150 radio hook ups_1926

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150 RADIO HOOKUPS

BY THE STAFF OF

Published by

THE E. I.COMPANY

37 Vesey Street

New York City



Printed in the United States of America

Copyright by .

THE E. I. COMPANY

1926

All rights reserved, including that of translation into foreignlanguages, including the Scandinavian

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150 RADTO HOOKUPS

Radio Symbo l s

THE radio set owner always wantsto know and learn more about his

. receiver-how it operates, what theTariolls parts do and in what manner theyfunction, Invariably, he seeks recourse. towell-written and popular articles, de-scribing these things in detail. In manycases, though the reader really under-stands the line of thought, he fails to

,

cmprehend the wiring' diagram, and lookson it as a meaningless maze, To alleviateor remedy this condition, we are presentingto our readers the very latest compilationof up-to-date radio symbols, covering theentire field of instruments and apparatusused in receiving circuits.This page with its invaluable contents willbe found most instructive and enlightening.

ANTENNA

If ®

V O L T ·

$~

SWITCH

$ETER

flLAMOIT

lOOP

~ . f . >CRYSTAL . +NTeNNA D E T E C T O R

DRY~CELL t t l - : - ~ ~

t ;1:

~

JACK

UINGLE

CffiCUIT

~lll ! ! !

~ ~ R E C E : I V E R S

~ ~ f ! f T~U:PI04E

R H E O S T A T - 1

3

U G H T N I N G

A R R E S T E R

G R O U N D

.



11)0RADIO HOOKUPS

Circuit Analysis

THERE are It) many drcuits-good,extra. good and nefarious ones-thata beginner is most apt to become b",-

wildered and throw up his hands and ex-claim, "I give up." Whether that startledyou at the time you entered the radio game-amost entrancing hobby, to be sure-doesnot mean that you are to be classed with thewell known "dumbells" that infest the radioart and go about acclaiming their superiorintellect-and inferiority complex I Rather,you are to be pitied. For since the begin-ning, there has been no fully compiled orcompletely classified list of all these circuits

which are continually the bane of one's ex-istence.'Perhaps there is a very good reason why

such a list has not been compiled. Per-haps, it is the very fact that the progress ofradio has been so rapid in the past fewyears, that it would have been an endlessand unceasing task to consolidate all ofthem into a handy classification. However,the in formation which appears for the firsttime, in this article, will be found to eb ofreal value to the experimenter and radio.man. It will serve as an unerring guideand be instrumental in showing what hasbeen done in the way of improving radio

reception and will probably open many newchannels which have remained dormantbecause these channels have been obscuredby lack of sufficient realization of existingconditions. Therein lies the real value ofthis work

There are but five avenues in which toclassify all the existing r$ceiving circuits.

From the above fundamental cir-cult of the 81mplest form. we haveihe circuli at the rl..t. Althoughthe fir.t one nile. a crystal detec-tor and the 1ilElC0ndone a. three-element tube. both a.re In the lameo&tegory a.nd are clalslfied &8 beloD~-Ing to the non-regenerative variety.Bnreau of Standard." mea.surements.bow tbat the tube is 25% more sen-sitive than the crystal, although the

lattor I'lv" 1 i O ' f o more elantS'".

Circuits can be, fundamentally, of the non-regenerative, regenerative, radio frequency,super-regenerative or super-heterodynetypes. To date, there are no other classesin which circuits may be placed, but un-doubtedly. although many leading engi-neers believe the contrary, it is probablethat new classifications will be evolved.The following list should be copied andfiled away, so as to be at hand whenevernecessary. It is advisable to memorizeit, since the information is well worthknowing and having at instant command.With two fundamental circuits to start

with, in the non-regenerative classification;and the choice of eleven different types ofdetectors; five fundamentals and two detec-ton in the regenerative classification; sevenfundamentals with seven separate modi-fications of but one of them in use withthree tyes of detectors in the radio fre-quency classification; three fundamentals inuse with three types of detectors in thesuperregenerative classification and fourfundamentals with the use of four differenttypes of detectors in the super-heterodyneclassification, it is indeed not surprisingthat many are at a loss which of 50 manyto choose. Again. one should not lose

sight of the fact that audio frequencyamplification can be of the transformer,resistance and choke coil coupling types.Also, push-pull transformer coupLing, push-pull resistance coupling and power amplifi-cation can be used. All this complicatesmatters Klore, hut by careful analysis it isnot only possible to designate the proper

TAP

E V E . R Y

lor

. _ _ _ - - ~ - I I . . . _ 1 1 1 1 +

~ J4.·6Y ·B ·Z 2~V .



150 RADIO HOOKUPS

2. REGENERATIVE.A. Auto-coupled.

1. Inductive feed -back"~. Capacitative feed-back.

B. Loose-coupled.1. Inductive feed-back.

2. Capacitative feed-back.

C. Regenerative reflex.1. Three element tube.2. Four element tube.

3. RADIO FREQUENCY.

A. UNTUNED.

1. Resistance coupled.

2. Impedance coupled.

B. Transformer coupled.

B. TUNED.1. Impedance coupled.2. Transformer coupled.

a. Loosely coupled.Positive feed-back.

b. Closely coupled.Negative feed-back.Losser,Absorption circuit.

c. N eu t, .aUaed.Hazeltine.

Rice.Farrand.

C. REFLD..1. Straight.

2. Inverse.1. Two element tube.2 Three element tube.

3. Four element tube.4. SUPER-REGENERATIVE.

A. Straight.A. Flewelling.C. Autoplex.

1. Two element tube.

2. Three element tube.

3. Four element tube.5. SUPER-HETERODYNE.

A. Straight.1. Tropadyne.2. Ultradyne.

B. Second Harmonic.

WLththe dl8COTery of

the three-element tnbecam.e the re.enerativedeteetoJ'. Regenerationincreasel the 'Volumea.nd sensitivity of a .etIn a very large degree.There 18 one drawbll4lk.however. that of radia-tion when the Bet Itartsto oscllIate due to over-regeneratloD. The a.bovediagram shows a three-

.•0005. elreolt regenerative receiver using tickler feed-baek. Regeneration can also he obtained throughthe use of a. tuned plate system, In whloh' casethe Internal oopaelty of the tube pIa:n an Im-portant role and by capacltatlv8 feed-back aa Inthe Relnariz circult. The single circuit regenerativeeet should be tabooed, &8 it Is a persistent peat

on aeeount of It II radJatlng' qualltlea. The diagramgive. complete deta.1Is lor the CODstructlon at the· Bet which 1. tamWarly knoWD .. the oldBtandby three-circuIt l'e.eneratlve.

dastificatiost of the ~rcuit but with a littlepractice one can readily resolve it into its

simplest fundamental form. ,

On these pages we will find a funda-

mental circuit and one of its best practicalforms and the experimenter need but fol-low the given specifications so that he canbuild up the receiver.It is taken for granted that the reader

has sufficient knowledge of circuits toknow the fundamental principles under-

lying their operation. If he has not, re-

course should be had to some of theexcellent books now on the market and .

obtainable at nominal cost.

With bllt a slight stretch of the imagina-tion, one can readily perceive the almostinfinite Dumber of circuits possible to make;and although the three element tube is byfar the most popular form of detector and

amplifier, with the crystal detector as a fardistant second, still the numerous circuit

combinations that are possible could not he

cornsummated and built up by the average

experimenter in years.

Reflex. circuits alone-there are hundreds

of them-e-find great favor in the eyes of theexperimenter. Then again the conduc-tively, inductively and capacitively coup-

led antenna systems further increase the

number of combinations.

1. NON-REGENERATIVE.A. Auto-coupled.

B. Loosely-coupled.1. Coheret.2. Crystal (with and without bat-tery).

3. Microphonie.... Electrolytic.

~. Magnetic.

6. Colloidal... 7. Tikker.

8. Heterodyne.

9. Two element tube.10. Three element tube.11. Sodion,

5



150 RADIO HOOKUPS

1. Electrolytic detector,2. Two element tube.

S. Three element tube.4. Four element tube.

Th~ lIuper-he-terodyne II a elrcult which workl on an entirely different print,llple from

thetle deserlbed previoosly. It i f : ! safe to aay tbat the super-heterodyne is one of the most

.elective sets and for tbis reason is used by many amateurs for short-wave (100 to 200 m) work.

Itreference Is made to the fundamental circuit, It will be seen that the circuit is comprlsed

of a. But detector a heterodyne oscillator, one stage of intermediate frequency transformation,

and a. second detector The success of the super-heterodyne Ues in the design of the inter-

mediate transformers which raise the wave-length of tbe incoming signals and thus allow

more accurate tuntng:. The well-known Tropadyne adaptation is shown here. This olrou11i

doe. not radiate, and, using a loop. pves very cood results.

'A'

- ! I ! I . . . .. ...J.------_:-·B.,.-t·

The field of the radio frequeney amplifier elreuit Is by fa.r the largest a.nd the gr_t

number of "dynes," "pIexes" and reftexes are the result of various ~ombination8 using radio

treq'n('lncy amplification. Note that the fundamental circnlt til represented as one stage of ~

tuned R.F., auto-coupled with untuned transformer coupling to II- DOn~J'egenera.tlvedetecl.tor.

The adaptation can be recognized as the neutrodyne circuit, which hRs given much Ia.tisfa.e-

tton, In analyzing the neutrodyne, It is at once seen that it belongs to the ra,dlo frequency

clallllification and employs tuned transformer coupllng, is neutralized by the Hazeltine method

and usee, in oomblnation, a. non-regenerative detecl.tor aDd two stages of tra.nsformer coupledandlo freqnency anlpliftcatlon.

6



150 RADIO HOQKUPS

A. v e r '1' InterNtlngdevelopment iii the su-pw-re&,eneJ'ative roomv-Ill'. The lIuper~relener-

.Uve .et worQ on anentirely dltrerent p..in-(llple f..om that of it.

predece •• or, The cir-cuit 18such as to allow• condition wbel'eby.lIclllatlons of both anaudio and radio fre-Quency nature are Betup. Due to the audio frequeney component, theIrrld assumes It "nel'a.ttvil reslitance value" andpaslee an enormous amount of current, thus.. reatly lntenalfylnir an Incomlnir sl&'nal. Ofeourse. there is the problem of coping with theaudio frequency "squeal:' as it Is caned. but theelrcult has been perfected to an extent wherott Js hal'dly noticeable. The well-known AutopJexreceiver I. shown as the adaptation of the tund8.D1ental. The circuit, which I. slmpllcityItself, ite.pable qf excellent results. Note absence of caplU)ities.

Crystal and Non-Regenerative Hook-UpsCircui. t No.1. shows a crystal detector

circuit using a two slide tuning coil asthe tuning element. The antenna is con-nected to one of the sliders and the groundto the other so that the inductance betweenthem may be varied. This arrangementpermits the antenna circuit to be tuned andalso the coupling between the primary andsecondary circuits to be changed to increasethe selectivity. The secondary circuit is

composed of the sectior of the coil com-prised between the top of the coil andthe slider connected to the ground. The

condenser C is a by-pass condenser ofabout .001 M.F. capacity. With the slidersas shown, the coupling tight.Circuit No. 2 is that of a crystal receiv-

ing set using a varic-coupler or loose

Clnult 1

coupler for tuning. The two circuits areseparate and the secondary coil may turnor slide inside of the primary, which maybe varied either by means of a sliding con-tact or switch and switch points connected

to taps on coil L. The secondary Ll isfixed and has the proper number of turnsto receive over the desired wave bands

when tuned by means of the variable con-denser C. Cl is the by-pass condenser of.001 MF. capacity. To tune this circuit,couple coils tightly, set condenser C at zeroand vary the primary for signal. Thenvary C until signal is loudest.

Clreult I

Circuit No.3 is similar to the circuit No.2 except for the addition of the variablecondenser in the antenna circuit. This con-denser permits finer tuning and also allows

wave-lengths shorter than the natural wave-l-ength of the antenna to be received. Thevariable condenser C 2 shown between theprimary coil and the ground permits ex-tremely sharp tuning and has the effect ofshortening the natural wave-length of theantenna exactly as if some wire were cutout of the antenna itself. With such a re-ceiver there are four tuning controls, theprimary tuning switch, the primary con-denser, the coupling between coils L- and L

1, and the secondary condenser C . The tun-ing of such a receiver is the 'same as thatof the circuit No.2 and the antenna vari-able condenser should be- set at maximumwhile tuning. When the desired signal istuned in the primary condenser is read-justed to obtain selectivity and finer tuning.

"I



15() RADIO HOOKUPS

Needless to say, the crystal detector shouldbe adjusted before tuning. This may bedone with a buzzer or by listening on some

local station which is easily tuned in.Circuit No. 4 is the same as No. 3 withanother additional improvement consistingin the tuning of the detector circuit byeans of a switch or slider on the second-ary coil. This arrangement provides anextra circuit for the detector and tele-

Clreuit S

phones which increases the signal strengthand selectively, Since this control is notcritical the tuning is the same as that ofthe circuit No.3, the inductance of coilL r being adjusted after the desired signalis tuned in.The two coils Land L 1 may be wound

on tubing or spider web fashion, with tapsevery 10 or 15 turns to vary the amount ofinductance in the circuit. The number ofturns on each coil varies, of course, withthe wave-length to be tuned in. If onlythe broadcast range is to be received, about

ClI-cult 4

50 or 60 turns of No. 20 D. C. C . wireshould prove suitable. The coupling be-tween the two coils should be variable soas to increase the selectively of the receiv-ing system whenever necessary. The twocoils may be mounted on a rod so as toslide along the same axis, or they may be

mounted on a hinge to vary the angle he-tween them.

Circuit No. 5 is - a simplification of theother circuits in that the number of controlsis reduced without sacrificing much of the

selectivity. In this arrangement coil 1 . . Lzomposing, with the condenser, the second-ary circuit, is tightly coupled directly overcoil L 1. In order to tune the primary cir-cuit a separate coil L 2 mounted at rightangles or at a distance from LI and vari-able, is used to tune the primary Or anten-na circuit. In this arrangement there areonly two controls, that is, the switch orslider on coil L 2 and the variable con-denser C.This circuit, on account of its simplicity.

is recommended to the beginners who donot know how to tune the more complicatedreceivers. It may be constructed as fol-

lows: Coil L 1 should consist of 60turns of No. 20 D.C.C. wire wound in asingle layer on bakelite or hard rubber.Directly over this winding should be

Circuit G

wound 6 turns of the same wire com-posing coil L. Coil L 2· is sim-ilar to L 1 but with a tap every 5 turns.Use 3" diameter tubing.Ci,.cuit No.6. When it is desired to re-

ceive long and short wave-lengths, the useof a series parallel switch is useful to con-trol the primary condenser in series or inparallel with the primary coil.

8



150 RADIO HOOKUPS

The two variable condensers C and C 1should be of the 43 plate type having acapacity of .001 mfd., preferably equippedwith a vernier. The telephone condenser

C 2 is an ordinary .001 mfd. fixed con-denser. In this circuit the antenna variablecondenser C is used in series to receive theshort wave-lengths; in parallel with theprimary coil to tune in the long ones.

7 v n f

Clrllwt 'J

Ci, .cui t No. 7 is similar to 1'$. 6 but withan extra double pole double throw switchconnecting the detector and telephones

either 'across the primary or the second-arvFor the reception of short wave-lengths

the two coils may be composed of a stand-ard variocoupler or loose coupler havingabout 60 turns 3 inches in diameter oneach coil, or the equivalent.

Circuit 8

For experimental purposes, or when great'Selectivity is not necessary. Circuit No. Smay be employed. In this circuit two vari-ometers are used for tuning instead of vari-able condensers or tapped coils. The firstone, L 1, tunes the antenna circuit, and theo.her L 2, the secondary circuit. .

' . . . . . . .

=T

Clr.,nlt 9

Circuit No.9 is similar to but will provemuch more selective than No.8. If inter-ference is experienced, the secondary canbe rotated so that it is at an angle to theprimary and the set returned. In this wayit will not be difficult to tune out mostinterfering stations. The variable con-denser shown at C may have a capacity of.0005 or .001 mid. The variorneter L2 is astandard instrument and should be of goodconstruction for best results. It will be

C 1

Circuit 10

Circuit No. 10 shows a singlet circuit re-ceiver using a two electrode tube instead ofa . crystal. Although it is only a little moresensitive than a crystal receiver, it does nothave to be adjusted and is always readyfor operation. The inductance LI may

(,,lrcult :t1

9



150 RADIO HOOKUPS

consist of the primary of a standard vario-coupler or it may be made by winding 60turus of No. 22 S.c.c. wire on a 3V2-inchtube. The winding should be tapped about

every six turns and two switch points areconnected to each tap. This will give aninductance that can be varied over thesame winding by two switches. A two-slide tuning coil may also be employed as

Clrcnlt 12

the tuner, instead of the tapped induct-ance. The variable condenser C1 has acapacity of .0005 mfd, A condenser of thissize usually consists of 23 plates. The by-pass condenser C2 is fixed and has acapacity of .001 rnfd.

Circuit No. 11 also uses a two-elementtube, but in this case a varicoupler is em-ployed for the tuner. The primary of this

variocoupler will consist of the same num-ber of turns as the tuner in Circuit No.10. Only one switch and one set of tapsare used 'to vary thd inductance. Thisprimary may be tapped every sixturns, which will give 10 switch points.

Circuit IS

The secondary of this coupler is made sothat it will rotate inside of the primaryand is wound with about 45 turns of No.24 S.c.c. wire. The variable condenser Clshould be about .0005 mfd. and the fixedcondenser, C2, is of the same capacity.A "B" battery of 22~ volts is used in

this circuit and greater signal strengthwill be had with this arrangement thancan be expected with Circuit No. 10. If

interference is experienced, the second"!ary may be turned so that it is at quitean angle to the primary and the set re-turned until the station again comes in

strong.Circuit No. 12 is the simplest of. all cir-cuits using a three-element tube and; asin the case of all preceding circuits, is 000-

regenerative. A fixed condenser of .00025mfd. capacity is placed in the grid circuitbetween the grid of the tube and the tunerand is known as a grid condenser. A gridleak (Rl ) is shunted aero 5S the grid con-denser and will usually be from one to fivemegohms in resistance. The usual by-passcondenser C2, is .001 mfd. and is connectedacross the phones and the "B" battery. A"B" battery is always used in a circuit em-ploying a three-element tube. The voltageof this battery will depend upon the typeof tube used. If a soft tube, such as aUV -200 is employed, the "B" battery willvary between 1 6 ~ and 22 ~ volts.With such a tube, when the rheostat-which in this case will have a resistance of

1 3 .

Circuit 11

six ohms-is turned up to a certain point,a slight hiss will be heard in the phones.For best results the tube should always beoperated just under this hiss.

CirC1d t No. 13. This circuit is similar to

No. 12, but employs a variometer L3, fortuning. The wave-length of the average

variometer, when used in series with theantenna, is too high to respond to the lowerbroadcast wave-lengths and a fixed con-denser of .00025 mfd. capacity should beplaced in series with the antenna to reduceit. The grid condenser in this receiver isa .00025 mfd. one, which is standard formost circuits. The tuning is very simple,the variometer being varied until the sta-tion is picked up. The resistance of therheostat R2 will depend upon the kind oftube used. The voltage of the "B" battery,will also depend upon the tube, but it willusually be not higher than 45 volts. A cir-cuit such as this, which does not use regen-eration, will have a receiving range ofabout 100 miles. '

1 0



150 RADIO HOOKUPS

Circuit No. 14 i!a circuit that wlllprove fairly selective. The antenna. sys-tem is tuned by means of a tuning coilwhich may consist of 60 turns of No. 22S.C.C. wire on a 3 ~ inch tube tappedevery six turns. The secondary, or gridcircuit is tuned by a standard variometerL a . The switch on the antenna coil isTaried until the desired signal is picked upand then tae fine tuning is done by meansof the variometer. If a UV-200 tube isemployed as the detector, it would be best

ClrCl11lt 15

to use a "B" battery that is tapped from16 ~ to 22 % volts, so that differentvoltages may be tried to 'determine whichgives best results. Care should be takenthat the positive of the HB" battery is al-ways connected to the plate through thephones. The by-pass condenser C2 is not

always necessary and the receiver shouldbe tried both with and without it, to de-termine which gives better results. Thiscondenser will be of about .001 mfd. andis not critical.

Circuit No. 15. In this circuit a vario-coupler is used in pla-ce of the tuning coilshown in Circuit No. 14. Also, the second-ary circuit is tuned by means of a variablecondenser of .0005 mfd. capacity, instead ofthe variorneter, Much greater selectivitywill be had in a two-circuit receiver of thislcin'd, as it is possible -to vary the couplingbetween the primary and the secondary coils

of the variocoupler. When tuning, theprimary switch lever is placed on the sec-ond or third tap and the variable condenservaried until a station is picked up. If nostation is heard, the switch lever is chang-ed to another tap and the condenser againvaried. Sometimes certain taps on theprimary will give better results than othersfor certain stations, but this can only bedetermined by experiment. As a rule,however, one certain tap on the primary ofthe variocoupler will bring in most sta-tions in the broadcast wavelength rangeand it will not be necessary to change toanother tap unless a great variation of

wave-length is required. This circuit will

give very good results, although as it isnot regenerative, stations further than lOOor 200 miles distant will not be picked upexcept under exceptional conditions.Circuit No. 16. Here is a circuit that will

prove far mo-re sensitive than any of theothers thus far described. In this receiverthe Sodion tube is employed as thedetector. A special form of loose coup-ler must be used with this tube, as veryloose coupling is required for best opera-tion. This tube does not have a grid, 'asis the case in a three-element tube, but in-stead it has a curved metal plate knownas the collector. The circuit for this tubeis similar to a standard vacuum tube cir-cuit, but it requires a potentiometer ofabout 50 ohms (R2) in series with a fixed

resistance of 150 ohms (R3) connectedacross the filament battery and rheostat :\5

shown. The primary of the coupler may betapped as usual, or it may consist of a fixedinductance with a variable condenser of_()Ol mfd. capacity in series. The second-ary of the coupler is tuned by a variablecondenser of .0005 mfd. capacity. Thiscircuit is very sensitive, especially on weaksignals, which makes it excellent for longdistance reception. A receiver using thistube cannot oscillate, is non-regenerative.and will not interfere with other receiv-inz sets.

Co/ketal- p/tlk,_- -~-- - - - -~ "

1 1 .

Cirenlt 16

Circuit No. 1 7. For the ian who livesin a district congested with many broad-cast stations which are 'difficult to separate,the receiving circuit shown in Fig. 17should prove of great interest. Nearlyevery fan who has built a set has givensome thought to wave traps, and it is thisprinciple which is used in this circuit.The coils used in the receiver may be

wound in basket-weave style or may be thesingle-layer inductances. In either case,however, they should be wound with No.14 D.C.C. wire in order to reduce the re-sistance of the circuit as much as possible.The inductance Ll has 20 turns and is

shunted by the variable condenser CI which

11



150 RADIO HOOKUPS

. . .

~~~~----~--~+90~

~~~~~--~~--~~~----~---O+22~

~--~---T----~----'_~~--_'---O-A

- - - - ~ - - - - - - - - - ~ - - - - - - - - - - - - - . - - - - - - - - _ O + A - Bhas a capacity of .001 rnf. The coils, L2and L3, which are in inductive relationshipto one another, have 50 and 15 turns, re-spectively. It should also be noticed thatthe inductance Ll should not be near theother two inductances, L2 and L3. Thecondenser C2 has a capacity of .0005 mfd.

CJ.rcuit 18

When local stations only are desired, andpure reproduction is wanted, a crystal re-ceiver in conjuqction with one stage ofaudio frequency amplification will give ex-cellent results. Such a circuit is shown incircuit No. 18.

Regenerative Hook..Ups

Clreult 18

CIrcuit 17

Circuit No. 19 shows the simplest formof regenerative receiver using a standardthree-element tube. This receiver is of theultra-audion type, and regeneration is ob-tained and controlled by means of therheostat R2 and the variable grid condenserC2. A fixed grid condenser of .00025 mfd.·capacity may be used, but if a variable oneof .0005 mfd. is employed, greater controlover the regeneration may be had. Thetuning coil in this circuit is a fixed induct-ance and may take the form of honeycomb

or spider-web coil of 25 or 35 turns. Thisis shown as LL The tuning is accom-plished by means of a variable condenserCI, which is in series with the coil andground and which has a capacity of .001mfd,

Clrculi !O

Circuit No. 20 shows another form ofultra-audion receiver using a variocouplerin place of a single coil. Tuning is accom-plished by means of the switch' on the pri-mary and the variable condenser Cl inshunt with the secondary. Regeneration inthis case is controlled by means of the.0005 mfd, variable condenser shown as

12



150 RADIO HOOXttPs

C2. It will be seen that the phones and"B" battery in this receiver are removedfrom the oscillatory circuit and the lowerterminal of the secondary, instead of being

connected to the "A" battery is run di-rectly to the plate of the tube. The gridcondenser may be variable if desired, andwill help to control regeneration, but this isnot necessary for good operation. In tun-inp" a receiver of this kind, the primary ofthe coupler is varied by means of the switchand the secondary circuit is tuned by meansof the variable condenser C1. If the vari-able condenser C2 has an of its plates inter-meshed, the tube will go into a state ofoscillation which will distort signals andcreate interference in nearby receiving sets.The remedy for this is to furnish less capa-

city by moving the rotary plates of the con-denser until the signals are clear and notdistorted. If the signal is not very loud,'more regeneration can be obtained by in-creasing the capacity of the condenser.

Circuit No. 21 is of the single crcut type

Circuit 21

and tuning is accomplished by means ofthe switch on the primary and thevariable condenser Cl of .001 mfd. ca-pacity in the ground circuit. Any wave-length may be -reached to the limit of thetuner by varying the switch and tuning

between the taps with the variable con-denser. The secondary of the coupler isconnected in the plate circuit of the tubein series with the phones and "B" batteryand regeneration is obtained by varyingtne coupling between the two coils. Whenassembling this circuit, and the primary andsecondary coils are parallel with each otherthe plate and the grid leads should alwaysbe connected to opposite ends of their re-snective coils. When these two coils areparallel, greatest coupling is had and thetube wil l be in a constant state of oscilla-tion. When a station is tuned in, thesecondary should be placed at such an '-

angle to the primary that the signal isloudest without being distorted, which

will usually be just before the tube goesinto oscillation. This oscillation pointis indicated by a click in the phones andat this point a squeal will be heard and

signals will become mushy and distorted.As stated before, never operate a regene1 "(J-live set 'With the tub, in an oscillatingcondition.

CIl'eult !~

In crau No. 22 we have another regen-erative receiver which uses the same tuningsystem as Circuit 19, but in this case regen-eration is obtained by means of a variome-ter La, in the plate circuit instead of thetickler coil. This variometer tunes theplate circuit to the same wave-length asthat of the grid circuit and when these twocircuits are exactly in tune, or in reson--ance, the tube will go into oscillation.

When a station is tuned in by means ofthe switch and series condenser, thevariometer is varied and as it approachesthe resonance point, regeneration will takeplace and the signals will increase greatlyin strength. It will be found easier if thegrid and plate circuits are both tuned at

Circuit II

the same time, as in this way, if any weakstation is in the range of this receiver, It

will then be picked up. This receiver, or ~in fact. any receiver shown in these pageswith the exception of diagrams 10, 11 and16, can be used with any of the threeelement tubes 'on the market. Great cafeshould always be taken that .the rightvoltage is used for the filament; as other-

13



150 RADIO HOOKUPS

wise the tube might easily be burned out.This receiver is also of the single-circuittype and consequently will not give verysharp tuning, although it is capable of longdistance reception if no interference is ex-perienced.Circuit No. 23 . Here is shown a very

simple single circuit regenerative receiverusing a single variometer for tuning andregeneration. This varia meter should in-variably be of small size, having no more

~"Q2S

Clreuit 2~

than 40 or 45 turns on the stator, and thesame number on the rotor. In this re-ceiver the stator of the variometer acts asthe tuner and is connected in the antennacircuit in series with a variable condenserCl, of .001 mfd. capacity. The groundis taken off at the intersection of the stator

and rotor, as shown. The other end ofthe rotor is connected to the plate of thetube through the "B" battery and phones.~A small variometer should be used becauseif one of standard size is employed in thiscircuit there will be too much wire onthe stator to tune to the lower wave-

Cll'euit :lCl

lengths. The by-pass condenser shown atC2, may not be necessary and the receivershould be tried with and without it to de-termine which connection gives the betterresults.Circuit No. 24 is a regenerative receiving'

set using two variometers, one of which isplaced in the antenna circuit for tuning

and the other in the grid-filament-plate cir-cuit for regeneration. As will be seen, the

filament connection is made at the junctionof the rotor and stator of the second vario-meter, The stator of this variometer isconnected between the filament and theground side of the tuning variometer. Therotor is connected between the filamentand the plate of the tube in series with thephones and the "B" battery. This vario-

meter should be of small size having nomore than 40 or 45 turns on the statorand the same number of turns on therotor. As this receiver will cause greatinterference under certain conditions, careshould be taken that it is operated correctly.Crcuit No. 25 shows a recever which

will prove very selective, and for a one-tube receiver is very hard to excel Astandard variocoupler is used for tuning.

A variometer is inserted in the grid, orsecondary circuit rwhich will give veryclose tuning. Another variometer of thesame size is used in plate circuit for regen-eration. A by-pass condenser C2, of .001mfd. capacity usually will be found neces-sary in this circuit. Contrary to thegeneral opinion, the tuning of this re-ceiver is not difficult. The primary switchis set on a switch point usually the third

Clreutt 26

or fourth, where broadcast stations willbe received. Both variometers should bevaried simultaneously, keeping just underthe oscillation point. In this way, as thetuning of the secondary circuit is changed,

the receiver is always at its most efficientpoint and weak stations can readily beheard.

Circuit No. 26 is the same circuit as No.25 with the exception that a variable con-denser is used to tune the secondary circuitinstead of a variometer. By using this va-riable condenser the tuning will be slightlysharper and a wider band of wave-lengthswill be covered. The grid leak Rlwill have as resistance from one to fivemegohms depending upon the type of tubeused. The tuning of this receiver is iden-tical with that of diagram No. 25. If in-

terference is experienced, the coupling be-tw~en the rotor and stator coils may be

1 4



150 RADIO HOOKUPS

loosened and the set slightly returned. Asthe rotor is turned at a. greater angle tothe stator, sharper tuning will be had. Ifthe angle is very great, the signal strength

wil l be lessened. but this is sometimes ad-visable to eliminate heavy interference.Under good conditions a'~receiver of thistype should have a receiving range of 800to 1,200 miles, if conditions are veryfavorable.

Circuit n

Circuit No. 27 is also a three circuit re-generative receiver, but in this case insteadof a variometer in the plate circuit for re-generation, a fixed inductance La. shuntedby a variable condenser C2. is used. Thisinductance should be approximately thesame value as the secondary of the va rio-coupler. A honeycomb coil of 50 turns wil l

give very good results in this position.The variable condenser C2, has a capacityof .0005 mid. The condenser C1, also hasa capacity of .0005 mfd. and is used to tunethe secondary circuit. The tuning of this

Clreuit 28

receiver foIIows the same method as em-ployed in diagrams 25 and 26, both conden-sers being varied at the same time. Thevariocoupler used in this circuit should beof good manufacture and should containfrom 45 to 50 turns on the secondary. Theprimary is tapped at every 8 or 10 turnsand is varied by means of a switch. It is

not necessary .that this primary be finelytuned. Try reversing the "A" battery leads

as one connection will work better withcertain tubes.

Cireolt !9

In circuit No. 28 we have the well knownReinartz circuit. This receiver will givevery selective tuning and is quite a favor-ie with the amateurs, This circuit wasoriginally designed for C .W. reception. butit will also give very fine results on radio-phone work. Coils Land Ll are woundin spider-web fashion on the same form.These coils have been described many timesin various radio publications and they maybe procured from any radiio supply dealer.L1 in this circuit acts as a tickler coil, butregeneration is mostly obtained by capacity

feed back through the variable condenserC1. This condenser has a capacity of .001mfd. The variable condenser C2. withwhich most of the tuning is done, may have17 or 23 plates. The grid condenser C3has a capacity of .00025 mid. and shouldbe of good blake. The "E" battery voltagewill depend upon the type of tube used.In circuit No. 29 is shown what is known

as the modified Reinartz receiver. At firstglance this circuit appears to be new, butit is nothing more than an untuned pri-mary circuit having capacity feed-back forregeneration. The instrument shown as Lis a standard variocoupler of the old type.

Clreolt 30

1 5



150 RADIO HOOKUPS

where the secondary may be revolvedthrough 180 degrees. The secondary wind-ing is connected to the end of the primarywinding as shown. The lower end of the

primary winding should be tapped everyturn for 10 turns and is controlled by aswitch. By using more or less turns bymeans of this switch. great selectivity isobtained. The variable condenser Cl has acapacity of .001 mfd. and is used to pro-duce regeneration. When tuning this re-ceiver the switch may be set on any pointand the rotor of the variocoupler turneduntil a station is picked up. Greater volumeis then obtained by increasing the capacityof the variable condenser C1. It is bestpractice to make both of these operations atthe same ~ime. ?s in this way the receivertan always be kept at the maximum point

of regeneration and very weak signalspicked up.

C',iroult 81

In Circuit No. 30 we have a simple re-generative receiver which combines selectiv-ity with long distance reception. The tunerof this receiver consists of a rewound vari-ocoupler. A coupler of the lBO-degree typehaving a.,.secondary winding of 35 to 40turns is recommended. The primary wind-ing should be removed and a new windingconsisting of 42 turns of No. 20 S.C.C. wirewound on in its place. This winding

willbe the secondary of the instrument. Theprimary consists of 10 turns of No. 18 orNo. 20 S.C.C. wire wound directly over thelower end of the primary and separatedfrom it by two or three layers of card-board or other insulating material. The-,;adable condenser Cl has a capacity of•0005 mfd. and should preferably be ofa vernier type. A non-vernier condensermay be used, but in this case a vernierdial is recommended. When connectingthe tickler coil, the plate of the tubeshould be connected to the lower ter-minal if. when the tickler is horizontal

in respect to the secondary, the grid isconnected tq. the top rerntinal o f this

secondary coil. If these connections arecorrectly made, there will be no need to re-verse the tickler connections afterward.

Clrcult !z

Circuit No. 31 shows a circuit with whicha fairly wide band of wave-lengths may becovered with efficiency. In this circuit twovario-couplers are employed and are shownas Land Ll, Regeneration is obtained bymeans of the secondary of the second vari-ocoupler acting as a tickler in the plate cir-cuit of the tube. To obtain regeneration.part of the winding 0 f the primary of Llmust always be used, and for this reason jt

is advisable that the variocoupler L havea secondary of about 30 turns. The vari-able condenser Cl, with which the sec-ondary timing is accomplished. has a

capacity of ,0005 mid. It will be foundthat for practically all broadcast stationsonly one or two taps in the primaryof Ll will be used. Experiment will

"l'*ClUit 81

determine which taps to use on the prj •mary of L for certain stations. As thesecondary of this first variocoupler canbe varied in its inductive relation tothe primary, very sharp and selec-tive tuning w in be had. 1£ the primarieshave sufficient turns. a wave-length ofa , o o o meters may be reached. The by-pass

condenser C2 will have a capaoty of .00-1mid

1 6



150 RADIO HOOKUPS

Circuit No. 32 also shows a three circuitregenerative receiver, but in this case thephones and the "B" battery are removedfrom the oscillatory circuit. It will be

noted that the grid return of the tube doesnot connect to the filament but goes to theplate through the plate variometer, In thiscircuit the grid leak R must be connectedfrom the grid to the positive side of the

CIrcuit 84

"A" battery. The values of the variousinstruments in this circuit are the sameas in preceding diagrams. The tuning ofthis circuit is no different than the otherthree circuit regenerative receivers shownthe variable condenser CI and the plat~variometer Ll phones and "B" battery areremoved from the oscillatory circuits, no

by-pass condenser will be found neces-sary. This circuit will be found extreme-ly sensitive fairly easy to tune and underf~vorable conditions will bring- in long-distance stations.

Clrenlt i5

Circuit No. 33 sh-ows a simple regenera-tive receiver that is slightly different fromthe standard circuits. A standard vario-coupler L is employed with a secondarywinding consisting of not more than 40turns. The primary should consist of about80 turns tapped every 10 turns and is em-

ployed with a variable condenser of .001!l'fd. in series with the antenna. The two

inductances, Ll and L2, are spider-web coilsof about 20 turns each. These two coilsare mounted stationary, itt inductive relationto each other and about three inches apart.

One coil goes to the grid of the tube andthe other is connected to the plate in serieswith the secondary of the tuner, the phonesand the "B" battery. The tuning is accom-plished by means of the primary switch and.the variable condenser. Regeneration ii iobtained by varying the inductive relationof the secondary to the primary. The leadson one of the spider-web coils should bereversed when the set is in operation, to de-termine which gives best results. As a ruleno grid condensed is required in this circuit,but one may be tried in the position shownat X.In Circmt No. 34 is shown a circuit that

is very little known, but which will provevery ~ffective in eliminating interference.As WIn be seen, any type of two or threecircuit tuner may be used in conjunctionwith this system to good advantage. In

Circnit 16

this case it is shown with a standard threecircuit regenerative receiver. The in-ductance L will consist of about 35 turnsof wire wound on a three inch tube. Thesize of this coil is only approximate as itwill vary in accordance with the size ofthe antenna employed. It might be ad-visable to wind 50 turns on a three-inchtube tapped every 10 turns so that thesize of the coil may be varied for anysize of antenna. The variable condenserC may be .0005 or .001 mfd. capacity. Itwill be noticed that only one connectionis made from the coil L to the primaryof the tuner. This connection should betried at both A and B, as one connectionwill work very much better than theother. The inductance L should not bein inductive relation to the tuner of thereceiver. When tuning this receiver itwill be found necessary to vary the eon-

denser C and the condenser C2 at thesame time, as both must be in resonance.

1 7



150 RADIO HOOKUPS

In Circuit No. 35 is shown a diagramwhich will prove very efficient being sel-ective and sensitive and at the same timevery compact. This type of receiver may

readily be used as a portable set. It

Cil'cuit '37

really consists of two variometers, thestators of which are both wound uponthe same form separated from each otherl~ inches. The stator winding of theplate variometer is continued for fiveturns on each side of the stator windingof the plate variometer as shown. Thisgives a combination of tuned plate andtickler feed-back. The proper number ofturns for both variometers is shown onthe diagram. It will be advisable to place

a fixed condenser (C) of .0005 mfd. inthe antenna circuit and provide two bind-ing posts so that the antenna may be

. rIh c

l 3 l i l i 1 J

C'.iroalt 88

connected directly to the variometer orthrough the condenser as desired.In Circuit No. 86 we have a receiver

which will prove very selective, especialIyin a district where many broadcast sta-tions are located. The condenser C maybe of .00025 mfd, capacity, but may beleft out if desired, as it is not absolutelynecessary. L may be a coil of 80 turns

tapped at every 10 turns, LX and L2 arethe primary and secondary of a vario-

coupler. In this case, the primary of thecoupler should consist of about 35 turnsof wire. L is not in inductive relation toLI but is coupled thereto by means of

a continuous loop of wire shown at L3.This loop should be wound three turnsaround each coil, as shown in the dia-gram. Most tuning will be done withthe condenser CI, which in this case maybe of .0005 mfd. The grid condenser C2is of standard size (.00025 mfd.).Circuit No. 37. In this diagram we have

a circuit using capacity coupling. Thiscoupling is accomplished by means of

Loop

CIl'cuit 89

condensers C and Cl, which are of .0005mfd. capacity. The main tuning induc-tance L is as usual, of about 80 turns,which may be tapped at every 10 or 12turns. Coils Ll and L2 may be the pri-mary and secondary of a standard vario-coupler. It will not be necessary to usetaps on the primary of this coupler, as afixed number of turns ( approximately35) will be sufficient when tunec' by the.0005 mfd. variable condenser Cl. Thecoil L2 is inserted in the plate circuit ofthe detector for regeneration. The by-pass condenser C3 is of .001 mfd.

Circuit No. 38 shows the well-knownCockaday circuit, which has proven very

Cll'Cult 4-0

18



150 RADIO HOOKUPS

popular. The antenna system is comprisedof coils Ll and L2. Ll is a single turnof bus-bar wire around coil L3. L2 con-sists of 43 turns of No. 18 S.c.c. wire

on a 3-inch tube. This coil is double bankwound and may be tapped every six turns.It is in non-inductive relation to theother coils. D3 consists of 84 turns of

Clrcn1t u

No. 18 S.C.C. wire and is also wound ona a-inch tube. L4 consists of 65 turns of

the same size wire and is wound on thesame tube, with LS, separated from itby about 7 S inch. Variable condensers Cand Cl have a capacity of approximately.0003 mfd. and are of the 17-plate variety.Where an outside antenna is undesira-

ble and only one tube is to be employed,it. is sometimes possible to use a loopwhen quite near a broadcast station. Thecircuit for this arrangement is shown incircuit 39. The tuner and tickler may beof any standard form such as a vario-coupler, honeycomb or spider-web coils.If a variocoupled is employed, it will be

necessary to use 35 turns of the outsidewinding as the secondary, A separateprimary winding may then be wound di-rectly over the secondary and should con-sist of 25 turns tapped every five turns.The condenser Cl may be of .0005 or.001 mfd. capacity. The condenser C2which tunes the secondary circuit shouldbe .0005 mfd. capacity. The rotor of thecoupler is, of course, used as the tickler.In circuit No. 40 is shown another one-

tube loop receiver. Two loops are usedin this circuit, one as the tuner and theother for regeneration, in the plate cir-cuit. The tuner is the larger loop con-

sisting of 12 turns of wire on a 2-footframe. As shown in the diagramt the

plate loop is placed in the center of thelarger loop and is so arranged that it canbe rotated similar to an ordinary ticklercoil. The number of turns in this loop

is not critical, being in the neighborhoodof 15. If desired, this loop may be of

the same size as the other and arrangedso that the distance between it and theother one may be varied. Tuning is ac-complished in this circuit by means ofthe condenser Cl, which is of .0005 mid.capacity. A by-pass condenser will usu-ally be found necessary in this circuitand is shown as C2.In circuit 41 is shown a standard regen-

erative receiver with the addition of awave trap in the antenna circuit. Thiswave trap is composed of a fixed induct-

ance L, shunted by a variable condenserC. The fixed inductance may be a honey-comb cot! of 50 or 75 turns or, if desiredit may be constructed by winding 4 5turns of No. 24 S.c.c. wire on a three-inch tube. The variable condenser is ofthe 23 plate variety and has a capacityof .0005 mfd. When it is desired toelimina.te the interfering station thevar-iable condenser should be adjusted untilits signal strength is at a minimum or

until entirely wiped out.Another type of wave trap which will

prove extremely efficient and which canbe incorporated directly in the receiver isshown in circuit No. 42 . This wave trapconsists of a primary and a secondarycoil. the secondary being shunted by avariable condenser. The secondary con-sists of 45 turns of No. 22 S.C.C. wirewound on a tube three inches in dia-

meter. The primary consists of 10 turnsof the same size wound directly over the

1 9



150 RADIO HOOKUPS

secondary and separated from it by asingle layer of cardboard. The variablecondenser C is of .0005 mfd. capacity.In circuit No. 43 is shown another

method of eliminating interference. Thisconsists of a variable inductance, L, inseries with a variable condenser, C, con-nnected from the antenna to the plate ofthe tube. In this case it will be necessaryto employ a variable condenser, C1, in theantenna circuit. This condenser may be of.0005 or .001 mfd. capacity. The induct-ance, L, may consist of 50 turns of No.22 S.c.c. wire wound on a tube threeinches in diameter and tapped every 10turns. The variable condenser may be of.0005 mfd. capacity. If desired, regener-ation may be obtained by inserting avariorneter of standard size in the plate

.Circuit 43

circuit of the vacuum tube at the pointmarked X.In circuit No. 44 we have a receiver

which operates fairly well without a "B"battery. This receiver is of the singlecircuit type using a variocoupler for tun-ing. The condenser Cl, may be either.0005 or .001 mid. capacity. The second-

J m e q .

ary of the variocoupler is in the platecifcuit of the detector tube for regenera-tion and should contain at least 80 turnsof wire. As no "S" battery is used the

phones are connected directly to the posi-tive lead of the "A" battery. A variablegrid leak of from one to five megohms

Clrcult 44

resistance will be found advisable andshould be connected directly from thegrid to the positive terminal_of the "A"battery. The grid condenser, C, may beof .00025 or .0005 mfd. capacity.

Where greater volume is desired, onestage of audio frequency amplificationmay be added to practically any detectorcircuit, and a diagram through which thisis accomplished is shown in No. 45. Itwill be noticed that this one stage ofaudio frequency amplification is used inconjunction with a standard three-circuitregenerative receiver. An audio-frequencytransformer must be employed as shownat T. The primary of this transformeris connected in the plate circuit of the de-tector tube in place of the phones. It isrecommended that A transformer with a

zz iv.,___...._-___._---.....l l lr l l l l l l l

ufv

_ 1 1 1 1 1 1 1 1 1 1 1 1 1 - - + - - - - '

(!,Ircl1lU 41

~o



150 RADIO HOOKUPS

60-90 V .

_ . . . . . . _ _ _ . . . _ _ _ . _ _ - . . . . j l l i l l I 1 1 1 1 1 1 1 1 11 - + - - - - - - '

ratio of not higher than 5 to 1 be em-ployed as otherwise distortion is liable

to occur. A hard or amplifying tube

such as a UV-201A or a C-30lA must beemployed as the amplifier. For best re-

sults it would also be necessary to usea higher plate voltage on this tube. As

a rule 45 volts will be sufficient for onestage of amplification and this is obtained

by connecting two 22 114-volt "B" bat-

teries in series.It is almost impossible to obtain an

audio-frequency transformer that will not

distort to some extent and for this rea-son a resistance coupled amplifier is

sometimes made use of. However, sincea resistance coupled amplifier will only

give about 2/3 the amplification deliveredby a transformer, it is not generally used

for one stage. A circuit using resistance

coupling is given in circuit No. 46. Itis shown in conjunction with a three cir-

cuit regenerative receiver, although any

type of receiver may be employed. The

Clreult 46

resistance shown at R should be of thenon-inductive type and of a value of 50.-

000 ohms. It will usually be found neces-

sary to use a higher "B" battery voltage

with resistance coupling than with trans-

formers. A grid condenser will also. berequired in the grid circuit of the a m -plifying tube as shown at C so that the

"B" battery voltage will not be impressed

upon the grid. The capacity of this con-

denser is not critical and may be from.006 to 1 mfd. As an amplifying tube

must be operated with a negative poten-

tial upon the grid a grid leak of onemegohm is connected from the grid of

the tube to the negative of the "A" bat-

tery.

In circuit No. 47 is shown another sys-tem of providing distortionless amplifica-

tion. Instead of a resistance a chokecoil is employed and is shown at X. Ifdesired. this choke coil may be construct-

• ( J O O S

c

G Q - 9 0 V .

--.----___,_---tJllllllllllllh-+ -.---~

Clreult n

2 1



150 RADIO HOOKUPS

ed by winding 5,460 turns of No. 34S.S.C. wire in 14 layers On an iron wirecore S~ inches long and r s inch indiameter. In winding it will prove bestto separate every two or three layersof wire with a piece of waxed paper. Ifan old audio frequency transformer theprimary of which is burned out hap-pens to be laying about, the secondarywill function very well as this choke coil.The grid condenser shown in this dia-gram at C should be of approximately.01 mfd. capacity. The grid leak con-nected from the grid to the negative fila-ment should be from 1 to 3 megohms,best determined by experiment. A hardor amplifying tube must, of course, beused in this circuit and a "B" battery

voltage from 60 to 90 is recommended.This type of amplification has been shownwith a standard three circuit regenerativereceiver, but it may be used with prac-tically any circuit. Although it will notproduce the same volume of sound as anamplifier using an audio-frequency trans-former, it will, nevertheless, give suffi-cient volume to operate a loud speakerwhen fairly close to a broadcast station.

Choke coil coupled amplification hasrecently received another impetus forbroadcast reception due to its faithfulreproduction of voice and music and theusual lack of distortion faun d in a cir-

cuit employing it. It is quite possible topurchase choke coils especially designedfor this purpose on the market today andin some cases a complete unit incorpor-ating not only the choke coi1 but also theblocking condenser and the grid leak forthe audio frequency amplifying tube maybe had. Using this unit, the constructionof an impedance or choke coupled ampli-fier is greatly simplified, as the onlyaccessory necessary for connecting up an

additional stage of amplification is theamplifying tube and a socket.It is sometimes undesirable to use a

stage of audio frequency amplificationwhen the ear phones are employed andsome means must be used so that thephones may be plugged in on the de-tector alone and the amplifier disconnectedfrom the circuit. In circuit 48 is shownhow this is accomplished by means of adouble circuit jack. This type of jackhas two outside and two inside springswhich normally make contact with eachother. However, when a phone plug isinserted the two outside springs discon-nect from the two on the inside, therebybreaking this part of the circuit and al-

lowing the current to flow through the

phones instead of the primary of theaudio-frequency transformer. A singlecircuit jack is connected in the plate cir-cuit of the amplifying tube so that thephones may be connected at this point'when desired. In this circiut the audiostage is shown in conjunction with theuntuned primary receiver described inNo. 30. It may be necessary to connecta by-pass condenser of .0005 mfd. or .001mid. capacity in the position shown at Cl.

In circuit No. 49 is shown regenerativecircuit in conjunction with one stage ofaudio frequency amplification using fila-ment control jacks. These jacks are very

convenient, since with their use it is un-necessary to turn off the filament currentto the tubes not in use. A little study ofthis circuit will show that when thephones are plugged into the first jack,the detector tube alone lights up and whenthe phones are plugged in the secondjack, both tubes are lighted. When theset is not in use it is only necessary toremove the plug and the filament currentis automatically cut off. An uatuned pri-

'------L--....L.------tmltll 1 1 1 1 1 1 . . . . . .+------

aroult 48

2 2



150 RADIO HOOKUPS

1-3.meg. - ,

Clrnlt 4 9 -

mary coup!er is shown as the tuner in of .01 mfd. A grid leak of one megohmthis circuit, although any type of tuner is connected from the grid of the tubemay be employed. A condenser of .0005 directly to the negative of the "A" bat-mfd. capacity is shunted across the sec- tery. In this circuit a variorneter isondary for tuning. Any type of receiv- shown as the tuner, and a .00025 mid.ing tube may be employed providing the condenser is placed in series with thecorrect "A" battery voltage is used. antenna to lower the wave-length.

Circuit No.5!. Those experimenterswho are familiar with the Reinartz circuitwill notice in the accompanying diagramseveral changes, viz., the absence of the

plate coil and the addition of a coil in theantenna circuit, which is for the purposeo~ detuning this circuit so that the effecton the tuning will be zero. Through thismeans the tuner can be calibrated beforebeing connected to the antenna, and itscalibration will remain constant, regard-less of the size and type of antenna towhich it may be connected. The greatadvantage of this detuning coil is the factthat it cuts receiver radiation to zero.For the R.F. choke coil, wind on an or-

dinary size drinking glass about 2~ inches

It sometimes happens that the primaryof the audio frequency transformer burnsout. In such cases the secondary may be

used as a choke coil amplifier and whenused in this connection will function ex-tremely well. The volume obtained maynot be as great as when a transformeris used, but the quality of reproductionwill be excellent. A diagram showinga circuit employing such use of a trans-former is given in circuit No. 50. Adouble circuit jack is also incorporatedso that the detector alone may be usedwhen desired. A grid condenser must, ofcourse, be employed in the grid circuitof the amplifying tube and has a capacity

Circuit G O

23



150 RADIO HOOKUPS

in diameter, 75 turns of No. 24 D.C.C.wire in jumble fashion. Slip off the tumb-ler and wind a few turns of thread aroundthe coil so that it will be self-supporting.The coil should be mounted as near theplate of the tube as is consistent withgood wiring practice and should not beplaced near any of the other coils.Around the same drinking glass wind

50 turns of the same size wire, making aloop for tapping at every tenth turn. Thiscoil Ll is mounted on the tuner panelnear the antenna connection. Connectone end of a 2-foot length of lamp cord

to the switch-point and the other to theantenna, leaving the other ends open.See Cl , Two pieces of magnet wiretwisted together may be used if desired.If selectively is too great. add to lengthof wire.

H the wave-length is to be 150 to 220meters, the coil L2 > is made as follows:On the same tumbler wind in jumblefashion, as before, 5 turns of No. 16D,C.C. wire, making a 3-inch loop fortapping; then continue for 15 turns withanother tap loop and then 5 more turns.Bind, as before, with thread. It will benoticed that there is a 4-to-l turn ratio

of antenna to ground and grid to ground.Maintain this ratio in any other coil thatis made. Also notice that the tuningrange is 150 to 220 meters, and that if acipher is added to the 15 turns that areshunted by the condenser, you will have150. and if a cipher is added to the totalnumber of secondary turns, which is 20.you will have 200, meaning that the ap-proximately range of any coil made withthe turn ratio, as above. may be deter-mined beforehand.Circuit No. 52 . For experimenters who

wish a circuit that is very selective, theone in the accompanying diagram is rec-ommended. The inductances, Ll and L2,

Circuit I'll

are wound of No. 22 D.C.C. wire on S-inch tubing and each coil has 50 turns.These two coils should be mounted atright angles, and there should be at least12 inches between centers. For extremeselectivity a separate unit might be builtconsisting of Ll and the .001 mf. con-denser. These two coils are linked to-gether by the coils indicated by the heavyline in the diagram. This connecting linkis a rubber-covered wire, having as lowa resistance as possible. There is one turnof this link coil around each inductance.If a separate unit is built, as mentionedabove, it might be placed two feet awayfrom the rest of the circuit. < The vario-meter in the plate circuit of the tube isfor regeneration.

? : ! . o O ' M F .

C,b'cult 15~

The type of vacuum tube that may beused is a UV-201A or C-30lA. The lengthof antenna should be about 125 feet al-though this is not very important. 'Circuit N 0.53. One of the most inter-

esting circuits for the experimenter is thehook-up shown in Fig. 53. It is an adap-non of the famous Hartley oscillator cir-cuit. The apparatus required for this cir-cui~ can be easily made by the average ex-perrmenter, The inductance L2 is wound?n a bakelite or hard rubber tube 3~inches 10 diameter and consists of 35 turns'of No. 18 D,C.C. wire, Directly over this

2 4



150 RADIO HOOKUPS

L 2

.OOIHr

..O O (J2 5 1 1 1 :'

CIrcuit"

winding is placed L1 which is 10 turns ofthe same size wire. The movable part ofthe coil, L3 is wound with 20 turns of No.20 D.D.C. wire on a bakelite tube 2%inches in diameter. The tube on which arewound Ll and L2 is placed with its axisparallel to the panel. In the end oppositethat which has the inductance Ll on it.drill two holes diametrically opposite totake the bearings of the rotor, L3. Thesebearings are made of small machinescrews. The rotor does not have to becontrolled from the front of the panel, asit remains in the same position after oncebeing set. 'I'he two variable condensersare placed at the left-hand side of thepanel with the inductances directly intheir rear. With this arrangement veryshort leads are the result.The tuning of the set is extremely

sharp, and as may be expected a vernier

control must be used on the .001 mfd.condenser. The close approach to thepoint of oscillation is evidenced by thefact that the circuit does not "spill over"into oscillations suddenly as is the casewith nearly all regenerators. As the re-generation control condenser is increased,the amplification increases continuously,gradually working into the condition foroscillation. The approach is so close thatboth the incoming signals and the regen-erative whistle can he heard at the sametime when the tuning is very close.The adjustment of the movable part of

the coil is made as follows: The set istuned for the longest wave-length it is de-

sired to receive, with the movable coil atright angles to the main coil. This is thesondition for least amplification or feed-the set just begins to oscillate. It need notbe adjusted after this, and it will be foundback. The movable coil is rotated untilthat the controlling may be done entirelyby the .00025 mfd. condenser.

This circuit will function on any sizeantenna, but it is advised that the totallength be limited to 120 feet. This in-cludes the lead in. The different sizes ofantenna are compensated by the tuningcondenser; that is if the set has been cali-brated and a different antenna is usedthen the readings will be different also.When constructing this set, be sure that

the rotor plates of the .001 mf. variablecondenser used for tuning- are connectedto the filament circuit. Its sometimes ad-visable to. connect this point, that is, the

filament circuit, to the ground. Making theconnections in this way reduces any bodycapacity effect that might otherwise be no-ticed when tuning.Circuit No. 54. Here is shown a re-

generative receiver in conjunction withtwo stages of audio frequency amplifica-tion.The tuner in this receiver is an un-tuned primary coupler and was describedin circuit No. 80. Audio frequency trans ..formers are used in the amplifier andshould not have a ratio higher 'than 5:1.A double circuit jack is inserted after thefirst stage so that the phones may beplugged in at this point. When' the loudspeaker is used. it is plugged into the

2 5



150 RADIO HOOKUPS

lingle circuit jack after the last stage. Ifa . good antenna is used with this receiver,fair volume will be obtained on the loudspeaker on the first stage when local sta-tions are received. The grid returns ofthe two amplifying tubes are connectedtogether and run to the nega tive terminalof a "C" battery which will have a voltageof from three to nine volts, dependingupon the voltage of the "B" battery. This"C" battery has its positive terminal COn-

nected to the negative of the "A" battery.A "C" battery is necessary when a high

voltage is used on the plates, as it cuts

down the current consumption and helpstoward the elimination of distortion.Circuit No. 55. The hook-up shown in

the accompanying sketch is the well-known Reinartz circuit. The efficiency of

'7SJliM3~

C1r~nlt 54

this circuit is due largely to the fact thatall the inductances are brought togetherand concentrated in one small space. Thecoils forming the aerial-secondary andfeed-back inductances may be wound on a2~-inch tube with No. 22 D.D.C. wire,The feed-back coil may be spaced about~ inch from satisfactorily on a groundalone without any antenna whatsoever. Itis also selective and easy to control, a "there are but two adjustments. The selec-tivity of this set the other. If a spider-web coil is used the all around efficiencywill be increased. The coils then are

wound on a form that is 1~ inches in di-ameter. The aerial-secondary coil is tappedat every turn for the first 10, the 12th turnis tapped and connected to ground andthe movable contact of the potentiometer,

Cl.reuit fill

26

is-/O tfetp'll11$

.00025 !1 r .



150 RADIO HOOKUPS

and from the 26th to the 75th turn thecoil is tapped every seven turns. The feed-back coil of 45 turns is tapped at every15th turn. The movable plates of the.000.5 mfd. condenser should be connectedto - the antenna and those of the ll-platecondenser which should be of the verniertype, should be connected to the ground.The inductance should be mounted at leastthree inches back of the panel so that theleads from the inductance will extend di-rectly to the switch points without cross-ing. The dry cell type of tube may beused, but the UV -201A type is recom-mended. With a potentiometer in thecircuit, as illustrated, this set, i f properlyconstructed, should be an excellent DXgetter.It is interesting to note that this circuit

was designed primarily for C.W. recep-tion, but it is one of the most selectivebroadcast receivers known today. The cir-cuit shown in Fig. 55 has only one tube,but audio frequency amplification may beadded very easily.Circuit No. 56. The accompanying dia-

gram shows a circuit that is extremelysensitive; so much so that it will operatevery satisfactorily.

I

II

'----- . . -. .

ClrtJuJt a e

The ground tap is taken from the cen-ter of one coil of the variometer. One endof this coil must go to the aerial bindingpost. When using a ground with no an-tenna, the ground is connected directly tothe antenna binding post. Because of this,this set is especially adapted to beingmade into a portable outfit. A dry celltube is recommended i f this is to be aportable set, although better results willbe found if a large tube is used.It may not be amiss here to say a few

words ,in regard to circuits that are adapt-

able to use in portable sets. Editors ofradio question and answer departments

often receive inquiries asking whether ornot this or that type of set can be used ina portable receiver. This question is one "-that can be answered by anyone knowinganything at all about radio if he will onlystop to consider the situation from a fewdifferent angles. The first important oneis whether or not batteries of large sizecan be carried. Then again, is more thanone tube used? Is a loop to be employedor can a regular aerial and ground beused? It is upon these points that the con-struction of a portable set hinges and noton the actual circuit to be employed. Prac-tically any circuit from a crystal detectorto a Super-Heterodyne can be made intosome type of portable receiving set. Theonly thing that is necessary for the con-structor to do is exercise a little ingenu-

ity in the placement and arrangement ofparts. For instance, grid and plate induc-tances in multi-tube sets should not be ininductive relation to each other. Theyshould be placed so that the windings runat right angles to each other or should be ~far enough apart so that there can be nointeraction between them. Another 'goodexample of this work is the angle at whichthe coils in a Neutrodyne are placed. Thisarrangement also reduces the inductiveeffect found between parallel coils. Thenagain, audio frequency amplifying trans-formers should be accorded the sametreatment. Place the cores at right anglesand distortion and noise win be reduced.And so we can see that the answer to thequestion propounded above is that practi-cally any circuit can be used in a portablereceiver if the instruments used are smallenough and if judgment is employed inarranging them.Circuit No. 57. In tll\ accompanying'

diagram is shown the fundamental circuitfor the Hartley oscillator and a pick-up

Cire1llt &7

coil for the Super-Heterodyne receiver.The inductance Ll is composed of liDturns of No. 22 D.C.C. wire wound on a3-inch tube. The pick-up coil, L2, has 10turns of the same size wire wound on the

same tube spaced about ~ inch from thefirst mentioned winding.

27



150 RADIO HOOKUPS

R eflex H ook ~U ps

Circuit No. 58. This type of reflex re-ceiver is sensitive, selective and gives sig-nMs of excellent volume and clarity Thequality of reproduction depends greatlyupon the inductive relations of the variouscoils, as will be seen by experimentingwith the circuit.The primary and secondary coils are

wound on a 3-inch tube of bakelite or hardrubber. The primary has 10 turns and iswound over the secondary of 50 turns,No. 20 D.C.C. wire being used. Thereare two ways of making the four-coil unit.One is to wind the coils in cylindricalform and the other is to employ spider-web forms. Sand F indicate the startand finish of a two-wire coil made bywinding two wires, side by side, on theform at the same time, the wire being nolarger than No. 26 D.C.C. Itis also ad-visable for one wire to have colored in-sulation So that there will be no dangerof confusing the windings. It has beenfound that the R.F. tube can be moreeasily neutralized if these two wires are

twisted together before winding them onthe form. Twenty turns of this twistedwire are wound on a spider-web form oron a 3-incll tube. This leaves four con-necting ends, two at the start, S, and twoat the finish, F. The S of one coil and theF of other coil are connected. On asecond spider-web form placed about ~inch from the first, are wound 45 turns ofNo. 22 D.C.C. wire. If the 3~inch tubeis being used, the same number of turnsmay be wound on, starting % inch fromthe starting end of the 20-turn coil. Atthe finishing end of the 20-turn coil isplaced the tickler, which has 22 turns ofthe same size wire. If spider-web forms

Circuit ISS

are used, the tickler may be about thesame number of turns, placed on one ofthese forms and variably coupled to thesecondary. It should be noticed that theantenna and secondary coils must not bein inductive relationship to the four coilsjust described.A reflex circuit that is very simple to

build and will prove quite selective is

shown in circuit No. 59. This is knownas the Harkness single tube reflex and

uses a special tuner and radio frequencytransformer. The secondary of the tun-

~ ~ 4~ __~~

{'.(reult li9

er is constructed by winding 55 turnsof No. 24 S.c.c. wire on a 3-inch tube.The primary is of 15 turns, wound di-rectly over the secondary and separatedfrom it by a piece of insulating paper.The secondary of this coupler is shuntedby a variable condenser of 17 plates. Thespecial radio frequency transformer shownas Ll is made in a similar fashion. Thesecondary is wound the same as the spe-

2 8



150 RADIO HOOKUPS

cial coupler but the primary consists of20 turns of wire. The secondary of thistransformer is also shunted by a 17-pla~econdenser. A fixed crystal detector IS

ordinarily used in this receiver, althoughany good crystal detector may be em-ployed. This receiver operates very satis-factorily without the use of any by-passcondensers that are commonly needed inother reflex circuits.

Cin:u1t eo

Another reflex circuit is shown inCirc1~itNo. 60. In this circut, instead ofa radio frequency transformer, a tunedimpedance coil is employed. This coil isshown as Ll and may be made by wind-ing 45 turns of No. 24 S.C.C. wire on a

3-inch tube. A variable condenser C1 of.0005 mfd. capacity is shunted across thisimpedance coil for tuning. Any type oftuner may be used, although in this casea standard variocouple- is shown, thesecondary of which is tuned by a 23-platevariable condenser. A 400-ohm potentio-meter shown as R is employed to keepthe tube in a stable operating condition.This type of reflex receiver will be found

much more selective than that shown indiagram No. 61 . The tuning condenseracross the secondary of the coupler andthe variable condenser across the tunedimpedance coil must both be tuned toexactly the same wave-length before anystation can be received. If the tube tendsto oscillate, the potentiometer lever shouldbe moved towards the positive side tocorrect this condition.In circuit No. 61 we have a simple one-

tube reflex receiver. This receiver incor-porates one stage of radio and one stageof audio frequency amplification. The

same tube is used to amplify at radiofrequency and after detection by the crys-tal shown as D, it again amplifies at

audio frequency. An ordinary vario-coupler may be used for tuning and thesecondary is shunted by a variable con- <,

denser of .0005 mfd. capacity. A potenti-

ometer shown as R is used so that thetube may be kef! from oscillating. Thisinstrument should be of rather high resis-tance; in the neighborhood of 400 ohms.It will be noticed that fixed condensersare connected across the phones and theprimary and secondary of the audio fre-

I quency transformers. These condensersare known as by-pass condensers and areemployed to allow the radio frequencycurrents to pass the high resistance. of thephones and the coils of the audio fre-quency transformers. .Circuit No. 6'2. So much has been said

about the popularity, low cost, and faith-ful reproduction of the reflex circuit, thatmany people are beginnin~ to realize itsimportance and are turning toward It.However, as there are so many reflexcircuits, it is often confusing to the lay-man as to just what circuit he shoulduse. The Rasla reflex circuit, as showr,in the accompanying diagram, is one ofthe simplest and most efficient receiversof this type it is possible to build.

01nult 81

By reference to the diagram. it will benoted that the antenna system is untuned,of a semi-aperiodic nature. The second-ary is tuned by .00035 mfd. condenser ofthe low loss type, but as will be noted.only a part of the secondary coil is in-cluded in the grid circuit. A small bal-ancing condenser tends to obviate the un-desirable creation of oscillations, and alsoserves somewhat as a volume control.Analyzing the circuit we see that it con-

sists of one stage of tuned radio frequency;lmplification, crystal detector, a reflexedstage of audio frequency and two stages

2 9



150 RADIO HOOKUPS

-A +A -8+Circuit Of.

of str.aig-ht audio frequency amplification.The radio frequency transformer is onethat is designed so that its impedance mat-ches that of the fixed detector, thus givingmaximum transfer of energy and efficientcoupling. A .00025 mfd. fixed condenseris shunted across the secondary of the au-dio transformer which is used for reflex-ing. A 30 ohm rheostat is necessary forthe careful adjustment of the detectertube, while a 6 ohm rheostat wilt handlethe audio frequency amplifier tubes verynicely.Circuit No. 63. In the accompanying.

diagram is the Acme reflex circuit, which

has three stages of radio frequency ampli-fication, a crystal detector, and three stages

of audio frequency amplification. Thereare but four tubes used, however, whichshould be of the UV-201A type. Thecrystal should be a fixed detector. Thisis one of the simplest and most powerfulreflex circuits that has ever been designedand if good apparatus is used in it, theresults should be all that can be expectedfrom four vacuum tubes and possibly evena little bit more. Use a good stablecrystal detector as this is an importantpart of the set. A permanent one is tobe desired, if simplicity is one of thepoints in view. .Circuit No. 64. The circuit of the In-

verse Duplex receiver is so made thateach tube performs its duty as a radio

Clheult a

s o



150 RADIO HOOKUPS

60-9011.

4--~-----I+ I/fllllll--~-~-B"

. . . . . . _ _ - - - ~ . . . . , _ _ - - - ~ - J i l l "t

' ;4 •

Circuit

frequency amplifier as well as an audiofrequency amplifier. This circuit is sodesigned that all parts of it are balanced,

which is not always the case in reflex cir-

cuits. This unbalancing of reflex circuitsis one of the chief causes of trouble inthis type of receiver. It is an excellentplan to thoroughly test the radio fre-quency stages of amplification before add-ing on the audio frequency stages. Inthe accompanying diagram the circuit is

shown with a crystal detector instead ofthe electron tube that has formerly beenused. This type of detector should giveexceptionally clear signals and the differ-ence in volume will be hardly noticeable.The primary and secondary coils are

wound on the same 3-inch bakelite or hardrubber tube and are wound with No. 24D.C.C. wire. The secondary has 50 turnsand the primary that is wound over thesecondary separated only by the insulation

Olrcuit 6.! i

64

of the wire; has 10 turns. The radio fre- .quency transformers are also wound on3-inch tubes with the same size wire asthat mentioned above. The secondary has50 turns and directly over this is woundthe primary of 6 turns. Instead of run-ning the grid return wire of the first tubeto the point marked A, it may be con-nected to the movable arm of a ",OO-ohmpotentiometer, which should be connectedacross the filament battery in the usualmanner. This is for getting the proper

bias on the grid of the first tube.In case the experimenter wishes to tryan indoor antenna with this circuit insteadof the outdoor antenna for which it is de-signed. the loop is connected directlyacross the first .0005 mfd. variable con-denser. This will eliminate the aperiodicprimary and the secondary coils of 10 and50 turns respectively. Excellent receptionhas been accomplished on a loop antennawith this circuit, but the outdoor antenna

p

3 1



150 RADIO HOOKUPS

i.recommended for all around good re-ception.The types of tubes that are best adapted

for use in this receiver are the UV201-Aand G~Ol-A. Although the smaller tubes

of .the 199 type may be used, they willsot give the volume that the larger oneswill produce. The crystal should be ofthe fixed type in order that there is notrouble from adjusting it during reception.Circuit No. 65. The S.T.-100 circuit is

a stage of radio frequency amplification,crystal detector, and two stages of audiofrefluency amplification. The S.T. - IDO isone of the easiest reflex circuits to build,there Dcing nothing tricky about it. The__Iprecautions in wiring a set should be•• served, as short leads from and totraasformers, etc. The antenna induct-

alice L1 should be a 35- or 50-turn honey-comb and the tickler coil should be a 75-turn honeycomb. The resistance betweenthe grid of the first tube and the positivefilament should be about 100,000 ohms.This is an essential part of the circuit andif unsatisfactory results are obtained with100,000 ohms, lower values should betried. The "E" battery of 100 volts maybe shunted by a 1 rnfd. condenser. Be-cause there is but one stage of radio fre-quency amplification the S.T.-IOO is notvery effective on long distance signals,Its chief use seems to be in obtaining veryloud signals within a 50-mile range. Alsothe reception on a loud speaker is muchbetter than when phones are used. Byapplying •. 5 to 9 volts on the grids ofboth tubes, the quality of speech and am-plification is materially improved.Circuit No. 66. The Inverse-Duplex cir-

.000.5.lOOf'

cuit shown in Fig. 66 is so arranged! thateach tube does the work of two. I manyreflex circuits some tubes do more workthan others and ·an unbalanced circuit re-sults with correspondingly poor recep-

tion. The Inverse-Duplex is 80 designedthat all parts of the circuit are balanced.Before the audio frequency stages of amp-lification are added, the radio frequencystages and detector should be tested. Alsobefore connecting any condensers in theset, they should be tested for sho.t cir-cuit. If the first part of the circuit func-tions satisfactorily, the two audio frequen-cy transformers may be added. This setis rather a difficult one in which to elim-inate howls, but by reversing the leadsto the transformers this trouble may beovercome. A loop antenna is the proper

type to use. Wind 8 to 12 turns of No.18 wire spaced ~ inch apart on the 18-inch frame. UV -201A tubes or those ofsimilar type should be used, as the set isdesigned to operate with storage batterytubes.The 400-ohm potentiometer that is con-

nected across the filament battery is usedin order to give the proper grid bias tothe first tube. As in every receiver em-ploying radio frequency amplification, thegrid bias is an important factor in thestabilizing of the set, as itallows the tubeto operate at the proper point on the gridvoltage-plate current characteristic curve.

The one big feature of this particularreflex circuit is that the tubes are notin any case overloaded. This is the troublewith the usual reflex circuit but by theInverse Duplex method, the tube that actsas the first stage of R. F. is the second

'---i_ 1 1 1 1 1 1 1 1 1 1 1 1 1 1 . .. . .. . . . !'-'"I

1~-Z2iy ~-------------------------~Orcutt 6 4 1

32



150 RADIO HOOKUPS

(Jircult 67

A. F., while the second R. F. acts as thefirst A. F. Thus the loads are balanced.If the set has a tendency to oscillate or

howl, try reversing the leads of the trans-formers one pair at a time until the noisehas stopped. The use of a "C" battery isgood practice in this as in any circuit thathas more than three tubes, because it notonly reduces ~'B"battery consumption, butalso greatly improves the quality of re-

ception.The loop antenna is of special design.

I t has 15 turns of No. 22 Litz. wire spaced; . . s inch apart wound in a spiral on sticksthree feet long.Use manufactured R.F. transformers

and in the audio amplifier do not usetransformers with a higher ratio than 5to 1.~A good many reflex circuits are hard

to get into correct operation as they arecritical and erratic. This one particularset, however, might almost be classed asan exception to the rule inasmuch as pos-

sibly thousands of them have been builtand practically all of them have workedperfectly without the least bit of trouble.Circuit No. 67. This reflex receiver

has a sensitivity determined by the utiliza-tion of three stages of radio frequency am-plification, one of which is tuned in orderto give a high degree of selectivity. Thisselectivity is increased by the use of a loopantenna.The radio frequency transformers can

be home-made if desired, and the specifi-cations are given below, but it is recom-mended that a standard type of trans-fonner is installed, as transformers are

more or less difficult to construct. Thefirst R . F. transformert Rl, baa a primary

winding of 33 turns and the secondary has105 turns, wound with No, 26 wire. Thewindings are of the "pie" type and themean diameter is 1 3 4 inches. Two of thepie windings are in the primary and threein the secondary, and there is also a littleiron used in the core. R2 has 75 turnson the primary and 400 turns in the sec-ondary, wound with No. 34 wire, the meandiameter of the coils being about ~ inches.

R3 is also wound with No. 34 wire andhas the same diameter. There are 225turns on the primary and 330 turns on thesecondary. Each of these transformershas a little more iron in the core than thepreceeding one. The audio frequencytransformers Al and A3 have a ratio of4 . to 1 and A2 has a ratio of 5 to 1. Thepanel may be about 15 inches long andthe depth of the cabinet about 8 inches.There is a crystal employed for rectifi-cation instead of a tube, because of itsmany well-known advantages.

The three stages of audio 'frequencyamplification are used to get enough vol-ume; it is possible to use as many asthree stages because of the staggeredcharacteristics and the balancing and op-posing of the stray fields of the trans-former systems. In the commercial re-ceiver there is a grounded metal panelused; the lowest connection line in theaccompanying diagram represents thisgrounded panel.Circuit No. 68. This is an English cir-

cuit that has found great favor amongBritish radio fans. It differs from theordinary form of reflex circuits in thatthe audio frequency amplifier has resis-

tance coupling instead of transformercoupling. As a resistance has no natu-

83



150 RADIO HOOKUPS

.005 Mr.

,25 M EG .

.0005 MF:

l M E G O H M S

. ( X I O S M E

50T

ral period of vibration it will not causethe howling which is so common in trans-former coupled reflex circuits. In Fig.68 the first tube acts as both radio andaudio frequency amplifier and the secondtube is the detector. In the plate cir-cuit of the detector is a resistance of 50.-000 ohms, shunted by the condenser.The grid condenser in the first tube cir-

cuit is used for blocking the plate voltagefrom the grid of the tube. The phones orloud speaker are connected in the platecircuit of the amplifier tube in series withthe primary of the radio frequency trans-former, which is preferably of the tunedtype and should be so adjusted that theeircuit will not oscillate at any settingof the condensers .•A plate voltage in theneighborhood of 10 volts, depending, ofcourse, upon the type of tubes employed,will be necessary for good receptlon.'.Fig. 69 shows the standard reflex circuit.The current from the crystal is passed

through a step-up transformer and ampli-fied by the tube. The head-set is includedin the plate circuit of the tube. A "C"battery and potentiometer are recom-mended in this circuit while experiment-ing, but may be dispensed with when thecorrect values are obtained. The 'actionof this circuit is as follows: The radiofrequency currents received by the an-tenna are amplified by the tube, detectedby the crystal, and amplified by the sametube at audio frequency. giving the sameresults that would be obtained from a setusing a one stage R.F. amplifier. detector.and one stage A.F. amplifier. Instead ofusing a tuned radio frequency transformeras shown in the diagram an un-tuned iron

Clrcult 68

core transformer may be used. There arevarious types on the market that will givegood results. The amplification that thiscircuit gives depends largely upon thecrystal detector and the values of the fixedcondensers and other instruments.Somewhat better results are claimed for

the circuit, Fig. 70. In this hook-up thesecondary of the audio amplifying trans-

former is connected to the grid side of thetuning circuit and not to the filament side.

CRYSTAI."--" . .

Circuit 69

9f course there an many other connec-tions that may be tried. such as groundingthe filament, connecting the crystal acrossthe primary coil instead of the secondarycoil, etc. When working properly a goodSIngle tube reflex circuit will give an am.plification of over 8,000 times.Circuit 71 is similar to circut 6 '9 except

34



100 RADIO HOOKUPS

Ciroult 70

that the transformer is omitted and the

currents are amplified directly from the

crystal. The fixed condensers shown are

not marked; it is up to the experimenter

to determine the correct values. The

amplification will be less than that of

circuit 10 as the transformer is omitted.

Slight improvements are embodied in

the circuit shown in Fig. 72. In the first

place the secondary of the amplifyingtransformer 1 S connected to the center tap

end of the coil connects to the grid and

of the secondary of the tuning coil. One

the other to a one-half megohm grid leak

connected to the filament. This makes

'mvs"tAL ®

O1reult Tl

a . bridge circuit and no radio frequencycurrents will pass through the audio trans-former and a by-pass condenser is un-necessary. This circuit is more stable

than the others. The plate circuit alsodiffers. Instead of the usual transformer.a single coil with a slider is used. Thisnot only tunes the circuit but regulatesthe amount of energy taken by the crystalThe coil may be a single layer windingof No. 26 wire on a 2~-inch diametertube. About 80 turns should be used.In the above circuits we have given the

approximate amplification possible. Thisis given as voltage amplification and notenergy amplification. If the voltage am-plification is given as 1,600, the energyamplification is the square root of this,

ctJ."CW t 72

or 40, and the sound will appear about40 times as loud, and not 1,600 times.In circuit 73 the radio frequency currents

are impressed upon the grid and filamentof the tube, repeated in the tuned platecircuit, and detected by the crystal de-tector; the rectified or audio frequencycurrents pass through the step-up trans-former and are impressed upon the gridand filament of the same tube. They areamplified by the tube and repeated in thetelephone headset. Thus the tube ampli-fies both radio and audio frequency cur-rents simultaneously. To explain- why wedo not obtain the amplification that weare entitled to, we must consider therectifying action of the tube as well asthat of the crystal. On account of therectifying action between the grid andfilament of the tube, the incoming radio

frequency currents build up a negativecharge on ..he grid side of the fixed con-

86



150 RADIO HOOKUPS

denser (C) across the secondary of the•audio transformer. This causes a reduc-tion in plate current and the signal isheard in the headset with the crystaldisconnected. With the crystal connected,the rectifying action of the crystal buildsup a negative charge on one side of thecondenser (Cl) connected across theprimary of the audio transformer. Thusfor each group of incoming oscillations anegative charge is impressed across boththe primary and the secondary windingsof the audio transformer, setting up acurrent flow in both windings, which,from the nature of the circuit, must op-pose each other, and unless the ratio ofthe transformer suits the constants of theother instruments, the transformer isuseless. I t is on this account that ex-perimenters have obtained as good resultswith the crystal and transformer removedas with them connected. Now that we

(',lrcult '79

know the trouble we will see how it canbe avoided. It may be well to mentionfirst that this circuit, Fig. 73, is one ofthe simplest and best reflex circuits inexistence today. It has the disadvantageof picking up audio frequency noises fromlighting circuits, the amount of disturb-ance, of course, depending upon the loca-tion of the set.Fig. 74 shows a circuit in which' the

rectifying action of the tube has no effecton the action of the audio transformer.This is accomplished by connecting twofixed condensers in the grid lead (C1) and(C). Condenser (C) is of comparativelylarge capacity, .002 mfds., for it mustpass both radio and audio frequency cur-rents. Condenser (C1) is of small ca-pacity, .00025 mfds., as it should by-passthe radio frequency currents only. Thegrid leak (R) is required. It should beof one-half to one megohm. With this

circuit, the negative charges that accumu-late on the grid must leak off through the

grid leak (R) ; they cannot leak offthrough the secondary of the transformeron account of the blocking condenser (C), '"

and therefore cannot balance out the cur-rent in the primary of the transformer.Experimenters should obtain very goodresults from this circuit. The remainderof the circuit needs no special commentas it is standard; all of the circuits shown

Circuit '4

in this issue and also last month's issueshould be tried out with the double gridcondenser.

A simplified reflex circuit with theadded improvement of the extra grid con-denser is shown in Fig. 75. All this circuit

requires is a standard three circuit tuner.A crystal detector and audio transformerare connected across the tickler windingof the coil. The secondary is connectedacross the small grid condenser as shown.Note that the condensers have been re-versed from the locations shown in Fig.U, merely to show that there are twoways of obtaining the same result.Peck's reflex circuits use no crystal

detectors at all. The tube is used as aradio amplifier, detector, and audio fre-quency regeneration, with an audio fre-quency transformer for the feed-backcoupler. Figs. 76and 77 show two of these

36



150 RADIO HOOKUPS

Cueult 76

circuits. Both are easily tried on thehook-up board, the only additional equip-

ment required being a variable grid leak.

Of course, with an audio frequency

feed-back connection, the circuit willhowl at audio frequency unless the feed-

back is controlled. This is accomplishedby adjusting the grid leak. If the circuitdoesn't work at first try reversing the

transformer connections. A variable grid

(:1l'olllt 77

leak should also. be tried across the pri-

mary of the transformer. The hook-up

shown at Fig. 76 has a tuned plate circuit

for regeneration; in Fig. 77 a tickler feed

back is employed. Honeycomb coils of

about 60 and 100 turns each may be used

in this circuit.

A simple reflex circuit that gives ex-

ceptional volume on local stations is

shown in Fig. 78. Thill hook-up is easily

connected on the hook-up board and re-

quires few clip and tip leads. A Rasco

R. F. transformer is used and the oscilla-tions are controlled by the potentiometer

CIrcuit '7S

The experimenter may try various sizes of

fixed condensers across the secondary of

the audio transformer and he may also

try two grid condensers as shown in Fig.

74. When the proper combination has beenfound a very good one dial single tube

receiving set can be made.

Many improvements are embodied inthe loop receiver shown in Fig. 79. The

tickler or feed back coil is mounted within

the loop, and may consist of two turns

mounted so that the coupling is variable.

Thus we have regenerative amplification.

Rectification is obtained by the crystal.

Circuit 7e

3 7



150 RADIO HOOKUPS

Radio Frequency Hook-Ups

When reception over greater distance isdesired with a crystal receiver, a stage ofradio frequency amplification may beplaced directly before the receiver with-

out altering the wiring in any way, provid-ing a variocoupler is used in the crystalreceiver. A diagram of this circuit isshown in circui: No. 80. The radio fre-quency amplifier consists of an amplify-ing tube and a tuner. The tuner in thiscase is an ordinary variometer with a.00025 rnfd, condenser in the antenna cir-cuit. The plate of the radio frequencytube is connected directly to the antenna

l ± l . o ' a D t I

I l I I. ~. . I I l l l1 1 1 J I +

('~rcuit 80

binding post of the crystal set and theground binding post is connected to thepositive terminal of the "B" battery. No

radio frequency transformer is employed,the variocoupler serving as a tuned radiofrequency transformer.In circuit No. 81 is shown a 2-tube re-

ceiver consisting of detector and one stageof radio frequency amplification. In thiscircuit a radio frequency transformer isemployed. The tuner consists of a standardvariocoupler with the=secondary tuned bya .0005 mfd, variable condenser. As regen-eration is not had in this circuit the tun-ing will be rather broad unless the coup-ling between the primary and secondary

Clrcnit 81

of the variocoupler is kept comparativelyloose at all times. A potentiometer of 400ohms is connected across the "A" batteryleads and the grid return of the amplifiertube is connected to the movable arm. Ifthe radio frequency tube oscillates, thepotentiometer lever should be movedtowards the positive side until the oscil-lation ceases. 1£ this lever can be movedall the way to the negative side withoutthe tube oscillation at any wave-length,the potentiometer may be omitted andthe grid return connected directly to thenegative "A" battery. A filament switchshown at B is employed so tubes may beswitched on or off and so the potentio-meter will be disconnected when the set

is not in use.

In circuit No. 82 is shown a radio Ire-quency amplifier using the tuned impe-dance system of amplification. In thiscase the tuned impedance coil consists ofa standard variometer connected in theplate circuit of the amplifying tube. Astandard grid condenser of .00025 mfd.,capacity is employed in the detector gridcircuit, and the grid leak is connectedfrom the grid directly to the positive leadof the "A" battery, as shown. In this

circuit it is essential that a potentiometerbe employed, as otherwise the radio fre-quency tube would be in a constant stateof oscillation. This potentiometer shouldhave a resistance of approximately 400ohms, A filament switch is also connectedin the negative "A" battery lead. Thetuning of this receiver will be foundfairly sharp. The secondary variable con-denser of the tuner and the plate vario-meter must both be tuned to the samewavelength for any given station. It willbe noticed that on the lower wave-lengths

3 8



150 RADIO HOOKUPS

Circuit

the potentiometer lever must be movedcloser to the positive side to keep thetube from oscillating.Circuit No. 83 shows another type of

tuned impedance radio frequency amplifi-cation. In this case, instead of the va rio-meter. a coil of wire shunted by a variablecondenser is employed in the plate cir-cuit of the amplifier. This coil shown at1, may consist of 40 turns of No. 22 S.C.C.wire wound on a tube 3~ inches in dia-meter. The variable condenser 'shouldhave a capacity of .0005 mfd. This typeof tuned impedance coupling will give

slightly better results as regards sharp-ness of tuning than that described in dia-gram 82. The grid condenser has a ca-pacity of .00025 mfd. and the grid leakhas a resistance of one megohm. Thepotentiometer shown at R must be em-ployed and should have a resistance ofat least 400 ohms. A variocoupler isemployed' in this circuit, the secondaryof which is shunted by a variable con-denser of .0005 mfd. capacity. As a radiofrequency tube in this type of circuit willoscillate very readily great care should be

82

ttaken that it is handled correctly so inter-ference is not created in nearby receivingsets.In circuit No. 84 is shown a radio fre-

quency receiver which if correctly builtand operated will give exceptional results.This receiver consists of one stage oftuned transformer coupled radio frequencyamplification with regeneration in the de-tector circuit. The coils L, Ll and L2 arethe primary, secondary and tickler of anuntuned primary coupler. This untunedprimary coupler was described in diagram30 in this book It will be noticed thatthis is circuit No. 30 with one stage ofradio frequency amplification connecteddirectly ahead of the detector. The tunerused in the antenna system consists of aprimary and secondary which is identicalwith the primary and secondary of coilsLand Ll. The secondary of this tuner isshunted by a variable condenser of .0005mfd, capacity. The untuned primarycoupler secondary must also be tuned witha condenser. of the same capacity. Bothc o n d e n s e r s must be t u n e d to the samewave-length to receive any station. As

Clreult 83

.0002$

39



150 RADIO HOOKUPS

Circuit M

the regeneration obtained in the detectorcircuit is equal to an extra stage of radiofrequency amplification, this receiver willduplicate the results of most three-tubeR.F. sets. No potentiometer is requiredin this receiver. '

Circuit No. 85. Where long distancereception is desired, together with simp-

licity of tuning; the circuit shown heremay be used. This consists of a tuneremploying two stages of radio frequency

amplification. As regeneration is not em-ployed in this circuit, a coupler should

be used which is capable of very loosecoupling between the primary and second-

ary. otherwise the tuning will be broad.A variable condenser of .0005 mfd. capac-

ity is employed across the secondary ofthe coupler for tuning. To avoid capacity

effects, this condenser must be connectedwith the rotary plates to the filament. Ifa good make of radio frequency trans-

former is used. the, tubes will oscillate

.0005

and consequently a potentiometer mustbe employed so that this oscillation can be

controlled.Circuit No. 86. Here we have a circuit

combining one stage of radio frequency

with regeneration in the detector circuit.

As one stage of audio frequency is alsoused, a loud speaker may be employed onpractically all stations received. The an-

tenna tuner consists of an untuned pri-mary coupler without the rotor. Theradio frequency transformer is an ordinary

untuned primary coupler, like that de-

scribed in circuit No. 30. The primary ofthis coupler must be wound with largewire, of not more than 10 turns. The

secondaries of both couplers are shuntedby variable condensers of .0005 mfd. ca-pacity for tuning. Both condensers must

be varied at the same time, as both sec-ondary circuits must be in resonance be-fore any station can be picked up. No

potentiometer is necessary in this receiver.

/-Smer·

p

-+-ttl 1111l0~--.L.---r-----J

111 !111111 1 ! I I I I I I I '

Cl,.eult 85

40



150 RADIO HOOKUPS

the grid return of the first tube beingconnected directly to the negative of the"A" battery. Properly handled, a circuitof this kind will be equivalent to one hav-ing two stages of radio frequency ampli-fication... Circuit No. 87. A long distance re-ceiver employing three stages of radio fre-quency amplification is shown in diagramNo. 87. This type of circuit may be usedwith a loop with excellent results, but ifdesired, a tuner may be employed with anantenna and ground. A variable condenserof .0005 mfd. capacity is employed fortuning and may be used to tune a stand-ard coupler or a loop. A potentiometer of400 ohms is connected across the "A"battery leads to control the oscillations ofthe tubes. Where a potentiometer is used,a filament switch should always be em-

fJmey.

Circuit 8G

ployed so that this part of the circuit i salways disconnected when the receiver isnot in use.Circuit No. 88. The obove diagram

shows a simple single circuit regenerativereceiver, having a stage of tuned impe-dance coupled radio frequency amplific-ation. A variable condenser C1of .001mfd. capacity ,and a honeycomb coil, La.having 35, 50 or 75 turns, form the an-tenna tuning circuit. Coils V and LSmay be those of a variocoupler, across theprimary of which i s shunted a variablecondenser, having a capacity of ,0005 mfd..L' acts as a tickler coil, and supplies re-generation in the detector circuit. A po-tentiometer is required to supply theproper grid bias to the radio frequencytube, and should have a resistance of be-tween 200 and 400 ohms. Two SS-turn

C.ircuit 81

41



150 RADIO HOOKUPS

/-----Potel1/iometer

Clrenlt 88

honeycomb coils may be used instead ofthe variocoupler, in which case the leadfrom the plate of the first tube is con-nected as indicated by the dotted line inthe diagram. The grid leak R of 1 meg-ohm is connected between the grid andthe negative filament binding post of thedetector tube.Circuit No. 89. This circuit is an ex-

cellent one for the reception of C.W. sig-nals. The four inductances shown arehoneycomb coils, their size depending onthe wave-length band to be covered. The

variable condensers C1

and C2

have a ca-pacity of .0005 mfd, and c a is .001 mfd.The plate voltage on the oscillator tube isnot critical and may be 45 volts. Thefirst tube, called the modulator, is connect-ed across the oscillating circuit of the os-cillator tube. The space between the fila-ment and the plate acts as a resistance,the value of which is varied by the in-coming signals impressed upon the grid.No "B" battery is necessary for the mod-

ulator tube, as its plate is supplied byhigh frequency current from the oscil-lating circuit.This circuit may also be employed for

the reception of broadcast programs bythe use of the proper size inductances.c.tCils U and U may be a variocoupler andinductances U and L' may be 50 and 25turns duo-lateral coils respectively. Thisrather unique circuit should prove of greatinterest.Circuit No. 90. In this diagram is

shown the Superdyne receiver, with two

stages of audio frequency amplification.V is four turns of No. 22 D. C. wirewound directly over the 42 turns of Lt.These windings are on a tube four inchesin diameter. V is 36 turns of the samewire on a rotor, which is 3~ inches indiameter. This rotor is inserted half wayinto one end of the four inch tube and isarranged with bearings for rotation. Theplate inductance coil is 45 turns of thesame wire, wound on a four·inch tube.

+

Circuit 89

42



150 RADIO HOOKUPS

CIrcuit 90

The variable condensers, which should beof the vernier type, have a capacity of.O{)05mfd. When constructing the set, itis important that the plate coil be at rightangles to the coupler to prevent any in-

ductive effects. This set wilJ give excel-

lent results also with a short indoor an-

tenna connected to the grid side of V'.the negative side of the "A" battery being

grounded. This eliminates V, which is

used for an outdoor antenna. A grid leak

is sometimes necessary, depending uponthe type of detector tube used and is

placed in the position shown by the dot-

ted resistance R.Circuit No. 91 . The Teledyne circuit is

one which has stood the test of time and

is famous for its extreme selectivity and

the fact that it will not radiate. This set

has a wave-length range of 200 to 550

meters and has the same dial settings atall times for a given station. The vario-

couplet' is a a-inch length of S-inch tubing

for the stator and a ~-inch length of213-inch tubing for the tickler coil. The

tickler L' has 28 turns of No. 26 S.S.c.wire and the stator U has 39 turns of

No. 24 S,S.c. wire. The inductance Uconsists of four turns of No. 24 S.S.C.wire, wound directly over L B , but sep-

arated by a strip of varnished cambriccloth. A standard variocoupler may be

used instead of V and V. For U wind

68 turns of No. 26 5.S.C. wire, tapped

at the fifteenth turn, on a S-inch tube.

Circuit No. 92. For the fan who wishes

a set that is stable and excellent for DX

work, we can recommend the one shownin Fig. 92. It is an English circuit andbuilt entirely of standard parts. The vari-

ometer in the antenna circuit and thevariocoupler that is used as a radio fre-

quency transformer should be of a high

grade, for the proper functioning of thecircuit is dependent upon their quality.

The 400-ohm potentiometer is used to

Clrcu.it Dl



150 RADIO HOOKUPS

,t)(J()SI1ld

place the correct grid bias on the radio

frequency tube. The cores of the audiofrequency transformers are shown con-neeted to ground, but this is optional.Connect the stationary plates of the vari-

able condenser in the antenna circuit to

the antenna binding post and those of

the variable condenser across the stator

of the variocoupler to the plate binding

post of the tube. UV -199 tubes will work

very well in this set, but it is recommend-ed that UV -201A tubes be used for the

best results. The audio frequency trans-formers should have a ratio of 5 or 5~

to 1. At least 90 volts "B" battery should

be connected to the plates of all the tubes

with the exception of the detector.

Circuit No. 93. To dwell at length uponthe wonders of the Neutrodyne receiver

would be rehearsing an oft told tale.

However, no series of circuits would becomplete without one. The hook-up shown

in Fig. 93 is the standard one that wasinvented by Prof. Hazeltine, except that

there has been .added two stages of audiofrequency amplification. A variometer

CIrcuit ~

may be usel'for obtaining regeneration.

This is placed in the lead from the plate

terminal of the third tube to the primary

of the next transformer. This will con-siderably improve the reception of weak

signals and giYe a mote uniform action

over the entire range of broadcast wave-

lengths. Do not try to force loud signals

by using too much "B" battery; 67~volts is usually sufficient and no more

than 90 should ever be used. The con-densers shunted across the secondaries of

the "neutroformers" have 17 plates and

by careful adjustments when placing the

dials on them, stations can be tuned in

at approximately the same readings for

all three. UV-201A type of tubes will be

best in the four amplifier stages and theUV -200 type should be used as a detector,although a 201A may be used.

Circuit No. 94. In Fig. 83 is shown anEnglish circuit comprising three stages of

radio frequency amplification and a detec-tor. 21 and 22 are choke coils and are

wound on a tube 2 inches in diameter, Us-ing 350 turns of No. 30 B. & S. gauge D.

ctrMllt 98



150 RADIO HOOKUPS

C.C. wire, Ll and L2 are made of 54turns of No. 20 B. & S. gauge D.C.C.wire wound on a 3-inch tube. The vari-ity of .0005 mfd. The three con-densers in the plate circuits of thetubes, C3 and C4, have a capacity

of .0005 mfd. and C5, a capacity of.00025 mfd. The resistances, R5, R6 andR 7, have a value of 70,000 ohms. There

are shown two resistances, R8 and R9,of a resistance between 50,000 and 100,-000 ohms, that may be used instead of thechoke coils. UV -199 tubes may be usedin this set, but UV -201A tubes will give

better volume. In this circuit althoughthree stages of radio frequency amplifica-tion are used. there is but one condenserto tune, controlling these three 'stages.With the other condenser in the grid cir-

cuit of the first tube, this makes the setas easy to tune as one with but onestage of radio frequency amplification anddetector.

Circuit No. 95. For the fan who islooking for a set that brings in the sta-tions consistently we can recommend the

circuit shown in Fig. 95. It has two sta-ges of transformer coupled radio frequen-

cy amplification, detector, and two stages

I(X)Ohm

POl

t"Jrcult H

of audio frequency amplification. One ofthe greatest advantages of the set is thatthere are but two controls-the .0005 mfd.condenser shunted across the loop an-tenna and the potentiometer that adjuststhe grid bias on the first two tubes. Any

good make of radio frequency transformermay be used. However, proper precau-tions should be taken to prevent any in-

ductive coupling between them. The con-denser should be of the low loss type and

a vernier adjustment is essential. UV-201A tubes are recommended for use in

this circuit.

Above it was mentioned that any goodmake of radio frequency transformerwould suffice in the plate circuits of the

first two tubes; it should also be stated

that the transformers should be builtaround laminated iron cores. When pur-

chasing radio frequency transformers, thebuyer should ascertain the wave-lengthband that the transformer is designed to

cover. If the receiver is designed ferbroadcast reception the transformersshould be designed to cover a wave-lengthband from 200 to 600 meters. The selec-tion of the radio frequency transformers

should be carefully made; as the receiver

+A-B'

CIJ'cult t5

45



150 RADIO HOOKUPS

Clrcult 86

will not function at maximum efficiencyunless there are exce'[len]; transformers in

the circuit.

Circuit No. 96. A new and ingenioussystem of resistance coupled radio fre-quency amplification is shown in the ac-

companying sketch. Not only are the

vacuum tubes used as amplifiers, but theyare also employed as resistances. Thechief feature of the circuit is the minimi-

zation, if not the complete elimination offoreign noises and distortion. The induc-tances LI and L2 are wound on a three-

inch tube. The secondary of 60 turns iswound on the tube first, over which isplaced a strip of varnished cambric for in-sulation. On this cambric is wound the

primary of 15 turns. The condensers Chave a value of .0003 mfd. The resistanceRl is 1 megohm and R2 is 2 megohms.

The second and fourth tubes are of theWD-U type because a separate filament

battery must be used for each. The other

three tubes should be of the UV-20lAtype for best results. If it is desired touse a loop antenna, the first coupler maybe eliminated and the loop may be con-

nected at the points marked X. As in

all resistance coupled amplifiers, the volt-age of the "B" battery must be higherthan in the ordinary tuned plate or otherstyle circuits. The exact plate potential

required will vary with the type of tubeused. The high degree of amplificationand clarity of signal obtained with this

circuit is truly remarkable. The construc-tion is well within the scope of the av-erage experimenter.

Circuit No. 97. The secret of this set'ssuccess lies in the blocking tube used be-tween the first and second regenerative

circuits. Oscillations are controlled en-

tirely by the two ticklers, there being no

potentiometer, which adds greatly to thesimplicity of control. The couplers are

alike as to size and windings. They maybe made with any ISO-degree variocouplerform. First wind on the stationary form

40 turns of No. 24 D.S.C. wire. Directlyover this winding, a strip of cambric

should be placed, over which are woundseven turns of the same wire. The tickler

coil should have 40 turns of the same

size wire. These three windings shouldbe wound in the same direction. The

variable condensers Clare .0005 mfd. and

+

A

~ - - - - - - ~ - - - - - - - - ~ - - - - - - - - - - - - - - - - - - ~ - - ~ ~ ~ - - ~ - - - - - - - - - - - - - - . _ - - ~ - - - - - - - - - - ~ : +c

Clrentt 9'l

46



I50.RADIO HOOKUPS

L_ i_ ~ _L ~-- .-----~.

C2 have a value of .0005 mfd., es, thegrid condenser, is .00025 mfd. R2 and RSare resistances having a value of 2 meg-ohms and the resistances R4 are am-perites. Results may be obtained usingeither a loop or an outside antenna. If aloop antenna is used, the primary of thefirst variocoupler is eliminated from thecircuit, the loop being connected in serieswith the secondary.Circuit No. 98. The circuit numbered 98

is one to delight the heart of the experi-menter. It requires six tubes, but everystage of amplification is coupled to thepreceding one in a different manner. Theexperimenter may vary these couplingplacements in any way he wishes.The constants are as follows: One is

a standard two-coil type of coupler withan untuned, fixed coupling, primary. Pri-mary "P" may consist of about 10 turnsof No. 24 D.C.C. wire wound at the end ofsecondary "S." This secondary consistsof about 50 turns of the same size wirewound on a three-inch tube, but spacedabout M inch from the primary.Unit two is a standard radio frequency

transformer. It will probably be best to

use a high-grade iron core radio frequencytransformer, as shown, rather than an aircore type.Unit three incorporates resistance coup-

ling with a plate resistor "R:' 'Variable be-tween 25,000 and 250,000 ohms. The work-ing value of this resistance will be close to100,000 ohms.Unit four shows how a variometer is

used for the tuned impedance type ofcoupling.Unit five shows 'a choke coil type of

coupling known as the "T. A. T." system.The natural period, or wave-length, of this

coil is outside of the operating rangeof

the set and functions mainly as an indue-

Circuit 98

tive resistance. It comprises about 250turns of No. 30 D.C.C. wire wound on a2~-inch tube.Unit six employs tuned impedance, but

instead of using a variometer, as in unitfour, a coil is shown tuned by a variablecondenser. This coil may consist of about50 turns of No. 24 D.C.C. wire on a threeinch tube.Condensers "C'; are blocking condensers

used to prevent the plate current being ap-plied to the grids of the tubes. They maybe of about .0005 mfd. capacity. The de-tector condenser, C1, is of .00025 mfd.capacity. Variable condensers C2 are of.0005 mfd. capacity, C3 is about .001 mfd.,C4 about .05 mfd.Resistances Rl are one megohm grid

leaks.

Clrcnlt 99

The potentiometer has a resistance of

200 to 400 ohms.

Circuit No. 99. Very few experimenters

are aware that audio frequency trans-formers may be used as shown in Fig.99. This hook-up is one Which will makethe set operate on a wave-length in theneighborhood of 6,000 to 10,000 meters

47



150 RADIO HOOKUPS

and up. As may be seen in the diagram

two variable condensers are employed,having a capacity of .001 mfd. (43 plates).If the experimenter has several types

of transformers on the bench, it wouldbe an interesting thing to determine what

sort of reception would result with sev ..eral stages of this sort of amplification.

There is no reason to believe that it

would not be possible to pick up the longwave stations using a circuit of this type,because the longer the wave-length, i, e. ,the lower the frequency, the more effi-ciently will the set operate. If the inputtransformer of a pair of push-pull trans-

formers is available, the tapped windingwould be used to change the wave-length,as tapping in one, either part of or the

whole winding would act as a differentamount of inductance in the circuit. This

transformer would of course be used in theantenna and ground circuit, as primary

and secondary... Circuit No. 100. It is a safe bet thatone out of every five receivers now on the

LU ~ r - - - - - - - - - - - - - - - - - - - - - -

size wire being used for the primary. A.0005 mfd. variable condenser is shunt.e,daround the secondary and will be found ...to give excellent selectivity. The regen-

erative qualities of the three-circuit tunerwill still- more enhance the receptive abil-ity of the receiver as a whole.Whether two stages of transformer ..

coupled audio, three stages of resistance-coupled or one stage of push-pull amplifi-cation are used, the circuit will give unex ..celled results when properly wired.For the beginner who desires to build

the tuner himself. the following inforrna-tion may be helpful. The primary con ..

sists of twelve turns of No. 12 D.C.C.wire on a tube three inches in diameter.The secondary can be wound on the same

tube about one-half inch away and con-sists of 55 turns of No. 16 D.C.C. Thetickler coil is wound with No. 22 D.C.C.on a smaller size diameter tube and con ..tains 34 turns. It should be mounted inclose inductive relation to the secondary

and should be variable in coupling to it.

•

. O O O S

-A0-----0-8IS +S O

Circuit

market is a regenerative set employing 8or more tubes. The owners of such a set

experience interference which often can-not be eliminated readily and many of

them resort to a wave trap as a remedy.By the addition of one tube more, it be-

comes possible to increase greatly therange and selectivitv of the set. The ex-tra tube is used -in the capacity of aradoi frequency amplifier, which through

the use of a small variable condenserknown as a neutralizing condenser, af-fords protection against radiation andserves as an aid to distance-getting.

The antenna is connected to a six turnprimary winding on a form S~ inches in

diameter. This winding is placed in thecenter and above a secondary consisting

of 00 turns of No. 22 D.C.C.1 the same

+ € 2 i . - - - - - - - - - - - - - - - ~1 00

If it is desired. a standard three cir-cuit coupler of the ordinary type available

on the market today may be used forthe tuning coil indicated by P, Sand T inthe diagram.

A word about the auxiliary equipment.The antenna should be a single wire about

100 feel long and well insulated. The

ground connection should go to a coldwater pipe and a good clamp employed

which will insure a permanent connection,The small neutralizing condenser wilt

have to be adjusted occasionally andshould have a value of 16 mfd. maximumcapacity.

Circuit No. 101. The receiver that is

shown in the accompanying diagram isone that is non-radiating if properly ad-justed, and extremely selective. How.

48



150 RADIO HOOKUPS

...._ 8 45 V . . . e 9OY.

Circuit 101

ever, a word of precaution should be in-serted here: if the set is improperly ad-justed it becomes a powerful squealer.Three bakelite or hard rubber tubes 2~

inches in diameter and 6 inches in lengthare required. First there is wound on 45turns of No. 22 D.C.C. wire and' }i of aninch away from this winding is wound 6turns of the same size wire, which is theprimary coil. The secondary winding is

then continued for another 45 turns, thusmaking two 45-turn coils in series on thesame tube. Then the compensating wind-ing of 6 turns is wound on, in theopposite direction from that of the othercoils on same tube.

SOfurns

.0005f.

Clr(luit lOt

The above description applies to two ofthe transformers, the third being slightlydifferent in that the compensating coil iswound on a small rotor which is placedat one end of the tube. This rotor is apiece of bakelite tubing 2 inches in dia-meter and one inch long, at one end ofwhich is placed the 6-turo winding. Hereit is unnecessary that the \Vindin~ be inthe opposite direction, as the coli itself

may be rotated through 180 degrees andthus change its polarity. This last coildescribed is used in the grid circuit ofthe first tube, the other two transformersbeing used in the second and third tubecircuits .

400.h

potentiometer

45 V . +

49' " ' , ..,.. .



150 ~ADIO HOOKUPS

1ST. 501:

.0 01 M F.

Circuit lOS

There is not shown in the diagram anyform of audio frequency amplification, butthis is placed after the detector in the con-ventional manner. Type UV201-A orCaOl-A tubes should be employed.The field of experimenting in radio is

very large. One fundamental circuit canbe used in many variations which willstill further resolve themselves into othersof more or less complexity. Thus, radiofrequency amplification can take place intypes of tuned and untuned circuits, bothof which may be neutralized and may

be effected by means of resistance, im-pedance and choke coupling, up to sev-eral stages of amplification.The same applies to audio frequency

amplification in the measure that severaltrPes of coupling may be employed; re-sistance, choke, transformer and push-pull,The detector tube can be regenerative,non-regenerative, superdyned or hetero-dyned. These different methods areadaptable to other variable factors, so

that the number of combinations possiblebecomes indeed great.The general tendency in circuit design

is the use of no more than three stagesof radio frequency amplification, thoughmost commercial receivers incorporatetwo steps. Again, two stages of trans-former coupled audio frequency ampli-fication are used to a greater extent thanother types.

Experiment [ There is a vast field forimprovement in circuit design and, lastbut not least, record the results of yourwork. Such records may become of great

value in the future.Circuit No. 102. The three-tube circuitthat is shown in Fig. 102 is not difficult

-A +A +6 +6-0 90\1. 45V.

of construction and, if properly made,

should give excellent results. The pri ...

mary and secondary coils, which are

wound on the same a-inch bakelite or

hard rubber tube, consists of No. 24D.C.C. wire. The aperiodic primary has10 turns and the secondary, over whichthe primary is wound, has 50 turns. Thetwo coils in the plate circuits of the radiofrequency amplifier tubes are 50 turns ofNo. 24 D.C.C. wire, wound on a a-inchtube. The grid leak across the secondtube is 1 megohm and that across thedetector has a resistance of 2 megohms.Circui: No. 103. Resistance coupled R.

F. amplifiers at wave-lengths below 600meters give rather mediocre results, butif a tuned circuit is used instead of theusual grid leaks, much better results· areobtained. Such a circuit is shown in Fig.

103 . The resistances should be variableso that they may be adjusted to preventoscillation of the circuit at any wave-

length.The antenna and secondary coils are

wound on a S-inch bakelite or hard rub-ber tube. The secondary of 50 turns orNo. 24 D.C.C. wire is first wound on thetube and over this is wound the 15 turnsthat form the primary. The two coilsthat are in the plate circuits of the radiofrequency amplifier tubes are 50 turns ofthe same size wire wound also on 3-inchtubes. The blocking condensers of .0005mfd. and .00025 mid. in the plate circuitsof the first two tubes should be testedbefore being installed, for, if they areshorted, the plate voltage will be intro-duced into the filament circuit. and the-tubes blown out.

60



150 RADIO HOOKUPS

Super Regenerative Hook-Upa

Circuit No. 104 shows a super-regenera-tive receiver which, if correctly construct-

ed and operated, will give remarkable re-

sults on all stations received. A loop isused for this type of receiver and is tunedby a variable condenser of .0005 mfd.capacity. Coil L is a honeycomb or duo-lateral coil of 1,500 turns and coil L1 isont of 1,250turns. These coils are shunt-ed by a fixed condenser C of .004 mfd.capacity. A standard variometer is in-serted in the plate circuit, which will con-trol the regeneration. A fixed condenserC1 is also shown connected across the

phones, but it may sometimes be dis-pensed with, with no loss in efficiency.When receiving, there wilt always be inevidence a high pitched whistle knownas the variation frequency. If this

leop

Circuit 104

whistle is too bothersome it may be re-duced by decreasing the size of the con-denser C.Circu·it No. 105 shows a simplified and

improved super-regenerative circuit knownas the Autoplex. In this circuit two vari-

ometers shown as Land Ll are em-ployed to tune the grid and plate cir-cuits. These variometers must be of goodmanufacture and should have a large valueof inductance. Only one honeycomb coilof 1,250 turns shown at L2 is used inthis receiver. This receiver will give everygood results with an antenna or groundalone, connected to point A. If a groundis to be used with the antenna, it shouldbe connected to point B. As a rule bestresults are obtained with an antenna ofabout 50 feet in length.A unique form of super-regenerative re-

ceiver known as the Flewelling circuit isshown in ,i"uit No. 106. This circuit does

not employ large sized honeycomb coilsas do most "supers," but instead, usesthree condensers of .006mfd. capacity each.The inductances Land Ll may be theprimary and secondary of an ordinary

A

Circuit 103

variacoupler. It might prove of ad'9'an-tage to have the primary of this couplertapped every 10 turns in the usual way.The secondary used as a tickler how.ever, must be wound with at le~st 100

turns of wire for the best results. Twogrid leaks shown as R are employed andmust be variable. The resistance of theseleaks will vary from 1 to 10 megohms.

Clreult 101

The' variable condenser C which is usedfor tuning, has a capacity of .0005 mfd.(23 plates). The "B" battery in this re-ceiver must be fairly large and can be ofany voltage from 90 to 150. A hard or

amplifying tube must be used in thisreceiver if best results are to be obtained.

51



150 RADIO HOOKUPS

A ground is not shown in the diagram,as' it is usually not necessary, but onemay be tried at the point shown as A.In circu;t No. 107 is shown a modified

and greatly simplified Flewelling circuit.The same tuning system is used in thisreceiver as was shown in circuit No. 106In any Flewelling receiver the tickler coilin the plate circuit must be wound withat least 100 or 120 turns of wire. Only

Circuit 107

one fived condenser of .006 mfd. is usedin this receiver. This condenser may beshorted by the switch F. so that thereceiver can be used as an ordinary singlecircuit regenerative set. When used

as a "super" the switch is thrown toas a super-regenerative set, local stationsquired, When used as a simple regener-ative receiver the switch is thrown topoint 2 and a ground is connected topoint B, as shown by the dotted lines. The

variable condenser Cl may have 11 or 2Sed. The grid leak R is variable and hasplates, but the smaller size is recommend>. ,a resistance of from 1 to 10 megohms.When this receiver is operating correctlyas a superre-generative set, local stationswill be strong enough to operate a loudspeaker.Circuit No. 108 . Although the Super

Regenera tive type of set is a more or Jessdifficult one to master. when the experi-menter does get it adjusted properly theresults obtained are gratifying. In Fig.lOS is shown a two-tube "Super" that pre-sents no great difficulties of construction.The inductance Ll consists of 16 turnsand L2 of 40 turns of No. 26 D.C.C.wire, both coils being wound on the sameS~-inch tube, with ~ inch between wind-

ings. The inductances of 1,250 and 1.500turns should be of the honeycomb coiltype and should be in inductive relation-ship with each other. The loop should beabout three feet square and have 10 turnswhich are spaced % inch apart. To op-erate at maximum efficiency, a UV -201 Atype of tube should be used and at least90 volts on the plate of the first tube,the oscillator and 45 volts on the plateof the second, which is the detector, al-though this latter figure may be varied.depending on the individual tube.Another type of super regenerative cir-

cuit is shown in circuit No. 109 and isknown as the Bishop Ultra-regenerator.In this receiver two fixed condensers Cland C2 of .002 mfd., capacity are em-ployed. A fixed resistance of 12,000 ohmsis shunted across these condensers. The

.00025

m t:

Clreult 108

52



150 RADIO HOOKUPS

tuning inductance L may consist of 80

turns of wire tapped every 10 turns and

the tuning is done by means of the vari-able condenser C, which has a capacity of

.0005 mfd. Regeneration is obtained by

means of the tuned plate method and avariometer of standard size is employed

for this purpose. A radio frequency chokecoil, shown as Ll is also inserted in theplate circuit between the variometer andthe phones and consists of a honeycombor duo-lateral coil of 400 turns. A fixedgrid leak is shown in the circuit, but itis always advisable to use a variable gridleak of from 1 to about 10 megohms.

Circuit lGD

Amplifier and O scillator H oC ?k-U psCircuit No. 110. In this diagram we

have a circuit of a 2-stage audio frequencyamplifier which may be added any stand-ard one tube receiver. Audio frequencytransformers are used and a ratio of nothigher than five to one is advised. Onesingle circuit and two double circuit jacksare employed. thus allowing either de-tector, first or second stage of audio fre-quency to be used. The output of thedetector tube is connected directly to thetwo input binding posts on the amplifier.A fixed condenser C is shown shuntedacross the primary of the first transform-er. This condenser is of low capacity,approximately .00025 mfd. and is employedto compensate for the capacity of thephone cords when the phones are re-moved from the detector circuit. If thiscondenser is of the right size there willbe no need of retuning when the changeis made from the detector to the firststage. The same "A" and "B" batteries

are employed for both detector and am-plifier.All that is necessary is to connect the

positive and the negative filament bind-ing posts of the detector to the respectiveterminals of the "A" battery and take atap off at 22% or 45 volts on the "B"battery and connect it to the plus "B"battery post of the detector on the re-ceiver. No wire need be connected to theminus "B" battery binding post on thereceiver as the negative circuit of the "B"battery is completed to the "A" batteryin the audio frequency amplifier.The type of tube to be employed in

this audio frequency amplifier circuit is amatter of preference. IfWD-ll. WD-12or UV -199 tubes are used, employ a 1~volt "A" battery for the first two typesand a 4~ volt "An battery and 25 toS O ohm rheostats for the last mentionedtype. "B" voltages from 45 to 60 can besafely utilized. If UV-201A or Western

o

C1rcalt 110

53



150 RADIO HOOKUPS

that may be varied from .25 to 1.0 meg-

ohm. The electron tube should be a tJX201-A or C301-A. in order that the plate

voltage necessary for the functioning ofthe stage of amplification may be appliedwith safety. The rheostat is placed in thenegative lead of the filament and the gridreturn, i. e., the lead from the grid leak,is connected to the negative lead, but be-tween the rheostat and the "A" battery.The plate voltage applied to the input sideof the amplifier should be about 45 to 60volts and that applied to the output shouldbe between 60 and 90 volts.

Circuit No. 112. Where an audio fre-quency amplifier is desired, which willgive very little distortion, three stages of

resistance coupled amplification are ret-ommended. Distortion is always presentwhen audio frequency transformers areemployed. and the circuit shown. wilt befree from this trouble. As a resistancecoupled amplifier does not give as muchvolume as one using transformers, threestages will be required instead of two. Theresistances R should be approximately 50~000 to 70,000 ohms. Grid condensers Care employed in the grid circuits andshould be of fairly high capacity, approx-

imately ~ mfd. These condensers mustbe employed so that the plate voltage isnot applied to the grid of the tubes. The

resistances shown as Rl are ordinary gridAudio frequency transformers have leaks of approximately ~ megohm resist-

many advantages, which need not be men- anee. Best results will be obtained withtioned here as they are so well known. a rather high "B" battery voltage and 120In Fig. 111 is shown a type of amplifier to 150 volts are recommended.that may prove to be a mosttinteresting n is necessary, no matter the type ofstudy and, at the same time. quite inex- tube employed, that a high HB" voltagepensive to construct. The only materials be employed, as there is a considerablenecessary are an audio frequency choke drop of potential across the resistances,coil which may he the secondary of an thus making the effective plate voltage aaudio frequency transformer, a fixed con- good deal lower than the actual voltagedenser having a capacity of .006 mfd. and of the "B" battery.

i a variable grid leak having a resistance' This circuit is shown to be used in con ..

Electric E tubes are used, a six volt "A"battery will be required, and 25 ohm rheo-stats i f those of the first mentioned typesof tubes are employed. "B" voltages from4:5 to 100 may be used.Circuit No. 111. Very few radio ex-

perimenters pay much attention to audiofrequency amplification because the detec-ing part of the circuit seems to hold amuch greater interest. However, the studyof audio amplification is a most interest-ing one, the ultimate goal being volumewithout the sacrifice 0 .£ purity of tone.

C,boeult 111

cInput

A+

Cireult 1U

54



150 RADIO HOOKUPS

l 1 1 pUt

7 0 1 / . /e o V .

_ l l l l l . I ' I l l l l l l l l l - - i ' - - - . . . . . . . . . . . . . _ - - - - '

junction with any standard receiving cir-cuit and is arranged so that the "A" and"B" batteries are common to both. Thereturn circuit to the filament of the firstresiatance-R is completed through the re-ceiver in use.Circuit No. 113 . Here is a three stage

audio frequency amplifier combining anaudio frequency transformer and resist-ance coupled amplification. The audiofrequency transformer is employed in thefirst stage and a double circuit jack is alsoused after the first amplifying tube so

that the phones may be plugged in at thisposition. The grid condensers in the gridcircuits of the last two tubes are of ~mfd. capacity and the resistances Rareapproximately 50,000 ohms. The gridleaks shown as Rl are of U megohmresistance and are connected directly tothe negative of the <lA" battery. One rhe-ostat of 10 ohms, shown as R2, is employ-ed "to light the filaments of the last twotubes. The same "B" battery voltage maybe employed for all three stages, but it is

Circuit 11S

recommended that the last two tubes havea much higher voltage than the first. Thisamplifier may be employed with any

standard one tube circuit and will giveexceptionally good results.Circuit No. 114. Here we have a two

stage audio frequency amplifier using thepush-pull method of amplification. In acircuit of this kind three tubes are em-ployed for two stages of amplification. Itemployed for the last two tubes. Thesecondary of the first transformer has itstwo opposite terminals connected to the

will be seen that special transformers all, grids of the tubes and the primary ofthe last transformer has its two end term-lnals connected to the plates of the tubes.Circuit No, 115, Another efficient form

of oscillator other than the Hardey de-scribed before is the Colpitts circuit. Inthis circuit, the coupling between input

and output is capacitative and can be va-ried by changing the value of the capac-ity C'. In effecting this change, the os-cillatory period of the circuit LC1C1C is

r-----~-----L~----------~WW~/Oohms~...u_. 7 l" V . 1 1 ' 0 V.

+ 1 -.'lllllllllllll--_------Ortntlt 114

55



150 RADIO HOOKUPS

changed, and it thus becomes necessaryto change the capacity t an amountnecessary to obtain the desired period ofoscillation.

It might be well to recall that in thecase of the Hartley oscillator, the couplingbetween the input circuit (grid), and theoutput circuit (radio frequency), was ob-tained by conductive coupling. As notedabove, the double adjustment is somewhatof a slight disadvantage when using theColpitts oscillator in practice. The ca-pacity C· has the high potential appliedto it and in order not to affect the oscil-latory circuit LC1CC

1a radio frequency

choke coil must be interposed betweenthe plate supply, as is shown. C' is agrid condenser while R is a grid leak.Due to the multiplicity of condensers it

Circuit 115

is best to check the frequency with astandard wavemeter, because the matterof calculating the frequency would resolveitself into a rather difficult job.Circuit No. 116. One of the simplest

oscillators is that devised by Heising. Thecircuit has a number of desirable features,which are evident upon reference to thediagram. By changing the position ofthe clip A, it is possible to vary the coup-ling between input and ou~put. This.foymof oscillator has found WIde appreciation

and is being used by many amateurs andexperimenters. Here again, as in the Col-pitts oscillator, the capacity-grid leak re-sistance method of obtaining the required"",

negative potential on the grid of the tube,is used.There are different modifications of os-

Circuit 116

cillators, but all are adaptations of thecircuits described.Circuit No. 117 . Another type of

oscillatory circuit is shown in Fig. 117 .Three honeycombed coils are ernplovedto form the nductances, and the 23~plate condenser is connected across thegrid coil for controlling oscillations. Thesame data for tubes that was indicated in

the former oscillator applies to this cir-cuit, too.Both of these hook-ups are given in

these columns because every Super-Het-erodyne circuit has as its fundamental,some such circuit for changing the in-coming frequency to the wave-length thatthe intermediate transformers are de-signed for, by heterodyning. Also theprinciple of oscillations and how they areproduced in a circuit should be thorough-ly understood by every experimenter.Circuit No. 118 . This circuit is a radio

frequency feed-back amplifying unit thatuses two tubes and is resistance coupled.

56



150 :RADIO HOOKUPS

...---.f+1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 - - - ---,r-----O

150 V . OutputInput

A

B

+

Circuit 118

two stages of audio frequency amplifica-tion, having filament control jacks. Theuse of these jacks will mean in the longrun a saving to the builder, as only thefilaments of the tubes that are being usedare lit. This amplifying unit can be builtas an integral part of a set, or can be builtin a separate cabinet for the experiment-er's work bench. If built as a separateunit, binding posts are used to connectit with the tuner. Four binding posts areneeded for the "Au and "B" battery ter-

minals and two for the input. A precau-tion to be observed is to place the trans-formers at right angles to each other toreduce, as far as possible, any losses thatmay occur.Circuit No. 120. The audio frequency

oscillator circuit, shown in the accompany-ing sketch, should recommend itself to theexperimenter who is interested in makingtests on loud speakers or any instrument

A.F. T.

I--..~

Resistances R1 are 10.000 ohms and R2are 50.000 ohms. The terminals marked"input" are connected to the tuning unitand those marked "output" go directlyto the detector tube. The output fromthe tube A is fed into the tube B, whichin turn is fed into the tube A againthrough the tuner. As this action is con-tinuous, the resulting input to the detec-tor tube is larger than with the usual typeof resistance coupled R. F. amplifier.It is best to use either the UV-201A

type tube with this radio frequency am-plifier, or the Western Electricvli," tubes,as with these it is possible to use highplate voltages. It is necessary to haveseparate "B" batteries having a voltagebetween 100 and 150 volts, as the voltagedrop across the resistance is very high.The resistances R1 and Rli may be of theLa"ie type.

C1Y,uit No. 1 19 . In this circuit are shown

A.F.r.,...---OP/oleof"

Delector

T o N / N t o s l o t

o f

O~/ector·

+ 1 1 1 1 1 1 . - - -f;---~--~-_--J..--f------'

'----41_ ~ 1 1 1 1 1 1 1 1 I 1 1 ~ ~ + 4 . _ 5 - _ 9 _ 0 J I . _ " ---..JL---. ~

Circuit 111

57



150 RADIO HOOKUPS

r--------, e---_~-f 1IIIrlllllllllt---_""67l-90V.

.006 HF.

that needs a source of audio frequencycurrent. By employing sufficient induc-tance and capacity in the circuit andusing a tap switch for varying the in-ductance, different tones may be obtained.The inductance is made by connecting

six 1500-turn honeycomb coils in seriesand bringing out to the switch-pointstwelve taps. These coils may be placedside by side and clamped in position bysome suitable means. Care should betaken that the fields of the coils assistone another, i..., that the winding isall in the same direction. If the outsideend of one coil is connected to the insideend of the next, the circuit should oper-ate correctly, It will be noted that thenegative side of the "B" battery is con.nected to one of the end coils, which wewin call the first coil, The filament ofthe tube is connected to the other leadof the first coil, where it is attached tothe second coil.

6-1500 H.C.COILS

Circuit no

It will perhaps be difficult to procuretwo condensers having a capacity of .06mf., so if the experimenter will build upten condensers of .006 mf. capacity eachand connect them in parallel, he will havethe equivalent of a .06 mf. condenser. Thevariable condenser shown will act as avernier adjustment to the frequency.

Super..Heterodyne Circuits

Circuit No. 121. In the circuit shown inFig. 121 there is incorporated a differentsystem of producing beat notes than iaemployed in any other Super-Heterodynereceiver. Amperites instead of rheostats -are used throughout. The 200 to 400.ohm potentiometer shown is used to givethe proper ,grid bias to the intermediatefrequency tubes. It is hardly necessaryto say that the apparatus should be soplaced that leads may be as short a.possible.

OiJoeu1t In

58



150 RADIO HOOKUPS

Circuit NtJ. 122. One of the complaintssometimes heard from users of super-het-

erodyne receivers is that the intermediatestages are wont to pass through to thesecond detector. ail the noises that arepicked up as static, and the like. Throughthe process embodied in the receivershown in Fig. 122, the maj ority of theseunwelcome noises are eliminated. No de-viation from standard super-heterodynepractice will be noticed in the circuit upto the plate circuit of the third tube.Instead of the intermediate frequencytransformer here, there is a resistance, atuned circuit and a grid leak.

The condensers C2 and C3 are of smallcapacity, .00025 mf. or less. Experiencewill show that the static and tube noisesare of audio frequericy and are usuallyloud in ratio t o the signal intensity.Therefore. the size of C2 effectually pre-vents their passage into the grid of thenext tube. The only possibility left tothem is to take the alternative paththrough the resistance Rl which is ap-proximately 25,000 ohms. Here they aredissipated in the form of heat, leavingonly the high~r frequencies to pass on.The detector and oscillator are of the

standard type. The tuning coil A maybe made by winding 64 turns of No. 18

S.C.C. wire on a 3-inch tube. The con-densers E and F have a capacity of .0005mf. The pick-up coil Dmay be 10 turnsof No. 18 wire wound at the end of theoscillator inductance tube, which is also3 inches in diameter. The plate and gridcoils, Band C, for the oscillator mayconsist of 40 turns for the former and 64for the latter, separated about one-halfan inch from each other on the tube. Theresistances R2 have a value of about threemegohms. Ll is a 400-turn honeycombcoil and. C4 has a value of .001 mf. capac-ity. L2, the tickler coil for obtaining re-generation. has between 8 and 15 turnsof No. 18 wire wound On a 3-inch tube.The definite number of turns cannot begiven as they will vary in different sets.In the hook-up no audio frequency is

shown. Any type amplifier may be addedat the output posts or incorporated in theset .. Circuit No. 123. The value of the Tropa-dyne need not be told to readers ofRadio News, as the merits of the circuithave been told in the August and No-vember, 1924, issues and in this book.

ClrcuJt 12'3



150 RADIO HOOKUPS

In the first place there are but six tubesused, giving as much volume as the aver-age set using more tubes. The selectivity

of this set is excellent. Two lengths ofthree-inch tubing, one three inches andthe other four inches long, are requiredto wind the coupler and the oscillator coilson. The primary and secondary coilsare wound on the 3-inch tube and aredesignated as AG and GF, respectively.The primary coil AG consists of 8 turnsof No. 24 S.S.C. wire and the secondaryGF is 50 turns of the same wire, bothcoils being wound in the same direction.On the B-inch tube that is 4 inches inlength, wind on 12 turns of No. 20 S.S.C.wire and then wind on 55 turns of thesame wire. On these two tubes the twowindings are spaced Y 2 inch apart. The

two variable condensers have a capacityof .0005 mf., i, e., 23-plate condensers.The remaining apparatus has the valuesindicated in the diagram. The frequencychanger tube, which is the first one atthe left in the diagram, is placed in thelayout of the apparatus between the twocondensers. This is done in order tomake the connections as short as possibleto this tube and condensers. The sizeof the panel necessary for this receiver isone 7 by 30 inches. which size allows suffi-cient space for wiring.Above are given the constants for a

coil that is used as a coupler when anoutside antenna is used. The coil isshown in the circuit diagram publishedon page 49 of this book, and is designated

by the same letters. Although this cir-

SOO 7i.Irn OL Coils

x

.001ttl'rI.

cult functions very satisfactorily on anoutside antenna, it performs "excellentlyon a loop antenna, and if this is usedthe coupler need not be constructed>The connections of the Tropadyne are

similar to the standard Super-Heterodyneexcept for the first tube. It will be not-iced, however, that there are no grid con-denser and grid leak in the circuit ofthe second detector. These two pieces ofapparatus were eliminated because it was- found that distortion was decreased to aminimum by operating the tube on the

lower bend of the tube's characteristiccurve. This is accomplished by connect-ing the grid return lead to the negativeterminal of the "C" battery, which actsas a grid bias for the audio frequencyamplifier tube. This applies a negative

potential to the grid of the detector, andheretofore very little or no current is ab-sorbed by the detector, and the selectivityof the intermediate amplifier is consider-ably improved. With a HC" battery of 9volts and a plate voltage of 45, the selec-tivity is so great that powerful local sta-tions otherwise broad in tuning are tunedin and out with the vernier alone. Thisbattery does not decrease the volume andthe quality of reproduction is remarkable.The data for the construction of the in-termediate transformers will be found in

this volume as referred to above. Thesetransformers are tuned by variable con-densers across the secondaries, so thateach transformer is operating on the samewave-length.

Circuit No, 124. Many fans are anxious

-4S-90r_~ IS!!!

Circuit 124

60



150 RADIO HOOKUPS

to experiment with the Super. Heterodynecircuit, but the expense of the equipmenthas prevented them. In Fg. 124 is showna circuit that has for its principle theSuper-Heterodyne method and the parts,are relatively inexpensive. The constantsof the coils are as follows: No. 20 D.C.C.wire is used for winding all the coils.L1is five turns on a 4-inch tube and V is35 turns on the same tube, starting ~inch from V L$ is four to eight turnson a a-inch tube and V is 27 turns onthe same tube, the latter winding beingtapped at the 13th turn. The three hon-eycomb coils in the plate circuit of thetwo tubes should be placed in a regu-lation mounting, so that their inductiverelationship may be varied. If a loop is

point increase the .0005 mfd.· condenserused with this circuit it is connected inthe places marked X, thereby eliminatingthe primary and secondary windings, L1and V. The set is tuned by the .0005mfd. condenser across the secondary andthe .001 mfd. condenser in the oscillatorcircuit. The three .0005 mfd. condensersshunted across the honeycomb coils needvery little adjustment after once beingset.The tuning of this circuit is not very

difficult. Place the .0005 mfd. variablecondenser in the La L3 circuit at a lowscale reading and slowly turn the .001

mfd. variable condenser, which controlsthe oscillator circuit, until a hissing noise

is heard. If no signals come in at thisreading one or two degrees and retune

the oscillator circuit condenser" until the

hissing is again heard. This is continueduntil signals are heard.Circuit No. 125. The Super Heterodyne

needs very little introduction to radiofans in general. However, as is true withevery fundamental circuit, there are manyvariations of it. In Fig. 125 is a standardSuper-Heterodyne method and the partsing the use of resistances and condensersinstead of the intermediate radio frequen-cy transformers. Almost all the valuesof the apparatus are shown in the dia-gram. At the points marked X in theconnections from the secondary of the

variocoupler, a loop antenna may be sub-stituted for a coupler. The two .001 mfd.variable condensers shunted across thehoneycomb coils, after once being set,need very little adjusting, the set beingtuned with the other three variable con-densers. However, if a loop antenna isused instead of the variocoupler, this willreduce the tuning controls to two. Theleads from the resistances and condensersshould be kept as short as possible. The6- and 22-turn coils may be wound on thesame S-inch tube, the 20-turn coil beingwound on a tube that will rotate freelyinside the 3-inch tube. The use of UV-

201A tubes is recommended for thiscircuit.

"8 ·A +A +4~V +90V

CJrcult U6

~ .. 5Q{)()(J-7QO()(JOlJm".

H... J I'f~ohm"

~·I I'1I!f¢m

61



"l'H~ RADIO CONS~RUC'rO'R"

Pattern No.7

HOW TO MAKE

The Hazeltine

Neutrodyne Receiver

Complete detailed instructions for building a five-tube

Neutrodyne receiving set can be obtained in the form of a

pattern which makes the construction of the set as simpleas a woman makes a garment from a dress pattern.

The contents of "The Radio Constructor" Set No. '1Packet consists of a four-page pamphlet giving a list ofparts required; full directions for drilling the panel; making

the neutroformers and neutralizing condensers; and the ad-justment and operation of the finished set. The packet also

contains two blue prints, size 18x30 inches, giving the actual

size panel layout, a perspective wiring diagram of the

various parts on the panel and base, and details for building

a suitable cabinet for the set.

All contained in a heavy manila envelope printed in twocolors, size 9x12.

Pr ice 50c. Prepaid

THE CONSRAD COMPANY, Inc.64 CHURCH STREET NEW YORK CITY

. . . .



UTHE RADIO CON STR U CTOR'·Pattern No. 14

HOW TO MAKE

THE GENUINE STANDARD

Super ..Heterodyne

This Super-Heterodyne pattern is one of the largestthings ever attempted in the way of blue prints with all

instruction booklet.

,It consists of two large blue prints, measuring 19%x

44 in. These blue prints are drawn full size so that thebuilder of this set has no difficulty whatsoever with.extra measurements. With this pattern comes a com-plete IS-page booklet, size 8xI2 in. It is the mostcomplete booklet of its kind ever made up. It describesevery detail of circuit, and shows how to proceed in thebuilding of the set. It lists the necessary parts requiredand tells not only how to make and assemble them, butalso. how to operate the completed set.

Here is an opportunity for every radio receiving set con-structor to build one of the largest and finest sets thathave so far been developed in radio.

Prie. $1 00 Prepaid

THE CONSRAD COMPANY, InC.

64 CHURCH STREET NEW YORK CITY



BUILD YOUR COCKADAY SET FROM A CONSRAD PATTERN

How To Make

A Cockaday ReceiverPattern No.6

The Cockaday four-circuit tuner is oneof the latest advancements in radio. Itsmain advantage lies in the fact that theset can be adjusted to the highest pointof regeneration, and tuning accomplishedover a wide band of wave-lengths with-out the necessity for readjustment theregeneration control. The set describedin our packet was designed and built atour own shop. All dimensions, size of

ete., are given, leaving nothing to theire, number of tums,imagination.The Packet consists. of a fully illustrated instruction Pamphlet,

size BY2x110 inches and two large Blue Print Patterns, 18 x £ .8

inches-c-one of the Actual Size Panel Layout with directions forbuilding a suitable cabinet, and one Perspective Wiring Diagramof the Set.Contained in a Two-Color Printed Envelope, size 9x12 inches.

Price S O C . Prepaid

How To Make

A Five Tube Cockaday ReceiverWith Push-Pull Amplification

Pattern No. 11

This pattern gives the complete as-sembly, wiring, adjusting and tuning de-tails for the new Cockaday five-tubereceiver with Push-Pull amplification.The set as described in our pamphlet ofinstructions is one of the best receiversfor the reception of distant stations due

to its remarkable selectivity. It is alsonoted for great volume, as the poweramplifier of the Push-Pull type used in .this set is, without question, a big improvement ove~- ....her formsof audio frequency amplifiers.Complete instructions in a four-page pamphlet. Size 8~xl1

inches. One larJ,! 'e blue print Pattern showing a Perspective WiringDiagram, and Full Size Panel Layout) both size 18x28 inches. Con-tained in a heavy two-colored printed envelope, size 9x12 inches.

Price S O C . Prepaid

THE CONSRAD CO., Inc.64 Church Street N. Y. c.



A 'O lO B O O K S !

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The biggest, finest Call Book=andmore

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NewRadio

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A Whole Barrelful of Useful, Val~uable Information for Set Users .

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in every issue a supplement ofS. Gernsback's Radio Ency- The fourth part contains ' , a ,

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SOLD ON A~L NEWSSTANDSPublished by THE CONS~~~O ., [ac., 64 Church St., N ew t_ , M .Y 4!'

,...;t;. .....) . . in n L 'til,

150 radio hook ups_1926

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