america's first and only national radio weekly the everyman 4 · 2019. 7. 17. · imitated...
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DEC. 3 MODERNIZING YOUR PHONOGRAPH 1.5 Cents
REG. U.S.PAT. OFF.
America's First and Only National Radio Weekly
THE EVERYMAN 4
It is this neat and accurate layout of parts which contributes largely to the remarkableresults obtainable with the Everyman 4.-See pages 8 and 9.
41=111111111111MMII
Getting Tube Characteristics at a GlanceSee Pages 12 and 13
Efficiency Date on the 4 and 5 -Tube Model DiamondSee Pages 10 and 11
RADIO WORLD December 3, 1927
The Famous S -M 440Time Amplifier
With a greater degree of selectivity,with a greater amplification factor-the440 Jewelers' Time Signal Amplifieroffers possibilities never before realizedin long wave amplifier construction. Itis more accurate-with a finer degree ofcalibration-than any long wave ampli-fier that may be built from standardparts today. It is housed in a copperand brass catacomb and its three radiofrequency stages and detector are indi-vidually shielded. The 440 Time SignalAmplifier is tremendously popular al-ready. Thousands have been sold, forit's the best long wave amplifier everdeveloped. It is tuned exactly to 112K.C., the 2627 meter wavelength of theNaval Observatory station at Arlington(NAA). Price $35.00.
We Could ChargeMore-But
A Better TransformerCan't Be Made
Imitated everywhere-never equalled-the S -M 220 audio transformer stands outtoday as the finest for audio amplificationthat money can buy just as it did whenintroduced a year and a half ago. The220 has been copied in one or more of itscharacteristics by every high-grade trans-former put on the market since then-inits rising low note characteristic or in its5000 cycle cut-off. That's proof that theprinciples of the 220 first introduced areright-that the market is still trying tocatch up.
Don't be misled by exaggerated claims-for it takes real core and wire to makea good transformer. The 220 has from25 to 50 per cent more steel and copperin its construction than any other trans-former on the market. That means ahigh primary impedance only throughwhich real bass note amplification is madepossible.
That's why S -M 220's and 221's arespecified in more popular receiver designs-why they have outsold every other trans-former in their price field. That's whythey're sold on an unconditional money -back guarantee to give better quality thanany other audio amplifying device avail-able.
We could charge from 25 to 50 per centmore than we do, but at no price can youget a better tt'ansformer. The 220 audiois $8.00, and the 221 output is $7.50. Theyare priced low, but not merely made tosell at a low price.
* * *
We can't tell you here about all thenew S -M developments, but if you'll sendthe coupon we will forward more fulldata on transformers, power amplifiers,complete light socket operation than youcan read in a week.
SILVER -MARSHALL, Inc.878-B West Jackson Blvd., Chicago, Ill.
SILVER -MARSHALL, Inc.878-13 West Jackson Blvd.,. Chicago.
Please send me complete information on the new1 S-111 developments, for which I enclose 10c
.1, Name
Address
Talk About Gifts! And About the Gifted, Too!The Holiday Gifts Number of Radio World will be the December 10
issue-alive with the Christmas spirit, full of ideas on what to buy for Christ-mas in the radio parts, accessories and set fields-Fit for Superlatives ThatRightly Ride on Santa's Sleigh.
Dated December 10, to press on Wednesday noon, November 30, on thenews-stands Wednesday, December 7, all over the United States, and inour subscribers' hands before December 7, the Holiday Gifts Number willbe a resplendent, inspiring, stimulating, pulling number.
EDITORIAL FEATURES INCLUDE"Three Months With the Great Recreator," by J. E. Anderson, Technical Editor."High Mu Tubes as Detectors," by Robert W. SandelL"Giving the Crackle. the Gate," by Tim Turkey."What Every Novice Should Know," by James H. Carroll, Contrthuting Editor."Welcome Radio Christman Gifts," by Herbert E. Hayden."The Everyman Four," as designed by Fred H. EhlertFront cover in colors, I. Ticktin, "The Caroler."
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RAP I 0WORLD
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A., (.1 b, 114:11
ew Rule: StopWhist/ing!Master Minds Developing Means to End Heterodyne Interference Between Sta-tions Assigned to Same Frequency - What Happens When Two Things,
Equal to the Same Thing, Are Not Equal to Each Other
Considerable work is being done both by the FederalRadio Commission and private interests with a viewof eliminating the heterodyne whistles which are caus-ing interference with radio reception.
The problem now is not so much interference be-tween stations operating on adjacent channels as theinterference between stations assigned to the samechannel but separated by hundreds of miles. The prob-lem now is to make these stations operate on exactlythe same frequency.
As yet the Commission does not require a closeradherence to the assigned frequency than 500 cyclesabove or below, although this deviation is far too greatto insure listeners against interference. The 500 cyclelimit is adequate to prevent interference between twoadjacent channels, but not to eliminate interferencebetween two stations nominally operating on the samefrequency, for then a deviation of no more than 5cycles above or below is permissible by the law ofhearing.
When practical methods have been worked outwhereby any two stations can be synchronized asclosely as this, it is safe to predict that the FederalRadio Commission will issue a ruling requiring themso to synchronize.
There are three methods now used for synchroniza-tion.
A report on an experiment in eliminatinginterference by heterodyne between twoWashington broadcasting stations operatingon the same wavelenth has been submittedto the Federal Radio Commission by thepresident of the Doolittle Radio Corpora-tion of New Haven, Conn., Franklin M.Doolittle.
The "beat note" method was used with areceiving set and telephone circuit, wherebyWDRC, New Haven; operating with 500watts on the same wavelenth as WAIU,Columbus, Ohio, using 5,000 watts, are pre-vented from interfering with each other.The frequency is 1,060 kilocycles (282.8meters).
Following is Mr. Doolittle's report infull:
Before we adopted the present arrange-ment the heterodyne was so bad that itruined our program for several nights.
I have rented a circuit from the Tele-phone Company between my home andthe transmitting plant at Beacon Hill,the two points being about five milesapart.
The output of the receiving set isconnected through a step-down trans-former to the line. The station endof the line is connected to the input ofa two -stage amplifier which compensates
A method of synchronization has been suggestedby Clive B. Meredith, of Syracuse. This involves theuse of a central oscillator kept at a constant frequencyof 10,000 cycles, from which all the transmitting sta-tions in the country would derivt, their operating fre-quencies by selecting the harmonics assigned to themby the government. The Commission is greatly in-terested in this scheme, as it seems to be a generalsolution to moat heterodyning interference.
If this scheme is adopted the standard frequencycould be distributed in at least two ways. It could bebroadcast as a modulation on a suitable short wavewith power enough to reach all interested stations;and it could also be transmitted by land lines and dis-tributed the same way that chain programs are nowdistributed.
The standard oscillator under this scheme could bekept by a Government agency at a centrally locatedplace, and its frequency could be held constant by wellknown means to an accuracy of one part in a millionover long periods of time. This would mean that thegreatest variation in a frequency of 1,000,000 cycleswould be one cycle per second. But as all stationsoperating on the same carrier would change by thesame amount in the same direction simultaneouslythere would not even be a trace of a heterodyne.
for the line loss. As the circuit is en-tirely by cable, the quality is decidedlybass. The line could, of course, be equal-ized, but this is not necessary for thepurpose, in fact, it is rather desirable toemphasize the bass.
Adjusts for Zero Beat
This arrangement allows the operatorat the station to hear the program as itis being received five miles distant, andif a heterodyne howl is present fromColumbus, he then adjusts until zero beatis obtained. This arrangement does notnecessitate passing radio frequencies overthe circuit, but employs the audio out-put of the receiver.
Our transmitter is of the master os-cillator type and we employ a crystal forchecking frequency, so that it is compara-tively easy to make the adjustment withcertainty and still not get away from ourfrequency. In this connection, our crystalchecks with Columbus within about 100cycles.
I have particularly wanted to watch theresults obtained with the system for aperiod of nights before giving you a re-port.
As to the results obtained, while themethod does not completely eliminate in-
terference, it greatly reduces it whenColumbus is very loud and for all prac-tical purposes eliminates it when they arecoming in with moderate volume.
Only a Hill LeftIn either case it eliminates the howl
and leaves only an unintelligible hissingsound in the background between breaksand soft passages in our program. Thisinterference sounds much like the hissingquality obtained when spark signals arereceived by the heterodyne method.
So far WAIU is the only one of thetwo stations sharing time on 1060 kilo-cycles in Columbus which has causedus any trouble. We have made the sameadjustment with WEAO and their in-tensity is so much less than that of WAIUthat it completely solves the situation asfar as they arc concerned. The arrange-ment is reciprocal in that it would, ofcourse, reduce interference in the vicinityof Columbus in the same manner.
We have hail such satisfactory resultswith this method of reducing interferencethat I am going to try an automatic con-trol which will start to function as soonas the heterodyne appears.
Has Faith in ItSo far this is merely an idea, but I be-
4 RADIO WORLD December 3, 1927
lieve it can be made to work and willsend you details as soon as I have had achance to try% it out.
The general plan of the scheme is tocontrol our transmitter with our crystaland to vary the frequency of the crystalby variation in temperature which is con-trolled from the receiving set at my home.
I may have difficulty with the controlas I have not worked out details but Ibelieve that it can be done by the com-bination of a tube arrangement and atuned relay. The relay would have to betuned to some subaudible frequency, say10 cycles, so that it would respond beforethe heterodyne became audible and wouldnot be influenced by program frequencies.
Incidentally, it would seem to me ifsuch a system is practical it might aidin chain broadcasting on the same fre-quency.
Orestes H. Caldwell, Federal Radio Com-missioner, discussed heterodyne interferenceand remedies as follows:
Even under best conditions we havefar too many stations to accommodateon 89 wavelengths. As long as 700 sta-tions are to be assigned places in thebroadcasting band, there are bound to beheterodynes under present methods, forthe Commission, against its better judg-ment has been forced to locate stationstoo close together to avoid interferenceunder conditions of maximum -reception.
That some heterodynes now exist, can-not be denied, but the transient charac-ter of most of these-here tonight andgone tomorrow-or gone even in the nexthour-indicates that they result from dis-tant stations wandering off their assignedchannels and straying into the adjoiningrights -of -way of the stations thus imposedupon.
With the help of the Radio Division ofthe Department of Commerce, frequentmeasurements observations are now be-ing made on all broadcasting stations tosee that they adhere to their wavelengthswithin the one-half kilocycle limit pre-scribed by the Commission.
Stations Must BehaveFor even the most perfect allocation
structure can be rendered useless if sta-tions do not walk the "ether chalk lines,"and keep on their assignments.
With the broadcasting channels filledto overflowing on the basis of stationseparation at distances necessary to elimi-nate heterodyning between carrier -waves,another avenue for relief is presented bythe engineering method of accuratelysynchronizing the frequencies of stationson the same channel, so that the onlyinterference will be cross -talk and notheterodyning.
For, as is well known, although theaudible signal of a 500 -watt station mayunder good average conditions be heard100 to 200 miles, its carrier under thesame conditions will cause heterodynes or"whistles" up to 1,000 miles. Heterodyn-ing results from the slight difference infrequencies of two stations on the samechannel.
The Beat NoteFor example, on the 900 kilocycle chan-
nel, if one station is operating accuratelyat 900,000 cycles, and a second stationwithin carrier -wave range is operating at900,250 cycles, the listeners between andat a distance from both stations will heara squeal which is the audible differencebetween the two frequencies-that is, amusical note of 250 cycles or about middleC on the piano.
If, however, the frequencies of thesetwo stations can be brought into suchclose synchronism that the difference be-tween their radio frequencies is less thanan audible frequency, the former hetero-dyne will disappear. The stations canthen safely be located closer togethergeographically up to a minimum distance
1060 KC. WEST-
O.o- otkio of,
0_ OopSOU CILetit
TWO TRANSMITTING STATIONS, ONE IN THE EAST AND THE OTHERAT THE SAME TIME. NO TROUBLE IS EXPERIENCED IN RECEIVERSIF ONE STATION STRAYS OFF ITS PROPER FREQUENCY BY A SMA/A 250 CYCLE WHISTLE IN HIS LOUDSPEAKER, WHICH WILL SPOIL I
HETERODYNE BELOW AUDI
where the program of one comes in loudenough to appear as "cross -talk" on theother.
This separation -distance where notice-able cross -talk occurs between stations,is from one -quarter to one -tenth of theseparation -distance at which heterodyn-ing or "carrier -wave interaction" becomesobj ectionable.
Hence if stations on the same frequencycan be accurately synchronized, it will bepossible to utilize our present channelsmany fold more effectively, and to elimi-nate heterodynes that now persist becauseof the close duplication of stations neces-sary on the same frequency channel.
Three methods for such station syn-chronization appear to promise excellentpossibilities :
Wire Control
1 Wire control of two or more stations from a common source of radio
frequency. This plan is being operatedwith success nightly between stationWBZ, Springfield, Massachusetts, and itsauxiliary WBZA, in Boston, a distance of100 miles.
These two stations operate on the 900kilocycle channel at precisely the samefrequency, without heterodyning. Whilethey deliver the same program, their suc-
cessful operation indicates the possibilityof synchronizing stations further apart, at"non -crosstalk" distances, and transmit-ting different programs.
Similar wire synchronizing of stationsis now contemplated in several other lo-cations. When further developed, thisplan offers an economic solution of thevery serious problem of chain -programoperation, where 20 to 40 channels arenow sometimes tied up with an identicalprogram. If such chain programs couldbe limited to one of two channels, ob-viously many channels now tied up wouldbe freed for other services.
Radio Synchronization
2 Radio synchronizing of stations. A re-ceiving set is installed 6 to 10 miles
away from the station to be synchron-ized. On this set, the incoming carrier -wave from the distance station on thesame channel is picked up, and transmit-ted by telephone to the station controlroom. By the zero -beat method, the lo-cal station is synchronized with the dis-tant station.
Cites WDRC-WAIU
Operation then continues withoutheterodyning, and this is accomplished
December 3, 1927 RADIO WORLD 5
1060 K.C. EAST --
t; WEST, ARE BOTH RADIATING THE SAME FREQUENCY, SAY 1060 KC,I1 FIELDS OF THE TWO STATIONS, AND LISTENERS ARE HAPPY. BUTII)UNT, SAY 250 CYCLES, EVERY RECEIVER IN THE FIELDS WILL HEAR
PION. SYNCHRONIZATION OF THE TWO STATIONS THRUSTS THE, OR AWAY DOWN TO ZERO.
under separations between stations whichwould produce terrific beats or howls ifthe ordinary method of approximate fre-quencies were employed. This plan issuccessfully employed by station WDRCat New Haven, Conn., to avoid a badheterodyne that would otherwise occurfrom the 5,000 -watt Station WAIU onthe same channel at Columbus, Ohio,only 500 miles distance.
Matched Crystals3It is only possible to synchronize two
. stations by controlling frequencieswith identical crystals.
Herewith is some interesting data on us-ing the crystals and beat method for syn-chronization, as stated by a member of Ra-dio World's Engineering Staff :
The difficulty with the matched crystalmethod is that the crystals may be iden-tical when they are at the same place andworking under exactly the same condi-tions, but they may vary by an audiblebeat frequency when they are in differentplaces and working under different con-ditions. The greatest variable here istemperature. Even quartz crystals varyin frequency slightly as the temperaturechanges, and it is not easy to keep thetemperature of two crystals exactly thesame when one of these crystals may beoperating in Florida and another in Maine.
Airsap4k.
Weather Not Only Factor
It is, of course, possible to use thermo-static control of the temperature of thecrystals, these thermostats being cali-brated and adjusted against the samestandard. This minimizes one variablefactor which might give rise to a differ-ence in frequency.
But it is not the weather alone whichdetermines the temperature of a crystal.It is also affected by its rate and ampli-tude of vibration. A crystal may vibrateso violently that it gets read hot. If onevibrates more than the other, the tem-perature of one will be different from thatof the other. But the intensity of the vi-bration also can be maintained auto-matically close to a standard.
While it is very difficult to changethe frequency of a crystal controlled os-cillator, small changes may be effected byintroducing damping of various degrees..Thus if the frequency of one of the crys-tals pulls away from that or the other,it is possible to bring it back, increasingor decreasing the damping. But this isof little avail unless the operator of onestation is able to tell when here is a beatbetween his own station and the other.Thus the matched crystal method of syn-chronization works well in conjunctionwith one of the other methods, for ex-
ample, that developed by Prof. Doolittle.When one operator hears a heterodyne.whistle between his own and othe otherstation he can change the damping on hiscrystal so as to effect synchronization,and when he has changed the frequencyhe can depend on the crystal to hold theadjustment for some time. Or he canchange the temperature of the crystal ifhe wants to introduce a somewhat greaterchange in the frequency.
Beat Method ExplainedThe beat or heterodyne is really a reg-
ular variation in the intensity of the re-ceived signal. If this variation in theintensity occurs at a rapid rate, between16 and 10,000 waxings and wanings persecond, it is heard as a whistle or squeal.The heterodyne may exist at a frequencyabove audibility but it will give no troublesince the ear will not detect it. In factany two transmitting stations will gen-erate a beat frequency above the audiblelimit. For example, stations WEAF andWJZ, operating on 610 and 660 kc re-spectively do generate a heterodyne of50,000 cycles in every receiver, and theintensity of this beat is quite strong whenthe receiver is tudned to one of the waves.This beat can be picked out with suitableequipment.
Anybody interested in this can make thetwo stations play a duet. It won't be apleasant or a concordant one but the twostations will perform at the same time.Here is the way it can be done. Tune ineach station with a separate tuner, butusing the same detector tube. Put theoutput into an intermediate frequencyamplifier tuned to 50,000 cycles. Detectand impress the result on a loudspeaker.An interesting point is to note what hap-pens when one of the waves is unmodu-lated, that is, in between numbers andannouncements.
Special BroadcastsFor Arctic Begin
Radio broadcasting again has linkedtogether the far corners of the earth,when KDKA, the powerful transmitterof the Westinghouse Electric and Manu-facturing Company at Pittsburgh, trans-mitted the first program of the 1927-28Far North Broadcast, on November 19.
In addition to KDKA, stations WBZat Boston, WBZA the synchronized op-erated station at Springfield and KYWof Chicago, all members of the Westing-house chain of stations, will in the futuretransmit the far north programs. KDKAwill transmit on 65 meters and their reg-ular wave of 316 meters, the others us-ing the regular waves only. Following isthe schedule:
WBZ-WBZA, 333 meters; December17, 1927 (Saturday), 11 o'clock, E. S. T.;January 7, 1928, (Saturday), 11 o'clock,E. S. T., and February 4, 1928 (Satur-day), 11:00 o'clock, E. S. T.
KDKA, 316 meters and 65 meters; De-cember 25, 1927 (Sunday), 11:00 o'clock,E. S .T.; January 14, 1928 (Saturday),11:00 o'clock, E. S. T., and February 18,1928 (Saturday), 11:00 o'clock, E. S. T.
KYW, 525 meters, December 3, 1927(Saturday), 10 o'clock, C. S. T.; January1, 1928 (Sunday), 10 o'clock, C. S. T.;January 28, 1927 (Saturday), 10 o'clock,C. S. T., and February 11, 1928 (Satur-day), 10 o'clock, C. S. T.
This is the fourth year of these broad-casts. To the trapper, traders, mission-aries and the mounted police, who main-tain world's outposts, the programs repre-sent the only link with civilization duringthe long winter months.
The programs consist of messages fromfriends and relatives, current news andbits of music. These have been translatedin English, Icelandic, Danish and for thefirst time this year in Esquimo.
6 RADIO 'WORLD December 3, 1927
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08-ALL-ELECTR1C AUDIO AMPLIFIER FOR PHONOGRAPH REPRODUC-TION AND AF CHANNEL OF RADIO, WITH B POWER SUPPLY FOR 210OUTPUT, USING VICTOREEN POWER TRANSFORMER, CHOKES, AUDIO
UNIT, RESISTANCE BANK AND RHEOSTATS
THERE are many thousands of old -style cabinet phonographs throughout
this country which have been in littleor no use since broadcasting became ar-tistic. Mechanically these phonographsare good: acoustically they are hopeless.They will rotate any record as well as themost up-to-date electrical phonograph,but they will turn the best record into aburlesque.
Every owner of one of these phono-graphs wants to know one thing-how canhe modernize it, thus salvaging his prev-ious investment, and obtaining the qualitya the Panatrope and the Orthophonic?
The first thing needed is to electrifythe phonograph. A first-class audio fre-quency amplifier with a suitable powersupply source will do that nicely. Thesolution can be worked out for direct orfor alternating current, or, indeed, withbatteries, for those whose homes are notwired for electricity. The present dis-cussion concerns the AC solution.
Two stages of audio amplification willbe needed. Hence, there are two'audiofrequency transformers, AF1 and AF2,and two amplifier tubes in the circuit. Thefirst of these transformers is used tocouple the amplifier to the phonographpick-up. Both transformers must be ofhigh quality if natural sounding outputis desired.
What the Circuit Is
The circuit for A C operation is to bewholly "electric," that is, no batterieswhatsoever are to be used, the tube fila-ments of both the amplifier tubes beingheated with alternating current, the gridbias voltages being taken from drops inresistors and a high -power B eliminatorbeing used for a power source. This isso arranged as to give 310 or 210 amplifi-cation-the kind the electric phonographshave.
One of the best AC tubes for a pre-liminary stage is the 1.5 volt. 1.05 amperefilament type which is large enough tohandle the load in the stage, and fromwhich hum can be easily removed bysimple balancing. This tube is CeCo M-26
on the circuit diagram and is in the CX326 and UX226 classification.
The last tube must be a power tube ofthe 310 type if phonograph volume withundefiled quality is to be expected. Thistube can easily handle an undistorted out-put wattage of about 1.75 watts, and thatis ample for all practical purposes.
The plate DC for this tube is soheavy that it is unsafe to pass it throughthe winding of an ordinary loud speaker.It is necessary to separate the DC fromthe AC and let the AC alone through thespeaker. This separation is accomplishedwith a high inductance choke coil Chland a condenser of from 2 to 4 mfd. Thesmaller condenser gives good reproductionbut the larger costs twice as much andgives about 10 per cent greater responsebelow 30 cycles. Some persons prefer thelarger value for technical reasons only,not because they can tell the difference inthe quality by ear.
By Pass Condensers Needed
It is always good practice to insert by-pass condensers at strategic points in acircuit, particularly when they improve theresults without in the least affecting thehigher frequencies. Three such conden-sers are to be found in this amplifier, andeach of them is a 1 mfd. unit.
One of these by-passes that portion ofthe resistance R3 which is used for a biasin the first audio amplifier. It is connect-ed between the low potential side of thefirst transformer secondary and ground.
The second by-passes that portion ofthe plate voltage potentiometer whichpertains to the first tube. It is connectedbetween the low potential side of theprimary of the second audio transformerand the negative side of the plate voltagesupply line. The third is simply put acrossthe total resistance R3 where it serves theuseful purpose of improving the qualityand increasing the amplification. Thesebypass condensers must not be omitted.
There is another interesting pointabout the filament circuit of the amplifier.Note that there is only one heating wind-ing which supplies both the 7.5 volt tube and
LIST OF PARTSAF1, AF2-One Victoreen 112 audio unit
(comprises two transformers)PT-One Victoreen 116 power trans-
Chl-One Victoreen 115 output unitCh2, Chi-One Victoreen 216 choke unitR5-One Victoreen 316 resistance unitRI, R2-Two Victoreen manganin 6 -ohm
rheostatsR3-One Centralab fourth terminal 2,000
ohm potentiometer, PF2,000R4-One Carter 100 ohm potentiometerThree Tobe 1-mfd. condensers No. 301Two Tobe 2 mfd. 1,000 volts condensers,
No. 602Three Tobe 4 mfd. 1,000 volts condensers,
No. 609One Tube 4 or 2 mfd. condenser (No. 602
or No. 604.)Four Frost UX socketsOne Pacent PhonovoxOne CeCo M-26 AC tube.One 310 power tubeTwo CeCo, R-81 rectifier tubesEight Eby binding postsTwelve feet flexible Celatsite wireOne 110 volt pilot light with Candelabra
socketOne 6 ampere fuse
the 1.5 volt tube. Of course the filamentof the M-26 tube is not connected directlyacross the 7.5 volt winding. Two rheo-stats are put in the leads to that tube totake up the excess voltage. Six volts mustbe dropped, and the voltage must bedropped symmetrically. That is, 3 voltsmust be dropped in each leg of the fila-ment. Hence the two 6 -ohm rheostatsRl and R2 are in the circuit, as diagram-med, and are put at half -setting.
The filament of the last tube takes allthe voltage that the heating winding hasto give.
Question of Balance
The Victoreen power transformer hasthe necessary winding that carries thecurrent of the 26 and the 310 withoutcore saturation.
Hum must be eliminated from the out-put. The way to do it is to balance thefilament circuits. It is customary to tapthe winding in the center and return theplate circuit to that point to effect bal-ancing. But this balancing is not alwaysaccurate enough to remove sufficient ofthe hum. A much more effective way isto put a low resistance potentiometeracross the 7.5 volt winding and return theplate circuit to the slider. This can thenbe set experimentally at a point wherethe hum disappears entirely. The correctpoint may be found considerably off cen-ter. R4 is that potentiometer. It canhave any value from 20 to 100 ohms, butthe lower values are preferable. It maybe improvised from a 20 ohm rheostat byisolation of the arm.
Now, let us return to Rl and R2. Theyhave another object besides dropping thevoltage to the proper value. They arealso used to balance out the hum fromthe first amplifier tube. For an absoluteminimum of hum the two tubes must beadjusted independently for no hum. ButR4 affects both of -the tubes, since theplate currents of both of them flowthrough its branches. When R4 is bal-anced for the last tube it may be away
RADIO WORLD 7December 3, 1927
ou Now Haveoff for the first. Well, if it is, the balancefor the first tube can always be effectedwith R1 and R2. To effect the balanceit may be necessary to insert all of R1 andnone of R2 or vice versa. The idealadjustment, of course, is when 3 ohms ofeach are used.
That puts the hum out of the set as faras the filament heating is concerned. Butif a transformer is used that unit carriesthe 26 filament current besides the 210filament current, hum will result.
Bias Considerations
How about the grid bias? There is thedouble slider rheostat R3 to take care ofthat. The fixed end of that rheostat isconnected to the negative side of thepower supply line. One slider is ground-ed and is connected to the slider of R4.The voltage drop in this is used as the biasfor the power tube. The second slider isleft somewhere between the first sliderand the end. The drop in this portion isused as bias for the first tube. If thetotal value of R3 is 2,000 ohms it will belarge enough to give a suitable bias forthe power tube, and that is more than thefirst tube requires, so both are taken careof.
And that concludes the discussion of theamplifier. We take up the power supply.
We start at Ps, which is a plug thatfits into any standard outlet. A fuse F isinserted in one side of the line as a pre-caution against short circuits. A six am-pere fuse is used. P1 is a small 115 voltpilot light to show when the power isturned on. It is merely a convenience.
PT is the Victoreen power transformerespecially designed for circuits like theone under discussion. It has three sec-ondary windings, or perhaps it has onesecondary, one tertiary and one quarter -nary. Anyhow, it has one extra 8 voltwinding and this is used to heat the fila-ments of two CeCo rectifier tubes, R-81.
Filtering Well Done
The transformer has also a high volt-age winding which supplies the plates ofthe rectifier tubes. The voltage is suchthat the DC voltage on the output side ofthe filter is 475 volts.
The output of the rectifier is well filt-ered, and therefore no hum get into theamplifier from this source. The filtering iswiade easy by the fact that a full waverectifier is used, but this fact has not in-duced the designer to skimp on the filter.Two chokes Ch2 and Ch3 of high induct-ance and low DC resistance are used. Theby-pass condensers 2, 2, 8 and 4 mfd. aredistributed so as to b'e most effective inremoving the hum.
The B plus terminal for the detector isleft unconnected. It should, of course, beconnected to the corresponding terminalon the primary of the first audio trans-former sinless the circuit is to be usedsolely for phonograph purposes.
Use for Radio Purposes
If the phonograph is to monopolize thiscircuit the leads from the pick-up, unitare connected across the primary of thefirst transformer. The Pacent Phonovoxworks well with or without B currentacross it. If the phonograph is to sharethe circuit with the radio set, the primaryof the first transformer is connected tothe detector in the usual way and the pho-nograph pick-up unit is plugged into thedetector socket, just as the makers of
DEFINITION BY ILLUSTRATION-THE PHONOGRAPH PHYSICALLYADAPTED TO MODERN QUALITY REPRODUCTION. THE ACCOM-PANYING ARTICLE DESCRIBES THE INSTALLATION OF B SUPPLYAND POWER AMPLIFIER. THE DETECTOR TUBE IS REMOVED. INTHE DETECTOR SOCKET THE PICK-UP PLUG IS PLACED INSTEAD
the pick-up units usually arrange matters.The B supply and audio amplifier of
course, may be used, as it most likely willbe used, also to furnish power and ampli-fication to a radio receiver. If the radioreceiver is already equipped with audioamplification, that is not used, but in-stead the audio amplifier in the phono-graph installation. The connection is madevery simply from the radio set by carry-ing a lead from a P post of the detectorsocket to the P post to the first audiotransformer on the phonograph cabinet.The B plus detector voltage is suppliedwithin the phonograph cabinet itself, butthe B leads for the radio amplifier tubeare fed from B plus No. 1 of the powersupply.
The B supply, power amplifier andphonograph pick-up as described aresuitable for installation in Victor, Bruns-wick, Aeolian, Sonora, Columbia andother upright models of phonographs ofthe style of a year ago or more, that iswhich do not possess the special horn andsound box with which the modern phono-graph are equipped. And what you are toget now is 310 amplification, which you findin the 104 speaker, and never in any merephonograph. You will use your radiospeaker for reproduction.
Personal Experiences
My own installation was made in anAeolian Vocalion. This instrument origi-nally cost me $125 and the furniture is justas good today as it was that day fouryears ago when I bought it. As probably85 per cent of the cost of producing a
phonograph in those days went into thefurniture, it was only natural that I shoulddesire to retrieve this investment. I feelmyself very well repaid for the installationI have made, because the quality of re-production is truly marvelous, due to thewise coordination of parts and choice oftubes. The plate voltage on the 310 is 475,and some such high voltage being neces-sary for adequate response on low notesin modern speakers.
The Aeolian phonograph has a large tinhorn in the tone chamber which is ratherdifficult to remove. First in any case, nomatter what phonograph you have, you mustremove the winding key by turning it count-er clockwise. Then you will be able to liftthe turntable off its seat. The next movewill be to take it out of the set so that youcan work on the horn. It will be necessaryto disconnect the graduola. The entire tub-ing may be removed as well as the frontknob. Then the set screws inside the cabinetare removed to permit lifting the horn outthrough the top. It is impossible to getthe horn through the front opening wherethe music formerly used to come out, inother words through the tone chamber door.
When working on the Victor models theslab is taken out of the rear cabinet walland the horn is brought out in that fashion.
In the case of the Victor, I had to supply3/4. inch long and 14 inch wide stove boltsso that the tone arm pedestal could befastened. The horn itself had containedan apperture for securing similar bolts butwhen the horn was removed it was necessaryto use nuts and as nuts of the correctthread were not readily obtainable it was
(Concluded on, page 291
B RADIO WORLD December 3, 1927
The Everyman 4(6WHAT set is the best? Have you
ever heard that question?" Per-sonally I do not believe any one set isthe best, so let's change the question to:"What set meets most of my require-ments the best?"
Having read the articles, description,claims, etc., made by F. C. Ehlert of theNew York "Sun" about his "borrowed -for -the -purpose" circuit, the "Everyman4," with the usual fans' pessimism, hav-ing constructed sets, from Super -Hetero-dynes to the three circuit tuners, myhopes still conquered my doubts enoughfor me to traverse the ten interveningblocks. One Monday, late on a Septem-ber afternoon, I went to ascertain howmuch truth there might be in so vast anamount of optimism!
The Author Is "Sold"I went I I saw! I was conquered!
After 6 P. M., when WNYC and WEAFwere both broadcasting, WNYC on 526meters using 500 watts, only 150 yardsaway, and WEAF on 492 meters using5,000 watts, located about a mile fromthe "Sun's" aerial, either could be tunedin, without any cross talk!
"Turn down the volume of WEAF andsee if WNYC is in the background," wassuggested. Not a whisper! Also, WHN,WGL, and WOKO, local stations, weretuned in. They are not distance, no, butare rarely heard in that location, regard-less of the set.
I immediately procured the necessaryparts and assembled the set. There weretwo or three friends around, waiting togive me the usual "I told you so." Butwhen the first signal was properly tunedin I heard:
"That's what I call real quality.""Oh! What a kick-what a wallop!""Look how selective it can be made,
and how easy it is to reduce that volume l"Quality-selectivity-volume!
DX Brought InFurther trials in New York City's down-
town and worst radio reception location,brought in WFI and WLIT of Philadel-phia during the day.
In Newark, N. J., WJAX, Jacksonville,Fla., and WSM, Nashville, Tenn., areheard with loudspeaker volume any timethey are on the air. Reports from Flush-ing, L. I., only a couple of miles fromWABC, are that the Pittsburgh station,KDKA, can be tuned in without trouble.
I have tuned in WBBM, Chicago, 390meters, when WMCA, a local using 500watts on the 370 meter wave, was on theair, before 10 P. M.
Another report was from Glen Cove,L. I. Under ideal conditions, high andperfectly installed aerial situated on ahill, on Saturday, October 29, at 10:30P. M., with WJZ and WEAF both broad-casting, KFI and WFAA were heard onthe loudspeaker with plenty of volume!This is exceptional, of course.
So many New Yorkers have now toldme that WOC, WSB, WLS, Chicago,Canadian and New England stations arereceived during the early evening, whenthe local stations are going full blast,that no doubt can possibly remain.
Analysis of CircuitNow let's have a few more facts. The
Everyman 4 consists of one very efficientstage of stabilized tuned radio frequency,a detector with or without regeneration-this latter not required for locals-and
By E. Bunting MooreThe Radio Kit Co.
two stages of excellent transformercoupled audio frequency amplificationwith protective output filter device.Three type -A tubes and one -71 type-four tubes!
The exceptional volume generated inthis circuit is attributed to the methodof conductive coupling used in the RFstage. Selectivity is derived from thevari-coupled antenna circuit, and thewonderful quality is assured by the useof well designed, large audio transform-ers.
The antenna coil is wound on 2 inchBakelite tubing with No. 24 silk coveredcotton covered wire, that is a silk layerover a cotton layer. The primary hasfourteen turns, the secondary sixty-six.The RF coil is of greatest importance. itconsists of sixty-six turns, tapped at thetwentieth turn and also at the forty-thirdturn. One tap supplies the proper valueof inductance for the stabilizing con-denser and the other for the B voltagesupply of the RF tube. The beginningof the coil goes to the regeneration con-denser. The tuning condenser, it will benoted, floats across this coil and the plateof the RF tube-not in the usual loca-tion across the grid and filament. Theseconnections are vitally important.
Advice on MountingAssembly is not at all difficult. I have
found that for correct spacing it is bestfirst to mount the two tuning condensers,regeneration condenser and filamentswitch on the panel. Then by holding thepanel against the front edge of the base-board the spacing is much easier to esti-mate. By keeping the audio transform-ers as near the rear edge of the 10x20inch baseboard as possible, it will befound that approximately one inch can behad between them and the coil, andanother inch between the coil and tuningcondensers.
Mount the transformers, using lugs toground all the cases, then sockets andtubestat holders, neutralizing condenser,RF choke coil and by-pass condensers ;finally the two remaining sockets
Here is another important detail.Mount the detector socket with the gridand plate terminals toward the panel, butthe RF socket with those terminals to-ward the rear of the set. Then mountthe tubestat holders close to each socket.The lugs of each holder can be bent upand toward the filament terminal, so thatonly another small lug placed on thesocket terminal need be soldered to theholder lug, making an easy connection.
The by-pass condensers may bemounted flat on the baseboard and slightlyunder the tuning condensers, if necessary.Do not mount the coils yet.
Wiring DirectionsNow wire the audio end first and carry
all the B and filament leads bunched to-gether to a cable and plug connector.The two filament terminals on the firstand second audio transformers go tominus C, and I use short independentwires, enabling the C batteries to beplaced in, or immediately attached to theback of the cabinet.
Now for the detector tube. Be surethe socket is mounted with G and Pterminals toward the panel, the RF socketthese point toward the rear of the set.From P of plate of the detector tubea wire goes to the RF choke coil, oneside of which has been attached already
to the post marked P on the first audiotransformer. From the same socket Pterminal attach a wire of about five inchesin length for connection later on to theregeneration condenser.
The ordinary shunt type of grid leakand condenser must not be used. Itwill bring disaster. Connect one end ofthe leak to the grid terminal of thedetector tube, and the other end to Aplus.
Coil ConnectionsNow prepare the antenna and ground
strip and attach the flexible lead of theprimary coil. The end of the windingnearest the fixed secondary coil goes tothe ground, the other to the antenna.
Mount a lug on the ground post also,for the filament negative.
Now by mounting the panel and theprimary control rod to the panel thesecondary coil may be mounted on thebaseboard, remembering the spacing-oneinch between the coil and condenser.Slightly bend the rod if necessary sothat the primary can be raised. Bytwisting this coil toward the rear of theset it can be locked on the rod to equalthe inch away secondary coil.
A couple of trials will show how easyit really is. The end of the secondarynext to the primary goes to the .5 mfd.by-pass condenser and on to the F ter-minal, or C minus, on the first audiotransformer, for the minus 4i volts. Twoseparate voltages of C are not absolutelynecessary. The RF and first audio canbe connected together and same voltageused. However, the diagrams show thesevoltages as separate.
The opposite end of the coil runs tothe stator plates of the tuning condenserand grid of the RF tube, and from thissocket terminal continues to the neutraliz-ing condenser.
The other neutralizing terminal con-nects with the forty-third turn tap of theRF coil. The twentieth turn tap goes toa .5 by-pass condenser and on to the 67volts of B. The P terminal of the RFsocket connects to the regeneration con-denser by as short a lead as possible, andfrom this same tube socket a wire goesto the rotor plates of the right-handtuning condenser and start of the RFcoil.
The sixty-third turn, or end of this coil,goes to the stator plates of the right-hand condenser and one side of the .00025grid condenser, whose other terminal isconnected to the grid of the detectorsocket.
This set will work from either good bat-teries, or a B eliminator if of good work-manship and with 60 mil current outputat 180 volts. Using a 171 type tube, 401/2volts of minus C will give fine quality.Of course the same tube can be usedwith either 135 or 157 volts of B, andthen 27 or 33 volts of negative C, respec-tively, would be needed. This will givebetter quality reproduction without tubeoverloading than the 112 type of tube,though not as much volume.
After wiring is complete, check care-fully against the diagram. Be positiveproper tubestats are inserted in theirrespective places. Connect the A batterycable wire to the A battery, plug in thecable plug, and turn on the switch. Ifthe tubes glow, the filament is 0. K. Ifnot. check up carefully.
[List of parts and construction datanext week.]
December 3, 1927
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CIRCUIT DIAGRAM OF THE FOUR TUBE DIAMOND. BREAK INMINUS A LEAD INDICATES S2.
By Campbell HearnIr HE interest in the Diamond of the
Air has continued unabated eversince its introduction about three yearsago. The demands for blueprints, for ad-ditional information about the circuit, andfor any possible improvements have beencontinuous.
While no circuit is so good that it cannotbe improved there has been no need ofmaking any vital changes in the Diamondof the Air. A good circuit never growsout of date. That does not hold of theparts of which the receiver is assembled.Parts have been greatly improved andwhen such parts are substituted for the olda general improvement results in the re-ceiver. Such changes have been made inthe Diamond with gratifying results.
Many fans want to know which is thebetter, the four tube Diamond or the fivetube circuit. There is very little differ-ence between them as to selectivity andvolume. The four tube Diamond containstwo audio frequency transformers; thethe five tube Diamond contains one trans-former and two resistance couplers. Theradio ends of the circuits are identical.It is considered by some that the qualityof resistance coupled amplifiers is betterthan the quality of transformer coupled
circuits. That was obviously true whentransformers were poor.
Building either the five tube circuit orthe four tube circuit is very simple. Forthe four tubes the socket next to the lastis removed from the socket strip and thesecond audio frequency transformer isput in its place, covering up the aperture.The circuit is then wired in accordancewith the four tube diagram. The resist-ance couplers which are now superfluousmay be removed entirely or they may bemerely disconnected from the circuit. Itmay be well to leave them in since it maybe decided some time to restore the fivetube circuit.
It is advisable that any one who buildsthe set should afford himself the benefitof the blueprints, which show the exactlocation and identification of each part,life size, and which therefore may be fol-lowed much as if it were templates, whichin some respects indeed they are.
The solenoid having been used in theoriginal model, it is advisable to adhereto that form of coil, which consists ofa single layer on a cylindrical form. Thecylinder happened to be one formed byquartzite rods, supported by Bakeliterings at either end. A small diameter is
LIST OF PARTSLOLl-One Bruno 99 antenna coupler.L2L3L4-One Bruno 99 three circuit tunerC1C3-Two Karas SFL .0005 mfd. conden-
sersR, R1-Two No. IA AmperitesR2, R7-Two No. 112 AmperitesOne Karas Harmonik audio frequency
transformerR3, R5-Two Poly -met .25 megohm resis-
tors with mountingsR4, R6-Two Polymet 1 megohm resistors
with mountingsRO-One Bretwood variable grid leakC2-One Polymet .00025 grid condenserC4, CS-Two Polymet .1 mfd. condensersJl, J2-Two double circuit jacksJ3-One single circuit jackFive Pacent X type socketsSi, S2-Two Yaxley battery switchesWXYZ-Four Eby binding postsOne 7x24 inch panelAntenna and ground binding postsOne pair of Bruno bracketsTwo Marco 4 inch dialsOne Marco 2 inch dial.
N. B.-For the four tube Diamond usetwo AF transformers and omit R3, R4, RS,R6, R7, C4, CS and one socket.
preferable, as it sets up a smaller fieldand there is less danger of magnetic in-terplay or stray coupling, which wouldresult in difficulty in controlling oscilla-tions. For the radio -frequency coil(LL1) this diameter may well be 2lAinches to duplicate the commercial coilsemployed, which were the Bruno 99 RF.In the case of the interstage coupler, or3 -circuit tuning coil, the same diameteris preferable again (L2L3L4).
For the 2% inch diameter form the pri-mary consists of 10 turns, 34 inch spacebeing left, then the secondary beingwound adjacent to the primary and con-sisting of 58 turns. The wire is No. 24, silk -over cotton or No. 24 double cotton cov-ered.
The 3 -circuit tuner is wound in thesame fashion, as to the stator form, butinside this there revolves the rotary form,which is 1 inch diameter and 1 inch high,and on which are wound turns of No. 26single silk covered wire until the wire al -
THE TOP VIEW DISCLOSES THE RIGHT-ANGLE RELATIVITY OF THE TWO COILS AND POINTEDLY PRESENTSTHE FRONT PANEL AND TOP-OF-SUBPANEL MOUNTING DETAILS.
December 3, 1927 RADIO WORLD 11
and F iveTube _Models
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CIRCUIT DIAGRAM OF THE FIVE TUBE DIAMOND
most completely covers the form, whichwill be about 38 turns.
If a 3 inch diameter form is used forRF coil the primary would consist of 8turns and the secondary of 47 turns,the same kind and insulation of wire be-ing used. The tickler, 2 inches diameter,would have 30 turns of No. 26 SSC.
Terminals of Coils
The coil terminals in the diagram aredesignated by letters. These should befollowed without alteration, except thatI and J may be interchanged. The coilterminals are as follows:
A is the beginning of the aperiodicprimary L, in the antenna circuit, and isconnected to the aerial. In the Brunocoil trace this lead to its origin on out-side of primary, though this post is atopposite end of the coil.
B is the end of that winding and goesto ground.
C and D should be watched carefully,as their source may be lost in the con-fusion of jack wiring. C is the begin-ning of the secondary Ll, and is the term-inal of the secondary which adjoins theend of the primary L (i.e., point B). Inthe laboratory receiver the Bruno coilswere used, and these have binding postson them, to which the coil terminals aresecured. The wire terminals are ntitbrought to the nearest binding posts, butthe wire is turned back, so that the wind-ing is thus given added support, hencethis is something to watch in determiningthe beginning and the end of a winding.It is easily done at a glance, but mightbe overlooked unless attention were calledto it.
C is the beginning of the secondarywinding and goes to that inside spring ofthe jack J1, which ultimately connects tominus A when the jack is closed.
D is the end of the winding and makesconnection to the other inside spring of
which ultimately goes to grid. Tracethis. Confirm the fact that the aerialgoes to outside of primary, grid to outsideof secondary.
E is the beginning of the RF plate coilL2 and connects to the plate of tube 1.
(Concluded on page 28)
5(---0 A+, B-O A -
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THE AUDIO END, UPSIDE DOWN VIEW, IS SHOWN AT TOP, WITHMOUNTING DETAILS CLEARLY REVEALED. THE OTHER VIEW SHOWSTHE POSITION OF THE AUDIO TRANSFORMER AND THREE CIRCUIT
TUNER. THESE ARE VIEWS OF THE 5 -TUBE MODEL
12 RADIO WORLD December 3, 1927
Cherchez La Voltage; TUBE CHART
Never Mind the Woman QUICKLY GIVESNEEDED FACTS
From E. T. Cunningham, Inc.It is unfortunate in a way that vacuum
tubes are very much like faithful horsesin performing the duties imposed uponthem. Tubes like horses will work andstrain at tasks that should never havebeen imposed upon them, until they crackunder the strain.
According to Roger M. Wise, chiefengineer of E. T. Cunningham, Inc., thefailure to realize that adjustment "by ear"of the voltages furnished by "B" powerdevices almost invariably results in theuse of excessive plate voltage, is fre-quently responsible for dissatisfaction onthe part of the listener at the service ob-tained from the tube,
This is particularly true of power tubes,with which reception, as judged by theear improves as the tube is overloaded asregards plate voltage.
Follow Instruction SheetComplete specifications and operating
characteristics of tubes are given in thesheet of instructions regarding theirproper use which tube manufacturerssupply in the cartons in which their tubesare packed. These specifications, regard-ing the proper filament voltage, platevoltage and grid bias to use with suchtubes and the uses to which the tubescan be put should be studied carefullybefore the set is designed and wired sothat full advantage can be taken of theknowledge gained by the manufacturersin the experimental and developmentwork which has been done with the tubes.
As a concrete instance it might be men-tioned that with a grid bias of 40 volts,the normal plate current drawn by aCX-371 power tube at 180 volts is 20 mil-liamperes whereas with no grid bias theplate current may run as high as 100milliamperes, dissipating so much heat inthe tube that the plate of the tube willbe heated to redness.
Measure CorrectlyWith the growing popularity of battery
eliminators, the tendency has grown toadjust the voltages supplied to the re-ceiver by such units entirely by ear.Since these eliminators and the condi-tions under which they are used varygreatly, it is almost impossible to deter-mine the correct settings merely by listen-ing to the receiver and adjusting theunit until reception sounds all right.
The variable adjustments of these unitsshould be set accurately to the receiverwith which they are used, a high re-sistance voltmeter being employed forthe purpose.
When once adjusted they should be leftseverely alone unless a change in tubeor tube types is made. The adjustmentshould preferably be made by a radioservice man who is properly equippedwith instruments to make the necessarytests. The man who installs the elimin-ator is the logical man to adjust it to theset. Nothing less than a reading of thevoltage delivered at each tap should beaccepted as a satisfactory test on his part.
Condenser Easily CuresNoises Due to Sparks
When the public first became consciousthat roars, rumbles and crackles werenot necessarily an adjunct of radiobroadcast there was a wide -spread beliefthat whatever the nature of noise it mustbe looked upon as a permanent institu-tion. So general was this belief thatmany communities passed legislationagainst vibratory battery chargers and insome towns mercury arc rectifiers werelooked upon with considerable disfavor.
One of the many important results ofa survey made by the Radio Manufactur-ers Association has been the establishmentof procf that while noise is threateningthe future of radio in every large com-munity it is nevertheless one of our mosteasily eradicable nuisances.
Just why this should be is easily under-stood if one comprehends the nature ofradio noises.
Sparking Causes TroubleMost of these disturbances are due to
spark emanation and a consequentbroadcasting of trains of high frequencycurrents which are cast off by the powerlines and picked up by receiving set col-lectors. The range of. the spark broad-cast would not be more than a few feetwere it not for the antenna effect of thelines leading from the source of trouble.
Once this was realized it became evi-dent that a cure, complete and instant,would be possible the instant one de-vised a means of keeping the high fre-quency currents from stepping back intothe lines. Of course the solution was aby pass condenser.
High frequency discharges go just asfar as they have to go and no farther.So a fairly larg' condenser connectedacross a spark gap provides for them apath that they much prefer to the milesof straight wire that otherwise they mighthave to travel.
The Easiest Way
A working circuit is provided for themwithout harm to the normal functions ofthe device which produced them, they re-main close to their point of origin andthe neighborhood is thus enabled to listento radio broadcast without that static ef-fect so noticeable in cities.
Nearly all disturbances can be si-lenced by these simple means. Wheresmall currents are consumed a conden-ser of a quarter microfarad will be foundsufficiently large. Where large currentsare required-as in elevator control sys-tems-the application of the cure is moreexpensive but the principles are thesame. In some elevator systems-particu-larly where they are old and worn andprone to sparking-condensers of somethirty microfarads have been required.But even so the expense of installation isa low enough price to pay for peace in theneighborhood.
Clicks and thuds often heard in a radioreceiver and caused by the sparking whencircuits are broken, such as the turningoff a light, travel some distances over thewiring. They can be eliminated with by-pass condensers.
A CHART containing in concentratedform all the principal characteristics
of all the Radiotrons on the market isan extremely useful adjunct to the equip-ment of any one who is continually work-ing with vacuum tubes and circuits. Sucha chart will give at a glance the answerto almost any question of design, elec-trical and mechanical, which may arise.
Such a chart has been issued by theRadio Corporation of America and isreproduced herewith. While this chartgives the average characteristics of theRadiotrons only it also applies accuratelyto the Cunningham line of tubes, and toother brands of tubes having similar char-acteristics.
Valuable InformationThis chart gives the general purpose of
every type of Radiotron, the circuit re-quirements of each tube, the type ofsocket to use with each, and the physi-cal dimensions of every tube.
Then it gives the filament, grid andplate voltage and current requirementsfor both detection and amplification, aswell as many other useful data.
Of particular interest in this chart arethe characteristics of the new UX-222screen grid tube. It has characteristicsradically different from those of any othertube. It has a static amplification factorin one case of 300 and in another of 60,depending on the value of the posi-tive voltage on the inner grid.
112A and 171A
The corresponding plate AC resist-ances are 850,000 and 150,000 ohms. Sucha tube then is eminently suited for re-sistance coupling both for radio frequencyand audio frequency amplification.
Another feature of interest is thechange in the filament requirements ofthe 112 and the 171 group. Tubes, nowrequiring only .25 ampere instead of .5,for the filament, are changed in designa-tion to 112-A and 171-A.
[See Chart on Next Page]
Two Black Crows Sign Upfor Columbia Broadcasts
Moran and Mack, known to vaudevilleaudiences, radio listeners and phono-graph record owners throughout the coun-try as the "The Two Black Crows," willhave a full hour's session in one of theColumbia hours to be presented over theColumbia Broadcasting system chain soon.
The last appearance of this inimitablepair was during the Radio Industries Ban-quet, last September, in N. Y. City.
WTIC Seeks New SiteSo Power May Go Up
HARTFORD.Believing that if the station is moved
out of the city the Federal Radio Com-mission will allow the use of higherpower, engineers of WTIC are seekinga site, ten miles outside of the city limits.
Their present plans call for the locationof only the transmitter out of the city,the studios to remain in the central por-tion of Hartford.
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14 RADIO WORLD December 3, 1927
The Laboratory SuperBy Edward Farrell
PANEL VIEW OF THE LABORATORY SUPER -HETERODYNE
ONE reason for the erratic perform-ance of some Super -Heterodynes is
the stray coupling between the modulatorand the oscillator. Sometimes this coup-ling bucks and sometimes it aids the in-tentional coupling. It may aid at onefrequency band and buck at another. Un-certain action results.
But it is not necessary to tolerate thisuncertainty. The Super -Heterodyne canbe made to function as certainly and ac-curately as the theory of the circuitwould lead one to expect. The secretis simply to limit the coupling betweenthe oscillator and modulator to the in-tentional coupling, eliminating others bysuitably designing the receiver.
The intentional coupling is usually in-ductive. If there is stray inductive coup-ling as well, it is only necessary to re-duce the intentional coupling between thepick-up coil and the oscillator. It is notwell to have very close coupling betweenthe oscillator and the modulator.
Two Ways to Do ItWhen the intentional coupling is in-
ductive all capacitive coupling must beremoved carefully. There are twomethods of doing it. First, the oscillatorand the modulator can be placed farapart ; second, they can be shielded.Both of these methods have been usedin the new Laboratory Super -Hetero-dyne, using the Jewelers Time SignalAmplifier. The oscillator is in the right-hand corner and the modulator in theleft corner, each completely inclosed inan aluminum shield. The distance be-tween the parts belonging to the twounits is so large that capacity couplingbetween the two is extremely small. Themutual inductance between the coils ofthe two units is so small that it has nomeasurable effect on the total coupling.The complete grounded shields aroundeach unit further reduce the stray coup-ling to the vanishing point.
Hence the shielding is advisable for theabove reasons.
There remains one form of stray coup-ling which may give rise to trouble, andthat is resistance coupling. Liberal useof by-pass condensers across the batteryor power supply leads solves that prob-lem.
In the new Laboratory Super -Hetero-dyne the coupling between the oscillatorand the modulator is as close to the in-tentional inductive coupling as it is prac-tcal to make it.
There is another unique feature in this
circuit and that is the intermediate fre-quency amplifier. That, too, is shieldedthoroughly as a whole and each stage init is shielded from the rest. That is, eachstage in the intermediate frequencyamplifier is set in a metal -inclosed com-partment, which is grounded. Hence therecan be no capacity or inductive couplingbetween the stages and oscillation in theamplifier as a result is thus eliminated.There may be a regenerative effectthrough the inter -electrode capacitywhich is not eliminated by the shielding,but as the circuit operates on one fre-quency only, this need never give anytrouble. In fact, the effect may be usedto make the circuit more sensitive.
As in the case of the radio frequencylevel, there will be some interstage re-sistance coupling in the intermediateamplifier, but by-passing the leads to thebatteries solves the difficulty here also.
The Time Signal FeatureAnother unique feature of the inter-
mediate frequency amplifier is that it hasbeen tuned to the frequency of theStandard time signals from station NAAat Arlington. The standard time signalsthus can be received directly on the re-ceiver without the use of the modulatorand the oscillator. This is an especiallyvaluable feature to jewelers, seafaringmen, and all others who are dependenton exact time.
But this is not the only valuable fea-ture of the frequency used. Arlingtonsends out the time signals on a frequencyof 112 kc. This is a much higher fre-quency than is ordinarily used for inter-mediate amplifiers. Two advantages ac-crue from the use of a high intermediatefrequency. First, the quality of the re-produced music will be better by virtueof the minimum suppression of the higherside freauencies. Second, the number ofsqueals in the output will be minimized bythe elimination of "repeats." A Super -Heterodyne in which the intermediatefrequency is low, say 30 kc., will squealat four times as many places as a Superworking on a frequency of 120 kc. It isclear, then, that a Super working on afrequency of 112 kc. is greatly superiorin this respect to a super working on afrequency of 30 kilocycles.
The audio amplifier in the SilverShielded Super consists of two stages oftransformer coupling with one generalpurpose tube and one power tube. Thetransformers used are SM 220.
The oscillator used in this receiver is
of the tuned grid type. This connectionmakes it possible to ground the oscilla-tor condenser and thus greatly stabilizethe tuning and operation of the set. Forreasons that are somewhat obscure thisexcellent form of oscillator is not used inmany circuits though it has many obviousadvantages.
The modulator is of the regenerativetype and the feedback is controlled with amidget condenser connected in serieswith the reaction coil. The steady platecurrent flows through a radio frequencychoke coil which is connected in parallelwith the feedback condenser and coil.The grid leak in the modulator has a re-sistance of two megohms and the gridcondenser a capacity of .00015 mfd. Thiscapacity is more suitable for the modu-lator than the larger capacity ordinarilyused in tliat it makes the circuit moresensitive.
A Few of the ManyThat the Laboratory Super -Heterodyne
is an all -satisfying circuit is proven byletters from delighted users. For ex-ample:
A Cambridge, 0., fan wrote :"This Improved Laboratory Super is
the finest I have yet built or heard ofSupers or anything else."
From Fredericton, N. B., came this:"Have neglected writing you since I re-
ceived the Improved Laboratory Super.Away down here in Canada is a greatplace to test Supers. There is less elec-trical disturbances and local stations,which enables one to test for distance.My friend (a professor at college) andmyself have done considerable testing inradio lately, and we cannot find a seteven in the Supers that will give the re-sults your Improved Laboratory receivergives. We have had KYW, Chicago, herein A. M., (8:30 A. S. T.) on loudspeakerusing short aerial."
An enthusiast from Iowa City, Ia.,wrote :
"Thank you much for your past as-sistance. I should say that the ImprovedLaboratory Receiver is by far the mostpowerful I have ever operated or dem-onstrated, and it has attracted wide-spread attention and interest here."
What DX He Gets!A Chicago user said :"After having had many different types
of radios, trying to find one that wouldsatisfy me as to tone quality and selec-tivity without success, I heard about yourImproved Laboratory Super and de-cided to try this model.
"Having such good results I feel Imust tell about it. I have never beenmuch of a DX hunter but since I havebuilt this set distance comes in like lo-cals and I am getting to be a DX fan.
"Most of the distant stations come inthrough locals. One night we had PWXand listened to them for one hour andforty-five minutes without any fading andas loud as my loudest local which is sta-tion WENR only two and a half milesfrom where I am located. I am using a50 foot outdoor aerial including lead-in.
"I cannot say enough for this set be-cause it does more than I expected. Any-one wishing to hear this receiver is wel-come to do so at any time."
fin the November 19 issue, the first parton the Laboratory Super -Heterodyne wasPublished. Last week, November 26 issue,constructional data was given.]
December 3, 1927 RADIO WORLD 15
ow Audio as the Floor(From Acme Apparatus Co.)
"Please turn down the radio!"Generally this request is made because
of the sounds, coming from the loud-speaker, have. gotten on somebody'snerves. Yet were this same somebodyseated in the studio of the broadcastingstation listening to the same orchestraplaying the same selection, the chancesare he would not only find the musicunobjectionable, but contrariwise a de-cided aid to relaxation.
The average set owner probably neverpauses to analyze why, in one case, theresult may be nerve wracking, and, inthe other, restful. He may think he hasthe best radio in the world; he mayproudly call the attention of his friends tothe "mellowness" of his loudspeaker, andto the extreme depths and power of thelower tones; but, if he cannot find re-laxation and a complete sense of realismin the music it produces-if the set mustforever be turned down-then, in allprobability, there is something seriouslywrong with it.
Piano Test a Good OneLet us suppose, for example, we are
listening to a piano selection and thatthe volume of sound coming from theloudspeaker is approximately that of apiano played in the same room. A pianoselection, incidentally, is one of the bestmeans of testing the quality of a receiv-ing set and speaker. If there is an un-due and recurring emphasis on certainnotes, in either the upper or lower regist-ers, the amplifying system has not a flatfrequency response.
Assuming the fault is not in thespeaker, this peak, or undue amplificationof a certain frequency, is generallyfound in the upper registers in the caseof transformer -coupled amplifiers andmay be attributed to poor amplifyingunits. When, however, an impedance orresistance -coupled amplifier is used, thisover -emphasis, when present, occurs gen-erally in the base notes, particularlythose having a very low frequency, andis usually caused by unwanted regenera-tion in the audio end of the circuit.
Evidence of DistortionIf the tones in the upper register of
the piano are pleasing and natural, butthe bass notes, even if they do not ex-aggerate one particular frequency, sounddrum -like, or resemble the roll of an or-gan, serious distortion is present.
In the long run, a speaker or amplify-ing system that favors or over -emphasizesthe low tones, is far more nerve wrack-ing, because of an indefinable lack ofdefinition and absence of brilliancy, thanis an amplifying system that affordsgood reproduction over a comparativelylimited range in the upper register.
For truthful reproduction, not onlymust the fundamental tones be present,and they are present in all but the mostdeficient speakers and amplifiers, but theovertones and harmonics must also be ac-curately recreated. Harmonics, it may bepointed out, are always in an integral re-lation to the fundamental tone responsi-ble for them. They may be two, three,four, etc., times the frequency, and aretidiest in the case of stringed instru-ments. Overtones, on the other hand,are never exact multiples of the funda-mental, and occur mostly in the case ofpercussive instruments, drums, reeds, thehuman vocal organs, etc.
Sometimes It's the SpeakerNow, this over -emphasis of the lower
registers, which is one of the most preva-lent faults of the present-day receiver,may be due to deficiencies in the speakeritself, or again in the amplifier; and theset owner would do well to borrow aspeaker that he knows gives excellent re-sults so that he may localize the trouble.It would also be well to investigate the Bpower supply. Engineers of the AcmeApparatus Company have found, for ex-ample, that the existence of an alternat-ing current hum, due to poor filteringeffects of the chokes used in the poorertypes of B power devices, will actuallymodulate the applied signal-a conditionthat frequently accounts for very pe-culiar effects as the frequency of the ap-plied signal approaches that of the resi-dual AC.
On the other hand, the B power supplymay also account for the absence of bassnotes. When music is played or a per-son talks or sings, frequencies come intoplay, varying, let us say, from 27 to 10,-000 cycles per second. When notes inthe lower registers are to be reproduced,the amount of current necessary is con-siderably increased over that required bythe higher frequencies.
Use Large CondenserUnless sufficient storage of energy is
provided in the B supply, these noteswill not be produced in exact proportionto the high ones, and may not even beheard. To obviate this possibility, a largecapacity condenser must be placed acrossthe B supply. This condenser must storeenergy so that any sudden demand formore the low notes can bemet. If, through a desire to reduce thecost of the manufactured eliminator, con-densers of insufficient capacity are used,not only will the bass notes be inade-quately reproduced, but the tendencytoward motorboating, which is a form oflow -frequency oscillation, will be in-creased.
With the development of the conespeaker the inherent resonance of thehorn of former days is eliminated, but,of course, the speaker cannot offsetfaults of the amplifier or B supply, orvice versa.
To obtain the very low and very highfrequencies engineers of the Acme Ap-paratus Company have developed anaudio amplifier that utilizes resistancecoupling for the first stage, transformerfor the second resistance again for thethird.
The Impedance LeakA feature of the third stage is the
utilization of an impedance, rather thana resistance, as the leak, which helps off-set any tendency to motorboating at thelower frequencies.
The reasons for the employment of animpedance leak are interesting. In anamplifier circuit utilizing a grid leak, aregular detector circuit results, and recti-fication occurs. To prevent this rectifi-cation, which is a prolific source of dis-tortion, Acme engineers have designed aspecial unit, incorporating the necessaryresistance and impedance, which drainsthe grid of its accumulated charge with-out affecting signal intensity. Wheretransformers are employed in the firstand second stages of an amplifier, evenwhen the ratios are different, distortionof a blurring nature may occur. This isa transient effect due to the continuousvariation in frequencies and can only beentirely eliminated by the use of an im-pedance or resistance stage after or be-fore the transformer stage.
For the highest quality in reproduction,a power amplifier should of course be uti-lized. A good speaker used with an ordi-nary amplifier-that is, one in which atube of the 201-A type is used in the laststage-will generally give sufficient vol-ume to satisfy its user, but it will be foundthat the reproduction is not, in most cases,faithful. This is due to the fact, assum-ing of course that the amplifier itself isnot deficient, that the last tube in ampli-fier is being overloaded.
By overloading is meant that the tubeis being used over a greater portion of itscharacteristic than is permissable for un-distorted output.
This distortion manifests itself particu-larly when strong signals are applied, andmay be entirely absent when the receiveris operating at half volume. Undistortedamplification means that the voltage to beamplified is delivered by the amplifier tubeto the speaker exactly as the amplifiertube received it from the precedingstage. The on'y change which the tubeis permitted to make is to increase theamplitude of the applied voltage.
Using ordinary tubes in the last stage,it will be found that as the volume in-creases the quality of the reproducedsignals become noticeably harsh and un-pleasant, because of the inability of theordinary tube to handle large volumes.
Constitution of Power AmplifierIt is quite possible that, even at the
low volumes, distortion is' still takingplace, possibly due to the improper opera-tion of the tube; but at low intensitiesit is not sufficiently great to be noticedby the average set owner. When using aproperly designed power amplifier suppliedwith the proper high voltage, results are,of course, tremendously improved.
A power amplifier consists essentiallyof a power tube, especially designed forthe purpose, and its accessories. Thepower tube may be either a 210 or 310.These tubes are designed to operate witha plate potential of 450 volts, and can-not, for this reason, operate properlyfrom the ordinary B supply.
Transformers capable of delivering thishigh voltage, have recently been devel-oped. Two rectifier tubes of the 216 Btype are frequently used with their fila-ments in parallel.
The filter system used with this typeof power supply cannot be made up withthe ordinary available condenser blocks,since most of these are designed for op-eration on 400 volts DC, while the 210amplifier is designed for 450 volts. It istherefore necessary that the condensersbe rated for continuous use at not lessthan 800 volts to take care of the in-crease in voltage if the filament of the210 tube is turned off.
In the power amplifier, one of themain reasons for distortion is incorrectC, or grid bias. Where a B power supplyis used, it is often difficult to tell whetherthe correct voltages are being applied.In the case of a milliameter reading tofifty mills, it can well be utilized as ameans of determining whether distortionis occuring from- this cause. The metershould be placed in the plate circuit ofthe power stage and the needle noted.If it fluctuates more than ten per cent.of the total reading, distortion is serious.
When the kick is downward, it general-ly indicates that too much C battery isbeing applied. When the kick is up-wards, or towards the high readings onthe scale, the C voltage is not sufficientand more should be added.
16 RADIO WORLD December 3, 1927
COUNT DEMONSTRATES FINDER
(Henry Miller)COUNT GUY DU BOURG DE BOZAS, WELL KNOWN FRENCH TECHNICALDIRECTOR WITH HIS WIRELESS DIRECTION FINDER WHICH HE DEM-ONSTRATED TO U. S. OFFICIALS IN WASHINGTON. THE APPARATUS INCONNECTION WITH THE RECEIVING SET SHOWN ON TABLE, IS USEDTO FIND SHORT AND LONG WAVE WIRELESS STATIONS, NO MATTERHOW FAR AWAY. THE DIRECTION FINDER OF THE SET CAN BESEEN STANDING BESIDE THE RECEIVING SET. THE INSTRUMENT
IS NOW BEING USED BY FOREIGN GOVERNMENTS WITH SUCCESS
News Agencies SeekShort Wave Licenses
On behalf of three publishing concernswho applied for licenses to operate shortwave stations for the dissemination ofnews to different points within the UnitedStates, the Federal Radio Commissionwill hold a hearing on January 10. TheNew York Times and the InternationalNews Service Company, both of NewYork, and the Examiner Printing Com-pany of San Francisco were the appli-cants.
The commission decided in a formalway, a couple of weeks ago, when an ap-plication was submitted by the San Fran-cisco Examiner to send out news be-tween San Francisco and -Los. Angeles,that such a license would not be granted,as long as it was possible to utilize othersources for this type of business, such as
the telegraph lines.As far as the transmission of news to
foreign countries is concerned, licenseswould be granted. The Hearst organiza-tion which operates the Examiner andthe International News have already beenpromised such a license, New York andHalifax to be the points between whichnews will be transmitted.
The commission states that although 89per cent of its time has been devoted tothe broadcasting service and clearing ofthe eighty-nine channels in the band, ithas always been aware of the fact thatthere are other bands used in the nationaland international communication that areto be given real consideration under theRadio Act of 1927. The news hearing isone of the first of these considerations.
69 Stations SrAir Clear(
So as to eliminate heterodyning andmake distant reception an easier task thanheretofore, the Federal Radio Commissionhas changed the status of 69 stationswhose frequencies lay in the 600 to 1,000kilocycles band. Some have been com-pletely lifted out of this choice region.
The Commission states that it realizesthere will be some stations adversely af-fected, but that they_ must be martyrsto better radio. The Commission alsosays that if it has erred it would be happyto allow a public hearing, so that factswhich warrant a station's shift to a bet-ter position could b'e heard.
In the N. Y. City district stations WJZ,WEAF, WOR and WABC have beengiven a clear channel, so that their highpowered transmitters may be heardacross the continent.
Some Protest, Others Praise RulingSome stations have already protested
against the Commission's ruling. Officialsof WAAM, Newark, N. J., which wastransferred from 860 to 1,120 kilocyclesand had its power cut from 500 to 250watts, stated that they would fight to afinish.
Officials of most of the other stations,however, have praised the ruling, statingthat they now are beginning to appreciatethe true value of the Commission. Oneprominent radio personality who wasoverjoyed with the ruling was A. H. Grebe,president of the Atlantic BroadcastingCompany.
"This is really a wonderful thing forthe whole radio industry," gloated Mr.Grebe. "The ideal conditions now madepossible will stimulate the sale of radiosets and equipment to a new high level,since listeners will be assured maximumservice in reception of both local anddistant stations.
"Previous to the recent chaotic condi-tions, it was not an unusual thing forEastern stations to be heard regularly onthe Pacific Coast and in some instanceseven farther. An example of what mightbe expected with a clear channel, suchas WABC will possess is found in the factthat WAHG, a 500 watt station which pre-ceded WABC, was often reported heard inAlaska and in Australia. That was whenall the channels were clear."
Ruling Explained By CommissionThe commission, in its statement, ex-
plains exactly how the new system worksout:
"The newly designated band includesimportant stations scattered throughoutthe United States. Over these clearedchannels it will thus be possible for ruraland remote listeners to pick up stations inall sections of the country. Listenerswith a particular taste for DX will also
SWEDISH USE NOVEL ANTENNAGothenberg, Sweden.
It is not necessary that the rooftop'sappearance be ugly, simply because an-tennas have to be installed. At least thatis what the township of Gothenberg say,for they have arrived at a scheme where-by the rooftop becomes a thing of beautywith the installation of antenna wires.Quite unlike that of those in New YorkCity.
A spider web antenna arrangement isemployed by the Swedish. The wires areall brought to a central ring. From herethey radiate to the roofs of many housesaround. The leadins are taken off thecenter of the wire.
December 3, 1927 RADIO WORLD 17
ken Up;for Big Onesfind the tracks cleared for them and allthe way across the continent in the caseof several of the Pacific Coast stationswhich have adequate power to deliver asignal in the East under good receptiveconditions.
"San Francisco can be heard for threehours after Newark shuts down on 710kilocycles. And Portland will come in onWEAF's wave length after the big LongIsland transmitter has closed for the night.
"KOA, Denver, as a mile -post for cross -continental radio tourists, will be heardwhen two 500 -watt stations in New YorkCity are off. And Porto Rico, which sharesLouisville's channel, will prove a long dis-tance southern test when the Kentuckybroadcaster has closed down.
Preference to Chicago Station"Chicago has been assigned some five
cleared waves, and while this is the largestnumber given to any single community, itmust be remembered that Chicago, by itsoriginal location, is in a position to fur-nish programs for the entire United States,both East and West, and for this reasonconsidered from the standpoint of thetremendous audience of remote listenerssurrounding Chicago, it was deemed de-sirable that this number of cleared chan-nels be freed for the Chicago broadcasters.
"Other centrally located cities in theMiddle West, such as Cincinnati, St.Louis, Cleveland and Detroit, are alsogiven the opportunity to share with Chi-cago in providing radio programs for thegreat Mississippi Valley and central West-ern audience.
"The South is particularly well repre-sented in this picture of cleared channels."
The Commission thinks that not untilJanuary 15 will the 600-1,000 kc bandbe completely cleared up, due to the manyhearings which it will, no doubt, have tohold. Immediately after this date, theCommission will make an attempt to clearup the higher frequencies from 1,000 to1,200 kilocycles.
PLAYS RARE AIRS
PAULINE WATSON HEARD RECENT-LY FROM WPCH, NEW YORK CITY
A concert artist who is heard occasion-ally on the radio is Pauline Watson,violinist, who features rare music, includ-ing particularly French pieces. Sheplayed her violin to advantage fromWPCH recently. Her own arrangementof "La Chante," a old French air, wasthe chief rendition.
Western SenatorsPlan to Broadcast
Washington.A national educational campaign
through the use of radio broadcasting isto be initiated in support of the legisla-tve program of the recently formedgroup of Western Senators who plan towork together for legislation of inter-est to the West.
The plan as outlined by SenatorBrookhart who represents the group callsfor the establishment in Washington of alow powered station broadcasting belowthe regular broadcast band. This station,the Senator said, is to be built and paidfor by the persons interested in the West-ern legislation plans. Programs broad-cast over this low powered station are tobe picked up by Station KTNT at Mus-catine, Iowa, which station, the Senatorsays, is able to reach most of the West-ern States.
A. K. ARTIST
EDITHA FLEISHER, SOPRANO WHOWAS RECENTLY HEARD IN THEATWATER KENT HOUR FROMWEAF AND ITS ASSOCIATED STA-TIONS. MANY LETTERS OF COM-MENT WERE RECEIVED.
P/c DUPE.
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aSCHEMATIC DIAGRAMS ILLUSTRATING HOW TELEVISION WORKS.
16 RADIO WORLD December 3, 1927
COUNT DEMONSTRATES FINDER
(Henry Miller)COUNT GUY DU BOURG DE BOZAS, WELL KNOWN FRENCH TECHNICALDIRECTOR WITH HIS WIRELESS DIRECTION FINDER WHICH HE DEM-ONSTRATED TO U. S. OFFICIALS IN WASHINGTON. THE APPARATUS INCONNECTION WITH THE RECEIVING SET SHOWN ON TABLE, IS USEDTO FIND SHORT AND LONG WAVE WIRELESS STATIONS, NO MATTERHOW FAR AWAY. THE DIRECTION FINDER OF THE SET CAN BESEEN STANDING BESIDE THE RECEIVING SET. THE INSTRUMENT
IS NOW BEING USED BY FOREIGN GOVERNMENTS WITH SUCCESS
News Agencies SeekShort Wave Licenses
On behalf of three publishing concernswho applied for licenses to operate shortwave stations for the dissemination ofnews to different points within the UnitedStates, the Federal Radio Commissionwill hold a hearing on January 10. TheNew York Times and the InternationalNews Service Company, both of NewYork, and the Examiner Printing Com-pany of San Francisco were the appli-cants.
The commission decided in a formalway, a couple of weeks ago, when an ap-plication was submitted by the San Fran-cisco Examiner to send out news be-tween San Francisco and Los. Angeles,that such a license would not be granted,as long as it was possible to utilize othersources for this type of business, such as
the telegraph lines.As far as the transmission of news to
foreign countries is concerned, licenseswould be granted. The Hearst organiza-tion which operates the Examiner andthe International News have already beenpromised such a license, New York andHalifax to be the points between whichnews will be transmitted.
The commission states that although 89per cent of its time has been devoted tothe broadcasting service and clearing ofthe eighty-nine channels in the band, ithas always been aware of the fact thatthere are other bands used in the nationaland international communication that areto be given real consideration under theRadio Act of 1927. The news hearing isone of the first of these considerations.
69 Stations SI-Air Clean
So as to eliminate heterodyning andmake distant reception an easier task thanheretofore, the Federal Radio Commissionhas changed the status of 69 stationswhose frequencies lay in the 600 to 1,000kilocycles band. Some have been com-pletely lifted out of this choice region.
The Commission states that it realizesthere will be some stations adversely af-fected, but that they. must be martyrsto better radio. The Commission alsosays that if it has erred it would be happyto allow a public hearing, so that factswhich warrant a station's shift to a bet-ter position could he heard.
In the N. Y. City district stations WJZ,WEAF, WOR and WABC have beengiven a clear channel, so that their highpowered transmitters may be heardacross the continent.
Some Protest, Others Praise RulingSome stations have already protested
against the Commission's ruling. Officialsof WAAM, Newark, N. J., which wastransferred from 860 to 1,120 kilocyclesand had its power cut from 500 to 250watts, stated that they would fight to afinish.
Officials of most of the other stations,however, have praised the ruling, statingthat they now are beginning to appreciatethe true value of the Commission. Oneprominent radio personality who wasoverjoyed with the ruling was A. H. Grebe,president of the Atlantic BroadcastingCompany.
"This is really a wonderful thing forthe whole radio industry," gloated Mr.Grebe. "The ideal conditions now madepossible will stimulate the sale of radiosets and equipment to a new high level,since listeners will be assured maximumservice in reception of both local anddistant stations.
"Previous to the recent chaotic condi-tions, it was not an unusual thing forEastern stations to be heard regularly onthe Pacific Coast and in some instanceseven farther. An example of what mightbe expected with a clear channel, suchas WABC will possess is found in the factthat WAHG, a 500 watt station which pre-ceded WABC, was often reported heard inAlaska and in Australia. That was whenall the channels were clear."
Ruling Explained By CommissionThe commission, in its statement, ex-
plains exactly how the new system worksout:
"The newly designated band includesimportant stations scattered throughoutthe United States. Over these clearedchannels it will thus be possible for ruraland remote listeners to pick up stations inall sections of the country. Listenerswith a particular taste for DX will also
SWEDISH USE NOVEL ANTENNAGothenberg, Sweden.
It is not necessary that the rooftop'sappearance be ugly, simply because an-tennas have to be installed. At least thatis what the township of Gothenberg say,for they have arrived at a scheme where-by the rooftop becomes a thing of beautywith the installation of antenna wires.Quite unlike that of those in New YorkCity.
A spider web antenna arrangement isemployed by the Swedish. The wires areall brought to a central ring. From herethey radiate to the roofs of many housesaround. The leadins are taken off thecenter of the wire.
December 3, 1927 RADIO WORLD 17
aken Up;1 for Big Ones
find the tracks cleared for them and allthe way across the continent in the caseof several of the Pacific Coast stationswhich have adequate power to deliver asignal in the East under good receptiveconditions.
"San Francisco can be heard for threehours after Newark shuts down on 710kilocycles. And Portland will come in onWEAF's wave length after the big LongIsland transmitter has closed for the night.
"KOA, Denver, as a mile -post for cross -continental radio tourists, will be heardwhen two 500 -watt stations in New YorkCity are off. And Porto Rico, which sharesLouisville's channel, will prove a long dis-tance southern test when the Kentuckybroadcaster has closed down.
Preference to Chicago Station"Chicago has been assigned some five
cleared waves, and while this is the largestnumber given to any single community, itmust be remembered that Chicago, by itsoriginal location, is in a position to fur-nish programs for the entire United States,both East and West, and for this reasonconsidered from the standpoint of thetremendous audience of remote listenerssurrounding Chicago, it was deemed de-sirable that this number of cleared chan-nels be freed for the Chicago broadcasters.
"Other centrally located cities in theMiddle West, such as Cincinnati, St.Louis, Cleveland and Detroit, are alsogiven the opportunity to share with Chi-cago in providing radio programs for thegreat Mississippi Valley and central West-ern audience.
"The South is particularly well repre-sented in this picture of cleared channels."
The Commission thinks that not untilJanuary 15 will the 600-1,000 kc bandbe completely cleared up, due to the manyhearings which it will, no doubt, have tohold. Immediately after this date, theCommission will make an attempt to clearup the higher frequencies from 1,000 to1,200 kilocycles.
PLAYS RARE AIRS
PAULINE WATSON HEARD RECENT-LY FROM WPCH, NEW YORK CITY
A concert artist who is heard occasion-ally on the radio is Pauline Watson,violinist, who features rare music, includ-ing particularly French pieces. Sheplayed her violin to advantage fromWPCH recently. Her own arrangementof "La Chante," a old French air, wasthe chief rendition.
Western SenatorsPlan to Broadcast
Washington.A national educational campaign
through the use of radio broadcasting isto be initiated in support of the legisla-tve program of the recently formedgroup of Western Senators who plan towork together for legislation of inter-est to the West.
The plan as outlined by SenatorBrookhart who represents the group callsfor the establishment in Washington of alow powered station broadcasting belowthe regular broadcast band. This station,the Senator said, is to be built and paidfor by the persons interested in the West-ern legislation plans. Programs broad-cast over this low powered station are tobe picked up by Station KTNT at Mus-catine, Iowa, which station, the Senatorsays, is able to reach most of the West-ern States.
A. K. ARTIST
EDITHA FLEISHER, SOPRANO WHOWAS RECENTLY HEARD IN THEATWATER KENT HOUR FROMWEAF AND ITS ASSOCIATED STA-TIONS. MANY LETTERS OF COM-MENT WERE RECEIVED.
R/oru/-e
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SCHEMATIC DIAGRAMS ILLUSTRATING HOW TELEVISION WORKS.
18 RADIO WORLD December 3, 1927
Resistor Used WronglyHas Surprising Ohmage
t3
1.2
2
0
0 0som
06
cti006
05
04
Ct 03
0.1
0 .1 2 .3
Curves Show nis, theVorio t on of Res S-tance w th Currentin Resistors
4 .5 6
FIG. 1
THESE CURVES SHOW THE VARIA-TION IN THE RESISTANCE OF RE-SISTORS MADE OF AN ARTIFICIALSUBSTANCE. THE VARIATION FORTHE HIGHER RATED RESISTORS ISVERY GREAT, AND THIS MAKESTHEM UNSUITABLE FOR PLATE
COUPLING RESISTORS.
Resistors are not always what theyare expected to be-fixed in value and ofthe value specified. This fact was strik-ingly brought out in a test on a numberof commercial resistors of an artificialcompound. The tests included five dif-ferent samples of as many different rat-ings of the same material. The resultsof these tests are shown in the accom-panying graphs. Resistance values inmegohms are plotted as ordinates and thecurrent load in milliamperes as abscissas.
The top curve in Fig. 1 is that of agrid leak resistor rated at 2 megohms.The first observation was made when thecurrent flowing through it was 36 micro-amperes. The resistance was 1.28 meg-ohms. As the current increased the re-sistance dropped very rapidly, and at 310microamperes it had dropped to .56 meg-ohm. This resistor was intended for gridlead use where the current through itwill not be more than a few micro-amperes.
More Than 2 Meg. in DetectorIn view of the rapid change in resist-
ance for low values of current it is prob-able that when used as a leak its re-sistance will not only be the rater 2 meg-ohms but much more.
The second curve from the top is thatfor a grid leak resistor rated at 1 meg-ohm. This also shows a very rapidchange of resistance as the currentthrough varies, but not nearly so greatas for the previous resistor. The first ob-servation was taken at 20 microampereswhere the resistance was found to be .92megohm.
Then the resistance dropped so rapidlyas the current increased that at 360 micro-amperes it was only .38 megohm. Byextending the curve upward beyond thefirst observed point it appears that at acurrent of 5 microamperes the resistanceis 1.1 megohms. Thus when this is usedfor the purpose intended the resistanceis close to the rated value.
The middle curve shows the resistancevariation of a 5 megohm resistor. Thefirst observation was taken at 60 micro -
By Pierre Raoul St. Ivesamperes, where the resistance was .38megohm. As the current increased theresistance dropped, first rapidly thenmore slowly, so that at 1 milliampere itwas only .14 megohm.
A Little Extrapolating
By extrapolating below the first ob-served point the curve may be extendedto the rated value of .5 megohm when thecurrent is zero. Since the resistor neverwill be used at zero current, this particu-lar resistor has been overrated.
The next curve shows the variation ofa high duty resistor rated at .1 megohm.The first observation at 165 microamperesshows a resistance of .12 megohm. Thevariation throughout the observed rangeof current is small and does not deviatemuch from the rated value. Por very lowvalues of current, however, the resistance
7 8 9 10 seems to rise to much higher values thanthe rated value.
The lowest curve shows the variationof resistance in a .05 resistor. Its re-sistance is substantially constant over thecurrent range observed, but it is slightlyover 60,000 ohms instead of 50,000 ohms.This slight underrating is of no import-ance for most purposes. This resistoralso was of the heavy duty type.
All these resistors were measured un-der conditions which would be met in theplate circuit of resistance coupled ampli-fiers, and the object of the tests was tosee whether grid leaks of this type couldbe safely used as coupling resistors. Itis apparent that the three of the higherratings are not at all suitable.
Seeks Greater Amplification
One reason for using high values ofresistance in the plate circuits is to securea greater amplification. This object isdefeated by the rapid decrease in theactual resistance of these resistors.Another reason for using high value re-sistors in the plate circuits is to flattenout the dynamic characteristic as possibleand thereby minimize harmonic distortionwhich results from the curvature of thecharacteristic. This object is not only de-feated by the rapid decrease in the coup-ling resistance but the dynamic character-istic of the tube and coupler is actuallycurved by it. Where the effective con-ductance of the tube increases the con-ductance of the coupling resistor also in-
,urrent 1n NiMampe res
iqhm
gernhilseririgollumbes-7 6 5 -4 -3 2 -I 0 2
Gr d Vo takeFIG. 2
CURVES SHOWING THE EFFECTOF VARIATION IN COUPLING RE-SISTOR ON THE DYNAMIC CHAR-ACTERISTIC. THE CURVATURE ISINCREASED BY THE VARIATION ASINDICATED BY THE DOTTED
CURVE.
creases so that the dynamic characteris-tic of the amplifier becomes greatlycurved and the harmonic distortion willbe considerable. The effect is shownqualitatively in Fig. 2, in which the fullline shows the dynamic characteristic ofa tube and a fixed coupling resistor andthe dotted line shows the characteristicof the same tube with a resistor the re-sistance of which decreases as the cur-rent increases.
Several Preferred to OneIt would seem that if a high plate re-
sistance is desired to take full advantageof the amplification factor of the tubeand at the same time straighten out thedynamic characteristic of the circuit thatit is better to obtain the high resistanceby adding many high duty resistors inseries than to use one of a high rating.
Most resistors available for couplingpurposes have a negative coefficient ofchange of resistance with current, just asthose represented in the accompanyingcurves. Some do not vary as much as thepresent, and when the variation is smallit is possible to use a single resistor ofhigh value for a coupling resistance.
Nearly all metals have a positive coeffi-cient of resistance change with current,or rather with temperature, and thereforeresistors made of such metals are pre-ferable for coupling resistors, particularlysince the change in resistance is quitesmall. But metallic resistors of the wirewound type are not practical in valuesof the order of 1 megohm, and metallicfilm resistors such as are commonly useddo not have the same characteristics aswire wound resistors.
200,000 Sets in Russia;47 Broadcast Stations
Washington.Radio fans are multiplying so rapidly
in the Soviet Union that the Governmentis steadily expending its efforts to keepup with the demand for receiving sets,according to a report from the CentralStatistical Administration to the SovietUnion Information Bureau here. Thenumber of receiving sets in use has nowreached 200,000, as compared with 116,000on February 1 last and 30,000 at the be-ginning of 1926.
Forty-seven radio stations now broad-cast daily programs. in the Soviet Union,where there was only one in 1924 and
nine in 1925. A dozen new stations arebeing built. There is now a broadcastingstation in every large city. Moscow hasfour stations, Leningrad two, and Khar-kov, the capital of the Ukraine, has two.
On the occasion of the recent celebra-tion of the tenth anniversary of the SovietState, a broad hook-up carried the pro-ceedings in Moscow, the capital, to re-mote parts of the country. Peasants inSiberia and in Central Asia, gathered intheir village club rooms, listened in onthe music and the speeches attendant onthe celebration in the distant capital. Allwere enthusiastic.
December 3, 1927 RADIO WORLD 19
PARTTHE sweetest melody grows stale through
over -repetition; the cleverest witticismloses its flavor through reiteration. So thestory of the Fen.way Concertrola can vergeon the monotonous. And yet when Hetero-dyne Smith and Eder Franklin returned toFred \Vundsam's apartment -laboratory foranother session, all three did little else buttalk about the Concertrola.
As we peek in upon the unholy trinitywe hear Franklin saying: Heterodyne, Ithought that you were going to get your setworking with RCA tubes in one night. I'llwager that you threw a couple of wirestogether and then went fooling around yoursuper. Hi. hi?
Heterodyne said: "I ran out of solder, tobe exact, and you know an electric set oughtto have all connections firmly joined. Be-sides," he continued, "I was too tired togive it the consideration it deserves. If Ican't do a job right, well, I lay off it; seewhat I mean?"
'Twill Be a Gift
In appearance Heterodyne was a rotundfellow given to Palm Beach suits with acurving cut that served to emphasize hisrotundity. His voice was low, his speechlong drawn out. Lazily he selected a cigarfrom his pocket, and then proceeded withthe rest of the process with slow haste.He exhaled from his lungs a cloud of pun-gent smoke, and without waiting for any-one to speak, remarked:
"Oh, I suppose I'll finish the set some-time between now and Christmas. I'm goingto make it as a gift to a friend, anyway."
Franklin stood facing his friend."I'm afraid," he said, "that some of your
ideas about multi -tube sets have been shock-ed. You know, old dear, pride is a bubble
The Fenway ElectricConcertrola
By Leo FenwayAssociate, Institute Radio Engineers
Cabinet Type of Concertrola Receiver.
and I think yours has been pricked. Foras long as I have known you, I've heardnothing from your lips but ravings aboutseven, eight and nine tube superheterodynes.You've often declared that a Super was thelast word. So you fondly dreamed. Yourdreams-like your prayers-perhaps, ascendedinto the empyrean.
Gives Demonstration
"They cluttered up the wings of Saturnand curdled the nightly sweetness of theMilky Way. Finally the answer is coming.Like a feather it is floating, darting, zig-zagging down and down-corning to rest inFred's battery model and mine made withMcCullough tubes.
"And, believe me, Heterodyne, we areshowing you that a real four tube set, likethe Concertrola, is capable of bringing ingreat DX stuff. with good volume and al-most perfect quality. Realism, Fred callsit."
"You said it!" Fred exclaimed. "Here'sa sample of what I call realism."
He snapped on the switch of his battery'model Concertrola and the little apartment-laboratory was suddenly electrified with theatmosphere of a night club.
Blare of the TrumpetHeterodyne started to speak, but just then
his attention was drawn to the center ofthe room where, it seemed, a gay and hilari-ous crowd were walking right out of theloudspeaker. It seemed to Heterodyne as ifthe decorations of blue and gold of the nightclub approved of his company. He felt asif he has passed through rows of congestedrevellers to a far table, glowing white andcrystal-a table far enough removed to per-mit unmolested indulgence in the arms ofMorpheus.
The trumpet blared; the saxophone
crooned and Heterodyne watched a coupleas they gave an exhibition of Spanish andApache dances. He saw the dancer seizehis partner by the waist as he swung herand whirled her and tossed her around theroom, and the lights turned red and blueand green, and when they turned white, hegrabbed her by the fragile waist and draggedher back into-the loudspeaker. Fred hadturned the set off.
"There's something about the music ofthose upholstered sewers," said Heterodyne,"that always gets me. However, let's getback to the Concertrola. What can youfellows tell me about it that I don't alreadyknow?"
Hope Is the Foundation
Almost every circuit which has made itsmark has had back of it some underlyinghope of a worth -while accomplishment.Franklin had this thought in mind when hesaid to Heterodyne, "The thing I like aboutthe Concertrola is the fact that the same set,apparently, can be used for batteries, Mc-Cullough tubes, R C A tubes and can beoperated on either alternating or direct cur-rent. The simplicity of the thing must strikea popular cord.
"And the fact that it can be operated forless than one cent per hour, proves that itis very economical.
"You know, fellows," he went on, "eventhe dry cell C batteries can be dispensedwith.
"It is a very simple matter to insert afixed resistance of about 3,000 ohms in thegrid return circuits of the first two tubes.This, of course, ought to be a variable re-sistance, such as the Royalty Truvolt or theCarter. A similar resistance of about 2,000ohms can be used in the first audio stage,thereby doing away with the nine volt C
(Concluded on page 26)
20 RADIO WORLD December 3, 1927A THOUGHT FOR THE WEEKAN SOS call at sea-a plea for help
-12 from a stricken countryside-a start-ling message from a man bird in the polarregions-a staccato cry of haunting, vivid-ness from a South American morass or aHimalayan fastness-a hundred differentcauses in a hundred different places for theuse of radio-all making for deep -throateddrama of the kind that holds the world tenseand makes the human heart respond infullest measure-all this is radio in 1927.
SIXTH YEAR
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TUBE CHARGES ISOLATEDWashington.
The Federal Trade Commission re-fused to mix up the anti-trust case againstthe R. C. A. and six others with thecharges by independent manufacturersthat the tube clause in R. C. A. licensecontracts is monopolistic. The set makersare compelled to sell R. C. A. tubes withthe sets.
The Customer'sTHERE is so much misleading adver-
tising appearing in the public press onalternating current tubes that radio saleshave fallen off to an alarming extent.Several reliable, but misguided, manufac-turers have over -done their job in sellingthe public on the idea of the "NoBatteries, No Eliminators-Your LightSocket Supplies all Power."
What is the result? People walk intoa radio store and demand a radio setor a kit of parts that will work directlyfrom the house wiring current. Theysimply want to "plug-in" and forget it-just as the adv. says. The customer ap-pears hurt and grieved when the dealertells him that no electric radio set hasever been built, or ever can be builtwhich does not require a so-called "Bbattery eliminator" or "power unit." Thecustomer is amazed and dumfoundedwhen the dealer tells him that the currentas it comes from the light socket is to-tally unsuited to operate any radio setwithout the use of power units.
My Word! Anything But That!"You mean by that," says Mr. Prospec-
tive Radio Buyer, "that I've got to useone of those old-fashioned sets or kitsof parts that requires an eliminator?Nothing doing !" And to prove that Mr.Prospective Radio Buyer means business,he removes his hand from the pocketthat contained the necessary wherewithaland leaves the store, muttering incoher-ently to himself, "Plug into the LightSocket-Bologny I"
After Mr. Prospective Radio Buyer hasvisited several stores, and heard the samestory in each, he decides that, perhapsit will pay him to wait until radio hasoutgrown the experimental laboratorystage and entered the phase of commer-cial utility.
In the meanwhile, the dealer has losta sale. The manufacturer has lost a cus-tomer. And the customer has lost hismess of radio pottage.
The blame for all this rests on some-body's shoulders. Somebody has beenmaking false statements which had re-acted to the disadvantage of the entireradio industry. October sales prove it.
The Standing and WalkingAll along the line dealers have been
"standing by" while customers werewalking by-customers who had themeans, and oftentimes the desire, to owna complete radio outfit, either electrifiedor all -electric.
Yet the customer and the dealer cannotdo business simply because several re-liable, although misguided, manufacturershave been applying wild superlatives inorder to put across their "all -electric" sets.
Back in 1926 the popularity of batteryeliminators, trickle chargers and the likewas very great, simply because to getwhat one wanted with a certain amountof truthfulness on the part of the manwho had it to sell was a matter of sim-plicity itself. Today all that is changed.
The radio manufacturer of yesteryear,who used to state that his receiver couldbe obtained with or without batteries, orwith certain types of eliminators, is inthe discard. In his stead has come theradio manufacturer, with psycho -analysisat his command. '°See my new set," heexplodes, "it works entirely without bat-teries, without eliminators-your lightsocket supplies all power!" See thesenew tubes?" he raves on, "there are ACtubes. They work right off the bat, fromyour 110-125 volt AC line. Great Stuff!Yes, sir. Right from your AC line!"
Facts Will OutYet, despite the glowing statements of
"Electric" Shockthe manufacturer, the unwary purchasersoon discovers-sometimes too soon !-that his set, like that of his neighbor, hastucked away in each corner, a B batteryeliminator and either a small storage bat-tery with a trickle charger, or in placeof the latter, a step-down or socalledheater transformer as a means for sup-plying the A current.
Of course the set is an electric set.And in nine cases out of ten, it is a goodelectric set. Moreover, there is nothingwrong with the current supplying methodsused by this particular manufacturer-ab-solutely nothing. But, there 'is SOME-THING DECIDEDLY WRONG WITHHIS METHODS OF ADVERTISING!
In telling the prospective buyer that hisset works without batteries or elimina-tors, he is not only guilty of downrightlying but he is also injuring his trade andthe trade of his fellowmen.
As often as not, the customer wouldbe satisfied with his product if the manu-facturer simply said that the set was anelectrified outfit, made so by virtue ofB eliminators and AC tubes, supplied bytransformers. The customer could evenunderstand that it was necessary to havesome sort of current supplying devices,just as he is obliged to have a battery,a generator and a gas supply in his car.
Like Self -Starter
Now, B eliminators, AC tubes and cer-tain A devices, which work from the lightsocket, are to the radio set what the self-starter is to the automobile. In the olddays, to get the old buss started one hadto get out and crank the thing-just as hehas had to use batteries. Then came theself-starter. It was handy, convenient,and represented progress in the automo-tive world. Still, the old wagon ran justas smoothly when it was cranked by hand!And the radio set will continue to runjust as smoothly when it is supplied bydirect current devices, such as batteries,eliminators and the like.
There is no reason to suppose that thenew AC tubes will work better or worsethan ordinary DC tubes. There is noespecially good excuse why the ownerof a radio set, now being supplied withcurrent from batteries or eliminators,should junk his outfit. Nor is there anysense in trying to dissuade the unversedtechnical buyer from becoming interestedin "self-starting" radio receivers. Butlet's tell him the truth about the matter.
Good But Will Be BetterWhile AC tubes are good at present,
they will become much better as dayspass into weeks. Because present-daymethods of manufacturing AC tubes arenot perfect does not necessarily mean thatthey will never improve. The difficultiesnow being experienced, which of coursecurtail production, will eventually beswept aside. In the meanwhile the radioindustry must carry on. Christmas iscoming. Little stockings must be filledto overflowing with the good things oflife. Even the stockings belonging tochildren of radio dealers must come in fortheir share. So the manufacturers who inthe past have been publishing misleadingadvertisements about their "all -electric -direct -from the light -socket -sets" mustabandon their tactics and get down tobusiness.
No electric set has ever been built ormarketed which does not require a so-called "B -battery eliminator" and a trans-former for the A current supply. Thesooner everybody understands and real-izes this, the sooner the radio dealer,manufacturer, jobber and salesman willhave turkey on the table.
December 3, 1927 RADIO WORLD 21
The Circuit One FlawAlone Positively Kills
(Continued from last week)
It is a simple matter to build a super -selective receiver. It is equally simple tobuild a super -sensitive receiver. Both ofthese can be attained with particular easewhen the intermediate frequency amplifica-tion method of reception is employed in thereceiver.
It is not difficult at all to build a receiverof startlingly realistic tone quality. It isnot particularly difficult to build a receiverwhich is easy to tune and to control. Bothare easy of attainment when the double de-tection method of reception is not employed.
The difficulty enters when an attempt ismade to combine these four desirable quali-ties into a receiver and to make that receiverapproach perfection in all. Hundreds ofradio engineers have met rebuff and failurewhen they have tackled this seemingly in-superable problem. They may have suc-ceeded in mastering any one, or any two,or even any three of the qualities, but notall four in the same receiver.
One Flaw Kills Circuit
There has been usually at least one flawin their product, a sufficient cause to consignit to oblivion.
But the failures of hundreds do not pre-clude the possibility of success of one. Whenthe problem to be solved is clearly delimitedand understood by some one, that one willhave gone a long way toward the solution.And if he has learned by the errors of
and profited by their successes, heis very likely to arrive at the optimum solu-tion.
One may truly say that a designer has at-tained the goal which many others havesought in vain-a receiver which is within afraction of a percent of perfection. Andhe attained the goal not only by avoiding theerrors of others and by taking advantage oftheir successes, but by introducing originalideas of his own.
In what respect did the designer take ad-vantage of the successes of others? By se-lecting the best possible parts for the re-ceiver, by selecting parts which fitted per-fectly in with the desired overall character-istic, by co-ordinating the characteristics ina scientific and logical manner, and by choos-ing the proper circuit.
The Intermediate Coils
In this way he took advantage of the re-sults obtained in scores of research labora-tories equipped with the best trained mindsand the best instruments.
For example, let us consider the inter-mediate frequency amplifier. This is thebackbone of any double detection receiver:Selectivity resides in it, sensitivity is itsmajor contribution, quality is related to it,and ease of control depends on it. Thereceiver either stands or falls on the per-formance of the intermediate amplifier.When the public renders its verdict of a re-ceiver of this type after a trial period, nodirect reference is made to the intermediateamplifier; but in every case that is whathas been tested.
In view of the great importance of the in-termediate frequency amplifier it is logicalto assume that special attention is given toit in the design of a great recreator. Wheth-er this is the case or not will be brought outwhen we examine the construction of theintermediate frequency transformer.
There is one more feature peculiar to thedouble detection receiver that always de-serves special attention. That is the oscil-lator. There are many types of oscillator
circuits. There is probably only one circuitwhich gives uniformly good results over theentire broadcast band. That is the one touse.
The oscillating circuit consists of the prin-ciple tuning condenser and a large by-passcondenser both in series with a split oscil-lator winding.
One of the problems in designing a doubledetection receiver is to retain a high degreeof selectivity and the higher audio notes atthe same .time. That is, high selectivitywithout side band cutting. Correct interme-diate coil design contributes to this.
Wave Form Distortion Avoided
There is a form of distortion which oc-curs in every set, and that is wave form dis-tortion. This form of distortion is moreserious than any other because it is theone that the ear notices first.
The amount of this distortion in the out-
put of a receiver depends on the design andon the tubes used, as well as on the voltagesused.
If adequate filament current, plate voltage,and suitable grid bias arc used, then theamount of wave form distortion depends onthe power handling capacity of the tubes.Particularly the detector, the first audio andthe second audio amplifiers.
If the detector is standard and if a 112tube is used in the first audio stage and a 171in the second, then the wave form distor-tion will be very small for all volumes prac-tical in an ordinary home. Such tubes areused in the circuit and the amount of waveform distortion in the output is wholly negli-gible and imperceptible.
The expression "ease of control" coversseveral things. It refers to the ease withwhich stations can be tuned in and sepa-rated from stations not wanted. In this re-spect it is a delight. The condensers mustturn very easily and without any jerks orlost motion. This greatly aids in bringingin distant stations. Then ease of control alsorefers to the modulation of the volume orthe adjustment of sensitivity. In this re-spect a circuit is simple when it has onlyone major volume control, perhaps a po-tentiometer controlling the grid bias on theintermediate tubes. In addition, and sec-ondarily, a rheost:t may be used for controlof the filament c.irrent in the intermediatetubes.
(Cor,tirued next week)
Baffin Party Received310 Stations in Arctic
What is believed to be a record forlong distance reception in the Arctic Cir-cle was made public by Edward Manley,radio operator of the Morrissey, who hasjust returned from a five months' tripwith the Putnam -Baffin Land Expedition.
From the Northern extremity of the ex-pedition's itinerary, in wild Fox Basin, atotal of 310 stations were "copied" byManley, using a three tube dry batterypowered short wave receiver of the re-generative type.
Relying solely on this three tube set,and its dry batteries for power, the Mor-rissey operator pulled in 204 stations fromthe United States on the 40 meter wave-length and 85 on 20 meters. A total of 18foreign countries were also in communi-cation in this manner with the party inFox Basin. They included 8 Canadian sta-tions, one in Greenland, two in SouthAmerica, one each in South Africa andNew Zealand, three Belgian, two French,one in Porto Rico and 2 in Labrador.
Got Time Signals DailyIn addition, Manley "copied" each day
the time signals from Washington, D. C.,which enabled Capt. Bartlett, the skipperof the Morrissey, to check his chronom-eters.
The Morrissey was the first ship toenter Fox Basin, carrying white men, ina hundred years. In the year 1822-3, twoships entered the Basin, but since thattime, until the Putnam party penetratedits icy fastnesses, no white man ever enter-ed its practically unexplored waters. Thefact that no white man had preceded themfor a full century did not, however, ob-scure the fact that the white man's sig-nals bad already penetrated the forbid-ding area. Station after station waspulled in at the operators' command dur-ing their stay in the Basin.
In addition to copying the signals fromthese stations, the radio apparatus of thePutnam Expedition proved invaluable inthe party's exploration in surroundingwaters.
Operated by Monroe Barnard, son of
George Grey Barnard, the sculptor, along wave receiver both B and Adry batteries, was taken by a number ofthe party on their 400 -mile trip in theMorrissey's whale -boat.
Proceeding eastward 100 miles andnorthward 100 miles, and thence return-ing to the ship, the whale -boat succeededin actually cutting a huge area off themap of Baffin Island. The receiver wasused for checking the chronometers,the exact time signals as received by theradio set being used to compute the dif-ferences in time between the GreenwichMeridian and their own location.
To this fact was largely due the abilityof the party to compute distances so ac-curately that their final measurementsshowed Baffin Island to be 5,000 squaremiles less in area than the preceding ex-pedition's map, until now universally ac-cepted, showed it to be. Inability ofprevious explorers to check their chron-ometers was given as the reason of theirfailure to measure accurately the ArcticIsland.
Included in the whale -boat party wereGeorge Palmer Putnam, his son David,young Barnard, George Weymouth, JohnA. Pope, Lawrence A. Gould and theEskimo Avalita.
Magnetic Pole Static -lessMr. Manley pointed out that these ra-
dio operations were carried on at a pointnearer to the Magnetic Pole than hadever before been done. For this reason,he said, it is of interest to note that thefurther away that the stations which werereceived were located, the more clearlythey came through. Very little static wasencountered, far less than at any otherplace known.
His radio power equipment on which heachieved his record "copy" of 310 stations,consisted of three Eveready Layerbilt 45volt dry B batteries on the short wave re-ceiver and Eveready dry cells and 22.5 voltvertical B batteries on the long wave re-ceiver.
22 RADIO WORLD December 3, 1927
LiteratureWanted
MHE names and addresses of readers of.1- RADIO WORLD who desire literature
on parts and sets from radio manufactur-ers, jobbers, dealers and mail order housesare published in RADIO WORLD on re-quest of the reader. The blank below maybe used, or a post card or letter will doinstead.
RADIO WORLD,145 West 45th St, N. Y. City.
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Roy C. Briggs, 708 North Spring St., Inde-pendence, Mo.
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L Leonards, 3016 Lycaste, Detroit, Mich.John D. Johnson, 2601 66th Ave., Oakland, Calif.R. C. Cosgrove, 17 Oakwood Road, Quincy, Mass.J. L. Crouck, 1401 9th St., Moundsville, W. Va.Joseph Linker, 81 Covert St., Brooklyn, N. Y.Thomas V. Wright, P. 0. Box 14, Mattoon, Ill.Fred H. Scheel, 440 20th St., Bettendorf, Ia.Arthur Bornd, Box 104, Macon, Ga.Radio Service Bureau, 1524 Macombs Road, Bx.,
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N. H.
The Radio TradeBest Programs Spoilt
By Poor Obsolete SetsBy Eric H. Palmer
Two thousand dollars a night tenors donot sound much better than the two bucksvariety on twenty dollar receiving sets,and of course it takes the finest instru-ments to record faithfully the thrills ofMetropolitan sopranos.
This holds true in the reproduction ofleading orchestras, now playing nightly-for invisible millions.
Obsolete sets, makeshift contraptions,or hauls from the job lot sales, all toocommon in the big cities, are inadequateto meet present broadcast conditions.
Their presence warrants a strike bythe foremost talent.
Certainly, it is not fair to judge theartistic merits of a program by such sets.Even much more important from theviewpoint of the listener is the constanttinny and blurring effects trying both earsand patience that follows the installationof bargain counter apparatus.
Modern Sets Do The TrickModern receivers, with their perfect
amplification, bring in the deluxe enter-tainments with fidelity, making radio asource of keenest enjoyment, as it ismeant to be and should be, and is, amongthe discerning.
There has been a lot of criticism, openlyexpressed, and presumably much moreprivately circulated, regarding the rela-tive merits of the stars who have ap-peared on the chain programs. In thecases which have come under specialnotice, investigation reveals that ancientcouipment, with rattling speakers("squeakers" would be more like it) giv-ing a blaring and distorting effect, wasbeing relied upon, constituting an insult,virtually, to the performers.
Because reproduction of song and mu-sic was not all that it ought to be, inthe experimental days, many brilliant art-ists refused to appear before a micro-phone. That is no longer the case.They are aware of the vastly improvedmethods of transmission ; they realizethat there are receivers which bringthem to the family fireside in a manneradding to their fame and glorifying theirart.
Replacement Not Fast EnoughYet a survey reveals that replacement
of unsatisfactory receivers has not beenas speedy as most artists imagined. Thatis why they have reasonable cause for
complaint over ensuing dant-age to theirreputations.
It is true that many thousands aretuning in on the Chicago Civic Operapresentations, for example, on receiversthat are unable to meet the proper stand-ards. Faulty amplification is the worstevil. Overloading the last stage is ruin-ous, but that has been obviated by thenew receivers, with their finer trans-formers and utilization of power tubes.
Modern receivers are essential for full-est enjoyment. Their superiority overthe old type of sets is more remarkablethan has generally been emphasised. Ad-vance in radio designs has been note-worthy. And the same holds true ofspeakers.
There is another consideration. Old-time sets (lid not possess the selectivityrequired by present conditions, with somany stations clamoring for recognition,on higher power than in the past. Un-less tuning is sharp, chaotic conditionsarise. Those who believe that broad tun-ing outfits are sufficient for local recep-tion, with which they profess to be satis-fied, find themselves hopelessly copingwith heterodyning. cross talk, andwhistles, all nerve -shattering, due to themany broadcasters actually humming in,particularly at this season.
What A Difference!
That there should be necessity for call-ing attention to these aspects of broadcastreception seems rather strange, in viewof the knowledge acquired by hundredsof thousands of people to whom radio wasonly a dream a decade ago ; but from in-formation gleaned from centres now sup-plied with chain programs for the firsttime there appears to be considerableground for justifying conclusions of thischaracter.
Feature events relayed through localstations are becoming more and morepopular in broadcasting.
This has brought about a feeling,among certain individuals, that "the oldsets will do just as well."
Were these same persons to hear theseprograms on 1928 sets and speakers, theywould feel as if they were leaving barn-yard noises to hear echoes from a cathed-ral.
It's about the same as comparing a flutewith a tin whistle.
Many Uses for `Homekaster'The Alpine Radio LaboratorieS, 30
Church Street, New York City, who areputting out the "Homekaster," a noveldevice for broadcasting through one's re-ceiver, report that many enthusiastic com-mendations are being received on thisuseful device.
Users also tell of many new ways ofusing it for instruction, entertainmentand amusement which will be compiled inan article soon to be released. Anotherfan writes suggesting that it makes theideal and most appreciated radio Christ-mas gift, fitting as it does all pocketbooksand creating a new use and interest inradio entertainment.
R. C. A. $4,141,355 AHEADThe statement of operations of the
Radio Corporation of America showedthat for nine months ending September30 the surplus amounted to $4,141,355.32.The gross income from sales, communi-cations, etc., amounted to $16.775.091.27.
STATION FOR EAST AFRICAWashington.
A license has been granted to theBritish East African Broadcasting Com-pany to operate a broadcasting station inNairobi, Kenya, Africa. Relayed pro-grams from the European stations willconstitute most of the transmitted ma-
terial.
December 3, 1927 RADIO WORLD 23
Some Interesting Circuit Designs
SCHEMATIC DIAGRAM OF AN EFFICIENT 5 -TUBE REGENERATIVE SET.
FOR HIGH AND LOW NOTE REPRO-DUCTION TRY THIS.
0
ce Lve-r
8 8, c>,3,0. ti
Cz
R2
)a -s4 A
HOW TO CONNECT UP AN EXTRA STAGE OF TUNED RF.
A DC B ELIMINATOR WITH PROVISION FOR CHARGER.
C1 CO C L2
rg
45
12NP
3
PLAC NG COILS THIS WAY WILLCAUSE SQUEALS HOW TWO ANTENNAS IN PARALLEL AFFECT TUNING.
74 RADIO WORLD December 3, 1927
Radio UniversityWhen writing for information give
A FREE Question and An-swer Department con-
ducted by RADIO WORLDfor its yearly subscribersonly, by its staff of Experts.Address Radio University,RADIO WORLD, 145 West45th St., New York City.
your Radio University subscription number.
rAtli
DB 180
B 135
BD ETB-
08CD5V
8-3 IVO LT
FIG. 580THE ELIMINATOR DESIGN REQUESTED
PLEASE SHOW how to hook up a 180volt B eliminator using a Raytheon BHtube with a Thordarson R171 power com-pact unit. I have a Clarostat, a con-denser block containing two 2 mfd. andone 8 mfd. high voltage fixed condensers,three 1 mfd. fixed condensers, a high re-sistance voltmeter (0 to 200), a milli-ameter (0 to 50), and a transformer witha one volt winding, all of which I wishto use in this eliminator. I am going touse the 1 volt transformer for lightingthe filaments of Armor AC 100 tubes.-ORRIN FLINTLY, Passaic, N. J.
The circuit diagram of this eliminatoris shown in Fig. 580. Each of the unitsis identified on the diagram. R1 and R2are 1500 ohm fixed resistors. R4 is avariable resistance, 50,000 ohms maxi-mum. R4 is the Clarostat. You willnote that the voltmeter is so connectedthat it is possible to read the individualvoltages for the detector, amplifiers, etc.The milliameter is inserted in series withthe maximum voltage post.
* *
I HAVE a Yaxley No. 60 double throw,double pole jack switch. I wish to con-nect it so that I can use either the an-tenna and ground or loop. My set is ofthe seven -tube model, having three stagesof tuned RF amplification, a detector andthree stages of double impedance audiocoupling.
Fig. 581 shows the method of hookingthis jack switch up.
* * *
SEVERAL MONTHS ago I saw a dia-gram in the Radio University columns ofRADIO WORLD of a trap circuit which useda 3 -circuit tuner, a 201A tube and a fila-ment rheostat. The primary of the coilwas connected to the antenna and to theground, while the antenna and groundconnections of the receiver were made tothe tickler and B plus terminals of theunit, respectively. Does not this trap cir-cuit also act as an extra stage of radiofrequency amplification? That is, will Iget more distance when this is installed?Will the tuning become more difficult?
(2)-I have a four -tube set using a re-generative detector and three stages oftransformer coupled audio, using low ra-tio transformers. A tuned plate is usedin the detector circuit. Would you ad-vise adding this unit to my set?
(3)-Should the extra unit be built in aseparate cabinet, or can it be built with-in the set? There is plenty of room inmy set for it.-GEORGE HAROLDS,Brooklyn, N. Y.
(1 and 2)-The unit is another stage ofradio amplification. With the set younow have, however, this addition should
BY ORRIN FLINTLY.not be made, unless with some otherchanges. Take the regeneration out ofthe detector tube circuit, so that youhave regeneration only in the radio fre-quency or trap unit. Otherwise the tun-ing will be very difficult. The additionof the unit will bring you more distanceas well as volume. The selectivity willalso be bettered.
(3)-You can build this unit in withyour present receiver. Be sure that youkeep the tuner coil away from the coilused in the detector circuit. See that allthe leads to the grid and plate are short.
* * *
I INTEND building the 5 -tube receiverdescribed by Tim Turkey in the August27 issue of RADIO WORLD. You will re-call that this receiver utilizes a tunedstage of radio frequency amplificationhooked up for loop operation, a regenera-tive detector and three stages of resist-ance coupled audio amplification. Pleaseanswer the following regarding this set.
(1)-I would like to use -01A tubesthroughout. Could this be done?
(2)-Will this necessitate the use oflower B voltage, e.g., 135, as well as acommon C for the audio tubes?
(3)-Can I use an antenna coupler inthe loop input circuit, so as to be able toemploy an antenna and ground?
(4)-I have a coil with a 6 turn primaryand a 62 turn secondary, both of whichare wound on a 21/2 inch diameter wind-ing with No. 22 single cotton covered wire.Could this be used?
(5)-What capacity variable condenserwould you suggest shunting across thesecondary of this coil?
(6)-Are there any changes to makewhen installing the coil? I do not wishto use the loop at all.-SANFORD DE-VORE, Los Angeles, Calif.
(1)-Yes.(2)-Apply 135 volts to the detector and
the three audio tubes. Use a separate41/2 volt C bias for the first two audiotubes and a separate 454 volt C bias forthe last audio tube.
(3)-Yes, with great success.(4)-Yes.(5)-Use a .0005 mfd. variable conden-
ser. Be sure that the rotor plates arebrought to the beginning of the second-aiy winding, which is next to the end ofthe primary winding, which should beconnected to the ground. The stationaryplates of the condenser are brought tothe end of the secondary winding.
(6)-No.* * *
I DESIRE to build the LaboratoryElectric which was described in the No -
FIG. 581THE LOOP -ANTENNA JACK SWITCH
ARRANGEMENT.
vember 12 issue of RADIO WORLD, on pages12 and 13.
(1)-What hookup wire do you recom-mend?
(2)-Which leads should I cable andwhich should 1 avoid cabling?
(3)-What is the value of the radiofrequency choke coil?
(4)-Is it necessary to incorporate acoupling transformer when using the 171tube?
(5)-What other tube may be 'em-ployed in the last stage of audio fre-quency amplification?
(6)-In the circuit diagram, only two .5mfd. fixed condensers are indicated, whilesix are specified in the list of parts. Arethe four other condensers, which are be-tween the arm of the potentiometer andone side of the line, one on each side ofthe .5 mfd. value?-LEONARD WAL-FORD, Kansas City, Mo.
(1)-Use regular flexible wire for thegrid and the plate connections. This ap-plies to the grid return, and the B plus,also. For the filaments, use heavy No. 14rubber covered wire. In case you aregoing to use a power tube in the laststage, such as the 210, then use the No.14 also, for the B lead.
(2)-Cable all the filaments and the Bplus leads.
(3)-Use a 85 millihenry Hammarlundchoke.
(4)-Although it is not necessary, it isdesirable.
(5)-The 210 will work great here. Thiswill necessitate the construction of aneliminator which will deliver 460 voltsat 50 milliamperes. The Victoreen powersupply, described in the Oct. 15, 22 and 29issues of RADIO WORLD can be used here.
(6)-Yes, this is the right idea.* * *
IN OCTOBER I built a 6 -tube set inwhich three stages of tuned radio fre-quency, a detector (non -regenerative) andtwo transformer audio stages were in-corporated. The set worked great. Idid not, however, at that time, placethe set in a cabinet. Recently I ac-quired one and put the set in. I, as wellas all the other members of the familywas really startled at the tremendous in-crease in volume and improvement inquality when the set was inserted intothis new cabinet. What could have hap-pened? I never was under the impres-sion that a set had to be installed in acabinet, before you could get the bestout of it, but this test seems to haveproved this to me. Is this so? The coilsand the condensers in the set are en-closed in shields. So as to make a neatjob, I shaved out grooves underneath thebaseboard, so that I could run the leadshere. I used insulated staples to hold thewires in place. Would this have any ef-fect on the results?-JAMES TRUMP,Camden, N. J.
Due credit can not be given to thecabinet proper. What probably hap-pened, was that a couple of leads whichheretofore were only making slight con-
December 3, 1927 RADIO WORLD 25
Ant
OOOOO
ONO' C ors2
OOO
FIG. 582THE CIRCUIT DIAGRAM OF THE 6 -TUBE RECEIVER REQUESTED BY PAUL FROWN.
tact were forced up against the termi-nals with which they were supposed tomake contact, so as to strengthen thecontact. In other words, if you took theset out of the cabinet and tightened upthe connections on these loose leads, theeffect would have been the same. Tryit now and see. Test all the connectionswith a battery and phones.
* * *
I HAVE decided to build a 5 -tube tunedradio frequency receiver and would liketo have the following questions answered.
(1)-Using the angle method of mount-ing solenoid coils, is it necessary to useshields? I have made up out of brass,some angles which you can adjust to anyangle you desire. This is accomplishedwith the aid of hinges which have beensoldered to the angles. The hinges havesprings, which are very taut. That is,they will stay put, without the angle fold-ing up, when pressure is applied. Afterthe proper angle is obtained, I intendusing a small spring to hold it in place.
(2)-I have coils which contain 20 turnprimaries, and 50 turn secondaries. Theseare wound on a tubing 3 inches in diame-ter, using No. 22 double cotton coveredwire. The spacing between the primaryand the secondary winding is onlyinch. Can these coils be used? Thesecondaries are tapped at the 12th turnfrom the beginning.
(3)-Is it all right to place the 5 tubesin a row, right next to each other?
(4)-Could I use a radio -frequencychoke coil and a bypass condenser in thedetector output circuit? How would a65 mil choke and .0005 mfd. fixed conden-ser do?
(5)-Is the correct angle of mounting,55 degrees? - WARREN KELMAN,Berkeley, Calif.
(1)-You don't have to use shields be-tween the coils. It wouldn't be a bad idea,however, to place the entire set in a metalhousing, this to be grounded. This willprevent the coils from acting as minia-ture antennas, thus causing them to pickup energy and which cause broad tuning.
(2)-Yes, these coils can be used.(3)-Yes. It will be necessary to watch
the grid and plate leads to see that theyare not placed parallel to each other.
(4)-Yes, use the values you specify.(5)-Yes.
* * *
I HAVE a 5 -tube receiver. It consistsof two tuned radio frequency stages, acrystal detector in an untuned radio fre-quency stage, and three stages of re-sistance coupled audio frequency amplifi-cation. The set worked splendidly un-til a month ago, when the signals becameso 16w that I could hardly hear them. Ithas been acting this way ever since. Ihave tried new tubes, batteries, crystaland checked up the antenna and ground.All are 0. K. I am beginning to thinkthat the trouble is in one of the resistors.Could they have burnt out?-THOMASMILLER, Troy, N. Y.
It is very possible that either the plateor the grid resistors are burnt out. It isalso possible that the fixed condensershave gone 'west.' Be sure that the con-tact between the tube prongs and the
socket terminals is all right. Dust usuallycollects here and acts as an excellent in-sulator. Test the leads going to the bat-teries, to see if there is a break alongthe line.
* * *
SOME MONTHS ago I saw a hookupof a 4 -tube set using a single tuned ra-dio frequency stage, a regenerative de-tector (3 -circuit tuner) and two trans-former coupled audio stages. The radiostage and the detector were tuned by avariable condenser having a common ro-tor. Would you suggest building a setof this type?
(2)-The set does not show any bypass condensers. I have noticed that inmany of the later models of receivers,such condensers of the 1 mfd. type areconnected between the B plus posts con-nected to all the plates and the minus Apost, even if there are four B plus posts.Could this be done with this set? Thereare three posts, one going to the detectorplate, one to the radio frequency and thefirst audio plate and the other going tothe last audio plate.-G. HENRY PHIL-LIPS, Pittsburgh, Pa.
(1)-It would be better to build thisset with two separate condensers. Theymay be hooked up to a drum dial whichwill make the operation similar to thatof a single dial. That is, although thesecondensers are individual, they may beturned at the same time, because of theproximity of the controls.
(2)-The bypass condensers wouldgreatly improve the set. They may beconnected as you . suggest. If the radiofrequency tube filament has no rheostat,insert one that has a resistance of 20ohms. The detector and audio tubes caneach be controlled by Amperites, thetype depending upon tubes used.
* * *
I WANT to build a six -tube set withprovision for a loop or an aerial, usingthe following parts :
Two .0005 mfd. variable condensers, aradio frequency coil and a 3 -circuit tuner,both of which have secondaries matchedfor these condensers, two untuned radio
frequency transformers (200 to 500meters), a pilot light, a filament switch,a single circuit closed jack, arid two audiofrequency transformers, both of whichhave a ratio of 2 to 1. Please give methe circuit diagram of a set with which Ican use these parts.-PAUL FROWN,Jersey City, N. J.
The circuit diagram of a receiver us-ing the parts you possess is shown in Fig.582. The radio frequency transformeris used in the first stage, the untunedtransformer in the next two stages, andthe 3 -circuit tuner in the detector stage.The audio transformers are, of course,used in the audio end. The filaments ofthe radio amplifier tubes are each con-trolled by a '10 ohm rheostat. The de-tector filament, and the audio tube fila-ments are each controlled by a 1A Amper-ite. The variable condensers are shuntedacross the secondaries of the tuned andthe 3 -circuit coils. C4 is a 1 mfd. fixedcondenser. The grid leak R3 has a re-sistance of 4 megohms. C5 is a .001 mfd.fixed condenser. C3 is a .00025 mfd.fixed condenser. La is the pilot light. Sis the filament switch. The single circuitjack is used for switching the antennaout and the loop in, or vice versa, bysimply putting in or out the plug con-nected to the loop. Use a 4%2 volt C bat-tery.
* * *
WOULD YOU advise building a re-ceiver using two tuned radio stages, adetector and three stages of resistanceaudio coupling with the first tube re -flexed? I intend using two double con-densers. Would they work all right?-F. MANUEL CORSSETT, Cleveland, 0.
No, such a set would be difficult tooperate. It is suggested that you buildthe set, leaving the reflexed stage out.The double condensers can be used, butit will be necessary to use small midgetcondensers across each one. These mid-gets have two stators and a common ro-tor just like their big brothers. Theircapacity is, however, about .00005 mfd.maximum, for each half.
Jllin DIO 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 $6for renewal from close of present subscription and your name will be entered in RadioUniversity. No other premium given with this offer.
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2o RADIO WORLD December 3, 1927
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Interesting Sidelightson the Concertrola
(Continued from page 19)battery. Naturally, you fellows saw all thison the blueprints. Why don't you, Hetero-dyne, use that method on your set?
Tracing the Blueprints"I had it in mind," Heterodyne retorted.
"I suppose you'd call it the B battery dropmethod. It shows on the blueprint that thegrid return of the tube to be biased is con-nected to negative B circuit, and the properresistance is then connected from this pointto the ground. I guess it's because thecathode or heater type of tube allows you todo this is the reason these tube have beenspecified. Now let's trace it again on theblueprint. Let's see, now. The grid returnof the first two tubes, which is now con-nected to minus of the three volt C battery,should be connected to the ground, also toone side of a 1 mfd. condenser, also to oneside of the 3,000 ohm variable resistance.So far, so good. Now, the other side of the1 mfd. condenser and the other side (mean-ing, of course, the side not used the firsttime), of the variable resistance should beconnected to the cathode of the tube-at thepoint where the C plus is now connected.Of course, it showS that the cathode mustnot be grounded when using this method.The variable resistance should be adjusteduntil the loudest signal is heard in thespeaker. Simple, hi!" -
"I had an idea," Fred cut in, "that youdidn't understand that much about radio,Heterodyne. But don't forget, you fellows,that no matter what changes you make inelectrifying your set, fundamentally the cir-cuit is the same as my battery outfit, thatis, from a radio frequency standpoint."
"Just one more question," Heterodyne ad-
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dressed his remark to Franklin, "What aboutthe rectifying tube. Have you had anytrouble with them burning out?"
"Yes and no. A good gaseous rectifiertube ought to last for at least 1,500 hours.Especially in the Concertrola, because thedrain on the tube is very light. Perhaps youknow that all gas rectifier tubes go west be-cause of 'gas fatigue.' This is,the breakingdown point of the gas used as an ionizingagent through impurities.
"A genuine gas rectifier, I'm using a C. R.A. with fine results in my set, is filled with99-78/100 per cent. pure helium gas. Theytell me that a C. R. A. tube has all partspurified in hydrogen atmosphere before as-sembly, so that no impurities can combinewith the helium. This can only mean -thatsuch tubes have long life, sustained output,with no gas fatigue. When my C. R. A.goes bad, Heterodyne, I'll send you a postalcard I"
"Well," Heterodyne assumed a recliningposture, and lit another cigar, "well, beforeI build my set I am going to find out allabout tubes, transformers and speakers. I'vemade out an examining paper, and when Ican answer all the questions which I havelisted, then I'll show you my speed."
Questions
He brought forth several sheets of fools-cap, upon which were the following ques-tions:
1-How many tubes are used in the Con-certrola?
2-Which tubes will produce the best re-sults, McCullough, Sovereign, R. C.A. or standard tubes?
3-How is the current furnished for theheater type of tubes?
4-What is the DXer used for?5-Is the Concertrola entirely shielded?6-Where is the power stage located, and
what tube is used?7-Does the set work from an aerial,
loop, ground or counterpoise?8-Is there even the slightest hum or
buzz, and if so, how can it be elimin-ated?
9-What is the 75 or 100 ohm potentio-meter used for?
10-How are the Concertrola Coils made?11-Why have Ferranti transformers been
chosen?12-Is the Concertrola a new type of elec-
tric set?13-How many connections, of what color
wire?(Concluded on page 27)
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December 3, 1927 RADIO WORLD 27
(Concluded from page 26)14-Can I use the Concertrola as a phono-
graph amplifier?15-What metallic phonograph pick-up
unit is specified?16-What is the actual cost, in dollars and'
cents, for operating the set? Whatis the cost of constructing it?
17-Is it possible to purchase a completekit of parts?
18-Who sponsored the Concertrola Cir-cuit?
* * *
(The first of this series of articles on theFenway Electric Concertrola appeared in theNovember 5 issue. Constructional data ap-peared in the November 12 issue. In theNovember 19 issue, it was described for usewith batteries, while last week data on howto electrify it with the RCA tubes weregiven. Some interesting pointers on wiringare given this week, while next week in theconcluding article, a complete summarizationof the receiver discussing all the importanthigh spots of the circuit will appear. Ques-tions will also be answered.)
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1,4
Flechtheim AppointsAdelman as Executive
Arthur M. Flechtheim, president ofthe A. M. Flechtheim and Company, Inc.,announces the appointment of Leon L. Adel-man as head. of the sales department andconsulting engineer.
Mr. Adelman's radio career began be-hind the counter of one of the pioneerradio stores. He was successively serv-ice engineer for the F. A. D. A. Co.,radio editor of "Science & Invention," as-sociate editor of "Radio News," assist-ant advertising manager and publicity di-rector for the Chas. Freshman Co., Inc.,and assistant sales manager for the Ham-marlund Manufacturing Co.
Interesting Issues ofRadio World
MAY 7.-Part I of the Six -Tube Adams -Griffin Shielded Set, by Dana Adams -Griffin.APRIL 30.-The Equamatic mixer whichcan be used with almost any "super" coils,by Herman Bernard.
APRIL 23.-How to measure the cut-off- in the resistance AF, by J. E. Anderson.
Constructional data on the Melo-Heald, aneleven- tube Super -Heterodyne, by Her-bert E. Hayden, (Part II). Part W ofthe four-part article on how to obtain bestresults with the Nine -in -Line Super -Het-erodyne, by Lewis Rand.
APRIL 16.-Part I of the description ofthe Melo-Heald Super -Heterodyne. by Her-bert E. Hayden. Part II of discussionon the Nine-inLitte Super -Heterodyne. byLewis Rand.
APRIL 9.-A five -tube shielded set em-ploying transformer AF, by Herbert E.Hayden. Part II of constructional data onPower Compact, by Lewis Winner. PartII of the four-part article on the Nine -in -Line Super -Heterodyne, by Lewis Rand.
APRIL 2.-(Fifth Anniversary Number)Part I of the four-part article on thesupersensitive Nine -in -Line Super -Hetero-dyne, by Lewis Rand. The three -tubecompact, a simple one -dial, three -tube regenerative set by Iasper Henry. Part Iof the two-part article on a Power Com-pact, the B eliminator with a stage ofpower audio frequency amplification byLewis Winner.15 cents a copy-all 6 issues for 70 cents
centsRadio World. 14$ W. 45th St., N. Y. City
Guaranteed "A" Power Unit-$13.75No better "A" Socket Power Unit can be obtained
even at twice this amazingly low price. No hum ornoise. Operates on 50 or SO cycles at 110 volts A. C.Approved by rigid laboratory tests of Badto News andPopular Duna Fuli.V guaranteed. Shipped complete,subject to inspection, on receipt of price-or C.O.D.it you wish. 5% discount if cash in full is sent withorder. Send order NOW! WORLD BATTERY CO.,1219 South Wabash Ave., Dept. 64, Chicago, Ill.
CeCo TubesTypes R81 and M26
SpecifiedBy H. B. HERMAN for
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Quality in a Radio Tube cannotbe measured by a micrometer.But the" Yard Stick" of experi-ence, technical skill and ex-clusive methods of manufactureshow unmistakably the superior-ity of CeCo Tubes in steadinessof performance, clarity, volumeand longer life.Radio authorities, includingBrowning, Lynch, Cockaday,Hurd, Best, Bernard, Henneyand many others endorse CeCo-the Tube ofLonger Life.
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DIRECT FACTORY SALE-Wholesale prices.Tremendous Savings. Selling direct to you. Heraare some of our many items: 30 Henry Choke,100 M.A., $2.19; 10 Henry Choke, 400 M.A. $5.48.Power Transformers for all kinds of Eliminatorsand for all types of A.C. Tubes, at Special LowPrices. EVERY ITEM FULLY GUARANTEED.Promptly shipped, upon receipt of order. Send forfree illustrated catalog today. Todd Electric Co.,Inc. (Manufacturers) 36 West 20th Street, Dept. D,New York City.
RADIO CABINETS AND CONSOLES-Beforebuying your radio cabinet or console see our cata-log. A postal card will bring it to you. Oddsixes built to your specifications. Standard sixesshipped promptly. FULBRIGHT CABINET CO.,HICKORY, NORTH CAROLINA.
MEN-SOUTH AMERICAN WORK-Oil, fruit,rubber companies. Expenses paid. South Amer.icon Service Bureau, 14,600 Alma, Detroit, Mich.
VALET AUTOSTROP RAZOR-The only razorthat sharpens its own blades. Highly polishednickel -plated, self -stropping Valet AUTOSTROPRazor, with one blade, in elvet lined metal case.Leather strop especially prepared, and completeoutfit in neat, lithographed carton. Mailed postpaid on rec.. t of 50c. SPECIAL: Send $2 forme -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.
SEND $1 for 8 weeks' subscription toRADIO WORLD, 145 W. 45th St., N. Y. C.
EDISON "A" BATTERIES-Threecell, 20-am-perehour; in neat metal cases. Price, $2.50 each;ten or more, $3.00 each. Cash with order. De-partment "B," 25 East South Street, Indianapolis,Indiana.
CHOKES WITH ADJUSTABLE CORE for cor-recting filter operation, range 30.11 to 100.H150 M.A., $5.75. Transformers -650 volts, $7.25;550, $3.50; 280, $2.00. Low voltage transformers tospecifications, $4.50. Write for lists. Radio PartsSales Co., Orange, N. J.
HERMAN BERNARD, managing editor ofRadio World, discusses radio topics of popularinterest every Friday at 6:40 P. M. from WGBS,348.6 meters, the Gimbel Bros. station in NewYork City. Listen in.
COMPLETE AND LATEST LIST OFSTATIONS appeared in Radio World,dated Oct. 29. Sent on receipt of 15c, orstart your subscription with that number.RADIO WORLD, 145 West 45th St., NewYork City.
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 or start your subscription with the firstof these numbers. RADIO WORLD, 145 West45th Street, New York City.
re°Ig rielar A BALDWIN 99" Icerspea
28 RADIO WORLD December 3, 1927
The Big Thrill ofDX, and at verySmall Cost to You
Everybody who owns a radio set likes totune in far -distant stations now and thenbecause not only is there a thrill in hearinga voice or instrument thousands of milesaway but one Verifies the fact that he hasa powerful receiver and that it is in goodcondition, if it is able to pick up theseweak signals. Now that the broadcastingstations are more suitably distributed as towavelength or frequency, fans are in abetter position to tune in distance. Be-sides, the weather is in their favor thesedays. But what kind of a set shall beused? You know very well that if theset can tune in distance once in a while,you can develop sufficient skill to make ittune in far -distant stations very often,virtually every night. Then when youhave visitors you need not boast aboutthe DX qualities of your set but simplytune the receiver and let them listen tostations thousands of miles away. Youmust be sure to have a receiver capableof responding to your distance -getting de-sires. You also want this set to have de-lightful tone quality, so that your owncritical ears cannot detect even a singleflaw in the reproduction. Indeed, evenmusic lovers who may be guests at yourhome will comment admiringly upon thebewitching tone of your receiver. Thenyou know you have something real. Theability to get distance and to reproduce theoriginal music without distortion dependslargely on the circuit design, and you willfind that the Diamond of the Air, eitherthe 4 -tube or the 5 -tube model, will liveup to your highest expectations. Howare you going to know which to build?Carefully inspect the textual data as wellas the blueprints that fully expound thetheory, operation, characteristics and am-plification of these two outstanding receiv-ers that differ principally in the type ofaudio amplification.
The 5 -Tube DiamondCan be constructed in a couple of hours.The authorized blueprints that make thisspeed and efficiency possible are just offthe press and will be shipped at once, to-gether with the new booklet of full textualexposition of construction, including thewinding of coils, how to connect terminals,what values of condensers and resistors touse, etc. The receiver consists of a stageof tuned radio frequency amplification, aspecially sensitized detector, first stage oftransformer audio and next two stages ofresistance audio. It is easily adapted toplaying phonograph records through theset and on your speaker. Get acquaintedwith this new delight.
The 4 -Tube Diamondrepresents the most that is obtainable fromfour tubes. A stage of tuned radio fre-quency amplification, a specially sensitizeddetector and two stages of transformercoupled audio. Follow the blueprint toamazing success. Build the set from partsyou have. Full instructions cover utiliza-tion of such apparatus. Thousands areeager to build an economical set of surpassing performance and amazing achieve-ment and this one is the most economical,the most scientific, and the least expen-sive in cost of parts and upkeep. Workssplendidly from batteries, either type 99or type IA tubes, and can be used withA and B eliminators, power packs, etc.,with great success.
Look over both of theseblueprints and read the text in both casesbefore choosing the receiver you are tobuild.
SEND NO MONEYJust fill out the coupon below and notewhat you get FREE.- - - - - - - -Guaranty Radio Goods Co.
145 West 45th Street, New York CityPlease send me one newly -printed official
blueprint of the 5 -tube Diamond of theAir, one newly printed official blueprint ofthe 4 -tube Diamond, and the textual datagiving full directions for constructing thesesets. I agree to pay the postman 75 centson delivery. Also, you are to send me, with-out extra cost, one Auto Strop SafetyRazor, one blade and one automatic razorstrop.Name
Address
City State
How to Connect Up AnyPickup in the Diamond
THE NEAT SUBPANEL WIRING, MOST OF WHICH IS DONE UNDERNEATH.NOTE POSITION OF THE BRETWOOD VARIABLE GRID LEAK.
(Concluded from page 11)F is the end of L2 and connects to B
plus 67% or 90, i.e., B plus RF.
sELR17-1Cle-Ra-Tone
Sockets
Shock AbsorbingThe choice for practically every prom-
inent circuit for several years. Among themost recent hook-ups for which it hasbeen specified are:Fenway Electric Concertrola, New Laborat-ory AC Receiver, Thompson Super 7.
o H. F. L. Nine -in -Line, Cornfield SuperSelective 9, Thompson A. C. Super, Mag-naforiner 9-8, L. C. 7.8, Lynch Sul:spree-sor Circuit, World's Record Super 10,Strobodyne 8, Melo Heald Fourteen, StJames Super, Two -Dial Equarniatic, Quail -tone 8, Knickerbocker 4, Hilograd Receiver,International One -Spot, Hot Spot Fourteen.
Push Type, on Mounting Base:Benjamin Oe-Ra-Tone Sockets 75c eachWithout Mounting Base Sac each
New Y Type SocketSpecially designed, for use with 5 -pronged
A. C. Radio Detector Tubes:For direct attachment to panel.. 90c eachFor mounting cm top of panel....$1.20 each
At all Radio Jobbers and DealersMade by
Benjamin Electric Mfg. Co.120-128 S. Sangamon St., Chicago
New York San Francisco247 W. 17th St. 448 Bryant St.Manufactured in Canada by the Benjamin Electrii
Mfg. Co. of Canada, Ltd., Toronto, Ontariotilat=t22.1ttatuttuutuntatan=2
G is the beginning of the detector in-put secondary L3 and connects to positiveA.
With the Bruno 3 -circuit coil mountedwith tickler on top, G is the lower bind-ing post for secondary. G does not con-note "grid" here, but A plus.
For Phonograph PickupIn the diagram of the Diamond are
shown two switches Si and S2. Si is themaster switch which controls the filamentcurrent in all the tubes. S2 controls thatin the audio amplifier alone. This ar-rangement of the switches was made whenit was desired to use the audio end of thecircuit independently of the radio frequencyend. The binding post arrangementWXYZ was included for the purpose ofusing either the radio or the audio endsof the circuit independently. Since thedevelopment of phonograph pick-ups the
amplifier is usually wanted forphonograph music independently of theradio amplifier and the detector. For thisreason it is desirable to be able to turnoff the radio frequency tubes and leavethe audio tubes burning. A slight rear-rangement of the filament switches isnecessary. The short lead between Siand S2 is simply shifted to the oppositeside of Sl, or next to the A battery. Thenneither switch controls all the filaments.It is necessary to turn on and off eachindependently.
VALET AUTOSTROP RAZOR-The only razorthat sharpens its own blades. Highly polishednickel -plated, self -stropping Valet AUTOSTROPRazor, with one blade, in velvet lined metal case.Leather strop especially prepared, and completeoutfit in neat, lithographed carton. Mailed postpaid on receipt of 50c. SPECIAL: Send $2 forone-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.
HERMAN BERNARD, managing editor ofRadio World, discusses radio topics of popularinterest every Friday at 6:40 P. M. from WGBS,348.6 meters, the Gimbel Bros. station in NewYork City.
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(Just East of Broadway)Please send me RADIO WORLD for months, for which
please find enclosedSUBSCRIPTION RATES:Single Copy $ .15Three Months 1.50Six Months 3.00One Year, 52 Issues 6.00
Add MOO a Year for ForeignPostage; 50c for Canadian Postage.
December 3, 1927 RADIO WORLD 29
Modernizing thePhonograph You Have
(Concluded from page 7)
necessary to buy three stove bolts and threenuts.
The details of actual construction insidethe phonograph can be worked out to one'sown satisfaction. There is ample room forsuiting one's convenience and taste.
In the case of the Victor phonograph therecord rack may be removed from the bot-tom, and the amplifier and B supply placedtherein. There is room to spare.
In fact, if one wants to include installa-tion of a radio receiver there is plenty ofroom in a Victor by using a 7x14 inch frontpanel for location behind the tone arm doors.This front panel has to be notched at thetwo top corners 1% inches in and 1/4 inchdeep.
The tuning condensers should be at leftand right, so as not to strike the springmotor or governor. The coils would haveto extend at left and right along the insidewalls at the top.
The main consideration is the choice of acorrect amplifier and B Supply and thephysical details are so easy to work out thatone will prefer the work of doing it him-self.
However, if any one has a Victor, Aeolianor similar phonograph and feels that heneeds assistance on the physical or electri-cal end, I would be very glad to have himwrite me care of RADIO WORLD.
(This is the first of a series of articles byH. B. Herman, on modernization of phono-graphs that, though bought only a few yearsago, are rum seldom, if ever used, and aretruly inferior, unless adapted for audioamplification and B voltage. Treatment ofmany kinds of installation will be discussed.)
A Simple WayTo Control Volume
One of the best volume controls as wellas a good oscillation control is a rheostatin the filament circuit of the first radiofrequency.tube. The rheostat should havea resistance of at least 20 ohms with a-01A tube and a six volt battery. It iswell to have an Amperite in series withthe rheostat to prevent excessive heatingof the filament.
When the tube is of the 60 milliamperetype the resistance of the rheostat mustbe much higher-from 75 to 100 ohms.
FERRANTIAUDIO FREQUENCY
TRANSFORMERSType AF3... $12.00 Type AFNo Better Transformers Available
If you haven't yet filledout and sent in thiscoupon do so now-Los FENWAY for DX! INC.,249 W. 53rd St., New York, N. Y.
Gentlemen: Tell me more about how Ican purchase a complete kit of Concertrolaparts and pay for it on the deferred pay -anent plan. No obligation, of course.
Quote your lowest cash price for thesame kit.NAME
ADDRESS
(R.W.)
P RITOrhe "SELF:::611iiika".13heostat
Your heart will beat pitter-patter with joywhen you turn on the switch aftercompleting the Unified Diamond
of the Air. This design con-sists of a balanced two -
stage RF amplifier anddetector, constitut-
ing the RadioFrequencyFountain, and athree stage re-sistance coupledchannel consti-tuting the AudioFrequency
Basin. Any otherform of audio may be
used. Send 50c for com-plete description of construc-
tion (issues of Sept. 17, 24, Oct.1, 8, 15).
Radio World, 145 W. 45th St., N. Y. C.
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It is the constant re-port from leading labora-tories as well as radioeditors and authors thatTobe condensers are supe-rior to all others tested.
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BETTER THAN ANY FIXED LEAK is theBretwood Variable Grid Leak. It allows adjust-ment of grid voltage to maximum sensitivity forreception of far -distant, signals, with distortion.The Improved 1928 Model De Luxe BretwoodGrid Leak, $1.75; or $225 for Grid Leak withBretwood Bullet Condenser attached, The NorthAmerican Bretwood Co.. 145 West 45th Street.New York Cite.
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With your trainingyou get free of extracost 6 great outfits ofreal Radio Practicematerial. With these6 outfits you canbuild 100 real Radiocircuits. This is thopractical kind of hometraining. You learn,to hold a lob-not 50paper ON TICEPAY -ROIL. Sendcoupon below Inc de-
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J. E. SMITH, PresidentNational Radio Institute,Dept. PC -7, Washington' D. C.
Dear Mr. Smith: Kindly send me yoUr 61 -page Fro.Book which tells about learning Radio for bigger pay.Also send information on your offer of 6 outfits of mate-rial free of extra cost. I understand this places me underno obligation.
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Town State
30 RADIO WORLD December 3, 1927
Good Back Numbers ofRADIO WORLD
The following illustrated articles haveappeared in back Issues of RADIO WORLDin 1927.
MAY 21. -Part I of a three-part articleon the Victoreen Portable receiver, byCapt. P. V. O'Rourke. Data on the newRaytheon cartridge.
MAY 28.-A three -tube reflex, using aspecial low pass filter system, by EdgarB. Francis. Part II on the Victoreen port-able receiver with layout data, by Capt.P. V. O'Rourke.
JUNE 4. -Part III of a three-part articleon how to construct an efficient portableVictoreen Super -Heterodyne, by Capt. P.V. O'Rourke. A complete discussion onthe RCA AC tubes.
JUNE 11. -Detailed discussion of a four -stage push-pull resistance coupled audioamplifier, by J. E. Anderson. The Suit-case 6, using a tuned RF stage, two un-tuned RF stages, regenerative detector andtwo transformer AF stages, by James H.Carroll. Balsa Wood for speakers, an ex-cellent discussion on bow this wood maybe employed for speakers, by H. B. Her-man.
JUNE 19. -The six -tube Equamatic, aneutralized two -stage tuned RF, three -stage AF resistance coupled set, by Her-bert E. Hayden. How to get the lownotes with transformer or impedance Al,by Dennis J. O'Flaherty.
JUNE Z. -The Lindbergh Plane Speak-er, an excellent cone type reproducer, byHerbert E. Hayden. A tube and set tester,by Herman Bernard.
JULY 2 --The Planofier 7, single controlsuper -sensitive set using resistance AFby R. F. Goodwin and S. S. Bruno. Dis-cussion on the new Freshman Equaphase,by Robert Sagala. Data on the six typesof units used for loud speaker operation,by J. E. Anderson.
JULY 9. -How to build a DC A supplywhere the line voltage is 220 or 240, byFrank Logan. Important data on RFchoke coils, by Horatio W. Lamson.
JULY 16. -How to use a voltmeter as amilliammeter, by D. Barretti. How tobuild a 4 -tube, 2 -control regenerative por-table set.
JULY n. -Building a 7 -tube Super foryour auto, using Victoreen IFT, by JohnF. Rider (Part 1). How to build a 6 -tubeneutralized set, using three tuned RF.two transformer AF, by John F. Rider.Inside dope on motorboating, by J. E.Anderson.
JULY 30.-A 5 -tube standard TRF setadapted to AC operation by the use of theORS 400 mill rectifier tube, with the aidof series filament connections, by RFGoodwin and S. S. Bruno. Shielding the11 -tube Melo-Heald Super -Heterodyne re-ceiver, by Clifford Denton. Part II ofthe two part article on the Super in theauto by John F. Rider. How to controlvolume in AC sets by D. Ferrup.
AUG. 6.-A three -tube regenerative Por-table with portion of the cabinet as thespeaker, by M. J. O'Reilly. The CashboxUnitune, an ingeniously contrived four -tubequality receiver by Wendell Buck. Howto use AC tubes by C. T. Burke.
AUG. 13. -Hints on constructing a por-table set, by Herbert E. Hayden. A seven.tube, two -control AC operated receiver byCapt. P. V. O'Rourke. Obtaining the Cbias in an ABC unit, using the BA Ray-theon 85 mill tube.
AUG. 20. -The Four AC, a four -tube re-generative set employing AC tubes. TimTurkey's argument on why rheostatsshould not be used as volume controls. TheDrum Powertone, a five -tube single con-trol set, using resistance coupled audio.
AUG. 27. -Part 1 of a four part articleon building the I -Dial Wit., a single con-trol, voluminous selective 5. tube set, byA. Irving Witz. A detailed explanation ofthe exponential type of horn by H. B.Herman. Details on the revolutionaryReisz condenser type of speaker. Con-structional data on a special 5 -tube, 2 -dialregenerative set, with three stages of AF,by Tim Turkey.
SEPT. 3. -Part I of a four-part dis-cussion on the new 1928 Victoreen Uni-versal, a super -sensitive 8 -tube Super -Heterodyne, by Capt. P. V. O'Rourke.Complete data on the three types of phono-graph pickups, by J. E. Anderson. PartII of the 1 -dial Witz, wiring hints em-phasized.
SEPT. 10. -The Puratone AC set, a 6 -tube duo -control receiver, using AC tubes,by R. F. Goodwin and S. S. Bruno. Part11 of the 1928 Victoreen Universal, dis-cussing the placement of parts. Part IIIof the 1 -Dial Wit. on the special place-ment of the coils.Any Copy 15c. Any 7 copies, $1.00 Allthese 17 copies for $2.00, or start sub-sription with any issue. Any 8 of thesenumbers sent as premium with NEW year-ly subscription. No other premiums al-lowed. RADIO WORLD, 141 West 45thSt., New York City,
HOMEKAST!!!The wonderful new HOMEK AST ER enables you tofurnish your own radio entertainments. It plugsInto the radio set, Just like a tube. With theH 0 M EKAST ER, anyone can announce, sing, ate.,before the transmitter In another room, and thesounds will be greatly amplified, coming out of the
loud speaker, lust as If the performer were at thebroadcasting studio. Mystify visitors and friends.Entertain the children.
Reverse the process and the HOME KASTER be-comes an extremely sensitive detective device. Theslightest sound In the room where the Innocent -looking loudspeaker stands, will be loudly repro-duced In the earpleee, which may be located In anyother part of the home.
HO ME K ASTER comes complete and ready to useFully .guaranteed. Orders filled In rotation. Send
deehiejevico,ry.money. order, or pay postman 55.00 upon
Approved by RADIO WORLD LaboratoriesAPLIN RADIO LABORATORIESSuite 429, 30 Church St., New York, N. Y.
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SHIELDED PLUG-INIntermediate
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alarms. Fully shielded, therefore verystable. Plug into any UX socket.Ideal for compact construction. Only2 Si" high, 1%" wide. Afr -core,sharply peaked and laboratory -matchedto sets. No alter necessary.
SET OF 4, $18.00Order direct If dealers caret supply.
Jobbers and dealers, mite for cata-logue sheets, samples, and discount..
Mississippi Valley Radio Company914 Pine Street St. Louis, Mo.
s; Brand new 20" disc speaker.X 4 beautiful designs on each1 speaker. Beautl ful - Efficient
IXIX -A gift that will be long
remembered.
Powerful British Short-wave Station on Air
Any one desiring to test the DX cap-ability of their short wave receiver cantry to tune in the powerful English short-wave broadcasting station SSW, atChelmsford, England, which sends out testprograms conisting of phonograph musicand talks, every day from 1 to 3 P. M.eastern standard time.
Many have already reported hearing thestation, Armistice day being one duringwhich most reports were received. Onthis day the Prince of Wales spoke inLondon. The reception was not verygood due to the heavy static which pre-vailed.
This Armistice program was also inter-cepted at Schenectady, and rebroadcastby WGY on the regular 380 meter wave.Persons who listened to this station re-ported that the reception was quite good.
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"Everyman 4"Its Possibilities Will Never Be Exhausted
FOR BEST RESULTS USE ONLY MUTER
AND OTHER SPECIFIED PARTSMuter Supreme Audio Transformer, First Stage $7.00Muter Supreme Audio Transformer, Second Stage 7.00Muter Clarifier and Tone Filter 5.00Muter Radio Frequency Choke 1.50Muter Variable Condenser ,75Muter Push -Pull Panel Switch .35Muter Moulded Fixed Condenser .40Muter Heavy Duty Grid Leak .50Muter Grid Leak Holder .15Muter Bypass Condenser .75Muter Tubestat .50
The number of owners of the Everyman 4 circuit is running into thousandsSelectivity, volume, distance, tone quality, ease of tuning, simplicity of con-struction, extreme low cost.
LESLIE F. MUTER CO.76TH AND GREENWOOD AVENUE CHICAGO, ILL.New York Representative: EDWARD J. BECKLEY, 154 Nassau St., N. Y. C.
December 3, 1927 RADIO WORLD
Three -Gang CondenserUses Drum Tuning
ear; ,itillIttli
NEW U. S. L. PRODUCT
The United Scientific Laboratories, Inc.,of 80 Fourth Avenue, New York City, re-cently placed on the market a drum con-trol to be known as the Scientific DrumControl Tuning Unit. This unit has beendesigned to meet the need for a depend-able, fine appearing drum control to beused in circuits requiring three gangedcondensers.
The escutcheon shield is made of bronze.The drum dial is made of pressed steeland is calibrated 0 to 100 with clear, boldfigures and markings. The drum actionis powerful and smooth and develops noblacklash. A friction drive rum is em-ployed at type .00035 mfd. three gangedcondenser is used. The condenser anddrive are completely assembled at fac-tory so that this unit comes completeready to be installed on sub -panel of re-ceiver.
Pittsburgh ExplosionVictims Comforted By Radio
Pittsburgh.News of the disastrous explosion which
rocked Pittsburgh two weeks ago was broad-cast to the public by Westinghouse stationKDKA less than an hour after it occurred.Authentic reports from the Equitable GasCompany were transmitted over the air atregular intervals. In addition to broadcast-ing the reports of the explosion, a specialprogram was given that evening for theAmerican Red Cross to aid them in a cam-paign to relieve the unfortunate people whosehomes had been destroyed by the disaster.
Tho thrill of orriving T:klo, JtiliztL andg!'etTts",'Zaele'vtt.f strand
en theit 9,000 Yo nibs Podaa with dJ
at vow-.i;!r.
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r°°"11and numerous newspapers!. ..aeaaaaa,ara,aaa,.ably peeked ate9.73 K oe c Inc eon
souse'rlst.elrIc'e.1.'elh'et puttll'''4,1u:S.71.difiointchz'realtru*"eiloentr 28,11 Ica he.,
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sus. i.e Sotto Street
Everybody's Talking About ItThere's a matins of reliable. boiled -down, and interesting informationIn 'Resistance the 'ControlVal.' of Radio." p10l1.1written - clearly Illustrated.This valuable hand -book on re-Ostenee in radio to worth dol-lars-send only 25 cants fatyour copy.
ARTHUR H. LYNCH, Inc.1775 Broadway, New York City
FLECHTHEIMSuperior Condenser
Specified for I andTube Diamonds
BY-PASSFILTERBUFFER
HIGH TENSIONAnd
TRANSMITTINGCondensers
for every use in alltypes of radio circuits
Accurate-capacity rating.Dependable-for continuous duty.
Write for CatalogueSpecial proposition for dealers and jobbers.
A. M. FLECHTHEIM & CO., INC.128 Liberty SL, New York
C R A
The REAL RECTIFIER TUBEGuaranteed for a full year.
If your Eliminator has failed you at a most criticalmoment-if its voltage drops suddenly after a fewweeks' use-then, you have never used a C. R. A. pureHelium gas filled tube. Because a C. R. A. tube inyour present Eliminator provides an unfailing, constantcurrent supply, dependable at all times. Approved byThordarson, Muter, Cornell, Mayolian, Bosch, Pathe-the list is endless. Specified by Leo Fenway for theConcertrola. At all good dealers. If yours cannotsupply you, send us his name, with your check ormoney order. Immediate shipment, prepaid.
PRICE, $4.50
(barleskAblettO.lamp Specialists for Twenty Years22-24-26 READE STREET :: NEW YORK
POWER SUPPLY
A new plate upply with maximum of 115 voila,nith 00011.1.ms for a 0 ootpot, constitute theTictorcen Posner Supply. The power transfermorwas specially designcd to ea wry 1110 b:nd withample safety margin. the choke unit weeadeto exacting speniticntions to assure mont efficientfiltering. the output unit was made to conform torequirements of low direct rurrent redstart,. withmullably Impedance at tho norkIng trvIluenelro.and the resittance unit was specially designed for
pabsolutelydependable ateelliirms of voltage ',tit -
t. Made with proper filter condensers and 5, logtwo UX-281 or 316-13 tubes for full wave rectifi-cation. this new Supply affords arresine depthof tone, richness of volume and flawless reproduc-tion evert itt enormous signal loads.
The construction of the Power Supply was de-scribed by J. E. Anderson In the Oct. 15 and 21issues of RAI/I0 WORLD. Bow to build theTictoreen l'ower Supply with an audio amplifieris described in October 29 Issue by the lamedistinguishe,1 engineer. In the present Issue ILB. Herman. coustical expert. tells Low to makea phonograph Installation.
The Victoreen 112 audio transformer unit i
used in conjunction with the previously mentionedapparellc to renititette one of the lineal inner rsupplies and audio amplifiers ever designed.
Everybody who has heard one has gone Intoecstacies and has wanted one Immediately for hInc.1f. Ertl,. the fullest and finest that radio Imeto otter and let the guests you entertain in yourhome see what a wise choice you make when Itcomes to selecting a suitable power supply andutlio channel. Critical persons who hare heard thisde luxe outfit amply marvel at the differenrebetween this and the ordinary B eliminator andordinary audio amplifier. The VIcioreen apparatusis moat extraordinary In ID performance becauseno pains are spared In the search for perfection.and every pier. of apparatus Is lasted three tinseland then once more for good measure to maresure that It measures up to the Victoreen standardsof flawlessness.
The 112 audio transformer unitTwo transformers In a single rasing constitute
the 112 unit. which amplifies with portent natural-ness. Use a 112 tube In the first stage and a210 In the last stage In connection with theVictoreen Power Supply.
The 112 unit may be used as the audio channelIn any receiver. Send for booklet am' learn how.Your Victoreen parts are obtainable at your dealer.Victoreen 116 power transformer 516.00Victoreen 216 choke unit 15.00Vletoreen 115 output unit 10.00Victoreen 316 resistance unit 3.00Vietoreen 112 audio transformer unit 22.00Victoreen manpanin rheostats, each 1.20
Write today for 1928 blueprintsand circulars
7XP GEORGE WALKER a.seas Citi[sWniliVUSMVseronti onto
RADIO WORLD December 3, 1927
THE R IS MADE
STRAIGHT LINE!IN electricity in all its forms, including radio, "R" stands
for resistance. Any resistor that is variable should varydirectly in proportion to the adjustment. In variable gridleaks this asset of "straight line R" has been missing. Butnow it is supplied-efficiently, perfectly-in
The New De Luxe Model
BRETWOODVariable Grid Leak
The improvements made in the newmodel-imported from England andreleased for the first time-are:
(1) Constant readings, (2) even dis-tribution of the resistance element, (3)support provided for optional base-board mountings.
By using the Bretwood Variable Grid Leak you improvetone quality, by avoiding detector tube overloading,achieved by correct leak setting. Thereafter the leak maybe varied for extremely distant stations, or may be left atthe original setting.
North American Bretwood Co., 145 West 45th St., N. Y. City.Gentlemen: Enclosed find $1.75. Send me at once one De Luxe Model Bretwood Variable
Grid Leak on 5 -day money -back guarantee. (Or $2.25 for leak with grid condenser attached.)
NAME
ADDRESS
CITY STATE
Inquiries Solicited from the Trade
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3.
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D>r'
The DE LUXE MODELwith Condenser Attached
The De Luxe Model BretwoodVariable Grid Leak specified byHerman Bernard for Radio World's
Four -Tube Universal Receiver.
The knob is hard rubber.
The shaft is durable brass, and can notjam or stick.
The brass lock nut, with milled edge, enablessingle hole panel mount.
The barrel is of hard rubber and houses thethe resistnace element and plunger.
The tugs are adjustable to any positionwithin the sweep of a circle.
The grid condenser is securely fastened tothe lower lug and requires no extra roses,as it is within the projection of the lugs.
The syphon container distributes a constantsupply of resistance element, making thereading straight line resistance, and pre-enting uneven distribution of the resistance
element.
The hard rubber pedestal affords the optionof perpendicular mounting, as on a base-
board.
Each Bretwood Variable Grid Leak andBretwood Bullet Condenser is guaranteedagainst mechanical or electrical imperfec-tions and is sold on an absolute five-daymoney -back guarantee.
If you're not delighted with results, thenwe're not even satisfied!