, and during the sync that the picture value would be useless. It is obviously preferable from every pulse. Most electrical interference gives a posi- point of view to use a DC coupled amplifier, tive peak, but interference which gives any point between full white and full a and this can be arranged quite conveni- small negative peak will produce no out- ently, but black. So long as the potential of the tests have shown that a resist- diode cathode is greater than the anode potential the valve cannot conduct. The instantaneous DC voltage on the anode of the VF stage is a well- defined quantity. At full white the anode voltage might be 220 volts. At black level it might be Zoo volts, and at " blacker than black " 190 volts. If the potentiometer is adjusted so that the anode and cathode voltages are substantially equal at black level, the diode will conduct at the corn - mencement of the synchronising impulse, as the anode voltage will then be higher than that of the cathode, and a voltage , will be developed across the load circuit. Such an adjustment would necessitate very constant operating conditions of the receiver. Accordingly, the diode is arranged so that it conducts, not at the black level, but at an appreciable distance into thé " blacker -than-black'-' zone. Theoretically, this should have no effect upon the synchronising impulse because it is straight- fronted, and a pulse, therefore, commences at the same instant irrespective of the point at which the diode conducts. Fig. 2 shows the actual connection employed. The diode cathode is connected not to the anode but to the junction of the resistance and the correction inductance in the VF stage. A small capacity exists PULSE DELIVERED BY PULSE APPLIED TO SHAPING between thé cathode and the heater, and it SEPARATION DIODE PHASE REVERSAL VALVE is very important to remove this from the correction inductance,' as otherwise a 4. The output of the resonant circuit might be Fig. sync separator consists only of the sync pulses, but these may not be of produced which constant amplitude. They are accordingly applied-4o a valve having a double -bend in its char- would cause phase trouble. Similarly, the acteristic.

www.americanradiohistory.com AUGUST 6th, 1937. Vrp@R@ogi 1117 WoT 11d Television- Scanning and Synchronising - Fig. 5. Condenser and resistance values ance- capacity coupling from the separat- are so adjusted that the critical voltage V2 ing diode proves entirely satisfactory in at which the tube will ignite occurs at a practice. The circuit diagram is shown time T2, and the time-base is normally in Fig. 4, and such an arrangement adjusted so that V2 is reached round about delivers a substantially constant syn- the time Tz, the exact firing being brought chronising impulse free from variation in about by the synchronising impulse. line voltage or output of the set. The During a charging cycle, at a time Tr, the stability of the phase- reversal valve is in- anode voltage VI is removed from the criti- creased by utilising a screen -grid valve cal zone, and, accordingly, if the tube operating at low voltage, and under such were to fire at that point it would not be V2 conditions slight variation in line volt- particularly susceptible to slight change in Va age has substantially no effect upon the anode voltage, because the change which output of this valve. might occur would still be beyond the Although a constant synchronising im- critical zone. Properties of representative pulse has now been obtained, it is still gas relays, and particularly the modern to find, if possible, some means helium -filled type, are such that it is quite W necessary S for rendering the time-base more stable easy to make the tube fire at a time Ti z T T2 and less susceptible to valve variation or if a suitable bias is applied to the grid. . TIME voltage fluctuation. A gas relay has the The application of a somewhat stronger -.- property of igniting at a critical anode volt- positive bias than usual at a time Tr will age. A gas relay, however, is, in effect, cause the tube to fire. As, however, the Fig. 5. When a condenser is charged accordingly, the tube con- tube is not in a critical condition at a time through a resistance the voltage rises in the a triode, and, way shown in the curve. stants are a function of the grid voltage. Tr, it is quite possible to make very large The normal method of operation is to changes in the actual anode voltage and just sufficient to cause the valve to fire at the required point. It is therefore in no way comparable in action with what has previously been termed a strong synchronising impulse. The magnitude of this voltage is just as critical and, in effect, as weak as that normally applied when the anode voltage is in the critical zone. Now, the circuit shown in Fig. 4 is known to give an extremely constant output irrespective of operating conditions. The necessary high magnitude but relatively weak synchronising impulse is, therefore, easily maintained. Some very interesting effects will be observed with this arrangement. It has been found possible to detune the receiver or lower the sensitivity to such an extent that the picture. is hardly visible on the screen, synchronism is perfectly main- This photograph clearly shows the pairing of lines which is brought about by incorrect adjustment but the of the time -base. tained, which is adequate proof that the system is operating according to the theory arrange the circuit so that the running also cathode emission without upsetting its advanced. It has also been found possible speed of the relay is substantially correct, functioning to any extent whatever. to forget the existence of any line or frame when only a minute change in grid volt- Now, the output of the limit phase -re- adjustments, and the receiver has been age is necessary to make the tube ignite. versal valve is entirely suitable for pro- found to give constant operation for in way touching these It is very obvious that a system which viding such a voltage. It is very important months without any functions by virtue of a critical anode to realise that, whilst this voltage is of controls. Moreover, it has been found voltage (and actually cathode emission) is comparatively high magnitude, it does not possible to substitute one gas -relay for one which is inherently unstable. 'It was represent strong synchronising impulses another both in the line and frame posi- for this. reason that the gas relay fell into because the voltage is such that it is only tion when the set is in operation, and disfavour and the squegging type of hard valve time -base became popular. The Sync Pulse and the Time -Base Tests carried out with a number of some representative gas -relays revealed .,.0....,.0110. 4.144.- ..r011.o..-.r interesting properties. Suggestions have .MSr...... -.4.'. +01101011111 .w ,.r0.. .a... IINONOIMPOOM.. previously been made for using a very ...-...-- .00000- .411.1100.1111101111. .a...... 1111rr.11ra. strong synchronising impulse, but the .4.rvI1MM magnitude of the impulse applied to the .,.... -.111111111110. ...1101.-,111111111111 grid seems to affect the fly -back time, .11011111111w .411i11/11 Ammo. .1.114..-rMr.41111i.r00111.1.11. whilst a strong pulse generally results in ..r..- .0.11..rlwrr ,41.r...rOM4r.. vamp. O...... the amplification of noise and possible in- .... -.4..., .nwl.. «411... .111, 4- ,+0.0. ,..e,r,11r. +11r...... 44. .1110. terference, and, accordingly, it seems that .Ilr1.-..1111A11M4 ..wM ,4.rrllMl.. ..r..k AIM* .1.40. .,..F .011..Ls M1Mb.- .11INMIN.1.1., .L» . 1,.,. .... such an arrangement is somewhat prone to Mar be upset by interference. The voltage/time curve of a typical gas relay circuit associated with a condenser charged through a resistance is shown in With correct interlacing the lines are all evenly spaced from one another.

www.americanradiohistory.com 178 WAr,s11@gg AUGUST 6th, 1937. WorDd Television -Scanning and Synchronising - interlace. One illustration shows an in- merits. Accordingly, if controls are pro- also to do this without in any way upset- correct adjustment giving'' a paired inter- vided for line and frame' adjustment, ting the interlace. lace," whilst the other shows a perfect operation is very easy because the ap- For some reason or bother, the merits interlace. These photographs were taken proximate form of the picture is never lost. of a scanning or synchronising system with a time exposure lasting for a matter This effect is due to the fact that the free seem to be immediately interpreted in of about 15 seconds. The sharp definition running speed of the time-base is lower

terms of its ability to maintain a stable of the lines or gaps between them indicates than the ignition speed. . interlace. The production of a stable inter- that the system has a high degree of sta- After comparing the system outlined lace in the writer's opinion is wrapped bility. The synchronising impulses are with more conventional arrangements, and

up chiefly with the maintenance of the developed across the anode load of the . after intentionally applying similar elec- wave front of the pulse, and adequate reversal valve shown in Fig. 4, and they trical interference to receivers operating separation. of the two time -base elements therefore appear to be suitable for appli- on standard lines and those on the system and an application circuit which ensures cation to any type of time -base through described, the writer is firmly convinced that there is no possibility of the frame any ordinary separating circuit. The ap- that the degree of stability and ease of relay being tripped by the line pulse. It plication network employed and means for handling is from every point of view a is very obvious that if the system used separating the line and frame impulses decided advance upon that of standard gives a synchronising impulse of exceed- appears to be one of individual taste. The technique. ingly constant magnitude, interlacing photographs shown were taken with the Through the co- operation of a Wireless should be simplified, and the system de- very simplest resistance -capacity filter for World reader, Mr. S. West, of Ipswich, the veloped, therefore, seems to be particu- line and frame pulse separation, which writer was afforded an opportunity of larly suitable for this purpose. In fact, seem to indicate that nothing very elabor- having the system tested at a distance of the control which it affords can be ad- ate is necessary. some seventy miles from Alexandra Palace justed to such a nicety that by alteration Finally, it should be observed that, where the field strength is very small and of the constants of the application net- should the line and frame speed of the the signal -to -noise ratio is low. It is re- work the phase of the frame impulse can time -bases be totally incorrect, or should ported that perfect synchronism is main- be varied. there be something wrong with the mag- tained at all times, and even during heavy nitude of the applied pulse, the screen interference, where, in the locality con- The Performance of the System effect is totally different from that given by cerned, more conventional methods have an ordinary synchronising circuit. In the given considerable difficulty. That this The two illustrations show that the frame direction there is no " roller -blind " should be the case seems very obvious frame impulse derived by this system is effect, the picture either completely fold- from consideration of the principle in- under very definite control. The photo- ing up or else " blinking " with a single volved, and the conclusions advanced graphs are enlargements from an opened fly -back apparent. In the line direction have only been arrived at after investiga- scan, which, in the writer's opinion, is the the same folding effect is obtained, and tion extending over a period of some only satisfactory method of examining an the lines never break up into jumbled ele- twelve months.

EVENTS OF Notes and News THE WEEK IN Misuse of Broadcasting the organisation of wireless and BRIEF REVIEW OUR B.B.C. is not alone in meteorological services in con - having to meet criticism for nection with transatlantic flights. every indiscretion before the The successful transatlantic microphone. A lady speaker in flights recently carried out have Loud Speakers in Warfare France recently exhorted her provided useful experience to IT is reported that in the Spanish listeners to keep in the fresh air assist in planning the necessary civil war public address equip- as much as possible during sum- organisation for the future. ment is now being used on both mer holidays and to avoid shut- sides in some areas for the pur- ting themselves up in " dusty Cossor Chief's Death pose of spreading political propa- cinema halls." A strong protest WE regret to record the death ganda. The propaganda takes the was at once made by the French on July 27th of Mr. W. R. form of endeavouring to persuade Union of Cinema Managers, who Bullimore, managing director of regarded this as damaging to their the opposite side that their case is A. C. Cossor, Ltd., and one of the The late Mr. W. R. Bullimore. hopeless and that their opponents interests. most esteemed personalities in the are everywhere victorious. radio industry. Turkish Radio Nationalised Mr. Bullimore joined the firm, Request for Wireless Museum Good Programmes Best ALL wireless and broadcasting in which he later acquired a con- Exhibits. Propaganda services in Turkey are likely trolling interest, thirty years ago. THE broadcasting authorities in to come under complete Govern- He was a pioneer in the manu- READERS of The Wireless 1 Germany have recently made ment control if proposals at facture of cathode -ray tubes, and World who may possess early 'a public declaration that the best present before the Government later produced the Cossor range examples of wireless apparatus, or propaganda for the State is good are made law. Efforts are being of valves, the popularity of which any other material suitable for programmes, cheap receivers, and made to increase the popularity enabled the firm to grow to be one illustrating the progress of wireless reception free from interference. of broadcast reception, and to this of the largest radio manufacturing from the earliest days, are invited transmissions, it was added, end it is proposed that there concerns. to assist the Exhibition Organ- The s e r s, Manufacturers' should be devoted in the main to should be no duty on imported Radio wireless receivers Association, Astor Hoùse, Ald- provide relaxation after the day's until the Turkish Sound Recording wych, W.C.2, who are planning a work. radio industry is in a position to A SERIES of visits has been manufacture sufficient sets for the wireless museum as a special fea- 11. arranged by the recently ture of the forthcoming Radio Eiffel Tower Television country on its own account. formed British Sound Recording Show at Olympia. AN interruption in the television Association, which will include a Any reader having " museum service from the Eiffel Tower Air Service Wireless tour of the B.B.C. Recording De- specimens " which he is prepared occurred recently, in order that REPRESENTATIVES from the partments at Broadcasting House to loan for this purpose should certain essential work could be British Air Ministry and the and at Maida Vale. first write to the organisers, indi- undertaken. Post Office, American Airways Information concerning the As- cating what he has available. Transmissions have now been re- and Imperial Airways, and various sociation can be obtained from Arrangements will be made to col- sumed, with sound on 206 metres Irish Departments concerned, held the Hon. Secretary, J. F. Butter- lect items selected and insure and vision on approximately 7 a Conference in Dublin recently field, 44, Valley Road, Shortlands, them. Write at once because metres as before. to continue the examination of Kent. there is very little time left.

www.americanradiohistory.com Wireless World, August 6th, 1937 119 AVC in PA Equipment ONE difficulty which often occurs in OBTAINING CONSTANT VOLUME LEVEL public address work lies in the variations in volume caused by movements of the speaker. He is usually The important part of the circuit is When the switch is in the upper position addressing a visible audience, and he shown in Fig. 1, and it will be seen that the connections to the diode are reversed naturally moves about to face different the scheme depends upon the use of a 6L7 and it consequently biases the 6L7 grid parts of the assembly in turn. The pick- valve as an AF amplifier. The full output positively and increases the gain with in- up of the microphone consequently varies of the first valve shown is applied to it, creasing signal strength, giving volume over quite a wide range, and an operator and a portion of the voltage only to an expansion. The third pole of the switch is required at the master gain control to RF pentode amplifier, which also has a then applies an initial negative bias to the bring up the amplification when he moves potentiometer in its grid circuit so that its injector grid, so that with a small signal away from the microphone and to reduce input can be precisely adjusted. The out- the gain is very small. it when he comes near it. It is, however, put of this valve is applied to one pair of The system is an attractive one on possible for this function to be performed electrodes of the 6H6 diode. account of its simplicity, but there is un- automatically by a type of AVC circuit. When the switch is in the lower position doubtedly some danger of amplitude dis- There are various possible arrangements no bias is applied to the diode, and it recti- tortion occurring in the 6L7, and careful adjustment of the operating conditions is likely to be necessary to reduce it to a minimum. In particular, it is important that the circuit should not be operated at too high a signal level, and in general the 6L7 should be followed by an AF stage and not directly by the output valve.

The Radio Industry P1111.00 RADIO has extended the technical training scheme for Service -men that was originated in October, 1934. Instruction is still by correspondence. . o Ferranti, Ltd., Radio Works, Moston, Man- chester, to, have issued a booklet describing at length the theory, construction and properties of electrolytic condensers. The publication is primarily intended for engineers and de- signers, but others may obtain copies at is. 6d., post free. O G O Gordon Equipments, Ltd., 25, Milton Street, London, E.C.2, have sent us a leaflet describing battery chargers of various types. An unusual feature of the chargers is That current is controlled, not by rheostat in the usual manner, but by changing tappings on the transformer.

The Supreme. Instruments Corporation of Greenwood, Mississippi, U.S.A., announces several new instruments, including a set- tester, an analyser and miniature cathode -ray oscillo- scopes with sin. tubes. The British agent is J. Toubkin, Faraday bouse, Todd Street, Man- chester, 3. - <> 0 Fig. i. -The circuit of the AVC system is shown here; it operates with the switch in the We are informed that The Tungsram Electric lower position. With the switch in the upper position the circuit functions as an automatic Lamp Works (Great Britain), Ltd., of 72, volume expander. Oxford Street, London, W.1, have a depart - ment devoted entirely to technical service on high power output and transmitting valves, and actually any compandor circuit will fies the AF output of the 6J7 and produces A folder of circuits dealing with AF power function. Such circuits are the reverse of a voltage across its load resistance which is amplifiers may be obtained on application to automatic volume expanders, and are proportional to the average value of the this firm. sometimes termed automatic volume corn- AF output. This voltage is applied 0 O O pressors. One arrangement which is de- through a simple filter to the injector grid Sound reinforcement equipment for the main in the July, 1937, issue of Elec- of the 6L7 and it it lecture hall at Leeds Training College has scribed biases negatively to recently been installed by Trix Electrical Co., tronics is particularly interesting in that it reduce the gain. Ltd. is possible to change from compression to The time- constant of the circuit is made expansion merely by means of a triple -pole high so that it does not operate on the The Performing Right Society announce that double -throw switch. Compression is used normal volume fluctuations of the voice during the past quarter thirty-eight composers on speech and expansion for the reproduc- but only and authors were elected to membership. after an appreciable fraction of a The tot-di membership of the Society is now tion of records. second. I,530-

www.americanradiohistory.com T20 Wireless World, .4ogust 6th, r,137

HE outstanding and, certainly as far as time is concérned, the predominating feature of the week's programmes is the relays from the Queen's Listeners" Guide for Hall of the Promenade Con- items of the programme will SMALL BEGINNINGS tures of London introduced in certs. The forty-third season also be heard from 9.45 A NEW series of talks en- the programmes. (the eleventh under the aus- (Reg.), the penultimate item titled ' ` I Saw the Start " will On Wednesday at '10.5 pices of the B.B.C.) opens on being Sibelius's Seventh Sym- begin in the National pro- (Reg.) comes a mosaic of words Saturday evening at 8.o, with phony. gramme on Tuesday at io. and music on the Thames. A Sir Henry Wood on the ros- During the Elgar concert, This series will bring to the dramatic narrative featuring trum for the forty -third suc- part of which comes to microphone people, famous in Hyde Park, London's famous cessive year. During the week Regional listeners at 8 on Tues- various walks of life, who " lung," has been prepared by under review listeners will day, Beatrice Harrison will have been privileged to see Jonquil Antony and will come have about eight hours of play Elgar's 'cello concerto. " great oaks from little acorns to listeners on Thursday at io Prom. relays. It is proposed Bach night (Wednesday) pro- grow." The talk on Tuesday (Reg.). this season to give listeners more relays but not in the piece -meal fashion of last year. The programme on the opening night will be broadcast in full from 8 -9.40 and io-- HASTINGS FROM 10.40 (Nat.). The concert THE AIR showing opens with a the White Rock British work, Pavilion to the right John Ireland's " A London of the pier ent_ance, Overture." There will be one It will be from here novelty, a concerto for harp that Harry Pepper will close Thursday's and orchestra by Germaine " Round the Fol -de- Tailleferre, of which this will Rois " show, be the first concert performance in England, with Sidonie Goossens solo harpist. Ger- maine Tailleferre was a member of the group of young French composers known as vides an hour and a half's will be given by Robert Hale, CAR RADIO " Les six," and a work of programme from 8.35 (Nat.), who played the leading rôle in HARRY PEPPER is again to hers was played at the Proms concluding with the Fifth one of the first revues to be go on a hair -raising chase from two years ago. Included Brandenburg concerto. seen on the London stage. Eastbourne to Hastings dur- among the items of this Paul Beard, who this year This was " Everybody's Doing ing the composite Fol -de -Rois opening programme is César leads the S.B.C. Symphony It," which was produced in concert, which will be broad- Franck's " Variations Sym- Orchestra of 96 players in the 1912. cast Nationally at 8.3o on phoniques " for pianoforte place of Marie Wilson, who Later in the series Margaret Thursday. Last year's suc- and orchestra with Irene will be deputy leader, will be Bondfield, the trade unionist cessful broadcast of three dif- Sharrer as solo pianist. solo violinist in the Tchaikov- and ex- Minister of Labour, will ferent companies has inspired Part of Monday's Wagner sky concert on Thursday, speak of the Labour Party, Harry Pepper to attempt an concert will be heard from which will be relayed from 8- and Lord Baden -Powell will even bigger affair-linking 8 -9 (Nat.), which will include 9.33 (Reg.). He will be heard describe how in 1907 he organ- four companies. The pro- the prelude to " Lohengrin " playing Tchaikovsky's violin ised an experimental camp of gramme, which will run for 7o and the trial' songs from " Die concerto in D, which w ill 21 boys on Brownsea Island, minutes, will be broadcast Meistersinger." The last two precede the Fifth Symphony. and how from that has grown from Eastbourne, Llandudno, the Boy Scout Movement Sundown (Isle of Wight) and which to -day has about Hastings by the respective Fol- 3,000,000 members in 49 de -Rois concert parties at countries. these places. It is the sixth of the series of eleven concert party pro- LONDON grammes being broadcast IT has often been pointed throughout the summer from out that the London Regional the seaside. Harry Pepper transmitter is not used enough will open the broadcast from as a disseminator of " local " Eastbourne and then, while items, as are the other Regional other contributions are broad- stations. This accusation can- cast from Llandudno and San - not, however, be levelled at the down he will dash in a car to programme planners this week, Hastings, where it is hoped he for we are twice to have fea- will arrive in time to join in the programme. The car will be fitted with a receiver so that he can listen to the pro- ROBERT HALE with his son and grammes en route. daughter, Sonnie and Ginnie, Everything must be timed photographed during the first of to a split second for this gem the Star Gazing series. He will be of concert party broadcasts, the first speaker in the series of talks " I Saw the Start " which which will reach its climax in begins this week. a grand finale given by the

www.americanradiohistory.com Wireless World, Angus! 6th, 1937 Outstanding the Week Broadcasts

HIGHLIGHTS OF THE WEEK at. Home and Abroad FRIDAY, AUGUST 6th four parties from Eastbourne, Nat., 6.25, Jack Harris and his band. Llandudno, Sandown, and Hours Back. 9.40, 7.30, Five singing together. PROMENADERS : a musical pre- Hastings, Kaleidoscope will be visiting sentation. will made possible by the This be Queen's Hall in Reg., 8, Variety from the Grand the use of a portable receiver 8.40, The their thousands Theatre, Doncaster. at the side of each stage, en- during the next Evenin; Sing -song at the Duke of eight York's Camp, Southwold. abling the members of the con- weeks. This photograph w a s Abroad. cert party to follow what is taken from the Bucharest, 8.20, Puccini s " La being broadcast from the other entrance to All Bohême." (La Scala recording.) points. The whole programme Souls Church SATURDAY. AUGUST 7th. will be linked up from one which lies between Nat., 4.45, Commentary on the Br oadcasting Dublin Horse Show. 8, Opening dramatic control panel at House and the night of the Proms. Broadcasting House. At least Queen's Hall. Reg., 8," Music Hall,- including Ann twelve microphones will be Penn, Norman Long and Marie used, at each point Harry Burke. 9, " Whose Road ? " : a and discussion between a motorist, Pepper will have one assistant cyclist and pedestrian. and two O.B. engineers. Sonny Miller having left the Berlin portrayed in song and Abroad, Island. In the next musical dance. Leipzig, 7, Strauss concert by the picture Dresden Philharmonic. BUDAPEST of the South Seas, A concert of Scottish folk which will be given on SUNDAY, AUGUST 8th. TWICE during Sunday's pro- Tuesday songs will be heard from Bres- Nat., 6.45. May Blythe, soprano and grammes listeners will be trans- at 7 (Reg.) they return to the lau at 7 on Sunday in one of a the Menges String Sextet. 9.5, ported to this Hungarian town. Island in order to give listeners series of programmes "Songs " Evening in Budapest." At 7.2o (Reg.) we are to hear an idea of how the Islanders of the Nations. ". From Leip- Reg., 4, Rawicz and Landauer : greet returning friends zig 8 on will two pianos. 6.15, Violin re- Tzigane music 'relayed from and visi- at the same day tors, and the festivities come of cital : Samuel Kutcher. 720, Budapest, then at 9.5 (Nat.) which " Finland, Land a Tzigane music from Budapest. comes the revival of the short go on throughout the day of Thousand Lakes," a pro- Abroad. musical story " Evening in their arrival. Sonny Miller will gramme of Finnish folk and Munich, 5.5, " Die Meistersinger " landscape in (Wagner). The Bavarian States Budapest." First broadcast be supported by the Three words, music, Theatres ' Festival performance. in 1934, this tells of a young Admirals, the Three Dots, and and song. MONDAY, AUGUST 9th. man's quest for a priceless the Paradise Islanders. Musical German folk songs and Nat., 635, Recital : Muriel Bruns - violin which succeeds because settings are by Eric Siday and dances will be rendered by the kill (soprano). 7, " Monday at of his love for a beautiful Hun- the production is by Ernest Station Orchestra and Choir Seven," including Annie Frind Longstaffe, from Leipzig at 7 on Wednes- (Berlin State Opera House) and garian girl. The production Larrie Adler. 8, Wagner Prom. will bring to the microphone O O G day. Reg., 8 " Green Fingers " : a radio for the first time in a variety FOLK MUSIC v G revue on gardens and gardeners. broadcast Michel Michaeloff LOVERS 9.45, Wagner Prom. of folk songs and MONASTIC Abroad. and his Zigeuner players. dances will have ample fare A RECITAL from the Court- Brussels I , 9, " Carillons of Flan- Charles Vaida, the Hungarian, this week from which to make ders." Piece for Radio.. their choice. This yard of the former Franciscan TUESDAY. AUGUST 10th. evening (Friday) at Monastery of the Barefooted Nat., 8, Melody out of the Sky. 6.4o, Monks at Saalfeld will be 9, " Green Fingers." 10, " I Saw Cologne makes its contribu- heard from Leipzig at 9.15 on the Start " : Robert Hale. 10.20, Thursday. Members Scenes from the Merry Wives of tion to the Radio of the Windsor (Nicolai). Exhibition stage in Rudolstadt Country Band will Reg.. 7, " Paradise Isle." 8, Elgar the form of folk accompany the Saalfeld Prom. 9.40, Hella Langdon, St. Cecilia Choir. The recital Abroad. INA SOUEZ, is Paris PTT, 8.30, Band of the Garde the to commemorate the death Républicaine. well -known soprano, of Prince Louis Ferdinand of who will be heard WEDNESDAY, AUGUST Ilth. this evening with Prussia, who was killed at Nat., 6.40, Medvedeff's Balalaika the B.B.C. Orchestra Saalfeld in 18o6, when the Orchestra. 8, Victor Sylvester at 9 (Reg.) and Prussians were defeated by and his ballroom orchestra. again during the Napoleon's forces. Prince 8.35, Bach Prom. Promenade Concert Louis Ferdinand was a gifted Reg., 8.35. ' Radio Rodeo" from on Saturday. the Union Cinema, Kingston. composer, and was the 10.5, " The Thames." and Bea Hutten, Viennese songs and dances given by nephew of Frederick the Great Abroad. singer, will take part in the West of Prince both Strasbourg, 8.30, Symphony con- German Folk Groups. and Henry, cert from the Casino, Plombières - show, which was written by Most German stations will great patrons of music. Be en- Ies- Bains. Vera Biro, daughter of the be relaying this display. tered the Army when very THURSDAY, AUGUST 12th. famous Hungarian playwright On Saturday, Hamburg's young, and that he should Nat., 7.45, " S.O.S." a new play Lajos Biro. The story will be day at the exhibition, two have become a sound practical by " Taffrail." 8.30, Round the told by Leo Genn. programmes of folk music musician and composer among Fol-de -Rots. v o 0 Reg., 6, The Scots Military ex- will be heard, at 4 and at 6. the distractions of a military Guardsmen's band. 8, Tchai- PARADISE ISLE These will also be relayed by life proves his energy and per- kovsky Prom. 10 " Hyde Park" LISTENERS may recollect that most German stations. At 8.10 severance no less than his Abroad. the last " Paradise Isle " pro- on the same evening, Berlin talent. The recital includes Brussels, 8.30, Smetana's " The Bartered Bride " from Vichy. gramme, broadcast in June, ( Funkstunde) promises an in- music of this Royal composer. concluded with the Girl and teresting picture of old and new THE AUDITOR.

www.americanradiohistory.com 122 Wireless World, August 6th, 1937 UNBIASED By FREE GRID

that each of us who uses light waves of An Unjust Charge any sort is similarly transgressing. Ignor- I SUPPOSE that a good many of you, ance of the law is, of course, no excuse, like myself, are keen motorists as well as any lawyer will tell you. a wireless enthusiasts and have, like It is obvious, therefore, that it is strictly . the effects of my exertions. most of the motoring fraternity, stood illegal for me to use lights on my car to from time to time in the Dock to answer convey to pedestrians or other vehicles the which had the effect of almost completely some trumped -up charge of infringing the information that I am coming, and it is smashing up the cycle. Among the few anti- motoring regulations. Possibly, there- this plea that I intend to put forward, with parts that were undamaged, I noticed the fore, you can help me in my present diffi- what success I will let you know when the small dynamo lighting set and this im- culty as, in a few days' time, I have to case is finished. In the meanwhile, if any mediately gave me the solution to my attend the court to answer an altogether of my legal readers can see any unforeseen problem. . unjust charge of driving without lights. snags in my defence, perhaps they will I concluded a hasty bargain with the As a matter of fact I have a perfectly be good enough to communicate with me injured cyclist regarding the disposal of the good excuse as I wanted to listen to a at once. Possibly one of you might care remains of his machine, my charge for very important programme at the time, .to argue the case for me. clearing up the mess being comparatively and since my dynamo is burnt out and light in view of the fact that part of the my car battery of rather ancient vintage wreckage would be of use to me. Need - I realised that it would not stand the Rural Radio Iess to say I soon hired a bicycle, and, strain of both wireless set and lighting, fixing the small dynamo to the forks and and consequently the latter had to go. IN spite of the much -vaunted accom- mounting my accumulator on the carrier I fully realise that, just though it be, this plishments of the Grid in the matter of at the rear, I set out on a charging expe- perfectly genuine reason will not be ac- bringing a power supply to the remotest dition. cepted by the non -radiominded sort of hamlets in the kingdom, its sponsors seem Aftergoing ten miles or so I began to individuals who compose the average to . have overlooked quite a number of consider that it was time to turn back bench of magistrates. localities. That this is so is amply proved as .I was beginning to feel the effects of by the large number of battery sets which my unwonted exertions. It occurred to A Novel Plea are still made and sold annually. If the me to look and see how the charging pro- Grid had done its work properly, there cess was going on before setting off on I have, therefore, been compelled to should be no need for battery sets at all the homeward ten miles, and I speedily ransack my mind for something more other than portables. got to work with a hydrometer and volt- suitable to put before- them and I flatter As it is, the negligence of the Electricity meter. To my astonishment I found the myself that I have succeeded. I am going Commissioners in not seeing that all their accumulator in exactly the same condi- to plead that I extinguished the lights promises are faithfully carried out has tion as before. Apparently nó charging to avoid infringing a far more important resulted in my undergoing very severe had been taking place at all. It was not law, namely, the Wireless Telegraphy Act. heart strain which -might easily have until I had dismantled everything in my proved fatal. I had been spending a few search for the fault, even to the stripping days in the country to recuperate my of the armature windings, that I suddenly forces in preparation for Cowes Week and realised that the wretched dynamo was quite naturally I took my wireless set an AC instrument. along with me. Unfortunately the country cottage where I stayed was not The Price of Pleasure wired for electric light or anything else in spite of the proud boasting of the Elec- The less said about my journey home tricity Board. The result was, of course, the better, but on the next day I put that I had to feed the heaters of the many through a trunk call to a large firm of valves in my superhet from an accumula- cycle dealers, only to learn that no DC tor. Unfortunately this is no joke when lighting sets were made. In reality this each valve takes i amp. and I was soon bad news saved money which might other- up against the charging problem in grim wise have been needlessly squandered on . . in the dock . . . earnest. a DC lighting dynamo. Metal rectifiers There was no proper charging station in are cheaper than dynamos, and it was not Now, as you know, this Act forbids the the village, although the keeper of the long before I had one of these rigged up use of a wireless transmitter without a general shop, I learned, "did" accumula- in series with my original generator. The licence, but it makes no mention of any tors; but at an outrageous charge to which only snag was that an evening's entertain- wavelength limitations. Presumably, there- I absolutely refused to agree. I was corn- ment meant a 3o -mile charging ride the fore, the veto applies to all wavelengths, pelled, therefore, to fall back upon my in- next day, and as at my time of life I am and so, strictly speaking, any form of sig- ventive powers for a method of charging no Ionger as active as I once was, I found nalling utilising light waves -which are my accumulator. At first I thought of that I could only just get back in time merely very short wireless waves -is sending for a battery of wet primary cells for the main programme each evening. illegal. If this is so, it does not merely of the Daniels type, but just as I was I am, therefore, not feeling as rejuvena- mean that Boy Scouts and similar bodies going out to the village post -office to send ted after my holiday as I might have done who utilise signalling lamps or flags with- off an order, I had the good fortune to if the Electricity Commissioners had not so out a licence are breaking the law, but see a collision between a cyclist and a lorry basely betrayed the trust placed in them.

www.americanradiohistory.com Trireless World, August Gth, 1937 Peto -Scott Televíslon Receiver A SUPERHETERODYNE FOR SOUND AND VISION RECEPTION

component not being re- an output of about 3,000 volts obtained tained as far as the tube is with the aid of metal rectifiers, the time - concerned, and also to the hase supply at about z,000 volts and using sync separator. Two a valve rectifier, and the receiver supply valves are used here -an for which a valve rectifier is again used. RF pentode for the sync On test at a distance of some six miles separator proper and a from the Alexandra Palace the apparatus diode for replacing the DC proved capable of giving good pictures. to enable it to function. In common with other receivers using This apparatus is all the single -sideband principle the picture mounted on a single quality is critically dependent on the chassis. tuning, which must, consequently, be car- The time -base contains ried out with some care. Good definition gas -filled triodes for gener- is secured, and the simultaneous tuning ating the scanning volt- of vision and sound enables the optimum ages, and each is followed point to be readily found once the initial by a two -stage triode am- adjustments have been properly carried plifier of the balanced out. type. The 12in. CR tube Owing to the absence of the DC com- is also mounted on this ponent of the signal on the tube, readjust- chassis, which also con- ment of the brilliancy control is needed tains the time -base, focus- when different studio lighting is adopted ing and brilliancy con- for different items. Severe interference has the effect of darkening the picture as a whole.

A front view of the equipment is shown on the left and the side view below clearly shows the individual units.

'\LECTRICALLY this apparatus The apparatus is available consists of superheterodyne vision from The Peto -Scott Co., and sound receivers of which the Ltd., of 77, City Road, is the oscil- London, E.C.r. at 6o gns. only common part it is sup- commences As a kit of parts lator. The vision receiver plied at 55 gus. with an RF stage fixed -tuned to 45 Mc /s ; then comes a triode -hexode frequency - changer, the oscillator frequency being trols. With the exception adjustable by means of a panel control. of the brilliancy control There are three IF stages but four IF' these are all mounted at valves, since the last stage consists of two the rear of the chassis, RF pentodes in push -pull feeding into the since they are regarded as diode detector which is followed by a pre -set controls. There single vision -frequency stage. are line and frame sync The sound receiver is built on the same amplitude potentiometers, chassis and starts off with a triode -hexode line and frame frequency frequency-changer. The triode portion is controls, picture height not used, however, for the vision oscilla- and width,. horizontal and tor supplies the local heterodyne for fre- vertical shift, and line and quency- changing so that sound and vision f ram e amplifier- balance can be simultaneously tuned with the same controls as well as focus- control. This valve is followed by one ing. The brilliancy con- IF stage, a duo -diode -triode detector and trol is brought out to the AF amplifier and a pentode output valve. panel in common with the Returning to the vision equipment, no tuning and sound and gain control is provided in the pre-detec- vision gain controls. The sync separation is good and the tor circuits but a potentiometer in the The tube and time -base chassis is synchronising is sufficiently stable to detector output enables the input of the mounted on the top deck of the frame, with render only occasional adjustment to the VF stage to be controlled. The output of the receiver in the middle and the power sync controls necessary. Bright pictures the VF stage is taken to the CR tube units at the bottom. There are three can be obtained in a well- darkened through a coupling condenser, the DC power units : the high -voltage unit with room.

www.americanradiohistory.com 124 Wireless World, August 6th, t937 PRINCIPAL BROADCASTING STATIONS OF EUROPE Arranged in Order of Frequency and Wavelength (This list is included .n the first issue of each month. Stations with an Aerial Power of 50 kW. and above in heavy type)

Tuning Timing ke/s. Positions. Metres. kW. Station. ke/s. Positions. Metres. kW.

Ankara (Turkey) ...... 152 1973.5 5 Leipzig (Germany) ...... 785 382.2 120 Kaunas (Lithuania) ...... 153 1961 7 Barcelona, EAJ1 (Spain) ...... 795 377.4 7.5 Radio Romania (Brasov) Romania .. 160 1875 150 Lwow (Poland) ...... 795 377.4 50 Hilversum, No. I (Holland) (10 kW. till 2040) 160 1875 150 North Welsh Regional (Penmon) .. .. 804 373.1 5 Lahti (Finland) ...... 166 1807 150 Welsh Regional (Washford Cross) .. .. 804 873.1 70 Moscow, No. 1, RW1 (Komintern) (U.S.S.R.) 172 1744 500 Milan, No. 1 (Italy) ...... 814 368.6 50 Paris (Radio Paris) (France) .. .. 182 1648 80 Bucharest (Romania) .. .. 823 364.5 12 Istanbul (Turkey) ...... 185 1622 5 Kiev, No. 2, RW9 (U.S.S.R.) .. .. 832 360.6 35 Irkutsk (U.S.S.R.) ...... 187.5 1600 20 Agen (France) .. 832 360.6 1.5 Deutschlandsender (Germany) .. .. 191 1571 60 Berlin (Germany) .. .. , . , . 841 356.7 100 Droitwich ...... 200 1500 150 Sofia (Bulgaria) ...... 847.5 354 1 Minsk, RW10 (U.S.S.R.) ...... 208 1442 35 Norwegian Relay Stations ...... 850 352.9 - Reykjavik (Iceland) ...... 208 1442 16 Valencia (Spain) ...... 850 352.9 3 Motala (Sweden) ...... 216 1389 150 Simferopol, RW52 (U.S.S.R.) .. .. 859 349.2 10 Novosibirsk, RW76 (U.S.S.R.) .. .. 217.5 1379 100 Strasbourg (France) ...... 859 349.2 100 Warsaw, No. 1 (Poland) ...... 224 1339 120 Poznan (Poland) ...... 868 345.6 16 Luxembourg ...... 232 1293 150 London Regional (Brookmans Park) 877 342.1 70 Moscow, No. 2, RW49 (Stehelkovo) (U.S.S.R.) 232 1293 100 Linz (Austria) ...... 886 338.6 15 Kalundborg (Denmark) ...... 240 1250 60 Graz (Austria) ...... 886 338.6 15 Vienna, No. 2 (Austria) ...... 240 1250 0.5 Helsinki (Finland) ...... 895 335.2 10 Kiev, No. 1 (U.S.S.R.)...... 248 1209.6 100 Limoges, P.T.T. (France) ...... 895 335.2 1.5 Vigra (Aalesund) (Norway) ...... 253 1186 10 Hamburg (Germany) ...... 904 331.9 100 Tashkent, RW11 (U.S.S.R.) ...... 256.4 1170 25 Dniepropetrovsk (U.S.S.R.) ...... 913 328.6 10 , Oslo (Norway) ...... 260 1153.8 60 Toulouse (Radio Toulouse) (France) .. 913 328.6 60 Leningrad, No. 1 RW53 (Kolpino) (U.S.S.R.) 271 1107 100 Brno (Czechoslovakia) ...... 922 325.4 32 I Tromsö (Norway) ...... 282 1065 10 Brussels, No. .2 (Belgium) .. .. . 932 321.9 15 Tiflis, RW7 (U.S.S.R.) ...... 283 1060 35 Algiers (Algeria) ...... 941 318.8 12 Saratov (U.S.S.R.) ...... 340 882.3 20 Göteborg (Sweden) ...... 941 318.8 10 ' Finmark (Norway) ...... 347 864 10 Breslau (Germany) ...... 950 315.8 100 Archangel (U.S.S.R.) .. .. 350 857.1 10 Paris (Poste Parisien) (France) .. .. 959 312.8 60 Rostov -on-Don, RW12 (U.S.S.R.) .. .. 355 845.1 0 Bordeaux -Sud -Ouest (France) .. .. 968 309.9 30 Budapest, No. 2 (Hungary) ...... 359.5 834.5 18 Odessa (U.S.S.R.) ...... 968 309.9 10 Sverdlovsk, RW5 (U.S.S.R.) .. .. 375 800 40 Northern Ireland Regional (Lisburn) .. 977 307.1 100 Voroneje, RW25 (U.S.S.R.) ...... 390 769 10 Genoa (Italy) ...... 986 304.3 10 Boden (Sweden) ...... 392 765 0.6 Torun (Poland) ...... 986 304.3 24 Banka- Bystrica (Czechoslovakia) (15 kW. 392 765 30 Hilversum No. 2 (Holland) (15 kW. till 2040) 995 301.5 60 after 1800) Bratislava (Czechoslovakia) ...... 1004 298.8 13.5 Geneva (Switzerland) ...... 401 748 2 Midland Regional (Droitwich) .. .. 1013 296.2 70 Moscow, No. 3 (RCZ) ( U.S.S.R.) .. .. 413.5 726 100' Chernigov (U.S.S.R.) ...... 1013 296.2 4 Ostersund (Sweden) ...... 413.5 726 0.6 Barcelona, EAJ15 (Spain) ...... 1022 293.5 3 Oulu (Finland)...... 431 696 10 Cracow (Poland) ...... 1022 293.5 2 Tartu (Estonia) 511 587.1 0.5 Oviedo (Spain)...... 1022 293.5 0.7 Hamar (Norway) ...... 519 578 0.7 Königsberg, No. 1 (Heilsberg) (Germany) .. 1031 291 100 Innsbruck (Austria) ...... 519 578 1 Parede (Portugal) .. 1031 291 5 Ljubljana (Yugoslavia) ...... 527 569.3 6.3 Leningrad, No. 2, RW70 (U.S.S.R.) .. 1040 288.5 10 Viipuri (Finland) ...... 527 569.3 10 Rennes -Bretagne (France) ...... 1040 288.5 120 Bolzano (Italy) ...... 536 559.7 10 West Regional (Washford Cross) .. .. 1050 285.7 50 Wilno (Poland) ...... 536 559.7 50 Bari No. I (Italy) ...... 1059 283.3 20 Budapest, No. 1 (Hungary) ...... 546 549.5 120 Paris (Radio Cité) (France) ...... 1068 280.9 0.8 Beromünster (Switzerland) ...... 556 539.6 100 Tiraspol, RW57 (U.S.S.R.) ...... 1068 280.9 10 Athlone (Irish Free State) ...... 565 531 100 Bordeaux -Lafayette (France) .. .. 1077 278.6 35 Klaipeda (Lithuania) ...... 565 531 10 Zagreb (Yugoslavia) .. 1086 276.2 0.7 Palermo (Italy) ...... 565 531 3 Falun (Sweden) ...... 1086 276.2 2 Stuttgart (Germany) ...... 574 522.6 100 Madrid, EAJ7 (Spain) ...... 1095 274 5 Alpes- Grenoble, P.T.T. (France) .. .. 583 514.6 20 Vinnitsa (U.S.S.R.) ...... 1095 274 10 Madona (Latvia) ...... 583 514.8 50 Kuldiga (Latvia) ...... 1104 271.7 10 Vienna, No. 1 (Austria) ...... 592 506.8 100 Naples (Italy) ...... 1104 271.7 1.5 Rabat (Morocco) ...... 601 499.2 25 Morayska- Ostrava (Czechoslovakia) .. 1113 269.5 11.2 Sundsvall (Sweden) ...... 601 499.2 10 Radio Normandie (Fécamp) (France) .. 1113 269.5 15 Florence (Italy) ...... 610 491.8 20 Alexandria, No. 1 (Egypt) ...... 1122 267.4 0.5 1 Cairo, No. (Egypt) ...... 620 483.9 20 Newcastle ...... 1122 267.4 1 Brussels, No. 1 (Belgium) ...... 620 483.9 15 Nyiregyhaza (Hungary) ...... 1122 267.4 6.25 Lisbon (Portugal) ...... 629 476.9 15 Hörby (Sweden) .. 1131 265.3 10 Tröndelag (Norway) ...... 629 476.9 20 Turin, No. 1 (Italy) ...... 1140 263.2 7 Christiansand (Norway) ...... 629 476.9 20 Trieste (Italy) ...... 1140 263.2 10 Prague, No. 1 (Czechoslovakia) .. .. 638 470.2 120 London National (Brookmans Park) .. 1149 261.1 20 Lyons, P.T.T. (France) ...... 648 463 100 North National (Slaithwaite) .. .. 1149 261.1 20 Petrozavodsk (U.S.S.R.) ...... 648 463 10 Scottish National (Falkirk) ...... 1149 261.1 50 Cologne (Germany) ...... 658 455.9 100 Kosice (Czechoslovakia) ...... 1158 259.1 10 North Regional (Slaithwaite) .. .. 668 449.1 70 Monte Ceneri (Switzerland) ...... 1167 257.1 15 Jerusalem (Palestine)...... 668 449.1 20 Copenhagen (Denmark) ...... 1176 255.1 10 Sottens (Switzerland) ...... 677 443.1 100 Nice -Corse (France) .. 1185 253.2 60 Belgrade (Yugoslavia) .. 686 437.3 2.5 Frankfurt (and Relays) (Germany) .. 1195 251 25 Paris, P.T.T. (France) ...... 695 431.7 120 Prague, No. 2 (Czechoslovakia) .. .. I204 249.2 5 Stockholm (Sweden) ...... 704 426.1 55 Lille, P.T.T. (France) .. 1213 247.3 80 Rome, No. 1 (Italy) ...... 713 420.8 50 Bologna (Radio Marconi) (Italy) .. .. 1222 245.5 50 Kharkov, No. 1, RW20 (U.S.S.R.) .. .. 722 415.4 10 Gleiwitz (Germany) ...... 1231 243.7 5 Fredrikstad (Norway) ...... 722 415.4 1 Cork. (Irish Free State) .. 1235 242.9 1 Tallinn (Estonia) ...... 731 410.4 20 Saarbrücken (Germany) ...... 1249 240.2 17 Madrid, EAJ2 (Spain) ...... 731 410.4 3 Riga (Latvia) .. .. 1258 238.5 15 Seville (Spain) ...... 731 410.4 5.5 Rome, No. 3 (Italy) , ...... 1258 238.5 1 Munich (Germany) ...... 740 405.4 100 Bilbao, EAJ8 (Spain) .. 1258 238.5 1 Marseilles, P.T.T. (France) ...... 749 400.5 100 Nürnberg (Germany) .. 1267 236.8 2 Pori (Finland) ...... 749 400.5 1 Radio Mediterranée (Juan -les -Pins) (Franco) 1276 235.1 27 Katowice (Poland) ...... 758 395.8 12 Dresden (Germany) .. .. 1285 233.5 0.25 Scottish Regional (Falkirk) ...... 767 391.1 70 Aberdeen ...... 1285 233.5 1 North Scottish Regional (Burghead) .. 767 391.1 60 Klagenfurt (Austria) ...... 1294 231.8 5 Stalino (U.S.S.R.) ...... 776 386.6 10 Vorarlberg (Austria) .. .. 1294 231.8 5 Toulouse, P.T.T. (France) ...... 776 386.6 120 Danzig ...... 1303 230.2 0.5

www.americanradiohistory.com AUGUST 6th, r937. WIpßllmA Wait]. 125

Toning kc/s. Positions. Metres. kW. Station. ke/s. Positions. Metres. kW. Swedish Relay Stations ...... 1312 228.7 - Vaasa -Vasa (Finland) ...... 1420 211.3 10 Magyarovar (Hungary) ...... 1321 227.1 1.25 Alexandria, No. 2 (Egypt) ...... 1429. 209.9 0.5 German Relay Stations .. .. 1330 225.6 - Turku (Finland) ...... 1429 209.9 0.5 Montpellier, P.T.T. (France) .. .. 1339 224 1.5 Miskolc (Hungary) ...... 1438 208.6 1.25 Lodz (Poland) ...... 1339 224 2 Paris (Eiffel Tower) (France) .. .. 1456 206 7 Dublin (Irish Free State) ...... 1348 222.6 0.5 Pecs (Hungary) ...... 1465 204.8 1.25 Rjnkan (Norway) ...... 1348 222.6 0.15 Belgian Relay Stations ...... 1465 204.8 0.1 Salzburg (Austria) ...... 1348 222.6 2 Bournemouth ...... 1474 203.5 1 Tampere (Finland) ...... 1348 222.6 0.7 Plymouth ...... 1474 203.5 0.3 Cairo No. 2 (Egypt) ...... 1348 222.6 0.5 Binche (Belgium) ...... 1487 201.7 0.1 Königsberg (Germany) ...... 1348 222.6 2 Belgian Relay Stations ...... 1492 201.1 0.1 Nottoden (Norway) .. .. 1357 221.1 0.15 Nimes (France) ...... 1492 201.1 0.7 Italian Relay Stations ...... 1357 221.1 - Albacete (Spain) ...... 1492 201.1 0.2 L'Ile de France (France) ...... 1366 219.6 2 Santiago (Spain) ...... 1492 201.1 0.5 Basle (Switzerland) ...... 1375 218.2 0.5 Belgian Relay Stations ...... 1500- 200 0.1 Berne (Switzerland) ...... 1375 218.2 0.5 Pietarsaari (Finland) ...... 1500 200 0.25 Warsaw, No. 2 (Poland) ...... 1384 216.8 7 Radio Alcalá (Spain) .. .. 1500 200 0.2 Lyons (Radio Lyons) (France) .. .. 1393 215.4 25 Karlskrona (Sweden) .. .. 1530 196 0.2 Stara - Zagora (Bulgaria) . . . 1402 214 2 Liepàja (Latvia) ...... 1734 173 0.1 SHORT -WAVE STATIONS OF THE WORLD Can Toning Can Toning Station. Sign. kc/s. Positions. Metres. kW. Station. Siger kc /s. Positions. Metres. kW.

Batavia (Java) ...... YDA 3,040 98.68 10 Madrid (Spain) ...... EAQ 9,860 30.43 20 Vancouver (Canada)...... VE9BK 4,750 62.63 - Lisbon (Portugal) ...... CSW 9,940 30.18 5 Kharbarovsk (U.S.S.R.) .. .. RV15 4,273 70.20 20 Bandoeng (Java) .. .. PMN 10,260 29.24 3 Caracas (Venezuela) ...... YV5RC 5,800 51.72 1 Ruysselede (Belgium) .. .. ORK 10,330 29.04 9 San Jose (Costa Rica) .. TIGPH 5,820 51.52 0.5 Buenos Aires (Argentina) .. .. LSX 10,360 28.99 12 Vatican City (Vatican State) .. HVJ 5,970 50.26 10 Tenerife (Canary Isles) .. .. EAJ43 10,360 28.94 4 Mexico City (Mexico) .. .. XEBT 6,000 50.00 1 Bandoeng (Java) ...... PLP 11.010 27.25 3 Montreal (Canada) ...... CFOX 6,005 49.96 - Lisbon (Portugal) .. CSW 11,040 27.17 5 Havana (Cuba) COCO 6,010 49.92 2.5 Motala (Sweden) ...... SBG 11,700 25.63 1 Prague (Podebrady) (Czechoslovakia) OLR2A 6,010 49.92 30 Winnipeg (Canada) ...... CJRX 11,720 25.60 2 Bogota (Colombia) ...... HJ3ABH 6,018 49.90 1 Paris (Radio- Colonial) (France) .. TPA4 11,720 25.60 12 Zeesen (Germany) ...... DJC 6,020 49.83 50 Daventry (Gt. Britain) .. .. GSD 11,750 25.53 10 -50 Boston (U.S.A.) ...... W1XAL 6,040 49.67 20 Zeesen (Germany) .. DJD 11,770 25.49 50 Miami (U.S.A.) .. .. W4XB 6,040 49.67 2.5 Boston (U.S.A.) ...... W1XAL 11,790 25.45 20 Daventry (Gt. Britain) .. .. GSA 6,050 4.59 10-50 Tokio (Japan) ...... JZJ 11,800 25.42 20 Cincinnati (U.S.A.) .. .. W8XAL 6,060 49.50 10 Vienna (Austria) .. .. OER2 11,800 25.42 1.5 Philadelphia(U.S.A.) .. .. W3XAU 6,060 49.50 10 Rome (Italy) .. .. I2R04 11,810 25.40 25 Skamlebaek (Denmark) .. .. OXY 6,080 49.50 0.5 Daventry (Gt. Britain) .. .. GSN 11,820 25.38 10 -50 Motala (Sweden) ...... SBG 6,060 49.50 1 Wayne (U.S.A.) .. W2XE 11,830 25.36 10 Chicago (U.S.A.) ...... W9XAA 6,080 49.34 0.5 Lisbon (Portugal) CT1AA 11.830 25.36 2 Lima (Peru) ...... OAX4Z 6,080 49.34 15 Prague (Podebrady)(Czechoslovakia) OLR 11,840 25.34 30 Nairobi (Kenya) ...... VQ7L0 6,083 49.31 0.5 Zeesen (Germany) .. DJP 11.850 25.31 50 Toronto (Bowmanville) (Canada) .. CRCX 6,090 49.26 0.5 Daventry (Gt. Britain) .. .. GSE I1,860 25.29 10-50 Hong Kong (China) ...... ZBW2 6,090 49.26 2 Pittsburgh (U.S.A.) .. W8XK 11,870 25.27 40 Johantesburg (South Africa) .. ZTJ 6,100 49.20 5 Paris (Radio- Colonial) (France) .. TPA3 11,880 25.23 12 Bound Brook (U.S.A.) .. .. W3XAL 6,100 49.18 35 Moscow ( U.S.S.R.) ...... RNE 12,000 25.00 20 Chicago (U.S.A.) .. .. W9XF 6,100 40.18 10 Lisbon (Portugal) .. .. CTICT 12,082 24.83 0.5 Belgrade (Yugoslavia) .. .. YUA 6,100 49.18 1 Reykjavik (Iceland) ...... TFJ 12,235 24.52 7.5 Manizal a (Colombia) .. .. H.I4ABB 6,105 49.12 1 Parede (Portugal) ...... CT100 12,400 24.20 0.35

Daventry (Gt. Britain) .. . . GSL 6,110 49.10 10-50 Warsaw (Poland) ...... SPW 13,635 22.00 10 Calcutta (India) ...... VUC 6,110 49.10 0.5 Amateurs .. 14,000 21.42 0.01 Pittsburgh (U.S.A.) ...... W8XK 6,140 48.86 90 to to Winnipeg (Canada) ...... CJRO 6,150 48.78 2 14,400 20.84

Lisbon (Portugal) ...... CSL 6,150 48.78 - 0.5 Sofia (Bulgaria) ., .. LZA 14,970 20.04 1.5 Parede (Portugal) .. .. CT1G0 6,200 48.40 5 Moscow (U.S.S.R.) .. .. RKI 15.010 19.95 25 San Jose (Costa Rica) .. .. TIPG 6,410 46.80 0.5 Zeesen (Germany) .. DJL 15,111 19.85 50 Valencia (Colombia) ...... YV4RV 6,520 48.00 0.5 Vatican City (Vatican State) .. HVJ 15.123 19.84 10 Riobamba (Ecuador) .. .. PRADO 6,620 45.31 2 Daventry (Gt. Britain) .. .. GSF 15,140 19.82 10-50 Amateurs ...... 7,000 42.86 0.01 Bandoeng (Java) ...... YDC 15,160 19.80 3 to to Tokio (Japan) . .. .. JZK 15,160 19.80 20 7,300 41.10 Daventry (Gt. Britain) .. .. GSO 15,180 19.76 10 Prangins (Radio -Nations) (Switz'l'd) HBP 7,780 38.48 20 Hongkong (China) ...... ZBW4 15,190 19.75 2 Budapest (Hungary)...... HAT4 9,125 32.88 5 Zeesen (Germany) .. DJB 15,200 19.74 50 Bangkok (Siam) ...... HS8PJ 9,350 32.09 20 Pittsburgh (U.S.A.) ...... W8XK 15,210 19.72 40

Madrid (Spain) ...... EAQ2 9,480 31.65 20 Huizen (Holland) .. PCJ 15,220 19.71 ' 20 Rio de Janeiro (Brazil) .. .. PRFS 9,500 31.58 12 Prague (Podehrady)(Czechoslovakia) OLRSA 15,230 19.70 30 Daventry (Gt. Britain) .. .. GSB 9,510 31.55 10 -50 Paris (Radio -Colonial) (Franco) .. TPA2 15,243 19.68 12 Melbourne (Australia) .. .. VK3ME 9,510 31.55 1.5 Boston (U.S.A.) .. .. W1XAL 15,250 "19.67 20 Hongkong (China) ...... ZBW3 9,520 31.49 2 Daventry (Gt. Britain) .. .. GSI 15,260 19.66 10-50 Jelöy (Norway) .. .. LKJ1 9,520 31.49 1 Wayne (U.S.A.) ...... W2XE 15,270 19.65 10 Schenectady (U.S.A.) .. .. W2XAF 9,530 31.48 25 Zeesen (Germany) .. .. DJQ 15,280 19.63 50 Zeesen (Germany) ...... DJN 9,540 31.45 50 Buenos Aires (Argentina) .. .. LRU 15,290 19.62 5 Suva (Fiji) ...... VPD2 9,540 31.95 3 Daventry (Gt. Britain) .. .. GSP 15,310 19.60 10-50 Prague (Podebrady)(Czechoslovakia) OLR3A 9,550 31.41 30 Schenectady (U.S.A.) .. .. W2XAD 15,330 19.57 18 Zeesen (Germany) ...... DM 9,560 31.38 5 -50 Zeesen (Germany) .. DJR 15,340 19.55 50 Lima (Peru) ...... OAX4T 9,560 31.38 10 Budanest(Szekesfehervar) (Hungary) HAS3 15,370 19.52 20 Bombay (India) ...... VUB 9,565 31.38 4.5 Hongkong (China) .. ZBW5 17,750 16.90 2 Millis (U.S.A.) .. .. W1XK 9,570 ...... 31.35 10 Zeesen (Germany) ...... DJE 17,760 16.89 50 Daventry (Gt. Britain) .. .. GSC 9,580 31.32 10-50 Wayne (U.S.A.) ...... W2XE 17,760 16.89 10 Lyndhurst (Australia) .. .. VK3LR 9,580 31.32 1 Huizen (Holland)) .. .. PHI 17,770 16.88 23 Philadelphia (U.S.A.) .. .. W3XAU 9,590 31.28 10 Bound Brook (U.S.A.) .. .. W3XAL 17,780 16.87 35 Sydney (Australia) ...... VK2ME 9,590 31.28 20 Daventry (Gt. Britain) .. .. GSG 17,790 16.86 10-50 Huizen (Holland) PCJ 9,590 31.28 20 Bandoeng (Java) ...... PLE 18,830 15.93 60 Prangins (Radio -Nations) ( Switz'l'd) HBL 9,595 31.27 20 Bangkok (Siam) ...... HS8PJ 19,020 15.77 20 Moscow (U.S.S.R.) ...... RW96 9,600 31.25 20 Bandoeng (Java) .. .. PMA 19,350 15.50 60 Rome (Italy) ...... I2R03 9,635 31.13 25 Daventry (Gt. Britain) .. .. GSM 21,470 13.97 10-50 Sourabaya (Java) ...... YDB 9,640 31.11 1 Wayne (U.S.A.) ...... W2XE 21,520 13.94 10 Lisbon (Portugal) .. .. CT1AA 9,665 31.09 2 Daventry (Gt. Britain) .. .. GS.; 21,530 13.93 10-50 Buenos Aires (Argentina) .. .. LRX 9,660 31.06 S Pittsburgh (U.S.A.) ...... W8XK 24540 13.93 40 Lisbon (Portugal) ...... CTICT 9.680 11.00 0.5 Davantry lilt Rritain1 noT 95 Kral 4Q U2 )tine

www.americanradiohistory.com Wireless World, August 6th, 1937

most useful rating. Whether ,it really is useful or not need not he argued, because such a number is no less variable than A PLEA FOR the number of birds on a tree in summer. A less direct but more definite figure is Ratings the strength of signal required to stir up MORE INFORMATIVE an agreed amount of sound- making power in the loud speaker. must With modern instru- IT be understood that the subject DESIGNATIONS ments it is quite easy this to specify such a week, though broad in scope, does figure, and in technical circles not refer in detail to naval personnel that is what is done. But do you think the general or municipal revenue. The idea is to By " CATHODE RAY" public can be to discuss the descriptions used for purposes got understand it? They much prefer to ask for a Silver of identifying articles bought and sold, " Stork " than a io- microvolt model. with particular reference to wireless sets. It is' con- take no interest in definite specifications ceivable, though, that if makers In the earliest days of commerce, when invariably even when the makers try to supply them. gave prominence to such figures (on men began to buy or barter flint axeheads an Thus the various models are distinguished agreed basis of measurement) in all their from those of their number who proved by extremely irrelevant names of birds or publicity, them and abstained from any funny to be specially adept at making beasts, or by a number which may or may business in the reckoning (instead of his own), of them, in time everyone chipping not have a meaning to the initiated, or they would come to have the goods were probably ordered simply some meaning (at best) by some such title as " 4 -valve for the non -technical public. as axeheads. But as powers of description AC Superhet." improved, a purposeful purchaser might Right from the beginning of the radio Even Less Logical have asked for a sharp, heavy axehead, industry it has been customary to rate " sharp and heavy enough to slay yonder receivers by the number of valves. So One might look mastodon." to the motor trade, as long as the results associated with aver- an older one than radio, for guidance This valuable development made so in agely competent employment of a team ' this rating problem. Unfortunately, little progress that in comparatively the of valves bore an approximate relationship rating of cars is even more modern history we have it on record that illogical than to their number, and accurate measure- that of wireless sets. individual offered (ad- They are generally an authoritative ment of results was not yet possible, this rated in horse -power, which in of stress) his by no for this pur- mittedly a moment system was as good as any. Later, when pose is not the engineer's for h.p. of 33,000 means negligible kingdom an entirely the one available type of valve was re- foot -pounds per minute, unspecified horse. Whether this contract but appears to placed by countless 'species and genera, conform to the : by the courts as following definition would have been upheld the mere number of them employed in a " One motor car horse -power valid in the event of an incurably lame (rated) is receiver became a very poor guide indeed the total cylinder cross- sectional horse being proffered must be left to Iegal area of an to the results obtained. On the Other engine necessary to develop one actual in their Own time. Iuminaries to decide hand, even a brief'specification of the types horse -power in the year 1903." The of valves" and circuits, embodied in the reason for this quaint custom presumably Meaningless, Fanciful, and Often name of a. product, lacks snappy sales is that the taxation system is based on it, Misleading appeal ; so well- intentioned efforts Were and the prospective owner is more con- made to restore the numerical indication cerned to know how much he will have on -day situation, Passing to the present of performance by substituting " stages " to pay than how much power he is going we find that it has deteriorated still further, for "valves." It was difficult to get to get. And so there are such anomalies so that the public allow an increasingly everybody to agree on the basis for as a 10 " horse -power " car actually giving large proportion of goods to be sold to reckoning the number of stages, and, as several times as much power as a 20 them under meaningless, fanciful, and in any case the buyer couldn't count them " horse -power " car. often quite misleading names. I refrain to make sure none were missing, the idea How remarkably similar by quoting all this is to from illustrating the matter flopped. Now that receiver design is the radio situation, where the number of on the even fictitious examples invented becoming more stereotyped, the number valves for a long time attained an arti- spot, because registration of such names of valves is beginning once more to have ficial importance because heavy royalties proceeds so rapidly that it is almost certain some faint significance. But it has no were exacted on every socket, and so each for libel that I would invite an action by more than that, and there is still the designer tried to make one valve give the But inadvertently hitting on one of them. absurd uncertainty about whether the results of another's two or three. And I you know what mean. rectifier is or is not a valve. the valve rating survives because it can The merchandise referred to, mainly The best form of rating, presumably, is be checked by anybody ; the buyer sus- of a domestic and personal nature, is the one that expresses most clearly the pects that by adopting a suitable method bought by persons of insufficient intelli- extent to which the appliance serves its of measurement (or possibly no measure- gence to understand informative specifica- purpose. Thus, if one assumes that the ment at all) the advertiser can make not tions, and sold by concerns who are purpose of radio sets is to receive the maxi- microvolts, like actual horse- power, tell slow to profit by this fact. But engineers, mum number of stations (as apparently the story he wants. scientists, and others who know too much one must in order to gain much money So for various reasons it seems unlikely to be hoodwinked by nonsensical trade by making them), it might appear that that wireless sets will come to be referred names insist on descriptions that indicate the number of stations receivable is. the to in terms that reveal what they can do ; definitely the quantity or quality of the in commerce, at least. Whether goods offered, and that commit the vender readers of The Wireless World to something he can be called upon to would profit by such information substantiate. A dynamo, for example, is is for them to decide -and say. not catalogued as being ' ` terrifically powerful " or "` superstrong," but is rated MIXING METAL AND GLASS in kilowatts, and if it catches fire when VALVES. A series of adaptors for developing that number the purchaser 4 -, 5- and 6 -pin bases has been stands on definite ground in dealing with introduced in America in order that the manufacturer about it. metal valve s may be used as re- Radio receivers are highly scientific placements for various types of pieces of apparatus, but are bought glass valves current during the last largely by the uneducated public, who five years.

www.americanradiohistory.com Wireless World, August 6th, 1937 127 Cossor Cathode-Ray Oscilloscope An Instrument for Testing shift, sync amplitude, and the time -base frequency ; there are two of these last, one being a switch which enables the charging and Experimental Work capacity to be varied in steps and the other a variable resistance for the precise adjustment of frequency. McCA I14I1-1 ,' The equipment is designed for mains supplies of IIo, 200, 220 and 240 volts AC at frequencies of 4o / loo c /s and it con- SPECIAL 9 -VALVE sumes 3o volt -amps. The tube normally supplied has a blue screen with an after -glow of less than a micro -second. Tubes with FOUR -WAVE SUPERHET a green screen and an after -glow of 5 seconds can be obtained, however. The writing DE LUXE

speed is . about 25 km. /sec. and the maximum useful frequency limit is some loo The De Luxe Model of this exceptional receiver includes kc /s. The time -base has a frequency range many interesting features, and combines unusual sensitivity of 4 c /s to 5o kc / s, with a sweep linearity with great flexibility of control. Only receivers now of four -fifths of the amplitude. on the market at very much higher prices can claim so The input impedance without amplifier high a standard of design and performance. or synchronising is z megohms ; without amplifier but with synchronising it is I megohm. With both amplifier and synchronising it is 0.22 megohm. The deflection sensitivity for an input to the Y terminal is o.66 mm. per volt DC. At the input terminal it is 2 mm. per volt RMS without the amplifier and 40 mm. per volt RMS with the amplifier. There are four ranges for current in the THE oscillograph is one of the most useful deflector coil, the maximum figures for each tools to the radio engineer and service range being 3 amps, 0.5 amp., Too mA, and man, and it also has wide application in 20 mA, with sensitivities of To mm. /amp., work. experimental Certain problems, in 59 mm. /amp., 0.22 mm. /amp., and I.I fact, cannot be readily solved without it, mm. /amp. DC respectively. and many others are greatly simplified by The instrument has been thoroughly (Comolete Its use. with 9B V.6. tested and found most satisfactory. The valves.) The Cossor Oscilloscope, Model 3332, in- controls are sweet to operate and con- a 4¡in. diameter cathode -ray tube of cludes veniently placed so that the apparatus is the gas -focused type. In order to correct very easy to use. The synchronising is good for origin distortion split deflector plates 4 wavebands : 12.8 -33, 79-80, 190 -550, 800 -200) oscilloscope is one which can be are employed. A linear time -base using a and the metres, Illuminated dial with principal station confidently recorhmended. It is priced at names. gas -filled triode is included and also a single - input voltage. The L20. Various accessories, including a stage amplifier for the camera, are available. Controls. -A feature of the receiver is the number apparatus, including the mains equipment, of independent controls fitted, making it extremely is completely self- contained in a case interesting to operate. These include : sensitivity measuring only I2in. x TSlin. x Ain. and it control (varying bias on RJF stage). Q.A.V.C. with weighs 22 lb. The tube is fitted with a INTERESTING CABINETS manual muting control for inter -station noise suppression mu -metal screen. 5-position wave -change and gramophone switch. Prog- Terminals are arranged at the rear of the ressive variable tone control operative on radio and gram. apparatus and per- FOR QUALITY OUTFIT Circuit in Brief -Aerial input to pre -selector circuit. radio frequency amplifier, latest type triode -hexode frequency mit direct connec- changer, 2 band -pass 1.F.T. coupled I.F. amplifiers, double tion to be made to diode detector, L.F. amplifier and special push -pull pentode 18 Valve Receiver and output stage. Heavy cadmium -plated steel chassis. Finest the X and Y plates, components and workmanship throughout. a n d the internal 5 Valve Amplifier Harries' tetrodes can be fitted in plrrce of pentodes in output time -base can be put stage if desired. out of action if de- A C. models ready for immediate delivery. d. Normally, A.C. D.C. models also in production, and will be available sire for delivery shortly. the input is applied STANDARD MODEL 12 GNS, to the Y plates as above, but with triode push -pull output, and fewer through an isolating controls fitted. condenser, and a switch permits the I IVI IPO RTA NT The prices a! which McCarthy Chassis are advertised amplifier's being include Marconi Royalties. " Wireless World " readers thrown in or out of should. for their own protection, make sure before purchasing any receiver that the quoted price includes circuit at will ; when the Royalty payment. in circuit there is an input gain control. All McCarthy receivers supplied complete with A tapped deflecting valves, knobs, pilot lamps, leads, mains cable and coil is fitted so that plug. 12 months' guarantee. (Valves 3 months.) current measure- Deferred terms on application, or through London ments can be made, Radio Supply Co , 11, Oat Lane, E.C.2. and the mains trans- Cash with order on 7 days' approval. Also write former is provided for illustrated catalogue of complete range of all with a winding McCarthy receivers. which gives a source of voltage for conve- MCCAIRTI -11 1RDIO ILTe nient calibration. A radiogramophone equipment with a Voigt 44a, Westbourne Grove, London, \V.2 The controls a r e corner speaker recently supplied to a special Telephone : Bayswater 320112. focusing, vertical order by Midwest Radio Ltd., of Clapham, London, S.W.4.

www.americanradiohistory.com 128 Wireless World, August 6th, 1937

listeners' recent letters of complaint, and it has been decided Broadcast Brevities that instead of sending placatory replies the B.B.C. should invite NEWS FROM services that the producer can plays should not last longer the grumblers to attend a meet- do the unseeing listener is to put than an hour, but if a longer ing at which they could further PORTLAND PLACE on a play with twenty or thirty period is unavoidable, as with air their grouses and get answers characters. Some who took Shakespearean productions, the straight from the horse's mouth. part in this panel emphasised play should be broken tip by a The Scottish officials believe The Vote on Drama the necessity of announcing the short interval. themselves to be so thick - characters in the order of their skinned that they are preparing THE B.B.C. has eight million Future Lines of Research and a quarter licensed appearance at the beginning as for the anticipated attack with listeners. Its potential listen- well as the end of a play, and It seems likely that as a result a composure that cannot be ing audience in Great Britain suggestions were made for the of the radio drama experiment said to be characteristic of the alone is twenty -six millions. frequent use of names in some similar method of listener national spirit North of the And invitations were issued a dialogue. It is pretty certain, research may later be applied to Twccd. however, that the only real talks, music, variety and out- few months ago to 349 of this te,) vast audience to form a panel solution of this difficulty will be side broadcasts, with, of course, the members of which would be the increasing use of television a continuation of the panel Television Enterprise prepared to answer questions for radio drama, with the com- system for drama and features. EVEN if longer programme bination of sound and sight. In most cases, however. about the drama productions the hours cannot be fore- which they heard broadcast. cast for television next autumn and winter, it is expected - 9,600 Verdicts that quality will be improved and a larger element of From the time the scheme topical interest introduced. was launched until it came to Some cf the subjects on which an end various changes took the camera may focus include place in the personnel, and at football matches (nigger and the conclusion the amateur soccer), air, car and boat races, critics numbered 353. Four scenes amongst the shipping on separate reports were called for the Thames, the opening of Par - from each critic, and some liame t and the Lord Mayor's 9,600 completed questionnaires Show, and scenes in the film were dealt with by the B.B.C.'s studios. Some of the events to Listener Research Committee. be televised will be taking place more than twenty miles distant Little Use for Melodrama fro.ri the Alexandra Palace The results show that, in the studio. main, listeners are not in- t terested in the relative merits of adapted stage plays, plays Big or Little Nationals ? written specially for broadcast- ENGINEERS at Broadcasting ing, adapted short stories, or House are still anxiously feature programmes. They want awaiting the threa'ened agita- just to be entertained, and it tion over the silence of the little follows that whatever plays are Nationals in London and the broadcast must be entertaining. North :ntil 5 p.m. A few com- Adaptations of . modern stage plaints have been made that plays have been voted to have those who are thus forced to the highest entertainment value, tune to the long -wave trans- and classical plays, especially mission from Droitwich, if they Shakespeare, are popular ; but want the National programme, Victorian melodrama - the are getting much poorer recep- sooner " Ticket -of -Leave Man " tion than was the case from the is forgotten the better -is cot medium-wave Nationals, owing much wanted. to the atmospheric interference inseparable from the long -waves More Comedy Wanted at this f .le of year. There is an insistent demand for more comedy ; but, alas ! Dividing the Spoils how hard it is to come by. The But the engineers are used con- B.B.C. to cry aloud for MOBILE TELEVISION CONTROL ROOM.- Inside the motor van fident that this situation will plays specially written for used for outside picture broadcasts. The car contains all the necessary presently right itself with the broadcasting ; for but the produc- apparatus the operation of three cameras and four microphones. change of season, and then the tion of some of these has met Two monitoring tubes used to check the transmissions are seen at question with mixed results, the end of the van. whether the London as, for in- and North Nationals shall be stance, Philip Wade's " Wait Music that Drowns Speech organisation would have to con- discarded for Me " (voted good) altogether will be and sist of more than one panel, as, :aced with a good deal more Richard Hughes' " We Gave Technical points to which members of the panel call atten- for example, in connection with equanimity than would be the our Grandmother" (not so talks, where different panels good). tion in their criticisms were that case if an agitation were to there is often too much musical would deal with various series, break out now. On the principle background and that it is tco and variety, where light enter- that half a loaf is better than Confusion of Large Casts tainment would be split up into loud ; music between speeches no bread, a section of opinion at One of the most important and scenes is indeed sometimes sections to be dealt with by Portland Place is in favour of problems of the future appears so loud that the listener has to different panels. contin ing indefinitely the use to be the need formmaking plays reduce the volume of his re- of these little Nationals from easy to follow. Confusion is ceiver and fiddle about with re- Away With Scottish 5 p.m. until close -down. Thus almost certain to arise in respect adjustment when speech is Caution Scotland, which has the use of of any play in distinguishing resumed. Sound effects also In the meantime, as an ex- the z61 -metre wavelength " in between the various characters, have been overdone on occa- periment, the Scottish Region perr _ .'ity," would win only and one of the greatest dis- sions. It is the opinion that officials have been going through half a victory.

www.americanradiohistory.com Wireless World, August 61/i, 1937 129

On The Short waves Q1ti;fl t IDEAS NOTES FROM A YOU T WITHOUT are more points of interest to ACCEP THEREdeal with this week than usual. LISTENER'S LOG QUESTION .. First, I must thank two readers, L.H.B.K., of Wembley, and D.W.H., of Great Clacton, for giving me useful informa- day (or perhaps on Sunday to observers NUMBER ONE tion regarding what must have been fairly with cloudless skies) of what looks like being general reception of the Berlin sound and the largest sunspot group ever seen. vision transmission on June 16th and 17th. With the appearance of this huge group In my replies to these correspondents I (or, rather, a whole colony of spots) short- suggested that there are probably three dis- wave conditions certainly did not deteriorate, tinct cases of ultra- high-frequency indirect and on Tuesday evening W3XAL 17.78 ray transmission. These may be Mc /s even on his omnidirectional aerial be- (a) The case of 9o-mile transmission between 5 and 8p.m. was almost a local sta- tween London and Coventry, for example, tion signal, for the first time for months. or between the higher frequency Daventry By the way, W3XAL (on 17.78 Mc /s) transmission (GSH 21.47 Mc / s and GSG uses an aerial directional on Europe between 17.79 Mc / s) and London, when bending 2 and 5 p.m., a non -directional aerial be- that appears to occur in the lower atmosphere tween 5 and 8 p..m., and on S. America within first few the miles from the trans- between 8 p.m. and 2 a.m. The directional mitter, and so greatly increases-the apparent arrays used are of the large horizontal V makes height of the transmitter aerial, after which type and are equipped with reflectors. SHAVING the path is more or less optical. The bend- One must say, however, that on the whole ing is probably due to the presence of water- the relatively simple stacked horizontal the hair grow faster vapour assisted by an inverse temperature array used by W2XAD gives superior results gradient. when compared with W3XAL's European (b) The case of reception of Berlin in this beam, and this in spite of the more favour- Ofcourse, the idea is all wrong, and has been country, which may possibly via a be highly able frequency used by the latter station. a misconception. Fortunately ionised region near the E layer. proved mere The In- you accept the idea or not no penalty tense E layer will reflect signals at glancing whether results, but when it's a question of condensers, to incidence at frequencies FIVE times as high Broadcast Transmissions as those found from vertical incidence pulse imagine one is as good as another can lead to endless trouble. Condenser design and manu- exploration. Although reception of broadcast pro- facture is a specialised job. So it's wiser to ignore That is 9 Mc / s "` vertical " reflection grammes may not have been too good dur- means possible " long distance " transmis- ing the period under review, technically, hearsay and to rely on established fact. sion on 45 Mc /s. In general the highest conditions have been good, and the fort- useful frequency may be found by multi- night started well with a count of 40 sun- A PROVED plying the vertical pulse limiting frequency spots on Friday, July 16th. (the " critical " frequency) by the secant During the " Five Hours Back " proof the angle of incidence of the transmitted programme both W3XAL and W2XAD CONDENSER FACT ray. were just as good here, but Tatsfield certainly improved the signal tó noise ratio Vertical and Glancing Incidence by at least 10 db's over my direct reception. T.C.C. CONDENSERS ARE On the other hand, my receiver preferred Energy projected at less than 5° from the hori- THE ACCEPTED STANDARD zontal is wasted on earth losses, and, in any case, W3XAL, but Tatsfield apparently stuck to owing to the earth's curvature the angle of incidence the more reliable Schenectady transmitter. OF EFFICIENCY at the F layer remains uealtered at 72.5° as the CONDENSER - projection angls at the transmitter is lowered from At 11.45 p.m. on Friday evening W3XAL 5° to 0 °, i.e., to the direct ray condition. was still just as good, but W2XAD by this THE NATURAL OUTCOME OF For short -wave working, therefore, it is best to send a pencil of rays between 5° and 15° from the time had reached local- station merit. horizontal. A thunderous bellow in the 17 Mc / s band OVER 28 YEARS For a given angle of projection approaching the on Sunday afternoon, July 18th, announced horizontal, bending will he secured from the E region SPECIALISATION more readily than from the F region when the ionisa- German oratory via DJE, an excellent tion of the E region exceeds half that of the upper layer. signal on 17.76 Mc /s. Later in the evening This is bec.use the effective angle of incidence at W3XAL was good again. the layer is greater (to the normal) the lower the layer height, therefore the secant or multiplying The highest frequency intercepted on factor is also greater. Tuesday evening was IRX on 24 Mc /s Vertical incidence =0 °. working PSN, accompanied a "Glancing" incidence =72.5" (F), 80° (E). by strong For vertical incidence the projection angle will, of echo of abnormal delay. course, he 00 °. Very strong signals from LSE, W2XS and Sec. 72.5 ° =3.33. Sec. 8O' =5.99. PPX around the 20 -21 Mc / s band were also (c) The classical example of extreme F2 a feature. region bending, that is, the reception of the In the 9 Mc / s band later both PRF5 and Alexandra Palace sound and vision signals W2XAF were surprisingly good, but PRF5 in Johannesburg, New York, etc. is worried nowadays by the new 10 kw Apparently, on June 17th the signals from Mexican XEOO (not XEWW as previously Berlin were so strong between 2.3o and 2.4o given), who also uses 9.5o Mc /s with others. p.m. as to be mistaken for Alexandra Palace Conditions were rather poorer on Friday in London. evening, July 23rd, although W3XAL In Great Clacton on both days the signals staged a come -back at 11.10 p.m. were stronger than those from Alexandra A feature of the evening's reception was Palace, i.e., both sound and vision. the good results from a Buenos Aires trans- T.C.C. The second point of interest is the grant- mitter on 18 Mc /s, performing an excellent ing to the G.E.C. at Schenectady of a licence relay of the speeches at the inauguration of ALL-BRITISH by the F.C.C. to use loo kw. on both the Argentine Administration's official short- W2XAD and W2XAF. A statement issued wave news service. Good reception of the by the company states : " The new trans- ceremony and speeches was also obtained CONDENSERS mitter will be a linear, radio frequency am- from LRX on 9,66 Mc /s. The Telegraph Condenser Co. Ltd., Wales Farm Rd., N. Acton, W.3 plifier and may be used on either of the This transmission was also advertised for two stations." LSX, but no signals were obtained on LSX's Thirdly, we have the appearance on Mon- normal frequency. ETHACOMBER. =39ß

www.americanradiohistory.com 130 Wireless World, August 6th, 1937

Tracking Down interference AWRITTEN 'answer to a parliamentary RANDOM RADIATIONS question the other day disclosed the fact that the G.P.O. employs 25o men whole - Towards Better Servicing time and spends some £90,000 a year in investigating the complaints made by owners THE course in radio servicing for teachers By of wireless sets about interference with their was recently "DIALLIST" in technical schools which reception from electrical machinery and so of Education in co- organised by the Board on. This means that on the average each operation with the Radio Manufacturers' complaint dealt mark beginning of a Weather and Wireless with costs rather more than Association may the z. As the service is free and to in and repair of available new era the maintenance THIS is not a note on the Heaviside layer, all, the holder of a ten -shilling receiving wireless in this country. Hitherto, the sets or atmospherics, or the full moon, or licence who is given help by the Post Office position hasn't been too good. There are anything of that kind. It deals with an in getting of know rid of interference obtains pretty servicemen-many them -who extraordinary case of our old friend, the good value for his money. The G.P.O. their job thoroughly and do sound, honest intermittent fault, which was found to be kind are people do excellent work, and I know of work. But servicemen of the other due to weather effects and nothing else. A many still far too numerous and one trouble is cases where they have tracked down Manchester expert was called in to examine serious interference to its source and have that it may be so difficult for the man who a set which sometimes produced ear -splitting servicing to obtain been able to persuade the owner of the wants to take up radio crackles for twenty minutes or so after it offending appliance the necessary practical training. There are, to install suitable sup- had been switched on. At the end of that pressor devices. The big trouble, though, is I believe, certain courses available both by time the noises would fade out, the set work- correspondence and by actual workshop in- that if he proves recalcitrant they can at ing perfectly. /Tote particularly that this present exercise no form of compulsion. struction. But it may not be too easy for didn't happen every day ; it occurred just a youngster to find either the time or the When the long -promised anti -interference now and then. The receiver had previously legislation does at last come into force both money to take them. If the course for been tested by others, who had tried various teachers means that it is intended to their lot and that of the listener will become expedients without success. It was now easier. develop a scheme for evening classes in wire- placed on the test bench for a fortnight and less servicing at centres in many parts of during the whole of that time it never once the country, the idea is quite excellent and played -up. Then came one of those sop- Listeners Can be Awkward, Too ! should be warmly welcomed. ping, steaming days that do happen in Man- Some listeners, too, are very unreasonable chester. The set was switched on : there in their attitude towards the G.P.O.'s efforts Side -lines and Main Lines were loud crackles for twenty minutes. to help them. Some time ago I had a most At the present time there are believed to Then the crackles died away and perfect re- indignant letter from a man who had been be 15,000 or more dealers in wireless sets in ception was obtained. Tests of a variety of suffering from interference so severe that the this country. Many of them originally took kinds showed nothing amiss, but a careful home programmes were completely ruined up wireless as a side -line, combining it with examination of the wiring, plus a bit of during the day -time. Six other households the selling of musical instruments, domestic quick thinking, gave the key to the prob- were affected and a joint complaint was electrical appliances, cycles, photographic lem. On a "hot" connection to one coil made. The cause of the interference was supplies, and so on. In some cases the side- far too much solder had been used. The found to be an electric motor in a workshop ` line developed so rapidly into a " main " blob " was within a hair's- breadth of near by. The proprietor stated ' that he litre " that it completely overshadowed the touching the chassis, though it just didn't didn't believe in wireless and refused to original business. Other men went straight touch. In wet weather condensation was spend a penny on making things better. He into wireless as a whole -time job. They had sufficient to produce a partial short between was, however, persuaded by the exercise of usually been, beforehand, keen amateurs in the blob and the chassis. As the set warmed considerable tact to agree to the fitting of the pre- broadcasting days and had learnt all up after being switched on, the moisture suppressors provided that he hadn't to pay that there then was to know about radio re- was dried out and the short ceased to exist. for them. The engineer reported this to the ceiving sets and their little ways. They A real teaser in the way of intermittent complainants, told them that the trouble have kept themselves constantly up -to -date faults ! could be cured at a cost of about a pound, and so have been able to give good service S ti and suggested that they should subscribe the to their customers. The man who took up How Doth the Little Crocodile amount between them. At this they all wireless as a side -line, on the other hand, ... ? went right up into the air, maintaining WHO inventor may also have been a keen amateur ; but he the of the crocodile clip wrathfully that the G.P.O. should bear the may equally well have known little or was I don't know, but we wireless cost. It has, of course, no funds from which nothing about the technical side. If he folk certainly owe him a debt of gratitude. it can draw for such a purpose. One would could find one w__o had passed through the If you go in at all for experimental work, have thought that the listeners would have amateur chrysalis stage to assist him, all for trying out new circuits as they are pub- found it worth while to secure permanent lished, and so on, the was well ; but in the course of time satisfac- crocodile clip lightens freedom from interference for a little under tory assistants became rarer and rarer. your task and results in a vast saving of three shilling a head; but they didn't, and time owing to the rapid way in which you for all I know they are still bearing it with Apprentices Again ? can make, break or change connections be- or without grinning! tween this point and that. It falls to my lot As time went on business in wireless sets ti L % grew enormously and manufacturers came to test a good many new receiving sets, and to expect the dealer to be able to tackle all for some quaint reason each one as it goes Radio -minded Denmark ordinary servicing jobs, it being understood on to the bench seems to have aerial and THE figures which the I.B.U. has issued that a defective set should be returned to earth connecting arrangements quite dif- recently of the numbers of wireless sets the works only when it had developed some ferent from those of its predecessor. Some- in use in various countries and the relation serious or intricate fault. This was all very times plugs of different sizes are used; some- that they bear to the population make in- well when receiving sets were fairly simple times there are screw -down contacts. To teresting reading. The highest percentage in their wiring and in their general make- keep on changing plugs at the aerial and of listeners is to be found in Denmark, up. To -day real skill and knowledge are earth ends of your leads is a bore. Croco- where very nearly zo per cent. of the entire often required to track down a fault reason- dile clips solve the problem, for all you have population own receiving sets, the actual ably quickly and to deal with it. To me it to do if there are plugs is to remove figure being one in every 5.2. Denmark, seems a thousand pities that the old appren- temporarily their insulating sleeves. The however, is in a particularly favourable tice system has so largely disappeared. In clips then take a good firm bite of the metal position, both geographically and otherwise. wireless servicing it would be peculiarly part that is left. They are better still Physically it is almost as flat as the pro- valuable. A boy with a bent that way could for screw- downs, for there is nothing then verbial pancake, the only two hills (they be entered as an apprentice with an to remove and they just go straight on. I certainly can't be called mountains) of any approved firm on leaving school and after, wonder, by the way, if you know the simple importance rise to heights of less than 600ft. say, five years he would be fully qualified tip for insulating crocodile clips so as to Any reader who has steamed or sailed past as a trained service -man. M it is, any num- avoid accidental short circuits? Just give the coast of Denmark will remember that ber of firms want servicemen ; but they them a couple of coats of Brunswick -black, you can see for miles inland. This means, want them fully fledged, and the supply just taking care afterwards to see that the points naturally, that it is a country very easy to isn't there. of the teeth are bright and clean. provide with broadcasting services. As its

www.americanradiohistory.com 7,7fpsIl®oo AUGUST 6th, 1937. MpH Random Radiations - data have to be used. Since there is no siech extreme length is only about 200 miles and thing as a wireless receiving licence, the its greatest width, including the islands, exact total of receiving sets legitimately in somewhat less, the whole country is well use cannot be ascertained. The official esti- covered by the Kalundborg and Copen- mate is 24 millions, which gives a hagen stations. Apart from this, Denmark proportion of one set to each 5.7 Americans. obtains excellent reception from many The most surprising statistics of all are those other European countries, especially Nór- concerning Italy. Here is a country with a way, Sweden, Germany, Holland and very good broadcasting service consisting of Poland. 15 stations, of which three are rated at 5o kilowatts, two at 20, three at ro, one.at Britain Next 7, one at 4, two at 3, one at 2, one at 1.5 The second place goes to our own country, and one at 0.2. Yet there are less than in which, on the licence figures, one inhabi- three -quarters of a million holders of receiv- tant in every 5.4 possesses a wireless set. ing licences, a proportion of one Italian in This is actually higher than the proportion 58. Italy thus makes a much poorer show generally allotted to the United States, than Russia, which returns a proportion of though this country does not appear in the one receiving set to every 41 inhabitants. I.B.U. list. In arriving at a figure for the The figures for France are one in 1o.4 and United States, estimates rather than actual for Germany one in 7.9. Letters to the Editor The Editor does not hold himself Logging Australian SW Stations responsible for the opinions RELATING to his remarks in July 16th of his correspondents issue of The Wireless World, perhaps " D. Exer " would be interested to know that VKzME, Sydney, Australia, is audible Most commercial receivers suffer from the on Sunday morning from 05.00 to 07.00 latter fault, resulting in woolly reproduc- A HIGH SENSITIVITY (G.M.T.). VK3LR, Melbourne, is also tion execrable to the sensitive ear. Per- audible occasionally. Signals seem to fade sonally, I have a particular grouch of my SPEAKER OF REALLY out after 07.30 or so. VK3LR should be own. I can at present pick up the National CONVENIENT SIZE audible on Saturday morning, between and Regional transmissions on a simple set 04.0o and o7.00, since it usually relays the consisting of an MHD4 feeding into a When operating conditions require local sporting commentaries at this time. PX4 valve, and although the reduction extreme sensitivity without demand- Sunday, July 4th, 06.30 -06.45, VK2ME, of power made in the National was a nasty ing the exceptional power handling R3, QSA3. Sunday, July nth, 06.30 -07.00, jar I still have adequate output to fill a capacity of the big Rola G1z -PM, the VK2ME, R6, QSA4 -5 ; 06.30-07.1.5, large -sized living -room. Both stations be- Rola F742 -PM is the ideal unit to VK3LR, R6, QSA4 -5. Sunday, July 18th, ing on the medium wave, of course, lends use. Its flux density of 11,500 lines 05.0o, VK2ME, R4, QSA3 ; o6.00, VKzME, itself to a simple switch -over arrangement per square centimetre is as great R6 -7, QSA4 -5 ; 06.30, VK2ME, R7 -8, much appreciated by members of my as that of the larger model, yet its QSA5 ; 07.0o, VKzME, R7, QSA5. family. Now I shall have to add a long - price is only 49/6. In other respects The receiver used is a temporary affair wave winding and an RF valve. also the F742 -PM is a remarkable (as I am on a visit from Melbourne), con- While I realise my own case is of no im- speaker. The transformer is rendered portance, I hope you will use sisting of a PMIHF regenerative detector. your influence damp proof and dust proof by means with a transformer- coupled pentode to persuade London listeners that the important change now being made by the of a special metal and compound (PM22) output. shield, whilst the use of the new With a directional aerial and a better re- B.B.C. is not in their interests, and that the sooner they wake up to the fact the magnet material " Alnico " greatly ceiver very good reception should be pos- without undue sible. D. J. COLE. better. SIDNEY H. MEAD. increases its efficiency weight. For battery set or extension Peterborough. London, N.W.6. - speaker use and for all replacement Set and Loud Speaker purposes where extreme sensitivity National Close -down is desired, the Rola F742 should be YOUR comment on the lack of notice WHILE I am in favour of " Diallist's " selected. Write to -day for details. taken by the public of the B.B.C.'s suggestion _ that a standard chassis decision to close down the London and should be offered alternatively (and at an North National transmitter is open to a appropriate price) in a de luxe cabinet of simple explanation. solid wood, I should be inclined to go fur- In common with several other people with ther and insist on a separate loud speaker - whom I have discussed the matter, I was not stood on top of the set, but in another not aware that any such step was to he part of the room; the speaker transformer, taken, but herewith I wish to lodge an too, should be in the set rather than fixed to emphatic protest. the speaker itself. It is pure nonsense to I believe the B.B.C. are under the im- say, as it has been many times, that sets are pression that the vast majority of listeners made self- contained in accordance with are in possession of sets that can pick up public demand, for don't we know that the WITHOUT TRANSFORMER 42 - lay public has to put up with whatever the any transmission from China to Timbuctoo. OVER' 8 MILLION IN USE I strongly disagree. While the abovef is an trade decides to provide? At one time the i exaggeration, of course, it is a fact that the energised speaker was so markedly more effi- majority of sets are either of the simple cient than the permanent magnet type that variety or, if of more ambitious character, there was some excuse for killing two birds sadly bowed down with years. with one stone and having the speaker field The reception of Droitwich in London is at hand to mop up surplus juice and save a open to two criticisms : - choke in the process; but now there is so (r) Atmospheric interference as a result little to choose' between the types that the 7lie Gf/ot;( 7-i>kedE R, yroduceig4 of the lower field strength. excuse has dissolved into hot air ! Anyone (z) Attenuation of the higher frequencies likely to insist on the energised magnet THE BRITISH ROLA CO.. LTD. brought about by the characteristics of the would also be just the sort of listener willing MINERVA ROAD, PARK ROYAL,N.W.10. long -wave coil windings -space does not to provide separate excitation. PHONE WÌLLESDEN - 4322 -3- 4 -5 -6. permit me to enlarge on this. Plympton. L. J. VOSS.

www.americanradiohistory.com < 3, Wireless World, August 6th, 5937

The British abstracts published here are prepared with the permission of the Controller of H.M. Stationery Office, from Specifications obtainable at the Patent (Mica, 25, Recent Inventions Southampton Buildings, London, W.C.2, price I - each. A selection of patents issued in U.S.A. is also included. MECHANICAL SCANNING Brief descriptions of the more interesting radio covering the area in question. Any OWING to the spiral arrange- slight variation in frequency of ment of the apertures in a devices and improvements issued on patents the transmitters is then of na con- scanning disc, the picture -area will be included in this section. sequence, as it only affects the re- scanned is actually wedge- shaped, lative spacing of the interference as shown at ABCD in Fig. 1, in- bands W. stead of the correct rectangular and focusing electrodes, nor spring base, which is made suffi- The presence of an aeroplane shape shown shaded. The reason through the centre of the aperture ciently flexible to. allow the aerial. K moving through the field is is that the aperture it A, being in the control diaphragm and dis- to be bent out of the way of a made evident by the fluctuations tortion of the picture results. tree or other obstacle, so as to in amplitude of the energy which According to the invention, an avoid damage. Afterwards it re- it reflects back to a receiver R auxiliary field is applied from out- turns automatically to its normal side in position. located outside the field. the tube order to correct upright Telefunken ges. fur Drahllose any false deflection produced The flexible mounting consists Telegraphie m.b.h. Convention, in this way. The field is derived of two helical springs, one placed from two semi-circular magnets inside the Other. The outer spring date (Germany) August 59th, which are 'mounted outside the is closely wound, and the inner 5935. No. 465022. tube. They are arranged to slide one stretched under considerable one inside the other, so that either tension. Both springs are insu- the like or unlike poles on each lated from the chassis, and are can be brought together in order short- circuited by a flexible con- to adjust the strength and direc - ductor, so that the signal currents tion of the required field. do not pass through them. Fernseh Akt. Convention dates Marconi's Wireless Telegraph (Germany) October 19t1í. 5934, Co., Ltd.,' and E. H. Trump. and February 28th, 1935. No. Application date October 241h, 464637. 5935. No. 464789. o o o o 0 0 0 0 TIME.BASE CIRCUITS SUPERHET. RECEIVERS BOTH the line and frame scan- A N fluctuation in the local - ning frequencies of a tele- oscillator frequency of a super - Method of locating aircraft by vision receiver are generated by het set, due to variations in the wireless. the same valve V. The line -fre- mains supply voltage, is apt to be- 0 0 0 0 quency condenser C is charged come troublesome when receiving through á saturated diode or other short -wave stations. PREVENTING "WHISTLES" constant- current device D, and is A method of automatically sta- HEN a set is receiving a given discharged through the valve. It bilising the frequency consists in W station, interference in the produces line -scanning oscillations, tapping the operating voltages for form of " whistles " is often caused under the control -of the synchro- the local- oscillator valve from a by the beating of the incoming car- nising- impulses applied to the grid potentiometer which is earthed at rier wave with its nearest neigh- bour on the frequency of the valve. - an intermediate point. The screen - scale- A second condenser Cs, for the grid voltage is tapped 'off from a usually 9 kc /s off tune. The figure framing frequency, is also shunted point on the resistance above the shows a simple circuit designed to eliminate this source of trouble. The output from the previous detector valve (not shown) is fed through a pentiometer P to the mid -point of Fig. I. - Illustrating h o w two coils L, L5, " trapezium " can be present which are reversely wound and with mechanical scanning tightly coupled together. Both apparatus. coils, in series with a leak resist- Fig. 2.- Method of arranging ance R, are in the input circuit of the apparatus to counteract the the valve V, and one of them is defect shown in Fig. 1. shunted by a condenser C, which is preset to tune it to the closer to the centre of the disc, " whistle " frequency of 9 kc /c sweeps out a shorter arc AD than the aperture B which is farther away. This so- called " trapezium " distortion becomes more noticeable as the number of scan- Generator of scanning oscillations using a single valve for line ning lines increases. and frame frequencies. According to the invention a remedy is found by deliberately across the same valve, but is earthed point, and a resistance be- introducing a certain amount of isolated from the first by an im- low that point supplies grid -bias. optical distortion, so that one pedance K. This condenser is The two resistances are of such effect compensates for the other. similarly charged through a diode relative value that the effect of any For instance, as shown in Fig. 2. Dr, and is discharged when fram- variation in anode potential is off- the film F that is being scanned is ing impulses are applied _ to the set by a corresponding change of inclined to the focusing lens L at grid of thé valve. The presence grid voltage. The screening grid one angle, whilst the scanning disc of the impedance K prevents the is biased to maintain the ampli- I{ is in inclined at another angle condenser Cr from losing more tude of the oscillations at . a the reverse direction. than a small proportion of its favourable level. Radio Akt. D. S. Loewe. Con- charge during the time that line - Radio Akt. D. S. Loewe. Con- vention dates (Germany) October frequency oscillations are being vention date (Germany) July 251h, and November 6th, 1934. produced by the condenser C. The 591k, 1935. No. 464609. o o o o No. 464835. valve V may be a tetrode or pen- Circuit to suppress adjacent - o 0 0 0 tode, or a gas- filled discharge de- " SPOTTING " BY WIRELESS channel heterodyne whistle. CATHODE =RAY TUBES vice. THE presence of an aeroplane, THE proper alignment of the Baird Television, Ltd., and or other moving conductor, The desired signals are developed electron stream in a cathode - E. E. Wright. Application date inside an area under supervision is across the resistance R, the coils ray tube may be affected (a) by October 29th, 1935. No. 465055. detected by the arrangement presenting only a small impedance stray magnetic fields originating o o o o shown in the Figure. Two short- to them, though a large one to the

outside the tube, or (b) by . fields, AERIALS wave transmitters A, B, are in- interfering "whistle." usually electrostatic, produced in- A SHORT vertical aerial, suit- clined at an angle to each other, E. K. Cole, Ltd.; G, Bradfield side the tube. Due to their in- 1- able for use on certain kinds so that the overlapping beams set and A. E. Falkus. Application fluence the stream does not pass of vehicles, particularly on tanks up an " interference pattern, " or date December 14t1í, 5935. No. axially through the accelerating for warfare, is mounted on a system of standing waves W, 464157..

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