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THE A. R. CO. VARIABLE CONDENSER

THE NEW "A. R. CO." VARIABLE CONDENSER

illustrated above is made in two capacities .001 mfd. and .0005 mfd. and is supplied unmounted only but with dial and knob if desired. The rotary plates are rounded on one end affording straight line capacity. The dial is of moulded composition, scale in white 0 100. Bakelite Knob. We can guarantee this condenser in every way as to quality, reliability and satisfaction. The low price is decidedly an innovation.

Capacity .0005 mfd.

.001 mfd.

PRICES : Unmounted $5.00

6.25

POSTAGE 10 CENTS

With Knob and Dial $6.00

7.25

A.R.Co. Amplifying Transformer - $5.00

u:

We take pleasure in announcing a branch store located # at 15 Temple Street, Portland. Maine, under the management of Mr. H. W. Castner.

ATLANTIC RADIO COMPANY

Incorporated

88 BROAD STREET BOSTON 9, MASS.

Branch

is temp; e street

PORTLAND, MAINE

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THE OFFICIAL ORGAN OF THE A.R

AUGUST, 1920

VOLUME IV

fC ONTENTS

The A.R.R.L. QSS Tests

5

A Ham on the Telephone

Tewpieye

6

Navy Receiving Equipment (Part II, Concluded)

L. C. F. Horle

8

An Efficient and Flexible Receiving Set

A. L. Groves

10

Our Radio Dime Museum

D. A. Hoffman

13

The New York Radio Central Station

14

Old "WCC", Cape €od

"An Old Timer"

17

Code Instruction Tables

17

Some Characteristics of the Underground System

18

A New Type of Variable

19

A Boardwalk Roller-Chair Radiophone

20

Clapp-Eastham % Kilowatt Hytone Transmitting

Panel

20

Editorials

21

The Operating Department

23

Who's Who in Amateur Wireless

31

QST's Directory of Calls

33

Amateur Radio Stations

35

With the Affiliated Clubs

38

Amateur Radio in Holland

Seefred Bros. -

40

Strays

41

The Heterogeneropliodynatron

Herbert Richter

44

Radio Communications by the Amateurs

46

Concerts de 2AB

53

Calls Heard .

54

Q S T to published monthly by The American Radio Relay League, Inc., at Hartford, Kenneth B. Warner (Secretary, A. R. R. L.), Manager and Editor.

Subscription price, $2.00 per year, anywhere. Single Copies, 20 Cents. Entered as second-class matter May 29, 1919, st the poet office at Hartford, Connecticut, under the Act of March 3, 1879. Copyright, 1920, hy The American Radio Relay League, Inc. Title registered at United States Patent Office.

THE AMERICAN RADIO RELAY LEAGUE, Inc. HARTFORD, CONN.

^WWWWWr-

89866 1

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The American Radio Relay League

INCORPORATED

"A national non-commercial organization of radio amateurs, bonded for the more effective relaying of friendly messages between their stations, for legis- lative protection, and for scientific growth."

President HIRAM PERCY MAXIM Hartford, Conn.

Vice President CHAS. A. SERVICE, JR. Bala, Pa.

A. E. BESSET Sunnyvale, Calif.

V. P. CAMP Brightwaters, L. L

J. M. CLAYTON Little Rock, Ark.

J. C COOPER, JR. Jacksonville, Fla.

F. M. CORLETT Dallas, Tex.

W. T. FRASER Buffalo, N. Y.

OFFICERS

Traffic Manager J. 0. SMITH 73 Hillside Ave. Rockville Centre, L. I.

DIRECTORS

W. T. GRAVELY Danville, Va.

F. H. HAMILTON Indianapolis

A. A. HEBERT Nutley. N. J.

HIRAM PERCY MAXIM Hartford, Conn.

C. R. RUNYON, JR. Yonkers, N. Y.

OPERATING DEPARTMENT

Treasurer A. A. HEBERT Nutley, N. J.

Secretary K. B. WARNER Hartford, Conn.

C. A. SERVICE. JR. Bala, Pa.

J. O. SMITH Rockville Centra, L. L

H. L. STANLEY Babylon, L. L

C. H. STEWART St David's, Pa.

K. B. WARNER Hartford, Conn.

M. B. WEST Waukegan, I1L

TRAFFIC MANAGER J. O. Smith

ATLANTIC DIVISION Manager Chas. A. Service, Jr. Bala, Pa.

Asst. Mgr., Central See. John DiBlasi 88 Sinclair Ave. Flushing, L. I.

Asst. Mgr., Southern See. Chas. H. Stewart St. David's, Pa.

EAST GULF DIVISION Manager J. C. Cooper, Jr. Atlantic NatL Bank Bldg. Jacksonville, Fla.

CENTRAL DIVISION Manager R. H. G. Mathews 1816 Carmen Ave. Chicago

Assistant Manager

Chas. H. Zeller 4782 N. Maplewood Ave. Chicago

WEST GULF DIVISION Manager Frank M. Corlett, - 1101 East Eighth St Dallas, Tex.

ALASKAN DIVISION

Manager Theodore A. Stocking Ketchikan, Alaska

ROCKY MOUNTAIN DIV. Manager M. S. Andelin Richfield, Utah

PACIFIC DIVISION Manager A. E. Bessey, Sunnyvale, Calif.

Assistant Manager

E. G. Arnold 181 No. 17th St., San Jose, Calif.

ST. LAWRENCE DIVISION Manager Albert J. Lo rimer 248 Mackay St Montreal, Que.

ONTARIO DIVISION

Manager A. H. Keith Russell 868 Mark ham 8L Toronto, Ont

NEW ENGLAND DIV. Manager Guy R. Entwistle 187 Sutherland Road Brook line, Mass.

ROANOKE DIVISION Manager W. T. Gravely 854 Main St Danville, Va.

DELTA DIVISION

Manager John M. Clayton 1801 Welch St Little Rock, Ark.

MIDWEST DIVISION Manager L. A. Benson 4942 Wiesehan Ave. St Louis

DAKOTA DIVISION Manager Russell H. Pray Valley City. N. D.

NORTHWESTERN DIV. Acting Manager, Royal Mumford Vancouver, Wash.

Address General Correspondence to Executive Headquarters, Hartford. Conn.

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AMdgdzine Devoted Exclusively to Amateur Ridio

The A.R.R.L. QSS Tests

The Bureau Tests End and the League Tests Begin.

AS this article is written, the A.R.R.L. Fading Tests are beginning all over the country, and we have every reason to feel that they will be as interesting and as successful in the securing of valuable data as were the co-operative Bureau of Standards A.R.RL. tests.

Readers who are not familiar with the tests are referred to the opening articles in the two preceding issues of QST, where complete details are announced. In each A.R.R.L. Division transmissions by well known stations have been arranged, and a form for checking the variation of audibil- ity is given. The Division Managers have appointed Fading Analysts for each section, and a uniform system of tabulating and studying the data has been adopted.

If we all pull together on these tests, much of scientific value should be accom- plished. It is hoped that every A R.R.L. man will feel it a duty to participate and aid in this important work. All stations are requested to keep their transmitting at a minimum during the time of these tests in their territory.

It is believed that experience in the conduct of these tests will show that the system being followed can be improved, so that rather than continue this first series indefinitely it has been thot advisable to announce Aug. 31st as the concluding date. Referring then to the schedule published in last month's QST, all schedules for dates after Aug. 31st are hereby cancelled. Division Managers will arrange for the broadcasting within their division, at the proper time, of any portions of their sched- ules not published in full up to Aug. 31st in the July issue.

There are two corrections in the New England Division schedule as published. Aug. 14th for IPG, read 1PY, Westerly, R. I. Aug. 28th, for 1WR, read 1AK, Fall River, Mass. 1KAY is Portland Me.

Now a word to the recorders. Make curves on as many transmitters as you can, but if the schedules call for transmitting on each test night by stations in adjoining divisions and you can get either one at will, pick out the one to which you will regularly devote your attention and record it every possible test night at that time. That is, do not switch your recording to a new station every night it is more important to have regular reports on the same trans- mitter, so that variations from normal re- ception may be noted. The recording form calls for a check-mark in the proper square. This works very satisfactorily where the swinging is gradual, but some stations fade so rapidly as to go thru most of their cycle during the transmitting of one group of letters. In such cases it is suggested that numerous small dots be tallied (possibly one per letter, even), to be connected by a curve immediately after the schedule. Another important thing is that a record on a station whose signals are extremely loud thruout the transmission will not show fading and will therefore be without value. If a station is regularly received with in- tensity 9, reduce filament current or cut out a stage of amplification. This will re- duce the strength to a value where changes in audibility will be readily noticed. But be sure to note on the record that this has been done and also, if possible, note during the QST call the strength with the' set in normal order.

Because progress in the Bureau of Stand- ards tests snowed that some rearrangement of the station network would add gTeatly to their value, the tests were terminated on July 17th. This was in accordance with the original scheme. Improvements in the methods of transmitting and recording are under consideration, and these will make it possible to plan future tests very satis- factorily. The network laid out for these first tests by our Operating Department

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QST

August, 1920

has worked to perfect satisfaction, and some remarkably fine work has been done by the participating stations. These men should feel that a difficult task has been well performed, and the Bureau wishes to thank them sincerely for their efforts.

As soon as the Bureau completes the tabulating of the data and draws conclu- sions therefrom, they will be announced thru the A.R.R.L. So far, the indications are that the phenomena are caused by re- flection or refraction of the waves, as has long been believed by many. Perhaps the most striking feature of the tests is that no cases of fading revolving around the trans- mitter have been observed, as was expected by many of us, but inverse curves have been noted both on opposite sides of the transmitter and, more important, on the same side of the transmitter at different distances. This last feature is intimately bound up with what is being called "pro- gressive fading", the occurrence of certain phenomena successively along the curve at different points in the same general line from the transmitter. The Bureau cites as an instance, a particular part of a curve on the signals of 2JU which began at Hartford with the letter A; at Bristol, Conn., with the letter B; at Laconia, N. H., with the letter G; and at Boston with the letter H. It is believed that a study of the distances, time factor, and phase relations in such instances will make it possible to determine the location of the reflecting media, if such exist, which caused the phenomena. From this we may hope to learn the nature of the medium, and so progress to methods for overcoming the fading evil.

The Bureau is of the opinion that the so- called changes of received wave length, as reported in QST by correspondents, are

largely receiving circuit effects. A regen- erative receiver is very critical as to fila- ment temperature and a small change in this factor causes marked tuning effects. These can be compensated for by readjust- ing the set, the operator receiving the impression that the incoming wave has changed. Another important thing is that the adjustment of a regenerative set that is best for strong signals is not the same as the best adjustment for weak signals of the same wave length, and as it is vir- tually impossible to tell whether a partic- ular adjustment of such a set is a tuning or regenerating adjustment, the operator is easily deceived into the belief that the wave length has changed. This would not occur in non-regenerative receivers, but the latter do not have the needed sensitive- ness. It is believed possible, however, for a transmitter emitting a band of wave lengths to fade out on one wave length at a particular receiving point and simultan- eously swing in on another wave, for the reason that two different frequencies when reflected or refracted by the same con- ducting mass or surface, do not interfere subtractively at the same point. Mr. Frank Conrad, of 8XK, has suggested that a send- ing station with two "humps" sufficiently far apart could send to a receiving set tuned to both waves with a very good chance of unbroken reception, and support- ing this theory is the observation that, so far as known, it is not possible to recover the signals of a fading C.W. (or modulated C.W.) station by retuning.

All in all, the QSS Tests are proving immensely interesting and promise to de- velop information on short wave transmis- sion problems which will prove of the highest value to us amateurs. Watch QST for further information.

A Ham On The Telephone

By Tewpieye

2PI make* hU debut in QST with a good one. Ever imagine what radio nomenclature must sound like to the uninitiated? This is a story about just that. Editor.

MR. JAMES BARNEY was an ardent "ham" and lover^ and often wav- ered in his fidelity between the two extremes. When in the equally captivating presence of one the other was generally completely obliviated, but he occasionally inoculated sentimental- ity into the ether by rather obvious code MSG's to his other affinity via the A. R. R. L. One afternoon, following a futile endeavor to raise some easily imposed- upon station who would accept his MSG

which according to cable count would have made its recipient a millionaire, he finally resorted to the telephone.

Now Mr. Barney was a resident of a New York apartment house and conse- quently suffered all their advantages and equally enjoyed their manifold discomforts. He frantically oscillated the unoffending phone hook, yelled profanely into the transmitter and placed his receiver in prox- imity to the mouthpiece without raising the slightest satisfying squeak, before he

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QST

7

An

QSS

ultimately replaced the damaged phone stand, and carefully noting that the re- ceiver was NOT on the hook, made his fuming way to the real estate office, in the building. He was there informed that ser- vice was NIL, owing to the absence of an operator, and that in all probability it would continue so for an indefinite period. Sensing a chance to make the maximum of money with the minimum of work, James offered his able self in the temporary ca- pacity of switchboard operator. Needless to say he was immediately accepted.

After settling himself with all possible comfort in the operator's chair his first act officially was to remove the caps from the receivers. Making a serious pretext of tightening some perfectly firm binding posts he savagely jammed a plug into Cen- tral.

"Number please?"

"QSD", in an interrogative tone.

"Number please".

"QSD QSD P-S-E".

"Do you want information?"

"No no". Then compre- hending that all operators did not necessarily come under genus radio, James condes- cended to the explanatory

"QSD what time have you?" "Four twenty-five." "OK Thanks old man, call you later." Crash, and the plug returned to its place.

After painfully setting his watch, the erstwhile operator, paying not the least attention to the frantic dropping of a paltry dozen or so annuncia- tors, again plugged Central and gave her the number of his lady love. There then ensued a beautiful half-hour conversation, interrupted but once when Mr. Barney smothered the persistent buzzer with his cap.

As soon as this conversation reached the ultimate of its many endings, James again experimented with his apparatus ere he felt competent to answer the now innumer- able calls- He jammed in half of the party plugs and leaned heavily on as many trunk buttons and anxiously awaited the result.

The inevitable happened. Half the popu- lation of the house answered with a con- fused "Hello hello".

James, not quite expecting this, was at a loss as how to reply, but his radio intelli- gence soon came to his rescue.

"Testing-testing de-de-de-dah," he bawled into the transmitter, and desper- ately yanked the plugs.

Having at last determined which were the party jacks by the above conclusive tests, he cautiously proceeded to answer calls.

Coming Swn

analysis

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the tha

repoi

Bustands" A. R. R. L. tests; a paper on the performance of our stations in these tests, by Mr. S. Kruse; some dope on the use of spark coils as a source o f modulated plate potential for C.W. tele- graphy; a cheap and easily-made rec t i f i e r which will five 350 watts d.c for CW. Watch for these articles.

"Hello, hello, O.K. now, shoot" "Connect me with the real-estate office, please".

"Sorry but they piped down about an hour ago." "They what?"

"Piped down, layed off, closed shop" ex- plained the sophisticated James, "I'll take an MSG for them though."

"Oh they are closed Well this is im- portant. Will you please give them a mes- sage as soon as they open?"

"QSR".

"What?"

"Sure thing, I'll relay the message. Shoot".

"Well, just tell them that the people be- low are making an awful noise. It's some sort of a telegraph affair, and their wires come right down outside of our windows. Our wash-woman was almost killed when she hung clothes on it last Monday. We can't sleep at all nights when it is buzzing, and our lights get dim and it is impossible to read. Also sparks fly from the ceiling in the dining room".

"Yes mam, that's outrage- ous. I shall report it and see that it is stopped." Mr. Barney made a mental reser- vation to replace his kick- back-preventer the next time he saw his set.

"Well", he soliloquized, it's sure lucky I got in on this. Gee, supposin' it had got to the office MIM. Ye Gods! Maybe there's some more Qf them flying around." _____ He plugged in on the apartment below his. "Hello, this is the office speaking. Are there any complaints you wish to file tills month, Mrs. Jackson?"

"Why, nothing in particular, only our. lights went out last night and haven't been on since."

"Oh yes, well er-er-the er-power com- pany shut off the juice last night, Mrs. Jackson, but it will be on tonight."

Behold another mental resolution: to re- place the fuses borrowed from the meter on the floor below.

"Well, now, I sure did nip that in the bud."

BUZZ, BUZZ, BUZZ.

"Hello-hello-hello-hel-l-l-l-oo. One, two, three, four, five, go ahead".

"Connect me with Mr- Stone's apart- ment, please, I've been trying to get you for the last half hour."

"Yes mam", and he shoved the plug into the handiest jack while he searched the list for Mr. Stone.

(Concluded on page 43)

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QST

August, 1920

Navy Receiving Equipment

By L. C. F. Horle Part II Concluded

Presented at meetiug of the Radio Club of America, Columbia University, March 26, 1920

Under the able direction of Prof. Hazeltine, who was then connected with the Navy Dept. in a consulting capacity, much research was done before the actual design was started and the various develop- ments of this research were incorporated in the SE-1420 receiver.

In the design of this receiver effort was made to secure wide wave length range, high selectivity, freedom from local interference, stability in regenerative am- plification, simplicity of operation, com- pactness, durability, and cheapness of construction.

In conformity with established practice, both tuned circuits have inductance coils provided with taps, six in number, and continuously variable air condensers giving overlapping wave length ranges from 260 meters up to 6,000 meters when the capa- city of the antenna is .0004, and up to 7500 meters when the capacity is .0009 microfarad. The practice of sectionalizing and disconnecting the unused portions of the windings to avoid "resonant coils" has been abandoned, the windings being now made continuous and merely short- circuited at the proper taps. This com- pletely eliminates "resonant coils" and allows of a simple and rugged construction. The arrangement is such that the coupling between the short-circuited and the active portions of the coils is loose, so that little loss is introduced.

The chief factor contributing toward high selectivity in this receiver is the choice of a higher ratio of inductance to

capacity than has hitherto been customary ; the antenna condenser having a capacity of .0015 microfarad, and the secondary condenser of .00075 microfarad, whereas the type SE-1220 and other receivers of similar wave length range had capacities of .005 and .003 microfarad respectively. Compactness and proper distribution of

Fi*. s. Pane] View. SB- 1420.

winding spaces are secured by reducing the size of the Litz wire used to 20 strands of No. 38 wire and by winding the suc- cessive taps in increasing numbers of banks.

Interference from short-wave nearby stations and from transmitting apparatus in close proximity to the receiver is elimin- ated by the use of grounded sheet-copper shielding completely enclosing and separ- ating the antenna and secondary circuits. To completely eliminate capacity coupling, the coupling coil is provided with a novel electro-static shield con- sisting of an additional winding placed over it, the capacity current in this winding inducing in the coupling coil voltage which exactly neutralizes that resulting from capacity current in the coupling coil. The coupling coil is placed in the secondary circuit instead of in the antenna circuit chiefly for the purpose of ob- taining sufficient coupling with- out the use of taps to secure the low wave lengths, as the in- ductance of the antenna would otherwise prevent this. To se- cure complete stability in regen- erative amplification, the stopp-

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QST

9

ing condenser and grid leak are discarded, and the grid is connected through the secondary inductance to a point on the filament rheostat selected to give a nega- tive grid potential or "bias" of about 1.3 volts with a Type SE-1444 tube, and about 2.2 volts with a Type CW-933 tube.

Oscillation control over the entire wave length range with both types of tubes above mentioned necessitates a large tickler, and in order to avoid resonant effects from this tickler at the shortest wave lengths, it is made in the form of a variometer, having a stationary part wound alongside of the secondary inductance coil, and allowing the plate circuit to be tuned.

The difficulty which frequently arises in short wave heterodyne reception from the capacity between the operator's hand and the secondary circuit (which may change the note sufficiently to make it inaudible) is eliminated by the use of an audio fre- quency choke coil and telephone conden- ser which prevents radio-frequency current from reaching the telephones.

The reteiver permits the use of either the crystal or the vacuum tube detector, and contains within itself the receptacle and controls for the latter. The terminals of the secondary circuit are brought out for connection to a radio-frequency ampli- fier when the crystal-audion switch is thrown to the left. The standard auxiliar- ies, such as the filament ammeter, test buzzer, push button, etc., are clearly shown in the photograph, Fig. 3. The con- struction is simplified and cheapened by the introduction of unit assemblies, en- abling the separate elements of the appar- atus to be assembled independently in- stead of being built into a single panel.

Following the design of the SE-1420 receiver came the need for a radio com- pass receiver of greater selectivity and sensibility than had been available previ- ously. The use of unilateral operation has been abandoned because of the diffi- culty in securing reliable bearings with the personnel available for operating the equipment. The possibility of using radio frequency amplification for this type of radio reception was investigated but it seemed evident while this investigation was being made that high power audio- frequency amplification would best meet the service needs, particularly since there was evidence at hand indicating that greater precision of bearing determination could be made if reception was done with the tube in oscillation. On the basis of this data the SE-1440 receiver was designed.

A series of amplifiers has been developed at the Radio Laboratory that should meet the needs of the service very satisfactorily.

They are designed (1) to supply moder- ately high audio-frequency amplifications where conditions are such that an ordinary antenna is available, or (2) to supply high audio-frequency amplifications where low antenna or loop reception is to be done over a great range in wave lengths, or (3) to supply high radio and audio-frequency amplification where extremely high ampli- fications are necessary and where the range in wave lengths is not greater than three to one.

Fig. 4.

Three Step Audio Amplifier (Electrically Shielded). SE-1699.

For use under conditions specified in

(1) , the SE-1600-A amplifiers are well suited. These amplifiers use two of the SE-1444 or CW-933 (Western Electric "J" J tubes in connection with the .two ' audio-frequency transformers.

The SE-1600-A uses iron core trans- formers. The coils of the transformers are machine wound with No. 44 copper wire. The layers are insulated from each other by means of paper and the whole coil impregnated with wax. The primary consists of 3900 turns and the secondary of 12,000 turns, the ratio being somewhat greater than three to one. The core is built up of 5-mil silicon steel. Three tele- phone jacks are provided by means of which the telephones may be connected in the plate circuit of the detector tube or in the plate circuit of either of the amplifier tubes.

For use under conditions outlined in

(2) the SE-1699 amplifier has been designed. (Fig. 4). This amplifier con- sists of three amplifying tubes and three

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QST

August, 1920

amplifying transformers of the audio- frequency type. The whole device is thoroughly shielded and every means adopted to make it free of disturbance due to interactions in itself or between it and other apparatus. It is designed to meet the need for very high amplifications where a wide range in wave lengths is essential. As such it is suited for opera- tion with receivers supplied with "audion control boxes" or with receivers equipped with vacuum tube detectors. A two point telephone switch provides for cutting out the last stage of amplification when necessary. Further control of the ampli- fication may be accomplfshed by adjusting the filament rheostat.

For use under the conditions outlined in (3) the SE-1611, SE-1613, SE-1615, and SE-1617 amplifiers have been designed. These amplifiers are of the radio-audio- frequency type and employ six SE-1444 tubes. Iron core transformers are used for both the radio and audio frequency amplifications. The radio frequency trans- formers are the only major details m which these amplifiers differ from one another, each amplifier having its transformer de- signed for maximum amplification over a definite range of wavelengths.

The ranges of these amplifiers are approximately as follows:

SE-1611 400 to 1000 meters SE-1613 1000 to 3000 meters SE-1615 3000 to 10000 meters SE-1617 6000 to 20000 meters In addition to the above series of ampli- fiers there have, been several types of amplifiers designed for special applica- tions. The most interesting of these is, perhaps, the SE-1493. This amplifier con- sists of 4 tubes and three radio-frequency transformers having a range of 400 to 1,000 meters. The last tube of the series acts as a detector. It is designed to meet the need for radio-frequency amplification of this range where audio-frequency ampli- fication in the form of the SE-1600 is already available and requires no "audion control box" for its operation.

This covers in general the trend of Navy Receiver development and illustrates the variety of apparatus required to meet the growing need of the service for special designs and purposes. No attempt has been made to emphasize the tremendous efforts necessary to perfect each detail under pressure of war conditions but the results of the work well justified this care- ful development.

An Efficient and Flexible Receiving Set

By A. L. Groves

We all know that Mr. Groves has done some exceptionally good receiving work, and in this article he describes the set with which he does it, in such a manner that anyone may duplicate his results. Mr. Groves is an exponent of the "three-coil" circuit for short waves as well as lone, but attention is particularly directed to the fact that for the reception of short waves the third coil is NOT a tickler, but instead forms the inductance for an Armstrong tuned-plate-circuit hook-upt a method which most of us have found superior to the tickler for amateur work. The diameter of the coils described by Mr. Groves was chosen after experimenting with every diameter from one inch to fifteen inches, and gave the best results. We are fortunate in having this pioneer work already done for us. This dope can be depended on. Editor.

AS numerous amateurs have expressed a desire to know what kind of a set I use in obtaining results re- ferred to in some of my previous articles in QST, I here present a full plan of my set, showing location of instrument, exact wiring methods, etc.

As will be noted, the set presents noth- ing radically new, unless we take into con- sideration the extreme simplicity of the whole layout, and this to a great extent accounts for the working efficiency of the set, for a set cannot work at greatest efficiency when hampered by unnecessary instruments and instruments placed on th%^ panel in such a position that long leads and numerous crosses occur. The audion is a very sensitive instrument and every inch of unnecessary wire, every un- necessary switchpoint or other instrument, has its effect on it. These little things

might not amount to very much taken separately, but collectively they amount to much, and no pains should be spared to have as few instruments as possible, wired with heavy wire as directly as pos- sible.

Fig. 1 represents a set 20 by 20 inches front panel, and 10 inches deep. The depth may be only 8 inches, depending upon the size of A and B Batteries used.

The switches 1, 9 and 10 are one inch switch blades. Condensers 3 and 13 are Illinois 13 plate condensers. Condenser 12 may be either 13, 23, or 43 plate, de- pending upon the maximum wave desired to receive from, using the DeForest honey- comb coils. If the 13 plate condenser is used, waves up to and including that of WII (formerly NFF) on 13,600 meters may be tuned to. A 23-plate one will just about take in NSS on 16,900 meters,

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while the 43 plate one will tune to about 20,000 meters. DeForest claims 25,000, but if you get 20,000 you will do well. In fact, under actual working conditions all of the DeForest coils have lower minimum and maximum waves than those listed in their catalogue. Coil L-600 deviates from their figures to a greater extent than any other. They claim from 4,000 to 12,000 meters with it, while its working range is approximately 2,200 to 8,600 meters.

1. B. Battery Switch.

2. Variable Grid Leak. 8. Grid Condenser.

4. Audion Socket.

6. Shelf for B. Battery.

6. Fixed Condenser.

7. DeForest S-Coil Mounting.

8. Aerial and Ground Connections. 9-10. Series-Parallel Switch.

11. Primary Condenser.

12. Secondary Condenser. 18. Plate Condenser.

14. Rheostat Dotted lines at top, B. Battery. Dotted lines at bottom. A. Battery.

The primary condenser, 4, should have a maximum capacity of at least .0015 mfds. and may be either the DeForest, Clapp- Eastham balanced or other standard con- densers designed for panel mounting.

Switches 9 and 10 throw the primary condenser in series with the aerial when both are thrown to the left as shown. If 9 is moved to the right, leaving 10 to the left the aerial is cut straight through and the condenser cut out If both 9 and 10 are thrown to the right the condenser is connected in parallel to the primary coil. This simple arrangement will be found more efficient than the usual 4-blade 8-point switches used for this purpose.

The rheostat, 14, used by the writer is

the Parkin, selected for its small size and

simplicity.

The grid leak must be variable and is of the switch-lever-pencil-mark type.

Point 6 is the junction point of the plate circuit, stopping condenser, and re- ceivers. The condenser used is the DeForest fixed condenser of .002 Mfds.. and from this point a regular lamp cord is run to the point where it is desired to attach the receivers.

The coil mounting, 7, is the regular DeForest 3-coil mounting, prefer- ably the ULC-4 00.

While the DeForest Honeycombs are excellent for long wave work, they are not suitable for best re- sults on the short waves, and at the time of writing this article a new type of coil called the Duo-Lateral Coil has just made its appearance. I hardly believe these coils will prove any more efficient on short waves than the honeycombs, as I wound three coils of this type by hand back in April on 2 % -inch cyl- inders and while it was not expected that the hand- wound coils would show anything startling, a comparison be- tween them and hand-wound honey- comb coils failed to show enough to warrant further experimenting with them, on the short waves at least For amateur waves, or we may say for waves below 600 meters, nothing brought out to date is more efficient (under actual working con- ditions) than the old time straight single layered coils.

The only previous objections to them was the inefficiency of the trans- former, when made in the regular primary- secondary loose coupler style with its sliders and taps, dead-end effects and clumsy couplings, etc. The loose coupler had its day in the days of crystal detectors, but it has no place in the modern tube set of today.

Fortunately it is an easy matter to build coils of the correct size to fit the DeForest Mounting for short wave work, which are used in exactly the same manner as the regular coils, thereby doing away with the dead-end effects, taps, sliders, etc., and at the same time producing a most efficient set. A little experimenting by each indi- vidual to produce the exact number of turns in each coil is necessary, but once the correct values are determined the results obtained will more than pay you for the little trouble and care you have taken.

The best coils to use are composed of Bakelite tubing 5% inches inside diameter with % inch wall, giving an outside dia- meter of 5 % inches, scinch Bakelite sheet- ing is secured to make the bands on which to mount the coils on the regular DeForest

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Plugs, which can be taken from your un- used DeForest shortwave coils.

The tubing is purchased in lengths rang- ing from 1 to 1 % inches wide if you wish to make the set from 200 to 600 meters from these coils, or if for short waves only, 200-300 meters, they may all be 1 inch wide.

20 turns of No. 22 SCC wire are wound on the first coil, which will give a minimum wave of approximately 200 meters when used in the secondary.

25 turns are wound on the next coil, and 30 on the next. These three coils will cover practically the entire amateur field

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of waves with efficiency in the secondary circuit. In winding the coils it may be well to remember that on a cylinder of this size, 20 turns approximately equals 200 meters, 35 turns 300 meters, 50 turns 400 meters, 65 turns 500 meters, and 80 turns 600 meters, with the secondary condenser close around zero capacity. As the neces- sary number of turns increases, wider cyl- inders and finer wire are used. The 600 meter secondary requires the 1 % inch cyl- inder wound with No. 30 SCC wire and this coil will give excellent results up to and including 800 meters. I leave it to the individual to wind as few or as many coils as desired.

For the plate coil, in most cases, one of the unused secondaries can be used. This depends somewhat upon the character of bulb used. The average Class 2 Marconi V.T., using three or four 22% volt B Bat- teries requires a coil of 15 turns for the plate coil on 200 meters and one of 35 turns for 600 meters. In tuning on short waves it must be remembered the inductive feedback from the plate coil is undesirable; consequently the plate coil is swung wide open, as far as it will go and the plate coil tuning accomplished by the plate condenser thirteen.

The winding of the primary coil or coils will probably cause the average ama- teur the greatest difficulty, as no idea can be given here as to just what size these should be. Not less than 10 turns should be used. Most amateurs will be able to

judge about what size to start on by