AUG. 13 PORTABLE CONSTRUCTION HINTS 15 CENTS

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- -America's First and Only National Radio Weekly

A Big Idea onBalsa Wood Speakers

An Analysis of Output Tubes

The Toto Power Well

AC TUBES MAKE 7 -VALVE SET BATTERYLESS

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SIDE VIEW of the AC Receiver (above), wit h catacomb assembly at rear. See page 4

( DISTORTION FOREVER See page 7)

TROUBLE SHOOTING IN RAYTHEON B ELIMINATORS

RADIO WORLD August 13, 1927

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SIXTH YEAR

Vol. XINo. 21

Whole No. 251August 13, 1927

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[Entered second-class matter, March, 1922, nt the pa at office at New York, N. Y., under Act of Match, if0.71

Some Hints on the Construction of

Aortable eceiverBy Herbert. E. Hayden

Photographs by the Author

i Hayden)

HOW a portable appears in ready -to -carry position is shown in the upper left-handphotograph. The lower picture at left shows the arrangement of the fixed radio andaudio transformers. In the center is a view of the set in an operating condition. Notethe speaker aperature in the cover. In the upper right hand photograph is a closeupof the front panel or case. The condenser knob is at left, with two rheostats at theright. The last photograph to the right shows the "inside works" of the set. Note

the speaker opening and mesh over it, on the cover.

HINTS on the successful constructionof a portable set often result in

space conservation and also a gain ofefficiency.

A stage of tuned radio -frequency am-plification, one of fixed radio frequencyamplification, a non -regenerative detectorand three stages of low -ratio transformer -coupled audio -frequency amplificationmake up a good combination. Only onetuning control is necessary.

A small suitcase, such as used by week-enders, houses the receiver, tubes, batter-ies, speaker and loop. How the partsshould be laid out is shown in the lowerleft-hand photo.

The radio frequency and detector sock-ets are placed in the rear of a piece ofpine, this being the baseboard. Theaudio frequency portion is the front. Thispart of the circuit is wired before beingplaced in the case.

Flexible Wire Used

The variable condenser is then put onthe side of the case, where the lock ap-pears. Volunfe controls, in the form ofa pair of rheostats may also he placed

here. The complete set call then be wiredup, using flexible wire.

The A and B batteries are placed along-side of the set. For A batteries, 4% -voltC batteries are used, while small 22% -volt batteries are used for B supply (90volts). A loudspeaker unit and midgethorn are used to make up a reproducer,this being placed between the batteriesand the side of the case, carrying thetuning condenser.

So that it will not be necessary to openthe case every time you desire to listen in,an opening is made in the cover, directlyopposite the opening of the horn. Wiremesh should be employed to hide the rawedges of the cut portion and prevent in-jury to the interior. This is shown in thelower right hand photo.

For best results a large folding typeloop is recommended. It is then possiblecompletely to dissemble the loop andcarry the complete receiver around incomfort. How compact it appears, whenin this shape is shown in the upper left-hand photograph.

The center photograph shows how thereceiver appears when in operation. Ajack, placed at the battery end of the

case, receives the plug of the loop. Bind-ing posts are placed near this point,should it be desirable to use an externalspeaker.

To hold the batteries in place, alumi-num stripping is located along the edgesclose to the speaker.

Constants Discussed

When shaving insulation off the wire,be careful not to take off too much, forthere will then be the danger of the bareportion touching some joints and causinga short, since at many points it is neces-sary to lay the leads in close positions.

One rheostat is placed in series with thenegative legs of the two radio frequencytubes. The other is placed in series withthe negative legs of the detector. Three4V-199 Amperites control the filament ofthe audio tubes.

The grid leak resistance should beabout 6 megohms, while the grid con-denser should have a value of .00025 mfd,Any type or size variable condenser .mayhe used, as long as it, matches the loop tobe used. Generally the .0005 or .00035 mfd.type loop is employed, with condenser tomatch.

4 RADIO WORL,D August 13, 1927

AC TUBES Make This 7 -Tube Set

FOUR VIEWS of the AC receiver. The front panel has two National dials, a volume control (at center), a switch and a pilotlight. A view from the top discloses the layout of parts. At bottom (left) is the binding post strip for filament leads, with thecommon center point connected to post at extreme left. The opposite side of the set (right) is the input, where the loop is con-

nected. The final audio biasing resistor is in full view.

THE introduction of AC tubes on themarket initiated a slow revolution in

radio design which will ultimately re-place the storage battery as completely asthe automobile has replaced the buggy.The new tubes are thoroughly practical,and any troubles can always be tracedto lack of technique on the part of thosewho have had the trouble.

There are many makes of AC tubes,just as there are many makes of directcurrent tubes. There are also many dif-ferent characteristics of these tubes.The ones used in the set about to bedescribed were Armor AC 100, exceptthat in the last stage was an Armor 71.

One of the outstanding facts about theAC tubes is that the filament is almostinvariably short and heavy, requiring alow terminal voltage and a high heatingcurrent. The reasons for such a filamentare that it retains its heat better than afiner filament and that the voltage dif-ference between the mid -point and eitherend is smaller, thus minimizing chancesfor the introduction of hum in the signal.The majority of AC tubes require a fila-ment voltage of one volt and a filamentcurrent of from one to 2% amperes, de-pending on the electron emission desired.

Use Heavy Wire for FilamentsWhen building an AC tube receiver, or

in adapting an old set to the new tubes,it should be remembered that the filamentleads must be very much heavier for thenew tubes. If AC tubes be put into thesockets of an old set and the voltage atthe filament terminals is changed to suit,nothing but failure can be expected.

The voltage drop in the leads will beso great that there will be very littlefilament current.

Very heavy leads are necessary, andthese leads must be heavy throughoutthe filament circuit, from the secondaryof the supply transformer to the tip of

the AC filament. This necessity caneasily be realized when it is recalled thatan 01A tube requires only one -tenth thecurrent required by one of the new ACtubes.

Countless fans will want to built theirown AC tube sets. Herewith is such areceiver, of seven tubes, in which all thefilaments are heated with alternating cur-rent.

There are one detector and five ampli-fiers which require 1 volt, and one ampli-fier which requires 5 volts on the fila-ments. Hence the supply transformermust have at least two low -voltage wind-ings.

Armor Tubes UniversalWith some other AC tubes it is neces-

sary to have the detector on a separatewinding, requiring 2% volts, as against1 volt, so three separate filament leadsfrom the set are desirable, to afford thisversatility. One of these should be from

the 5 -volt tube, one optional from thedetector, and the third from the 1 -volttubes in the set. The leads for the powertube and the detector need not he of soheavy wire as those for the amplifiers.The windings on the transformer shouldcorrespond with respect to voltage andsize of wire to the requirements of theset. The National power transformer forAC tubes meets all these winding require-ments.

There are two potentiometers employedin the filament circuit of the set. Oneof these, P1, is connected across the fila-ments of the 1 -volt tubes, with its sliderconnected to the point corresponding toC plus. The slider is set at the electricalmid -point on the resistance of P1 forminimum hum.

When to Use P2The second potentiometer P2 is left

unconnected in the diagram but is locatedso that it can be placed across the de -

B Eliminator CostsNON -TECHNICAL owners of radio

receivers in which all or a part of theplate voltage is obtained from the light-ing circuits often look with suspicion atthe radio set as a booster of the monthlylight bill.

They just know that it is the radio setwhich is responsible for the great increasein the bills, because before the set wasinstalled the bills were just a fraction ofwhat they are now. But the radio set isan innocent victim of this misplaced sus-picion.

Let us take a typical example to showhow gross was the injustice of blamingthe set. The set in particular had fivetubes. Two of these tubes were operatingon dry cells entirely, and therefore they

drew no power from the house line.The total plate current drawn by the

other three tubes was about 15 milliam-peres. This is a conservative estimatebecause one was resistance coupled anddrew less than one milliampere and theother two tubes were properly biased andthe total plate voltage was only 170 volts.The voltage of the house line at theterminals was 120 or less. Hence thepower supplied by the line to the radioset was 1.8 watts.

Cost 11, Cents per MonthThe set was used an average of four

hours daily or a total of 120 hours everymonth. Hence the energy taken from theline per month was 1.8 x 120 watt-hours,

liuolist13, 1927 RADIO WORLD

BkTTERYLESS By Capt. Peter V. O'RourkeContributing Editor

l'RE IS A BATTERYLESS SEVEN -TUBE SET, made so by using Armor AC tubes, in conjunction with a B eliminator and1

drop C elimination. A loop picks up the RF energy and is tuned by a .00035 mfd. condenser. The next three stages are tuneda three -gang condenser C2, the sections being A, B and C. Across the A and B sections is a double balancing condenser

a C2b. In the detector circuit C2c is a separate midget. Three RF, detector and three Hiler double impedance AI' constitutethe circuit.

-;tor filament in the same manner thatis connected, in case an AC detectorthe cathode heater type is used. TheOrion of P2 is indicated. Of course,h Armor tubes throughout, the ACis for detection as well as for ampli-

ition.;ince the voltages across the potentio-ters are low and the currents through

filaments are high, it makes very little'erence if the potentiometers draw aall additional current. Therefore the:entiometers may have low resistances.renty ohms would be sufficient if suchtentiometers can be obtained. Certainlyhigher resistances than 200 ohms needused.To potentiometer is needed for the_ment circuit of the power tube because

5 -volt secondary winding has a cen--tap which serves the same purpose.

Affords VarietyThe grid bias voltage for the power

e is obtained from the voltage dropa resistance R2. This should be var-le and its maximum value may be

1)00 ohms so that the correct grid biasa be obtained for a variety of tubes and,te voltages. The grid bias for theler amplifier tubes is likewise obtainedm the voltage drop in a resistor, R3.e value of this resistor need not beire than one or two ohms. The gridurn of the detector tube is to the mid-int of P1 (or P2 if that is used). anderefore the grid is kept at the averagetential of the filament. It can be kepta small positive or negative potential

with respect to the mid -point by insertinga small battery in series with the gridleak.

There are three stages of radio fre-quency amplification and a detector-four tuned stages-in this receiver. Threeof these are tuned with a single control,a three -sectional Cardwell condenser be-ing used. The coils in these tuners arePowertone. The first tuner consists ofthe pick-up loop and a single unit Card-well condenser. As a means of keepingthe three -gang condensers in step amidget condenser is connected across onesection and a double midget across theothers.

Catacomb Assembly UsedThe audio frequency amplifier is of the

double impedance type and contains threestages with an output filter. The stop-ping condensers and the various audiochokes together with all the seven socketsare built into one unit or catacomb. Thisforms a very compact assembly whichoccupies little space. Even the outputfilter is built into the catacomb, an AldenTruphonic unit.

The volume is controlled by means of a500,000 -ohm Electrad potentiometer, R4,placed across the grid impedance follow-ing the detector tube. This is the logicalform of volume control placed in thebest position.

The pilot light is connected in serieswith the 254 -volt winding when the de-tector is not on this winding, otherwisethe pilot light is connected in parallelwith the detector tube filament. Pilot

1®' per Month to Run- .216 kwh. The cost of electric energy

this case was approximately 7 centskwh. Therefore the total cost of the

,erg -y taken by the set per month wasightly over 1% cents.Of course, the initial outlay and de--eciation must be considered in the totalJst.But the electric bills in the house hadivanced from about $3 to $6 per month.,There did the extra power go to? Well,ere were 16 lights in the house goingi average of 4 hours daily. Most ofese lights had originally been 25 wafters.hey had been replaced by 50 waiters.ow, what is the cost of the energy nec-sary to keep sixteen 50 -watt lightsoing four hours a day for 30 days? The

wattage is 800 watts. The number ofhours per month is 120. Hence theenergy used per month is 96 kwh. At 7cents the bill should have been $6.72. Thisfigure is within a few cents of the billactually rendered by the electric companyone month.

Excluded ItemsThe cost of 1% cents given above for

the operation of the radio set was onlyfor the power taken from the line by theplate circuits of the tubes. Of courseit does not include the cost of the drycell B battery, which was used to boostthe plate voltage and to supply the RFand the detector tubes. Neither does itinclude the cost of charging.

lights of this voltage requirements canbe obtained in any electrical supplystore.

The filament switch S is connected ,inseries with the primary of the AC 'fila-ment supply transformer and also the Beliminator transformer. This completelycontrols the power supply and no relaysare necessary. It can be placed on thepanel.

A rheostat RI is shown in the diagram.It is connected in series with the 1 voltwinding for limiting the filament current.It must be of very low resistance andvery heavy wire because the currentwhich it will normally carry is high andthe voltage drop in it must always becomparatively small. About .5 ohm isrecommended.

A loop seryes as the collector of energy.The next two RF stages have asingle two -section Cardwell Balancet(double midget) across the tuning con-densers, and a separate balancer acrossthe remaining part of the three -gangcapacity.

One Soprano VoiceGets Over, Anyway

With three ears training under G. S.DeLuca, Myra Bender is able to demon-strate a soprano voice well adapted tobroadcasting. It has been said that so-pranos do not register well on the mi-crophone. However,the mellow quality ofMiss Bender's voicemakes it possible forher to number herradio audience of at-tentive listenersaway up into thethousands.Her first appearance

was in an operaticprogram under Mr.DeLuca in the studio Myra Benderof WSM, Nashville, Tenn., more than ayear ago. Since that time at frequentintervals she has broadcast. While shedoes not engage in any of the so-calledjazz numbers her work has graduallydeveloped into the field of the popularnumbers. Light opera and musical com-edy selections are treated, nimbly by herinterpretations.

Miss Bender sings each week for WSMat 10 P. M. on Monday.

RADIO WORLD August 13, 1927

A BIG IdeaIn Building a LataBalsa Wood Speaker

By H B. HermanAcoustical Expert

THE paradox of lightness and rigidity is an essential ofthe type of speakers operated by an extending stylus,e. g., cones and flat surfaces. For the flat type Lata Balsawood furnishes all the lightness that one would require. It islight beyond expectation, being only half as heavy as cork, andif you toss a slat of the speaker sounding board into the airit will waft to the floor something like a feather.

The rigidity is supplied by lateral arms or fins, which arecemented to the thin slats on the 3/16 -inch edge of the fins.By the terms of such an outline it is possible to construct aBalsa Wood speaker that does any number of things, evenone that slights the low notes and has a natural period some-where above 400 cycles.

Will Work the Other WayAlso it is possible to favor the low notes immensely, andhardly be able to catch the hisses and other sibilants. Onewants them, too, for they are the readiest indices of the highaudio frequencies.When we try to judge by ear alone the operation of anyspeaker we naturally listen for the low notes-those of theoboe, bassoon, contra -bassoon, organ, bass viol, and drums-and again for the consonants of speech, especially the th, s, z.Next our ear perhaps inquires into the middle range. Neverdo we find-if our ear tells us the truth,

which' it doesn't do always-that anyspeaker handles all notes equally well.Such a speaker has not been built yet toperform by the electromagnetic methodand never will be, unless the laws ofphysics are amended.

The response obtained from the BalsaWood speaker that I built is entirely satis-factory to me and delights all visitors.The method of construction is applicableto the Balsa Wood kits as now obtainable,and may be used on any of the threestandard sizes. My own speaker framemeasures 43 x 24 inches.

All -Around ServiceThere is a well-rounded low note re-

sponse, delightful to hear, because or-chestras, including symphonies in par-ticular, are lost without full reproductionof the low notes that lend character andpersonality to the music.

The middle register is well taken careof, but has pronounced resonance peaks.These are not objectionable in actualpractice, for they simply make the ampli-fication stronger on some few notes, orwithin some few narrow regions and gen-erally go unnoticed. Trained acousticalears will hear these peaks and acousticalengineers will remark upon "the humpin the curve," but there isn't any speakermade that uses a sounding board as dia-phragm, nor horn type, either, that hasn'tits peaks and hollows.

In the higher audible frequencies thesepeaks are less pronounced than in themiddle register of the Balsa as I madeit. No doubt it would be possible tolower these peaks, and a suede or felt--baffle would do it, but my own speakeris so satisfactory that I don't think I'lleven attempt to improve it in that direc-tion, but prefer instead to outline how itwas built, so that others may follow thedirections to the delightful goal.

HOW to build the Balsa Speaker withgenuine Lata Balsa Wood, fully described,including acoustical theory, by H. B. Her-man in the June 11 issue. Send 15, forcopy. Radio World, 145 West 45th Street,New York City.

PART VIEW of the front of the author's Lata Balsa Woodspeaker. The sides of the frame are at left and right. Fourslats are used, instead of the conventional five, thus allowinggreater spacing between slats, improving response. Part ofthe speaker magnet is shown at the crossarm. The protrudingpoints are not the magnet poles, but the ends of the two

upper fins.

The central idea is that the soundingboard, consisting of the slats and thefastening ribs, should be stiff without be-ing inert, hence there must be extraordi-nary freedom of movement of the sound-ing board where the stylus or driving pinis fastened to the thumb -nut. The smallslab of wood-Balsa or otherwise-intowhich this thumb -nut fixture is driven,may be half an inch square, or larger.

The lower frequencies vAll not ordinar-ily be slighted, so attention is focused,inornentarily on the higher frequencies.If we use a good receiver, with a fineaudio amplifier, we should be able to hearhisses (like escaping steam) with greateffect. And this we will do, if we takeadvantage of the higher frequency re-sponse of the individual slats.

Individuality PreservedInstead of doting on the idea that in

union there is strength, we accept that asan incidental fact and try to get as muchof the individual character of each slatinto the sum total as is possible. Let eachindividual slat preserve its own identity,so far as possible, rather than to mergeits individuality into a general ensembleof low -note reproduction and sacrifice ofhigher pitches.

By widely spacing the individual slats,as shown, the easy swing is 'achieved, andless power is required to drive the sound-ing board. By the same process betterhigh note response is attained, as well asan improved result in the middle range.Undoubtedly some "humps" are causedby this very means, that is, intensitysomewhat over -pronounced, but this maybe regarded as a shifting, rather than asan addition.

The humps are transferred from onerange to another, without being mate-rially increased numerically.

Besides, the speaker is thus able tooperate with a given natural period of310 cycles, or slightly lower than that ofthe Western Electric 540 AW, which theBalsa Wood speaker, properly made, isquite likely to outperform, when a West-

ern Electric or a Lata Balsa unit is used.The speaker was made of four slats,the extra room being taken up in thespacing between slats, so that one slatwas left over from the kit supply. Theribs number five, one across, and foursemi -diagonally.

The wide piece of wood showing inback of the speaker is the crossarm, andthis is of heavy wood. To this crossarmthe unit is attached. The stylus is af-fixed to the small wooden slab. It is im-portant to avoid having these semi -diag-onal fins contact directly with the cross -fin. An annoying source of rattles ispresent when these joints are improperlymade, and also if the stylus or driving pinis not firmly fastened, or the slab thatholds the thumb -nut catching the pin isnot cemented firmly. There is no inherentor mysterious rattling tendency in thespeaker, for if rattles occur you cantrace them down and get rid of them.

A glance at the photograph shows howthe semi -diagonal fins terminate. Nearlyhalf an inch separates the fin terminalsfrom the cross -fin. The slab will haveto be big enough to cover the four pointshandily. Imagine the black square in thecenter of the photograph to be the slaband you will get the idea.

All Rattles Are CurableAs for rattles, these arise from loose

joints or splits. Look to the ends of thefins. Unless carefully cemented down,these surely will get loose and rattle.Inspect the whole length of the fins, andtug slightly at them, in searching forloose joints.

Do not forget the corners of the slats, asthese will get loose, if not properly ce-mented down. In fact, after building thespeaker, and letting the cement dry, it iswell to use a little pressure on the cement-ed joints, to make sure everything is downtight, and if it isn't, to do some more ce-menting, and some more waiting, untileverything is dry and tip-top, for then youwill have one of the finest speakers inthe world.

August 13, 1927 RADIO WORLD 7

ME FOR Distortion Forever!By Tim Turkey

ORCHESTRAS (like Vincent Lopez', shown above) are full of low notes. Tim Turkeydotes on them and explains in a novel article why he is in favor of one kind of distortion.

MOST radio receivers show the char-acteristics of a dromedary; they

have a big hump in the middle. Somereceivers show the characteristics of acamel; they have two humps on top.Many receivers are nondescript mongrelswhich partake of the characteristics ofboth the above types.

The characteristics of all loudspeakersare very humpy and bumpy. The dif-ference between a good loud speaker anda bad one lies mainly in the distributionand intensity of the humps. Some ofthe speakers have nothing to show below100 cycles. Others rise to great heightsjust beyond the 50 mark. Most speakersof the so-called better variety are per-fectly dumb above 5,000 cycles, whilesome of the worst speakers are as silentas a giraffe up to 500 cycles. Those ofthe mediocre variety are just like themajority of the receivers; they have ahump in- the middle, or a series of humpsin the middle, with nothing to show ateither end.

When the characteristic of a receiver iscombined with the characteristic of someloudspeaker a very indefinite overallcharacteristic results. The overall maybe much better than either of the com-ponents, or it may be infinitely worse.

Matter of Psychology

It will be better if the humps of theone coincide with the hollows of theother; it will be worse if the humps ofthe one coincide with the humps of theother. But even when two mediocrecharacteristics combine most favorably,the result is not far from mediocrity.

But whether the output of a radio in-stallation pleases the listener or not hasnothing to do with the number and in-tensity of the humps and hollows. It hasnothing to do with the distribution ofenergy in the highs and the lows or in themiddles. Nothing at all; it is purely apsychological matter. A person can be-come accustomed to like almost anything,no matter how atrocious it may be tothe senses at first exposure. The sensesbecome fatigued and do not care whatgoes on around them.

Quinine is bitter on first taste, but itloses its bitterness after a short exposureto the tongue. Sugar is sweet at first,but only for a little while. The senses of

touch, smell, sight and hearing respond tostimuli in a similar manner. So when aperson has been exposed to an especiallyatrocious radio reproduction for a while,his much punished auditory nerves havebecome exhausted and no longer giveheed to the stimulus, while the nerveswhich have not been subjected to muchactivity are still alert and take it all in.

Set Bad, Owner InnocentSo it comes about that the person who

possesses a very bad radio installation caninnocently and conscientiously rave aboutthe unexcelled quality of his set. Hisfriend, whose ear is still undefiled, cannotdisillusion him, because hearing is believ-ing, and as the two do not hear the samething in the same way, there is no com-mon basis of argument.

The only way to convert the man withthe bad set is to expose him unknowinglyand exclusively to the reproduction of areally good set for some time. After sucha course of treatment, the first thing thepatient would do on hearing his own setwould be to plug his ears. But it wouldbe better for everybody if his first actwould be to throw it into the furnace.

There is some form of distortion in aradio installation which is really not anoffense to the listener. Suppose that thereproduction is such that the lowest tonesare greatly exaggerated in comparisonwith the higher, but that the falling offtdward the higher is even and gradual.Also suppose that the tubes in the set arelarge enough to handle all the energyrequired for the low notes. Such repro-duction is preferred by many persons be-cause of the so-called mellowness. Evenpersons with highly sensitive ears will nottake offense at such reproduction. At notime is a crime committed against theeardrums.

Plea for the Low NotesAfter all, the low notes in the music

constitute the foundation upon which thecomposition rests, and the higher notesare often only embellishments.

Instruments may show that the low notesare exaggerated and the higher are sup-pressed and thus that there is considerabledistortion in the reproduction, yet I preferto listen to such music just because the lownotes can be heard. I have not yet beenable to enjoy any reproduction in which

the high notes were accentuated to thedetriment of the low.

Some persons may prefer to listen tothe receiver which brings out the sopranowell and does not bring out the bassoat all. Such sopranophile individuals arefortunate, in that they need not buy afirst-rate receiver nor even a fair loud-speaker to satisfy their demands. It isthe individual in each case who deter-mines whether the reproduction soundsgood to him.

The judgment of quality also dependson what type of broadcasts is beinglistened to. Orchestra music is best whenthe receiver gives due emphasis to thelower tones, say, the bass viol, the tuba,the bassoon and the drum. This is particu-larly true of dance orchestras. Bandmusic is also best when the low notes arenot slighted.

Violin and Voice

The violin sounds best when the highernotes are brought out, and it does notmake much difference whether the lowscome out at all, because they are notin the original. The same applies to so-pranos.

Reproduction of the speaking voice,whether of high or low pitch, sounds allright if it is intelligible. For intelligibilitythe notes below a 100 are not necessary,but the highest audio notes are very de-sirable. If the esses stand out clearly,no particular effort is necessary to under-stand what is being said. The sibilantslike s, th and the like require notes upto about 10,000 cycles.

Statement of Likes

An excellent orchestral combination tolisten to is the Balalaika orchestra, whereonly large sized mandolins are used. Themiddle frequency is mostly used, with afrequent dip into the bass. And whenthey go down there it's really wonderful.I could sit for hours and hours andlisten to them. String ensembles are alsogood bets.

Especially do I enjoy the above com-binations,,witgn they render pieces writ-tegrirn ithe,bass 'portion of the scale.

The ,grost eldlightful thing to listen to,I think, is a song requiring string pluck-ing in the bass scale and played by acello or bass viol.

8\ (`R A Dj 0 WORLD Cc ,r 1,-, v August 13, 1927

Bias In An A B C UnitHow It Is Obtained In the Toto Power Well

The diagram of the TotoFIG. 2

Power Well, including series filament connections of thereceiver, and grid biases.

[Part I of this article on the constructionof the Toto Power Well-an ABC elimin-ator-was published last week, issue ofAugust 6. Part II, the conclusion, follows.]

PART IITHE grid bias for the power tube in

the Toto Power Well is obtainedfrom the drop in the resistance Rl. Theresistor used is a 2,000 ohm AmscoDuostat. One end of this resistor is con-nected to the most negative point in theeliminator and one of the sliders is con-nected to the mid -point of the secondaryof the heating transformer. By movingthe slider away from the negative end, theentire filament, so to speak, is lifted inpotential by the voltage drop in the re-sistance.

Since the grid return is connected tothe negative end there is established avoltage difference between the mid -pointof the filament and the grid, with thegrid negative. The value of this bias isthe product of the plate current in thepower tube and the resistance of that partof RI which is used. Since the plate cur-rent in the 371 tube with 180 volts on theplate is about 20 milliamperes, the voltagedrop in the 2000 ohm resistance will beabout 40 volts, the correct value under thecircumstances. If the plate voltage in-creases, the required grid bias is alsogreater, but this does not necessarily re-quire a change in the setting of the re-sistance Rl.

Automatically ChangesThe adjustment is more or less auto-

matic, because as the plate voltage in-creases the plate current also increases;and as the plate current increases thevoltage drop in 121 increases. However,when a different tube is inserted intopower socket it is necessary to readjustthe setting of RI, even when a new tubeof the same type is inserted. If it werenot for this fact the resistor R1 couldbe made fixed.

In Fig. 2, which is a clarified copy ofFig. 1, is shown how the filament circuitsof the other tubes in the circuit shouldbe connected. They are all in series, sothat all the tubes get the same amount

of filament current. The current is con-trolled with rheostat R4 (a Power Claro-stat). The voltage drop in R4 must bethe difference between the output voltageof the filter and the voltage required bythe tubes in the amplifier. In the caseshown there are five filaments and theserequire a voltage of 25 volts. Supposethat the voltage across the output ter-minals of the filter is 220 volts, the dropin R4 must be 195 volts. The currentflowing through the rheostat should beabout .25 ampere. Hence the resistanceshould be 780 ohms. It should be variableup to at least 1,000 ohms so that thecorrect adjustment can be obtained.

The power dissipation in rheostat R4will be nearly 50 watts. Hence it is nec-essary to have a rheostat which will standa considerable current.

Methods of Getting BiasThe manner in which the grid bias

voltages are obtained in the series con-nected tubes is interesting. The detectortube is placed at the bottom of the series,that is, next to the negative side of thefilter. The grid return is connected tothe positive end of the filament. Nonegative bias could be given this tubewithout inserting a resistor in series withthe filament below the detector tube. Theother tubes in the circuit are amplifiersand need negative bias.

Each tube can be given a bias of atleast 5 volts by connecting the grid re-turn to the negative end of the filamentnext below, as has been done for all ofthem in the drawing. For three of thetubes the bias can be made at least 10volts by connecting the grid return tothe next filament below but one. Thefirst two tubes from the positive end canbe given a maximum grid bias of 20 and15 by connecting the grid returns of theseto the negative. side of the filter. Fromthis possibility it would appear desirableto make the first tube on the positive sidea semi -power tube to feed into the outputtube and to obtain its plate voltage fromthe B plus max binding post. This tubemust not take more than 25 ampere onthe filament.

The plate voltage available for the out -

LIST OF PARTSBA-One Raytheon Type BA tube.PT-One Acme Apparatus power trans-

former for BA tube (.2 kw).AF-One Acme Apparatus audio trans-

former.OT-One Acme output transformer.Cl, Cl-Two 1,000 volt Flechtheim buf-

fer condensers, each .1 mfd. (one unit).C2-One 4 mfd. 1,000 -volt Flechtheim

condenser.C3, C4-8 mfd. each, made up of four

each of C2 type.R1-One Amsco Duostat, 2,000 ohms.R2-One Electrad 5,000 -ohm 25 -watt

Truvolt variable resistor.R3-One Electrad 10,000 -ohm 25 -watt

Truvolt variable resistor.R4-One Power Clarostat.R-One Electrad 1,500 -ohm 25 -watt

Truvolt fixed resistor.C5, C6, C7-Three Flechtheim 1 mfd.

250 -volt by-pass condensers.Two Acme Apparatus Co. choke coils

for BA tube (BA2).Eleven binding posts.One 5 -ampere fuse and one porcelain

fuse socket.One extension cord and lamp socket

plug.Two vacuum tube sockets.One CX-371 tube.One 20x10 -inch board.One shielded case (optional).

put power tube is about 180 volts, since40 volts of the 220 volts output are usedfor grid bias. The maximum plate volt-age available for the first tube in theseries, counting from the positive end, is200 volts, since 20 volts have been used bythe four filaments below it. The lowtube in the series, that is, the detector in .

this case, could be given a plate voltageof 220 volts if desired.

Constants DiscussedHowever, the proper voltage for the

detector is much less and the correctvalue ;s obtained from the drop in theresistance R5, an electrad 25 -watt Truvolt,1,500 olsms. R3 is an Electrad Truvolt of10,000 ihms, 25 watts. R2, another 25 -watt Electrad Truvolt, should have amaximum resistance of 5,000 ohms, andshould be variable.

The rectifier is a double wave BA Ray-theon which is capable of delivering acurrent of 350 milliamperes. The powertransformer PT is an Acme 200 wattcapacity. It has a tapped primary foradjusting the input to various primaryvoltages. It has also two center -tappedsecondaries, one for the rectifier and onefor the filament of the output tube.

The Flechtheim buffer condensers CIare of .1 mfd. and capable of withstand-ing 1,000 volts continuously. C2 is a 4mfd. Flechtheim condenser of the samevoltage rating. C3 and C4 are 8 mfd.units, each made up of two 4 mfd. blocks.The remaining condensers, C5, C6 andC7, 1 mfd. each, need not have a ratinghigher than 250 volts.

The filter chokes Ch are two AcmeBA2 heavy duty chokes each having aresistance of 166 ohms. This low re-sistance, 332 ohms, makes the regulationof the filter satisfactory even for currentsgreater than 300 milliamperes.

The parts of the Toto Power Well areassembled on a 20 x 10 inch woodenboard.

August 13, 1927 RADIO WORLD 9

How Well Not How FarQuality Rules and Power Tubes Play Big Part

AS the novelty of radio has graduallydisappeared, and more interest is

-taken in it purely as an instrument toreproduce with fidelity both music andspeech, the listener and engineer havegiven more and more thought to the tonalqualities of the broadcast receiver. Thevast radio audience today is first of allconcerned in how well it can hear. Howfar is a secondary consideration.

It would seem to the average listenerinexperienced in radio experimentationthat all that is necessary to increase vol-ume is the addition of a stage or two ofaudio frequency amplification to his exist-ing equipment. This is true to a certainextent, but as we are interested only inquality volume, the design of the appa-ratus used in the "stage or two" of audiofrequency amplification is of great im-portance.

A speaker, which does the actual re-producing of sound, is an energy oper-ated device and as the energy is derivedfrom the last audio tube alone, the un-distorted volume obtainable from aspeaker iV usually dependent upon theenergy output of this tube and no other.

Handling Ability ComparedThe energy is measured in milliwatts

and the following table gives the poweroutput of the tubes now in common use,with the plate voltage necessary to ob-tain full output:

Undistorted PlateTubes Output . Voltage

UX 120 110 135UX 226 160 180UX 112 195 157UX 171 700 180UX 210 1500 425

In order to obtain the maximum poweroutput that a tube is capable of deliver-ing, it is necessary that a sufficientlylarge voltage be placed on the grid of thetube to operate at its maximum output.

At the same time certain conditions,however, must be satisfied to prevent dis-tortion in the tube itself. First, the gridmust not be allowed to become sufficientlypositive to draw any appreciable amountof grid current, and second, the plate cur-rent must at no portion of the cycle beallowed to fall so low that distortion becaused by curvature of the plate currentcurve. The input voltage which may beapplied safely to a tube without causinggrid distortion is fairly well indicated bythe grid bias voltage. Actually the effec-tive grid swing permissible in volts

R. M. S. is V2

2or .707 times the grid bias.

Things to Guard AgainstThe solution of the problem of quality

volume is threefold, embracing tubes,transformers and speakers wherein dis-tortion of various sorts and causes tendsto develop.

It may be well to state here that thereare two apparent forms of distortion toguard against in any audio amplifier:frequency distortion and waveform dis-tortion. Frequency distortion, whichreally is not distortion at all, but therelative differences in the amplification ofdifferent frequencies, is caused by one oftwo things, either a coupling device thatis not capable of even performance over

By A. R. WilsonEngineering Department, General Radio Co.

.Peak volucS1010

2 'Effecti.v3.4'Ss relts

-3

-4

o or f0. NI NO /10 2,0 270 270 300 .00 30

r Peak valueS volt,

FIG. 1

Diagram showing the relationship be-tween the peak and effective values of analternating voltage. The full curved linerepresents a wave of alternating voltagehaving an amplitude of 5 volts. Thedotted loop represents the effect of thenegative halt of the wave on an alternatingcurrent voltmeter. The effect is positiveand is equal to the effect of the positivehalf of the wave. The peak value is theamplitude, in this case 5 volts, and thisis the value that is measured on a peakvoltmeter. The effective value of thevoltage, or the root mean square (R.M.S.)value, is equal to .707 times the peakvalue. In this case the R.M.S. value ofthe wave is 3.535 volts. It is the effectivevalue of the voltage that is measured onpractical AC voltmeters. When the ACvoltage has been measured on such ameter, the reading must be divided by.707 to get the peak value. The peakvalue determines the electric stress oncondensers. It is also the voltage thatshould be regarded as the input voltageto vacuum tubes when adjusting grid bias.

the audio range, or the improper match-ing of impedances of the different cir-cuits.

It is extremely important from a fre-quency viewpoint that the impedances ofthe various circuits bear a definite rela-tion to each other.

To obtain a maximum transfer of volt-age from one circuit to another (and weare interested in this respect only in volt-age and not in energy), the impedance ofthe transformer primary should be atleast two or three times that of the tubecircuit at the lowest frequency which wewish to amplify.

Waveform DistortionWaveform distortion in the amplifier

itself is caused by either an over -loadedtube or saturation of the core of the audiotransformers.

With the present-day standards oftransformers, however, saturation from apractical standpoint may be entirely dis-regarded. Obviously the remedy for anoverloaded tube is the reduction of theinput signal or the increase of grid biasand plate voltage, thus permitting thetube to be worked on the straight por-tion of its grid voltage plate currentcurve.

Assuming one to have an audio ampli-fier and tubes of the standards of twoor three years ago, the most radical im-provement in quality would be broughtabout by the replacement of the last audio

tube by one of the new power tubes, suchas the UX 171 or UX 210.

This would increase the power handlingcapacity of the amplifier 50 to 100 timesand this power handling capacity of anamplifier is something that is not verywell understood by the average man, yetit is extremely important if faithful re-production is to be obtained.

In order to produce the same intensityto the ear, say at 60 cycles, many timesas much power is required as at 1,000cycles.

Need of PowerA somewhat disconnected yet fitting

illustration would be the comparison be-tween a tuba player and a cornet playerin a brass band. The tuba player ex-pends much more energy, but to the earthe cornet is louder. In the case of theloudspeaker far greater power is neededto supply the energy than was hereto-fore thought necessary to reproduce bassnotes properly, and it is even very doubt-ful if the tubes on the market today arecapable of supplying to the speakerenough energy to reproduce these lowfrequencies with the same intensity as thehigher frequencies, unless a 50 or 100 wattpower tube is used. This would requirea type of plate supply device, which fro.,1an economic point of view, would be en-tirely out of the question.

While it would seem that increasingthe energy output of an amplifier wouldresult in extremely loud reproduction, thisis not necessarily true.

A loud sound may be doubled in in-tensity-that is, the energy doubled-andthe ear may hardly detect the change.This fact will explain in some measurewhy many people are not able to notethe difference in the volume produced bya UX 171 and UX 210 tube, although themaximum output of the UX 210 is d ublethat of the 171.

Tube Fixes LimitationEverything else being equal, the repro-

duction, when using the UX 210, shouldappear much better on the lower fre-quencies-actually it is about the same,because the lower plate impedance of the171 permits a greater transfer of energyfrom tube to speaker at these frequencies.

The power handling capacity of anamplifier using present day transformersis more or less limited by that of thetubes used, since the largest possible por-tion of the negative side of the grid volt-age plate current curve is available forthe actual plate voltage used. While re-sistance or straight impedance coupledamplifiers are better from a purely fre-quency standpoint, the power handlingcapacity is decidedly limited, as there isa certain rectifying action of a strongsignal caused by the time action of thegrid condenser and leak, and their pur-pose, even from a frequency standpoint,is often defeated by the improper use oftubes.

Sound EconomiesA man will quite frequently pay from

$10 to $20 for an impedance coupled am-plifier only to use a 201A tube in the laststage, and it is very doubtful if the im-provement in quality in this case is evennoticeable to the ear. This is only an -o+1 -1,.- example of insufficient power re -q to reproduce bass notes, although

(Continued on next page)

RADIO WOkLD August 13, 1927

Righting Anything WrongIn a B Power Supply

[From Raytheon ManufacturingCompany]

There are few elements to cause troublein the Raytheon -approved radio powerunit using the B or BH type of tube.More often the trouble is to be found inthe associated receiver and wiring. How-ever, when genuine trouble does develop,it may be readily located and remedied;and the following suggestions are offeredby the Raytheon engineers as an aid toradio enthusiasts and radio service menalike in facilitating such work.

Inoperative Receiver: If the cause,through a process of elimination, is foundto be in the radio power unit, then thefollowing suggestions may be considered.However, as often as not the trouble isprimarily in the receiver itself, or morelikely in the connections and wiring be-tween the receiver and the radio powerunit. Sometimes, when a B power unitis connected it a receiver where the gridsof the amplifying tubes are not biasedwith a C battery, the high voltage maysoon paralyze the tubes. This may beremedied by inserting proper values ofC battery for each tube.

No Voltage At Given Tap: The logicalplace to begin the hunt for trouble in aradio power unit is at the resistor bank,and then work backwards through thefilter, rectifier tube, and finally the trans-former. It is assumed, of course, that the110 -volt alternating current is known tobe flowing through the transformer pri-mary when the radio power unit is turned"on," and that the rectifier tube is notvisibly damaged in any way. Of coursethe current is turned "off" before any partof the radio power unit or associatedwiring is handled, to avoid dangerousshocks, excepting output voltage tests.

An open -circuited or burnt -out resistorwill result in no voltage from the tapit controls. If the 10,000 -ohm fixed re-sistor becomes open, in the case of the Bpower unit, the detector voltage will im-mediately increase so that in the tunedradio frequency receiver the signalstrength will be greatly diminished, while

in the regenerative receiver there will beconstant oscillation.

The simplest method to locate a defec-tive resistor is by means of a high -resistance voltmeter, connected to eachtap in turn. In fact, this device is essen-tial in adjusting B power voltages to anyreceiver, in place of the cut -and -trymethod. In the absence of this device, a15 -watt, 220 -volt incandescent lamp maybe employed. It should glow a dull redon the full output and on the inter-mediate tap of the B power unit. If itlights equally bright on the detector tap,it is an indication of an open or defective10,000 -ohm fixed resistor.

If the tap voltages are found satisfac-tory, and the receiver still does notoperate well, the trouble may be due toan open or an omitted by-pass condenser.A short-circuited by-pass condenser willact the same as a short-circuited resistor.

No Voltage at All Terminals: This con-dition can be caused by an open circuitin the wiring, transformer, choke coils ora broken-down filter condenser.

With power disconnected from the Bpower unit and the Raytheon tube re-moved, a click should be heard in thetesting telephone when connected in ser-ies with battery between plate terminalof rectifier socket and the plus B of thepower unit. A click should also be heardbetween either filament terminal of therectifier socket and the minus B of theB power unit. These clicks should be ofequal strength. If one filament terminalgives a much louder click than the other,it generally indicates a defective buffercondenser. If no click is heard on eitherfilament terminal, then the transformersecondary is open -circuited, or the centertap of the transformer does not connectto the minus B side as it should.

The circuit continuity of the trans-former itself may be tested by the clickbetween the two filament terminals of therectifier socket, with tube removed. Ifthe transformer secondary tests O.K. onthe foregoing procedure, there must ofnecessity be an open circuit in the minusB lead.

Station and LoudspeakerLimit the Tone Quality

(Continued from preceding page)the frequency characteristic of an imped-ance or resistance coupled amplifier isessentially a straight line from 30 cyclesupward.

A very interesting laboratory experi-ment along these lines proved that wherea pure 60 cycle note from a vacuum tubeoscillator was fed directly into the gridof a UX 210 tube, the full output of thistube did not produce even an audiblesound at this frequency. All low fre-quencies are not entirely lost, however,as their harmonics are reproduced, butwith much less intensity, and the funda-mental pitch is usually obtained by thebeat note of a second and third harmonic.

Watch Last Stage TubeIn reviewing the subject of power

handling capacity of an amplifier, -eare many other more important phas oconsider than the particular methoi.

coupling (transformer, resistance, or im-pedance). It is a well-known fact thatno better quality can be expected thanis radiated from a broadcasting stationor that can be faithfully reproduced bythe loudspeaker - regardless of whatcoupling method or combination of meth-ods may be used.

Bearing in mind that the frequencyrange of the better broadcasting stationsis something like 80 cycles to 5,000 cycles,and the better loudspeakers cut off at80 cycles at the lower end and 7,000 cyclesat the upper end, also remembering thatthe better transformers in use today arecapable of even amplification between 60cycles and 6,000 cycles, the selection ofthe amplifier tubes and proper operationfor maximum efficiency of those tubesshould receive more consideration than isgenerally given to amplifier tubes, par-ticularly the last stage tube from whichthe loudspeaker is operated.

A short-circuit in the secondary of thetransformer can be most easily checkedby connecting a 25 -watt, 110 -volt lamp inseries with the primary. The current isnow turned on in the usual way, but withthe rectifier or Raytheon tube removedfrom the socket. The incandescent lampshould glow dull, if at all. If it glowsbright, either the transformer secondaryor one of the 0.1 mfd. buffer condensersis broken down. With the lamp still inthe primary, the rectifier tube is insertedin the socket. If the secondary connec-tions are O.K., and the Raytheon is opera-tive, the lamp will increase in brilliancy.The buffer condensers, if suspected, maybe disconnected from transformer second-ary and rectifier socket, so as to be testedseparately for short-circuit.

Testing the Raytheon: All Raytheontubes are thoroughly tested and aged atthe factory under full rated load beforebeing packed and shipped. Thus a newRaytheon can be depended upon to func-tion properly. It should provide satis-factory service for about a year of normaluse-at least a thousand hours of radioentertainment. After serving nearly itsfull life, the voltage output of the Ray-theon, previously maintained at a uniformhigh level, begins to drop off. When suchcondition obtains, the voltage controlscan often be adjusted to bring the voltageup again to the desired value, and manyweeks or months of good reception en-joyed before the tube is finally discarded.If the Raytheon gets warm when the Bpower unit is in operation, it is sufficientindication that the rectifier tube is operat-ing. If there is any doubt about theproper functioning of the Raytheon, thesimplest check is to replace it with a newRaytheon and note the results with theradio receiver left unchanged for a faircomparison.

Excessive Hum: This condition may becaused by an incorrect connection in thefilter circuit, such as a condenser by-passing a choke coil. The hum should in-crease when either choke coil is short-circuited in turn. If the hum does notincrease, the circuit connections to thatchoke coil should be checked, and if foundcorrect, then the choke coil should bereplaced by another of similar character-istics. Make sure that one side of theA battery is grounded.

Importance of High -Resistance Volt-meter: Those desirous of operating a Bpower unit or a Raytheon A -B -C radiopower unit, as the case may be, shouldhave a voltmeter whose resistance is atleast 100,000 ohms, with a full scale de-flection of 200 or 250 volts. Such a meterwill permit of adjusting the resistancesfor the proper output voltages when con-nected with a given radio receiver. Notonly is this of great benefit when theinitial installation is made, but it will laterbe of use in making adjustments to takecare of line voltage fluctuations, changesof receiving tubes, etc. Correct readingsare impossible with inexpensive, low -resistance type of voltmeter.

Motorboating, or troublesome audiooscillations which cause fluttering in theloudspeaker, are generally due to condi-tions in the audio amplifier, and may becorrected by satisfactory adjustment ofthe amplifier.

Replacement Tube: It is of utmost im-portance that the existing tube in theradio power unit be replaced by the sametype of tube. The substitution of an-other type may lead to serious trouble.

SPLITDORF INSURES EMPLOYEESSplitdorf-Bethlehem Electrical Co. of

Newark, N. J., has insured each of itsemployees for $1,000. Announcement ofthis group insurance contract was madeby Walter Rautenstrauch, president.

11.

August 13, 1927 RADIO WORLD 11

The usual B eliminator comprises atransformer to step up the voltage, arectifier to convert the alternating cur-rent into direct current, a filter circuitto smooth out the remaining irregularitiesor ripples in the rectified current; andfinally, a resistance network which dividesup the output into the various voltagesrequired for the radio set. Of these vari-ous elements, none is more important thanthe filter system, which determines thetrue worth of the B eliminator or radiopower unit, as well as its useful span oflife.

There are just two elements in the filtersystem-the choke coils and the conden-sers. Little can go wrong with the chokes,provided they are properly designed inthe first place, and of ample inductanceand carrying capacity for the job at hand.

But there is no end of possibilities fortrouble -with the condensers, if they arenot properly selected in the beginning. Itis false economy to install cheap, under-sized condensers in a B eliminator orradio power unit. Not only is there likelyto be excessive hum, due to improperfiltering, but the life of such condensersis relatively short, resulting in the earlydiscarding of the entire B eliminator un-less it is torn apart and rebuilt. Goodfilter condensers, more than any otheritem, determine the cost of the really goodB eliminator, which proves cheapest inthe long run.

Basis of Buffer FiguringIn the first place, the filter condensers

should have sufficient dielectric to with-stand the full voltage of the device overmany years of service, and also to with-stand the occasional peaks or surges whichmay run two or three times the maximumoutput voltage.

It is wise practice, therefore, to employfilter condensers of about twice the outputvoltage; in other words, for the 200 -voltmaximum output B eliminator, the filtercondensers should be of 400 -volt workingvoltage rating, and so on. The condensernearest the rectifier is subjected to thegreatest electrical strain, since the currentat this point is not entirely straightenedout and therefore has decided peaks involtage. It therefore follows that the firstcondenser in any B eliminator should haveample dielectric strength. If condensersof different dielectric strength or voltagerating are employed, then the first filtercondenser should rate highest as a meas-ure of protection.

There are three filter condensers in theusual two -section filter system. The firstcondenser, or that nearest the rectifier,does not have much influence on the huinor smoothing of the output current. Itis intended rather to maintain the outputat a fairly fixed voltage, despite the fluc-tuating current drain. It serves for theregulation of the rectifier.

What Second and Third DoThe second condenser controls the de-

gree of hum, and any increase in thecapacity of this condenser, within reason-able limits, reduces the hum in conjunctionwith the proper choke coils.

The third condenser controls the tonequality at full volume, because it acts asthe virtual electrical tank of the Beliminator, by providing an ample reserveof energy to meet the unusual drains,particularly the deep, bass notes, placedon the B supply. This condenser shouldbe as large as possible, say even up to8 mfd. or more. The usual manufacturedB eliminator can be materially improved

Eliminator Condensers'Functions Are Analyzed

by placing additional condensers, say 4to 6 mfd. in capacity, across the minus Band plus maximum B terminals, in build-ing up the last condenser in the filtersystem for the best tone quality.

In the case of the Raytheon rectifier,the buffer condensers are of real concern.Only too often the B eliminator manu-facturer or builder will employ ordinary.1 mfd. condensers of lowest voltage rat-ing for the buffer condensers, not realiz-ing that these little units are subjected tothe greatest strain of all, inasmuch asthey are across the split secondary of thetransformer, receiving A the AC output.

The buffer condensers for the RaytheonB should be of 400 -volt AC rating. TheRaytheon BH should call for 600 -voltAC rating condensers, while the RaytheonBA, or A -B -C radio power unit, shouldcall for 1,000 -volt AC rating condensers.As these buffer condensers are of verysmall capacity (0.1 mfd.), the added costof the higher voltage rating is very slight,and it will prove more than worth whileto use the highest possible voltage ratingin order to have the added safety.

Point of Upright MountingWith ample dielectric strength in the

buffer condensers, the radio enthusiast isassured of long life for his B eliminatoror radio power unit, without worryingabout broken-down buffer condensers andthe dangerous shorting of the trans-former secondary.

The Dubilier engineering staff has givenspecial attention to the buffer condenserproblem, and has worked out a designwith the two sections carefully balancedand mounted in a case that provides thenecessary shielding for the prevention ofexternal field.

It is good practice to mount condensersin an upright position, although this isnot imperative. However, the centilationof condensers is an essential too oftenoverlooked, even by some manufacturersof radio power units. Condensers shouldnot be subjected to the heat from therectifier tube or the resistors, although itis not uncommon to find filter condensersexposed to a heat of 130 degreesFahren-heit.

Paper condensers, with the impregnat-ing compound necessarily of low meltingpoint, cannot stand up under continuousheat. They should be protected from anyheat in the radio power unit by sufficientspacing, by partitions, or by ample venti-lation, if saf,. and long operation issought.

CIVIL SERVICEThe United States Civil Service Commis-

sion announces the following open com-petitive examination:JUNIOR PHYSICIST, $1,860 A YEAR

Applications must be on file with theUnited States Civil Service Commission,Washington, D. C., not later than Septem-ber 3. The examination is to fill vacanciesin the United States Naval Research Lab-oratory, Bellevue, D. C., in the. Bureau ofStandards, and other branches. The -en-trance salary is indicated above. Higher -salaried positions are filled through promo-tion. Subjects to be rated: General physics,30%.; mathematics through calculus, 30%;practical questions on each optional subjectchosen, 40%. The optional subjects areelectricity, heat, mechanics, optics, physicalmetallurgy, and radio. Senior students willbe admitted to the examination but willnot be certified for appointment until aftertheir graduation.

Full information may be obtained fromthe United States Civil Service Commis-sion, Washington, D. C., or the secretaryof the board of United States Civil ServiceExaminers at the post office or customhousein any city.

Trade Body to RunShow in Cleveland

Cleveland.Cleveland's third annual radio show has

been scheduled for November 8 to 13, in-clusive, and will be produced under thebacking of the newly organized RadioTrade Association of Northern Ohio. Theshow will be managed by Herbert Buck-man, who has been elected as secretaryof the association with the show manage-ment as his principal duty. Buckmanmanaged the annual Cleveland AutomobileShow for the last five years for the Cleve-land Automobile Manufacturers' andDealers' Association.

This year's show will be a new under-taking for the association. Previous radioshows have been held without organiza-tion backing, as private enterprises.Members of the Radio Trade Associationof Northern Ohio have guaranteed theestimated cost of the show and will sharepro rata in its profits. The show is tobe held in Cleveland's municipal auditor-ium. Headquarters for the associationhave been established at the office of itsmanaging director, 5005 Euclid Avenue,Cleveland. Officers of the association are:President A. H. Baier, Cedar -Lee RadioCo.; vice-president, H. W. Seabury, LakeStates General Electric Supply Company;treasurer, Louis N. Talk es, ClevelandStorage Battery Company; and the fol-lowing directors: Warren R. Cox, RadioApparatus Company, and William Bowie,Dreher Piano Company.

Tyrman Opens Up With Bang -Up LineErnst Tyrman, noted radio expert and

designer of high -quality radio apparatus,has designed an entirely new line of pre-cise parts that will assure the users ofefficiency, accuracy, simplicity and beauty.These are produced under his supervisionin the laboratories of the Tyrman ElectricCorporation, Chicago, and are carefullytested before shipment.

First in the line are the new Tyrmanvernier drums for one and two controlreceivers. A beautiful large escutcheonencloses the drums and verniers; thecenter knurls enable fast tuning of bothcontrols in single movement, while thetwo verniers on the side provide hairlineadjustment. A new accomplishment ofTyrman genius is a fine line of radio fre-quency transformers, type 8-70, 200 to 560meters, type 8-71, 160 to 360 meters, type8-80, long wave type. The new Tyrman

-audio transformers are a decided achieve -

ment in tone and volume. There are threetypes, one a 3:1 ratio; a power inputtransformer and a power output trans-former. To add the final touch of effi-ciency there is the line of Tyrman shieldedsockets for all types of tubes.

These parts are all of the highestquality, reasonably priced and are de-signed to fit the terminals of the newKurz-Kasch Capacity connector which isan extremely utile terminal device whicheliminates approximately 80% of wiringand soldering and acts as by-pass con-denser. Mr. Tyrman has also designedthe Tyrman Ten, a powerful receiverwhich is said to give wonderful results,using all these parts and allowing a clear10 kilocycle separation with confining ofall necessary fields. It is also reportedto have one -spot advantages. Mr. Tyr -man is President of the Company and A.Hintze, Jr., vice-preside-nt.-J. H. C.

12 RADIO WORLD August 13, 1927

Crowd's Roar DwarfedBy Skyscraper Horn

THREE of the exponential horn loudspeakers installed on the roof of WestinghouseBuilding on the occasion of the landing of Commander Richard E. Byrd and the

other

When Commander Richard E. Byrd,his crew and Clarence Chamberlin landedat Pier A in New York from a receptioncommittee boat the crowds along lowerBroadway were informed of their move-ments by a battery of gigantic loud-speakers installed on the roof of West-inghouse Building, 150 Broadway. These

speakers were connected to a radio settuned in on a wave carrying a descriptionof the event. Thus the people in thestreet who were not able to get closeenough to the landing place to see forthemselves could follow the event as Gra-ham McNamee saw it.

The loudspeakers were so powerful that

IT IS possible with the aid of a 45 -volt B battery and a 4 -volt C battery to obtainthe necessary 40i -volt bias for the 171 or 371 power tube when using 180 volts onthe plate. The 416 -volt battery, which is a regular C battery, is simply reversed inconnection. That is, instead of connecting the plus of the 11 -volt battery to theminus of the 45 -volt battery, the minus of the 436 -volt battery is connected to theminus of the 45 -volt battery. The plus of the of -volt battery is then connected to

the regular C connection in the amplifier.

Tests WavesTill ExhaustedReports of the results of the short wave

tests conducted by the General ElectricCompany from May 28 to June 4 arebeing received from all over the world,indicating the complete success of thetests.

Radio auditors had been asked to ob-serve reception of special transmissionsover two twenty-four hour periods, aweek apart. The engineers were inter-ested only in reception at great distances,since the short wave signals usually skipthe first 400 to 500 miles. Beyond thisdistance and up to 12,500 miles radiolisteners reported what kind of receptionthey got. Such details as volume, fading,distortion, intelligibility, static, carrier in-tensity quality and modulation were noted.By careful analysis of the reports nowcoming in from all over the world theengineers will try to learn what wave-length, what power and what time of dayare best for reaching a definite objective.

W. A. Waters, engineer and manager ofthe Manawatu-Oroua Electric PowerBoard, of Palmerston North, New Zea-land, gave a most exhaustive log andgraph showing the comparative strengthof the 22 and the 32.77 meter transmis-sions. The concluding line of his reportfor June 5 was: "Went to bed, unableto keep awake any longer."

An exhaustive report was also receivedfrom G. S. Daughtin of Stratton & Co.,Ltd., radio manufacturers of Birmingham,England. Mr. Daughtin reported that oneor the other station was audible over theentire twenty-four hours during which thetests were conducted. During daylighthours Mr. Daughtin recorded better re-ception from 2XAD, while 2XAF operatedon 32.77 meters was received best duringhours of total darkness. When it wasdark at the receiving end and light at thesending end, 2XAD was received best.When it was light at the receiving endand dark at the sending end the 2XAFsignals were most reliable.

FIDELITY MEASUREMENTS WIDEThe standard of fidelity is now

measured between frequencies of 4,000and 10,000 cycles. The input voltage isheld constant to give normal output at4,000 cycles modulation, and with a modu-lation of 30% for all frequencies.

the words of the announcer could be dis-tinctly heard over the din in the streetthree-quarters of a mile away.

The speakers used were of the expo-nential horn type, a development of Dr.Joseph Slepian and Clinton R. Hanna ofthe Westinghouse research staff, andwere 14 feet long.

"The horn is based on the fact that ahorn does not amplify sound, as is popu-larly supposed," said Mr. Hanna, one oftheinventors, "but increases the amountof sound radiation by permitting a greaterload to be placed on the vibrating dia-phragm at the small end. With this pointestablished, it was shown mathematicallyby Dr. Slepian and myself that the ex-ponentially shaped horn is the most uni-form sound radiator and hence provides amaximum volume of sound without dis-tortion.

"The horn used for the Byrd celebra-tion has an effective length of 14 feetand can reproduce sounds ranging fromthe lowest notes on the tuba to the high-est notes on the piccolo!"

August 13, 1927 RADIO WORLD 13

Static to SaveHuman Life

Static is to become a benediction tomankind. It is to be put to work toforecast the weather, to save life andproperty at sea, on land and in the air.A new device which automatically meas-ures the intensity and direction of staticwill be the means of transforming radiofrom curse to a blessing.

Lieutenant F. W. Reichelderfer, incharge of the Aerological Section of theBureau of Aeronautics, United StatesNavy Department, disclosed the imme-diate plans for installing half a dozenradio weather indicators, or devices formeasuring the intensity and the directionof static atmospheric disturbances. Theyare to be placed at the following navalair stations: Pensacola, Florida; CocoSolo, Canal Zone; Guantanamo, Cuba;or the Weather Bureau station at SanJuan, Porto Rico; Anacostia, D. C.; Lake-hurst, N. J.; and Hampton Roads, Va.

The type of static recorders used exten-sively in European countries will be in-stalled at these naval air stations. Infact, the device adopted by the Aero-logical section of the Bureau of Aero-

HOUSE WIFE boughte ectric bill increased toor 13ic worth of juice.

a B eliminator and, reading above wattmeter, found her$6 a month from $3. She used her set 100 hours a month,The solution was that she bad changed all her house lamps

from 25 watts to 50 watts.

nautics is a design of an Englishman andit is being manufactured in France.

The Hydrographic Office of the NavyDepartment with the cooperation of BellTelephone Laboratories have also madeefforts to transform static from the baneof radio reception to a blessing. H. T.

EXPERT SAYS DISTORTION IMPROVES

Friis, one of the radio engineers of BellLaboratories, has developed a static re-corder. This instrument and anotherspecial design developed by LieutenantE. H. Kincaid of the Hydrographic Office,will be represented in the static recorderinstallations on board ships.

HIS DANCING

AN ACOUSTICAL EXPERT, residing in the lower East Side of New York City, recently reported to Radio World's engin-eering department that he found that distortion in dance music improved his dancing to a great extent. This, he stated, he hadchecked up with the aid of a cathode ray oscillograph, part of his elaborate laboratory in the cellar of his home. The expert isshown at left rear, beside the Ensco 3 -ft. cone, dancing with his lady friend, who is all smiles. The expert is none other than Tina

Turkey, whose article entitled "Me For Distortion Forever," is pu Wished in this issue.

14 RADIO WORLD August 13, 1927

C Battery EliminatorIs a Four -Point "Pot"

By Buck ZeymarOne of the most useful devices brought

out recently is the multiple slider, wire -wound potentiometer. It can be used forgetting almost any desired values of gridbias for different types of tubes andmodes of operation of them. How thiscan be done in one case is illustrated bothpictorially and schematically in Fig. 1.

Point (1) is connected to the negativeend of the filament or to the negativeterminal of the A battery, as indicated.The other points are connected to thevarious grid return leads according tothe value of grid bias required.

The bias is obtained from the voltagedrop in the resistance of the potentio-meter. Therefore there must be a directand steady current flowing through theresistance. This current is usually ob-tained from the sum of the plate currentsof the tubes in the receiver, after thiscurrent has been filtered and smoothedout. The value of this current is notthe same in all sets, hence a generousvoltage drop is established in the resis-tance of the potentiometer, means being'provided for varying the voltage dropused for bias.

Sliders Tap Whole RangeIt is here where sliders come in. Any

slider can be set so that the voltage dropbetween it and the filament end of R,at (1), has any value between zero andthe full voltage drop in the potentiometerresistance. And it is possible to get asmany different grid bias voltages as thereare sliders.

The highest grid bias required in ordi-nary receiving sets is 40.5 volts, which isthe correct value of a 171 tube with 180volts on its plate. Suppose that the sumof the plate currents is 25 milliamperes.This current is sent through the poten-tiometer as shown. Suppose now thatthe total resistance in the poten-tiometer is 2,000 ohms. The voltage dropin it will be 50 volts. But only 40.5 isnecessary for the power tube. The sliderconnected to point (3) is then set so thatthe voltage drop between (1) and (3), is40.5 volts. This requires 1,620 ohms be-tween (1) and (3). It may be that an-other value of grid bias also is requiredin the set, say 10.5 volts. This can beobtained by setting the slider connectedto (2) so that the voltage drop between(1) and (2) is 10.5 volts. The resistancerequired between these points is 420 ohms.Any other values less than 50 volts canbe obtained if desired.

Of course, it is not easy to set the slid-ers by any known resistance value, norto regulate the total current flow to gov-ern proper bias.

May Decide by EarThe best way of determining the values

of the bias is to measure them with a highresistance voltmeter, as the ordinary typeof voltmeter will not do. The sliders areset according to the voltmeter reading.However, few experimenters have suchvoltmeters, so can use instead the char-acteristic curve of a tube, or, what is muchthe same, a vacuum tuhe voltmeter. Theplate voltage being assumptively known,a bias is introduced in the grid circuit bymeans of a battery, and the plate cur-rent is read. Then when the same platevoltage is applied to the receiver tube,assuming the same tube or same type of

tube and the slider is varied until theplate current reading on a milliammeteris the same as it was when the batterybiasing test was made.

However, it is possible to make quitesatisfactory settings by ear, hence onemay build a total O eliminator, consistingonly of such a potentiometer, and put itinto use simply by making the potentio-meter the common connection of A andB sources, so that the plate current flowsthrough it.

An Economical Hint

The plan works out very well as dia-grammed, when B eliminators are used,particularly eliminators of the 180 -volts -at -60 -mils type, or equivalent high-pow-ered variety. But where B batteries areused, or for any other reason it is de-sired to drop less than the total voltageoccasioned by all the plate current pass-ing through 2,000 ohms (the potentiometerR), then instead of connecting B minusof the eliminator or battery to the pointindicated in Fig. 1, this point (4) is leftblank, and the potentiometer is madepartly a rheostat by that action. The Bminus lead from battery or eliminator isconnected instead to point (3), and thisbecomes the most negative, yet only somuch so as its setting determines.

Thus the total voltage drop, all of whichis at the expense of the B supply any-way, is kept to a minimum.

FIG. 1A photograph of a double slider potentio-meter used for obtaining two values ofgrid bias in a receiving set, and theschematic diagram of the total C battery

eliminator.

Quality and SelectivityMust Not Be Exceeded

Entire Broadcast Band

Idea/ReceiverTvnini Bond

'Os

cZi

i-..--/OKCH /RV A Zr-Y. Over Selectivity - Poor Qu'atity2. No Selectivity - Good QualityJ. Good Selectivity - Good Quality4) The Idea/ Curve - Perfect Quality and Selectivity

CHARACTERISTIC CURVES exemplifying the effect of the selectivity of circuits.upon quality reproduction. It will be noted that where the selectivity is very good,the quality is quite poor, while with no selectivity, the quality is good. The idealcurve, where both the selectivity and quality are good, is also shown.

ssoirc

August 13, 1927 RADIO WORLD 15

Radio University A. FREE Question and An-swer Departmene coni-

ducted by RADIO WORLDtor its yearly subscribersonly, by its staff of Experts.Address Radio University,RADIO WORLD. 145 West45th ST.. Now York City.

When writing for information give your Radio University subscription number.

FIG. 555A diagram showing how to put a seriescondenser in the antenna circuit to adaptthe receiver to the shorter waves in the

broadcast band.

MY SUPER -HETERODYNE is greatfor volume and selectivity but it will notbring in many stations without a squeal.Is there any way of clearing up the signal

. and what is the cause of the squeal?-ROBERT L. TAGGART, Jacksonville,Florida.

You will find a discussion of this subjecton page 8 of last week's issue (August 6).Remedies are suggested in that article.

* * *

WHAT IS the cause of a growling noisein my reflex receiver when I tune in astation? The trouble occurs when bothcircuits are tuned to resonance.

(2)-Body capacity is very troublesomein my receiver and it is particularly an-noying when the set is in the growlingcondition. What can be done to relievethis situation? -TABOR WILLIAMS,Newark, N. J.

(1)-The growling noise is undoubtedlydue to radio frequency oscillation whichis not strong enough to produce a highpitched squeal. One remedy for radiofrequency oscillation is to put a resistorof about 5000 ohms in the plate circuit ofthe tube which is oscillating-usually theRF tube preceding the detector.

(2)-By-pass condensers across theaudio transformer windings will help inthis case because these condensers willlower the RF potential of the rotors ofthe condensers.

* * *

MY RECEIVER works fine on thelonger waves but it is not good on shorterwaves. How can I improve the sensitivityof the receiver on the short waves?-JOHN SNIVELY, Emporia, Kansas.

One method of making your set moresensitive on the short waves is to insert aseries condenser of .0001 mfd. in the an-tenna circuit as illustrated in Fig. 555. Forlong waves the regular primary windingis used, but for the shorter waves a fewturns of the secondary are used as theprimary. A simple switch can be in-stalled to make switching from one con-nection to the other.

0/c/ tube.8d2 se

D,toc,tor Unit

0111.1.1.10G

A

C61,3

,I..H10111111P11

E9 111

/t -r- 0- Ur

/Own.

03

O 3000M,

FIG. 556

The circuit diagram and the baseboardlayout of single tube receiver requested

by Elmer Swanson

FIG. 557The correct connections in receiver em-ploying unified control and a C -300A de-

tector tube.

regenerative circuit with which I can getall the local stations on a headset. Willyou please publish a diagram and base-board layout of such a circuit?

ELMER SWANSON, Chicago, Ill.* * *

IS IT NECESSARY to make anychanges in the connections of a TRF set

to adapt it to the use of the new detectortube, that is, the CX-300 A? My setemploys unified control.

CHARLES RITTER, Waupun, Wisc.The only change you need to make is

to connect the grid return from the de-tector to the negative end of the filamentinstead of to the positive. See Fig. 557.

Join RADIO WORLD'S University ClubAnd Get Free Question and Answer Service for the Coming 52 Weeks

This Service for Yearly Subscribers OnlyHave your name entered on our subscription and University lists by special number.Put this number on the outside of the forwarding envelope (not the enclosed returnenvelope) and also put at the head of your queries. If already a subscriber, send $11for renewal from close of present subscription and your name will be entered in RadioUniversity. No other premium given with this offer.

[In sending in your queries to the University Department please paragraph them so thatthe reply can be written under or alongside of each query. Write on one side of sheetonly. Always give your university number.]RADIO WORLD, 145 West 45th Street, New York City.Enclosed find $6.00 for RADIO WORLD for one year (52 nos.) and also enter myname on the list of members of RADIO WORLD'S University Club, which gives mefree information in your Radio University Department for 52 ensuing weeks, and send

me my number indicating membership.

Name

Street* * *

I AM desirous of building a single tuber.

City and State

16 RADIO WORLD August 13, 1927SIXTH YEAR

The First and Only National Radio WeeklyMember, Radio Publishers Association

Radio World's Slogan: "A radio set far every home."

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EDITOR. Roland Burke HennessyMANAGING EDITOR. Herman BernardTECHNICAL EDITOR. Lewis Winner

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lames H. Carroll

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order. Business Opportunities ten cents per word, $1.00minimum.

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CIRCUIT DIAGRAM of a standard non -regenerative detector and one stage oftransformer coupled audio frequency am-plification, wherein hard (01 A type)

tubes are used.

(Herbert Photos)A SPEAKER, modelled after Col. Charles A. Lindbergh'splane, The Spirit of St. Louis, and made of Lata BalsaWood exclusively. That quaint and commanding figurein metropolitan commerce, known as Blau, the Radio Man,

is exhibiting the pride of his ear.

Music Tastes Being TestedRadio audiences in New York and the

East are now being given an opportunityto name their favorite composers, to tellwhat types of music they prefer, whatkind of announcements they like, and toindicate in other ways their tastes inbroadcasting, in answer to a questionnairebeing distributed in connection with TheNew York Edison Hour.

The questionnaire is believed to be theonly one of its type 'ever sent to the radiofans. It is based on two years of broad-casting experience during the EdisonHour, which now goes on the air everyTuesday night over WRNY.

Seventy-five thousand of the question-naires are being distribtited. The answers,which will be carefully tabulated, are ex-pected to yield much valuable informationconcerning the tastes of the radio listen-ers. They will show, for example, whether

Schubert or Sullivan or some other com-poser leads in popularity, and whethermusic like H. M. S. Pinafore, by SirArthur Sullivan, or the Overture to Tann-hauser, by Richard Wagner, is the favoritetype of music.

The answers to these and to other ques-tions will be used in preparing the futureprograms of the Edison Ensemble, di-rected by Josef Bonime. Quesions re-lating to broadcasting at other hours,such as household talks and cookingclasses, are also included.

A long list of the world's most famouscomposers is submitted so that everyonewill have an opportunity to vote for hisfavorite. Names like Mozart, Bach,Beethoven, Brahms, Mendelssohn, ICreis-ler Rachmaninoff, Rubinstein, Sullivanand Verdi are a few of those furnished tovoters.

1111111111MEN 11111111111.

.1111111MINIIM

1111111MMIK

0 0 0THE DIAGRAM at left illustrates the wrong way to place coils if you are attempting to construct a non -oscillatory receiver. Atthe right, the correct method is diagrammed, e.g., the popular Ne utrodyne angle method. Shields may be used to aid the killing

off of any stray energy which may feed back, and cause oscillation.

August 13, 1927 RADIO WORLD 17

Daily WeatherReports to AidAirmen in West

Washington.Because of the pressing need of

an early morning aviation weather fore-cast for the Pacific Coast, steps are beingtaken by the Department of the Navy toarrange a daily broadcast that will servethis area, the Office of Naval Operationsof the Department announced.

The statement pointed out that shortageof funds prevents immediate establish-ment of this service, but "at the latest,the broadcast should not be delayed be-yond the next session of Congress."

The full text of the statement follows:"The Navy Department is taking steps

to arrange a daily aviation weatherbroadcast to serve flying activities on thePacific Coast.

Will Be Like NAA Signals"The broadcast will be similar to that

established in April of this year, which istransmitted from the Naval Radio Sta-tion at Arlington, Va. The Pacific broad-cast probably will be transmitted fromSan Francisco at an hour just prior to thebeginning of regular flying operations.

The need for such a broadcast has beenrecognized for some time, and efforts tobring about early action have recentlybeen given impetus by communicationsfrom the Commander -in -Chief pointingout the inadequacy of the present broad-cast

"The new broadcast would be designedto meet the needs peculiar to the PacificCoast.

Wants Early ActionA number of reports from vessels in

the Pacific would be included in order togive information of storms approachingfrom that ocean and some of the Alaskanand Aleutian Island reports would alsobe included for the same reason.

Owing to shortage of funds for thisspecific purpose, it is uncertain as to whencomplete arrangements can be made, butat the latest, the broadcast should not bedelayed beyond the next session of Con-gress, when that body will be requestedto appropriate a sufficient sum to makethe broadcast possible."

Crystal Control KeepsStations to Legal Wave

An oscillating crystal is not to be mis- the frequency territory assigned to an -taken for a crystal detector capable of other station.sustaining oscillations in an electric cir- The Federal Radio Commission an-cuit like a tube amplifier. An oscillating nounced that one of the New York sta-crystal is a crystal driven at one of its tions strayed 25.6 kilocycles from itsnatural frequencies by a vacuum tube assigned frequency. Had this stationoscillator. It is no different from a loud- been crystal controlled it would havespeaker driven at one of its natural fre- stayed within 500 cycles of the assignedquencies. frequency, the maximum deviation al -

An oscillating crystal can be used in an lowed by the Commission.electrical circuit to replace both induc- What Governs Responsetance and capacity. The elasticity of thecrystal takes the place of the capacityand the mass of the crystal takes theplace of the inductance. The advantageof the crystal over an equivalent electri-cal circuit is that it has a negligible re-sistance or power loss. It is extremelysharp in tuning as a consequence.

Kept Close to FrequencyA broadcasting station which is crystal

controlled can be held to its assigned fre-quency to within a few hundred cyclesby virtue of the extreme selectivity of thecrystal, whereas a station controlled byan electrical circuit will often wander into

High frequency communication employ-ing frequencies above 10,000 kilocycleshas been made possible by crystal control.

The frequency or frequencies to whicha crystal responds depends not only onthe material of which it is made but alsoon the dimensions. Hence a crystalwhich has been ground in the shape of asquare cornered block will have threefundamental natural frequencies. It willalso have many harmonics of these fre-quencies.

The usual crystal employed for crystalcontrol is quartz, because this remainsmost constant during temperaturechanges and is the most selective.

Half of Stations OffWaves, Says Bellows

Washington.The result of the survey of the broad-

casting situation by members of the Fed-eral Radio Commission shows, accordingto Commissioner Henry A. Bellows, that50 per cent of the stations have failedto comply with the ruling prohibitingthem from deviating more than 500 cyclesfrom their assigned frequencies.

Aug. 15 has been set as the deadlinefor corrections of the mechanical defectsresponsible for the deviations. Thosestations which have not adjusted theirfrequencies by that time will not get thenew sixty-day licenses which will be is-sued that day.

Stations have come to realize the seri-ousness of their situation and are tryinghard to right matters.

Automatic Set PickedBy Bertaud for Flight

Lloyd W. Bertaud and James D. Hill,planning a non-stop flight to Rome in asingle motored Fokker monoplane, decid-ed to carry a complete radio installation,according to B. E. Smith of A. D. Card-well & Co., Brooklyn, constructors ofthe radio equipment. The operation ofthe transmitter will be entirely automaticand will be carefully guarded againstbreakdown. The call letters WRHP willbe sent continuously, interspersed bydashes, to enable ship and shore stationsto obtain bearings of the plane at alltimes.

A CW SetThe transmitter will be of 100 watts

and of the continuous wave type. It willhe adjusted for transmission on 600 and800 meters. The electric generator which

will furnish the power is located on oneof the wings of the ship, in conformitywith recent practice. The generator willhave two windings to furnish both highand low voltages for the operation of thetubes without any intermediate apparatus.The total weight of the transmitter willbe eighty-two pounds.

The receiver to be installed on theship will be a two -tube, battery -operated,regenerative set which will cover the waveband between 450 and 900 meters.

Value to Be GreatThe radio installation should prove of

great value to the flyers in case of un-favorable weather, and it will undoubted-ly be the means of saving the flyer'slives in case they should be forced downin the ocean.

Commission ThreatensFrequency Violators

Washington.The Radio Commission intends to en-

force strictly the order requiring that sta-tions remains within half a kilocycle ofthe frequency assigned to them.

The commission has not specified anyparticular method of holding the waveconstant. Stations are at liberty to chooseany system which is effective. The bestmethod is by means of quartz crystalcontrol. Crystals are now plentiful on themarket and they are inexpensive. A sta-tion can also employ the method in whicha meter is so arranged that it rings a bellas soon as the frequency of the stationnears the deadline of 500 cycles eitherside of the assigned frequency.

Bullard Will AttendParley as Delegate

President Coolidge has appointed RearAdmiral William G. Bullard, Chairman ofthe Federal Radio Commission, as dele-gate to the International Radio Confer-ence to be held in Washington Oct. 4.Secretary of Commerce Herbert Hooverheads the American delegation.

More than 50 countries will be repre-sented at the conference, at which prob-lems relating to international radio andtelegraph communications will be takenup.

New Station in BrooklynWLTH, succeeding station WFRL,

operating on 218.8 meters, opened onAug. 1 in the Leverich Towers Hotel,Brooklyn, N. Y., by permission of theRadio Commission. The station is underthe supervision of S. J. Gellard. The chiefannouncer is J. Leon Sherman. J. A.Birch has charge of operation and man-agement.

The transmitter is located in the Ja-.maica Bay section of Brooklyn to insureclearness in broadcasting. Besides themain studio in Leverich Towers Hotelthere is a branch in Manhattan.

18 RADIO WORLD August 13, 1927

"LAB" 525 FEET UPBrooklyn Station Soldto Klan Weekly Forum

The Federal Radio Commission hasauthorized the sale of station WTRC,Brooklyn, to the Independent PublishingCompany, Washington, D. C. This com-pany is publishing the Fellowship Forum,a weekly newspaper largely devoted tothe furtherance of the principles of theKu Klux Klan.

Although the Commission gave per-mission for the transfer of ownership andlocation of the station it has not yetissued a license to the new owners. It

is thought, however, that the approvalof the transfer of the station implies thatthe Commission has decided to issue alicense for operation of the station onthe old wave of 1,470 kc and the power of50 watts in Washington, D. C.

The programs to be broadcast by theFellowship Forum station, according toJames S. Vance, publisher of the Forum,will be of a patriotic and fraternal nature.

WTRC shares the wave on share timewith fifteen other broadcasters.

Morrissey in TouchWith World by RadioThe George Palmer Putnam expedition

to the Arctic is keeping in constant touchwith the world by .means of radio. Theradio operator, Manley, has been in con-versation with both European and Ameri-can stations. At the time of the Dempsey -Sharkey fight the expedition picked upthe New York Times broadcast and learn-ed almost as soon as the ringsiders ofDempsey's victory.

Jewelers Sue WHNSummons and complaint have been

served in a suit brought by SchwartzBrothers, jewelers, against Marcus LoewBrooklyn Agency, Inc., which controlsstation WHN. An effort will be made tocollect $10,000 damages for alleged fail-ure by the defendant to broadcast hourlythe time and to mention each time thename of Schwartz Brothers for one year.

The service was discontinued, it is al-leged, on the ground that the stipulatedprice of $1,000 was too low.

Interesting FallaciesA loudspeaker can be operated with

the output of a -99 type tube withoutany distortion whatever.

* * *

It is not necessary to use a grid batterybecause the quality and volume are justas good without it.

* * *

I receive signals from transcontinentalstations without any interference of anykind and the signals are perfect.

* * *

Last minute substitute programs are themost popular, especially when the listen-ers are kept in ignorance of the cause ofthe substitution.

* * *

Practically all new ideas in radio havebeen contributed during the last threeyears.

* * *

Marconi was the first man to transmitelectromagnetic waves.

* * *

The best way of controlling volume isby throttling down the filament currentof the power tube, because in that tubethe volume is the greatest.

* * *A current of 10,000 volts was sent

through the line, or putting it analogous-ly, a current of 10,000 feet flowed throughthe river.

Speaker ImpedancesAre Easy to Compare

In the output of a push-pull stage thecurrents in the two tubes are in oppositephase. When the loudspeaker is put inthe common plate supply lead no signalcan be heard unless the two are unbal-anced, because only the difference be-tween the outputs of the two tubes iseffective in the speaker.

When two speakers are connected atthe same time to the output tube of areceiver they should be connected inseries. This insures better quality thanif the speakers are connected in parallel,particularly if a tube with high outputresistance is used. Connecting the speak-ers in series usually about doubles theimpedance of the load, while connectingthem in parallel cuts the load impedancein two.

When two speakers are connected inseries to a tube the output power is divid-ed between the two in proportion to theirimpedances. If one speaker has twice theimpedance of the other it will take two-thirds of the output.

When two speakers are connected inparallel they share the power inversely astheir impedances. That is, if the imped-ance of S1 is twice that of S2, then S2takes twice as much of the power as SI.

Voltage Is the Thingin Interstage Coupling

In designing devices for coupling onetube to another in an amplifier we arenot in the least interested in transfer ofenergy or power, but only in voltage. Weso design the circuit that the greatestvoltage step-up per stage is effected withthe least distortion of the waveform andthe least difference in amplitude gainfrom the lowest to the highest essentialfrequency.

To talk of matching transformers tothe tube impedances for greatest step-up in voltage is nonsense. Yet for sevenyears we have heard it repeated parrot -

fashion several thousand times.

DeMille in DebutLauds Radio Influence

Los Angeles-Cecil B. de Mille, movingpicture director and producer, made hismicrophone debut recently over KNX.He accredited radio as being one of thegreatest forward movements of the dayand declared that it had gone a greatway in molding the viewpoint of theAmerican nation to better things.

THE HOUSE on top of the high steeltower is a new radio research laboratoryadjunct of the great factory of SteiniteLaboratories Co. This unique laboratoryis electrically heated and it is perched

525 feet over the Missouri River.

Bouck on ResistorsPublished by Amsco

The importance of reliable resistors inradio reception has stimulated severalmanufacturers to the publication of book-lets on the uses of these important units.The latest of these is "The Amsco Re-sistor Handbook." (Amsco Products Inc.,416 Broome Street, New York City, 25c.)This booklet covers the characteristics ofresistors in general and the Metaloidtype in particular.

"The Amsco Resistor Handbook" hasbeen prepared for the manufacturer by"Leh Bouck and contains a wealth of in-formation interesting and instructive tothe amateur. An endeavor has beenmade to tabulate the various data rele-vant to B and C eliminator design in aform readily applicable to the require-ments of the amateur designer. Progres-sive tables have been prepared which en-able the builder of an eliminator to calcu-late, first the approximate current whichhis receiver will draw from the line powerdevice, secondly the output voltage underthis load, thirdly the ohmage of thevarious resistors required to drop thismaximum voltage to the optimum poten-tials of the various tubes (RF, detector,etc.) and lastly the wattage dissipation re-quirements of the chosen resistors.

Glee Club HeardThirty members of the Glee Club of theUniversity of North Carolina broadcast

a program of songs from station WEAFfeaturing five negro spirituals and worksongs. The singers were en route toEngland to visit the birthplace of Wil-liam Shakespeare at Stratford -on -Avon,to sing the same songs broadcast fromWEAF. The trip is sponsored by Am-bassadors Alanson B. Houghton (GreatBritain) and Myron T. Herrick (France).The proceeds of the concert will go todefray the expenses in replacing theShakespeare memorial theatre which wasruined by fire more than a year ago.

August 13, 1927 R A 11 1 0 \V 0 R 1) 19

THE RADIO TRADE

R. C. A. Sues Another Eby Has a New SocketOver Atwater Kent With a Spring Contact

The Radio Corporation of Americabrought suit against E. B. Latham & Co.,jobbers, 550 Pearl Street, New York City,to recover damages and profits because ofsale of Atwater Kent receivers. The suitis for patent infringement and is on theAlexanderson tuned radio frequencypatent No. 1,179,073, which was recentlysustained by Judge Thacher in New Yorkagainst E. J. Edmond & Co., an AtwaterKent distributor.

It is claimed that E. B. Latham & Co.must account to the Radio Corporationfor large profits on many thousands ofradio receivers, which were not licensedunder the Radio Corporation patents.Many important radio manufacturers arelicensed under these patents, but no li-cense has been given to the AtwaterKent Company.

Patent's LatestIs Neat Phonovox

THE PACENT PHONOVOX placed ontop of a phonograph record. The volumecontrol (left) and the plug for insertionin the detector socket of a radio set, also

are shown.

The Phonovox is the latest additionto the well-known Pacent line of radioessentials. It is an electric pick-up orconnecting link between radio and thephonograph. When it is placed on a re-volving phonograph record and connectedto the radio amplifier, the record will bereproduced on the loudspeaker with allthe advantages of modern audio amplifi-cation loudspeaker reproduction.

The Phonovox is based on the opera-tion of a balanced loudspeaker armatureand partakes of all the sensitivity anddistortion -free characteristics of sucharrangements. The unit is highly effi-cient, light in weight and attractive inappearance. For hookup particularswrite to Louis G. Pacent, 91 SeventhAvenue, New York City, and mentionRADIO WORLD.

Freshman SalesExpert Makes Trip

Martin Zatulove, supervisor of sales ofthe Charles Freshman Company, manu-facturers of Freshman radio receivers, ismaking a flying trip through the South-west and Pacific Coast States.

Mr. Zatulove is acquainting authorizedFreshman dealers with the sales promo-tion plans of the Freshman Company forthe coining season.

The H. H. Eby Manufacturing Com-pany, Inc., 4710 Stenton Ave., Philadel-phia, Pa., prominent binding post andsocket manufacturers, are now producingan improved model universal type socket.It has a three-point wiping spring con-tact, which is the full length of the prong,thus giving a perfect contact. It ismoulded in Phenolic material, with astipple finish. The top of the socket isexactly the same size as the tube base.It may be mounted either above or be-neath the suhpanel.

Lynch DistributesLata Balsa Line

The Balsa Wood Reproducer Corpora-tion announced that Arthur H. Lynch,Inc., 1775 Broadway, New York, will dis-tribute Lata Balsa kits, reproducer unitsand art model reproducers.

In commenting upon the contract re-cently signed, Mr. Lynch said: "LataBalsa reproducers, either made up fromthe kits or in the very attractive artmodels which are now being offered incomplete reproducers, produce a mellowtone which is very pleasing. When usedin combination with a resistance -coupledamplifier, they reproduce music andspeech with wonderful fidelity.

"Many manufacturers of cone speakersare beginning to realize the advantagesoffered by Lata Balsa from the viewpointof acoustic properties and the advantagesof attractive designs which these newreproducers make possible. Our engin-eering staff will be pleased to consultwith any speaker or set manufacturers in-terested in applying Lata Balsa to theirpresent or future models.

"Our combination with the Balsa WoodReproducer Corporation and the BalsaWood Products Company is very attrac-tive and conducive to large sales. Allof the sales-domestic, foreign, jobbersand manufacturers-from now on will bemade through our New York office, 1775Broadway."

White Will DirectAt Industries Fete

Major jr. Andrew White will act asmaster of ceremonies at the fourth annualradio industries banquet at the AstorHotel in New York on September 21st,the week of the New York Radio World'sFair.

More than sixty broadcasters will carrythe program from the banquet to listen-ers throughout the country.

LiteratureWanted

THE names and addresses of readers ofRADIO WORLD who desire litera-

ture on parts and sets from radio manu-facturers, jobbers, dealers and mail orderhouses arc published in RADIO WORLDon request of the reader. The blank below may be used, or a post card or letterwill do instead.

RADIO WORLD,145 West 45th St., N. Y. City.

I desire to receive radio literature.

NameAddressCity or townState

E. Helecker, 2606 East 22nd St., Oakland, Calit.Birger Ericson, Box 17, Orebro, Sweden, Eu-

rope.R. F. Burton, U.S.S. New Mexico, Bremerton,

Wash.C. E. Ruppelt, 302 Hutchinson Ave., Canon,

burg, Pa.William Bryant, 425 Inero St., Frankfort, Ky.J. F. Scanlon, 675 Ingraham Ave., Calumet City,James P. Beatti.,, 9432 Hayes Boulevard, Detroit, Mich.G. Warren, Goo,c Lake, Iowa.Charles R. Smith, 628 East Lehman St..Lebanon, Pa,John G. Frank, P. 0. Box 276, Hudson, Mass.N. Chiafery, 83 Pansy St., Rochester, N. Y.R. J. Kirkman, 116 W. 45th St., N. Y. City,N. Y.Julian Crowley, 326 Elizabeth St., Monroe, Wash.C. Bloedorn, 1304 Detroit, Denver, Colo.Spencer Gay, 27 Pleasant St., Waverly, N. Y.V. S. Black, 427 Myrtly, Monrovia, Calif.J. E. Witcherm, Box 832, Willows, Calif.Chester L. Davis, Ph.D.. School of Engineering

of Milwaukee, 163 East Wells Street, Milwaukee,Wisc.

NEW CORPORATIONSAdvertisers Broadcasting Company, Newark.N. J. 60 shares, COMMUTE (Atty., TheodoreSilver, Newark, N. J.)

New Yaxley Line ReadyThe new line of Yaxley approved radio

products for the season of 1927-28 is nowready for the trade and the fan. Amongthe newest features is a highly efficientautomatic power control for switchingB Eliminator and trickle charger, oreither, thus making any receiver a power -operated set. It comes in two types, theNo. 444, that keeps the voltage drop lessthan 2 -10th volt, when used with setshaving a current draw equivalent to four.25 ampere tubes and up to eleven .06ampere tubes, and No. 445 multiple type,having no voltage drop, suitable for allset, and especially recommended formulti -tube sets.

Cable connector devices, air-cooled rheo-stats, including types with filamentswitch, convenience outlets, midget bat-tery switches, inductance switches, two -stage switches, jack and junior jackswitches, jacks, pup jacks, plugs of everydescription, nameplates, cable markers, aline of pilot lights and grid resistances,filament resistances and resistance unitsfurnished in seventeen sizes from one to400 ohms, all accurately rated. An illus-trated price list covering the entire linewill be sent to those interested uponapplication to the Yaxley ManufacturingCompany, 9 South Clinton Street, Chi-cago, Ill.-J. H. C.

THE 5 -TUBE DIAMONDFully described by Herman Bernard in

a booklet, with diagrams, including blue-print, and sent on receipt of 25 cents.The Diamond is automatically adaptableto phonograph pickup. RADIO WORLD,

145 West 45th St.. N. Y. City.

20 RADIO WORLD August 13, 1927

FLECHTHEIMSuperior Condensers for Socket

Power Circuits AreUNCONDITIONALLY GUARANTEEDNot to Break Down in Use If Operated

At or Below Their Rated VoltagesFlechtheim Quality Condensers

In compact aluminum cases, are designedfor Socket Power Sets and Power Am-plifiers, with a working voltage up to600 volts D.C., and in Filter Circuitsfor plate supply. Accurate when madeand remain accurate within 5% of theirrated capacities.

Capacity BI -Pass Filter250 Volts 450 Volts

.10 mfd. .60 .70.25 .70 .73.50 .75 .85

1 .90 1.202 1.50 1.654 3.00 3.25

14 MM. Block Condenser $10.00Mfd.

0.1-0.1 mid. H. V. Buffer Condenser $1.50We also make 1,800.volt D.C. working voltagecondensers and 2,000 D.C. working voltage trans-mitting condensers in 1. 2 and 4 mfd capacities.

Inquiries from the Trade SolicitedManufacturers Supplied

A. M. FLECHTHEIM & CO., Inc.275 BROADWAY NEW YORK

Telephones WORth 7150

COMPLETE AND LATEST LISTOF STATIONS

appeared in Radio World, dated Aug. 6. Senton receipt of 15c., or start your subscription withthat number. RADIO WORLD, 145 West 45thSt., New York City.

Wire -Wound VariableResistors Delight Moss

"The adoption of all variable wire re-sistances for use in battery eliminatorsand electrified receivers, is one of thegreatest steps toward the general accep-tance of eliminators by radio fans," saidArthur Moss, of Electrad, Inc.

"Ever since the advent of battery elim-inators there has been a need for variablepower resistances which could be insertedinto a battery eliminator and make pos-sible for the fan the adjustment of hiseliminator to suit the requirements ofhis receiver. With fixed resistances, thefan was obliged to use the availablevoltages, whether or not they suited hisneeds. This ofttimes resulted in the ap-plication of excessive voltages to sometubes in the receiver and insufficientvoltages to other tubes. Some fans werefortunate and the eliminator just matchedthe receiver.

With fixed wire resistances in theeliminator available, the set builder was

FLECHTHEIM CONDENSERSBEST BY TEST

Dealers! Write for Attractive Proposition!VENUS RADIO CORP.

142 LIBERTY STREET, NEW YORK CITYSole distributors of Flechtheim Condensers and

Imperial "B" Cases for these states:N. Y., N. J., Conn.

WATCH EXPIRATION OF YOUR SUBSCRIPTION

Subscribers will note that the end of their subscriptions is indicated on the labelson wrappers. If your wrapper shows a date earlier than the current issue, please sendpayment for renewal. Changes in expiration dates on wrappers appear two weeks afterreceipt of renewal. PLEASE ALWAYS INDICATE WHEN SUBSCRIPTION IS ARENEWAL.

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Indicate if renewal.Offer Good Until Street AddressSept. 10, 1927

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definitely limited with respect to the num-ber of tubes he could use in the con-templated receiver. But with variableresistances in the eliminator, the onlylimiting factor is the current output ofthe eliminator, since by adjusting thevoltage controlling resistances he canobtain any desired current and voltageoutput combination within -the limits ofthe eliminator. A like condition is exist-ant with tapped wire resistances. Whiletapped wire resistances afford a certainfreedom of operation, they are not equalto continuously variable units, since thenumber of taps is definite and additionaltaps are impossible.

"Hence it will be of utmost advantagefor the constructor of a battery eliminatorto utilize variable all -wire resistances inplace of fixed resistances for reducing theoutput voltage to the required value. Itis not a matter of the present need, al-though this is great enough, but ratherof viewing the future and making pro-vision without an additional cost forwhat may follow. The fact that a re-sistance is variable does not detract fromits degrees of efficient operation. It canbe made to carry any value of currentor wattage, and in practical value of re-sistance."

FiRv iniiHMA4NiASTERPIEct

AT AUTHORIZEDFRESHMAN DEALERS ONLY

2100 intelligent questions

2100 correct answers

Ratings of 62 celebrities

and

THE SUPER -TEST

SeriesThe second question book

8THE VIKING PRESS

Sent, postpaid, for $1.60THE COLUMBIA PRINT145 West 45th St.. New York

Nine -in -Line SuperDescribed In the Issues dated April 2. 0. IP and29 In such a clear manner that the veriest novicesac Warn all shout It. This circuit has 'mawIts worth In distance, selectivity. volume and hoemsality. Semi fiCio for these Issues sr sand Ityour subscription for one year and get these scale'es a premium. RADIO WORLD, 145 West 45that., Nest York City.

August 13, 1927 RADIO WORLD 21

AIR ORCHESTRA FOR FAIR

(Herbert Photos)THE WORLD'S first flying orchestra, which will shortly make a jazz tour of theUnited States. They will stop off at the leading cities, playing at broadcasting stationsand suecial functions. Listeners to WFI, Philadelphia, have already been entertained

by this organization, headed by Harry MacDonald. Four planes are used.

BIG VOLUME FROM PICKUPWhen the electric pick-up used for put-

ting a phonograph record on the radioamplifier and speaker is efficient thevolume will be very much greater thanwhen the detector tube feeds the amplifier.An adequate and suitable volume controlis essential if the reproduction is going tobe satisfactory. This volume control canbe associated with the electric pick-up orit may be in the amplifier.

ELECTRADCertified Radio Parts

Why Is the Karas Equamatic the MostEfficient Receiver Ever Designed?

Write Us for Full Information

KARAS ELECTRIC CO.4039 HB, No. Rockwell St., Chicago, Ill.

VICTREENSuper CoilsSend for Folder

Geo.- W. --Walker Co.an Carnegie Avenue

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Make any Good ReceiverBETTERcc,

TUBESC.E. MFG. CO.Providence

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HOW TO BUILD RADIO WORLD'S Four -TubeUniversal Receiver fully described by HermanBernard in the March 12, 19 and 26 issues ofRADIO WORLD. Send 45c and get these threenumbers. RADIO WORLD, 145 West 45th Street,New York City.

LIGNOLETwo -Tone Panel Chosen for the O'Rourke AC Sot.After a thorough canvass of the field for a frontpanel that combined the highest electrical efficiencywith beauty unsurpassed two-tone Lignole was chosenby Capt. O'Rourke for the AC set. The most dis-criminating radio engineers and designers regularlychoose Lignole, the NEW specially treated wood thatmeets all panel requirements.

LIGNOLE CORPORATION OF AMERICA508 South Dearborn Street CHICAGO, ILL.

RADIO WORLD'SQUICK-ACTRONCLASSIFIED ADS

10 CENTS A WORD10 WORDS MINIMUM

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A PAYING POSITION OPENto representative of character. Take orders shoes.hosiery direct to wearer. Good income. Perma-nent. Write now. Tanners Shoe Mfg. Co., 8-710C St., Boston, Mass.

THOUSANDS OF RADIO BARGAINS. Write,OMAN, 156 Concord, St. Paul, Minn,

NEW DE LUXE BST RECEIVER-S-Tube Set,resistance coupled audio, built-in C eliminator, gen-uine mahogany cabinet. Price $60. Five-da7money back guarantee. GUA1I.ANTY RADIOGOODS CO., 145 W. 45th St., N. Y. City.

- VAIFET AITIOSIROP -,RAZOR--The -only razorthat sharpens its own blades. Highly polished,nickel -plated, self -stropping Valet AUTOSTROPRazor, with one blade, m velvet lined metal case.Leather strop especially prepared, and completeoutfit in neat, lithographed carton. Mailed post-paid am receipt of 50c. SPECIAL: Send $2 foeone-third of a year subscription for Radio World(yearly price $6), mention this particular ad, andcomplete "Pal" set will be sent as a premium.If already a subscriber, your subscription will beextended three months. THE COLUMBIA PRINT,145 West 45th Street, New York City.

LINDBERGH PLANE SPEAK F-11. Pictures andexplanatory article appeared in Radio World datedJune 25, 1927. Sent on receipt of 15 cents or startyour subscription with that number. Radio World,145 W. 45th St.. N. Y. C.

COMPLETE AND LATEST LIST OFSTATIONS appeared in Radio World, datedAug. 6. Sent on receipt of 15c., or startyour subscription with that number.RADIO WORLD, 145 West 45th St., NewYork City.

Hands Off, Navy PolicyThe Navy Communication Service has

made it knows that it does not approve therequest made on it for relaying inboundcommunications in competition with domes-tic commercial companies as being againstthe policy of the United States' Govern-ment.

The Navy Communication Service willhandle messages addressed to members ofthe Naval personnel at sea from theirfamilies. This is necessary because of thegreat difficulty met by commercial com-panies in locating the person addressed.

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LATA BALSA WOOD KITS24 x 13 86.3036 x 21 8.0043 x 2A 10.00

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SET OF 3 POWERTONE COILS, $2.00

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One official booklet describing In detailhow to build this famous set, wind coils,etc.

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145 West 45th Street, New York my

22 RADIO WORLD August 13, 1927

Good Back Numbers of

RADIO WORLDThe following Illustrated articles have ap-peared In back Issues of RADIO WORLD,1926-1827,

1926

Oct. 9-A Practical "A" Eliminator, by ArthurH. Lynch. Building the Equamatic, by Capt.P. V. O'Rourke.

Oct. 18-The Bernard, by Berm Bernard. Rowto Box an "A" Supply, by Herbert D.Hayden.

Oct. 23-The 5 -tube P. C Samson, by Capt.P. V. O'Rourke. Getting DX on the Ber-nard by Lewis Winner.

Oot. 30-14ts Sing!etre' Receiver, by Herbert N.Hayden. HOW to Get Rid et Squeals, byHerman Bernard.

Nov. 8-Reduction of Interference, by A. N.Goldsmith. Variation. of Impedance.. by J.E. Anderson

Nov. 18-The 4 -tube Hi -Power Set, by HerbertE. Hoyden. A Study of Eliminator., by Her-man Bernard.

Nev. 20-Vital Pointers About Tub.. by Cant.P. V. O'Rourke. The 4 -tube Diamond ofthe Air, by Herman Bernard.

Dee. 4 --The regenerative 5 -tube Set. by CanP. V. O'Rourke. The 8 -tube Lincoln Super,by Sidney Stack.Winner's DC Eliminator. by Lewis Winner.

Dem 18-Selectivity on One Tube. by EdgerSpears. Eliminating Interference, by J. E.Anderson.

Dee. 25-A New Coupling Device. be J. M.Anderson_ Function .f iminatera by Her-man Bernard.

Ian. 1, 1927-The 2 Tube DeLuse Receiver. beArthur H. Lynch. The Twin -Choke Ampli-fier, by Kenneth Harkness.

Jan. 8-Tuning Out Powerful Local.. by J. 15

Anderson. A Choice Superheterodyne. brBrunsten Brunn. The 2 -Tube De Luxe Re-ceiver, by Arthur H. Lynch (Part at.

' Jan 15 --The DeLuxe Receiver. by Arthur H.Lynch (Part 3) The Simple Meter TootCircuit by Herbert E. Hayden. The Super-heterodyne Modulator Analyzed. by J. E.Anderson.

Ian. 22-The Atlantic Radiophone feat, by LewittRand. An Insight Into Realaton. by J. B.Anderson. A Circuit for Great Power, bySidney Stark.

ten. 29-The Harkneas H.13-27 Receiver (Part 1),by Kenneth Harkness. Use of Biasing Re-sistors, by J. E. Anderson.

Feb 5 -5 -Tube, I Dial Set, by Cain. P. V.O'Rourke. The Harkness K11-27 (Part 2),

by Kenneth Harknoes. What Produce. Tonequality, by J. E. Anderson.

Feb. 12-Phone Talk Put On Speaker, by Her-bert E. Hayden. All Batted. Eliminated,

by Herman Bernard. The Harkness KH-27Receiver. by Kenneth Harkness (Part 8).Conclusion.

Feb. t 9 --The 8 -Tube Victoreen, by Herman Ber-nard (Part 1.) The Big Six Receiver. by

Wentworth Wood. "B" Eliminator Problem,by Wm. P. Leer. The Mandrel Circuit. byCopt P. V. O'Rourke. The 8 -Tube Victereen.

by Herman Bernard (Part 2). Conclusion.Feb. 28-The 5 -tube Diamond In a Phonograph,

by Hood Astrakan. How To Read Curves. byJohn F. Rider. Proper Tubes for 5 -ValveReceiver, by J. E. Anderson.

Mar, 5-Introduction of 4 -tube Universal. byHerman Bernard. Discussion on DX, byCapt. P. V. O'Rourke. Sensible VolumeControl, by Chae. Gribben.

Mar. 12-Ten Tell -Tale Pointe. by 7. B. Ander-son. Hew To Figure Realstors, by FrankLogan. The 4 -tube UM 1, by HermanBernard, (Part .1

Mar. 19-Psycho-Analysing Circuit. by TboniaeL McKay. The Universal. by Herman Ber-nard (Part 2). How To Use Wave Trap,by James H. Carroll.

Mar. 28-The Universal, by Herman Bernard,(Part 8). Film of Current in a Vacuum

Tube, by Radoliffe Parker. Breed...Ling sirs'1300611).

April 2-Facts Every Erpertraenter Should Know,by J. E. Andenon. A Ship Model Speaker,by Herbert E. Hayden. The 8 -tube Com-pact. by Jasper Henry. The Nine -hi -LineReceiver, by Lewis Rand (Part I.)

April 9-A 5 -tube Sledded Set, by Herbert H.Hayden. The Power Compact, by Lewis

Winner. The Nine -In -Line Receiver. byLewis Rand, (Part 2.)

April 16 --The Schoolboy's Set, by Wally Frost.The Melo-Heald 11 -tube Set, by Herbert H.

Hayden. The Nine -in -Line Circuit (Part8), by Levels Rand.

April 23-The Melo-Heald Set, by Herbert EHayden (Part 21. The Nine -In -Line. by

Lewis Rand. (Conclusion). How lerenuendes Are Cut-off, by J. EL Anderson.

April SO-A 1 -tube Portable, by Jasper Jellicoe.A Ship Model Receiver, by Smedley Farns-worth. A Double Three Foot Cene, by W.H. Sinclair.

May 7-The Adam. fl -tube Set, by DanaAdams -titian (Part 1). A 2 -tube Portable,by Hood Astrakan. How to Improve Super -Heterodyne Sets, by John L. Barrett.

May I4 --A 8 -tube Portable, by Herbert E. Hay-den. The Adams -Griffin Receiver, by DanaAdams Griffin. (Conclusion).May 2I-The Victoreen Portable Receiver, byCapt. P. V. O'Rourke. A Low -Pas. Filter,by J. E. Anderson.

May 28-The Console Cone, by Thorvald Larsen.The 3 -tube Reflex by Edgar B. Francis. TheVictor.n Portable Receiver, by Capt. P. V.O'Rourke. (Part 2).

Any ropy, 15e. Any 7 copies. 31.00. Allthese 32 copies for $4.00, or start subscriptionwith any issue. Any 7 of these numbers sent asPremium with NEW yearly subscription. No'other premiums allowed. RADIO WORLD, 145West 45th Street, New York City.

Rickard Says Fight BroadcastHurts Sale of Cheap Seats

EDITOR RADIO WORLD:Tex Rickard, the boxing impressario, is

still of the opinion that broadcasting offights hurts the "gate." He maintains thatit keeps the prospective purchasers of thecheaper seats away from the ringside.There may be something to that, but any-body who ever had one of the cheaper seatsknows that it was not broadcasting whichkept him away from the ringside but that itwas rows upon rows of higher priced seatsthat kept him away.

He prefers to listen in because by so do-ing he can hear what is going on about the

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COMPLETE DETAILS on what ohmage re-sistances may be used with B eliminators to alsoobtain C bias, were given by Frank Logan in theMarch 12 issue of RADIO WORLD. Either send15c for his issue or begin your subscription withthis issue. RADIO WORLD, 145 West 45th St.,New York City.

ring which he probably could not do werehe occupying one of the cheaper seats,

He listens in because he can not afford topay the price for a seat close enough to thering to see without a telescope and to hearwithout an amplifier.

But Mr. Rickard's idea of solving theproblem is interesting. He suggests that thelisteners -in contribute freely of the coin ofthe realm for the entertainment which theyget, and to pay in proportion to the degreein which they feel themselves entertained.The promoter would assume the role of thewaiter who lives by a meagre salary andbounteous tips, or the preacher who lives bywhat he can get out of the hat that has beenpassed around.

No doubt if every radio fan who listenedin on a fight sent in a dollar in appreciationof the entertainment there would be enoughcoin to pay expenses, with a little left overfor the stockholders. It would not be nec-essary to sell any tickets but all the ringside seats as far out as the Palisades couldbe turned into compliments.

This would be a solution of the rising costof boxing promotion only once. After thatone fight the fighters would not he satisfiedwith a paltry half million for their services,but they would demand five million each.The others rendering service in connectionwith the fight would make proportionatedemands.

J. H. MESH,Fulton, N. Y.

World "A" Power Unit --$12.75Autonatieally provides even, unvarying "A" current fromyour light socket Absolutely noiseless. Assures fulltone quality from your set and wider D. X. range. FamousWORLD quality-at less than halt of the cost of any 6:mi-ler equipment. Shipped complete, subject to inspection onreceipt of price, or C.O.D., if you ,,Rah. 25 amp. unit forsets of 4 tubes or less, $12.75. 60 amp. unit for setsof 5 tubes or more, $15.75. 5% discount if cash in fullis sent with order. Send order today. World Battery Co.,1219 So. Wabash Ave., Dept 52, Ch!mgo. 15.

ONLY A QUARTER!25 CENTS, GENTLEMEN!

Buys a blueprint of 5 -tube Diamond ofthe Air and booklet on how to build it IRadio World, 145 West 45th Street, NewYork City.

Be sure to take RADIO WORLD along with you on your vacation,or read it while you are at your summer home so that you will not miss acopy; send $1.50 for three months subscription and RADIO WORLD willbe sent to you all summer. RADIO WORLD, 145 W. 45th St., N. Y. C.

FILL OUT AND MAIL NOWSUBSCRIPTION BLANK

RADIO WORLDRADIO WORLD 145 West 45th Street, New York City

(Just East of Broadway)

Please send me RADIO WORLD for months, for which

please find enclosed

SUBSCRIPTION RATES:Single Copy $ .15Three Months 1.50Six Months t 3.00One Year, 52 banes 6.00

Add $1.00 a Year for ForeignPostage; 50c for Canadian Post-age.

August 13, 1927 RADIO WORLD 23

THE INQUIRERIN THE RECEIVER described in the

July 16 issue of RADIO WORLD by BrunstenBrunn can the taps in the primary of thesupply transformer be used for a volumecontrol? What is the best method ofvolume control? Please give the valuesof R2, P1, the condensers used in thecircuit and the inductance of coil L9.Lloyd E. Jones, Walla Walla, Washington.

The control placed in the primary ofthe power transformer can be used tocontrol the volume of the receiver if de-sired, although this is not recommended.There are better methods of controllingthe volume. R2 inserted in the plate cir-cuit of the first radio frequency ampli-fier is used for this purpose. It throttlesthe current in the plate circuit of the tubeand thus prevents the transfer of energyto the second tube grid. P1 is a highresistance potentiometer by means ofwhich the input voltage to the first audiofrequency amplifier is controlled. R2should have a resistance of about 200,-000 ohms and PI should have a resistanceof at least 500,000 ohms. These two con-trols taken in conjunction with the con-trol in the primary of the power transfor-mer are adequate to control the volume.The values of the condensers in thecircuit should be as follows: Cl, .00025mfd.; C2, C4, C6, each to match the coilwith which it goes; C3, .0005 mfd.; C5,.005 mfd. or higher; C7, 4 to 10 mfd.; C8,C9, each .1 mfd.; CIO, C11, each 4 mfd.;C12, 8 mfd. or higher; C13, 4 mfd. Thetotal inductance of the choke coil L9should be about 50 henrys and it shouldhave a low resistance both to direct andalternating current, that is, it should bewound with heavy wire on a good sizedsilicon steel core.

WANT DISTANCE?Kelp your detector tube get far-away stations with a

T I S 0 NVARIABLE GRID LEAK

attached in a second - 75 centsat your dealer or direct from

TILSON & TILSON154 Nassau Street New York

0111M

SICKLESShielded Tuned Radio TransformerThe ideal coil for the Na-aid Localized Con-trol Tuning Unit, and for Truphonic Cata-comb Assembly.Widely adaptable to all leading controlunits. This transformer is compact, sturdy,sharp -tuning. Prevents both outside andlocal interference.

PRICE 52.00

Send for CatalogOTHER SICKLES

No. Coil Prices24. Browning -Drake $7.50 Set18A. Roberts Circuit 8.00 Set25. Aristocrat Circuit 8.00 Set

THE F. W. SICKLES CO.142 UNION STREET

SPRINGFIELD MASS.

IN AN ARTICLE by Robert F. Good-win and Stuart S. Bruno in the July 16issue is a description of a 'compact elim-inator. There are three resistors con-nected to A- which are marked 3,000,

2,000, 150 ohms, the 150 -ohm unit beingtapped. Will you kindly explain the pur-pose of these?-George Bizek, Butte,Mont.

The 3,000 -ohm resistor regulates theplate voltage to the detector tube, sincethe voltage drop in it is 45 volts. The2,000 -ohm resistor supplies the grid biasto the power tube, since the voltage dropin this is 40 volts, the required value of a371 tube. The tapped 150-ohni resistorsupplies the bias bi the other amplifiers.

Everybody or

Nobody?If It's a Product You Manu-facture, the Answer Is "Every-body"-If It's the Extent ofYour Personal Financial Re-sources, the Answer Is "No-body." 4

Secrets Should Be Imparted to Nobody.You Would Not :spend Any Time, MuchLess Any Money, Arousing Anybody's In-terest in What Is Nobody's Business. ForInstance, How Old Your Wife Is, or HowMuch Money You Have in the Bank.

If You Have Something to Sell You Want EVERYBODY toKnow It. Perhaps you have a new product this season, and yourfirst real problem is to ESTABLISH it as an entity. Or you mayhave the same excellent line this season as you had last. But youdon't want the radio buying public to forget you, as it quickly will,unless you keep your name and product constantly in the fore-ground.

You Must Sell the Consumer-The Jobber Will Fill the Dealer'sOrders When the Public Demand Makes the Dealer Send in theOrders, Therefore-Create that public demand. Advertise your product in the

Fourth AnnualRadio World's Fair Numberof Radio World, which will be published September 17,two days before the Fair opens, and will be circulatedthroughout the entire United States by that date, aswell as being distributed to thousands upon thousandswho attend the Fair, at Madison Square Garden, NewYork, September 19 to 26, inclusive.

Radio World is America's First and Only National Radio Weekly,dated every Saturday and Published every Wednesday, and cir-culating among home builders of sets, purchasers of factory -madesets, and also among the retail, jobbing and manufacturing trade.

Advertising forms for the Fourth AnnualRadio World's Fair number-the predomi-nant issue-dated September 17, closeTuesday, September 6, at noon. For rates,see editorial page.

"Tell It to Everybody"Magnetize Your Dollar.Give It a Pulling Power ItNever Had Before.Advertise in the Fourth AnnualRadio World's Fair Number.

RADIO WORLD (Advertising Manager), 145 West 45th StreetNew York, N. Y.

Write or Telegraph for Reservations-or Telephone BRY ant 0558 or 0559

RADIO WORLD August 13, 1927

Good Back Numbers of

RADIO WORLDThe following Illuetrated articles have op-p.eated in back Issues of RADIO WORLD I1926.1927i

1926

Oct. 9-A Practical "A" Eliminator, by ArthurH. Lynch. Building the Equamatic, by Capt.P. V. O'Rourke.

Oct. 16-The Bernard, by Herman Bernard. Howto Box an "A" Supply, by Herbert B.Hayden.

Oot. 23-The 5 -tube P. C Samson, by Capt.P. V. O'Rourke. Getting DX on the Bee-isard by Lewle Winner.

Oct. 30-The Dingletrol Receiver. by Herbert B.Hayden. How to Get Rid of Squeal., byHerman Bernard.

Nov. 8-Reduction of Interference, by A. N.Goldsmith. Variations of impedances. by J.E. Anderson

Nov. 13-The 4 -tube Hl -Power Set, by HerbertE. Hayden. A Study of Eliminators. by Her-man Bernard.

Nev. 20-Vital Pointer° About Tubes. by Cant.P. V. O'Rourke. The 4 -tube Diamond ofthe Air, by Herman Bernard.

D ee. 4-The regenerative 5 -tube Set, by Cap.P. V. O'Rourke. The 8 -tube Lincoln Super,by Sidney Stack.Winner'. DC Eliminator, by Lewis Winner.

D ee. 18-Selectivity on One Tube, by EdgarSpears. Eliminating Interference, by I. II.Anderson.

Dee. 25-A New Coupling Device, be I. B.Anderson Funetion of Eliminators. by Mer-man Bernard.

Jan. 1, 1927-The 2 Tube DeLuse lbseelver. byArthur H. Lynch. The Twin -Choke Ampli-der, by Kenneth Harkness

Jan. 8-Tuning Out Powerful Loeals. by J. NAnderson. A Choice Superheterodyne, by

Brunsten Brunn, The 2 -Tube De Luxe Re-ceiver, by Arthur H. Lynch (Part 2).

' inc. 15-The DeLuse Receiver, by Arthur H.Lynch (Part 3) The Simple Meter TeatCircuit by Herbert E. Hayden. The Super-heterodyne Modulator Analysed, by J. E.Anderson.

Ian. 22-The Atlantic Itadlophone feat, by LewisRand. An Insight Into Reeleton. by J. B.Anderson. A Circuit for Great Power. bySidney Slack.

lee. 29-The Harkness KH-27 Receiver (Part I),by Kenneth Harkness. Use of Biasing Re-sistor.. by J. E. Anderson.

Feb 5 -5 -Tube. 1 Dial Set, by Capt. P. V.O'Rourke. The Harkness 1111-27 (Part 2),

by Kenneth Harkness. What Produce. ToneQuality, by J. E. Anderson.

Feb. 12-Phone Talk Put On Speaker, by Her-bert E. Hayden. All Batteries Eliminated,

by Herman Bernard. The Harkness KII-27Receiver, by Kenneth Harkness (Pert 8).Conclusion,

Feb. I9-The 8 -Tube Victoreen, by Harman Ber-nard (Part 1.) The Big Six Receiver. by

Wentworth Wood. "B" Eliminator Problem.by Wm. P. Lear. The Phasatrol Circuit. byCant P. V. O'Rourke. The 8 -Tube Victereen,

by Herman Bernard (Part 2). Conclusion.Feb. 28 --The 5 -tube Diamond In a Phonograph,

by Hood Astrakan. How To Read Curve., byJohn F. Rider. Proper Tubes for 5 -ValveReceiver, by J. E. Anderson.

Mar. 5-Introduction of 4 -tube Universal. byHerman Bernard. Discussion on DX. byCapt. P. V. O'Rourke. Sensible VolumeControl. by Chas. Gribben.

MU. 12-Pen Tell -Tale Palate, by J. E. Ander-son. Hew To Figure Resistor., by PrankLogan. The 4 -tube Universal, by HermanBernard, (Part .)

Mar. 19--Paycho-Analysing Circuit. by ThomasL. McKay. The Universal, by Herman Ber-nard (Part 2). How To Uee a Wave Trap,by James H. Carroll.

M sr. 28-The Universal. by Herman Bernard,(Part 3). Fltw of Current in a VacuumTube, by Radcliffe Parker. Broadouting HOP -net Ism.

April 2-Facts Every Experimenter Should Know,by J. E. Anderson. A Ship Model Speaker,by Herbert E. Hayden. The 3 -tube Com-pact, by Jasper Henry. The Nine -in -LineReceiver. by Lewis Rand (Part 1.1

April 9-A 6 -tube Slelded Set, by Herbert N.Hayden. The Power Compact, by Lewis

Winner. The Nine -in -Line Receiver. byLewis Rand, (Part 2.)

April 16-The Schoolboy's Set, by WallY Froet.The Melo-Heald 11 -tube Set, by Herbert E.

Hayden. The Nine -in -Line Circuit (Part5), by Lewis Rand.

April 23-The Melo-Heald Set, by Herbert EHayden (Part 2). The Nine -in -Line. by

Lewis Rand. (Conclusion). How Frequen.elm Are Cut-off, by J. E. Anderson.

April 30-A 1 -tube Portable, by deeper Janice..A Ship Model Receiver, by Smedley Farns-worth. A Double Three Exit Gene, by W.H. Sinclair.

May 7-The Adaros-GriMn 8 -tube Set, by DanaAdams -Griffin (Part 1). A 2 -tube Portable,by Hood Artrakan. How to Improve Super -Heterodyne Sets. by John L. Barrett.

May (4-A 3 -tube Portable, by Herbert E. Hay-den. The Adams -Griffin Receiver, by DaneAdams Griffin. (Conclualon).

May 21-The Vietoreen Portable Receiver, byCapt. P. V. O'Rourke. A Low -Pas. Filter,by J. E. Anderson.

May 28-The Console Cone, by Thorvald Larsen.The 3 -tube Reflex by Edgar B. Francis. TheVtctoreen Portable Receiver, by Capt. P. V.O'Rourke. (Part IL

Any may. 15e. Any 7 melee. 91.00. Allthese 32 copies for $4.00, or start subscriptionwith any Issue. Any 7 of these number. rent aspremium with NEW yearly subscription. Noether premiums allowed. RADIO WORLD, 145West 45th Street, New York City.

Rickard Says Fight BroadcastHurts Sale of Cheap Seats

EDITOR RADIO WORLD :Tex Rickard, the boxing impressario, is

still of the opinion that broadcasting offights hurts the "gate." He maintains thatit keeps the prospective purchasers of thecheaper seats away from the ringside.There may be something to that, but any-body who ever had one of the cheaper seatsknows that it was not broadcasting whichkept him away from the ringside but that itwas rows upon rows of higher priced seatsthat kept him away.

He prefers to listen in because by so do-ing he can hear what is going on about the

l' -lendable "14" Flattery Power

100 Velt Ed.sesNon -Destructive, Rechargeable "B" BlattfY withcharger. Shipped dry with solution, 912.00.140 Volt with charger. 917.00.SEND NO MONEY PAY EXPRESSMANWrite for our Free illustrated 24 -page

BookletSEE JAY BATTERY COMPANY913 Brook Avenue New York Olh

p I S for 100Voll °ILETube Efficiency

Only Amperite eappllee automatically the nelf-adjusting filament current your tubes require.Eliminates hand rheostats. Simplifies wiring. In-sist on Amperite. Accept nothing else. Price $1.10

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7h4"SELF-ADJUSTING"RheartatCOMPLETE DETAILS on what ohmage re-

sistances may be used with B eliminators to alsoobtain C bias, were given by Frank Logan in theMarch 12 issue of RADIO WORLD. Either send15e for his issue or begin your subscription withthis issue. RADIO WORLD, 145 West 45th St.,New York City.

ring which he probably could not do werehe occupying one of the cheaper seats.

He listens in because he can not afford topay the price for a seat close enough to thering to see without a telescope and to hearwithout an amplifier.

But Mr. Rickard's idea of solving theproblem is interesting. He suggests that thelisteners -in contribute freely of the coin ofthe realm for the entertainment which theyget, and to pay in proportion to the degreein which they feel themselves entertained.The promoter would assume the role of thewaiter who lives by a meagre salary andbounteous tips, or the preacher who lives bywhat he can get out of the hat that has beenpassed around.

No doubt if every radio fan who listenedin on a fight sent in a dollar in appreciationof the entertainment there would be enoughcoin to pay expenses, with a little left overfor the stockholders. It would not be nec-essary to sell any tickets but all the ringside seats as far out as the Palisades couldhe turned into compliments.

This would be a solution of the rising costof boxing promotion only once. After thatone fight the fighters would not be satisfiedwith a paltry half million for their services,but they would demand five million each.The others rendering service in connectionwith the fight would make proportionatedemands.

J. H. MESH,Fulton, N. Y.

World "A" Power Unit --$12.75Automtimlly provides even, unvarying "A" current fromyour light socket Absolutely noiseless. Assures fulltone quality from your set and wider D. X. range. FamousWORLD Quality-at less than half of the cost of any slmi-iar equipment. Shipped complete. subject to inspection onreceipt of price, or C.O.D., if you wish. 25 amp. unit forsets of 4 tubes or less, $12.75. 80 amp. unit for setsof 5 tubes or more, $15.75. 55'1, discount If cash In fullis sent with order. Send order today. World Battery CO.,1219 So. Wabash Ave.. Dept. 82, Ch:cago,

ONLY A QUARTER!25 CENTS, GENTLEMEN!

Buys a blueprint of 5 -tube Diamond ofthe Air and booklet on how to build it IRadio World, 145 West 45th Street, NewYork City.

Be sure to take RADIO WORLD along with you on your vacation,or read it while you are at your summer home so that you will not miss acopy; send $1.50 for three months subscription and RADIO WORLD willbe sent to you all summer. RADIO WORLD, 145 W. 45th St., N. Y. C.

FILL OUT AND MAIL NOWSUBSCRIPTION BLANK

RADIO WORLDRADIO WORLD 145 West 45th Street, New York City

(Just East of Broadway)

Please send me RADIO WORLD for months, for whisk

please find enclosed

SUBSCRIPTION RATES:Single Copy $ .15Three Months 1.50Six Months 3.60One Year, 52 Issues 6.00

Add $1.00 a Year for ForeignPostage; 50c for Canadian Post-age.

August 13, 1927 RADIO WORLD 23

THE INQUIRERIN THE RECEIVER described in the

July 16 issue of RADIO Wean by BrunstenBrunn can the taps in the primary of thesupply transformer be used for a volumecontrol? What is the best method ofvolume control? Please give the valuesof R2, P1, the condensers used in thecircuit and the inductance of coil L9.-Lloyd E. Jones, Walla Walla, Washington.

The control placed in the primary ofthe power transformer can be used tocontrol the volume of the receiver if de-sired, although this is not recommended.There are better methods of controllingthe volume. R2 inserted in the plate cir-cuit of the first radio frequency ampli-fier is used for this purpose. It throttlesthe current in the plate circuit of the tubeand thus prevents the transfer of energyto the second tube grid. P1 is a highresistance potentiometer by means ofwhich the input voltage to the first audiofrequency amplifier is controlled. R2should have a resistance of about 200,-000 ohms and P1 should have a resistanceof at least 500,000 ohms. These two con-trols taken in conjunction with the con-trol in the primary of the power transfor-mer are adequate to control the volume.The values of the condensers in thecircuit should be as follows: Cl, .00025mfd.; C2, C4, C6, each to match the coilwith which it goes; C3, .0005 mfd.; C5,.005 mfd. or higher; C7, 4 to 10 mfd.; C8,C9, each .1 mfd.; C10, C11, each 4 mfd.;C12, 8 mfd. or higher; C13, 4 mfd. Thetotal inductance of the choke coil L9should be about 50 henrys and it shouldhave a low resistance both to direct andalternating current, that is, it should bewound with heavy wire on a good sizedsilicon steel core.

t.

NMI

WANT DISTANCE?Help your detector tube get far-away stations with a

TILSONVARIABLE GRID LEAK

attached in a second - 75 centsat your dealer or direct from

TILSON & TILSON154 Nassau Street New York

11

SICKLESShielded Tuned Radio TransformerThe ideal coil for the Na-ald Localized Con- trol Tuning Unit, and for Truphouic Cata-comb Assembly.Widely adaptable to all leading controlunits. This transformer is compact,. sturdy,sharp -tuning. Prevents both outside andlocal interference.

PRICE $2.00

Send for CatalogOTHER SICKLES

No. Coll Price.24. Browning -Drake $7.50 Set18A. Roberts Circuit 8.00 Set25. Aristocrat Circuit 8.00 Set

THE F. W. SICKLES CO.142 UNION STREET

SPRINGFIELD MASS.

IN AN ARTICLE by Robert F. Good-win and Stuart S. Bruno in the July 16issue is a description of a compact elim-inator. There are three resistors con-nected to A- which are marked 3,000,

2,000, 150 ohms, the 150 -ohm unit beingtapped. Will you kindly explain the pur-pose of these?-George Bizek, Butte,Mont.

The 3,000 -ohm resistor regulates theplate voltage to the detector tube, sincethe voltage drop in it is 45 volts. The2,000 -ohm resistor supplies the grid biasto the power tube, since the voltage dropin this is 40 volts, the required value of a371 tube. The tapped 150 -ohm resistorsupplies the bias to the other amplifiers.

4111111M1111

Everybody °r

Nobody?If It's a Product You Manu-facture, the Answer Is "Every-body"-If It's the Extent ofYour Personal Financial Re-sources, the Answer Is "No-body."

Secrets Should Be Imparted to Nobody.You Would Not Spend Any Time, MoochLess Any Money, Arousing Anybody's In-terest in What Is Nobody's Business. ForInstance, How Old Your Wife Is, or HowMuch Money You Have in the Bank.

If You Have Something to Sell You Want EVERYBODY toKnow It. Perhaps you have a new product this season, and yourfirst real problem is to ESTABLISH it as an entity. Or you mayhave the same excellent line this season as you had last. But youdon't want the radio buying public to forget you, as it quickly will,unless you keep your name and product constantly in the fore-ground.

You Must Sell the Consumer-The Jobber Will Fill the Dealer'sOrders When the Public Demand Makes the Dealer Send in theOrders, Therefore-Create that public demand. Advertise your product in the

Fourth AnnualRadio World's Fair Numberof Radio World, which will be published September 17,two days before the Fair opens, and will be circulatedthroughout the entire United States by that date, aswell as being distributed to thousands upon thousandswho attend the Fair, at Madison Square Garden, NewYork, September 19 to 26, inclusive.

Radio World is America's First and Only National Radio Weekly,dated every Saturday and Published every Wednesday, and cir-culating among home builders of sets, purchasers of factory -madesets, and also among the retail, jobbing and manufacturing trade.

4Advertising forms for the Fourth AnnualRadio World's Fair number-the predomi-nant issue-dated September 17, closeTuesday, September 6, at noon. For rates,see editorial page.

"Tell It to Everybody"Magnetize Your Dollar.Give It a Pulling Power ItNever Had Before.Advertise in the Fourth AnnualRadio World's Fair Number.

RADIO WORLD (Advertising Manager), 145 West 45th StreetNew York, N. Y.

Write or Telegraph for Reservations-or Telephone BRY ant 0558 or 0559

RADIO WORLD August 13, 1927

A Great Deal for a Very Little!Ordinarily This Seems Too Good to Be True, But Here Is An Instance of Complete Verification

The New De LuxeModel BreteoodWith Condenser

Attached

WHEN you are deciding on whatparts are to go into the receiv-er you are about to build, un-der no circumstances dismiss

the grid leak with only casual con-sideration. Respect the grid leak assomething well worthy of expertchoice.

The best course is to select a va-riable grid leak with an ample re-sistance range, one that may bemounted on baseboard, sub -panel orfront panel, as you prefer.

Such a leak is the BRETWOODVARIABLE GRID LEAK, which isnow on the market in new de luxemodel, representing improvements

in mecnanical strength, electrical efficiency andutility. Higher Efficiency

You should use a variable grid leak like the- - - - - - -- -North American Bretwood Co.,

145 West 45th Street, New York City.Gentlemen: Enclosed find $1.75. Send me at once one

De Luxe Model Bretwood Variable Grid Leak on 5 -daymoney -back guarantee. (Or 5225 for leak with grid con-denser attached.)NAMEADDRESSCITY STATE

Inquiries Solicited front the Trade

BRETWOOD VARIABLE GRID LEAK in a setyou are about to build, or should put one in yourpresent receiver, because it will enable you to gethighest operating efficiency from the detector tube.As nearly all tubes used as detectors draw grid cur-rent, the resistance value of the leak is importantfor biasing and discharge purposes. Not only canexactly the right degree of flow be established todiscard excess electrons, but the grid -to -filamentimpedance is so affected as to afford best selectivityunder the circumstances. Only a variable leakgives this precision choice.

You prevent overloading of the detector tube bycorrect leak setting. This improves tone qualityconsiderably. Often if your set sounds distorted,this is immediately and permanently remedied.Hence you reap greater volume, better selectivityand purer tone quality-all by the simple insertionof a BRETWOOD DE LUXE MODEL VARIABLEGRID LEAK.

Selected by BernardThis efficient instrument so uuck Herman

Bernard that he prescribed it for his latest and mostpopular circuit, Radio World's Universal Four -TubeReceiver.

The BRETWOOD DE LUXE MODEL VARI-ABLE GRID LEAK costs $1.75-a small enoughprice for so much efficiency. If desired, a .00025mfd. BRETWOOD BULLET CONDENSER is sup-plied, mounted on the leak, at 50 cents extra.

Note: The Bretwood Leak's range is .25 to 10 meg.Dealers: Send in your orders direct!

B. S. T. CONE SPEAKERGuaranteed to give Satisfaction in

Tone, Volume and AppearanceAdjustable to Volume Desired

18 inches in diameter edged in GoldBraid, Art Metal Base can be placedon highly polished surface withoutdanger of scratching.

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Satisfaction Guaranteed or Money Back

GUARANTY RADIO GOODS CO. 145 West 45th St., New York