THE PRACTICAL RADIO JOURNAL 26 th Year of Publication

No. 905. FRIDAY, JANUARY 1sT, 1937. VOL. XL. No. 1.

Proprietors : ILIFFE & SONS LTD.

Editor : HUGH S. POCOCK. The New Year Editorial,

Advertising and Publishing Offices : Promise of Many Developments DORSET HOUSE, STAMFORD STREET, LONDON, S.E.s. 7 might have been supposed that, should pave the way for conditions of Telephone : Waterloo 3333 (So lines). wireless being no longer in its reception, especially in large towns, Telegrams: "Ethaworld, Sedist, London.' infancy, and broadcasting having better than anything which has hitherto COVENTRY : Hertford Street. now been with us for some fifteen been enjoyed. The probability exists, Telegrams: Telephone: "Autocar, Coventry." 52 ro Coventry. years, the year which we enter upon also, that changes in wavelength alloca- with this issue would show promise of tion in Europe may come about, BIRMINGHAM: no remarkable changes or develop- resulting in an improvement, at least Guildhall Buildings, Navigation Street, L ments of importance. Yet from all with the larger of : transmitters, Telegrams Telephone : "Autopress, Birmingham." . 2971 Midland (q lines). appearances the very reverse will apply, reception . conditions as far as ad- because no time in of MANCHESTER : 260, Deansgate, 3. at the history jacent- channel interference is con-

Telegrams : Telephone : wireless have there been more positive cerned. "Muffe, Manchester." Blackfriars (4 4412 lines). indications of really important achieve- Promises have been made that, in GLASGOW : 26B, Renfield Street, C.2. ments in view. the broadcast programme field, 1937 Telegrams: " Inge, Glasgow." Telephone: Central 4857. Short -wave developments, both in will see an increase in the exchange of PUBLISHED WEEKLY. ENTERED AS SECOND the broadcasting and general corn- national, programmes, thus helping to CLASS MATTER AT NEW YORK, N.Y. munication fields, are being planned improve cultural relations as between Subscription Rates : on a big scale in almost every country one nation and another. Home, ¡s is. 8d. ; Canada, LI Is. 8d. ; other in the world and new services are countries, £I 3s. sod. per annum. promised for early in the New Year. Receiver Progress As many of the circuits and apparatus described in These The B.B.C. has several additional pages are covered by patents, readers are advised, before In the sphere of reception it is making use of them, to satisfy themselves that they would transmitters in preparation for an not be infringing patents. im provement in the Empire service, difficult to anticipate how important and these transmitters may be expected may be the changes which may develop. to be in operation during the year. Short -wave reception circuits will un- doubtedly improve and many refine- Television Hopes ments which have already been CONTENTS disclosed in theory may be expected Page Television has passed through its to find their way into practical applica- earliest stage of development as a tion. The electron Editorial Comment. . .. 1 multiplier, the service with fair success, and if tele- development of which in connection Microphones : Pressure and Vel- vision is to provide a lasting service in with television has been greatly stimu- ocity .. 2 the future, then it is certain that 1937 lated, still holds promise of staging a Broadcast Research 5 Receiver must see important programme changes revolution in amplifying circuits ; A New Detector Circuit . . 6 in addition to improvements on both whether or not progress in this direction Broadcasting in the Balkans 9 the transmitting and receiving side. will be sufficiently rapid to promise any If no means are found to improve the radical changes in the nature of re- Current Topics . . 11 programmes of the television service ceivers during the year it would be Ferranti Arcadia Set 12 Review out of present funds, then an alternative unwise to anticipate, but that in the Unbiased . . 1-1 event of 1937 might be a new financing electron multiplier we have a potential The Beam Power Tube . . 15 scheme. revolutionary influence in receiver de- Listeners' Guide for the Week 16 With the commencement of the sign will not be disputed. Principal Broadcasting Stations 18 year the B.B.C. enters upon a new The Wireless World enters this year lease of Brilliant Television 20 ten years' renewal of its upon its twenty- seventh year of pub- Charter. lication, and we may hope that the Broadcast Brevities.. 22 1937 should show the introduction record of events which its pages will Letters to the Editor 23 of the much -discussed legislation to chronicle will make this one of the Recent Inventions ...... 24 control electrical interference, and this most interesting years of its existence. Wireless World, January ist, 1937

PRESSURE Microphones AND VELOCITY Main Characteristics and Applications By F. N. G. LEEVERS, B.Sc., A.C.G.I. of the Two Types

IT has been frequently stated that of below a mean value which is the atmo- all the links in the broadcasting trans- AN explanation of the essential spheric pressure. It is this alternating mission and reception chain the micro- difference between the two variation of pressure to which pressure phone microphones and the loud speaker are by far principal types of microphone and respond. the weakest as regards both efficiency and The air pressure at any point is indi- a discussion of the properties, fidelity. Although they occupy such cated in the diagram by the density of the particularly with regard to direc- extreme positions in the chain, the reasons particles ; hence variation of pressure due for their shortcom- tional characteristics of examples to sound waves involves the movement of ings arise from the in common use. the air particles towards or away from the NO SOUND very similarity of A B source of sound. Particles cannot move in functions. any other directiop unless their Fig. 1. - Dis- influenced by they are both SOUND ...... placement of air another source of sound, and they will electro- acoustic de- P R P R particles under only move about a mean position which vices, and while the influence of sound waves. remains constant. Except when very close electrical measure- to the sound source, the velocity of the ments of a high order of accuracy can be the air particles. This re- grouping is shown displacement of the air particles is pro- made with comparatively simple and inex- in the accompanying table. portional to the variation of pressure. pensive apparatus, the same cannot be Reference to a suitable illustration of the From the last paragraph it can be seen said of acoustic measurements. Further, propagation of sound in air will indicate that a microphone which responds to acoustic conditions have a very important the fundamental differences between the " particle velocity " will only indicate the effect on the results obtained both in two types of microphones. In Fig. i the component of this velocity' which lies along laboratory measurement and in practical line of dots indicates the positions of air its " major," or sensitive, axis. Since use. particles along a straight path radiating pressure microphones respond equally to it is perhaps not surprising, therefore, from a source of that in the case of microphones the choice sound situated to the of types suitable for commercial use was, left. When no sound until a few years ago, very limited, being is emitted from the confined almost entirely to various types source the particles of carbon transmitter. In recent years, will be equally however, the rapid increase in the variety spaced, as indicated of uses to which the microphone is put, A B. When a sound many of them involving very adverse con- of given frequency is sslDaNti ditions, has led to intense research, and emitted by the 1111111111m. this has resulted in the production of a source, waves of number of new designs, in which good high and low pres- frequency and amplitude characteristics, sure will radiate from EQUIVALENT MICROPHONES OF THE PRESSURE AND VELOCITY TYPES.

Electrical Pressure Type. Velocity Type. Characteristic. (a (b) Electro -Dynamic r. Moving Coil Ribbon 2. Inductor Piezo- Electric Sound Cell Differential Capacity Non- directional Differential Condenser Condenser

together with low noise level, have been Fig. 2.- Diagrams a and b show a velocity achieved. They include the " ribbon," ribbon microphone in the " inductor," the moving coil, the front elevation and crystal, the differential crystal, the con- section, while c is a pressure ribbon micro- denser, and the differential condenser Dl ,//////ae microphones. These various types are phone with enclosed back. A moving -coil (e) usually regarded as belonging to categories type is shown in (d) determined by their method of converting diagram d. acoustic to electrical energy-i.e., they belong to ' one or other of the electro- it-i.e., they will traverse our particular sound waves arriving from any direction dynamic, piezo -electric, or capacity types. row of air particles from left to right, as (neglecting special effects due to size and In practice, however, it is far more indicated at P and R respectively. At a shape of the microphone itself), the direc- useful to group them under the two main fixed point anywhere along our line of tional characteristic, or " polar field,"

headings of pressure and velocity, accord- particles the pressure will appear merely constitutes the major , difference between ing to whethe they function by virtue of to rise and fall as each wave passes. The the performances of the two types. the pressure variation or the velocity of pressure will actuálly alternate above and Having outlined the different acoustic ist, 1937 MmIlsoo 3 JANUARY WopIldt Microphones- construction of a typical moving-coil very low, so that several cells are usually operations involved in the two types of microphone, and a close resemblance to a assembled in series-parallel to increase the microphone, let us return to the three main small moving -coil loud speaker is evident. output while keeping the impedance at a electrical categories, i.e., electro- dynamic, No baffle is used with the moving -coil reasonably low value. The impedance is piezo -electric, and capacity, comparing the microphone, but the back of the dia- of a capacitive nature, so that, although main constructional features of the velocity phragm is usually enclosed as in the case capacity in the connecting cable will not and pressure examples of each. of the inductor type. affect frequency response, it will reduce The main details of a ribbon (velocity) The moving coil may consist of many the available output, as it does in the case microphone are shown in Fig. 2a. A very turns of thin wire instead of the single of a condenser microphone. thin light strip of conductor of the In general, a condenser microphone aluminium is sus- ribbon type ; hence consists of a small condenser in which one pended by its two the impedance is electrode is stationary while the other is ends in an intense much higher, being free to vibrate under the influence of transverse m a g - usually in the sound waves in such a manner that the neighbourhood of spacing and therefore the capacity be- netic field between 2 CRYSTAL LAMINATIONS the pole -pieces. The CEMENTED TOGETHER 20 ohms. The need tween the electrodes varies. Such a micro- ribbon is corru- f or a matching phone does not generate voltage as the gated concertina- transformer close other types do, but if the condenser is fashion at right - to the microphone charged from a battery through a high angles to its length is thus avoided. resistance, variation of the capacity of the to give it sufficient Turning to piezo- condenser will cause charging and dis- flexibility to permit electric micro- charging currents to flow through this free movement in a phones, it w a s resistance, and the voltage drop across it backwards and for- shown in a pre- will thus vary, with the movement of the w a r d s direction, vious articles that free electrode. while avoiding any voltages were pro- danger of its mov- duced by bending Condenser Microphones Fig. 3.- Diagrams a and b show, respectively, of ing sideways so as velocity and pressure crystal microphones. a certain type to touch the magnet crystal element. If An early form of electrostatic loud pole-pieces. Both front and back of the such an element is sufficiently thin and speaker consisted of a metallic diaphragm ribbon are open to the air, as shown in flexible and is supported at one end, or at insulated from and mounted in close the side view (Fig. 2b), and the adjacent the two ends as indicated in Figs. 3a, the proximity to a perforated metal grille. A magnet poles are shaped to give the unsupported portion will be free to vibrate similar construction has been modified to minimum obstruction to sound waves. in sympathy with air vibrations, thus form a condenser microphone of the the ribbon, or at any rate most causing distortion of the laminations and velocity type as shown in Fig. 4a. In the Since type, of it except for the ends, is free to move setting up voltages across the electrodes. more familiar pressure- operated with the vibration of the air, In this form, the crystal mircrophone is however, the fixed electrode is solid and in sympathy as alternating voltages are induced in it. velocity- operated and is sometimes called completely encloses the air dielectric in q,b. Although a These voltages are very minute, and to a " differential " element. If two such shown Fig. diaphragm resistance loss in connecting cables elements are mounted back -to -back of duralumin foil has been extensively used avoid made gold -up transformer is usually fitted in against spacers at the ends, closing the for many years, a new type of a step has successful. The design of the housing of the microphone above the sides by a flexible seal will form a small leaf proved the leads to the air space between the elements as shown the fixed electrode varies considerably magnet, thus keeping In some cases it ribbon very short. in Fig. 3b, and any variation in pressure with different makers. of the surrounding air will cause both is solid with shallow channels or slots cut Pressure -type Microphone elements to bend in- wards or outwards By enclosing one side of the ribbon as the case may be, while still leaving the other accessible to causing voltages to sound waves, as shown in Fig. 2c, the appear across both i ribbon becomes sensitive, not to air - sets of electrodes. INSULATION particle velocity as before but to the varia- This constitutes a tion of pressure in front of the ribbon pressure - operated VENT compared to the mean pressure on the crystal microphone, DIAPHRAGM enclosed side. This is usually called an w h i c h is usually NDIAPHRAGM ribbon micro- called a sound cell. " inductor," or pressure- FIXED. phone. Of course, the method of enclos- In commercial types ELECTRODE ing the back of the ribbon has a great the sound cell is M.asaS4 effect on the results obtained. A solid mounted in a rect- ,,,, backing cannot be placed very close to the angular paxo1in S ribbon, or no movement will result from frame and enclosed (a) (b) changes of pressure, while a hollow air by thin paper which cavity cannot be used, since an enclosed is varnished to pre- quantity of air has mass and elasticity and vent the ingress of Fig. 4.- Velocity and pressure condenser microphones. therefore a natural frequency at which it moisture which will resonate. The interior of the cavity would disintegrate the crystals. The in it, while in others a small hole through is therefore fitted with suitable baffles and natural frequency of the sound cell is kept the back communicates with the outer air, damping material to avoid this. The very high in the audio scale by using thus allowing the mean air pressure be- arrangement sometimes takes the form of crystals of small dimensions. The most hind the diaphragm to remain at atmo- a long folded tube. popular type at present in use employs spheric level under all conditions. In one Increased efficiency may be obtained crystals which are less than half an inch version a second smaller diaphragm, fitted from the pressure -dynamic microphone by square, and the natural frequency is over in a compensating chamber behind the attaching a diaphragm to the moving 12,000 cycles per second. fixed electrode, can move to allow element, when it is found convenient to The voltage output from single cells is equalisation of pressure through the vent use a coil of wire in a radial magnetic field ' Improved reproduction from discs, The hole, while preventing the entry of mois- instead of a ribbon. Fig. 2d shows the Wireless World, April z4th, 1936. ture, dust, etc. WIpA.mg, JANUARY ist, 1937 WoreDd Microphones- complicated for efficiency. The non - Although the velocity types of crystal directional type of ribbon microphone and condenser microphone included in the which responds to pressure instead of above descriptions have not come into velocity has largely superseded the general use, the following practical obser- velocity- ribbon in film work. In open vations, which refer to ribbon -velocity air work, owing to the absence of walls microphones, would also in general apply and similar sound-reflecting surfaces, un- to them. wanted sounds can sometimes be " tuned The polar response curve of a out " by careful positioning of the velocity velocity microphone is of the cosine, or microphone, in the same way as unwanted " figure eight," type as shown in Fig. 5. stations can be " tuned out " by using Here XX is the major axis and the a directional frame aerial with a radio set. response r to a wave arriving at an angle Trouble, however, is usually experienced 0 to the major axis is : from wind noise, even when a wind baffle r = OA Cos 0 is used. thus the response at right angles to the As stated previously, the pressure Fig. 7.- -Polar response of radial type crystal major axis is zero. The response to the microphone should theoretically respond microphone at various frequencies. Curves " back " OX is similar, but opposite in equally to sound waves arriving from all are taken at different sound levels for the phase. Fig. 6 shows polar curves for a directions. Practical considerations, how- sake of clarity. commercial ribbon microphone taken in cially available with transmitter elements the open air, and the general shape can be little more than rin. in diameter, and appreciated although focusing at high they have proved to be non -directional up frequencies is evident, and is probably to relatively high. frequencies. Piezo- due to the design of the field pole- pieces. crystal elements are usually even smaller Ribbon microphones have in- become than this. Fig. 7 shows the polar dia- creasingly popular for use in broadcast gram of- a crystal microphone incorporat- studios on account of this limited field of ing two cells just over ¡in. square, and it response. They are not liable to pick up will be seen that the field of response is unwanted sounds direct except at the back extremely regular up to 8,000 cycles. The of the microphone, and the effects of tendency for the diagram to become ellip- studio reverberation and echo appear to tical at high frequencies was due to a be reduced considerably. The placing of small felt mounting at the sides of the artists is, however, rather critical, and case. more than one microphone is usually Fig. 6. -Polar response of ribbon -velocity necessary to " cover " a number of artists. microphone at x,000 and 5,000 c /s. Studio Requirements The has used author seen as many as five ever, have usually prevented this being attained. Most types, particularly the in- In most forms of studio recording, the

ductor, the moving . coil, and the older less polar response varies over the fre- types of condenser microphone, are fairly quency range, the less complicated the large compared with the wavelength of microphone is to use. When acoustic the higher audio frequencies they are re- conditions are bad, the most usual fault

quired to pick up. ' The bulk of the is excessive reverberation or boom at low microphone therefore tends to cast an frequencies, and the only method of reduc- acoustic shadow to sound arriving from ing this electrically, is to attenuate bass. behind, and since this effect is only con- If, however, the microphone has a good fined to the higher frequencies, good tonal polar response at high frequencies, there balance is obtained to sounds arriving is obviously less need to attenuate bass. direct to the front of the microphone, but On the other hand, if conditions are good, sound arriving by other paths due to echo, the microphone will pick up reverberation reverberation, etc., is Fig. 5.- Theoretical polar response curve of a velocity microphone. decidedly b o o my and unintelligible. in balancing the various sections of a This effect is fur- PRESSURE large orchestra. ther increased by re- Care has to be exercised when working flection of the sound near to a velocity microphone, since the waves by the dia- PREESSUR particle velocity is no longer proportional phragm a n d its & VELOCITY to pressure close to the sound source. It mounting. Since the is not advisable, therefore, to croon right reflected wave is in into a ribbon microphone. But, who phase with the in- knows ? It might be a blessing in dis- coming wave at the guise ! diaphragm, the re- The velocity microphone was used for sultant pressure on i talking -film recording, but in this case its the diaphragm is in- i extremely - d i r e c t i o n a l characteristics creased. This again turned out in practice to be rather a dis- only occurs at high advantage. A broadcasting artist can be frequencies where told where to stand, and how to speak, the wavelengthis but a film artist must be allowed reason- small, and when the Fig. 8. Theoretical polar field of combined pressure- velocity able freedom of action. It is possible to sound source is in microphone. follow an artist about a film set with the front of the . micro- microphone, if this is suspended from a phone. Both these effects can be mini- and other indirect sound in its correct suitable boom, but if the microphone has mised by keeping the bulk small and tonal balance. to be rotated by remote control until it streamlining the casing of the micro- When picking up sound from a number faces the artist each time he turns his phone. of artists, there is usually little to be head, the whole business' becomes too Condenser microphones are commer- gained by using more than one pressure wflIA,®00 JANUARY 1st, 1937 WoAcl 5 Microphones- microphone, unless separate control is re- quired, as in vocal items with music Broadcast Receiver Research accompaniment. When two pressure NEW G.E.C. LABORATORY AT COVENTRY microphones are used in one room, the effect of mixing the two will usually T\ O centres of radio investigation of electrical development is reasonably free approximate to the pick -up from one have hitherto been maintained by from disturbances caused by his fellows, a microphone placed in an intermediate the General Electric Company ; one number of small laboratories, each suitable position. If sources of sound are widely for research proper at Wembley and the for one or two engineers and an assistant, separated, of course the position is other for works development at Coventry. have been provided on the ground floor of different, and individual microphones are The growth of manufacturing activities has the building. Each of these laboratories is caused congestion of provided with signal generators and stan- the space allotted to dard testing equipment, while special equip- experimental work, ment that is not so frequently employed is and so it was de- installed in other rooms. cided early in the year to erect a Isolation from Interference separate building for the development of Work requiring the total elimination of receivers. electrical interference is carried out in a, The new r a di o screened room, in which special arrange- laboratory at Coven- ments are made to prevent interference be- try is divided into ing brought in from the mains. Isolation about twenty - four proves so effective that it is impossible to re- separate offices and ceive even the most powerful transmitting laboratories, and it station or locally generated interference has been built in without an external aerial. two floors, enabling Mechanical development work includes a life test where receivers and components are tested under every conceivable adverse condition of use ; for in- stance, tropical conditions can With the help of draping and furniture, be reproduced as an aid domestic acoustic conditions are simulated to development of receivers in the listening room. capable of withstanding over- as conditions. Another the correct ction is responsible for then almost essential to obtain the maintenance of the test - balance in the reproduction. i n g apparatus throughout Pressure microphones of one form or the laboratory and alsosfor another are widely used in film recording. the design of special appara- As mentioned earlier, the straightforward tus ; in addition, it acts in an technique involved in their use is a very advisory capacity on any new important factor, particularly in view of tests that may be necessary the difficult situations frequently met with in the final inspection depart- in this class of work. ment of the factory. The preceding notes have treated the Finally, mention must be pressure and velocity microphones as made of the circuit investiga- entirely separate types, but mention tion section, for which four should be made of the possibility of com- bining the two in one instrument, and in so doing retaining the better features of each in a modified form. The full -line The screened room, curves of Fig. 8 are theoretical polar from which all out- diagrams of pressure and velocity trans- side interference is mitters. In the case of the velocity dia- excluded. grams the two halves are opposite in sine. If the maximum output in the two cases the ground floor be made equal as shown, at all fre- rooms to be made quencies, the result of combining the two reasonably sound- proof for work requir- will be the algebraic sum of the diagrams, ing silence and free- as shown in dotted lines. dom from mutual This heart -shaped diagram indicates a interferences. microphone having a relatively even re- Laboratory work sponse over a wide angle at the front proper is supple- while being practically dead at the back. mented by final This would seem to be an ideal charac- listening tests on teristic in most types of work if it remains speakers and com- independent of frequency, and no doubt plete receivers. These further developments will produce such a tests are carried out in a room in which microphone in practical form. One of the small laboratories, fitted with equipment for electrical In dealing with the various types average acoustic con- development work. of ditions are simulated microphone, the question of frequency by furnishings and drapings, etc. Half a separate rooms are available. Here infor- response has been deliberately avoided, dozen receivers at a time can be tested and mation from sources within or associated since on this score there is little to choose compared, remotely controlled relays being with the G.E.C. organisation is sorted out, between the best examples of each type, installed for rapidly changing from one to classified, and examined to see how far it is particularly when the appropriate equalis- another. applicable to present or future develop- ing circuits are used. To ensure that each worker in the field ments in radio receivers. Wireless World, January Ist, 1937 New Detector Circuit SOME causes of distortion with APPLYING NEGATIVE FEED -BACK TO the diode detector are dealt with in this article and a new detec- THE ANODE BEND RECTIFIER tor circuit is discussed which, by the application of negative feed-back, offers the possibility of a higher 111LE the performance of the resistances which give a resultant R2 corn- standard of quality. As the diode detector has been fully posed of RA, RB and Rc in parallel. The efficiency is higher than that of in issues of The neglected because treated past RF bypass condenser is a diode, the system is an attractive Wireless World, the several its value is normally so low that the effect criteria for distortionless rectification are on audio frequencies is not applicable. Fig. one. still a mystery to many. The realisation 3 shows the general circuit for a tapped of a low level of distortion in the AF RI. In this case, R2 is the resultant of the output of a diode detector subjected to same components shown in Fig. 2. In deeply modulated signals depends largely each case the coupling capacitor CI is con- on the magnitude of the ratio of the AC sidered as having negligible reactance at By W. N. WEEDEN and DC output loads. The ideal con- audio frequencies. dition is obtained when this ratio is Figs. 4 and 5 show the modulation capa- unity, which can be realised only with bility of a detector system for the cases direct coupling. If the AC load is appre- where Ri is untapped and tapped re- rigorous, the results are indicative of the ciably lower than the DC load, the ability spectively, the tapping being at the centre magnitude of the distortion involved when of the diode to handle a high percentage of of RI. It is evident that this arrangement a diode is not properly loaded. modulation is limited. increases the modulation capability of the In view of the serious distortion caused, The accompanying curves were furnished detector at the sacrifice of AF output. it would seem advisable to make more use to the writer by the Hygrade Sylvania of the direct- coupled circuit, wherein the Corporation, in whose Application Harmonic Distortion grid of the first AF tube is connected Laboratory they were made. These directly to the diode load (with no coupling curves were plotted from data obtained Unfortunately, while this data shows condenser). For the best results, the AVC by graphical methods involving the that as low a value of Ri as possible is should be of the amplified and delayed characteristics of the diode utilised in desirable, there are other factors (such as type advocated by Cocking, not only to American duo -diode triode and pentode loading, limited power handling capacity keep the input to the diode constant but valves -both glass and metal -such as of the last IF or RF stage, etc.), which to insure a constant DC or bias voltage the 6Q7 and 85 valves. The diode must be considered in current design. being applied to the grid of the AF valve. characteristics were taken with conditions Figs. 6 and 7 indicate the harmonic These defects of the diode are, of course, representing a generator impedance (cir- distortion (2nd to 5th inclusive) of the AF much smaller than those existing in other cuit feeding diode) of approximately output when a signal of roo per cent. detectors, but a new type has just been roo,000 ohms, which was considered as modulation is applied to a diode detector developed which would appear to be even typical, and a signal of 3o volts peak was loaded for various modulation capabilities. better than the diode. This new circuit assumed.. These results are based on the assumption was recently announced by the Hygrade In the preparation of this data, the that the distortion is the effect of cutting Sylvania Corp., who kindly furnished the conditions first considered were those off a portion of one half of the AF sine following curves to the writer, and it where the diode load resistor Ri (Fig. i) wave. The harmonic components given possesses several very real advantages. is a single unit and not tapped. Fig. 2 are those analysed in the cut -off portion Although this announcement was made by shows a typical case of the several shunting of the wave. Although not absolutely Sylvania as part of their service to en-

TO AVC CONTROLLED VALVES C3

Fig.1 Fig 2 Fig 3

Fig. r. The conventional diode circuit in which the DC load is Ri, but the AC load RI and R2 in parallel. Fig. z. In some cases more complex arrangements are used. Here RA, RB and Rc all reduce the AC load resistance. Fig. 3. The ratio of DC load to AC load can be made more nearly unity by tapping RI, but at the expense of a loss of output voltage. JANUARY ist, 1937 Wpsilmg 7 WOgIlcl New Detector Circuit - diode. Fig. 8 shows the schematic circuit be necessary to rearrange the circuit so gineers, the circuit was developed by the with the load resistors which were varied that proper delay voltages could be pro- RCA Licensee Laboratories of New York to obtain the data shown in the accom- vided not only for the purpose of pre- City, and to them is due the credit. panying curves. It is to be noted that Ri venting the functioning of the AVC circuit represents the load resistance at DC, while on weak signals, but also to avoid trouble F loo R2 constitutes an AC load in parallel with due to the no- signal voltage across RI. RI, thus reducing the total AC load corn - It is interesting to note that the signal W0 90 at pared with the DC load. voltage applied to the detector valve aa In Fig. 9 is shown the percentage Z0 80 WZ modulation which this detector system will 100 handle with minimum inherent distortion when loaded with different ratios of AC to 90 DC loads for various values of Ri. Fig. io I 0'2 04 08 08 1 12 14 16 80 R2 IN MEGOHMS shows the same data on modulation capa- bility plotted as a function of R2 for dif- 70 Fig. 4. -These curves show for a number ferent common values of RI to make the of values of Rs the modulation depth with information more readily applicable to 60 which the detector can deal without dis- design work. ; R2 is the total shunting value of tortion 90 100 150 200 250 300 350 400 450 the resistances following RI. Fig. II is similar to Fig. io, but gives the modulation capability of a system wherein RI IN THOUSANDS OF OHMS Considerable interest has been aroused Ri is mid-tapped so that R2 is across only by the development of this detector, partly Fig. 9. -These curves show the modulation because of its so- called " infinite input capabilities of the new detector for a 6C5 Br- valve with 3o volts RMS input and 250 volts impedance." It is actually a triode anode - MODULATION HT supply ; R = R21(Rt -I- R2). bend detector having a high resistance CAPABILITY load in its cathode circuit. This load re- 70% in this new arrangement is equal to sistance is by- passed for carrier frequencies, 95% the voltage generated in the undamped and as it is common to both anode and grid secondary of the HF transformer as long circuits, degeneration or negative feed -back 95< as no grid current flows. In a conventional large in its freedom from o plays a part 2 3 4 5 2 3 4 5 2 3 4 5 diode, however, the voltage is reduced by harmonic distortion. HARMONICS the damping of the detector. The valve used for these tests is the Fig. 7. The distortion occurring when the Type 6C5, a metal valve with an AC re- modulation is ioo per cent. and so greater sistance of approximately ro,000 ohms than the capability of the detector is here and an amplification factor of 20 at normal analysed.

loo half of the DC load. It is obvious that this > arrangement increases the modulation I- capability of the detector, but reduces the 90 AF voltage output by one -half. W R áÚ 80 While the new detector circuit has the ZZ

very desirable features indicated above, it ocF 70 Fig. 5. -These curves give the same informa- must be pointed out that a separate AVC a'WG tion as those of Fig. 4, but for the case when channel is necessary, as AVC voltage can- Ri is centre -tapped, as in Fig. 3. 060 not be obtained from this system. It has î 500. Its input impedance is nearly a pure been found that regeneration is not a 01 02 03 04 05 08 07 0'8 capacitive reactance which becomes a part serious problem if care is used in the R2 IN MEGOHMS of the tuned circuit without loading it, and circuit design and layout. this results in a considerable improvement Fig. io.-These curves give similar informa- 9, but in form. in gain and selectivity, with simplification tion to those of Fig. a different in design of coupling devices. From this operating voltages. This valve was used point of view, the infinite impedance de- as being indicative of characteristics suit- tector is a distinct advantage over the con- able for this service, and an equivalent in ventional diode. Likewise, its modulation the British range is the MHL4. Valves capability is better than that of the diode, having amplification constants appreciably and it is the purpose of this article to higher than this do not have as satisfactory present data on this characteristic in a form modulation capabilities. which can be compared with those already From limited personal experience with given for the conventional diode. this device it would seem that its power sensitivity or efficiency is several times 15 that of the diode, although not so great as that obtained from the same valve in o a conventional circuit as anode detector. Fig. 8. -A new detector circuit embodying negative feed-back is shown here. It is an 10 anode bend detector with the load resistance r/: .N R7 = 100.0000 Q70 75 80 85 90 95 50,0000 RI in the cathode instead of the anode _Ó, 90_ 00 ....M PERCENTAGE MODULATION CAPABILITY circuit. F-F_ rr 1540 ZJm Opa 80 1111011...... 1.. Fig. 6. -The amplitude distortion resulting While AVC voltage cannot be obtained when a zoo per cent. modulated signal is directly from this detector as from a diode, á20 applied to a detector having the modulation 70...... 0 0'1 0.2 03 0 4 . 5 0 8 0 it is entirely possible for the grid of the R2 IN MEGOHMS capability shown is indicated by this curve. AVC amplifier described by Cocking' to be .... The arrangement functions as a linear connected directly to some point on this resistor or detector load. would Fig. rI.-The modulation capability of the rather than square law detector, and in cathode It detector is shown here for the case when that respect is the same as the ordinary 1 The Wireless World, June 12th, 1936. Ri is centre -tapped to feed R2 through Ca. s WIpISIl®Eg°. JANUARY ist, _1937 Wopild New Detector Circuit - interest to some readers. Low -cost re- accurate ; (5), short -wave scale too small This is explained by the negative feedback ceivers with a limited number of valves will and often a long way " out." The ideal or degeneration, the use of which is always undoubtedly continue to use the diode dial would have none of these bld(on its accompanied by decreased power sensi- detector, as it is possible to utilise the DC escutcheon. It would be a real Irr icator of the setting of tuned circuits ; tivity. The writer used the 56 valve for his output of such a detector with fair effi- the it would experiments. be complete, it would, be perfectly legible This valve is an indirectly ciency and almost no additional cost as and it would mean what it said. heated triode with an anode resistance the basis of a simple AVC circuit. There- of io,000 ohms and µ =14. With a load fore the test of the new infinite impedance Can It Be Done ? or cathode resistance of 50,000 ohms the detector will come in its application and Must it remain an unattainable ideal? output was four to five times that of a adaptation in the higher-priced receivers Or can it be worked out in practical form? diode. The sensitivity would be still greater in which an extra valve would be of little I see no reason why it should not, at any with larger values for Ri. This gain is not significance. In such a circuit, the new rate in the " luxury " set. The scale itself would have to be due entirely to the added efficiency of the detector should prove superior to any but large, and this at once detector, as raises the objection that it would spoil the the input to it, or output of the direct -coupled diode, and even then, look of the set.. There are two ways out of the RF amplifier, increases with decreased it should win out because of the freedom this. One is to arrange for the dial to be loading, and it was not possible to isolate from damping on its input circuit. How- covered when it is not actually in use. The these effects in the limited time available. ever, time alone will tell, and we must second is to inscribe the scale on. a long In closing, the writer's views on the await the release of the next few receiver piece of non -stretching material mounted value of this new development may be of models before judging its merits. on rollers-only a portion of it is then seen at any time through a suitable aperture. To obtain reasonable accuracy the scale must be properly marked out in the first instance, and probably either it or the pointer must be capable of adjustment. For perfect ac- curacy hand calibration would be necessary, RANDOM RADIATIONS and I do not see why this should not be done, either as a regular thing or as an " extra," in big sets selling at largish prices. Well, A Happy New Year these are some ideas which may help to AVERY happy New Year to all readers. By "DIALLIST" start interested brains working. May it be a good one for reception and S % % crammed with interesting radio develop- Identifying Announcers ments ! I haven't much doubt that we are going to witness some big steps forward Two Hobbies THE B.B.C. sprang a Christmas surprise on us by publishing not only the names during the next twelve months, fors in THE market for the smaller set would, of several departments of wireless of its announcers, but also their portraits we seem to course, be enormous ; but what of the be just on the verge of making and the times at which they would be at the real ad- big one costing real money ? Provided that vances. Television, for instance, is full of the public was properly educated up to its microphone during the week. Myself, I've possibilities. On the technical side we are advantages, I believe it would soon sell never been able to see why announcers likely to hear a good deal more of big- screen readily. There's another hobby, photo- should be anonymous any more than com- reception, probably by a variety of graphy, which has developed on much the mentators or compères. I rather like the methods. And before the year is out we same lines as wireless, though far more American system : their announcers tell you should know much more than we do now slowly. At first cameras for the amateur who they are at the beginning and at the about the behaviour of the ultra -short waves were expensive, difficult to operate, and not end of the programme for which they are of the order of seven metres. There may very efficient. Then came the era of the responsible. Broadcasting, after all, is, or be some surprises in store there. Those simple, compact camera at a moderate should be, something rather intimate, for it who are responsible for the entertainment price. Such a camera is capable of taking brings the people in the studio right into side of television should have had time to reasonably good pictures of straightforward our homes. For that reason my view is discover its most suitable applications and subjects in favourable circumstances, and it that anything like a cold, impersonal atti- to work out a technique worthy of it. Tele- is still much the most widely used. But in tude should be avoided, particularly in the vision programmes, in a word, should the last few years highly efficient cameras case of announcers, whom we hear so often reach the stage of providing real entertain- intended for amateur use have made their that we look on them as old friends -even ment for all and not just material for the appearance in both medium -sized and if we don't know their names. Possibly you experimenter or a short-lived thrill for the miniature form. They cost a great deal of won't agree with me, but will feel that man -in- the -street. money, for they have fine lenses, wonderful matters are best left as they are. ti ti ti shutters and all kinds of fittings that make S : S for first -rate results in all circumstances. Corner Cabinets What of Receiving Sets ? Costly though they are, these cameras have big sales because they do produce SOME time ago suggested a year will, I believe, see the I that receiv- THIS rather a results. If people will pay Aso or more corner would ..change in the policy of many manu- for ing set in a cabinet be a camera because they're not content with very popular in the homes of to -day, where facturers. They are coming to realise that what a cheaper one can do, wouldn't they the public may be divided into two main space is often at a premium. A reader be equally willing to plank down a writes to tell me that he has built a set of classes from the wireless point of view : on hand good price for the very best in wireless sets? the kind and that he finds it a boon and a the one there are those who neither There's only one answer to that question, I demand nor appreciate high quality of re- blessing. He decided. that sides for the think : they would. production and are prepared to pay only a cabinet were not necessary and made it to modest price for their sets ; on the other, ti % % fit snugly into a special corner. The frame- we have those who want good quality com- work is simplicity itself-just three legs bined with first-rate all -round performance, The Ideal Dial with a couple of triangular shelves for the and are quite ready to pay handsomely for THERE should be a fortune awaiting the mains unit and the set and a top of the same their receiving equipment. At present the man who invents a first -class tuning shape. He finds, as I thought would be the tendency is rather to concentrate on the dial. So far I've come across a good many case, that the acoustic properties of a corner medium -priced set, which may be just a that I like pretty well, but none that hasn't cabinet are particularly good, the walls act- little too good and to expensive for the its shortcomings. Common defects are : (r) ing as extensions of the baffle formed by the one class of listeners . though not good only a few of the receivable stations shown front and throwing the sound -waves from enough for the other. I should not be sur- on medium and long wavebands ; (2) the loud speaker into the room in a very prised to find at the next exhibition two names of stations sometimes not too easy pleasing way. A radiogram can be made on chief ranges of receivers : first, the small, to read ; (3) marking so inaccurate that a the same lines, but the front-to -rear depth simple superhet, priced at well under fro, wanted station does not come in when you required for the turntable means that the and, secondly, the large superhet with all turn the pointer to the setting indicated ; cabinet has to be rather wide. Even so, it kinds of refinements and selling at from L20 (4) metre or kilocycle scales (if present) takes up less space than a rectangular to /30 or more. often too cramped and seldom sufficiently cabinet. Wireless World, January ist, r937 9 Broadcasting in the

By A. A. GULLILAND Balkans

FOR a long time past the Balkans hitherto been rather backward, there is a EUROPE'S SILENT have been by far the most back- very definite movement afoot to come into ward part of Europe from the point line with the rest of Europe, and a ioo- CORNER TO MAKE of view of broadcasting, and al- kilowatt station is now in course of erec- though in certain parts of the peninsula tion at Vakarel, which is about 20 miles ITSELF HEARD there are big developments afoot it must from Sofia, the capital. This station, as still be considered as the most inarticulate well as serving Bulgaria, is likely to be part of the continent so long as two out heard at very good strength, even at day- of the six countries comprising it are with- light hours, in the Southern part of Jugo- Bulgarian licence holders number only out any organised broadcasting service. slavia. Probably also it will be well re- 20,000, this being but o.3 per cent. of the ceived in parts of population, which compares rather un- Rumania. The Bul- favourably with the 20 per cent. in the garian language is, case of this country, but this is largely due of course, a to the absence of cheap receivers, a defect Slavonic one not which it is said the Government are in- greatly dissimilar tending to remedy, possibly by the pro- to Serbian, and the vision of a " people's " receiver. Vakarel station will In the neighbouring country of Jugo- therefore provide a slavia broadcasting is in rather an unsatis- good alternative factory state owing to the fact that there programme for is, some uncertainty whether or not the those Jugoslays Government is going to take over the ser- who are within vice. The Government is particularly i ange. anxious for more stations of greater power This will not to be built, partly in order to counteract the broadcasts in various Jugoslav dialects which are coming from the other side of the Adriatic. The various companies which own most of the existing Bulgarian peasant musicians stations will not augment taking part in a broadcast their power nor build from the present low-power additional ones until the Sofia station, which will shortly be replaced by a new Government agrees to ex- loo kW. transmitter now tend their existing conces- being built at Vakarel, about sions -which have still 20 miles outside the capital city. The partially finished some time to run -for a station buildings are seen on large number of years. At the right. present the country has to put up with stations of These two countries are Greece and Albania, and while one can possibly understand the absence of broadcasting in the case of the latter country, it is astonishing to find that at Athens, the ancient centre of the civilised apply in the case of Rumanian listeners. world, no attempt has been made to build Apart from Vakarel there are already a proper station. It is true that there aro in existence 2 -kW stations at Varna and rumours to the effect that stations are also at Stara Zagora, and it is interest- being planned at Athens and at Tirana, ing to note that these are supplied with the Albanian capital, but no official infor- programmes from Sofia by means of mation is obtainable with regard to them. wired wireless, although in the case of These two countries are the only ones of Varna a fair amount of use is made of the any size without a broadcasting service, local studio. The Bulgarian broadcast- as in the rest of Europe only the tiny ing service is run by the State and, apart states of Liechtenstein, Andorra, Monaco from the building of the new high - Broadcasts are made in eight languages from and San Marino remain without trans- powered station at Vakarel, the autho- the Jugoslavian short -wave station in mitters. rities are engaged in the erection of large Belgrade. Mme. Bety Popovic makes all the Of the remaining Balkan States, new studios in Sofia and it is expected English announcements. Rumania and Turkey have by far the best that these will be available sometime dur- relatively minor power, 5 kW. in the case and most carefully organised broadcast- ing 1938. They will be by far the largest of Ljubljana, 0.75 kW. for Zagreb, and ing services. In Bulgaria, which has and best in that part of Europe. 2.5 kilowatts for Belgrade, although the IO VITigIlmr,, JANUARY ist, WopIld 1937 Broadcasting in the Balkans - like our own Daventry transmitter, em- Belgrade company are actually erecting a ploys various wavelengths to suit the time DISTANT 2o- kilowatt station in the capital. of the day and the particular locality at There are plans to build a ioo-kilowatt which the programme is aimed. At pre- RECEPTION NOTES station in Belgrade, a Zo- kilowatt station sent programmes are broadcast in no less AT any time within the next week or two . At Skoplje, and a 2o- kilowatt one at than eight languages. The total number Zagreb, a new big American station should together with come into operation. Or perhaps I should a smaller one of say that a big American will become bigger. about 3 kilowatts in The station in question is the Mexican Split. Until the XEAW, at present rated at rather over 5o Government grants kilowatts, which is shortly to blossom out the required long as a " three -figure " transmitter with an term of concessions, output rating of ioo kilowatts. One would or takes over the think off -hand that with this power XEAW whole of the broad- should be well heard over here ; but for casting some reason or other stations in Central service them- America don't seem to reach us anything selve s, however, like so well as those in the United States these plans are not or South America. likely to be brought XERA, for example, is not often re- to fruition. ported ; yet this station has been working The Government for some time with a power of between has, however, 300 and 40o kilowatts. realised Mexico is a huge country -how big you the advan- don't realise until you use an atlas. tages of making Actually its area is only slightly less than Jugoslavia's voice that of France, Germany, Italy, Spain and heard in the world, Portugal all put together. It's not surpris- and for this purpose ing, therefore, that it should have a good is at present con- number of broadcasting stations, though its centrating on the A later photograph showing the rapid progress being made in com- population is not much greater than that waves. pleting the Vakarel mast and station buildings. The mast is expected of Holland and Belgium. In the latest list It was to be finished by the time this article is in print. for this reason that that I have by me no less than 67 Mexican stations are shown. As some zo of these the Belgrade short-wave station came into of listeners in Jugoslavia is at present are rated at i kilowatt or more, Mexico being some months ago. Its power isat about Zoo,000, the population being 14 should provide good hunting for any D -X present 1.5 kilowatts, but this is likely, to millions, but this figure could undoubt- enthusiast who wants to break new ground. be raised to io kilowatts or even 20 kilo- edly be largely increased by the provi- At present there is only one station rated watts at a fairly early date. This station, sion of more and better transmitters. at Soo kilowatts in the United States. This is WLW, of Cincinnati, Ohio, whose licence to use such great power is still officially experimental. The station has, however, proved such a success owing to its enormous service area that half a dozen others TELEVISION PROGRAMMES have applied for permission to increase their power to the same figure. In the United States atmospherics are far worse Friday, January 1st, to Thursday, January 7th than they are here, and one can well under- stand the importance of high power as an The principal items only of each day's 9, Repetition of 3 programme. 9.15, Film. aid to obtaining a satisfactory signal -to- programmes are given. The system to be 9.25, Repetition of 3.25 programme. 9.35, noise ratio at considerable ranges. It will used each day is given below the date. British Movietonews. 9.45, Cabaret, with The not, therefore, be surprising if permits are Transmission times are from 3 -4 and Television Orchestra. granted 9 -10 daily. to most of those who have applied TUESDAY, JANUARY 5th. for them, though so cautious are the Vision Sound (Marconi-E.M.I.) Federal Communications Committee that 6.67 m. (45 Mc/s). 7.23 m. (41.5 Mc/s). the licences are likely to be provisional and 3, The Orchestra and its Instruments : 1- Strings. Philip Thornton will show with subject to withdrawal at very short notice FRIDAY, JANUARY ist. examples of old stringed instruments how the should the spread of the big stations at (Baird.) modern violin, etc., has been evolved. 3.20, medium ranges be found unduly great. 3, British Movietonews. 3.15, Women's British Movietonews. 3.30, Theatre Parade- There seems to have been a certain Interests -" Marine Parade " -a forecast of scenes from the Whitehall Theatre production, amount of reshuffling of the wavelengths of fashion. 3.30, Michaelson-topical quick -fire " Anthony and Anna." artist. 3.45, Cabaret. Norwegian stations, and so far as I can 9, Repetition of 3 programme. 9.20, Gaumont make out most of the published lists con- 9, Gaumont British News. 9.15, Demonstration British News. 9.30, B.B.C. Dance Orchestra. tain a few errors at the moment. Here is by men of the R.A.F. Boxing Association. what I believe to be the correct list : 9.30, Repetition of 3.3o and 3.i5 programmes. WEDNESDAY, JANUARY 6th. - (Marconi-E.M.I.) Metres Station kW. SATURDAY, JANUARY 2nd. 3, Gaumont British News. 3.10, Record - 221.1 Nottoden 0.15 (Baird.) breaking - Sir Malcolm Campbell with the 222.6 Rjukan 0.15 3, Gaumont British News. 3.10, Val Rosing and " BIuebird " interviewed by Cecil Lewis, fol - 235.1 Stavanger 0.5 his Band with Anne Lenner. 3.25, Winter Iowed by a film of the Utah record. 3.30, Film. Christiansand 0.5 Sports - Ski -ing hints for beginners by Com- 3.40, Seventeenth Picture Page. 245.5 Narvik ... 0.3 mander Jack Shirley, R.N. (retd.), illustrated by 9, Repetition of 3.10 programme. 9.20, Film. 352.9 Bode, 10 mannequins appropriately attired. 3.45, Val 9.30, Eighteenth Picture Page. 9.50, British Poragrund 1 Rosing and his Band. Movietonews. 386.6 Fredrikstad 1 415.4 Bergen ... 1 9, British Movietonews. 9.10, Repetition of 476.9 Tröndelag 20 and THURSDAY, JANUARY 7th. 3.10, 3.25, 3.45 programmes. (Marconi- E.M.I.) 578 Hamar ... 0.7 864 Finmark 10 MONDAY, JANUARY 4th. 3, British Movietonews. 3.10, Underneath 1,064 Tromsö 10 (Marconi-E.M.I.) London-Talk on Antiquary by G. F. Lawrence. 1,186 Aalesund 10 3, New Styles in Hats. 3.15, Film. 3.25, " In 3.20, Film. 3.30, Scenes from The Old Vic 1,153.8 Oslo ... 60 Search of the Electron " -talk by Dr. H. production of " Hamlet." Stafford Hatfield illustrated with experiments. 9, Cabaret -The Television Orchestra. 9.30, Some of the smaller fry should be inter- 3.35, Gaumont British News. 3.45, Starlight- Film. 9.40, Repetition of 3.10 programme. esting quarries for the sensitive and selec- Billie Houston. 9.50, Gaumont British News. tive set in expert hands. D. EXER. Wireless World, January ist, x937 rü

News of the Week in CURRENT TOPICS Brief Review the Imperial College of Science the nearest town for charging. Hungarian News -Broadcasting and Technology, Imperial In- Meanwhile the Italian " People's Service which sent its informa- American Wireless stitute Road, South Kensington, Receiver " is to be reduced in tion over the ordinary landline Prosperity S.W.7, and closes at 9 p.m. on price so that it will be available to telephone subscribers at cer- Thursday, January 7th. to a large class of people. Italian tain times of the day. This THE past year has been one of radio employees are reported to arrangement was very similar to the most prosperous ones Australian Broadcasting have had their salaries and the. Electrophone system which known so far as the great U.S. Dispute wages raised by 8 per cent. in used to be in vogue in this broadcasting chains are con- ALL hope of broadcasting run- conformity with new financial country before the days of cerned. Between them they ning commentaries from the arrangements made in other broadcasting. have collected six million ster- famous Victoria Park racecourse branches of industry. ling in advertising fees, and one have been dashed to the ground. International IF Channel ? of them has increased its income Oslo Police Adopt Radio The broadcasting authorities THE American Federal Coin - by sixty per cent., compared were refused permission to broad- THE use of wireless patrol cars with munications Commission is 1935. cast from Victoria Park by the by the police authorities has now considering a proposal now penetrated to Norway, and More SW Stations racing authorities. Accordingly already referred to in Wireless they made arrangements to give the Oslo police have acquired World that an international ¡NORTHERN Europe is soon a running commentary from a ten cars and have built a ro- channel should be estab- likely metre in middle IF 1 to make its voice building overlooking the course. transmitter the lished. The idea is that all heard in the world to a far A legal injunction has now been of tile city. The police au- transmitters throughout of the other Scan- the greater extent than at present, obtained to stop even this. thorities world should be prevented from owing to the rapid extension of dinavian countries are said to be Wireless for Everybody still considering the question. using a certain given channel, the SW broadcasting services this being reserved for the IF which is taking place there. IN an effort to popularise radio Pioneer Announcer Dead amplifiers of receivers. By this Work has been started on a still further, the Hungarian means a good deal of inter- roo -kw. station near the Ice- Government is to reduce licence IT seems a little difficult to ference would be cut out, and landic capital, while Finland fees and to take steps to enable think of announcers before at the same time, owing to the has a new 20- kilowatt station in valve sets to be used in remote the era of broadcasting, and yet standardisation of the inter- course of construction. Several villages not supplied with elec- they did exist, as we are re- mediate frequency, the cost of stations of power ratings from ro tricity. It is hardly likely that minded by the death of Charles superhets would be lessened. to 20 kilowatts are 4planned for this will be done by extending Scherz which has just occurred. Scandinavia. The Swedish Gov- electricity to these villages at Not only was he the very first Wired Wireless in ernment has granted a million present, but in all probability announcer at the Budapest sta- Sweden kroner towards the cost of arrangements will be made for tion, but in pre -broadcasting EXPERIMENTS have been erecting new stations at Lulea, motor -vans to collect villagers' days he held the same office in tried by the Post Office Karlskrona and Helsingborg. accumulators and take them to connection with the original authorities at Karlshamn, in Sweden, with a view to radiating New High - powered broadcast programmes over a Stations telephone line simultaneously is stated that the two Polish with three ordinary conversa- IT stations at Lwow and Wilno tions. Very successful results will shortly be radiating on 50- have been obtained so far, and kVW. The work of rebuilding these Post Office engineers from the transmitters has been carried out neighbouring country of Norway entirely by Polish engineers. At have visited Karlshamn to the same time, it is stated that study the system. It is quite the Czechoslovakian Govern- likely that wired broadcasting ment has under consideration an may eventually play an im- extensive programme of station portant part in Scandinavian building. Two new loo- kilowatt broadcasting, more especially in stations are being planned, one Norway, owing to the difficulties at Neutra and the other near of reception due to the moun- Brno. The Neutra station will tainous nature of the country. probably take over the wave- length of Bratislava, the latter Anti - Interference still continuing to work in some Legislation ? other part of the radio spectrum. THERE is a distinct possibility The present Brno station is, that now television has however, likely to be closed come upon the scene there will down. be early legislation to compel the fitting of suppressors to the New Test Apparatus ignition system of cars and other JUDGING from the advance prolific radiators of ultra- short- information received, the in- waves. As is well known, the terests of the wireless industry Government is still considering will be well represented at this the report of the I.E.E. Com- year's. Exhibition of the Physical mittee, which recommended Society. In the trade section that statutory powers be sought most of the leading manufac- to enforce the fitting of sup- turers of measuring apparatus MICKEY MOUSE MOVES HOUSE. -As a result of a contract recently pressors to eliminate interference have taken stands, and the re- completed between Walt Disney- Mickey Mouse, Ltd., and " His to broadcasting. The coming of search sections can be relied Master's Voice," apparatus has now been installed at the " H.M.V." television is likely to hasten the to provide demonstrations Recording Studios at St. John's Wood to transfer Mickey Mouse and upon Silly Symphony films from the sound track of the film to disc records. Government's decision if one of the latest developments. The The apparatus constructed for " His Master's Voice " is believed to may be permitted to read be- Exhibition opens at 2.30 p.m. on be the only one of its kind in the world, and incorporates intricate tween the lines of a recent state- Tuesday next, January 5th, at filters to obtain a constant speed with absence of jerkiness. ment made by the P.M.G. 12 Wireless World, January ist, 1937 Ferranti Arcadia

AN ALL =WAVE long waves and inductive coupling for the short-wave range. The frequency-changer SUPERHETERODYNE valve is a heptode, and special precautions havé been taken to short- circuit oscillator WITH VARIABLE coils not in use in order to avoid inter- ference with the performance on the short- SELECTIVITY wave band. The variable -mu pentode IF amplifier functions at a frequency of 125 kc /s, and is fed with the output from FEATURES. Type. -Table model the frequency- changer through an IF superheterodyne for A.0 mains. transformer in which the coupling between Waveranges. -(1) 19 -51 metres. the primary and secondary windings is (2) 200 -550 metres. (3) 900-2,000 varied by the " Tone " control on the metres. Circuit.Heptode frequency- front panel. changer- var. -mu pentode IF amplifier-double- The visual tuning indicator is common diode-triode second detector- triode output to the anode circuits of the frequency - OMPARED with last season's valve. Full -wave valve rectifier. Controls. - changer and IF valves. A double-diode- model, which we reviewed in the (1) Tuning. (2) Volume and on -off switch. triode fulfils the function of second issue of February 15th, 1935, the (3) Tone (variable selectivity). (4) Waverange. detector, AVC rectifier, and first LF 1936 -7 " Arcadia " at the same (5) Noise suppressor switch. Price. -15 amplifier. A switch is included to alter price represents an appreciable advance guineas. Makers. -Ferranti, Ltd., Moston, the conditions of the control in the IF in value for money. It has the same high - Manchester. amplifier. Normally this valve is sup- power triode output valve, but the earlier plied with delayed AVC through a reducing stages now include such additional refine- potentiometer. To effect noise suppression ments as variable selectivity, inter -station leading place in the range of Ferranti between stations the switch changes over noise suppression, and a short-wave range. table models, the circuit is full of detail the AVC supply for the IF amplifier to the On the mechanical side the tuning scale refinements, and there is no indication signal rectifying circuit, which is unde- has been improved- particularly from the whatever of any attempt to cut costs by layed, and to compensate for the conse- point of view of short-wave working -by introducing simplifications which might quent change in initial . bias the resistance the addition of the " Magnascopic " impair the performance. The aerial tuning optical device, and the loud speaker has circuit, for instance, is a well- thought -out- been modified to improve the bass design which incorporates an image Complete circuit diagram. The coupling response. rejector circuit. A band -pass filter with of the first IF transformer is variable and is actuated by the " Tone " As befits a receiver which occupies a mixed coupling is used for medium and control.

0 o . e 9

2 DET O--

X*.

PICK -UP

VOLUItIE CONTROL rT0-ll 111 . OISE SUPPRESSOR T SWITCH T Wilpg.®@o JANUARY 1st, 1937 MyIld in the return lead of the CIF valve is increased. Resistance -capacity coupling detector MAGNASCOPIC DIAL is employed between the second OPTICAL SYSTEM and the triode output valve, the bias for which is derived from a potentiometer across the main HT supply. The suspension of the cone in the ,moving -coil loud speaker fitted to the " Arcadia " receiver is given a greater degree of freedom than usual, and as a result the full and smooth bass response is RECTIFIER of perhaps the most pleasing aspect the VALVE quality of reproduction. The high -note IF R4 response is adequate, but does not extend AMPLIFIER to the point where local interference noises VALVE VPT4 are accentuated. If the tone in the top register is a little hard, the use of a triode in the output stage ensures that it is free 2nd DETECTOR from any tendency to " peakiness." VALVE Selectivity H 4 D When using the set in Central London with a considerable input from a full -sized FREQUENCY outdoor aerial, the variable selectivity CHANGER VALVE OUTPUT control was without much effect on the VHT4 VALVE quality from London Regional. On the L P 4 West, Midland and North Regionals, on the other hand, it behaved quite normally and gave as wide a choice of tonal balance as the ordinary resistance -capacity type of tone control. The variable selectivity aspect of the control was most con- vincingly demonstrated when the set was tuned r" `Wireless World to the Deutschlandsender. This COPYRIGHT station was badly interfered NOISE SUPPRESSOR with by both SWITCH Droitwich and Radio -Paris with the con- PICK UP trol in the " High " position, but the back- TERMINALS ground cleared up progressively as the " Low " position was approached until Extension loud speaker terminals are mounted on the loud speaker itself. A special type of finally there was only an occasional suspension has been provided in this model. " splash " on deeply modulated passages. Unlike many variable selectivity controls, condition of highest selectivity as soon as individual degrees, and is magnified and the signal strength of the wanted station the tuning control is moved in search of projected on to a ground glass screen is little affected by the setting of the con- another station. immediately above the main tuning dial. trol: By an ingenious mechanical device On the medium -wave band only one For fine tuning an effective scale length of the set is automatically returned to the channel was lost on each side of the over 6ft. is thus made available, and it is London Regional and National trans- a tribute to the mechanical accuracy of the mitters, and elsewhere adjacent channel slow- motion drive that no trace of slip or separation was possible when required. backlash is revealed by this high mag- At least twenty stations were available at nification. good strength during daylight The cabinet measures EXTERNAL programme r8in. high x 6in. LOUDSPEAKER on this range alone. There was a second wide x ro4in. deep, and is in walnut with channel whistle at about 465 metres on the macassar ebony inlays and ebonised feet. medium -wave band and another at 1,20o on long waves. a metres the Reliable reception of American broad- Club News casting was obtained on the short-wave The Surrey Radio Contact Club lower volume band, but at a somewhat At a recent meeting an instructive lecture level than was at first expected having entitled " Valves, Their Design and Use," was regard to the undoubtedly high intrinsic given by Mr. L. Grinstead, M.I.E.E., of the sensitivity on this range. The limiting Mullard Co., who is a club member. On Janu- feed back at low ary 5th, at 8 p.m., a lecture on Electrical Mea- factor was microphonic suring Instruments and their Uses will be frequency whenever a strong carrier was given by a representative of Messrs. Everett, impressed on the aerial, and such was the Edgcumbe and Co., Ltd. The lecture will be strength of WzXAD that the maximum held at the Alhambra, Wellesley Road, West available setting of the volume control was Croydon. Hon. Secretary, Mr. E. C. Taylor, \V, 35, Grant Road, Alidiscomle. not more than one -third of its range from G5Z the minimum position. This gave all the The Radio, .Physical and Television Socy. volume necessary for proper enjoyment of At a recent meeting Mr. J. G. Hobbs, but not A.M.I.R.E., lectured on short -wave transmit- the programme, enough to let the ters. Methods of generating oscillations at neighbours know that one's set is capable radio frequency and of modulating them were of transatlantic reception ! dealt with. A low- powered transmitter was Tuning on the short-wave range with demonstrated. Meetings of the society are the aid of the " Magnascopic dial is as held on Fridays, at 8 p.m., at 72a, North End " Road, W. Kensington, W.14. Those interested precise as one could possibly wish. The should write to Mr. V. R. Walker at 49, Fitz - i8ó-degree translucent scale is divided into James Avenue, West Kensington, W.r4. T Wireless World, Jañuary ist, 1937

invent some really first -class incidents which would give us all a little excitement? As things are, the errors they usually make are duller even than the truth and, 'good- ness knows, that's usually dull enough. UNBIASED What would, I think, appeal to many 1940 or an people would be a scrapbook of me, when he has sold a midget plus other future year. The B.B.C. the customer has some A Boom in Midget Sets extension loud speaker, would then be able to give full rein to their told him that he invariably installs the IHAVE been very surprised at the loud speaker on the other side of the room interest which readers have taken in either on a flat baffle suspended from the my scheme for remote control of tuning. picture rail or in a box baffle. What has astonished me most of all, how- The above facts seem to me to be quite By ever, is the enormous interest that there enough to prove that the public do want appears to be in the question of remote remote control, but not at the expense at tuning control in general which our manu- poor quality, or of having a bulky set facturers neglect almost entirely. drawn up to their armchair, but there is My authority for stating that there is an more to come. In a very large number FREE GRID enormous amount of interest in the subject of cases the purchasers of these midgets ask is derived from dealers, several of whom that the absurd little loud speakers be have written to me about it. It appears out of the sets and space utilised for taken without risk of contradiction that they know of this interest, not merely the installation of a better output stage imagination because of the number of enquiries they to pay quite by anyone while, if they secured the ser- for which they are willing they receive, but because of something far One dealer, in fact, vices of one of our tame astrologers, substantial sums. to out a more convincing. This something is the he is going the whole hog would, I feel sure, be able put mentions that for the growing number of midget sets of foreign and actually rebuilding midgets in this really first -class programme. As origin which they are selling. any specific orders, for, pending 1919 scrapbook, I'll bet that they manner without from Now you might think, as I did, that he has no difficulty in selling try to tell us that peace -as distinct he says, on June 'this growing popularity of midgets merely them when he points out that when this the Armistice-broke out officially showed that the public taste from the is done they form almost a perfect remote 28th or July 19th. point of view of quality of reproduction control unit without any sacrifice of was becoming more and more depraved, quality. although, it is true, it might possibly be Range is, of course, sacrificed, as it is Wanted: An AC Battery thought that an alternative reason for the purchase of these sets was that the WE have all heard of the various average listener was getting more and arrangements adopted to prevent ia,iN,iugu,t. out should the more tired of having to keep on jumping ,N, the electric light going Such ' devices are up to change the programme i power supply fail. and was prepared to put up usually adopted by hospitals in their with the inferior quality of operating theatres where a lighting failure midgets if he could be spared might be fatal, and usually consist of a operating in con- this Jack -in- the -box business ; battery of accumulators indeed, this was, I learn, the junction with a relay, so that it comes on real cause of the great popu- automatically when the power supply larity which the midget fails. achieved in America. These arrangements are, I believe, The reason why my corre- mostly designed and sponsored by the big spondents know that the accumulator manufacturing companies, midgets they sell are bought for the con- but nobody seems to care two hoots. about venience of remote tuning control, and the predicament of the unfortunate " all - definitely do not indicate any decline of electric " householder when the supply musical taste on the part of their pur- This Jack -in- the -box business fails during the night. He wakes up 'in chasers, is rather an unusual one. It the morning and either finds that all the they are of the appears that a large proportion of the usually convenient only to employ a clocks are stopped, or if purchasers of these sets nowadays buy picture rail aerial, but even this difficulty self -starting type, they are all wrong. It a separate loud speaker of normal quite easily by using a is of little use, of course, trying to get the also can be overcome up proportions and ask the dealer to dis- transmission line to couple to an external wretched accumulator companies to rig connect the internal loud speaker" and aerial. I hope, therefore, that with this an automatic " keep -going " arrangement provide terminals for connection to the irrefutable evidence before them of a to get over the difficulty, for, of course, extension instrument which they purchase. public demand for a remote control unit, all the clocks are AC ones, and as I have Now a large proportion of the distor- our manufacturers will step on the gas found out from personal experience, not tion in a midget set -but by no means all and do something about it. a single manufacturer has bothered to -is the miniature loud speaker, and this turn his laboratory staff on to the problem purchase of a separate one of normal pro- of designing an AC battery. What some portions gets rid of this. But this fact Who Blundered ? of them keep their costly research depart- does not merely prove that the public ments for I'm sure I don't know. taste of quality is growing. It proves also IWAS very surprised to find that in their I certainly know one man who has that the public wants real remote control 1908 Scrapbook the B.B.C. had, by solved the difficulty, but, then, he happens with the loud speaker on the other side of some strange oversight, got all their facts to have the good fortune to be on DC and the room, and are not content to adopt correct. I dare say, however, that some has naturally installed a motor generator the makeshift which many manufacturers poor devil has got it in the neck for it by to operate his AC clocks. Obviously, it so fatuously recommend, namely, to place now. I must confess that hitherto I have has been quite simple for him to arrange a normal set by the side of the armchair never been able to understand the B.B.C.'s for the automatic switching on of a battery and thus risk eventual deafness by having attitude in the matter of these scrapbooks. of accumulators to keep the DC motor the loud speaker bellowing in their ear all As they don't usually bother about going in the case of a supply power the time. In every case, one dealer tells accuracy, why not do things in style and failure. Wireless 1VorJd, January 1st, 1937 IS The Beam Power Tube IN America there are in widespread use should be 25o volts and the grid bias 16 volts, many output systems which are em- while the no- signal anode and screen currents ployed comparatively rarely in this are ago mA. and ro mA. The optimum load country. The Class " B " stage, it is true, impedance is 5,00o ohms. With fixed bias is widely known, but rarely used except in the anode and screen currents increase to battery- operated equipment. The Ameri- 140 mA. and 16 mA. with the maximum can designer, however, has been rather fond signal input, and the power output is r4.5 of using this system in mains -driven appara- watts ; with automatic bias, however, the tus where a large output is required, but currents rise to rio mA. and 15 mA. respec- owing to the distortion which it introduces tively, and the output is 13.8 watts. The there has been a tendency of late to discard distortion is z per cent. and nearly all third it. Instead, a method of operation known harmonic. as Class " AB " is becoming widely used. Much greater output can be secured by . A Class " AB " stage is one which oper- operating under Class " AB " conditions, ates under Class " A " conditions for but without running into grid current. As moderate signal inputs, but under semi - the following table shows, as much as 34 Class " B " conditions with a large input. watts can be obtained from a pair of 6L6 Class " A," of course, refers to the normal valves with only z per cent. distortion ! operation of an output valve with anode Even this is not the limit of output ob- current flowing during the whole cycle of in- AN tainable, for if grid current be permitted it put voltage and no grid current. A Class is possible to obtain no less than 6o watts " A " stage can contain one valve, or two in AMERICAN from two valves ! For this output the push -pull, and the latter introduces the anode and screen supplies must be 40o and least distortion of any system. OUTPUT VALVE 30o volts and - 25 volts bias is needed with As the term is used in America, Class 8o volts peak AF input. With no- signal " B " refers to a state where two push -pull the anode and screen currents are 102 mA. valves are used under such conditions that the usual tetrode negative-resistance kink, and 6 mA., but rise to 230 mA. and zo mA. one valve handles one half of the input however, special plates are included and upon the application of the full input. The wave form and the other valve handles the internally connected to the cathode. These optimum load is 3,800 ohms, and 35o milli - other half. The valves are consequently plates are not in the direct path of the watts driving power is required in the grid biased at about the point of anode current electron flow, but act to confine it in the circuit. The distortion introduced by this cut -off. In this country such a stage is form of a beam, and it is from this feature stage is only about .2 per cent., but the total usually entitled QPP, and Class " B " refers that the valve takes its popular title of the distortion is likely to be much greater, since to the particular case when grid current is " Beam Power Tube." The characteristics unless the driver stage is very well designed permitted to flow. In America the term obtained are similar to those of a pentode. and operated it will introduce more than Class " B" covers both conditions. It is an indirectly heated valve with a the output stage. ampere at 6.3 volts. With systems such as these, a very large heater consuming o.9 " Like all valves of the pentode type, the signal input is required to secure full out- When used as a single-valve Class A ' 6L6 has a high AC resistance, and this is put when triodes are used, and this leads to output stage it difficulties' in the preceding stage, which needs 375 volts for' TWO 6L6 VALVES IN CLASS "AB" must supply a considerable amount of power the anode, 25o volts if grid current is permitted. It so happens, for the screen -grid, volts grid Anode volts ...... 400 400 400 400 therefore, that multi -electrode valves of high and -9.0 Screen volts ...... 250 250 300 300 amplification factor are more convenient. bias. The anode Fixed grid bias ...... -20 -20 -25 -25 Peak AF input volte (grid to grid) 40 40 50 50 No- signal anode current ...... 88 88 100 102 ru A. +300v +400v Max.- signal anode current ... 126 124 152 156 mA. No- signal screen current ...... 4 4 5 5 mA. Max.- signal screen current ... 9 12 17 12 mA. Load resistance ...... 6,000 8,500 6,600 3,800 ohms Power output ...... 20 26.5 34 23 watts Distortion, 3rd harmonic ... 1 2 2 0.6 per cent.

and screen currents disadvantageous for the highest standard of are 24.0 mA. and quality. The makers consequently recom- o.6 mA. respectively, mend the use of negative feed -back' with and it will give an the circuit of Fig. r.' This reduces the output of 4,20o milli - effective output resistance so that the loud watts into a load of speaker is properly damped, and it also 14,000 ohms. reduces amplitude distortion. A larger When a pair are signal input is required, however. The used in push - pull values to be assigned to the condensers under Class " A " shunted across each half- secondary of the conditions the input transformer depend on the charac- teristics of that transformer and must be determined experimentally. In some cases resistances, or resistances in series with For the highest condensers, are better. quality reproduc- The 6L6 is a metal valve, but . a glass- tion negative feed- 6L6G, having -HT back is recom- envelope counterpart, the the mended. same characteristics is also made. In this country it is obtainable from The Premier The American 6L6 is a valve which Supply Stores, Jubilee Works, 167, Lowey enables a very large output to be secured Clapton Rd., London, E.5. quite easily. It is actually atetrode con- taining the usual cathode, control grid, makers quote two sets of operating condi- space -charge grid and anode. In- order to tions, for fixed and for automatic grid bias. The Wireless World, Nov. 6th, 1936. prevent the characteristics from containing In both cases the anode and screen potentials 2 R.G.A. Review, July, 1936. r6 Wireless World, January ist, 1937 Listeners' GuIde described for listeners by S. J. de Lotbinière, the Director of Outstanding Outside Broadcasts, who is going to Holland as commen- for violin and orchestra. Suk, tator for the B.B.C. who died last year, was a lead- The Royal wedding is bound ing Czech composer, and the to make itself felt in the pro- son -in -law of Dvorák. grammes of Holland. Some of The Special Recital series for the special features from Hil- this week comprises Tudor string music, which will be versum I are : a radio play, " The Marriage of a Princess," played by the Willoughby The recitals at 8.55 on Sunday ; relay at String Quartet. 9.4o on Tuesday from a special will be given in the National programme on Monday at festival ; the marriage cere- mony and commentaries from 8.3o, Tuesday at 7.10, Wed- to. 10 a.m. to 1.40 p.m. on nesday at 7.40 and Thursday Thursday, followed at 3.10 by at 9.2o. her fiancé, H.R.H. PRINCESS JULIANA with THE GAY 'NINETIES Prince Bernhard of Lippe -Biesterfeld. H.H. A PROGRAMME with t h e Their marriage will occasion special broadcasts from Hilversum I, and the wedding ceremony on title, " The Eighteen -Nineties," January nth will be heard by National listeners. has been prepared by M. H. Allen and Barbara Burnham, " HAPPY and Good New that all the peoples of the earth a relay of the rejoicings from and will be broadcast at 9.30 Year to all Peoples of may live in perfect peace. The the Dutch East Indies. to -night (Friday) in the the World " is the English contribution is very National programme. This title given to the simple, just church bells from MUSIC should provoke reminiscent special half -hour programme Westminster Abbey and a DURING last week the tooth chuckles and sighs among the arranged by the International country church. anniversary of the birth of the elder generation and provide younger listeners with an inter- Broadcasting Union for Sun- . 0 Russian composer Balakirev day at 5, when twenty -three IN RETROSPECT (1837 -1910) was celebrated esting and colourful glimpse of European countries will send IT is.quite a common occur- in the Special Recital series, a mode of life that has irrevoc- messages of greeting. Actually rence at the beginning of the songs and piano music being ably vanished. The 'Nineties it will be a recording, as the year to look back over the year broadcast, and on Saturday at were a period of great artistic time of forty -five seconds that has just passed. We shall 8.15 (Nat.) Constant Lambert activity and also of an intense, allotted to each country does be given an opportunity of will conduct a concert of Bala - in every sense of the word, not allow for any delays. Ger- doing this in the National pro- kirev's orchestral works, in- Bohemianism. many has been accorded the gramme on Wednesday at cluding the incidental music for The producers hope by j udi- privilege of making the tech- 9.2o, when Laurance Gilliam " King Lear." It is interesting cious use of quotations, com- nical arrangements for the presents " Twelve Month to note that in this music the ment and music to present a transmission, which, having Back," a retrospect of 1936. composer introduced two Eng- sound picture that will catch been already recorded, will be lish folk tunes. the true spirit of those days. broadcast from Berlin and re- SHAKESPEARE The first of the special layed by most European sta- ON four Sundays during the orchestral concerts broadcast GREETINGS tions, including the London first quarter of this year full - from a studio will take place on from twenty - of under the three European Regional. dress productions Shake- Sunday at 9.5 (Reg.) countries will be Switzerland will start the speare's plays will be broad- direction of Sir Henry J. broadcast from programme, it being the home cast. The first of these comes Wood. The programme in- Berlin, the main of the Union, and other coun- into the week under review, cludes Vaughan Williams' control room of and which is seen in tries, except Germany, which when Peter Cresswell will pro- " London Symphony," the centre, and closes the programme, will fol- duce " Much Ado About Carl Flesch will be the soloist relayed through- low according to the French Nothing " for National lis- in Joseph Suk's " Fantasy " out Europe on alphabet. The only countries teners at 5.35. This exquisite not participating are Spain, tragi- comedy was last broad- Greece, Bulgaria and Albania. cast ten years ago. Some of thè outstanding features of this varied pro- DUTCH ROYAL WEDDING r' gramme will be a selection THE marriage of Her Royal ti from Jean Sibelius's " The Highness Princess Juliana, Melody of the Chimes " from Crown Princess of Holland, Finland ; greetings from village with His Highness Prince children in Belgium ; a greet- Bernhard of Lippe -Biesterfeld, ings " telegram " sung by " La will be the occasion of an hour - Chanson Romande " from and-twenty- minutes' broadcast Switzerland ; and a poem en- for National listeners on Thurs- titled " For the Wounded," re- day morning at I1. The cited by David Knudsen from scenes outside the Church of the Oslo National Theatre, in St. Jacob at The Hague before which is expressed the wish and after the ceremony will be Wireless World, January ist, 1937 17 or the Week tdcasts at Home and Abroad

STERNE AND THOMSON MORE VARIETY WITH such collaborators for A NEW series of mid -week a radio show as Ashley Sterne music -hall shows starts on and A. A. Thomson one can- Tuesday at 9 (Reg.) with the not but feel that it will be really title " Palace of Varieties," funny. On Wednesday at 8 made up of short acts. To give (Reg.) and Thursday at 9 the necessary atmosphere, two (Nat.) listeners will be treated rather talkative members of to "Snapdragon," which deals, the audience will discuss the in a way that only Sterne and show from the stalls of the LESLIE JEFFRIES, who will come to the microphone with the Grand Thomson can, with the age -old imaginary music hall, and by Hotel, Eastbourne, Orchestra on Sunday at 5.3o (Reg.). story of a princess rescued so doing act as compères. the act which includes the Falstaff as presented by Shake- from a dragon by the prince. Among those billed for this famous Dance of the Appren- speare. Rome follows at 8 with This should be well worth the first show are Ray Meux, tices, as well. .as Walther's another La Scala, Milan, relay, time spent in listening. Jackie Heller, and Vine, More Prize Song and the Grand Pizzetti's three -act " Debora e . . 0 and Nevard. After eighteen Finale. . Jaele." Radio -Paris at 8.45 " MONEY WITH MENACES " months' absence listeners will The one transmission on transmits Massenet's " Cen- four AFTER a lapse of over also hear the return of " The Saturday which will be of drillon " -the French version years we are to have another Disorderly R o o m," with double interest to English of that darling of old and play by Patrick Hamilton, Tommy Handley and Co. speaking listeners comes at young alike, Cinderella. whose " Rope " was such a 7.5 O O O from Berlin ( Funkstunde), On Tuesday at 7.10 Stutt- success in 1932. From the CRICKET whence a studio interpretation gart and Deutschlandsender the scanty details available EACH day's play during the of Nicolai's " Merry Wives of give a studio performance best description one can give third Test Match between Windsor " is to be broadcast. of Puccini's four -act " La is that " Money with Men- Australia and the M.C.C., at The composer has followed Bohême " with Erna Berger in aces " is a study in suspense. Melbourne, will be described very closely the amorous the rôle of Mimi. for some Tune in, prepared by C. B. Fry for English adventures of our own Sir John THE AUDITOR. thrills, on Monday at 9.35 listeners and broadcast at 8.3o (Nat.) or Tuesday at 8.15 a.m. (Nat.) on Friday, Satur- OF THE WEEK (Reg.). day, Monday and Tuesday. HIGHLIGHTS o A record of the commentary FRIDAY, JANUARY 1st. Monday, January 4th (cont.) SWING MUSIC will also be broadcast at Nat., 7.30, The Air -do- Wells. Reg., 6, The Luton Band. ¶Violin WE are to hear a relay from Recital : Henri Temianka. 8, I p.m. each day. 8.30, Viola Recital : Lionel New York, in the first of a Tertis. 9.30, " The Eighteen - The Two Leslies and Bertha series of broadcasts by leading 0 0 . Nineties." Willmott. Abroad. American dance bands headed OPERA Reg., 6.45, Talk : Car Upkeep - Buying a Car. 7.30, B.B.C. Leipzig, 7.10, Beethoven Concert " America Dances," on Wed- TO-NIGHT. (Friday) Turin Orchestra (C) and Muriel Brun - from the Gewandhaus. nesday at 8 (Reg.), when and Milan give us the in- skill. TUESDAY, JANUARY 5th. Benny Goodman and his Or- estimable privilege of hearing Abroad. chestra will play swing music. a performance at the Scala, Leipzig, 6.30, Concert from the Nat., 6.25, Reginald Foort at the Gewandhaus. Theatre Organ. ¶A Nation of Milan, that home of grand Shoppers : The Shopping Public. Sunday. Below opera and Mecca of every SATURDAY, JANUARY 2nd. Talk by Helen Simpson. 7.50, (left) is the choir singer. At 8 we shall hear Nat., 9.20, Music Hall. 10.40, Carroll Levis and his Discoveries. of " La Chanson Mignon an The B.B.C. Orchestra and May Reg., 8.15, " Money with Menaces." Thomas' " " - 9, " Palace of Varieties." Romande, "which Busby. will sing Switzer- opera which owes its popu- Reg., 6.15, Band of His Majesty's Abroad. land's greeting, larity to the grace and charm Scots Guards. 8.15, Peter Yorke Stuttgart, 7.10, '` La Bohême." and (right) Tyro- and delicacy of its music. At and his Orchestra. 9.20, " Sicilian lean "star 8.5o Stockholm relays from Expedition." 10.25, Henry WEDNESDAY, JANUARY 6th. singers," whose Act Hall's Hour. Nat., 8, " Snapdragon." 9.20, song will be Aus- the Royal Opera House III Abroad. " Twelve Months Back." tria's message. of Wagner's " Mastersingers," Vienna, 6.15, " The Gipsy Baron " Reg., 6, Reginald King and his -operetta (Strauss). Orchestra. 8, " America Dances." relay from New York. SUNDAY, JANUARY 3rd. Abroad. Nat., 5.35, " Much Ado About Radio -Paris, 8.45, Gaubert concert Nothing." ¶Recital - Mary from the Salle Gaveau, the corn - Jarred and Pouishnoff. 9.5, poser conducting. B.B.C. Theatre Orchestra and Revue Chorus. THURSDAY, JANUARY 7th. Reg., 5, " A Happy New Year to Nat., 11 a.m., Marriage of Princess All the World "- Continental Juliana relayed from The Hague. Relay. 9.5, Symphony Concert: 6.40, B.B.C. Military Band. Carl Flesch (violin). 7.40, The Fol -de -Rots. Abroad. Reg., 6. From the London Theatre. Berlin, 7, " Love Songs Grave and ¶B.B.C. Orchestra (C) and Gay," songs from opera, operetta, Antonio Brosa (violin). 9, singspiel and film. " Snapdragon." Abroad. MONDAY, JANUARY 4th. Deutschlandsender, 7.30, The Great Nat., 7.20, Mulic Shop. 7. 935, German Symphony Composers. " Money with Menaces." No. 1- Beethoven. 7 C' Wireless World, January ist, 1937 PRINCIPAL BROADCASTING STATIONS OF EUROPE Arranged in Order of Frequency and Wavelengi:h (This list is included in the first issue of each month. Stations with an Aerial Power of 50 kW. and above in heavy type) Toning Timing Station. kc/s. Positions. Metres. kW. Station. ke,'s. Positions. Metres. kW. 814 Ankara (Turkey) ...... 153 1961 5 Milan, No. 1 (Italy) ...... 368.6 50 Kaunas (Lithuania) ...... 153 1961 7 Bucharest (Romania) ...... 823 364.5 12 Brasov (Radio Romania) (Romania) .. .. 160 1875 150 Moscow, No. 4, RW39 (Stalina) ( U.S.S.R.).. 832 360.6 100 Hilversum No. 1 (Holland) (10 kW. till 1540) 160 1875 100 Agen (France) ...... 832 360.6 0.5 Lahti (Finland) .. .. 166 1807 150 Berlin (Germany) ...... 841 356.7 100 . Moscow, No. 1, RW1 (Komintern) (U.S.S.R.) 172 1744 500 Norwegian Relay Stations ...... 850 352.9 - Paris (Radio Paris) (France) .. .. 182 1648 80 Sofia (Bulgaria) ...... 850 352.9 1 Istanbul (Turkey) ...... 185 1622 5 Valencia (Spain) ...... 850 352.9 3 Irkutsk (U.S.S.R.) ...... 187.5 1600 20 Simferopol, RW52 (U.S.S.R.) .. .. 859 349.2 10 Deutschlandsender (Germany) .. .. 191 1571 60 Strasbourg (France) ...... 859 349.2 100 Droitwich ...... 200 1500 150 Poznan (Poland) ...... 868 345.6 16 Minsk, RW10 (U.S.S.lt.) ...... 208 1442 35 London Regional (Brookmans Park) .. 877 342.1 70 Reykjavik (Iceland) ...... 208 1442 16 Linz (Austria) ...... 886 338.6 15 Motala (Sweden) ...... 216 1389 150 Graz (Austria) ...... 886 338.6 7.5 Novosibirsk, RW76 (U.S.S.R.) .. .. 217.5 1379 100 Helsinki (Finland) ...... 895 335.2 10 Warsaw, No. 1 (Poland) ...... 224 1339 120 Limoges, P.T.T. (France) ...... 895 335.2 1.5 Luxembourg ...... 232 1293 150 Hamburg (Germany) ...... 904 331.9 100 Leningrad, No. 1 RW53 (Kolpino) (U.S.S.R.) 232 1293 100 Dniepropetrovsk (U.S.S.R.) .. .. 913 328.6 10 Kalundborg (Denmark) ...... 240 1250 60 Toulouse (Radio Toulouse) (France) .. 913 328.6 60 Vienna, No. 2 (Austria) ...... 240 1250 0.5 Brno (Czechoslovakia) .. .. 922 325.4 32 Vigra (Aalesund) (Norway) ...... 253 1186 10 Brussels, No. 2 (Belgium) .. .. 932 321.9 15 Tashkent. RW11 (U.S.S.R.) ...... 256.4 1170 25 Algiers (Algeria) ...... 941 318.8 12 Oslo (Norway) ...... 260 1153.8 60 Göteborg (Sweden) ...... 941 318.8 10 Moscow, No. 2, RW49 (Stchelkovo) (U.S.S.R..) 271 1107 100 Breslau (Germany) ...... 950 315.8 100 Tromsii (Norway) ...... 282 1061 10 Paris (Poste Parisien) (France) .. .. 959 312.8 60 Tiflis, RW7 (U.S.S.R.) ...... 283 1060 35 Bordeaux- Sud -Ouest (France) .. .. 968 309.9 30 Finmark (Norway) ...... 347 864 10 Odessa ( U.S.S.R.) ...... 968 309.9 10 Rostov -on -Don, RW12 (U.S.S.R.) .. .. 355 845.1 20 Northern Ireland Regional (Lisburn) .. 977 307.1 100 Budapest, No. 2 (Hungary) ...... 359.5 834.5 18 Genoa (Italy) ...... 986 304.3 10 986 Sverdlovsk, RW5 (U.S.S.R.) . .. .. 375 800 40 Torun (Poland) ...... 304.3 24 Boden (Sweden) 392 765 0.6 Hilversum No. 2 (Holland). (15 kW. till 1540) 995 301.5 60 Banka- Bystrica (Czechoslovakia) (15 Ill . 392 765 30 Bratislava (Czechoslovakia) . .. .. 1004 298.8 13.5 after 1700) Midland Regional ( Droitwich) .. .. 1013 296.2 70 Geneva (Switzerland) .. .. 401 748 1.3 Chernigov (U.S.S.R.) ...... 1013 296.2 5 Moscow, No. 3 (RCZ) ( U.S.S.R.) .. .. 401 748 100 Barcelona, EAJ15 (Spain) ...... 1022 293.5 3 Ostersund (Sweden) ...... 413.5 726 0.6 Cracow (Poland) ...... 1022 293.5 2 Voronoje, RW25 (U.S.S.R.) ...... 413.5 726 10 Oviedo (Spain).: ...... 1022 293.5 0.7 Oulu (Finland)...... 431 696 1.2 Königsberg No. I (Heilsberg) (Germany) .. 1031 291 100 Harnar (Norway) ...... 519 578 0.7 Parede (Portugal) ...... 1031 291 5 Innsbruck (Austria) ...... 519 578 1 Leningrad, No. 2. RW70 (U.S.S.R.) .. 1040 288.5 10 Tartu (Estonia) 522 575 0.5 Rennes- Bretagne (France) ...... 1040 288.5 120 Ljubljana (Yugoslavia) ...... 527 569.3 6.3 Scottish National (Falkirk) ...... 1050 285.7 50 Viipuri (Finland) ...... 527 589.3 10 Bari No. I (Italy) ...... 1059 283.3 20 Bolzano (Italy) 536 559.7 10 Paris (Radio Cité) (France) ...... 1068 280.9 0.8 Wilno (Poland) ...... 536 559.7 16 Tiraspol, RW57 (U.S.S.R.) .. .. 1068 280.9 4 Budapest, No. 1 (Hungary) ...... 546 549.5 120 Bordeaux -Lafayette (France) .. .. 1077 278.6 12 Beromünster (Switzerland) ...... 556 539.6 100 Zagreb (Yugoslavia) ...... 1086 276.2 0.7 Athlone (Irish Free State) ...... 565 531 60 Falun (Sweden) ...... 1086 276.2 2 Klaipcda (Lithuania) ...... 565 531 10 Madrid, EAJ7 (Spain) ...... 1095 274 5 Palermo (Italy) ...... 565 531 3 Vinnitsa (U.S.S.R.) ...... 1095 274 10 Stuttgart (Germany) .. .. 574 522.6 100 Kuldiga (Latvia) ...... 1104 271.7 50 Alpes-Grenoble, P.T.T. (France) .. .. 583 514.6 15 Naples (Italy) ...... 1104 271.7 1.5 Madona (Latvia) ...... 583 514.6 50 Morayska- Ostrava (Czechoslovakia) .. 1113 269.5 11.2 1113 Vienna No. 1 (Austria) ...... 092 506.8 100 Fécamp (Radio Normandie) (France) .. 269.5 10 Rabat (Morocco) ...... 601 499.2 25 Alexandria, No. 1 (Egypt) ...... 1122 267.4 0.25 Sundsvall (Sweden) ...... 601 499.2 10 Newcastle ...... 1 122 267.4 1 Florence (Italy) ...... 610 491.8 20 Nyiregyhaza (Hungary) ...... 11.24 267.4 6.25 Cairo, No. 1 (Egypt) ...... 620 483.9 20 Hörby (Sweden) ...... 1131 265.3 10 Brussels, No. 1 (Belgium) ...... 620 483.9 15 Turin, No. 1 (Italy) ...... 1140 263.2 7 Lisbon (Portugal) ...... 629 476.9 15 Trieste (Italy) ...... I 140 263.2 10 Tründelag (Norway) .. .. 629 476.9 20 London National (Brookmans Park) .. 1 149 261.1 20 Prague, No. i (Czechoslovakia) .. .. 638 470.2 120 North National (Slaithwaito) .. .. 1149 261.1 20 Lyons, P.T.T. (France) ...... 648 463 100 West National (Washford Cross) .. .. 1149 261.1 20 Petrozavodsk (U.S.S.R.) ...... 648 463 10 Kosice (Czechoslovakia) ...... 1158 259.1 10 Cologne (Germany) ...... 658 455.9 100 Monte Ceneri (Switzerland) ...... 1167 257.1 15 North Regional (Slaithwaite) .. .. 668 449.1 70 Copenhagen (Denmark) ...... 1176 255.1 10 Sottens (Switzerland) ...... 677 443.1 100 Kharkov, No. 2, RW4 (U.S.S.R.) .. .. 1185 253.2 10 Belgrade (Yugoslavia) ...... 686 437.3 2.5 Nice -Corse (France) ...... 1185 253.2 60 Paris, P.T.T. (France) ...... 695 431.7 120 Frankfurt (and Relays) (Germany) .. .. 1195 251 25 Stockholm (Sweden) ...... 704 426.1 55 Prague, No. 2 (Czechoslovakia) .. .. 1204 249.2 5 Rome, No. 1 (Italy) ...... 713 420.8 50 Lille, P.T.T. (France) .. .. 1213 247.3 60 Kiev. RW9 (U.S.S.R.) ...... 722 415.4 35 Bologna (Radio Marconi) (Italy) .. .. 1222 245.5 50 Kharkov. No. I, RW20 ( U.S.S.R.) .. .. 722 415.4 10 Narvik (Norway) ...... 1222 245.5 0.3 Fredrikstad (Norway) ...... 722 415.4 1 Gleiwitz (Germany) ...... 1231 243.7 5 Tallinn (Estonia) ...... 731 410.4 20 Cork (Irish Free State) ...... 1240 241.9 1 Madrid, EAJ2 (Spain) ...... 731 410.4 3 Saarbrücken (Germany) ...... 1249 240.2 17 Seville (Spain) ...... 731 410.4 5.5 Riga (Latvia) ...... 1258 238.5 10 Munich (Germany) ...... 740 405.4 100 Rome, No. 3 (Italy) ...... 1258 238.5 1 Marseilles, P.T.T. (France) ...... 749 400.5 90 San Sebastian, EAJ8 (Spain) .. .. 1258 238.5 1 2 Pori (Finland) ...... 749 400.5 1 Nurnberg (Germany) ...... 1267 236.8 Katowice (Poland) ...... 758 395.8 12 Juan -les -Pins (Radio Côte d'Azur) (France) 1276 235.1 27 Scottish Regional (Falkirk) .. .. 767 391.1 70 Christiansand (Norway) ...... 1276 235.1 0.5 North Scottish Regional (Burghead) .. 767 391.1 60 Dresden (Germany) ...... 1285 233.5 0.2e Stalino (U.S.S.R.) ...... 776 386.6 10 Aberdeen ...... 1285 233.5 1 Toulouse P.T.T. (France) ...... 776 386.6 120 Klagenfurt (Austria) ...... 1294 231.8 5 Leipzig (Germany) ...... 785 382.2 120 Vorarlberg (Austria) .. 1294 231.8 5 Barcelona, EAJ1 (Spain) ...... 795 377.4 7.5 Danzig .. 1303 230.2 0.5 Lwow (Poland) 795 377.4. 50 Swedish Relay Stations ...... 1312 228.7 - West Regional (Washford Cross) .. .. 804 373.1 70 Magyarovar (Hungary) ...... 1321 227.1 1.2i JANUARY ist, 1937 Wtpisil@og Wwild.

Tuning Tuning Station. kc /s. Positions. Metres. kW. Station. ke /s. Positions. Metres. kW.. German Relay Stations ...... 1330 225.6 - Miskolc (Hungary) .. 1438 208.6 1.25 Montpellier, P.T.T. (France) .. .. 1330 224 1.2 Paris (Eiffel Tower) (France) .. .. 1456 206 5 Lodz (Poland) ...... 1339 224. 2 Pecs (Hungary) ...... 1465 204.8 1.25 Dublin (Irish Free State) ...... 1348 222.6 0.5 Antwerp (Belgium) .. 1465 204.8 0.1 Rjukan (Norway) ...... 1348 222.6 0.15 Courtrai (Belgium) ...... 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 Chatelinean (Belgium) ...... 1492 201.1 0.1 Nottoden (Norway) ...... 1357 221.1 0.15 Wallonia (Belgium) .. 1492 201.1 0.1 Italian Relay Stations ...... 1357 221.1 - Nimes (France) ...... 1492 201.1 0.7 L'Ile de France (France) ...... 1366 219.6 0.7 Albacete (Spain) ...... 1493 201.1 0.2 Basle (Switzerland) ...... I375 218.2 0.5 Santiago (Spain) ...... 1493 201.1 0.5 Berne (Switzerland) ...... 1375 218.2 0:5 Liege (Radio Cointe) (Belgium) .. .. 1500 200 0.1 Warsaw, No. 2 (Poland) ...... 1384 216.8 2 Verviers (Belgium) .. 1500 200 0.1 Lyons (Radio Lyons) (France) .. .. 1393 215.4 25 Pietarsaari (Finland) ." ...... 1500 200 0.25 Stara -Zagora (Bulgaria) ...... 1402 214 2 Radio Alcalá (Spain) í:i00 200 0.2 Vaasa -Vasa (Finland) ...... 1420 211.3 0.5 Karlskrona (Sweden) ...... 1530 198 0.2 Alexandria, No. 2 (Egypt) ...... 1429 209.9 0.5 Liepüja (Latvia) ...... 1737 173 0.1 Turku (Finland) ...... 1429 209.9 0.5 SHORT-WAVE STATIONS OF THE WORLD Call Tuning Calt Tuning Station. Sign. kcls. Positions.. Metres. kW. Station. Sign. kc/s. Positions. Metres. kW.

Ponta Delgada (Azores) .. . . CT2AJ 4,000 75.00 0.05 Bombay (India) .. .. VUB 9,565 31.36 4.5 Kharbarovsk (Russia) .. . RV15 4,273 70.20 20 Millis (U.S.A.) .. W1 XK 9,570 31.35 10 Caracas (Venezuela) ...... YV2RC 5,800 51.72 1 Daventry (Gt. Britain) .. GSC 9,580 31.32 15 San Jose (Costa Rica) .. . TIGPH 5,820 51.52 1 Lyndhurst (Australia) .. VK3LR 9,580 31.32 1 Maracaibo (Venezuela) .. YVSRMO 5,850 51.28 1 Philadelphia (U.S.A.) .. W3XAU 9,590 31.28 10 Vatican City (Vatican State) .. HVJ 5,970 50.26 10 Sydney (Australia) . . VK2ME 9,590 31.28 20 Trujillo (Domenica) ...... HIX 5,980 50.16 0:2 Eindhoven (Holland) PCT 9,590 31.28 20 Mexico City (Mexico) .. XEBT 6,000 50.00 1 Prangins (Radio -Nations) (Swit 'l' 1) HIII. 9,595 31.27 20 Moscow (Russia) ...... RW59 6,000 50.00 20 Moscow (Russia) .. .. RAN 9,600 31.25 20 Montreal (Canada) ...... CFCX 6,005 49.96 0.07 Rome (Italy) . . '2R0 9,635 31.13 25 Havana (Cuba) . COCO 6,010 49.92 0.5 Sourabaya (Java) .. .. YDB 9,650 31.09 1 Prague (Podebrady) (Czechoslovak ia) OLR 8,010 49.92 - Lisbon (Portugal) .. .. CT1AA 9,655 31.07 2.5 Singapore (Malaya) .. .. ZHI 6,018 49.85 0.09 Buenos Aires (Argentina) .. LRX 9,660 31.06 5 Bogota (Colombia) .. .. H.13ABH 6,018 49.85 1.6 Lisbon (Portugal) .. . . CT1CT .9,650 31.00 0.5 Zeesen (Germany) .. WC 6,020 49.83 50 Madrid (Spain) .. .. E:1Q 9,860 30.43 20 Panama City (Panama) .. HP5B 6,030 49.75 0.1 Bandoeng (Java) .. PMN 10,260 29.24 3 Calgary (Canada) .. .. VE9CA 6,030 49.75 0:1 Ruyaselede (Belgium) .. ORK 10,330 29.04 9 Boston (U.S.A.) .. . . W1XAL 6,040 49.67 10 Bandoeng (Java) .. PLP 11,010 27.25 15 Miami (U.S.A.) .. W4XB 6,040 49.67 2.5 Stockholm (Sweden) .. SMSSX 11,700 25.63 0.5 Barranquilla (Colombia) .. HJ1ABG 6,042 49.65 0.15 Winnipeg (Canada) . . . CJRX 11,720 25.60 2 Daventry (Gt. Britain) .. GSA 6,.050- 49.59 15 ' Paris (Rallio- Colonial) (France) TPA4 11,720 25.60 12 Cincinnati (U.S.A.) ...... W8XAL 6,060 49.50 10 Daventry(Gt. Britain) .. GSD 11,750 25.53 15 Philadelphia (U.S.A.) . . .. .W3XAU 6,060 49.50 10 Zeesen (Germany) .. .. DJD I1,770 25.49 50 Skamlebaek (Denmark) .. OXY 6,060 49.50 0.5 Boston (U.S.A.) .. .. WIXAL 11,790 25.45 10 Manizales (Colombia) .. HJ4ABL 6,070 49.45 0.15 Vienna (Austria) ...... OER2 11,800 ...... 25.42. 4.5 Penang (Malaya) .. .. Z1IJ 6,080 49.40 0.05 Rome (Italy) .. .. 2RO 11,810 25.40 25 Chicago (U.S.A.) .. .. W9XAA 6,080 49.40 0.5 Daventry (Gt. Britain) .. GSN 11,820 25.3& 15 Nairobi (Kenya) . .. .. ' VQ7LO 6,083 49.31 0.5 Wayne (U.S.A.) .. .. W2XE 11,830 25.36 1 Bowmanville (Canada) .. .. CRCX 6,090 49.26 '0.5 Lisbon (Portugal) .. CT1AA 11,830 25.36 2 Hong Kong (China) .. .. ZBW2 6,090 49.23 2 Daventry (Gt. Britain) .. GSE 11,860 25.29 15 Johannesburg (South Africa) .. ZTJ 6,100 49.20 5 Pittsburgh (U.S.A.) . . W8XK 11,870 25.27 40 Bound Brook (U.S.A.) .. .. W3XAL 6,100 49.18 35 Paris (Radio-Colonial) (France) .. TPA3 11,880 25.23 12 Chicago "(U.S.A. ) .. W9XF 6,100 49.18 10 Moscow (Russia) .. .. RNE 12,000 25.00 20 Belgrade (Yugoslavia) 6,100 49.18 1 Lisbon (Portugal) .. .. CT1CT 12,082 24.83 0.5 Manizales (Colombia) .. HJ4ABB 6,105 49.15 0.3 Reykjavik (Iceland) . .. TFJ 12,235 24.52 7.5 Daventry (Gt. Britain) .. GSL 6,110 49.10 15 Parede (Portugal) .. .. CT100 12,400 24.20 0.35 Calcutta (India) .. .. VUC 6,110 49.10 0.5 Warsaw (Poland) ...... SPW 13,635 22.00 10 Wayne (U.S.A.) .. .. W2XE 6,120 49.02 1 Amateurs ...... 14,000 21.42 0.01 Havana (Cuba) .. .. COCD 6,130 48.92 0.25 to to Halifax (Canada) ...... VE9HX 6,130 48.92 0.2 14,400 20.84

Pittsburgh (U.S.A.) .. . e W8XK 6,140 48.86 40 Sofia (Bulgaria) ., .. I.ZA 14;970 ' 20.04 7 Winnipeg (Canada) .. .. CJRO 6,150 48.78 2 Zeesen (Germany) DJL 15,111 19.85 50 Lisbon (Portugal) .. .. CSL 6,150 48.78 0.50 Vatican City (Vatican State) HVJ 15.123 19.84 10 Caracas (Venezuela) .. .. YV3RC 6,150 48.78 1 Daventry (Gt. Britain) .. .. GSF 15,140 ...... 19.82 10 Parede (Portugal) .. .. CT1GO 6,200 48.40 5 Tokio (Japan) . . .. JZK 15,160 19.80 20 Trujillo (Domenica) . . .. HIZ 6,320 47.50 1 Daventry (Gt. Britain) . . GSO 15,180 19.76 10 Caracas (Venezuela) .. .. YV4RC 6,375 47.05 1 Hongkong (China) .. ZBW4 15,190 19.75 2 San Jose (Costa Rica) . . .. TIPG 6,410 43.80 0.5 Zeesen (Germany) .. .. DJB 15,200 19.74 50 Barranquilla (Colombia) .. HJIABB 6,450 46.52 1 Pittsburgh (U.S.A.) .. .. WBXK 15,210 19.72 40 Valencia (Colombia) .. .. YV6RV 6,5.20 46.00 0.5 Eindhoven (Holland) PCJ 15,220 19.71 20 Riobamba (Ecuador) .. PRADO 6,620 45.31 1 Paris (Radio -Colonial) (France; TPA2 15,243 19.68 12 Guayaquil (Ecuador) .. HC2RL 6,670 45.00 0.2 Daventry (Gt. Britain) .. GSI 15,260 19.66 10 Amateurs .. .. 7,000 42.86 0.01 Wayne (U.S.A.) .. .. W2XE 15,270 19.65 1 to to . Zeesen (Germany) .. .. DJQ 15,280 19.83 50 7,300 41.10 Buenos Aires (Argentina) .. .. LRU 15,290 19.62 5 Prangins (Radio -Nations) (Switz' 'd) HBP 7,780 38.48 20 Daventry (Gt. Britain) . . GSP 15,310 19.60 10 Quito (Ecuador) .. .. HCJB 8,210 36.50 0.25 Schenectady (U.S.A.) .. W2XAD 15,330 19.57 18 Budapest (Hungary) ...... HAT4 9,125 32.88 5 Szekesfehervar (Hungary) .. HAS3 15,370 19.52 20 Havana (Cuba) .. COCH 9,430 31.80 1 Zeesen (Germany) ...... DJE 17,760 16.89 50 Rio de Janeiro (Brazil) .. PRF5 9,500 31.58 5 Wayne (U.S.A.) .. .. W2XE 17,760 16.89 1 Daventry (Gt. Britain} .. GSB 9,510 31.55 15 Huizen (Holland) .. PHI 17,770 16.88 23 Melbourne (Australia) .. VK3ME 9,510 31.55 1.5 Bound Brook (U.S.A.) . . W3XAL 17,780 16.87 35 Hongkong (China) ...... ZBW3 9,520 31.49 2 Daventry (Gt. Britain) .. GSG 17,790 16.86 10 Jelöy (Norway) . . . . LKJ1 9,530 31.48 1 Bandoeng (Java) .. PLE 18,830 15.93 60 Schenectady (U.S.A.) .. W2XAF 9,530 31.48 30 Daventry (Gt. Britain) .. GSH 21,470 13.97 10 Tokio (Japan) . . .. JZI 9,530 31.48 20 Wayne (U.S.A.) .. .. W2XE 21,520 13.94 1 Zeesen (Germany) .. .. DJN 9,540 M.45 50 Daventry (Gt. Britain) .. GSJ 21,530 13.93 10 Suva (Fiji) .. .. VPD2 9,542 31.45 50 Pittsburgh (U.S.A.) ...... WBXK 21,540 13.93 40 Zeesen (Germany) .. .. DJA 9.560 31.38 50 20 Wireless World, January ist, 1937 Brilliant Television THE PRINCIPLE OF By "CATHODE RAY"

CUMULATIVE SCREEN technical knowledge is necessary in order what is reflected can be used, and of this to appreciate the terrific difficulty that is only a minute fraction strays through the ILLUMINATION overcome. small aperture of the camera lens and If a 405 -line system is considered, the of this less than one two -hundredth part number of " spots " that go to make up impinges on any particular " spot." And the picture is over 200,000. All of these this only for an infinitesimal fraction of a ONE may have one's doubts as to are scanned every 25th of a second ; so second. Photography has made wonder- the ability of television to keep in the space of one five -millionth of a ful strides. But the latest ultra- super- the great general public per- second an almost microscopic spot on the hypersensitive film needs thousands of petually amused, or as to the screen of the camera has to release enough source of enough money to spread the said energy to control 17 kilowatts ! There is amusement thickly over the whole of the available for doing this no intense heat or Enormously simplified diagram of British Isles ; but even if television is a other concentrated activity. No disruptive several successive stages in the re- flop on one or both of these energy can be allowed to smite Miss construction on the receiving screen of complete an image by means of the Scophony counts it will almost have been worth Elizabeth Cowell's sensitive face ; only the light relay. The progress of the trans- while, just for demonstrating how extra- gentle force of light. And of this only mitting scanner over the object is ordinarily ingenious some people shown at the left. At the receiver a can be. constant source of light L shines RECEIVER through the relay cell C along which The experienced technician - PICTURE SCREEN waves of extremely high frequency are or professional the last LINE propagated from left to right by a amateur -is BEING to call attention to the extreme SCANNED quartz oscillato r. The intensity of the waves is controlled by the tele- ; that is left cleverness of his works vision signal and results in more or to popular writers and greenhorns. less light getting through on to the Though obviously reluctant (having screen. The scanning mirror S pro- just said that) to indulge in the usual \ jects on the screen not only the light wonder " and " amazing " lan \ being controlled at that instant, but TRANSMITTER also that which has been controlled guage, I do think that some of the 3(ANNIPIG RAY during fifty previous instants, thus work that is being done in the cause illuminating a much larger portion of of television is enough to force re- the screen at any one time. luctant murmurs of admiration from between the ordinarily unemotional lips of even the hard- boiled tech- times this length of exposure to make nician. It is not necessarily un- a picture. dignified. There is a difference There you have some idea of the between the superficial flitting on the problem. The Iconoscope, in effect, wings of the daily Press from one lengthens the exposure to a twenty- inaccurate and hysterical " wonder " fifth of a second -something with to another and the real joy to be . which photographers and electron derived from intelligent admiration engineers can do things. of some scientific problem beauti- Instead of using a simple light - fully solved. sensitive cell to deal with each spot There may be several ways in of the picture in turn, with no time which a desired result can be to collect much of a " signal " from achieved, and they may all work any of them, the Iconoscope ingeni- equally well in practice ; yet one of ously contains millions of cells, all them may give far more pleasure to working all the time to provide a nice contemplate than the others. To use fat signal for the scanning Tay to an old- fashioned term, it is more collect each time it touches them. "elegant."" The ray, as it were, reaps the crop The ordinary motor car gear bo:: that has been steadily growing ever is an example of a practical solution since it passed that way before. that is not elegant. One of those Theoretically there is 200,000 times Frenchmen who come out with pithy as much time for the signal to observed develop, which helps quite a lot. epigrams from time to time PICTURE DEIN that " it is brutal, but it works "--or GUILT UP But that such a pretty idea should words to that effect. The Constan- .,, really work is the most wonderful tinesco gear, on the other hand, thing of all. excels in elegance, but is never used. The - Marconi- E.M.I. Company Several ideas that have already can scarcely be said to have been in a blaze of publicity, but appeared in the field of television are I working it is very surprising UV compared with it the Scophony so beautiful that I Yp Imi to find that they actually work - system is still quite a dark horse. apparently quite well, too. One of And at least one of the ideas that them, the Iconoscope, has already apparently has been made to work received a fair measure of admira- is even more wildly improbable than tion. In this the layman, unfortun- the Iconoscope. It is also consider- ately, is unable to join, because some ably more difficult to understand. I JANUARY ist, 1937 WIpallisoo zr WOpIld Brilliant Television - This illustration may be somewhat am afraid the following venture may be fanciful, but the medium of a liquid is not an example of the blind leading the blind, selected at random, for the light relay con- .> but I trust that both will not altogether sists of a liquid cell- in which waves are McCA perish miserably. ' propagated by a quartz crystal, the The Iconoscope tackles a difficulty at strength of waves at any instant being for the finest value in the transmitting end ; the Scophony light controlled by the television signal. relay concerns the corresponding problem Although the cell is not carried along at the receiver. The television picture on bodily at scanning speed (obviously !) the All-Wave Receivers which you gaze is an illusion. It is not a same effect is obtained by passing a beam picture at all ; it is only a single tiny spot of light through it and then deflecting it of light. Because the human eye keeps by means of a mirror drum or other on seeing after the object has moved optical scanner. So, instead of the light away, a single spot of light moving whirled across the screen being in the form rapidly about over the whole field is able of a spot it is more like a comet with a to represent a complete picture. A single long tail. The brightness of the light soldier might look to the enemy Iike a depends on the strength of the waves in whole army if he appeared at different the liquid through which the light has to points in rapid succession. pass (this is a result of a very subtle pro- If the " definition " of television comes perty of light which I have not time to into the " high " category, the spot must explain). be very small and must move very rapidly. Suppose a strong wave passes a bright

So even if . it is extremely bright, the light. Then when the transmitter is scan- picture as a whole may look quite faint, ning Mr. Baldhead the cell is pushing out because the light is distributed over (say) a series of strong waves which move from 200,000 times the area. the head of the comet to the tail. Now 6 ALL -WAVE Hence the need for thousands of volts (this is a clever part of the scheme) the VALVE on a cathode -ray tube in the attempt to backward velocity of the waves in the SUPERHETERODYNE make the point of light so intense as to liquid is contrived to be equal to the for- illuminate the whole area satisfactorily. ward velocity with which the scanner (complete with B.V.A. Valves) The Scophony system dispenses with carries an image of the cell across the Improved edition of this popular receiver (praised " Wireless cathode -ray tubes and is faced with the screen. So any particular wave continues World " test reports). Heavier gauge cadmium -plated steel light chassis. Iron -cored I.F. transformers give even better per- problem of producing enough to cast its influence on the same spot on formance. No increase in price. through a device that can control the in- the screen, just as the whirlpools set up Brief Specification: 8- stage, all-wave band -pass superhetero- dyne, 7 tuned circuits. D.A.V.C. with " squelch " circuit valve tensity at the requisite rate. by the moving boat are stationary on the for noise suppression. Illuminated " Airplane " dial. Octode water, or a man walking down a rising frequency changer. 3 -5 watts pentode. Switching for gramo- loo-2 000 The Comet's Tail escalator at the same speed stays in the phone pick -up. Wave ranges: 16.5-5o, zoo -33o metres. time. number to the same place all the A sort of opposite As the transmitter ray moves off the "De Model receiver that main- Luxe" Iconoscope would be a bald head on to the black velvet the cell of light on tained the appropriate degree shuts down the wave intensity. all the time, suddenly McCARTHY ALL -WAVE SIX every spot of the picture The head of the comet lets through no necessary) each time it was changing (if light on the screen, though the rest of it with be very delightful, scanned. That would is still busy pouring out light to give an radio frequency aware it remains to be but so far ás I am representation of the glistening stage goes some adequate invented. However, Scophony pate. Gradually (if a scanning velocity of illuminating fifty or way towards it by 10,000 miles an hour can be called more spots simultaneously. gradual) the weak wave influence spreads Now it is obvious that to constitute a part of be prepared down the cell, and a corresponding picture these fifty spots must in a of intensities it is keeping the screen state dark- to consist of as many different is built up, not only fifty different ness. So the picture of light. It is also clear that cell that is responding simultaneously by the end of the signals cannot be broadcast from moment to moment to the signal from over one channel. At one instant a bald also by a ` ` tail," fifty resulting in the transmitter, but man's head is being scanned, spots long, that preserves the imprint of ; five -millionth a very intense light signal a previous signals. ray has (complete with of a second later the scanning This account of the matter does not, of velvet gown of E9 B.V.A. Valves) slipped off on to the black course, do justice to the full beauty of the his companion, and if the head illumina- invention, but it may perhaps give some "De lure " 6 valve receiver with f valve performance (specially tion on the receiving screen is to be sus- recommended for tropical and foreign reception conditions). of the ingenuity with which the Built on special 16 period it must be done idea cadmium- plated gauge steel chassis. Varley tained for a further problems are being tackled. It may also iron -cored I.F. mils. Litz -wound tuning coils. 3 wave -ranges something that has taken the imprint -x6.5 -z000 metres. Illuminated " Airplane " dial with princi- by help to convince some of us would -be in- pal station names. Micro -vernier z -speed drive. was shot forth some time of the light that might be more profitably Circuit comprises : Pre -selector radio frequency amplifiera ventors that we (operative on all wavebands), triode- herode frequency changer, earlier. occupied selling bootlaces. double band -pass coupled I.F. amplifier, double diode -triode When a boat is being rowed across a detector. D.A.V.C. applied to 3 preceding valves. L.F. amplifier and pentode output. Variable tone control and still lake each stroke of the oars causes a volume control operate on radio and gramophone. whirlpool that remains visible for some MAZDA TH2620 All McCarthy receivers supplied complete with distance in the wake. It is possible to E heater characteristics of the Mazda valves, knobs, pilot lamps, leads. mains cable and imagine that the boatman might vary the TH262o have been changed, and the plug. 12 months' guarantee. strength of his strokes according to some valve now requires 23 volts at o.2 ampere Deferred terms on application, or through London instead of 26 volts. When using the valve Radio Supply Co., 11, Oat Lane, E.C.2. code. Every two seconds he 7 recondite receiver designed for the older pattern, Cash with order on days' approval. Also write a different stroke, yet the in a for illustrated catalogue of complete range of all would. enact therefore, a resistance of 15 ohms must be McCarthy receivers. scene of any one stroke would continue to inserted in the heater circuit. The new type register its intensity on the surface of the will be designated by a different type number, IMcCAIRYf1Y IRA®ILIII® ILTDd water, while a number of new ones were and henceforth the valve will be known as 44a, Westbourne Grove, London, W.2 being created ahead of it. the TH232o. TeleNhone: Bayswater 32012. 22. Wireless World, January 1sf, 1937 BROADCAST NEWS Business as Usual in 1937 FROM WHAT will the year 1937 bring for listeners in the BRh; VITIf+S PORTLAND wa y of programmes? So far as the main lines of policy are con- in mid- air." One writer, for more people are awakening to PLACE cerned there is not likely to be instance, asked Broadcasting the fact that the sound trans- much change.. Mr. Cecil Graves, House for hints on how to keep mission from Alexandra Palace Controller of Programmes, feels bulldogs; another inquired what is exceptionally good. Music and that the general ideas which he kind of work Shakespeare would dramatic critics, after the first beat all records for high -speed has worked out during the past be writing if he were alive to- few minutes of watching a show, description in his accounts of the year do not call for any exten- day. This kind of letter scarcely remark on the brilliance and Olympic Ice Hockey Games at sive revision, but his aim will comes within the sphere of con- depth of the sound accompani- Garmisch. continue to be to shorten items structive programme criticism, ment-and this without any pre- And now the tale is being with the idea of securing greater for which the B.B.C. hungers. conceived notions as to the per- taken up by David Miller, variation and contrast. formance to be expected of ultra - another keen commentator, who short waves. will accompany Tommy Wood - Pickings for the Multitude That Co -axial Cable Actually the common sound rooffe to the " O.B." box at The New Year will be a trying ALTHOUGH the co -axial transmitter at the television sta- Harringay Rink on January 14th one for the B.B.C. financially. cable between Broadcasting tion is giving a nearly even to give Regional listeners an Everyone looks like getting some House and Alexandra Palace has response between 5o and 1z,000 account of the Ice Hockey Test extra pickings -the Performing not yet been used for television, cycles. Match between England and the Right Society, the Society of it has not been forgotten. High Resident Canadians. Authors and Playwrights, the frequency measurements of quite An " Ultra Short " Relay? London players have improved dance band leaders, even the an interesting kind have been It has been suggested that the out of all knowledge in the last staff. In the latter case, how- carried out. With the installa- transmitter should be used for year, and it is expected that the ever, increases will be given on tion of television cameras and relaying the National or Regional home team will more than hold a. strictly graduated scale, and necessary control apparatus at programme when not required their own with their opponents. however good an official's work In any case, the commentary may be he will be limited to the should be well worth listen- maximum for his particular ing to. grade. Thus an increase of £z5- so will be considered quite sub- stantial. This is the first step in O.B. Chief for Holland preparation for the coming of a TALKING of running com- staff association and the intro- mentaries, Mr. S. J. de duction of Civil Service condi- Lotbinière, the B.B.C.'s outside tions. As regards the extra pay- broadcasts chief, has decided ments to outside organisations, that he will himself visit the listener naturally will not Holland to give the running benefit, as he has already been commentary on Princess receiving the best that they have Juliana's wedding on to offer. January 7th. W. It was de Lotbinière who thrilled London with the late - A Growing Infant night commentary on the Crystal THE library of recorded Palace fire. When news of the material at the B.B.C. now disaster reached him at his North numbers some 4,000 items and London home, he rushed to includes examples of every phase BROADCAST ECONOMY. When the O.B. engineers in Sofia make Sydenham by car and arranged of contemporary activity. no a business trip they find the horse -cabs are not such a strain on the in record If the petty as the more modern taxi. O.B. time. more books were written, if the cash contemporary historian were en- shrouded in impenetrable silence headquarters the coast would be for television purposes, but A Listener's Referendum for evermore, posterity would clear for the first long -distance official opinion is opposed to this THE year 1937 may see the'first still be able to get an accurate television experiments, but for a for the very good reason that the determined effort on the part line on the political, religious variety of reasons the engineers transmitter is already called upon of the B.B.C. to discover the and literary tendencies of the age are not forcing matters in this to operate for double the amount likes and dislikes of its thirty -odd by means of a " play -back " of direction. of time required of each tele- million listeners. Mr. R. J. the records preserved by the vision transmitter. Although at Silvey, the official most actively B.B.C. over the past few years. Ca'canny the moment actual transmission concerned, favours the question- times are few, heavier demands ten kn.. ten te,1 Staff at Alexandra Palace are naire system, whereby listeners are likely in the near future, and What busy enough putting out a good sufficiently interested to respond They Want to Know signal on the spot. When a rock it is undesirable that the rate of to a microphone appeal would THE mailbag of the B.B.C. steady picture can always be depreciation of the sound trans- be supplied with forms on which has contained during the relied upon it will be time to mitter should be disproportion- they could register their pro- past twelve months an aggregate consider transmitting from ately high. gramme preferences. of 16o,000 letters from listeners studios at " B.H." The first A useful indication of the on programme matters, and to television transmission from probable response may be had that extent correspondence has headquarters may be expected Ice Hockey Test Match from the appeal which is now helped towards a better under- at about the middle of this year. NOTHING in the " O.B." being made to televiewers. The standing between the B.B.C. repertoire has been found to form sent to those who respond, t_.-+ d, ca 'o, and its public. But the under- equal ice hockey matches in besides containing questions standing is no doubt more fully speed and excitement. Partly apropos height of aerial, ease of developed on the part of the Super - quality Trans- this is due to the inherent live- tuning -in sound and vision, B.B.C. than on the part of some mission liness of the game and partly to interference, etc., will give listeners; for the latter's demands NOW that the overwhelming the new spirit of verve and dash ample space for programme are not always easy to satisfy - novelty of television is be- imported into the running com- eulogies or the ventilation of and inquirers are perforce " left ginning to pass off, more and mentaries by Bob Bowman, who grievances. Wireless World, January Ist, 1937 2 Letters to the Editor The Editor does not hold himself responsible for the opinions of his correspondents.

Service Prospects imply that for a given grid voltage of the AT the present time I am working as a control valve (V2 in the original diagram) radio tester at is. 1d. per hour. I have the anode voltage -anode current charac- been at this job for six months, and find teristic is a straight line. This is very it a very monotonous and soul-destroying nearly true for anode voltages in excess of job. I have had no previous experience about 75 V, but is by no means'so at lower of radio, excepting a three months' course voltages. at a radio college. I have recently been If the operating conditions are so chosen wondering as to the prospects in this field. that the anode voltage never falls below Perhaps you would be so kind as to en- this figure reference to the curves of the lighten me about this. 6D6 shows that the impedance is about I have commenced studying for the 100,000 ohms at zero grid volts and 1 A.I.W.T. and A.M.I.R.E. examinations. megohm at zo volts. Under these con- Would these be of any use in getting out of ditions the fraction of the signal voltage the rut and gaining a better position? applied to the grid of the amplifier valve V3 Radio servicing would appear to be rather would vary between 0.5 and 0.91 respec- an attractive occupation, but how does one tively, giving an expansion range of less gain the experience to be able to service all than 6 db. makes of receivers? In order to increase the upper limit of As regards myself, I am twenty -eight attenuation it is necessary to operate the years of age, and was educated at a public control valve at low anode voltages. If school. I feel I have reached the age when distortion is to be avoided, therefore, it I should settle down to a career. and I am would seem necessary to restrict the applied afraid at my present position I should signal amplitude to very small proportions- always be somewhat of a " casual labourer," an argument which applies with hardly less and be treated as a mere labourer replace- force than in the case of the " variable -mu " able at a moment's notice. method of control. B. D. CORBETT. I should be very grateful for any helpful London, S.W. r r. suggestions your readers may offer. ENQUIRER. " W.W." Receivers a satisfied user of Olympic S.S. and Contrast Amplification AS Quality amplifier, I am sending you the new method of volume particulars of my equipment, as it may pos- ALTHOUGHexpansion described by Mr. W. N. sibly interest other users of this fine outfit. OF STERLING (I) Aperiodic input coil wound from data Weeden in your issue of December 18th Used originally .n connection with co'nage of seems to offer several advantages over pre- given by a contributor in " fir. W. " under unvarying weight and fineness, the adjective heading " LF components in HF circuits." sterling is now used to describe any article vious methods, I would draw attention to or quality of unvarying excellence. Just (2) Reaction winding removed from L5, as so the phrase " a G.12 equipped set " denotes a misconception. The writer says : " It will it was found unnecessary. (3) RrS replaced a radio receiver the quality of which is beyond be seen that such a circuit should cause no al` doubt. Since the manufacturer who by 400- megohms distortion as the control valve is used only variable resistance and wishes to economise on components usually used as RF volume control, and in the out- twins with the speaker it stands to reason as a variable resistance, eliminating the that you can rely absolutely on any set in effect of curvature of characteristics as put stage two r8 -watt triodes feeding two which this 12in.. high fidelity. unit is installed. B.T.H. speakers modified as follows: No. 1, Manufactutera know from their sales this encountered when the control valve is saason that it pays to install G.12's. Listeners utilised as a variable -gain amplifier." spider removed and centring obtained with who arrange a demonstration at their dealers invariably come to the same conclusion ' Now, it must be remembered that the four silk threads stretched from outside of coil anode voltage of the control valve is not to four adjusting screws, cone doped with celluloid varnish a G.12 D.C. kasillustrated! complete with constant, but varies over a small range pro- for distance of Transformer. Mounting portional to the amplitude of the signal 3 inches from centre, leather surround im- Stand. Handle and Base .. £5 5 0 which it is desired to attenuate. If ampli- pregnated with glycerine. G.I2 D.C. with Mounting Stand, Handle Speaker No. z used without and Base, but without tude distortion is to be avoided, therefore, alteration Transformer ...... £4 16 0 the AC resistance of the valve must be and mounted in a horizontal position in G.12 D.C. Stripped, but with Trans- strictly constant over this range. cabinet close to floor with resonator bars £1 4 0 of different woods (no data for choosing G.12 D.C. Stripped and without Trans- The quotation given above would seem to former ...... £315 0 these) arranged in Venetian blind form When ordering please state Field Resistance and across the baffle. Speaker No. I is mounted Impedance of Transformer required.) in orthodox position on Celotex baffle 6.12 P.M. less Transformer ...... £4 16 0 4ft. 6in. x 4ft. in cabinet, which is built G.12 P.M. with Transformer .. ... £5 5 0 throughout of ¡in. oak. For Public Address work both the P.M. and Ener- gised Models can be supplied with a 15 ohm Voice In conclusion I would say that, compared Coil at an additional with charge of 3 - any of the commercial HF jobs I have Write for Folder A. heard, the " W.W." Olympic S.S. sets a standard which would be difficult to equal OVER 7 MILLION IN USE and well -nigh impossible to better. Thanking you for a superlative design. Belfast. G. McAULEY.

Television Range THE television sound transmissions are received here on an ordinary detector and 1 LF S.W. receiver. The ll ótl4 7írte.s! lteducett This house is about miles from the e The latest Western Electric studio micro- 70 phone which has been specially designed not Alexandra Palace and in the shadow of the THE BRITISH ROLA CO.. LTD. Downs on the southerly side. only to have equal sensitivity but also a MINERVA ROAD, PARK ROYAL,N.W.10. uniform frequency response for sounds W. W. WOODMAN. arriving from any direction. Chichester, Sussex. PHONE WILLESDEN 4322 -3- 4 -5 -6. ,1 Wireless World, January zst, ¡937

MODULATING SYSTEMS T a class -B modulator two descriptions valves are used in push -pull, Brief both as regards their anodes and of the more in- Inventions grids, the latter being so biased Recent no teresting rad o that anode current passes in the absence of a modulating signal. devices and improve- an initial muting -bias applied to ALL =WAVE RECEIVERS The arrangement is economical in ments issued as patents the suppressor grid of the low fre- THE various tuning components power -output, but it necessitates the use of a push -pull transformer, be included in this quency pentode VI, and brings the of a multi- wave -band set are will loud speaker into action. A arranged inside compartments which is not only expensive but section. switch S. ganged to the main tun- formed between the radial parti- also creates difficulties in securing ing knot,, cuts out the automatic tions and circular end walls of a a uniform response over a wide tuning effect if and when the set supporting member, which is band 8f signal frequencies. AUTOMATIC TUNING is being operated manually. rotated about a shaft to bring According to the invention the RELATES to automatic tuning Murphy Radio, Ltd., and G. B. them into operative relation with use of a transformer in such an in- and noise suppression circuits. Baker. Application date March a set of stationary contacts. This stallation is rendered unnecessary in which an initial error in tuning 191h, 1935. No. by arranging one modulator in 453$58.o couples 'the appropriate units at is corrected by a pentode valve o o o each position of the wave -band shunt with the carrier -wave ampli- T(' arranged to have a pronounced SENSITISED " MOS.tIC " switch. fier, and the other in series with Miller effect, or variation of input SCREENS The British Thomson- líouston it. so that the first modulates one capacity with slope. APIHOTO- SENSITIVE screen Co., Ltd. Convention date half of each carrier wave. and the The voltage applied from a diode of the " mosaic -cell " type, (U.S.A.) October 31st, 19 34. No. second the other half. TC as used for transmitting television I) to the suppressor grid of 454188. Marconi's Wireless Telegraph alters the mutual conductance of signals. consists of a very large 0 0 0 o Co., Ltd., and W. T. Ditcham. that valve, and therefore its effec- number of photo -electric globules. Application date March 27th, LIGHT FOR LISTENERS tive input capacity, which, in mutually - insulated from each 1935. No. 454259. is indirect lighting turn, controls the frequency of the other, and laid on a backing sheet IT stated that o o o o local -oscillator circuit LO. To en- of insulating material. It is desir- 1 creates a favourable " atmo- sure automatic correction, the cir- able (a) that the distribution of the sphere " for listening to a broad- D.C. AMPLIFIERS cuits Fr, l' , of the diode I) are cells should be kept uniform. and cast programme. The inventors certain cases, as for instance IN in television, it is desirable to use DC amplifiers rather than transformer -coupled circuits which cannot transmit the DC com- ponent necessary to keep step with changes in the average or overall brightness of the picture. DC amplifiers are, of course, known, but they suffer from a ten - dency to " drift." That is to say. the output current is apt to in- crease or decrease gradually, even with no signal input. over a period of several minutes. In order to overcome this ten- dency in a television system where t he picture signals are separated by intermittent synchronising im- pulses, tire latter are utilised to apply such a bias to the grid of the amplifier as will keep the out- put steady. The synchronising - signals are applied to the grid of a valve initially biased below the cut -off point, and when drift occurs, they set up a potential drop in the output of that valve which is then applied to offset the TC drift. Marconi's Wireless Telegraph Co., Ltd. (communicated by A. W. l'ance). Application date April i sl. 1935. No. 45-1511. o o o o TELEVISION SYSTEMS FRUM the standpoint of clear- ness in detail, the smaller the scanning aperture is made the bet- ter, but this finally reduces the sensitivity of the device to a point Arrangement of the circuit for automatic tuning correction and interstation noise suppression. where it is difficult to ensure a satisfactory signal -to -noise ratio. tuned, one a little above and the (b) that the ratio of the photo- accordingly fit one or more lamps According to the invention, the other a little below, the correct sensitive area to the total area of inside a wireless cabinet which is first aperture over which the elec- intermediate frequency. Both the screen should be as near unity provided with a translucent cover tron stream is swept includes a circuits are coupled to the output as possible. At the same time the of frosted glass. so that when the screen perforated by a smaller of the IF valve V, so that if the leakage resistance between in- set is switched on luminous rays aperture. The small aperture receiver has been left slightly " off - dividual cells should be kept high. are projected upwards from it. determines the degree of detail, tune " one of the circuits Fr, F2 To secure these results the The upper part of the cabinet is whilst the large aperture raises the builds up more energy than the screen is prepared by a photo- ventilated to prevent excessive amplitude of the signal well above other, thus producing an excess mechanical method which consists heat. the " noise " level. voltage in one of the load resist- in applying to a backing sheet of Etablissements i'ictor. Conven- D. T. Farnsworth (assignor to ances Rr, R2. mica a " resist " of bichromated tion date (France) December 12th, Television Laboratories Inc.). No. The excess voltage is fed to the glue on which a fine " mesh " 1934. No. 4,54o61. 2037711. (U.S.A.) suppressor grid of the pentode TC, pattern is printed. The " nega- and, by varying its mutual con - tive" is then developed and ductance, changes the frequency washed, and a coating of silver is The British abstracts published here are prepared, with the permission of the local- oscillator circuit LO applied by " sputtering " so that of the Controller of 11.)1. Stationery Olrlce. front Specifications until the initial error in tuning is when the resist is removed the obtainable at the Patent Office, 25, Southampton Buildings, London, regular of automatically set right. Simul- silver is left a pattern W.C.2, price 1 - (ech. A selection of patents issued In U.S.A. it) taneously the voltage produced separate elements. also included, across RI, R2 by a station of C. J. Whilems. Application date " worthwhile " strength removes April 8th, 1935. No. 454937 rei THE PRACTICAL RADIO JOURNAL 26th Year of Publication

No. 906. FRIDAY, JANUARY 8TH, 1937. VOL. XL. No. 2.

Proprietors : ILIFFE & SONS LTD.

Editor : EDIl'ORIAL CONNEN7, HUGH S. POCOCK. Editorial, that ships' transmitters, with a few Advertising and Publishing Offices : Waveband Allocations modern exceptions, are not yet employ- DORSET HOUSE, STAMFORD STREET, ing any frequency -controlling LONDON, S.E.I. Demand for Transmitter adequate device, resulting not only in the occu- Telephone: Waterloo 3333 (So lines). Efficiency Telegrams: "Ethaworld, Sedist, London.'. pation of a much wider band of CONSTANTLY increasing de- frequencies than is necessary for trans- COVENTRY : Hertford Street. mission, but limiting also the potential . Telegrams: Telephone: mands on wavelengths for radio Autocar, Coventry." 5210 Coventry. communication purposes have efficiency of the receiver because it is BIRMINGHAM: resulted in a tightening of regu- required to be broadly tuned for the Guildhall Buildings, Navigation Street, 2. lations to ensure the efficiency of reception of an unsteady transmission. Telegrams : Telephone : Then, again, there is the question of ' Autopress, Birmingham." 2971 Midland (4 lines). transmitters so that, whilst maintain- ing their allotted frequencies, they the continuance of obsolete spark MANCHESTER : 260, Deansgate, 3. should interfere as little as possible transmitters. Ultimately, we know, Telegrams : Telephone: r Ilife, Manchester." Blackfriars 4412 (4 lines). with the proper working of their spark transmitters will disappear, but immediate neighbours in the wave- the question now raised is whether it is GLASGOW : 26s, Renfield Street, C.2. reasonable for Telegrams: "IIife, Glasgow." Telephone: Central 4857. bands which , have been allotted to the period of their disappearance to be so protracted. PUBLISHED WEEKLY. ENTERED AS SECOND them. Crystal control of transmitters CLASS MATTER AT NEW YORK, N.Y. on many wavelengths, especially where congestion is serious, is becoming com- Subscription Rates : Menace to Communication pulsory, and nowhere, perhaps, is more Home, £I is. 8d. ; Canada, LI is. 8d. ; other countries, £I 3s. Tod. per annum. strict adherence to allotted frequencies In an authoritative article in The so necessary as in the case of broad- Wireless World of December 25th deal- As many of the circuits and apparatus described in these pages are covered by patents, readers are advised, before casting. Broadcasting stations in ing with the year's progress in com- making use of them, to satisfy themselves that they would not be infringing patents. America and in Europe can no longer mercial wireless it was pointed out deviate from their allotted frequencies that there are now about 15,000 ships without breaking in to the trans- fitted with wireless throughout the missions of other stations adjacent to world, and that of these no less than them, and in the common cause it has 8,000 are still equipped with spark CONTENTS become essential that deviation should installations. Page not take place. If it could be argued that for the Editorial Comment.. 25 But whilst on certain wavebands purpose of safety of life at sea a wider of Scanning in Television .. 26 these precautions are being taken, band frequencies is required by indignation is growing over the casual transmitters than in other radio corn- Wireless as Personal Luggage 30 and obsolete methods adopted by munication services, then surely it Transmission Lines 32 transmitters in other wavebands at could equally be suggested that where Current Topics .. 35 least as valuable for communication efficient communication, especially such Unbiased . . .. 36 purposes. Wavelengths on a generous as is required in cases of emergency, is New Osram Valves . . 37 scale have been allotted for maritime to be effected it cannot well be done Random Radiations 38 wireless, and no one would question in wavebands which are cluttered up On the Short Waves .. 39 the necessity for maintaining an alloca- with spark transmissions or CW trans- Listeners' Guide for the Week 40 tion adequate not only for marine mitters whose frequency is not suitably traffic but more especially in the Finding the Ultra -short Band 42 controlled. interests of safety of life at sea. The When it is considered how extremely Programmes Television 43 impression, however, is that the wave- valuable every available band has Broadcast Brevities. . . . 44 bands allotted for marine purposes are become to -day it seems highly desir- Dropping Filament Volts . . 45 being abused because of the obsolete able that we should satisfy ourselves New Apparatus Reviewed.. 46 nature of much of the apparatus that the most efficient use is being Letters to the Editor 47 employed. There have been strong made of every available transmission Recent Inventions .. 48 criticisms emanating from America channel. 26 Wireless World, January 8th, 1937

PRINCIPLES of scanning as employed iu Scanning in modern television are discussed in detail in this article. Scanning is shown to be the factor which is chiefly re- By W. T. COCKING sponsible for the greater complication of television receivers as compared with ordinary broadcast sets. amount of light passing and falling on the photo-cell will be the same in the two cases, and hence the current will be the THE mechanism of sound broad- it is true, and some process analogous to same. There is nothing electrically to dis- casting is by now well known, the above is actually adopted.. It is neces- tinguish between the two pictures. and even the completely non- sary to transmit more than mere varia- If a lamp be arranged to have its bril- technical have some idea of the tions in light intensity, however, and it is liancy controlled by the photo -cell current processes involved, how the sound waves just this something more which creates it can obviously illuminate a screen, and in the studio are converted into electrical ninety -nine per cent. of the difficulties of any shade between black and white can currents by the microphone, and höw they television. be obtained by varying the current, and modulate a radio -frequency carrier wave In order to see what is required, let us hence by varying the light on the photo- which is eventually radiated from the take one of the simplest possible cases. cell. If the transparencies used at the transmitting aerial. At the receiving end, Suppose we wish to transmit a picture transmitter are quite plain but of varying too, it is understood that the aerial picks which is in the form of a transparency- degrees of shade, perfect reproduction will up the carrier of the desired station, and that is, a piece of cinema film. If we be obtained. When a blank clear piece of celluloid is that this is amplified and selected from place a lamp on one side Of it and a screen put in, the receiving screen will those of unwanted stations in the RF cir- on the other, and use a suitable combina- be brightly illuminated ; when a blank grey transparency is used, cuits ; after detection AF currents are pro- tion of lenses, we can project the picture the receiving screen duced which operate the loud speaker and on to the screen as in the cinema or will be grey, and when an opaque sub- cause it to set up sound wave which are stance is inserted the receiving lamp will counterparts of those existing originally go out and the screen will be black. in the transmitting studio. Many people who have quite a good Elementary Scanning knowledge of the principles of sound broadcasting, however, have little idea Suppose we call half-illumination grey. of the processes involved in television. It Then, when either of the designs shown in is either a complete mystery, or it is erro- Fig. I is put into the transmitter, the re- neously believed to be neither different in ceiving screen will be blank but grey. It !"1 will be evenly illuminated essence nor more difficult than telephony. (a) (b) to correspond In many of its aspects television is with the total amount of light passing through the transparency, but there will exactly analogous to telephony, certain Fig. r. -Two simple " pictures " for the stages, in fact, differing only in degree but be no detail at all. transmission of which an elementary Now, if we use not in kind. There is, however, one funda- scanning system can be used. four photo -cells at the mental difference, and it is one which transmitting end, and arrange that only the light makes television very much more complex " magic -lantern." a different passing through one -quarter of With the picture falls than sound broadcasting. This difference arrangement of lenses we can on each, it is clear that obviously we can is the necessity for scanning. reduce the size of the have four lamps at the receiver, picture instead of each illuminating If it were necessary only to transmit enlarging it in the usual way, so that the one -quarter of the changes in the intensity of light, no real image on the screen is much screen. If each photo -cell is connected to smaller than lamp which difficulty would exist. Changes in light the transparency. is a is placed to illuminate the It obvious that it correct quarter intensity can easily be converted into will still be a complete picture, and all the of the screen, it is clear changes in an electric current, or can be detail will be there. that such simple designs as those of Fig. i can be transmitted. made to produce a current which is pro- Now, if we make this image small portional to the light, by allowing the light enough, we can substitute the sensitive of to fall on a suitable type photo -cell. surface of a photo -cell for the screen, and PHOTO -CELLS Once the current variations are secured, we have our picture on the end of the cell. the process could follow the normal lines The cell then causes a current to flow in TRANSPARENCY 2N 3 of sound transmission and cause the carrier the external electrical circuit which is pro- amplitude to vary in sympathy. portional to the total amount of light fall- ing on it, and to nothing else. LAMP Variations in Light Intensity If our picture is of simple type, such as one black oblong and one white, as in On the receiving side, too, the apparatus Fig. I (a), each of half the picture size, would be similar to the ordinary broadcast it is clear that, as black is the absence of set, but the output would be used to make light, the light falling on the cell will be 0 the brilliancy of, say, a neon tube vary the amount passing through the white SCREEN in accordance with the carrier modula- oblong. The current will be proportional tion. Television would in these circum- to this amount of light. Now, suppose LAMPS stances involve no more than replacing the that the picture is of the form shown in microphone by a photo -cell and the loud Fig. I (b) ; it is of the same size, and the speaker by a neon tube. total area of the two black squares is the Unfortunately, a picture cannot be same as that of the black oblong in (a), Fig. 2.-A method of transmitting and transmitted in any such simple receiving extremely simple pictures. As manner. while the area of the white squares is the explained in the text, only diagrams such as Light variations have to be transmitted, same as that of the white oblong. The those of Fig. i can be dealt with. Wireless World, January Sth, x937 27

to occur in one of these bits, then distor- tion is present, for this area is reproduced as a uniform shade between the two origin- ally making it up. Because of this, sharp outlines in a picture tend to become television blurred ; instead of a sharp transition from AN black to white the one may merge into the other through a boundary of grey. AUTOMATIC It is clear that the definition of the Suppose we insert the design in squares picture will depend upon the number of as in Fig. 2. The light from the lamp JIG -SAW PUZZLE little hits, or elements, into which we can shines through the transparency, and the light passing through each of the four squares falls on its correspondingly num- bered cell. The cells are connected to four lamps which glow in accordance with the A raster photo- photo -cell current. It is clear that no light graphed on the end passes through square i, hence no current of a cathode -ray flows from cell i, and lamp i is dark, and tube The individual gives no illumination on square i of the lines cannot be seen, but the frame fly- receiving screen. Similarly with square 4, back lines are appa- cell 4, and lamp 4. With squares 2 and 3, rent. These disappear however, light passes and the cells pass when a picture is current to lamps 2 and 3 and illuminate received. squares 2 and 3 of the receiving screen. It is clear also that the oblong design of

break it up. With one element, that is, an attempt to transmit the picture as a whole, we obtain no detail at all nor any recog- nisable picture. With an infinite number of elements a perfect picture would be ob- Fig. 3. -Owing to re- tained and the received picture would be tentivity of vision, the in no way inferior to the original. number of connecting wires in the arrange- In practice, we have to be content with ment of Fig. 2 can be a finite number of elements, which means reduced to two only that the picture must in some degree be by adopting switching. imperfect. Whether the imperfections are visible as such to the eye or not depends largely upon the size of the picture. We all know that the ordinary half- tone illustration will not bear examination be reproduced by this slightly different from through a magnifying glass because it Fig. I (a) can also its predecessor. number means, and if it were inserted, squares i Each picture is thrown on the screen as a is actually made up of a large eye does not see and 2 will be black and 3 and 4 light. whole, but there are slight gaps between of little dots. The Now, it is not necessary that all cells successive pictures of which the eye is un- these in the normal size of the picture be connected to their respective lamps the aware if there are sufficient pictures a but readily detects them when an whole time, for, owing to the retentivity second. In general, at least twenty-five attempt at enlargement is made. In the of the eye, it is possible for the current to pictures a second are needed if the decèp- same way, a larger number of elements are any or all lamps to be interrupted without tion is to be complete and flicker avoided. needed in television for a large picture there being any visible effect, provided than for a small if the apparent quality is that the time of the interruption is suffi- Practical Television to remain the same. ciently short. It is consequently possible In practice, it is neither convenient nor to replace the multiple connections be- In television we cannot even throw a necessary to break up the picture into a tween the cells and lamps of Fig. 2 by the complete picture on the screen instanta- number of dots in the manner of a half- two wires of Fig. 3 if suitable switching is neously. We are only able to transmit tone ; it is sufficient to break it up into a introduced. It can be seen that if con- changes in light intensity, so that we have series of parallel lines. One of the sim- tact I on Sr is closed when contact i on to break up the picture in little bits, trans- plest of scanning methods to understand S2 is closed, and so on, each photo -cell is mit the light intensity of each little bit in is one which is widely used in experimental connected in turn to its appropriate lamp, turn, and then reassemble them in their apparatus and it employs the cathode -ray and if the switches are rotated sufficiently correct order at the receiver. All this must tube at both transmitter and receiver. rapidly and continue time after time to be done in one -twenty -fifth of a second ! This is not the place in which to describe sweep over the contacts, the appearance of Each little bit into which we break up the cathode -ray tube in any detail, and it a continuous picture will be obtained. the picture must be transmitted as a uni- is sufficient to say that it is in many re- This is at the base of scanning, which is form shade corresponding to the average spects analogous to the valve. Types an essential part of television. With the depth of this portion of the picture. If employed in television have a high " magic- lantern " a picture is thrown on the picture over this area is also of a uni- vacuum and the flattened end carries a to the screen, and it remains there the form shade, this is no drawback, but if it fluorescent screen upon which the picture whole time. In the cinema a series of pic- really involves a change of depth, as when appears. The tube contains a number of tures is thrown on the screen, each very the transition from black to white happens electrodes to which suitable, and usually 28 WflpgS00 JANUARY 8th, '937 WorDd Scanning in Television - moving spot, but which the eye cannot Now the photo -cell differs from the eye high, voltages are applied, and the result detect as such. in one particular : it sees the raster as it is that a thin pencil of electrons travels Now if in addition to this we apply a truly is-a flying spot of light -and not as the length of the tube and strikes the similar voltage, but one which rises in the eye does as a solid evenly illuminated fluorescent screen. The screen conse- value more slowly, to the vertical de- quently fluoresces in the immediate flecting plates, the path of the spot will vicinity of the impingent electrons and a be different. Referring to Fig. 4, the spot will now trace out a line AB which is

A slightly sloping and the rapid fly -back at c------B the end will no longer return it to D the start A, but to a point C immediately beneath it. The second line traced by the spot is consequently not coincident with the first, LENS CATHODE but is the new line CD immediately ;Tit., TUBE beneath it and parallel with it.

E Building up the Raster F In this way, it is easy to see that the Fig. 4. -This diagram illustrates the way in spot can be made to traverse a rectangle which a raster is built up. on the screen in a series of parallel lines Fig. 6. -One method of scanning in trans- mission is shown here. spot of light appears. The size and sharp- and that if the speed of the spot is suf- ness of this spot of light can be controlled ficiently rapid it will appear as though the by adjusting the voltages applied to the whole rectangle were illuminated. When rectangle. Asa result the amount of light tube and its intensity can be regulated by the last line EF has been traced, both reaching the photo -cell is continually varying the voltage applied to a control the vertical and the horizontal voltages varying. As the spot crosses the screen electrode which is usually termed the grid. fall to zero and the spot returns to A to in its process of building up the raster, the Merely by varying this voltage the spot start tracing out a new series of lines light from the screen which passes through intensity can be varied continuously from coincident with the first. the film to the photo -cell is also moving full brightness until it is extinguished. In television terminology, the number across the picture on the film. On a light The screen of a tube may be 12in. or so of horizontal lines traced by the spot in the part of the film, nearly all the light passes in diameter, while the size of the spot may rectangle is known as the number of lines and the photo -cell current is large ; on a be no more than o.o25in. in diameter, so in the picture or that at any instant it illuminates only a frame. The num- minute portion of the total area of screen. ber of times the The position of the spot on the screen is rectangle is com- readily controllable, for the electron beam pletely covered by can be deflected electro- statically by the spot in one applying voltages to deflector plates built second is the pic- into the tube or electro- magnetically by ture or frame fre- passing currents through coils suitably, quency, while the mounted around the tube. rectangle itself is Now if we apply a voltage to the hori- called the raster. zontal deflecting plates which increases A raster photo- linearly with time, it is easy to see that the graphed on a tube. spot will move steadily across the screen. The number of lines If the voltage is then reduced to zero has been greatly re- almost instantaneously, it will fly back to duced so that the formation is clearly seen. The frame fly -back line can be seen, but the line fly -back is too rapid to show.

Whether or not the lines composing the dark part, hardly any passes and the raster are visible as such depends photo -cell current is small. upon their number, upon the size of the In this way, the picture is divided up frame and upon the distance from which into strips and the varying light and shade it is viewed. Under average conditions in each strip is converted by the photo -cell they are barely detectable when there are into variations in an electric current. At more than 240 lines. the receiving end, this current sets up a Let us now consider the case of trans- voltage which modulates the beam of the mission. We can set up a raster on the cathode -ray tube, making the spot of light screen of a cathode -ray tube and it will on the screen vary in intensity in accord- appear somewhat as in Fig. 5. If we now ance with the variations in the original place a cinema film in front of the screen picture. It is then easy to see that the Fig. 5. -The complete raster appears very we can obviously see the screen only picture will appear on the screen of the much as shown in this drawing, but the the film we shall see pic- number of lines actually used is so much through and the receiving tube provided that the spot of greater that they are barely visible. ture against the illuminated background light is flying over the screen in exact of the raster. If we replace our eye by a accord with the spot of light in the trans- its original starting point, and if the volt- photo -cell so that the arrangement of mitting tube. In other words, exact age again rises it will again move across apparatus is that shown in Fig. 6, the light synchronisation of transmitter and receiver the screen. It is easy to see that if this from the screen will, after passing through is essential. If synchronisation is not process is carried out sufficiently rapidly the film, fall upon the photo -cell and set maintained, there will be no picture, for, a luminous line of light will appear on the up a current proportional to it in the although the spot of light will be brighten- screen-a line which is actually merely a electrical circuit. ing and darkening correctly in accordance JANUARY 8th, 1937 WIp®Il@g3 29 WOplld Scanning in Television - cated, depending as it does on the nature formers or by condensers of not more than with the dictates of the transmitter, the of the supply mains. For instance, it is laid o.or mfd. capacity. of different points of down that terminals for pick -ups, etc., in Permissible temperature rise, which is relative positions the maximum rise above room be wrong. AC sets need not be isolated from the wiring expressed as a lightness and darkness will if they are metallically connected to the temperature, depends on the material of the In practice, other transmitting methods earth terminals or if they are not live case, being highest for metal and non- are often used, but the basic principle of (" live " is defined as at a potential with ignitible substances. scanning is the same as the method respect to earth, but for the purposes of the In order to determine the accessibility of described here. specification, the object is not considered live parts, a special form of testing prod, It is often convenient to think of the to be live if (a) its potential above the maxi- described as a " Standard Finger," which raster as a Whole, for this way it is visible, mum of 5o volts is derived from a dry simulates the shape and size of the human but it must never be forgotten that it is battery, or (b) if the maximum current finger, has been devised. of the specification, which cost 2s. never actually in existence. The raster is which can flow in the event of a short- circuit Copies 5 milliamperes). In each (by post, 2s. 2d.), are obtainable from visible to earth is limited to in reality nothing more than the DC and AC /DC sets, pick -up terminals must the British Standards Institution, 28, result of a single small spot of light which be isolated by means of double -wound trans- Victoria Street, London, S.W.r. is performing the complicated -evolutions which have been described. It has to cover the whole picture in 1/ 25 =0.04 second and one line in 0.04 / 240 = o. 000i66 Railway Signalling by Wireless second ; with a picture ratio of 4 :3 and allowing as much detail in the horizontal THE development of ultra -short wave coloured lights in the cab of the engine. as in the vertical direction the spot can be technique has led to a considerable There are four buttons at each control box considered as lying on any point for only increase in the number of special and by means of these the audio -frequency 1/ 32oth of a line, or o.0oor66 j 32o = applications of radio for communication modulation impressed upon the carrier -wave 0.000,000,5 second. over short distances in cases where it would is varied to correspond with the constants of wire any one of the four signal -lamp circuits. The flying spot of light which builds up not be possible or convenient to use a applications There is a -fifth circuit to enable ordinary the picture in the receiver and which link. One of the latest of these is in connection with railway shunting. spoken orders to be given when necessary via causes the electric current to vary in In large shunting yards, communication a control point and a loud speaker on the sympathy with the detail of the picture in between the official in charge and the transmitter thus rests on any point for the engine- driver has always been no more than one -half of one -millionth of a matter of some difficulty, but the a second ! It is consequently not surprising problem seems to have been that one of the major difficulties in the past completely solved by a wireless has been to obtain adequate illumination. signalling system which has been installed at the shunting yards at Malmö in southern Sweden by the Aga -Baltic Co., of Stockholm. The actual transmitter is in- stalled alongside the track, and the Safety ordinary overhead electrical distri- bution cables are used for an aerial. Precautions Control boxes are placed in differ- ent parts of the shunting yards so Specification for Mains -Driven that the official in charge can direct Sets the engine- driver from the posi- tion which happens to be the most UNDER the self -explanatory title of convenient at the moment. There " British Standard Specification for are four principal orders used in Mains- Operated Apparatus for Radio, shunting work, and to save time Acoustic and Visual Reproduction (Safety these are given by means of Requirements)," a booklet has just been issued by the British Standards Institution. At the outset, it should be pointed out that these " Specifications," though often referred to loosely as " Regulations," do not carry the force of law. Nevertheless, they do carry considerable weight, and the present publication represents the labours of a committee on which there was direct representation of such bodies as the Post Office, the Home Office, the B.B.C., the Institution of Electrical Engineers, the R.M.A., and the R.S.G.B., etc. Since the preparation of the last specifica- tion dealing with safety precautions in The transmitter is installed in a special mains -operated apparatus, many important housing alongside the track. On the left have taken place. In 1931, when the shunting official is seen using one of the changes special control boxes to communicate with B.S.S. 415 was issued, most mains -driven the engine- driver. sets were worked through the intermediary of battery eliminators instead of by built -in power units, and high -definition television engine. When any of the four signal lights had not been developed commercially. are used, the engine- driver's attention is These and other changes have all been taken attracted by an audible note from the loud into account, and the specification now deals speaker. with AC, DC and AC /DC apparatus of the The apparatus has been used in conjunc- types specified in the title. tion with steam locomotives and also elec- Safety precautions are, of course, inti- tric ones, using the overhead type of energy mately linked up with the questions of connector. No difficulty has been experi- enclosure and isolation. Rules for enclosure enced in eliminating electrical interference are comparatively simple, as they are more in the case of the latter. So far, the installa- or less common to all types of apparatus, tion has been a pronounced success and its but the question of isolation is more compli- use is likely to be extended to other yards. Wireless World, January 8th, 1937 Wireless BLAZING THE TRAIL FOR PORTABLES

By " WANDERLNG WAVE "

most painstaking, and not at all easy- going. Yugoslavia, now a popular holiday country for Britishers, only requires a Customs certificate that the_ set has been brought in. One then goes to the post office, at the first stop, with this and registers the receiver-free of charge. Listening is then free for three months. longer, In the Bay of Kotor, Dalmatia. If one stays the duty must be paid WEN I set out some time ago for and a proper licence taken out. In a long journey through a num- But, in spite of my happy experiences, Austria, now famous for winter sports ber of European countries I I should strongly advise getting really first- where many readers may be going this had some misgivings that if hand and up -to -date information regard- season, the Customs look upon your re- I took a portable receiving set with me I ing a portable or car receiver before ceiver as part of your personal baggage. should experience some exciting moments starting on any extensive tour of Europe. Listening is allowed for one month after with strange -looking and foreign -speaking Given time, the Consular authorities will passing the frontier without further for- frontier guards. Previous requests for in- write home and find out, or the central mality. It suffices to show your passport formation about the treatment of travellers postal authorities will answer an enquiry with the date stamp of the frontier station with portables at various Consulates and very promptly. In Turkey, for instance, if the authorities should come to check. even Embassies mostly resulted in shrugs there are very stringent regulations, and If one wishes to remain more than one and the wise counsel that I had better the set will either be sealed or duty more month a short-term licence can be taken leave the set at home if I wanted a than the value of the set must be paid. out for two or up to a period of three pleasant trip, as some Customs officers I have never been to Turkey, but from months. This costs the ordinary fee of might look upon the instrument; as a bomb, what I hear of their officials they are all two shillings per month and an -extra or in any case there might be difficult formalities. I already saw my set lying at some fron- tier station carefully tied with that special string Customs have and well sealed while I watched the tail end of my train vanish in the distance. Looking back I smile. In some countries there are no regulations regarding portable sets. I may or may not have been the very first case. In one country 'I certainly was the very first portable user to come to the notice of the postal authorities, and here I really " blazed the traiI," as travellers with portables will in future be handed a temporary licence, and will not have to go either as pirates or pay for listening for a period of three months. In another country where, according to regulations, the Customs ought to have demanded a deposit of the duty, and where the set should have been sealed until the arrival of a licence from the postal authorities, the officials were really human, turning an en- tirely deaf ear to my declaration that this was a radio receiver, and they abruptly turned their backs on me when I tried to insist. For obvious reasons I am unable to disclose the name of this country ; it is unlikely that anybody would ever go there with a portable from Britain, and if they did they would no doubt be treated in the same friendly, if unofficial, manner. In a Hungarian wayside inn a portable set is really a novelty. Wireless World, January 8th, 1937 s Personal Luggage

Austrian shilling for the licence. In Ger- many portable owners on a short stay and car receivers require a licence taken out at the first convenient post office. Price : Rm. 2 per month. There are other countries in Central Europe with similar arrangements. Why take a portable ? I was often asked this question. The ordinary listener will probably never bother to carry a

" I logged Warsaw on the Fisherman's Bastion overlooking the Danube in Budapest."

much larger, and German or Italian stations or were in- weighs 8.5 kgs. audible. In Sofia, where I used a local with batteries. The receiver, Daventry came rolling in on the inconvenience of short waves. Scottish National and having to lay out London Regional came in later on the an aerial and use same set, a powerful five -valve superhet. myself as an earth with special aerial, but they were badly or any convenient marred by atmospherics, whereas Breslau body of metal near- and even Hamburg romped in like locals. by was outweighed by the strength of reception. The set has four valves, and is a straight Wireless Aids two- circui_ receiver with a tiny moving - coil speaker. In the Aircraft trains in Germany THE Air Ministry investigations into the reception was only various " blind " landing systems for possible at the sta- aircraft have now reached the stage of prac- Droitwich received in a wine -cellar in Vienna. Note the manner in tical tests, and three different systems have which wine glasses are filled. tions, as the dy- of the car been installed at Croydon Aerodrome. namo In broad outline the working of these In Yugoslavia train heavy receiver (and most portables are caused interference. " blind " landing systems is as follows : heavy) in addition to his other luggage, reception was possible. My car was either There are three different beams ; the first, especially as hotels usually have some pro- fitted with anti- interference gadgets or a horizontal one, gives a well- defined path vision for listening-in nowadays. But else, perhaps, the dynamo did not operate of approach to the aerodrome from a dis- there is the case of the car receiver, and in the daytime. tance of 10 to 15 miles. For this a wave- also of the man who goes farther afield into Using the metal bodywork as an earth length of 9 metres is used. The second a country where newspapers in an under- and myself as an aerial I got excellent re- beam is a vertical fan-shaped one situated between r and 2 miles from the aerodrome. standable language arrive too late to be of ception of Budapest in a car going at a a of Having passed this the aircraft continues interest. With a portable one can tune in speed of 6o miles an hour at distance along the horizontal beam, until, As it to fly at a home station at night and get the news about ten miles from the transmitter. a distance of about 30o yards from the land- quickly. I happened to be away at the was an open car I soon discontinued the ing ground, a second vertical beam is passed. time of the devaluation in France and experiment. At noon one day I logged These vertical beams both operate on a Switzerland, and was grateful for the Warsaw on the Fisherman's Bastion over- wavelength of 7.89 metres. chance of listening to the news in a lan- looking the Danube in Budapest, and The systems being tested are suitable for guage I could understand, because even got Droitwich in the cellar of a " Ieuri- conditions in which the visibility is so poor the best waiter or hall porter will not trans- gen " wine inn in Grinzing (Vienna). that the ground cannot be seen at a height late the essentials properly out of the local Speaking generally of my reception ex- of Soft. It is hoped that further develop- I found I could always ments will enable these systems to be em- paper. periences, that ployed under the very worst conditions. Reception results largely depend on the rely on the German stations, and farther The Air Ministry emphasises that, at type of receiver. I chose the newly produced south -east down the Danube the Italian present, the three systems, supplied respec- German " Olympia " portable, as I found stations came in reliably. With the ex- tively by Standard Telephones and Cables, it to have the most convenient shape and ception of Droitwich, in Vienna I was Ltd. (Lorenz), the Plessey Co., and Mar - weight. It is flat like the old type of unable to log a single S.B.C. station. coni's Wireless Telegraph Co., are being Remington portable typewriter, and not Either they were blotted out by powerful used for experimental purposes only. Wireless World, January 8ik, 1937 Transmission Lines AS the author points out, A FORM OF "TUNED CIRCUIT" WITH A ordinary lead-in wires are generally impracticable for certain NUMBER OF INTERESTING APPLICATIONS types of short -wave aerials, as the length of the lead -in might well NOW that general interest is turn- At first sight it might not appear that amount to several wavelengths. ing more and more towards distributed quantities introduce any great Transmission lines or " feeders" shorter and shorter waves, it is complications, because, after all, resist- are necessary in order that the becoming really necessary to ance is distributed throughout the length associated apparatus may be con- understand how they work. As waves of a wire, and, nevertheless, the circuit veniently placed with respect to change only in length and not in nature as diagram picture of a lump of resistance the aerial. they become shorter, the same principles joined up by means of resistanceless wires apply to them as to any others. There is quite equivalent for purposes of reckon- is no definite boundary between long and ing. Even when the wire forms a coil, short or very short waves. The reason so that resistance and inductance are dis- action of such a system. Transmission why they appear to behave differently is lines or " feeders " are a practically neces- that phenomena slight enough to be neg- By sary part of any short-wave station, for lected at one wavelength are predominant it is inconvenient to install the receiver at another. If a tuning coil and con- M. G. SCROGGIE, B.Sc., (or transmitter) in mid -air, and inefficient denser for long waves are connected up A.M.I.E.E. to bring the aerial right down on to the by leads a foot long, one can reasonably apparatus. How do the connecting wires regard the inductance and capacity of the affect the circuit, apart from joining it to one circuit to be concentrated in the coil and tributed among another and com- the aerial? Is there a likelihood of serious pletely mixed, it is perfectly allowable to loss or mistuning? of resistanceless think them as a coil in The answer is that if things are properly series with a non -inductive resistor. The arranged the feeder need have practically is not quite so simple with the dis- thing no effect on the circuit, but that if it is tributed capacity of a coil, but when (as in not properly arranged it can have most w.v.vvYVVVVVVVVVONW,,. all is practical examples) it small, it can undesirable and disturbing- effects. be assumed to be due to a fixed condenser (a) in parallel with the coil (Fig. I). Things are not at all so easy when one Parallel Feeder Wires considers a " long " wire. Every section In order to be able to derive any simple of it, however small, has some inductance general principles it is necessary to start and some capacity to earth or to the return by assuming that the there-and -back lines (b) lead. Even if it is divided up into only are parallel. Things become very much two or three sections, each of which is (d) more complicated otherwise. There are looked upon as a " lumped " capacity and two practical forms of the parallel line inductance (Fig. 2), it is obviously quite - Fig. 1. -The resistance of a piece of wire is two similar wires or rods mounted side by distributed throughout its length, as in- a difficult problem to calculate the single side, and a wire, rod, or tube mounted dicated by (a) ; but in a circuit diagram if quantity that could be connected across centrally inside a larger tube. The minor any account were taken of the resistance at the terminals AB so as to be equivalent. all it would be shown as a concentrated differences between these will be explained resistor connected by non -resistive wires (b). later ; their fundamental principles are the And any coil is a mixture of inductance, same. resistance, and capacity as suggested by A A few things fairly easy to see with- (c) ; but can be considered more simply as a system of unmixed quantities (d). out any mathematical working. If the line has nothing connected at the far end, and condenser rather than in the leads. The is very short (compared with a wave- coil is a lump of inductance and the con- length), and particularly if the wires or denser is a lump of capacity, to put it T T T oB tubes are close together, it forms a con- crudely. But when the wavelength is very denser. The leads to a component, if run short the inductance and capacity contri- Fig. 2. -A very rough equivalent of a pair of closely parallel, have the effect of a small buted by the leads can certainly not be parallel wires. The inductance and capacity neglected, nor can they be regarded as con- are considered as concentrated in three centrated at any particular point. They separate sections. are distributed. And when you have done it, the result How much more, then, is this so when only holds good for one particular fre- still longer wires are used -for aerial and quency. earth connections, say. It can be taken If the wire is subdivided into a larger as a rule that a lead is "long," i.e., has number of imaginary sections in order to important amounts of distributed capa- get nearer to the actual thing, the calcula- city and inductance, when it is an appre- tion becomes still more perplexing. But ciable fraction of the wavelength. A wave- when the number of sections is made infi- Fig. 3. -A short length of open parallel line connected to a circuit as at (a) is equivalent length of 1,50o metres, for example, being nitely large -which is exactly what we to a condenser (b). approximately one mile, there is no need want for depicting real life -it is a rela- to worry about a few feet. But 5 metres tively simple mathematical problem, but capacity across the component (Fig. 3). is only about r6ft., so an aerial lead -in not quite simple enough to expound here. But if the line is short-circuited at the may even be several whole wavelengths. What is more important is to visualise the far end, and particularly if it is widely WAY ®Il@ §@ JANUARY 8th, 1937 33- WCHild Transmission Lines- other distances, other wavelengths can tain walks of life, because such extreme spaced, it is equivalent to an inductance. similarly be checked. selectivity is most valuable for stabilising It is, in fact, a single -turn frame aerial This otherwise delightful method is un- the frequency of ultra -short wave trans- (Fig. 4). fortunately subject to certain errors. If mitters. Quartz crystals, commonly used The closer together, the more the capa- the wires are far apart they are liable to for the purpose, become increasingly city ; the farther apart, the greater the be influenced by other objects-or bodies, difficult to apply as the wavelength is inductance. Now, wavelength is closely as the textbooks gruesomely delight to related to inductance L, multiplied by call them. None should be allowed within capacity C. You know the famous for- several line widths at least (Fig. 6). Then the simple calculation is also some- mula : wavelength = 1,885 LC. In a parallel line these two things, L and C, are what invalidated by the length of the shorting connection at the far end of the line being appreciable in comparison with the length of the line itself. On the other hand, it is essential for the wires to be very exactly parallel, and if they are close together it is difficult to make them so, because a small inadvertent displacement Fig. 6. -When the parallel wires of a is then an appreciable fraction of the total resonant line are far apart it is difficult to keep everything, including the operator and spacing. other parts of the apparatus, outside a radius There are two important characteristics of several widths. Proximity of such objects of a resonant circuit that we have not yet introduces disturbing effects on the considered in relation to a transmission wavelength. Fig. 4. -A short closed line (a) is equivalent line. There is what is generally known to an inductance (b). as the " Q " -the ratio of reactance to shortened ; whereas the reverse is true of resistance-which is a measure of the these cylindrical transmission lines. so related as to produce a result that is sharpness of resonance or the selectivity. Cylindrical " lines " have also been much simpler than one would have ex- adapted recently by the American Bureau pected. It turns out that when the resist- of Standards for receiver tuning. Using WAVELENGTHS ance and leakance are comparatively them as intervalve couplings in four 0 'Y.4 Y.2 34 1 114 1Y2 13(4 2 slight (which is what one naturally tries stages an amplification at 200 Mc /s very hard to bring about), the product LC (i4 metres) of no less than 200,000 has depends entirely on the length and not at been obtained. all on the distance apart of the wires. When the wires are placed farther apart, " Metallic Insulators " the loss in capacity exactly balances the gain in inductance, and vice versa. It is Another rather startling application is familiar, of course, that one can tune to the so-called " metallic insulator." The a given wavelength by using any one of higher the Q the higher the resistance to ACCEPTOR an infinite number of combinations of L which a circuit is equivalent at the wave- length of resonance. (and the and C that make L x C up to the right 1 lower the resistance at amount for that wavelength. It is neces- T other wave- lengths) The resistance of a suitable -wave line sary to find a combination by calculation, 5 quarter is so high it is measurement, or trial, and sometimes it is that actually superior to any ordinary sort of insulator, is quite a long job. But a transmission line and pre- ` ferred for that purpose !' " does not imply distinc- Insulating (' transmission materials account for increasingly serious from reception, is the tech- tion but just Fig. 5. -The various lengths of parallel line losses as the wavelength descends into the nical term for this sort of line) is actually equivalent to acceptor and rejector resonant far simpler, because one merely cuts off a circuits. The diagram could be extended indefinitely to show longer lines, for the length proportional to the wavelength. same conditions recur every half -wavelength. The equivalents of a rejector circuit (L and C in parallel, giving a very high re- In this respect a transmission line is sistance at the wavelength of resonance), similar to any other tuned circuit; but it is and an acceptor circuit (L and C in series, interesting to know that extraordinarily a small resistance reson- giving very at high values of Q can be reached. A good TAPPING ance) for open and closed lines of various figure for the ordinary coil- and-condenser lengths, can easily be seen from Fig. 5. combination is ioo, and 200 is excep- COPPER And it is also easy to see how to extend the A given in a on INNER TUBE tional. graph paper INSULATOR scheme to longer lines. " Frequency Control by Low Power - Factor Line Circuits " ' shows. Qs up to Direct Wavelength Measurements 52,000 ! And these are for the very shortest wavelengths, at which great diffi- can illus- This information bé further culty is experienced in minimising losses COPPER trated by an example or two. Take the in the ordinary ways. To obtain any- OUTER TUBE very first line shown. If you make an thing like this it is necessary to adopt the exaggerated wire hairpin, five feet long, concentric construction, with massive you can substitute it for a parallel tuning copper tubes of large diameter (Fig. 7). coil and condenser, and it will resonate at When one is exhorted to search for 4 x 5ft., which is 6.1 metres. In fact, this efficiency in short -wave work by keeping is the basis of a useful method of measur- within small dimensions, it is interesting ing wavelength. An oscillator is tuned to observe that the ultra -efficient circuits Fig. 7.- Section of tubular " line " of the until the " hairpin," when it is connected compare in size with naval guns so large type used for stabilising the frequency of across a few turns of the tuning coil, as to be prohibited by the Washington ultra -short wave transmitters. makes no difference to the wavelength of Treaty. This effort is worth while in cer- 2 .. Development of Transmitters for Frequen- which is the oscillator, then 6.1 metres. 1 C. W. Hansell and P. S. Carter, Journal cies above 300 Megocycles," N. E. Lindenblad. By short- circuiting the parallel wires at T.R.E., April 1936. Journal I.R.E., Sept. 1935. 3-1 JANUARY 8th, 7937 MYRA 1 Transmission Lines - to work efficiently together they must be assumption that the resistance due to high - ultra- shorts. Another advantage (for matched. A 5,00o -ohm power valve does frequency losses is small. That is to be de- fixed wavelength working) is that the line not work to best advantage when it feeds sired, not only to make theory simple, but is insulated only for the desired wave- a 5 -ohm loud speaker. To obtain proper to make practice effective. A conducts has length ; all others are short- circuited to matching a step -down transformer is earth. needed as a go- between. The same rules The other variable factor that fixes the govern the connection of an aerial to a characteristics of a line is the width or valve, or a telephone instrument to a b` spacing. It has already been explained cable. A transmission line, serving as a 500 that this is equivalent to the L/C ratio in link between two units, ought to be 0 400 PARALLEL an ordinary tuned circuit. Of the in- matched at both ends. Generally it is WIRE LINE_ numerable combinations of L and C that advantageous to construct the best and can be adopted for tuning to a given most efficient line, as.a line, regardless of 300 wavelength, the higher the ratio L/C the impedance ; and then match the terminal higher the impedance. A widely separated apparatus to it by means of transformers 200 AI .mal pair of wires corresponds to a large coil or otherwise. If the line were made to PPP tuned a 100 AIT BR.E4 .1ÑE by small capacity. It is not fit the tuned circuits and aerials at its ends, BEST FOR purely a matter of spacing ; it is obvious it would nearly always have to consist of HIGH Q that for a given separation the concentric widely separated wires. This is undesir- 01 2 3 4 5 10 20 304050 100 20 tubular type has a higher capacity than a able in several ways. It does not lend RATIO a/b pair of thin párallel wires. itself to low -loss construction. Among In transmission line calculations a other sources of loss is a high radiation Fig. 9.-Characteristic impedance of parallel - rather special quantity is used-the so- resistance. The object of using a line wire and concentric feeders of various called characteristic impedance. It is feeder for a transmitter is to avoid having dimensions. equal 4,71/ cc, the radiation from the aerial is to where l and c are the in- -which a lower ductance and capacity per unit length usually a special directional array -upset high- frequency resistance in the by the lead -in doing some aerial business form of tube than the same amount of on its own. And similarly in a receiving metal as a rod or wire. And it would be is very delightful if the metal could be sup- i station the object to prevent the lead -in from picking up interference, which it ported in air alone. The necessity for supporting 7 readily does unless the wires are close to- insulators, being unfortunate, 1 leads one to work according to the prin- gether. " i ciple "little and good." Comparatively infrequent Concentric spacers of high -class material, Feeders such as the latest ceramic products, are adopted. In fact, the best form of line is the con-. An incidental and centric. Besides likewise rather un- enabling the resistance desirable effect of these inevitable 1 1 to be kept low-because tubes are par- insu- 1/4 34 lators is that where they are situated they 1/2 ticularly good in minimising " skin LENGTH OF LINE IN WAVELENGTHS cause a local increase of capacity ; which effect" at ultra -high frequencies -it has mismatches the the very valuable line, to an extent, how- advantage that the ever, that should not be important Fig. 8.- Curves showing the equivalent outer conductor be in any of (full) can earthed and it well- constructed reactance a short-circuited or open then specimen ; and also re- (dotted) line of varying lengths. completely screens the inner " live " sults in the line being shorter wire, which is unable radiate than it to or to pick should be according to simplified up. But obviously such construction is theory. (foot, metre, etc.) . It is not the imped- This is always found to be so, to a greater ance of the line itself as might be sup- accompanied by low impedance, so some or less extent, in practice. posed, for that depends on the length, form of step -up is generally to be pre- but is the resistance of the load which it ferred to direct connection. Fig. g gives can be used to supply with maximum some idea of the impedances of both con- efficiency. centric and parallel wire lines. New Radio Factories Before explaining this important point Suppose an aerial having an impedance it would be advisable to finish consider- of goo ohms is to be connected to an Prohibited ing the behaviour of the line itself. oscillator circuit of i,600 ohms by means ARECENT Examples have so far been confined to of a parallel wire feeder with a spacing of decree issued by Berlin's Ministry of National Economy prohibits the first in Fig. 5 -the closed quarter - 20 wire diameters. The impedance, according to Fig. 9, is 36o ohms. By the opening of any new factories for the wave type. At intervals of half a wave- making of wireless sets or component parts. length the sa me rejector resonance using a feeder -to -aerial transformer with a recurs. And it goes further than this : No factory Half-way between these, and also at half - ratio of v/36o : goo, or I : 1.6, the aerial at present turning out, say, condensers may wave intervals, it becomes an acceptor. is made to look like 36o ohms to the extend its activities to include resistances, As the length is adjusted between one of feeder, and therefore matches its charac- coils or any other components outside its these critical distances and the next, the teristic impedance. This means that, own special line. Set makers may not line behaves as a capacity or inductance, apart from the slight feeder losses, things manufacture parts save those that they use covering all values from zero to infinity. work as they would if the aerial were con- in their sets ; component manufacturers are nected straight to the forbidden to market complete receivers. Fig. 8 shows how these electrical charac- oscillator without There appear to teristics are related any intervening line at all. Of course, be two underlying inten- to the length. When tions. The first is to prevent waste of raw the curves go off the to infinity another transformer, or its equivalent, paper the materials by over-production ; the second, line becomes a rejector, with very high. with a ratio of s/ i,600 : 36o, or 2.1 : I, is to make the wireless industry as much of an resistance ; when they cross the zero line needed between oscillator circuit and all-the- year-round trade as possible. The it becomes an acceptor, with very low re- feeder. decree certainly does not aim at reducing sistance. So a short -circuited line may And it is necessary to make the feeder the production of wireless sets below the sometimes play the part of an open cir- of exactly the right length, which means nation's requirements or at making them more expensive ; cuit, and vice versa. any multiple of half a the Government is far too wavelength. It conscious of the value of broadcasting Now to deal with characteristic im- is not essential for it to be physically just to do pedance. anything of that kind. One fears, though, It is well known that if two so long ; various electrical circuits can be that it may have the effect of stifling that pieces of electrical apparatus that are in arranged to adjust the equivalent length. healthy competition which is the greatest any way related as generator and load are Our whole theory has been based on the stimulant to progress and development. Wireless World, January 8th, 1937 35

EVENTS OF THE Current Topics WEEK IN BRIEF REVIEW Russian Television Paris Exhibition R.A.F. Communications Received Here THE French P.M.G. recently THE radio station at Man- arets of the local Mosque by television laid the foundation stone of chester airport has now the Muezzin. This picturesque EXPERIMENTALsignals coming from Mos- the Radio Pavilion in the great been added to the list of those Oriental figure has now, in the cow are reported to have been exhibition which is to be opened with which R.A.F. machines case of at least one Mosque, picked up by a Birmingham in Paris during the coming may communicate. Such com- given place to the loud speaker. amateur. summer. munication is, however, limited At Singapore the G.E.C. have to DF and emergency calls. just completed the installation USW Broadcasting North African Activities of loud speakers in two of the minarets of from Ameri- THE number of listeners in Ideal Home Exhibition the Masjid Sultan PROGRAMMES the in Mosque, two similar instru- can ultra -short wave broad- French possessions EASTER Tuesday will see the ments beginning N. Africa is now not far short being installed in the casting stations are opening of the 1937 Daily body of the building. to be reported in this country. of 1oo,000, and it is increasing Mail Ideal Home Exhibition at On a recent Sunday afternoon daily. French Morocco accounts Olympia. This famous annual Australian loud signals originating from for 30,00o of these, Algeria for show will remain open until S.W. Boston were heard on 7 metres. 50,000, the remainder being in April 24th. Transmissions Tunisia. The greater part of DURING January, Sydney the population of these countries VK2ME will transmit Turkish Radio An Electrical Muezzin on Reorganisation speaks Arabic, and an increas- Sundays from o600 to o800, and ing demand is making itself felt MOST people who have woo to 1600 has G.M.T., using a THE Ankara Government for a larger number of talks in dwelt in Moslem countries frequency of 9,590 kc /s (31.28 appointed a German, Dr. and also for native are familiar with the Call to the Arabic, metres). A transmission will Herzberg, to supervise music. Prayer uttered from the min- also be given on Mondays from of reorganisation broadcasting 1400 to 1600 G.M.T. Mel- throughout the country. Dr. bourne VK3ME will be heard was the Herzberg formerly from 09oo to 1200 G.M.T. daily, of the Deutsche Theatre director except Sundays, on a frequency in Berlin. of 9,510 kc /s (31.50 metres). Canadian Regional Scheme Out -of -date American Sets WHEN thinking of the aver- THE regional scheme adopted age type of wireless re- by the B.B.C. ten years ceiver used by model for listeners in the ago is to serve as a U.S.A. we are apt to be to be made critical a new arrangement of the quality of reproduction by Canada in forming control There associated with it, but we have centres for broadcasting. never supposed that any but the are to be five regions in Canada, most Ontario, Brit- up -to -date receivers were namely, Quebec, to be found in American homes. ish Columbia, the three prairie and the three mari- It Is somewhat surprising to provinces, learn, therefore, that according time provinces. to the Federal Communications Committee, which has just taken Japanese News a census of the age of receivers hundred wireless sets have used in rural areas in U.S.A., no SIXbeen presented to the light- less than twenty -five per cent. house keepers around the are of 1929 vintage or earlier. Japanese coast by the Dowager Empress in order to relieve the Horn -loaded Loud monotony of their existence. Japan has now followed the Speakers example of many other countries ON January 13th next Mr. in radiating multi -lingual broad- P. G. A. H. Voigt is giving casts. English, French, Ger- a lecture to Golders Green and man and Spanish are to be the Hendon Radio Physical Society languages used. on horn- loaded loud speakers at Regal Cinema, Golders Green, Illicit Use of Call Signs commencing 8.15 p.m. Anyone interested is invited. IT is reported that lately there has been a great increase in Institute of Wireless the undesirable habit of illegally using amateur transmitting call Technology signs. In most cases this trouble AT a special meeting held re- is due to the activities of cently, certain amendments pirates, but, unfortunately, concerning fees and subscrip- were passed, there is reason to believe that MOBILE AMPLIFYING EQUIPMENT installed in a motor -van and tions the result of in some instances genuinely supplied by Ross & Robinson, Ltd., East Acton, London, for special which will be of great benefit licensed transmitters, with a public address use. Rack -type assembly is employed with battery to the younger members of the kink for practical joking, are chargers in the base and above them three 14 -watt G.E.C. amplifiers. industry wishing to become stu- concerned. In most cases these They can be used singly or collectively. Two gramophone turntables dent members or associates of represent them- are included, also two DC -to -AC converters, which can be seen mounted the Institute. Full details con- call -sign pirates on the top and adjacent to the units of the three large loud speakers. selves to be transmitters situ- cerning the Institute may be These have a range of seven miles. The equipment is so arranged from Secretary ated in Persia or some other that in the event of any single unit failing it can immediately be obtained the at out - of - the - wáy part of the removed from the circuit by switches without affecting the operation 4, Vernon Place, Southampton world. of the remainder of the equipment. Row, London, W.C.r. Wir®II®og y oplica 'JANUARY 8th, 1937 UNBIASED, ,, / Wireless on the Stage ISUPPOSE that most of you have, at some time or another, suffered at the hands of the various automatic cigarette lighters which infest the market. I do not refer to the all -mains variety which are emanate from her throat and that of the sold for use at, home, but to the type hero. intended to be carried in the pocket. It was not until the next act, when the Usually either the petrol runs out at an same thing occurred, that I began to Mrs. Free Grid's " At Home." awkward moment or else the flint arrange- connect the effect with my cigarette ment which ignites it goes on strike -or, lighter. In this instance the interfering I happened to be paying a visit recently rather, refuses to do so. noise was much greater, since all the to a well -known Harley Street ear Many laudable attempts have been players seemed to be giving tongue to it. specialist in order to obtain his made to produce an all- electric one in A few further experiments confirmed me advice in the matter of a sprained which a wire is made red hot by the pas- in the view that my lighter was the cause ear drum from which I was suf- sage of a current from a battery in the of the trouble, but I entirely failed to see fering as a result of foolishly consenting same manner as those which run from the the reason for it. The lighter was ob- to be present at one of Mrs. Free Grid's mains. Unfortunately the current taken viously a transmitter-of limited range, of " At Homes," when she was entertaining is so heavy that the battery soon wilts, course -but how on earth it could affect a few of her lady friends. After giving me and the device is really no better than the the vocal chords of the actors I failed to the necessary advice, the specialist de- petrol variety. I have of late been see, until I confided the whole story to a cided that, owing to my fed -up appear- devoting myself to the solution of this stage -door acquaintance at the supper ance, I was probably suffering from problem, and I flatter myself that I have table that night. gastric trouble also, and very kindly succeeded and am hoping to get some The explanation proved astonishingly offered to conduct me in person to a fellow manufacturer to take up my idea commer- simple. It appeared that some time ago fee-snatcher down the street, who spe- cially. Needless to say, I have made up a well -known actor suddenly forgot his cialised in disorders of the alimentary a model for myself, and its action is very, lines in the middle of an important play tract. very simple. It consists merely of a and was not able to proceed even with Having arrived there, I was amazed at miniature induction coil operated from a the help of the prompter, and had the the number of dyspeptics of woebegone flash lamp battery through the usual mortification of being compelled to read aspect whom I encountered in the waiting make and break arrangement. The spark his part from a script. This lapse of room, for, although I was fully aware that at the secondary is ample for lighting memory proved to be the result of shock digestive troubles had increased enor- cigarettes, and the current taken from the following a recent motor accident. The mously of late owing to the ever -increasing battery is far smaller than by the hot theatrical world was so upset by this tempo of eating caused by the presence wire method. contretemps that all actors and actresses of jazz orchestras in our restaurants, I had been fitted with micro -wave receivers did not think that the number of victims suitably disposed about their persons, the of these synthetically produced alimentary loud speaker being concealed in their irregularities was as great as I :found it headdress or just below the collar, to be. I was so impressed that when at according to the part they were playing. length I obtained admittance to the Each receiver was tuned to a slightly presence of the great man himself I could different wave -length corresponding to the not refrain from commenting upon it. various transmitters in the wings, where I was greatly surprised when he sat both male and female prompters, who blamed it all on to the effect of wireless, actually read the words from the script. but my surprise turned to disgust when The performers kept up the illusion that he expressed the view that my sympathy they were doing the talking by moving was wasted upon these unfortunates. their lips in sympathy with the words Needless to say, I demanded to know in coming from the loud speakers. To mem- what way wireless caused digestive (rou- bers of the audience the illusion was, in bles, apart, of course, from the very " Confided the whole story to a stage -door fact, far better than in the cinema, where obvious one of listening to some of the acquaintance." the voices of the various characters on the B.B.C. programmes which are frequently screen appear to emanate from their lips apt to produce feelings of nausea. As- Now it so happened that a few days although everybody knows full well that tonishment is scarcely the word to express after the completion of my invention I they come from one loud speaker com- my feelings when he trotted forth the old paid a visit to the theatre with a young mon to all. My lighter, being nothing story about wireless waves affecting lady from the country, as I had promised more nor less than a small flatly tuned people's health. I protested that this old her mother, an old friend of mine, to keep ultra -short-wave transmitter, naturally bogy had been exploded long ago, and a watchful eye on her daughter during her upset the apple -cart. that one would have to descend to wave- visit to London. During the course of an lengths far below the most ultra of ultra - impassioned appeal of the hero to his lady shorts before any physiological effect was love, in the middle of the first act, I drew Murder Will Out observed. out my cigarette case and, after handing THERE is an old saying accredited to He pointed out that to a certain extent it to my young friend, I offered her my Dr. Johnson or George Robey -I this was true, but that it had been found lighter. We were rather surprised to hear forget which-to the effect that our edu- that even ordinary broadcasting wave- the sweet voice of the heroine, who had cation is never completed, and I must say lengths could have a detrimental effect on just commenced a speech, drowned out by that I have found more truth in it than is the alimentary tract provided that the a raucous roaring which appeared to usually associated with these wisecracks. field strength was intense enough, and NVflwigllsm JANUARY 8th, 1937 37 7"InOO pIlcl Unbiased- Official Radio Service Handibook. By J. T. between the grid and anode circuits of a that it was for the purpose of protecting Bernsley. Published by Gernsback screen -grid valve is impossible must not be the public from this effect that the Publications, Inc., 99, Hudson Street, taken literally. B.B.C. had built all its Regional stations New York, N.Y. Pp. i,008. Price $4. While these points somewhat mar the THE first half of this book deals with book, judged as a whole it contains much well from of away large centres popula- servicing methods and types of circuits, of merit, and the whole field of modern re- tion, and not for the reasons usually while the second gives valuable information ceiving. equipment is well surveyed. given. I naturally pointed out that if this concerning American receivers. The book Although written from the American point were really the case, the station engineers, opens with a consideration of the basic of view, the general sections are naturally spending long periods, as they did, within circuits which in one form or another are applicable also to British apparatus. The a few feet of the transmitting apparatus, employed in every receiver. The treatment second half of the book, however, is of would have suffered severely. is very elementary, however, and by no major interest only to those handling He surprised me still further by telling means free from errors. It is, for instance, American sets, and to them it should prove me that even this had been thought of by stated on page 24 that "triodes have an very valuable indeed. It contains a vast capacity quantity of information, including inter- all -wise who had internal plate to filament which the B.B.C., suitably does not exist in multi-grid tubes, and mediate frequencies and component values, protected their engineers from such a which would serve to resonate any large in- of a large number of receivers. metallic screening. calamity by means of ductance in the plate circuit to a particular The book is well printed and bound ; the To effect this, my friend explained, all the frequency." A screen -grid valve may not circuit diagrams are rather small for legi- engineers had been compelled to wear have an appreciable direct anode -cathode bility, however, and this is accentuated by pants and vests made of steel wool in capacity, but it most certainly has an out- the rather peculiar valve symbols adopted. place of the ordinary sheep's variety. It put capacity at least as great as that of a These are intended to show the base pin con- was due to the same cause, explained the triode. Whatever valve may be used, the nections as well as the symbol, but, unfor- specialist, that no lady engineers were to inter -electrode capacities are important. tunately, the result is sometimes almost im- possible to unravel. W. T. be found on the B.B.C. engineering staff. Similarly, the later statement that reaction C. It appears that they absolutely refused to replace their pants and vests -or what- ever it is that women wear in place of these garments -by ones made of steel wool. With regard to the vast crowd of NEW OSRAM VALVES sufferers whom I met in the waiting room, HE majority of AC indirectly heated heptode, the X42, and this again requires their troubles were due, I learned, not to valves consume 4 watts in the -3 volts grid bias and has a conversion con- their living too near a wireless station, but T heater, but in the new Osram range ductance of 0.49 mA /V. Owing to the short to the fact that in the early years of broad- most specimens consume only 2.4 watts.. The electrode assembly adopted, satisfactory casting they had been persistent oscil- standard 4 -volt rating is adhered to, but the operation is claimed on wavelengths as low lators, and were now hoist with their own heater current has been reduced from r as 15 metres. petard, and were therefore not deserving ampere to o.6 ampere. In addition, it is The H42 is a triode of the high amplifica- be made much tion factor type. Its AC resistance is of any sympathy. The intensity of the claimed that the series can 66,000 than has ohms, and the mutual conductance is 1.7 within a few feet of an more uniform in characteristics etheric radiations older types. In general, mA / v, so that the amplification factor is 112. valve in a state of been possible with ordinary receiving fairly wide tolerances in characteristics have At -2 volt grid potential the mutual conduct- oscillation is, as he rightly pointed out to to be permitted, but improved manufactur- ance is 1.5 mA /V. and with a coupling me, far greater than that due to the ing methods have allowed them to be con- resistance of 0.25 megohm a stage gain of radiations of a broadcasting station even siderably tightened in these new valves. over 5o times can be secured with sufficient at a spot only a few miles away. This is quite important in practice because it permits the set designer to obtain a more consistent performance A Range BOOKS RECEIVED from his products. If the for in- Two Hundred Metres and Down, by Clinton normal tolerance, - of AC Types B. De Soto, pp. 184. Published by the stance, is ± 20 per cent., American Radio Relay League Inc., on mutual conductance, the West Hartford, Connecticut, U.S.A. designer has to arrange for Price T dollar. his set to be capable of giv- the many amateurs who to -day enjoy ing adequate amplification OFthe facilities afforded for private experi- with valves zo per cent. mental radio transmission, few can be fully below standard and at the cognisant of the difficulties the early ama- same time for it still to be teur pioneers had to surmount, nor of the stable with valves zo per many signal achievements performed by cent. above standard. The amateurs in the face of discouragement by importance of more uniform the radio engineers in the past. valves is thus greater than These and many other matters of particu- might at first appear, and lar interest to the present-day amateur and, should be a great help to in particular, to the beginner, form the sub- the designer of broadcast receivers. undistorted output to load a PX4 type valve. ject matter of Two Hundred Metres and With the exception of the output pentode, A duo -diode -triode, the DH42, is also Down. the new valves all have top -grid connectors, available, and the triode section has charac- It is the story of amateur radio, and even in the case of the triode. This leads teristics very similar to those of the H42, though it deals with the subject from the to a reduction in the inter -electrode capa- but a somewhat lower mutual conductance. American amateur's point of view, it is cities and may, in certain circuits, reduce The remaining valve is the N4z output wide enough in its scope to take in account, mains hum. pentode. In this valve the heater consumes and make due acknowledgment to, the valu- The first valve of the series is the W42 a rather greater current, r ampere, but is able contributions in the short-wave fields variable -mu RF pentode. Under normal still low for a pentode. With 25o volts ap- made by private experimenters elsewhere. operating conditions it takes '.6 mA. anode plied to screen and anode, the grid bias The difficulties that have beset the ama- and 1.9 mA. screen currents, with 25o, Too should be -16.5 volts and the screen and teur in the past are by no means over, so and -3 volts for the anode, screen, and grid anode currents are 5.5 mA. and 34 mA. res- that an appreciation of the manner in which respectively. The mutual- conductance is pectively. The output into the optimum they were approached as and when they 1.5 mA/ V., but although this seems low it load of 7,000 ohms is 3 watts for 7 per cent. arose should prove invaluable were the ama- must be borne in mind that it is the figure distortion. Using two valves in Class teur movement to find itself faced with simi- effective under normal operating conditions. " AB," however, 5.5 watts output can be lar problems in the future. H. B. D. The frequency- changer in this range is a secured for 4 per cent. distortion. 38 Wireless World, January 861, 1937

Random Radiations By Viewers' Views Wanted valve containing two control grids, one with "DIALLIST " IWAS interested to hear the B.B.C.'s a high magnification factor and the other with a low. By means of suitable circuits recent request to owners of television 0 sets and to viewers in public demonstration the output of the second detector is divided, rooms to write in to say how they liked the the upper and middle audio frequencies " true readings." From stations known to programmes. The B.B.C., I'm sure, wants being passed to the low -mu grid and the be good wavelength keepers (British, to make a success of the transmission, low frequencies to that with the high mu. German and Swedish stations are very A makes it possible to though it is working under considerable diffi- potentiometer reliable) it is now easy to plot a curve of culties. There's not a great deal of money regulate the proportion of either part of dial readings against true readings, and available, and some artists, at any rate, the output that is applied to these grids. from this you can read off the real wave- should receive more for a The first AF valve acts both as an length or frequency, whatever untruths the think that they re- of the televised turn than for one broadcast from amplifier and as a combiner pointer may be telling. Similar curves are ` separated frequencies. With the tone- ' sound studio. Then it's something plotted for the long waves and the short the " in normal position of a to have two different methods control potentiometer its waves. handicap is to the of which demands its there a marked bass " lift " owing of transmission, each low is a greater amplification given to the audio own special studio technique. That frequencies. If desired this can be further Winged Words matter which seems likely to right itself, accentuated by reducing the upper and for it is suggested that in the near future JUDGE LILLEY had some caustic remarks middle audio-frequency input. Similarly, to make about certain hire -purchase the alternations may be monthly or at even down reducing the longer responsible for the the bass can be toned by agreements the other day when dealing with intervals, those to the high-mu grid. It's an ingenious is in use any time input various little bits of bother that had arisen system which not at devo- system which seems to have possibilities. ting their energies to research and develop- from them. In one case a man was not ment. Not a bad idea that, though I think satisfied with a set bought on hire -purchase that the suggestion made in these notes and took it back to the dealer, who ex- some weeks ago that one plant should be For Easy Tuning changed it. The manufacturers contended moved bodily to Birmingham is better still. II, your set has a scale of metres or kilo- that the dealer had no authority to do so cycles the odds are that it won't be very and sued the purchaser for a sum of money. % % % accurate- unless, of course, you calibrated The judge told the defendant that he had Damage in Transit it yourself by hand. Sometimes, indeed, not a leg to stand on as a clause in the agreement stated that the dealer was not the AGOOD many radio sets are sent down these scales are so inaccurate that the identification of stations is made a difficult maker's agent. He described it as " an for testing purposes each year to my absolutely iniquitous state of affairs," and home in the country, and the proportion matter. Here is a simple way of obtaining accurate readings-as accurate, at all events, I feel that he was entirely justified in so which won't work when unpacked and con -. as the size of the scale and the fineness or doing, for, clause or no clause, the man who nected up is quite remarkable. I presume sells the set, installs it and services it is that all are in working order when they otherwise of the pointer will permit -which I have found so useful that I pass it on for definitely and understandably regarded by are despatched and that the damage occurs the public as the agent of the manufacturers. en route. The packing is pretty good, and the benefit of readers. Obtain a piece of graph paper and mark it off, if yours is a It is only natural that this should be so, I don't often find that a carton shows signs since many set makers will not accept a of having been ill- treated on its journey. wavelength scale, from zoo metres at the left to 55o at the right along the bottom returned set unless it comes through the Yet here's the kind of thing that happens. dealer. And, as a rule, all complaints from An expensive set was received some ten days edge. Mark off the left -hand edge in exactly the same way from zoo metres at purchasers are referred by them to the dealer before Christmas. When plugged into the who sold the set. lighting mains and switched on it refused the bottom to 55o at the top. Thus the to do anything but howl. Clearly a break- zoo -metre point is common to both sets of markings. A kilocycle scale will run from Something Must Be Done About It down in a decoupling circuit ; after a long search a lead was found adrift and re- 1,50o to 500, 1,500 being the common point Judge Lilley did not remain content with soldered. The set then worked well for á at the left-hand bottom corner. Label the the mere utterance of winged words. He few hours, after which it gave out once bottom scale " dial readings " and the other translated them into action by making an more. This time a " dis " in the output order for payment at the rate of a few pence circuit was diagnosed, and examination dis- a month, which means that the plaintiffs closed another broken joint. will have recovered in full by about 1967. The whole question of radio hire -purchase undoubtedly needs straightening out. Manu- Faulty Soldering facturers, I know, don't want to saddle the Both of the connections that caused dealer with too heavy a burden of re- trouble were badly made, one of them being sponsibility. Still, everyone must feel that a typical " dry joint." It seems to me that they go a little too far in that direction when in factories more care is required in solder- they make out that he is not their agent. ing or in testing joints after they have been A vast proportion of the public now buys made. Most amateur constructors make a its wireless sets on hire -purchase. Those practice of testing their joints by giving who do so are the least able to withstand each lead a pull after the solder has set. financial and other knocks, and it is only Though it isn't infallible, this method does just that the whole position should be made usually show up a dry joint. But prevention completely fair to both buyer and seller. is better than cure, and the one certain way of ensuring against dry or otherwise faulty % % % soldered joints is to see that the surfaces Talks from Tokio over which the solder is to flow are per- THE Japanese Broadcasting Association fectly clean. If they aren't, a rickety junc- has, I see, just started a series of special tion is almost inevitable. broadcasts in a good many European languages, including English. One has picked up transmissions in English before Ingenious Tone Control now from Japanese short -wave stations, but recently come LECTURES ON TELEVISION are a regular new programmes from Tokio are to IN an American set I have feature in the programme provided for their these across a system of tone control which members by the International Short -Wave be on much more ambitious lines. The is new to me and may be also to many Club (London Chapter) who hold meetings at owner of a short-wave or " all -Nave " readers. The basis of the system is the use 8o Theobald's Road, London, W.C.i, every receiver can't complain nowadays tha t there as first AF amplifier of a multi -electrode Friday evening at 8 p.m. isn't much to be heard in English ! Most JANUARY 8th, 1937 WApK@To 39 %WpIld European countries with short -wave stations hard to work this out (I've one or two 28 and 56 Mc /s apparently did not meet have regular English transmissions. In shadowy schemes in my head already) and with favour ; perhaps it might have met addition. to the United States, Kenya, India if it could be done it would add greatly to with a better response if The 14 Mc / s band and Australia, you can find news and talks one's pleasure in using the short -wave range. had been added to those to be retained with coming in our own language from countries higher power ? in many parts of the world. There's no Another Silencer One would hate to feel that the height of the British amateur's ambition is to ex- need, therefore, to be a linguist to derive Talking of nasty noise elimination reminds waves change Sunday afternoon pleasantries on entertainment from the short - me that some genius in the States has Mc / s (Oh, Boy, the QRM !) and to collect though I have heard talks in alleged English a silencer, or rather a quietener 7 brought out WAC with a signal that could just be that were more difficult to follow than they for the too-loud loud speaker. Details are to copied ! would have been had the speakers kept not disclosed, but it is said to work like a their own tongues ! the intention My sympathies are with those who are charm. I gather that prime building diamond arrays and roo -watt is that it shall be used voluntarily by those from neigh- 56 Mc / s crystal-controlled transmitters in A Short -wave Idea who receive complaints their an endeavour to span the Atlantic once ON the tuning dial of any set that takes bours that they are overdoing it a bit in the con- again. in a range of short waves there are large decibel line. But it is said to be a tiny some, many, in hand, and There are, of course, or who areas which the seeker after broadcasting traption, easily concealed the will not agree, but that, perhaps, remains blank so far as speech and music are there is something more than a hint that the draws unobserved to be seen. concerned, since they are given over to ship victim may be able to slip it Turning now to reception conditions stations. Unfortunately, into the receiving set of his noise -loving and commercial addicts during the past fortnight, we find that the they are far from blank in the matter of neighbour. I know quite a few din late evening results have, in general, been loud and nasty noises -and you generally whose loud speakers I would willingly poor, frequen- feel very although the daylight seem to strike the most ear -piercing morse " spike " in this way could I but that cies have generally been good. when the manual volume control is the cure would be permanent. It seems to signals the listener The outstanding signal on Thursday even- as full on as it will go. If any manufacturer me, though, that the first act of ing, December 17th, was W2XAD at 6.3o wants a neat and attractive idea to work whose loud speaker's voice had been reduced p.m., with W3XAL inaudible (possibly not cooing of a sucking out here is one for him with my blessing. from a lion's roar to the working), and W2XAF fair at 9 p.m. consists in devising a tuning dial that will dove would be to take a look inside the set The Siamese transmitter Bangkok on It enough himself, to automatically silence the set, or very nearly -or, if he wasn't expert 19 Mc /s was, however, fairly good during whenever a portion of the band is send for the service man. In either event so, and the afternoon. reached which is untenanted by broadcast- the silencer would soon be discovered Sunday afternoon 'provided excellent re- would be short- lived. ing stations or amateurs. It shouldn't be peace ception of many of the U.S. " apex " high - fidelity stations on 30 -40 Mc /s. Among the outstanding stations was W3XES, a Colum- bia System Transmitter probably relaying WCAV on the very high frequency of On the Short Waves 4o Mc /s (approx.), and reception was spoilt, however, by interference from of reports of recep- 470v. 40 mA gives 14o RF peak volts out a police IRECEIVE a number transmitter WIXAO, Boston, Mass. tion of my 3o -watt ro -metre phone on 28 -29 Mc /s, providing adequate drive for from the U.S.A. and the final choke -controlled amplifier, a Conditions were good on Sunday evening transmitter G5- (December 2oth), too, and at 5 p.m. both elsewhere when working on 28.26 or 29.16 DET5. been more interesting On the other side of the balance sheet, W3XAL and W2XAD were very good ; Mc /s-but none has W2XAD was still very good at 6.3o p.m. than a recent note from my friend G2MV one is very sorry to report a very poor re- regarding the " anomalous " reception of it sponse to my request for correspondence on By II p.m. only the 6 Mc /s stations re- on the borders of Surrey and the subject of the amateur bands. mained, the outstanding signal being in Westerham, who Kent. My transmitter is situated not far My suggestion that the 14-7 -3.5 and WIXAL, Boston, on 6.04 Mc /s, was be exchanged roo per cent. intelligible, in spite from Clapham Common, and normally, when 1.7 Mc /s bands might possibly practically in operation in the late evening, gives a weak for the right to use powers up to r kW on of heavy QRM from S. American trans- and steady signal in Westerham, about R2 / 3 mitters. on the " R " of an RME69 receiver, but Conditions remained fair during the clearly audible. Christmas week, but, as usual, W2XAD, the During the daytime, however, and in par- best signal, showed signs of failing before ticular during the afternoon of Boxing Day, close -down at 8.45 p.m. the signal from G5- reaches much higher I did not do much listening on Christmas levels, and even surpasses G5BY of Croydon Day, but noted that WzXE was good on Mc (250 watts ?) in field strength at Westerham. 21.52 /s during the afternoon. (Croydon is also much nearer to Wester- On Boxing Day the outstanding feature ham.) was the performance of the ro-metre (28 It is also reported by GzMV that a very Mc /s) U.S. amateurs, some of them remain- interesting phenomenon is also observed in ing good signals until 7.30 p.m. ; and on the case of the 56 Mc /s (5 metres) harmonics December 27th, not only were conditions of certain London amateurs, which only be- on 28 Mc /s good to the U.S., but also to come strongly audible round about ro a.m. Europe, in particular the Latvian station and 4 p.m. at his location. (YL2BB), working G5AU, was a good signal This variability in signal strength of the during.the morning. various ultra -high frequency transmissions The outstanding 28 Mc /s signal, however, is probably not confined to amateur trans- was W9BHT using Boo watts and diamond missions, but can also probably be observed antenna directional on England, surpassing on the television transmissions from Alex- easily WzXE on 21 Mc /s. Strangely andra Palace, though in this case it may enough, as if to complete a day of queer probably be masked by the higher power conditions, W8XK appeared on 15.21 Mc /s which is in use. This fading is probably at II.20 p.m., and remained quite a fair due to changes in the ionisation of the signal for some time. newly discovered C and D layers in the lower Conditions were very poor again on Mon- atmosphere, which were mentioned in these A RADIO GLOBE. This 9 -inch globe is day, December 28th, but appear to be im- notes some months ago. designed to meet the needs of short -wave proving again at the time of writing ; and, Whilst on this subject I should like to listeners. The rotatable discs on the base at 11.55 p.m. PMN Bandoeng on 10.26 Mc /s if the Editor will permit me, that show standard time zones corresponding to is coming through exceedingly well on the remark, hour of the listener's local time, while my ro -metre phone transmitter must be any loud speaker, as it does most nights and the outer disc includes lists of stations in The signal is very stable and very nearly unique in this country, in that each zone. A curved rule for measuring afternoons. all its eleven valves are of British make and Great Circle distances in either nautical or of high quality, but at present is suffering a Russian design ! In fact, I am very proud of the land miles is also provided. The globe is of slight morse interference from DN 41 final doublet, which for an input of American origin. station. ETHACOMBER. Wireless World, January 8th, 1937 Listeners' Guide for the productions, which will be pro- duced by John Watt and Francis Bolton on Wednesday at 7 (Nat.). Should this prove a success it will be the forerunner of a number of such programmes. m rla ICE -HOCKEY IT needs a super- commenta- tor to give a running com- mentary on an ice -hockey match. We all remember Bob Bowman's animated efforts. Now he has gone to Canada as ` ' 0.B." director for Canadian broadcasting, in his place we shall hear David Miller from Harringay Stadium on Thurs- day at 9.3o (Reg.). He will describe part of the match between Harringay and the ACH Friday evening for STOCKHOLM'S SKYLINE- showing the Town Hall (left -centre) and Resident Canadians. the next six weeks the spire of the Riddarm Church (right- centre). Sweden provides the m m m twenty minutes of European concert on Tuesday, which will be relayed by many Conti- the nental stations and the London Regional. OSCAR WILDE programme time will "LADY WINDERMERE'S be taken up with what is called FAN," the melodramatic play " European Exchange." day at 4 (Nat.). When it is subject was the Pioneer Health Each realised that in 1929 the Race- Centre at Peckham. by Oscar Wilde, will be broad- programme will consist of an course Betting Control Board A pamphlet cast for National listeners on interview in a B.B.C. studio containing de- estimated the probable annual tails of the to Sunday at 9.5. Val Gielgud with a member of some talks be broad- trade turnover of betting to be about cast during has secured a strong cast, or profession in this the first three country 230,000,000, this series of months-of this which includes Lydia Sher- and, immediately following, year can be ob- a talks should be enlightening tained free wood as Lady Windermere, map or woman in on application to a similar and controversial. the B.B.C. Publishing Austin Trevor as Lord Darling- trade or profession in one of six Depart- ment, 35, High ton, Ronald Simpson as Lord countries will be interviewed in At the present time there is Street, Maryle- great diversity of opinion on bone, London, W.I. Windermere, 'and Carol Good - a foreign studio by Moray m ner as Mrs. Erlynne. McLaren, Assistant Director of the subject of the Church and Features and Drama. Mr. its position in the world, and EUROPEAN CONCERT McLaren will spend a week in on Tuesdays from January IT is now Sweden's turn to each of the following cities 12th to February 16th at 9.20 provide the next European making the necessary arrange- (Nat.) well-known and authori- concert. This will be heard ments -Paris, Rome, Vienna, tative speakers will give talks at 8 (Reg.) on Tuesday. The Warsaw, Berlin, and The under the general heading of Swedish Broadcasting Orches- Hague. In the details of these " Church, Community and tra will be conducted by Nils broadcasts the B.B.C. are care- State." This week's speaker Grevillius, and the soloist will ful to state that they will be will be Sir Walter Moberly, be Joel Berglund, baritone. non - political and uncontro- and his subject " The Present versial -just a straightforward State of the World." FROM THE CHORUS presentation of types here and Topicality being the keynote THE B.B.C. Talent Scout, abroad. This week's pro- of the new series of talks -cum- Francis Bolton, has put for- gramme will be given to -night discussions which will be held ward the argument that most at 9.20 (Nat.), when Moray each Monday evening in the stage and film stars graduate McLaren interviews somebody National programme until from the chorus, and he has, in Paris. March 15th no details will be therefore, changed his policy m m available in advance. The of search, and is now con- BROADCAST TALKS theme, however, will be the centrating on this idea. He MANY interesting series of social experiments taking place has asked theatres if they have talks are included in the in this country at the present any outstanding and promising synopses for the first quarter time. Howard Marshall will, youngsters in the front row. of this year. Some are con- on each occasion, be in the Some of these will be heard in tinuances of series already studio, and will ask the various " The Front Row," a pro- running, others started . last people taking part in the talk gramme featuring girls from week, while some commence -there may be as many as six the choruses of current London this week. at a time - questions about John Hilton, who gives their work and its relative another of his fortnightly talks importance to the ordinary G.B.S. as caricatured by Max entitled This Way Out " on person. The series started last Beerbohm. His light- hearted " historic play, " The Man of Des- Thursday at 6.2o (Nat.), opens week, when, under the title of tiny," will be produced twice a series on gambling, on Sun- " It's Happening Now," the this week by Barbara Burnham. Wireless World, January 8th, 1937 41

Outstanding Broadcasts HIGHLIGHTS OF THE WEEK FRIDAY, JANUARY 8th. Nat., 730, Symphony Concert. at Home and Abroad 9.20, European Exchange - \Week France. 10, B.B.C. Theatre Orchestra and Peter Dawson. SADLER'S WELLS Princess of Kensington," by since 1922, when the work to Reg., 6, " A Princess of Ken- THE second act of Mozart's Basil Wood and Edward Ger- be heard to- night, " Don Gill sington " -Comic Opera. 9, Recital, Pierre Fournier ('cello) "` The Marriage of Figaro," of man. This will be broadcast the Green Stockings," was and John Wills (piano). which has its scene set in the from 6 to 7 (Reg.). Section C performed in Rome. Abroad. Countess' boudoir in the (forty players) of the B.B.C. Saturday's only real opera Warsaw, 7.15, " The Tales of Count's castle near Seville, will Orchestra with Section B broadcast is Mulè's " Dafni " Hoffman " -Offenbach. be heard in a relay from (twenty -eight voices) of the from Rome at 8. Mulè is a SATURDAY, JANUARY 9th. Sadler's Wells on Saturday at B.B.C. Chorus will support contemporary composer, born Nat., 6 45, Metropolitan Police 8.55 (Reg.). As is customary, Elena Danieli (soprano) and in 1885. He has written Band. 9.20, Music Hall. this will be preceded by a five - Reg., 4, The Fol de Rols. 730, The Jan van der Gucht (tenor), the several operas, and also inci- Alfredo Campali Trio. 8.55, minute introductory talk. soloists. Joseph Lewis will dental music to the Greek Act II of " The Marriage of m m m himself conduct the orchestra. tragedies performed at Syra- Figaro," from Sadler's Wells. SHAVIAN -? o cuse. Sunday's performance of Abroad. Radio Paris, 8.45, Concert of the BERNARD SHAW wrote " The A LONG CONTRACT " Rigoletto ' at the State Société Nationale de Musique. Man of Destiny " in 1895, and ONE of the most popular of Theatre, Weimar, to be relayed SUNDAY, JANUARY first 10th. this was performed two light orchestral programmes by Leipzig at 7, should be Nat., 630, Victorian Melodies -X1. years later at 7.55, Service from St. Martin- Croydon and has in-the -Fields. 9.5, " Lady twice been broad- Windermere's Fan " (Wilde). Reg. 5, Enfield Central Band and cast. It will again Alleyne and Leonhardt (two be heard on Mon- pianos). 6, Shanties ; B.B.C. day and Tuesday Men's Chorus. 9.5, Hastings of this week at Municipal Orchestra and Jan van der Gucht. 8.3o (Reg.) a n d Abroad. 9.4o (Nat.) re- Leipzig, 7, Verdi's " Rigoletto," spectively. It pro- from Weimar. vides an enter- MONDAY, JANUARY 11th. Nat., 6.40, B.B.C. Empire Or- chestra. ¶Entertainment Parade SPEED AND EX- No. 8. 8, Social Experiments -2. CITEMENT charac- 8.30, B.B.C. Dance Orchestra. terise commentaries Reg., 6, Reginald King and his on ice hockey Orchestra. ¶B.B.C. Orchestra (C) matches. We shall and Frank Manchester (piano). be taken over to 8.30, " The Man of Destiny " Harringay Stadium (Shaw). on Thursday to hear Abroad. an account of part of Hamburg, 930, A relay of part of the match between entertainment evening from the Harringay and the British Seamen's Mission, Ham- Resident Canadians. burg. TUESDAY, JANUARY 12th. taiñing glimpse of that extra- each week is that given by worth tuning in. For the Nat., 7.50, Songs You Might Never ordinary person who w a s Van Phillips and his two or- afternoon there is a concert Have Heard -2. Wan Phillips later to become Emperor of chestras, in which he alter- version of Strauss' " Fleder- and his two Orchestras. 9.40, a nates old and new numbers maus " from " The Man of Destiny." France while he was still Kalundborg at Reg., 6, Cambridge Heath Salva- young man, and though a played by a small orchestra 2.25. tion Army Band. 8, Swedish General, still obscure. The time and a full band. He has just The late -night concert from European Concert from Stock- is two days after the battle of received another contract for Frankfurt and Stuttgart on holm. 9.20, B.B.C. Theatre a further period of Orchestra. Lodi, and Napoleon is lodged thirteen Monday at I1 includes arias Abroad. at an inn on the road to Milan. consecutive weekly broad- from " The Flying Dutch- Leipzig, 5-7, German Folk Songs Listeners in general, apart casts, which now brings his man," " The Mastersingers," and Dances. from the large number who contract to twenty-six succes- and " The Valkyrie " by that WEDNESDAY. JANUARY 13th. are undoubtedly convinced sive programmes. I think this fine bass - baritone Wagner Nat., 7, " The Front Row "- Shavian admirers already, will is the longest contract ever singer, Rudolf Bockelmann. artistes from the chorus. 7.45, Bach Concert. be well advised not to miss given by the B.B.C. to an out- Verdi's "` A Masked Ball " side orchestra. Reg., 7.30, Talk-The Cavalcade what happens to be a play He will be will be heard from Milan on of the Thermometer. 9, Recital, which might well have been heard this week on Tuesday at Sunday and from Rome on Geza de Kresz (violin) and Nora written specially for the micro- 8.3o (Nat.). Tuesday. On both occasions Drewett (piano). A cast the transmission commences Abroad. phone. distinguished Strasbourg, 8.30, Fifth subscription will be in the production, OPERA AND OPERETTA at 8. concert from Palais des Fêtes. is Of m which in the hands Bar- FROM Rome to - night THURSDAY, JANUARY 14th. bara Burnham. (Friday) at 7.4o comes the BRITISH SEAMEN Nat., 7.40, The White Coons. m work of a most interesting con- A PROGRAMME Of special 9.20, B.B.C. Theatre Orchestra. COMIC OPERA temporary composer, Ezio interest to English listeners Reg. 6.20, the Victor Olof Sextet. TO-NIGHT we are to hear Carabella, who has distin- will be radiated by Hamburg 9, Al Collins and his Dance Joseph Lewis's concert ver- Orchestra. 9.30, Ice Hockey guished himself mainly as the from 9.3o -10.15 on Monday. commentary. sion of the comic opera, " A composer of symphonic works It will consist of part of an Abroad. performed at the Augusteo evening's entertainment from Cologne, 7.10, Festival Concert Details of the week's concerts. His success in a the British Seamen's Mission celebrating the tenth anniversary Television programmes of the forming of the Cologne will be found on p. 43. genre relatively new to Italian in Hamburg. Radio Orchestra. composers has been assured THE A UDITOR. --- --I Wireless World, January 8th, 1937 42 Fíndín2 the Ultra -Short

F. MAINPRISE Band By B. W. rotated to show beforehand any " blind - GUIDANCE IN or who live at a spots " due to resonances in the chokes transmitting stations in the wiring. If these are present, the dial distance from THE 5 -METRE readings must be noted. The wire on its experience difficulty in FXPERIMENTERSusually supporting batten is now brought up close - high - frequency finding ultra REGION coil in close cases it is not easy to so that the coupling is signals, and in many coil, and an unfamiliar receiver proximity to the receiver tuning determine whether L its earthed end. The required frequency. The preferably near even tunes to the is and the are the sound tuning condenser again rotated, chief signals to be expected out of television stations, in the 58 Mc/s, it will tend to pull the receiver receiver will be found to be pulled channels of the over several degrees megacycles, and the amateur out of oscillation. Coupling can be effected oscillation, probably region of 40 The coupling coil is now experimental transmissions between 56 in several ways, but in our case the on the dial. simplest and most convenient is to employ gradually removed until its effect is barely and 6o megacycles. and the dial reading noted. The professional method of determining a small coupling coil in the centre of the perceptible, close to the The wire is resonating on some frequency frequency (or wavelength) is to couple _a wire, and to bring this coil z is probably a little below the 56 transmitter to a Lecher Wire system, and oscillating receiver. Reference to Fig. which will show the distribution of current and Mc /s end of the band, owing to the load- it now voltage in an excited k -wave aerial, and it ing effect of the coupling coil, and will be seen that the current has a point of remains to fix the band with greater maximum valué, or anti -node, at the centre accuracy. of the length, while there are voltage, anti - nodes at each end. DESCRIBING a simple method of locating the Accordingly the coupling coil is in- 5 -metre band with the help of a length of Fig. 1-Distribution of current and voltage at the current wire and an oscillating short -wave receiver. By in a half -wave aerial. serted anti -node, but its an appropriate alteration in dimensions, any other locate the positions of the voltage anti - effect will be to load -short waveband may be found. nodes. At the same time an absorbtion the aerial and decrease ultra wavemeter is calibrated from the trans- the natural frequency. 1 mitter for future use. The writer finds, The wire should, however, that the erection and operation therefore, be shortened slightly. The short -wave receiver is now switched of the Lecher Wire system is tedious when The length of wire is best supported on on, and made to oscillate weakly at the working single- handed, and the following midget stand -off insulators, mounted on, low- frequency end of the amateur 14 Mc j s method has for some time past been em- say, a loft. batten, one inch square in band. The fourth harmonic on 56 Mc /s ployed with satisfactory results. It has section. These battens are readily obtain- is looked for on the ultra- short -wave the advantage of requiring only a length able from the local timber yard, where receiver, and will probably be found at a of supported wire, and a receiver tuning they should at the time of purchase be slightly lower dial reading than that preferably to wavelengths around zo planed to a smooth finish, as later they marked as resonant with the wire. The metres. The details given apply to the form excellent aerial or reflector supports SW receiver is slowly tuned to 15 Mc/ s amateur 56 -6o megacycle band, as opera- if given a coat of waterproof varnish. In and the fourth harmonic followed on the tion on this band is carried out in most our case the extreme insulators are 8ft. USW receiver, thus marking the other end parts of the country, whereas the television apart, the wire being broken at the middle of the 56 -6o Mc /s band. transmissions are chiefly limited to the and secured to a pair of insulators each In practice the whole operation can be London area. The values to be given can one inch from the centre. These two in- carried out in a few moments, and has easily be changed to cover the 40 mega- given very good cycle band, or other parts of the spectrum. results. The method is A given length of wire has a natural by no means novel, wavelength or frequency, and if supplied but it has seldom had with energy will radiate a portion into attention drawn to it, space. Conversely, if the wire be suitably as far as the writer is coupled to a source of energy of suitable aware. The only point frequency it will absorb a portion of the calling for mention is energy. The natural half -wavelength of a that if the SW receiver wire is given by the formula : Fig. 2 -Half -wave aerial with coupling coil ; a length of 8 feet is oscillating too between outside insulators is suitable for the 5 -metre band. strongly, an excessive Length (in feet) 460,000 - Freq. in kilocycles. number of beat notes the constant in the numerator differing sulators are bridged by a wire some 4¡ will be heard on the USW receiver or a with various authorities and conditions. inches long (including the portions round frequency -changing effect will become From this formula it will be seen that a the insulator terminals) which is bent to evident by the reception of short-wave long resonates in the middle of form a rough coil. (Fig. 2). broadcasting stations, as recently pointed wire 8ft. up the 56 -6o megacycle band. If then, this The ultra- short-wave receiver is made out in The Wireless World. For picking wire be coupled to a receiver oscillating on to oscillate, and the tuning condenser the beat notes, the USW receiver should Wfip®Il®02 JANUARY 8th, 437 Miltd Finding the Ultra -Short Bands the feeders can be of any reasonable attend. There will be a special ISWC broad- - that cast for short -wave listeners on Wednesday, have the super- regenerative circuit ctit length. January 27th, from 233o to 0030 G.M.T. from out. The feeders of the matched impedance the Rome 2R0 station on 9,630 kc /s (31.13 m.). clipped on to the tuned circuit After the wire has been employed for aerial are The Croydon Radio Society determining fre- The second half of the winter session has quency, it can now commenced, and a cordial invitation is ex- readily be employed tended to non -members to attend the meetings, as an aerial or held at the club's headquarters in St. Peter's Hall, Ledbury Road, South Croydon, full de- reflector. The tails of which can be obtained from Mr. E. L. coupling coil is now Cumbers, 14, Campden Road, South Croydon. removed, and the wire can be coupled to the receiver by several methods, as Television Programmes shown in Fig. 3. The principal items only of each day's In (a) " voltage " programmes are given. The system coupling is em- to be used each day is given below the ployed. The feeders date. Transmission times are from 3 -4 and 9 -10 daily. are first cut one - quarter wave in Vision Sound length, and run 6.67 m. (45 Mc /s). 7.23 m. (41.5 Mc /s). parallel, about two FRIDAY, JANUARY 8th. inches apart, by (Marconi-E.M.I.) light spacers, the 3, First Aid -I ; Accidents in the Home. centre portion is bent Surgeon -in -Chief of the St. John Ambulance Brigade. 3.15, Gaumont British News. 3.25, into a single -turn All- coloured cabaret. coil, coupled to the 9, First Aid -I ; Accidents in the Home. receiver tuning coil, Assistant Surgeon -in -Chief of the St. John and, with no con- Ambulance Brigade. 9.15, British Movietonews. nections to the ends, 9.25, Repetition of 3.25 programme. these are equally cut SATURDAY, JANUARY 9th. down until reson- (Marconi-E.M.I.) ance in the centre of 3, The Irish Players in " The Workhouse Ward " the required fre- -Comedy. 3.25, Film. 3.35, Gillie Potter and Prador. 3.50, British Movietonews. band is ob- Fig. 3 -After the half -wave aerial has served its purpose as a Irene quency to a receiver by one of the methods is calibrating device, it can be coupled 9, Ord Hamilton, composer and entertainer, at tained. Resonance shown here. In diagram (c) the " V" portions are each 2.6 ft. long, the piano. 9.5, Stars and their directors-Anna indicated by the tapped I ft. on either side of the centre. Parallel downleads are 3.4 in. Lee. 9.10, Film. 9.20, Repetition of 3 pro- oscillation test as be- apart, and of any reasonable length. gramme. 9.40, Gaumont British News. 9.50, fore. One feeder is Gillie Potter. symmetrically about the then taken to an end of the 8 -ft. wire, while of the receiver, MONDAY, JANUARY 11th. the other feeder is left free of connections low -potential point, and about one -third (Baird.) except to its securing stand -off insulator. the way up. In circuits of the split Hartley 3, British Movietonews. 3.10, Scenes from the The 8 -ft. aerial has, of course, its centre type, a condenser of 0.005 mfd. should be Arts Theatre production of " The Soul of insulators bridged by a straight wire. included in each feeder to isolate the HT Nicholas Snyder." 3.25, Film. 3.35, Leonard of the valve. Henry. 3.45, Dancers and the Television In (b) " current " coupling is shown. voltage from the grid Orchestra. The feeders are approximately of half a Considerable gain in signal strength can 9, Repetition of 3.45 programme. 9.20, Film. wavelength, and are coupled to the generally be obtained by erecting a re- 9.30, Cabaret including Gwen Farrar. 9.50, receiver as before, except that there is no flector behind the aerial. The reflector is Gaumont British News. mounted on a batten, in the same bridging length across the centre of the 8ft. best TUESDAY, JANUARY 12th. wire. The length of the feeders is cut to way as the aerial, and in the simplest form (Baird.) resonance when connected to the aerial so has no connections for feeders whatsoever. 3, Sidonie Goossens (Harp,). 3.10, Gaumont that the whole system resonates on the For 56-6o Mc / s it should be a couple of British News. 3.20, " The World of Women " desired frequency. inches longer than the calculated half - -I, Setting a play. 3.35, Film. 3.45, Peggy Cochrane (Violin). A " matched impedance " system is wavelength, and spaced a couple of inches shown in (c). The dimensions are for farther from the aerial than a quarter - 9, Repetition of 3 programme. 9.10, British are Movietonews. 9.20, Repetition of 3.2o pro- 58 Mc / s, using feeders of about 20 -gauge wave, in general, but these dimensions gramme. 9.35, Film. 9.45, Repetition of wire, and the advantage of this system is best determined by trial and error. 3.45 programme. WEDNESDAY, JANUARY 13th. (Baird.) 3, London Galleries ; Talk by John Piper. 3.15, Film. 3.25, Nineteenth Picture Page. News from the Clubs 3.50, British Movietonews. The Mid - Cornwall Short -Wave and issued to members and ultimately it is hoped 9, Gaumont British News. 9.10, Repetition Television Society to obtain a transmitting licence for the society. of 3 programme. 9.25, Film. 9.35, Twentieth This newly formed society is making s1 ady The Secretary, Mr. E. K. Jensen, 5, Furzebeam Picture Page. progress, and a beginners' hour has been Terrace, Bideford, will be pleased to hear from prospective members. THURSDAY, JANUARY 14th. started. Morse instruction is another of the (Baird.) club's activities. Headquarters are at St. Austell, and full information will be given to The International Short - Wave Club 3, Home Affairs ; discussion with photos and those interested if they will write to Mr. P. The London chapter of this club holds meet- diagrams between the Rt. Hon. Herbert O'Neill, 1, Warleigh Villas, Saltash, Cornwall. ings every Friday at 8 p.m. at 8o, Theobalds Morrison and John Hilton on London's Green Road, Holborn, London, W.C. r. These meet- Belt. 3.20, Gaumont British News. 3.30, Bideford and District Short- Wave ings arc open to all and there is a club room Music Makers -Carroll Gibbons. 3.40, Scott S lciety for the use of members, this being equipped Gordon's Marionettes in " Old -Time Music This society is making excellent progress. with receiver, transmitter and library. Hall." 3.50, Cabaret. Premises have been obtained for a permanent The Brighton chapter of the above club will 9, Repetition of 3.3o programme. 9.10, club room and apparatus is being installed for be opened on Saturday, January 23rd, at 7 Repetition of 3.4o programme. 9.20, British power supply, reception and receiver testing. p.m. in the Brighton Technical College. All Movietonews. 9.30, Repetition of 3 programme. Two more artificial aerial call signs have been in the vicinity who are interested are invited to 9.50, Cabaret. Wireless World, January 8th, 1937

would get it " in the neck " whichever way they voted. The suggestion is quite untrue. The feeling now seems to be Broadcast Brevities. that the B.B.C., subject to its own prerogatives, treats its of workers comparatively hand- Ultra - Short- Wave Relay year. These latter include the equipment in the early part new studio premises in Glasgow, the year. Its completion will somely. Although a few cases HERE is good news for lovers the be followed by a start on the of inequality of treatment may quality reproduction. In which may be ready by of autumn, when we shall see the new transmitter for the south- have cropped up here and all probability the B.B.C. will west of England. there, appeal to higher ultra -short- return of Scottish broadcasting shortly establish an to its spiritual home. The new authority almost invariably wave service for the relay of the teí, tc, means that matters are righted. National programmes, the trans- studio premises in Swansea will on the roof be complete and occupied by Smashing -up Portland mitter being situated the spring, and a start will be of Broadcasting House. Place. is made on new studio premises in More Staff for Television If and ewhen the decision Belfast. AN army of demolition men is made, probably in the next about to get busy in Port- GRADUALLY the staff list at month or two, it will largely be land Place, and B.B.C. staff Alexandra Palace is enlarg- due to the excellence of the now occupying seven of the ing to cope with television pro- sound transmitter at Alexandra NEWS FROM doomed houses are to be moved gramme developments. Last Palace. Music critics -and not to nearby premises, the location only music critics-have been PORTLAND of which is being kept secret. able to forget the picture at times in their enjoyment of the PLACE sound reproduction. (T h i s sounds too good to be true, but it is true.) Provinces Also ? In this connection the B.B.C. also has its eye on the pro- vinces, believing that, where CHANGING possible, facilities accorded to SCENES. The also be wreckers will the Metropolis should shortly be busy available to the Regions. The demolishing all logical development would be these houses in to install ultra- short-wave trans- Portland Place mitters at each of the provincial to make room centres for relaying either the for the exten- National or the Regional pro- sion of Broad- grammes to listeners who were casting House. go the extra Seven of the prepared to to houses are at trouble and expense of picking present occu- up high- fidelity transmission. pied by the Eventually, of course, these B.B.C. ultra - short - wave transmitters might be called upon to handle television, but that is another story. New Transmitters The Corporation has already week Mr. Reginald Smith, fresh had copious experience of pour- from the world of the theatre, As r e g a r d s transmitting up as Assistant Stage New Year Building stations, the three new Empire ing quarts into pint pots, and joined Activity ánd aerial at will, no doubt, find a temporary Manager. Unlike many of his transmitters The only tribe, " Reggie " is a stage IN addition to the start which Daventry will be completed in home for everybody. so as people in the block who must manager who can also act ; he is to be made in 1937 on the the early part of the year, was recently playing in Bernard to provide an improved service find accommodation elsewhere extension of Broadcasting are the occupants of a Nurses' Shaw's " The Millionairess," House, the year will see the in- for listeners overseas in time for day for the The transmit- Institute. For them the Cor- performed the other auguration of other building the Coronation. has a building first time at Bexhill. Mr. Smith of ter at Beaumaris will be poration bought schemes and the completion on the opposite side of Portland was for years with André Charlot various works which were in opened shortly, and the station for Place. in revue production-an experi- hand towards the end of last at Stagshaw will be ready ence which should help consider- ably in the job of putting over B.B.C. Staff Association ? " peppy " programmes in tele- at vision. Pe ysarn of the first activities ONE"B.H." when the new Governors are settled in will be Installing the President a close investigation of schemes of America's most spec- arianglas presented by Mr. St. John ONE lane ligo B tacular " O.B's " -the in- lhp Pym, Director of Staff Organisa- auguration of the President- Conway tion, for the formation of a comes to British listeners on Bay staff association. January zoth. Particulars of Time marches on, however, the event-of the commentaries umarismas ey,C and since the idea of such an from airships and 'planes by ace an first promul- Conway association was announcers at strategic points enaiStr lanfairfeC gated, desire for it on the part of along the processional route- ber the staff seems to have waned. appeared in these columns on 3rw Tynÿgroes ' alycafn December firth. or Wrongs Righted A specialised anglicised com- iC Critics of the B.B.C. have mentary will be given by Felix ortDino L representa- siencvn Bethesda D Igárrog made much capital of the sug- Greene, the B.B.C. gestion that the ballot for or tive in New York. " Geograph is " The B.B.C. will pick up the is site of the next B.B.C. against an association was a BEAUMARIS, in the Isle of Anglesey, the ceremonies at Tatslield, via station to take the air. Wales, Northern England, and Ireland will forced one, i.e., that numbers profit most from the new transmitter. of the staff feared that they 2XAD and zXAF. Wireless World, January 811z, T937 4;

Dropping Filament MÇcAR 111Y Vfor the finest value in Oh All -Wave Receivers !

A 0.2 -ohm and a r -ohm resistance made as de- Making scribed in the text. Resistances to Operate Four -volt

AC Valves from Five - In order to make the resistances compact volt or Six - volt LT and easy to accommodate, they can be wound in the form of a loose coil using Supplies for a former a tin. rod or a pencil, though when made in this form it is advisable to 6 employ enamelled or silk -covered wire. VALVE ALL -WAVE S U PERM ETERODYNE Resistance Values THERE are occasions when it is re (complete with B.V.A. Valves) quired to employ a four -volt AC If we take the case of a rectifier requir- Most popular receiver with " Wireless World " readers. The heated valve ing 2.5 amps. at four volts and the valve " Wireles World'.' says; "Sensitivity of the set on all three in place of one taking wave bands cannot fail to give satisfaction . . . excellent five volts or more, the replacement of an is to be used on a five -volt supply, the results on the short -wave band." early -type five -volt total resistance will now be only 0.4 ohm, Brief Specification : 8- stage, all -wave band -pass superhetero- HT rectifier by a dyne, 7 tuned circuits. D.A.V.C. with " squelch " circuit valve modern one being a typical case. or 0.2 ohm for each filàment lead. In this for noise suppression. Illuminated " Airplane " dial. Octode case five frequency changer. 3 -5 watts pentode. Switching for gramo- Ín itself this is not a difficult problem, strands of wire are needed, each phone pick -up. Wave ranges : x6.5-5o, zoo-55o,Soo- 2,000metres. since the surplus volts can quite easily be again ein. long ; for five one -ohm resist- dropped across a resistance, and the value ances in parallel gives 0.2 ohm. Twisted of this resistance is easy to find from Ohm's together and wound as a coil, this length Law. Thus, if one volt has to be lost and of wire takes up;only about ein. when the the valve takes one ampere, dividing volts turns are slightly spaced. by current we obtain a resistance value of It is not uncommon to find six-volt one ohm. windings on some old pattern mains trans- The question now arises as to the best position for the resistance. It could, of course, be inserted in one of the filament leads, though a better plan would be to divide it into two equal parts and include half the total amount in each lead, as shown at R in Fig. r, thereby preserving the symmetry of the circuit.

Choice of Wire The gauge of wire to use is of some im- 6 VALVE ALL -WAVE portance, as it is always advisable to avoid an excessive rise in temperature whenever SUPERHETERO DYN E possible. (with radio frequency stage) While there is considerable latitude in the choice of it Performance (made possible by use of multi-electrode valves) wire, might be useful to equal to that of many 8 valve receivers. 8 stages, 8 tuned know that No. 28 SWG Eureka will com- circuits, covering 3 wavebands- x6.5 -z000 metres. Illumin- ated " Airplane " dial (different coloured lights automatically fortably carry 0.5 amp. For currents switched in for each wave range), giving principal station greater than this, two or more strands names, with micro -vernier z -speed drive. Circuit in brief: Pre- selector circuit, radio frequency amplifier twisted together can be used, the required Fig. z. -The voltage- dropping resistances (operative on all three wavebands), triode -hexode frequency changer, double bandpass I.F.T. coupled I.F. amplifier, number being the filament current in amps. are joined in the filament leads as shown double diode -triode detector and L.F. amplifier. D.A.V.C. divided by 0.5. above. applied to 3 preceding valves. 3 watt pentode output. Variable tone control and volume control operative on radio No. 28 SWG Eureka has a resistance of or gramophone. ohms per yard, but for all practical formers, and for All McCarthy receivers supplied complete with 3.914 a four -volt one -amp. valves, knobs, pilot lamps, leads, mains cable and purposes this may be taken as 4 ohms. valve a resistance of two ohms will be re- plug. 12 months' guarantee. Deferred terms on Where one volt has application, or through London Radio Supply Co., to be dropped and quired. Two strands of the wire men- 11, Oat Lane, í4.C.2. Cash with order on 7 days' the current is one amp., the resistance approval. Also write for illustrated catalogue of tioned, each i8in. long, twisted together complete range of all McCarthy receivers. should have two strands of wire, and, and coiled, will provide a one -ohm resist- dividing it into two parts of 0.5 ohms each, ance capable of carrying one amp. Two MCAIDIEII IDÁDIIC simple calculation shows that each strand such resistances are, of course, needed, and should be of one ohm. This is obtained each takes up about thin. only. 44a, Westbourne Grove, London, W.2 with gin. of No. 28 SWG Eureka. H. B. D. Telephone: Bayswater 3201/2. 46 Wireless World, January, 8th, 1937 New Apparatus Recent Products of the Reviewed Manufacturers

ROTHERMEL -BRUSH MICROPHONE will make little reduction in the overall MODEL B -1 sensitivity. Supplies are obtainable from R.A. CRYSTAL microphones of the " sound Rothermel, Ltd., Canterbury Road, High cell " type are widely used for cali- Road, Kilburn, London, N.W.6, and the bration work and high quality reproduction, price is L6 1os. complete with mounting but their price has hitherto put them socket. beyond the resources of many who are transmitting and interested in experimental SOUND SALES "SUPER AUDITORIUM " public address work. LOUD SPEAKER Sound Sales " Super Auditorium " loud The new Model B -r bridges the gap be- speaker with dual suspension. tween the inexpensive diaphragm -actuated THE strenuous conditions of PA work will types and those with multiple cell con- soon reveal any weakness in the struction. It employs a single cell which mechanical design of a loud speaker, and when the applied frequency resonates with their natural period of transverse vibration. is mounted on a spring suspension inside an many types -even in the larger sizes - attractively finished dull chromium case. which have an adequate reserve of power - This proved to be the case, but the results handling capacity for domestic use develop were entirely negligible as far as the general faults of various kinds if they are pressed radiation from the loud speaker was con- into service for use with PA amplifiers. cerned, as the area of the strips is only a For this reason Sound Sales, Ltd., have small proportion of the radiating surface. developed a special loud speaker for use with To make quite sure that damage will not their power amplifiers, and although power - occur as a result of the coil fouling the pole handling capacity and reliability have been pieces, a gap of ,Ain. has been provided, in given precedence, the frequency response is which the massive magnet coil produces a also outstandingly good. The output at field of no less than 12,000 lines per sq. cm. ro,000 cycles is at the same level as that in The " Super Auditorium " is rated to the lower middle register, and there is a handle 15 watts when fitted with a proper gradual rise, but no pronounced peak in the baffle, and the price is ¿12 complete with region between 1,000 and 5,000 cycles. output transformer. The trough at 7,000 cycles was investigated and found to be solely a property of the axial response, and could not be detected in listening to the general radiation from the The Radio Industry diaphragm. THE Belling-Lee Set Lead Suppressor, Type One of the principal points of failure in 1256, has been discontinued in favour of highly stressed diaphragms is in the annular an all -wave suppressor (Type 30o, price 21s.) surround which is usually relied upon, which is effective on wavelengths above ro together with the centring spider, for sup- metres -and to some extent even below. The is Type 300, which is rated at r amp., now be- port. Parallel action achieved in the comes the standard suppressor for connection Sound Sales speaker without any assistance in the power supply lead. from the surround, which is made of flexible 4 0 woven material. The suspension is shared 0 0 a centring spider and a series of Alunize. Ltd., of 34, North Street, Rugby, by rear has developed a metallurgical process for radial strips which permit an excursion of joining together parts of aluminium and its the coil of approximately tin. at low fre- alloys. Those who are interested in the appli- quencies. It might be expected that the cations of the process to wireless work are in- Rothermel -Brush Model B-I sound cell strips would develop appreciable amplitudes vited to apply for particulars. piezo -electric microphone.

The characteristic is, of course, quite free from any resonances that might be asso- a,, with an auxiliary diaphragm, and ciated i the cavity resonance of the cell itself, III" in the region of 6,000 cycles, is so Ì probably 15 I '`""` . ,.,M1 well damped that it causes no coloration. The sibilants are reproduced without o 111 emphasis and speech is remarkably natural. LI p M 5 The only difference in quality between the Wireless World expensive G2S2P against P.. COPYRiGnT B -r and the more which it was tested was in the extremely 10 Ell high frequencies associated with sound, such as the jingling of keys. The putput level of the B -r is -72 db., _2ó f i.e., an amplifier with a gain of 72 db. IIi! would be required to give an output of I volt RMS for a sound pressure of I dyne FREQUENCY per sq. cm. The internal capacity is of the order of o.or mfd., so that the external capacity of. leads, which are in any case Axial response curve of Sound Sales " Super Auditorium " loud speaker on irregular baffle without effect on the frequency response, (area approx. 22 sq. ft.), microphone distance 4ft., power input r watt. Wireless World, January 8th, 1937 47 Letters to the Editor The Editor does not hold himself responsible for the opinions of his cdrrespondents

SW Fade Out had been a good X9, so that listening was practically impossible. On IT may the day of be of interest to some of your December 3rd there was practically no readers to know of a remarkable effect static. which I observed on Thursday, December I should be very interested to know 3rd, 1936. whether any of your readers experienced a II II II I was listening to GIA on approximately similar complete " fade out " on this date, ge 15 metres at noon G.M.T., and was receiving and also whether any reason can be given him at about R5 as against his usual R7 /8, for it. P. F. M. BARRETT. when suddenly, at 12.15 p.m. G.M.T., he 4th Dec., 1936. began to fade, and within three minutes had Gold Coast Colony. disappeared completely. [This " fade out " was commented upon I promptly tuned in to Daventry (GSH) by Ethacomber in The Wireless World of on 13.97 metres. bringing him in at R4 in- December 25th, 1936, page 670. -En.] stead of his usual R7 /8, and within a few seconds he had disappeared as well. I then tried to tune in the numerous CW Valve Nomenclature which always to found work- stations, are be IHAVE read ing on wavelengths between 13 and 28 with interest a paragraph in the columns of " Diallist " in metres, but there was no sign of 9. single one which he of them and the ether seemed completely pleads for a more appropriate name to de- dead. scribe what we know as a " valve." I tested the set in case any of the com- I notice that he considers the word valve ponents or the batteries had failed, but all is less apt for an amplifier than a rectifier. I were in order, and the ignition systems of think in this case he is thinking of some lorries passing on the road could be clearly kind of non -return or safety valve for his heard, so the set was not to blame. mechanical analogy. The type of mechani- At 12.55 p.m. G.M.T. I tuned in again on cal valve that I visualise in this connection is the type for controlling flow of liquids fa 13.97 metres and found Daventry coming in the at a strength of R8, and GIA about the or gases by means of a handle (what is same. known as a tap when on a small scale). t I happened to mention this complete With this analogy one can consider the i small energy required to " fade out " to a friend of mine at 2 p.m. turn the tap or THE " ROLLS -ROYCE " G.M.T. the same day. He said that he also valve to correspond to the grid potential and OF LOUDSPEAKERS had experienced a similar complete fade out the powerful flow of fluid to correspond to between the times mentioned by me, the strong electron flow. Used to denote perfection, the term and Rolls -Royce has become part of the could not pick up any stations at all between With this outlook I do not think the -word valve is quite so inappropriate in describing English language. When it comes 13 and 5o metres on his eight -valve short - amplifiers. (The flow of water in a small to radio sets nothing denotes perfec- wave superheterodyne. tion so surely as the use of a Rola My set is a straight four -valve short -wave tube can actuate a valve of another tube G.12. No manufacturer would use set with a pentode output, battery operated, carrying far more water.) a speaker of the very highest quality with plug -in coils. The night of December It seems a little difficult to find a more unless he intended his whole set to znd had been very thundery, without a descriptive name applying in general,to all be worthy of its reproduction. The storm actually taking place, and the static radio valves. The only one I can think of is Rola G.12 is a high fidelity 12" electron flow control tube, or electron -con- diameter unit of unsurpassed per- trol tube. formance. Already manufacturers I am afraid this would delight none but have found that it is the models with the Teutonic mind. G.12 speakers that show the greatest sales increase. He guided by their May I suggest that an entirely new word experience- install Rola G.12's in should be coined? I submit electrol, a your receivers. shortened form of electron control. G.12 D.C. (as illustrated) Stripped and This word, unfortunately, loses most of its without Transformer ... £3 15 0 descriptiveness. However, G.12 D.C. Complete with Transformer. no word which Mounting Stand, Handle is descriptive in one language can be fully and Base £5 5 0 descriptive in another. G.12 D.C. with Mounting Stand, Handle and Base, but without In this case I may mention the standard- Transformer ... £4 16 0 isation of the names of the chemical ele- G.12 D.C. Stripped, but with Trans- former ...... £4 4 0 ments. They are quite non -descriptive in (When ordering please state Field Resistance and any modern language, and yet they have Impedance of Transformer required.) G.12 P.M. less Transformer ...... £4 16 0 been accepted by all countries. 0.12 P.M. with Transformer ...... £5 5 0 London, W.C.i. J. ARNOLD. For Public Address work both the P.M. and Ener- gised Models can be supplied with a 15 ohm Voice Coil at an additional charge of Rejecting Whistles Write for Folder A. 7 IAM so sorry to see from your issue of OVER MILLION IN USE 1511 December 25th that my previous letter had quite failed to soothe Mr. Baggally- perhaps his Christmas holiday has now suc- ceeded in doing so. It seems to me that the matter could only be fully argued out in a long and very high -brow letter, which I am certainly not going to write. After all, the proof of the is in NEW GERMAN pudding the eating. My whistle -filter Jfte I1iOt>/ttj 7tfleist lr0duce/t.i DIRECTION FINDING suits me better than his, and I would not EQUIPMENT. To obtain the most accurate THE BRITISH measurement possible the Telefunken Co. for the world quarrel with him if, in spite ROLA CO.. LTD. have made use of a cathode -ray tube mounted of that, he prefers his own. MINERVA ROAD, PARK ROYAL,N.W.10. in the convenient manner shown in appa- P. K. TURNER. 'PHONE WILLESDEN 4322 -3- 4 -5 -6.. ratus of recent design. Isleworth. 48 Wireless World, January 8tk, 1937

50 Wireless World, January i5th, 1937 The Time-base By W. T. COCKING

HOW SCANNING IS EFFECTED in Television AT THE RECEIVER

N television transmission the subject AN essential part of all television receivers embodying cathode is scanned by a spot, which may be ray tubes is the time base, for it produces the voltages of light as in the Baird system, or may be the end of an electron beam necessary for building up the raster. In this article, the method as in the Emitron camera, which traces of operation of the conventional type including a gas filled triode out a series of parallel lines. If the picture is described. is to be reconstituted correctly on the screen of the cathode -ray tube, it is neces- Fig. r, the spot must start at the left - The correct is sary for the spot caused by the impinge- pattern obtained on the hand top corner (A) and move steadily screen ment of the electron beam on when the voltages on the deflect- the fluores- across the screen to (e). It must then ing plates cent screen to make exactly the are of saw-tooth wave -form same return to the left-hand side of the screen, with, of course, traversals as the spot in the transmitter. the correct frequency, but to a point (c) slightly below (A), and Now the position of the spot on the then trace out another line to (D), and so screen can be altered by A deflecting the on until the full number of lines has been electron beam either electrostatically or completed. The spot is then at the point electro - magnetic- (E) in the right -hand bottom corner, and c a 1 1 y. Both it must now return to the original point (A) methods are used in order to trace out a second series of D and are some- lines immediately over the first. times combined. In television terminology, a line is one Electrostatic de- complete cross traversal of the screen and flection is prob- a frame is one complete vertical traversal ably the one more via the whole series of lines. The raster widely adopted, is the resulting rectangle composed of however, so that parallel lines. at first we shall consider only this. The conven- Fig. 2. -A section of a raster is shown here tional cathode- in greatly exaggerated form. The spot two travels along AB to trace out a line and ray tube has then flies -back along BC in preparation for pairs of deflecting the next. plates built into it, and it is only phase, and amplitude. An ideal wave- necessary to apply form is that shown at (a) in Fig. 3. The suitable voltages voltage rises linearly along (AB) with to these plates to respect to time and then falls instantane- make the spot per- ously to zero along (BC) ; in practice, zero form any gyra- fly -back time is impossible, and the tions we please. waveform is more like that shown in (b). There is no figure Here the rise of voltage along (AB) is the or pattern which same as in (a), but the fly -back (BC) occu- the spot cannot Fig. 1. -The raster is built up by the spot traversing a series of lines across the screen pies a finite time. The time (AC) repre- trace with suitable of the tube. sents one complete period of the wave. voltages applied The waveform given by a poor time - to the plates. This In actual fact the spot does not trace base is shown in (c), and it will be seen is because there out a pattern exactly like that of Fig. r, that the voltage rise along (AB) is no are two pairs of but one shown in greatly exaggerated longer linear. This will cause distortion plates at right form in Fig. 2. The spot moves steadily of the picture by cramping the right -hand angles ; with only from (A) to (B) and traces out a line which side. A perfectly linear time -base is The electrode struc- one pair of plates, is not quite horizontal. Having arrived probably impossible, and all types tend ture inside a cathode - the movement of at (B) it rapidly flies back to (c), tracing to give some curvature to the voltage ray tube : note the the spot is re- out the dotted line (Bc) ; the next line (CD) wave. This is very small in a good time - two pairs of deflecting plates. stricted to a is parallel to the first, and so on. The base, however, but careful design is straight line. actual time taken for the traversal of each necessary. When there are two sets of plates, how- line must be a definite figure, depending The circuit of a simple time -base is ever, we can apply two forces at right on the transmission, ' and must be held shown in Fig. 4, the valve being a gas - angles to the electron beam, and so cause constant within very close limits. The filled triode. This kind of valve differs it to move in any direction. time taken by the fly -back would ideally from ordinary hard valves in several For television purposes, the spot must be zero, but this is impossible; it must be ways. For our present purposes, its build up a raster on the screen by tracing very much less than the line time, how- most important attributes are that it takes out a series of parallel lines. Referring to ever. no anode current until the anode voltage Wireless World, January 8th, x937 47 Letters to the Editor POINT5 Of The Editor does not hold himself responsible for the opinions of his correspondents 11000' CT SW Fade Out had been a good X9, so that listening was practically impossible. On the day of may be of interest of IT to some your December 3rd there was practically no readers to know of a remarkable effect static. it' die /?oIft which I observed on Thursday, December I should be very interested to know 3rd, 1936. whether any of your readers experienced a I was listening to GIA on approximately gip EM similar complete ' fade out " on this date, 15 metres at noon G.M.T., and was receiving and also whether any reason can be given .... him at about R5 as against his usual R7 / 8, for it. P. F. M. BARRETT. when suddenly, at 12.15 p.m. G.M.T., he 4th Dec., 1936. began to fade, and within three minutes had Gold Coast Colony. disappeared completely. [This " fade out " was commented upon I promptly tuned in to Daventry (GSH) by Ethacomber in The Wireless World of on 13.97 metres. bringing him in at R4 in- December 25th, 1936, page 670. -ED.] stead of his usual R7 /8, and within a few seconds he had disappeared as well. I then tried to tune in the numerous CW Valve Nomenclature stations, which are always to be found work- I1-IAVE read with ing on wavelengths between 13 and 28 interest a paragraph in the columns of " Diallist " in which metres, but there was no sign of 2, single one he of them and the ether seemed completely pleads for a more appropriate name to de- dead. scribe what we know as a " valve." I tested the set in case any of the com- I notice that he considers the word valve ponents or the batteries had failed, but all is less apt for an amplifier than a rectifier. I were in order, and the ignition systems of think in this case he is thinking of some lorries passing on the road could be clearly kind of non -return or safety valve for his heard, so the set was not to blame. mechanical analogy. The type of mechani- At 12.55 p.m. G.M.T. I tuned in again on cal valve that I visualise in this connection 13.97 metres and found Daventry coming in is the type for controlling the flow of liquids at a strength of R8, and GIA about the or gases by means of a handle (what is same. known as a tap when on a small scale). I happened to mention this complete With thïs analogy one can consider the ` small " fade out " to a friend of mine at z p.m. energy required to turn the tap or THE " ROLLS -ROYCE " G.M.T. the same day. He said that he also valve to correspond to the grid potential and OF LOUDSPEAKERS had experienced a similar complete fade out the powerful flow of fluid to correspond to between the times mentioned me, the strong electron flow. Used to denote perfection, the term by and Rolls-Royce has become part of the could not pick up any stations at all between With this outlook I do not think the word valve is quite so inappropriate in describing English language. When it comes 13 and 5o metres on his eight -valve short- to amplifiers. (The flow of water in a small radio sets nothing denotes perfec- wave superheterodyne. tion so surely can a as the use of a Rola My set is a straight four -valve short -wave tube actuate valve of another tube G.12. No manufacturer would use set with a pentode output, battery operated, carrying far more water.) a speaker of the very highest quality with plug -in coils. The night of December It seems a little difficult to find a more unless he intended his whole set to 2nd had been very thundery, without a descriptive name applying in general,to all be worthy of its reproduction. The storm actually taking place, and the static radio valves. The only one I can think of is Rola G.12 is a high fidelity 12' electron flow control tube, or electron -con- diameter unit of unsurpassed per- trol tube. formance. Already manufacturers I am afraid this would delight none but have found that it is the models with the Teutonic mind. G.12 speakers that show the greatest sales increase. Pe guided by their May I suggest that an entirely new word experience- install Rola G.12's in should be coined ? I submit elecfrol, a your receivers. shortened form of electron control. G.12 D.C. (as illustrated) Stripped and This word, unfortunately, loses most of its without Transformer £3 15 0 descriptiveness. However, no G.12 D.C. Complete with Transformer. word which Mounting Stand, Handle is descriptive in one language can be fully and Base £5 5 0 descriptive in another. G.12 D.C. with Mounting Stand, Handle and Base, but without In this case I may mention the standard- Transformer £4 16 0 isation of the names of the chemical ele- G.12 D.C. Stripped, but with Trans- former .. ... £4 4 0 ments. They are quite non- descriptive in When ordering please state Field Resistance and any modern language, and yet they have Impedance of Transformer required.) G.12 P.M. less Transformer ...... 14 16 0 been accepted by all countries. G.12 P.M. with Transformer ...... £5 5 0 London, W.C.T. J. ARNOLD. For Public Address work both the P.M. and Ener- gised Models can be supplied with a 15 ohm Voice Coil at an additional charge of 3-. ;7. Rejecting Whistles Write for Folder A. IAM so sorry to see from your issue of OVER 7 MILLION IN USE December 25th that my previous letter had quite failed to soothe Mr. Baggally- ti perhaps his Christmas holiday has now suc- ceeded in doing so. It seems to me that the matter could only be fully argued out in a long and very high -brow letter, which I am certainly not going to write. After all, the proof of the pudding is in the eating. My whistle NEW GERMAN DIRECTION FINDING -filter Tie 6f%t,l Wue4s/ Itodueets suits me better than his, and I would not EQUIPMENT. To obtain the most accurate THE BRITISH measurement possible the Telefunken Co. for the world quarrel with him if, in spite ROLA CO., LTD. have made use of a cathode_ -ray tube mounted of that, he prefers his own. MINERVA ROAD, PARK ROYAL,N.W.10. in the convenient manner shown in appa- P. K. TURNER. PHONE WILLESDEN 4322- 3- 4 -5 -6. ratus of recent design. Isleworth. Wireless World, January 8th, 1937 48

of the received picture. The par- ticular compass reading that Brief descriptions occupies the centre of the receiver of the more in- screen at the moment of the sud- Recent Inventions den change then indicates the teresting radio required bearing. devices and improve- resistance R in the anode circuit of BROADCAST RELAYS One advantage is that only a the first detector valve V of a IN order to allow each subscriber single wavelength is required to ments issued as patents receiver. When the in a wired relay system to transmit both the picture and the superhet is will be included in this switch S is moved to the upper control the tone response of his directed beam, whilst a second bearing -indica- section. pair of contacts the voltage across own loud speaker, without affect- that the critical

" IMPACT " AMPLIFIERS " cold " electron- amplifier A consists of a series of open or network electrodes arranged, in in- creasing order of potential, along the axis of a series of concentric cylinders biased to a relatively higher potential. The first series of electrodes A ... D are aligned inside the cylinders As ... Cr, the biasing voltages for each being tapped off from a common source of HT. The whole of the elec- trodes are enclosed in a cup - shaped collector K carrying the highest potential. An electron entering the device at E strikes against the first open- work electrode A, and the Arrangement of the circuit for using the cathode -ray tube in a television receiver as a tuning indicator. secondary electrons so produced are accelerated and strike in part R deflects the electron stream so as ing other subscribers' instruments tion is shown with sharp discrimi- against the next plane elec- to indicate whether or not the which may be connected in nation. trode B and in part against tuning is correct. The degree of parallel, a variable resistance Marconi's W. T. Co., Ltd.; the open-work cylinder Ai. This deflection that indicates resonance shunted by a fixed or variable R. K. Kemp and D. L. Plaistowe. process is repeated at the can be controlled by adjusting the choke is inserted, as a unit, in Application date March 27th, electrodes B and Bi, until the am- tapping point P. On moving the series with one of the supply leads. 1935. No. 454256. pified stream reaches the final switch S to the lower contacts A switch allows the unit to be 0 0 0 0 stage D, from which it passes to scanning-voltages are applied to brought into operation or short- SHORT -WAVE RESONATORS so the out- the collector K and to the deflecting plates of the circuited, as required. Tl lE Figure shows a resonator or cathode -ray tube from the usual G. A. Barden and Goodmans oscillatory unit used for ultra - time -base circuit (not shown). (Clerkenwell), Ltd. Application short waves. It consists of a Marconi's Wireless Telegraph date January 17th, 1936. No. central conductor A fitted at each Co., Ltd., and A. A. Linsell. 454903. end with hell -shaped portions B Application date March 11th, o o o o

1935. No. 453499 DIRECTION = FINDING BY 0 0 0 0 TELEVISION BAND -PASS COUPLINGS THE bearings of a ship relative THE Figure shows a coupling to a distant beacon- station suitable for handling television are transmitted to it by television, or other signals having a band- so that the required information width greater than 20 k /cs. The is shown directly in visual form. coil A in the anode circuit, say of A picture of a compass scale, sur- the first intermediate- frequency mounted by the name of the bea-

Electrode assembly in the cold Method of coupling an ultra - cathode -ray -type amplifying short wave aerial to a high valve. " Q " oscillatory circuit. put lead Z. The amplifier work, and C having flanges Bi, Cr without inertia and in a vacuum, to increase the capacity between without any gas -filling. The them. One of the flanges Br is electrodes are preferably coated adjustable relatively to the other. with cesium oxide to increase The unit oscillates by virtue of its emission. distributed inductance a n d The British Thomson -Houston capacity. Co., Ltd., Convention date (Ger- One advantage of the unit is many), March 7th, 1935. No. that there is very little damping, 454133. so that the frequency is stable, 0 0 0 0 whilst another is that it produces Wide -band inter -valve coupling circuit for television reception. TUNING INDICATORS no external field. The part A is THERE is a known type of provided with an aperture to tuning indicator in which the valve of a superhet receiver, is con station, is transmitted omni- admit a single wire loop L which deflection of the spot of light on tuned approximately to the lower directionally. At the same time a couples the resonator to a dipole the fluorescent screen of a small limit of the frequency band, whilst directed ' beam " is swung aerial D. cathode -ray tube shows when the the coil B in the grid circuit of the around the horizon from the same N. V. Philips' Gloeilampen- circuits are accurately in resonance next amplifier is tuned to the transmitter, and this is used at the fabrieken. Convention date (Ger- with the incoming signals. upper limit. A third coil C, receiving end to produce a sudden many), March 18th, 1935. No. According to the invention this coupled to the other two, is tuned change in the overall illumination 454208. idea is applied to a combined substantially to the middle of the sound -and -picture receiver, the frequency band. Each circuit is cathode -ray tube normally used to damped by parallel resistances R, The British abstracts published here are prepared, with the permission reproduce the televised picture Ri, R2, whilst the mutual coup- of the Controller of H.M. Stationery Office, from Specifications being utilised to show also when ling between the coils is adjust- obtainable at the Patent Office, 25, Southampton Buildings, London, the circuits are correctly tuned. able. W.C.2, price t/- each. A selection of patents issued in U.S.A. is As shown in the Figure the L. R. Merdler and Baird Tele- also included. cathode -ray tube C is arranged to vision Ltd. Application date be switched momentarily across a March 18th, 1935. No 453847. THE PRACTICAL RADIO JOURNAL 26 th Year of Publication

FRIDAY, JANUARY 15TH, 1937. VOL. XL. No. 3.

Proprietors : ILIFFE & SONS LTD. Editor : EDITORIAL COMMFNT HUGH S. POCOCK. Editorial, to -day the cheapest of valve receivers Advertising and Publishing Offices : Programme Distribution DORSET HOUSE, STAMFORD STREET, (and crystal sets can be ruled out LONDON, S.E.r. Conditions Have Changed to -day) can rope in a choice of several Tekphone: Waterloo 3333 (5o lines). B.B.C. programmes from nearly any Telegrams: "Ethaworld, Sedist, London.' WHAT has become of the part of the country. COVENTRY : Hertford Street. rumour current a year ago This being so, the necessity for the Telegrams: Telephone: its en- a Autocar, Coventry." 52ío Coventry. that the B.B.C. was pro- B.B.C. to plan programmes posing to put programmes tirely on the assumption of local BIRMINGHAM : which were mainly of an educational listening has disappeared, and whilst we Guildhall Buildings, Navigation Street, 2. are all agreed that for the very best Telegrams : Telephone: character permanently on to one or two "Autopress, Birmingham." 2971 Midland (4 lines). quality in musical reproduction it is exclusive wavelengths ? The idea at necessary to take the programme from MANCHESTER : 260, Deansgate, 3. the time was hailed as a promising Telegrams : Telephone: solution of the present unsatisfactory the local station, the need for extremely "Iliffe, Manchester." Blackfriars 4412 (4 lines). state of affairs where educational high quality does not exist in the case GLASGOW : 26B, Renfield Street, C.2. matter gets sandwiched in amongst of broadcast talks, or, in fact, for any Telegrams: "Iliffe, Glasgow." Telephone: Central 4857 lighter material programmes, spoiling type of transmission which does not PUBLISHED WEEKLY. ENTERED AS SECOND the composition of both, and nearly call for the reception of a wide fre- CLASS MATTER AT NEW YORK, N.Y. always resulting in the broadcasts of quency range. Subscription Rates : an educational character being cur- Home, Lx is. 8d. ; Canada, £I is. 8d. ; other. tailed or compressed to a point where Service Area To -day countries, £I 35. rod. per annum. they cease to be of very much use as If it were possible to plan wave- As many of the circuits and apparatus described in these educational material. pages are covered by patents, readers are advised, before lengths in Europe on the basis of making use of these, to satisfy themselves that they would There is room, we believe, in the not be infringing patents. reserving certain stations for talks planning of broadcasting for talks and and other material not requiring a lectures instead of being confined to a wide frequency band it might then be maximum of ten or fifteen minutes, to possible to find room for the extension be extended, say, to half an hour, or of frequencies for special stations CONTENTS even an hour, so as to deal more pro- devoted to music. perly with the subject matter, provided It would be interesting if the B.B.C. Page that alternative material of a lighter Engineering Department would make character is always available on other Editorial Comment ...... 49 available a map of the country indica- wavelengths for the benefit of those The Time -base in Television .. 50 ting each transmitting station with the listeners who prefer it. service area which is claimed for it, Noise : Some Notes about Radio and see how far B.B.C. programme Enemy No. 1 . . 54 Better Reception distribution policy on this basis fits in Programme Mixing 56 We must not lose sight of the fact with the considered opinions of listeners Current Topics . . 59 that transmitters have improved in in the areas concerned. We believe The Physical Society's Exhibition.. 60 efficiency and at the same time highly that the B.B.C. to -day is far too con- sensitive receivers have been brought servative in its estimation of service New Apparatus Reviewed .. .. 6.3 down in price so that they now come area, because it does not appear to Eddystone All -World Eight 61 within the reach of a very much have appreciated sufficiently the change Listeners' Guide for the Week 66 greater proportion of the listening in reception, as well as transmission, Improving the Simplified Volume community. A few years ago it could conditions which have taken place. be argued, with a good deal of evidence Nor does it take into full consideration Expander . . 68 in support, that satisfactory reception that probably fifty per cent. of the 70 Random Radiations of the B.B.C. stations other than the programme material is of such a nature Broadcast Brevities 71 local transmitter was available only to that the highest quality of reception is Recent Inventions ...... 72 persons of considerable means, but not necessary to full enjoyment. 50 Wireless World, January 15th, 1937

The Tim e -b a s e By W T ` ° " °`

HOW SCANNING IS , EFFECTED in Television AT THE RECEIVER

N television transmission the subject AN essential part of all television receivers embodying cathode is scanned by a spot, which may be ray tubes is the time base, for it produces the voltages of light as in the Baird system, or may be the end of an electron beam necessary for building up the raster. In this article, the method as in the Emitron camera, which traces of operation of the conventional type including a gas -filled triode out a series of parallel lines. If the picture is described. is to be reconstituted correctly on the screen of the cathode -ray tube, it is neces- Fig. I, the spot must start at the left - sary for the spot caused by the impinge- The correct pattern is obtained on the hand top corner (A) and move steadily screen when the voltages on the deflect- ment of the electron beam on the fluores- across the screen to (B). It must then ing plates cent screen to make exactly the are of saw -tooth wave-form same return to the left -hand side of the screen, with, of traversals as the spot in the transmitter. course, the correct frequency, but to a point (c) slightly below (A), and Now the position of the spot on the then trace out another line to (D), and so screen can be altered by A deflecting the on until the full number of lines has been electron beam either electrostatically or completed. The spot is then at the point electro - magnetic- (E) in the right -hand bottom corner, and C g ally. Both it must now return to the original point (A) methods are used in order to trace out a second series of D and are some- lines immediately over the first. times combined. In television terminology, a line is one Electrostatic de- complete cross traversal of the screen and flection is prob- a frame is one complete vertical traversal ably the one more via the whole series of lines. The raster widely adopted, is the resulting rectangle composed of however, so that parallel lines. at first we shall consider only this. The conven- Fig. z. -A section of a raster is shown here tional cathode - in greatly exaggerated form. The spot ray tube has two travels along AB to trace out a line and then flies -back along BC in preparation for pairs of deflecting the next. plates built into it, and it is only phase, and amplitude. An ideal wave- necessary to apply form is that shown at (a) in Fig. 3. The suitable voltages voltage rises linearly along (AB) with to these plates to respect to time and then falls instantane- make the spot per- ously to zero along (BC) ; in practice, zero form any gyra- fly -back time is impossible, and the tions we please. waveform is more like that shown in (b). There is no figure Here the rise of voltage along (AB) is the or pattern which same as in (a), but the fly -back (Bc) occu- the spot cannot Fig. 1. -The raster is built up by the spot traversing a series of lines across the screen pies a finite time. The time (AC) repre- trace with suitable of the tube. sents one complete period of the wave. voltages applied The waveform given by a poor time - to the plates. This In actual fact the spot does not trace base is shown in (c), and it will be seen is because there out a pattern exactly like that of Fig. i, that the voltage rise along (AB) is no are two pairs of but one shown in greatly exaggerated longer linear. This will cause distortion plates at right form in Fig. 2. The spot moves steadily of the picture by cramping the right -hand angles ; with only from (A) to (B) and traces out a line which side. A perfectly linear time -base is The electrode struc- one pair of plates, is not quite horizontal. Having arrived probably impossible, and all types tend ture inside a cathode - the movement of at (B) it rapidly flies back to (c), tracing to give some curvature to the voltage ray tube : note the the spot is re- out the dotted line (Bc) ; the next line (CD) This is very small in a good time - two pairs of deflecting wave. plates. stricted to a is parallel to the first, and so on. The base, however, but careful design is straight line. actual time taken for the traversal of each necessary. When there are two sets of plates, how- line must be a definite figure, depending The circuit of a simple time -base is ever, we can apply two forces at right on the transmission, ' and must be held shown in Fig. 4, the valve being a gas - angles to the electron beam, and so cause constant within very close limits. The filled triode. This kind of valve differs it to move in any direction. time taken by the fly -back would ideally from ordinary hard valves in several For television purposes, the spot must be zero, but this is impossible; it must be ways. For our present purposes, its build up a raster on the screen by tracing very much less than the line time, how- most important attributes are that it takes out a series of parallel lines. Referring to ever. no anode current until the anode voltage Whpgsog JANUARY 15th, 1937 Worlld 51 The Time -base in Television - sequently none between anode and cases the high HT voltage will be needed rises to a definite figure, which depends cathode of the valve, which is therefore for other purposes. on the negative grid bias applied, and non -conductive. As soon as S is closed, A practical time -base is usually much that once anode current starts to flow however, there is a current through the more complex than the simple circuit of nothing will stop it but the removal of circuit, and the potential across C rises Fig. 4, but this is not because the basic the anode voltage. For instance, if we until it finally equals the battery potential gradually raise the anode potential there if the valve does not strike. This is shown will be no anode current until the potential by the curve (AB) of Fig. 5. reaches, say, zoo volts. The valve will then strike and pass a very heavy current Generating the Saw -tooth Waveform Now let us start again, and assume this time that the valve is adjusted to strike at an anode voltage much less than the (a) battery voltage. The voltage across the condenser rises along (An) as before until it reaches the value of the point (c). At this point the valve strikes and discharges the condenser ; its voltage consequently Fig. 5. -If the discharge valve failed to falls strike the condenser voltage would rise as shown by (CD), until the point (D) along AB. When it is operating it varies is reached and the valve again becomes along ACDEF. non -conductive. The condenser voltage (b) again start's to rise along (DE) ; when it circuit is different but because a time - reaches the valve (E), the valve again base generally includes a push -pull strikes and discharges the condenser until amplifier. Two time -bases are, of the voltage falls to (F), and so on. course, needed in a television receiver, It is easy to see that the rise in voltage one to produce the line scanning pulses during the charging stroke cannot be and the other to produce the frame linear, for the rise in voltage across the pulses. For reception of the Baird condenser increases exponentially. It is, transmissions the frame frequency is (e) however, possible to replace the resistance 25 c/s and the line 25 x 24o =6,000 c /s, ó R by a saturated diode, or, more usually, one cycle being reckoned as one charge a pentode. With such a valve the AC and one discharge of the time -basé con- resistance tends to infinity, which means denser, or the time (DF) in Fig. 5. For that the current through it tends to be the Marconi -E.M.I. transmissions, the independent of the voltage. By using a frame frequency is 5o c/s and the line Fig. 3. -The ideal scanning waveform is pentode instead of a resistance in the 5ox202.5= IO,I25 c /s. shown at (a) and a more practical form at (b). A poor waveform appears in (c). if the voltage is maintained. If the voltage is gradually reduced, the current continues until the voltage reaches a cer- tain minimum of perhaps 20 -40 volts, when it suddenly ceases. When the valve is conducting, the grid bias has no effect and the current cannot be stopped by increasing the bias. When the valve is not conducting, however, the anode potential at which it strikes depends on the grid potential, and the more negative the grid the higher the anode voltage required. Referring now to Fig. 4, suppose the switch S is closed. Initially there is no voltage across the condenser C, and con- An experimental double time -base for television reception is shown here.

charging circuit the condenser voltage Now in the cathode -ray tube it is rises very nearly linearly. necessary for the mean potential of each As an alternative, it is possible to retain pair of plates to be unchanging if inter- the resistance, but to permit the condenser action between the two sets of plates is to charge to only a fraction of the battery to be avoided. Such interaction results voltage. Inspection of the charging curve in distortion of the raster. A constant (AB) of Fig. 5 shows that the initial rise of mean potential can be obtained by feed- voltage is very nearly linear ; we can have ing each pair of plates in push -pull. At a linear time -base, therefore, by only the present time, push -pull working utilising this portion of the curve. seems almost essential when double Both methods are widely used, and electrostatic deflection is used ; it is not which is the better depends very largely essential, but may be desirable, when upon circumstances. As regards cost, we electro-magnetic deflection is used for have to balance an extra valve on the either or both of the scans. one hand against four or five times the HT The next thing we want to know is from the time -base, Fig. 4. -The fundamental time -base circuit voltage on the other. This is not really the output required using a gas -filled triode. a fair comparison, however, for in many and here those unfamiliar with cathode- 'Wfipasooopfll JANUARY 15th, 1937 The Time -base in Television - form shown in Fig. 6. The valve VI is although the normal voltage rating is ray tubes will receive a shock. The a gasfilled triode, and functions with RI exceeded, the anode current is not large. actual figure depends on the tube and and CI in the manner already described Most specimens of this type of valve its operating voltages, but is generally in conjunction with Fig. 4. The resist- stand up to the work well, and with a about I,000 volts! The sensitivity of a ance R2 is included for the purpose of valve such as the AC/P, a gain of the tube is expressed as so many millimetres accelerating the fly -back ; at first sight order of Io can be obtained, so that a deflection for i volt applied between the this seems impossible, but is actually voltage change across CI of only about deflecting plates, and it is usually in- true. Grid bias is secured from the versely proportional to the third anode resistance RI', which has a heavy cur- voltage. With a tube of about loin. rent fed through it from the HT supply diameter working at some 4,50o volts, via Rio. the time -base output required is about The saw -tooth wave appears. across (a) 1,000 volts. CI R2 as already explained, and is As a matter of fact, this is not quite as applied to the grid of the amplifier V2 bad as it seems, for it is the total change through the usual resistance-capacity of voltage required between the plates of coupling C2 R3. Amplified potentials the tube, or the voltage represented by appear across the load resistance R7, and (CD) (DE) (EF), etc., in Fig. 5. If we were are taken off through C5 to one of the ln) using a sine instead of a saw -tooth wave- pair of deflecting plates. A portion only form we should need an output of 5óo of the anode voltage of V2 is tapped off volts peak or 35o volts RMS. The and fed through C3 to the grid of V3, deflection with a sine -wave of 35o volts which thus provides across its anode load RMS applied to the plates will be the R8 an equal and opposite output voltage same as that with I,000 volts amplitude which is communicated to the other of of saw -tooth waveform, for the total the pair of plates through C6. swing of a sine -wave is twice the peak This is all quite straightforward, but it value, or I,000 volts. must not be forgotten that if the saw - 7.,7 tooth waveform is to retain its original TIME A Modern Time -base shape after amplification, the amplifier must be free from amplitude, frequency, The output circuits of the time -base, distortion. resistance Fig. 7.-A practical saw -tooth waveform is and phase With shown at (a). As explained in the text, the therefore, need not be designed to handle coupling the HT voltage must be greater fly -back can be accelerated by the insertion as large a voltage as one might at first than the total amplitude of the output of of resistance in series with the condenser. suppose. _If they will handle 35o volts one valve. . In this case it must be When the resistance is too high, the wave- RMS of sine waveform without form is that shown in (b) but like that of (c) ampli- greater than 500 volts, and as the full when the correct value is used. tude distortion, they will also handle the voltage cannot be utilised, at least loo 1,000 volts total change of the saw -tooth volts would normally be needed ; more 50 volts is needed. When we have waveform. 700- Moreover, if we use two often 1,000 volts is used. 1,000 volts HT available, we can easily obtain such a voltage with negligible departure from linearity, and we accord- ingly employ a charging resistance RI. For the avoidance of frequency distor- tion it is necessary to make the coupling condensers and grid leaks large enough, and to keep stray capacities at a mini- mum. The frequency range required is greater than one would at first imagine, for it must extend from the fundamental time -base frequency to something like twenty times that value. Phase distor- tion is avoided by the same means as frequency distortion, but the require- ments are much more stringent. One can safely say that if phase distortion is negligible, then frequency distortion is also negligible, but the converse is not necessarily true. Before concluding, it may be remarked that the frequency is controlled by RI and CI, and the amplitude by RI'. The controls are, however, greatly inter- dependent. Two time -bases are needed for television reception, of course, and need differ only in the values of com- ponents ; a common HT supply can be used, but good smoothing and decoupling Fig. 6. -In practice a push -pull type amplifier must follow the relaxation oscillator of Fig. 4 are required. in order to obtain adequate output for the deflection. In practice, minor modifications are adopted in different cases. A fixed re- valves in push -pull for the output, each The quiescent anode voltage of V2 sistance of 0.5 MQ is usually included in handles only one -half the output, so that and V3 is likely to be of the order of series with the variable RI of 2 M12 in each need give out the equivalent of 350 volts, and when giving full output it order to safeguard the valve. The con- only 175 volts RMS, Soo volts. may swing from loo volts to 600 volts. denser CI will usually have a capacity of A practical time -base for television pur- It is the general practice to employ 0.2 F. for the frame scanning and poses with modern tubes thus takes the valves of the MH4 or AC /P type, for 0.0005 µF.- 0.0015 µF. for the line. JANUARY 15th, 1937 WflpsIlmo '53 Woptd. The Time -base in Television Aerials for the short and ultra -short waves Communication," as it is described, is true - there is no The value of the resistance R2 is very have a chapter devoted to them, and some in every sense of the word, for types of directional aspect of the subject it does not deal with, in the case of the frame scan- novel and interesting important are discussed and illustrated with dia- and thus it forms a valuable handbook for is in- arrays ning time -base. Its function to grams giving constructional data. both the beginner and the experienced crease the speed of the fly -back, and it " The Standard Manual of Amateur Radio short -wave experimenter. H. B. D. does this in spite of the fact that it neces- sarily slows up the rate of discharge of the condenser ! At first sight this appears to be a contradiction, but it can be seen that the voltage applied to the amplifier is actually that across CI and TELEVISION RI in series. At the instant when the fly -back commences there is no current through RI, and the voltage applied to the amplifier is equal to that across Cr. IN ITALY If RI were not present this voltage would fall exponentially as Cr discharges. When it is used, however, the discharge current sets up a voltage across RI which New Safar is in opposition to the voltage across CI, and it is the difference between these Receiving voltages which is applied to the amplifier. If we examine the waveform of the generator we find that without resistance Equipment it is similar to that of Fig. 7(a). When RI is included the initial fly -back is very rapid, but if its value is too high the spot describes the loop shown in (b). When RI is correct the waveform is like that of (c). In the writer's experience RI is critical in the frame time -base and should be about 30 ohms. It is not always necessary, however, and it is generally better to omit it than to use too high a value. It is usually unnecessary if a r,000 -ohrp resistance is included directly in the anode lead of the frame discharge valve, as is sometimes recommended by valve makers in order to limit the dis- charge current. In the case of the line time -base, RI is THAT Italy is well to the fore in the much less critical and must be higher in design of television receivers is exem- value -1,000 ohms is satisfactory. plified by the illustrations reproduced here of the latest Safar equipment which was shown at the Milan exhibition. It consists of an ultra -short wave com- bined sound and vision superheterodyne Short-wave Manual receiver with a band width of 3 Mc /s and Handbook. -Four- it employs seven valves. The time base, The Radio Amateur's and power unit teenth edition. 536 pages with over synchronising apparatus illustrations and diagrams. Pub- together account for eight more valves, 50o in all. lished by the American Radio Relay making fifteen is designed for television League Inc., West Hartford, Connecti- The receiver Price i dollar in the systems of 375 lines and interlaced pictures cut, U.S.A. giving fifty frames per second. U.S.A., I dollar 25 cents elsewhere. IN order to include all the latest develop- ments in amateur radio, the 1937 edition of the A.R.R.L.'s publication, The Radio Amateur's Handbook, has had to be con- siderably enlarged, and it now contains 424 pages of valuable information on short- and ultra- short-wave technique. Over Zoo new illustrations have been added, and prac- tically every chapter has been revised and contrast control, sound output control and brought up to date. one for focusing the image. Apparently The design and construction of transmit- the tuning is pre -set, as there is no external ting apparatus takes up a large share of adjustment provided for this. the book, though the all- important matter As one of the illustrations shows, a very of reception is, nevertheless, dealt with at neat and compact assembly is adopted, the adequate length. cathode -ray tube being mounted in a sturdy The Handbook is essentially practical, metal frame which serves also to support the and adequate data is provided to enable loud speaker and control panel. The tube anyone to construct the apparatus so well is not viewed direct, but the image is described and illustrated in both the receiv- reflected in an inclined mirror mounted in ing and transmitting sections. Though com- the top of the cabinet. paratively high -power transmitters pre- Simplicity in operation is one of the prin- This new Safar television receiver is a dominate, there are many designs suitable cipal features of the Safar receiver, as only product of the Soc. An. Fabbricazione for operation with the limited power input three controls are provided. They are Apparecchi Radiofonici, of Milan, and the Mustomarily used in this country. on /off switch, with which is combined a price is 9,000 lire, or approximately ¡too. -t Wireless World, January 15th, 1937 Noise---Some Notes Abouì

By "CATHODE RAY"

N legal circles a " noisy " wireless set is one that is too loud, and which thereby constitutes a nuisance to the owner's neighbours. In the technical sense, however, noise is something for Some of the which possibly the neighbours are respon- possible sible is sources of and the wireless set the victim, and the various it is not bound up with the volume of classes of reproduction. Generally it is the pro- noises des- grammes that cannot be reproduced loudly cribed. Indi- vidual sources that are most affected by noise. Noise, are denoted by briefly defined, is anything undesirable reference . that is reproduced along with the desired numbers,, -. programme or signals ; except that other which are ex plained in the programmes or signals are generally dis- accompanying tinguished as interference rather than key. noise. When lay friends come to tell us of their noise troubles they report them all as " atmospherics," and think something of themselves for being so clever as to use the them, it very seldom right word. Alas for noises, of which there is a great variety - noise caused by the movements of elec- is right } When thunderstorms are in the buzzes, hums, whines, hisses, rattles trons in conductors and valves appears as only - immediate neighbourhood -usually almost as many sorts as there are electrical a hiss, familiar to every owner of a really a few days a year -then atmospherics cer- appliances. The domestic vacuum cleaner sensitive superhet. A very valuable article tainly are unmistakably present, even is a typical example. on it by A. L. M. Sowerby was published ; in when listening to the local station and Rather curious noises sometimes result recently.' More recently still one reads of thundery weather generally they may pro- from internal faults. Hum -low- pitched the work of V. D. Landon, of the Radio vide a noticeable accompaniment at least for AC and high for DC -are too familiar Corporation of America, who has been to distant -station reception. The descrip- to need description. An open- circuited investigating this class of noise. tion of atmospherics as " coal -cellar load- valve grid produces a characteristic Landon made up a pair of amplifiers on ing " noises has not been bettered, I think. " singing " usually composed of a mixture one chassis, each amplifier with five stages They are also rather like the sound of of low- and high- pitched hums. Various and a high gain per stage, so that the hiss waves breaking on a beach, except that types of groans, whistles, " motor -boat- due to the first valve was amplified until it they do not occur at anything like regular ing," and " frying " may be caused by more than fully loaded the last valve when intervals. sundry receiver faults. running " all out." The exact frequency It is this irregularity, and also the pro- By the way, I need hardly mention that to which the amplifiers were tuned was not longed tumbling nature of the " crash " or disconnecting the aerial is the standard 'so very important -actually they were grind," that distinguishes atmospherics method of distinguishing between internal what would be called IF amplifiers, work- from man -made (really machine -made) and external noise causes. But it is just as ing on the American frequency of 15o kc ¡'s noises, or internal faults. The nearest well to remember that even a noise due to -and both used band -pass couplings to thing to them is the rattle or clatter due to an internal cause may be modified, give a fairly level response over a band of a bad contact, which may either be in- reduced, or (more rarely) even eliminated frequencies and a very sharp cut -off each ternal (in the set itself) or in the electric when the aerial is taken off. side. They differed only in the fact that light or other wiring. The usual clue to one amplifier was nearly sixteen times as this common type of noise is that it gener- Technically Not Noise broadly tuned as the other. The object ally corresponds to a disturbing move- was to check theoretical calculation of how ment. Somebody walking about or bang- The " monkey chatter " caused by the the sharpness of tuning affects the amount ing a door may stir an electric house wir- side -bands of an adjoining broadcast sta- of noise ; or, what is more to the point, the ing fault to life ; the wind disturbs a bad tion may be classed either as noise or inter- ratio of noise to desired signal. This sort joint in aerial or lead -in ; and the time - ference ; and so may whistles. By calling of noise being left over after all avoidable honoured procedure when an internal bad them " interference " I can get out of hav- sources have been blocked up, it is im- is is to knock and contact suspected thump ing to say anything about them here ! portant to know as much as possible about the set and its parts individually and col- Lastly we come to a type of noise which its haunts and habits. lectively. is different from all others in being These are the results of Landon's tests. Most other intermittent noises are unavoidable if very high amplification is He found that if both amplifiers were sharper than atmospherics-more of the used ; at any rate, until somebody markets adjusted to the same signal gain the nature of clicks. Lifts and other machinery a convenient method of keeping certain broadly tuned amplifier gave about four making and breaking current are of this parts of the receiver at the absolute zero times the amplitude of noise, whether the type. Some sorts of electric signs cause of temperature (273 degrees below zero clicks at very frequent intervals. And so Centigrade), and then that wouldn't do for we come by easy stages to continuous valve noise. This basic, fundamental 1 The Wireless World, Oct. 9th and 16th, 1936. Wireless 'World, January 15111, 1937 55

completely during their impact. The programme is suppressed, too, so the success of the scheme obviously depends No. 1 on the noises being of a practically radio Enemy instantaneous character. Then there is the very complicated but (we are told) very successful system in- vented by Armstrong, which necessitates an entirely different sort of transmitter as __....._._-.--- well as receiver. It is rather too involved to explain in detail at a tail -end like this, but the general idea is that, instead of making the radiation from the transmitter ....,i...f .. fluctuate in strength to correspond with ! the programme or signals being sent out, it is kept at full strength all the time and varied in frequency. The receiver must be designed to translate these frequency variations into amplitude variations again ; and it is then found to be less responsive to noise than the orthodox type. But as this system takes up a much wider band of frequencies than ordinary broadcasting, it is perforce relegated to the ultra -short waves. Even here it will scarcely appeal to the domestic listener ; but more is likely to be heard of it for commercial work. The degrees of success that are being KEY achieved in rendering receivers immune 1. Electrical appliances from noise must not be seized upon by 2. Faulty switch contacts owners of interfering apparatus as an 3. Lightning (atmospherics) excuse to roll the onus on to the listener, for not only do most of the methods neces- 4. Motor -car ignition systems sitate a great increase in cost and com- 5. Traffic signals plexity (which has to be multiplied by on all (to use present -day peaks were measured 6. Illuminated signs the number of receiving stations affected), the root - mean - terminology) fronts. or 7. Trams and trolley -buses but the cure is only partial. Still, it is a square values (i.e., the Everybody knows about effective values used 8. Aerial touching branches suppressors, Post Office in AC measurements) 9. Defective aerial connection forms and vans, anti - aerials, were taken. As the 10. Arc across broken lamp interference broad amplifier filament screened television sixteen feeders, and proposed covered nearly 11. Faulty valve ; any stage times the band of legislation to compel (a) 12. Valve hiss ; chiefly first electrical noise -producers frequencies of the stage sharp one, this result to abate the nuisance. 13. Bad contact confirms the well - Where noises are, in the known theory that the meantime at least, un- amplitude of this sort abatable, it is possible to valve or circuit design the receiver so that they are of noise -fundamental (b) hiss -is proportional to the square root limited to a maximum equal to the signal. of the band width. But it was not pre- The " click " sorts of noise consist of a viously known quite so definitely that sharp peak lasting only a very brief the rule would apply to peaks. Incident- moment but perhaps many times the ally, the highest peaks were about four amplitude of the signal or programme. c times the RMS voltages in each case. So although it does not appear a very Rod achievement to reduce it no more Another Advantage of Selectivity drastically than to a condition of equality with the desired sound, yet the disparity (d) Landon also studied the effects of the in duration gives a better result than one type of noise coming in from outside and might think. being used consisting of sharp clicks. The interest- I remember limiting systems If the amplitude of a section of broadcast ing result emerged that, whereas the fifteen years ago, consisting simply of programme is represented by (a), the addi- RMS values of noise voltage at the output dimming the filament of a valve ; but the tion of interfering noise of the " click " such as is caused by many sources were still proportional to the square root thing has been much better thought out type Still, it only might look like (b). Note the high ampli- of the band width, the peaks were directly and applied since then. tude but short duration. A " limiting " ; be useful for making Morse proportional to the band width in the reckons to . system is of some help but cannot do better apparatus described they were therefore readable, and not for providing a back- than (c). A self- suppressing scheme which silences the receiver at the instant of the some sixteen times greater with the ground of complete silence for the of music. click leaves small holes in the programme broadly tuned amplifier. This shows the zesthetic enjoyment (d), but this is less noticeable than either importance of making the amplifier as For helping with that there is the (b) or (c). selective as possible, even apart from the " Q.S.T." system (described in The question of interference from other Wireless World, March 27th, 1936), which great thing that, when the need justifies, stations. makes the " click " shut the door in its some impression can be made on the only These various sorts of noise are being own face. The noises are lifted out of the remaining limitation to the range of radio tackled with considerable energy just now programme by suppressing the amplifier communication.

.56 Wireless World, January 15th, 1937 Programme M By RECENT DEVELOPMENTS IN THE DESIGN OF J. A. G. MITCHELL DRAMATIC CONTROL UNITS Design Section, The British Broadcasting Corporation WHEN broadcast plays were first produced, what amounted virtually to a new medium of artistic expression was born, and the technique of control introduced many new problems, some of which are still in process of the programme when instantaneous inter- solution. When the B.B.C. recently introduced a new dramatic control ruption becomes necessary. unit it was decided to extend certain facilities and to incorporate two new The mixing arrangements normally em- ones in the revised design. ployed in dramatic control units were such that each source of programme was separately controlled by a potentiometer, COMPOSITE programmes, such as would still mean a great strain on the and the outputs from these control multi- studio broadcast plays, are available echo rooms, so it was decided potentiometers were arranged in two produced by mixing the various to limit the number of echo rooms re- groups and connected to a central mixer. studio outputs together. This quired to one. It was then possible to fade out mixing is done on a dramatic control unit When producing certain types of play, either group on the central mixer. by a producer or his assistant. The general features of a dramatic control unit have been frequently described in various publications and it is not proposed to re- peat the description here, except where it is considered necessary to make clear the function of the recent additions. In the early types of dramatic control units, when it was desired to superimpose artificially produced echo on the pro- The front panel of the unit, showing right -hand and left -hand group controls. The indepen- gramme from any studio, it was necessary dent channels and mixers are mounted on the centre panel. to use one echo room for every studio re- quiring echo. This arrangement had the like the recent adaptation of " The Thin Usually an additional source was provided obvious disadvantage that there were not Man," certain effects are obtained by which was not associated with either always available a sufficient number of abruptly cutting the programme, or part group but which was combined with the echo rooms for the programme commit- of it. Hitherto, this has been done on the output from the central mixer. ments. When it became necessary to pro- fade potentiometers, and no matter how The circuit of this mixer originally was vide a new unit at Broadcasting House in agile the producer may be, the .effect such that, while one of the groups was 1934 the circuit was so arranged that only obtained is a rapid fade and not a clean - being faded out, the programme level from two echo rooms were necessary to give cut break. It was, therefore, agreed that the other group iémained constant, and the full facilities required. In the pro- the new unit should incorporate a key in vice versa. It was, therefore, not possible vincial studio premises, however, this each channel potentiometer circuit to cut for a producer alone to fade one group out and the other in on the central mixer ; INCOMING CHANNELS INCOMING CHANNELS INDEPENDENT when this was desired for a production in GROUP N91 GROUP N92 INCOMING CHANNEL the past, other operators were employed to r aid the producer by fading the individual t channels of one of the groups. In order to overcome this difficulty was CHANNEL CHANNEL it proposed MIXERS MIXERS to divide the central mixer into two con- trols, one controlling all sources on the ECHO CHANGE- ECHO CHANGE- OVER RELAYS OVER RELAYS left -hand side of the panel while the other would control those on the right - hand side. The methods by which the foregoing re- quirements have been met will now be CENTRAL MIXER described. The system adopted for producing echo effects in the dramatic control unit sup- OUTPUT plied to Broadcasting House in 1934 is LOUD SPEAKER 1 ECHO shown in Fig. 1. It will be seen that AMPLIFIER AMPLIFIER N91 two echo rooms are necessary, one asso- MICROPHONE ciated with the channels of group i and the other with the channels of group 2. LECHO,ROOM N91 As already explained, it was desirable, when designing the new unit, to arrange f Loup SPEAKER the circuits so that only one echo L ECHO room AMPLIFIER AMPLIFIER would be required. The N92 LI circuit was MICROPHONE therefore, changed to that shown in Fig. 2. This diagram shows two sources con- ,ECHO ROOM N92J nected to channels r and 4, while echo for these two sources is controlled via chan- Fig. Schematic diagram 1.- of a dramatic control unit of 1934 ; two echo rooms are used. nels 2 and 5 respectively. It will be seen JANUARY zsth, 1937 NW MUM 57 WópIld Programme Mixing- In Fig. 2, channel 7 is shown as the inde- be connected to the same side of the mixer that the output from each channel poten- pendent channel. Similarly, the two out- as that source. If this were not done tiometer is taken to a change-over relay. puts from the echo mixer are combined in when echo was being added on a pro- When this relay is inoperative the channel an amplifier having two inputs. The out- gramme and the central mixer was potentiometer is connected via the central put from this amplifier is taken to a loud faded from one group to the other, it would mixer to the output of the DC unit, but speaker in the echo room, where a micro- mean that the source would be faded out while the echo remained at full. strength. AMPLAIFIER AMPLIFIER B The sources are connected to the dramatic OUT1 OUT2 OUT,1 OUT control unit channels in the con- trol room by connecting the amplifier out- _L I .1 i_ 1_ _L put jacks to the input channel jacks of the CHANNE, CHANNEL unit with MIXERS MIXERS 4 double -ended cords. Two sets of input channel jacks are provided; one ECHO CHANGE- ECHO CHANGE- set is labelled " DC Input Direct," OVER RELAYS OVER RELAYS z while the other is designated " DC Input Echo." The programme contacts of these jacks -i.e., the tip and ring connections -are commoned, while the sleeve connec- IN1 IN2 IN1 IN2 tions of the " DC Input Echo " jacks are CENTRAL CENTRAL MIXER MIXER wired to the negative winding of their re- ECHO MAIN CONTROL CONTROL spective echo change -over relays. By con- OUT1 OUT2 OUT1 OUT2 necting the sleeve contacts of the ampli- IN3 .-`- MAIN fier output jacks to the negative of a bat- IN2 AMPLIFIER OUT IN1 IN2 tery and the positive winding of thé echo IN 1 ECHO change -over relays to the positive of the AMPLIFIER THESE MIXERS ARE same battery, the particular channels de- OUT MECHANICALLY COUPLED sired may be connected to " echo " when the sources are connected to the input

rLOUD SPEAKER echo channels in the control room. MICROPHONE AMPLIFIER Instantaneous Interruption MICROPHONE In order to meet the conditions outlined ECHO ROOM _J in the introductory paragraphs, whereby a sudden break in the whole programme Fig. 2. -The new control system, with only one echo room. or a part of it is required, a- " cut key " was introduced into the circuit immedi- when it is operated, the channel is con- phone picks up the programme. The ately after each channel potentiometer nected via an auxiliary potentiometer output from this microphone, amplified to and each half of the mixer. The method associated with the central mixer to an a suitable extent, is connected to the same of connecting the key is shown in Fig. 4. echo amplifier and thence to the echo amplifier input as the independent chan- A magnetic release has been fitted to the room. nel. Thus, with the channels connected key, which operates when the associated The central mixer, which virtually con- as shown in Fig. 2 the main output from channel potentiometer is faded out. The sists of four potentiometers electrically amplifier " A " is controlled by channel i switching for this is arranged on an auxi- separated but mechanically coupled to- and the amount of gether, is shown in Fig. 3. The four echo required for this outputs from this mixer consist of two programme is con- CHANNEL COMPENSATING main and two echo outputs. In order to trolled by channel 2. RESISTANCE combine the outputs from the main mixer Similarly, the main and the independent channel, an amplifier output of amplifier having three separate inputs is provided. "` B " is controlled by 4 channel and the INPUT amount of echo by CHANNEL OUTPUT channel 5. If it o c,OO should be required to LL add echo to the source CHANNEL FADE o connected to the inde- POTENTIOMETER pendent channel, any channel on either side Fig. 4.- Circuit of one channel, showing the operation of the of the mixer may be cut key. used for this purpose. If this is done, great care is necessary in liary row of contacts on the channel operating the panel to ensure that the potentiometer. This facility has been pro- appropriate echo channel potentiometer is vided so that the panel operator may faded in and out at the same time as the avoid having to release the key manually independent channel. if it is not desired to do so before the It will therefore be seen that echo for channel is faded out. It will also prevent these two sources is mixed in the echo mistakes occurring due to the operator amplifier and the mixture passed to the forgetting to release the key. The keys echo room. The strength of any con - associated with the central mixer differ o stituènt of the echo mixture may be re- from those associated with the individual IN1 IN IN1 IN lated to that of its direct source by means channels because it is necessary to break ECHO AMPLIFIER MAIN AMPLIFIER of the associated fade controls on the DC the output from the echo mixer at the unit. The fact that the DC unit is pro- same time as the output from the mixer Fig. 3.-Circuit arrangement of the central vided with a central mixer makes it essen- is broken. Thus the keys following the mixer. tial that the echo for any source should mixer have two sets of change -over con- 58 Wpidgeo * JANUARY 15th, 1937 WmIld Programme Mixing - The confusion caused by the loose use tacts, while those connected to the of for " specific permeability in terms of DISTANT channels have only one set.. that of air as unity," and also as a dimen- The central mixer in all previous sional symbol, is clearly pointed out ( §92b), RECEPTION has into an ana- NOTES dramatic control units has consisted of but not the author fallen logous error when he tacitly assumes that two potentiometers on the one shaft, and S it is exceedingly difficult at the present the specific heat of water is dimensionless? time to obtain information from they were so arranged that when one of (§ 78). The dimensions which this assump- Spain, I wonder whether any reader these potentiometers was being faded out tion assigns to " Thermal Entities " will not can help in solving a problem. Here it is: the other remained at maximum. In the be generally accepted without, at least, A friend who knows the country well gave revised design these two potentiometers some opposition. me recently what he described as a complete have been mechanically separated so that Useful tables of physical and engin- official list of Spanish stations. From 410.4 they may be separately controlled. It will eering constants are given, many of the down to 238.5 metres the list is in entire now be possible for a producer to mix the latter being the result of the author's own agreement with those published monthly in two groups of sources at whatever level experience. Mention must also be made of The Wireless World. But below this mark the valuable collection of reprints of rele- there is an astonishing difference. vant matter from papers and articles by On 201.1 metres, for instance, the pub- Rucker, Fitzgerald, Henderson, Heaviside, lished lists show only two stations, Albacete and Maxwell. C. R. C. and Santiago, rated at 0.2 and o.5 kilowatt respectively. In my friend's list there are no fewer than 33 small Spanish stations using this wavelength, nearly all with a Television Programmes rating between o. r and 0.2 kilowatt. The principal items only of each day's Then on zoo metres Radio -Alcala (0.2 programmes are given. The system kW) is the sole Spanish station appearing in to be used each day is given below the the lists with which we are familiar, though date. Transmission times are from my friend's contains a round couple of Details of the magnetic " cut key," which is 3 -4 and 9 -10 daily. dozen. If his information is correct, Spain here shown in the " operated " position. Vision Sound possesses -or did possess before the present 6.67 m. (45 Mc /s). 7.23 m. (41.5 Mc /s). troubles began -no fewer than 65 broadcast- he desires instead of being limited to a ing stations, the great majority being small straight fade on one group only at a time. FRIDAY, JANUARY 15th. relays working on one of two common wave- This new dramatic control unit will (Baird.) lengths. not be so large as the fifteen -channel unit 3, Friends from the Zoo introduced by David It may perhaps assist investigators if I supplied to Broadcasting House in Seth- Smith. 3.15, British Movietonews. give the names of a sample half -dozen of the 1934, 3.25, Cabaret. 3.50, Film. " unknown nor will it be equipped with the compli- stations " stated to be occupying 9, Gaumont British News. 9.10, Repetition of each wavelength. On 201.1 metres Malaga cated switching circuits included in that 3 programme. 9.25, Film. 9.35, Cabaret. (0.2 kW), Melilla (0.2 kW), Cordoba (o.1 unit for special overseas programmes. kW), Tarragona (0.2 kW), Gijon (o.z kW), With these exceptions and the modifica- SATURDAY, JANUARY 16th. and Ceuta (0.2 kW); on 200 metres, (Baird.) San- tions described above, the new unit will tander (0.2 kW), Toledo (o.z kW), Algeciras be similar in all respects to its predeces- 3, In Your Garden -The Construction of a (o.z kW), Valencia (o.1 kW), Salamanca Small Lily Pond : by C. H. Middleton. 3.15, sors. The time is rapidly approaching Gaumont British News. 3.25, Caricatures by (0.2 kW), and Pontevedra (0.2 kW). when it will be impossible to add more " Goodenough." 3.35, Cabaret and the Tele- Anyone who has tried of late for medium - facilities to this type of unit, otherwise vision Orchestra. wave American stations will agree that con- been very the finished product will be too cumber- 9, Repetition of 3 programme. 9.15, British ditions have patchy. On many some for operation by one man. Movietonews. 9.25, Repetition of 3.25 and nights there is very little to be heard from 3.35 programmes. the United States. And then after perhaps a long period of disappointment one finds a MONDAY, JANUARY 13th. night on which they are to be heard " all (Marconi-E.M.I.) round the dial." On these good nights the BOOK REVIEW 3, Arts League of Service. 3.20, Gaumont strength of some U.S.A. stations is phen- Cartoons. The Theory of Dimensions and its Applica- British News. 3.30, Cabaret omenal. WBZ is generally the star, coming tion for Engineers. By Dr. F. W. Lan - 9, Repetition of 3 programme. 9.20, British in at almost local- station strength. But it Movietonews. 9.30, Repetition of 3.3o pro- does not stand alone, for full loud speaker chester, F.R.S. 314 + xxiv pp. Pub- gramme. lished by Crosby Lockwood and Co., volume may be obtainable from WCAU, Ltd., London, 1936. 12s. 6d. net. TUESDAY, JANUARY 19th. WOR, WPG, WHAM, WTIC, KDKA and several others. THE appearance of this book is timely, (Marconi- E.M.I. ) 3, Elisabeth Pollock Impressions. 3.5, If ,the- U.S.A. stations are uncertain, those since the International Electrical Corn - - in South America are generally much more of 1935 has provisionally decided Musical Instruments-II. 3.20, British Movie - mission " reliable. It -is rather curious that the South to adopt the M.K.S. (Giorgi) system of elec- tonews. 3.30, Scenes from the Lyric Theatre production of " Charles the King." Americans so often come in well when the trical units," as we read in the preface 9, Repetition of 3 and 3.5 programmes. 9.25, North Americans are poor and vice versa. (p. xiii). It is not clear whether this is in It is also very fortunate for the long- distance in place of, C.G.S. Gaumont British News. 9.35, Joan Luxton's addition to, or the Children's Theatre Company in " Cinderella " man, for heterodyne and jamming would " absolute " system, but in either event it as presented at the Embassy Theatre. otherwise ruin many transmissions is time to take stock and clarify our ideas. Italy, in addition to building a new and The reader of this book, unless he has a WEDNESDAY, JANUARY loth. group of (Marconi-E.M.I.) much more powerful short-wave very exceptionally logical and tidy mind, transmitters, is determined to increase the will be surprised at the loose and incon- 3, Russell Swan -the Theory of Magic Ex- number of her medium -wave stations. There sistent notions he has hitherto been content pounded. 3.15, Film. 3.25, 21st Picture Page. 3.50, Gaumont British News. is to be a new station in Sicily and another to entertain and the pitfalls whose exist- at Ancona. Where the wavelengths are to Re- ence he never realised. The author im- 9, Yvonne Arnaud at the piano. 9.15, come from it is rather hard to see unless the partially reviews the many systems of petition of 3 programme. 9.25, British Movie - tonews. 9.35, 22nd Picture Page. new stations are to be used as relays and to physical units and entities which have been work in synchronisation with their parent proposed from time to time, as used not THURSDAY, JANUARY 21st. transmitter. D. EXER. work, also in only in electrical but (Marconi- E.M.I. ) ; many mechanics and thermodynamics " 3, Fashions in Furs-A Display by Mannequins. views are expressed and ventilated, no posi- - 3.10, Masks and Mimes. 3.25, British Movie * [The small power of the transmissions and tive conclusion is recorded " (p. xv). How- tonews. 3.35rGeraldo and his Orchestra. the inability to resolve any worth -while signal ever, Dr. Lanchester has given Perry's 9, Repetition of 3 and 3.10 programmes. 9.25, from many stations working on a common " Engineers Unit of Mass " the Slug, a hard Cook's Night Out. 9.40, Gaumont British wavelength are reasons for the omission of knock, and has scored a hit clean over the 'News. 9.50, Eric Wild and his Teatimers with these stations from the lists we publish at pavilion ! Ann Lenner. intervals.-En.] Wireless World, January 15íh, 1937 .59 CURRENT T OPICS News of the Week in Brief Review America's Wireless Tax The building of there is no the new broad- ALTHOUGHlicence fee for wireless users casting station in recently erected the U.S.A. the Government at Dairen, Man- gets money from listeners in an chukuo. A special indirect manner, for it levies an radio exhibition, excise tax of five per cent. on at which the receivers, gramophones, and G.E.C. has a other domestic electrical equip- stand, is being ment. In 1936 this revenue staged in the amounted to five million dollars. station buildings. A Floating Service Station down from the various cricket WHAT is probably a unique grounds depot for servicing wire- direct less receivers exists in Alaska. to the wireless New Radio Link vice, has recently been on and cable headquarters, and the It is housed in a yacht off the an aeroplane coast, and belongs to a Seattle ANEW regular telephone ser- tour of India service has proved so effective vice has been inaugurated and the neighbouring Dutch that the fall of a wicket is known radio firm. Apart from ser- East Indies in connection vicing radio receivers possessed between Rome and Addis in London almost as soon as the Ababa. with plans to develop Indian dismissed batsman has arrived by the scattered population of broadcasting. The system in use this part of the world, it also back at the pavilion. Oslo Radio Exhibition in the Dutch East Indies is simi- undertakes repairs to the trans- lar to Coronation Illuminations mitting THE habit of holding wireless that suggested for India. and receiving apparatus The proposed Indian system in- ELECTRIC installed on board various ships. exhibitions seems to be on lighting w i 11 the increase. The latest country cludes the provision of a first - naturally play an important New Tunis Station to join the ranks is Norway, and class service over a restricted part in the decorations for the ASUM of ten million francs an exhibition is to be opened at area by four medium -wave Coronation in May. Flood- has just been set aside by Oslo to -day (January 15th), and stations. The limited nature of lights, neon tubing and plain the French Government to build will remain open for a fortnight. the range as compared with and coloured lamps will be a high -powered broadcasting The leading feature of the ex- broadcasting in this country is employed on an unprecedented transmitter in the neighbour- hibition will be a demonstration because of the heavy atmo- scale by local authorities, hood of Tunis. The station will of television, using German spheric interference in India. trade associations and other What is described as a second - bodies, as be erected on high ground and apparatus with 375 -line scan- well as by private will probably have a power of ning. The exhibition authorities class service is to be given by individuals. To -day's special from 120 to 150 kilowatts. It is are consequently anticipating means of four short-wave issue of the Electrical Review likely that it will be.ready for that at least 50,000 visitors will stations. forms an illustrated guide to the products preliminary tests by the end of attend the show. In view of the New French Scheme of over a hundred the year. fact that there are less than a manufacturers of illuminating UNDER the new system of devices and equipment. It grouping French broadcast- also contains special articles ing stations, the fourteen prin- putting forward suggestions for cipal State transmitters are decorative schemes. arranged together as follows :- Group A : Radio -Paris, Bor- S.B. to All Stations deaux, Nice and Montpellier. A WORLD -WIDE link -up of Group B: Paris (PTT), Mar- broadcasting stations is to seilles and Grenoble. take place on January zoth on Group C: Eiffel Tower and the occasion of the inauguration Lyons. of Franklin Roosevelt's new Group D : Strasbourg and term of office as President. Rennes. What is Your ? Group E : Lille, Toulouse and Wavelength Limoges. ACCORDING to reports re- No two of these station ceived from France, M. de groups will have the same type Martini, a well -known scientist, of programme on the same even- has stated that the various cells ing, but one or other type of of the human body radiate transmission may be repeated a electro- magnetic waves which second time within a week. It are in every respect similar to AN AUTOMATIC TIME SWITCH is fitted to this new German Tele- wireless ones, funken receiver. The time at which is hoped that the economy of except that they the mechanism is set to switch on are very much or off is shown by the indicator above the built -in clock. talent and money thus achieved shorter than any may result in a better standard so far used for wireless com- Preparing for 1941 quarter of a million licence - of programmes. munication. The wavelength THE first stone of the building holders in Norway, this shows varies between zo and 45 to house the great Italian very great confidence, although The Test Matches millimetres. In conditions of ill - exhibition, in which radio and doubtless many visitors will THE arrangements made for health it has been noted that television are to play a very pro- come from the neighbouring conveying news from Aus- these radiations are altered in minent part, was laid recently country of Sweden. tralia to this country in connec- wavelength, although it is not by Mussolini. This exhibition, tion with the series of Test yet clear whether this is a cause which will be held in Rome in Indian Broadcasting Matches now being played are or an effect. It is said, how- 1941, is intended to exceed any MR. C. W. GOYDER, the said to be more elaborate than ever, that these discoveries open so far held from the point of well -known chief engineer anything hitherto attempted. up an entirely new field of view of size and importance. of the all -India radio ser- Special lines have been laid therapy. Go Wireless World, January 15th, 1937 The Physical Society' feature of the Claude Lyons wavemeter and mains or battery operation is now avail- Many Important Type 724A, so that increased accuracy by able by an internal change -over plug. An interpolation is possible from the readings interesting feature is the provision of a Developments in given by the 2700 scale. The indication is spring stop on the attenuator to avoid acci- by valve voltmeter, and the range of 16- dental damage to the thermo-couple in the 50,00o kc /s. is covered by seven interchange- monitoring meter. Radio Measuring able coils housed in robust bakelite mould- ings. In the Marconi -Ekco Type TF37o pre- Apparatus cision wavemeter the tuned circuit is con- nected in the anode of an RF pentode and L coupled to a high- impedance valve volt- meter. Sensitivity control is provided which FOR many years now the wireless in- enables a high degree of frequency dis- dustry has been represented by a crimination to be obtained. To eliminate steadily increasing proportion of the temperature effects duralumin plays an im- exhibits at the Annual Exhibition of portant part in the construction of the con- Scientific Instruments and Apparatus at the denser, which is driven from a worm reduc- Imperial College of Science and Technology, tion gear. The coils are self- contained, and South Kensington. Those who were fortu- are mounted on the turret principle, which is nate in being able to visit this year's Ex- an important feature of many of this year's hibition on January 5th, 6th and 7th will Marconi -Ekco instruments. agree that the advance both in quality and Standard signal generators may be re- variety of those instruments which may be garded as developments of the fundamental regarded as the fine tools of the research wavemeter, and this year big improvements worker and manufacturer was a stride where are to be noted in ease of handling and in previous years it had been a step. The accuracy of calibration, particularly in the Protection from overload is afforded by a accumulated experience in the use of signal maintenance of modulation depth with mechanically operated tut -out in the Model generators has resulted in the development change of audio -frequency. The new G.R. 7 Avometer. of vastly improved types, and the influence Type 605A standard signal generator shown is a good of television and short-wave reception is re- Lyons is The Marconi-Ekco TF390 ex- by Claude a very fine example of ample new flected not only in the cathode -ray tube the latest practice. has a range of of the short-wave signal genera- It tors which are appearing as a result of the exhibits, but also in 9.5 kc /s to 3o Mc /s in seven bands, which, the extension of the increased activity in the spheres of television instead of plug-in coils, are now selected by and frequency range of means of a switch. The instrument is short-wave reception. The range is 20 Mc /s, is amplifiers, variable entirely AC operated, but can be rapidly con- -100 and the output brought out frequency oscillators verted to operation if to terminals at the end of a flexible screened battery desired. The cable. and wavemeters. power supply unit is controlled by voltage Fundamentally, the arrangement of the circuit is the same as that of the standard regulators of the saturated core type, and the signal generator, voltage output is constant within ±o.t micro- but the monitoring meter is in this case an acorn valve voltmeter. The Claude Lyons volt below 3 Mc/ s and not more than output range of instrument is from 1 G.R. precision ±0.4 microvolt at 3o Mc / s. The external the wavemeter Type microvolt 0.1 modulation characteristic is within to volt. 724A. The inter- flat i db. Plug -in coils are used in the from 15,000 cycles, and a further im- Claude Lyons changeable coils 30- Type 6o4B short-wave signal generator to provement is to be found in the provision are rotatable. cover a range from 3 to too Mc of a buffer valve to prevent reaction of /s. A the capacity attenuator is attenuator setting on the carrier oscillator. arranged to give con- There is little doubt that the wavemeter tinuous adjustment of output from 5 to A very useful feature of the latest Type 10,000 microvolts is the fundamental instrument for all TF144 Marconi -Ekco standard signal genera- which appears at the end of a detachable screened lead. A useful branches of wireless activity, and the instru- tor is an auxiliary fine tuning control ments shown ranged from laboratory sub - to facili- adjunct is the rod antenna sectionalised into accurately calibrated and designed three lengths giving field strengths in standards of phenomenal accuracy and tate the checking of selectivity curves. The the ratio of 1, to and too with a constant input stability to simple absorption instruments frequency range of the instrument is 85 kc /s in workshop of 1 volt. designed for rapid checking the to 25 Mc /s covered by eight coils selected or in the field. Among the service test oscillators the The very beautiful Sullivan -Griffiths Weston Model E692 is worthy of note. This dynatron oscillating wavemeter (range : too - compact oscillator is provided with a series 30,000 kc /s), with its stable inductance of plug-in coils giving a range of funda- standards and frequency stability of two mentals of too kc /s to 25 Mc /s. parts in a million, is now provided with a Continuing our examination of what may direct- reading scale giving an accuracy of be termed " sources " we come to audio - 0.01 per cent. for " rough " measurements oscillators, in which a widely increased where the ultimate accuracy of 0.003 per range is required for measurements of tele- cent. by interpolation methods is not vision apparatus. An example of the type required. Direct -reading interchangeable of instrument which this new demand is scales are also fitted in the new Type RBoo likely to produce was provided by the universal wavemeter (range : 30- 15,000 Marconi -Ekco beat frequency microvolter kc /s), which can be used as an absorption Type TF336. The present frequency range or dynatron wavemeter without change of of the instrument is 50- 150,000 cycles, but calibration. Of special interest, in view of we understand that it is hoped shortly to the advent of television, is the new Sullivan extend this range to 3 Mc / s. The output is absorption wavemeter with a The new G.R. standard signal generator Type 2.5 microvolts to 3 volts controlled by a sub -standard 6o5A is entirely AC operated and covers the range of 5 -42 metres. A valve voltmeter range 9.5 kc /s to 3o Mc /s without the use of twin unit attenuator. detector is provided, and a direct-reading plug -in coils. For normal acoustic work the Claude accuracy of o.ot per cent. and 0.03 per cent. Lyons Type 713A beat frequency oscillator by interpolation is possible. internally by a rotating turret. The RF has the very wide range of to- 20,000 cycles Straight -line frequency variation is also a. screening has been considerably improved, on a single scale. A subsidiary control gives eless World, January 15th, 1937 6:

speed meter movement is calibrated directly Marconi -Ekco Type TF329 indicates values in db. for a 50o -ohm load and the correction of " Q " from 25 to 5co on a special open chart is povided for other loads between 5o scale, and has a frequency range of 5o kc /s and 5,000 ohms to 50 Mc Is-again provided by a turret of Among DC and power frequency AC eight coils. The range of the Salford meter Exhibition meters the Model 7 Avometer is of special is 20 -500 for "Q" and fco kc /s to 5 Mc /s interest. It has no fewer than 46 ranges for frequency. incremental variations of ±50 cycles at any which include scales for capacity measure- Special test sets for the direct measure- part of the scale. The output is 13o volts ment and power output, the latter with a ment of capacity are no novelty, but the on open circuit or 2 watts into 2,000 db. scale referred to 5o milliwatts. Instead Sullivan -Griffiths logarithmic capacitance ohms. A balanced push -pull detector circuit of the customary fuses this instrument is bridge is an instrument of unusual refine- is employed, and the harmonic content above protected from overload by a cut -out which ment. It makes use of the special form of too cycles is less than i per cent. Means depends for its action on the inertia of the condenser employed in the firm's beat oscil- are provided for checking the performance to pointer. The latter is not rigidly connected lator and has a remarkably open scale for ensure that unsuitable load conditions will to the moving coil but is held by a spring small capacities -of the order of ¡in. be- not result iu increased harmonic content. mechanism. Any abnormal acceleration of tween I micro -mfd. divisions near the zero Muirhead and Co., Ltd., have introduced the coil causes a deflection relative to the end of the scale. The range is from a resistance- capacity controlled audio oscil- needle, which releases a pawl and opens the I micro -mfd. to 200 mfd.- direct reading - lator employing an improved type of circuit breaker. In general, the cut -out with a uniform accuracy of 0.2 per cent. circuit due to Dr. N. L. Yates -Fish. A fre- operates an overload before the needle has throughout. Another instrument deserving more than one -third of the scale. quency range of is obtained by a traversed special mention is the Cambridge high - to-t -beat move- single sweep of the variable air condenser For many measurements dead frequency capacity meter, which is also of ments, which are at the same time quick in and the instrument covers 20- 20,000 cycles the bridge type and is energised by a self - in three ranges. The oscillator is mains action, are required, and Ernest Turner contained battery -driven oscillator Ltd., were showing with a operated and has an output of watt. Electrical Instruments, frequency of the order of 200 kc /s. The some fine examples of this type in 24in. and So much for calibrated sources of input. scale is calibrated from o to 500 micro -mfd., 3¡in. sizes. Zero to full scale occupies only Valve voltmeters and other means of mea- and there is a range switch giving six 82 milliseconds and the over -swing does not suring the output as modified by the multiplying factors from x o. t to x5. A I millisecond. apparatus under test appear logically to exceed centre zero galvanometer indicates balance, come next for consideration. With few Rectifier type AC meters with millivolt suitable input and the accuracy of scale reading is of the exceptions all modern valve voltmeters are ranges and making use of same order as are now available, and that of the bridge dial. The mains operated, and in all cases it will be transformers overall accuracy is 0.5 per cent., of this type were shown by Elliott and on the found that special precautions are taken to examples lowest range (5o micro -mfd.) capacities can keep the input impedance high. In re- Bros. As regards the rectifiers themselves the model be measured to 0.2 micro -mfd. designed Muirhead valve voltmeters for both Westinghouse have introduced a new The size, which is de- routine testing of condensers should mains and battery operation the grid ter- in the iomA instrument be greatly the addition of extra ele- facilitated by the Tinsley Type minal is mounted in a mica window and the signed to permit 45(15 RF capacitance and if this is subsequently desired. power -factor window and the grid condenser is sulphur ments tester. Lu this instrument The Cambridge versatile galvanometer a direct reading with special thermo- of power factor is given on the scale of a can now be supplied self-contained for addition or replacement, in reflecting galvanometer which junctions, forms parts of the sensitivity is adjusted at the a valve voltmeter across a which tuned circuit energised from works to conform with the scale of the instru- a I,000 kc /s Everett Edgcumbe and Co. Oscillator. A measure of capacity is ob- ment. Finally, tained by the reduction have developed an electrostatic voltmeter of the standard the HT circuits associated With tuning condenser, the dial of which is pro- for testing vided with -ray tubes. This instrument has adjustable limit stops. The cathode valve voltmeter deflection ranges of 0- 2,000, 0 -4,000 and o -8,000 volts gives a measure of the " goodness " and the instrument has been arranged to of the condenser and of about 200 microamperes at interchangeable scales carrying appropriate take a current calibration curves, full scale deflection on each range. or a general scale with Both in the laboratory and test room a series of curves for interpolation may be for measurement of fundamental used. bridges in electrical quantities are essential, and Before leaving test gear the Marconi -Ekco this category the Type TF373 universal - Type TF339 inter -electrode capacity test impedance bridge shown by Marconi -Ekco is a good example. Marconi -Ekco coil magnification meter and makes use Type TF329. It is mains operated of the Maxwell circuit for induc- insulated. An important feature of these tance and the usual ratio arms for instruments is that the meter scale is linear capacity -resistance measurements. above 0.2 volt. The mains models have The appropriate circuits are three ranges, viz., o -2, o -To and 0 -50 volt. selected by a single switch, and for The Weston Model 669 is an AC operated AC measurements a self -contained instrument with six ranges, the lowest of oscillator provides a frequency of which is 0 -1.2 volt and the highest o -16 1,000 cycles. The overall ranges volts. The calibration accuracy is stated to avaiable are o-roo henries, o -too be within 3 per cent. from 4o cycles to 50 mfd., and o -t megohm. The scales Mc is and the input capacity has the excep- and range switches are calibrated tionally low value of 4 micro -mfds. directly in inductance, capacity, Although the instrument was not available and resistance, and the bridge can when we visited the stand, Claude Lyons also be used for the measurement now list an ultra- high -frequency valve volt- of power factor and coil magnifi- meter employing a " probe " containing an cation. RCA micro -wave triode valve. The Special meters for measuring accuracy of this instrument is given as 1 per coil magnification were shown by Cossor wids -range television line amplifier. cent. from 20 cycles to 50 Mc /s. Marconi -Ekco and the Salford Elec- With valve voltmeters we may include trical Instrument Co. In principle these set should be mentioned. A known voltage output power meters and in this category depend upon the injection of a known from a too kc /s oscillator is applied through the Marconi -Ekco Type 34o is a good voltage in series with the coil under test and an attenuator and the capacity under test example. The input is variable from 2.5 to a high- quality air condenser. A valve volt- to a tuned circuit the dynamic resistance of 20,000 ohms and the range is o. t to 5,000 meter indicating the volts developed across which can be adjusted to a known value. milliwatts. In the Type 586 G.R. power level the tuning circuit is calibrated directly in The volts developed across the circuit are indicator shown by Claude Lyons, the high- coil magnification units (wL /R). The indicated by a meter preceded by an 62 WIp®Il@g0 JANUARY 15th, 1937 ÑOpIlI The Physical Society's Exhibition- sound is controlled to give a non -directional expansion incorporating a circuit due te amplifier, and for a standard deflection the characteristic. The earphone is of 35 ohms Mr. C. E. Palmer Jones in which exact sym- attenuator is calibrated to read capacity. impedance, has a sensitivity of r,000 bars metry is achieved by using a negative feed- The range is from o.000r to r micro -mfd., and suitable valve adaptors are provided. Valve bridges are important items of works +10 aaa..aa. a.a.asa.i IMIaa..aa. +Io and instruments incorporating +9 saM..saUMaa a .la.saal..l aaaaaa..MIIaa.. +9 equipment, a..MIaa. aaa.aaaa.aMaasa=.ai aaasaalaasaal.asasaIII.asrn +8 bases for all current types of valve were +B aaaaaaaa. 111aaaaaaaaaisaaaasa.a aaasaMaasaU. +7 ----811-81111111--aa..aaaaa. aIN..sW.i aasaaasaala.aaasaIMa.saII.. +7 shown by Automatic Coil Winder and +6 402 -A. MICROPHONE a..asuaasaai a.aaa..aIMa.sa ....i +6 aasasaa s 'aaa..\aa.. +5 Electrical Equipment Co., Ltd., Everett +5 sa TYPICAL CHARACTERISTIC. sasaaaasaaa..saINaa aaaaaaaazsr.¢a ..Oaa \.. Edgcumbe and Co., and Marconi -Ekco. A +4 sa..saaasaalaasaal.a sasaaaasaa sr/ .saas 1a. +4 +.3 sa.asaaa saaaaaa. aaaaaaaWfivMsaaaaa/1I..aa1 .. +3 of asaasaaaa sasaaasaa u +2 noteworthy feature the latter instrument Vf +2 sa.asaa. saaasaaaa .ar...aaNaiao.a.rsa sSMaaaM.. .a=a.as 118a. is that the valve sockets, which naturally Ij +1 saa.asaa1Masaaaaaaaaa saalaa.Z..ala. nmiiimm =r ,: +1 aaalaaaa %S.saa..a.Ca 1 o come in for a good deal of hard wear, are D saa..aaINI.QII6Msaa.asa.111 . -1 saaaasasaa ï w aaa.asaasa ::C::5;::, replaceable. Ci asas aa.a saaa.aaa -2 2 o° 90° aria ANGLE IN aa..aaa..aasaa a.sa.1m[1 Among new valves were noted the Mazda 3 aala. DEGREES a.. 3 -MIME =MIMEaala.-saal.asaalll IMaaa..saar 4 V312 and PA2o non - microphonic mains - 4 aO.a o MN aasa. MMsa aaasa.l. aMaa aal.rIMIIaaa.asaMa 1 5 operated triodes and the Mazda " acorns," 5 MUMMER 60 aala.-saaaasaala.MIMIsaa..aaa.S, 6 aaa 90 aa.. MIIsaIN..saa.. 6 applications of which were exhibited in the asii I50 aa.. IIMsaa..saa.. 7 7 MICROPHONE asas a=. IMMaa..saa.. forms of a " probe " voltmeter and a low - 8 asas 180 aa.. saIMaaa.. 8 a.aa..sa=11Maa.. .Ma..saa..a a a.. 9 powered 7o cm. transmitter. -9 saaaaaaaaa811öii a s a.. a a a.. asaa.. sIIII.. a a a.. -10 sasaaaasaa saIN.asUaa aa...aaa.111 p Cathode -ray technique, as might be ex- s N p. ± N A VmN O O O OOV00t00 8 o $ § pected, was well to the fore, though the s$88o 8 8 8 8x88° emphasis was on applications to engineer- FREQUENCY - P'S. ing problems rather than to television. Apparatus in which a transient auto- Response curves of Standard Telephones Type 4o21A microphone for five angles of incidence. matically. brings up the beam to recording The maximum deviation between 4o and zo,000 cycles is 6 db. brilliance with a time lag of less than a Tele- micro -second was shown by Standard per volt, and is flat within ± 5 db. from back amplifier for the expander with the phones, and a similar principle was a feature loo to ro,000 cycles. same constants in the feed -back circuit as of the Cambridge Instrument three- element The sensitivity of the Muirhead -Williams those used in the volume- compression con- oscillograph. microphone, in which the bulk of the micro- trol. The idea was developed primarily to phone is removed from the sound field by overcome line noise, but it could be ex- the use of a long narrow conduit, has now tended to broadcasting or gramophone been increased to 5 millivolts per bar, which records if listeners were to adopt a is comparable with that of any high -fidelity standardised form of expansion control in microphone, and it should find wide applica- their receivers or amplifiers. tion in work where it is desirable to avoid The remaining exhibits dealt with disturbance of the wave -front. cathode -ray research. The B.T.H. Research At this Exhibition on generally finds some Laboratories showed a method of plotting instances of wireless technique being bor- potential lines in the electrode system by rowed by other trades and professions. As immersing a large -scale section of the an example, the Salford electric micrometer elements in an electrolyte arid following the may be cited. This instrument was designed equipotential lines with a probe electrode for keeping a check on thickness and /or connected to a pantograph. Methods of alloy constitution in foil -rolling mills, and measuring screen surface charges, and a is, in effect, an application of the principles special tube design for transient recording, of screening. Pairs of coils mounted in a working with voltages up to 15,000, were yoke are placed in opposite sides of the foil among the Edison Swan research exhibits. as it emerges from the mill, and one pair The G.E.C. Laboratories, Wembley, were is supplied with constant current from an showing special tubes with fluorescent oscillator at about 12 kc /s. The other pair screens illustrating the principles involved is connected to the rectifier and meter, in the electron multiplier, and a really and the DC is a measure of the thickness beautiful device known as the electron Non-directional moving coil microphone and resistivity of the foil. shown by Standard Telephones. Among subjects of allied interest deaf aids undoubtedly hold an The Cossor stand was devoted exclusively important place, and to cathode -ray apparatus, and the exhibit on the Multitone included some newly designed film and drum Electric stand the cameras, single- stroke time bases, and a novel triple high- vacuum oscillograph em- ploying cylindrical tubes housed in zin. Salford electric micrometer f o r diameter Mumetal screens. A link with checking the thick- television was established on this stand by ness and composi- the exhibition of a wide -range line amplifier, tion of metal foils. designed for battery operation, with an overall gain of Zoo and a frequency range microscope for viewing what might be from to cycles to 5 Mc /s. latest designs, incorporating automatic volume termed the " emission texture " of a It was disappointing to find so little control and negative reaction for both tone cathode surface. Two discs with r mm. reference to work in conjunction with loud and volume controls, were shown. Research apertures spaced r mm. apart are supplied speakers, a very intriguing demonstration into the type of characteristic required for with suitable potentials which give the elec- promised in the research section having different types of deafness is being carried trical equivalent of a microscope immersion failed to materialise at the last moment. out by a new form of optimum amplification objective. The assembly is sealed into a Some really excellent earphone quality was meter in which the response and general tube at the appropriate distance from the heard, however, at the Standard Telephones level under actual listening conditions can cathode to be investigated and throws a stand, where a new moving-coil microphone be independently controlled for both ears. magnified image of the emission on a and an earpiece constructed on parallel lines If the exhibits in the Research Section did fluorescent screen. Two tubes comprising were demonstrated in conjunction with the not prove this to be a vintage year for wire- different methods of depositing the oxide Standard OB amplifier. The microphone less enthusiasts they could have no reason coating on a cathode were shown side by (Type 4o21A) is spherical, with an opening to complain of less than their fair share of side, the images, resembling micro- photo- at the top surmounted by an acoustic screen interest. The Post Office exhibits included graphs of metallurgical specimens, being of in which the ratio of absorbed to transmitted a demonstration of volume compression and striking brilliance. Wireless World, January 15th, r937 63

Both these units have been tested and found satisfactory in every respect. The oscillator functions correctly on both medium and long waves, and the signal-circuit coils New Apparatus are closely matched in inductance so that good preselection can be obtained. Recent Products The inductances of both sections of the oscillator coils in the two - and three -gang models agree satisfactorily with the maker's of the Manufacturers figures, which are the correct ones for Reviewed accurate tracking with condensers having shaped vanes in the oscillator section. M.R. PIEZO- CRYSTAL MICROPHONE is employed, it does not give rise to noise The coils are well made and the design IN the construction of this microphone in operation in ultra short -wave sets, and is such that their assembly in a set is easily special precautions have been taken to from examination of its construction it arranged. The wavechange switches are fit- design a case that will be non- resonant, so should continue to prove satisfactory after ted with non -oxidising contacts and are of that the effect of enclosing the crystal unit prolonged use. will not alter its characteristics in any way. There are five different sizes in the series, The ene used is cut from a special stone viz., 15, 25, 45, loo, and 160 m -mfds. respec- for which is Claimed the required features. tively, the first three mentioned having Apart from this, the stone employed has a extra wide spacing between the plates. most handsome grain, and in its finished A useful feature of these condensers is and polished state gives the microphone a their small size, for the 160 m- rnfds. model most distinguished appearance. is not appreciably larger than the 15 m- rnfds., since it is assembled on the sanie size end plate. The capacities of several specimens have been measured, the results being tabulated below :- TABLE.

Nominal Measured Measured Type. Capacity Minimum Maximum m -mfds. (max.). Capacity Capacity (m- mfds). (m-mfds). Varley three -gang Nicore coil unit, the Model BP111 for superheterodyne sets with M.R. Crystal ;t., 15 (0.000015 mfds) 3.2 13 microphone Z I O kc; s IF amplifier. mounted in 92 25 (0.000025 ) 3.2 22 a pattern that should not dwarf - pattern 92 45 (0.000045 3.5 42 give trouble, even table stand. ) after long use. 92 100 (0.0001 ) 4.0 99 The two models tested are the BPII2 and 92 100 (0.00010 ) 5.0 157 the BPI ri and they cost 13s. 6d. and 21s. respectively. The other condenser tested was a slow- motion reaction model of 0.0002 mfd. capa- BULGIN BAYONET -CAP LAMPHOLDERS city. This has a -in built reduction drive THE screw -in type bulb generally used having a ratio of 1. is known as lo¡ to It for illuminating the tuning scale does The microphone has an excellent charac- the Type 87, and is made in three sizes, occasionally come loose, viz., 0.0oor, 0.00015, and may then give teristic, its output being well balanced and 0.0002 mfd. rise to annoying crackles in the is made loud speaker throughout the entire audio scale of frequen- It throughout of brass, and its whenever the set is moved or minimum capacity was found be touched. In cies. Though it was subjected to a very to 19.5 order to eliminate one possible cause of in- searching test, and actually compared with terference, however remote, A. F. Bulgin a high -grade laboratory microphone, only and Co. have introduced a new range of one minor resonance could be detected. lampholders for use with midget bayonet - This is quite high up in the audio scale, and cap lamps. only has the effect of imparting a very These are made in the same wide variety slight sibilant accentuation, which might of styles as the M.E.S. screw -type holders. quite well pass undetected under normal Lamps for this new holder are also obtain- conditions of use. able in the sane range of sizes and filament It is a microphone that can be confidently consumption as the Bulgin M.E.S. bulbs. recommended for public address work, home So far, we have not been notified of the recording, for amateur transmitting, and for prices of these new fittings and lamps for any occasion where a microphone capable Selection of the new Webb short -wave them, but it is understood that this infor- of giving very high quality of reproduction condensers. mation will very shortly be available. on speech or on music is required. The makers are M.R. Supplies, Ix, New m- mfds., while the maximum value was Oxford Street, London, W.C.1, and the price 0.000202 mfd. is L5 Tos. The stand shown in the illustra- The Type 92 costs 4s. up to 45 m- mfds., tion costs 15s., finished in chromium. and 4s. 6d. for the larger sizes. The o.000r, Various alternative styles are also available. 0.00015, and 0.0002 mfd., Type 87, reaction condensers cost 5s., 5s. 3d., and 5s. 6d. WEBB SHORT -WAVE CONDENSERS each respectively. NEW range of condensers for use in A short- and ultra- short -wave apparatus VARLEY NICORE COIL UNITS has recently been introduced by the Webb THE latest series of Nicore coil units made Condenser Co., Ltd., 34, Hatton Garden, by Varley (Oliver Pell Control, Ltd.), London, E.C.I. Cambridge Place, Burrage Road, Wool- Bulgin new bayonet -cap lampholder. Known as the Type 92, they are wich, London, S.E.18, contains two models assembled on a single end plate of an insu- for use in superheterodyne sets. One is a MOBILE AMPLIFYING EQUIPMENT lating material described as " Stealan." three -coil assembly with band -pass input Specially shaped brass vanes are used, circuits for a 110 kc /s IF amplifier, while the caption accompanying the photograph IN of the PA van a spindle. The single bearing is is for use 465 equipped by Ross and also brass the other with an IF of kc /s, Robinson, and reproduced on Current Topics of sufficient length to give rigidity to the and has a single tuned input circuit, a band - page in last week's issue, the range of the loud rotor assembly. pass input filter not being essential for good speakets should have been given as several Though a friction contact with the rotor second -channel rejection with the higher IF. miles, and not seven miles as stated. 64 Wireless World, January 151h, 1937 Eddystone All -Wo.

FEATURES. Type. -Table model battery superheterodyne with interchangeable waverange units. Waveranges (supplied with receiver) (7) 13.4 -34.6 metres. (2) 27.2 -69.2. metres. (5) 240 -573 metres. Circuit.- Var.mu pentode RF amplifier - pentode oscillator - pentode frequency -changer - two var.mu pentode IF amplifiers- double- diode -triode second detector - push -pull triode output valves. Controls. - A BATTERY (1) Tuning. (2) Volume. (3) Amplification. (4) Tone. (5) On-off switch. Price. -Receiver SUPERHETERODYNE DESIGNED FOR USE only, £27 10s. Loud speaker £3 10s. Makers. - Stratton & Co., Ltd, Eddystone Works, Broms- IN THE TROPICS grove Street, Birmingham, 5 THERE are many all -wave re- ceivers which from the point of view of long- distance short-wave ditions which are'likely to be found any- denser, as well as the IF transformers, are reception can be confidently where on the surface of the earth. Both totally enclosed in this way. In addition, recommended for use in any part of the the cabinet and the chassis are aluminium all vital leads carrying HF currents are world. For the most part, however, they alloy castings, protected by a hard conducted through copper tubing, which, follow domestic broadcast receiver prac- crystalline enamel. Valve holders, coil in the case of the valves, is taken to tice in chassis design and layout, and bases, etc., are of a special insulating within a fraction of an inch of the caps. although in a few details the construction compound known as DL9, which has a may have been modified with an eye to wide application in short -wave work. Trouble -free Wave -changing the export market, there seems always to Porcelain pillars are used as anchor- be an element of uncertainty regarding ages for the wiring and for supporting In multi -range receivers the wave - the time that will elapse before the wooden small components, while every soldered change switch has always been one of the cabinet or even some vital part of the joint is painted over to obviate sub- most vulnerable points, and although chassis will disintegrate in the hot and sequent deterioration from corrosion. important improvements have recently humid atmosphere of the Tropics. The decision to use a cast chassis has been made in switch design, the makers No such uncertainty exists in the case presented the designers with an excellent have in this case wisely played for safety of the " All -World Eight," for the de- opportunity of improving the electric by providing interchangeable coil units signers have made a complete break with efficiency of the circuit by thorough housed in cast aluminium boxes, together the constructional conventions of broad- screening. Both above and below the with their trimmers. Three coil units are cast receivers and have built with an eye chassis is divided into cells by integrally provided as part of the standard equip- to permanence under any climatic con- cast webs, and the main tuning con- ment of the receiver, and additional coils

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.. AMPLIFICA CONTROL

An input RF amplifier and two IF stages give good sensitivity and a push -pull output stage excellent volume for a total HT consumption of only 8 mA. Wireless World, January 15th, 1937 65

can be supplied to bridge the gaps be- performance on the short -wave ranges is which provides . upwards of twenty or tween the standard ranges, thus giving a really the result of an exceptionally good twenty-live continental transmissions in complete coverage from 13.4 to 2,000 signal -to -noise ratio, and if the more daylight, adjacent channel selectivity was metres. powerful continental short -wave stations possible with the exception of the two fail to rattle the loud speaker in the Brookmans Park stations, where one manner to which we have become accus- channel was lost on either side of their tomed, this is only because of the restraint normal settings when using the set in exercised by the efficient AVC system. Central London. There is, in fact, very little difference in The tuning dial is driven by a two -

the signal strength and steadiness of the speed reduction gear with ratios of 22 : I principal short -wave programmes from and 115 : I. The calibrations for the d Eight either side of the Atlantic, and we were three inductance units supplied with the particularly impressed with the excellence set are engraved on a glass scale, behind and reliability of the morning programme which the pointer moves with the mini- The circuit is designed for use either from Pittsburgh W8XK, on 13.9 metres. mum of parallax error. There is also an with a normal single wire aerial or with The. quality of reproduction from the arbitrary o -Too scale, for which a calibra- a doublet. There are eight valves in the permanent magnet loud speaker unit de-. tion curve is supplied in the case of any circuit, the first of which is a variable-mu signed for use with this receiver is well extra inductance units which may be sub- pentode RF amplifier. The oscillator is a suited to distant reception. It is true sequently purchased. The tuning scale is separate valve and is coupled to the fre- that on account of the small baffle area backed by a white background which is quency- changer grid through a small there is not much true bass, but, on the spaced away from the glass panel, and we think it would have been an advant- age, in view of the low current consump- tion of the set, if a dial light could have OUTPUT VALVES been provided. Our reason for making this P 220S suggestion is that on account of the low FREQUENCY CHANGER VALVE background noise is DETECTOR VALVE L 2 1 D D there every possi- SP210 bility that the receiver may be inadver- 2nd I F AMPLIFIER VALVE V P 210 tently left with the valves running.

I F R F AMPLIFIER VALVE 1st AMPLIFIER VALVE Actually the measured LT consumption VP 210 V P 210 was 0.52 amp. and the HT current con- sumed at 120 v. varied from 5 -8 mA, de- pending upon the setting of the amplification control. This is a receiver which provides VOLUME reliable long- distance reception with CONTROL unostentatious efficiency, and its construc- tion and workmanship are such that it can be confidently recommended for use in any part of the world. C " OSCILLATOR VALVE =1 SP210 ' h News from TUNING CONTROL the Clubs The Faraday Radio Society ON -OFF A. crystal -controlled transmitter SWITCH and other ` °Wireless World apparatus has been placed COPYR IOHT at the disposal of this Society by the L.C.C. The club is run in conjunction with the Walsworth Men's Institute INTERCHANGEABLE AMPLIFICATION CONTROL and membership is restricted to men of 18 years INDUCTANCE UNIT of age or over who reside in the L.C.C. area. A very full programme of lectures and visits to places of radio interest has been arranged, and later in the season it is hoped to be able Both cabinet and chassis are aluminium alloy castings. Close- fitting lids give access to to carry out geophysical prospecting experi- the valves and interchangeable coil units. ments as a change from the usual type of field - day. Morse classes and lectures are held every capacity. There are two stages of IF other hand, there is complete absence of Tuesday and Wednesday at 8 p.m. at the club's false headquarters at the 'Nelson School, Trafalgar amplification, and the double- diode -triode resonance, and the top register is of Street, London, S.F. Full details of the which follows them performs the usual the type which gives clarity without society can be obtained from the Secretary, Mr. functions of signal rectification, AVC emphasising background noise. In fact, 1. Sykes, 39, Wallington Road, Seven Kings, supply and first stage AF amplification. throughout the period of the tests no Essex. The RF amplifier and both IF valves are necessity was felt for making use of the The Halifax Experimental Radio Society there is a variable initial tone control either on controlled, and short waves or This society holds meetings at 7 p.m. on bias derived from a potentiometer across normal broadcast bands. Thursdays at their headquarters, Room No. 13, the grid bias battery. This provides a Friendly- and Trades Club, St. James Road, and efficient control of over -all Halifax. The entrance fee to the society is I / -. smooth On Medium and Long Waves Full details can be obtained from the Hon. Sec., sensitivity and contributes materially to Mr. W. Milner, " Ryburn Radio," Sowerby the ease of handling the receiver. The Although the receiver has been designed 13ridge, Nr. Halifax. consists of two triodes in primarily for short -wave reception, output stage the The Croydon Radio Society push -pull, with a fixed tone control across performance on the medium and long A very interesting programme has been ar- the anodes' which is brought into. opera- wave broadcast bands could not well be ranged for the second half of the winter session, tion by means of a switch. improved upon if the set had been and readers who are interested are advised to The performance of the receiver is at designed from this point of view. On the write for full particulars to Mr. E. L. Cumbers, first somewhat deceptive, for it lacks the long waves the selectivity gives clear re- 14, Campden Road, South Croydon. Next Tues- which often passes for effi- ception of day, at 8 p.m, a. lecture will be given ou excess vitality Deutschlandsender without the modern sound -film technique at the society's ciency in many of the popular all -wave necessity of calling in the aid of the tone headquarters at St. Peter's Hall, Ledbury receivers. But its quiet and unobtrusive control, and on the medium waveband, Road, South Croydon. 66 Wireless World, January 15111, 1937

FOR the twelfth of their Scrapbook programmes, Charles Brewer a n d Leslie Baily have chosen the year 1922. From for of view of listeners Listeners' the point Guide the main feature of that year the Guilds or Companies of CONTRASTS Workmen whose calling had A VARIETY trifle which may something in prove, through its presenta- common with the sentation, quite amusing to lis- subject of the play teners, is a little programme of -for example, this contrasts called " Between Our- pageant of the selves," which will be broad- Deluge was first cast Regionally on Thursday at acted by the 8.40. Edward Cooper, who has now become famous for his sophisticated songs at the SCRAPBOOK COLLABORATORS. piano, will provide a contrast Charles Brewer and to Jimmy Rogers, American Leslie Baily (with light pianist, who will play spectacles), going the piano and sing the " over their script at sweet " one of the Dramatic songs so popular in the United Control panels. States. Archie Campbell, pro- ducer, has also enlisted Eileen Waterleaders and Drawers of Hunter and Elisabeth Welch, contrasting in and the Dee. Clifford Lawson - both style and was probably that it marked given in the New Year, material. They will also give a season, will Reece, a new recruit to the the beginning of the organised the seventh of the glimpse of the of by Drama and Features Depart- divergence activities of the B.B.C. The be devoted to works artistes' material on each side first regular broadcast of the Handel. It will include the ment, will make his début as a producer with this broadcast of the Atlantic. British Broadcasting Company Oratorio, "Alexander's O O O took place from 2L0 on Feast," which was first given of his own adaptation on Sun- direction at day at 4.30 (Reg.). MUSIC November 14th, and Mr. under Handel's THE Sunday evening orches- J. C. W. Reith was appointed Covent Garden in 1736. The ,. - SPORTING COMMENTARIES tral concerts will be resumed General Manager on Boxing tenor solo will be sung by this week other THREE sporting events will at 9.5, when Kath- Day. Personalities connected Walter Widdop, the leen Long will play Suddaby, be commented upon for Mendels- with the early days of broad- soloists being Elsie sohn's Pianoforte Concerto in casting will come to the micro- Freda Townson, and Norman listeners during this week. On Philharmonic Saturday, from 2.20 -4, Cap- G Minor. The London Sym- phone in this programme, and Walker, with the phony Orchestra, under Clar- Harold Dawber will tain Wakelam will be at address their listeners on the Choir. ence Raybould, will give changes that have taken place play an organ concerto. Twickenham to describe the play during the Rugby Union Haydn's Symphony No. 22 during the past fourteen years. Sir Hamilton Harty, owing (" The Philosopher ") and illness, will be unable to con- football match b et w e en Outside the broadcasting to Rimsky - Korsakov's " Sche- sphere the year 1922 was a duct this programme as was England and Wales. This will be be the forty -ninth Rugger herazade." great one for light musi- arranged, and his place will Three new orchestral works Boult. The match between these two cal entertainment, and taken by Adrian by British composers will be " Decameron Nights " at Drury first part will be heard from countries. 'Lane, Phyllis Dare as " The 8.15 to 9.5, and the second Part of the snooker match Lady of the Rose " at Daly's, from 9.25 to 10.45, both in the between Joe Davis and Horace and the " Cabaret Girl " at the National programme. Lindrum at the Corn Ex- Winter Garden were some of 0 0 0 change, Coventry, will be com- the successes which will be re- "NOYE'S FLUDDE " mented upon by Sidney Lee at called. Another resounding THIS pageant play, though 8.45 on Monday (Reg.). theatrical success was " Tons intended in the first instance Lionel Seccombe will be at of Money," the first of the for children, should appeal the Empire Pool and Sports famous Tom Walls -Ralph also to many adult listeners. Arena, Wembley, on Tuesday Lynn farces, which enjoyed a Most of the miracle plays were for the contest between Benny run of 737 performances. first performed in churches by Lynch and Small Montana (the Politics will, of course, be the clergy and choir, many of holder) for the Fly- weight touched on, and other home them being written in Latin. Championship of the World. and foreign affairs with which About five hundred years ago, At 9.40 he will give a round - " Scrapbook for 1922 " will be however, whole cycles of plays by -round commentary for Re- concerned will include the rise existed in English and were gional listeners. to power in Italy of Mussolini, performed by laymen at stated - 4 ó the formation of the Irish seasons. CORSICAN Free State, Princess Mary's The Chester Cycle from FOR some months past Max wedding, and the death of which " Noye's Fludde " is Kester and Spike Hughes have Lord Northcliffe. The pro- taken begins with a series of been working on a musical play is a GREENE, the B.B.C. gramme will be ` heard on dramatisations of the early called " Bianca," which FELIX based on a representative in New York, will Thursday at 9 (Reg.) and again stories of the Old Testament. Corsican love tale Hall. Max be responsible for making all the Nationally the following day. Each of these little plays was story by Anthony arrangements for the relay by 0 0 0 traditionally given by one of Kester will be producing this on the National transmitter on SYMPHONY CONCERT Wednesday at 9 (Reg.), with Wednesday from 4.5o to 5.45 of THE programme of the r Thea Holme, Arthur Gomez, the inauguration of President Details of the week's Roosevelt. Commentaries and B.B.C. Symphony Concert Television programmes Jan van der Gucht, Gabrielle sound pictures in the true from the Queen's Hall on will be found on p. 58. Casartelli and Foster Carlin American style will be heard Wednesday, the first to be among the players. from the processional route. Wireless World, January 15th, 1937 67.

Vikings. The concert will also Outstanding Broadcasts be relayed by American stations.

at Home and Abroad OPERA he SATURDAY'S performance Week of broadcast for the first time in Carl Rosa Opera Company at SHOPS Gluck's " Alcestis," broadcast a programme on Saturday at Manchester in 1921. This week's contribution on from Rome at 8, should be a 6.45 (Nat.) under the direction Another music drama, this Tuesday at 7.3o (Nat.) to the rare treat. This classic was of Joseph Lewis. One of these time from the pen of the series of programmes " A first produced in Vienna in is a " Saxo- rhapsody " by modernist French composer, Nation of Shoppers " is a dis- 1767. Later, when produced in Eric Coates, which will be Darius Milhaud, will be heard cussion on the relative merits of Paris, it was bitterly criticised played by Sigurd Rascher and on Saturday evening. This large- and small -scale retailing. by the Italian school, which conducted by the composer. will be the first performance The " big business " side will accused the master of compos- The other two works are in England of " Christopher be sponsored by Sir George ing for the understanding and William Lovelock's " Second Columbus," a musical drama not for the ear. Suite for Orchestra," and Ben- in two parts and twenty-seven The story follows jamin Britten's " Soirées Musi- scenes. The story deals with the Euripides' familiar cales," a suite of movements discovery of America by play. For the less on themes by Rossini. Benja- Columbus, but is treated fastidious lover of min Britten is a young East throughout in a symbolic and opera, Radio -Tou- Anglian composer, and Wil- semi -mystical vein, and great louse at 10.15 on liam Lovelock, a Doctor of play is made of the symbolism the same day offers Music on the staff of the contained in the name of Chris- one of its excellent Trinity College of Music, topher Columbus -the " Christ it potted " versions. London. bearer," and in French, the This time it is " Dove " or bringer of light. twenty -five minutes Musical Dramas Just as Noah dispatched a dove of Massenet's opera, " Thaïs and Talmaae," a 'from the Ark to find land, so "Werther," music drama in one act by was Columbus sent out from the founded on that Colin McLeod Campbell, will Old World to discover the New. be broadcast to -night at 7.20 This performance will be given VALUABLE DIGITS. (Nat.). The composer will con- before an audience in a studio Mantovani, who with duct and the soloists will be at Maida Vale and will be heard his Tipica Orchestra Joan Cross and Edward Reach. Regionally from 7.3o to 10.5 will be heard again It was first produced by the with a short interval at 8.5o. on Sunday afternoon, has, it is reported, r- insured his hands for HIGHLIGHTS OF THE WEEK ten thousand pounds. FRIDAY, JANUARY 15th. Monday, January 18th (contd.). Nat., 7.20, " Thais and Talmme." Reg., 6.40, Organ Recital by Guy Schuster and that of the " small romance of Goethe which is 8, Musk from the Movies-Louis Weitz. 7.30, Eden Phillpotts' shop -keeper " by W. Herman said to have caused an epi- Levy and his Symphony. 9.20, " The Runaways." 8.45, Snooker Kent and Captain Harold Bal- demic of suicides. European Exchange -II, Italy. Commentary. 9.40, " Invitation to the Waltz." Abroad. four, M.P. The chair will be On Sunday Strecker's Sing - Reg., 6.40, Car Upkeep -Inclusive Radio- Paris, 8.45, Ex- Service taken by Ronald Gartland, spiel, " Aennchen von Tharau, ' Costs. 8, The Trial of Mrs. Authors' and Composers' Concert. M.P. comes from Berlin (Deutsch- M'Lachlan. 9.30, The Rocky TUESDAY, JANUARY 19th. o o landsender) at 7. Mountaineers. This should Abroad. Nat., 7.30, Discussion -A Nation WELSH SONGS please lovers of the modern in Milan, 8. Symphony Concert. of Shoppers. ¶Variety from THE Swedish choir Sanger - music. Morecambe Winter Gardens. kretsen have given themselves That SATURDAY, JANUARY 16th. 9.40, " The Runaways." perennial Christmas- a very difficult task by learning time . favourite, Nat., 4.20, Recital- Spencer Reg., 6.40, From the London " Hansel and Thomas (tenor) and Harriet Theatre. 7.45 and 8.55, The a number of ancient Welsh Gretel," comes from Radio - Cohen. 6.45, Sigurd Rascher Liverpool Philharmonic Society's songs for a special half -hour Paris at 8.45 on Wednesday. and the B.B.C. Orchestra (C). Concert. 9.40, Boxing Commen- tary. programme which will be First produced at Weimar two 8, Music Hall. all Swedish days Reg., 4, The White Coons. 7.30 Abroad. broadcast over before Christmas in 1893, and 9, " Christopher Columbus " Berlin, 7.10, Relay from the Phil- stations on Thursday at 8.15. it found its way the very next -Milhaud. harmonic Hall, Berlin. This programme comprises year to London. In England, Abroad. WEDNESDAY, JANUARY 20th. some of the best known Welsh of all operas it holds the record Sottens, 7.30, Folk Songs of Italy, Nat., 7.30, Van Phillips Spain, France and America. and his songs from the seventeenth for the number of perform- Two Orchestras. 8.15, and 9.25, century and earlier. ances. SUNDAY, JANUARY 17th. Symphony Concert from the - Queen's Hall. ¶" The c Nat., 5, The Church of To- morrow Little Show Radio cabaret. ICELANDIC DEDICATED TO THE FÜHRER Kenneth Ingram. 7.20 "- -I, Reg., 8, " Bianca " by Max Kester. A Music programme of THE first part of a symphony " Edwin and Angelina." 7.55, 9.40, Scottish Dance Music. Scottish Service from Glasgow unusual interest will be heard dedicated to the German Chan- Cathedral. Abroad. from all Danish, Swedish, Nor- cellor, Adolf Hitler, will be Strasbourg and Rennes, 8.30, Sym- Reg., 4.30, " Noye's Fludde." 7.15, phony Concert. wegian, Finnish and Icelandic heard during the relay by Fred Hartley and his Novelty stations on Monday at 7. Ice- Berlin at 7.10 from the Phil- Quintet. 9.5, The London THURSDAY, JANUARY 21st. old Symphony Orchestra and Kath- Nat., 6.40, B.B.C. Orchestra (E) landic and Norse songs harmonic HalI_in Berlin. The leen Long (piano). and Tapia Caballero (piano- from the past 1,000 years, composer, Joséf Reiter, will be Abroad. forte). 7.40, The Air -do- Wells. sung by the Reykjavik 75 on the day of the broadcast. Munich, 6.20, " Carmen " (Elec- Reg., 6, Band of His Majesty's Y.M.C.A. choir and played He was born in the same town trical recording). Coldstream Guards. 8.40, " Be- tween Ourselves " -An Intimate by the Trocadero ensemble, as Hitler and has written MONDAY, JANUARY 18th. Entertainment. 9, Scrapbook for will be relayed from Reyk- numerous works, including ten Nat., 7.20, " The Music Shop " -8. 1922. javik, the capital of Iceland. oratorios and five operas. His ¶" It's Happening Now " -3. Abroad. The songs will be sung in.the Symphony has four movements 9.35, Rhythm Music-Reginald Hilversum, No. 1, 7.45, Symphony Foort at the Theatre Organ. Concert from the Concertgebouw. Norse tongue, which was and takes two hours to per- L spoken by the ferocious form. THE AUDITOR. Wireless World, January 13th, 1937 improving the By W. N. WEEDEN Simplified Volume Expander AVOIDING WASTAGE OF to move the expander ahead of the power hand, when a bridge is operated near its stage, as it was determined that no appre- balance point, only a small change in re- OUTPUT POWER ciable amount of power should be lost. sistance of the opposite arms is required to This change entailed the addition of two cause a large increase in unbalance cur- transformers, as shown in Fig. 1. The first rent. As the change in resistance of a lamp . is designed to couple the plate or plates of filament is limited by its temperature co- LTHOUGH the lamp -bulb volume the intermediate AF amplifier to an imped- efficient, it is obvious that, in order to expander is ideal from several ance of a few ohms. The second trans- secure a large increase in unbalance cur- points of view, it unfortunately former is used to match the output of the rent by a minimum increase in input volt- possesses several drawbacks, of Wheatstone bridge formed by the two re- age, the bridge must be operated close which perhaps the most important is loss sistors and two bulbs to the grid or grids to balance. of efficiency through wastage of at least of the output stage or its driver. Still another advantage accruing from 5o per cent. of the output power. The This change adds greatly to flexibility, this low -level, near- balance operation is next most serious shortcoming is the lack particularly if the volume control is in- the increase in the time constant or lag of flexibility through inability to control serted after the expander. In this case the the degree of expansion, in addition to degree of expansion is completely divorced the fact that the expansion depends from the output level at which one wishes our issue of April 24th, 1936, largely on the output level ; if one listens to listen. It also permits of the substitu- IN at a level several db. below that for which tion of variable resistors for the fixed units the writer of this article explained the lamp bulbs were calculated but little forming two arms of the bridge, which a simple compensating circuit for expansion will result. allows one to obtain almost any degree of restoring the original volume con- Coupled with the first objection is the expansion by the simple means of setting fact that many amplifiers which can easily the degree of initial or no- signal un- trasts in reproduced music. He now deliver sufficient undistorted power without balance. If the bridge is perfectly describes a new way of using the the expander do not show up so well when balanced under these conditions, any saine principle in such a manner that called on to supply several additional watts signal will cause an infinite ratio of in- the original to light two insignificant lamp bulbs. In crease. This method of control was not certain shortcomings of America we use many amplifiers in which applicable to the expander as it was origin- method are overcome. the power tubes are operated as Class AB' or even AB2. These amplifiers hich results from can usually supply the fact that the 5 to Io watts thermal inertia of with but little dis- a filament is tortion, as they greater at lower are generally oper- temperatures than ating in straight near incandescence. Class A with such Not only is outputs, but when smoother and more asked to double this pleasing operation output their har- secured from this monic distortion in- increased delay, creases rapidly. but there is also Although this quite a decrease in form of expander third harmonic dis- possesses these tortion. This dis- shortcomings, i t tortion results from has several advan- the rapid action of tages, such as ease the expander, of maintain- which may operate ing valves in a Fig. 1.- Illustrating the interposition of the volume expander in the AF amplifying circuit. on the peaks of in- balanced or dividual low - matched condi and ready adaptability ally shown, because the power loss is a frequency cycles, causing a serious change to any amplifiof fair power -handling function of the unbalance, and with per- of wave -form. The delay caused by the capacity. fect balance far too much power would be increased thermal inertia causes the expan- Recognising both the advantages and lost for practical purposes. This may per- sion to operate on the envelope instead of disadvantages, Mr. L. A. De Rosa, en- haps be explained more clearly by stating the individual wave. gineer of Electrad, Inc., leading manufac- that a bridge operated with a large degree Due to the great amount of expansion of turer of volume controls in the U.S., set of unbalance must experience a large which this circuit is capable, care must be to work on the problem of eliminating its change in the two opposite resistance arms exercised to use only a sufficient degree weak points while retaining its advantages. before an appreciable change in the un- of expansion to restore the reproduction The first change or improvement was balance current takes place. On the other to something near its pristine or uncom- JANUARY 15th, 1937 7174.®@o 69 WOAdi Improving the Simplified Volume Expander - pander. Of course, if a single valve is pressed state. More than this will cause employed, it will be necessary to employ music to become very unnatural and un- only a conventional single control of the pleasant. In operating, it will be found type used in resistance -coupled amplifiers McCA 1`'\ THY that a good balance (for a barely audible or for following a diode detector. Good signal) will give tremendous expansion, transformers should be employed if the while less expansion will result as the re- frequency response of the remainder of for the finest value in sistances opposite the lamps are made less the equipment is good and if high- fidelity than that of the cold lamp filament. If, reproduction is desired. on the other hand, the resistance arms are In many cases where receivers or gramo- All-Wave Receivers ! made greater than the filament resistance, phone amplifiers are equipped with a output will decrease with increase in input, driver stage, or with a stage from which resulting in compression. one watt can be extracted, it will be pos- In closing, a few suggestions regarding sible to build the expander into the ampli- the values of the parts may be in order. fier. Also, if the amplifier is not up to The amplifier feeding the expander should date from the viewpoint of power -handling have an output of at least one watt, and capacity, the expander with a more may well be the driver stage of a QPP out- modern output stage may be added to the put stage, or of a Class AB or Class B amplifier externally. output stage. In most cases one or two in- Where transformer coupling of an in- directly heated triodes, such as are nor- ferior nature is employed in an older am-

£7 6 VALVE ALL -WAVE SUPERHETERODYNE (complete with B.V.A. Valves)

Improved edition of this popular receiver (praised " Wireless World " test reports). Heavier gauge cadmium- plated steel chassis. Iron -cored I.F. transformers give even better per- formance. No increase in price. Brief Specification: 8- stages all -wage band -pass superhetero- dyne. 7 tuned circuits. D.A.V.C. with " squelch " circuit valve for noise suppression. Illuminated " Airplane " dial. Octode frequency changer. 3 -5 watts pentode. Switching for gramo- phone pick -up. Wave ranges: 16.5-5o, 2oo-55o, Roo -a, oeo metres.

McCARTHY ALL -WAVE SIX with 6 watt push -pull output

Fig. z. The improved volume expander in practical form. A, expansion control, comprising two 5 -ohm ganged rheostats ; B, volume control, comprising two potentiometers, o.r5 to o.5 megohm, also ganged together. mally used to feed an output stage, will plifier, it might be desirable to replace the suffice, provided that they are worked at transformers by resistance couplings, sub- maximum plate and grid voltages. They stituting for the first- or second -stage valve are coupled to the expander by means of one which can deliver the requisite power an output transformer designed to couple for operating the expander properly. such tubes to a very low- impedance speech (complete with coil -i to 4 ohms. The lamps employed B.V.A. Valves) in this expander were of the automobile The Radio IndustryJ type -6 -8 volts, 3 candle- power -while DtJE to the increased cost of raw material, 6 valve all-wave superheterodyne with similar specification, performance, etc., to above, but with large push -pull output the two resistance arms are composed of it has been found necessary to increase giving 54 -6 watts. a dual 5 -ohm rheostat recently announced the price of Belling -Lee " Eliminoise " screen cable (Type No. 1221) from 8(1. to rod. per Has illuminated " Airplane " dial with principal station names, by Electrad under the type number 66o8 tone control and volume control (both also operative on yard. It is pointed out that this increase is gramophone), full provision for gramophone reproduction. (tandem control). If unable to secure such in direct proportion to the rise in price of the A really high quality 5 receiver, with exceptionally large a control, two -ro-ohm rheostats may be raw material and that the cable, having undistorted output, and fine performance on all 3 wave employed, although the balancing of the copper braid screening, uses more metal than ranges. normal conductors. bridge and control of expansion will be n All McCarthy receivers supplied complete with much less convenient. The bridge output valves, knobs, pilot lamps, leads mains cable and An Everett, Edgcumhe Visual Valve Tester plug. 12 months' guarantee. is coupled to the following tube through has been supplied to the National Physical the Radio Research Deferred terms on application, or through London a transformer designed to couple a ribbon Laboratory for use at Radio Supply Co., 11, Oat Lane, E.C.2. Station at Slough. microphone to one or two grids. Both Cash w'th on 7 Also 7 - order days' approval. write be capable of operat- for illustrated catalogue of complete range of all transformers should An unusual application of sound -amplifying McCarthy receivers. ing at about 20 db. levels without satura- technique has recently been put into effect by tion. If possible, the main volume con- the G.E.C., which has installed an elaborate Á111 IRA 1110 ILTE, trol should follow the expander, and might loud- speaker announcing system at the Heston McICA -N L and Isleworth Fire Station. All members of 44a, Westbourne Grove, London, W.2 well consist of a dual potentiometer across can be summoned immediately the brigade in Telephone; Bayswater 3201/2. the grids of the stage following the ex- cases of urgency. Wireless World, January 15th, 1937 Random Radiations By " Hollywood Bound thing about the size of the screens used for DIALLIST " home cine projection. The use of anything Cecil Lewis is to leave the Alexandra much smaller means that in scenes where a SO Palace and the production of television at any considerable number of people is shown the Espagne or Fritto Misto No. r. And there's programmes, for some little time, figures are too tiny for details to be brought nothing rate. It's a pity, for with his wealth of that you can do to mike things out properly. I've no doubt that the bigger any better. You've got to grin (with teeth - ideas and happy knack of putting them screen will be with so very long. have been us before gnashing) and bear it, or tune in to some- into concrete form he would Intensive work is being done, and some as the scope of thing else - probably to find sooner or later more and more invaluable ideas seem very promising. But work of that it television expanded. Still, he couldn't very also suffers in the same way. If this kind can be very ; often scenario tantalising so stations on the medium -wave band are to well refuse the offer to make a film when the goal seems in sight some unsus- continue to attract listeners at a distance, . of his book " Sagittarius Rising," and the pected snag crops up that may mean start- of the the authorities at their next conference will B.B.C., realising the importance ing all over again almost from the begin- him from his contract have to consider seriously ways and means opportunity, released ning. of overcoming with them. He will be away for six months, sideband splash. Possibly for two years beyond single -sideband transmission may provide anyhow, and possibly " Loud Speaker " the final solution. that. With Sir John Reith, Arthur Bur- rows, P. P. Eckersley, and Stanton Jeff- Future generations will probably be ti ti % reys, Cecil Lewis can claim to be a puzzled over the ways in which we came to " founder- member " of the B.B.C. And coin the amazing collection of inappropriate Could You Have Found This One ? now of that quartet only Sir John Reith wireless terms that we have handed down AGOOD many years ago, when loud remains with the Corporation. to them. Could anything, for instance, be speakers were rare and reception was much less descriptive than " pick -up " c.r mostly done by means of headphones, some " accumulator " ? And the " loud Small Beginnings term of us were rather annoyed by the bragging of speaker " is no mean example of the in- a youngster, who told us all incredible when one what mutts we It seems almost eptitude of our radio words. To say that were at fault -finding (faults were pretty comes to look back that the B.B.C. can a loud speaker reproduces music to perfec- frequent in the receiving from its small begin- sets of those days), have grown so rapidly tion is almost as absurd as to claim that r. and undertook to run to earth any defect fourteen years ago. At ! nings just over violin has an Oxford accent " Loud in a quarter of an hour at the outside. It that time the entire staff, from programme speaker " is actually a pre -wireless term. was quite nicely filled one simple, he said, for anyone who builders to engineers, just It's a shortened form of " loudspeaking tele- had a voltmeter and a milliammeter very large room. The broadcasts -all and phone." Such contrivances were used in would use such brains as Heaven had given given from a single studio in Marconi House the Navy and for commercial purposes long Bur- him. Would we care to put him to the -were quite informal affairs. Arthur before wireless reproductions had pro- test? I offered functions of programme to put his set out of action rows combined the gressed beyond the headphone stage. And in such a way that he announcer, producer and leader of the earliest wireless wouldn't find the director, loud speakers (you re- fault in twice the time he'd suggested, guar- the children's hour. He also did the work member the old Brown Type H ?) were to be undertaken by anteeing not to inflict permanent injury on that was afterwards literally loud- speaking telephones, since any component. control room, which didn't then -ist. All I asked was that he the they consisted of nothing more than a large should be out of the room for two Whilst an item was in progress he e'tood and sensitive telephone receiver provided minutes. of headphones He went. He came back. He produced the near the door wearing a pair with a horn. voltmeter to a small receiving set. If any and the milliammeter and pre- connected a sumably he used the performer was " blasting " a warning sign MIN brains of which he liad told us. What he found was that the set lit up to make him move farther from the Sideband Splash microphone. Conversely, those who were was completely silent, though he obtained coming over too faintly were moved nearer. SOME time ago I predicted in the columns the correct readings with his instruments at Those waiting their turn to broadcast of The Wireless World that sideband every testing point. Don't read any further sat round the studio -and just occasionally splash, or sideband splutter, as some prefer until you have thought it out and found someone failed to notice that the micro- to call it, would become one of the biggest your solution. phone had been switched on! interference problems as more and more high -powered broadcasting stations came Dirty Work ! ti. L ti into action within the L'nits of the medium- Thought it out? Solved the problem? I Bigger Screens wonder ! Well, here's all that I had done. NE desirable improvement in television During the two minutes that he was out room o``JJ reception is an increase in the size of of the I'd unscrewed the caps of the the viewing screen. I don't mean that we 'phone earpieces and removed their dia- phragms. The victim pretty well had that want real big- screen television in our homes ; that, when it comes, will be for theatres set to pieces before his half -hour was up, and cine houses. But we do need some- but he didn't find the defect, and when I produced the missing diaphragms from my pocket his face was worth seeing. A rather similar case very nearly proved my own undoing a little later on when loud SELF -FEEDING speakers were in general use. Here again SOLDERING IRON was a set that was completely silent. Here again correct voltage and current readings The special advan- were obtained throughout the receiver. The tage of this new loud speaker, when tested separately, proved it be. What, then, soldering "gun," re- to be all that should had happened? Just a plain short- circuit across cently introduced in wave band. It is certainly one of the the jack into which the loud speaker was America, is that one of the user's hands is major annoyances of to -day in the recep- plugged. The plate current of the last valve is always left free. Solder from a magazine tion of foreign stations. You tune in an was passing right enough, but it wasn't contained within the body of the tool is fed enticing musical programme from Pad - passing through the loud speaker. You may to the heated tip of the iron by the action of Schmellburg and it is ruined by the " zit - imagine that it took quite a while to spot pressing the trigger. zitt-zitz -zit " of a speech from Château-en- that one!! Wireless World, January 15th, 1937 7r Broadcast Brevities B.B.C. Station No. 2 NEWS FROM THE Northern Ireland transmitter at Lis - nagarvey is really the dark horse of the PORTLAND PLACE B.B.C. Isolated from its companions by a big strip of sea, enjoying a power second countries became available ; for it was seen only to that of Droitwich, and boasting that Germany, with 7,937,907 licensed lis- one of the most modern antenna systems in teners, led Great Britain (7,897,518 licences) Western Europe, Lisnagarvey is a station for the first time in broadcasting history. to be reckoned with. Investigation proved, however, that the position was not so unsatisfactory after all. Tests at Dawn Germany's figures included 550,185 free Just now there is unwonted activity in the licences, whereas Great Britain has only early dawn at Lisnagarvey. Every Thurs - 45,767 free licences, which are issued to the day morning this month, from 6.3o to 8, blind. Further, Germany's population is the station is radiating a special series of some 75 per cent. larger than Great tests. Britain's, and by that token alone her If you remember it, tune in on 307.1 licence figures should be higher. metres on January 21st and 28th while the breakfast egg is boiling. You may make Televising the Moon ? an interesting discovery. A WELL- INTENTIONED telex ie4 er made an interesting suggestion last Beaumaris Warms Up week which cannot, alas! be carried out. MEANWHILE, a new, though humbler, He proposed a television tour of the moon. B.B.C. transmitter has been warming Up to a point the method suggested was up in the past week or two. The new Welsh ingenious. It was that an Emitron camera relay station at Beaumaris, which is syn- be clamped to the eyepiece of a high -power chronised with West Regional on 373.1 telescope mounted on the terrace at Alex- metres, began relaying the late dance andra Palace. If the telescope were music on January znd, and the engineers trained on the moon, televiewers would, of course, obtain tap Pqewc splendidly magnified ewbiggin-by-the-Sea búSWest Ca views of the lunar kr¡,date. mountains and cra- Myth ters ; in fact, each wshain television set would Oelaval arLley itself be a telescope. Ea rsdon Whitley Bay ` THE BLUE RIBAND Pontel and N.E. REGION. Situated As the possession of the Blue Ribandinarks the ton NEMOUTH ship that is faster than the vessels tedoi Goer P1xhShield -. 17 miles west of New- all of her ón-t e- a I Heb- SOUTH SHIELDS day, so the possession of a Rota G-12 marks .rbrid castle and 5 miles N.E. the set that is ahead of contemporary models areden of Hexham the new in design, construction and quality repro- am sydon don high -powered trans- duction. Not only does a G.12 give you the ATESHEAD finest reproduction that it is possible to obtain, ar.gley Stnçksf eld alq, mitter at Stagshaw, in- but the mere fact of its being fitted in a receiver itto n Línt:zford opfela Wash in SUNDERLAND dicated by the cross, proves that the manufacturer has put quality alle rida le Birtley awll. first in selecting his components. That the cheet.er'i n,t,on will serve a large well - public appreciate this is shown by the greatly eyB( e ow Ryhope populated area. The increased Ed mond, e6' -Spring sales of G.12 equipped models re- \lanchlandú,.; te treet station buildings are ported by radio set manufacturers all over the ñi\eiW Feld PI" a ham harbour nearing completion and world. Get full particulars to -day. West Ne He5letlun AlleriheadsAl .. '

The British abstracts published here are prepared with the r-ermission of th, Controller of 11.51. Stationery Office, from Specifications obtainable at the Patent Office, 25, Southampton Buildings, London, W.C.2, price 1 - eac'r. Recent Inventions A selection of patents issued in U.S.A. is also include I.

Brief Descriptions of the more interesting radio Since the variations of potential scanning in vertical sections re- devices and improvements issued as patents at the anode of D are in phase - quires a wave of the form shown opposition with those at the in Fig. 2, comprising a normal will be included in this section cathode of D1, the first diode saw -toothed oscillation and the always works one amplifier valve whilst the second always works TELEVISION " CAMERAS " circuits A, 13. The point of con- the other. Ir this way tite neces- it is nection is taken in each case from IN a television " camera," sity for using an expensive push - more convenient to focus the the midpoint of a variable tuning - pull input transformer is avoided. picture to be transmitted on to the condenser and a fixed condenser in At the same time, since the diode surface of the sensitised electrode series with it. It is stated that voltaCe is approximately double which faces away from the " gun " the inherent capacity of the resist- that of the applied signal, the part of the cathode -ray tube ance coupling -link does not affect arrangement gives increased sensi- rather than on to the surface the symmetry of the overall reson- which faces towards it, though the tivity. ance curve of the amplifier, nor is Magyar lf'olframlampa. Con- latter is the usual arrangement. the width of the cl:rve affected by With the usual construction of vention date (Hungary). Novem- the tuning of the circuits. ber 23rd, 1934. No. 454618. mosaic -cell electrode, however, the N. l'. Philips Gloeilampeafab- 0000 former method reduces the effici- rieken. Convention date (Ger- ency of scanning, since the electron niclny), June 121/1, 1934. No. FLUORESCENT SCREENS stream from the gun must first 454435. IN order to prevent the so. called penetrate the aluminium backing- 0000 tailing " effect or the draw- plate of the electrode before it can DIODE RECTIFIERS ing out of the spot of light into a reach the layer of sensitive cells Tdiudca D. Di are con- comet -like patch. due to the and discharge them. nected in series, so as to form gradual decay of the action of a According to the invention this a voltage- doubler, across the input fluorescent screen, the screen is difficulty is overcome by using a of a push -pull amplifier. The out- maintained at a certain fixed tem- Television picture divided into construction of electrode in which sections (Fig. I) and indicating the usual minute globules of order of scanning. Fig. 2. - sensitised material are replaced by Wave form of the scanning a large number of small metal oscillations employed. " plugs " which extend through from one side to the other of th. electrode, and are sensitised only series Of rectangular waves shown at the ends which receive the in clotted lines. The latter are image of the picture. This allows produced by periodically " switch- the electric charges built up by the ing " the saw -toothed oscillator. action of the light rays from the One advantage of the method is picture to be scanned and 'dis- that the individual scanning -lines charged more effectively by the in each zone or arca are kept rela- electron stream projected from tively short. the cathode or " gun " end of the J. L. Baird and Baird Tele- tube. Also, since the *parts of vision, Ltd. Application date the electrode not occupied by th. April 41/1, 1935. No. 454588. plugs are impervious to the pas- 0000 sage of electrons, the new electrode serves to minimise the effects of SCANNING SYSTEM both photo -electric and electronic THE picture to be televised is " secondary " emission. focused through a polariser Marconi's !fireless Telegraph upon an electrode surface built up Co., Ltd. (Assignees of L. E. of a large number of small bi -re- Flory). Convention date (U.S.A.) fringent light -cells. These cells February z8ih, 1934. No. 454422. are made active (in the sense that 0 000 they are " opened " to the light) RF AMPLIFIERS by the impact of the electron IN order to ensure substantially stream from the " gun " of a uniform amplification over it cathode -ray tube. The cell elec- definite band of frequencies, wit h trode is placed inside the cathode - a sharp cut -off outside this band, ray tube, whilst the polariser is the anode and grid circuits of the Detector circuit using two diodes followed by a push -pull amplifier. located outside it. valve are coupled through a vari- In operation the scanning stream able resistance. put resistance is divided into two perature at which this undesired from the gun, opens each cell in As shown in the figure, the vari- equal parts R, Rr, connected on effect is found to be reduced to a turn and so allows light to pass able resistance R is arranged in each side of the cathode line so as minimum. through from each corresponding parallel with an inductance L to make the arrangement sym- The temperature varies with the small area of the picture in succes- across t he tuned input and output metrical particular constituents used to sion. The arrangement can be make the screen, but it is kept at used either for transmission or the desired level by making the reception. end -wall of the cathode -ray tube J. L. Baird and Baird Tele- double, and circulating a hot fluid vision, Ltd. Application date inside the intervening space. April 41h, 1935. No. 454589. J. C. Wilson and Baird Tele- 0000 vision, Ltd. Application dale April 51h, 1935. No. 454601. PERMANENT MAGNETS o000 ANalloy suitable for a per - manent magnet is made from SCANNING SYSTEMS aluminium, iron, cobalt and nickel \STEAD of scanning the picture mixed together in such proportions in a series of complete horizon - as to represent a true chemical t.1 or vertical lines, the process is compound. That is, each element commenced first over the area is present in proportion to its marked r, Fig. 1, which is one - chemical valency. This is stated third the overall width of the pic- to increase both the molecular ture, and is scanned horizontally. density of the alloy, and the inten- Next the area 2 is similarly sity of its magnetic moment. scanned, followed by the other T. Hamilton- Adams. Appli areas in the sequence marked. cation date April znd, 5935. No. Method of obtaining uniform amplification over a band of frequencies. This combination of horizontal 454567. THE . PRACTICAL RADIO s:::`O'1` JOURNAL // +, 26th Year of Publication rt., . / // 1

No. 908. FRIDAY, JANUARY 22ND, 1937. VOL. XL. No. 4.

Proprietors : ILIFFE & SONS LTD. EDITORIAL COMMENT Editor : HUGH S. POCOCK. Broadcasting on Ultra - the new transmissions is already being Editorial, shown, particularly by enthusiasts in Advertising and Publishing Offices : Short Waves London, who stand to reap the first - DORSET HOUSE, STAMFORD STREET, fruits of the scheme. A vast number LONDON, S.E.s. Interesting Possibilities Opened Up of Metropolitan listeners may expect Telephone: Waterloo 3333 (So lines). Telegram(,: "Ethaworld, Sadist, London.' to be able to take advantage of the T,,,, is not the first time that we service with the help of extremely COVENTRY : Hertford Street. have made reference to the simple apparatus -at least so far as - Telegram,: Telephone: Autocar, ((Sentry." Sato Coventry. possibilities of ultra- short- the radio -frequency side of the set is

BIRMINGHAM: wave sound broadcasting, for concerned. Guildhall Buildings, Navigation Street, 2. as long ago as May, 1935, we were dis- "That the use of ultra -short waves Telegrams: Telepphone : cussing on this page the potential would enable very high quality sound re- ., Autopress, Birmingham." 297! Midland (; lines). importance of these wavelengths for production to be achieved has long been MANCHESTER : 260. Deansgate, 3. high quality transmissions. We then recognised, but it is probably because Telegrams: Telephone: w I lifie, Manchester." Blackfriars 4412 (q lines). said " although we seem to have settled of the extremely high standard of clown as the result of some years of reproduction attained by the Alex- GLASGOW : 26e, Renfield Street, C.2. experience to the idea that medium andra Palace sound transmissions that Telegrams: "Ilille,Glasgow." Telephone: Central 41357. wavelengths are ideal for general broad- attention has been focused on this PUBLISHED WEEKLY. ENTERED AS SECOND is CLASS M.ATrER AT NEW YORK, N.Y. casting purposes, it interesting to matter in recent weeks. speculate as to whether this view will Subscription Rates : hold in the years to come. An Opportunity Home, Ls Is. 8d. ; Canada, £s Is. 8d. ; other countries, £1 35. sod. per annum. " Quite obviously, any drastic or hasty change could not be contem- When these transmissions are started A c Many of the circuits and appaaalus described in Oyese plated, for the scrapping of medium - from Broadcasting House and extended, pages are covered by patents, readers are advised, be/ere making use of them. to satisfy themselves Thal they mould waveband transmitting stations, even if as we hope they may be, to other parts not be in/ranging patanes. the advantages of so doing were of the country, it is very desirable that immense, would render sets in universal the opportunities provided should be use obsolete as well as the transmitting made use of to the very best possible stations themselves, and such capital advantage. In our view, it is a de- CONTENTS loss could not be entertained. plorable waste of opportunity to make " But, nevertheless, the coming of use of the ultra -short waveband Page television on ultra -short wavelengths associated with television for the trans- Editorial Comments 7S does open up the possibility that sound mission of sound from film records or, in broadcasting on these wavelengths may fact, to use it for any purpose other Synchronising in Television .. 71 gradually achieve popularity amongst than those programme items which Holland's New Broadcasting House 7' listeners to a point where regular listen- justify high quality. We would like to ing as at present, on the medium see these ultra -short wavelengths de- Current Topics . . .. 81 wavelengths, may go out of fashion. voted exclusively to the transmission Simplifying the Beat Frequency Earlier this month we published a of music and other items where quality Oscillator .. .. 82 note to the effect that in all probability really matters. Unbiased .. .. 85 the B.B.C. will shortly establish an Perhaps in the future more and more ultra- short -wave service for the relay of the local broadcasting in Listeners' Guide for the Week 86 this of national programmes, the trans- country will be done on wavelengths of Random Radiations 88 mitter being situated on the roof of this order, thus releasing other channels Broadcast Brevities.. 89 Broadcasting House. There is every in the present broadcasting bands for The Loud Speaker and the Cabinet 90 probability that this news will be con - the transmission of longer talks and firmed in the very near future and the other material so much needed for Letters to the Editor...... 92 possibilities which this experiment educational as well as for entertain- On the Short Waves.. 92 opens up are extremely interesting. ment purposes, and for which high Recent Inventions ...... 94 Keen interest in the possibilities of quality transmission is not essential. 74 Wireless World, January 22nd, 1937

r

HE complete separation of the synchronising impulses from the vision signal is essential Synchronising in for stable pictures and some form of amplitude filter is necessary. The requirements are discussed in this article and various types of filter are TYPES OF AMPLITUDE FILTERS described. By W. T. COCKING

ONE of the greatest difficulties secured in this way ; indeed, it is usually the spot occurs. It is not possible to work which arises in television re- possible to hold an intelligible picture for with the spot brighter than this without ceivers is the problem of syn- no more than a few seconds. a loss of detail. chronisation. It is well known Something is required to force the time - This point of defocusing must corre- that scanning is effected by causing a spot bases to function with extreme regularity, spond to white in the picture. The of light, or its equivalent, to traverse a and this is. provided by thesynchronising operating conditions must thus be ad- series of parallel lines across the picture. impulses in the transmission. At the end justed so that when the carrier is In the receiver the picture is built up by of every line traversal an impulse is pro - modulated no per cent. the grid potential a spot of light traversing an identical series vided which trips the line time -base at just reaches this point of defocusing, and of lines across the screen of the cathode - precisely the right moment and so forces when it is modulated 3o per cent. it is at ray tube. it to operate in step with the 'transmission. the point of extinction of the spot ; the In most cases electrostatic deflection is Similarly, at the end of every frame a difference between these two points is used and the electron beam which causes much longer pulse, or a long series of usually of the order of 20 volts. These the light spot by striking the screen is de- pulses, is provided for keeping the frame conditions are shown in Fig. 2, and it will flected by means of suitable voltages time -base in step. be seen that the synchronising impulses applied to the two pairs of deflecting Provided that the pulses actually ap- plates. These plates are mounted at right plied to the time -bases are a faithful copy angles and the horizontal deflection for of those impressed upon the transmission, producing the lines is obtained by apply- good synchronising is not difficult to ing a rapidly varying voltage to one set secure. It is important, however, that DEFOCUSSING w OCCURS of plates while a slowly varying voltage the pulses should be as nearly the same as o applied to the other pair moves the spot the original ones as possible, for if any- Z vertically and so opens out the otherwise thing is added or subtracted the stability J superimposed lines into a raster. of the synchronising is likely to be greatly For distortionless reproduction of the reduced. picture it is necessary that at any and Now both the Baird and E.M.I. trans- every instant the light spot be relatively missions include synchronising impulses NEGATIVE GRID VOLTS in the same position as that in the trans- of similar type. The intelligence neces- mitter. The permissible tolerances are sary for the production of a picture is very small indeed and quite small varia- conveyed by variations in the amplitude tions are sufficient to destroy any of the carrier. The amplitude is varied semblance to a recognisable picture. between 30 per cent. and Too per cent. of its maximum value for the picture signal proper and between zero and 3o per cent. tl ¡lilt il,! ,II) ll for the synchronising i i 1111 iii iii u 1 ii ini illl i u 11111111 ii, ui u ui Imil l üi o impulses. 41, 1 1 --30% The carrier wave- Fig. characteristic curve of a CR '1'''''+'''iillïi' '' "ïi i"'11;1ji1i 111I 111' form thus takes the 2.-The --1oo % form shown at (a) in tube is shown above with the applied wave- form below. The picture signal is applied (a) Fig. 1, and it will be :to that it sweeps over the useful part of seen that the syn- the curve and the synch. pulses represent a chronising pulses signal which is "` blacker than black." really consist of a complete cessation of fall upon a part of the tube characteristic the carrier. After where it is inoperative. They appear on (b) rectification, the de- the picture merely as a uniform black tector output takes band at the edge. the form shown in The output of the detector is positive ; Fig. I. -The IF waveform takes the form shown at (a) where the (b) and is applied that is, an increase in modulation depth carrier is regularly interrupted for the synchronising pulse. After directly to the causes the detector output voltage to is of the type shown (b). detection, the waveform at cathode -ray tube for increase in a positive direction with re- modulating the spect to earth. The change of detector Self- running time -bases are usually em- electron beam. The tube has a character- output voltage during a synchronising ployed for generating the scanning volt- istic like that of Fig. 2. At a certain impulse, however, is in a negative direc- ages, and it is theoretically possible to negative grid voltage the light spot is ex- tion; in other words, there is a certain secure correct results merely by adjusting tinguished and this voltage must natur- mean detector output, and during the syn- the controls so that they produce the ally correspond to black in the picture. chronising pulse the output falls below correct frequencies. In practice, however, As the grid voltage is made less negative this value. It is consequently in the no time -base will operate sufficiently the spot gets brighter and brighter until a wrong phase for operating the time-base. regularly for satisfactory results to be point is reached at which defocusing of A phase -reversal stage could be inter- TI'ireless World. January 22nd, 1937

+H T Teevisiön R5

posed, but this alone would not be 1 sufficient, for the effective amplitude of the synchronising pulses would no longer V3 be independent of the picture signal. This would occur because of the necessity for using intervalve couplings which re- R2 I move the DC component. If we have a series of pulses such as those of (a) in Fig. 3 developed across a resistance RI, C2,.. C4FR4 then the pubes developed across the resist- C.1.

-GB OG C R TUBE

Fig. 5. -One method of synch. separation is shown above. The synch. separator is the diode V2 and the triode V3 is used as an amplifier and phase -reverser.

state after many cycles of such pulses. length of the Ily -back depends in some The amount by which B is negative be- degree upon the amplitude of the pulses, tween pulses depends upon how frequently the operation will be affected. Actually, the pulses occur and how long they are the different lines will tend to start at maintained. If their amplitudes vary, different times, and so they will be slightly then the mean negative value between displaced and reduce the definition of the pulses will not be a constant and the posi- picture. tive amplitude of the pulses will vary. It is consequently necessary to filter Now suppose that we obtain a detector out the picture voltages in such a way output voltage, such as that of Fig. 4 (a), in which the syn- Fig. 3. --A resista ; ce -condenser combination chronising impulses cannot deal fatthtully with a waveform of are in the right the type shown at (a) for it removes the DC component. The waveform after the coup- phase. It is true ling is that of (b) ; only the changes of voltage that the picture are properly reproduced. signal is now in the wrong phase, but ance R2 are not identical. They can be this need not worry very nearly the same in shape if the pro- us at the moment. duct Ci R2 is large enough, and the total If we use resistance - change of voltage will be the same. capacity coupling, When the voltage at the point A moves the true output volt- as shown from zero to a positive value and age will take the back again to zero, that at the point B form shown in (b) in moves from a negative value through zero a greatly exagger- to a positive maximum less than that of ated manner. Two point A and then back through zero to the successive lines are original value negative with respect to shown as having a earth. This is, of course, for the steady widely different pic- ture content as evi- denced by the different amplitudes of the picture volt- J ages. When this is Fig. 6. -An amplitude filter which operates with an IF input gives passed through a extremely good results in practice. The RF pentode is operated with coupling which re- an anode supply of about 6 volts only moves the DC component, the magnitudes of the voltage that the amplitude of the synch. pulses changes tend to remain unaltered, but is independent of the picture content. near extremes of voltage tend to settle There are several ways of doing this, and themselves at equal positive and negative one that has been used is shown in Fig. 5. values about the zero line. The tendency The valve Vr is a diode detector of is for the sum of the positive and negative normal type and the voltage developed values over a period to be zero. across its load resistance Ri is of the form It is thus clear that the absolute posi- shown in Fig. i (b), and is applied tive amplitude of the synchronising pulses directly to the cathode -ray tube from the will vary with the picture content. The appropriate terminals. The valve Fig. 4.- The effect of an RC coupling is to V2 make the synch. pulses of different effective pulses will still occur at the right time to acts as a "synch. -separator," while V3 is amplitudes when the picture content changes. trip the time bases, it is true, but as the an amplifier and phase -reverser. 76 WilpigIliSM JANUARY 22nd, 1937 WopDcol Synchronising in Television - cathode and the diode ceases to conduct ; volt. The mode of operation of the cir- When the picture output has a total the grid potential of V3 then becomes cuit is unaffected by this fact, but it must swing of 20 volts on modulation changes 5 volts above earth. No further increase be taken into account when choosing from 3o per cent. to zoo per cent. the in the voltage across RI can affect the grid values of components. change of voltage across Ri due to the voltage of V3, for synch. pulse is 20 x 3/ 7 = 8.6 volts. The the diode has be anode of V2 is returned through R2 to a come non- conduc- OS I point about 5 volts positive, the voltage tive. VSG i 4t)'5 V B 07 being conveniently obtained from a resist- The synch. pulse W ¢ VSG = 27 V ance R3 in the cathode circuit V3. thus changes the grid w 0'6 Now, during the synch. pulse, there is potential of V3 from ai no voltage across Ri, and the resistances 5 volts above earth J 1 0'5 5 000 RI and R2 with V2 thus form a potentio- to about 3 volts, so Va z / meter across R3. The voltage across that the grid poten- 04 VSG H this last resistance is in such a direction tial changes by some Z 11 w that the anode of Vz is positive with re- 2 volts in a negative 0.3-- spect to its cathode-, and this valve is con- direction. The Ú , sequently conductive and has a resistance anode potential con- /I- Va ó Ra. The grid of V3 thus has a potential sequently rises by a 0 0 2 1J1- of 5 voltsx (Ra +R1) / (Ra +R1 +R2) greater amount and ao1 with respect to earth ; the grid potential we obtain an output i 1l I can be negative with respect to cathode, from V3 consisting 0 1 1 -4 3 2 0 1 3 4 5 6 +8 however, for an initial bias resistance R4 of a positive pulse GRID VOLTS is included. With suitable values for the for each synch. resistances the grid may be 3 volts above pulse, all pulses Fig. 9. -The characteristics of the Cossor MS Pen measured under earth. being of the same the conditions indicated are shown here. For good operation at Vs, = 27 volts, the input should not be less than io volts peak on Now suppose that the synch. pulse amplitude, irrespec- loo per cent. modulation. ceases. The voltage across RI returns to tive of the picture 8.6 volts and then rises higher during the content. It is thus quite permissible to An alternative circuit is shown in Fig. 6 ; picture signal. We now have two volt- use resistancy- capacity coupling from the the detector remains as before, but no use ages in opposition acting on V2 ; there is anode circuit of V3 to the time -bases. is made of the synch. pulses in the de- Referring again to tector output. Instead, they are derived Fig. 5, it will be directly from the intermediate frequency. noted than an IRF The intermediate frequency is applied to choke is included the grid of V2 through C2 ; this valve has with a by -pass a characteristic with very sharp top and capacity C2. These bottom bends of the type illustrated in components are em- Fig. 7, and the valve is biased just beyond ployed to prevent anode current cut -off. The IF input the application of waveform is drawn below the curve and IF potentials to V2. it is easy to see what happens. The Such potentials negative half -cycles of input cause no necessarily appear to change in the current. Very small posi- some degree across tive voltage changes also cause no cur- Rz, and if applied to rent, but larger changes cause a rise in V2 the negative half - anode current. When they are large waves will render enough, however, they fall on the flat top V2 conductive at the of the characteristic and cause no further w r o n g moment. change in current. Care must be taken in the disposition of The IF Synch. Separator Fig. 7. -The operation of the filter of Fig. 6 can readily be seen from the choke, for it the characteristic curve, for the vision signal falls on the flat top and only the synch. pulses appear in the anode circuit. easily picks up The operating conditions are adjusted mains hum which so that with 3o per cent. modulation the the 5 volts across R3 tending to make the will be superimposed on the line scanning. crests of the positive half -cycles of input anode positive and the voltage across RI In the writer's experience even heater come well above the top bend, so that the tending to make the cathode positive or wiring must be kept well away from it ! changes of amplitude due to the picture the anode negative. When the voltage In addition, the anode -cathode capacity modulation come on the flat top. At first across RI exceeds that across R3, the of V2 must be kept as small as possible, sight this would appear to offer perfect anode becomes more negative than the otherwise the picture frequencies will pass separation of the synch. ptilses, for it through it and reach V3 even when V2 is would seem that they should all be of the non -conductive. same amplitude. The output obtainable depends on V3 This would be the case if the modula- and its operating conditions, and by suit- tion envelope were solid. It must not be able design can be made as much as 20 -40 forgotten, however, that this envelope volts. The ordinary time -base, however, only indicates the peaks of the IF wave- does not need more than a tenth of this form. In effect, we are distorting this amplitude, and in some cases it is possible waveform by limiting the peak to a con- to replace V3 by a transformer. It stant amplitude. Instead of the current TIME -- should be noted that in the foregoing ex- waveform on each IF half -cycle being a planation it has been tacitly assumed that half sine wave it will take the form shown Fig. 8. -When the picture amplitude is a diode ceases to conduct as soon as its in Fig. 8 (a) when the amplitude is only a small, a single IF half -cycle takes the form anode is negative with respect to its little greater than the value needed to of (a) in the synch. separator, but when it is large it is more like (b). This results in cathode. This is not the case in practice, bring it to the top bend in the valve the vision signal having some effect on the and a diode usually conducts until the curve. When the input is much larger synchronisation. anode is more negative than about -_ than this, however, it tends to the form IIr

JANUARY 22nd, 1937 WOIl 77 Synchronising in Television - volt instead of 3.5 volts. As a screen - through the valve capacities, provided of Fig. 8 (b), and it is easy to see that the grid valve is used, there is little risk of a that reasonable precautions are taken in area enclosed by the curve is greater. leakage of the input to the output circuit the layout. In view of this the anode current of the valve will be greater when the picture amplitude is large than when it is small. This may not at first be clear, but it will be when it is remembered that the anode In Next Week's Issue current with a large input is not equal to THE LIST OF PARTS REQUIRED the value of the flat portion of the curve, The Wireless World Certain components of other makes but is less than this. The current is actu- but of similar characteristics may be ally a kind of mean value of the in- used as alternatives to those given in stantaneous values during the RF half - EXPERIMENTER'S the following list cycles, and will obviously be constant only 2 IF transformers, 465 kc /s (special) if all the RF half -cycles are constant. Varley BP97 It follows that this circuit cannot give 2 IF transformers, 465 kc/s (special) perfect separation of the synch. pulses IF AMPLIFIER Varley BP98 1 IF oscillator unit, 465 kc /s (special) and that the amplitude of the pulses will IN every class of experimental work it B.T.S. depend in some degree on the picture con- 1 Volume control, io,000 ohms, wire -round is often necessary to depart from the tent. An improvement is obtained if the Haynes orthodox, and radio is no exception. 1 Volume control, o.25 megohm, tapered, characteristic does not have a flat top but (without switch) Polar-NSF V/4 one which falls with increasing voltage, as New ideas frequently arise, and putting them into practical form usually entails Condensers: shown by the dotted curve of Fig. 7. 2 o.000r mfd. mica T.C.C. "M" considerable constructional preparations, With a curve of this nature the current 1 0.0005 mfd. mica T.C.C. "M " tends to constancy with increasing input, though much of this work can be avoided 1 0.01 mfd. mica T.C.C. "M" by having available some standard units Io 0.1 mfd. tubular T.C.C. 250 for the falling characteristic tends to off- 14 mfds., 450 volts, dry electrolytic set the increased area of the IF half -cycles T.C.C. 502 effective over the main portion of the. 150 mfds., 12 volts, dry electrolytic T.C.C. "FT" curve. High -gain Selective Unit Operating Conditions Embodying some

It is now pertinent to enquire how we Novel can obtain such a characteristic. A close Features approximation to the ideal can be ob- tained from an RF pentode operated under suitable conditions, and the curves of Fig. 9 show the results with a Cossor MS Pen with 5.05 volts HT voltage. With this exceedingly small anode volt- age a saturation effect soon sets in and gives a remarkably sharp upper bend to the curve, particularly with 40 volts screen- potential. As grid current flows, it is important to take the characteristics with the resist- ances in circuit and for these curves R2 and R3 had values of 9,000 ohms and 5,000 ohms respectively. With 27 volts screen -potential the normal grid bias should be about 3.5 volts and the peak IF input during zoo per cent. modulation not less than about ro volts. On 3o per Resistances : cent. modulation, or more, the grid poten- to which the experimental parts may be 2 250 ohms i watt Dubilier " F " 5 1 watt F tial will be slightly positive and the added. Loco ohms Dubilier " " 1 2,000 ohms watt Dubilier " F " envelope of the modulation will fall on the An IF amplifier can be regarded as one 3 20,000 ohms é watt Dubilier " F " flat top. The small degree of over - such unit, since, by the addition of a fre- 1 50,000 ohms 2 waft Dubilier " F " biasing found with a grid potential of quency changer, a superheterodyne re- I 100,000 ohms watt Dubilier " F " 2 I megohm watt Dubilier " F volts reduces the effect of interfer- ceiver is quickly assembled, and various " 3.5 1 30,000 ohms I watt Dubilier " F " ence and valve noise on the synchronising. arrangements of the signal circuits can be 1 50,000 ohms I watt Dubilier " F " With this circuit the output is positive easily compared with the minimum of I 10,000 ohms 2 watts Dubilier " F " in sign and has a maximum possible am- trouble. An IF amplifier has been de- 17,50o ohms 3 -5 watts Dubilier Spirohm I Switch, double -pole, double -throw plitude of 3.5 volts for the conditions signed mainly for this purpose, and, being Bulgin S114 quoted. Actually it will be slightly less. self- contained, should be very useful to 2 Screened valve top connectors Bulgin P64 It is, however, sufficient to control time - the amateur experimenter. I Plug valve top connector Belling-Lee 1175 bases of the type embodying gas -filled It consists of two 465 kc / s IF ampli- 1 Five-way connector Bryce triodes, and gives excellent results. fying stages, with eight tuned circuits, a 3 Valve holders, 7 -pin, chassis mounting, with - Should a larger output be required at diode detector, AVC, IF beat oscillator, out terminals Clix V2 any time it is easy to add a stage of and one AF amplifier. Sensitivity and AF I Valve holder, 5 -pin, chassis mounting, with- will reverse volume controls are embodied, also a out terminals Clix VI amplification. This the I Panel bush, tin. bore Bulgin Type C phase, so to obtain a positive output from switch which, when the beat oscillator is 1 Shaft coupler, tin, bore - Bulgin the amplifier a negative output is needed in use, renders AVC inoperative. 2 Stand =off insulators Eddystone 1019 from the synch. separator. This is readily Its sensitivity is high, and the selectivity 1 Aluminium chassis, 14 x 8 x zfin. B.T.S. 1 Brass rod, loin. long, ¡in. dia. obtained by biasing the valve on the top is adequate for the usual requirements of Valves: instead of the bottom bend, and for curve reception on all broadcast wavebands, in- 2 VMP4G (metallised), I MHD4 (metal - A, Fig. 9, we should use a bias of +o.5 cluding the short waves. lised) , I M114 Osram Wireless World, January 22nd, 1937 F1o11and's New Broadcasting

THE recently opened Dutch Broadcasting H.Q. is one of the most up -to -date in Europe and has excited favourable comment even in America. Our contributor has made a personal inspection of the building, as a result of which he is able to give a very detailed description of it.

Holland is the listener's paradise. There are no licence fees and no publicity broad- casts. The Dutch listener joins, of his own free will, a listener's organisation and pays a voluntary annual subscription which goes to pay for his programmes. There are four great organisations in Holland, three of which are in some manner con- nected with political or religious parties, and one of which is entirely neutral. The first of these is the Avro which, incident-

HE new headquarters of the General Association for Wireless Broadcasting at Hilversum which was completed in July,. 1936, may go down' in history as the " house -177 which impressed America " as an American was so intrigued by the Avro's new house that he desisted from his pro- jected tour of other Continental broad- casting houses and even invited one of the two Dutch architects responsible for the Hilversum house to America to ad- vise on the plans for various new studio centres which Columbia are building.

A distinctly modern note is struck by the architecture of the new A.V.R.O. building at Hilversum. The dance - music studio (above) is seen from a gallery provided for visitors. The large concert hall, which has seating accommodation for five hundred people.

ally, has the largest number of members. Owing to the wavelength situation the four organisations have to share two trans- mitters so that each can only get half a week's broadcasting time. Avro's new house is intended for a dual purpose, broadcasting and public enter- tainment in the non -broadcasting periods. As it may occasionally happen that the two may overlap, the house has been so the constructed. as to separate public enter- Wireless World, January 22nd, 1937 79

®ESCRIPTION OF THE NEW A.V.R.O. -louse ßUILDING AT HILVERSUM tainment section from the actual broad- casting section. The house is semi -circular two ' ` shells.'" This is bridged by special By " A\DERI\ G WAVE " and is situated a few yards from Hilver- thresholds Nvhich prevent persons from eum's ultra -modern Town Hall. As some stumbling over the gap in the doorways readers may inquire why at Hilversum but which do not give mechanical connec- audience will not make too great a differ- and not in The Hague or Amsterdam, I tion. The doors are in steel frames and ence. In all the studios, except in the talks would like to explain that Hilversum is are of specia' contraction. A bar closes and chamber music ones, part of the walls the traditional home of Dutch broadcast- them tightly at top, centre and bottom, have panels with two coatings, one absor- ing and is only half an hour by express and during my brief visit my guide felt a bent and the other reflectant. train from Amsterdam. certain amount of fatigue after opening In the larger radio drama studio a small The broadcasting section contains seven and closing them. section of the far part of the floor has been raised and railed off to resemble a small stage. Two floor surfaces are provided, one stone, the other wood, to give actors the possibility of creating various effects when walking, possibly also for " step- ping." Apart from the effects' studio, the big drama studio has a door built in, ex- actly similar to that in the Lausanne house, for effects use. It resembles a cupboard. Large photos mounted under glass are a feature of the talks studio. The dance - band studio has a gallery with a number of seats for a small audience. The an- nouncer's studio can hardly be called a

Inside one of the control rooms which contains a bank of gramophone turntables. The microphone (seen below) is for the use of the control engineer when it is necessary for him to make an announcement.

studios, two for drama and one each for talks, chamber music, dance music and effects, also one for the announcer. The " public " section contains a large concert hall with a seating capacity for an audience of 50o persons. The concert hall is constructed in the same manner as the other studios as it is also used for broad- casting. It can be converted into a theatre, complete with a fully equipped stage, orchestra pit, etc., or it can be used as a modern cinema. The two sec- tions of the house are connected by a large restaurant with kitchens and other neces- sary offices. The main feature of constructional im- portance is the complete separation of the inner studio from the outer " shell " of the building. Each studio is placed on independent foundations so that there can be no carriage of sound from one studio to the other. The architects have reverted to the age -old principle of pillar construc- The walls in the concert -hall are sub- studio at all. It is a semi- circular glass tion originally used by our heathen fore- divided by a long prismatical section with " cage " which juts out into the first -floor fathers on the shores of Swiss lakes. Each three different coatings sound absorbent, hall. Triple sound -proof windows are studio is placed on pillars which pass semi -absorbent and reflectant, so that the provided so that the announcer on duty through hollow sections of the outer shell, acoustics of the hall can be suited to any can watch who enters or leaves. and end on their own foundations. A form of broadcast. The seats are heavily In the large entrance hall on the ground substantial air space is left between the padded so that the presence of an floor the visitor is confronted by the 80 Wñp@Ilcogo JANUARY 22nd, 1937 ` o pIld. Holland's New Broadcasting House - kept permanently at io deg. Centigrade. foreign stations' programmes. The Avro, "Avro Clock." This clock gives the time - Two control rooms and a sound- record- at present, use specially large records of signal but the small microphone which is ing room are provided. Most of the control glass which are coated with some kind of placed in front of it behind the glass equipment was supplied from Germany.; gelatine material. These records run much panel is not actually used. A special The organ in the concert hall, on the other longer than the usual size. " mike " is placed above the clock for hand, was built by a British firm. The From the above brief description, in the actual broadcasting of the signal. To control rooms are so fitted that the control .which I have attempted to pick out the the right of the large hall there is a small engineer can operate three gramophone more salient features of the Avro's new board room, and the house also contains turntables for reproduction as well as house, readers will see that the general watch the outgoing transmission. In the design and construction of broadcasting sound -recording room it is rather surpris- studios have greatly changed during the ing that a German receiver, and not a past years. It is no longer thought suffici- Dutch one, is used for the recording cf ent to place the studios as a whole on separate foundations, but they are indi- vidually isolated as well. The Ravag's new house in Vienna, which is nearing Television Programmes completion, follows the same principles. The system to be used each day is given below the date. Transmission times are from 3 -4 and 9 -10 daily. The Radio Industry Vision Sound READERS of 6.67 m. Mc /s). 7.23 m. (41.5 Mc /s) our recent article on the (45 " beam " power valve, Type 6L6, may be FRIDAY, JANUARY 22nd. interested to know that American -made trans- (Marconi- E.M.I.) formers to suit this valve are available from The Radio Mart, 19, John Bright Street, Bir- Songs at the Piano : Nancy Logan. 3.10, 3, mingham, 1. Transformers for both RF and First -Aid -II, Accidents on the Road. 3.25, AF applications are Gaumont British News. 3.35, Television Gang 0 supplied.0 : An All-Scout Revue. Show In the report on the Eddystone " All World 9, Repetition of 3 and 3.10 programmes. 9.25, Eight " which appeared in last week's issue, British Movietonews. 9.35, Repetition of HT consumption was given, in error, as 5 to 3.35 programme. 8 mA. Actually the correct values for the particular set tested were 8 to 12 mA. SATURDAY, JANUARY 23rd. O (Marconi-E.M.I. ) Certain increases have been made in the 3, Ballroom dancing ; a novel method of in- prices of Avo instruments ; as examples, the struction by Alex Moore and Pat Kilpatrick. DC Avominor now costs Z2 5s.. and the Uni- 3.20, British Movietonews. 3.30, The White versal Avometer 13 gns. Coons Concert Party. . o 9, Music Makers : William Primrose (viola). Among the Ediswan employees to whom presentations were 9.10, Stars and their Directors : Victoria recently made on the com- Hopper and Basil Dean. 9.20, Gaumont pletion of fifty years or more of service with British News. 9.30, Repetition of 3.3o pro- the company is Mr. William Hutt, whose job gramme. it is to attend to the pumping of large rectify- The time -signal clock in the entrance hall. ing valves. Mr. Hutt, aged 67, has been with The microphone shown, however, is not the MONDAY, JANUARY 25th. Ediswan for fifty-four years. one actually used for broadcasting the signal. (Baird.) 3, Theatre Parade -Excerpts from Nancy a small lecture hall for visiting listeners. Price's production of " Whiteoaks " from the Playhouse Theatre. 3.20, Sea Stories -Com- Tuesday evening is the Avro's " at home " mander A. B. Campbell. 3.25, The World of in Hilversum just now and special trains Women -II. 3.40, British Movietonews. are occasionally run from vàrious towns. 9, Repetition of 3 programme. 9.20, Gaumont 'As each of the studios forms a hermetic- British News. 9.30, Repetition of 3.25 pro- ally sealed unit, suitable provision of gramme. 9.45, Cabaret. fresh air presented a number of problems TUESDAY, JANUARY 26th. which provided food for study by two pro- (Baird.) fessors at the Delft Technical University 3, Billy Malony (comedian). 3.10, Gaumont for over a year. It was found that all British News. 3.20, Ice -hockey explained. precautions which were taken to prevent 3.40, Film. 3.50, Togo -Japanese Juggler. the actual air ducts from carrying sound 9, Music Makers : Helen Perkin. 9.10, Repeti- were not sufficient to obviate it travelling tion of 3.2o programme. 9.30, Leslie Weston (comedian) . British in air, notably from studio to 9.40, Movietonews. 9.50, the actual Starlight : Claire Luce, with William Walker. studio. As it was not practicable to in- crease the length of the ducts, special WEDNESDAY, JANUARY 27th. baffle chambers were introduced which are (Baird.) coated with sound absorbent material, 3, London Galleries : II. Discussion on " The Picture in the Modern Home." 3.15, Film, and which deadens possible air -borne 3.25, Twenty -third Picture Page. 3.50, British sounds. By this means it should, Movietonews. theoretically, be possible for a hundred 9, Jean Melville : Songs at the Piano. 9.10, trumpets to blare in the dance -music Repetition of 3 programme. 9.25, Gaumont studio without even a whisper of sound British News. 9.35, Twenty- fourth Picture percolating out of it except through the Page. microphone. THURSDAY, JANUARY 28th. To cut the number of possible sources (Baird.) of electrical interference down to a mini- 3, Syncopated Harp Solos by Mario Lorenzi. New Pilot Radiogramophone Model íU355 mum it was decided to cool the air in 3.10, Home Affairs : II. Discussion on the incorporating a superhet all -wave chassis Future of Trade Unionism. 3.25, Gaumont covering 56 -52 metres in addition to usual summer by means of water pumped up British News. 3.35, Cabaret. below medium- and long -wave bands is designed from a well 169ft deep (situated the 9, Cabaret. 9.10, Timber Building and Tourist for operation from AC mains and the price house) and not to use other means of Camps- Discussion. 9.25, British Movie - is 22 gns. ; there is a universal model at refrigeration. The water in this well is tonews. 9.35, Cabaret. 24 gns. Wireless World, January 22nd, 1937 8r

Special PA Number

THE issue of The Wireless World for February 5th will be primarily devoted to the subject of CURRENT TOPICS Public Address equipment and applications. neighbourhood. It is antici- omission will result in a great EVENTS OF THE Recent developments in appa- pated that although 5 -kW saving owing to the high cost WEEK IN transmitters will be employed, of auxiliary water- cooling. ratus will be described and special the useful range will only be articles will deal with various BRIEF REVIEW about 35 miles owing to heavy R.A.F. Dinner aspects of this subject, which is atmospheric interference. These THE Annual Reunion Dinner growing in importance so rapidly. Siam Calling medium -wave transmitters will of the past and present There are to -day uses for PA aerial mast, an officers of the Electrical and equipment of every category, ranging ANEW short -wave station is have only one arrangement which has given Wireless School, Royal Air from domestic requirements to the to be erected in Siam by very satisfactory results else- Force, Cranwell, is to be held extensive outfits used in connection the Telefunken Co. It will be Furthermore, water - at 7 p.m. to- morrow (January for purpose of where. with addressing large outdoor used the dual cooled valves will not be used, 23rd) at the R.A.F. Club, Picca- handling traffic to ships and audiences. is that their dilly. broadcasting musical pro- and it anticipated grammes. American Programmes for Europe IN answer to many demands from listeners on this side of the Atlantic the well -known short - wave station Boston WIXAL has advanced the time of its daily half-hour for Euro- pean listeners by 14 hours. It will now begin at 9.30 p.m. (G.M.T.), this being far more convenient for European lis- teners than the former time of II p.m. Wireless for the Blind THE amount so far received by the British " Wireless for the Blind " Fund as the result of Mr. Christopher Stone's broadcast appeal on Christmas Day now amounts to ¿Io,000, but it is hoped that this sum will be greatly increased as contributions are still continuing to arrive. The address of the Fund is 226, Great Portland Street, Lydon, W.I. Indian Plans CERTAIN modifications have been introduced into the All -India radio service scheme. It decided that Bombay, has been " FIVE -METRE " ATLANTIC SUCCESS. The crystal -controlled Programmes for Danish Delhi, Calcutta and Madras are transmitter at G5BY, operated by H. L. O'Heffernan, which, as Exiles to be provided with Io- kilowatt reported on the correspondence page, put the first five -metre signal short -wave transmitters. across the Atlantic. It is remotely controlled and feeds a diamond PLANS are being made in The medium -wave transmit- aerial system, the power input to the final amplifier being between Denmark to supply pro- ters are intended to supply the loo and 25o watts. Above is shown a general view of the station grammes from the homeland to needs of those actually dwelling with the receivers, monitors, modulation panel and controls for afl Danes who are living in various large transmitters on the left, while on the right is the 25o -watt 20 -, 40- parts of America, and for this in the cities and their and 8o -metre Below is seen the five -metre transmitter. transmitter. purpose a special 5 -kW beam transmitter is to be put into operation. It will work simul- taneously with the present SW transmitter at Skamlebaek. It

is hoped that the new station . will have a very considerable range. Index and Binding Case THE Index for Volume XXXIX of The Wireless World, July to December, 1936, is now ready, and may be ob- tained from the publishers at Dorset House, Stamford Street, London, S.E.1, price 4d. post free, or with binding case 3s. rd. post free. 82 Wireless World, January 22nd, 1937 Simplifying the Beat Frequency AN INEXPENSIVE AUDIO -FREQUENCY GENERATOR THE author describes an audio - frequency test oscillator in By C. Y. EDWARDS, M.Sc.Tech. which the design has been simpli- fied by using a triode -hexode as OST quality enthusiasts will voltmeter. Readings of the voltmeter are a mixing valve. This avoids have felt at some time or other plotted against audio frequency, taking troubles due to " pulling" between the desire to test their receiving care to keep constant the depth of modu- y gear for response over the lation. the two oscillators whole range of useful audio frequencies. Regarding methods of obtaining various No matter how carefully one may calcu- audio frequencies, consider first the use of late circuit values, it is generally true to standard frequency records,, pick -up and say that several parts of a set affecting amplifier. This is an expensive equip- bined in a rectifier, and the audible overall response are still rather doubtful, ment and an AC voltmeter is almost " beat " or difference frequency is and an actual means of testing the fidelity essential for monitoring the output. One separated from the rectifier output by of the electrical side is very valuable. alternative to this is an audio oscillator of means of a low-pass filter. Examples of these doubtful quantities are the straightforward tuned circuit type, but Many commercial oscillators of this the high-note attenuation due to tuned a very large number of coil changes is type contain up to nine valves, and may circuits in RF and IF amplifiers, character- necessary to cover a range of 3o to zo,000 cost over £zoo, but much of the compli- istics of tone compensation circuits, c /s, and the output varies considerably cation required to secure extreme stability deficiences of the output transformer, etc. with frequency. of frequency and uniformity of output A variable audio -frequency source can The heterodyne or beat -frequency oscil- over the range can be dispensed with for by itself be used for measurements on the lator gives a continuous change of the purposes under consideration. The AF side of the set and by using such a frequency from zero to the required upper oscillator described and illustrated here generator for modulating a radio -fre- limit simply by turning a knob, the output employs the circuit given in Fig i. It quency oscillator, one can include the remaining practically constant. The oscil- attains a high standard of performance

Fig. Complete of the oscillator, the i.- circuit diagram positions of inter -stage screens are indicated. Values of components : Cx, C6, o.ox mfd ; C2, ; 2 ; C7, 0.0001 mfd C3, C4, C5, Cal, C13, mfds C8, C9, 0.0005 mfd ; Cio, Cx2, 4 mfds ; C14, CIS, C16, 8 mfds (electrolytic) ; C17, C18, o.1 mfd. Rx, 200,000 ohms ; R2, Rxo, 10,000 ohms ; R3, R14, 20,000 ohms ; R4, R5, R7, R8, R11, 50,000 ohms ; R6, Ris, 30,000 ohms ; Rg, ioo,000 ; x ; ohms R12, R13, megohm R16, Soo ohms. L1, L2, 17 millihenrys ; L3, 34 millihenrys ; L4, L5, 300 millihenrys. signal- frequency portion of the set in an lator consists essentially of two high - with only three valves, the principal con- overall response test. The procedure is to frequency oscillators, the frequency of one tribution to this notable simplification connect a dummy resistance load in place of which can be varied by about io,000 being the use of an electronic mixing of th( loud- speaker speech coil and to con- c/s by making a portion of its tuning valve, actually a triode-hexode, Type nect across this a rectifier or thermionic capacity variable. The outputs are corn- X4r. This valve has very low capacity Wireless World, January 22nd, 1937 83

in Fig. 2. It consists of 86o turns of No. proach to a logarithmic frequency 36 DSC wire on an ebonite bobbin of the calibration above 5o c/s will be obtained, dimensions shown, tapped at about one - i.e., a straight line graph on paper with oscillator third and two- thirds of the total turns. the frequency scale logarithmic and con- Flexible leading -out wires should be used denser dial scale plain. The actual for the ends and tappings. Failing a seam- calibration curve of the oscillator described between the control grids in the mixing less screening can for this coil, a good is shown in Fig. 4, together with the out- portion, and the oscillators can be coupled alternative is a can built up from copper put curve. This straight line means also directly to these grids without trouble due sheet with the seam carefully soldered. that a certain angular movement of the The coil is tuned to a frequency to ' ` pulling in " and wave -form distortion of ap- condenser will multiply the frequency by at low frequencies. This pulling into step proximately 70 kc /s by a 0.0005 mfd. a constant factor at all parts of the scale, of the oscillators has usually been com- compression type condenser, those illus- for instance on this model an octave is ob- bated by means of isolating tained by a movement of some amplifiers or a balanced bridge 24 degrees, and piano scales input system to the detector. can be obtained by turning the Another great advantage of dial 3 degrees at a time at any the hexode over the usual part of the scale. Obviously a anode -bend triode is its ability good condenser of brass con- to give a large output voltage struction and easily taken to at the difference frequency pieces is desirable, and the one without distortion, thereby elim- illustrated is an old Lotus corn - inating intermediate AF stages ponent, square-law and of 0.0003 before the output stage. Heptodes mfd. capacity before alteration. do not appear satisfactory since The AC voltage at the grid of this pulling -in occurs at too high a oscillator should be at least to frequency, and zero setting be- volts, and a check by valve volt- comes inaccurate. The normal meter is useful. method of biasing the X41 by The detector output is filtered cathode resistance is also useless firstly by a tuned by-pass (L3, for the present purpose, for no C8) for the fixed oscillator fre- matter how well this is decoupled quency. This is absolutely it will give rise to serious " pull- essential if serious " pulling " is ing " at low frequencies. Bias is to be avoided, for unless the obtained automatically by the anode is substantially shorted to grid rectification which occurs in cathode at this frequency, the the fixed oscillator. voltage at the anode due to the The components are mounted fixed oscillator pulls the variable on a chassis of aluminium 121 x oscillator through the capacity 9'1 x I4 inches, with a front panel from anode to outer control grid, of tin. aluminium loin. wide and which is not particularly small. 74in. high. The whole slides into The tuned by -pass consists of a a sheet metal box providing good low -loss coil L3 of about 34 mH screening from other apparatus. and a screw -down condenser Screens above and below the similar to those used in the oscil- chassis separate the variable lators. The coil consists of 1,300 oscillator components from those turns of 36 DSC, on a bobbin of of the fixed oscillator and output the same type as before (Fig. 2). stage. Alternatively, two of the G.E.C. The fixed oscillator is straight- coils already mentioned may be forward. The tuned coil Li, of used in series. The correct setting approximately 17 mH in the can be found instantly with a model illustrated, is made from one coil Disposition of the principal components and cathode ray oscillograph, or a valve volt- of a G.E.C. Superhet Five IF transformer arrangements of the inter -stage screens are the coil or a rectifier milliam- shown in this plan view. meter across which was obtained through The Wireless meter in series, or failing these, the correct World manufacturers' surplus columns. setting is that which gives the lowest These are probably unobtainable now, trated being supplied with the IF trans- pull -in frequency. All other unwanted formers and a suitable substitute coil is illustrated previously mentioned. About frequencies are cut down to a negligible one -twentieth of the grid voltage developed is applied through a screened lead to the X41 control grid. Thorough anode de- I/83/8 I coupling is needed, or the tendency to 111111111111PIM!\11111 pulling is increased. 111/MIDINIMMIMI The variable oscillator coil L2 has the ..WHi.T` same number of turns as the first, but is \\\1II.....M ..r.---\ untapped and has a tightly coupled re- 111111pPt!':71iga\ action coil of about one half the number ®.®i.'.iNt7J of turns. Three condensers are connected across the tuned portion, a 0.0005 mfd. I3IA!iIMUM screw -down trimmer as before, a small i®/ neutralising condenser for zero adjustment 11111111 and the main variable condenser. This condenser has to be free from slackness n the bearings and must have each vane cut Fig. 3.- Shaping of the variable condenser different rotor plates ; original shape shown by dotted of the away and filed to a shape, copy- \. Fig. 2.- Dimensions ebonite former on lines. The form of the largest plate is par- which the oscillator and filter coils are ing as closely as possible the diagram, Fig. ticularly important, as it determines the wound. 3. If this is done carefully, a good ap- calibration up to i,000 c /s. 84 WIpig,@00 JANUARY 22nd, 1937 WopIlcól Simplifying the Beat Frequency Oscillator- cause a visible vibration of the milliam- it now to the oscillograph the time base is amount by a low -pass filter, single T meter needle which becomes stationary at adjusted to one -eighth of this frequency, section, with two good coils of o.3 henry, zero frequency. The neutralising, con- giving a stationary picture of 8 cycles. L4, L5 (Postlethwaite " Kinva," 3s. 6d.) denser, operated from the front panel, is Synchronising should be only slight. The mounted at right angles, and a shunt con- for finding this setting accurately. The oscillator frequency can now be reduced denser of 0.0004 mfd. theoretically, but range of the oscillator is increased by re- to give pictures of 4, 2, I, á and á cycles, which can be cut down the frequencies being octaves below the to about 0.00025 mfd. fork, e.g., 512, 256, 128, etc. These points to give slightly less are noted, the oscillator is turned back to attenuation at Io,000 so fork frequency, and the time base speeded c/ s. The correct ter- i 40 up to give a picture of 1 cycle. Multiples mination is supplied i 20 of the fork frequency o can now be obtained, by the 50,00o -ohm e.g., 3 times fork frequency when 3 cycles 00 1 o+ volume or output appear on the screen, and so on up to BO 5 io control RI'. or 12,000 c /s. Coupling to the out- 60 . /V77 0 Another solution of the problem of put stage is by a good 40 5 calibration is to be found if one can 2 -mfd. condenser and 20 7 o borrow a set of standard frequency I- megohm leak. Bias / records. These are played on the gramo- 0° o' g888°g°g 8 8 is obtained by a resist- c9 8 4'8888 a c anm ggSB$o phone and the oscillator set to the fre- Ci th 7 mm CO- fJ ^ ance R16 in the Ñ f0 quency of each track in turn. negative HT lead de- FREQUENCY IN CYCLES PER SECOND coupled as shown. Fig. 4.- Calibration and output curves of the original model. This is the only method, excluding battery or separate ducing the capacity of both trimmers. The bias supply which will work down to fre- tuned by -pass circuit should be adjusted Pye quencies below 10 c / s.- No output trans- at this stage. former is fitted, but resistance coupling A rough calibration and check on scale Polishing through a 4 -mfd. condenser is suitable for shape over the first part of the scale can Outfit be obtained by direct comparison with a high- impedance loads and powers up to FOR RENOVATING CELLULOSE 300 mW. Using choke or transformer out- piano, knowing middle C to be 256 c / s, put, nearly one watt could be obtained. the octave above 512, the octave below FINISHED CABINETS In the interests of a well -maintained out- 128 and so on. If the graph so obtained DURING the past few years put at high frequencies, the metal cases of on logarithmic paper is running straight, considerable attention has been given to the design condensers CI' and C12 should be stood - it can be produced to cover the top two and construction octaves with fair accuracy, especially if of cabinets for off from the chassis by blocks of 4in. radio receivers, and the modern version is ebonite and insulated. Power supply is the condenser has been carefully copied. indeed quite a handsome piece of furniture. from AC mains, using a Type HT8 West- Complete calibration can be done very Like many other articles that are in daily inghouse metal rectifier and a smoothing quickly from one good tuning fork, pre- use, however, it is not always possible to choke of over loo henrys, actually a ferably of frequency i,000 or 1,024 c /s, avoid slight damage to the polished surface. field replacement component of if access can be had to a small cathode As the majority of radio cabinets are now speaker cellulose ohms resistance. There should be ray oscillograph with linear time -base. finished, the surface cannot be 2,50o renovated in the same no great difficulty in rearranging the The procedure is to let the oscillator warm way as french pol- set its zero ished cabinets, so that those who might feel supply circuits for battery operation. up for half an hour, then and inclined tune it to the fork frequency. Connecting to undertake the work themselves are debarred from doing so since the cor- For Use as a Modulator rect materials to use are not generally known. The arrangements for supplying and Pye Radio, Ltd., have now come to the modulating a radio -frequency oscillator rescue by introducing a polishing outfit especially compiled are very . simple. The HT supply is taken for dealing with cellu- through a separate anode resistance which losed cabinets. Its purpose is for renovat- ing and be, by a switch at its " live " not for applying the polish to bare can joined wood. Known as end to the output valve anode when modu- the Cabinet -aid Polishing Kit, it contains several bottles of solution, lation is required. Practically any radio tins of special compound, brushes, cloths and oscillator will be suitable provided that it all the necessary impedimenta for restoring contains no decoupling circuit in the the polished surface of a cabinet to its orig- anode, or by -pass condenser greater than inal appearance. say "0.0003 µF. The Wireless World Test A perusal of the instruction book reveals Oscillator is a suitable type, and necessary that the work entailed is not difficult, nor is modifications would be the use of an AC it beyond the skill of the average person ; valve, type MH4, leaving out the modu- the methods of removing scratches, stains and other blemishes are all very clearly and lator and taking out the " top " end of fully explained. the feed RF choke to a terminal for con- The Kit is contained in a portable case, nection to the heterodyne oscillator. measuring rod x rod x 34 in., and it can Heater current for the valve is also sup- be secured to a wall or the back of the plied from the audio oscillator transformer. work -bench, yet quickly removed when- The design of oscillator described, using ever necessary. the same coils and trimmers, requires the Servicemen will find it a valuable adjunt following approximate settings. Screw the to their equipment since after overhauling trimmer home and then a receiver it can he returned to its owner, fixed oscillator not half a turn. With neutralising only in good working order, but also back about with its external appearance greatly en- condenser mid -way and main variable hanced. condenser set at zero, adjust the variable Considering the amount of material it oscillator trimmer until the beat note heard contains, this polishing outfit is very reason- in a pair of phones comes.down to zero able in price, for it costs but 17s. 5d. frequency. The very low frequencies Pye cabinet -aid polishing kit. complete. Wireless World, January 22nd, 1937 85

the court's stern question of Guilty or Not Guilty, been compelled to hang their heads in shame and murmur " I done it." There must also be a great number who, like myself, have stood unjustly accused UNB before the Bench listening to the lying calumnies poured out by some witness for some considerable time past retailers of the prosecution, and it is A Hint to the P.M.G. these infernal machines have been puzzled to these unfor- tunates I would speak so I might BROADCASTING has a lot to answer by a steady upward tendency in their sales that that for in adding to the sum total of curve, which has reached such alarming human misery, for apart from the feeling proportions of late that factories making By FREE GRID of melancholy which is introduced into them have had to work overtime. The the our homes by the solemn dirges of base suggestion that doctors were getting pass on to them a tip which I have re- B.B.C. on Sunday afternoons, to say a rake -off from the manufacturers in re- cently proved to be invaluable. of nothing of the negroid noises week- turn for certain advice to their patients In the past I suffered so actors often at the days, we learn that thousands of has proved to be quite groundless, and it hands of the Law and its pencil -licking and musicians who depended directly or appears that the whole trouble is due to satellites, who swore away my reputation the stage for their living indirectly upon the fact that since the coming of the all - as a car -driver as cheerfully as though I wave set many people allow their loud were their mother -in -law, that I deter- speakers to drool away throughout the mined to put a stop to it. I accordingly entire twenty -four hours, some set manu- installed in my car the very latest thing facturers actually encouraging this repre- in amplifiers and automatic home record- hensible habit by selling sets without a ing apparatus, and replaced my radiator switch to turn them off. cap with a microphone which was suit- Certain unscrupulous people, disturbed ably disguised as a very ornate kind of by this diurnal and nocturnal bellowing of mascot such as is fashionable nowadays. their neighbours' loud speakers, and Setting out one afternoon in search of worried by the fact that it kept their my quarry, it did not take me long to run children awake at night, have become so foul of a myrmidon of the law who began lost to all sense of decency that they have as usual to attribute to my car a speed purchased these violet -ray instruments, which the manufacturers' catalogue did not for the purpose of using them in a not claim for it even in its most moving legitimate manner, but in order to induce passages. There ensued, of course, the their neighbours to silence their loud Certain advice to their patients. usual exchange of pleasantries before I speakers by making their output intoler- was permitted to move on after having have been reduced to the bread line owing able even to them. Anybody who has my licence particulars taken just like any to the unfortunate fact that former lived within range -and it is a pretty ex- common felon out on ticket -of- leave. On patrons of the theatre and concert hall tensive one -of a violet -ray machine will the appointed day it did not surprise me to now prefer to stay at home and listen in. know very well what I mean. This re- hear from the v,itness -box the usual dis- But I digress. What I wanted to say grettable habit has, I learn, gone on torted version given of my conversation was that in spite of all these base charges spreading until it has now reached such with the constable, and I speedily asked which certain vested interests are wont to alarming proportions that in certain dis- permission to " put in " a gramophone levy against broadcasting, it is an ill wind tricts it is almost impossible to use a loud record as evidence. that blows nobody any good, and I am speaker after midnight. Sensation is a word I hate and detest, constantly coming across instances of old - but I can honestly think of no other to- fashioned trades which owe the continu- describe the effect which the playing over ance of their existence to broadcasting. Justice for Motorists A striking instance of the sort of thing ISUPPOSE that there are very few of I mean started soon after the war. Prior my readers who, in common with my- to the war, as you may know, one of the self, have not at one time or another stood staple trades of this country was the very in the dock at one of our police courts. 1 necessary hairpin industry. Came the am not, of course, intending to cast any war and women flocked in their thousands reflections on the honesty of Wireless as near to the front line as they could World readers. They are, I suppose, as get and found that, owing to the playful honest as the readers of any other habits of pulex irritans, it was desirable journal ; in fact, probably more so owing that the hair should be kept short, and to the good example set them by this thus was a new fashion born and an old paper. There are, however, many crimes and honourable industry apparently with which you may be charged nowa- Like any common felon. doomed. Fortunately, however, the days without the slightest suggestion of growing demands of home constructors dishonesty being imputed to you. Such of my record had on the court. Even for hedgehog transformers suggested an crimes as mayhem and arson, for in- the principal witness against me stood obvious use for the unwanted hairpin, stance, to say nothing of murder and man- amazed at the volley of abusive language and, although this type of component has slaughter, may be freely committed by a about me which poured forth in his voice long since disappeared, it gave the neces- person whose word is his bond without from the portable gramophone which I sary breathing space to enable the indus- damaging his reputation for honesty. had brought to court with me. Needless try to reorganise itself. However, it is not these particular to say, this, coupled with the meek and By far the most noteworthy case where crimes that I have in mind at the moment mild protests which the record irrefutably broadcasting has proved to be the saviour so much as motoring offences. Although indicated as being my part in the discus- of an industry, however, is one that has many of my readers, such as wireless sion, immediately influenced the Bench in only just been brought to my notice. You manufacturers, may be far too poor to be my favour ; so much so in fact that they have, I take it, all heard of those instru- car owners, there is still a goodly number, not only acquitted me but made a special ments known by various fancy names I feel sure, who are members of the order to the effect that all previous such as high-frequency vibrators and honourable company of road hogs, and endorsements on my licence were to be violet -ray generators. It appears that for have oft -time, in answer to the clerk -of- wiped off forthwith. so Wireless World, January 22nd, 1937 Listeners' Cuide for the FOUR distinguished Con- He is well known as the corn- Boult will be conducting, and HIGHLIGHTS OF THE WEEK 1 tinental are poser of Violets," the soloists will be Astra Des- conductors " Wild FRIDAY, JANUARY 22nd. to appear in B.B.C. " Rise and Shine," and other mond and Roy Henderson. Nat., 6.25, Recital : The New concerts this week. light operatic successes. Maria The Croydon Philharmonic English Singers. 8, Scrapbook To -night (Friday) at 9.4o in Elsner and Jan van der Gucht Society, which has 158 mem- for 1922. 9.20, European Ex- the National programme Dr. will be principal vocalists. bers, will render the choral change-3, Austria. Reg., 6, Reginald King and his Heinz Unger, permanent con - Stoltz' " Wild Violets " will, work. Orchestra. 7.30, The Shep- ductor of the Leningrad Wire- incidentally, be broadcast herds' Feast from Caldbeck. less Orchestra, will, for the twice next week. " TWENTY YEARS AFTER " Abroad. first time, conduct Section D Werner Janssen will conduct PETER CRESWELL, a pro- Warsaw, 7.15, Warsaw Philhar- monic with Uminski (pianoforte). of the B.B.C. Orchestra. The the London Symphony Orches- ducer in the Drama Depart- programme will consist of tra in a studio concert on Tues- ment, has been puzzling as to SATURDAY, JANUARY 23rd. to Nat., 4.35, Jeanne Dusseau (soprano) Schubert's Overture " Rosa - day (Reg.). He has not yet how he was to keep up the and Tom Jenkins (violin). 8, munde" and D'Iahler's conducted in England, but has broadcast standard of " The Music Hall, including Florrie " Fourth Symphony." This given English works in Three Musketeers " with the Forde and Wilkie Bard. symphony, which lasts for over America, where he has con- broadcast version of " Twenty Reg., 4, The Air -do- Wells. 6, The Friary Brewery Band. 8, Dis- an hour, includes a soprano ducted the New York Philhar- Years After," a sequel to this cussion on the Tipping System. Abroad. Brussels, I, " Rossini in Naples," three-act opéra- comique. SUNDAY, JANUARY 24th. Nat., 6.30, The Richard Crean Orchestra. ¶Dr. Samuel Johnson: feature programme. 10, Piano- forte Recital : Jan Smeterlin. Reg., 5, B.B.C. Military Band and Arthur Fear. 630, Sunday Orchestral Concert. 7.55, Service from Romsey Abbey. Abroad. Frankfurt, 7, Guila Bustabo (violin) in the Museum Society's Concert. MONDAY, JANUARY 25th. Nat., 7.20, Ninth Entertainment Parade. 8, It's Happening Now : IV. 9.35, " Twenty Years After (Dumas).

Reg., 7.30, Recital : Alexander Kipnis (bass). Van Phillips and his Two Orchestras. 8.30, Robert Bums' programme. Abroad. Deutschlandsender, 7.10, Gala con- cert. TUESDAY, JANUARY 26th. Nat., 8, " A Southern Maid." 9.20, Church, Community and State : III. 10, Music of John Ireland. A WANDERING MICROPHONE will introduce clowns and performers at the Bertram Mills' Circus, Olympia, Reg., 6, Band of His Majesty's to Regional listeners on Tuesday at 7.3o. The commentator will describe the waiting animals arranged for Royal Marines (Chatham Divi- their turns and try to convey the expectant atmosphere behind the scenes. sion). 7.30, Relay from the Circus, Olympia. ¶Organ Recital : C. H. solo, which will be sung by monic Orchestra and the book. " The Three Musket- Trevor. 9, " Twenty Years eers " possesses in itself an all - After." Elsie Suddaby. Chicago Symphony Orchestra. Abroad. On Sunday at 6.3o (Reg.) Werner Janssen has just been pervading rhythm and a speed Breslau, 7.10, " Land of a Thou- the Orchestra will be con- honoured by the Finnish Gov- which leaves the reader breath- sand Lakes " -a radio trip to ducted by Volkmar Andreae, ernment in appreciation of his less. Patrick Riddell, who Finland. who will come specially from interpretations of Sibelius, adapted it for broadcasting, WEDNESDAY, JANUARY 27th. Zürich for the occasion. Pro- whose Third Symphony he added to this by the clever Nat., 7.10, Palace of Varieties. 8.15 and 9.50, Symphony Con- - in which he divided the fessor Andreae is the per will conduct during this con- way cert. panent conductor at the Zürich cert. Last Sunday he married dramatic scenes into short, Reg., 7.45, The World Goes By. Tonhalle, and will conduct a Miss Ann Harding, the actress. staccato situations interspersed 9, " A Southern Maid." Abroad. rhapsody of his own for violin --- 0 0 with effects and music. The same will be Strasbourg, 8.30, Municipal Or- and orchestra, in which the FIRST BROADCAST method chestra from the Palais des Fêtes. A NEW choral work by applied to " Twenty Years soloist will be Steffi Geyer. THURSDAY, JANUARY 28th. Later in the evening, at 9.5 Vaughan Williams, entitled After," which, although not so Nat., 6.20, This Way Out : John (Reg.), Robert Stoltz, from " Five Tudor Portraits," will well known as " The Three Hilton. 8.15, Music from the Vienna, will conduct t h e be broadcast for the first time Musketeers," is nearly as ab- Movies. ¶Orchestre Raymonde. Theatre Orchestra in a pro- during the symphony concert sorbing and should make a Reg., 7.30, " Songs you Might Never have Heard." 8.15 and 9.50, gramme of his own works. at the Queen's Hall on Wed- first -class radio drama packed The Royal Philharmonic Society's 1 nesday, which will be relayed with thrills, romance, and his- Concert from the Queen's Hall. Nationally from 8.15 to 10.35, tory. It will be heard Nation- Abroad. Details of the week's with a twenty- minute break at ally on Monday at 9.35 and Kalundborg, 7, Tchaikovsky's and Television programmes Berlioz' Versions of " Romeo and will be found on p. 80. 9.3o, during which the news again Regionally on Tuesday Juliet." bulletin will be given. Adrian at 9. 11 Tess World, Januar.). sznd, 1937 87 Outstanding Broadcasts at Home and Abroad

BURNS' BIRTHDAY music, so the Northern people THE 178th anniversary of have adopted the Anglo- Ameri- the birth of Robert Burns will can words. Some of the world's be celebrated in a special pro- most outstanding recordings by gramme of his works on Mon- famous bands have been day at 8.3o (Reg.). Instead selected for this programme. of inviting distinguished people - <- e to the microphone to tell listeners what Burns means to DON JUAN them and the poet's place in THE week's principal event literature, the B.B.C. has de- in the Swedish programmes is cided to allow Burns on this a concert by the Berlin Phil- occasion to speak for himself harmonic Orchestra, which is through his works. playing under the direction of Eugen Jochum the Don Juan Symphonic Poem by Richard SHEPHERDS' FEAST Strauss, and Beethoven's AN actuality broadcast from Eroica Symphony. The con- the Oddfellows' Inn, in the cert will be relayed from Stock- Lakeland village of Caldbeck, holm's Konsertförening on Cumberland, of a Shepherds' Monday at 7.10. Meet will be heard to -night in 4 the Regional programme at OPERA 7.3o. It will be the occasion BUCHAREST commences the of a half -yearly " meet," when week's opera broadcasts with MUSIC FOR thirty or forty flockmasters its usual relay of the Royal WIND IN- and shepherds from the Skid - Romanian opera programme STRUMENTS daw, Saddleback, and Cald- at 6.35 to -night (Friday). beck Fells gather together to will be played by the entire wind section of the Symphony Orchestra Transmissions by this station on Monday at 8.3o (Nat.). Part of the brass section is seen in this identify stray sheep. These are of much greater general in- photograph. meets are essentially occasions terest in these days, since all of conviviality, for after the programmes are now relayed leged to hear Tauber sing- will be heard from Hamburg business side has been carried by the high -powered National ing the title-rôle at the at 7.10 on Sunday. It is highly out there is a dinner, followed transmitter, Radio -Romania opera's première in that city, probable that many of the song by songs and stories. The (Brasov). At 7.10 to -night where it is enjoying almost numbers of this operetta will financing of these feasts comes Königsberg reveals to us a staggering success. prove to be popular hits, as from the sale of unidentified little -known side of the emin- Hamburg announces one of Grothe's art is of the type that sheep. ent composer of German lieder, the less- familiar of Mozart's makes a very strong appeal to - <> Hugo Wolf. This composer operas, " La finta giardini- the man -in -the- street. its RHYTHM MUSIC was responsible for only two era," for 7.10 programme <- <

reproduction of genuine bass, the very high notes, transients, and so forth. If the set RANDOM RADIATIONS is of the " all- wave " type, it will give you a certain number of European stations and two or three of the more strongly received An Automatic Dial By "DIALL 1ST " Americans in the ordinary way, and a some- FROM an Isle of Wight reader I have re- what wider selection when conditions are ceived a interesting favourable. particularly letter agent of I picked on the subject of dials. " I have given the the manufacturers. When up my local week first Why Not Specialise ? question of dials a lot of thought in the paper last the thing past," writes he, " and have come to the that struck my eye was a displayed adver- What does seem to emerge from an tisement by the owner of a radio shop, which examination of is conclusion that the ideal method is one in current receivers that so ran : " XYZ IS YOUR. LOCAL AGENT few manufacturers ; which there is no need for skill or feats of try to specialise the . and there followed list of memory. These conditions seem best satis- FOR ," a majority are content to produce the stan- half a dozen well -known makes of receivers. fied by something on the automatic tele- dard- performance set and to rely for variety I contend that the public does regard the upon cabinet design and gadgets connected phone principle." He tells me that he has man in wireless maker's almost such a dial for his own set, the shop as the mainly with tuning. There are well -known completed agent, and that it has every reason for doing firms which specialise in particular lines in having picked up the necessary parts at junk when shops for just over LI. To obtain any one so this kind of advertisement appears. radio, but this kind of thing doesn't go And haven't you seen, both outside shops as does in, for of fifty stations, the first four letters of nearly far as it instance, its and in their windows, signs reading : cars, cameras, home cine apparatus, or such name are dialled in the familiar way. Or, for such and such sets I also if he wants to play records, dialling GRAM "Agent "? mundane things as furniture, clothes, and find frequently in the trade papers adver- ! see causes the necessary switching to be done boots I must say that I'd like to more and brings the gramophone motor into tisements headed : "Agents wanted," put firms devoting their chief energies to battery in by firms which require representatives in sets, others getting a name for " all- wave " action. A most ingenious idea, and one this district or that. The position certainly mains receivers that seems to have great possibilities. One of really fine long- distance needs clearing up. I'm no lawyer, but I performance, others concentrating on big un- criticism, though, occurs to me : what hap- can't see how a man can be an agent and !) pens if you dial HILV or BRUS or TOUL distorted (really undistorted volume, and an agent ! or LYON? Hilversum, Brussels, Toulouse yet not so on. and Lyons all have two stations apiece. ti % Guns and Wireless Sports Models Many Sets : Too Little Variety You can't imagine any two things much UST how many different more different than the shotgun and the An automatic dial covering fifty stations sets there are J on the market I don't know, but the wireless set. Yet there's a useful parallel would probably be ideal for ordinary to be drawn between them. If you're buy- I number must run to a good many hun- domestic use, but am afraid that it would dreds. Yet, when you come to examine ing a gun you can purchase a machine -made hardly satisfy the hard -bitten experimenter weapon that bears the necessary proof marks his catalogues or pay a visit to a big wireless or the D -X enthusiast -at least not for you for 5 or a little more. You can also pay personal us who into showroom, can't, I think, help being own use. Most of fall struck by the lack of variety. What I'm a hundred guineas or more for a gun that either or both of those classes have two re- driving at is this : Most manufacturers have is hand -made throughout of the very finest ceivers. One is for the family ; the other a three -valve battery set, and possibly a materials. Admittedly, a rabbit or a par- use our- for ourselves alone. The sets we battery superhet with four or five valves. tridge or a pheasant isn't any more dead, selves bear much the same relation to In the mains class they have three -valve whether it's shot by a five -pound or a domestic receivers as sports cars do to cars straights, three -valve superhets, and here hundred -guinea gun. Equally, a distant sta- of the " family bus " type. But there's one and there a set with five, six, or seven tion can be chalked up in the log, whether : wants big difference the motorist who a valves. It seems to me that we have too it is received after miracles of tuning on a sports car doesn't have to build it him- many sets capable of what one may term small, cheap set or with ease on one of many self ! Why shouldn't set manufacturers try standard performance. By " standard per- valves. But with the good gun -and with the in sports models wireless receivers? They formance " I mean that the receiver is sen- good radio set-you do know that you have ought to go pretty well, for the number of sitive and selective enough to bring in the something that will enable you to do your- enthusiasts is large. majority of the higher-powered European self justice. There are a good many firms He'd stations working on individual channels, and which turn out first -rate and costly guns. What Need They all specialise in something. It may be " radio sports that it has an output sufficient for the aver- Here are my ideas about the age room, the quality being satisfactory so weight, or balance or barrel length, or fine all, should certainly model." First of it long as one is not over -critical about the finish. But all of these firms do pretty be obtainable in two separate parts : the well. Wouldn't radio firms do just as well radio set proper (from the RF stage to the if they specialised on similar lines? second detector) and the low- frequency am- plifier. In this way both those who put sen- ti ti ti sitivity above all else, and those who regard Performing Rights high quality in reproduction as the most THE forebodings of strife between the desirable of ends, would be able to satisfy B.B.C. and the Performing Right their requirements. Also, either half of the Society, the rumours that the Society might set could be replaced as needed by some- call a " strike " of its members, and so thing more up -to -date. In the radio half forth, appear to have been hatched in the both sensitivity and selectivity of a high mare's nest that is so frequently discovered but widely variable order would be needed. by seekers after " sensations " when the We should also look for a large tuning dial B.B.C. has to come to any important de- either accurately calibrated or capable of cision. So far as one can see, the facts are such calibration. In low- frequency ampli- that when the agreement between the two fiers the experimenter could make his own bodies came to an end on December 31st choice according to the amount of undis- the Society was asking for more than the torted volume needed. Well, it's just an B.B.C. was prepared to offer. Both sides, idea, and, of course, my notion of the sports however, consented to refer the matter to receiver probably wouldn't be the same as arbitration, and the matter will no doubt yours, but I think there's something in it, be settled amicably. Few listeners will feel don't you ? that the P.R.S., whose members supply so ti. 1 .. AUTOMATIC DIAL. From America comes much of our wireless entertainment, does a practical device on the lines being suggested not deserve to receive for distribution The Agent Question in the columns of this page. By inserting a amongst them more than the roo,000 a RECENTLY, I referred to some comments finger in the slot indicating the desired station had under the old agreement. by its call sign and rotating to the lower year which it by Judge Lilley on hire -purchase agree- central position, the set is brought imme- The Ullswater Committee, you may remem- ments. If you remember, he was most diately into tune without noise from inter- ber, recommended that the B.B.C. should scathing about a clause which stated that vening stations. Ordinary knob control can be liberal in its treatment of composers and the retailer who sold the set was not the also be used. authors. Wireless World, ,Tanuar_y 22nd, 1937 Sy

m e Broadcast rev ¡, i: L e s...,...._®.._...... ,.._.a.._....,...... Engineers in Trouble ford to provide a separate West NEWS FROM PORTLAND PLACE oN their own ground the Regional programme to those B.B.C. engineers are su- listeners in the West of England +as<.uaeras aueaaesauac -waeuwaeoe-acso-7 preme, but when who now take their Regional it conies to From July until they close writing his own choosing a name they suffer programme from the Washford script for transmitter on 373 metres (804 down on the opening of the new variety shows as well as reading from the same mental ague that transmitter in South Devon the and adapting afflicted William Shakespeare. kc /s). The latter will then be- other people's - Bournemouth and Plymouth and here his long experience " As You Like It " a n d come the separate Welsh transmitter. Listeners who at low -power transmitters will should stand him in good stead, " Twelfth Night, or What You radiate the newly constituted for he was writing Will," were not worse efforts in present receive the National pro- and pro- gramme from the National pro- West Regional programme. ducing radio dramas for the the direction of titles than Lisna- Leeds station way garvey (which scarcely anybody gramme transmitter at Wash - back in 1924. ford will be asked to use Droit- Nigg Calling Few members of the B.B.C. had heard of till the Northern staff can equal Ireland transmitter opened) or wich. When Burghead was opened this record. Moorside Edge -a pale euphem- Two New Transmitters the Aberdonians put in a plea ism beside Slaithwaite, the for more power at their local Not So Dangerous rightful name for the locality. The construction of two ad- station, which operates on only ALTHOUGH R. A. Rendall, ditional transmitters to provide I kW. Their hopes will be more the new Assistant Director No Prizes, but . . . a Regional programme to the than realised in the near future, of Television, finds his Alexan- South dra Palace job full And now coast and South -west of fcr the B.B.C. has decided to of thrills it it appears that the England on a lacks the spice of danger new permanent basis erect an entirely new transmit- which South -West of England will be begun entered into the job of transmitter is causing shortly. The first ter at Nigg, outside the city, setting another of these will work on high broadcasting on its feet in pother on the upper floors of power which will have 5 kW. of aerial and will be situated in South power. Palestine. Soon after his arri- Broadcasting House. "Start val in Jerusalem in September, Point " bold, vigorous de- -a 1935, the riots began and there scription -will not do, appar- RADIO were times when the ently, as the transmitter may broadcast- DESK ing station stood in danger of be more than a mile or two from SET.- attack by malcontents. the famous headland, and the Probably because the dissatis- Devonians being none too lavish fied elements failed use of place- names, to realise in the there the true value of broadcasting, are no other likely titles that ap- the station escaped peal to the engineering mind. and Mr. Rendall and his associates were What is wanted is a really able to start the tri- lingual glamorous name which would ser- vice- English, Hebrew and comprehend the whole of Arabic -in comparative quiet. " Lyonesse," this romantic land Ca

IDEAS FOR the impedance of the coil may be many times higher than normal. The " stan- dard " set drives the loud speaker with a pentode, of course ; so not only is the bass IMPROVING peak emphasised, but also the distortion at full output rises much above the designed amount. Altogether, a bad business unless QUALITY something is done about it. (3) There is normally a falling -off in the By bass, because a small cabinet is a poor sort of baffle. It might be possible to com- "CATHODE RAY" pensate for this by faking the amplifier circuits to give a rise ; but, if successful, this would probably only magnify the evils resulting from (i) and (2). A cut -away view showing the general arrangement of One can compensate for a steady falling - the Stromberg- Carlson acoustic labyrinth. off anywhere, but it is quite a different matter when there are sharp peaks, be- cause it is impracticable to ensure that the compensation (if one is clever enough to ISTENERS may be classified broadly there is anything at all like full -level re- it is probably produce it) corresponds exactly with the : first, those who go production of the top notes, into two sorts irregularities every time and all the time. J into a shop, buy a standard type concentrated into one or snore fearful of set consisting of a box (or, peaks around 3,000 -4,000 cycles. Even according to the catalogue, " a fine the specialist loud speakers are a bit shaky Balancing Out a Resonance of the cabinet -maker's craft ") in the extreme top. I was interested to example seems to be the reason why the chassis and a moving - hear the designer of one of the best -known That containing a receiver some time loud speaker, stick it in some con- " quality " speakers confess that improve- acoustic resonator, proposed coil fitted to some American venient place in the house, and switch it ment at this part of the scale is almost pure ago and actually has done all, broadcast receivers, hasn't come to any- and off when they feel like it ; secondly, cut -and -try. Then, when he on close off part of in spite of the sales- the room plays a great part in determining thing. The idea was to those who realise that, leaving a man's description, the standard type of set the result. the space inside the cabinet, opening to form a cavity resonat- is not the ultimate in perfect reproduction, But I am not concerned just now with narrow to the un- and who therefore go to one of the few the top end, which is very disputed terri- ing equally and oppositely Fig. z shows the specialist suppliers, or build or assemble tory. At the other extreme of the scale desired resonance. 2 the results carefully selected units into a system which the problems are fairly clear, though it is general scheme, and Fig. to . en- much less compact than the by no means clear how they can be solved claimed. Whether it was possible is generally work walnut masterpiece referred to above. It within the framework of the cabinet- sure these results without individual : questionable. is almost certain to have the loud speaker in aker's craft. The troubles are these on each receiver appears separate from the receiver, and mounted in (I) The cabinet is like a short organ pipe, a door, bookcase, large baffle, or very and resonates to some particular fre- special kind of box. quency, usually about 100 -150 cycles - right in the middle of the bass. Result : Limitations of Mass Production The tubby, boomy effect familiar every- where. (2) The loud speaker cone and To give the mass -producers their due, coil as a whole resonates at some low fre- they are always prepared to consider incor- quency. Good care is taken to see that this porating any advances made in the art of peak does not hit the cabinet resonance, good reproduction so long as it 'does not for that would be terrible ; usually, it is make their products too (a) bulky, (b) somewhere around go cycles. The acoustic heavy, (c) fragile, (d) unselective, (e) ex- resistance at this frequency is low, so there pensive. If they were to design up to the is little to stop the resonance building up standard of their knowledge, there would to a large amplitude, and the coil travels always be some features that would con- so far backwards and forwards that it flict with these commercial requirements, comes out of the uniform magnetic field and so the " standard set " is always rather and causes distortion. It is possible to less good than the best efforts of the make the suspension floppy enough to put specialist. The gap is not so wide as it the resonance safely below the audible once was ; when, for example, the largest range, but this carries the practical objec- valve that could be used in a " popular " tions that the coil must have a much wider receiver ha :1 an output of about a third of gap in which to move without fear of foul- a watt. ing the magnet pole pieces, which, in turn, Where do imperfections still exist? At means bigger magnets, more energising the high -note end of the scale there is a power, lower sensitivity, or perhaps a tendency to cut off altogether; but, assum- combination of all three, to say nothing of ing the price will run to a properly exe- the suspension being less easily manufac- cuted variable selectivity system, the tured and more easily damaged. The Fig. 1.- Outline of the method of opposing limitation is imposed by the peaks and mechanical resonance in the bass is re- the cabinet resonance by means of a reson- hollows of the cheap loud speaker. If flected in an electrical resonance whereby ator built into the cabinet. (After Olson and Marsa.) Wireless World, January 22nd, 5937 9r

+2

15 Ìl WITHOUT . t, - LABYR NTH nd 10 11 McCA TI--` the 11 r1 1 I lid i for the finest value in U t D 5 Cabinet WITH LABYRINTH All-Wave Receivers ! 10 t More highly worked -out systems, de- 1 15 i signed not only to eliminate the evils of 1 cabinet resonance but actually to convert - 20 / the sound wave from the back of the loud á 8 8$Wg°s speaker into an asset, have been marketed FREQUENCY IN CYCLES PER SECOND in America under the name of ' ` The Magic Voice," and in this country under less Fig. 3. -Curves showing effect of the acoustical labyrinth in eliminating cabinet fanciful descriptions by Voigt. I don't resonance. describe them in detail now, because this (After 1 :. Olney.) was done in The Wireless World of August rinth simply introduces a very high 28th last. But another American system,' acoustic resistance into the " circuit," and embodied in Stromberg- Carlson receivers, flattens out the peak. Fig. 3 shows the is also quite interesting. It is called the extent to which it is effective. At higher " acoustic labyrinth " ; the name suggests frequencies there is no reason to suppose its purpose, which is to make the sound that the difference is appreciable. from the back of the speaker lose itself. Even more striking is the effect on the The same device is familiar to motor electrical impedance of the speech coil, 6 VALVE ALL -WAVE cyclists and others ; not, it is true, under which in the example tested was nominally the name " acoustic labyrinth," but as a 24 ohms. Without the labyrinth it jumps SUPERHETERODYNE up to 200 ohms at one point ; with the labyrinth this peak is reduced to about (complete with B.V.A. Valves) one -third (Fig. 4). 15 Improved edition of this popula, receiver (praised " Wireless A test made with the labyrinth in posi- World" test reports). Heavier gauge cadmium -plated steel chassis. Ironcored I.F. transformers giv.: even better per- lo tion, but without the absorbent lining, formance. No increase in price. r+t WITHOUT showed 1 ,A---- RESONATORS simply appalling results. So it is Brief Specification: 8- stage, all -wave band -pass superhetero- 5 dyne, 7 tuned circuits. D.A.V.C. with i : not advisable to go half -measures in trying " squelch " circuit valve t 1. for noise suppression. Illuminated " Airplane " dial. Octode 1 frequency 0 such a device. changer. 3 -5 watts pentode. Switching for gramo- t . phonepick-up. Wave ranges: 16.5 -5o, eoo-55o, 000 -2,000 metres. --- The peak, by the way, is unusually low in the scale ; in most loud speakers it would WITH RESONATORS be much more harmfully placed. 10 McCARTHY ALL -WAVE SIX It should be observed that this 15 " silencer " is not equivalent to an ordi- with 6 watt nary baffle, which causes weakening and push -pull ZO pp reinforcement output M Ç i0tf tOD ?OÓÑO S 88 of sound at certain frequen- N t7 Ó ÑE nmO,O cies depending on its dimensions. It may FREQUENCY IN CYCLES PER SECOND therefore sound a bit " down " in the bass when compared with other systems. Fig. 2.- Result claimed for the resonator The of bass system. method control that one uses ( After Olson and Massa.) is decided by individual requirements or " silencer." The construction can be seen (more probably) by what involves the least unsightly appearance or the least effort from, the picture ; instead of allowing the to air at the back of the speaker to commu- arrange. How many people really carry nicate with the inside of the cabinet, it is out for themselves half the things that they led through a pair of felt -lined covers - hold to be technically right? the space between is to prevent overheat- (complete with ing of the magnet the lower 200 B.V.A. Valves) -into part of A the cabinet, which is divided by two hori- 180 6 valve all-wave superheterodyne with similar specification, zontal partitions so as to treble the length II performance, etc., to above, 100 ri but with large push-pull output before reaching giving 5ÿ -6 watts. the opening into the outer I 1.4----LABYRINTH 140 Has illuminated " Airplane " dial with principal station names, air. The total length of the tunnel is I Ì tone control and volume control (both also operative on about 6ft., and the cross- section 4in. x 120 jÌ gramophone), full provision for gramophone reproduction.

1 8in. The walls are everywhere lined with 100 A really high quality receiver, with exceptionally large á Ì undistorted output, and fine performance on all 3 wave inch -thick rock wool -a material that is ranges. ao ; WITH LABYRINTH very effective in absorbing sound. 1 All McCarthy A 60 t receivers supplied complete with closed air space with hard, reflecting / \ valves, knobs, pilot lamps, leads mains cable and plug. 12 months' guarantee. walls is analogous to a low -loss tuned cir- 40 rr illi litic. cuit both respond sharply to a particular Deferred terms on application. or through London 20 r Radio Supply 11, frequency, and, while this may be very Co. Oat Lane, E.C.2. 0M Cash w th order on 7 days approval. Also write good in a radio tuner, it is highly undesir- d 8 8 gQ°,gS 8 8 S 8 8 88§ 8 for illustrated catalogue N n e !...W of complete range of all able in a reproducer that is supposed to McCarthy receivers give " level " characteristics. The laby- FREQUENCY IN CYCLES PER SECOND McICAIR1fI11-11 IR,tIDIIc ILTD, 1 Described by Benjamin Olney in The Fig. 4. -The labyrinth has also an indirect 44a, Westbourne Grove, London, Journal of the Acoustical Society of America, influence on the impedance of the moving W.2 October, 5936. coil, as shown here. (After B.. Olney) Telephone: Bayswater 3201!2.® 92 Wireless World, January zend, 1937

It must not be forgotten that 66ft. of wire at a given height is considerably more effi- cient on 28 Mc /s than on 7 Mc /s, and this Letters to the Editor fact, together with the lower noise level (except for car ignition), more often than The Editor does not hold himself responsible for the opinions of his correspondents. not more than balances out the increased ground attenuation on 28 Mc /s, with the Super- regenerative Receivers one's work, and desirous of putting the best result that a greater local direct -ray range may be obtained on 28 Mc /s for a given on the Super - into it, when one does not know whether IN his interesting article power on any of the lower frequencies. regenerative Receiver in your issue of or not he will be wanted on his job to- than ! My contention is that the job of the ama- 25th, Mr. E. L. Gardiner briefly morrow I would like to inform " En- December teur is to pioneer the most difficult things in describes some features of his practical cir- quirer " that I have worked side by side degrees, short -wave radio and not the easiest ones, cuit (Fig. 3) and then remarks that the with university men, with B.Sc. Personally who were being paid is. 3d. an hour! and the first step towards doing this is to remainder is self -explanatory. drop use of jargon and to use I can follow To any young man contemplating enter- the start I do not find it so, although scientific terms, and so think scientifically him throughout the earlier stages of the ing the radio branch of engineering, my advice is " don't." Take up a branch where whilst retaining the admirable " camara- article. die " and good sportsmanship that already He refers to the hexode section of the ability is appreciated, even if it does mean valve, the valve specified the sacrifice of a subject you love. exist. multiple although Frankly, I know some professional engi- is a triode- pentode and the modes of opera- " SADLY DISILLUSIONED." However, is a Hampstead, N.W.6. neers graduated from the amateur ranks tion are not identical. that feeder be fundamental principle of who still think that lines should detail. But the multiples of or half wave- consists in the use of a quench- cut to quarter the circuit Five Atlantic lengths, and who presumably have never of sharply peaked waveform, Metres Spans ing oscillation heard it is desirable to terminate a it is clearly explained how this is gener- ITHINK you may be interested to know that and feeder line in its own characteristic or surge ated in the circuit of Fig. i by the over - that my " 5 -metre " signals were impedance, for which purpose one - or Class C " operation of an ampli- received in the United States at 15.xo quarter biasing " wave matching transformer is often used. fying valve. In Fig. 3, however, all grids G.M.T. on 27th December, 1936, by Mr. to cathode, and the control R Victor Ruebhausen, W2HXD, of Bronxville, I realise, of course, that when it is de- are returned to use one of wire on number does not appear to function as in Fig. I. New York. sired piece a of different bands it is almost impossible to How, then, is the overbiasing obtained? His report checks exactly with : (a) What use a correctly is Also,' as the space currents of both sections I sent, (b) the time of sending, (c) the fre- terminated feeder, but it always desirable to use such a feeder if pos- of the triode- pentode pass through the quency used, (d) the tone modulation fre- R the characteristics of the quency, and (e) the method of keying (car- sible. lower part of The most elegant coupling to the detector appear to be rier being keyed -:lot only the tone modu- and perhaps the only decidedly complex, and the reasons under- lation). solution of this particular difficulty appears lying the choice of this system are not at all I was transmitting modulated CW sig- to have been made by the " Collins Com Nor is it obvious how it nals from a crystal controlled transmitter on pany " with their Soo -ohm twin tubular self- explanatory. " feeder " and associated aerial, is possible to employ positive or negative 56,208 kc /s, operating with wo watts input although to the final amplifier and feeding a " Dia- there must be hundreds on the other hand quenching as _stated. thèir I feel that some amplification of this sec- mond " aerial system, beamed on the U.S. who have reduced signal by means of a " Collins Coupler," or whatever thing tion of the article would be very valuable. His receiver was a 7 -valve superheterodyne. the Incidentally, the author may be inter- This is, I believe, the first time ever is called ! Finally, I would welcome still ested to note Fig. 4 in my article on the that a " 5 -metre " signal has spanned the further Super- regenerative Receiver in the Novem- Atlantic, the previous best distances being letters on this subject for a final discussion ber, 1936, issue of The Wireless Engineer, around 1,200 -1,400 miles between the soon. where the choice of a waveform bearing central and eastern portions of the U.S. last Leaving amateur affairs therefore for the resemblance to his is with the object May. time being, one turns to a recent statement some the Astronomer Royal, Dr. of better selectivity. M. G. SCROGGIE. HILTON L. O'HEFFERNAN. by Spencer Bromley, Kent. Croydon. G5BY Jones, to the " Union Radio Scientifique Internationale," in which the following in- teresting table concerning Bright Solar Eruptions is given : - Service Prospects reference to " Enquirer's " letter WITHin a recent issue of The Wireless On The No. of No. of Mean Daily World, I would like to state briefly my Year. Bright Radio Area of experience as a radio engineer. Solar Fadings. Spots. I went straight from school to an engin- Short waves Eruptions. of 18, after three eering college at the age and 1932 12 1 163 years' study, at great expense to my par- IMUST start by thanking all those 1933 5 0 88 ents (who fondly imagined that the pro- amateurs and short -wave listeners who 1934 5 2 119 fession was worth while), I graduated with have so kindly written in response to 1935 25 8 624 1,200 the usual diplomas, etc. Armed with these my repeated request in my last notes. 1936 28 20 -and six months' practical experience -I From their letters it is clear that the (Feb. -June) (approx.) sallied forth, brimful of enthusiasm, to British amateur is definitely wedded to the obtain a post. Soon, however, the wind was 7 Mc /s and lower frequency bands, and taken out of my sails, when I found that the considers that 100-150 watts to be about the It now seems fairly certain that the best offer I could get was rid. an hour (less optimum power to use for all except short sudden severe " magnetic storms " of the than a common labourer), and no guaran- distance quasi -local communication. sunspot maximum years are due to " Bright tee of a job beyond one hour! I do not I should like to make it clear that I I- we Hydrogen Eruptions," and not directly to think this needs further comment. Appar- no quarrel with those who desire to use the sunspots as previously thought, and as I ently, radio firms make a practice of short skip- distance channels ; my point is pointed out for the first time a number of engaging men (many with university rather that the use of these low- frequencies years ago night-time fadeout (and mag- degrees) just when they are busy, and then is too easy and should perhaps be reserved netic storms) are generally due to a lack of at an hour's notice consign them to the for those who have just obtained their sunspots. Labour Exchange ! They appear to have licences, or who for other reasons are only Turning now to the conditions during the no regard for the men, nor the profession. occasionally able to transmit, although this period now under review, signals were fairly One would like to know what would hap- point applies more particularly to 3.5 and good on Thursday, December 3ist, but PMN pen in any other industry if highly trained 1.7 Mc /s than to 7 Mc /s, which is rseful Bandoeng was spoilt by a bad heterodyne technical men were treated in this manner. as a night frequency in the sunspot mini- during the late evening transmissions. It certainly does not conduce tri attracting mum years for long- distance communica- A high spot in the early hours of New the best brains, and it is impossible to tion, but could well be superseded by 28 or Year's Day was W8XK on 11.87 Mc /s., enter the industry full of enthusiasm for 56 Mc /s for direct -ray communication. at 3 a.m., broadcasting a news reel of the JANUARY 22nd, 1937 J`Ii TP,ShOgl WarcIlcl " Twelve News Events of the Year " -the day, January 4th (although COCH, Cuba final scene, of course, dealing with the was good on 9.4 Mc /s at midnight), but abdication of King Edward VIII, the recovered on Tuesday, the ultra -high fre- characterisation being excellent. quencies being very good during daylight, At 7 p.m. Friday the best U.S. signal was W3XAL and W2XAD were excellent and WrHQN on 28 Mc /s, followed by W3XAL 16 Mc /s stations were still audible at mid- and W2XAD, the quality of the last named night! being a little low- toned. On Wednesday evening, January 6th, an Incidentally, I understand W2XAD outstanding signal was WIXAL on 11.79 changed from high -power to low -power Mc /s at 11 p.m., but one must not forget modulation on December 27th, with a con- to congratulate the B.B.C. on the excellent sequent two -fold increase in power, this Dance Music relay at 8 p.m. from C.B.S. station certainly provides an excellent signal since, although the signal was fading badly until close -down every evening and is by to me, there was an almost complete absence far and away the most outstanding broad- of fading or noise on the relay. caster heard on this side of the Atlantic. The falling -off in signals was again notice- Conditions were still good on Saturday, able by Friday, January 8th, and by Mon- January 2nd, and solar activity was noted day, January iith, they were quite poor, be to still high, but diminishing ; signals on which agreed with our estimate from the 28 Mc /s from the U.S. were still good at previous week, failing the appearance of 7 p.m. or later, although it appears to be new and unexpected sunspots. impossible to get a signal into the U.S. from Nevertheless, fairly strong signals this were country on 28 Mc /s after 6 p.m. at experienced from W2XE on 21.52 Mc /s the moment. during the earlier afternoons -and last With the falling sunspot activity night week on 17.76 Mc /s from 5 -6 p.m. conditions became distinctly poorer on Mon- ETHACOMBER.

THE LATEST PHILIPS PROGRAMME LIKE "SHEFFIELD" Four Types, Including ON STEEL a Receiver of Unique People who want good cutlery look for the word "Sheffield." People Construction who want a good radio set look Philips Type V5 all - first to see if it is G.12 equipped. wave superhetero- For the is used Rola G.12 brings oat the dyne for AC mains. on DC supplies. best that a set can give and no Finally we corne to the manufacturer would install such a Type V5, an all -wave super- speaker in a receiver that was not ALL the new Philips sets are table model heterodyne for AC mains only, at 8 guineas. capable of securing the very highest superheterodynes covering 16.7 to .)1 It employs the saine valve arrangement as quality reception. Ask your dealer metres in addition to the normal broadcast the Type 748, but there is no separate to demonstrate a set with one of bands. Three are based on designs shown chassis, the components being fixed to lugs these 12" high fidelity units or if at Olympia and include the " Adapto- moulded on the back of the you are a manufacturer let us show cabinet. Tho you that visor " tilting tuning scale. loud speaker is recessed, and the illumin- even though the G.12 Type 794 is a development of the seems expensive it will assist in the Type ated tuning scale slopes forward from the sale of your product. 797 and now has a cathode -ray tuning G.12 P.M. (as illustrated) less Trans- indicator, a new former ... £410 0 cabinet with larger 0.12 P.M. with Transformer ...... £5 5 0 im- G.12 D.C. Complete with Transformer, dial, and an Mounting Stand, Handle proved output stage. and Base £5 5 0 The AC model costs G.12 D.C. with Mounting Stand, Handle and Base, but without 15 guineas and the Transformer £4 10 0 DC /AC 16 guineas. G.12 D.C. Stripped, but with Trans- The battery receiver £4 4 0 Type 714B con- G.12 D.C. Stripped and without Trans- tinues unchanged at £315 0 (When ordering please state Field Resistance and 14 guineas. Impedance of Transformer required ) Type 748 employs For Public Address work toth.the P.M. and Ener- Imee a 4 -valve circuit gised Models can be supplied with a 15 ohm Voice with an octode fre- Coil at an additional charge of 3,', Write for Folder A.

Rear view of Philips OVER 7 MILLION IN USE Type V5 receiver showing method of mounting of com- ponents directly in the moulded cabinet.

Zie GUOt14 7Liie4t eB rtuliiCe`r,i quency changer, pentode IF amplifier, base of the grille. The dimensions of the double- diode- triode detector and high -slope set are 161 x 131 x 61in., and altogether it is THE BRITISH ROLA CO.. LTD. pentode output valve, and costs I21 a very effective design. Only tuning and MINERVA ROAD, PARK ROYAL,N.W.10. guineas for AC and 13- guineas for volume controls appear at the front, the 'PHONE WILLESDEN 4322 - 3- 4 -5 -E. DC /AC mains. A built -in converter waverange switch being mounted at the side. Wireless World, .January 22nd, 1937 94 i Brief descriptions of the in- teresting radio RecentInventions devices and improve- space -waves tend to become hori- HF COUPLINGS zontally polarised in the process ASERIES of tuned high -fre- ments issued as patents of reflection, and so give rise to quency circuits are reactively will be included in this false DF readings. coupled together in such a way This property of the Adcock that the effective band -width can section. aerial may, at times, prove very in- be varied, without moving the convenient, for instance, during centre of the resonance curve periods of intense " night effect," either up or down the frequency TELEVISION as it then prevents all reception scale. This allows the selectivity it is necessary to and communication breaks down. of the circuits to be altered, whilst IN transmission short keep pace with and reproduce According to the invention this keeping them symmetrically tuned Colpitts oscillator for ultra in the overall " bright- contingency is met by providing about the centre of the received waves using a specially designed changes valve. ness " or general illumination of a one or more frame aerials F, F1, carrier -wave. The coupling scene. Such changes occur corn - which will receive horizontally system is particularly suited for as compared polarised waves, and can be the intermediate-frequency stages can reverse its phase and so tend paratively slowly, oscillations. with the changes which reproduce switched in at S, Si in place of of a superhet. receiver. to damp out the details of the picture, the aerials A -B, as and when the Hazeltine Corporation (Assignees As shown in the figure the the actual circuit L, C is branched and special steps must be taken to necessity arises. of D. E. Harnett). Convention oscillatory in the radiated Marconi's Wireless Telegraph date (U.S.A.) May 3151, 1934. across the anode and grid, the reproduce them valve then operating as a Colpitts signal. Co., Ltd., and S. R. Smith. Ap- No. 455619. invention a plication date April loth, 1935. o 0 0 0 oscillator. A blocking condenser According to the grid from the HT is pro- No. 454955. OSCILLATORS Ci protects the cathode -ray transmitter o o o o SHORTWAVE source, whilst a choke K isolates vided with a screen electrode AVALVE is used for generating side with the source from the oscillatory cir- which is covered on one SUPERREGENERATIVE oscillations, having a fre- cuit. a layer of photo -electric material, RECEIVERS quency of the same order as the coat- Standard Telephones and Cables, and on the other side with a T\\° valves A and B receiving transit time of the electrons from !Ieising). The the aid of Ltd. (Assignees of R. A. ing of fluorescent material. modulated carrier -waves of cathode to anode, with Convention date (U.S.A.) April picture to be transmitted is different frequency, such as the ordinary reaction as distinct from and 25th, 1935. No. 4549o2. focused on to the first layer, o 0 0 0 the resulting emission of electrons transmit the picture. COUPLING COILS is used to coupling coils, provided " detail " signals. the fluorescent layer TWOwith a common adjustable Meanwhile powdered -iron core, are mounted is being scanned by the electron -ray tube. on a base- plate, and enclosed stream from the cathode " to form as it is lit up, add- to inside a screening " pot Each spot, a compact tuning -unit, which can the illumination, and therefore to the correspond- be used either for an input circuit the emission, from or as an intervalve coupling. ing spot on the photo -electric emission of To ensure uniform " gain ' over layer. The "extra' one of to this cause is ap- the usual broadcast range, electrons clue the coils is designed to have a plied to regulate the amplitude of ac- natural or inherent frequency the radiated carrier -wave in which changes in lower than any frequency to cordance with the slow the other is intended to be tuned. brightness of the scene. The movable core enables the Marconi's Wireless Telegraph mutual coupling between the coils Co., Ltd.: H. M Dowsctt; and to be adjusted to an optimum L. E. Q. Walker. Application value. dale April 18th. 1935. No. Johnson Laboratories Inc. (as- 455356 0000 signees of A. Crossley and H. E. Meinenta) . Convention d a t e DIRECTIONFINDING (U.S.A.) April loth, 1934. No. THE so- called Adcock aerial 454873. consists of two pairs of 0 0 0 0 antennae A, Ai and B, Bi which LOUD SPEAKERS are spaced apart and coupled AMOVING -COIL speaker is through horizontal transmission constructed with a number of lines L to a central receiver R. diaphragms, each handling a dif- Its advantage is that it does not ferent section of the audible band respond to horizontally polarised of frequencies. The diaphragms waves, so that it is free, when are arranged about a common used for taking the bearings of a -line, and are operated by from any centre distant transmitter, for television using super -regeneration and a single the same magnetic movement but error caused by signals reflected Receiving system Such quenching valve. through independent speech-coils, from the Heaviside layer. which are all located in the same sound and picture signals of a the more usual Barlehausen -Kurz air -gap. The speech coils may be television programme, are back - circuit. The spacing between wired up in series or in parallel, coupled to work as super- regenera- the grid and cathode is made and are set as close together as tors, and are both " quenched " less than one - quarter the dis- possible without obstructing each from the same local oscillator tance between the anode and other. The arrangement presents valve V. It is stated that the cathode, and is preferably only a compact and inexpensive speaker arrangement is stable and over- one -eighth that distance. The ob- unit, capable of giving a high out- comes the interference frequencies ject is to allow the electrons to put of sound. which arise when two separate pass outside the control of the grid J. Sharp and J. McGrath. Ap- oscillators are used to provide in- at an early point in their path to plication date January 15th, 1935. dependent quenching. The ampli- the anode, before the grid voltage No. 455208. fier A is quenched from the anode circuit, and B from the grid cir- cuit of the common oscillator V, as shown. Preferably the connec- The British abstracts published here are prepared, with the permission tions are decoupled to prevent the of the Controller of 1í.M. Stationery Office. from Specifications risk of interaction. obtainable at the Patent Office, 25, Southampton Buildings, London, L. H. Merdier and Baird Tele- 11.C.2, price 1 - each. A selection of patents issued in U.S.A. is vision, Ltd. Application dates also included. Modification of Adcock aerial April 9th and July 5th, 1935. No. system for direction -finding. 454945. THE PRACTICAL RADIO JOURNAL 26 th Year of Publication

FRIDAY, JANUARY 29TH, 1937. VOL. ZL. No. 5.

Proprietors : ILIFFE & SONS LTD.

Editor : HUGH S. POCOCK. EDITOR IA _L, COMMENT Editorial, Advertising and Publishing Offices : thing, and must always be in process DORSET HOUSE, STAMFORD STREET, The Wireless Vocabulary of revision in order to cope with the S.E.r. LONDON, changes in ways of thought and prac- Telephone: Waterloo 3333 (So lines). Telegrams: "Ethaworld, Seelist, London.' Glossary of Standard Terms tice. Consequently, old words must be abandoned or changed in meaning, COVENTRY : Hertford Street. TO write Telegrams: Telephone: those who The Wire- or new ones introduced when they " Autocar, Coventry." 5210 Coventry. less World and to those who become necessary.

BIRMINGHAM: read it, the question of ter- The compilers of the Glossary have Guildhall Buildings, Navigation Street, 2. minology is of equally vital accepted many terms that are doubt- Telegrr ms : Telephone: importance. Unless some kind of code less unpalatable, on the grounds that Birmingham." 2971 Midland (4 lines). "Autopress, is used, writers on our subject cannot they have become firmly established, MANCHESTER : 260, Deansgate, 3. possibly convey their ideas without but a determined effort is made to Tde;;rams : Telephone: "IIiHe, Nla nchester." Blackfriars 4412 ({ lines). undue verbosity and circumlocution, displace " condenser " and " capacity " and it is clearly essential that the in favour of " capacitor " and " capa- : 26B, Street, C.2. GLASGOW Renfield chosen should be generally " " is Telegrams: "Iliffe, Glasgow." Telephone: Central 4057. code -words citance." The word insulator accepted and understood among their deprecated, " insulant " (insulating PUBLISHED WEEKLY. ENTERED AS SECOND CLASS MATTER AT NEW YORK, N.Y. readers. material) being suggested in its It is for this reason that we welcome place. Subscription Rates : the newly- published Glossary* of elec- ; ; other Home, LI Is. 8d. Canada, £I is. 8d. of countries, £r 3s. rod. per annum. trical terms, which the avowed Defining Interference object is" to standardise and co- ordinate Ae many of Ike circuits and apparatus described in these electro- technical terms used in the A chance seems to have been missed pages are covered by patents, readers are advised, before the making use of tkem, to .satisfy themselves that they wouid British Empire." The new edition for clearing up the confusion that so not be infringing patents. deals not only with the terminology often arises when one is unduly of radio communication in general but economical with words in talking about with television and cathode -ray tubes. the various kinds of interference to It also defines the language of electrical which reception is subject. " Jamming" CON'T'ENTS fundamentals -the foundations of wire- is a word of such respectable antiquity less technique. that we sometimes hesitate to use it Page In general, the compilers of the for fear of puzzling the newer genera- is, Editorial Comment 9 ;; Glossary have been animated by the tion of readers. It however, re- same aims as those that influence the tained in the Glossary, and, quite Experimenter's IF Amplifier ..96 preparation of this journal : to " con- rightly, defined as interference due to Synchronising Problems in Tele- form to current usage, except where unwanted signals. The word " inter- . 100 vision . .. .. such usage appears to be erroneous ference " itself is defined as applying H.M.V. Television Receiver Re- or misleading." But perhaps we our- to all kinds of disturbances. Surely viewed .. 102 selves assign rather greater importance much trouble could have been avoided Current Topics 10<; to usage, preferring a term that is by using " jamming " in the sense Unbiased .. . .. 106 universally accepted and understood defined, " interference " for machine- New Apparatus Reviewed 107 even if it is inapt and inelegant, to an made disturbance, and " atmospherics " Listeners' Guide for the Week 108 expression that may confuse the reader. (which also appears) for the efforts of It is realised, however, that, like the Nature ? Fading : Vicissitudes of Waves in English language itself, the language It is, perhaps, not surprising that Space ...... 110 of wireless is a living and growing no attempt has been made to define 112 Random Radiations that invaluable word " signal " which Broadcast Brevities 114 * British Standard Glossary of Terms used in may mean all sorts of things. It is to the Editor 115 Electrical Engineering. The British Standards however, the word itself Letters Institution, 28, Victoria Street, London, S.W.I. noted, that Recent Inventions .. .. 116 l'rice 7s. 6d. ; by post, 8s. is actually used in the definitions. 96 Il'iveless World, January 29th, 1937 The Wireless World experimenter's I F Amp1ifier¡

SUPERHETERODYNE THE IF amplifier de- scribed in this article UNIT EMBODYING AVC, was evolved especially for BEAT OSCILLATOR investigating the relative merits of different styles AND ONE AF STAGE of short-wave frequency - changers, and as it proved so useful it T may seem rather unusual to con- is possible that others also engaged in sider an IF amplifier as a separate short -wave experiments Wright be in- self -contained unit as it is generally By II. B. DENT terested in the arrangement regarded as an integral part of a employed. superheterodyne receiver. In experi- It provides a reasonably high degree has been adopted in the first place. mental work, however, one does not of amplification, has good selectivity Generally, it is the frequency- changer always follow orthodox practice, and this portion that ; and embodies several features not suffers most if an RF stage applies particularly in the development had not previously been incorporated its of short -wave receiving apparatus. usually included in the orthodox need may soon be felt and either a The equipment in the average amateur IF amplifier. separate unit is added or, if space permits, station rarely retains for long the tidy appearance given it on first installing a short -wave set and possibly holes of a transmitter, all sizes drilled in them as changes Fig. i. Theoretical circuit diagram of for the main object of the experimenter and alterations are made. the IF unit in which is included also one is to try out new ideas so that in a very Rarely, however, does it become neces- AF stage and a 465 kc, s oscillator. The short time the various chassis soon be- sary to make any drastic changes in the two IF amplifiers are not operated at come not maximum sensitivity, but if more gain is only an eyesore but absolutely IF amplifier of a short -wave superhet, required the bias resistances R5 and R12 unusable owing to the vast number of provided, of course, a satisfactory design can be changed for lower values.

R2 R10 R11 1,00017 1,000'1 7,500!1 1,000 0 014 0001 mfd

R4 1 M Ti T2 T3 T4 3 2 1 3 2 2. 3 2 m ó Ó

4 J M 4 / I 3 1

INPUT

R7 4 = C1 20,0000 C2 01 mfd 0'01 Id ò R5 C3 2501,

' 01 mfd C5 01 mfd R6 10,000,

I RF VOLUME CONTROL A F VOLUME CONTROL Wireless World, January 29111, 1937 97 - th additional parts are somehow accom- useful in practice and quite a number of of the frequency- changer while the other modated on the main chassis. different styles of frequency- changer, end of the winding is connected to the line. Then again someone gives a glowing with . and without an RF stage, have HT description of the results obtained with a quickly been assembled and compared on After the first pair of coupled circuits certain type of frequency- changer or even the same IF amplifier with the minimum is a variable -mu RF pentode which is - an idea may suggest itself. Further expenditure of work and time. joined to the AVC line and this is the only alterations are contemplated and Possibly others interested in the short valve so controlled. The second IF is best eventually things become so unsatis- waves may find the idea attractive also ! stage, which feeds the detector, factory that valuable time has to be The IF amplifier was designed to give omitted from this circuit as the full devoted to completely rebuilding the set. a fairly high gain, be reasonably selective, sensitivity is needed to provide adequate The writer has passed through all these embody AVC and also an IF beat -oscil- bias voltage for the AVC line. When an RF stage is employed in the receiver unit this valve can with advantage be joined to SPEAKER -PLUG SOCKET line, on the short waves it is - SPEAKER PLUG the AVC but 120 r, not desirable to include the frequency- C\ 10 HENRY, /' l II changer even though it be a variable -mu K\ \°) 1,500,' valve. RECEIVER -PLUG 2,500 100 4V 25/1 Between the first and second IF ampli- SOCKET SPEAKER FIELD fiers are four tuned circuits arranged as two coupled pairs. As they are orthodox pattern IF transformers they could be 14 mfds 250 V coupled together by a small capacity be- á Wolms s 230V e mfds 8 mfds tween the high potential end of one a FUSE 2 V secondary circuit and the high potential 375V-0-375V AC 120mA MAINS end of the other primary circuit. Yr Y FUSE The capacity needed for optimum or COM slightly sub -optimum coupling is, how- B r,,fil j.-. ever, very small, being of the order of one 6A 1n-mtd. or less. Such small capacities are ~AVb750u not necessarily difficult to obtain in prac- -41 tice, but they are difficult to repeat unless 50 mfds . 50 V

Fig. 2. A power supply unit embodying the output valve could be constructed to the circuit

shown here. -

stages and eventually decided to segregate lator which could be brought into use by the various parts of the set, making the the turn of a switch for CW reception at frequency- changer, the IF amplifier and the same time rendering AVC inoperative, the power pack as separate units with the as it is a hindrance rather than a help output stage incorporated in the power when receiving Morse. It embodies an pack. IF sensitivity control as .well as an AF This scheme has so far proved very volume control. A good method of injecting the IF beat oscillations was found to be by using the triode section of a duo -diode -triode as the IF oscillator and the two diodes strapped together as the second detector. R19 30,000 As the output valve employed was a PX4 some AF amplification was needed after the detector, and this is provided by a general- purpose triode with a parallel R20 : 3 ratio AF 50.000 n feed coupling to a i transformer. This component is accom- KILOCYCLES OFF RESONANCE on the power pack, but the modated Fig. 3. Frequency response of the two IF cn penultimate AF stage is in the IF unit. eight tuned circuits. ',ad /Th stages including the e' If necessary, headphones can be used The intermediate frequency is 465 kc /s. -f`-9ez after the first AF stage, though it has not -6g3 been found necessary to resort to them so a-e-.g B4 one has access to a signal generator and

5 far as all reception can be effected on the of V4 3.4.-® (9 can measure the response the amplifier V3 loud speaker. with different coupling capacities. One Two IF stages are used operating at a way of obtaining the capacity is to join frequency of 465 kc /s. In all, there are an insulated wire to each end of the cir-

4 , eight tuned circuits and these provide cuits and run them parallel for a half -an- 4 5 adequate selectivity for most of the short- inch or so, but the capacity so derived will Cla cla 50mfds wave bands. It is not too selective for vary considerably with the thickness of 4 reds c good- quality reproduction of telephony, the insulating sleeving and the closeness so that the amplifier is well suited for use of the conductors. + y on any of the short -wave broadcast bands An alternative method of coupling is to and it gives good adjacent -channel selec- join the two circuits by a non -inductive tivity. The complete circuit diagram of resistance, and as this lends itself better C15 tr1 mfd the unit is shown in Fig. r. to repetition it is adopted in the present The input is applied through a screened case. The value used is one megohm. lead to the first IF transformer, and this In the circuit diagram the middle pair lead will normally be joined to the anode of the four coupled circuits are each shown 98 JANUARY 291h, 1937 `'©1kó1 Experimenter's IF Amplifier - The coil unit for the IF beat -oscillator former from the AVC line and joining it shunted by a resistance in dotted lines. has been made especially by B.T.S., and to the chassis. This is an optional addition, and may it also embodies the grid condenser Cr4 The change is effected simultaneously sometimes be helpful should it be desired and grid leak R18, and accordingly these with switching on its HT supply, and both to slightly " flatten " the response. As components, while shown in the theoretical these operations are effected by the double - shown by the response curve in Fig. 3, the diagram, are not visible in the illustra- pole, double -throw switch Si. overall selectivity is not unduly high, and tions, neither are they included in the list Neither the assembly of the components only in exceptional cases will these resist- of parts. As supplied, this unit is tuned nor the wiring requires any lengthy de- ances be needed. Their values could be to 465 kc /s under similar working condi- scription, as the work is quite straight- between o.i and 0.25 megohm each, while tions, and it is essential to avoid upsetting forward and easily followed from the draw- at the same time the coupling resistance the adjustment, because the oscillator can ings and illustrations. R4 may be reduced to about 0.5 megohm. be utilised, as will be explained later, in When mounting the IF transformers it is Reference to the illustrations will show lining up the IF circuits. important that they be assembled in the that two of the IF transformers are fitted correct positions and the right way round. with screened leads coming through the Beat Oscillator Two of them have screened leads at the top of the cans, while the other two have top, and their position on the chassis is all connections made below the chassis. When the IF oscillator is in use, AVC readily found by reference to the illustra- The IF units with screened leads are the is rendered inoperative by disconnecting tions. On the drawing of the underdeck Varley Type BP98, the others are BP97. the grid return lead of the first IF trans- wiring a figure is marked against each hole

8 { 11 >I4 1111111

R6I.tcoo 2 - 9 C2 ,, Cl OI4C n

__ . R5 1

E C3 R3

T3 R4I o 5/8 ® 7 .C. C10 3` . _ E Cf R2 1

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Fig. 4. Layout of the components and the practical wiring plan. JANUARY' 29th, 1937 Wtamo 99. WOIl'N.. Experimenter's IF Amplifier- accurately marked in order to allow for plifier has a slightly different input circuit, through which the soldering tags of the easy rotation of the rod in the panel bush. as the AF transformer is shown parallel - transformers protrude, and these numbers It has not been thought necessary at the fed. The anode decoupling of the penulti- are the same as those on the base plates present juncture to give a detailed descrip- mate AF stage being contained in the IF of the IF transformers. When mounting tion of the power pack, for some latitude unit, it is omitted from the power pack, them they should be orientated, so that the is permissible, and possibly an existing so that one of the 8 -mfds. electrolytic numbers agree in every case, for they are unit can be made to serve the purpose. A condensers and one resistance are not re- not all mounted with the figures in the suggested unit is shown in the theoretical quired, otherwise the construction and same order of rotation for all four trans- circuit Fig. 2, which is very similar to wiring can be the same. formers. Another matter that requires that of the power pack designed for the Lining up the circuits of an IF ampli- attention is the connection of the leads from the base of the IF beat -oscillator coil unit. The red lead joins to the anode pin of the D -D- triode, the yellow lead to chassis, and the grey lead to HT posi- tion via resistance R17. The grid connection is on top of the screening can. - The sensitivity control which sets the minimum grid bias for the first IF valve is mounted direct on the end piece of

The wiring and all the small components are located on the underside of the chassis and this view shows clearly the position and manner in which they are accom- modated. the chassis, but the AF volume control is All -Wave Super Seven, described in The fier at the correct frequency is not easily assembled close to the AF valve and oper- Wireless World of August 7th and 14th, accomplished without the aid of a modu- ated by a long brass rod. It is positioned 1936, constructional details of the power lated test oscillator. In the present case by a small bracket bolted to the side of unit being given in the latter issue. a calibrated test set could be dispensed the chassis, and its position should be That suggested for use with the IF am- with, but an RF oscillator covering 465 kc /s will be needed. There are usually enough spare parts in the ama- THE LIST OF PARTS REQUIRED teur's workshop for a temporary unit. Certain components of other makes but of similar characteristics may be used When the oscillator is rigged, a few to those given in the following list as alternatives turns of wire can be coupled to the coil i. 2 IF transformers, 465 1cc /s (special), TI, T3 1 50,000 ohms watt, R17 and its ends clipped across the grid and Varley BP97 Dubilier chassis of the second IF valve. 2 IF transformers, 465 Icc /s (special), T2, T4 I loo,000 ohms '; watt, R21 Varley BP98 Dubilier With the IF beat -oscillator working, 2 I megohm watt, 1 IF oscillator unit, 465 kc /s (special), i R4, R13 i.e., switch Sr turned clockwise, and the B.T.S. Dubilier AF volume control set to maximum, an 1 30,000 ohms 5 watt, Rl9 - 1 Volume control, io,000 ohms, wire-round, R6 note be heard in Haynes Dubilier audible will the loud 1 50,000 ohms i watt, R20 speaker when the temporary oscillator ap- 1 Volume control, 0.25 megohm, R14, tapered (without switch) Polar =NSF V/4 Dubilier proaches the frequency of the IF oscillator. I 10,000 ohms 2 watts, R9 Adjusting the temporary one to give a Condensers: Dubilier C12 note of about 400 c/ s, the trimmers on the 2 0.0001 mfd. mica, C9, 1 7,500 ohms 3 -5 watts, RIO T.C.C. " M " Dubilier Spirohm last 'IF transformer, T4, can be adjusted. I f .GOES mfd. mica, CI1 T.C.C. " M " I -pole, SI for strongest signals. I 0.01 mfd. mica, C2 T.C.C. " M " Switch, double double -throw, Bulgin S114 This process can then be repeated on the O. mfd. tubular, LI, C3, C4, C5, II 2 connectors Bulgin CO, C7, C8, CIO, C13, C15, C17 Screened valve top P64 earlier stage without, of course, altering T.C.C. 250 1 Plug valve top connector Belling =Lee 1175 the tuning of the temporary oscillator. 1 Five.way connector Bryce 14 mfds., 450 volts, dry electrolytic, CIG As the various circuits come into reson- T.C.C. 502 3 Valve holders, 7 -pin, chassis mounting, with- ance the coupling of the pick-up coil 15o mfds., 12 volts, dry electrolytic, C18 out terminals Clix V2 on T.C.C. " FT " 1 Valve holder, 5 -grin, chassis mounting, with- the temporary oscillator will have to be out terminals Clix VI : loosened to avoid overloading. Resistances 1 Panel bush, tin. bore Bulgin Type C 2 250 ohms watt, R5, R12 as described, and with 1 1 Shaft coupler, tin. bore Bulgin Constructed the " F Dubilier " 2 Stand =off insulators Eddystone 1019 valves mentioned, the amplification of the 5 5,000 ohms watt, R1, R2, R3, R8, RII - 1 chassis, 14 x 8 x 2l in. B.T.S. Dubilier " F " two IF stages alone is just under 1,000, 1 Brass rod, loin. long, tin. dia. and with 25o volts HT the consumption of 12,00o ohms watt, R22 Dubilier " F " Valves : the- whole unit is 3o mA, or 32 mA with 3 20,000 ohms é watt, R7, R15, RIG 2 V11P4G (metallised), 5 11HD4 (metal- Dubilier " F " lised), i MH4 Osram the IF beat -oscillator working. 7 1r") Wireless World, January 29th, 1937 Synchronising Problems ir

j- SHE method of operation of the usual form of time -base, em- OBTAINING STABLE PICTURES bodying gas -filled triodes for generating the necessary saw- tooth waveforms for scanning, has been By IN.. T. COCKING described in a recent articles in The Wire- less. World. The method of separating the synchronising impulses from the vision Now a self- running time -base is not by thus easy to see that to ensure regular signal by means of an amplitude filter has itself sufficiently regular for television pur- operation without displacement of the lines also been treated.2 The provision of a poses, and synchronising pulses are pro- it is necessary to make certain that all the good time -base and amplitude filter, how- vided in the transmission for the express synch. pulses have the same amplitude. ever, are not sufficient for the maintenance purpose of keeping the time -base in regu- of perfect synchronisation over long lar operation. Matters are so arranged The Synchronising Pulse periods. The line synchronisation is that just before the anode voltage of the usually good, but it is difficult to prevent valve has risen to the discharge value, a This can be done in the amplitude filter the frame from wandering. positive pulse is applied to the grid. The to a very close degree of perfection, and The problems of synchronising were grid potential is lowered and the striking such a filter is essential to prevent the not discussed in the article referred to voltage so far reduced that the existing ever-changing amplitude of the vision above dealing with the time -base, and it is anode potential is sufficient to start the dis- signal from affecting the amplitude of the necessary to understand how it is carried charge. synch. pulses. With such a filter, the out before the difficulties can be appre- The anode voltage is thus never allowed amplitude is only likely to vary to an ap- ciated. The basic circuit of a time -base to reach the normal no- signal striking preciable degree when interference is voltage, for the synch. pulses arriving present. During the synch. pulse the at regular intervals cause the valve regu- carrier amplitude falls to zero, but if inter- larly to become conductive at precisely ference is present the receiver output will the right moment. The times of discharge not fall to zero but only to the interference of the condenser are thus exactly con- level. As this will rarely be constant, we trolled. There is, however, no control shall have a varying amplitude of synch. over the time of commencement of charge pulse, and the interference will not only be which follows every discharge and repre- evident by its appearance on the picture sents the start of each line or frame. It but also by upsetting the synchronising. is assumed that the discharge is the same Fortunately, in cases where the inter- every time, so that at the commencement ference level is low compared with the of each charging action the valve anode amplitude of the synch. pulse in the voltage is the same. carrier, its effects can be removed as far If the starting voltages are not the same, as synchronising is concerned by slightly the lines will not be in perfect alignment over- biasing the valve used in the ampli- but will be slightly displaced relatively tude filter. In practice, it is possible to to one another, and this will naturally secure a synchronising output which is reduce the definition to a. serious degree. very constant in amplitude, and hence

Fig. i. -The basic circuit of a time -base embodying a gas -filled triode is shown here.

is shown in Fig. I, and it will be remem- bered that the action is as follows : at the start, the valve is non -conductive and the condenser Cr charges through R2. When the voltage across Ci, which is also the anode voltage of the valve, reaches a cer- tain value, the valve suddenly becomes conductive and the condenser discharges through it. At a certain critical value of anode potential the valve again becomes non -conductive and the condenser again starts to charge and the whole cycle to repeat. The maximum voltage at which discharge takes place depends on the grid bias and increases as the negative grid bias is increased. The lower critical volt- age at which the discharge ceases, how- Fig. 2. -A commonly used method of feeding the synch. pulses from the amplitude filter VI to the frame and line discharge valves V2 and V3. ever, depends chiefly on the design of the valve, and only to a minor degree on the bias. Now the final anode potential after the dis- very regular operation of the time -bases. charge depends in some degree upon the Now, in practice, we have two time - r The Wireless World, January 15th, 1937. amplitude of the synch. pulse which bases, one for the frame scanning and the I The Wireless World, January 22nd, 1937. brought the discharge about. It is other for the line. With Baird transmis- Wireless World, January 29th, 1937 IOI

series with the grid of the frame control valve V2 while a condenser C3 is shunted from grid to the earth line. This resistance and condenser form a very simple and rather crude low -pass filter. Owing to the television great difference in the frequencies to be separated, however, the filtering action 7-,HE separation of the synchronising pulses from the vision signal by proves adequate in practice and the writer 1 has found suitable values to be 20,000 means of an amplitude filter was dealt with recently in " The Wireless ohms and 0.003 µF. for the resistance and World." In this article the frequency separation of the line and frame capacity respectively. In general, it is not necessary to filter pulses is treated out the frame synch. pulses from the line time -base, but it can readily be done by including a high -pass filter. Again a crude sions, the one will be running at 25 c / s and value at which the valve will strike, but it type suffices, and sufficient discrimination the other at 6,000 c / s ; at the end of every should not do so until the frame pulse can be obtained with the aid of C2 and R4. line a short synch. pulse is provided to arrives. In practice, however, it very By making these components of fairly low trip the line time -base, and at the end of often happens that one of the last few value, the frame pulses can be attenuated every frame a longer synch. pulse to trip line pulses of the frame trips the valve appreciably, and with R4 about 20,000 the frame time -base. A circuit which one and so discharges the condenser 'a little ohms, C2 can be o.00r uF. or even smaller. commonly sees recommended is shown in Fig. 2 in abridged form. The valve V1 is the amplitude filter, and it feeds only the synch. pulses to the gas -filled triodes V2 and V3. It will be observed that both line and frame pulses are fed to both valves. As far as the line time -base is concerned there is little harm in this, for the long frame pulse merely means that it will hold the line time -base inoperative during this time. As this corresponds to a black edg- ing on the picture, it is not visible. It does mean, however, that the discharge of the condenser is unusually complete during the frame pulse, with the result that the first few lines are displaced slightly when it again operates. This is evident by a slight displacement of lines at the extreme top of the picture. This does not occur with the Marconi - E.M.I. transmissions, for with these the synch. pulses are different. There is no Fig. 3. -The inclusion of a simple low -pass filter R3 C3 in the grid circuit of the frame time- long framing pulse, but a long series of base greatly improves the stability of the synchronising. pulses and the line time -base is kept oper- ating normally the whole time. earlier than it should. The result is that It will, of course, be understood that the the picture cannot be held and moves as a circuits given in this article are incomplete whole in a vertical direction. in the sense that the various decoupling The Synch. Pulses and the Time - Apart altogether from the synch. pulses, and by -pass components have been base there is a considerable degree of coupling omitted, and that the gas -filled triodes will, between the two time -bases with the in practice, necessarily be followed by Now let us look at the frame time -base ; -filled triodes with the circuit of Fig. 2 the line pulses are arrangement of Fig. 2. Gas amplifiers. Various other methods of fre- applied to it as well as the frame pulses, pass a fairly heavy grid current when the quency separation are possible, but the and this seriously affects the operation. condensers discharge, and voltages are set simple filters indicated here appear to be Instead of the voltage across the condenser up across the grid resistances, and applied all that is necessary. Certainly they per- growing to a definite figure and the frame from one valve to the other. The coup- mit stable synchronisation to be obtained synch. pulse then being applied to the tri- ling by this means is quite sufficient to over long periods, and this is not possible ode, we find that the grid potential regu- interlock the two time -bases, and it is without them. larly changes at the end of every line while easily possible to obtain a steady raster It should be pointed out that in the the anode voltage is growing. in the absence of any synchronising article " The Time -Base in Television " Consider the case at the start of the first signals. The effect is thus useful in in The Wireless World for January 15th, line of a frame. The anode voltage of the development work on the time -base cir- 1937, the references to Ri in the three con- frame control valve is at its minimum and cuits themselves, but is undesirable during cluding paragraphs on page 53 are the grid at its maximum negative voltage. normal television reception. incorrect. Wherever Ri appears on this The anode voltage steadily rises, and after In the writer's experience it is necessary page read R2. an interval the line synch. pulse arrives. to include a filter circuit to prevent the line synch. pulses from being applied to the It does not cause the valve to become con- SPECIAL PA NUMBER ductive, however, for the anode potential frame time -base. Fortunately, quite a in view of the widely Next Week's Issue will be primarily devoted to is not high enough. The voltage still con- simple filter suffices the subject of Public Address equipment, its tinues to rise, therefore, in spite of the line differing frequencies and its use has the problem; and applications to both large and pulses, which thus have no adverse further merit of preventing interaction due small requirements. A review of modern outfits microphones, loud effect. to the grid current of the gas -filled triodes. and accessories, including to speakers and valves, will be included. Now consider what happens when we A circuit which experience has shown Special articles will deal with recent develop- get towards the bottom of the picture. The be satisfactory is given in Fig. 3, and it will ments and various aspects of this subject. anode voltage is now getting close to the be seen that a resistance R3 is inserted in 102 Wireless TVorld, January 29tlr, 1937 H.M.V. Television

Receiver MODEL 901

TELEVISION reception is still something of a novelty, and STRAIGHT VISION in all its aspects is full of in- terest. Unlike the usual sound AND SUPERHET receiver, there is as yet no hint of stan- dardisation, and most television sets are SOUND RECEIVERS quite different from one another in nearly all their details. To the technically minded this is but an additional attrac- FEATURES.- Type.-Ultra- tion. shorf-wave sound and vision receivers The H.M.V. television receiver is really with cathode -ray tube viewed through two sets in one, for the vision and sound an inclined mirror. Circuit: (Sound channels have only the initial circuits in Receiver) Superhet,with triode-hexode common. The vision receiver is a straight FC,RF pentode IF, duo -diode-triode set with six RF stages feeding a diode detector, pentode output. (Vision detector. The coupling between the last Receiver) Straight set with 6 RF RF valve and the detector is a two -circuit stages and diode.detector. Deflection : band -pass filter, but single- circuit coup- Electromagnetic. Controls: (Sound) lings are used elsewhere. The eight tuned (1) Tuning. (2) Volume. (Vision) circuits thus employed are not all tuned (1) Sensitivity. (2) Contrast. (3) Brilli- ance. (4) Line Hold. (5) Frame Hold. (6) System se- lector switch. (7) On-off switch. Subsidiary Cc ntrols.- (Vision) (1) Form. (2) Focus. (3) Width. (4) Height. Price. -95 gns. Makers. -The Gramo- ployed. An economical sound receiver phone Co., Ltd., 98- thus results, and the signal -noise ratio 108, Clerkenwell Road, is maintained at a high level. The IF London, E.C.1. valve is followed by a duo- diode -triode which feeds the output pentode. Returning to the vision equipment, the The first t w o detector output is fed to the cathode -ray stages are common tube through a potentiometer which per- to both vision and forms a function exactly analogous to the sound channels, for AF volume control of a sound receiver ; the frequency - it is, however, called the " Contrast Con- changer of the trol." A sensitivity control operating on sound receiver de- the early stages is fitted in addition. rives its input from It is interesting to note that RF pen- the output of the todes are used throughout the RF ampli- second RF stage. fier, even in the last stage. This is, of Because of the RF course, only possible because of the amplification thus special cathode -ray tube employed, for obtained, the tri - this can be fully modulated with an input ode-hexode f r e - of some ro volts only. The tube contains quency - changer no deflecting plates, for electromagnetic operates with a deflection is employed, the necessary reasonably large in- currents of saw -tooth waveform being put, and one IF generated by the two time -bases. stage only is con- Hard valves are used for generating the sequently em- initial potentials ; one screen -grid valve is used for the frame scan, and another for the line scan, and their outputs are ampli- In this rear view of the receiver the vision - fied by means of output -type pentodes. to the same frequency, but certain stages receiver chassis can be seen at the left and Essentially, therefore, each time -base em- are staggered, so that an overall response the time -base chassis on the right. The bodies only two valves, but a number of curve is obtained which is sensibly flat tube is in the centre with the sound receiver behind it and the mains equipment at the others are used in conjunction. Two RF over a wide range of frequencies on either bottom. pentodes are employed in order to separate side of 45.0 Mc /s. the synchronising pulses from the vision 29th, 1937 WApishoo .ro3 JANUARY IopIld signal. These valves are fed from the de- and viewed through an inclined mirror In practice, once these controls have tector output and with them is associated mounted inside the lid of the cabinet. been properly set, they need only occa- a diode in order to give more complete The overall dimensions are only 371in. sional adjustment. Experience with the separation of the frame synchronising high by 24kin. wide by i6fi in. deep. receiver shows that not only does the syn- pulses. The controls are grouped around the chronising hold throughout a transmission, The one and only triode in the vision CR tube and covered by the lid when but that if the controls are left set cor- circuits is employed in the time -base to this is closed. The vision circuits are pre - rectly the set can be switched on for a ensure correct operation on both Baird and tuned and cannot be varied by the oper- subsequent transmission without any ad- E.M.I. transmissions. The synchronising ator ; a tuning control for the sound re- justment being needed. When changing impulses are not the same in the two ceiver is fitted, however, in addition to over from one type of transmission to the systems, and this valve enables the time - a volume control. The vision controls bases to function correctly on both. The are the sensitivity and contrast controls, power unit contains three rectifiers, of which are equivalent to pre- and post- which one supplies the high voltage detector volume controls respectively and necessary for operating the CR tube. are used in the same manner. In addition It will thus be clear that the total of there is a Brightness control which varies twenty -two valves is made up by a seven - the grid bias applied to the CR tube and valve vision receiver, a four -valve sound hence the mean illumination of the picture. receiver, a four -valve double-time -base, Controls for varying the frame and line and a three -valve power supply unit. In scanning frequencies are also included, addition three valves are used for sync. and there is a switch to change over the separation and one for ensuring proper circuits to suit either the Baird or the operation on both systems of transmission. E.M.I. transmissions. There is also an All are hard valves of types readily on -cuff switch. This completes the controls obtainable. proper, but a small panel covers four small As might be expected, the apparatus knobs, which permit minor adjustments occupies a considerable amount of space, to be made at rare intervals to compen- but this is much less than one might sup- sate for the ageing of valves. pose, for great care has obviously been Of these four, the first is the " Form taken in the disposition of the different Control," which permits any cramping of units. The tube is mounted vertically the left -hand side of the picture to be cor- rected. The second control is for focus- ing the spot on the CR tube, the third for varying the width of the picture, and the fourth for altering the height. Once set by the installing engineer, these controls require only occasional adjustment. The operation of the equipment is ex- tremely simple, and the instructions accompanying it are lucid. Since few are yet acquainted with the procedure, it may be as well to summarise here the details given in the H.M.V. operating instruc- tions. These assume that initially none of the panel controls are correctly set. After setting the System Selector Switch for the appropriate transmission (Baird or E.M.I.), the steps are as follows: - i. Turn the Brightness control fully to the left. 2. Switch on. 3. Turn the Sensitivity control fully to the left. Upon removing the right -hand side -panel 4. Turn the Contrast control fully to the the under side of the time -base becomes right. accessible and also the output valve of the sound receiver and the rectifier valves in 5. Slowly turn the Brightness control the mains unit. until a faint illumination appears on the screen. Then turn back until variation of the this just disappears. other, however, some 6. Turn the Sensitivity control to the Line- and Frame -Hold controls may be right until traces of the picture appear needed. In the interests of tube life, it is on the screen. Continue turning advisable to turn down the Brightness con- until a light and dark pattern appears trol fully when switching off, and not to on the screen. turn it up again until the set has been 7. Now slowly turn the Frame Hold con- switched on for half a minute or so. Simi- trol until the pattern formed on the larly, the Brightness control should be screen, which will be moving from turned up no more than is necessary to top to bottom or bottom to top of the screen, becomes stationary. give a good bright picture, for excessive 8. Turn the Line Hold control until a brightness increases the wear and tear on steady recognisable picture appears. the CR tube. 9. Bring up the half -tones if necessary The receiver has been thoroughly tested by manipulating the Contrast control for a considerable period in north -west in conjunction with the Brightness London and used with the special resonant control. aerial and feeder supplied by the makers. The removal of the left -hand side -panel of After this the sound is tuned in by the It has given consistently good results, the the cabinet exposes the side of the vision receiver and enables one end of the sound tuning control provided, and the volume picture being extremely bright and thus receiver to be seen. adjusted to the required level. enabling entirely satisfactory results to be 77)4 WpsIlimo 'JANUARY 29th, 1937 WOpIld. H.M.V. Television Receiver Model 901- sign that the controls ate not properly set, of freedom from ignition interference. In secured without any darkening of the and this is quite possible, in spite of spite of this, however, interference was by room. Normal illumination, daylight or apparently good synchronising being no means troublesome ; it had no artificial, apparent can be retained and all details secured, for the synch. hold is so strong effect on the synchronising, and was only of th,,e picture still seen. that considerable latitude in the setting occasionally visible in the form of spots on The size of the picture is about loin. by of the controls can be tolerated. Unless the picture. This speaks well 8in., for the and the optimum viewing distance the settings are correct, however, inter- screening and the feeder system adopted. is about 6ft., the detail and contrast being ference may cause momentary faults. Sound reception was equally satisfac- extremely good. The synchronisation is The testing site was close to a main road tory and of a really high standard practically perfect, of and it is very rare in- with a eunstant stream of traffic and also quality. The equipment is, of course, for deed for a frame to slip or a few lines run close to a bus -stop, so that the conditions AC operation, and it consumes 230 watts. out. Indeed, when this does occur it is a were hardly ideal from the point of view The receiver is supplied complete with a special resonant aerial and feeder and is priced at 95 guineas. This includes in- stallation by the company's engineer of New Murphy both aerial and set, and maintenance of Deceivers receiver and cathode -ray tube for one year. The valves, of course, carry the First Four 1937 Sets all Table Models usual three -months' guarantee. THREE of the four new models re- corresponding to the station wavelength. 'cently announced by Murphy Radio, Having selected a station from the list, Ltd., Welwyn Garden City, are fitted all that is necessary is to watch the corre- Television Programmes with a tuning scale of more than usual in- sponding leading line and tune until the terest. Hitherto the firm has shown some terminating circle The system to be used each day is given is bisected under the below the date. reluctance to print station names on the dial, stationary index line. Wavelength scales are Transmission times are preferring to give a plain wavelength cali- from 3 -4 and 9 -10 daily. brated scale for use in conjunction with a Vision Sound separate station list. The usual " station 6.67 m. (45 Nies). 7.23 M. (41.5 Mc,/s). calibrated " dial was not regarded as a FRIDAY, JANUARY 29th. satisfactory solution, for a knowledge of (Baird.) station wavelengths is necessary if a 3, British Movietonews. 3.10, Friends from laborious search through a crowded list of the Zoo -II, Animals introduced by David Seth -Smith. 3.25, Film. 3.35, Ord Hamilton and his Twentieth Century Melodians. 9, " Heard in Camera "- dramatic thriller in one scene with Tod Slaughter. 9.15, Gaumont British News. 9.25, Repetition of 3.10 and 3.35 programmes. SATURDAY, JANUARY 3oth. (Baird.) .3, Punch and Judy -Bruce McLeod. 3.10, Gaumont British News. 3.20, In Your Garden -II. C. H. Middleton demonstrates planting. 3.35, Film. 3.45, Cabaret. 9, Nancy Logan songs at the piano. 9.10, A cathode -ray tuning indicator, British Movietonews. 9.20, Repetition of inter -station noise suppression and 3.2o programme. 9.35, Cabaret. a new type whistle filter, are MONDAY, FEBRUARY 1st. features of the new A34 Murphy (Marconi-E.M.I.) superheterodyne. 3, The Orchestra and Its instruments -III, " Wind " Philip Thornton. also provided the top of the ;- 3.20, Gaumont at British News. 3.30, Light Entertainment with drum to assist in finding stations the Television Orchestra. not included in the list, which is 9, Repetition of 3 programme. 9.20, British confined to transmitters well with- Movietonews. 9.30, Cabaret. , in the range of the instrument. TUESDAY, FEBRUARY 2nd. The A34, a revised version of (Marconi-E.M.I.) the previous A3o set for AC 3, Demonstration by the Women's League of mains, has the new scale, and is Health and Beauty. 3.15, British Movie- fitted with a cathode -ray tuning tonews. 3.25, Act II of " The Marriage of indicator, a whistle filter and Figaro " by the Vic -Wells Company. inter -station noise suppression. 9, Light Entertainment. 9.20, Gaumont British There is a DC / AC model (tire News. 9.30, Act III of " The Marriage of Figaro " by the Vic -Wells Company. D34), and the price in each case is LIr ros. WEDNESDAY, FEBRUARY 3rd. There are two battery receivers. (Marconi- E.M.I. ) The B33 is a development of the 3, Patricia Rossborough : Syncopated Piano Songs, and Tony B27, with a triode- pentode fre- Raglan, Musical Chef. 3.20, Gaumont British News. 3.30, Twenty -fifth quency- changer, and a QPP pen- Picture Page. tode in the output stage. Auto- 9, Ballroom Dancing demonstrated by the In the tuning scale fitted to the new Murphy B33, A34 matic bias is provided, and there English Amateur Dancing Team. 9.20, British and D34 receivers, the station names are arranged in are only two liT leads. The Movietonews. 9.30, Twenty -sixth Picture Page. alphabetical order. alphabetical tuning scale is in- THURSDAY, FEBRUARY 4th. corporated, and the price, with- (Marconi-E.M.I.) names is to be avoided. A fundamental out batteries, is J ro r5s. 3, Children's Fashion Parade. 3.15, British step forward is taken in the new Murphy Finally, there is the B31, a " straight " llovietonews. 3.25, Dancing Programme. 3.35 dial, for the station names are arranged in HF- det -LF receiver, based on the 1323, with Film. 3.45, Starlight-Carroll Gibbons. alphabetical order with a suitable colour automatic bias and a new high -slope pen- 9, The Composer at the Piano- Norman Mack - scheme to differentiate between medium- and tode output valve. The cabinet has been forth. 9.10, Cook's Night Out -II, Marcel long -wave stations. redesigned, and a new full -vision tuning Boulestin's cooking demonstration. 9.25, The tuning " dial " consists Gaumont British News. 9.35, Boxing of a rotating scale similar to that of the " 28 " series is England v. Ireland at the Alexandra Amateur- cylinder marked with a series of leading now fitted. The price is j6 ios., without Boxing Club Tournament televised from the lines terminating in small circles at points batteries. Concert Hall, Alexandra Palace. Wireless World, January 29th, 1937 Í0; CURRENT TOPICS EVENTS OF THE Gold Medal for Television has worked stations in all other Pioneer continents, but this is the first WEEK IN time that all continents hays THIS morning (January 29th) been able to communicate with Mr. John Logie Baird will each other simultaneously. BRIEF REVIEW be presented with the gold New SW Station Planned medal of the International A Malagasy Exhibition Faculty of Sciences for his con- TAIE present unofficial Swedish tributions to advancement in ACONSIDERABLE amount of short -wave station which the science of television. The curiosity was recently works on 25.63 metres with a presentation will take place dur- aroused among the inhabitants power of 500 watts will shortly ing the annual general meeting of Madagascar by a wireless ex- be replaced by a ti -kW station of the Faculty at the Central hibition recently held there. It working in the neighbourhood of Hall, Westminster. was the first of its kind and was 19 metres. very successful, judging by the Listening in Palestine attendance figures. Portugal's SW Plans THERE was a considerable in- French SHORT waves are to be em- crease in the number of Amateurs' Year ployed as a means of com- licensed listeners in Palestine Book munication between Portugal during 1936. At the end of 1935 THE 1937 edition of the yearly and her African Colonies. Tele- there were slightly more than review issued by the French funken apparatus is to be used 12,000 listeners. These had amateur organisation, " Réseau in the proposed stations. It is risen to nearly 19,000 by . the des Emetteurs Français," has intended that the stations should end of October, 1936, the latest just made its appearance. It be used for the relaying of broad- date for which official figures gives a complete list of all cast programmes as well as for have been received. French and French Colonial ordinary communication work. Meeting amateur stations, and other U.I.R. valuable data concerning the Kabul Calling THE new session of the Inter- amateur movement in France IT is anticipated that broad- national Broadcasting Union and her Colonies. Its price is THE WORLD'S LARGEST casting will shortly be intro- will take place in Berlin from three francs, and it can be ob- STUDIO will be housed in the into Afghanistan, and February 22nd to March 3rd. tained from new Brussels Broadcasting duced the headquarters of House, now nearing completion. already plans are being made for At this session the precise date the organisation at 6, Square de of the annual Congress, which The tower of unusual design the erection of a 2(3-kW station la Dordogne, Paris, 17. seen in the picture, which shows in Kabul, the capital. It is will be held in Switzerland one corner of the new building, hoped that the station will be during June, will be settled. G6RG Destroyed by Fire is reserved for the activities of ready for service in the latter The Algiers Station THE well - known amateur the television department. part of the year. THOSE who make a practice transmitting station owned by Mr. Bryan Groom, of The of both sound and vision, on a New French Stations of listening to foreign higher frequency than that stations will have missed the Hollies, Galashiels, has been ACERTAIN amount of dis- familiar gutted by fire. A new trans- adopted by the B.B.C. Sound is voice of the Algiers being sent out on 62 megacycles, satisfaction is being ex- station during the past few mitter which was under con- has thus taking it below the five - pressed in some quarters in days. The reason is that the struction also been des- France owing to slowness in get- troyed. metre mark, while vision is on transmitter has gone into dry megacycles. It will be ting on with the building of the dock for reconditioning. It is 52 new too- kilowatt Radio Colonial Wireless for Mountaineers noticed that the separation be- hoped to have the station work- tween vision is transmitter near Paris. Com- ing IN order to lessen the risk cf sound and ten again on February 1st, and megacycles instead of 3.5 as in ment has been so unfavourable very greatly improved results mountaineering in Austria a that the authorities are seriously are anticipated. small portable SW transmitter the case of the Alexandra considering the installation of a has been designed by Professor Palace, which transmits sound 25 -k«' transmitter to allay Remarkable Amateur Feat Benz for installation in moun- and vision on 41.5 and 45 mega- public feeling until such time as FOR the first time in history, tain huts so that calls for help cycles respectively. the big transmitter is ready. according to a report re- may be sent out in case of acci- Morse Speed The new Limoges station is to ceived from the American Radio dent. The transmitter will be World's have an initial power of too kW, Relay League, amateur trans- fully automatic and when set Record and arrangements are to be mitters situated in each of the into operation will send out its THERE appear to be many made so that it may be quickly continents have established own call letters together with claimants for the speed raised to 200 kW if and when communication between them- the distress call, so that no time record in the receiving of mes- desired. selves. In a little over twenty will be lost in locating the par- sages in morse. Most of them, minutes each station had ex- ticular hut concerned. however, appear to have re- An Indian Tatsfield changed greetings with the ceived at a speed of only 50 or AN elaborate receiving station others, and their voices were re- French Broadcasts to 6o words per minute. No is being planned by the All - corded by another amateur, and Schools recent claimant seems to have India radio service. It is to be the record was immediately AT the instigation of M. Jean approached the speed achieved erected in Delhi, and one of its played back to them. The Zay, French Minister of in 1935 by Mr. T. McElroy, of principal functions will be to amateurs taking part were situ- National Education, a regular Boston, who, in open competi- pick up S.W. broadcasts from ated in the U.S.A., Colombia, programme of broadcasts to tion, set up a record of 69 Europe and America and pass England, Egypt, India, and elementary a n d secondary words per minute, there being them by landline to various Australia. schools has been inaugurated. only one error in the message Indian broadcasting stations for This feat was the result of These broadcasts are given which he took down. In the relaying. For this purpose an careful planning, in which through the Eiffel Tower case of these super -speed tests intricate system of directional among other things, the most Station. a typewriter is used for taking aerials is to be used. In addi- suitable hour of the day had to down the message, as it would tion, the station will be em- be chosen. This was exception- Below Five Metres be practically impossible to ployed for keeping a check on ally difficult, owing to the varia- THE television experiments write at this speed with any the wavelengths of Indian sta- tion of time in these widely being carried out in the pretence to legibility. An auto- tions, and also for research work different parts of the world. On U.S.A /by the National Broad- matic transmitter is used for in connection with atmospherics. previous occasions one station casting Company are, in the case sending. 7106 Wireless World, January 29111., 1937 UNBIASED B.B.C. Mangles History STUDENTS of horse- racing and other By FREE GRID vulgar pastimes of that nature are never tired of telling us always to stick There is only one thing that is troubling like a limpet to the form book when me, and that is that I may be doing the making our investments, and not to be led B.B.C. less than justice, for Mrs. Free astray by secret tips or information straight Grid, like all of her sex, is only too glad from the horse's mouth. The reason for to rush, to the assistance of anybody or this is that even if a good horse does anything that looks orthodox and re- spectable, and she has given it as her firm occasionally let us down badly, it will A motley collection of mongrels. always turn up trumps in the long run. opinion that it is my set which has de- I must confess that I have never had veloped a fault and is deliberately distort- put away the unworthy thoughts which much luck on the turf myself by following ing the truth, for, as she rightly remarked had been welling up' into my mind. to me, " You yourself have in the past this system but, all the same, I am . a firm It appeared from the explanations that had a lot say about believer that anything worth while will to the distortion in were given to me that the use of dogs for certain sets." I can, therefore, only say always be found to run true to form in the assisting in the design of wireless sets had long run, and I am very pleased to say that I am perfectly willing for the B.B.C. come about in purely accidental manner. to send its technical experts that I have found the B.B.C. to be in this to examine my As most of us know, dogs appear to take set so that this reprehensible fault can be category. absolutely no notice whatever of the sound cleared up. While they are here they It was only a week or two ago that I was of a wireless set, no matter whether music might also care record chiding the B.B.C.'s history- mangling de- to examine the or voices are coming from the loud speaker. made on my home recording outfit, in case partment gently about letting us down The explanation given by scientists for this they thought, as I. confess I did myself at rather badly over the igo8 Scrapbook is that it is due to the absence of the first, that my ears had deceived me with which was broadcast without a single psychic link. Nobody, of course, knows regard to these chronological fantasies of chronological error. It was, however, I exactly what is meant by the psychic link the Intelligentsia( ?) at Headquarters. am pleased to say, merely a momentary any more than do the scientists themselves, lapse on the B.B.C.'s part, and no doubt but, obviously, they are expected to say the member of the staff responsible for it Wireless Manufacturers something in an attempt to explain the has long since been hanged, drawn and inexplicable, otherwise their reputations quartered. I knew in my heart that such Buy Pups would suffer, and so, like the wireless an out and out thoroughbred as the B.B.C. ON the face of it there would seem to be experts in similar circumstances, they couldn't fail to return to proper form be- little connection between broadcast- trot out some meaningless jargon. fore long, and I was very pleased to see ing and dogs, unless it be the manner in Probably nothing more would have been that the recent " Twelve Months Back " which the B.B.C. treats its listeners. How- heard about the affair had not a dog hap- programme proved me correct. ever, it is not that sort of connection which pened to be present during the testing of a I wish to talk about. It appears that television receiver, when the animal sud- nowadays animals play all sorts of unsus- denly gave a low growl and committed pected roles in the development of our hara -kiri by launching itself through the wireless sets. Only the other week we were end of the cathode ray tubq,,nd collecting hearing about a firm which is using white a few thousand volts. It was only after ants to find out all about the proper ma- further experiments with other dogs had terial to use for the insulation of its proved that it was not the vision which tropical sets, and now it is dogs. was the cause of this strange behaviour It was, as a matter of fact, purely by that some genius evolved the theory that The Intelligentsia of Portland Place. chance that I learnt about the dogs. I had it was the intense realism of the human happened to pay a visit to the works of a voice which was the cause of the trouble, They soon showed us that they had well -known set manufacturer in order to dogs simply not recognising the human given up the delicate and thankless task look into the method of making television voice as such when listening to ordinary of sticking meticulously to such an absurd sets, and as I emerged from one of the medium or long -wave broadcasting with thing as the truth, by giving us, with a workshops I was surprised to hear a mot- its restricted frequency range.

challenging take- it -or- leave -it air, . the ley collection of barks, ranging from the Further experiments revealed the fact wrong date for the commencement of the deep baying of a St. Bernard to the shrill that not only did various breeds of dog Queen Mary's maiden voyage. They re- yapping of a wretched Porn. My guide, respond differently to the musical scale, served their master stroke for later on in noticing my astonishment, informed me but even different specimens of the same the programme, however, and, believe that the noise came from the kennels. breed showed marked variations in their me, it really was a master stroke worthy In order to satisfy my curiosity, he led response curve. It was not very long of the best traditions of Broadcasting me across to where the kennel maids were before an ingenious laboratory worker House. Not content with getting all tang- attending to the wants of as motley a col- thought of the idea of cutting production led up with ordinary historical dates, lection of mongrels as it has ever been my costs by doing away with costly labora- which I feel sure we one and all found so fortune to see. I could not for the life of tory gear and employing a collection of 'tiresome at school, the B.B.C. programme me see what part they played in set dogs " peaking " at different frequencies wallahs put the tin hat on everything by development, although I well recollect that in order to test the high -quality ampli- getting mixed up about the Corporation's many years ago certain prominent set fiers of television sets for undesirable own domestic history and telling us that manufacturers, in order to encourage sales, resonances, and the result has been the the regular television service from the made a practice of selling, or rather giving springing -up of an entirely new industry, Alexandra Palace was inaugurated by the away, a pup with every set they disposed as dog- fanciers have already turned their P.M.G. on November ist. Tut ! tut ! And of. Still, I thought those bad old days attention to the breeding of special hand - on the Sabbath, too! were happily gone for ever, and I hastily calibrated dogs. Wireless World, January 29th, 1937

to be suitable for use at radio frequencies as high as 44 Mc / s without introducing any appreciable loss. The two conductors, which consist of No. New Apparatus 26 SWG enamel wire, are laid parallel and spaced about i mm. apart, the insulating material used being very tough and quite Recent Products moisture proof; it will thus withstand the most severe climatic conditions. It should find a useful application in ama- of the Manufacturers Reviewed teur transmitting circuits, since the feeder is capable of carrying up to 1.5 amps. of RF. Thus it could be used in all cases where the KINVA WHISTLE FILTER The primary winding is tapped for supply input to the final amplifiers does not exceed to 150 or Zoo to 250 volts at pOSTLETHWAITE BROS., Church Hill, voltages of zoo 200 watts. c / s, and with adjustment for volt- for 40 to Too More than usual interest attaches to this l Kinver, Stourbridge, Worcs, have ages between these limits. long specialised in whistle filters, and among cable, since for television reception resonant their latest developments is a model des- aerials with low- impedance feeders are gener- cribed as the A5. ally the most satisfactory. -Lee 72 -ohm transmission line This is designed to give a sharp cut -off The Belling is obtainable in reels containing 65ft. and above 7 kc / s with maximum attenuation at the price is 6s. 9d. about 9 kc % s. It is intended for use in sets having a comparatively wide frequency band for high quality of reproduction, and where BULGIN PRECISION RESISTANCES heterodyne whistles from adjacent channel W,TIRE -WOUND resistances with a high stations are sometimes very troublesome. order of accuracy in regard to their The standard A5 model is for connection ohmic values are now obtainable from A. F. in the anode circuit of an AF valve of be- Bulgin and Co., Ltd., Abbey Road, Barking, tween 7,000 and 20,000 ohms AC resistance Essex, in values ranging from o.1 ohm to thus and it will carry 10 mA. of DC. It z megohm. serves for D -D triodes and most general -pur- Enamelled wire is employed, and it is pose triodes that would be used as penulti- wound on a slotted former with the direction mate AF amplifiers. of winding reversed in adjacent slots. Since As the anode current flowing through the the formers are of small diameter this method choke affects slightly the actual cut -off fre- of construction results in a satisfactory non - quency, details of the valve that will be used inductive winding. The former is then en- and its anode current will enable the makers closed in a tube of bakelised material for to supply the correct windings for the cut- Universal type mains transformers made by protection. off frequency wanted. Pye. These resistances are rated at one watt and The whistle filter is, of course, only needed an accuracy guaranteed to be better and A clearly- marked plug board indicates have when this type of interference is present, 2 per cent. The sample tested, a 2 -ohm whether the primary is adjusted for the Too - than arrangements have been made 2 on a laboratory accordingly or the zoo -volt range. model, measured ohms it out of action when receiving the using a ratio giving to put There is a static screen between the prim- Wheatstone bridge local station and other signals not subjected is effected by a double - ary and the secondaries and two terminal to interference. This switch, switch that can be mounted points for including a mains on -off pole two-way are impregnated through- on the panel of the set. while the windings accessibly out. The HT secondary is rated for 6o mA. after rectification and a DC output of either 25o or 350 volts can be obtained. Three LT windings, each of 4 volts and giving 2, 3 and 4 amps. respectively, are included; all these have centre tappings. Tested on full load and with a MU12 rectifier the smoothed DC output was 36o volts at 6o mA., while the LT windings gave, Bulgin wire -wound precision resistance, with their respective loads, 4.2 volts each. Model Rss of 2 ohms value. As short LT leads were used in the test assembly the slight excess in voltage is de- measurements to the nearest o.oi ohm. Its sirable as this allows for the voltage drop on accuracy may.thus be said to be better than the much longer leads that would be used in 0.5 per cent. a set or amplifier. These resistances will be found valuable The transformer is quite silent in operation for shunts and series resistances in multi - of and there is no trace of hum as is sometimes range meters as well as in the construction in which accurately adjusted Kinva 9 kc,'s whistle filter, Type A5. encountered if the core is not tightly test apparatus clamped. It is also satisfactory in respect of resistances are needed. The A5 9 kc /s whistle filter costs zzs., and its temperature, as the core and windings Up to 5,000 ohms the price is 6s. each. a K81 type switch for use as described is were only warm after a long period of Over this value the prices increase progres- available at is. 1od. operation on full load. Being a skeleton sively to 245. for one of one megohm. model there is, of course, ample opportunity dissipation. PYE MAINS TRANSFORMER for heat The price is 21s. and the makers are Pye The Radio Industry THE modern production plant installed by Radio, Ltd., Cambridge. LEAFLETS describing several new Marconi - Pye Radio for the manufacture of the Ekco measuring instruments are now avail- mains transformers used in their receivers is able. The most recent introductions are a Uni- now producing a model designed for home BELLING -LEE LOW- IMPEDANCE versal Impedance Bridge and two Inductance constructors' use. FEEDER Comparators. as it AND LEE, LTD., Cambridge One model only is available, but has jqt EELING equipment will JA-0 Road, Enfield, Middlesex, have Tannoy sound -reproducing the widest possible application, compatible Arterial shortly be installed in the Leicester Municipal with reasonable cost, it should satisfy the introduced a low -impedance transmission Cattle Market, where it will take the place of majority of requirements since it is suitable line, or feeder, which is designed to match the runners who have hitherto been employed for use in any set or amplifier with a power the impedance at the centre of a di -pole to take messages from one part -of the market output up to 3 watts. aerial. Its value is 72 ohms, and it is stated to another. Io8 Wireless World, January 29th, 1937 Listeners' Guíde for

Outstanding Broadcasts musical impression of the TEST CRICKET South Seas and provide a pro - THE fourth Test Match be- at Home and Abroad gramme which would appeal to tween Australia and the M.C.C. the imagination. at Adelaide being a very deci- He has himself written the sive one, reports on it will be THE first of a series of he has just been appointed book for these broadcasts, eagerly awaited by listeners feature programmes conductor of the New York describing many of the scenes each morning. The B.B.C., which will deal with a Philharmonic in succession to and the origins and reasons with the co- operation of the subject of the greatest Toscanini. behind much of the folk music Australian Broadcasting Com- interest and importance to lis- of the South Sea Islands. As mission, will, at 8.3o a.m. on teners-the actual work that is " A DEEP DEPRESSION . . ." far as is possible the music, Friday (to -day), Saturday, done behind the scenes before A TEN -MINUTE insight into which has been arranged by Monday and Tuesday, broad- a programme goes out from the preparations necessary for Eric Siday, who has also spent cast Nationally a ball -by -ball Broadcasting House-will be the compilation of the weather much time in the South Seas, commentary on the last ten given on Sunday at 9.5 (Nat.). minutes of each day's play The subject chosen to inaugu- by Victor Richardson, followed rate this lifting of the veil is by a résumé by Alan Kippax. that of outside broadcasts. A An electrical recording of these typical programme will be fol- commentaries will be broad- lowed throughout the various cast at I p.m. each day. stages from the germination of o > the idea in the fertile brain of SHAKESPEARE S. J. de Lotbinière or some LOVERS of Shakespeare will member of his department to be pleased to know that " The the end of the transmis- actual Merchant of Venice " is to be sion. broadcast on Sunday. Al- The production of this first though a shortened version for programme in the series " In the microphone, lasting from the Making " will be in the 5.35 to 7.5 (Nat.), it will be hands of Felix Felton, who well produced, for Barbara may subsequently enlighten Burnham has it in hand. The listeners on how a Music Hall part of Shylock will be played programme is built up ; what AT THE HELM. Martyn C. Webster, the producer, at the Midland by Ernest Milton, who has happens each time a play is Regional dramatic control panel. The production of " Wild Violets" many times on Monday and Tuesday taken the part in put on, or what arrangements of this week will be in his able hands. stage productions. have to be made in order to broadcast a symphony concert. reports which are issued from will be played on genuine the Meteorological Office is to Hawaiian instruments. The " WILD VIOLETS " GHOSTS OF LONDON he broadcast at 6.5o on Wed- vocal parts will be sung by the THE book of this romantic MARK LUBBOCK and Wilfrid nesday. The microphone will Three Admirals (a male trio) operetta is by Bruno Hardt - visit the offices Rooke -Ley combine . on Sun- various at and the Three Dots -a femin- Warden and the music by day to present another of their the Air Ministry, Adastral ine trio new to broadcasting. Stolz There is, as many programmes, " Ghosts of Lon- House, Kingsway, thereby This South Sea Island musi- people will recall, a prologue don /' to be broadcast at 5.3o giving listeners some idea of cal programme, ' ` Paradise of 1932 with the main action (Reg.). Music and dialogue how weather reports are pre- Isle," is to be broadcast are used to recall famous occa- pared from details provided to -night at 8.20 (Reg.) sions in London's musical his- by R.A.F. aerodromes, light- tory, and in this programme house keepers, coastguards, etc. SWEDISH MUSIC famous visitors to the Metropo- 0 0 0 LISTENERS to the Regional lis whose works will be heard SOUTH SEAS programme on Sunday at 6.3o will include Wagner, Chopin SONNY MILLER, the American will hear a medley of Swedish and Berlioz. song writer, spent much of his songs, marches and dances re- ,> > life until five years ago in the layed from Stockholm. The HALLE CONCERT South Sea Islands, with Hawaii Swedish Broadcasting Orches- ON Thursday the Hallé as his base. He decided on tra and Choir will be con- Concert at Manchester will be leaving that something must ducted by Nils Grevillius and heard in the Regional_ pro- be done with the colourful im- the principal soloists will be gramme at 7.30 and 8.45. The pressions he had gained from Kerstin Torlind and Set Svan- orchestra will be conducted by his life in the South Seas. holm. John Barbirolli and Walter Some six months ago in Lon- The programme has been Gieseking will play the solo don he met Eric Maschwitz, previously broadcast in part in the Rachmaninoff the Variety Director, and out- Sweden and was originally de- Pianoforte Concerto No. 2. lined to him a series of broad- vised for Swedes abroad with The main orchestral item casts which would give a the idea of bringing back will be Elgar's Second Sym- musical memories of their THE CELEBRATED CONDUC- phony in E flat. This will r homeland. It should there- TOR, Boyd Neel, brings his Details of the week's be John Barbirolli's first fore provide English listeners string orchestra to the studio Television programmes at 8 on Saturday to give an broadcast since his return will be found on p. 104. with a kaleidoscopic picture of hour's programme from the from the United States, where L_ Sweden. National transmitter. Wireless World, January 2961, 1937 109

comique, relayed by Paris PTT HIGHLIGHTS OF THE WEEK at 1.3o. On Monday evening from Radio -Paris comes two FRIDAY, JANUARY 29th. hours of Terrasse's comic opera Nat., 6.25, Pianoforte Recital: York Bowen. 7.20, Kentucky and operetta starting at 8.45. the Week Minstrels. 8.20, National Lec- It is said of Terrasse, who died ture-Engineering, by Sir Alex- in 1923, that if his melodic ander Gibbs. 9.20, European taking place thirty years imagination had been more Exchange-IV, Poland. varied he would have been one earlier. It was produced at Reg., 6.45, Car Upkeep- Running Drury. Lane in 1932, and has In. 7.30, " Five Quid Pro Quo, of the most remarkable com- radio play. 8.20, Paradise Isle. posers of humorous music. had a long run recently in the 9.20, Excerpt from " Humpty- provinces. For the broadcast Tuesday brings " Othello " Dumpty " at the Prince of Wales' from the Stras- on Monday at 8 (Reg.) and Theatre, Birmingham. again, this time Tuesday at 7.5o (Nat.) the Abroad. bourg and Rennes stations at Revue Orchestra and Midland Warsaw, 7.15 Warsaw Philhar- 8. From the Municipal Opera monic Orchestra and W. Kampff House on Thursday at 7.10 Revue Chorus will be con- (pianoforte). ducted by Reginald Burston Frankfurt relays Bizet's " Car- SATURDAY, JANUARY 30th. men," with Marion Hunten in with Martvn C. Webster as Nat., 8, The Boyd Neel String the name part. At 7.3o the producer. Orchestra. 9.20, Music Hall. <- G Reg., 6, Worthing Municipal Or- same evening the second act of " COO -EE " chestra. 8.50, Act II of Rossini's \Vagner's immortal " Tristan " The Barber of Seville " from THE above is the title given and Isolde " will be relayed Sadler's Wells. 9.35, Pianoforte from the Royal Opera House to an all -Australian entertain- Recital : Marie Zoldesi. ment which will be broadcast Abroad. by Stockholm. on Wednesday at 8.15 in the Strasbourg, 8.30, Operetta Evening. MISCELLANY Regional programme. The SUNDAY, JANUARY 31st. ON Saturday at 7 Swedish for this entertainment Nat., 5.35, " The Merchant of action stations will relay excerpts at the Bondi Surf Venice." ¶ B.B.C. Orchestra (C) takes place wife Club, LADY JANET CLERK, and Yves Tinayre (tenor). 9.5, from Stockholm's winter revue Bathers' Life Saving of the British Ambassador in In the Making-I. those taking at the " Folkets Hus " Theatre. Sydney. Among Paris. A half- hour's pro- Reg., 5.30, Ghosts of London -II, Three orchestras combine to are Albert Whelan, the. gramme of her music will be Musical Memories. 6.30, Swed- part give a concert from Frankfurt Australian Boys, Nina Devitt broadcast from Radio -Paris at ish music, relayed from Stock- 8.3o to -night (Friday). holm. 7.10, The Bickershaw on Sunday at 7. Malony. and Billy Colliery Band Basque folk -lore will con- c- Ages." It is the ancient but Abroad. stitute the programme from Leipzig, 7, " Euryanthe "- roman- MUSIC still popular process of pre- Paris PTT on Wednesday at AN programme tic opera (Weber). attractive senting the truth swathed in a when songs and dances for the MONDAY, FEBRUARY 1st. 8.30, has been arranged cloak of humour that will be Con- Nat., 7.20, Music Shop -9. ¶It's Çtuten's Hall Symphony illustrated by means of this on Wednesday, when Happening Now-V. 8.30, Piano- cert broadcast. forte Recital Orloff. 10.45, Walter Gieseking will play the The Little Show-radio cabaret. Grieg Pianoforte Concerto. Reg., 8, " Wild Violets." The other works in the pro- COMMUNITY SINGING Abroad. broadcasting Lyons PTT, 8 30, Symphony Con- gramme will be Symphonic THE Danish authorities are endeavouring cert. Poem, Paris, by Delius ; a to teach the listening public a TUESDAY, FEBRUARY 2nd Haydn Symphony, "` The number of popular old and Nat., 7.50, " Wild Violets." 9.20, Swan of Tuonela " ; and " The new national songs. Listeners " Church, Community and State" Return of Lemminkainen," by -IV. ¶The Edric Cundell Sibelius. The concert will be have been asked to join the Chamber Orchestra. 8.15 and 9.3o Choir of Skaarup Seminarium Reg., 7.30, Phyllis Dare assisted by broadcast at Arthur Klein. 8.10, Midland (Nat.), and Sir Thomas in community singing. The event will place on Mon- Parliament-" Profit Sharing in Beecham will be conducting. take Industry." will be At the Sunday Orchestral day night at 7, and Abroad. to be broad- the first of a series. Frankfurt, 7.10 " Dancing Down Concert this week, the Centuries."-Classical dances, cast at 9.5 (Reg.), Paul Beard, <. and dances of to -day. leader of the B.B.C. Sym- OPERA phony Orchestra, will be the LISTENERS have two operas WEDNESDAY, FEBRUARY 3rd. to choose from this evening Nat., 7, Carroll Levis and His soloist in the Tchaikovsky Discoveries. Wan Phillips and Violin Concerto, (Friday). At 7 Stockholm His Two Orchestras. 8.15 and On Thursday, from 10.20 to offers Acts 1 and 2 of Verdi's 9.30, Symphony Concert from " from the Royal the Queen's Hall. 11.15 (Nat.), Zoltan Székeley " Othello PERMANENT CONDUCTOR of Opera House, Stockholm, with Reg., 8.15, " Coo-ee "- all- Austra- and Béla Bartók, the modern- entertainment. 8.40, the Berlin Station Symphony ist Hungarian composer, will the Swedish star, Martin "lianBroadway." Orchestra. Heinrich Steiner of violin Ohman in the name part, Abroad. will conduct the radio orches- give a recital and tra in a programme of works piano music. Bartók will play whilst at 7.10 " Der Frei - Breslau, 7.45, Max Trapp conducts concert of his own works. by Verdi and Puccini from Ber- a group of his own piano solos schütz " (Weber) comes from lin on Sunday at 7 and 8.1o. and, with Székeley, Bach's Breslau. On Saturday, Milan THURSDAY, FEBRUARY 4th. Sonata in B Minor and his own broadcasts Mussorgsky's opera, Nat., 7.40, The Fol -de -Rois. 10.20. of the sea and the mountains Recital : Zoltan Székely (violin) Sonata No. 2 for violin and " Boris Godunov, " evidently with modern Basque music and Béla Bartók (piano). will concerto. in Mussorgsky's original scor- Reg., 7.30 and 8.45, Hallé Society's be heard. ing with all its technical faults, Concert from Manchester. 9.40, At 7.10 on Thursday SATIRE in preference to Rimsky -Kor- My Piano and I : Patricia Ross - Deutschlandsender relays part sakov's improved arrange- borough. of the Rhineland carnival from AN interesting retrospective Abroad. programme will be broadcast ment. Frankfurt, 7.10, Carmen Cologne. This carnival con- from Copenhagen to -night at Sunday brings a matinée (Bizet) from the Municipal Opera tinues until Shrove Tuesday, 7.20 under the heading performance of " The Tales of House. February 9th. " Satirical Revues Through the Hoffmann " from the Opéra- THE AUDITOR. I70 Wireless World, January 29th, 1937

Fading VICISSITUDES OF WAVES IN SPACE RADUALLY the problems that By "CATHODE RAY" next door to a man who runs an electric used to give us most of the fun motor with a sparking commutator and in the old days are moving into refuses to do anything about it so long as the back seats. About twelve themselves intolerable if handled by an the law can't compel him) the useful am- years ago I remember being rather old set. plification may be very limited ; but al- amused at the suggestion of fitting a Although this problem is therefore far though Man may in this respect, as pro- volume control. With the fractional - less acute than it once was, it cannot be verbially in others, be vile, Nature her- kilowatt transmitters and bright-emitter written off altogether just yet. I have self is not blameless and is responsible receiving valves (the famous " R " emphasised that AVC acts in a purely for an irreducible minimum of noise in the triodes !) of the period there was, in negative sense ; it cannot supply what receiver itself' which is well within the general, never any surplus volume to con- isn't there. If fading is so severe as to range of moderately priced sets ; to say trol. That is hardly our trouble now, bring the wave at the receiving aerial to nothing of atmospherics. when W2XAD overloads even a modern zero, or at any rate beyond the maximum output stage unless the set is held down capabilities of the receiver to amplify to The Limiting Factor by AVC. As for the local station, only a useful volume, it is obvious that AVC is one ten- thousandth of the receiver's full helpless to overcome the effect. And So although at first sight noise reduc- amplification is actually brought into use. although there is practically no limit to tion appears to be a problem quite In the early days nothing whatever had the amplification that can be provided by separate from fading it is actually the sole been devised for combating fading, and it modern technique, it is useless .to apply factor that decides how much fading can was perfectly normal for reception to be- more than the amount that brings up be eliminated by the receiver, now that come more or less inaudible from time to noise to enough volume to drown any pro- ' Inherent Receiver Noise : The Wireless time. This was accepted in the same gramme. In " noisy " situations (e.g., World, October 9th, 1936. spirit as " atmospherics," heterodyne whistles and income tax. Owing to the enormously greater strength of modern VOLUME ABOVE NORMAL transmitters the first of these evils, though still present as before, is now relatively (a) 1927 unimportant ; and the necessity (if one can say so) for the second has been re- RECEIVER SENSITIVITY moved. The less said about the third (FOR FULL VOLUME)

the better. VOLUME BELOW NORMAL Fading, like atmospherics, is still with STATION SIGNAL STRENGTH AND us as a natural phenomenon ; but the VOLUME VARIATIONS effect in the listening -room is largely neutralised by the automatic adjustment of amplification unobtrusively carried VOLUME INAUOIBLE out in the receiver by AVC. It is im------NOISE LEVEL

portant to realise that AVC cannot supply B what is not there. So it would have been TIME -.. no use bringing it forward in the earliest days of broadcasting, when (as I have just recalled) there was no amplification (b) 1937 or volume to spare. The height above sea level of the whole of England could not be brought to a uniform level of one thousand feet simply by cutting the hills down to this figure. But it could be done STATION (theoretically) with Tibet, where the NEARLY LEVEL VOLUME SHORT RANGE general level is upwards of 15,000 feet. -_._._- RECEIVER (FULL VOLUME) ' , 'VOLUME BELOW NORMAL (SHORT RANGE RECEIVER) Amplification to Spare NEARLY LEVEL VOLUME - - -- -NOISE LEVEL MF VOLUME BELOW NORMAL (LONG LONG RANGE First, then, there must be plenty of RANGE RECEIVER ) RECEIVER amplification, so that even in the worst T'iME -- (FULL VOLUME) troughs of fading there is enough in hand to give adequate volume ; then during the Fig. r. the early days more favourable periods the surplus is -In of broadcasting, receivers required a strong signal to give full output (see (a)) so the volume- suggested by the heavy line- corresponded with signal strength and thrown away to the correct extent by the faded with it. Although fading of signals still takes place now (see (b)) even a " short superhet " AVC system. So successfully is this is sensitive to a much weaker signal and the surplus sensitivity is taken up by AVC, giving nearly accomplished in modern receivers that constant volume (dash -dot line) except when the fading is very severe. A more sensitive programmes which appear quite steady receiver is then helpful (heavy full line) and the volume drops only when the signal is lost below the noise level in any case. (The " volume " lines suggest only the degree of constancy, and may in fact be fading enough to render are not meant for comparing the volume given by different receivers).

JANUARY 29th, 1937 Wfp®ll zrr W©rld Fading- idea of how waves perform. Sea waves they are close enough in frequency for this amplification and AVC can be made prac- do not provide a good illustration of this to occur less often than about 10,000 times tically perfect without necessarily going unless they are at some distance from the a second the result is a heterodyne whistle. off a commercial basis. shore, which unfortunately is not the most The number of waves emitted being of the Now although in these days of hun- popular aspect for unemotional scientific 'order of a million per second -and many dreds of kilowatts it may have become the contemplation of them. Their effect on times more on the short wavebands -it is exception rather than the rule for other- some floating object, such as a buoy, is to not very likely that two separate stations wise good transmission to dive periodic - move it alternatively above and below the would send out exactly the same number ally below the noise level or even to dip even during as brief a period as one their extremities in it, there is a tendency second without very special means being for listeners to make more use of the very adopted for doing so. The B.B.C. work distant stations. After all, everybody groups of stations (e.g., London, West does not buy an " all -wave " set for and North Nationals) on the same fre- prestige alone. So fading may even yet quency with very great accuracy, and be the main restriction on foreign unless the receiver is so close to one of " travel." There is another thing : when them that the waves from the others are fading is at all bad, though not neces- negligible in comparison they combine to sarily so bad as to be out of control alto- give less or more than normal, and fading gether, it is often accompanied by serious is probable. distortion. At the moment no simple method that could reasonably be applied Fig. 4. -When waves (a) and (b) are not quite Helping or Hindering to the ordinary broadcast receiver to cure of the same length the result is a wave that alternately waxes However, that is quite an exceptional . such distortion is in sight. and wanes -a beat note. case. But waves from any one station normal sea level. This corresponds to are invariably of the same frequency (or the voltage, alternately positive and nega- length) as themselves (obviously !) It tive, generated in an aerial when radio will also be evident that if two waves waves move past it. Unfortunately for from the same station travel to their the analogy, it is rare for two sets of destination by different but not- too -diver- waves of comparable magnitude to be set gent routes there is at least a possibility up on the surface of the ocean simultan- that they will arrive at sensibly the same eously. It sometimes happens in the strength. Therefore, if anything happens wash of a large vessel ; or it can be ob- to cause waves from a particular station served on a smaller scale in a pond by to behave in such a way that some reach the receiver an odd number of Fig. 2. -If two waves (a) and (b) arriving at half - wave - lengths the same place are of the same length (or frequency) and are in step (or phase) the behind others of the combined result is a wave (c) stronger than same strength, they either. cancel out com- pletely. Fig. 5 Various methods of combating fading shows this dia- have been developed for non -broadcasting grammatically. If services ; of these the diversity reception the indirect route method, described some time agog is per- were a Iittle longer haps just within the reach of very am- than that shown bitious amateurs. But even if one is the waves not Fig. 5.- Showing how waves radiated in phase from the transmitter would in a position to take advantage of the may arrive completely out of phase at the receiver owing to the arrive by it a whole more advanced methods, they are inter- greater distance of one route, thus giving zero signal at the receiver. wavelength behind esting for their own sake and as demon- the other and strations of the truth of theories about dropping stones therein. If at any point would therefore strengthen them ; or, radio communication in general and fad- -the buoy, for instance -the two sets of technically,. be in phase with them. A ing in particular. Which reminds me I waves are arriving in such a way that the crests of one lot always coincide with the crests of the other, and troughs likewise, the result is to increase the effect on the buoy. On the other hand, if they arrive ( a ) so that crests always coincide with troughs they weaken one another, and, if they

( b) happen to be exactly equal, they cancel out completely and so far as the buoy is concerned there is a dead calm. The (c) second set of waves causes the first to fade DISTANCE out. TRANSMITTER® -- DEPENDS ry ON WAVELENGTH The same principle applies to waves of I STRONG AND CONSTANT/ other sorts -sound or radio, for example. ll Fig. 3. -If the waves (a) and (b) are of the RECEPTION ALWAYS same length but arrive half a wave out of A broadcasting station is a source of step the result is a wave weaker than either ; waves, which spread out and become or if (a) and (b) are of equal strength, a weaker the farther they go. Other stations complete fade -out takes place. are putting out waves at the same time, have said nothing about but because they are of different fre, what fading quencies really is. they are not in step and there is no possibility of them either strengthen- To understand it one needs a fairly clear ing or cancelling one another contini

2 ously. The most " How the B.B.C. Relays America," The they can do is to Fig. 6. -An imaginary " target " around a Wireless World, May Ist, 1936. strengthen and cancel alternately, and if broadcasting transmitter. Explains itself. 112 JANUARY 29th, 1937 WOFlld Fading - wave, though too weak to produce a com- Having already overstepped my usual still greater lag would cause them to he plete fade, may yet be appreciable. Even bounds, I cannot take space to go into out of phase again, and so on. if it is completely absent -and at great detail about how liability to fading An indirect route might be produced by distances the curvature of the earth sees to depends on wavelength and time of day reflection. Ultra-short waves are reflected that -the shifting and uncertain character (and to some extent on other more obscure from wires, large metal structures, or the of the reflector, on which one now depends factors such as sunspots) and how one can surface of the earth ; and it is very easy entirely for reception, causes variability of thereby try for distant stations at the most to demonstrate the results by moving a results. Furthermore, there is the possi- auspicious times ; but I hope shortly to portable ultra -short wave receiver about bility of two or more sets of indirect waves go on to explain why fading is often when the television transmitter is on.. conflicting among themselves. This is accompanied by distortion ; and how Within a movement of a few feet the particularly so in long- distance short- advantage is taken of the nature of fad- signal may be completely extinguished. wave reception. ing in overcoming it. The longer waves need larger reflectors, and these are provided by Nature mainly during hours of darkness in the form of atmospheric layers at various heights above the ground -about 5o miles and more. RANDOM RADIATIONS At very short distances from the trans- proof that good reception is possible at mitter the reflected waves, if any, are By "DIALLIST" ranges greatly exceeding the original esti- weaker than those received direct, and mate of twenty -five miles. At such places Records as Bedford, Reading, Guildford, and South- is or on any A Novel Way of Playing .there no fading at any time end, for instance, good results are regularly wavelength. That may be called " local ACANADIAN reader sends me some in- teresting information about " radio - obtained. Success with both sound and vision station reception." phonographs " and radio sets in the is also reported from Brighton, but I believe At a greater distance-how much Dominion and the U.S.A. He confirms what that in that case the aerial is a very high greater depends chiefly on the wave- I said some weeks ago about there being one standing on the crest of the Downs. length ; it is less for short than for long a revival of interest in recorded music. In any event, the Alexandra Palace station waves, but a typical distance on the Very few radiograms are, however, in use, covers a large and densely populated part of medium band is.7o miles -the direct wave the tendency being to employ a turntable and the country, and the number of people who has been weakened by being dragged over pick -up in conjunction with the wireless set. are within range is greater by hundreds of If conditions Many of the latter have no pick -up ter- thousands than was originally estimated. the surface of the ground. When the Birmingham transmitter gets make a reflected wave possible, the greater minals, and even if these are fitted subse- sufficient AF am- going, about one -third of the population of it to go is offset by the quently there is often not distance has available for record playing. The the country may become potential tele- it easily plification smoother travel by air, and may difficulty has been overcome by the appear- viewers. happen that it arrives at practically the ance of an ingenious little appliance in which ti ti ti sanie strength as the ground wave. So it a heptode oscillator is modulated by the Portables for Football Fans ? only has to be in the opposite phase for about 1,50o kc /s pick -up. The output at NEXT time I go to see a of the receiver Twickenham to reception to be extinguished completely. is fed to the input terminals big Rugger I am firmly resolhed in as if it were a broadcast- match As the reflecting layer is not a fixed and tuned just to take with me a tiny portable set with a so as it goes ; but, mirror, but is more like the shifting sur- ing station. Good, far of headphones. is of the possible pair No, dear reader, it face of a ceiling of cloud, the strength and as he says, " I hate to think not that I want to listen whilst watching effect of a flock of these rigs being used phase are usually constantly varying and to the croonings of Henry Hall's sweetie - in, say, a large apartment building in a so it is easy to imagine how the pro- bereft vocalists or, indeed, to music of any city ! " gramme fades in and out in an entirely kind. What I desire to hear is Captain irregular manner. This reflection takes Wakelam's comments on the game that I Tuning Indicators am watching. place on the ordinary broadcast waves 'Flu and other things had My Canadian correspondent also com- compelled me until the day of the Welsh only at night ; so there is a zone around ments on a paragraph which appeared match to attend all my Rugger matches in each station where reception is perfectly some time ago in these notes criticising the spirit only this season, the body being at normal in daylight but fades badly after use of a cheap and nasty moving -iron milli - home and the ear, so to speak, glued to the dark. Still farther away the direct wave ammeter as tuning indicator in an expensive laud speaker. And when at long last I was is weaker than the indirect, so exact can- receiving set. This instrument broke down able to be a spectator in the flesh, I realised cellation is impossible and fading is less and threw the set out of action. " Hasn't as never before that Nature has failed to violent. Abuse of is still very it occurred to you," he asks, " that a cheap endow me with the eagle eye Of the expert the B.B.C. moving violent, however, because the better re- meter, by virtue of its lack of a commentator, who seems to see every minute coil, must be more reliable than a more ex- point of the game and to be able to name ception of the more distant (foreign) pensive type? " Frankly, I can't see eye any player unerringly, even though he (the stations convinces listeners that the home to eye with him there. I've half a score of player, that is) be covered in a solid sheet transmissions (which, unrealised by them, moving -coil meters of various kinds that of mud from head to foot. The match - are at a disadvantage through their very have been in constant service for years, and watcher's portable is a grand idea. It has nearness) are palpably inferior to those I have never had any trouble with them - another application, too. The real enthu- abroad. save once when an assistant in an absent- siast, torn by conflicting loyalties, could minded moment essayed to measure the watch one match and " hear " another with - Sky - Waves Only EMF of a 150-volt battery with a o -2 milli its aid ! ammeter! But I do agree with my corre- best of all into the zone. spondent when he says that the Worth Having These latter come third indicators for general use is that of the Here the ground wave is nearly exhausted ` electron -ray " type. The man- in -the- OFTEN I've wondered why car radio by its conflict with town and country, to street is apt to fight shy of meters, but he doesn't catch on in this country to the say nothing of the pinpricks of countless can't disregard a light that winks at him same extent as in the United States. One receiving aerials, and daylight reception as he tunes. reason is possibly that we need a second set, whilst Americans is poor or nil unless the magnification of - ti ti ros. licence for the car After don't have licences at all. It's queer how the receiver is exceptional. dark Television Ranges great a deterrent even small licence fees are they come romping in, thanks to the re- SOME time soon, I suppose, either the to some people. I've heard of well -off folk flection from the upper atmosphere. But B.B.C. or some go -ahead manufacturer who won't take on an extra manservant there is still a likelihood of fading, though will publish a map showing the service area (whom they could perfectly well afford) be- it is less likely to be of the very bad type of the London television station. Such a cause of the 15s. licence involved, though characteristic of Zone 2. There are map would be an immense help to the pro- this represents but a minute percentage of several possible causes. The ground gress of television, for there is now ample the man's wages. I think we miss a good JANUARY 29th, 1937 WApIgh00 113 WoEIld. deal by not being more car -radio minded. I Well, no more stations and no noticeable don't mean that I want to have the wireless increase in the volume from the weaker ones set on all the time that I am driving. I that he was already receiving. don't, but it is certainly a boon to be able to flick over the switch and to have music What is Needed or other entertainment will long, lonely McCA THY at on The modern set undoubtedly deserves a drives. A boon, too, to have the sporting good aerial, but if yours is of reasonable commentaries, the news so on bulletins, and length, 25 -3oft. in height, well insulated and there for the switching when you drive out unscreened for the finest value in the by high trees or buildings, into country in summer time. Once there's probably not very much wrong with you've driven a wireless -fitted car you'll it ; an extra foot or two of height never want a " silent one won't All -Wave Receivers ! " again. make all that much difference. What is % . °_ bad, though, is when the service man who puts in the set tells those who don't know The Aerial Problem the ropes that an indoor aerial is just as good THOUGH there's not a little nonsense as one out of doors, or that the set will work spoken and written about receiving perfectly well without an earth. I've come aerial efficiency, I do think that many of across one or two instances lately of this us don't do our sets too well in the way of kind of thing, and some of them are enough collectors, and for this I am rather disposed to make one weep. One concerned an ex- to blame the man who installs the set. When pensive mains set capable of first -rate per- I say that there's a deal o' nonsense talked formance. When I first heard it I was horri- and written about aerials I have in mind fied at the amount of background noise. In- this kind of thing. A man I know had what vestigation showed that there was no earth ; I should describe as a perfectly good aerial the fellow who installed the set, having well above the average standard. A observed that it was going to be a bit of a friend ( ?) who inspected it told him that if job to make a good earth connection, had he could raise the far end another five feet assured his victims that there was no need he might expect wonderful results- though for it. And I've found before now a good he wasn't doing too badly as it was. Wish- existing outdoor aerial removed and the ing to have the very best, he had the altera- poorest of indoor aerials substituted to cover 6 tions carried out at considerable expense, up lack of sensitivity in a dubious receiving VALVE ALL -WAVE for there were certain difficulties. Result? set. SUPERHETERODYNE (complete with B.V.A. Valves)

Improved edition of this popular receiver (praised " Wireless World" test reports). Heavier gauge cadmium- plated steel chassis. Iron -cored I.F. transformers giv.: even better per- Distant Reception Notes formance. No increase in price. Brief Specification: 8- stage, all -wave band -pass superhetero- dyne, 7 tuned circuits. D.A.V.C. with " squelch" circuit valve SO many different figures are given for are a few pre- breakfast time selections on for noise suppression. Illuminated " Airplane " dial. Octode the total of U.S.A. broadcasting frequency changer. 3-5 watts pentode. Switching for gramo- frequencies of guaranteed accuracy : First phone pick -up. Wave ranges: 16.5 -5o, 200 -55o, R00-2,000 metres. stations that I had the curiosity to Monday in the month, KTSA, San Antonio, tot it up when examining the other day Texas ; 1.o kilowatt, 55o kc !s, 6 -6.15 a.m. the latest list sent to me by an American First Tuesday, WRR, Dallas, Texas, 0.5 kW, McCARTHY ALL -WAVE SIX friend. I made it (E. and O.E. !) 663. This 1,28o kc /s 6 -6.15 a.m. First Friday, represents a very considerable drop from WACO, Waco, Texas, o.1 kW, 1,4zo kc /s, with 6 watt the total of some ten years ago, when there and KNOW, Austin, Texas, o.1 kW, 1,50o push -pull were about Boo stations broadcasting in the kc /s, both 6.45 -7.15 a.m- Second Friday, output States. The reduction is probably accounted WJAG, Norfolk, Nebraska, t.o kW, 1,o6o for chiefly in two ways. kc /s, 6.3o -7 a.m. These transmissions are First of all, many of the original stations regular fixtures for some months to come. who were very small fry started to advertise All times given are G.M.T. local business or scholastic or religious (yes, From a kind correspondent I learn that religious !) undertakings. They were the Greek broadcasting scheme, of which I swamped as bigger stations with more am- gave details some time ago in these notes, bitious programmes carne along. Next, is hanging fire to some extent. It may be many of the older stations could not conform quite a while before the too- kilowatt Athens to the Federal Communications Board's station materialises ; but it has been arranged standards of frequency keeping. They that a provisional i5-kW transmitter shall therefore either relinquished voluntarily or be put into action within a month or two, (complete with forfeited involuntarily their licences to and this is now being constructed. As broadcast. soon as the big station is completed, the 15- B.V.A. Valves) The surviving 663 stations include a very kW plant will be moved to some other 6 valve all-wave superheterodyne with similar specification, large number in the o.1 -o.5 kilowatt class ; in centre Greece. Greek listeners have for long performance, etc., to above. but with large push -pull output but all have brought their transmitting been amongst the worst served in civilised giving s1 -6 watts. plants sufficiently up to date to lie able to countries. Their only station, at Salonica, Has illuminated " Airplane " dial with principal station names, keep within the very narrow limits of wave- has operated only every now.and tone control and volume control (both also operative ou then (and gramophone), full provision for gramophone reproduction. length wandering that are all that is allowed more then than now, if I may so put it), with in that very enlightened country. Every the result those who possess A really high quality receiver, with exceptionally large that receiv- undistorted output, and fine performance on all 3 wavy station, whether it has an individual chan- ing sets have to rely almost entirely upon ranges. nel or works with anything up to a score foreign transmissions for their radio enter- more of wavelength All McCarthy receivers supplied complete with or partners, lias to tainment. And Greece herself has remained valves, knobs, pilot lamps, leads mains cable and submit to a monthly " solo " test by the a country almost unheard outside her own plug. 12 months' guarantee. central authority to ensure that it is capable frontiers. At any rate, I don't remember Deferred terms on application, or through London of keeping, without undue deviation, to the that I have ever come across anyone here Radio Supply Co. 11, Oat Lane, E.C.2. straight and narrow path assigned to it. who has succeeded in logging Salonica. If Cash with order on 7 days approval. Also write for illustrated catalogue of complete range of cli Since the stations engaged in frequency the new Athens station achieves an indi- McCarthy receivers checks work on cleared channels, some of vidual channel it should be receivable even them may be of interest to those D -X enthu- with t5kW, and when the too -kW trans- ILTW, siasts in this country who are wont to class mitter gets to work good 1(CIRIiI IRAIDIIc reception after 44a, Westbournei Grove, London, W.2 any U.S.A. medium -wave station rated at dark should be regularly recorded. I .kilowatt and more as a " local." Here D. EXER. Telephone: Bayswater 3201/2. I T J Wireless World, January 29th, 1937

Great rivalry exists at Broad- casting House between the pro- ducers of the various Services concert parties. So far listeners Broadcast Brevities appear to favour " Flying High," the R.A.F. concert party produced by Charles Shut Your Eyes NEWS FROM Brewer. NO B.B.C. department is more A Territorial Show anxious than " Outside PORTLAND PLACE Broadcasts " to receive helpful Continuing the " Services " from listeners. The tradition, a Territorial Forces suggestions Palace Concert Hall on Thurs- few days. The antiquated many well - concert party will probably be trouble is that next, February 4, is giving studios in Rosemount Terrace meaning correspondents put for- day heard after the next " Eight the engineers cause for excite- are to be scrapped in favour of Bells " broadcast, and then, ward the most impossible ideas. will more or less palatial head- has ment. The Emitron camera some time in the summer, Mr. Joly de Lotbinière on a platform some quarters at Beechgrove House, a of acid be placed " Flying High " will return to been compiling number 1'ft. from the ringside, and in Beechgrove Terrace. Up till tests which listeners might ap- the microphone. Charles Brewer order to determine camera angles, recently this was the residence is investigating all sorts of possi- ply to their ideas before passing councillor. First the amount of " panning " re- of a respected town bilities in extending these Ser- them on to the B.B.C. quired, and necessary lighting, It is one more addition to the he suggests that proposed vice shows, which go with a the television O.B. men have long list of buildings converted swing and revive many old " O.B.s " should be considered boxing ring from their original state for the ex- constructed a model memories. from the point of view of about ift. square. Even with purpose of broadcasting. ; value pense secondly, news an accurately designed model, value ; and The Eight Millionth thirdly, atmosphere however, there is a " snag " con- Strange Origins fourthly, " commentability." To December 31st, 1936, lighting ; if 2,00o The B.B.C.'s research build- last -named elusive cerning the ON test for the watts of light are used for the ing at Nightingale Square, Bal- licensed listeners in this quality, listeners 'are asked, be- transmission, ham, was originally a convent, country numbered 7,960,573, an in their ideas, to actual television fore sending one -tenth scale models of the while Avenue House, Clapham. increase of 579,145 in twelve shut their eyes and describe the require miniature also a haunt of engineers, was months. Within the next week while their lamps would proposed broadcast bulbs of the flash -lamp type the residence of a former or two the eight millionth licence friends listen for entertainment At the Governor of Brixton prison. may be issued, and the occasion who would taking 20 watts. value. (And people is no such minia- The original Cardiff transmitter should merit a song and dance would be real moment there help in this way ture bulb available. was in a sub -station of the elec- on the part of the Post Office friends.) Models are destined to play an tricity supply adjoining the and /or the B.B.C. Brighter O.B.s " increasingly important part in Great Western main line ; the tc7) pro- Leeds headquarters was for- North Wales Service Apart from the Coronation the devising of television merly a Friends' Meeting House, , O.B. Depart- grammes, and the boxing match pl OGI \MMES for broadcast- broadcasts, the which ment has big ideas for infusing ' ing from Penmon, comes into full service on new blood into next summer's IF TELEVISION COMES 1, will be received by outdoor events. Probably more to the Budapest studios February to County Hungarian listeners who land -line from Bangor, or via time will be devoted from Cardiff or any Cricket. Racing will receive new become " viewers " may Bangor instance, have the added pleasure other studio in the B.B.C. sys- treatment, too. For Lili Filotas con- Gold Cup will of seeing tem At the programme the Cheltenham (right) and Gitta Natter trol desk the level can be con- be relayed instead of the usual who are now announcers because trolled and quality checked. In Hunt Cup, principally on the studio staff. facilities for quality is attempt to addition, Golden Miller to checking will be available in a win the Gold Cup for the sixth for this is also room acoustically treated time in succession. It purpose. From the control desk hoped to cover the Lincoln will go the pre- the programme to Handicap, which has never control room for preliminary viously been broadcast. the Grand amplification and thence to The Derby and the transmitter, which is housed in National will, of course, remain a building sixty -eight feet long in the broadcast racing calendar. by forty -five feet wide. Wanted : A Word Painter Synchronisation Amateur boxing will also re. The circuit of the transmitter ceive more attention, and it is resembles those of the two most hoped to cover the national recently built transmitters at amateur championships, Uni- and private houses were taken and Burghead, in over as B.B.C. in Lisnagarvey versity boxing and the Army premises that the same system of series meetings. Bristol and for the new Penmon station. modulation is employed. The Actually, of course, very Penmon transmitter, however, is little material has gone un- But the most lowly origin scale could be claimed by the original on a considerably smaller tapped by the O.B. Department and as a result there are certain in the last ten years, but a new Newcastle transmitter, which life in and was differences in layout. source may be found in the began a cowshed programme will be promoted to a stable yard. As the " country scene." The micro- identical with that put out by phones will be taken to plough- experiment is only the fore- te", te71 tG-1 the Welsh transmitter, special ing matches, country fairs, runner of many more. It is Battleship in " B.A." ? care will have to be taken over meetings horse shows, coaching quite likely that a small street the forecastle synchronisation. The high -fre- And a search dummy and cattle markets. model may be built to determine THATof a battleship should be quency input to the Penmon is now afoot for a " word - best " set up " for televising Broadcast- transmitter originates from a land- the erected in BA studio, painter " who can describe the Coronation procession. ing House, is one of the sugges- valve oscillator, the frequency of scapes. The post would have realistic which is stabilised by a tuning Wordsworth. tions for imparting a suited Mr. William Nigg Is Not Everything atmosphere to Mungo Dewar's fork. The frequency of this fork tel NEWS of the projected Nigg fourth edition of " Eight Bells," is itself controlled by a crystal Television at the Ringside transmitter, referred to in to be broadcast regionally on at the Washford transmitter, the television these columns last week, is not February Toth. The orchestra two being linked by land -line. THE forthcoming is thus broadcast of an amateur the only thing that has de- and cast may be dressed in naval Accurate synchronisation boxing match from Alexandra lighted Aberdonians in the past uniform. ensured. Wireless World, January 29t11, 1937 II, Letters to the Editor The Editor does not hold himself responsible for the opinions of his correspondents

Sound Recording nation by recording and printing the sound- THE publication of two articles on track with an ultra- violet light. This results " Sound Recording " by S. R. Eade in in a more clearly defined wave -form at high the November 27th and December 4th, frequencies, say, at 9,000 c /s, and conse- 1936, issues of The Wireless World once quent better sound- quality in the projected again exhibits your awareness of readers' positive print. (For a full explanation see requirements, and I beg the courtesy of The Journal of the Association of Cine- your space to discuss several of the points Technicians, December, 1936- January, and topics raised by these interesting 1937.) One of the first films to employ articles. this new method is " The Garden of Allah," To avoid confusion I will enumerate the now showing in London, although it must points :- be confessed that the improvement is not (i) In Part i the author refers to the very noticeable aurally. Blattnerphone magnetic recording system. The second development conies The original equipment has been consider- America, and is a sub -standard sound film ably developed, and with the metallurgical recording instrument. It consists of a researches of Dr. Stille has evolved into a 2,000 ft. reel of 16 mm. film which is " cut " medium -quality apparatus. The latest ex- or imprinted by a diamond -pointed stylus. ample of this modern technique is the Mar- and forty parallel sound tracks are produced coni -Stille Recorder- Reproducer, Type across the entire width of film, except for M.S.R.I., as used by the B.B.C. It has an the two sets of sprocket holes. As each overall frequency response of from 70 to track is cut and filled the stylus shifts a-tto- matically to 5,000 e /s, within plus or minus 2 db. the next adjacent space. The Incidentally, it may be observed that the film record plays -back immediately, and one total cost of the complete equipment is reel lasts approximately thirty -seven hours. (Cf. " The L1,435, and the price of 3,000 metres of Phone- Reel " in The Wireless special steel -tape, i.e., 3o minutes' run, is World, November zyth, 1935.) OF THE FIRST WATER f, I9. Ilford, Essex. DONALD W. ALDOUS. (For a short survey of foreign methods A diamond of the first water is of magnetic sound recording, see Radio - amongst the finest of the world's Craft, March, 1936.) Service Prospects jewels. A radio receiver that is (2) In Part 2, page J94, column 2, para- APOINT of great interest to me is raised G.12 equipped is amongst the finest graph 4, line 7, the word " positive " should by " Enquirer " in your issue of Janu- of the world's wireless sets. The be " negative." This will be apparent, for ary 1. I am employed fact that a Rola G.12 is fitted is a as servire engineer guarantee not when the copper " master " is stripped off by a fairly large firm of retailers, only of the most I work faithful reproduction but of wax which is the high the recorded blank, positive, about twelve hours per day for five days, quality of every component in the the grooves appear as ridges or in relief. The and four hours on the shop half -day clos- set. For no set that is not correct order in processing is as follows : ing. My wages, two guineas and sixpence, thoroughly good throughout would recorded wax- blank or "filled blank" ( +), plus commission, is good pay as I am only be equipped with this outstanding speaker. copper ' ` master " ( - ), series of copper just twenty one, the work is pleasant, and Every listener should install a G.12 because " mothers " ( + ), the necessary number of is better than the conditions in factories it means better reproduction. Every manu- stampers, working matrices or dies ( ), and where the wage I was offered - was twenty- facturer should install G.12's in so the final pressed disc ( +). eight shillings- thirty -five shillings when I their more expensive models, (3) I agree with the author's conclusion was twenty -one. because they increase sales. In that " in the light of home recording re- If " Enquirer " can quickly diagnose the either case you will find that there quirements . . . photographic methods particular chassis he comes in contact with, is no better speaker made to -day. are too expensive and require complicated experience will come quickly. If I were apparatus operated with considerable tech- he I G.12 P.55. (aa illustrated) with Trans- would obtain a good test meter and sonner £5 5 0 nical skill. . It would have been oscillator, and the Wireless Service Manual, G.12 P.M. less Transformer ...... £4 16 0 perhaps wise to have included in the fore- digest this, and then go out for a, G.12 D.C. Complete with Transformer, going the phrase " at present," because I service job at, say, two pounds per week. Mounting Stand, Handle have recently been informed of two firms and Base ...... £5 5 0 There is a shortage of even moderáte ser- G.12 D.C. with Mounting Stand, Handle in England which are experimenting to com- vice men, and when and Base, but without experience is gained a Transforme, mercialise an amateur, or home, sound -filin man of thirty with his own gear should .. ... £4 16 0 recording apparatus, together with cheap G.12 D.C. Stripped but with Trans- easily claim three fifteen to four pounds a former ...... £4 4 0 usable film stock. Therefore one may ask week. Forget the letters for a while and 6.12 D.C. Stripped and without Trans- sound -on former ...... £3 15 0 whether the -film system will ever get sonic experience in your own lab. wholly supplant the disc system. Manchester. ENGINEER. (When ordering please state Field Resistance and (4) I disagree with the statements made Impedance of Transformer required.) in the three paragraphs preceding For Public Address work both the P.M. and Ener- the The Croydon Radio Society ' gised Models can be supplied with a 15 ohm Voice elm last of 2 ; a sound Part quality of .t interesting lecture was recently given by Coil at an additional charge of 3 -. high order is possible with certain disc re- Sir. P. G. A. H. Voigt, of loud speaker fame, cording equipments (e.g., the apparatus who, of course, dealt with his own particular Write for Folder A. described by Mr. Bradford in The Wireless subject. The lecturer pointed out the striking World for September 25th, 1936), and the effects which the acoustic properties of a room OVER 8 MILLION IN USE difficulty is not even one of playing -tinic had on loud speaker reproduction and he de- duration, but the chief problem is to devise plored the modern style of room which im- an inexpensive and effective synchronising 1 rted a harsh tone to the efforts of the B.L.C. Next Tuesday evening (February 2n1) is one mechanism. of the club's loud speaker nights at which (5) I now give sonic information about members bring their instruments for compara- two recent developments in the sound re- tive tests to be made. This always arouses cording field, which I believe will interest great interest, and anybody who desires to readers. attend will be cordially welcomed. The meet- /itQ The first is known as " ultra- violet c _po- ing is at 8 p.m. at the Society's headquarters Wot/dj Wstest Re rcoducets sure," which is a new R.C.A. Photophone at St. Peter's Hall, Ledbury Road, South Croydon. Full particulars THE BRITISH . method of obtaining improved emulsion of the society may ROLA CO., LTD. be obtained from the Hon. Pub. Secretary, MINERVA ROAD. PARK ROYAL,N.W.10. resolution of the film and better definition Mr. E. L. Cumbers, 1.4, Campden Road, South of the images presented by the lens combi- Croydon. PHONE : WILLESDEN 4322 -3- 4 -5 -6. rió Wireless World, January 2917, 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, Southampton Buildings, London, W.C.2, price 1 - each. Recent Inventions A selection of patents issued in U.S.A. is also included. Brief Descriptions of the more interesting radio of the second or control emitter. SUPER = REGENERATIVE CIRCUITS devices and improvements issued as patents The principle can be applied to be included in this section. valves whether used as amplifiers APENTODE valve is used as a will .or generators, and also to cathode - local oscillator for quenching resist- rav tubes. a super- regenerative circuit, the electron -emitting surface is covered the condenser C through a insulating laver of artifi- ance R by the action of the grils As shown in the Figure, a cen- grid and screen -grid being back - with an emitter F controls the emis- cial resin, on which is laid a per- G, Gr, a diode valve D being in- tral coupled ; magnetically. Or the sion from two other emitters Fi, to forated metal plate which acts as serted, as shown, in order to grid may be capacity -coupled voltage on the grid F2, which are located on opposite the anode, and the quenching a control grid. The latter is prevent the of glue, to GI from building -up much in ex- sides of it and co- operate with oscillations applied to the screen covered with a layer separate anodes Ai, Az. Control separate it from a second grid, cess of the cathode. The operation grid, the pentode being shunted pf the oscillator depends upon the grids G are inserted in the space across the circuit to be damped. which is also covered with an insu- a fact that variations in the poten- between the centre and outer As shown in the Figure, the lating laver to separate it from emitters. So far as the external third grid, and so on. Metal -foil tial of the first grid causes corre- pentode P is the super- regenera- variations in the poten- circuits are concerned the emitters path is Leeds are connected to the various sponding -tor. Its anode- cathode tial of the second grid, within the Fr and F2 are connected as a limits allowed by the diode D. common cathode, the two grids G E. L. C. White. Application and the anodes Ar, As being date March 21St, 1935. No. similarly treated. 455497. P. Schwerin; Electronic De- o o o o vices, Ltd., and H. C. Atkins. Application dates January 14th CONTROLLING ELECTRON and March 9111, 1935. No. EMISSION 455137. 0 o 0 0 THE_ rate at which electrons are liberated from a sensitised CATHODE =RAY TUBES surface, either under the effect of AS an alternative to the usual an incident light -ray or as the method of controlling the in- result of bombardment by other tensity- of the light spot, the electrons, depends to some extent cathode K of a cathode -ray tube upon temperature, of which there is so constructed that its emis- is an optimum value for different sivity is not uniform throughout, emissive surfaces. but varies from one end to the Accordingly means are provided other of its length. to control the temperature of the An electron image of the various electrodes, say, in a multi - cathode is first focused by an ex- grid electron -multiplier of the cold - cathode type. For instance, the hollow circuit using a pentode as the quenching valve. electrodes may be made Super- regenerative and supplied with heating or cool- ing fluid through glass pipes sealed shunted by a choke coil K in series - grids to allow the application of with a back -coupled oscillator suitable biasing -potentials. into the bulb of the amplifier. valve V. The oscillations from the The upper or " plate " electrode E. E. Wright and Baird Tel,-- valve V periodically reduce consists of a metal of different vision, Ltd. Application dale the anode voltage of the pentode electron -emitting properties to the April 15, 1935. No. 451973. so that the latter is swung on to first or cathode electrode, so that the low- impedance part of the an electron discharge takes place BROADLY speaking, the ob- ject is to produce an electron curve. At these times it quenches across the assembly of electrodes, Electrode assembly of the the oscillations in the main circuit under the action, say, of alight -ray, discharge device capable of high amplification and, in the case of cathode -ray tube described in L, C, which is shunted across the and is controlled or amplified by Patent No. 455237. anode and grid and connected be- the potentials on the various tween the two tuning -condensers " grids." ternal magnetic coil M on to a showo'to the cathode. N. F. Philips Gloeilanrpen- screening electrode E prbvided D. M. Johnstone and Baird fabrieken. Convention date (Ger- with a central aperture. Modula- Television, Ltd. Application date many), March 9th, 1J37. No. tion is then effected by swinging April 17th, 1935. No. 455298. 454826. the image to and fro, over the o o o o o 0 0 0 aperture, by means of the deflect- DF AERIALS ing -field set up across two plates GENERATING "PEAKED" P. This causes the number of AFRAME aerial used for direc- OSCII.I..ITION5 electrons passing through the aper- tion- finding on an aeroplane AFIVE -(:RIU valve -V is used to ture (and reaching the fluorescent when not in is arranged so that generate a ' peaked " or saw - screen) to vary in accordance with into a re- use it can be withdrawn toothed oscillation by discharging Electron discharge device em- the strength of the signals applied cess in the fuselage, where it is plates P. weather, bodying subsidiary cathodes to to the protected from wind and control the emission. J. C. Wilson and Baird Tele- and adds nothing to the head re- vision, L ld. Application date sistance of machine. the a thermionic valve, to secure a April 15th, 1935. No. 455237. When required for taking bear- high degree of sensitivity by using ings, the frame slides out of the electrodes which are spaced com- TO minimise the danger of col- which is carried recess on a yoke paratively widely apart. Two lapse, clue to external air - by guide- tubes, and is firmly electron -emitting elements are pressure, it is desirable to make posi- locked in the fully retracted used in the same tube, the first the glass envelope of a cathode - tion. A centre spindle allows the acting as the cathode proper and rav tulle of uniform thickness frame to be orientated about a the second acting to control the -throughout. Instead, therefore, base- plate, which is marked with volume of emission from the first. of introducing the leads for the a compass scale. In other words, the first emitter high- potential electrodes through SIro1 t Bros. (Rochester and may be said to act as the anode of a thickened stub, they are sealed - Bedford), Ltd., and A. G. Parks. the second, since it collects ele_- in at the junction between an Application date August Ist, 1935. trons from it, and as a cathode so tipper and lower part of the tube, No. 455164. far as the main discharge through close to the electrodes in question. o o o o the stream is concerned. This allows the tube to be made in DRY= CONTACT AMPLIFIERS Control is effected either by two parts, which are of uniform ASERIES of dry -contact elec- altering the potential- gradient be- thickness and are butt -welded to- trode- surfaces are arranged tween the two emitters, or by gether. to act both as a detector and am- deflecting the electron stream pass- Ferranti, Ltd., and M. K. Tay- plifier in much the same way as a Circuit arrangement of saw - ing through the space between lor. Application (lat.' April 16th, thermionic valve. A cathode or toothed oscillation generator. them,.also by varying the heating 1935- No. 455499.