Modern-Wireless-1933

October, 1933 MODERN WIRELES i

Vol. XX. No. 82.MODERNWIRELESS. OCTOBER, 1933. Page Page

Editorial . ..279 What Are Waves? 331 Introducing the K4 .. ..280 On the Test Bench 333 The Kendall Step System.. Scophony Television 336 The K4 Circuit .. 228398 Questions Answered . 338 How to Build the K4 . 295 The Radio Newspaper .. 340 Operating the K4 306 The Pick-up in Practice 342 The Performance of the K4 ..310 Round the World of Wireless 344 An Invisible Ray Burglar Alarm ..312 Reflections of a Radiotic 345 The Mystery Station of Switzerland 313 Kendall's Corner.. 348 Spotlights on the Programmes 315 Trouble Tracking 351 Long -Distance Mistakes .. ..317 " " Record Review.. 352 The Future of German Broadcasting 318 At Your Service .. Real Gramophone Tone Control ..321 HintsandTipsforthe My Broadcasting Diary .. . ..323 Handyman .. 356 Faults I Have Found.. ..325 " Death at Broadcasting House " 358 Aerial Circuit Selectivity.. ..327 China Takes the Air .... 381 Round the Turntable.. ..330 Radio Notes and News of the Month384 As some of the arrangements and specialties described in this Journal may be the subjects of Letters Patent the amateur and trader would be well advi ed to obtain permission of the patentees to use the patents before doing so. Edited by NORMAN EDWARDS. Technical Editor: G. V. DOWDING, Associate I.E.E. Radio Consultant -in -Chief :P. P. ECKERSLEY, M.I.E.E. Scientific Adviser: J. H. T. ROBERTS, D.Sc., F.Inst.P.

100testswith8turns

The of the knob... Sherlock Holmes of Radio

No other single Radio testing is revolutionised by the Pifco instrument in ROTAMETER. The key to its simplicity lies the world makes in the octagonal knob with its eight marked alltestsmore faces -" The Sign of Eight." The symbols on easilythan the these faces give a range sufficienttotest Pilco ROTA - everythinginradio.Just turn the knob ME TER. Any component or circuit for test desired, connect the part or circuit can be tested quickly and surely. Makes up to the ROTAMETER, and the result is 100 tests. BRITISH MANUFACTURE there in the window of the instrument. The Pifco ROTAMETER tests everything. RANGES: Even itself !The BATTERY TEST registers ROTAMETER 1.-0-8 volts.For low-tension voltage the voltage of the three No. 495 radiometer Patents Penchn9 test. cells inside the ROTAMETER. Another point 2.-0-30 volts.For grid -bias voltage about this wonderful instrument is the Safety 0-.E13iV2o1htstRao-n.Voes test. Fuse which safeguards it against damage by 0- 30 Volts 3.--0-250 volts. For high-tension voltage careless handling. 0- 100 A 0-250 Salts 0-250 test. BatteryTest for." A 4.-BATTERY TEST. Get your radio dealer to demonstrate the Pifco Fr .a ResistATest 5.-0-20 M.A. For individual valve test. ROTAMETER to -day.If any difficulty, write directtoPIFCO,LTD.,HighStreet, ro,Ristane;Z:trt 'n1,01

ROTAMETER TO .3 MODERN WIRELESS October, 1933

AMONG TABLE RADIO SETS The Superhet Concert Seven combines the very latest improve- qments in radio science, such as delayed automatic volume control (which eliminates fading of long-distance programmes), static suppressor (which prevents the amplification of any signal in the BECAUSE " mush "), and real adjacent channel selectivity.It provides not only a range of stations to satisfy the inveterate station hunter, but also a tone to please the most sensitive musical ear. IT IS A SUPERHET To prove its supremacy needs but a fractional turn of. the tuning SEVEN qknob-to prove its supremacy as a musical instrument, just listen ! Here is the realism of the Concert Hall itself-a tone that is true IT HAS CONCERT to life 1The technically minded will find further details to TONE & VOLUME interest them in the brief specification below. But besides being good to hear, the set is also remarkably good IT HAS DELAYED qto look at.Altogether, an instrument you will be pleased to listen to, pleased to look at, and, since itis made by " His AUTOMATIC VOL- Masters' Voice," proud to own.Price 22 Gns. (or by Hire UME CONTROL Purchase).

IT HAS A SPECIAL BRIEF STATIC SPECIFICATION : Superhet Concert SUPPRESSOR Seven IT HAS ADJACENT Model 467 Seven - valve (inc. CHANNEL rectifier) superheterodyne circuit SELECTIVITY Marconi valves. Automatic Volume Control. Illuminated Scale with wavelengths and station and names.Duplex tone control. Movingcoil, mains -excitedloud- speaker.Sockets for gramophone pick-up. BECAUSE Power to operate three additionalloud- speakers. Height - 1 ft. 7} ins. IT IS BUILT BY Ikidth -1 ft. 51 ins. Depth-- n ins "HIS MASTER'S VOICE" TRUE8TO0LIFE RADIO & RADIO GRAMOPHONES The Gramophone Co., Ltd., 98-108 Clerkenwell Road, London, E.C. Price does not app(y I.F.S.) October, 1933 MODERN WIRELESS

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kk%-\ Vol. XX. No. 82. viviiitt0/4BRITAIN'S LEADING RADIO MAGAZINE October, 1933

Two Outstanding Contributions-The K4 and " Death at Broadcasting House."

\ this special issue of MODERN WIRELESS we are pleased builders would feel that the set was not beyond his to present to our readers two features of outstanding powers. importance, namely, the exclusive contribution by It was doubted at first whether such a method could Mr. G. P. Kendall or the construction of his latest and be adopted in practice, but we think readers will agree mostingeniousreceiver-The K4 ;and,secondly, that Mr. Kendall has achieved his ambition when they the opening instalment of a new and thrilling serial read the following pages giving the fullest possible details story, " Death at Broadcasting House," which has been for the construction of his latest and finest receiver.For specially written for readers of this magazine by two there is no doubt that not only are the technical merits very well-known B.B.C. personalities-Mr. Val Gielgud, of this receiver obvious to the initiated, but as the article is the Director of Dramatic Productions, and Mr. Eric read they become increasingly easy to follow and to Maschwitz (under the nom -de -plume of Holt Marvell), understand, even for the veriest tyro. the newly -appointed Director of Variety. We feelconfident that in presenting the K4 we are offering readers of MODERN WIRELESS a chance to The Finest Ever Published build a receiver which, in every sense of the phrase, will THESE two features alone, we never let them down." think, go a very long way to making this issueof Our New Serial Story MODERN WIRELESS oneofthe WE shouldverymuch finest ever published.To begin welcome letters from with, Mr. Kendall's K4 isun- readers concerning our doubtedly goingtoprovethe new innovation in radio jour- outstanding 4-valver of the year. nalism-the introductionofa The receiver has two very distinct radio serial story. In the past we andimportantnovelties - the have from time to time pub- Step System of construction and lished radio short stories,but the tone -levelling principle. we think we are right in saying Whendiscussingwith Mr. that this is the first time any Kendallthevariouspossible wirelessmagazine hasever methods ofpresenting the K4 offered to its readers a full-length receiver toreadersof MODERN novel in serial form by two very WIRELESS, Mr. Kendall suggested well-known iiauthors.We hope that he should not only deal with you will enjoy the story-and the problems arising out of his we hope, as all Editors and all new set in a way which would authors must-that it will keep make animmediate appeal you in suspense, and that not to the more technically -minded until the very last instalment reader of this journal, but should will you guess the name of the at the same time explain-when miscreant who brought " Death necessary at length, and always to Broadcasting House." At with clarity of detail - the any rate, although the chances actualdetailedprocess of are you will suspect most of the constructing the K4 thateven characters at one time or another, the most inexperiencedofset - we promise you a big surprise !

The Inventorof the K4, G. P. KENDALL, B.Sc. and the Step System fully described in this issue.

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1111 LS 'r sented -ree with " Modern Wireless '' October, it MODERN WIRELESS October, 1933 0DUCING

Here at last is the fundamentally new principle in set construction for which we have been waiting. The long stagnation is now at an end, the flat baseboard system is dead so far as the bigger set is concerned, and the way to better radio is open. The K4 isbased upon this remarkable new invention, and it marks a definite stage in radio progress.No constructor can afford to ignore the possibilities it offers to him, for not merely does it possess the super efficiency of the new system, butit introduces also certain valuable electrical developments. --The Editor.

fellow designers, or that you can de- to use it myself.My reason for this tect a superior strain in what I am was two -fold :first, anything of the writing.The truth is far otherwise, sort was quite obviously unnecessary o stunt or not to stunt ?-thatfor I have really an entirely sympa- in the case of the K4, for reasons which was the first question I had theticunderstandingofwhatis you will discover in a few moments, to decide when I began to indeed a very difficult problem :the and, secondly, it clashed with a much - think how I should introduce myK4 designer knows that he has a superfine cherished ambition of mine, which is receiver to the radio public. The way set to present, yet he also knows that to re-establish my old relations with I have put the question makes it look the readers of radio journals have been the readers of this magazine, based on like the beginning of a vulgarisedso surfeited by the repeated use in complete frankness on my part, and, version of Hamlet's soliloquy, I admit, the past of all the laudatory adjec- but the problem was a serious one to I am proud to remember, a con- me, all the same. tives in the dictionary that they have siderable measure of trust and confi- You see, for some time now the become very hard to impress ! dence on theirs. people who provide the home con- Now let me tell you why I think structor with set designs have been The Inevitable Comment it is quite unnecessary to go in for feeling rather at a loss when it came It is therefore only natural that he any kind of startling stunts in order to presenting any kind of" extra should seek for some striking way of to make sure that my readers shall demonstrating the superiority of his realise that the K4 is, in actual sober special " set, because all the super- truth, a set of the greatest importance latives have been used and over -used new creation.I should be the last to blame him for so doing, because I to every home constructor in the until they have lost all the force they country. ever possessed ! have done the very same thing myself in the past. It is really very simple :the tre- Designer and Reader mendous step forward which the K4 Indeed, I believe I was one of the represents is based upon a fundamen- The only thing to do, it has seemed, first,if not the very first, to carry was to carry out some spectacular tal invention which is so obvious 'in out a test tour with a new receiver ! its nature thatithas only to be " stunt " with the set, and rely onIn the year 1925, I think it was, I explained for its importance to be this to convince the reader that the made a tour of the Western, Midland, realised.Like all really notable in- instrument was indeed something out and Eastern Counties to investigate ventions, it usually provokes some of the ordinary.Sometimes a series and demonstrate the performance of such comment as, " Why on earth of notable radio personalities would be a portable superheterodyne which I didn't we think of that before! " invited to give their opinion of the subsequently described in MODERN set ;sometimesthereceiverwas WIRELESS. Forecasting Changes taken round the country on a test I would never, therefore, criticise It has indeed the beautiful simpli- tour.But the aim was always thea designer for using the " stunt " city of the essentially good idea, so same, that being to demonstrate to method of introducing a new and im- that one can grasp its importance the reader that the set was really an portant set. at a glance.It is true that one can important one. As you see, I have no real prejudice only understand its more far-reaching Please, dear reader, do not think against the stunt method of intro- effects on set design after some study, that I am here being unkind to myduction, but Iquickly decided not but itis obvious at once that its

280 October, 1933 MC DERV WIRELESS jj

By G. P. KENDALL, B.Sc. effect must be to cause some quite markably well pleased with myself ! pass principle ;I regard both gang- revolutionary changes in all future I'm sorry about that, for I hate it, but ing and band -passing as much over- sets. really I'm in a quandary. You see, I rated pastimes.They are sometimes By that remark, by the way, I do know that the new system is of very necessary, it is true, but I think they not mean that I think that other great importance, and if I don't tell should be avoided when possible. designers will copy my system, but I you about it in good strong terms, no do confidently expect (and hope !) one else will do it for me ! Balanced Reproduction that they will try to get my effect Now that we have thus cleared the 1'he selectivity of the K4 tuning with the aid of methods of their own. ground somewhat, Ithink we can circuits is extremely high-so high, proceed with the actual introduction in fact, that the reproduction would The "Step " System which these ramblings of mine are be definitely low -toned and poor if In passing, I should like to remark intended to effect. nothing were done to counteract the that I have just re -read those last Readers of " M.W.," allow me to effect.Accordingly, the set is pro- few paragraphs, and two things strike present the K4, a four -stage receiver vided with adjustable tone correction me :the first is that I have entirely in which you see for the first time my of a very efficient type which enables failed to emphasise sufficiently the new Step System, which Ifirmly the user to obtain properly balanced great importance of the new system. believe will be found to mark an im- reproduction under all conditions. I can see that I ought to have used portant turning point in the history some of those old favourite phrases of home construction. like " epoch-making " and " marking The receiver employs one variable- a new era " !The second point, which mu S.G. valve, with special razor- strikes me even more forcibly,is sharp tuning circuits which are neither that it all sounds as though I was re- ganged nor arranged on the band-

Mr. Kendall at work in his laboratory, using some of the actual apparatus employed in the researches whose fruits are embodied in the K4. He is seen adjusting a beat -frequency oscillator the output of which modulates the radio -frequency oscillator in the middle of the picture.

281 MODERN WIRELESS October, 1933 A Masterpiece of Modern Design

Actually it does a great deal more, outfromallpreviousfour -valve all incorporating some improvement as we shall see later, but for the receivers.In conjunction with the or other.So far as I can gather what moment I will content myself with Step System they place it far ahead annoyed the keen constructor was remarking that this, to my mind, is not merely of previous sets, but also, that he realised that these claims were the proper way to design a modern I am confident, of any four-valver mostly true, and the continual gentle receiver. likely to be brought out during this drip of new ideas made it impossible There are many other special and coming season. for him to settle down and build any original features in the circuit, but So confident am I of this that I do set without feeling that it would be we must leave them for the moment, not intend to publish another four - rendered semi -obsolete by the next and just note in conclusion that the valve design for the rest of the season ! issue of his favourite journal. setisprovided withaClass B For that period I shall be content to Accumulated Advantages output stageofthebest modern let the K4 stand, and I believe that it type, so that good quality moving - will not be equalled, let alone beaten. Only too often the result was that coilresults can be obtained with a That is a strong statement, but my he waited and waited to see what very small consumption of current. faith in the merits of the Step System was coming next, and before he is such that I am sure that it will be knew it the season was over and he New Developments justified by events. had been obliged to put up with his It has actually been my deliberate old set the whole time. The only Sofar 1 have emphasised the design all along to produce a set which cure for this irritating state of affairs importance ofthe Step System in I could allow to stand for a whole that I can see is to do as I have done making the K4 the truly remarkable season, for it has seemed to me forwith the K4. receiver which it is, but I do not want some time that a more definite and Each design for a particular type it to be thought that this is the only settled state of affairs was an impera- or class of set should contain not feature of the set. tive need in the sphere of home con- merely one good idea, but such an As a matter of fact there are a struction. accumulation thatitrepresentsa number of important new develop- For a long while now I have been sufficiently marked advance on all ments of a purely electrical nature in getting the impression that the con- previous types and designs for the the circuit, and these alone would structor was growing tired of being same class, so that it can stand for, at have been enough to make it stand offered a continual succession of sets, any rate, one whole season. Some Secrets of tfie Success of tfie .7C4

The arrows you see here indicate some of the electrical features which help to make the K4 the most remarkable receiver of the day. 1drawsattention to the special low resistance tuning coils; 2 indicates theseparatetuningcontrols; 3 isthe control of the " tone -levelling " circuit, and 4 is the Class B output valve.

282 October, 1933 MODERN WIRELESS

.INDALLSTEP SYSTEM

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developed the metal chassis system to a high pitch of perfection from his IN the last issue of MODERN WIRE- doesn't, and until we realisethe point of view.His point of view, un- LESS an oldfriendof minefact we shall not see the need for fortunately, is not that of the home contributed a provoca tiv e anything better. constructor, and that is why attempts article(" Time for a Change," by Of course, the panel and baseboard to introduce the chassis for general P. Woodward) in which he sought to system is a great step forward on the use by the latter have always failed. show that theso-called American previous method which used a panel The fact is that the metal chassis system of set construction, using a only, but it is far from perfect, and is too hopelessly inflexible to suit the vertical panel and plain horizontal it is a source of wonderment to me home constructor. baseboard, is now out of date andthat we have put up with it for so due for replacement. long.It must be something like eight It compels him to stick rigidly to I suppose I ought to confess at this years now since the " American "the exact types of components for stage that I put him up to it, for at system first became popular, and thatwhich the chassis was designed, and that time I had finished the develop- it makes it almost impossible for him ment of my StepSystem, and I ever to make any alteration in his set when once finished.He has conse- wanted to start an exchange of views Mr. Kendall considers the which would help to make people Step System one of his quently no chance of bringing it up realise that there was at any rate a most important contribu- to date or trying new developments possibility of a new development to in the future, and that is a state of tions toradio progress. affairs which does not appeal to the replace the old method. Here he explains how he You see, we have been using the has put an end to a period real experimenter. flat baseboard system so long that I of arrested development The Value of Layout knew it had become one of those which has lasted nearly Although the metal chassis may institutionswithgreatbigroots eight years, and goes on to not suit our requirements so perfectly which take a tremendous amount of show how his new system as it does those of the commercial pulling up !Pulled up they shall be producesastriking in- man producing thousands of exactly if I can manage it. crease in the efficiency of similar sets, nevertheless it can teach a receiver as well as in the us a great deal.If we study the way Prepare for a Change ! ease of construction and in which it permits a more efficient But it is going to be such a tough wiring. layout and better wiring to be ob- struggle that I felt that a little pre- tained we shall begin to see where the liminary propaganda work would be ordinary baseboard scheme falls short, a help, and that must be my excuse is a most extraordinary time for any- and what sort of system we require for my littlebit of artfulness lastthing to remain in vogue in such a if we are going to improve on it. month. rapidly developing science as radio. The main thing about the chassis I think I shall be forgiven for it method, we shall discover, is that it when the reader realises how im- Metal Chassis Limitations provides a considerable increase in portant itis to him to understand The only explanation that I can the number of surfaces on which we what a very great improvement can see is that they have been eight years can mount our components.This, in be obtained in the performance of a of amazingly swift progress in theturn, means that we shall be able to radio set by the use of an improved development of circuits, valves, and space them out better, and position system of construction. components, so that we have almost them so that the connections between To achieve a clear understanding forgotten about thepossibilityof them are shorter and more direct. of the point we must first clear our improvement in the broader aspects We are also able to separate out cer- minds of the idea that the accepted of set construction methods. tain circuits as a whole from others horizontal baseboard method serves The commercial designer,tobe with which they might interact un- itspurposewellenough,forit sure, has been awake to it, and has desirably.

'283 MODERN WIRELESS October, 1933 G. P. K. Explains a Fundamentally New System

These points give us a clue to theapplication, for that is not the case, the cost of the set ; all you require is main failing of the ordinary flat base- but I do maintain that they do not a very simple wooden framework board type of construction, which is provide the universally useful and made of some piecesof plywood that it gives us only one plane on quite complete solution of the problem costing only a shilling or so. which to assemble our parts.That which we require to displace finally The principle on which the Step plane is, of course, additional to the the out-of-date flat baseboard system. System is based is really very simple. panel, and it is the reason why the Such a solution my new StepItisjust a matter of a carefully " American " system was found su- System provides, and does it with worked out increase in the number perior to the older flat panel method. such amazing success that I venture of " assembly planes," a point which to predict that in six months' time willbereadilyunderstoodupon Eight Years of Stagnation inspection of the various photographs The older scheme gave one surface the ordinary flat baseboard method will be dead, except perhaps for the accompanying thisarticle and the only,i.e. the panel, and when the others in this issue. baseboard was added to this we im- very simplest kind of sets.I am mediately found that we could achieve fully convinced that itis the most importantsingleinvention which Framework Arrangements a better layout and we built a set The Step framework actually gives which worked better in consequence. has been seen in the world of home construction for years. fivesurfacesfor the mounting of Since it was perfectly obvious that components, as against one for the the improvement was due to this Thereaderhas,Ihope,been ordinary baseboard or two for the increase in the number of available through my introductory article and got a general idea what it is all about raised baseboard.Those surfaces are " assembly planes," it seems to me arranged in a way which is the result rather extraordinary that no one took and how the K4 came into being, and by now he will be wanting to haveof some months of experiment and the logical further step of increasing thought, and which makes it possible the number stillfurther,until he the Step System explained in detail. to lay out the components in such found he had got as many as he could I hope, however, that he will bear with me while I deal with just one relativepositionsthattheactual advantageouslyuse. Ithink the circuits of the receiver are spaced out reason cam only be, as I have already more preliminary matter before starting upon my main subject.I want from one another in a way never suggested, that it was at just about before achieved, while the wiring is that time that the great spurt of made incredibly direct and easy to do. progress in electrical design was be- Now let us refer to one of the photos ginning, and attention was distracted " I am fullyconvinced that it is the most impor- showing the inside of the K4, compare fromthequestionofmechanical this with the drawing of the Step construction. tant single invention which has been seen in the world framework which will be found in Whatever the cause, the result these pages, and see if we can get an has been eight years of almost com- of home construction for years." idea of the actual way in which the plete stagnation, so that to -day the framework is arranged.It will be panel and baseboardsetisstill observed that it consists of only four practically universal among designs to explain that the Step System is pieces of plywood, which have a thick- for the true home constructor. that most exceptional thing, an in- ness of three -eighths of an inch, and True, there have been attempts, vention without a " catch " in it. are fastened together with screws so some achieving a certain measure of as to form two " steps " on different success, to popularise a sort of wooden A Shining Exception levels, two of the pieces of wood version of the commercial chassis, and It is only too true that in the vast forming supports between the two in some cases quite a good effect has majority of cases we discover that steps. been obtained by raising up the base- new things, while they may be better Component Accommodation board a few inches on supports, so than the old ones which they replace, that the underside became available contain some sort of drawback which One of the step surfaces runs across for mounting components. was absent from their predecessors. the back of the set, at the level of the baseboard in the old-fashioned system, Out -of -Date System We get our improvement, in otherand on this are mounted the valves However, none of these ideas made words, at a certain price, which was and the L.F. amplifying components ; a sufficiently fundamental attack on probably the fact at the back of the mind of the unknown philosopher who also a couple of little terminal strips the problem, and they mostly hadoriginated that sapient saying about for the aerial, earth, and loudspeaker quite considerable defectsoftheir roses and thorns. terminals.This forms surface number own, chiefly in making the set more one. ,difficult to build.For example, most The Step System is a shining ex- Immediately adjacent to it is the of them compelled the constructor to ception.It is the means of making second step, raised up to a height of bore a lot of holes in the wood andsets more efficient, which might be 2i in. above the first level. Both pass wires through them to makeexpected to involve increased diffi- surfaces of this step are available for connections between parts on the cultyof construction, yetitalso mounting components, and we will upper surface and others underneath, makes them easier to assemble. call them surfaces numbers two and and this made wiring a rather trouble- It produces much better wiring, yet three. Itwill be noted that the some business. it also makes the wiring far easier to height of the step is such that there I do not want to give the impression do.It does all this, yet it does not is room for quite large components that these methods have no legitimate involve any noteworthy increase in on either of its two surfaces. 284 October, 1933 MODERN WIRELESS

These two views of the upper and lower surfaces of the K4 will give the reader a preliminary idea of the amazing improvement in layout and wiring efficiency which the Step system automatically produces. The lower picture in particular gives a good impression of the wonderful accessibility "to all parts " a feature of importance in set design which has been far too much neglected during the lasteight years of development in home construction technique. MODERN WIRELESS October, 1933 Step by Step in Solving an Eight -Year -Old Problem

The remaining two pieces of wood In practice this means that itis componentsofthedetectorstage are placed on edge between the two ridiculously easy to solve completely are placed on the underside. Step pieces, and form the means of what was one of the most difficult of Here we see the clue to the remark- assembling the two together to make all set design problems when a flatable efficiency which can be got by the framework which you see in the baseboard was used, namely, the building a set on the Step System.It photos.In addition to serving this spacing out and proper separation is just a natural and, indeed, inevitable purpose, however, their inner sides of the tuning circuits and H.F.- consequence of the fact that for the provide two further assembly planes carrying circuits generally from the first time the set can be laid out with which we will call surfaces numbers other portions of the receiver. proper separation and isolation for four and five.These are not used for In the older sets it was practically its vital H.F. circuits, without resort- the mounting of components in the impossible to do this properly, and ing to a mass of screening which, while K4, but it should be noted that they it frequently happened that one found it certainly has the desired effect of areavailableforuseonfuture the tuned circuits all mixed up with preventing feed -back and instability occasions. battery supply circuits, low -frequency in the H.F. stage, cannot be con- amplifying circuits, assemblies of de - sidered desirable from any other point What You Might Miss coupling components, and very likely of view. These four pieces of wood consti- tute the Step framework proper, but it may be as well to point out in PUTS A BIG SET INTO SMALL COMPASS passing that if an existing cabinet is EarywrE PANEL to be used for the K4 another piece of ply of the same thickness and measuring 18 in. long by 1 in. wide will be needed.This will be used for stiffening thepanelalongits lower edge, but I will explain the point in detail in the constructional article which will be found in later ,pages. The reader has now got a general idea of the way the Step System frameworkisarranged,andit becomes possible for him to see a little more clearly what an extra- ordinaryandtrulyrevolutionary improvement it renders possible in set layout and wiring. 7 PLY WOOD USED THROUGHOUT FOR CHASSIS TOP MEMBER - A = /8 "x4 t'2" Let us take first the question of 5/DE MEMBERS - BBC =/O "x 2 fr.2" layout. I hope the reader will bear Borrom iteEk feeR _D = /8"X 2 P2 with me while I explain these things, Here is the Step framework on which the K4 is built, showing that the new system and not become impatient to get on possesses the perfect simplicity which is the hallmark of the truly meritorious invention. to the details of the set itself, because itisextremelydesirablethat hea mass ofloss -producing screening. Little Screening Required should understand the points I am Now look at the K4 and you will discussing. see that the tuning circuits are lifted Note that in the K4 the only If he does not he may fail to realise up on the second step and isolated screen is a very simple littleaffair what an important development the from all the other circuits in a way intended just to stop electro-static Step System really is, which mightwhich would have needed a layout feed -back between certain wires and so easily lead him to decide not to of quite twice the size even to ap-components in the grid and plate build the K4, and thus miss his proach by the old methods. circuits of the S.G. valve.Otherwise chance of sharing in the improved As a matter of fact, it could not the only screening required isjust results which willbe obtained by have been more than approached by the conventional amount of " can- those who do build it. anysizeofnormally constructed ning " now given to such components single -surface baseboard. as coils and H.F. chokes. The usual A Drawback in Older Sets Actually, you will see that the H.F. foil -covered baseboard and large par- Very well, then ;the first thing to department is grouped almost entirely titionscreenarerenderedtotally be noted is that the system increases on the upper step, the tuning con- unnecessary by the proper separation the number ofdimensions,soto densers and other controls occupying from each other of all those circuits speak, in which a set can be designed, their usual positions on the panel. which might otherwise have inter- so that it becomes possible to space The tuning circuits are confined to acted objectionably. out circuits from one another by the upper surface of the step, along As a matter of fact, the little screen arranging them atdifferentlevels with the components associated with which is actually present in the final vertically as well as spacing them out the H.F. intervalve coupling arrange- model is not really essential, and the horizontally, as in the older schemes. ments, while the various accessory set will work quite well without it!

286 October, 1933 MODERN WIRELESS Perfect Spacing is Essential for Efficiency

The Step System puts the valves where they belong- Symmetry of panel layout is achieved with ease on the Step System.Note how well all in a row at the back of the set. balanced and conveniently placed are the controls of the K4, yet how ideally direct I only added it because I found that and short are their connections. withcertainvery" lively,"i.e., efficient, screened grid valves the set portant point of the two.There is was not quite so completely stable as no need for me to explain at length I could wish.Instead of using a here, for even the most casual glance screen I could have moved the coils mixed up, and given the isolation at the photographs cannot failto farther apart, and so made room to which is so desirable for them. show that the wiring of the K4 is space out the grid and plate circuits So much for the virtues of the Step quite unlike that of any preceding a bit more, but this would have upset System in giving a more efficient lay- receiver. my panel layout badly, and I chose out. Now let us see what it does for Observe how it runs straight from the screen instead.It is far too small the wiring of the set, for I am not point to point, and yetisbetter to cause any of the troubles onesure that thisis not the more im- spaced out than is customary in any sometimes gets from too elaborate set of the kind in which the wires are screening, in any case. alllaboriouslybentintospecial SUMMARY. shapes and run by circuitous routes The Lavish Hand in order to keep them apart.The By the by, don't let me give the The Step System :- factisthat the flexibilityof the impression that I am arguing that all (1) Makes a really efficient lay- Step System is such that it is easy to screening is bad ;the truth is that out possible for the first time. lay out the parts for a set in such screening can be perfectly harmless, (2) Dispenses with all elaborate positions that ideal wiring can be but that it must be done with great screening. got in where practically every wire cunning for that to be the case.As (3) Makes a set far easier to goesstraightfromonepointto build and wire. another, yet is perfectly spaced out so often done, with a lavish hand and (4) For the first time provides a very little thought, it is most definitely positive guarantee that every from allothers with which there apt to produce losses in the H.F. constructorwillmake an might be undesirable effects. circuits which are not necessary. exact copy of theoriginal If the reader will bear all these wiring. Easy and Quick Wiring (5) Achieves this most important As a result, the wiring of a stepped points in mind, and go over the photo- effect automatically and with- graphs, he will be able to trace out out the need for any conscious receiverisnotmerelyperfectly the way all the H.F. circuits have effort on the part of the con- spaced, but it is also as direct and been taken out from the conglomera- structor. short as well as can be.In a word. tion of stray wiring, decoupling con- (6) Surely justifies the use of the it is efficient. densers, screening, and general odds word revolutionary ? The fact that all important wires and ends with which they are so often run straight from point to point and

287 MODERN WIRELESS October, 1933 New Ideas, New Simplicity, New Performance Values need no bending to shape or running unimportant wires like filament con-the points to be connected and pull round corners is one obvious reason nections, all those in the tuned circuitsit tight. why a Step setissoeasyand and so on going quite straight from This in itself is a development of quick to wire up.Not one single wire point to point. great significance, for it means that in the K4 needs to be bent into any What this means in making the sethere for the first time is a set for the particular shape, and the whole set easy and quick to wire up need hardlyhome constructorwhichcanbe can be wired up correctly with the be explained, for it is quite obvious,duplicated with almost perfect accur- aid of the following rule :wherever but what is not so evident is a veryacy by everyone who builds it. possible, run each wire in a straight important subsidiaryeffectof the Assured Satisfaction line between the points which are method which I must emphasise.It to be joined. follows from what I have explained So long as suitable makes of com- that the run of the wires is reallyponents are used the wiring quite Duplication with Accuracy automatically becomes a perfect copy fixed by the positions of the com-of that of the designer, and all without If there is an obstacle in the way, ponents, i.e.by the designer of theany difficulty or even effort on the take the wire round it by the shortest set, and not by the constructor, sopart of the constructor!Surely that possible route.It will be found that long as the latter obeys the injunctionis a great step forward in assuring to stretch every wire straight between this occurs only in the case of quite thesetbuilderof completesatis- THE VIRTUE OF KEEPING TO A STRAIGHT PATH ! faction at the end of his labours ? Always in the past there has been a feeling among constructors that the sets they built might not function so well as the original models of each design, simply because the spacing of the important wires had been less successfully done. For this feeling of uncertainty the designer himself has been to some extent to blame, for he has, I think, tended to exaggerate the importance of lead spacing. Importance of Spacing Making all due allowance for such possible over -emphasis, the fact remains that sets built to the same design but wired differently would undoubtedly perform with varying degrees of efficiency. That feeling of uncertainty has been banished completely and finally by the Step System.No longer need the constructor have the slightest doubt that he will be successful in making so perfect a copy of the originalwiringthathecanbe assured of duplicating precisely the original results. And now a final point before we leave the Step System. I want to make it very plain that spacing is reallyofgreater importance than length of leads, especially in ensuring stability with high -magnification H.F. stages. The common idea that the length of the leads is a fair measure of the efficiency of the wiring is really due to rule -of -thumb design methods. It was discovered that short leads often meant a set which worked well, and it was not realised that the real reason was that short leads gave less chance ofinter -actionwithneighbouring In old-fashioned sets the vitally important H.F. coupling choke was often stowed awaywires, even if the spacing was not too in some corner where it could neither be got at nor wired efficiently.See how the Step , good. System treats it: perfect accessibility, perfect directness of wiring.

288 October, 1933 MODERN WIRELES3

my object was to get the desired results with only two tuned circuits IF you were to assemble the K4 if I possibly could. circuit on the old-fashioned panel I regarded this as very important, andflatbaseboard system, I for it seemed very clear that gang believe it would still be the best four - tuning was out of place in the kind valve battery set so far described. of set I had in mind :the receiver As a matter of fact, I did all my ex- I wanted to design was to appeal perimental work on the circuit with A full description of the care- to the home constructor who makes a the aid of a test receiver made up hobby of radio, and to him, I know, fully engineered circuit whose ganging is merely a nuisance which in that fashion, and it was only when detailsaretheresultof I had developed the circuit to such a several years of research, has to be tolerated when there are pitch of perfection that I was sure it with a complete explanation three or more circuits for the simple was the best I had yet handled, then, of the important principle of reason that he has only two hands. and only then, did I allow myself the " ToneLevelling " which Why Ganging? luxury of rebuildingon the Step plays such a vital part in System. After all, why should he have to giving the K4 its extra- have his sets ganged ?" One -knob No "Hocus-Pocus " ordinary efficiency. tuning " wasfirst 'introducedfor This, of course, was a very impor- the benefit of the lay public who, poor tant precaution, becauseifI had souls, know nothing of the finest started with a " stepped " receiver been studying the problem of getting hobby in the world and find even anddone my experimentalwork areallysatisfactoryperformance onedialtoo much for them at therewith,it would have been sofrom the battery set, and carrying times. easy to think that I had developed the out researchon both thebroad The novelty of the thing at first circuit to the desired efficiency when general aspect of the question andattracted the rest of us, and I think all that I was getting was the normal on the specialised detail problems the publicity talk that went on in improvement due to the Step System which are involved in it. favour of the new ganged sets when alone. they appeared must have made some When I refer to " developing " Only Two Tuned Circuits impression upon us ;but before long the circuit to the required degree of My aim from the first was to give we got a clearer view of things and efficiency, I do not want to give a the battery user the same volume and began to see that the set for the false impression.I am not pretend- quality which is available to the mains general public has really little or no ing to be able to take just any set owner, and a standard of selectivity relation to the one which appeals circuit and perform some sort of and sensitivity adequate to ensureto the hobby man. magical hocus-pocus over it until it real programmes from a large number All that the general public wants becomes the very last word in super of stations whenever conditions per- is a set with the best possible per- " hot stuff " receivers ; anyone who mit.The first object only became formance and appearanceatthe could do that would beableto capable of attainment with reason- lowest cost and with the least trouble produce one of these special " star " able economy of H.T. current when in operation.The home constructor, sets whenever he wanted to, and to " positivedrive "outputcircuits itistrue, wants performance and the best of my belief there is no such were developed, while the second I appearance at low cost, too ; but a set individual living. soon found depended upon the usemeans far more than that to him, oftunedcircuitsofconsiderably for the pleasure which its construction The Origin of the K4 lower H.F. resistance than those inand use gives him depends toa The actual process by which suchuse when I began my investigation. large measure upon the success with sets come into being is very different, The last is a point which I should whichitprovideshimwithan for they are essentially the result of like to explain, for it is rather im-opportunity to exercise the know- quite a long period of thought and portant.What I actually found was ledge and skill which it has taken him research on general lines which only that so long as I used tuning coils years to acquire. gradually crystallises into an investiga- of the comparatively high -resistance tion in some definite direction, usingtypes which were current until quite A Misleading Way a particular circuit as a basis.The recently, it was necessary to use three Thefinestoflife'sintellectual final development of the circuit totuned circuitsto get the sortof pleasures is surely to be found in the highest possible pitch of efficiency results I wanted, and that in turnjust that same use of acquired skill is thus largely a matter of experi- meant band -passing and gang tuning, and knowledge in some worth -while mental work on its smaller details, with all the expense and troublesome accomplishment, and thatispre- the broad outlines having been settled adjustments which those two thingscisely what a good hobby gives us. long before. bring in their train.For this reason Radio does it to a superlative degree, So it was with the K4. I turned my attention to the problem and brings us as well the pleasure For more than two years I have of higher efficiency tuning coils, for and interest of entertainment from

289 MODERN WIRELESS October, 1933 G. P. Kendall Explains the Principles which- all the corners of the earth, which is results which have to suffice for the A little while ago this would have probably one reason why it is beyond general public.Only in exceptional been considered a highly criminal question the finest hobby of them all. cases is it a successful substitute over proceeding, for everybody was then Be all that as it may, it must be the whole of the timing range, more infatuated with the idea of band-pass agreed that a considerable part of the particularly in the home -constructed circuits, and the principle of L.F. pleasure of using a radio set is, to the set, so itis my contention that itcorrection was little appreciated out- keen experimenter, a matter of using should only be used in such receivers side certain commercial laboratories one's skill in operating it.After all, when it is really necessary. where it was being developed. it is the possession of that skill which I saw a great deal of this research, distinguishes the experimenter and Litz Wire Researches and did some ofit.myself, with the constructor from the layman as an To get the results I wanted withresult that I became convinced of operator, and enables the former to only two circuits, I soon discovered, the fat that herein lay the solution get better results from almost any meant better coils than were generally of my problem. receiver. available until quite recently, and so Let me explain.Instead of using gfie Starting 'Joint of tfie gC4's evetopment

Iii

Z..T

Here is the elementary outline of the circuit on which the final highly perfected K4 arrangement is based.This diagram is intended to serve as an introduction to the fully detailed one on a following page, which shows the complete K4 circuit with the Tone Levelling device, the instantaneous signal -quenching scheme which is operated by the on -off switch, and all the other special features. What ganging does, we are some- I have spent a good deal of time onall the tiresome and expensive com- times told, is to enable the laymanresearches into the use of what isplications of the band-pass circuit, to get as good results as the skilledcalled Litz wire for the purpose ofin order to avoid the weakening of operator, but I think this is a most lowering the resistance of the coils. thehigheraudiblefrequenciesin misleading way of looking at the The results I got soon proved that I relation to the lower ones, the L.F. question.Actually, what it does is was on the right track ; but, of course, correction method puts the balance to enable the layman to get fairly it was not very long before the special rightagain by theuseoflow - goodresultswhere previouslyhe iron -cored coils began to be heard of,frequency amplifying circuits would have got little, but at the same and therein I found the entirely satis-which have what is called a rising timeitprevents theskilled man factory solution of my problem. characteristic. from getting any better performance, The two tuned circuits of the K4 By this is meant that they amplify as he generally would if he could use will therefore be found to contain coilsthe weakened upper frequencies more his skill in making separate adjust- of the Colvern " Ferrocart " type,than they do the over -emphasised ments. which I have found to be very satis-lower ones, and if the one effect is factory representatives of the newcunningly set off against the other, A Poor Alternative class of high -efficiency coils.These the result is reproduction of a per- Gangingisjust a rather crude circuitsare arranged togivethefectlynormal,correctlybalanced mechanical substitute for the skilled maximum selectivity, without regard tone. fingers and trained ear of the ex- (at this stage) to the effect on quality To get this,of course,calls for perienced operator, giving passable of reproduction. considerableskillon thepartof

290 October, 1933 MODERN WIRELESS Make the K4 His Greatest Achievement the designer, and it can really be corrected, even for those cases when in the range of control afforded by achieved only in the large set which reaction is being used almost up to the the leveller there will be a point at does not use reaction.Even then practical limit.In other words, it which a correct balance is obtained. thereisliableto be some slight has such a steeply rising character- Further, this point of correct balance amount ofregeneration going on istic that it would result in the re- can always be found for any par- whichwillvaryinintensityat production being a little too " bright " ticular transmission, whatever amount different points on the tuning range, at all times, and decidedly so when no of reaction may be in use. so that the correction will not be reaction is being used. exact for all stations. This gives us our " margin of con- "Tone " Without Risks trol," and makes true tone levelling It is an extremely quick and easy "ToneTone LevellingLevelling" possible. We achieve it by providing adjustment to make, for one merely The principle, by the way, provides inour over -correctedL.F.ampli- gives the leveller knob a twist one a very interesting example of thefying circuit a device that I call away or theother, and in a few way the commercial designer works ; leveller, whichisineffect a tone moments a normally balanced tone can instead of aiming at a well-nigh impos- control of a special type operating be obtained.It is not an adjustment sible standard of perfection at every entirely in a downward direction ; that calling for frequent re -setting, for it stage of his receiver, he allows an is, with the control set at one end of will usually be found that one adjust- imperfection to occur at one pointits travel it has no effect, and then ment will serve for all distant stations where it may have some sortof when it is taken round towards the which needreaction,anotherfor incidental advantage, and then cor- other end of its range it lowers the those which do not (these are in the rects it with an imperfection in the tone progressively. majority, of course), and a third for oppositedirectionatsomeother Since westartedwithatone the local station. point in the set. The result is just as qualitywhich wastoohigh,or Actually, it is not a critical adjust- good as that obtained by the less " bright," it follows that somewhere ment, and quality is quite bearable practical" theory merchant," and the method yields a great reduction THE K4 POSSESSES SELECTIVITY IN EXCELSIS ! in the cost and complication of the receiver. It fails, however, in the case of the set which uses reaction, because the amount of correction needed varies according to the amount of reaction being applied at any given moment. Thereasonisobvious : reaction varies the sharpness of tuning, and it is this which governs the amount of L.F. correction required. To get over the difficulty in the caseof my ideal receiver, I have adopted aprinciple whichIcall " tonelevelling,"whichisone of the very important features of the K4. Getting Correct Balance At first glance you may think that this consists merely of the use of a tone -controlled device, such as has been used many times before, but actually it is something much more than that.It is, indeed, a develop- mentofthehighestimportance, without which (or some equivalent) no set of this type can in the future be considered complete. This is how it functions :we start by so arranging our tuned circuits (in the interests of selectivity) that they produce low -toned reproduction, with an excess of low and a deficiency An important feature of the K4 is the method of achieving high selectivity.There is the of high frequencies, due to the ex- usual control in the form of an adjustable capacity in the aerial lead, but there are many treme sharpness of the tuning.We other features which play their part.The H.F. resistance of the tuned circuits is exceptionally low, and it can be forced to extremes by reducing the amplification of the follow this up with a low frequency variable -mu S.G. valve and applying strong reaction at the detector stage.This restores amplifying side which is a little over- the lost volume, and quality is maintained by an adjustment of the tone leveller.

291 MODERN WIRELESS October, 1933 The First Set in Which the Secrets- if it is completely out.What this general idea of the basic principle potentiometer which provides the bias means, of course, is that the range of on which the electrical design of the adjustment on the S.G. valve. Observe control is only just sufficient for the K4 is founded. that one element of the three-point purpose, so that it is not possible to It is really just as important in its on -off switch for the whole set con- make the quality unpleasant by put- way as the " Step " principle, which trols a connection in this potentio- ting the leveller right out of adjust- is the basis of the mechanical design, meter circuit in such a way that in ment.Its effect is just sufficient to and has just as much to do with thethe off position the current from the enable you to get properly balanced wonderful performance of the set. biasbatterythroughthepoten- tone at all times, without the risk of Now let us see more in detail how tiometeriscutoff,but thefull any unpleasant noises due to wrong these various effectsare obtained. voltage of the battery is then applied settings. First, the sharp tuning of the in- to the grid of the S.G. valve. dividual circuits, and hence the high

A Basic Principle selectivity of the set as a whole, is . Reaction Arrangements These questions will, of course, be due to the very low H.F. resistance The result is that as soon as the set gone into in greater detail in the of the coils, to the use of a compara- is switched off any signal which was separate article on the operation oftively small series aerial condenser, beingreceivedwillbeinstantly the set.It must be remarkedin a special tapped input and tapped grid quenched out by the excessive bias passing, however, that the levellerlead in the H.F. intervalve circuit, on the S.G. valve. This is important, has another important use, that being and the use of a variable -mu screened for if the signal were allowed to go on toreduceheterodyneinterference grid valve. for the brief instant while the valve when it is necessary to do so even at a filaments were cooling off there would slight sacrifice of quality, as is some- Maintaining Quality be a considerable risk of damage to times the case.It is possible to set the This last is only an indirect cause, the Class B output valve. various controls so that there is ait is true, the point being that with In thedetectorstage you will considerable cutting off of the highest such a valve the volume of a given observethatmattershavebeen audio frequencies, and a consequent station can be turned down by means arranged with much care to secure reduction in the strength of an inter- of the bias control and then brought the maximum sensitivity and enable fering whistle.The selectivity of the up again by the fairly strong use of the best possible use to be made of K4 being so high makes this an reaction, whereupon tuning becomes reaction.Note the way the reaction unusual occurrence, but thereare even sharper.Quality is maintained circuit is arranged, with a 500 -ohm. occasions when it is the lesser evil. meanwhile, of course, by the levelling resistance to prevent parasitic oscilla- This is a brief and by no means process. tions,the .0002-mfd. by-pass con- exhaustive explanation of the im- A novel detail refinement which denser from plate to filament, and the portant development of tone levelling, may be noted at this point concernsnow unfashionably large capacity of but it will serve to give the reader a the connections of the 50,000 -ohm the grid condenser. Iffie JC4 Secrets .revealed AITAI HT,/.2 HT+4 COMPENSATING Z 7k190I.VC

.011"'I''re0000 D 8 A 684 60-0000 GRID H.FG C ato 0003 MAD MAX CI

4SPIALCo/L 7ave CONTROL

C9 MAD

002 CIO WO FUSE ON -OFF 00 I Hr wi rcH /0\ L.7

-NANVVVVV` 50,000 OHMS 2 Voz.ehtfeccvvreoL. 1111IIII GB. Here is the ercuit which co-operates with the Step system construction to make the K4 such an outstanding achievement inreceive r design. Many of the special features can be understood from this diagram, but the vital principle of tone levelling canonly be followed from the description in the text.

292 October, 1933 MODERN WIRELESS -of the" Tone -Levelling " Systemare Revealed

Following after the detector youis, and how far ahead of contem- The essence of commercial design will see a transformer -coupled L.F. porary design. work is that it is conducted within stage, and it is here that most of the To sum up, I think we may say sharply defined limits, of which cost tone correction is done, the trans- thatitisthefirstsetin which is only one.The designer who can former used being of the " compen- modernengineeringmethodsof get his results successfully within the sating " type.A certain additional balanced design have been combined limits which he must respect has to tendency to a rising characteristicwith all those features which the exercise a degree of skill and ingenuity isobtained in the Class B output home constructor values most.In which is far in advance of that re- circuit, where I have omitted the quired under the free and easy con- usual tone -lowering condenser and PERFECT SPACING ditions which usually obtain among resistance for that express purpose. those who provide designs for the home constructor. Conserving the H. T. There are other points of a special Attention to Details nature in the circuit, but they are To get his results in spite of the mostly matters of detail, and can be limitations imposed upon him, the taken for granted. The one exception commercial man mustobviously is the tone leveller, which consists devote much thought and research of the fixed condenser of .01-mfd. to his problems, and the training capacity and the variable resistance which he unconsciously receives is of 50,000 ohms which you will see of the utmost value in teaching him in the plate circuit of the detector. that no detail is so small that it can In effect the condenser is shunted to a be taken for granted.Every one greaterorlessextentacrossthe must be scrutinised most carefully, primary of the compensating trans- and nothing must be regarded as former, and so has a variable by- too trivial to receive its due share of passing effect on the higher frequencies attention. controlledby thesettingofthe Let me take an extreme example of variable resistance. the way he must go into even the This method of tone adjustment, most seemingly minute details if his by the way, has an important in- work is to be as successful as it should cidental advantage which should be be.It may come as a surprise to the mentioned. Itwill,of course, be reader to know that a good designer known to the reader that the H.T. will go so far as to devote anxious consumption of a Class B stageis thought to the question of the kinds proportional to the strength of the of screws to be used in assembling signals which itis handling, and a his set, but it is true. moment's thought will show that it is First, there is the question of the bad policy to allow undesired fre- material of which the screws shall quencies to get as far as the output be made, the general choice being stage and then tone control them out between brass and plated iron (or of existence. A beautiful example of the way the Step mild steel).The iron screw is cheaper To do so is merely to waste H.T. System ensures perfectly accurate spacing and also stronger, so that a smaller in amplifying them, and then throw of every lead.All that the constructor size can be used, but it is prone to has to do is to stretch the wires between them away, soto speak.In the the points to be joined and pull them tight. rust if exposed to a damp atmosphere. K4 the levelling system ensures that Consequently, you will often find that H.T. is only used to amplify fre- making that combination, of course, iron screws are used in mains sets, quencies which are actually wanted Ihave been sofortunateasto where the designer knows that the and will be allowed to reach the beableto draw upon both my slight warmth from the valves will loudspeaker. considerable experience of commer- keep the inside of the set fairly dry, cial design and an acquaintanceship whereas in battery sets brass screws Combined Advantages oftenyears'durationwiththe are more likely to be seen. I rather stress this point, because likesanddislikesofthehome the opposite procedure is so common constructor. Saving Money that the reader may wonder why Of the two I really do not know In sets for certain overseas markets, Ihave not followed the fashion. which has been of the greater value of course, the effects of damp must Actually,thisisjustone more to me. One sometimes sees commer- be borne in mind very carefully, and illustrationofthefactthatthe cial designs spoken of in a mildly here the screws are practically certain design of the K4 has been engineered, patronising sort of way in journals to be of brass.Many of the other and not merely strung together on devoted to amateur radio matters, materials of the set will in these cases the lines of abstract theory. but those who do thisare really also be chosen with due thought for There, we have now completed our thereby convicting themselves ofa their damp -resisting powers. survey of the K4 circuit, and I think great lack of understanding of the Having decided upon the material the reader will be beginning to get an commercial man and his aims and for his screws, the designer who knows, idea what a remarkable set it really methods. his job will next go over his set in

293 MODERN WIRELESS October, 1933 Valuable Lessons from Commercial Work detail to see whether he can reducefromcertainobviousmechanical which rather illustrates my point. any further the number of differentlimitations, the rivet or eyelet system The reader will probably have noticed sizes of screws required in its assembly.has the serious drawback that once a that in many Class B sets the output The fewer the sizes needed, of course,part is attached by this method it is circuit is just a maze of by-pass con- the larger the quantity of each thaton for keeps, and a surgical operation densers, put there for the purpose of will be required, and so the lower the is needed to get it off ag combating the well-known tendency price at which they can be bought. Serious problems connected with ofpush-pullcircuitstogenerate Fewer sizes mean money saved in oscillations of a high audible or super - handling the screws in the stores, ERRORS RULED OUT audible frequency. and alsoin the operations of the Just how strong this tendency may buying department of the firm.In or may not be in the case of a modern some casesit may even pay to " B " stage, no one seems to have eliminate one or more of the shorter taken the trouble to try to find out. lengths and use a longer one which is Instead, the warnings of the valve required at some other point in the makers as to the dire consequences set,butnotalways, because the of allowing a " B " valve to oscillate longer screw is more expensive, so you would appear to have led to a panicky can see what complicated questions determination to put in every possible even the smallest details can raise for kind of a " stopper," with the result thecommercialworker,and how that the cost of the set goes up by involved his task really is. quite a number of totally unnecessary shillings. Problems of Servicing In some cases he has even to con- The Oscillation Bogy sider whether he shall use screws at Now look at the circuit diagram of all,or decide instead in favour of the K4, and you will see that a single rivets or eyelets.This method of 002-mfd. fixed condenser is all I have assembly has many advantages in a provided to prevent these dreaded set built upon a metal chassis, for the effects.I have done all I can to make materials are considerably cheaper the set go into audio oscillation, and than screws and nuts, and assembly is it just will not do it, so you may be speeded up a great deal. pretty confident that here also I have Instead of the comparatively slow saved you some money ! process of inserting screws and tighten- Actually, I believe the oscillation ing up nuts, the assemblers have bogy hasbeen very muchover- merely to drop the rivet or eyelet in estimated in the case of Class B place and a punch does the rest. You cannot fail to produce a perfectly wired circuits, especially in those which are From the designer's point of viewcopy of the K4 design if you just run your wired up with a little care.Where the method has also the importantleads straight from terminal to terminal. I have found it troublesome, curiously advantage of making as near certain enough, is in the quiescent type of as is humanly possible that everyservicing therefore arise, and they circuit. partwillquiteautomaticallybemay be so weighty that the method In the K4 the single condenser of securely attached, a matter which isis ruled out.Imagine the struggles 002 mfd. is adequate, and itis not otherwise dependent upon the skillof a serviceman trying to replace a even critical in value.Actually, the and care of the assemblers. rivetedpart with hislimited tool only capacity in the set which can be The reason why the system is notequipment, while the customer calledcriticalis the one of0002 universally used is a good example ofwatches him !Actually, any set of (detector anode by pass).If this be the way the commercial designer mustthis kind has almost always to be much increased the set will not oscillate weigh up all the factors and balancesent back to the factory for even the at the bottom of the dial, probably one thing against another. Apartsimplest of replacements. on the medium waveband. It is therefore considered suitable only for those very simple kinds of sets, mostly of the battery -operated TONE LEVELLING variety, which can be depended upon SIGNAL QUENCHING In the tone -levelling system used to need very little servicing.It may Typical of the thoroughness of in the K4, Mr. Kendall makes the occasionally be seen in mains sets, Mr. Kendall's design work is the first properly -engineered appli- but itis rather rare in the bigger provisionintheK 4 of a cation of the modern principle ones, and when it is seen therein it special device to quench the in- of tone correction to the needs of denotes either a quite unusual degree coming signal the instant the L.T. the home constructor's type of of confidence on the part ofthe switch is opened.The emission set. Theresultisperfectly designer, or else the fact that he has of the " B " valve is thereby safe- balancedtone underallcon- been over -ruled by the production guarded, yet the cost of the set ditions, with complete control by department ! is not increased, again a very the user. After which digression I should like characteristic touch. to return to a detail of the circuit 294 October, 1933 MODERN WIRELESS

00060\koom,. \\01 0\00 BuILD E

00000000001

Superb Performance-Unparalleled Ease of Construction-Automatic Accuracy of Wiring IIMAGINE that if any designer has If,of course, you buy your Stepand you will soon find it can't be ever failed to remark that his frame ready-made, the question will done ! latest set is particularly. easy tonot arise, and I expect itwill be It doesn't matter, however, because build, it must have been the result of possibleto do this,for the usualall you need do isto refer to the pure forgetfulness !It's just one ofenterprising firms are pretty sure to drawing in my separate article on the those things that one does always say, offer it complete and ready for use. Step System and you will see exactly and of course it is always true, because I don't know what the price will be,what has to be done.All that I am there is progress in these matters, and but it should be very moderate, anddoing here is to suggest that it is best so well -designed sets get more andno doubt those who are not fond of to start by fixing the two short spacing more simple to build as time goes on.carpentry will take advantage of thepieces to Step No. 1 (bottom member). Unfortunately, however, the idea fact. In doing so, be careful to see that has gradually come to be taken as a you get the two edgewise bits parallel matter of course, and now that I The Best Start to each other, and at right angles to have to introduce a set which marks Even if the constructor decides tothe piece which forms Step No. 1. a really substantial step forward inmake his own framework he will findThis done,the wider piece which simplicityofconstruction,I wantit a perfectly simple job, but if h3forms Step No. 2 must be screwed to some stronger word than " easy " tolikes woodwork as little as I do hethe other edges of the spacer pieces. emphasise the fact !My vocabularywill be well advised to do as I did and To see where this should be attached doesn't seem equal to the task, for allget the local joiner to cut the fourreference should again be made to the the superlatives that I can think of atpieces of wood to size for him, sodrawing which I have already men- the moment either understate the case that he has merely to screw them tioned.As a guide I would mention or else sound positively hysterical, sotogether. that the front edge of Step No. 2 I think I'd better let it alone and trust I should have got the screwing doneshould come exactly over the rear edge to the reader to see for himself thatbut for the fact that I was anxious toof Step No. 1, without overlapping at the ease of construction of the K4preserve the secret of the Step Systemall, another point which will become issomething inquiteadifferent as long as I could.I was obliged,clear after inspection of the drawing category from that of any set builttherefore, to do it myself, and muchand almost any of the photographs. on the old-fashioned panel and base- as I dislike working in wood I must board plan. confess that it proved such an easy Making a Strong Job and quick job that it was over long To make a really strong job it is The Step Frame before I reached the stage of mutteredbest to glue the joints in addition to Let us therefore make a start andprofanity to whichI am usuallyscrewing them together,andthe see what we discover as we go along.reduced by such operations. easiest way to do this is to assemble We might well begin with the Step This is what has to be done. Youthe frame first of all without the framework, for that may have struck take the piece of wood which measuresadhesive, then take it apart again the reader as a possible source of 18 by 21 inches (Step No. 1) and to theand smear the joint surface lightly difficulty, and we may as well findends of this you screw the two shortwith any convenient " sticker " like out right away whether any awkward- pieces, edgeways toit.Not very" Seccotine," after which it can be put ness is really involved in putting itlucid, did I hear you sayWell, youtogether again finally. together. try and put it clearly in wordi yourself By the way, it pays to Seccotinc " MODERN WIREESS October, 1933 Your K4 Can be as Good as the Original just one joint at a time, screw that Panel drilling is a job we all under- accordingtothe typeofcabinet one together, and then go on to thestand, I think, and I am not going towhich will eventually house the set. next. No doubt if one was sufficientlyinsultthereader'sintelligence byIf this will cover the screws they may careful it would be satisfactory totelling him how to do it.There are, beofthe C/S head variety, but treat all the joints at once and thenhowever, one or two points peculiar to round heads are to be preferred in proceed with the assembly, but inthe Step System, or to the K4, tothose cases in which they are left practice it would be found awkward towhich I must direct his attention. exposed by the cabinet -work. handle all those bits of wood with The important point really concerns sticky places at each end. An Important Point the position at which the framework There is no real need to put the First, there is an important littleis attached to the panel, for it is not finished frame aside for the joints todetail about the method of attachingdifficult to go wrong here.The point set, because they will be held quitethe panel to the Step framework. isthis :the side members of the sufficiently by the screws, and youThis is done by passing screws throughframe must be fixed at such a height could if you wished go straight aheadthe panel and into the ends of thethat there is a space ofin. between and mount the components in theirtwo woodenside members of thetheir undersides and the lower edge places. However, you really want theframe.These screws should be ofof the panel. panel with all its parts mounted there-fair length, since they have to stand Let me make thisquiteclear. on to help you with the interior layouta considerable strain while the set isExamine one of the photos showing of the set, so if you next drill the panelbeing handled, and I suggest fin.the finished set, and imagine that it and attach the various componentscnes, round or countersunk heads,is standing upon a table, out of its which belong there it will give the framework joints a chance to harden a bit. THE K4 READY

Thisis what YOUR K4 will look like when itisfinished and ready for work, for the beauty of the Step System is that it makes it as certain as anything can be that the constructor will make a perfect copy of the original.

296 Oct( ber, 1933 MODERN WIRELESS

WITHOUT A DOUBT THEY MUST INCLUDE SELEC- WHAT ARE THE PRIMARY TIVITY RANGE - POWER. ESSENTIALS FOR A FIRST- THE K4 ANSWERS " YES " CLASS RECEIVER ? TO THESE THREE MAIN REQUIREMENTS.

The second Stepprovides accommodation for the grid - biasbattery, in the position occupied by the three plugs seen in this view.In many cases asingle 9 -volt unit will suffice, but two can be connectedin series when higher voltages are required. cabinet.Resting in contact with the Instead, we may in some cases want home in the cabinet, but I found that table will be the lower edge of the to fix in this position a much narrower better support was given if the fillet panel and the underside of Step No. 1 strip of wood than a Step for the was removed from its original place (the one on which the valves arepurpose of stiffening the lower edge and refitted in a corresponding posi- mounted).The lower edges of the of the panel.This must be done in tion along the bottom of the cabinet, side members of the wooden frame some suitable fashion,forifitis so that the lower edge of the panel (the two spacing pieces which separate merely supported at the ends where it rested against it. the two steps, and are placed on is screwed to the side members of the edge) will not touch the table, but will Step frame it will be rather whippy, Panel Support have a space ofin. underneath them. and the controls of the set will be When thisisdone some small difficult to operate. screws can be passed through holes A Third Step There are various ways of producing in the lower edge of the panel and This space is equal to the thickness the desired stiffening,the simplest into the fillet, whereupon the panel of Step No. 1, and would leave room being the one I used myself.This will be found to be well supported. for another strip of plywood to be applies to those cases in which theSuitable positions for the holes for screwed to the underside of the side cabinet is of the type where the set these screws are indicated on the members ifdesired.Thus, a thirdpushes in from the front, and in panel drilling diagram. Step could be fixed so that it was which a little strip of wood called a If the cabinet employed is of the close up against the back of the panel, fillet will usually be found running kind in which you push the setin at the same level as Step No. 1.In across the top of the cabinet inside. from the back, this method of panel some sets I can imagine that such an It is intended that the upper edgesupport will not serve, and itis in addition might be helpful, but it is of the panel shall rest against thisthese cases that the extra strip of not needed in the K4. fillet when the set is pushed right wood should be attached to the Step

297 MODERN WIRELESS October, 1933

B 41/2J ALL IT NEEDS Here are the actual dimensions of thelittle screen whichis allthat the K4 needs to ensure adequate stability. A comparison with the elaborate screening of earlier types of receivers will help the reader to a better understanding of the remarkable efficiency of layout spacing which can be achieved with the aid of the Step System. To dispense with elaborate screen- 311 ing not merely makes construction easier,butremoves apotential source of losses of various kinds. You can get your K4 screen ready cut to these sizes and bent to shape. r 4ER/AL

ONLY FOUR TERMINALS LE The battery leads take the form of flex connections 6 made direct to the appropriate points on certain components in the receiver, so the only terminals which the set needs are those for aerial and earth, and loudspeaker. The drilling points and dimen- EARTH sions for two little ebonite plates to carry these terminals will be found in the diagrams on the -41;4;211 left. tt Note that they form a right- and left-hand pair, and bear thepoint in mind carefully when i countersinking the holes for the screw -heads. L2e/LL/NG DETA/LS QE 7A:frown/AL gz. o c A -s

TUN/ 2y"CONDENSER CONDENSER ROLE

\ ON- OFF r,,' rf I 1 ,-J:5;:1//roCL: ,, , %LS

: - 1 ntr- , 1 repvz- , ...- (co,v I'%L' ,--. j 1 e , Af; HOLE .1L \-,/ 'I;i-i I \ VOLUME\ 4 Az -- Co,vr,ecx - _- 4,,,,oce o ROT ;11E TER 2/ .3" 3, 3" /8" 6° 6" -Z4-37/1: PANEL DR/LL/NG D/AGRAM The sizes for the holes given here are correct for the spe.:ifl.id mikss of components.This is a point which should be taken into account if any changes are made in the makes actually used.

298 October, 1933 MODERN WIRELESS

Real Moving -CoilVolume

frame itself,This strip should be ofthat I have done something whichmounted, and the position for this is the same thickness as the rest of thewould have been better done differ-not critical, so long as it is just lined woodwork, i.e. g in., 18 in. long, andently, I just reach for the book andup by eye with the other unit. Next about 1 in. wide, and it should bemake anotetherein,insteadof the two wavechange switching rods screwed to the side members, so that it wasting time in calling myself names. should be slipped through the coils, runs along behind the lower edge ofThen when the time comes for thethe long spindle being placed in the the panel. " How to make it "article to beF3 unit and the short one in the F10. written, I go through my notes andThe long spindle, of course, reaches No Piecemeal Wiring see that my readers are duly warnedto the panel and is inserted in the To secure the maximum supportnot to do likewise. By the way, thebushofthecontrolknob,being for the panel, screws should be driventitle of the book, it is to be under-secured therein in the usual manner through holes in its edge as before,stood, refers to myself, not to mywith a grub screw. and into the stiffeningstrip.The esteemed readers ! same positions will serve for these The first thing I discover from my Linking the Coils screws as those referred to in con-notes on the K4 is that it is advisable The short spindle is linked up by nection with the previous method, and to mount certain parts in Step No. 2means of the Telsen coil ganging de - the drilling diagram should, therefore, be consulted. ONE KNOB CONTROL OF WAVECHANGING The stiffening strip, by the way, should not be fixed in place until the wiring of the set is finished, in order that access to the various parts on the back of the panel may be as easy as possible while the wiringisbeing done.The strip does not get seri- ously in the way, but things are a trifle more accessible if it is not there. With some sets, it is best to wire up the parts on the panel, as far as possible, before screwing panel and baseboard together, but there is not the slightest need to do so with any set built on the Step System. Every component on the panel remains completely accessible after the panel is attached to the frame which replaces the baseboard of the old-fashioned set, and can be wired up with the greatest of ease.The assembly of the set can, therefore, be carried right through to its conclusion, and then the wiring can similarly be done as one completejob. Thereisan obvious saving of time here, and the elimination of the risk of wiring errors due to carrying out the operation in two stages.

Order of Assembly The wavechange switching spindles are linked so that they may be controlled from the There are just one or two special customary single knob on the panel, and it is interesting to note that the linking device points I should mention about the must be earthed as shown on the Construction Chart by the lead marked AN. assembly process which will save thein a particular order if the job is tovice, the fitting of this being quite constructor time and trouble, beingbe as easy as possible.This is howobvious upon inspection.See, how- mostly things which I did wrongyou should set about it :Fix first of ever,that the twocoilswitching myself when Ibuilt the first K4.all the F3 type coil unit, taking carespindles are in the same positions In this connection, the reader mayto line it up accurately with the holebefore you finally tighten up the grub be amused to learn of alittlein- in the panel forthewavechange screws of the ganging link, otherwise stitution of mine which enables me spindle, slipping the spindle into place you will find that one unit is switched to make quite certain of including allto act as a guide while you do this.to long waves when the other is on such points in my articles for theOf course, you will also be careful tomedium. To guard against this just benefit of those who will follow insee that the coil is mounted the rightsee that the flat on each spindle points my footsteps. way round,so that the terminalsthe same way. Whenever I build a set I havecome in the positions shown on the With the two coil units in position beside me on the bench what I callConstruction Chart. and their controls linked up success- the " Silly Ass Book," and when I find The F10 type coil should next befully, you should next proceed to fix

299 MODERN WIRELESS October, 1933 " Unscrambling " the Radio Receiver

This photograph of Mr. Ken- dall's wonderful new set was deliberately taken (at his own request) from the angle which makesthewiringlook as confused as possible.The set emergestriumphantly from theordeal, asthe designer knewitwould, and as the photo conclusively proves; yet if this same circuit were assembled on conventional lines the result would inevitably have been such that nodesignercouldpossibly have allowed the view to be published ! Vdriey,, r.oiosrlsxmg W.ofivt%

300 October, 1933 MODERN WIRELESS Novelty in Design, Novelty in Performance

the 0005-mfd. fixed condenser which actual explanation.It is a perfectlywith athinner and more flexible goes alongside the F3 unit.If youstraightforward job,in which thematerial than is commonly used. examine the wiring blueprintyou photographsandchartwillgive I used, and strongly recommend, will find that a connection comesyou all the information you need, butordinary tinned copper wire of No. 20 away from one terminal of this con-the same warning as to taking reason-gauge, which can be pulled straight denser and goes down through a holeable care to position the parts cor-with very little strain, especially if it in the Step to a terminal of the .0003-rectly should perhaps be repeated. is given a preliminary straightening mfd. condenser underneath, and the As regards the two little terminalbefore use.(Cut it up into lengths hole for this should next be boredplates, one of which will be seen atof about 18 in.,and give each a close up alongside the condenser.Iteither end of Step No. 1, these can, ofgood stretching by clamping one end rather depends on the kind of weaponcourse, be cut, drilled and fitted within the vice and pulling hard on the you are going to use to make the hole,their terminals at any stage of theother with a pair of pliers.) but in some cases it may be easierproceedings, but I should advise that just to mark out the position for thetheir fitting should be left until the Straight Wiring Methods condenser first and then bore the holewiring of the set is finished as far as For the best results, the wire used before actually fitting the componentit can be done without them.The should not be thicker than the gauge in question. reason is simply that they make it aIhave mentioned,but thenext little difficult to wire up certain parts Avoiding Accidents thinner (No. 22) could be used if at either end of Step No. 1 if they areNo. 20 cannot be got.If you find it With the hole bored and the .0005fitted too soon. This applies moreimpossible to purchase eithersize condenser in position, you should nextparticularly to the L.T. leads for thelocally, and don't want to wait until fit the .0003 condenser on the under-set, i.e., the flex lead which goes offit is obtained for you, by all means side of the Step, taking care not toto the battery, so don't forget to fituse one of the heaVier sizes, like No. 18, cover up the bole you have made.this before you fix the loudspeakerwhich are commonly sold for the pur- An obvious point, perhaps, but I haveterminal plate. proved in my own person that it is pose, but you must expect to find that quite possible to forget it !(What I you will then have to take a little actually did was to fit the two con- SOONER OR LATER you extra trouble to get the neat and densers first and then try to bore the will build a set on the Step perfectly spaced wiring which is so characteristicofthe Step System hole afterward's, which led to a heavily System. Why not build the when the " pull it tight " method can underlined entry in the " Silly Ass K4 NOW, and begin to get Book.") be used. The next components to be fitted the benefit of the wonderful What you will have to do, you will should be the binocular choke and efficiency of the new system discover, is to cut each wire to length the series aerial condenser (the com- right away? Why tolerate and fit it in place very much as though pression type, besidethe F10 coil you were wiring up one of the older that old-fashioned receiver types of sets, so that you will have lost unit), also the output choke at the any longer? other end of the Step. This completes one of the benefits of the new system. the upper surface of Step No. 2, with You will still have the advantage of the exception of the fitting of the I have now crossed out all the en-straight leads, of course, so that it screen, which should be left until latertries in the " Silly Ass Book," inwill still be much easier than it used to because it gets in the way if fitted tooother words I have warned you of allbe in those sets in which the leads had soon, making the set less easy tothe pitfalls into which I fell myself, asto be bent into all sorts of complicated manipulate while the various partswell as certain others which I man-shapes in order to dodge obstacles are being fitted to the underside ofaged to dodge, but which would beand secure proper spacing. Step No. 2. less obvious to anyone who has not studied the Step System as exhaust- No Risk of "Shorts " Obvious and Simple ively as I have.All the rest of the If you are using the thinner gauge, These parts, comprising the reac-construction of the set is really abso-and pulling each lead tight, there is tion choke, anti -parasitic resistance in lutely obvious and simple, and I amjust one point at which you must the reaction circuit, and sundry fixed not going to presume to teach theexercise care, and that is in making condensers,should be fittednext. readers of " M.W." how to do it. any connections between components The only point for comment here is When we come to the wiring, how-on the panel and others on the Step the rather obvious one of remindingever, there are certain points which I framework. If you pull these too tight the constructor to take reasonable thinkI ought to explain, becauseyou will find that the panel is drawn care to copy theoriginallayout,there are special aspects of the jobout of true and becomes bowed, so because it must be remembered thatwhich are peculiar to the Step System. be a little gentle with all these leads. in the Step System itis the exact In the first place, you will remember It is the custom to encase the leads position of the parts which settles thethat the general rule for wiring aof a radio set in insulating sleeving run of the wires, and hence the cor-stepped receiver is to stretch eachor other protective material, but this rectness of their spacing. wire between the appropriate pointsis not strictly necessary in the case When you have finished both sidesand pull it tight.Now, to do thatof the majority of the leads in the of Step No. 2 you can turn your atten-easily and without putting a heavywiring of the K4, because they are so tion to Step No. 1, and here there arestrain on the terminals of the com- well spaced and held in position that it reallynospecialpointsrequiringponents you should really wire up (Continued on page 304)

301 MODERN WIRELESS Octol-e-, 1933 COMPONENTS

THE COILS POTENTIOMETERS FIXED CONDENSERS One pair Colvern Two 50,000 -ohm Two 5-mfd. conden- Ferrocart coils, type wire -wound poten- sers,T.C.C., or Dubi- F10 and F3, with one tiometers. Graham lier, Telsen, Lissen, etc. 44 -in. and one Farish,orWearite, Theseserveas H.F. switch coupling rod. Igranic, Lewcos, etc. by-passes,and must Separate coils, not Onlyoneofthese therefore be of the non - the type on a com- componentsisactu- inductive type.Their mon base,arere- ally used as a poten- capacity is not critical, quired for the K4, in tiometer,theother and if you have some order that they may serving merely as a of any size round about be mounted side by variable resistance. the one specified you side in the positions This latter is the tone - should try them.If the set is to be used with seen inthe photo- leveller control. a mains unit, however, do not go below .5 mfd. graphs. Thecoils play a very important part in the design of the K4, and alternative types would involve SEVEN -PIN HOLDER FIXED CONDENSERS circuit alterations.The F3 is used for the One seven -pin valve One eachofthe tuned grid coil, with the F10 as the aerial coil. holder. Benjamin, or following sizes : Wearite, W.B.,etc. .01, .0003, 0002 mfd. A good holder is very Dubilier,orT.C.C. importantfor the Itisessentialthat REACTION CHOKE Class B valve.Just these should he of the imagine the difficulty . Onereactiontype edgewise type, with H.F. choke.Graham of tracing one poor terminals in the posi- Farish in original de- contact among seven !tions shown in the photographs, for the sake sign,actuallyofthe Be careful,also,toof the Step System wiring. screened type, but this see that you wire up isnot essential ;anthis holder according to the positions of its unscreenedtypewill terminals, having first mounted it exactly as FIXED CONDENSERS shown on the Construction Chart. be satisfactory. A few good alternative makes One each of these are these :Telsen, Bulgin, Wearite. sizes : -002 and In choosing a choke for this position some 0005 mfd.T.C.C., attention should be paid to the placing of the FOUR -PIN HOLDERS or Telsen, Dubilier, terminals, in order to ensure that the wiring Lissen,etc. Of shall run as in the original design. Remember Three ordinary these two conden- that the Step System calls for component four -pin v a I v e sers the one of 0005 terminals to be placed in certain definite holders.W.B., or must be of the edge- positions if full advantage is to be taken of Benjamin,Telsen,wise type as above, since it fits into a small its " straight-line " wiring features. etc. The K4,in space between the screen and the second coil conjunction withunit. - modern valves,is not prone to micro - phonic effects, hence TUNING CONDENSERS itis not necessary OUTPUT CHOKE to select holders of the very elaborately sprung One Class B out- Two .0005- type.Certaintyof contactisthe main put choke. Sound mfd. variablerequirement nowadays. Sales in original set. condensers. In the case of this Graham Far component and the ish, orPolar Class B input trans- Utility, etc. It TERMINALS former it is possible is essential Four indicating to choose alterna- that the pro- terminals, one marked tivetypes from jection of the aerial, one earth, and leading makes such condensers be- two loudspeaker. as Varley, Ferranti. hind the panel Igranic, or Belling & R.I.,Telsen,etc, should not exceed three inches, otherwise they Lee, Bulgin, Clix, etc.The reader is urged, however, to study with will foul the iaised " Step " baseboard. No battery terminals are required for the K4, care Mr. Kendall's remarks on this subject in because the battery flex leads are connectedhis article on the operation of the finished set. direct to appropriate points on the internal wiring. There istherefore nofull-size SLOW-MOTIONDIALS terminal strip. COMPENSATING TRANSFORMER Two slow- motiondials. One compensat- Ormond, or REACTION CONDENSER ing transformer, Igranic, etc.In One 0003-mfd. reac- type D.P .35.Var- ordering these be tion condenser. Telsen, ley, or Telsen, R.I., careful to specify or Polar, Graham etc.This compo- thesizeofthe Farish, J.B., etc. A nent forms an essen- condenser solid -dielectric compo- tial part of the tone - spindles. nent was usedhere, levelling scheme, The type used but, of course, any good and great care must ontheoriginal condenser the construc- be taken to comply set were chosen tor may possess can be withtheauthor's fortheirclear used. specification.Any andwell -gradu- A capacity of .0002 ordinary trans- ated scales, which mfd. wouldserve, so former here would make accurate logging easy.The movinglong as a detector of the "lively " type is used,put the whole system of tone compensation cursor carries a " hair -line " indicator whichthe larger capacity being used in the original out of action and impair the quality given by permits very close readings to be taken. to provide a reserve of safety. the sot.

302 October, 1933 MODERN WIRELESS FOR THE

DRIVER TRANSFORMER ON -OFF SWITCH One Class B in One three-point on. SCREWS put (or driver) off switch. Bulgin Packetofas- transformer Q.M.B. type. The sortedscrews. Ferranti type A.F. third contact is used Peto-Scott. A 17(C). For general to switch off the bias suitablesize is notes on the ques- battery from the pre - No. 4 and round tionof alterna- detector volume con- headsare pre- tive types, refer to trol and to operate the ferable.A selec- the remarks made instantaneous signal - tion of lengths such as1, 4, and 4 will in connection with quenching circuit. Thisbe required, but the actual assortment will the output choke. lastisan importantdepend upon the particular makes of com- Note that the ceaure-tap terminal on thefeature of the receiver, since it has to safe-ponents used in building the set. secondary of this transformer is marked "G.B.," guard the health of the Class B output valve. but since no bias is used on the particular B valvein the K4, thisterminaliswired straight to the filament circuit.It would be WIRING MATERIALS connected to the grid battery with a Marconi- Six yards No. 20 or Osram B.21 valve. `se gauge tinned copper wire, five yardsin. COMPRESSION CONDENSER sulating sleeving, a few One 0003 mfd. inchesofscreening compressioncon- material for anode lead denser.Telsen orof S.G. valve.Goltone Igranic, Polar, etc. or Lewcos, etc.Itis This componentto be noted thatthe provides a form ofuse of a comparatively selectivity controlthin gauge of wire for which enables thethe leads is important if the full benefit of the easy wiring of a Step System receiver is to be set to be adjusted to individual aerials and obtained.This point is fully explained in the article on the construction of the K4 receiver. local conditions generally.On very small aerials it should be short-circuited. WIRE -END GRID LEAK BINOCULAR CHOKE One 2-meg. grid One screened leak with wire binocularH.F. ends. Lissen or choke. Telsen Telsen, Dubilier or Graham Igranic, etc.This Farish, etc. A componentis component of fitted direct to the high efficiency appropriate ter- is essential here, STEP FRAME minals of the detec- for it has a very One complete StepSystemframework, tor valve holder. important dutytoperforminthe H.F. amplifying circuits. or set of pieces of wood for making.Peto- FIXED RESISTANCE Scott. The necessary information as to sizes, method of assembly, and so on, are given in One 503 -ohm the special article on the Step System else resistance and where in this issue. holder. Graham Farish " Ohmito " SCREEN orsimilartype. OnespecialK4 Thefunction of screen. Peto-Scott. thisresistanceis A detailed drawing to prevent para- givingthedimen- sitic oscillations in the reaction circuit, and sions of this screen its value is not critical.500 ohms is the willbe found else- conventional figure, but any value from 300 where. Itisan to 1,000 ohms was found to serve the purpose interesting tribute to satisfactorily. the efficiency of the Step System layout H.T. PLUG AND FUSE of the K4 that so small a screen is all One combined that the set needs PANEL AND STRIPS H.T.- plug and to ensure adequate One panel, 18 in. x 7in. and two terminal fuse. Belling & Peto-Scott. Lee.Costsvery stability. strips or plates, 21 in. x If in. little, butmay or Becol, Permcol, etc. save a good deal some day. Ifit ever blows make sure that you have found the COIL CONTROL GANGING LINK cause before replacingit,but note that a Onecoilswitching fairly heavy rating oneisneeded for anyganging controllink. Class B set. Telsen. Thisdevice isused for the pur- PLUGS AND CONNECTORS poseoflinkingup Seven battery plugs. theswitching spin- two L.T. spades, anddlesofthetwo -coil one " anode connec- units sothatthey tor." Belling & Lee,may be operated by a single knob on the front ofthe panel of the receiver.Full in- or Clix, Bulgin, etc.structions for the fitting of the link device are -given in the constructionalarticle which Formarkingssee precedes this component list.The knob shown here is one of those which are supplied Construction Chart. with the coils.

301 MODERN WIRELESS October, 1933 Real Moving Coil Quality ispractically impossible for short-number on the market, be careful toI agree that this is only the D.C. circuits to occur. see that each lead really is of exactlyresistance, and the H.F. resistance However, itis needed at a fewthe correct length, for if you use leadswill be somewhat higher, but it, too, points, so you may as well use itwhich are even a little too long thewill quite obviously he negligible. throughout for the sake of appearance. slack in them will prevent you from Now let us take a look at the wiring It certainly makes a set look bettersecuring the proper automatic spacingas a job and see what has to be done. and provides a certain measure ofwhich is such an important feature ofHere we immediately discover an safety in case of some metal objectthe Step System.Instead, they will incidentaladvantageoftheStep being dropped into the interior of thesag about and it is quite possible thatSystem which was not at first appar- instrument at any time. some will approach each other whichent.Instead of having to tell the ought to be well apart in the interestsconstructor which wires to insert first Negligible Resistance of stability. and which to leave until the last, I In wiring the original set, I covered By the way, it is just possible thatam in the happy position of being ACCURACY AUTOMATICALLY ACHIEVED

The spacing of the wiring in a Step System receiver is settled by the positions of the components, and is therefore under the complete control of the designer.The constructor for his part has merely to take a little care to copy the layout, and then he can be sure that his wiring will automatically become a perfect facsimile of the original.The point is well illustrated in the photograph seen above, but in examining this it should be borne in mind that wires which appear to approach very close to each other when crossing are really in entirely different planes.

all leads with a good grade of Systoflex someone may object to my use of aable to tell him that every wire is so of rather small bore, and this cer-thinner gauge of wire for connections completely spaced or,atleast,so tainly made the wiring look very neat on the ground that such wire must accessiblethat itdoes not matter when done.An alternative methodhave a higher resistance.Well, so itwhich he puts in first and which last. would be to use one of the varioushas ; but believe me, it is still so low special proprietary materials which as to be absolutely negligible in com- Wire in Any Order are already provided with an insulat-parison with the other resistances in The wiring can, in fact, be done in ing cover, but beware in this case that circuit. absolutely any order, and you may the wire within is not too thick to be The resistance of No. 20 gauge wiredecide to wire up by circuits, or to entirely satisfactory for the" pull is just under 24 ohms per 1,000 yards, work from one end of the set to ;the it tight " method. so the resistance of an average sortother, or to wire each " step " separ- Also, if you use any kind of readyof lead, which I will assume to beately, or to proceed quite haphazard, prepared leads, of which there are a6 in. long, will be 004 of an ohm ! (Continued on page 376)

304 October, 1933 MODERN WIRELESS WIRING eh WORDS

IMPORTANT.-The order in which the leads are given in the table below is not intendedto be taken as a guide to the order in which the wiring should be done, but is merely a convenient sequence for checking.The actual order of wiring is discussed in the text. In this table, " front " means nearest to the front of the set, i.e., nearest the panel." Rear" means nearest to the back of the set.The terms " right " and " left " assume that the set is being looked at from theback and from above.The reference letters of the leads will be found to be marked against them on the wiring chart.

Lead Le ad. Refer- Refer- ence Points to be Joined. ence Points to be Joined. Letters Letters.

AA Left terminal of on -off switch and L.T. neg. spade terminal.BK Plate or anode terminal of third valve holder and. plate ter- AB Right-hand terminal of on .off switch and ditto of tone - minal of " Class B " input transformer. control resistance. BL Front filament terminal of third valve holder and ditto of AC Right-hand terminal of tone control and left-hand terminal fourth.(See also BC and BR.) of volume control. BM Grid -bias terminal of " Class B " input transformer and AD Right-hand terminal of volume control and G.B. -1 plug. G.B. + plug.(See also CN.) AE Moving vanes of reaction condenser and No. 8 on F3 coilBN Right-hand grid terminal of input transformer and one grid unit. terminal on fourth valve holder.(Identify by position AF Fixed vanes left-hand tuning condenser and No. 1 on F3 coil on wiring blueprint.) unit. BO Left-hand grid terminal of input transformer and remaining AG Moving vanes left-hand tuning condenser and right-hand rear grid terminal of fourth valve holder. fixing screw of F3 coil unit.(See also AM, AO and CA.)BP H.T. + terminal on input transformer and H.T. +4 plug. AH Centro terminal of volume control and moving vanes of right- (See also BT.) hand tuning condenser.(See also CB and AJ.) BQ L.T. - spade terminal and H.T. - plug.(Wander -fuse.) AI (not BR L.T. + ditto and front L.T. terminal of fourth valve holder. used.) (See also BL.) AJ Moving vanes of right-hand tuning condenser and No. 5 onBS Right-hand "A" terminal of output choke and rear anode F10 coil unit. (See also AH and CB.) terminal of fourth valve holder. AK Fixed vanes of right-hand tuning condenser and grid of firstBT H.T. terminal of output choke and H.T. terminal of input valve. transformer.(See also BP.) AL Fixed vanes of right-hand tuning condenser and No. 1 onBU Left-hand "A" terminal of output choke and front anode or F10 coil unit. plate terminal of fourth valve holder.(See also CP.) AM Right-hand front fixing screw of F3 coil unit and left frontBV One secondary terminal of output choke (correct one will ba fixing screw of F10 unit.(See also AG and AO.) determined by test) and lower loudspeaker terminal. AN Front fixing screw of screen and coil ganging link.(Flex.) (Through hole No. 2.) AO Right front fixing screw of F3 and No. 5 on F3 unit.(SeeBW One secondary terminal of output choke and upper loud- also AG, AM and AP.) speaker terminal.(Through hole No. 3.) AP No. 5 anl No. 6 on F3 unit. BX Middle terminal of on -off switch and right-hand terminal of AQ No. 7 on F3 unit and front terminal of .0005 fixed condenser. .002-mfd. fixed condenser.(See also CN and CO.) AR Front terminal of .0005 fixed condenser and front terminalBY Centre terminal of tone -control resistance and front terminal of -0003 ditto. (Through hole No. 1.) of .01 fixed condenser. AS Right-hand terminal of binocular choke and rear terminal ofBZ Fixed vanes of reaction condenser and left-hand terminal of 0005 fixed condenser. 500 -ohm resistance. AT Right-hand terminal of binocular choke and anode connectorCA Moving vanes of left-hand tuning condenser and right-hand for S.G. valve. (Flex, screened.) terminal of 0002 fixed condenser. (See also AG and CF.) AU Left-hand terminal of compression condenser and No. 7 onCB Moying vanes of right-hand tuning condenser and front F10 coil unit. terminal of right-hand 5 fixed condenser.(See also AH AV Right-hand terminal of compression condenser and aerial and AJ.) terminal. CC Front terminal of left-hand -5 condenser and rear terminal of AW Earth terminal and rear filament terminal of first valve right-hand 5 condenser. (See also CD and CF.) holder.(See also AY and CD.) CD Rear terminal of right-hand -5 condenser and rear filament AX " A " terminal offirst valve holder and H.T. +1 plug. terminal of first valve holder.(See also CC, AW and AY.) (Flex.)(See also CE.) CE " A " terminal of first valve holder and rear terminal of AY Rear filament terminal of first valve holder and ditto of left-hand -5 condenser.(See also AX.) second.(See also AW, BD and CD.) CF Front terminal of left-hand 5 condenser and right-hand AZ Front filament terminal of first valve holder and ditto of terminal of 0002 fixed condenser.(See also CA and CC.) second.(See also BB and BC.) CG Grid terminal of second valve holder and rear terminal of BA Grid of second valve holder and right-hand end of 2-meg. -0003 fixed condenser.(See also BA.) grid leak.(Actually done with the wire end of the leakCH "A" terminal of second valve holder and front terminal of itself.)(See also CG.) reaction H.F. choke.(See also CL.) 13B Front filament terminal of second valve and left-hand endCI (not of grid leak. (As above.) (See also AZ and BC.) used.) BC Front filament terminal on second valve holder and ditto onCJ Plate (or anode) terminal of compensating transformer and third.(See also AZ, BB and BL.) rear terminal of reaction choke.(See also CK.) BD Rear filament terminal on second valve holder and ditto onCK Plate (or anode) terminal of compensating transformer and third.(See also AY and BJ.) rear terminal of -01 fixed condenser.(See also CJ.) BE Left-hand terminal of binocular choke and H.T. +2 plug. CL Front terminal of reaction choke and right-hand teim'na' of BF H.T. terminal on compensating L.F. transformer and H.T. +3 500 -ohm resistance.(See also CH and CM.) plug. CM Right-hand terminal of 500 -ohm resistance and left-hand BO Grid -bias terminal on compensating transformer and G.B. terminal of -0002 fixed condenser.(See also CL.) -2 plug. CN Grid -bias terminal of " Class B " input transformer and BH Grid terminal on compensating transformer and grid terminal right-hand terminal of .002 fixed condenser.(See also of third valve holder. BM, BX and CO.) BI (not CO ..Right-hand terminal of 002 fixed condenser and rear filament used.) terminal of fourth valve holder. (See also BJ, BX and CN.) BJ Rear filament terminal of third valve holder and ditto ofCP ..Left-hand terminal of 002 fixed condenser and front plate or fourth.(See also BD and CO.) anode terminal of fourth valve holder.(See also BU.)

305 MODERN WIRELESS October, 1933

To make a good setisonly volume with the input and output half the battle :you must How to get super results from components specified.If you want operate it under the proper the super set.Notes on the to use other valves let me urge you conditions if you want to give it a choice of valves and batteries, to take the obvious precaution of fair chance to show you what it can the uses of the special con- asking the valve maker as to suitable do.Still more so is this the case if trols, output matching, aerial typesoftransformers and output you have built a really superlative adjustments, and everything chokes, so that you may be sure set like the K4: to get to the full you need to know to get your that you are getting conditions as the marvellous results of which it is K4 working at concert pitch. favourable as can be obtained by capable you must becareful,in using the exact specified components fairness to the design, not to use some and valves.The same advice applies, unsuitable valve or other accessory 9 -volt grid -bias unit.This is a point of course, to those who contemplate which might let down the performance to bear in mind, because in the K4 making a change in the make or type to the merely " good " level. the only valve requiring much bias of input transformer or output choke : is the S.G., none being used on the When in doubt on a Class B question, Causes of Disappointment output stage and only some 4i orask the maker of the valve. Totheexperiencedconstructor 6 volts on the driver valve. these may seem very obvious remarks Another short -basevalve which Function of Class B to make at the beginning of a prac- gave excellent results is the Mazda In general, I do not advise that tical article like this, but I must ask S.215V.M. changes be made in this part of the him to bear with me, because I have For the second socket I advise a set if they can be avoided, because I seen so much of the disappointment valve of the " special detector " type, know how easy itis to get things which is caused by the less experienced such as the Mullard P.M.2D.X., which wrong in a Class B stage.I have operator making changes which seem again was my standard for the final given some good combinations, and to him perfectly innocent. testsoftheset.Anothergood I should be very much happier if There is only one safe rule in these specimen of the type is the Cossor I thought that everybody would stick matters, and thatisto make no 210 Det. to them. changes unless you are absolutely Now we come to the question of certain your experience is great enough Choosing a "Driver batteries, and here I want to correct to enable you to predict the result When we come to the driver andwhat seems to be a very common with complete certainty. Class B stages we reach the point misapprehension.The proper func- After which rather portentous begin- where some discretionisrequired. tion of Class B amplification is not ning.letus get down to details, My own preference is for the rather to permit large sets to be run from making a start with the question of larger type of valve here, for the ridiculously small dry batteries, but valvesfor theset.For thefirst consumption isstill very moderate, to enable us to get real moving -coil positionyouwantametallised and it is no longer so essential to get volume and quality from a battery variable -mu typeofscreened -grid things just right in the output circuit of the normal size for the type of set. valve, and for most of my tests I to get a large volume without any To get such volume at all in the used the Cossor 220V.S.G. This is what risk of possible blasting. past has meant the use of batteries of is called a " long -base " valve, which Accordingly,I used as a driver quite prohibitive voltage and capatity, means in practice that you will want either the Osram or Marconi L.P.2, the accumulator type being practically some 18 volts of bias available for or the Mullard P.M.2A., while the essential.We can now do it with dry full control of volume. Class B valve was a Cossor B240. batteries or normal voltage, and it is A " short -base " valve which Excellent results were also obtained only reasonable that we shoulduse deservesspecialmentionisthe with the Mullard P.M.2B. batteries of fair capacity, just as we Mullard P.M.12M., with which you These combinations will give ex- have always done in the past for our will find that you only require a tremelygoodqualityandgreat bigger sets. 306 October, 1933 MODERN WIRELESS The Master Set at Work

After all, the old rule about veryor else a single one, according to explained.Plug No. 2 is the one for small batteries being false economywhether he uses a long or short base the driver valve, and requires usually stillholds good.The largersizes variable -mu valve. 44 volts.If, however, you find that will still last longer than the extra The H.T. voltages should be as you can giveit6volts without cost seems to indicate, so that this is follows.Plug No.1should go in causing the set to overload easily, by definitely the proper way to get full the 60 -volt socket, No. 2 in the one all means do so, and cut down your value for our money.If we have giving 72 volts, No. 3 in the 110 -volt H.T. consumption. previously used an output valve of the point, and No. 4 in the 120 -volt. These are all the preliminary adjust- super -power type it is quite likely that (The voltage of the battery must, ments, and now we can turn to we shall find that our H.T. batteries of course, not be less than 120 volts). operating questions proper, leaving last longer with a Class B valve, If the battery used has no 110 -voltthe matter of output circuit adjust- but it would be foolish on that account socket, remove the plug from the ments until later. to start buying a smaller size. H.T.+3 lead and join this wire to the The actual handling of the two In the case of the K4 what is called H.T.+4 plug, so that both may go tuning dials is a matter which I am the standing "or" nosignal " in the 120 -volt socket. sure I need not explain to the readers H.T. current will often be under 10 of this magazine.The art of keeping milliamps., the exact figure depending Preliminary Adjustments two dials in step is one which I know upon the setting of the volume con- It will be noted that no mention is they understand, and they will merely trol, which has the incidental effectmade of any adjustment of H.T. have to find out where a few known ofvaryingthe anode currentof voltage for the purpose of gettingstations come in before they will be the S.G.valve.This consumption, smooth reaction.Actually, one never able to start tuning in all Europe. by the way, is that for the whole uses reaction so intensively with the set. K4 as to need this condition.As a Selectivity Controls matter of fact, you will probably find A very important adjustment is Grid and Plate Voltages that there is a slight " growl " as the that for the degreeofselectivity When reproducing a fairly strong set goes into oscillation, which I find required for any given purpose, and signal the current may run up to an very useful for reminding one that a this I must explain fully.First,it average of 15 or 20 milliamps., but it set with Class B output should be should be noted that there is a main must be remembered that this is not allowed to oscillate as little as possible. control in the form of a compression continuous and there are frequent The reason is that if a strong carrier condenser in the aerial lead, and this rest periods.Even so, it is obviously is tuned in when self -oscillationis should first be screwed right down. no job for the smallest type of battery, going on in a really powerful set the Unscrew only as much as you find and it will pay to buy one of theresulting appalling yell makes the necessary to get the selectivity you larger sizes,just asithas alwaysoutput valve drink H.T. at a rate need.On small or medium aerials done. which is not good for one's pocket. you may well be able to leave it at The L.T. and grid -biasbatteries The question of grid bias is simple. maximum, while on very small ones, are an obvious matter, and the reader Plug No. 1 supplies the bias for the especially of the indoor variety,it will require no guidance here beyond variable -mu (adjusted by the volume may even be advisable to short it a reminder that he will want either control), and should be given either right out with a piece of wire across two 9 -volt G.B. units joined in series, 18 or 9volts,as I have already its terminals. Controls 211fitcfi Conquer 9isiance

A pictorial guide to the K4 controls.Nos. x and 2 explain themselves; 3 is the wavechange knob; 4 controls reaction;5is the volume or sensitivity control; 6 is the tone -levellerknob; and 7 is the on -off switch wherein one contact operates the instantaneous signal quencher.

307 MODERN WIRELESS October, 1933

control and bringing up the reaction YOUR CALIBRATION GUIDE a little at a time until you find that In this table will be found a selection of stations which have been found useful for a further reduction of volume cannot calibration purposes, with their readings on the first dial of the original receiver.If the constructor determines the variation of his own instrument for a few of these he be made up by means of reaction, will soon be able to locate many others by a simple process of proportion, and so and the station is becoming too weak, proceed to calibrate his set.Note that the dials were divided into 180 degrees. and then you will know that you have reached the limit of the K4. Station. Dial Reading. Station. Dial Reading. I venture to predict that you will Gavle . .. 45 Milan .. 113 very rarely do that in practice without Magyarovar 49 Barcelona .. 120 Cork.. 57 London Regional 123 finding that you can get the desired Fr camp 601 Hamburg 130 station clear of interference ! Kiel.. 63 Scottish Regional 132 Beziers 68 Toulouse .. 136 Adequate Power Reserve Belfast 70 Leipzig 1371 Trieste 731 Midland Regional 140 The essential point to graspis, Gleiwitz 75 Katowice .. 143 that the amplification of the set is so London National 79 Athlone 145 great that you very rarely indeed Bari.. 83 Belgrade .. 150 Hellsberg 87 Stockholm .. 153 will find it either necessary or desir- Lisbon 89 Rome.. 1541 able to have the volume control full Viipurl 94 Beromiinster 159 on, so that there is an ample reserve Hilversum 96 Langenberg 163 of power to enable this method of North National 1001 North Regional 164 West Regional 103 Prague 171 selectivity increase to be employed Goteborg .. 108 Florence .. 172 with good effect.A simpler way of Breslau . . 1091 Brussels 1731 looking at the matter is perhaps to say that, in those cases where you need This is just an initial adjustment bring back the volume by means of a extra selectivity, you get it in the to suit your local conditions, size of very moderate application of reaction, main by using reaction to make an aerial; and so forth.The adjustment you will get enough selectivity for alreadysharply -tunedcircuitstill to suit the exact needs of any par- any normal case.Indeed, the selec- more razor-edged, and to enable you ticular transmission in order to free tivity of the K4isquite excep- to do this without making the station it from interference is performed very tionally high if no more than thisbecome unbearably loud, you cut simply from the front of the panel. isdone, and in many places this down on the volume control. In general, you will find that if will be the normal way to operate it. Thisisa somewhat generalised you first turn the volume control For special stunts, like separating account of the matter, and a full down a little, so that there is a per- some difficult pair of stations, just technical explanation would take a ceptible drop in the strength of the carry the process alittlefurther. number of other factors into consider- station you are listening to, and then Keep going back on the volume ation, but it will serve our present purpose.All that we need tore- , member in practice is to keep the volumecontrolbackenoughto enable us to apply a spot of reaction now and again without producing excessive volume. Remarkable Selectivity Skill can be acquired and put to good use in juggling with these two controls, but there is no need to fear that good selectivity cannot be got until such skill has been obtained. On the contrary, the natural unaided selectivity of the K4 is quite good enough to delight most people, and it is only the very super variety of station -separationwhichcallsfor anything more.Even a very moderate use of the special method I have described will suffice to set up con- ditionswhichwillachievemost remarkable feats of selectivity. Of course, it is to be understood that it is only the presence of the tone -levelling device which enables this method to be used with such good effect.It could be used after a fashion in many sets, although it would not achieve the same effects unlesssimilarultra -lowresistance, The grid -bias voltage required by the K4 depends upon the type of variable -mu S.G. valve employed.The space on the second Step will accommodate either a single 9 -voltspeciallyarrangedtuningcircuits unit or two connected in series. were provided, but the result on the

308 October, 1933 MODERN WIRELESS How to Get Correctly Balanced Tone quality of reproduction would put it missionsound much deeper -tonedNow, here I am going to give a rather out of court so far as most peoplethan it should be.My intention hereunconventional piece of advice :don't were concerned. was to provide you with a sort ofworry too much about theory, but In the K 4, however, you haveemergency device for the reduction oftryallthe possible output ratios only to make a slight adjustment heterodynewhistlesinthosefew which your chokeortransformer ofthe toneleveller and excellentcases where they cannot be removedoffers you. qualityis obtained even when re- bymorelegitimatemeans.This The treatment of Class B valves action is being used quite strongly.should happen only rarely, but it isis still rather empirical, and the final In general, you will find that theoccasionally of great value to be abletest must always be the old " Try it knob should be turned about half -way to get rid of a whistle, even at theand see ! "Therefore, even if you round for the reception of the strongercostofmakingthetransmissionthink you know the correct ratio for distant stations, and fully round tosound a bit too " mellow," as itis your speaker and valve, try all the the right for those stations on whichstill sometimes called. others which may be available. Note, you have to use a good deal of re- by the way, that the type of speaker action in order to achieve selectivity The Normal Setting required forthe K4 is the of a specially high order. At all other times you will pre-ordinary variety with a winding for For the very strongeststations, sumably keep away from the extremeuse with normal, NOT Class B, valves. upon which no reaction will be usedleft-hand position of the tone level-(It may at a pinch have a winding for and the volume control will have toler, and just set it to give normal,pentodes, but this does not,as a bebroughtwellback,thetoneproperly -balanced reproduction. Itrule, lead to satisfactory results). leveller will require to be turned a The speaker (preferably a moving good way round to the left(anti- coil, of course) should be connected clockwise), otherwise the tone will ACCESSORIES FOR up to the speaker terminals of the probably be found a little too bright. THE K4 set, and then you can go and try the This is particularly the case with the Such'matters as valve types, battery various output ratios by altering the local station, of course. sizes, etc., have been dealt with in the connectionstothe secondaryter- text.The following notes may also be useful in showing makes which minalsoftheoutputchoke.To Range of Control have been used with the set and found emphasise the fact that this should You will discover that the difference suitable. be done,I have had theseleads in tone between the midway position H.T. and G.B. batteries :Ediswan, shown with arrow -head ends on the and one with the knob turned fully Exide, G.E.C. and Block Batteries all produce suitable units.The latter, of ConstructionChart,thus indicating round to the right is not very great, course, are of the H.T. accumulator that the wires should be tried on each so that you will have to listen care- type. pair of terminals in turn until the fully on a suitable item to hear it, Loudspeaker : Blue Spot and Celes- tion. arrangement is found which Ores the but this is as it should be.At the best quality. other end of the range (turned fully to the left), the control acts muchis very easy to do, you will find, for A Guide to Stations more strongly,andthelastfew it is by no means a critical setting. Finally, let me add a word about degreesproducequiteamarkednor is the ear really sensitive in the the" calibration guide,"whichis lowering of tone. matter, having become used in thegiven elsewhere. This is intended as a This, again,isintentional, for Ipast to sets which give nothing likegeneral guide only, for no two sets will have provided here a greater rangea true balance ! give exactly identical dial readings. than you will ever need for quality And now we come to the question of Of course, the list should not be reasons alone-that is to say, thatgetting a correct adjustment in thetaken as an indication of the total the control is at all times and in alloutput circuit, without which goodnumber of stations received during cases capable of making any trans -qualityisin any case impossible.my tests ! ALL READY TO GIVE YOU YOUR BIGGEST RADIO THRILL !

The complete installation ready for initial testing and adjustment. Itis always easier to do this before putting a set in its cabinet.

309 It MODERN WIRELESS October, 1933

Great volume, razor -edge selectivity, transcontinental range, moving -coil quality,the master set gives youthem all. F there is one thing I dislike above As a matter of fact, I should per- greater handicap thanisgenerally all others, it is to appear to make haps have said that there used to be realised. As an operator he is usually exaggerated claims for some new black sheep in this particular flock, for much more skilful than a member of receiver design.I know, too, that the I do not think that any of the people the non -technical public, itis true ; home constructor nowadays is rather who used to indulge in exaggeration but even so he cannot hope to compete quick to feel that such claims are are with us now. on quite equal terms with a man who being made, as a result of certain ex- The real reason for the trace of has been knob twisting for anything periences he has had in the past, and cynicism which I have observed in the up to perhaps twenty years, and that that knowledge makes me anxious to constructor's outlook of late is some- again must make a difference to the be doubly careful in what I say. thing less simple, I believe.I think results which he will get. I have no fear as to the opinion it is due to a certain lack of mutual The net result of all this is that the which will be formed by those who understanding between designers and constructor should realise that the wait until they have built the K4 and their public which should be cleared results obtained by the designer are found out for themselves what it will up, and that must be my excuse forintended to be taken as a guide in do, but what I am afraid is that if Ienlarging upon the point at suchestimating the efficiency of any par- say what I really think about the length. ticular set in comparison with others. performance of the set, there will be The trouble,Ithink, has been He must understand that before a great many readers who will imme- simply that it has not been suffi-he can equal those results fully the diately say to themselves, " This man cientlyclearlyrealisedthatthe constructor must expect to have to is obviously a direct descendant of results which any set will give in the spendsometimebecomingfully Ananias ! " and not even consider acquainted withthereceiver and building it.I feel pretty confident graduallyaccumulatingalogof that my old friends among the readers Mr. Kendall gives a very stations identified by the exercise of of " M.W." would not react thus, carefullyconservativeac- a good deal of patience. but there must be many newcomers count of the performance of who might, and hence my quandary. hislatest achievement, as Ahead of Its Time has always been his custom. With all that for a preamble, I feet Clearing Up Doubts His explanations of the stan- that I can now go ahead and say Mind you, I can quite understand dard to be expected in the something about the actual perform- constructor's own hands is ance of the K4.I am considerably how itis that the constructor has ofhis come to be a little sceptical about verycharacteristic emboldenedinsodoingbythe the claims he reads, for he has often policy in these matters. knowledgethatthestandardof had experiences which must shake operating skill and technical attain- his faith in human nature a bit. ments generally of the readersof Most emphatically, however, I do hands of its designer are not neces- MODERN WIRELESSisvery much sarily the same as the constructor higher than that of the average group not mean that exaggerated claims are The designer, it made by set designers nowadays. On will get from it. of home constructors." M.W." has the contrary, I do not believe thatmay be assumed, is a very highly alwaysbeenthemoreadvanced reputable designers ever do it.There skilled operator, he knows his set constructors' paper. intimately, and he normally uses an The performance of this set is such are black sheep in every flock; but purposes you can be very sure that if a designer accurate wave -meter for that I believe itwill be found an has been taking a prominent part in of station identification. entirely satisfactory means of receiv- radio for a number of years his posi- ing home and foreign programmes tion makes it absolutely impossible Experience Teaches not merely for this season, but in for him to do otherwise than to give The constructor, on the other hand, all probability for several seasons. a carefully accurate account of the has to learn how to get the best from In other words,itisdistinctly performance in his hands of any set the set, and he very rarely possesses better than it need be at the moment. he describes. a wave -meter, two facts which are a Itpossessesareserve ofboth

310 October, 1933 MODERN WIRELESS What the K4 Will Do in Your Hands sensitivityandselectivitywhich for by the small room in which the like than run the risk of being called should enable it to cope quite easily tests were made. a liar for giving lists of stations which with any even remotely probable in- On the medium waves there was look impossible with only four valves crease of congestion in the ether and naturally less reserve of power, but the reductions of transmitting power even here quite a number of stations Try It Yourself ! which it seems inevitable will eventu- gave really excellent volume, and, of Some idea of the number of stations ally occur. course, the quality of reproduction on which I got can be obtained from the A considerable degree of control all good transmissions was of a very list I give elsewhere for calibration of selectivity and sensitivity is pro- high standard indeed once the correct purposes, but it must be remembered vided for, and so the set can readily output ratio had been found which that this list gives merely the more be adapted to very widely differing suited the speaker. important and reliable stations.Be- conditions. After dark things were, of course, yond this I do not intend to go, for very different,and areally good I prefer that the reader should size Impressive Performance string of medium -wave stations could up the technical merits of the K4 As an example of this adaptability be received with the greatest of ease design for himself and realise from I may mention that my first tests at really fine volume. that survey what the performance with the set in its final form were I regard this test as being of great must be. made on an aerial of the kind which importance, for a good performance I believe that I can trust to the I know many unlucky people are under very bad conditions alwaystechnical knowledge of the readers compelled to use for lack of room. impresses me more than an abso- of " M.W." to lead them to a full It was only twelve feet high and lutely staggering one under normal appreciation of the merits of this fourteen feet long, which really meant conditions. definitely revolutionary design better that it was little, if at all, better than Even with the controlssetfor than any long-winded description of an indoor one. volume, as they had to be most of mine. I am confident that the importance PRELIMINARY RESEARCH WORK of the Step System and the electrical developments which are now combined with it in the K4 are so com- pletelyself-evidentthatIshould merely be wasting the reader's time if I in any way laboured the point. After all,if the merit of the basic invention is as great as I believe it to be, there is no risk that it will not at once be appreciated at itsfull value immediately it is disclosed. I am quite content to allow it to stand or fallby what is really the onlytruetestofaninvention, namely, that it should from the first be capable of securing full recognition with only the simplestand most straightforward explanation. So far as this first K4 issue of " M.W." isconcerned, therefore,I am going to limit myself to the general account of the set's performance which you have just read.Next month, of course, I shall be contributing further Mr. Kendall is seen here repeating, for the benefit of the camera, some of the preliminary calibration work on the apparatus he designed and built specially to assist him in the articles about the set, and then per- researches which have produced the K4. haps I shall feel free to say a little more about the results I got in my Under these adverse conditions I the time in this case, there was an full-sized aerial tests. set the selectivity control at minimum ample reserve of selectivity, and a and turned up the sensitivity fully, number of the well-known stunts, like Comparing Results and then was able to receive quite a separating Langenberg and North By then the reader will have had good number of foreign programmes Regional, were performed with ease. a chance to try his own K4, and I at satisfactory speaker strength in Later tests on an average sort of think he will be interested to compare daylight. Thevariouslong -wave aerial produced results which I do not my results with his.In doing so, he stations such as Kalundborg, Huizen, intend to give in great detail, because will be making an interesting check Eiffel Tower, Radio Paris, and so on, they were so extraordinarily impres- on my claim that the Step System were all capable of providing a real sive that they made me think I had makes it almost impossible for him to programme, and in many cases called struck a " freak " night time.And produce anything except a well-nigh for some reduction of sensitivity toagain, I would rather the constructor perfect electrical and mechanical copy keep the volume down to that called found out for himself what they were of the original model of the K4.

311 MODERN WIRELESS October, 1933

A MAINS DRIVEN INVISIBLE RAY BURGLAR ALARM

The application of infra -red rays to burglar alarms is not new, but their production on a commercial basis shows how reliable the scheme has been proved to be.

Although infra -red rays come within the spectrum of light - waves, and are capable of affec- ting photo -electriccells, they are invisible to the eye.This, together with the fact that any- Thetwophotc- thing solid such as a human graphs at the top of bodywillinterrupttheirpassage, renders themidealfor the page show the detecting the passing of an unauthorised person through a door- transmitter from way or across a room. which the infra -red rays originate. On Thus, the burglar stealthily creeping between glass -topped the leftitisseen, jewel counters, crosses the path of the invisible light.The with cover removed, infra -red ray from the small transmitter ceases to fall on the beingpluggedinto receiver, the resistance of the photo -electric cell in the latter the mains. The small electric motor at the changes, the current through it drops, a relay closes. top turns the shutter, AS GOOD AS whichcoversthe CAUGHT sourceof " light." Thethiefisasgood as caught! As soon as the contact points on that relay touch, the building LIGHT - isfloodedwithlight,bells ACTUATED clang, watchmen come running, RECEIVER and soon the criminal is in the Of the other three pictures, hands of the law.Science has the upper one shows the scored another triumph. small receiver which is also The scene just depictedis plugged into the mains.So made possible by quite simple long as the rays eventually apparatus such as that illus- reachthisinstrument,it does not matter what course trated on this page, which is of they pursue in getting there. Siemens make and design.

A NETWORK OF RAYS The two bottom pictures illustrate how the rays may bereflected back and forth so as to coverquitealarge area.Inthisway a burglar would not necessarily be safe even if he crawled alongflaton the floor. The mirrors need not bemountedconspicu- ously, and could easily be arrangedtolook quite innocent.

312 October, 1933 MODERN WIRELESS 011willno OF 14YfTERYCTATION fWITZERLOND

Our Special CorrespondentinSwitzerland visits the third and latest of the Regional broadcasters in that country, and tells "Modern Wireless" readers about the studios at the foot of Monte Bre. By A. A. GULLILAND

Another half an hour's wandering To my great relief he passed with a right under the frowning nose of a pleasantGriiss Gott."Wiping my fortress took me to the sign -board brow, I followed him, and found that intimating that beyond the fence lay he had only been going to shooting military territory.In Berne I had practice.But after that I had had attempted to obtain permission to enough and returned to the main visit the Ceneri transmitter. The road.At the summit of the Ceneri Minister of Posts referred me to the pass I discovered the main entrance to military authorities, who regretted not the broadcasting station, which is well TRAVELLING through the Gotthard to be able to furnish me with a pass guarded by a sentry complete with tunnel past Airolo, where the as the station stands in the very heart box. former Swiss President Motta of the Ceneri fortress, which is part In spite of my escapade, I had been owns an hotel, then sweeping down the of the great Gotthard fortifications. unable to see more than the masts of valleyoftheTessin, you getto the station.I therefore decided to Bellinzona, the capital of that canton. A FALSE ALARM climb up the hillside opposite to see It lies close by the river Tessin and is Just as I was taking a photo of the if it would be possible to get a glimpse surrounded by small hills crowned high barbed-wire fence,Iheard aof the station building from there. withfrowningcastlesfromolden motor -cycle approaching from behind. times.I arrived there in the evening Perspiration poured off me. I thought GIVING UP THE ATTEMPT in quest of Switzerland's third national that I had been spotted and that I This, incidentally, entailed crossing station :the Monte Ceneri trans- would be arrested and locked up fora ravine twice and having a friendly mitter. spying. When I turned round, there, pushing tussle with a youngbull right enough, was a soldier with his which refused to move off the moun- DIFFICULT TO SEE rifle slung across his back approaching. tain track. But it did not give me the Bellinzona has no studios (they are desired view. As I got closer to some at Lugano), so I left next morning by kind of buttress up the mountain aide, train.Looking out of the window to I thought it better to give up and the right you have a wonderful view returned to Rivera to continue my of Locarno and the Lago Maggiore. journey to Lugano and the studios Sharp eyes are required to discern the there. mastsofthe broadcastingstation Geographically the Ceneri station straight ahead against the green hill- is in the centre of a triangle formed side in spite of their coat of red and by imaginary lines connecting the white paint.After about 12 minutes' three towns Bellinzona, Locarno and run they came- closer, but just as I Lugano.It is visible from both sides was going to take a photo of them the of the pass.On one side it seems train banged into the Ceneri tunnel. pressed against the wooded mountain At the other end, a few hundred side, on the other itis silhouetted yards from its mouth, we stopped at against the sky with a background of Rivera Bironico.Getting out of the far-off hills. train I looked round and found that we must have passed right under the INDEPENDENT OPERATION transmitter. The Monte Ceneri station was built for any wavelength between 400 and ON MILITARY GROUND 1,200 metres.It has been testing Aboutthirty-fiveminutes' walk since April last on 1,156 metres. Under up the newly -made Ceneri road tookThe studio building at thefoot of the new Lucerne plan it will obtain a me to what seemed close to the station. Monte Bre, in Lugano. wavelength around 250 metres.The

313 MODERN WIRELESS October, 1933

A CURIOUS STUDIO THAT FORMS A CUBE power in aerial is 15 kw., the altitude light.Walls are yellowish, the ceiling over.The walls are treated similarly is 627 metres plus masts 125 high.It dark red and grey.The studio itself to those in the big room, and the isthe only station in Switzerland can be divided into two by means of engineer told me that this adequately which has in reserve its very own grey curtains. The windows of double prevented any acoustical reflections. power station,a groupofDiesel A small talks' studio goes off from the engines. Should at any time the " cube." Then there is the announcer's electric supply from Lugano break studio. A winding staircase takes one down,thestationcan operate from it straight up into the control independently. Therefore Monte room. Ceneri actually can be called not SAD INTERVAL SIGNAL onlythemysterystationinthe fortress, but the war -time station of Radio Lugano's interval signal is an Switzerland, as in the case of a war exact reproduction of the bells of the Ceneri could continue operations even Campane di Pazzalino, a church in the if the enemy were close by. old Roman style, close to Lugano. Arriving at Lugano railway station, The sad melancholic tones are typical high up above the town, I asked one of the Tessin and its inhabitants. leaudizione ofthepolicemen, intheir brown Ente autonomo per uniforms and brown helmets resemb- radiofoniche nelle Svizzera Italiana ling topees, the way to the broadcast- is the rather complicated name of the ing studios.He pointed right across company exploiting the Ceneri station the town, and I understood that I under the directionofMr. Vitali. would have to go down and across to Europe's youngest broadcasting the other side, to thefoot ofthe director.Signorina Nini incorporates MonteBre,. Iwalked along the the voice of Radio Svizzera Italiana. promenade close by the deep blue wi,53).0@o,'Egz,@tsg,6:Kg3,5L;,0,0 immovable water of the lake, through t. apark, andreachedthe Campo ,'.7. USING UP ODD 6, VISITORS, KEEP OUT! The barbed g, Marzio, a sports ground, and the broad- wire fence which surrounds the Monte RESISTANCES casting house situated at one corner. Ceneri station to prevent visitors from Q Series orparallelconnections6 coming too close. V for resistances will often enable THE STUDIO BUILDING utv the desired values to be obtained. The brown building contains four glass are high up in the walls. Sixteen from components on hand. studios and offices.The main studio by II metres and 7 metres in height %0@00@i5g00e%,Fg@ O''-'&'(c[C isexactlyrectangular;undesired is the size of this studio. acousticeffectsareprevented by What seemed to me a curiosity was ITis, often necessary to make use, means of alternate panels of wood and the form of the medium studio-an for automatic grid bias or other cellotex.The decoration is tastefully exact geometric cube, six metres all purposes, of a resistanceof a value which cannot be found among the constructor's spare components. In such cases itis useful tore- member that, by connecting two or moreresistancesinseriesorin parallel, various odd values can be made up. ADD THEM TOGETHER When resistances are connected in series their total resistance is equal to the sum of their individual resistances.Thus the result of connecting three resistances (values 500, 800 and 1,000 ohms) in series would be 2,300 ohms. Connected, however,inparallel, the total resistance is equal to the reciprocal of the sum of the reciprocals oftheindividualresistances.Or, 1 1 1 1 235.3 ohms. 500 + 800± 1000 = You can easily work out for yourself the varying values which you can SIGNORINA NINIcaught inthe act of broadcasting the time signal.She was securewith the resistances in your educated at the Scottish school in Alexandria and speaks fluent English. possession.

314 October, 1933 MODERN WIRELESS SPOTLIGHTSonthe PROGRAM

Comment and Criticism on Recent Radio Entertainment. TRYINGiton the dog was a is not outside the scope of the "effects" to do with it.Certainly his whole- popular proceeding in the old department's coconuts. hearted advance publicity methods music -hall days.Sir Harry Thereisa very sharpdivision showed a little unusual ingenuity. Lauder owes his success to havingbetween radio andstage. Val been put on as a " trial turn " at one Gielgud has realised this from the What is Radio of the halls.Non-stop variety saw beginning.That is why radio drama Costing Us ? the revival of this custom.I could is better than radio variety. tell you of more than one variety Mrs. Westlake is a hundred years artiste whose first engagement resulted A Step in the old.She lives at Stratford -on -Avon. from a public audition-and of many She refuses, with stubborn resistance, Right Direction to listen to " that wireless," main- more whose hopes of fame and fortune All the same, the first of the Eric were sadly dashed in the same way. taining with perfect logic that she got Maschwitz shows in No. 10 studioalong verywellfor ninetyyears These publicauditionscertainly under the Bridge was a very definite saved the management many hours of without it and she will get along just step in the right direction.Whether as nicely without it now. worrying about what their patrons the show was good radio technique is wanted.If a trial turn went down I wonder ifshe is missing very well, he was " retained for a further THE LADY ANNOUNCER much ?Or, rather, whether she is week."If he got the " bird," then missing as much as some people would the manager added the " sack." like to make out.Listening takes up Now the B.B.C. is trying the same quite a lot of our spare time to -day. ideawithitsSaturday afternoon What have we sacrificedforit ? variety" First Time Here." How Reading, perhaps-conversation cer- thisisgoing to helpinselecting tainly.And how manyof our good turns for the evening shows I children will be able to play any can'timagine. Nothingwillbe instrument for themselves, with the achieved which could not just as well possible exception of the gramophone? be done at a private audition. A few letters from listeners cannot, by Classified any stretch of the imagination, be Talking taken as popular opinion. Many years ago I went shooting. However,it makes a very good I had never gone shooting before and story. I was then, as I am now, a pretty poor hand with a gun.My host was The Clare of sympathetic(hemight wellhave the Footlights been seeing the amount I was paying The undoubted successofthe him fortheprivilegeofwasting Broadcasting Theatre at Radiolympia cartridges over his land) and offered has not had altogether wholesome me some advice. effects on the programmes.Some " Look here, old man," he said, oftheproductiondepartmentat A new picture of Mrs. Giles Borrett, who "you just go on shooting at two - Broadcasting House seem to have has now quite settled down to her duties minute intervals for a bit.There's at Broadcasting House.Mrs. Borrett is been caught in the glare of the foot- the wife of a naval officer. a law of averages which says you must lights,aswitnessthepermanent hit something." introductionofthe" EightStep dOubtful.That it was good enter- There have been occasions on which Sisters." tainment, and a distinct improve- the B.B.C. Talks have seemed like Not even the kindest critic would ment on what we have been having, that.Just go on talking long enough admit that these young ladies are is very definite. on every subject under the sun and distinguished for their voices, while PossiblyEricMaschwitz'sown you're bound tointerest someone their dancing, excellent as it may be, commentary on the turns had a lot sooner or later.However, no such

315 MODERN WIRELESS October, 193: C. B. Cochran Invades the Studio accusation can be made against the I quote the following from the doubt that Mrs. Borrett (whose photo- programme of talks for the coming correspondence columns of the Radii' graph is on the preceding page) does season. Times. her job very well.Still, I feel there A greatamountofcarehat' " Our 'Erbert had just come in to was a little justification for that letter. obviously been spent on thinking them tea as the Lady Announcer was readin' As a friend of mine put it the other out, and the man who finds nothing the News Bulletin ! Mum,'e sez, evening : to interest him will indeed be a dull `ain'tshe got a rarthersorrerful " Mrs. Borrett of the B.B.C. dog. Makes her announcements in a minor key." Brighter News In the Programmes Bulletins TESSA DEANE Stunt Broadcasts Perhapsthemostencouraging Miss Tessa Deane, modestly de- That Fail scribedin" Who's Who ofthe announcementisthepromiseof Theatre " as an actress and vocalist, I feel that it will be only a matter better News Bulletins on Saturday wasoneofJohnWatt's many of time before the B.B.C. announces nights.I have long wondered how triumphant radio discoveries. as part of its programme the stupen- many people were really interested AfterappearingasCarlottain " Silver Wings " in 193o, she achieved dous spectacleofforty Arabs on tolearnthatthepopulationof fame for her excellent rendering of forty camels beating forty drums, Norwich had increased by point two - Rose, the barmaid, in A. P. Herbert's probably relayedfrom Algeriato five per cent, or other such world - light opera, " Derby Day," and aroused give even more local colour. shattering items. If the thirty -minute The fact that the beating of forty " radio newspaper "caninfusea drums would have, in itself, no enter- little colour and life, a " little corro- tainment value would not matter, any borative detail into an otherwise bald more thanitmatteredtheother and unconvincing narrative,"then evening when the programme was the news will become, as it should interrupted for half an hour to hear have done long ago, a part of the eight pianos and an unannounced programmes. drum render that masterpiece of song The first of these " news reels," as plugging-" I Cover the Waterfront." they are to be called, will be broadcast Actually the eight pianos were of on October 14th.I advise listening no more entertainmentvalue than to it. two would have been, while the drum was,frankly,atrocious.Still,it The Place of made a spectacular programme an- Agriculture nouncement, soI presume nothing Farmers have always been rather else mattered. chary of politicians.I once heard Burt it wasn't worth keeping us out thecandidateforanagricultural of our beds for ! constituency ask a farmer what a plough was used for, so there's nothing Broadcasting and very surprising in that ! Mr. Cochran Lately, Major WalterElliothas It is no secret that the claims of done a lot to alter this opinion, and the the serious attention of Broadcasting C. B. Cochran as a suitable person- talks to farmers have been charac- House. Was starred in one of the " Songs ality to supervise the B.B.C. pro- terised by an unusual amount of grammes were put forward recently common sense. from the Shows " programmes, under thedirectionofJohn Watt-and in certain quarters.While there is no The programme of farming talks for overworked the postmen who had to possibilitiy of such a thing as that the autumn will make interesting deal with her " fan " mail happening. C. B. will have a hand in listening for plenty of listeners who Was heard again in the broadcast version of " Derby Day," in which she the programmes on October 14th, are unconnected with agriculture but sang the part she made famous. when he introduces the show " Mr. interested in its problems. Tessa Deane is undoubtedly one of the best and most individual of the Cochran Presents The Lady light sopranos of broadcasting-and It is thirty-one years since Cochran's one who is not heard nearly enough first show and many happy memories Announcer in the programmes. P. C. will be stirred by the songs to be In the ordinary course of events it sung by some of the original artistes. is probable that most of us would have voice ?' Oh,bequiet !'Isez, One of Henry Hall's last jobs before accepted the introduction of a lady 'praps that's the lady's eddication !' sailing for America was to arrange a announcer as part of the natural " Then 'Erbert suddinly discovered selectionof representativetunes progress of the B.B.C.The advance that 'e 'ad backed a winnin' double, from the numerous Cochran produc- publicity, however, which was quite and with a smile 'e said,Well, Mum, tions, and he will conduct the B.B.C. out of all proportion to the importance it doesn't matter much 'ow sorrerful Dance Orchestra " on the night." of the event, turned the whole thing one gits the noos, as long as one does With Cochran and Chariot in the into a nine days' wonder and invited git it !' " programmes, the autumn looks like criticism which would otherwise have Chivalry forbids any elaboration being a gay one. lain dormant. of this theme.Besides, there is no PATRICK CAMPBELL.

316 October, 1933 MODERN WIRELESS

D1STANCt MISTAKES

The unwary listener who goes in for titularly where reaction is concerned. items of this nature, are all important. long-distancereceptionisliable to Whenever using reaction, advance it Attention to such points can make fall into numerous traps unless he has a little at a time, and check up the success out of failure. the good advice of an oldhand to tuning in between each small increase. On small sets the reaction control help him.In this article some of the Ganged receivers are probably more simply must be smooth ; any sign of more common causes of poor results common these days than those with ploppiness will have to be removed. from distant stations are dealt with by separate tuning dials and, due to Lower H.T. voltage, different values A. S. CLARK the great amplification provided by of grid leak, different detector valves, modern efficiency, trimming is far less variation of the reaction coil, if this IFEisfar too short to learnimportant than it used to he.But is possible, are all ways of tackling while you may get quite a number of the smoothing out of reaction. it _4f everything by first-hand experience, and thewiseare prepared to profit by others' mistakes. Improves Selectivity Although the errors dealt with in the While writing about reaction,it following paragraphsare not ones is a mistake to imagine its one and into which the old hand at distant only use is to bring in or increase the reception is likely to fall, their reitera- volume of weak stations. It makes an tion will prove helpful to the new- ideal improver of selectivity. comer to this fascinating branch of And now threesmall points to finish off with.Too big a capacity radio reception. The careless adjustment of a preset condenser may completely upset the on the gang condenser trimmers limits Gradual Movements tuning of a receiver. the wavelength range.Keep their sittings as small as possible. Desirable the more powerful Continentals when Toobiganaerialmayupset First ofall,let'sclear up right trimming is a good way out, this state selectivity. You'll probably get more away the question of why. one person of affairs is fatal to the covering of stations properly with a medium- is able to get so much more out of a really great distances. sized aerial.And don't forget the certain set than another. Is distance - Adjust the trimmers carefully on importance of making a log. searching an art ?Is it something weak reception, and don't assume inborn that cannot be learnt?Cer- they are going to stay put for ever. tainly not, except perhaps so far as Check them over occasionally. the quality of patience is born in one. If you change a valve or a fixed Experience and practice in handling condenser,orsimilarsmallcom- receivers certainly helps in bringing ponent, the trimming may be thrown in those very, very faint foreigners, out and require re -setting. Even the but what really counts is the way You effects of time on the aerial may alter go about turning the dials.Gradual its electrical constants, which may, movements are always desirable. in turn, make further setting of the Unless you know the exact setting trimmers a necessity. for the station you are after, and no matter whether the set has single - Points to Watch dial tuning or not, the dials must be The finding of the absolutely best turned slowly, and every carrier or setting for the trimmers may seem sound which may be a station must asmall point-byitselfitmost be investigated.Itis the biggest certainly is-but there are other small mistakeouttoswishthedials items, and together their detrimental backwards and forwards quickly, and effects may be detracting from the then pronounce that " There's nothing results as much as quite a big fault. much on apart from the locals." A partly run-down battery, dirty Another mistake is to assume that contactstobatteriesorinvalve Small faults may not appear important the settinw of one control can have holders, valves that are losing -but they mount up ILook atthis theirfaulty S.G. anode lead for instance ; no effect on any of the others, par- emission, and dozens of other small it may ruin reception.

317 MODERN WIRELESS October, 1933

" Let there be noise! " he begged. " There can't be, you fool ! " re- ERMANwireless is rapidly taking torted the pilot." That's the whole theplaceoftheevening point of the thing." newspaper. TheTeuton " There must be ! " said the fren- doesn't require his news quite as red- zied commentator. hot as the Anglo-Saxon. Conse- A passenger who happened to have quently the radio has time to step in amechanicalcontrivanceneatly while the Berlin equivalent of Fleet packed up as a present for his chil- Street lingers over itslatenight dren,offered to provide noiseof finals.Not thatitiscorrectto approximately the right sort.The say that anything to do with wireless I Herr Direktor who told me the story merely " steps " in Germany.It didn't say whether the pilot shot him rushes.It owns a flying squad with or whether the commentator em- itsownrecord -makingvans. The recent revolutionary changes It have made radio in Germany an braced him ! hypnotises the Post Office into sup- affair of intriguing interest.The plying unlimited lines.It comman- tremendous part which news and RECURRING NEWS BULLETIN deers express trains.It proposes to politicalpropaganda playinthe German wireless seems to me to possess daily programmes is the subject of its own planes.And the this unique first-hand commentary. concentrateonnews.Anypro- result of all this is that everything gramme at any time may be inter-

rupted in order that listeners may take part in some happening a mile awayorseveralthousandmiles away. The News Budgets, " illustrated with sound atmosphere because they are generally from records made on the spot, recur at intervals during the day and they are admir- ably balanced.The German is interested in sport, but he does not exaggerate its importance.It is to him physical training and amuse- ment, but not business.It ranks far below politics and patriotism in the Brown Germany of to -day.In fact, a parody quoted to me in Berlin aptly describes the situation.

which happens during the day ig repeated onthe wireless at nine o'clock in the evening.It is not merely described by a sympathetic young man ofdoubtlessgodlike appearance, with the sort of voice every woman wants to marry.It actually happens to an accompaniment of all suitable noises.Some- times the noises are unsuitable in order to be more realistic,as, for instance, when a record was being made of a new silent motor fitted for the first time to an aeroplane.The commentator was so worried lest his METHODS OF PROPAGANDA by radio in Germany are shown in these listeners shouldn't realise that the two photographs.Above is a mobile loudspeakervan,invaluable for elec- record was being made on the plane tionpurposes,while below aNazi demonstration is listening to a rousing that he ordered the pilot to open the broadcast speech. In Germany to -day the greatest possible use is made of throttle, or exhaust, or anything that the loudspeaker for propaganda purposes, and the broadcasting service has would show the engine was really there. been placed under the control of the State.

318 October, 1933 MODERN WIRELESS

'NI, \ ,:,,,,- ".s, :, .:.

s.,:v ....., -,,,,.. \,,,,a .$ , \ BROAD CASTING " Sport is of our life a thing apart. 'Tis the English whole existence."

Consequently,onthewireless, sport is reduced to reasonable dimensions, and a good deal of time given to what I should call representative national life.One of the best broadcasts was made from a moving train.A commentator was apparently passing from carriage to carriage talking to the passengers. Above or in between the usual sounds of travel, came scraps of conversation. HITLER'S STRONGEST WEAPON " I'm goingl to Hamburg." " Because my niece is getting married, etc." " I also am going to Hamburg, but it is an affair of business." The impression was extraordinarily intimate.One felt one was looking into the minds and purposes of a trainloadof people who were no

IN CHARACTERISTIC ATTITUDE Herr Adolf Hitler addresses his Brown Shirts during a visit to the famous port of Kiel. longer strangers.One even imagined that one would recognise them, if one met them. Hitler has introduced a complete innovation in the form of the National hour which all stations are obliged to relay.During this period there is a certain amount of classical German music, while the rest of the time is devoted to politics with a suitable bias. An official in Berlin said to me frankly :" The radioisHitler's strongest weapon." SENSATIONAL POLITICS And whenIcounteredwith, " How much of your programme is political ? " he retorted, " All of it." But this does not mean that Brown Germany listens to the sort of debate POTTED NEWS. Running commentaries and eye -witnessaccountsof which nightly sends the House of important events in Germany are made during the day and reproduced inthe Commons to sleep.Nazi politicians news bulletins the same night. A real radio news -reel 1 are theatrical in that they appeal by

319 MODERN WIRELESS October, 1933

"A STUPENDOUS CRESCENDO OF SOUND" every popular means to audiences who nobody thinks of time. The audience, young brown-shirtedGermany to can be enthralled by sound as well as whether it is in the hall or listening look forward towards peace rather sight. in a draughty shed on the Baltic than backwards to the War.Their " The marriage of Hitler's oratory coast, remains mindless, motionless, objective was a sensible revision of to the thunder of the air " (as it was a sounding -board for the eloquence the Treaty of Versailles, so that, once described by a contemporary writer) of the man who believes in Germany. and forall,theWar couldbe is something new in the history of forgotten. I heard no militarist sensation.Listening to the record THE GREAT CREED propaganda. of a Nazi meeting is as stimulating as Hitler never discusses, argues or " Wehave enough unemployed of attending one.The floodlights and explains.He asserts,heattacks, our own. We don't want to have to the flags are missing, but one hears appealing thus to the convictions copewithotherpeople's,"said and feels the excitement of the packed which have so long lain fallow, deeply Hitler. BROADCASTING A FIRE GERMAN Every German carries a newspaper SPORT tucked into a bulging pocket, but AND for news, as well as inspiration, he RADIO depends on the radio. Sport interests There was a 'fireinBerlin.A theGerman whole block was burning.Before but he does not the flames reached the roofs, simul- exaggerateits importance. taneouslywiththefirebrigade Consequently arrivedtheradiovan. While on the wireless ladders and hoses were brought into sport is reduced action, in a cloud of smoke, amidst to reasonable dimensions.It the hiss of steam and the crumbling ranks far below of old masonry, the record -makers politics and (and record breakers) started work. patriotism. EXPERIENCED BY ALL By the time they'd finished they audience, the hush of expectation, buried beneath the weight of Ver- were unrecognisable, but two hours the broken comments, then, from saillesobligations ;so that every later all Germany, listening in farms far away, the tramp of marching man in the audience feels that- andflats, factories, cafés and clubs, feet.The music swells so that it is " Germany cannotbeasecond- knew what it was like to be in the like a tidal wave on which the black class nation.Something is going to middle of a fire. battalions of the bodyguard with the happen.Ithasgottohappen. " Nextyear, that sortofthing death's head on their caps are swept We must follow our leader-he is will be done from an auto -gyro," into the hall.One hears the audience not an accident, he is German destiny. said the youngest director.Which rise as one man.There is no shuffling Follow and our day will come as is just simply typical. of feet.It is a stupendous crescendo surely as to -morrow's sun ! " of sound, to which one's pulses march At the end of one of these great MUSICAL FAIRE in unison. meetings, to which I had listened togetherwithsomefourmillion " WHAT IS ADOLF HITLER ?" people all over Germany, I asked a " Heil, Hitler ! " stolid young engineer :" What would When the salute crashes into the happen if Hitler died ?Could the air, one has no difficulty in seeing party carry on ? " the thousand arms uplifted or the He looked at me as if I blasphemed. young, bronzed faces alert with new " How could he die until his work hope. isfinished ? " The music dies.Somebody speaks slowly and with repetition-a Te NO WAR PROPAGANDA Deum, in which phrases recur like the Here is the explanation of Ger- beat of a hammer on an anvil. many's faith, and the airisthe " Germans,prepareyourselves ! proper ,clementforthepromul- Perish the alien in our midst. What gation of the new religion.Where is Adolf Hitler ? Our hope, our faith, Russiasays : " Greetings, Com- our future, and our leader ! " rades, Moscow speaking " ;where Militarybandsthunder. Men America descends to " Good evening, shout and women sob. folks " ;Berlin preludes itsaerial Representative nationallifeishere Hitler rises, and there is silence. bombardment with "German y, wellportrayed by a typical country familyatsupper,withtheradio In a rough and powerful voice he awake ! " providingitsquota tothe general speaks.Onehour,twohours- Yet the speakers I heard urged conversation.

320 October, 1933 MODERN WIRELESS

REAL C IRAWICIPH 0 114 IE PrID INI IE C IM I ROIL

0E late particular attention has shunted across the pick-up, or an Details of how to construct units inductance in series with a resistance been paid to the necessity of which will add realism to your tone correction when repro- record reproduction, and which in series with the pick-up. ducinggramophonerecords.Un- can be adjusted to suit anyone's Now, with the arrangement I am fortunately, many ofthe arrange- taste. about to describe a much more desir- ments devised are almost worse than By H. E. J. ORTON. ableresponseisobtainable.The useless from both the musical and arrangement has also the advantage technical standpoints, inasmuch as that it can be adjusted, by the turning they attemptto make good the An average electrical recorder is ofknobs,toallow for individual deficiency of the bass by attenuating adjusted to have a response curve variations inpick-ups, reproducers, the treble more and more as the showingafalling offof sensi- and so on. frequency rises, resulting in a general tivity at the bass and extreme treble; deadness of reproduction. this being, of course, intentional. More Realistic For perfect tone correction, our There are two alternative arrange- Perfect Correction reproducingapparatusshouldob- ments possible ;one enables a life Certaintone - controllingtrans- viously have a response which corrects to be given to the bass only and formers have been put on the market recording errors.The arrangements the other compensates both bass and of late which are useful (though not condemned above fall very short of extreme treble. idealfor gramophone work),but the mark. In the usual way, the bass " lifter " generally these necessitate structural These arrangements take various provides all the correction necessary alterationsof the receiving equip- forms, but usually they are either a to make record reproduction much ment. capacity in series with a resistance more realistic, the additional aid of the SIMPLY -MADE UNITS TO COMPENSATE FOR BASS AND TREBLE

The unit to the left is one which improves the bass reproduction, while that above gives a " lift " at both ends of the freqth ncy scale MODERN WIRELESS October. 1933 top " lifter " being needed only when The device, in either form, is most the remainder of the apparatus has suitable when used with amplifying CONCERNING an unusually poor high -note response. equipmentwhich is not ordinarily METAL FOIL The circuit arrangements and the pushed to the limit. .4precautionary idea and a helpful values of components are shown in There are two particular reasons tip. the accompanying diagrams. why this should be the case.The Low -frequency transformerpri- one is because the use of the filter mariesorsecondariesarequite tends to reduce somewhat the input TIEN the baseboard of a set is suitable for the inductances in both to the set ;and the other is due to the covered with copper foil or a " lifters."For thebass" lifter," fact that for a given seeming loudness, metal chassis is used, great the primary of a good transformer or more power has to be expended if a care must be taken to prevent shorts the secondary of a cheap one suffices ; reproduction has a correct, proportion to this. for the treble " lifter," the secondary of low notes thanif the middle and In particular a disc of thin card- of a fairly good transformer. top predominate considerably. board or thick paper should be placed As can be gathered, none of the between the valve holders and the values is very critical, considerable Indications of Balance differences in values having, jugded If the set does not give sufficient from the aural standpoint, only neg- amplification, a good step-up trans- 0/5C 0FM/iv C4ROBOARD ligible effect upon the performance of former, wired up as in the diagram, is the lifters. sometimes useful. In actual practice, the two knobs Avoid Interaction are varied together until a suitable The two tone -controlling resistances, balance ofhigh and low notesis 8,vseao,akw which can be ordinary volume con- obtained. trols with one outside terminal not in If a good balance has been obtained use, should be wired up so that if both it can generally be checked by observ- knobs are turned in the same direction ing whether upon turning the volume the resistance in circuit of one control slowly down the illusion of moving is increasing, while the resistance in farther and farther away from the Screws which might touch the baseboard circuit of the,other is decreasing. music is produced.With equipment foil can easily be prevented from doing so by a piece of card. CONNECTIONS FOR COMPENSATOR AND " STEP-UP " baseboard to prevent the underside of 56,0,000 OHM5 30,000OHM5 the terminals touching the baseboard. This precaution is also necessary -m/yr 0 with some makes of preset condensers and grid -leak holders in which the terminal screws are countersunk into 475 the base. /00 H INFO .56;000 OHMS 0 0 REDUCING HAND - Low NOTE ComeENsoaroR NIGH NOTE COMPEA/5/77-0, CAPACITY EFFECTS F ryou are troubled atallwith hand -capacityeffects,anim- provement can often be effected by fixing an earthed shield on the /ivvrrr back of the panel behind the tuning condenser.In many cases this will give a complete cure, but even if it 0 0 does not do this itis bound to do some good. x873 SHOWING USE OF 5r4P-UP 7,9/Y5FORMER T1//Y/NC, CONDENSER The schemes in the top two diagrams are specially suitable for amplifiers with a surplus of power.The bottom scheme will help with sets of limited output. The gadget can be made up as shown giving sufficient output, another good inthe photographs,oritcan be test of balance is to note at what arranged on the motor -board or some- strength a singer's voice sounds to where in the set.Wherever it is put, have the right amount of weight and care should be taken to avoid un- to be in the same room as the listener. desirableinteraction with theset Should the reproduction need to be and mains equipment-if such belouder than the singer's voice for it used. to have thecorrect balance,the As can be seen from the diagram, proportion of bass should be increased; A metal screen behind the panel in the the corrector is connected between or, conversely, the proportion of bass vicinity of a tuning condenser will often the pick-up and the set. should be diminished. stabilise tuning.

322 October. 1933 MODERN WIRELESS

The B.B.C. and the Music Halls the action of a daily newspaper Britain might even now IF Sir John Reith revealed one half of the plans for have ceased regular television transmissions. combating the opposition of the music halls, I fear The Governors, after consultation with Sir John Reith that he would bring down upon the B.B.C. the and the Chief Engineer, Mr. Ashbridge, had definitely wrath of the entire entertainment industry.The trials agreed to announce the abandonment of all television and tribulations involved transmissions apart from a few experimental broad - in the B.B.C.'s fight for..

supremacy in the field of castsonultrashort- ..

waves. Then came the music would be as noth- Keeping a critical eye on the affairs of the B.B.C.,

newspaperarticle de- ing to the bitter attacks our Special Correspondent comments frankly and .. which thestageand ** nouncing this action and impartially for the benefit of listeners on the policies

variety chiefs wouldat .. callingforthsuch an

and personalities controlling British broadcasting. radio once launch. uproar from the

trade that the B.B.C. at Even a few of the more

Inirrnless suggestions laid once climbed down and beforethe Boardof within a few hoursde- Governors would cause an outburst of indignation from cided to continue the existing television programmes. Mr. George Black and others.Sir John's proposal- Apart from the effect which this has had upon the made half facetiously-to erect a big B.B.C. Broadcast- development of television, it illustrates very clearly the ing Theatre roused some of them to fury and certainly power of the Press over the B.B.C.In this case that did nothing to relieve the tension. power was applied to some useful correctional purpose The Governors have rightly taken the view that the and is the most outstanding instance I remember of a music halls are acting through fear-fear, that is,of newspaper having shown the B.B.C. the right course to competition from outside the industry-and have agreed adopt on any important question of policy. that non -aggression and an attitude of sympathetic understanding is the best line for the B.B.C. to adopt at THE NEW MIDLAND REGIONAL present. Symphony by Sir Edward Elgar The crop of rumours regarding the symphony that Sir Edward Elgar has been commissioned to write for the B.B.C. is not surprising considering the unusual reticence that is being observed in official quarters.Neither the B.B.C. nor Sir Edward will disclose when or where the symphony is to be given its first performance, yet both deny that the privilege is to be given to the Halle Society. Presumably itwillfirstbeheardin London next spring. There are rumours, too, concerning the fee that the B.B.C. has promised for the work that Elgar is now busy I am told that it is the on in his Worcestershire home. Workmen busy on the new B.B.C. station. They are constructing biggest sum ever paid for a commissioned musical workthe huge concrete foundation for the Diesel engines that will and runs into several thousands of pounds. supply the power for transmitting. Television Transmissions to Continue The Power of Droitwich The inner history of the television discussions at Many will seek an explanation but few will know the Broadcasting House will some day make interesting reason for the secret decision of the B.B.C. to make pro- reading.Meanwhile, it is worth recording that but for vision at Droitwich for an extension of power from 100

323 MODERN WIRELESS October, 1933 The B.B.C.'s Big Programme Drive kilowatts to 200 kilowatts.If it were thought on the the country, is to deliver an address on " The Trans- Continent that this excessive power might be used there mutation of the Atom," presumably dealing with his would be general indignation. Hence the secrecy and the researches in the famous Cavendish Laboratory where he official statement that " the licensed power of Droitwich is popularly said to have " split the atom." is only 100 kilowatts." Relays from Sadlers Wells The Nationals to Go Two relays from Sadlers Wells have been fixed for The shutting down of three of the National trans- thismonth. They are" Snow Maiden " (Rimsky- mitters has now received official sanction.The three Korsakov), of which Acts 1 and 2 will be broadcast on stations affected-London National, West National and North National-will definitely close down when Droit- A POLITICIAN FACES THE " MIKES" wich has passed its final tests. There is now some question as to whether Scottish National could not profitably be transferred to the Highlands. Seeking a Super Studio Search for a new concert hall, to take the place of No. 10 " underneath the arches " by Waterloo Bridge, has been widespread. The Maida Vale skating rink is favoured, but there is also a more advanced group that demands nothing less than Albert Hall.

"C. B. Cochran Presents..." We are now in the thick of the B.B.C.'s Big Programme Drive (as they call it), so it is natural that we should expect something outstanding in the way of variety programmes and light entertainment generally.There need be no disappointment, for on Saturday, October 14th, comes the much -talked of reminiscences entitled

" C.B. Cochran Presents . .."in which the great impresario will himself take part.The programme is a The Governor of New York State making an appeal to the public by means of radio.Politics have a much larger part in the programmes in America than in this country. Thursday, October 5th, in the London programme ;and " Cavalleria Rusticana " (Mascagni), relayed on Friday, HENRY HALL October 13th, also in the London programme. AUTOGRAPHS Special concerts booked for the near future include : A KetelbeyConcert,fromKingswayHall(London, Saturday,October14th) ;Military Band (National, CONDENSER Friday, October 6th). The popular leader " An Unlikely Tale of the Crimean War," entitled " The of the B.B.C. dance Pride of the Regiment " will be heard from the Regional orchestra autograph- on October 14th. The last " Prom " of the season on Saturday, October ing a condenser for a 27th, is to be broadcast throughout with a short break blind radio enthusiast. for the News Bulletin. The soloists in this concert are * Stiles Allen, Samuel Worthington, and Maurice Cole. A Civil Service B.B.C. ? straightforward co-operation between Cochran and Henry The sharp division of the B.B.C. staff into " Ad- Hall, and consists, naturally, of practically nothing but ministrative and Creative " leads some of the higher musical hits from Cochran's successes. officials at Broadcasting House to believe that the time " First Time Here "-the Saturday variety matinees- is not far distant when one half of the B.B.C.'s work will continue throughout the month, and there is much hope be run by CivilServants. The reorganisationhas of discovering talent in this way. definitely paved the way for this move, and it would be On Tuesday, October 3rd,is a burlesque by the but a formal change to make the Administrative staff Melhuish Brothers, produced by Martyn C. Webster, and Civil Servants. on the following day Billy Merson puts on his revue. Sir John Reith's view is that the creative side of broadcasting can never be run by people whose only qualifica- A Talk by Lord Rutherford tions are that they have passed an entrance examination. The next of the B.B.C.'s National Lectures, two or three Come what may, the question is sure to be considered of which are broadcast annually,is on Wednesday, during the grand parliamentary inquiry that is to be held October 11th, on the National wavelengths. Lord prior to the granting of a new Broadcasting Charter in Rutherford, probably the most outstanding physicist in 1936.

324 October, 1933 MODERN WIRELES3

IHAVE recently com- Wide, first-hand experience of trouble -tracing in all kinds of receiv- work ;another reason is pleted investigations ers well qualifies the writer of this feature to advise readers how to that service work very into a fault-or, rather, locate faults in their own sets. Condenser breakdown on mains naturally produces preju- a series of faults-which receivers due to incorrect centre -tapping, and crackles caused by a diceswithregardto was not only baffling but variety of faults are two of the subjects dealt with this month. certain components which also extremely expensive are found from experience in the amount of replacements that Thus it was. that I found myself to give repeated trouble. the trouble involved. hurrying with all possible speed to the Suffice it to mention that the con-

A recently -purchasedradiogram scene of these disasters with the most densers in this particular type of radio- -in the 100 -guinea class-behaved dire threats overhanging me as to my gram had already earned themselves perfectly well for exactly one week fate if I did not manage to clear upthe title of -Tot len." after its installation and then sud- thetroublecompletelyandper- denly refused to function at all. manently. Thinking It Out Some readers may have guessed the However, there was no doubt that A Weekly Occurrence causeoftherepeatedcondenser in this case the condensers were blame- An engineer was sent for to dis- failure by this time from this descrip- less, and I therefore set to work to cover the trouble, and found that the tion ;in case that is so I feel I must find some other cause for the repeated main reservoir condenser had broken failure. down, and since the set had been left USE THE RIGHT TAP Now, assuming good, condensers, on after the breakdown-the worthy what can cause a complete break- owner imagining that the trouble, was down of dielectric insulation ? a break in the programme-the recti- Excessive peak voltages-right ! fier valve had been short-circuited for And whatwillcauseexcessive some minutes and consequently had peak voltages ? completely lost its emission. A faulty mains transformer-again Quite naturally, the engineer sus- quite right ! pected that the condenser had been I tested the secondary H.T. wind- faulty and replaced it with a new one. ing and obtained the correct reading When a new rectifier was fitted all across the outers-800 volts. was well again. Next I. put the A.C. meter across But not for long ! the outers and the centre tap in turn. After another week's service the And here I found the cause of all same fault occurred again. the trouble. Exhausted Patience The Guilty Component And since all good engineers are The centre tap 1% as not a centre incurable optimists, the same remedy tap at all ;it was, electrically speak- was applied and the same assurances Unsatisfactory tone and poor quality o ing, 40 volts out of centre, so that given as before that from then on reproduction are sometimes traceable to the peak voltages developed on the the receiver's performance would un- the use of the wrong tappings on the " larger "sidewereprobablyas loudspeaker's input transformer. Incorrect doubtedly accord with the glowing matching of output to speaker thus results, much as 100 volts above normal ! accounts of the manufacturer's adver- and the circuit becomes unbalanced. If you should experience this type tising agent. of trouble with your mains set, it is I will not weary the reader with a offer some explanation as to why the as well to test for this fault before more detailed account of the history trouble had not been more fully indulging in reckless expenditure on of that set beyond mentioning that investigated at an earlier date. new condensers and rectifying valves. the same fault occurred again and It is, however, extremely unlikely again, and- An Unsavoury Reputation that you will find such a fault on a Eventually the unfortunate owner's One reason is that engineers are good commercial type of mains trans- patience came to an end, and he tooknot normally given full details of the former. up his pen and wrote several regret- " histories " of the various receivers Full immunity is assured, of course, table and heartbreaking things which to which they have to attend-for if you fit a thermal delay switch to. reached He Who Must Be Obeyed.this would' involve a colossal and, in the power pack so that peak voltages. at the Service Depot. most cases, unnecessary amount of are entirely prevented.

325 MODERN WIRELESS October, 1933 A New Cause of Fading Reception

While we are on the subject of It was only after a very long period and unfit for further service, but in rectifiers, here is a useful tip in regardof looking for such loose joints- most cases complete repair can easily to A.C. mains receivers. . which did not exist-that 1 began to be effected. When you are carrying out testssuspect the real cause of the trouble. The cause of the irregular behaviour or making such alterations to the set Confirmation was obtained when I of a carbon element volume control connected up a different receiver to is either that dust and dirt have got AVOIDING A SHOCK the same " picture -rail " aerial andin on to the track or that the track obtained the same fault. itself is worn or scratched. The trouble in this case was that the steel piping through which the Reversing the Element house wiring was run was improperly In thefirstcase the remedyis earthed and consequently caused a obvious, and careful cleaning of the varying degree of screening of the element and the " wiper " will nearly indoor aerial. always set matters right. Fixed condensers of z mfd. and upwards I was able to cure the fault by very In the latter case a little ingenuity may be tested by being momentarily con- careful and laborious earthing of the will usually produce the desired effect. nected across an H.T. battery, then left for conduit. In nine cases out of ten, the track ten minutes or so, and afterwards dis- charged-a good snappy spark indicating Even now there is a lot of crackling wearsatone end-that is, at the the condenser is O.K. Use a wooden handled maximum " end where the control instrument for the shorting. RISKING SHORTS has been used most. The simple remedy is to dismantle which require constant working of the components, remove the carbon the receiver for checking purposes, element and to reverse it ;this means 4 a great deal of time is wasted in that the " maximum " or worn end waiting for the A.C. valves to warm will now be in the " minimum " posi- up after each time of switching on. tion, so that not only will it seldom be This difficultyis avoided by the used, but the amplification of the set simple expedientof removing the at this point will be so low that any rectifier valve from its socket when- irregularities of contact will be in- everitisnecessary to render the audible. chassis " dead." Such repairs, of course, do not apply to " logarithmic " or " graded " con- Reasons for Fading trols. The L.T. is still fed to the set, of course, so that the valve cathodes Pick -Ups that Hum are constantly at working temperature Here is a little trouble concerning and the signals will be received as pick-up arms that is often encountered soon as the rectifier valve is returned and usually endured unnecessarily. to its holder. When a metal -cased pick-upis This " dodge " does not apply, of taken in the hand, either to change a course, when you are making adjust- needle or to place the pick-up in the ment to the power pack itself. record groove, a loud hum or crackle I am constantly coming across new is produced ;as soon as the operator reasons for fading signals. removes his hand the noise ceases. I have already mentioned several This is caused by the pick-up casing in this series, and I thought that INeat flex ends are always a safeguard being insecurely earthed and currents had covered all the likely ones. against short circuits, which in the case of are induced in the pick-up coils when However, a new one has reared its a mains unit might be particularly harmful. Justone stray strand of theflexis the potential of the casing is altered. ugly head and looks like making a sufficient to cause trouble. real nuisance of itself. NEON -TUBE TESTER The most distressing feature of thewhich I am not convinced is genuine trouble is that it will affect a very" man-made static." large percentage of the ever-increasing When a " mains aerial " is used it number of owners of powerful re-is easy to sec that the fluctuation in ceivers who operate them on smallsignal strength will be even more indooraerialsor,worsestill,on pronounced, for the conduit in this " mains aerials." case entirely surrounds the " aerial wire. Confirming Suspicions After longuse, volume controls The symptoms are sudden changesoften become noisy in operation, and of volume on all stations, sometimesparticularly is this the case with those accompanied by loud crackles andthat employ a carbon track for the resistance element. clicks, and are, in fact, identical to A neon tube in series with two testing those which obtain when faulty joints I have seen many of these com- points and with the mains isuseful for exist. ponents discarded as being worn out continuity tests of components.

326 October, 1933 MODERN WIRELESS

'6YOLIVER HALL D.Sc.

be tackled first of all in the aerial circuit of a wireless receiver.The more selective we can make the aerial circuit, the better chance we shall have of obtaining a good measure of THE most difficult wireless problem The results of some extremely selectivitythroughoutthe whole of to -day is undoubtedly the interesting experiments which receiver. problem ofselectivity. In prove how closely volume and When the problem of selectivity everywirelessreceiver,home -con- selectivity are interlinked. in the aerial circuit is attacked experi- structed or of commercial make, this mentally,the most strikingthing problem exists to a greater or less Similarly, there are few receiversabout the results is the manner in degree. which,onthe medium broadcast which selectivity is gained only at the There are few receivers which are wavelengths, are sufficiently selective expenseofvolume.Thisisvery sufficientlyselectiveon thelong - to give Prague and Langenberg clear clearly shown by a series of experi- wavelength band toseparatethe of North Regional, at least in thements recently carried out by the EiffelTower and Warsawtrans- North of England, or to give Breslau writer. missions from each other completely, clear of Poste Parisien, or Hilversum The aerial used in the experiments and to give Konigs Wusterhausen at clear of North National and Scottish was a good outdoor aerial of standard good strength without interference National. size, and the earth connection was of from Daventry Nationalor Radio Now it is fairly obvious that this proved efficiency.Using aerial and Paris. difficult problem of selectivity should earth and a coil tuned with a variable 30 tt NOAERIAL-SERIESCONDENSER FIXED AERIAL-SERIES CONDENSERI0002MF1D O OCLEAROFDAVENTRY 0 CLEAR OFDAvENTRY EIDAvENTRYHEARDFAINTLY 0 DAVENTRYHEARD FAINTLY

20 ODAVENTRYHEARDDLSTINMY

30 o do/0 280 (,) 2 -4260 cc --.1 0 cc Ce I-- 0 0 0240 03

260 220 FA 9 ./. ,C 4C ....1 -..j. . ,,, 240 200 o4.62 I--- 4., >220c.4 .180 s I-cx ¢ -.1 Fig.2. L...I =4. 200 Nc o c4 or 160 CI c L'i 3 N. 1 -180 . 0 Q. 0 2o 40 60 80 100 ''' 2 /6 , READINGS OF CONDENSER DIAL tr IN x The Fig. i curve was taken under the conditions given in Table 1, ce and shows how the "spread of Daventry was sufficient to cause a background on Motala and Radio Paris.With a fixed condenser 20 40 60 80 '00 of .0002 mfd. in series with the aerial there was a very considerable READ NOS OF CONDENSER DIAL reduction in Daventry's " spread " (Fig. 2).

327 MODERN WIRELESS October, 1933

TABLE 1. Coil 110 feet of No. 32 D.C.C. wire.Variable tuning condenser .0003 mfd. AERIAL CIRCUIT No aerial series condenser.

@ SELECTIVITY * Dial reading.. 1 01 101 201 30 1 40 1 50 1 601 70 80 90100 Strength of Day. Nat. . 1 0 I 0 1 1 2 1 5 1 15 1 25 10 1 0 0 a I I 1 a --Continued OZt;3 g&iPgtVq4siglw.:.'4'veC- TABLE 2. Coil110feet. Tuning condenser .0003 mfd. Aerial -seriescondenser 0002 mfd. condenser, measurements were made, Dial reading.. 0-70 1 80 1 85 1 88 1 90 1 92 I 94 1 96 1 100 ' by means of a Moullin voltmeter, of Strength of Day.at. [ 0 1 1 1 8 1 21 1 18 1 8 1 4 1 2 1 0 the strength of Daventry National. The circuit diagram of the very Daventry National was heard through aerial -series fixed condenser in circuit. simple apparatus is given in circuitMotala and Radio Paris when the The beneficial use of an aerial -series Diagram A.For convenience,the receiver was tuned to these stations. fixed condenser of .0002-mfd. capa- Also Daventry was heard distinctly city is at once seen from Fig. 2.With DIRECT -COUPLED enough through Warsaw and the no aerial -series condenser, the AERIAL Eiffel Tower transmissions to spoil " spread " of Daventry National, as reception of those two stations. A Huizen, however, was quite clear WITH SERIES of Daventry. CONDENSER In the next experiment an aerial - B series fixed condenser of .0002-mfd. /WOUL /N capacity was brought into circuit, as VOLTMETER shown in circuit Diagram B.Read- ings were taken of the strength of Daventry National over the whole of /1/10C/L L //11 VOLTHE TER the tuning condenser.These readings Measurements were carried out on are given in Table 2, and are shown 71orDaventry,seventymilesaway, in the form of a diagram in Fig. 2. using a simple tuning circuit con- On the same diagram is drawn, for nected to a Moullin voltmeter. The gain in selectivity with a fixed comparative purposes, a tuning curve condenser in series with the aerial forthecoilwiththis.0002-mfd. readingsoftheMoullin voltmeter was only achieved at the expense of volume. were made on an arbitrary scale, the values given being strictly comparable A 66 SLIMMER" CURVE shown, was approximately from 20 throughout the experiments. 1111 to 80 divisions, i.e. over 60 divisions The coil used in the first experi- FIXED AERIAL -SERIES on the dial of the tuning condenser. _CONDOISE71.000IMID With an aerial -series condenser of ments consisted of 110 feet of No. 32 ['CLEAR OF DAVENTRY gaugeD.C.C.wiretunedwitha ODA/ENTRY HEARD FAINTLY -0002 mfd., the " spread " of Daven- variablecondenserof maximum try National, as shown in Table 2 capacity .0003-mfd.Readings of the F19.3. and Fig. 2, is from 80 to 98 divisions, strength of Daventry National were i.e. over 18 divisions on the dial. taken at every tenth division of the 141 variable condenser dial from 0 to 100. ... Another Advantage These readings are given in Table 1, .:,. t 240 Another advantage arising from the and they are illustrated in Fig. 1. Pp use of an aerial -series condenser is also X220 shown by comparison of Figs. 1 and 2. Daventry's Spread I In Fig. 1 the available range of the In order to show how the trans- 200 coil is seen to be from 245 to 160 mission of Daventry National spread 1-: kilocycles, i.e. 85 kilocycles.In Fig. 2 over the condenser dial and so inter- 180 1 the range of the same coil is seen to fered with the receptionofother be from 315 to 182 kilocycles, i.e. 133 long -wave stations, a tuning curveZ a kilocycles. 6070 80 90 100 for this coil of 110 feet of wire is also READINGS OF CONDENSER DIAL Hence, not only did this .0002-mfd. shown in Fig.1. As will be seen The use of a -000r-mfd. series condenser aerial -seriescondenserreducethe from this diagram, with thiscoil, reduced the volume by 25 per cent. spread " of Daventry National, but

TABLE 3. Coil110feet.Tuning condenser .0003 mfd.Aerial -series condenser THE RESULTS COMPARED .0001 mfd. PII.1. Dial reading 1 92 1 910 1 9155 1966 1 98 1100 MAXIMUMS7RENGDI2I. Strength of Day. Nat. I a-900 I 9°2 1 4 1 14 1 1 6 1 2 9 .1 11°

TABLE 4. Variable aerial -series condenser at .0001 mfd. i

Dial reading.. .. 1 30 1 38 1 47 I 521 56 1 59I 60 I 64 I 67 70 1 74 I 80 :11° 0091MFD .00005M I 1 1 Strength of Day. Nat. 0 1 1 2 4 1 10 1 20 21 1 10 1 4 2 1 1 1 0

P. pato A Variable aerial series condenser at .00005 mfd. °20 30 40 50 60 70 80 60 70 BO 170

I 1 I 1 1 1 READINGS Dial ReadingI60 62 64 66 68 1 69 70 71 73 76 I 78 OF CONDENSER 0 AL

I 1 1 I 1 1 I 1 I 1 1 Strength of Day. Nat- -.. 1 0 2 6 10 12 10 6 2 0 Here we have three curves drawn to the Variable aerial -series condenser at .000025 mfd. same scale for comparison, and the loss of volume duetothereductioninthe Dm) reading ...... i 70 I 72 1 74 1 76 1 79 capacity of the series condenser can be Strength of Day. Nat...... 1 0 1 1 3 1 2 1 0 clearly seen.

328 October, 1933 MODERN WIRELESS

015@ga$D6lb %EffiEM655.,J.:',Wg the capacity value at this setting AERIAL CIRCUIT 2 VARIABLE AERIAL -SERIES being approximately .00005-mfd. CONDENSER AT .00005 MFD Lastly, the " spread " of Daventry g SELECTIVITY g OCLEAR OF NORTHRec. was taken for a setting of the variable g -continued g 0 NORTH REG. HEARD RIMY D taNORTH REG. HEARD Oi97 series condenser of .000025-mfd. ap- g.A.(83ggsE30300C3643(gg4M NORTH REG. HEARDLOLIOLY proximately. The threesetsof readings are given in Table 4, and are it also increased the tuning range of shown as a diagram in Fig. 4. the coil. With Daventry audible through the Increasing Selectivity Warsaw andEiffelTowertrans- With the variable series condenser missions, selectivity would hardly be set at .0001-mfd., Daventry could be considered satisfactory.Accordingly, heard faintly through Radio Paris and in the next experiment, a fixed con- through Warsaw.With the conden- denser of -0001-mfd.capacity was ser at .00005-mfd., Radio Paris was 1/4-) used as an aerial -series condenser. *r) 640 clearofDaventry,but Daventry Readings taken of the strength of could be heard faintly through the Daventry National over the tuning 2 420 Eiffel Tower and Warsaw signals. condenser dial are given in Table 3, With the condenser at .000025- and are illustrated in Fig. 3.A tuning mfd., Radio Paris, Eiffel Tower and curve is also drawn in Fig. 3. 2600 Warsaw were all clear of Daventry. cr580 A reasonably good measure of selec- Reduced Strength 1,1 tivity was thus obtained. The firstthing to notice about LZ560 Fig. 3 is the reduction in the strength A Typical Example of Daventry.With no aerial series Looking at Table 4, however, we condenser the maximum strength of 40 60 80 100 READINGSOF CONDENSERDIAL see that this selectivity was obtained Daventry was 25 units (see Fig. 1). at the expense of a big reduction in With an aerial -series condenser ofand with an aerial -series condenser the strength of Daventry National. .0002-mfd., the maximum strength of .0001-mfd., the maximum strength With the variable aerial -series con- of Daventry was 21 units (see Fig. 2) ; of Daventry was 16 units (see Fig. 3). denser set at its maximum value of .0001-infd., the maximum strength TABLE 5. Coil 40 feet.Aerial -series condenser .0001 mfd of Daventry was 21. Dial reading .. 65 1 68 I 69 1 72 I 74 75 I 78I 85 ' With the condenser set at a low I I I 1 I I Strength of North Reg. .. -.. " 01 2 6 10 23 10 6 2 0 enough value to give a necessary TABLE 6. Coil 40 feet.Aerial -series condenser -00005 mfd. degree of selectivity for the receiver (Continued on page 380) Dial reading .. 1 70 I 74 751 176 1 77 1 78 I 781 1 80 82

Strength of North Reg. 1 0 1 2 I 6 1 10 1 14 1 10 1 6 1 2

I I TABLE7. Coil 40 feet.Aerial -series condenser .000025 mfd. I Fi 9 11 VARIABLEAERIAL-SERIES Dial reading ...... CONDENSERAT .000025MFD re 0 2 0 Stngth of North Reg...... ".. I 81 I 83 I 85 OCLEAROFN. REG.

VARIABLE AERIAL-SERIES CONDENSER Reducing the value of the aerial - ft. AT 0001 MFD. series condenser from .0002 to '0001- o 6 25 IQ mfd. brought about a reduction in i.... c, .5 i.3 20 0 signal strength of Daventry from 21 to Lei k- - 0 CLEAR OF N. REGIONAL Li FF.55" F?"4 16, roughtly a 25 per cent reduction. N. ILEG.HEAAD FAINTLY /54Some compensation, however, is seen 680 f\ 0..vi 'i. N.REG.HEAR0 LOUDLY in the " slimmer " strength curve of , /0 !Fig. 3. o ' 660 oc 5? Further Experiment 1-.. . In the next experiment a slightly vi 700 0.1 W640 .. different coil was used, and a variable Z

04' ' aerial -series condenser. The "spread" aCe ' 68 1 LI44 r V 4''' of Daventry was first taken for a kj620 CO 0 '41 : 661 4 setting of the aerial -series condenser t7-44 4.1 at its maximum capacity, approxi- -J 'is 600 Stu , 64 , mately .0001-mfd. CC, ikg I

,..4 1 O ,1..Z. ''' 0.. w co ip The " spread " of Daventry was 62/ 4 `.`:1' ,t e' . then taken for a half -way position of 580 t 0Cr T the variable aerial -series condenser,2 ..4 k 60 l' P, 171 4: ct 4, 4.4 ,. . NORTH REGIONAL TESTS Qr560 1- / % '4 n ki 58 2 % CY For the medium waveband tests the aerial (74 2 coil was tuned by a 0003-mfd. condenser, k 56) 4., and the curves in Figs. 5, 6 and 7 show the 2 effect on volume and selectivityofde- 60 80 /00 60 80 I00 creasing the aerial -series capacity. READINGS OF CONDENSER DIAL

329 MODERN WIRELES3 October, 1933

least.Itisan excellentpieceof electrical and mechanical engineering. It is, of course, the product of a world-wide famous gramophone concern, who should (and undoubtedly do) know what itisdoing where record reproduction is concerned. Making Allowances The response curveisexcellent, TAN showing that adequate allowance is made for deficiency in bass recording By on the record without in any way TONE ARM overdoingit.Many pick-upsfall News of the Record Wor-Piek-up too- short of the ideal by over -emphasising siderations. the bass " lift " in their design, but Columbia have not fallen into this mistake. THErecord -producing war is goingdesigners, having put good apparatus The high end of the musical scale on apace.Better and betterinto the radio and L.F. amplifier side,is well rendered, too, the reproduction valuefor money (and whathave tried to cut down cost on thebeing brilliant without being scratchy little money !)is being provided, so pick-up. or harsh-another score over many that there is not the slightest excuse of the designs that have come my for the owner of gramophone or radio- Specialised Knowledge way.At the price of 32s. 6d. the gram not to have a large percentage This is a false economy indeed, forColumbia pick-up is excellent value of the latest dance hits and otherthis link in the chain need not beand I have no hesitation in recom- numbers in his record library. expensive to be good, but will un- mendingittoradiogram owners doubtedly ruin the whole instrumentand constructors. On the Humorous Side if it is of poor design. The most recent gun to be fired in There is a number of pick-ups on Preventing Induction the war is that by the Crystalate the market which can be termed first- Three leads are provided with the Gramophone Record Manufacturingclass, and I try to test as many ofinstrument, two for the L.F. feed, Co., Ltd., who have produced thethem as possible so that I can trulyand the third for earthing the frame " Rex "records at the astonishingjudgethequalitiesof commercialof the instrument.This is a valuable price of one shilling.They are ten - feature, especially inch double -sided discs of undoubtedly A TRULY EXCELLENT PICK-UP where mains sets high quality from the playing point are concerned, and of view, and they represent remark- a certain amount able value. of A.C. induction The first issue arrived on September intothepick-up 7th,and consistedof15records may take place. comprising a wide variety of bands and The pick-upis artistes. There were Chick Bullock, the moderatelysensi- famous American Radio artiste, and tive, givingan Dan Donovan, whose voice is so well output of0.75 known to listeners. volts r.m.s., while On the humorous side, Sandy Powell its impedance is of leads the way, and it is interesting to the order of 4,200 know that his records on Broadcast ohms at 800 cycles. have passed the three -million mark. The D.C. resis- He is assisted in the list, on another tance is 1,350 ohms record, by Charlie Higgins. or so, while a volume control of A Weak Point 50,000 ohmsis The rest of the fifteen are equally recommended as excellent value, and should be heard most suitable by by all gramophone owners who are the makers. out for real bargains. Of proved make, this pick-up is fine value for money.It High Notes But however good a record is, it has just the right amount of bass compensation, and the arm cannot give ofits best unless the will remain fixed in a raised position for needle changing. This latter value, reproducer is properly designed, with ofcourse,pre - a good amplifier and loudspeaker,apparatus I have to hear, and it issupposes that the amplifier charac- and, most important, a pick-up thatsurprising how excellent many are.teristics are reasonably straight, for if can handle the musical variationsThere are others which are not well - the latter is prone to over -emphasise with ease and precision. designed,ofcourse, but they are the high notes, as it may well do where The pick-up has been the weakbecoming increasingly few. a pentode output valveisused, a point in a great number of radio - The Columbia pick-up is the latestvolume control of lower value may gramophones I have heard recently,addition to my test bag, and 'I feel be more satisfactory, 10,000 to 20,000 and I fear that too many commercialthat it is truly a case of last but notohms being suggested.

330 October, 1933 MODERN WIRELESS WHAT ARE WAVES ?

lighting of the screen so long as the liquid in the dish is kept immovable. As soon, however, as the water (or mercury) surface is stirred up by some mechanical effect, there will be WAVESare everywhere :all phy- Now, it will be readily understood a marked change in the appearance sicalphenomena, whether how invaluable such a demonstration ofthescreen.Such an effectis acoustic, thermic, optical or would be, not only for purposes of exerted by an electrically operated electric, even those occurring in the instruction but for the solution of tuning fork arranged over the liquid, interior of atomic systems, are due to many problemsinscientificand which, by means of a point carried by wave motion. engineering practice ; theoretical specu- one of its branches will stir its sur- In order to arrive at a closer under- lation being superseded by or being face, producing ripples and trains of standing of Nature and the way she supplemented with the much more waves, in the same way as throwing behaves, a more definite knowledge convincing evidence of actual tests. a stone into a pond. of wave motion-how it arises and how it assertsitself under a variety of Shaded Picture circumstances-isfoundindispens- It's called an "Ondoscope "-the apparatus atthe head of this In fact, byso doing, onlythe able. page-andit shows up wave- light from the horizontal parts of the form in a strikingly clear manner liquid surfaceis allowed to reach Insurmountable Difficulties hithertoimpossible.Compli- cated wave combinations on the and illuminate the screen.All in- Though the formation and pro- top of a bath of liquid are pro- clined portions of the ruffled surface, jected on to a screen for exami- pagation of waves is illustrated most on the other hand,willbe kept simply by throwing a stone into water, nation. By Dr. ALFRED GRADENWITZ. in the dark more or less by a stop no means of actually visualising how interceptingthebeamsoflight, -in accordance with laws common to thus projecting on the screen a beau- allof them-they behave on being lendingitselfto tifully shaded picture of a train of reflected, refracted or diffracted was An apparatus waves passing over the liquid surface so faravailable.Allendeavours such a demonstration has just been with all such alterations as can be made in this direction bad met with devised by Professor E. Charbon, of Lille University, and is termed the effected by the most diverse means. insurmountable difficulties. However,inorderthatthese Even in the case of light there was " Ondoscope " by its inventor.Its phenomena may be watched and no possibility of demonstrating actual design and its very interesting mode of working are briefly outlined in the A DOUBLE EFFECT " RECORD -LIKE " WAVES following paragraphs. Reflecting Prisms The " Ondoscope " primarily com- prises an electric arc and an optical system projecting this on a screen. If the latter were struck direct by the light of the arc, a brilliantly illuminated surface only would be visible. As it is, however, the beams of light are deflected from their straight course by a reflecting prism throwing them (through a lens) vertically downwards on a flat dish filled with water or mercury. The latter (or else, in the case of a Fig. A simple wave -form produced by water -filled dish, its silvered bottom) Fig. 2 : With two " points," and viewed a single " point."Itis very much like will reflect the beams of light back with a steady light, this stationary wave- thewater movement produced when a upwards on another prism, deflecting form is produced. stone is dropped into a pond. them once more into theirinitial gauged with even greater ease and wave motion, all optical phenomena horizontal course. In fact, the ad- accuracy, the " Ondoscope " can be illustrating the behaviour of beams dition of reflecting prisms will make combined with some sort of " Strobo rather than trains of waves. no difference to the uniformly bright scope," i.e.with a device which, as

:331 MODERN WIRELESS October, 1933

CRISS -CROSS EFFECTS The waves shown in the left-hand picture (Fig. 3) are similar to those illustrated on the right of the previous page, but this time are viewed with anintermittentlight. On the right (Fig. 4) are waves from single" point "beingreflected from a ruler.

The light -flashis,in the present case, given the form of a rotating disc comprising a hole near its circumference, and enables trainsof waves to be watched either at rest or *nterred from the following, effects at considerably reduced speed. permanent illumination.lf, on th, an intermittent illumination. If the tuning fork has a single other hand, this device be resorted to Supposing a disc on which a radial pointtherewillappearonthe i.e.inthecaseofintermittent stroke, i.e. a straight line from thescreen a sequence of circular wave illumination, there is a perfect change centre to the circumference, has been trains of remarkably plastic effects, in the picture projected on the screen, traced, to be the two original rotatedatcon- THE " ONDOSCOPE " PRINCIPLE IS QUITE SIMPLE circular trains of siderable spec d, waves being seen the rapidly mov- distinctly,starting stroke cannot ing from the two any longer be dis- points, crossing cerned.If, how- each otherand ever, the disc be formingmost lightedintermit- beautifulfigures tently-say, once (Fig.3). When for a brief interval photographing during each rota- the phenomenon, tion-thestroke the picture, as in will be distinctly Fig. 3, is obtained seen on a seem- in the case of a A diagrammatic representa- ingly immovable tion of the apparatus em- very short expo- disc. ployedinobtainingthe sure, whereas the photographs of wave -forms one in Fig.2is Rotating which are reproduced on obtainedbya this page. The light inter- Disc ruptor may be used, or not, more prolonged lf, on the other as desired, and its speed may exposure, ofthe hand, the flashes also be varied. .14 order of a second. of light follow up In Fig. 4 a cir- one another more cular wave is rapidly than the shown whichis discisrotating, reflected from the the stroke will appear to move for- which, in accordance with the actual edge of a ruler, the reflected train ward-while in the case of a slower adjustmentoftheintermittently of waves seeming to start from a sym- succession of flashes it will: be seen to illuminating " Stroboscope, " are seen metrical point. move backward at a low rate of speed. either to remain at rest or to move (Continued on page 382) slowly forward or backward-a beau- ELLIPTIC REFLECTIONS tiful phenomenon of which Fig.I REFRACTION OF WAVES gives at least a certain idea. Permanent Illumination When two points, instead of one, are used, the picture shown in Fig. 2 of two trainsof hyperbolic wave trains is obtained without the flash - lighting device,i.e.in the case of

The waves on the left (Fig. 5) are produced at the lower focus of the ellipse, but the reflected rays are focussed at the upper focus.On the right (Fig. 6) the waves are seen passing from water to mercury and thus being refracted.

332 October, 1933 MODERN WIRELESS

The R.I. Auto -Para feed "Metaplex " Baseboards THE R.I. Auto-Parafeed Trans- Our comments regarding some One of the most useful materials former is one of the latest ever placed before the home con- developments of the parallel - interesting new components. structor is " Metaplex," the metallised feed method.It is a very compact baseboard manufactured by Messrs. component, having a nickel -iron core R.I. product embodies curves calcu- Pet o -Scott. of high permeability and a system of lated on a decibel basis, and these Itisparticularly useful now so internal shielding. give a clearer idea of the actualmany set designs specifyshielded Butinsteadoftheusualfour response of the device than do voltage baseboards."Metaplex " is a stout terminals, it has only three, and is amplification curves. plywood on the surface of which metal thus correspondingly easier to connect has 1 een sprayed. in circuit. Butacompletelyhomogeneous Nevertheless, alternative methods PROTEC- layer is deposited, due to the employ- ofconnectionarestillavailable, TION ment of a patented process instead although thesatisfactoryratioof FROM oftheinefficientparticle -separated 1-4 is maintained. DUST layer that might be anticipated from The primaryinductanceis85 a normal spraying process. henries, and the resistance of the One ofthe The result is perfect shielding. And primary is 1,100 ohms. The secondary enclosedTelsen totally it is shielding with which it is very winding has a resistance of 3,900 differential easy to make connections, for screws ohms. reaction con- can be driven through the metal layer It is a very well -made component, densers. with the wood beneath without the and its shape is distinctively original. necessity of special boring or drilling The price is 6s. 9d.On test the operations. R.I. Auto-Parafeed functionedad- A Telsen Condenser Finally, the price of " Metaplex mirably,asensiblystraightline We particularly recommend the is sufficiently low to make it com- amplification being given. attention of constructors to the newpetitive with ordinary wooden base- It is interesting to note that the Telsen differential condenser.Itis boards ! descriptive literature concerning this afirst-classcomponent,available at a particularly reasonable price. SPRAYED WITH METAL FOR PARALLEL -FEED It is of the completely enclosed type, the vanes being protected against both dust and mechanical damage.And even though it is encased, its size is rather less than the average. A pigtail, very firmly anchored, is provided. Various values are available from 0003 mfd. to .0001 mfd., each at 2s. The samples we tested were found tobeentirelyinlinewiththeir specifications. The capacities were as specified and, what is even more " Metaplex " baseboards, made by Messrs. important in many cases, the two Peto-Scott,providescreening andalso halves were perfectly balanced. simplify, wiring. The movementissmoothand, indeed, the component is a delight Short -Wave Condensers to handle. We consider it to be among British Radiophone have recently Simplification of the connections for auto - transformer coupling is provided by this the three best differentials made, quite gone into production with a short- R.I. component. irrespective of price. wave variable condenser that

333 MODERN WIRELESS October. 1933 Items for Class B and Short Waves embodies several valuable novelties A Good Battery Also,athirdterminal isnow of design. We have had the opportunity of provided so that either the H.F. or It is mounted on a base of porce-testing a Millgate H.T. battery.It L.F. winding can be used separately lain material and, with the exception or the component employed in special ofthat,thereisnegligiblesolid FITTED WITH filtering circuits. dielectric-practicallynoneatall A FUSE As readers will doubtless know. inthe electro-staticfield. Losses the R.I. "Audirad " is a combination arethereforereduced toamin- of H.F. and L.F. chokes. imum. Wherever an L.F. choke is normally The vanes are of hard brass and specified, such as for smoothing in a are very rigidly assembled, as is also An incor_ mains unit or set, or as an output the robust frame. porated fuse is choke, the " Audirad " can be used. The pigtail is arranged in accord- one of the features But it has the added advantage that ance with the latest technique.It is oftheMillgate it chokes at H.F. as well as L.F. kept at tension and is led out from the H.T. battery. This is an enormous advantage in a hollowed spindle. is of the standard capacity type-at smoothing circuit.Very often there Mechanically this British Radio- least the one we tested was-and it is FOR H.F. AND L.F. phone condenseralsoreflectsthe fitted with a fuse. greatest credit upon its manufacturer, While not being an entirely novel for the movement isquite above idea, this scheme is one that has much criticism. to commend it, for the safety device is placed in the one spot where it S.W. CONDENSERS can be of the greatest use, i.e. at the source of power itself. In this way even the battery leads are prevented from carrying a danger- ously high current. We gave the " Millgate " our usual series of period test discharges and the battery showed up well under them. The voltage drop was delayed, and was even over the cells. Ganged andsinglevariablecondensers The R.I. "Audirad " Choke specially constructed by British Radiophone for short waves. That extremely useful component, The new Radio Instruments " Audirad " theR.I. Audirad "choke,has choke can be used for H.F. or L.F. separ- The condenser is available in two beenstillfurtherimproved.Its ately or as a combined component. types, a singlet for normal purposes resistance has been dropped to below are H.F. irregularities on the mains -- and a two -gang forsuperhet and 500 ohms, and its general efficiency indeed, there always are to some other special purposes. has been raised. extent-and frequently they are so AN ATTRACTIVE FERRANTI SPEAKER -AMPLIFIER bad that mains H.F. chokes have to be brought in to deal with it. If an " Audirad " had been used in the first place this would be quite unnecessary. And inasmuch as it costs no more than most ordinary L.F. chokes, it is not surprising that even in its original form it proved an exceedingly popular component. With the added improvements and no increase in price, it should com- mand very big sales this season, Ferranti Class B Speakers Ferranti,Ltd.,are now making specialClass B loudspeakers, and this will, we feel sure, be good news to constructors. Their speaker -amplifierisa particularly interesting and important production. As its name suggests, it is The recently introduced FerrantiClass B " speaker and amplifier combined.The a combined Class B amplifier and plain speaker on the right shows up the simple nature of the amplifier components. loudspeaker. October, 1933 MODERN WIRELESS Simplifying the Construction of Radio Receivers

The accompanying photograph' will WIDE RANGE AVAILABLE valves and mains resistances,etc. give you a very clear idea of its general Anotherfinelittlewire -end com- appearance and size, for the speaker ponent made by Telsen which we shown in the same picture is of normal can also strongly recommend isthe proportions, and is,of course, the Telsen small tubular condenser. same type as figures in the speaker - This is made in values from .0001 amplifier. mfd. to .006 mfd., and retails at ls. The unit is all complete for con- In addition thereis a O1 mfd. at necting to practically any existing Is. 3d., and a 1 mfd. at Is. 6d. battery set.And the addition is a Despiteits extreme compactness quite simple one to carry out. and low price, this Telsen condenser The result of adding a stage of is tested to 1,500 volts, and it is a " Class B," and in particular one com- most efficient and dependable com- posed entirely of Ferranti apparatus, ponent. Constructors owe a great can easily be appre- debt to Telsen for producing such ciated. desirable apparatus at such prices. Actually, the power There is also a Telsen high -voltage output is increased electrolytic condenser to which we many timeswithout must draw our readers'attention. greatly adding to the This is a very attractive component, H.T. consumption. and is as well designed and made as Examples of the Telsen resistors which are anything of its kind we have ever available in various wattage ratings. seen. HIGH VOLTAGE A valuable practical feature is that ELECTROLYTIC very tough.Also, it does not tend it is supplied with a special bracket CONDENSER to fray. for mounting on any type of base- It is a tight fit over the wire, but, board or chassis. Beingofthe dry type, There are two types :the one is for this Telse n condenser being flexible and compressible,it a working peak voltage of 275 volts. may be mounted in any can be pushed back to bare the end and4-mfd.,6-mfd.,and8-mfd. position desired. of the wire, which, when exposed, is clean and all ready for connecting. WIRE -END CONDENSERS 'A Convenient Material When the connection is made the The wiringofasetisgreatly covering can be slipped up to complete facilitated by " Pull -Back," a new a neat and tidy job. material due to British Radiophone. We use quite a lot of " Pull -Back " It consists of tinned copper wire in our Research Dept., and find it a covered by a flexible treated fabric. great time-saver. This is an excellent insulator and is Telsen Resistors WIRING WITH "PULL -BACK" The Telsenresistorswith wired ends are available in an extremely wide range of values.Also they can be obtained in 4-, 1-, and 2 -watt and. on demand, 3- and 6 -watt ratings. The 4- and 1 -watt types, ranging from 250 to 500,000 ohms, cost only Is.each, and the 2 -watt types in values from 250 to 100,000 ohms, retail at 2s. each. Their wire ends render them very useful to the constructor, for they Another Telsen production.Fixed con- can with great ease be wired into or densers which can be wired into circuit. added to a set.Also, this feature makes them easily interchangeable. models list at 3s. 6d., 3s. 9d., and 4s. We haveusedaconsiderable respectively ;the other is for a maxi- number of them for various purposes mum peak voltage of 500 volts, and and have found them consistently the 4-,6-, and 8-mfd. valuescost satisfactory.Those we have checked 4s. 6d., 5s. and 5s. 6d. respectively. for resistance have been found to be These are astonishingly low prices, accurately rated and their values are it must be mentioned. maintained after they have been sub- Itshouldalsobeaddedthat, jected to current flow or used in being of the dry type, these Telsen The wiring -upof a receiver,sgreatly simplified by the use of Radiophone " Pull - areasofconsiderabletemperature electrolytics can be mounted in any Back " insulated wire. change ;such as close to large power position.

335 MODERN WIRELESS October, 1933 reproduce a picture as nearly like the original as possible. The explanation is that it greatly o SCOPHONY TELEVISION simplifies the process of scanning. In o A NEW DEVELOPMENT ordinary methods of television the Described by J.C. JEVONS. picture is scanned or cut up into a or number of parallel lines by a rotating The scanning method of this new system is such that to and fro movements 0 disc, which must effectively scan from o only are necessary-no up and down motion being required.Great b top to bottom of the picture, as well simplification of the apparatus is thus achieved. as from side to side. Z; ATeee:e:AC#ZorsroresVZe:e'«e'..eoze'...e.or.,:,:e'.e'..or.e.e-or.e ..e....e.,='..e .0...re...0..ezezeze:0:, A "Straight -Line" Process By first transforming the picture ROSPECTS are looking distinctly The Scophony system depends, ininto a single straight line, the whole brighter just now, so far asfact, upon the peculiar actionof of the scanning process can be reduced Ptelevision is concerned.One certain kinds of lenses or mirrors. to a simple to-and-fro movement in hears of new methods of approach Most of us, at one time or other,one plane, for instance, a uniform being opened up, and of a steadyhave been amused at the distortedhorizontal " sweep." No up and down stream of invention which is concen-image produced by the ordinary con-motion is necessary. trated on the object of bringing realvex or concave mirror.The kind of It therefore becomes possible to television into the home. thing, for instance, that is sometimesreplacethelargeandrelatively - In America and Germany especially placed outside a restaurant to in-clumsy rotating disc by a single small the technical Press is all agog withdicate the liberality of the fare pro-mirror, which need only vibrate to recent developments in the cathode-vided inside. and fro 12 to 15 times a second. ray receiver, and we may be sure that On entering,the customer sees Space is saved and driving power is Britishdesignersarenotlagging himself drawn out to a lean lath -likereduced.In addition the problem of behind. Infact,thereare good synchronisation is simplified because grounds forstating that a larger THE SCHEME EXPLAINED the mass of the moving mirror is so measure of success has already been 3 6' much less than that of a rotating disc. won with cathode-ray reception than is generally realised, and that before M Ei"ACEN.V Converting Back long some surprising results will be LINE cruzE The initial distortion of the picture made available to the general public. into a " straight line " image presents no insuperable difficulty.The effect Length and Breadth PRoefr kiEw OF 5rEpRwo . introduced by one optical arrangement Meanwhile we have to record the MIRROR 41311 iS40:W)tae° can always be reversed by a second. enterprise of Messrs. Ferranti, who 1.10[11 are backing the work of a British OR/GRNAL. PicruRE In other words, at the receiving end the " line " of light signals produced inventor-Mr. G. W. Walton.This The special stepped mirror splits the picture firm intends to place on the marketto be transmitted into sections, and at thefrom the neon lamp is converted back at an early date a new television - same time forms it into one line. intotheoriginaltwo-dimensional receiver possessing unusual features picture by interposing a distortion - which make it quite distinct fromfigure which, one might say, repre-reversing lens between the lamp and either the rotating -disc or the cathode-sented length without breadth.As the viewing screen. he leaves the premises, a second mirror (Continued on page 383) ray type of instrument. transforms him into a replete person \ / of overwhelming breadth. Fidelity Via Distortion I Considering that an ordinary mirror will do this kind of thing, Mr. Walton conceived the idea of going a step 11 further and producing an optical I r arrangement capable of actually trans- ....,:_.,----_--,_.___. 0_..__,4 .- 11, ,iii1/11) forming an ordinary two-dimensional image into a single straight line. of,:----.a kr-_.*-- -_..,42 At first sight one might wonder ,*....,,_:....,..,.. what advantage is to be gained from introducing such distortion-since the r i i4,._.-.,,,,....."-----..-_._:___----7------.! "i 1 object of television is naturally to j,, 1 , ------;--(L - -,..':--.-":": ----", I Basing his theory on the principles which are used to produce those weird effects sometimes seen in distorting mirrors out- / - side restaurants, the inventor of Scophony I - television set to work and produced an optical arrangement capable oftrans- -/ \ . forming a two-dimensional picture into - _..c. I- a single straight line.Thereby, of course. considerably simplifying scanning. / i I\\ October, 1933 MODERN WIRELESS

Wherever wireless terms are understood "Ohmite" means

"The " Better than wire wound." Best Pep Resistance'

Sate maximum current carryingcapacityof ' Ohmites." RE !STANCES 100° F Temperature Rae OHMITE Ohms. Milliamps.Ohms. Milliamps 1,000 40 20,0008 2,000 35 30,0006'75 The most popular and efficient type of fixed 3,000 29 40,000 6 4.000 24 50,000 5.5 5.000 20'25 60.000 5 resistance for all general purposes. "Better 10,000 12 80.0004'24 Othervalues 100.000 3'5 than wire wound."All values, prorata Safe maximumcurrent carrying capacityof 50 ohms to 5 megohms. " Ohmites " Heavy Duty Type. 100' FTemperature Rise HEAVY DUTY TYPE 2/3 Ohms. Milliamps. Ohms. Milliamps 1.000 80 20.000 16 2,000 70 30.000 13'5 3.000 58 40,000 12 4,000 48 50,000 11 5,000 40'5 60,000 10 10.000 24 80.000 8'48 Other values pro rata 100,000 7

Ensure a safeandefficient Aerial and Earth. The new AEROFICIENTKIT provides all you need. Complete 6/6

Send a postcard for our new Catalogue, which describes all our products. Advertisement of GRAHAM FA R IS HLTD., Masons Hill,BROMLEY, Kent. 41111.11.1.Export Office :1112, Fenchurch Street. E.C.3. 337 MODERN WIRELESS October, 1933

A Simple Addition audible when I have triediton gauge of wire in series with the mains G. M. (Erith).-" I have heard aanother set of similar type to my leads.One choke can be tried to lot about Class B amplification, and own. commence with, and this should be I have been wondering whether I " My setisastraight four,' joined first in the positive mains lead can convert my present set without having an S.G. H.F. stage, a grid - and then in the negative lead, in order leak detector and 2 L.F. valves." to find out which gives thebest completely rebuilding ? The set results. inquestionisan ordinary S.G., This is a very difficult question for us to answer in the absence of certain Or, alternatively, one choke can be detector and 1 L.F. ' three,' and the inserted in each lead, and a large valvesareabatteryvariable -mu vital details.Presumably the D.C. followed by an `H.L.' type with a unitisworkingwellwithinits condenser of 1 or 2 mfd. connected small power in the output stage." capacity, and that you are not trying across the mains unit side of the two to take more current from its tap- chokes. We have received numerous ques- There are commercial chokes avail- tions similar to yours. pings than theyareintendedto supply ? able which are specially designed for No doubt you have seen reference this job, and ordinary H.F. chokes, made in this journal to the special ii.1118111111111111111111111111111111111111111111t1III11111111111111111110.1 such as are used for reaction or shunt - ClassBunitsthatareonthe feed purposes are, of course, not suit- market. You could quite easily add TECHNICAL QUERIES able, owing to the thin wire used. one of these to your existing set, DEPARTMENT These special D.C. chokes are called joining the input terminals for the Are You in Trouble With Your Set upon to carry the whole of the current unit on to the existing loudspeaker The MODERN WIRELESS Technical Queries passing into the D.C. mains unit, and Department isin a position to give an terminals on your set, having first unrivalled service. The aim of the depart- therefore have to be robustly con- removed the loudspeaker. ment is to furnish really helpful advice, in connection with any radio problem, structed. Theseunitscompriseadriver theoretical or practical. Full details, including the revised scale of transformer, a " Class B " valve, and charges, can' be obtained direct from the Class B and G.B. a suitable output transformer ;and Technical Queries Department, MODERN WIRELESS, Fleetway House, Farringdon A. J. (Southsea).-" Am I right are available, in many cases, with a Street, London, E.C.4. A postcard will do. On receipt of this all the in supposing that a Class B valve built -on loudspeaker of the moving - necessary literature will be sent to you, free operates without negative grid bias, coil type. and post free, immediately.This application will place you under no obligation and that in a Class B receiver no Such units are suitablefor any whatever. EveryreaderofMODERN grid bias whatever is employed ? " normal type of circuit having one WIRELESS should have these details by him. An application form Isincluded You are right in one respect-and L.F. stage, and their addition does which will enable you to ask your questions so that we can deal with them expeditiously thatisthattheClass B valve, not necessitate any alterations to the and with the minimum of delay.Having this form you will know exactly what in- with the exception of two makes, is set. formation we require to have before us in designed to work without any nega- Thereceiver, of course,must order to solve your problem. London Readers, Please Note :Inquiries tive grid bias, the centre point on the not employ an output filtercircuit should not be made in person or by phone to Fleetway House or Talus House. winding of the driver transformer or output transformer, since the input being joined direct to the" earth terminals for the amplifier unit have tllinullllllllIlinllllIllIllnnlnlnllunlnllllllllllllnllllllilI to be joined in such a way that they line," i.e. L.T.-, H.T.-. Assuming that you have chosen the On the other hand, the driver valve are in series with H.T.-1- and the requires grid bias, the amount neces- output valve of the set. correct model for the job and that your valvesareproperlybiased, sary depending upon the typeof Unwanted H.F. Impulses there is just a possibility that a cer- valve used, but generally being between 3 and 6 volts. A.J.(Crouch End).-"I have tain amount of H.F. is being picked recently replaced my H.T. battery up by the mains, and subsequently Hence the use of Class B does not with a D.C. mains unit, and the modulated by the D.C. ripple in the eliminate thegrid -bias batteryal- results I obtain are perfectly satis-. supply. together. On the other hand, the factory except that there is a trace of Any H.F. picked up in this way grid battery need only be a small hum which is always present in the may appear in the output circuit ofone-about halfthesizeofthat background. the receiver, since it is liable to be normally used in the case of super- " The unit itselfis a very good induced into the set's wiring. poweroutputvalve. Thegreat one, and I do not think that the hum The most satisfactory remedy is to advantage of Class B isits power can be due to any faultin the insert one or two well -insulated H.F. and H.T. economy, the savingin design, especially since no hum was chokes wound withasubstantial G.B. being a minor matter.

338 October, 1933 MODERNWIRELESS Smooth silent perfect

MEGITE POTENTIOMETER VOLUME CONTROL OHMITE RESISTANCES The most popular and efficienttypeof The elementisoffinenickel -chrome wire fixed resistance forallgeneral purposes Better than wirewound:. embedded in bakelite.The action is through a Allvalues, 50 ohmsto 5 megohms. 1'5 watt. 116 Heavy Duty Type, 2!3. slipper plate, giving a smooth, positive contact, 3 watt. absolutely silent operation and making broken contactsimpossible. Threeterminaltype. Singleholefixing. Complete with operating knob. PRICE Resistances 25,000 ohms and over, 4/6 KONE KAP GRID LEAKS A good grid leak of the carbon type,fits most condensers and holders. Supplied in values of 5,I, 2, 3,4 and 5 megohms. Price d. STANDARD GRID LEAKS Counterpart of the Kone Kap, but fitted with Terminal Ends for easyandsure contact. Made in values of 5, f,I,2, 3,4 and 5 megohms. Price d.

Ensure a safe and efficient Aerial and Earth. The newAEROFICIENTKIT provides all you need. Complete 11.,a//6 Send a postcard for new catalogue describing all our products.

Advertisement of GRAHAM FAR ISH LTD., Masons Hill, BROMLEY, Kent. IMMOMMICExport Office :1112, Fenchurch Street, E.C.3. :339 MODERN WIRELESS October, 1933

AN EXCLUSIVE "M.W." ARTICLE- THE RADIO NEWSPAPER A description of how the German R.R.G. Company providesits news servicefortheRegionalstations

is able to send messages to the central office and to any of the otherlocal companies. USED BY BRITISH POST OFFICE A teleprinterservice wasrecently made available bytheBritishPost

C;) tromgsberg THE German Central Broadcasting Company, the R.R.G., R P.O. Haus Oes .Prohtloser carries on a very active news service for the benefit of Hamburg Rrodfunla Diefur the various local broadcasting companies of Germany. Political and other news issent out from Berlin to be broadcast by stations all over Germany, and Berlin receives in turn local news from these stations. An English invention, the teleprinter, has been installed by the R.R.G. to handle this news service.The teleprinter is kat, Leipzig a machine for sending messages tires/au by telegraph and contains a key- frat),,lurt boardlikethat of an ordinary typewriter.As the operator of the sending machine types asen- Stuttgart tencethereceiving Muncher machine types the same sentence simultaneously letter by letter, whether anyone is in attendance at the receiving machine Office to private subscribers, who can or not.Thus informa- dial through to any other subscriber tion typed on the tele- and type a message. If the other sub- printer in Berlinisin- scriber is away the message remains stantaneously in type at, ready typeduntilhe returns. The say, Leipzig. A switch- German machines are manufactured ing system permits any under the same patents by a German number of local stations firm. An amusing evidence of their toreceivethe same English originisthe German name message simultaneously. for the teleprinter -the "Start -Stop Orthe local station Fernschreiber," "start " and "stop " being in English.

THE MACHINES EMPLOYED The bottom photo shows the machine which both transmits and receives messages. In the circle is the switchboard being operated, and on the right of it a transmitter -receiver. The top picture is a general view of the installation, and shows the switchboard, the fuse -board (on the wall) and three smaller machines for speeding -up transmission.The two smaller machines, with keyboards, are operated in the same way as the transmitter - receiver, but instead of transmitting the message direct they punchitin code on a paper tape.This paper tape can be fed through the transmitting machine on the extreme left of the picture at more than twice the speed at which an operator can type. This special type of transmitting machine can therefore send on one pair of land -lines twice as much matter in a given time as the ordinary transmitter -receivers. The general arrangement of the whole system is outlined in the map. The various sources of news are connected to a central office where the news is sorted out and the bulletins forwarded to the distributing section.The latter is directly in contact with the important stations throughout Germany, and is able to put one station in touch with another should this be desired. A. BROWN. October, 1933 MODERN WIRELESS

NEW and better than many at double its price

PI PTRANSFORMER ThePIP transformeristhoroughly MEGITE sound in construction and design and POTENTIOMETER gives a result equalling and often better VOLUME CONTROL The elementis ofthefinenickel. than others at a much higher price. chrome wire embedded inbakelite. The action is through a slipper plate, giving a smooth,positivecontact, absolutely silent operation and making Indistinctiveredcase broken contacts impossible. Three terminaltype. Singleholefixing with nickel terminals. Complete with operating knob. PRICE 3/6 Made in 3 :1 and 5 :1 25,000 ohms. and over 4/6 ratios. PRICE

VALVE HOLDERS These Valve Holders have exception- allylowloss mouldedbases,the insulatingmaterialbetweensockets being reduced to a minimum.Con- tacts are of phosphor bronze, sturdy in Ensure a sate and efficientAerial and Earth. The new design. AEROFICIENT KIT provides all you need. Complete 616 Four Pin F ye Pin Seven Pin Send a postcard for our new Catalogue, which describes Type, 6d Type, 8d. Type 1/3 n11 our products Advertisement ofGRAHAM FAR ISH LTD.,Masons Hill,BROMLEY, Kent. IA Export Office:11/12, Fenchu-ch Street, E.C.3. 341 MODERN WIRELESS October, 1933

By G. V. DOWDING, Associate I.E.E.

Ir is extremely easy to add a pick-Here are some valuable hints and tipsin the set we now have three L.F. up to almost any radio outfit,forradiogramenthusiasts,including valves and that constitutes a very but itis by no means easy topractical methods of avoiding pick-uppowerful amplifier.And, as such, it make it give really good results. instability. will prove extremely sensitive-far And, generallyspeaking, the more sensitive than is desired for the " gram " reproduction of the average average modern pick-up. set compares very unfavourably with On the other hand, lead screening This will be proved by the necessity that of the radio side. is sensible and satisfactory and will of applying drastic volume controlling, But .I will deal with the question kill an incipient howl. or, if there is no volume control, by of quality later on ;first the pick-up As a matter of fact, this and otherexcruciatinglyloudsquealing and RESISTANCE VARIATION things of a similar nature I regard as roaring. almost essential for all pick-up in- A Complicated Ideal stallations. Perhaps I had better Obviously, then, an input volume describe them in detail. control for the pick-up is essential. The leads which run from the set And if, when this is applied, the to the pick-up should be of shieldedsquealing leaves off and there is still wire, with the shielding connected toplenty of volume, it may not be the earth terminal of the set by meansnecessary to do anything further. of the shortestlead possible using Alternatively, the amplification of stout wire. the "detector " valve can be cut down, (Note that I say " earth terminal If the volume control is connected in this of the set " ; the reason is that it may THE CORRECT METHOD way the value of resistance across thebe desirable to dispense with an earth pick-up will alter every time an adjust- connection from the receiver.) ment is made. The pick-up arm ought also to be must be made to work. And that isconnected to the set's earth terminal, not so simple as it sounds. and in the case of a clockwork turn- Apparently, quite stable receiverstable motor this needs thesame will develop the most rabid of squeals treatment. the moment a pick-up is switched in. Even when the pick-up leads are There are certain external specificsshielded, however, they must still be widely recommended forstopping kept as short as is possible. With this method the resistance value is such squeals, but my experience is All this having been done, the theory constant, the position of the slider simply is howling ought not to occur. But it determining the voltage applied to the grid that they do little good in really bad of the valve. cases. often does !And the constructor probably feels quite hopeless about it.but such a scheme is not to be recom- Remedies to Try It is true that he can still try themended to the inexpert contructor. For example, it has frequently been simple expedient of changing over the Of course, the ideal is to have an said that to insert a transformer be-pick-up leads. Nevertheless,itis input volume control for each of the tween the pick-up and the set is anseldom that that does the trick. valves, so that the input to each almost certain cure. Now let us pause for a moment andvalve can be independently adjusted. I am not sure what the purpose ofstudy the conditions that probably But that is not making for simple the transformer is supposed to be, exist. radio ! but Iwrite from first-hand experi- No doubt the pick-up has been A better method for general use ence when Isay that itis hardlyswitched into the detector circuit andwould be to take the pick-up direct worth trying. I have never yet knownthis now becomes an L.F. inputstage.to the first L.F. valve and ignore the it to do any good. If there were two ordinary L.F. stages (Continued on page 388)

342 Cctober, 1933 MODERN WIRELESS

"When better Condensers are possible

build them" Graham Faris'',

ZELOSVARIABLE CONDENSER

A superb component, possessing extreme rigidity of construction, mechanical perfection of moving LITLOS parts and high electrical efficiency. VARIABLE CONDENSER Compact and efficient.Accurately gauged bakelite dielectrics and solid brass pigtail connections to moving Negligible H.F. loss, large accessible vanes. All capacities up to "0005 mfd. in tuning straight-line capacity and differential types. terminals, shaft provides easy Each 2/

ganging.Capacity '0005. mfd. EACH

FIXED CONDENSER In a complete range of capacities, uprightorflatmounting. Every condenser is tested on 750 volts D.C. Capacities accurate within fine limits. D0005 mfd. to"004 mfd. 1 /-

'005 mfd. to"01 mtd. - - 1 /6 Ensure a safe and efficient Aerial and Earth. The new AEROFICIENT Send a postcard for our new Catalogue KIT provides all you need. which describes all our products. 6/6 Complete. Advertisementof GRAHAM FAR ISH LTD., MasonsHill. BROMLEY,Kent Export Office :11112 Fenchurch St.,E.C.3. 343 MODERN WIRELESS October, 1933 ROUND THE WORLD OF WIRELESS

Items of interest in Germany, Austria and Switzerland reviewedinpictures

THE STATION IN A FORTRESS Monte Ceneri, thenewhigh - power regional station of Switzerland,issituatedinside afortress, which accounts for the barbed wire and the sentry - box. Visitorstothestation are met at the gate and firmly forbidden to enter. THE MAN WHO MATTERS inGermanyis EugenHad- amowsky, who isresponsible for the future of Nazi broadcasting. On theleft is a generalviewofthemast, station buildings and staff house at Bisamberg, the Austrian station which works on a wavelengthof 517 metres, with an aerial power of 100 kilowatts.

BISAMBERG'S 300 -KW.VALVES on showforthefirsttimeatthe openingofthe new Austrianhigh - powerstation. Right, isthenew German nationalreceiver,theresult of co-operation between several manufacturers and the Government. October, 1933 MODERN WIRELESS

The B.B.C.'s Lady Announcer- A Great Scientist-Those" How- to -Listen Reformers-Harking back to Writtle. By " PROSPERO "

The Mistress of the the" mike " !The married lady's for living for another umpteen years. voice is intoxicating, but hubby alone What an inspiring gesture, ye senile Microphone has the patent rights. wrecks of sixty who doze over the THE B.B.C. is simply amazing. To worship that voice, as I have fire or potter aimlessly in a greenhouse, That organisation is crammed worshipped Cecil Dixon's, is to verge clad in carpet slippers and shapeless with gallant ex -officers of all on the actionable. It isn't done. garments. I'll wager that Sir Ambrose branches of his Majesty's forces, pro- Give me liberty tr male announcers. will celebrate his new lease of life by fessors, experts, possibly even savants, The plain truth is that the B.B.C. putting out a further thesis on side - not to mention literary young men. fearedthat theelect lady would bands, embellished with some of the Somehow, by what agonising pro- inflame the hearts of her listeners most profound mathematics. cess we shall never know, it decides unless she had the damping protection Ifthereisonethingthathe to appoint a woman announcer to of a wedding -ring. They do notenjoys, it is a rollicking battle with the London station,and thenitencourage " fan mails "at Broad- another scientist over something full failsmiserablybyappointinga casting House. John Knox wouldn't of cosines and .J-1.May he have married lady. like it. plenty more of them, for his services This shows less imagination than to the world are immeasurable and a Dutch cheese.As a salesman, the An Adventurous Inventor he deserves all the mathematics there B.B.C. is much less successful than My admiration forSir Ambrose dy Thomas Carlyle would have been at Fleming now knows nobounds. are.He can have all my- and a hawking lip -sticks. He was married in July.And why dx Its understanding of human nature not ?After all, he is only 83. partly -used logarithmforwhichI is not so profound as that of the chief Having invented the thermionic have no further use. numismatist at the British Museum. valve, he has now hit upon a device "Rather Like Drinking " So it appointed a The kindly reformers who marriedlady asA NINE -CENTIMETRE of late have been telling an announcer. TRANSMITTER the public " how to listen " Forheaven's understand little of human sake,letus not nature, I fear, if they hope divulge this to the that people aregoing to Latinraces,lest use broadcasting other than we lose Portugal as it pleases them. as an ally, France Listening is as a place in which rather like drink- to learn Russian ing. Youmay from waiters, Spain drinkwithdis- as an onion -bed, crimination, mak- andItalyasa ing all the motions source ofhair- of the connoisseur, dressers. sniffing the wine, Think,just rolling the brandy think, of the thrill round a huge withwhichthe goblet,inquiring B.B.C. might have anxiously about titivatedthe vintages, corks and nerves of many of the like. its clients had it Or you may planted a maiden,This radio apparatus, shown at the Century of Progress Exposition in Chicago, has been aptly christened the " Beamcaster."The waves employedare only nine centi-take a good load heart -wholea n dmetres long and are projected by the parabolic reflector behind theshort aerial to whichof liquoraboard fancy-free,before the engineer in pointing. everyday,not

345 MODERN WIRELESS October, 1933 Radio as a Running Accompaniment caring greatly what it is so long as it is There is no department of our lives a drop of summat good. Or you may which some uplifter will not try to swillall day and half the night, teach us to manage, and the answer neither knowing nor caring what it to his horrified questions is eternal- is, how much, when or why, until " I like it." the stuff has no power to stimulate or please you and becomes merely a This Month's Fable bad habit. Oncetherewas anInterfering So it is with listening, and prettyPerson who went aboutadvising little books will not alter it.Just Inferior Folk to improve their minds. imagine grandma turning up,say, He had large red ears and a wife who page 39 in order to see how to listen said that she adored Poetry and Old on Wednesdays ! Masters and things. He tried to improve her mind, but she hurled a Listen As You Like It lamp at him, and quite Spoiled his Why, bless the old noblewoman, Beard. she only uses the radio as a running One day he began to interfere with accompaniment to her endless tales a Cooper's Mate who was listening to offire and flood,diseases she has some Jazz. known, notableoperations, DAME NELLIE MELBA singing selected deathbed scenes and, into the microphone of the first British broadcasting stationat over all, the aura of Queen Writtle, to which the writer refers Victoria, Mr. Gladstone, in his reflections. Dickens, the Crimea and The Silence of Dean Maitland. loudspeakerandlistento Listen as you like it. You Jazz on both sides at once ! " pay for thestuff.Squan- Moral: Don't try to teach deredelectricpower and lions to eat boiled celery. worn-out valves help business men to pay for their golf. Performing Lions You will find that practice And speaking of lions re- in listening while you read a calls the attempt, which took book or play cards will train placeinParliamentlast your ears to swivelabout session, to interfere with the like those of a horse-a useful training of wild animals to accomplishment if you have perform those featswhich lots of females in your family. have pleased circus -goers for You can hear 'em all at once ! ages.If the education of HARVESTING AT WASHFORD CROSS, near Minehead, Somerset.In the back- lions involves discipline it cannot be ground arethe500 -feet masts ofthe worse for the lion than for the school- B.B.C.'snewWestRegionalstation boy. which radiates both National and Regional Afterall,isthere such avast programmes. difference between a four -legged lion " My good fellow," said he, " whyand a piano -playing one ?Consider I do you not give ear unto the Works Leo has a mane ;but so has Moses of the Masters and Read Good Books,Wosselstraum, thepianist. Leo's so that you may Develop your Mindnailsare nicely trimmed ;so are and become as a Pillar of Light and aMoses'. Both have to go through the Fount of Wisdom ? " hoop, and both are expensiveto " Are you a Piller and a Fount-maintain. ing ? "replied the Cooper's Mate, When Leo is temperamental and recoiling slightly but with space forreluctant to perform he is subjected more. to the cracking of a whip, and when " In my humble way . . ." Moses threatens to break his contract began the Interfering Person, bridlingand marry the manicurist, by gum ! with pride. his manager cracks the whip. But the Cooper's Mate interposed. The only vital difference between " And if I do what you say, is therethem is that Moses can run his fingers any chance of my growing like you ? " through his mane and wind up the " Certainly ! Why not ? " answeredpiano stool. But then, Leo could eat the Pillar, in a tone of Hearty En-his manager ! PHYLLIS LAUGHTON, who has gone to couragement On a television screen their own Hollywood as a " director of diction" for a film company, shows an airline pilot how " Then," said the Cooper's Mate,mothers could not distinguish between to speak clearly into a microphone. " buzz off !I am going to buy another (Continued on page 378)

346 October, 1933 MODERN WIRELESS

9.000"HANDS_IFMORETHAN EIGHTY ACRES OF FLOOR.SPACE THE GREAT HIVE OF INDUSTRY WHERE COLUMBIA SETS ARE BORN! Huge, towering buildings of concrete, glass, turning out with ease a thousand sets a day - and steel... aseloquent in their clean severity six thousand a week.And yet withthis of line, as in their materials, keen, relentless tremendous production there iscoupled the modern efficiency... most exact microscopic accuracy in a thousand What you see illustrated here is only a tinydetailsof each set,togive you the part of thegreatfactory where performance and finish the world expects from Columbia sets are made-only a Columbia, at Columbia prices. Ask to part of the largest and most hear any of the four Columbia up-to-date radio factory in models listed below at the the world. It is capable of nearest Columbia dealer.

ColumbiaBattery Sets can be bought at prices as low as . Send NOTES' Z4 - 4 T.OS VAR. couponbelow for 1fullparticulars.

COUPON: To The Columbia Graphophone Co. Ltd., 98Clerkenwell Road, London, E.C.x. THE C.O.A. BATTERY THE C.O.A. BATTERY 3 -VALVE BATTERY SET,ALL - ELECTRIC RADIO- RADIOGRAPH FOUR,FOUR, Model 1001-anModel 1005.A highlyGRAPH FOUR, Model 620- Please send me particu- Model 1003 - thebattery entirely new standard ofselective set with band-a low-priced all -mains radio- lars of the new Columbia Radiogram with an all -mains performance and eco- passtuning,at an un- gram, embodying every models without obligation. performance : three - stage nomy from a battery set. usually low price. In- modern development. Band- band-pass receiver. Columbia Columbia Constant Constant Quality Amplifica- Quality Amplification.ductively coupled band- pass aerialcircuit. Screen - NAME tion. 65 amp. hour L.T.Triple action volume pass aerial circuit. Screen grid high frequency amolifier. battery. 1 75 v. H.T. battery control.60 amp. hour grid, high -frequency am- Energised moving -coil speaker including 9v.G.B. Auto- accumulator. 175v. plifier.Permanent -mag- Wave range, 200-550 med. ADDRESS matic flood -lighting of scales coded H.T. battery, in-net moving coil speaker. and 1000 - 2,000metres. from switch M.W.-L.W.- cluding 9 v. G.B. battery.Single tuning knob forSingle knob tuning for three Gram. Permanent magnet Marconi valves. Alterna- gang condenser. Volume con- moving coil speaker. Marconi tive Aerial tappings and threegangcondenser.trol operating on radio and valves. Walnut cabinet of pick-up connection. Marconi valves. gramophone. Marconi valves. fine workmanship. 70 One. 11 Gns. £8.15.0Fine walnut cabinet. 23 on,. (Prices not valid in LES.) M . W. 347 MODERN WIRELESS October, 1933

IKCINID RIMER

In this section Mr. Kendall will This month'ssubjectisthe discuss month by month those vexed oneof " dressing -up " topics which strike him as re- sets, and somestrong views quiring his attention.If one may are expressed on the question. judge by his opening remarks, we Mr. Kendall explains his general shall see fireworks here before policy in the matter of cabinet long. work.

I'vE been told that I can have this achieved one of the greatest forward cornerof MODERN WIRELESS strides in its history.New valves, all to myself, and do just what new components, new circuits. I like with it, so long as I don't let will not occupy the whole of the space Class B andquiescentpush-pull the paper in for a libel action or trywhich I have been allotted, simply amplification, super -efficiency tuning to start a political argument.Well, because I feel that I must not run the coils; hosts of other important new it is more than ten years since I wrote risk of distracting the reader's atten- things. my first article for " M.W.," and in tion for a single unnecessary moment all that time I've never had such afrom the one thing that matters. Increased Efficiency chance, so, believe me, I am goingThe K4-and all that the K4 means These developments alone would to make the best of it to the world of home construction. have made it imperative for every Iam convincedthatthisset constructor who wants to keep up to A Promise ! heralds such a revival of enthusiasm date to build a new set this season, When, as I must confess happensin home construction that the man and they do so definitely mean that pretty often, I feel that I want to who holds back and goes jogging on better radio is within the reach of heave a metaphorical brick at some- with some old set from last year, or everyone that I cannot see how we one else's glass house, this is where I even the year before, will quickly find could fail to be fired with a fresh access shall do it. himself just as hopelessly left behind of enthusiasm for " the finest hobby When I get up on one of thoseas if he had stuck to that ancient in the world."Only one thing was dreary November mornings, take a crystal set which now lies forgottenlacking to make this season com- look at the world, and decide that in the attic.I therefore feel that it is pletely memorable, and that was a it is all wrong, this is where I shall my imperative duty to do everything in my power to make it as certain as development in the efficiency of our tell the radio part of it what it ought methods ofsetconstruction com- to do about itself. I possibly can that every one of my parable in importance with the other When I come to the conclusion that new things. somespeciallywhiskerypieceof WHO SHOULD CHOOSE ? Here there had been a condition of technical conventionality cannot be stagnation for many years, to which endured any longer, this is where I it has been my privilege to put an end shall announce a crusade. by the invention of the Step System. One thing, however, I do promise, In this we have an improvement in and that is that I will voluntarily add easeofconstruction,efficiencyof a third to the pair of Editorial taboos layout and certainty of correct wire - which I mentioned in my first sen- spacing,whichisfullyequalin tence :Iundertakethatinno importance to the other developments circumstances will I discuss the B.B.C. which the season has brought us. programmes ! A New Set Essential What the K4 Means Either the Step System orthe That is a promise which I shall find wonderful profusion of new valves, very much easier to keep than you components and circuit improvements, Mr.Kendallstronglymaintainsthat might think, for I gave up getting all the choiceofcabinet work,especially would alone have made it imperative hot under the collar about the subject if it is to be elaborate, should be left to for every live constructor to treat a long time ago.After all, it's really the constructor. himself to a new set this year.The no use, and it is such a simple matter two together mean that even a faint- to build a set like the K4 and then readers realises to the full the im- hearted one (if there is such a person invite the home authorities to watch portance of the occasion. among the readers of " M.W.") must your dust as you depart on a tour of Just think :at the outset of thisdo it, for to be out of the swim this Europe in search of fare to suit the season we have seen such a flood of year means to fall most hopelessly mood of the moment. You will getnew developments of a purely tech- behind the times. it, too, if you are using a K41 nical nature that it was obvious from And that is why I don't want to This month I am not going to make the first that 1933 would be remem- divert attention from the K4 by very full use of my " Corner," and it beredasayearinwhichradio talking about general matters, even

348 October, 1933 MODERN WIRELESS

ofGREATstrength

()SRAM " CATKIN" VALVES I. ANODE TERMINAL DIRECTLY CONNECTED-LOOSE CAP IMPOSSIBLE areessentialformodern 2.INSULATIONBETWEEN ANODE & SHIELD 3.PRECISION INSULATORS receiver practice. Immensely LOCKING ELECTRODES strong yet compact in design 4. HEXAGONAL SCREEN GRID 5. AIR COOLED ANODE they are constructed to micro- 6. CONTROL GRID scopically precise limits and STRAIGHT WIRE CONSTRUCTION 7. METAL ANODE TO GLASS therefore allow forgreatly VACUUM TIGHT JOINT 8. PRECISION INSULATOR improvedset performance. LOCKING ELECTRODES A set equipped with OSRAM 9. FILAMENT CONNECTIONS THEONLY WELDS IN THE ELECTRODE SUPPORT SYSTEM " CATKIN" VALVES gives the HIMETAL CAPPING SHELL.GIVING MINIMUM GRID-ANODE CAPACITY highest quality reception. I I. RUBBER MOUNTINGANTI.MICROPHONIC 12. INSULATED STEEL CLAMP SUPERSEDING DELICATE PINCH OF GLASS VALVE The all -metal construction of 13. GLASS CIRCULAR SEALGIVING MAXIMUM OSRAM "CATKIN" VALVES is INSULATION SPACING BETWEEN WIRES I4.METAL SHIELDGIVING MECHANICAL a radical departure and results PROTECTION AND ELECTRO STATIC SHIELDING prove beyond disputethat theydefinitelygivemore uniformresults,complete TYPES AND PRICES freedom from microphonicity MS4B High Efficiency Screen - and more effective screening. Grid A.C. Mains Valve - 17/6 VMS4 Improved Variable Mu AchangetoOSRAM"CATKIN" Screen -Grid A.C. Mains VALVES isachange to Valve 17/6 faultless radio reception. MH4 High MagnificationDe- tector A.C. Mains Valve -13/6 MPT4 Power PentodeA.C. Mains Valve 18/6 (Other types to follow) 0$(7:11) Sold by all Wireless Dealers WRITEfor the OSRAM VALVE GUIDE (1933Edition)sent post free. Made in England. awes Covered by World " CATKIN " is the Trade Mark of the Patents. M.O. Valve Co. Ltd., manufacturers and patentees. FOR A.C. MAINS RECEIVERS MET AL INSTEAD 0 F GLASS Advt. of The General Electric Co. Ltd., Magnet House, Kingsway, London, W.C.2.

349 MODERN WIRELESS October, 1933 Trenchant Comments on Topics of the Day though there are some things I'mand at no point in my articles do I designed for it by the specialist firms, burning to say about the bewildering show it all dressed -up in a pretty- and from amongst these I suggest variety of output load requirements pretty cabinet.On the contrary, that the constructor should make his of the Class B valves we are beingevery photo was taken to illustrate choice.I have already heard that offered, the ingeniously inconvenient its technical features, in which alone Messrs. Peto-Scott have such a cabinet way the anode, grid and filamentI am interested. in hand, and although I have not yet terminals are mixed up on the new The one and only exception is the seen it I expect that it will be well seven -pin holder, and other griev- picture which you will find on the worthy of consideration. ances of the moment. cover ofthisissue. Here it was necessary for purely pictorial reasons Self -Contained Receivers The Designer's Task to enclose the receiver in some sort There iA a rather obvious exception All that must wait for another time. of a case, so I chose the plainest andto my argument about cabinets in This month I am going to content simplestrectangularwoodenbox general which I should perhaps men- myself with just one little fling on awhich I could find ! tion, lest the reader should some day subject which is actually connected think he has caught me breaking my with the K4, and the way I have Not a Suggestion ! own rules ! I am referring here to the presented it purely on its technical Do not, please, think that this is treatment of those designs wherein the interest, without what I call furnituremy suggestion of the kind of cabinet cabinet really forms an integral part appeal.This is rather a sore point which should be used, for it is nothing of one scheme, such as the entirely with me, for I cannot for the life of of the kind.The K4 is worthy of a self-contained mains set. me see why designers should think really handsome cabinet, but I am In these cases that they must show a set all dolled - not going to presume to tell my the assembly of up when they have it photographed. readers what sortof design will the various units I maintain that a technical de- best harmonise with therest of and their proper signer's job is to design the technicali- their furniture, andI am leaving spacing from one ties of the set, and he should not waste the choice entirelyintheir own another is of some his energies on the purely artistic hands. importance,and questions of cabi- so thecabinet net design. That, TO ILLUSTRATE THE POINT ! work really con- too, is a special- stitutes a part of ist's business, t h emechanical calling for quite and electrical different gifts, and design.In these the technical man circumstancesit doesnot,asa is difficult to see rule, shine at it. what the designer In any case, the can do except to choice of a cabinet work on the basis design is a matter of some particular inwhichtastes cabinet. differ enormously, and it seems to On Another me that it is one Occasion which should be Whether this is left to the man or is not the who is going toThis photo was taken at the same time as the one seen on the cover of this issue, and isproper way to de- build andlivereproduced here because it shows more clearly the "plain rectangular wooden box" tosign a mains set with the set-in which Mr. Kendall refers. for the home other words, the home constructor. By the by, I was not strictly correct constructor is a matter on which I To me it appears that this is purely when I referred to the picture on the have views of my own which I pro- a furniture question, which is rightcover as being the one and only pose to ventilate more fully on another outside the scope of the technician. exception totheruleI made in and more suitable occasion. There His part, Iconsider,is just to see having the set photographed ; actually is one other type of self-contained that his set has the over-all dimen- two views were taken for the cover outfit,however,in which I must sions to permit it to be housed in a design, and only the most suitable of admit it seems essential for the de- cabinet of one of the standard sizes, these was used for the purpose.The signer to choose the cabinet work, and then leavethe constructor to other one, I fancy, will be used to and that is the radio -gramophone. choose the particular design which illustratethis page, and it was a Here the mechanical design of the appeals to him. sudden recollection ofitsexistence outfit is more than half the battle, that made me add this explanatory The run of the leads to the pick-up, A Technical Achievement paragraph. the placing of the motor in relation That, at any rate, is the principle That being done, I can return to to the amplifying circuits, the position on which I have worked in presenting my point, which is just this :the of the speaker, and many other points, the K4.I put it forward;entirely on importance of the K4 is such thatmust all be taken into account if the its merits as a technical achievement, specialcabinetswill no doubt be best results are to be obtained.

350 October, 1933 MODERN WIRELESS

As the Query Editor Of MODERN current than the makers of the battery

WIRELESS, I meet with a wide intend the cells to give ? variety of faults, and I have Under this heading the Chief of Dry batteries are made in different recently had quite a numIter of letters !! the " M.W ." Query Department i! capacities, the discharge rates depend- on these lines : :: discusses some of thedifficulties ing upon the size of the cells.The " I am using dry batteries for my which can often be so troublesome. popular type of battery with the :: This time he dealswith an H.T.:: H.T. supply, and I cannot understand smallest sizecell may perhaps be battery problem. why they run down so quickly. The rated at 10 milliamps., the double batteries I use are of the 120 -volt capacity at 15 milliamps., and the type, and when I first connect them very largest at 20 to 25 milliamps. up the results are all that can be to deliver currents up to 10 millliamps. I give these figures merely as example, desired.After about a week I notice and you try to make it supply, say, and I have not any particular make of that the volume commences to de- 20 milliamps., then you are putting battery in mind ;but reference to crease, and a particularly nasty form a100 per cent overload onthe the catalogueof any oneofthe of distortion sets in. cells, thus decreasing the life of the leading battery manufacturerswill " The reproduction sounds harsh, battery enormously. at once reveal the effect of battery and theloudspeaker emitsnoises But the main pointis,what is capacity upon current output. which sound like a fault Now if you take one of the in the instrument itself, A USEFUL FAULT FINDER smallest batteries and con- although I have proved nect it to a set which con - that my particular speaker sumes 20 milliamps. or more, is in perfect order. you are expecting far too much from the cells and, in Overloaded Cells consequence, you haveto ." Replacing the battery makefrequentrenewals ; with a new one immedi- whereas, if you purchased a atelyremediesmatters, battery of the right capacity, and a voltmeter test reveals you would get much more a drop of as much as 40 economical working. volts in the old batteries which, I am told, could Something Wrong quite easily account for the But let us take a case, not symptoms I have just de- where a small capacity bat- scribed. tery is harnessed to a set Can you give me any whose anode current demand idea why these batteries isfairly high, but one in should last such a short which the correct type of time, when my friends are battery is being used. In a able to make theirs last for Those who have A.C. orD.C. mains will find that a neon lamp'case such as this, obviously provides a convenient means of testingforcontinuity.The several months ? " lamp is joined in series between the mains and the component to the battery can only run This type of query is by be tested.A glow indicates continuity, and an absence of glow a down rapidly when there is no means easy to deal fault in the winding or component under test. a fault somewhere in the set. with, owing to thefact Grid bias is one of the first that the same trouble maybepro - causing thesetto take so much items that should be checked up. The duced by a variety of causes. current ?In the first place, readers total anode current taken by any re- Obviously, the batteryisbeing who come up against trouble of this ceiver is dependent upon the value of asked to give out more current than descriptionmustaskthemselves the negative bias applied to the grids it can do economically ;or, in other whether the battery they have in- of the various valves, and the valve words, it is being overloaded. stalled is up to the work demanded that shouldatonce come under If,forexample,you have an of it.That is to say, does the set, suspicion is that in the output stage, H.T. battery whose cells are intended when working properly, take more (Continued on. page380)

351 MODERN WIRELESS October, 1933 exciting film, and, if it were made, the music under review would thrill the most sophisticated audience. The story is well-known ;the music belongs to the school of realism, and will perhaps shake many theories to death.But now and again, realism is healthy and invigorating, and so we fly to realism in art.Well, here it is-real full-blooded stuff.Absorb the story and hear the Berlin Grand Symphony Orchestra re -tell it to you inmusic.- IfSchubert'sErlkOnig makes you shiver, this will thrill you too. For Lesser Occasions It would not be fair to overlook Here is a selection of the latest releases, including a batch of six opera recordings andsome of the orchestral pieces of less two brilliant examples of pianoforte technique. substantial texture.I cordially welcome a fine performance of the Secret HE first of the good things which what terrifying sound for the ordinary Marriage Overture by Cimarosa on thegramophone companies folk.Never mind the title-the music H.M.V. DA4404.Gay music this, have been saving up for us is most attractive, shapely and grace- easyofunderstanding,dashingly against the longer evenings indoors ful, really Mozart at his best.As a played by the Berlin Philharmonic. have appeared.The lighter fare to violinist he knew how to write for You will like Vienna Memories recalled which we have very properly been the instrument, and the soloists-by EdithLorand'sOrchestraon treated is quite overshadowed by the Sammons and Tertis-interpret him Parlophone R1588.They are not the impressive banquet now announced. magnificently.An interesting feature tunes the title might suggest. Here arethechiefitemsofthe is in the fact that the orchestra (the Two excellent up-to-date numbers- " menu." London Philharmonic) plays so large Whistling Under the Moon and She's a part, the actual solos being few. Everybody's Sweetheart Now (Columbia Opera But always, so good is the recording, DB1169)-are finely played theme First-an abridged It Trovatore on the instruments of the two soloists are songs from " Heads We Go " by six Columbia records.This idea of clearly heard.There is a real musical Columbo's Tzigane Orchestra.Per- " concise opera " is one of the finesttreat onthesefourColumbias haps the most attractive ofallis things which has been done for the (DX478-481). H.M.V. B4466. Here Marek Weber's gramophone enthusiast for a long Orchestra plays Beethoven Menuett in time. Thewholeconceptionis Drama G and theEntr'acteGavotte from Everything is of the indeed lavish. Now for something more dramatic- "Mignon." Gems, anyway, but more very best. Artists and orchestra with a stirring symphonic poem.This is sparkling than ever in this perform- international reputations (from thethe Mazeppa Symphony (Liszt) on ance. Scala,Milan)-superbperformance Parlophone R1579-1581. The adven- inevery department - magnificent Song and Choral recording-and the best and mosttures of the hero would make an The best of the vocal records this popular arias and choruses only, hand- month are the choral ones. Especially picked with a fine sense of what the COMPLETELY EQUIPPED delightful is that by the Choir of St. public wants. Mary's School, Bridgnorth, on Colum- There are few operas which contain bia DB1166.These young children music which lingers so long in the sing most charmingly Arne's Lass memory as this, and I say without With The Delicate Air and Handel's qualification that the singing of the Oh ! Had I Jubal's Lyre.This choir Anvil and Soldiers' Choruses on these shows evidence of magnificent training records is at once magnificent artistry and the cultivation of a remarkable as captivating to the trained ear as to musical sense. that of the whistling errand -boy. The TherecentfestivalofEnglish catholicity of musical appeal could not Church music at the Crystal Palace has be better illustrated.But all these given an impressive record in Colum- records are as good as can be, so why bia DX498. Some 4,000 voices sign discriminate ? 0 God, Our Help in Ages Past and There are six 12 -inchrecords in How Goodly Are Thy Tents with Hail ! the free album (Nos. DX486-91), with Gladdening Light.The latter two are a leaflet, for 24s.On no account miss exceedingly beautiful. them ;you will be bound to buy at As to solos, try Essie Ackland's least one or two. This car, used by Mr. Borlase Matthews in singing of Somerset's Song of Sleep- connection with political work, is provided one of the best we have.The other For Mozart Lovers with a public address amplifier and loud- side is Danny Boy (H.M.V. B4465). This work speaker, the amplifier being built into the From Verdi to Mozart. luggagecontainer.The constructional Tauber sings Ma Curly -Headed Baby (Concertante Sinfonie for Violin and work was carried out by Mr. Matthews in in German with astonishingly pleasant Viola [K.364]) has perhaps a some- his own workshop. (Continued on page 380)

352 October, 1933 MODERN WIRELESS

YOU BE THE JUDGE (0- yOtA INCONTISTAME EVIDENCE

. . .I place before you the actual EVIDENCE of where your set is right or wrong.I am giving you conclusive and all-inclusive evidence of radio faults and efficiency. Igive you-not just the circumstantial evidence of amperes, volts and ohms, no mere hypothesis,butproved and tested ACCURACY.I present the precision of the AvoMinor, a younger brother of the famous Avometer, the instrument thatisso accurate and efficient thatitispreferred and insisted upon by the world's foremost technical experts and service engineers. This in itself is evidence enough that nothing less than the AvoMinor is dependable enough for you."

iteAVOMIN OR \ TELLS THE WHOLE TRUTH Now YOU can test YOUR set-examine it,locatethefaults,getfirst-class results from it-with the ease and precision of the technical expert.You can test ACCURATELY with the AvoMinor -testcircuits,valves, components, batteries and power units.There is no test you need that you cannot make with the AvoMinor.It gives TEN differentrangesofreadingsin milliamps, volts and ohms.It is a moving -coilcombination testing instrument with a total resistance of 100,000 0-10,000ohms ohms. Full scale deflection 0-60,000 isobtainedwithonly3 0-1,200,000 milliamps. No other instrument 0-3 megohms in the world gives you, at such a convenient price, so many tests with such dependable accuracy.

Ask your radio dealer to show you the AvoMinor. Be satisfied with nothing less. DEFERRED Remember, it's accuracythatisall- TERMS important.In case of difficulty, write if desired. for fully descriptive folder. Write for particulars. THE AUTOMATIC COIL WINDER & ELECTRICAL EQUIPMENT CO. LTD., Complete sts handsome case with pair of leads and interchangeable Winder House, Douglas Street, London, S.W.1. Telephone:Victoria3405-7 Irocodile clips and testing prods 353 MODERN WIRELESS October, 1933

Seeing is Believing " ChoosingYourCondensersand Some trade news and views that Resistances." ORE and more radio manu- will prove of interest to readers, facturers are publishing per- whether or not they are connected with the radio industry. The Oldham "Wakes formance curves of their pro- Members of the trade are invited Much asthe Lancashire worker ducts. This is a wise move, for there to send items of interest or photographs to be included under this looks forward to the yearly " Wakes" is much truth in the saying that heading. in his district, twenty thousand people " seeing is believing," and not nearly who are affected by the trade suc- enough use has been made heretofore cesses of Ferranti Ltd. have agreed of the graphical method of giving to miss the Oldham Wakes this year visual indication of a component's or Several pages are devoted to the owing to the enormous business done even a set's characteristics. description and illustrationof the by the- famous transformer manu- The use of curves to illustrate and metallisedresistancesunderload. facturers at the Radio Exhibition at prove visually the goodness of any Permanence curves are given, and Olympia. product is sound publicity, and if it humidity, temperature and voltage As far as I know, nothing approach- continuestobecome popularthe characteristics also figure in the very ing this has ever occurred before, for public will expect to see curves of all full details provided. the Wakes are part of the life of Lan- types of components. The colour code resistances, with cashire, and it must mean a tremen- the necessary code for translation dous sacrifice for such a vast number Unjust Criticism purposes, are listed ;while the latest of people to give them up. I am fully in accordance with the ignition interference suppressors for idea, for the purchaser of a trans- car radio reception, and other anti - The Latest "Radiomag former,forinstance,has a " Number 5," the best, so right to be told by the makers AN INGENIOUS DEVICE far, of all the Telsen " Radio- exactly how it will behave- mags " has appeared, and I not expected to buy it and should like to congratulate the find out for himself.At the editor on the contents.It present moment the position is covers in excellent fashion a a little hard on the non -curve wide aspect of radio, and is firms, perhaps, for the excel- particularly generousinits lence of their components may contents. be unjustly criticised simply Beside the full list of Telsen becausethey donotbear components, beautifully pre- graphicalevidenceoftheir sented incolour, thereare quality ;but in time I hope numerous practical articles on allradio manufacturers will such vitally interesting sub- come into line and label their jects as " Class B," the new goods clearly with efficiency Telseniron -coredcoil,the curves. choice and care- of H.T. bat- Those who are first with this teries, and so forth. method of publicity are bound Also, complete details are to reap reward in the form of provided for the construction enhanced prestige, as well as The " snatch thief will have a thin timeifthis device of six up-to-date home con- of increased sales. shown by the American Westinghouse Co. at the Chicago structorreceivers,andfor World's Fair comes into general use.As the handis passed through the opening in the grille it interrupts a beam three of these full-size blue- An Excellent Book of light directed upon a photo -electric cell and so causes a prints are included with every The latest move in curve barrier to be raised. copy. At 3d.theTelsen publicity that has come to my " Radiomag " represents won- notice is an excellent book issued by interference devices, complete a most derfulvalue, and a production of Dubilier, in which the full range of fascinating book. which Telsen Electric Co. can rightly condensers and resistances are not Itiswell worth every MODERN be very proud. only described and priced, but are WIRELESS reader getting a copy of accompanied by hints as to their use the book, which is gladly supplied on A New Output Valve and with many valuable curves show- receipt of a card to Dubilier Con- The term " maximum undistorted ing clearly their performances under denser Co. (1925), Ltd., Ducon Works, output," as applied to a valve, has workinreo-ntlitions. Acton, W.3. The title of the book is probably beenthe source of more

354 October, 1933 MODERN WIRELESS The Latest News from the Radio Trade misunderstandingthan anyother it takes 4 volts on the filament against worth consideration, including moving - term in radio. The public have been the 6 volts needed by the D0.25, coil Radiometers and Electrometers ; told often enough that something ofthus making the valve very much in fact, there is a meter for every the order of 500 milliwatts is ample more useful, bringing it into line with radio purpose. the other A.C. valves. A VALUABLE GUIDE The amplification factor is of the Bravo, Scotland ! order of 3.8, and the impedance is When this appears I hope to be at 600 ohms. With an optimum load of Manchester at the Northern National 4,000 ohms the valve will give up Radio Exhibition, following on the Choosing your to 5 or more watts output from aLondon and ScottishShows, and maximum" signal "inputof65 before I go I should like to wish all CONDENSERS volts R.M.S. trade friends the very best of business AND in the North of England. Still Growing London and Glasgow have had RESISTANCES Pifco Ltd., of High Street, Man-well -attended exhibitions, and I do chester, have a most attractive range not think that Manchester will fail in of radio meters designed to cater for that regard. An up-to-date wirelessusers. Among them the Glasgow took, its first official radio guide for the expert will find instruments that can show toitsheartin enthusiastic bereliedupontogiveaccurate'fashion, and I must compliment the Constructor and readings for a whole host of tests, Corporationontheirlivenessin Set User whilst the novice whose interests are publicising the show.All over the limited to the building of a radio set city we were confronted with neat, will find low -price meters which cannot but highly visual, blue notices showing fail to save him both time and money the way to the Kelvin Hall, wherein DITHER in construction. was the exhibition, and these indica- The new Pifco Rotameter at 29s. 6d. tors were invaluable to those who did is the star performer in the range. not know Glasgow very well. This sensational meter gives 100 radio Following this an illuminated tram- tests-no other single instrument so car paraded the various tram routes easily covers all the tests the Pifco advertising the show, and announcing The new Dubilier book descrited on the Rotameter undertakes.One needle its presence by means of two loud- previous page bears the attractive cover illustrated here.The book contains prac- pointer operates on eight different speakerspushingout gramophone tical data of value to every set builder. dials, the dials being so arranged as music.The idea was an excellent one, tobeinstantlyavailable by the and was particularly applicable to for" ordinary "listening, and yet turning of an octagonal knob. Glasgow, where the trams are the main many sets use valves capable of pro- ThereareotherPifcoproducts means of locomotion. viding four or five times thiiit amount. Why this discrepancy ? COMPARING THE OLD WITH THE NEW The reason is really simple. While a general level of some 500 milliwatts is ample for domestic purposes, this doesnot takeintoaccount loud passages, such as big bangs on the drum, which come along every now and then. To cope with these, larger output -carrying powers are necessary than are provided by 500 milliwatt valves.Thus often valves having a capabilityof2,000milliwattsare used to takecareof thesepeaks without overloading. For all normal purposes the usual triode or pentode output valve will look after the peak passages satisfactorily, but where alittlelarger volume is required something very much " bigger ' in the way of a valve is necessary.To meet this require- ment Mullard have produced a new output valve of the 400 -volt anode potential class which is to take the place of the D0.25, for long a favourite among amplifier constructors. Here is an interesting comparison- a horn type gramophone of thirty-five years ago and The new valve is the D0.26, and the latest H.M.V. radio -gramophone, which plays up to eight records continuously.

355 MODERN WIRELESS October, 1933

HINTS AND TIPS FOR THE RADIO HANDYMAN

Ideas that are well worth remembering CLAMPING by all constructors. Sonic of them are Noisy Laminations-Removing Solder bound to provide just the help you need PIECES -TiceEarthConnection-Avoiding one of these days. Dust-Cutting Bolts.

wsinamilminsiimmismnionolunni intionammilminimmunimminialiE Loose Laminations the iron tube and plug firmly with a LOOSE laminations in an output clothes peg, or piece of wood cut filter choke or a smoothing for the purpose. choke are often responsible for Avoid That Dust strange noises emitted from a receiver Dust often has no effect on a set; -even with the loudspeaker discon- which makes many constructors care- nected these noises still continue. less about it.They leave a receiver Inseveral typesof chokes the Strong clamps should be used to stop loose standing without its cabinet until a stalloy stampings are held together laminations from " talking " or humming. thin film of grime covers it. by themouldedcase ;with this True, most of thedirt can be type of choke loose laminations are moulding bulges and eventually breaks, removed easily ; but it's the little bit difficultto cure, and should a re - and usually results in the breaking of left that does the harm.This works internal connecting wires. its way into the components, and THE TWO METHODS may causethemostobscureof 1Removing Unwanted Solder troubles. Difficulty may be found in removing A dust -sheet fixed along the front the nuts from terminals to which edge of the bench or table on which wires have been soldered. you experiment will keep your appa- If the terminal is held in a vice, ratus spick and span. Hem the and a very hot soldering iron is heldsheet round the edges, and use a on it, the solder will melt and the length of beading to secure it. nut will be easily run off. When you are at work the dust- sheet hangs out of the way down in KEEPS OUT THE DIRT front of the table. Cutting Without a Hacksaw How to remove surplus solder. The method To cut thick material with pincers on the left may be used with terminals that is almost impossible in the ordinary are still mounted. way, because sufficient power cannot placement by a similar make und be supplied by the hand. type fail to cure the trouble, the only SHORTENING BOLTS solution is to remove the complete choke from its case and construct angle pieces so that the laminations may be clamped together. It has been found by experience that it is very unwise to attempt to force packing pieces between the core This simple tip w Ikeep your set perfectly and the side of the case,for the clean while undergoing repairs or alterations. A FIRM CONNECTION Alternatively,theterminal may be held in a gas flame with a pair of pliers.The latter method is only applicable to all -metal terminals. Iron Pipe Earth A sharp tap with the hammer-the pincers will cut quite stout -sized bolts. When a length of iron piping is buried into the ground as a means of The necessary power is forthcoming, providingasatisfactoryearthing though, from a short blow with a point,itisadifficultmatter to hammer. The rod or bolt isfirst ensure aperfectelectrical contact held at the point at which the cut is with the connecting wire, owing to desired. the fact that soldering is out of the The pincers holding the material question and drilling a hole for a to be cut are then placed on a hard nut andboltis not always con- surface, such as a concrete floor, and Soldering to an iron pipe already buried in venient. hit with a hammer, as shown in the the earth is not easy, but the alternative method of connection illustrated here is A simple remedy, however, is to illustration. One sharp, powerful blow quite satisfactory. fix the connecting wire in one end of is all that is necessary.

366 October, 1933 MODERN WIRELESS

iSt

. .and performance provesthere'snone as goodas COLVERN FERROCART COILS"

Made under licence from the patentee HansVogt.

Thereareverydefinitereasonsforthe efficiency of Ferrocart Coils.Their advantages are fully explainedinabooklet whichwe have written. Maywe send you a copy ? It'sfree. Mr. G. P. Kendall used FERROCART Coils in the "K4" described in this issue. One F10. One F3. Mounted on aluminium base <

COLVERN LIMITED, ROMFORD- ESSEX. C London Wholesale Depot: -- LVERN 150, King's Cross Road, London, W.C.2 357 MODERN WIRELESS October, 1933 AT

Opening ofour Radio

The introduction of a serial story tainly an innovation, but one which clink like a common the story has not only been written by snatcher !'Is 'Igh but centres round an imaginary crime a n d Mightiness, Consequently,the authorsare lying in the corner atmosphere and describing the scene of'iscelllike a to detail. drunk! Too prand I wish to emphasise, on behalf of to speak, eh ? sake of verisimilitude, the description Well,youwon't tecturalfeaturesofBroadcasting lookso'igh and not mean that in the story presented to mighty when they there is portrayal in the characterisa- take yer outter the B.B.C. with whom the storyis swing. Didn'tI characters areentirely products of tellyer we'd get been made of designations officially yerone day? B.B.C. staff. Didn't I swear the day yer rolled me over in the mud to another piece of Turkish delight. that I'd get even " I don't know why you wanted to with yer ? " listen to the beastly thing," she said. There was a " You're getting morbid, Madge ;but pause, and then the I suppose it's natural for you to be 1. voice shrilled suddenly on a new note, interested in crime, Simon's job being a note of terror. what it is. You ought to have got him " BROADCAST OF DEATH" " What's this ? Keep away !Good to listen ;he might have been able THE whiningCockney voice, 'eavens I You-" The voice broke to explain it.I never can follow those vibrant with passion, echoed off, dwindled to a ghastly, choking radio plays-they're too complicated." weirdly through the darkened gurgle. Then silence. " Oh, you like to see the blood, room. Beginning as a whisper, it rose Jane," said Mrs. Spears laughingly. until it was almost a scream.It was " For goodness sake, Madge, turn it " You'd better stick to the talkies. the unmistakable voice of a man with off, and let's have some light on the They're more your line.But you a grievance ;a man who had been subject. That sort of stuff fairly gives must admit it does help to listen in given an opportunity to takehis me the horrors." the dark. It was perfectly clear to me revenge ;the snarl of an under -dog Madge Spears laughed, got up from what happened." turned at last to bite. her chair by the fire, switched on the " Well, what ? " askedJane. " So we've got yer at last !Who'd lights, and snapped off the switch of " Blessed if I could follow it." 'ave thought it would 'ave come to the wireless set. " The scene before was plain enough. this ? The bloke who fancied 'e could Her sister-in-lawblew her nose They'd arrested the Scarlet High- trick the whole lot of us, shoved into vigorously, and then helped herself wayman and put him in a cell.Then

358 October, 1933 BROADCASTING OUSE Chapters great, new

"Thriller " sogloomylately,itmighthave " Have you had any luck to -day ? " cheered him up." The detective took an empty pipe " You'd better have a bit, my dear," out of his pocket and stared at it said Jane inconsequently, " before I gloomily. intoMODERN WIRELESS iscer- eat it all.Besides, it's so bad for the " Not a thing.They've got away we feel our readers will welcome, for figure.But I know that if I was a with it this time.We'll never catch two very well-known B.B.C. officials, Scotland Yard Central Inspector I'd 'em now. Clever ;I hand it to 'em." at Broadcasting House. have something better to do than " Well, you couldn't help it, Simon. thoroughly at home in creating an listen to plays about murders. They You've done all a man can." of the crime with the greatest fidelity have enough trouble with the real " Perhaps a good bit more than ones, poor dears. Isn't Simon awfully some men," said Spears gloomily. the authors that although, forthe late, Madge ? " " And all I've got for it has been an of some of the technical and archi- " Oh, he's been at it day and night hour on the carpet in front of the House are strictly accurate, this does lately.That dreadful business down Assistant Commissioner, no less.He readersof MODERN WIRELESS at Wapping.You know, Jane,I seems to think I can work miracles. tion of those members of the staff of think the B.B.C. ought to do a lot The soldier ! " concerned.Both the events and the more " But Mrs. Spears' opinions " Let's talk about something else, theimagination,althoughusehas as to the shortcomings of the British Simon,"saidhissisterbrightly. applied tocertain members of the Broadcasting Corporation were not for " Madge has been giving me the THE EDITOR. the present to be revealed. creeps with her %rand -new wireless The front door of the little Norwood set." villa slammed ;there was a clatter " Oh, that thing !What have they the other man-you know, the gaolerin the umbrella -stand and a click of given you to -night ?How to cook -was sitting there and swearing at the latch, and Central Inspector Simon earthworms against a background of him ; but actually it wasn't the high- Spears stood in the doorway. chamber music ? " wayman in the corner of the cell, He was a young man for a Central " Shut up, Simon !It was jolly but simply a bundle of his clothes. He Inspector,butwithan excellent good, wasn't it, Jane ?One of those crept up to the gaoler from behind record of service behind him.This romantic plays, all about a famous and strangled him, as you heard." evening he looked dog-tired, and his highwayman the Bow Street Runners " Isee,"saidJane,munching shoes and trouser -legs were splashed couldn't catch. There was a wonderful placidly." But what I like on the with mud. Just over six feet tall, with murder in it, too.I turned off the wireless is a nice military band, and, of broad shoulders and narrow hips, he lights, and Jane couldn't bear it. 1 course, Henry Hall and Christopher lookedsomethingof amixture had to switch the set off again ;it Stone and his gramophone records. between a soldier and an athlete. was so life -like when the gaoler was I don't believe in these plays. They're " Sorry I'm so late, Madge," he strangled ! " either Shakespeare and all talk, or said." Kept at the Office as usual- Central Inspector Spears snorted. else they're like this Scarlet High- that Wapping business !Hallo, Jane. " Life -like, my foot !These play- wayman stuff, and give you night- I didn't expect to see you to -night." wright chaps have all the luck. They mares." He dropped wearily into the nearest can invent their murder, commit their " Well, I suppose some people like chair. murder, and solve their murder, and them," said Madge Spears, " or they " I hope you've got some dinnerhave everybody telling them how wouldn't do them so often.After left for me, old girl. I'm dead beat." clever they are ! Perhaps the Assistant all, they did that one awfully well.I " The girl'llhaveitready in Commissioner would like a few of wish Simon bad heard it.He's been five minutes, Simon," said his wife. them at the Yard."

353 MODERN WIRELESS October, 1933

" It was the realest thing you ever that the operator might flashthe keep the story moving, too, but at heard, Simon." cue -signalsto the scattered actors, timesit'stoo tricky. The more " Oh, rats, Madge !Give the wire- orchestra, announcer, effects -men, and mechanism you introduce, the greater less a rest and get that girl to hurry so on, who go to make up the play. the risk of something going wrong.I up with my food.I've had all the The transmission of such a play, must go down and say a word to the stuff about murders that I want for which might employ as many as cast, and pull Rodney Fleming out of to -day." twelve studios, was always a " nervy " the 6A Listening Room ;and' then, " You're an old bear with a sore business. what do you say to a drink, Des- head."said his wife. " Exactly on the minute,"said mond ? " But she went to the door all the Hancock, the Balance and Control " Nothing more you want,Mr. same, ruffling his hair affectionatelyengineer, rubbing his hands together Caird ? " asked the third man, the on the way, and disappeared in the and flexing his fingers. engineer on duty. direction of the kitchen. For an hour and five minutes he " No, thanks," said Caird." But " I wish you'd heard it, though, had sat at the Panel, " mixing " the I wish your people would make sure Simon," persisted Jane. output of the various studios in the that thosereturn -lightsfromthe Spears got out of his chair. transmission of the radio play, " The studios don't fail again." " Oh, for Lord's sake, Jane," he Scarlet Highwayman " ;and for an He jerked his thumb towards the said, " chuck it.I'm going to wash hour and five minutes his fingers had indicator on the wall. my hands." played with these knobs and switches " I nearly broke my neck clashing Left alone, his sister picked up the much after the fashion of an organist down to 6A on that infernal cork- box of Turkish delight, and delved at an organ. screw staircase between the sixth and into its messy interior.She was still On his right, Julian Caird, B.B.C. seventh floors, and for allI know holding it when the telephone rang. Dramatic Director and producer of Hancock may have messed up the " Hallo ! " she said, picking up the this particular play, wiped his fore- whole play during those minutes I receiver in her other hand." Yes, head with his handkerchief and stood was away."And hegrinnedat this is The Laurels-yes, he's just got up. Hancock, whom he knew tobe back. Who wants him ? Oh ! " " Thanks,Desmond,"hesaid. absolutely reliable. And she drew in her breath rather " You did very well.Lord, what an " As a matter offact,Julian," sharply." Scotland Yard ? evening !Once, I thought we should saidHancock," thatscene went tell him. . . ." nevergetthrough. Thisplay's considerably better than it ever did taught me a thing or two, at any rate. at rehearsal.Parsons really got it II. This elaborate technique of ours is this' time.He 'died'likea good "THE PLAY'S THE THING" amusing for the playwright and in- 'un.He really did what you told teresting for the producers-helps to him.Must have been influenced by AT precisely twenty minutes past ten on the same evening, the DRAMATIC DERARTNNIT. red light-indicating a broad- D.C. PANEL No. I GROUPING cast transmission in progress-on the 11 wall of the Dramatic Control Panel Room on the eighth floor at Broad- TA I 1611611 acme casting House went out.The three men sitting in front of the Dramatic 001010100 10 1-1

ControlPanelgavesimultaneous I Iyc1FA 16 s 166I bc1 sighs of relief ;the atmosphere, so OPERATED BY Mfl fibi CCge (OR Al RA C-RALAric.c' tense until a moment ago, eased per- Rep LCn rRI-)

'ceptibly as for the first time for more FISISI: ?remodel:Ion Tir than an hour the men " on the Stage Manager

panel " (as B.B.C. slang has it) were --NCS4 FALE I H1(itivgAymAN able to relax. preehmr 1"14 A curious room, this, much photo- REHEARSALS June 21st) 2.33 - 5.00 (Any single stolid) ) graphed by thePress and much 22ed TO: Juno23rd) June -20th-- L3.30 sought after by visitors to Broad- 1.30 R.I.C. (Control Room) 24th) ) June 29th 2.00 casting House. Rather like a control Balance & Control 25th ) All atulioa except )10.30 -.1.33 RA 5.00 Announcer,. Executive 26th tower in some ultra -modern submarine House Superintendent --a complication of electrical gear programme Routine STUDIO ALLOCATION standingoutinstarksimplicity SA TheatreOrchestra 60 Effects ) Subailiary againsttheship'sgreyofwalls, 6E GramophoneEffects 6C ) Coat Studios. ceiling and carpet. 6A gain Cast Studio 7C )

The most important object in the NOTES room wastheDramaticControl Panel itself, a long, grey desk holding EA.!. Micropeone in 6) essential. the switchboard that is the brain - centre of a modern radio play ; a M. double row of volume control knobs, each capable of amplifying the voice This isthe memorandum, initialled by Ian Macdonald, the of its particular studio to a roar or studio manager, and circulated to all responsible for the broad- diminishing it to a whisper ;a single casting of " The Scarlet Highwayman," which shows how the row of switches, each connected with a green lamp in a studio below so studios were allocated.

366 October, 1933 MODERN WIRELESS elementary Watson... -WITH ANALL-IN-ONEII

0" The invaluable assistance of an ' All -in -One' Radiometer enabled me to track down the trouble with this radio set very quickly.The t°710trnS411 SO VI Op transformer was burnt out.If the fault had S 1%

irfi I trr 140000 been anything else, however, I could have 0.200i1 401%?. 0 Opp run, mw traced it just as easily and as quickly with LOwoTEWS$ok this marvellous instrument to help me." PIFC ALL INONE The " All -in -One " Radiometer well deserves its name-" The Sherlock Holmes of Radio." Every radio owner needs it, because by its aid Standard Model "All -in -One" he can be assured of perfect radio performance Radiometer for Battery Sets only, as shown at all times.The " " tests valves, here. Price... 12'6 circuit,batteries,condensers,transformers, and any other components,registeringa verdict on each in a few moments. There is no other instrument in the world like the " All -in -One " Radiometer.Ask to seeit demonstrated at your radio dealers, or write direct to- PIFCO LTD., High Street, MANCHESTER, or 150, Charing Cross Road, London,W.C.2.

De Luxe Model for Battery Sets, Electric Receivers and Mains e2.2.0Units.Price !PA 361 MODERN WIRELESS October, 1933 the atmosphere.It waspretty tin" 3612 sheet about the gills.He muttered murderous during that mess-up with ,,,,, To scaal r wt... something aboutourrottensyn- the lights.You looked as though um! tt=1..7Z.C..... tin Mite thetic air in the studios and going you were going down to strangle MCC. M.. 4111.1 outside the tower for some fresh. someone ! CMOS .164,. I hadn't time to do more than swear Pao ilet Hancock was joking-but Caird 22. at him, but I noticed he was looking didn't laugh. seedy when he came this evening." " I'm sorry, Mr. Caird," said the " Well, he finishedhis partall engineer." But everything was - 2.4 hir 2S. .3.1, US - right, anyhow," said Hancock. " You tested as usual. idl.b go first." Just a bad luck Ate breakdown." MLR A121,1. S. Mo.LeelreLe I .blerb. fee " Yes," said Caird." You always I...... ,..ye.. .7. ',... III. say that.Well, as a transmission's :ealLie 'ea.. liabel fnnleev"... . le be nat.. te here to -night and gone to -morrow, ) mesa 'nose Liy-eut THE BODY IN THE STUDIO no one cares.Good -night." And UV,. flea, Peas111 114,01(rber. I. jULIAN CAIRD started down the he and Hancock went out of the room. corkscrew staircase, then ITU. 16,41411 ftel.., Deere.r.5 I.,/ As they strolled down the stair- turned suddenly. case and through the swing doors /me bet* .... ! .%)" " Oh, Desmond," he said," just on the seventh floor which led into Me,..410 have a look in 7B and 7C in case the inner tower of the building, in .c a olor seliey Perm. .,... there's anyone still there.A good Gbar.."..eDerlard . many of this cast have never broad- which all the studios were grouped. ,...... r... .r, e...en multi J.," Hancock took Caird's arm. Ilan. Spe.;. V cast before, you know.They may " You know, Julian, I think you udi. 111.1.11.ae I...... have stayed where they were to the want a holiday,"hesaid." I've leerge Sashite 2.,,, end." never seen you get so worked up. :IC Hancock nodded, and moved back You've been on the jump all the The dramatis persona of " The Scarlet along the passage.As he did so, evening." Highwayman,,, who found themselves the door on his right at the head of Caird stopped, and for a moment unwilling actors in a real life drama I the stairs opened, and .a dark young leaned his back against the wall in man in a dinner jacket, with very the narrow passage.Even the care- " In the 6A Listening Room." smooth black hair brushed straight fully subdued modern lighting did " What the deuce is he doing there?" back, came out of the 6A Listening not conceal the shadows under his " Well, I didn't want him in the Room. eyes and the hard lines of jaw and D.C. Room," said Caird." Actors " Hallo, Julian," he said." Had cheek bones under the tightly -drawn are a curse, but authors are intoler- you forgottenall about me ? I able. skin.As he took out a match to Besides, he wanted to be able thoughtitwentterriblywell.I lightacigarette,hishands were to see some of it going on, and ascouldn't have asked foritto be shaking. most of the big scenes were in 6A, better done." he could watch through the glass " I couldn't have done itif you " Oh,I'mallright,"hesaid panel.And hewasexpectinga abruptly. It'sonly this infernal hadn'twrittenit,Rodney,"said telephone call,soIarranged with Caird." Coming down ?I want to play.Ican't remember aworse Control Room to put it through to see the Drydens.Leo was looking ten days in all the four years I've the telephone in the Listening Room, awfully seedy, but I thought perhaps beenhere.First,allthetrouble where he couldn't disturb anyone we could get him and Isabel to come about the Drydens, with Rodney else. I wonder if Dryden'sall out to supper.I'm just waiting for Fleming at me all the time to throw right ? " Hancock. You might congratulate 'em out of the cast because they " Dryden ? " asked Hancock. him-he did marvels on the Panel." couldn't, or wouldn't, act together. " Why ? " " Of course," said Fleming." By Then that row with Evans, who won't " Oh, of course," said Caird, " I the way, thanks awfully for fixing remember that he's here to do what didn't tell you.You remember when that telephone call for me." Itell him and not to push his oar I got the message through from Con- " It was against all regulations and into what doesn't concern him. I trol Room that the return -lights had instructions," said Caird." But I'm didn't mean to go for him, but just failed and bolted down to warn Ian glad " when we were due to start he came Macdonald in the studio ? " He was interrupted by the shouting barging into my office and started " Yes." of his own name which came, rather a long rigmarole about the psychology " If you remember,it was just muffled, from a studio farther along of acting and what a mistake it was beforethebig ballroomscenein the passage. to expect Isabel Dryden to give a Studio 6A.Just as I got to the top " That'sHancock,"saidCaird. good performance when she and her of the spiral staircase on my way " What on earth husband were always fighting.It's back to you, almost exactly where The door into 7C was flung open, time that man did a straight job we are now, I ran into Leo Dryden. and Hancock burst into the passage of his own work and left others to Of course, he ought to have been " Come here,Julian,forGod's do theirs ! " downin 6A getting ready for his sake ! " he said." Quickly.There's TheBalance andControlman scene. Instead,he wascoming been an accident ! " smiled and took Caird's arm again. towards me from the directionof Fleming and Caird stared at each I betyou'llfindit'sbeen a the lifts." other for a moment ;then joined crackingsuccess.Comeon,let's " What the devilwas he doing Hancock in the studio doorway. butter up the cast and tell them all there ? " In the far corner, almost under the how good they were.Where did you " Exactly what 1 asked him.He microphone standard,lay a man's say Fleming was ? " was looking frightful-whiteasa body.

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Caird started forward. left eye, he viewed the _proceedings shoulder for about twenty-five years, " I suppose he's fainted," he said. with that slightly aloof geniality which and though genial he was a disciplin " Give me the water -jug, Desmond." was characteristic of him. arian and choleric. Behind the three of them the door The hands of the big black and " What thedevil " hesaid, shut automatically. green clock facing him on the wallturning sharply in his seat." What 7C was astudiowithspecial at the back of the tiny stage pointed is it, Caird ? " Then he remembered acoustictreatmentremovingall to twenty-eight minutes past ten. The that the red transmission lights were natural echo, and at that moment last turn, a famous Cockney cross- still on, and noticed the astonished Rodney Flemingfeltacutelythe talk pair, delivered their final wise- glances of the occupants of the ad- oppressive, almost sinister atmosphere crack into the grey, torpedo -shaped joining seats.But before he could of the room, with its single shaded microphone suspended between them lower his voice to repeat his question light,its thick carpet and queerly and the band -conductor, smiled and Caird had whispered urgently : padded walls.The ventilation was bowed at the audience, and walked off " Might I speak to you alone, sir, perfect, but he felt he wanted to draw the stage. The limes at each corner of outside ?It's rather important," and unusually deep breaths. the gallery went out ; the studio lights led the way towards the door of the . " It's no use, Julian," said Hancock. went up; and the band crashed into gallery. " And you'd better not touch him, its final number.At that moment General Farquharson frowned, or anything else." the general felt a hand on his shoulder. stumbled over the quite exceptionally " What do you mean ? " said Caird. It was fortunate that the number large feet of the lady in the seat next " It's Sidney Parsons," inquestion wasto him-who happened to be the said Hancock. " He's American andmother of one of the chorus girls- dead. Strangled. No " hot," for no one apologised handsomely, and followed wonder that scene was hadtapped Caird out into the passage. so well played !" General Far- " Well, Caird, what is it ?Are you quharson on the ill ?You're as white as a sheet." Iv. THE GENERAL TAKES CHARGE NINEfloorsbelow, inthespecial Vaudeville studio at Broadcasting House, professionally known as BA, the evening's hour of variety was going unusually well.No " act " had rung up from one of the Halls to say that they were very sorry but they would be bound to be two or three minutes late ;no comedian had wandered from his carefully censored script to insert a doubtfuljoke and shock thousands of suburban listeners.The new Director of Variety, always an enthusiast for experiments, had introduced a small chorus who sang and kicked with gratifying vivacity ; and more than one listener remarked that the studio audiencesoundedless mechanicalthanusual that evening. Prominent amongst the audience, in the centre of the gallery, sat General Sir Herbert Farquharson, theCorporation'sAd- Fleming and Caird stared at ministrativeController. oneanother for a moment ; Tall,distinguished -look- thenjoined Hancockinthe ing,andwhite-haired,studio doorway. witha cropped mous- Inthe farcorner,almost tache, and an eyeglassunder the microphone standard, immovably fixed in hislay a man's body. October, 1933 MODERN WIRELESS

Julian Caird seemed to have some the general register surprise, so that coming upstairs with me ?I know it difficultyinreplying. He stoodhis eyeglass fell to the floor with a soundsabsurd,butthere'severy against the wall, his throat moving tinkle of broken glass. reason to suppose that he's not only convulsively. Through the heavy rubber -sheathed dead, but murdered." " I'm sorry, sir," he stammered at door behind them came a final chord " Murdered !This isfantastic, last," but Ithought you should from the band and the sound of the Caird. What have you done ? " The know at once.There's been an-an audience applauding. general was surprised. No doubt accident up in 7C ! " Said Caird " They'll be out ofabout that! An accident ? " BA in a minute, sir. Would you mind " I put a studio attendant on the " One of my actors," Caird went on. door of 7C, sir, and warned my studio " We've just finished a play on the other wave - length, sir-` The Scarlet Highwayman.'Oneof the fellows in the cast was a man called Sidney Parsons.Hancock found him in 7C at the end of the show. He was dead." " Dead ? " echoed the general.And for the first time in his life Caird saw MODERN WIRELESS October, 1933 manager, Macdonald, and Bannister." " Bannister, your ' Effects ' man ? " " Yes, sir.Guy Bannister. ABOUT THE AUTHORS warned them to keep the sixth and Mr. G IELGUD,besides being the B .B .0.Productions Director, seventhfloors' clear, and told the housesuperintendent to telephone is himself the author of several radio plays and successful to the police. It was only then that I books, including the thriller, " The Broken Men." heard you were in the Vaudeville studio, sir.1 came straight to you as Mr. MARVELL, the recently appointed Director of Light soon as I knew." Entertainment, is also a radio dramatist of repute, and is " You seem to have been pretty well known to listeners for his " Good -night, Vienna." sensible, Caird. We'll go up." The general leading, they went up Together, they know the scene and the subject of their new into the main entrance hall, where story as no one else could. they met the house superintendent emerging from his office. " I'm glad you're here, sir," said mal homes ;that they should be " No, sir, of course not," stammered the latter. " This is a terrible business. completely unconscious that Higgins.And for the first time looked Scotland Yard are sending along a " sudden death " (from which theyhis questioners in the face." I'm detective and a police surgeon." prayed so regularly to be delivered) sorry,sir. Ididn't know it was The general glared. had struck within the very walls of important. Imisunderstood you, " Are you sure this is necessary ? " thebuildinginwhichtheyhad Mr. Caird.I was off duty at the end he said sharply." All this means the watched a variety programme being of the play, and I've an important most distressing kind of publicity." radiatedontheNationalwave- engagement.That's how it is." " I don't see what else we can do, length. " You musthaveunderstood," sir," said the house superintendent persistedCaird." Iwas perfectly defensively. " I've seen the body. V. definite.You weren'tto leave till I It's a clear case of a killing, sir. I PECULIAR CONDUCT OF came back." " I'm sure I'm very didn't touch anything." HIGGINS sorry." " Akilling ! InBroadcasting Well, it can't behelped," said House, of all places ! Good heavens ! " o Julian Caird's relief not even the general testily."Let's get on." the general's abounding energy said General Farquharson. " How But Caird had remembered was it the thing wasn't discovered could withstand the effort of something. until the end of the play ? " taking seven flights of stone stairs two at a time. On the fifth floor he was " Justaminute,sir. There's " Parsonswasmurderedwhile something else.Look here, Higgins, playing a character in the course of merely walking quickly, and on the you were on duty during the play, the play. He was alone in 7C," said sixth floor landing he even paused for weren't you ? " Caird. " Great Scott,sir, do you a breather. The studio attendant nodded. realise that everyone who heard that It was during that momentary play must have heard him die ? Pretty check that there was a surprising " Just exactly where ? " unique in the annals of crime 1 " interruption.Heavy boots clattered Higgins moistened his lips with his " We don't know yet that it is a down the stairs from the seventh floor, tongue. crime," snapped the general." Don't and an elderly man in a brown overall, " I was at the north end of the jump to conclusions ! " He turned to with his head ducked forward so that studio corridor on the seventh floor, the house superintendent :" Have he could hardly see where he was sir.On the door leading into the this detective fellow sent straight up going, humped into the Controller and passage that takes you out of the to the studio as soon as he comes. almost flattened him against the wall. tower." Don't let the news spread. Above all, Between shock and indignation the " Why was that ? "askedthe don't talk to reporters if they get general was momentarily speechless. general. wind of it.Caird, you come with me. But Caird recognised the man as the " I remember I asked Macdonald I'm going up there now. No, damn it studio attendant whom he had set on to put someone there," said Caird. all, we won't wait for the lift !If I guard outside the door of 7C after the " If that door's not watched you get can walk up seven flights of stairs, so discovery of Parsons' body. peoplegoingthroughthetower can you. You're thirty years younger " What the devil are you doing here, corridor, using itasashort cut, than I am." Higgins ? " he snapped." Didn't I during the transmission.We've often The audience from BA was surging tell you to stay by the studio door ? " had trouble that way. It was essential into the hall, some of them laughing The man mumbled something in a complicated play like to -night's and chattering, most of them staring apologetically. He was tall and weedy, to keep the corridors clear.That's about with unabashed curiosity at with an untidy fair moustache and just what I was getting at.I had the Eric Gill statue of the Sower, an unhealthily white face deeply lined. to go down to 6A from the Panel flanked by the mahogany reception His pale eyes slid from side to side Room during the transmissionbe- desk on the one side, and the book- in their sockets like a cornered cat's. cause one of the return -lights failed. stall for Corporation publications on " What'sthemeaningofthis, I went along the seventh floor studio the other.And as Julian Caird fol- Higgins ? "rasped the general, re- corridor.Higginswasn'tonthat lowed the general's long legs up the coveringhisbreath." Why have door when I went through it.Where stairs,it seemed to him incredible you disobeyed orders ? " were you, Higgins ? " that that audience should be wander- Higgins did not answer ;and Caird " I was on the door all through the ing out to the normal trains and buses added sharply : transmission," said the studio atten- which would bear them to their nor - " Did you go into the studio ? " dant sullenly.

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SEVENTH FLOOR " Not unless he went into the studio. LISTENING ROOM sir." (F/Pminy) The general gnawed his moustache. EMERGENCY UPPER PART- OF " We'll discuss your conduct later, Ex/ 7- STUDIO 6A //e991115 Higgins," he said at last. " Caird, on 9uaro9--, Z rEN/NG Room take him down to the house super- 8tP7rNER intendent's office.See that he waits ROOMS] there and that there's somebody with him until we want him again. I expect the police will wish to have a word with him. Higgins' jaw dropped. " Did you say the-police,sir ? STRIRS UP GRAMOPHONE I've not done nothing." EPPEcrs " I'm not saying you.have," said the general." I've no, time to discuss it now. Take him down, Caird.I'm going up to 7C and will wait there." TRIR5 DOWN " Very well, sir," said Caird." If you don't mind, I'll come up by way " Damn it, Higgins, I've got eyes Ground plans of the studioson the of the 6th floor artistes' waiting -room. in my head ! " began Caird angrily, sixth and seventh floors at Broadcasting The Drydens, Rodney Fleming, Mac- but the general interrupted him. House, showing Studio 7C where the donald and Bannister are still waiting " Now, Higgins," he said quietly. body of Parsons was found and the there." " Don't make things worse by lying. Listening Room, where Rodney Fleming You'veobviously beenneglecting " All right. Keep 'em there! " waswaitingfor histelephonecall And the general bounded up the final your duties this evening.This is a and watching the actors in Studio 6A. serious matter, and you, may find yourself in a very awkward position SIXTH FLOOR CIRCULAR STAIRCASE ifyouaren'tcompletelyfrank. TO SEVEN TN FLOOR L /FT5 Where were you when youshould STU 0106A have been on duty at that door ? " IT) (/4.4/N Boo r or Higgins fidgeted miserably ;and o CR5 r W/771.57-vao 1RNRCER) suddenly Caird was struck with an (-I) A overwhelming feeling of pity for him. 0 LISTENING ROOM LOUNGE The man looked so ill and thin and 0 A miserable, facing the magnificently no o cir( STUDIO6D authoritative figure of thegeneral. STUDIO6sSTUDIO 6cSOUND 6E And he could have sworn there were To EFFECTS A (CROWD(CROWD (Bamnster tears in those shifty eyes. SCENES)-SCENES)and Staff ) For about thirty seconds longer, Higgins faced it out.Then his nerve CORR DOR 5TAIRS UP GR AlOPWONE failed him. EFFECTS " I'll tell you, sir," he said." I suppose you'll give me the sack, but OFF/CE5 I'd have got that anyhow, after to -night.It's agirl,sir. One of those girls who work in the canteen 5raffe5Dowtv flight of stairs, once more taking them in the basement.We've been sweet two at a time. on each other for some time, but it " But she didn't come, sir.It's was coming to no good, what with nothing to do with her.I swear she VI. me being married and everything. didn't come." MR. LEOPOLD DRYDEN IS And yesterday she wrote me a letter " Very proper of her," said the and gave me the chuck.Well,it outraged general." Well ? " ANNOYED isn't easy for me to go down there, " I waited as long as I dared, sir, till was a strange group that Caird sir, as you know.I've no business a minute before I knew the play ended, ITfound on his return to the waiting - inthe basement, andthehouse at twenty minutes past ten, and then room on the sixth floor.On the superintendant had spoken to me I went back to the door. So I was there extremeendofthelong,fawn - about it, anyway.So I wrote her a when Mr. Caird and Mr. Hancock coloured couch sat the author of the note and asked her to come up and came down from the Panel Room." play, Rodney Fleming, his expression meet me in one of the offices on the " That's true," said Caird." He a mixture of boredom and exaspera- seventh floor during the transmissionwas clearing up oddments inthe tion. He was smoking a cigarette and to -night, while I was on duty.I corridor, emptying ash -trays, and so watching Leopold and Isabel Dryden gave her ten o'clock as the time in my on.That's why I told him to wait under slightly lowered lids.Leopold note, and that was when I went to outside 7C till I got back." Dryden was fretting up and down the the office." " Did he know anything about narrow space between the couch and The general snorted.But Higgins the "said thegeneral,and the wall. With his rather long fair hair went on hurriedly : then suddenly stopped. indisorderandhismagnificent

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NAME N VALVES ADDRESS TU ht.W UNIVERSAL MODERN WIRELESS October, 1933 physique, his undoubted good looks disreputable chorus girls, without so towards Caird, looking more leonine seemed a little too theatrical to be much as a by-your-leave ? I appreciate than ever. quite genuine. He was acting a part your position, Mr. Macdonald.You " I won't stand for it," he almost with his usual brilliance-the part of have to do as you're told, but I have shouted." All this mystery -making thebaffledtemperamentalartist. myself to think of-my standing andand humbug !Ionlydidyour Isabel, his wife, sat next to Fleming, my reputation. Suppose this got about infernal broadcast to oblige Isabel. watching him closely. She was a very as a story !It might do me infinite She made such a point of it. And you, pretty girl, not more than twenty-six, harm.Perhaps now you'll be good too, Fleming, of course, as you were with that unusually attractive com- enough to 7, good enough to say you'd written the bination of fair hair and dark brown " Oh, I'm so glad you've come,' play for me.I've never believed in eyes. Julian,"saidIsabel,jumping up. broadcasting for plays.I wish I'd I wish they'd let Leo go," she " You mustn't mind Leo. But do let never touched this one with the tongs. whisperedanxiouslytoFleming. him go now, even if you want to I'm not used to this kind of treatment, " He's been so seedy all the evening, keep me. I'm so afraid he's going to Caird, I tell you. If this is the way in and he wasn't a bit himself even at be ill." which you're in the habit of treating dinner." " Nonsense ! "said Drydenvio- artists--" Meanwhile Dryden was delivering a lently. He broke off. Over Caird's shoulders speech con brio at the unresponsive he could see two men walking slowly head of Ian Macdonald, the studio along the passage towards them. The manager. That impassive Scot, with a first was General Farquharson, looking head that looked as ifit had been very grim, and behind him was a lean carved out of teak, who had never individual in a dark blue serge suit, carrying a bowler hat. They halted,andtherewasa moment's silence. " I'm extraordinarilysorrythat you should all have been inconveni- enced,"saidthegeneralgravely. " But it was unfortunately necessary that you should wait for the arrival of this gentleman.He has a few questions to ask all of you." " And who the devil--" began Dryden. No, no, not quite as bad as that ! " said the newcomer, putting down his howler bat." My name is Spears- Central Inspector Spears of Sccitland Yard." To Rodney Fleming, who thought of himself 'not only as a young man - about -town and a most promising author, but also as a student of humanpsychology, thereaction among the little group in the waiting- roometo Inspector Spears'arrival was of absorbing interest.Even he himself, though he knew of the murder and had anticipated the appearance t of the police, would have confessed to a tautening of his nerves when face to face with a representative of Scotland Yard. 66It may be murder," said Spears Isabel Dryden put one hand to her quietly. Dryden recoiled a step. For a moment thebreast and V went so white that he arrogant assurance left his face." Well, suppose it was afraid she was going to faint ; is murder," he said. " Do you suggest that I or my wife have anything to do with it ? but Ian Macdonald only said,I'm glad to see you, sir," in precisely the been known to be disturbed by any But his face twitched suddenly as same way as he had been known on a crisisinthe historyofbroadcast if with a spasm of pain, and he satformer occasion togreet a dusky drama, gave the impression of listen- down on the, sofa. potentate paying a visit of inspection ing with the greatest interest and " Can Itell them yet, Julian ? " to the studios.It was a little dis- sympathy. asked Rodney Fleming quietly from appointingthatLeopoldDryden " But I tell you it's an outrage," his corner. should so ostentatiously have taken Dryden was declaiming as Caird came " Tell us what ? " said Isabel. the cue for his next " scene," for take along the passage." I insist upon " Not just for a minute, please," ithedid,withunexceptionable some sort of explanation, at any rate. saidCaird. " We won't belong technique.Hepausedjustlong Are my wife and I to be kept here all now." enough to allow Spears' introduction night asifwe were a coupleof Dryden got up again and strodeto " register " in the minds of the

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(Proprietors: Oliver Pell Coning Lid) FOREMOST AS PIONEERS Advertisement of Oliver Pell Control Ltd., Kingsway House, 103 Kingsway, London, [V .0 .2 Telephone :Holborn 5303 371 MODERN WIRELESS October, 1933 ethers ;then walked up to Generalwhatsoever to detain us unless you of photographers dealt with what Farquharson and looked him very choose to put us under arrest.And I had once been Sidney Parsons. straight in the eyes. don't imagine you're impudent enough Studio7C,withitsartificially " ScotlandYard,"herepeated orstupid enoughto do that.I padded walls, its uniform grey colour, witheringly. " Indeed. Most shall be glad to be at home to you was clearly appropriate for the setting interesting.So I've been kept wait- to -morrow morning, if you call upon ofthescene. LeopoldDryden, ing about here to be questioned by the us at our flat, at a reasonable hour-thought Fleming, would have appre- police, because some lady has mislaid I mean not before eleven o'clock in the ciated it.The only furnishing con- her handbag, or a ten -shilling note is morning.You'll find the address in sisted of a sofa, three or four small missing from the gentlemen's lava- the telephone book." metal and canvas chairs, a round tory !Luckily, one of the Board of And holding Isabel's arm tightly black table on which stood a water Governors of this Corporation is a within his own, he walked past the carafe and a glass, and a microphone member of my club.You've not general and Spears along the passage fixedhead -highonafour -legged heard the last of this, I can tell you." to the lift without looking back. stand. The general did not blink an eye- " Should I hold them ? " inquired When Spears and his companions lash. Ian Macdonald impassively. entered the studio the photographers " Mr. Dryden," he said. I have Spears shook his head. were just packing up their apparatus. apologisedto you fortheincon- " IthinkI'lllet him cooloff. There was a strong smell of mag- venience to which you have been put. There's plenty to see to here.I'dnesium, and smoke was still curling You will realise the necessity for it, best get myself familiar with your about the ceiling. The body of Parsons perhaps, when I add that a man, box of tricks, Mr. Caird, and find how lay where it had been found, almost one of the company engaged in the the land lies.I can do my question- under the microphone, but now it was play which you have just performed, ing in the morning." decently covered with a rug. The met his death in one of the studios Rodney Fleming stoodup andsergeant stood by the littletable, to -night." brushed cigarette ash off the lapelson which he was sorting out with Isabelstifledalittlecry,and of his dinner -jacket. deliberation the contents of the dead Fleming caught her sharply by the " Then canIgohome ? "he man's pockets. The divisional surgeon, wrist. inquired. a lantern-jawed individual with pince- " Steady, Isabel," he whispered. " If you don't mind, I'd like you nez, a shock of white hair, and quite But Leopold Dryden was not to and Mr. Caird with me," said Spears. astonishinglyshinytrousers,was be daunted or thrown out of his stride. " As I understand it, you were on two sitting on the sofa scribbling on the " Needless to say, I am more than of the loose ends of this play, and I'd back of an envelope with a pencil. distressed to hear of such a thing," like to know how it looked from the " Hallo, Spears," he said, looking But,first hesaid,throwing back hishead. various points of view. up. " You hardly need have bothered " But it seems to me that you are of all, I'll go back to the studio where to spoil my beauty sleep for this.I doing your best here to turn tragedythe body was found.They should suppose there'll have to be an autopsy into farce. Am I to understand that have finished taking the photographs as a matter of form, but the thing's my ,wife and I have been kept to be by now." clear as daylight." questioned by the police because some " Just as you like, inspector," said " Well ? " asked Spears. leaveyouin poor devil has been unlucky enough to thegeneral." I'll The medical man peered athis die on your premises ? "His tone charge, Caird.I think the inspector pencilled scribble. changed from indignation to deepest should see that man Higgins before he goes.I shall want you in my office " Strangled from behind," he said. sarcasm." Or perhaps you believe The fellow who did the strangling it to be a case of murder, and propose first thing in the morning, before I see the Director -General.What a wore gloves.I don't need you to tell to arrest me on suspicion ?Is that me that, Spears.I'm sure there's it?" thing to have happened here !I can hardly believe it, even now.Good- not much argument about when he " It may be murder," said Spears 2, night." was killed quietly. And he walked briskly down the " We must have heard him die ! " Dryden recoiled a step.For a said Caird excitedly. moment the arrogant assurance left corridor. his face. " No jumping to conclusions, please, VII. Mr. Caird," said Spears reprovingly. At that moment Isabel got up from THE TORN SCRIPT " You think you heard him die in the sofa, and put her hand through your play,don't you ? Suppose his arm.The touch of her fingers TIKE most busy men with onlyhe didn't play his death scene him- seemed to act upon him like the voice 4limited time for reading, Julian self ? " of a prompter, for he patted her hand Caird was a great reader of de- and turned back almost fiercely to tectivestories.Broughtupon " By Jove, that's an idea ! " said the detective. " Raffles," " Arsene Lupin," " Sher- Rodney Fleming. " Well, suppose it is murder," he lockHolmes," and " Trent's Last " We don't know anything yet," said." Do you suggest that Ior Case," he now devoured the exploits said Spears." I'm just looking for my wife have anything to do with it ? and debated the respective merits of facts at present. How long's he been Do you propose to question us at this Inspector French, Colonel Gore, and dead, Arbuthnot ? " time of night, just after a performance, Lord Peter Wimsey.But somehow " I'vetold you before,Spears," when we are both dead -beat ?I not all his familiarity with the fiction said the surgeon, " only fools pretend didn't know you'd been driven to of crime had prepared him for the ex- to answer that question accurately. fall back on third degree methods at traordinarily matter-of-fact methods But he's not been dead more than two Scotland Yard.I can tell you this, withwhichSpears,hissergeant, hours, I can tell you that. He didn't Inspector Spears, you've noright his divisional surgeon, and a couple take much killing, poor little brute

372 October, 1933 MODERN WIRELESS

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Wretchedly under -nourished ;poor " You've got a note of the contents " Thank you, Mr. Caird. And per- physique ;and the worst set of teeth ofthepockets,sergeant ? "said haps Mr. Fleming will come along

I've seen for years." Spears. . between three and half -past ? " " I knew Parsons was in rather a " Yes, sir." Rodney Fleming nodded, and lit bad way," said Fleming." I knew " Very well. What's this,Mr. the last cigarette from his case. him slightly-recommended him to Caird ? " He held out a wad of typed " I suppose," Spears went on, " it Caird for the part, because I knew he sheets, tied together with tape at the wouldn't be possible for me to get was so hard up." top left-hand corner. There were about something to eat ?I was home late " Thanks," said Spears." You can fifty sheets of this paper, which had and got called out again before I could tell me more about that later.Any- something of the substance and feel get at my supper." thing else, Arbuthnot ? " of blotting -paper. " My dear inspector," said Flem- " I don't think so-nothing useful." Caird raised his eyebrows. ing," there's one advantage about " Have you got your photographs?" " That's a script of the play," he having to detect crime in this sort of asked Spears, turning to the other two said." Our actors read their parts, wholesale establishment. Idoubt men. you know. They don't have to learn ifyou'llget. champagne, but the " Yes, sir." ,em.,, canteen's excellent ;I know it well." " Very well.You can get along. " It was lying just beside the body, " I'lltell you what," said Caird. Send the two men you will find in the sir," put in Sergeant Ring. " We don't want to go down to the hall up for the body. Now, sergeant, Spears sat with the script in hiscanteen and eat under the eyes of a have you searched the studio ? " hands, staring at it. lot of Variety Artistes waiting for an The detective-sergeant-Ring, by " That's my play all right," said Empire transmission.We'll go into name-was a thin foxy -faced man, Rodney Fleming lightly." There's one of the Listening Halls and I'll have with bulging pale blue eyes and slim the title on the outside page, and some coffee and sandwiches sent in hands which looked as if they should everything." to us." have belonged to a pianist rather than " Exactly," said Spears. " Perhaps The night -service lift dropped them to a policeman. you can tell me, Mr. Caird, if it is usual to the basement floor, and Caird led " You can see for yourself,sir," for your actorsto mutilatetheir the way into Listening Hall No. 1. he said." This room's as bare as a scripts ? " Rodney Fleming threw himself into board. The carpet's too thick to take " Mutilate them ?They scribble one of the deep armchairs with un- any impression, and whoever did this on them sometimes-make notes or disguised satisfaction.Spears stared job knew too much to leave anything cue marks in the margin. Why ? " about him, frankly bewildered by this behind him.Here are the contents Spears held out the script. queer room with its modern furniture of the pockets, sir." " Either Mr. Parsons or someone and decoration, its lighting so self- Spears walked over to the table, else," he said slowly, " has torn half consciously subdued, and its big loud- and as Caird watched the detectivethe outside sheet of this away.It speaker raised on a platform in front fingeringdispassionatelyone little was torn in a hurry, for the edges are of a carefullydesigned modernist object after another, he was again jagged.I wonder why ? " scene indicating two blocks of sky- conscious of that strange sense of the VIII. scrapers and a stretch of river. pathetic which had struck him when INTRODUCES EVANS-AND " Make yourselfcomfortable,in- he and the general had confronted THE BLATTNERPHONE spector," said Caird." This is where the studio attendant on the staircase. RATHER more than an hour later, we put distinguished listeners, Press There was something indescribably when Caird and Fleming were representatives and other swells, when wretched and forlorn about the little almost reconciled to spending we want them to hear our stuff as it pile of coppers, the paper packet of the rest of the night as initiators of really ought to sound.I'll go along ten cigarettes, three-quarters empty, the detective into the mysteries of to the canteen and order the food." theinevitablepawn -ticket, the Broadcasting House, Spears slipped an He turned right-handed along the soiled handkerchief, the three loose elastic band round his notebook and passage towardstliecanteen, and keys on a piece of knotted string, put it into his pocket. stopped abruptly. the chewed stump of pencil, and the " I won't bother you any more " Hallo, Evans ! " he said." What shabby pigskin pocket -book, so ob- now, gentlemen," he said." I think the deuce are you doing here at this viously sole relic of very distant better you've shown me about as much as time of night ? " days-containing a few grubby papers I can absorb." " I happened to be working late," andasolitaryten -shillingnote. They had visited the D.C. room and said Stewart Evans, without troubling Who on earth, thought Caird, could studios ; they had explored passages to disguise the insolence in his voice. have found it in his heart to strike and examined mechanism, until Rod- He and Caird disliked each other down such an insignificant weakling, ney Fleming for one was heartily sick heartily,and unfortunately Evans an opponent so blatantly ill-equipped ? and tired of the whole performance. was oneofCaird'sdepartmental What motive could there possibly be Now once more they were standing subordinates.He wasolder than for the sudden throttling of a creature outside the door of Studio 7C. Caird, and took few pains to conceal so patently set towards the Embank- " I'll begin my questioning of in-the fact that he had little respect ment and the dosshouse ?He turned dividuals as to their separate move- for Caird's authority and none for his to Fleming with a shiver. mentsto -morrowmorning,"said judgment.He was a tubbylittle " I suppose you find it interesting; Spears. " I'll begin with the Drydens, man,alreadygrowingbald ;un- Rodney ?' he muttered. " But, per- as they were good enough to give me doubtedly clever ;emphatically am- sonally, it gives me the creeps to see an appointment. Perhaps I could see bitious ;but cursed with a record of Spearsfingering thatpoordevil's you two gentlemen after lunch ? " failure in various lines of activity, all things as if he was choosing kidneys " I'llbe quite freeat half -past of which couldbe tracedtohis for breakfast." two," said Caird. temperamental inability to get on

374 October,1933 MODERN WIRELESS

IllMM111=1111112 PETO-SCOTT Peto-Scott are pioneers inRadio and Television. Our service to the British publicwas intro- EVERYTHING duced in 1919, and during four- ENAMELLED teen years of Solid Service and Satisfaction we have established RADIO a reputationforfairdealing WIRES that defies competition. BUILD "11(4" 1 YOUR WITH A 1. High dielectric strength and free from pinholes. PILOT AUTHOR KIT 8 SPECIAL2.Itis tough and will tuptehocIsfilictickicFoimrs-t withstand severe CASH ORC.O.D. handling. K IT "' A'ponents, including CARRIAGE PAID In sealed carton. exact Peto-Scott ready- to specification. Com- drilledreadypanel,Ter- 3. Enamel is highly plete down to the last minalStripsand FEATURES elasticandwillnot screw, with all neces- woodfor " K4 "M6-12-0 readily fracture. sary wire, screws and Framework, 1 e s s or 12 monthly payments flex. Valves and Cabinet. of12/ - 4.Willresist tempera- HIT " B." As Kit " A," but with HIT " C." As Kit " A." but with tures which would Valvesonly.Cash orC.O.D.. Car- Valves and Cabinet. Cash or C.O.D. riage Paid, £811713, or 12 monthly CarriagePaid£911519, or 12 char any fibrous payments of 16/3. monthly payments of 18/.. insulation other than asbestos. Specified Valves 521513. Peto-Scott Universal Cabinet 18/6 5. Under ordinary con- THESE ARE THE PARTS THE AUTHOR USED: E A d. its 1 ditions, retains all Pair COLVERN Ferrocart coils, F10 and F3 ... 1 5 0 qualitiesyearafter 1 VARLEY type D.P.35 compensating transformer ... 11 8 1 FERRANTI A.F.17(c) Class B input transformer .. 15 0 year. 1 SOUND SALES Class B output choke ...... 9 0 1 TELSEN screened binocular H.F. choke ...... 4 6 6. 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Axed condenser ...... 1 3 wire, both under and 1 DUBILIER 0003-mfd. fixed condenser ...... 1 3 over the enamel,is 1 GRAHAM PARISH " Ohmite " 500 -ohm resistance and holder ::: 2 0 1 LISSEN 2-me f. grid leak (wire ends) ...... 1 0 accuratelyconstant, 3 2 6 1 BENJAMIN 7 -pin valve holder _. ... - ...... 2 0 makingitidealfor 1 BULGIN QMB 3 -pt. on -off switch, type 8.87 ...... 1 9 coil winding. 4 IGRANIC indicating terminals ...... 1 0 7 BELLING -LEE wander plugs ...... 1 2 2 BELLING -LEE accumulator spades ...... 4 8. Entirely British made. 1 BELLING -LEE S.G. anode connector ...... 4 1 TELSEN coil switch -coupling link ...... 6 4 PETO-SCOTT wood strips for K4 framework ...... 1 6 1 PETO-SCOTT ebonite panel, 18' x r, ready drilled ...... 6 6 2 PETO-SCOTT terminal strips, 3" X le ...... 6 1 BRITISH RADIOGRAM R4 screen, 7e X 3/1" ...... 1 0 The B.I. have been manufacturing enam- 6yds.20 gauge tinned copper wire;5yds.insulatedsleeving;flex, 2 6 elled wire since it first came into use, and KIT " A," CASH OR C.O.D., CARRIAGE PAID £6 12 0 long experience, constant research and the use of the finest machinery available CASH - C.O.D - or H.P. have led to the production of B.I. enam- PILOT PBTO-SCOTT CLASS B CONVERSION KIT PERMANENT -MAGNET MOVING -COIL SPEAKER elled wires of a consistently high standard Converts your present Battery Send withtappedInput Set to Class B Amplification. transformer for power of quality.For all fine windings where Completewithallnecessary or pentode. components, includingdriver 5 .1 " Itsperformance transformer, Class B output is superior to several economy of spaceisessential,thereis choke, W.B. 7 -pin valve holder,only I have tried at prices Cosner 2408valve,wireand from 52/6 to 67/6," nothingtocomparewiththeperfect screws. etc.Pull -sine Blueprint, assem- writes a satisfied bly instructions and diagrams. 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375 MODERN WIRELESS October, 1933

" Death at Broadcasting House." you were staying up to hear the result 6EA4):;b00Eg@OE's1,&6PE3,0@EgOl'-ca -continued of your efforts." HOW TO BUILD THE K4 2 witb his fellow men.He belonged " What do you mean ? " said Caird. -continued from page 304 specialisedsection ofCaird's " Oh, Rodney, this is Mr. Rylands, 83.) to a C,0ce -f3o,f,443o,sn9gD department, whose members devoted one of our Empire Service announcers themselves to the composition and -Mr.Fleming, and--er-erMr. just as you like.The only point to production of programmes which did Spears." observe is to see that you keep some not come within any of the usual " All,"said Rylands, " must be sort of check to ensure accuracy, but categoriesof drama, music,talks, forgiven to the artistic temperament. thisisa very obvious precaution. and so forth.Members of Programme We blattnerphoned the transmissionProbably the easiest way is just to Research, as they were called, had of' The Scarlet Highwayman' and work by Steps, as I did myself, wiring considerable latitude in methods and we are transmitting it to the Empire first the valve Step (No. 1), then the hours of work.They were extremely in "-he glanced at his wrist -watch underside of No. 2, the top surface of valuable members of the Programme - " exactly seven minutes' time.I No. 2, and finally the leads which run Branch, and were equivalently diffi- just wanted to see that the loud-merely between thevariousStep cult as an administrative problem, speaker had been plugged -in in here. surfaces. as Caird, with whom departmental I must telephone to Control Room," In wiring up the valve holders, responsibilityfortheir worklay, and he vanished into the telephone -box in the corner of the Listening Hall. by the way, you will find that the knew to his cost. filamentleadsdonotrun veil, - Spears looked puzzled. " Iheard your playto -night," " Blattnerphone ? " he said. straight from point to point, but must Evans went on." I'lladmit you " Yes," said Caird slowly." It'smake their way round intervening can handle that stuff, Caird.But how a way of recording a programme on a obstacles.There is consequently no you reconcile it with your conscience steel tape so that it can be re -trans- very great point in pulling them quite to put it on at all, beats me. Why mitted. We have to do a good deal tight like the other leads in more the devil not give 'em East Lynne of it for Empire work." important circuits.If a little slack is and have done with it ? " " Re -transmitted ? " left in them they can be pushed down repeat ed a little out of the way. " My dear Evans,"saidCaird, Spears. " Do you mean to say " I don't want to be offensive, butthat- " Only three leads call for holes to sometimes-and particularly when I'm Rodney Fleming sat up. be bored in the wooden frame for very tired, as I am now-I wish you'd " By Jove ! " them to pass through, and of these mind your own business.I put on " Of course,"said Julian Caird. one (from -0005 condenser on top of ' The Scarlet Highwayman' because I never thought of it.What a fool Step2to-0003 underneath) has I believe there are a lot of listeners I am !I was only thinking how already been mentioned.The other who likeit.But ifit's any satis- maddeningitwas that here you two are those from the speaker ter- faction to you, I wish to heaven I'dhad a crime with almost any number minals to the secondary terminals of never touched the damned thing." of witnesses, and as none of them theoutput choke. (Icallthem " Conscience pricking ? " inquired would have known it was a crime, secondary terminals, by the way, Evans. their evidence wouldn't be an earthly. because this component really acts " Oh, rot ! " snarled Caird. " You'll But as it is )3 as an auto -transformer.) know all about it in the morning. Spears smacked his fist down on the These leads need not actually be What have you been working on ? desk in front of him. taken through holes, because they You aren'tusuallyinthehabit " You mean you've got the play could be brought up round the edge of burning this amount of midnight recorded ? " he said, and even in his of the Step nearest to the panel, but a oil." voice there was a thrill of excitement. somewhat neater appearance is ob- " I like to work in my office at " You mean we can hear that actual tained by drilling holes for them, night,"saidEvans." The atmo- scene over again ? " so I did it.These connections, by the sphere's sympathetic.No telephone " We can hear that scene," said by, should not be made permanent calls ;no idiots coming in to ask me Caird," not only over again, but until the right ratio which suits your why Ihaven't initialled a lotof over and over and over again.As particular speaker has been found by tomfool forms. I can get something often as you like.I wonder if the test, so just attach them temporarily done.Good -night, Caird." murderer thought of that ? " to the choke terminals when first And he trotted away. wiring up the set. Cairdorderedsomesandwiches (Nextmonth'slonginstalment of A point to which Iwould par- and coffee, and went back to the Lis- " Death at Broadcasting House " will ticularly direct the reader's attention teningHall.Rodney Fleming was be no less exciting.Here is a sample concerns the earthing of the screening lying back in his chair almost asleep. cases of the coil units and their wave - Spears was sitting very upright in Almost furtively,Caird change switching rods and the ganging a tubular steelchair, studying his looked round atthe faces.Which link.All this metal work must be notes. of them, he wondered, shared his own properly connected to earth, and the " Food in a minute," said Caird, feeling of horror as they listened toway to do it is clearly shown on the with a joviality he was far from this voice of a dead man-a man constructionchart wiring diagram. feeling. Hallo,Gerald.What is most of them had seen alivelittle Note the connections to certain of the it ? " overtuenty-fourhoursago,and fixing screws of the coil units and the whose corpse now lay on a mortuary The door had burst open and a I) short flex lead to the connecting arm distracted looking young man in a slab of the ganging link. dinner -jacket came into the Listening Don'tmiss next month's issue of The important point here is to see Hall. MODERN WIRELESS, on sale November thatareallygood connectionis " Hallo,Julian. Ididn't know 1st.) (Continued on pag, 378)

376 October, 1933 MODERN WIRELESS

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%*&68463V685EMigiNMEgEMDEM, I mentioned just now that certain F.D screening cases require to be earthed, qe. HOW TO BUILD THE K4 qi3 g REFLECTIONS OF q3 and it occurs to me that the reader g -continued from page 376. D may wonder whether it is by an over- A RADIOTIC @ g -continued from page 346. r$ OS sight that no earthing connection 0001? CegeggOZ *Svg*OS is shown for the cases of the screened o13130id*O60043194913043434S obtained at each spot, and this means H.F. chokes and the screening of the that you should carefully scrape away anode lead of the S.G. valve. them unless Leo's tail became untied the enamel on the coil base around This, as a matter of fact, is quitefrom his off hind leg, where it had each place where a wireisto be intentional,for such earthing was been fixed so that he should not flick connected. Note also that a piece offound to be quite unnecessary and the studio furniture out of place. bare wire must be used for the lead served no useful purpose, so it was which runs from a fixing screw of one omitted.The anode lead of the S.G. Thoughts on Radiolympia unit to a fixing screw of the other valve, by the way, consists of a short As Ifiltered my tortuous way one, because this lead passes underpiece of single flex, just long enough through the other sardines on the the lower edge of the screen andto reach to the top terminal of the opening day, one word constantly contact here is desired for the purposevalve, and encased in any of the came to my mind : Writtle.Yes, of earthing the screen itself. usualmetalscreeningmaterials. Writtle, Essex, where was the first Great care must be taken to see that British broadcasting station, amateur Perfectly Straightforward thisscreeningmaterialdoesnot stations not counted ;the first studio All the rest of the wiring is per- happen to touch the live terminal at complete with noise effects and uncles. fectlyplainsailing,and the con- either end, or it may cause slight A far cry to this first-class London structor can go ahead with it by just instability instead of preventing it. Show, packed with people, at which a following the construction chart pre- When the wiring has been com-radio trade employing hundreds of ferably in conjunction with the verbal pleted as far as it possibly can be thousands collaborated with a huge wiring instructions which I give inwithout the two terminalplates, Corporation numbering its clients by the pages of this article.The latter which must not be fitted yet, the millions, at ten shillings a client. would really be sufficient without the battery leads should be attached, and The thought tempts me to commit diagram if gone through with just a then the terminal plates can go on. one of the worst of journalistic sins little care, but the two together will You will see where the battery leadsby remarking that allthis demon- be found to make everything veryconnect upon the diagram, butI strates that radio evidently filled a clear and easy to follow. should just explain that the H.T. long -felt want. But I will not, because I should like to stress this fact a negativeleadismerelyashort the Editor already wants to see me little, because the Step System is a extension from theL.T.negative about a " succulent bivalve " and an new thing, and the form which the " spade " terminal, with the usual " it subsequently transpired." wiring diagram takesisnaturally fuse plug fitted upon its end. unfamiliar, hence the reader may at Our Way Best first glance be inclined to think it not This Show, though ! Had it occurred so easy to follow as that of a set built in America the U.S.A. Press would on the older flat baseboard plan. The L.T. Switch have rioted in purple captions such In actual fact it will be found that Mr. Kendall likes his L.T. switches to as "Radiocracy Return to Prosperity"; there is no such difficulty as soon as go on upwards and off downwards. If " Dial Bugs Hit Hay Happily After the new scheme becomes familiar, you prefer the conventional arrange- Huge Hear -feast." but to make quite sure that no one ment, mount the switch the opposite way up.This makes no difference to We, on the contrary, shall do our has the slightest trouble in following the wiring. best to deprecate tip whole matter, the connections I have added the whilstburstingwithsatisfaction. " wiring in words " table. I like our way, though. I've had too In connection with the battery leads much fever in my time to hanker Checking the Connections Imust explainthat the diagram after fevered enthusiasm. Iwouldsuggestthatagood makes no attempt to indicate suit- As Sam Pepys would have said, method isto use the diagram to able lengths for them, for the simple " Lord, to see the women and the identify the particular wire, and then reason that this depends so much boys." I began to wonder where use the verbal key to check the exact upon the kind of cabinet in which the papa was, till I bethought myself of connections which are concerned.In set will ultimately be housed.For the source of wealth, the City. this way you will find all the leads my own use I always make them become very easy to follow out, and quite short, because I like to have the Earning the "Needful " if you cross out the reference lettersbatteries close up behind theset, Papa was still there, in the dust of each in the table as you insertwhere I can get at them easily forand heat,earningthe" needful" the wire in question, you will have a.voltage adjustments, but those who and hoping to get down to Olympia useful check on the completeness of use their sets under more domestic for an hour. Some idgit recently said the wiring when you have finished. - conditions will have different require- that slavery did not existinthe By the way, you will understand ments. Empire, too! that the wiring chart is divided up With that I think I can leave the One last sinister reflection. Can the into two parts merely for the sake of reader to get on with the building of B.B.C. live up to the manifestations clarity.The actual wiring of the set his K4.I think he will get a pleasant of the Show ?That mighty surge of contains all wires shown on either surprise over the job, for I don't think humanity needs and demands alimen- sectionofthediagram :the twohe will be quite prepared for the tation from something greater than sections have to be added together, extremely easy nature of the task, in itself.Is the B.B.C. really greater so to speak. spite of all I have said. than the British Public ?

378 October, 1933 MODERN WIRELESS

(Allthesegiftbooksare strongly boundinbrightly coloured covers and contain features of interest to boys of all ages.They are splendidly illustrated with photographs and drawings, and some contain beautiful coloured plates. Ask your newsagent or book- seller to show you them all.

TheWorld'sGreatest Engineering Achievements Here's a magnificent new Annual, which describes the wonderful romance of the world's greatest feats of engineering. Experts have written the intensely interesting articles which tell the fascinating story of Man's struggle with and conquest of the forces of Nature. This remarkable new book is crowded with hundreds of illustra- tions, photographs, drawings and four full -page colour plates. Modern Boy's BOOK OF ENGINEERING 7/6 School and Adventure TalesFor the Boy with a Hobby Every boy will revelinthe big This splendid book is packed with budget of ripping school and adventurebrightly -written articles on practically All AbouttheMechanical talesin the HOLIDAY ANNUAL. every hobby and subject appealing to the boy of to -day.Every boy who is Marvels of To -day Here he can meet all the jolly school-keen on making things and finding out boy characters of Greyfriars, St. Jim's, howthingsworkwillwant the The MODERN BOY'S ANNUAL is and Rookwood Schools, whose merryHOBBY ANNUAL. Itis profusely packed withfascinatingarticleson pranks cannot fail to entertain.Thereillustrated with hundreds of photographs ships, aeroplanes, railways, racing cars are lotsof other interesting features,and drawings that show " how " in the too, including pithy poems and puzzles, simplest way.There are also two large and motor -cycles, the films, and other and four fine colour plates. folding photogravure plates. mechanical marvelsofthe modern world. What modern boy doesn't revel HOLIDAYANNUAL 5'.. HOBBY ANNUAL 6/. in reading about these fascinating subjects.There are also three complete Grand Stories of Gripping Adventure adventure stories, two coloured plates The POPULAR BOOK OF BOYS' STORIES containsamagnificent and numerous photographs. collection of thrilling adventure stories that's too good to be missed.The 1934 edition of this famous annual has been enlarged to 192 pages of gripping mysteries, tales of the Wild West, and exciting stories of sport, etc. !In fact, every phase of MODERN BOY'S adventure is represented in this grand, all -fiction annual, which is splendidly illustrated. ANNUAL 6f- On Sale at all Newsagents and POPULAR BOOK OF BOYS' STORIES 2/6 Booksellers. 379 MODERN WIRELESS October, 1933 gess,s3ssossssssesstsq3 miinster,Langenberg, Prague and maximum strength of North Regional a AERIAL CIRCUIT Florence quite impossible. Stock- was reduced to2, and even then, SELECTIVITY holm and Vienna could be received Langenberg and Prague were impos- -continued from page 329 with faircomfort, although North sible, although there was only faint Regionalwasaudibleduringthe interferencewith Beromtinster and S. EA0g)@Eggi silent periods of these two stations. Florence. To get this degreeof Munich was clear of North Regional, selectivity, however, the maximum used in the experiments, the maxi- but the observations could not be strength of North Regional had to be mum strength of Daventry was 3.continued at or beyond Belgrade's reduced from 23 (see Fig. 5) to 2 (see This reduction in strength from 21 to 3 tuning,because Midland Regional Fig. 7). is typical of the kind of reduction came in. Summing up theresultsof the necessary to obtain the degree of experiments now described, we arrive selectivitydemandedbymodern At Half -Way Position at an important conclusion.Where reception conditions. Next, theaerial -seriescondenser the aerial circuit of a wireless receiver A similar series of observations on was put to its half -way position, the is made to have, by means of an themedium -broadcastwavelength capacity being approximately -00005- aerial -series condenser, the degree of band, with North Regional as the mfd. The" spread "ofNorth selectivity demanded by modern re- powerful station, showed the same Regional is shown in Fig. 6, the actual ceptionconditions,that degreeof kindofresults. Thecoilused strength figures being given in Tableselectivity is obtained at the expense consisted of 40 feet of No. 32 D.C.C. 6.There was a decided improvement of the strength of signals received wire, and this coil was tuned by a in selectivity with the condenser atin that aerial circuit. -0003-mfd. variable condenser. The this setting. Although Langenberg aerial -series condenser was variable and Prague were impossible, Bero- Small Aerials Indicated and of .0001-mfd. maximum capacity. miinster and Florence could be heard We, as listeners, cannot control the with a fair degree of comfort, the output of our broadcast stations and, More Serious Interference interferencefrom NorthRegional if we could, it is doubtful if we should With the aerial -series condenser at being there the whole time, of course. demand a return to the one -kilowatt its maximum value, the " spread " Rome and Vienna were quite good, transmittersofa few yearsago. of North Regional is shown by the the interference from North Regional Hence, there remains the obvious figures givenin Table5. These being faint. suggestion that we should cease to figures are shown as a diagram in The aerial -series condenser was then erectlargeaerialsof maximum Fig. 5, and a tuning curve is drawn turned to a setting of approximately efficiency and that, instead, we should in the diagram. Interference was .000025-mfd. Figures for the strength content ourselves with small aerials much more serious than in the case of North Regional are given in Table which pick up far less strength and so of the long -wave stations.North 7, and the figures are shown in the give us a better chance to obtain Regional made receptionof Bero- form of a diagram in Fig. 7. The selectivity.

%69,00@%$150 and unmistakable,isthatfeeling earth.Those who are fortunate in which transfigures the performance possessing a rnilliammeter can easily "M.W.'s" RECORD into a thing of beauty.One may test for a fault of this typd by insert- REVIEW meet each separately ;it is rare to ing the meter in the H.T.- lead, as -continued from page 352 find so glorious a blending of the two. if to measure the total anode current Eileen Joyce will astonish you, just taken by the valves. ',894Rc83(g349 q`19 44831904 as she has astonished everybody who Then the valves should be pulled resultsonParlophoneR020223. has heard her. Please hear this record. out of their holders, or, alternatively, the filaments switched off. Henley's Invictus is put over with (536P1'.6eREgiEPaaERAtEg,,,-R.%%Q,3 In these greateffect by Norman Allin on circumstances no anode current should Columbia DB1157, with a splendid TROUBLE TRACKING flow, and therefore the meter should rendering of The Blind Ploughman to -continued from page 351 not register. If the needle takes support it. up a position along the scale, then VEPEPtcAr%$MMDEPESegE84@@EA*15V this is proof that a leakage current assuming, of course, that the outputis getting back to the earth line, and Pianoforte Performances is not Class B. A new star has arisen in this sphere the various condensers can be dis- The grid -biasvoltage should beconnected, one by one,untilthe Eileen Joyce, from Tasmania. Her checked over with a voltmeter, and fault is found. childhood is so obscure that even her the positions of the various plugs age is not accurately known, but her in the battery verified. Due to Leakage romantic upbringing and training has Too little grid bias increases the Readers will understand that wht n produced genius with as much empha- anodecurrentconsumption. A the valves are removed from their sis as you care to give it.If you reversal of the grid -bias leads, so that holders, or if the filaments are cold, would know just how perfect and positive is applied to the grid of the such as they would be when the L.T. brilliant technique can become, hear valve, will increase the anode current accumulator is disconnected at the her play two Concert Studies on enormously ; but such a fault is not on -and -off switch, any current which Parlophone E11237. likelytoexistforlong,because flows and causes the meter to take up One is Liszt's F Minor and the the valve itself would lose its emission. a reading must be due to a leakage. other De Schlozer's A Flat Major. Anotherpossibilityisthatone Another possible source of leakage Theamazingfacilityleavesone of the by-passing condensers in the is a badly insulated lead which is gasping, but not only is this attribute sethasdevelopedaleak,thus allowed to rest upon a metal -covered so outstanding, but behind it, clear permittingasteadydischargeto baseboard or an earthed screen.

380 October, 1933 MODERN WIRELESS

The working wavelength is440 metres.It is interesting to note that by means of supplementary apparatus the transmitter can be used also CHINATAKES for radio telegraph work. One wonders how the programmes THE oftheNankingstationwillbe AIR! developed. Willtheyconsistof those monotonous, high-pitched The 75 -kilowatt transmitter at Nanking is cer- songs which some of us have heard on Chinese gramophone records ? tain, in the opinion of A. Brown, to have an Or will the younger generation of important influence on a civilisation which has Chinese listeners demand Western jazz ? been "frozen" for many centuries. Will the Nanking Director of Pro- grammes follow the example of the B.B.C. and develop a special tech - NE of the principal disadvan- in instead of going out to do their tages of being a Chinaman day's fighting and that the bandits has been the impossibility of will settle down into amateur con- spending a really comfortable evening structors. sittingcross-leggedon thefloor As a matter of fact, Nanking is listening to the radio. not the first broadcasting station in Floods,famine,civilwar,and China.There have been a few low - bandits-they are no more toa powered stations with an input of Chinaman than a rainy Saturday 1or 2 kw., but they have been afternoon is to us.But imagine a scattered over a densely populated rainySaturdaywithoutaloud- countrynearlyhalfthesizeof speaker !And then you will realise Europe. why millions of Chinamen shouted " Hee-Pee-Poo-Ray ! " when the.;big MODERN PLANT new broadcasting station at Nanking The historyofbroadcastingin firstsaid" Hallo, everybody ! "- China may be said to have begun or, rather, the Chinese for it. with the opening of the Nanking station, which, With its 75 kw., will HOPES FOR PEACE compare for range with Miihlacker We may even hope that the pro- or Breslau.That means that the grammes will be so good and begin majority of those 400 million China- so early in the morning that the men will be able to tune -in to their generals will stay at home to listen - favouriteannouncer, and over a hundred million Chinese kiddies will Five members of the native technical staff very proud of their station, which smile gravely and politely at the is the most powerful in China. honourable efforts to amuse of the honourableUncleTingand the honourable Auntie Sang. pique of radio drama ?His problem The new station is up to date in will be somewhat similar to that en- both buildings and. equipment. countered here in the broadcasting The station develops its own power of music -hallperformances, for by means of a four-stroke Diesel Chineseplaysconsistmainlyof motor of 600 horse -power coupled interminable speeches which depend directtoanalternating -current for their interest upon the accom- generator.This generating plant is panying dramatic gestures and pos- housed in thefirstof the three turings of the actors. buildings.In another building are the transmitter, transformers, and A NEW ERA DAWNS switchboard. One may guessthatthenew Nanking stationwillleadto the PROGRAMME POSSIBILITIES Westernisation of Chinese taste in The transmitter is a quartz -con- music, drama,and entertainment trolled, seven -stage Telefunken valve generally. transmitter with a modulated aerial The civilisation which has been output power of 75 kw. and a 70 per frozen for thousands of years into centdepthofmodulation. The traditional formsis bound to be aerial system consists of two self- profoundly affected by the cosmo- A view taken from one of the masts of supporting masts 120 metres high, politaninfluenceofbroadcasting. Nanking shows the Western style of with a five -wire T aerial.The dis- architecture in the station buildings, Those millions of Chinese are on the with the broad valley of the Yangtze- tance between the masts is about thresholdof a tremendous adven- kiang stretching away in the distance. 250 metres. ture.

381 MODERN WIRELESS October, 1933 In the manufacture of these batteries various specialised processes are THE DEMAND FOR " PLATE -LESS " involved and the machinery employed is naturally costly.In spite of these ACCUMULATORS facts,BlockBatteries,Ltd.,are In order to produce sufficiently large supplies, Messrs. Bloch Batteries, Ltd., marketing L.T. and H.T. accumu- have had to open the new factory mentioned in these notes describing the construction of their unique batteries. latorsatprices which aretobe commended. EPOEg006ADE'D& a0E6g8)003000 THAT theinterestinbattery - Leonard Fuller, now Chairman of qi3 driven receivers has not dim- Block Batteries, Ltd. WHAT ARE WAVES? inished, and the ability to meet In the new accumulator the active -continued from page 332 big demands have surely both been materials are so put together that 6/3 demonstrated by Block Batteries, Ltd. they need no grid leads, glass case, eGeG(831M9g43019,830c13430,0G, The demand for Block plate -less etc.,forsupport,thecylindrical Wonderful pictures are obtained 'accumulators since their innovation negative electrode, with its bakelite when inserting into the liquid an only a few months ago has already " skin,"itself holding together the elliptic profile and causing the waves outstrippedthecapacityofthe entire battery. to start from one of its foci. The original factory, andrecently new The positive is a central core ofreflected waves then seem to start works were opened at Barking, Essex, paste formed solid with the electrode from the second focus, both trains to cope with the situation. by a patented process. being circular (Fig. 5). The output from this new plant Any other phenomena characteristic when in full swing will be considerable, Even Discharge of the behaviour of waves may be but it was confidently predicted by Thiscirculargrid -lessformation illustrated similarly, e.g. the way they theManagingDirectorofBlock compels an even discharge throughout are diffracted around a narrow open- Batteries that the venture was but a the active paste, ensuring that no ing, their refraction on passing from preliminary to even greater under- " buckling " can occur. In relation to water into mercury, etc. (Fig. 6). takings. size and weight almost double the Charbon's " Ondoscope," as already The revolution in battery design ampere -hourcapacityisobtained. suggested, may as well be used in represented by the " plate -less " type Moreover, no " leakage " discharge can solvingallsortsof problems,e.g. is the culmination of a search for a occur when the accumulator is off load. ascertaining the most advantageous perfectbattery continued through The principles of the L.T. accumu- form (from an acoustic point of view) three generations of Fullers, finallylator have been applied with equal of loudspeakers, the acoustic condi- perfectedandpatentedby Mr. success to the Block H.T. batteries. tions of halls, wireless studios, etc.

is aregular A REGULAR It ANNUAI.. kello* BOOK fora Ci-AOMS aregular grip- book ok REGULAR 700pages d its over An contains andarticles. of FELLOW! kiction hundreds ping are areits pictures-therekirst-class-soHUMS andall C them, plates. ill coloured w beautAul isgood-boysyou're WAl. it.A ANN reading tireok thisyearye, never togive A what doubt solved in iseasily book. problemsplendidgikt the getthis Now on Sale at all you Bookstalls and Newsagents, 12/6

382 October, 1933 MODERN WIRELESS

OEPOPEPa EPEP6 EP*EDEPEP SCOPHONY TELEVISION 8, -continued from page 336 q3 Et. ' qickM3130*&?98431360Gq319000q3 Mr. Walton has been able to design various optical systems to produce the effect he desires. In one arrangement he uses an " echelon " mirror, that is, a mirror in which the surface is broken up into a number of steps, each " step " reflects a corresponding strip of the original picture, and throws it into one straight line with the strips reflected from the other steps. The Transmitting End In another arrangement the stepped mirror is replaced by a complex lens having various angles of refraction, so that apicturefocused on one surface emerges from the opposite surface as a single straight line. At the transmitting end the picture is first automatically converted into a single " line " of varying light and shade values in the manner already described, by a stationary " stepped " Now* mirror or by special lenses.In this form it is scanned by a second small vibrating mirror, which is the only YouCAN GIVE UP moving element in the system. In reception the process is reversed. The incoming signals when applied MANCHESTER to the neon lamp cause it to " flicker" dry battery STAN D continuously.The flickers are then thrown on to a special mirror or lens system, which automatically trans- 54 forms them into a two-dimensional EXPENSE shape and so reproduces the original picture on the viewing -screen. PLATE -LESS -NESS REMOVES ALL OBJECTIONS TO H.T. ACCUMULATORS Vest -Pocket Scanner 1. YOU endured the constant expense of dry batteries The advantage of the system lies in - because H.T. accumulators were so unwieldy. Or getting rid of the usual rotating -disc perhaps you put up with the existing type of accumulator ? scanner-which must necessarily be far larger in size than the picture to 2. To -day there is no need for either.The invention be reproduced-and replacing it by a of the Block plate -less cell, with its double capacity, permits comparatively small and easily -con- a H.T. accumulator that is half the usual bulk -6o v., 5,000 trolled vibrating mirror. m.a.h. from a coloured bakelite casket hardly bigger than a For instance, the moving mirror dry battery ! used in the Scophony receiver is so 3. Give up the old expense, the old small that it can be carried in one's ThisBlock L.T.nuisance.Give yourself the economy (and accumulator is no waistcoat pocket, whilst the driving bigger than an or-comfort) of H.T. initsmodern, most dinary 4o a.h. type, motor used to operate it consumes yetlasts twice asperfect, cheapest form. only a small fraction of a watt. long per charge! As in all Block cells, v. 5000m.a.h. arx4rxsi" lid. its cylindrical negative is also the cell's Weight 1 6 lbs. GOOD NEWS FOR CONSTRUCTORS container, the posi- V. 5000 m.a.h.8-3/16"x4rx5Ylid. tive being a central A guarantee of performance and a real after -sales column. No grids Weight 8 lbs. service will be the principal features of the new needed, therefore " Ace " sealed kits which Messrs. Marcus, Overton more "active ma- Radio Ltd. are now producing.Kits of parts and terial "andless accessories ofall MODERN WIRELESS receivers weight; also its cir- 0 will be available, and Mr. Marcus, who has for cular form ensures many years been connected with the home c on- Double capacityfar more thorough structor's interests, will be personally responsible action. ACK for the prompt despatch of every order.Only the PLATE -LESS ACCUMULATORS highest quality conponents will be used in these L.T. 80 a2 hy: 11/6 new " Ace " kits. Block Batter' s Lt.t.,Abbey Rd ,Barking, Essex. Tel : Grangewood 3346/7 The address of the new firm, to which inquiries may be sent, is 62, Borough High Street, London, &I..1. 383 MODERN WIRELESS October, 1933 Here's the 'I NEW 1934 Handbook!

New blue -printsand circuitsforthecon- RADIO NOTES and structionofMains Units. Battery Chargers. and Units for energising NEWS of the MONTH tow voltage M.C. speakers.Helpful hints and technical datafor those interested in mains working.Complete detailsofthe THE Public Affairs Institute in wide rangeofmains units,transformers. The Scottish Exhibition chokes,batterychargers,amplifiersand New Yorkhasformeda This year's Radio Exhibition at the condensers manufactured by Heayberd-the committee oninternational Kelvin Hall, Glasgow, was the most Mains Specialists ! All completely revised broadcasting under the chairmanship successful of its kind ever held in and up to date.Fill in the coupon below and ofDr.NicholasMurrayButler, send with 3d. stamps for your copy NOW ! Scotland. Duringitseightdays, President ofthe Columbia Broad- nearly80,000peoplevisitedthe Mr casting System which controls ninety- Exhibition, and orders have been two stations in the United States. Address booked which will keep manufacturers Members of the Committee include M Vr and dealers busy for many months the Marquisof LothianandSir ahead. Evelyn Wrench. The Committee will aim at providing Wireless or Radio? an intelligently -planned interchange A correspondent to the " Northern of ideas throughout the world via Dispatch" asks why the stupid and the medium of trans -oceanic broad- meaningless term of " wireless " as casting. used for broadcasting is not entirely discarded in favour of the vastly MONARCH OF THE MAINS. Linking the World more suitable word " radio." 10, FINSBURYSTREET, LONDON, E.C.2. It also plans to form world-wide Thisparticular correspondent thinks One minute from Moorgate Und. Stn. links between persons prominent in that wireless seems particularly in- .q! European,American,andAsiatic appropriate as there are probably affairs by means of broadcast talks, more wires used in this than any other AVE YOU HAD debates, etc., and it is hoped that the modern invention ;whilst " radio " Hparticulars of the famous Magnum " Short Wave Adaptor, collaborationof broadcasting com- isa much more descriptive term, which is now available for every type of receiver ? panies in all three continents will be shorter, nicer -sounding, and-last but Full particulars, with a list of short-wave station, and free trial offer, on request. obtained. by no means least-accurate. BURNE-JONES & CO. LTD., 296, Borough High St., London, S.E.1. Autumn Talks Unique Tribute to "A.T.B." Among the new autumn talks will Sixmonthsafteritsexclusive IliallAtieltettlnal191111901111 be an ambitious series under the title introduction to home constructors in of " Taking Stock." Various speakers " Popular Wireless "and MODERN ADVERTISEMENTS will survey a whole range of British WIRELESS, Automatic Tone Balance achievements in literature and art, hasbeenacquiredbyMarconi's As far as possible all advertisements Government,socialservices,and Wireless Telegraph Co., Ltd. appearing in "Modern Wireless" industrial resources. This tribute to the importance and are subject to careful scrutiny before originality of " A.T.B. " emphasises publication, but should any reader Describing His Experiences once again the service rendered to the experience delay ordifficultyin getting orders fulfilled,or should Mr. S. P. B. Mais will travel from home -constructor public by these two thegoodssuppliednotbeas end to end of the United States, journals. advertised, information should be starting at Jamestown and travelling " A.T.B.," the inventionof Mr. sent to the Advertisement Manager, via San Francisco and back to New G. V. Dowding, Associate I.E.E., our " Modern Wireless,"4,Ludgate York. Each week a talk by Mr. Mais Technical Editor, was created especi- Circus Lordon, E.C.4. describinghisexperienceswillbe ally for " P.W." and " M.W." home L relayed across the Atlantic. (Continued en page 385) FAMOUS DESIGNERS CHOOSE FAMOUS COMPONENTS i I Mr. G. P. KENDALL chose only SOUND SALES TYPE B.C. CLASS "B" OUTPUT CHOKE 9'- Sendfor Descriptive Literature Mof all our components N.B.-It pays to follow the designer's lead- SOUND SALES LTD., EACH if you want the best results! TremiettGrove Works, JunctionRoad,Highgate,N.19. October, 1933 MODERN WIRELESS

,*RADIO43 NOTES AND ZS, NEWS OF THE MONTH --continued from page 384 2 2 ,5z3s043,,cNy3q3c830,4g2m. constructor set designs, and the fact that the patent is now to be included in the British Licensing Pool after having been purchased for a considerable sum of money, is, we believe, an event without parallel in radio journalism. A Russian Giant There seems to be no doubt to -day that the most powerful station in the European ether is Moscow, for the new 500 -kilowatt transmitter, when operating on the long waves, can be heard clearlyin London, even in daylight. Itissaidthatitstremendous increase in power will make it audible throughout practically the whole of Europe. Another Power Increase Plans are being made for increasing to 120 kilowatt the present 8 -kilowatt stationknownas P T TParis. Although the studio will be in Paris itself,the new transmitter will be T. C. C.means erected in a suburb some twelve miles away. When the new station is on the air in the middle of next year it .... will probably have cost somewhere SAFETY about £1,000,000 to construct. Absolutely Soundproof AL WAYS The B.B.C. has made arrangements Research - intensive to use the largest of the H.M.V. studios concentratedresearch - Creating the means to at St. John's Wood for a series of solve the ever present problems of Radio - orchestral concerts. Anybody passing Rejectingallbut what experience has found z00% right.That is the job of the vast T.C.C. by this studio, however, need not organisation-that is why none but the perfect expect to hear the London Symphony product findsits way to the storeroom.But Orchestra, either practising or when it even more, that is why T.C.C. spells SAFETY is broadcasting, for the walls of the at all times. Throughout the world the " con- studio are over fourteen inches thick. denser in the green case " is synonymous with condenser efficiency-whatever the need there is a T.C.C. to fulfil it-adequately--the reason for No Letter Box ! the choice of T.C.C. by all the leading set designers. The Radio Correspondent of the " News Chronicle " let loose to an astounded world the other day the fact that there is no letter -box in the B.B.C.'sheadquartersat Portland Place.It appears the other morning a holiday relief postman paid his first visit to Broadcasting House with a nice big bundle of letters, and for some ALL-BRITISH minutes stood scratching the back of his head trying to find out where to CONDENSERS put them. The Telegraph Condenser Co., Ltd., Wales Farm Road, N. Acton,W.3. Itisratheramazingthatthe £1,000,000 headquartersofBritish broadcasting has not got a letter -box ! (Continued on page 386) 385 MODERN WIRELESS October, 1933 MARCUSOVERTON *COS*********019 Divided Opinions RADIO LTD - This controversy seems to have 62, Borough High Street RADIO NOTES AND NEWS OF THE MONTH g raisedaconsiderableamountof London Bridge, S.E.1. argument. Some newspapersside 0 -continued from page 385 Sg 4i3 withtheB.B.C.and some with 83g34304343434gt?,4?9,8943943ET4 Sir Austen Chamberlain, Mr. Lloyd c.

George,and Mr.Churchill ;but tp With Lawrence of Arabia despiteall the arguments and the `` "K.4" KIT `4',p Colonel Dawnay, the new Controller brickbats which have been thrown, " ACE " SPECIFICATION. nobody seems to have raised the 1 Pair Colvern Ferrocart Coils, types F.10 & s. of Output at the B.B.C., who recently F.3 1H.I.Varitonecompensatingtransformer, question as to whether the average 8 took up his duties, has had a distin- 1 Ferranti AF17C input transformer 150 listener wants to hear these leading 1 Sound Sales Class B output transformer ... 100 guished career, and while in the Army 1 Graham Parish binocular screened H.F. choke 46 lights of politics one way or the other. 1 Bulgin screened H.F. choke, type H.F.9 36 he was associated with the famous 2 Polaraperture0005tuningcondensers, After all, perhaps one day somebody with slow-motion drives ...... 150 Lawrence of Arabia.It is said that 1 J.B. 0003-mfd. reaction condenser ... 26 Lawrence once remarked, " I would will wake up to the fact that the 2 GrahamParish 50.000 -ohm wire -wound 9 0 B.B.C. is an institution supported by 1 Polar preset condenser 1 6 sooner have Dawnay with me than a 2 Dubilier 5-mfd condensers, type 4 0 publicmoney, andthat however 1 Dubilier 002-mfd. condenser, type 670 1 3 thousand camels." 1 Dubilier 0005-mfd. condenser, type 670 1 3 admirable Sir John Reith's dictum 1 Dubilier 01-mfd. condenser, type 670 2 0 Let's hope the B.B.C. staff eventu- 1 Dubilier 0002-mfd. condenser, type 670 1 0 may be in theory-that the public 1 Dubilier 0003-mfd. condenser, type 670 1 0 ally agree that Colonel Lawrence was 1 Erie 500 -ohm resistance ... 1 0 must not expect what it wants- 1 Erie 2-meg. grid leak... 10 right ! 3 W.B. 4 -pin valve holders 1 6 inevitably the B.B.C. will find that 1 W.B. 7 -pin valve holder ... 1 6 1 Bulgin QMB 3 -point switch, type 8.13 the public will demand and get what 4 Belling -Lee indicating terminals 210 Mr. Roger Eckersley 7 Belling -Lee indicating wander plugs ... 11 it wants. 2 Belling -Lee spade terminals1 4 Mr.RogerEckersley,who has If it wants to hear Sir Belling -Lee S.G. anode connector, No. 1029... 2 Austen Chamberlain, Mr. Churchill, 1Coll switch coupling link ... 6 hitherto been known as Director of 1 " ACE " K.4 framework . 2 6 1 " ACE " panel. 18' X 7., drilled to sPecifi- Programmes, has had his title changed and Mr. Lloyd George, they will be .. 4 0 heard ! 2 " ACE " terminal strips, 3" x 1#',drilled 9 will 1 " ACE " K.4 type screen. 74 X 34. 1 0 and be known infuture as Connecting wire, ilex, screws. etc. ... Director of Entertainments. His new " ACE " K.4 ELT A (Cash or C.O.D.) £6 7 6 How Many Are There ? 4 Valves to specification £2 5 3title means that he will concentrate " ACE " K.4 Kit B (Cash or C.O.D.) £8 12 9 We have often asked the question ANY COMPONENT SUPPLIED SEPARATELY. on lighter programmes, and will be " ACE " H.4 SIT EASY TERMS. in these columns : How many people KIT A. As abovespecification.£61718, or twelve responsible for this section to Colonel monthly payments of 12/, are there to -day who have television KIT B. As above specification, and including valves, Dawnay. £73/1219, or twelve monthly payments of 16/3. sets, and who really make a habit of KIT C. As above specification, including valves and Besides Mr. Roger Eckersley, there " ACE " brand table model cabinet in antique OAK, looking -in to the B.B.C.'s television £911013, or twelve monthly payments of 17/9. are also a Director of Variety, a KIT D. As above specification,including valves and broadcasts ? ACE " brand De Luxe consolette cabinet in antique Director of Light Entertainment, and OAK, fitted with W.B. PM4a Microlode loudspeaker, Guesses have been made from time £12/9/9, or twelve monthly payments of £11316. a Director of Radio Productions. NOTE. Easy terms can be arranged on any combina- to time, some people saying that tionofkit and accessories to your choice. Write for quotation. there are at least 50,000 television 8.4 " ACCESSORIES. Broadcasting Politics Ever -Ready 9-v. G.B. battery ... 1 0 sets in use in Great Britain alone ; Ever -Ready 120-v. 11.T. battery ._ 15 6 Block new plateless accumulator, 80 amthrs. 11 6 Sir Austen Chamberlain, Mr. Lloyd but, despite repeated invitations to Block 120-v. plateless H.T. accumulator, 000 George, and Mr. Winston Churchill M.P.R. eliminator,; with trickle charger for the Baird Company, and to others 5 -valve receiver, type AC2T0 ... 3 12 6recently addressed a joint letter to W.B. P.M.4a moving -coil speaker ...2 2 0 concerned, we have never yet received Belling -Lee unit gramophone pick-up...... 1 2 6 Mr. J. H. Whitley, the Chairman of Belling -Lee volume control for above ... 4 0 an authoritative answer to the ques- Garrard No. 30 double -spring turntable .. ...1 5 0 the B.B.C., on the question of the We stock everything connected with Radio. Component tion. parts,speakers,H,manufactured receiversmains units, broadcasting ofpoliticaladdresses. etc. CAS C.O.D. ANDEASY TERMS. .001L731P'CIN The three distinguishedpoliticians On What Authority ? MARCUS. OVERTON RADIO LTD., 62, Borough High St.' London Bridge, S.E.1. protest that the exclusion from the The " Sunday Dispatch " reported 'Phone Hop 4431. Please supply Cash/C.O.D./Terms list of political speakers of all but the other day that there are 3,000 for which I enclose £ a d. speakers nominated by the Party Cash/Deposit. people in the British Isles now con- NAME Leaders or Party Whips denies fair ducting television research work of ADDRESS Oct., 33. expression to independent and non- an extensive nature.What isthe TRADE SUPPLIED. officialviews,andtheyaskfor authority for this statement ? Famous Maker's Offer. PIANO -TONE / independent speakers to be added to CABINETS 7 DAYS' FREE TRIAL the list. Television in Germany (or 10/- Monthly) Piano built(Pat. 8123). The German scientists are also concen- acousticTonebringsaline thrill. Mr. Whitley's Reply trating on the television problem, (Radio -Press, B.B.C..3.000 clientele). Mr. Whitley, in his reply, statedand at the recent German Wireless MAKER'S PRICES 351 -to £15 Photographs and List FREE. that while the B.B.C. had no desire Exhibition,inBerlin,imagesof Piano - Tone LIST PI CKETTS cabinets, to curtail freedom of speech, it could 40,000" picture points " and 180 FREE (M.W. Albion. Rd.. Bexleyheath not guaranteethatallshadesof lines deep were shown.It is even opinion could be given in any series. reported that the engineers at the

This led to another letter from Witzleben station hope very soon to WE invitereadersto Sir Austen Chamberlain, Mr. Lloyd be able to reach this high standard for George, and Mr. Churchill, in which general transmission purposes. support our Advertisers they regretted to receive Mr. Whitley's

-care being taken to accept refusal of their request and expressed A Queer Charge ! onlyannouncements of the opinion that a precedent had been Three highofficialsoftheold established by the effective exclusion, Reich Broadcasting Company-Dr. reputable firms! from the point of view of broadcasting, Magnus and two colleagues-were S of all persons not nominated by the recently taken toaconcentration 100-1>1110000-4>41-1>400(11100000111-e>0 Party Leaders or Party Whips. (Continued 011 page 387) 386 October, 1933 MODERN WIRELESS %@Egg4&:[email protected]@@% France's Plans g RAD I 0 NOTES AND Et France is out to have the most SECRETS OF NEWS OF THE MONTH a powerful wireless system in Europe. The French Minister of Posts and g --continued from page 386 Eg Telegraphs recently gave an indica-

, 5943'1;t4: e.slecp tion of the rather grandiose plans France has in mind-plans which, if camp near Berlin. They were charged, put into effect, would cost the nice CELESTMN among other things, with accepting little sum of £10,000,000. excessively high salaries ! They have now been removed to a A B.B.C. Rumour prison on a further charge of commit- A recent rumour concerningre- SUPREMACY ting a breach of trust while in office. organisation at Broadcasting House It is also declared that the corruption has it that Colonel Dawnay is lookingNo. 1. alleged' in Berlin broadcasting circles intothequestionofB.B.C.em- is to be found in Leipzig, Breslau, and ployees devoting their time to writing Acoustically Cologne. plays,lyrics,music,etc.,forthe microphone. Perfect Charming and Capable It is said that this practice has got Cabinets ! Some two years ago we met Dr. to cease, and that full-time employees Magnus in Berlin, and found him a The cabinets in which Celestion must concentrate all their ideas and Moving -CoilLoudspeakers are very charming and extraordinarily energies on their regular jobs. housed are acoustically designed capable man.It is hard to believe This will be rather a pity, for there as part of the speaker and not that these far-fetched charges will be is no doubt that some of the regular only as an attractive article of proved against a man of his type. furniture. As a result, reproduc- employeesatBroadcasting House tion over the whole range of have been responsible for many of the frequenciesIsof thehighest Herr Dr. Schaffer best programme items.For example, Celestion quality. Whilst in Berlin we also had an Holt Marvell, who is, of course, Eric It is such attention to detail that opportunity of meeting the late Herr Maschwitz in reallife(the B.B.C. puts Celestion in the forefront of Dr. Schaffer, who was, of course, the DirectorofVariety),haswritten modern loudspeaker design. The name Celestion stands for high -

1 1 11 11511111in ti s minimum !I in n a is us is la i in nu 1111111111i1 quality reproduction combined with unfailing efficiency. ORDER YOUR NOVEMBER " MODERN WIRELESS " NOW Celestion speakers can be supplied to match any set or type There will he further long articles about G. P. Kendall's of output. Great New Set next month. Ask your dealer for ademon- stration,or write for full details. And more chapters of " Death at Broadcasting House." PPM 39 Cabinet Model £3-10-0 Also we are presenting a comprehensive guidetothe PPM 9 Chassis Model E1-15-0 VALVES OF 1934 Celestion Ltd., London Road, in which all modern valves, includingthe many new Kingston -on- Thames. specialtypes,willbeinterestingly and informatively described. ;. MAKE SURE OF YOUR NOVEMBER "M.W." NOW

USUAL PRICE 1/- ON SALE NOV. 1st E.

brilliantChief Engineer atBerlin many good things for the microphone, Broadcastingheadquarters. Dr. including" Good -night,Vienna " ; Schaffer was a Jew, and a few months whilst " Red Tabs," one of the best ago our readers will remember seeing of all broadcast plays, was written in the Press that, on being deprived by Val Gielgud, the present Director of his position of Chief Engineer, and of Dramatic Productions. because he was so worried by the persecution of his race, he committed Good Material Essential suicide. Shouldthiscreative output be stifled because some of the successful American Influence writers for the microphone happen to The French Wireless Exhibition, be employees of the B.B.C. ? One which was held recently in Paris,would have thought that Colonel showed the remarkable influence ofDawnay would have been only too American design.The French manu- anxioustogetgoodmicrophone facturers have been badly bitten bymaterial, even if it was contributed the superheterodyne bug, and hardlyby the office boy.Heaven knows, ELESTION a single French set of any importance good programme materialishard the Very SoulofOliusic used a straight circuit.Five- and enough to come by,without un- seven -valve sets ranged in price from necessarilyrestrictingthecreative THE FOREMOST NAME aboutFrs.1,400 toFrs.2,500 output of the staff at Broadcasting Itst SOUND REPRODUCTION (E17 to £31 approx. House. 387 MODERN WIRELESS October. 1933

Here is one thing that is often done that pick-up makers commonly design a THE PICK-UP but which can easily be avoided: a theirinstrumentstogivecertain volume control is wired up so that it results when a specific value of resis- t.c IN PRACTICE C, tg imposes a varying resistance on the tance is connected across them. That -continued from page 342 pick-up.Which means to say that, is why it is desirable to purchase a a 6i,'3 gf3t3t3oocimv3c-sgs3,2gtqg as the volume is varied, so the pick-up pick-up either with a built-in volume tone is altered. control, or to adhere to the maker's detector.Two valves are ample for There is definitely a right and a specificationregardingit,though, the majority of pick-ups. wrong way of connecting up a pick-up generally speaking, the values are The achieving of apparent stability volume control. And the right way is fairly standard. does not necessarily mean that good sothat the resistanceacrossthe Anyway, this is practical proof of quality is assured.There is a con- pick-up does not alter. the incorrectness of connecting a pick- dition where, although there is no It may or may not be widely knownup, as in Fig. 1. squealing, L.F. retroaction is occurring and causing severe distortion. tgaS)6,M@&00@s3e-OZ4006g6gREg has to be considered. The usual solu- The needforgood decoupling 6t, FOR CONSTRUCTORS tion is for an on -off switch to be assumes vital proportions in pick-up provided so that the lights can bP work, and any shortcomings in this Details of a convenient dusting - Ar, brushandusefuldial-light turned on and off independently of direction are almost certain to cause scheme. the set's on -off switch. trouble. t") 1313ca34343436QW36'243e0f33134143*. The drawbacks to this scheme are Ilikearadiogram tobede - that two switches have to be in the coupled " up to the eyebrows," every CONSTRUCTORSwhoutiliseold off position when the set is turned off, anode circuit on the L.F. side (includ- parts whenrebuildingre- and also the possibility that the dial - ing the detector) having its separate ceivers arevery often con - lights might be left burning when the decoupling circuit. fronted with the set was not operating. difficultyofre- Both these are avoided if the con- 111i111111t1111111111111111111111111111111111111111111111111111111111U moving dust from nections are made as in the diagram. NEXT MONTH behind theter- No current can pass through the dial - minalsofcom- lights when the set is switched off, ponents. This MORE ABOUT _== but the lights can be extinguished inde- dust is likely to pendently of the turning -off of the set. causecrackling .7=7, THE K4 DWI LIGHT and similar noises if allowed to remain. L.TSATTCH 0/AL 1/61 -IT A simple method of avoiding this SFYITCN - and another long instalment of is to make use of an old toothbrush; -P.."DEATH AT BROADCASTING HOUSE" which will be found useful for dusting Fianannumaanamanammanammananaimmaa both the terminals and the mouldings. Amateur record results at their best Double Switching TO LT seldom quite equal good radio results, The advantages and attractions of and so it is very important to remove illuminated tuning dials are many, any distortion -causing obstacles in the but with battery receivers the question ggivfHaeot-R of economy of low-tension current The dial -light cannot get left on

gives fullest instructions for building D FERRANTI the Short Wave Super -Set that was Jestedhalf -wayacrosstheworld. 2 SHORT WAVE CLASSB.,4 CHART post Free 11 Ask your dealer or send stamps to FERRANTI LTD., Dept. MW, HOLLINWOOD, LANCS.

PAGE PAGE ' Chums " .. .. 382 New London Electron Works, Ltd. Cover iii INDEX TO ADVERTISERS Dubilier Condenser Co. (1925), Ltd. Cover ii Peto-Scott Co., Ltd... .. 375 Picket Bros. (Cabinets) . 386 Ferranti, Ltd... 388 PAGE Pifco, Ltd... 277& 361 Amalgamated Press, Ltd., Gift Books General Electric Co., Ltd. (Osram) 349 for Boys .. 379 .. Sound Sales, Ltd. .. 384 Automatic Coil Winder Co., Ltd...353 (Gecophone) 367

(Batteries)373 Telegraph Condenser Co., Ltd... 385 Block Batteries, Ltd...... 383 Graham Farish, Ltd...337, 339, 341,343 Tungsram Electric Lamp Works, Ltd.369 British Blue Spot Co., Ltd. .. rt3T Gramophone Co., Ltd. .. ..278 British Insulated Cables, Ltd. .... 375 Varley Products ...... 371 Burne-Jones & Co., Ltd...... 384 Heayberd, F. C. & Co. 384

Carrington Manfg. Co., Ltd. . . .. 377 Jackson Bros. (London), Ltd... 377 Celestion, Ltd...... 387 All communications concerning advertising in " ModernWireless"mustbemade to Colvern, Ltd. . . . 357 Marcus, Overton Radio, Ltd... 386 John H. Lile, Ltd.,4,Ludgate Circus. London, Columbia Graphophone Co., Ltd. .. 347 E.C.4. Telephone : City 7261. Clarke, H. & Co. (M/cr.), Ltd. .. ..363 Modern Boy " 377 Printed and published by The Amalgamated Press, Ltd., Fleetway House, Farringdon Street, London, E.C.4on the 1st of each month.Address for Advertisements : John H. Lile, Ltd., 4, Ludgate Circus, E.C.4. Telephone : City 7261.Registered for transmission by Canadian Magazine Post.Subscription rates :Inland and Abroad, 17/- per annum ;8/6 for six months. Sole Agents for Australia and New Zealand :Messrs. Gordon & Gotch, Ltd. ;and for South, Africa: Central New. Agency, Ltd.-October, 1933. S.G. 388