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SPECIAL DOUBLE NUMBER
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WRITE NOW for your copy of the. complete N.P.L. Report giving irrefutable proof of the value and merits of Mullard P.M. Valves with the wonderful P.M. Filament. Full valve guide and instructions to secure better results from your radio. An opportunity that should not be missed by any radio valve user. 1. .99ts- The ciT4 Mullard Wireless cpX3V Service Co., Ltd. Milliard House. Denmark St. 1C\-5 London, W.C.2 rC Please send me a copy of you, N.P.L. I Mullard AVA Brochure and Valve Guide giving me full par - THEMASTER. VALVE titulars why valves with the wonderful P.M. Filament will improve my radio receiver. THE RADIO VALVE WITH A PUBLISHED I m
NATIONAL PHYSICAL LABORATORY TES Add ess
ADVT. 1HE MULLARD WIRELESS SERVICECO., LTD., MULLARD HOUSE, DENMARX STREET,LOND:N,W.C.2
ii
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CONTENTS A Selective Three .. 183 Listen to America Direct ByJ.H.REYNER,B.Sc. (Hons.), A.M.I.E.E. By A. V. D.HORT.B.A. How Wireless Components are Made. Sets That You Can Build .. .. 241 No. 2 189 Things Every Operator Should Kncw ..243 By CaptainJACK FROST,M.I.R.E. By G. P.KENDALL,B.Sc. How to Make Your Own Screened Coils191 How to Use a Wavemeter 247 All Round Europe with Plug-in Coils ..193 By J. H.REYNER,B.SC.(Hops), By C. P.ALLINSON,A.M.I.R.E. Choose Your Own Circuit .. ..252 Mr. Gumplethorpe's Christmas Party201 ByBRIAN ST. CLAIR, Making Use of Your Supply Mains..207 Operating the "All -British Six'..' Workshop Hints .. 257 The " Economical Two " Further Notes on the "Night Hawk" 263 By W. Q.KAY. Some Solutionsto Your Superhet Are You Satisfied With Your Set? 223 Puzzles 265 By L. H.THOMAS By JOHN HNDERDOWN. Loud -Speaker and Receiver in One 226 An Experimenter's Base -Board 273 The Radio Play of the Future.. 233 By H.BRAMFORD. ByMADGE TITHERADGE. Apparatus Tested.. 280
On the inside-the business side-as well as on the outside of the panel, fit " Utility " Components.This is the " Utility " Micro - Dial that isusually fitted by thepeople who" know."The " UtilityMicro -Dial begins where other dials finish.The best adjustment with n ordinary dial is the preliminary movement of the " Utility," in which slow motion mechanism gives the finest possible tuning after the dial has provided coarse adjustment. Unlimited movement. No backlashCan be fitted to all makes of Condensers. Insist upon " Utility" Micro -Dial ; No -Capacity Change -Over Switch; Low Loss Condenser Jack and Plug; Push Pull Switch-All good dealers stock them.
COMPONENT./ "Utility " Condenser. Price .0005 IV - WILKINS &WRIGHTLT! Price .0003 14/ - when fitted with KENYON ST. BIRMINGHAM this Micro -Dial. 611:11111M111111 osa
A In replying to advertisers, please mention THE WIRELESS CONSTRUCTOR., 181,
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A t> v 4.V.AYA,VAVAVAVAVACreWiNre7Gat)(I° 6 ev47 The Truth About the Tests. vs Not only do S.T. valves represent the highest le el of Ith,
vale design and manufacture to -day, but whenever .41'.* or wherever you get an S.T. you know that that AT particular -valve has been app oved by John Scott- z1,1 Taggart, F.inst.P., A.M.I.E.E. V, 1> You take your package home, knowingithas ,..4 actvally been in his own hands, and it is almost as if P., Scott. aggart himself wereaanding. by you, con- 44 fidently waiting for your set to spring Into new life as you put his p c. ed valves into your set.if it so rids g., D too good to be true, read the following Stat itory ,.....1 Declaration made before a Commissions for Oaths : V, .14 STATUTORYDECLARATION. , I, JOHN SLOTT-TAGGART, ca 2, Melbourne Place, in IQ! I;0' the County of London, do solemnly and sincerely declare V.V., 4 that: , .14 (x)I am the Managing and TechnicalDirectorof 17,, S.T.Limited and am responsible for the maintenance :.c1 of the high standard of S.T. valves. VA (2)The test department is under my immediate control, ,VI and every S.T. valve is given a number of tests li& which include a factory test, a laboratory test, in 3 N which a minimum of nine electrical measurements V > are taken with precision meters, a test in a receiver p on broadcasting, and a final laboratory test identical PI, Ct to the previous one in which the same nine or more .1? .(41 measurements ,are taken by a different technical gi Al.? assistant. (3)Only those valves which pass all four independent N WA tests are sold, and after I have satisfied myself that ...4 a valve is within this specification, it is packed in a I> carton bearing a certificate containing a white space < ,._v4 on which I sign my initials. I> D (4) No single valve has been issued by S.T. Limited ...41 which has not passed the required tests, and every ,t V, carton bears my initials which, without exception, s .,,, have been affixed with my own hand and pen. 9, And I make this solemn declaration conscientiously _all Q',4 believing the same to be true and by virtue ofthe tt Provisions of the Statutory Declarations Act of 1835. 5 P", SI r04%/SCO'l V, ...1"
, 11c!, 4 Declared at so, Norfolk Street, Strand, S :4 in the County of London, this 19th'day , ,Z.I of November, 1926, before me, ,,,C1 VA P, Litl )i.a.19C. L.det ) fi-nztj L'I' V, V ',..1 A Commissioner for Oaths. 4 TYPES AND PRICES. I> 1:),4 2 VOLT. 41 Co I> (H.F.) . 141. ..,,, S.T. 21 0.1 amp...... S.T. 22 (L.F. and 0.1 amp. .. 141. 4 li:* 4_ S.T. 23 (Power). . 0.15 amp...... 18/6 4 11 ST. 41 (H.F. and DVIT.0.1 amp...14/- t>, Q S.T. 42 (Power) ..0.I amp. .. 18/6 ,9 1:11. S.T. 43 (Super Power)0.25 amp... 22/6 V' 6 VOLT. 4 S.T. 61 (H.F. and Det.) 0.1 amp...18/6 trt. S.T. 62 (Power) ..0.1 amp... -16/6 S.T. 63 (Super Power) .0.25 amp... 22/6 0'
182 In replying to advertisers, please mention THE WIRELESS CONSTRUCTOR.
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Published by The Amalgamated Press (1922), Ltd., The Fleetway House, Farringdon Street, E.C.4. A SELECTIVE THREE
By J. H. REYNER B.Sc. (Hons.), A.M.I.E.E.
Here is the set to build for this Christmas!The construction is simple, the coils you can make up yourself, the set is easy_ to operate and you can expect excellent results from its up-to-date circuit and design.
THERE are many readers nowadays apart from the copper screening cases increaseinefficiency over the usual who wish to avail themselves of which are now so familiar. arrangement, with the result that a the latest developments in high - very selectivereceiver is obtained. - frequency amplification, but who Home -Made Transformers The circuit used for the receiver in preferifpossible to make up their In the present set a more or less questionisa standard split -primary own high -frequency transformers. standard circuit has been utilised, but arrangement. An ordinary auto - Recent improvements have been con- special home -constructed transformers coupledaerialcircuitis utilisedto fined principallytothe production have been made for the benefit of apply the signals to the grid of the and standardisation of various types those readers who prefer actually to first high -frequency valve.The anode of plug-in high -frequency transformers constructtheir own apparatus.At circuit of this valve istransformer - made to fit a standard 6 -pin base, so the same time, by winding thecoils coupled to the grid of the detector that they may be used either inside or specially,itispossible to obtain an valve, the secondary of the tranformer 183
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being tuned. The primary is wound in neutralisethereceivercorrectlyin two sections, one being the primary the manner described later, when no BUILD THIS SET WITH: proper and the other the neutralising danger from this trouble will arise. One ebonite panel, 21 in. by 7 in. by section. Aerial Coil Winding One suitable cabinet, with baseboard, A Popular Arrangement The first operation in the construc- Siin. deep.(Peto-Scott Co., Ltd) A straightforward transformer - tion of the receiver is the making up Two .0005 and one .00025 "lateral of the high -frequency transformer and action " variable condensers. (Ripaults.) coupled note -magnifier is included for Two 3i in. and one 2i in. diameter ribbed ebonite formers, each 3 in. long. (Redferns.) TEST REPORT Three valve holders.(Lotus.) Three fixed resistors, to suit valves The following stations were received, all on the loud -speaker, using used.(Peto-Scott Co., Ltd.) an aerial about 60 ft. by 20 ft.,12 miles north of London:- One L.F. transformer, A.F.3. (Ferranti, Ltd.) Reading on Reading on One H.F. choke. (Metro -Vick.) Station. Aerial Dial. :-tation. Aerial Dial. One .0003 fixed condenser.(T.C.C.) Rosenhugel 44 ardiff 110 One 2-megohm leak.(Dubilier.) Brussels ... 16 Breslau ... 125 One baseboard mounting neutralising Barcelona... 49 Newcastle... 135 condenser and threedialindicators. Birmingham 53 Bournemouth 145, (A. F. Bulgin & Co.) Ecole Superieure 62 One on -off switch. (Wright & Weaire.) Munster 148 Four terminals. Frankfurt 71 297 -metre band ... 152 Bern ... 79 One battery plug and socket, 7 -way. 294 -Metre band ... 157 Glasgow 84 One spring clip. 163 Hamburg 87 288.5 -metre band Two pieces of ebonite 2 in. by 41 in., Cassel... 180 bY 42 in. Toulouse ... 90 Litzendraht, 9/38, about 40 yds. (London Manchester 95 Malmo ... 190 220 Electric Wire Co. & Smiths, Ltd.) London 103 Gleiwitz Quantity of Glazite and a few inches of The tapping on the aerial coil requires occasional alteration for the flex. best results.The readings on the second dial are about 10 degrees lower Radio Press panel transfers. than those given above. Approximate cost, O. mitted, or theuse of the stranded the third stage, thus giving the very aerialcoil. For these, some special wire gives rise to a higher resistance popular combination of one high -fre- 3 -in.diameter flangedebonite tube than would be obtained with a solid quency, detector, and one note -magni- has been utilised.The particular tube conductor.In the presentinstance, fying valve. in the present instance was obtained therefore, thethreetappingshave Screening has not been employed, in from Messrs. Redferns, and had eight been made by looping the wire out to" order to minimise thecostofthe flanges thereon.The aerial coil car- the terminal and back again, and just arrangement. The presenceofan ries 50 turns of" Litz "wire, this baring the insulationat theactual electro-static screen 'between the first +2
two stages would undoubtedly be bene- ficial,but excellentresultscanbe obtained without itsuse, and it has been omitted in the present instance. H T. L2 No Radiation L3 In order to obtain a satisfactory degree of sensitivity a reaction wind- CZ ing hasbeenplaced on the trans- former to permit capacity -controlled S reaction of the " Reinartz " type to be obtained as required.Since a defi- nitereaction isprovidedinthis manner, the first valve can be per- 0.405 fectly neutralised, which enablesthe 0 receivertobe handled without any danger of interference to the neigh- bours due to radiation. It must be borne in mind, however, that this non -radiating condition only E obtains when thefirst valve isdefi- nitely and correctly neutralised. When Fig. 1.-The switch disconnects both the L.T. andthe N.T. batteries. this is the case the last stage may be permitted to oscillate without danger. being composed of 9 strands of 38 gauge. point of contact without breaking the It ispossible, however, to obtain a Similar conductorto thismaybe wireitself. stable position on the receiver when obtained from the London Electric it is not quite correctly balanced.In Wire Co.Tappings are taken on this Dealing with " Litz " such cases a small amount of energy aerial coilat 5,10, and15 turns. Particular care must be takenin willfilter through to the aerial and Tapping this " Litz " wire is a matter carrying out this operation that none cause radiation. Particular care of some difficulty, owing to the fact of the strands of the 38 -gauge wire should be taken, therefore, to that no broken strands must be per - are broken. It is best to clean the 184
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wire with a very small piece of fine differentvalve,butprovidedthe other. Inthiscaseithas been emery cloth.First remove the cover- detector valve is of a high impedance, obtained by windingtwowires ing over thewholeconductor, and a tapping at about half -way across together side by side. then gently clean off the enamel on the coil will be found to give consider- It is therefore necessary to cut off a the indiVidual strands by means of the ably sharper tuning without appre- length of 10 or 12 ft. of wire and emery cloth. The conductor may then ciable loss in signal strength. thentowindthesetwolengths be soldered to the particular terminal Thissystemhasthereforebeen together on the former, so thit we in question. adopted in. the case in question, and have alternately a wire of the primary The actual method of bringing out the centre -tapping on the Litz wind - and then a wire of the neutralising the connections both on this coil and on the high -frequency transformer is worthy of note.Holes are drilled at E&Z.7:-50 r + &CONDENSER MOY/N4M.ArEs the end of the former, through which Lire
small 6 B.A. screws are inserted. They ) roComoovsex . are held in position with a nut, while CRIO FIXED PLATES On top of this a soldering tag is held in position with, a second nut.Both 4k, I CENTRE TAP '717 6RIO the wire from the coil and the connec- tions to itare soldered to this, the 1111 wire from thetapping pointbeing brought through a hole in one of the AERIAL TAPS flanges along the top of the former Figs. 2 and 3.-Details of the aerial coil (left), and the secondary of the under the winding proper. H.F. transformer (right). H.F. Transformer The high -frequency transformer is ing should be made by looping_ the winding throughout the whole length, constructed in a similar manner. ,---The wire outtothe terminal and back thus obtaining a very tight coupling. secondary coil consists of 50 turns of again without definitely breaking the For these windings 22 -gauge wire was Litzendraht, as with the aerial coil. wire in an exactly similar manner to utilised for mechanical consideratitms There is, however, a separate tapping the tappings on the aerial coil. and ease of winding, but ifdesired on this winding which is taken to the finer gauges of wire may be used with grid of the detector valve, as will be Two Formers equal efficiency. seen from the circuit diagram.By The primary, neutralising, and re- this means the detector valve is not action windings are placed on a simi- Connections connectedacross thewhole ofthe lar former of 2 in.diameter, which The actual method of winding is -tuned circuit. slides inside thesecondaryformer. shown in Fig. 7,theprimary As is well known, when grid -rectifi- The overall diameter over the flanges windingbeing from A to D, and cation is used, the valve introduces a is just over 2a in., so that the former the winding 0 toB. certain amount of extra damping into just fits comfortablyinside the Itisimportant to remember these the circuit.The effect of this is very secondary former. connections and to ensure that they considerably minimised by tapping the With thesplit -primary method of are connected in the correct manner neutralising, as has previouslybeen when actually wiring the receiver up. emphasisedinthese columns, itis If the connections are wrongly made, then the neutralising winding will be connectedinthe wrongdirection. This point, however, will be dealt with later on in the article. Direction of Windings The primary former also carries the reaction winding, which consists of 20 turns of a suitable gauge of wire.In this case 30 gauge wire was employed for the purpose. The reaction winding is wound in the same direction from start to finish as the neutralising and primary windings, and when the con- nectionsarecompletethe primary I former is inserted into the secondary former in such a direction that all the windings are in the same direction. The direction is again important, as All the battery leads are otherwise the reaction winding will be brought oat to a special in the wrong direction and will pro- plug at the rear of the duce extra damping insteadof an baseboard. increaseinsignalstrength. This, however, is not such a serious fault as valve across a portion of the circuit necessary to have a very tight coupling havingtheneutralising winding only, and in this case, using a D.E.5B between the primary winding and the wrong, because it can easily be seen or similar type of valve for the detec- neutralising winding.In the case of whetherthereactionwindingis tor, a tapping at about half the coil the standard transformers this is ob- wrong, whereasifthe neutralising is satisfactory There is actually an tained by a definite over -winding, one winding isincorrectly connected they optimum tappingpointforeach winding being wound on top of the fault is somewhat difficult to trace. 185
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3" 2//2.--.
AE /AL
21
Fig. 4.-Drilling dimensions for the panel are given in this scale drawing.Blueprint No. C1073A.
TOP LIPS OF BASEBOARD
Fig. 5. ---The coils should be mounted in the positions shown here. Blueprint No. C1073B. 186
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Mounting safeguard against wrong connection of minals of the receiver, and to connect batteries. the wires direct on to the Multi -plug. These transformers may thenbe A particular point is the double -pole mounted on the baseboard in the posi- push-pull, switch used for switching the REAcraw) PRIMARY AND tion shown in the wiring diagram by set on or off.This not only breaks the NEUTRAL/MN& simply screwing -them down on the filament circuits, but disconnects the WINDINGS WOUND baseboard,asmallpieceofleaf TO6Froie-R5toeSr H.T.- from L.T.-E, thus rendering Sloe eboniteorinsulatingclothbeing the set " dead " when itis switched placed in between the formers and the off. This saves the windings of the swarms* baseboard in order to prevent leakage L.F.transformerandalsoavoids END °PA. across the windings. C A 1.1 me Orme* The assembly of the remainder of END ere. thesetiscomparativelystraight- Fig. 7 -The arrangement of the wind- forward.Mount n$ the three con- ings on the inner former of the H.F. densers, the on -off switch, and the four transformer. terminals on the panel in the posi- tions shown in the panel diagram. Testing Having made these connections, the WIRING IN WORDS set is now ready for test.It is advis- Join a flexible lead with spring clip to Aerial: able to utilise some form of safety terminal. device when first testing out, in case Join Earth terminal to moving vanes of variable condenser Cl, to one end of LI, to anyconnectionshavebeenmade Ione filament contact of V1,V2and V3, and 2 wrongly.One of the simplest devices 2 to L.T. - and 0.13. + pins of Multi -plug. is to include a fuse or small flash -lamp Join other end ofLIto fixed vanes of Cl, to fixed vanes of neutralising condenserC2, Fig. 8.-Showing how the tappings are bulb in the negative lead from the and to grid of Vi. high-tension battery.Should the H.T. Join remainingfilament contactsof VI, brought out to soldering tags. 1V2and V3 to one end of resistors RI,R2 circuit theninadvertently come in andR3respectively. trouble ifit is desired to make any contact with the L.T. circuit, the cur- Join together remaining ends of R1, It2 alterations to the set when it is still rents will burn out the fuse or flath- andR3,continue to one end ofL4,moving vanes of variable condensersC3andC4,and switched on. lampbulbbeforethevalvesare i to one outer contact of switch S. damaged, and in this way considerahle Join anode of VI, to C end ofL3. Battery Leads Join moving vanes ofC2to D end ofL2. expense can be saved. Join fixed vanes ofC3to remaining end ofL4. Having completed the wiring of the In testing out, place the reaction , Join A end ofL2(andL3)to H.T. +2pin 1 of Multi -plug, and to top telephone terminal. set, it is next necessary to connect the condenser, on the right-hand side, to Join centre tap ofL4to one end of fixed leads on to the plug of the Multi -plug the minimum position (with the plates condenser C5 and leakR4. all out).Then set the two tuning con- Join other end ofC5andR4to grid of V2. connector unit.All the contacts on Join one end ofL5to fixed vanes ofC4. this plug will be found to be engraved densersapproximatelyto the same, Join other end ofL5to one end ofB.F. plainly.It 'is very convenient to use reading and tune in to the local eta - choke, and to anode ofV2. Join other end ofR.F.choke to PLATE one of the battery cords now on the terminal ofL.F.transformer TiT2. market, such aa,for examplethe Join H.T. + terminal of Ti T2 to H.T. + 1 pin of Multi -plug. " Lewcos " or the " Magnum." These Join GRID terminal of TiT2to grid ofV3. Join GRID BIAS terminal of Ti T2 to IG.B. -pin of Multi -plug. iJoin anode ofV3to lower telephone terminal. Join remaining outer contact of S to H.T. - pin of Multi -plug. Join two centre contacts of S to L.T. + pin of Multi -plug. ,.... When the condensers are mounted, the three dial indicators may be inserted in the correct positions.The panel should then be screwed to the base- board and the remainder of the com- ponents mounted on the baseboard in the positions indicated.Ample space is provided, and no difficulty should be experienced atthisstage. The instrument is then ready for wiring up. Wiring The neutralising con- Wire up the receiver in the manner denser is placed between shown.It will be noted that all the the coils, the reaction battery connections have been brought variable condenser being to a Multi -plug, which consists of a that seen on the left in number of pins arranged round the this photograph. circumference of a circle.The battery leads themselves are taken to a plug consist of a number of flex wires of Lion. The approximate settings will carrying a number of sockets which suitable lengths, fitted with plugs at be obtained from the test report which fit over the pins and thus make con- one end and terminal tagsat the is given elsewhere. Ilection to the receiver.This is made other, and bound up into one complete .n such a way that the plug cannot be cord.For our purpose, of course, it Neutralising .asserted in the wrong manner, so that is necessary to cut off the terminal The receiver may now be neutralise:I, he arrangement provides an adequate tags, which normally go under the ter - (Conelnded on page 229.) 187
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COMPONENTS ARE MADE
Ni; 9 THE PvIAKING OF ThIE RECEIVING VALVE. (Continued)
- B Y ;,CAAP_TA1N JACK MOST, 'KUM,
Continuing the description of the construction of receiving valves, commenced in last month's issue,Capt. Frost deals with thefixing of the electrodes and the bulb, the processof evacuating thevalve and the final tests before the finished product is ready for your receiver.
IDESCRIBED in my lastarticle Electric Welding be adjusted ready for axing before the making of the foot of the The next journey which the foot of they are actually welded. For this, valve and of the anode, grid and the valve makes is to another bench, special examiners with tiny instru- filament, and to me these minor parts mentsadjusttheexactdistance where a girl attaches the grid of the between the three parts of the valve of the valve have become most inter- valve to its support by electric weld- and then pass them to the welder. esting and have a most important ing, and the anode of the valve to The examiners make quite sure that part to play in the function of the its support in the same way. " The the length of the filament and the valve which, in turn, is essential to little machine which does this weld- disposition ofgrid andanode are receptionwhere valvereceiversor ing looks very much like a tiny vice, correct. valve amplifiers are used.All these the two sides of the vice being two odd parts have to be assembled, and poles through which acurrentof The Bulb this is how it is done. electricity is passed. A spark jumps The next step in the making of the across the gap between the two parts valve is the making of the bulb.The Fixing the Electrodes The foot of the valve with its sup- ports has to be attended to first of all.The supports themselves have to be bent into the correct position to take the parts to be fixed to them. You may have noticed that in various types of valves the filament, grid and anode are in different positions.The positions of the electrodes just depend on the type of valve which is being made. To fix these the supports for the electrodes have to be bent.A very wonderful machineis used for this. First of all the foot of the valve with its supports is put into the front of the machine,a stamp comes down and bends the support wires to the requiredposition. Downalittle shoot and out of the machine comes the valve foot. This shootis just like those used for underground rail- way ticket machines. A girl examines the valve foot and passes it into an- Forming the spirals for valve grids.The tray in front contains grids othermachinewhichsimplydeals ready for mounting. with the two filament supports, and flattens the ends of them or bends of the vice -like instrument, and as it glass bulbs go into the valve works them so that the filaments may easily jumps, melts a tiny portion of metal looking very much like empty electric be held.Then another machine takes of the support, which very quickly light bulbs, open at the narrow end. that valve foot and also the length becomessolidagain,holdingthe A girl takes a bulb, and, twisting it offilament wire which I described anode to the piece of metal which quickly in her fingers, puts the closed last monthasbeing cut up and forms its support. end of the- bulb into a hot gas flame. tabbed, and fixes it to the filament With very special types "efreceiv- This softens the glass at the centre supports. ing valves the anode and grid have to and top of the bulb.With her other 189
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How Wireless Components are Made-continued
hand she takes a thin glass tube, and avoid strain and possible breakage to be used when the valve is sold and softeningthistoo,sticksthethin the glass. usedonthereceivingset.This tube on to the top of the softened Exhaustion applied voltage is connected for about bulb, pulling it out a little to make The next stepis pumping. For 30 minutes, pumping taking place all a tiny hole where the two meet, and this the valve, is turned upside down the time.Then the current is cut off turns it quickly with both hands all and the thin glass tube sticking to and the bulb of the valve is heated the time that itis cooling down in its top is attached to a similar tube at the point where the thin glass tube the air.The bulb now appears just on the pumping machine by softening has been connected to it.Our valve like a diver's helmet with the air tube the glass by heating.The pumps are has now been sealed at both ends and fixed to itstop. You could easily set to work and all the air and gases blow down the thin glass tube into are sucked out of the valve.Whilst the bulb. pumpingisgoing on,acoveris Shaping the Bulb drawn over the valve and it is really Thebulbthengoestoanother thenina typeofoven whichis instrument with dollies similar to the heated to about 400 degreesCenti- one whichIdescribedlast month, grade. This throws gas out of the used for the making of the glass foot actualglassofthebulb and the of the valve.The bulb is put into a pump sucks the gases out of the bulb dolly, and passes into a flame which itself as fast as the glass throws them cuts off the unwanted piece of glass intoit. The valve then gradually at the bottom of thebulb, making cools down. the whole bulb of the correct length Whilst pumping isstillgoing on, for the valve which it is to be.As the four small wires from the foot of the dollies revolve and pass through the valve are connected to electric hotter and hatter gas flames, a steel circuits, which pass a current through instrumentopensoutthesoftened theelectrodes. The filamentis glass at the foot of the bulb to the heated by this means almost to melt- correct distance to take the flange of ing point, in order to liberate gases the foot, which I described in my last from the metal of which the filament article. is composed.The anode of the valve A general view of the exhausting room Another machine with dollies takes is heated until it is bright red and in a valve factory. the bulb andalsothe foot of the is also subjected to what is known as valve, with its grid, anode and fila- " electron bombardment "from the exhausted of air and of gas. The ment attached to it, and with the four filament.This liberates gas from the glass and the metal of the electrodes wires which run to the supports of anode as well as from the filament, have been made to give out any gases the electrodes fixesitinto the bulb. and the pump sucks the gases away which they may contain, and these Theglassisjoinedtogetherafter whilst this is happening. gases have been taken from the valve. All of this can only occur to bright emitter types of valves. Dull Emitters With dull emitters theprocessis the same up to and including the freeing of gases from the glass of the valve by bakingitat 4C0 degrees Centigrade.The valve is then sealed off in the manner which I have just described, and is passed to whatis calledthe" eddycurrentbench." We stillhave,in the caseof dull emittervalves, thefreeingofthe anode from gases. This is done by heating the anode by means of what is called an " eddy " current.There ismagnesium in the anode of the dull emitter valve and the eddy cur- rent process causes the magnesium to be volatilised. Whenthistakesplacethegas given off by the anode of the valve is sucked up and istaken ontothe The glass tubes attached to the bulbs, through which the gases are inside of the glass walls of the valve withdrawn from them, may be seen on the valves t,the right. and is kept there by the volatilised magnesium.This beingsoftenedby hotgasflames. Sealing -Off. givestothedull After coming out of this machine we emitter type of valve which is treated have our valve looking just as your The number of volts to which the in this way the silvered appearance valve does now, except thatit has anode of the valve is subjected varies which you all know so well. Both attached to the top of it this funny between300and2,000,dependent types ofvalvesare thencarefully looking glass tube and, of course,it upon the type ofvalve being con- examined for what iscalled " fila- has not yet any legs or any marking. structed.The voltage applied to the ment emission "characteristic,and When it leaves the gas flame it has filament of the valve is low, by com- to test the hardness of the vacuum in- togothrough anannealing oven, parison, and yetisslightlyhigher side the valve. which allows it to cool gradually to than the voltage which will ordinarily (Concluded on page 285.) 190
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@Et@Ewt@EffiEffict, 63E65kmEgEmeez Eng@EgO@PMEg60Et0EgE84,Wg@OO&@FEREPE3).0.&005,)0@Fit@Ei5 How to Makeyour ownScreened Coils Eg By W. Q. KAY Many constructors are anxious to try the new screened coils, which have been embodied in a number of well-known and successful sets recently, but have been prevented from doing so by considerations of expense. From the instructions given here you will be able to make your own coil screens.
- cq43g9ssq3c59eocT3c59,2o/3 043 QinG19000c33(83413 cE3430G'Oq3,500GG.
THERE are many people who wish daces them must be absorbed from the tances as shown in Fig. 1.-It was then to try the new circuits incor- coilitself,sodetractinginsome possible to observe the effect of the dis- poratingscreenedcoils but measurefromitsefficiency. The tance upon the resistance of the coil, who are unable or unwilling to pur- actual screened coils,as used in the and this is shown in the curve given chase the commercial components now various receivers, are in the form of in Fig. 2. on the market.In such casesit'is It will be observed -that at distances possibletomakeup one'sowu away from the coil of2, in. or more screened coil,and this has already the effect of the screen is practically been done in a large number of cases. negligible, the resistance of the com- Thereare,however, certain factors bination beingalmost the same as which have to be taken into account, that of the coil itself.At a distance as otherwise the results will be of a of1in.the effect of the screenis disappointing nature,anditisin appreciable,while ata. distanceof order to clear up any misunderstand- 1- in. it is beginning to increase some- ing on thispoint that the present k NORMAL RESISTANCE Of COIL what rapidly.Beyond this point the article has been written. Y2 resistancerises very rapidly indeed, ,OLITANCE BETWEEN SCREEN AND CON(INCHES) and very heavy losses are introduced The Original Design Fig. 2. - Illustrating graphically the into the circuit, but it will be realised Theoriginalscreenedcoilswere effect on the coil resistance of placing from the curve shown that at 1 -in. designed asaresultofcareful the screen in different positions. distance the effect is not very serious. research, inorder to ascertain definitely the effect of bringing metal a compromise . between the considera- Another Type screens near to a coil.The screening tionofefficiencyandtheequally A similar series of experiments 'was works by virtue of the fact that eddy important consideration of compact- carried out with the screenat the currents are set up in the screen, and ness.One of the advantages of the end of the coil, instead of at the side these produce magneticfields which screened coil lies in the fact that the . as shown in Fig.1, and here it was actinoppositiontothe magnetic receiver can be built up into a much found that the distance at which the fieldof the coil.At the same time smallerspace than would otherwise losses began to increase rapidly ,de- the screens, if they are connected. to bepossible, and thereisno doubt thata.' compact constructionina pended largely upon the shape of the earth, form a static shield around the coil. With a -short, fat coil,itis coil so preventing anycapacity receiver is very desirable. necessary to have a distance of 1in., coupling from the coil to other parts Now the farther away we go from but with a somewhat longercoila of the circuit. acoil the less does the strength of the magneticfieldbecome. Conse- distance of 1 in. sufficed. quently the less must be the counter - These results,therefore, were col- Little Efficiency Lost magnetic field produced by a screen, lected and co-ordinated, and the re- This eleetro-static screening, as the and thus the less 'the eddy currents sult was the production of the screened elimination ofcapacityeffect is set up therein.The eddy currents in coilaswenow knowit. Itis Coa UNDER rear thescreen,infact,automatically adjust themselves to counteract the effect of the magnetic field existing at that partimilar point, so that the fur- ther away we remove the screen from the coil,- the less does the energy loss become, while the screening remains every bit as effective in that the effect of the magnetic field outside the coil 4tk" is still practically negligible. Fig. 3.-The dimensions of the screen are given here. Experiments Fig.I.-- The distance between the because of this necessity for an ade- screen and the coil has a considerable The experiments were conducted in quate clearance between the coil and bearing on the efficiency of the latter. the first place and were made with a the screen that a certain supervision viewtoascertaining howfarthe at Elstree has been exercised on the called, has verylittle effect on the screen should be from the coil in order various makes ofscreened coils,in efficiency of the coil.Itis the pre- to obtain reasonably satisfactory order that they shall all comply with senceofthe eddy currentsinthe results.Fortunatelyitwasfound the necessary conditions. metal (by means of which the magnetic that thelossesintroducedinto the screening is produced) that gives rise coil obeyed a somewhat peculiar law. to the additional losses. A simple coil was taken and its high - Minimum Dimensions
This must beobvious,sincethe frequencyresistancewasmeasured. It is not possible to reduce the size eddy currents must be produced from A sheet of metal was then brought of thecoils very much ifthey are somewhere. and the energy which pro - near to thecoilatdecreasing dis- to retain their efficiency. but it was 191
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Effi673, HOW TO MAKE YOUR OWN SCREENED COILS-cont. NEWS IN ADVERTISEMENTS .11 found that a 2 -in, coil could be made a circular disc of ebonite or wood of ft) reasonably efficient.This means that a suitable diameter to fit the screen 130q3C3GGGO&SIG4X?9C301319c39s. the screen must be at least 3 in. in with which it is proposed to use it. Now thattheChristmasbuying diameter, if it is made circular, and season is almost here our readers will should preferably be alittlemore, The Screen have an active interest in the adver- if this can be afforded.There is, in The screen itself may be made of tisementsappearinginthisissue. fact, an increasing tendency nowadays copper tube,or may be made by Below will be found a few.paragraphs, to make the screens somewhat larger giving inbrief,the main points of in diameter, and thisisall to the interestcontainedincurrentan- good, provided that a suitable arrange- nouncements. ment can be made as regards the Messrs.CollinsonPrecisionScrew connections, so that the base does not Co.,Ltd., are announcing an addi- become unduly large. tional item to their range of low -loss 2*" inductance formers. This manufac- End Clearance turers' series of coils are all in con- formitywiththe standardsix -pin Apart from the diameter, however, arrangement, but the ribs may now the actual depth of the screen from be obtained either plain or threaded. top to bottom is of considerable im- portance, and in many cases thisis Itisinteresting tonoteinthe made too small.A clearance of 1 in. advertisement of Messrs. Metro -Vick above and below the coil itself should Fig. 4.-Connections to the terminals Supplies,Ltd.,that the tfirstfour be provided, and, if possible, still more beneath the base.The dimension given prize -winners in the 4 -Valve Receiving clearanceisdesirable. The actual refersto the hole cut in the outer Set Class, in a competition organised height of the screen, then, depends ebonite ring. bythe" Sunday Chronicle and upon the size of the coil in use, but Evening Chronicle,"heldatthe this question of clearance at the end obtainingacylindricalcylinder of Manchester Wireless Exhibition, used is one which makes considerable dif- some sort, such as a circular box or certaintypesof" Cosmos "S.P. ference to the efficiency of the re- cocoa tin, and wrapping round this a Valves. sulting arrangement, and should be piece of fairly stiff copper foil or thin borne in mind very carefully. copper sheet.This may then be sol- It is suggested by Messrs. Gent and In ordertorender the screen as dered up to make a complete tube, Co., Ltd., in their advertisement that flexibleaspossible,so thatinter. after which it can be withdrawn from byinvestinginaTangentH.T. changeable coils can be used for the the cylindrical mandrel.A cocoa tin Battery Eliminator your radiowill different wavelength ranges, different should not be used fortike screen not let you down during the Christ- circuits, and such -like, a six -pin type itself, as it is constructed of tinplate, mas holidays. of coil was devised, with six sockets which is iron covered with a coating in the base of the screen, so permit- of tin, and this will introduce very A Christmasappealismade by Messrs.Will Day,Ltd.,inwhose announcement many interesting pro- ducts are featured. It is stated in the advertisement of *** Messrs. A. 0. Cossor, Ltd., that after 2,000hoursofcontinuoususe-a Up-to-date wire- period equivalenttotwoyears less equipment is ordinary wear and tear-the Cossor used by the com- filament is as supple and as pliable as batants in the war it was first made. in China.A 120 wattcombined The" Layerbilt,"anewH.T. transmitter a n d battery by the manufacturers of the receiver is seen in Columbia Battery, is now being mar- thisphotograph. keted by Messrs. J. R. Morris.It is claimed in this company's advertise- ment that the life of this new battery is35to 52 per cent.longer than *** ColumbiaExtra Heavy Duty H.T. Battery. Messrs. S.T., Ltd.. show in detailed tabular form the recommended types ting a wide variation in the type of heavy losses.The metal used for the in the S.T. series of radio receiving coilinuse. When making upa screenshouldbeeithercopper or valves for use in receivers ranging screened coil, therefore, the first thing aluminium. from one to six valves. to do is to obtain six valve sockets, Brass may be used if it is good, soft or other suitable sockets fitting ,a stan- brass, but thishas a much higher Messrs. Rexo Engineering are an- dardOn.pin. Theseshould be resistance than copper, and is not so nouncing an exceedingly useful pro- mounted up in a Southern Cross for- good as either of the other two metals. duct in the shape of the " Junit Self - mation, the arrangement of the pins Inparticular,hardbrasshasa Soldering Wire."This line will make being shown in Fig. 5.The spacing tendency to be magnetic, and this a very strong appeal to readers whose between the centres of the pinsis will introduce further losses, so that experience with the soldering iron may in. on both arms of the cross.These . copper or aluminiumispreferable. be limited, and to them it is recom- pins should be mounted centrally on (Concluded on p. 272.) mended for use. 192. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 TIME WIRELESS CONSTRUCTOR - wararerawwwnwmifsrwarannirmorowarawwwwwiware ALL ROUND EUROPE WITH PLUG-IN COILS By C. P. ALLINSON, A.M.LR.E. A three -valve set with two stages of high -frequency amplification, the design of which needs no special coils or transformers, but enables you to use plug-in coils of standard pattern.The H.F. stages are neutralised and the set is non -radiating. THERE must be thousands of wire- resistance of the order of 100,000 or less experimenters who possess a SOME SPECIAL 250,000 ohms, in this lead resulted in number of plug-in coils of the a greater degree of amplification being conventional type who would like to FEATURES OF THIS SET obtained, while any -trouble due to use them in a thoroughly up-to-date 1.-You can use your old plug-in parasitic oscillations was also guarded H.F. amplifying circuit and who have coils, yetafullyneutralised against. so far given little heed to most of the circuit is employed so that full present neutralised circuits on account amplification is obtainable from Parasitic Oscillations of the fact that special coils are re- both H.F. valves.' This question of parasitics is a very quired,thesebeingeitherofthe 2.-The set is selective because it important one, since it becomes exceed- centre -tapped type or else inductances isneutralised, anditsselec- ingly difficult to use more than one or mounted on special bases. tivity can be controlled. two stages of high -frequency amplifi- I therefore decided to go into the 3.-You can obtain the full benefit cation if a circuit is at all liable to question and see whether it would not of reaction in the detector cir- generatethem. Eventhecircuit be possible to evolve a high -frequency cuits, thus securing the maxi- shown in Fig. 1 might conceivably de- amplifierwhich,whilefullyneu- mum range and selectivity. velop trouble of thisdescriptionif tralised,wouldneverthelessenable 4.-The set is simple to handle, a four or more stages were employed.I ordinary plug-in coils to be employed. gang -controlledcondenserre- have used four stages successfully with The rather obvious solution of using ducing the tuning controls to this circuit, but itis possible that a two small coils in series, with a con- two, while the set is completely slightly different lay -out might have nection going between them, was at stable except when you wish to introduced the trouble that - I was once ruled out, since it meant that make it oscillate by the use of trying to avoid. nearly double the numberofcoils reaction. If, Therefore, I could find a scheme would be required for a receiver incor- 5.-The set is non -radiating. whereby the centre tap was abolished, porating any such scheme as this, and not only would the circuit be suitable I therefore put the problem on paper for plug-incoils,but it would also L3 L3 C3 Fig. 1 (left) and Fig. 2 (right).-In order to simplify these diagrams, the H.T. battery is shown connected to L.T. the L.T. battery being omitted.In practice H.T. - would go to L.T. -F. + H -F CHOKE H -F CHOKE HT. OR RESISTANCE ORRESISTANCE eliminateanychanceof before me to see whether some method to the grid and the other going to the entirely could be arrived at theoretically which anode throughasmalladjustable trouble occurring through parasitic would hold possibilities of working in capacity C2, which is used for neu- oscillations being produced. practice. tralisation. The centre of the grid coil is connected through a high -frequency The Solution Evolution choke or a resistance to L.T. -. The The solutiontotheproblemis I hal% for some time been working output inductance L2 is the primary shown in Fig.2, and it appears so with a form of neutralised H.F. cir- of a high -frequency transformer, of ridiculously simple that I can almost cuit in which a centre -tapped grid coil which the secondary is tuned, a suit- hear you say, Why, anyone could is used, and in order that the reader able degree of coupling being arranged have thought of that! " And so they may see exactly what has been done I between the two. could-but, as far as I am aware, they show this iu skeleton form in Fig. 1. In the original circuit,as it first have not done so. The tuned grid circuit consists of an became known, the centre point of Ll As will be seen from the simplified inductance Ll tuned by a variable was connected directly to low-tension. circuit in Fig. 2, what has been done condenserCl,whichisconnected I found, however, that placing a high - is; that the choke (or resistance if pre- asshown,withonesidegoing frequency choke (as shown), or a high ferred-some circuits work better with 193 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor E WIRELESS CONSTRUCTOR January, 1927 All Round Europe With Plug -In Coils-continued the one rather than the other) has tively stopping the valve from work- with a view to adding it to an existing been transferred to the bottom of the ing by preventing any flow of plate H.F. amplifier. coil Ll.It is obvious that this choke current. Thiswouldundoubtedly does not provide a return path to the occur in nine cases out of ten if the Layout grid of the valve were left free.That An examination of the photos will increased efficiency is obtained by the show that everything that is not abso- use ofthischoke asindicatedin lutely required on the panel has been BUILD THIS SET WITH- Fig. 1 has been amply proved by a removed from it, and the only cornt One ebonite panel, 21 in. by 7 in. byin. number of experiments. ponents mounted thereon are the two (Ebonart). One cabinet for same, with baseboard, 131 in. deep (Peto-Scott Co., Ltd.). One .0005 Cyldon double gang con- denser (Sydney S. Bird). *** One .0005 and one .0003 variable con- denser square -law type (Igranic Electric Co., Ltd.). The coils and leak Sevenbase -mounting single coil resistanceshave holders (Wright & Weaire). here been re- One H.F. choke (Ussen, ltd.). moved,toshow Two 100,000 ohm resistances (Varley clearly the layout Magnet Co.). of the components Three " Clearertone "valve holders (Benjamin Electric Co.). Three fixed resistors (Burne-Jones & *** Co.,iwotd.). vernier dials (Beard & Fitch). One on -offswitchand one slow- motion " Indigraph "(Igranic Electric Co.,iwotd.). neutralising condensers(Peto- The Final Circuit tuning and one reaction condensers Scott Co., Ltd.). and the on -off switch.The left-hand Two .002 fixed condensers, type 600A, If,therefore, the sole function of condenser tunes the aerial, the gang and one .0003 grid condenser and 2- the choke is to prevent the valve from is in the centre, and to the right is megohm leak (Dubilier Condenser Co., getting blocked, does Ltd.) it not much reaction.Batteries are connected to Two terminals,Aerialand Earth matter at what point on Ll it is con-- the set by means of special battery (Belling & Lee, Ltd.). nected.If it is to be removed from cords, whileaerial, earth and tele- One set of battery cords, five -way the centre, then the logical place to phone terminals are mounted on the (London Electric Wire Co. & Smiths, put it is at the bottom of the coil as baseboard behind the panel.In order Ltd.). shown in Fig. 2, and this is the basic that the 'phones may be most con- Two telephone terminals, two strips circuit which is used in the receiver veniently connected to the set, the tele- of ebonite, screws, etc., for mounting which is described here. phone terminals are close to the panel, components. A number of photographs are given through which a hole has been drilled. Quantity of Glazite for making con- on this and other pages showing the The telephone cords are passed through nections. general appearance of the receiver.I this hole, and the experimenter is not Radio Press panel transfers. have made this a three -valve set, con- unduly tied down to the set on account Approximate cost .. £12. sisting of two stages of high -frequency of half his 'phone cords being used up and a detector valve. Nolow-frequency in reaching to terminals at the back of amplifying valves have been included, the cabinet. filament for H.F.currentsinthe for the simple reason that most ex- If you will next have a look at the Fig. 1 circuit.If it does,it is not perimenters eitherhavetheir own views taken behind the panel, you will acting as a choke.Its sole function ideas, and very definite ones, I find, see that all the components are well indeed would appear to be to anchor. about low -frequency amplification, or spaced out,ample room beingleft the grid and prevent its building up else they already have an amplifier everywhere for the wiring, while the a high negative potential, and so effec- which has specially been constructed coils are spread well apart and put at 0+1 HT+ -2 L6 V2 4 Cs 002 C3 was C4 L, /00.000 + R50,4743 R2 L.T. 1 /00,000 OHMS c, / GANG CONDENSER Jr Fig. 3.-The complete circuit of the set described. C2and C, are neutralising condensers, while C7 is the variable condenser for reaction control. 194 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR All Round Europe With Plug -In Coils-continued right angles to each other so as to grams of this description.For those may be used.The use of resistances reduce, as far as possible, any inter- who prefer a diagram showing the wasdecidedon,sincechokesare tetion. actual connections on the set itself, rather liable to pull into tune on the this will be found on another page. long waves and uncontrollable oscilla- Double Gang Condenser tion may result. The double gang condenser seen in Points in the Circuit Matched Coils the centre is used to tune the second The aerial is loosely coupled to the The two coils L4 and L6 are tuned 2l" 6%2" 0 s Fig. 4.-Drilling dimensionsmay betaken fromthis front -of -panel drawing.Blueprint No. 10074A. H.F.anddetectorcircuits,while, firstvalveandisuntuned,the by two condensers C3 and CS, which since the aerial is coupled to the first coupling between the aerial coil Ll are gang controlled, so that only one H.I. valve, a separate condenser has and the grid coil L2 being fixed.Dif- dial is required to be adjusted to tune been used to tune it, so as to allow for ferent degrees of coupling may, how- these two circuits.It is therefore ad- any variation.There are settings- at ever, be obtained by using different visable that L4 and L6 be as nearly which the aerial seriously affects the sizes of coil in the aerial.This also matched as possible, and if you have tuning of the first H.F. valve, so that enables the maximum efficiency to be not got a pair of accurately matched the use of a three -gang condenser was extracted from the receiver on the coils I would advise you to get them. decided to reduce different wave bands. Coils made by manufacturers of known efficiency.Even with the double gang The first two valves utilise the same reputation are,iowever, produced to there is a very slight loss at the bottom circuit,theneutralising condensers such near limits of accuracy that it of the scale, but it is so slight as to being shown at C2 and C4.High re - will in general be found that two coils of the same size made by the same firm will be nearly enough matched for use in this receiver. All the coils used in this receiver, except the H.F. choke, are plug-in coils, and although it is usually under- stood that a special coil should be used in a Reinartz circuit, the use of plug- in coils has one definiteadvantage that, to my mind, far outweighs any disadvantage they may possibly have. Reaction I have found in the course of ex- periment that the most efficient con- ditions forreceptionusing the Reinartz circuit are obtained when the reaction winding is not only as small as possible, but also as loosely coupled to the grid circuit as possible, while as small a value of capacity as possible is used.I have found that this effect Note that the coils are arranged is very marked, though the values of in such a way as to reduce un- coupling and inductance required do wanted coupling effects. not appear to be very critical. be more than compensated by the resistances have been used intead of By using a plug-in coil for the reac- greater ease in handling that results chokes, and these are connected be- tion coil in the receiver I am describ- from the use of the gang. tween the bottiim of the -grid coils and ing it is possible to try out various The theoretical circuit diagram is L.T'. -, being shown at R4 and R5, sizes of coil in this position, while it 'shown in Fig. 3, and this gives the full while L8 is an H.F. choke which is isasimple mattertoloosenthe details required for wiring the set to used in the plate circuit of the detec- coupling.The actual position of the those who are used to reading dia- tor valve so. that Reinartz reaction coil as I have got it in the set allows 195 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 All Round Europe With Plug -In Coils-continued a small reaction coil to be employed, choice of a gang condenser, andif ebonite split away at all as the drill while little more than a third of the another one is to be used instead of comes through, such damage as is done reaction condenser is usually required the make I have fitted it should be will be at the back of the panel, where to make the detector oscillate. chosen with the greatest care, or else it does not matter.The fixing screws Judging by the results obtained, I the performance of the receiver may for the condensers should be well coun- think the constructor will be well ad- be seriously affected. tersunk,soasnottofoulthe vised to place the coil holder in the vernier dials which have been fitted. same position as I have done. Drilling Having mounted the components on Only four largeholes need to be the panel, this should be fixed to the Components drilled in the panel, these being for baseboard, and the support for the The components required for con- the spindles of the condensers and the gang condenser should be adjusted so structing this receiver are given in the on -off (a drilldoes that it is level.It is important that accompanyingtable. Thoughthe switch fin, this be done at once, as otherwise a names of the manufacturers have been these); the holes for the fixing screws considerable strain may be placed on given, so that those who wish to copy for the condensers and the panel are the panel, causing it to warp and lose the set in its every detail may do so, smallones,and,therefore,area its fiat surface. I would say here that the use of these wimple matter.It is advisable that in After this, mount the other com- definite makes is not essential to the the case of the big holes small drills ponents on the baseboard, and for this functioning of the set, provided always be put through first, to act both as a purpose the back -of -panel wiring dia- that any parts substitutedareof guide to the larger drill and also to gram shown in Fig. 5 should be con- equal quality to those I have used. allow the drilling to be done from the sulted, since not only doesit show Particular care should be taken in the front of the panel.Then should the (Continued on page 199) O C5 0 0 Ol./TIA .0005 Save.", C3 '0005 L.114714; n grarATIL BASEBOARD 2/5( 1.3WA 4/8" 2Aka Cs '002 0000/ems OE a L7 R a V2 & NT EARTH AER/AL Fig. 5.-The layout shown here should be carefully followed. Blueprint No. C1074B 196 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR ' WOW - 0400 Heat Cossor bids film the Destroyer do kis worst new Cossor Point One is working you have WITHIN every valve lurks direct evidence that the harmful effect of the grim spectreof heat. heat has atlast been countered.After 2,000 hours of continuous use the Cossor Sometimesas in the case Kalanised filamentis as supple and as of a bright emitter-he completes pliable as on the day it was first made. his deadly work speedily. The This is equivalent to two years of ordinary frequent stretching and contracting wear and tear. when the currentisturned on. The crystalisation of the metal due Small wonder that tens of thousands of The Valve wireless enthusiastsare turningto this to the filament being incandescent. long -life valve as a means of cutting down These are his two favourite avenues with the the cost of Radio.For the Cossor Point of attack. One in addition to giving an exceptionally Kalenised long service-consumes only one -tenth of But even Dull Emitters are not filament an ampere.Seven of them takeless free from his insidious onslaughts. current than one bright emitter.While TYPES AND PRICES. its electron emission is so intense and the Quite a number work at a com- No.210D. With Black Band. An ideal user obtains such a wonderful wealth of paratively high temperature and super -sensitive Detector. Con- 1 Al_ power and richness of tone that Broadcast- the fragile filaments fall easy victims. sumption.Iamp. at1'8 volts-1--1 ing takes on a new standard of performance. No. 210H. With Red Band.Pre- eminent among H.F. valves. 1 A / There is one valve however, which bids Consumption ' I amp at1'8 voltsA -xi - See your Dealer about these new valves him do his worst.The Cossor with its improve any Kalanised filament.Because not even a The new Cossor Stentor Two without delay-they will No. 215P.With Green Band.For Receiver. suspicion of a glow isvisible when the Power Valve use-ideal for Super Sets. Consumption .15 amp. at 1.818/6 volts Gilbert Ad. 63oo. Issued by .4. C. Cossor Ltd., Higirbury Grove, London, In replying to advertisers, please mention THE WIRELESS CONSTRUt'TOR. 197 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 AISCZAPr4:. 4t.°11140X-ArrcbOsit 1 Panel, 22 by 21 by I., drilled and polished. Built according tothe diagram 1 Baseboard, 24 by 9 by 1, and four supports, supplied these components will 21 by 24 by 1. make a set thatwill bring 1 Set of Four Matched Intermediate Fre- Radio to its peak of power quency Transformers. and performance. 1 OscillatorCoupler,500 - 2,000 metres. Include the Bowyer -Lowe I Base to hold above. Super Heterodyne Kit 2 Square Law Condensers .0005. 2 Vernier Condensers. inyourGiftsthis be): Xmas-it will bring 1 SingleFilament Control >zt..- Yni"G Jack. Tn6 :vow 14/..\ lasting and con- '00.1."VI0Vk ViV-VV.Ve 7 Anti -capacity Valve stantpleasure. SInkl-AVItiicfcrakt. Holders. 4 Supplied in an 2 Brass Brackets. 36 Tinned Copper attractive Soldering Lugs. B o x, 24 Lengths 1/16 Square Tinned0 10. Copper Wire. Fie 4(i THE BOWYER-LOWE THE " POPULAR " RADIO NEWS CONDENSER contains particulars and is an example of Bow- 111111111/ illustrations of all our yer -Lowe precision and trustworthy compo- 00.0. 00 quality. Tested and nents-alsotwo con- guaranteed accurate structional articlesof before dispatch. interest to amateurs. Recommended by fore- THE SUPER A Portable Set and a Pour most experimenters. Valve Receiver are tally illus- Supplied with 3 in. dial trated and described.lid. in .0003 M.P... 10/- HETERODYWE KIT stamps will secure year CODY- .00c5 .. 10/6 Get it now. , . .0. ykyeiro 00 .0. Announcement by the Bowyer -Lowe Co., Ltd., Letchworth, Herts. 1.", 41:40Pr=r9 iiiir/rP01&'4*-41V-Z-? 401: 198 In replying to advertisers, please mention THE WIRELESS CONSTRUCTOR. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR All Round Europe With Plug -In Coils-continued (Conttnued front ixtge 196.) The H.T.-leadisconnectedto and plug the H.T. negative the actual connections of the receiver, L.T. + as marked. A brass strap has wander plug into the H.T. battery, but it is also a scale drawing of the also been fixed over the battery cord, and, joining the two positive plugs baseboard. so that, in the event of an accidental together,insert themfirstinthe Iwouldstronglyurgethecon- pull being given to this, the connec- lowest positivetapping,carefully structor not to depart from the lay- tions to the wiring of the set itself watching the valves the while, so as out used, and this for a number of will not be strained or pulled out of toseethat no variationintheir reasons.The most important of these place.The lead ending in a green brightness occus.Ifthis does not WRUNG IN WORDS. Join Aerial terminal to socket of Ll coil vanes of C5 (gang condenser nearest panel). Join remaining side of CO to socket of L6 holder. Join remaining filament contact of V2 to coil holder and to plug of L7 coil holder. Join Earth terminal to plug of Ll coil holder. remaining side of 112. Join plug of L8 coil holder to one side of Join grid contact of VI to socket of L2 coil Join- remaining filament contact of V3 to fixed condenser CO and leak 116, and to fixed holder and to fixed vanes of Cl variable con- remaining side of 113. vanes of C5 (gang condenser nearest panel). denser. Join anode contact of V1 to moving vanes of Join other side of CO and R6 to grid contact vef Join plug of L2 coil holder to moving vanes C2 and to socket of L3 coil holder. of V3. of Cl, fixed vanes of C2 neutralising con- Join plug of L3 coil holder to remaining side Join anode contact of V3 to one side of denser and one side of resistance R4. of Cs to one side of CO, to plug of L5 coil holder R.F. choke and to fixed vanes of variable Join other side of R4 to one side of resistors and to H.T. + 1 lead of battery cord. condenser C7. R1, R2 and 113, one side of resistance 115, and Join remaining side of R5 to fixed vanes of Join moving vanes of C7 to socket of L7 to L.T. - lead of battery cord. C4 neutralising condenser, to socket of L4 coil holder. Join other side of its to one filament con- coil holder, and to moving vanes of C3 (gang Join other side of R.F. choke to one telephone tact of VI. condenser remote from panel). terminal. Join remaining filament contact of V1 tq Join plug. of .1.4 coil holder to grid contact Join other telephone terminal to H.T. + 2 screen of gang condenser C3 05, to one side Of of V2 and to fixed vanes of C3. lead of battery cord. fixed condenser C8 to one filament contact of Join moving vanes of C4 to anode contact Join remaining aide of switch S to L.T. + and V2 and V3, to one side of switch Sand to fixed of V2 and to socket of L5. R.T. - leads ofbattery,cord. is that the positions of the coils have wanderplug isthe H.T.+ for the happen, try a higher value, and, if all allbeen carefullychosen soasto H.F. valves; and the red one is for is well, the set may be connected to the reduce any stray coupling to a mini- the detector, the black one being the aerial. H.T.-. mum, and the two coils that are to Coil Sizes to be seen on the back edge of the Testing baseboardareplacedfurther away It is now necessary to plug in the from the detector circuit than from Now test out the L.T. and H.T. cir- correct coils, and the following are the the H.F. circuit.This has been done cuits.For this plug any .assortment sizes I have found most suitable :-L, owing to the fact that reaction is used of coils into the various holders, and and L, will be 35 and 50 respectively, in the detector circuits. insert three valves into the holders, or a Gambrell A and B, while for wave- the correct resistances being used in lengths above about 400 metres a larger Wiring conjunction with them and the parti- coilmay beusedintheaerial, cular L.T. battery that is being used, such as. a 40, or even a 50 on some Before commencing the wiring, the Next connect the L.T. leads to the aerials, or a Gambrell B1 or B. Be - two terminalstrips foraerial, earth and 'phones should be made and fixed into position, and then the low-ten- sion side of the wiring shouldfirst be completed, while a hole should be drilled in the panel to let the 'phone cords come through.Next put in the H.T. leads, which may, as far as is convenient, be bunched with the L.T. leads, and complete the rest of the connections afterwards. If there is any doubtastothepolarityofthe plug-in coils to be used, especially in the case where an assortment of coils is on hand, it would be as well to arrange the wiring so that leads may easily be reversed till the correct con- nections have been found. This is most simply done by connecting the coilholderswithshortlengths of flex; when the best way of connecting the coils has been found the permanent leads may be put in. Battery Connections In connecting the battery cords to the set, I have cut off the spade tags at the set end, and soldered the leads This view of the set should be studied in conjunction with the wiring directtofourwireswhichhave diagram and instructions. been fixed under a small brass strap; battery, and, pulling out the switch, low 300 metres, a smaller aerial coil this will clearly be seen in Fig.5. see that all three valves light up cor- will be found an advantage, and I have Thisisa convenient arrangement, rectly.Also, remove the three re- used a 20 or 25 (or a Gambrell " a ") since it enables the wiring up of the sistorsoneatatime, argil see with better results than those given by set to be completed first, and the bat- thatthecorrespondingvalvesgo the larger coil. tery cords to be connected afterwards. out. Now connectthe'phones, L3 and L4 will be both 50's (or two 199 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 19.27 All Round Europe With Plug -In Coils-continued Gambrell B!s), while L, L and L, was impossible to use the receiver for need to be reversed.If, however, an should be 50, 50, and 20 or 25 respec- long -wave reception.As itis,itis increase in signal strength is obtained tively (B, B, and " a " in the Gam- perfectly stable on both long and short without theset oscillating, even at brell range). waves and forms anidealreceiver the highest reading of the reaction con- L, and L2shouldbeasnearly since both can be received with equal denser, a larger reaction coil should be matched as possible,since these are efficiency. tried. the two coils which are tuned by the The coils used are aerial 150 and L2 gangcondenser,andvariouscoils 250, and 200 and 250 for L L, and Neutralisation should be tried till a well -matched pair 114, .L. respectively, . while a 100 will I have found that the circuit em- is found. How this is to be done will do for reaction. The actual coils I em- ployed results in far less capacity than be described later in the article. ployed were Glambrell's, and these were isusual being requiredto stabilise If greater selectivity is required the D and F for aerial and L2, E and' F the set, and, with the two neutralising TEST REPORT. The dial readings forstations received with the set aro given in the following table.These readings were takenafter the new wavelength scheme had come into. operation. Dial Wave Dial Wave Dial Wave Setting. Station. Length. Setting. Station. Length. Setting. Station. Length. 11.5...Karlskrona 190 42.5...Bournemouth.306.1 65.5...H a mburg 428.6 13.5...Kristinehamn 202.7 43 ...Newcastle .312.5 73:..Elberfeld 468.8 23...Karlstadt 221 44.5...Dublin 319.1 74...Lyons... 476.2 25 229 46...Belfast ...326.1 75.5...Berlin 483.9 27.5...Koenigsberg 24-L9 48.5, ..Petit Pa risien . 340.9 77 ...Birmingham 491.8 52 30...Gleiwitz 250 ...Cardiff .353 79...Zurich? 500 52.5...Leipzig 357.1 30.5...Stettin 252.1 81.5 r usSels 508.5 361.4 31...Kiel 254.2 53 ...London . ....Resenhitgel 517.2 56.6... Stuttgart 379.7 32.,.Malmii 260.9 . 57.5...Manchester. 384.6 33.5... Antwerp 265.5 58.5...Toulouse 389.6 12...Hilversum 1050 38 ...Dortmund 283 . 39...Berlin 1300 59.5...Frankfort 394.7 40...Dresden 294.1 60.5...Glasgow ...405.4 40 ...Daventry 1600 42 ...Munster 303 64.5... Rome...... 422.6 47...Radio -Paris 1750 size of the aerial coil and the primary for 11, and L and E, F and D for L,, condensers set at zero, with some makes coils L, and 11, may be reduced.This L2 and L,.This covered a range of of valve the set is perfectly stable over effectively loosens the coupling between about 1,000 to 3,000 metres, and the the whole range.Ifthereis any the various circuits and 'gives the re- readings given in the table of stations doubt, however, the set may be neu- quired added sharpness of tuning. received wereobtained withthese tralised in the usual manner by turning coils. out the valve and -rotating the neu- Long Wave Coils tralising condenserstillapointis On the long waves the following coils Sharp Tuning found at which the signaliseither were_ used and the results given will If you are at any distance from the entirely eliminated or reduced toa guide the listener in searching for the local station, it may take a little find- minimum; this may, of course, occur various stations.There was no need ing, since the tuning on thisset is at the lowest settings of the neutral- ising condenser. * Distant Stations Amplifiersa n d Both valves are dealt with in this loud -speakers are manner in turn, an& a distant station used for many may now be searched for.In view of purposesbesides the fact that the gang condenser is wirelessenter- probably not balanced up correctly for tainment.A ta use with your particular coils, it may demonstration of be necessary to increase reaction till tanks before thereceiverisoscillatinggently. the Dominion Having picked up a good strong car- Premiersthe rier,resolve it by reducing reaction orders givent o and returning as may be necessary till the tanks were the transmission is heard clearly with- made audibleto out distortion,retune on the aerial the spectators by condenser, and bring the station in as means of 1 o u d - loudly as possible.Now loosen the speakers. grub screw which locks the back con- denser on to the operating arm, and *** insert a tummy bar into the adjusting disc(whichisprovided with holes to readjust the gang condenser, since rather sharp.Once it has been found, drilled round itsperiphery for this the tuning was fiat enough to allow the effect of reaction should 'be tried. purpose), and rotate the two halves any slight difference to be neglected. If. Wcreasingthevalueof the of the gang condenser independently Theuseofresistancesinsteadof reactiOn condenser does not produce till the greatest signal strength is ob- chokes at R, and 12.3 was absolutely any increase in signal strength, the tained from the station heard. necessary, forif chokes were used it connections to the reaction coil L, may This adjustment should preferably 200 (Continued on page 287). PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR ,1i E. oci.n. ra l i/Age.0 SSE MEikir,,,, p IT is always rather a trying time order to discover what is inside them; if you are to believe their statements, for fathers of families, like you no onetoreplacethesaidcaps they are fed,despite the vastbills and me (if by any chance you are omittingthediaphragms-ifthis that you receive, on nothing but stale not a father of a family you are at ever happens to you, as it once did bread,rancidmargarine,defunct any rate a son-or possibly a daugh- to me, I'll wager that you will spend horses, dish water and rice _pudding. ter-and therefore know what fathers more than an hour or two in tracing havetoput up with),whenthe that fault.There is no one to bor- youngreturnfromschoolforthe row our gridbatteriesfordriving Mr. Gumpletherpe Differs Christmas holidays.The period from electric motors; no one to play havoc Mr. Gumplethorpe was quitean- themiddleofSeptembertothe in our workshops or to deplete our noyed with me when I talked to him middle of Decemberis one of the stocks of screws, nuts,studs,plugs, in thisstrain at the beginning of happiest ofthe glad wirelessyear. pins and washers. December. Hesaidthatitwas The new autumn set has been brought wrong to take such an attitude. If intocommission and as the nights my boys did thingslikethat they grow steadily longer and longer our The Awakening must have been very badly brought prospects become brighter and Yes,life during that periodisa up.His, he assured me, were always brighter. beautiful dream, almost too good to perfectlittleangels, anditwas a be true.We feelall along that we sheer pleasure to have them about shall wake up soon, and sure enou h when he was engaged in either the A Beautiful Dream we do one day in December, when t constructionor the operation of a With the lads safely away at school houseissuddenlyfilledwitht e wireless receiving set. I could not lifeis really worth living, for there strangenoisesthatannouncethe help remembering as he spoke how in isno one to laugh at us when we return of the young to the bosom of the past lie had come almost weeping accidentally touch H.T. - and extra family.Glad though we are to to my study forconsolation when H.T. + at one and the same time; see them again, we realise that the Horace and young Ben had immersed thereisno one to guffaw when we best days for wireless are over for his superheterodyne inthe bath in speak ofthecracklingnoisesthat another nine months, for by the time order, as they said, to see if it would come from the loud -speaker as atmos- that they haveleftusagainthe work under water, or when they had pherics; no one to giggle when the nightswillbe growing shorter and half-filled his accumulator with wash- blob of solder that we have been care- the horrible summer seasonwillbe ing soda in order to give to a, young fully conveying towards an intended slowlybut surely beginning to draw friend apractical demonstrationof joint fallsoff on to our left thumb; on; we most look forward to results whattheyhadbeenlearningat thatgrow slowly less and less school about the chemical action of wonderful. acids and alkalis. However, I said A Seasonable Design The wise man spends some of his spare time just before the holidays begininconstructingacompletely boy -proof receiver, housed in a locked steel cabinet, which will bring in the local station and nothing else, which 1 cannot be made to howl, becauseit has no knobs to twiddle, which can- not be picked up and dropped, be- .... a blob of solder .... cause it is screwed to the table, which falls on to our left thumb. cannot be short-circuited, because the .... a completely boy -proof receiver. batteries and all the leads are inside thelockedcase,which cannot be no one to point with a smirk to the " improved "by. young enthusiasts, nothing, forit was quite delightful dangling earth lead when we have because its interior is completely. in- to meet a, soul like Mr. Gumplethorpe, spent a couple of lurid hours in a accessible. Another fairly successful Who could be cheerful even in the fruitless search for the cause of " no courseis to buy half a ton of the face of approaching adversity. signals "; no one to borrow our best assorted wireless scrap advertised by two -voltdull -emitters,and'torun disposalsfirmsandtoturnthem them, resistor -less and bright, from a loose on this. With any luck they The Invitation six -volt accumulator; no one to con- will be so busy sorting it out first of It was shortly after the return of duct in our absence experiments with alland thenin constructing things our families that, meeting me in the our high-tension battery to see how that they will not be ready to howl street one day, he told mo that he and big a spark it will give; no one to until it is time for -them to go back his wife were arranging a Christmas unscrew the caps of our telephones in to the seminary of learning, where, party for some forty or fifty youngsters 201 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 Mr. Gumplethorpe's Christmas Party-continued and begged me to come in and give Gumplethorpe cheerily. " Never mind, Hamburg gave us the same tune as him a hand." Of course," he said, " I I will put it right in a minute, and London had started with, and followed am going to give them a wireless show; then you will hear what wireless really this up with the same foxtrot (" Von there's nothing they like better than should sound like.I want you all to dem Wursthaus ").Madrid, when we that.Both Horace and Ben aro jolly tell your fathers when you go home got there, had alsoa woman an- helpful, I can tell you. They have nouncer, who told us that we would joined the wirelessclubwhichwas now,,have uno foxtrot°.It was fol- started at their school last term, and lowed by the ancient dance with which They know quite a lot about it now. London and Hamburg hadstarted. I get them to do all sorts of odd jobs " Splendid° dansoper loskiddos," for me.In fact I have hardly been said the announcer. inside my workshop since they came home."" And if I were you," I re- A Discovery marked, " and wished -to preserve my " Horace! Ben! " called Mr. presentcheerful frame ofmind,I Gumplethorpe, looking worried." I would refrain from going inside it.It wonder where those boys are.I wish was only yesterday that Horace and .... had immersed his they'd come and give me a hand." Ben were telling me what a job they'd superheterodyne in the bath .... " I'll go and look for them," I called, had to make a hole through a brick making for the doer.I went quietly wall _withyourthree -eighthsinch what wonderful reproduction of music Upstairs to their room and peeped in. drill."Mr. Gumplethorpe turned a you have heard." He switched off, Ben was sitting holding to his ear littlepalefor a moment, but fiddled about with things, and then a. piece of rubber tubing which pro- brightened up at once when he remem- switched on again.There was a brief truded from the wall-I realised then bered (as I had forgotten), that he had silence, which was rudely torn by the the reason for the hole that had been borrowed that drill from me the pre- strains of what sounded like the world's made with my drill. Horace, as I vious week.Feeling that I should cer- worst gramophone with a sore throat. entered, was speaking with his lips tainly be needed to help at the party, It was braying out some antediluvian close to a microphone button-I had I agreed to go and to do my best. dance tune.When this came to an given him one for a Christmas pre- end a shrill and rather queer voice sent.On the table beside him was an The Pike de Resistance told us that we had justheard the antediluviangramophoneandtwo The first couple of hours of the party Savoy Havana Band, and that we were records. " Broadcastinga statione di passedoffwithoutahitch. Mrs. now to have a foxtrot from the Troca- Roma," I heard as I came in. " Habe- Gumplethorpe had provided an ample dero." I did not know that they had bimus nuoc unam. foxtrotam.Spag- tee, and so heartily did the youngsters lady announcers at 2L0," Isaid to hetti,vermicelli,andante ma non slipintoit that they seemed quite Mr. Grumplethorpe. " Everything troppo." He turned on the gramo- quiet and drowsy for some little time seems to have gone mad to -night,' phone, looked round and saw me. wailed he. after.They were just beginning to What onearth . . . ? "I recover their animal spirits (and prob- Round Europe began.Horace placed his fingers to ably to think about supper) when Mr. his lips and pointed to a large notice- Gumplethorpe announced that he would As the foxtrot was even worse than SILENSE. When the foxtrot had now let them hear some wireless.A the previous piece, Mr. Guniplethorpe come to an end he moved the switch screen in a corner of the room was decidedthathewouldnowleave and came towards me." Isn't it top- removed, and behind it was disclosed Londonalone - " something wrong ping? " he inquired." We were sure his latest set, surmounted by a giant with their transmitter, of course "- that dad would have a breakdown, so loud -speaker.I looked for both Horace and go over to Hamburg.With the we arranged to see him through.It and Ben, wanting them to give me a took us quite a long time to rig it all hand in moving the screen, but they up."" I expect,'I said, " that it appeared to have vanished. I pre- wilt take your father quite a long time sumed that Mr. Gumplethorpe had to liveitall down. Mea,ptime,I sent them on some useful errand, and rather think that he wants you, and thought no more about it. pirhaps you would not mind telling him that I have just heard that I am Dance Music ? urgently required at home." " First of all," said Mr. Gumple- thorpe, " we will havesomedance music froth 2L0.Now, boys, choose your partners! " With -a beaming Horace pointed to a large notice. A SELECTIVE ONE -COIL smile he switched on.From the spout of the loud -speaker there issued the aid of a wavemeter he tuned in. As SINGLE -VALVE SET. most appalling din that I have ever before, there was a moment of silence heard.It was as if plates were being to begin with, though Mr. Gumple- smashedby the hundred,tea-trays thorpe was quite sure that his wave- E regret that in the description banged with hammers, cannon crackers length was right.Then a voice, amaz- ofthe aboveset,whichap- explodedandgigantic sheetsof inVylikethat of2LO's lady an- peared in the November, 1926, issue American cloth slowly ripped from end nouncer, saidasGuten Abend, every- Of. THE WIRELESS CONSTRUCTOR, the to end. Bewildered, Mr. Gumplethorpe body. Wie geht es Ihren? Haben Sie circuit diagram (Fig. 2 on page 33) stood stock still for a minute or so, meinen Pfeder gesehen?.Nein, aber was incorrectly shown.The variable not knowing what to do. ich habe die Tinte gesehen," or some- condenser C shown connected across thing like that.The lady announcer the top half of the coil L, in Fig. 2. Quality ? appearedtohaveratheraqueer should be connected across the lower He was just going across to the set German accent, but I supposed that half of this coil.The -wiring diagram when the din suddenly ceased. " Some she was a little nervous about her new. of the set (Fig., 4) is correct in, this little thing gone wrong," said Mr. job.Another curious thing was that respect. 202 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR VICO toW1111V444 4444 MLR 2411fre AN ENTIRELY NEW type of Dull Emitter Power Valve combining outstanding per- formance with economy in operation. The D.E.P. 215 is for use in the last stages of Receivers or Amplifiers operating from a two -volt accumulator. It embodies just those characteristics which combine to make the ideal power valves :- MAJESTIC VOLUME, CRYSTAL-CLEAR TONE, PRICE LONG LIFE and VERY LOW CURRENT CONSUMPTION. The filament is exceptionally robust and rigid, and has a large emission surface. Type D.E.P. 215 used with the correct H.T. and grid bias voltage recommended in the accompanying table Write forMarconi will handle great volume with a purity of reproduction Valve Literature- hitherto unobtainable. containing detailed Filament. Grid High Low particulars of the Marconi Posi- Bias Tension. Tension Valve Type tion Volta M Battery D.E.P. 215 and other VoltsAmps types. Volts.AmpsSupply. Two -ValveD.E.2 H.F.Det. 1.8 0.12+2 60 1.6 ,-.1 Set D.E.P.215L.F. 1.8 0.15-9 120 4.6 g Three- D.E.2 H.F.Det. 1.8 0.12+2 60 1.0 g MARCONI POWER VALVE Valve D.E.P. 215I L.F. 1.8 0.15-3 60 2.5 - Set D.E.P.2152 L.F. 1.8 0.15-9 120 4.6 TYPE D.E.P. 215 ' Four- D.E.2 H.F.H.F. 1.8 0.12 0 60 0.8 i for 2 -volt Accumulators. Valve D.E.2 H.F.Det. 1.8 0.12+2 60 1.0 - Set D.E.P 215 I L.F. 1.8 0.15-4.5 80 3.3 78, Fil. volts D.E.P. 2152 L.F. 1.8 0.15-9 120 4.6 Fil. current... o15 amps. Anode volts...... 120 max. Marconi Type D.E.R. or other 2 -volt valves are Amplification factor ... 6.25 also suitable for the high frequency detector or Impedance ...... 625o ohms first low frequency stages. THE MARCONIPHONE COMPANY, LTD. Regd. Office :- Head Office: - Marconi House, Strand, London, W.C.2. 210 -212, Tottenham Court Road, London, W.I. Till HOWES? RADIO TRIUMPH In replying to advertisers, please mention THE WIRELESS CONSTRUCTOR.: 203 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 The B.B.C. listen to their own programmes thro Phones FITMENTS THE PRICE IS SO SMALL ! CLIX WANDER PLUGSwith patented helical spring plug ensuring perfect contact for all types of H.T. 2D. Batteries.Red or Black insulator. gq= CLIX PIN TERM INALS-a most convenient tag forgeneral use, supplied 2D. with red or black insulator. CLIX PARALLEL PLUGS with resilient fitting having extraordinary ralialexpansionand compression. Red or black insulator. PLUGS 2d. SOCKETS id. CLIX SPADE TERMINALS, especially suitable for making con- nections where terminals are already NO one must be more critical in fitted. Prevent twistingor break- 2D. ing of wire. Red or black insulator. listening than the control en- gineer. Ericsson (British) 'Phones are ALL THE ABOVE ARE FITTED WITH THE PATENTED BRIDGE WIRING CHANNELS. used throughout the B.B.C.'s studios. Small wonder too!Designed by acoustical experts, they to day are supreme for their tone apart from their astonishing sensitivity. Listeners tellus, " They sing where other makes are dumb."Their sensitivity on DX CLIX (Taper) PLUG SOCKETS and short-wave work is something wonderful. From a Radio Engineer:- with As a practical man let me congratulate you on your tele- phones.I was not surprised to notice them in use at the INSULATOR (Taper) ADAPTER local B.B.C. station." Three resistances, 120, 2000, 4000 ohms, one price. PLUG 9D. SOCKETS each. TAPER RPTERS 1/2 De;each. At all good dealers.Write to -day for fully INSULATORS 1 D. illustrated lists- /2 each. ERICSSON TELEPHONES Ltd., BLSHES, in six I/ D. 67.73, Kingsway, London, W.C.2. colours 72 pair. Obtainable from your wireless dealer. ERICSSON AUTOVEYORS LIMITED mom= 411°;SUPER. SENSITIVE 84, VICTORIA 'STREET, WESTMINSTER, S.W.T. TELEPHONES 'Phone: Victoria 309.Telegrams: "A tit °vow, Sows!, London." 14 -01A 204 In replying to advertisers, please mention THE WIRELESS CONSTRUCTOR. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR Egio&E8,6g)EnEmaaEmocgowgoo matic repeater of 2LO's programmes, those componentsthatwerereally on a wavelength which has very few worthy of the name? WHAT IS DAVENTRY advantages and many " snags."Per- Yours faithfully, a haps if the B.B.C. realised how many HOWARD CHILTON. DOING ? of us are turning to the foreign sta- Addiscombe, Surrey. E?? tions for amusement they would take cm*g343,83c5m9eggl3t3*4913g some active steps in the matter. EM'EgC85@0EgeEgEffiCt@aCi?) SIR,-I am afraid that I may be Yours truly, DOUBTFUL accused of regarding wireless periodi- J. L. CowLiwo. cals, as mediums forcomplaints of Dorchester, Dorset. IMPROVEMENTS every description, but I feel sure that e894944?)143do, qw3G,I)? I shall not be thought selfish if I voice fgEgegigVeXtes.E8vgtMWISREP SIR,-I read Mr. C. P. Allinson's my grievance in connection with the 0- 0) admirable article on " Gearing as an Daventry station. LOUD -SPEAKER TONE @ Aid to Wireless " with much interest, 0 0, CONTROL g but Icannotrefrainfrom asking ag a 43egmYs** *43343.:43pes,83f90 SIR,-With regard to the letter from Mr. M.K. O'Dwyer' pubishedin November issue, under the heading of " A Loud -Speaker Hint," I really do not see how any advantage can be gained by shunting the last L.F. transformer primary instead of the laud -speaker itself.My own experience is that a condenser of about .001 across the last L.F. transformer has just the same effect as one of .003 or so across the loud -speaker itself.Similarly, if more than one note -magnifier is used, about .0005 across the first primary should put things right.It is all a question of choosing the right capacity. Yours faithfully, M. J. LoVATT. Folkestone. irgE8efig5@cffiegEggge, ctcg % The Earl of Clarendon4left) arriving in England afterhisvisittoCanada. IS "LOW -LOSS" Mr. Eric Dunstan, well known as an Lord Clarendon isto take over the announcer at 2L0, has been appointed duties of head of the new B.B.C. next .OVERDONE? General Manager of the Indian Broad- January. casting Company. 4?9930q43613d43Gcg3013(8914:1943' whether it is really as necessary as we Why is 5XX, with its 25 kilowatts, Sra,-Although I should not think seem to think nowadays.When one relegated by the I3.B.C. to the posi- of belittling the numerous improved really thinks things over, did we not tion of a mere relay station? Here in makesofcomponents now on the do just as well and derive just as much the 'south-west of England it is safe British market, is there not a danger enjoyment from radio with the old tosaythatallownersofvalve - that we are carrying the " low -loss " ebonite -end" high -loss "condensers, receivers, if they want a good alterna- idea too far? When it was the special and even those made at home from tive programme, turn, not to Daven- privilege of a fewofthe highest - sets of plates?Does one obtain any try (from which it is never forthcom- qualitycomponents tobe stamped stronger signals nowadays, and is the ing) but to Hamburg and other Ger- low -loss,"thiscoinedwordpos- process of tuning -in very much easier? man. stations, which are more easily sessed a meaning. Now, however, any I shall always keep pleasant memories received than any of the B.B.C. sta- new components that are produced are of my first three -valve set, with seven tions except the local (6BM), and also almost automatically branded as " low - controls on thepanel,all equipped send out really enjoyable programmes. loss."Surely, in comparison with the with brass pointers and ivorine scales Daventry was, I thought at first, to very best of each type, many of them What do other readers really think be a station which would show the rest must be seriously inefficient I Isit about this? of Europe " how it should be done." not time that we started again, and Yours faithfully, Instead, it is little more than an auto- applied terms like " low -loss' only to Bedford. ' JOHN H. Huai. 205 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor " THE WIRELESS CONSTRUCTOR January, 1927 Evolved to meet the new conditions of Radio THE new OldhamO.V.D.cannotbe compared with any other accumulator. It is unique.It has beers specially evolved to meet the new conditions created by the growing popularity of dullemittervalves. The O.V.D. is the first slow discharge accumu- lator which can be charged rapidly.The idea of a slow discharge accumulatorisnot new. They have been on the market for years. But- owing to the thickness of their plates-the greatest possible care has been necessaryto ensure the full charge being given.Common sense will prove why this is so. The ordinary slow discharge accumulator holdsits charge because it has two thick plates-negative and positive.But because its plates are so thick it takes many hours for the electrolytic action to penetrate its inmost recesses.And long slow charging is a nuisance. Oldham saw the disadvantages of the thick plate and has evolved the new laminode plate possessing all the advantages of thickness but none of its disadvan- tages.The Laminode plate fitted to the O.V.D. is three plates in one.It uses a girder -like construction which prevents buckling.And yet because of its greater surface area it can be charged within 8 hours. Any Oldham O.V.D. will hold its charge for weeks- even months-without attention.Local action has been practically eliminated. FACTS FOR VALVE USERS. If you haveaone -valveSet an O.V.D. will last you 180 hours at a charge if you use the new valves taking I amp.With a two -valve Set you will get72hours use.If you use 06 valves you will require two 0 V.D cells in series.Under these conditions the two -valveSetuser will get140houtS and with three valves 80 hours. TheO.V.D.is thusthemosteconomical accumulator you can buy for dull emitter use. Special Activation Process Batteries Thenew 3ILD O.V.D. the slowdischargeAccumulator which can be fully charged in 8 hours OLDHAM & SON, LTD. Made by the Makers of the : Denton, Manchester OldhamH.T.Accumulator : London Office & Service Depot : 60 volts £2 100 80 volts £3 6 8 : 5/6 : 6, Eccleston Place, S.W.1. (Charged ready for use 100 volts £4 3 4 120 volts £5 0 0 Phone:Sloane2701 : -merely add acid) Solidoak base3/6 extra if required. Gilbert Ad. 6328. 206 In replying to advertisers, please mentionTHE WIRELESS CONSTRUCTOR. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR .- MAKING USE OF YOUR SUPPLY MAINS (Continued) By J. H. REYNER, B.Sc. (Hons.), A.M.I.E.E. Charging Accumulators from A.C. Mains-Rectification Methods--High-Tension Direct from the Mains -Smoothing CircuitsA.C. Systems for Direct Supply. T N the last issue of THE WIRELESS good hard service.A particular ex- having to insert'series resistances such CONSTRUCTOR some of the methods ample of this type of instrument ?as as lamps, or suitable resistors,itis available for charging accumula- been running at Elstree for some two possible by using a transformer to step tors from D.C. mains were discussed, months, practically day and night, and down the voltage to a suitable value. both high-tension and low-tension bat- has given very little trouble. One oftheadvantagesofalter- teries beingconsidered, andit was nating currentisthat itis possible shown thatthe requisiteapparatus Chemical Rectifiers by utilising a transformer, similar in need not be by any means compli- Another method ofrectifyingthe generaloconstructionto the ordinary cated. low -frequency transformer usedin a current is to use some form of chemi- wireless receiver, to vary the voltage The Problem with A.C. cal rectifier.Certain metals when in- serted in a chemical solution possess of the supply. We can put in a volt- In the case of charging accumulators the property of passing current better age of 220 volts on one side, and take from A.C. mains,the problem isa in one direction than in the other, out a voltage.of 6 or 8 on the other little more difficult.It will be obvious and, in fact, almost completely sup- side without any difficulty.Moreover, that'siniply connecting the A.C. mains pressing the reverse current so that if on the 6 -volt side we take a current across the accumulator ina similar of 4 amperes, then on the200 -volt again the necessary rectification effect side we should only take a Current manner to that adopted with direct isobtained.Several such 'rectifiers current would not be of any use what- will no doubt be known to readers. of between one -tenth and one -fifth of ever,becausethecurrentfirstis an ampere, depending upon the effi- flowinginonedirectionand then ciency of the transformer, so that we in the other, and the effect on the Valves actually consume very much less cur- accumulator would be to charge it and Another method is by development rent in charging than is the case with then to discharge it immediately after- of the thermionic valve principle,in D.C.In the direct -current charging wards, so that the overall result would which an ordinary two -electrode valve we have to waste energy by passing it be nil. is made with a very large filament through a resistance, whereas in the, Rectifying It is therefore necessarytoadopt some .form of rectifier in order to ob- tain the necessary charging effect.By ** * this means we arrange to cut out the currentinonedirection,and only Modifications leave the current in the other direc- have recently been tion.If then we connect the battery made in the 2L0 up in such a way that the current that aerial,tocure does flow is -in the direction necessary certain "blind to charge it up, then we shall obtain spots " within its a continual charging effect, since the range of service. current which would tend to discharge This novel view is the battery has been eliminated. takenfromthe base of one of the Vibrating Reed masts. These rectifiers may takevarious forms.They may be of the vibrating reed type, in which a form of buzzer *** is employed, which is made to vibrate backwards and forwards at the same frequency as that of the supply. By carefuldesign the device can beso arranged thatit only completes the capable ofpassing severalamperes. case of A.C. the energy wasted is very circuit through the battery when the The well-known Tungar Rectifieris much less. current is in the right direction, and an excellent example of this system. during the other " half -cycle,"asit Generators and Converters is called, when the current isin the Advantages of A.C. Another method of charging accumu- opposite direction, the circuit is suit- We have therefore considerably more latorsfromthealternating -current ably broken. trouble when charging with A.C. than mainsis by theuse ofamotor - Such devices are somewhat difficult D.C. owing to the necessity for pro- generator or rotary converter.These to design, and unless careis taken vision of this rectifying arrangement. are instruments in which the alter- they arenot altogether satisfactory. Thereis,however,oneadvantage nating currentismade todrive a Thereare, however, models onthe which offsets this to a large extent, smallmotor. This motoristhen market which are capable of givingand that is the fact that instead of coupled to a generator which supplies 207 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 Making Use of Your Supply Mains-continued direct current at the required voltage. from the mains. We have here the Various modifications of this principle difficulty that any fluctuation what- Remedies are often employed.For example, the ever in the high-tension voltage will Now there are two ways of over- motor may be madetodrivethe cause a hum to be set up in the comingthistrouble.Inthefirst rotatingrectifier,which is supplied - receiverwhichisconnected to the place we can connect a large con- withalternating current through a H.T.unit.Obviouslyifwe are denser across the positive and nega- transformer arrangement, so that the utilising alternatingcurrent for tiveleads coming from the mains necessary .rectification effect is power supply we have a very large unit to the receiver.If we have a fluctuation. What happens is that bucket with a hole in the side, and we rectify the current so that only we fillit with water above the level one half of the wave is utilised, soof the hole, then we shall obtain a that we are really obtaining a series jet of water coming from the hole, of pulses of current all in the same due to the, pressure of water above. * direction, but not by any means of Now we canfillthis bucket with a * * steady value. jug periodically, and provided we keep A typical rectify- the level of the water above the level ing valve, as used A.C. Hum of the hole from which the jet is com- for A.C. rectifica- ing, we shall obtain a more orless tion. If we applied this raw A.C., as it steady stream of water. isoften called,to the receiver, we In a similar manner we can con- should obtain a powerful hum which nect an electrical bucket or condenser would completely drown any signals across the leads from' the H.T. unit. which would otherwise bereceived. We draw off from this condenser a Even on the local station the hum supply at a certain voltage. We feed would completely swamp any signals, into the condenser pulses of current and arrangements must therefore be every so often which may be likened made to eliminate the effect of this to the filling up of the bucket with obtained by a rotating device.There water from a jug.In this way we arequiteanumberofdifferent shall obtain a fairly steady supply on charging plants which partake in vary- -1046640 the output side, so that the condenser ing degrees in one or other or both /00 HENRIES thus tends to reduce the effect of the of these principles. 2-4 2-4 pulses. Afro. How it Applies Valve Rectification T Referring backtoourbucket Charging H.T.accumulators from Fig. 1.-A suitable smoothing circuit analogy, it will be obvious that if the A.C. mains can be effected in a similar for eliminating current fluctuations. manner.All that is necessary in this level of the water is only just a little case is that the transformer ratio shall higher than the level of the hole, then be so chosen that the voltage applied variationofvoltagetosuch an the actual force at which the jet will extent that itispossible to receive emerge from the hole will vary con- across the H.T. accumulator is satis- signals from, distant stations. tinually.When we have just put a factory.In this case an exactly simi- fresh jugful in, the water will come lar arrangement for charging can be D.C. Ripple up fast, and as the water runs away adopted, but, as in the case of D.O., so the pressure will gradually fall off thenecessarycurrent is very much In the case of direct -current supply, and the jet will come out with less smaller.Since the charging current is we have not the same fluctuation, but force. The extent of this variation only of the order of 50 milliamps, it can thereisnevertheless a small varia- depends upon the relativeratesof be handled by a fairly small two -elec- tion due to what is usually known as the flow of water from the jet, and trode valve. The ordinary types of " commutator' ripple." Direct cur- valves on the market do not pass suffi- rentissupplied bya machinein cient current, but there are now quite which the currentis collected from a number of special rectifying valves segments of a large rotating switch from which a selection can be made. known as a commutator, the purpose In some cases where suitable circuits of which is to ensure that the voltage are used, it is possible to dispense with shall always be in the same direction a transformer altogether, although a andapproximatelyatthesame rectifier is still necessary.This is only strength at the moment when itis advisable, however, where the voltage collected by the brushes. There is, of the accumulator to be charged is however, a very smallvariationas Fig. 2.-The required H.T. voltage may somewherenear, although naturally the brushes pass from one segment of be tapped off in the manner shown. lower than, that of the mains. the commutator to the next, and this The roblem of supplying low-ten- produceswhatisknownascom- the filling up of the bucket by means sion and high-tension current direct mutator ripple. of the jug.In other words, in the from the mains is much more difficult There are also other slight fluctua- high-tension unit it depends upon the because arrangements have to be made tionsknown as" toothripples " demand made upon the unit in high- so that no e3leterious effects such as which are produced by a peculiar for- tension current and the actual feed hum cother noise shall be noticed in mationofthearmaturesofthe current from the rectifiers. the wi ?less receiver,and consider- generators, all of which have a very It will be obvious that if we have able trouble has to be taken in order small but perceptible effect. We can- a large condenser we have a greater to overcome this tendency. not therefore apply these voltages to reservoir- action thanif we have a our receiver, or we shall again have small one. We can take a given cur- a hum, this time not so powerful as rent out of a large condenser without Direct H.T. Supply in the case of raw A.C., but neverthe- producing suchaseriousdropin We now come to the question of less sufficient to introduce unpleasant voltage as would be the case with a supplying high-tension voltage direct disturbances. (Continued on page 2111.) '108 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR Refinement It is the small defect that often mars your radioreproduction. Not enoughpressureonthe anode, or perhaps too heavy a Time Tells grid bias will completely spoil an evening'sprogramme. Check USE " HART "Wireless theselittleinaccuracieswith a reliable HighResistance Accumulators in prefer- measuring instrument-in other words check them with a Weston ence to dry batteries-always. Voltmeter. Weston Model 506 PinJack You will quickly note the Voltmeter is designed specially and thelonger tomeasureaccuratelyboth difference, filament and plate voltage.It is you use them the greater anotherofthe wide range of Westonproductswhichare will be your appreciation of recognised as standard through- out the world, and it reveals the their undoubted merits. same excellence of design and workmanship for which the name There are models for all low Weston has been famous since and high tensionwireless 1888. Either this Model, or for those circuits. who prefer it, the Weston Panel mountingVoltmeterwilldo much to ensure that perfection of reproductionwhich isonly possible when a careful adjust- ment is made of the filament and anode voltage. Refinement in such details leads torefinementinresults,and THE BATTERY OF QUALITY economy in operation - which in turn means extra life to your Valves and Batteries. " RAY " HIGH TENSION ACCUMULATORS 20 VOLT -14/8 ;30 VOLT --221-. WESTON Pin Jack Voltmeter "ENDURO" low tension ACCUMULATORS Price complete with testing cables 2 VOLT, 10 AMPERE HOURS ACTUAL -6/ - 2: 10 : 0 Write to -day to Dept. W.C.5, for full details of all " HA RT" models and booklet, " The Right Way to Use your Wireless Batteries," Post Free. WESTON STANDARD THE WORLD OVER 4ART ACCUMULATOR CPU' Pioneers since 1888 ARSHGATE LANE. STRATFORD. LONDON. E. 15 Weston Electrical Instrument Co. Ltd. TehplrowA Melylond1361 1362 136 3 and 1364 ... Slurwroom BELFAST. BIRMINGHAM. BRISTOLCARDIFF 15, Or. Saffron Hill, DUBLINtuetge1t, GLASGOW. MANCHESTER WESTMINSTER C., YORK London, B.C. I Goodall Ad. In replying to advertisers, please mention THE WIRELESS CONSTRUCTOR. 209 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRIJUOR January, 1927 aremarkable offer!I.1.5 PATENT N9 2 413 53. "Slektun Coilsera completely enclosed In a Er se en, will not c9eikc be affected ty claw or dust. We particularly wish to draw your attention to the unique patented method of spacing (as illus.- trated). which enables us to obtain almost twice AseA as much air -space between the highest potential points or turns of any other plug-in Coil on the market. At the same time we claimthe maximum inductance without increasingthe size windings. brought about by the use of The World's finest Coil wedge-shaped Ebonite Separators. We can only supply Coils in sets, for any other Coil in circuit with "Slektuns will naturally We are confident of our claim that "Slektun " Coils are the not produce perfection owing to the finest that have ever been produced, and to support our conten- difference in the direction of the winding. tion give below details of a test made by the National Physical The following sets are available at once: Laboratory.Compare these figures with those of any other Coil: DAVENTRY. " Slektun " Coil Inductance: Self Capacity : A set of 2, viz.: 200 and 250 ... Price15/- 3.,200. 250 & 300... Price 20/- of 200 turns 1770 Micro -Henries3 Micro -Micro Farads 4.. 150.200,250&300 Price 25/ - These figures constitute a record in As manufacture of Inductance Coils. BROADCASTING. A set of 2, viz.: 35 and 60 ... Price9/- So confident are we that you will obtain unprecedented results 3 35. 60 & 75... Price 14/- that we are prepared to forward " Slektun " Coils direct to you, 4 35, 50, 60 & 75 Price 17/6 carriage paid, at the reduced prices and on the condition that if Remember this : The "Slektun Coil gives the you are not entirely satisfied with them, they can be returned lowest distributed Capacity and Resistarce with within 7 days and money refunded.Read the details alongside the highest inductance. (All cases are the same size.) And now forward your order at and forward your order at once.This offer is only open for a once to avoid disappointment-Orders taken limited period strictly in rotation. A?e THE alles SECRET lektun"Registered Trade Mark. OF SELECTIVITY rgke oils AUTOMATIC COIL WINDING & ELECTRICAL EQUIPMENT Co,L td. Wellington House, BuckinghamGate,. London &W I. 210 In replying to advertisers. please mention THE WNIELE SS CONSTRUCTOR. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR Making Use of Your Supply Mains-continued from page 208 small -condenser. Thus, thelarger betweenthevariousvalvesinthe be obtained by using other voltages of thecondenser,thegreateristhe receiver and cause oscillations to be lamps. For instance, three 100 -volt smoothingeffect,andinfact con- produced.We all know the effect of lamps would divide the voltage into densers of 2, 4, 6 microfarads, or even a high resistance in the high-tension three parts.In this case the lamps more, are used in order to provide an battery dire to a defective cell or a would not glow at their full brilliancy. adequate reservoir action. run-down, battery. Any resistance such We could,again,use four50 -volt as this is often quite sufficient to set lamps, which would give us four tap- Another Method the receiver in a state of continuous pings, the arrangement being fairly oscillation, and this cannot be checked flexible. We have, however, a second method by any means other than elimination of smoothing the effect of the fluctua- of the fault5, component. A choke coil A.C. Systems tions of current, and that is by using in the high-tension lead would tend to a choke coil.It is well known that produceasimilareffect,andto In the case of alternating current an inductance coil offers a high im- counteract this a large condenser is supply we can if desired use a similar pedancetoanyvaryingcurrent, placed on the receiver side ofthe method, or we can utilisea trans- although its only effect on a steady choke coil, so tending to obviate any former in order to supply the voltage current is that due to the resistance coupling due to its presence. we require from the mains.In this of the wire itself.If, therefore, we case, however, we have to provide a have a coil having a large inductance rectifying valve in order to make the it will offer a very high impedance to Practical Details current or voltage uni-directional, and any varying current,butwillnot it is also very convenient to light the affect the steady direct current which The final smoothing circuit there filament of this valve from the_ mains we require for high-tension purposes. fore is as shown in Fig. 1, consisting as well.Generally, we require a step- For smoothing units it is customary of two large condensers with a choke down transformer to light the filament to use iron -cored chokes, and some- coil in between them.If values are thing similar to the primary of an used such as are marked in the dia- ordinary low -frequency transformer, or gramthis will be found to provide even a choke coil as used for a choke - adequate smoothing in the majority capacity unit, is suitable for the pur- of cases. pose.The effect of this is to smooth The application of this prinCiple to out still further any variations of cur- the various types I of supply is quite rent which are not taken account of simple. Consider the case of direct by the reservoir condensers connected current first.We need only connect acrossthe mains a high resistance across -the mains. capable of carrying a fairly heavy, steady current.For example, if we A Further Addition have 200 -volt mains, and we connect A simple circuit like this, however, across them aresistance of10,000 is not quite suitable for wireless pur- ohms,then this resistance will carry Fig. 3.-When valve rectification is used a steady current of 20 milliamps.In with A.C. mains, it is convenient to addition to this; we shall have the cur- light the valve filament from the mains, rent taken by the receiver in question, rectified current for H.T. supply being which will have to flow through part drawn from the terminals on the right. of the resistance, and this therefore must be added to the current -carrying of the valve. capacity of the resistance.Altogether The circuit in Fig. 3 a resistance capable of carrying about shows the simplest arrangement,in 60 milliamps should be used in order which the voltage of the mains is taken to provide for an adequate margin of through a rectifying valve direct to safety. the smoothing unit. If such a resistanceisconnected Earthing across the mains as shown in Fig. 2, then we can take a tapping on the The disadvantage of the circuits in resistancewhich willreducethe Fig. 2 and Fig. 3 is that one side of voltage from 200 to 120, which is what the mainsisusually connectedto we require, and across this we can earth.As the H.T. negative is also connect our smoothing unit as shown connected to earth, there may be some in the figure: 'his will remove any trouble arising from this factif it so trace of commutator ripple, and will happens that the positive of the H.T. supply us with a steady high-tension is connected to earth on the mains, as voltage of 120 volts. may easily be the case.In order to avoidthis,therefore,thereceiver An Alternative shouldbeconnected toearth,not direct, but through a large 2 micro - In place of a resistance we can use farad condenser, if either of the cir- a series of lamps if we so desire.For cuits shown in Fig. 2 or Fig. 3 is to example, if we have 200 -volt mains, be used.There are other arrange- By means of loud -speakers a large we can connect two 100 -volt lamps in ments,however,moreparticularly crowdwasenabledtofollowthe series.This will divide the voltage when alternating current mains are to Armistice Day service at the Royal into two equal portions of 100 volts, be used, which obviate this difficulty. Exchange. and we can take a tapping at the These are some of the problems which centre point, so obtaining 100 volts have to be considered in the design of poses, because the presence of a choke high-tension supply.This is in many suitablesmoothingunits,the con- coil such as this in the high-tension casesa more practicalproposition. struction of which need not bo outside feed circuit may introduce coupling Further subdivisions may, of course, the scope of the average constructor. 211 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 OPERATING THE "ALL -BRITISH SIX" By H. E. HASSALL Suitable Valves and Voltages-Neu- tralising - Calibration -- Operating Notes - Settingsfor Long -wave :,WtniMgeaittravf, Stations. FITLL constructional details of the " All -BritishSix "were pub- lished in the last issue of THE WIRELESS CONSTRUCTOR. The follow- ing additional notes will, it is hoped, be of assistance to those readers who have already made up the set or are contemplatingits construction. High -Tension Theremaining lead to the L.F. amplifiers must have at least 120 volts. Valves The detector lead (H.T.1) should be The H.F. transformers are designed tried with 60 volts.If this tends to Neutralising tomatchvalves having an average make the reaction control too lively it impedanceof30,000 ohmsand an may be reduced.60 volts is a good The neutralising condensers control- amplification factor of 20.This type ling the 3 H.F. valves are mounted to average value. The H.F. lead (H.T.2) the rightof of valve should therefore be used in may have120volts. Thewriter each holder, and it is the H.F. stages and as the detector. found the fullestamplification was necessary to neutralise each valve pro- Using six valves, the first L.F. stage possiblewith this voltage, and the perly before any attempt is made to may have one of the small power receive distant stations. valves,suchasthe S.T.62, D.E.8 First of all place the moving vanes L.F., D.E.5, P.M.6, etc. The last about a third of the way in, then tune stage must be .a power valve of .a low LONG -WAVE STATIONS in the local station, -plugging the loud- impedance type capable of handling speaker in the first L.F.Each dial considerablevolume, -as otherwise On aset of transfor- must-be accurately tuned for the overloading will occur. mers wound for the longer strongest signal. Take out the fixed When using six valves the following waves thefollowingsta- resistor(ofthefirstvalve)from combination will be foUnd to give the tions were received at good the holder. Signals should still be fullestamplification,combined with loud -speaker strength with heard. Rotate the condenser until selectivity and tone quality :- the first L.F. stage the signal is entirely or almost elimi- H.F. Stages.--D.E.5B. alone:- nated.Replace the resistor and pro- ceed to neutralise the second and third Detector.-D.E.5B. Station. Condenser First L.F.--S.T.62. Setting. H.F. valves in a similar manner. Care Second L.F.-S.T.63. Radio -Paris ...164 should be taken to obtain the point of Daventry ...152 silence or minimumsignalineach Grid Bias Moscow ...... 136 case, as unless the valves are properly It is important to have at least 18 ,Karlsborg ...226 balanced the receiver will not -func- volts grid bias on the second stage Konigswuster- tion efficiently. L.F. valve, if the S.T.63 is used.If hausen (Berlin)118 other valves of this type are used, a. Soro 102 Calibrating the Dials manufacturer'slistshould be con- Kbely ... 95 Those readers who are not used to sulted as to the correct grid bias. Hilversum ... 88 handling a set of this description will A largo number of stations come in Lausanne...... 64 find the tuning fundamentally differ- at loud -speaker strength with the first ent from that of the ordinary non- L.F. stage only in use, and in many selective receiver. There. are four cases overload this valve. To over- dials, and until all are turned accu- come the consequent bad qualityit receiver was perfectly stable. In some ratelytothe stationyou wish to was necessary to transfer the power cases, owing to slight differences in receive, you will not hear anything valve in the last stage to the first L.F. wiring, etc., the H.F. stages may be (unless youareclose to thelocal holder, increasing the grid bias accord- founddifficultto control with this station), ingly.It is, of course, important to voltage.The remedy is to reduce the Plug in a pair of telephones in the do this, otherwise little difference in H.T. andtry,say,90 volts as an firstL.F. stage.Say,for example, the quality of tone will be apparent. average value. that we wish to obtain Oslo, Sweden. 212 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR Operating the "All -British Six"continued This station comes in on my receiver on a distant station, as the local sta- togo round the stations,and at at 108 on each dial.At the first test tionsignalistoo strong enable night, when all stations on the broad- theactual readings were: -1st dial this to be done accurately. Suppose cast band are working, they come in (from left) 110, 2nd 109, 3rd 108, and we wantanother station,Bourne- on the loud -speaker all round the dial. 4th106. Get a friend to hold the mouth, for example-Oslo is at 108- rotor of the fourth dual condenser. moveeach dial to 110 and Bourne- Removing the Shields Unscrew the dial from the spindle and mouth will come in.A touch on the It is desirable to point out to experi- move it, up, two degrees.It will now reactioncontrolto just under the menters who make up this receiver read108: Alter the dials of the oscillatingpoint,andthee-station that they should take care when re- second and first condensersto read should be at full loud -Speaker strength. moving the shields not to drop them 108.Itis important that the rotor Itisa golden 'ruletomove each in the set, as although the Glazite should not move when this adjust- dialin successiononly one .or two wiring used has an insulating cover- ment is carried out. degrees at a time. ing, a short may be caused on soldered The dials will now all read 108, and joints, with consequent destruction to this setting will be accurate over the, Practice is Necessary the valves. The writer has twice whole scale of the second, third and Do not be disappointed if you do dropped the shields in the set, but fourth condensers.The first (aerial) not get a large number of stations the luckilythecontretemps wasun- condenser will also be approximately first night.Rome was not built in attended with any evil results.There the same.It may possibly vary one a day, and readers who have no ex- is always, however, a possibility of fus- or two degrees on the lower end of perience of receivers with H.F. stages ing the filaments, and it is thought the scale. During the preliminary must be prepared to devote an hour necessary to advise readers to take care. operation thereactioncondenser or so to learning the correct manipu- It should be pointed out that the plates should be in the 'zero position. lation of the. controls.I have stig- dial settings given above for certain FOR THE BEST RESULTS NOTE THESE POINTS:- Insert the special H.F. transformers in the screened coil bases. Place valves of the types recommended in each of the six valve holders. Make sure that the fixed resistors are the right ones for the valves and accumu- lator used, Neutralise the H.F. stages with the three neutralising condensers on the baseboard. Move the dials slowly, one or two degrees at a time, keeping them relatively in tune. Use reaction sparingly to increase the volume from the station located. Using Reaction gestedpreviouslythat telephones stations were those which applied to Assuming that we have got Oslo at should be usedforthe preliminary the oldwavelengths. - The general 108, try the effect of increasing the tuning stages.As soon as one be- principlesofcalibration remain, of reaction control.It will be found to comes familiar with the handling these course,unaltered. build up signal strength, and the set can be dispensed with, and the loud- shouldgosmoothly in and out of speaker pluggedin.Itisperfectly oscillationwithout" backlash."If easy to tune in any station on the this is not possible, try the effect of loud -speaker once the set is calibrated reducing the voltage on the detector without resortingtotelephones. valve. Once you have tuned in a distant It is necessary to calibrate the dials signal r-Qcurately it is a simple matter 213 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 CONTROLLING THE BROADCAST WAVELENGTHS The New Wavemeter at the London Station IN orderthatthebroadcasting Beforethenewwavelengthswere the London station was demonstrated stations of Europe may keep as actually tried out, it was thought that a few weeks ago by Capt. Eckeraley, accurately as possible to the posi- possibly crystal control of the various the Chief Engineer of the B.B.O. The tions assigned to them under the new transmitters might be employed.By crystal -control method is not used, the scheme of wavelengths, which came this means the transmitting apparatus wavemeter being simply an accurately calibrated instrument for keeping a check on- the actual wavelength on which transmissionistaking place. A separate wavemeter is provided for eachstation,each meterbeing designed to cover a frequency band of 20 kilocycles. Captain Eckersley (fourth from left, Indicating Devices demonstrated the The wavemeter consists of an in- newwavemeter, ductance shunted by a capacity, and which can be seen suitable indicating devices.A flash - on thetable,to lamp bulb is used to give a rough in- representatives of dicationofthe wavelengthofthe the Press. transmitter, the lamp glowing most brightly when thetransmitter and as wavemeter are intune.For more * accuratereadingsathereto -couple and galvanometer are provided. In practice the wavemeter can be used to check the wavelength of the station to which it belongs, and also into operation on November 14, 1926, would be so controlled that practically to note the positions of the stations each station is provided with a special no deviation from a predetermined oneitherside,sincea frequency wavemeter. wavelength would be possible. separationof10, kilocyclesisthe These wavemeters are all calibrated general rule.The central reading of at one central Bureau, thereby ensur- London's Wavemeter each meter records the wavelength of ingthegreatest possibleaccuracy. The actual wavemeter to be used at the station immediately concerned. A Perfect Job. A combination of the three essentials-precision, efficiency, finish- that's what makes JacksonCondensers foremoston themarket to -day. J. B. Condensers embody all the most modern developments in Condenser design, and their inclusion in practically all the Star Sets is an indication of the value placed on them by the scientific radio experts of the present day. THE J.B.,S.L.F. Double reduction PRICES, complete with 4' Bakelite Dial. friction drive. .0005 mfd 11/6 Ratio 60-1. .00035 mfd 10/6 .00025 mfd 10/- J.B. Condensers are precision instruments, made to last a lifetime, and designed to simplify tuning and yet possess that selectivity which marks a really good condenser. In both the original J.B., S.L.F., and also the True Tuning S.L.F., the vanes are designed on a new principle to avoid crowding at any part of the scale.In addition, the vanes are supported at tips to ensure correct spacing. Friction surfaces are machined to a fine limit of accuracy, preventing all possibility bf lost motion. THE J.B., TRUE TUNING S.L.F. PRICE, complete with 4' Bakelite Dial. .0005 mfd...... 16/6 .00035 mfd...... 15/6 .00025 mfd I5/ - 8. POLAND ST -OXFORD s Uelephone- LONDON - V1/.1 GEI,RARD 7414 In replying to advertisers, please mention THE WIRELESS CONSTRUCTOR. F14 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR THE " ECONOMICALTWO " By W.Q. KAY. This dual-purpose Set may be used for local or dis- tant reception with equal efficiency. By means of panel -operated switches, the two valves may be used as H.F. and detector or detector and L.F., reaction being provided with either combination. (b) A high -frequency valve and IN arecentarticleinIFireless, detector with resistance coupling. entitled " Economical H.F.," TEST REPORT some circuits were given showinghow The following stations- were re- (c) A ' detectorvalve and low -fre- the benefit of a high -frequency valve ceived at good 'phone strength on quency resistance -coupledampli- could be obtained concurrently with an aerial about 60 ft.long and fier. other benefits which tended. to reduce 20ft.high,12milesnorth of Special Valves itseffectivecost. Forexample; London:- ' When the last of these three is used, althoughtheadvantagesofH.F. Breslau, Bournemouth,. namely,adetector andresistance - amplificationarebecoming realised, Newcastle, London, Hamburg, coupled note -magnifier,itwill give there are many people who do not fee] Glasgow, Frankfort. comfortable loud -speaking on the local justifiedin adding a high -frequency The 'Settings on the aerial con- station,sufficientfora small room. valve simply and solely for the purpose denser are given on the accompany- of increasing their range. ing graph.The settings on the BUILD THIS SET WITH- If,onthe otherhand,arrange- tuned -anode condenser were about One ebonite panel, 14 in. by 7 in. by ments can be made so that the high - 10 degrees higher in each case. 3/16th in.(Radian.) frequency valve can be put to another 'Co One suitable cabinet, with baseboard purpose when distant stations are not 9 in. deep. being received, then the extra advan- Two .COOS ultra low loss S.L.F. variable tages obtained suchacircuit condensers with 4 in. dials.(Fornio Co., willcompensatefortheadditional Soo Ltd.) cost.Various Circuits were !given in Two double pole change -over switches. the article in question, and the pre- us (Wright & Weaire.) sent receiver is a modification of one Two " Dimic " coils and bases.(For of the circuits so put forward. 12. 400 the lower broadcast band, two No. 1 coils will be required, while for Daventry one or two No. 3 coils may be used, as Possible Circuits will be seen in the description of the Inthisparticularreceivertwo set.)(L. McMichael, Ltd.) valvesare employed. An arrange- One filament rheostat.(Etherplus.) ment of switchingisincorporated so One panel mounting neutralising con- that it is possible to use the receiver denser.(Igranic Electric Co., Ltd.) 2000 Two valve holders. (W. & B.) in three different ways :- 50 100 /50 (a) A high -frequencyvalveand DIAL SETTING Two fixed condensers, .0003 and .001, detector with tuned -anode coupling. two 2-megohni leaks and one .25-rnegolmz leak.(Dubilier.) Four terminals. One 7 -way batterycord. (London Electric Wire Co., & Smiths, Ltd.) C3 Quantity of Glazite. .0005 Radio Press panel transfers. C.A.T. Approximate Cost : £6. .000, H.T. 1110 In order to do this it is necessary to 1111 useaveryhigh -impedancevalve. There are several types of valve now on the market having an impedance of 70,000 or 80,000 ohms with an ampli- ficationfactor ofabout 35. Such L.T. valvesaretheCosmosBlue -Spot, which may be obtainedineither the 2 -volt orthe 6 -voltseries, ortheEdiswanR.G.2,which is a 2 -voltvalve ofsimilar char- acteristics.The use. ofthis type 0 E valveisalso beneficial when the cir. cuit is being used as a high-frequenc:c Fig. 1.-The switch 51 is used to reverse the filamentbattery connections to the set as required. amplifier, as will be seen shortly. 215 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 The " Economical Two " continued Circuit The circuit of the arrangement is shown in Fig. 1.It will be seen that there are two switches provided. 'The node circuit of the first valve con- tains a double -pole change -over switch, by means of which either a tuned cir- cuit or a resistance can be included in the circuit.When the receiver is to be used as a tuned -anode H.F. set the tuned circuit -is included.If it is * * * to be used as' either a high- or low - frequency resistance -coupled amplifier the resistance is included in the cir- (a) cuit.The selectionof one or other oftheselasttwo arrangementsis Fig. 2.-These are obtained :by -theuseof asecond the circuits avail- switch, which reverses the connections ableinthe set. from the L.T. battery. (a)H.F.(tuned Changes Required tector-bothanode)andde- HT- The three possible combinations are switches " down." drawn up in skeleton fashion in Fig. 2. (b)H.F.(resis- It will be seen that in the first case, tancecoupled) i.e.H.F. and detector with tuned -and detector-S1 anode coupling, we require the grid - " down" and S2 leak on the first valve to go to the " u p ."(c) De- negative of thefilament,while the tector and L.F.- grid -leak on the second valve should go bothle switchesup.11 to a more positive potential.In the second case, i.e., high -frequency and (h) detector with resistance coupling, the same arrangement of the grid -leak is required, but the tuned circuit is re- resistance. placed by the In the thirdcase,wherewerequire a detector and resistance -coupled note - * * H magnifier, . we have to connect the grid leakof the first valve to the positive of the filament so that it may act as LT+ a detector, . and that on the second r valve should go to the negative of the filament,preferably- through a grid - bias battery as shown. Reversing Switch (C) This necessity for change -over has nected through a grid -bias battery witha singlestageofresistance - been allowed for by the incorporation to the other side of the filament.By coupled L.F. is only of the order of of a simple reversing switch on the placing the switch in one position we 11 volts, then we shall get the differ- ence between this voltage and the 2 fit"- 34". , < A.3P $-* 21/1/-1,-. V -04-td voltage of the L.T. battery applied to N the grid leak.In any case it will be 2fi 411 a. small positive voltage, so that we 0040 obtain the necessary rectifying effect. A /AL . .. RrACrION or 0. Moreover, the 2 -volt valves only re- " \ quire a small positive voltage, whereas it for the 6 -volt class a somewhat larger I" 7r. positive biasis required for efficient fato s il Q. rectification. The arrangement pro- , - s $ -"- vided ensures that thisis the case . automatically, so that by using 11 volts li4lici irr grid bias we are actually obtaining a M satisfactory condition of affairs.- to . R 52 When the position of the switch is 413i. 4--- y - reversed we connect the grid -leak of thefirstvalve to L.T.positive, in 14" ) which position it will rectify satisfac- Fig. 3.-Blueprint No. C1075 A of this drilling diagram may be obtained. torily, while the second valve is con- L.T. battery.The grid -leak on the then connect thefirst valve to L.T. nected through a grid -bias battery to first valve has been connected to one -negative and a second valve through L.T. negative, thereby ensuring that sideof the filament,and the grid - the grid -bias battery to L.T. plus. it givesdistortionlessL.F.amplifi- leak on the second valve has been con - Now, since the grid bias necessary cation. 21,6 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January 1927 THE WIRELESS CONSTRUCTole-- 1/4 USE LISSEN FIXED CONDENSERS, TOO. Mica and Mansbridge Type. MICA TYPE. Small energy -conserving con- 111=7056"6"4.-";;A densers-notethenewcase which enables the condenser to be used upright or flat.At present the new case is available only in the most used capacities, butwillquicklybecome a LISSEN standard. Capacities:-.0001 to .001 1/- each (much reduced) .002 to .006 1:6 each (much reduced). Accurate to 59,-they never leak-they never vary. LISSEN Mansbridge Type CONDENSERS. To afine LISSEN quality condenser is addedthespeciallymouldedcase-the condenser cannot short circuit on to its case. The new LISSEN case protects you if the condenser is used in any circuit connected straight on to the electric light mains.And due to our new policyof direct -to -dealer distribution this LISSEN Condenser costr no more than the ordinary type. .01 to .09 .. 2'4 c wos LISSEN FIXED GRID LEAKS. leftone oor faheory Who earns your money? during the summer of 1925, soaked in rain, baked by sun and the Who spends it? Who chooses resistance value of these leaks never altered. All capacities.Previously 118. Now 1/- each. your parts for you? Improve every circuit by using LISSEN parts wherever you can- save money too-for now you get keen prices as well as fine quality. No set published by any periodical could use only one make of parts or could use the same QUALITY make of transformer, for instance- it would RHEOSTATS. not be fair to advertisers if they did not all Previously 4/. have a share in this kind of mention. BUT NOW -2/6 LISSEN quality-look how they YOU ARE FREE TO CHOOSE YOUR OWN are made-the wires cannot move and short circuit-the PARTS. contact brush rides firmly yet smoothly-theheat -resisting Your transformer, for instance.Never again pay a high former cannot soften-there price for your transformer no matter what may be are accessible terminals --and specified--- the new LISSEN has revolutionised all previous the combined knob and ideas of transformer price and performance. pointer will fit flush with the neat photo -engraved dial when So good is it that all our own high-priced models, which mounted. Lastly,notethe irresistible appeal of the price, have been on the market and largely sold for several made possible by our big pro- years past, have been unhesitatingly withdrawn in favour duction programme, backed of this new LISSEN. by our new direct -to -dealer The fine tone and great power of thisnew distribution policy, which cuts out all wholesale profits. Previously NOW LISSEN Transformer have been proved by the LISSEN7 ohms rheostat, patented ... 4,- .. 2 6 trade-they are largely usingitfor their own 35 built-up sets PP Potentiometer, 400 ohms 416 Itfully amplifies every noteevery Harmonic-every VP .. 2'6 Overtone.Choose the new LISSEN. First for its EVERYONE LISSEN ONE -HOLE FIXING, OF COURSE. Performance.Secondly for its Price. Baseboard mounting type same prices as above. ACTUALLY TEST IT FOR SEVEN DAYS-IF NOT A VALVE HOLDER FOR CLEARER, SATISFIED THEN, TAKE IT BACK TO YOUR BETTER SIGNALS. DEALER'S, OR SEND IT BACK TOUS. 411111, Becauseofitslowcost Our new direct -to -dealer policy of distribution (which and low capacity qualities, cuts out all wholesale profits), aided by our huge pro- the LISSEN Valve Holder ti duction programme and the special plant installed to playsitspartingetting clearer, louder signals. Sent turn it out, have enabled us to sell this new LISSEN Trans- outreadyforbaseboard former at an unheard-of low price. mounting, as shown, it can AND GUARANTEED FOR 12 MONTHS. alsobeusedforpanel 1/1..11, mounting by bendingthe TEST IT FOR SEVEN DAYS. springs straight. Turns ratio 3 to 1 Resistance ratio 4 to I LISSEN Valve Holder (patented), previously 1,8 Use it for 1, 2 or 3 stages L.F. It wilt suit every circuit and every valve you will want to use. NOW 1/. each. LISSEN LIMITED, 8-16, Friars Lane, Richmond, Surrey. Managing Director : Thomas N. Cole. Many are using LISSEN Transformers in "N" Circuits. Li 3 I . 7 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 HAVE A "PILOT" SET THIS XMAS THE "ECONOMICAL TWO "- and be sureof your entertainment ! continued THE Receivers shown below are selected from by acknowledged experts, made by skilled work- Layout a wide rangeof instruments which are men and finallytested under actual working The layout of the receiver is simple guaranteed to do all that is claimed for them. conditions.A signed certificate of test and a and straightforward.The two tuning Each of theSets illustrated here have been designed tuning chart are given with each instrument. condensers have been mounted sym- THE SOLODYNE. metrically on the panel, while the fila- ment resistance controlling the two " 5 Valves -1 Dial - valves is mounted at the bottom in the 50 Stations." centre, and the neutralising condenser, The most popular Set of the season. whichisalso used for reaction pur- Merely rotating the one dial brings in poses, is mounted at the top.The two station after station with amazing clarity and remarkable volume.There is no change -over switches are mounted at better five -valve Set and none so simple. the two bottom corners of the panel; the one on the left-hand side operates onSetyl £2450 the change -over between the tuned Royalty, extra, £326 circuit and the resistance, while the other switch operates the change -over Complete with Oldham L.T. and H.T. Accumulators, 5 Marconi Valves, additional Coils for long -wave reception, Battery leads and Amplion Radiolux Loud Speaker, Marconi Royalty Paid.. £47 12 6 on the battery connections. BEST IN ALL Neutralised H.F. EUROPE! Reference to the circuit shown in Fig. 1 will show that a neutralised arrangement has been adopted for the ---The high -frequencyvalve. Thisensures ALL -BRITISH that adequate results may be obtained when the receiver is being used for SIX. long-distance work.At the same time with the system incorporated reaction effects may be obtained by increasing Designed by Mr. H. E. Hassall-a London Amateur- MONO -MODEL. this set was entered for the recent New York International the neutralising condenser, which pro- Competition for Amateurs and gained third prize in the I Control -100 Stations. videsa smooth and progressivein- multi -valve class.This was the highest award for any Similar in design to the original, except that special single. European entry. We are theonlyfirm authorised by Mr. control mechanism is fitted, so that the four condensers may crease in signal strength up to the Hassell to make up these sets for sale, and in order to safe- be rotated in unison by means of a control fitted at the left oscillationpoint. The-particular guard buyers a certificate signed by NIT. Hassell is given hand side of the cabinet. For sheer efficiency and simplicity arrangement is such that this reaction with each instrument. of operation this Set has no rival in the whole of Europe. effect is obtained on the first circuit ORIGINAL MODEL, as illustrated,£33 15 0 only, complete with B.B.C. Coils .. . set °^''' £37 5 0 irrespectiveofwhetherthe Marconi Royalties, extra to either of these prices, £3 15 0 second tuned circuit is in operation or Accessories required.-Oldham L.T. and H.T. Accumulators, 6 Marconi Valves, Battery Leads, not.It is thus possible to obtain the Arraplion Radiolux Loud Speaker and additional coils for long -wave reception .. £23 0 0 desired reaction effect whichever of the three arrangements are being utilised THE MONODIAL FOUR. in the .receiver. Mother ofourrangeofsingle -control Receivers, designed togive Loud -Speaker Construction results on all B.B.C. Main Stations and the nearer Continental ones.Selective to a degree No terminal strip has been -provided and amazingly simple to handle. on this receiver, but a battery cord has -been utilised instead. Set only£19 0 0 The ends of the Royalty extra, £2 100 wires have been taken direct to the appropriate points on thereceiver. Complete with OldhamL.T.and H.T. This will save the expense of a ter- Accumulator, Marconi Valves, Battery Leads, Amphora Loud Speaker and additional coils minal board, and is quite as efficient. for long -wave reception £39 17 6 The first operation in making up the receiver is to lay out the components on the panel, and mount them up as WE INSTAL THESE SETS FREE WITHIN FIFTY MILES required. Beyondthat distance we willinstal a Set upon payment of our operators travelling and out-of-pocket expenses. The panel may then_be screwed into Installation does not include erection of aerial and earth. _ position on the baseboard and the ORDERAT ONCE FOR INSTALLATION BEFORE XMAS. various components laid out at the 17.-n-E119T-RA11) iirAFEVETEITS7O12X214 hack.The layout is quite simple, and LWe have acquired the sole manufacturing rights forI no trouble will arise if the diagram is these celebrated instruments, each of which is guaran- Thereare many Sets of followed.The receiver is then ready Iteed accurate within* 1 metre.An indispensable up-to-date designinthe boon to the enthusiast: Fun particulars on request. I for wiring up.The wiring has been Pilot Manual and among ) them you cannot fail to find taken by the shortest route, and is one to suit your individual very simple.It will be observed that requirements. Profusely Ltd. the moving plates of the condensers illustrated. POST PETO-SCOTT Co 6d.FREE. Registered Offices, Mail Order and Shouworn: obtaintheir contactintwo ways. 77, CITY ROAD, LONDON, E Cl First of all, there is the connection on_ BraNgiaes: LONDON: 62. High Hama, W.C.1. WALTHAMSTOW .230, the- bracket itself, which is in contact THE PILOT MANUAL, Wood St. PLYMOUTH: 4, Boa of 'Wand Place.LIVERPOOL: with the moving spindle,whilein 4, Naechsater Bt. addition there is a flexible pigtail on the end of the moving plates, which has been soldered to a small extension HITCH YOUR AERIAL TO A " STAR" ! piece coming from the main connec- P.S.6341 tion. 218 In replyingto advertisers, please mentionTHE WIRELESS CONSTRUCTOR. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor Tanuary, 1927 THE WIRELESS CONSTRUCTOR The "Economical Two "-continued Testing tension, the higher the better. Actually First of all place both the change. Having completelywired there- the receiver was tested on 60 volts over switches in the " up " position. ceiver,it may then be tested out. only, and gave very good results, but This connects the arrangement as p Connect it up to the batteries in the an increase in the high-tension voltage detector and low -frequency amplifier. normal manner.A voltage of 60 to to 120 volts resulted in considerably The local station may then be tuned in 100 volts should be used on the high- louder signals. on the left-hand dial in the normal Top EDGE Of BASEBOARD. C.A.T. 0001 BASEBOARD 14"x95* 3/8" Fig. 4.-Care should be taken that the two switches are correctly connected. Blueprint No. C1075B. 219 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 The "Economical Two"continued manner, and reaction effects may be By placing both switchesinthe together little by little a few degrees obtained on the neutralising condenser " down "' position we change over to at a time.It will be found by this at the top of the panel. the high -frequency arrangement with means that alittle practice enables tuned -anode combination.When this the various stations to be picked up Reaction Control isdone the' signal' strength will,of quite easily, and the reaction setting In order to obtain smooth and pro- course, be somewhat reduced, but it will be found to remain in a sensitive gressive control of the reaction the will be found that the range of recep- condition over a considerable portion of the scale.Once the station has beenfound,itsstrengthmay be increasedbycarefulretuning and readjustment of the reaction. * A Warning Particular care should be taken not Thebaseboard to allow the receiver to oscillate any componentsa r e more than is necessary, because itis so disposed as to . not non -radiating, and any oscillation allow of the sim- which is produced will cause radiation plest wiring from the aerial with interference to arrangementt o the neighbours.After a little practice the switches. it will be found quite easy to pick up all the stations required without oscil- lating, and simply using the reaction *** condenser asa means of increasing the strength when the station has been finally tuned in. Results tion is considerably increased, and a As a guide to the positions in which largenumberofstationsnunbe the stations will be found the accom- received with comfort.For this pur- panying -test report will be of service. pose 'it is only necessary to adjust the This is by no means a complete test filament rheostats should be adjusted second' dialtoapositionapproxi- report of,the number of stations which mately the same as that of the first. can be received on theset,butit to give thebestconditions. Unless servestoindicatethe positionsat this is done the reaction will be found . . which the variousstations may he to go in with a plop, and may con - Searching expected, and the reader will no doubt The reaction .control should be ad- be able to log a considerably greater WIRING IN WORDS. justed so that the receiver is just off number of stations. Join earth terminal to contacts 2 and 7 of the oscillating point the whole time. For the reception of Daventry only, switch Sr, to centre tap of Li coil base, to one filament contact of Vz and V2, and to one side of It will"be found that the same setting a single No. 3 Dimic coil may be used leak R2. of the filament rheostat which gives in the first circuit and the resistance - Join aerial terminal to one side of C.A.T. the best results with the detector and coupled L.F. arrangement used.Far condenser. Join other side of C.A.T. condenser to one end low -frequency arrangement also gives Radio -Paris andother long -wave of Li coil base, to fixed vanes of variable con- excellentresults with the H.F. and stations theresistance -coupled H.F. denser Cr, and to one side of fixed condenser C2. Join the remaining sides of C2 and R2 to grid contact of VI. Join other end of I,x coil base to moving vanes of Ci, and to moving vanes of reaction condenser. Join together contacts x and 8 of Si, continue to remaining filament contacts of Vx and V2, and attach the G.B. + battery lead. Join one side of fixed condenser C4 and leak R4 to grid contact of V2. join other side of R4 to G.B. - battery lead. nA ad Join the other side of C4 to anode contact of va * Vi, to fixed vanes of reaction condenser, and to contacts 4 and 6 of S2. The battery cord Join together contacts 4 and 6 of Si, and attach the L.T. - battery lead. issecured in Join together contacts 3 and 5of Sr, and position by means continue to one terminal of rheostat Az. of a wooden block JoinH.T. -and + battery leadsto other terminal of Rz, with a recess on Join contact 2 of S2 to fixed vanes of variable the lower side. condenser C3, and to one end of L2 coil base, Join contact i of S2 to centre tap of L2 cot base. *aA ea Join contacts 7 and 8 of S2 toopposite ends of leak R3. Join remaining end of L2 coil base to moving vanes of C3. Join together contacts 3 and 5 of S2, continue to one telephone terminal and attach the H.T. +- battery lead. Join the other telephone terminal to anode contact of V2. detector setting.Start off by tuning scheme may be used as a trial.if this ceivably have a certain amount of in to the local station as before, and is not satisfactory, a second No. 3 coil backlash.This may be remedied by adjusting the reactionso that the should be obtained and the tuned - suitableadjustmentof theH.T. receiverisclearof theoscillation anode arrangement employed. This voltage and the filament brilliancy. point.Then proceed to move the dials will be found to give every satisfaction. 220 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR SUPER POWER 040,i0 ct0:10%:0,104040:V040.,..0%. o Do your signals improve in Fitan S.T. Super Power qualityasyoutone them Valve in your last valve holder down in strength?If they whenever you have two stages o do, it is a sure sign that your ofL.F., and it will respond valves are being overloaded. lightly and faithfully to every Don't blame your loudspeaker fluctuation in the music and or transformers.Ninety per will give that sense of reality which cent. of that huskiness or diaphragm brings the artiste to your own fireside. rattle which spoils the sudden glorious You only need one of them, so buy o high notes of a soprano or the rich low it for your Christmas festivities.It isa new type of valve altogether, .v notes of the organ is attributable solely to the fact that your last valve will havingaverylong andstraight O not handle those suddenincreases dynamic curve, every user will enjoy of grid voltage, amounting sometimes music that is vivid and alive.Get Q to 1,0:10%.Your valve begins to yours now. Price rectify either because of grid current S.T. 43 for 4 -volt accumulator orthroughmomentarily operating S.T.63 for 6 -volt accumulator22/6 on a bend of the anode curve. SEE ALSO PAGES 182 and 237. ,,r-c919s-ara-raNs0549 afieValve with theaoicienvoice\ 22l. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 RECUPERATING AGENT in the HELLESEN DRY BATTERIES is the secret of uniform, silent and economical H.T. supply.Choose a Hellesen Dry Battery as a Xmas gift for your wireless friends and you H.T. RADIO ACCUMULATORS have the two fold satisfaction of knowing that your gift is " the best in the world " of its kind 1927 IMPROVED MODEL. and also that it will be appreciated. TOprove our absolute confidence in these Wireless reception to -day demands H.T. Bat- accumulators, we guarantee, if you are teries with recuperating power to withstand not satisfied, to accept return within21 long and frequent usage.Make the Hellesen days from purchase date, and refund money secret your Xmasgiftand long thoughthe in full, provided battery is returned intact battery may last the appreciation will out -live it. to the Agent from whom it was purchased. Ask your dealer for a Hellesen Dry Battery, it C.A.V. H.T. Accumulators representan will cost you no more, it only gives you more. epoch-making advance as compared with dry batteries. When dry batteries are down, they 60 volt "WIRIN" 12/6 are done, and frequent renewals make them 99 volt "WIRUP" 21/_ more expensive.C.A.V. H.T. accumulators POSTAGE EXTRA. will last for years, and only need recharging All types, voltages, etc., in Double and Treble capacities approximately every four months.They for H.T. and L.T. Supply.Ask your dealer for the give bigger volume and are silent in operation. type to suit your set and get the maximum service, or The crackling noises with reception, caused by write us for full particulars. the chemicalaction ofdry batteries are entirely lost when the C.A.V. H.T. is used. Obtainableatall Radio, Electrical and General Place your order to -day and so shorten your ' Stores,Harrods,Selfridges,etc.,or direct from regrets for not using one long before. A. H. HUNT, LTD.,°Tr CROYDON, SURREY SUPPLIED FULLY CHARGED 60 VOLTS. READY FOR USE, ABSOLUTELY COMPLETE IN CASE, AND WITH DISTILLED WATER FILLER - -601- Our illustrated Catalogue will be supplied on application. cuti6,w>,__sray7A ACTON, LONDON,No W. 3. Telephone: Chiswick 3801 'T l'Erevace Eranch Exchange) Val'elgrhandPa... 222 In replying to advertisers, pleasementionTHE WIRELESS CONSTRUCTOR. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR Are You Satisfied with Your Set ? By L. H. THOMAS There are a number of minor alterations which can be made in existing sets, which may give improved results. Selectivity is essential in these days and satisfactory reaction control is an immense aid to good reception. How to improve your set in these directions is discussed in these pages. TT is probably quite safe to say that achieved,thegreatestproblemof the aerial by five feet simply for the most of us cannot conceive the sen- modernradioreceptionhasbeen purpose of removing it from its sup- sationswe shouldfeelifwe solved. porting mast by this distance. One owned a receiver which would receive It is obvious when one thinks it over, too often sees aerials with the free ends any station we liked to name, free of however, that once a signal of any within eighteen inches or two feet all interference of any kind; in short, kind whatever has been received clear in a manner worth listening to.This of all interference, jt may be ampli- is probably because those who design fied up to practioally an infinite de- receivers are often apt to be a trifle gree, and will still be received with short-sightedon one point, namely, Just its original clarity. that whatever is done to a receiver to Here,then,isadefinite goal to snake it more sensitive to weak signals aimat.Itis,in fact,simply the will be a hindrance, and not a help, if question of selectivity, which is now interferencefromsomeunwanted the first requirement in any receiver source is being received at the same thatisnot intended simply to re- time as those signals. ceive the local station and nothing else at a distance of five or six miles. Interference To amplify a signal received on a The very first point of all radio re- non -selectivesetis simply to make ception is to obtain a signal (no matter matters infinitely worse; to amplify a signal from a selective set has nothing whatever against it.It has, in fact, E been said that about 50 per cent. of Fig.1.-This is the conventional circuit the radio reception of to -day consists employing magnetic reaction. Compart of amplified interference. with Fig. 2. Improving Selectivity of a metal mast-and even wooden First of all, to produce a selective masts behave as earthed bodies in wet circuit,all stray resistances must be weather. cut down to the bare minimum. High resistance in any radio circuit is recog- What to Expect nised as having very bad effects, but itis the resistances of which we are The earth, also, may in nearly every unaware that cause trouble.To tune case be improved. Large buried plates sharply it has been proved time after are infinitely preferable to water -pipes, time a circuit must- have a low resist- but good buried lengths of wire laid ance.One is rather apt, on remem- outunderneath the aerial are even bering this, to instal a set of " low - better. One must not expect, how- loss coils and condensers and leave ever, to improve the aerial and earth the matter at that.There are, how- system and then go in to the set and ever, other considerations.The aerial tunein stronger signals than were and earth must have as low a resist- ever, received before-it is the selecti- ance as possible; there are few aerial vity, not the sensitivity, that will be systems that could not be improved by greatly improved.It must be remem- 15 or 20 per cent. as a result of an bered throughout that what is wanted afternoon spent on them. The wire is is not a loud noise-it is a clear signal not the only part of the aerial that that can be amplified into a strong can account for excessive resistance-it signal. What would the Duke of Wellington must be remembered that anything, If the aerial system is poor, i.e., of have thought ? For the Armistice Day whether it is a conducting material or high resistance, much of this poorness celebrations at the Royal Exchange, not, that comes too close to the aerial may be communicated to the secondary public addressloud - speakerswere can cause a very material increase in circuit by being " coupled into it." placed at convenient points. itsresistance,thus broadening the The loosest possible coupling should tuning. then be used, so as to confine any bad how weak)free of allinterference. The aerial must therefore be kept effects of the aerial circuit within that This is, unfortunately, nothing like so well away from walls, gutterpipes, circuit as much as possibW. Once easy as it sounds.Many, perhaps, do chimneys, trees, and the mast itself. more, a weaker signal may result, but not realise that, once this end has been In most eases it would pay to shorten it will be a clearer signal. 223 411 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor `THE WIRELESS CONSTRUCTOR 'January, 1927 Now Granniecanlisten ! "THAT Wireless " Grannie used obtain pure, faithful Loud Speaker tosay," was no good-she reproduction from yourCrystal never could hear whatthe Receiver. No Valves. No accumu- man wassaying ! "That was lators.Just the Crystal Amplifier before the 313r0W11 Crystal Amp- connected to your Set and lifier came. Now she the Loud Speaker. The sits and listens to the onlyaccessory needed Loud Speaker working isa 4/ volt dry bat- from the little Crystal tery. What more ideal Set. Forhoursand -for wayofenjoyingthe hours !Now sheap- faithful broadcast ? You get the preciates the boon Radio results of your friend the broadcastingcan be. interpretation. valve -user without any Mostly everyone, now, Price of Crystal Amplifier, of the worry,trouble and can work a Loud expense his accumulators SpeakerfromaCrystalSet £4 4 0 cost him. without the use of a single valve. See your Dealer about the Crystal If you live within fifteen miles of a Amplifierto -day. Get him to The H.Q. B.B.C. Station (or eighty miles from demonstrate it on one of the nine The HI. 20 inches high Daventry)theZrown Crystal IBrown Loud Speakers.You'll be 120 ohms. /5 5 0 2000 or 4000 ohms. Amplifierwillenableyouto sureto want oneforyourself. 2000 ohms. 15 8 0 £6 0 0 9000 ohms. £5 10 0 S. G. BROWN, LTD., Western Avenue, North Acton, W.3. Retail Showrooms :19. Mortimer Street, W.1 ;15, Moorlields, Liverpool ;67, High Street, Southampton. Wholesale Depots:2, Lansdown Place West, Bath; 120, Wellington St.. Glasgow; 5-7, Godwin Street, Bradford; Cross House, Westgate Road, Newcastle; HowardS.Cooke & Co.,59,CarolineStreet,Birmingham.Robert Garmany, Union Chambers, 1, Union Street, Belfast, N. Ireland. Gilbert Ad. 6355. 224 In replying to advertisers, please mentionTHE WIRELESS CONSTRUCTOR. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR any type of terminal can be made in ARE YOU SATISFIED WITH YOUR SET ?-continued a manner to be described here. Materials The materialsrequiredareas Short Leads Fig. 2.The whole of the' secondary follows : -A fewinchesofbrass To keep the resistance' of the aerial coil is still tuned; also note that it is tubing,6/32 -in.diameter,anda circuit down, if possible, take a lead the half on the " earth "side that length of 3/32 -in. diameter brass rod. straight from the lead-in tube to one is coupled to the reaction coil. The internal diameter of the tubing end of the primary coil, the other end, should be such that the rod just fits of course, going to earth, also in as. Advantages it easily.To make a tag a piece of direct a manner as possible. The same A further advantage of a set rigged tubing1in.longisrequired, and up in this fashion is that, on account fin. from one end a slot is cut in it of its very loose aerial coupling, and nearly half way through, as shown in also its " split " secondary, radiation Fig.1. Next a- 11 -in. length of the is reduced.The method of placing the brass rodiscut off and scarfed at coils should be as in Fig. 3.. Note that one end (see Fig. 1). the two halves of the secondary coil Assembling should not only be at right -angles, but also as far away from each other as Now bare I -in. at the end of the can conveniently be arranged. flex lead which is to carry the tag, Actually the coupling of the primary turn back the braid covering and tie to its associated half of the secondary ar SLOT SCARFED MAE 3.HERE Berec HERE Roy should be of the order of 45 degrees. # The reaction coil and the other half \\NINN. of the secondary may be arranged with /NSULAT/ON TURNED E fixed coupling, control of the degree of BACK AND TORN ENOS OR Fig. 2.-By splitting the secondary coil oscillation being obtained by means TIED E. and applying reaction to one half, the of a condenser across the telephones SOLDER HERE effect on tuning of varying the reaction and the H.T. battery, or by some other ccr,-Kccza coupling will be reduced. equally well-known method.This is, J> however, unnecessary, since by split- Fig. 1.-Details of the assembly of the should be done with the secondary cir- ting the secondary circuit it has been tag are given in these drawings. cuit-the lead from the " top " end made possible to control reaction by of the coil should be taken as shortly means of the coils alone without up- it down securely with a few 'turns of and directly as possible to one end of setting the tuning. cotton. Bend up the ends of the the grid condenser, the other side of wire strands slightly and push the The construction of a receiver on the flex into the tube till the bared ends which should be soldered directly on to linesindicatedwillbe found well thegridterminalofthedetector justemergefromtheslot.The worth while; if signals are weak they scarfed end of the rod is then pushed valve.(The same remarks apply, of in from the other end of the tube as course, if high -frequency amplification PRIMARY is employed.) REArti far as itwill go' thus wedging the Thesecondarytuningcondenser ends of the flex.The assembly should mustbe of thevery best possible now be clamped in a vice to hold the quality, and the moving plates should, rod in the tube, and the slot filled up of course, be connected to the filament 1 with solder. Any superfluous solder and earth, or bad hand -capacity effects may then be 'filed off, when the joint will result. will be practically invisible. Reaction Difficulties Finishing The rod may be left straight as it Now, dealing with the reaction cir- is, or it may be bent round into the cuit, many difficulties are encountered. IN In the standard " three -coil tuner " SECONDARY shape of a hook, as shown in Fig. 2. SECONDARY(1) In either case a " flat " should be (Fig. 1), the great trouble is that when filed on the projecting part of the the degree of reaction is varied, the Fig. 3.-The coils of the Fig. 2 circuit rod,sincethiswill make it much coupling of the reaction coil has an should be arranged as shown here to easiertoclamp under aterminal effect not only upon the secondary cir- minimise unwanted coupling effects. head.Ifthehookismadewide cuit L2, C2, but also on the primary enough to pass over a 2B.A. terminal circuit. Thusthese three circuits can be amplified with the knowledge shank, it will also usually be possible really " interlock," and an alteration that they will still be intelligible, and in any one of them makes it necessary not swamped with interference from a FLAT FILED ONRoo to re -tune the other two.When the hundred sources. coupling of the reaction coil to the secondary coilis loosened, 'the wave- length of the secondary circuit drops ** * immediately, and a constant " fumb- (80(89,90Sa'gtN313SQ13. ling " with both hands is necessary. F/N/SHED TAG Fig. 2.-A flat filed on the finished tag A Remedy NEAT TAGS FOR will enable aterminal tosecure .a Thisdifficulty may be easily sur- FLEX LEADS better grip on it. mounted by " splitting " the 'secondary to use this form of tag with telephone coil into two portions,set at right f',4.150684,wr terminals, by passing the point of the angles to each other.The aerial coil flex leads are used, whether hook through the hole drilled in: the may then be coupled to one and the NVHENin the form of telephone cords, terminal body. reaction coil to the other.The varia- or as connections in a set, the ends An improved finish will be given to tions of coupling of the reaction coil of the flex quickly fray out with use the tag if the end of the tubing at will then not act inductively through if they are not finished , in some way. which ,the rod is inserted is bevelled the secondarycoil and primary cir- Neat tags which form a secure and off for a short distance. cuit.The circuit is now as shown in convenient method of connection to E. J. C. 225 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 LOUD -SPEAKER AND RECEIVER IN ONE By R. J. O'CONNELL There is much to be gained by building your loud -speaker into the receiver cabinet, especially where appearances and available space are considerations.No elaborate constructional work is involved in the design given here, and the attractive appearance of the completed receiver will be apparent from the photograph on this page. IN the United States of America it and this condition is fulfilled by a two - from the London station, and as the is quite common practice to build valve set, comprising a detector valve greatest possible purity was desired in the loud -speaker intoareceiver, without reaction and a singlelow - the reproduction of this station's pro- designed to operate normally with this frequency amplifying stage.There is grammes, a circuit was used consisting accessory. Forsomereasonthis in such a circuit only one control, the of a crystal detector followed by two system does not seem to have caught aerial tuning condenser, and once the resistance -capacity coupled valves; on in this country,and itisthe local station has been tuned in, the re- this gives really excellent results. writer'sintentiontoshowinthis ceiver may be turned on or off by a article the advantages of building re- suitable switch arranged in the fila- Cabinet Design ceivers on these lines. Modifications. ment battery circuit. Having decided on the circuit to be are obviously possible, but the arrange-. employed, the next step is the design ment shown should befoundquite At Greater Distances. of the receiver itself.If the cost- of satisfactory. the cabinet is tobe keptlow,the At a distance of more than 15 miles smallest efficient loud -speaker that can from the local station another valve be obtained should be used. will probably be required to bring the The cabinety whichcontainsthe signalsuptogood loud -speaker author's loud -speaker setis shown in strength.This additional valve may the photographs and drawings. Should be added as a low- or high -frequency the reader desire to construct a dupli- amplifier, and the function which the cate of this design, the following par- additional amplifier is to perform must ticulars are given. depend on the particular circumstances 6" of the case.It will usually be found Components Required best to add a high -frequency valve if For constructing theloud-spealier k 7" Fig. 1.-This gives the dimensions of the wooden panel carrying the loud- speaker. ca oa ca It would be very unusual to use a gramophone which had a horn several The loud -speaker feet away from the instrument.In isheldtothe the writer's opirlion itis just as in- panelby three convenienttouseawirelessset angle brackets. separated fromits loud -speakerby long leads.When a set is built in a cabinet which also contains the loud- *** speaker, these long leads are avoided and the whole general appearance of the receiving apparatus is improved. Suitable Circuits Of course this idea is applicable to any receiver which will operate a loud- speaker, but it is most Atseful when a set employed merely for local station the distance from the local station is part of the set the following parts are reception on the loud -speaker is to be more than 30 miles. By using an required:- used. A set of this type may be built aperiodic transformerforthe H.F. Onecabinet,specialtype,with from a number of simple circuits, and coupling, the controls of the receiver baseboard measuring 6 in.by 7in. some indication of suitable arrange- will not be increased in number. The by 17 in.(Pete -Scott Co., Ltd.) ments may be useful.It is desirable author's own receiver was designed for One hornless loud -speaker. (Ultra that the controls be few in number, use at a distance of about nine miles Elec. Co., Ltd.) 226 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR by means of bolts and nuts. The LOUD -SPEAKER AND RECEIVER board may now be screwed to the base- board and the construction of the set IN ONE ---concluded commenced. The Receiver One piece of polished wood, 7 in. by 6 in., having a circle of a diameter of Thereceivershouldbebuiltso 5 in. cut out of the centre.(Carring- that the first valve of the set is the ton Mfg. Co.) furthest from the loud -speaker and the Three small angle brackets, quantity last valve nearest to it.The variable condenserandallthecomponents of cotton wool, small bolts and nuts, should preferably be of types which and woodscrews. can readily be mounted on the base- board.The battery lead may be one of the multi -way battery leads now obtainable. A holeisdrilled in the back of the cabinet, through which leads pass out.The high-tension posi- tive lead isconnected direct to the negative terminal of the loud -speaker, 2Y/6' 7 411 and a lead from its positive terminal istakenouttothehigh-tension Fig. 2.-The three brackets may be made of strip brass from the details battery. Bove the shown. Conclusion When "the receiver part is finished Contruction it may be placed in the cabinet, after snow-line/ The construct&nal workisquite which thelast operation should be , simple and should be commenced by carried out.This consists in filling in $44i1 ..."iii, fixing' the loud -speaker to the small the space round the loud -speaker with board.First of, all place the screen cotton -wool, which should be lightly a face downwards over the hole cut in packed in between the loud -speaker, trA NKr- 44.;:Lif, this board, and nextfixthe lloud- the sides of the cabinet and the base- speaker in position by putting the board.This will minimise any slight small brackets over each of the three resonanceorjarringeffectswhich nuts and securing them to the board might otherwise be noticeable. Constancy, silenceand strength, planned to Nature's generous scale,thevery qualities which are essential ina small wire wound 0000000 0 0000000 is connected in the usual way to the anode resistance ifitis to achieve its object loud -speaker, the device would be used -purity of reception. A PLUG AND JACK (g4 in the following manner : -A repre- The Mullard EVER -REST Wire Wound Anode sents the tip of the plug, which, being Resistanceisconstantinvalue,silentin REFINEMENT operation, and possesses a degree of mechanical positive, should make connection to the strength which is unique, inasmuch as itit cti3 positive side of the loud -speaker via achieved withoit sacrificing efficiency or bulk. G'ef9gGc590gfdOcR413 43(g40g0c89 the connection tag A,, A2 representing A Resistance wound on a textile fibre core, B represents the sleeve of perfectly covered and interlopd with the same WHEN using a plug and jack in this lead. material eliminating all self c parity with this the plug, which providesconnection advantage :that thefinemetallic wireis conjunction with a loud- with the B, tag, lead B passing to the rendered absol:.tely free from every particle of speakeritis often necessary mechanicalshecx. The temperatureco- other side of the loud -speaker.The efficient is negligible, the resistance is not set to provide upon the actual receiver two in wax but sin -ply covered with a thin layer to additional terminals,as well as the allow perfect dissipation of heat. jack, in order to be^ able to connect A, up the telephones if necessary, either 2 ASK FOR THE RESISTANCE WHICH HAS togetherwiththe loud -speaker, or BEHIND IT ALL THAT IS BEHIND THE separately.Matters may ,be simplified, FINEST VALVE. as described in this article, by those Mullard EVER -REST Wire Wound who are fond, of small constructional Anode Resistance (80,000 aed jobs, by adding to the plug two small B2 100,000 ohms) .. 5' - terminals, as shown in the accompany- Complete with Holder 6'6 ing diagram. The drawing shows a 411,...Aora,v, Other Values to Specification. from plug ofthetypeobtainable Mullard Grid Leaks and Condensers : Messrs. Igranic, Ltd., but thoae of an Typo Grid B 0.5 to 5.0 megohms ..2/6 ingenious turn of mind will, no loubt, Type Grid 13 combined with .0003 mfd. A2 Condenser Type MA be able to adapt the idea to other types A, Type MA Condenser .0001 to .0009 mfd. 2,6 of plugs. Fig. 1.-The addition of the terminals Typo MB Condenser .001 to .01'firs]. 3r - It will be seen from the diagram Al and B.1 adds to the utility of the plug. thattwosmallholesare drilled through the ebonite side pieces of the plug inidentical positions with the positive side of the telephones is there- holes to be found in each of the con- fore connected to terminal A and the nection tags. These tags are then remaining side to terminal B,.The secured by means of two small termi- loud -speaker andtelephones may be nals, as will be seen in the drawing, used at one and the same time when the two halvesoftheplug being these connections are made, or the clamped together finally in the usual telephones may be disconnected, using manner. theloud -speakeronly,or the loud- speaker may be disconnected from the WIRE WOUND ANODE RESISTANCE The Device in Use instrument end, using the telephones Supposing that we have a jack only only. The MULLARD WIRELESS SERVICE Co., Ltd. upon the receiver and that the plug H. B. Mullard House, Denmark St., London, W.C.2 In replying to advertisers, please mention THE WIRELESSCONSTRUCTOR. 227 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 7/0 0 A 0 t . ' G 4. ' 0 IP iii. 0 'ts4 4 ) s // / / 0/az //,/' p4 rue a fl /awe/ ,rnahaamv/ .A=1E116 i11111 TRANSFORMERSINTO 228 In replying to advertisers, please mention THE WIRELESSCONSTRUCTOR. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR the reaction control to increase the becauseonce the positionsofthe A SELECTIVE THREE strength. When first searching for the various stations have been definitely various stations,itis permissible to logged it will be found possible to tune -concluded from page 187 allow the receiver to oscillate by in- in the stations required on the two creasing the reactioncontrol. The dials,utilising thereaction control carrier of the station may then be simply to maintain the receiver in a and for this purpose telephones should tuned in, and the reactionrotated sensitive condition. be connected across the output ter- back until the receiverisjust not minals. Now remove the fixed oscillating. resistorcontrollingthefirst(high - Wives frequency)valve. Signals will pro- The valves in use should be of the bably still be heardatfairlygood high -impedance typeforthehigh - strength.Retune the two tuning con- .frequency and detector valves, and a densersuntil the signalsare accu- suitable L.F. or power valve for the rately tuned in.Now screw down the laststage. Valvessuchas the neutralising condenser with the D.E.5B., P.M.5, P.M.3, 'P.M.1H.F., ebonite screwdriver supplied, until a B.4H., B.5H, :Cossor Point One H.F. position is obtained where the signals and similar types are suitable for the vanish.The locking nut should be firsttwo,whileany corresponding slackened off during this process, in power valve is satisfactory in the last order to enable the screw to travel to stage its fullest extent.When the correct position has been found the locking Results screw may be screwed down, and the The list ofstations showninthe condenser thus fixed in position. attached report gives some idea of the The actual minimum point will be settings for the various stations.It found to be fairly sharply defined, and was taken just after the change -over a little care should be exercised in this in wavelength occurred, so that a full operation to ensure that the receiver is C. and completetestreportwasnot correctly balanced.When this opera- Showing the connections to the H.F. deemed advisable in view of the pos- tion has been satisfactorily performed, transformer. siblealterationsbeforethisarticle the fixed resistor for the first valve appeared in print.The various read- may be replaced, and the receiver is Provided the receiver has been cor- ings, however, will serve to indicate ready for use. rectlyneutralisedaspreviouslyde- the approximate positions on the dials scribed, this operation will not cause .oftheprincipalstations,and the Tuning any interference, but at the same time actual settings of other stations may Tuning -inissimplya matterof need only be adopted during the pre- easily be logged after a little experi- rotating the two dials together, using liminary trying out of the receiver, ence has been obtained on the receiver. P-4 '-.10-41,-*-4-0--40-4,-.1--44-4,-----,-4-4.- :1111111iillillilliiiiiiiiiiiiiiiiiiiffitiiiiiiiinomminmiliiiniiimmiiiiimuilmliniou± EE THE HOUSE FOR REAL EE size .7g. this The F--- CHRISTMAS PRESENTS were hold E Are you preparing to give your friends a Jolly coilswould Moving Block EE If Christmas with yOur Wireless Set ? r L.-= iota§ = E lhetheinsecurey Cannot Fall If so these- components must appeal. The vernier movement = SPECIAL COILS wound with Litz Wire exact ---7, comprises threesets ,---- 'to " Wireless World " specification. of enclosed precision =---- f.- Mounted on Base, 32/6 the pair. machine -cut gears, L-17- and reduces the speed BRANDES Straight-line frequency C9ndensers of the moving block = -00o5 18/6 each. 0003 18/- each. by eight times. = ALL BLANK FORMERS and BASES Side plates, coil blocks ready and in stock for 1927 five -valve set. _. and knobs in artistic -g_ --f-: Patent No. bakelite mouldings. E AMPLIFEX LOOP. The only loop aerial adapted E- 244,251 All metal parts heavily = for the reception of all European Broadcasting. --.- nickel plated.Made 7.. Special Price, £3. -ff for left as well as right (Send for descriptive folder-free.) PRICES: hand. = - -f- VARLEY split H.F. choke, 12/6. Two Types: = EE For outside panel mounting: Two -a a 7/. Highest Grade Ebonite-Sheet, Rod and Tube- Three -ways 10/11 E always in stock and cut to your own size while .= For inside baseboard mount- you wait. =. ing, with 6 -in. handle: EH Two-way lorriurs .-Z; T OUR INTERNATIONAL RADIO CATALOGUE (3rd Three.way 12/8 VERNIER a Edition) Will be sent to all enthusiasts sending 64. to T. cover cost of postage and packing. Made by the makers of ..,.. the famous Lotus cOIL HOLDERS, Buoyancy Valve Holder. WILL DAY, Ltd. (Dept.13) ,_- -_-:. 19, LISLE STREET, LEICESTER SQUARE, E: GARNETT, WHITELEY & CO., LTD. LONDON, W.C.2. =_. Telephone: Telegrams: = Lotus Works, Broadgreen Rd., LiVerpool. =E Regent 4577. Titles, Westrand, LOndon. = fill11111111111110111111111111111111111i1111111101_001111Mliii111:111illliffilli11111111111111111111H1 hn replying to advertisers, please mention THE WIRELESS CONSTRUCTOR. 2'2.9 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 Igranic Gang Condensers. Igranic" XLLOS " Coils (Extra Low Loss). Igranic Gan g IIGRANIC Condensers are Igranic " XLLOS " fittedwithsmall Coils are wound Micro " Con- in a special method densers with ensuring v e r y which the sections high efficiency and can be accurately lowselfcapacity. balancedwithout Sealed Bakelite alteringthere- shell protects wind- lative settings. ings against damage The accurate for and atmospheric square law tuning changes, ensuring is thus preserved absolute constancy and the full tuning 1* in tuning.Spacing range is man- r of plug and socket talned.Each section .0005 mad. square law. eceivers variable from 9/16 in. Twin Gang ..£2 100 up to 2 in., with air space between. Triple Gang ..£3 150 Made in 10 sizes for wavelengths from 220 to 3,200 described Metres. PRICES:from 3/9 each. Igranic-Pacent Super " Audwformer.19 in this The Igranic-Pacen.t Super" Audiokrmer has a remarkable am- plification curve resulting in uniformity issue over a very wide range oftheaudiblefre- quencies. Massive iron circuits and unique coils result BUILD your receivers with inthereproduction being extremely pure Igranic Radio Devices and and uniform. T h robust construction assure yourself lasting and the care taken in Igranic-PacentS.L.F. satisfaction. itsmanufactureen- sure long trouble - Condensers. EveryIgraniccomponentis free service. Igranic-Pacent S.L.F. Condensers give true -straight- PR ICE 24/6. line -frequency tuning. The plates are of brass rivetted designed and manufactured with As used in the " Monodial." and soldered together, losses are neglible and minimum scrupulous care by highly -skilled capacity extremely low.Substantial dust -proof bearing ensures smooth, silky turning movement. engineers, and each component Igramc-Pacent PRICES :.00035 mfd. 14/6 .0005 ,, 1818 contains special features which Variable Resisters. make it unique. The Igranic- Parent Variable Here are some of the Igranic Resisters combine all the advantages components which you will need offixedresisters for receivers described inthis with the adjusta- bilityof a rheo- issue.Others are :- stats. The contact arm is easily ad- Igranic Coil Holders. justed so that any resistancewithin ipph reg Igranic Valve Holders. the range of the can he Igranic" on " and " off " Switches. resister 1111111111111X111111111111P obtainedquickly IgranicFixedCondensers and and easily. Grid Leaks. Made in resistances of 6,10, 20, 30 and 50 ohms. variable over the whole range. Igranic Terminals, Sockets, and PRICE .. 1/8 each. Wander Plugs. Igranic Filament Rheostats. IgranicMicro Condenser. Igranic Square Law Condensers, The Igranic Micro Condenser is a miniature condenser which is particularly suitable for neutrodyning and etc., etc. for all cases where extremely small capacity variations are required.Suitable for panel or baseboard mount- ing. The Bakelite cover protects the plates from dust ordamage. Maximumcapacityapproximately .00004 mfd. PRICE, with Knob .. 5/6 With it in.' Indigraph "Knob and Dial 6/6 I WRITE FOR THE Bracket for Baseboard Mounting ... 6d. I NEW IGRANIC Igranic " Indigraph " CATALOGUE LIST Vernier Knob and Dial. No. J. 180. Igranic Variometers. TheIgranic Indi- 1:: Igranic" B " and "BL" type Variometers are graphVernier Knob literally " wound on air." no solid supporting material andDialisavery being used on the windings. Losses are consequently handsome slow motion reduced to the minimum, whilst self capacity is also dial with an extremely extremely low. A very smallairspace smooth movement, separates rotor and stator windings so that entirelyfree from the variometers have a wide tuning range. backlash. Two scales A paxolin tube surrounds the windings as a providedreadingin IGRANIC ELECTRIC Co. Ltd. protective measure. opposite directions Igranic "13 " type Variometer, range 280-- from 0 to 100.Space 149, QUEEN VICTORIA ST., LONDON 650 metres. PRICE 12/6 isprovidedonthe WORKS, BEDFORD. dialfor recording Igranic "BL" type Variometer, range 700-- readings. 2,400 metres. PRICE 18/-. PRICE... 7/6 1 230 In replying to advertisers, please mention THE WIRELESS CONSTRUCTOR. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR A page of information of interesttoall constructors. ANYONE who has dismantled an old used electrically at all, the sleeve of meat of the other may cause over- receiver in order to use the parts the plug connecting with the upper running of the filament. for a more modern set will have met bent contact and the tip with the lower It should be noted that when valves with the difficulty of removing nuts one. High-tension positive, in this case, are used in this way it will be best to from terminal shanks to which connec- use separate grid -bias cellsfor each tions have been soldered.A certain valve, with theirpositiveterminals amount of solder usually remains in connected to the filament negative of the end threads of a terminal shank the valve concerned.This isadvis- when the connecting wire has been able since the filaments of the valves pulledoff,so that the nut becomes will be at different potentials relative fixed so tightly when an attempt is tothenegativeterminalofthe made to unscrew it that it has even- To ANODE accumulator. tually to be cut off, - Fig. I.-In the single open circuit jack A die of the correct size for the ter- the tip of the plug connects with the minal shank isinvaluableonsuch upper contact. who are converting their old occasions.With its aid the thread of THOSEreceivers with magnetic reaction the shank may be cleaned up in a few couplingto use circuitsof the moments, making the removal of the therefore, goes to the lower bent con- tact, though in most other jacksit " parallel feed " type with a variable nut a simple matter, and leaving the will be taken to the upper contact. condenser for reaction control would terminal as good as new. do well to note that the smooth action ofthiscontroldependsinlarge FOR those who like to study economy measure on the employment of a suit- HENEVER a length of threaded in battery current consumption able H.F. choke between the valve rod is to be cut, b great deal a point worth noting is that it is more anode andthe telephonesorL.F. of trouble in trimming up the cut end economical, where this is possible, to transformer. It may sometimes be will be saved if a die is first run on to connect valves in series rather than in necessary,forexample,toutilise the rod.After the cut has been made, parallel.Assuming that a 6 -volt accu- different chokes for the short- and either with a hacksaw or a pair of mulator is used, when 6 -volt valves are long -wave broadcasting stations. A wire -cutting pliers; the die is run off employed,theymustobviouslybe choke which is suitable for the lower again over the cut end, leaving a clean wired up in parallel in the ordinary band may come into resonance with thread for nuts to be put on. This way. When 2- or 3 -volt valves are in the grid tuned circuit on the longer does away with the filing of the end use, however, three of the former or waves,causinguncontrollableoscil- which would otherwise be necessary. two of the latter may beinseries lation. across the terminals of the accumula- tor.The current taken, from the accu- and jacks, as developed now- mulator is then that of one valve only. HOW manypeople, one wonders, PLUGSadays to perform quite a number Thismethod of connection is study the slip of paper which of switchingoperations,providea specially applicable to low -frequency manufacturers enclosewiththeir simple and attractive method of put- amplifiers,in which the valves con - valves? This sheet ordinarily gives ing the telephones or loud -speaker in full data about the correct filament, circuit, and possibly, too, of switching anode and grid voltages to use, and low -frequencyamplifyingvalvesin TO ANODE usuallyaseriesofcharacteristic and out of diircuit. Care should be curvesfor different anodevoltages. taken, in connecting up the jack con- The maximum filamentand anode tacts which connect with the telephone voltagesareusuallytobefound plug, -to see that the same side of the onthevalveitself,butthecor- plug, and therefore of the telephones, To H. r+ rectgridbiastousewith,for is always connectedtohigh-tension example,alow -frequencyamplify- positive. Fig 2.-The tip of the plug, in this ing valvecannot be given satisfac- Theconventionalpracticeisto double closed circuit jack, connects with torily except by, means of the curves. arrange for the tip of the plug to go the lower contact.The primary of an It is a good scheme to keep these valve always to H.T. positive, and the jacks L.F transformer may be cut in or out data with the set, so that the required should be wired accordingly. In Fig. 1, as indicated. informationisto hand whenitis for example, the tip of the plug makes wanted. If you increase the anode connectionwiththebentcontact nected inseries areall performing voltage on the last valve of your set, blade, while the sleeve connects with similar functions.It is not usually for instance, from 60 to 100 volts, you the body of the plug.Particular care satisfactory to use valves of the .06 can find out in a moment the correct is necessary to avoid confusion when a ampere type inthisway, however, amount of grid bias to add for good double circuit closed jack (Fig. 2)is since the effect of the anode current reproductionandeconomical opera- used.Here the body of the jack is not of one valve passing through the fila- tion. 231 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 Barretorsiaand Fixed Resistors arealready obsolete from the high initial cost Further, the no per cent,efficient APARTof these; it is ridiculous that you Fixed Resistor does notexist,and should be compelled to buy a new frequently you are heating your Fila- Resistor,atan averagecost of ments much beyond thenecessary 2/6,everytime you change your stageforcorrect emission, thereby Valve. shortening the life of your Valves. The IC ariableFixed Resistor is set to the correct resistance in a few After this they " stay put," and are operated moments, after which it functions like an by the pull -push switch like the ordinary ordinary Fixed Resistor, but-should you Fixed Resistor, or bythe" Microstat change your Valve, a slight turn either Master Rheostat, which gives even wider way of the V.F.R. concerned and yofi - range of control. Resistor isreset to suit that particular Best of all, the cost of 3/ Valve. the Microstat V.P.R. is an and this is "'stageoranyVilve and lasts firever Made and guaranteed by the Manufacturers of the World Famous " Microstat." LIFFORD ENGINEERING CO., LIFFORD LANE, King's Norton, BIRMINGHAM FullyCovered under Patents 21852and 26363/2'6. c.I "Woodwright" 232 In replying to advertisers, please mention THE WIRELESS CONSTRUCTOIC1 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR 10 DODCI El FrripmEmFlECIEEEEEEtEEDEEED000000EJEEEEEEEEEEEEESEOEDoanEl:11Li00CannEE 0El 0El 0 THE RADIO PLAY OF THE FUTURE El El By MADGE .TITHERADGE El Radio plays are something new in the history of the drama, and ordinary stagecraft is inadequate for the new conditions.Is there a future for the radio play ?What does broadcasting demand of the author and producer ?The views expressed by Miss Madge fl Titheradge on these and other questions that arise are of special ll interest at the present time, when there is a wide divergence of O opinion on the suitability of drama for broadcasting. El O O DUO-EEEEDEEE=EEEEFFIEEEE0000E0b00CJEEEDEEEE10E000EEEE00 is expressed, from any other form of actors.In direct contradistinction to art. The novel, where every action the writer of a screen scenario, he is important for the development of the writing a play in which everything theme can be described, every char- must be spoken and nothing seen.He acter painted with scrupulous detail, has no tradition of technique to guide every essential conversation recorded, hintlikehisfellow -craftsmanwho and every detail reproduced with the writes plays for the theatre. fidelity of a painting, is probably the most complete form of expression. Fresh Scope for Authors Next in completeness is the stage play, which is similar but more con- It will thereforeberealised that Miss Madge Titheradge. centrated, and limited by the writing for the radio " stage "will exigencies of the theatre and of time. havetobecomequiteaseparate The technique hereis more difficult branch of play -writing,and as the 11 is at once easy and amazingly diffi- than that involved in writing a novel, general opinion is in favour of a great cult to prophesy concerning what but at least the dramatist knows that future for radio drama, it seems only developments will take placein in presenting the play to the public reasonabletoanticipatethatvery the performance of plays by radio.It much of the character of his dramatis clever brains will be attracted to the iseasy because thereis no past to persona: can be suggested by make-up, task of writing it.Itis, of course, draw upon ; radio plays are an entirely facial gestures, costume, scenery, and foolish to suggest that radio plays can new branch of art, as yet almost un- all the other subsidiary arts which go ever take the place of the conven- ploited, and with a technique, too, as to the production of a good play.He tional theatre, for the two forms of yet hardly defined.The producer of may even have the satisfaction of see- entertainmentareutterlydifferent. wireless plays is still often in the dark as to the best way to " get over " a certain effect which he wants to make; he has an entirely new technique to learn, or, more correctly, perhaps, to create, for there is no one to guide * him, since ten years ago a broadcast * play was still unknown. studioThe Icene of in the the Prophecies London station For this reason it is easy to dogma- during the broad- tise about what might happen.There casting of a play is always a chance that one may be -"ThePassing right !But in view of the immense of the Third Floor potentialities latent in radio drama, it Back." is equally likely that the prophet may be quite wrong; that he will entirely 234. overlook some cleverinnovatorwho " . oaf might come along some day and intro- duce new notions of his own which will entirely revolutionise the present ideas of what a radio play should be; ideas which to a certain extent are ing his play immensely strengthened They can exist side by side and are by at present naturally an extension or by the personal charm and appeal, or no means mutually exclusive, as some a modification of those applying to the good acting of one actor or actress. have rather superficially supposed. production of plays on the legitimate stage. Difficulties What Does Radio Demand ? The author of the radio play is with- There are a few characteristics of A New Technique out any of these aids.He is writing the radio play which will survive, no That a new technique is necessary for a band of performers who will be matter what innovations areintro- is amply proved by the fact that a invisible to his audience.His action duced by the new race of radio play- radio play is different, by reason of the must either he suggested by effects in wrights.In the ideal radio play there limitation of the medium in which itthe studio or related by one of the will probably be but few characters, 233 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 was installed near a tram route on a THE RADIO PLAY OF THE FUTURE-continued very bad and low aerial ;it was poor, the local station being only just heard on the loud -speaker, but by adding another stage of L.F. the set worked because the audience have only one thingwhichisalready' lovedand satisfactorily, and has been in use for slender means ofidentifyingthem, familiar, it is also true that new and twelve months. e.g., by their voices.These characters unsuspected beauties reveal themselves My next was the " Melody Three " will have to be very clearly defined, at a second hearing. This type of (Modern Wireless, March, 1926), which and,asitwere," characteristic " stage play, written, of course, without gave splendid results, receiving Lon- characters; personalities which reveal the slightest intention in the world of don, Bournemouth and Cardiff on L.S. and suggest themselves by the words its ever being broadcast,isparticu- and many other B.B.C. stations on they say and their manner of saying larly suitable for radio purposes. ''phones from Southampton, also many them, so that the audience of listeners foreign stations on L.S. and 'phones. shall have no difficulty in identifying The Best Way - This setwasso good that I made each one as he or she speaks." The The man or woman who listens to another " Melody Three," and hoped Play's the Thing," is a very old but an unknown play broadcast may find toenteritintheWorld'sFair a very true dictum, and it is particu- at times that it is difficult to follow, if recentlyheldinNew York,but larly so of the broadcast play, where it is one which has not been written through a technical defect, which I specially for broadcasting.He misses had trouble in locating, I could not thevisiblespectacle,allthelittle get the set to work right, and when I actions on the stage which count for did locate the defect it was too late so much in the interpretation of the to enter my exhibit.I only had half piece. ' an hour to try out the set in New But he is in a supremely happy posi- York before Ireturned to England. tion if the broadcast play is one which Still, during that time I got in quite he has already seen performed on the a number of stations with very good stage, for then his memory supplies all selectivity and purity.This set I tried the blanks, and being already familiar at Southampton with splendid results. with the show, he is able to follow it The set is now installed at Liverpool. pleasurably and easily. The recent with, I believe, very good results in- broadcast of certain of the Gilbert and deed, -receiving many stations on L.S. Sullivanoperaswasanexcellent and 'phones. example of :this liking for the already My next and last set is the v Day - familiar, this pleasure of the known. low Three," which I tried out recently in New York (I am an engineer on A High Standard Needed s.s. Olympic). on an aerial consisting But in order to stand a second, third or fourth hearing a play must be very good of its kind, and it seems possible from this that next in popularity to plays specially written for broadcast performance by writers versed in its particular technique will be the classics At the Bodmin Beam Wireless Station, of the legitimate stage, from Shake- opened for communication with Canada. speare down to the more prominent This picture shows the standard wave - dramatists of the present day. Such meter. plays always merit a second hearing; the listener, aided by his memory of .there is perhaps less scope than on the performancesinthetheatre,will legitimate stageforoutstanding to " star "actors,and a very definite appreciate much that hefailed demand for competent acting and con- notice before. summate elocutionary powers. Incidentally, the cause of drama will benefit, for in spite of Charles Lamb's statement that plays lose by being per- Catering for all Listeners formed, there are thousands who would It is very difficult to theorise about not care to read a good play, but who the type of play which is most likely will be delighted to listen to it, and in to find favour. Certainly in considera- doing so open for themselvesfresh tion of the vastdiversityoftaste avenues of pleasure in life. among the millions of listeners great care will have to be taken to see that whatever is produced possesses as wide egtagoact ooe aDEmivgailggo an appeal as possible, whether itis Another view at the Bodmin Station drama, comedy, or farce.Here again RADIO PRESS SETS ' showing the aerial coupling cails the technique of the playwright will be taxed to the utmost. He will have to AT SEA c1 produce something which appears to of an ordinaryelectric 3/22 cable be true to life, and to produce this 000f3ggiggl3i3/3 hanging down the ship's side, with the effect under thelimitationsof the Sra,-Having built several radio sets ship as " earth."Seventeen stations broadcast performance must, I think, fromparticularsgivenin your were received, covering 263-492 metres. beextraordinarilydifficult. Great various publications,I thought you WEAF at 4 miles could be cut out in creditisdue tothose pioneers who might like to know the performance of 4 degrees on the dial.All who heard have already succeeded. same.First, I built two reflex sets, this set remarked upon its wonderful It is often said that " a play worth one of which was splendid on my selectivity and volume with purity.I seeing is worth seeing twice." Such aerial (which is a poor one, being in tested this set out against an American a statement is true of every worth- a valley, and badly shielded on three 5 -tube " Federal " set and an English while book or play, for apart from the sides by a tall building and trees, and set, " The Best That.Money can Buy " universal pleasure of recognising some- only 70 ft. total length).The other 4 -valve set, and could at any time pick 234 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR RADIO PRESS SETS AT SEA -continued NOW A Brandes CONDENSER STRAIGHT LINE FREQUENCYSLOW MOTION LOW LOSS. out more stations clear with no back- It will be obvious from the table given Motion Low Loss Condenser has been ground, and with far greater volume below of new B.B.C. wave -lengths, that a specially designed to provide a Straight Line andpurity. is" hair - Selectivity condenser in which the dial reading varies Frequency tuningcharacteristicandto fine." directly as the frequency will give a more bring in the B.B.C. Stations well spaced Through hearing thisset,several uniform separation of stations than one in out overthe major portion of the dial, friends are making same for them- which the dial reading varies directly as whilst, at the same time maintaining selves. thewave -length.Thisisparticularly thecompactformwhichisso Lately I have been working this set apparentin thelowerwave -lengths. veryessentialin a back of - panel on my aerial at Southampton, with Brandel Straight Line Frequency Slow instrument. the following good results:- Bournemouth.-Good L.S. strength on two valves; too much on three, all out. London.-ModerateL:S.strength on three valves. Madrid.-ModerateL.S.strength on three valves. Barcelona.-Moderate L.S. strength on three valves. The following table shows the new wave -lengths of the B.B.C. stations with their corresponding frequencies :- Call Sign. Station. Wane-leng'h. Frequzncy. 2BD Aberdeen 491.8 metres. 610 kc 5 IT Birmingham 5 SC Glasgow 405.4 0$ 740 2 ZY Manchester 384.6 780 2 LO London 361.4 830 ,, 5 \VA Cardiff 353 850 ,, 2 BE Belfast 326.1 920 5 NO Newcastle 312.5 6 BM Bournemouth 306.1 980 2 LS Leeds 297 1,010 Bradford 294.1 1,020 A new wireless station was recently Other Relays 288.5 1,040 opened by the Post Office at St. Albans. With this condenser a positive movement for approximate setting is obtained by turning The receiver of which the panel is seen the 4 in. diameter dial which is provided with finger grips for this purpose. The final here is used for high-speed automatic critical setting is obtained by turning the 21 in. knob which actuates the slow motion reception. mechanism. Low dielectric losses and the complete absence of backlash are ensured. Vienna.-ModerateL.S.strength PRICE :-0005...18/6 ;-0003 18/- on three valves. (From any good dealer.) Newcastle.-Quiet L.S. strength on three valves. Numerous Advantages :- Alsoseveralunidentifiedforeign 1. A handsome 4 in.dial engraved with clearly 9. The Slow Motion is transmitted to the moving marked divisions and provided with finger grip vanes through a carefully designed friction clutch stations on L.S. and 'phones. for the approximate setting of the condenser. by means of a train of wheels having a finely On the high wavelengths results are 2. The large knurled knob in. diameter operates knurled surface which ensures a very smooth poor at present.Daventry very weak the patent vernier mechanism for fine or critical reduction movement without jump or slip. on L.S., others just heard on 'phones. tuning. 10. Specially designed spring bearings keep the train 3. A minimum quantity of highest quality ebonite of wheels in intimate contact and by exerting a Shall try a differentcoil and H.F. ensures low dielectric losses. gentle pressure on all the moving parts entirely choke later on. 4. The single hole fixing bush has a knurled face to eliminate backlash. I hope soon to make the " Mono - ensure a firm grip on the panel. This condenser will provide a Straight -Line - 5. Ballbearingsfittingintocone -shapedraces Frequency tuning characteristic withthe dial "(Wireless,Vol. 5, No. 11) prevent shake and backlash. stations within the B.B.C. frequency range well spaced over the dial.The shape of the Moving I must thank you and your staff for 6. A pigtailflexibleconnectionensures perfect vane is designed to provide a small compact contact between the frame and the moving vane condenser having a straight -line -frequency tuning your most interesting publications and system. articles, which are so clear and helpful characteristic without taking up a large back -of - 7. Brass vanes and spacing collars chemically cleaned panelspace.Most otherS.L.F. Condensers to all interested in wireless work. ensure perfect contact. have a long, narrow vane with a very wide swing, Wishing the Radio Pressfuture 8. Conical bearings at base prevent shake and back- taking up a lot of valuable space at the bock of the success, lash. panel. Yours faithfully, BRANDES, Ltd., 296, Regent St., W.1. Works :Slough, Bucks. CECILJ.HARNETT. Southampton. Inreplying toadvertisers,please mention TnEWIRELESS CONSTRUCTOR. 235 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR. January, 1927 ...... 0000000000000000.0oo70000000=C -C -0<50450i,>000<>00...-^0 8 LISTEN TO AMERICA DIRECT A SINGLE -VALVE SHORT-WAVE SET By A. V. D. HORT, B.A. A simply constructed short-wave set, covering a wide range of wave -lengths, with which you may expect to hear the short:tvave American broadcasting stations and many other interesting transmissions. 00000C-C>Q00000.00000000.00000<>00000O00 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR The Championship Winner's Recommendation. MESSRS. S.T.,LTD., have received a letter (open to inspection at their Offices) from Mr. R. W. Emerson, the British Amateur who won, in the face of world-wide competition, the champion- ship at the International Exhibition at Amsterdam. This letter is of extreme interest to " The Wireless Constructor " readers, because it bears eloquent testimony to S.T. valves and further offers readers the opportunity of hearing them for themselves. You cannot do better than follow the advice of the world's leading amateur and use S.T.s in your Elstree Six, Solodyne, or other set. Extract from Mr. Emerson's Letter :- You will, no doubt, be interested to hear the results I have obtained with the new S.T. valves, which I immediately obtained on seeing the announcements. First of all I tried them in the actual Elstree Six with which I won the International Gold Medal at Amsterdam. Using S.T.61, S.T.62, S.T.63, In this order, I obtained with the set results considerably better than those given by other makes I had been using, and that is saying a great deal.I have since tried them in several other sets I have built, including the Solodyne with equal success, and I am frankly delighted with the results, and as the current consumption is so small they are extremely economical. They give really high amplification and are exceptionally pure in reproduction. My Elstree Six has created so much interest that I am having to give demonstrations to friends, etc., and I shall be happy to let anyone hear it working with S.T. valves if an appointment is made. 3, St. Ann's Terrace, R. WALDO EMERSON. St. John's Wood, N.W.S. 1 VALVE. 3 VALVES-continued. 5 VALVES-continued. 2 Volt. 4 Volt. 6 Volt. 2 Volt. 4 Volt. 6 Volt. 2 Volt.4 Volt. 6 Volt. ELF., detector,1 S.T. 21 S.T. 41 S.T. 61 2 H.F., detector,1 S.T. 21S.T. 41 S.T. 61 Detector 1 S.T. 22S.T. 41S.T. 61 L.F. (resist-2 8.T.21 S.T. 41 8.T.81 8.T. 62 2 L.F. (resist-2 S.T. 21S.T. 41 E42. 61 Dual valve and ance or choke)3 SN. 23S.T. 42 ance or choke3 S.T. 21S.T. 41 S.T. 61 crystal 1 S.T. 23S.T. 42S.T. 62 followed by4 S.T. 22S.T. 42S.T. 62 1 H.F. and de- 1 S.T. 21 S.T. 418.T.61 t r a n sformer), or tector 2 S.T. 21 B.T. 41 S.T. 61 e.g., Nighthawk S.T. 23 2 VALVES. 3- 83. 22B.T. 419.T. 61 5 S.T. 23S.T. 42S.T. 62 Or or Dual, detector,1 S.T. 23S.T. 42S.T. 62 S.T. 43S.T. 63 Detectorand L.P. 1 S.T. 22S.T. 41 S.T. 61 L.F. (e.g. 32 8.T. 22S.T. 41S.T. 81 (transformer) 2 S.T. 23S.T. 42S.T. 62 Valve Dual) 3 S.T. 23S.T. 42S.T. 62 2 H.F., detector,1 S.T. 21 S.T. 41 S.T. 61 or S.T.43or 8.T.63 2 L.F. (tram-2 S.T. 21S.T. 41 S.T. 61 Detector and L.F. 1 S.T. 21S.T. 41 S.T. 61 former fol-3 S.T. 22S.T. 41 S.T. 61 or2 S.T. 23S.T. 42S.T. 62 H.F., dualand1 S.T. 21S.T. 41 S.T. 61 lowed by esist-4 S.T. 22S.T. 41 S.T. 61 c(resishoke)tance detector(e.g.,2 S.T. 23S.T. 428.T.62 ance or choke) or or BlewIlex) or S.T.43or S.T.63 e.g. Special Five S.T. 42S.T. 62 H.F. and detector1 S.T. 21 S.T. 41 S.T. 61 3 S.T. 22S.T. 41 S.T. 61 5 S.T. 23S.T. 42S.T. 62 2 S.T. 22S.T. 41 S.T. 61 4 VALVES or or 8.T.43 S.T. 63 Dual, crystal and H.F. detector, 21 S.T. 21 S.T. 41S.T. 61 L.F. (e.g.S.T. 1 8.T. 23S.T. 429.T. 62 L.F. (trans-2 S.T. 22 S.T. 41S.T. 61 2 H.F., detector,1 8.T. 21S.T. 41 S.T. 61 100, Elstrefiex,2 S.T. 23S.T. 42S.T. 62 former)' e.g.,3 S.T. 22S.T. 428.T. 62 2 L.F. (two re-2 S.T. 21 S.T. 41 S.T. 61 etc.) Monodial,Four-4 S.T. 23 S.T. 42S.T. 62 sistances,two3 8.T.21 S.T. 41 S.T. 61 valve Family . or S.T.43or S.T.63 chokes or one4 S.T. 22S.T. 41 S.T. 61 Dual and detec-1 S.T. 23S.T. 42S.T. 62 of each either or or or tor (e.g.twin2 S.T. 228.T.41S.T. 61 H.F., detector, 21 S.T. 21 S.T. 41S.T. 61 way round) S.T. 21 S.T. 42S.T. 62 valve) L.F. (r esist-2 S.T. 21 S.T. 41S.T. 61 5S.T. 23 S.T. 42S.T. 62 anceor choke3 S.T. 22 S.T. 42S.T. 62 Or or Two duals and1 S.T. 23B.T. 42 S.T. 82 followed by4S.T. 23S.T. 42S.T. 62 S.T. 43S.T. 63 crystal (e.g. or or transformer) or or Distalle x) S.T. 43S.T. 83 (but inEvery- 8.T. 43B.T. 63 6. VALVES 2 S.T. 23S.T. 42 S.T. 62 or or man Fourthe S.T. 43S.T. 63 3rd valve should i H.F., detector,1 8.T. 21S.T. 41 S.T. 61 be same as 2nd) 2 L.F. (tram-2 S.T. 21 S.T. 41 S.T. 61 former) grid3 S.T. 21 S.T. 41 SN. 61 H.F., detector, 21 S.T. 21 S.T. 41 S.T. 61 rectification 4 8.T. 22 S.T. 41 S.T. 61 3 VALVES. L.F. (trans-2B.T. 22 S.T. 41S.T. 61 e.g.,All British5 S.T. 22S.T. 4282. 62 former fol-8 S.T. 228.T.42S.T. 62 Six Or Detector & 2 L.F.1 S.T. 22S.T. 41 82. 61 lowed byre- or or or S.T. 23 (both trans.) 2 S.T. 22S.T. 42S.T. 62 aist a nc e or S.T. 21 S.T. 41S.T. 61 6 S.T. 23S.T. 43S.T. 63 3 S.T. 23S.T. 42S.T. 62 choke) 4S.T.238.T.42S.T.62 Or Or or or or S.T.43or 8.T.68 S.T. 42S.T. 62 S.T. 43S.T. 83 2 H.F., detector,1 S.T. 21B.T. 41 S.T. 61 3 H.F., detector,1 S.T. 21.S.T. 41 S.T. 61 Detector and L.F.1 S.T. 21 S.T. 41 S.T. 61 L.F. (trans-2S.T. 21 B.T. 41 8.T. 61 2 L.F. (trans-2 53.21 S.T. 41 S.T. 61 (choke or resis-2 S.T. 22S.T. 42S.T. 82 former) 3 S.T. 22S.T. 41S.T. 61 former) anode3 8.T.21 S.T. 41 S.T. 61 tance followed3 S.T. 23S.T. 42S.T. 62 48.T. 23S.T. 42S.T. 62 bend rectifica-4 S.T. 238.T.42S.T. 62 by transformer) or or t 1 o n,e. g.,5 S.T. 23 S.T. 42S.T. 62 S.T. 43S.T. 63 2 H.F., detector, 1 S.T. 21 S.T. 41S.T. 61 Elstree Six 6 S.T. 23S.T. 43 S.T. 63 L.F. (resistance2 S.T. 21 S.T. 41 S.T. 61 Or or Detector & 2 L.F.1 S.T. 21 S.T. 41 S.T. 61 or choke) 3 8.T. 21 8.T. 41S.T. 61 S.T. 42 S.T. 62 (two resistances2 S.T. 2183. 41S.T. 61 4 S.T. 23S.T. 42S.T. 62 or two chokes)3 S.T. 238.T. 42S.T. 82 5 VALVES. B H.P., detector,1 S.T. 21 S.T. 41 S.T. 61 o Or 2 L.F. (resist-2 S.T. 21 S.T. 41S.T. 61 S 2.r 43B.T. 63 2 H.F., detector, 1 B.T. 21 S.T. 41 S.T. 61 ance or choke3 S.T. 21 S.T. 41S.T. 81 2 L.F.(trans-2 8.T. 21 B.T. 41 B.T. 81 followed by4 S.T. 21 S.T. 41S.T. 61 H.F., detector, 1 S.T. 21 S.T. 41 S.T. 81 former), e.g.,8 8.T.22 S.T. 41S.T. 61 t r a nsf ormer),5 S.T. 22S.T. 42S.T. 62 L.F. (trans-2 S.T. 22S.T. 41 S.T. 61 Bo lo d yne ,4S.T. 22S.T. 42S.T. 62 grid or anode or former),e.g. 3 S.T. 23S.T. 42S.T. 62 Magic Five, or rectification 8.T.23 Spanspace Three. 1927 Five. S.T.23 6 S.T. 23S.T. 43S.T. 63 AllConcert. 5 S.T. 238.T. 42S.T. 62 Or Or Simplicity Three or 8.2.43or S.T.61 S.T. 42 S.T. 62 If you are unable to obtain an S.T. valve from your local retai write direct to us or call.All valves will be sent by post and insure by us against breakage.C.O.D. orders executed on receipt of post -card. See also vases 182 and 221. S.T. LTD., 2, Melbourne Place, Aldwych, LONDON, W.C.2. (Next to Australia House.) In replying to advertisers, please mention THE WIRELESS CONSTRUCTOR. 237 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 In two sizes : '0903 mfds. ... 14/6 '0005 mfds. ... 15/6 Vernier Dial as illustrated 4/6 extra. Is there anything so absurd -under thenew Geneva planthe ordinary Condenser covers 39 Wavelengths between 0 and 10 on the dial, but only 2 wavelengths between 90° and 100°. WITH Jazz Bands and Grand Opera no more, no less.From end to end of the almost inextricably intermixed in an dial therefore 100 wavelengths each of 10 overcrowded ether no wonder the new kilocycles separation are covered. Geneva wavelength plan was necessary ! But compare this new standard of perform- What is this plan and how does it affect ance with the ordinary condenser.From you? 0 to 10-bearing in mind of course, that all Briefly, the Geneva plan is to apportion a other conditions are unaltered-the ordinary share of the ether to all countries wishing condenser covers 39 wavelengths.Practi- to Broadcast. Not every country can obtain cally 4 wavelengths to every degree on the as many wavelengths asit dial, while atthe opposite requires.Great Britain end of the scale the last ten receives nine exclusive wave- The Eureka degrees will barely span 2 lengths. But-and here is the wavelengths. great point to bear in mind- gives you real How absurd !Such a jostling there is to be a separation of selectivity of stations just where we need 10 kilocycles between each the most effective separation. wavelength. Not 10 metres The new conditions of Broad- but10kilocycles. Metres have been casting demand the use of a Eureka Ortho- ignored in these calculations.The Eureka cyclic with its even separation, step by Condenser also abandons metres and deals step, all the way up the scale. with kilocycles. It gives orthocyclic tuning. Instal these magnificent Condensers on your Set now and enjoy realselectivity. The velvety smooth That is to say, it gives an even separation Vernier dial-all metal and therefore a perfect shield- between wavelengths no matter where they is a pleasure to use.Because gears are eliminated, may appear on the dial-crowding is impos- backlash is impossible, while the superb workman, ship of the whole instrument will improve the sible.With the Eura Orthocyclic 10 appearance of any Receiver.Order them from your degrees cover 10 wavelengths_ precisely- Dealer without delay. ETZMA CONDENSER. 238 Adv!. Portable Utilities Co. Ltd. Fisher Strut, 11" Gilbert Ad. 6325. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR Listen to America Direct-continued Lions to it.The reaction condenser, one end of the grid condenser,the laying the panel face downward, drill C must be ofsoundconstruction, latter component being so placed that theholesfortheanglebrackets since contact between its plates will one ofitssoldering tags maybe through the holesinthebrackets themselves.In the set illustrated on A these pages these holes were tapped out, 4 B.A. and cheese -headed bolts inserted from the back. Clearance holes may be drilled if preferred, and bolts countersunk in the panel used, with nuts at the back of the panel to hold it to the brackets. External Connections The condensers may nobe mounted on the panel, and the wiring carried out.For low-tensionpositive,low- tension negative, high-tension positive, Fig. 2.-The holes and high-tension negative,theter- requiredinthe minals on appropriate components are used.For the aerial and earth, two panel are few in terminals are required, mounted on number. Blue- a small piece of ebonite attached to print No. C1076A. the baseboard. Operation The flexibleleads required for the battery connections will be noted in the wiring diagram and wiringin- structions. When the set is complete, *** a valve, preferably of the high -im- pedance type, should be inserted in the holder, the L.T. leads connected to the accumulator, and the rheostat set /11 to the correct position for the valve used.About 40 to 60 volts H.T. may le be pluggedin, after testing in the 8" sl usual way to see that the wiring is obviouslyresultinshort-circuiting secured direct to the grid terminal correct,and that the H.T. isnot thehigh-tensionbattery. Ifany of the valve holder. across the valve filament. troubleis experienced here, such as The 6 -turncoil may beplaced in noises owing to dust on the plates, Mounting the H.F. Choke the aerial position,with the 9 -turn a fixed condenser of about .001 capa- The H.F. choke is fixed by means city may be placed in series with the of a 4 B.A. countersunk screw passed variable. through the baseboard from below. Before this component is fastened in Components position, it will be as well to solder The list of components required for a short length of connecting wire to building the set will be found in the itslowercontact,asthis becomes accompanying table.It will be noticed rather awkward to reach with the sol- thatnocabinet is includedin dering iron when the choke is screwed thislist.Constructors may obtain down. a cabinet for the set if they desire Fixing the Panel to do so, but it is recommended that When thebaseboardcomponents the set be used normally without one. havebeenmounted,thenecessary Apart from the fact that the presence of the wood in close proximity to the coils might detract somewhat from the performance of the set,it would not *** be so easy to move the coils or to ad- The flexible leads just the coil tapping clips inside a tothebatteries cabinet when altering or adjusting the should not be wavelength ranges. made longer than is necessary. Construction The construotion of the set is not*** adifficultmatter. The baseboard components should be mounted first, including the angle brackets which holes should be drilled in the panel and 12 -turncoilsinseriesin the support the panel.Three bushes are forthe tuningandreactioncon- other sockets.Place the grid (1) and provided by the makers of the coils densers, the telephone terminals, and' reaction condenser(3)clips on the to hold the coil plug strip away from alsoforthe wood -screwsalongits end turns of the resulting 21 -turn coil the baseboard.One of the screws bottom edge.Before fixing the con- and the earth clip(2)at the inner holding the valve holder to the base-- densers, attach the panel to the base- end of the 9 -turn portion. With re- board passes also through the hole at board with three screws, and then, action at zero. set the tuning con- 239 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 LISTEN TO AMERICA DIRECT -continued. denser toabout the middle ofits scale.Then slowly increase the reac- tion condenser, when about one-third of the way round its scale oscillation will commence. Adjustments . If this is in order, rotate the tuning SCREEN condenser overitswhole scale,and see that oscillation can be obtained WIRING IN WORDS. All directions are given as viewing the set from the back. Join Aerial terminal to first socket at right end of coil mount. Join anode contact of valve holder to moving vanes of variable condenser C2, and to lower end of R.F. choke. Join top end of EX.' choke to one telephone terminal. Join a flex lead to the other telephone terminal, and attach a battery wander plug to its free end for connection to H.T. +. Join one filament contact of valve holder to one terminal of filament rheostat Ri, to Earth terminal, to moving vanes and screen of vari- able condenser C1, and to second socket from right end of coil mount. Join two flex leads to remaining terminal of R1, attaching a battery wander plug to one fOr connection to H.T. -, the other being for connection to L.T. +. Join a flex .lead to the remaining filament PHONES contact of valve holder, for connection to Join grid contact of valve holder to one side of fixed condenser C3 and leak Es. Join other side of C3 and 112 to fixed vanes of Ca. Join flex leads with clips to the following points : -(1) Side of C3 and R.2 Which is eon- . meted to Cl;(21 Earth terminal, and (3) Fixed vanes of C2. At every point. Ifthere are any " dead spots," that is to say, points at which the set refuses to oscillate, ro H7:- this can usuallybe putrightby changing the aerial coil and inserting the smaller one.For the best signal strength, however, when dead spots are not troublesome, the larger size of coil should be used. When a station has been located on the tuning condenser, an improvement in signal strength can be effected by L.T. moving the earth cliptowardsthe reaction clip end of the coil. The 4- L.T. setting of the tuning condenser will then be decreased, while the reaction BASEBOARD settingwillneed tobeincreased 9", r 8"x3/e" slightly. Some Results When the receiver was first tested, forexample, KDKA onabout60 metres was tuned in with the grid and 0 reaction clips in the positionsgiven len above, and the earth clip at seven turnsfrom thereactionclipend. ®11 @0®00I0 010 Shifting the earthclip three turns towards the reaction clip produced a noticeableimprovementin signal strength, the words of the announcer being quiteclearandundistorted. This was during the KDKA " Dinner Hour Programme," whichistrans- mitted between 11.15 p.m. and mid- night, G.M.T. Thereactioncontrolshouldact smoothly for the best results, no click Fig. 3. --The layout is quite straightforward and ample room is allowed being produced as the set goes in and for the components. Blueprint No. C1076B. (Concludedon page 279.) 21P PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR SETS THAT YOU CAN BUILD egMgge@VMEgEg.''EDaQ A,* Afterwards ashortprogramme of stations heard onthe set,between r".1 .4t music followed,including syncopated, approximately 38 and 50 metres.-En.1 " AUSTRALIA ON TWO (g4 songs and dance music.The Station finally closed down at 22.59 hrs. B.S.T., VALVES " 6g3 the announcer'sconcludingremarks ** being: " We are now closing down. It eeseeeezeeeezzezee'Se SIR,-I have constructed the two- is now 4.59p.m.Eastern Standard valve short-wave receiver (" Australia SIR,-With reference to your request Time.Good afternoon, everybody." on Two Valves ") described by Percy for reports of American transmissions All announcing and the items were W. Harris, M.I.R.E., in the August on the " Australia on Two Valves " perfectly clear (crystal strength), but WIRELESS CONSTRUCTOR. You may be set,describedby Percy W. Harris, subject to a small amount of fading. glad to hear the results. M.I.R.E., in the August issue of THE Nailsworth, Glos., The coils,by the way, are home- WIRELESS CONSTRUCTOR, I beg to re- September 28, 1926. made, being self-supporting, of No. 14 port that the American Station WGY P.S.-My " stud " of sets includes S.W.G. bare copper wire. was logged last evening at 22.40 hrs. the" Midget," one of your crystal Amateur Morse stations come B.S.T.I enclose a detailed report.I sets, and one of your L.F. amplifiers. tumblinginfromallquarters- made the set as specified by you with Brazil, France, Germany, Italy, the exception that a different H.F. *** U.S.A.,and,notleast,two Aus- choke was used from the one specified; tralians. I have had it in use some four weeks SIR,-I have constructed the " Aus- The " star " performancewason now.The only difficulty experienced tralia on Two Valves " set as given in October 3.At 12.30 a.m. (Summer was with the reaction, which would the August issue of THE WIRELESS Time)I heard thestation2XAF, Schenectady, commence their evening's programme.The wavelength as an- nounced was 32.79 metres.The whole of the programme, until the station closed down at 2.40 a.m., was heard perfectly. At 2.40 the announcer gave out that the station was closing down 'until the time signal at 9.30 Eastern Standard Time. 2XAF joined with Stations WGY, WFBL, WHAM, etc.,for a relayed programme from Buffalo Theatre. A special time signal (at 7.12 E.S.T.) in connectionwithanexpeditionin Brazil was also broadcast. My aerial is a standard PMG, 40 ft. high at the free end.The earth is a buried plate.There was very little fading,and atmospherics were not The "Australia on Two Valves" short-wave iwt, described in the troublesome. August issue of " The Wireless Constructor." Yours faithfully, E. R. WESTLAKE. " plop " ;but this has been cured by CONSTRUCTOR, with a few alterations Shrewsbury. using a 4-megohm grid leak, instead of in components used.My short-wave the 2-megohm, so that the reaction is coils are home-made, and all three coils FiD063)0@rg613 "063,000RE3R%00 delightfully smooth. are made up the same way with large Some more articles in your various gauge wire.I understand that you E§ THE " SCREENED COIL periodicals on the short waves would, are anxious to have reports on this set. 21. I am sure, be very well received. I have not heard, KDKA, perhaps on SINGLE -VALVE " SET Thanking you for your past courte- account of my not having the correct sies, also for many happy and instruc- size coils in use. GOOeeeeeee-,teeeee e tive hours. My aerialisa standard 100ft., SIR,-May I be allowed to express Yours faithfully, 35 ft. high, and earth a copper sheet my appreciation of the " Screened -Coil N. JONES. about 2 ft. 6 ins. by 2 ft., sunk about Single -Valve " Set, described by Mr. The reception from WGY was as fol- 5 ft.in the ground. I am using a W. H. Fuller in the September WIRE- lows :--September 27, 1926.22.40 hrs. BTH power valve B4 for detector, and LESS CONSTRUCTOR? I should like to B.S.T. Aerial -40ft. twin, 30ft. a Marconi DE8LF for amplifier. see still more sets employing screened high.Earth-buried sheetofzinc, I must say itis a very interesting coils,fortheselectivity.obtainable with 25 ft. of wire. little set, especially to those who are from this single -valve receiver is really The Station was tuned inat the well up in Morse. astounding.Although I am within a. exact moment that the announcer was Wishing THE WIRELESS CONITRUC- mile or so of the Birmingham station, opening the programme. He stated TOR every success. I very seldom employ the wave -trap at that they were about to broadcast a Yours faithfully, all. I have received nearly thirty special programme for the benefit of stations already. Britishlirteners,toenablethem E. W. H. HELPS. ifurs faithfully, (WGY) to receive reports.Then fol- Bath. K. C. BARRER. lowed the wavelength,32.79metres. [Our correspondent sends a list of 35 Birmingham. " 241 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE W3RELESS CONSTRUCTOR January, 1927 PHILIPS H.T. SUPPLY PHILIPS RECTIFIER UNIT TYPE 450. Gives from 20 to 160 volts approximately. Charges radio batteries from 2-6 volts at r3 Ensures a supply of current to work any set amps. consuming 3o watts. A full wave valve efficiently using standard types of valves. rectifier using the specially con stru cted Philips Consumption is approximately 5-ro watts. Rectifier Valve and Resistance Lamp which Output variable from 2 tappings.Safe and automatically regulates the current supply. silent in use. Price complete £7 : 10 : 0 Needs no attention. Price complete £4 : 0 : 0 Both Units for Alternating Current. TWO PHILIPS PRODUCTS VERY SUITABLE FOR XMAS PRESENTS Ask your dealer to demonstrate. Advt. Philips Lamps Ltd., Philips House, x45, Charing Cross Road, London, W.C.2. 242 to replying to advertisers, please mention THE WIRELESS CONSTRUCTOR. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor ;January, 1927 THE WIRELESS CONSTRUCTOR Cakulating Fixed Resistors-Dangers of Excessive H.T.- Using a SupertPower Valve. recommendation of a rather elaborate ODERNpractice istending which shouldbe stronglyimpressed ...more and more in the direc- uponall new users of these types. procedure constitutea strong argu- ..tiou, of the use of interchange- With these valves itis really impos- ment, in favour ofa properly -calcu- ablefixedresistorsfor the filament sibleto usetherough-and-ready,lated fixed resistor? controlof valves,and whileitis method of judging by eye when the., beyond questionthatthismethod correct filament temperature has been Excessive H.T. possesses great advantages in the way reached. A very strict rule should Another valve point- over which I of compact lay -out and exact con- therefore be made never to use these myself have gone wrong in the past trol, it involves certain difficulties in valves with an accumulator of much and which may be a stumbling -block such cases as the working of two- and highervoltagethanthefilament to others concerns. the amount of H.T. six -volt valves in the same set which ratingwitha variablefilament which it is safe to apply the ordinary require consideration. rheostatunlesssomedefinitepre- typeofsmallpowervalve. The caution can be taken tolessen the makers of these valves usually specify Easily Solved risk of overrunning. a maximum value of 120 volts, but it The difficultyis not a serious one, isa. temptation to use rather more at and once the user has worked out the Dangerous times when one is trying to make a solution for himselfthe matter For example, to run an " invisible " valve ofthis type do duty for one becomes very simple, with a. pleasing type of filament rated at 2 volts or capable of handling a bigger output. degree of exactitude of control which even 3.8 volts from a 6 -volt battery is a real safeguard to the newer types withavariable resistanceandno of " invisible glow "dull -emitters. means of checking the voltage applied Caution Needed The amount of arithmetic involved tothevalveissimplyasking for No doubt the figure given by the is slight,since the calculation solely trouble.If a variable rheostat must, makers is one which allows a reason- concerns the current through and the be used in such a case, probably the able margin of safety, and it can be voltage drop across the fixed resistor. safest course to adopt isto buy or exceeded in moderation,especially for The first step isto find the voltage borrow a reasonably good voltmeter, short periods, Without harm, but the whichmust he dropped acrossthe resistor to bring the supply (Sewn to the correct' voltage across the valve filament.To do this, simply subtract the rated voltage of the valve from the voltage of the accumulator; thus, ** a two -volt valve used with a six -volt accumulator gives a drop of few volts The studio at the across the resistor, and the next -pro- 3L0, Melbourne, ceeding is to find the value of resist- Station isattrac- ance which will pass the desired cur- tively furnished, as rent whenfourvoltsareapplied this photograph across it. shows. How to Calculate It Ohm's law wild serve our purpose, and we require to use the fdrm which `da ea * states that the resistance is equal to the voltage divided by the current. In the case considered the filament current may be, say, a tenth of an ampere.Dividing four by one -tenth connect it directly across the filament use of high voltages for any length of we obtain forty ohms for the value of terminals of the Ntalve socketitself, time may easily resultin a spoiled the necessary fixed resistor, and the and then turn up the rheostat care-'valve.Thereforeitis evident that same process will give us the required fully until the meter shows just the the only safe way of handling a large information for each valve in the set. figure recommended by the 'makers of output correctly is to use one of the the valve and nomore. Note the larger types of power valve with a "Invisible Glow " Valves exact setting of the rheostat, and he sufficiently long availablecurvefor Mention of " invisible glow " valves careful never to exceed this value in the variations of grid voltage which reminds me that there Is a warning future.Incidentally,does not this are applied to it. 249 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 THINGS EVERY OPERATOR SHOULD KNOW Christmas Bargains -continued from page 243 forConstructors IF you propose building your own Set for Christmas, time Is now an important factor.The famous Super -Power Valves Pilot" schemefor assisting home constructors will save you much time, because you can obtain all the When these newer types of super- components you require in one parcel from us and as we supply panels already drilled so that everything fits snugly power valves are used, however, there into position. the actual assembly can be finished exceed- are again pitfalls for the novice, and ingly quickly. Most important of all, however, the " Pilot " service, under the direct control of one of the best known some hints may perhaps behelpful. Radio experts, definitely Inthefirstplace, theusermust GUARANTEES radically revise his ideas of grid bias YOU GOOD RESULTS andits magnitude,for these valves Here is a short selection from our very wide range of Sets, which we know from actual experience are absolutely Panelalizs: No. 5. reluire a very much larger amount to reliable :- bringtheiranode current down to THE "ALL -BRITISH SIX." reasonable proportions and to make fa.d. full use of the virtues of this type. Complete set of parts .. 20 3 6 Here isa Panel Red Triangle" Polished Panel, drilled. 0 156 Actually, something in the neighbour- Polished Mahogany Cabinet .. 33 0 hood of 20voltswillgenerallybe that will not split needed when working with the maxi- THE "SOLODYNE." Complete set of parts .. 13 17 0 mum permissible H.T. voltage. Red Triangle" Polished Panel, drilled 0 11 6 or break or crack Polished Mahogany Cabinet .. 45 0 DO you know how itfeels to split A Heavy Load THE "MONODIAL FOUR." your panel just when you have Complete set of parts .. 1073 Even then the anode current is still Red Triangle " Polished Panel, drilled .. 08 0 almost completed your drilling? No, fairly large, and it is really not satis- Polished Mahogany Cabinet .. 2 50 you don't-if your choice fell on Resiston. THE " SPANSPACE THREE," For ResistonPanels(likeRadion)are factory, in my experience, to attempt to use these valves with anything but Complete set of parts .. 6 150 made throughout from nothing but pure " Red Triangle " Polished Panel, drilled .. 0 100 rubber. Because of this they are tough the larger -sized H.T. batteries.I am Polished Mahogany Cabinet .. 1 10 0 yet not brittle.They are strong.They at present using one of them with the "PILOT "H.F. and DETECTOR SET. will not break.Or split.Or crack.They maximum H.T. voltagewhich seems THOUSANDS SOLD! can be sawn with ease and with safety. safe, and the anode current is 14 milli - Complete set of parts .. 1 169 They can bedrilledwithoutdifficulty amps. " Red Triangle" Panel drilled and engraved.. 0 8 6 and, when tapped, will take a good thread. Probably this is a little more than Polished Mahogany Cabinet .. 1 1 0 Thus, when the home constructor buys a isnecessary, but it gives an idea of "PILOT " TWO -VALVE AMPLIFIER FOR ABOVE. £ a. d. Radion or Resiston Panel, in one of its 17 the sort of demand which the H.T. Complete set of parts .. .. 2 183 sizes, he knows that even though he is not battery must be prepared to meet, and " Red Triangle " Panel, drilled and engraved 06 6 quite an expert with the drill or the saw, itis evident, when the consumption Polished Mahogany Cabinet .. 0 176 IIThisis a splendid opportunity for acquiring he isin very little danger of ruining his of the rest of the set is remembered, either a Two -Valve Set or a Four -Valve Com- panel. Itsveryconstitutionfacilitates thattheordinarysmall -cellH.T. bination capable of tuning in many Continental easy working. battery wouldbeseriouslyover- Stations in addition to B.B.C. ones. If, in the past, Your experience of ebonite worked. Personally,Ialwaysuse has been discouraging you'll appreciate the H.T. accumulators for such work. THIS MONTH'S SETS. We can supply all the parts for the following sets described worth of Resiston.Its perfect insulation. in this issue :- Its superfine surface (which no hand has " All Round Europe with Plug-in Coils." touched sinceitleftthefactory)..Its %00000000e0000EPOOVA " A Three -Valve Set " by Mr. J. H. Reyner. colour permanence and its strength. " Economical Two." "Short Wave Single Valve Set," For the sake, perhaps, of a few pence, will O A READER BUILDS 0 " Multiple Circuit Crystal Set." you court failure and disappointment by OTHE SPANSPACE THREE'0 Here again " Pilot " Service will help you to build these choosing an unnamed panel in preference to Sets satisfactorily in time for the Christmas Holidays. one bearing such a name as Radion or ANY PART OR PARTS SUPPLIED Resistion-names which give you positive sE?9cE300cD&C9ZOOZ(8300Z00 assurance of lasting satisfaction? SEPARATELY. Sin,-I am writing to thank you for DETAILED LISTS ON APPLICATION. the design of " The Spanspace Three " Send for the Radion Book dur If acompletekitofcomponents Isordered, Marconi in the November issue of THE WIRE- .3j Royalties amounting to 12/6d. per valve holder are payable, In its twenty-four fully illustrated pages are LESS CONSTRUCTOR. Since the publica- tion of your " Star " programmeI Send three penny stampsfor detailsforbuilding four unique Receivers the new edition of the " Pilot togetherwith many useful have wanted to try my hand at one Manual,"Fully illustrated, it wireless hints Book,' of them, but have boon deterred by contains details ofmany up- th Radion the cost.The " Spanspace Three," to-date Sets. Useful information free. Art of on assembling, solderingand send me, The Gentle however, being so reasonable, I built testing also included. Pleasewith thebooklet, .c."3an' it,and completed it over the week- together ones panel: ...... end.The first station I tuned in was choosing ...... Toulouse,andIthengot London, THE PILOT MANUAL, Name ...... Bournemouth, Newcastle, and nine or ...... ten Continental stations (which I did ...... Address.. not stop to identify) in about half an hour.The voluine is greater and the PETO-SCOTT CO., Ltd. tonebetterthan detector and two Head Office and Works: L.F.s which I built the new set to 77, City Road, LONDON, E.C.1. replace. BRANCHES :62, High Holborn, London, W.C.1. WALTHAMSTOW-230, Wood Street. Yours faithfully, PLYMOUTH-Bank of England Place. H. B. EVERSHED. LIVERPOOL -4. Manchester Street. American Hard Rubber Co.,Ltd., 13a, ForeSt., E.C.2 Woking. G.A. 6339. P.S.6339 244 In replying to advertisers, please mentionTIIE WIRELESS CONSTRUCTOR.. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE. WIRELESS CONSTRUCTOR 1. +Rs A "WEILL IFOUND" 46,101040016°-A --M When the tall Clippers in all their pride raced for the wool and tea markets of the world, they had to be well found and seaworthy. And being well found didn't end with having good "sticks, rigging, and running gear," it implied a tip-top condition from the varnish on the truck down to a clean bottom. It was attention to details more often than not which decided the issue of these stern chases-the details which, as far as one could see, " didn't matter." "02 It is, perhaps, a far cry from Clippers to Condensers, but it is certainly a fact that many people regard Condensers as being a detail that " doesn't matter." And still more numerous are the people who say that cheap condensers seem to give just as good results as expensive ones. The fact is that cheap condensers do not give as good results as expensive ones. If they did, we should not be interested from any point of view in making the more expensive variety. And the second fact-namely that the Dubilier Condensers sold number more than all other makes put together-points to the fact that the great majority of people value a well -found wireless set and insist on seeing that itis equipped with Dubilier Condensers. Do you? DUBILIER ADVT. OF THE DOBILLER CONDENSER CO. 4x955) LTD. 240 DUCON WORKS, V7CTORTA ROAD, N. ACTON, W.3 In replying to advertisers, please mention TiE WIRELESS CONSTRUCTO/i 215 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 MINI .1111 MO irg Asking for it - Economy No scrap or waste, all parts inter- Think of an accumulator which doesn't changeable and reasonably priced. wait until you've got Madrid to give Simplicity Everything ready for assembly, no up work and sit down and think upon cutting, drilling, filing, screwing or itssins.Think of an accumulator soldering. Sets of any power can be con- which never leaves without notice ; Speed structedordismantledinthe which says :" I say, old man, what minimum of time. about a spot of juice ? " An accumula- The constructor can start in a small tor which asks for re -charge. Adapt- way, if so inclined, completing, say, ability an efficient one -valve receiver, then You have ? Then you've thought of adding another section, converting the P. & R. Gravity Float-the accumu- to two -valve and so on. Variety New circuits can be tried out the lator which tells you, by a glance at its same evening with ease, and valuable floats, whether it is fully charged, half- data recorded. charged or needing re -charge. No Tools With the exception of a small box spanner we supply, tools are un- Now think of these other reasons why necessary. your next should be a P. & R.Think Supplies We list everything required to build acrystal,singleormulti -valve of anti -creep terminals, of anti -spray receiver, also series of adaptors for vents, of hefty plates strong to resist use with users' own components. bucklingevenonprolongedshort Prices All parts are numbered and tech- circuit.Think of inter -cell connectors nically described in our lists with which are copper -cored, of terminals prices.The components are of the highest quality and can be supplied and connector bars burned -on as well singly or as required.If your dealer as cast -on. does not stock, we will send direct onreceiptof remittance or Now-but only, mark you, if you think C.O.D. that's the kind of accumulator worth Service Our Service Sheets (price 3d. each) thinking about-send a p.c.to Peto printed in loose leaf form, can be and Radford, 5o, Grosvenor Gardens, obtained, and give Blackadda en- thusiasts easily understood informa- S.W.r, for booklet of complete technical tion and diagrams of various up-to- details. date circuits of merit. Efficiency Results from our sets are equal to any on the market of the same power, and the veriest no.ice who follows our instructions can feel confidence in the result. AND Our method of numbering the holes Finally in the ready -drilled base, as well as PETO & RADFORD all components and wiring points, renders construction literally " as ACCT! M U LATO RS easy as A B C." The Blackadda renders obsolete the old-fashioned The beginning and the end in laborious method of home construction and opens freshvistasfor amateur andexpertalike. Pow ER Have you written for the Blackadda circuit Dsi book (price 1!-) ? BLACKADDA RADIO CO., LTD., 1850A.D.S LER GATE, DERBY. 'Phone : Derby %Lame : Blackadda, Derby. 246 In replying to advertisers, please mention THE WIRELESS CONSTRUCTOR. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor Jarivary, 1927 THE WIRELESS UONSTRUCTOR HOW TO USE A WAVEMETER By J. H. REYNER, B.Sc. (Hons.), A.M.I.E.E. One of the most useful accessories which the listener can possess is a wavemeter. Such an instrument is simple to use and invaluable as a guide to unknown stations and as an aid to fusing them in without tedious searching. Mr. Reyner desciibes here how a buzzer wavemeter works, how it should be used, and how by the use of a suitable circuit it will give quite sharp tuning. THERE isan increasing demand The circuit of the to -dayfortheuseofwave - meters among wirelessexperi- "Razor -Sharp Wave - menters.Eventhose who possess meter " shown here receiverswith which theyarewell is discussed in these satisfied and who are not contemplat- ing any change can nevertheless find pages. considerable use for an instrument of thistype.Itwillbeofinterest, therefore, to review the mechanism of a wavemeter, and how it can be used. It will readily be seen that there are low-tension batteries, not to mention thing like onefifty -thousandth of a a. variety of uses to which a wave - the valve, so that for the average pur- second. meter can be put, and that it repays poseitis not a convenient instru- itsvalue time and timeagainin ment.Inthemajorityofcases, The Spark actual practice. therefore, the former type of instru- Now in a spark transmitter the con- ment, namely the buzzer wavemeter, denser is charged up to a very high Haw it Works is of more general service. voltage by means of an induction coil A wavemeter is toall intents and or a transformer. The coilis not purposesa small miniaturetrans- A Simple Transmitter connected directly across the condenser It produces trains of damped mitter. The simplest type of wireless trans- but there, is a shark gap series, as oscillations similar to those radiated showninFig.1.When thecon- from a. sparktransmitter. The mitter consists of a condenser and a coirArrangementsare madeto denser voltage reaches a certain limit, powerfulinterferencecausedbya charge the condenser to a high volt- theinsulationofthesparkgap sparktransmitterisonlytoowell age and then to permit it to discharge breaks down and thecurrent flows known.A buzzer wavemeter produces through a coil, which it does in an through the coil and across the gap, oscillatory fashion.That is to say the producing a spark. SPARN 6AP current first of all discharges through Itisbythismeansthatthe the coil, .but owing to the inductance periodical charging of the condenser thereof it does not stop flowing when z the condenser is completely discharged. The effect, therefore, is that the con- CONTACT denser charges up to some extent in TO --60ZD SLYER Tc theoppositedirection,overshooting BATTERY CONTACTS Fig. 1.- The elementary circuit of a the mark as it were. spark transmitter. When this cycle of affairs is finished COIL the condenser is charged, but in the ARMATURE. a similarsort of effect,only on a opposite direction.It therefore will much smaller scale, so that the signal discharge again, producing a pulse of Fig. 2.-The essential parts of a buzzer isnot unpleasant,but is currentintheoppositedirection. suitable for a wavemeter are shown in produced This again overshoots the mark, and this drawing. neverthelesseasilypickedup and so the condenser is charged up once tuned in. more in the same direction as at first. This continual charging and discharg- is obtained, the discharge occurring, Types as we have just seen, when a critical ingofthecondenser proceedsfor voltageis reached. The discharge Wavemeters may be of two kinds. some time, the successive charges be- takes place very rapidly, so that the There is first of all the buzzer wave - coming smaller and smaller owing to apparatus is in a condition of equili- meter, which consists, essentially of a the loss of energy due to the passage brium again when the condenser is tuned circuit energised by means of of the current through the coil, and next charged up, and we obtain one a simple buzzer.Secondly, thereis other factors,so thatintime the trainofoscillatorycurrentevery the heterodyne wave -meter, which pro - oscillation dies away. time the condenser is charged. &leescontinuousoscillations, sus- Actually something like10 or12 tained by means of a valve.Although discharges take place in an ordinary the uses of this latter instrument are circuit, but owing to the extremely Wavemeter Operation many and varied, it requires for its high frequency of these discharges the Now a buzzer wavemeter is designed operation the presence of high- and whole operation only occupies some - to produce a similar effect in a nearly 247 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 How to Use a Wavemeter-continued similar manner. In thefirstplace positionwhereitagain comes up vibrate, and for this reason some form we must arrange to charge .the con-against the contact Pin so making cir- ofspringcontactisusuallyto denser of the circuit periodically andcuit once more.The whole cycleis be desired, rather than a definite stop to allow it to discharge through thethen repeated, so that the armature which pulls the buzzer armature up coils. The charge and discharge is-is continually pulled away from and with a jerk.These points, however, arranged in a spark transmitter byallowed to return to the contact pin. are rather outside the scope of the pre- means of -aspark gap which auto-In a buzzer the armatureis made sent discussion, but are inserted to matically ensures that the condenser small and fairly stiff, the result being indicate why suchwidely differing shallcease to be charged up, andthat it has a very high natural fre- shall discharge through the coil whenquency, and will vibrate a large num- the voltage reaches a certain limit. ber of times per second.The actual This arrangement is not convenient in frequency ofvibration variesin a buzzer wavemeter, and a mechanicaldifferentbuzzers from between 200 change over is arranged for. -This isand 1,000 cycles per second. brought about by the medium of the Instrumentsofthis ;type can be buzzer itself, which is an instrument purchated quitecheaply. Simple carrying a vibrating armature, some- types of buzzer are usually provided what similar to the mechanism of anwith a fixed ,note, whereas the better Fig. 3.- A circuit sometimes used in ordinary electric bell. and more reliable types are usually buzzer wavemeters. provided with an adjustment whereby The Buzzer the note of the buzzer can be altered prices riflefor buzzers generally.It The buzzer consists of a coil of wire, by varying the tension on the arma- willusuallybe found thata good anarmature whichis attracted ture.It doei not follow that a buzzer deal of exasperation and temper can thereby, and a contact pin.A dia- having a variable note is necessarily be saved by purchasing -a good instru- gram of the arrangement is shown in merereliable,butthebetter -class ment. Fig. 2.When the current is switched buzzers are 'often provided with a on, it passes through the contact pin, variable note. Circuit through a contact strip carried on the Now an instrument such as this can Points of Design - - magnetic armature of the buzzer' and be used to set up trains of waves in then through the coil ofthe. buzzer The design of a buzzer is a matter a similar manner to a spark trans- back to the battery. The magnetic of some skill in order that a clear and mitter by utilising a circuit, such as effect of the coil attracts the armature steady note shall be obtained. Owing is shown in Fig. 3. Here it will be seenthat thebuzzerisconnected across the variable condenser C. As long as the armature remains in con- tact with the contact pin, therefore, thevoltageof the battery is applied across thcondenser C (apart from a small drop in voltage on the buzzer winding). Current,however,flows through the buzzer and the coil L, and,resultsin the armature being pulled away from the contact pin, so breaking the circuit. Tuning When this occurs, the condenser 0 discharges through the coil in oscil- latory fashion, so producing a train of waves.Now, as u -e have seen, the armature of the buzzer is continually being attracted and pulled away from the contact pin several hundred times persecond,andateachoneof thesewegetatrainofwaves set up in the oscillatory circuit LC. Consequently, if we place this instru- ment- near to a wireless receiver, we shall radiate small trains of wireless waves at the particular wavelength to which the circuit 'LC happens to be The construction of a buzzer wavemeter is not a complicated matter, tuned. since few components are required. Wavelength Checking .4r moving portion of the buzzer, and to the incessant making and breaking pulls it away from the contact pin. of the contact, platinum or gold -silver We can tune in the wireless receiver The circuitis thus broken, and the contacts have to be provided in order to this wavelength, and we shall hear tttractionon thebuzzerarmature that a clean contact shall be ensured anotesimilartothatofthe herefore ceases. every time. Moreover, the form of the .buzzer.It will be found that this contact has a great deal to do with note canbetunedinexactly the Frequency the steadiness of the note, much de- same wav asan ordinarywireless Thespringinessofthearmature pending upon the freedom with which signal.If wealter the settingof then causes it to return to its original the armatureitselfisallowedto (Continued on page 251.) 248 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR 7Ae Natural 7one oudSpeaher SCREENED COILS. MODEL RS.1.O Made to Radio Press (Oak) specifications and fullyguaranteed. 17:7:0 For the longer evenings Amplion Loud Speakers are made in a variety of sizes and styles and represent the most comprehensive range inexistence. Prices are from38/-to £1313s. Obtainable from GRAHAM AMPLIONDEL,CtititU4rA M P L I ON STOCKISTS, Limited, Radio Dealers 25,Savile Row, or Stores. London, W.I. Series " ktellOti No. Type of Coil. Price. Metres. Each S.C.rSPLIT PRIMARY AERIAL COIL.. .. 250/550 5/6 We will gladly send you our latest lists upon request. S.C.2SPLIT PRIMARY AERIAL COIL.. .. 1,000/2,coo 5/6 S.C. 3 SPLIT PRIMARY H.F. TRANSFORMERS 250/550 7/6 S.C.4SPLIT PRIMARY H.F. TRANSFORMERS 1,000/2,000 7/6 S.C. 5 SPLIT SECONDARY HY. TRANSFORMERS 250/550 7/6 S.C. 6SPLIT SECONDARY H.F. TRANSFORMERS r,00d/rocio11i- S.C. 7REINARTZ COILS ...... 250/550 7/6 S.C. 8REINARTZ COILS ...... 1,o0o(2,000 11) s S.B. grSCREEN COMPLETE, with 6 -pin base .. .. 9/ - For MONODIAL Circuit M.C. x xDAVENTRY ...... 1000)200013/6 M.B. x2SPECIAL BASE 1/6 " " - ' s , For ALL BRITISH Circuit Ilta:en't':", = S.C. 53B.R.C. ..-.. .-. .. .. ' .: 250/500 10/6 .G44 S.C. 14DAVENTRY ,...... 1000/200014/6 S.B. 9SCREEN COMPLETE WITH BASE .. .. 9/ - 10 000 cvN?.3 WE GUARANTEE PROMPT DELIVERIES. If any difficulty in getting Radio Press Report !!! %"41411;44ilie; supplies from your local (Extract) Dealer, send direct to us. Although the stand- Nov. 18th, 1926. ard of quality has IE I I been raisedprices Hydra Condensers operate perfectly TRADE NOTE. " I may say that the coils are very reasonable. atallvoltages up to 700 D.C. WE GUARANTEE haveproved perfectly satisfactory Capacitiesstocked Guaranteed precise within 5 to 10 PROMPT DELIVERIES. are from .0t011 mfd. per cent. of their rated capacity -J on teNt." to 10 mfd.1 mid. and to maintain rated capacity (Letter Signed) J. H. REYNER, 2/9 ;2 mfd., 3 9; 4 through all variations in tempera- B.S. (lions.), A.C.C.I.. mfd., 6/-;etc., etc. ture. From all good dealers. A.M.I.E.E, Technical Manager, HydraCondensershave a resistance of 200 megohnu per 1 mfd. guaranteed ELITREE RADIO LTD. "1"4"4"4001%"""0100%"""~ (Radio Press Laboratories). Manufacturing Co., Ltd. Louis Holzman Telephone : VICTORIA, 1644. 109 K1NGSWAY. LONDON.,W.C. 2 45, Horseferry Road, London, S.W.1. Parrs Ad. In replying to advertisers, please mentionTHE WIRELESS CONSTRUCTOR. 249 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR nuarA 1927 Pat. No. 256833 Pro. Pat. No. 20339 WIRELESS ACCESSORIES The Grid Leak Is not discernible, being totally enclosedin Bakelite Valve Holder Quality guaranteed by over 50 years' Base electrical manufacturing experience. WINDOW -PANE INSULATOR Regd. No. 705625. (Patent No. 233880.) Somethingnewand good Made ofbest quality enamel coated ebonite, theseinsulatorstake advantage oftheex- incomponent design cellent insulating pro- pertiesofglass,and at the same time avoid losses by keep- ingthelead-inwell away from The latest LOTUS walls. Rubber rings form a water- tight joint against the pane.The cone keeps triumphisa Combination a portion of the insulator dry in wet weather. Grid Leak and Valve Holder PRICE 3/6 each. A special drill, with instructions for making hole inglass, supplied with which eliminates unnecessary each insulator. wiringand solderingand STRAIGHT LINE FREQUENCY CONDENSER (Low Loss) makes for economy incost A precision instrument, the design of which ensures perfect mechanical con- struction with high electrical efficiency. and space. The rotor plates are earthed eliminating hand capacity effects.It is also com- pletelysilent when adjustments are Guaranteed efficient in con- being made. Perfect electrical contact is obtained by struction and design. means ofa flexible phosphor bronze pigtail connection. each. B.6150.00025 mfd. 1116 From all Radio Dealers B.616o.0005 mid. 13/- B 601.VERNIOMETER Combination Grid Leak and Terminal Valve (Patent 253612.) Holder ..3/9 A most ingenious device for applying slow motion to variable Condensers, coil holders, variometers, etc..consisting of an ebonite dial and knob (o --18o°1fittedwith worm -wheelbracketandworm -spindle,micro- Terminal Valve Holder ..2/6 meterbarrelandpointer,completewith fixingscrews.Gearratio240-I.Fitted Valve Holder without Terminals 2/3 with instantaneousrelease.Backlashen- tirely eliminated.Rand capacity reduced to a All Anti-Microphonic Type. minimum.Suitable for the following makes of condensers.Silvertown, Burndept, Igranic, Polar, Sterling, Ormond, Jackson, Devicon, Utility, Ashdown, Lamplugh, Ediswan, Edison -Bell, Bowyer -Lowe, Atlas, W. & M., mous A.J.S. etc.Price 6/-. each. Combination AN AD) TO ENTHUSIASTS. We have prepared a logging chart for recording GRID LEAK BUMEANCY VALVE HOLDER wavelengths, condenser settings,etc.,of those Anti-Micrephonic stations which require careful calibration to tune in. A copy of this chart, printed on stiff card with hanger, can be obtained free of charge at any of our Branches or from any high-class dealer. Garnett, Whiteley & Co., Ltd. MAKERS: LotusWorks, BroadgreenRoad,Liverpool. THE SILVERTOWN COMPANY, Makers of the famous 106, Cannon St., London, E.C.4.Works : Silvertown, E.16. " Lotus" Vernier Coil Holders BELFAST. DUBLIN. LONDON, BIRMINGHAM. GLASGOW. MANCHESTER. BRISTOL. LEEDS. NEWCASTLE -ON -TINE. CARDIFF. LIVERPOOL. PORTSMOUTH. SHEFFIELD. 2.7,4) In replying to advertisers, please mention THE WIRELESS CONSTRUCTOR. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR firs, FAVAVAVAVAVAVAVAVAVAVA 71i 110W TO USE A WAVEMETER N 0. -continued from page 248 RF-PA O. 4 Headphones; Loudspeakers, and Transfor- mers re -wound& reconditioned equal to new Rheostat tf AN UNSOLICITED TESTIMONIAL. . the condenser, then we shall vary the " Thanks to the excellent manner in which. wavelength of the wavemeter, and we it was reconditioned, the results achieved have been astounding.It is very gratifying shall have to tune our receiver to a to find a firm that really turns out a first-class different position in order to obtain job, as 1 leave had very disappointing experi- ences with firms who have advertised as ex- the note of the buzzer once again. perts, and whose workmanship has been far lid It will be clear at once that this from good." Varley menet Co., Proprietors. forms a very convenient method of Coil Dept. Oliver Pell ascertaining the wavelength of a re- Woolwich, Control, Ltd. 07 ceiver.We can have a standard, coil and condenser, and we can calibrate AR LEY them in conjunction with each other and the rest of the circuit, so that for each setting of the condenser we 10 know exactly what the wavelength of SOLDERER SUPERSEDED the combination is. 4 If, then, we wish to .tune our re- A' ISCROS- I toriPttEASiLYAPPLI15. Inside ceiver to a given wavelength,itis IDIECMSuRESETTIR 5150155 . 4 only necessary to set the condenser 11,c. A RHEOSTAT is ingeniouslyingeniousl 14 r 0 of the wavemeter to a point corre- 0 4 built inside this dial.Only sponding to that wavelength, and at 11,;.gh '4 space of 21' diameter is r this point the instrument, when the bvias.40rragi T trivi ta switchedon, will radiate Muter 401Ars A*RtSCROS" root !VERY COFTACT buzzeris Send for List 5 required in front of the panel $signals of that exact wavelength. We RRISCROS COMPANY, 50. GRAY'S INN ROAD, LONDON. W.C.I. and 7/16" at the back. Thus can then bring the receiver near to the instrument, and tune the receiver it.valuable space is saved,. wir- in,as previously described. A HOME FOR ing is made easier and the YOUR WIRELESS SET Igappearanceofthepanel % Another Use OUR STANDARD CABINETS IP Another use for the instrument is itimproved. areDUSTPROOF 4 in finding the wavelength of a par- and house the whole The movement is extremely it ticular station which has already been apparatus,leavingno tuned in on the receiver.In this ease parts to beiaterfered smooth andavery fine ti with. Slade on mass we operate the arrangement in the production lines , variation is possible.Thetd reverse direction,so to speak. We hence the low price. Provision is made to 2 dial (made of genuine Bake- take panels from /6 by 7 ttp to 3o by lite)is marked 0 to.100 and 18 in. SpecialCabinets fortheELSTREE a nickel -plated pointer p SOLODYNE, NIGHT HAWK, etc., now It guides the adjustment. $ ready.Write for free particulars. MAKERIMPORT Co. to Fixingis by the one -hole 4 Dept. 20, 50a, LordStreet, LIVERPOOL. method. 4 tis po. NickelPlated Dial Indicator. Made inthree1 \ Fig.4. - By connecting the buzzer types, 6, 15 andirdi across part of the coil only, sharper Yakted ileidaifert >4 30 ohms resist-' iii tuning is obtained. AS C000 AS NEW!! Panel, ancesre spec- 14 ;Except Weco L.P.'s, and low capacity N lively. Each types).Minimum D.E. Current 0.15 sold at the very 01 leave the receiver tuned in, and vary amps when repaired. Resistance moderate price 4 ALL BRIGHT & DULL EMITTERS in, I/ial. of the setting of the condenser C, hold- ilfieListed at leas than 10/- % MINIMUM CHARGE -5/- ing the instrument near the receiver, VALCOLTD.. Dept. C.. Tabor 0 until the buzzer note is heard. The Grove Wimbledou.S.W ®Soldering2/9 to particular point at which the buzzer Patent .,----...' signals are loudest is observed on the 246435 Obtainable from4 4 rTag.4 One Hole all up-to-date 10, condenser, and the wavelength at this ACCUMULATORS Fixing. dealers. point read a. This is then the wave- I 0 t44length of the station to which the ON EASY PAYMENTS High Tension Accumulators built up from 20 Volt set is timed. sections (T5/- each).Example: 60 Volt H.T. 45/ - CASH or 12,6 DOWN and 6 monthly payments of B E ruj 7A LI I N § 6/-.Carriage Paid. Satisfaction or money back, Identifying Stations Write for Lists to DEPT. 13, COVENTRY DIRECT fRIPPLIES It will be appreciated that an in- LIMITED, 23, Warwick Row, COVENTRY - 110 54f -contained g strumentofthis nature isalmost I I i day Wireless(hoodssupplied invaluable, particularlyifit can be on easy payments. constructed in a cheap manner. With RHEOSTAT 0,the new wavelengths which are at o, Out of sight, out of mind. V present beingtriedout;allone's EBONITE BUSHES g old friends are lost, and itis neces- FOR MOUNT/NO_, PERFECT 4 THE BENJAMIN ELECTRIC 1.,TD.,4 ON WOOD. Brentwood Works, Tottenham, N.I7. 00 sary to find them allagain. Con- INSULATION. 0 4 Order looter 1/- Two required is The Benjamin Batteryry Switch gives Perfect versely,there isa large number of send I Ad. Postage. foe each hole. current control and costs only 113. stations which can now be received NUMBER g I 3 3 4 5 6 OA Hole in Buwl, SBA, 4B.4, 2EA, 1/e, 31W. 3,,e, 7/16" very well, hut which can only be iden- Price each:Id. Id. Id.lid.Id. 2d. Id. i I e ra 74! iVAVA 6 ;Van avAVAVA I YAW AV il tified as a result of patient waiting, DAREX RADIO CO., Waldram Rd., Forest Hill, London, S.E.23. (Continued on page 278.) TRADE SIIPPLIED In replyingto advertisers, please mention THE WIRELESS CONSTRUCTOR. 251 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 iff CHOOSE 11111111MIN YOUR OWN CIRCUIT A Multiple Circuit Crystal Set WORMI1 I By BRIAN ST. CLAIR A set which, without undue complication, permits of the testing of a number of circuits, making it possible to discover the best possible arrangement for individual circumstances. THE multiplicity of circuits which fourteen different capacity values that desired, the accompanying list of com- are open to investigation by the can be placed in series with aerial. ponents and materials employed crystal user has done much to The best value should be determined by should be referred to, brit readers can enhance the popularity of the crystal experiment, and will depend on the bear in mind that substitutes may be receiver, apart from any other con- size and type of aerial in use at the made where desired.The Eelex ter- siderations, such as cheapness, purity time.Aerial terminal 2 is brought out minals, plugs,and sockets are admir- of signals, absence of renewals, battery to a flexible lead and plug C, which ably adapted for the desired flexibility costs, etc.; and itis both interesting canbeinsertedintooneof two to enable the alteration of circuits to and instructive to try out several cir- sockets. take place rapidly, but Clix wander cuits in order to ascertain which par- . The wicket marked A is joined to one plugs and sockets will also serve for ticular onemeets the needs of the side of the, moving coil of the vario- the purpose. moment. Questions of selectivity are of meter, while B makes connection with paramount importance in those situa- the junction of the fixed and moving Construction tions where interference is experienced, coils.The remaining side of the fixed The initial task to be undertaken coilpassestothe earthterminal inthe construction of this receiver AERIAL through a loading coil Li, joined to is the drilling of the panel, and for terminals 3 and 4, which can be short- this purpose reference must be made circuited by a link consisting ofa to the drilling diagram of Fig. 3.The MULTIPLE hXED flexible rubber -covered wire with two panel components can then be fixed in Cf CONDENSER DETECTOR plugs. position, and a large proportion of the 2 * ed The wooden sides to the baseboard take the place of metalangle brackets. 77 EARTH *** Fig. 1.-From this basic circuit of the setitwill be apparent thatmany circuit variations are available. and the demands of the crystal user have not been neglected in this direc- tion. Wavelength Ranges wiring undertaken beforethe base- The crystal receiver described in this board-which inthis particular case article has been designed with a view One side of the variable condenser had wooden side brackets-is screwed to providing a set which will enable is joined to another flexible lead, ter- to the panel.The wiring should then many circuitsto be tried,at least minating in a plug F, so that it can be completed- according to the wiring those which can be covered with the be joined across the whole of the vario- instructions. aidofavariometer,variablecon- meter (plug into D)or only across denser, loading coil and multiple fixed the fixed coil (plug into E).In addi- Easy Wiring condenser. tion, provision is made for inserting For the benefit of those constructors various fixed condensers (C,) across 0, who do not feel at home with the sol- Possible Circuits in order to increase the range. dering iron, it will be interesting to A short study of the theoretical dia- Reception of the localstation or note that only at two points have I used gram of Fig. 1 will enable the scheme Daventry is possible with one of several solder-i.e., at the junctions to the adoptedtobecomeapparent. The circuits, the receiver being simple to crystal detector screws. aerial can be connected to either of operate, since the change over from Even this soldering can be avoided terminals 1 or 2, the former connection one circuit to another is effected with if longer screws are employed. The bringing into circuit a multiple fixed ease. flexiblewirepassingthroughthe condenser C which gives a selection of If an exact duplicate of the set is bushed holes C and F in the panel 252 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR Choose Your Own Circuit-continued should be just long enough to enable spectively. Theappropriatepanel This is done by plugging C into A. the terminating plugs to be inserted transfers can then be affixed to the shorting 3 and 4, and leaving F discon- into sockets A or B and D or E re- panel in the usual manner, thus com- nected.Connect the aerial to terminal No. 2 in the first place, and slowly rotate the variometer dial until sig- V nals are heard, and then adjust the ON a crystal so that it works on a sensitive SSOS so .... spot.Now try the effect of inserting the multiple fixed condenser C,in -14 series with the aerial, by connecting .... - the aerial to A and adjustingthe # I I # I,i. 1 1 II) `\ Crki 7- 4 e. (I) spring clip so that various capacity values are employed.Retune each ., time, and thus ascertain which, value ....1.... gives the best signal strength. (a) --...,=. (b) .- (C) Further Experiments V Another experiment which will no SO SUSI doubt give interesting results is to find ... ABM the best combination of capacity and inductance which suits your own par- ticular aerial.This shouldfirst be III tried with diagram (b), the only altera- I I tion from the previous circuit being ,i, 1 I ) IF. the addition of the variable condenser . 0,inparallel with the variometer, effected by plugging F into D. (d) (e) ..-- (1 With the aerial initially joined to No.2terminal, tunein thelocal V station with the minimum capacity u.ues and maximum inductance, and note 4Pes InSO the signal strength. Now increase the imo IS capacity slightly, and reduce the in- ductance correspondingly, and again 1.14 note the signal strength.Repeat this .11. 1 for several readings, and then insert iif.i. I i ... various values of C, in series with the ... chaliging the aerial connection A to No. 1 terminal, and repeat the pro- ZIP cess.In this way you can ascertain = the combination best suited to your (g) (h) -,,-- 01 aerial in order to give maximum signal Fig. 2.-Some of the possible circuits are shown here in their simplest strength. form.The lettered and numbered diagram of Fig. I may be used as The circuit of diagram (c)should a key to these circuits, together with the instructions in the text. also be tried by changing F from plug D to plug E. pleting the construction of the receiver. The main feature desired by many BUILD THIS SET WITH- We now come to the testing opera- constructors in a crystal receiver is a One" Trolite "panel(mahogany tions, and in order to see that the set fair measure of selectivity.While an finish), 10 in. by 7 in. by in.(F. A. Hughes & Co., Ltd.) z.. One cabinet to suit, and baseboard 6 in. deep. (Pickett's Cabinet Works.) /71 Ogti.4.144 r' One .0005 ultra low loss S.L.F. variable *** A condenser. (Formo Co., Ltd.) One variometer. (Claude Lyons.) One multiple fixed condenser. (C. A. Fig. 3.-The di- Vandervell & Co., Ltd.) mensions for the One baseboard mounting coil holder. symmetrical panel (Burn -Jones & Co., Ltd.) layoutmayb e One crystal detector. (Watson Jones, takenfromthis Ltd.) scaledrawing. Two fixed condensers,.001 and .002, Blueprint No. with one pair of clips.(L. McMichael, C 1077A. Ltd.) Six T2 L.C. terminals, marked "Aerial" (2), " Earth," "'Phones " (2), and one * ea with plain top. Two T2 S. terminals, six sockets and four T14 plugs. (J. J. Eastick 4 and Sons.) 10" One spring clip. (Peto-Scott Co., Ltd.) isworking satisfactorily, the easiest auto -coupled aerial arrangement does Radio Press panel transfers. plan will be to arrange the circuit not generally give such a high degree Clarke, rubber -covered flex and wood as a simple variometer receiver, as in- of selectivity as a separate aerial wind- screws.Approximate cost.. £4. dicated at(a)in the composite dia- ing, it has many points in its favour, gram, Fig.2,given on thispage. and the difference is not very marked C 253 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 The name Don't play with fire! does not rotate The head does not come off. The slot' and nut-, rununnecessary eliminatesoldering. risks !Play for safety The finish is andseethatyour Battery Eliminator perfect throughout: utilizesT. C. C. 600 Standard Large Insulated Model volt D.C. Test Mans - (polished black bakelite), Type B, bridge Condensers. 9d. each.Popular Model (non - They areguaranteed. insulated), Type M, 6d. each. They are reliable. 28 different engravings stocked.Catalogue free on request. They are safe.The fact thattheyhavebeen USING an ordinaryused on domestic lighting 300 volt Condensersupply for many years BELLINGLEE in your Battery Elimin-is proof of their worth. TERMINALS ator is like using a fret -Thescoreofyears .ddvt. of BELL! VG e LEE, Ltd., Quennsany Works, Ponders End, Middlesex. saw to fell a tree.Itwhich are behind every E.P.S. 14. was never meant for theT.C.C. Condenser-years job.For your Batterybrimful of experience in Eliminator it is too muchmanufacturing large 4 - toexpect an ordinaryton power Condensers Our latestproduction,the Condenser tested to 300and little 2 -ounce Mans - C.E. volts D.C., to do the workbridgeCondensers PRECISION FLOATING of a 600 volt T.C.C. Con-(millionsofthem)is VALVE -HOLDER denserspecially madesufficientto commend showsgreatimprovements for Battery Eliminators.them. A hastychoice may upon others. You have no guaranteemeanendlesstrouble. By its use the distortion due to that it will stand up toPause before you choose vibrations transmitted to valve filaments is entirely eliminated thenecessay, pressureyour Condenser - then and a receiver fitted with it for a long period.Don'tyou'll buy T.C.C. acquires a perfectly clearback- ground which facilitates the reception of distant stations. Of very low capacity and en- BUY tirely non microphonic the T.C.C. C.E. PRECISION FLOATING VALVE -HOLDER is ideal for \Condensersthey're its purpose. ,British Made from Bakelite and fitted Price 2/3. each. with soldering tags and terminals. There are also the well-known C.E. PRECISION RHEOSTATS AND PGTENTI3METLRS. T. C. C. 600 volt D.C. Test Mansbridge Con- Perfectly smooth and silent in action, Bakelite densersforBatteryEliminators come in Formers, Silvered Dials, fitted with soldering tags 1,2,4,5, 8 and 10 mfds. capacities of 5, and terminals. Always specify C.E. PRECISION. 7 & 15 Ohms. - 2/9 each. fOR unosT T.C.C. Condensers 3o & 5o Ohms. - 3/- (Tested and Guaranteed) Dual Rheostats & RECISI CEP ErficIENCY, for Battery Eliminators Potentiometers 3/9 C. EDE & CO., LTD., BYFLEET, SURREY Advt. Telegraph Condenser Co., Ltd., N. Acton, W.3 7 e:e p Arme :Byfieet 2 2 6. Telegrams: " CePrecise, Byjleet." .4. 6345 254 In replying to advertisers, please mention THE WIRELESS CONSTRUCTOR. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR Choose Your Own Circuit-continued in a crystal set.The variometer lends Results itselfquite well to an auto -coupled the ordinary plug-in coil and conden- scheme, and the change is effected very In my own particular rase, when serarrangement canbe tried with simply in this receiver by plugging 0 tested on an aerial of average size and little trouble.Remove the shorting into B alkl leaving F disconnected for efficiency about 9A miles north-west of link between terminals 3 and 4 and the first trial.This gives us circuit London, that station came in at par- arrange it across terminals 2 and 3. (d), and it is seen that the aerial is ticularly good strength, while selecti- Thisshortcircuitsthe variometer. joined to the junction of the fixed and vity was best with Ca = .0002 and 0, Plug C into A and F into.D, and insert moving coils of the variometer. about one-third of the way round on WIRING IN WORDS. Join socket A to spindle of variometer, to one side of crystal detectocand to socket D. Join other side of crystal detector to one telephone terminal. Join terminal 3 to one end of variometer, and continue to one side of 1.1 coil holder. Join socket B to other end of variometer, and continue to socket B. Join terminal 1 to terminal 000 of fixed condenser Cl. Join terminal4to remaining telephone terminal, and continue to moving vanes of variable condenser C2 and to one side of fixed condenser C3. Join remaining side of C3 to remaining side of Ll coil holder and to fixed vanes of C2. Join a flex lead to fixed vanes of C2, pass it out through socket F and attach a plug. Join two flex leads to terminal 2.Attach a spring clip to one for connection with Cl, pass the other out through socket C, and attach a plug. Join together two plugs with a short length of flex. a No. 50 or 60 coil intoposition for L, (or, of course, the equivalent in let- tered makes), and we have the arrange- ment (g).The .local station can now be tuned in on C while the effect of theseriescondenser 0, can also be tried. ForthereceptionofDaventry the last circuit can be used if desired by altering L, to a No. 150 or 200 plug-in coil. With the particular vario- meter used in this receiver itis pos- sible to receive Daventry by resorting to circuit (h).Plug C into A, F into D; insert a .001or.002condenser in the clips for C, and short termi- nals 3 and 4.That station can then be tuned in on the variometer or the condenser Cl, as desired. An Improvement An arrangement which is to be pre- ferred and which I found gave stronger and more selective signals is that shown at (i).' Plug C into B and remove the short between terminals 3 and 4 and employ a No. 60 plug-in coil for L,. Tuning can be effected on C, or the variometer, whiletheaddition of a .0001condenserinthe Caclipsis Fig. 4.-The wiring of the set is quite simple. The length of the - worth trying if such a size is handy. flex leads carrying plugs should be adjusted so that connections can Other Circuits be easily made to the necessary sockets.Blueprint No. C 1077B. The circuits (g) and (i) will be found quite suitable for Daventry, and in the Tests should be made both with and the dial.Tests for the best capacity situation previously mentioned signals without the aerial condenser C signal andinductancebalance shouldbe were quite good, the station being strength being noted. A big improve- made, the time spent in this manner about 70 miles away.The experimen- ment in the selectivity will be brought being well justified by the results ob- ter will findthat this receiver will about, however, if C. is added to the tained, since it enables the maximum enable him to obtain very interesting circuit by plugging F into D, which efficiency to be secured.The effect of results,and the simplicityofthe gives diagram (e).Thisis a very altering F to E should also be noted. arrangementand the rapid change interesting and efficient arrangement, over from one circuit to another will, andis perhaps the best circuit for Comparing Coils no doubt, recommend themselves to many purposes. A comparison of these results with many readers. 255 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 These strange words were broadcast into space the other week when Mars came within the chatting distance of 42 million miles.The chat, however, was all on our side, and several theories exist as towhy ouradvances met withnoresponse. One enthusiast writes :-" Assuming that Mars enjoys Illustrated above is our artist's the blessing of Radio, we take too much for granted idea of Mars and the Martians, that their instruments are as efficient as our own.In Others, doubtless, have different the transmitting set used down here by us ORMOND conceptions. But however Condensers were employed, and the fact that ORMOND much at variance opinions on Condensers are not, up to the present,available in this point may be,no two Mars would amply accountfortheirfailureto opinionsexist. asfaras establish contact." ORMOND Condensersare We agree.Infact, we are convinced that the concerned. Inthisallare ORMOND Condenser, with its slow-motion friction unanimousin acclaiming ORMONDasconsistently drive,ball bearings and easy mounting, has a the best. ready market awaiting it in that distant sphere. ORMOND S.L.F. CONtENSER With 4 in.Bakelite Knot* .0005 microfarad 20/- .00035 .. 1916 59/ - .00025 With Dual Indicator Dial. .0005 microfarad 21/6 Regi7tered .00035 ..21/- .00025 .. 20/6 Ratio 55-I 199-205PentonvilleRoad,King'sCross,London, N.1 Telephone--Clerkenwell 9344-5-6. Telegrams-"Ormundengi, Kinross." Factories-Whiskin Street and Hardwick Street, Continental Agents-Messrs. Pettigrew & Merriman, Ltd. Cletkenwell, E.C.1 Phonos House,' 2 & 4 Bucknall St., New Oxford St. W.C.1 236 In replying to advertisers, please mention THE WIRELESS CONSTRUCTOR. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CON STRUCTOSI WORKSHOP HINTS FOR THE HOME CONSTRUCTOR Home-made Cabinets-Easy French Polishing-Mahogany Panels and Jacks-Soldering Leads to Jacks-Tagging without Solder-Neat Wire Bending-Erinoid and Ivorine. HOME-MADE CABINETS of the same length as the bottom piece as it was put on, and the surface would ALARGE number of constructors and half an inch higher than the end _be spoilt by the smoothing pad unless now make their own cabinets for pieces (1 inch higher, if the baseboard a lubricant were used.Oil is employed complete sets and for small pieces of is inch thick).The lid, E, will be for the purpose, but its use renders apparatus such as wavemeters, valve 1 inch longer than the bottom piece, to the polish cloudy. To remove this The method of give an overhang of 1 inch at each cloudiness a process known as testers and the like. end, and 1 inch wider than the bottom " spiriting off "isnecessary, which constructing cabinets from ply -wood, piece in order to allow it to cover the requires a great deal of practice for described recently in these notes, is a back and have an overhang of half itssuccessfulperformance. Fortu- simple and inexpensiveone,which an inch in the front. nately for amateur cabinet makers a produces a wonderfully good looking If the wood is ordered ready cut and new type of french polish is now avail- article. Those who like something rough finished, a cabinet of this kind able, which is so simple to use that more solid can now obtain from one can be screwed together in a very short anyone can obtain a splendid finish firm, at any rate, parcels containing time, and providedthatreasonable with it; it requires neither oil nor a every piece of wood required for the care is taken over the work the result subsequent spiriting off. construction of a cabinet, ready cut is distinctly pleasing.The overhang- tosize,squaredup,andrough ing edges of the lid should be slightly finished.These parcels are made up How It Is Done for various standard sizes, but anyone rounded off either with a plane or with who wishes to make a cabinet of dif- a rasp,beingsubsequentlyfinished The process of applying it is as fol. ferent dimensions can obtain all the with sandpaper. lows:-The wood isfirst of all sand- necessary pieces of wood by sending papered until it has a satiny smooth- exact particulars of his requirements ness.Mahogany, teak and other hard with his order. woods suitable for wireless cabinets are close grained, and do not require any filling up. A little of the polish is pub Simple Construction on to a pad of cotton wool covered This immensely simplifies the busi- with a piece of old linen. This is ness of cabinet making, fOr cabinets applied to the wood withacircular of wonderfully good appearance can motion, working in lines from one end be made by simply screwing the ends, to the other.Only a small area should top, bottom and back together with- be dealt with at a time, and the pad out a single dovetailed or halved -in should be worked out quite dry.Any joint.A plain, but exceedingly use- smears disappear of themselves as the ful type of cabinet is seen in Fig. 1. polish dries, and a good surface re- As the inexperienced may easily make Fig. 1.-A plainbutuseful type of sults. When this process is completed, mistakes in measuring up when order- cabinet may be constructed in this the work should be set aside for the ing supplies of wood, it may be as manner. polish to dry.As soon as it is quite well to give a hint or two on this. hard, it should be rubbed down with The bottom, A, which should be of * a piece of the finest glass-paper, wiped half -inch or three -quarter -inch wood, ** offwitha smoothclothand re - will be 1 inch longer than the sliding EASY FRENCH POLISHING polished. In thisway the veriest baseboard and inch wider.The end beginner can produce a beautiful high pieces, B,B, will be inch thick and ()THING gives a cabinet a better 'polish on his cabinets.I have made inch higher than the panel ;their appearancethan frenchpolish- considerableuse ofthissimplified length will be equal -to the width of ing.Ordinary french polish is, how- french polish, which certainly gives a the bottom piece.The batten, C, will ever, exceedingly difficult to use, and much better appearance than the oil be 1i or 2 inches wide, inch thick, none but a practised hand can produce finish with which Iwaspreviously and of the same length as the base- even passable 'results withit. The content for home-made cabinets. board.The back piece, D, may be difficulty is this.Owing to its shellac, One brand of this polish is known of soft wood inch thick.It will be basis the polish would becoine tacky as " Lightning " polish. 25Z PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 Workshop Hints-continued MAHOGANY PANELS AND insulation, for the insulation is as good of the metal used for the tags makes as if the panel were of solid ebonite. soldering difficult.It is a good tip JACKS always to give these tags a rub over THE useof mahogany panelsis ** with a file before soldering, and then becomingincreasinglypopular, to tin them well. and they are perfectly satisfactory so SOLDERING LEADS TO JACKS long as the metal parts of all compo- The Best Way ONE maker at any rate has pro- duced a fan -tailed jack, but the The tags of most jacks have little EBONirE MAHOGANY majority are content to arrange the slotscutinthem near theends, PANES tags so that they lie parallel to one though many constructors make no use another and very close together.For of these.This is an unwise practice, this reason the task of soldering leads for a much more secure job can be ).4.8.A.CoustrEnsumor to jacks may be a rather troublesome tScREArs one, particularly in the case of those like the double filament type, which have as many as six connections.The Fig. 2.-A hole of ample size should processisvery much simplifiedif be drilled in the wooden panel before before soldering begins a pair d small mounting the jack. flat -nosed pliers is applied to each tag in turn.In a 4 -point jack the top tag may begivenabiggish bend nents which come into contact with the upwards and a slight twist tothe Fig. 3.-This type of tag isuseful for wood are at the same potential. A right, the second a small bend up- stiff or flexible wire connections. complication,however,ariseswhen wards and a twist to the left, the jacks are used, for the body of a jack third a slight bend downwards and a made, by making fulluseofthem. is in connection with high-tension posi- and the fourth Before you solder a lead, /bend its end tive.Further, when jacks are used in twist to the right, abigger benddownwardsanda into a little hook.Pass this over the two low -frequency circuits and placed twist to the left. When tags are dealt end of the tag, pull it into the slot close together upon the panel, minute with in this way, one has much more and then clamp it tightly by squeez- leakages may occur,quitesufficient, is also con- ing the wire hard with the largest as I have found to my cost, to cause a room to work in, and there siderablymore spacebetweenthe pair of pliers that there is room for. considerable amount of noisiness.A " live "points when solderinghas When thisisdone, the connections very useful method of mounting jacks been done. are more or less self-supporting, even on mahogany panels is that shown in without soldering, and they are net Fig.2. Foreach jackanebonite Wiring -up nearly so likely to work loose under strip 1inches wide and 1?-,inches in Always remember whenyouare the effects of jarring or rough usage length is used.In this is drilled a hole wiring up jacks to make the most as are those made by simply embed- just large enough to take the neck of difficult first. Suchis ding the straight end of*the lead in the jack, which is firmly clamped up in human nature that the temptation a blob of solder. the ordinary way.Two 4B.A. clear- always is to deal first of all withthe ance holes are also made as shown in easiest ones, and to put off thosethat * * the drawing.In the panel is made a are very troublesome tothe last.If this is done, one's difficulties are very TAGGING WITHOUT SOLDER hole whose diameter is such as to allow THOUGH the practice of soldering every possible connection is not now looked upon with such favour as it was, owing to the liability of sol- dered joints to deteriorate, there are many who like to tag the ends of all leadsthatarefixedtoterminals. The generators in Tagging in the ordinary way entails the PostOffice the use of solder with its attendant WirelessStation drawbacks.Itis,however,possible at St. Albans used to tag leads neatly and quite securely for supplying cur- by means of the method shownin rent to the valve Fig. 3.In the tail of the tag three filaments. small holes are drilled of a diameter just large enough to pass the wire in use. Thisisthreaded throughas shown inthe drawing,after which the tag and the wire are flattened out with a hammer. For dealing with flex leads a very useful form of tag is the sleeved variety, which are often to be bought very cheaply in, gross it to clear the nut and washer of the muchincreased,fortheavailable lots from firms which deal in W.D. jack by about inch all round.The spacewillprobablyhavebecome surplusgoods. Thestrands,first front edge ofthisboleshouldbe distinctlysmall. Manyconstruc- tightly twisted together,are thrust slightly chamfered off.Two holes for torshavefound,nodoubt,that into the sleeve, brought out of the thefixingscrewsaredrilledand connections soldered to jacks have an hole at its far end and taken through countersunk in the panel, and the jack annoying way of coming adrift after the second hole provided. When flat- is fixed in position.If this method a month or two for no apparent rea- tening has been done with a hammer, is employed, there need be no fear that son.This is due largely to the fact the job is as firm and as secure as noisiness will occur owing to defective that in some jacks the nickel surface could be desired.(Fig. 4.) 258 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR WORKSHOP HINTS-continued Before to turn the tool in the opposite direc-Broadcasting NEAT WIRE BENDING tion, that is, clockwise, which brings INEVER botherabout tagging the stud B against the standing part ofwas thoughtof ends of leads which are attached the wire and enables a neck to be to terminals, but I like to make neat formed. Thelittleinsetdrawing loops in them.Those who are par- shows a finished loop made in this way. ticular about the appearance of the By using three different tools one can wiring of their sets will appreciate the always make a loop that is a perfect improvement made by forming loops fit for 2, 4 or 6 B.A. terminals.Be- neatly, and not just bending them sides looking particularly neat, loops anyhow. Fairly good work can be of this kind make for secure connec- done with a pair of round -nose pliers, tions, since as they are entirely closed but there is one objection to their use there is muchlesschance oftheir for this purpose.The " noses " are slipping, and so causing a terminal to tapered, and itisthusdifficultto slacken. make loops which are a good fit for terminals of various sizes. *** A Useful Tool ERINOID AND IVORINE Instead of pliers I use the little T DO not think that many construe - Deseriptire home-made tool shown in Fig. 5.This tors have realised the possibilities leafletsfinin9 is made from a piece of stout sheet for wireless work of erinoid, ivorine full particulars oftheseboo brass, one end of which is rounded off and other similar materials. They have famous Varley been employed to some extent for products, on dials, but that is about as far as their applleattan. use has gone.These materials can, as a matter of fact, be employed in a The Varley Magnet Company large number of other ways.Most of them are quite good insulators, their were specialising in the design and con- resistance being greater than that of struction of every form of intricate coil mahogany or other hard woods.Since winding.In scores of the biggest elec- they can be obtained in a large variety of plain colours as well as in mottled trical undertakings in the country- amongthemtheElectric Railway Fig. 4.-Another form of tag which can forms, thin sheets of these materials be satisfactorily attached to a Rex lead can be used most effectively as veneers systems of Great Britain-the Varley without solder. for panels of wireless sets. winding has enabled automatic electrical devices of every kind to be brought to and bent over at right angles.The A Suggestion for Panels their present state of perfection. other end is pointed to form a tang, Many peopledonot careabout With the growth of Broadcasting, the which is inserted into a tool handle, using mahogany panels, since they like being wedged tightly, if necessary, by a colour contrast between the panel Varley Magnet Company, realising that driving a couple of headless nails into itself and the cabinet of the set. Why their long and successful experience in the handle, one on either Side of the not then make the panel itself of hard coil winding gave them advantages broad part of the tang.' Into the flat wood and coverit with a sheet of possessed by no other firm inthe part bent over at right angles to the erinoid thick inanycolour 'country, produced, firstly, the Varley tang are screwed two pieces of stud- that you may fancy?A novel and ding placed fairly close together.I attractive effect can be produced by Bi-Duplex Anode Resistance,and, use three ofthesetools,provided using a sheet of white material for secondly, the Varley Multi -cellular HY. respectively with2,4 and 6 B.A. the purpose.Such letteringasis Choke,bothwire -woundonthe studs. To make a loop, place the needed,aswellasdialindicator famous Bi-Duplex system and both bared end. of the lead between the marks, can be made with Indian ink, infinitely superior to any similar pro- studs-a little practice will show how and the resulting jobisdistinctly ducts on the market to -day. much must be allowed to protrude- pleasing. Thereisnottheleast trouble about keeping the material What has happened in the Electrical clean, for it does not collect' dust to world is now taking place in the Radio the same extent as does ebonite, and world proper.Varley components are it can be restored at any time to its used by the biggest institutions in the original whiteness by being Wiped over with a damp cloth.If you prefer a country to ensure that the public shall blackpanel,you canobtainthe get the benefit of real purity of tone, material in this hue ;itis,in fact, and constancy of perfect reception. manufacturedinmorethansixty All the best Dealers stock Varley pro. colours, shades and blends. ducts. &MATO loon And why stop at the panel?Re- If you have any difficulty send Fig. 5.-This easily -made tool enables cently I showed how cabinets could he us the name and address of your Dealer the constructor to make neat loops in constructedverysimplyfromply- we will supply immediately. a moment. wood. You can if you wish substitute for ply -wood erinoid or ivorine in any and twist in an anti -clockwise direc- desired shade, for it it can be obtained tion, holding the wire so that it does in sheets from 2 mm. to 20 mm. in not slip from the studs.The wire thickness.It takes, as we shall see seen in the drawing on the tool has in a moment, a delightful finish, and THE VARLEY MAGNET CO., been bent in this way, which is the Ifitisused,cabinetsofstriking (Proprietors: Oliver Pell Control Ltd.) Granville House, Arundel St., London, WAR. first part of the process.The next is appearance can be made at very small Telephone: City 3393. In replying to advertisers, please mention TffE WIRELESSCONSTRUCTOR. 259 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 - . # p Ow -4674r?NO 1 11114 ,i;i4 Write for SECONIY i4,,,...... Free List. Quallt9 ...1,?.....------...... ,. Supeitine QUALITY -...s! ...... 571---' ...;,.- ,--- --. ,II WE DO NOT elc10)1.t.ie MANUFACI-71.112 ,N, 1r eeso LOW GRADE 'ilIF"w GENU1N MATERIAL ,,A.1 ook 2'000 ER MOM ...7 Wthat ''ItgaGyfi '124d4 u`g' eb4"..14.05. dclealat fOr PRICES -:--- /11, '. THICKNESS. HIGHLY POLISHED. MATT.STANDARD GLOSSY. AIATIOGANY. EL-- tin. Per sq. in. Id. .9d. 1.1/3d. IV in. Per sq. in. .75.1. .66d. .6d. ld. /II Address Trade Enquiries only to:-P. C. MICHELL, Managing Director. RS TRELLEBORGS EBONITE WORKS Ltd., AUDREY HOUSE, ELY PLACE, E.C.1 This mark is your guarantee of good workmanship. It is a safeguard against hidden faults-an earnest of good results.It is stamped on very reliable 11111111111 11 I II II ,-:.---I components. IllustrationshowsVarioCoupledInductance W.G.i, fitted with special tapping switch 2oot5 goo metres,price59/6.W.r.tappedinductance ,;-.9, with six tappings 1 goo metres,251-. A MONUMENT IN THE //' .9,.., MARCH OF PROGRESS. ._ The FORMO SHROUDED Trans- WE 'IT former is theuniversal favourite. Lancashire Agent : Made in Ratios 1-1,1-2,1-3 1-4 & 1-5 Alexander COMPMO 17'Ssciaias, 1-3 & 1-5 for lit & 2nri Stages. 1B, Coopertreet, SEND FOR CATALOGUE AND DESCRIPTIVE Manchester. WRIGHT & WEAIRE, LTD., LITERATURE OF COMPLETE FORMO RANGE, 1 '3lasgow Agent: 740, High Road, Tottenham, N.17. THE FORMO COMPANY. CROWN WORKS. CRICKLEWC'OD, N.W.2 C. G. Tidetnan, Telephone: Tottenham 3132. Telegrams: Inland, 'Phone :Ramp. 1787. 17, Cartick Street, "IVritewea, Tottlane, London." Foreign, "Write. Manchester: Mr. J. B. Levee, 23, Hartley St. C.2, Glasgow. wea, London." 1E.6-4 Levenshulme. 'Phone: Heaton Moor, 475. 11111(111111111 STEEL PLATE FLOR " THE BETTER BATTERY- The World's finest H.T. Accumulator ACCUMULATORS per volt. FOR OUTSTANDING FEATURES HIGH TENSION 60v-f28 0 ECONOMICAL 80v-£2 17 0Reliable Service 120g-£40 0 Only 11= per volt. Constant In handsome Voltage Oak Cabinets Absolutely Noiseless. with carrying PURITY OF No Acid. No Fumes. handle. TONE Last a Lifetime. Sendto -day for illustrated Brochure : Dealers send at BATTERIES, LTD., REDDITCH once for generous LONDON OFFICE Shaftesbury Avenue, W.C.2. SMITH FARMER & CO. trade terms. 6. BROAD STREET PLACE, E.C.2. 4.1*ItSIEST'VALVE CONToos, by Lising A'P')Ej / Canbeassured ofdythe Potentiometer, WHEN you are setting outto Resistance, 6,13 or 300 ohms3s. 6d. 30 ohms - 2s. 6d. Resistance,50 ohms 3s. British purchase radio apparatus, first throughout. lookthroughtheadvertisementsin NEW TOD GUARANTEED RESISTANCE your copies of "THE WIRELESS (Potent No. 225132) Smooth and dead silent in operation; perfect insulation;positive stops for " Off " and " Full On " positions; a travel from " Off " to CONSTRUCTOR." You can feel " On" in two turns of the knob, easy to fit; occupies minimum panel space.Every one carries our written guarantee to replace it free if the ofyourrequirementsbeing slightest defect be found within 3 months from date of purchase. certain Of all dealers or direct If ordering direct state postfreefrom Solo whether one or two hole suitably and satisfactorily met. Manufacturers- am fixing is desired. sPEE,DwELL WORKS, QUEEN S T ie1,,,ST, HITCHIN umussee Alo" er 4 ri 260 In replying to advertisers, please mention THE WIRELESS CONSTRUCTOR. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor 'January, 1927 THE WIRELESS CONSTRUCTOR For theseSets WORKSHOP HINTS-concluded describedfl to issue:- THREE-VALVE- cost.Another use for this material is to be found in the naming of ter- THREE-VALVE "ALL minals.Small discs or squares can be ROUND EUROPE" cut out, upon which, the nature of AND THE any particular terminal can bein- scribed in Indian ink. If a 4B.A. "ECONOMICAL TWO" clearance hole is: drilled in these they USE can be placed between the terminals and the panel upon which they are mounted. Easy to Work Allofthese materialsarevery pleasant to work with.They can be cut with a hacksaw and drilledor tapped aseasily' asebonite,more easily infact, since owing totheir slightly softer nature they show prac- tically no tendency to split when they are drilled or to strip when tapping is being done.All of them will take a beautiful finish, and will repay any Christmas- trouble that is spent upon them to produce it.They differ from ebonite, "PEERLESS" RESICON CONDENSERS- Uniform Tuning. Low ElectricalLoss. from the workshop point of view, in No Backlash. A PrecisionInstrument. one important respect.When you are How willyou Capacity. working ebonite it is not advisable to .00025 Complete with Dial 15/- (With Dial and Vernier) 17/6 run drills at too high a speed; with .0003Complete with Dial.. 16/6 spendit? any of the materials mentioned the (With Dial and Vernier) 19/- speed can hardly be too high. .0005Complete with Dial.. . 18/- (With Dial and Vernier) 20/6 Finishing "PEERLESS" REEOSTATS- JUN IOR JUST sitting in front Like ebonite, these materialsare Resistance easily moulded to any desired shape elementim- of the fire, listening - by immersing them in hot water prior mune from in, snug and happy. damage. Will tooperations.They are thus par- safely carry It's something to look ticularly suitable for making formers current of two valves. forward to as long as to carry the windings of rheostats and OFF position you know your Radio potentiometers. They are less hard provided. upon tools than is ebonite, which will Definite Stops will be in perfect order. make short take the edge off drills or lathe cutters circuit im- Here's a suggestion- more rapidly than metal. To obtain possible.Complete invest in a TANGENT a high finish begin by removing, with with nickelled H.T. Battery Elimin- a medium grade of glass paper, any dial.One-hole fixing. Three atm' and your Radio scratches that may have been made. types: 6, 15 will not let you down. This having been done, wrap a piece or 30 ohms.Price Z 6 each. Give yourself one for of finer glass paper round a fiat piece DUAL of wood and work over the surface. Has two windings-a resistance of 6 ohm with a a Christmas present. continuation on to a 30 ohm strip winding. Follow this with a piece ofi the finest Resistance wire wound on hard fibre strip under Absolutelysilentin glass cloth, and finish off by dressing great tension and immune from damage.One - operation. Ample out- with a mixture of beeswax and tur- holefixing,terminalsconvenientlyplartd. Contact arm has smooth silky action.All metal put for thelargest pentine and applying plenty of elbow partsnickel -plated. Complete withebonite receiving set. greasewitha selvyt "polishing combined knob and dial. Price 3/9. cloth. -and Fixing "PEERLESS " Price complete in metal case with These materialspossess onegreat FIXED advantageoverebonite:piecesof RESISTORS connecting plate - - £7-15-0 Made invarious them are quite easily' stuck together sizes. Suitable with glue.Any good fish glue is quite for all types of suitable for the purpose.It should, valves. however, be remembered that the glue Price 1/3. takes some time to dry, which makes it advisable for the surfaces which are to be joined to be left under pressure until the joints are theroughly set. All of thesematerials,if verythin sheets are used, show a slight tendency to warp.1 have, therefore, 'found it best when employing them as veneers From all good either for panels oy. for cabinets to fix dealers or LONDON: NEWCASTLEITYNE: direct:- 25 Victoria Street, TANGENT House, them in position -both by screws and S.W.x. Blackett Street. bya layer ofglue, If, however, Bedford Electrical & Radio reasonable care is exercised, they will Co., Ltd., GENT & CO. Ltd., Faraday Works, be found most satisfactory inevery 22, Campbell Road. Bedford. LEICESTER. way. In replyingto advertisers, please mention THE WIRELESSCONSTRUCTOR, 261 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 As usedinthe MONODIAL LOSSES described in " Wireless " Oct. 30. "THE inductances used have an extremely low self -capacity so that the 200- to boo -nitre and GAINS band is covered by a movement of about 90 degrees Losses are disastrous in S.L.F. Condenser design. on the dial and itis possible to proportion the coils so that the whole of this waveband comes approximately above the critical point on the dial The more supports there are below which there is any risk of the matching not between the fixed and moving holding good. Another effect of reducing the size of the induc- vanes the greater is the leakage. tances is to reduce their H.F:--resistance and so produce an increase in efficiency." The Bretwood is the only condenser made that has only TWO supports COMPLETENO EXTRA FOR MATCHED COIL COILS KITS and losses are therefore reduced to to standard specification (long wave and short wave coils) are included in the following prices : a greater minimum thanthat of Split Primary H.F.Trans- any other design. former, B.B.C. 9/6 Split Secondary H.F. Transformer,B.B.C... 9/6 Lose nothing, but rather gain greatly Tapped AerialCoi1,13,13.C. 5/6 Reinartz Coil,B.B.C. 9,'6 in selectivity and general reception Matched Coils for"Mono- results by fitting dialReceiver pair19) - SpecialCoils for " Span - PRICES : BRETWOOD space Three pair18/ - S.L.F. LOW -LOSS CONDENSERS THE COLVERN FORMER .0005 - 17/6 CAN BE SUPPLIED WITH Free illustrated folders of all Bretwood Components EITHER PLAIN RIBS OR .0003 -14/9 on request. THREADED RIBS, 40 T.P.I. Send postcard or full particulars .00025- 14/- Grid Leak de Luxe--Auto-Audio Frequency ofColvernProvedProducts. Amplifier-Filament Rheostats-Valve Holders .00015- 13/6 -Coil Plugs-Switches. COLLINSON PRECISION SCREW Copper Screen with Stan- CO., LTD., Obtainable Send P,c for copies by return of post. dard 6 -pin Base .. 8/6 from all Screen complete with Base Provost Wolks, Macdonald Road, & unwound Coil ..12/6 Dealers. BRETWOOD LTD., Former & Base, unwound 6/ - Walthamstow, LONDON,E.17. Formeronly 4/ - LONDON MEWS, MAPLE ST., LONDON, W.1. Base ..1/6 Telephone-Walthamstow 532. ALSO AT 150, RING'S CROSS ROAD, W.C.1 Parrs Ad. OBVIOUSLY THE BEST Geta"BELDEN"1671 AIR -SPACED BRAIDED AERIAL Something entirely new and gives the best re- Balancing Condenser is the sults. Each strandis insulatedwithenamel NEUTROVERNIA and then braided so as BECAUSE: to offerthe maximum It has the widest capacity range, approximately2/38 micro microfarads. signal receiving surface. It cannot short-has ebonite di -electric. Extra flexible and suit- Is one -hole fixing for panel mounting. able for either indoor or As now supplied is adaptable for either panel or baseboard mounting outdoor use.Price 3/3 without extra charge. per no ft. coil. The capacity change is proportional to the rotation ofthe knob, i.e., each turn is equal to approximately 6 micro microfarads. It can be fitted with direct reading dial (price Is. 8d.), enabling a return " MIDGET " to be made to exactly the settings previously logged. FRICTION TUNER It is all enclosed, making it dust and damp proof. This will add t00% to the efficiency of The knob does not screw in or screw out, but merely rotates. your set.It can be easily fitted to any Is ide ' riot only as a balancing condenser, but as a capacity reaction set;is self-adjusting.All metal parts control and vernier condenser. heavily nickel -plated.Highly polished It is a precision lob throughout Bakelite knob and rubber washers. Com- write for complete plete with fixing instructions.9d. each. and the price is only details of all 5/6 Gambrel l products. Trade enquiries invited. OBTAINABLE FROM LEADING DEALERS. THE STANDARD INSULATOR CO., LTD. GAMBRELL BROS. LTD. Winsley House,Wells St.,Oxford St.,London,W.1 76, VICTORIA STREET, LONDON, S.W.1 'Phone; Museum 5978. Parr's Ad. 262 In replying to advertisers, please mentionTHE WIRELESS CONSTRUCTOR. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR D...... 0 FURTHER NOTES on the "NIGHT HAWK' By PERCY W. HARRIS, M.I.R.E. Alternative Components-High-tension Supply-Trying for America. SINCE writing the notes on the America with it, here are a few hints " Night Hawk," which were pub- that will help you. lishedin the November issue of (1) First of all, do not attempt to CKS this journal, I have had an opportu- listen before midnight.It will be a nity of trying a number of alternative sheer waste of time, save in a few makes of components in this set, and favourable localities, such as Cheshire, have made several structural changes where occasionally American stations in order to include them. have been heard before midnight. (2) Remember that past experience Alternative Components has, shown the most favourable time I canrecommend any good make for reception from America is between of variable condenser in this set, pro- 1 and 3 a.m.This corresponds with vided it does not occupy appreciably 8 p.m. to 10 p.m. in the New York more space thanispermissible. I zone,or7 p.m. to9 p.m.in, the have tried several makes of 250,000 - Chicago district.At that time it will ohmresistance,andfoundthem be dark all the way across.It is rare are made of nickel silver springs, equally satisfactory, and I have also for reception to be effected on the with pure silver contact, and testedMessrs.Peto-Scott'sfieldless broadcast band from American Bakelite insulation throughout. stations when one or both stations is Tags are tinned and spread fan coils,and find them well up to stan- wise for easy soldering. dard.As to valves, a large number in daylight. (3) Do not attempt to search all over Jack No. Jack No. 2. of makes have been tried with satis- single Clr- Single Cir- factory results, although there is no the broadcast band on one evening. cult (open) cult (closed) 6 Conditions are very freaky, and if you question that in the first three stages Jack No. 3. Jack No. 4. valvesdesignedforhigh -frequency concentrate on a small band, such as Double Clr- Filament1/9ingle that round about 380 metres, you will cult Con- work and resistance -capacity coupling trolS . give the best results.The neutralising have a reasonable chance of hearing Jack No. 5. position varies with different valves, WGY, which comes in very strongly ment Double Con - but once it has been found for a par- trol ticularvalve,itremainsinthis TELEPHONE PLUG, 1/6 setting for the durationof the life of the valve. CLAI.IITONJE , The high-tensionsupply needs to be adequate for a modern five -valve set, LOUD SPEAKERS and the " Night Hawk " is no excep- Senior Model, 2,000 ohms.W. 265 For this reason I * on 120 ohms.W. 266 tion to this rule. £5 0 0. JuniorModel, 2,000 ohms.W. 267 The "Night 120 ohms.W. 268 Nawk "receiver, of which con- £215 0. structional details CLARITONE HEADPHONES appearedinthe W. 216. 20/0 October issue of "The Wireless Constructor." ASHLEY WMELESS TELEPHONE Co. Ltd. 17, Finch Place, LondonRoad, LIVERPOOL. cannot recommend the very small -size when conditions are good.If you are high-tensionbatteries,and,ifyou fortunate enough to tune in a station, have them, a high-tension accumulator leave the set alone for a little time will prove most economical in the long and listen.Without your touching run.If you use dry batteries I would the dial the signal strength will in- strongly recommend thelarge type crease and decrease, sometimes slowly specially designed formulti -valve and sometimes rapidly.This will be sets. duo to natural conditions, and will not be anything to do with your set.Re- America on the "Night Hawk" member that in long-distance recep- If you are building the " Night tion of this kind, patience will do far Hawk " receiver and decide to try for more than twiddling the dial. In replying to advertisers, please mention THE WIRELESSCONSTRUCTOR. 263 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 111011011101110111OMMICEE11111111011110111 14,AAAA.AAAAAAAAAAAAAAAAAAAAAil Glut owl the WORRY of uncertain High Screened Coils Tension Batteries. Install one of ATL ,S "B" BATTERY ELIMINATORS and lead the way to Brighter Radio. Models forA.G. Upkeep negligible. and D.C. Current. Silent & Efficient. VariableVoltages. WE GridBias. Full GUARANTEE waverectification. everyinstrument. We make them goodGood judges make them famous Manufacturers ofthe famous " ATLAS " Plug -In Coils, and Fixed and Variable Condensers ;alsosole manufacturers of the Super Selective Reactor Formers. H. CLARKE 8/CO.(Mar.)Ltd., Atlas" Works, Old Trafford, Manchester These Screened Coils and Trans- en" tiVinr XI V VO 'NY`.411 formers have been designed in collaborationwiththeRadio Press Laboratories and are suit- PRECISION TheEtherplusStraight Line Frequency Condenser able for use in all Radio Press is an instrument of precis- ion. It has a low minimum circuits embodying Screened Coils capacity and gives an even distribution of frequencies over the whole range.It> has a self centring ball race and cone bearing. Prices and Particulars Each avir.Ar i..us+ Nallimon No. Wir8o .0005 12/- each Split Primary Aerial Coils (250-550 metres)6/- Front alldealersor front (with 4" knob dial). (1000-2000 ) 6/. Split Primary FI,F. Transformers M. & A. WOLFF, (250-550 metres) 10/. 9-15, WHITECROSS STREET, LONDON, E.C.1. (1000-20(0 )10/. Split Secondary H.F. Transformers (250-550 metres)10/- ,,(l000 -20J0 )14/. Reinartz Coils (250-550 metres)...... 10/. (10(0-2000 ) 14/ - Screens, complete with 6 -pin base...... 15/. THIS OUT FOR CABI N EIS Send for FREE li,t illucGating Cabinets as ,hown itr All enquiries for Lewcos Radio Products should Modern Wireless," etc.. etc., and for our additional be made to your local dealer.Descriptive leaflet But elfin No 1. gladly sent on request to THE NAME LONDON ELECTRIC WIRE ADDRESS COMPANY & SMITHS, LTD. (Write in blOck letters please.) CARRINGTON Mfg. co., Ltd. Playhouse Yard, Golden Lane, London, E.C1. 18-20, Normans Buildings, Mitchell St., Central St., E.C. 1. Trade enquiries especially invited. liDousomumEmmeomanomosom Telephone: Clerkenwell 6903. 264 In replying to advertisers, please mention THE WIRELESS CONSTRUCTOR, PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 192:7 THE WIRELESS CONSTRUCTOR DOMEEDOCIT-30E300000000000E000011EMDEEDEEEDODEEEEE00000000000009009E0OLIECIE0E000EOLGEE ID El O 9 O 0 O 0 0 0 d SOME SOLUTIONS TO YOUR 0 E 0 0 0 SUPERHET PUZZLES 0 E 0 E 0 El By JOHN UNDERDOWN 0 El 0 O 0 E 9 El A fault in a superheterodyne receiver, preventing it from functioning properly, is often difficult to 0 El 0 locate, and much time may be wasted "on a wrong scent."If you have encountered any of the E 0 CItroubles mentioned here, you will find useful information given to enable you to set matters right. 0 O 9 El E Fl El DEEEEEE0E000ME2EOEEHEEEEEMEMEEICEICIDEEItIEECIEEEEOEEE DF1FlEEEIMOOM EECEIECIOOF FIDIEIDEELI7EE IN a recentissueof this journal socket in turn and the filament in Almost Normal Behaviour (October, 1926) I gave details of eachcasewascontrolledproperly. When the long -wave potentiometer how various super -het.arrange- AllH.T.positiveleadswere then was adjusted, after having tuned in ments might be tried with a minimum joined together and were tapped into to the silent point between the normal amount of trouble. This articleis a comparatively low voltage socket of two heterodyne whistles, no telephony intended to deal with a number of the H.T. battery, and since the fila- could bp heard, but by very careful faults peculiar to super -het. circuits ments did not increase in brilliancy searching signals at crystal strength inorderthat,shoulddifficultybe it was assumed that all was correct, were obtained from the ledal station. experienced,readers will have some andnormalH.T.voltagesforthe The symptoms therefore were that the idea of where to look for the faults. valves in use were applied. set was -behaving exactly as a super - The potentiometer controllingthe het. should do, excepting that all the Puzzling Symptoms intermediate -frequency amplifiers was usual phenomena were much weaker In alongandsometimesbitter set about midway, in which position than should have been the case and experience with various super -hetero- this part of the receiver was stable, only very weak telephony could be dyne sets,I have found that minor and tuning was carried out in the heard. faults in components have very far normal manner upon the frame aerial reaching effects and often appear to condenser C, and the oscillator con- Substitution Tests implicate any other component than denser C,. A general deadness was the one actually responsible. experienced, however, the usual clicks To eliminate the valves as being The ,first real difficulty which I met oftheoscillator going out ofthe responsibleforthedifficulty,these withwasexperiencedwithaset oscillatingconditionwhenintune were tried individuallyina single - employing a separate oscillator with the frame circuit being present, valveset, allappearingupto arrangement, two intermediates, the but at very poor strength.Similarly standard; fixed condensers and grid- OSC HT.+F. F. & OFT FRAME AERIAL V 4 Ce Fig. 1.-A straightforward superheterodyne arrangiment, employing a separate oscillator valve. usual first and second detectors and a the long -wave side could be made to leaks were replaced by others known transformer -couplednotemagnifier, oscillate, and upon rotating the oscil- to work effectively, and the potentio- the main .part of the circuit being lator condenser, in conjunction with meter was checked for continuity, but indicated in Fig. 1. the frame tuning condenser, it was no faults were located. Testing foundthattheusualheterodyne carrier whistles, usually denoting that The Solution Upon completion ofthe wiring a a carrier wave is being received, were Finally,indisgust,. the wiring of valve was insertedinto each valve heard. the whole set was stripped down and 26/$ PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 SOME SOLUTIONS TO YOUR SUPERHET PUZZLES-continued NewRadically Different the springs of the anti -vibratory valve holders, normally hidden when these It's allbattery.With components are screwed to the base- every cubic inch packed board, were examined. All was in to capacity, it contains order here, but finally close examina- about 30 per cent. more tion of the metal valve sockets, which electricity - producing were embedded intheusualcom- material.All chance of position moulding, showed that the insulating material was,in the case loose or broken connec- of one valveholder,slightly over- tions avoided by contact lapping the edge of the metal, so that of full area of carbon plate the plate leg of one of the valves was against zinc plate. Price not making contact. 25/-.No increase in Satisfactory Operation price over old type. Uponremovingtheoverlapping insulatingmaterial fromthevalve 9 holder in question and re -wiring the set, it was found to function in a very satisfactorymanner,mostofthe main British stations being received atgoodloud -speakerstrength,as were a large number of Continental transmissions also. THE MOST IMPROVED H.T. BATTERY YET MADE Introducing Reaction To sharpenthe tuning andgive Absolutely new in construction-perfected through years of research in the improved range, an excellent scheme greatest commercial laboratories known to science, the newCOLUMBIA to adopt is to utilise a split frame in LayerbiltB " Battery is as superior to the old type of " B " battery as themanner showninFig.2.In many casesthisispractically equi-7 a valve set is to a crystal. valent to adding an H.F. valve and Heretofore, all H.T. batteries have been made of cylindrical cells- has the merit of giving considerable no one knew how to make them any other way. The newCOLUMBIA improvement withoutnecessitating Layerbilt isnade of flat layers of current -producing elements the purchase of a further valve with compressed one against another, so that every cubic inch inside the consequent increase offilament and H.T. current.With arrangements of battery case is completely filled with electricity -producing material. the Fig. 2 type, however, I have come Layer -building heightens the battery's efficiency by increasing the into contact with a number of cases area of zinc plate and the quantity of active chemicals towhich the in which somewhat similar symptoms plate is exposed. were experienced to those given pre- viously. After the most rigidlaboratorytest,more than 30,000 of these new COLUMBIA Layerbilt H.T. Batteries were manufactured and tested by The Local Station Only fuse under actual home receiving conditions. These tests prove that on sets It is sometimes found that only the of four or more valves the life of this battery is 35 to 52 per cent. longer than local station is obtained, and that at the famous COLUMBIA extra Heavy-duty H.T. Battery No. 4770, which poorstrength,whilstwhetherthe oscillatorvalve isalightorex- up to now has been recognised as the mostpowerful and longest -lived H.T. tinguished makes but little difference. Battery manufactured. Occasionally bringing this latter valve The new Layerbilt principle is such an enormous stride forward in radio into operation prevents any telephony battery economy that the National Carbon Company will bring out other being heard.When this happens, the troubleisusually due tothefirst sizes and voltages in this Layerbilt form as quickly as new machinery is detector, V,inFig.2,oscillating. installed.For the present only the extra Heavy-duty 45 volts size will be Thefirststepto take thenisto available-READY JANUARY 1ST, 1927. decrease the H.T. on the first detector down toa very low value,of the Buy the new COLUMBIA Layerbilt No. 4486.It far exceeds the perform- order of 20 or 30 volts, when it will ance for which COLUMBIA Radio Batteries have alwaysbeen famous. be found, in most cases, that the set It is by far the most economical source of H.T. current obtainable. behaves in the normal way, provided the oscillator. valve V, can be made Manufactured and guaranteed by : to function correctly. NATIONAL CARBON COMPANY. Agent : Feeble Oscillation If only feeble oscillations are obtain- J. R. MORRIS, able, the difficulty is often due to the IMPERIAL HOUSE, KINGSWAY, W.C. employment ofunsuitablecoilsfor the grid and plate coils 02 and 03. These two coils should be similar in size and should not be coupled mag- netically.When the coils used here Columbia are of very inefficient type the oscil- lator valve may oscillate only in a Dry Batteries veryfeeblemanner. Improvement can often be obtained by employing In replying to advertisers, please mentionTHE WIRELESS CONSTRUCTOR. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR Some Solutions to Your Superhet Puzzles-continued a valve whic% oscillates more readily, filter position is high, an H.F. choke and to substitute a variable condenser suchascertainoftheresistance - may have to be inserted at the point of larger size than C,.The variable coupling types, whilst an increase of X. condenser can then beadjusted to the applied H.T. is sometimes helpful. bring thefilterinto tune with th( Tuned Intermediates intermediate transformers T, and T2 A Last Resource When the primary and secondary slight adjustment being made to the windingsofthefilterandinter- oscillator condenser with each adjust As alast resource, when all else If failstoprevent . thefirstdetector mediate -frequencytransformersare ment of the former condenser. taking on the oscillator'sfunction, the reaction arrangement should be discarded temporarily and the whole 214 oftheframe,stilltuned byCl, oa should be connectedacross. the grid and filamentofthefirstdetector. The receiver panel Attention may then be confinedto of the Marconi the oscillator, other coils and valves beam station being trieduntilthispartofthe which was com- receiver behaves in a more healthy p le t e d recently. manlier. Finally the split -frame Thereceiveron scheme may be reintroduced, if neces- the left is for sary, with a smaller condenser in the signals from South Africa and C, position. that on the right Reaction Effects Lacking for those from The converse of the previous Canada. trouble, namely, difficulty in obtaining reaction effects with a split -frame,is -usuallytraceableto thefirstinter- it -Ye * mediate transformer orfilter(Fin Fig. 2).In order to sharpen iv the tuning of the long -wave side,itis tuned bysmallcondensersincor- when matters are balanced up here fairly common practice to employ a poratedin theseunits,andupon itis found that the long -wave side suitablefixedcondenser, C, endeavouring to balance the long side oscillates more readily and selectivity shown dotted, across the primary. of it is found that clicks are heard and isimproved,asuitablefixedcon- the transformer in the anode circuit signals disappear, a short in a tuning denser should replace C or alterna- of the firstdetector,this condenser condenser should besuspected,and tivelythevariableone shouldbe often being incorporated within the thekit shouldbereturned to the retained. transformerunit.This,ofcourse, makers for examination and report. Valve Characteristics actsasa bypass and prevents the Fortunately this fault is by no means requiredchokingeffectfrombeing a common one. It sometimes happensinpractice obtained. Poor Selectivity thatthevalvesemployedinthe The Solution intermediate -frequency positions vary The selectivity of a superheterodyne widely in characteristics.The result Often a simplemethodofover- set should be of a high order, and of employing such valves may be to coming thistroubleistoplace the when thisispoor the matching of give risetoveryweirdsymptoms, often seeming to implicate the H.T.+Osc. oscillator more than any other part of the set.If suspected, the valves shouldbe changed roundinorder diDt----9-aHI+ DE7: that those most suitable for the inter- F mediate -frequency amplifier positions R3 may be used. An individualvalve maybere- sponsibleforoneintermediate -fre- FRAME quency stage oscillating on its own, AERIAL HI with the resultthatthepotentio- meter has to be taken practically over tofullpositivebeforetheinter- mediate -frequency side is stable. This, of course, results in the inter- POTENT F_t mediate -frequencystages being par- ticularly insensitive when adjusted to L.T. function just belowtheoscillating condition. A good indication as to which inter- Fig. 2.-The use of a split frame aerial with a superheterodyne receiver' mediate -frequency valve is responsible will often produce a noticeably improved performance. may be obtained if the long -wave side filterin the anode circuit of one 'of thefilterandintermediatetrans, is, just allowed to oscillate gently, the the intermediate -frequency ampli- formers, for example F, Ti and T, of gridsoftheintermediate -frequency fying valves, its place being taken by Fig.1, isoftenresponsible. The amplifiers being touched in turn.If the transformer which would other- first step to take in a case of this only one valve is oscillating, a much wise be employed there.Where, how- kind is to remove the fixed condenser louder plop' will be obtained when its ever, the self -capacity of the primary acrossthe primary winding of the grid is touched with the finger than winding of the transformerinthe filter transformer F, if this is possible, that given by the others. 267 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 Loa(PRONOUNCED SIL-DON) triumphs at NEW YORK CAMSTERDAN1 AT AMSTERDAM the International Gold Medal was awarded to an " Elstree Six" fitted with CYLDON Condensers. At the Radio World's Fair, New York, September, 1926, the 2nd and 3rd prizes were won by receivers fitted with CYLDON Condensers. These were " Mewflex " and "All British Six " respectively.Allin competition with American and European receivers. Verb. Sap. IIIIM11111! u.116111 1.'114 \ *j:In G -Ai //1 = 20/1 eh Man. I , 00 ~4;-.111OMII: II liy=11411311.1 .11_4 (41S/ a'1)2% CYLDON GANG CONDENSERS 2 GANG £210s. 3 GANG £3 -10s. 4 GANG £4 -10s. (Prices without dial.) .0005 mfd.27,6,.0003 The complete range of CYLDON Condensers consists, DUAL CONDENSERS :mid. 25/.,With dial. in addition to the Gang Models, ofthe Dual, .ono517/6,.000316/6, SQUARE LAW : .0002516/.,.0002 15/6. the Square Law and the S.L.F. Models in the With dial. .0005151f, .00c3515/-, following capacities and prices :- S.L.F. MODELS : .00025 14/6. Dial 2/... CYLDON TEMPRYTES--THE BEST METHOD OF VALVE CONTROL CYLDON TEMPRYTES areBritish made and unconditionally guaranteed.Can be supplied in correct resistance for any Valve.When Send forparticulars buying state resistance (ohms) required or be of the Cyldon WA VE- sure to give name of Valve and voltage of accumulator supplying current to the Valve. M ET ER-it identifies unknown stations and CYLDON TEMPRYTES....2/6 snakessearching and testingoutsimplicity itself. HOLDER MOUNTINGS....1/6 If unable to obtain CYLDON Products locally write direct to : SYDNEY S. BIRD & SONS, CYLDON WORKS, SARNESFIELD ROAD,ENFIELD TOWN, MIDDLESEX Telephone :ENFIELD 0672. 268 In replying to advertisers, please mention THE WIRELESS CONSTRUCTOR. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor J anuary, , 1927 THE WIRELESS CONSTRUCTOR IS IT WORTH WHILE ? By a Critical Listener Distant reception and good quality: can theygohand in hand, or are they alternatives which cannot be obtained together ?Decided views are expressed in this article, which raises many points of interest to a large number of listeners. AS the- popularity of broadcasting comes to comparing wireless with the the possibility of purity in reproduc- as ameans ofentertainment real thing,but with that point of tion will be converted. increases and the time is not too - view I entirely disagree. far distant when the radio receiver Choosing the Right Valve willberegardedas partofthe Unsuitable Apparatus ordinary house furniture, the listener So long as the receiver is well made In the majority of sets some form is becoming more and more particular and the right circuitis used in con- of general-purpose valveis used for as to the quality of reproduction. junction with therightvalves and the detector stage, and it should be A greatnumberofthegeneral loud=speaker,theresultsaredis- remembered that since for the best public hankers after the distant sta- tinctlypleasingaridinno *ay results the impedance of the primary tions,hopingthatthesemay, be - unmusical. Unfortunately, in many windingof theL.F.transformer received with an absence of interfer- cases the conditions just given are should be suitablefor the typeof ence and. distortion such as they are notcomplied with, and oneoften detector valve chosen,it isnot any accustomed to when listening to the finds a listener using a valve in his valvechosenindiscriminatelythat local station: Arguing alongdathese set which is quite unsuitable for the will givea reproduction which ambition lines, I ask the queSTion- circuit ;in fact, only the other day a satisfies one's interpretation of Isit worth while? case .was brought tolight where a purity.Itis unfortunately not pos- listener, thinking that he was doing sible to give definite figures regard- Multi -Valve Sets right, was using a special yeaistance- ing the impedance of this winding, capacity coupling valve in series with for practically every type of valve has - In the firstplace,before one can hope to receive the majority of the anL.F.transformer which was a different impedance.One of a cer- distant stations at loud -speaker strength,itis necessary to possess a receiver which incorporates no. small number of valves, and apart from the_ expense involved in the construction -X- * of such a set, it is rarely that one is able to listen to a dislant .station free from Morse interference, local oscilla- f` Since music is tion, and the. like. Certain multi.. music the world valvesetswilladmittedly do their over, what does it jobs properly, but these usually incor- matter whether it porate special coils or screens or both. comes from but a anditis notwithin thefinancial fewmiles away ability of all of us to incur the expense instead of necessaryinthebuildingofsuch hundreds ?" receivers. Natural Reproduction To the man of modest means the local station must serve as the main centreofamusement,thereforeto receive this station with the greatest possible purity, rather than the con- designed with a ratio suitable for use tain make of valve will quite likely quering of distant reception, becomes with one of the popular power valves. haveanimpedancedifferentfrom the chief ambition. Further, since The result in this case was distinctly that of a similartype of valveof music is music the world over, what unpleasantand - fullyjustifiedthe another make,. but we can comproMise does it matter whether it comes from condemnationit geceived. to some extent by using a first stage butafewmiles away insteadof transformer of reputable manufacture. hundreds? Amplifier Faults These components are suitable for A weak argument to meet that of the The causes of poor reproduction are use aftera detector valve and the " distance " listener, with his talk of many and varied, particularly in the makers have in most cases based their fascination,hisglory in conquering low -frequency portion of the circuit, designs upon the assumption that a distance, and so on, but for all that and since the most common form of valve ofrelatively highimpedance an argument which to many of us is L.F.amplificationisby means of will be used as a rectifier. a perfectly sound one. transformers, some ofthesecauses Provided that onlyone stageof Some listeners say that even the will be discussed in the hope that at transformer couplingisused, thew local station is a poor show when it least some of the sceptics as regards should belittledifficulty in obtain- 269 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 Isit Worth While ?-continued inggoodquality,but where two and though it will be appreciated that with them is, so far as radio is con- stagesareemployed,morecareful itis not possible to deal with every cerned, an evening spent in painful operationisnecessary,forthe best point and every type of circuit which indulgence. You are askedif you results. may affect good reception, it will,it would care to hear Radio -Toulouse, Inaudible Oscillation ishoped, be recognised that almost anduponexpressingtheobvious as much experimental and pioneer desire (obvious in that to give a nega- Many home constructors are fami- work can be spent in making the most tiveanswer wouldprobablyoffend liar with the fact that a newly -made of the local station as can be devoted your host)Radio -Toulouseistuned amplifier sometimes howls untilthe to receiving our Continental friends. in.Some moments pass in listening, connections tothe primary winding Possiblythislatterhobbywill whentheoperatorexpressesthe of the second transformer are bringresultssooner, butneverthe- opinion that it is not quite so good as usual, and proceeds to readjust the set. During this operation he hits upon another station and is not con- tent until this is tuned -in and identi- fied. Satisfiedupon thispoint, he decides that it is a good evening for receiving Radio -Milan, San Sebastian, Oslo,and many others,withthe A general view of result that instead oflisteningto roomthetransmitting at the Radio -Toulouse as you were content Bodmin Beam to do, the evening has been spent in WirelessStation, hearing snatches of music of doubtful showing the con- origin and talks in foreign languages trol table in the which you do not understand. centre. Itis-yme thatone hastoured Europe in imagination, it is true that one hasheardpracticallyevery language spoken in Europe, but since ** one's desire was to listen to music in anintelligent manner-isitworth while?' This knob -twiddling in search .of " distance " when one really wants music is much the same as giving a gun to an angler to catch salmon with reversed, but few know that though lesscarefuladjustmentsandthe -he may land his fish, but the amuse- no howl is heard the amplifier may discriminatinguseofvalveswill ment is gone. stillbe oscillating-atafrequency quickly show that one is progressing above the audible range.In such a along the right lines. aooe,szio%oceeoecoofgEs)ao case distortion will, of course, be most marked, and after reversing connec- Local or Distant ? 0 A " FILLING " FOR OLD tions to see whether that will effect a In conclusion, letit be saidthat cure, the disposition of the two trans- whereas there will always be listeners 0 EBONITE PANELS formersinrelationtoeachother who hankerafter the foreignand 413 should bevaried,observingthe other distant stations, there will at c5g000f3f3(fNX90G0t113g0(89&E3 results as regards purity. the same time always be listeners who WHEN one is re -designing an old desire tolisten to the localstation receiver and bringing it up to Grid Bias only.The arguments of these latter date, it nearly always -happens One of the biggest reasons for there asto why theyare contentwith that there are a certain number of beingso many scepticsastothe bridging a relatively few miles, when holesinthepanelwhicharenot purity which they say that wifeless itispossible to cover several hun- needed in the new design. is unable togive,is thecomplete dreds, is largely built upon the fact Chatterton's compound is often used absence of understanding of grid bias. that interference by shipping, hetero- to fillthe unwanted holes, but this It is,of course, essential to use the dyning of the desired station, and so substance has a way of contracting and correct grid bias as specified by. the on render the transmission a hopeless not properlyfilling, the holesasit makers of the valve employed, or in noise of mush and Morse. cools and sets.A softer substance is cases where no printed directions are Anotherreasonforthelackof much easier to work, and the con- given, the characteristic curve should enthusiasm in receiving distant sta- structorwillfindthat the wax of be examined.In this latter case the tions is that when one has actually which" Dictaphone "cylindersare proper grid bias may be read off by picked up the desiredstation,. what made is admirable for the purpose. dropping a vertical from a point half- isoffered other than entertainment The easiest way of filling a hole is to way along the straight portion of the similar to that of the local station? lay the panel on a smooth board, place curve to the left of the ordinate; the " Faust " transmitted by Hamburg a lump of the wax in the hole, and pointwheretheverticalcutsthe is no more " Faustif it comes from apply to it the tip of a heated poker negative grid volt scale indicates the Hamburg than ifit comes from Bir- or old soldering iron.The wax should correct grid bias value to use for that mingham or Aberdeen ;further, since be melted down till it is rather above particular H.T. voltage, and inall a much more elaborate set is required the level of the panel surface. A piece cases this should be regarded as an to pick up these foreign stations at of rag is then wrapped round a small indispensable condition. loud -speakerstrength-isitworth- block of wood to form a pad, and vv_ien while? the wax has set the superfluous wax Experiments The " Wander Lust " around the hole is rubbed down with It is attention to such small details Many listeners known to the writer the pad.The filling takes a polish, as these that makes the reception of may be placed in the class of distance which matches well with the surface the local station really worth while, enthusiasts, and to spend an evening of a polished panel. A. V. D. H. 270 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR THIf IfTHE NI -N0 The Verni-Nob does all the work of a Vernier attach- ment or Vernier dial and PRICE increases the selectivity of your set. Positive drive.No backlash. 6d. io to I reduction with 3" dial. I6 to x reduction with 4' dial. From all dealers, Over 8,000 were sold during the By post, 71d. Wireless Exhibition at Olympia. Fitted in a few moments. "CENTADYNE" Screened Coils THE FOR NEUTRALISED CIRCUITS 11#1. A. P Made to Elstree Laboratories speci- ficationand officially approved. Company, for all star and other circuits described in " Modern SUITABLEWireless," " Wireless Constructor," and " Wireless," employing 246, Gt. Lister Street, 6 -pinstandard coils. PRICES OP COILS WITH 6 -PIN PLUGS. BIRMINGHAM. 250 to550 tl000 to 2,000 metres. Aerial Coils, split primary .. 4/6 4/6 each H.P. Transformers,split primary and optional reaction ...... 7/6 7/6 each H.P. Transformers, split secondary ...... 7/6 7/6 each IIII111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111 Reinartz Coils IN- each Copper Screen with 6 -pin base ...... 151- each Unshielded 6 -pin base for standard Coils when used without screen ,. .. - 4/- each Ask your retailer or write for catalogue 573/s of Efesca Components SAFE AND SU and circuits employing them. FALK,STADELMANN 8e CO., LTD., 83/93, Farringdon Road, E.C.1. and at Glasgow, Manchester, Birmingham, Newcastle and Dublin. EEDDYSTO Nn SAFETY LEAD-IN. 1 THE EFESCA (PRO. PAT.) FIXED RESISTOR Comprising base with " Plug-in " resistance bob- bin instantly interchange- ablewithoutdisturbing BEST OF ITS KIND. wiringconnections, for baseboard mounting. ¶ All contacts are positive and enclosed. 6 ¶ It is operated in comfort from inside. Made in six sizes, 2/6 each. Push the knob in and your set is isolated, with the aerial joined directly to earth. Spare resistance bobbins, ¶ Pull out, and the aerial lead is brought through to the set ready for use. r/o each. ¶ Easy to fix-nothing to go wrong. " SLEEP AND FORGET." Price 3/6 complete. LENGTH 10 inches OVERALL. THE EFESCA "CONCENTRA" " EDDYSTONE " AB SORBOS. NEUTRALISING CONDENSER A new departure in design.The moving electrode Pat. No. 9618. telescopes into afixedcylindricalplate being Your set should have them.They take up operated by a wormed spindle with long insulated all outside shock, thus giving longer valve life. 6/- handle providing 6 to s ratio vernier movement. Prevent microphonic noises, and stop entirely While primarily designed for neutralising, itis any strangeleakagetoearth,ensure greater equally suitable for use as a midget reaction Con- efficiency.They prevent marking or scratching EACH.denser.Arranged for either baseboard or panel thefurniture. Easytofix, Mount your mounting. cabinet on them to -day. ! Price 2/3 per set of 4. Obtainable from all high class dealers. Send fora rosyofourlatest If any difficulty Write direct to the completecatalogue of "EDDY - manufacturers. STONE" radio products. IIIIIIIiiiiillllllllllilllllllllllllll STRATTON & CO., LTD., Balmoral Works. Birmingham. In replying to advertisers, please mentionTHEWIRELESS CONSTRUCTOR. 271 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 How to Makeyour own Screened Coils-concluded from page 192 One reader has made his screened coils Another Method essential.The actual earth terminal by using aluminium hot-water on the base is connected usually to the bottles, winch are just about the right Another way of snaking the tube is copper sheet on the base itself. It is diameter,cutting -offthetopin to take a cardboard cylinder, which necessary to ensure thatthecover which the screwed stopper is placed, shouldbewellshellaced or waxed, shall also be effectively connected to and using the remainder; which fermi; and to wind copper foil round the out- earth, and normally the only way in a very suitable screen. side, thecopperfoilbeing lightly which this can be done is by ensuring soldered in order to keep- it in place. that it makes a good and sound con- This construction is somewhat simpler tact with thebase. than the tither, but the presence of Another methodof.achievingthe the cardboard near to the coil may results isto make the base of fairly introduce extra. losses, which are un- thin copper sheet cut to a larger dia- desirable. Paxolin or ebonite would meter than is actually necessary.It be better. may then be slotted all round the cir- 3" 4Y2" cumference, and the protruding disc bent in order to make a form of cup, Connection to Screen over which, or inside which as the case I It isfinally necessary, having con- may bc, the cover may be fitted.This structed the cover with its top and isa -form-ofconstruction,however, the base with the proper base piece, which requires very careful handling, Fig.5. --To conform to the standard to have some means of making con- and is liable to give trouble except in arrangement the terminals should be tact between -the base piece and the the hands of an expert. marked as shown. The Base Having decided thereforeonthe screen itself, turn or file up a base of ebonite or wood of sufficient dia- meter tofittightlyinside the end of the tube.It is now necessary to cut out .a piece Of sheet copper of the same diameter as this base piece, and to drill in it six large clearing holes, so that may be Placed over the base, * os * the holes being toallow the -six sockets to be screwed into the base without A new viewof shorting" to the copper piece. This theexperimental copper piece should then be screwed wireless station at Kensington, in position, so thatit forms a base Maryland. This to thescreen,the only holesbeing is to be used by those at which the sockets are screwed the U.S.A. Bureau in. of Standards for studyingthe Terminals problems of fading and atmospherics The whole base,withthecopper piece in place, should then be screwed on to another base which will carry the *** seventerminalsrequired. Six of these terminals are required for con- nection to the six sockets, -whilethe seventh terminal is taken to the screen itself in order to earth the component. The connections to the six pins are as shown in Fig.4, and this is the standardconnection adopted. It should be followed out if it is desired to use -standard coils. When the base has been mounted upon the terminal block,the screen should then be fitted over it, in -order remainder of the screen.In the par- Important Points to ensure that it makes a good fit. ticular model described,in which a If tube has been employed in making copper tube was used, this has been It cannot be too. strongly emphasised, the cover, -it will be necessary to cut provided for by a small strip of phos- however, first of all that the clearance out another disccopper to fit over phor -bronze, which has been screwed must beasstatedearlierinthis the end of the copper tube, And this to the base piece in a convenient posi- article, -1. in. at least at the sides of should then be soldered in position to tion.This is so shaped that when the the coil, and 1 in. at least from each make agoodelectricaljoint. If cover is placed over the base the end end of the coil to the top and bottom aluminium tube is used, then the top ofthis phosphor -bronze spring rubs of the screen respectively.Secondly, must be made a very good fit,and on the inside of the tube, and so makes it is also essential that the screen itself must be held in position with screws, contact therewith. shall be effectively connected to earth, asaluminiumcannotreadilybe Various other methods will suggest as otherwise all sorts of peculiar and unpleasant results may follow. soldered. - themselves, but some sort of device is 272 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR 080E108808080888800808008008888800080080000808800880 0 0 0 0 0 0 8 AN EXPERIMENTER'S BASE -BOARD 0 8 0 By H. BRAMFORD 0 0 0 8 A " unit" method of arranging a 0 set in experimental or even in per- 0 manent form, possessed of con- siderableflexibilityand allowing 0 ample freedom for the ingenuity of theexperimenterinlayingout 0 components. Some suggestions for 0 mounting components aregiven, 0 0 and the accompanying photograph 0 shows part of a possible layout for 0 a two -valve set. 0 0 0 0 0 08000008880880080 088080088880880800880880080 APIECE of apparatus which should whom those who desire an article of Method of Use be most usefulto the experi- finished and pleasing appearance should Details are given in the diagram of menter is a device whereby he procure it in either a plain or relished the actual base -board, which consists can rig up any desired circuit with state.The base -board mentioned is an of a piece of wood ins.. x 252' ins. speed and ease and without the usual independentitem,butthosewho Strips are securedtothis base, as confusion and disorder.This article desire it could easily have fitted to it shown, which are cut from I -in. square describes a unique type of base -board a polished mahogany cover ofsuffi- wood.Two dozen mounting bases will which may be used for this purpose, cient depth inside toallowforthe next be required.The best way to and which presents so neat an appear- housing of the average type of com- %ake these is to procure a perfectly ance in any stage of use that one ponent.Alternatively, the base -board square piece of wood 24 ins. x 9 ins. might almost say that not only is it and fittings may be home madein and divide it into three one way and suitable to the experimenter himself, accordance with the details given in eight the other way.Square the wood but also that itis a most desirable the diagram. thus divided with the aid of a steel articleforthe average set maker. Components square, and then proceed to cut off Practically speaking,itdispenses the 24 pieces.Each piece provides an entirely with ebonite panels, which in As regards the actual components to independent base for the mounting of itself is a most important feature from be used in conjunction with this base- some component, or for the building many points of view.The idea itself board, practically any type may be of aunit. When the components is worked out somewhat on the lines employed, but the principal idea is to chosen are mounted upon the pieces in of a draught -board,which to some choose such components as are most this manner it will be seen that they extent was the means of providing the suitable for mounting upon wood bases, -may be placed in any desirable posi- suggestion in its crude state. and that are also equipped, as far as tion upon the base -board and are held Practically everybody who -makes a possible, with terminals instead of only in position by each other, and also by set at some time or other wishes to dis- solderingtags. Aspracticallyall the raised strips which form part of mantleitfor certain alterations or components are now obtainable with the base -board.It is a simple matter for some modern improvements.This this fitting, it is not difficult to choose to transfer a piece from one position to another. Laying Out a Set 1 2 3 4 5 6 7 8 3"1 We will suppose, therefore, that we have 24 components, one component mounted upon each ofthepieces. 9 10 11 12 13 14 15 16 Thesecomponents, for thesake of argument, will consist of the necessary parts for the average type of four - valve receiver.First, we may place 17 18 19 20 21 22 2 3 24 each part in the most desirable position for wiring -up purposes, not forgetting at the same time to consider the rela- tive positions of each unit as regards 24" \ P e- W000 ..57771P 3/8439. efficient arrangement. Having placed the parts in the most suitable manner, they may be quickly wired up by means Fig. I.-The necessary dimensions for the base -board and the loose of a series of varying lengths of insu- wooden squares are given in this drawing. lated flex, each piece having each of particular base -board idea allows for suitable ones.The base -board allows its extremities equipped with a spade this to be done at any time without for 24 units in all, which should be terminal. the usual scrapping process having to quite sufficient for the average receiver Wiring be gone through. up to,say, four valves.Those who If,ashas been suggestedabove, wish to use more or fewer components the components chosen are all provided Material may, however, do so, in which case the with terminals, this connecting -up pro- The special base -board is obtainable base -board is increased or reduced in cess will notbedifficult. Absolute from Messrs. Peto Scott, Ltd., from Adze accordingly. safety is ensured if insulated flexible 273 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 7 % s a valve r everyposition inanyset/ S.PI8/13 OU try one valve after another in this or that (BLUE SPOT) stage, and listening critically you persuade Extra High Amplification. Filament voltage 1.6-1.8v. Filament Current 0.09 amp. yourself that the result is a little better or a Amplification factor 35 Price 141 - Mutual little worse.Then, perhaps by chance, or very Conductance 0.5mA p.v. Impedance 70.000 ohms. likely on personal recommendation, youtrya Cosmos S.P. Valve, and realise with delight that S.P I8/G no straining of your ears or the exercise of super- (GREEN SPOT) criticalfacultiesisrequiredtorecognisethe High Amplification. immediate increase of pep and volume obtainable. Filament voltage 1.6-1.9 v. Price 14/ - Filament Mirront 0.2 amp. How is it then that such a distinguishable difference, Amplification factor 15 Mutual Conductance 0.85mA ne. such a distinct improvement, can be obtained ? Impedance 17,000 ohms. The explanation lies in the unique Shortpath construction, which, without sacrificing anything in rigidity, reduces the S.P I8/R path the electrons have to travel to a minimum impossible (RED SPOT) with other methods of construction, resulting in efficiencies Last Stage L.P. Valve. Filament voltage 1.5-1.8v. Itis Price 14/ - Filament current 0.3 amp. and impedances hitherto unobtainable. not over- Amplification factor 7 stating the case to say that this scientific construction marks Mutual Conductance 1.0mA P.S. the most notable advance in valve manufacture since their Impedance 8,000 ohms. earliest development. DE 55 " Cosmos " Valves also have this distinction :they are Low Consumption C.P. designed to be most efficient for one particular purpose. Filament voltage 5.5 v. Price 18/6 Filament current 0.09 amp. They are not general purpose valves in the commonly Amplification factor 9 Mutual accepted sense, and, whilst functioning admirably in many Conductance 0.5mA p.v. Impedance 18,000 ohms. positions, there is always one particular application in which they will give super results. S.P 55/B Manchester Wireless Exhibition Price 18/6 (BLUE SPOT) Extra Blab Amplification. "SundayChronicle" and"Evening Filament voltage 5.5 v. Chronicle"£500WirelessResearch Filament current 0.09 amp. Competition. Amplification factor 35 e/ Mutual Conductance 0.65mA p.v. In the 4 -valve Receiving Set Class : Impedance 55,000 ohms First prize winner used 4 "Cosmos" S.P. Valves. Second prize winner used 3 "Cosmos" S.P. Valves. S.P 55/R Third prize winner used 2 "Cosmos" (RED SPOT) S.P. Valves. Power Valve. Fourth prize winner used 1 "Cosmos'' Filament voltace 5.5v. Price Filament current 0.25 amp. S.P. Valve. Amplification factor 6 22/6 Mutual Conductance 1.7mA p.v. Impedance 3,500 ohms. METRO-VICK SUPPLIES LTD. (Proprietors: METROPOLITAN -VICKERS ELECTRICAL CO. LTD.) Metro -Vick House - 155, Charing Cross Road, LONDON, W.C.2. In 274 In replying to advertisers, please mentionTHE WIRELESS CONSTRUCTOR. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONS TR17CTOTI acnWADES363tn63,41'.0cXg06_15 O 0 AN EXPERIMENTER'S BASE -BOARD --continued O 0 ig3 GRID LEAK TROUBLES O 0 wire is used for this purpose, and the equipped with five terminals, arranged O 0 general appearance of a circuit so made as shown. Theswitch providesa eEPE84E55@e@WgEg&OftEM3 will be quite equal to the appearance means of switching off the filaments of the valves. produced by the conventionally wired - WITH reference tothe efficient up receiver.If alterations are to be Telephones working of a detector valve, made, little trouble is experienced in A 'phone or loud -speaker unitis probably the most important this direction, as one component may shown at (d). Here the use of two point of allis to make quite certain be taken out or another added, or terminals and a jack is employed in that your grid leak and condenser are thepositions of various components order that 'phones or loud -speaker may altered.Some ingenuity is called for, not only of the correct value, but also be used at will.A by-pass condenser ofareliablemake, and constant. however, in, the design and arrange- ofanydesirable ment ofeachparticular component capacity may be A grid condenser for a detector valve unit. clipped in. shouldhardly ever be larger than .0003 ;the writer has found a very Special Units Grid Condenser and Leak marked difference in the operation of One unit,(a)inFig.2,should A grid -leak unit (e) may be made as the set, even when several condensers obviously provide a means, of connect- shown; A variable grid leak may be of a cheap kind, all of which pur- ing the aerial and earth leads.It is employed, or alternatively a fixed leak ported to be of this capacity, were a good idea to arrange this unit so of any value may be clipped in.The tried. Make sure thatthevalue that the base piece is provided with clip -in fixed condenser provides again reallyisthat stamped on the con- three terminals.One terminal should a means of adjusting the value of this denser, by using reputable makes only. connect to one side of a clip -in con- component to suit any type of circuit. denser, the other side of the clip -in condenser should connect to another Six -pin Base Eliminating "Mush" terminal, and the remaining terminal The last unit shown (f) carries a six - Thegrid leak is another difficult should be independent for the earth socket base for use in conjunction with point.Very often that slight back- connection.Thus we may employ con- any coil of the six -pin type. ground in a set that sounds like faint stant aerial tuning. These few suggestions should enable interference from Northolt or Leafield the constructor to carry out his own is really due to the grid leak.In the H.T. Battery ideas. writer'sshort-wavereceiverseveral The next necessary unit to consider The device is of considerable use to different makes of gridleaks were is an H.T. battery unit(b). Here those who wish to try out circuits for tried, and one was found that was ob- viouslysuperiortotherest,the I .7' HT N. Lir 3 - absence of " mush " when this par- I111111111' ticular one was connected in circuit 1111H a 11#111H IIJII 111111k 1111111111Hr. 111111111, 11911111 being most conspicuous.Here, above all other things, is the necessity for absolute constancy. Values A grid leak that varies in value will cause an overlap to appear one day which vanishes again on the next, and will make the set oscillate furiously on one occasion and not atallon another. These are, of course, extreme cases,buta" self -variable "grid (a) (C) leakwillbe a constant sourceof trouble.Once again, keep to reliable makes, and trouble of this kind will notoccur. Anotherobjectionable effect,. also caused by a defective grid leak, is a slight tendency of the set to burst into a " howljust as it is brought up to the oscillation point. Ifthisoccurs, it will generally be found that the grid -leak value is too high. L. H. T. (e) (f) ** * Fig. 2.-By careful arrangement of the components on the squares, the wiring of the set may be kept simple, with adequate spacing of the ADDRESS WANTED components. informedby Messrs. WE Dubilierare Condenser Co.(1925), four terminals are mounted as shown new ideas before actually incorporating Ltd.,that they havereceivedan upon an ebonite strip.Three smooth- them in a receiver. A photograph of inquiry from a Mr. R. Anderson, of ing condensers are connected from the the base -board is shown, giving some London, for details concerning their H.T. negative terminal to one of the idea of the appearance of the device " Hiloten " Battery Eliminator.No H.T. positive taps in each case. with certain components mounted on address was given on the letter.If it ready for wiring up.Those com- Mr. Anderson will forward his address Low-tension and Grid Bias ponents which have no holes for wood - to the above firm, they will be pleased An L.T. and G.B. battery unit may screws are secured withbolts from tosupply himwiththerequired be made as shown at (c).This unit is beneath the squares into tapped holes. information. 275 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 READERS BUILD THE "NIGHT HAWK" The "Night Hawk" receiver was described in our October, 1926, issue. SIR,-I am writing to congratulate I am working with Cossor .1 valves Mr. Percy IV. Harris on his latest sue. from a 2 -volt accumulator.All three cess," The Night Hawk." I have of' my condenser dials match, which constructed this set for a friend, -and makes tuning very simple, and the had only one night for testing_ but in reaction condenser brings in or cuts that one test I received twenty-eight out a station or unwanted signals. stations on the loud -speaker, the best The set is rather prone to oscillate, known beingHanover, Stoke-on- andneedscarefulhandling. The Trent,Bradford,Leeds,Barcelona, great snag I am up against is an Nottingham, Hull,Cardiff, London, incessant ringing in the loud -speaker, Manchester, Bournemouth, Hamburg, which is very objectionable.Is there Newcastle, Munster, Radio Toulouse, any way of remedyingthis,asit Birmingham, and many others. entirely spoils anything but the band? What I like the set best for is that If this can, be overcome I think you though I have always had a job to get have as near a perfect set as one could 're stations up north they fell in on this get and you are to be congratulated set. on designing it.-Yours faithfully, Wishing THE WIIIRLESS CONSTRUCTOR E. MAJOR. every success.-I am, yours faithfully, Carshalton, Surrey. London, S.E,"6. -E. A. LONGDON. SIR,-I have now completed build- Sut,-As per your request for re- ing the " Night Hawk " and find it marks on the. " Night Hawk," I have very satisfactory indeed. completed the set and am delighted I can tune in about twenty stations, with the result.London comes in at foreignand British,at good loud- terrific strength and wonderful purity. speaker strength. The other evening we listened to the I am only using four valves, 2.H.F., concert from Hamburg, and it was all detector, and 1.L.P., and I am using that could be desired, the amount of 140 volts H.T.This gives me ample " mush "being negligible.Working volume.I am sending a photograph from your chart I have tuned in most TheNight Hawk" set constructed by of the set.-Yours faithfully, of the stations mentioned at various Mr. A. Woodcraft. A. WOODCRAFT. strengths, all on the loud -speaker. Norbury, S.W.16. THOUSANDSof wireless enthusiasts pay high tribute to T.M.C. LOW CAPACITY KEYS because they are so efficient and adaptable to many different switching requirements. If tyou do not know these useful switches, ask your dealer to show you one. You will find that they have a smooth, rapid make - Low Capacity Keys and -break, with a positive lock in each position, and that it is practically impossible for the moving parts Made in three models. to get out of adjustment, so small is their movement. No. I.12 point, 3 position.. 71 - Observe the non-oxydising " gold -silver "contacts, No. 2. 6 point, 2 position.. 4/ - and the tinned connecting points, ready for soldering, No. 3.ag. point, 3 position.14/ - also how effectively the springs and contact arms are insulated from the frame. Packed in attractive black, red and You can obtain T.M.C. Keys in two pleasing finishes :-Bright yellow labelled cartons. Nickel Plate and LncquPred polished brass. TRY THEM they will help to solve your switching problems. Ask for the new T.M.C. Catalogue at your local Wireless T.M.0 Low Capacity Keys can be used for REMOTE Control, Multi -valve, series -parallel, and battery snitching. Change over Shop-or we will send a copy free on request.Please from Head -set-to Loud -Speaker, etc. mention the name of your usual dealer. Telephone Manufacturing Co. Ltd. HOLLINGSWORTH WORKS. WEST DULWICH. S.E. 2L 'Phone : Sydenham 2460/1. Telegrams :Bubastis, Dulcrox, London." i=11.1.1101111.1111=1111111.1..1.111111M.111 276 - In replying to advertisers, please mention THE WIRELESS CONSTRUCTOR. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR DON'TuseSolder- WIRE YOUR SETWITH TheDuvarilealc T'' 'JUNIPATENTED I R CROSS a JOINS JOINS -"....,,,...... TERMINAL JOINS .....-...--.---""" &IAJUJ SCUM Perfection No. 17 S.W.G.(square section). In coils (in cartons),per coil1!- PRICES . In 2 feet lengths....per length2d, in Variable DON'T SAY WIRE- SAYJUNIT ! Grid Leaks! If unobtainable from your dealer - sendP.O. for sample coil in carton, price If- postfree. Fit your receiver with a Duvarileak Vari- REXO ENGINEERINGCOMPANY able Grid Leak. 2, RAVENSCOURT SQUARE,LONDON. W.C. It enables you to increase the selectivity and the purity of your reception by apply- . . . ing to the grid the exact resistance de- manded by your particular detector valve. The Duvarileak eliminates all the failings Faithful Reproduction often associated with variable grid leaks of Every Note in the past. is achieved by the The resistance material, which it has taken RADIAX LOUD SPEAKER us years to evolve, has a hard surface.It Whatever the name, whatever the price, we retains its resistance value indefinitely, and affirm that our Loud Speaker will at least equal and in most cases far surpass any other in purity the rolling ball contact (see inset) reduces and faithful reproduction.Itissensitive to wear to a negligible quantity. The result is weak signals and yet will handle large volume. that the Duvarileak remains variable and ORDER TO -DAY UNDER THIS GUARANTEE. Size : We will refund cash if you are not satisfied with 21"x 12". givesaconstant valuefor any given the performance ofthe Speakerand return it setting of the dial.It carries the Dubilier within 5 days undamaged. YOU TAKE NO RISK. PRICE Guarantee to give complete satisfaction, Send stamp for lists of Radiax Sets for Constructors, 50/ - Low -Loss Coils, and all components. Deferred and is obtainable of all Dealers, Price 7/6. RADIAX LTD.,44,Accessory House, Palmer payment Place, Holloway Road, LONDON, N.I. if required. The Duvolcon for Loud Speaker volume controlisthe same in appearance and Parr 's Avt price as the Duvarileak.Suitable' for use with any Loud Speaker. Use LEBRENCO RadioProducts May we send you our new Catalogue in which these and all other Dubilier Products are fully described ? 1 VARIABLE FIXED CONDENSERS , Compact, dust - proof and highly Price 716 each efficient. Every one tested on capacity bridge. 0.0001 to 0 0005 mfd. 1/- each. 0.001to 0.003 mfd. 2/- 0.005 & 0'01 mid... 2/6 FOR BASEBOARD OR PANEL MOUNTING, (Post Free 2a. extra.) DUBILIER onuoth and reliable In operation, ensuring oecnrate grid control. Wide Resistance Range, 50,050 ohms to10 megohms.Entirely new SOLID Resistance Elementisused. Cannot pack or seize. No carbon, graphite or liquid used. Absolutely silent. PANEL type, ADVT. OF THE DUBILIER CONDENSER CO. (1925)LTD. or with tome for BASEBOARD MOUNT- DUCON WORKS, VICTORIA ROAD,N. ACTON, W.3 ING. Price 3/- each. (Post free 3d. cam.) TELEPHONE: CHISWICK 2241-2-3. E.P.S. 249 Obtainable from all Radio Stores, or direct from LEBRETON ENGINEERING Co., Windsor House, Victoria St., London. S.W.1 In replying to advertisers, please m ention THE WIRELESS CONSTRUCTOR. 22.7i PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 How to Usea Wavemeter-continued from page 251 for hours it may be, in order to re- A Better Circuit by a special circuit the buzzer could ceive some announcement from the be almost entirely isolated from the station concerned. With a wavemeter This, however, does not give com- tuned circuit, and this gave a remark- the wavelength of the transmission pletely .satisfactory results, and ableincreaseinthesharpnessof may be determined, and this at once various devices are adopted in order tuning.Moreover,the arrangement narrows down the choice of possible to reduce the effect of the buzzer on in question only required the addition stations to a much smaller field. the tuned circuit. One methodof of a fixed condenser, so that it did not involve considerable expense. The Final Design Theactualmethod employed has been incorporated in the Radio Press Envelope No. 14, the " Razor -Sharp The control -room Wavemeter," which gives full details operatorat 3L0 of the circuit, with constructional de- inMelbourneis tails showing how a simple wavemeter able to watch the can be made up on these lines. As studio and to an example of the completeness with which the buzzer has beenisolated make the neces- from the rest of the receiver, it may sary adjustments be mentioned that the natural wave- for the items length of the circuit LC by itselfis transmitted. notappreciablydifferentfromits wavelength when the buzzer circuit is connected across it.This is a state of *** affairs which cannot be achieved by any of theordinarymethods,and results in a very much more accurate instrument. Sharp Timing doing this is shown in Fig. 4. Here the buzzer is connected across only a In order to be of real use, however, small portion of the coil.The effect Calibration Difficulties Removed it is necessary that the tuning on the of switching on the battery causes a The use of this special circuit also wavemeter shall be crisp and sharp. suddenpulseofcurrentto flow enables one of the biggest difficulties Thisisa matter of careful design through this portion of the coil, which of a home -constructed wavemeter to once again. Thecrudecircuit is stepped -up by a transformer effect, be overcome.There are many ways in shown in Fig. 3 is more or less hope- and so charges the condenser. This which a wavemeter may be made up lessforreallysharpresults. The effect of the buzzer connected across results in a somewhat weaker signal quite simply and cheaply, yet at the the tuned circuit is to introduce con- siderable damping,and makes the signalsveryflatlytuned. Itwas mentioned that thevoltageofthe ** * battery was practically applied across the condenser C.In order to ensure Anotherglimp 3 that thisisso,itiscustomary to of 3L0, the Aus- shunt the coil of the buzzer itself with tralian broad- aresistance,sothatabigpulse of current flows at the instant when casting station at the armature comes into contact with Melbourne, show- the contact pin so ensuring that the ing some of the condenseris charged toas high a "Uncles and value as possible. Aunts" and other members of the An Improvement station staff. This at the same time increases the damping which is introduced into the circuit, and the tuning is apt to be somewhatflat. Inoperation,the exact tuning point may be facilitated bygraduallyremovingthebuzzer wavemeter further .and further away strength, but at the same time the same time there is always afterwards from the reeeiver.As this is done the effect of the buzzer on the coil is very the difficulty of calibrating the coil signal strength will be found tofall considerably reduced, and materially and condenser in use, in order to know off rapidly, but at the same time the sharper tuningisthe result. the wavelength of the combination for tuning will become narrowed down. Even this circuit, however, possesses the particular settings ofthe con- So the band over which the buzzer can certaindisadvantages. Itwasin denser.With this particular circuit it be heard on the wavemeter willbe order to overcome these disadvantages has been found that, provided that narrowed down very considerably, and that I undertook some experimental the instrument is made up exactly in it is possible by this means to obtain work extending over several months accordance with the specification, the a reading withafairdegreeof in order to find the best type of cir- calibration remains appreciably con- accuracy. cuit.It was eventually found that stant.It is therefore possible to pro- 278 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR on this model, owing to the consider- able effect exercised by detail changes HOW TO USE A WAVEMETER in the construction.With the vari- ELECTRADIX -concluded able condenser specified it was possible to get down to about 30 metres with BARGAINS -No. 206 the 9- and 12 -turn coils in series, and Haveyou boughtyourONE -METER yet ? the earth clip at the ninth turn. WAVEMETER SALE. Bargain prices W.D. Service vide a calibration chart in the actual By moving the clips inwards from meters, calibrated for us by Sullivans to N.P.L. envelope, so that when the instrument standard. Short Wave Forward,"cost£10. the two endsit was possible to go 40/100 metres, 35/-; Broadcast Townsend, 35/-; is made up itis already calibrated. lower, but, probably owing to dead- No. 671. Townsend,- 280 1,600 metres, 50/- Such a proceeding is naturally of con- end effects,betterresults were LR Townsend,120/4,000 metres £4;LongR siderable assistance totheamateur Forward,- 75/3,000 metres, f.4 10s.. ; for 60/4,000 achieved by removing the 12 -turn coil metres.Heterodynes, Browns and Mark II., with who wishes to possess a wavemeter for and using the 9 -turn only.With this calib.valve,90/3,000 metres,£5,or150/3,000 himself. metres,£410s.Original cost £15, and all guar- coil, and with the earth clip at the anteed accurate.Ondia Wavemeter prices reduced centre turn, a check on a wavemeter to 83 10s. A Useful Accessory SALE CLEARANCE LOUD -SPEAKERS, was obtained down to 25 metres, and Western Electric Table Talkers, 35/- model, 2,000 As was stated at the beginning of it would oscillate readily at settings ohms, 17/6; 3 -guinea models, 32/6; T.M.C. Loud- this article, thereisanincreasing speakers, 2,000 ohms, 12/6; Fuller Sparta, 4 -guinea considerably lower. The smaller models, 50/-; Texas Cone, bronzed, 40/-; Sterling tendency to usetheseinstruments. aerial coil was used for these lower Magnavox Concert Speaker, 55/-; Large Sereneda, They take up very little accommoda- with Tone Control, 30/-. wavelengths. RELAYS.Weston, 20/-; G.P.O.,40/-;Magnetic tion, and repose in a corner quite un- Generally speaking, the number of Relays, 10/-; Dixon Telearchic Filament Distant obstrusively.A dry battery serves to reaction turns may be the same as the control Switches, auto. on and off in pol. case, 15/-. energise the buzzer, and will last for In Brass case 17/6.The latest invention. grid turns for the lowest wavelengths, AERIAL BOX PANELS Containhigh - grade a considerable period.Yet there are and slightly less as the wavelength is aerial Ammetr H.T. Condenser, Quick -break those occasions when it is particularly Rotary Switch, 4 -pin Plug, with four 6 ft. lengths of increased. Definite rules cannot be coloured H.T. Flex. Cost 45/-.Price to clear. 16/6. desired to get some clue as to identity laid down, however, and test with the ALTERNATORS. 500 -cycle type, 52a.The won- of a particular station, or perhaps it particular set constructed is the only derful 200 -watt Newton & Watford A.C. for H.T. and is desired to tune in the receiver to Television transmission.Cost £28.Bargain, U. reliable guide. 800 DYNAMOS for Home Charging. Fitted Auto. a particular wavelength, and in such Cut-out, 12 volt, 250 watt, ex -RAF., £3. cases the wavemeter proves an almost ALL SIZES A.C. AND D.0 Send us your enquiries. inestimable boon. 6ffitThVgEg:AbS5CMEgEgegEROCAR A few 100 volt, 5 amp. Silvertown left.Commutator and slip rings to stye either D.C. or A.C. A Bargain at U.Motor Generators work to give 350 volts Tracing Faults DAVENTRY COILS FOR qi 100 m/a H.T., totally enclosed, 14. CUT-OUTS, Lucas charging,12volts, 8 amp. Those readers who make up numerous THE SPANSPACETHREE'3j compound wound, 13/6. sets, often in skeleton form for their Transformers for 50 rn/a H.T., 37/6. 10 -in. SPARK COILS.Large Marconi, 17 ; Cox own amusement,will findawave - 4943694349(830 *0;f1Q X-ray, £10; 2 in. Sterling, 15/-;I in. ditto, 5/6. meter particularly usefulintesting GYROSCOPES. Navy Torpedo stabilizers. Beautiful workmanship. For Television experimenters. Cost out such receivers. This is particularly THE coils for use in the " Span - £25.Price 15/-. the case in multi -valve circuits, such space Three " on the Daventry RES. BRIDGES. .005 to 100 ohms, 35'-; G.P.O.. as the " Els-tree Six."By means of .01 to 10 meg., £7 10s.; Galvo Universal Shunts, wavebandarewoundinan 35/-; 10,000 ohm Dial type, £6 lOs. a wavemeter it is possible to test each exactly similar manner to those for the MARCONI No. 55 7 -VALVE SET. 6 in.pol. circuit individuallyby holdingthe Mahogany de Luxe Cabinet, £12. Valves, 10'- each ordinary broadcast band, the connec- 500 v. OHM -METERS to 10 megs., with voltmeter wavemeter near to thatcircuit,so tions being exactly the same as those 250 and 500v., £810s. ffreatly facilitating the tracing of any given in the November issue. PRECISION INSTRUMENTS. Fineststockin fault which may develop.At the same London. 2,000 to select from. Mov.Coils to 500m/a. The windings, of course, are different etc., 224.3 -range Milliammeters, 374 ;2 -range time, when dealingwithacircuit insize,and arecarriedout with Voltmeters, 6/120, 11/6; 0-30 volts, 10/- 120 volts, which is somewhat tricky to operate 201-; 600 volts, 55/-; 0-1,000 volts, 13 ;1,500 No: 40 s.s.c. wire on the same type of volts,£4 10s. ,2,500 volts, 16 ;S9 Mov. Coil until the settingS of the condensers former. The first unit carries an aerial Siemens Cell 'testers, 15/-; 250 mla or 500 mia have been logged, the use of a wave - Thermo Meters Nis windingof80 turns, and a centre - ULTRA.ONEME .-The finest instrument with meter will save a considerable amount tapped secondary of 350 turns. the widest range ever offered. Every Constructor of trouble. needs one. Instrument, 501.;Multipliers.616. The second unit carries only a tingle The Radio Star. These are just a few of the' uses to winding, exactly as in the case of the AMPLIFIERS. Marconi 3 -valve L.F. Transformer which a wavemeter may be put. There shorter wavecoil,witha tapping coupled Selector for one, two, or three valves. Tested are numerous others, also, and there and guaranteed, £2 10s.Cost £18. roughly one-third of the way from the CHOKES. -1,000,1/6. Double, 400 and 1,000 ohms are various tricks and dodges which end of the coil.The winding itself 6/6; 3,000 ohms, 4/6.Large Smoothing Chokes. the reader will find out for himself. consists of 350 turns of the same wire, 10/....2 mfd. Ex W.D.Condensers, 2/6. There can be no doubt, however, that WIRE, nese, 22 -gauge cotton enam. indoor wire, 1/6 No. 40 s.s.c. lb. Super Aerial, bronze, all gauges in stock. Nays, with the enormous number of stations 7/23 enamel Super Aerials, bronze, 3/. 100ft. 540 now working a wavemeter isa most oz. reels, 28 gauge S.C.C. wire makes two Broad- cast coils, 4d. each.Earth Wire.Flex. rubbered, desirable asset. 1/. dozen yards,100 yards coils cheap. Loud Speaker Extension Wire, &. 100 yards. Twin Litz Questions & Answers Wire, 6d. yard.Stally Transformer Wire, 113 lb. Stampings, E or TO. 1/. doz. PLUGS AND JACKS, 2i..pair.Micro. Trans- LISTEN TO AMERICA DIRECT IMPORTANT NOTICE formers, 10/. and 5/-. Micro -Insets, 1/...Micro- phones, 5/... Hand Transmitters, 12/6. Electric Bella, -concluded from page 240 1/6. Morse Keys, Lucas, 216. Aerial Line Erecting IN consequence of the change Sets, 2/6 each.Heterodyne. Plug-inInductance in ownershipof" THE Blocks with two H.F. coils, 4/6. WIRELESS CONSTRUCTOR," SUNDRIES. Coil Winders, solid brass, 13 removable arms, 5/-.Patent Double Terminals for pin or out of oscillation.Adjustment of the readers are requested to note spade 6 type for 4d. nickel.Valve templets, self that the service of Questions mark, 3d.H.F. chokes, 1/6, 2/6, 3/6, 4/6. L.T. and H.T. voltages will assist in and Answers service is tem- POLAR BARGAINS. Condensers,.0003,4/6. obtaining this condition. Insome Polar Rheos, 1/3.Polar Univ. 2 coil holde.r, 3/6. porarily suspended. Eureka Dialdensers, 4/-4Polar Intervalve Frans - cases the use of a 5-megohm leak in Afurtherannouncement formers, 10/-. place of the 4-megohm specified may regarding thisservicewill effect an improvement in this direc- appear at an early date. " 1,000Bargains" Cattilogue.600Illus. Stamp 41. tion. Attention is also drawn to IT WILL SAVE YOU POUNDS the notice regarding the Free Wavelength Range Blueprint service, which will ELECTRADIX RADIOS It is impossible to state with any be found on page 286. 218, UPPER THAMES STREET, E.C.4 certainty what will be the exact wave- St. Pad's and Blackfriars Stn. 'Phone : City0191. length range of any set constructed In replying to advertisers,please mention THEWIREI.F.SS CONSTRUCTOR. 279 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 Apparatus 61911011°1117.11111 tesled. 11N 11110. 0001 111.010110 -- For " The Wireless Constructorat our Elstree Laboratories. Safety Wander Plug ring to which an earth external to the bush screwed into the base.The fixed MESSRS.A.H. HUNT, LTD., building is connected.There is only plates are placed well away from the have sent us one of their safety a small gap between the screwed rod moving plates, so as to obtain a low wander plugs for test.This wander and this brass ring,so that in the minimum, which is further provided plug consists of a small screw lamp event of a high static charge collect- for by the special curved shape of the holder which is provided with a plug ing on the aerial it is claimed that it opposing edges of the plates. The fitting to enable it to be inserted in will discharge straight to the earth spindle is provided with a lock nut, so the usual high-tension battery. On across this gap rather than go through that the condenser may belocked the sideis a small terminal under the set.The rest of the brass rod after the correct setting is obtained. which the lead itself may be fixed. passes through an ebonite tube, and Terminals or soldering tags may be A smallflash lamp screws into the there is a stout terminal at the far employed when making connections. holder and acts as a fuse, thus pre- end for connecting the lead-in to the On test the component showed a venting the valve from burning out set.The safety gap is totally enclosed minimum capacity of two micro -micro - should a short take place. soas toprevent leakage occurring farads, the maximum being nineteen. When placed on test it was found owing to rain. This is quite satisfactory for all prac- thatwhenthiswanderplugwas When placed on test it was found tical purposes, and can be considered that the insulation resistance was in- as complying with the standard speci- finity, while the capacity between the fication. lead-in and the earth ring was found Panel Brackets to be negligible.An insurance guar- antee is supplied with each of these ikArEssns. BURNE-JONES & CO., components, under which damage to LTD., have sent us samples of personal property or third party will their " Magnum " panel brackets for be paid up to £100. Neutralising Condenser Peto-ScottCo.,Ltd., MESSRS.have sent us one of their new pattern of neutralising condensers for test. In this component the spindle which carriesthemovingplates passes through a bush located in the centre of a bridge -piece of insulating mate- rial, which is carried at the top of two pillars of similar substance fixed An ordinary flash lamp bulb screws into Messrs.A. H. Hunt'ssafety A panel bracket of the type submitted wander plug. by Messrs. Burne-Jones & Co., Ltd. placed in series with the H.T. lead- test.These brackets, which appear to inandthebatterythenshorted beconstructedofcastaluminium, across a .06 valve, the safety lamp though light in weight, are solid and burnt out without the valve being robustinconstruction,whileboth damaged in any way. - faces have been machined, so that when Thisisa well -finished and useful in use the panel will be held at true accessory whichcommends itselfto right angles to the baseboard. many amateurs as a simple means of Each arm of the bracketsispro- protecting valves from being burnt vided with two holes for fixing pur- out - poses, andthese accessoriescan speciallyberecommended incases Safety Lead-in where heavy components are mounted PRESSLAND have sent The Peto-Scott neutralising condenser, on the panel. MESSRS.usone of their safety lead-in designed to havealow minimum tubes for test. capacity. Filament Rheostat The aerial lead-in is attached to a --heavy terminal, fixed at one end of a to the base. This forms the main WE havereceivedsamplesof length of brass screwed rod.This rod bearingofthespindle, the bottom baseboardmountingfilament passes through the centre of a brass bearing being carried in a small metal rheostats from Messrs. Lissen, Ltd. 280 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR J RADIO COMPONENTS ensurereliable sets. Constructors who desire smooth working and effi- The " Cosmos" Rheostat. cient sets use" Cosmos "Precision Components. The "Cosmos " Rheostat. The principal features of the " Cosmos " Filament Rheostat are its sturdy construction andreliable,smoothmovement.Thecontactarm cannot easily be damaged, having its movement on the inner side of a porcelain bobbin which carries the windings. Other pleasing features of this Precision Rheostat are the handsome knob and dial, ONE HOLE fixing, and the small space it occupies. Made in four types, two of which are double wound for DULL or BRIGHT Valves and one a Potentiometer. Description Ohms I Current Price Single Wound 6.0 1.0 amp. 4s. H. Double 20 .9 5s. Od. 34 .2 5s. Od. The " Cosmos" Permacon. Potentiometer 300 - 6s. Od. The "Cosmos" Permaconisan idealfixed condenser being light in weight, of guaranteed accurate capacity, and having the lowest possible losses. The dielectric is mica, and each condenser is tested at 500 volts during inspection. Nickel -plated cases give them a particularly neat appearance. .001 mad. .. 18 .002 .. 1 /10 .005 .. 2/8 .0003 (with clips for grid leaii) 1 /8 .01 .. 3/9 The "Cosmos" Coupling Unit. Real purityofrepro- duction can only be obtained withresistancecapacity coupling. The " Cosmos " coupling unit with a suitable valve is as effective as an ordinarytransformer -coupled The " Cosmos" Coupling Unit stage.Itavoidsalldistortion and effects considerable and spring valve holder. economies in first and operating cost. Designed primarily for use with the " Cosmos " S.P. Blue Spot Valves, it can be used successfully with any valve having an amplification factor of 30 or more. Type " 0," the Unit alone.. 8'6. Type " V," the Unit incorporating spring valve holder (as illustrated) 10 6. Suitable valves for use with this unit are" Cosmos "S.P.18;Bat14 - and "Cosmos" S.P. 55 B at 18,5. Metro -Vick Supplies Ltd. (Proprietors :Metropolitan -Vickers Electrical Co., Ltd.) METRO-VICK HOUSE, 155, CHARING CROSS ROAD. LONDON. W.C.2 P54 Ask your dealer for these attractive folders on " Cosmos" Valves, Sets and Components. C In replying to advertisers, please mention THE WIRELESS CONSTRUCTOR. 281 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 Apparatus Testedcontinued These rheostats are similar in con- for connecting to the rotor plates, a " Enhansa " Indoor Aerial structiontotheir well-known panel copper pigtail is provided. WE have tested a sample " En- mounting type in that the winding is The capacity ofthe condenseris hansa " indooraerialfor- carried on a strip of insulating mate- rated at .0003 by the makers, and when warded to us by Messrs. Ward & rial, which is bent round a moulded placed on testits actual value was Goldstone, Ltd.,ofPendleton, Man- insulating former.Terminals or sol- found to be .0003.Its minimum value chester.This aerial consists of three dering tags Are provided for making was .00002,whileat broadcast fre- strands of silver -braided cable, connections, whileaspecialshort quencies its losses were negligible. approximately 4 yards long, carrying spindle is employed so that the rheo- Theinstrumentisrobustlycon- at each end a reel -type porcelain in- stat may be mounted flat on the base- structed and well finished, and can be sulator, while at one end there is a ter- board.The resistance can be set to . fully recommended. minal for making the necessary con- any required value within its limits, nection to the lead-in wire. and, so long as an " on " and " off " Battery Switch The aerial can be very easily hooked switch is included in circuit, need not up, and is especially suitable for ses- be altered again. ROTHERMEL RADIO ame during the summer months for The rheostats received were of the JfESSRS.CORPORATION OF GREAT use as a temporary outdoor aerial, and bright emitter type, and when placed BRITAIN, LTD., have submitted to should prove exceptionally useful to on test it was found that they all had motorists who take receiving sets with a resistance of 7 ohms, which is the them. figure given by the makers. The maxi- Tested on a two -valve receiver at a mum positiongiveslessthan one - distance of seven miles from 2L0, the tenth of an ohm, while the wire em- aerial gave verygoodresultscon- ployedis of a heavy gauge, so that sidering its size, London being heard several amperes can be passed through at good loud -speaker strength, whilst this resistance without overheating. on a crystal set signals wore received This component isrobustin con- at fair telephone strength. struction, and can be recommended for We can recommend this aerial under use. conditions where a long outside aerial Variable Condenser is either impracticable or undesirable. received a straight-line Duros High -Tension Unit WE havefrequencyvariablecondenser for test from Messrs. Formo, Ltd. MESSRS. A.F.A. Accumulators The construction of this component LTD., have sent us for test one incorporatesseveralnovelfeatures. of theirDuroshigh-tension units. Only a single bearing is employed, and This unit is of monobloc construc- this is of the cone type, arrangements tion, compact insizeandlight in being made for adjustments to take up weight.When discharged at a rate wear. The stator plates are supported of60milliamperesitscapacityis at one place only, the insulation being stated to be 1,800 milliampere hours. arranged so as to be out of the main field of the condenser. As in most S.L.F. condensers, the vanes are somewhat long, and in order The " Yaxley " battery switch. us for test one of their " Yaxley " battery switches. As the name implies, this compo- nent is intended for insertion in one of the battery leads for use as an " on - and -off " switch. A smalllever actuates a earn made ofinsulating material,whichpressesagainsta spring contact as the knob is rotated, thus closing the circuit. Connections may be made by means of two soldering tags, and a positive stop isprovidedfor" on and " off "positions, which are indicated The Formo S.L.F. variable condenser. by means of a small engraved plate placed in position on the panel under One of the Duros high-tension units. the fixing nut. The lever .on the to eliminate any possibility ofirre- switch knobalsoservesto lock the The plates are separated from each gular spacing at the tip, small sup- knob on the spindle, and it is provided other by a strip moulded into the glass ports to both the rotor and stator with a knurledendforeasy with- container, while the top of the cell is vanes have been fitted.The compo- drawal. filledin with pitch, tappings being nent is of the one -hole fixing type, and We can recommend this component provided at every 2 volts.The vent isprovided with a standard 1, in. as being a workmanlike job, and it plugs are held together on a common spindle for the dial.Oonneotions may providesasatisfactorymeansof strip of indiarubber, this being an ex- be made either by terminals or solder- making or breaking the low-tension cellent idea, since the single vent plugs ing tags, while, as an additional means circuit. do not get lost,. 282 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR Apparatus Tested-continued Several of these units have been in that improvements to the mechanism " Hypower " Insulator have been made by the makers, so that use for some months as a 60 -volt high- ESSRS. SPRING WASHERS, tension battery, and when originally LTD., have sent us one of their the maximum load which can be taken charged their voltage was found to be by this instrument is far greater than " Hypower " Insulators for examina- in earlier models, while overloading inthe neighbourhoodof66volts. tion and test. After two months' use the voltage still would in no way affect the performance This insulator, which is of the rod of this model. registers above 60, and the cells appear type,is made ofporcelain with a to be in excellent condition in every glazed surface, and is provided at one way; the battery is silent in action. end with an aerial tensioning spring. Using this product for the aerial in- sulator so that the spring has a slight tension,thewirewillremain taut under varying conditions. The insulation resistance was found to be infinity, while the capacity to earth introduced by itsuseis con- siderably lower than the average.It is stated that the breaking load of this insulator is 500 lb., a figure far in excess of the maximum load likely The " Hypower " insulator isfitted to be applied by the largest amateur with a spring to keep the aerial taut. aerial. This is a useful fitting which can be The makers advise giving this cell recommendedforaerialinsulation, a slight boosting charge every four to either for reception or transmission. five weeks, but this has not been found Celestion Loud -Speaker necessary in the case of the unit under E have received one of their A3 test. models from Messrs. Celestion Although we have not as yet been Radio Co. The new model "Celestion" loud- able to give this cell a very stringent This model is an advance upon the speaker. test,the results so far obtained are one originally produced by this firm. On test it was found that the repro- very favourable, and we have no hesi- Instead of being contained in a square duction given by this instrument was tation in recommending this high-ten- mahogany case, the two top corners have of exceptionally fine quality both on sion unit. been bevelled off. We also understand speech and music, the tones coining out MAGNUM SCREENED COILS RAZOR-SHARP WAVEMETER. As described by Mr. J. H. Reyner in R. P. Envelope No. T4. NEW STANDARDCOILS AND PRICES. MAGNUMScreeningBox, completewith SOLVE THE H.T. PROBLEM. Complete set of parts, includilpails covering 6 -Pinbase (Standard spacing and cross by constructing the H.T. Unit as described by ino-T,000 metres. formation) Mr. P. W, Harris is " Popular Wireless." - 155. £4 4 0 Complete set Valve The instrument ready wired and tested. Split Primaries. s.d. of components including £5 00 Aerial Coil .. 250/550 60 25 100 Coils for the above can be supplied as follows :- H.F. Transformer.. 250/550 10 0 No. i Coil iiio-boo metres 10/ - Aerial Coil .. 1000/2000 6 0 The instrument ready wired and tested86 0 0 No. 2 Coil 600-2,000 metres .. 101- H.F. Transformer.. 1000/2000 10 0 Plus royalty, 12/6. 3 -PinCoil mount with brackets.. .. Split Secondaries. F. Transformer.. 250/550 10 0 .F. Transformer.. 1000/2000 14 0 Restarts Coil 250/550 10 0 Reinartx Coll 1000/2000 14 0 Price per set of S Screens and Coils, 250/550, for the Elstree Solodyne £3 11 0 Set of Screens and Bases I.F. Trans- formers, Fitter and Oscillator for the 8 -Valve Super -Het. described In October iNsue SS 100 NOTE.-Where a complete set of Compo- ALL BRITISH SIX. nents, together with a drilled panel, is pur- AsdescribedinDecemberissue" Wireless chased, Royalties at the rate or 12s. 6d. per Constructor." 8 -VALVE SCREENED COIL SUPER -HET. valve holder are payable. Complete set of Components. As described by Mr. G. P. Kendall in October issue "Modern Wireless." Complete set of components. 82450 £2516 0 BURNE-JONES & CO., LTD., Manufacturing Radio Engineers, The set ready wired and tested. The set ready wired and tested. £31 00 £32 0 0 Magnum House, Plus Royalties, £6 100 Pins Marconi Royalties, £3 r50 Listsdealing withtheabove,including the 296, BOROUGH HIGH ST., MAGNUM TAPPED. TRAP COIL. Selective 3" All -Round Europe "and other LONuON, S.E.1. As used hi De Luxe wave -trap, described is sets described in this issue together with Elstree Telephone HOP 6207. Six,Elstree Solodyne, Night Hawk, Distailex, Telegrams: "Btriomag. heart, London." November 27 issue" Wireless.' etc., etc., sent on receipt of stamp. Cables; "Eurjomag, London." 1744 In replying to advertisers, please mention THEWIRELESS CONSTRUCTOR 283 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 Apparatus Tested-continued particularly well.The articulation is ready and handy means of doing this of the condition of each flash lamp clear on speech, while musical items neatly and efficiently, whileahole cell, while with loads connected to it are well reproduced. drilled through the centre of the link from a suitable battery it may be enables wander plugs to be used in usedasaninspectionlampfor " C.W." Battery Container and the conventional manner. examining the interior of a set. Safety Wander Plug When placed on testit was found Safety Wander Plug that at 6 volts a current of .42 ampere VVE havereceivedsamplesof was passed by this lamp withoutit various components from The safety wander plug consists of beingburntout. Underworking Messrs. TheJ. E. B. TradingCo., asmallflash lamp holdei provided conditions, however, it was found to including their " C.W." Battery Con- give ampleprotection,andevena tainer, " C.W." Safety Wander plug, single.06 type valve was not burnt battery tester andinspectionlamp out when placed across a high-tension combined, and some of their' -special battery with this safety wander plug battery links. in series with one of the battery leads. The battery containerconsistsof In view of the high current taken two metal trays sliding one within the by the filament of the lamp itis not other, of suitable dimensions to take advisable to use this plug as a means ordinary flash lamp cells. The con- The C.W." extensible battery of testing an H.T. battery, since the tainer allowsahigh-tension battery container. of any desired size to be made from cellsofthisilescription,the whole with a specially long wander plug for battery being kept secure and tidy in thecentrecontact,whileasmall the battery tray. swivelling brass arm makes contact The component isfinished in black with the outside part of the holder. japan enamel, and is provided with a When this is used in the negative lead of a high-tension battery,itisin- metal knob at each end. tended that the lamp should burn out in the event of the high-tension bat- Battery Links terybeinginadvertentlyconnected -:2 The battery links are special double - across the valves, thus preserving the The "C.W." combined safety wander. ended clips, by means of which the latter from damage. plug and battery tester. flat spring contacts on each flash lamp It is also intended for use as a bat- load is considerably higher than would cell may be linked with succeeding terytester,since the brightness of be imposed upon thebatteryunder and preceding cells.They provide a the lamp will give a rough indication normal working conditions. FINE "Two gears' SIZESAR'l CRAF 1 9DESIGNS25 CABINETS delau MADE IN OAK AND MAHOGANY American Type No. 2. cost me Panel Size Oak.Mahog. £300" Depth. 14 x 7 x 81 24 0 29 0 " Iwas £3 a week 18 x 7 x 9i 290 36 0 poorer for fully two 16 X 8 x 9i 28 0 33 0 years because I hesi- 21 x 7 x 9i 33 0 40 0 tated so long about American Type No. 2. Any Size to Order. Baseboards Free - starting an I.C.S. Course.That's clear enough.Since I woke up and began my vocational training with the I.C.S. I've been given a Radian, Resiston or CARRIAGE PAID ETAAANtrinItEr!: rise of £150 a year, but I'm certain I would have got it two years Ebonart Panels supplied. sooner had I sent in that I.C.S. Coupon when I first saw it. FULLY ILLUSTRATED THE ARTCRAFT COMPANY, " It's strange that so many young men fail to see that they don't get CATALOGUE FREE. 156. CHERRY ORCHARD ROAD. C60 DON. more money because they don't qualify for it-that they are losing £ s. d.aU the time through neglecting to obtain a special training." Get out of the rut by taking an 1.L.S. Course. It will provide you with a sound and practical training in your own home and in your own CHEAPER THANUSING THE MAINS time, all by correspondence and at a cost well within your means. Eliminators Eliminated by There are no real difficulties and no heavy demands upon your time.1 he I.C.S. method is simple and The WESTAM practical. Let us tell you just how you can use it I. C. S. EVERLASTING to your own great advantage. is theoldest and largest H.T. ACCUMULATORS Write to.day for full information as to how the I.C.S. correspondenc only Requiresre-etirgingtwice year can help you in your chosen vocation. There are 300 school in the I.C.S. Courses, of whichthe following are the most world a Volt. 2 Amps. important groups 6D. ENTIRELY BRITISH. FULLY GUARANTEED. WIRELESSENGINEERING (an entirely new Course) - Advertising Engineering (all Professional Exams. 60 Volt Model 30'- Architecture branches) Salesmanship 20 v. 10/6, 30 v. 167-, 90 v. 45!-, Building French and Spanish Showcard Writing 100v. 50/.,120v. 60/, Commercial Art General Education Textiles SCRAP YOUR DRY BATTERY. Commercial Training Market Gardening Window Dressing All models, catalogues and spare parts Draughtsmanship Plumbing Woodworking from any dealer, or (Pleasemention thesubject in which you are most interested.) WESTAM ACCUMULATORS, International Pat. No. 1093626 CLEMENTS ROAD. LONDON. E.6. Correspondence Schools, Ltd. 172, InternationalBuildings, Kingsway, London,W.C.2 284 Inreplying to advertisers, pleasemention THE WIRELESSCONSTRUCTOR. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR IGRANIC'S BIG PRICE FINSTONI COILS. - B.B.C. REDUCTIONS. Aerial, 5/8. S.P. Trans, 7,8 CALLER'S COLUMN HOW WIRELESS COMPONENTS IGRANIC TRIPLE- HONEY5.2 Trans, 7 /6.Reloads, 7;8. NOT SENT BY POST. COMB INDUCTANCE COILS,Daventry Aerial, 5,6.S.P., 7,8. 30,2/9; 40,2/9; 50,2/9; 60, Terminalss ithN. andW. ARE MADE SA.,11/-. Reinartz,11/-, ld. ;Nicker, lid. ;Spade Tags 3 /- ;75, 3 /3;100, 8 /8 ;150,Screen and Base, 9-. S.L.F. CONDENSERS 8 /9 ;200, 4 /-; 250. 4 /13:300, 8 a IC Soldering, 88, doe. ES, (Concluded from page 190) 4/9; 900, 5 /8 ;500, 7 /- ;750, LtTor Bushes, .1d. Screw Wander READY Flogs, 23., 3(1., 9d. pair.Flog 9 /13; 1.250.14/-; 1,500, 16 /- LOW LOSS wad Socket, It. or B., 3d,Sta- Cantons Ap. F. -Coupler 250 / plee 4 a ld. Valve Pins, 2 a ld. 500M.,4/8.PaoentS.L.F.. SQUARE LAW 6/11 4 or 2B.A. Rod, 3d,ft. Earth .0003, 14/8 ;.0005. 18 /8.Low This variable Capping Lou Dual, .0005, 27/8. Micro Tubes -Copper, 2/3;Climax, Condenser la /-Fine 7/22 Aerial, 100 ft., Condenser..00004, 5;8.Dial, simply mar- When thisisdonethosevalves 1 /- extra.Vernier Balancing 1 ; Special Heavyweight, Do.,5/8.IndiagraphVernier vellous value. 2/8. PhosphorBrener,49 which stand. the test are " capped." Knob mid Dial, 7;8. Microvarn. It cannot be strands, 100 ft., 1/- (limited). 8,8." E " Type L.F. Trans- equalled in Twin Flex, R. d B., 12 Yds., There are two parts to the cap of the formers, latest shrouded model price or Qual- 1/4, 1/8, 2/--.Miniature Silk ity..0005 Twin Flex. 6 yds., 13d.Maroon valve,theshelland theinsulator. 3-1, 15/-; 5-1, 16/-. Lighting Flex, 6 yds., 9d.In- The cap is pasted on to the base of KRANC0.-Midget Hal. Con By poet, 5 /11, '1'4/1 I sulator., 2 for /id. Tinned 8/9.Panel Brackets, pale 1/- '0003 or .0005.. 6/11Copper, 1 /16th sq., 1d.2 ft the shell.The insulator is fixed into extra. D.C.C. Wire, 11b. reel, 20g, 9d. Vernier. 1/. With Knob and Dial. 711122g. 104., 24g, 11d., 26g, 1 /- position into the shell and the four LISSEN Post 64. Set. 28g, 1/1.Battery Boxes, with copperwires,which youremember LISSENOLA.13 ;6. L.F. TRANS-L.F. TRANSFORMERS, - Fer-G vudValueinNon,Micro- covered leatherette, 2 /11 FORMER, 8/6. 85 OEM RHEO-ranti A.F.3, 25 /-A.F.4, 17 /8 ;PHONIC VALVE HOLDERS.Metal, 3 /9, Ebonite, Grade "A," were fixed to the foot of the valve, STAT, 2/6. ELF. OR L.F.Eureka Concert, 25 /- ; 2nd StageBoard Mounting, 1/8. cut while you wait.3 /16th is CHOKE,10;-. FIELDLESS21/-; Baby let or 2nd, 15 /- ; ad sq. inch. ;i in. is Id. sq. in. are threaded between the valve legs, COILS, 18 , 8. GRID LEAKS.Kelm, 151-; Poems shrouded,ADICO H.T. has Highest GradeStock sizes cheaper ; 7 x 5. 1 /3 ; which you will notice are usually slit F.,1 /.. DITTO. VARIABLE,10'/6;Success (Black), 21 /- ;Test Award. 60-v., 6 /11 ;100-v.6 x 6, 1 /8 ;8 x 6, 1 9 a 6, 2 /6. ALL PARTS AVAILABLE,Royal , 20 /-; Ormond newest 13/11.Post1/6 each. 1/11 ;10 x 8, 3 /-; 12 x 9, 4 /-. for this purpose.The wire is cut off Linen 11071. 8 /4.(Various nuni-model, 15 /8 ; Viaates'Supra, Also .cheaper quality for crystal bees stocked.) 10 /ILCroix5-1,3-1, 4 /8. AMPLION.-Large stocksofsets. Special offer In Crystal and soldered to the leg of the valve Marconi" Ideal,"all stages,LOUDSPEAKERS. 88 /-, 46 /-.Bets.8/11,7/8,6/11,8/6, to which it applies, two of the leads VARLET. - Anodes, 7 /8. /- each.C.A.V., 15 Pie, 88/-.All models stocked. 12/8. Alsoin enclosed cabinet, 250,000 ohm, 9/8.B.F. Choke, 22 /ILGambrel!. 2 deem, 25 /13.VALVES. -Cosmos S.P.18, Redwonderful value, 18/11- AME- going to the two 'filament legs, one to 9/6, 121. Ideal Junior, 18, 6R.I., 25/-.or Green, 14 /-.New Bine Spot,RICAN TypeOak Cabinets, Multi -Ratio, 25/-. 14/-. Mallard.Ediewan,with baseboard, take /2 x 8 the anode leg and one to the grid leg. BEARD & FITCH (Success).- ebonite, 10 /8 ;12 x 9, 11 /fa; B.F. and L.F.Chokes,each, Osram, Marconi, lioseor. Bright16 x 8. 18/11;18/11. Any Thentheshell ofthevalve is 10/8.Midget Nest. Condenser.FIXED CONDENSERS. -Dubi-D.E. and Power, 8/-,14/-,else in 8 days. Handsome panel 7/8. " Black " L.F.Trans-Her, .0001 2, 3, 4, 5, each 2/6.18/8,22/6. 24/6.80/-,82.switches, DPDT, 1 /8 ;SPDT, " pinched"bymeansofa hand former. 21 /-. Bullard PM, 1,2,3,9,5,6 001. 2, 8, 4, 5, 6, each 3/-.stocked. 1/-.(Highest quality). machine on to the insulator and the Grid Leak, 2/6.Edison Bell, Lightning Arresters, 1 Wave- MeMICHAEL.-Bal. Condenser,.001, .0001, 2, 3, 4, 5, 1 /-; .002,CHOKES.-Coemoe H.F., 6 /6 ;lengthPermanentDet.,6d. cap is fixed by this means. 4/9. AllFixedCondensers.3. 4, 5, 6, 1 /O..0003 and gridLlesen H.F. or L.F., 10/- each.Red Diamond Penn. Detector, B.F. Transformers, each IV-.leak, Bi-.McMichael with clips Dhabi Coils, 10/-. Success L.F. or H.F. 10/- each.8/-;liberty. 8 /8 ;Brownie, Bases, 2/0..0001 to .00005, 2/6 each..001A.J.S., 15/-, with unit, 20/-.al- ; Ra., 6 /- Cry -stale, Final Tests BENJAMIN. -BatterySwitch.to .006, 8 /- each. Shaw's Genuine Hesite, sea led, 1 /3. ORMOND PRODUCTS. fkl.; Neutron Wyray, 1/8; Valve Holder, 2/9.With Square Law Low -Los,.0005, After cleaning and dusting -for the Grid Leak, 5/3. With CondenserMYRRH - TONES, LEWCOS. Dayette,2/13 ; Splendid enclosed 9 /13;.0003, 8/8 (1 /8 each less noCrystal Detectors, on base, 1 /-, valve becomes very dirtygoing and Leak, 7/-. Sell -containedPETO-SCOTT, BOWYER LOWE Geared. Rheostat, 2 /9. vernier); Friction 1 /8,1 /13. Micrometer,1 /9 : through so many hands in this viv- ETC. .0003,15 /- ; .0003.14 /8 ;Service, do., 2/9 (with crystal). PEERLESS. -6or30ohmSCREENED COILS. - B.B.C..00025, 1316; Straight LineP. d P. Switchee, 1/-, Non- a final test is made with instruments Rheostat2,13. Fixed Random250-530metres. TannedFrequency Friction Geared, .0000microphonic V.11., 1 /8. Solid (State Naives), 1/6. Primary Aerial Coils, 6 11 -Ft 20 /- ; .00035, 19/6.S.L.F.,Rod Eb., I Baeeboard, 8d recording the emission, vacuum and Transformers (Split Primary and.0005, 12 /-; .00025,11 /-. SQ.2 -wayGearedCoilHolders, J. B. JACKSON,BROS.-Reaction), 10/-.Split Second-LAW LOW -LOSS DUAL. .0005,2 /11,8/11. Penton,Lotus, general behaviour of the valve.It is S.L.F. with 4 in. dial, .00035ary H.F. Transformers, 10/-. forElstreeSix,16/11each.Polar ,Newey stocked. Back or glass 10/6..0005, 11/8.New TrueReinarta Transformers. 10 /-.OrmondFrictionDial,10/-.panel,W.L.L., 4/11; Kay marked andstamped on the Tuning B.L.F. with Slow-motion5XX same prices with exceptionFilament Rheostats Dual. 2 /6 ; with the various markings necessary Dial, .0000. 16/6, 00035, 16/8.of Reinert,: and S. Secondary6 °tuns or 30 ohms, 2/-. Poten-Bay, /11. g drillsfor1-h. .00028, 15/-. (Bel bearings).these are 14 /- each. tiometer, 900 ohms, 2/8.LB.52114, 1/8. 'Phone Cords, 1/-, to it and the valve is ready for issue Shrouded, latest model, 15 /- 1 /8.L-8., do., 118, 1 IR H.T. for use by you on your receiving set. FORMO. and L.T. Leads, 4 -way. 1 /11. Ultra Low -Loss Variable 8.L.F. MONODIAL RECEIVER RADIO MICRO VALVES..06,Ow old friends ADICO Bat- Condenser, .0003 or .0005, 9/-.(" Wireless") - 4 A.P.V. teries, 60 -volt (not one in a It has taken a long time to describe Form° L.F. shrouded, 10/8. 13-v.,6 /11 ; .25, 2-v., 6/11.,1,000 has to be returned). I Molders. 19 /- ;R.I. Multi L.P.,Power, .8, 8 /IL, Power, .1,will change anyfault. Price allthis,yettheprocessofvalve EVERYTHINGinDemand 25 /- ; Pacent Super L.F., 2418 ; /11. (Power are 8-4 volts.) : f .F. Varley Choke, 9/8 ; VarleyPhillips' 4 -Electrode.4 -pin for6/11. Adico, Everready, Sie- making,frombeginningtoend, Stitched for Wireless. mens.Hellesens,60-v.,and BARGAIN DEPT. 250,000 ohm Remetance, 9 /8 ;Unidyne, 8/11.Poet 6d. each.100-v., all1.6 Batteries here. thoughso complex,israpidlycar- Hugequantitiesof windowOn and ON Switch.1.03 ; 2 Jacks, ACCUMULATORS. - 2-v. 90,(Columbia always stocked). coiled and goods which have 6 /- ;4 Fixed Resistors, 10 /- ; Dr. Helper L.S.Unit, nickel, ried through to ensurea maximum 2 B.E. Neutralizing, 10 /- ; 1 7 /11 ;'2-v. 60. 9/11; 80, beentakeninexchangefor 14 /11. Dr. Beeper De -Luxe sale at ridiculous prices.Bar-Pranco Midget, 8 /9 ; 2.00'2 12 /8 ;2-v. 100, 14 /11; 4-v. 40, output within the minimum space of gains not sent by post. Fixed, 4/-;2 H.F. Trana-13 /11 ;4.v, 60, 3.7 /11 ;4-v. 80,Senior, 4,000 ohm Loud-epeaker, time necessary to efficiency. formers, with 6 -pin base, ready26 /8;6-v. 60. 911 /8 ; 80,85/-.Radio Micro "Saar," for use, 12 /8 each :and OR-35 /8.Also another good make,fine value, 22/8. DR. WEIMER. 9,000 Adjustable Phones (4,000ohms),'.MOND GANG DUAL, 82/-. '1/8 extra on each of above.STOP (I - Adjustable 11/8. Special Cheap Model,List Total, ZS 15e. 9d. Post 1 I-. ohm Headphones (Nesper pat- The two larger photographs.of valve 8/8.Loudspeaker Unit, 14/11If the complete lot taken I will tern). double leather headbands, manufacturing a,pparagibus which (4,000 cance).Grande de Luxedespatch,carriagepaid,for WHY PAY BORE P 741pr. Loud -speaker.4;000ohms, 27 19s. 6d. BUY THE COMPOIOIMTCALLERS : MAKE OUT YOUR accompany this article are reproduced 37/6.All postage extra. NOSICE.-1 can supply hand-PARTS,includingWireand1,121 FOR A SPECIAL QUO- some American Type Solid oakand Wiring Diagram for the TATION. by courtesy of the General Electric ,HEADPHONES, all 4,000 ohnw.Cabinets. hinged lid for Panel.PP 2v.. L.F. and Detector Circuit Go., illustrating the making of Osram -N. & K. STANDARD PAT-14 x 7 x 1. Beteeboard, 14 in.All Goods Best Quality to 301 -OUR NOTED 1 -VALVE and TERN, 7 /11pair. N. & K.deep, 25/11.Post, 2/- extra. Post FREE. CRYSTAL SET, in solid polished valves at their works. genuine, new lightweights, 11 /8Ebonite Panel, 14 x 7 x 0, 51-, cabinet, complete With valves, 18/6. Dr. 11estaer, 10/8 andPost. 1 /-. American Cabinet. 12 x 8 x 7,'phones, H.T. and L.T. Units, 12/11.Telefunken, adjustable hinged lid, panel fitted, 17/8.AerialEquipment,Daventry genuine (20/- model), 14/11. Coil. Extraordinary Value, 6D,%w oe tv.,-,@&mge Brunet, 11/9, 12/11, 14/8. 3 COD. STANDS. -Lotus 2 -way,45 /11. Carriage, 2 ,-. models. 7 /--.3 -way, 10 /6 ; (extensionASTOUNDING 2 Valve Am - handles extra).Polar 2 -way, 6 ; VALUE in L.F.p 'er, 25 X11, ERiCASON (Continental) EN.. 3 -way,9/8. SterlingTriple, a THE 4 /11 Amplifiers inor COMPLETE Dr. (Pont 6d-) 21 /-, Kay Ray, geared 2 -way,handsome withvelves, a V /11 9 -way, geared, 8 /11. g, BRITISH HEAD -DRONES polished box,ma. ana L.T. " DISTAFLEX TWO " q3 Penton2mvay,geared,6/-.I valve, 18111. Units, 44 /6. Brown's Featherweight. 20 /-. Imperial 2 -way vernier lmob,13/- Carriage 1/8. Carriage, 21 -. (% Brown's A Type (Reed), lei-. 4A94343c3 q343oe QT3c43 lieo B.T.H., 15 /-. Sterling. 20/-.THIS MAGNIFICENT 2 -VALVE WATMEL PBODIKTS. GANG CON DENIERS. THORPE K4 9/6 SET (D. & .0002 or .0003 and Grid Leak, DUAL .0005. VALVES, 6 -pin As shown in handsome polished2/6,Sliced Condenser, all caps,ORMOND, with dial 32 /- T.HE design of the screened coils American type cabinet, with 22/-. Variable 0.1.. 2,11la 0. 5CTIZON, no dial ..50 /- SUNDRIES. Dull emitter Valves and Coils,meg.). Anode, 50,000 to 100,000, TRIPLE .0005. . used in Radio Press sets is the Newey 2 -way geared coil -stand, 65. 8/8.Ditto, 10,000 to 75,000, ORMOND, with dial ..40 /- 13/8. 4 point condenser 17/6.(MarconiToopa/.id),ear, 8 /6.8 /6. Ants Chose L.F. Coupling.CYLDGN. nu dial 70 /- result of a careful combination of effi- 16/-, " R.I." New Type AerialOR with Valvm, Igranic Coils,18/6. Poet extra. IGRANIC no dial ..75/ - ciency and compactness.After experi- Tuner, nos.Gambrel' Neutro-H.T. 100 v., L.T., Aerial Equip - vernia, 5/6. mental, Leads, and 26/- Loud LOT 08. PARTS IN STOOK FOR THE ments at our Elstree Laboratories cer- Speaker,taxpaid.The Lot.V. Holders, 2/3.With Termi- FOLLOWING WEST END DEPOT FOR 2610s.Od. nals. 2,41.2 -way Coil Stand,ELSTREE SIX, SOLODYNE, tain standard -have been found neces- " (Borne -Jones). Carriage 51-. 7/-, 8/-.3 -stay, 10/6. 12/ - MEWFLEX, ELSTREEFLEX, sary, and unless these are adhered to 1927FIVE AND ALL THE CALL HERE FOR Lime°, Bentatuin Radio Micro, Voltron' Cosmos, Mallard, Ediswan, Marconi CHIEF CIRCUITS. loss of efficiency may result. COMM, Ogrem, Jackson (LB.), Dubilier, McMichael, Success, Beard & Fitch, Bowyer Lowe, Lewes, Igranie, Eureka R. 1., Ormond, Utility, Form°, Edison Bell, Ferranti, Polar, Newey, P.M Magnum,FineBritishValves ! Thefollowingmakesofscreened plmaz email High Prices : ALL LINES IN DEMAND STOCKED. PURATONE (RUBOR) coils have been tested at Elstree and WE HAVE Tao GOODS I I CALL AND 'RN no. SPECIAL DOLMA TO RADIO CLUBS, GENUINE EXPERIMENTERS. 2 -volt foundto conformtothestandard BE SUEZ YOU ARE AT RAYMOND'S. 3-3.5 .06 .. each ail 1 specification, being therefore suitable for the " Distaflex Two " and other Radio Press sets incorporating screenedcoils : - Bowyer K. RAYMOND 4SILJAR2ill'EETi standard HOURS .. 9.15to7.45 Back ofDaly'sTheatre, Lowe, -Collinson, Copex, Efesca, SATURDAY..9 to8.45 Nearest Tube, Leicester Square. Lewcos, Magnum, Wright it Weaire. SUNDAY .. 11to 1 'Phone :Gerrard 46?7. In replying to advertisers, please mention THEWIRELESSCONSTRUCTOR. 285 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 ME NEW MIMS JACKS & PLUGS FREE BLUEPRINTS IMPORTANT NOTICE TO READERS IN consequence of a change in the ownership of THE WIRELESS CONSTRUCTOR and MODERN WIRELESS, the free blueprint service has been discontinued as from 1st December, 1926. A Revised Scheme for the supply of blueprints is in course of preparation, and announcements concern- ingitwillappearinearly issues of " POPULAR WIRELESS." E@OEgEgE0,9iD@EMOee000E8)06g) Keep a steady pressure on the tap g ql wrench, and as soon as the tap tends g A NOTE ON v to jam, remove it from the hole and q3 clear away any material that may have LOTUS JACK g TAPPING (13 stuck in the flukes;this jamming is SWITCHES g This push pull switch usually preceded by a springiness or is designed to occupy +9,83e02 e:19i349q9t903081343 " give " in the tap-so take warning. the minimum space. beingonly Itin. Do not " lay " on your job when tap- deep. Of thefinest WHEN drilling a hole for tapping Bakelite, it has nickel remember to make it smaller ping or you will make the hole too big silverspringsand and possibly break, the tap. contacts, of pure silver. thanthefinishedsizeyou Soldering contacts can Finally, do not buy cheap taps or be made to suit any want; if youdonot, the tap will wiring. nearly" drop "throughandno dies, since they are often made from PRICES: cheap steelof doubtful No. s as illus. 4/. thread will result. An approximate quality and Others from .-2/9 ideaofthesizerequiredcanbe improperly hardened andtempered. gainedbytakingoneandthree- Broken taps and spoiledworkare quarter times of the likely to 'result from their use, so that size, i.e.,three -sixteenthsfora they do not pay in the long run. quartertappedWhitworth. There W. J. H. are a number of different threads in use,includingWhitworth,British Association, Gas, Metric,etc. These eo@eoeorg,00000afg6gamm all have a different pitch, i.e., the dis- tancebetweenthecentreofone ft AN OBSCURE VALVE thread to the centre of the next.But FAULT the wireless worker need only trouble aboutthe.BritishAssociationor e eeeegEge6g$33 ts.eale3o,s6e " B.A.," as itis called.This has a The name ' LOTUS ' is very fine thread which is most suitable your guarantee of sound for wireless work. MISBEHAVIOUR on the part of a set using dull -emitter valves is results and solid Taps often due to partial loss of emission satisfaction. of one or more of the valves. Itis usual to employ three taps, The general symptoms ofloss of From all Radio Dealers. although two will do at a pinch. These emission are weak signals arid failure are first, second and plug or bottom- to oscillate., A general " dead sensa- ing taps. Naturally one commences tion " about the setisoftenattri- with the first tap ; this is the one with butable to this cause, and itis im- thegreatesttaper and little or no portant that these symptoms be known, ininurs thread at the end.Thisis followed as results may often be temporarily by the second tap, namely, the one improved by increasing the filament '4ACKSSWITCHESPLUGS' with a slight taper; and lastly, the voltage applied to the valve. This, plug tap. however, generally results in the com- Made by the makers ofthe Keep Straight plete destruction of the dull -emitting famed 'LOTUS' Vernier properties of the filament, and though Coil Holders and ' LOTUS' Great care should be taken when the valve may be run for some time Puoyancy Valve Holders. using the tap to keep it vertical, as a after as a bright -emitter, it will not slanting hole will show up if the screw - last very long. When the behaviour Garnett, Whiteley & Co.,Ltd. head projects.If your hole happens of the set gives the slightest reason to Lotus Works, to have run a little out of true in the suspect that the emission of the valve Broadgreen Road, Liverpool. drilling,careful tapping can correct is defective, the first thing that should it, but care will have to be taken if be tried is the substitution of another t;":',IF;M:.1777::(n:?-7AT.7717-7-Aff;:irig you do not wish to add a broken tap valve. to a badly -drilled hole. L. H. T. 286 In replyingto advertisers, please mention THE WIRELESS CONSTRUCTOR.. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR WIRELESS Capable, trustworthy men with spare time who ALL ROUND EUROPE WITH wish to substantially increase income required where we are not fully represented. Applicants must have practical knowledge of installation PLUG-IN COILS of Set and Aerial, be a Householder or live with patents, and be able to give references ; -concluded from page 200 state age and experience.Address Dept. 22, GENERA'. RADIO COMPANY LIMITED, Yes- RadioHouse. Regent Street,LONDON, W.1. be made somewhere about the 400 - That is. the metre mark,sothatthe balancing ON& OFF SWITCH shall remain as accurate aspossible as used in both on the higher and lower wave- RADIO PRFSS lengths.. PRIZE SETS. e *0000000800002; If the two coils L, and L0 are badly matchest it will be found that the two The EVERY LOUDSPEAKER halves of the gang condenser will have :Choke of Critics to be adjusted so that one is a large A wise .choice number of degrees in front of or behind too, theytort DESERVES theother. Ifthisisthecase, MULLARD then different' pairs of similarly -rated Only 110 each. coilsshould hetriedtilla pair is DIAL INDICATORS MASTER found with which both condensers are No. 1 Type .9d. pair. nearly set the same. A variation of 5 No. 2 -3d. each. VALVES No. 3 ..2d. each. or6degreesisapproximately the The accepted method for maximum permissible divergence, accurate dial reading. - Ask for MGM 709936 Multard P. M. Power Valves. though the set will work quite well GRID with a larger:differencethanthis. BIAS CLIPS Under these circumstances, however, it e-- as used in ozzozozoozzzonis highly probable that weak trans- 'MONODIAL missions will not be received at all. 6d. pair. Some Results (as illustrated) Pocket Battery PICKETTS CABINETS When Itriedouttheset on a Size made for short screened aerial about two miles 41-d. each. from 21,0, in conjunction with a low - BRITAIN'S BEST ! frequency amplifier, I was able to re- OBTAINABLE FROM BEST DEALERS OR For your OWN Set-GUARANTEED as supplied to WORLD'S PRIZE W INNERS & GOLD MEDALLISTS ceive a number of stations on the loud- .4 24 41 ./...\os'l ..7;;;'-/:"N - 'TY Mt. R. R. Anspach, awarded 1st Prise at Chicago speakerwithonly onestageof Exhibition, writes " My success was greatly L.F. at a strength equal to,if not 9-10-11,CURSITORSTREET, helped by your splendid work in waking my Cre...o.re ER's' LAME , E -C Cabinet." greater than, that which I can ob- Mr. R. W. Emerson, International Gold Medallist, writes - The Cabinet for my Solodyne was all tain with a four -valve set, using only that could be desired in workmanship and finish:' one stage of H.F. and two of L.F., "Drawing Room Five.") FROM thus definitely proving that the circuit " MI -British Six." used in this receiver is a highly effi- " Elstree Solodyne." cient one. A mile of wire " Davlow Three." 45 /- Cabinets for every Radio Press Set or your OWN sizes. It was found possible to tune in just Envelope of Cabinet Designs No. 21 FREE. on thirty stations in half an hour, PICKETTSCabinet (W-Cr) Works. Bexleybeath. andamong thetransmissionsre- ceived I have picked out those which were heard at reasonable strength with only one stage of Lie., many of them, as stated,beingatloud -speaker 0ERINGABousti strength.Without any low frequency 50 et) all these stations are heard at excel- lent strength in the 'phones, some of THE FOR them, indeed, rather too loud for com- SUPER PERFECT fort.The dial readings refer only to TERMINAL CONTACT the gang condenser, since the aerial condenser will vary according to cir- wound theWatmel way AMMO cumstances. L, and L. were both The special windings of the Watmel Auto -Choke axe done by expensive and abeolutely up-to-date machines IISI lEftlft"AP45 Gambrel!B,the makerssupplying which lay the wire exactly parallel and interweave specially matched coils if desired. cotton strands between each layer.Cotton acts as CAND MarCOUPLERS., binder, and insures perfect insulation.Get to know Tuning was found to be delightfully the other reasons for the nee amplification and natural - simple, and, since the reaction control toned reproduction possible only with the very seldom required touching, it was easy to go from station to station just 2 on two dials.Selectivity was good, Brass : 24d; Nickelled : 31d each. COMPLETE Bournemouth being receivedat two Simple and effective. Insert the wire through the miles from 2L0 with only slight inter- base unit Into the hole in the eteip of the terminal, tighten up the lock nut and perfect contact results. ference. NO soldering required. Wire 160, 26., Coll, 8 ft. AUTO -CHOKE rarer« pow et4 NWT 110WerelY.WelePWIOWNWPte PRICE 18,'6 TIXIT 8D 002 A SetbeforeChristm aa- From our dealer or direct from- payment after! YOU can have that newSet in time for Christmas. THE WATMEL WIRELESS CO., LTD. for connecting Junction wires without Soldering. Untler the Skew times system you can have 332a, Goswell Road, London, E.C.I. any Receiver upon asmallinitialpayment-the All Dealers or direct orders over 2/6 post free. balance in easy monthly instahnents. Components and Clerhenwell 7990. OMMInivE P.P.,"Serail,' fliftlUisi Accessories, too ISend to -day for Catalogue " W "to : 1114evo ...clines SALES 00., 77, CITY ROAD, Lancs., Yorks. and Cheshire Representative, L. H. REID & CO.." Mr.J.B. Levee, 23, Hartley St., Levenshulma _32. VICTORIA ST. LONDON. Soal,./_. E.C.I. Manchester. Telephone: 475 Heaton Moor. Wen Ween.U.01.11%O.A. 6343 Inreplying to advertisers, please mention 'THE WIRELESSCONSTRICTOR. 287 PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 INDEX TO ADVERTISERS. PAGE PAGE PAGE Agar (W. H.) ...... 288 General Radio Co., Ltd. 287 Picketts Cabinet Works .. . .. 287 American Hard Rubber Co. .. .. 244 Gent & Co., Ltd. 261 Portable Utilities Co., Ltd. ..238 Artcraft Company (The) .. .. 284 Graham (Alfred) & Co. 249 Radiax, Ltd. 277 Ashley Wireless Telephone Co., Ltd... 263 Hart Accumulator Co., Ltd... 209 Radio Instruments, Ltd. Automatic Coil Winding & Elec. Equip- Holzman (Louis) Cover iv 249 Raymond (K.) .. ..285 ment Co., Ltd...... 210 Hunt (A. H.), Ltd. .. 222 Autovoyors, Ltd...... 204 Igranic Electric Co., Ltd. 230 Reid (L. H.) & Co. .. sip ..287 Batteries, Ltd...... 260 International Correspondence Schools, Rexo Engineering CD... .. 277 Silvertown Co., The Bedford Electrical & Radio Co., Ltd.261 Ltd. O G 284 .. ..250 Belling & Lee, Ltd...... 254 Jackson Bros. .. G O 00 214 Smith Farmer & Co. .. ..260 Benjamin Electric Co. .. .. 251 Kriscros Co. 410 251 Standard Insulator Co., Ltd. ..262 Bird (Sydney S.) ...... 268 Le Breton Engineering Co. 277 Stratton & Co... 271 Black (A.) ...... 00 .. 288 Lifford Engineering Co. .. 00 00 232 S.T., Ltd. .. 182, 221,237 Blackadda Radio Co...... 246 Lissen, Ltd. 217 Taylor (C.) 288 Bowyer -Lowe Co., Ltd. .. 198 London Electric Wire Co. and Smiths, Taylor (J. H.) & Co. .. 288 Brandes, Ltd...... 235 Ltd. 264 Telegraph Condenser Co., Ltd. 254 Bretwood, Ltd...... 262 Makerimport Co. .. 251 Telephone Mfg. Co., Ltd. 276 British L.M. Ericsson Mfg. Co... .. 204 M.A.P. Co. 271 Trelleborg's Ebonite Works .. 260 Brown (S. G.), Ltd...... 224 Marconiphone Co. Ltd. .. 203 Valco, Ltd. .. .. 251 Bulgin (A. F.) & Co. .. .. 287 Metro -Vick Supplies Co., Ltd. . 274,281 Vandervoll (C. A.) & Co., Ltd. 222 Burne-Jones & Co., Ltd. .. 283 Morris (J. R.) 266 Varley Magnet Co. 251,259 Bush House .. .. 00 ..288 Mullard WirelessServ.Co.,Ltd. Watmel Wireless Co., Ltd. . 287 Carrington Mfg. Co., Ltd. .. .. 264 Cover ii, 227, 287 Wavio, Ltd. 260 Caxton Wood Turnery Co. .. .. 288 New Times Sales Co. .. 287. Western Accumulator C. 284 Clarke (H.) & Co. (Manchester) .. 264 Oldham & Son, Ltd. .. .. 206 Weston Elec. Instrument CO. . 209 Collinson Precision Screw Co... .. 262 Ormond Engineering Co., Ltd. .. ..256 White (A. W.) .. 288 Cossor (A. C.), Ltd...... 197 Peto & Radford .. .. 246 Wilkins & Wright, Ltd. 181 Coventry Direct Supplies, Ltd. .. 251 Peto-Scott Co., Ltd. .. .. 218,244 Wolff (M. & A.) 264 Darex Radio Co...... 251 Philips Lamps .. ..242 Wright & Weaire.. 260 Day (Will), Ltd...... 229 Dixon (L.) & Co. . . 279 Dubilier Condenser Co. (1925), Ltd., 245,277 RELIABILITY CABINETS : Ede (C.) & Co., Ltd...... 254 WIRELESS GUIDE Oak, fumed and waxed. Mahogany, French polished. Eton Glass Battery Co. .. .. 288 Kew Edition No. 9 ready. Complete OAK. MAIL Falk, Stadelmann & Co., Ltd. .. .. 271 ReferenceBook, and PriceList of 21" x 7" x 131"22/6.... Ferranti, Ltd...... 228 everything in Wireless. Send Postcard 210 x 8" x 8" 19/6. 22/,Cariiage Paid. Finston Mfg. Co., Ltd...... 249 Now.It's FREE.Trade Supplied. 14' x 7" x 9" 15/....17/6.Specials quoted Formo Co. 10' x x 6" 12;6....14/6. by return...... 260 JH TAYLOR Er CO 9" x 6" x 14i6. Gambrell Bros., Ltd...... 262 so r2 ADIO HOUSE Garnett, Whiteley & Co., Ltd. 229, 250,286 ACA U L AY ST HUDDERSFIELD W. H. WHITE, 5 Saxon Street, Leicester. THE WIRELESS DOCTOR will call (London and Home Counties) and put you right, it your set is troublesome.No cure, no charge.Sets installed. maintainedandbrought uptodate.ElstreeSolodyne demonstrated. PAXTON WIRELESS CABINETS ALEXANDER BLACK. 1-a,Woodville Grove, K. 16. CliSSold 3887. All Polished with new enamel that gives a glass hard surface 2 VALVE AMPLIFIER35/ 1 -Valve Amplifier 20/-, as new.Valves, D.E. 067/-, that cannot be soiled or scratched. Ebonite or Radion Panels Headphones 8/8 pair. New 4 -Volt Accumulator 13/, Supplied and Perfectly Fitted at low extra cost. SENT FREE.- New 60 -Volt 1T.T.. guaranteed, 7/-.2 -Valve All Stn. Set, Catalogue of Standard Wireless Cabinets in various sizes 24.Approval willingly.Write fur free bargain list. and woods. C. Taylor, 57, Studley Road, Stockwell, London. WET H.T. BATTERIES THOUSANDS OF SATISFIED CUSTOMERS. British made (round or square) Leclanch,". Glass Jars 2i x rI x 11, for wet H.T. Units.Waxed 1/3 doz., plain 1/- doz., sines 1/- doz.Grade 1 saes 1/6 doz.Grade 2 sacs 1/3 doz.Special Non -Bolder and non -corrosive Plug - ELSTREE SOLODYNE.Panel 21" : 7" fitted16"Baseboard, drop down Socket Connector and Zinc combined. Reg. design.Each cell a tapped unit, 2/6 doz. Large sacs 3/- doz. Acid proof Beaded Front Door. Fumed Oak 61/-, Dark Oak 65/-, Mahogany polished 68/6. varnish Bd. Jar (Black). Carriage and Packing extra. Raised Panel 51- extra.Packing Case 5/- extra. Sendlid. StampforinstructionsandList. Askusaboutthe" Unique"Voltmeter. ELSTREE SIX.Panel 42" x 9" fitted In" Baseboard. Open Type. Fumed ETON GLASS BATTERY CO. or Dark Oak 80/-.Mahogany polished 90/-.Packing Case 7/6 extra. 46,St.Mary'sRoad,Layton,E.10 MONODIAL. Panel 14" x 7" fitted14" Baseboard. Fumed Oak 3316, Dark Oak 35/-, Mahogany polished 39/6.Packing Case 6f- extra. 1 DI A ).1.41', 3 ilLQA NIGHT HAWK. Panel 16" x 8" fitted 14" Baseboard. Open Type. Fumed Buy your Wireless partsX11 Ifrit Oak 33/6, Dark Oak 35f-, Mahogany polished 39/6.Packing Case 7/- extra. direct from the WarehouseDill flirt, FIVE FIFTEEN. Panel 24" x 7" fitted 8/" Baseboard two Front Doors. Fumed atWarehouse prices.0111 triffIg Oak 40/-, Dark Oak 42/6, Mahogany polished 48/,Packing Case 7/6 extra. Every known component in stock.11111111M Write NOW for list. 11111II1.III THE 1927 FIVE.Panel 27r x 7" Sloping Front, as originally described. 35, Shudehlll, Fumed or Dark Oak 38/-, Mahogany polished 48/-.Packing Case 7/6 extra. BUSH HOUSEMANCHESTER RESIN -CORED, EVERYMAN THREE,Panel 20" x 8" fitted 8" Baseboard. Fumed Oak 33/6, Dark Oak 35/-, Mahogany polished 39;6.Packing Case 6/. extra. AGARS' RADIO SOLDER. 1/4. Guaranteed , 4?.. EVERYMAN FOUR. Panel 26" x 8" fitted 8" Baseboard.Fumed Oak 35/6, Non -Corrosive. V*4.-...,,;,,,,,, Dark Oak 37/6, Mahogany polished 41/6.Packing Case 7/. extra. British Made. Usedexclusivelybyall Telephone Manufacturers, CASH WITH ORDER.CARRIAGE PAID U.K. PROMPT DELIVERY. GovernmentDepartments, [SIAM ARMIN eta.No Flux required. Makes a perfect joint. Packing Case Money repaid if Case returned within 14 days Low melting point.Eliminates inctsy Flux. Carriage paid to Works. The Sale solder for RadioandElectrical Work. Per 1/- Carton. Obtainable from Leading Stores, Electriciam, Radio Dealers, Ironntongers, or Post Free direct from: CAXTON WOOD TURNERY CO., MARKET HARBOROUGH. W. H. AGAR, 19, Whltecross Place,Wilson 8t., LONDON,E.C.2. In replyingto advertisers, 'Please mention THE WIRELESS'. CONSTRUCTOR.. PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor January, 1927 THE WIRELESS CONSTRUCTOR This receiver will appeal to every musicalear The PURAMUSIC Designed by Mr. C. P. Allinson, A.M.I.R.E., and des- cribed by him in the December issue on sale December 1, this five -valve receiver employs two stages of high- frequency amplification and two stages of L.F. magni- fication.It has been designed to give the best possible reproduction from the local station or 5XX, but will, inaddition,receiveotherBritishandContinental broadcasting. Theillustrations giveanexceed- ingly accurate im- pression of the finishedreceiver. 1 lv.ONTHLY BUY YOUR COPY TO -DAY The outstanding features ofthis receiver include-the purestpossible reproduction of speech and music ; consistent reception at ERN distances of 5o or 6o miles ;the elimination of reaction in the detectorcircuits ;the WIRE L El SS useofa lay -outthat gives the utmost stability and the use of a modern neutralised obtainable from all Newsagents, Booksellers or Bookstalls, or direct From the Publishers. -Subscription Rates 13/- per annum (13/6 per high -frequency circuit. annum Canada and Newfoundland). Lesser periods pro rata. friailted:74&of.,4S,4" PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor THE WIRELESS CONSTRUCTOR January, 1927 Efficient Working is Low Distributed Capacity It is not high impedance value alone that makes for efficient working; -but the combination of the correct impedance for each valve in use, and lOw iron, self - capacity and resistance losses. The R.I. Multi -Ratio Transformer fully meets these demands.From its range of impedance values you can always choose one to operate correctly in conjunction with the valve, while the quality of iron in the core together with the possibility of working without a too high fixed impedance keeps both the iron and internal resistance losses to a minimum.The patented system of winding places the self -capacity at the extraordinarily low figure of 18 micro-microfarads. Various types of valves are to -day recommended for use With different makes of loudspeakers, and it is equally essential that the impedances of the other valves should be suitablymatched with those of the transformers in use. A transformer with one fixed impedance value may only suit one valve out of six, but the R.I. Multi -Ratio Transformer can be adapted to suit them all. PRICE 25/- i'Vrile for /lie THE MARK OF BETTER RADIO .1(171. R.I., Ltd., 12, Hyde Street, New Oxford Street, London, W.C. 1. Published on the 15th of each month by the Proprietors,ins AMALGAMATED PRESS (1922), LTD., TheFleetway House, Farrinedon Street, London E.C.4, and printed for them by TaxA VENCE PRESS (L.Upeott Gillat :on, Ltd.). 55-57, Drury Lane, London, W. 2. Advertisement offices Messrs.J.ILI- Lile, Ltd..4. Ludgate Circus, London. E.C.4.Registered for transmission by Canadian Magazine Post.Su_scriptionrates:Inland and Abroad. es. 6d. per annum; Canada only, Is. 6d. per annum.Sole agents for Soutn Africa :The Central News Agency, Ltd.; sole agents for Australia and New Zealand :Messrs.GordontGatch,Ltd.;sadfor Canada :The Laporte,' News Co. (Canada), Ltd. V PDF compression, OCR, web optimization using a watermarked evaluation copy of CVISION PDFCompressor