AWE APR 1929 .Pdf

AMATEUR WIRELESS, APRIL 6, 1923 "BRITAIN'S FAVOURITE THREE -1929 MODEL

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Vol. XIV.No. 356 Saturday, April 6, 1929

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Advt.of The Ever Ready Co. (G.B.), Ltd., Hercides Place, London, N.7. You will Help Yourself and Help Us by Mentioning "A.W." to Advertisers St 5 0,-,,-.,,,-,,,,,,--),,,,,--..-,,,,,,.,-,,-,--,,,,,,,--,,,,,,t.e73..c_<-.:Itc.-...--1,t,_..-,)-1c,-)Iate7)w-1--)c),--4te7ir.v.._>ttel:1 C APRIL 6, 1929 No. 356,Vol. XIV C S C S 5 C 5 Ontatzur ue ,

5 and Radiovision 5 The Leading Radio Weekly for the Constructor, Listener and Experimenter § = ---Editor : BERNARD E. JONES

Technical Editor :J. H. REYNER, B.Sc., A.M.LE.E. :: Research Consultant: W. JAMES :: Assistant Editor: H. CORBISHLEY § ricete7)---)clec7.1e-lca-)t,:7)tc)t.4:7)e)--7-1-. t.')r--)t.--)t71wle-.)t--1t.:ItIte7Ite7).+ctoit%)t-oc,tclte%)t-v.,.ett7)c-)t4.2)r---7it.&>0.4n.,.)0 Is There Jamming ?-Fultograph Filmed !-" Hot" News-Exit Jeffrey- The General-Don't Swear !-Next Week Is There Jamming ?-Why is it that 5 \ X on April 7, when General Higgins, when thinking of towns with "broad- the new leader of the Army, will conduct casters in every block" one always starts a service to be relayed from the Congress with New York? Apparently the U.S. has Hall, Clapto,n, London, E. not the monopoly of jamming, for the Don't Swear!-Has it ever occurred evening paper in Toronto, Ontario, gives to you when listening to the running com- every day the programme of five stations mentaries, such as the. football broadcasts in Toronto itself, nine stations elsewhere and the Boat Race relay, what a tempta- in Canada, together with a schedule of the tion it is for the commentator to make programmes of seventy stations in the ejaculations which the microphone and United States. some of the millions of listeners might not Fultograph Filmed!-A film entitled like?After all we are only human, and :The FultographStoryhas been incor- it is very natural that a keen sport enthu- porated in Pathe Pictorial No. 571. This siast should forcibly and fiercely vent his has been booked by over, a thousand feelings in ungentlemanly style when, say, 'cinemas throughout the country, and is a good pass is dropped !The B.B.C. makes expected to be showing in most districts thoughtful provision for this, often, by ,within a week.Incidentally, perhaps all placing a large notice, "Don't Swear !" in broadcastpictureenthusiastsarenot frontoftherunningcommentator's 'aware of the fact that experimental tests "mike." are being made at the Royal Airship A New Rela y!-A clever skit is to be [Works at Carclington in the course of Before its time-a spark transmitter and receiver given on April 9, under the fascinating in use, in 1902, at Streatham Fire Station. A ,which weather maps are beingtrans- telephone is now used. title of "A relay from the National Radio mitted by the Fultograph system and Station in Erewhonia."This programme, received in a number of places in theregretted by alllisteners.Nevertheless,which consists of typical scenes from British south of England. There is obviously ahe should be able to do some good worklife, is said to be founded on a study of [big future for this sphere of picture broad-for the "talkie" people, and they are cer-B.B.C. methods made by a Northern casting. tain to be congratulated on the initiativeErewhonian representative during a visit " Hot" News-And, while on thethey show in getting good men like JeffreytoLondon! subject of Fultographs, a word of praisewith ready-made experience. " The Proms."-The B.B.C. has de- 'must be given to the Wireless Pictures The Genera/-A broadcast which willcided to hold an eight weeks' season of people for the way in which they arebe of particular interest to all members ofPromenade concerts again this year, start- starting to fulfil their promise about givingthe Salvation Army is that from 2L0 anding on Saturday, August 17, and conclud- listeners real news pictures. Boat -tic471cce7iciw-icar.e7o.ce7icace,lece7ne7e.e7lote7i0ing on October12.Sir Henry race photographs were broadcast § PRINCIPAL CONTENTS Page §Wood will be the conductor.The within an hour and a half of the5 " Proms."seriesisone much race, you may remember, and even- Current Topics .. 515 appreciated by listeners-" high," § ing papers contained pictures of the 14 Audiences at Once.. 516 " mezzo " and " low -brow." Grand National wired, via Fulto-5 Improving Your Portable Next Week-So many people graph, from Aintree. § Electrical Recording at Home.. 551187 1like reasonably simple and self-con- Exit Jeffrey-A loss to broad -5 On Your Wavelength.. 519 5tained sets, particularly if electric - 'casting and a gain to "talkies" is§ Cutting Out Needle Scratch.. 523 5light mains can be used, that the WIRLLESS Mr. R. E. Jeffrey, who, we learn, ci My Wireless Den .. 524 5Am ATEUR Technic al has resigned from the staff of the§ Points About Exponential Horns 525 §Staff is sure next week's set will be B.B.C. in order to take charge of a winner. It is a "simplicity" two- the sound production department5 Without Fear or Favour 527 §valver, working entirely from A.C. of British International Pictures,§ Britain's Favourite Three Up-to-date 528 §mains and using the new directly - Ltd.Mr. Jeffrey has, of course,§ The "Arcadian Portable " Afield 531 heated Valves and a simple rectifier been associated with broadcaSting§ "A:W." Tests of Apparatus 532 §for H.T. No H.T. batteries to run for the past six years, and the fact §downoraccumulators § Radiograms 534 to"go of his leaving the sphere in which Our Information Bureau 537 5phut" just when there is a good he is at present best known will beClcev.lcoicacatoitoice:macatatacac,at&vlwIcioie,.7)05 Programme to be beard (imam WireiT 516 APRIL 6, 1929 I AUDIENCES I AT ONCE ! Political Broadcasts Made Possible by Wireless By An " A.W. " CORRESPONDENT and other sounds similar to atmosphericsgrids are connected together to the second- being introduced.Now, it is a curiousary of a special to to i Marconi Ideal trans- fact that noises one would hardly noticeformer, but the output circuits are inde- when listening to speech on headphonespendent. It is therefore possible to control assume serious proportions when the wholethe input to individual lines and a fault on is raised to loud -speaker level.This mayany one line will not affect the others. A easily be confirmed on any wireless set.listening point and volume control are also Unless,therefore,the inputisstrongfitted to each circuit. enough to ensure an output intensity well above that of any interference, the amplifiedTwenty-six Trunk Lines! results are rather like those obtained when The final unit at the trunsmitting end RECENTLY I described in AMATEURtrying to receive a distant station duringwas a thirteen -way change -over and moni- WIRELESS how land -lines were useda thunderstorm toring panel from which radiated twenty- for a giant political" S.B." of speeches from Repeaters solve the problem, as withsix trunk lines, each of the thirteen circuits Newcastle simultaneously to a number ofthem we are able to start with a moderatethus being duplicated again.The spare other towns. From this, shall we say,input; send this over a limited distance,lines were used for communication between "modest," beginningtheschemehasat the end of which it is still well aboveengineers at the input and output stations, grown until when Mr. Lloyd George spokethe noise level; then amplify again to theenabling the engineer in charge, to watch last week at the Albert Hall, in London, hisallowable limit, pass on over the nextthe whole system from his position at the words were carried to thirteen other townssection and so on, finally feeding it into theAlbert Hall itself. power banks and loud -speakers at the hall. At each receiving end there were one or DERBY NOITINGHAM This, then, is the procedure adopted in alltwo engineers in charge of a standard " B" the great political relays. amplifier and power bank of from four to WOLVERom. LEICESTER sixteen LS5A's, depending on the size of A Record audience and number of loud -speakers. HA LES WORG4 NORTHAMPTON At Mr. Lloyd George's relay,whichThe latter were of the well-knOwn Marconi - creates a record for this type of "wiredphone moving -coil type with rubber dia- FENNY STRRTFORD broadcasting," the first MANNIW,TREE stage was, of course, the ST ALSRNS microphone, a Marconi- Reisz,followed by a RP MSGATE specialdoublemicro- phone amplifier placed immediately below the SOUTH, platform.The ampli- BOURN fierincorporatestwo 0 REPEATERS RELAYS stages, resistance -capacity coupled, with Map showing the towns in which Mr. Lloyd volume control and a George's speech was simultaneously heard pitch -raising device, and over L000 miles of special P.O. trunk -necessary because the lines.Great care was taken to preventcapacity of a long tele- interference or "cross -talk, and repeatersphone line acts like a (special valve amplifiers) were inserted atcondenseracrossthe land -line points en route. circuit and cuts off the The repeatersusedon long-distancehigher frequencies. By land -linearetheoutcome ofworkartificially distorting the done on valves and low -frequency amplifiersinput - over -emphasis- The distributing panel for twelve of the fourteen circuits -another example of the manner in whiching the high notes and the requirements of broadcasting haveharmonics-it is possible to counterbalancephragm, this equipment being standard stimulated improvements in the techniquethe effect and obtaina natural output,for public speech and music reproduction. of allied sciences. The entire amplifier panel is duplicated, In the old days, when there were noand in the event of a fault in either the repeaters, it would have been practicallychange over may be accomplished in a No fewer than 191 trawlers and drifters impossible to relay a speech over morefraction of a second by means of twocarry wireless apparatus. This evidence of than a moderate distance and amplify it forswitches. the value of wireless in small ships was a large audience with any degree of success. Following this comes the "distributor "furnished by Mr. Kellaway at the recent In the first place, a long line is bound topanel, 'consisting of fourteen valves inmeeting of the Marconi Company. This pick up interference from electrical sourcesparallel-one feeding each line and one thefigure is about one -fifth of all the trawlers and tends therefore to be "noisy," clicksamplifier in the Albert Hall itself.Thewhich might be fitted. APRIL 6, 1929 517 rnaterx Wirc.14s) IMPROVING YouRPORTABLE

Here is a Series of Hints Showing How the Utility of a Portable May Be Greatly Increased IT is probably safe to state that portablefor both economical and efficient workingpanel and the jack -switch placed in the and transportable receiving sets at theof the set to use an external H.T. battery"in" position.To reconnect the internal present time are used as much in the homeof the power or super -power type particu-accumulator the foregoing procedureis as out of doors, in fact, this type is takinglarly where, as is the case with manyreversed. the place of the more conventional patternpresent-day portable receivers, a super-Additional Loud -speaker to a greater and greater extent. power valve isfitted in ,the last stage. There are, however, one or two difficultiesNaturally there arises the difficulty of One of the most useful improvements that arise in the use of a portable in theconnecting up the external H.T. batterywhich can be made to an existing portable home due to certain limitations in theand disconnectingthe internal batteryor transportable receiver is a provision for design.For instance, the H.T. batterywithout interfering with the wiring of thethe quick connection of external head- incorporated in most portable sets is-dueset with its attendant risks every time onephones, loud -speaker, picture receiver or to the necessity of keeping down the weightwishes to transport the receiver. amplifier.The necessary requirements in and bulk to a minimum-of small capacity this case are very simple and merely and is therefore an uneconomical proposi- TO ANODE OF LAST necessitate the fitting of a jack and two VALVEIN SET tion when used on other than out-of-door TO valve sockets to the panel and slight occasions. LOUD-SPEAALR PLUG alterations to three wires as shown by NEC. TERMINAL IN SET Fig. 3. When this is carried out the act of Use a Super -capacity Battery plugging in any external piece of apparatus, For continuous indoor working with a JACK automatically cuts out the existing loud- TO LIMO -SPEAKER - portable receiver it is an excellent plan IS rLT+ I ri SET TO EXTERNAL PHONES,speaker which is fitted to the receiver. LOUD -SPEAKER,, PICTURE TOH.T.1-1 SOCKET ON PANEL FOR RECENER ORAMPLIFIER Provision for Meters TAPPING N.T.1-1 TAPPING FROM EXTERNAL H.T. SUPPLY Fig. 3.Method of wiring jack for use of ON INTERNAL external loud -speaker or picture receiver Among the minor improvements which N.T. HATT Efiy may be made is the fitting of points on the JACK :WITCH There is, however, as shown by Fig. (Continued at foot of next page) 11:T.+ I a simple method of permanently altering VALVE. LEC SOCKETS III the wiring by the addition of a small jack - PANEL OF SET WIRIK TO HT -- of switch and two or three valve leg sockets SET1 which enables either the internal H.T. 7E51 H:T.+2 battery or any external H.T. supply such To HT.- - - as a power type battery, H.T. accumulator or mains unit to be connected into the LT.VOLTS TEST TO H.T.+2 SOCKET ON PANEL JOINED TO LT.+0R- TAPPING ON circuit by pushing in the jack -switch and WRiCHEVER IS -*4 .\-:TOSOCKET ,LOWED TO INTERNAL TO MT -WIRING IN SET NOT CONNECTED GS+ BATTERY plugging the leads from the external H.T. TO NT. - SOCKET on PANEL FOR GRID BIAS H.T. +2 TAPPING FROM source into the sockets on the panel. The TO C.ES- - - BATTERY TEST EXTERNAL H.T. SUPPLY photograph in the heading, for instance, shows a mains unit used in this manner. Fig. 1.External H.T. supply may be used Fig. 4.Arrangement of testing points for in this manner To enable the receiver to be used for voltmeter SOCKETS ON outdoor work the external supply leads are 701-17:+ PANEL FOR "f- simply removed from the panel of the set CONNECTion OF 08/S/NIIL INSET L,W EXTERNAL L.T. JACK and the jack -switch is pulled out. IV/R/Ya ACCUMULATOR ON PANEL Ri*A' An Alternative Accumulator PLUGS FOR socierTray In cases where the frequent recharging of SHOAT/NS SDCATT.S! PNNEL FOR TO LT - P/HENNOTI/S//Yo CONNECT/ON WIRING the small internal accumulator is a' diffi- IN SET nf/a/ANNETE:9 I OF culty, a jack -switch and socket may be 19/L149/14117 -AP fitted on the panel, in.a similar way to that TO L.T.+ TERMINAL CONNECT TO WIRE OF INTERNAL for connecting the external H.T. supply; THAT WAS, ORIGINALLY TOL.S+ ACCUMULATOR. the wiring alterations in this case should be JOINED TO L.T.+ TERMIWil INSET TERMINAL OF INTERNAL made as shown in Fig. 2. To connect up an ACCUMULATOR. Fig. 5.This diagram shows how amilliam- Fig. 2.This diagram shows how external external accumulator the leads from this meter may be inserted in the anode circuit of L.T. may be obtained should be plugged into the socket on the the last valve master WireLzSi 518 PRIL 6, 1929 ELECTRICAL RECORDING at HOME ANEW system of gramophone record -diamqnd is pressed or hammered in& particularly devised for home use,into the substance of the record has been developed in the laboratories ofdisc and forms the grooves, the Stuttgart Broadcasting Co. The paten-without previous preparation of tee is Oberregierungsrat Rammelsberg, ofthe disc. The disc material is Wernigerode, in Central Germany, and hisnon - inflammable ,celluloid, invention has been developed by Mr.about L in. thick, both' sides of Formis, who probably will introduce it atwhich can be used. Immediate- the Berlin Wireless Exhibition this comingly after recording, any ordinary September. gramophone using an electrical The new process opens up many hithertopick-up, an amplifier and loud- unthought of possibilities and briefly is asspeaker can play whatever has follows : A microphone, in the case of musicjust been impressedOn the Making gramophone records at homeby the 'a high-class Reisz microphone, will havecelluloid. The record can be Rammelsberg System to be used, but for ordinary speech it is -played sixty orseventytimesbeforeand, as in recording, to use arubber disc quite sufficient if one earpiece of a head-wearing out.The record disc, while theunder the record. phone be used as a microphone. Therecording is being done, is carried by a currents coming from this microphone aregramophone table in the usual way, exceptLong Records passed through an eight -stage amplifier.that a special rubber -pad is interposed For records that will last longer than From here the impulses drive the usualbetween table and disc. ten minutes or a quarter of an hour, Mr. commercial gramophone pick-up. The For making a number of records it isFormis proposes using an endless non- action of the pick-up is thus reversed or,necessary to use copper or zinc instead ofinflammable celluloid band which will be in other words, the pick-up becomes acelluloid discs and to use the metal recordpassed under the recording diamond by motor. A small diamond takes the place of as a master.For playing the celluloidmeans of two rotating cylinders some dis- the pick-up needle and, in operation, thisrecord it is necessary to use a fibre needletance apart. G. DONALD.

"IMPROVING YOUR PORTABLE"bility of dangerous shocks being received A small frame aerial containing about (Continued from page terminals. 15 turns wire (the best number of turns should be found by panel to which a voltmeter may be appliedOutdoor Aerials fordeterminingH.T.,L.T.,and grid experiment) wound in a square with 1 -2 -in. bias voltage, or for temporarily, connecting Where no provision is made onthe setsides is connected up to the outside aerial milliammeter into the anode circuit of OUTPUT and earth and shunted by a .0005 -micro - the last valve in order to determine whether TRANSFORMER farad variable condenser. This frame aerial that valve is working at its best. and condenser is then brought to within These testing "points" may take the TO Dlf,TANT, a fciot or so of the frame aerial in the port- form of valve sockets fitted near one side LOUD-5PE4KE.R able set and the latter tuned in the ordinary of the panel, as shown in Figs. 4 and 5 manner ;the external frame condenSer should also be adjusted until best results respectively. As the use of a milliammeter SOCKETS Oft PANEL necessitates the actual breaking of the OF SET are obtained.Stations which previously circuit a "bridge" or re -connecting attach- Fig. 6.Output transformer connections for came in weakly will now be heard at con- ment formed by fixing two small wander distant loud -speaker siderably increased volume, without appre- plugs to each end of a short length of flex ciable reduction of selectivity. must be utilised to re -make the circuit after OUTDOOR Obtaining Directional Effects using the milliammeter. AERIAL Finally mention should be made of that Two Loud -speakers at Once VARIABLE little -used component the turn -table. Good CONDENSER Incidentally this "break" in the anode turn -tables can now be obtained quite circuit may be employed for the connection cheaply and are easily fitted to an existing of an external loud -speaker in series with, portable or transportable receiver. The and, of course, additional to, the internal advantages of a turn -table are twofold as instrument.This means, of course, that its use enables the set to be placed on a both internal and external loud -speakers polished table without risk of damage to will be operating at the same time and if the surface and at the same time the whole desiredtheextra instrument may be receiver can easily be turned round to any situated in another room. In cases where desired position. the leads to the second loud -speaker are of EARTH A dispatch from Prague states that at any considerable length, however, it will How to add external aerial and earth be advisable to employ an output trans- Fig. 7. Poderbrady,wherethemainwireless former for feeding this instrument, so thatfor connecting up an outdoor aerial andreceivingstationinCzecho-Slovakia is there will be no possibility of H.T. leakage,earth the method of using the outdoorlocated, the Czecho-Slovak Post Office is or unwanted capacity to earth or-in theaerial and earth without interfering withinstalling a short-wave transmitting station event of a mains H.T. supply unit beingthe wiring of the portable set shown byfor telegraphic communication with used with the set-to prevent the possi-Fig. 7 may be used. America. APRIL 6, 1929 519 (1,LPtir wire

("114 Kiasile.e&s.e/e An Unexpected- Emergency London. At any rate, I nearly always findgraphers who took them in every possible T WONDER how many readers have hadin talking to people from distant parts ofattitude with absurd backgrounds, and, of ' 1 the delight of arranging to give a displaythe country that they consider the Londoncourse, always with the camel -like affair of how to receive a musical programme, andprogrammes far better than their own, andon which was supported a very ludicrous then at the last moment to find that thefrequently say what a shame it is that theybusiness which held the microphone. set, which worked so well the previouscannot always have them. So far as I can After this well -thought-out campaign, night, has developed a subtle fault?Isee, two completely different programmeswhich some wireless papers are suggesting myself have had this occur on two occa-sentoutsimultaneously fromvariousshould be repeated, it was discovered that sions. The first instance was when I hadpoints would be absolutely sufficient forMiss Dulcet's voice was always the same, promisedaspecialconcertto somethe whole country's requirements. If onlywhether she was Mrs. Wiggins or Joan of musical high -brows. As the time for thetwo programmes had to be provided eachArc, and also that her very comfortable concert to begin drew near, the set de-day good fees could be paid the artistesfigure was firmly embeded. in the minds veloped crackles and in a very short spaceand the very best talent in all departmentsof listeners.It became irritating to hear of time the signals could only just be heardcould be secured. the same voice one day as the fat girl of with the ear close to the loud -speaker. Life in the Old Joke Yet Peckham and next evening as Melisande. Hasty tests with instruments showed that You remember the story of the joke? A Stage Parallel one of the intervalve resistance couplingsI have referred to it on several occasions To return to the anonymity edict. There had ceased its useful functions owing to ain these columns. In case you have joinedis much to be said for it.If an artiste has burn out or fault in the wire. the great band of AMATEUR WIRELESSa flexible voice-and how few have-it is A Bright Idea readers since it was last mentioned, here ismuch better to leave the listener his or It was then a few minutes to the timethe history.In one of the very earliesther own mind picture of the character than when the concert was due to begin. Threenumbers of AMATEUR WIRELESS I per-to picture some very worthy, but very critical musicians were wagging their headspetrated a joke about Adam having pos-ordinary, person speaking the words of the in a knowing fashion and the nearest radiosessed a loud -speaker made from his spareplay. There are some cases where it would dealer's shop, a mile away, was closed forparts.This spread all over the world indo no harm, but it must be remembered the evening.It was an emergency whichthe most astonishing way, appearing withthat on the stage the dress and make-up caught me napping, for it is rarely that aor without an illustration in papers ofdivest the artiste of much of his very own wireanoderesistancegivesupthepractically every European country, asappearance.Seldom in a costume play ghost after a couple of month's service.well as those of distant parts of the world.does the artiste put up outside the theatre Resistance bobbins from the junk box onlyA reader sent me a Japanese paper con-a picture of himselfas,for example, totalled about 4,000 ohms, and everythingtaining it and others reported its outbreakShylock unless he is dressed for the part. seemed lost when a bright idea struck me.in the most astonishing places. About threeThe same should apply to radio drama; In less than five minutes a high -resistanceyears ago the joke won a prize in anbut, of course, it can't be done. moving -coil milliammeter was in the anodeAmerican paper which had previously There is, of course, another point which circuit of that valve, and 200,000 ohms ofannounced that it was not the slightestmight be stated.So many of our well- resistance did service as an anode couplinguse sending in anything that was notknown actresses and actors mumble their that night. It was an interesting, experience,absolutely original !It hadn't cropped up,words that really anonymity is in their and the moral is that a high -resistancethough, for quite a long time; in fact,favour. They must realise this. However, instrument has more uses than one. I had begun to think that the dear oldI don't suppose the projected boycott by thing was at last dead. Not a bit of it,many of these famous artistes will ma- A Surprise though; I happened to switch on 5GB orterially affect radio drama. Anonymity is A somewhat astounding announcement2LO-I forget which it was now-thevery interesting. is that in future provincial main stations other night when an entertainer was at Sunday are to rely upon local artistes to supply thework, and sure enough out it came I majority of their star turns. It is said that Dull and dreary Sunday broadcasting the local spirit must be encouraged, and Why Have Anonymity? continues. Having educated a large section this is held to be the way to do it. Con- The B.B.C. new dramatic producer hasof the public to expect entertainment on sidering that as soon as an artiste, whethernot been long in the saddle, yet his per-Sundays, the B.B.C. now proceeds to drive he be instrumentalist, vocalist, ventrilo-sonality is beginning to be felt. His latestits converts out of their homes to places of quist, entertainer or whatnot, makes a beedecision, that'of not publishing the namesrefreshment and those evil cinematograph line for London and higher pay as soon asof artistes speaking the lines of plays, haspalaces ITrue, Sandler sometimes comes ever he has begun to attract any attentioncaused severe heart burnings among thoseto the rescue with a bright spot of music in his own home town, I am rather afraidwho take part in radio productions. Nowand there are occasional symphony con- that provincial stations are going to comewhat is the position? certs;but,inthe main,the Sunday off rather worse than 2L0 over the deal. Some years back the B.B.C. laboriouslyprogrammes save such a lot of filament I am hoping that somebody has got holdbuilt up a repertoire company of playerscurrent ! Religious broadcasts can be of the wrong end of the stick in makingchosen for their voices and ability to speakinteresting, we all know, but this type of such an announcement, for I can reallylines clearly and well and with a certainbroadcast rapidly reaches the saturation " hardly see how such a silly course could beamount of meaning. Not content with thatpoint unless there is some powerful micro- taken. Actually it is quite on the cardsbright idea, they proceeded to fix up aphone personality to hold the attention. that though the B.B.C. is striving to givewhole string of plays for months ahead toAs it is, the Sunday programmes seem to thepublicalternative programmes bybe played by these chosen people, who, nohave degenerated intoa repetitionof means of the regional scheme and in otherdoubt, had a comfortable little contract.hymns just as irritating as the " plugging " ways, the provincial public does not wantSo far, so good, but their next step wasof popular songs. On Sunday, Savoy Hill alternative programmes: what it wants ispossibly the worst.They hired photo-takes its finger off the pulse of the nation emateur Wirelesi 5'2.0 APRIL 6, 1929

C 0 4 0 On Your Wavelength ! (continued) * order to gratify a few "extremists." Wholand -line and were. received in the Morningpentode. Too few turns mean poor signal is responsible ? Post office within twenty minutes of theirstrength;too many spell poor quality. Pictures and Squeaks having been taken. Anyone who saw the American Sets To -day reproductions in the Saturday issue of the Sunday is usually the field -day for thepaper must have been astonished by their Looking through advertisements in the experimenter. There must be hundreds of catalogues of 'American wireless manufac- excellent quality. This, of course, opens upturers, one cannot fail to be struck by the thousands of wireless gentry who looka wonderfulfield,fortheFultograph upon Sunday afternoon as being sacred totransmitter is quite portable, so that it cansize of the receiving sets in use in the the soldering iron. Aerials are pulled downbe taken to the scene of almost any import-States to -day. It may come as a surprise and put up again, new sets are tried out,ant event. All that is needed then is a smallto some readers to know that the average new loud -speakers put on, and modernemergency dark room in which to developAmerican set nowadays contains no less components put in.Therefore, Sundaythe films.The negatives are then putthan six _valves, whilst many have seven afternoon, after the concert transmissionstraight on to the photo -electric transmitteror eight. They are not super -heterodyned, would be an ideal time for prolongedand sent over the land -line to their destina-for that type of set is not greatly used now; Fultograph transmissions and "squeak"tion. No less than eight pictures of themost of them, infact,are absolutely tests. In regard to "squeak" or low -Boat Race were sent out within a little overstraight receivers, containing two or three frequency note tests, I find that individualan hour of the finish and those who receivedH.F. stages, a rectifier, and two or three B.B.C. engineers have peculiar ideas as tothem had a splendid piece of wirelessnote -magnifiers. The American wants his their utility.Their attitude is that theyentertainment.I think that a prophecy Iset to be able to bring in a big number of consider very few people could make use ofmade some months .ago is likely to be ful-stations at full loud -speaker strength, and such tests and that the remainder would befilled this year. I said then that we shouldit must be also sufficiently selective to cut completely mystified and probably ledhave a picture of the finish of the Derbyout a local station at very shortrange. astray into the ranks of oscillators.The The high -frequency side is not, as a rule, success of such tests would, of course,broadcast the same evening. designed for big magnification per stage; depend on the manner in which they were Heating by Wireless what the makers aim at is comparatively put over. The B.B.C. can rest assured One of the lay papers rather went in offsmall magnification from each valve. that all AMATEUR WIRELESS readers willthe deep end the other day by giving its What of Television? know how to make use of "squeak" tests. readers to understand that they might I am writing my notes earlier this week Our Good Sets shortly warm their houses by means ofunder orders from the Editor, who informs Truth totell,our receiving sets arewireless.The actual facts are that inme that, owing to Easter, this issue goes to getting so good that we want something alaboratory experiments, heat transmissionspress two days earlier than usual, and I little more scientific than broadcast musichave been made over very short distances,should not be surprised if, before my readers for making comparisons between trans-and that it has been proved quite possiblesee these words, _the Postmaster -General formers, chokes, and loud -speakers. Theto carry out this kind of thing on a veryhas not publicly..annnunced the results of broadcast of individual pure notes onsmall scale. There is considerable differencethe B.B.C.'s recent tests of Baird television. various parts of the musical scale is the onlythough, between producing in a coil of wireWhile I have been unable to obtain official method which will enable us to make furthera degree of heat that can be measured onlyinformation,I learn from a number of progress towards perfection. Therefore, letby the most delicate instruments, andspecial sources that the tests were successful us have a weekly half-hour of low -frequencycreating in a living -room the lkind of fugfrom the Baird point of view and very calibration tests and let that hall -hour be atthat you and I like on a cold winter's night.significant to the P.M.G. and to the broad- the time most convenient to us-Sunday. The transmission of heat by wireless is onecasting authorities. Indeed, I rather expect The Grand National of the things that will probably come in thethe P.M.G. to announce his personal faith far away future, but it is most unlikelyin the system and to explain his proposals Temporary sets were erected in thou-that something of the sort will happen next sands of offices for the reception of the for giving it further broadcasting facilities week, or anything of that kind. So there isof an experimental nature. I believe most running commentary on the Grand National.no need for you to rush off and sell your I penetrated into one West End office in of the witnesses were impressed by the fire -grates and gas -stoves, just at once. extraordinary improvements made by Mr. time to hear this most successful broadcast Baird in recent months and by the amount on a real "Heath Robinson " crystal set. A A Pentode Point wire had been slung out of a window for an of detail and degree of illumination dis- aerial and the set consisted of a few turns I am very fond of the pentode valveplayed by the transmitted image. Doubt- of bell -wire on a roll of cardboard, and amyself, though I come across from time toless there is a big difficulty to be overcome- crystal detector. Someone had forgottentime numbers of people who have triednot so much in the system itself, but in the to bring a "pukka" set, and as everybodythem and given them up in disappoint-great width of the frequency band which ment, since they have been unable towould be occupied by the transmission and else had brought their headphones some-obtain from them the kind of quality thatthe consequent risk of general interruption thing had to be done about it.Bell -wire was produced from an old store cupboardthey want. The whole trouble with theof speech transmission-and this difficulty, and some bright youth found a small piecepentode is to obtain exactly the rightI expect, has delayed the P.M.G.'san- impedance in the output circuit. Get thisnouncement.Mr. Baird will have our of crystal in his pocket ! A drawing pin andand quality is beautiful; fail to get it andhearty congratulations and those of all a couple of paper clips completed the set, Output which gave satisfactory signals on six pairsit may be very much lacking. reasonable people should it be found that transformersare now availablewhichthe test's were of such a nature as to cause of headphones ! exactly suit the pentode valve. One thatthe B.B.C. to change its attitude, and I -and Pictures I am very pleased with has a tappedshall be the first to congratulate the B.B.C. A triumph was scored by thestill -secondary, so that it may be adapted tothemselves on what I hope will be an picture people by the transmission ofsuit the particular loud -speaker which isannouncement of their goodwill to the photographs illustrating both the Boatto be used with the valve.With theBaird system.And, between ourselves, Race and Grand National. Pictures of theMoving -coil loud -speakeritisessentialAMATEUR WIRELESS ought to come in for latter were sent from the course over theto windthecoilexactly tofitthea good word, too. THERMION. APRIL 6, 1929 521

SHOCK -PROOF! Here you see the double length of When you buy your Screened Grid Valve insist Cossor filament on the one which will give you the longest famed forits service-choose Cossor.These illustrations colossal emission. Note the show why the Cossor Screened Grid Valve is seonite bridge the most robust-the most dependable-and holding it rigidly the most uniform Screened Grid Valve made in position. in Great Britain. Remember that this wonderful new system of Interlocked construction is to be found only in the Cossor Screened Grid Valve. No other make of Valve has Around the two these outstanding features of design. stout grid supportsis wound thefirstgrid, electrically welded at twenty-five NOISE -PROOF! points. Noises are generally due to loose elements in a valve. In the Cossor Screened Grid Valve the Note theenor- elements are interlocked. Even under the mous siren th hardest blow individual movement is impos- and rigidity of sible. The Cossor Screened Grid Valve is built the screen.See like a bridge. Every joint is scientifically weld. how itisbuilt on fourstout ed to ensure long life and complete rigidity. supports and capped bya metal bridge - piece anchored to seonite insu- BREAK -PROOF! lator. Never before has such a wonderful system of construction been used in any Screened Grid Valve.Even the hardest blow cannot disturb Finally, obserte the construction the perfect alignment of the elements which oftheanode. are rigidly held at top and bottom. As a Actually two rec- result every Cossor Screened Grid Valve tangular nickel retains its characteristics throughout its ab- plates are used normally long life.For any Screened Grid and for greater Receiver choose Cossor. Accept no substitute diagonallyrigidity each is -for there is no adequate substitute for the ribbed. Cossor system of Interlocked- construction. Technical Data. Cossor 220 S G (2 volts, .2 amps.) and 415 S.C. (4 volts, .15 amps.) Max Anode Volts 150, Impedance 200,000, Amplification Factor 200, Grid Bias 1.5 volts at max. anode Volts. Price teach)2216 Demand the

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Pease Mention "A.W." When Corresponding with Advertisers &attarWelts,' 522 APRIL 6, 1929

You may save pounds by reading the April Number of the " Wireless Magazine," now on sale. The following contents list indicates the wealth of really useful and interesting features (illustrated with over 130 photos and diagrams) offered to readers :

Valves to Use in Your Set. ' Continental Appreciation. Start Radio with the Clipper What You Want to Know About Two for £51 ; Wired Wireless. A Broadcast Revolution. Short-wave Relays from Under My Aerial. Colombo. If Your Set Starts Motor -boat- Wiring Your New House for ing.By W. James. Radio. More About the Lodestone Loud- Seeing When Distortion Occurs. speaker. By W. James. Hints for Success on the Short Waves. GRAMO-RADIO SECTION A Wireless Fictionary. Can You Cut Out Needle Scratch ? The Letters of Priscilla Playne- Where to Place a Volume Control. Smythe. Is Gramo-Radio at a Standstill ? Radio Quarrels in the United If I Were Bass Deaf. By H. T. States. Barnett. The Dynamic Three. A Set A Good Pich-up. By W. James. for A.C. Mains. Designing Scratch Filters. By It's Better with a Baffle ! J. H. Reyner, B.Sc., When Air -liners Talk by Radio I A.M.I.E.E. Half Hours with the Professor.- The University of the Ether. Amp SolvestheTuning By B.B.C. Officials. Problem. Our Cartoonists f` Review " Japan's Pirate Listeners. Some Broadcasters. Broadcast Music of the Month. "Show Me the Way to Co By Studius. Home."Verse. In Tune with the Trade ! A Safe H.T. Unit for D.C.Leaves from a Listener's Log. Mains. By W. James. By Jay Coote. Is the Aerial Doomed? Loud -speakersfromaNew Studio Audiences. By Tommy Angle. By Kenneth Ullyett. Handley. The Drum -Major.A Four- A Visit to Savoy Hill. valver for Quality. My Radio Week -end. By A Cone Loud -speaker. J. Godchaux -Abrahams. 4eaders' Questions Answered. Wavelengths of the European Using the Melody Maker on- the Stations. Short Waves. Wireless Fallacies, New System of Focused Radio. What Readers Think of Our Sets. Reference Sheets. Compiled by The Dominions Four. Can, be J. H. Reyner, B.Sc., Converted into -a Short-wave A.M.I.E.E. Super -het. A Free Broadcast Map. Full-size Blueprints of all sets described in this issue -are available at half-price until April 30th APRIL 6, 1929 523 emaw Wirere.5 Cutting Out// EEDLE SCRATCH /One of the advantages of Gramo-Radio Reproduction is that surface noises associated with all Gramophones can be almost eliminated.In thisarticle our Technical Editor describes various filter systems which are used to this end. OPINION is divided as to the desira-which have given a distinct measure ofquencies above 4,000 to 5,,000 cycles pet bility of fitting special filters to cutsuccess. second were cut off, quite an appreciable out the noise of the scratch on records One of the complications of the problemportion of the scratch was removed.The which are reproduced through the mediumis that the average loud -speaker is by noscratch,infact,ceased to be evident of the wireless set. One of the advantages during the playing of the record, and only of electrical reproduction is that one can VVVVVVVVVVVV bepame apparent when the music ceased, juggle with the frequency response from R which, after all, is sufficient for our purpose. the record as one wishes. For example, it These tests, incidentally, were taken on a AIMPLIPER is well known that the bass on a gramo- moving -coilspeakerwhichhadbeen phone record cannot correctly be repro- I definitely proved to go up to frequencies duced because the movement of the needle 4 above 8,000.Moreover, aural tests con- Fig. 2.Simple R.C. Filter ducted from opinions given by independent listeners indicated that there was little means a good reproducer in the upper frequencies. The taking of response curves on loud -speakers is quite a fascinating subject.. Thedifficulties in the way of producing a true response curve to which one could swear are so large as to render the problem almost impossible, but itis a /000 MVO 1000 NW fairly easy matter to obtain a comparison Fig. LEffect of Shunt Condenser of the relative radiation at different fre- 500 /000 2000 1000 woo to reproduce frequencies below 200 cyclesquencies, and the number of loud -speakers becomes so large as to be -impracticablewhich commence to cut off in the regioh Fig. 3.Cut off with R.C. Filter under ordinary conditions. We can, how-of 2,000 to 3,000 cycles per second is quite ever, if we wish, put in an amplifier whichsurprising.There are few loud -speakersloss of brilliance if frequencies above 5,000 has a rising characteristic at the bass endindeed of the average cone type which willwere omitted.Indeed, it takes a very to compensate for this defect. Whetherreproduce faithfully about 4,000 cycles percritical ear to distinguish the difference. the results would be altogether desirable issecond, and in the average case the response Consequently, if we can retain the fre- entirely a different story, but the instanceisfalling gradually the whole time forquencies up to this limit and cut them ofi serves to illustrate the flexibility of elec- above, we shall obtain a certain measure trical reproduction. t0002csv of elimination of the scratch, resulting it The problem of scratch is more con- a greater clarity of tone. With the ordinary loud -speaker, as has been pointed out, we cerned with the upper end of the frequencyP/C/(-a' spectrum, for it is here that the noises con- C can reduce this limit somewhat and com- stituting the scratch predominate.It is mence our cut-off in the neighbourhood of not possible to say that scratch only 4,000 cycles per second, since the loud- occurs at or above any definite frequency, Fig. 4.A better form of Filter speaker itselfisnot likely to giveus for in point of fact it is due to a con- very much above this point. This was the glomeration of noises occurring throughoutr,000 1,50o cycles before this point isprinciple which was adopted in making the whole of the audible range, but there isreached. the tests, and it has met with quite a good little doubt that scratch does predominate Now tests actually made with a verymeasure of success. We now have to con- in the upper registers. sharp cut-off filter indicated that if fre-sider the methods by which we can achieve The question is whether we, can mini- this cutting -off of the upper frequencies. mise scratch by cutting off a, certain pro- NUA/PDUETD The simplest method is to connect a portion of the upper frequencies. At first RESONANCE condenser across the pick-up or some suit- sig1kAhislseems heresy, and indeed nit4anv able portion of the amplifying circuit. individuals claim that the whole idea of a This, however, is not a satisfactory method, scratch filter is impracticable and unwork- because it causes a gradual reduction of able. I myself do 'not hold this view, for, the output, so that not only shall we as in most other aspects of wireless, a great reduce the frequencies above the cut-off deal depends upon the personal factor, and point, but also considerably affect the fre- also upon the amount of compromise which quencies below.It is indeed difficult to is deemed advisable. At any rate, I havef00 /000 2000 icoo woo consider this as a cut-off in the ordinary conducted a number of tests at Elstree Fig. 5.Cut off with L.C. Filter (Continued on page 538) APRIL 6, 1929

W JAMES Weekly Tips, Constructional For the end Wireless Theoretical- Amateur fl Neutralising Snag G.B. from A.C. H.F. stage may be affected by small matters Ihad a rather interesting experience the The grid bias for power valves suppliedthat are apt, at least for a time, to pass otherdayinconnectionwithawith high-tension of zoo volts or more mayunnoticed. neutralised receiver which was suppliedamount to as much as 40 or 5o volts, and I have in mind the case of a quite ordinary with high tension from an A.C. mains unit.dry batteries are often employed. But whenreceiver having three valves.The first It was pointed out to me that with thea mains high-tension unit is used it is notwas of the shielded type, and it was followed power plug one way round in the socket thevery difficult to arrange a rectifier andby a detector and power valve in the usual et could not be stabilised, but yet normalsmoothing circuit for the grid bias. straightforward manner.But the com- working was obtained when the plug was plaint was made that the expected results reversed !I tried neutralising the receiver were not being obtained because squeals and myself.I had not the time to spend on howls were produced- sometimes even making numerous tests, but the trouble was before the reaction was adjusted to the completely cured by connecting a high fre- point where the anode circuit of the high - quency choke in one of the wires to the frequency stage would oscillate. primary of the transformer.This choke Troisicomer ' Now the loud -speaker usually stood on was afterwards fitted in the mains unit. Mho* the cover of the receiver, and if high -fre- It should be noted that an ordinary Fig. 1.An A.C. Grid Bias Unit quency currents were passing through the choking coil may become too hot and loud -speaker Ord there would be trouble. eventually burn out if used in this manner. When the rectifier is of the WestinghouseThere would be coupling between the input typeonlyoneadditionaltransformerand output circuits, in this instance the Low Notes and Motor -boats winding is required and, of course, a smooth-aerial connecting wire and the loud -speaker In order that the low notes may being circuit.A suitable arrangement iscord. magnified by a resistance -capacity -coupledsketched in Fig. I, which shows a half -wave Tests were therefore made, and showed amplifier, or one of the popular types havingrectifier, a resistance -capacity filter, and athat the strength of the. howl could be varied a resistance stage and a transformer stage,tapped resistance. The amount of the A.C.by altering the position of the loud -speaker it is necessary that the coupling condenservoltage to be delivered by the transform'ercord, which seemed to prove that high - be ofsuitablecapacity in comparisonis dependent upon the type of rectifierfrequency currents were flowing in the with the resistance of the grid leak. and the grid bias required, but will usuallyspeaker circuit. not be more than 40 or 5o volts.Condenser The condenser is marked c in the diagramc may have a capacity of 2-microfarads, Fig. 2 and the grid -leak R. Usual values are Buzzing Chokes! .005-microfarad and 2 megohms, but when Iron cored components such as low -fre- the very best quality of reproduction is quency inter -valve transformers or choking desired the coupling condenser c may be of L.S. coils are liable to buzz unless the iron or steel microfarad and the grid leak R have a laminations fit accurately together and are resistance of f megohm. well bolted in position. It is not unusual to There is a disadvantage, however, in come across an output choke, for example, employing components which pass the very which is so constructed that it is actually low notes; and this is that motor -boating is possible to hear the broadcast by placing likely to be troublesome in the absence of the ear within a foot or so of it. Obviously special filters.It is therefore just as well so such a component must introduce distor- to design the low -frequency amplifier that tion, and it is, therefore, desirable to guard the very low notes which the loud -speaker 1Z+ against looseness or poorly fitting parts by isnot capable of reproducing correctly tighteningallfixingboltsand, when shall not be amplified. KT - necessary,by jamming togetherloose Ordinary horn type loud -speakers and Fig. 2.A typical R.C. arrangement laminations with pieces of cardboard or certain cone types, too, do not reproduce the wood. very low notes, and it is therefore hardlyresistance R.I, a value of f o,000 ohms and It is sometimes rather difficult to locate worth while employing an amplifier whichR.2 of 3o,000 ohms. A choking coil may bethe particular lamination which is vibrating. will magnify them. The low notes may beemployed instead of resistance R.I, but aA cure may, however, sometimes be effected resistance is, of course, much cheaper. reduced by cutting down the capacity of by varnishing the core sheets in order that the coupling condenser or the grid leak's they shall tend to -stick together, but on resistance, and it is sometimes possible toA Mysterious Howl occasion it is found that an odd piece has employ a value as low as .00r microfarad It is surprising how the results to bebeen built into the core and is the cause of with a .I-megohm grid leak obtained from receiver fitted with anthe trouble. Thi.: piece must be removed. APRIL 6, 1929 Cmateur Wtrelersi

Points Rho ores

4R THERE isno doubt but that the matched impedance type it is only neces- exponential horn is an excellent form sary to form the double flare merging at of reproductive amplifier, but many con- By H. BRAMFORD the input, as shown, and this may have some structors are disappointed in the results advantage over the single outlet, but both obtained owing to the fact that the generalfrequencies, and the size of the mouthsections must be perfectly alike in shape design has not been well considered. Theof the flare will govern the total range ofand construction. The square section horn, secret of perfection lies in the correct shapethose frequencies. The best way to plot outof course, is easier to make in wood than of the horn. a shape for any given purpose is first toone of round section. The best horn for tonal reproduction isdecide the space available for the mouth, Readers who do not wish to go to the the wood horn, but good hard ply -woodwhich should be as large as possible, andtrouble of constructing a horn of the type should be used.Soft wood will absorbthen determine the overall length. Wheredescribed will be' interested to know that sound instead of reflecting it. Then, again,the horn is to be folded in any manner,an excellent range of non-metallic ex- the seams must be made a perfect fit anddecide upon the formation of the fold,ponential horns are marketed by Messrs. which is of no great importance providingScientific Supply Stores. These horns are the curves are graceful, and from thismade in both straight and folded patterns, calculate what the overall length will be,the latter type being particularly useful allowing for bends. when space is a primary consideration. By reason of the good general design, Plotting the Horn approximately even response to all fre- Now plot on paper, as shown in the sketch,quencies above 13o cycles is obtained with the straight horn, and divide it into avery little falling off down to 6o cycles. number of equal parts, each of which is On fitting a well -designed exponential termed a pitch. Now the width or diameterhorn to a loud -speaker base in place of the at each pitch should be directly proportionalordinary short metal horn, one is imme- to the distance, as will be noticed, anddiately impressed by thefullness and whatever size horn is made, these propor-"body" of the reproduced music, while tions will ensure that the horn will possess fairly good acoustical 4 SON properties. One cannot give any particular hard and fast rule, as so many will well pinned andwish to house the 24'1 glued withnohorn in some existing cracks or crevices.cabinet. The idea is pitch When the hornthat at each alternate ishousedinapitch the diameter, -4- 24"- cabinet it shouldor width, should be bepadded withdoubled, getting as 1111 felt where contactmuch length to the /2. III is made betweenhorn as possible, and the external sidesstarting,ofcourse, A logarithmicex- and the points offrom a small neck. ponential horn made contact with theFor a2 -ft. square by the Scientific Supply Stores.The cabinet in order tomouththelength Dimensions of straight and folded types of exponential horns actual model is isolate the hornshould not be less 5 ft. 6 in. long entirely as a sound -than five feet, and this may be taken asthere is a total lack of the "blare" and reproducinga fair basis upon which to work. " tinniness" usually associated with horn

chamber. Having plotted the straight horn in thisloud -speakers. Now as regardsmanner to the best advantage possible for The fitting of the unit, which may be thedesignforgiven conditions, the rest of the job merelyeither a horn loud -speaker base or of the obtaining the bestamounts to plotting a corresponding shapegramophone attachment type, should be acoustical pro-to any curvature, and this should be quitecarefully carried out, as a really airtight perties. The shapeeasy to do, as the main essential is to watchjoint is essential for good results. Suitable should be such asthat the ratio of increase is the same atunits for use with these exponential horns to give an equalequal pitch distances along the entireare the Brown, Amplion, Nissen,and ratioofcut-offcurve.For an exponential horn of theBullphone gramophone units. natew W raT 526 4PF: IL 6, 1929 THE BATTLEOF THE GIANTS JOTTINGS FROM MY LOG :: By JAY COOTE IEITHER the title of a silent film nortransmission I heard a series of faint noteswe have Moscow, Motala, Zeesen, 5XX, that of a talkie, but merely a recordwhich to my mind would coincide with anLahti, and Eiffel Tower working daily in of the nightly struggle which is takingautomatic broadcast of .a very thin buglean already crowded corner of the ether. place between high -power stations and thecall.This was repeated at intervals ofDo you know that Zeesen now threatens forecast of the general battle which mustabout ten seconds before speech was heard.to increase its power to zoo kilowatts; 'that inevitably take place in 1930-! Generally speaking, the station is off theEiffel Tower, still on a nominal 55, con- For some clays I have been trying to getair by, latest, 9 p.m. G.M.T., except ontemplates pushing up to roo kilowatts; a good reception from Lahti, and up tospecial nights, when an operatic trans-and that Warsaw has decided to erect a;

quite recently at every attempt the Eiffelmission is given; but the best time to" super " with 5o kilowatts in the aerial? I Tower has baulked my efforts. Not thatsearch for it is towards 7.3o to 8 p.m. If No special mention has been made of anyone, I believe, wants to hear the Parisyou happen to hear the Swedish languageHilversum, Kalundborg, Leningrad, Huizen transmitter, for its programmes are very-an easy one to recognise in view of theor Kovno, which do not come within the poor in comparison with those offered toopportunities offered to us by Motala-affected broadcast band limits; yet these us by other studios, but the fact remainsdo not jump to the conclusion that youare all transmitters of which the concerts' that its power (some 15 kilowatts) and itshave necessarily tuned in to a Scandinavianare easily capturable in the United King-! position in the long -wave band greatlytransmitter, for at 7.45 p.m. nightly Lahtidom.Itisunfortunate, however, that interfere with the 13roadcasts of the Finnishputs out a news bulletin in both Finnishthey fall within the areas of spark inter -I station. and Swedish, in view of its mixed popula-ference. tion. Lahti ,The high -powerstationisratedatOn the Medium Band Fortunately, at times, the Eiffel Tower20 kilowatts, and on favourable nights the In the medium band the menace is even' wavelength is subject to variations; onsignals are very powerful. Possibly, withgreater, for on any evening now we may one or two nights, as it wavered from itsan outside aerial the nearer Eiffel Towerexpect experimental tests from the new, course, so Lahti was effectively captured.may swamp them, but with a frame youOslo transmitter with actually 6o kilowatts: On March 23 I was able to hold the Finncan make use of its directional propertiesin the aerial, and Bucharest in the near, for more than half an hour at full loud-and cut out the French broadcasts. Lahtifuture will also contribute a 24 -kilowatt speaker strength, and during that periodon an air line must be roughly 1,15ovoice. Turin, it was officially stated at the, gleaned a mass of information. The call ismiles from London; itis worth tryingopening ceremony, is eventually to become, given out now by a male, now by a ladyto get. one of the largest stations in Europe; yeti announcer; it varies from Lahti, Lahti, to Rome contemplates the erectionofal a longer announcement, for sometimes atMore Crowding 50-kilowatter and Prague is imbued with! the end of an item you may hear "Huomio ! This tussle to disentangle two powerfulthe same ambition. Add to these Langen-1 Huomio !Suomen Yleis Radio Lahti Hel-stations from one another, although per-berg and Daventry 5GB, which are no! sinki"; but on days when a Swedish trans-haps not the ideal aim of a wavelengthweaklings, a threat by France to put upi mission is given (on Fridays from the high -plan, if not carried too far breaks thea super -power station in Strasbourg as al power station, on Tuesdays from Helsing-monotony of "you press the button, we docounter -blast to Freiburg and Stuttgart,I fors only) you will pick up words in thethe rest" class of reception and leaves onethe new Bratislava station, two further Scandinavianlanguage,namely :"Givwith the feeling that something has beenadditions to Czecho-Slovakia, and Switzer- akt !Giv akt Finlands Rundradio Lahtiaccomplished.But you can have tooland's intention to build twin semi -giants Helsingfors." much of a good thing, and this is what Iat Gros de Vaud, and Suhrental, and you' Apparently the station puts out noforesee for 193o. have a fair picture of what 193o may interval signal, but preceding the main At present, of the high -power stationsbring us-the Battle of the Giants !

LOUD -SPEAKER VARIETIES FREQUENCY MODULATION; extraordinary amount of ingenuity THE increasing congestion on the ether,1 ANhas been expended upon loud -speaker particularly in the zones reserved for; development. In addition to such standard broadcasting, draws attention to a new models as horn, cone, and moving -coil method of modulation which has recently speakers, with their many modifications in been developed with the object of reducing: design, one notes the appearance of the the width of the sideband fringe accompany- electrostatic type in which 'variations in ing the wavelength allotted to each station.; Voltage, as distinct from current, are used In the new system of transmission, to set a large diaphragm into audible instead of varying the amplitude of the vibration. transmitted carrier wave, the latter is kept Another ingenious application of the at a constant height or level, but the waves electrostaticprincipleistheso-called are more crowded together in certain partgi "corona" speaker in which voltages derived than in others, the relative "spacing" being from a low -frequency amplifier are applied controlled by theappliedmicrophone to a surface which has initially been charged currents. By using this method of frequency, up to a point just short of that at which a modulation it is possible to confine the' silent brush or corona discharge occurs. width of the resultant side -bands to approxi-i Theadditionallow -frequencyvoltages mately ioo cycles, as compared with normal create disturbances in the air molecules widthsof5,000cyclesandupwards' adjacent to the charged surface, and in requiredin" amplitude"modulation this way set up sound waves. B.A.R. Lilian Braithwaite-An Impression by Lissendensystems. M. N. APRIL 6, 1929 527 teur Wireks< WITHOU ouFAVOUR HuMOLict

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I 1 A Weekly Programme Criticism by Sydney A. Moseley of sports commentaries was-more expression and less tricks.Onethe book was "by accident," and I can T' notweek bad, although the Grand Nationalitem in particular-De Falla's "Spanishwell believe it.I am sure that no one did not sound as thrilling as it was lastDance "-was rendered by him in such anwould sit down and dish up such stuff year..Difficult to find the real reason.understanding manner that the melodydeliberately. seemed to live; in fact, it did live. Possibly the number of horses participating 4. 4*

made the job of impromptu description hard. Messrs. Lyle and Hobbis coped with Ann Penn-although good-has a fault Are the provincial dance bands up towhich I dislike.It is staleness. She fails the task like stalwarts, but the odds werebroadcasting standards ?_I was listening against them. to vary her programme sufficiently, and to Paul Raffman's band from Birmingham,one tires of even the best material. This and one could not fail to make a comparisonfault is certainly not confined to Ann. "I am glad to see that you have all ofbetween this and London bands. RoffmanOthers need pulling up for the same reason. a sudden 'gotreligion',"writesH.B.may sound well enough in a dance hall, butWish Wynne, for instance. (Who said I had?) "But I am sure that,it does not follow that what serves well in devout churchman as you must now be,a dance hall will broadcast well.I should imagine that Raffman's band is quite good you cannot be in favour of the kind of "The-shall I say?-abdication of Fred Sunday broadcast which Was given us fromto dance to "in the flesh," but there aren't enough instruments in this combination toElizalde's Savoy Band has given us the 5GB recently." He gees on to enumerate opportunity of hearing regularly what is the items thus :"5-5.30, Children's Ser-make it a success over the ether. adjudged by the experts to be 'the finest vice; 5.30-5.45, Old Testament Reading; dance band inthecountry,' "writes 5.45-6.55, Church Cantata; 6.3o Religious The Count of Como was spoilt by mumb-"Harold,"myadviseron matters Service in Welsh; 8-8.45, Religious Ser-ling.The music was tuneful enough, butsyncopated. "The bandinquestion Charity Appeal; then anthe continuity was absolutely lost.Theis that led by Ambrose at the Mayfair hour of Handel's music." few words I heard lead me to believe thatHotel." Well, if H.B.-reads my notes as closelyI didn't miss much Well, I don't like to be too dogmatic as he pretends, he would know (1) that I

myself about dance orchestras, but there am' not a devout churchman (being merely J. H. Squire has indeed a flair for findingseems to be something in what "Harold" content to be devout) and (2) that I haveor personally arranging tasteful musicalsays. Ambrose's band has a quiet rhythmic done, and am still doing, my best for brightmedleys. Let us hear the octet play againway about it which is a relief from the Sunday broadcasts. these arrangements of excerpts from well-blaring crudities of other orchestras.I

known and well -liked selections and songs.gather, by the way, that in Ambrose we Are not we getting rather too muchForinstance,"Everybody'sMelodies"listentothe highest paid violinistin Teddy Brown? There is a sameness aboutand "A Potted Concert in One Item" areEngland him. His tinkly bits all sound alike andingeniously his "stunt" endings are sterotyped, if notarranged.

identical. Moreover, he is hardly an expert saiiophonist-his tone is too fuzzy to be agreeable. Why doesn't he give us a good Julian Rose programme on his xylophone alone? Heexcels himself as is quite capable of doing this. an announcer. Well-somewhat of a contrast to A reader "views with apprehension" theour"refaned" threatened return of -Schubert's Unfinishedannouncers,so Symphony" twicenightly."He wasthat one must "forced to complain" about it not longlaugh with him.

ago, and now finds that after a lull it is beingserved up again."Although a All Aboard masterpiece, it does not stand constantfromBirming- repetition,andI solemnly assuretheham was another B.B.C. that in putting it over so 'Oftenof those self- they are helping to ruin it as a classic."praisedselfrevues After which solemn warning there is onlywhich turn -out one thing for the B.B.C. to do-give itto be common- once nightly 1 place variety.

Inthe official Broadcasting Takes the Place of the Newspapers.-The photograph Joseph Szigeti gave us a pleasing violinprogramme it shows a crowd outside a London wireless dealer's listening to the recital. His playing is of the kind I admirewas statedthat. result of the Grand National mate= wIrdoi 528 529 moltur Wirk5

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=: NEITHER apology nor explanationvoting. There is no reason to suppose thatowners can see that this is a good point,along the winding, listeners close to adenser to the other so that for is needed in deseribing - this newalthough developments in wireless are saidbecause, although plug-in coils are by nopowerful station may have cause to com-local reception, when the very version of Britain's " Favouriteto move quickly the voting would be anymeans as dead as the proverbial dodo, in aplain of lack of selectivity.'Well,thisgreatest strength is needed, and selectivityD.C. resistance of the primary of the L.F. Three," one of the most successful threesdifferent to -day, and the fact which will be III does not matter very much, the series con-transformer cuts down the H.T. voltage valvers which has been described by themost obvious to present owners of the A GREAT FAVOURITE. denser can be cut out of circuit. to a suitable value for the first L.F. valve. " Favourite" or to those who were interested This set was first produced at the beginning of 1928 as a result of an "A.W." For the reception of the more distant A trouble which is likely to arise when a AMATEUR WIRELESS Technical Staff. competitiontodecide the most popular circuit.So satisfactory have been the There is an interestinglittle bit of in its design on first publication is that the results obtained by constructors of the "Favourite," and' so insistent has been transmissions adjacent to the wavelengthpower valve taking a large H.T. current history behind the original version of thepresent receiver bears very much the same the demand for new facts about this set, that we considered a 1929 edition of the of the local station, however, judicious useis employed is that motor -boating may be " Favourite.'. It will be remembered that itoutward appearance.Indeed, the end in "Favourite" advisable.So here is Britain's "Favourite Three" with all the of .the series pre-set condenser will be found set up, or the tendency to L.F. oscillation latest improvements, and it is one of the best " threes" you can make. an almost complete cure for inter - view with which this set was designed 114.01111 011111 was, first, to present owners of Brit-general-purpose set of this naturecoil difficulty has been overcome in this newstation lamming. ain's " Favourite Three " a chance tochanging is nothing better than a bother.edition by the incorporation of a smallSimple' Tuning add and incorporate just those refine- The six -pin -coil can be of the dual rangevariable condenser of the pre-set type, which ments which a year's progress hastype and a simple push-pull switch on the can, if desired, be placed in series with the This will not be found an extra com- made possible, and not entirely topanel allows of either the long or the shortaerial lead. plication when tuning, because for modify the set to gratify some newwavebands to be received.Alternatively, There is a flex connection from the aerialmost purposes the condenser can be craze; and, second, in the light ofthe very short waves can easily be received. terminal of the panel, to the other end ofpre-set at one intermediate value our readers' voting in 1928 and With a plain coil arrangement, even if awhich is attached a spade tag. This can bebetween the possible extremes subsequent technicaltapping is taken to an intermediate pointshifted from one side of the pre-set con - (say .000r-microfarad), and developments, to present to this will be suitable for all all readers the opportunity distant station reception, to make up a really good WAVE -CHANGE SWITCH ON PANEL while the condenser can be practical three, with- cut out altogether by out any unnecessary changingover the ,frills or limitations of pasition of the spade performance. tag for local station reception.There is Modifications ample spaceavail- As it is expected PRE-SET able on the panel for that a large number of set con- CONDENSE R the mounting of a structors who perhaps have an entirely FOR -.7;i`-.:LECT- pre-set condenser if the design really different type of set will want to make IVITY necessitated it, but the job is adjusted up this" 1929 Favourite Three," itis at such infrequent intervals that there The wiringis is no real point in disfiguring the lay- Ample space is particularly necessary to describe it with the object of allowed for the simple explaining the whole set to these new- out of the panel and complicating the components was described only last year in "AMATEUR comers.Present owners of" Favourite w:ring by shifting the pre-set conden- WIRELESS," No. 294, and its special point Threes" will readily see the additions which ser from the baseboard to the panel. accentuated. The same trouble is likely to DUAL RANGE A common H.T. lead for the anodes of all arise if a mains eliminator is employed and, of interest was that it embodied the circuithave been incorporated and can modify COIL votedfirstin an AMATEUR WIRELESS their own receivers accordingly. There is three valves is a feature which will be in rare instances, builders of the original competition which had been organised anot the slightest need to make up an obvious from the circuit diagram, and this, Britain's "Favourite Three" (and inciden- little time before the publication of the entirely new set and only the minimum of of course, makes for simplicity, since it tally of many other receivers having a " Favourite Three." parts will have to be scrapped. ANT1-MOTOR BOATING UNIT means that only one H.T: potential has to common H.T. tapping) may have had -" Choose your circuit" was the theme of By far the most obvious feature is that a be applied. The voltage on the detector difficultyinpreventingmotor -boating the competition and the " Favourite " was six -pin coil has taken the place of the This photograph shows the modifications that have been made to bring Britain's valve anode is, of course, cut down by the when working from the mains. the material, form of the most popularprevious plug-in coil arrangement. All set " Favourite Three " Up-to-date resistance of the R.C. coupler, while the Well, any such troubles are now obviated

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-1" ['Air WtreleD 530 AMR/I, 6, 19.29 " BRITAIN'S FAVOURITE THREE UP-TO-DATE" (Continued) in the 1929 edition by the incorporation of a Push-pull switch (Lotus, Lissen, Trix, 50,000 -ohm resistance (Graham-Farish, motor -boating stopper in the H.T. circuit.Wearite). Lissen, Dubilier, Mullard, R.I. & Varley). This consists simply of a fixed condenser Panel brackets (Bulgin, Cameo). 2-mfd. fixed condenser (Lissen, DOilier, and 20,000-ohni resistance in series with Dial indicator (Bulgin). T.C.C., Ferranti, -Mullard). the primary winding of the L.F. trans- Three anti-microphonic valve holders how -frequency tratisfOrmer(R.I. and former. This is a complete cure for motor -(Benjamin, Lissen,- Burton, Wearite). Varley, Lissen, Philips, Mullaid, Cossor boating in a receiver of this type. It will be .0003-.000025-mfd.pre:set condenserIgra.nic). seen from the photographs that the con-(Forniodeiiser type J, Igranic). ' .Grid -bias battery clips(Bulgin): Two ,.0003-mfd: fitted con-black and one red wander plugs (Clix). 0000b17a5 ,NVVVW 0 HT+denser with series clip Baseboard,16 in.by gin.(Pickett, togggad mey.ohm (Dubilier, Lissen, Gra-Clarion, Camco). 5 ham-Farish, Mullard). Connecting wire (Glaaite). One yard of 2-megohm grid leakthin flex (Lewcoflex). I/ iC) (Dubilier, Lissen, Gra- Seven terminals, marked : Aerial, Earth, 1 ham-Farish, Mullard). L.T.-I-,L.T.-, L.S.-,L.S. 6 Six -pin coil base(Belling -Lee, Eelex, Igranic). (Tunewell, Lissen, Lew - The following constructional details will cos, Peto-Scott). be of interest to those who are making up the High -frequency chokeset, while those who are simply adding the (Lissen, R.I. and Varley,tit -bits, as it were, may pass on to the Burndept, Polar, Tune -operating details which will be given. 2/ oL.T+ well, Trik). A new blueprint is available, and can be me Resistance - capacityobtained, price Is., post free, from Blue- r(20005) coupling unit (Dubilier,print Department, AMATEUR WIRELESS, Short -00025 LT- wove T -Lissen, R.I. & Farley,58-61 Fetter Lane, London, E.C.4. This is a Stitch Graham-Farish, M u 1 -great help in building up the set, because 68.-2 Imid). (Continued at foot of next page) The Circuit Diagram 1BLUEBLUEPRINT PANEL /6..0' denser is placed on the baseboard quite N'AW /7' close to the R.C. coupler. AERIAL -"N -444 Long and Short Waves AERIAL RHEOSTAT TUNINGCONDENSER REACTION TUNING "Y2 For the benefit of those who are making fi mosmfd CONDENSER up the " Up-to-date Three " as a new cad00025/r/// receiver, it must be explained that in its 0 new guise, or rather with the addition of its latest improvements, it is a very good receiver for general work. In practically every part of the country it should be LS+ capable of giving good loud -speaker recep- WAVE CHANCE tion of 5XX, 5GB, and a local station. In 5W/ rcti most cases a healthy batch of foreigners -4*-- should also be easily receivable on the loudspeaker, provided, of course, that a good level of baseboard---? aerial is employed and there should really BASEBOARD be no need to use phones in order to get a /6-ir.9-x proper amount of enjoyment from the set. SEM/ VAR/ ' e 13 COND" If you are making up the set as an 729 1'1.F:1/AVE .6voo2.5( entirely new venture you will require for 68 to its construction the parts mentioned in the DUAL RANG appended list. Comparison of this list CO/L with existing receivers will see what needs to be purchased by present possessors of a "Favourite Three" who wish to bring it 7b9rd up to date. Components Ebonite or Bakelite panel, 16 in. by 8 in., ON and strip, 4 in. by 2 in. (Becol, Raymond, To Paxolin, Radion). 813A) 0 9 A 0000.0 .0005-mfd. variable condenser, log mid - DETECT 0 Tord line type (J.B., Polar, Ormond, Burton, VALVE CR1198145 Burndept). 2 Brr mid .00025-mfd. variable condenser, log mid - H.FCHOKE line type (J.B., Polar, Ormond, Burton, 32 Burndept). Ebonde sf.x2 7 -ohm panel -mounting rheostat (Lissen, Igranic, G.E.C., R.I. & Varley). The Wiring Diagram.Blueprint available, price APRIL 6, 1929 531 entaleurWixel2 The ARCADIAN PORTABLE AFIELD SOME HINTS ON ITS OPERATION dial readings of the stations which an average London amateur will wish to receive when working the "Arcadian" out of doors, are as follows : On the short waves- London, 98 degrees, Daventry 5GB, 140 degrees; on the long waves-Croydon, 8o degrees; Hil- versum, ioo; Daventry 5XX, 145 degrees and Radio Paris, 170. - As the main condenser dial is WITH the instructions for building thegets a little " behind " or "ahead" of thegradually turned from zero to 180 degrees "Arcadian Portable" published lastother, and this can be corrected quiteby means of the thumb control, the knob week and in the previous week, AMATEUReasily simply by placing a small correctingof the pre-set condenser should be slowly WIRELESS Nos.354 and355,readersor balancing condenser across one circuit. screwed in a little at a time, in order to interested in portable sets have had an This is just what has been done in thecorrect for inaccuracies of ganging. opportunity to make up this excellentpresent receiver.Thus, when operating If, for any reason, it is desired to get at 1929portable. Inlastweek'sissuethe "Arcadian" the knob of the gangingthe "internals" of the receiver while it is in sufficientoperatingnotesweregivencondenser (which, as a matter of fact, is aoperation it is better to move the loud- to enable those listeners who had com-pre-set condenser mounted on. a woodenspeaker side of the cabinet rather than the pleted the construction of the receiverpanel) should be adjusted in conjunctionset side, for the loud -speaker can be removed and loud -speaker unit to get the wholewith a thumb control, and at the extremewithout disturbing the batteries.It may portable working as soon as possible. ends of the Main condenser scale the gang-be necessary to do this, for instance, in order Thumb Control ing condenser will be found to be relativelyto adjust the reed movement of the loud- As stated in the specification of theimporfhnt. speaker or to vary the H.T. or screen -grid " Arcadian," the fact that itisto tall The circuit of this portable is a veryvoltages. intents and purposes a one -thumb controlefficient four-valver, andif used as an One little point which may be mentioned receiver is a great operative advantage;indoor transportable the receiver can beas the result of an extended practical test it is interesting to note how this works.made to give Some very startling results inof the "Arcadian" is that it is wise to see If you take an ordinary H.F. and detectorthe way of DX getting. that' all the battery plugs are a tight fit receiver it will be found that if logarithmic in their sockets before closing up the sides condensers are employed for tuning, the dialFull Volunie Oat -of -doors of the receiver.Loose plugs and faulty settings will be approximately the same over As a portable, however, only the stationsconnections can cause a deal of bother in the middle portions of the scales, andwhich can be received at full volume areportable sets, and troubles of this kind are any variation between the settingsofreally of interest, because when out of doors,greatly accentuated if the receiver is used the H.F. and aerial condensers will beand for dancing at picnics, and so on, fullin a car, and in consequence the "works" noticed only at the extreme ends of theloud -speaker strength is an asset., As aare severely jolted about before the set is scale.This is simply because one circuitmatter of interest it may be stated that theput into operation. "BRITAIN'S FAVOURITE THREE UP TO DATE" (Continued fronz preceding page) on the one sheet are incorporated a wiring For the variable connections, such as themanage to make a very good job of "com- diagram, drilling guide, and layout template.lead from the aerial terminal to the pre-setmoning"theframeworkofthetwo. When drilling the panel do not forget thecondenser, and the three leads to the gridcondensers and the moving arm of the holes for the mounting brackets and thosebias battery, thin rubber -covered flexiblerheostat with this one connectionfixed through which wood screws are passed inwire, such as Lewcoflex, is best employed.between the components and the panel.In order to attach the panel to the baseboard.The grid bias connections are taken asthe present design this busbar has been The blueprint can be used in a veryfollows : One from the moving arm of thetransferred to a more accessible position, as convenient fashion for showing the exactfilament rheostat to the positive batterywill be seen by the photographs. positions of the baseboard components. Itsocket; one from the G.B. terminal on the As usual, this receiver can be seen in the is rather important to adhere as closely asR.C. coupler to about the 3 -volt tapping onSomerset Street windows of Messrs. Self- possible to the dimensions given in thisthe G.B. battery; and finally one from theridge, Ltd., and London listeners should original design and no difficulty will beG.B. negative terminal on the L.F. trans-take advantage of this excellent opportunity found in doing so, for there is ample spaceformer to the 71/2 or 9 -volt tapping. to see the way in which this very popular to spare on the baseboard and panel. A wiring point which will be of interestthree has been brought up to date. Wiring -up should be carried out with rigidto owners of existing "Favourite's" is that wire, and in this particular instance in orderthe connection which formerly made con- TheRadioCorporationofAmerica to make the job of wiring -up as simple astact with all the one -hole fixing devices onrecently issued its annual report for 1928, possible, bare wire, and not insulated wire,the panel has now been dispensed with asshowing total gross income of $101,851,603 such as Glazite, has been employed. it is possible that some constructors did notand net income of $23,661,990, Mateur Wtreig.D 5-32 APRIL 6, 1929

"A.W." TESTS OF APPARATUS Conducted by our Technical Editor.J. H. REYNER. B.Sc. (Hons.). A.M.I.E.E.

Grawor Loud.speaker The construction of the new Polar Idealspeaking, has thh overall dimensions of 3 in. ALOUD-SPEAKR of a novel conereaction condenser which we have receivedby ra in., while at the base are attached type is the Grawor and ari instrumentfor test is particularly robust.The mov-two cardboard flaps which facilitate the of this type has been received for test from.ing plates are held in position by an insu-tacking of the battery to the baseboard, or Messrs. Henry Joseph, II, Red Lion Square,lated moulding at the panel end in whichother methods of fixing.Convenient term- High Holborn, London, W.CA. A cone ofa cone and ball bearing is fixed : the bearinginals are provided and the polarity indica- a resultant rectangular form is employed inat thefarther end and the slow-motiontions are clearly moulded on the insulating the Grawor and the diaphragm itself isdevice are clamped to insulated supportscompound at the top of the cell. composed of four damp -impervious sectorswhich form part of the main moulding. It may be remembered that cells of this joined together by strips of pliable material.Although the fixed plates are clamped attype have been used in AMATEUR WIRELESS Each strip has a maximum width' equidis- receivers and we have found them entirely tant between the apex and the edge of the satisfactory and very convenient in use. diaphragm, and this gives a useful degie-ee G.E.C. Reed Movement of elasticity. The edges of the diaphragm are attached GENERAL .ELECTRIC CO., by means of a Pliable surround to a light Magnet House, Kingswa.y, London, W. wooden chassis which is really capable of are well known as manafacturers of high- producing a sufficient baffle effect without class loud -speakers of the cone type; it is further enclosing of the back of the dia- therefore to be expected that the new cone phragm. Nevertheless, for domestic reasons which has been recently -ffitroduced by the it is usually desired to operate the instru- Poen- Reaction Condenser G.E.C. would be a well -designed article. ment in a cabinet and an attractive range Actually this is an- inexpensive unit and of loudspeakers complete in cabinets isone end only, they are amply rigid add eamu di sea a straightforward magnetic system. obtainahha The chassis are made in threenot be appreciably distorted even wee E eery effort is made to keep the com- sizes, namely I2.1 in..,16 in. and r6 in..considerable pressure is applied to them. ponent compact :the electro-magnet and square, and each is fitted with a Grawor Two small knobs are lifted, the outer ofarmature are mounted in a metal cradle reed movement. which is fired to a spindle mounted to thewith dimensions of 312 in. by OA in. by The resultant tone is very pleasing andmain spindle and controlling the slow mo- 1/2 in. high :these dimensions do not take not unnaturallydeep..Speechisverytion ball gearing.The slow motion ratiointo account the length of the reed, the natural and not tinged with that "boom-is approximately 20 to t.The second knobadjusting knob or the terminals.Itis inesS" so often produced by cone -typeis attached to the main spindle and givespossible when building portable sets, to lend-speakers.Which appear to give a verya t:tratio.The motion is smooth andmount the unit inside the cone, even if the "rel3irecluction ofthe ordinary musicalfree from stiff spots. coneangleissomewhatobtuse.The Complete with one hole fixing device andarmature, comprises a strip of metal firmly frequey ran v. ' ' terminals OA component makes a most useful reaction condenser.The total length oftire; component is2 Y2 in.,whilstits width is in.We found the maximum capacity was aa micro-microlarads. The makers are Wingrove and Rogers, Ltd., Mill Lane, Old Swan, Liverpool.

Siemen's Grid -bias Battvy - TH.ERE are many points in a receiver at which it is very convenient to place a small r 1/2 volt grid -bias battery in order to obviate the need for taking' G.B. leads out to tappings on an external battery. For example, a midget r I/2 -volt cell can Grawor Loud -speaker conveniently be incorporated in the screen - G. E.C. Reed Movement grid H.F. stage in order to provide the Potar Reaction Condenser necessary bias, while in the case of anfixed at one end and lying over an electro- TN these days of high -magnification screen-anode -bend detector, it is a. good point tomagnet at the other. '. grid valves, it seems almost unnecessarysee that the necessary biasing voltage is We tested the unit in conjunction with to fit a slow motion control to thereaetioa;generated fairly close to the valve itself andseveral cones including a good quality but, having used such a condenSer; in difa;ee-.that lengthy grid leads are not trailed aboutfloating cone.The results were quite good, eat types of circuit, we are conireenced thatthe receiver. music and speech being reproduced with it forms an aid to tuning and adds pleasure A convenient little bias battery whichclarity and pleasing tone.Although the tothisoperation.Thisisparticularlyfulfilsalltheserequirementsismanu-strength of reproduction was not quite as true in the case of 'portable receivers whenfactured by Messrs. Siemens Bros. !Se Co.,high as some expensive units we have tested the reaction ematxol is of 'far greater im-Ltda..' ofWoolwich,London. Exter-the overall performance is satisfactory and par lance. nally the cell is rectangular and, roughlythe unit may be recommended, APRIL 6, 1929 533 emaw," WtreiT Xe CeSSe/We brad 1911.11roffir PRICWWIA

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Four, Suit -case Model. for batteries and accessories.Fitted 12 equal payments of50;-5 with hinged lid and detachable front ROLLS-CAYDON, latest Suit -case Model. and back in solid Oak and French Packing case fcr Polished. Price each £3 5s. same, return- 12 equal payments of 30,9 able5(-extra. Delivered to approved accounts against first payment. Carriage forward HEAR THEM ALL AT OUR SHOWROOMS PORTABLE CABINETS. The " EASY WAY " A special line of portable cabine's covered in Leatherette. knows no limits in Radio.Whatever you need-finished receiver, Various Colours.Each. .. 30/ - kit of components, or accessories-send us a note of your requirements Finished in Oak or Walnut, Hand Polished.Each ... 35/.. and we will quote our easy terms by return. Carriage on one 3/-; or two 4/6 extra. Ourbeautifulillustratedart catalogue gives details of a corn- POST TODAY \\,1;\\ I /_/;///; 4.- 2 prehensive range of Sets, Acces- sories, and ConstructorsKits. Please send your Free Art Catalogue. ,ror TSSeeST;111//n24010 Thirty-two pages crammed with wonderful opportunities for the Name (/////7- radio enthusiast. ' Mailthe coupon inunsealed Address OC/./P//' envelopeunder stamp. DO IT NOW I A.W. 6 '4 PETO SCOTT CO., LTD. (THE BE/T IN THE WE/T) 19 LISLE STREET, LEICESTER SQUARE,LONDON,W.C.2. CITY ROAD, LONDON, E.C.1. 62, HIGH HOLBORN, LONDON, W.C.I. or,Iletient 0922 'lei 11'5,14, thieitl,1 4, MANCHESTER STREET, LIVERPOOL. 33, WHITELOW ROAD, CHORLTON-CUM-HARDY, MANCHESTER. Please Mention "A.W." When Corresponding with Advertisers (i maw Wirete5 534 APRIL 6, 1929 In order to reduce serious interference,, the French broadcasting authorities are endeavouring to obtain permission for the Eiffel Tower to lower ,its ivaVelength to 1,47o metres; in the meantime -the transmitter suspended the broadcast of the midday concerts for"one week in order to carry R(TDIOGR(IMS out a shortening of the aerial. Russia is holding its first radio lottery on April 15. The broadcasting authorities recentlyreceivedauthorityfromthe takn during the Boatadapted for the microphone and will beSoviet Union to organise a national lottery PHOTOGRAPHSRace were transmitted experimentallybrOadcast from London and Daventryin which the prizes to be won consisted of by the Fultograph process from Daventrysome time in May. wireless transmitters, loud -speakers, and 5XX between -2 and 2.45 p.m. on the same " That the broadcast play is not a satis-other radio material.Two million tickets afternoon. fact'ory form of art" is the subject of ahave been issued at 5o copecks each (about The Glasgow Bach Society's concert ondiscussion which will take place between6d.); all profit derived from this under- April 8 in the Stevenson Hall is to be putMiss Naomi Royde Smith and Mr. Comptontaking is used for the development of "on the air." The broadcaSt will includeMackenzie at the 5GB studio on April 19.wireless instruction in schools and work- the Concerto in C major for three pianosSavoy Hill is providing the disputantsmen's clubs., and strings, the Concerto in D minor forwith microphone facilities to enable them From a Continental source it is reported solo violin and strings, which is a trans-to decide whether the broadcast play canthat the Baird International Televibion cription of the Concerto in D minor for soloever "get over." Company, Limited, has now concluded pianoforte andsstrings, and one item riot by The Foden Motor Works Band havecontracts with some seven European sta- Bach-a suite for strings from the sym-been declared eight times chafinpions oftions for the transmission of. living pic- phonies of William BoYce. the Belle Vue Contest at Manchester; lasttUres; Berlin will be one of the first Con- Northern listeners will be interested toyear they were awarded the challenge cuptinental cities to be so equipped-to be hear that "George." and "Wullie" are tooutright. On April 8 both London andclosely followed by Radio Paris. retuili to the Aberdeen studio on April 12.Manchester, will broadcast their concert. Test transmissions have been satisfac- Sometwoyears ago a meeting of these two Square Pegs, a polite satire by Cliffordtorily carried out with the new Vienna "worthies"(created by Arthur Black)Bax, and The Dear' Departed, by Stanleyshort-wave transmitter, and it is stated was 'a weekly feature of Aberdeen pro-Houghton, will be found in the varietythat details of the official times of broad- grammes. programme given to 5GB listeners oncast, wavelength, and power will be shortly The French P.T.T. has now definitelyApril 20; as usual; Clapham and Dwyerissued. The station will relay the Vienna decided on the site of the new high -powerwill contribute their spot of bother. entertainments. Strasbourg transmitter; the station is to be On April 18 the Newcastle studio will The high -power short-wave Dutch wire- erected at Brumath, some 14 miles frompresent a new revue entitled Tyney Trifles,less station at 'Huizen (PCL) works on the city. from the pen of the Gateshead humorist,18.4 metres between it a.m. and 5 p.m., Anthony Hope's famous novel" TheE. A. Bryan; the cast will include Saland on 38.8 metres from 3 p.m. to I a.m. Prisoner of Zenda," which scored so greatSturgeon, Doris Miller, Tom Heenan, andG.M.T., thus giving daily a fotirteen-hour' a success both on stage and screen, is beingHarold Earnshaw, all popular favourites. public telephony; service.

MR. FLEX RECEIVES A CALLER- I WAS PASSINGTHIS WAY ,j N\ 1VEBEENIKrTRODBLE (I:VE LEFT THE. .------c, WITHMYWIRELESS V\,...,s/114...... _-4THEDOG,OLD CAR.DEW DOOR.OPEI.I.-1)--,-.... MAN), AND ,-(.,----___rEL:y 1,, THOUGHT i.:-.- 11 __,r2 cr.,-,_?1 ?.\ k" --__--- . I'D JUST , 7oy. ',, .31 MY SET WOULD BE Pop N /1"-) - )),--- WORKING FINE ,' ift!, ' -e I ' ):-.---- (II 111A ' I ' S ,,, -,' ,:// . ' -/'.' "II AND THEN SUDDEmy illiariliff 'illli / ----i \ I lk lidfiriff ---- kii , ,'/ if/ 10P.HA! HA, 1\i.i441illi!', lihhil, ' 1 40 lit, ...-. n. YOU'LL LAUGHWHEN 511)114".. f! '' '4 , ...... ,..1-11 1 TELL you ABOUT IT f; 0 ."01111I -7)

-- .------, -.-=--, --2-; , -: -. -- -:... ,--....-,.. . -- ,--,. - -- ...._ --__. .- - : --_,..-- --. - - - ; , "7- : . -, ------7 -- - - -..------; - ----:":-----'------' .11KINg ------'---c.------%----. '.---= _----;" -----., ------:%,- -AND WISHES HE'D CALLED WITHOUT HIS DOG! ./ 1T'5THAT DOG, OLD MAN .....-.. ./"----\ 4pft. vii".,,I ^N7N I WAS GoiNc. To TELL YOU,i ' WHILE I WAS' --.N \ % * ;--, ABOUTHIM. SHUTTING ( -- aC-..... ^ / I - , NA, /4, 100 HE'SMADE -r), c` V THATGA ROES) 400, /\ .,/7,-, 7' , ,, QUITE 04\ 1-.' DOOR. YOU1L 1,, ;'ie - A f - 0 '' ,k 'AHAB1T '., .1% , DOGRAO _-..- %) /I If, ///f, ,--,. ,// / ; OF , ;III 7 /, .e/T '11 II' .,/7. / lir4-.7 oUT 7'ile''' '''CHEW! 1 444/ WC1 '111!Iiill f/ ' ' ''' . lirAli if ''' 1, MY EARY4 , VI --- II,,--. 4., MELLO, 1 l 41 R. / \ .\_\. 11'10111 - ' ' WIRE. ''h galli110, , 'Now , N\ -.--7.--,:,... I ,. ..,Iti

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- - - - -"'-::<=--'.------. ,---- - APRIL 6, 1929 535 ImateWi4relei WRIGHT & W EA! R E, Ltd. Little 740, HIGH ROAD, COA/fP0A/E TS TOTTENHAM,N.17. before W. James "Special 3" Coils ..25/- pair mend W. James "Binowave" Coils 25;-st \\\ 4

Q Aerial Coil...... 15/- each Q S.P. H.F. coil .. 21/-,, Q Screened -grid Coil.. 21/- f f eaves Q Reinartz coil...... 21/- f , Q Mullard "Master 3" Star Coil 15/- ,, much Dual Range Tuner, W.G.2, as used in FERRANTI Circuits13/- los alter ARCADIAN PORTABLE spend

Coils ...... 1016 Screens.. .. 9/6 each H.F. Choke, 6/6 each CLAIXITE Anti -capacity Switches, simplifies all soldering 2 -way, 6/- each FLUXITE is sold in tins, SOLDERING price 8d., 1/4 and 2/8. Push-pull Switch with Another use for Flux-SET, complete Terminals, 1/- each ite : Hardening Tools 7/6 Wave -change Switch and Case Hardening. Ask for leaflet on or LAMP with Terminals, 1/6 each improved methods. only 26 FLUXITE LTD., WRITE FOR LISTS (Dept. 326) Rotherhithe, S.E.16 Telephones: Tottenham 3847 and 3349 III .A=MMINISMINIMMIIMESISIO! BUILD THIS SET ! THE COMPLETE KIT OF PARTS "SCIENTIFIC" including Attachi D. X. 5 -Valve Case. Here isthe famous D.X. Transformer which is setting a standard in value for . . money and is already known wherever TOURIST £4196 radio is heard of.A really first-class less valves and piece of workmanship, conscientiously PORTABLE made in accordance with modern scienti- batteries. fic principles at a price that places it An all-round set for every occasion at a popular price. within reach of all. Wavelength range 250-550 and 1,000-2,000 metres. Write to us for leaflets and particulars of this transformer and give one a trial. An efficient and reliable self-contained 5 -valve receiver. Ideal for 8/- Retail holidays, motoring, boating, or home use. Will receive 2LO, 5GB, You cannot fail to be delighted. 5XX, Paris, Berlin, Lahti, Hilversum, etc., etc., on self-contained Ratio 3 to Ask for particulars of our new circuit, the D.X .3. aerial and speaker.Easy to assemble.Results assured. D.X. COILS LTD., 542 Kingsland Road, E.8 SCIENTIFIC SUPPLY STORES 126 Newington Causeway, London, S.E.1. 'Phone: Hop 4177.

Famous FORMO COMPONENTS as used in this fP BUILD and OPERATE in' Set and in all Notable Published Circuits ONE EVENING,A, 10111111111;i115

FORMO-DENSOR 2/ - In four variable capacities

"1928 " LOG CONDENSER 5/- '0005'00035'00025 )5141474/ TRANSFORMER -OUTPUT FILTER CHOKE "DE LUXE" MODEL COILS SG I & 2 '0005 6/- '00035 4 Components Throughout 25/ - '00025 '00015 10/6 each VALVE HOLDER 1 /3 SEND FOR CATALOGUE. THE FORMO CO., CROWN WORKS, CRICKLEWOOD LANE, LONDON, N.W. 2 WIIIIMINEM[ 'Mention of "Amateur Wireless" to Advertisers will Ensure Prompt Attention emote= Wirelesj 736 APRIL 6, 1929 "linen -diaphragm"construct-orsformed LETTERS TO their opinions of M.C. reproduction. They must have been pretty ghastly !The con- THE EDITOR ventional " Det,, 2 L.F." or " H.F., The Editor does not necessarily agree with 2L.F.,' With 120 volts H.T., will most the views expressed by correspondents. decidedly not cope with a M.C. speaker, To the many "plodder"" in the search *C Round the World with an "A.W." Setfor quality reproduction, via M.C. speakers, SIR,-Having had your "Home andthe extravagant claims of some of your Voce Abroad" set during my trip round the" linen-ites " must be somewhat amusing. world, I felt I ought to write and let you I have bifilt ydur "linen" speaker, and Seductio know the excellent results obtained at theagree that it is good-exceptionally good. different places we visited. But in moving -coil class-no, decidedly When off watch at night I used to listennot. regularly to 2)(AF all along.the Mediterl ,1'o conclude, it is an established medical ranean. 5SW and PCJJ were easily ob-fact that a very high percentage of the tained in Australia. Melbourne was heardinhabitants of these islands is partly or in the Suez Canal, and now with coilswholly-" tone-deaf " ! 2, 4, and 6 or 7, according to the type of F. S. (London, N.). detector valve in use, Huizen comes in on 16.88 metres.I added one stage L.F. for Mr. Frank Newman good speaker results, and feel quite dis-CIR,-I was pleased to see my photo- appointed if unable to listen for some sta, graph among "Broadcast Artistes of tion about 2,000 miles away. The chiefthe Month" itt No. 354 of your excellent difficulty,however, isthe difference inpaper (page 444), but must beg you, if time, but the other morning, quite onepossible, for the insertion of a correction. hour aftersunrise, 2XAF was coming I left Lozells Picture House, Birming- through on the loud -speaker. ham, on February 7 (when I gave my last B. (Annan). broadcasf)to go to the New Empire Theatre, Leicester Square, as one of the Foreign Valves two solo organists there. At the Empire SIR,-IentirelyagreewithJ.D.B.I have the largest cinema organ in this Cyldon condensers, freely ac- (Ulster) that the cheaper foreign valvescountry-a Wurlitzer organ. nowledged by allto be the lack " pep.'! I must explain that my pre- FRANK NEWMAN (London, W.). finest radio condensers in the vious letter was only written in the same world, are now within every- strain as the article which prompted it, body's reach. 5XX Quality The famous Cyldon standard: i.e., valves were being compared solely by SIR,-I have followed the correspondence of qualityandworkmanship their mutual conductance valui.s: and as in AMATEUR WIRELESS for a consider- remain the same ;Cyldon con- such the particular make of Austrian valve densers at the new prices are able time and note that W. J. F., (Redruth) mentioned was- equal to English.It willexperiences the same trouble that one hears absolutely identical with those be remembered, however, that I mentioned alreadyextensively chosen by °mall sides in Penzance. 'No one can deny designers and experts: that the Part of a valve which is of 'para-that the quality of 5X X varies considerably Use Cyldon mount importanceisthe filament, thein such short periods as twenty-four hours. condensers in quality of which,. I admit, is doubtful inThe programmes are only comparable to yourthey new are set, the cheaper valves. mincemeat, especially when from 8 p.m. mechanically As he appears to have been unfortunateto 8.3o p.m. "Daventry only" a talk is as -well as with the foreign valves he has bought, Isandwiched in on any subject. electrically would suggest that J.D.B. should try Why we should be penalised, -I really am perfectand those made by the Dutch firm Philips, areuncondi- at a loss to understand.Thus, again the tionally guar- which are .sold in France at 37.5o andtit -bit Of the evening is usually 9135 to anteed for five 55 francs (ordinary and power respectively).ti.o, which is after country listeners have years. J. S. (London, S.W.). gone to bed. Ask your local dealer for complete list of reduced prices. A Linen Speaker Controversy I imagine that A. M. H. (Coventry) has ..... a number of stations at his disposal, and REDUCED PRICES Several letters have appeared in BEBE Syneliiaiune Log Midline, your correspondence columns latelyis not a 5XX listener only.Should this .000t 5/- Twin .0005Square Law correspondent visit ' Cornwall, he will be .000r55/6 37/6 andS.L.F. from readers who have constructed linen - .00026/- Triple .0005Condensers diaphragm loud -speakers.While makingwelcome to try the experiment of listening .000e5 7/- 52/6 .0005 10/- allowances for the exuberance developedto 5XX for one week. when suddenly becoming the possessors of Perhaps A. M. H. would be interested to loud -speakers 'very imich superior in per-know that 5GB is not comparable with forncance to anything they may have pre-such stations as Turin, Toulouse, Nuremberg viously owned, such remarks as "equal to,and Stuttgart at one quarter of the power, or better than, any moving -coil speaker Iand as an alternative programme it is useless LDONhave heard" Cannot be allowed to passto us here. BRITISH Six (Penzance). without comment., CONIDEINSEIRS -The plain- fact is that, to people with a ,5 YEARS GUARANTEE musically trained ear (and they are com- NEXT WEEK SYDNEY S. BIRD Co' SONS, paratively -few), the M.C. speaker, operated O'Cyldoiz" Works, Enfield Town, Middlesex. under correa) conditions, is hi -comparably An All -from -the -Mains "Two" in a- -class by itself.One wonders what Don't Miss It! conditions obtained when your enthusiastic APRIL 6, 1929 537 ittrifc ur

0010011400

ilefilliiils60," ddl1111111111100

RULES .-Please write distinctly and keep to the point.We reply promptly by post.Please give all necessary details.Ask one r,tiestion at a time to ensure a prompt reply, and please put sketches, layouts, diagrams, etc., on separate sheet; containing your narn End address.See announcement below. Address Queries-Alta:mutt Wzavr rss Information Bureau, 58/61 Fetter Lane`, London, E.C.4 - Aerial Types. Damaged Valve. Q.-Why is it that most amateurs use a single -QVVVVVWVVVVVVVVP Q.-Recently one of my valves was dropped wire aerial for their receiving stations when, from a height of about 3 ft.to the floor and, according to what can be seen from photographs> When Asking although the filament isintact,the valve no of professional stations and warships, the use of 0 longer works. Can you suggest what has happened? a multi -wire aerial of the cage or " sausage " Technical Queries type appears tobe the type most favoured by A.-It is possible that th.e electrodes have the people who should know which isthe best PLEASE write briefly become misplaced and either ,the filament is aerial.-A. P. (Godalming). touching the grid or the latter is touching the A.-Multi-wire aerials of the type you refer and to the point anode. A defect of this kind can be traced by to possess a large capacity and as a fairly large A Fee of One Shilling (postal order testing with a battery and meter, between the capacity aerialis required for transmitting or postage stamps) must accompany grid and filathent or grid and plate legs of the purposes it explains why such aerials as you each question and also a stamped valve for short-circuits. If no readingis have seen in photographs are in common use 0 addressed envelope and the coupon obtained in either case the valve is all right on in professional circles. The receiving aerials which will be found on the last page. this score, and probably one of the wires. may of these stations and ships, however, are of the Rough sketches and circuit diagrams have broken off between the electrodes and the single wire type and if it were possible to see 0 can be provided, but it will be neces- legs.. This can be remedied by removing the more detail in the photographs in question or sary to charge a special fee (which will base and completing the broken wire.If the even to visit the stations or ships themselves it be quoted upon request)fordetail electrodes themselves are damaged, or their would be seen that quite a small single wireo> layouts and designs. positions altered,itis improbable that this aerial is in use in addition to the large main valve will work properly again ; in any case its aerial.-L. C. MMAAAAAAA.A.A A characteristics will be materially altered.-B.

SMALL ANTI - CAPACITY SWITCH NO CAPACITY 1:1 -signedtoeconomisespace. CHANGE -OVER Arranged for panel or baseboard - SWITCH mounting. Fixed contacts mould- Made in rye.% natterns-knob and ed into a bakelite arc; moving lever -6 size" toeachpattern. contacts of double nickel -silver Contacts are self-cleaning, and the spring-excellentelectrical unique design minimises electro- connection. static capacity. A very popular No. W.igohtr pole change over 4 6 COMPONENT/ switch. le 2 6 -pole Lever Pattern /3 3 6 - shown .. ,, /4 4,, 7,6 For Perfect Switches ask for but other sizes /5 5 9 6 from .. 3i - /6 6 9,6 and see that you get "Utility 99 The final perfection of a set demands first-class switches."Utility" Switches lead the market to -day by their good value. .. every switch is dependable, and will please you as much by its appearance as by its service.Ask your local dealer to show these switches to you. Write to the makers for a complete list of " Utility " Dials, Switches and Condensers.

WILKINS & WRIGHT, Ltd., "Utility" Works, Holyhead Rd., Birmingham

TO HOME CONSTRUCTORS! ITO OBTAIN THE BEST RESULTS Build the Peerless " Resonic 2" FROM YOUR UNIT USE A Anyone canbuildthisset in 60 minutes.No drilling.No soldering.All Wires cut and bent.JUST ASSEMBLEandthen immediately enjoy the radio f. 5 entertainment, whichisof splendid toneand comesinat good loud -speaker 5 volume.Circuital'owsuse of standard naive(IH.F. & 1Power).Blueprint CAMCO and easily followed Dia- i 1 Z1, fo.1._ gram of Connectionsin - eluded with every set. Cabinet and hill Kit F CABINET supplied in Carton. Send Coupon for Latest List. CARRINGTON MFG. Co. Ltd., Camco Works, SandersteadRd.,South Croydon b, 13.15.0 ? Telephone-Croydon 0623 (2 lines) ottu,,./,,,Irani Send me your Latest List. .11d,.1crS, 0." THE BEDFORD ELEC. I Name TRICAL & RADIO CO., i Regd. No..156o02 LTD., 22 Campbell Rd., A Address__ ... i BEDFORD. Li 0.1.00.....1.....1....4.1..116.1.16...... 00.11.4....0...... 14.1.0,.../.11WISSIO..".....1 A.W. Olkaa.S.A. mama1 164,) 533 "CUTTING OUT NEEDLE SCRATCH"ever, we. fall very rapidly down to the (Continued from page 523) normal curve indicated by the dotted line, sense of the word, since all that is happen-after which the frequencies are cut off more or less uniformly to an increasing extent. FIXEDing is the gradual diminution of the output It will be seen that the effect of this 4 in a manner somewhat similar to that 4 resonance has sharpened up the cut-off very 4 indicated in Fig. i. 4 CONDENSERS An improved form offiltercan beconsiderably. It is still not a really sharp obtained by connecting a resistance incut-off, and such a result can only be obtained by:the use of a number of sections 4 Fully Guaranteed ! series with the condenser. This acts as a Have been tested by Faraday House potentiometer arrangement. At the lowerall made up in a similar manner. ' This, 4 Laboratories and arefullyguaranteed frequencies the reactance of the condensercombined with the proper design of the for capacity insulation and voltage tests. is very high compared with the resistance,value of inductance and capacity to accen- Capacity is clearly engraved on the case tuate the resonance effect, enables particu- 4 as shown. TRIX Fixed Condensers have and therefore nearly all the voltage is 4 real ruby mica insulation and copper foil developed across the condenser.At thelarly sharp cut-off filters to be made up. The reader, however, who wishes to experi- 4 built into Trixite moulded cases. Fara- higher frequencies the reactance of the 4 day House report is given with every con- ment can do this by using an arrangement denser sold.Complete with terminals condenser becomes small, and we move 1 rapidly down the potentiometer, as it were,such as that shown in Fig. 4, using high - and soldering tags. frequency chokes for the inductances and .4 so reducing the output. The form of cut-off The TRIX HY, CHOKE obtained with an arrangement of this sortvarious values of condenser until he obtains .4-4 the required cut-off. It is preferable to use -4 The TRIX H.F. Choke is eminently suitable for is illustrated in Fig. 2.It will be seen to use in every type of receiver.Works evenly over have some form of cut-off point, althoughchokes having a really high inductance, -4 a waveband of5 metres to 3,000metres. Can be such as the Lewcos, Bulgin SG type, or the 4 mounted either horizontally or vertically. this is not very great. Price 5/6 each Burne-Jones. With such chokes a capacity of the order of .005 will, be found to give 1 PRICEA Better System the required results. from A better form of filter is that shown in Fig. 4, where we have an inductance in series with a condenser. This again acts as WIRELESS IN PARLIAMENT I./"a sort of potentiometer. At low frequencies (From Our Own Correspondent) each the inductance has little effect, while the MAJOR OWEN asked whether there condenser presents a high impedance, so was any provision in the regulations that most of the voltage isdevelopedrelating to wireless licences whereby totally across the condenser. At high frequencies,incapacitated persons might be excused the Manufacturers : on the other hand, the inductance has apayment of the annual licence. ERIC J. LEVER (TRIX) LTD., large effect, while the condenser has only Lord Wolmer said the answer was in the 8/9 Clerkenwell Green, London, E.C.1 Phone :Clerkenwell 3014/5 a small impedance and most of the voltagenegative. The only wireless licences issued is developed across the inductance. As ourfree of charge were those issued to blind output is connected across the condenser,persons under the provisions of the Wireless THE ONLY UNIVERSALLY we are only left with quite a small amountTelegraphy (Blind Persons Facilities) Act, STANDARDISEDCOMPONENT and we obtain a cut-off. 1926. IN RADIO_Li; The cut-offhere, however,isaccen- Type "B"6(1.1 tuated because a resonance occurs at some We are to hear a Kennedy -Fraser recital Type " M " transitional point between the two effectsfrom all Scottish Stations on April rr. This 44d just considered. Without this .resonancewill be given from two studios. From Glas- Type "R" the cut-off would be somewhat as indicated 3d. -gow the Station Orchestra will play a by the dotted line in Fig. 5. The resonanceselection of the Kennedy -Fraser melodies TyPe"8" occurs, however, at a point where theand the Rev. Kenneth MacLeod will tell curve is beginning to fall away, and thissome of the island legends on which the has the effect of increasing the voltage onsongs are based.From the Edinburgh the output. The voltage developed acrossstudio,Mrs.Kennedy -Fraser,Margaret the condenser, indeed, may even exceedKennedy, and Patuffa Kennedy -Fraser, that on the input, so that not only do wewill give a recital of the songs.Some of

TERMINALS maintain the curve level, but we actuallyMiss Patuffa Kennedy-Fraser's songs will Belling Lee List.. (jneenSWaY WOr4S. cause it to rise slightly. As soon as thisbe sung to her own accompaniment on an Ponilun's End.Mdx. artificial boosting effect has finished, how -old Celtic harp. The completion of the new big broad- 111111112111111121 111111111111111111111111111111111111111111111:casting station in Prague, which is being PRICE THE LATEST SCIENTIFIC installed by the Standard Electric Com- =17/6 DEVELOPMENT IN CONE UNITS pany, will be in operation during the course British made Specially Recommended for the Linen Diaphragm of the year. 48g1 Moving Coil im reproduction The Lassophone Triangle Fork Reed Balanced Armature Cone Unitisatriumph ofBritishinventive geniusant work- In the Royal. Gazette, which is the official .= for any set manship. Reproduces all frequencies equal to a moving coil speaker on publication of the Spanish Gbvernment, mg any set. ems Guaranteed not to overload on the most powerful set. appears an order approving the project put a Specialty recommendel for use with The Linen Diaphragm forward by the Radio Society of Argentine a and i5unequalled by any other unit. a The LASSOPHONE for the establishment of wireless com- a municationbetweenSpainandthe aoms Fork Reed Balanced Armature Cone Unit a Manufactured by Argentine. .1= H. H. LASSMAN, F.R.A., A.M.I.R.E. Picture transmissions on the Fultograph a (Dept. A.W.), 429 Barking Road, East Ham, E.6 system are shortly to be carried out daily smi ememmillewilivellelemmoolicumaby the Prague and Bratislava broadcasting M.B. stations. APRIL 6, 1929 539 efisoieurWtrdez, RADIO -EQUIPPED TRAINS DOMINION " GRAWOR " MOST of the long-distance expresses in Comes to your aid ! Austria are now equipped with receiv- THE " SECTORPHONE " ing apparatus for the reception of broadcast LOUD - SPEAKER CHASSIS concerts, special carriages being reserved embodying the famous for passengers desirous of passing away the " Grawor " DoubleMagnet time with these entertainments. A charge Unit and an entirely new and of roughly sixpence per hour over and Patented design of diaphragm above the railway fareismade; and has set a new standard in statistics show that the service has rapidly reproduction. gained in popularity; whereas from Septem- Every independent test has proved ber to December, 1926, io,000 travellers these statements. had paid fees to listen to the concerts, fir The " Grawor" Unit fitted has a 1928 the figure had increased to loo,000. powerful double' Magnetic System. It has been proved that some 70 per cent. Balanced armature of the passengers carried on trains at some movement. Perfect time during the journey now visit the Reed adjustment. radio compartment.Generally speaking, Carries full loads only transmissions from the Vienna station without a vestige of BROWNIE are nowproducing 2,000 distortion. are tuned in, but as occasions arise, so Dominion Vernier Dials a day. SECTORPHONE' listeners are given opportunities of hearing That is why it is possible to offer this Chassiswith many of the German entertainments.In high-gradedialatthewonderful "GRAWOR" Unit order to avoid any possible interference price of 3/6. mounted ready for the carriages containing both the receiving The mechanism is aspecial non - immediate u s e . backlash designwitha reduction Size, 12 %in. square sets and headphones are lighted by gas ratio which makes fine tuning easy (see illustration). only. Arrangements are now being made without becoming tedious. Price. With Double Magnet Unit 53/ - with neighbouring countries to provide a Obtainable from all wireless dealers With Single Magnet Unit 48/ - similar service on international trains. in beautifully finished plain black or lovely grained mahogany bakelite. Obtainable from all Dealers, or direct. The San Francisco studio of the National HENRY JOSEPH, Broadcasting Company (U.S.A.) reports 11 Red Lion Square, London, W.C.1 that its musical library, consisting of some Sole Agent and Licensee for Great Britain 0,000 pieces of music, is valued at about ,65,000 ESS. 1:LSON Sc. WORKS LONDON, N.W. MINIIMMMEMM, TUNEWELL RADIO with our DUAL RANGE COILS pRODUCTS and CHOKES CLARION THREE LISSEN THREE THE NEW THREE SPRING COSSOR THREE WAVECHANGE SWITCH and all other Here is another line at a popular price. Made with the same precision and finish as all Bulgin Products which have made them world famous. Will SCREEN -GRID fit all panels from paper thickness metal to a" Ebonite by the unique method of design.Highly polished CIRCUIT COILS knob, plating, and fitted with 3 terminals. at 21/- per pair SEND FOR OUR FREE 56 PAGE CATALOGUE & WIRELESS .11.1 'JU:7 L Range 20012000 A. F. BULGIN & CO., 9-10-11 CURSITOR ST., CHANCERY LANE, LONDON, E.C.4 H.F. Choke for Panel Mount- ing, Valve Holder Massive All PurposeBase, or6 - pin 5/9 each. Base Mounting. Amateur Wireless HANDBOOKS each 2/6 net. MULLARD DUAL The Shielded Four -elec- The Practical " Super -het " COILS trode Valve. Book. 7/9 & Loud -speaker Crystal Sets. Perfect Broadcast Reception. 10/6 Wireless -controlled Mechan- ism for Amateurs. 'The Short-wave Handbook. TWO - PIN The Wireless Man's Work- The Practical Wireless Data COILS shop. Book. all types TIIEBOOK OF THE NEUTRODYNE, by J. H. Reyner, B.Sc. (Hotrs.), A.M.I.E.E. Price 1/6 net, or post free for 1,9 from Illustr,tion of our Cossor Circuit Dual 1/6 Aerial Coil, showing base mounting and switch control. Of all Newsagents and Booksellers or by pmt, 3d. 54 STATION RD., extra, from Cassell& Co., La Belle Saavage, E.C.4. TURNER & CO LONDON : N.I I so UNIV.V.,0411.CIIMI004041=1,0M041.0411M00.4041M104MEN,EMPNIAM.Ii0101.0.11.0.11.1MO.G.I.F0.11111.1141M APRIL 6, 1929 ti mating' Wireless 540 04)00.0*****.00.4+41104440.04,4:404.*.*Itto.0400040.4041.43.044).4).0404).0 FULL-SIZE BLUEPRINTS FOR EVERY REQUIREMENT

Each blueprint shows the position of each component and every wire, and makes construction a simple matter.Copies of " Amateur Wireless" and of " Wireless Magazine" containing descriptions of all these sets can be obtained at 4d. and Is. 3d. respectively, post free.Index letters "A.W." refer to" Amateur Wireless" sets and" W.M." toWireless Magazine" sets.

All -wave Mains Three (HF, D, Trans, Rectifier SEVEN -VALVE SETS CRYSTAL SETS -Price 1/6) All these 6d. each, post free. All-purpose Short-wave Three (D, RC, Trans) AAWW:447 is. 6d. each, post free. Screen -grid Q -Coil Three (HF, D, Trans)..AWiso N.uper Set AW64 Simpladyne (Super -het) WM22 ,`Best -yet" Set .. AW154 New -style Mains Three (HF, D, Trans-Price AW165 1/6) .. AW151 rezo Crystal Receiver All -Round Three ( RC, Trans) AWi55 WMz5 Two -programme Set James Special Three(HF, D, Trans).. AWs56 PORTABLE SETS WM50 Centre -tap Set .. All Britain Three (HF, D, Trans) .. AW158 4 Bantam Three (D, RC, Trans) .. AWI6o Holiday 3 (D, 2 Trans).. AW3 z 5- ONE -VALVE SETS Hartley, Dual -range Three (D, RC Trans) .. AWi66 Table Grand 4 (HF, D, 211C) AW93 1116 Listener's Three (HF, D, Trans) Price 4c1. free Attaché Portable 2 (HF, D) AW96 AWto5 sl- All these is. each, post free. with copy of "A.W." . .. AW169 Daventry Portable (D, Trans).. Binowave Three (D, RC, Trans) .. AW172 Daventty Loud -speaker Portable (211i, rHartley DX AW27 Clarion Three (SG, D, Trans) .. .. AW 75 D, RC, Trans). . . AWt o7 /6 AW7i Economy One 5929 Favourite Three (D, RC. Trans) .. AW:79 Town and Country .(HF, 'D, RC, 'Trans)AWt t 1/6 AW78 Loud -speaker Special Five -guinea 3 (HF, D, Trans).. . WM29 House and Garden (SG, HF, D, RC, Ultra -sensitive Hartley One AW1o3 Trans).. AW116 z/6 Super Reinartz One .. AW1 27 Mains Three-valver (D, zLF) WM34 AWt4o Tuned -anode from the Mains (HF, D, LF) WM43 "Best -yet" Portable (SG, D, z Trans) ..AW136 1/6 Beginners' One-valver Metropolitan (D, zLF) .. WM413 House Portable (SG, D, RC, Trans)..AWs 68 /6 Long-range Hartley .. WM54 WM6 Everyday (D, 2 Trans).. WM5z Arcadian Portable with Linen -diaphragm Reflexed One for the Loud -speaker Music Charmer (D, R.C, Trans) WM6o Loud -speaker (half -scale) AW177 s/6 WMt 16 Special One Britannia (0, RC; Trans) WM67 Springtime 2 (D, Trans) WMiz WMI27 Reinartz One .. Pole -to -Pole Short -waver (D, RC, Trans) ..WM89 Countryside 4 (HF, D, z Trans) 1/6 Glee -singer Three (D, 2 RC).. WM92 Chummy 4 (HF, D, RC, Trans) WMSo 1/6 TWO -VALVE SETS Aladdin Three (HF, D, LF) . WM95 Chummy 4 (with modification fc r LS and Inceptor Three (SG, D, Pentode) Price is. 3d. H .. WM8oa1/6 - All these Is. each, post free. with copy of "W.M." WMto5Pilgrim Portable (D, Trans) .. WM94 1/6 ;Wide -World Short-wave (D, Trans) .. AWiI All -wave Screened -grid Three (HF, D, Pentode WMs so Empire Short-wave AWz8 Gramophone Three (D, 2RC) WM115 WM' t7 AM PLI FIERS Next Step z (D, Trans) .. AW34 Standard Coil Three (HF, D, trans) Centre -tap 2 (D, Trans) .. AW42 Festival Three (D, 2 LF-Dual Imp) .. WM118 All these Is. each, post free. Rover 2 (HF, D) AW53 Wide -world Short -waver (SG, D, Trans) .. WMtzo General-purpose_ 2 (D, Trans).. AW55 New Year Three (SG, D, Pentod..e) WMiz3wm:24 Utility (RC, Trans) AW68 3o/-2 (D, Trans) AW6 The Q3 (D, RC, Trans) .. Screened -grid HF Unit .: AW75 ,Trapped Reinartz (D, Trans).. AW92 Lodestone Three (HF, D, Trans) .. WIV1129 One -valve LF Unit .. AW97 "Q" 2 (D, Trans) AW99 Simple Screen Three (HF, D, Trans) .. WM131 Super -power Push-pull.. AW86 Long Distance Two (HF, b,) . AW1 so Dynamic Three (SG, D, Trans) WMI36 Hook on Short-wave .. AWio4 Three Two (D, Trans). AWis2 Purity Amplifier.. AWioS DX Headphone Two (HF, D) AWI34 FOUR -VALVE SETS Add-on Distance -getter.. .. AWL 17 ;Ace of Twos (D, Pentode) .. AW143 Screened -grid HF Amplifier .. AWi38 Home Two (D, Trans). _ AWs46 "A.W." Gramophone Amplifier (3RC) .. AWi6z ,Chapman Reinartz Two (D, Trans -4d. with All these Is. 6d. each, post free. Searcher Unit (HF) . AW176 copy of "A.W.") . AM's 48 "Q" 4 (HF, D, RC) _ _ . AW98 Gramo-radio Amplifier (2 v.) . WM72 AW157 Super -power Unit (a v.) . WMso3 'Globe DX Two (SG, D.j Explorer Four (HF, D, RC, Trans) .. . ANVizo East to West Short-wave Two (D, Trans) ..AW159 Summertime Searcher (2HF, D, Trans) .. Signal Booster (HF Unit) WMt28

Beginner's Two (D. Trans.) .. AWs7i Overseas Shortwaver (HF, D, 2 Trans) AW133 Auditrol Amplifier . WM132 'Auto Two (D, Trans) AW174 Ranger Four (SG, D, RC, Trans) .. .. AWI45 British Broadcast z (D, Trans) WM44 Facility Four (HF, D, 2 RC-Q-coil) WM56 MISCELLANEOUS ,Two -programme 2 (D, Trans).. Broadcast Picture Four (HF, D, 2RC) .. ' .. AW163 Q -coil 2 (D, Trans) WM62 The Orchestra Four (D, RC, Push-pull) .. AWi67 WM69 Adaptor for Short-wave Super 6 AW6ra -16 Crusader (D, Trans) .. All Europe Four (2FIF, D, Trans) .. .. AWI73 AW73 sl- Flat -dweller's 2 (HF, D) WM76 Revelation (HF, D, RC, Trans) H.T. from A.C. Mains.. Two-Daventry Two (D, Trans) WM97 "A.W." Moving -coil Loud -speaker ..AW97 ii- Simplicity (HF, D, 2 Trans) .. . WM49 H.T. Eliminator for A.C. (r)o v. output)AWroz Tetrode Short-wave Two (SG, D) WM99 Astral (HF, D, 2 RC) ...... w_ M53 WMio7 L.T. and H.T. Mains Unit (DC) AW123 51- Key -to -the -Ether Two (D, Pentode) Trapped 3-4 (D, zRC Paralleled) - ..WM6t AWi3t -/6 Meteor Two (D, Trans) . WM114 Gramo Radio 4 (D, RC, 2 Trans Push -Pull)..WM7o Knife-edge Wavetrap WM135 All -metal Eliminator for 1-.; T... AWt35 1)- Clipper Two (D. Trans) .. Q-coi[4 (HF, Trans, RC)- .. ..WM71 Duplex:diaphragm Loud -speak& ..AWI42 if- Screened grid 4 (HF, D, zRC) .. .. .WM77 Power -plus Loud -speaker AW149 THREE -VALVE SETS Five -pounder Four (HF, D, RC, Trans) .. WM91 Linen -diaphragm Loud -speakerwith Frame -aerial Four (HF, 0, 2RC) .. . wWm,0)M8,5 Baffle AWt 52 I-T- All these Is. each, post free. Touchstone (HF, D, RC, Trans) .. ... Pedestal Cone Loud -speaker AW:64 Short-wave (D, RC Trans) AW5o Reyner's Furzehill Four (SG, D, 2 Trans) .. WWIJI2 Listener's Speaker, price 4d. with copy of Ether -searcher (D, RC, Trans) AW52 Economy Screen -grid Four (SG, D, RC, Trans) WMII3 AW 170 -14 Standard (D, 2 Trans) AW56 Binowave Four (SG, D, RC, Trans) .. .. WM119 Arcadian Linen -diaphragm Loud -speaker Hartley DX (D, RC, Trans) AW63 Standard -coil Four (HF, D, zRC) .. .. WMI22 (full-size) AW177a5/- Broadcast 3 (D, RC, Trans) . AW76 Dominions Four (zSG, D, Trans) .. .. WMI34D.C. Unit (H.T.) AWt78 if- Selectus 3 (HF, D, Trans) AW8i The Drum Major (HF, D, RC, Trans) .. .. WIVI137 Wavetrap WM64 if -- Q -coil 3 (D, RC Trans) AM+ Portable Cone Loud -speaker ..WM73 th Clarion 3 (D, z Trans) AW88 "Junior" Moving -coil Loud -speaker ..WM8t 1/ - Miniature Hartley Three AW vas FIVE -VALVE SETS Universal Short-wave Adaptor WM8z 1/ - Summer -time DX Three (HF, D, Trans) ..AW io6 Linen -diaphragm Loud -speaker WM90 I/ - .Three -valve Mains Receiver (HF, r), Trans) ..AWto9 Valveless A.C. Power Unit for L.T. WMioo-/6 British Station Three (HF, D, Trans) .. AW122 All these Is. 6d. each, post free. Valveless A.C. Power Unitior H.T. ., WM tot -16 AW25 Optional Two -three (D, zLF) AWs24 Individual 5 (2HF, D z Trans) Simple Cone .. . ,WMist if -- "Simpler Wireless" Mains Three (D, 2"LF) AW126 School 5 (HF, D, zRC) AW85 Buzzer Wavemeter . ..WM121-/6 Simplicity Screen -grid Three (HF, D, Trans)AVV132 "Q" Gang -control Five (zHF, D, z Traria) AWx6i James H.T. Unit for A.C. Mains ..WM125 if -

"Proms" Three (D,RC) ; AWr37 Exhibition 5 (zHF, D, RC, Trans) .. WM33 Lodestone Loud -speaker WM' 26's /- Adaptable Three (D, z Trans).. AW139- Phoenix (2HF, D, 2LF) WM4z James H.T. Unit for D.C. Mains ..WMI33 11 - New -style Baffle Three (D, RC, Push-pull- 1928 Five (zHF, D, 2 Trans).. ..WM46 Price 1/6) .. AWt4t All -the -world 5 (zHF, D,.211C) ..WM63 Cataract 5 (HF, D, RC, Push-pull) VVM9 Empire Five (zSG, D, RC, Trans) WM796 Send, preferably, a postal order Fidelity Five (HF, D, RC) .. (stamps over sixpence in value unacceptable) to ALL SIX -VALVE SETS BLUEPRINTS ls. 6d. each, post free. Amateur Wireless Short-wave Super -6 (Super -het, Trans) AW67 Adaptor for above (see miscellaneous list) AW67a OF SETS ARE Nomad (zHF, D, RC, Push-pull, Trans) ..WM31 Blueprint Dept., 58/61 Connoisseur's Six (zHF, D, RC, Push-pull) WM88 -E.C.4 FULL-SIZE Eagle Six (3HF, D, RC, Trans) WM106 Fetter Lane +11.,41,+#.41...+411.041.+4100,04.0.444.....****41.60.440000.0.060.00. APRIL 6, 1929 541 enuauirWintit: ROADCAST TELEPHONY BRITAIN'S FAVOURITE (Broadcasting stations classified by country and in order of wavelengths) THREE DE LUXE Kilo-Station and Power Kilo-Station and Power Kilo.Station and Power OUR -KIT OF SPECIFIED PARTS as advocated Metres cyclesCall An (Kw.) Metres cycles Call Sign (Kw.) Metres cycles Call Sign (Kw.) in this issue of " AM:" GREAT BRITAIN 291.3 2,030Radio Lyons 1.5 ITALY Supplied for . 82/ - 25.5311,752Chelmsford 301 997Bordeaux (PTT)0.5 277 2,084Turin 0.5 or 15/4 down and co monthly payments of 8/-. (5SW) 15.0 305 982Agen 0.3 333 900Naples (Napoli)1.5 This includes a full-size blue -print. Cabinet in Oak, 243.9 1,230Newcastle (5NO) 1.0 105.6 981Marseilles (PTT) 0.5 387 775Genoa 3.0 17/6 extra. MULLARD, MARCONI, or COSSOR 258.6 .2,260 *Leeds (2LS) 0.13 322 930Vitus (Paris) 2.0 443.8 676Rome (Roma) 3.0 Valves for this set 33/6 extra. SPECIFIED KIT, 270.3 2,209 *Sheffield (6LF)0.13 536 892Petit Parisien 0.5 456 658Bolzano 0.3 COMPLETE withMULLARD valves,OAK 288.5 1,040 *Bournemouth 351 846.7 Algiers (PTT)._2.0 604.2 595Milan 7.0 Cabinet, reo-Volt EVER -READY Battery, (313M)1.0 370 811Radio LL, Paris LO EXIDE Accumulator,and AMPLION CONE 288.5 1,040 *Bradford (2LS)0.13 382.2 785Toulouse (Radio) 9.0 JUGO-SLAVIA SPEAKER -Cash Price £8 18s. 6d. or can be 288.5 .7,o4o *Edinburgh 400 749Mont de Marsan 0.1 308.3 973Zagreb (Agram) 1.25 supplied on our gradual payment system, 33/ - (2EH) 0.35 914 724Radio Maroc 582 515Ljubljana 5.0 down and ro payments of16/6. 288.5 1,040 *Hull (6KH) 0.2 (Rabat)2.0 427 TorGrenoble (PTT)1.5 LATVIA 288.5 1,540 *Dundee (2DE) 0.13 529 567Riga The H.IL KIT FOR 294.1 2,02o *Liverpool (6LV) 0.13 430 697Radio Flandre 2.0 ','FAVOURITE THREE" 294.1 1,020 *Stoke-on-Trent Lille 0.25 LITHUANIA Containing only first-class ALL -BRITISH parts, (5ST) 0.13 448 C68 Paris (Ecole 2,020 748.4Kovno 15.0 and will give first-class results.Complete with 294.1 1,020 *Swansea (5SX)0.13 Sup., PTT) 0.7 473 635.1 Lyons (PTT) 5.0 paneldrilled,baseboard wireand 60/- 302.6 991.1 Belfast (2BE) 1.0 NORWAY screws 311 964Aberdeen (2BD) .1.0. 1,487 201 Eiffel Tower 8.0 242 1,240Rjukan 1.0 or 11;6 down and 5 payments of 11/6. 323 928Cardiff (5WA) 1.0 1,748 .r7rRadio Paris 8.0 297 1,010Notodden 0.7 358.9 838- London (2L0) 2.0 365 820Bergen 1.0 DID YOU BUILD THE " CLARION 378 793Manchester GERMANY 387 775Fredriksstad (2ZY) 1.0 219 2,370Flensburg 1.5 387 775Aalesund 1.0 THREE" 2 - 303 757 *Plymouth (5PY) 0.13 240 1,250Nfirnberg 4.0 459 653Porsgrund 1.0 PROVED A TREMENDOUS SUCCESS. 401 748.3 Glasgow (5SC) 1.0 250 x,aoo Kiel 0.7 496 604Oslo ...... 1.5 Our customers report wonderful success from this 482 622Daventry Ex. 250 1,200Cassel 0.7 500 600Tromso 1.0 set.Twenty stations obtained on loud -speaker. 4.0 (5GB) 25.0 263.2 1,140Cologne 560 350Hamar...... 0.7 OUR KIT OF PARTS, cash price, £4 4s. 1,562.5 z52 (Daventry 267.8 1,120Muenster 1.5 (5XX) 25.0 272.7 1,100Kaiserslautern 1.5 POLAND or 15/- down and 5 payments of 15/-.Complete 314 95,5 kit with MULLARD Valves, £6 9s. 6d., or 18/ - * Relay stations. tRelays 2L0. 280.4 r,o7oKonigsberg 4.0 Cracow 1.5 283 1,o6r.Berlin (E) 0.7 336 890 . Posen 1.5 down and, so payments of 12/-.Oak Cabinet, AUSTRIA 283 r,o6rStettin... 0.7 416 72x Rattowitz 10.0 14 X 7 in., 14/6 extra. 248 1,209Linz 0.5 283 z,o6rMagdeburg 0.7 456 658Wilno 1.5 CLARION THREE Coils (Tunewell) 21/- per pair. 277.8 1,080Salzburg (under 317.5945Dresden 0.75 1,395 215Warsaw 10.0 TITAN COILS-BULGIN, WEARITE, 15/- each. construction)0.5 321.2 937Breslau 4.0 DUNHAM Tuners, 9/6; switch for same, 2/9. 326.4 gigGleiwitz 6.0 354.2 847Graz 0.5 317.5PORTUGALLisbon CTIAA (Wed. 456 694Klagenfurt 0.5 329.7 9roBremen 0.75 945 GRADUAL PAYMENTS 456 t94Innsbruck 0.5 361.9 829Leipzig 4.0 and Sat.: 10 -midnight) Any Kits, Speakers, Valves, Batteries, etc., supplied 510 577Vienna 20.0 374.1 8o2Stuttgart 4.0 on terms. All transactions are financed by ourselves, ROUMANIA and that alone will assure you of courteous treatment. 891.6 766Hamburg 4.0 896.3 757Bucharest 4.0 BELGIUM 421.3 712Frankfurt 4.0 Write us, state your requirements; it gives us pleasure tosupply you on our GRADUAL PAYMENT 0.25 455.9654Danzig 0.75 RUSSIA 220 2,360Chatelineau 458 654Aachen 0.75 SYSTEM. 250 1,200Schaerbeek- 825 363.5Moscow (PTT) 25.0 Brussels 0.5 462.2 649Langenberg 25.0 925 323Homel ...... 2.5 Carriage Paid onallcashorders. 975.4 631Berlin 4.0 275 7,4290 Ghent 0.5. 1,000 30oLeningrad ... 20.0 Terms Cash, C.O.D. or Gradual payments as desired. 1,070Liege 0.5 537 559Munich 4.0 1,44 208Moscow 30.0 280 566 53oAugsburg 0.5 312 91 o Arlon 0.25 1,635 278Kharkov 15.0 H. f3 B. RADIO CO. 10.0 565 530Hanover 0.7 612 e85Brussels 577 520Freiburg 0.7 SPAIN 34 BEAK ST., REGENT ST., London, W.I. 1,650 182Zeesen 20.0 277.8 r,o8oBarcelona Ger.: 2834 CZECHO-SLOVAKIA 1,650 18/Norddeich 10.0 (EAJ13)2.0 265 1,130Kosice 2.0 309 97oOviedo (EAJ19)0.5 r93.7 1,004Bratislava 4 0 GRAND DUCHY OF 348 857Barcelona(EAJ1) 3.5 142 873Prague (Praha) 5.0 LUXEMBOURG 370 8orSeville (EAJ5) 0.5 432.3 694Brunn (Brno) 2.4 1,280234.2 Radio Luxembourg 0.25 400 75oRadio Espana LO DENMARK 404 744San Sebastian(A 839 883Copenhagen HOLLAND 81.4 Eindhoven 426.7 703Madrid (EAJ715.0 (Kjobenhavn)p1.0 9,554 456 658Salamanca 1,155 r59Kalundborg 7.5 (PCJ) 25.0 38.8 - Kootwijk (EAJ22) 0.55 ESTHONIA (PCL) 32.0 (Wed. 12.40 G.M.T.) SWEDEN 408 735Royal (Tallinn) 1.3 281 1,149Horby 10.0 337 889 Huizen (until 0.4 5.40 p.m.)5.0 265 1,230Trollhattan FINLAND 833 gooFalun 0.5 371 e00Helsingfors 1,073279.5 Hilversum (ANRO) 5.0 346.8 865Goteborg 0.0 (Helsinki)0 8 438 655Stockholm 1.5 1,504 49 Lahti 20.0 1,152 262 Huizen (after 5.40 p.m. and on 645.5 550Sundsvall FRANCE Sundays) 5.0 770 390Ostersund 2.0 Scheveningen - 1,200 250Boden 2.0 80.75 9,755Agen 0.25 1,152 262 223Motala 30.0 200 9,50oFecamp 0.3 haven 5.0 1,825 211.3 1,420Heziers 0.1 SWITZERLAND 233 2,260Bordeaux(Radio HUNGARY 408 739Berne 1.0 Sud-Ouest) 2.0 548 548Budapest 15.0 489.4 613Zurich 0.6 245 1,224Lille (PTT) 0.8 080 441Lausanne 0.6 252.1 1,190Juan-les-Pins 0.4 ICELAND 760 395Geneva 0.5 253 1,185Montpellier 0,25 333.3 gooReykjavik 10 1,010 297Basle .....0.25 254 1,180Rennes (PTT) 1.0 2552,275Toulouse (PTT) 1.0 IRISH FREE STATE TURKEY VVYVVVYVVVVVVVVVVVVVVVYVVYYVV 268 1,2228 Strasbourg 0.3 2212 1,352Cork (5C K) 1.5 1,232 243Stamboul 5.0 274 1,592Limoges (PTT) 0.5 411 730Dublin(2RN) 1.5 1,840 163Angora 5.0 Do You Want to Know About -? Wireless symbols and contrac- April 13Hip-Hip-Hoo-Radio, arevue.Booksand CHIEF EVENTS lyrics by Graham Squiers: music by Shirley tions? Accumulators? Laws of OF THE WEEK Goodall. A.C. circuits? Current -carrying CARDIFF capacitiesandresistancesof April9 The second concert of the Newport Choral wires? Details of coil windings? LONDON AND DAVENTRY, 5XX Society (31st season). What April 8 Roumanian national programme. TheReinartzcircuit? 9British national programme, a burlesque. MANCHESTER valves touse ? What " blue roThe Cherry Orchard, a comedy by Anton Chekov, arranged by Dulcima Glasby. April 13The Conquering Hero, a play by Allan Monk - glow " means? A vaudeville programme. house, arranged by Victor Smythe.

ixB.B.C. symphony concert, relayed from the These are only representative of Queen's Hall. NEWCASTLE It 13The GlasgowOrpheusSocietyConcert, April 13Alibis, a play by Harold Melvill. the thousands of questions you relayed from the Queen's Hall. GLASGOW can "ask " the DAVENTRY EXPERIMENTAL, 5GB April 13Running commentary on the Scotland v. Edin- April 9The Cherry Orchard, a comedy by Anton burgh Association Football International,Letts'Amateur Wireless Chekov, arranged by Dulcima Glasby. from Hampden Park, relayed to London and Daventry. 1929 Notebook Diary f t toA vaudeville programme. 11 R.B.C. popular orchestral concert, from the People's Palace, BELFAST 1 /9(Post Free) from this office 2/9 ff lz" Requests," an orchestral and vocal pro- April 13A concert by prizewinners intheBelfast" gramme. Musical Competitions (1929). AAAAAAAAAAAAAAAA.AAAA.AAAAAAAILAA QMAW' Wireig5 542 APRIL 6, 1929 SOME BENEFICIAL EF- FECTS OF WHICH YOU WIRELESS & HEALTH MAY NOT BE AWARE EACH fresh scientific discovery plays itsNov, it has been found that in many casesto visit his surgeon so frequently as before. own part directly or indirectly in theof diminished sensitivity, not actual or even That wireless will tend to longevity will health and longevity of the human race.partial deafness, the use of the ear -phonesbe admitted by all I think; one of the most Mention need only be made of the Roentgenwhilelisteningtotransmissionshavetroublesome conditions which a doctor is rays,Finsen's light therapy, the Curiebrightened up and stimulated the .hearingcalled upon to treat is that of persons who discovery of Radium, etc., in order to seeconsiderably.The vibrations received bydeplore the fact that old age is creeping on how far-reaching and beneficial legitimatethe drum of the ear have apparently actedand that the world has no further use for use of such scientific phenomena are inas a stimulant with- satisfactory results,them. such diseasesas commonly affectthethese being demonstrated when the audit- human anatomy. ory apparatus is put to ordinary use-A New Interest One's thoughts turn naturally to thein other words the patient finds that 11.0 or Many a piteous sight has been noted. sense of hearing when wireless is men-she " hears " better.As we reach middleprior to the wireless age, of people of tioned, for instance, for it is with our audit-life there are few who retain the specialseventy years or over, practically awaiting ory apparatus that we appreciate the trans-sensesatnormality;glassesmay betheir end, with most interest in life gone. missions sent over the ether for our enter-required for reading for example.Tissues One of the neatest sets I have seen for tainment or education.It is remarkableharden, become less elastic-, less sensitive,quite a time was a five-valver constructed how one finds in active practice such a largeand by the, same method as correctiveby a retired clergyman who had decided percentage of adults, say over the age ofglasses are used in mild eye cases, so wethat he was of no further use on this sphere. forty-five or so, who suffer from deficienthave at hand a very pleasant remedy inHere was an old man who did not know the sensitiveness in one or other ear, at timesheadphones and loud -speakers of a milddifference between a hacksaw and a chisel in both; a simple experiment is easily. madecorrective for incipient ear trouble. who had acquired the art of " keeping by those of, or over, the age mentioned if There. is a further advantage in someyoung." they will test the hearing of each earcases as well.One patient complaining It might be said that this old minister alternately with a watch which has aof an oversupply of the natural wax of thewould have found similar benefit from pronounced " tick." ear canal has found a considerable improve-other hobbies. ..thisI question very ment since using a wireless set; in this easemuch, however, for sustained interest in A Help to the Deaf it is likely that the offending wax is notwireless construction and use seems to be The chances are that by testing by placingpermitted to "ball up" as it did previously,illimitable, more especially as the date is the watch near the ear, then graduallythe vibrations received preventing this.not far distant when the other important drawing it away, it will be noticed that oneAnyhow there is no other reason one cansense. . seeing moving objects willbe organ is more sensitive than the other.think' of, for the patient does not requirebrought into play. Doc PAGE. wwwwwwwwwwwww HELLESEN of thenew DRY BATTERIES `74wsule LE E. 661.1.134G- DON'T SPECULATE andSocket "Alittle flutter now and then is relished by the wisest This eagerly awaited product incorporates several unique advantages. men," but I cannot und1r- High -voltage and loty-voltage plugs standwhypeopleshould FAME are a different size- a safety device wish to gamble where H.T. ISNNFRAY which prevents any possibilityof. GRIPPED valves being burnt out. The whole Batteriesareconct product is beautifully finished ahl HellesenBatteries are so insulated throughout.Made by the consistent,so reliable and COPPER makers of the famous Belting -Lee (RIPPED terminals.Price 9d. (Panel portion they bring you in so great a 3c1. each; Rex portion Ed. each). return in ampere -hours for Ask for the new Belling -Lee Wander PRICES the money you spend, that- CURET WEL Plug-the firstinsulatedWander Standard Capacity as Ridleyremarked-they LERCIDED Ilug on the market to be engraved. " Wiray "9 -voltGrid Choice of14engravings, Bias Type ... 2/- justify the gilt edge which PLUG WELL " Wirin " 60 -volt H.T. appears round the container. SHROUDED Type ... 10/8 " Wirup " 99 -volt HT. Next time you need a new Pray. Pa.. Type .. 18/. H.T. Battery ask your dealer NAME Wisol " 108 -volt H.T. for a Hellesen, remembering Type ...20/. NO SOLDERING Tsoble Capacity. that the Triple capacity bat- " Kolin " 60 -volt teries do not even cost twice Type ... 1-9/. as much as the correspond- " Kolup " 99 -volt H.T ing Standard capacities ; an Type 32/3 investment, not a speculation. /HURT'S 3-fELLESEN DRY BATTERIES INSTRUMENTS POLYMET4 MICA &.PAPER CONDENSERS BELLING LEE HAND & CYCLE LAMPS, TORCHES, ETC

Advt. of BELLING & LEE, Ltd., Queensway Works, Ponders End, Middlesex A. Ii. HUNT,LTD., CROYDON, SURREY APRIL 6, 1929 543 entateurWireie INCREASING YOUR RANGE WITH the coming of summer, H.F. TRADERS amplificationismorethanever K. RAYMOND DON'T FORGET OUR important in order to get winter -time range27 & 28a, LISLE ST., LONDON, W.C.2 Come to LEICESTER SQUARE TUBE. from a set; and one of the best ways ofThis address is at the back of Daly'sWHOLESALE getting to know about H.F. amplification Theatre. Phones: Gerrard 4637 and 2821 HOURS OF EVERY DAY 9 to8 DEPT. is to read "The Book of the Neutrodyne," SATURDAY 9 to9 by J. H. Reyner, B.Sc. (Hons.), A.M.I.E.E. BUSINESS SUN. MORN. 11 to 1 QUICK OPEN : (Cassell & Co., Ltd.). This is not a technic- SERVICE 9 to 8 EVERY DAY ally worded text book, but is in every wayCLARION THREEALL LINES 9 to 9 Saturdays understandable by the man in the street; KIT OF PARTS (" A.W." 9-3-29) STOCKED. 11 to 1 Sunday Morn, and in the hundred -and -twenty -odd pages Anyothernanoenser,H.F. Choke, or L.F. Transformer. WE STOCK, WHOLESALEBulgin All -wave Tuner 15/6 supplied byaddingbalance. ANDRETAIL BritishGeneralAll - of the book are contained some most help- 2 Polar .0005, No.3,at5/9. .0001Reaction 4/-.BULGIN FERRANTI wave Tuner ...18/6 2 Dual rangeC.T.Coils,withReaction(Tunewell),EKCO AMI'LION Wates'3in1Test ful hints and information on neutralised Anode, 10/6; Aerial, 10/6.3 Lotus or Formo V.H. at 1/3.CELESTION IGRANIC Meters ... 8/6 H.F. amplification, making the whole well Formodenser, "J," Dubilier 1 mfd.,2/6..01 Fixed.LISSEN M.P.A. Lotus Cond., .0005... 5/9 T.C.C.,1/9.3-meg. Lissen or Edison Bell,1/,S.O. B.F.EDISWAN COSSOR Lotus Cond., .0003...5/6 worth the price of is. 6d. Choke,I'eto - Scott, 5/.. H.F.Choke,Lissen,5/6.SIX -SIXTY COLVERN Colvern Master 3 Star L.F. Transformer, R.I. & Varley, 15/-.Ebonite Strips.CYLDON Melt -IMAM Dual Coil...... 17/6 14x7 Ebonite Panel.Screen, 81)(6.8EngravedTerminals.WATMEL LEWCOS Wearite Dual Wave HOW H.T. IS MADE ! Push-pull Switch, Flex, Plugs, 16-g. Wire,2 S.M.Dials. POLAR CLIMAX Tuner ... 15/- Post Free ORMOND J.B. Wearite Standard Load- RECENTLY an AMATEUR WIRELESS The Lot 70/- PYE POLYMET ing Coil ... 7/6 representative had the opportunity .0002Fixed and Series Clip 16 extra. T.C.G. DUBILIER Dubilier B.C. Cond., The above Kit with VALVES 2v. LOTUS W.B. friction control, .0005 of seeing a novel film which has been pro- AMERICAN TYPE S.G. 22'6.D10/6.P 12/6.PHILIPS MULLARD and .0003, each...12/ - CABINET, POLISHED OAK (Mallard or Six -Sixty) and all standard components,Ditto, thumb control 15/6 duced for Siemens Bros. & Co., Ltd., of COLOUR, BASEBOARD, valves,etc. Ever -Ready,Telsen Radio grand ...12/6 Woolwich, showing the whole process of H.T. 120v., L.T. 2v. 45. Siemens,Exide Batteries.Telsen Ace... 8/6 CLEARTRON Brown H.Q. Speaker... 6t71- manufacturing H.T. batteries.It really £4 .17. 6 S.G., 2v. 12/6 Amplion A.C.2,39/6

Carriage 4/- up to 200 miles,C.T.15, L.F. or H.F.. 41. model for... 21/- is most interesting to see the deal of care 6/- over (U.K.), pass. train. TUNEWELLM.P.A. Popular Plaque ALL PREVIOUS OFFERS CANCELLED. Speaker ... 29/6 expended in the manufacture of small dry Massive All Pur- Ormond Turn -table for cells, and it is to be noted that a represen- TUNEWELL pose H.F. Choke 59 Portables... 6/- tative of Messrs. Siemens will be pleased to CLEARTRON Dual Range Coil 7,9 show the film at any wireless club meeting. CLARION Master 3 Star - 3/11 BULLPHONE GRAMO UNITS, 15/ - Club secretaries should communicate direct VALVES COILS 5XX do. - 5/9 ANODE or AERIAL Globe DX pr. - 21/-CONE do. 15/ - to Messrs. Siemens. l'creen Grid 2v. 12/6 B. Picture 4 pr.- 21/ -WONDER L.F., 10/6 UsualTypes 4/- each 10/6 each Dual Range for ex- A WORLD TIME INDICATOR R.C. and Power 6/-ea. Push-pull panel mtg. isting Cossor, ORMOND VEANY DX enthusiasts will have found Lissen Sets, each 10,6 latest 5 -valve HANDSOME OAK POLISHEDNo alteration needed. -VI the need for some form of chi rt orSPEAKER CABINETS 13 x 13 x 6 PORTABLES indicator which will show them the exact Post LISSEN PARTS £ 1 5 time at any part of the world corresponding 12/111/3 ALWAYS IN STOCK. TRADE SUPPLIED. to Greenwich time. This demand has'now BLUE TRIOTRON140p. CATALOGUE been supplied by Messrs. J. H. Willis & Co., SPOT25 ILLUSTRATED Iiisivich Road, Norwich, who have pro-. 661i (101) VALVES ALL LATEST duced a world time indicator. The chart, 4 POLE ADJUSTABLEH.F., Det., R.C., 5/2 each ; COMPONENTS BALANCED ARMATURE,Power, 6/9.2-v. or 4-v.Price 1/-, which is credited which is of stiff board, carries a rotatable GENUINE66K. Post 4d.(10/- Free). on first 10/- order. central disc which' is simply turned round OR Special Price for and the times can be read off direct without DARIO RADIO -SETS OF PARTS CABINET MICRO any calculation. 2-v. or 4-v. G.P. 5,'6 over 25/- given BLUESPOT Super Power .. .. 7/6 where possible. Super H.F., 2-v. or 4-v. 7/6Kindly forwardlistof Cannot guarantee exact12" CONE Post 3d. each. goods required (or call). Another Russian broadcasting station pattern of front panel, has been installed at Turuchansk on the but all good designs. Carr. Pd. The Lot.BRITAIN'S FAVOURITE 3 borders of the Polar circle. Placed, as it is (DE LUXE) A.W. 6/4;29 in the wild and dreary Tundra of theTRIOTRON UNITOrmond Leg .0005, 61.; .00025, 56; 7 -ohm panel Rheo Northern Jenissei district, it is the only4 -Pole Balanced WithCabinetas2 6 ; 3 Benjamin V.H., 416; Formodenser Type "J," 011shown above and 12"2/-; .0003 and series clip,2/-; 2-meg. Leak,1/-; means of communication the trappers andArmature Eest Tunewell All purpose H.F. Choke, 5/9; R.C.C. Unit Carr. paid.17/6 Cone 27/6Free. Dubilier, 7/-; 50,000 ohm wire wound, 5/6; 2-mfd. the explorers have with the outside world. Mansbridge, 3/6 ; L.F. Transformer R.I. Varley 15/- ; (add balance any other). Push-pull &witch, 1'3, com- EK CO H.T. GENUINE plete with Panel Brackets, Indicator, G.B. Clips, "Amateur Wireless and Radiovision." Price 6 -pin Base, Connecting Wire, Thin Flex, 7 Engraved Threepence. Published on Thursdays and bear- UNIT 3F12BLUE SPOTTerminals, EBONITE Panel 16 x 8, and 16 x 9 Base- ing the date of Saturday immediately following. For use with S.G. Valves. 66 K (101) board. A.C. with Valve and The above lot63/° Cash with order. Post free to any part of the world : 3 months, Royalty ...78/6 25/ - Carriage and Packing, 2,'6 4s. 6d.; 6 months, 8s. 9d.; 12 months, 17s. 6d. D.C.3F12 37/6 Adjustable 4 Pole Postal Orders, Post Office Orders, or Cheques D.C. 3F12 S.G. 39/6 Balanced Armature. SIEMENS, Ever Ready, LISSEN, Hellesen should be made payable to" Bernard Jones OSRAM MUSIC MAGNET H.T. Batteries.Large stocks. Publications, Ltd." MULLARD, SIX - Kit ofParts andValves Goods despatched Cash on Delivery General Correspondence is to be brief and ES :12 :6 SIXTY. MARCONI,C.O.D. (pay postman) at slightly increased written on one side of the paper only.All BOOKLET FREE. OSRAM, COSSOR, charge. sketches and drawings to be on separate sheets. TITAN COILS EDISWAN VALVES Contributions arealways welcome,willbe 15/-TRADE SUPPLIED &W. SPECIAL COUPON (64) promptly considered, and if used will be paid for. Lewcos Q Coils Queries should be addressed to the Editor, and S.G. VALVESQ.A. 15/-Q.A.M. 21/-FOR EVERY 30/-you spend retail the conditions printed at the head of " Our MULLARD 22/6 Q.A.R.21/..Q.S.P. 21 /.YOU CAN buy ONE of the following for SIX -SIXTY 22/6 Q.S.G. 21/. information Bureau" should be closely observed. COSSOR 2216 LOTUS Q.A. 1 5/. 3d.each extra (on this Coupon) Communications should be addressed, accord- OSRAM22/6 Q.S.P. 21/. Q.3 Star 151.IPF. Choke, Silk Loud -Speaker Cord, 9 -volt Grid ing to their nature, to The Editor, The Adver- Bias, Pair Panel Brackets, .0001 Reaction, 2 mfd. tisement Manager, or the Publisher, "Amateur Mansbridge, 100 ft. Insulated Aerial, 4- or 5 -way LEADING HOUSE for KITS OF PARTSBattery Leads, 30 ft. Coloured Connecting Wire. Wireless," 58-61 Fetter Lane, London, E.C.4. See weekly Advts. all wireless papers. :e!tieforlittnie.3 544 1 PAUL 6, 1929

THE LARGEST -WIRELESS . on wavelengths varying toe4eeti7i0bo PREPAID ADVERTISEMENTS. and 2o,00p metres. Advertisementsunderthisheadarecharged STATION IN ASIA. THREEPENCE PER WORD, minimum charge The aerial is' supported on eight -masts THREE SHILLINGS. JAPAN,JAPAN, with its recently opened high -each 825 ft. high, Which, in view of the DEPOSITSYSTEM risks of earthquakes in that country, have As the Publishers cannot accept responsibility for the power telegraphy station at Nagoya, bona tidesof advertisersinthispublication,they have now possesses the largest long -wave trans-been specially constructed for the purpose. introduceda system of deposit which itis recommended should be adopted by readers when dealing with persons mitter in the world. The gigantic electricalEquipped with the latest automatic tele- withwhom they are unacquainted. Iti3here explained. Intending purchasers should forward to the Publishers plant is capable of putting 550,000 milli -graph transmitters, this new giant station the amount ofthe purchase money of the article advertised. amps in the aerial. can deal with wireless traffic at the rate of This will be acknowledged to both the Depositor and the Vcndor, whose names and addresses must necessarily be The Nagoya transmitter and the receiv-one hundred and twenty words per minute. given.The deposit isretained until advice is received ol thecompletion of the purchase, or of the article having ing station at Yokkaichi keep Japan in tcen returned to and accepted by the Vendor. In addition constant touch with all corners of the globe to the amount of the Deposit, a Fee of 6d. for sums of 61 WORTH WRITING FOR and under, and is. for amounts in excess ofEl, to cover postage, etc., must bo remitted at the same time.In cases of personsnot resident within t:1-3 United Kingdom, double AMOST attractive illustrated booklet, Ices arecharged. The Rolls-Royce of Radio describing Eloden loud -speakers of The amount of the Deposit and Fee must be remitted by is the 50 Range PostalOrder orRegisteredLetter(Cheque; cannot bo various types, can be obtained from Messrs. vocepted), addressed to F. L., Lesingham, 53 Victoria Street, West- "AMATELlItWIRELESS," ADVERT ISFIIENT DEPARTMENT, DIX-ONEMETER 58/61, FETTER LANE, LONDON, E.C.4. The High-grade Radio Tester minster, S.W.I. PATENTS,-Trade Starke, Advice' Handbook free.-S. T. King, Regd. Low Price High Value Worth ILO Pentodes and screen -gridvalvesare /Vent Agent, 146 Queen Victoria 'Street, London. fullydescribed,togetherwithsome EARN MONEY ATHOME. You can earn money at home in whole Instrument in Case 55, - or spare time writing Show -Cards for us. No canvassing. we train Yon helpful operating notes, in a new booklet by poet by our new simple method and furnlah the Outfit free. We Multipliers each 6'6 'imply both men and women with steady work at home, no matter issued by the Edison Swan Electric Co., a here you live, and pay yon cash for all work completed each week, Complete Radio Outfit under our legal guarantee.Fnll particulars and Booklet free.Write E.4 : 10 : 0 Ltd., 123-5 Queen Victoria Street, E.C.I. zt once or call. Show Card Service, Hitchin. LOUD -SPEAKERS.R.K. Cones fitted B.T.H. Mov- Copies can be obtained on application EBORITIt PANELS-Special offerat greatly reduced prices in ing Coil, 100 surplus at only 76 each.Marconi blahoganite and Polished Black. guaranteed .12 x 3, 117;12 x 6, 3/2: Moving Coil Magnet Pots, 6 volt, 20 -.GRAMO. (meniionink :AMATEUR WIRELESS), and will 12 x 8, 4/2;14 x 7, 4/:';18 X 7, 5/6:16 x 5/8: 'M TO, 6/4; post free. MOTORS. Genuine Panatrope Gramophone Motors, 1 rade invited. Bannister and Fltton,27 Milurow Read, Rochdale. run direct off mains supply, fitted Turntable, etc. be found very useful when operating Edis- Few only,37'6each. Worth £410s. CHOKES. win pentodes and screen -grid valves. FREE: INVENTOR'S GUIDE ON PATENTS.T.A.A., 253(A'. Round's Output L.F. Chokes by Marconi, for feed Gray's Inn Road, London, W.C.1. from power amplifiers.Latest model, 756. CON- DENSERS. New Sterling, 2 mfd., genuine Mansbridge WIRELESS OPERATING APPOINTMENTS:fees payab'e after qua'ity Condensers to 940 volts, at reduced price of 2 10 only. inqticar boarding students.) Morse Lasses. Wire esti School, Manor Capacity Meters £8 ; Wheatstone Recorders £12 ; AN interesting experiment recently took Gardens, Honoway, N.7. Multi -Micro Galvos. 60/- ; Res. Boxes 17;6 ; place in Moscow when a short-wave Hydrometers 1!6 ; Relays 6/6 ; Remote Switches 15'- ; 12 in.SparkCoils£10. Weston601.;Micro telephony transmitter was taken up by an Ammeters for Grid bias testing, 35/- only. engineer in an ordinary gas balloon. Com- Fine! Edition of our Surplus Bargain, in Radio and Electrical Send stamped addres,ed enreroye for large munication with the earth was easily estab'- CLIX (1.4 ready. sale lest.SAVES RADIO USERS POUNDS THE PIN WITH li-theclevenat heights exceeding 4,00o MANY PURPOSES metres (13,000 feet). Two-way communi- The ideal fitment for all types of ELECTRADIX RADIOS, home -constructed coils,forwall - 218, Upper Thames St., cation was maintained continuously for plugsandconnectorsgenerally. Blackfriars Stn, Underground Rly, City 0191 The resilient principal on which the two days and two nights on a wavelength plug is constructed, guarantees perfect contact,The shank is provided of43 metres, the transmissions being with two nuts and allows connections to be made with ease.The WET H.T. BATTERIES simultaneouslypickedup byOdessa, whole is nickel -plated. Solve all H.T. troubles CLIX COIL PIN SELF -CHARGING, SILENT, ECONOMICAL Vladivostock, Minsk, and Leningrad. CENTRE JARS (wand) 21" li" sL 113 doz. PARALLEL 2d. Zincs, New Type, 10.1. doz. SACS 1/2 doz. Senator Marconi and Mr. David Sarnoff, Sample do,(18 volts), complete withbands each. From all Dealers. and electrolyte 411, post9d.Sampleunit, head of the Radio Corporation of America, Write for Clis Catalogue. 6d.Illustrated booklet free.Bargain list tree. AMPLIFIERS, 30/- 3 -VALVE SET, £5. have been elected to the board of directors LECTRO LINX LTD. A. TAYLOR, 57 Studley Rd., of the Gramophone Co., Ltd. (His Master's 254 Vauxhall Bridge Rd., London, S.W.1 Stockwell, London. Voice). W. D. Terrell, chief of the U.S. Radio 22 in. LINEN SPEAKERDivision of the Department of Commerce, ALL COMPONENTS,comprising- in his annual report to the Federal Radio SATISFACTION Wood Lengths (drilled), 4 61" x r Post Free. Commission states that ,during the year Brass Stretching Screws (far super- Cash with for to Meccano strip), 8 Wing Nuts 8/6 order. ending December, 5928, 9,093 inspections and Quick Service and Washers, Linen, Dope, Screws, With 66K "Blue etc., Extension Rod with Sleeve.Spot" Unit 41/6 were made of the radio installations on We give you BOTH! Rubber2/-extra American and foreign vessels clearing P.S. Our large Stocks and extensive range include Sets and Speaker made up complete, less unit and baffle 36i - Accessories of every des:I-lotion, and which enables us ARCADIAN PORTABLE ports. These inspections showed 235 cases to give almost immediate delivery of anyth.ng you may Linen Speaker Kit (or made up) supplied. of defective apparatus and lack of proper r quire for Cash or on the. EASIEST DEFERRED TERMS. Send us a list of your requirements and let LOWNE ELECTRIC CLOCK CO.equipment or personnel. 113 quote you by retu n.Lists Free. Cirainaphones and Records on Easy Palmeri, Tenn* Boone. St., Lee, London, S.E.13.- 'Phone Lee Green or43 ' V V '. Buy "THEALL EUROPE THREE" Let "Amateur Wireless Q Abook ofclearinstructionsfor6d. WIRELESS STORES makingthisefficient3 -valve Set net. WALLINGTON - . - SURREY From abookseller, or PITMAN'S,Parker St., W.C.2 solve your problems

SUPPLY UNITS FOR A.C. MAINS ' HIGH TENSION LOW TENSION Incorporating Westinghouse Metal For Multi. -Valve Receivere Rectifier. Guaranteed silent:No valves. Noexpensive 2,4 or 6 volts .at an amp. replacements. No renewals: No attention computing from uaranteed Complete Units from 47/6 7 DAYS' FREE TRIAL AGAINST CASH. 47/6 THE TULSEMERE-MANIG. CO., Dalton Street, West Norwood, S.E.27. 'Phone: Streatham 673s:

COUPON mutat:-Wirele5 Available until Saturday, APRIL 13th, 1929 APRIL 6, 1929 111 mauls- Wirek

DUBILIER Buildyour FIXED Set with CONDENSERS Lotus MICA Components CONDENSERS Types 610 and 620 .00005 to .0009 - 2/6 .00 I to .006- 3/- .007 to .009- 3:6 The best of circuits Type B 775 cannotproducea .0I- 4/- - 8/6 good set if you use

.5 ' 37/6 cheap shoddy com- IntermediateCapacitiesatpro- ponents.Ask your portionate prices. dealer for Lotus.

Every Lotus Com- ponent is a well con- Type 610 Type 620 structed, reliable unit built to do its partic- PAPER ular job, accurately DIELECTRIC and without fail for a long life. CONDENSERS Don't forget- get Allcapacities from Lotus Condensers Lotus. .ot upwards. from 5,-. Lotus Dual Wave .otto.1,each 2/- Coil, 16/-, 16.6, ZU, Lotus Valve .125 and .2,each 2/3 Holders, 1/3. .25and .3, each 2/5 Lotus Remote Control, from 30/ - 4and .5, each 2/6 for 2 rooms. .o, each 2/6 2 .0 ,each 3/6 Other prices on application. DUBILIER for DURABILITY "TOREADOR SCREEN -GRID FOUR" This set incorporates the latest dm,elopments in Receiver I I design-full constructional details free on request. From all RadiG Dealers. DUMMER 1E00E1DM CONDENSERS coistoositsis Made by Garnett, Whiteley and Co., Ltd. If unobtainable from your dealer, Advt. of Dubil ter Condenser Co., (192 5)Ltd. , Ducon Works, Victoria Lotus Works, Broadgreen Rd., Liverpool write direct to us giving his name 3:;IC;44" and address. W." 44444 1/1.1 MARA Road, N. Acton, London,' W.3

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Intervalve nobettet -Vrequencybnd V atley Low can 1.and V or you theR. `tralls=- Conpling,. than. Line Cony coobistation.StraiglnCapacityproducts tv:Verrninal farrous'Itensive an tb.ese of forraer of dyeass dcrag,- Both canboast le.the01.1tCOVCICboth arapli.bcation ate and line vaaeverldeslt vesearcb,straight by nation shown the 1:tcally as outby cnoles, carried 4j-carnival tests Laboratoryour volurne side the Vaysicalone allthee.. under the ell-sloes of On be theuse possiblywIt'lle rcransforraercolld Couple that coTtdittorts,CaCacity Bi-clARIelt.and noroal the a°farla3quality and out'Resistanceon ID. addbeautydegree wire-wound---resultswhich ina systemof torte parity toreception-day . footla to 4-:rerrninalin realtso V arley used - and is rarely R.1. Favourite The Transformer effici- Line "Britain'stoits Straight De tributeclesign. the -_-_-another andhigh-clas's Three"ency

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u a'foto., lf unobtainable front your dem'er, BBL Advt. of Dubilier Condenser Co., write direct to us giving his nume (1925) Ltd. , Ducon Works, Victoria and address. .LC1 SOO TRAD. 0.44/e Road, N. Acton, London, W.3 232/C Mention of "Amateur Wireless" to Advertisers will Ensure Prompt Attention APRIL, 13, 1929 545 matey Wirtle5

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-C APRIL 13, 1929 No. 357.Vol. XIV,

,5 5 5 5 5 Lr s 5 s 5 5

. 5 and 5 5 5 The Leading Radio Weekly for the Constructor, Listener and Experimenter 5 S .---Editor : BERNARD E. JONES ---= 5 5 § Technical Editor :J. H. REYNER, B.Sc., A.M.LE.E. :: Research Consultant : W. JAMES :: Assistant Editor :H. CORBISHLEY 5 0,,,,,,,,,,,,,,,,,..3,,,,,,,,,,,,,,,,),,,,,,),,,,,,,,,,),....,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,--,..),7,0 That B B C Ban-A Radio Hero-Radio at 103 !-" TalkiesPitare Booming-The Unseen Five Hundred-" Threes,'and " Fourspl

That B.B.C. Ban-There is still much 1 bringing Wagner up to date, and by means 'ado about nothing-namely, the B.B.C. of microphones and loud -speakers "there ban on the announcement of names of dance are brought on the stage the voices of a tunes.It has been suggested, We know, chorus of 500 (sic !) for whom there would that this ban is the result of interested be no room in front, of the footlights." people having used the microphone as a With the unlimited possibilities of electrical means of publicity.However this may be, public address and gramo-radio, what giant we are rather inclined' to agree with a operas Wagner could have produced ! 'correspondent who says that itis not a Wireless and. Weather-So the old 'coincidence that there is more variety in the rumour that wireless causes bad weather is programmes while the ban -is in action ! still afoot ! We have never seen any A Radio Hero-1.'et another wireless statistics to prove the point but here are operator hero. In this case he is R. Osbjorn- some figures from the Royal Meteorological son, the operator of the ill-fated cargo Society, which,if you are aloverof steamer Selje. He remained at his post in statistics, may kill the old rumour once and the sinking vessel, sending out calls for help for all."The average rainfall in England until the generator room was flooded, and requires for its production roughly 330,000 the transmitter went out of action. He then horse power per square mile, night and day went up on deck to find that the other throughout the year.The total horse - members of the crew had gone to the power used by all broadcasting stations in steamer Kaituna (with which the Selje was Gt. Britain and Northern Ireland is under in collision) without realising he was left The City of Glasgow leaving Croydon, with 55 horse -power; the corresponding figure for behind. He managed 'to sound the ship's which it will be in radio communication, on Europe being about .400 horse -power. Any siren just as the vessel sank in shark -infested the first trip of the Air Mail Service to India effect of broadcasting on weather would water. filna of Boris Godounov. If technical develop- -therefore be duetosub -homoeopathic Radio at 103 !-At Chelmsford, Essex,ments keep pace with these giant artisticdoses of less than one in r,,000,000,000 I is what the newspapers call " a wonderfuland commercial forecasts, then there shouldApplying the same arithmetic to domestic young woman"-she celebrated -her io3rdbe a great deal in . " talkies " to interestaffairs one finds that to produce a year's birthday last week !In a recent interviewwireless fans. rain for the tennis court by means of an the good lady, after airing her views on The Unseen Five Hundred-Incident-electric kettle, would cost over L800." We modern girls and short skirts, said that sheally a new use is being found for loud-cannot vouch for these figures, but they has only two interests in life.One is pre-speakers on the stage. At the Chavlotten-sound convincing ! paring for the ' celebration of her1 o4thburg Opera House in Berlin, they are Radio at Brooklands-An "A.W." birthday and the other is listening- cief..ce7)w.3wIce7o.acce7o.acaf.acolt.ace%ne2lf.e0 Correspondent who ,was at Brook - in. We wish her many More years § landsattherecentopening in which to enjoy her hobby. - PRINCIPAL CONTENTS Page the season, had his § §meeting of g, Talkies " are Booming-If § 'Current Topics...... 547 § ardour damped by the rain, but one is to believe what one is told Policing the Ether ...... 548 was cheered to find' the old familiar by film stars themselves, soon no5 Baird Television-Facilities at Last !.. 548 loud -speaker "putting" over gramo. cinema in any civilised country will5 An All -mains.. Two5495 music during intervals. be showing "silent" films. " Talkies" 5 Circuits for You to Try 551 § "Threes " and " Fours " -

will be all the rage. Douglas Fair- § My Wireless Den . . 552 § This week we deal at greater length i

banks and Mary Pickford (his wife) § On Your Wavelength.. .. 555 § withtheup-to-dateversion of i are talking about a giant combina- Wireless Control of Mode':,' .. ..557 "Britain'sFavouriteThree "-a 5 5 tion in which Warner Bros. are to For the Newcomer ..... , ..558 really good " three" -for broadcast take part. Charlie Chaplin has not Without Fear or Favour .. ..'559 5reception. Next week we are to have yet definitely "fallen," but Chalia-§ " Britain's Favourite Three ".. ..560 5an efficient four-valver designed by pine, the: famous singer, is a new- § "A.W." Tests of Apparatus .. ..562 § our Technical Editor, Mr. J. H. corner to the cinema and will prob- §Experiments with Neon Tubes .. ..563- 5 - Rey- ner, witli dual -range, simplicity ably appear in talking films this C Can We Amplify on Short Waves?.. ..566 C of control, and "super" perform - summer.Irfcidentally he has been ' Radiograms ...... 568 ance. InCoto,a"four" worth, offered Lroo,000 to make a talking1:1t,nte'etatocit~.stoatenti.e,von~itafoicaloiter743§'waiting for I el:mien( WiretT 548 APRIL 13, 1929 An Account of Dr. POLICING Reisser's Station THE ETHERin Germany By Dr. ALFRED GRADEKIWITZ an imposing arrayprises a large number of receiving sets for of the most effi-wave ranges of from 12 to 2,000 metres. c ie n twireless These receivers are accurately calibrated receivers, byso that any station can ube identified with means of whichabsolute certainty. any wireless Two lines connected with the preliminary station inGer-amplifier room, at the . Voxhaus head- many or else-quarters of the Berlin broadcasting station where in Europeservefortransmissionandtelephone An interior view of Dr. Reisser's Ether -policing Station orbeyondthecommunication respectively. seas could at a All connections between sets on the one T HAD, of course, been acquainted with themoment's notice, be heard. hand and the switchboard on the other are 1 excellent work done by Dr. Reisser for Apart from superintending what is goinglaidout permanently under thetable the Reichsrundfunk-Gesellschaft (Germanon in the ether, checking, controlling andcarrying the apparatus. Switch panels are Broadcasting Corporation) in policing thepolicing the German stations and comparingprovided at every operator's seat. A 4 -volt ether,superintendingtheactivitiesoftheir performance with the working ofcircuit serves to supply the heating current, German transmitting stations and perform-foreign stations, this laboratory is intendedalternating -current mains supply the anode ing a number of other useful duties.Hisfor the occasional re -transmission of Germancurrent, and H.T. accumulators are also "den" turned out to be the snuggest, mostor foreign broadcasting stations to theavailable. up-to-date, and best equippedwirelesstransmitters of Berlin and stations con- There are in all, four outdoor aerials, laboratory I have yet come across. nected up to Berlin. 4o, 3o, J5, and so metres in length respec- There, all around the walls, could be found The equipment of the laboratory corn -tively, in addition to frame aerials. BAIRD TELEVISION FACILITIES AT LAST! A Letter from the Postmaster -General to the Baird Television Development Co., Ltd. Sir, so far as is practicable without impairingprobably be necessarytoutilise for the The Postmaster -General has consideredthe broadcasting service, for continued andreproduction of vision wavelengths out- the results of the recent television demon-progressive experiments with the Baird ap-side the bands now being used for speech stration, in conjunction with the Britishparatus and he would assent to a stationtroadcasting. These Lands, as you are Broadcasting Corporation, and his techni-of the British Broadcasting Corporationdoubtless aware, are already highly con- cal advisers, and he has reached the follow-being utilised forthis purpose outsidegested and itis important therefore, that ing conclusions which accord generallybroadcasting hours. He understands thatthe Company should press on with ex- with the opinions of those who witnessedthe Corporation would agree in principle toperiments on a much lower band which thedemonstration. The demonstrationthiscourse, provided satisfactory termswillbe notified tothe Company in due showed that the Baird system was capablewere negotiated between the Corporationcourse. on that occasion of producing with suffi-and the Baird Company. In conclusion, it is necessary to empha- cient clearness to be recognised the features It will probably be essential that anysise that in granting facilities for experi- and movements of persons posed for theexperimental demonstrations of televisionmental demonstrations in which the public purpose at the transmitting point.It isshould be accompanied by the broadcastingcan if they so desire take part, neither the not at present practicabletoreproduceof speech and, in consequence, two wave-Postmaster -General nor the British Broad- simultaneously more than perhaps two orlengths and twotransmitters would becasting Corporation accept any responsi- three individuals or to exhibit any scene orrequired. It will not be possible to providebility for the quality of the transmission or performance which cannot be staged withina second transmitter in a suitable localityfor the results obtained.The object of the

a space of a few feet in very close proximitywhich will avoid interference with impor-demonstrations is to afford the Baird Com- to the transmitting apparatus. tant wireless services in Central Londonpany a wider opportunity thanthey at In the Postmaster -General's opinion theuntil the completion of the new station ofpresent possess for developing the possibili- system represents a noteworthy scientificthe British Broadcasting Corporation atties of their system of television and for achievement ; but he does not consider thatBrookmans Park, which is expected to beextending thescope and improving the at the present stage of development tele-ready in July.In the meantime, itisquality of the reproductions. While the, vision could be included in the broadcastingsuggested that the Company should openCompany will not be precluded from selling programmes within the broadcasting hours.negotiations with the Corporation as to theapparatus to anyone who desires to pur- He bases this view not so much upon thefinancial and other arrangements whichchaseit,the purchaser must understand quality of the reproduction which furthermay be necessary, and it would probablythat he buys at his own risk at a time when experiments may be expected to improve,be advantageous to them to enter upon dis-the system has not reached a sufficiently as upon the present limited scope of thecussions of the technical aspects with theadvanced stage to warrant its occupying a objects which can be reproduced. Corporation's Chief Engineer. place in the broadcasting programmes. The Postmaster -Generalis,however, In order to find room for a television (Signed) G. E. P. MURRAY. anxious that facilities should be afforded,serviceinbroadcastinghoursitwillGeneral Post Office March 27, 1929. APRIL 13, 1929 549 Ornate= Wirete-

A No -trouble Receiver for those who have A.C. Mains-Sale and Simple and last until their initialin view, and for ordinary broadcast recep- cost, of a shilling or so, istion a really good two-valver is as much as forgotten ! many folk require. _ This receiver will find a If you glance at the photographs you warm reception from twowill see that the whole receiver is very classes Of AMATEURWLRELESScompact, when the factis taken into readers.First,thereareaccount itisall complete and that no the experienced people whoexternal batteries or accumulators have realise the difficulties whichto be housed. The one lengthy flex lead AYEAR or so ago people used toattend obtaining H.T. and L.T. from A.C.to a convenient lighting plug does the say how nice it would be if bat-mains and in working a two-valver fromtrick ! teriescould be dispensed withalternating current without any humming To beginners the baseboard may seem altogether in wireless Sets, and how theor motor -boating. to present a rather fearsome appearance, scope of radio would be widened if the Second,therearethose programmeand this is perhaps because, in addition to whole business of operating a receiverenthusiasts who do not care very muchthe normal components necessitated by could be reduced simply to the simple jobabout the technical side of their sets, butthe circuit, the baseboard carries the few of tuning -in and switching on and off. who have always wanted Well, since then mains eliminators havesomething which has no been developed, and the lucky possessorsbattery bothers. A large Receiver section of either A.C. or D.C. mains, of any normalnumber in this latter class voltage, can now work their sets directwillpossiblygetthe fio:n the public supply.Thus they canreceiver made up for them dispense with the high-tension batteryby one of their more tech- -a costlyarticle,particularlyifthenical friends. receiver is a large one-the accumulator, Just what this "two" which formerly required laboured journeyswill do isthis.It will to the charging station at all -too -frequentgive ample loud-speake r intervals, and even the grid -bias batterystrengthfromamain if desired. broadcasting station up to about twenty-five miles or High- and Low-tension from sodistant.Atgreater the Mains distances than this it will This set is a "two," entirely self-con-still give satisfactory loud- tained, and takes both H.T. and L.T.speaker strength, but there "juice" from A.C. mains.In this par-will not be that amount Mains section ticular instance the grid bias is obtainedof volume in hand which from an ordinary 9 -volt battery, becauseis . alwaysdictatedby in a receiver of this type the extra corn-purity critics. The receiver section and the mains section are entirely separate plication in order to obtain smooth D.C., There is no reason why, as this picture shows G.B. from A.C. mains is hardly worthif the mains are fairly quiet in working,extra " gadgets " which provide both H.T. whil3.Grid -bias batteries are so cheapheadphones should not be used and quiteand L.T. -- a respectableD.X. Of course, to constructors of AMATEUR reception log obtained..WIRELESS sets, one set can hardly ever Loud -speakerworkingbe more "difficult" to construct than atnormaldistancesanother, because it is child's play to mount fromB.B.C.stationsthe components and just as simple to wire is, however, the " dailythem up with the aid of a combined blue- bread!'ofthistwo-print and wiring diagram.And, while valver, and it has beentalking of blueprints, don't forget that one designed primarily forcan be obtained for this receiver, price is., ,those who want broad-postfree,from AMATEUR WIRELESS, cast programmes with-58-61 Fetter Lane, London, E.C.4.

2Acc2 Co outbattery troubles. Technical readers will be anxious to It, has-been designed asunderstand the working of this all-from- aim atwo-valverbecauseA.C. "two:' and the rather less technical ZAN? 4/11172 quite a large numberenthusiasts must forgive thefollowing =1\2NA-a ofthosewho makebrief description and analysis of the cir- 6.8-cao up thisreceiverwillcuit.They can pass on direct tothey The circuit diagram of the All -Mains Two have to keep economyconstructional details. ITICLUItt APRIL 13, 1929

" AN ALL -MAINS TWO (Continued from preceding page)

Basically, and leaving out the mainsthat the dual -range scopeisobtainedthe plug in the lighting socket the set eliminator part, the set is of the ever -simply by short-circuiting one section ofworks and when you remove it it stops popular "det. and one L.F. (trans.)" type,the winding for the short waves, bothworking If you care to do so, you can and transformer coupling has, of course,sections being in series for the long waves.controlthereceiver by theordinary been employed in order to give a satisfac-There are two tappings on that portion oflighting switch. The current consumption the winding whichisis not worth considering, for it is very small. not short-circuited on The only difference which --thecon- the medium waveband,structor should make when building up and by means of a flexthisset,as distinct from an ordinary connection which makesbattery -operated " two," is to take the contact with either onemost particular care to get the connections or other of the tappingsright first time. Of course, if you are care- the degree of selectivityful to check the wiring over with a full- can beveryeasilysize blueprint, marking off in pencil each controlled. wire as its actual counterpart in the set is A leaky grid detectorchecked as O.K., you can't go wrong. is employed with the For the construction of this "two" you lower end of the gridwill require the following components, and leak taken to a tappingfor the guidance of those who want to on apotentiometermake up the receiver exactly as described winding across the filaments.The reasonit should be explained that in each case Construction for this will be obvious when it is explainedthefirst -mentioned componentisthat is quite Simple that both the valves employed are of theused and illustrated in the original set. tory degree of loud -speaker strength. new A.C. directly -heated type, and it is Semi-Reinartz type reaction is employedthereforeimportanttogetaproper and the tuner is of the dual -range typemedium tapping for the grid leak. with incorporated moving reaction. Aeanti-motor-boating unit is inserted in From the circuit diagram you will seeseries with the primary of the L.F. transformer, and will be found of inestimable 'BLUEPRINT TUNER("W8,454T;"Vf PANEL .9.4' advantage in getting the best out of the MA W/80 ro nnyp la R setwithout any tendency whatsoever A2 towards uncontrolled L.F. oscillation. The 24" unit consists simply of a 20,000 -ohm fixed ThAr a -Az resistance in series with the primary winding of the L.F. transformer and a 2 -micro - farad fixed condenser between this junction point and earth. The Mains Section Now for the mains -supply section.In

BASEBOARD the present set a Marconiphone power 14.rxrx Of transformer (type M) is used and is arranged to provide double -wave rectifica-

0002 tion(inconjunctionwithasuitable 0262 .0002 mfd rectifier valve) for H.T.; a separate wind- Ilme 0/47 ing with a centre tapping, gives the neces- 41 No sary "juice" for lighting the filament of the rectifier, while yet a third winding -and the wiring is no more complicated L.F. CET' 0 0 provides .8 volts of A.C., which is taken than w;th an ordinary receiver 0 05 0 .ji0 lit80 direct to the filament of the receiving 0 VALVE valves. The alternatives are those which have, as /7002 There is really nothing to go wrong, andnear as possible, the same electrical charac- the combination of power transformer,teristics and (in most cases) very similar BIT rectifier valve, and smoothing choke anddimensions. condensers is comparatively cheap (much Ebonite or bakelite panel, 9 in. by 6 in. cheaper in the long run than batteries),(Raymond, Becol, Ebonart, Paxolin). and entirely safe and foolproof. .0005-microfarad variable condenser So far as the operation of the set is con-(Igranic,J.B.,Lissen,Polar, Ormond cerned, the panel carries a .0005 -micro -Burton). farad tuning condenser, the knob of the All -wave tuner (Wearite, type WG2). reaction control with which is mounted Baseboard,13 in.by 9 in.(Pickett, concentricallythe wave -changeswitch,Clarion, Camco). and terminals for aerial, earth, and loud- Three valve holders(Burton,Lissen, speaker. Benjamin, Wearite). C VALVE At the back of the set is a flex connection .0002-microfarad fixed condenser with MA INS TRANS A C MAINS which is taken to any convenient lightinggrid -leak clips (T.C.C. S.P. type, Dubilier, No switching is needed, for thereMullard, Graham-Farish). The wiring diagiam.Blueprint available, point. price 1/ - is no ." juice" to waste. When you insert (Continued on page 576) APRIL 13, 1925 551 CIRCUITS FOR YOU TO TRY 111111111111111111111Inun1I11111111111111111114. From time to time our Technical those who are experimentally in- Editor has described various cir- clined; on this page are two more cuits of particularinterestto ...... which willrepay' investigation IRECEIVED an inquiry a few days agoan L.F. valve or one of the newspecial, arrangement pure and simple, and isa from a reader who was anxious to trydetector valves made by the Mullarddevelopmentofthewell-knowndual - one screen -grid valve. and one ordinaryCompany. The reason for this is that theimpedance system. Dual -impedance coup- H.F. valve in conjunction with "Q " coils.heavy negative grid bias causes consider-ling is a system in which high-tension is He said that he felt that a circuit such asable increase in the resistance of the valve,supplied to the anode through a low -fre- this ought to give him good selectivityand this is liable to affect quality unlessquency choke. The L.F. voltages are by- with comfortable signal strength, passed to the next grid through which' itundoubtedly will do. /2" acouplingwithachoke,it willbeunderstood,theusual Moreover, if the apparatus is fairly 90K well spaced there should be little leak being replaced with a choke. danger of trouble from instability. The values of the coupling con- At any rate, a 'circuit of this denser and choke are so chosen nature is an interesting one to .1". that aresonance,occurs between hook up, and the details given in the two in the bass regions, in Fig. i will Make it clear as to' how consequence of which the ordinary such an arrangement could be tendency of thecurvetofall adopted.The aerial circuit con- away at about zoo cycles is ar- tains one of the latest type of rested, and in place a slight reson- aerial coils, the QAA.This, as;00:05 Fool ance peakisintroduced which readers will remember, -isa' new WIN keeps the curve fairly level down form of tapped aerial coil, which to quite low values of frequency. gives better selectivity and better Such an arrangementsuffers wavelength range than the older 1.(.1" from the disadvantage that no form of QA coil. The only 'differ- step-upisobtained,andthe ence in its use is that the aerial circuit shown in Fig. 2 illustrates is connected to terminal No. 4 1256 QSP a system in which the advantages instead of to terminal No.r, 6 of the dual -impedance coupling are retained together with a step - the same .000r or a pre-set con- Fig. 1.A combination of screen -grid H.F. and ordinaryH.F. denser being used in the aerial valves used in conjunction with a " Q " coil ,up effect. The H.T. supplyto circuit. the valve is fed through a good This circuit feeds the screen -grid valve.arrangements are so made that the actualmake of low -frequency choke, while the This has been placed first in the circuit inresistanceof the valve under working -low -frequency impulses are passed through order to avoid coupling between the laterconditions is approximately that for whichthe coupling condenser on to the primary circuits and the aerial.It is sometimesthe transformer has been designed. of a 6-i transformer. For this purpose a found that alteration of the aerial or its good form of 6-i transformer, such as the capacity has an effect upon the neutralisingA Dual -impedance System Igranic typeJ,should be used. of the ordinary form of H.F. circuit, and Another circuit which is of interest is If the coupling condenser is made of the for this reason the neutralised stage hasthat shown in Fig.2.This is an L.F.order of .05 rnicrofarad we shall obtain a been placed second. Following the screen - resonance between this coupling condenser grid valve is a QSG coil, a screen -grid trans- and the primary inductance in the neigh- former giving rather more selectivity than bourhood of ioo cycles per second. This the tuned -anode arrangement. will result in the bass being very well main- The neutralising stage is placed third tained,perhaps evenslightly, boosted, and feeds an anode -bend detector.It is which will allow for the defects in the becoming an axiom-as, indeed, it should remainder of the amplifying system, in- be-that any receiver employing an appre- cluding the loud -speaker.At the same ciable measure of high -frequency ampli- time, owing to the fact that we have a fication should utilise an anode -bend de- 6-1 transformer, we shall obtain a large tector, because the grid detector overloads step-upsothat the system,although seriously if the signal strength is at all large. apparently a 'little cumbersome at first The L.F.stagesarenot shown.The sight, is one having considerable promise. detector may be followed by a resistance - The arrangement can be used following coupled arrangement or,ifdesired, by a valve having quite a high resistance, transformer -coupled circuit, in which latter Fig. 2.A development of the dual -impedance with a correspondingly high amplification caseit will be preferable to use either system factor. nuitem Wiry] 0, 552 APRIL 13, 1929 EN c2Q=W JAMES WeeklyTips, Constructional For the and Wireless Theoretical- Amateur

Metal-panel Matters tuning.Ordinary mica condensers havefrom the soldering iron will loosen the WHEN a metal front panel is used it isreasonably low losses, however, and maycap of the resistance or grid leak, or even necessary to take steps which will en-be used in this position. disconnect the '`internals" of the component.Grid leaks in particular should sure that only parts which are earthed shallCutting out the " Stray " make contact with the metal and that all be handled carefully. other parts are insulated. Tuning coils having a small stray field are popular just now and, indeed, I haveThat H.T. Spark It is usually not very difficult to arrangefound this type of coil to be practically Many a beginner has felt there was that the various switches and tuning con- perhaps something wrong with the wiring densers shall have the side which makesessential for use in circuits with shielded contact with the panel at earth potential,valves.There are several forms of con-of his newly constructed receiver because but in an endeavour to effect this one orstruction, and a particularly simple one isa small spark is produced by brushing the two weak points may be left.As anshown in Fig. 3. high tension lead across the positive ter- 0 minal of the battery.The spark is quite example I will take the case of a tuned harmless, and is dye to the large condensers anode circuit (Fig. 1). in the receiver charging or discharging. Plates A of the variable condenser are It is not unusual for three or four con- connected to earth and plates B (the fixed densers of one or two microfarads each, to ones) are joined to the anode of the shielded be included in an ordinary three -valve valve. The full voltage of the H.T. battery receiver, and, collectively, they will store is, therefore, across this variable condenser, quite a fair amount of electricity. and the battery would be short circuited Anyone who has connected a 2-microfarad were the plates 4 touch. Fig. 3.Scheme of coil with small stray condenser across an H.T. battery and then This arrangement may correctlybe field placed a screwdriver between the terminals termed a dangerous one, although when a Here, one half of the coil is wound in theof the condenser will be familiar with the good component is employed the chancesreverse direction from the other and thespark created.It is only to be expected of a short-circuit taking place are remote.two halves have an equal number of turns.that when the high-tension wire is drawn Nevertheless, one would feel better satis-The efficiency of such a coil is naturallyacross the terminal of the battery sparks fied with the circuit were a protectingless than that of a coil having a straight-will be prochiced and they may give the condenser included in series (Fig. 2). forward winding and of the same bulk, but this is usually a matter of no great RAWECO/1 Nr+teo 0604 importance. What is important, however, RN0.05; is the distance separating the two halves. It will be clear that if the two parts were PROTECT/YE COIL widely separated the coil would have a ICONDsz,. relatively large stray field which is therefore reduced as the two parts are brought together. In practice a separation of about E li ar/4 -inch is often employed with good results although it should not be thought that such a coil has no stray field.It is certainly small, and would be smaller still were the two parts Wound even closer Fig. 2.A protecting Condenser for Fig. 1 together.There is a practical side to the question, however, and a designer so adjustsnovice quite a surprise until it is realised the various factors that the best of all-to what they are due. 0+ round results are obtained. Fig. 1.A simple circuit for a metal panel A Soldering Tip The safety condenser may have a value There are occasions when, either because NEXT WEEK: of .002-microfarad or more, and it needof lack of space or the need for economy, not necessarily beof the type havingone is tempted to solder connecting wires A FINE mica insulation.If this condenser has tooto anode resistances or grid leaks instead small a capacity the tuning range of theof employing suitable holders.The prac- FOUR-VALVER circuit would be restricted and a poortice of soldering wires is, however, not, condenser would reduce the amplificationalways to be recommended for the reason' By J. H. REYNER and have the effect of broadening thethat unless great care is taken the heat APRIL 13, 1929 553

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THOSE who have a direct -current supply of electricity in the house for lighting, sometimes consider they are not so fortunate as those having an alternating -current supply. Whilst it must be admitted that it is much easier and cheaper to obtain a supply of current for filament circuits, orforbattery charging, from an alternating -currentsource, the user who has access to direct current of 200 volts or more is generally the more fortunateintheeasewith which current for high tension may be secured.

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2 iclv,e4 eie dowt..01.0%%°^1.0."%0 A Wonderful Broadcast haven't already got one, and you can haveentitled to his own opinions about the THE broadcast of the funeral cere-ail the variety that you want. governments of other nations, but it is cer- monies of the late Marshal Foch was, tainly quite out of place to broadcast I think, one of the most impressive wireless Economy in DX Forrealefficiencycombinedwithcriticisms, especially as the B.B.C. is now occasions that we have ever had.One economy in Icana Government department. People something, though, struck me as a very great long-distance work times forget that broadcasting knows no strongly recommend a set of the type thatfrontiers. pity.The commentator was absolutelyI am using now, which contains only three Actually 5GB and 5XX are first-rate, making one see every scene and regularly tuned in by dwellers in countries every incident; but he spoke in. French,valves.The firstis a screen -grid H.F.all over Europe, and criticisms such as and thousands of those who listened inamplifier, the second an anode -bend recti-that referred to must give widespread this country must have been unable on thisfier, and the third a pentode. The totaloffence. account to follow closely what was going on.filament consumption at 4 volts is only .35ampere, whilst the H.T. drainis A Good Selection On such an occasion one would have17 milliamperes. This may seem a good The B.B.C. did us very well indeed in thought that the B.B.C. would have haddeal, but it must be remembered that thethe matter of holiday programmes at its own commentator and have conductedset is used for producing a big volume ofEaster. Those responsible are to be con- its own broadcast of the proceedings. Sosound, and I don't know that you cangratulated on the way in which they far as I can make out, they simply relayedmanage with much less nowadays if youexactly matched the holiday spirit by the the broadcast by Radio -Paris, picking it upwant first-rate quality. choice -of programme items.I am sure by wireless at Keston.I am almost sure I find that the pentode will take morethat the big output of light entertainment, that this was the case, since when I tunedgrid bias than the characteristic curvevariety,- tuneful music, and humour was in Radio -Paris direct I found C.W. inter- appreciated far and wide. ference in the background, and this samewould lead one to expect, which means C.W. was distinctly audible when onethat one can cut down the H.T. current considerably.Normally a pentode with "A Noteworthy Scientific turned to 2LO, 5GB, and 5XX. i5o volts on the plate and screen grid, and Achievement " Try for These given a bias of about 71/2 volts negative, The Postmaster -General is to be con- There are some wonderful stations attakes something over 20 milliamperes togratulated on his excellent summing up of work just now below 30o metres.If youits own cheek. Experiment shows that athe recent official tests carried out between have not a set of coils that will drop downgood deal mofe grid bias can be appliedthe Baird Television Development Co., to the lower portion of the broadcast bandwithout producing any trace of overloadingLtd, and the B.B.C. The purport of his let me counsel you to beg, borrow, buy, oror distortion.. communication to the Baird Company indicates that we can look forward to real make them at once, if not sooner. I am not Another Saving exaggerating in the least when I say that "seeing -in" in a relatively short time. With a three -valve set of this kind oneWith television as an ally, broadcasting Turin, Hoerby (the big Swedish station),saves also in other ways.Screen -grid Cologne, and Nuremberg are receivable on will take on a new interest. valves and pentodes are rather expensive, The other day I read an article in an favourable nights with the quality and, ifbut if the whole set contains only three the set is reasonably, well furnished in the American paper which questioned whether " toobs" there is clearly a big economy inwireless broadcasting would be so effective way of H.F. amplification, all the strengthcomponents. In fact, all that one wants is of the local. So powerful are Turin and ifitwere accompanied by television. Hoerby on good nights that full loud-two pairs of coifs (one for the medium andSumming up the situation, the writer held one for the long waves), two .0005 -micro -that he who travels by the wireless with speaker strength is obtainable with a three -farad variable condensers and one midgets valuer, and if the first valve is of the screen - imagination for his guide may enter into a pair of H.F. chokes, three valve holders,those realms of gold which are closed to grid kind you probably won't have anya good low -frequency transformer, an out- need to use reaction. Other stations that those who,seeingall,blindly seek a put transformer, the usual fixed condensers,certainty. can be quite marvellous below 30o metresand an on -and -off switch. In addition to are Flensburg,Kaiserslautern, Limoges,these, a volume control is also desirable, Doubly Girded and Cork. Taking the broadcast band as afor the huge amplification available is often I am afraid, however, that the arguments whole, the number of quality stations nowconsiderably more than one needs.Theput forward were far from convincing. receivable is wonderfully big. pentode is a delightful valve to use, since,Imagination is a wonderful asset to the -and Some Others owing to its enormous amplifying powers,individual when applied in the right direc- In addition to those mentioned I findquite a small applied grid swing producestion, but to use that as an excuse for dis- a big output in the plate circuit. It is per-countingtelevisioniscertainly wholly that- real alternative programmes-that is, wrong. To the amateur this new science those providing music that can be listenedfectly stable and gives a dead quiet background. opens up what may be regarded as a virgin to with genuine pleasure-are obtainable field of investigation, and for that reason from Huizen (especially when he is using An Error -alone we shall welcome its appearance. the long waves), Radio -Paris, Kalundborg, I was very sorry to find the B.B.C.Of late, I have been making a careful study Motala,Hilversum,Budapest,Vienna,allowing the talk recently given on foreignof the problems involved and find that Brussels,Langenberg, Frankfurt, Stutt-affairs to include certain rather scathingonce the elementary principles are thor- gart, and Barcelona.I don't mean thatremarks about the policy of a very dis-oughly understood "seeing by wireless" is you will hear every one of these stationstinguished man who is the leader of one ofreally only slightly more complicated than on any night of the week, but you will cer-the great allied nations. "No politics " issound reception. tainly find in normal circumstances thatsupposed to be the rule of the B.B.C., and you have half a dozen or more first-rateexcept that our own domestic affairs may "Listening " With Your Eyes! foreign transmissions from which to choose.be dealt with at election time this rule Have you ever seen speech or music? Fit a good high -frequency stage, if youshould be strictly adhered to. Everyone isNo, I am not taking flights into the realms moleur Wireko 556 APRIL 13, 1929

S. On Your Wavelength !(continued) 41 of fancy, but am perfectly serious. Myscheme, as thereby the light flashes arecut out the needle scratch. But I aip afraid thoughts over the week -end had beenseen in their proper place, and not actuallythattherearetoo many mechanical centred round that very absorbing scienceas a sequence. That is why the minimumgramophones in use for the gramephone which has been so much in the public eyenumber of complete picture scans is usuallycompanies to do anything like this. of late, to whit television, and I was won-given as fifteen per second, corresponding dering how long we should have to waitto a disc speed of 90o revolutions per Sound Films before regular transmissions took place, sominute. Images viewed under these condi- The boom in talking pictures has resulted that it would then be in the public eye intions are really excellent. in a steady flow of engineers and programme more senses than one. I therefore turned builders from the B.B.C. to the film studios. on my favourite set (perhaps one of these Needle Scratch R. E. Jeffrey, the B.B.C.'s chief dramatic days I shall let you into the secret as to The general use of electric gramophoneproducer, has moved his tent to Elstree, which one this is), and having tuned in apick-upshascreatedtwogreatnewquickly followed by K. V. Wright, "0.C. fairlystrongsignalIsubstitutedan"schools of thought." One huge section ofNoises," and about half a dozen engineers: ordinary neon lamp, just a simple beehivepick-up users is in favour of the abolitionAll these people have been absorbed by pattern, for the loud -speaker. of the irritating background noise causedone producing concern only !Meanwhile, You should try this for yourself, as theby needle scratch. The other section, thethere is keen competition for the services previously audible signals now becomeminority movement, agrees with all theseof some of the leading B.B.C. engineers in visible, inasmuch as you can see theadmirable sentiments, but expresses theboth sound film and gramophone recording flickerings of the lamp in place of hearingview that any electrical or mechanicalstudios. the vibrations of the diaphragm. Whereas" damping "introduced forcutting out Fieldless Coils and Reaction in this instance the flickerings were due toneedle scratch must inevitably reduce the In many sets nowadays astatic coils are passages of music interspersed with speech,strength of high notes, harmonics, andused to prevent interaction effects and to I knew that if I had been able to tune insibilants of speech. The "minority move-minimise eddy current losses where screen- the characteristic television note, the lampment" resigns itself to the awful presenceing is employed. A difficulty sometimes flickerings would then have been repro-of needle scratch, rejoicing in the morepresents itself when the grid coil of the ducing the reflected light from the objecteven response of their gear toall thedetector valve is of this kind and it is being televised.Actually, this providesmusical frequencies. desired to make use of reaction.The the gradations of light and shade that Cutting it Out trouble is, of course, that one half of the enable us to distinguish form, and all that coil is wound in one direction and one in remains is to arrange the series of light Naturally, the decision as to whetherthe other. The reaction coil tends, there- flashes over a surface or area correspondingyou will cut out needle scratch or notfore, to ginger up one half of the coil and to that occupied by the object we desiredepends on the type of pick-up you use andto do just the opposite to the other. I have to see. its particular resonances in relation to thecome across several cases where friends band of frequencies carrying* the scratch.who had made their own coils were very, A Glowing Plate for a Canvas The use of a fairly "blunt" filter circuitmuch puzzled by failure to obtain proper Put into more familiar language, this iswhich will shunt frequencies of the orderreaction effects. Investigation showed that the same as saying that a picture must beof 6,000 cycles is the most effective weaponthe end of the grid coil remote from the formed- out of the succession of light andforcutting down thescratch withoutreaction coil had been wound clockwise shade in just the same way as the artistinjuring the tone values too much. Butand theother end anti -clockwise,the forms his picture by a succession of brushthe design of such a circuit is tricky, andreaction .coil itself being wound clockwise. touches on a canvas. In actual teleVisionthe capacities of the condensers employed,If the usual plate and grid connections are practice this is effected at the receiver byetc., will vary according to the type ofmade, the reaction coil then exercises a employing a scanning disc having the samepick-up used and other factors. The easiestreverse effect upon the end of the grid coil number of holes and running in syn-way is to shunt a condenser in series withto which it is coupled and rather queer chronism with the disc at the transmitter.a variable resistance across the pick-upresults occur. The rule is always to wind What we may regard as the canvas is theleads,respectivevaluesbeingaboutthe reaction coil in the same direction as glowing plate of the neon lamp, it being.t microfarad and o-5,000 ohms. Variationthat of the grid coil to which it is nearest. borne in mind, of course, that the actualof the resistance will then alter the amountIf this is done and capacity control is used neon lamp is not like those we use as nightof "damping" on the needle scratch asa short series of experiments will serve to lights, but has a comparatively large, flat,required. determine the position for the reaction coil rectangular -shaped positive plate.Now, Another Remedy which gives the optimum degree of coupling. when the first hole of the transmitter disc explores a line across the object and lets Personally, I have used neither filter nor An Unexpected Emergency the reflected beams of light fall in succession" integration" (shunt condenser) for some Doubtless I had the sympathy of readers upon the "photo -electric microphone" sotime in connection with my own pick-up.last week when I described how I was "let the receiver disc has a hole which exploresI don't buy any but the best records anddown" by the burning out of an anode a line across the glowing plate of the lamp,endeavour to reproduce them as well asresistance just when I had promised- a and it is seen bright in one spot and darkpossible, neglecting the question of needlespecial concert to some musical high- in another as it flickers. scratch. The blare of the brass and thebrows. I told you how I used a moving -coil high harmonics of the violin, as well asmilliammeter in the plate circuit, in place Creating the Form speech sibilants, come out very well andof the resistance. Well, I must crave still With perfect synchronism between theI am satisfied. Any kind of filter circuit isfurther sympathy-this time for a slip of transmitter and receiver discs the successionbound to cut these down; and I'd soonerthe pen !Of course, I meant to say that I of lines build up an image identical in lighthave the scratch than that !If the gramo-used a voltmeter, and not a milliammeter and shade to the original form, the spreadphone companies made their records within place of the defective and now defunct of the light impulses over a surface creatinga terrific resonance on musical notes aroundanode resistance.Itiscertainly a tip this form. Naturally, this process must be6,000 cycles, then one could employ aworth remembering, for most enthusiasts effected at sufficient speed to prevent thefilter on the reproducer to diminish thishave a high -resistance voltmeter. eye from dwelling on the mechanics of theresonance, which would at the same time THERMION. APRIL 13. 1929 557 Cmaw:Wu-Q-1T THE WIRELESS CONTROL OF MODELS By MAJOR RAYMOND PHILLIPS 'Part Two- THE RECEIVING GEAR

r - 1-1Elast article dealt with the con -the circuits of the receiver are so arranged 1struction of a simple "spark" trans-that a morse key can if desired be used with The Complete Receiving Gear mitter arranged to function each timethe transmitter. Before giving construc- selected words are spoken into a specialtionaldetailsof thespecialreceivingenamelled copper instrument wire to a microphone. As there may be enthusiastsapparatus, it will be well briefly to referresistance of too ohms gives excellent who would like to possess a radio trans-to various types of model electric locomc-results. A pneumatic magnetically -operated tives suitable for wireless control.Manydashpot will have to be made specially. mitter fitted with a special microphone, and The device shown by Fig. 3 functions per- morse key, the latter can be inserted in themodel electric locomotives are fitted with primary circuit of the small spark coil aspermanent -magnet type electric motor.fectly, and is fairly simple to make. An shown in Fig. i. When using the morse keyThis only involves the necessity of reversingordinary wooden block (such as is used for it is advisable (for some experiments) tothe flow of electric current to the "con-mounting electric light switches) gin. by disconnect the microphone circuit, other -ductor," and " outer " rails of a model3 in. will provide a base, and the electro- railway in order to cause a model locomo-magnet shoskrn should have cores r 1/2 in. 0 long by % in. diameter, and the bobbins SPRRK CRP tive to run forwards, or backwards, as desired. It sounds like a fairly simplebe wound with No. 25 -gauge enamelled operation, but unfortunately it means intro-copper wire. ducing slight complications in a selector, The armatureofthe electro-magnet or distant -control switch fitted in receiving apparatus. SPRRI( 60/4 NORSE Sequence Control ;TY For simplicity of control the better plan MITCH is to have a model electric locomotive (as 4tRallArr shown in Fig. fitted with " sequence" re- RIWYGEMINCT versing mechanism.This involves switching electric current "on " and "off." The Fig. 1.Circuit for key control of transmitter reversing mechanism fitted to such a model wise there would be a risk of signals beinglocomotive functions in "sequence," so transmitted when not required. that each time electric current is switched Such a method is useful where a numberon to a model railway the locomotive will of controls have to be effected in "run forwards, or backwards in sequence. and where it is necessary quickly to passAs the mechanism acts very rapidly, it is not Fig. 3.The pneumatic " dashpat " over contacts on a selector drum whicha difficult matter to cause the model to may not at the time be required.Forrun in the same direction on two successiveshould be made of soft iron, 6,in. long by instance, the writer often found it necessaryoccasions if desired, as it is only necessaryr in. wide by -116- in. thick, and at one end when manoeuvring his well-known wire-to switch electric current "on," "off," and(which should be bent at right angles) there less controlled airship quickly to pass a"on" again quickly. This type of locomo-should be fitted a piece of vulcanised fibre tive is also fitted with a lockingI% in. square by It in. thick. Two screw- lever, so that the running positionthreaded holes should be made in the fibre can be fixed if desired. to accommodate two % in. No. 6B.A. brass The construction of special re-screws, the latter to form contacts.The ceiving apparatus suitable for usetwo spring contacts shown in Fig. 3 should with the microphone transmitterbe made of No. 26 gauge hard brass sheet, will now be described. The follow-each contact being % in., wide. The main ing components (some of whichcontact should be 3in. long. The shorter can be purchased "ready-made")one (de-coherer contact) should be 3 in. long. Fig. 2.Photograph showing under -carriage of will be required :coherer,de- model locomotive coherer, relay, special selector, two (To be continued) ordinaryelectric -lightswitches series of contacts in order to select circuits(5 -amp.), pneumatic dashpot device, eight connected with the different electric motors,large terminals, and about four yards of so that steering and general control could flexible electric -light wire. tRI MOLES rapidly be effected. The coherer can be purchased ready- e made. A de-coherer simply comprises the Alternative Use --4-- --f-- -t- movement of a 3 -in. electric bell. A suitable SLOT -w.r 701 It will be necessary to construct specialrelay can be purchased from almost any receiving apparatus for use with the micro-dealer in wireless apparatus, but an old -(1)- phone transmitter already described, butG.P.O. type rewound with No. 36 -gauge Fig. 4.Base for Selector entaitur wt 558 APRIL 13, 1929 ...... _., ...... _...... __- ...... _ I th ill LOW-FREQ 111 ill For the Newcomer to Wireless:TRANSFORUENCYMERS Iii WOULD you mindclearing up -' smaller the inductance of that winding.primary when a normal currentis

mattersaboutlow -frequency - I think -I see what you are driving at.,passing I can give you a good rule of

transformers ?I was told the other clayIt comes to this; the bigger the step-upthumb. that they can give perfect reproduction,ratio the smaller must be the inductance What is that?

1111 but in a book that I have just beenof the primary. The minimum inductance value for 111 reading, I find that they must always Exactly, and this means that yougood resultsisfivetimes as many 111

111 lead to distortion. cannot use atransfornier with a bighenries as there are thousands of ohms 111 When was your book published? step-up to couple a high- or even ain the valve impedance. That is to say, Three or four years ago. medium -impedance valve to the nextif the rectifier has an impedance of Iii Then the writer was quite correct, forone, 20,000 ohms you want a transformer lit at that time even the best transformers I don't quite follow that. with 5 by go or ioo-henry inductance to were a long way from perfect. If there's not to be a suppression offollow it.Supposing that you want to And can we obtain real quality fromcertain notes the impedance of thecouple note-mag. number one to note- them to -day ? primary winding must be kept highmag. number two by means of a trans- I. Certainly we can, if we purchase first-at all frequencies. Now the impedanceformer and that the first has an imped- rate components and use them as theyof a transformer primary depends veryance of 6,000 ohms, then a 3o -henry should be used. largely upon its inductance and if theprimary is needed. 111 How do you mean? inductance is not big enough the imped- But supposing that they don't state

111 The secondary of a transformer cannotance will be too small at low frequencies,the inductance value? contain more than a certain number ofwith the result that there will be a Then you are pretty safe in taking it II turns for various reasons; and obviouslysuppression of the bass notes, for theythat a 2o,000 ohm valve is the highest if we want a step-up ratio the primarywill not be properly amplified. that can be used satisfactorily with must have a smaller number of turns. Can you give me any kind of rule totransformer coupling and that for this That's quite clear. go by? class you must not use a bigger step-up 111 III Since you cannot increase the number Several! than about 3 to 1.For the 8,000 -ohm of secondary turns it's plain I think that Well, please fire away. type of valve a 4 -to -I transformer may the only way of obtaining a big step-up In the first place don't use transformerbe used whilst a 6 -to -1 may follow valves i is ratio is to have a few turns on thecoupling after an anode -bend rectifier.of 5,000 to 6,000 ohms impedance. A primary. You will find that the resistance -capa-really big step-up such as 8 to r can be

That seems obvious. city method is better here.Next, ifused with advantage only after quite low III The fewer the primary turns thethe makers state the inductance of theimpedance valves. FROM ACROSS THE "DITCH " JOTTINGS FROM MY LOG ;: By JAY COOTE HAS it ever struck you to what extentnight, drink a large glass of -" andfurt-artz-Main and Kassel must now be radio has annihilated distance? folloWed the name of a well-known Belgianfamiliar to you all. Recently, during a period when thebeer ! Channel was blotted out by a bank of fog, In this bulletin one finds references to it took some friends of mine almost antinned tomatoes, radio components, the " CUTTING OUT THE entire day to cross from Calais to Dover;names of seaside resorts at which you are on the same evening, when they called oninvited to spend your holidays, and appa-HIGH-TENSION BATTERY" me, I was able to switch them over torently cofitracts are made with advertising A Patented Circuit Brussels (their native city) by the merefirms, for the same publicity is given out WHEN our Te.chnical Staff prepared' turn of a wrist. Through the loud -speaker,nightly. the article "Cutting Out the High-: the news bulletin which interested them Radio Belgique receives no subsidy fromTension Battery" that appeared on pages, was received as if the announcer had beenthe State, and relies entirely on voluntary485 and 486 of our March 3o issue, we in the same room, yet he was on the othercontributions. For this reason appeals arebelieved that the circuit on which the side of the "ditch" I made to listeners to buy listening cards,article was based was common property.' On many evenings, instead of potteringthe cost of which is 25 francs per annumSince publication of the article, however,' around in an aimless manner, I devote(under 3s.) or entreats them to becomeMessrs. E. K. Cole,Limited, "Ekco" some time to individual stations.In viewpatrons at the cost of ioo francs yearly. Works, London Roads Leigh -on -Sea, have of the fact that Radio Belgique is now By the way, all the transmissions fromcourteously drawn our attention to the playing with a higher powered transmitter,Brussels regularly close down to the playingfact that the circuit in question is fully, I have followed its programmes more care-of " La Brabanconne " on a gramophonecovered by their patent 'No. 262567.It fully than hitherto.At the end of whatrecord. follows, therefore, that readers may only,

is usually an excellent musical programme, - construct the D.C. mains unit described in you will be treated to a very remarkable Another station to which I listenedthe article for purely experimental pur- series of announcements, inasmuch as theyregularly during the last few nights is thatposes, since only the patentees and their comprise the latest news items, political,of Frankfurt, of which, for some reason oragents have the right to make and sell a social,or commercial, interlarded withother, the reception has gradually becomeunit built in accordance with that circuit. advertisements and puffs.- On one occa-' weaker. 'Although the studio has a very We express to Messrs. E. K. Cole, Limited, sion following the details of a particularly' full day, when I was last in that city, Iour regret that, being unaware of their gruesome murder, the announcer ended upascertained that the bulk of the work ispatent, we quite inadvertently used the with : "If you want -to sleep soundly to-done by one announcer whose call, Frank-circuit as the basis of our article. APRIL 13, 1929 559 nuuctsr WtJ WITHOU

I 1/

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A Weekly Programme Criticism by Sydney A. Moseley WHAT beautifully expressive music is " That's what I asked you. Where do A young author who is doing enter- Grieg's !The holiday programme ofyou live? " prising work in the production line is Holt the great Norwegian composer's works " Ware !" Marvel. He tells me that I "gave away" was incomparably rendered by the Wire- How the music -hall audience roared I his identity. Did I? He ought to be proud less Symphony Orchestra, Kate Winter, of it if I did. He is certainly brimful of and Maurice Cole.What poetry, what ideas, and I gather we shall soon be listen- longing there is in "First Spring." And It's quite a useful thing to barge intoing to more of his work. what grotesqueness in the "March of thepeople whose work you criticise, or people

Dwarfs." In pre -wireless days the multi-well up in the world of wireless who . tude knew only "Peer Gynt." Now thesecriticise you !For instance, I had some- And, yea, verily, among others, whose thing to say about Lance Sieveking's pro-names are familiar to readers, whom I met duction recently. in the flesh was my old tried and trusted "I don't forget you wrote, 'Keep yourfriend, Captain Eckersley. As a matter of hand out of the till,' " he said as we walkedfact, I got him to televise for the first time away from Savoy Hill, "but my. next pro-in history !But about all this I shall have duction will have an equally big caste." to refer readers to my " secret history " Well, if the money's worth it, Lance,book which I hope to write one day.

we'll break no more lances.(Oh, cheap I cheap !) Another chat I had was with R. E.

Jeffrey. He believes a visual audience is essentialtothetemperamentalradio Sieveking, by the way, made a spiritedartiste.I think Eckersley would dissent. defence of those at the B.B.C. who workSo do I.Still, R. E. J. is frightfully keen seriously and conscientiously on behalf of the listener.Productions that go overon the future of "sight and sound" enter- badly apparently hurt the producers astainment, and I wish him luck. much as they hurt listeners. I have, however, paid tribute to the type of earnest Sullivan's Ivanhoe is little known. Why? worker at Savoy Hill. Because it was "grand opera" and unlike the rollicking Sullivan airs that helped to pack the Savoy Theatre.Still,itis a I was glad to hear from such an eminentbeautiful opera, and one is grateful for the expert as Professor Appleton that he andopportunity of hearing it. 11 SS Ge.--ipeammti, others supported my "clean radio" cam- Miss Jessie Matthews-as our artist sees herpaign. Apparently the comments in this page ha've been closely followed.

and other musical treasures are being disclosed to people whose musical souls were We shall have to mind our pros and half-starved. cons, for the wife of another radio pro-

fessor tells me she reads us "first" each Songrecitalby Olga Haleygood.week. Frank criticism may rub some of "Serenade" by Strauss has become a bestthe victims up the wrong way. Honesty is singer. Oh, by the way, where did Esthernot the best policy if you desire to " keep Coleman get her translation of " I Lovein" with everybody. As it happens, I don't Thee "? wish to keep in-or out-with anybody except the bulk of my readers. And this sort of unexpected tribute helps me in my Interesting,isn'tit,to watch jokesattitude. grow? "What's your name? "' "Watt !" Professor d'Andrade is another interest- " That's what I asked you.What'sing personality who told me he had kept your name?" certain cuttings of mine. But the subject "Watt !" turned out to be-spiritualism !I wonder, And now the variation. by the way, whether we shall hear any "Where do you live ?" more of those spirited and well-informed " Ware I" talks of his. An impression of Jack Hobbs malkur Wtretesi 560 00000000000000.0-0000000<> FOR the benefit of those who did not , have the opportunity of reading the constructional article last week which 4 6 dealt with an up-to-date version of that ever -popular receiver " Britain's Favourite Three,"it must be explained that so RITAIN'S insistent has been the demand for new facts about this set that it was deemed advisable to produce an absolutely up-to- date version. You may remember that the "Favour- Further Details Hon) to( ite" owed its inception to a competition which was held in AMATEUR WIRELESS in order to decide the most popular circuit. The "Favourite" was the result, and was published at the beginning of 1928 and both in outlay and in the continued expense, iv it embodied everything that an amateurmonth by month, between a three-valver Those who take an interest in the work..- required for general-purpose reception: and ,a four-valver; in very many cases theing of their receivers will perhaps care to necessity to own a " three " is quite clearlyexamine the various features obvious from 4 Popular Combination dictated. Well, if it is to be a "three," thethe circuit diagram. The detector operates At the time when it was produced high -next question which automatically ariseson the leaky -grid principle, and frequencyamplification had not been is :is it to be used mainly for "family"this is because at normal ranges developed to the extent which it has beenwork or for DX reception ? and owing to the fact that there is to -day.As most readers of AMATEUR no high -frequency amplifier pre- WIRELESS will be aware, high -frequencyA Double -purpose Receiver ceding the detector, there is no stages, once the playthings of more or less If the set has as its main duty to receivetendency fortheleaky-gridg experienced set operators, can now safely5XX, 5GB, and the local station at goodsystem to be over -loaded. be included in the specification of general-loud -speaker strength, but when the rest As iswell- purpose receivers. of the family has gone to bed pater-known, the great Some very popular three-valvers havefamilias likes to put up a good showingadvant a g e been described in AMATEUR WIRELESS,against some of the neighbours' super-hets ofemploy- and these, while designed for the "wirelessand multi -stage screen -grid job postes, thening the man in the street," have included whatan H.F. stage is essential.This, of course, anode -bend would once have been considered a difficultmeans that there isonly one low -fre-system, quency stage, and unless theinstead circuit is carefully designedof leaky - and the very best compon- grid rec- entsareused, the home -tification, isto be broadcastingresultsmayfound when the input suffer. to thedetectoris ' On the other hand, if thealready fairly large, three - valver is used just asand thereisa an alternative to the gramo-danger thatthe phone and only Daventryproper functioning of the condenser and and the local station are toleak, in the leaky:grid system, might be bereceivedatadequateupset by the comparatively heavy grid volume, then two L.F. stages voltage. and no high -frequency stage is the obvious arrangement. COMPONENTS REQUIRED Ebonite or bakelite panel, 16 in. by 8 in., and strip, This is just what is done 4 in. by a in. (Becol, Raymond, Paxolin, Radion). iri the:case of " Britain's Fav- .000s-mfd. variable condenser, log mid -line type (J.B., Polar, Ormond, Burton, Burndept). ouriteThree," and, as we .00023-mfd. variable condenser, log mid -line type The Circuit of " Britain's Favourite Three " (J.B., Polar, Ormond, Burton, Burndept). have said, when it was voted 7 -ohm panel -mounting rheostat (Lissen, Igranic, stage to operate, namely, a stage of screen - (in 1928) ,to be themost popular circuit, G.E.C., R.I. & Varley). Push-pull stvitch (Lotus, Lissen, Trix, Wearite). grid H.F. amplification. screen -gridstageswerenotsuchan Panel brackets (Bulgin, Camco). Dial indicator (Bulgin). But there are still many reasons whyeveryday matter as they now are. Three antimicrophonic valve holders (Benjamin, three-valvers with two stages of amplifica- With the additions described in the 1929 Lissen, Burton, Weaiite). .0003-.ocio023-mfd. pre-set condenser (Formo- tion on the low -frequency side, and with model it is in every sense an up-to-date denser type J, Igranic). .0003-mfd. fixed condenser with series clip (Dubilier, no H.F. boosting whatsoever, are very three, capable of giving a good show without Lissen, Graham-Farish, Mullard). popular,andwhy,if thevoting any unnecessary frills. a-megohm grid leak (Dubilier, Lissen, Graham- Farish, Mullard). were takenagain,three -valuers with- Six -pin coil and base (Tunewell, Lissen, Lewcos, A Popular Type Peto-Scott). outH.F.mightconceivablynotbe High -frequency choke (Lissen, R.I. and Varley, swamped by their more distance -getting As even the least technically -minded Burndept, Polar, Tunewell, Trix). Resistance -capacity coupling unit (Dubilier, Lissen, counterparts with one H.F. stage. reader will gather from a cursory inspection R.I. & Varley, Graham-Farish, Mullard). 50,000 -ohmresistance(Graham-Farish,Lissen, The whole question resolves itself on theof the photographs and theoretical circuit Dubilier, Mullard, R.I. & Varley). point of economy, both as regards valvesdiagram, " Britain's Favourite Three " is z-mfd. fixed condenser (Lissen, Dubilier, T.C.C., Ferranti, Mullard). and running costs. of the ever -popular detector, R.C., and Low -frequency transformer (R.I. & Varley, Lissen, There is quite a big step of differencetransformer -coupled L.F. type. Philips, Mullard, Cossor, Igranic). 561 &attar Wire!5

131

Amszalcrutammimuclaiis in the accompanying valve table, valves suitable only for ordinary requirements 19 are given ; that is to say, the last valve is of the normal power or large L.F. type, capable of dealing with a reasonably exten- VOURITEFIRE sive grid swing, and giving an output for one of the larger cone type or smaller moving -coil loud -speakers. SATE There are, however, still larger power valves on the market, and in cases where exceptionally large output is required one 'et `Kest Results of these may be used, provided that a corresponding alteration in H.T. and grid - ..,111.,1111..4.11110,10,1111.11' bias voltage is effected. A glance at any list of typical two-volters in this super -power class shows such valves The various technical merits and de- conventional,that is,foran R.C. asthe Cossor 23oXP, the Marconi or merits of each system have been discussed stageimmediately following a detectorOsram DEP24o, Mullard PM252, Ediswan in the pages of AMATEUR WIRELESS, butvalve. PV225, Mazda P227, and Six -Sixty 23oSP. it may be taken for granted that in a The anode resistance used in conjunction For a preliminary test, tune in the local general- purpose receiver,with these components has a value ofstation. To do this fully screw in the knob suchasthis"Britain's.25 megohm, and in series with this is theof the pre-set condenser and with the Favourite Three," a n d50,00o -ohm resistance, which forms partreactioncondenser at practicallyzero, where there is no ampli- of the anti -motor -boating unit. slowly rotate the main tuning condenser fication preceding the rec- until the desired station is heard. tifier,thegridcondenser 1929 Modifications Then reaction may be adjusted until and leak system is prefer- :Theadditionstotheoriginal1928 volume is at the required degree and the able.The values for the"Favourite" are the following : The plug-inknob of the pre-set condenser can be condenser and leak are con-coils are scrapped in favour of a six -pin slacked off a little, if desired, though there ventional,being. o o o 3 - dual -rangecoil,andthe wave -changeis really no need to do this in the case of microfarad and 2-megohmswitch is placed on the panel just belowlocal station reception, which is generally respectively. the centre tuning condenser; a pre-setfree from interference.H.T. and G.B. Alittlehintwhichcondenser is incorporated in order to givevalues can then be adjusted to a nicety may be appreciatedthe very best selectivity; this condenserand an attempt may then be made to tune is that with someis mounted on the baseboard detector valves and and can be put in or out of under certaincircuit as required, simply by :NAVE -CHANGE SWITCH ON PANEL working conditionschanging over a flex con- slightly better sen-nection from one termind: sitivity, thoughto another ; the third addition sometimes attheis an anti -motor -boating unit PRE-SET expense of purity, is ob-which enables a high value CONDENSER tained if the value of theof H.T., a large power -valve FOR SELECT- grid leak is raised somewhat-to, say, 3or a mains eliminator to be IVITY or even 5 megohms. employed without any fear The values of the condenser and leak of motor -boating. -PIN in theR.C. couplingsystem are also As a matter of fact, pos- DUAL RANGE sessors of old "Favourites" COIL Grid -bias battery clips (Bulgin).Two black and one red wander plugs (Clix). will find very little difference Baseboard, z6 in. by q in. (Pickett, Clarion, Cameo). between the operation of the Connecting wire (Glazite).One yard of thin flex ANTI-NICTORBOATING UNIT (Lewcoflex). new set and the 1928 edition. Seven terminals, marked :Aerial, Earth, L.T.+, L.T.-, H.T.±, L.S.-, L.S.-{- (Belling -Lee, Eelex, Valves and battery details This picture shows the 1929 modifications Igraine). are, of course, relatively important.For the guidance of new con-in someofthemore easilyreceivable Six -volt Valves to Use with the structors of the "Favourite" a tableis foreigners. lip -to -date " Favourite Three" given showing a selection of six -volt -valves If interference from thelocal station Make Det. 1st L.F. Potter which will work very well in combination. seems to cover an unduly large section of the Cleartron.. CT25F CTz5 CT25X As in most other receivers, 2- and 4 -volttuning scale, the knob of the pre-set con - denser can be slacked off, thus reducing the .. DE5o equivalents can be used and the final Cosmos decision with regard to type rests almostcapacity until the required selectivity is Cossor .. MoRC 6ioLF 6i oP entirely with the set user and the type obtained. Ediswan .. RC6io LF6io P V610 of accumulator he has available. The simple push-pull switch on the panel Marconi .. DEHM o DEL6i o DEP6 1 o It is recommended that about 12o -volts changes over from the long- to the short- Mazda .. RC6o7 GP6o7 P615 H.T. should be used, in conjunction with awaves and this is a convenient point 9 -volt grid bias battery, and about 3 -volts-Which will be most appreciated by users of Mullard .. PM5B PM6D PM6 negative G.B. being applied to the firstthe former edition of the set and who may Osram .. DEHM o DELM o DEP6 1 o L.F. valve. have had cause to grouse at the job of Six -Sixty .. 6o75RC 6o75fIF 6 x oP It is opportune at this point to note thatchanging over thecoils. WireLz..,5 APRIL 13, 1929 entatent 562 UMW "A.W." TESTS OF APPARATUS Conducted In our Technical Editor. I. H. REYNER. B.Sc. (Hons.), A.M.I.E.E.

New Wearite H.F. Choke a half's time, is to turn the knob on the A 7 i2 in. cone is attached at the periphery r -r HE Wearite H.F. choke has, since itsfront of the Setalite unfit the setting ofto circular pieces of chamois leather and is 1 inception, earned a good name for1-3o is obtained on the dial. This is all thefinally clamped to a small baffle board itself because it will operate in a reliablewinding that is needed, and the instrumenthaving overall dimensions of loin. square. manner from below 20 metres up to wave-then goes on ticking,until the properThe baffle board is covered on the outside lengths exceeding 2,000 metres. Thisperiod has elapsed, when two contacts arewith green baize, so that it can be fitted if shows that the value of inductance isclosed and the set is -switched on. desired to a larger baffle without loss of sufficiently great and theself -capacity signal strength or tendency to rattle. sufficiently small for efficient choking both During our tests we connected several on the high and the low wavelengths. units in position, in turn, and affixed an A new model of this popular component extra 2 ft. baffle; the results obtained were has recently been put on the market. This quite pleasing, the reproduction from high- differs from the older form in that the two class units being good and free from unde- terminals are placed on the base instead of sirable rattle, even when large volume out- one being on the base and the other at the puts were obtained.This cone assembly top of the former.Tests which we con- can be recommended. ducted on the old and the new type of Polar Ideal Condenser choke indicate that the new type has a Setalite Time Switch THE Polar Ideal variable condenser is slightly higher self -capacity owing to the well-known as a robust instrument of positioning of the terminals. This, however, The Setaliteiscapable of switchinghigh-class design fitted with a reliable and is scarcely noticeable, being less than oneeither on or off at any predetermined time,smooth slow-motion device working on an micro-microfarad and in practice no differ-and a simple push-pull switch on the sideinteresting and practical system of ball - ence in the operation of the instrumentof the case arranges for it to switch on orbearing. off as required. We have tried one of these Readers will probably be interested to switches in conjunction with an ordinary set and have found, that it gives a very satisfactory degreeof accuracy. Floating -cone Unit THE advent of the moving -coil speaker withitsfloatingdiaphragmhas demonstrated the advantages of using a floating diaphragm with magnetic vibrating armature units.If a diaphragm is free to

New Wearite H.F. Choke Polar Ideal Condenser could be discerned over the entire working know that this condenser may now he range. obtained with a drum dial, a form of control As before, the finish and appearance of which has recently become popular owing this choke are excellent.The makers, of to the neatness of such a fitment. course, are Messrs. Wright and Weaire, Ltd., The drums of the Polar condenser consist of 74o High Road, London, N.x 7. of two insulated mouldings having a diameter of 23/4 in.; these are knurled to afford An Automatic Time Switch a suitable finger grip.l3etween ,the two IT is very annoying to miss the beginning drums a cylindrical ivorine scale is fixed of a much -desired programme simply and this rotates directly with the left-hand because one forgets to switch on the set at drum. The right-hand drum is attached to the proper time. Also, if a set is to be left the slow-motion spindle giving a reduction in non -technical hands it is satisfying to of approximately 20 to 1. know that it can automatically be switched Fitting this condenser to a' panel presents on and off without any chance of the other A. W. Knight's Floating Cone no difficulty whatsoever. A portion of the controls being upset. move at the periphery there is more chancepanel must be cut away to take the neat These two needs are supplied by thethat the motion will take place as a wholeescutcheon plate and allow the drum to, Setalite, which is an automatic time switch,rather than in small segments. project slightly.The actual condenser is manufactured by Setalite,Ltd., Morley We have recently tested a floating cone,held in position by drilling two holes on the House, Regent Street, London, W.I.Itmarketed and submitted by Messrs. A. W.panel on the left of the drum and placing incorporates a clock -work mechanism whichKnight and Co., of r8o Tower Bridge Road,screws through these into two brackets needs no special winding. S.E.r.This is simply and inexpensivelyprovided on the instrument. All that it is necessary to do in order tomade but is an efficient article of its kind The makers are Messrs. Wingrove and make the set operative in, say an hour andand capable of giving good reproduction. Rogers, Arundel Street, Strand. APRIL 13, 1929 563 =tear wire

rEXPERIMENTSWITHNEONMBES crhatYou Can Make

The Neon Tube has many peculiar repayinvestigation.Thisarticle characteristics which will well gives some suggestions for itsuse AMATEURS who have. experimented cap with a pair of pliers and pull off the Z:1, with neon tubes have found that they cap gently, thus revealing the resistance. can successfully be used for many purposes Remove the resistance, and after making formerly only served by the more costly suitable connections between the lead-in By H. F. LEECH wires and contact lugs,fix the cap on again.If it is afterwards required to use the lamp across .,1111111111111111111111111111111discharge takes place between two metallic the ordinary lighting electrodes in a rarefied atmosphere of neon gas, which latter possesses a remarkably low -ionising potential and a comparatively 111111111111111high electricalconductivity. TM neon lamp requires about 200 volts across its SOn°1111111111111NIVAINIterminals-. According to modern standards, the vacuum is an extremely soft one, pres- 111111111111111111211111111sure being equal to several millimetres, or even a centimetre of mercury. A slight trace of helium is also contained in the "space," and possibly also a very slight e,111111111111/411111111111111 trace of hydrogen. 0 o-vvvvvw Contained in the brass cap of the lamp /0 4- Hr - is a safety resistance, usually consisting of WO K a quantity of fine wire wound on an earthen- 11111111211111111111111111 A detector circuit using a neon tube HO 115/20 /2S /Y.0 /SS HO /15 /50 /51ware or cardboard bobbin. This resistance Fig. 1.Characteristic curve of neon lamp must be removed before experiments aremains, an ordinary lamp should be used in undertaken, as its presence would seriouslyseries, since after removal of the resistance three -electrode or two -electrode valve.Itinterfere with the action of the lamp, par-any overload in the current would blow is intended here to give an outline of theticularly when dealing with high -frequencythe neon lamp if connected alone. propertiesandcharacteristicsofneoncurrents. tubes with a view to There is no need to damage the brassCharacteristics of the Neon Lamp helping the amateurcap in removing the resistance : the cap is Fig. i gives the characteristic curve of to form an idea ofconvenient for plugging the lamp into thea typical neon lamp. No two lamps have what can be donestandard bayonet ldmpholder.The bestthe same characteristic curve.The un- with these lamps. Itprocedure is as follows :Grasp the glasssteadiness of the discharge position gives should be understoodbulb firmly in the left hand and carefullykinks in the curve. The extinction and that the results areheat the brass cap in a small fiame, beinglighting-up potentials are not identical, in obtainable using anycareful not to allow the flame to play onthat the discharge will not commence make of neon tubethe glass.This has the double effect ofbefore a certain minimum potentialis whichoperates onmelting the solder which secures the lead-inapplied, but once the lamp glows the about 200 volts, thewires to the contacts, and of softening thepotential necessary to keep it alight may electrodes being ofcement which holds the bulb in the cap;be lower than that required for starting iron and situated fair-so that it is a simple matter to grasp thethe discharge. ly wide apart. There Ina lamp containingelectrodesof areseveral makes unequal size the conductivity is not the on the market, such same both ways, the lamp conducting as Philips and Osram, HAVE YOU NOTICED and a slight variation -that the standard values for of the characteristic leaky grid rectification are,in will,of course,be England : Condet.ther, .0003 produced by using mfd. ;leak,2 megohms ;in different types. This France : condenser, .00015 variationmaybe mfd. ;leak, 3 megohms ? It easily met by an ad- would beinterestingto know Fig. 3.Arrangement for production of justment of the re- what are the standard values in oscillations sistance and capacity other countries, why there should values in the figures bedifferences,and on what better when the larger, electrode isthe cathode. Should the lamp. be _inserted in The Raytheonneonof circuits shown. reckoning,thedecision of the tube as used for tele- In the neon tube a respective values has been ar- its socket the wrong. way round,, the glow vision purposes luminous ionised gas rived at. appears at the, smaller electrode, and less makur WiretT 564 APRIL 13, 1929 current passes through the lamp thanor three seconds up to about 20,000 per-a tuned -aerial circuit should replace L2 - when it is connected in the normal manner.second by suitably adjusting R and c. Thec2.Each aperiodic discharge from the A typical lamp tested in this manner, usingpotential drop in R should be approximatelylamp gives a kick to thecircuitL2C2, about 200 to 220 volts, passed aboutequal to the potential drop in the lamp forwhich oscillates in its own natural period 15.4 milliamps in the normal direction,best results. until the next kick is produced to keep but only 12.8 milliamps in the reverse These pulsationsarereally detachedthe oscillations going.If the lamp is dis- direction. A neon lamp requires a smalleruni-directional surges, and not sinusoidalcharging at the rate of 20,000 per second minimum ignition voltage when the smalleroscillations ;therefore, we must expect anand, the circuitL2c2 is tuned to a fre- electrode is used as the cathode. enormous number of harmonics to bequency of L000,000, a kick is administered present. Cause a lamp to pulsate at aboutto L2C2 once every fifty oscillations, and so, Rectification by Means of 15,000 per second, and listen on a hetero-if L2c2 possesses low H.F. losses, prac- a Neon Lamp dyne receiver, and a strong C.W. note willtically undamped oscillations will be sus- The propertieS already explained are allbe heard on a wavelength of about 20,000tained in it. due to the fact that a neon lamp does notMetres; then tune the receiver down, and obey Ohm's law, and this fact, togetherwe come to harmonics of two, three, four,The Neon Lamp Transmitter, and five times the fundamental wavelength. Only vety, small power is available with The higherthefre- quency tuned-i.e., the lower wavelengths-the 0601 more congestedthese THIRD harmonics become. Be- ELECTRODE low 400 metres the har- L2L/ monics are feeble,but Fig. 4.Arrangement of neon lamp oscillator come in in very rapid for a 300 -metre wavelength succession.

Maintenance of Oscillations If an oscillatory circuit,coupledtothe a neon lamp circuit, be tuned to one of the short -wave -harmonics, this harmonic will predominate more strongly than the others. 1-11117___NTERRUPTER Fig. 4 gives an excellent arrangement for a 220K Fig. 7.Method of obtaining rectified H.T. neon lamp oscillator to generate oscilla- Fig. 6.Another modulator circuit from spark coil tions of 300 metres wavelength. Connect with the power of partial unilateral con-the neon lamp to produce the pulsations,a neon lamp circuit, as standard lamps ductivity, makes it possible to rectify, toas in Fig. 3, except that an inductance LIconsume only 5 watts; since they pulsate a- certain extent, oscillations occurring inis put in series with the lamp. Adjust Ronly at almost extinction point:about only a circuit.The rectification, however, isand ct so as to cause the lamp to pulsate watt is available for use.If the lamp is incomplete and is really inferior to a goodat as high a frequency as possible. Theoverrun on -about 400 volts the glow will crystal rectifier, and thus this use will not -inductance LI must be of such a valuechange to a- pale violet colour.This en- find a very extended application. that in conjunction with cf it will tune toables the lamp subsequently to pulsate on Fig.2 shows a circuit suitable as athedesiredfrequency-I,000,000perhigher power, 1pecause once the lamp has detector circuit.In series with a pair ofsecond-although, strictly speaking, thebeen overrun it requires a considerably telephones, a high variable resistance a,circuit LIcris not really a tuned cir-higher voltage to work it afterwards, and and a H.T. supply of 200 volts, is a neoncuit owing to the inclusion of the lamp.also this overrunning causes it to pulsate lamp. c is a large capacity by-pass con- on a higher fundaniental frequency and to denser. This condenser is absolutely essen- give stronger harmonics. The oscillatory tial.The resistance should be adjusted properties of a neon lamp, then, are greatly until the lamp glows very feebly and the improved by about twenty minutes' over- receiver then tuned in the usual manner. running. It is highly important that the supply Production of Oscillations current be absolutely regular and constant. A neon lamp is capable of converting a OThe frequency is not determined, by a D.C. supply into regularly pulsating cur- tuned circuitthe fundamental lamp fre- rent.Fig. 3 gives a suitable arrangement. quency, that is-but is chiefly a function When the supply is switched on a rapid of the supply circuit and the large con- series of pulses will -pass through the lamp, denser in the lamp circuit.Should small when the resistance is adjusted so as to variations occur in the supply current, the cause the lamp just to glow. The frequency Fig. 5.Neon lamp as modulator fundamental pulsation frequency of the of the discharges depends on the rate atOnce the circuit L2C2 has been tuned tolampwill vary.These variationsare which the supply current through the ,000,000 per second a slight adjustmentenormously magnified in the selected har- resistance R. can charge up the condenser cof c1 or a will briag a harmonic into exactmonic, and hence the necessity of keeping to the ignition potential of the lamp.Itsynchronisation with L2C2.The couplingthe supply constant. will be readily seen that decreasing thebetween LI and L2 must be tight. High - resistance increases the frequency of thefrequency chokes may be inserted in theThe Neon Lamp as a pulsations,and,also,the smaller thesupply leads as shown. in Fig. 4, though the Speech Modulator capacity of c, the higher will be the dis-resistance R may be high enough to keep The susceptibility of the oscillations to charge frequency. Any frequency may bethe oscillations out of the supply leads. any variations has a great advantage in obtained from. say, one pulse every two To use the arrangement as a transmitter (Continued on page 574) APRIL 13, 1929 565 QmateurW,,,i,5

Grid Three Screened and The'Ferrantiforboth long- is areceiver possessing -wavestations, and cap- medium goodselectivity, inherently reproduction. excellent able of WC. and ota-tot station, good thelocal includes Besidesperformance of Con- 5GB, the number to of a fair according receptionprogrammes, Xeocomets. tinental of thelistener. situation the READY. charts areNOW rite direct. THE Full-sizedealer orw Ask your ANDCONTROL. 10CONSTRUCT CHANGING. SIMPLE NO COIL SOLDERING -- SCREENED NO LTD.HOLLINVVOOD FERRANTI GRID LANCASHIRE THREE

IGRANIC " 3 " TYPE INTERVALVE TRANSFORMER AND OUTPUT 1716 ...... Name ...... rn Two Designed and built to the high standards of Igranic Small, neat, and handsome, but with a straight line IGRANIC quality, this L.F. Choke is made for use asan inter - performance and a purity and constancy of amplifica- Fa vourites valve coupling or as an output filter choke.The tion far above any transformer in itspriceclass. winding is in two sections so that different inductance The wonderful results from this instrument are only Use them values may be obtained.Exceptionally high induc- possible because of its special windings and ultra - for valve tance with very low self -capacity.Particularly suit- permeable iron core enabling bulk and cost to be able for experimental work. reduced without any sacrifice of efficiency. and Ratio 3:1 for use after valves of 10,000 to 20,000 maximum ohms impedance, or 6:1after valves of 5,000 to efficiency See them at your dealers 10,000 ohms impedance. orwritefordetailsto Department D.1 1 7.

\I7 OtieenVicleriaS\ IGRANIC 4 irr " F " TYPE la, -1 Works BEDFORD L.F. CHOKE

To Ensure Speedy Delivery, Mentiin "A.W." to Ad'ertii-ers inateia Wirdes1 566 APRIL 13, 1929

Some Considerations of a By J. H. REYNER, Possible New Method B.Sc., A. '.I.E.E.

MATHEMATICS are troublesomecan deal entirely in symbols and- formulae,reasonable wavelength band.Others, on things to the average man at theand can deduce from them other forintlae,-the. other hand, claim that with correcj best of times, and indeed the amateurwhich upon examination may indicate andesigned apparatus and careful construc- prefers, as a rule, to leave such mattersentirely unsuspected state of affairs.Thetion, realamplification is possible, strictly alone, confining his attention toengineer or physicist in his turn investigatesalthough this may not be of a very- high theactualpractical'resultsobtained.the practical way of carrying out the neworder.Even an amplification of 2 or .3 Nevertheless, there are undoubtedly occa-methods disclosed, and in general he pre-serves to give a margin of reserve over and sions on which a mathematical analysisfers to carry a mental physical picture ofabove the ordinary detector circuit, which serves a very valuable purpose. what ishappening,using mathematicsmakes tuning easier and tends to minimise Perhaps one of the most interestingmore as an aid than as a primary structurethe disadvantages of fading. examples of thisisthat of Maxwell'son which to build his ideas. The net re- theory of light. Long before the end ofsult, however, is generally progress, forPossibilities last century, Clerk Maxwell evolved hiseven if the mathematics prove incorrect, -Any suggestion that an amplification of wave theory of light, which he worked outowing to insufficient knowledge regardingthe order of io to 15 is possible would seem, to fit in with the facts known in thosethe assumptions or for some other unfore-on the face of it, ludicrous. Yet a recent days. Having decided the general prin-seen cause, a train of thought is starteddetailed analysis on the, operation of the ciple upon which he thought light radia-which usually results in an interestingstandard three -electrode valve, published tions were operating, he investigated thedevelopment. by F. M. Colebrook(JournalI.E.E., subject and made a complete mathe- vol. 57, page 157), indicates that there are matical analysi. This went far ahead ofDivided Opinions certain unsuspected effects taking place practice in those days, and not only pre- The problem of amplification of the veryby the utilization of which we may obtain dicted numerous effects concerning light' short wavelengths has been exercising thea distinct amplificationon these high waves which were ultimately found to beminds of radio engineers for some consider-frequencies. true; but also foretold the existence ofable time past.Opinion is very much The first thing that emerges from the wireless waves. divided on this subject. One school stoutlyanalysis is that the maximum amplifica- He said we should find that such etheraffiwns that,' although a high -frequencytion is obtained from a valve not quite at vibrations which we now know as wirelessvalve can be made to hand on high -fre-the point where the anode circuit is tuned waves would be capable of production,quency energy with no serious loss ofto resonance, but at a point where the that they would obey the same laws asvolume-i.e., so that it is not definitelyimpedance of the anode circuit is slightly light vibrations, due allowance being madeworse than a simple detector arrange-inductive. This effect is almost negligible for the difference in frequency, and hement-it cannot be made to give anyat- ordinary broadcast frequencies, but on gave various estimated theories regardingappreciableamplificationeffectoverashort waves the difference is appreciable. their operation.It was not This doesnot mean that until the beginning of this there- are two tuning points, century, many yearS after the for the apparent tuning point first predictions,that wire- will be that where maximum lesswaves were actually signal strengthis. Obtained, produced and found to con- and one automatically tunes formtothelawswhich the condenser until this max- Clerk Maxwell had laid doWn imum amplificationis pro- for them.Still, in those days duced.Thefactremains, the full signifiCance and the however, that at this point enormous applications of the the circuit is not really tuned, newvibrationswere not but is slightly undertuned, so realised, and it remained for that the impedance is Marconi to make thefirst inductive. practical utilisation ofthe - When this is, -the case a new discoveries. resonance effect occursbe- So to anincreasingex- tween the anode circuit and tent the pure mathematicians the internal capacity of the have started theengineers valve, and, due to this, the thinking. The mathematical voltage developed on the out- mind is quite distinct from put may be more thanin thatoftheengineeror times the input, in being the American Broadcasters you may have heard on the short waves from . . .. - physicist. A mathematician KDKA-The Happy Wonder Bakers (Continued on page 569) APRIL 13, 1929 30/ mate=Wire19755 Ask to heara "PHANTESTRA" the guaranteed Loud -speaker Get a Phantestra Loud-speaker- the best in the world-for these reasons: 1. New patented features giveit greater sensitivity, yet render overloading almost impossible. Itis HAVE you had your copy thus uniformly exquisite In tone. of this descriptive fold- 2. It is of unusually beautiful appear- er and blueprint ?It tells ance.The unit itself is unique in you how to build the 1929 design. Imperial 3-the latest and 3. It gives " straight line " repro- most modern set you canrlr HE famous Watmel ductionoverthe whole musical Double Range Tuner scale. wish for.It also tells yougives your set accurate 4. Itis unaffected by dust or cli- how you can at very littlecontrol over the tuning on matic conditions. expense convert sets of oldall waves between 250-600 5. With any good wireless setit metres, and at the push of design into up-to-date re-aswitch,1,000 - 2,000 gives greater volume and infinitely ceivers giving remarkablemetres. A beautifully purer reproduction purity s tabi lity and volumemade and handsome look- AND ing instrument selling at 6. It is guaranteed for five years Drop us a card to -dayifthe remarkable against defective material or work_ your dealer cannot supply . 12 price of manship.Prices from £6 - 6 - 0 IllustratedCatalogue sent on request. PHANTESTRA(RENN'S GRAMOPHONES & WIRELESS)LIMITED 221/2 CAZENOVE ROAD WATMEL WIRELESS CO., LTD. IMPERIAL WORKS, HIGH ST., EDGWARE LONDON, N.16 Telephone : Edgware 0323 Telephone : Clissold 0136, 6614, 0203. AID As specified and used in the "All off the Mains" Receiver described in .0P' this issue. f\i-c/,v BRITISH GENERAL SMOOTHING CHOKE A special choke designed to eliminate the application of excessive H.T. to the last valve through the loud -speaker. Prevents the possibility of permanently injuring the speaker by burning out the winding. Ensures greatly improved signal strengthwithout BASE- PANEL distortion; also especially BOORARD MOUNTING designedforuse as a TYPE smoothing choke for eliminators or " straight from main " sets. C.E&M.BurToN PROGRESS WKS. From all good BERNARD ST. WALSALL dealers or direct. PRICE /- British General Manfg. Co. Ltd.,Brockley Works, London, &EA RUPERT COLLINS S

Don't Forget to Say ThatYouSaw it in "A.W." maker Wirete5 568 APRIL 13, 1929 Dragon's Bride; itis to be heard from Belfast on April 22. In this short play she will herself take the part of Ju-Jube, a R DIOGR(INISvillage maiden, and will be supported by a 4., Harold Clements as Liquorice, a deep-dyed villain, and Olive Groves as a princess. 47.7fing ISTENERS to 2L0 and 5XX will be The Belfast Wireless Orchestra is prob- given anopportunity of bearing Mrs.ably making more appearances in outside Baldwin on April 28, when she is to makehalls than any other B.B.C. orchestra. On an appeal on behalf of the National Birth-a recent visit to Londonderry to give a day Fund, for Maternity Services. concert in the local Guildhall, a journey The concert to be given at Queen's Hallof nearly one hundred miles had to be on April 12 and to be conducted by Sirundertaken by road through some of the Henry Wood will consist entirely of Wagnerwildest parts of Ulster. music.The soloists for the evening are In Scotland it is necessary to employ Walter Widdop and Tatiana Makuschina. at least one stage of H.F. amplification it On April i8 a special broadcast version5XX is to be received at loud -speaker of the Nine O'Clock Revue is to be givenstrength. The B.B.C. admits that in from 5GB.Morris Harvey, part -authordistricts where there is no prepondering and one of the principal stars in thesignal from 5XX,itisnotpossible, original production at the Little Theatre,without some form ofdirectiveaerial London, will be responsible for its presenta-system, to render a set sufficiently selective tion before the microphone. The perform-to receive 5XX free from interference by ance will be repeated on April 20 for theZeesen without seriously impairing the benefit of listeners to 2L0 and 5XX. quality of reproduction. Act I of Richard Strauss's opera, Der An idea which is proving popular in Rosenkavalier; which opens the CoventScottish broadcast programmes is that of a Garden opera season on April 22, will be"musical tour" of the country north of the relayed to 2L0 and 5XX.During theTweed, each town,village,ordistrict following weeks 5GB listeners will also bevisited being marked by the rendering of given opportunities of hearing excerptssome song or melody closely associated ENGINEERING from some of the performances. with it. PRECISIOIW:a Mr. George Allison on April 13 will Some districts on the south sideet deliver a running commentary on theGlasgow are being troubled just now by a Bestriding the Tyne like a Colossus, international football match, Scotland v.peculiar fading of the transmissions from this inspiring new bridge leaps the England, which is being played on that great waterway in one span, a perfect the local B.B.C. station. No solution of the example to Newcastle-and, indeed, the date at Hampden Park, Glasgow; it is toproblem has yet presented itself, but it is world-of the skill and precision to be be relayed to both 2L0 and 5XX. noticed that the fading is usually at its found in twentieth-century engineering. A polite satire, entitled Square Pegs, byworst between 6 and 8 p.m., while there is No less worthy examples of crafts- Clifford Bax, is the title of one of the shortno trace of it during the morning trans- manship are to be found in the products missions. of J.B.Infinite care and accuracy, and plays to be found in the 5GB evening a flair for turning a good design into a entertainment on April 20; it will precede A dispatch from Rome states : plans for perfect one, have raised J.B. precision The Dear Departed, a comedy of lowera powerful wirelessstation which v ill instruments to an unassailable position middle-class life, by Stanley Houghton. of good repute. transmit and receive has been approved Here is their neutralising condenser Wagner's romantic , opera, The "Flyingby a commission which isacting as a -an example of J.B. Engineering Pre- Dutchman, has been chosen as the work toprovisory Government of the Vatican. cision. So far ahead of all other models be broadcast from the London studio onThe Papal wireless will enable the Vatican that it cannot go wrong.Extremely April 24; the cast includes Miriam Licette,to communicate with the whole world simple, and incorporating the best pos- John sible materials. Harry Brindle, Hughes Macklin, and have a power equal to the Italian Armstrong, Arthur Fear, and Evelyn Arden,station at Saint -Paul. The performance will be conducted by On March 29 the wireless station of the Percy Pitt. Eiffel Tower began to broadcast on a shorter PRICE Spanish Shawls, a novel entertainmentwavelength, 1,47o metres, in the hope that speciallywrittenforthe"mike" byits reception would be improved and Radio Edmund Wynschenk, a Birmingham solici-Paris and Daventry would not be impeded 3/6 tor, will be presented at the 5GB studio onin their service. The new wavelength will April 17. To use the author's own words,be used until the Ministry of Posts, Tele- "the book with lyrics has been takengraphs and Telephones publishes its study from the Spaniards when they weren'tof the most suitable wavelengths for the looking " Eiffel Tower. Short-waveexperimentersshouldbe According to a report issued recently by interested in the programme offered by theGeorge Engles, director of the American Cardiff station on April 13, for on that National Broadcasting and Concert Bureau, evening they will hear E. U. Ridgway, andmusicians in the United States owe more hispartner, Frances Gayton, who arethan a third of their income to wireless. PRECISION believed to be the first artistes to broadcastOut of a total of £6,000,000 spent on music across the Atlantic on five metres ! in the United States during the past year, INSTRUMENTS Mabel Constanduros is responsible forhis statements show that the broadcasting Advt. of Yackson Bros., 72, St. Thomas' St., London, Telephone: Hop 1837. another comedy en casserole, entitled Thecompanies have contributed fully Z2,5oo,000. APRIL 13, 1929 569 0 =tau WitviT " CAN WE AMPLIFY ON SHORT WAVES ?" (Continued from page 566) amplification factorofthevalve.In other words, we can obtain a greater amplification from the circuit than that given by the valve itself.It should be remembered that we are dealing with ordinarythree -electrodevalves,which have an appreciablecapacity between anode and grid, and it is due to this that the resonant effect is obtained. There is nearly always some qualifying factor which has to be taken into account. In this case it is a fairly serious one, apart from any question of stability and avoid- ance of self -oscillation. The anode circuit of the valve has a very marked effect upon the input circuit. We are accustomed to regard the input circuit, i.e., the grid -filament circuit, of the valve as of practically infinite impedance. Where grid current is actually flowing, as in the detector circuit, this, of course, is not the case, as has been pointed out in certain recent articles, but for pure amplification, where we bias the valves if necessary with a negative voltage to avoid any flow of grid current, we usually assumethattheinput impedanceis infinite. This, however, is not the case, the input impedance being not only finite, but 'relatively low under normal conditions.At the point where the maximum amplification occurs on short waves the effect is to introduce a relatively low resistance across the grti circuits. In a particular instance 14 YOUP considTred of amplification at 28.3 metres the shunt was as low as 300 ohms, the damping effect of which would be enormous and would prevent the tuned circuit connected across the grid and filament from deVeloping any appreciable voltage whatever, 0ito A Cause of Failure? Indeed, it is probable that this unsus- INYOUR pected shunt -resistanceeffect has been the cause of the failure to obtain satisfactory amplification on short waves hitherto. /1\31°1te,. Not only would it prevent any develop-. GETAN ment of the resonance effect just discussed, but it would prevent the first circuit from tuning satisfactorily, and thus nullify the effect of the amplification from the valves, if any, right at the commence- vioTH4/1 ment. The difficulty may be combated by methods ordinarily used to minimise the effectof shunt -resistanceacross tuned otst POWER viute circuits, but such methods usually result in such a loss of signal strength as to render the gains of other causes of no avail. Whether this is the case or not in the present instance remains to be seen, but if it does not prove to be so, then we can look forward to a new system of short- wave amplification which may conceivably give results superior to any yet obtained. "A.W." Solves Your Wireless Problems 0 emateur Wireless 570 APRIL 13.1929 ETTERS TO THE EDITOR ten, for

eccivers The Editor Les not necessarily agree With Correspondenceshould be briefand to the the views expressed by correspondents. point and written on one side of the paper. Linen Speaker Improvements by the local stations on Sunday, as this SIR,-Very many congratulations on thewould seriously interfere with the small -set linen -diaphragm loud -speaker.Itisowner searching abroad. wonderful.Your readers might be in- H. S. H. (London, W.) terested to hear how I overcame its two defects,namely uglinessand ungainly SIR,-I am glad to see that AMATEUR size.I screwed four twisted oak legs toV.-.7 WIRELESS isat last taking up the TO ALL USERS OF THE the inside of the large frame and made thecudgels on behalf of the Sunday listener. COSSOR MELODY MA- KER, MULLAH() MAS- speaker into a table!Five -inch boardsI hope you will get Mr. Moseley interested TER THREE,R.C.TEIRES SOME, 613 MYSTERY placed round the inside of the same framein the subject,becausehisviews are RECEIVER, TITAN 2 & 3 VALVES, Etc. between the legs act as a good baffle. Thenoticed even by those at Savoy Hill. I am top was covered with fine -mesh wire net-one of thousands who don't want to' listen Many listeners have ting to make a levelsurface. Over the topto religion at all, and I object most strongly EXPERIENCED DISAPPOINTMENT with reception owing to the SHORT- is then placed .a "table cloth" of darkto the best part of Sunday evening being COMINGS OF DRY BATTERY H.T. supply. We have been experimenting brown velvet.Light objects, such as adevoted to it.Fortunately, I possess five with ourwell-knownSTANDARD PERMANENT WET BATTERIES to vase of flowers, can then be put on thevalves, and have all Europe -to choose produce a model specially suitable for this type of receiver and can confidently "table," andthespeakerisentirelyfrom;therefore,I have least right to reremmend our NEW TYPE F.6, as being idealforthe work. Itsspeciallyhigh disguised. K. L. D. (Richmond). growl; but, then, if I hadn't been driven capacity and "NON RIPPLING" FLOW CF CURRENT arefactorsthatensure out of my own country to find entertain- satisfactoryperformance from these SUPER SETS which demand SUPER H.T.This Battery is Organ Broadcasts ment I wouldn't need five valves. guaranteed to give perfectresults,is SELF RE- GENERATIVE, recharges itself overnight and LASTS FOR SIR,I--- would ask your permission to C. S. (Birkenhead). YEARS. Send NOW for the FREE STANDARD BATTERY BOOK. STANDARD BATTERY MODEL F. 6 consisting support your contributors, Mr. Sydney of 84 No. 3 cells assem- Stoeke3 be, bled, In 3 UniblocCon- jpgro,d,, Stases, Moseley and also Mr.J.B. Ingles,of SIR,-The Sunday programmes are very Miners with lid and all Stores, accessories complete. & Radio Maim. Hawick, in their endeavour to get better good as they are. To be of any use a Cash £316s. 61. or 13'5Cash or Deferred downand five equal pa".,,. broadcast organ music. service must come from a church. Studio monthlypayments of 13, 5. Immediate delivery. W. E. C. in his recent letter raises seriousservices are paltry. 5GB and 2L0 need doubts as to whether he really knows any-not have them simultaneously, however. The Standard Wet Battery Co., Dept. A.W., thing about organs and organ music, inWhat about a little real organ music (not 184-188 Shaftesbury Avenue,London,W.O. spite of his forty years of critical listeningcinema piffle) that the B.B.C. often give all over the world. when the breadwinners are at work !But, Recently I heard the Stoll organ, andfor heaven's sake, don't give the B.B.C. a this, in my opinion, would be far morechance to inflict Jack Payne's pains on us. suitable to broadcast. The gentleman whoLet us have one day of comparative peace ! plays this organ is undoubtedly a musician, P. P. P. (London, N.). not a musical conjurer. The organ itself, too, is really an organ-unlike most cinema Linen -diaphragm Speakers instruments. SIR,-Allow me, as one of your regular I might add that I hold no brief what- AMATEUR WIRELESS readers, to con- ever for the Stoll apart from expressinggratulate you on the huge success of the my appreciation of the performance of" Linen -diaphragm Loud -speaker." I built their organ and its player. one a week afterit was published in G. H. G. (Croydon). AMATEUR WIRELESS. PreviouslyI had Sunday Programmes been using a good make of horn -type loud- SIR, Regarding " Thermion's " sugges-speaker, which. I exchanged for a Blue Spot TREBLE -DUTY TERMINALS unit. As soon as I connected the unit and I.Hole .0 top.Takes T.14 or 2DW Wander tion re church services via wireless, I Plugs. switched on I was quite satisfied at parting 1. Engraved top.40 types.Positive Red, maintain (I) that all licence -holders under Negative Black, and 6 different colours. with my horn speaker. Volume, as well as E. To take spade or similar connection. the present conditions are really entitled 4.For connecting 'phone or similar ends. the fine bass, is a 'credit to this fine speaker. 5.Tab to simplify soldering if 1 to alternative programmes or a return of desired. I used' three-ply oak for the baffle, and 6.Slot with lock nut to take2"--7 I 5s. on their licences; (2) if we are to have under -panel wires. completed the speaker by adding a fret- T2LC) 44d, each, or totth- Z7.44°!`' alternative programmes they should be out indicating tops (T2LN) 4 really alternative. work front. No more horn loud -speakers 3d. each. 5 Write for Booklet 578. for me. W. H. G. (Newport). 6 It naturally follows, then, that although J. J. EASTICK & SONS any who may be so inclined may have a Eelex House, 11E Bunbill Row Appreciation Moorgate, London,E.C.1. broadcast church service on the one wavelength, those who are not so inclined need SIR,-Thanks for information re ampli- not at the same time be obliged to listen fier.The troubleis now remedied. OUR BLUEPRINT SERVICE to it, but instead may be amused withoutLet me also thank you for the great help Constructors of receivers described inthis journal having to seek this from foreign stations oryour excellent articles have given me. should make full use of our Blueprint Service and go withott. They are just what the amateur wants. avoid all risk of failure. 1 Nor do I favour too much broadcasting S. F. (Altrincham). APRIL 13, 1929 571 OACAST TELEPHONY (Broadcasting stations classified by country and in order of wavelengths) Kilo-Station and Power Kilo-Station and Power Station andPower Metres cyclesCall Sign (Kw.) Mars cycles Call Sign (Kw.) MetrescyclesKiCall (Kw.) GREAT BRITAIN 291.3 r,o3oRadio Lyons 1.5 ITALY 0.5 276 2,08oTurin *11411ERIE Wan" 25.53 11,751Chelmsford 301 997Bordeaux (PTT) 7.0 805 982Agen 0.3 33:1 gooNaples(Napoli) 1.5 (5SW) 15.0 3.0 243.9 1,230Newcastle (5NO) 1.0 505.6 98% Marseilles (PTT) 0.5 0.13 322 93oVitus (Paris) 2.0 443.8 676Rome (Roma) 3.0 E3E I tigmasop= 258.4 1,i61 *Leeds (2LS) 0.3 270.3 1,109 'Sheffield (6LF)0.13 336 892Petit Parisien 0.5 456 658Bolzano 268.5 2,040 'Bournemouth 854 846.7 Algiers (PTT) 2.0 504.2 595Milan 7.0 (6BM) 1.0 870 8/rRadio LL, Paris1.0 Why the tens of k3 382.2 785Toulouse (Radio) 9.0 JUGO-SLAVIA 288.5 r,o4o 'Bradford (2LS)0.13 308.3 073Zagreb (Agram) 1.25 thousands who listen- 288.5 r,o4o 'Edinburgh 400 749Mont de Marsan 0.4 414 724Radio Maroc 452 664Belgrade 4.0 (2E11) 0.85 582 515Ljubljana...... 5.0 inpraise Celestion. 288.5 2,040 'Hull (8KH) 0.2 (Rabat)2.0 288.5 1,040 'Dundee (2DE)0.13 428 7ozGrenoble (FM")1.5 LATVIA 294.1 1,020 *Liverjeaol (6LV) 0.13 430 '697Radio Flandre 529 567Riga 2.0 9.94.1 .1,020 'Stoke-on-Trent Lille 0.25 INCOMPARABLY:a 448 168 Paris (Ecole LITHUANIA (5ST) 0.13 2,000 150 Kovno 15.0 294.1 r,oao 'Swansea (5SX)0.13 Sup., PIT) 0.7 ETC 1.0 973 635.r Lyons (PTT) 5.0 NORWAY sugargligoog 302.6 99/./ Belfast (2BE) 1.0 1,470 203Eiffel Tower 8.0 242 1,240Rjtikan 1.0 311 964Aberdeen (2BD) 8.0 323 928Cardiff (5WA) 1.0 1,748 271Radio Paris 297 r,oroNotodden 0.7 BritishMaterials. British 858.9 838London (2L0) 2.0 365 82oBergen 1.0 378 793Manchester GERMANY 387 775Fredriksstad 1.0 Craftsmen.British Through- (2ZY) 1.0 219 z,376Flensburg 1.5 387 775Aalesund 1.0 out. Thorough testing. Such Nurnberg 4.0 Ei7-7 398 ;57 'Plymouth (SPY) 0.13 240.1,250 959 653Porsgrund 1.0 a combination isessential 401 748.3 Glasgow (5SC) 1.0 250 1,200 Kiel 0.7 496 604Oslo .. 1.5 482 622Daventry Ex. 250 .7,200 Cassel 0.7 500 booTromso 1.0 to produce an instrument (5GB) 25.0 263.2 1440Cologne 4.0 566 35oHamar 0.7 which can definitely rank 1,562.5 192 fDaventry 267.8 2,120Muenster 1.5 272.7 1,100Kaiserslautern 1.5 POLAND as "Incomparably Superior" (5XX) 25.0 314 955 1.5 Relay stations. tRelays 2L0. 280:4 1,070Konigsberg 4.0 Cracow ETIg. 283 1,061Berlin (5) 0.7 336 890Posen 1.5 AUSTRIA 283 z,o6rStettin 0.7 416 721Kattowitz 10.0 283 2,06zMagdeburg 0.7 456 658Wilno. 1.5 248 2,209Linz 0.5 1,305 215Warsaw 10.0 277.8 1,478oSalzburg (under 817.5945Dresden 0.75 4E. construction)0.5 821.2 937Breslau 4.0 6.0 PORTUGAL 354.2 847 Graz 0,5 $26.4 919Gleiwitz 317.5945Lisbon CTIAA (Wed. 03 456 694Klagenfurt 230 909Bremen 0.75 and Sat.: 10 -midnight) CELESTION 456 694Innsbruck 0.5 361.9 829Leipzig 4.0 520 577Vienna 20.0 374.1 802Stuttgart 4.0 ROUMANIA 891.6 766 Hamburg 4.0 395 757Bucharest 4.0 THE VERY SOUL OF MUSIC BELGIUM 421.3 712Frankfurt 4.0 220 1,360Chatelineau 0.25 455.9 654Danzig 0.75 RUSSIA Lig 250 2,200Schaerbeek- 458 654Aachen 0.75 825 363.5Moscow (PTT) 25.0 The only Pier Proof eour State- Brussels 0.5 462.2 649Langenberg 25.0 925 323Homel 2.5 mentiftobear Celestims Muria 275 2,090Ghent 0.5 476 630Berlin 4.0 1,000 300Leningrad 20.0 You ran do so without obligation at NOE 280 0.5 537 559Munich 4.0 1,444 207Moscow 30.0 1,070Liege 0.5 any good Wireless Dealers, or at our 312 9i oArlon 0.25 566 53oAugsburg 1,6e5 178Kharkov 15.0 Showrooms. Modelsrangefrom 612 t8oBrussels 10.0 566 530Hanover 0.7 .0.10.0in oak ormahogany. 677 520Freiburg 0.7 SPAIN Made under Licence. CZECHO-SLOVAKIA 1,650 182Zeesen 90 0 277.8 z,o8oBarcelona 1,650 182Norddeich 10.0 (EAJ13) 2.0 The new Celestion Booklet is free and 265 1,230Kosice 2.0 309 Oviedo (EA J19)0.5 278 z,o8oFeriby (testing) 12.0 970 giirs you briefly and interestingly all GRAND DUCHY OF 348 857Barcelona(EAJD 3.5 particulars.Mail the coupon below 299.3 1,060Bratislava 4.0 370 8orSeville (EAJ5) 0.5 342 873Prague (Praha) 6.0 LUXEMBOURG for your copy now! 1,280 234.2 Radio Luxembourg 0.25 400 75oRadio Espana...1.0 432.3 694Drums (Brno) 2.4 40/ 744San Sebastian DENMARK HOLLAND (EAJS)0.5 426.7 103Madrid (EAJ7) 3.0 CELESTION LTD. (DEPT.. 4 339 483Copenhagen 81.49,554Eindhoven (Kjobenbavn)1.0 456 658Salamanca KiNOSTON - ON THAMES. (PCJ) 25.0 (EAJ22) 0.55 1,155 259 Kalundborg 7.5 88.8 - Kootwijk (PCL) 32.0 Showrooms: ES'THONIA (Wed. 12.40 G.M.T.) SWEDEN 106, VICTORIA STREET, 408 935Reval (Tallinn) 1.3 261 2,149Herby 10.0 337 889Huizen (until 265 1,130Trollhattan 0.4 LONDON, S.W.1 FINLAND 5.40 p.m.)5.0 333 gooFalun 0.5 371 tooHelsingfors 1,073 279.5 Hilversum 346.8 865Goteborg 6.0 (ANRO) 5.0 1.5 (Helsinki)0 8 rfaHuizen (after 438 655Stockholm 1,101 199Lahti 20.9 1,152 545.5 550Sundsvall 5.40 p.m. and on 770 390Ostersund 2.0 FRANCE Sundays) 5.0 1,200 25oBoden 2.0 30.75 9,755Agen 0.25 1,152 262Scheveningen - 1,325 223Motala 30.0 2001,500Fkamp 0.3 haven 6.0 211.3 1,420Beziers 0.1 SWITZERLAND 233 1,260Bordeaux (Radio HUNGARY 406 739Berne 1.0 Sud-Ouest) 2.0 548 548Budapest 15.0 489.4 613Zurich 0.6 245 1,224Lille (PTT) 0.8 680 44rLausanne 0.8 252.1 1,190Juan-les-Pins 0.4 ICELAND 760 395Geneva 0.5 253 1,./85Montpellier 0,25 833.3 gooReykjavik 10 1,010 297Basle 0.25 254 r,./8oRennes (PTT) 1.0 255 1,775Toulouse (PTT) 1.0 IRISH FREE STATE TURKEY 268 1,//8Strasbourg 0.3 222.2 1,35 Cork (5GE) 1.5 1,232 243Stamboul 5.0 274 1,692Limoges (PTT) 0.5 411 73)Dublin(2RN) 1.5 1,840 163Angora 5.0

CHIEF EVENTS POLITICAL BROADCASTS

OF THE WEEK T is welcome news for those who take an WHEN A BETTER LOUD -SPEAKER LONDON AND DAVENTRY (5XX) Iinterest in politics, to note the number ISMADE -- CELESTION WILL of political speeches to be given before the MAKE IT. April 16.De Courville's Hour.

17.A Military Ceremonial by the and Battalion,dissolution of Parliament.Each speech the Norfolk Regiment, relayed from Aldershot. 18. A Symphony Concert, relayed from the Queen'slasts about half -an -hour, and the starting EC "Hall. Please send me a copy of the Niw Celestion Book- .--M-- time is 9.15 p:m. The programme. of future E17:4 tea Post to Glutton, Ltd., Kingston-on-Thames.E.0 'PP 19.A Vaudeville Programme. speeches is as follows :April 16, Govern- 101 DAVENTRY EXPERIMENTAL (5GB) ment; April 19, Opposition, Liberal; April NAME April 17.SpanishShawls, a revue byEdmund 22,Government; April25,Opposition, Wynschenk. ADDRESS 18. A Programme of Selections from the MusicalLabour; April 3o, Government; May 3, Comedies. Eel A Discussion on Broadcast Drama. Opposition, Liberal.During the time of Of 19. DEPT.JTS CARDIFF the General Election one opportunity will April is."Young Wales," a programme contributed by be given to each of the three political some of the Winners at the Annual Inter -parties to broadcast a speech. Collegiate Eisteddfod, 1929. entateur Wags) 572 APRIL 13, 1929 WHICH MAINS WIRE IS EARTHED? brownie IEADERS may recall that information was given under the above heading in a recent issue, regarding the testing of the mains for polarity and earthing. It should have been stated that when testing for the polarity of the mains, one wire of the lamp adaptor should be connected to one wire of the lamp -holder, thus leaving one wire from the adaptor free and one wire from the lamp -holder free.These two wires should be kept well apart and after plugging a suitable lamp in the lamp -holder the adaptor should be inserted into one of the lamp sockets of the house. The two free wires should then be dipped into a glassEVERY VALVE SET the of ordinary tap water. Bubbles will be seen `DOM to rise from the ends of both wires, but more bubbles will be seen to rise from the endUSER HEEDS A Slow Motion Diall of the wire which is negative. A Vernier Dial at 3/6 ! Bring your set NvATEs up-to-date by fitting this slow motion Having determined the polarity and dial.The mechanism is of special marked the house -lamp socket accordingly, LT -AMP non -back -lashconstruction which the next step is to find out which main is voRADIO TEST METER makes very fine tuning easy. Finished earthed. You may have a baseboard full of components-BUT you can- insmoothblackorbeautifully grained mahogany bakelite,this Negative or Positive? not hope to obtain really perfect QUALITY in reception unless unique dial gives high-class finish you have that perfect set control ensued by accurate Volt and One wire of the lamp socket should be Amp readings!All you want is a Wates Mater. With its three to every set in which it is included. readings on one dial feature it has an immensely withr range of connected to an earthed object such as the usefulness-yet it costs no more than single purpose instrum ,nts. lead covering of the mains or a water pipe, Obtain one now and let it reveal what a world of difference lies whilst the other wire should be connected in the expert handling of your sat.Obtainable from your dealer to the negative main of the house. Pro- or direct, complete with explanatory leaflet. iirouunie Stocked by Halford's Stores, Curry's Stores, and all radix vided there is a lamp in the holder and the dealers. LULY lamp does not light the negative main is READINGS 0-150 VOLTS earthed.If the lamp lights then possibly 0- 6 VOLTS INELSON ST. WORKS, LONDON, N.W,1 the positive main is earthed. To make sure, 0- 30 MILLIAMPS 11-5 5,C00 ohms. connect the unearthed wire to the positive Can be used as main, leaving the other flex still connected a Pole Finder with earth. If the lamp does not light then PRICE TUNEWELLthe positive main is earthed. If the lamp with our DUAL RANGE COILSdoes light, then it may safely be assumed that neither main is earthed. In every case 8/6 and CHOKES Crystallised black the lamp should be rated at the full voltage finish. a THE STANDARD CLARION THREEof the mains and should light up at full WET BATTERY brilliancy. Co.(Dept. AM.), LISSEN THREE 184-183, If ,the lamp only lights up at half brilli- Sha,tesbury Avenue, COSSOR THREEancy the mains should be treated as though LONDON, and all other neither main is earthed. If the lamp lights W.C.2 at full brilliancy on one wire and very dully SCREEN -GRID on the, other, then there is a faulty earth CIRCUIT COILSon the mains at the time of testing, and the M. B. at 21/- per pair mains should still be treated as thoughIlYVVVYYTTY777TYYTY*77VVVVYVVIN Range 20012000 metres neither main were earthed.If your negative main is earthed you may certainly con- LINEN SPEAKER H.F. Choke for Panel Mount- COMPLETE KIT ing, Valve Holdersider yourself lucky to a -certain degree, lo. Woad cut to lengths, Rubber Tubing, Massive All Purpose Finest Irish Linen, Dope, Brackets, Base, or6 - pinbut when in doubt treat them as though It.etc., with Blueprint and full instruc- 5/9 each. neither main were earthed.This means Os ticns.Make this and have the best. Base Mounting, IP' /m placing a large capacity fixed condenser - 111,- BLUE SPOT (adjustable) Unit, 25/- 1> Cabinet for LISTENER'S THREE "I MULLARD between the earth terminal of your receiver 11. los or BANTAM THREE, Oak 11/6, Mahogany 116.4 DUAL COILS and the actual earth wire. The condenser Cash with order. and All post free. -Britain's should be- either..5 or 1 microfarad capacityP". IMPERIAL RADIO CO..1 Favour - and should be capable of withstanding P 72 VICTORIA STREET, LONDON, S.W.1. he Three double the voltage of the house mains. IsAlsisIkisAskAA.AA.AA/ds.AAAAAskAA.A.IsA Dual Coils Finally, when testing or using the house 7;9 and 10,6 ..... mains always work on the house side of Messrs. A. F. Bulgin & Co., of 9-11 TWO - PIN the house fuses, and not on the supply sideCursitorStreet,London,E.C.4,have COILS of the house fuses. issued an interesting booklet illustrating all types tion of our Cossor Circuit Dual and describing a selection of foreign -made Aerial Coil, shoWing base mounting components which Messrs. Bulgin import from 1/6 and switch control. Let "Amateur Wireless" 54 STATION RD., direct from all parts of the world. The TURNER & CO LONDON : Nal list number of this booklet is125, and solve your problems readers can obtain copies on application. APRIL 13, 1929 573 mateur Wtre

.0\0"1","&iliz,

80/1/1/111111111111110, RULES .-Please write distinctly and keep to the point.We reply promptly by post.Please give all necessary details.Ask ons tmestion at a time to ensure a prompt reply, and please put sketches, layouts, diagrams, etc., on separate sheets containing your nams and address.See announcement below. Address Queries-Amaxitun WIRELESS Information Bureau, 58/6r Fetter Lane, London, E.C4 Indoor versus Outdoor Aerials. an indoor aerial, but most satisfactory resultsto calibrate and use it?-S. M. (Blackheath). are obtained when a stage of H.F. is used. A.-Tune in any -station working between Q.-I have been informed that if I erect and the wavelength limits you mention, and set use an indoor .aerial I shall stand a better chance-A. L. 0 o)1/40, 0V the wavemeter buzzer in operation. Turn the of getting distant stations than I do at present tuning dial of the wavemeter until the sound with an outdoor. aerial.I have a finer -valve set, 0 of the buzzer is heard in the phones or loud- with one stage. of what is known as K.F. ampli- 0 When Asking speaker with the greatest intensity.If the fication, and was assured by those from whom the buzzer can be heard over a great range of set iris purchased that this set would be capable adjustments, move it farther away from the of getting foreign stations on my speaker. I can Technical Queries set. When you have decided with which only get about two foreign stations and only 0 wavemeter setting the buzzer is heard at three British stations, the latter being London, PLEASE write briefly the greatest strength make a note of the read- 5GB, and 5XX. . Can you account for the and to the point ing. Do this with as many stations as practic- apparent paradox regarding an in, aerial able.Now either .make a table showing,the being better for foreign stations when my outdoor A Fee of One Shilling (postal order relation between the wavemeter readings and aerial will not get them P-F. K. (Fulham). or postage stamps) must accompany wavelength or draw a graph showing this. In A.-This " apparent paradox "iseasily each question and also a stamped order to pick up a station with the aid of the explained. When using an outdoor aerial close addressed envelope and the coupon wavemeter, set the latter to the reading corres- to a broadcasting station the amount of energy which will be found on the last page. ponding to the wavelength of the desired actually picked up by the outdoor aerial from Rough sketches and circuit diagrams station, and set the buzzer in operation. Then the local station is sufficient to swamp out all can be provided, but it will be neces- alter the tuning of the set until the buzzer By using an indoor aerial the sary to charge a special fee (which will is heard most strongly, when the set will be weaker signals. be quoted upon request)fordetail tuned to the station. Cut off the buzzer and amount of pick-up from the local station is layouts and designs. considerably reduced,thus permitting the 0 listen for the station itself.To find the wave- selection of signals from more distant stations. length of an unknown transmission which This is" practicable only in sets having at least has been tuned in, adjust the wavemeter until one H.F. stage to offset the reduced pick-up ofWavemeter Calibrating. it is most strongly heard, and then find the the aerial.In some cases quite good results Q.-Ihave abuzzerwavemetercoveringwavelength corresponding to the wavemeter can be obtained with a plain detector set andfrom 25o to 50o metres.Will you tell me howreading.-R.

8E09 149 1.510/1. N C C 207 rnateur Wig tle.1 574 APRIL 13, 1929 " EXPERIMENTS WITH NEON TUBES (Continued from page 564) DISPOSAL SALE that one can obtain extremely sensitive of High Grade Electrical and modulation by inserting the secondary of TO PERFECT RADIO Wireless Apparatus by the a modulation transformer in series with the supply leads.Fig. 5 gives a suitable R.A.F. and C.P.O. circuit for neon lamp modulation. Although In addition to their own extensive range, METERS -Milli -ammeters,allranges,15'.to2216. the neon lamp may be no better as a PETO SCOTT offer YOU Every Known 0 to 500 volts, 451..Weston Meters. all ranges to 1,600 Radio Receiver or Component -all on volts.Elliott, etc., Testing Sets. E.108, 4 ranges, amps. modulator than the ordinary three -elec- and volts, 45/-A.C. Hot Wire, f amp., 4/..Frequency Meters, various ranges Capacity Meters, ES; Wheatstone trode valve, yet it is certainly much cheaper Recorders, £12; Multi -Micro Galvos, 60/-; Res. Boxes, and is capable of giving excellent results. EASY TERMS 17/6; Hydrometers, 1/6; Relays, 6/6; Remote Switches, The following list is merely representative, and 15!-; 12 in. Spark Coils, £10.Anode Converters from we ask you to fill in the coupon below or send us A.C. or D.C. Mains for outputs of 400 to 800 volts. How It Modulates a list of your requirements. H.T. Generators in stock, 50 watts to 2 kw. Weston 90/ - Micro Ammeters for Grid Bias testing, 35/. only. Across the aerial circuit is shunted the COSSOR MELODY MAKER. Send on'y 1.01., balance in 11 monthly instalments of 14/7. TRANSMITTERS.R.A.F. Iin. Spark with A.T.1. and lamp in series with the secondary of a MULLARD MASTER THREE STAR. Send only 10/-, all fittings, in polished mahogany case.Cost £15. Sale, modulation transformer m and a high- balance in 11 monthly payments of 15/3. 15/. each; 100 watts, 25/-; 250 watts, 50/.. 2 -Valve Aircraft ditto, with Osram valves.Speech or Morse, tension supply.Adjust the resistance R LEADING MAKES OF H.T. ELIMINATORS from 40/- each.No. 1 Tapping Keys, open type,with mas- 917 down.Balance in 11 monthly payments of 417. sive contacts, 6/- each.Transmitting No. 51 KD, with until the lamp glows feebly. When the ARCADIAN PORTABLE. Kit of parts (see "A.W." aluminium cover, double contact, fine work, 7/6 each. microphone is spoken into the potentials March 30), Send only 20/-, balance in easy payments. Morse Practice Sets, with Buzzer and Key on Mahogany ETUDE 120 -VOLT H.T. ACCUMULATOR, 2,500 m'a panel, 8/6 each.Morse Recorders, for making picture set up across the transformer vary the hours. Send only 6/11, balance in 11 monthly payments machines,35/-each.SparkGaps, 2/-Artillery conductivity of the lamp, owing to its non- of 6/11. Electric Torches and Battery, 2'6. ALL MAINS TWO.Kit of parts (see this issue), send TRANSMITTING VALVES.6 volt 40, 100, 200, and linearcharacteristic,causing a varying on'y 15,'-, balance in easy in ta'ments. 250 watts, from 4'6. dampingeffectontheaerialcircuit. OSRAM MUSIC MAGNET. Send only 20,'-, balance WAVEMETERS by Townsend, Paul, Silver town, Gam- in 11 monthly payments of 21/9. brel!, and Marconi, from 151.. Another and preferable circuit arrange- Build your own set the Easy Way NOW ! LOUD -SPEAKERS. R.K. Cones fitted B.T.H. Moving ment is shown in Fig. 6.Here a third Our Catalogue contains allleading makes of Re. Coil, 100 surplus at only 7/6 each.Marconi L.S. Mag- electrode is formed by neatly sticking a ceivers, Accessories, Kits of Components for the nets, 6v. for moving coil cones, 20/-.Gramo. Motors, Home Constructor. Genuine Panatrope Motors, run direct off mains supply, coat of tinfoil to the outside of the bulb by JilaitCondon in unsealed envelofre under Id. stamb. fitted Turntable, etc.Few only.3716 each.Worth £4 10s.Chokes.Round's Output L.F. Chokes by means ofshellacvarnish.Thetinfoil CO. Marconi, for feed from power amplifiers.Latest model, should cover the whole of the bulb, but on 7/6.Condensers. NewSterling, 2 mfd.,genuine PETO SCOTTLTD. Mansbridge Condensers to 440 volts, at reduced price of no account must it be allowed to touch Please send me your big Iliustratel Lists. 2/10 only. the cap of the lamp or any other conductor NAME L.T. ACCUMULATORS.Celluloid, 2 volt 20 amp.. 3/.; 4 volt 20 amp., in case, 6/3; H.T., in Ebonite, 1,000 at earth potential.Bind a piece of copper ADDRESS m/a hours: 60 -volt, 19/6; 90 -volt, MI.; 120 -volt, 39/-; wire round the bulb so as to make good 3-v. Inert Dora, 1/3.Cell Fillers, 1/6.Hydrometers, 'A. W. 1114 1/..Petrol Testers, 2/6. contact with the tinfoil.This wire should Free Demonstrations and Advice ty Qualified Engineers at NEW CINEMA ARC LAMPS, 50/-.Leitz Lab. Arc then be connected to the grid of the oar Shops Lamps, 5 a., 55,'-. oscillator valve. 77 City Road, London, E.C.1 INSULATORS. H.T., in porcelain and ebonite, from 2, HIGH HOLBORN, LONDON, W.C.1. 6d. each. Empire,Insulating Cloth for Coils, Chokes. When the lamp glows the bulb -space 4, MANCHESTER STREET, LIVERPOOL. etc., 1/. roll of 100 sq. in,4 -Pin Plug and Sockets, Ed. 33 WHITELOW RD., CHORLTON.CUM.HARDY, pair.2 -Pin do., Wall Plug and Baser, 5 amp., 10d. - becomes semi -conductive, and the capacity MANCHESTER. MARCONI AERIAL ADJUSTERS, 30 to 300 Micro - effect of the outer coating with the interior, henrys, 4/6. forms an excellent conducting path for If eavy Rubber Insulated Lead-in Wire, copper strand coil. 2i- doz. yards.3/22 VIR Cable, 50 ft. coils, 1/-.Silk H.F. currents. The most effective modula- Flex, 1/6 doz. yards. tion is obtained by using a tuned grid cir- 52 PETROL -ELECTRIC GENERATING SETS.Air Force Portable, 1 kw. 50/70 volts 20 amps. from £20. cuit and shunting the absorption modula- 150 Electric Bench and Portable, 110 and 2210 v. Drills, tor across this. By adjustment of the grid from £3 10s.Electric Hand Blowers, 220 v.,17/6. Immersion Heaters, 110 and 250 v., 3/6.Electric Sauce- circuit tuning condenser a very flexible pans, 5/..12 v. Carburetter Heaters, 2/6. control of the extent of modulation is RECEIVERS. NewR.A.F.Aircraft3 -Valvesemi - portable, I Det., 2 L.F., 3 anti-pong Holders, Remote obtained.The polarising potential for the Control, Variable Condenser, and Rheostat.All tested on Broadcast, 27/6.R.A.F., 5 -valve ditto, with Valves neon lamp may be derived from the £4.Or fitted in polished Mahogany Cabinet with S.M. oscillator high-tension if desired. Dials, £6 10s.Burndept 6 -valve Super -Het, with valves and 2 frame aerials.New and O.K., TN 10s.Lht £45.3 -valveL.F.Amplifiers,30/, TwinLoud- Rectified H.T. from a Spark Coil speaker Wire, per 100 yds., 3/..2 -Pin Wall Plugs and Sockets, 10d.Remote Tuning Controls, fitted 2 varia. Fig. 7 gives the connections for obtain- condensers and rheo., 21- each. ing H.T. supply from a spark coil, and is ELECTRIC POCKET TORCHES, with new " Ever - suitable for use with C.W. and telephony Ready " Battery, 2/6.Hand Lanterns, ditto. 4/6. Airs1 Safety Lamps, 2 volts, 7/6.25 volts Candle Lamps, 6 . transmitters.The condensers should be each.Radiator 250 watt 110 -volt Lamps for Charging, 24. built to stand very high peak voltages. ELECTRIC BELLS. G.P.O. Circular,2/..Outdoor, When the interrupter of the coil " makes" 1/6.Sounders,10/-.IroncladBells,5/-.Pushes, 6d.; Multiple Pushes, 2/6; A.C. Bell Transformers, 12/6. the circuit only a low voltage of a certain SWTICHGEAR. Every description of radio and electric polarity is set up in the secondary, and, power switch and fuse gear at lowest prices; 6 -way this is insufficient to drive any -current Burndept switch boxes by Lucas, 3/6; 2 -pin wall plug and base. 250 v., 10d. 10 amp. porcelain switch fuses, with base through the lamp. At "break,'' however, and handle, 1/2 pair; small 250 v, 3 amp, porcelain fuses, radio receivers 3d.: twin bell wire, 1/6 per 50 yard run; 1-18 V.I.R. a high potential is set up across the secon- cable, 5/6 per 100 yds.; test thermometers, 1/6; petrol dary, and this easily passes through the THE CHOICE OF EXPERTS gravity testers,2/6; battery acid testers, 716; Morse recorders, minus ink -well and wood base, make fine auto lamp and charges up condensers c r and "NIKOLA" CONES units for home-made picture machines, W.. C2. For PURITY, VOLUME and. ADAPTABILITY Since only tlui " break" currents get Standard Chassis, cone floating in kid on felt -fronted Final Milian of our Surp:us Bargains in Radio and Etecfrion clamping -board, with screw -clamp to take any unit, Goods ,eady. Send stamped addressedenverope. SAVES through the lamp, and these are always of RADIO USERS POUSDS. the same polarity, it follows that the con, Read Mr. Reyner's test report in this issue PosT 14/6 FREE ELECTRADIX RADIOS densers are charged with D.C. Probably KNIGHT & CO., 6 ChaperSt, London, E.C.2 two neon lamps will have to be connected Tel :Cleikenwell 4715 218 Upper Thames St., London, E.C.4 in series, as one lamp may not stand a Blackfriars Station, Underground Railway. City 0191. back -voltage of more than 200. _ " A.W." Solves Your Wirelesi Problems a

APRIL 13, 1929 575 outuoriltwele

BLUEPRINTS IVeitg,=".97:=7=',.;::'d-criptions of all these sets can be obtained LEADING HOUSE FOR at ls. 3d. and 4d, respectively, poet free. Index letters "A.W-" refer to "Amateur Wireless " sets and " W ,M." K.RAYMOND' to " Wireless Magazine "sets. All Post Free KITS OF PARTS27 & 28a, LISLE ST., LONDON, W.C.2 See Weekly Advts. Come to LEICESTER SQUARE TUBE. CRYSTAL SET (6d.) Any list of components over 25/- quoted Thisaddress Is at the back of Daly's for at a special price, where possible. Theatre.. Phones:Gerrard4837 and 2821 Z929 Crystal Receiver .. AW165 HOURS OF EVERY DAY9 to 8 SATRDAY 9 to 9 ONE -VALVE SETS (1s.each) BUSINESS SUN.U MORN. 11 to 1 Beginners' One -valve AW 140 Reinartz One .. WM127 DON'T FORGET OUR TWO -VALVE SETS (IS. each) WHOLESALE DEPT. ro CTN. HOURSOF BUSINESS AS ABOVE. East to West Short-wave Two (D. Trans.) -AW1.59 WE STOCK, WHOLESALE AND RETAIL Beginner's Two (D, Trans) AVV17t Auto Two (ID, Trans)... .; AW174 BULGIN FERRANTI WATMEL LEWCOS EKCO AMPLION POLAR CLIMAX AW t8o All -Mains Two (D, Trans) CELESTION IGRANIC ORMOND 3.B. "Q "-coil (D, Trans) WM6z .. LISSEN M.P.A. PYE POLYMET Key -to -the -Ether Two (D, Trans) WMto7 EDISWAN COSSOR T.C.C. WMx14. r1UBIIIER Meteor Two (D. Trans) .. WM135 SIX -SIXTY COLVERN LOTUS W .B. Clipper Two (D, Trans) CYLDON''XeMICHAEL PHILIPS MULLARD and all standard components, valves, etc.Ever -Ready. THREE -VALVESETS (Is. each) Siemens, Exide Batteries. All -wave Mains Three (HF, D, Trans, Rectifier)AW144 All-purpose Short-wave Three (D, RC, Trans) AWI47 BRITAIN'S VALVES Screen -grid Q Cuil Three (HF, D, 'Frans) ..AWI5o Mullard, B.T.H., Marconi, All -Britain Three (HF, D, Trans) AW158 FAVOURITEEdison, Osram, Cosmos, Bantam Three (D, RC, Trans).. AWitio Cossor,Six -Sixty,Det. Hartley Dual -range Three (D, RC, Tram) .. AW 166 THREE (De luxe)H.F., L.F.,R.C., 10/6 each. Listener's Three (HF, D, Trans) price 4d. free Ormond Log .0005, 6'.;Power 12 6, S. Power 151-, with copy of "AW" AW169 .00025, 5/6; 7 -ohm panelS.G. 2216, Pentode 25'-., The Binowave Three (D, RC, Trans) . AW172 Rheo 2;6;3 Benjamin Clarion Three (SG, D, Trans) AW175 V.H., 4,'6; Formodenser CLEARTRON 1929 Favourite Three (D, RC, Trans) ,. AV( -179 Type "J," 2 - ; .0003 andScreen Grid, 2 volt, 12;6. Everyday (D, 2 Trans) . WM52 series clip, 2i-; 2-meg.Usual Types, 41-; Power, All -wave Screen -grid Three (H17, 13, Trans.) WMIto Leak, 1;-; Tunewell All Post 6d. (3 post free). Standard Coil Three (HF, D, Trans) WM1 17 GENUINE IDEAL BLUE SPOTpurpose H.F. Choke, 5/9; Festival Three (D, aLF-dual Imp.) _ WM118 Adjustable Power 66K (101) R.C.C. Unit Dubilier, 7/-; Wide -world Short -waver (SG, D, 'Trans) WM12o 4 -pole Balanced Armature 50,000 ohm wire wound,TRIOTRON New Year Three (SG, D, Pentode).. WM123 5/6; 2-mfd. Mansbridge,H.F., Det., R.C., 5/2 each ; The Q3 (D, RC, Trans) WMx24 Complete with Cord 25/-3/6;L.F. TransformerPower, 6/9. 2-v. or 4-v. Lodestone Three (HF, D, Trans) WM129 R.I. Varley,15/-;(add Post 6d.(3 post free). Simple Screen Three (HF. D, Trans) .. W0413: HANDSOME OAK POLISHEDbalance any other), Push- RADIO - Dynamic Three (SG, D, Trans) .. WMI36 SPEAKER CABINETS 13 x 13 x 6 pull Switch, 1/3, completeDARIO with Panel Brackets, In- MICRO FOUR -VALVE SETS (1s. 6d. each) Post dicator, G.B. Clips, 6 -pin2-v. or 4-v. G.P. 5/6 12/111/3 Base, Connecting Wire,Super Power .. .. 7/6 Overseas Short -waver (HF, D, zTrans) AWi33 Thin Flex,7 EngravedSuper H.F., 2-v. or 4-v. 7/6 The Ranger( SG, D, RC Tram) AW145 BLUE " Terminals. EBONITE Post 6d. (3 post free). Broadcast Picture Four (HF, D, 211C). ..AW163 Panel 16 x 8. and 16 x 9 Orchestra Four (D. RC, Push-pull) AWt67 SPOT la5/-Baseboard, 2 41n. Dials.ORMOND All Europe Four (2 HF, D, Trans) .. AW173 66K (101)Shown above.The above lot...L 8.51. Drum Diai , 5/-; Rheostata,6, -coil 4 (HF,D, RC,Trans).. WM7I 4POLE ADJUSTABLECash with order. .s/ 15, 30 ohm, 21-; Midget .0001 max., Five -pounder Four (HF, D, RC, Tram) WM9t BALANCED ARMATURE,Tunewell Dual Coll 6 -pin,9/-; Log .0005 sad 4 in. Dial, 6/-; Touchstone (BF, D, RC, Trans) Log. .0003 and4 in.Dial, 5/9. WMIo9 GENUINE 66K. 7/9 Lewcos Short Wave,S.L.F. No. 3 same pree. We always Reyner's Furzehill Four (SG, D, 2Trans) .. WM112 20/45 or 40,90, 7/6. stock all ORMOND PARTS. Economy Screen -grid Four (SG, D, RC, Trans) WM113 OR Binowave Four (SG, D, RC, Tram) WM119 LATEST SQUIRE 97 Standard -coil Four (HF. D. 2 RC) .. .. WM x 22 CABINET RIGID ALUMINIUMCRADLE, FLOATING CONE. Dominions Four (2SG, D, Trans) .. W1V1134. CLAMPING BOARD ASSEMBLED ANDSPARE/5/6 The Drum Major (HF, D, RC, Trans) WMx 37 BLUESPOT CONE KIT FOR . Our model 97 is supplied assembled complete with duplex woven floating cone, °tamping hoard AND a Kit of Parts for making kraf t cone. FIVE -VALVE SETS(1s. 6d.each) Cannot guarantee exact12" CONE Diameter of cone 911n. pattern of front panel, OR COMPLETE WITH HANDSOME 15 in. The lot " Q " Gang -control Five (2HF, D, zTrans) AW161 but all good designs. Carr. Pd. The Lot. - Poet free Empire Five (2 SG, D, RC, Trans) .. WM96 CABINET and BLUE SPOT UNIT 66K (U.K.) Widelity Five (HF, D, a RC) . WM13o (Genuine Ideal Adjustable) TRIOTRON UNIT Goods despatched Cash on Delivery (pay po4tmanc)haatrsglieghtly increased SIX -VALVE SETS(1s. 6d.each) 4 - Pole Balanced WithCabinet as C.O.D Short-wave Super -6 (Super -het, Trans).. AW 67 Armature/76 ORshown above and12" Eagle Six (3 HF, D, RC, Trans) .. WMto6 Adjustable1 Cane 27/6 r,t. CLARIONKIT OF PARTS ('A.W." THREE 9-3-29) AMPLIFIERS (Is. each) Q COILSIPolar .0005, No. 3,at5/9. .0001Reaction 4/-. Screened -grid HF Amplifier AW138 Dual range C.T.Coils,with Reaction(Tunewell), " A.W." Gramophone Amplifier (311C) AWi 62 LEWCOS Anode,10/6; Aerial, 10/0.3 Lotus or Fenno V.H, at 1/3. Searcher Unit (1 -IF) AVV176 Formodenser, "J," 2/-.Dubilier 1 mfd., 2/6..01 Fixed. True -tone (3. valves) (Trans, RC) WM47 QA 15/- T.C.C., 1/9.3-meg. Lissen or Edison Bell, 1/..S.G. H.F. Grarno-radio Amplifier (20 (Trans) .. W0472 QSP, QAR, QSG,Choke,Peto - Scott,5/.. H.F.Choke,Lissen,5/6. Signal Booster (HF Unit) .. . .. WM128 QAM, 21/- each.L,F. Transformer, LI. d, Varley, 15/,Ebonite Strips. Auditrol Amplifier WMx32 14x7 Ebonite Panel.Semen, II Engraved Terminals. Push-pull Switch, Flex, Plugs, 16-g. Wire,2 S.M-Dials. MISCELLANEOUS (h. -each) LOTUS Post Free QA 15/- The Lot 70/- H.T. Eliminator for A.C.. (zoo v. output) AWtoz .0002 Fixed and Series Clip I/6 extra. L.T. and H.T. Mains Unit (D.C.) - AW /23 QSP 21/- VALVES2v. Listener's Speaker, price 4d. free with copy of QM3 STAR 15/ -TYPE POLISHED CABINETS.C. D 10/5.P12,13. "AW" - AW170 Complete with Switch. 120v., 2v. 45. (Mallard or Sin -Sixty) Arcadian Linen -diaphragm Loud -speaker (Fu COLVERN DUALCOILS, ALL CIRCUITS. CLEARTRON

AW177A size) AW 7 8 £4 . 17. 6 S.C., 2v. 12/6 D.C. Unit(HT) C.T.15, L.F. or H.F. . "Junior':Moving-coil Loud-speak:1r St WEARITE TUNEWELL Carriage 4/- up to 200 miles, . 4/- Universal Short:waVe Adaptor WM82 Dual Wave Toner 15/-.H.F. DUAL RANGE COILS0/- over (U.K.), pass. train.C.T.15 x Power .. 6/ - WIMI2t Choke 6,6.S.W. Choke 4,6. Clarion Aerial, 10:8.Clarion An- ALL PREVIOUS OFFERS CANCELLED. Buzzer Wavemeter (6d.)_ 2 -way Switch 6,'-.3 -way Switch ode.10 0.Lissen Three, each 10/6. H.T. Unit for A.C. Mains .. WMx25 7,-.Loading Coil 7,6.Titan Cossor Three, each 10 6.All 5.0. Lodestone Loud -speaker .. WMI26 Coil Unit 15 -. Circuit Coils 21, -.pair, 200,2,000. James H.T. Unit for D.C. Mains WM133 Massive H.F. Choke, 5 9.HillardA.W. SPECIAL COUPON (64) Dubilier N.C. Condensers, FrictionDual Coil, 7,9, P.M. 151.Six - Control, .0005 and .0003, each 12,-.pin Bases. 2,-. FOR EVERY30/-youspend retail PORTABLE SETS Thumb Control, ditto, 15,6.Telsen Radio Grand L.P..12:6.Telsen YOU CAN buy ONE of the following for House Portable (SG, D, RC, Trans) AW163 1/6 Ace L.F., 8,6. Brown HA. Speaker,Copper and Aluminium Screens, all AmplionA.0.2.,21,-. sizes,or made toorder,P.W. each extra (on this Coupon) Arcadian Portable (SG, D. z Trans) with £3,3,0. Screening Boxes, 12,8. P.W. Load- 3d. 1/6 ld.PA. Popular Plague Speaker, linen -diaphragm loud -speaker (half -scale) AWx 77 29,6.Ormond Turn -table for Port-ing Coils, 7.6.Rothe Wave Selec- H.F. Choke, Silk Loud -Speaker Cord, 9 -volt Grid Chummy 4 (with Modifications for LS ables,C-.Halpin All -wave Tuner,tor, 12.6.Tunewell Dual 3 Star,Bias, Pair Panel Brackets, .0001 Reaction, 2 mfd. wms04i/o British General Tuner, 18/8.7,9.Combinel Wave Q 3 Star, and HT) 15,6. 12:6. Scott's All -wave Tuner, 13 Mansbridge, 100 ft. Insulated Aerial, 4- or 5 -way Wates 3in1 Test Meter,816. Battery Leads, 30 ft. Coloured Connecting Wire. Lotus Condensers, .0005, 619; .0003,DX Set 4 short wave, 7,6. DX L.P. 5,6.Colvern Master 3 Star DuaStandard Ratio, 8,'-.Weilo L.P.S.M. Dial, 12 yds. Lead-in, Fuse and Holder, 12 Send, preferablY, a Postal Order (stamps over sixpence Coil, 17 6. Power, 11;6.Weilo Standard, 8/6.Nickel Terminals, 60X Coil, Permanent Detector, in value unacceptable) to Blueprint Service Battery Switch, .0003 and 2-meg. Leak, 6 -pin Coil CATALOGUE -(144 pp.) Illus rated. V- Credited 10/- Orderbase, 12 yds. Twin Flex. 100ft. Indoor Aerial, 55-61 FETTER LANE (er Free with 101- Order)...... AMATEUR WIRELESS LONDON E.C.4 mateur WtreIT 576 APRIL 13, 1929 " AN ALL -MAINS TWO " R.I. & Vaxley, Lissen, lilullard, Dubilier). PREPAID ADVERTISEMENTS. Mains power transformer (Marconiphone Advertisementsunderthis headarecharged (Continued from page 55o) THREEPENCE PER WORD, minimumcharge model M). THREE SHILLINGS. 3-megohm grid leak (Dubilier,T.C.C. Smoothing choke (British General, R.I. DEPOSIT SYSTEM S.P. type, Mullard, Graham-Farish). As the Publishers cannot accept responsibility forthe and Varley, Ferranti, Igranic.) bona fidesof advertisersinthispublication, they have .000z-microfarad fixed condenser (T.C.C., Small panel brackets (Magnum, Camco). introduced a system of deposit which itis recommended should be adopted by readers when dealing withpersons Dubilier, Mullard, Graham-Farish). Grid -bias battery clips (Bulgin). with whom they are unacquainted.It is here explained. Five2-microfarad fixed condensers Intending purchasers should forward to the Publishers Connecting wire (Glazite). the amount of the purchase money of the article advertised. (Lissen,Ferranti, Dubilier, T.C.C., Mul- Flex and adaptor (G.E.C.). This will be acknowledged to both the Depositor and the Vendor, whose names and addresses must necessarily be lard). Red and black wander plug (Clix). given.The deposit is retained until advice is received of vo-ohm baseboard -mounting potentio- the completion of the purchase, or of the article having One yard of thin flex (Lewcoflex). been returned to and accepted by the Vendor. In addition meter (Lissen, Igranic). With the blueprint as a drilling guide to the amount of the Deposit, a Fee of 6d.forsums of£1 High -frequency choke (Lewcos, R.I. and and under, and 1s. for amounts in excess of£1, to cover and layout template,those who have postage, etc., must be remitted at the same time. In cases Varley, Wearite, Burndept). of persons not resident within the UnitedKingdom,double tackled set construction before will be tees are charged. Low -frequency transformer (Cossor,quite capable4of making the first steps in The amount of the Deposit and Fee must be remitted by PostalOrder orRegisteredLetter(Cheques cannot be Mullard, Lissen, Ferranti, R.I. & Varley,building up this "two." Novices should, accepted), addressed to British General). however, be guided solely by the construc- "AMATEUR WIRELESS," ADVERTISEMENT DEPARTMENT, - 20,000 -ohm resistance (Graham-Farish, 58/61, FEiisR LANE, LONDON. E.C.4. tional instructions which will be given in 'EARN MONEY AT HOME.You can earn money at nom,.,,, i note er spare time writing Show Cards for us. No canvassing. We train Y., next week's issue, and which will deal boat by our new simple method and furnish the Outfit free. We Imply, both men and women with steady work at home, no matter fully with small snags which might arise. s here you live, and pay you cash for all work completed each week, under our legal guarantee.Full particulars and Booklet free. Writs A point which will be of great interest +.t enee or call. Show Card Service. Hitchin. to London listeners is that this all -from - WIRELESS OPERATING APPOINTMENTS: fees payable after qua. ify- EASY TERMS ing Ifor boarding students.) Morse classes. Wire.ess School, Manor the -mains " two" will be exhibited in the Gardens, Holloway, N.7. Somerset Street windows of Messrs. Sel- BUSINESS FOR SALE.Wireless Business, Bournemouth, well estab- We specialise in the supply of all good quality lished, exceedingly low rent, and very good prisitiou, £500 including Radio Apparatus on deferred terms.All well- fridge, Ltd.- stock.Write "P" Smith's, Square, Bournemouth. LINEN SPEAKER.Drilled Bolt, Tapped and Screwed Extension to fit known kits of parts now supplied from stock. It is always a help to be able to see aBlue Spot. No Soldering, 2/6. Bramhall, 53 Branton St., Birmingham. LOWEST TERMS. set actually in the " flesh " before building ENGINEERS-IMPORTANT homy,. Owing to the unprecedented growth of this Institute, brought about by the -Success of our students, CASH ORDERS are dispatched POST FREE it- up. Intending constructors within easy we have been compelled to take much larger premises in Oxford Street. and in most cases by return. If you wish for something more than a "bread and butter" lob, you owe distance of Messrs.Selfridge's premises it to yourself to investigate our Service. Our handbook "ENGINEERING Send List of requirements to OPPORTUNITIES" has pointed the way to better things to over 15,000 would be very well advised to take a glance of your fellows.It contains details of A.M.I.Mech.E., A.M.I.C.E., A.M.I.E.E., A.M.I.A.E., City & Guilds, G.P.O. Exams., and describes LONDON RADIO SUPPLYco. at the set in the Somerset Street' windows over 60 home study Courses in all branches of Electrical, Mechanical, and Motor Engineering.In a brilliant article, Professor A. M. Low 11 OAT LANE, NOBLE ST., LONDON, E.C.2 before making it up themselves. shows clearly the chances you are missing. The book and our advice are quite free. We guarantee "NO PASS-NO FEE." Don't delay, send a 'Phons,: NATIONAL 1977 postcard-now. (State Branch or Exam.). We promise that it will be a minute of your time well spent. British Institute of Engineering Techno- logy, 109 Shakespeare House, 29-31 Oxford Street. London. W.I. The The Practical Electricians' Pocket Book-This handy reference book has been " TONE SUPERB" issued for thirty years, but the 1929 edition Assembled Baffled Floating Cone Chassis IL The "Tone Superb" 16 -inch fretted hasbeenentirelyrevised.Measuring front6 -plybarEedfloatingcone chassis, repi °duces music and speech instruments, power -station plant, boilers, amazingly natural. Capable of enor- Super Long Range switchgear, illumination, wiring, pyrometry, mous volume ifrequired. Total absence of chatter or metallic noise, 5 Valve PORTABLE armature construction and repair, dynamos, which is common in metal frame Is the World's Greatest Entertainer transformers, overhead transmission, sys- chassis.Can be fitted into a frame Ba'ance can be paid on easy monthly instal- YOURS FOR forming a cabinet in a few moments, menus graded to suit your pocket. Every tems, and electric furnaces are just a few of making a speaker, equal to any expen- desc ipt.on of Wireless Sets. Accessories, Lout 1 0/ the section headings. A 'valuable section sive model.Is in itself an attractive Speakers, Accumulators, etc., on the easiest piece oHumiture, supplied complete. terms. Also Gramophoncs. Records, etc. for the wireless amateur is a tabular list of Beautifully french polished, in rich Illustrated lists free. ' DOWN dark Oak or Mahogany. Any unit can central stations throughout the United he fitted in 5 minutes.All holes are accurately drilled, and bolts supplied. v WALLINGTONKingdom and Ireland, giving details of the If stplied with Blue Spot milt fitted, oF-Id supply voltages and the systems used. It is 25s. extra, _Triotron, 17s. 6d. extra, WIRELESSSTORES SURREY. Hegra, 21s, extra. published by "Electricity," 93 Long Acre, If above chassis supplied complete in London, W.C.2, price 25. 6d. nett (2s. rod. attractive, hand -polished 17 -in. Oak cabinet to match, price27s. 6d. gCOMPLETE postage paid); and contains 596 pages with Ditto in' Mahogany, 5s. extra.Price of Chassis only, as illustrated, 21s. Thoemfpamoeus 'LUTONIA many illustrations. Complete withCmpone"n3tsV*ils(dit Illustration ofChassis,Send lid. stamp for further detailed in - ing Long and Short Wave Tuner,inc all with both sides removedformation and convincing proof of the assembled readyforwiring in handsome Oak showing method Of unitcapabilities of the "TONE SUPERB" Cabinet, suin. x 7in. with special oval panel. mounting Chassis and other interesting components LUTONIA RADIO SUPPLIES,1,WadesPlace, WARRICK RADIO, 16 BertherRd., Hornchurch,Esses Mile End, E.1. Phone: East 454z "Amateur Wireless and Radiovision." Price Tel., Hornehurch, 230. " Threepence. Published on Thursdays and bearing the date of Saturday immediately following. THE 31-GUI1IA FINISHING TOUCH for your ARCADIAN PORTABLE Post free to any part of the world : 3 months, REPAIRS 4s. 6d. 6 months, Os. 9d.; 12 months, 17s. 6d. AnymakeofL.F.Transformer, Loud -speaker Postal Orders, Post Office Orders, or Cheques or Headphonesrepaired anddispatchsd within CABINETS for this MODEL 48 HOURS-TWELVE MONTHS' GUARANTEE Beautifully hand french -polished with all wooden parts complete should be made payable to" Bernard Jones itlt earls repair.4/- Post Free. Mahogany Finish , 25/- Carriage Publications, Ltd.' Terms to Trade Solid Oak . 30/- and Packing General Correspondence is to be brief and Solid Mahogany.35/.. 31- extra TRANSFORMER REPAIR CO. Personal guarantee of satisfaction, or filmy returned. written on one side of the paper only.All "Service" Dept. 214 High Street, Colliers Wood, London S.W.19 F. W. RAMSEY,63Shaftesbury St.. LONDON. N.1.Clerk 7139 sketches and drawings to be on separate sheets. 1 Contributionsarealways welcome,willbe promptly considered, and if used will be paid for. E THE LITTLE CELLS THAT SATISFY Queries should be addressed to the Editor, and t&e13OF S //IIt;Ritdi0 - Layton PrimaryH.T.Battery, PI Porous Pot Cells,ig SI & S2 Sac Cetla. All compkete for assenSIY- the conditions printed at the head of " Our Information Bureau" should be closely observed. P1 Ie!.elc ..59..!?-181.3°471. 1- Communications should be addressed, accord- SI ed. ...3/-...5/3...12/.. E BE/7 IN THE WE/T) ing to their nature, to The Editor, The Adver- 10 tistt slant, LEICESTER SQUARE. tomMel.w.C.11. "Easeful" Filler :I -pint 1/..; Pint 1/6. Post 34 extra almal orr,e Zit.we Z. %Ant for tisement Manager, or the Publisher, "Amateur OPEN TILL.711.4.4. = Send lid stamp for booklet giving full particulars to- WRITE FOR OEM GATALOGY1 THE LEYTON BATTERY Co. Wireless," 58-61 Fetter Lane, London, E.C.4. POSTAGE 66 Wit 10 CATI1RS -305 CHURCH ROAD LEYTON COUPON tau ateurWirelesi Available until Saturday, Lf APRIL 20th, 1929 APRIL 13, Ill maturWreI

smith ONANDLISTEN! LEWCOS " Coilswill fittea and Quality Of Give t- ed Tone Ree e 117011,, 'Lleprolit

vivisprovmoos

B.F. . TRANSFORMER FOR CENTRE TOUCHSTONE QAS COIL AND TAPPED FOR LODESTONE COILS "MULLARD RECEIVERS (Pat. No. 271334). MASTER 3°." Wavelmgt hrange 235550 in.,ta es.

BINOCULAR COILS (Pat. No.211373). CHOXE

All Lewcos Medium - wavecoilshavea REGD. rangeof235/550 RADIO PRODUCTS metres and can thus be used for any Obtainable from Stock of all Radio Dealers. stationin G r ea t The LONDON ELECTRIC WIRE COMPANY AND SMITHS LIMITED, CHURCH ROAD, LEYTON, E.10. Phone :Walthamslow 2531. Grams : Lewcos, Phone, LondonLEWCOS RADIO Britain. PRODUCTS FOR Trade Counter and Cable Sales. 7 Playhouse Yard, Golden Lane, E.C.4 FETTER RECEPTION. Pit*Kitire.010212P2&KoKeniPlal5gir402102/412KgSKAP211412kW.Iti&S02*&.****Cit4P2P2tArAnKolreAl

AT THE PRICE V. /EAR 1 hese ere the actual words of a user. ,t Weilo Trandormtrs are1CO%sound. Can he relied upon as a really excellent job.Annzin ! COMPOAIS purity of maximum amplification.Guaranteed 2 yecrs. Why pay high prices-specify Weilo ! Adtfor details of our Push -Pull Trandormrt. 11 b -Model 10, Ratios 1-1,3-1,1-1,5-1,25-1 W. James "Special 3 " Coils 25/- pair

8 6 A 3-1, -I-1, 5-1 Wriff for interesting Catalogue of N.S.F. W. James "Binowave" Coils 25/- 9 9 nSWei,o-Conobonent, to- S. LEWIS & CO., LTD. (13.-..pf. A.W.), 39 Victoria Street, ARCAD/AN PORTABLE Coils each 10,'6 Screen .. 9'6 H. F. Chokes .. 6;'6 Battery Switch, G22 (with terminals) Valve Holder, LAS5 2/6

Grid Leak Clips -/6 PANELS FOR ALL CIRCUITS Coil Formers (unwound) pair7'6 Dual Range Tuner, W.G.2, as used in FERRANTI Circuits15'. Registered Trade Mark ALL FROM THE MAINS TWO Dual Range Tuner, W.G.2 pair 15:- The originalBECOL Low Have you seen the new . .. Los; Former,made in BECOL Pinless Former H.F.. Choke . 6,16 sizes1" up to 4" outside LOOK FOR diameterin lengths up to and Base, which is abso- H.T. Choke ,,21/ - 36 in.The former that re- TRADE lutely foolproof ?If not mains rigid when wound. MARK send for particulars. Valve Holder, anti-microphonic, LAS5 each 2,6 DO NOT BE PUT OFF WITH AN IMITATION. Write for copy -ofBECOL Handbook on WirelessCircuits.Full data of windings and ifluhtraticns.Price 4c1. Post Free. WRIGHT & WEAIRE, Ltd, 740,HIGH ROAD, TOTTENHAM, N./7. Sole Makers: Telephones; Tottenham 3847 and 3848 THE BRITISH EBONITE CO., LTD., HANWELL, LONDON, W.7 Please Mention"A.W."When CorrespondingwithAdvertisers entatturWiretzsi APRIL 13, 1929 MAR iv

TESTED once

TESTED twice

TESTED 3 times

Not only are all components of Marconi Valves tested at every stage of manufacture, but before they can get Into the purple box bearingthe name Marconi the ce C?". completed valves have to pass the following triple test.

i *(4 , t The " qualifying" or Factory .7: + e e" aye test. teiree 0,,,s ee ' . ,>t:, ce - I (." C, tis 4'')itZt.. °V :q5, (4.00°I The "passing out" or Stock 17", 9 -....,.., , 17i 0,..., test.

v4c. c°.; ',6cfr'e' 'iC17' '/./.. The." third degree" or He7.d- _ . 4i 'Ox44..". - io 4 .. ' ("o - .ey4",''.. . :- quarters test. ,7 `.1' e, . ,...i'.e, Pe ---,, (-,.?,..' ,11'r<$ '?, o ..-..... Marconi. Valves are consistently ati4 '', good because (hey are triple tested. 4'./.44 1--- P-9? -`?.,A .1i.4',:).:1_, Write for Marconi Value Cats- C : ..tp ,...`Vq 7 v .a°_ lo ue IV-. 520 gitiing particulars and character:s is cures of all ;- t..014-eb *ks types, mention'ns AMATEUR 444115 WIRELZSS." . .Aect 115,e001..6St& ''l '"14:./6,,,0 TRIPLE TESTED The Marconiphone Co., Ltd., 210-212. Tottenham Court Road, London, W.1

M. V. 25-r3.2. --Showrooms: Marconi House, Strand, W.C.2 Printed in Enkland: l'ublished by Bernard Jones Publications, Ltd., 58/61 Fetter Lane, London, Sole Agents for South Africa: CENTRAL News ADEACY, Lt :TIED.Sole Agents fur Australasia: GORDO:4 A Gorcn, LIMITED.Saturday, Apri! 13t9-21 AMATEUR WIRELESS, APRIL 20 W) TWO SETS: "E5-5-0 PORTABLE" 86 "STABILITY 4"

Every a Thursdau0

Vol. XIV.No. 358 APRIL 20. 1929 OmakurWird,s1 of hehasts CENTRE TAPPED COIL ectreception MOSE, ONEOS VOS ILEA NA/SITEISSIRUCTIVE 11LESE Cholce. D)ubleTapped O'1VVETS'Frequency and (CT.) R.3sllighTapped Centre SUPER R.34 (X)Coils. COIL Q Coils. Coils. R.3s Six -Pin R.36StandardCoils. Binocular Cils.Coils. R.3/ Screened Dual ap . R.38 NV av etr R.39 Potentiometer. forScreened FixedSix -pinCods. R4°R.4.3 Super Transformers QSG"1-1.V. It.47 Valves. Radio Grid Coilsunscreened.ofLevccos DualRange range RASSheetillustrating R.Asa Products.

H.F. CHOKE

Q COIL.

÷ '6' X'A-.°c, oSv. / ii '''''(6*.ts'''.' .....:,.,, .\.V., AO° c.' -.)..Veil- / ..o%-' , , 4,,,z, .7- .,,,,--*0 / ..,c, , z,.-g.,, ..\.,-,§,-, ....c H.F.TRANSFORMER ,, - ,,,-, e 6c,,,,e, , TOUCHfoSrTONE / . ,/ .k,PSN' ,-1,, :r, e -c_P .s* LODESTONEand e` -J s.\'). \e>. / I-EwccRAD - RECEIVERS it'L'tb'e'' ,,,, FORRule-118N, 0;4 PRODfir--S ,\..-,,,..\- LETTER- / (s -c' /

Don't Forget to Say That You Saw it in "A.W." APRIL 20, 1929 577 e=tawWireiT

Vtt0 NEARLY 50%

THE reason for this astonishing reduction is that by concentrating on one type only, we feel that we are able to give the public the finest Horn Loud Speaker in the World at a very reasonable price. This speaker has the original world-famous H.1 Base mounted on a polished mahogany pedestal and is fitted with a "Q" shaped horn, finished in black or brown enamel. The height of the instrument is 20". Experts acknowledge that a horn type loud speaker gives louder signals with less valves. They state also that it gives better long distance reception, than can be obtained with the cone.Therefore, owners who have only utilised the cone can now purchase the very best horn type loud speaker for £3. 3. Od.Ask your dealer to show and demonstrate this wonderful speaker to you.It is precisely the same speaker which has helped so much to build up the reputation of S. G. Brown, Ltd.

MI 8350 Advt. S. G. Brown, Ltd. Western Ave., 71. Acton, London. 1V

Don't Forget to Say That You Saw it in ."A. W." CI:tatter Wtrell!, 578 APRIL 20, 199

DOES YOUR SET CONSUME FOR satisfactory and economical service you must use H.T. Batteries of correct capacity. The following table is a useful guide to the battery you should install:

Ever Ready " STANDARD" Series. W.16-66volt. The " WINNER "Series. Winner 66. The" POPULAR "Series. 12s. 6d, 01 X 31 X 3/,for Is. 6d.91 x 3 x 21, for 6 milliampere Popular 2-66 volt. 9s. 6d. 91 x 3 I x 3.Small Capacity, 6 milliampere emission. emission. These batteries represent the fines0 for 6 milliampere emission. value for money based on cost per These batteries are good value for money, and at the In brown metal containers. hourofserviceforlowpower stated emission satisfactory service is guaranteed. Suitable for the usual two - receiving sets. valve sets. Ever Ready " HIGH CA- Power Capacity, forro-16 PACITY " Series. W. 34-66 milliampere emission. Popu- volt. 22s. r4f X 51 X 3, for lar Power 64. 14s. 6d 10-16 milliampere emission. X5 X3. These batteries represent the finest Theseunitshave largecapacity valuefor money for high power EVER REAfg 7R cells and will give economical ser- receiving sets. T fam-cor; vice with power valves requiring X XX heavy emission of current.

11tRit',Ot k.V,RtI 1 -"ItAt)... ..,

1 1,-,I RAT -1 -A . to,Stytt A" 7 TREAD e4 -.s, .. Aip

EVER READY The Ever Ready Company provides a suitable and reliable Battery of any voltage for every set. Ever " SUPER r " Super Capacity SUM?. I ReadyBatteriesareconvenient, 21s. trouble free, give purity of tone, 45 volt. 4a x St x 8, for and are the handiest form of H.T. 16 milliamperes and over. supply.

These batteries will give reliable service on any high power set known,

O e4* R BRITAIN'S BEST BATTERIES

Advt. of The Ever Ready Co. (G.B.), Ltd., Hercules Place, N.7. Advertisers Appreciate Mention of !`A.W." with Your Order 0 ten i7)ten c2)c,a § APRIL 20, 1929 No. 358.Vol. XIV N C N 5 5 5 5 S ub 5 S . 5 5 5 5

6.5 The Leading RadioWeekly for the Constructor, Listener and Experimenter =----Editor : BERNARD E. JONES 5 § Technical Editor :J. H. REYNER, B.Sc., A.M.I.E.E. Research Consultant : W. JAMES Assistant Editor: H. CORBISHLEY E Controversial Politics I-and Politics byWire-People's Palace " Pops "-- ElstreeRivals Savoy Hill- Fultographand Weather-KDKATelevision ControversialPolitics !-The formidable rivals to anything that series of political broadcasts organ- the B.B.C. has done in this respect, ised by the B.B.C.iscertainly and although those now being con- having its effect.Following the structed are only temporary, one is first political speech a prominent 7o ft. long, 4o ft. wide and 25 ft. daily paper came out with a glaring high. Two more giant rooms, which poster "An Amazing Broadcast." will be as big as anything in Holly- Well, the B.B.C. won't need any wood, will be started in a month or outside defence. We've asked for so. The talking -film engineers are these controversial speeches, and in adopting the flannel draping which the opinion of AMATEUR WIRELESS, the B.B.C. people appear largely to it is far better to have them, and to have dropped. have daily papers fighting over the The Operas-The opening night effects on the following day, rather of the opera season is April 22, and than to have continued with the on that occasion Act Iof .Der dull incontroversial stuff that was Rosenkavalier is to be given from the put out before the rule was changed. Royal Opera House, Covent Garden, Controversy keeps the papers alive, to 2L0 and 5XX. It is a fact worth and the same medicine is good for A new use for radio !This armoured car, designed for the noticing 'that arrangements have rough roads of. India, has a complete transmitter and, the microphone. receiver.It is here seen being tested in London. been made whereby during the -and Politics by Wire-More- season, listener's to 5GB will also be over,the microphone isn't having thepeople have said, to be regretted that thegiven the opportunity of hearing excerpts monopoly of politics.Great strides arelocality of the hall is against the possibilityfromtheoperas.Wagner'sromantic being made in the land -line relays ofof having the same kind of "gate" as wouldopera,The Flying Dutchman,isbeing political speeches, as was described recentlyobtain were the concerts held elsewhere :produced in the Savoy Hill studios on in AMATEUR WIRELESS.Baldwin andbut for the " mike, " environment must takeApril 24, the cast including many " stars," NevilleChamberlainhave,onseveralsecond place, and acoustics come first !but it will be heard from 2L0 only. occasions, addressed audiences in other hallsIncidentally, La.ndon ROnald seems to be Fultograph and Weather-The secret by land -lineandloud -speakers(withputting in some very hard work, which iswas disclosed in these columns recently wireless -type amplifiers), but in no case haswell justified by results. that Fultograph apparatus has been tried the number of unseen audiences exceeded Elstree Rivals Savoy Hill-They areout in high circles, namely, at `the Royal nine.But now we have Lloyd George'sgoing great guns at Elstree's "talkie"Airship Works 'at Cardington. A weather speech to no fewer than twenty-eightstudios. Thestudiosthemselvesarechart was recently prepared and trans- centres, the land -line arrangements Ocatencatice7icence7a.a.e,ne:aacencat.encete7,13mitted via Fultograph to the Royal necessitating about 3,000 miles of § 5Meteorological Society at South route wire.Apparently the big PRINCIPAL CONTENTS § Kensington, and following this a political leaders pin faith to the Page general inference and weather fore- loud -speaker, and they have not Current Topics.. 579 5cast was also sent. We have seen

been loth to take advantage of the Captain West Leaves the B.B.C. 580 both the chart and the printed re-

microphone. The £5 5s. Portable .. * 581 port, and both are excellent. As is People's Palace " Pops "- 5 Economy With Fibre. Needles .. 582 well known, the "straight line" test The B.B.C.'s series of orchestral -5 Sources of H.T. Supply 583 is most severe on wireless picture - concerts from the People's Palace § In My Wireless Den .. 584 machines of the Fultograph type, On Your Wavelength.. 587 and there are plenty of such tests in the East Erid of London seems to § going. very well. An AMATEUR The Subtleties of Volume Control 589 in weather charts ! For the Newcomer 590 5 WIRELESS representative, who was ic.Y .. KDKA Television-Here's a tip, atthePalace.duringarecent N Without Fear or Favour 591 "listen"forKDKA's television broadcast, found the arrangements § The " Stability Four 592 broadcasts on 63 metres, between very similar to those employed on § "A.W." Tests of Apparatus 596 ro and II G.M.T., on Mondays, previous occasions, and there is no An All -mains " Two ' 598 Wednesdays and Fridays: speech on doubt but that the hall is quite good Wireless Control of Models 600 25 metres; 6o -holedisc; turning acoustically.Itis,asso many left to right, at 1,200 r.p.m. (I mutest Wtrele-!5 580 APRIL 20, 1929 CAPT. A. G. D. WEST LEAVES THE B.B.C. Research Chief Turns Over to Radio Gramophone and Talkies In about the middle of 1923, the engineer-interesting in that it was indirectly the ing organization began to get into shape"cause" of all the fading and dissolving and take over the operation of stations fromtechnique of modern radio plays. the manufacturers.There came the neces- It was found necessary to set a number sity for an experimental section and Captainof microphones in the woods at Oxted, and West was called in to investigate certainswitch on the particular microphone which problems and form his own Developmentwas nearest to the singing nightingale. Department.At the end of5923,hisClicks and noisy changeovers from one "flying squad" was formed and I had themicrophone to another could not be per- honour of being appointed his assistant.niitted, and the duplication of microphone I am now appointing myself his " Boswell"!amplifiers meant the transport of much additional gear to the spot. Thereupon, the' The First Relay fade or dissolve from one microphone Capt. A. G. D. West One of the first problems of Captainanother was evolved and successfully used THE B.B.C. has been suffering heavyWest's department was the design of afor the first time at Oxted. losses lately, particularly on its engin-"wireless link," to be used for relaying eering " front." The advent of talking filmsAmerican broadcasting. In those days, theResearch has attracted many engineers and severalreception of a weak station on a too -metre The constant expansion of the engineering of the leading " programme " people, in-wavelength was no easy matter, screen -side of the B.B.C. made it necessary for a cluding R. E. Jeffrey, the producer, to thegrid valves, neutrodynes and low -loss coilssub -division to be made in the experimental rather more prosperous parish of Elstreenot- being general at that time. Never-design and research work carried on by the (Herts), which isEngland's Hollywoodtheless, a receiver which included six H.F.Development Department. Captain West (Cal.). The latest important move is thatvalves, transformer coupled, was success-was appointed chief of a new section,' of Captain A. G. D. West, the B.B.C.fully used, the stability being maintainedResearch, and I(his faithful Boswell !) research chief, who has just resigned inby careful design and the use of low - order to take up an important position oncapacity sausage -shaped valves.It the technical side of the H.M.V. Gramo-seems a great pity that this type of phone Company. valve, with its obvious advantages, Captain West will be chiefly rememberedshould be abandoned in favour of by listeners in connection with the manythe type of valve and holder that startling " stunts " he carried out in thehas now become standard. early years of broadcasting, such as the I well remember the days-and first American broadcast relay, the trans-nights-we spent in a cold little hut missions from aeroplanes, railway trains,at Biggin Hill Aerodrome, playing divers' helmets and the like, but most of hisabout with this elaborate trans- work has been carried out " behind theatlanticreceiver.Unfortunately, microphone."I met Captain West whenthe signals of the distant KDKA the original B.B.C. Development Depart-.did not become steady or strong ment was formed at the end of r923, theuntil the London station had closed first year of British broadcasting. He haddown and a relay was impossible. come to the B.B.C. after having been aHowever, on the last day of 1923, Wrangler with distinction in the mathem-half -an -hour'srelayof KDKA atical tripos at Cambridge and achievintwas carried out and we heaved a 1st class honours at the London Universitysigh of relief and went home ! in his stride. He also worked with Sir Ernest Rutherford and Professor Apple-Stunts ton at the Cavendish Laboratory for a year. After the first relay came any Captain West served in all three servicesamount of stunts, and Captain West kept J. A. Murray and myself busy during the war, but was concerned particu- Capt. West engaged in research work for the B.B.C. larly with radio work in the R.A.F. Wheninall kinds of awkward places, peace "broke out," he went to Cambridge.from aeroplane cockpits to the top offollowed him. Studio acoustics, reverbera- Big Ben tower.Transmissions had to betionofauditoriums,measurementsof The. Development Department relayed by wireless from the Old Vic. tomicrophone, amplifier and loud -speaker When the B.B.C. first commenced broad-Savoy Hill owing to the unsatisfactoryefficiencies now formed the programme of casting, the stations were actually operatedland -line, and a short-wave transmitterthe department by theradiomanufacturers who hadwas erected on the roof of a public house One of the first inventions of Captain West erected them. Birmingham, for instance,next door to the theatre. The impulses fromafter taking up the question of acoustics, was maintained by the Western Electrica microphone in the footlights were radiatedwas the practical supply of an artificial Company, and London and Newcastle byfrom this aerial and picked up on a super-echo on transmissions from highly damped the Marconi Company. Broadcasting offi-heterodyne at Savoy Hill. small rooms.It seems a pity that the cially commenced in November, 1922, but Anothermore straight -forward stuntB.B.C. are to lose the services of such the actual B.B.C. engineering staff number-was the picking -up of the song of the night-an experienced and enterprising research ed only about half -a -dozen for many months.ingale. This particular effort was especiallyworker as Captain West. APRIL 20, 1929 58i maw Wire ,

THE 5050 PORTABLE Weight and size are two important considerations in portable receiver design. In this Instrument both have been kept within reasonable limits by the use of an external aerial and separateloud- speaker many cases give a greater pick-up Two valveholders(Lotus,Wearite, than a midget frame aerial, and doesLissen, W.B. Burton). not entail the same complications, .000r-mfd. fixed condenser, and .0002- either in itself or in thereceivermfd. fixed condenser(Lissen, , Dubilier, which follows it. T.C.C., Mullard, Graham-Farish). The receiver has been Grid -leak holder (Lissen,Dubilier, designedas atwo-valver,Graham-Farish). and no H.F. stage has been 3-megohm grid leak (Lissen, Dubilier, incorporated,so -thatinitialGraham-Farish, Mullard). costisas low aspossible. High -frequency choke (Igranic, Burn- Indeed, many amateurs willdept). have at hand most of the Low -frequency transformer (Philips, Mul- necessary parts for the construc-lard, Cossor, Ferranti). tion of this portable "two." Special dual -range coil (Peto Scott). THAT when the fine weather comes theEven if all the parts have to be purchased, Connecting wire (Glazite). out-of-doors call may be stronger thanthen the receiver is still an economical Four terminals, marked Aerial, Earth, the attraction to the radio bench is almostproposition, because it may save the costL.S.-F, L.S.- (Belling -Lee, Eelex, Igranic). a foregone conclusion, except in the case ofof a portable gramophone. This, with a Three red and three black wander plugs very hardened "hams." Portable sets havesuitable stock of records, might cost double(Clix). ilong passed the experimental and labora-the price of the radio "portable," and still Two spade terminals (Clix). tory -stages, and nowadays they are notwould not be capable of giving entertain-Receiver Arrangement confined to the expensive class. ment of endless variety. As the circuit is a two-valver, there is no A blueprint is available for this set, which Light and. Compact difficulty of operation to contend with,can be obtained, price is. post free, from and this point will be appreciated by allAMATEUR WIRELESS, 58-61 Fetter Lane, In this new portable the AMATEUR WIRE- London, E.C.4. f.ESS Technical Staff has set out on a newwho, when out of doors, have no time An examination of this track which is bound to have many fol-themselves to meddle about with trickyblueprint, or of the small reproduction controls, nor would they hand over an un-given herewith, clearly shows the layout manageable set to inexperienced friends.of the receiver and the general idea of the Nowadays the operation of a two-valvercontaining cabinet. These features will be is within the capabilities of everyone, justa great advantage to constructors who, in a as everyone can change the needles andset of this type, should get a clear idea of the put a new record on a gramophone, and sogeneral arrangement of the components it is just the thing for picnic and similarbefore starting to make up the receiver. occasions at a reasonable distance from a So far as the receiver portion itself is station. concerned, this is constructed somewhat in The following parts will be required fora conventional manner, with a small base- this receiver, that is assuming that youboard at right angles to the panel.This have to purchase all new parts and havearrangement is eminently suitable for this not several of the components at hand. (Continued at foot of next page) Potential constructors, however, who are attempting to cut the initial cost of this The Circuit of the £5.5.0 Portable receiver should be guided by the type ofThis picture ;lowers. This set is a simple, straightforwardcomponents mentioned in the followingshows t We - two-valver, of just the type to which alllist, and if those actually specified are notrear of the amateurs are accustomed for indoor broad-available the most approximate equiva- receiver cast, reception, and it is contained in alents. should be used. icabinet which is not hampered with loud- Speaker or frame aerial. List of Components This means that in quite a small carrying Ebonite or bakelite panel, i4 in. by 7 in. case there is the maximum possible battery(Becol,Raymond, PetoScott, Radion, space; you have not to make a special loud-Paxolin). speaker unless you feel so inclined, and Baseboard, 123,(1 in. by 4% in. (Clarion, you have not to bother about winding aCamco, Pickett). frame aerial. .0005-mfd. variable condenser It is intended that this receiver should(Polar, No. 3, Lissen, Burndept, J .B., be used with an existing loud -speaker, thusOrmond, Burton). saving the cost and time of making up a .000r - mfd.reactioncondenser special instrument for use exclusively with(Bulgin, Lissen, Peto Scott, Ormond, the portable set; and, moreover, that aBurton, J.B., Polar): short improvised aerial should be slung up Two push-pull switches(Lissen, wherever convenient,forthiswillinPeto Scott, Wearite). APRIL 20, 1929 Cingite" 582 ECONOMY WITH FIBRE NEEDLES How To Make a Simple Culler AUSEFUL little device for cutting fibrenut. A small link pinned over the' bevelledcorrect angle. The wood used for the block needles may easily be made from aneedle rest will allow theneedle to beshould be preferably hard and a piece of piece of wood and an old Gilette razor blade.inserted in the groove and held in positionoak or mahogany will do for the purpose. The fibre needle is much better than thefor cutting. The razor is then just drawn A small handle should be attached to the ordinary steel needle, especially for gramo-down and a perfect cut is made at therazor blade to make the gadget easy to' radiopurposes; butof handle. The -blade may be course, when these are used removed at any time for re- a cutter is needed if economy setting or replacing with a is to be studied so that the GILLETTE RAZOR BLADE new blade.It will be found needles 5an be re -cut.As that with this device the cut a rule, a needle can be cut will be perfectly sharp and and re -set as many as four there will be no burred edges times. The important thing at any point of the needle. to see to is that the cutting For the rest of the details the angle is correct. drawing isquite easy to First, takea block of follow and self-explanatory. wood, r in. by r in. by Owing to the fact that in., and take a cut out with this cutter an extremely of this at an angle of 45 fine cut may be made, it degrees, as shown inthe will bo possible to make a drawing.Also make a saw - maximum number of cuts cut as indicated, and a bev- before the needle is finished elled edge at an angle of with.As this cutter trims 6o degrees with a V cut for the needle at the correct the needle to sit in.The angle, itisalso important accuracy of this last detail that when the needle is used, is important, but the work WOOD BLOCK'V it should be set in the pick- is quite easy to do if care 1?Ye*X laig x%3' up at the correct playing is taken. The razor blade angle and this should bb at is pivoted in the sawcut arid 6o degrees to the surface of held by means of a screw and A pictorial diagram showing the construction of the cutter the record.

" THE £5 : 5 : 0 P ORTAB LE " (Continued from preceding page)

particular set and, above all, having the The tuning of the set is carried out withswitches andtwo variablecondensers advantage of conventionality, it can bethe aid of the special portable coil whichmounted thereon.All the parts can be made up without any additional difficultieshas been developed for *use in receivers ofmounted on the baseboard and there is no by those who are accustomed to makingthis type, and which will be a standardneed to leave the positioning of any to a ordinary receivers. Moreover, the arrange-feature in AMATEUR WIRELESS portables.later stage in order that the wiring can be. ment of the receiver components in thisIt was, you may remember, used in themore easily carried out. way allows of ample battery space in theArcadian Portable, described in AMATEUR Rigid insulated wire is advisable for cabinet. WIRELESS, Nos. 354 and 355. This coil hasmaking thepoint-to-pointconnections, the advantage of cover-because in a )Sortable set, which is apt to PANELing13411 both the mediumbe subject to bumps and jolts, connecting AERIAL CONDENSER ,.ososmId - andthelongwave.wires in the inside of the set are apt to L. wAvEcHANcire RirA 0 SWITCH bands, by an externaltouch. This might cause short circuits were nwirypIoArs 4 switch on the panel,bare wire used for connections, and, of

andanincorporatedcourse, the extrThouble entailed by the Oti reactioncoil givesbaring of the ends of covered wire when smooth controlofconnecting up is very small. LS- I REACT/ON EAR77i CONDENSER oscillationon both In our next issue some further construc- vow mis LT SWITCH,,, bands. Ithasbeentional particulars, including the details of

&saw,/ 0./?°\% designed by thethe case together with operating notes AMATEUR WIRELESSand a test report, will be given. 2V I Technical Staff for the Readers in the London district who con- jobin hand. Aparttemplate making up this set are advised to from being very efficientsee it for themselves where it is displayed and convenient in usein the Somerset Street windows of Messrs.' it is compact. Selfridge & Co., Ltd. 7,- 441 With the aid of the oOo)Oi blueprintwhichcan In future, except in the case of imminent 0002mfd 0 0 be used to show theperil, ships at sea are not to use the SOS DETECTOR VALVE drillingcentres,thesignal; in circumstances in which help is HT - LT+ Li- panel canbedrilledrequired, but no immediate rescue is asked The Wiring Diagram.Blueprint available, price 1/ - and the terminals, twofor, the letters XXX are tote transmitted. APRIL 20. 1929 mateur Wiretes5, SOURCE, UPPLY

I. THE DRY EATTERY By R. W. HALLOWS iTN this series of short articles I am goingampere per valve throughout the set was adifferent sources. First of all its life will be 11. to sum up briefly the points for andnormal high-tension load. This being so,short and, secondly, during an eveningt 'against the four commonly -used methods ofa high-tension battery made of tiny cellsreception, a big fall in the voltage will take high-tension supply-the dry battery, thesufficed for any ordinary set and makersplace. Short life means naturally frequent wet Leclanche battery, the accumulator,naturally put on the market numbers ofrenewals and therefore undue expense. A and the battery eliminator. Not only thebatteries of a capacity which, though small,heavy drop in voltage means "end -of -the - beginner who contemplates installing awas quite sufficient for all ordinary needs.evening" distortion due to the fact that the valve set, but also the old hand who mayThese batteries were made up of the sameplates of the valves, and particularly the think of making a change in his H.T.cells that were used for flashlamp refills,output valve, in the set are starved, whilst supply system, may find them of use, sincecells measuring on the average % in. inthe grid bias remains almost unchanged. they embody the results of long practicaldiameter by 2 yi in. in height. Five or six If -you double the load upon a dry cell, experience and of extensive laboratoryyiars ago no other kind of dry -cell H.T.B.you do much more than halve its life. ' tests. was generally obtainable. Batteries with cells of the size mentionedFit the Battery to the Set Satisfaction with Dry Batteries thus became the standard components and The sound rule is always to make the One meets many people who swear at,the pity of it is, that though valves havebattery fit the receiving set with which it is !ratherthanby,the dry high-tensionaltered enormously, many people still failused. If it does so the voltage drop during !battery. I am going to be so bold as to sayto realize that any other kind of batteryan evening's run is small and the life of -the !pat I have never yet come across a case ofexists. battery is long.If it does not . .well, unsatisfactory results with this type of With the exception of the R.C. valve allperhaps now you zee what I meant when I battery in which the user had not himself tomodern triodes have a much lower plate -said that the man who found dry -cell filamentresistancethantheH .T.B.'s troublesome had him=elf to blame. original G.P.valves. Of the Whatever you do, ascertain as soon ass tetrodes, the screen -grid valvepossible the load put on the H.T.B. by your uses about four times as muchset. Should you not possess a milliammeter, platecurrentasthese earlybuy one or borrow one. When the load bright emitters and the space -exceeds five milliamperes, but is less than charge grid valve may require aeight,a double capacity battery may great deal more. A single pen-;suffice, though a treble will be a better tode passes normally about asinvestment. A treble capacity battery can much plate current as from four-undertake loads between the latter figure teen to twenty old G.P. valves.and about 12 milliamperes; above this the largest capacity H.T.B. made is by far the Some typical dry H.T. batteries The Question of Size most economical investment. blame for his trouble, or was not more Now the dry Leclanche cell in its most But the use of undersized dry batteries deserving of the hard words uttered thanup-to-date form is a very efficient piece ofis not the only source of high-tension was the component that moved him toelectrical apparatus; but it has naturally itssupply troubles.There are many who wrath. Though I touch wood as I write it, Ilimitations.Just as a little boiler canplump for the cheapest articleoffered, make extensive use of dry H.T.B's, and indeliver only a moderate quantity of steamirrespective of quality. To them I would :the last five years I have not had one singlethough the pressure may be quite high, sosay that our countryisregarded by instance of trouble traceable to a faultythe small dry cell can supply but a modestforeigners as the happy hunting ground of !battery or of failure On the part of a batteryamount of current if it is to do itself justice.thedumper.Batteries made onthe ito give long and faithful service. The whole The dry cell is in some respects very like aContinent and of a quality so appalling that !secret of success with the dry -cell high-boiler. The fuel in its case is zinc instead ofthey could find no market elsewhere, are itension battery'. may be summed up incoal One of the most important charac-exported to us --and they sell like the seven words :" it must be up to its load. teristics of this kind of cell is that when it isproverbial hot cakes. placed under load, the internal resistance If you want freedom from trouble with ;Modern Conditions rises, with a resulting fall in the terminaldry H.T. batteries do not be above taking a At one time of day when we all used,voltage. word of advice from one who has tested out because there was nothing else, the bright - The standard cell of the dimensionsthe majority of the patterns now on the emitter general-purpose valve, we thoughtalready mentioned cannot possibly ,supplymarket. iin plate volts andgave no heed at all to theeconomically more than 5 milliamperes of Buy batteries that are big enough ; buy plate circuit milliamperes. This was quitecurrent for about three hours out of thethose turned out by first-rate makers and natural since the plate -filament resistancetwenty-four. Ask it to do more than thisyou will have little cause to quarrel with the of the valves was high; about one milli -and you are courting trouble from twodry -cell battery for high-tension supply. =blur Wren 584 APRIL 20, 1929

WeeklyTips, Constructional For the and Wireless Theoretical- Amateur Screen -grid Voltage but still, it &uld be heard during silentmentioned. Anode bend rectification may THE manufacturers of shielded valvesperiods in transmissions.Various thingsbe employed with ease and this method is recommend that when the anode vol-were tried, but it was not until the detectorshown in the diagram. valve itself .was covered with tin foil and tage applied to the valve is I20, the shield Winding a Frame voltage shall be 6o or 86 volts according toearthed that the noise disappeared.The the type.I have found, however: thatcoating of the inner glass wall of the bulb When constructing an ordinary tuning because there are differences as betweenof modern gettered valves is responsiblecoil or high -frequency transformer one one valve and another, arid between circuits,for peculiar effects at times, but earthed tinemploys wire of such a gauge that the best it is quite desirable when the best possiblefoil can often be relied upon for shielding. results will be obtained.Sometimes the results are sought for to regulate the screen object is to produce a coil having the H.F. Troubles lowest possible losses, or perhaps, to build voltage.The recommended voltage may - be used to commence with, but the effect One of the reasons, I find, for instabilitythe most effective coil of a certain bulk. of increasing or reducing it should alwaysoccurring in sets having a stage of H.F. A frame aerial is really only a tuning' be tried. coil of relatively large dimensions.As a' rule, the sizes are fixed by other considera-, " Quiet" Detectors tions, such as the space occupied b'y the' Valves having ahighmagnification receiver proper, its batteries and loud- factor are often used for detection with speaker. It is, therefore, necessary for the the result that a bad contact in the valve, or designer so to arrange the windings of the a slight defect in its design, may give rise frame aerial that the best advantage will to microphonic noises or howling.It is be taken of the amount of room available.

thereforequiteessentialto employ a But here a difficulty often crops up. "quiet" valve for detection, as any dis- The wire employed must be sufficiently' turbances which originate here are greatly strong and well insulated for the purpose. magnified by the low -frequency amplifier. This may prevent one from usirirg the best In portable receivers in particular, great gauge of wire as determined by electrical care has to be taken to select suitable efficiency, but fortunately, the amateur is specimens. able to obtain quite good results on frames' The non -rigid valve holders are not of normal sip by using a stranded wire.] always sufficient to prevent a shock being This wire may be purchased in lengths of transmitted to the valve and additional A stable H.F. circuit roo feet and may be recommended for the'; means have sometimes to be employedamplificationispoor filteringof high -medium wavelength winding of a frame I before satisfactory results can be obtained,frequency currents.The best practice isaerial. A rubber band which fits tightly over theto provide an anode filter circuit, which bulb is a help in minimising a certain typemay comprise a resistance and by-passRadio in the Garden of hoWling, but sometimes it is necessarycondenser or some other form of filter Those who cannot afford a portable to surround more than one of the valveswhichwill limitthe amount ofH.F.receiver to take into the garden during with cotton wool.However, I have nocurrent flowing through the H.T, circuits. periods of fine weathef should not overlook doubt the time will arrive when the manu- In this connection I can recommend thethe fact that even lengthy extension leads facturers will be able to guarantee that allcircuit shown above. Here the anode cur-fitted to the loud -speaker will be satis- valves will be quiet in operation. rent for the high -frequency amplifying valvefactory provided an output transformer or (which in this instance is of the screen -gridfilter circuit is used.These two parts A Strange Whistle type), has to pass through a high -frequencyprevent the flow of the high-tension current A few days ago I was trying a receiverchoke and the tuned -anode circuit Lc isthrough the extension leads and loud- which was suppliedwithhigh-tensionjoined between the anode of the valve andspeaker and, therefore, remove the chief, current from a mains unit.This unit wasits filament. difficulty. built into the receiver, with the result that a A fixed condenser is, of course, employed It is not advisable to employ a twisted certain amount of coupling might havein series with the tuned circuit in order topair of flexible wires unless they are rela- been expected. It appeared from my, tests,prevent the anode coil from short circuitingtively short as the capacity may have the however,thatthere was no couplingthe H.T.This circuit has a number ofeffect of lowering the tone of the repro- between the transformer and chokes of theadvantages in addition to the one alreadyduction.I have heard people remark that eliminator, and the transformer and output a good deal of power must be lost because, choke of the set. of the resistance of lengthy extension leads, What I did find, however, was a form of Let Amateur Wireless " but as a matter of fact, the losses are capacity coupling. This produced a rather negligible when the loud -speaker is of the high-pitched whistle. It was not very loud, solve -your problems. usual high resistance type. APRIL 20, 1929 585 inateur Wtre-LT INTERLOCKED ELECTRODES MAKE Cossor Screened Grid Valve- SHOCK-PROOF ! These illustrations show why the Cossor Screened 10Here you see Grid Valve is the most robust-the most depend- the double length 2.Around the of Cossor filament two stout grid sup- able-and the most uniform Screened Grid Valve famed for its colos- ports is wound the made in Great Britain.This wonderful new sal emission. Note first grid, electric- system of interlocked construction is to be found the seonite bridge ally welded at holding itrigidly twenty -fire points. only in the Cossor Screened Grid Valve. in position. NOISE-PROOF I Note the enor- 3. 4.Finally,cb- Noises are generally clue to loose elements in a mous strength and serve the construc- valve.In the Cossor Screened Grid Valve the rigidity of the tion of the anode. screen,See how Actually two elements are interlocked. Every joint is scientifi- it is built on four rectangular nickel cally welded to ensure long life and complete stout supports and platesa re used and rigidity. Even under the heaviest shock individual capped by a metal for greater rigidity bridge - piecean movement is impossible. chored toseonite each is diagonally insulator. ribbed. BREAK -PROOF I Only Cossor Screened Even the hardest blow cannot disturlIpthe perfect alignment of the Electrodes which are rigidly Grid Valves have inter- braced at top and bottom. As a result, every locked Electrodes Cossor Screened Grid Valve retains its characteristics throughout its abnormally long life. For any Screened Grid Receiv er choose Cossor. Accept no substitute-for there is no adequate substitute for the Cossor system of Interlocked construction.

Technical Data. Cossor Coes., 220 S.G. (2volts, .2 amps.) and 410 S.G. (4 volts, 1 ampere Mac Anode Volta 150, Impe dance 200,000, Amplifi- cation Factor 200, Grid Screened Grid Bias 1.5 volts at max - anodePrice Volts. 22/6 THE ONLY SCREENED GRID VALVE A. C. Cossor Ltd.. High bury Grove, London, N.S. WITH INTERLOCKED CONSTRUCTION

Don't Forget to Say That You Saw it in "A.W." (imam WireIR.si 586 ite'RP4 20. 1929

111111111111111111111111111111111111111111111111111111111111111IE PORTABLES HOW TO CHOOSE, BUYBUILD & OPERATE

Over ioo portable sets, with details 5 Some of the other features are :-How of circuits, wavelength ranges, dimen- 5 will Broadcasting Affect the General sions, weights and prices are described 5 Election ? by B.B.C. Officials -What 5 in the illustrated supplement of the Are Alternating Currents ? Amp and ProfessorMegohm Discusssome May Number of "Wireless Magazine." 5 Fundamentals-Russia's Revolution- Special articles include " How to Get 5 5 ary Radio, by J. Godchaux Abrahams Best Results from a Portable," by 5 -THE TWINFLEX, a modern reflex the Assistant Editor, " Designing a 5 two-valver without crystal detector- Portable,"by W. James." THE 5 GRAMO-RADIO SECTION-THE WAYFARER," a portable designed 5 5 AT-HOME THREE, acomplete by J. H. Reyner, illustrated below, 5 installation fori retc. etc.

WIRELESS MAGAZINE FOR MAY. ON SALE ON APRIL 24TH. [- ORDER YOURS NOW ! APRIL 20, 1929

KI241...Getaikete .04.,0%.00....mt,000ftoftio

The Portable Set considerations, the battle was almost woneffect if a mixture of the two. Coming to THE bright weather of the last fewon broken records, and cases of the wrongtelevision, we find that the effects of phase days has brought out all the portablerecords being sent with the right film !relationship are frequently misunderstood. sets-and the dull programmes have sentThen again, the " cutting " and editing ofIfthe speedsofthe transmitter and them in again IMany listeners have settalking pictures made on disc systems wasreceiver scanning discs are identical, but forth in their cars and on their boats downalmost impossible. there is a phase difference, it will be found the river with portable sets to carry music B.B.C. Losses that actual definition is unaltered. There wherever they go, so to speak. is no blurring of the image on the screen, Of course, the great demand is for dance One hears almost daily news of B.B.C.but merely a displacement.It then only people going over to the "talkies." Captain music. Whohasbeandownthe becomes necessary to "frame" the picture Thames,forinstance,without hearingA. G. D. West, the head of the B.B.C.correctly on the screen. The effect can be dozens of gramophones blaring out " SonnyResearch Department, has not gone by thesaid to resemble what happens on a cine- Boy" or its equivalent?Personally,Isame route, but instead has joined the,matograph screen when a picture appears regard this type of music on the river asH.M.V. Gramophone Company.Captainshowing a scene with the head of an actor anything but an attraction, and am pro-West will be remembered by listeners inat the bottom of the screen and his feet bably in the minority when I hope thatconnection with the first American broad- at the top. the B.B.C. will not add to the jazz plugging.casting relays, the nightingale, and all Lack of isochronism will evidence itself On the other hand, light orchestral music,kinds of "stunt" broadcasts, from aero-as a distorted or blurred image, but not trios, and military band broadcasts wouldplane concerts to talks from the Flyingalways lack of synchronism. If we bear in be very acceptable, and would probablyScotsman footplate and the murky depthsmind that we can have isochronism with- replace the noises created by some of theof the Thames. His work, however, hasout synchronism, but never synchronism " behindthe wheezy gramophones.If the cost of ex-been mostly very much without isochronism, then there will not tended daytime programmes of this typemicrophone," many problems of which hebe any difficulty in comprehending the true has effectively solved. Captain West will proved toogreat,thenbroadcastsof state of affairs. To achieve the best tele- selected records would be a good alterna-be in charge of the electrical side of thevision results the synchronising methods tive. One of the most enjoyable symphonyH.M.V. Company's activities, which are toemployed should be practically automatic concerts I have ever heard was picked upbe greatly extended in the near future. in action, and the simplicity of Mr. Baird's one summer evening at the end of a little Synchronism and Isochronism arrangement contributes in a large measure pier on Coniston Lake. My pipe, my rod, I see that the recent renewed interest intoitssuccess.The use of a separate and my portable set seemed to be in har-television has given rise to flirt* argu-channel for communicating a synchronising mony with the beautiful surroundings,ments on the question of synchronism.current adds to the complication of working. and the dramatic power of Brahms ,wasJudging from a demonstration that I hadand by dispensing with this the British enhanced by the grandeur of the moun-the" opportunity of witnessing the otherinventor has made a big step in theright tains. Now, if it had been jazz ... day, this problem appears to have beendirection. Bad Business solved in an ingenious and effective manner Radio Jerks Please don't think that I'm a jazz hater!in the Baird system. From conversations An American doctor, I see, has just been I simply hold the humble opinion that jazzI have had and articles I have read, how-telling the world that the early morning is more in place in the drawing -room, withever, I find that it, is not so much thephysical exercises-the daily dozen, they the carpet pulled back, than in the beauti - details of working that call for comment ascall them over there-broadcast by wire- ful surroundings of the open country, river,the effects produced when perfect syn-less stations are far from being as health - and lake. Possibly I am hopelessly outofchronism is absent. A word on this mattergiving as many people imagine. He does date, and that the present discontentofwould therefore appear to be seasonable. not believe in the rude awakening that the portable radio set manufacturers _will Where people often stumble is in con-ensues when an alarm clock, set to rouse eventually force the B.B.C. to flood thefusing synchronism and isochronism. Wethe sleeper in time for his morning exercises, countryside with " Sonny Boy" at twenty -can have two mechanisms in isochronismgoes off with its horrid explosion of sound minuteintervals,asishappeninginand yet not in synchronism, and there is ain the early hours. Here I cordially agree America. Let us hope that the B.B.C. willdistinction which should always be bornewith him, for I must confess that in the old compromise by broadcasting daytime con-in mind, especially where television is con-proverb I have always been more struck certs of light orchestral music and as fewcerned.If two machines are running inby the folly of the early worm than by the ballads as possible." The Floral Dance,"isochronism it means that they are run-luck of the early bird. The doctor goes on "Cherry Ripe," and similar songs havening at identical speeds, but are out ofto say that radio jerks so far from making been "plugged" far too often. step. An accurate clock in the Britishthe United States a nation of athletes, bid Islesisinisochronism withanotherfair to turn our horn -rimmed cousins into Talking Films accurate clock in the U.S.A., but obviouslya race of nervous wrecks. We haven't yet The " talkies " seem to be booming inthey register different times at the samehad the early morning daily dozen over London, at any rate. The great technicalinstant, and hence are not in synchronism.here, and personally I don't very much battle of the "gauges" is coming to an end,To achieve synchronism, speed and phasemind whether we have them or not, so the sound -on -stripfilm systems beatingmust be identical;thatis,the clockslong as they don't bring in a law making the synchronised gramophone record andshould register the same time at the sameparticipation in the revels compulsory. other types of sound recordings.Photo-instant. graphic recording and reproductionof Valve Rumours sound has been brought to a high state of . What to Remember A non -wirelesspapercontainedan efficiency, and the quality of this type of In a photo -telegraphy system, absenceannouncement the other day that we might recording now surpasses that of the disc.of ,synchronism evidences itself as a dia-expect in the not far distant future high - The weakest link of the chain is still themond -shaped picture for consistent abovefrequency amplifying valves with amplifica- loudaspeaker.But, apart from technicalor below normal running, or in a wavytion factors in the region of I,000 to 2,000. A matter Wink!, 588 APRIL 20, 1929

t0 s0 On Your Wavelength !(continued) I have heard similar rumours from timepronounced lower bend and a very longon occasional nights has anything like to time, and I am far too old a bird to saystraight portion in its characteristic, sofirst-rate reception of distant stations been' that anything is impossible in wireless.that no distortion may be produced whenpossible. We seldom had, anything like the Still, somehow, I don't see such valvesthe local station is modulating deeply andbig signal strength that we used to associate reaching the practical stage, at any rate,is producing some pretty pronounced peaks.with short-wave transmissions a year or until a great many more ether waves haveThe screen -grid valve now gives me high -more ago, and fading was almost invariably flowed round our aerials. It is one thing tofrequency amplification satisfying all mya great nuisance. At the present moment make a valve with a huge mag. factor andwants; with either the pentode or the low -there are signs of a very distinct improve- quite another to be able to get out of it theimpedance output valve and proper L.F.ment in short-wave reception.The day- amplification that in theory it ought tocircuits, first-rate audio -frequency amplifi-light stations PLE and PLF '(formerly ANE be able to give. You can quite easily rig up,cation is obtainable. Once our rectificationand ANH) at Bandoeng, in Java, can be for instance, two B.F. stages in cascade,is as good as our H.F. and L.F. magnifica-picked up almost whenever they are work- each provided with a triode with an ampli-tion, there will be little to grumble about ining, and after dark quite a number of fication of 2o. But you will not get out ofwireless reception. Americansare coming throughextra- the two anything like an overall magnifica- ordinarily well.If your short-wave set has tion of 20 by 20 or 400, neutralise you Can You Spot It ? been laid up now is the time to bring it out. never so wisely.So also with the screen - Now, then, you fault-finding experts, grid valve. It gives a wonderful degree ofhere is a little problem for you. The set is a Still At It amplification, but it does not quite live inthree-valverwithascreen -gridvalve Though there is undoubtedly much less practice up to its theoretical magnificationcoupled by the parallel -feed method to anof the oscillation nuisance than there used factor. anode -bend rectifier which is followed byto be, Ham -Handed Henry and Oscillating An Obstacle resistance coupling and a low -impedanceOswald still' show us at times what they There are several very serious obstaclesoutput valve. On the Monday night when Ican do if they try. But- the worst person of in the way of the practical use of hugewent to bed it was working perfectly;all is he who oscillates good and plenty H.F. amplification. Perhaps the moston the Tuesday afternoon when I pushedright through some particularly interesting important of these is that, when receptionthe loud -speaker plug into the jack nothingprogramme from the local station. One of conditions are such that with a moderatebut large chunks of silence issued from thethis fraternity absolutely spoilt a fine degree of amplification one would call themspout of the instrument. The batteries wereconcert for me and hundreds of others a practically ideal, there is always in realityright up, all the valves were in good order,few nights ago, and I can't really think that a great deal of parasitic and other forms ofand there were no disconnections anywherehe enjoyed it very much himself. There is interference in the background, thoughin the wiring inside or outside the set.no excuse nowadays either for the squealer we may hear nothing of them. Increase theWhat is that you say? Oh, no, the aerialor for the squeaking set.If your apparatus magnification and up they come. There is,was not earthed. begins to misbehave itself, as sets will at in fact, much the same difference between A Simple Matter times, refusing to function without howls, the broadcast band tested by a normal I wonder just how long that fault wouldfor heaven's sake don't begin a long series set and by one with huge amplification ashave' taken most beginners and not a fewof experiments, using the local station's there is between a drop of water seen firstold hands. to spot.Though he hates towavelength, during the evening programme. with the naked eye and then under theblow his own trumpet, your "Thermion"If you really feel that you must locate the microscope. Another point not alwaystracked it down in about a minute. For-trouble without delay let me counsel you realised is that the - rectifying valve isward the milliainmeter !Connect it into theto go down to the bottom of the broadcast distinctly limited as regards the amplitudecommon H.T. negative lead. Remove allband and to make your adjustments with of the oscillations with which it can deal.the H.T. wander plugs 'except those con-the help of one of the powerful transmis- We have long been told that the grid -leak -nected to Vr.Current is shown to be sions that you will find down there. and -condenser rectifier "packs up" underpassing.Try the same experiment with the influence of big grid swings, and we A Spring Clean V3. Again the juice is there. But what of F9r years now Mrs. " Thermion" has have been led to believe that the anode -V2, the detector?The insertion of its bend rectifier could deal with almost any- been urging me to turn out the shelves of wander -plug all by itself produces never athe several cupboards which are devoted thing that you like to apply to it.This,quiver of the milliammeter needle. Another however, is not so, for even with a single to my wireless bits and pieces. For years valve is substituted; the result is the same.have been promising to do so, and for years H.F. stage the local station at mediumWhen this kind of thing happens the first range may overload an anode -bend rectifier junk hasbeensteadilyaccumulating. thing to look at is always the filamentFired with sudden energy the other day, I on occasion. circuit. Here there is no rheostat or fixed We Still Need It undertook the task. I really did. We wire- resistor and the wires running to the fila-less folk are a curious race.We find it For years now in these columns I havement terminals are obviously as they should been begging makers to turnout a specialised difficult to give or throw anything away. be.Just to make sure, try an old bright -There is always a feeling that if we do so it detector valve. There are one or two on theemitter valve(a most useful possession market to -day, and very good they are, so will be just the very bit or piece that we for testing purposes, since it lights up soshall want when we tackle the next radio far as they go. It is still, though, an exceed-obviously) or a flash -lamp tester in the inglydifficultfeat,as any who have job. And so our shelves harbour an increas- holder. There is no answering gleam.ing stock of components that grow steadily experimented in the matter know only tooSince the wires are as they should be, the well, to obtain anything like perfect and more and more out of date. We shall never holder must be at fault. Examination dis-use --the things; then, why not get rid of undistorted rectification of strong signals.closes a break in one of the spring connec- The valve that I have in mind would be theni. You will find, as I find, that there are tions between the valve socket and theany number of youngsters whose enthusiasm speciallydesignedfortheanode -bendfilament negative terminal. system.Its amplification factor would be outruns their purses to whom you can give quite low, for it is rectification: and not A Short-wave Improvement your unwanted stuff with the certainty amplification, that we want primarily from The short waves have been considerablythat it will be thoroughly appreciated and the detector valve. It must, though, have abelow par all through the winter, for onlyput to useful purposes. TH E APRIL 20, 1929 589 ernattnr WIrelez, ubtlefies of umeControl

THE maximum amount of output to bestations to be heard at the full strength.matically limited provided a reasonable obtained from a receiver is funda- All this is rather obvious, but yet thelife is expected from the battery. Therefore, mentally determined by the arrangementlistener with a three -valve set does occa-when it is remembered that an ordinary of the last stage in the set. By the last stagesionally expect to obtain more volume from,power valve may easily be fully loaded is meant the valve or valves, 1. la+ when it is used in a two -valve itspower supply, andletus receiver for the reception of the not forget, the loud -speaker with local station,it is obvious that its filter circuit or transformer. a volume control must be em- It does not matter how ManyV ployed to limit the input to the amplifying valves areincluded last stage of a receiver having in the receiver-one can only fully more than two valves. load the last stage.Thus, the set There are many methods for may comprise a detector valve controlling volume.I have dis- in addition to the last stage; in cussed de -tuning and the effects of this instance probably only the varying the amount of reaction local station and perhaps 5XX or Iv:-when a condenser control is used 5GB will be heard at the maximum in previous articles.The other possible strength.I am assuming, methods depend upon the arrange- of course, that the receiver is tr: mentofthevalves andthe used at a place not too far from couplings employed. the local station in order that Any control must obviously be fully so connected that it affects the thelaststagemay be Volume control for resistance coupling loaded. Fig.1. strength of the signal applied to The addition of a further low -frequency the grid of the last valve.A variable re- amplifying stage, or of a high -frequency sistance or other device connected to the stage, cannot possibly alter the amount of loud -speaker itself may be used to cut the volume to be obtained from this station down the volume, but it certainly cannot without distortion. These additional valves be recommended, as there is no control magnify theweakersignals,however, over the input to the valve which may with the result that more distant stations therefore be greatly overloaded. may be heard at the full strength.The The best position for a volume control point I particularly wish to bring out is depends upon the type of receiver. When this : that when the same type of output the set includes a detector and two low - valve, output circuit, loud -speaker and power frequency stages the control is best con- supply are used, the maximum amount nected to the inter -valve coupling between of volume to be obtained without distortion the detector and first low -frequency stage. is identical, regardless of whether the set There are several satisfactory schemes. includes low -frequency or high -frequency Thus, when a resistance -coupling is em- magnification. The only differencein ployed, as in Fig. r, the anode resistance or Fig. 3.Tn this case adjustable resistances performance will be in the number of are placed at ross the transformer (Continued at foot of next page) say, the local station, than another listener having only a two -valve receiver. He may, of course, appear to obtain greater volume because he has a reserve of power, but if he does, and the two output circuits are identical, it must be accompanied by distortion as the result of overloading. More power Output without distortion can only be obtained by increasing the + high-tension and grid bias, or by fitting a Tau: larger output valve or a combination of valves for parallel or push-pull working. But in many instances the high-tension Fig. 2.With choke coupling the choke has to be obtained from a dry battery and Fig. 4.Here use is made of a ged-bias may be tapped then the size of the output valve is auto - transformer -secondary tapping APRIL 20, 1929 emaim.Wtrete5 590

111 LOCAL 111 For the Newcomer to Wireless : CONDITIONS

- AN you tell me why it is that thoughvalley. You know, for instance, that my One of the commonest, though it is CRobinsonand I use exactly theown set is pretty good, though my aerialnot always realised, depends upon the 1111 ffi same kind of receiving sets he receivesis down in the valley. You remember thenature of the soil. 11

111 many foreign stations at much greaternight that.' took it up to Smith's house How do you mean ? strength than I do, whilst some of theon the hill? If clay happens to come very near the hi -more distant ones that he gets simply Rather. You were astonished at thesurface, almost any kind of earth con- do not come in at all on my set ? improvement in its performance. nection will give reasonably good results. That is one of the queerest problems I was. In fact I found that I was whatSuppose, however, that there is a thick in wireless. We know that reception isI should call half a valve better. I meanlayer of chalk or gravel, even a large earth affected by local conditions though therethat when I substituted a triode for aplate well buried may prove inefficient. 111 is still considerable uncertainty aboutscreen -grid H.F. valve the set did justNot everyone knows how important it the actual causes of the differences inas well in Smith's house as it usuallyis to get down to the clay subsoil. range and signal strength that are founddoes in mine. I have heard that underground veins in various localities. Then if your house is on low-lyingmay affect reception. Can you tell me something about them?ground I suppose it is best to have as It has been proved that they certainly One thing does seem pretty certain.high an aerial as possible? can and that even large systems of buried In- the great majority of cases we find In theory, yes, but don't forget thatwaterpipes and so on may have an that greater all round signal strength isa very high aerial is an excellent collectoradverse effect.It is quite possible that obtained from an aerial at or near thenot only of signals that you do want, butmetallic veins may be responsible for also of atmospherics and other parasiticsome of the blind or partially blind spots 111 top of a hill than from one in a neighbouring valley. noises as well as of spark signals. Onethatoccur.Sheffieldpresentedthe Why is that? has to compromise, as in so many otherB.B.C. with a very difficult problem, II i It is probably due to the fact that thewireless matters. possibly owing ito the big slag heaps in aerial down below is to some extent What other causes are there of differentthe locality which contain large quan- screened by the hills on either side of thebehaviour in different houses? tities of metal...... " THE SUBTLETIES OF VOLUME CONTROL " (Continued from preceding page) the grid leak may be tapped.The twothe grid leak as before. A tapped choke iscontact is connected to the grid and the arrangements are indicated in the figure,indicated in Fig. 2, and it should be notedspindle is of metal, a howl may be pro- at A and B respectively. (H.T. filter circuitsthat the whole of the choke is included induced if the fingers touch the spindle. The are omitted for simplicity) and it shouldthe anode current. grid -connecting wire should, therefore, be be noted that the whole of the anode as short as possible and a knob of generous resistance, or grid leak, is included in theTransformer Control size be employed. circuit. Sometimes a transformer is employed to The methods described above are the The quality of the reproduction is notcouple the detector valve with the first low -more important ones suitable for employ- changed by either of these schemes, andfrequency valve. An adjustable resistancement in sets of the detector and one or two there is little to choose between them fromconnected across the primary winding as inlow -frequency type. When a high -frequency an electrical point of view, but it is probablyFig. 3 may then be used with every satis-stage is used other methods of control easier in practice to arrange a potentiometerfaction. A suitable resistance would havemay be advisable. type grid leak. the maximum value of about roo,000 ohms. When a choke -coupled stage is used be-Alternatively, an adjustable high -resistance WOS, Jefferson City, Missouri, is said to tween the detector and first low -frequencywith the maximum value of about 500,000be the only state-owned radio station itt valve the choking coil may be tapped, orohms may be connected across the second-America. ary winding, but it is better to employ a resistance joined across the primary. This resistance will carry a certain amount of current and should, therefore, be of suitable construction. A further scheme is indicated in Fig. 4 Here the secondary winning of the transformer is tapped and a switch is employed to connect the grid bias to one of the tappings.I do not recommend this scheme, because a special transformer must be used and further, its frequcncy characteristics will change with the amount of the secondary included in the circuit. Probably the best arrangement when a resistance - coupled stage is used is that which includes a potentiometer type of grid leak. A suitable component is not very expensive and occu- pies only a little space.It is sometimes \ necessary to take particular care with the D51.2.4.4 A An impression of Arnold Eagle, the conductor wiring or hand -capacity effects may give Julian Rose, the famous Hebrew of Shepherds Bush Pavilion Orchestra trouble. Thus, for example, when the sliding Comedian-a caricature APRIL 23, 1929 591

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A Weekly Programme Criticism by Sych IWAS interested in the appeal on behalfas I came through the door. Wonc of the Aylesbury After -Care Associa-how she keeps up her form.

tion which was made by Lady Ampthill. I wrote about this subject of Borstal two The first of de Courville's " Gay Sp or more years ago, and I remember, whengave us many laughs and fair ente my book came out, that it was suggestedment, and a good many sketches, b that my sketches on the convict of to -dayis bound to compare it with Chariot's

'would be of interest to listeners. However, I was told that the subject Chariot was quite good ; but then, was " too morbid " IBut, as in so manyperhaps de Courville has something other instances, there has been a changeup his sleeve. of mind.

Thanks are due to "Gay Spa The Salvation Army Service from thegivingus the opportunity of h Congress Hall, Clapton, was a rather dif-Imito. Here is real talent. His bird ferent affair from those services I used totions were excellent. Let's have m hear in East London thirty years ago.him and his family of farmyard habitues.

But the "congregational song" was the Reader," writing from a seaside resort, same :" Just as I am, without one plea." Fred Duprez was most -emphatically notthat my criticismofcertainwireless Very nicely rendered, too. at his best. As a solo turn Duprez is quitecomedians is unfair.

good. In the revue he did not have enough " Over the Easter holidays I had occa- How extraordinarily popular isJackto do, and when we did hear him he soundedsion to see a certain wireless turn and, Hylton with his band. The relay from therestrained and totally unlike his usual self.remembering your criticism of it in the

LondonPalladium, however,showed past, settled down with a certain amount clearly that visual audiences have more of "Harold "-my tame lowbrow-has aof scepticism.However, I found their the game than listeners. lot to write this week about our friend Sirantics-rather than their wit-extremely Jack in the limelight, with full effects,Walford. He writes :- funny. May I add that you cannot really 'gets over well when you see him. I heard "Sir Walford Davies, in his talk at 9.15do a turn of this description full justice and saw him do the "Babette" numberlast Tuesday night (an unearthly hour forunless you see it." quite effectively, but he cannot reallya music lesson) said that a friend of his I myself have made this reservation sing for "nuts," and the uninitiated listenerrecently had asked exactly what he (Sirwhen criticising comedians. However, my may well have wondered what all the fussWalford) was aiming at in his talks.Icorrespondent finishes up on a note of was about. No doubt, television will comeagree with the friend. A talk on musicalhope : "When we get television perhaps to Jack's aid. technique is totally out of place in the latethis difficulty will be overcome 1"

evening.If it And, by the way, half an hour of dancewere given in music in the middle of an ordinary pro-the afternoon, gramme-by Jack Payne (or by anybodyso that school else,for that matter)-does not amusechildren could those of us who don't dance, and wholistenand consequently feel a certain sameness aboutderivebenefit thesehotch-potches.Afterhours,cer-therefrom,it tainity; but not on Saturday nights betweenwould be much 7.36 and 8 o'clock, when the majority ofbetter." ordinary listeners want a little variety in As a matter the programme. offact, Sir

- . Walford is on Now, what could be more popular thanintheafter- the People's Palace concert by the B.B.C.noon. Indeed, Symphony Orchestra, well conducted byhe appears to Sir Landon Ronald and Percy Pitt ? Frombe going " William Tell" to "Les Preludes" thestrong. programme was full o' plums. And with Megan Thomas as vocalist and Pouishnoff A correspon- as the pianist-what more do you want 1 dent who signs himself" TenA NEW "TALKIE" STUDIO. One of England's largest "talkie" studios has been I heard 'em all a -laughing at our MabelYears a Motor -built at Elstree. The photograph shows the interior of the sound -recording cabinet 592 593 matter Wirek5

13g is quite feasible, but the energy transfer at the other end of the scale would then be so small that the receiver would be hopelessly

insensitive. . . . With an ordinary arrangement, the circuit STABILITY FOU is most lively at the bottom end of the tuning scale and if we so arrange the A Loftin -White Receiver Embodying "Q" Coils. By J. H. REYNER, B.Sc., A.M.I.E.E. coupling that there is no tendency to self - oscillation at this point, reception at the towards the bottom end of the tuningafter another by merely rotating two dialsgrid circuit, in which case a reaction effectoccurs depends upon the anode circuit. top of the scale would be very poor indeed, range where the voltage induced fromwithout any reaction control. A further is obtained, or it may be in such a directionWiliere the anode circuit is inductive, that and an enormous quantity of reaction primary to secondary is greater by reasonsomewhat important aspect of the questionas to oppose the grid circuit in which caseis to say, possesses in general the character- would have to be applied.It is here that of the higher frequency of the current. Inhowever, arises from the methods adoptedadditional damping is introduced. istics of a simple coil, the energy feedback the constant -coupling system is of use for consequence, we obtain a transference of to stabilise the receiver. This condition of affairs is exactly theis positive and self -oscillation or a tendency if we can arrange the constant energy energy which decreases as the wavelength Oscillations in a high -frequency amplifier same to the reversal of the. direction ofthereto will result.If the anode circuit is transfer over the whole scale and further- increases somewhat as indicated in Fig. x resistive, the feedback has no effect what- more arrange the coupling to be such that (p. 594).If, however, we arrange a capacity ever while if it is capacitative, the feedback no oscillation occurs then we have not only tapping in the circuit we can obtain the 1-1A: CH014-6- is negative and damping is introduced a stable receiver, but one which is uniformly reverse state of affairs,for the voltage instead of any tendency to oscillation.It sensitive throughout the wavelength scale. developed across the condenser increases 0 may not be quite clear how the anode as the frequency is reduced, this being .00/ s circuit can pass through these various The basic circuit by which this is accomplished is shown in Fig, 2 (p. 594.) H.T. to exactly the opposite to the voltage developed IMO ODD/ n " i I states, but we can consider a simple tuned the H.F. valve is obtained through an H.F.

across an inductance or transferred across circuit. 000 -1i I choke.The high -frequency currents are a mutual inductance such as is constituted by the primary and secondary of a high - Stability passed through a fixed condenser on to the primaryofthetransformer whichis frequency transformer. 0 G If we vary the frequency of the current, 1 2 coupled to the secondary in the ordinary AN then at low frequencies the effect of the manner.The primary current, however, Constant Reaction condenser is small and most of the current The effect of a capacity coupling there- L flows through the inductance, giving us a

13g is quite feasible, but the energy transfer at the other end of the scale would then be so small that the receiver would be hopelessly

.,,,,..0 /HAVE often been asked whether it isfore, is to transfer energy in 'increasing predominantly inductive anodecircuit. possible to produce a receiver similarquantities as the wavelength is increased, When the frequency is tuned to resonance to the old "M.C." receiver, utilisinggiving an arrangement similar to that with the circuit, both the coil and condenser "Q" coils.The "M.C." receivers whichshown by the dotted line in Fig. 1.If the IiiI I have equal effects and tend to balance each were popular about two years ago havetwo effects can be balanced accurately we other out leaving us solely with the resist- many adherents even in these days ofcan obtain a transfer of energy over the --4Dia-r06.8+ ance of the circuit.The circuit is thus whole scale. purely inductive or nearly so, while at the screen -gridvalvesandothermodern -01.1- practices, and the view which is expressed This in itself may not be a particularly higher frequencies the current prefers to is that if these receivers can be broughtimportantmatter. Itsadvantage in ea -2 flow mainly through the condenser and the circuit becomes predominantly capacitative. up to date by the use of dual -range tuningpractice is that we can put in a small Fig. 3. The Circuit Diagram arrangements such as are provided by thereaction control which is adjusted to give Thus, with an ordinary circuit like this, at "Q" coil, they would then be quite up toan operating point relatively near to theoccur because of the feedback which isreaction in in a simple reaction circuit, and in the tuning point and above it, the circuit is preient-day standards. oscillation point, so that the receiver is intransferred through the internal capacity practice we can actually obtain either of thestable while on the other side the The matter has 'accordingly been put toa state of liveliness, and this control thenof the valve. This feedback depends, to atwo conditions or any condition inter-circuit tends to be unstable and may the test in the Furzehill laboratories and Idoes not require to be altered in tuninglarge extent, upon the nature of the anodemediate between them. It is thus possibleactually burst into oscillation. found that it was possible to obtain goodfrom one station to another.The originalcircuit. It will be quite clear, withoutto obtain a point at which the feedback It may be thought that it should results using standard types of "Q" coil."M.C." Three and "M.C." Four possessedgoing into detail, that energy transfen-edneither helps nor opposes the grid circuit,be possible to weaken the coupling to The results were slightly below the oldthis property to quite a marked extentback in this manner may be such as tobut has no effect whatever. such an extent that the circuit never standard, this being due principally to theand it was possible to tune in one stationcoincide with the energy alfeady in the Which of the three poSsible conditionsactually bursts into oscillation.This `,fact that for best results somewhat critical An end view of the " Stability Four " values of magnetic and electric coupling must be used in the high -frequency trans- having passed through the primary winding former. This would have necessitated the does not go straight to earth, but is caused design of a special "Q " coil for the purpose to pass through a fixed condenser which and I felt that this would be undesirable. also forms part of the secondary circuit. Since I could obtain quite good results Voltages are induced in the secondary, without any difficulty on the standard therefore, from two causes. QSP coil, I felt that this would be the more Eirstly, there is the magnetic induction satisfactory solution. between the primary and the secondary windings, whilesecondly,the primary The Loftin -White Principle current in passing through the coupling The Loftin -White 'principle embodied in condenser C sets up voltages which are the M.C. receivers and in the ,present automatically introduced into the second- version consists in the use of a combined ary circuit. We thus have voltages intro- magnetic and capacity coupling in the duced from both magnetic and capacity high -frequency transformer,This is done coupling and as we have seen, these can for the following reasons. be so balanced that we can so arrange An ordinary transformer having a mag- matters that the two effects balance and netic coupling operates mere efficiently These three photographs show practically all the constructional features of this fine receiver give us a nearly constant coupling. 1 ...1 APRIL 20, 1929 ematturWirelgO 594 Old Tenants and New Lodgers JOTTINGS FROM MY LOG By JAY COOTE EVEN in the broadcasting world, leasesthe moment the Paris station opens itsLe Bourget Aerodrome operates, but in expire and are renewed or granted totransmission you will hear a rapid volleypractice it has been .found that the two new owners. Such is the caseof Mont-in French which, unless you are a linguist,transmissions are clear of each other.To pellier (France) which,' after having limpedmay prove a puzzle, The Paris announceralleviate further the trouble experienced along for some months, suddenly gave uprattles off the following in double quickby Paris fans, the authorities have decided the ghost and blossomed out afresh as atime :"lei les stations radiotelephoniquesto curtail. the Eiffel Tower broadcasts in unit of the P.T.T. provincial broadcastingdu reseau de l'Etat de PEcole Superieure desthe ear future, The station will be silent system. That it has not yet got into itsPastes et Teldgraphes de Paris et les Posiesfrom midday to 2 p.m., from 5 to 7 p.m., full stride is demonstrated by the fact thatde radiodiffusion de la Tour Eiffel, Lille,and the evening concert will terminate at its transmissions have not yet been placedRennes,Toulouse, Limoges, Lyons, Bor-8.40 P.m. on a regular basis, and it has not yet beendeaux, Grenoble et Marseilles," after which, definitely included in the Ecole SuperieureI take it, he falls back breathless in his Listeners to WGY (Schenectady) and net. You can, however, pick it up now andarm -chair I to KDKA (East Pittsburg) or to their again in the region of 253 metres, but its respective short-wave stations may be wavelength is wobbly, for at times youEiffel Tower Interference given the opportunity of hearing messages will find it above Rennes, at others below Talking of Paris reminds me that theexchanged with the Byrd Antarctic Expe- PTT Toulouse. Eiffel Tower has again been experiencingdition.These U.S.A. stations broadcast These three stations aredifficulttotrouble, as shoals of protests have reachedon alternate Saturday nights, KDKA at identify individually as they devote thethe authorities in regard to thq, interfer-6 p.m. and WGY at 5 p.m. G.M.T. As it is major part of the day to relaying the Parisence caused by its transmissions. La Tourthought that the general public may be broadcast, and seldom work on their own.for some time has been anxious to reduceinterested in these communications, KDKA Lack of funds prevents their claiming theirits wavelength to r,47o metres in order (East Pittsburg) has made arrangements independence from the mother station orgive itself more elbow -room, and thus freeto rebroadcast the replies from members of of giving any display of local initiative.itself from its immediate neighbours.Atthe Byrd Expedition.' KDKA operates Owing to its numerous provincial parasites,first sight, the choice of wavelength wouldon 306 metres and its short-wave relays on to -day PTT Paris is unable to put out aappear to be an unfavourable one, in view24.5, 26, 63, and 65 metres; WGY on 380 concise call. If you are lucky to tune in atof its close proximity to that on which the31.4, and 21.96 metres. " THE STABILITY FOUR" (Continued from preceding page)

The value of the phasing condenser cr(Raymond, Becol, Ebonart, Paxolin). roo,000-dlimresistancewithholder is so adjusted as to make the whole anode Two ebonite strips, 2 in. by 2 in., and(Graham-Farish, R.I. & Varley, Mullard, circuit just capacitative so that the circuitstrip 8 in. by _gin. (Raymond, Becol,Lissen, Dubilier). is completely stable throughout the wholeEbonart, Paxolin). 2-microfarad fixedcondenser(T.C.C., range. The smaller this condenser is made, Cabinet, 18 in. by 7 in., with ro in.Lissen, Dubilier, Ferranti, Mullard). the more stable does the arrangementbaseboard (Miscellaneous Trading, Clarion, Low -frequency transformer (Lissen, Cameo, Pickett). Two .0005-microfarad variable condensers (Burton, Lissen, Ormond, Utility,J.B., figleNITICPolar, Igranic). COUP' 1/4V .000 r-rnicrofarad reactioncondenser "IC. (Dubilier, Burton, Lissen, Ormond, Utility, .fMill101. -C6V/PL/heJ.B., Polar, Igranic). Four valve holders (Lotus, Benjamin, ..07PRC/TYLissen, Burton, W.B., Wearite). C01/191//0 Q.A.A. coil (Lewcos, Lotus, Wearite, FREQUENCY Stone). Fig. 1.If the magnetic and capacity couplings Q.S.P.coil(Lewcos, Lotus, Wearite, Fig. 2.A practical Constant -coupled Circuit are equal a level curve is obtained Stone). Filament switch (Lissen, Benjamin, Trix,R.I. & Varley, Ferranti, Mullard, Phillips). become, but it also loses efficiency;ifWearite). Eleven terminals marked Aerial, Earth, desired a pre-set condenser may be employed Two .002, one .000r and one .0003 -micro -L.T.+, L.T.-, H.T.-, H.T. G.B.+, hi place of the fixed condenser used. A G.B.-r, G.B.-2,. L.S.-I-, L.S.- (Eelex, condenser having a value of .00r has beenfarad fixed condensers (Lissen, Dubilier, T.C.C., Mullard, Graham-Farish). Igranic, Belling -Lee, Burton). used in the actual receiver, but the value Connecting wire (Glazite). of this is a matter for experiment. Two high -frequency chokes(Wearite, Lissen, Lewcos, Dubilier, R.I. & Varley). 1% -volt cell (Siemens G.T., Lissen, Ever This briefly is the underlying principle Ready). utilised in the present receiver, the full One 2-megohm and one .25-megohm Next week full constructional details will circuit -of which is shown on the precedinggrid leak (Dubilier, Lissen, T.C.C., Graham -be given together with a reduced repro- pages (Fig. 3). Parish). duction of the blueprint of the layout. In Two grid -leak holders (Lissen, Dubilier,the meantime readers who desire to have a Components Required Graham-Farish). copy of the full-size blueprint may obtain The following is a 4ist of components Resistance -capacity coupling unit (Gra-this from the offices of AMATEUR WIRE- required to build the set : ham-Farish, type z, R.I. & Varley, Mullard,LESS 58-61 Fetter Lane, London, E.C.4, Ebonite or bakelite panel, 18 in. by 7 in.Dubilier, Lissen). price is. 6d, APRIL 20, 1929 595 0 mate= Wtretzzsl

THE CHANNELTinvoitt% Theright unit for the p" ortabli builder Blue Spot 66A Unit is far and away the finest Unit available for the man who requires really superlative quality of tone from his portable.It is wonderfully 4O DARIOVALVES, sensitive, responds equally well over the whole audio range, and will give splendid results on any normal output stagebetween 60-180 volts. Ask your dealer to demonstrate one to you .... youwill buy it. F. A. HUGHES LCO., LIMITED 204.6 GT. PORTLAND ST., LONDON, W.1 Distributors for Northern England, Scotland and North Wales- H. C. RAWSON (SHEFFIELD & LONDON) LTD., 100 LONDON ROAD, SHEFFIELD;185 PRINCESS STREET, MANCHESTER. 10 YOU

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TWO VOLTS FOUR VOLTS I General Purpose, General Purpose, .05 amp. 5/6 .5;6 H.C.C., .06 amp. ...46 R.C.C., .07 amp. 5/6 Super -Power, .18 amp. vs Super -Power, .1 amp...7/6 Super H.F. & E.C.C. Super H.F. & R.C.C. '7/8 .18 amp. . 7/3 .1 amp. Penlodion, .3 amp...21, Pentodion, .15 amp. 21,, 56 7/6 E From your dealer or direct : IMPEX ELECTRICAL LTD., SPOT (DEPT. J), 538, HIGH ROAD, LEYTONSTONE, 66A Unit LONDON, E.11. 21,6 You will Help Yourself and Help Us by Mentioning f!A.W." to Advertisers 0 matterVirelesi 596 APRIL 20, 1929

41.11M1=111111MIIMINIMIN,

"A W "TESTS OF APPARATUS Conducted by ourTechnical Editor,I. H. REYNER. B.Sc. (Hons.). A.M.I.E.E.

The TeKaDe Trickle Charger cork into which two tubes are fitted. OneSquire Large Cone Unit of these bends over in the form of a spout, WE have recently tested a very interest- AGREAT deal of technical...matter has ing metal trickle charger known as thewhilst the other acts as a valve control. To been written on the correct sizes for TeKaDe; this is made in Germany and isuse the device the glass container is filledcone and moving -coil loud-spealters. Some marketed in this country by Dr. Nesperwith the electrolyte and placing a fingerassert, particularly in the case of a moving (Ltd., Colindale Avenue, Hendon. Someon the top of the valve tube, the containercoil loud -speaker,that a small -diameter idea of its compactness may be gauged cone is preferable, while others say that if from the fact that its overall dimensions the cone material can be made sufficiently are as follows :53/4 in. by 3 in. by 21y4 in. rigid, the larger varieties will give the better

high. The secondary voltage is applied to results. a special form of metal rectifierwith which We have recently completed a test on a we have not previously had experience. Squire aluminium cradle frame fitted with a This comprises a series of sheets of thin woven cone having a diameter of 16 inches. foil in contact with a treated metal plate. Surrounding the aluminium frame is a The rectifier is provided with large cooling small wooden baffle designed to be used in fins in order to work at a low temperature. conjunction with a larger baffle, the recom- TV output is taken to three terminals so mended size being some 3 _ft. by 2 ft. by arranged that either 4- Or 2 -volt accumula- 2 ft. 6 in. We tested the assembly with the tors may be charged. recommended units, and found that these We found that the charging was approxi- could easilybe fitted, the design of the chassis mately .5 amp. at both 4 and 2 volts. If a having been well thought out. With the 6 -volt accumulator is charged on thy 4 -volt Easeful Battery Filler particular cone supplied the "speech was tap, the current falls to .26 amp., The inclined to be slightly muffled, but there efficiency is approximately 18 per cent., butis inclined until the spout rests above thewas no doubt that the reproduction had when itisconsidered that the mainscells to be filled; then by removing theboth life and body. The sensitivity was up consumption is only 12 watts or approxi-finger from the valve the liquid pours outto standard. mately one -fifth of the power taken by anand can be stopped at a moment's notice by The manufaqurers also provide special ordinary electric light lamp, the unit mayreplacing the finger. paper for building up this type of diaphragm be termed economical.Although during Although primarily designed for fillingto go with the cradle frame; one may Leclanche cells, this article has other uses which will suggest themsplves to readers. All those who are troubled with this difficulty should obtain one of these fillers. Ready Radio H.F. Choke ALTHOUGH many well -designed general purpose H.F. chokes will operate efficiently on the ultra -short wavelengths below zoo metres, it is often considered advisable for maximum results on these wavelengths to utilise a separate choke having a lower natural inductance and, more important still, a lower self -Capacity. TeKaDe Trickle Charger Provided the inductance exceeds a given value, the efficiency of the choke on the our tests, the unit was made to charge forultra -shortwavelengths depends almost Squire Large Cone Unit a number of hours on end, the rectifier andwholly on the self -capacity. transformer remained noticeably cool. This We have recently tested a short-wavetherefore try the effect of various types of instrument can be recommended to readers.choke, manufactured by the Ready Radiopaper.The maker is Frederick Squire, 24 Supply Co., of 159, Borough High Street,Leswin Road, N.16. A Simple Battery Filler S.E. MANY readers must have experienced We found that the inductance value was the difficulty of filling small Leclanche17,000 mics., which in practice is sufficient Knight's Floating Cone Unit.-Last cells with solution; this process, in fact,to give adequate choking.This was con-week, on page 562, we gave a test report may occupy a considerable tithe owing tofirmed by a test made over a wavelengthon a most satisfactory floating -cone unit the care needed to prevent spilling therange extending from below 15 metres upmanufactured by Messrs. Knight & Co., of electrolyte. to roo metres.The first peali occurred6 Chapel Street, London, E.C.2. It is to be We have received a very useful devicejust below ioo metres, indicating that theregretted that the address was incorrectly known as the Easeful filler, made by, thecomponent was ceasing to function at thisgiven in the report. The correct address is Leyton Battery Co.,of Walthamstow,wavelength. that above, and was correctly stated in London, E.This article consists of a This little component should appeal toMessrs. Knight's advertisement on page large bottle, fitted with a large -diameterreaders. 574 of the same issue. APRIL 20, 1929 597 mutat( Wray -3, BROWN'S H.Q. /BUY THE BEST RADIO ONLY THE ON OUR EASY TERMS WORLD- THE DUAL RANGE FOUR VALVER / as described in this issue. FAMOUS OUR KIT contains only the finest HIGH CLASS BRITISH PARTS. SPEAKER Polished Ebonite Panel drilled ready with strips. Contents List sent Free with pleasure. PRICE Previously sold at ffi. i5 .17. 6 OR can be purchased on our Gradual Payment System.Cabinet 17/6 extra. NOW 3 GNS. 21/8 down and so monthly payments of 10/10. Valves also extra. or 11/8 down and 5 monthly payments of CLARION THREE 11/8. This Years' Wonder Three OUR COMPLETE KIT contains only the highest class British made components. Made by firms of high repute (R.I., ORMOND, BULGIN, LISSEN, POLAR, LOTUS, IGRANIC, etc).COM- PLETE KIT OF PARTS. Cabinet in Oak, 14/6 extra. Three suitable valves BROWN'S .BABY SPEAKER for this set, 45/6 extra.(Mullard, Cossor, Marconi). . SPLENDID TONE AND AMAZING VOLUME. OR 15/- clown and 5 payments of 15/-. BLUEPRINTS FREE WITH ALL£4 ORDERS.4 or 8, 6padyomwenntasnodfmonthly28- 3.7 NOW 221- BRITAIN'S FAVOURITE THREE DE LUXE Specified Kit of parts.Panel drilled including baseboard, screws and wire.PRICE,(10 21. BLUE SPOT UNIT 66K DUAL RANGE COIL 7/6 extra.Or 15/4 down and 10 monthly payments of 8j- 0 WITH NEW MODEL BLUE SPOT CHASSIS Cabinet in Oak for this set, 17/6. COSSOR CONVERSION KIT 37/6 Convert your old COSSOR MELODY MAKER into a MODERN SCREEN -GRID THREE. or 141- down and 4 monthly payments of 7/-. COSSOR KIT containsallnecessaryparts, includingVALVE, 2 COILS, BLUEPRINT, etc. PRICE OR 10/- down and 7 monthly payments of 7i6. 57/6 .yr,CELESTION BURNDEPT S.C. 4 -VALVE PORTABLE Brings Europe's finest broadcast programmes to your home.Beautifully made. Light weight. MODEL C10 Our gradual payments for this set. £2 down and 12 monthly payments of £2 Is. 4d. WONDERFUL PURE Any Kits, Speakers, Valves, Batteries, GRADUAL PAYMENTSetc. supplied on terms.Write us, state TONE your requirements; it gives us pleasure to supply you on our GRADUAL PAYMENT SYSTEM. Carnage paid on all cash orders.Terms Cash, C.O.D. or Gradual Payments as desired. OAK £5.10.0 or £.1 . 0 . 0 down andto H. & B. RADIO CO. monthly payments of 10/6. 34 BEAK ST., REGENT ST., LONDON, W.I. Ger : 2834.

111=111111111111111111111.11111, DR. NESPER TEKADE TRICKLE CHARGER 100v. to 125v., or 200v. to 240v. A.C. For charging 2v. and 4v. Accumulators. Simply fix plug into lampholder thenattach spade terminals to accumulator and switch on. Price 29/6

A4 - volt Accumula- tor can be charged any time the Setis not in use Patents pending atcostof ld. .. .

DR. NESPER LTD., Colindale Avenue, Hendon, LONDON, N.W.9 4,14112,, RUPERT COLLINS SERVICE Mention of "Amateur Wireless" to Advertisers will Ensure Prompt Attention Citnakitr Wire 598 APRIL 20, 1929

Last week a technical description was given of the working arrangements of the All -Mains Two, a simple transformer - coupled two -valuer obtaining both H.T. and L.T. from A.C. mains.Here are some concluding constructional notes and hints on operation more convenient to screwly.There is no switching to be done, for in in place and wire up mostorder to bring the receiver into operation of the baseboard partsit is necessary simply to insert the mains beforethepanel com-plug into a light point.The anti -motor - ponents are added.Noboating unit should effectively prevent difficulty should_ be ex-the possibility of L.F. instability. periencedin completing On the receiver side a point which will the baseboard assemblybe noted is that the tuner is provided with providing the blueprint istwo tappings, namely AI and Az and a used as a guide both forflex lead can be taken to either one or the AFEATURE about this set which willpositioning and wiring up the components.other, according to the degree of selectivity appeal to constructors is that withoutAssembling the Components required. The tapping Ai gives the greater number of turns in the aerial coupling. sacrificing neatness of layout, or complicat- A brief explanation of the layout, which ing the construction in any way, the mains The changing from the short to the long section is kept quite distinct frorm themay at first seem rather complicated, maywaves and vice versa is obtained simply by be helpful.Between the aerial coil andpushing and pulling the centre knob of the receiver section, although both are mountedcondenser is situated the .0002-microfarad on the baseboard. A list of componentsfixed reaction condenser and the 2 -micro was given last week to serve as a guide tofarads condenser in series with the earth Simply insert the mains those who' re making up this set. Althoughlead.These components are placed side plugintoa the cost of this set may appear to be re-by side. latively higher than an ordinary two-valvei, Then, in a row, looking from the front light point it should be born in mind that there are no'end of the baseboard we have the detector batteries to purchase. valve (with the grid condenser and leak in The Mains Section front of it), the H.F. choke in the detector The mains portion comprises, primarily,plate circuit, the L.F. transformer and, atransformercarryinga number of tappings,finally, the L.F. valve. a rectifier valve, a smoothing choke and the At the back of these is a second group requisite number of large capacity smooth-of components, also almost in a line. These ing condensers.As explained last weekare, from, left to right, the potentiometer the tappings on the transformer(one(to the moving arm of which is taken the winding of which, of course, is connectedlower end of the 3-megohm grid leak) and directly across the mains) provide fullat the back of it one of the 2-microfarad voltage H.T. to the rectifying elements ofsmoothing condensers.Next are two 2- the valve, a supply of alternating currentmicrofarad fixed condensers in parallel, L.T. to the filament of the rectifier valveforming a 4-microfarad bank. In front of and, finally, 2.5 -amps at .8 -volts for thetheseisa 20,00o -ohm fixed resistance filaments of the receiving valves.If youwhich forms one part of the anti -motor - care to glance at the theoretical circuitboating unit. The 2-microfarad fixed -con- diagram the whole arrangement will bedenser which forms the second part is just made quite clear. at the back of the L.F. transformer. tuner. The larger rotating knob, of course, Now, so far as construction is concerned At the back of this group of components,is the reaction control. from left to right, are placed the smoothing a blueprint will be found a great asset to Valves to Use this particular instance and, of course, aschoke, rectifier valve, power transformer usual, one is obtainable for this set fromand grid -bias battery. So far as valves are concerned the AMATEUR WIRELESS, 58-61 Fetter Lane, Wiring up should be carried out withMarconi or Osram directly -heated valves London, E.C.4. The price is r/- post free. rigid insulated wire, such as Glazite in orderare those for which the receiver has been to prevent the possibility of short-circuits.particularly designed.The H.L. .8 valve The Layout When the wiring iscomplete carefullyshould be used as a detector and the P .8 as The first use to which it can be put is as acheck it over in conjunction with the blue-an L.F. valve. drilling template for the panel. The panel,print and, if you feel capable of doing so, of course, carries simply the aerial tuningwith the theoretical circuit diagram. condenser (on the right looking from the Owing to a printing error,it was, in front) the aerial tuner and, below, fourOperation somecopiesof AMATEUR WIRELESS terminalsforaerial,earth,and loud- So far as operation is concerned theNo. 356, not made clear that the price of speaker respectively.All these parts canreceiver can be treated very much as.4 and .5-microfarad Dubilier paper di- be mounted, but the panel should not, atthough it were a straight -forward detectorelectric fixed condensers is2S.6d.,as this stage, be attached to the baseboard.and one L.F. set, deriving H.T. and L.T.stated in the advertisement of Messrs. In this set it will, indeed, be found muchfrom batteries and accumulators respective-Dubilier on cover iii of that issue.

.. APRIL 20, 1929 599 mateurit

WE' `IT Little COAiPOIV-AnS before W. James "Special 3" Coils..25'^ pear mend W. James "Binowave" Coils 25;" ARCADIAN PORTABLE Coils each10/6 Screen .. 9/6 saves 4 4

H. F. Chokes . 6/6 Battery Switch, G22 (with terminals) 1/- much Valve Holder, LAS5 2/6 Grid Leak Clips -/6 alter Coil Formers (unwound) 7/6 Spend Dual Range Tuner, W.G.2, as used in FERRANTI Circuits15/- FLUXITE ALL FROM THE MAINS TWO simplifies all soldering Dual Range Tuner, W.G.2 pair 15/- FLUXITE is sold in tins, SOLDERING H.F. Choke .. 6/6 price 8d., 1/4 and 2/8. SET, complete H.T. Choke .. 21/- Another use for Flux- ite : Hardening Tools Valve Holder, anti-microphonic, LAS5 each 2;6 and Case Hardening. 7/6 Ask forleaflet on or LAMP improved methods. FLUXITELTD., WRIGHT & WEAIRE, Ltd. (Dept. 326) 740, HIGH ROAD, TOTTENHAM, NM. Rotherhithe, S.E.16 Telephones; Tottenham 3847 and 3848

%cr HELLESEN DRY BATTERIES WHEREVER YOU GO The days are lengthening and not build your ownwireless SOME GOING ! portable set?We can supply you will be spending more and I saw a 99 -volt Hellesen H.T. more time outdoors.Add to cabinets from 30/-,and complete kits of parts for construct- Battery the other day that Your enjoyment whether on the had accidentally been left on ing any type ofset.We can short circuit. river,inthecountry,or at also supply immediately any of home in the garden, by having So great was theenergy the well-knownwireless or given off thatthesealing aportableinstrument.Why gramophone portables including: compound had melted away and the battery was twisted WILL DAY PORTABLE 5 VALVE ... 16 Gns. PRICES and contorted. Standard Capacity McMichael Screened Grid Super Four.The best " Wiray "9 -voltGrid The irrepressible Ridley on yet offered to the public ... 35 Gns, Bias Type ... 2/- seeing it remarked thatit Wirin " 00 -volt had evidently waxed hot, but Selector V in Blue Leather Case, complete 30 Gns, Type ...10/6 " Wirup " 99 -volt H.T. I couldn't help wondering if Selector Screened Grid III, in Oak Cabinet 20 Gns. Type ... 18/. there was any other make of Marconi V. Walnut finish, complete ... 28 Gns. " Wisol "108 -volt H.T. battery which would have I Type ... 20/ - and all well-known makes of Portable Gramophones. Treble Capacity. withstood the strain as this " Kolin "00 -volt H.T. Hellesen did and still show Type ... 19/- 27voltson opencircuit Have you had particulars of our most simple " Kolup "99 -volt H.T. Hire Purchase Terms ?Any set or kit of Typo ... 32/1 afterwards. componentscanbepurchasedthisway. --- I /i////, /,4, or,vasenesivAitvishcsio \,-- ///,, it tIELLESEN DRY BATTERIES INSTRUMENTS I Ii POLYMET, MICA & PAPER CONDENSERS HAND & CYCLE LAMPS, TORCHES, ETC (THE BE/T IN THE WE1T) 19 LISLE STREET, LEICESTER SQUARE, LONDON,IV.C.2. A.H. HUNT, LTD., CROYDON, SURREY Velvbuile: filaile.t) 'keret 0921tad OW1 ' jelf,jiains:7111,,,)Vral fdricl,',undone - To Ensure Speedy Delivery, IVention "A.W." to Advertisers mateur Wtrcl P is 600 APRIL 20, 1929 THE WIRELESS CONTROLOFMODELS PART TWO -THE RECEIVING GEAR (Concluded) By MAJOR RAYMOND PHILLIPS PTHE pneumatic arrangement of the1 in. The electro-magnet should be wound Two 5 -amp. switches are fitted at each "dashpot " simply consists of small bel-with No. 25 -gauge enamelled copper wire.end of the case. These are for insertion in lows similar to those made for piano players. the coherer and main circuits respectively. Any dealer in piano player componentsThe Selector Mechanism The remaining components, consisting of will supply the bellows. The latter should The mechanism of the selector is quitea brass pedestal and brass spring contact be mounted as shown in Fig. 3 (No. 357). Asimple. It consists of a brass contact leverfor a vertical type of coherer, can be made. hole drilled in the top of the wooden part3 in. long by 1/2 in. wide by-116- in. thick, For a pedestal it is only necessary to of the bellows, and fitted with a woodentapered at one end to which is secured a piece of .005 in. hard brass sheet to form Terminals connected a rubbing contact with two other contacts towtocts e,99o949 with OWnei/coilv mz`h cal/WI °petaled /one/m.411/c mounted on the wooden base. An actuating leveysfityy 60ashpolOeme lever r % in. long by 1/4 in. wide made of brass sheet in. thick is loosely secured CZ4j ;-7.jged/1 to one end of the round soft iron rod which \\ / passes through the core of the electro- Fig. 7.The selector magnet with contacts t fr magnet. It will be observed on reference to .ifgee/ Fig. 6 that the soft iron rod is bent at right - moaeekere/01dh894v angles at one end and passes through a, slot cut in the brass plate, forming a base for Ta/701/>g, the components of the selector. One end of 1 L aeUe the actuating lever is V-shaped to engage t§1 with a double V -cut in the contact lever. Fig. 6.The selector electro-magnet A small spiral spring made of No. 28 -gauge Fig. 5.Details of selector base hard steel wire iszecured to the other endsolder a piece of round brass rod 3/4 in. plug, is useful for adjusting the admissionof the actuating lever, and the brass plate.long by % in. diameter in the centre of a of air to the bellows, as a small slot can beIt will be apparent that when the electro-brass disc r % in. diameter byin. thick. cut at the side of the plug, and enlarged asmagnet of the selector is energised, the When the soldering is completed it will desired.The object of the bellows is toactuating lever will engage with the contactbe necessary to drill a hole 3,132 in. diameter retard the upward movement of the arma-lever causing the latter to move in eitherdown the centre of the pedestal to admit the ture of the electro-magnet, and so closedirection, thus opening or closing a circuitsupport or shank of the coherer. Another for a period a circuit connected with theconnected with the two contacts mountedhole should be drilled and screw threaded selector electro-magnet. This is necessary,on the wooden base.The whole arrange-transversely through the shank of the otherwise there would be a risk of thement is clearly shown in Fig. 7. pedestal so that a No. 6B.A. screw, % in. selector not functioning correctly. The Case nERigt 7 TERmpyms7 The remaining parts for the receiver comprise a case and the coherer. WHERER ORCII/I It is advisable to construct a case to OSNTGI/ accommodate a sheet of glass at each side, as it is well to be able to watch the mechan- NR//Y SW/101 ism in operation: The size of the case should be r8 in. °TERM/M P long by 14 in. wide by 14 in: deep, and it Nshould be fitted with a removable par- Fig. 8.Details of receiver case tition (see Fig. 8). The upper half should Fig. 9.Method of mounting coherer The construction of the special selectorcontain the coherer, decoherer, relay, andlong, can be inserted to hold the shank of should not present any serious difficulties.31/2 -volt dry battery, the latter an ordinarythe coherer.Three / in. holes should then When commencing the construction it willpocket -lamp battery. be drilled in the base of the pedestal for be necessary to cut a brass plate 5 in. long The lower portion of the case shouldthe purpose of securing it to the partition by z in. wide by -1in. thick as shown incontain the magnetically operated pneu-in the case containing the components. Fig. 4 to form a base for mounting thematic dashpot device, and the specialA brass spring contact 31/2 in. long by 1/2 in. various components. The brass plateselector. Four holes should be drilled in thewide should next be made by cutting the should he mounted upon a wooden base,top of the, case to accommodate four largesize required from a piece of No. 28 -gauge and four terminals fitted to the base, andterminals ;the latter being arranged tohard brass sheet. The whole arrangement wired up to the selector electro-magnet,hold two aluminium rods 1/4 in. diameter byis shown by Fig. 9. and contacts respectively as shown in4 ft. long to form an aerial. The top of the All components are now ready for assemb- Fig. 5. case should have a hinged lid. ling. It will be well to commence by secur- The magnet of the selector (Fig. 6) should Two holes should next be drilled in eaching the coherer pedestal, arid spring con- be f y4 in. long with a soft iron core % in.end of the case to accommodate four ter-tact in position on the wooden partition of in diameter.The latter should be drilledminals for connecting .to an accumulator,the case by the brass wood screws already to allow a soft iron rod 11 in. diameter toor other source of electrical energy anddescribed. When this is done the coherer pass freely through the centre of the core.(in the case of a model electric railway) toshould be placed in position, and the At one end of the round rod there shouldthe "conductor," and "outer" rails -of adecoherer, or tapping device (i.e. electric be secured a soft iron armaturein. bymodel railway. (Cot:chided at foot of page 602) APRIL 20, 1929 601 0mo/es( WireiT r.....s...... solv..00mm.s...... "...os.m...... sa....e...... 1...s...... o....61, TO HOME CONSTRUCTORS! I HERE IS THE i Build the Peerless " Resonic 2" OAK WIRELESS CABINET Anyone -.canbuildthisset in6() 'minutes.No drilling.No soldering.All Wires cut and bent.JUST ASSEMBLE and then immediately enjoy theradio YOU ARE LOOKING FOR entertainment. which isofsplendid tone and comesinatgood loudspeaker i volume.Circuitallowsuse of standard valve (IH.F. & I Power).Blueprint and easilyfollowed Dia- .. gram ofConnectionsin- :i Do not put a fine piece of i eluded witheveryset. i work into a fourth -rate box Cabinet and full Kit ! supplied in Garton. i i Install a " LAN GM ORE " i 13.15.0 1 and be proud of your set. i Obtainable from Thesecabinets are made in the o: i alldealers, i following sizes :- THE BEDFORD ELEC. i No. 1.Panel, 16 in. x 7 in. TRICAL & RADIO CO., ! Cabinet, 2 ft. 6 in. high, Regd. No. 456002 LTD., 22 Campbell Rd., i ft. Nos. & 2 BEDFORD. 8 in,wide,12 in. I !.. deep. No. 2.Panel, 18 in. x 7 in. 27/6 Cabinet, 2 ft. 6 in. high, 1 ft.to in. wide,12 in. Each deep. No. 3.Panel, at in. X 7 in. Cabinet, 2 ft. 6 in. high, CLARION CABINETS ft.tin.wide,12 in. Nos. 3 & 4 deep. Are manufactured in the cabinet- No. 4.Panel, 18 in. X 8 in. 32/6 Cabinet, 3 ft. high,t ft. making centre of London, by loin, wide, lz in, deep, Each experts in woodwork. We can All the above with Battery Shelf, enclosed back quote you for any size or type of and sides, and double doors in front of same, receiver or loud -speaker cabinet 10/- extra. in solid oak or mahogany PACKED and SENT CARRIAGE PAID to ANY ADDRESS in GREAT BRITAIN All are fitted with hinged top, heavy baseboard, etc., and a tray underneath gives accommodation for batteries.London made.Highly finished in Jacobean style. Please note this price does not include Panel. Other sizes and styles, prices on application. Trade enquiries invited. CLARION RADIO FURNITURE THE MISCELLANEOUS TRADING CO. LTD. Phone: 'Phone: Hol. 4894. 143 High Holborn, London, W.C.1 Bishopsgate 6371 Mansford Street, London, E.2

411110M1.0411.1.000.2.0...... 0001.10.1111,0404M.0042.100.1.1,C.11101M011110. Amateur Wireless HANDBOOKS each 2/6 net.

The Shielded Four -elec- The Practical " Super -het " aar Book. Here isthe famous D.X. Transformer trodeValve. which is setting a standard in value for Loud -speaker Crystal Sets. Perfect Broadcast Reception. money and is already known wherever Wireless -controlled Mechan- radio is heard of. A really first-class The Short-wave Handbook. pieceof workmanship, conscientiously ism for Amateurs. made in accordance with modern scienti- The Practical Wireless Data fic principles at a price that places it The Wireless Man's Work- within reach of all. shop. Book. Write to us for leaflets and particulars of THE BOOK OF THE NEUTRODYNE, by J. H. Reyner, B.Sc. 8/' Retail this transformer and give one a trial. (Hons.), A.M.I.E.E.Price 1/6 net, or post free for 1;'9 You cannot fail to be delighted. Ratio 3 to I Ask for particulars of our new circuit, the D.X.3. Of all Newsagents and Booksellers or by post, 3d. D.X. COILS LTD., 542 Kingsland Road, E.8 extra, from Cassell E3 Co., La Belle Sauvage,E.C.I.

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"1928" LOG CONDENSER 5/- '0005'00035 '00025 TRANSFORMER -OUTPUT BRITISH FILTER CHOKE "DE LUXE" MODEL COILS SG 1 & 2 25/- 0005 61. 00035 10/6 each Components Throughout '00025 '00015 VALVE HOLDER 1/3 SEND FOR CATALOGUE. THE FORMO CO., CROWN WORKS, CRICKLEWOOD LANE, LONDON, N W 2 Don't Forget to Say That Yon Saw it in "A.W." 602 APRIL 20, 1929

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/4/MilligISO" /*///01111111100 RULES.-Please write distinctlyand keep to the point.We reply promptly by post.Please give all necessary details.Ask one question at a time to ensure a prompt reply,andplease put sketches, layouts, diagrams, etc., on separate sheets containing your name and address.See announcementbelow. AddressQueries-AstaTuuaWIRELESS Information Bureau,38/6r Fetter Lane, London, E.C.4 Loose Material in Valves. matter. Can you assist me in this respect ?-W. A.set which you wish to sell.Further, request Q.-I have some cheap foreign valves which,(Cardiff). information regarding what royalty feeis althoughstillfunctioningquitewell,have A.-You should address a letter to Marconi'srequired and any other details which will facilitate your selling the set.-L. C. developed a rattle inside when shaken.I have 0 0 traced the cause to a small deposit inside the V° V \°A)/ VV / 7 bulb and this appears to be a strip of metal. Poor Earth. Am I likely to do any damage. if I continue to Q.-I find that when I disconnect my earth use these valves ?-J. B. (Wandsworth). When Asking wire from my receiver I get much louder signals A.-The strip inside the bulb is not a part and better results than with the earth wire con- of the electrodes but is a small piece of magne- nected.Can you account for this and suggest sium which did not become used up in the Technical Queries how I may get the better results with the earth exhausting process. Originally this magnesium PLEASE write briefly lead connected.Without the earth lead the set was attached to one of the valve electrodes, is very prone to oscillation when tuning.-G. D, but has become dislodged and has fallen off. and to the point (Sevenoaks). Do not shake the valve more than you can A Fee of One Shilling (postal order A.-Your experience points to the earth lead help as this loose piece of magnesium may or postage stamps) must accompany having a high -resistance.You should try to touch two electrodes at once and so cause a each question and also a stamped find a better earth connection and in this " short."Should you take the valve out of addressed envelope and the coupon respect we should suggest a shept of copper the set at any time see that the piece of magne- which will be found on the last page. about 2 ft. square sunk at least 4 ft. below the sium is at the bottom of the bulb before Rough sketches and circuit diagrams surface of the ground.Several lengths of replacing the valve in use.-C. L. can be provided, but it will be neces- insulated copper cable should be soldered to Home-made Sets sary to charge a special fee (which will the earth plate and all of them should be taken Q.-I have a four -valve home -constructed set be quoted upon request)for detail direct to the earth terminal of the set. Be sure which I now wish to sell in order that the cash layouts and designs. to use copper wire for the earth leads and also so obtained can be expended for the building of a for the aerial, as this ensures a reasonably five -valve set.I know that a royalty is payableg.tMAA, AZAAM, MAIMn low -resistanceand thereforegoodresults. in respect to patents and I have no wish to evadeWireless Telegraph Co., Ltd., Marconi House,Using a smaller aerial tuning coil or reversing the payment of this, but I do not know to whomStrand, London, W.C.2, and state in yourthe connections to the reaction coil may also I should address a letter for guidance in thisletter that you have a four -valve home -builtimprove matters.-C. L.

" THE WIRELESS CONTROL OF MODELS "(Continued from page 6o3) bell movement) should be so mounted thatthe coherer, or else there is a loose con-is ready for use, it will be well to carry out when it functions its hammer strikes thenection somewhere in the wiring. the first wireless test by tapping the morse coherer. key in the transmitter, when the COHERER WITH The relay should be mounted either PEDESTAL receiving apparatus should instantly at the side or behind the decohering function. When this is done, and if AERIAL device. /7ERIgL everything is satisfactory the micro- In the lower portion -of the case phone fitted to the transmitter can the magnetically -operated pneumatic be tested by speaking the word dashpot device and selector should "stop" in a loud voice near the be mounted alongside of each other. COHERER diaphragm.The receivershould CIRCUIT then instantly function the same as Everything will now be ready for BATTERY wiring. when tested in the ordinary way. Ordinary electric light twin flex It will be found that best results is excellent for the wiring. A wiring RR/1Y SWITCH are obtained when the aerial rods diagram is shown by Fig. io. are oppositeand parallel to one IRE/AY When the wiring is completed it CONTACTS another. will be necessary first to test out the If it is desired to control a model whole apparatus electrically. ORSHPOT SWITCH electrictrain,thelocomotiveof 4V IICCUM.1"OR 4 VOLT The4 -voltaccumulatorwhich VEIICE CO/Y/YECTIO/YS FROM which is fitted with a " sequence (BELLOWS 17CCUAto supplies electric current for operating/WSW, OTHER SOURCE Or reversingmechanism,itisonly the various mechanisms should be EL EC TRICNL E./VERO 1'1 necessary to connect the remaining fully charged and the dry battery in two terminals of the receiver with good condition. Being assured of lilt the " conductor " and "outer " rails these important matters, the switch SELECTOR of a model railway, and close the 9CONTRCIS inserted in the coherer circuit being SELECTOR switch (secured to the receiver) in- closed, the selector should function ELECTRO serted in the main circuit, when some instantly each time two of the aerial Ago/YET MODEL extremely interesting effects can be terminals are short circuited. produced by shoutingthe words The apparatus is now ready for a Fig. 10.The circuit arrangements of the Receiving Gear "ahead," "stop," and "back," in wireless test.Should the apparatus sequence intothemicrophoneof, fail to function, it will generally be found Assuming everything is in order, and the the transmitter. ,:that either there are insufficient filings intransmitter described in previous articles (CoxcLusioN) APRIL 20, 1929 603 mateur Although attempts were made by several European transmitters, Vienna was the only short-wave station able to secure two - 12(9°DIOGR(IA/1-43Way communication with the Zeppelin airship on its recent flight across Southern Europe. Messages from Dr. Eckener, its ®April 8 the north regional studioscommander, were received on i,o2o.metres. were removed to Broadcasting House, Manchester, which comprise, in addition Announcements are now made from to the necessary offices, a concert hall, twoPC J (Hilversum) in the Dutch, German, storeys high, with a gallery foi an audienceFrench,Spanish,and Portugueselan- of about eighty people. In the same build-guages. ing accommodation has been found for a Arrangements have been made for the dramatic and sound -effects Studio and theregular relay by the Italian broadcasting necessary echo -room. stations, of performances from the- Scala Listeners should not miss the vaudevilleOpera House, at Milan; the Royal Theatre, MAKE programme to be broadcast by 2L0 andTurin; the Carlo Felice, Genoa; the, San 5XX on April 27, for during the entertain-Carlo Theatre, 'Naples; and the Royal ment they will hear the Albert SandlerOpera House, at Rome. THESEand Trio, Ronald Frankau, Claud Hulbert and Since the opening of the Turin and Enid Trevor, Deslys and Clark, and ClaraGenoa* broadcasting stations the number Evelyn, the musical -comedy star. of registered licences in Italy has attained On the occasion of the Newspaper Press6o,000; it is computed, however, that there At Home ! At Once ! Fund Dinner, to be held at the Mayfairexist in the country nearly one, million: pirates, and drastic steps are to be taken MEN !Here is the chance of a lifetime ! Hotel on April 23, the London station will A GOLDEN opportunity in every sense of relay the Prime Minister's speech propos-to induce these illicit owners to legalise the word. It is an opportunity for you to their status as wireless listeners. participate in the BIG PROFITS now being made in ing the toast of " Journalism." On this the Electrical and Wireless Industry-a business which has enlarged enormously of late years but whieh has evening Sir James Barrie's manuscript of The new short-wave transmitter to be not yet reached a tenth of the size to which it will his short play The Twelve Pound Looh iserected at Rome will possess a power of eventually attain.My new and improved patents are in increasing demand everywhere because they are such to be auctioned, by Sir Herbert Morgan,some12kilowatts in the aerial.It has a vast improvement upon all others; this I can prove and the sale will be included in the broad-been decided to adopt two wavelengths, to you by Certified Tests. cast. namely, 25 metres for transmissions des- On May i Billy Mayerl will pay a returntined to the Italian colonies in Africa and A Genuine Spare- visit to the Savoy Hill studio to give8o metres for Europe.The 50 -kilowatt another illustrated talk on the playing ofhigh -power broadcastingstationto be Time Business ! dance accompaniments. installed in the capital will be supplied by With my improved and Patented Process the work A Mad Mummer's Bright Dream, bythe Radio Corporation of America towards is so easy that the whole of the family-including the the end of the_coming summer. children-can help.Even though you have no know- Charles Brewer, with Tommy Handley in ledge of Wireless or Electricity you can commence at once to turn your spare time into CASH and earn the part of Mummer, should prove a lively It is proposed that a Scottish Council anything up to entertainment on April 23; he will befor Schodl Broadcasting should be set up, assisted by a strong cast. consisting of twenty-fi'o members repre- The Eternal Waltz, a musical burlesquesenting the various bodies dealing with education in Scotland. 300a Year/ by Leo Fall, is down for broadcast from No expensive " plant " or machinery and no special skill is required.I will supply you with all details 2L0 and 5XX on May 3; the book is by The musically inclined of Messrs. Har- entirely free of charge.Your kitchen or any small R. E. Jeffrey. land & Wolff's employees are proving outbuilding can be your workroom. Nobody can encroach upon your business, because it is protected themselves capable of providing a Belfast under Royal Letters Patent. In a Festival of Music and Drama to be given at Canterbury Cathedral during thewireless programme from their own re- ME9 week August 19 to 24 the B.B.C. will pro-sources. The Queen's Island Military Band vide the orchestra, of which the conductoris the only flat -pitch military band, in the II GUARANTEE is to be Dr. Adrian Boult. country, and is already well known on your profits-only a limited number am Apart fromthe ether, while the Male Voice Choir has allowed to manufacture, so your market choral, orchestral, and 'chamber concerts, can never be overcrowded.If necessary, gained distinction at many contests. I arrange to purchase all your stocks. the dramatic side of the festival will in- Thus you are positively certain of profit ! This is not adying " industry, but a clude Everyman, acted outside the Cathe- In view of the dissatisfaction of Edin- rapidly growing one.It has been estab- dral, and Marlowe's Dr. Faustus, presented lished over a decade and is competing suc- burgh listeners regarding the quality of cessfully against big combines.It offers a by the Norwich Players from the Madder -transmissions, the B.B.C. point out that tremendous opportunity. market Theatre. there is a system of lines available on a Send at once for Full Free Particulars. Don't hesitate -this is a Straightforward, Genuine, Honest Proposi- It is expected that within the next fewz4 -hour basis between Glasgow, Dundee, tion.Commence to earn easy Extra £.£5's NOW and weeks experiments in broadcast televisionand Edinburgh.Hence,ifthetrans- become an independent Master Man. on the Baird system will be made throughmissions of 5XX as received at Edinburgh SEND THIS FORM NOW ! the Konigswusterhausen transmitter. Inare unsatisfactory, due to fading, inter- the meantime Berlin (Witzleben) is testingference or other causes, the London pro- the Mihaly Telehor apparatus for the trans-gramme can be taken from the relaying , "Amateur Wireless " COUPON mission of cine films, on a frequency ofreceiver at Dundee or Glasgow, or a local To Mr. V. ENGLAND-RICHARDS, I The England -Richards Co., Ltd., 9,000 kilocycles. programme substituted. 1210, King's Lynn, Norfolk. I According to a Vienna wireless journal, s0,-Please send me at once, and FREE, More than 500,000 letters were received full details as to how I can Make Money at I atransmission from Rosenhuegel wasfrom protesting listenerS when the Federal Home In my spare time.I enclose 2d. stamp j for postage. picked up at Chicago, Illinois, U.S.A., onRadio Commission ordered a reduction in Print your none and address boldly in capital I letters on a plain sheet of paper and pin this I February 26 last. The Affierican fan statesthe broadcasting time of station WGY at Coupon to it. that he was using a 14 -valve receiver 1 Schenectady. L" Amateur Wireless," 20;4/29. APRIL 20, 1929

TO PERFECT RADIO From Our Own Correspondent In addition to their own extensive range, PETO SCOTT offer YOU Every Known 1VIR. DAY asked the Prime Minister Radio Receiver or Component-all on whether, in view of the increasing public interest in broadcasting, consulta- EASY TERMS tions had taken place this year with the The following list is merely representative, and we ask you to fill in the coupon below or send us leaders of the opposition parties of the a list of your requirements. House with a view to broadcasting the forth- THE FIVE GUINEA PORTABLE,described in this coming Budget speech. issue. Send only 10!-, balance in easy payments. COSSOR MELODY MAKERSend only10/-, balance Mr. Baldwin said he had no reason to in11monthly instalments of14/7. think, since the question was last raised, MULLARD MASTER THREE STAR.Send only 10/., balance in11monthly payments of15/3. that there was any change in the general LEADING MAKES OF H.T. ELIMINATORSfrom feeling of the House that the broadcasting "POPULAR" TRANSFORMER 417down.Balance in11monthly payments of4/7. of its proceedings was undesirable. When planning your new setensureperfect ARCADIAN PORTABLE.Kit of parts (see "A.W." amplification by including a Brownie 'Popular. balance in easy payments. March 30),Send only201-, Sir W. Mitchell -Thomson informed Mr. Transformeras recommended by AMATEUR EXIDE 120 -VOLT H.T. ACCUMULATOR 2,500 rota Day that the -present number of wireless WIRELESS for use in a number of their special hours, with crates.Send only6/11, balancein 11 circuits.The core iron and the windings, which monthly payments of6/11. receiving licences issued free to blind per- are the very finest obtainable, are assembled in the "A.W." ALL MAINS TWO.Kit of parts.Send only famous Brownie Factory; while all the delicate 15/-,balance in easy instalments. sons under the Wireless Telegraphy (Blind parts areprotected by an attractive moulded Buildyour own set the Easy Way NOW! Persons Facilities) Act, 1926, was 14,372, Bakelite casing which seals the whole transformer against any atmospheric interference.Send P.C. Our Catalogue contains an leading makes of Re- representing a remission of licence revenue to Dept. 23 at address below for free booklet. ceivers, Accessories, Kita of Components forthe Wireless without Worry." Home Constructor. of £7,186 a year. Mail Confirm in unsealed enyeloke under Id. shrink. BROWNIE WIRELESS CO. (G. B.) LTD. Nelson St. Works,MorningtonCrescent, PETO SCOTT Elk TRADE NOTES LONDON, N.W .1 Please send me your big Illustrated Lists

NAME SUBSTANTIAL reductions have recently

ADDRESS been made in the price of Cyldon condensers, and a folder giving details and the A.W. 20 4 11=111mil OIM 101 Imam Nom= e OMNI latest prices may be obtained from Sydney Free Demonstntions sadAdvice by QualiSei Engineers at car Shops :- S. Bird & Sons, Cyldon Works, Sarnesfield 77City Road, London, E.C.1 Road, Enfield Town, Middlesex. 62, HIGH HOLBORN, LONDON, W.C.1. 4,MANCHESTER STREET, LIVERPOOL. Price reductions have been made in con- 33, WHTIELOW RDANCHORLTON.CUM.HARDY, M CHESTER., nection with Siemens H.T. batteries for portable sets, we are informed by SiemensTUNEWELL Bros. & Co., Ltd., of Woolwich.The pricewith our DUAL RANGE COILS 44 TONE- SUPERB " of the 126 -volt battery, type 1075 has-been reduced from 3os. to 25s. and that of the and CHOKES Baffled Floating Cone o8 -volt type 1077 battery from 25s. to CLARION THREE 2 1 s. 6d. It should also be noted by construc- Employing a 16 -in.Baffle with our famous 10 -in. tors of portables that the length of the LI SS EN THREE impregnated kraft cone. well-known 6o -volt popular type battery Completely asserr bled cone COSSOR THREE of correct angle, suspended has been increased from with extrasuppleskin. inches to 9 and all other The reproduction ofthe inches. Bess withoutsacrifice of SCREEN -GRID the Treble, is really Garnett Whiteley & Co., Ltd., makers amazing. Supplied as illustrated of Lotus sets and components, inform us CIRCUIT COILS withpamphlet showing method of unit mounting. that they have now taken offices at 125 at 21/- per pair High Holborn, London, W.C.r. The Lon- PRICE 5/6, post 9d. Range 20012000 metres don representative of the firmisMr. for Panel Mount- Write for further details. W. J. Holland. H.F. Choke Massive All Purposeing, Valve Holder WARRICK RADIO The Mullard Wireless Service Co., Ltd., Base, or 6 - pin 16 BERTHER ROAD, HORNCHURCH, ESSEX of Mullard House, Denmark Street, London, 5/9 each. Base Mounting. W.C.2, have issued .a number of leaflets for insertion in readers' Mullard catalogues. MULL AR DUAL CABINETS for ALL "A.W." CIRCUITS These leaflets, replacing the leaflets VR47, CODILS That set you've constructedit's worthy, of a first-class and cabinet isn't it?Yes!Well then let me have particulars, 54 and 55, and VT17, which should beBritain's (panel and baseboard size) and we will house your set in a destroyed, deal with the PM6, PMIHF,Favour- well made hand french -polished cabinet, at a price well Within ite Three your reach, under aguarantee of satisfaction or money back. PM256 and DO/4o valves respectively. Baseboards 9d. per square foot cut while you wait. Dual Coils For promptness, courtesy and satisfaction deal with:- Two new leaflets have also been issued7/9 and 10/6 F.W. RAMSEY, 63 ShaftesburyS:., London, N.I. Clerk7139 giving details of the DFA9 and DO/2o valves. TWO - PIN OUR BLUEPRINT SERVICE A- constructor's chart for building up the COILS all typesIllustration of our Cossor Circuit Dual Constructors of receivers described in Ferranti type No. 5 A.C. H.T. supply unit HertenCoil,and susliztgoiltxt. mounting this Journal should make full use of (giving an output up to 200 volts and loo from 1/6 our Blueprint Service and avoid all risk milliamps as required), has been issued by RDi of failure. TURNER & CO. fINISZTIO:N 164111.11101.010,1111116. Ferranti Ltd., Hollinwood, Lancashire. APRIL 20, 1929 605 ematturWireiT I)ROADCAST TELEPHONY (Broadcasting stations classified by country and in order of wavelengths) "GRAWOR" Hilo-Station and Power Kilo-Station and Power Kilo-Station and Power Metres cyclesCall Sign (Kw.) Metres cycles Call Sign (Kw.) Metres cycles Call Sign (KW.) Comes to your aid ! GREAT BRITAIN 291.3 1,030Radio Lyons -. 1.5 25.5311,752Chelmsford 302 999Bordeaux (PTT)276 2,c8o 0.5...TurinITALY 7.0 THE " SECTORPHONE " 204 982Marseilles (PTT) 0.5 333 gooNaples (Napoli)1.5 - (58W) 15.0 293.9 x,230Newcastle (5NO) 1.0 305 98sAgen 0.3 387 775Genoa 9.0 LOUD - SPEAKER CHASSIS 258.4 r,i6zLeeds(2LS)... 0.1:1 322 930Vitus (Paris) 2.0 443.8 676Rome (Roma).- 3.0 embodying the famous 27(1.31,109Sheffield (6LE)0.13 336 89aPetit Parisien 0.5 Bolzanolan 0.3 288.5 1,040 Bournemouth 353 849Algiers (PTT) 2.0 ta2 56;85 7.0 " Grawor " DoubleMagnet (61351) 1.0 370 817Radio LL, Paris 1.0 382.2 7.55 Toulouse (Radio) 9.0 JUGO-SLAVIA Unit and an entirely new and 288.5 1,040 Bradford (2LS)0.13 308.3 973Zagreb (Agram) 1.25 288.5 ',noEdinburgh 400 749Mont de Marna 0.4 414 724Radio Maroc 452 664Belgrade ,,,.....4.0 Patented design of diaphragm , (2EH) 00.2 7 3/5Ljubljana 5.0 288.61,040*Hull (6KH) 0.2 (Rabat)2.0 has set a new standard in 288.5 1,040 *Dundee (2DE)0.13 928 701Grenoble (PTT)1.5 LATVIA 288.57,040*Liverpool (6LV) 0.13 430 697Radio Flandre reproduction. Lille 0.25 523 367Riga 2.0 204.1/Aso*Stoke-on-Trent Every independent test has proved 551') 0.13 448 (68Paris (Ecole 0ITIrovAnNo IA 294.1 2,020 *Swansea (5 X)0.13 Sup., PTT) 0.7 2,0f, 0 150 15.0 these statements. 302.6 gg.t.7 Belfast (2BE) 1.0 473 635.1 Lyons (PTT) 5.0 311 964Aberdeen (2BD)1.0 1,470 203Eiffel Tower 8.0 ,240NOREIrkAanY The " Grawor" Unit fitted has a 323 928Cardiff (5WA)... 1.0 1,755 271Radio Paris 8.0 242 z 1.0 powerful double Magnetic System. 358 838London (2L0)... 2.0 1,010 Notoddea 0.7 GERMANY 978 793 Manchester 32 ,,69 Bergenraeiesui 1.0. Balanced armature Flensburg 1.5 (2ZY) 1.0 219'1,370 38057 drknsrad movement. Perfect 996 757 Plymouth (SPY) 0.13 go 7,250N kitbag 4.0 1.0 401 748.3 Glasgow (6SC) 1.0 250 1,200Kiel 0.7 693 1.0 Reed adjustment. 482 62aDaventry Ex. 250 7,200Cassel 0.7 1.5 Carries full loads (5GB) 25.0 263.2 1,740Cologne 4.0 1.0 without a vestige of 1,504 zga 1Daventry 267.8 1,120Muenster 1.5 608 350Maniac 0.7 (5XX) 25.0 273.1 1,09.5.8 Kaiserslautern 1.5 distortion. Relay stations. (Relays 2L0. 280.4 1,070Kilnigsberg 4.0 SECTORPHONE' 284 1,056.7 Berlin (E) 0.7 314 953 Cracow1.5 AUSTRIA 284 1,056.7 Stettin 0.7 1.5 Chassiswith 248 2,209Linz 0.6 2847,056.7 Magdeburg 0.7 V76, 5 78:20 1Piattnowitz 10.0 " GRAWOR " Unit 277.81,090Salzburg (under 817.5 945Dresden 0.7a 956 658Wilno 1.5 mounted ready for construction)0.5 320 937Breslau 4.0 1,395 2/5Warsaw 10.0 254.2 847Gras 0.5 326.4 grgGleiwitz 6.0 immediateu s e. 456 694Klagenfurt 0.5 929 910Bremen 0.75 PORTUGAL Size,12 V2in. square 456 094 )nnsbruck 03 801.0 Le' 4.0 317.5945 Lisbon CTIAA (Wed. (see illustration). 620 577Vienna 20.0 874.1 8o2Stuttgart and Sat.: 10 -midnight) 991.6 766Hamburg 4.0 BELGIUM 423 Frankfurt 4.0 Price. With Double Magnet Unit 53/ - 0.75 ROUMANIA With Single Magnet Unit 48/ - 220 7,360Chatelineau 0.23 455.9 654Danzig 805 757Bucharest 4.0 249 1,203Schaerbeek- 456 651 Aachen 0.75 Obtainable front all Dealers, or direct. Brussels0.5 462.2 649Langenberg 25.0 RUSSIA 275 7,090Ghent 0.6 476 63oBerlin 4.0 825 363.5Moscow (PTT) 25.0 280 1,070Liege 0.5 537 559Munich 4.0 925 323Hemel....1 2.5 HENRY JOSEPH, 312 gtoAnonl 0.25 566 530Augsburg 0.5 1,000 300 Leningrad 20.0 11 Red Lion Square, London, W.C.1 512. .85Brussels 10.0 566 530Hanover 0.7 1,442 208Moscow 30.0 577 5soFreiburg 0.7 1,6a5 178 Kharkov 15.0 Sole Agent and Licensee for Great Britain CZECHO-SLOVAKIA 1,050 r8aZeesen 20.0 265 7,128Kosice 2.0 1,650 38aNorddeich 10.0 SPAIN 278 x,080Feriby (testing) 12.0 314 956Oviedo (EA J19)0.5 299.3.7,000Br'tislava 4.0 GRAND DUCHY OF 350 855Barcelona(EA J1) 3.5 VISIT THE 343 873Prague (Praha) 6.0 LUXEMBOURG 370 8orSeville (EAJ5) 0.5 400 750 432.3 694Braila (Brno) 2.4 1.280334.2 Radio Luxembourg 0.25 Radio Espalia 1.0 405 744San Sebastian DENMARK HOLLAND WIRELESS 883Copenhagen 31.49,554Eindhoven 427 '703 Madrid (0Jj78))(81 (Kjobenhavn)1.0 (PCJ) 25.0 436 658Salamanca s 6oKalundborg.7.5 38.8 Kootwijk (EAJ22) 0.55 EXHIBITION (PCL) 32.0 ESTHONIA (Wed. 12.40 G.M.T.) SWEDEN (April 15 to May 8) 408 735Reval (Tallinn) 1.3 825.6 813Huizen (until 261 1,750H firby 10.0 5.40 p.m.)5.0 265 1,230Trollhattau 0.4 FINLAND 1,075 279.2 Hilverstun 333 gooFalun 0.5 374 £00lielsingfors 346.8 865Goteborg 0.0 YORK HOUSE (Helsinki) (ANRO) 5.0 0 8 1,f 32 262Huizen (after 437 686Stockholm 1.5 Southampton Row, London, W.C.1 1,542 199Lahti 20.0 5.40 p.m. and on 645.5 55oSundsvall 1.0 (Corner of Theobalds Road) 770 390Ostersund 2.0 FRANCE Sundays) 5.0 1,082 ifsScheveningen. 1,200 25oBoden 2.0 DEMONSTRATION OF ALL SETS 80.75 9,755Agen 0>25 1,942 223Motala 30.0 200 1,500Fecamp 0.3 haven 5.0 Dealers HIRE-PURCHASE ARRANGED 211.3 7,420 0.1 HUNGARY SWITZERLAND 238x,a6oBordeaux (Radio 408 739Berne 1.0 A HIGH-CLASS SHOW OF ALL THE Sud-Ouest)2.0 548 548 Budapest 15.0 489.4 613Zurich 0.0 245 1,254Lille (PTT) 0.8 680 44rLausanne 0.0 LATEST SETS 252.1 1,190Juan-les-Pins 0,4 t ICELAND 760 395Geneva 0.5 253 2,185Montpellier 0,25 833.3 gooReykjavik 1.0 1,010 297Basle 0.25 254 r,s8oRennes (PTT) : 1.0 2551,175Toulouse (PTT) 1.0 IRISH FREE STATE TURKEY 208 1,118Strasbourg 0:3 222.2 1,311Cork (5CK) ...1.5 1,232 243 Stamboul 6.0 274 7,592Limoges (PTT) 0.5 411 732Dublin(2RN) 1.5 1,840 163 Angora 6.0 "A.W." Solves Your Wireless Problems

Partsfor" Britain'sFal7ourite Three." -In the advertisement of Messrs. 1.11)/ecoot_ct H.' & 13. Radio, Ltd., which appeared in RADIO our issue of 6, the price for the kit of o components for " Britain's Favourite Three PRODUCTS de Luxe" does not ,iticlude the dual -wave coil.If this coil is required the total cost is increased by los. 6d.The number of the Blueprintofthis famous set,by it RECEIVER atirrQ the way, was 'not very clearly printed in TO DATE!te.\ some copies.Readers wishing to order it UP should note that the number is A.W. 179. Fit a Bulgin Multi Coil and Electrostatic Condenser as illustrated. The alteration can be effected in half an hour.aiii14 If you will forward to us the diagram of your present con- Seventeen stations are now licensed for nections, we shall be pleased to show you the new wiring. ' PRICE5/6EACH television in America, They will broadcast SEND FOR OUR FREE 56 PAGE CATALOGUE & WIRELESS MANUAL on three short wavebands, ranging from A.F. MAIN & CO., 9-10-11 CURSITOR ST., CHANCERY LANE, LONDON, E.C.4 2,000 kilocycles to 2,95o kilocycles. 441

ernakar Wtrete 606 APRIL 20, 1929 both using crystal sets purchased about LETTERS TO 1923. ELECTRADIX I would like to have "Thermion's" views THE EDITOR on this, but I think you will realise that BARGAINS The Editor does not necessarily agree with we are not unreasonable in pleading for the GRAMOPHONE MOTORS.Electric A.C. or D.C. the views expressed by correspondents. Powerful full size Panatrope model with vertical double retention of the little time we do have on suspension slung electric motor with silent reduction Sundays.-G2AX (London, N.). drive to 12 in. Turntable.Aluminium frame, overall dimensicns 111 in. long x 61 in. wide x 81 in.high. The " Home and Abroad Two " Total weight 8 lbs. 8 ozs.Identical type used by leading Publid Broadcasts Gramophone Companies for big halls. Motor wound 100 SIR,-I am sending an appreciation of volts for use on any mains voltage with series lamp or SIR, It has been suggested that broad- fixed resistance.Takes 20 watts only.This B.T.H. the "Home and Abroad Two." I have Electric Gramophone Motor is a very efficient and reliable just finished it and get such good results, casting theatres should be opened.I instrument, which is capable of playing two hundred 12 -in. records at the cost of one unit of electricity. With a lamp having had KDKA within about an hourthink perhaps the following experience or small resistance, the motor can be operated on any may be of interest.I have. control of a supply circuit from 50/250 volts D.C., or 100/250 -volts of wiring up the set,-R. (Battersea). 25/60 cycle A.C. The Motor is silent in operation, and public hall in the centre of Portsmouth and the speed perfectly constant. Every precaution has been taken to minimise wear and vibration. List Price, £6 6s. " Britain's FavoUrite Three " applied to the magistrates for permission Sale price, 45/., and guaranteed O.K. SIR,-Having waited a week to see theto hold concerts on Sunday nights. This CHOKES. Special offer of 30 Henry large output coupling was refused, but I was allowed to repro- or smoothing Chokes by the Marconiphone Co., Capt. details of the 1929 "Favourite,"I, Round's design.It is a really good choke for a load of duce the B.B.C. programme between the 100 to 160 milliamps it is still a long way from saturation: hasten to congratulate you on a fine set. The only choke, at a popular price, which can be used for I have been using the 1928 "Favourite"'hours of 8 and to p.m. The result was a smoothing, where series connected filaments are used. complete failure. As an Output Filter Choke it can be used equally well since its publication and welcome the no - after asuper -power valve, or several power valves in On the first Sunday about 270 attended. parallel.Listed, 27/6.Sale price, 7/6. coil -changing idea .-T. (Tipton). TRANSFORMERS. B.T.H. latest design Intervalve and The service came from St. Martin -in -the - various special ratios, 10/. each. B.T.H. POWER Model Fields and was followed by a good concert. for 220 volt, 50 cycle A.C. mains. With centre tap L.T. 5XX Programmes for two rectifier valve supply. centre tap L.T. for Amplifier The set employed was quite a good one. filaments and centre tap H.T. for Anode supply.List SIR,-Your correspondent ".British Six"By the end of the evening I formed the 65/-. Sale 25/. only. (Penzance) says he imagines I have a MOVING COIL LOUD SPEAKER PARTS. opinion that, whatever might be the suit- Genuine B.T.H. Rice -Kellogg CONES fitted11 in. number of stations at my disposal. Suchability of the programme for home recep- Moving Coil and flexible floating leather edge with flange is not the case. I have a two -valve setAnd, for fixing to baffle board.Slightly soiled only 7/6 each. tion, it was perfectly hopeless for public A few only Marconiphone centre -suspension CONES except at lunch-time, I use only one y41ve with brass rod to fit on magnet and with 1 in. Moving reception.There are nearly always long Coil at apex.10/. each. and headphones. intervals between the items, which would ELECTRO-MAGNET POTS. Marconiphone 6 -volt My set is tuned to 5XX, and I rarely Magnet Pots.Brand new, takes amp. Just the thing hardly be, noticed if one is reading a book, for your home-made M.G. speaker. Takes I in. Moving try to receive any other station. The onlybut which are very noticeable in a public Coil. 20/. each. times I have heard foreign transmissions 3.VALVE POWER AMPLIFIERS. For working direct hall.The charitable appeal, news and off mains supply A.C. Fitted B.T.H. Power Transformer have been relays from Daventry from theweather report are all exceedingly dull. for 2 -valve Rectifier. Resistance and Transformer coupled sets of friends a few times. with Choke output. Cost £30.Sale price, £4 5s. each. That my opinion was shared by the D.C. mains model, 65/.. 3 -Valve receivers, 27/6. All I can say about foreign programmesaudience is proved by the fact that on the WESTON MICRO GRID -BIAS METERS. One should is that what I have heard of them-except be on every wireless set.Sensitive Moving -coil, flush second Sunday only about half the number Panel Model 375 with 21 in. dial; indicates 30 -millionths for the relays-I can very well do without. of an ampere per Division for use in Grid Bias circuits for turned up, and on the third and last adjustment to zero G.B. current.Excellent as Milli - I don't like the whole of the British pro-Sunday the audience had dwindled to 40. voltmeter, Bridge Galvo, Micro -ammeter or Heterodyne grammes, but some of the things I dislike Wavemeter Indicator as needle in centre zero.These Of course, if I had had the freedom to fiatne357.e.ters are Listed 65/.. but are offered during Sale are enjoyed by others, and the many appre-reproduce any programme Iliked, the ciations I have heard have been made by WIRE. There is such a terrific variety of insulated wire of all result might have been different, but I do gauges, copper and resistance wire that it would take a listeners who, like myself, listen to 5XX page tolist it. We must therefore ask customers to kindly not think that any public broadcasts are specify the sizes that interest them and we shall be pleased and 5GB programmes. likely to be very popular Until the broad- to quote. Principal items are wire for winding short wave -A. M. H. (Coventry). inductance coils 22 -gauge copper cotton -covered over casting authorities realise that people want enamel. This is specified in the Service to prevent losses, List, 2/.16.; Sale price, 1/3 per lb. i oz. reels silk -covered Sunday Broadcasting wireless for amusement-not for education 28 -gauge wire, 4d. Fine 5-36 silk -covered wire, 12 yards, is 9d. Heavy twin flex V.I.R. 35-40, 2J6 per dozen yards. nor religion-and also realise that it Twin red and black flex, 12 yards, 1/6. Single enamelled cIR,-I am an interestedreaderofdesirable to shorten breaks between items. and cotton -covered insulated wire for phone extension, "Thermion's" columns which appear 100 yards, 10d. Twin bell wire, 2 colours, 3/- per 100 yards. -F. P. (Sbuthsea). Single 1-044 Insulated V.I.R. Cable. 5/6 per 100 yard coil. in AMATEUR WIRELESS, and usually I am PHONE CORDS. Single, 6d. Double head, 10d. Browns in agreement with suggestions he makes Our Best Comedian ? indestructible double headphone cords,1/.. Loud- speaker long twin cords, 8d. from time to time regarding broadcasting. SIR, -I notice with regret in your issue April Edition of our Surplus Bargains fn Radio and reerrieal But there is one point on which, I think, Goods ready.Send stampedaddressed envelope forlarge sale dated March 3o that Mr. Moseley con- list.SAVES RADIO USERS POUNDS. a certain amount of unintentional unfair-siders Leonard Henry our first comedian. ELECTRADIX RADIOS ness appears; that is,the extension ofI had 10 re -read the paragraph to make 218 Upper Thames St., London, E.C.4 broadcasting hours on Sunday. sure that my eyes did not deceive me, and Blackfriara Station, Underground Railway. City 0191. The unfairness lies in the lack of con-I consider it a great insult to Tommy sideration (to my mind) for the amateurHandley.Had Mr. Moseley heard his transmitter, who would, in that event, losechoice of comedians last week and again V7VVYTTYYVVYYYTYVVVYVVVYYMVthe only remaining time of freedom left tothis week, I feel sure that he would have him for daylight research. I think you will Solved ! agree that we are entitled to a certainaltered his opinion. --N. S. (Leicester) amount of -Aught, as we pay considerably You will find all those little pro-more for our licences. We much regret that in the advertise- blems that crop up when you are Ifall B.C.L.'s were technicians andment of Messrs. Partridge & Mee, which experimenting solved in the capable of building and operating highlyappeared in our issue of March 3o, the efficient receivers, then everything wouldblock of the Heavy Duty choke appeared Letts' Amateur Wirelessbe O.K., but, as it is, there are still crowdsupside down. If readers will refer to the 1929 NOtebook Diary of crystal sets about, and with these-article in the same issue on "How to well, in my own case, I cannot key evenObtain H.T. Supply from the Mains" they Post free, in two bindings,1/9and2/9a 5 -watt transmitter without wiping outwill see the correct way of mounting this AALAAAAA my neighbours on either side, who arechoke. APRIL 20, 1929 607 ((maim- PAT

Magazine "001 el'17Mfo Amateur 7: containing ds-:n1 Orders sent by return BLUEPRINTSrriptionsof all these sets can be obtabited at Is. 3d. and 4.1. respectively, post free. C. 0. D where possible. Send Index Sitters " A.W." refer to "Amateur Wireless" sets and " W.M." order PAY POSTMANK. RAYMOND to " Wireless Magazine " sets. girlPost Free 27 & 28a, LISLE ST., LONDON, W.C.2 Come to LEICESTER SQUARE TUBE. CRYSTAL SET (6d.) This address is at the back of Daly's 1929 Crystal Receiver . Aw165 Theatre Phones Gerrard 4637 and 2821 HOURS OF EVERY DAY 9 to8 ONE-VALVE SETS (1s. each) SATRDAY 9 to9 BUSINESS SUN.U Beginners' One-valver Aw 140 MORN. IIto 1

Reinartz One . wmi27 DON'T FORGET OUR each) ALL LINES TWO -VALVE SETS(Is. WHOLESALE DEPT. STOC KED. East to West Short-wave Two (D. Trans.) AW159 HOURS OF BUSINESS AS ABOVE. /XVIII 71 Beginner's Two (D, Trans) Auto Two (D, Trans)... AW174 WE STOCK All -Mains Two (D, Trans) .. AW18o WHOLESALE & RETAIL VALVES Key -to -the -Ether Two (D, Tram) WM1o7 Bulgin, Ferranti, Ekco,Mallard, B.T.H., Marconi, Meteor Two (D, Tram).. W114114 Amplion, Celistion, Igranic,Edison, Osram, Cosmos, Lissen,M.P.A.,Ediswan,Cossor,Six -Sixty,Dee. WMI35 Clipper Two (D. Trans) Twinflex (Reflex) .. WM138 Cossor, Colvern,H.F., L.F., R.C., 10,6 each. Cyldon, 117e1li.lael,Watmel,Power 12/6, S. Power 15/-, THREE -VALVE SETS (ts. each) Lewcos, Polar, Climax, Or-S.G. 22/6, Pentode 25,'-. mond, J.B., Pye,Polymet, MI -wave Mains Three (HF, D, Trans, Rectifier)AWt 44 T.C.C., Dubilier, Lotus,W.B.,B.T.H.Tone-arm with Pick- All-purpose Short-wave Three (ll, RC, Trans) AW147 Philips, Mallard and all stan-up complete - -451- Screen -grid Q Coil Three (HF, D, Trans) AWt5o dard COM pon en ts ,al yes ,le.D.X. Auto -Track Tone -arm All-BritagiThree (HF, D, Trans) AW158 10/- Bantam Three (D, RC, Trans) AW t 6o Watmel Tone -arm -7,6 Hartley Dual -range Three (ll, RC, Tram) AW166 TRIOT RONGoodman Cone Chassis Listener's 'three (HF, D, Trans) price 4d. free U.S., Det., R.C., 5,2 each ;Assembly 16,6

with copy of "AW" AVI/169 Power, 6/9.2-v. or 4-v.Squire 97 do. 15/6 The Binowave Three (D, RC, Trans) AW172 Post 6d.13 post free). Blue Spot do, - 12/6 Clarion Three (SG, D, Trans) AW175 GENUINE IDEAL BLUE SPOT R.1.-Varley Pick-up - 03/-

AW 179 1929 Favourite Three (D, RC, Trans) Adjustable Power 66K (101) DARIOMR AI DCIR 0O- Everyday (D, z Trans) WM521 All -wave Screen -grid Three (HE, D, Trans.) WMIto 4 -pole Balanced Armature 2 -v. or 4-v. C.P. .. 5/6CLEARTRON WAI117 Complete with Cord Super Power ..7/6 Standard Coil Three (HF. D, 'Frans) /-Super H.F., 2-v. or 4-v. 7/6 VALVES Festival Three (D, 2LE-dual Imp.) .. WMtt3 Wide -world Short -waver (SG, D, Frans) WM120 HANDSOME OAK POLISHED Post 6d. (3 post free). Power or R.C.- 6/- New Year Three (SG, D, Pentode).. .. WM t23 L.F.,H.F. or Det. 4/ - The Q3 (D, RC, Trans) WNIx24 PEAKER CABINETS 13 x 13 x 6 Lodestone Three (HF, D, Trans) .. . WM 29 LISSEN PARTSScreen Grid. 2v.12,6 Simple Screen Three (HF, D, Trans) .. .. WM 13 t 1 2 / 1 1 r,o3" ALWAYS TN STOCK. POST 6e1. (3 Post Free). Dynamic Three (SG, D, Trans) .. .. WM136 " A.W.,"April20th. At Home Three (D.2RC) . WM141 A.W. FOUR VALVER 1929 BLUEn SET OF PARTS -2 Ormond .0005 at Reaction .0001 at FOUR -VALVE SETS (1s. 6d. each) SPOT da5/-V-.4 Sprung Valve Holders at 1)3.Q.A.A. Lewcos, 66K Shown above.Q.S.P., 21/-. Two .002, one each .0001 and .0003 fixed, 57-. Overseas Short -waver (HF, D, 2Trans) AW133 H.F. Choke Wearite, 6/6. Ditto Watmel, 5f- (add balance The Ranger( SG, 0, RC, Trans) .. AWI43 OR CABINET any other).2 meg., 1/-..25 meg.,1/-.2 G.L.K. Holders, Broadcast Picture Four (HF, D, 211C) . AW 63 R.C.C. Unit Lissen, 4/-.i00,00 ohm res. with holder, Orchestra Four (D. RC, Push-pull) .. AW 67 5/6. 2 M.F.D. Dubilier, 3/6. Lissen L.F., 8/6, complete All Europe Four (2 HF. D, Trans) .. AW173 BLUESPOT with L.T. switch. 2 Strips. Handsome panel 18x7. Stability Four (H.F, D, RC, 'Trans) AWx 82 1.1 Engraved Terminals.Connecting Wire. Base- 5 "Q "-coil 4 (HF,D, RC,Trans).. WM7t 12" CONE board.18x10. CARRIAGE PM)) U.K. Five -pounder Four (HF, D, RC, Trans) ..WM9t The Lot Carr. Pd. Touchstone (HF, D, RC, Trans) WM1o9 CLARION THREE KIT OF PARTS Reyner's Furzehill Four (SG, D, zTrans) WM112 Aluminium Cradle with ("A.W." 93-29 Economy Screen -grid Four (SG, ll, RC, Trans) WM ti3 Fitted Floating Cone 9"2 Punt .0(105, No.3,at5/9. .0001Reaction4,'.. Binowave Foul (SG, D, RC, Trans) 'WM [ 19 Cannot guarantee exact 2 Dual range 4.7.T. (Tunewell), Anode, 10/0; Aerial, Standard -coil Four (HF, D, 2 RC) WM122 pattern of front panel,Takes all Bal. Armature10/8.3 Sprung V.H. at 1/3. Formoden,ser, "J," 2/-. Dub- Dominions Four (2SG, D, Trans) .. WM134 but all good designs. Units. Post Free7/11ilier 1 mid., 2/8..01 Fixed, T.O.C., 1/9.3-meg. 1/-.8,0 The Drum Major (HF, 13, RC, 'Frans) .. WM t37 ILK Choke, Peto - Scott, 5/.. 11.F. Choke, Lissen, 516. TUNEWELL L.F. Transformer, 11.1. & Varley, 15/s.Ebonite Strips. DUAL RANGE COILS LEWCOS 140 Ebonite Panel.Screen, 8/x6. FIVE -VALVE SETS (1s. 6d. each) LewcosC.A.C.5,10,6;C.A.C.20 8 Engraved Terminals. Clarion Aerial,10 6. Push-pull Switch, Flex, Plugs, 10-9. Wire, 2 S.M. Dials. Clarion An- 12 6; C.S P.5, 1016; C.S.P.20, " Q " Gang -control Five (2HF, ll, aTrans) AWOL ode,10 6. Lissen Three, each10 6. The Lot 70/- II c -T FREE Empire Five (a SG, D, RC, Trans) .. WM95 Cassor Three, each10 8. All S.G. 12,6; P4 to 14, 3/- each; PI6 to .0002 Fixed and Series Clio I 6 extra. Fidelity Five (HF, D, 2 RC) WM13o Circuit Coils 21,- pair, 200 2,000.22,4". each. Touchstone Coils, MassiveH.F.Choke,5,9. Mallard311/. pair. C.T. Coils, 316, 5/3. CLEARTRON Six - VALVESfor CLARION DualCoil, 7,9, P.M. 10AL Q Coils Q.A.,15/-; Q.S.P., 21 -; S.C., 2v. SIX -VALVE SETS (1s. 6d. each) pin Bases, 2,-. S.C. 2.216. D 10/6.P 12/i. .. 12 6 Q.A R ,21/. ;Q.A.A.,15,-; C.T.15, L.F. or H.F... 4 Short-wave Super -6 (Super -het, Trans).. AW 67 Q.S.G.. 21!-.All Incas Products. (Mallard or Six -Sixty) Copper and Aluminium Screens, all C.T.I5 x Power . 6'. Eagle Six (3 HF, D, RC, 'Frans) WITho6 sizes,or made toorder, P.W. Screening Boxes, 126. P.W.Load- LOTUS Q COILSUltra Short Wave Co:IsB. FAV. 3 (DE LUXE) SET OF PARTS, ingCoils, 7 6. Bailie Wave Selec-QA, 15 - ;QSP 21-,for Cossor New Melody 63 . AMPLIFIERS (ts. each) tor,12 6. Tunewell Dual3Star, See issue April13thfor Screened -grid HF Amplifier AW138 79. Combined Wave Q3Star.MASTER 3 STAR 15 '-Warr) and p./ PAIR LIST OF PARTS. . 12 8.Scott's All -wave Tuner,13/6. Coltone (Post 61.) / " A.W." Gramophone Amplifier (3RC) AVV162 4 ALL LOTUS PARTS. Tunewell Dual Coil 6 -pin, DXSet short wave,7,6.DX L.F. 7/9 ; Lewcos Short Wave, Searcher Unit (11E1 ...... AW176 Standard Ratio. Weilo L.P. Gramo-radio Amplifier (2v) (Trans.) WM7a Power,118.Weilo Standard,8;6. ECKO UNITS20/45 or 40/90, 7/6 extra. DubilierK.C.Condensers, FrictionTRI °TRIM . Signal Booster (HF Unit) WMi28 For use with S.G. Valves, Control,.0005and.0003.each12,l-. O R M O N D W/Mr32 Auditrol Amplifier Thumb Control, ditto,15 6.Telsen4 Pole BalancedA.C. with Valve and S.M. Drum Dial, 5/-; Itheost ats.6, Radio Grand L.F., 12,6. Telsen Royalty - 78/6 15,30 ohm, 2/-; Midget.0001 4/..: Log .0005 and 4 in. Dial, #31-; MISCELLANEOUS (ts. each) Ace L.F.,8.6.BrownH.Q.Speaker, Armature 81,12 87/6 Log. .0903 and4 in. 23,3,0, AmplionA.0.2.,21:-. D.C. 3F12 S.G. - 39/6 Dial, 5/9. H.T. Eliminator for A.C. (zoo v. output) ,.AWio2 M.P.A. Popular Plaque Speaker,Adjustable Unit17/6 B.L.F. No. 3 same price. We always ALL ECHO EASY TERMS clock all ORMOND PARTS. L.T. and H.T. Mains Unit (D.C.) .. AW123 2918L Ormond Turn -tableforPort- ILLUSTRATED Listener's Speaker, price 4d. tree with copy of ables,6:-. Bulgin All -wave Toner. 15,8. British General Tuner,18 h. "AW" . AW170 1,000 Mile RANGE on Tour 1927 COSSOR Arcadian Linen -diaphragm Loud -speaker (Full- Wateg 3in 1 TestMeter,8,6. CATALOGUE Lotus Condensers,.0005, 6 9; .0003. (144 pages).1/- refunded on LIST OF PARTS FOR CONVERSION AWynA 5 6. Colvern Muter3Star Dual first 10'. order. SCREEN ASSEMBLY -2 EX T R AS- Cossor S.G. DT.tnit (We)1: . AW s78 Coll, 17 6. Coil Holders, McMichael Bin-Valve type 220 - -2216 Universal Short-wave Adaptor .. WM32 W EARITE QUO TATIONSocularChoke, Peto-ScottPair of Ilighwave Coils Buzzer Wavemeter (ed.) .. WM121 Dual Wave Tuner15;-.H.F. .0001.PeerlessRheostat, 12/6 PAIR H.T. Unit for A.C. Mains .. ChokeB.B. S.W.Choke 4;6. FOR SETS OF PARTSDubilier 1 M.F.D., Insulated'2 Cossor Pattern S.M. Dials 2 -way Switch B'-.3 -way Switch Lodestone Loud -speaker .. WM t26 OVER 25/. INVALUEWire, 2 Coils for 200/ on/ - 61- PAIR James H.T. Unit for D.C. Mains WMt 33 7,'-. Loading Coil7,6. Titan BOO metres. Post Free zrPI POST EXTRA. Short-wave Adaptor for Dominions Five WA114o Coil Unit15 -. (where possible) LATEST SQUIRE 97 A.W. SPECIAL COUPON (64) PORTABLE SETS RIGID ALUMINIUM CRADLE,FLOATING CONE. House Portable (SG, D, RC, Trans) ..AW163 116 CLAMPING BOARD ASSEMBLED AND SPARE15/6FOR EVERY30/- you spend retail Arcadian Portable (SG, 13, 2 'Trans) with CONE KIT FOR .. linen -diaphragm loud -speaker (half -scale) AWt 721/6 Ocr model 97 i s supplied assembled complete with duplex woven CoatingYOU CAN buy ONE of the following for one, clamping beard AND a Kit of Parts for making Matt cone. £5.5.0 Portable (D.Trans.) AWISi Diameter of cone St In. 3d.each extra (on this Coupon) Chummy 4 (with modifications for LS OR COMPLETE WITH HANDSOME OAK Thelot H.F. Choke, Silk Loud -Speaker Cord, 9 -volt Grid and HT) -. W M801 1;6 CABINET and BLUE SPOT UNIT 66K poet treeBias, Pair Panel Brackets, .0001 Reaction, 2 mfd. Wayfarer Portable (Super -set) WM139 1;6 (Genuine Ideal Adjustable) (U.K.) Mansbridge, 100 ft. Insulated Aerial, 4- or 5 -way Battery Leads, 30 ft, Coloured Connecting Wire. Send, preferably, aPostal Order (stamps over sixpence OSRAM MUSIC MAGNET LEADING HOUSE forS.M. Dial, 12 yds. Lead-in, Fuse and Holder, 12 in value unacceptable) to Blueprint Service Kit of Parts and Valves, Nickel Terminals, 60X Coil, Permanent Detector, 53 : 12 :6. :Battery Switch, .0003 and 2-meg. Leak, 6 -pin Coil 55-61 FETTER LANELANE KITS OF PARTS!base. 12 yds. Twin Flex. 100 It. Indoor Aerial. AMATEUR WIRELESS FETTER Booklet Free. Please Mention "A.W." When Corresponding with Advertisers entattur Whate) 608 APRIL 20, 1929 CHIEF EVENTS WITH THE AIR MAIL PREPAID ADVERTISEMENTS. Advertisementsunderthis headarecharged THREEPENCE PER WORD, minimum charge OF THE WEEK TO INDIA ! THREE SHILLINGS. Wireless Communication en route DEPOSIT SYSTEM LONDON AND DAVENTRY As the Publishers cannot accept responsibility for the Covent Garden opera. WIRELESS is playing a vital part in bona fidesof advertisersLithispublication, they have April 22 introduced a system of deposit which itis recommended St. George's Day programme. 23 the organisation of the new air snail should be adopted by readers when dealing with persons ,, 24 The Flying Dutchman, an opera by Richard Wagner. service to India, inaugurated on the morn- with whom they are unacquainted.Itishere explained. St. Joan, by George Bernard Shaw, Part 1. Intending purchasers should forward to the Publishers 25 ing of Saturday, March 3o, when G-EBLF the amount of the purchasemoney ofthe article adverlised. St. Joan, by George Bernard Shaw, Part 2. 26 This will be acknowledged to both the Depositor anti the (the Imperial Airways liner City of Glasbow) Vendor, whose names and addresses must necessarily be DAVENTRY EXPERIMENTAL 5GB given.The deposit ,s retained until advice is received of left Croydon outward bound for Paris and the completion of the purchase, or of the article hearing April 21An orchestral programme. Basle, carrying the mails on the first stage been returned to and accepted by the Vendor.In addition ,, 22The Flying Dutchman, an opera by Richard to the amount of the Deposit, a Fee of 6d. for sums ofEt Wagner. of their seven days' journey. ' and under, and is. for amountsin excess ofit, tocover 25B.B.C. orchestral concert, relayed from the postage,etc.,must be remitted at the same time. In ,rases People's Palace. As full particulars had appeared in the of persons not resident within the United kingdom, double 26Covent Garden opera. Press regarding the itinerary of this air- fees are charged. The amount of the Deposit and Fee must be remitted by CARDIFF liner, its time of departure, and the arrange- PostalOrder orRegisteredLetter(Cheques canner be April 27 A popular request programme. ments made for wireless communication accepted), addressed to "AMATEUR WIRELESS," ADVERTISEMENT DEPARTMENT. MANCHESTER en route, a good many wireless enthusiasts 58/61, FEUER LANE, LONDON, P C.4. A programme of musical comedy memories. doubtless followed the progress of the April 26 PATENTS,-Trade Marks, Advice Handbook free.-D. T. Kin;, ABERDEEN flight by radio. Patent Agent, 146 Queen Victoria Street, London. April 22 A variety programme. Those who are able to read morse may EARN MONEY AT HOME. You an earn money at home in whole cr spare time writing Show Cards for us. No canvassing. We train you have picked up the inter -aerodrome message by post by our new simple method and furnIsh"the Outfit free. We BELFAST ropply both men and women with steady work at lrome,.no matter April ZZThe Dragon's Bride,amusical comedy enin C.W. on 1,40o metres from GFK, the where you live, and pay you cash for all work completed each week, casserole, by Mabel Constanduros. under our legal guarantee. Full particulars and Booklet tree. Write Croydon air -port "route service" station, at once or call. Show Card Service, Hitchin. informing the Continental aerodromes that WIRELESS OPERATING APPOINTMENTS: fees payable after qualify. the huge twenty -seater Argosy machine ing (for boarding students.) Morse classes. Wire:ess School, Manor An attempt is being made to providehad duly departed with its passengers, Gardens, Holloway, N.7. Greece with a broadcasting system; abaggage, and mail. monopoly is to be offered to a concession- Even listeners who are unacquainted naire for a period of twenty years, at thewith the language of dots and dashes could SATISFACTION end of which the transmitters would passfollow the subsequent conversations in and Quick Service into the hands of the State. The schemeradio -telephony on 90o metres between We give you BOTH! callsfor the erection \of a high -powerthe pilot of Imperial LF and the operators Our large Stocks and extensive neap include Sets and station at Athens. at Croydon and the Continental aerodrome Accessories of every description, and which enables us to give almost immediate delivary of anyth'ng you may stations. W. 0. require for Cash or on the EASIEST DEFERRED Radio Paris has been equipped with a TERMS. Send us a list of your requirements and let Fultograph picture transmitter' and broad- us quote you by retu-n.Lists Free, casts are experimentally carried out daily The series<4 forbee -keepers Gramophones and Records on Easy Payment Terms at 6.15 p.m. G.M.T. broadcast from the Scottish stations last year proved so successful that a further ,WIRELISS STORES

and more elaborate series has been ar- WALLINGTON . 'SURREY BURY YOUR CONTACT TROUBLES ranged for 1929 in collaboration with the ScottishBee -keepers'Association.The WITH THIS CLIX SPADE. talks will be given fortnightly on Thursday WET H.T. BATTERIES CLIR Spade Terminals are obtainable Solesall H.T. either nickel or lead -plated.The latter, evenings. troubles for use with accumulators, often less SELF -CHARGING, SILENT, ECONOMICAL resistance to the flow of L.F. current, JARS (waxed) Ss" x 11" sj. .. 1/3 dos. and is not easily affected by acid. Zuns, New Type. 101. dos. SACS 1/2 dos, The patented method ofwiring these tia mole do,(15 volts), complete with bands and electrolyte 4/1, post9d.,Sample unit. terminals ensures a positive grip, perfect 64. contact and no risks of shorts. Red or "Amateur Wireless and Radiovision." Price illustrated booklet tree.Bargain list free. Black insulators. Threepence. Published on Thursdays and bear- AMPLIFIERS, 30/.3VALVE SET, f5. Chosen for the ing the date of Saturday immediately following. A. TAYLOR, 57 Studley Rd., Signal Booster" Stockwell, London. " Dynamic Three" Post free to any part of the world : 3 months, "Drum Major" 4s. 6d.; 6 months, 8s. 9d.; 12 months, 17s. 6d. Patented. in the " Wireless Magazine." Postal Orders, Post Office Orders, or Cheques Write for the Clix Catalogue. should be made payable to" Bernard Jones 50/- as shown 2d. LECTRO LINX LTD., Publications, Ltd." EACH 254 Vauxhall Bridge Road,5.W.1 General Correspondence isto be brief and written on one side of the paper only.All sketches and drawings to be on separate sheets. Contributions arealways welcome,willbe LOEWE RAM promptly considered, and if used will be paid for. Queries should be addressed to the Editor, and 4 Fountayne Rd., WIRELESS CABINETS the conditions printed at the head of " Our Tottenham, N.15 MAKE YOUR OWN Information Bureau" should be closely observed. Send stamp for Free catalogue and price Communications should be addressed, accord- WARRICK RADIO, ARTISTIC FRETTED FRONTS, list. ing to their nature, to The Editor, The Adver- for Loud -speaker, Gramophone,orPortable !cabinets. Many designs. Sizes: is in. to 24 in. Prices :1 /6 to 5/6 WOODWORK, 199 HIGH ROAD, LEE, tisement Manager, or the Publisher, "Amateur Special sizes for " Lion" chassis, and " Linen " speakers. LONDON, S.E.13. Wireless," 58-61 Fetter Lane, London, E.C.4. Rend for Illustrated List.Tradeinvited. WARRICK RADIO, 16 BE'RTHER RD., HORNOHURCH, ESSEX. FOR A.C. MAINS _r,-/ SUPPLY UNITS LOW TENSION HIGH TENSION ,- Incorporating Westinghouse Metal For Multi -Valve Receivers Rectifier. Guaranteed silent;No valves: 2, 4 or 6 volts at i an amp: No expensivereplacements; No renewals. No attention Components from Complete Coils Irons Guaranteed 47/6 7 DAYS' FREE TRIAL AGAINST CASH. 47/6 THE TULSEVIERE MANFG, CO., Dalton Street, West Norwood, S.E.27. 'Phone: Streatham 6731:

COUPON mateur Available until Saturday, APRIL 27th, 1929 APittl.! 20, 19214 Ill

DUBILIER VARIABLES MINME11111aUSIMMITMENNINMEIMM FOR INVARIABLE EFFICIENCY

K.C. CONDENSER With knob, dial and slow-motion 12/ device, 60 '00D3 or 0005 Without knob, dial or slow-motion device, 00D3 or .0005

K.C. DRUM CONTROL CONDENSERS With Drum Control and slow- Your set will do all motion device, 00fl3 or 0005 15/6 thatthedesigner TripleK.C.,each condenser claims for it if you use .0003 or .0005 38/3 Lotus Components. Triple K.C. Combination of 0003 and 0005 40/- Every Lotus unit you use is a sturdy, ac- curatelink towards MIDGET perfection. The best WWI Renaot bakelite, the best Controls, CONDENSER from351. metals and the best WI 2 row., A small variable condenser British workmanship for panel mounting 00005,0001 or .0002 5/6 gointoallLotus Components a n d every one is severely Dubilier tested before it comes for Selectivity ! to you. When you buy your components ask for "TOREADOR SCREEN -GRID FOUR." LotusComponents ThissetIncorporatesthelatest and ensure your set's developments in Receiver design- Lobs Varian Condensers, full constructional detailsfree on success. from 51. request. From all Radio Dealers. fi DUBILIER '0441ID0000NEKSIUES.e CONDENSERS 011.1111111111:1111,11111:11:1;tiii'llIthlli=r"- GARNETT, WHITELEY. & Co., Ltd., LIVERPOOL Ammommiammmors IIf unobtainable from your doe IL /4... Advt. of Dubilier Condenser Co., dealer,writedirectto us 3)9 4,C (1925) Ltd., Ducon Works, Victoria giving his 'name and address. 7.0.1 WWI Road, N. Acton, London,W.3 f023 Please Mention "A.W." When Corresponding with Advertisers lv APRIL 1.0, 1929

THE STANDARD L.Fchoke FOR COMPARISONTrieotily kind The highest tribute that its could possibly be paid to of ourwire -wound Anode Resistances, and yet one thatisliterallytrue. Practically every research laboratory in the United Kingdom uses R.I. and Varley Anode Resistances L -they can rely on these .world-famous products- they know that they are practically dead accurate in every instance. Behind these real " stan- dar& " of comparison is ,the story of the Bi-duplgx winding. As far back as 1896, it first came into being; each year has seen further improvements, untilto -daythisper- fected science has placed in the hands of the wfr publicnot)lessnot only GreatBritain, but of the worldone of the big achievements of radio science.

The R.I. & Varley Choke is the only one of its kind. With numerous applications it possesses the same degree of real efficiency in each -case. Firstly, it is a really good choke, for eliminator smoothing circuits. On a load of -100 milliamps it is still a long way from saturation pointin fact, it is the, only choke, at a popular price, which can be used for smoothing where series connected filaments are used. As an Output Filter Choke it can be used equally well affer_a single power valve, or after several super -power valves in parallel. One has indeed only ,to refer to the pages of any of the Wireless Section C of our Cata- Journals of to -day to realise -the extent to which the R.I. & Varley L.F. Choke is being used by the logueLfree on application Technical Experts in this country. -gives full particulars of These Chokes have a huge iron circuit, adequate

our complete rangeof inductance, and Low Resistance. tlieiefamousproducts. Write for Section E of our Catdogue-free.on application -for full particulars. . Prices, corn. lete- with 28 14 Henries. 0-100 ma, - - Unitrersal Holder, from '10 ohms D.C. Resistance 5/6- to 17/6 1 : 10 14/7 Henries, 0100m,'a 120 ohms D.C. Resistance, 1 1 :0 Don't forget we make a reonife;ful L.F. Low Ten- sion Choke. Mice Wier THE MARK OF BETTER RADIO ,igsna!). Hotne,-103 hing-nray,Lcindori.

Printed in -England: Published by ilernardjones Publications, Ltd., 58/61 Fetter Lane, London, E.C.4 Sole Agents for South Africa; CENTRAL NEM s AGENCY, LIMITED.Sole Agents for Australasia ; GonooN & GOTCII, LIMITED, Saturday, April so, 1,92g AMATEUR WIRELESS, APRIL IT, 11/23 CUTTING OUT POWERFUL STATION AT 1 MILE

Saturday, April 27, 1929 CUTS OUT LONDON AT I ILE

SEE PACE 621

Registered at the G.P.O. so a Naospapst saattur Wtrele:c) A FRIL 27, 1929

0450BREAKS

Because months of Fr tient research have been devoted to their perfection, Mullard Pentone and Screened Grid valves break all records for ,super.efficient performanceThey have the lowest current consumption combined with the highest efficiency of any valves of their type on the market. We have never used the public as our research department. We wouldn't risk losing even one of our friends to satisfy an experiment, certainly not after all the years we've been together, up and down every European broadcasting station. You can take our wordforit,Mullard Pentene and Screened Grid Vrlves are perfect to the last detail, modern to the minute. Otherwise they wouldn't be stamped with the Mullard P.M. monogram.

Mullard.THE MASTER.- VALVE Advert :-The Mullard Wireless Service Co., Ltd., Mullard House, Charing Cross Road, London, W.C.2. .4 rks.

Mention of "Amateur Wireless" to Advertisers will Ensure Prompt Attention APRIL 27, 1929 609 matt= Wirelers5

BLUE SPOT 101

A speaker of unusual design, thousands of satisfied owners. striking yet not obtrusive, the Ask your dealer to demonstrate Blue Spot 101 takes its place the Blue Spot 101 to -day. among the world's leading loudspeakers. To say that the Blue It is driven by the Blue Spot Spot 101 speaker reproduces 66K unit which is also obtain- perfectly both speech and music ableforconstructorsasa is to endorse the opinion of separate unit, price 25/-.

F. A. HUGHES & CO., LTD., 204-6 Great Portland Street, LONDON, W.i Distributors for Northern England, Scotland and North Wales: H. C. RAWSON (SHEFFIELD & LONDON) LTD., zoo LONDON ROAD, SHEFFIELD; 185 PRINCESS STREET, MANCHESTER.

You will Help Yourself and Help Us by Mentioning !`A.W." to Advertisers (Luau,- Wu-eik. 610 APRIL 27, 1929 ONLY

In the Cossor Screened Grid Valve all the inherent weaknesses of valve design have been eliminated. By means of the Cossor wonderful new Cossor system of construction-illustrated here-each ele- ment is rigidly secured top and bottom. Screened Grid Even under the hardest blow individual movement is impossible. The Cossor Screened Grid Valve is Valves-- SHOCK -PROOF Noises in a valve are generally due to loose elements. In the Cossor Screened HAVE Grid Valve the elements cannot become loose because they are rigidly braced together and because every jointis scientifically welded. The Cossor INTERLOCKED Screened Grid Valve is NOISE -PROOF !, Even the heaviest shock cannot disturb ELECTRODES the perfect alignment of the electrodes in the Cossor Screened Grid Valve. It Here you seethe 2. 'Aroundthetwo is the most robust and the most de- double length of Cossor stoutgrid supportsis pendable Screened Grid Valve made filament' famed for its wound the firstgrid, in Great Britain. The Cossor Screened colossal emission.Note electricallyweldedat Grid Valve is the seonite bridge hold- twenty-five points. ing it rigidly in position. BREAK -PROOF For any Screened Grid Receiver choose Cossor. Accept no substitute-for there is 3.Note the enormous 4. Finally, observe the strength and rigidity of construction of the anode. no adequate substitute for the Cossor the screen.-See how it is Actually two rectangular system of Interlocked Construction. built on four stout sup- nickel platesare used ports and capped by a and for greater rigidity metal bridge -piecean- each is diagonally ribbed. choredtoseonite insulator.

Technical Data. Cossor Comer 220 S.G. (2volta, .2 amps.) and 410 S.G. (4 volts, 1 ...vms, Max Anode Volta 150, Impe- dance 200,000, Amplifi- Screened Grid cation Factor 200, Grid Bias 1.5 volts at max - de Price(each>Volta. 22/6 BRITAIN'S STRONGEST AND MOST

C. Cossor Ltd., Highbury Grove, Landon N.J. DEPENDABLE SCREENED GRID VALVE 8446

Advertisers Appreciate Mention of !`.4.W." with Your Order Ell

5-APRIL 27, 1929 No. 359.Vol. XIV 5 5 5 5 5 5 5 S Lift , 5 5

5 and . ' 5 5 5 The Leading Radio Weekly for the Constructor, Listener and Experimenter 5 5 5 = Editor : BERNARD E. JONES = § 5 Technical Editor :J. H. REYNER, B.Sc., A.M.I.E.E. :: Research e...oiisultant: W. JAMES :: Assistant Editor: H. CORBISHLEY ljtaticatatzzctacearc7).)c)catc7IcatIce%)cceir47.)catc7ecat7.0.atIt.ear.act,e7o.e:57)tc.acte73catar.:tc7435 Television to Come-Portable Set Licences-Free Radio-A Gipsy Told Me !- A Popular Set-D.F.on Ships-How Much to Broadcast ?-Holidays at Home Television to Come-As was D.P. on Ships-Radio direction - always the case, and without great finding equipment is standard on so justification, television developments many ships that it is apt to be for- in this country have been shrouded gotten, and its marvels overlooked. 'with mystery. Therefore at present Yet here we have a report from the we cannot give any definite details, master of a ship fitted with modern but from a reliable source we learn D.F. equipment and it is nothing 'thatnegotiationsaregoing on but a piean of praise. The particular between Baird and the B.B.C., and apparatus employed incorporates a itis hoped thatactual broad- very small frame aerial in the chart casts may be made in the very near room,' and the master states that .future. There is, of course, a certain every passage would take longer 'amount of technical ground work to were he not aided by radio. be covered, and quite a deal of the How Much to Broadcast?- 'difficulties which Baird has success- Theannualstatementof the fully overcome have been described NationalBroadcastingCo. (in from time to time in AMATEUR A NOTABLE "O.B."-Majoregrave before the microphone on the occasion of his speech on arrival at Southampton. He America)statesthat9,000,000 WIRELESS. broadcast his impressions of "speeding." dollarswas expended by that Portable Set Licences-It is welcomesongs written by Mr. Jack Mosdell, a clerkcompany during 1928 for artistes' fees, wire news, as announced recently, that thein a Government office. He took up song -network and general overhead expenses. P.M.G. has sanctioned the use of one port-writing in his spare time on the adviceConservative estimates place the weekly able set without additional licence by theof a fortune teller who told him that herevenue of the N.B.C. from commercial owner of a permit for a set at a fixed address.would succeed in this direction, although heaccounts at more than 200,000 dollars. This The only snag is that when a set is usedhad never before atterpted to write a song.sum does not include entertainment which away -from the home address, the owner must A Popular Set-Our Technical Depart-must be supplied by the adVertiser. carry the licence with him, and produce it ifment has received so many requests for Holidays at Home-The correspondent necessary. This somewhat savours ofinformation regarding the fitting of thein a daily paper has found' a new reason motorists' driving licences, which servemost up-to-date improvements to thatto grumble at B.B.C. talks 1 He says that a very little purpose, even for identification.popular set "Britain's Favourite Two"recent broadcast talk on the merits and Nevertheless this concession is well worththat they are at present engaged on a newbeauty of Switzerland as a holiday resort having and one can't expect officialdomversion.The 1929 "Favourite" will beshould not have been given. We are doing to descend to practicality ! published in an early issue.Keep a lookour best to boost our own holiday resorts," Free Radio-Some good work is goingout for it! says this cm -respondent, ' and it stems some- ahead in theprovisionoffree0,,,),,,,It,,,tatv.,,..it,,,te,1t.,t,,,,,,,,A.e,1w.,uplu,1,,,lowhat short-sighted if not definitely unfair to give talks on Continental ,wireless sets in mining areas where§ PRINCIPAL CONTENTS Page 5 distress is particularly acute. This , attractions."Well, that's as good a § Current Topics ...... 611 is possible by means of co-operation . reason to grouse as any between the B.B.C. and the Central§ Broadcast in- Picture Artistes 612 § A New S.W.Tester-The Council for Broadcast Adult Educa- The " Stability Four " .. .. 613. § § This Modern Music 1 615 §Vienna short-wave transmitter car- tion. Altogether, free sets are being ries out tests every Tuesday and suppliedintwelvelocalitiesin In My Wireless Den 616c § On Your Wavelength 619 Thursday on a wavelength of 49.4 South Wales and about the same metres; in the course of a week or number in Durham and Northum-§ Cutting Out 2L0 ..-621 N § How it Happened ! ..622 §ten days this experimentalpro- berland. Efforts are being made to gramme will, be extended to Wed- interest the local residents and it is§ Without Fear or Favour ...... 623 § More About the " £5 5 0 Portable " ..624 §nesdays and Saturdays.Ithad suggested that they should form been hoped to carry out a simul- listening groups for discussion. "A.W." Tests of Apparatus - .. ..626 Radiograms ...... 628 taneous broadcast of the Vienna evening concerts with Rosenhuegel A Gipsy Told Me!-There is a§ Some Recent Loud -speaker Developments ..'630 N little bit of romance attached to§ Cabinet Making at Home ...... 632 §and the . new short-wave station, a new song which was included in a§ Secrets of the Test Room ...... 634 §butitscloseproximity to the recent De Courvillerevue, Gay§ Broadcast Telephony...... 638 §high -power transmitter is causing Sparks.This is one of the firstClte9)Ge5Ite:"104t.e'ltelte9VG)tc:76telteVententelte7)WIte:71tGlte;11:1trouble. emate= Wirell!, 612 APRIL 27, 1929 LBROADCAST ARTISTES IN PICTURE

LEFFPOUISHNOFF.-Thisbrilliant VERA GILMAN.-A favourite and fre- pianist has had an almost spectacular career MAY BLYTHE.-One of the best known quent broadcaster. This clever young actress since his early appearances at Queen's Hall. of the B.N.O.C. stars,she has probably was heard on April 13 in the revue, " Hip- ht his early broadcasts he was known as the broadcast more than any other singer.Her Hip-Hoo Radio." Both as singer and actress, " mysterypianist." He has justgiven principal roles have been in " Hansel and she has scored in many popular productions. another series of recitals. Gretel," " Cavalkria Rusticana," and " Carmen."

HELEN OGILVIE.-Frequently heard of late from21,0and provincialstations, Miss Ogilvie is a member of the Carl Rosa Opera Company and was heard in its first broadcast of " Faust." She possesses a wide MAURICE YACOBSON.-A clever pian- CECIL BAUMER.-A famouspianist range of tone and a clear diction. ist and composer, and holder of the Stanford known by his many appearances at the great Scholarship; his works include many songs classicalconcerts. Recently, following on and orchestral works.Best known are his many earlier broadcasts, 1w gave a series of setting of Vaughan Williams Mass in B minor, recitals from 2L0. and the Beggar's Opera Fantasia.

EDWARD CLARK. The popular musical director of Newcastle station, Mr. Clark has i1.10II MARY OGDEN.-A well-known Man- hada wideContinental and British MAUD COUPER.-One of the earliest of chester singer, famous in oratorio work.She musical experience. He seas closely connected all broadcast elocutionists, Miss Couper has has broadcast in Rossini's " Tell" with a season of the Russian Ballet. won fame in Scotland for her treatment of and many other musical programmes. realScottish humour. Sheisalways a favourite at London Scats gatherings. APRIL 27, 1929 613 omattur Wux) v,

A Lof tin -White OY Receiver Embodying I. H. REY N ER, " Q" Coils B.Sc., THE aerial circuit is coupled by the To obviate this,a stoppercircuit has use of a "QAA" coil, this being the new Last week the principle upon which been connected in the detector lead consis- form of "QA" coil having centre tap this receiver, which provides constant ting of a ioo,000-ohm resistance with a arrangement so that the aerial can be con- reaction effects, operates was describ- 2-microfarad condenser shunting it to earth. ed.In the article below an explana- nected to a tapping on the coil instead tion of the circuit is given, together The circuit is thus generally of a straight- of across the whole coil. By this means, with the necessary information for the forward character, the principal advantages both the wavelength range and the selec- construction of the actual set as shown in use being (first) the circuit does not tivity are somewhat improved over the by the photographs. require any neutralising, while at the same older form of "QA" type. Any reader, time it gives a good measure of high - however, who possesses a " QA" frequency amplification, enabling coil can utilise it in this position oll.r. distant stations to be obtained if he wishes, in which circum- with greater ease and local sta- stances the aerial is connected, tions to be cut out by means of throughits pre-setcondenser, these two tunes, and (second) a to terminal No.iinstead of uniform transfer of energy over terminal No. 4. thewholescaleso thatthe In the anode circuit we have reaction adjustment is tolerably the H.F. choke and a phasing constant.Thisconstancyhas condenser, whence thecurrents been arranged to apply princi- are led through to a primary pally to the short-wave band and winding of a "QSP" transfor- itwill very probably be found mer. A .CO2 fixed condenser, is that the reaction adjustment is inserted as a coupling condenser not so good on the long waves. in series with the .0005 tuning This, however,is again due to, condenser. The value of this the use of a standard "Q" coil, coupling condenserdetermines for, as has already been pointed thet xtentofthecapacity out, it was not considered advis- coupling. In the present instance This is a reproductionof thecircuit diagram shown last week able to produce a special coil for this value was chosen because this, particular purpose. with the value of magnetic coupling giventransformer -coupled, a Lissen Super trans- Both the "QAA" and "QSP" coils are by the "QSP" coil the reaction demandformer being used in this instance. Despitestandard items and can readily be obtained was approximately constant.Reaction isits relatively low price, this instrument hasfrom any dealers.It has been found in cer- obtained by capacity control, the windinga really super performance, and, in fact,tain instances that the reaction control is between terminals 2 and 6 being utilisedthe principal difficulty I had with its usenot as constant as is desirable, in which case as is usual in the case of -the "QSP" coil.was that it was rather too good and gaveslight variations of the value of the .002 Following the detector, there is a resist-me trouble due to battery feedback whencoupling condenser may be tried.This ance -coupled stage while the final stage isthe arrangement was used on an eliminator.condenser must not be reduced seriously

Two pictures of the rear of the "Stability Four." Other photo- graphsappeared in last week's issue 614 APRIL 27, 1929 =imomm.mom " THE STABILITY FOUR " (Continued from preceding page) or the tuning range of the circuit will beselectivity, rendering the tuning of theis to increase the signal strength slightly affected.It may be increased if necessarycircuit sharper. The actual current con-and to make the reaction control smoother. without serious effect, the larger the con-sumption of the particular model describedTest Results denser, the less being the capacity coupling.was only 7 milliamps with a ioo-volt On test,I found the receiver behaved battery using the following valves : Batteries and Valves well.Although the reaction control was H.F. B.T.H. HF2ro The receiver should be connected up to Det. . Mullard PM r A the batteries in the customary way, the 1st L.F. Osram HL2r0

voltages being as follows : Either two, four, 2nd L.F.... B.T.H. P227 or six volts may be used for the L.T., depending upon the valves in use, while aTuning voltage of roo to 120 is satisfactory for the The method of tuning is to set the right- H.T., there being only one H.T. tap. Gridhand dial approximately to the position /./

.4 or- ow. IIII .1141iiiiiith. AI 1' I 1.1 ,..11 I 741111111\ , 111111114, r am -

API'O ?HY!'

00D evening, listeners all-especiallya matter of fact, to carry out a series ofable to digest the bread, cheese, and beer \--/ invalids !" says Sir Walford Daviesreception quality tests of 2LO's trans-withoutshuddering. Andyet, inthe atthe commencement ofhismusicalmissions over a period of months. I had toparallelcase of music, it is being done lectures,and onemillionnon -Musicallisten. nightly by way of the loud -speaker. listeners promptly switch off their sets.I know that this happens, because I was atSpoon-feeding the Classics The Moderns one time exceedingly unmusical and regu- Night after night I listened to music of all The tendency of modern composers is to larly committed this sacrilege. That is tokinds, classical-ancient and modern, jazztreat melody as quite a secondary con- say, I played no musical instrument andand military band, hearing the same piecessideration to tempo and phrasing. (Musical was incapable of absorbing any musicplayed time and time again and graduallylisteners will probably have given me up in becoming aware of the existencedisgust, so it hardly matters if I don't use of those particularclassics whichthe correct technical terms.) That is why come in the "hackneyed " category.it is so difficult to listen to at first. Genera- I began to find that the less familiartions of melody makers have drugged our music, which required some effortmusical senses to anything which is the least of the brain, gave me much morebit out of the ordinary.Chinese music pleasure than such compositions asdoesn't mean a thing to us, and yet, to the Rachmaninoff's" Prelude,"thatgood people who regularly listen to it, it is cheery musical description of a manprobably as dramatic as Tchaikovsky or as being buried alive. The recurringsentimental as Ketelby.Itis, indeed, a. - themes in symplienies began todifficult matter to get out of the musical interest me, and Irealized, the"rut, but if one really tries a new musical dramatic power of, forinstapce,diet in carefully graduated doses, a new Tchaikovsky's Fourth Symphonymusical pleasure will be discov&ed.- and the charm ofElgar's very Ultra Molern "I had to listen .. ." English music. For a time, Edward German was a " best seller," so far - It is the caviar -and -champagne stage that except that of the order of " In a Monasteryas I was concerned. Stravinsky, Scriabin,seems to upset most of us.Bartok, Con- Garden " and " Yes, We have no Bananas."and Bartok were, of course, merely un-stant Lambert, Schoneberg, and the later So you see that when such an ignorantpleasant noises, and there " didn't seem toStravinsky works seem to be as colourless person as myself ventures to express anybe anything " in Hoist. and potent as vodka. I can't say that I opinions on music, they will be from the understand or fully appreciate these com- point of view of the "man in the street,"The Aftermath posers,particularly Bartok.But I am .and will be unbiased by a musical educa- The result of this course of forced musicalwilling to try to understand Bartok, and tion.Sir Walford Davies has always hadculture left me in mid-air. At three " bees in his bonnet "-Bach, Brahms,least, that is what I thought at and Beethoven ; I don't suppose he has everthe time, for I still obtained listened to a dance band sympathetically.a great deal of pleasure from In fact, it was probably his unsympatheticlistening to jazz music, especi- references to jazz which turned us awayally when it was composed by from listening to his lectures. a new man named Gershwin. Itis this " middle " stage of The Classics musicalappreciationwhich About four years ago, I probably had thehasbeenreachedbythe same reaction to. classical music as many ofmajorityofradiolisteners, you have now. That is to say, symphonywho are, in spite of themselves, and chamber music concerts came out of myfar more musical than that pool. loud -speaker and went in one ear and cameunfortunate" man in the out of the other ! Bach indicated a moaningstreet."The appreciation of Chinesemusic is probably as dramatic as Tchaikovsky noise, Brahms raised hopes of a Hungariangood music is much the same as or as sentimental as Ketelby dance and Beethoven sometimes remindedthe appreciation of good food. There is,I am quite sure that a great deal of pleasure me of something I had heard at the cinema.first, the bread -and -cheese and beer stage;and musical mind -broadening will be the That was all.And then-alas !-I wassecondly,the lemon soleandChablisresult of such an effort, even ifit be forced to listen to all these dull classicaltaste; and- lastly, the gourmet's judgmentunsuccessful.Constant Lambert's "Rio fogies' music and, worse still, to the noisesof good caviar and bad champagne.ItGrande," with its curious drum breaks and invented by composers who were still livingwould seem impossible for the gourmet,syncopated piano, interested me as much as and had not yet died in poverty !I had, aswith his very sophisticated palate, to be (Concluded in third col. of next page) 0nm/ear Wirdeo 616 APRIL 27, 1929 EN WI WJAMES Weekly Tips, Constructional For the and Wireless Theoretical- Amateur Loud -speaker Position Improving Selectivity The grid circuit of a mains -operated valve A RECEIVER is generally installed in a I am often asked how the selectivity of ais very liable to collect small alternating corner of a room or in some positionreceiver may be improved without muchvoltages which, being magnified by the where it is conveniently placed as regardstrouble or expense, and I always reply thatreceiver, will be heard as hum. the aerial and earth.Very often I find thethis can be done by connecting a fixed con-Arranging the Earth loud -speaker is put by the side of thedenser in the aerial circuit.This fixed receiver, or even on top of it, regardless ofcondenser should be joined between the A question which is very often asked is the fact that the quality of the reproduc-aerial and the coil included in the aerialwhat is the best size of earth wire to employ? tion is dependent to no small extent uponcircuit (Fig. i). Sometimes I find a relatively thin connect- thepositionofthe, loud -speaker with A good value to try is .000! microfarad.ing wire is used between the receiver and the reference to the furnishings of the room. The inclusion of a fixed condenser- of thisearth connection and on other occasions I This is a point that is often overlooked.capacity in the aerial circuit may reducehave noted that a thick wire or a conductor It is surprising how the quality may changethe signal strength by a small amount.such as 7/20 is used. Personally, I employ a as the loud -speaker is moved about theThis will probably not matter so far as thestranded cable in order that the actual room, and a position can geneially belocal station and Daventry are concerned,resistance of the earth circuit shall be as found which is convenient and where thebut may be serious when receiving the morelow as possible. best all-round xesults are obtained. By thedistant stations. It is, therefore, advisable A covered conductor is considered rather way, have you listened to a loud -speaker into -have two aerial terminals, one of whichbetter than a bare one and it should, of the bathroom?If not, do so, and then course, be treated as an extension of the listen outside the bathroom with the door fien:Q/ Stied/ye aerial. Do not fasten it to walls and do not open, and then partly open, noticing the .6.Candoyset lead it into the house too close to the changes in the quality aerial wire. As I have before mentioned; I generally prefer to use a buried earth Anchoring L.F. Transformers plate rather than a water pipe for the actual Many makes of inter -valve transformer are provided with a terminal or other connection that is joined or fastened to the: metal case of the instrument. It is provided ,4 THIS MODERN MUSIC", in order that the user may conveniently (Continued from preceding page) Fig.I.An arrangement by means of connect the case to earth or an equivalent which the degree of selectivity is very Gershwin's" RhapsodyinBlue,"the point, such as the negative side of the low- easily controllable jazz classic. Stravinsky's "Soldier's Tale" tension battery, as it is found that low - is really a fantastic ballet and did not frequency howling and instability mayis joined directly to the coil and the otherbroadcast well; nevertheless, having some often be prevented by this means. through a fixed condenser. idea of the grotesque dancing and figures The questionthereforearisesastoA Mains Point that "went with" the music, I obtained whether all transformers should be pro- quite a lot of entertainment and not a little vided with a metal case that may be Receivers which are supplied with theiramusement. You should bear this in mind earthed.Numbers of them are not, butfilament and high-tension current throughwhen listening to ballet music in particular. have a moulded cover.Their manufac-suitable apparatus from alternating -currentStravinsky's " Firebird " is relatively easy, turers have evidently decided that it is notmains are very common in America andasis his " Petroushka,' the composition essential to provide a metal cover whichwill no doubt in time be popular in thisin which he successfully imitates a street may be earthed, and practical experiencecountry.They have the great advantageorgan by clever orchestration. indicates that stability, and freedom fromthat when once they are satisfactorily howling,arenot dependent upon theinstalled maintenance is negligible. Sympathy employment of this form of cover when only Occasionally a new valve has to be fitted, The object of my article is to show that a one transformer is included in a receiver.however, and according to my experiencenon-musical person can obtain a great deal When two or more are used, the metalthis should be carefully effected.I haveof enjoyment and pleasure from the more cover may be an advantage, but I havefound that a hum may be heard from theadvanced classical and modern music, and found that no general rule can be made.loud -speaker when the grid pin of the valvefrom the advanced and specially orches- Everything depends upon the arrangementis a relatively loose fit in the holder. It is,trated jazz, if he will only listen sympa- of the set or amplifier, the amount of thetherefore, wise to open each of the pins inthetically. You can take it from me that amplification, the types of valves employed,order that all contacts shall be good ones.there is something in it, even if it only takes and other factors.I have even found us out of the quagmire of sugared melody instances where the best results were to be NEXT WEEK: into which we have been sinking.I must obtained by no' connecting an earthing wire stop.There'sabarrelorganoutside to the case of the transformer; A SHORT-WAVE ADAPTOR playing "Sonny Boy " I APRIL 27, 1929 617 ematxx.wwdeJ 0 BANISH INTERFERENCE THE TWO BEST GET AWAY FROM YOUR NEIGHBOUR'S SCREENING WITH A P.R. MAST Everybody knows thatto have a high aerial is to get THINGS EVER extra powerful signals. The difficulty of fixing up a high aerial is banished if you fit a PATENT P.R.WIRELESSMAST OFFERED TO YOU Ort Feet high. In :3 4..1° sections of s lin. Steel tube tapering to And both are British made to the hilt.Both are sent you in. Carriage, Lon- on the money -back -if -not -satisfied principle. don, 1/6; Midlands, 216; elsewhere, 3/6. We don't want you to keep anything you buy from us-as Weight 24 lb. Two masts for 28/6. you can easily understand it PAYS US BETTER for you to -311reecettioiTsgil3enin4. return the goods than harbour spleen. We want you to be Steel tube tapering to21/6 in. Carriage, London, 2/-; Mid- satisfied and give us the CHEAPEST ADVERTISEMENT lands, 31-; elsewhere, 4/-. Weight, 34 ib.Two masts for 40;-. -tell your friends we play the game. We have sold more goods through people telling each other they WERE The "Super" SATISFIED than by all the advertisements we have paid hundreds for. You have seen our advertisements formore than two 'years-you have Mast doubted mailorder houses - yet 42Feet high. In sections of reason it out-could e keep on heavy spending hundreds in advertising ti tn' unless we had THE GOODS ? ? ? Steel29/6 tube tapering to t We still, and always will, stick in. A real bargain. Carriage. London. to our guns. Try one-no 2/6; Midlands, risk-if not fully satisfied 3/6; elsewhere,4/6, thatitequalsyour Weight, 46 lb. favourite at any price, Two masts55'-. your money will be Rare made refunded by return. P Steelin You are the sole judge. MASTSlengths, 9 feet from r I in., tapering to tin., and are supplied with cast- ironbedplate, H.R.H. THE steel ground pegs. PRINCE OF stayrings,gal- WALES vanised steel flexible wire stays cut says : to lengths, pulleys, "SUPPORT bolts, and fullest BRITISH erectinginstruc- INDUSTRY." tions. No further outlaynecessary. LIST OF DULL EMITTERS NO HOLES Fil. Imp. Amp. TO DIG TypeVolts Amp. Ohm; Fat

PR 2 2 .095 28,000 13 B.F.Del. ONE MAN'S PR 3 2 .095 15,000 8 L.F. JOB 2 VALVES 316PR 4 2 .095 120,000 32 11,0. OR MORE PR 93.5-4 .063 18,000 14 11.F.Det. Any intelligent man can assemble and erect a P.R. Mast in POST FREE. Each PR103.5-4 .063 10,000 8.7 L.F. a couple of hours.The Mast being tapered, it is easy for PR11 3.5-4 .063 28,000 40 R.C. anyone to raise it from the ground into position.The wire C.O.D. Post 4d. PR175-6 18,000 17 rope is sent cut to size-a saving of endless worry. EXTRA. PR185-8 .1 9,500 9 L.F. Minimum Radius 3 it. 6 in. The easiest Mast to erect. POWERPR195-6 .1 £0,000 40 R.C. Each. GUARANTEE.-Money refunded if not satisfied Post 4d.PR20 2 .15 7,000 , 6 Power 7 PR40 4 .15 7,000 6 and the Mast is returned within 7 days. The WHY USE PIM 6 .1 5,000 6 simple instructions are so clear, that mistakes SUPERPOWER Iv cannot be made. Each PRI20 2 .3 2,750 4 8.P. FOREIGN 12/6Post 4d. P11140 4 PAINTING. 2,500 4 B.P. Any protective coating applied before dispatch gets so VALVES ? All valves dispatched under guaranteeW damaged by the Carriers that it is essential to paint the UARANT Money Back m Full if not satisfied within Mast before erection.All P.R. Masts are sent out oxide - 7 days. All valves carefully packed and breakages replaced free. finished ready for painting. One coat of P.R. Colloid Thereisa lot of talk covering applied-a 10 minutes' job-to all parts of the about unemployment -- Tell us your set-we will send correct 'Valves. Matched Mast when ready to erect sets dead bard in an hour and yet no less than TWO Valves extra.All orders executed by ream of post. protects it against all weathers. MILLION FOREIGN PRICE OF ACCESSORIES. Valves are sold annually P.R. Colloid Covering sufficient for a Mast-with brush, in this country !!! RADIO PRODUCIIN 2/6.Halyard Log Line-Ryland'spatentrot -proof; We wantthistrade. Sent For 26-f t. Mast, 1;6. 344 t., 42-f t., 2/6. Per 100 f t., 3/-. We don't want protec- C.O.D. Note.-Double length supplied to make lowering of Aerial tion. We only want if desired. easy. you to know thatyou A HIGHLY EFFICIENT AERIAL. can buy a better valve, P.R. Aerial is made of 14-28 High Conductivity Pure fullyguaranteed,for Copper Enamelled Wire-each strand insulated from its 3 6. British made to Telephone neighbour to give the highest signal strength obtainable. the hilt. Optasite Poi! City 3733 100 It., 4/3; 50 ft., 2/3. Office Tube. 17-58 PATGIZNO5TEQ.- SQUAI2,6 THE ONLY VALVE WITH A LONDON WRITTEN GUARANTEE AS SWF TO PERFORMANCE & LIFE. Don't Forget to Say That You Saw it in "A.W." PR1L 27, 1929 .0.404.0440.44<44.4.40.000.4.0.0tinatta4 Wags., 618 A sketch of 2L0 The May "Wireless Magaiine" Meets All Your Portable Needs ! Whether you intend to build or buy, everything you want to know about the modern portable is dealt with in the May number of the " Wireless Magazine " which includes an extra 16 -page Suoplement, printed on special paper,givingdetailsof more than 100 portable receivers now on the market. TeU your friends about this great number

THREE SPECIAL

- PORTABLE ARTICLES.

Lo you know that GETTING T H E to get the best results f BEST FROM A MODERN PORT- a portable the edge of the ABLE. By frame aerial must be pointing D. Sisson Reiph inthe direction of the broadcasting station? Many other (AssistantEditor). practical points of thiskind are discussedinthe May " Wireless Magazine." THE WAYFARER. A Five -valve Port- able Super -het des- No matter how much you know about radio,you will cribed by J. H. Reyner, B.Sc., always find many articles in the " Wireless Magazine "- that A.M.I.E.E. you will understand and appreciate.Amongst its 45 features (TechnicalEditor). HOW I SHOULD this month there are articles to suit everybody's tastes- -a DESIGN A FORT - detailsfor ABLE. By Here you see disclosureof Russian broadcastingactivities, W. JAMES J. H. Reyner's Wayfarer-A port- building four fine sets, a radio detectivestory,hints for Research Consultant able five -valve Super - decorating a linen -diaphragm loud -speaker, etc., etc. You can- het which weighs only 271b. not fail to find something of particular interest toyourself.OTHER CONTENTS OF THIS ISSUE Valves to Use in Your Set TheDominionsFour. Wavelengths of the Euro- Converting It to A Short- pean Stations wave Super -het In Tune with the Trade ! Under My Aerial.Hal- Do Your Pets Like Radio ? yard's Chat on the How Will Broadcasting Month's Topics Affect the General Elec- Is Your Turntable True? tion? By B.B.C. Officials Speed Traps for Records What Are Alternating Cur- Noisy Electric Drives rents? Amp and Professor Building Your Own Megohm Discuss Some Gramophone Fundamentals The Best Dance Records. Leaves from A Listener's By H. T. Barnett Log. By Jay Coote Planning your Aerial. By Curing Threshold Howl E. H. Chapman, M.A. The Twinflex. A Modern The Music Listener. By Note the attractive appearance of the At-home Reflex Two-valver with- C. Whitaker -Wilson Three, which has self-contained out Crystal Detector TheHorse -powerof A batteries.It costs less than £6. Japan Has the Most Power- Kilowatt ful Station BroadcastMusicofthe The Inevitable Radio-in Month. By Studius By using the Special Coupon to be found in the U.S.A. Novelties and New_Appa- every issue of the " Wireless Magazine " you can A Countryman's Diary ratus Tested How the Law Acts When Reaction-A Mixed Busi- get for half - price a full - size constructional Your Aerial Collapses ! ness ! blueprint of any set ! Speeding News by Air- Reference Sheets. Compiled andRadio,Too ! by J. H. Reyner,B.Sc. 09444000.00Get Your Copy of 66 Wireless Magazine" To-day-Price 1/- APRIL 27, 1929 619 urWirete

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The Regional circuits are a very good case in point.Itof wiring a fixed -resistance with a value of AFTER taking a look at the new'as proved to us conclusively by expertsabout a quarter of a megohm between the regional station at Brookman's Park,that transformers did, must, and alwaysgrid of each low -frequency valve and its not yet completed, I feel justified in ven-would distort. We hurled our transformersnormal connection. This is a cure of a kind, turing the opinion that this station will beon 'tothe rubbish heap in ordertobut it does not strike at the root of the the "last word" in broadcast transmitterfit R. C.couplers. Then super -expertstrouble, and the best way really is to pre- 'design. Machines, switchboards, and quiteshowed that R.C. had a little way ofvent, rather than to cure. Your set may be a lot of apparatus are already in the build-suppressing certain frequencies. Meantime,quite blameless when the batteries are new, ings, and the actual transmitting gear willtransformer designers were busy, and beforesupposinglthat it works from a dry H.T.B., soon be assembled. The whole outfit willlong they produced components guaranteedbut astime- goes on quality becomes be entirely self-contained, current beingto deal faithfully with any sand from thesteadily worse and worse.You put the generated by dynamos driven byoilroar of a lion to the squeak of 'a bat. Thedistortion down probably to the fact that engines, and oil being supplied to thetransformer came into favour again, butthe plate voltage is declining, whereas it is engines from a huge gasometer -like tank.we all nodded wisely and said that where, due not so much to that as to the rising There is a studio in the building which willyou had two L.F. stages only one of ,themresistance of the common H.T.B. which may be used for tests and emergencies. must be transformer coupled:'Arid wereach astonishingly high figures.I have told each other just why' this was so.known a 44 -cell battery, which still showed Disguised! There certainly was distortion if two trans-over 4.0 volts on a good meter, develop a For some reason or other the B.B.C.formers were used, but very few haveresistanceof nearly 5,000 ohms --quite haven't been encouraging callers at thereally understood why it came about.enough to cause all kinds of L.F. worries. 13raokrnan's Park station, and the " Press Actuallytransformers,ifoffirst-rateYou can end your L.F. troubles and improve are, for the moment, strictly not adMitted.quality, were blameless; the nasty noisesthe quality of almost any ret by simply Therefore, in order to find out the positionwere due to something quite different. fitting de -coupling circuits consisting of a of things for your especial benefit, I really suitable series resistance with a path to had to assume :the disguise I have often Back Couplings earth, via a fixed condenser, for oscillations. referred to in my lighter paragraphs.. No, When a common source of H.T. is usedThe effect is to keep oscillating currents I'm not joking this time !. I did assume awe provide the valves of the receiving setclean out of the source of H.T. supply and disguise, and I did succeed in passing thewith a very simple way of metaphoricallythus to prevent undesirable couplings. " guards " and having a good look insideputting their thumbs to their noses and the mysterious building. I won't say whatlaughing at us.In saying "common," by Short-wave News the " disguise " was, because the B.B.C.the way, I am referring to the fact that I mentioned recently that short-wave may read this paragraph-and I may wantthey all shared it, though matters are madeconditions were showing a very marked to use it another time ! very much worse if it is also common inimprovement. At the time of writing they the cheap and nasty sense. The resistanceare about as good as they have been for Tice B.B.C. Rush of this H.T. source is at the root of thetwelve months or more. On any afternoon As I have said before, quite a number oftrouble, for it serves to link up valve withwhen he is working you can be pretty surs B.B.C. people, particularly from the en-valve' in a way not contemplated by theof picking up PLE from Bandeong in gineering side, have turned over to talkingdesigners of sets. The result is that we -getJava, whilst W2XG, the American end of picture activities. The successful negotia-an undesirable feed back or reaction effectthe transatlantic telephone service, is to be tion of half a dozen contracts has put thewhich may have most unpleasant results. -heafd very powerfully .on a wavelength that spark to the gunpowder with a vengeance. varies from time to time. I have had beauti- Rumours 'of huge salaries to be earned Theory and Practice Ing reception lately from W2XAD, the elsewhere have had effect. The production The detector valve may be quite a19.56 metre relay of WGY, as well as from manager of one film -producing firm hasnuisance in this way. In theory its plateW2 X0, which transmits the same station's told me that he has had between thirtycircuit contains only D.C. and audio -fre-programmes on 21.96 metres, KDKA is and forty applicationslor jobs from B.B.C.quency oscillations.In practice a certainnearly always to be picked up by way of engineers as the result of a small announce-amountof radio -frequencyoscillationsW8 XK on 25.24 metres, and NV2XAF which ment in the Press that his firm contem-generally manage to find their way through.-relays KDKA on 31.46 metres, is excellent plated entering the " talkie" field.By theWith the kind help of a common ' H.T.unless interfered with by a miserable C.W. way, I didn't tell you that all the trtsource we may find the firstnote-magnifyingsignal that for some unexplained reason people say " talker " now-" talkie " is avalve oscillating quite happily at radio -appears to have adopted the same wave- relic of a past age. frequency. In this case there is no howling,length. The Nairobi station, 7LO, is easily The chief sound engineers of half a dozenbut reception is very woolly and the loud-picked up, as a rule, on 31 metres.There production unitsalready formed havespeaker emits a distinct plock whenever theare several good transmissions from the been taken from one B.B.C. experimentalfinger touches or leaves the grid terminal ofContinent, the best of which are DOberitz section alone. The meetings of the "soundthe valve holder. Then note-mag. number(AFK) and Madrid (EAR' ro). section" of the Society of Motion Pictureone may become back -coupled to note-mag. A Good Combination Engineers will be like a reunion of B.B.C.number two to such an extent that audio - people, now become hated rivals ! frequency oscillation occurs, and we get For short-wave work just now I am using either a howl or that disgusting successionagrid -leak -and -condenser detector,fol- L.P. Troubles of pops which is known as motor -boating.lowed by a pentode valve, with transformer Funny-isn't it --how often in wireless coupling between the two. This I find an we cast aside some circuit or component The Remedy exceedingly good combination, for it gives only to re -discover it later on and to return You can sometimes cure L.F. howlingone splendid signal strength, with none of to it full of enthusiasm.Low -frequencyor rnotor-bOating by the simple processthe noisy background that one is apt to get APRIL 27, 1929 ematturWirdT 620

is 4 On Your Wavelength !(continued) even with the most carefully designed two -exploring or scanning disc comes into being, For Cone Users stage note -magnifier. This combinationsince it enables a spot of light to traverse The cone type of loud -speaker is del gives me really good loud -speaker receptionthe object being televised and thus permitservedly very popular, for if it is given a of a number of American stations on anythe cell to convert the varying -light inten-fair chance by the use of the right kind of, favourable evening, and it is delightfullysities into electrical pulsations. valves in the right kind of receiving set it' easy to work with, since there is only one Exploring or Scanning? provides reproduction of wonderful quality) tuning control and a reaction condenser. Cones, however, do repay a little attentions This short-wave set has also a larger set of The lecturer lodged a plea for the use ofnow and then. On this point I speak with! coils, which enables it to be used for recep-the word "exploring" as against "scan-experience, for I have an old friend nowt' tion of the kcal station. ning" where television is concerned, attri-that by the exercise of a little care I have buting the latter word to American origin.kept in every bit as good condition as The Portable Licence It is surprising how the term which is firstwhen it was first acquired.First of all, The concession made by the Postmaster -applied to describe a new process shows adon't forget that permanent magnets are General to portable -set owners will be verytendency to retrain, and since scanning wasnot really permanent. They tend in course much appreciated, except possibly by thoseused initially itis now adopted fairlyof time to lose a certain amount of their who have already taken out a second licenceextensively.A Chambers'sDictionaryoriginal strength. When this happens the and cannot get their money back ! The newseems to offer little solution to the differ-instrument may become overloaded with regulationisthat,provided that youence _etween the two terms, for scan isa volume considerably smaller than it already have a licence for a stationary setgiven' to examine carefully, to scrutinise,"could originally handle with ease.Re - at home, you need not take out another forand explore is given " to search for the pur-magnetising costs only a shilling or two,1 the portable, but if you are using the latterpose of discovery, to examine thoroughly."and it is well worth while to have it done) away from home you must carry the licenceWe are so often apt to use the word scanperiodically. with you and produce it when requested toin the relation of a quick glance that it is do so by duly authorised officials.Picnicsmall wonder that it has been applied to Another Trouble parties, therefore, may receive visits, sincetelevision, for obviously the object being Here is another point that may be found the local lists obviously won't show thetransmitted is disintegrated by the spot-useful. One of my cones, whose magnet names of motorists who have come fromlight at a rapid rate. On the other hand,was known to be in first-rate condition, some little distance. The best tip, by thewhereas a quick glance by a person is surebegan -to " zizz" when certain notes were, to miss detail, our television eye will not fail way, is not to carry the licence in your being reproduced at fair strength.I knew' pocket, but to gum it inside the case of thein this respect; so perhaps the palm shouldthat no overloading was taking placei portable.It will then always be at handbe awarded to " exploring."Official tele-within the receiving set, so that obviously when asked for, instead of having been left'vision terminology will, no doubt; settlesomething was wrong with the loud -speaker, in the pocket of one's other coat. this question in the near future. itself.On. examining the mechanism, Have You Ever Thought of It? found that several small screws had worked! - A Television Society Lecture Has it ever occurred to you how aston-a little loose; probably owing to the con- Although itisof recent birth, I wasishingly cheap is the wire of which we usestant vibration to which they are sub -1 made to realise the other evening that theso many yards in making those sets whichjected. When these had been tightened' Television,Society is a very live one. I paidfor some queer reason are called wireless?up all signs of the trouble di',appeared.1 a visit to the Engineers' Club and listenedFor coil making one buys a pound reel of, to a paper by Mr. J. Cameron Renniesay, No. 26 double-cottOn-covered wire for Wireless Plays entitled, "Some Notes on Exploring."about four shillings.That reel contains I am :glad to see that a good deal more Lord Angus Kennedy was in the chair; andsome three hundred yards of 'wire, drawnattention is being paid nowadays to the' prior to the lecture proper an informal dis-with astonishing exactness to a standardchoice of plays that are really suitable for cussion took place, and it was a delight.todiameter 'and covered with two layers ofbroadcasting. Heaps of modern dramatiC, see the earnestness with which memberscotton insulation. To make a 6o -turn .coilworks don't fit in a bit, mainly because participated. on a3 -inch former we need roughlythey rely so much upon stageeffects,' In introducing his topic, Mr. Rennie15 yards of wire, or one -twentieth of awhich, of course, one cannot have-except formulated some rather novel linesofpound, of which the cost is rather overthe " noises off " part of them-from the thought, and compared and contrasted thetwopence.' Even of the very 'fine wire,loud -speaker. Shakespearehasalways five human senses-feeling, tasting, smell-which must be queer stuff to - handle inbeen a favourite with wireless folk, and ing, hearing, and seeing-in their relation--the making, one gets an almost miraculousthough they haven't realised it, the reason ship to exploration. The first three are veryamount for one's money. When you buyis largely that Shakespeare had to write limited in their scope; but, since the lastNo. 36 .41:c:c. at gs. 6d. a pound you obtainfora stage which had little or nothing in, two depended up -On wave motion g highwell oVerla, mile, whilst No". 45, which sellsthe way of effects. In his day, at the old frequencies for their action, it was sug-at about 22S. 6d.' "enamelled or 16s.Globe Theatre, the scenery consistedat gested that possibly in some hithertodouble silk covered, runs out to eight milestimes of a blackboard upon which was! ..u.nreyealed fashion, feeling, tasting, and-to the pound. chalked up, "This isthe sea shore of smelling may be governed by wavelengths Bohemia" or something of that kind) at a frequency bordering on. zero !In con- Shakespeare relies, then, mainly upon his nection with the human eye; if has to be ADAPT YOUR SET dialogue, and that is why his plays broad-: educated to perform its natural function- in cast so well. One or two -excellent modern an efficient manner, Nit when we turn to TO THE SHORT WAVES playwrights are engaged, I` heat', on plays the televisioneye, namely, - the photci- WITH THE UNIQUE written particularly .for broadcasting, and electric cell, it does not lend itself to such a very special attention will be paid to, theirt process.It cannot take in -a whole scene, ADAPTOR TO BE production.I. am sure that all listeners but has to be Made to explore it spot byDESCRIBED NEXT WEEKwill look forward with the greatest interest' spot at a rapid speed.This is where the to hearing the results. THERMION. APRIL 27, 1929 621 mateurWLr IN ER CUTTING OUT 2L0 SQUARE IT is always gratifying toTIMTHEIT SUCCESS proportion of the reports .I. hear of readers' successWITHe7ire,_ receivedregardingthe withoursets.Corres- " Clarion Three" have pondence ofthis nature been fromdealers who forms, of course, quite a have sold kits and parts considerableportionof %Id formakingupthe the daily postbag, and \#4 "Clarion"to AMATEUR we always prefer letters which laud theirWIRELESS, Nos. 352 and 353.As it wasWIRELESS readers.They, in their turn, praise in plain facts hnd, preferably, give afelt that this was an average -man set andhave received appreciation from the pur- station log, rather than those which talk insomewhat out of the ordinary on accountchasers on account of a good investment vague terms of wonderful reception and,of the good performance it could put up,for a little money and have passed the after all, are rather empty pmans of praise.and yet at the same time be simple toappreciations on to us. The AMATEUR WIRELESS Technical Staffbuild and operate, we diverged somewhat To take just one instance, Messrs. K. likes to have reception reports, whetherfrom our usual course and placed the set inRaymond, of 27 and 28a Lisle Street, good, bad, or indifferent, because this is onethe hands of an enthusiastic AMATEURLondon, .W.C.2, have made a speciality of way in which a census can be taken ofWIRELESS reader, living in the Londonthe "Clarion" largely on account of the readers' opinions and popular demandsarea.This test report was published infact that they have found this to be one of supplied.Therefore if you have built anAMATEUR WIRELESS, No. 353, and it isthe very few sets that get distant stations necessary only to repeat that this indepen-while London is working !And this at a dent tester succeeded in receiving thirty-distance of one mile from 2L0 ! one stations at full loud -speaker strength ! In consequence, the "Clarion" is being used largely as a demonstration receiver, Wonderful Results and every day during programme time As is always the case, the results obtained woe with any super -performance set receive rf sceptical reception on the part of a few as amateurs who still cling to 000025 old-fashioned receivers and AIFO ideas, and never take the trouble to modernise either andrealise what amazing resultscanbeobtained with the aid of present-day 'Da constructional facilities. The "Clarion Three" has met with a most enthusiastic OLI' This photo-receptionfromordinary graph shows thelisteners and from wireless as- as° main constructional it of the "Clarion Three " features of the " Clarion "dealers. Quitealarge The circu AMATEUR WIRELESS set, thereisa large crowd do not hesitate to write The Clarion Three was tested at the London workshops of Messrs. Raymond, within a mile of the gathered round the Lisle AMATEUR WIRELESS London aerial and in an area wherein 5GB and 5XX are only faintly received on most sets, owing to Street Depot judging the to shielding of the aerial.Although the aerial wire is about 6o feet from the ground, the proximity of about it. neighbouring roofs gives it an effective electrical height of only a few feet, ' Clarion " for themselves. With the Clarion attached to the business end of the aerial however, conditions were found to be en- The"ClarionScreen - tirely different.Both the long and the short-wave Daventry's came in at good loud -speaker strength Recently, at the request and quite free from any kind of interference,Greatly to the surprise of the operators, Radio Paris of Messrs. Raymond, some grid Three" is a case in was also received on the loud -speaker without any interference and with excellent strength against a point.This was designed, background of silence. The test was mode early in the evening when not many foreigners were on members of the Technical the air. On the short waves it was notable that Langenberg was received well enough to provide a given a thorough testing, complete evening's programme had this been so desi.-ed. Staff tested the set while End described in AMATEUR (Continued at foot of next page)

lh: interest that the " Clarion Three " has continued to arouse is evident from these photographs taken outside a well-known London wireless dealer's a few days ago 622 APRIL 27, 1929 t This story of the loss of four perfectly good valves may HOW IT HAPPENEDe } serve as a warning to you IN recounting an experience which befellorL.T.circuitthroughthereceiver.with the copper screen and point marked a. me quite recently I. do so to warn Nevertheless with the H.T. battery con- The result was disastrous for although the others of what might happen should theynections in place and the valves in positionL.T. switch was " broken " the valves blew. do the self -same thing as I did. in the set I was unfortunate enough to blow A glance at Fig. 2 will make clear the up four perfectly good valves.complete path for the H.T. current through -0/201K+ A reference to Fig. I willthevalvefilaments. Many alternative 601Na+ make things quite clear. I wasconnections for the battery system sugges-

.4 N.E ejLtincifORT.ORCEI/T Fig.1(left). The STOPRar 1 circuit with which \I0 C' I 0 I HZ. tests were being 101 made I Fig, 2 (right).The I pathoftheH.T. I it NT - current is shown by the arrows L.1:+

Itallhappened ted themselves as a like this. I was con- means of avoiding a ducting some experi- H. Z-.1 recurrenceofthe ments with a new HT trouble, but the one screen - gridvalve -ON.'+2 I finally settled upen portableand asI is shown by Fig. 3, didnot want the POs/,,On, c-6 COMMON- Evenso,Inow -°(,---77-/Rif PO/NT troubleofdiscon- AOR FUSE take the precaution z.7.-- SW/70/ nectingtheentire TO IT of disconnecting the setof connections si7 - H.T.leadsfro m tot h ebatteries -4---c:No o L.1: -P thebatteriesand a n d withdrawing 011+ also pulling out the valvesfromtheir my valves each Figs. 3 and 4.How such an accident can be prevented is shown by these diagrams timeItriedan holders. Once bitten, experiment, r merely switched off the valveexperimenting with the 2-mfd. condensertwice shy, is a motto I shall remember for filaments and took very good care to see thatbetween a and b to find its best position insome months to come. A few alternative no straggling wire from the H.T. supplycircuit.It had already been connectedsystems of battery connections are shown side of the set came into contact with thebetween points marked a and b and I wasby Fig. 4. positive L.T. feed wire. trying it between points marked a and c. A final word of advice to owners of, The circuit I was testing was that shownThis position did not seem so satisfactoryscreen -grid valve sets.Fit a` safety fuse: by Fig. r.From this it will be seen thatas position a and b and in trying to dis-between the negative H.T. wanderplug of when the filament switch was broken noconnect and wire up again to this position the battery and the negative H.T. terminal current could pass from the H.T. circuitone end of the wire camein contactor wire on the set. ADSUM.

" CUTTING OUT 2L0 IN "Clarion Three" Components they authorised us to inform readers that LEICESTER SQUARE " Ebonite panel, in. by 7 in.,and two strips, onethey themselves would have pleasure in 6 in. by 2 in. and one z in. by z in. (Becol,. Raymond, (Continued from preceding page) Ebonaet, Radion). sending a blueprint, gratis and post free, to London was working, and succeeded in Baseboard, 14 in. by 9 in. and cabinet (Pickett). every reader making application. We Two .0003-microfarad variable condensers (Polar No. 3, obtaining stations quite free from inter-Formo, J.B., Burndept, Lissen, Burton). understand that Messrs. Selfridge still have .000i-microfarad reactioncondenser (Burton,J.B., ference. Lissen, Polar, Ormond). a limited number of blueprints available, Another reason why the "Clarion" is Two dual -range centre -tapped coils, one aerial coil andand readers may obtain one by addressing one anode coil with reaction (Tunewell). popular is because it necessitates the very Push-pullfilamentswitch(Bulgin,Lissen,Trix,a post card to the Radio Department, Wearite). minimum of components for the maximum Three valve holders (Lotus, Lissen, W.B., Benjamin, mentioning AMATEUR WIRELESS, or by in the way of results. As a matter of interestBurton, Formo). making a personal call. Pre-set series aerial condenser (Formodenser Type J., it is perhaps opportune to give the com- Igranic). So far as the operation of the complete 1-microfarad fixed condenser (Lissen, Dubilier, ponents list. Mullard). set is concerned, there is nothing at all to As with all AMATEUR WIRELESS sets, a .ox-microfarad fixed condenser (Dubilier, type 61o,worry about in this. The panel carries an Lissen, T.C.C., Mullard). blueprint has been prepared to assist con- .000z-microfarad fixed condenser (Dubilier, Lissen,on -off switch, which controls the filaments T.C.C., Mullard). structors of the "Clarion Three," and this 3-megohm grid leak (Lissen, Dubilier, T.C.C., Mullard).,of all valves, two tuning condensers, the' can be obtained, price Is., post free, from Screen -grid H.F. choke (Peto-Scott). dials of which can be set practically in step H.F. choke (Lissen, R.I. & Varley, Polar, Trix, Wearite, the 'Blueprint Department of AMATEUR Burndept). and a midget reaction condenser, which, in WIRELESS, 58-61 Fetter .Lane, London, L.F. transformer (RI. & Varley,. Ferranti, Lissen,most cases, is used simply as a volume Philips, Igranic, Marconiphone, British General). ' E .C.4. Screen, 81 in. by 6 in. (Parex, Peto-Scott) control. Simplicity itself ! Eight terminals marked, Aerial, Earth, L.T.A- , It will be remembered that when theH.T.+H.T.+z,L.S.+ , L.S.- (Belling -Lee, Eelex, Igranic, Raymond) "ClarionThree "wasfirst,published, One yard thin flex (Lewcoflex). Let "Amateur Wireless" Messrs. Selfridge & Co., of Oxford Street, One red and one black wander plug (Clix). Quantity of No. 16 gauge bare connecting wire (LewcoS). solve your problems London, W.1, thought so highly of it, that Two slow-motion dials (Brownie). APRIL 27, 1929 623 =lair Wtretess WITHO

MUSIC

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A Weekly Programme Criticism by Sydney A. Moseley HAVE you been to the People's Palacetouch with these men of the moment. Charlot's Charity Hour was welcome, concerts.You should go. The bestWhat memories our grandparents wouldalthough it consisted merely of are -hash and cheapest concerts in thecountry.have had of Pitt, General Gordon, Dickens,of old numbers, some of which have been Every listener should make it a point toetc. played so often that we know them inside go to an occasional B.B.C. outside trans - Let us remain conscious of this wonderout.

Mission. Besides being a change, you hearof ours which was denied our forebears. quite a lot. + Istill hear good accounts of Vernon

Regimental marches with brief descrip-Bartlett's talks. His is a difficult job in all So far as the Mile End concerts are con-tions by Walter Wood, quite interesting,conscience, and that he has been able to cerned, here are a few points : Percy Pittbut I didn't much care for the Glasgowmake good up to now is all to his credit.

Singers.

I wonder if any listeners are intrigued Dora Maughan -a caricature The correspondent who asks the Editorby the personalities of those who deliver to interest me in the Sunday programmesthe lessons on Sunday afternoons.The must be a new reader. (He is none the lessspeakers remain anonymous, but I have welcome because of that 1)If not, he hasgood reason to believe that many well- surely overlooked my repeated criticismknown men are very willingly brought in of the very thing he wishes me to criticise.forthis purpose.One is an ex -Prime However, we shall persevere with our taskMinister.

of reforming the seventh -day programmes. Let us not have to depend on Continental Not long agoIremarkedinthese programmes 1 columns on the unsuitability ofPhilip

I was not able to hear the second "Gay Spades," but everybody has been telling me that it was splendid. "One of the most entertaining hours I've heard yet" is one emphatic opinion. Charlot appears to have scored a bull's-eye this time.

and his ear. What's wrong with it ? Any- "Memories of Leslie Stuart" was staged way, a habit not to be encouraged-if it issuperbly by the Birmingham station.It not too late. Apparently he felt the fullestwas a treat to hear again such undying confidence in the violas, for he had histunes as "Dolly Daydream" and "Lily of back'to them most of the time. Refresh-Laguna" -and played and sung so well. ment arrangements too stupid for words. Couldn't you imagine how the middle- Can't the B.B.C. see to this? You have toaged folk were enraptured ?Couldn't you line up and buy tickets, estimating thehear them saying : "Ah !You can't beat amount you propose to spend ! the good old songs. This modern-(sniff !) -jazz can't be compared with them." Of The idea of bringing Miriam Licettecourse, that irredeemable friend "Harold" down for one song only is difficult to under-has his point of view. He says :- stand-particularly sincethereareno "All those slow, mournful songs about encores.I suggest that notice of there'fair lilies' give me the creeps': What the being no encores in either half should bepublic needs is good solid rhythmic peppy clearly stated in the programme. syncopation-and then some-" W. H. Berry as Lissenden sees him Need I say he belongs to the moderns Brown's Dance Band which often accom-

Walter Widdop had a good reception. panies variety from 5GB.According to He is a real broadcasting artiste, since he Foden's Motor Works possess a versatilerecent correspondence on this matter, my lets us know what he is singing about.brass band. They do not confine them-point of view was shared. However, my How do you think both these popularselves to the usual overtures and selections,latest correspondent asks me to revise my artistes look in the fleshGo and see ! but reach out to other musical fields.opinion because " they are showing marked

Ronald Whitehead, who was the vocalistimprovement these days.In fact, their Was Segrave's talk really impromptu ?in a recent programme, has a bass voice ofstandard is now so good that they remind Sounded much too good for it. What adepth and purity. Did you hear him singone of a certain snappy little combination wonderful thing it is to get into intimate"Drinking" ? which used to broadcast from the Savoy." mateur Wpb 624 625 =tear Wis.elt5 0-00%.,00000000000

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THEappeal of the portable is in no valves of the D.E.P. class, capable of

sense an inexplicable one. It is, in dealing with an adequate grid swing take fact, simply an extension of the no more than .15 -amp. filament current. MORE ABOT THE 5:5:0 PORTABLE1U enthusiasm which every truelover of Larger valves, say of the DEP24o type, are wireless discovers when he has the oppor- really hardly necessary in a portable set. MAKING THE CABINET : AERIAL EFFICIENCY : VALVES AND TUNING tunity to take hisreceiver cut of doors. The " L'5 : 5 : o Portable," the receiver 1..ms, SUITABLE TWO -VOLT VALVES section of which was described last week, wood. The overall dimensions are 13% in. suited for the " L5 : 5 : o Portable"re-it is not to be expected that a two-valver israthermore troublesome toerect to use with is an ingenious little receiver which, apart by 13%2 in. by 4% in.One of the largerceiver is the linen -diaphragm loud -speakerwill be worked on the fringe of what thein a hurry, whereas insulated wire can be from its attraction on account of the low sides of the cabinet is a lid by means of described in AMATEUR WIRELESS, No. 355. B.B.C. calls the service area of any mainslung about almost.anywhere required. THE " £5 : 5 : 0 PORTABLE "

initial cost, fills a definite niche which, wewhich access can be gained to the back ofA blueprintisavailable forthis unitstation.To get the best from any two-Bare wire is, however, perhaps better for believe, has not yet been covered in port-the receiver and the battery compartment.and by slight modification of the dimen-valver, portable or otherwise, and even withthe earth lead as there are many occasions Mahe Detector L.F. 0 1 able receiver design ; that is to say, although On the other side of the cabinet is thesions of the cabinet a linen -diaphragmthe best of outdoor aerials, it should be(such as when working a portable on the 1 receiver panel which, of course, as men-loud -speaker could easily be added. Most river and so on) when a direct earth can it is a portable and can be used out of doors worked generously within the allotted range. 4 Cosmos .. .. SPI6/G SPI8/RR with equal facility to that provided by a tioned last week, is r31/2 in. by 6 in.The listeners,how- More particu-easily be made.

Wrod on POSIT/ON (FRAN& set incorporating a frame aerial, it can be internal dimensions of the battery compart-ever, who make corners AND BASEEVARD larly is this the CossoR .. .. 2I OHF 220P ment are, roughly, 121/2 in. by 7 in.Thisup the "5:5:o case with port-Batteries and Valves used as a transportable or even as a some- EDISWAN .. .. HF2I0 PV2I5 1 time indoor set, on account of the fact that allows of the fitting of an H.T. battery,Portable" ables from which Batteries and valves are always an important point in a portable because to an outdoor aerial is employed. amply able to stand up to the job of supply-will prefer METHOD OF fair volume is MARCONI .. .. HL2 10 DEP2I5 ing anode juice for the detector and powertouseitin SECUR/NO expectedeven some extent there must be a compromise DOOR Small Size valves, and also the provision of an ade-conjunction perhaps at thebetween valves capable of dealing fully MAZDA .. .. GP2I0 LF2 15 A convenient feature is the smallness ofquate accumulator and a grid -bias battery.with some im- expense of spar - and adequately with the job in hand and .. MULLARD .. PMI/IF PM2 The baseboard on which the main com-promptu form BAITER,' tan purity. the batteries which can be carried to supply the dimensions of the containing case. SPACE their requirements; of course,the two . . This can easily be constructed from 1/2 -inch ponents of the receiver are mounted formsof aerial slung OSRAM . . HL2I0 DEP2I5 a shelf which is mounted on smallup just wherev- A Suitable limits in this respect are size and weight. 1 wooden ledges at each side of theerconvenient. Aerial An accompanying table gives a selection SIX -SIXTY .. .. 2I0FIF 215P ,o/Pftvd of suitable two -volt valves and most users receivercabinet. The baseboard Reallyt h e For the aerial has the dimensions 12 Y8 in. by 4% in. aerial difficulty itissafetoof this portable will prefer to use two- A value of 120 -volts H.T. should be andthis,with the panel,slides isveryoften carry asmallvolters if for no other reason than that agiven to the anodes of the valves, and, as largely exagger- reelofabouttwo -voltaccumulatoris,ofnecessity, mentioned, the battery compartment is easily into the cabinet and forms a complete tinit. ated when dis- 3o ft. or 4o ft.smaller, capacity for capacity, than a six - - quite capable of

cussing the r=edofwire,pre- volt accumulator. containing.an ad- Advantage of Separate Aerial working of out- ferablyinsula- Four- or six -volt valves can, of equate dry .bat- For the reasons enumerated last AMBER FEET 1-1/NCE HOLE course, be used and there may be tery.. With most # of-doorswire- 'this diagram shows all thenecessary details of the case ted. Bare wire,

week, neither frame aerial nor special less.Of course with insulators, some listeners who will prefei to do power valves

loud -speaker is incorporated in the so in order that they may use the about71j2to 9

same valves as are used in a home voltsgridbias cabinet.If any further argument be neededitremains; only to be set andpossibly eventheset will be necessary. pointed out that the addition of a accumulator. 0 loud -speaker considerably increases So far as valve types are con- 0 the cost of a portable receiver, and cernedthe detector should be a

asmost enthusiastshaveloud- general-purpose valve with an im- 0 speakers of their own in use in con- pedance of about 20,000 ohms. junction with a home set, the con- Grid condenser and leakrectifi-

1 struction of aspecial - instrument cation is employed and the detector for the job is not always necessary. stageisfollowed by an efficient medium -ratioL.F.transformer. 4 Of course, for those who want to

make the'! : 5 : o Portable " a As is well known, these two factors have

somewhat more ambitious receiver, a primary bearing on the selection of a many types of loud -speaker can be valve for a detector stage. The great point

The 0 modified to suit the dimensions of about the power valve is that it should be arrangement thepresentportable. A loud- economical in filament consumption. This of receiver and

speaker of the type which is eminently This is a plan view of the actual receiver portion of the " £5 : 5 : 0 Portable " presents no great problem nowadays for case is quite simple

0.0 0 .0 00 0 mateur Wpb 624 625 =tear Wis.elt5 0-00%.,00000000000