HOW LONG .SHOULD YOUR VALVES AST 9Amateur Wireless,Jul 19

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No. 525. Vol. XX I. JULY 2, 1232

e RAD1OVISION

BRITAIN'S LEADING RADIO WEEKLYFOR CONSTRUCTOR, LISTENER d EXPERIMENTERELDI-TOR :

BERNARD E. JONES TECHNICAL EDITOR : RESEARCH CONSULTANT:H - R EYNER B.Sc.. A.M.I.E E. W . JAMES.

ASS/STA/VT ED/TOP:H. CORBISHLEY.

v144 :A 6A" PORTABLE " WEATHER

°.1-1HE Clerk of the Weather seems to haveI decreed that, for a few weeks at any

rate, we are to have weather suitable forportable sets out of doors ! The suddenspell of fine weather may have remindedyou that you have no suitable set to takeout into the open. Well, a new " A.W."portable set' is being described next week.Don't miss it. It is ideal for indoor oroutdoor working.

THE SCHOOLS BROADCASTSTHE Schools Broadcasts officials are

getting busy again and the CentralCouncil for school broadcasting has beenreconstituted under the chairmanship ofLord Eustace Percy. The idea is that theCouncil will draw up a long programmeas a guide for the Schools Department of -the B.B.C. Sir John is taking an activeinterest. such " finish" that they

NEW RADIO POLICE !

HOW THEY WRITE

Not Too Many Grumbles !THE B.B.C. is busy on its postbag in

connection with Scottish Regional.It seems that forty-six per cent. of thecorrespondents are getting satisfactoryreception, while only 6.4 per cent. areexperiencing trouble. Reports from out-side the service area total 35.7 per cent.,which augUrs well for Falkirk's power.Only one per cent. of the letters arerequests to visit Falkirk, which shows thatthe dour Scots temperament has not yetbeen shaken by the new broadcastingconditions.

THE " KING " OF JAZZ

Which is the Most Popular ?SOME of the recent corners among dance

bands which broadcast are showingare proving

The new wavelength -checking station on the roof of the Reichspost station at Tempelhofin Germany. The cperators are seen working on the special wavemeters

worthy rivals of the old -established com-binations, which have had things more orless their own way for some years past.Ambrose -revolutionised the dance musicfrom the. Dorchester Hotel; MauriceWinnick did a similar service at theCarlton; and Roy Fox gave listenerssomething new from Monseigneur. WithHenry Hall presiding over the B.B.C.'sown dance music from Broadcasting HouseBA studio, this phase of entertainmentseems to be growing more virile than ever.

UP MONT BLANC

Taking a MicrophonetBENCH outside broadcasts

are making another attempt to followan ascent of Mont Blanc with a microphoneand portable amplifier. Last year, whenan unsuccessful attempt at an ascent wasmade, the broadcast gear broke down.This year they are taking no chances anda short-wave transmitter is being carriedwith the mountaineering party. A short-wave super -het. at the base station willlink up by landline with Lyons so that theO.B. can be broadcast.

HENRY HALL'S FIRST VIOLINCYRIL HELLIER, the newcomer to

Henry Hall's band, has made good asfirst violin. He ought to be good-he waswith Jack Hylton's band for several years,and is a soloist of experience. Henry Hallintends to arrange for special orchestra-tions to emphasise this player's talent as asoloist.

A POSTPONED CEREMONYIT is expected that the Prince of Wales

will unveil the memorial at Thiepvalon August Bank Holiday, and O.B.engineers will go over with mikes andamplifiers to carry out the job. It will berecalled that the ceremony was postponedowing to the tragic death of M. Doumer,who was to have been present at theunveiling fixed for last Whit Monday.The customs officials are now familiar withthe O.B. gear, but in the early days alot of -trouble was caused by the curiosityof the officials, who wanted either to con-fiscate the apparatus, or to take it to bits !

NEXT WEEK : A GOOD 4 -VALVE PORTABLE FOR INDOOR OR OUTDOOR USE

entavair Wu-elt 2 JULY 2, 1932

r -N EW S 87) 0,0 SSIP "°F THE :WEE: K. 1-continuedATTACKING AN AIR RECORDTHERE are to be busy wireless scenes

at Hanworth when the Hon. Mrs.Victor Bruce attacks the duration (re -fuel-ling) record in the air. She is taking vitalwireless gear up in her British plane, andhopes to be in the air for about four weeks !A transmitter in a van is being used tokeep up regular communication.

STRAIGHT FROM EGYPT !

More Talkative Than The SphinxMHE new Anglo-Egyptian telephone1 service was used when the relay was

attempted last week between the EgyptianMinister of Communications in Cairo, theEgyptian Prime Minister, and Mr. StanleyBaldwin and the Postmaster General inLondon. Not a bad test for the new long-distance radio -telephone service. Rugbyand the super -bets. at Baldock were used,of course.

BY LINEAND, talking of long-distance relays,

the B.B.C. is making more frequentuse now of the Continental line through tothe German Broadcasting House. TheSamson and Delilah broadcast last weekwas from the Municipal Opera House atCharlottenburg, the suburb of Berlin inwhich is the Broadcastinr, House and thecentral control point for the relay. B.B.C.engineers worked with the German R.R.G.landline experth.

NEW GERMAN STATIONSWE hear that the new plant has already

been ordered for Munich and in aboutthree months the power will go up. Itmay be necessary to shift the wavelength,just as the new Leipzig and Frankfurtstations have had to " swap " theirpositions in the ether. The higher powerfrom Munich will make a big differenceto the German Regional scheme.

FILM TECHNIQUEADRIAN BRUNEL, playwright, film

producer, journalist and broadcaster,has written a comedy sketch entitledGood Morning, Boys, which will be givenin a forthcoming London Regional vaude-ville programme. Brunel was responsible

for the first British " talkie,"Elstree Calling,and The Constant Nymph film. His micro-phone adaptation of his -own stage play, TillTo -morrow, was one of the B.B.C.'s recentsuccesses. Apparently film technique helpsin getting the right kind of stuff for the"mike," especially now that "talkies" arehere.

BROADCAST AGAINORTHERN engineers arelookinab out for interesting

outside broadcasts. and for thethird year in succession thequaint Tynwald Ceremony willbe made available to NorthRegional listeners by means of arunning commentary on July 5.The Tynwald is the Parliament ofthe Isle of Man and has a con-tinuous history of nearly athousand years. It is only ex-ceeded in antiquity among theParliaments evf Europe by theIcelandic assembly known asAlthing.

"INVESTIGATION" INSCOTLAND

PPARENTLY the discussionta about Scottish broadcastinghas not ended with the deputa-tion to Sir John Reith. We hearthat Mr. David Kirkwood, themember for Dumbarton, is takingmatters up with the Secretary ofState for Scotland. 'What he isparticularly interested in is thedispute between .Mr. CleghornThomson and musical bodiesabout the broadcasting of con-certs of the Scottish Orchestra.Mr. Kirkwood wants a ScottishBoard of Directors !

PROGRESS AT WEST REGIONALTRINGS are going smoothly at Wash-

'ford Cross, after the aerial masttragedy, the result of which is depicted mthe pbbtograph on this page. The engineershave been told that the building will beready in all probability by September.

Looking down towards Broadcasting House. The famousAll Soul's Church is in the foreground, and the first relayedService from here was broadcast last week, the Broadcasting

House control room being used

ABRA-KADAHRA !

JASPERMASKELYNE, the magician of

Maskelyne and Devant fame, is writinga revue entitled Magic in the Air speciallyfor broadcasting ! It will be heard sometime next month. Mr. Maskelyne will havethe assistance of Mr. John Macdonell in theproduction of the revue, so the B.B.C. isnot going to let Mr. Maskelyne have it allhis own way in making the ether vanish !

ECHO WANTED !41STENERS have complained recently

of the lack of echo on some' trans-missions from the new London studios. Itappears that while the reverberationperiods of the studios are fine for theperformance, a little additional echo ontransmissions is somc times needed from thelisteners' point of view. Are the Broad-casting House echo -rooms working yet?

The mishap at West Regional. One of the new steel masts crashed recently when partly erected, with fatal results. The supportsbroke and it collapsed from the huge insulating base, ma and injuring two

JULY 2, 1932 3 inatP_ur Wtrel.e.si

IN this country the bug -bear of atmos-pherics seldom makes wireless reception

impossible, though in many countriesthere are months in the year when every-thing is blotted out by these annoyinggrinding and crashing noises.

Probably the peak month of atmosphericdisturbance in this country is July, and

AERIAL

EARTH = SETThis diagram shows how a high resistance,which may be of the spaghetti flexible type,can be shunted across the aerial and earthterminals of the set to cut down severe

atmospheric discharges

the trouble is accentuated in very hotweather. Many readers write in to knowhow they can cut down atmospherics,thereby showing that the exact natureof the phenomenon is not clearly under-stood.

Atmospherics are caused by lightningdischarges in the atmosphere, or by thegradual equalising of potential betweencharged clouds or a cloud and the earth.

Two important facts should be noted.For one thing, these atmospherics haveno particular frequency. So they cannotbe tuned out by ordinary means, nomatter how many circuits are employed.Secondly, and this is important, theatmospherics may be many times morepowerful than a distant station, so whenconditions are bad it is useless to introducevery much amplification, for this meansthat the atmospherics are amplified in thesame ratio as the required signal, and theresult is unbearable.

Sometimes you may be in doubt as towhat is causing the background noises inthe set-it may be atmospherics or it may

IN FACTS ABOUTATMOSPHERICS

This is the season when atmospherics are apt to be troublesome,and all listeners will therefore be interested in this topicalarticle, wherein the causes and partial cures of the trouble are

simply explained.be a running -down battery. To provethis point, disconnect the aerial andearth. If the trouble stops you maythen take it that atmospherics are thecause.

One of the first facts the listener dis-covers about atmospherics is that, nomatter how carefully the set is tuned,they still persist in coming through,though with diminishing intensity as thewavelength is decreased.

The aperiodic nature of atmosphericsmakes it very difficult, if not impossible,to eliminate them. They affect the tuningcircuits of the set by what is known asshock excitation.

It is generally agreed that if a sufficiently,powerful signal is applied to a tuningcircuit it will oscillate at its resonantfrequency-at the frequency to which itsinductance and capacity tune. This willhappen, note, at any incoming frequency,so long as the energy is sufficiently power-ful.

An illustration may -help. If you have atuning fork of a certain pitch or frequencyit will vibrate at that frequency when anear -by piano produces a note of thatfrequency. Any other note may be struckon the piano without affecting the tuftingfork.

Shock EffectsBut now supposing you hit the fork

with a hammer-it will be set into vibra-tion at its pitch or frequency, in spite ofthe fact that the hammer has no particularfrequency. It is shock excited, and in asimilar way atmospherics, of no specialfrequency, but of considerable amplitude,will set a tuning circuit into oscillation atits resonant frequency-and then, ofcourse, the noise is amplified by thevalves and heard in the loud -speaker.

Scientists and engineers have tried foryears-ever since wireless began-to getrid of atmospherics, but without any realsuccess. Various ideas have been triedout, but usually they are so complicated,and involve so much waste of energy,that the average amateur would dismissthem as impracticable.

Of the several Ways of cutting downthe intensity of atmospherics, probablythe most useful is to alter the Along, high aerial seems to pick up atmos:-pherics much more easily than a lowaerial.

But we must tread warily here. For ifthe aerial is lowered its signal pick-upefficiency will be reduced, and that meansmore amplification for a distant station.

The extra amplification might well bringup the atmospherics to unbearable level,and all the aerial alterations would be somuch waste of time.

Let us put it this way. If -the requiredincoming signals can still be heard atgood strength on the lowered aerial, thatis, without adding to the amplification,then the ratio of signal to atmosphericswill have been increased, and the effectwill be a reduction of the interference.

Cutting Out AtmosphericsBearing this argument in mind, you

will see that under certain conditions aframe aerial will also help to cut downatmospherics, always provided that exces-sive amplification does not follow.

Another stunt is the connection of afairly high resistance across the aerial -tuning circuit, to act as a drain for thestatic discharges. Nothing much lowerthan ioo,000 ohms should be used,otherwise the signal strength will beimpaired.

Buried aerials are sometimes recom-mended as a method of cutting down

EARTH LEAD

EARTHLEFT

By disconnecting the normal aerial andconnecting the earth lead to the aerialterminal of . the set, as shown here,atmospherics can often be eliminated, andreception of the local can be enjoyed even

when conditions are very bad

atm3spherics, but of course the signalstrength is greatly reduced also. It isoften worth trying the earth as an aerial,and leaving the earth connection blank.This reduces the average set to local -station range, but often completely cutsout the atmospheric disturbance.

ernoleur Wiretzzsl 4 JULY 2, 1932

THE "New Regional Three" is a mostsimple set to control, so that detailed

description of the operation is unnecessary.This is one of the many points which justifyits title of " Regional." Before the batteriesare connected and the valves inserted,though, it is advisable to check over allthe wiring to make sure that there are noshort circuits.

It was recommended in4lae constructionalarticle last week that the square cornersystem of wiring should be adopted asthis makes for neater connections in thepresent set. This means that not onlyhave you to check over the positions of thewires, but it is advisable to test the con-nections at each soldered joint to makesure that a wire which appears to makegood contact with a terminal or spade tagactually does so and is not prevented frommaking electrical contact with the othermetal surface because of a thin layer offlux. This applies not only to the rigid -wire leads, but to the flexibles.

Do not twist the high-tension and low-tension groups of wires- before attachingwander plugs and spade tags respectively.The number of flexibles is cut down to aminimum as there is only one high-tensiontapping for the whole set.

Solid di -electric condensers are used fortuning so the usual precaution of makingsure that the vanes do not touch isunnecessary. It is advisable, though, tosee that there are no short-circuits any-where cotse, that the wander plugs makegood contact in the battery sockets, that

GETTING RESULTSWITH

THE NEWREGIONAL THREE

Listeners in B.B.C. Regional areas will beinterested in this further description ofa three-valver which is designed for goodquality reception. First details of thiseasy -to -build set were given last week

the pre-set condenser vane is not jammedtoo tightly down by the screw adjustment,and so on.

When these details have been attendedto you can get ready for a first test. Thevalves need careful choosing. A selectionof suitable two -volt valves is given in theaccompanying table and from these youwill be able to make your choice. If, forany reason, you use 4- or 6 -volt valves,then equivalent types should be chosen.

SUITABLE VALVES FOR THE " NEWREGIONAL THREE "

Make Detecter L.F. Power

Milliard ... PM1HL PM2DX PM2A

Marconi HL210 L210r"

L" 2

Omni ... HL210 L210 LP2

Mazda ... HL210 HL210 P220

Cossor ... 21OHL 210LF 220PA

Six -Sixty i 21OHL 210D 220P

Lissen ... HL2 L2 LP2

If the set is to be operated from batteries,then a double- or triple -capacity i2o-voltjob should be used. The H.T. consumptionof the "New Regional Three" is low, but astandard capacity battery will not giveanything like the life of a double- or triple -capacity job on a three -valve H.T. currentdrain. A 9 -volt grid -bias battery should befitted in the clips on the baseboard and theconnections made as shown.

The set can take its high-tension from

the mains, if a unit such as the AtlasA.C.244 is used, or one of the equivalenttypes by Ekco, Tannoy, Lissen or Regen-tone, for example.

Provided the set is' worked- not too farout of the Regional service area an indoOraerial can be used if it is not convenient toerect an outdoor wire, but as there is nohigh -frequency amplification in the set,exceptional range cannot be expected. Agood earth is an advantage in any case.

The operation is extremely easy. Screwdown the knob of the pre-set condenserso that the value is at maximum and turnthe knob of the reaction condenser back-wards and forwards, making sure that theset goes gently in and out of oscillation.The anode resistance and anti -motor -boating resistance are so chosen that if agood detector valve is used, its anode volt-age will be just right for smooth reaction.No other variation of the high-tensionvoltage is possible or necessary.

Turn the main tuning condenser untilone of the local stations is picked up.You will probably find that slacking offthe knob of the pre-set condenser sharpensthe tuning by an appreciable amount,without cutting down the volume.

You should in every case be able to geta clear background between the local,National and Regional transmitters. Ad-justment of the grid -bias voltages may benecessary to get the tone right and cutdown the high-tension consumption.. Thispoint is particularly important whenworking from batteries as a slightincrease in the bias voltage may cut downthe high-tension current without impairingthe tone.

COMPONENTSThree-ply panel 12 in. by 5 in. and seven -ply

baseboard 12 in. by 6 in. (Cameo, Peto-Scott).Two .0005 -mid. bakelite variable di -electric

condensers (Lissen, Polar, Telsen, Utility).

FOR THE " NEW REGIONAL.0003-mfd. maximum pre-set series aerial

condenser (Sovereign, type "J", Formo,Ormond, R.I.).

High -frequency choke (Lewcas, type M.C.,

THREE "Two yards thin flex (Leweoflex).Five wander plugs marked H.T.-,II.T. ,

G.B.-G.B.-!-,G.B.-1, G.B.-2 (Belling -Lee, Clix,Eelex).

Three-point shorting switch (Bulgin Lissen, Lotus, Telsen, Wearite, Climax, Two spade terminals marked L.T.1-," Junior," Lissen, Readi-Rad, Wearite, Varley, Igranie, Tunewell). L.T.- (Belling -Lee, Clix, Eelex).Tunewell). Low -frequency transformer (Lissen "Torex" Pair of grid bias clips (Bulgin).

Filament switch (Bulgin " Junior," Lissen,Readi-Rad, Wearite, Tunewell).

Telsen, Lotus, Igranie, Varley, Ferranti, R.I.,Climax). ACCESSORIES

Three 4 -pin valve holders (W.B., Lissen, 1-mfd. fixed condenser (Dubilier, Lissen, 120 H.T. battery (Ever Ready, Lissen,Telsen, Lotus, Clix, Wearite, Junit, Benjamin). T.C.C., Telsen, Sovereign). Pertrix, Drydex).

Dual -range aerial coil (Lotus). Two terminal blocks (Sovereign, Junit). 9 -volt G.B. battery (Ever Ready, Lissen,.0002-mfd., .0003 -mid. and .008 -mid. fixed

condenser (Telsen, Lassen, Dubilier, T.C.C.,'Four terminals marked Aerial, Earth,

L.S. f-, L.S.-, (Belling -Lee, Clix, Eelex).Pertrix, Drydex).

2 -volt accumulator (Exide, Lissen, EverFormo, Ormond, Graham -Parish). Two spaghetti resistances, one 60,000 ohms Ready, C.A.V., Pertrix, Fuller).

2-megohm grid leak (Lissen, Dubilier, and one 30,000 ohms (Tunewell, Bulgin, Mains unit (Atlas AC244, Ekco, Tannoy,Graham-Farish, Telsen). Lewcos, Igranie, Varley, Lissen, Readi-rad, Lissen, Regentone).

1-megoinn grid leak with wire ends (Lissen, Telsen). Loud -speaker (R. & A., type 40, Blue Spot,Dubillerj. Connecting wire (Glazite). Rola, Ormond, W.B., Lissen).

JULY 2, 1932 5 matextr Wye] 0)

flow LONGSitouLDYOUR VALVES LAST

Just how long a valve should last is a question that is frequentlyasked. It is shown in this article that for many reasons it is

false economy to continue to use valves beyond a certainlength of time

rir HERE is a great temptation to use1 valves much longer than the makers

intended. Many listeners boast of the yearsof service they have obtained from valves,little realising how much efficiency is beingsacrificed. Several readers have writtenrecently to know just how long a valveshould last, meaning how long before thereis a definite falling off in the characteristics.This article, based on the considerableexperience of a valve manufacturer, shouldanswer the question.

Battery ValvesLet us consider the most popular type of

valve, which is the valve with a battery -heated filament. The heart of the valve

ANODE

CURRENT

INCREASES

AMPLIFICATION

DECREASES

to the i,000 hours mark, efficiency is con-stant, but the ensuing falling off may notimmediately be noted.

It is generally taken that r,000 hourscorresponds to the total use of a valve overa period of a year. So that normally wemight say the one -hundred -per -cent effici-ent life of a battery valve is a year in theset. But owing to natural human instinctsto get the most out of everything it is verylikely that such a valve would continue togive satisfaction, of a sort, for perhapsanother year. The outside limit of a batteryvalve should be taken as two years.

Here the reader may, with some justice,ask why we should arbitrarily set a limit toa valve's usefulness ; why, indeed, we should

not go on using thevalve until it completely

VACUUMDETERIORATES

FILAMENTLOSES ITSEMISSION

IMPEDANCEDECREASES

How a valve deteriorates with age is clearly shown in this picture

from the life point of view is of course, thefilament, since this is the electrode emittingthe electrons.

If we plot amplification of the valveagainst time, we find that a practicallystraight line is maintained for about Locohours, after which the amplification dropsoff considerably.

With most of the battery valves atpresent on the market there is a tendencyfor the valve efficiency to improve over thefirst three or four hundred hours, due to thegradual hardening of the vacuum. Then up

" gives up the ghost."The answer is that arather old valve, quiteapart from loss ofefficiency in terms ofamplification, may beextremely greedy of an -node current. This im-portant point is all toooften ignored.

Costly-RunningTake the example of

a detector type of valvewith an impedance ofsay 20,00o ,ohms. Sucha valve might, duringthe normal span ofr,000 hours life, take ananode current of rimilliamperes. But whenthe valve gets old thefirst effect of senile de-cay is a drop in theimpedance.

Now it is well known that the lower theimpedance the higher is the anode current.Thus a power valve with a low impedancetakes much more anode current than ahigh -impedance detector valve. Ourzo,000-ohms detector might. easily dropwith age to 15,000 ohms, and the anodecurrent would rise accordingly, perhaps to21 or' more milliamperes.

For one valve this increase is not perhapsvery important, but just consider thequestion from the point of view of say afour- or five -valve portable, and then

remember that such a set has only astandard -capacity battery. The net in-crease in anode current might easily be 6 or8 milliamperes, which would have the effectof shortening the life of the high-tensionbattery very appreciably.

One of the most forcible argumentsagainst using old valves in a set is thegreatly increased running cost. The pointto be emphasised is that old valves oughtto be scrapped before their sensitivity fallsto zero, because in the interim period thevalve is being used with excessive anodecurrent.

With mains valves the life is usually lessthan for battery valves, and D.C. valveshave a shorter life than A.C. valves. Per-haps the modern mains valve for A.C.working will have a useful life of r,000hours, and then the trouble /will be not somuch loss of filament emission as thedevelopment of grid emission, which tendsto increase the anode current and so destroysthe vacuum.

Many mains -operated sets that have beengiving entire satisfaction suddenly producevery bad quality, indicating that the powervalve has gone " soft," through increasedanode current, set up by the grid emission.

To sum up: your valves should last a yearwith average use ; they may still be usedafter that period, but only with a decreasein amplification and an increase in runningcosts. Take two years as the outside limitof valve life.

On July 6, North Regional listeners areto hear a recital by George Pritchard onthe organ of the College of Technology,Manchester.

For his Midland Regional gramophonerecital on July r r. Robert Tredinnick hasarranged a " non-stop" variety programmeafter the manner of the variety pro-grammes now a popular craze. The vocalnumbers will be interspersed with banditems as in a modern music hall.

Some brilliant examples of the work ofone of the most distinguished of Europeancomposers will be given on July 4, when aSibelius concert is relayed from Queen'sHall to National listeners. The concerthas been arranged under the auspices ofthe Sibelius Society and the LondonSymphony Orchestra will be conductedby Robert KajannS.

mototIc Wire lets) 6 JLLY 2, IS32

WHAT IT IS FOR

THE HIGH -F E UENCY CHOKE)WELL named, the high -frequencychoke, for its job is to choke

back high -frequency current. It doesthis by virtue of its impedance. Anycoil of wire offers some impedanceto the passage of high -frequencycurrent, but for the special functionof choking back a special coil mustbe used, or the maximum effect willnot be obtained.

For example, if the choke coil hasa large self -capacity, some of thecurrent will find its way through thecapacity, in spite of the high impedanceof the winding.

The self -capacity is formed bycurrent flowing. through adjacentturns of the coil, and is of coursepresent to some extent in all coils.But a well -designed coil has its turnsarranged so that this self -capacityis reduced to a minimum.

One of the essential requirementsin a high -frequency choke, as used inthe reaction circuit, or in the anodecircuit of the detector, is that thenatural wavelength, as formed bythe inductance of the winding and the

self -capacity, shall be well outsidethe range of wavelengths with whichthe set is dealing.

0At A is shown the symbol used in circuitdiagrams to denote a high -frequency choke.At B is shown the usual construction of achoke for medium- and long -wave tuning.At C is a choke specially designed for shortwaves, where a very low self -capacity isessential, with quite a moderate inductance

A good choke will have a naturalwavelength above 2,000 metres. If

the wavelength comes within the set'stuning range instability will be causedas the set is tuned to the wavelengthat which the choke tunes.

It might be asked why we couldnot design the choke so that withquite a small winding its high self -capacity tuned to above the top limitrequired ! The answer is that the

'high self -capacity would entirelycounteract the choking action of thewinding, and high -frequency currentimpeded by the winding would passfreely through the self -capacity.

This happens when a normal high -frequency choke is used on shortwaves where owing to the enormouslyhigh frequencies, the slightest sign ofcapacity is enough to cause by-passing.

For short-wave sets it is necessaryto use a special choke. Fortunatelya relatively small inductance is enoughto impede high -frequency on the short-waves, and of course the small windinghas a small self-capacity-usually byspacing the turns on the choke former,or by tapering the two ends.

HOTSPOT

WHEN the new German high -power trans..Vnutters take the air, Europe may possibly

sit up and take notice, for I understand thatin the case of both Leipzig and Breslau thesignals are likely to shake up the ether. Forsome time past the Telefunken company hasbeen experimenting with 3oo-kilowatt valvesand there is a possibility that some of themmay be included in the new installations.Leipzig and Breslau are likely to be heardshortly; in fact, by the time these lines are inprint you may have picked up their first tests.Frankfurt -am -Main will follow immediately asthe transmitter is now ready. Bear in mind thatLeipzis,b and Frankfurt are to exchange wave-lengths.

Notwithstanding the fact that the cost of thelistener's tax in Germany is-at par-sixtimes what it is in the British Isles, the

OUR LISTENING POSTBy JAY COOTE

financial position of the broadcasting com-panies is such that stringent cuts and economieshave to be carried out. In future there will notbe such a variety of programmes as arrange-ments have been concluded between theindividual cities for a more regular inter-change of entertainments. You may alreadyhave noticed how frequently Berlin, Breslau,Heilsberg and Leipzig broadcast a commonprogramme. and how Stuttgart and Frankfurtswitch over to each other's studios at differenttimes of the day and evening. In the same way

A general view of the site of the Florence station recently opened by the ItalianBroadcasting Company. The two masts are each 300 ft. in height, and the

transmitting installation consists of a Marconi equipment of 20 kilowatt;

Munich, -Miihlacker, Frankfurt and Langen-berg will link up to feed their respective areas.

By this time the fate of the new broadcastingschemes in Spain will have been decided andthe outcome of the Government's final decisionwill be anxiously awaited. So far the mostpopular plan is the one which calls for twotransmitters in the neighbourhood of Madrid,one of 220 kilowatts to work on a long wave-length and a zo-kilowatter to operate on themedium -wave band. In addition, Barcelona,Valencia, Seville and Corunna are to be given a20 -kilowatt station each and Bilbao must becontent with one of so kilowatts. The Barce-lona press, by the way, has already protestedand demanded for Catalonia a transmitter ofat least 6o kilowatts.

What is actually happening in regard toRadio Luxembourg is not quite clear. Con-siderable publicity has been given to the newstation and yet I am informed by a corres-pondent that the zoo -kilowatt transmitterwhich was to be installed there has provedunsatisfactory and that the shareholdersrefused to take it overt In the meantime it isstated that plant of lesser power has beenOrdered elsewhere. However, we can only waitand see what happens.

The Brussels StationsApparently Radio Schaerbeek may, after all,

prove an alternative to the Brussels No. r andNo. 2 studios, for since its re -opening its signalsare decidedly stronger. The new station isSituated at Crainham some six miles from theBelgian capital and possesses a studio capableof accommodating a large orchestra. TheBrussels studio is connected by landline toone or two of the most popular music -halls andrestaurants and in future the programmes arelikely to provide interesting items.

PTT Paris has taken on television trans-missions, which are broadcast every Mondayand Tuesday between 5 and 5.45 p.m. and onThursdays and Fridays between 4.45 and5.30 p.m. B.S.T. Vision is transmitted on447.1 metres and sound on 296 metres. Youmay have heard fragments of the latterbroadcast when tuning. in Hilversum.

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AN IDEA FOR THE B.B.C.T is a good many years ago now thatthe B.B.C. staged a particularlyinteresting competition. I wonderhow many readers are old enough

wireless hands to remember it. In thestudio a series of noises was produced.There were about twenty in all, I think; andthey included such things as striking amatch, hitting a tack with a hammer (theydidn't give us hitting a thumb in the pro-cess l), tearing calico, jingling keys, and soon. Listeners were asked to write downwhat the noises represented and the correctlist of answers was then published. Arevival of this competition would be especi-ally interesting nowadays, owing to theenormous improvements made, not only inbroadcasting microphones, but also inreceiving sets and loud -speakers. In theoriginal competition such a small part ofthe range of sounds that went to make upeach " noise " was actually transmitted andreceived that it was probably mainly amatter of chance whether anyone was ableto give the right answers or not in manycases. To -day, almost if not quite the wholeof the range of sounds can be' transmittedand received. There probably exists some-where in the archives- of the B.B.C. a listof the sounds that were sent out, and I wouldvery much like to see a repetition of theprogramme staged.

47,

DO YOU REMEMBER ?OW many of you, I wonder, canremember clearly just how elemen-tary reception of wireless pro-

____ grammes was ten years ago ? Withthe best of receiving sets then available nota single sound of the pedal notes of theorgan could be heard. I well recall tuning -in the first organ broadcast with a setwhich was at the time just about as good asa wireless set could be. Though the organwas a fine one, its music sounded exactlylike that produced by the kind of portablearmoniums that queue entertainers use.

The other night we heard the relay of theAldershot Tattoo and marvelled at thewonderful way in which the drums of thebands of eighteen battalions came through.Do you remember the first Tattoo broad-cast ? The drums then sounded rather likehail pattering on a corrugated iron roof.And perhaps the funniest thing of all in thatbroadcast was the sound of rifle shots.Many people could not hear the shots at all,and to those whose sets could reproducethem in any way, they sounded more like

.the splutterings of a soda -water siphon thananything else. Broadcast dramas wereoften excruciatingly funny where they weremeant to be tragic, owing to the queer wayin which the " effects " came through. Wehave certainly advanced a lot sincethose days and there are very fewsounds now which cannot be reproducedrealistically.

THE IMPORTANCE OF SPEAKERSENSITIVENESS

HE importance of sensitiveness in aloud -speaker is not always realised.If you give the matter a little

L> thought, though, you will soon seethat it makes a great deal of difference tothe fidelity or otherwise of reproduction.Look at it in this way. The more sensitivea loud -speaker, the smaller the currentfluctuations necessary in the plate circuitof the output valve to give you the volumeof sound that is desirable. Hence, with asensitive speaker, smaller grid' swingsapplied to the output valve will do all that,is necessary. The less these swings, withinreason, the better will be the performancesof the valve, since it will always have some-thing in hand in case an abnormally bigswing comes along. With an insensitivespeaker the last valve is often workingpretty well all out all the time, and everynow and then you get distortion, due tooverloading.

If the loud -speaker is sensitive, this kindof distortion with its very unpleasanteffects does not occur. -Another point ofimportance is that you can bring in distantstations with less use of reaction. Or,again, you can obtain the necessary volumeof sound by using an output valve with asmaller magnification factor and capable ofhandling larger inputs. If, when you arehaving speakers demonstrated, your choicelies between two whose tone is equallypleasant, I would recommend you to go forthe more sensitive of the pair.

4,16

WHERE SHOULD IT BE ?- AM conducting a little friendly war

with certain makers of loud -speakerssi I over the question of the output

J transformer. They maintain that itshould be mounted in or on the speaker,whilst I claim that it should, if possible,form part of the receiving set. One of thechief reasons for my contention is this.Many of us operate the speaker at a con-siderable distance from the receiving set.If the transformer is incorporated in theinstrument the whole of the plate currentin the last valve must necessarily passthrough long leads. I, personally, wouldmuch rather keep a direct current of, say,25 milliamperes at 200 volts inside the setthan have it coursing through long lengthsof flex or other wire. With the transformerinside the set the speaker leads have, ofcourse, only the oscillating part of the cur-rent to carry.

And there is another reason why I am allagainst building the transformer into theloud -speaker. Heaps of sets nowadayshave output transformers inside theircabinets. You install a speaker with abuilt-in transformer, and what exactly areyou to do ? You certainly cannot use twotransformers and there are only two pos-sible solutions. One is to eliminate the

set's own transformer; the other is to fiddleabout with the speaker and alter its wiringso that the speech coil windings are con-nected directly to its input terminals.

4",BRIGHTER SUNDAYS

- ROM what I hear, the B.B.C.'sbrighter and longer Sunday pro-grammes are being very muchappreciated by listeners. The music

seems to have been most happily chosen, sofar, and I haven't come across anybody whohas anything but appreciation to express.The provision of longer Sunday programmesis certainly a step in the right direction.It is, incidentally, one that I have beenUrging in these columns for more thanfive years, and I am more than glad to seethat something has at last been done. I amnot satisfied yet, though, and I still havehopes that the B.B.C. will one day give usthe Sunday programmes that we ought tohave. I have always said that they shouldbe the very best of the whole week, and thatview is, I know, shared by innumerablelisteners.

.1044

LAYOUT AND STABILITYWAS referring the other week to theneed for careful layout when dealingwith modern high -frequency valves.I had an interesting example of this

on an experimental chassis with which Iwas working at the time. The receiver inquestion was one employing a high -fre-quency valve followed by a detector and apentode. The whore set was built up on ametal chassis and the coils were included incans in the usual manner. The layoutunderneath the chassis was reasonablytidy and most of the leads were compara-tively short, so that I expected to obtaingood results. Up to'a point, this hope wasjustified, but I .was troubled with aninstability which occurred towards thebottom of the medium -wave scale. NothingI could do had any effect on this trouble.The H.F. valve was de -coupled, and so wasthe detector, but I improved thede-couplingarrangements in order to make sure this wasnot responsible for the trouble.

40.50

HOW FEED -BACK IS SET UP0 success attended these experiments,and I was rather puzzled to knowwhat to try next. As the coils wereall completely screened, there was no

apparent possibility of stray coupling, butI got hold of a piece of wire and began tomake sure of the earth connections. Witha chassis it is often possible to obtain cir-culating currents in the metal itself, and asthe metal has appreciable resistance thisdevelops small voltages which are sufficientto cause reaction or even self -oscillation. Ifound that this had been happening in the.present instance. The earth return from the

Imam- Wvel.esj 10 jL LY 2, 1932

On Your Wavelength! (continued)

H.F. circuit was not taken to the chassis atthe nearest point, but through a lead abouttwo inches long to a common earthin,,, pointwhere several other leads had joined, On the,face of it, this looked as if it would be themost suitable plan, but it so happens that,owing to the meeting of the several leads,the currents from various points of thecircuit were all flowing through one smallportion of the chassis and a feed -back wasset up rather in the same way as a high-tension battery will cause motor -boating,due to its own internal resistance. Anyhow,I connected the' earth return from the H.F.valve straight to the chassis at the nearestpoint, and the whole trouble was overcomeforthwith.

4'00THE WRONG WAY

HE other day I was listening to afriend's set when the owner, for noapparent reason, decided to try theeffect of altering the grid bias.

Opening up the innards, he promptlystarted to prod the grid lead up and downthe G.B. battery in a most light-heartedway-whilst the set was still going, markyou ! Now this is quite the wrong way todo it, as I promptly pointed out. Everytime the grid is left "in the air" and thenjammed back to " bias " the valve getsquite a nasty jolt. No doubt it is quitecapable of standing up to this kind oftreatment for quite a long time-becausethe modern 'valve is a pretty robust pieceof work-but there is such a thing as thelast straw. After all, it's quite a simplematter to switch the set off before alteringthe bias, and then to switch it back again to,note the effect.

.3104,

SPEED COMPARISONS'ROADCAST programmes travelthrough the ether with the velocityof light-namely, 186,000 miles asecond-which, curiously enough, is

slightly faster than the speed at which

an 'electric current flows through an ordi-nary conductor. Over short distances,telephone transmission is almost as speedyas wireless, but for trunk calls where thewires are " loaded " it falls distinctlybehind. For instance, speech currents travelover an unloaded line at approximatelyi8o,000 miles a second, the slight retarda-tion being due to the self-inductance of thewire. But when the line is pupinised, as isnecessary to prevent distortion over longdistances, the building -up of the externalmagnetic field introduces quite a consider-able delay. Actually the speed drops tobetween io,000 and 20,000 miles a second,according to the particular note -frequencyinvolved. High notes on a loaded line tendto travel at a different speed to low notes,and telephone engineers have to adoptspecial measures to prevent distortion dueto this cause.

4-511441

FASTER THAN LIGHTN certain cases, particularly in beamwireless, it is necessary to feed anextended aerial system with radio -frequency currents which are

strictly " in phase" with each other, soas to secure the best directional effect.Since some parts of the aerial system arespaced farther away from the power -supply point than others, this can only bedone by regulating the speed at which theelectric currents flow along the feeder -lines.In other words, the currents supplying themore distant sections are " speeded up"relatively to those energising the nearbysections. Usually this is done by " loading "the shorter feed -lines so as to retard thecurrent flew along them, but it is also pos-sible to advance the phase by insertingseries capacity in the longer lines, so thatthe currents, in effect, seem to travel at aspeed even greater than that of light. Thisappears to me to be going one better thanEinstein, though it is a point that only themathematicians can decide.

ELECTRIC -LIGHT. NOISES

HAVE come across recently quite a,number of places in which noisyreception occurs when the electriclights in the house, in which the set

is used, are switched on. The owner of theset is naturally rather puzzled, for hecannot make out why it should be that theset emits noises while the lights are on andall is quiet before lighting-up time. Thereare two possible causes. The first is thatthe wires between the switch and one ofthe lights are rather close to the set. Whencurrent is switched on impulses from themare picked up and noisiness occurs. Butthe commonest cause is that one or otherof .the electric -light bulbs in the house fitsbadly in its socket and wobbles slightly. Ihave even known one case in which a loosebulb caused noisy reception to people twodoors away. If you find that your set isnoisy when the lights are on it is as well toget an electrician to examine the wiringof your house, or of the room in which theset is used, and to go over the switches andthe fitting of the bulbs in their holders.

NEW VALVES FOR OLD SETS- HERE must be thousands of receiv-

ing sets in use which are three, four,or even five years old and are stillgoing strong. All is well, as a rule,

until one or other of the valves gives .outand must be replaced. Then comes adifficulty of no mean magnitude. The setwas designed for the inefficient valve avail-able in its heyday, and if you place in itsholders modern highly efficient valves theresult may be that it flies right off thehandle, so to speak, and becomes uncon-trollable. Some makers, though they don'tadvertise them, still have a stock of oldvalves, and these can be obtained by specialorder. It is, I think, better to obtain theolder pattern valves than to try to usemodern valves in an old set. This appliesparticularlyto the high -frequency side of setsusing unneutralised tuned -anode or tuned -transformer circuits. THERMION.

PERSONALITIES IN THE WEEK'S PROGRAMMES

4.7.32NAT/ONAL

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JUL; 2, 1932 11

ARE SPONSORED. AiSr AMW

PROGRAMMES COMING?

The mo let of Radio City-America's new giantsponsored programme centre

WHY has the vexed subject of spon-sored programmes been revived just

recently ? Partly, perhaps, the talk isinspired by the growth of foreign -stationactivity in putting over programmes forEnglish listeners paid for by advertisinginterests in this country. But principallythere is the increasing fear that theTreasury may suddenly decide to appro-priate the whole of the licence revenueand tell the B.B.C. to fish for itself formoney among the seas of commerce.

First of all, are we quite clear what wemean by a sponsored programme ? Theidea originated in America, where it isextensively practised at the present time.The broadcasters arrange a programme,which is paid for by an advertiser, whosequid pro quo is a microphone acknow-ledgement, either of the firm or of thefirm's products.

The firm thus seeking advertisement bymeans of a broadcast programme is saidto " sponsor " the programme, which willusually be something in the popular line,in order to leave a pleasing impression onthe listener's mind. Such is the allegedpoWer of association that if you arepleased with the programme ideas of, say,a toothpaste firm you will, eventually,feel constrained to clean your teeth withthat particular firm's pastelThe B.B.C. Licence

Such a method of utilising the broad-casting services of the country is actuallyvisualised in the licence under which our

B.C. operates. Not many listeners seemo realise this, so I will briefly quote the

relevant clause." The Corporation shall not, without the

consent in writing of the Postmaster -General, receive money or any valuableconsideration from any person in respectof the transmission of messages by meansof the stations . . . provided that nothingin this clause shall be construed asprecluding the Corporation from broad-casting matter provided gratuitously by.any person with or without an achnow-?edgement of, such provision by means ofthe broadcasting service." (The italics aremine.)

There it is., set down in black and whitein the licence-so do not imagine thatthere is any political obstacle in the Waya! an immediate introduction of thesponsored -programme idea.

A question raised by Alan Hunter, who outlines thepresent position of the B.B.C. in relation to sponsored

programmes

Yet, in spite of this explicit provision inthe licence of the Corporation, there hasnever been any real attempt to exploitthe idea. The reason is obvious enoughto anybne acquainted with the ideals ofthose behind our broadcasting. The aimis public service, and this Is deemed,rightly or wrongly, to be incompatiblewith a widespread interference with theprogrammes by outside commercial inter-ests.

And while the licence revenue is con-tinually growing, in spite of the diminishingpercentage retained by the B.B.C., therehas been no financial reason why outsideinterests should be consulted or encouraged.

It comes to this, then, that while theB.B.C. is assured of its present source ofrevenue, that is, from the licences, it willsteadfastly set its face against the ideaof sponsored programmes. Yet if theTreasury grabbed the whole of the revenuefrom listeners' licences, the attitude atPortland Place would inevitably have tobe changed.

To me it seems rather improbable thatour present system will be radicallychanged before the Charter expires in1936. We are, in a way, a model ofmonopolistic broadcasting, and there isso much to be said for our system that aprogressive young country like Canadasees fit to renounce its commercialisedsystem and set up a Government controlledbroadcasting authority in its place. Andthis decision was taken after all the" big guns" of the American broadcasting

CLEANING THE VANESScratching noises when you move the

vanes of a condenser can generally be

cured by pushing a pipe cleaner betweenthe vanes to get rid of the dust. Makesure you don't alter the vane spacing sothat the condenser " shorts."

11.1fflaiRtrEL MMMM .... aaaaaaaaaaaaaaaaaa CH.0 ........... ......

chains had given evidence in favour ofsponsored -programme broadcasting.

Still, such considerations may not weighas heavily as I imagine they do, and weare left to speculate what would happenin the event of a Treasury appropriationof the entire licence revenue.

One suggestion immediately arises-double the present licence fee. Make it Liand then the present system of programmecompilation could be retained, and at thesame time the revenue to the Treasurywould be very substantial. Would listenerspay the extra fee ? I know it would hitmany listeners hard, though the burdencould be alleviated by payment of half -yearly or even quarterly instalments.

Failing an increase in the licence fee,and assuming a total appropriation by theTreasury, What are we left with? A B.B.C.faced with the problem of finding themoney to carry on the broadcastingservice.

An enormous amount of re -organisationwould have to follow, because some formof liaison between the programme depart-ments and the advertisers paying for theprogrammes would be wanted.

The American ParallelIt is fatally easy to compare broad-

casting in this country with that ofAmerica, but not so easy to rememberthat while we are on a little island, Americais a vast continent. The point is thatadvertising by radio in America is oftena coast -to -coast affair, involving dozens ofstations all over the continent.

Compare that with our simple littleregions, with only two stations in each,and then some of the real programmedifficulties become apparent.

I mean, while all discussion on thesponsored -programme idea seems to revolveround the listener point of view, the moresordid question as to whether such ascheme would pay in such a relativelysmall area of transmission is seldomraised.

To sum up, I should say that if spon-sored_ programmes do come it will bethrough lack of revenue, and that canonly be visualised by some move on thepart of the Treasury, Those who havecome round to the view that sponsoredprogrammes are not necessarily a panaceafor the present defects of the B.B.C. willsurely join with me hi hoping that itsre zenue is left alone.

en,nip,,,wtretz:5) 12 JULY 2, 1932

A NEW TELEVISIONSCANNING SYSTEM

A Novel Idea Described by Morton Barr

IN television the picture or scene to betransmitted is first split up into a

large number of elementary areas, and thelight or shade of each of these is transmittedseparately and in rapid succession. Tosecure the effect of smooth motion it isiecessary to traverse the whole of theicene in this way from twelve to fourteentimes in a second.

In reception the process is reversed.Each signal element is applied in successionto a neon lamp, and the resulting variationsin light intensity from the lamp are thrownin correct sequence on to a viewing screen,the distribution being effected so rapidly

Figs. lA and 1B, showing how current flewwill affect an adjacent conductor

that the complete picture is reconstituted atleast 12 to 14 times per second.

Mechanical ScanningThe ordinary method employed for

breaking -up the picture at the transmittingend, and for reassemblinot' it in reception,depends upon the use of a rotating discfitted with spiral holes which "scan" the

( C

Fig. 2Ashowing the courseof travel of the

scanning spark

whole scene once during each completerevolution of the disc.

The use of such scanning discs is opento certain objections. On the one hand itplaces a limit on the size of the picturethat can be transmitted in reasonable de-tail, and on the other it leads to difficultiesin synchronising the disc at the transmitterwith that used at the receiving end. Arotating disc possesses considerable inertia,so that comparatively large forces must beapplied to check or accelerate its rate ofrevolution.

Both difficulties would disappear if itwere possible to use a scanning device of anon -mechanical nature. Where there is nomass there is no inertia, and not only can

very high speeds be employed, but suchspeeds can be controlled or regulated by theapplication of comparatively small forcesor impulses.

A Recent DevelopmentThe latest advance in this direction is

based on the following well-known principle.If an electric current is flowing anti-clockwise through a coil of ' wire A, Fig.IA, as shown by the arrow, it will tendto move an adjacent straight wire B,carrying a down -flowing current, bodilyto the right, as shown by the dotted lines.On the other hand, if the direction of thecurrent in the wire B is reversed, so thatit is flowing upwards as shown in Fig.113, the thrust on the wire is also reversed,and the latter will be moved bodily to theleft.

Next, suppose the wire B to be replacedby an electrode system C, Fig. 2A, (shownin greater detail in Fig. 2B). The electrodesconsist of a pair of interleaved wires C, Cr,arranged so as to form a sinuous pathfrom one end to the other. The top wireis positive, the second negative, the nextpositive, and so on.

If now an arc discharge is started atone end of the electrode system, byapplying a high -frequency voltage to thepoint M in Fig. 2B; the- pulse of currentforming the arc flows in a downwarddirection. The influence of the current inthe surrounding coil of wire A thereforecomes into play. The conditions are similarto those illustrated in Fig. IA, and thearc (which corresponds to the current inthe wire B) at once starts to move bodilyalong the two electrodes towards theright-hand side.A "Free -moving" Arc

When it reaches the other- end of thetop track, owing to the fact that the outerelectrode is positive and the inner negative,the arc is forced to travel around the

WATCH THE BIASWhy have long leads out to an external

bias battery? There is much less chance

of interaction if the battery is in clips onthe baseboard and the leads are short anddirect.

corner in the manner indicated by thesmall arrows. Once it has turned the cornerit is obviously changed into an upwardly-moving current, so that it will be nowurged to the left by the current in thesurrounding coil. As it reaches the endof the second traverse, it is changed oncemore into a downward -moving currentand is accordingly impelled in the opposite direction. The process continues until thearc has completed the whole zig-zagcourse from top to bottom of the electrodesystem.

It is extinguished at the bottom andimmediately restarted by a suitably timedvoltage impulse applied to the free end, M,of the top electrode.

We have, in fact, provided a free -runningsource of light which automatically scansthe picture from side to side and from top tobottom in the same way as a rotating disc.

High-speed ScanningSimilarly, the speed at which each com-

CI

M2

- -4

Fig. 2B, showing the arc path

plete traverse is repeated depends solelyupon the frequency of the voltage impulsesapplied to the top end, M, of the electrodesystem.

In practice the scanning arrangement isenclosed in a light -proof casing, and thelight from the rapidly -moving arc isfocused by a lens either on to the pictureor on to the viewing screen.

At the transmitting end, the lightreflected from the picture is received by aphoto -electric cell, the output from whichis used to modulate the outgoing carrierwave in the usual way. In reception theincoming signals are used to vary thevoltage applied across the electrode system,so that the resulting arc changes in inten-sity with the varying light and shadevalues of the original picture.

SynchronisingSynchronising is effected very simply.

The high -frequency voltage (used to"start" the arc at the transmitting end) issuperimposed on the actual carrier waveused to radiate the signals. It will thereforeautomatically start up the arc at thereceiving end at the same time as that atthe transmitter.- Subsequent timing signals are also

radiated each time the transmitter arcpasses round one of the corners of theelectrode system, by arranging a smallprojection at each "turning point" so asto shorten the length of the arc. This mo-mentarily decreases its resistance andautomatically applies a timing -impulse tothe carrier wave, which it utilised at thereceiving end to keep the local arc accurate-ly in step with the one at the transmitter.

a

JULY 2, 193213 matter Wirelitz.s5

Jeanne de Casalisof " Mrs. Feather " fame

ONE of the most distinctive recentbroadcasts was Derek McCulloch's

Going South. As the programme stated,it consisted of a series of local cameos ofthe Southern States as seen through theeyes of a coloured Pullman conductor.The idea was wholly to set an atmospherefor a broadcast of Negro melodies. Thismight easily have failed and have resultedin a production that was a mere excusefor dragging in the songs, however wellthey may have been sung by the TempleQuartet. As a matter of fact, they werevery well sung.

It turned out very differently, largelythrough the playing of the Pullmanconductor by Percy Parsons. His deepvoice-one of the deepest I have everheard in a production of this kind-seemedto establish the character of the Pullmanconductor right from the start. One feltthat this nigger was a cut above the generalrun of niggers, and that he took an honestand affectionate interest in the songs ofhis own country.

The whole production was so strongatmospherically that I, for one, quiteforgot my present surroundings. In thewireless sense, this is very high praise.At least, I mean it to be because I havemaintained all along that productionswith a single thought behind them are the

nly kind suitable for wireless transmission.

I heard the first of the two relays fromCanterbury Cathedral. I found myselfwondering why the B.B.C. orchestra mustgo to Canterbury in order to broadcast.I felt that, in these days when musicalwork is so hard to obtain, it might havebeen a better arrangement for the orchestrato have been composed of men notregularly employed by the B.B.C. Morethan one professional musician has spokento me on the matter. I think the B.B.C.might take the hint.

I wonder if anyone noticed a charming,but unrehearsed effect at the end of theprogramme ? The orchestra was playingWagner's exquisite Siegfried Idyll. Ihappened to be sitting at a table with ascore in front of me. As the work drewto a close, just after the well-known

TALKS ABOUT

NEGRO MELODIES

passage where the flute imitates a sort ofbird -call, I became conscious of soundsnot represented in the score. Both mywife and I thought a bird was singing in thegarden at first, but it was dusk. Whenwe listened more carefully we realisedthat the bird was in Canterbury. Wecould distinctly hear him in the loud-speaker; he was probably near the cathedralcloisters and had decided to join in ! I amno ornithologist and therefore do notpresume to suggest what type of bird itwas; it would hardly be a nightingale sonear a city ! It is interesting, especiallybecause it recalls Beatrice Harrison'ssuccess with her 'cello. At all events theeffect made a charming conclusion to anattractive programme,

The Pink, Pink Vase made a good radioproduction. The plot was entertaining,but I thought the best part was the musicby Leslie Woodgate. I congratulate Mr.Woodgate on writing music distinctlyEnglish in type and on not being afraidto write up to a high level musically.

Did you hear the fifth Hazard ? I wasamused at Mr. Weston Martyr's style innarrating his story. He invited any of

PROGRAMME POINTERSTheoretically the value of an alternativeprogramme is to provide a choice of enter-tainment, the two programmes being presum-ably of equal value and of the same highstandard of performance. In practice thishas not been so-perhaps it is too much toexpect. The scheme has worked out in themain to provide sharply contrasted matter,such as a symphony concert versus a lightorchestra programme or something like" Songs from the Shows." That, in thebroadcast sense, is good alternating becauselovers of symphony are not disappointed atmissing the light orchestral music any morethan devotees of light songs mind missing aBeethoven concerto. I have noticed, how-ever, cases of less fortunate alternating.My weekly work of choosing items for reviewin this journal has taught me that the pro-grammes are not always watertight in thisrespect. Saturday, June 18, offered anexample. There was a good vaudeville onthe London Regional at 8.45. The play" Waterloo" was on the National at 8.I began with the play, but I switched into theRegional about 9.10 in time to hear Jeannede Casalis. I should like to have continued,but wanted to hear the Hazard at 9.2o onthe other programme. This is not goodalternating. A vaudeville should be opposedby chamber music, or at least by somethingthat will appeal to people who do not likevaudeville.

us to accompany him in our imaginationon a voyage in a schooner. In mentallyobeying his wishes I stepped aboard quitegaily. Long before he had finished Iwished myself anywhere but on that boat.There are luxuries in this world I amcontent to miss; that was one of them.

Waterloo was quite a success, especiallythe scene before the battle. I criticise theguns in the battle scene; I think a deeper -toned drum would be more effective forthat sort of thing. The one used soundedto me like an -ordinary kettle -drum. Thebest part of the play undoubtedly was thescene in St. Helena. It brought .outNapoleon's characteristics. NormanEdwards and Val Gielgud are to be con-gratulated upon producing what mightwell become a wireless classic. It willcertainly stand repetition each June 18.

I have not heard as much vaudeville thisweek as I- generally do, but what I haveheard was, on the whole, good. It wascertainly a lift -up in vaudeville to haveTom Burke and his Human VoiceOrchestra, particularly as they sang anattractive arrangement of Chaliapine'sfamous song, " When the King goes forthto War." There were some very pleasingchoral effects. Mr. Burke's singing of thelast verse (where the serf is laid to rest)was really beautiful.

Another singer attracted my attention,partly on account of his good singing butalso, I fear, on account of the words of hisfirst song. Surely it is not good enoughto expect us to swallow sentiments like"she dims the light and holds me tight" ?I appeal to Mr. Geoffrey Gwyther to givehis present lyric writer a pension and tryagain. The day has long passed since weappreciated rubbish of that kind.

The most brilliant turn I heard during theweek was Jeanne de Casalis in another othose amusing " Mrs. Feather " episodesMrs. Feather is now one of the mos.attractive, and also most inconsequen tmicrophone personalities. Her " creator "is certainly one of the best vaudevillebroadcasters because she always keeps aneye on the microphone. Every line isdelivered for her invisible audience. Thereis no difficulty in following any of hertelephone conversations-however dis-tressed she may become at being misunder-stood by the person at the other end-because she words her dialogue so that heraudience gets both sides.

WHITAKER-WILSON.

Cn WireiT

WIRELESS set userscan be placed under

three headings. Firstly, wehave those who are sosituated that they areentirely dependent on bat-teries, both high and lowtension. Secondly, we havethe group which finds itquite easy and convenientto use an accumulator, but,having the mains in thehouse, would like to usethem for the high-tensionsupply, thereby avoiding theregular expense of high-tension battery replacement;and, thirdly, we have thosewho desire their sets to beentirely mains driven. Inworking out the design for the "Mascot"receiver, described in Nos. 509-510, allthree classes were borne in mind, but asprobably most listeners require batteryoperation, the battery model was the firstto be described:

The three distinguishing properties ofthe "Mascot"-selectivity, quality andpower, are all connected with one specialand inherent quality of the set-stability.In a set which is really stable, particularlyat the low -frequency end, very loud andpure signals can be obtained when usingmodern output valves with quite aneconomical high-tension consumption. Atthe same time, however, to get a really bigvolume of undistorted power an outputvalve capable of handling the power must

14

This photograph shows the unitconnected to the "Mascot" receiver

be used and such valves are necessarilygreedy of high-tension current. As practi-cally the only distortion of loud signals inthe "Mascot" receiver results from over-loading the output valve, many readershave written me asking that a high-tensionmains unit should be designed specially forthe "Mascot" so that such a super -powervalve can be economically used.

This week, therefore, I propose describingthe special "Mascot" mains unit which hasmany interesting features. Made to matchthe "Mascot" both in height of panel anddepth of baseboard, it can either be"boxed" separately or combined with the"Mascot" receiver in a cabinet made totake a panel 25 in. by 7 in. It is, asyou will see from the drawings andphotographs, extremely simple to con-struct. A feature is that so long as it isturned on, the word " On" appears inbrilliant red letters in the small window onthe panel above the on -and -off switch.Also it contains inside a special safety fuse

arranged to protect both the unitand the valve itself. If any oneof the condensers breaks downthe fuse blows at once, as no morethan roo milliamperes can passthrough it.H.T. or All Mains

A further important point isthe inclusion of a power resistancebetween the choke and the output

The " Mascot " mains unitis of particularly simple

construction

4condensers which can be changed to suitvarying conditions. For example; modernbattery valves are designed to run with amaximum high-tension voltage of 150, whilethe mains, valves will safely stand 200.

H.T. only or All -mainsThe " Mascot " mains unit is designed to

supply high tension for both battery setsand all -mains -driven sets, this resistance isselected at the time the set is built so as togive the correct output voltage for eithertype of valve. Further, a 4 -volt winding,capable of giving 4 amperes if necessary, isprovided for the heater current of the mainsvalves. When using this set with batteryvalves the two 4 -volt terminals are leftdisconnected and in this case serve onlyto light the pilot lamp behind the windowthat shows the word " On."

Limiting the VoltageAs this unit is designed to give an output

voltage of 200, and battery valves aredesigned to run at a maximum high-tension of 150, provision is made to inserta resistance in order to reduce the voltageto this latter figure if desired. The valueof this resistance is dependent upon thevalves used, but a safe rule is to use a4,000 -ohm power resistance if the outputvalve is of the drdinaty power type, anda 2,cod-ohm resistance if it is a super-power valve such as the Mullard PM252,

15

ASCU( MAINSPERCY W. HARRIS describes a simple unitfor converting a battery -operated set for use

on the mains)Mazda P22oA, Cossor 23oXP, Marconi orOsram P24o, and so on.

The CircuitIn previous articles I have discussed

various types of mains units and you willbe interested to examine the theoreticaldiagram showing how this particular unitis made up. The input from the mainscomes to a quick make -and -break mainsswitch which disconnects both sides of themains, and from here to the primary of amains transformer. On the primary sideof this transformer you will find four ter-minals, marked " 50 P.," " 200," "230,"" 250." One wire from the switch goesalways to the terminal marked " 50 -13."and the other goes to 200, 230 or 250;depending on your mains A.C. voltage.The output terminals are provided in threegroups, two of them are 4 -volt windingseach with a centre tap, and the third set isthe true high-tension winding giving 23ovolts on either side of the centre tap.

Heater SupplyThe two 4 -volt windings have to be very

carefully insulated from one another, forone of them (that on which the centreterminal is marked "4 amps.") is designedfor the low-tension heater; the other, whichhas its centre terminal marked " a amp.,"is for heating the filament of the rectifiervalve. .:You might think that one winding

would serve for both purposes, but onexamining the circuit diagram you will seethat the centre tap of the 4 -volt a -amp.winding supplies the positive H.T. ter-minal, therefore 'this winding is at high-tension all the time.

A pair of leads is taken from the 4 -volt4 -amp. winding to the 4 -volt outputterminals and another pair to the panel -mounting pilot light behind the redwindow. This little pilot lamp takes avery small current, so that the additionalload on the winding is negligible. Thevalve, as you will see, is a full -waverectifier and the two ends of the high-tension winding go to the two platesrespectively. The opposite ends of thiswinding are alternately positive and nega-tive and each time each plate of the rectifiervalve becomes positive the current flowsacross the space between the particularplate and the filament.

Simple and InexpensiveConsidering the conventional way, the

flow of current is always from the plateto the filament, and as each plate is alter-nately positive a series of pulses of high-tension current pass across the vacuum tothe filament, through the heater windingand from the centre tap of this to the filter.Immediately after the centre tap the roo-milliampere fuse is placed so that all thecurrent through the rectifying valvepasses through this. From the fuse a lead

goes to the first choke and totwo z-microfarad condensersin parallel, through the choketo the series resistance, fromthis to two more 2-microfaradcondensers in parallel, andthence to the high-tensionpositive terminal. As explain-ed in previous articles thechoke with the two pairs ofcondensers (naturally, it docsnot matter whether we havetwo 2-microfarad condensersin parallel or one 4 -micro -farad) forms a very simpleand efficient smoothing unit.The resistance is includedbetween the choke and theoutput condensers so thatit is fully shunted by these

-To P.C. Maths

PILOT

liGHT

Fuse

LE Cliche

InterchangeableResistance

4mr each

4114amo.

The circuit of the mains unitis quite straightforward

IRCUIT AND COMPONENTSEb nei, 7 in. by 7 in. (Peto-Scott, Readi-Rad, Beeol, Lissen).

nal strip, 7 in. by 2 in. (Peto-Scott, Readi-Rad, Bowl, Lissen).Baseboard, 7 in. by 10 in. (Peto-Scott, Readi-Rad, Cameo).Mains transformer (Heayberd, type 715).Smoothing choke (Varley Nichoke II, Lissen, Atlas, Telsen, Igranic, R.I.).Four 2-mfd. fixed condensers (Lissen, Telsen, Ferranti, Dubilier, T.C.C.).2,000 -ohm or 4,000 fixed resistance and holder (Varley, Lissen, Igranie, R.I.).9 -pin valve holder (W.B., Lissen, Telsen, Igranic, Benjamin).Two -pole mains snap switch (Wearite, type G.42 : Bulgin).Pilot light (Readl-Rad, Buten).100 ma. fuse and holder (Microfuse, Bulgin, Belling -Lee).Four terminals, marked H.T.-, H.T.+, 2 L.T.A.C. (Belling -Lee," B " BulgIn, Clix, Eelex).Connecting wire (Glazite, Quickwyre,Mains flex (Lewcos).Mains plug (Bulgin)Valve, DW2 (Mullard) or 50613TJ (Cossor).

Te

type

CI mate= Wtreliz!)

condensers and at the sametime adds to the smoothingeffect.

As the "Mascot" receiveris designed for one high-tension positive, the neces-sary voltage dropping forthe detector being includedin the set itself, there is noneed to have more than onehigh-tension terminal. Inthis way our unit is bothsimpler and less expensivethan otherwise would be thecase and readers will savethe expense of building amains unit with severalvoltage tappings when theseare not likely to be used.

(Continued on next page)

BLUEPRINTN°R.W350

TooMainssOnwi-atcft 2k2

RC.Mains

BRSEBORRD10x7'

Rectifier Valve

INTERCHANCEARL RBIS.

- 0

MEM

PIINEL7kr

W00111111

CHOKE

The layout and wiring diagram of which afull-size blueprint is available, price 1;-

11---04MOsoms.m.0.0411.04040100.1111P0.M.O.M.P.0.104MO WO,04M.O..1.3.020.43.moemi.patimo.m041=11.010404M.0.10..1.tA

Cn WireiT

WIRELESS set userscan be placed under

three headings. Firstly, wehave those who are sosituated that they areentirely dependent on bat-teries, both high and lowtension. Secondly, we havethe group which finds itquite easy and convenientto use an accumulator, but,having the mains in thehouse, would like to usethem for the high-tensionsupply, thereby avoiding theregular expense of high-tension battery replacement;and, thirdly, we have thosewho desire their sets to beentirely mains driven. Inworking out the design for the "Mascot"receiver, described in Nos. 509-510, allthree classes were borne in mind, but asprobably most listeners require batteryoperation, the battery model was the firstto be described:

The three distinguishing properties ofthe "Mascot"-selectivity, quality andpower, are all connected with one specialand inherent quality of the set-stability.In a set which is really stable, particularlyat the low -frequency end, very loud andpure signals can be obtained when usingmodern output valves with quite aneconomical high-tension consumption. Atthe same time, however, to get a really bigvolume of undistorted power an outputvalve capable of handling the power must

14

This photograph shows the unitconnected to the "Mascot" receiver

be used and such valves are necessarilygreedy of high-tension current. As practi-cally the only distortion of loud signals inthe "Mascot" receiver results from over-loading the output valve, many readershave written me asking that a high-tensionmains unit should be designed specially forthe "Mascot" so that such a super -powervalve can be economically used.

This week, therefore, I propose describingthe special "Mascot" mains unit which hasmany interesting features. Made to matchthe "Mascot" both in height of panel anddepth of baseboard, it can either be"boxed" separately or combined with the"Mascot" receiver in a cabinet made totake a panel 25 in. by 7 in. It is, asyou will see from the drawings andphotographs, extremely simple to con-struct. A feature is that so long as it isturned on, the word " On" appears inbrilliant red letters in the small window onthe panel above the on -and -off switch.Also it contains inside a special safety fuse

arranged to protect both the unitand the valve itself. If any oneof the condensers breaks downthe fuse blows at once, as no morethan roo milliamperes can passthrough it.H.T. or All Mains

A further important point isthe inclusion of a power resistancebetween the choke and the output

The " Mascot " mains unitis of particularly simple

construction

4condensers which can be changed to suitvarying conditions. For example; modernbattery valves are designed to run with amaximum high-tension voltage of 150, whilethe mains, valves will safely stand 200.

H.T. only or All -mainsThe " Mascot " mains unit is designed to

supply high tension for both battery setsand all -mains -driven sets, this resistance isselected at the time the set is built so as togive the correct output voltage for eithertype of valve. Further, a 4 -volt winding,capable of giving 4 amperes if necessary, isprovided for the heater current of the mainsvalves. When using this set with batteryvalves the two 4 -volt terminals are leftdisconnected and in this case serve onlyto light the pilot lamp behind the windowthat shows the word " On."

Limiting the VoltageAs this unit is designed to give an output

voltage of 200, and battery valves aredesigned to run at a maximum high-tension of 150, provision is made to inserta resistance in order to reduce the voltageto this latter figure if desired. The valueof this resistance is dependent upon thevalves used, but a safe rule is to use a4,000 -ohm power resistance if the outputvalve is of the drdinaty power type, anda 2,cod-ohm resistance if it is a super-power valve such as the Mullard PM252,

15

ASCU( MAINSPERCY W. HARRIS describes a simple unitfor converting a battery -operated set for use

on the mains)Mazda P22oA, Cossor 23oXP, Marconi orOsram P24o, and so on.

The CircuitIn previous articles I have discussed

various types of mains units and you willbe interested to examine the theoreticaldiagram showing how this particular unitis made up. The input from the mainscomes to a quick make -and -break mainsswitch which disconnects both sides of themains, and from here to the primary of amains transformer. On the primary sideof this transformer you will find four ter-minals, marked " 50 P.," " 200," "230,"" 250." One wire from the switch goesalways to the terminal marked " 50 -13."and the other goes to 200, 230 or 250;depending on your mains A.C. voltage.The output terminals are provided in threegroups, two of them are 4 -volt windingseach with a centre tap, and the third set isthe true high-tension winding giving 23ovolts on either side of the centre tap.

Heater SupplyThe two 4 -volt windings have to be very

carefully insulated from one another, forone of them (that on which the centreterminal is marked "4 amps.") is designedfor the low-tension heater; the other, whichhas its centre terminal marked " a amp.,"is for heating the filament of the rectifiervalve. .:You might think that one winding

would serve for both purposes, but onexamining the circuit diagram you will seethat the centre tap of the 4 -volt a -amp.winding supplies the positive H.T. ter-minal, therefore 'this winding is at high-tension all the time.

A pair of leads is taken from the 4 -volt4 -amp. winding to the 4 -volt outputterminals and another pair to the panel -mounting pilot light behind the redwindow. This little pilot lamp takes avery small current, so that the additionalload on the winding is negligible. Thevalve, as you will see, is a full -waverectifier and the two ends of the high-tension winding go to the two platesrespectively. The opposite ends of thiswinding are alternately positive and nega-tive and each time each plate of the rectifiervalve becomes positive the current flowsacross the space between the particularplate and the filament.

Simple and InexpensiveConsidering the conventional way, the

flow of current is always from the plateto the filament, and as each plate is alter-nately positive a series of pulses of high-tension current pass across the vacuum tothe filament, through the heater windingand from the centre tap of this to the filter.Immediately after the centre tap the roo-milliampere fuse is placed so that all thecurrent through the rectifying valvepasses through this. From the fuse a lead

goes to the first choke and totwo z-microfarad condensersin parallel, through the choketo the series resistance, fromthis to two more 2-microfaradcondensers in parallel, andthence to the high-tensionpositive terminal. As explain-ed in previous articles thechoke with the two pairs ofcondensers (naturally, it docsnot matter whether we havetwo 2-microfarad condensersin parallel or one 4 -micro -farad) forms a very simpleand efficient smoothing unit.The resistance is includedbetween the choke and theoutput condensers so thatit is fully shunted by these

-To P.C. Maths

PILOT

liGHT

Fuse

LE Cliche

InterchangeableResistance

4mr each

4114amo.

The circuit of the mains unitis quite straightforward

IRCUIT AND COMPONENTSEb nei, 7 in. by 7 in. (Peto-Scott, Readi-Rad, Beeol, Lissen).

nal strip, 7 in. by 2 in. (Peto-Scott, Readi-Rad, Bowl, Lissen).Baseboard, 7 in. by 10 in. (Peto-Scott, Readi-Rad, Cameo).Mains transformer (Heayberd, type 715).Smoothing choke (Varley Nichoke II, Lissen, Atlas, Telsen, Igranic, R.I.).Four 2-mfd. fixed condensers (Lissen, Telsen, Ferranti, Dubilier, T.C.C.).2,000 -ohm or 4,000 fixed resistance and holder (Varley, Lissen, Igranie, R.I.).9 -pin valve holder (W.B., Lissen, Telsen, Igranic, Benjamin).Two -pole mains snap switch (Wearite, type G.42 : Bulgin).Pilot light (Readl-Rad, Buten).100 ma. fuse and holder (Microfuse, Bulgin, Belling -Lee).Four terminals, marked H.T.-, H.T.+, 2 L.T.A.C. (Belling -Lee," B " BulgIn, Clix, Eelex).Connecting wire (Glazite, Quickwyre,Mains flex (Lewcos).Mains plug (Bulgin)Valve, DW2 (Mullard) or 50613TJ (Cossor).

Te

type

CI mate= Wtreliz!)

condensers and at the sametime adds to the smoothingeffect.

As the "Mascot" receiveris designed for one high-tension positive, the neces-sary voltage dropping forthe detector being includedin the set itself, there is noneed to have more than onehigh-tension terminal. Inthis way our unit is bothsimpler and less expensivethan otherwise would be thecase and readers will savethe expense of building amains unit with severalvoltage tappings when theseare not likely to be used.

(Continued on next page)

BLUEPRINTN°R.W350

TooMainssOnwi-atcft 2k2

RC.Mains

BRSEBORRD10x7'

Rectifier Valve

INTERCHANCEARL RBIS.

- 0

MEM

PIINEL7kr

W00111111

CHOKE

The layout and wiring diagram of which afull-size blueprint is available, price 1;-

11---04MOsoms.m.0.0411.04040100.1111P0.M.O.M.P.0.104MO WO,04M.O..1.3.020.43.moemi.patimo.m041=11.010404M.0.10..1.tA

eittaltur Wirelesi 16 JULY 2, 1932

NHy missDEAT

A CURIOUS POINTWONDER how many readers have

I noticed when testing a set having ascreen -grid stage that an adjustment to theaerial circuit may apparently affect theamount of the reaction?

You will notice this when the set hasdifferent aerial tappings or a condenser inthe aerial circuit -working as a volumecontrol. First, adjust the reaction nicely,so that the anode circuit is just oscillating.

Then alter the aerial circuit in some way,such as by connecting the aerial to adifferent tap or changing the setting of theaerial condenser. The circuit may have tobe re -tuned and you may find that theaerial circuit is now oscillating.

Actually, the aerial circuit is coupled tothe anode circuit by the stray circuitcouplings, including the tuning condensers,the coils, wiring and valve. When theaerial circuit is brougtit into tune with theanode circuit the aerial absorbs a littlepower from the anode circuit and the set isvery sensitive when both circuits are justoff the oscillating point.

If now the aerial tap or the value of theseries condenser is altered, the load ischanged. This affects the condition of thecircuit which may now oscillate or befurther from the oscillating point.

CHANGE THEM AND SEEUSUAL values of grid condenser and

leak resistance are .0003 microfaradand 2 megohms. In many cases betterresults are obtained when parts havinglower values are fitted.

Thus the grid condenser can be reducedto .000i microfarad. There will usuallybe no loss in sensitivity and in some casesthere may be a slight gain. But thequality will usually be much improved.It is the higher notes that are strengthenedand in many sets the circuits cut downthe top notes with the result that a distinctimprovement is noted.

If the grid leak is lowered from the 2megohms to say z megohm or even .5, theresults from the point of view of qualitywill be still further improved. It is possiblethat the reaction circuit will need a littlealteration when the values of the gridcondenser and leak have been so reduced,but probably a change in the voltage ofthe high-tenSion will put this circuit right.

As a matter of fact, the anode voltageto the detector should always be as highas possible in` orderto reduce the chancesof overloading. Detector overloading isresponsible for much bad quality.

Wate4WIllats_____coNsTRUCTIONAL

e itiEroPETIcAt

WJAmEsTHESE TINY COILSARE large tuning coils doomed? One

might think so if one considered thesmall size of many commercial coils.

A small coil used in an aerial circuitcannot produce as strong a signal acrossits ends as a larger coil, however, providedboth are properly used. With a largecoil, having the aerial 'connected to a tapor through a primary windinff''' of a suitablesize, the signal strength is bound to begreater than from a coil of smaller size.

20

12

5

50 to 55turns 3:0i4

Tapping a coil for the testdescribed in the accom-

panying paragraph

A few experiments soon prove this.You can make a three-inch coil having5o or 55 turns of No, 26 wire, taking tapsat 5, 12 and zo turns. Join it as in theaccompanying sketch, using a .0005microfarad tuning condenser.

Note the selectivity and signal strengthusing first the aerial tap at the fifth turn.

Next take the aerial to the twelfth -turntap. The selectivity will not be quite asgood, but probably the strength will bemuch greater.

Finally, take the aerial to turn 20. Iftests are also made using a one -inch coilor coil of i1/2 inches, the difference in theresults will at once be noticed: Thequestion of screening may turn one to thesmallest coil that will do the job, butwhen screeninor'' is not essential a largecoil is much to be preferred.

A POWER -GRID POINTA QUESTION that is often asked is

why does the anode current of adetector valve, working as a power -gridrectifier, or as an ordinary grid circuitrectifier, fall off when a signal is tuned in.

Briefly the current falls off because thegrid goes more negative when a signal isbrought in, and the stronger the signalthe more negative is the grid made.Therefore, the anode current is reducedby the signal.

If you increase the bias applied to a

power valve the anode current is reduced.The same thing happens with the detectoror any other valve. As you increase thebias the current is reduced.

A weak signal makes the grid of thedetector a little more negative, and so theanode current falls off a slight amount.A stronger signal still further lowers thevoltage of the -grid, making it still morenegative, and this reduces the anodecurrent still more. ,

The reduction in the anode current isan indication of the strength of the signalsof the detector. A strong signal mayreduce the current to a very low value.Distortion is bound to be introduced ifthe current is reduced to too low a value,and a pre -detector control must be fittedso that this can be avoided. The strengthof the output depends upon the percentageof modulation. Do not therefore confuse thestrength of the low -frequency output withthe strength of the radio -frequency signal.

THE "MASCOT MAINS UNIT(Continued from preceding page)

The value of the power resistancechosen will,as I mentioned earlier in thearticle, depend whether you are usingmains valves or battery valves, and, ifyou are using battery valves, on whetheryou are using the power or super -powertypes. There is no point in using anythingbut the super -power type when you havesucha powerful mains unit as the additionalhigh-tension costs you no more.

For the rectifying valve you can useeither a !Midland 'D W2or Cossor 5o6BIT forthe condensers you can use either a pairof 4-rnicrofarads or two pairs of z -microfarads. The low-freqnericy choke shouldbe a good one" and 'suitable alternativesare given in the list of components. Sofar as the resistance is concerned, this mustbe of the power type capable of carryingthe full current. Do not be tempted touse spaghetti resistances which, whileexcellent for the purpose for which theyare designed, are totally unsuited forcarrying heavy Current. Operated from a unit of this description,

the "Mascot" or any other set will befound much more powerful.

The "Mascot " mains unit is primarilydesigned, of course, for use with the" Mascot " receiver, which has only onehigh-tension tapping. Next week I willtell you how to use this unit with otherreceivers fitted with several high-tensiontappings, and a screen -grid valve

JULY 2, 1932 17 ChnuteurWtrelesi

Mr Percy Harris uses four!IL SSEr

Ma nsbricNe

lype Condensers

in the

P. W HarrisMains Unit

This Lissen Mansbridge TypeCondenser is specified by Mr.Percy Harris in the P.W.H.Mains Unit described in thisissue. Keep closely to thespecification for this com-ponent, for upon the re-liability of the condensersyou use depends the perforcemance of the MainsUnit you build.

2 mfd. Price

LISSEN FIXEDMICA CONDENSERSThese Lissen Mica Fixed Con -der s.irs are leak -proof. Theynever vary. They deliver all theirstored -up energy. Guaranteedaccurate within 5';0 of markedra,acity. Can be mountedupright or flat. Grid -leak clipsincluded free witheach condenser.

.0001 to .001

.002 to .006, NM1'6.

6

Lissen again in the New Regional 3LISSEN

BAKELITE DIELECTRIC

VARIABLE CONDENSER

This is a Lissen miniatureprecision variable condenserfor coupling and reactioncircuits. It is a well -designedand sturdily built component;the moving vanes are definitelylocated and inter -connected.For tuning, .0005 mfdFor Reaction, .0001and .0003 mfd. Price

6

When the specification saysLISSEN -stick to LIS:5EN!

0.53111TO REX

TRANSFORMERThis Lissen Torex Trans-former makes a big cut inthe cost of any set withoutsacrifice of quality. It is ahigh-grade silicon steelcane transformer, givingremarkably even amulifi-caticn over the whole bandof audible frequencies. Aneat, compact component;its moulded bakelite caseis hermetically sealed andcompletely insulates thewindings. Proofag. inst shorty g,leaka e or mois-ture. 6

LISSEN LIMITED, WORPLE ROAD, ISLEWORTH, MIDDLESEXMention of "Amateur Wireless" to Advertisers will Ensure Prompt Attention

moteur WUete-S1 18 JULY 2, 1932

(SETS OF DISTINCTION MEM MIME MIMEO EINEM MIMI MIEN NINO

9heMARCONIPHONE SUPER

1-"'"" PORTABLE FOURMakers : The Marconiphone Co., Ltd. Price : 13 Guineas

ONE of the most pleasing _portables ofthe upright cabinet type tested this

season is the Marconiphone model shownby .the illustrations. At least, I think so,and I have had the set onfor a long week-end without finding anything to complainabout.

You may take it that this portable repre-sents the very best in modern technique,giving a performance that would be credit-able in a much more cumbersome instal-lation. And when you realise how compactand convenient is the walnut cabinet ofthis portable, which houses everythingneeded for broadcast reception, the attrac-tion is still more enhanced.

A Neat DesignAs soon as you open the back of the

cabinet, and take stock of the interior; youcannot help appreciating the neatness .ofthe design. I suppose the general layoutwould be considered Conventional. Thereis a four -valve chassis at the top, notablefor the generous amount of metal screening.Below is space for the batteries, which com-prise the usual rob -volt high-tension unitof standard capacity, a non -spillable two -volt accumulator and a 9 -volt grid -biasbattery.

These batteries are firmly wedged intothe compartment, and there is no chanceof any of them coming adrift, even withfairly rough transportation. One of thefeatures of the set is the use of threemetallised valves, only the power valvebeing non-metallised.

The first valve is a Marconi S2 I screen -grid, followed by a Marconi HL2 detector.This is coupled to another HL2 for thefirst low -frequency amplifying stage. Thencomes the power output, which is a MarconiPT2 pentode-an ideal valve for a portable,since it gives ample output without toogreat a drain on the high-tension battery.

Small Current Requirements.I have checked up the total anode -cur-

rent consumption, which is just under tomilliamperes-not at all excessive in viewof the ample undistorted output. Thehigh-tension battery should last two orthree months with average rise: - -

Although entirely self-contained, this sethas provision for the external connectionof a loud -speaker, for a gramophone pick-up, and for an aerial and earth.

The self-contained loud -speaker is of thebalanced -armature cone type, giving a verypleasing response. Speech is particularlygood, and there is an entire absence of

" woofiness," even when listening to foreignstations:'

Music comes through with a satisfyingall-round tone, and up to the ample limitof the pentode power valve there is no sign

_of distress. For loud reproduction I foundit necessary .to make a slight adjustment tothe loud -speaker unit, there being a neatknurled knob fitted .for this purpose on thegrille at the front of the cabinet.

Simple ControlHere also we find the controls, which are

vinced that the operation is essentiallysimple, in spite of the number of knobs.Actually there are no superfluous controls,all those incorporated being essential to theefficiency of the performance.

True to its name, the tuning of the Mar-coniphone portable is " super "-at least forthe type of set. The two London stationswere readily eliminated, and I was able toget plenty of foreigners clear of interference.On the long waves Radio Paris wasabsolutely clear of Daventry, and wasindeed a very powerful signal.

FRAMEAERIAL

FORMER

AERIALDETECTOR E NTODEASIR EARTH

METALCHASSISCONST RUCTION

the salient features of the MarconiphonePortable Four

as well thought out as the chassis, which issaying a good deal. At the top is thetuning escutcheon, with a dial clearlymarked in wavelengths for medium- andlong -wave bands.

This scale is worked by the knob on theright, which also controls the two -gangcondenser. There is a trimmer knob atthe centre, -and -reaction is controlled by aknob -on the left.. --

_By far. the neatest of the controls is theknob - controlling the wave -change andbattery on -off switching. This is locatedbelow the main controls just mentioned,and in addition to working the three -position switch this knob actuates a scale,which clearly shows which circuit is in us c,that is mediuin waves, long waves or"off."

After a weekend with the set I am con -

This picture shows

DirectionalSelectivity

' By taking advantageof the directional effectof the frame aerial, Iwas able to get Zeesenalmost clear of bothRadio Paris and Dal/ -entry. The set appearsto be equally good onboth wavebands.

Although of the up-right type, this set isvery convenient tocarry around. Thereis a strong handle onthe top of the cabinet,and a turntable underthe base.

- SET TESTER.

A West Country pro-gramme will be givenfrom Cardiff on July

4 when a West Countryone -act play by

Laurence Housman, entitled The Calledand the Chosen, will be heard.

On July 14, Ulster listeners are to hearthe first relay of light music from the SlieveDonard Hotel, Newcastle. This musicwill be broadcast from the main loungeof the hotel, and will be played by SibbaldTreaty's Shove Donard Orchestra.

A folk -song programme will be givenby the Western Studio Orchestra forWest Regional listeners on July 12.

The United Methodist Conference isbeing held this year in Zion Church,Kingswood, Bristol, in July and on Julyro a service will be relayed from the Churchto West Regional listeners.

JULY 2, 1932 19 rnateur

EVERYTHING ELECTRICAL

Use the valve withthe highest overallamplification of any2-volf Screen -Gridvalve in the world

The OSRAMS.22 can besupplied eithern.etallized of

clear.

MADE INENGLAND

CHARACTERISTICSFilament voltsFilament currentAnode voltsScreen -Grid volts -

2'0 max02 amp150 max

75 maxImpedance - 200,000 ohmsMutual conductance 175 ma/volt

Price

1616Specially recommendedfor use in 3evalveScreen=Grid Kits and Sets

For detector and L.F. sellOSRAM H.L.2 and L.P.2

srarnS.22

Screen -Grid H.F. Amplifying Valve

MUTUAL CONDUCTANCE-1.751.75 maivolt

Compare this with any other 2 -volt screen -grid valveSPECIAL POINTS'-Combined high slope and low inter -electrode capacity add ranleto the'Set.Combined adequate electrode clearance and rigid design meanabsolute reliability.These outstanding advantages are obtained by the use of the:-

Wembley Filament(Used in "New Series' OSRAM 2 -volt Valves)

The filament that gives 10% GREATER ELECTRON EMISSIONthan any 2 -volt filament obtainable.osrain

valve.EXTRA QUALITY WITHOUT EXTRA COST

SOLD BYALL

WIRELESSDEALERS

Advt. of the General Electric Co., Ltd., Magnet House, Kingsway, London, W.C. 2

Mention of "Amateur Wireless" to Advertisers will Ensure Prompt Attention

a num, Wiretes, 20 JULY 2, 1932

A weekly review of new components and tests of apparatus conducted byNEW ATLAS TRANSFORMERTHE Atlas transformer which we have

received for test is interesting inhaving one of the smallest iron circuits wehave yet seen. A steel of very high per-meability has obviously been employed,since there are only four laminations in thecore.

The coils appear to be of the cotton inter-weave type impregnated after winding,which gives immunity from breakdown dueto moisture and similar causes.

The whole is housed in an attractivegreen bakelite case, measuring 3 in. by1% in. by 2 in. high.

The instrument is said to be suitable foreither direct or parallel feed. With theparallel feed connection we obtained aresponse as shown on the accompanyingcurve. The primary inductance with no

A new low -frequency transformer by Atlas

D.C. flowing was 43.5 henries, the valuedropping to 5 with 2 milliamps D.C.'

GOLTONE MAINS CONNECTORTT Is most important that a .goOd Shock-', proof mains connector should be- usedbetween the supply mains and the receiveror battery eliminator. This is, of -course,normal in the case of cOnimerciallylinad.eapparatus, but is not always so in amateur -made apparatus.

A well -made baseboard -mounting plugand socket connector is that made byMessrs. Ward & Goldstone, Ltd., ,andknown as the " Goltone",Mains Connector:In this connector the socket, which is of,black or brown moulded bakelite, takes theplace of the usual plug on the end ot-theconnecting cable, while the plug is made forbaseboard mounting in. the actual receiveritself.

In this way when ,the. socket is removedit is impossible, normally speaking, toobtain a shock from the mains, as the pinsof the plug are then dead. If it is requiredto mount the plug directly on to the receiver,it can be very simply removed from the

S 033 Si 8 IIll

small metal bracket With which it is sold.The socket connector retails at 8d., and

the two -pin plug at rod., and they can berecommended for general use.

BRYCE MAINS TRANSFORMERA MAINS transformer of the stripped

ri type without the usual terminal boardis often useful. The Bryce type AB25ois intended for general average use.

1111111111111/1111111111111111M1 flifiemli LABORATORIES II11,11111=111111111111 1 -Ft. CALIBRATION CHARTaIllaiLPMMT.021111111111111110111111.1Z1cEi&M211011I MENEM111111111111111111111111111 IMINIMIINi3i111111111M11111111111111=11111111riummouummuummumou110111111MIPM1111111\111011U11111111MMAIIIIIIIIIIIIIIIIMMMIIMIIIP211111111111111111010.111401116/11111111111.1111111111MIIIIIIN61111111111111 111=1111111111111111111It 1 InResponse curve obtained with the Atlas

transformer on parallel feed

In addition to the tapped primary wind-ing, three secondary windings are provided,the high-tension winding and two low-ten-sion windings, one of which is suitable forthe valves of the receiver and the other forthe rectifying valve: All these windings are,of course, centre tapped.

The transformer was wired into a recti-

in

500

teD

I00

a k,

I I I I

PURIM. LABONTORIM?:7,,,.''COL/11/1071Off CIVA1BR PE MANS

TRANSFORlL1ER

-"ala......-,

'VI-

-I0>

AILLIAMPERES DCto 00 30 40 5

Voltage variation curve of Bryce AB230transformer

fying circuit, the valve employed being aU12 type with a 4-microfarad reservoircondenser.

On open circuit the high-tension voltagewas 240 + 24o volts, while the low-tensionvoltages were 4.2 and 4.3 volts.. With aD.C.. load of 3o milliamperes the D.C.,output voltage was 234. The actual varia-tion otthe D.C. voltage with direct current

J. H. Reyner, B.Sc., A.M.I.E.E.load can be seen from the chart with thisreport.

The output voltage of the low-tensionwindings was in each case 3.8 volts on load,the load being respectively 2 and 3 amperes.With all the secondary windings open -circuited, the power consumed was only1.8 watts, giving an efficiency of the order of95 per cent. under normal working con-ditions.

WEARITE POTENTIOMETERAN interesting wire -wound potentio-

meter which we have tested this weekis that made by Messrs. Wearite. Thispotentiometer is built up in a mouldedbakelite casing which is provided withlugs to enable it to be mounted on thebaseboard. At the same time the poten-tiometer is suitable for single -hole fixingon the panel in the usual way. The resis-tance element, which is either plain or

One of the new Wearite components-aganged dual potentiometer

graded as required, is wound on a strip offibrous material.

The moving arm, which is spring con-trolled, is interesting in that the actualcontact is made by means of a small brass,roller. In this way there is no rubbing onthe very fragile resistance wire, and along life is ensured. The potentiometer:under test had a resistance of 25,000 ohms,'but values up to ioo,000 ohms may beobtained.

Provision is made for ganging two suchvolume controls together, a detail which issometimes useful, as for example in areceiver using variable -mu valves andhaving in addition to file volume -controllingfacilities thus afforded, an auxiliary controlon the aerial circuit. The volume controlsare well made and can be recommendedfor general use.

A concert party new to the microphonewill be heard by North Regional listenerson July 7; these are the Arcadian Folliesfrom the Victoria Pier, Blackpool.

JULY 2, 1932 21 m Lear Wiraesi

a

RffDIOGROPMSAE C ITAL of music by de Severac will

be broadcast by Michael Mullinar inthe Midland Regional programme on July 3.

General Higgins, leader of the SalvationArmy, is to attend a luncheon given in hishonour by the Salvation Army at Fish-mongers' Hall on July 5. The General'sspeech will be relayed in the Nationalprogramme.

Philip Ridgeway returns to the micro-phone on July, 19, with a new programmeunder the old title of the RidgeVvay Parade.On that date it will be heard by Nationallisteners and will be repeated in theRegional programme on July 2o.

An organ recital by Henry C. Hodgsonwill be relayed from St. Mary's Church,Nottingham, to Midland Regional listenerson July 4.

A farce by F. Morton Howard, entitled"Future Arrangements," will be given byMidland Regional artistes on July 5.

A recital of gramophone records ofBirmingham artistes will be heard by Mid-land Regional listeners on July 8,when theprogramme will be presented by RobertTredinnick.

The B.B.C. is planning to link up schoolsin the North of Scotland and the mostremote rural districts in the Western Isleswith the National wireless talks on educa-tional subjects. The problem in these dis-tricts, of course, is that of reception, andit is understood that if Education Commit-tees object to the expense, the B.B.C. maybe willing to loan sets.

Ronald Frankau and his Frankau-Opti-mists will be relayed from the Grove ParkPavilion, Weston -super -Mare, in the WestRegional programme on July 6.

Mr. John Davies gives a talk for WestRegional listeners on Welsh Pioneers ofWireless on July. 8. Mr. Davies, recallsthe part that his tug -boat May took inthe experiments by Marconi betweenLavernock Point, Brean Down and FlatHolm.

The Mission to the Out -door Blind forlasgow and the West of Scotland has now

4' increased the number of wireless installa-tions granted to blind persons to 1,441.The Mission received an allocation of zoosingle -valve sets from the British Wirelessfor the Blind Fund, and most of these havebeen installed.

The recently issued B.B.C. pamphlet"Scotland Calling," announced that aregular series of feature programmes wouldbe included in the summer and earlyautumn. A Chaumer concert has beenarranged for July 2. These " Chaumer "concerts used to be a favourite entertain-ment of the farm labourers of Aberdeen-shire when they gathered round their bothyfire after the day's work was done.

The first of a new series of summerdramatic programmes for West Regionallisteners will be given on July I, under thetitle of Summer Laughter.

A genuine lightning switch incorporating the4 UNENCELLED FEATURES enumerated.£100 INSURANCE GUARANTEEFree Insurance Policy against damage to your set bylightning given with every Bulgin Lightning Switch.

EXCLUSIVE FEATURES1. Fuse in circuit when set is 4. Quick make and break actionin operation. (A unique feature never before2. Discharge gap. incorporated in a lightning switch.3. Indicator denoting "On" SELF CLEANING CONTACTSor "Off." under control of a powerful spring).The whole mounted in a handsome Bakelite case, with insulated

control lever.

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Send 2d. Postage for 75 -pp. Catalogue and Manual

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11

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J.B. THUMBCONTROLSA gentle pressureand they revolvethe condenservanes smoothlyand slowly.Hairline Visor.Neat panel appear-ance. All metalparts insulatedfrom condenser.

Type No. 1 .. Plain 4/6Type No. 2 .. Vernier 6/.

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Supplied with black bakelite panel plates.Mahogany finish 6d. extra. PRECISION

INSTRUMENTS

J.B. DRUM DIALIts smooth andpowerful frictiondrive will moveyour condenservanes the merestfraction of an inch.Ivorine reversiblescale.

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Advertisement o Yachson Bros. 72 St. Thomas' Street, London, S.E.1 Telephone: lisp. 1837

Onudeur Wirelesj 22 JULY 2, 1932

/Il

JACK HYLTON.-Leader ofhis famous dance orchestra

ESTHER COLEMAN.-She has broadcast for theB.B.C. nearly 180 times

LILIAS MACKINNON.-Apopular solo pianist

grife-N A 1111vMinh, un

SIR FORBES ROBERTSON.-The famous English actor, whobroadcasts although he has

FREDERICK LAKE.-First retired from the theatrical worldbroadcast early in 1924

HORACE STEVENS. - Well-known in connection with thesymphony concerts at Queen's

Hall

WALTER TODD(left).-Humorist and

entertainer

ANNE THURSFIELD (below).One of the first of the noted

classical singers to broadcast

JELLY D'ARANYL-She washeard at a recent Sunday

studio concert

IT is a mistake to classify grand opera ashighbrow; before the advent of wireless

it was not so considered. I know severalpeople who used to go regularly to CoventGarden more or less because it was " thething" to go; I expect you also know thattype of person.

Even though admittedly the initialattraction was Covent Garden in the heightof the opera season, these people did notfind opera too much for them. The musicitself, in many eases, was a little lofty,perhaps; on the other hand, there were thedresses, the scenery, and (above all) theacting and the actors' voices to compensate.And so opera flourished because quiteordinary intelligent people could appreciateit.

I think I am not far wrong in suggestingthat only a small percentage of regularopera -goers have ever been equally regularsymphony -goers. An audience at a sym-phony concert, or one of the Proms, is verydifferent in character. Apart from theabsence of a show of actual fashion, sym-phony -goers are usually a trifle moreadvanced in music.

It is quite one thing to sit out an opera,with all the help one receives from whatone actually sees as well as hears; it isquite another to sit out a concert of sym-phonic tone -poems and concertos wherethere is so much less to see. When itcomes to -a matter of listening to an operaor a symphony concert by, wireless, thechances of their being appreciated aremuch more equal because one sees nothingin either case. From that I am inclined to

A PLEA FOR MORE

OPERATICCONCERTS

By Whitaker -Wilson

argue that an operatic broadcast does operaharm so far as the average listener isconcerned.

If that listener has never seen an operahe is, bound to regard the music he hears inmuch the same light as he would regardthe performance of a choral work-as amedley of voices and orchestra.

If he has seen an opera, and hears partor the whole of it broadcast, he is probablygoing to find himself a little confusedbecause he is saying to himself : "Let mesee; what are they doing on the stagenow?" That sort of thing does not helpthe beginner who is _striyi,ng to appreciateArt.

I asked some time ago for more and moreoperatic concerts, by which I meant-andstill mean-that excerpts, rather thanentire scenes or acts, should be rendered inthe studio. Here there is no question ofscenery and the consequent strain ofattempting to visualise while listening;moreover, it does not matter.where one is in

the story. The whole effect is a song or aduet-sung in English, of course-care-having been taken to choose excerpts thatwill carry conviction. Such concerts havealready been given, and with great success.What I hope the B.B.C. will do is toincrease the number and give a series-like the Sunday night symphony concerts--in which a definite plan is adopted withthe direct intention of popularising operaby cutting parts where there is too muchplot (which generally means recitative) andkeeping to the more plain -sailing scenes.

My idea is that the B.B.C. shall, by adefinite series of broadcast operatic con-certs, popularise and familiarise each of thebest-known operas.

At a concert in the Winter Gardens,Cheltenham Spa, by the Cheltenham -Municipal Light Orchestra on July 13,songs will be given by Alfred Butler.

Archie Wallen's Concert Party presents" Farce," a farcical fantasy of fun fromthe Jephson Gardens, Leamington Spa onJuly 13, and their programme will berelayed on the Midland Regional wave-length.

An important Shakespearean productionwill be broadcast from Belfast on July13, when As You Like It is presented.Owing to the length of the play, certain" cuts" have been made, but in the mainthe essentials of the play have been pre-served. Incidental music will be playedby the Radio Septet.

JULY 2, 1932 23 ittulatt

I MPROVI NG DETECTOREFFICIENCY

WHEN a valve manufacturer changesV V the characteristics of a certain valve,

we are accustomed to find that thenew characteristics have values which aregenerally supposed to represent a higherefficiency than the original valve type.

Yet the Mullard Company have recentlyannounced revised data for their go4Vindirectly -heated detector valve fromwhich, on the face of it, the new valveappears to be less efficient than the earlierform of the same valve. -

There must be some very good reasonwhy a valve having a slope of 2.2 milliamps 'per volt should be substituted for onehaving the very high slope of 6.5 milli -amps per volt.

When sought out and finally trackeddown, the explanation is reasonable enough,and understandable. But as it upsetsmany pre -conceived notions of what the

PostcardRatio

LiteratureGET THESE CATALOGUES FREE.

Isere" Observer" reviews the latest booklets andfolders issued by well-known manufacturers. Ifyou want copies of any or all of them FREE OFCHARGE,just send a postcard giving the indexnumbers of the catalogues required (shown atthe end of each paragraph) to " Postcard RadioLiterature," "AMATEUR WIRELESS," 58-61,Fetter Lane, E.C.4. "Observer " will see thatJon get all the literature you desire.

That Aerial EquipmentNOW that the fine weather is here it is

time to overhaul your outdoor aerialequipment. As the first step in this direc-tion, get the sheets issued by J: J. Eastickand Sons describing the new combined -knife switch, lead-in tube, and lightningarrester. The whole outfit is obtainable invarious sizes. 787G.E.C. Meters

Here's the latest G.E.C. booklet, ahandy eight -page' production (PublicationM6r6o) describing measuring instrumentsfor all 'kinds of radio jobs. They are not atall expensive and have a laboratorystandard of accuracy. Some of the smallertypes can very well be mounted on thepanel or on the cabinet front of a set.

788New Tekade Speaker

I have just received details of the newtype S 4o balanced -armature speaker unitintroduced by Tekade Radio and Electric,Ltd. It is tapped to match the impedanceof the windings with the valve output andcan be obtained either in chassis or corn-plete cabinet form. Incidentally, it is aBritish -made job. OBSERVER 789

characteristics of an efficient detectorshould be, a simple statement- of the factsof the case may be of interest. In the firstplace, it must be remembered that indetection we are dealing primarily withradio -frequency energy, and that at radiofrequencies very small condenser capacitieshave comparatively great effects on thebehaviour of 'a circuit. A three -electrodevalve forms, in itself, a complicatedelectrical network equivalent to an arrange-ment of very small condensers and resis-tances, the " plates" of these condensersbeing the electrodes of the valve.

Of these small condensers, the mostimportant is the one formed by the gridand anode because it acts as a link betweenthe anode and grid circuits. The effectof the grid -anode capacity is equivalentto that of a condenser of much greatercapacity connected between the grid andcathode, and the greater the effectiveamplification of the valVe, the greater willbe this "reflected" capacity.

What are the practical results of thiscapacity shunting the grid circuit of thevalve? The chief result is that it providesa path whereby part of the energy in thegrid circuit, which should be available toexcite the grid and so produce a highdegree of effective amplification, is dissi-pated and wasted. Moreover, the existenceof this "reflected" capacity changes theeffective tuning capacity andnpsets theganging of the condensers. This effect isknown as the "Miller " effect, and itsextent depends, as we have seen, on thefrequency of the signals handled, upon thevalue of the inter -electrode capacity of thevalve, and upon the effective amplificationfactor.

Now in designing an indirectly -heateddetector valve to have a high value ofmutual conductance, which means in effect,a high stage gain and comparatively lowimpedance, it is necessary to reduce tothe minimum the distances between theelectrodes. This means two things : first,that the inter -electrode capacities arebound to be of considerable magnitude,and second, that the impedance of thegrid -cathode path within the valve willae comparatively small. The one willincrease the losses due to "Miller" effect,and the other will increase the dampingdue to the flow of grid current. Thecombination of these phenomena is equiva-lent in effect to an impedance shuntedacross the grid circuit or input circuit ofthe valve, and is therefore usually knownas the input impedance.

The sum of these losses is thus dependentnot upon the simple value of the mutualconductance of the valve, but it variesapproximately as the square of the mutualconductance. While, therefore, the pro-duction of high -slope detectors is intendedto give extreme sensitivity, that is to saya large modulation output voltage for agiven signal voltage, the extent to whichthe slope can be increased with advantageis limited by the increasing losses due toinput impedance.

CASH -01B. -11.P. Immediate Delivery

NEW REGIONAL 3Described last week

64A:: Author Kit with ready -drilledKit panelLess Valves and Cabinet.

CASH or C.O.D.or 8 monthly payments of 518.

L

KIT El," AuthorKit, with Valves, butless Cabinet,CASHor C.O.D. E3 3 9or 12 monthly payments

41 '-KIT ..C," AuthorKit, complete withValves and Cabinet.CASHor C.O.D. E3 16 3or 12 monthly payments

or CIO. of 7,-.

Specified Valves £1 2 9, Cabinet 12/6

3 VALVERADIO- GRAMOPHONE

Described in "A.W." 21st May, 1932.KIT "A" Author Kit,with Ready drilled Panel, less

Valves, Cabinet, Motor, Pick-up andSpeaker and Batteries.

CASH or C.O.D. £2 16 6or 12 monthly payments of 5/2.

Selected C.O.D. Lines-You paythe postman-we pay postchargeson orders value over 101-.

1 Peto Scott, Tablegrain cabinet 1 /3 0LB. it A. loudspeaker, diaphragm (rgPe 33) 16 61 Cabaret triple -spring motor .

R Values as spealbed 1, P311II L:1, P Inn r ;1, P112 .. 1 2 9

KIT BITS

EASIWAY ITEMSJUST

COSSOR MELODY MAKERMODEL 335Complete with Valves, Speaker and SendCabinet. Employs Costsor Variable -MuS.G., H.F. stage, Detector and Power 1 4/6Valves. Cash Price 8711716. Balancein 11 monthly payments of 14/6. only.... ammemormesommrsnamseinanks..,

W.B. PERMANENT MAGNET MOVING- SendCOIL SPEAKER P.M.3. Complete with 3 -ratio A fieinput transformer. Cash Price 62/1216.Balance in 11 monthly payments of 4/10. onlyEPOCH "20 C" PERMANENT MAGNETMOVING -COIL SPEAKER. With 3 -ratioinput transformer. This speaker will handleup to 5 watts. Cash Price 41/15/0.Balance in 6 monthly payments of 6/6.EPOCH J.I. PERMANENT MAGNET -MOVING -COIL SPEAKER with 3 ratio input transformer

Cash Price 62/S/0Balance in 11 montldy payments of 4/2.

R & A CHALLENGER PERMANENTMAGNET MOVING -COIL tSPEAKER. Withspecial Ferranti multi -ratio input trans-former. Cash Price 41/15/0. onlyBalance in 5 monthly payments of 6/6.W.B. PERMANENT MAGNET MOVINGCOIL SPEAKER. Type P.61.4. Complete withTransformer. Cash Price IRMO.Balance in 7 monthly payments of 5/9.

BLUE SPOT SPEAKER UNIT ANDCHASSIS, TYPE 100U.

Cash Price 81119(6.Balance in 7 monthly payments of 5/5. onlyATLAS ELIMINATOR, TYPE A.C.241. SendThree tappitags, S.C., detector and power. Output,120 volts at 20 m/ a. Cash price, 82/19/6.

66/Seaonly

Send

5/9only

Send

4/2onlySend

6/6 -

Send

5/5

5/6Balance in 11 monthly payments of 5/6. only

`"irsto7.scorrco.7.1777,EiVii;17767171177.7.7Please send roe C.O.D./CASE/1LP

KIT "A"Parts as intimated

for which I enclose d d_..CASHALP. Deposit.NAME

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West Lnd Showrooms: 62 1-60 Holborn, 11.1.G .1

runtaar Wu-etes3 24 JULY 2, 1932

REGINALD FOORT ON

BROADCASTING FROM THE CINEMAReginald Foort, F.R.C.O., the popular broadcast cinema organist, tells how

he arranges his organ broadcasts

Reginald Foort at the console of a big cinema organ. Themicrophone at the right is for " talkie" recording

WHEN I met Mr. Reginald Foort afterone of his popular Regal broadcasts

he was busy checking over technical detailsof a new idea of his for cinema organbroadcasts. This may come into practicein connection with forthcoming broadcasts,but at the moment it is strictly " hushhush."

Foort is certainly the most enthusiasticcinema organist in the country. Inchatting, he reminded me of the old. NewGallery days of 1926 when he firstpopularised organ broadcasting from thatwell-known West End cinema.

The Early BroadcastsIt was more or less the result of an

accident that organ broadcasts of thatkind were ever given in this country.Fred Kitchen had a large orchestra at theNew Gallery in those days and the B.B.C.experts went round to make a test for anorchestra broadcast once a week. Theyarrived early and happened to hear Foortpractising on the organ.

They realised what a novelty that organwould be in the broadcast programmes,

IN THE

so it was arrangedthat Foort shouldbroadcast once aweek from 5 to 5.15p.m.

The broadcastwas an instantan-eous success : somany enthusiasticletters were re-ceived that Foortwas soon asked tobroadcast for awhole hour eachweek instead ofonly fifteen min-utes; later on,occasional eveningbroadcasts werealso arranged.

"The B.B.C. engineers fix up theamplifiers in one of the dressing roomsand plug into the Reisz microphoneswhich are permanently installed in thetheatre. A separate flex is permanentlywired up to the console and an indicatorlight connected. When the announcer inthe studio has finished, he touches abutton which signals the control men toflash the red lamp, and then I start.

Organ Broadcasting Technique" After leaving the New Gallery I went

down to a very fine organ at the Regent,Bournemouth. Here the broadcast wentover specially installed lines from thetheatre to Bournemouth control roomand thence over ordinary Post Officetrunk telephone lines via Southamptonto London. The Post Office treated mybroadcast as an ordinary trunk calllasting an hour, and it cost the B.B.C.about LIo for lines alone every time Ibroadcast. Owing to the number ofrepeaters and line amplifiers en route,there was frequently considerable difficultyin keeping the lines free of intermittent

humming and

AMPLIFIER ROOM

At the amplifier panels of the recording gear in a cinema used inconnection with Reginald Foort's organ records and broadcasts

other linenoises.

"On oneoccasion agale clearedaway a longsection of'phone lineand it wasover a fort-night beforeI was ableto broadcastagain.

"The B.B.C.engineerstwice reject-ed the organin the Regal,Marble Arch,as unsuitablefor broadcast-ing, so when

I went there I had thirty-seven altera-tions made by the builders and then, I amglad to say, it was O.K. As the organ wasin use in the cinema every day, these altera-tions had to be carried out during thenight. The work took eight weeks andwas finished on Christmas Day, when Igave my first broadcast on this organ,so there was no time to try it or practiseon it. It was an eerie experience sittingalone in the theatre, on Christmas Day,of all days, playing to millions of listeners."

There is a small check wireless receiverin Foort's own room at the theatre, andtold me he listens on this to many organbroadcasts.

-" It is a pity that the B.B.C. have not agood studio organ," he said. " Some ofthe foreign stations are much morefortunate. There is a good organ in themain studio at Munich, I am told, andin one of the Hilversum studios there is afine three -manual ' Standaart ' speciallydesigned for broadcasting.

" There are many obvious difficultiesin the way of broadcasting on an organin a theatre. In most cinemas the pipesare a hundred feet or so above the organist'shead, so that the sound is thrown straightout into the theatre, through a tunnelabove the proscenium arch. In one theatreI was in one got the effect of playing withcotton wool in one's ears, so it was difficultto hear just what was going on. Themicrophones are usually hung up in frontof the acoustic tunnel so that they hear 'in the same way as the audience in thetheatre. The organist down below canonly judge what it sounds like, up above.There are so many snags which ordinarylisteners don't appreciate.

" The popular American organist, JesseCrawford, has a splendid three -manualorgan, specially designed and built forrecording and broadcasting in a studio.He broadcasts on this and gramophonerecords made with it are on sale over here.It must lie gratifying to be able to broad-cast and make records under such idealconditions."

UP-TO-DATE RETAILINGSET builders in London will be interested

to know that new premises have beentaken by Messrs. Districts Supplies, Ltd., of256-258 and 26o Bishopsgate, London,E.C. There are six separate soundproofdemonstration rooms and sets and com-ponents can be tested under ideal con-ditions. Of particular interest is a specialopening offer competition, in which setsand radio -grams figure in the prize list.

Memories of Tefry's, the Apollo, Shaftes-bury, Gaiety, Daly's, Coliseum and DruryLane are enshrined in a National programmeof July 5 entitled " Thirty Years of MusicalComedy."

JULY 2, 1932 25 =kw Wirdeo

Loud -speaker CracklingsSIR,-A permanent -magnet moving -coil

speaker, which I added recently to myreceiver, has now developed cracklingnoises during reception. I have reverted tomy original cone -type speaker temporarilyand find this does not give rise to thecrackles. It would seem, therefore, that thecrackling originated in the new speaker.Can you help me ? A. D. (Doncaster).

It would appear that the moving -coil in yourspeaker has got out of centre and is rubbingagainst the walls of the magnet. If yourspeaker has a centring adjustment deviceyou should find it a simple matter to loosenthe centring nut or screw and re -centre thecoil. If you do not feel equal to the task, weadvise you to return the speaker to themakers for re -adjustment. -En.

Voltmeter and Ammeter Tests

STR'-Ihave been endeavouring to dis-

cover a fault in my receiver which issupplied by an accumulator for L.T. and amains unit for H.T. I first tested theoutput voltages from the mains unit andfound that the maximum voltage availablewas 120 volts. The output is supposed tobe at least 15o volts. This I remedied bychanging the tapping on the mains trans-former from the iio-volt tapping to the135 -volt tapping. The output now indi-cated by the voltmeter is about 16o volts.Nevertheless, I still fail to obtain, receptionand must conclude I still .have a faultwhich cannot be traced with my meter.Can you assist me in this matter, please ?

B. L. (Leeds).Testing the output voltages of the mains

unit only indicates that the mains unit is ingood order.. The voltage readings you obtainare not accurate and are doubtless in excess ofwhat you imagine them to be. We do notrecommend you to use a voltmeter, unless ithas an internal resistance of at least r,000 ohmsper volt. If you want to test your set to dis-cover the fault; you should get a milliammeterand check the current consumption of eachindividual valve. The test may be carried outby disconnecting the wire normally connectedto the anode terminal of the valve under testand joining this wire to the positive terminalof the meter. A further wire from the negativeterminal of the meter should then be connectedto the anode terminal of the valve under test.When the receiver is switched on the currentflowing in the anode circuit of the valveshould be indicated by the meter. If no readingis indicated, no anode current is passing. Thecomponents throughout the anode circuit ofthe valve should then be tested for continuity.If the components are in good order, the valveitself may be faulty. The voltages on theanodes of the valves must be correct if thecurrent consumption of the valves, as indicatedby the milliammeter, is correct. The milli -ammeter test of a valve circuit is almost aninfallible one. -ED.

Receiver Building and PatentsSIRS I that the more

important patents in regard to wirelesshave lapsed and that it is now possible tomake up a straightforward receiver forsale without paying rcyalty. Can you

advise me whether I am correctly informedor whether it is still not possible to manu-facture a wireless receiver without payingroyalty. R. McT. (Fife.)

It is very unlikely that you will be able,even now, to make up a receiver which doesnot infringe some patent or other. Althoughcertain patents have expired, there are stillmany in existence. The whole question is onecalling for a complete knowledge of the patentposition and we think yoUr best plan would beto employ an agent who is conversant withthis. -En.

The Regional Scheme and theHighlands

SIR,-As a reader of your periodical sinceits beginning, I was interested to read

Mr. Alan Hunter's article on the B.B.C.'slatest plans. Mr. Hunter states : "Now,we are up against the fact that to completethe Regional Scheme there are not enoughwavelengths." Exactly ! The RegionalScheme is the root cause of the lack ofwireless reception in the Highlands, andother parts of Great Britain. The B.B.C.have cut their coat without the necessarycloth, and their so-called finished articleis a misfit.

We in the Highlands have been agitatingfor the past nine months for a Regionaltransmitter to provide for local pro-gramme material. The B.B.C. refuse togive us a Regional transmitter, becausethey have used,. up their wavelengthelsewhere, without having previously con-sidered the requirements of Great Britainas a whole.

This argument has been strcngly repre-sented to the B.B.C. in the course of theHighland agitation of the last nine months.I have already proposed to the B.B.C. wehave enough medium wavelengths withwhich to cover the whole of Great Britainwith Regional programmes if they will useDaventry 5 x x as the sole transmitter ofNational programmes. The new and morepowerful Daventry will cover the whole ofGreat Britain, and when this new trans-mitter is complete we shall have threemedium wavelengths to spare for use asRegional transmitters. This plan wouldgive the Highlands, north Wales ana otherparts presently blank all they require.

But for their stupidity and lack ofvision, the B.B.C. would have had thisplan in operation long ago.. Their presentscheme is deplorable and displays aconstructive plan of very poor merit.ANDREW MURRAY, Provost, Town House,

Dingwall.

A Really Wonderful SetC IR,-I should like to add my apprecia-

tion of a really wonderful set -the" Simple Super." It's quite a poor night ifI cannot get between fifty and sixtystations at full strength. lgr. James saidthe set gave him a' good deal of pleasure todesign, but this must be' nothing to thepleasure of the many builders. It's thebest set I've ever constructed. "

A. W. T, (London.

Newallta SalesGEVERYTHING RADIOEASIEST TERMS

IMMEDIATE DELIVERYCOSSOR MELODY

(MAKERModel 335. Complete with valves, Wii hSpeaker and Cabinet. Employs Cossor

14/6Variable -Mu S.G. H.F. stage, Detector andPower. Cash Price 47/17/6.Balance in 11 monthly payments of 14/6. order

SUPER V.3. KIT ("Radio for the Million") for Withmains, including valves, cabinet, speaker, and AO laA.C. mains equipment. Cash Price 415/11/3. !GA,/Balance in 11 monthly payments of 28/6. order

COSSOR ALL -ELECTRIC. MELODY MAKER, WithType 235. Complete with Valves andCabinet. 7/4Cash Price 49/9/6. 1Balance in 11 monthly payments of 17/4. order

*W.B. PERMANENT MAGNET MOVING -COIL WithSPEAKER P.M.3. Complete with 3 -ratio input 4/10Ira Cash Price 42/12/4.1/atan...2 in 11 monthly payments of 4/10. order000000 11*

R & A " 100 " PERMANENT MAGNET MOV- WithINC-COIL SPEAKER. Complete with multi -ratio C/Ainput -transformer. Cash Price 42/17/6.Balance in 11 monthly payments of 5/4. orderBLUE SPOT SPEAKER UNIT AND CHASSIS, WithTYPE 1000.

Cash Price £1,196.Cash Pricein 7 monthly payments of 5/5. order

W.B. PERMANENT MAGNETMOVING -COIL SPEAK ER With

Type P.91.4. Complete with Transformer 519Cash Price IM/21O.Balance in 7 monthly payhtenti of 5.9 Order

R.& A. CHALLENGER, PERMANENT MAGNETMOVING -COIL SPEAKER. With special Ferranti Withmulti -ratio input transformer. Will operate from a2 -valve itet up to a passer amplifier. Cash Price

41/15/0 orderBalance in 5 monthly payments of 6 6CELESTION P.P.M. PERMANENT -MAGNETMOVING -COIL SPEAKER, with impregnated Withdiaphragm and dual -impedance input transformer. a 16

Cash Price 42/716. V/Balance in 7 monthly payments of 616. orderULTRA IMP PERMANENT -MAGNET MOVING- WithCOIL SPEAKER, with input transformer.

Cash Price 42/15/0. 5/-Balance in 11 monthly, payments of 5/-. orderBLUE SPOT PERMANENT MAGNET MOVING- WithCOIL SPEAKER 8.100, kith input transformer.

Cash Price 43/15/0. 6/11Balance in 11 monthly payments of 6/11. orderCELESTION MOVING -COIL SPEAKER R.P.M.12. WithComplete with step-down transformer.

Cash Price 27/0/0.12/10Balance in 11 monthly payments of 12/10. orderATLAS A.C.188 ALL -MAINS UNIT. Two variable Withand one fixed tappings. Trickle charges 2, 4, or6 v. at .5 amp. Cash Price e6/0j0. gBalance in 11 monthly payments of 11/-. order*ATLAS A.C. ELIMINATOR, TYPE A.C.244. WithThree tappings S.G., detector, and power. Out- c /6put, 120 volts at 20 ma. Cash Price B2419/6.Balance in 11 monthly payments of 5/6. orderEPOCH J.1 PERMANENT MAGNET MOVING- withCOIL SPEAKER with 3 ratio input transformer: A /2

Cash Price, £2/5/0. 9r/Balance' in 11 monthly payments of 4/2. orderANY ITEMS ADVERTISED IN THIS JOURNALSENT C.O.D. IF VALUE OVER 10/. SENT ALL

C.O.D. CHARGES PAID.

6/6

To NEW TIMES SALES CO.56 Ludgate Hill, London, E.C.4Please send me (a) Free 1932 Catalogue

(b) for which. I enclose

first payment of E 11

Name

Address

Cf maIeur WirdeSi

The ACME ofCRAFTSMANSHIP

High GradeRADIO GRAMOPHONE

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Estimates Free. Estd 1S66.

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II or components of equivalent value. :II Wonderful offer to introduce the Radialaddin Club. III If rite lot gmtleulars. s. 'enclosing lid. ,/,,mi.) RADIALADDIN CLUB, Dept. ig. A.W., 47/48, Burners St., London, W.I. 31,,,,,,,,, 1-...2l .1110111111111111111MIIIIM1111110

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TAYLEX WET H.T. BATTERIESNew Prices: Jars 1/3, Sacs 1 /2. Zincs 1 Od. Sampledor.IS Volts complete with bands and electrolyte 4/ 1 post 91.Sample unit 6d. Illus booklet free. Bargain list free.AMPL IF IERS 30/.. 3 VALVE ALL-STAT ION SET O.A. TAYLOR, 57. Studley Road, Stockwell, LONDON.

for ' M as cot ' H.T. UnitSoundly constructed of selected steel andwire, and carefully tested before delivery-Heayberd 715 Mains Transformer was thenatural choice of Mr. Percy Harris for usein his Mascot' H.T. Mains Unit. Youcannot do better than r A.W.' Technicianswhen choosing Mains Components-selectHeayberd. Model 715 Transformer assurespowerful and accurate delivery with perfectvoltage regulation.

SECONDARY OUTPUTS230+'330V. 2+2V. 2+2v

4 amps.3oma. I amp.

MODEL71528/6

POSTTO -DAYI enclose 3d. in stampsfor descriptive Lists ofHeayberd Transformers, Com-ponents and Mains Units, willshelpful circuit diagrams.

M

Address

10 FINSBURY ST.,LONDON, E.C.2.

(One minutefrom Moor -

gate Utt-derg'd

St'n

Can

26

the Highlands Expect BetterBroadcasting?

J1 LY 2, 1932

ALTHOUGH it is an indubitable factthat Falkirk will provide most of

Scotland with a greatly improved serviceof broadcasting-far better signal strengthand better variety of programmes-wemust not overlook the limitation in therange of medium -wave stations, no matterhow high the power.

It is true that the great bulk of Scotland'sfour million odd inhabitants dwell insidethe reliable service area of the Falkirkstations, or will come within the serviceof the Aberdeen relay. But there is aminority, getting on for a million people,who are outside the service areas of Falkirkand Aberdeen, and these Highlanders are" kicking " at conditions.

I understand that the number of licencesinside the service areas just mentionedtotals 212,292, which does not seem a veryhigh figure. But we must remember thatregional high -power broadcasting hashardly begun in Scotland.

Meanwhile, of the potential listenermarket in the Highlands, there are atpresent only 27,039 licencees. The per-tinent question of the moment is whetherthis meagre section of the total licencees ofScotland can be expected to expand.

From recent reports on the situation,as issued by the B.B.C., it is obvious thatthe problem is at present unsolved.

One of the biggest hopes of the future liesin the increased power of the Daventrylong -wave station, which, on 120 kilowatts,at its Droitwich site, should penetrateeven to the Highlands with a reliable signalbearing the National programme.

Various suggestions have been made tothe B.B.C. for covering Scotland with abetter signal than has been obtained sofar, and the officials have carefullyexamined the most attractive of thesesuggestions-without finding any solution.

The first suggestion, and one verywidely expressed, is that Daventry shouldbe moved nearer to Scotland-not theplace, but the high -power long -waver ! Itis pointed out that the best strategicalposition for our long -waver is in thecentre of England, so that it covers themost densely -populated areas.

But even with the new high -powerlong -waver in the Droitwich site, the

greatly improved aerial system and thehigher power will mean a materially bettersignal in the north of Scotland.

Another suggestion is that the power ofthe Aberdeen station should be increased,and that it should be put back on its oldwavelength. 'The answer to this sugges-tion is that no matter what medium wave-length the Aberdeen station might workon, even a power of 50 kilowatts wouldnot provide a reliable service in the com-plaining areas.

Still another suggestion, again based onerroneous technical ideas, is that thepower of the Falkirk transmitters should beincreased. The limitation in the servicearea of a medium -waver is determinednot so much by the power as by the nightfading, which would occur long before theHighlands were reached, even with con-siderable power increase.

Although there does not seem anyimmediate hope of improving the lot ofthe Highlander, apart of course from theimminent increase in Daventry's power,we should not lose sight of the fact thatthe B.B.C. has to provide a service forthe whole of the British Isles; and in viewof the limited number of wavelengthspopulation figures must be taken into ac-count when considering the distributionof the stations. A. S. H.

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WHEN SUBMITTING QUERIESPlease write concisely, giving essential par.

titulars. A Fee of One Shilling (postal order),a stamped addressed envelope, and the coupon onthe last page must accompany all letters. Th3following points should be noted.

Not more than two questions should be sentith any one letter.The designing of apparatus or receivers cannot

be undertaken.Modifications of a straightforward nature can he

made to blueprints, but we reserve to ourselvesthe right to determine the extent of an alterationto come within the scope of a query. Modificationsto proprietary receivers and designs published bycontemporary journals cannot be undertaken. -

Readers' sets and components cannot be testedat this office. Readers desiring specific informa-tion upon any problem should not ask for it to bePublished in a forthcoming issue, as only queriedof general interest are published and these only atcur discretion. Queries cannot be answered bytelephone or personally.

Readers mdering blueprints and requiringtechnical information in addition, should addressa separate letter to the Query Department an.1conform with the rules.

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JULY 2, 1932 Wit -91T

CAS27

ING STATI NSBroadcasting Stations classified by country and i n order of wavelengths. For the purpose of better comparison,

the power indicated is that of the carrier wave.Kilo- Station and Power Kilo- Station and Power Kilo- Station and

ll'etres cycles Call Sign (Kw.) Metres cycles Call Sign (Kw.) Metres cycles Call Sign.GREAT BRITAIN

25.5311,751 Cill'iMSiOrd(G5S \ V) 16.0

211.37,420 Newcastle 1.2114.3 1,400 Aberdeen 1.024_.37,238 Belfast 1.0201.0.1,247 London Nat 50.0288.5 r,o.pi Swansea 0.15288.5 r,u4a Plymouth 0.15288.5 2,040 Bournemouth 1.0288,5 7,o4o Scottish National 50,0288.5 2,o4o Newcastle (temp.) 1.0101.5 995 North National 50.0309.0 968 Cardiff 1.0355.9 843 Loudon Regional 50.0376.4 797 Scottish Regional 50.0398.9 752 Midland Regiohal 25.0480 625 North Regional 50.0

1,554.4 293 Daventry (Nat.) 30.0AUSTRIA

218 r,373 Salzburo' 0.5245.92,229 Linz 0.5285.2 1,053 Innsbruck 0.5352.1 852 Gra/ 7.0453.2 662 Klagenfurt 0.5517 5(1 Vienna 15.1)

also testing on1,253.3111.7rom 7.0p.m.(Mon., Wed., Sat.).

BELGIUM207.3 2,447 Franchimont 0.2209 1,435 Antwerp 0.4210.11,428 Liege (Seraing) 0.15215.31,393 Chatelineau 0.2215.52,392 Bruxelles

Conference 0.2215.57,392 Liege 0.1220 1,364 Binche 0.3230.31,304 Radio Wallouia 0.3241.5 2,441.8 Liege (Lap-) 0.1245.9 1,220 Radio Schaerbeek 0.3209.31,114 Liege ( Coin te) 0.4283 /' o6o Brussels (SBR) 0,5337.8 888 Brussels (No. 2) 15.0509.7 558.4 Brussels (No. 1) 15.0

BULGARIA318.8 941 Sofia (Rodin:. Radio) 1.0

CZECHO-SLOVAKIA58 5,17.2 Prague 0.5

249.6 2,20/.8 Prague (2) 5.0263.81,137 Morayska-

Ostrava 11.0279.32,074 Bratislava 14.0293 7,022 Kosice '2.5341.7 878 &nun (Brim) 35.04884 614 Piague 120.0

DENMARK281.21,067 Copenhagen 0.75

1,153 260 Ralundborg , 7.5also on 31.51 m. (9,520 Kes.)

ESTONIA 413 725 Athlone 60.0298.8 2.004 Tallinn 11.0 ITALY465.8 644 Tartu 05 25.4 1-2,810 Rome (2R0) 15.0

FINLAND 247.7 2,222 Trieste 10.0291 1,031 Viipuri 13:0 273.7 2,095 Turin (Torino) ... 7.0368.1 825 Helsinki . .... 12.0 280 1,072 Bari (testing) ... 20.0555.5 542 Tampere 1.0 312.8 959 Genoa (Genova) 10.0

3,796 367 Lahti 54.0 318.8 94.2 Naples (Napoli) 1.5FRANCE 331.5' 905 Milan 7.0

220 2,363.7 Beziers - 0.5 368.1 825 Bolzano 1.0X2.42,348.6 I, ecamp 10.0 441 680' Rome (Roma) ... 50.023.6.2 1,267 Bordeaux- 500.8 599 Florence (Firenze) 20.0

SudOuest 2.0 526 570.3 Palermo 3.0249.62,201J Juan-les-Pins 0.5 LATVIA

198.51,520 Riga (tests) 16.0625 572 Riga ...... 15.0

254.7 1,177.2 Toulouse (PTT) 1.0265.41,130 Lille (PTT) 1.3271.4.1,705 Rennes 1.2286 1,049./ Montpellier 0.8279.5 1,073 Radio Lyons 10.029.3.71,021.5 Limoges (FTT).- 0.5304.9 984 Bordeaux (PTT) 13.0e0e.6 972 Radio Vitus 1.0

also on 43.75 in. (6,865 Res.)315 95o 31arseilles 1.6

Power(Kw.)

329.7 910 Poste Parisien ... 85.0 ' NORWAY345.2 869 Strasbourg (PTT) 11.5 235.51,274 Kristianssand 0.5370.4 8.zo Radio LL (Paris) 1.0 240.6 1,247 Stavanger 0.5

' also on 33m.(9090 Kos.) -364 824 Bergen 1.0384.4 779 Radio Toulouse 8.0 367.6 826 Fredriksstad 0.8447.1 672 Paris (PIT) 0.7 493.4 608 Trondheim 1.2465.8 644 Lyons (PTT) ... 1.5 1,083. 277 Oslo 00.0

566 530 Grenoble (PIT) 2.0 POLAND1,445.7 207.5 Eiffel Tower 13.5 214.2 1,400 Warsaw (2) 1.91,725 274 Radio Paris 75.0 235 7,283 Lodz 2.2GRAND DUCHY of LUXEMBURG 312.8 959 Cracow 1.51,250 240 Luxemburg (temp,) 1.0 335 896 Poznan 1.9

GERMANY . 380.7 788 Lvov . 16.1),19.73715,200 Zeesen (DJB) .... 8.0 403 734 Katowice 12.0

31.389,550 Zeescn (DJA) ... 8.0 563 533 Wilno 16.0217.11;332 Ktinigsberg 0.9 1,411.8 212.5 Warsaw 120.0213 2,373 Flensburg 0.6 PORTUGAL232.2 1,292 Kiel ' 0.25238:91.256 Nurnberg 2.0245.9 1,220 Cassel 0.25253 2,184 Gleiwitz 5.0259.3 2;257 Leipzig 2.0269.81,112 Bremen 0.2276.5 1,085 Heilsberg ... -60.0283.6 2,058 Magdeburg 0.5283.62,058 Berlin (1.,;) 0.528:3.62,058 Stettin 0.5318.8 94/ Dresden 0.25325 923 Breslau 60.0360.5 833 Miihlacker 60.0372.2 8o6 Hamburg 1.5389.6 77o Frankfurt 1.5389.6 770 Leipzig (testing)120.0419.5 7.25 Berlin 1.5453.2 662 Danzig 0.5472.4 635 Langenberg 60.0532.9 563 Munich 1.5559.7 536 Kaiserslautern 1.5559-.7 536 Augsburg 0.3569 530 Hanover 0.3509.3 527 Freiburg 0.25

1,634.9 183.5 Norddeich 10.01,634.9 283.5 Zeesen 75.02,525 319.3 Konigswuster-2,900 203.5 hansen (press) 15.04,009 75 ditto

HOLLAND296.12,013 Hilversum* 8.5

1,071.4 ado Scheveningen -Haven 10.0

1,875 26o Huizen 8.5.20 Kw. Station testing

HUNGARY211.2 1,417 Budapest (2) 3.0550 545 Budapest (1) 18.5

ICELAND1,200 25o Reykjavik 21.0

IRISH FREE STATE224.42,337 Cork (OCR) 1.2

LITHUANIA1,985 155 Kaunas 7.0

NORTH AFRICA363.3 825.3 Algiers (P'IT) 16.041.6 722 Radio Marop

(Rabat) 6.0and 32.26-m. (9,300 Kes4

241.6 2,242,8 Oporto 0.25282.21,063 Lisbon (C1 IAA) 2.0

also on 31.25ROMANIA

391 761 Bucharest 12.0RUSSIA

348.8 860 Leningrad RV70 20.0358 838 Moscow (Exp.) 15.0385 779 Stalin() (RV26) 15.0389.6 770 Archangel 10.0473.2 634 Sebastopol 10.0502.4 597 Niini Novgorod 10.0644 465.8 Kazan (RV17) 10.0720 426.6 Moscow (PTT) 20.0824.2 364 Sverdlovsk R V5 50.0849 353 Rostov (Don) 4.0937.5 320 Kharkov (R V20) 25.0

1,000 300 Leningrad 100.01,032.6 290,5 Kiev 25,01,071.2 28o Tiflis 35.01,103 272 Moscow Popoff 75.01,171.5 256 Taschkent 25.0

1,250 240 Bakou 35.01,271.5 236 Minsk (RV10) _35.01,301 23o Moscow (Trades

Unions) 165.0also on 50 in. (6,00o Hes.)

1,380 227.5 Novosibirsk 100.01,482 203 Moscow 100.0

also on 46,6 in, (6438 Kos,)1,600 187.5 Irkutsk . 15.0

SPAIN252.3 1,289 Barcelona (EA J15) 6.0267.6 1,121 Valencia 8.0348.9 86o 13arcelona(EAJ1) 8.0363.1 815 Seville (EA15) 1.5411.4 729.2 Madrid (EAJ7).... 2.0424.3 707 Madrid (Espaila) 2.0450.6' 557 San Sebastian

(EAJ8) 0.6SWEDEN

231 1,30z Malmo 1.25257 ,,z66 Florby 10.0307 977 Falun 0.5321.9 932 Goteborg 10.0435.4 689 Stockholm 55.0541.5 554 Sundsvall ...... _ 10.0770 389 Ostersund 0.6

1,229.5 244 Boden 0.61,348.3 222.2 Motala 30.0

also on 49.46 in. (6,065)SWITZERLAND

244.11,229 Basle 0.65245.9 2,220 Berne 0.5403 743 Sattens 25.0459.4 653 I3eromuenster MO700 395 Geneva 1.25

TURKEY1,200 250 Istanbul 5.01,538 395 Ankara 7.0

YUGOSLAVIA307 977 Zagreb (Agram) 0.75430.4 697 Belgrade 2.5574.7 522 Ljubljana 2.5

The New "LANGMORE" Ho. ClRADIO GRAMOPHONE CABINETS

These cabinets are very strongly constructed ofselected Oak. Size overall, 3 ft. f- in. high by 21 in.

wide by 15 in. deep.THE TOP SECTION. Size, 43 in. high by 18 in. wideby 14 in deep, gives ampleaccommodation for gramophonenr niclo-up;THE CENTRE SECTION. Sire, 10 in. high by 18 in.wide 6y 14 in. deep, is for the Wireless Set, to take a paneleither 18 in. by 7 in. or 18 in. by 8 inTHE BOTTOM SECTION. Size, 16 in. high by18 in. wide by 133 in. deep, gives accommodation for Loud-speaker and Batteries. With "GALLEON," as illus-

." traced, or - CATHEDRAL " Fret Fronts.Wooden panels to ft, with oval aperture, 12 in. by

53 in., 21- extra.The whole of the back is enclosed by double doors, co thatall parts are easily accessible. ALL are fitted with hingedtop, heavy platform to take a 12 -in. turntable for theGramophone, and a substantial baseboard for the Wireless

Set.BEAUTIFULLY FINISHED JACOBEAN OAK

The MISCELLANEOUS TRADING Co. Ltd.ES. Et IT. New. Oxford St., London. W.C.IPhew: Holborn 4994. Trade Inquiries Invited

49/6 eachPacked FREE and sentCarriage Paid to any address

in Great B. itain

OURBLUEPRINT

SERVICEConstructors of re-ceivers described inthis Journal shouldmake full use ofour Blueprint Ser-vice and avoid all

risk of failure.

Advertisement of Belling El Lee, Limited, CambridgeArterial Road, Enfield, Middlesex.

CHARGINGD.C. SETS A.C.

If you are interested in the profit-able charging of a number of RadioCells and a few Car Batteries at

one time, write us for details.SILENT - EFFICIENT - SIMPLE

LESLIE DIXON ogr218, Upper Thames St., E.C.

SET CRACKLING IS ANNOYING!

IF IT'S YOUR

SWITCH

eachlitPostFres

-PatentsPending

FIT THE" BUSCH" SWITCHand ensure perfect switch contactlThere is no contact point to turnsround, and when you "switch ouyou have contact like a sower

switch.They are as cheap as the inferiortype tut tar superior in operation.

From your local dealerSalford's Cycle Stores, or

BUSBY & CO., LTD. (Patentees)Dept. A.W., PRICE ST., BIRMINGHAM

REPAIRto Blue Spots 5/-, Loudspeakers, Head -

I" phones and Transformers 4/- each.Mains and Eliminators quoted for. Prompt Service.12 months' guarantee. Trade invited.laud -water Repair Co., 2 SHIPKA ROAD, Ram London

niateur Wirdeej

PREPAID ADVERTISEMEN ISAd'vertisements under this head are chargelTHREEPENCE PER WORD, minimum charge

THREE SHILLINGS. DEPOSIT SYSTEM.As (he publishers cannot accept responsibility for the bons

(Ides of advertisers in this publication, they have introduceda system of deposit which it is recommended should beadopted by readers when dealing with persons with whomthey are unacquainted. It is here explained.

Intending purchasers should forward to the Publisher:the amount of the purchase money of the article advertised.This will be acknowledged to both the Depositor and theVendor, whose names and addresses must necessarily begiven. The deposit is retained until advice is received ofthe completion of the purchase, or of the article havingteen returned to and accepted by the Vendor. In additionlo the amount of the deposit, a Fee of 6d. for sums cf £1sad under, and is. for amounts in excess of £1, to coverrestage, etc., must be remitted at the same time. In casesct persons not resident within the United Kingdom, doubleIces are charged.

The amount of the Deposit and Fee must be remitted byf ostal Order or Registered Letter (Cheques cannot berecepted,) addressed to"AMATEUR WIRELESS" ADVERTISEMENT DEPARTMENT,

58/61 FETTER LANE, LONDON, E.C.4.

PATENTS. -Trade Marks, "Advice Handbook" free. -B. I. hing Regd. Patent Agent, 146a Queen VictoriaStreet, London.DETAILED INFORMATION ON ANYTHING RADIO.-We elucidate all those difficulties in connection withshort-wave transmission and reception, including obtainingthe amateur transmitting permit; dependable advice onbroadcast and radiogram problems; full details, includingdiagrams. Charges : 3/- per query ; four or more, 2/6 each.Questions involving elaborate treatment quoted for byreturn.-11adio Technical Agency, 2 Westgate Chambers,Newport, Mon.

REPAIRS-Undy Loud -speakers and all classes and typesof radio and electrical equipment. Conversions D.C. toA.C. and vice versa. Long -wave coils fitted to Americanreceivers, etc. All repairs guaranteed. Best -qualitycomponents only used. Write for quotation to ExpressRadio Service Co., Dept. A, 5 Great Chapel Street, OxfordStreet, W.I. (Special terms to traders.)

WEEDON POWER LINK RADIO CO. -New service totheir many clients. Transformers, Loud.speakers, Pick-ups, any make or item - repaired as new 3/6. Articlesreturned to you C.O.D. Post. Eliminator repairs quotedfor. Supervised by specialisgs. Note new address. -185.Earlham Grove, Forest Gatc, London, E.7.

GILBERT INDUSTRIES GUARANTEED BARGAINS. -Three -gang .0005 Tuning Condensers by Polar, split endvane trimmers, with or without slow-motion cidive. List1.2ricce, 35/-; our price, 10/6, post free. Maths Triduformers.

ceptionally heavy job, with core of 32 stalloy, clampedin rigid girder frame; tagged and marked 210; 230, 250volts tapped input, 50-60 cycle; 4 volts 4 amps. centre -tapped filament winding, 4 volts 2 amp. rectifier; 325-0-825secondary, at 85 ma. Worth 50/-; offered at 15/-, post free.Polymet Electrolitic Condensers, 8 mfd., 435 working, volt-age. List, 12/6; our price, 4/-, post free. Stalloy andLohys' stampings and bobbins cheap. Small 20-k.Constant Inductance Eliminator Chokes. List price, 7/6;our price, 3/6, post free. Output Chokes tapped forpentode, or suitable for smoothing. List, 17/6; offered at6/-, post free. Satisfaction or money refunded. -GilbertIndustries, 519 London Road, Westcliff-on-Sea, Essex.

WIRELESS AS A CAREER. -Those already engaged inthe radio industry and those who would like to obtainemployment in this interesting profession should write for

copy of our booklet, sent post free withNorthern Counties Wireless School, 55-57 Guildhall Street,Preston.

SALES BARGAINS. -Simple Super Kits £6 5 0. S.T 300Author Kits, £2 15 0. Meteor III Kits, £2 14 0. Cosmic

£2 4 0. Challenger DIX. P.M. Speaker, £1 6 0. W.B.P.31.4, Speakers with Transformer, £1 16 0. Send usyour requirements, quotations per return. ServweilWireless Supplies, 74 Gough Street, London, E.14.

PART EXCHANGE RECEIVERS at Bargain Prices, over-hauled, guaranteed; state approximate requirements forquotation.s.-Coutts, Wireless Engineers, Morley.

BUY BRITISH !-The " Tonic " Self -generating Trickle -charger Kit keeps 2 -volt L.T. accumulators fully chargedat home. Electric mains unnecessary. Inimitable forremote places. Obtainable only from maker, 7/- each;postage, 9d. -Williams, Netherend, Cradley, Birmingham.

DRUMSKIN PARCHMENT CONE PAPER. Timbrous,resonant, tough -reproduces the full acoustic range, 1/ -sheet (24 by 18 in.). Post free. -Gaunt, Caledonian Road,West Hartlepool.

CYCLES 1 MOTOR -CYCLES ! RADIO I Send for particu-lars of our system of trading. Do not be held up forsupplies.-Brookmah Rapid Radio Service (head office),105 Spencer Street, Birmingham.

INIRELESS COMPONENTS. -All makes supplied. Specialdiscount home constructors. Also Cabinets. New leafletready. -Send to Imperial Radio, 18 Summerhill Street,Birmingham.

BANKRUPT BARGAINS. -List free with 3v diagram.All parts, speakers, pick-ups, eliminators, valves, keenestprices. Ask requirements. Quotes return. Modern parts:liken in part exchange,-Btitlin, 143B Preston Road,Brighton.

28

FERRANTI FROM 18S2 TO 1932WE have just attended a most interest-

ing exhibition staged by Messrs.Ferranti, Ltd., at Bush House, London,this being one of the features of the firm'sfiftieth birthday celebrations.

It was on. September 15, 1882; that thelate Dr. Ferranti's original company wasestablished, and the intervening fifty yearshas seen remarkable strides in the progressof the existing company.

Although most of us are apt to think ofFerranti in connection with such highlights of the -radio industry as the AF5transformer, we must not overlook the factthat this firm has very wide ramificationsin every part of the electrical industry.

The interesting exhibition arranged atBush House emphasises this fact, and wewere able to inspect such products asFerranti meters, including those used in thegrid system, huge transformers, and instru-ments for household electricity supply.

Then we saw the now well-known Fer-ranti electric clocks for use on frequency -controlled mains supplies, Ferranti electricfires for hanging on the wall, as well as theordinary type, and many other products.

The outstanding exhibit of the radiosection is the new Ferranti seven -valvesuper -het band-pass console, which willundoubtedly prove to be one of the hitsof the season. To sell at the low price of22 'guineas, this new set employs all thelatest super -het ideas. A great deal ofmoney must have been spent on the toolsfor:the production of this set, which incor-porates coils and condensers of great

_precision.

"Amateur Wireless and Radiovision." PriceThreepence. Published on Thursdays and bear-ing the date of Saturday immediately following.Post free to any part of the world : 3 months,9s. 6d. 6 mariths, 8s. 9d.; 12 months, 17s. 6d.Postal Orders, Post Office Orders, or Chequesshould be made payable to " Bernard JonesPublications, Ltd."General Correspondence is to be brief andwritten on one side of the paper only. Allsketches and drawings to be on separate sheets.Contributions are always welcome, will bepromptly considered, and if used will be paid for.Communications should be addressed, accord-ing to their nature, to The Editor, The Adver-tisement Manager, or The Publisher, "AmateurWireless," 58-61 Fetter Lane, London, E.C.4.

EASY TERMSWE supply all cool quality Radio Receivers, Components 0,

and accessories on deferred terms. We carry adequate PgF.: stocks and can gins PROMPT DELIVERY.0 12 EXIDE W.H. HIGH-TENSION ACCUMULAT033 (121 oft.r ,g,. coo° Inia). Large capacity type. Quit Price .. 5.3 15 5 ,,,74

BB Or 5'. with order and 10 monthly payments of 711). Ere. Carriage charged on all orders from Scotian].rd This is the best and cheapest fora of High Tension supply .9.,

zr. sobers the electric light mains are not available: 2E. Send list of requirements, and quotations mil be sent by return. "d

Price list l'ItEb,' au request.

_La LONDON RADIO SUPPLY CO.,(ESTANCED N.a. It, OAT LANE, NOBLE ST LONDON, E.C.2 HfilI",,4,i;

1100055011E001011100001EDENDEOLICEXEMEGIONIMINTERIEN

MICROFU GOLD FILM FUSESspecified by P. W. Harris for the " MASCOT MAINS UNIT"NEW FLAT TYPE from 50 m/a upwards.

Fuses 6d. Holders 6d. Complete 1/..This is a gold fuse -not wire.

000. tell? al rel.y105% B. i:ish.OW rya ..1111

'-"

MICROFUS e -S, Ltd., 36, Clerkeowell Road, E C.ITelephone: Clerk. 4049

JULY 2, 1932

FULL -.SIZE BLUEPRINTSWhen ordering, reuse sent Postal Order NOT STAMPS

CRYSTAL SET (6d.)1931 Crystal Set .. AW3O8

. ONE -VALVE SETS (Is. each)

B:B.C. One -valve -

Short-wave One -valuer . AAWW3347Easy to Build One

TWO -VALVE SETS (1 each)Aw344

The 25/- Two (D, Trans)*

°PT; Pen.).AAW309

Big-ovS°Itlrr 2 (e 11,7\ v,

Inexpensive A.C. 2 (D. Trans.) ..

W31

Midget Two (D.RC.) . AAAAAWWWWW33333443336886()

Ten -Station Two (D, Trans)Big -Power Melody 2 (D. Trans) Ever Tuned Regional Two (D, 'Trans!.. WM241

New Economy Two (D, 'Frans)

Station -finder Two (D, Trans) .. .. WM253Music Lover's Two (D, 'Frans) ..

WM265WM260

Family Two' D, Trans) .. WM275Screen -grid Two (SG, Trans) WM289Economy A.C. Two (D. Trans) WM286

THREE -VALVE SETS (Is. each)35/- Three-valver (D,2RC) . AW323Baby Three (D.RC, Trans) .. AW3241932 Ether Searcher (SG,D,Pen.) AW325Wide World Short -Wave Three (D,RC, Trans) AW332New Favourite Three (D,RC, Trans) AW334Home -lover's All -electric 3 (SG, D, Trans.) AW335'The P.W.H. " Mascot " (D,RC, Trans) AW337

AAA WWW3144419New Regional Three (D,RC, Trans)

Home -lover's Battery 3 (SG, D, Trans)£8 Radio -gram (SG, D, Trans)

Five- oint Three (SG Trans) ' . WM212New rookman's Three (SG,D,Trans) .. WM218Five -point Short -waver (D,RC, 'Trans) .. WM223Band-pass Inceptordyne (SG,D, Trans) .. WM244Ether Marshal (SG,D,Trans) .. WM247Meridian Short -waver D,RC, Trans) .. WM256Five -advantage three ( Frans) . WM257Everybody's Radiogram (SG, D, Trans) .. WM258Double Band-pass Three (SG, D, Trans) . WM259Everybody's Radiogram (with Automatic G.B.) WM262New Economy Three (SG, D, Trans) .. WM263New Plug-in Coil Three (D, 2 Trans) .. WM270Transportable Three (SG, D, Trans) .. .. WM271Multi-Mag Three (D, 2 Trans) . WM288

FOUR -VALVE SETS (is. 6d. each)Everybody's Radio -gramophone.. AW310Four Star 4 (SG,

RD,

RC, Trans).. AW31850/- Four (SG, IS, C, Trans) .. AW331.Five -Point Four (SG, D, RC, Trans). .. WM216Brookman's Three -plus -one (SO,D,RC, Trans) WM233Ether Rover (SG, D, RC, Trans) WM266Quadradyne (2 SG D. Pen.) .. WM273Double Band-pass Four (SG, D,RC, Trans) .. WM274Everybody's Radio Gram. (SG, D, RC,Trans) WM276A.0 Quadradyne f2 SG, D , Pen) .. WM279Ideal A.C. Home Super (Super -het) WM290

FIVE -VALVE SETS (1s. 6d. each)A.C. Britain's Super (Super -het) AW322James Short-wave Super (Super -het) AW328Simple Super (Super -het) AW340Ideal Home Super (Super -het) WM280Easystunme 6.0v(SAupLerv-hEet)s..

SET (1s. 6d. each), .. WM284

Century Super (Super -het) . AW287A.C. " Century Super " (Super -het) ..

AWMains Unit (1/-) . .AW29259A5Super 60 (gtiper-het) WM229A.C. Super 60 Radio Gramophone (Super -het) WM239A.C. Super 60 (Table Model) .. .. WM245Super 60 (with Wearite base) .. .. WM249Super 60 (with Lewcos base) .. .. WM2511932 Super 60 (Super -het) . , .. WM2691932 A.C. Super 60 (A.C. Super -het) WM272SEVEN -VALVE SETS (1s. 6d. each)

Ss nu ee rr SS ee nn oo rr ((wS uepaerri eh et

base and frewcosLewcos.. WWMM226561

PORTABLESHiker's Two (D. Trans). .. . AW345Town and Country Four (SG,D,RC, Trans) WM282Everybody's Portable (Super -het) .. . WM291

AMPLIFIERS (1s. each)Add-on I -1.F. Screened -grid Unit .. AW296Universal Push-pull Amplifier . .. AW300"AM." Record Player(LF, Push-pull) AW319Quality Amplifier (DC), 1 /6 .. .. WM264A -P -A (Power Amplifier for A.C. Mains) WM275A -P -A Radio Unit (SG,D) .. .. WM281Economy Gramophone Amplifier . WM277

MISCELLANEOUS (is. each)" A.W." Tone changer (6d.) .. . AW288" A.W." Selectivity Unit (6c1.) .. AW290A.C. Trickle Charger .

Amateur's Linen SpeakerD.C.H.T. Unit AwW330127

*Output Unit for Pentode Sets .. AW316Short-wave Plug-in Adaptor . . AAwW32296

thenShort-wave.WSearcherSuper-het

hc hoerrt -wave Adaptor . . . . . . AW 339

rAdaptoromotor*board A W333

Big H.T. Unit for A.C. Mains ..Loud -speaker Tone Control .. .. WM234" W.M." Linen Diaphragm Loud -speaker WM235

Voltage Regulator

TS uwpoe-rM6 iOn

e

A Simple Mains Unit .. .. WM283

Autc udanpittor for Short .Waves

WM285CopiesSlior tc-rtahs;

Dig iirreel eestomar ( g6a.d u) (. v;, :earl me teAr.)

eur Wireless.ei 8. .7

tinning descriptions of most of these sots can be obtainel at ls. 3d. sal4d. respectively, post tree Index ..letters "A.W." refer to "AmatoWireless " sets and "Whi." to 'Wireless fdaxasine."Address letters :

AW305

Amateur Wireless Blueprints Dept., miS,',r4t!..Ete.1.

INFORMATION BUREAU

mateurWireksi COUPONAvailable until Saturday

FEE 1/- JULY 9, 1932

JULY 2, 1952

IF you use WestinghouseMetal Rectifiers, the pre-

vailing 'wind" will alwaysbe favourable - constantand adequate voltage withno replacements. Then,there will never be a 'de-pression" in your homebecause "the rectifier hasburnt out", or "t"e out-put of the eliminator is

dropping". Send 3d.stamp to Dept. "A.W."for a copy of "The AllMetal Way" giving fullparticulars.

The Westinghouse Brake & Saxby Signal Co., Ltd., 82 YorkRoad, King's Cross, London, N.I.

An Amazing Offer from

SELFRIDGE'SRADIO DEPARTMENT

SELFRIDGE'S PRICE 1

MOO Ira cotMw

!

Usual price 32/ -

Will play 2 full12 -inch electricalrecordings or 3-4average 10 -inch

records

500 EDISON BELL MOTORSMade of the highest quality materials obtainable. Enhance thevalue of any Gramophone, completely silent, 12 -inch velvetcovered turntable. Inside or outside Turntable Brake, newpattern speed indicator, winding key, escutcheon with fibrebrushes, 3 motor holding screws with rubberand metal washers. (Postage 1. 9 extra) PRICE 5/6

SELFRIDGE'S radio Department, First Floor, OXFORD ST, LONDON,W.1.

ill

natfAu IlitreLT

A miniatureMARVEL

SIZE-2r long x 1;v" wide x ft" high

Nom..

SPECIFIED FOR THE"NEW REGIONAL THREE"

TheILIEWCOS

H.F. CHOKE(Type M.C.)

Price 216

Qualities such as those embodied in theLewcos Type M.C./H.F. Choke are seldom

found in even more expensive and largerchokes. Rigorous tests have proved thatmaximum choking effect is obtained with ease,

and its small size makes its use especiallysuitable where space is limited.

The exceptionally low price of this componenthas already established it as a permanent

favourite amongst both experts and amateurs.

WIRE YOUR SETwith Glazite Wire.,====Price 6d. per soft. coil.

,-.

LEWCOS RADIO PRODUCTS FOR BETTER RECEPTION

THE LONDON ELECTRIC WIRE COMPANY AND SMITHS LIMITEDCHURCH ROAD LEYTON, LONDON E.10

Advertisers Appreciate Mention of "A.W." with Your Order

mateur Wi-rdesi iv JULY 2, 1932

BLUE SPOTPERMANENT

MAGNETCHASSIS

75/-HIRE PURCHASETERMS ARE AVAIL.ABLE FOR ALLBLUE SPOT PRO.

DUCTS.

BRITISH MADE

"Ah tor mah wife she was aloud speaker las' night"

"What ! Yo' called yo' wife a loudspeaker an' yo' is still unharmed?"

" Yeah, she's heard a Blue Spot Speakeran' jes' took it for a compliment."

No wonder-the rich mellow notes that flow sofreely from all Blue Spot Speakers have a charmthat passes the power of words. They clothespeech with dignity; they impart to music majesticgrandeur or simple sweetness ; in a word theyreproduce so perfectly that all realisation of themechanical vanishes as at the touch of a wand.

Take the Blue Spot Permanent Magnet Chassisillustrated below, for example. It is a luxuryspeaker with a degree of sensitivity and flexibilitythat is as high as it can well be. Every note in?e whole musical scale is reproduced by it soaadkriand freely, that the difference between it and

othetspeakers is the difference between a first yearpupil and a prima donna.

Ilk wonderful performance of the Blue SpotPermanent Magnet is due to the exclusive type ofmagnet used, although the superlative design andthe specially designed cone play their part. Anywaythe result is the same-the most perfect moving -coil speaker ever produced. Write for CatalogueNo. A.W.40.

TIM 1611111AV 111311.114 CDMIPANY airi)BLUE SPOT HOUSE 94/96 ROSOMAN STREET ROSEBERY AVENUE LONDON E C

Telephone: Clerkenwell 357o. Telegrams: "Bluospot, Isling, London."Distributors for Northern England, Scotland and Wales: H. C. RAWSON (Sheffield and London), Ltd., too, London Road, Sheffield

22, St. Mary's Parsonage, Manchester; 37, 38, 39, Clyde Place, Glasgow

Printed by The Sun Engraving Co. Ltd., London and Watford. Published by Bernard Jones Publications, Ltd., 38-61 Fetter Lane, London, E.C.4.Sole Agents for South Africa : CENTRAL NEWS AGENCY, LIMITED, Sole Agents for Australasia : GOttooN & GOTCH, LIMITED Saturday, July 2, 1932