Radio News for April, 1921 673

CIRCULATION LARGER THAN ALL OTHER RADIO MAGAZINES COMBINED RADIO 20April Cents 1921

Over 100 Illustrations NEWSREG. U.S. PAT.OFF. Edited by H. GERNSBACK

A NEW RADIO INSTRUCTOR SEE PAGE 686.

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www.americanradiohistory.com Radio News for April, 1921 673

Specify No. 766, Eveready Wireless Station Specify No. 763, Eveready Airplane Wireless Battery. Standardized for use in the U. S. Navy Battery. Standardized for use in the U. S. Signal Corps Aviation Section Here's your power-plant! 'THE Eveready Vacuum Tube All the skill and experience of the Plate Battery was especially de- Eveready engineers have been poured signed for radio outfits. It is packed into this battery and sealed up. tight with electrical energy that will Once you know the power and en- send your message singing through durance of the Eveready Vacuum space to the receptive antennae miles Tube Plate Battery, you will never away. be satisfied with less. But be sure The Eveready is known every- you get the genuine. Sold by lead- where as the battery of endurance. ing dealers everywhere. Name of It stays on the job till the last second. dealer in your locality on request. AMERICAN EVER READY WORKS of National Carbon Company, Inc. 226 Thompson Avenue, Long Island City, New York Chicago Atlanta San Francisco

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VOL.1a2 FOR APRIL NO. 10 /,;

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Underground Loops...By H. Gernsback 677 The H. C. of L. and Burned Out Ampli- fying Transformers Radio Communication By Cyril O. Smith 691 By J. H. Dellinger 678 An Ideal Receiving Set for Short and eat Get Your Friends Interested 680 Long Wave- Lengths By E. G. Shalkhauser 692 New Universal Range Receiver By Arthur H. Lynch 681 Short Wave Radio Vacuum Tube Trans- mitter and Regenerative Receiver with Tests of Insulating Material for Radio Two -Step Audio Frequency Amplifier Use at the Bureau of Standards By Walter Hyndman 693 By S. R. Winters 682 Conduction of Electricity Thru Vacuum Aeroplanes and Radiogoniometers and Gases with Application to Design By Armstrong Perry 683 of Radio Apparatus. First Part By E. M. Sargent 694 $10o Portable Radio Prize Awards of ia`1 0_ Ì Contest . 684 Who's Who in Radio -Sir Oliver Lodge 695 A "B" Battery of the Edison Storage With the Amateurs 696 Type By W. H. Farr 685 Correspondence from Readers 698 A New Radio Instructor 686 Club Gossip 699 First Annual Amateur Radio Show and Radio Digest 700 Convention 687 Found by Radio 701 The Radio Dealer and the Beginner By Armstrong Perry 688 The Radio Constructor 702 Junior Section 704 Quenched Gap Transmitters 689 By Jesse Marsten A Complete Receiving Set for 25c 1111111111E1 111111UI1UIUIIII IIIIIIr rl1111: Rillt By D. Adams 705 )11. John ^\\ .. 4 -. Non -inductive Resistances and How to V Make Them By P. F. Geagan 690 Junior Constructor . 706 'I Continuous Wave Multi -Stage Receiving I- Want -To -Know 707 -Taggart 690 Circuit By John Scott News from My Statior New German Radio Recording Device.. 6ó1 By G. Ridleak V. T. 708 --aaa;01 of each month at included. ALL accepted contributions are paid for on Publication. NEWS is publlaht on the 25th novel RADIO are 12 numbers per year. Subscrip- special rate is paid for experiments; good photographs accompanying 233 Fulton Street, New York. There them are highly desirable. tion wonted (ne i2.ó0 a09year. II S. coin as well as S. Stamps RADIO NEW S. Monthly. Entered as second -class matter June Single copies, 20 cents each. A sample copy will 6th, 1919, at the Post Office at New York, N. Y.. under the Act of foreign coins or stamps) be drawn to sent gratis on request. Checke and money orders should March 3, 1897. Title registered U. S. Patent Office. tbpyright, 1921, by be ENTER PUBLISHING CO., INC. If you should E. P. Co., Inc., New York. The Experimenter Publishing Co., 233 Falten seder of EXPERD copies be not mis- The change order that Street, N. Y., N. Y. Contents of this magasine are copyrighted and sent amer y, ins must not be reproduced without giving full credit to the publication. carried youro L.drÑo copies be ad- communications and contributions to this journal should RADIO NEWS, 233 Fulton Street, New York. P. A D I O NEWS is for sale at all newstande in the United States dreat to Editor, full postage has been and Canada; also at Brentano's, 37 Avenue de l'Opera. Parla. Unaccepted contributions cannot be returned unless Pnbliaht by EXPERIMENTER PIIBLISHING CO., INC. 233 Fulton Street, New York City _2 H. GERNSBACK. President S. GERNSBACX. Treasurer R. W. DE MOTT. Secretary aSIlY:/j \. A \SL, -a^.. l'_. =i-=-`.= , \\__ , ^' /11_li- .:"-\__\ - www.americanradiohistory.com Radio News for April, 1921 675

50,000 NAVY TYPE OHMS A. C. 50,000 ohms A.C. at 800 cycles. Weight 9 oz. complete with headband and RESISTANCE in our polarity indicating cord, Price $14.00. Navy Type HEADSET

Special attention of all who are using Vacuum Tubes How We Get An Impedance To get the highest efficiency from a station equipped with vacuum of tubes it is absolutely necessary to use a headset of very high impedance. In our Navy Type Headset with an impedance of 50,000 Ohms 50,Ooo ohms A.C. at Boo cycles we have accomplished something There are four bobbins in each headset- never before two to each earpiece. Each of these bob- possible in a commercial headset. The extra high bins is wound with 10,000 turns of insu- impedance of this new model makes it ideal for vacuum tube lated copper wire. Because of the difficulty reception. of winding small wire the greatest number of turns in any other headset is less than 7,500. No other manufacturer has been This headset is exceedingly high pitch in tone and is -consequently able to approach 10,000 turns without making his headset too bulky, heavy and fragile very sensitive to high pitch signals. To anyone wishing to receive for practical use. Consequently no other trans -Atlantic or Pacific signals our High Impedance Navy Type headset has over 25,000 ohms impedance at Headset is indispensable. 800 cycles. In spite of the fact that there are over 40,000 It is the most sensitive headset built regardless of price and it is turns of wire in our High Impedance Navy Type Headset it weighs only 9 oz. backed by one of the most liberal guarantees ever written. Read complete with headband and cord. Its our offer below. compact, sturdy build insures comfort, reliability and long life. BRANDES Matched-Tone HEADSETS 100c% Receiver Satisfaction While Brandes Matched Tone Headsets on the diaphragm less current is required justable to any size head. Check nuts hold are very light and comfortable they are so to produce audible signals and the space the adjustment. built that there is no This headband is rust- sturdily danger of and weight of unnecessary amplifying proof, strong and light. them losing their adjustment through hard mechanism is eliminated. usage. The shell is made of thick, rigid Our headsets are aluminum and the cap of hard vulcanized Brandes also now equipped with Matched Tone Headsets are new style conducting cords which indicate rubber. The parts are all securely anchored carefully matched in tone and permanently the polarity by hand by skilled workmen of the receivers. This elimi- who do noth- adjusted at their highest point of efficiency. nates any danger of ing but make Brandes Headsets. All of our models are demagnetizing the re- equipped with im- ceiver when used in connection with vac- Because the action in our headsets is direct proved headbands which are instantly ad- uum valve detectors. You can try our High Impedence Navy Type Headset without We want you to give our risk High Impedance Navy Type Headset a trial. comparisons with the headset you are now using. We want your judgment on it. We back this headset with the most liberal set in If it isn't a better head - every way than any you have ever used or seen, or if guarantee ever placed behind a wireless instrument. Here is our offer: reason whatever you are dissatisfied for any Send us $14 and we will mail a High Impedance Navy Type Headset. with your purchase, mail the headset back to us and we will refund your money immediately Try it for ten days. Give it every test you can devise. Make rigid question. Tear out and without the coupon in the corner of this page and use it now. Transatlantic and Superior LISTEN TO THIS We also make two Other models. These are for "I have listened in with many different makes of phones USE THIS COUPON NOW amateurs whose requirements during my am wei ma om MN are not exacting ten years' experience but I never was so , enough to warrant the use of our Navy Type. pleased with others as I was with your splendid and C. BRANDES. INC sensitive Navy (R.N.A.) set. " -w ' ' Room 823, 32 Union Square -New York City. TRANSATLANTIC HEADSET "These Navies have been in continuous service for seven years and have given excellent results. " C. N. Inclosed find $ Please "After using -E, mail me the Impedance of 25,000 ohms A. C. at 800 cycles. a pair of your Navy Phones for ten years. items checked below. It is understood 11 I believe that I am qualified to say that there are none return them that I may Weight, oz. complete with hew headband and better, " C. L. within, 10 days if unsatiefectory is .env -F. way and you will refund my money polarity indicating cord. Equal to the best head- I have not found any of my friends' receivers to equal promptly. sets of other makes. Price, $12.00. Brandes Navy in clearness, sensitiveness and lightness" Put X here. H. C. M. - Navy phones Navy Type Headset SUPERIOR HEADSET 'Tour are light, durable, made right, look (High-ImpedEaace) $14.00 right, and work right. " -H. I. V. "They must improve Transatlantic Wound to 2,000 ohms D.C. Weight, 14 oz. com- with age, for I have four other Headset $12.00s$182..0000 plete with headband and polarity high price sets, but I always go back to the Navy Set" Superior indicating cords. C. B. II. - Headset A good headset at the low price of $8.00. "I have a New Head Band Headset pair of your Navy phones here which I took (Fits $ 1.75 to France with me and used all through the war. They old style Superior only) Both these models are guaranteed to give entire were the best phones we had and much lighter than any 16 -page catalog, 5e coin or stamps. satisfaction. issued set " -B. V. D. (Names on request) Name (Please Print Plainly,) Address

City State

www.americanradiohistory.com 676 Radio News for April, 1921

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PUBLISHED EVERY MONTH IN RADIO NEWS BY CONTINENTAL RADIO AND ELECTRIC CORPORATION

No. 183 Tusks C. W. Inductances, unassembled 10.00 TRANSMITTING TUBES Mail Order CHOKE COILS Acme 1% Henry, 500 MA Single Coil $6.00 Acme 1% Henry, 500 DIA Double Coil 8.00 Service- Acme 1% Henry, 150 MA Single Coil 4.00 RADIOTRON UV-202 The Continental Store in New York Acme 1r/% Henry, 150 DIA Double Coil 6.00 has long been famous as the fairest. C.E.Co. ZRX. 8 Henry 150 MA Single pleasantest, and quickest place to Coil Choke 3.75 Radio Corporation brings out new buy radio goods in the city. The Continental Mail Order Dept. 5 watt power tube. Continental is now becoming even more noted, TELEPHONE TRANSMITTERS thruout the United States, for these has big supply of first shipment. some reasons. Sterling Microphone $2.50 Let Continental Service serve you, (Ward Leonard) order direct from this advertise- RESISTANCES These new Radiotrons are pro- ment, and expect: Ward Leonard Resistance, 5000 ohm $1.70 duced in the great lamp works Accuracy: Speed: Courtesy Ward Leonard Resistance 10000 ohm 2.95 of the General Electric Com- Ward Leonard Resistance 1500 ohm 1.50 pany. They are of an improved Ward Leonard Resistance 12000 ohm 3.50 for long Lavite Resistance 48000 ohm for type, specially designed Radio Frequency amplifiers 3.00 operating life, and unequalled sensitiveness. We have a gen- MODULATION TRANSFORMERS erous supply of these wonderful Acme A -3 unmounted $7.00 new tubes, and can supply you cw Acme A -3 semi -mounted 5.00 with all the necessary equip- Acme A -3 unmounted 4.50 ment for a first class C. W. APPARATUS C.E.Co. ZRM Modulation Transformer 4.50 transmitting station.

We are making a specialty of every- GRID LEAKS thing used in C.W. transmission. MODEL UV- 202 -PRICE $8.00 Marconi 1, 2. 3, or 5 megohms $1.25 If there is any item you need, not Variable 5/a to 5 megohms, 10 listed below, write us for further Chelsea 5 watts. Filament voltage 7% volts. Fila- values 3.00 information and prices. ment current 2.35 amperes. Plate voltage Chelsea Oscillator 3.00 350 volts.

C.W. INDUCTANCES METERS (WESTON MODEL 301) Be the first in your section to use the Radio - 202! in your order Your No. 181 Tusks C.W. Inductances $7.50 Model 301 0 -3 amperes flush $8.50 tron Send today! tube will come by return mail!_ No. 181 Tuska C.W. Inductances, un- Model 301 0 -5 amperes flush 8.50 assembled 5.00 Model 301 0 -50 Volts flush 8.50 No. 182 Tusks C.W. Inductances 10.00 Model 301 0 -100 Milli- amperes flush 8.50 0 -3 Amp. $15.00 No. 182 Tuska C.W. Inductances, un- Model 301 0 -300 Milli- amperes flush 8.50 METERS (Hot Wire) 0 -5 Amp 15.00 assembled 7.00 Model 301 0 -500 Milli- amperes flush 8.50 No. 127 Gen. Radio flush 0 -1 Amp... $7.75 0 -10 Amp 15.00 No. 183 Tuska C.W. Inductances 12.50 Model 301 0 -800 Milli- amperes flush 8.50 No. 127 Gen. Radio flush 0 -3 Amp... 7.75 No. 127 Gen. Radio flush 0 -10 Amp.. 7.75 TRANSFORMERS (For C.W. Work) No. 127 Gen. Radio flush 0 -5 Amp . 7.75 BALDY 'PHONES Acme 200 Watt, mounted $20.00 Used by H. D. Selvage in first RHEOSTATS Acme 200 Watt, unmounted 16.00 amateur trans -continental spark Acme 50 Watt, mounted 15.00 reception. (3300 miles). Used 214 Gen. Radio front or back mounted $2.50 in the Trans -continental relay Paragon Rheo. front or back mounted 1.75 Acme 50 Watt, unmounted 12.00 test, Jan. 18. "Equal to Mesco Porcelain base 1.40 one and two stages of MOTGR GENERATORS radio amplification." BUZZERS FOR BUZZER MODULATION Type "C" $18.50 International 500 V 100 Watt AC Type "E" $20.00 Century 168 Buzzer 2.50 Drive $99.00 Type "F" $21.00 Meseo 2.50 No. 55 Buzzer International 500 V 100 Watt DC Slesco 251 .95 Buzzer Drive 110 00 Electric Specialty Co. 350 V 50 Watt HIGH FREQUENCY CHOKE COILS $1.50 AC or DC 97.00 Electrodyne Rectifier consists of 500 V Transformer and 2 rectifying vacuum tubes all Mounted ready for use. No. 25 R T Rectifier less tubes $35.00 (r \\ No. 25 V T Vacuum Tube Each 7.00 PARAGON R. A. TEN TRANSMITTING 'l'UNES $7.50 Gen. Radio Drum switch 6.50 Amplifying Short Wave Regenerative Receiving Set JEWELL METERS (Model 33) We can fill your order 0 $6.50 for one of -1 flush these genuine Paragons by return 0 -3 flush 6.50 mail. "The weaker the signal, the 0 -5 flush 6.50 stronger the amplification." Wave - length 160 to 1000 meters. Am- PARAGON 0 -50 Volts flush 6.50 plification 100 times. Two -year 0 -500 Volts flush 15.00 guarantee. Price Eighty -Five Dol- lars. RADIOTRON 0 -50 Dlil. Amp 6.50 0 -100 Mil. Amp 6.50 COMBINATION 0 -300 MIL Amp 6.50 0 -500 Mil. Amp 6.50 Frice CONDENSERS The Paragon Detector JEWELL THERMO AMMETERS WE 21 AA 2 MFD tested at 500 volts unit is complete with VT 0 -1 Amp $15.00 $11.00Complete Each $2.65 socket, filament rheostat, Dubilier 25 MFD Mica Condenser tested at 1800 Volts $6.00 grid condenser, grid leak, and Dubilier .0005 Grid Condenser for binding posts, with the Radio - transmitting sets .... 2.00 tron UV zoo, it makes a com- High Voltage Variable Air Condenser CONTINENTAL will stand 1000 V. Capacity .001 plete VT Detector outfit. MFD. Just the condenser for your RADIO AND ELECTRIC CORP. Antenna circuit $30.00 PARAGON UNIT - - - $6.00 I. DiBlasi, Sec. J. Stantley, Treas. Radiotron UV 200 - - $5.00 Note -Please make remittance by P. Complete Unit - - - - $11.00 Dept. C 33--6 Warren St., New York O. Money Order or bank draft. www.americanradiohistory.com H. GERNSBACK- Editor ROBERT E. LACAULT- Associate Editor . Vol. 2 APRIL, 1921 No. io ,,,,,,,..,,,.,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,im,,l,,,,,,,l,,,,,l,,,,,,,,,,,, neatrrrt,,n,,,a. InflInU,,,,,,,,,,,,, ..,,,111,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,1,,,,,,,,,,,,,,,,,,,,,,,,,,11M ,.,,,.,,,,,,,,,,,,,,,,, ,,,,,,,,,,,,,1,,,,,,,,,,,,,,,1INIw,M,,,MII® Underground Loops N' our July, 192o, issue we said editorially as follows: rotating the loop by the shaft which carries the wheel and "It is therefore safe to say that in twenty -five years the indicating disc. Any such combination can be used. hence there will be no such thing as a big ponderous In pointing out the importance of their new system, the aerial mast even for the powerful radio stations send- inventors say: ing messages all around the globe. Probably no aerial "In connection with receiving apparatus employed as a will be used at all. Perhaps no ground either. Before we radio compass, because of directive effects as obtained, for reach that stage someone will go and bore a shaft into the example, by a rotatable absorbing coil structure, the accu- earth, possibly a thousand feet deep, and hang an insu- racy of determination of direction of a source of radiant lated wire into this shaft. He will probably astound the energy is sometimes materially interfered with by objects, world by finding that by means of this arrangement as conducting masses, or earth formations near the ab- messages can be sent and received all over the globe just sorbing structure, with resultant distortion of the electric as easily as having a huge mast towering a thousand feet or magnetic field, or both, causing a variation of the deter- into the clouds. mined direction from the true direction: By employment A few weeks ago there was issued a patent to Messrs. of the new underground loop the disturbing effects of T. Appleby and L. M. Knoll, a patent which seems to mark distortion are materially reduced. And irrespective of dis- quite an advance in radio. Not that there is anything new tortion effects, the critical maximum or minimum response about underground radio. We have spoken of it a good in the receiving apparatus is more sharply defined, whereby many times, and its principles are pretty well understood. when the apparatus is so suitably shielded, its directional The directive qualities of a buried straight -away aerial or compass properties are improved." are also well understood, but the underground loop invented In plain English, it seems that the new loop should make by Messrs. Appleby and Knoll, not only seems to be well it possible to receive and send messages with much greater suited for directive effects, but prevents interference and accuracy as far as direction is concerned than was possible other disturbances as well. It was hitherto conceded that heretofore. the underground aerial was effective only for receiving, It is interesting to note that the inventors mention that but not for sending, but the inventors of the new under- the loop is not only effective under ground, but can be used ground loop have made it possible to transmit as well. By under water as well. This should be of much interest to means of the new system, which will be described at length ship owners, for it is here where very accurate direction in our next issue, the loop as well as the apparatus is finding is of prime importance. It seems that if the in- used under ground in a cavity especially prepared for this ventors' hopes are carried out, we will soon witness a loop purpose, and the loop as well as the instruments is thus installed down in the hold of a vessel (providing it is not shielded entirely from the outer atmosphere, thereby doing steel plated), from which the signals may be either received away almost entirely with static. or sent. The loop has done wonderful things in the past It had been found in previous experiments with the few years, and it seems certain that in the next decade, Rogers' Underground Aerial that it becomes possible to most of our cumbersome aerials will be relegated to the greatly reduce static by its use. It therefore does not come scrap heap. Already the loop is coming into more and more as a surprise to understand that static is suppresst almost favor. Amateurs are recognizing its great importance and entirely by means of the underground loop. are beginning to install loops where heretofore aerials were The inventors rotate their loop in the usual manner by used. Of course, it must be understood that a loop is of means of a wheel and graduated indicator for direction not much use unless it is used in connection with an ampli- finding purposes, but it is of course possible, as they point fier of at least two or three stages of amplification. Using out, to reverse the combination by using the loop under crystal detectors with loops yield practically no 'results. ground and by extending the shaft above ground, and thus H. GERNSBACK.

IMPORTANT TO NE WSSTAND READERS: In order to eliminate all waste and unsold copies, it be- This costs you nothing and you will be assured of your comes necessary beginning with this month to supply news- copies. Hand your newsdealer a slip of paper on which dealers only with a sufficient amount of copies for which write your name and address with a request to reserve a they have actual orders. Please note that your news- monthly copy of RADIO NEWS for you. This will he the dealer will be glad to reserve a copy for you every month. only way to assure you of your copy hereafter. www.americanradiohistory.comC77 678 Radio News for April, 1921 Radio Communication Elementary Explanation of the Principles of Radio Telegraphy and Telefone By DR. J. H. DELLINGER Bureau of Standards. Washington

Fig. 1. On the right is a tuning fork used to show the analogy between electric and sound waves. Fig. 12 on the left is a complete radio telefone set using five vacuum tubes to produce can easily produce waves on a rope by high frequen- that cy oscillations. shaking the free end. This illustrates A phonograph a wave always consists of some sort of used to send to- and -fro motion. Waves can be slow or music is wave We can- shown in the fast and of different -length. photograph. not see electric waves, as we see ripples or the waves on a rope, but there is nothing special or mysterious about them. We cannot see sound waves. If a tuning fork (Fig. 1) is struck it gives off sound waves, which, starting at the tuning fork, travel Editor's Note: and received at another. These radiated out into the air in all directions like the Despite the fact that countless experi- waves are electric waves, but they have all ripples referred to. menters are familiar with the principles of the characteristics of wave motion possesst Sound waves are produced by the motion Radio, the Editors that this article would by other kinds of waves, such as sound of the metal prong of the tuning fork. be of interest to the numerous new ama- waves or even the simple waves produced As the prong moves back and forth it teurs who have just started in the game. in water when a pebble is thrown into the causes the air next to it to move back and forth. This motion is handed on to the MESSAGES are now sent without surrounding air and so moves out to a wires between any points on the great distance in the air just as the ripple earth's surface, in the air, or under on the pond spreads out. The slight to- the ocean. It is possible to sit down and -fro motion of the air spreading out in to the telefone in your house and this manner is called a sound wave. talk to persons not only in distant cities Electric waves also consist of a certain but to persons sailing on the ocean or fly- kind of to- and -fro motion. Just as the ing in airplanes. The principles which motion of the tuning fork causes alternat- make wireless or radio telefony possible ing pressure in the surrounding air, simi- are really not difficult to grasp. While a larly whenever an alternating current flows great deal of mystery has been made of in an electric circuit the to- and -fro motion radio, as a matter of fact everything about of the current causes alternating electric it is simply a part of principles and ideas pressure in the space next to the wire. This well known to science. Since the results to- and-fro or alternating electric pressure achieved in wireless communication are in the space surrounding the wire affects somewhat striking, the newspapers lose no the surrounding space and spreads out in opportunity to use them to incite, the won- exactly the same way as a sound wave in der of the people. Fig. 11B. This is the Amplifier Used in Con- air. The radio telefone is not a particular in- junction With a Loop Aerial of the Type Shown When the key is presst an alternating strument; that is, when you talk into a on the Opposite Page. current is produced in the wire and a spark radio telefone you do not necessarily talk occurs at the spark gap, which lets one into anything different from the ordinary pond. Much can be learned about the way know that an electric current is flowing. telefone on your desk. Sometimes people radio waves act by watching the spreading It is to be noted that this apparatus pro- talk of a radio telegraph or even of a radio, out in circular rings of ripples on water. duces at the same time sound waves, light indicating an idea that some particular, Other simple types of waves are also pro- waves and electric waves. The electric wonderful apparatus accomplishes the feat duced by ordinary mechanical means. One waves are also called radio waves and it is of communicating from one place to another without wires. As a matter of fact, radio is a system or method involving a great many instruments and appliances. 1111.,11ni.,.,i,,,1111211 Some of the instruments are very interest- Fig. 9. On the ing indeed, among them being the electron right are a tube, of which more will be said later. few of the The history of radio is all comprised various vac- own lifetime and has been a uum tubes within our actually in steady conquest of distance obtained by use for trans- radio communication. It increases from mission and three -fourths of a mile the first year, reception. The tubes 6 and 7 when Marconi performed his startling are high first experiment, to thirty -four miles power tubes the next year across the English chan- delivering 250 watts each. nel, and so the distance has steadily The smaller risen. Last year the distance finally rose types, 2, 3, 4, to 12,000 miles. This is the limit, since are used for reception and 12,000 miles is half way round the earth. amplification We cannot communicate any further than and the tubes this unless we exchange signals with other 1 and 5 are planets. To be sure the newspapers had transmitting tubes for low us communicating with Mars in April, powered sets. 1920, but this must be discounted. The word "radio" suggests its own explanation. It means to radiate. Radio communication is carried on by means of www.americanradiohistory.com Radio News for April, 1921 679

Fig. 5 A. On the left two tuning forks are used to demonstrate the phenomenon of resonance. Xf some wax is fixt on one of the tuning forks as may be seen on the one placed on the right, this changes the frequency of the sound waves and when the former is struck the latter does not respond. Fig. 14. On the right is a complete radio compass station, by means of them that radio communica- including a tion is carried on. loud talker. It is an interesting fact that radio waves are really of the same kind as light waves. We are all familiar with light waves and it The waves are radi- should help to make radio waves less mys- ated and spread out terious to know that they both are electric more effectively the waves. The difference between light and higher the frequency. radio waves is the frequency of alterna- The ordinary low fre- tion. Thus electric waves are much more quencies used in the common things than is sometimes sup- alternating current s posed. Electric waves are used for many which light our houses purposes, their use depending on the fre- alternate very slowly. quency of the waves. This is shown by Such waves traytravel the following table showing the frequencies readily along wires. In of the various kinds of electric waves. By order to get a wave frequency is meant the number of vibra- which will travel ef- tions per second or the number of to -and- fectively thru space, fro alternations of the electric pressure as higher frequencies the wave travels out thru space. must be used; that is are not, however, as high as the frequen- Waves Produced by Vibrations per Second why the frequencies cies of light waves. Light travels in straight Commercial Alter- shown in the table for lines, which is one of their characteristic nating Currents .25 to 500. radio communication differences from the low- frequency waves Telefone Currents 16 to 3,000. of alternating current power which follow Radio moon to 30,000,000. along wires. Radio waves are intermediate Heat and Light 3,000,000,000,000 to in character between the two, and can 3,000,000,000,000,000. travel in straight lines and also travel along X -Ray 3,0,000,000,000,000,000. conducting wires. Radio waves are differ- All of these waves travel at the same ent from light waves also in that they go speed. These electric waves are of an en- thru ordinary walls of buildings and other tirely different nature from sound waves. obstacles which are opaque to light. Sound waves are not at all electrical; they We are now ready to consider how an consist of actual to- and -fro motions of the electric wave may be produced. air particles and travel with a speed of Whenever there is an electric circuit in about t,000 feet per second. The speed at which alternating current is flowing, an which electric waves travel is much greater electric wave starts out just as a sound Fig, 6. Diagramatical Arrangement of Vacuum wave starts out from a vibrating tuning than this; it is so great that the passage Tubes Showing the Principle of the Amplifier. of any kind of electric wave is practically fork. A powerful sound can be produced instantaneous. The various kinds of elec- by using a very large tuning fork, and tric waves shown in the table are much make a large number of vibrations per similarly a powerful electric wave is pro- alike in many ways but they have some second. duced by making some part of the electric characteristic differences. It is to be noted that these frequencies circuit large in dimensions. The antennae used in radio work, as is well known, often consist of long conductors supported on very high towers. A mechanism for producing a radio wave, therefore, is simply an enlarged or extended portion of an elec- Fig. 13. tric circuit in which an alternating current Here is a is made to flow. In the space near the an- complete portable receiver tenna, alternations of electric pressure are using a loop produced just as alternations of air pres- aerial which sure are produced around a tuning fork. is fixt inside At any instant the electrical condition of the box. The signals are the space around an antenna which is send- detected and ing out radio waves, could be shown by a amplified to diagram such as Fig. 5. The arrow on such an extent that the line extendine- between the antenna and when the horn ground indicates that the electric pressure is fixt on the at a particular moment is in the direction box, music indicated. When the current changes in and speech as well as radio direction, the direction of this electric pres- signals can sure will be reversed and the electric pres- be heard by sure already mentioned will have handed several per- on sons in a its effect to the surrounding space. Thus room. This the effect of an electric pressure is handed apparatus on and spreads out thru space, the direc- was designed tion of this pressure at by the Bureau any point con- of Standards. stantly alternating as the direction of the current in the antenna producing it alternates. Lines of electric pressure alternating in direction are thus constantly spreading out from the antenna just as the ripples www.americanradiohistory.com (Cnnhnnpil nm anca tirnl 680 Radio News for April, 1921 Get Your Friends Interested

THERE is no an umbrella aerial time like the receive a message present, ama- from "somewhere" teurs, for get- while walking on ting busy and Madison Avenue. interesting some of The antenna was of your friends, rela- the spiderweb type tivesor neighbors in altho it is really an the fascinating game umbrella type aerial of Radio. Fellows and sewed on a who "hang out" even- parasol; the receiv- ings at the pool- er of the smallest room, dance hall, or kind, was a wonder movies for want of and using a water some place else to hydrant as a ground go may be just wait- the two "Radio but- ing a chance to take terflies" (that's the up the work and name for female will jump at the op- "Radio bug") could portunity if a "bug" hear the voice of will only make the somebody, probably suggestion. a bug, telling them Aside from the something funny, if interest and enjoy- we believe the pho- ment a fellow gets tograph showing out of learning ra- their smiling faces! dio and making his After being intro- own instruments, he duced to the radio is gaining knowl- bu - - - tterflies, we edge and education took a look at the that can be devel- set which evidently oped into a prof es- was of the smallest sion or trade. Many type being built at bright boys and the present time. young men who are This Photograph Shows the Latest in Portable Radio Sets. The Aerial is Sewed on an Umbrella and The detector was spending their even- a Hydrant is Used as a Ground as Shown in the Right Hand Photograph. On the Left is a View only a crystal, but of the Two "Ope" Listening in to a Fone Conversation While Out For a Walk. These Two "Ops" just wait until some ings in idleness or Midnight Frolic. bad company simply are Miss Peggy and Alice Brady, of the Ziegfeld small V. T.'s come because they haven't out and then we found an interesting "hobby," will make warm, cosy room, the amateur's receiving shall see some real portable sets. good members for amateur radio clubs, if set brings him all the latest news, concerts A novel feature in this girl's set is that in once interested in the work. by great singers sung many miles away, and the cover of the box is a mirror and the There is undoubtedly a big future for he is able to hear European stations in con- customary powder "tank" and puff ! And the amateur of today in wireless telefony, versation with the United States. the box containing all these instruments is as it will assuredly take the place of the Now, boys, there is an additional reason only 5" x 4 %" x 3'1/2". telefone within a few years. There will for getting interested in radio. The "rea- In a word Radio is becoming more pop- then be many good positions open for the son" being shown in the accompanying pho- ular every day among the public, and it is young man who now comes in on the tographs. Some of you fellows may not (Continued on page 709) ground floor and gets a thoro, practical have known it, but many of knowledge of radio. the fair sex have gone in There is also a great deal of pleasure for radio and more are tak- connected with amateur work, especially in ing it up all the time. They the long winter evenings. Seated in a are making good at it, too. What could be more interesting than a radiofone conversation during a long, lonesome evening with a sweet- voiced girl on the "other end "? Wait until the radiofone becomes more universal and we pre- dict many a ro- mance will b e started just this very way. Not only in winter, but in summer as well, Radio is mighty interesting; with the spring the portable sets appear and many a one gets busy on t h e construction of a complete station to be used during the vacation at camp or on week -end trips. Just recently, in New York City, we saw two girls

Here is a Girl Who Owns a Real Set. The Girl and the Set with a "vanity . A Girl Amateur Receiving Some Instruction on C.W. Sets at Are in Brooklyn, N. Y. case" receiver and the Radio Convention Exhibition of the Second District.

www.americanradiohistory.com Radio News for April, 1921 681 New Universal Range Receiver By ARTHUR H. LYNCH coupling coil, which is of the rotary type controlled by the dial - knob,- located in the upper left - hand corner of the panel. Maxi- mum coupling is obtained when the setting is at 5o and minimum when at o. In series with this coupling coil is the grid variometer, controlled by Inside View of the Universal Receiver, Note on the Left the A New Receiver Including a Short Wave Regenerator and the dial -knob Long Wave Set and in the Center the Switch Changing From a Long Wave Set, With Detector and Three -Stage Amplifier. shown at the low- Short to Long Waves. er section of the ALLTIIO most amateur reception is panel, to the right of the antenna condenser sign, telescopically mounted in the large carried on within the range of 3,000 control. Wave -length is increased or de- Cellulak cylinder, and a coil of bank -wound meters, many experimenters being creased in this circuit as the figures on the litz wound on the exterior of the cylinder. satisfied to limit their waves to in- dial indicate. A shunt capacity of .0002 The amount of inductance desired is thrown corporate that of NAA, there are mfds. is thrown into this circuit when into circuit by the specially designed switch times when the copying of transoceanic sig- waves above soo meters are desired. located in the lower right -hand corner of nals are of interest and value. It is to fill The regeneration and amplifying actions the panel. With each step of inductance this purpose that the set herein described of the plate circuit are produced by means thus added, the wave -length is approxi- was devised. In the sense, that it mately doubled, as 55o, 1,100, 2,200, will cover all wave -lengths in use, it etc. A tickler coupling is provided may be called a "station" receiver. wound on a ball- shaped wooden There are two main groups or form, orientated in the long wave wave -lengths, the first, iso -68o me- field by means of the . dial -knob ters, is broken up into smaller di shown just above the inductance visions which interlap, their ranges switch. In conjunction with the being 150-375 and 280 -680, respec- tickler winding there is a seven point tively; the second, 550- 2o,000 meters, by-pass condenser, controlled by the is for the long wave operation. As second switch at the lower left of will be observed from the photo- the panel. These last two elements graph the wave -length change, from are for use in regulating the regen- the first or short wave section to the erative action. Altho the degree of second or long wave section, is ef- Lad selectivity where a single circuit is fected by simply throwing the anti - employed can never be as great as is capacity key which may be seen in found in coupled circuits, a resultant the central lower part of the panel. signal strength is found to exist af- The two intermediate ranges of the fording the same consistent opera- short wave section are controlled by tion. the switch, so marked and located THE DETECTOR AND AMPLIFIER above and to the left of the detector c-i Gm CIRCUITS, filament rheostat. The two main In its entirety, the tube circuit sections or circuits, with relation to Complete Hook -up of the New Receiver Embodying Several comprises a detector and three -stage this anti -capacity change-over, have New Features. audio frequency amplifier, entirely been designed in such a way as to under automatic control, and em- have them terminate or be separated by it, of the plate variometer, indicated on the bodying several improvements. The trans- at the points of minimum reaction between panel. This variometer functions thruout formers are of a new and rugged de- the active and the dead circuits. the entire range of the short wave plate sign, which does away with the difficulty THE SHORT WAVE ARRANGEMENT. circuit. which occurred so frequently in the past The primary circuit consists of a vari- THE LONG -WAVE CIRCUIT. when the windings have been cut by the able condenser in series with the primary The receiving is done on long waves, by sharp edges of the core. The tube sockets of the variocoupler adjustable in single means of a single circuit. The inductance and amplifying transformers are mounted turns and groups of six turns. is composed of a number of universal on a bakelite bracket, fixt behind the panel. The secondary circuit comprises the wound coils of special dimensions and de- (Continued on page 728) Some New British Apparatus

A complete receiver, two photographs of which appear on this page, has recently been placed on the market in England. The set is composed of a receiver using honeycomb coil inductances and fitted with a V. T. detector which acts at the same time as oscillator for the reception of undampt waves. The other part of the set is a three -stage audio frequency amplifier having but one filament control rheostat. When used together, these two instruments make a very sensitive receiver tuning in any wavelength, on the short aerial that the Eng- lish amateurs are permitted to erect. The receiver itself may be used alone if desired and itself forms a complete unit, A Complete Autodyne Receiver Using Honeycomb Coils for Tuning. The V.T. is Used as Detector but with the amplifier, signals are amplified and Oscillator and Only One Knob is Adjusted enormously and with a loud talker may be to Tune the Different A Three -Step Audio Frequency Amplifier Using Circuits at the Same Time. heard very far from the set. R Tubes. Only One Rheostat is Used to Con- www.americanradiohistory.com trol the Filament Current of the Three Tnhaa 682 Radio News for April, 1921 Tests of Insulating Materials for Radio Use at the Bureau of Standards By S. R. WINTERS

rfHE quality of paper made by the General Bakelite used, rather than the Company or Condensite Com- excellency of the var- pany of America. These lami- nish, is a determining nated insulating materials are factor in manufacturing used in vast quantities for radio insulating materials, if making panels and parts of we are to accept with a de- apparatus for radio and other gree of finality the conclusions electrical equipment as well as of a series of comprehensive for technical and commercial tests conducted by the Radio uses. Moulded materials con- Communication Section of the taining the same varnish are National Bureau of Standards. used for making countless The experiments involving the numbers of small parts in circumspect examination of electrical apparatus of varying properties entering into the kinds and in other products; construction of wireless appa- notably, records for talking ratus were negotiated by J. H. machines. The specimens sub- Dellinger and J. D. Preston, jected to measurements to de- the tests running thru a period termine their electrical, me- of years. The specimens sub- chanical and thermal properties jected to the rigid observation consisted of actual sheets of were obtained from various material as regularly supplied manufacturers, the investiga- On the Upper Left Hand Photograph is Shown How Some Bakelite Plates for commercial use. To illus- tion having its inception with Are Tested Under High Tension and High Frequency Current. Behind the trate, for radio measurements an insulating company who in- Table Are a Receiver and a Wave -meter and on the Shelf Over the Table is a Sensitive Galvanometer Used for Measurement of Losses in Dielectric. condensers were made up using voked government analysis by On the Right Hand Photograph Can Be Seen the Shield Fist on the Table an actual slab of material reason of its product suffering Between the High Tension Apparatus and the Various Meters. The Lower such as is used in the con- View Represents the Test of Dielectrics With as Supply of a reputation of alleged infe- a C.W. Set a struction of apparatus ; that is, riority from criticism of rival High Frequency Currents. Note on the Right the H, T. Storage Battery. regular stock supplied by the companies. manufacturer. The conclusion of the Bureau of Standards phenol varnish, creating a composite prod- DETERMINING TENSILE STRENGTH. is that there is no outstanding superiority of uct in slab form of many layers. The one material over any other. That is, one The method of measurement in deter- process of manufacture involves the react- mining the tensile strength involved the use company can produce a product of qual- ing formaldehyde am- ity commensurate any other of a mixture of and of samples 12" long by I" wide with the with that of a phenol concern provided due attention is pledged monia or equivalent product upon width reduced in the center to y ". The to the properties of the material and the at high pressure and temperature. The transverse strength test involved the use of factors entering into its composition. The heat applied is about iio degrees Centi- a rectangular 12" specimen, loaded in the investigation included the class of mate- grade. The varnish is soluble in alcohol, center of a io" span. Brittleness was de- rials enjoying popularity, namely, those of sheets of paper being dipt into the solution termined in this fashion : A piece 3" long the phenol or occasionally denominated and a sheet of specified thickness built up. was inserted in a vise, a hammer on a pen- the bakelite type. A wide variety of elec- Under a heated pressure of i,000 pounds dulum arrangement delivered blows to the trical and mechanical properties of the ma- to the square inch in a hydraulic press the material, and the distance of the swing be- terials were measured, altho the principal process of manufacture is completed. yond the specimen was used to compute the object of the tests was to determine the Insulating materials of the laminated type energy necessary to break the material. Fa- miliar was the method of revealing the suitability of materials for radio uses. The were investigated from these sources : The nature of the materials resolved itself into Continental Fibre Company, who manu- hardness of the specimen; merely, pressing a steel ball into the material and two general classes, the laminated and facture bakelite - dilecto ; Westinghouse then moulded products. They contain a phenol Electric Manufacturing Company, producer measuring the diameter of the indentation. by preparing and weighting a small square resin or varnish of the general type in- of bakelite-micarta ; Formica Insulation vented by Doctor Baekeland. The moulded Company, makers of formica; Diamond sample, subsequently giving it a 24 -hour materials are a combination of the phenol State Fibre Company, who manufactures bath in water, and then measuring the prod- varnish with a filler material in ground or condensire - celoron. The Formica uct, the absorption of the insulating mate- Company rial was made known. pulverized form, the composite product be- uses as a varnish a product termed red - The result was ex- ing poured into a mould and shaped as de- mano!. produced by the Redmanol Chem- presst as the percentage change of. weight. sired. The laminated materials are made ical Products Company, while the other As to electrical measurements, the volume hv catrnratinv lavare ,nf nano .,,i4h 4hP rmmnaniecwww.americanradiohistory.com Pmnlnv enmr fnrm of halra14P Radio News for April, 1921 683 Aeroplanes and Radiogoniometers By ARMSTRONG PERRY

SUPPOSE you were navigating an AMATEUR CAN TRY AVIATOR'S METHOD. then pick up another station and repeat the aeroplane, a mile above the ocean, en- The radio amateur can get most of the process. velopt in clouds so thick you could sensations of the lost airman finding his This method is crude and these observa- not see a hundred yards ahead, going way if he will use his ingenuity and his tions alone will not tell you which end of a mile a minute, with only an hour's imagination. your arrow points toward the sending sta- supply of gas and you didn't know in Construct a loop aerial by winding an- tion. If you are not sure of the location which direction you were flying nor where tenna wire on a wooden frame four feet, look at a map in your geography, but ordi- you could find a landing place. six feet or eight feet square. The larger narily you should know where you started, What would you do? the loop, the more energy it picks up. On which way you flew and the general direc- Use your radiogoniometer, of course. the other hand, the larger the loop, the tion of important radio stations. What- This instrument with a long name, which more static and other interference it picks ever your results, you at least will begin means radio compass, is not hard to under- up. to understand the principle of direction stand if you know the principles of radio. Use No. 22 annunciator wire. For re- finding. Those who do not may skip to the next ceiving Zoo -meter waves -the maximum Another way to practice is to take your paragraph while I explain it to those who wave -length which the law permits ama- receiving outfit and, in a day's journey, do. They will understand what I mean teurs to use in transmitting -only one turn chart the directions of the same stations when I say that it or one type of it con- of wire is needed. For 600 meters, use from several different points. sists of : (a) two loop aerials, triangular three turns. For t,000 meters or over, use IMAGINATION INSTEAD OF APPARATUS. in shape, mounted at right angles to each twenty turns. If you have no radio apparatus at all, other on a common vertical axis; (b) two The spacing of the wires is important. you can do it all in imagination. field coils, also mounted at right angles to If you have an 8 -foot frame, space the Here we are up in the air. each other on a common vertical axis, with turns I's" apart; on a 6 -foot frame Tie "; Dah -de de -dah de -dah, in comes NAA. a variable condenser in series with each; and on a 4 -foot frame 1/4". You may have While he shoots his message to someone (c) a search coil mounted somewhere you turn the at the center of these field knob of the radiogoniome- coils, on the common axis ter and nail him at 230 °. but free to on in- turn it Dah -de de -dah de- de -de- dependently; (d) a receiv- de, there's ing set, preferably NAH. You with a draw a bead on him at 275° valve amplifier. These dif- You plot the lines. From ferent elements must be the point of intersection tuned to each other and to the stations you extend another to show whose signals the distance covered by our are to be picked up. The machine, at standard wave roo MPH in the -lengths are three minutes since we pickt 30o and 600 meters. up the last station. Even the beginner will understand what I mean Are you sure you know when I say that by turning where you are? Check it a knob on the radiogonio- all up and make sure, for meter you can make the in- it's a lonesome job dropping coming signals sound loud- into the ocean sixty miles er or weaker. from land, even if in imagination you have a flying CALLS FOR TEST LETTERS. boat. The airman is always at A station pointer will liberty to ask any radio make your work quicker station to send the test let- and possibly more accurate. ter, de -de -de -dah, for two You can make one in half or three minutes at a time an hour. while he is getting his bear- Lay a dinner plate on a ings. sheet of cardboard and The knob turns the search draw a line around it. coil and it also turns an in- Center a tea plate inside dicator arrow. When the the circle and draw another signals are loudest, the around the tea plate. arrow points exactly to- Remove the plate, find the ward the sending station. Inside View of the Radio Room Aboard an Aeroplane. Note in the Upper Left Hand Corner the Receiver. On the Right is the Amplifier Mounted on a Frame center of the circles and Quickly the airman draws a With Elastic Suspension to Avoid Vibrations. mark it. Divide the cir- line on his chart or map, cumference strip into 36 showing this direction. He spaces of io degrees each. also indicates North and the direction of two or three aerials on one frame, connect- If you have patience, mark all 260 degrees, his flight as shown by his magnetic coming in the single turn, the three turns or beginning at zero for north and going pass. the twenty turns, whichever you need for around as the clock hands travel. Then he calls another station and notes the station to which you want to listen. Make three cardboard arms -straight on directions on the chart as before. Disconnect your flat top aerial and con- both edges -long enough to reach from If necessary he calls a third. nect the loop aerial, in series with the center to circumference. Fasten the three The point where the lines meet is ap- primary circuit of your receiver. The loop at the center with one pin. proximately the position of his machine. aerial is not grounded, nor connected with Cut away as much of the cardboard as Of course he has to make allowance for the earth. you can so that you can see your chart the distance traveled while making his ob- Listen in until you hear a station. thru the holes when the station marker is placed upon it. servations. Write down the call letters, then turn He knows the geographical locations of your loop aerial until you get the loudest Now instead of drawing lines upon your the stations called, or can find them by signals. The plane of your aerial then co- chart, you lay the station marker upon it, looking up their call letters in his list. Per- incides with the direction of the advanc- with zero at the north. As you pick up haps one is in New York, one in Boston ing radio waves. In other words, an arrow your stations, adjust an arm to show the and one in Norfolk, Va. It does not take stuck thru your coil, passing between the direction of each. him long to decide where to steer to find wires on each side and parallel to the earth If the observations could be made simul- a landing place. would point toward the sending station. In taneously, the center of the station marker His calculations might not be exactly practice, operators usually find the mini- always would show the position of our air- correct on account of the variations of mag- mum position-the position in which the ship. But they cannot, so we have to al- netic compasses and the difficulty of plot- signals are faintest -for the maximum is low for the fact that we cover five miles ting the curved surface of the earth on a harder to determine exactly by the ear. or so every three minutes. flat chart, but he could correct his course Maximum is always just go °, a quarter of Games like these will soon lift you out by using his eyes when he was out of the a circle, from minimum. of that class of boys who have nothing to clouds and nearer the earth. Draw lines on a chart, as the aviator did, (Continued on page 752) www.americanradiohistory.com 6S4 Radio News for April, 1921 Awards of $100 Portable Radio Prize Contest FIRST HONORABLE MENTION

On the left is a view of the complete portable set, which was awarded the first honorable mention, while on the right is a detailed view of the panel.

...111111 11111111,111111111111111111111

transformer when carefully constructed, THIS set is of my own design and ground clamp with me, so that in case has them all beaten for compactness, and in construction. there should be a water pipe handy I could most cases in efficiency as well. This A good idea of the size of this set get a ground that is without doubt, supe- transformer will tune to a wave -length of may be obtained by comparing it rior to the one mentioned above. approximately 800 meters. It measures, a with the receivers lying beside it, as The set itself is built a small wood- minimum diameter of /z"T for the second- shown in one of the photographs, and also en cabinet, made of ?g"Ig" material taken ary, and a maximum diameter of 13/"' for by comparing it with the hand holding it from a cigar box, and given a good oak the primary, and is 34" in height. as shown in another. Altho it is small finish. A small lock taken from a Gillette The secondary consists of 320 turns of enough to slip into any coat pocket, includ- razor case is used to fasten down the lid. No. 32 S. C. C. wire, and is tapt once every ing the aerial and ground, it has given me It measures 4%" by 2%" by 2%" over all. forty turns, giving eight taps. These eight exceptional results. taps are connected, one tap each, to the The outfit itself, as already stated, con- eight point switch shown in the upper right sists primarily of a one -wire aerial, ground hand corner of Fig. 1. connection, receiving set, and a pair of five The primary consists of 232 turns of No. hundred ohm fones. 3o S. C. C. wire. Every other turn of the The aerial is composed of two strands of No. 3o bare copper wire twisted into one; one hundred feet long, and a lead of fifty feet taken from one end. To carry in the pocket it is wound on a typewriter rib-

To 77-ans f To Groux! ToAeria/ To Trans! Figure 2

Inside View of the Set. Note on the Right the Primary Coil Removed to Show the Second- ary and Taps. Most every Radio "Bug" has a different idea of what would be the most efficient tuner for portable sets. Some prefer honeycombs, others ordinary tuning coils, others bank wound tuning coils ; but I that the ring wound or doughnut type think Figure I Figure 3 Fig. 1 Shows Layout of the Panel. In the Center are the Primary Unit and Multiple Switches and Hook -up of the Receiver Showing the System on the Right the Secondary Switch and Detec- of Tuning With Unit and Multiple Switches. tor. Fig. 2 is a Side View of the Primary Com- bination Switch. bon spool and when to be used, it may be first sixteen is tapt, giving eight taps. These suspended between two trees, buildings, taps are connected to the eight point sec- etc., by throwing over a stone or other tion of the primary switch. The remain- handy weight, to which a string has been der is tapt once every eighteen turns, giv- attached, and then drawing the aerial up ing twelve taps, which are connected to after it; but first however, fastening a the twelve point section of the primary 2 -wire cleat at each end to insulate it. switch. These leads are less than / " long. I have tried several kinds of aerials, such This method of tapping allows very fine as the loop aerial, tree aerial, etc., but have tuning. found that a one -wire aerial like the one The primary switch is made interpolat- described above, will give the best results ing to conserve space, and is constructed with portable sets using crystal detectors; as shown in Fig. 2. besides, having the added advantage of be- A crystal detector is employed, using a ing able to be rolled up very compactly, so very sensitive piece of radiocite. The cup that it will along with the necessary insu- is the cap from a battery binding post and lators and twine, readily go into a hip is fastened to the bakelite panel from the pocket. back by an 8 -32 machine screw. In this The ground connection is simply a fig" cup the radiocite is fastened by wedging copper plate, 21/2" wide, by 4" long, to tin foil around it. The contact, or cat - which a length of No. 18 copper wire is whisker, is a piece of No. 28 brass wire, fastened for the lead. To ground the set, filed to a point at one end, and fastened the plate is laid preferably in a pond, river to the panel by means of another machine or other body of water or, such not being screw at the other. available, is buried a foot or so in as moist Photograph of Mr. William F. Marquardt, De- A small fixt condenser, made trom two earth as can be found. I also carry a signer and Builder of the Portable Set. (Continued on page 752) www.americanradiohistory.com Radio News for April, 1921 685 A "B" Battery of the EdinrStoraeType By W. H. FARR

THERE is probably no one item in "pasted" or filled with lead oxide, it will about 4%" long and i°e" in diameter. These the equipment of the amateur radio hold a charge only a short length of time have been filled with alternate layers of station which gives so much annoy- and will have to be charged every few nickel oxide and flake nickel under heavy ance as the "B" battery. Of course days. Finally the lead cell is heavy, and pressure. The negative elements are flat most amateurs use some form or usually not readily portable, and the sul- pockets of perforated steel about 3" long, other of dry cells, as these are convenient, phuric acid is rather dangerous to handle. %" wide and A" thick, containing spe- readily obtained, and the comparatively low ADVANTAGES OF EDISON CELL. cially prepared iron oxide. The electrolyte first cost makes them appear to be the In contrast to the above facts, the Edi- is a 21 per cent. solution of Potassium Hy- most economical type of battery. The dry son storage cell has many advantages. It droxide in water. cell, however, is far from being ideal, and is the most rugged and dependable of any Of course it is necessary to obtain a stor- has many weaknesses. In the first place, type of storage cell, and is practically "fool- age cell and completely dismantle it in the dry cell is rather short lived at best, proof." It deteriorates very slowly when order to obtain the material for construct- and especially so in the smaller sizes, which standing idle, and is not injured by standing a "B" battery as described below. How- are usually used in radio work. It has an ing partially or fully discharged. Also it ever, a large number of these miniature aggravating habit of running down even is not damaged by accidental short circuits cells can be made from one storage cell. when not in use and often gives out just It will stand a high charging rate, even up The plates of the size shown in Fig. 2 have when it is wanted the worst. When once to 30o per cent. of normal, without any in- 32 elements in each positive plate and 24 exhausted, it cannot be renewed, but must jury, which means that it can be brot into in each negative plate. These elements be thrown away and a new supply pur- service very quickly when found to be run are easily removed from the grids in which chased. Another fault of the dry cell is down. The discharge curve is quite flat, they are held, and as they are very sub- that the voltage gradually drops as the cell which means a very constant voltage thru- stantially constructed, there is no danger deteriorates. In fact the discharge curve out the whole period of discharge, a fact of breaking or injuring them in handling. is rather steep. The result is that It will be noted that the elements are when used with vacuum tubes which a very convenient size for making require a critical adjustment of the test tube cells, it being possible to plate voltage, the number of cells in build a cell into a test tube as small the circuit must be adjusted from as %" in diameter. In building the time to time to compensate for this cells described below the writer cut gradual drop in potential. the positive tube off to the same length as the negative one for con- MANY PREFER STORAGE CELLS. venience in handling. In view all these facts, many of of DESCRIPTION OF "B" the more progressive amateurs have BATTERY. abandoned the use of dry cells for The following is a description of "B" batteries, and are using, instead, one of the complete `B" batteries of small lead storage cells. There are sixteen cells as built and used by the many advantages to be gained by the writer. As will be seen in Fig. I, use of storage cells for this purpose. the battery is contained in a hard- On account of the greater current wood case 4y," square by q" high. capacity, a storage battery makes The individual cells are contained in possible the successful use of a po- glass test tubes %" in diameter and tentiometer for voltage control. 5" long. The test tubes were blocked When used with dry batteries it in place in the case and the interven- usually runs them down too fast. As ing space poured full of melted par - a rule the voltage of a storage cell is affine. This is a very convenient much more constant than that of a method of holding the cells in place, dry cell, which is a very desirable and it also eliminates any danger of feature in a "B" battery. One of breakage. Each cell is closed with a the biggest advantages, however, is one -hole rubber stopper having an the fact that a storage cell can be so air vent consisting of a short glass easily recharged when exhausted. (A tube drawn down to a small opening small electroyltic rectifier for this at the lower end. The connections purpose can easily be constructed by to the Edison elements are made the experimenter.) Finally the life with nickel wire (to avoid corro- of a storage battery is infinitely sion), the wires being simply twisted longer than the best dry cell made. around the elements (not soldered to The facts which have been men- them). A small block of I" sheet tioned above apply to both types of hard rubber is placed between the and elements storage cell, the lead -acid type A Practical "B" Battery May Be Built With Elements at each end to act as a sepa- the iron -nickel -alkali, or Edison type. From an Edison Cell. This Photograph Shows a Portable rator, and they are held together with A comparison of the characteristics Battery and a Complete Element Removed From a Tube. rubber bands. The terminal wires of these two types will disclose are threaded thru the rubber stop- several facts which affect their pers. This construction renders the use as "B" batteries. One advantage of which is not true of either lead storage cell practically air tight, which is neces- the lead -acid storage cell is its compara- cells or dry batteries. This is a very de- sary to prevent deterioration of the solu- feature in a "B" battery. On ac- tively high voltage, about two volts per sirable tion. A complete cell with the exception cell. Also, they are rather easily made, count of its ruggedness, its life is longer of the test tube a lead cell. is some- is shown at the right in that is if the positive plate is not "pasted" than that of storage It Fig. or filled with active material. On the other what lighter than a lead cell and is better I. hand, the lead cell has the disadvantage adapted to portable sets. A battery of sixteen of these cells gives that it requires considerable care to keep The many superior qualities of the Edi- about twenty -four volts when fully charged. it in good condition. It should be charged son Storage cell as described above, con- The voltage remains remarkably constant, at regular intervals, and not allowed to re- vinced the writer that it would make a very on one test only dropping two volts in main in a discharged condition for any satisfactory "B" battery. It is not mar- three weeks. In fact, it has been found length of time, to prevent sulphating. An keted in suitable form for such use at necessary to charge these batteries only sometimes ruin present, but the design of the plates lends accidental short circuit will about once in three or four weeks. it. To secure the best results it should be itself readily to the building of small cells, A "B" requires so little charged at a low rate, which means a long as will be seen from the following descrip- battery that charging period. There is considerable de- tion of the construction of the Edison cell. trouble to maintain and that is so depend- terioration even when the battery is not in The plates of the Edison Storage cell, as able in its performance is a great con- use, which means that it must be charged will be noted in Fig. 2, consist of steel venience in the radio station, and the ex- just about as often whether in use or not, frames or grids, which hold in place the perimenter who is willing to take the to keep it in good condition. If the cell tubes or pocket of active material. The trouble to construct one will be amply re- does not have positive plates which are positive elements are perforated steel tubes, paid for his time and labor.

www.americanradiohistory.com 686 Radio News for April, 1921 A New Radio Instructor

UP to the present time, the black- This clever idea greatly helps the stu- A vacuum tube is used as generator of board in most of the Radio Schools dents to understand the practical opera- oscillations in the transmitting circuit was used to demonstrate to the stu- tion of a set and at the same time shows and as a detector autodyne in the receiv- dents the various hook -ups of the the diagram of connections in a clearer er. The set is of the Io -watt type and sets used aboard the ships and in manner than any drawing made on the can tune any wave -length from 35o to land stations. blackboard can do. 2050 meters. The theory The photo- of the func- graph which tioning w a s appears on first explained this page and then shows a practical c o m plete d e m o n- I -KW. C.W. strations were transmitter made on a of the same set itself ; but type as the sometimes one described. this was not The power very clear to is generated some of the by two 500 - students who watt tubes could not fol- which may be low the vari- seen in the o u s circuits center panel and undcr- and which stand the are supplied rôle of each with either apparatus A.C. or recti- when the set fied A.C. at a was in oper- tension of ation. 3,000 volts. To over- This panel set come this, which is corn - and make the plete in itself e x planations includes the more clear, V.T. rectifi- the Radio ers and the Engineers of generating the Tele- and tuning funken Co. circuit. It have designed A Complete 1-R.W. C.W. Set Fiat on Panels for Use in Radio Schools. On the Right Are the Transforme-s may be used and Rectifiers; in the Center the Power Tubes a special and Generating Circuits, and on the Left the Tuning Elements for Radio - panel, O n of the Circuits. fony as which are fixt well. all the instruments composing a set. The The panel set shown on the front Several other panel sets, representing wiring is apparent and the set may be cover of this magazine represents a com- the various sets in use, are used in teach- operated as a regular set. plete C. W. transmitting and receiving ing the students and this method has When a course is made, the teacher station with an intermediate tuned cir- proved far can show the various elements of the set superior to the system con- in working order and show what happens cuit which is used as wave -meter to sisting of teaching the theoretical and when a change is made in the circuit or calibrate both sending and receiving cir- then practical action of a circuit. the set tuned. cuits. Indoor Aerials and Choke Coil Amplifiers By P. Jessup HE first part of this article deals with feet long. In addition to the amateurs, one, but either will work O. K. The indoor aerials and the second with long wave undampt comes in equally choke coils I am using at present still T choke coil amplifiers. well. POZ and LCM have been copied have the original iron core and the un- Using an indoor aerial and a two -step about 20 feet from the fones, using a used primary. One of them is from a amplifier, I have heard amateurs up to 2 -step amplifier. %" spark coil and the other from a 6" 1665 miles in New Mexico, Texas, Kansas, My receiving set consists of honey- spark coil. Any garage will sell you old Nebraska and North Dakota. Using a comb coils, audiotron, Illinois variable Ford spark coils very cheaply. As for crystal detector I have pickt up amateurs condensers, home -made 2 -step with efficiency, well, I get signals from choke up to Zoo miles in 3 districts and com- Moorehead amplifying bulbs and Bald- coils from two to three times as loud as mercial stations up to 300 miles. win fones. The set is spread out over a from amplifying transformers. The aerial is a ten strand inverted L, table with short, direct leads. (Continued on Page 709) strung up in the attic. It is 25 feet long CHORE COILS and the wires are spaced two feet apart. My good results on ama- It is made of bell wire, No. 18 insulated teur wave is made possible and about 25o feet were used. It runs by the use of chcke coils in east and west and is directional to the the amplifier. Choke coils west. The flat top part is about 35 feet are substituted for amplify- above the ground. The lead -in is taken ing transformers. from the western end and is about 26 A choke coil is merely the secondary of a spark P coil. Any spark coil secondary from a 1" to a 6" coil will make a fine choke coil. The primary of the P spark coil is not used and may be removed if desired. F/Q J .e ! -A- -B- A good iron core is neces- Hook -up of an Amplifier Using Choke Coils Instead of Trans- Diaeram Showing How a Choke Coil May Be sary. A closed iron core formers. Note That Some Stopping Condensers Are Used in Substituted for an Amplifying Transformer. is better than an open the Grid Circuits,

www.americanradiohistory.com Radio News for April, 1921 687 First Annual Amateur Radio Show and Convention

WE walked into the spacious Penn- Navy, too, gave some interesting demon- ways well attended and attracted as large sylvania Hotel Roof Garden on strations with a loud talker, signals from a crowd of radio enthusiasts as the demon- the 23rd floor and stepped into distant stations and radiofone music being stration of the small radio controlled auto- the first annual amateur radio distinctly audible all over the big exhibition mobile which took place twice a day in the show and convention. A noisy hall. hall. welcome greeted us and momentarily our The Signal Corps and Navy weren't the Mr. B. G. Seutter won the world's cham- friend who accompanied us and who was only ones with loud talkers. Several other pionship code speed contest, attaining a talking at the top of his voice could not exhibitors were demonstrating them and speed of 48 3/5 words a minute. There be heard any more. In other words our the air was filled with music and signals were more than 6o operators in the contest. hearing suddenly became jammed and that made the "ham" feel right in his ele- The prize given the winner of the title was stayed so for most of the time that we ment the moment he stept into the hall. a handsome silver cup, 14 inches high. took in the show. The reason of course One of the most interesting exhibits was The following firms had booths at the was the dozens of loud talkers scattered the Radio Controlled Car which was de- exhibition: all over the place, one trying to outshriek scribed at length in our June, 192o, issue. Acme Apparatus Company, Adams -Mor- the other. There were dots and gan Company, American Electro- dashes coming in at a high staccato Technical Appliance Company, with a sledge hammer effect, while American Radio Relay League, wireless telefone music received American Radio and Research Cor- from a great distance shrieked into poration, Burgess Battery Com- our poor ears until our hearing al- pany, Chicago Radio Laboratories, most stopt functioning. Clapp- Eastham Company, Conti- Thus was our reception of the nental Radio and Electric Corpora- Radio 'Show under the manage- tion, De Forest Radio Telefone ment of the Executive Radio Coun- and Telegraph Company, F. M. cil of the Second District. This, Doolittle Company, Experimenter by the way, was the first annual Publishing Company ( RADIO amateur radio convention and ex- N E w s), Federal Telefone and hibition which was held March 16, Telegraph Company, A. H. Grebe 17, 18, and ig at the Pennsylvania & Co., Manhattan Electrical Sup- Hotel in New York. ply Company, W. J. Murdock Com- The affair was a great success pany, Pacent Electric Company, and will long be remembered by Lehigh Radio Company, Radio Cor- the amateurs fortunate enough to poration of America, Radio Dis- be present. During the four days tributing Company, Ship Owners' 7,000 visitors were in attendance Radio Service, Inc., Shotton Radio and took keen interest in the dis- Manufacturing Company, Super plays of Radio apparatus and the Radio Laboratories, The Radio interesting programs arranged for Club, Irvington, New Jersey, C. D. every one of the four days. The Tuska Company, United States De- convention closed Saturday night partment of Commerce, Radio with a banquet attended by several Every Day During the Radio Show Examinations for Licenses Service; United States Army, Sig- Were Made by the Radio Inspector, Who Also Calibrated Wave_ hundred wireless men, many of Meters Free of Charge. This Photograph Shows Some Ama- nal Corps, Radio; United States whom had never met before but teurs Taking the Examination for a License. The Transmis- Navy, Communication Service ; who had often pickt up each other's sion Was Automatically Made by the New Model of Omni- Westchester Electric Appliance Co., Transmission. sigs. graph, Insuring Perfect Inc. ; Westinghouse Electric and Practically all of the Radio man- Manufacturing Company, Wireless ufacturers were represented and in many This made a hit not alone with the ama- Press, Y. M. C. A. Radio Schools. of their booths the new wireless apparata teurs themselves but with all the visitors The Executive Radio Council of the Second on exhibit attracted a great deal of atten- and it was uncanny to see the car move District who arranged the convention ex- tion. and obey orders from Mr. Glavin. The hibition is composed of two representatives One of the especially interesting exhibits car moved back and forward and turned from each of the following Clubs: was that of the Army and Navy. They around very easily. It was propelled by a Y. M. C. A. Radio Club, New York. had a big display of all the sets used in the twelve volt storage battery and did not Stuyvesant Radio Club, New York. Signal Corps and aboard ships. Field sets miss once except when signals became The Radio Club, Irvington, New Jersey. of various power were exhibited in the jammed from one of the radio exhibits that Yonkers Radio Club, Yonkers, N. Y. Signal Corps booth and music sent from was going at full blast a few feet distant. Radio Traffic Association, Brooklyn. the Bedloe Island Signal Corps station via Lectures were given every day by promi- Bloomfield Radio Club, Bloomfield, N. J. radiofone was heard almost continuously, nent Radio Engineers for the benefit of the Westfield Radio Club, Westfield, N. J. thanks to the big loud talker installed. The amateurs present. These lectures were al- (Continued on page 71o) Eliminating Shellac in Coil Windings By WILLIAM G. WHEAT

In winding the coils for a Variocoupler e C and Variometer for use in a regenerative set, the following method was used to hold ] the wire on the tubes without shellac. Illustration, Fig. 1, shows the secondary of Figure / the Vario with the overcast of silk thread. Fig. 2 shows the method. The needle is e forced thru the tube at A and brot up at B where a knot is tied. From B the A C E needle is forced thru tube at C, brot D. From D to C under and up at back then A o up again at D and over to point E. The same method is used around rests of coil. Figure 3 Fig. 3 shows the primary. The sewing Figure 2 starts at A over wire to B, thru tube to A Long Winding May Be Fixt as Well Without Fig. 1 Shows the Sewed Windings on a Vario- C and from C over to D. This method Shellac, as a Short One. This Allows the Ex- meter, While Fig. 2 Shows the Method of Fixing wire perimenter to Use the Wire Again for Other the Winding Once it is Done on the Cardboard holds the wires rigid and gives the windings Purposes if He Decides to Change or Improve a' Tube. a great efficiency due to the lack of shellac. Set.

www.americanradiohistory.com 688 Radio News for April, 1921 The Radio Dealer and the Beginner By ARMSTRONG PERRY

1' OT long ago I went into a store DATA DEALERS SHOULD GIVE. history of every big concern shows the conducted by one of the leading From my own experience and my obser- value of "catching 'em while they're dealers in radio apparatus and vation of other beginners, I believe every young." asked for materials for making a dealer in amateur apparatus and supplies A bright boy, properly instructed, can, stopping condenser to shunt around should make sure that a beginner receives sell to boys better than most older sales- my fones. I found that they had no tin foil with his first purchase, the following: men. It is hard for adults to get the boy's nor oil paper. All they could supply was (f) Diagrams of three or four types of point of view. Often the older salesmen wire and binding posts. antennae adaptable to country or city know too much about radio. They talk Another time I tried to purchase the conditions, with list of all materials over the head of the boy customer. He "makin's" for a loading coil. Wire and needed, approximate cost, and instruc- looks wise, not wishing to appear ignorant, binding posts were available, but no card- tions where to get them; but goes away mystified. With another board tube nor shellac nor material for (2) Diagram of simplest receiving outfit boy he feels more at ease about asking making a base or panel. which will bring in signals in the lo- questions. Wishing to erect an aerial I purchased cality where it will be used, with the One subject neglected by dealers is the wire from another house on another occa- simplest possible explanation of what handling of government and commercial sion, but I had to go elsewhere for screw - happens from the time the waves are traffic. In fact it seems to be overlooked eyes, side cutting pliers and a soldering pickt up until they produce audible by the whole amateur fraternity. The tool. signals in the fones and the energy whole emphasis is on the experimental side, In Pennsylvania I the different hook- met a youngster, son ups, the various types of well -to -do parents, of apparatus. The be- who had put a con- ginner gets the im- siderable sum of pression that the money into a toy ERE is an article which no radio dealer can afford to miss. whole fun of radio is radio outfit. He had in experimenting, and been unable to bring We consider it one of the most important articles on the even when he gets a in any signals with it transmitter to add to and I did not succeed subject ever written. It contains a gold mine of information his receiving outfit he any better. seems to think that In Maryland a boy for all those who can see the great opportunities in the amateur the squeaking off of brot me a battered radio game. There are more ideas and more common sense con- unreadable signals at old 75-ohm head fone five words per minute and a cup from a tained in Mr. Perry's article than has been our good fortune to see is the whole game. crystal detector and Anyone who has tried asked me how he in many months, and we have publisht some good ones.- Editor. to copy ship -to -shore could rig up a wire traffic knows the aw- and hear something. ful ultimate results of

Every week I re- IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII11IIIIUIIIIIIIIWIWWIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII IIIWWII IIIWIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIHIIWIIIIW11IIIIIIIIIIBIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIWIWIIIIWIIIIIWI11 this point of view. ceive letters from be- From my experience ginners who are stuck with boys I can say for the lack of a little advice which the passes into the ground; positively that for one boy who can ex- dealer who sold them their first apparatus (3) List of apparatus required, with periment intelligently and get results that should have given them. prices; are worth while there are fifty who by fol- All these things have set me thinking (4) List of other apparatus which would lowing explicit directions could set up a about the ways of radio dealers. I have increase the efficiency of the station, receiving station and learn to copy traffic been working with boys for a little more with a brief but clear statement as to rapidly and accurately. All they need is than twenty -five years. In that time I have what each piece would do; for someone to show them that it is worth known over four thousand between the (5) Exact but brief instructions about set- while. ages of twelve and eighteen. A large part ting up the station; If this type of boy had been encouraged of my work has been helping them with (6) Instructions telling exactly what to before the war he would not only have their hobbies. I have been a beginner in do to bring in signals after the appa- multiplied the sales on radio stuff, but he many things. I think the radio dealer fails ratus is hookt up ; would have been a big help in the navy to appreciate his opportunity with the be- (7) A list of stations which the beginner during the war. What every navy vessel ginners. should be able to hear, with wave- needed in the war was a chief who could BOYS TAKE TO RADIO. lengths and instructions about tuning keep the apparatus in working order and It is easier to interest a boy in radio the apparatus to those wave -lengths; some gobs who could send and read sig- than in anything else I know of. The sub- (8) Schedules on which these stations nals. What they got was a lot of short - ject is getting good general publicity. The work. so that the beginner will know term students who did not know enough boys' magazines are pushing it. The tech- positively that at certain hours there of either theory or operating to be of any nical magazines take good care of the ama- will be something to pick up; use until they had been on board two or (9) Operating hints -for example, "Keep three months. teur from the time he reaches the point BOY SCOUTS SHOULD BE INTERESTED. where he knows what they are talking your fingers off the crystal ;" (Io) Strong advice about reading the radio There is an unworked gold mine of radio about. Many high schools give their pupils profits in the Boy Scouts of America. a few lessons on it. The radio schools ad- laws and obeying them; (II) Equally strong advice about obeying There are half a million of them, the cream vertise alluringly the salaries of radio op- of American boyhood. Every of them erators and their opportunities for travel regulations of the fire underwriters one and local electrical departments; has to learn the International Code among and the advantages really are such as any other things before he can get out of the boy might envy. When the dealers find a (12) Friendly advice about how to save money by building apparatus, with tenderfoot class and no scout likes to re- way to capitalize the boy's first enthusiasm, main a tenderfoot long. Signalling is a help him to get an outfit for what he can suggestions as to books which will show him how to do it. major subject with the scouts in all their afford to pay, make sure that he installs it training. There is a merit badge for wire- efficiently, brings in signals and learns to HAVE SETS WORKING IN STORE. less which they can earn. be a in radio read them, there will jump To keep the boy's interest you must help In addition to all this the U. S. Navy business which will make all previous him to get signals at his own station at the Radio Amateur Bureau handles the outgo- records look like thirty cents. earliest possible moment. If you can find ing traffic from the national headquarters A boy is bound to be a small customer at him a chance to hear something the day in New York to the local headquarters first. If he is made to feel that fact too he first visits the store it will help a great everywhere. The other navy stations all keenly he is less apt to become a big one. deal. I often wonder why more dealers around our coasts have shown their will - He is lways willing to purchase to the do not have simple outfits in operation in ;nsrness to broadcast messages. With the limit o his funds -that is the way boys their shops. The man who lets a boy put help of these high power transmitting sta- go into things -but his family of course on the fones and bring in a station for the tions the Boy Scouts of America have an is putting the brakes on. They think it is first time all by himself will be his friend opportunity to become the biggest radio only another notion and will soon pass out for life and the amateur wouldn't buy so organization in the United States. During like the rest. In ninety -nine cases out of much as a binding post of anybody else the war the scouts distributed Io.000,000 a hundred their opinion will be justified if he had to walk ten miles for it. pamphlets for the Committee on Public In- unless an intelligent dealer makes sure that Of course, it takes time to sell to boys formation in a single week. covering prac- a how starts ria-ht and keens on. and www.americanradiohistory.comthe sales are usually small, but the f Continued on sage rx2a Radio News for April, 1921 689 Some Notes on Quenched Gap Transmitters By JESSE MARSTEN

N spite of the tremendous interest dis- circuiting the gap at that point. This "pit- Again under the same conditions, the radio- played in continuous wave transmission, ting" further intensifies the non -uniformity lion of the self cooled gap is greater than particularly of the vacuum tube type, it of the gap, and renders the surfaces far that of the blower cooled. These consid- is refreshing to note that all interest in more irregular than they originally were. erations point to the use of the self cooled spark transmitters has not entirely dis- In order to insure uniform separation of gap rather than the blower cooled. There appeared, and that development and im- the surfaces the insulating gasket must also is another point, not to be ignored altho it provements in the design of spark transmit- be of uniform thickness, and if compress- does not influence the operation of the gap, ters are still taking place. There should be ible, must be equally compresst at all points. namely that the use of the self cooled gap more discussion of this phase of radio The gasket will be discusst a little more enables us to dispense with the entire transmission in the amateur periodicals, for fully below. One further consideration blower cooling arrangement, which means a spark transmission has not left us for good, with regard to proper distribution of the considerable saving of space and money. as yet. and still plays a very prominent spark is the machining of the gap surface The best method of self cooling is to part in radio communication. Practically proper. Very often the gap surface is poor- utilize the property of heat radiation, by most of the ship to ship and ship to shore ly machined, leaving the edges and rim of employing cooling flanges made of a good transmission in spark stuff, as well as a the gap surface irregular and ragged. heat conductor, as copper. These cooling goodly part of overland. Sparking then tends to take place over these flanges are attached to the backs of the A recent article describing a new points at the very edge of the gap surface gap surfaces and thus conduct the heat quenched gap design by Henry Hallberg which is very undesirable. To avoid this away. They should therefore have com- gives rise to these remarks, and makes it the gap surfaces should be rounded at the paratively large surfaces exposed to the desirable to outline briefly some points in edges, which in the first place eliminates air. To facilitate cooling, the flanges might quenched gap operation and design. The the ragged edges, and in the second place be composed of two rectangular copper essential feature of quenched spark opera- increases the separation distance of the gap sheets connected together at the sides but tion is the speedy dissipation of energy in surface at the edges and thus prevents open at the tops to allow of good air cir- the primary circuit with high damping of sparking at the edges. culation from bottom to top. The ques- the primary oscillations. thus leaving the Gaps should be as nearly air -tight as pos- tion arises whether copper is the best mate- secondary tc oscillate at its own natural sible. Gaps which leak air do not give a rial to use for the flange surfaces. There is frequency with very low damping, and with a rapidly varying current thru the gap, and no interference clue to the primary circuit. naturally there are eddy currents flowing The more quickly the primary oscillations in the copper flanges which increases the are dampt out, the more the action assumes heating to some extent. Consequently the the nature of true impact excitation, with ideal material for the cooling flange is one resultant secondary oscillations of one fre- which has very low specific heat, as copper. quency with negligible decrement, which is but a high specific resistance. Brass and the object to be desired. bronze, to pick two metals at random, have One of the means used to obtain this ef- quite low specific heats, almost as low as fect is to couple very closely the primary copper in fact, and have much higher spe- gap circuit to the secondary antenna cir- cific resistances. Brass would be preferable cuit. This facilitates the quick transfer of because of its lower cost. primary energy to the secondary circuit, Some further considerations and sugges- which assists in damping the primary oscil- tions in the design of quenched gaps fol- lations more quickly. This. tho effective, low. The gasket should be made of ma- is not the most important means. The terial which is very incompressible, for greatest assistance in this direction must be otherwise, when two sections of the gap are sought in the extremely rapid quenching of tightly bolted together the spacing between the spark, with restoration of the high in- the gap surfaces may be much lower than itial resistance of the gap in a very short the required spacing, and if there are high time and consequent reduction of primary spots on the gap surfaces pitting and short - oscillations to zero. This will practically Diagram Showing a Typical Quenched Gap. Sev- circuiting may result. Fish paper is good leave the primary circuit open, thus pre- eral Elements Are Used for High -Powered Sets material for this purpose. If the gasket is venting the undesired interaction between But They Are All of the Same Type. treated with some special preparation, as the secondary circuit and primary. It is many are, it must be such that heating of for this reason that the problem of uniform discharge, hence the uniformity of the gasket will not impair its insulating quenched gap design is so very important. the spark note is destroyed, which intro- properties. As far as the writer is aware Some of the important considerations in duces reception difficulties. The irregular- no gap has yet been made without the use their design and conditions which good ity of discharge of a quenched gap which of a gasket. If the problems of keeping gaps must fulfill will be briefly enumerated. leaks air excessively is evidenced by a pe- the gap air tight and aligning the gap sur- In the first place the gaps must be short culiar hissing note. The addition of too faces could be met without the use of a ones. It is well known that the longer (in. much air leakage further results in increas- separating gasket, this would be the best length) the spark the more easily it maining the conductivity of the gap with greater plan. tains itself and the more difficulty in ex- difficulty in quenching. The gap should be designed with a very tinguishing it which makes the short gap The gap must be effectively cooled. The simple short- circuiting device. For even in very desirable. But since the power de- hotter the gap the lower its resistance, the hest designed gaps poor ones may be pends upon the voltage it is necessary to hence cooling of the gap assists in restor- found. If it is desired to cut these out of have a series of short gaps. rather than ing the gap to its initial high resistance service short -circuiting them is far simpler one long gap, over which the condenser and thus facilitates proper quenching. In than removing and replacing. It takes voltage can be distributed and thus in- the first place the sparking surfaces must much less time. It may also be desired to creased power obtained. Hence the best be made of very good heat conducting ma- short- circuit good gaps just to cut them type of quenched spark gap is the one sim- terial. This is exceedingly important, for out of service at times. ilar to that described by Hallberg and sim- the heating at the gap is excessively high. The gap should be designed with a view ilar to the Navy type, a number of short for the maximum gap current is many to facilitating removal of gaps. Some gaps gaps connected in series. times more than the ammeter reading. are designed so that they are clampt tightly The sparking surfaces should be uniform Consequently silver or copper is best for by a heavy bolt between two end plates. and the separation distance should be the this purpose. A consideration of results To remove one gap requires loosening the same at all points. In the first place a uni- with both blower cooled gaps and self holt until the Bans are movable, taking the form separation and uniform surface in- cooled gaps leads to the conclusion that gap out and replacing it. Then the whole sure a uniform distribution of the spark the seif cooled gap is superior. The blower outfit must be tightened again. It is far over the entire sparking surface, and not, cooled gap, tho effective in cooling. facili- better to have each gap a separate and dis- as in poorly made gaps, a concentration of tates leakage of air into the gaps by blow- tinct unit fitting in a spring device, each the spark in one or two spots with resultant ing cool air into the gap with pressure. pmt mechanically independent of the others. excessive heating at those points and poor Furthermore, it is found that under the All that is necessary is to pull'the gap out quenching. In the second place if there same conditions of operation, i. e., for same of the spring holder and insert another. are high spots on the sparking surfaces the power. same wave -length, etc., the blower There must, of course. he provided a spark will tend. as indicated just now, to cooled gap current is higher than the self simple and ready means for connecting in concentrate at these points, resulting in the cooled gap current, consequently the blower as many gaps as desired. This is neces- so- called "pitting" with danger of short- cooled gap heats more than the self cooled. (Continued on page 746) www.americanradiohistory.com 690 Radio News for April, 1921 Non -Inductive Resistances and How to Make Them By P. F. GEAGAN

where we wish to change the Ohmic resistance of the circuit without changing its inductance or wave -length we must so arrange that the inductive or reactive volts are eliminated. There are several methods of doing this : one is to wind the wire back upon itself as in Fig. I, the effect of this is to place the fields of the two wires in opposition and since the current flowing is of the same value in both wires but in opposite directions, the fields neutralize each This diagram other and there is no self- induction present. shows several coils connected in types of non - A number of these inductive re- series and with contact points taken off be- sistances and tween coils over which a contact arm moves some new ways to wind oives us a variable non -inductive resistance, them. Fig. 4 Fig. 2. shows some Another method of construction is shown models of var- in 3. one of re- iable resist- Fig. Two conductors, ances which sistance wire and one of copper wire of the will be found same size and length are laid parallel to useful in sev- each other with opposite ends connected to eral cases. the circuit and a sliding contact provided. .,,11,,,,,,,,,,,,,,,,,,,11,111,,, Then as we move the slider along the hires the same length of the copper wire is cut out of circuit as there is of resistance wire cut in or vice versa, thus keeping the inductance constant, since the inductances of the two wires are the same. This method would be applicable only for small resistances as the length of wire required for large resistances would be too great. For larger resistances a somewhat similar arrangement may be employed as in HE term "non- inductive resistance" or direction to the current producing it. These Fig. 4. Two discs or rings of the same "non- inductive winding" is frequently reactive volts being in opposition to the size wire are wound with the same number T met with in electrical and radio litera- flow of current have the same effect as a of turns of the same size wire, one of cop- ture. By this is meant a special arrangement quantity of resistance placed in the circuit per and one of resistance wire. The two of the wires composing the resistance or would have. windings should be as near as possible du- winding so that there will be no reactive The formula 27rNL expresses the re- plicates of each other. Opposite ends of volts present when an alternating or oscil- actance value where N equals the fre- the coils are connected to the circuit and a lating current is passed thru the circuit, the quency, and L the inductance of the cir- sliding contact bearing on both the rims or resistance as defined by Ohm's Law being cuit, and the formula 2IrNLC expresses the peripheries of the coils will produce the the true opposing factor instead of the im- reactive volts value where N equals the fre- same effect as in the case of the straight pedance as in alternating circuits of in- quency, L the inductance, and C the cur- wires but with a greater range. The slider ductive winding. The reactive volts in an rent flowing. contact should be pivoted as nearly as. pos- alternating current circuit is the result of It will be seen then that with any change sible at the center of the discs in order to the field of force surrounding the wires in the frequency we will get a different avoid eccentricity, and the coils set up so springing out from and collapsing back value of reactance if the circuit be induc- that the end binding posts are at opposite upon the wire carrying the current, and this tive. The inductance value of a circuit is ends of the circuit. Still another way of field cutting the wire at right angles pro- also determined by the rate at which its mounting would be to fix the sliding contact duces an E.M.F. in the wire in a counter field cuts the conductor, and so in circuits stationary and rotate the two coils. Continuous Wave Multi -Stage Receiving Circuits Employing Retroaction and Self -Heterodyne Principles By JOHN SCOTT -TAGGART IN a recent paper read before the Wire - Some further examples of the use of this ranged that the first valve acts as a retro- less Society of London, the present author principle are given in Figs. I and 2. In the action amplifier, or, in other words, a means drew especial attention to the value of former arrangement. the aerial circuit L,C, of introducing negative resistance into the retroactive amplification in the case of con- is tuned exactly to the incoming continuous aerial circuit. The coupling between R, tinuous wave reception. The problem no waves, the value of C, being kept at a mini- and L, is adjusted to the point just pre- longer involves lessening the decrement of mum. In the anode circuit of the first valve ceding self -oscillation. The amplified oscil- incoming wave -groups, as in the case of is a retroactor coil R,, whose coupling with lations are, after a second high- frequency spark signals, but lessening the effective re- respect to L, may be varied. The condenser magnification, heterodyned by the last valve, s'stance of the aerial circuits. In other Cs will usually be omitted. The magnified the coupling between R2 and the inductance words, the positive resistance of the aerial potentials across R, are passed on to the in the anode circuit of the second valve circuit is almost completely neutralized by grid G2 of a second valve, thru a blocking beind adjusted to produce self oscillation in what is equivalent to putting a negative re- condenser whose purpose is to insulate G2 (Continued on page 748) sistance in series with it. from the positive side of the anode battery H. In the anode circuit of the second tri- ode is an inductance shunted by a condenser, C,. This circuit is tuned to a frequency slightly to one side of the incoming frequency. The magnified oscillations are now applied to the grid Ge of the last valve, which functions as a detector. The anode circuit of this last valve contains the telefones T, shunted by a by -path condenser, a retroactor coil, R., coupled to the in- In This Hook-up the Two First V,Ts. Act as and In This Receiving circuit, Double Peed Back Radio Frequency Amplifiers and the Third as ductance in the anode circuit of the preced- Reaction is Produced in the First and Third a Detector. ing valve. The circuit is normally so ar- V.T. Circuit, Giving a Very High Amptifcatio,'. www.americanradiohistory.com Radio News for April, 1921 691 New. German Radio Recording Device FOR receiving by means of tape recording apparatus, a new set of connections was evolved and has been tried out, as is shown in the cut. For receiving apparatus, a receiver of the type E -5 of the Telefunken Company is suitable, which is available for the reception of wave -lengths up to 17,500 meters by the addition of extra condensers C, and C4 to the regular condensers C, and C,. From the terminals of the second condensers, the leads go to the intensifier and thence to a high frequency intensifier and then on to a set of three tube, low frequency intensi- fiers. Between these two there is a resonating circuit, without iron core, which In This Recording Circuit, the Super - an Autodyne Effect is Used, The Signals is tuned to the pitch of the aerials. The Are Detected by the First Two Tubes, regular coupling thus gives a very sharp Then Amplified by a Three -Stage Am- resonant correspondence. plifier and Again Magnified by Two Pliodynatron Tubes, Delivering Suf- The low frequency audion has in its heat- ficient Current to Act as a Relay. ing circuit an adjustable resistance W, by ÚI1110 - which the heating current can be regulated so that the signals will come thru the in- volts and the negative grid of the second to get good results. If high resistance re- tensifier clear and without disturbance from tube has a negative potential of 18 volts. lays are used in advance of the printing statics. To obtain a strength of current The secondary winding of the first induc- apparatus, especially careful adjustment is suitable for the reception of printed char- tance U, is adjustable by a variable con- not required. acters, there are two intensifying tubes denser C. for the pitch of the receiving back of the low frequency intensifier with The arrangement is available for high system, and the first grid of the rectifying speed reception without further modifica- very sharp characteristics. The Siemans audion with its 45 volt potential is con- and Halske double grid audions R, can be tion ; the calculation of its single parts pre- nected with the cathode thru a condenser sents no particular difficulty. Especially to used here ; the first is used as an intensi- C. of I,000 cm. capacity. This connection the fier; the second as a rectifier. The connec- be noted are the small requirements in prevents the production of waves of greater way of batteries; two heating batteries (A tion from the low frequency intensifier to frequency which occur within this tube, the first audion, and from this to the sec- batteries) and two heavy current batteries and can bring the system to proper pitch. (B batteries) are all that are required. ond one, is done by inductances U, and U2, The strength of received back of current one E -5 receiver with the first and secondary windings of the rectifying audion is so great that a If uses in place of the 15,000 and 6o,000 turns respectively. writing with high frequency intensifier an audion apparatus adapted for it, as for in- receiver, The audions require go volts potential. stance the Wheatstone receiver, can be used one obtains a very widely available arrangement even for small waves giv- Their first grid is adapted for a potential without further modifications ; the re- of 45 volts, while the second grid of the sistance of the winding of the electro mag- ing sharply defined sounds. first two has a negative potential of three nets should be raised to about to,000 ohms *Abstracted from the Elektrotechnische Zeitschrift. The H. C. of L, and Burned Out Amplifying Transformers By CYRIL O. SMITH Principal Royal School, Honolulu BEING interested in very high audio - but sixty -six volts on the plate, and there that they are not going back on us as the frequency amplification as applied we were, left with seventeen coils on our primaries did. to the modern load- talker, to allow hands, with primaries gone, but other- The hook -up we were using before the of our radio classes taking down the in- wise still in the ring, or rather on the modification made necessary by per- coming signals from any part of a large core! sistent break -down on the part of the assembly hall, the writer. with I'm afraid At this point let me say that here in transformers, was an external heterodyne many another, has found that in the final Hawaii we suffer from excessive humid- and a detector -amplifier circuit as given analysis all real radio troubles of the ity at times, and on several occasions by De Forest in catalogue D, on page 25, past year may be put down to trans- during the last few weeks the pen of the with one "A" Battery and two "B's "- former performance, or rather the lack of hygrometer on my triple recorder has this second "B" Battery being used to it. wandered off its own field and trespasst boost the amplifiers. After the school had discarded nine on that part of the chart generally given The diagram below shows the very Acme Transformers, and other unfor- over to temperature, -so that without simple changes in the circuit made at tunates right around us had burned out doubt our transformer requirements are each stage to adapt this set to use one over a dozen more, the local agents wrote severe, and very possibly no blame may coil only of the transformer, and will be the manufacturers for replacement coils attach to the manufacturers, but blame found suitable to most other hook -ups as and on the arrival of two dozen our hopes or no blame, what were we to do? it stands. Only one stage is shown, but revived. Buying new coils had proved useless, all are treated in the same way. Our share of the plunder amounted to so the thot occurred to use what we A. With all batteries switched off, eight coils (at two dollares apiece) yet had,- utilize our secondaries just as they place a jumper across each amplifying a few days ago the last three of these were, even leaving the burned -out or transformer from Primary one to sec- gave up the ghost at one fell swoop with otherwise open- circuited primaries within, ondary one. A and make use of the coils in such a way B. Do the same with jumpers from that the least possible change in circuits primary two to secondary two. need be made to adapt them to our ex- C. Insert a small stopping condenser isting sets. in the grid circuit. Within five minutes the change -over D. Place another small stopping con- was made, without so much as removing denser in circuit from lower secondary the transformers from their panels, yet to filament, then turn on your batteries, even with the low voltage at present in and listen in use (twenty -two on the electron relay, The extra condensers required, two per and an additional forty -four on the am- stage, are simply used to prevent battery plifiers) there is no shadow of a doubt currents from being carried where they in the minds of any of us but that we are not wanted, and such stopping con- When it Happens That One of Your Amplifying are getting better amplification and less densers may be built up in a few minutes Transformers is Burnt Out, Just Connect it as with foil and glass, or better still, using Shown by the Dotted Line and Introduce Some extraneous noise than with our double Stopping Condensers Into the Grid Circuit and coil transformers, and furthermore the foil and mica. it Works Again. impedance of these secondaries is such (Continued on page 75o)

www.americanradiohistory.com 692 Radio News for April, 1921 An Ideal Receiving Set for Short and Loni Wave - Lengths By E. G. SHALKHAUSER

detector a nd first stage amplifier and one between firs t and second stage amplifier, Fig. 3 is used for the A switch of Plate No. 3 and places t h e aerial condenser in series with the an- st tenna when de- Pig, 3 Pig 2 sired. General Layout of the Front Panel of this Complete Receiving Inside the Set. Complete Hook-up of the Set, Showing the Combination Switch TO VARY Set. Note That a Loud Talker is Incorported Contacts to Change From Long to Short Waves. -WAVE-LENGTHS

IN a past issue of RADIO NEWS the de- To vary the wave -lengths from short to ments have shown that even the capacity sign and construction of an ideal radio long or vice versa, the switch of Fig. 7, effect between the two wires leading to the cabinet were outlined. The particular designated as "wave switch" on Plate No. receiver is enough to affect the signal features and advantages of this cabinet 3, is used. Additional aerial inductance, strength, and switch connections formed over those used heretofore were point- primary and secondary inductances for the by heavy brass plugs and jacks, will give ed out and in acknowledgment of the many various wave -lengths are controlled by a result that can be anticipated without gratifying reports received by the writer turning the switch. The contact segments going into experimental proof. The plug let it be said that the cabinet design has shown in Fig. A and B, Plate I, should be shown in Figs. 4 and 5 and pins are met with general approval for its adapt- made of phosphor bronze to give the de- made of hard rubber or composition ability and ease of construction. It seems sired springiness and insure the best con- fibre and drilled to receive the cords. certain that the more progressive amateur tacts. They are drilled as shown and fast- A small metal plate or disc to make con- will sooner or later build his transmitting ened as per Fig. 2 of the same Plate. The tact with the outer springs shown in Fig. 6 and receiving panels in more attractive numbers and letters on the above men- when the plug is inserted, is attached to and business -like cabinets, which also will tioned Figs. of Plate r correspond to like the tip end of each pin to which the cords afford maximum protection and accessibil- designations on the circuit drawing of are soldered. These contact discs must be ity to the instruments. Plate 2 and refer to the contact points turned outward to make connection with In what follows, a receiving set of the mounted on the rear of the panel. By trac- springs one and four of Fig. 6. This proc- most universal and efficient post -war type ing thru the circuit and noting how the ess of construction requires a little skill has been worked out and made ready for segments form the closed connection on the and patience, but is not too difficult to ac- usc. So many circuits are available which contact points for both the short and long complish. The results obtained are well have given and still give exceptionally good wave -lengths a clear idea will be had as worth the best efforts. The springs of results, but to a more or less spasmodic de- to how this switching arrangement can ac- Fig. 6 are of the dimensions shown in Fig. gree. Under adverse weather conditions complish what is desired. Fig. 2 shows a C and bent at the dotted lines. Phosphor or in totally different localities such a line- cross section of the method of mounting bronze is the best material to use as it is up of apparatus may or may not satisfy the segments, and how these form the con- of the desired resiliency and always makes us. The thing to guard against most of all nections between the contact points. It good contacts. To obtain the proper con- is an arrangement of complicated wiring should constantly be kept in mind that to nections to the springs the numbers one, systems and intricate apparatus construc- insure good results good contacts thruout two, three and four correspond to like num- tion. Nothing seems to meet the fancy of the receiving circuit are of the utmost im- bers on Plate 2 at the jack associated with the average amateur more than to have a portance. High resistance connections in- the first. bulb. The jack connections at the network of wires and a switch which prob- crease energy, consumption and produce first and second stage of amplification are ably will work a half -dozen ways with as correspondingly weaker and fainter signals. the same as the one for the detector bulb. many different combinations. This sort of Be sure to make good contacts and con- The object of having a combination of an outlay may give a pronounced appear- nections. contacts connected in this manner is to give ance and would even at times work well, This switch has also been designed to the maximum flexibility to the set without but for all- around reliable work only the reduce to a minimum capacity effects so undue loss of time in switching from one more simple and less complicated circuits frequently encountered in switches of the stage of amplification to the other. The do the business. common type where large amounts of metal circuit thru the three audion tubes and In a complete set arrangements should are used to complete the connections. transformers remains closed as long as the be made to receive both long and short In Figs. 4, 5 and 6 of Plate I another plug of the receiving set is not inserted in wave -lengths with equal ease and reliabil- feature of this receiving set is shown. the jack. With the plug in the first posi- ity. To be able to switch instantly from These figures give in detail the plug and tion only the detector tube is in operation. short wave coils to those of longer wave - spring contacts used in conjunction with The springs are separated, but contact is lengths is essential. This can be accom- the telefone headset. In the ordinary plug made with the upper and lower springs plisht in a simple way without the loss of and jack used in telefone switchboards the (one and four) which complete the circuit undue amount of energy from the trans- mass of metal, of which the jacks are made, from the `B" battery thru the telefones mitting station. The best means is found prohibit their use in radio work. Experi- back to the filament. Upon withdrawing in the correct construction of the switch- the plug from its position the springs auto- ing apparatus. A design, which has thru matically close and complete the circuit one year's use proved very efficient and re- thru either one of the transformers to the liable will be described. first stage of amplification. In the second On plate No. I the switches used in this jack, therefore, the detector tube remains in and its to particular receiver are shown in detail. FçJ operation output transferred The hard rubber disks upon which the con- the second tube in the circuit. And in the tact segments, shown in Figs. A and B, are third jack the complete circuit is in opera- mounted, are cut from %" stock to the re- tion and maximum signal strength obtained. quired sizes. (All the dimensions are given TWO TYPES OF TRANSFORMERS. on the drawings.) Disc of Fig. 3 is of the Two types of transformers have been same size and general construction as that J featured in this circuit, any one of which of Fig. r, but has only two contact seg- F96 c may be used as desired. It has been found ments counted. Switch of Fig. i is used F F,5 7 very advantageous to be able to employ for the T switches shown on Plate No. 3, Constructional Details of the Combination either radio frequency coupling or audio of which two are required, one between Switches and of the Special Plugs for the Fones. (Continued on page 732) www.americanradiohistory.com Radio News for April, 1921 lî9 i Short Wave Radio Vacuum Tube Trans- mitter and Regenerative Receiver With Two -Step Audio Frequency Amplifier By WALTER HYNDMAN, I. A. T.

appearance. T h e o o outfit is (with the o cJ o o exception of the o o transmitter) o f nxr aa: conventional design. I have tried to arrange the various switches, dials, etc, so as to be convenient and easy to control. The receiver is ö provided with an AM gara ixra/Ye r Jtur' 1 a or, Avf a amp/ Fir ,r pn adjustable " B " Front View of the Three Units Comprising the C.W. Set and battery, as the the Receiver With Two -Step Amplifier. Note the Well - new tubes are of Back View of the Complete Set Showing Arrangement of Planned Design of the Units. the low vacuum Parts Inside the Cabinet, type. A small con- IN these days of the introduction of denser is placed around the fones, and a simplest possible. A more elaborate one C.W. for amateur use, most of us are shelf is screwed to the panel, and sup- may of course be substituted. No meters worrying over the type of set to install. ported at the rear by a brass bracket, to are included, as most amateurs will wish The great bulk of amateur operators still hold the `B" battery. If a standard tapt to use theirs for various experimental pur- stick to the good old spark, which accounts "B" battery, the taps may be permanently poses. However, for those who wish a for the amount of interference most of us soldered to the contacts of the "B" battery H.W. ammeter on the panel, the wave- are complaining of. A few fellows who switch. If this type of battery is not used, length switch could be moved to the po- are lucky enough to be provided with one made up of Eveready cells should be sition occupied by the small double pole plenty of cash, have installed powerful used. The tube sockets are screwed to Trumbell switch, and the ammeter placed "fone" or C.W. sets. We all would like to, wooden shelves which are screwed to the in the upper right hand corner. I would but motor -generators or rectifiers and panel. prefer Remler rheostats. Binding posts are transformers cost a lot of money. The In the transmitter, the Century buzzer provided on the panel for connection to the only obvious remedy is an outfit that will and the small transformer (the dimensions oil -filled Murdock condenser. work on a six -volt battery or other similar of which were given in November RADIO The two -step audio frequency amplifier source of power. NEWS) are mounted on a shelf fastened to is very compact, and could be used in con- When I read the article by Mr. H. M. the panel and supported at the rear by the nection with other outfits. In its design I Pruden in November RADIO NEWS I de- same brass strip which holds up the rear have followed the suggestions of F. R. cided that it was just what we have been of the inductances. This is shown in the Pray in November RADIO NEWS which I looking for, so I proceeded to design a rear and side views on the plan. The think are excellent, as they do away with compact cabinet set in accordance with his transfer switch is placed on the lower right the expensive plug and jack method used data. hand side of the transmitter and is the in practically all amplifiers on the market I have much today. As the "B" pleasure in placing battery for the the results of my amplifier is rather work before you. bulky, I decided to The three units place the battery comprise a com- outside, as the plete station, 11 H, amateur will prob- which, if carefully [. Q Amp/i/ems ably need it in his made, should prove Regenerrro/w iPttrp/or various experi- lllcient, up -to -date 'General Hook-up of the Complete Set. Note on the Left the C. W. Transmitter Working With One ments with other -Volt and o f pleasing Sis Battery. (Cont. on P. 709) Construction of Transformers By BEN H. WOODRUFF

LL transformers, from your little mately to the output wattage. tuting the primary voltage we find that a Thordarson to the ones which handle To begin with, it is necessary to know total of 172 turns will be required. By A thousands of volts, operate on the exactly what the transformer is to be used looking at the table we see that No. 18 same principle, induction. They all con- for, or to know the voltage and amperage B. & S., is the smallest wire which will sist of an iron core with the primary and wanted. Suppose a transformer is wanted safely carry 5 A. Substituting the sec- secondary windings. to operate on ordinary to V. 5 A. 6o cycles, ondary voltage we find that the total num- In this article we will deal with the con- giving a voltage of 12 and the maximum ber of turns will be Ig. Since the wattage struction of efficient transformers, i. e., amperage. (Continued on page 730) where the input wattage is equal approxi- Here we must know what size core we are to use. It is best to increase the size of the core as we increase the length. So we will use a core 2" X 2", a total cross I

section of 4 square inches. - a-

Applying the formula for 6o cycles : VX6.25 b- Piq. f = number of turns when X is fiq 2 The Windings of the Transformer Are Made on X a Form of This Type Before Being Mounted on the cross section of the core in square Arrangement of the Iron Core Showing How the the Core. inches and V is the given voltage. Substi- Iron Strips Are Interleaved at Each Corner. www.americanradiohistory.com 694 Radio News for April, 1921 Conduction of Electricity Thru Vacuum and Gases With Applications to Design of Radio Apparatus By E. M. SARGENT First Part AN investigation of the subject of REMOVAL OF IONS FROM A GAS. and the current described above thru a electrical conduction in gases and When either a positive or negative ion gas are currents ordinarily referred to as in a vacuum discloses many facts comes in contact with a cold metal sur- ''not following Ohm's law." In all four that are of peculiar interest to the face it gives up its charge to the metal. of these cases the effective resistance or radio experimenter, particularly if Recombination to form molecules then impedance of the medium is a variable that the investigation is conducted from a non - takes place near the metal surface. Ions is a function of the voltage and when the radio point of view. Some of the out- may be removed from a gas by passing the proper value of resistance for a particular standing characteristics of electrical cur- gas thru small diameter metal tubing, or voltage is substituted in the equation the rents when passing thru gases are outlined thru metallic wool. calculated current will be correct. The below, after which follows a more prac- ions are smaller than same is true of alternating currents where In general, negative is function not tical discussion of their importance when positive ones. All particles in a gas in the the effective resistance a applied to the design of radio telegraph ap- steady state have the same amount of of the voltage but of the frequency, and paratus. the "resistance" must be broadly inter- kinetic energy (% mv2). Therefore since preted total Gas in its normal state is non- conduct- the positive ions have many times the as the impedance to current ing for most practical purposes. For ex- mass of the negative ones, the nega- flow. For all alternating current cases ample, when a telegraph line is operated, have much greater ve- E tive particles I in a no account is taken of the leakage current locities. This can be experimentally proved = -. Statements this paper that thru the air from the wire to Z that flows by blowin' an electrically neutral gas thru law the ground. This leakage current is so a a The current doesn't follow Ohm's then metal tube having small diameter. must be taken mean small as to be entirely negligible when com- gas may emerge from the tube with a posi- to as outlined above. pared with the leakage thru insulators, etc. tive charge. This is due to the fact that IONIZATION OF A GAS BY INCANDESCENT Nevertheless, it is there. Where high volt- in the short time the gas was passing thru SOLIDS. ages are used, particularly voltages high the tube, more negative ions than positive If a negatively enough to cause sparking, gas currents be- reached the walls of the tube, due to their electrified body be brot come of importance. near an incandescent pure metal it will be discharged, but if brot near an incandes- Currents are conducted thru a gas by cent oxide will be unaffected. A positively small carriers called ions. These ions are 11111111 charged body will be affected in the oppo- of two kinds, one having a positive charge 1111111 MIMI site way. The metal will not discharge it and the other a negative one. Negative 11MMIll but the oxide will. This is an important ions usually consist of single electrons. A 111111101111 fact to be considered when selecting ma- normal gas contains equal numbers of posi- terial for vacuum tube filaments. tive and negative ions. r%INMESá/tagé:2: The electrification produced by incandes- Even when undisturbed physically, as cent solids depends on four factors: is kept in covered glass jar, when a gas a I. the small particles that make up the gas The temperature of the wire. The are higher the temperature the greater the are in constant motion, and collisions Voltage speed continually taking place between the mole- with which the particles are shot off ions. When collisions take place Figure I from the wire. They have more kinetic cules and energy at high temperature and therefore between molecules and ions, some of the This Curve Shows the Current in a Spark Trans- are mitter. Point A Represents the Saturation Point. are capable of producing greater ioniza- molecules are disrupted and new ions tion. collisions take place formed, while when 2. Pressure of gas. between ions of unlike sign the charges higher velocities. Thus more negative the are formed ions than positive were discharged and the 3. Nature of the gas. neutralize and new molecules 4. The nature When the gas has stood for some time un- gas emerged with a positive charge. of the incandescent wire. disturbed it reaches a steady state at which The charge on an ion is about 3.5 x Io-1P Even in a vacuum electrification is pro- new ions are being formed at the same in practical duced on bodies near incandescent solids. electro static units. Expresst This rate at which they are recombining to form units, each ion contains about 1.17 x Io-u) electrification is due to particles leav- molecules, and the total number of ions in coulombs of electricity. When a current ing the solid. Edison noticed in connec- the gas is then constant. When this state of one ampere is flowing in a circuit, one tion with experiments on electric lights is reached, each particle has the same flow- that negative electricity escaped from glow- coulomb of electricity per second is ing amount of kinetic energy as the others. ing past each point in the circuit, or .855 carbon in a high vacuum. This is called the Edison effect, the Ions are produced in gases in any of the x Io-'° ions pass each point in the circuit after discov- per ampere of current. erer. Emission of negative particles how- following ways: ever is not confined to solids. physically When two plates are immersed in a I. By heating. "Heating" gas, The saturation current between an in- means increasing the amount of kinetic en- the saturation current that will flow de- the candescent wire and a cold cylinder or plate ergy in each particle of the gas. When pends only on the ionization between b the kinetic energy is increased, collisions plates. For a gas of uniform ionization can be expresst in the form I = ae, c- - will be more frequent and greater forces the saturation current will then be inverse- B will take part in them. These greater ly proportional to the distance between the where O is the absolute temperature of the forces will break up a greater number of plates. The current thru a gas with con- wire and a and b are constants. molecules, thus forming more ions. stant distance between electrodes follows When the hot wire is surrounded by gas 2. By the electric spark. This is a spe- Ohm's law in that the current is propor- instead of being in a vacuum, the electrons cial case of heating, altho the initial ioniza- tional to the voltage for very small e.m.f.s. ionize the gas at high temperatures and tion takes place in a somewhat different only and quickly reaches a saturation point thus produce positive as well as negative manner, and will be discusst later. at which increase of voltage has very small ions. 3. By the electric arc. This is also a effect on the current. The reason for this The source of ionization is at the sur- case of heating. is that there are only a limited number of face of the incandescent metal. The same 4. By i adio activity. Radio active sub- ions available and that when the voltage number of ions will then be produced no stances have the power of dissociating the gets large nearly all the ions are carrying matter what the distance between the elec- molecules of a gas in the vicinity of the current and a further increase in voltage trodes is. Therefore the saturation cur- radio active substance. Here the ionizing cannot cause an increase in current until rent will be the same for a given incan- is done not by the interbombardment of the voltage gets large enough to create descence regardless of the distance between the gas particles but by the bombardment more ions. This case will be discusst un- plates as the saturation current depends of the gas by the particles that are ejected der spark gaps. only on the number of ions available to from the radio active substance. These The statement that the current does not carry current. The voltage required to particles travel with extremely high veloci- follow Ohm's law made above should be produce this saturation current however ties, some approaching the velocity of light strictly interpreted to mean that there is varies greatly with the distance between and are capable of producing very high not a straight line variation between cur- the plates. ionization if allowed to act for some time rent and voltage. There is no known cur- If ionization is confined to the surface of on a gas in a confined space. rent that does not exactly follow Ohm's the incandescent metal, the current between 5. Light, particularly the sun's rays and law if the law is properly applied. Cur- the metal and a cold plate will be carried illuminating sources strong in ultra violet rents thru the electric arc, electric spark, by ions of one sign only, even tho ions of light produce ionization to some extent. plate www.americanradiohistory.comto filament current in a vacuum tube, (Continued on baae 7a6) Radio News for April, 1921 695 Who's Who in Radio No. 3 SIR OLIVER LODGE, D.Sc., LL.D., F.R.S. S( IR OLIVER LODGE was born on the discharge of small condensers, which thru liquids. When the current passes June 12th, 1851, at Penkhull, near led him on to the observation of oscilla- thru a conducting solution of a salt, the Stoke -upon- Trent. At the age of tions and waves in wires. Inasmuch as he molecules of the salt are torn asunder, and eight to the Newport Gram- entirely accepted Maxwell's views, and its constituents travel in opposite direc- he went and on for several years eagerly strove to verify them, there can tions. From certain observations mar School, where scarcely be any doubt that if I had not an- certain suppositions their speed of travel he was subjected to the strenuous classical ticipated him he would also have succeeded could be calculated. But Lodge was the education of fifty years ago. At fourteen in obtaining waves in the air, and thus also first to devise a simple and direct experi- he was taken into business to help his fa- in proving the propagation with time of ment manifesting the travel and enabling ther, who was in failing health. But his electric force" (Electric Waves, p. 3). the speed to be measured. His experiment love of Science was developing, and, work- Prepared by his own researches Lodge at confirmed the previous calculations and the ing in the evenings, he prepared himself once recognized the immense importance theory upon which they were based. examination of the of Hertz's discovery, and thru him and Another celebrated research was in a for the matriculation investi- London, and for the Inter- thru Fitzgerald the knowledge of it was very different field, consisting in an University of rapidly spread in this country. It was gation of the passage of light thru a mov- mediate Examination in Science, taking at largely due, I believe, to British apprecia- ing medium. first class honors in Physics. In 5872, tion that the value of Hertz's work, and of For this research, and for his researches the age of 21, he gave up the idea of a the theory of Maxwell which inspired it, on electric waves, he received in 1898 the commercial career, and went to University was so soon recognized in Germany. Rumford Medal of the Royal Society, one College, London, to pursue mathematics In the earliest years of investigation of of the highest honors which the Society can his other scientific studies without in- electro- magnetic waves Lodge was ever to bestow, for it is not confined to our own and of and terruption. In 1877 he took the Degree the fore, devising modes of creating countrymen. Science at London in the Sub- detecting the waves, investigating their Everyone in Birmingham by this time . Doctor of knows Sir Lodge is not ject of Electricity, and became Dem- that Oliver onstrator and subsequently Assist- only a great experimenter but also a of Physics in Univer- brilliant expounder of his own work ant- Professor of of Ever sity College, London. In 1881 he and the work others. first Professor of Phys- ready to take up new ideas, he ab- was elected sorbs them, makes them his own, and ics at Liverpool in the newly -founded University College, now the Univer- has in the highest degree the art of In 1887 he was communicating them. The lecture sity of Liverpool. he a Fellow of the Royal Society. which gave in the Town Hall made some years ago on Radium was a In 1888 he received the honorary de- LL.D. from the University great example of this power. Seiz- gree of ing the idea that matter of St. Andrews, the first of an ever - and electric- increasing list of such distinctions, ity are identical, he set it forth in a was made a corre- way which will long dwell in the re- and later he membrance sponding member of several foreign of his hearers. learned societies. In 19oo he was There is one more contribution to chosen by the Crown as the first science, tho of an indirect kind, which Principal of the University of Bir- deserves special mention -his Presi- mingham. In 19o2 he received the dential Address to section A of the honor of knighthood on the Corona- British Association in 1891. For two the King. reasons that address was remarkable. tion of In he of It is impossible here to give an it advocated the foundation adequate account of the brilliant sci- a National Physical Observatory, and entific career of which this list of so started the movement which led, distinctions forms some recognition some years later, to the establishment by his fellow -workers and by the of the National Physical Laboratory Crown. I can only mention briefly a at Bushey, supported, tho far from few of the researches which have adequately, by the Government, and won for him a place among the fore- controlled in a large measure by the most physicists of our time. The learned Societies. This institution is scientific work for which Sir Oliver doing most excellent work even in is most famed is a long series of re- its infancy, and is destined, we may searches, begun more than twenty hope, to a sturdy manhood. In that years ago, on the discharge of elec- address, too, he advocated, with more tricity and the accompanying phe- courage than would now be needed, nomena. Starting with an investiga- the right to recognition of investiga- the behavior of lightning Sir Oliver Lodge, a Pioneer in Radio, in 1896, Sent Wireless tions in the borderland where physics tion into Signals Over a Distance of Several Hundred Yards. and into the best method of guarding and psychology meet-the region of against it, which gave us most valu- psychic research - investigations on able knowledge on the construction and dis- properties, writing papers, giving lectures, such subjects as thot transference or tel- position of lightning conductors, he was led and spreading far and wide a knowledge epathy. And his interest in the subject and to make experiments with lightning on a of the new wonder. Among his most bril- his advocacy of its claims to recognition as minute scale as manifested in the spark of liant discoveries was that of the "coherer" worthy of study has gone far to change electric machines and thence to the surg- for detecting the waves. With this detec- the attitude of scientific men from one of ing or oscillating character of the dis- tor he devised the first practical wireless ridicule to one of, at any rate, toleration. charge along wires, in which he obtained telegraph, sending signals over a distance This advocacy of the study of psychic many new and interesting results. of several hundred yards. phenomena is sufficient evidence that Sir This was all pioneer work, done before Oliver is no mere laboratory student; but PIONEER IN RADIO. Marconi took up the subject, and Marconi further evidence that he is much more than One very remarkable experiment is now undoubtedly built upon the foundation a mere man of science, that he is animated well known under the name of Lodge's which Lodge had laid. by deep sympathy with his fellow -men, is Resonating Jar. We know now that Lodge Whatever developments and changes may supplied by his readiness to help in every was really dealing in these experiments be made in the system of wireless teleg- movement for social improvement and re- with the electro- magnetic waves in air dis- raphy, there can be no doubt that Sir Oliver form, and by his writings on philosophical covered by Hertz in 1888, and there can Lodge will always be recognized as one of and religious questions. he no doubt that if Hertz had not made the founders of the system, as a pioneer in Under his guidance the University has the discovery we should have very soon researches upon which others have built. developed in many' ne'w directions. In his learned it from Lodge. Indeed, Hertz efforts for educational WORKS IN OTHER BRANCHES OF SCIENCE. development and himself says: "Professor Oliver Lodge, in reform his colleagues are proud to follow Liverpool, investigated the theory of the He has been a pioneer, too, in other di- a leader with whose aims they sympathize, lightning- conductor, and in connection with rections. One of his most interesting re- a leader whom they regard with esteem and this carried out a series of experiments on searches was on the passage of electricity affection. -

www.americanradiohistory.com 696 Radio News for April, 1921

THIS Department is open to all readers. It matters not whether subscribers or not. All photos are judged for best arrangement and efficiency of the apparatus, neatness of connections and general appearance. In order to increase the interest in this department, we make it a rule not to publish photographs of stations unaccompanied by a picture of the owner. We prefer dark photos to light ones. The prize winning pictures must be on prints not smaller than 5 x 7". We cannot reproduce pictures smaller than 31/2 x 3 % ". All pictures must bear name and address written in ink on the back. A letter of not less than 100 words giving full description of the station, aerial equipment, etc., must accompany the pictures. PRIZES: One first monthly prize of $5.00. All other pictures publisht will be paid for at the rate of $2.00. m,,,,,,, u,,,imummoemme,uummumumulminimmm,,,lllllllmusimilontImmilsommtimummumennommeernemertmumm llll rini,umillon,,,,,ummi,,,i R. N. Oakley's Station THIS MONTH'S PRIZE WINNER

ceiving set : Composite, DeForest coils, tickler circuit, with 2 -step audio frequency amplifier. Control panel (lower right hand corner of set) provides means for easy

control ' of receiver, the antenna, ground, fones, and batteries being controlled thru it. Connections on the receiving set are exceptionally short; none outside the cabinets is over two inches in length except the antenna and ground. The batteries are in- Looks like a stalled behind the control panel. I have real station, heard NPO and NPM to LCM and OUI; eh! Wouldn't NBA to NPA, and amateurs it be grand, in seven dis- boys, if all of tricts. The transmitter is made of 1/ as had such a K.W. non-synchronous rotary gap set, room for our wave -length 375 meters, Dubilier condens- sets, instead of a corner in ers, edgewise wound copper strip oscilla- the attic? tion transformer, all mounted on rear of switchboard. I have had no results as 111,,,1,,,,,,,,11,,,,1,,,.,,1,,,,, 15,000 volt arc lighting system precludes possibility of work on short waves. Short wave receiving may be done only when the arc lights are out, averaging about two hours per month. Daylight work is impossible on account of other work. Experi- ments are being carried on however, and it is hoped to escape this interference soon. I have a C. W. tube set under construction, as also a short wave variometer receiver. Following is a description of my station, feet long; 1 cage, inverted L, 5o feet to 86 5YB: feet, 55 feet long. Ground: Counterpoise, R. N. OAKLEY, 5YB, Antennae: t inverted L, 86 feet high, 15o water mains, rods driven in ground. Re- Jackson, Tenn. Clifford W. Spur's Set My set consists chiefly of receiving ap- regenerative circuit and gives excellent re- consists of four wires too feet long, spaced paratus, as the photograph clearly shows, sults on both long and short waves. Many three feet apart. It is 5o feet high, being the only transmitter used being an arrange- of the European stations have been heard, supported between two steel masts. The ment of two Ford coils, connected in se- and American stations on both coasts. The fones used are Brandes Superior, and ries. These answer the purpose very well loose coupler is used for spark stations Murdock's 3,000 ohms. for local work until a half K.W. trans- only. CLIFFORD W. SPUR, mitter, which is now under construction . My aerial is of the inverted "L" type and Rdo. 3FP, Toronto, Canada. is installed. The receiving apparatus consists of two complete sets, one using crystal detectors, ,,,,11111,1111,,1,,,,,,,1,,,,,,,1 and the other an audiotron bulb. The To avoid crystal set has a wavelength range of 4,000 QRM Cliff meters and consists of a loading coil, Navy uses only two coupler, variable condenser and two de- one-X.W. Fori coils for tectors. In the Audion set, a large Navy transmitting, coupler and also a set of honeycomb coils but he owns a is used for tuning. Change from the real nice re- coupler to coils is made by means of a ceiving set, the feature of 4 -pole D. T. Anti -capacity switch, which which is the can be seen directly below the primary coil. Kewpie doll, The D. P. D. T. switch on the switchboard which sets the clock on is for changing the aerial and ground from Arlington one set to the other, and a similar switch time every on the left end of the cabinet changes over day. the telefone leads. The three dials across the top of the panel control the primary, 7.01.111.1111111111111110111.114 llllll 1111110 secondary and grid condensers. The circuit used is a standard three -coil

www.americanradiohistory.com Radio News for April, 1921 697

B. VENEGAZ'S STATION

As I have never seen anything publisht about Mexican stations in your interesting Radio magazine, I am sending you a view of mine which is almost entirely home- 111111111,,,,,,,,11111,1,,,,,1111 made. It seems that My transmitting station is composed of they have a few good ones a I" spark coil, a Leyden jar type home- in Mexico, made condenser, two homemade gaps, too. This quenched and rotar» oscillation transform- complete sta- er and inductance, tion is almost aerial also homemade. entirely home. To supply the current to my coil, I use a made, and yet step -down transformer. has a very good appear- My receiving set, which can tune in any ance. wave -length between 25 and 15,000 meters, is also homemade. I have a loading coil, 5" x 20 ", a long wave coupler, variable condensers, an audion detector and a loud talker. My fones are Holtzer Cabot. I obtain very good results with this set and every evening I pick up all of the big American stations. H. HELLER'S STATION

Here it is, at last ! I have been holding ing with a friend of mine a few houses placed on a board, four feet long and one this up for some time trying to get at least away. My sending set consists of Mesco foot wide, into a closet. Amateurs in the a half decent photo of my station. After /" spark coil, Dubilier Army type con- neighborhood visiting my station ask my monkeying with the camera, this is what I denser, Murdock Midget spark gap, and opinion as to the best magazine and I have got on a thirty second time exposure, in a half lighted room. Regarding my aerial, it is sixty feet long, fifty feet high, four wires, and separated by 2 -8 -foot long pine wood spreaders, having High power two coats of shellac. I use bell wire spark QRMer, and get dandy results. Look! In the photo can be seen a Radio cabinet Here is an- I built containing a variometer, and below other good a boy who uses it DeForest .00i mfd. variable condenser. only 15 watts. This occupies % of the cabinet space and We compli- the other Y of the cabinet is occupied by ment Hym an audion and for that and detector two -step amplifier. for his good To the left of the cabinet is a general radio receiving set. variable air condenser. I generally use my Navy type loose coupler for tuning, 1111111111111101110111111111111111,0 and H. C. coils for long wave -lengths. A loud talker can be seen in the upper right hand corner, which makes Radio telegraphy and telefony audible in any part of wireless key. Giving this set an input of told them, RADIO NEWS first, "QST" sec- the house. I have a pair of 3,000 ohms, 15 watts, I am able to call another friend, ond, and "Wireless Age" third. My call Electro Importing Co.'s receivers, and a about % mile away. letters are 2BFG and would like to hear pair of 2,200 Western Electrics, and get In emergency, I use a small portable ga- from amateurs who hear me. fine results. I use a Stromberg- Carlson lena crystal set, having wave lengths up to HYMAN HELLER combination telefone set for communicat- 6Oo meters. This complete station is all 134 Amboy St., Brooklyn, N. Y.

STATION OF DANA L. DARLING

The following is a description of my on a regenerative set with two steps of sending. Radio station at Greenfield, Mass.: The amplification. I hear most all the stations on the Atlan- receiving consists of a Duck Navy coupler, For transmitting I am using spark coils, tic coast as far south as Key West and many Stromberg Carlson fones, crystal and but this set is temporary. There is a inland stations including amateurs. All audion detectors and a variety of variables. -k.w. set under the table, but as we will these are heard on a crystal detector. I also have a cabinet tuner which was used not have electricity put in before spring DANA L. DARLING, before the war. At present I am working the set cannot be used. Call IRBM. Greenfield, Mass. The Radiofone at the left of the table is homemade. I obtained the hook -up from the July RADIO NEWS. My antenna and ground connection are not perfect, but I got satisfactory results. I have found out that a good ground is needed more than a good aerial. At present I am using three aerials, The High Tension Room! On the Left is a Radiofone But it two for receiving Here is Dana's Receiver. It's a Good Looking Little One Does Not Work. The Microfone's got a Cold! and the other for With Coupler 'n' Everything. www.americanradiohistory.com 698 Radio News for April, 1921 Correspondence from Readers

SOFT TUBES NOT EFFICIENT AS that his figures are correct, this raises the carry on as before; those who criticise the AMPLIFIERS. price of material to so cents, and we have seemingly senseless covers must be new Editor RADIO NEws: not yet begun to figure in the cost of pack- "bugs" who don't know the "worth" of In your February issue you publish an ing, the actual material of which amounts RADIO NEWS or else are altogether too article by Mr. Gordon D. Robinson, of the to over 15 cents per tube; so that so far as deeply devoted to their art. Therefore United States Naval Academy, which is in- cost of material is concerned, a vacuum don't appreciate a little joke once in a tended to explode the old idea that a hard tube costs many more times the amount while. tube is not necessary as an amplifier. given by Mr. Boddington. Congratulations, Mr. Editor-you ex- As I have personally received a letter If we followed Mr. Boddington's reason- plained conditions very nicely in "Editor's from Mr. Robinson stating that the soft ing, the cost of cattle should be the cost Note," November issue, so I trust you will tube mentioned in his article is the A -P of the water and feed on which it subsists, receive no more kicks on a cover for RADIO Electron Relay, I am taking the liberty of since that is the only material entering into NEWS. I also trust and hope that Mr. In- replying to same. There is no doubt but the finisht product. structor at Savannah, Ga., snaps out of his what a soft tube will serve as a very ex- Mr. Boddington also ignores the cost of hop soon and comes to the realization that cellent amplifier under certain very limiting labor and other overhead expense which radio was not invented for him personally. conditions, and from Mr. Robinson's ar- must be incurred in assembling, exhaust- He'll just' have to get used to conditions ticle it appears that his tests were made ing, testing, packing, selling and shipping now existing. under the limiting conditions which I shall tubes. He also dismisses the amount of Such as NVL trying tq work commer- describe. royalty to be paid on such tubes by saying cial traffic on boo while a local radio ex- The amplification constant of any tube is that it "would naturally increase the cost pert is filling the ether full of "Radio directly a function of the distance between a little," but such statements are obvious Ridicule." the upper and lower flat portions of its generalities made without any supporting I'll say better have a little of this said static characteristic curve. These flat por- proof. ridicule on a magazine cover, than to have tions of the curve are commonly termed the Mr. Boddington would perhaps generous- it all out in the ether as QRM. upper and lower saturation limits. In a ly concede to us the cost of the tube plus J. D. KOLESAR, U. S. N.., hard tube the distance between these satu- overhead, plus patent royalties, plus a fair Officer in Charge ration limits, and hence its amplification return on our invested capital, and no Radio Compass Station, constant, is increased by the application of doubt figures that these should constitute Cattle Point, Wash., increased potentials to the plate until the the cost of vacuum tubes. But he should via Friday Harbor. tube breaks down or ionizes with the fa- remember that unless we are to get back to the ancient miliar blue glow. Since our soft tubes system of barter and trade, we EXPERIENCE OF OPS. ON "OTHER break down at 4o or 5o volts, while the are compelled to distribute tubes thru job- SIDE." hard tubes may be operated on as high as bers and dealers, with both classes of dis- Editor RADIO NEWS : 50o volts, it must be apparent that for tributors requiring a fair profit in order to do business in In regard to the article by H. K. Dunn proper amplification in the second, third, or and order to make it pos- in your February issue, a amplifier, a sible for customers, such as Mr. Bodding- it may be of in- more steps of multi -stage terest to add the experience op- soft tube can hardly be employed. ton, to obtain any article which they want of army immediate erators on the "other side." In addition, for proper amplification - by application to their dealer. The division The manufacturer, jobber and dealer are, to which I have reference without distortion -the static characteristic operated with the British in curve must be a straight line and such a of course, in business for the purpose of Northern improving France and the reception of FL commu- curve is universally obtained in a hard tube. their respective states of health niques on the ground Distortionless amplification is absolutely and should not be expected to make any sets was frequent profit enough to merit an order from the Signal necessary for the reception of radio tele- for this service. I do not like to Officer forbidding continue this discussion further and will the practice, owing to fone communication. In a soft tube, how- the operator's attention being taken from ever, the static curve is very rarely, if ever, not impose on you for more of your valu- his regular able space, but in watch. a straight line, and is often accompanied by closing would like to We used the well -known kinks which may profitably state that if Mr. Boddington will put up a French three - be employed, stage (3Ter) amplifier in connection with by carefully adjusting the filament current suitable bond guaranteeing to produce tubes the regulation for us at the price "aerial," ground pegs set or plate potential, so as to secure extraor- mentioned by him, we about 5o meters shall be willing to offer him a position apart, connecting to the dinary sensitiveness. Using a soft tube, as amplifier with No. io equivalent stranded therefore, as an amplifier for radio tele- Chief Engineer at a salary of not less than wire, $6,000.00 per year. weatherproof insulation. fone speech, considerable distortion would I do not think that the amplifier char- occur would make the use a PACIFIC RADIO SUPPLIES CO., which of such acteristics have any bearing on the sub- tube valueless. By ELLERY W. STONE, ject, as like results General Manager. were obtained with the There is no doubt but what a soft tube British amplifier which had different trans- may be used as a suitable amplifier in a former ratios stage single of amplification for the re- Any infantry signaller with the 27th di- ception of telegraphic signals, but this is a MORE PRAISE FOR RADIO NEWS. vision can verify the above. very limiting condition, and in the ordinary LEE KNOWLSON, Editor RADIO NEWS : case of multi -stage amplification, particu- 26 Mt. Vernon St., larly for reception where no distortion must I have been a constant reader of your Newport, R. I. be present, hard tubes are the only ones "finisht product," namely RADIO Ni:ws, and which can be successfully used. am here to convince anyone that I find it ELLERY W. STONE, a very helpful magazine; one that all ama- MONTHLY ISSUE ENOUGH. General Manager of the Pacific Radio teurs should be proud to receive monthly. Editor RADIO NEWS : Supplies Co. Altho I'm not exactly an amateur now - Concerning an article in a recent copy that's what I'd be termed on the outside. of RADIO NEWS, I wish to say that the So am taking this opportunity of express- question of issuinv that magazine bi- WHY V.T.'S CANNOT BE SOLD ing myself on RADIO NEWS, to all whom monthly is akin to absurd. It takes at least CHEAP. are concerned. a month for one to read and grasp all the I have been buying RADIO NEWS at mag- educational matter in RADIO NEWS. Editor RADIO NEWS : azine stands ever since it was first pub - Of course, if you purchase it simply for Some time ago you very kindly gave me lisht, in fact ever since I first became in- the purpose of reading the various an to contribute our on fiction opportunity views terested in radio, and have always found stories contained therein from time to the prices of vacuum tubes, and I should it an interesting magazine,-regardless of time, or if you only wish look like to at the to avail myself of this privilege again. covers -full of news and helpful diagrams pictures, then what you need is a weekly In your February issue you print a letter to anyone who is anxious to learn. edition, but for the majority of amateurs from a Mr. Boddington, who proceeds to I note in one of your last issues that and professionals who desire to extract show that the vacuum tube companies are there seems to be an increasing squabble something of value from their reading, realizing a profit of 2,80o per cent. over a suitable cover for RADIO NEWS. once a month is plenty. It is difficult to believe that any educated Some like it, others don't ; those that don't I have communicated with exactly person in this day and age would attempt -namely Mr. Instructor, K. C. school, Sa- twenty -one amateurs in Scranton, Pennsyl- to estimate the cost or value of any prod- vannah, Ga., in the November issue. vania, and find that in every instance but uct solely on the basis of the material used As you know, due to human nature, you one, they voiced my opinions. Keep up the therein. As a matter of fact, Mr. Bod- can please some people some of the time, quality and never mind the quantity, w" dington has quite ignored the cost of the others the rest of the time, but you can't can't have both. Yours successfully, base, for which we are charged 25 cents please all the people all the time. S. M. BODDLNGTON, apiece, f. o. b. Newark. Even assuming So I'll say keep it up, Mr. Editor, and Elmhurst, Pa.

www.americanradiohistory.com Radio News for April, 1921 699

UNION COLLEGE RADIO CLUB. TECH HIGH RADIO CLUB. The League has been going only six months The first code class of the Union College Radio At the 34th meeting of the Tech Radio Cum, and we have 35 members. Anyone wishing to Club was held recently in the electrical engineer- on February third, Mr. Metcalf of the Magnavox become an associate member, that is any ama- ing laboratory. Special instruction is being given Co. gave a very interesting talk about the Mag- teur who lives where he can't attend the meet- by expert club members to any who wish to take navox loud -talker. He also gave the history of ings, write to the corresponding secretary or vice - up the practice. The affair is free of charge and the Magnavox, as well as explaining the principle president, Frank Hollingsworth, of Russiaville, is open to all persons interested, townspeople as involved in this electrodynamic receiver. As Ind. well as college students. Those who own head - the Tech Science Club attended this meet,n5, fones are requested to bring them with them. much interest was stimulated along the lines of The radio club is receiving letters daily MASSENA HIGH RADIO CLUB. from radio. The Massena High School Radio Club was or- colleges and organizations of a similar nature, The next day an assembly of the student body complimenting the members of the club upon ganized during the fifth week of the present school then was held. At this assembly a radiofone concert year. The following officers being elected: Presi- work. was given. This was only made possible thru Several reports of the radio club's activities dent, Frank Bailey; secretary, Earle Plante; treas- the courtesy of the Magnavox Company and Ser- urer, Arthur Robinson; instructor, Frank S. have been reported in various radio magazines, geant Travers, of the Signal Carps, located at the while in almost all of stations heard French. eastern reports Presidio, San Francisco, with whom plans for a Regular meetings are held every Monday eve- from, the Union club is mentioned. In addition lecture and music reception were made. ning at 7 P.M., at which code practice, radio to this, the members of the Schenectady organ - A small two-wire aerial not over 75 feet long zation have written several for publication theory, construction and physical phenomena are articles and 40 feet high was used, and another stretch of given and studied. Any member of the high school dealing with the work of the organization for bell wire wrapt around a water pipe serving for a technical magazines upon the requests these is invited to join the club, his club rating being of ground. Together with this a three -step power based upon the results obtained from written ex- magazines. Letters have also been received from amplifier using 400 volt "B" battery was employed newspapers asking information in regard to the aminations given by the instructor. after stepping up with a two -step amplifier. Most Monthly dues of 25 cents are charged, fines club, its organization and details about the col- signals could be heard all thru the balls and in lege general. being imposed for back payment and for unex- in front of the school very distinctly. cused absences from the regular meetings. The radio club is doing a valuable work in ad- After President Wallace Brainard, of the club, vertising the college in the Eastern part of the Correspondence with amateurs and other radio had made a short talk on the subject of telefony, clubs is invited. Address Frank S. French, In- country. That this fact is appreciated was shown the bulbs were turned on. The radiofone speech by a recent act of the publication in which structor, Massena High School Radio Club, Mas- board of Sergeant Travers was about fifty times as strong sena, N. Y., care Massena High School. the radio club was set aside together with the as an average man's voice, being in fact too loud, athletic teams as an organization representing the because of the echoing. After Sergeant Travers college as a whole and therefore exempt from the BENNINGT'ON Y. M. C. A. CLUB. had completed his lecture, he played a few records The Radio Club the Bennington Y. M. C. A. Garnet tax. on the phonograph, after which the concert was of The new apparatus is to arrive soon. was organized March 11, 1920, and has held expected terminated. Another interesting feature of the weekly meetings at its headquarters in the local The club will then be able to communicate by assembly was an experiment with an Ingersoll radio with any Dart of the country under favorable Y. M. C. A. regularly, except during the sum- watch which was held up to a microfone. The mer recess, when recognized activities ceased be- conditions. It will give the radio club one of ticking of the watch could be heard very distinct- the best sending and receiving sets in the coun- cause of temporary depletion of membership caused ly all thru the auditorium, much to the amuse- by the school vacation. The club started 18 try and will be far superior to those owned by ment of the student body with many larger colleges. members in charge of S. C. Lyons and elected During the week eight members were enrolled the following officers: Gen. Sec., H. W. Winslow; in the radio club, probably on account of the CHARLOTTETOWN WIRELESS CLUB. president, I. Pelsue; corresponding secretary, F. stimulated interest. We now have our meetings Cowan; and treasurer, E. Ransom. now has The Charlottetown Wireless Club was organ- every Thursday afternoon at 3.15 P. iv'. It ized Saturday evening, Dec. 4, for the purpose of upon its rolls the names of about 40 young then, among whom are promising helping and encouraging radio amateurs in Prince MANHATTAN ASSOCIATION. some very amateurs. Edward Island. The membership is 15, with The Manhattan Association Thru the generosity of Mr. Winslow of the Y. M. of Radio Scouts C. A., the club now possesses a -appointed numerous additional "hams." started November 5, 1920. well Since then it has risen radio room, a receiving outfit with single stage We are fortunate in securing for a clubroom in the amateur radio field to a very high point. the wireless classroom of the Navy League. The amplifier, a 14. K. V. A. spark transmitter, and a The club now has a membership of 25 and is small, Navy League wireless station (XEN) is also at open for more members. The requirements are: but complete X-Ray outfit. Some good our disposal. It consists of a Y.-K.W. transmitter, work has already been performed with the re- You must be a member of the Boy Scouts and ceiving apparatus, altho the long and short -wave regenerative receivers with know something about radio. The club meets transmitter has not two -step amplifier. We hope to send complete yet been officially operated, due to lack of a sta- every Saturday afternoon at 3 P. M. The club license. description with pictures as soon as possible. owns tion There was organized, recently, a a wonderful transmitting set which was do- branch of the club at S Shaftsbury, Vt., and as The officers elected at the organization meeting nated by the Washington Cutting Co. It is for the ensuing year are: Gerald Maddigan, ;4.-K.W. several of the members have private stations, there multiple gap, 500 cycle set and can is plenty of opportunity for team work. All chairman; Robert Weeks, vice -chairman; Nelson reach a distance of 50 miles during the day and Rattenburg, secretary- treasurer; Walter Hyndman, communications should be addresst to Mr. Fred at least 200 miles at night. Members have talked Cowan, School Street, Bennington, Vt. chief operator and instructor. A library com- to amateurs in Maine. They also have a receiving mittee of three was also appointed. We will be set. The operating room is fixt up in the latest pleased to correspond with Canadian amateurs. style with brass tubing connections as on snips. A WIRELESS DANCE. Address us: Charlottetown Wireless Club, Navy They also have a six -wire cage antenna, one of On March 3 the Technical Research Society of League Building, Charlottetown, P. E. I., Canada. the first in the city. The radio room is open every Steel High School, Dayton, Ohio, held an day in the week and visitors are welcome. The unique wireless dance at a local dance hall. The THE COLUMBIA RADIO CLUB. club is supervised by Mr. M. Schwartz, a Boy music was furnisht by the McCook's Aviation The Columbia Radia Club held its first regular Scout executive. There are also some noted ama- Field radiofone It was received at the dance hall meeting Feb. 25 at their headquarters at 4 Roland teurs among the members such as the President, and amplified with a Magnavox amplifier to a Ave., Baltimore, Md. Officers were elected as Joe Pollock, 2BP; Secretary, Mr. Sparks; Chier sufficient intensity for dancing. Several of the follows: J. Stewart Davis, president; Clyde Friz, Operator, Benedict Goldman, 2VA. latest records were played on the victrola at Mc- treasurer; Wm. G. Buck, secretary. Since then The headquarters is 73 Madison Ave., New Cook's Field. The dance was well attended and one honorary member has joined. The purpose York City. an advertisement in the newspaper brot grati- of the club is to create an interesting and instruc- fying results. Here is a fine idea for radio clubs tive interest in radio te,egraphy and telefony. At ELIZABETH, N. J., RADIO CLUB. The Junior Radio Club of Elizabeth, N. J., holds and other organizations who can arrange to get the present time an efìi,.ient dampt -wave and some nearby station to transmit music. Also C.W. receptor has been installed, a short -wave re- meetings every Friday evening at 7.30 at the this home of Mr. E Gundrum, 303 Cherry served as an excellent advertisement for the so- generative set is nearly finisht and a sending set St. The ciety. of ample range is being installed. Code practice purpose of this club is to get all Elizabeth and is also being arranged for. Correspondence from vicinity amateurs together for relay and experi- Address mental work. Mr. Gundrum entertains the club other clubs is invited. all communications and other radio LONG BEACH RADIO AND RESEARCH to J. Stewart Davis, at above address. visitors with music from many ASSOCIATION. different radiofone stations. All amateurs wish- The Long ing to join should communicate with Mr. Gundrum Beach Radio and Research Associa- IPSWICH RADIO CLUB. at the above address. tion was organized December 20th, 1920, by a The Ipswich Amateur Radio Club held its first few live wire amateurs to carry on and to further Plans are under way for a permanent club room. radio in this city. meeting Friday, Feb. 19, at 7.30 P. M., at the The club has 10 members at the present time and The officers of the association house of the president. The following officers are: Mr. Moore, president; Mr. Lithgow, vice - would like to have more. Fellows you do not president; Mr. Stiles, were elected: President, Gould; vice - secretary-treasurer, and Clarence have to have a high powered transmitter to be- Mr. Collier, corresponding president, Raymond Cook; secretary- treasurer, Wil- come a member of this club, just as ordinary send- secretary. liam Burke. There were eight members The association boasts its own club room present. ing or receiving outfit. Code practice is held and a total of twenty At the next meeting there were fourteen present. at every meeting for those who cannot master members. At present you are not required to pass a test to obtain admit- It was decided to hold meetings every Friday at the code easily. into members' houses a tance the association. The dues are fifty cents the until club house can be a month per member; obtained. The dues are forty cents a month. No THE HOOSIER RADIO LEAGUE. this money goes to defray fee the association's expenses and to buy magazines is charged for admission. The Hoosier Radio League held its semi -annual and needed apparata. The purpose of the club is for radio researci, officers' election Tuesday evening, March 1, at Meetings are held every Monday night at 7.30 work and to aid beginners in learning the code. the public library, in Kokomo, Ind. The follow- o'clock We have a very capable president and he is help- at the club room, where lectures which ing officers were elected: have been assigned at the previous ing members greatly by preparing them for gov- President, Kenneth Schneiderman, of Kokomo; meetings are licenses. given. ernment vice -president, Frank Hollingsworth, of Russia - Anyone We would be pleased to correspond desiring to communicate with a live - with other ville, Ind.; secretary, Walter Lanterman; treas- wire association out for members, clubs. Address all communications to William urer, Vincent Guerin; corresponding secretary, should corres- Burke, Fellows Road, Ipswich, Mass. pond with the secretary, Mr. W. A. Stiles, 445 Wayne Bennett. Cedar Avenue, Long Beach, California. www.americanradiohistory.com 700 Radio News for April, 1921 RADIO DIGEST THEATRE MUSIC SENT BY but a limited sphere of application. It is A NEW METHOD OF PRODUCING RADIOFONE. in the performance of this function that HIGH- TENSION DIRECT The latest thing in providing entertain- radio finds such an important place in mili- ment by radiofone in Pittsburgh is the tary aeronautics. The dots and dashes of CURRENT. sending out of portions of the program the Morse code transmitted from the trail- By M. Schenkel. given at a downtown theater. This is ing aerial of the airplane carry to the ears accomplisht in the same manner as the of the artillery battery commander the cor- For many scientific and practical pur- church services at the Calvary Church in rection for each shot fired, enabling him to poses, small high- tension direct currents the East End. Telefone transmitters placed group his hits on an invisible target with a are required. Sometimes a few milliam- in the theater collect and transmit the sound degree of accuracy as great as is possible peres are all that is necessary. Generally, over a special telef one wire to the radio when the target can be seen, or bring to a accumulators in series have been used, but station of the Westinghouse company in waiting general news of enemy troop move- they are very inconvenient, so that high - East Pittsburgh (Radio KDKA), where it ment observed from the air. tension machinery has sometimes been emis then sent out by radiofone. Squadrons of Attack Pursuit Planes can ployed, or even electrostatic devices, in be maneuvered in flight by means of the which a condenser is always used. The SECONDARY ELECTRON EMIS- wireless telefone from the airplane of the condenser is certainly simple and cheap, SION FROM COPPER SURFACES. .,Imiliungssumummummientigittuttniummilmimmttettmuumniimm,,,,,l,il,,m,,,,,,,,,,,,,,,_ but its voltage rapidly falls off. In order By I. Garnett Barber. to keep up the voltage, some method of SYNOPSIS charging it continually must be used. Secondary Electrons from a Copper Sur- Radio Articles in the Among these plans may be mentioned those face Bombarded by Electrons. -The meth- April Science and employing rotating contact pieces, which od used was to measure the current flow- connect the condenser intermittently with ing to the bombarded plate as a function Invention the poles of an alternating- current source of the grid potential. By using sufficiently of power, those employing valve cells, and low pressures the ionization effect was Radio "Talk" Relayed to Land Lines. lastly the so- called vacuum valve tubes. made negligible. (i) The coefficient of With special diagrams showing the Delon's device, which has already been de- secondary emission was found to increase various elements comprising the scribed by Lichtenstein, is among those somewhat with the energy of the primary complete radio and wire telefone which employ rotating contact pieces. electron up to 500 volts, but never exceeded circuit from the Avalon station, Greinacher has used valve cells to produce 1.5 per electron; the coefficient was in- Catalina Islands, to the S. S. direct -current voltages up to Io,000; but creased by heat treating the plate and was Gloucester on the Atlantic Ocean. both these plans have the disadvantage that greatly decreased by raising the tempera- One of the interesting points shown an external source of power of relatively ture of the plate. (2) The energy of the in diagram for the benefit of radio high voltage must be provided, for a sin- secondary electrons was always less than students is the curves of the dif- gle condenser can at most be charged to a that corresponding to a fall thru five volts, ferent currents in each part of the voltage which is equal to V2 time, the ef- yet owing to the roughness of the sur- radio and wire system at any fective voltage of the external source. face an accelerating potential of about io moment. With Delon's and Greinacher's methods, volts is required to release most of the Audio - Frequency Amplifier in the former of which employs two condens- secondary electrons from the plate. (3) France. By Robert E. Lacault. ers and two valve cells, the maximum volt- As to the origin of these rays, the fact This article is of exceptional in- age that can be reached is 2.83 times that that their maximum energy is always less terest to all radio men and is re- of the source of alternate- current power. than the energy of the primary rays and plete with photos and diagrams of In order to produce Ioo,000 volts on direct the shape of the curves obtained both in- the various hook -ups used in mul- current it is necessary to have an alternate dicate that the secondary electrons are not tiple -stage audion amplifiers of the voltage at least of 40,000 volts; this re- reflected electrons. French Army type. quires a good deal of space and many accessories. Reflection of electrotonic rays with en- U. S. Bureau of Standards Radio ergy below Soo volts, from a copper sur- News. In the present article a new plan is described face seems to be zero, or at least small. The Oracle- Question and Answer which also employs condensers, but Column. the necessary alternate- current voltage is STABILITY CONDITIONS IN much less than before. Let us suppose an VACUUM TUBE CIRCUITS. Electricity from the Air. The latest alternate- current source of power repre- By R. D. Duncan, Jr. development in this little known sented by the winding W in Fig. I. Let it SYNOPSIS branch of science. With wash be joined in series with the condenser drawing and diagrams showing ap- C Condition for Sustained Oscillations in and the valve tube V; then, as the current paratus, etc. passes in the new direction in the winding, Vacuum Tube Circuits. -After reviewing Do not fail to read H. Gernsback's the fundamental requirements for such os- the condenser is changed to the maximum wonderfully entrancing story of a value of that voltage, and let us suppose cillations in any three electrode vacuum trip in the latest space flier. Mr. fundamental equation for this maximum value to be .V2. While in tube circuit, the Gernsback's article describes all of this the plate current of a tube with a linear first half cycle -i. e., during the charg- the principal types of interstellar ing of the condenser-the voltage the volt- ampere characteristic : 1p (vp -l' iivg) of - flying machines and many extreme- winding is opposed to that of the condens- Ro is differentiated, dvp/dip is put equal - ly interesting scientific as well as er, in the other half they will both be in to the load resistance in the plate circuit R2 physical phenomena are interest- the same direction, so that the winding, to- and thus the equation : w = -(s -I- Ro/R2) ingly dwelt upon. gether with the condenser, will have a dvp /dvg is obtained as a general relation maximum 11113110111111111111111111111111111111111111111111111,,,1111.111111111111,1,,,,,1111111111111111,111111,1, voltage of 2V2. The arrows in between the constants of any oscillating Fig. I are intended to show this. The new circuit: R2, the internal resistance of the squadron commander or from the ground arrangement consists in adding another plate -filament path Ro, the amplification easily as a company of infantry is han- condenser and valve tube, so that the sec- constant w and the derivative of the plate dled. By the same means, a machine en- ond condenser becomes charged when this voltage with respect to the grid voltage. gaged in aerial combat and outnumbered maximum voltage of 2V2 occurs. This sec- This expression is evaluated for five stand- may call for assistance. ond condenser, then, becomes charged with ard types of circuit: Hartley, Colpitts, Bombing planes lost in the fog or dark- the maximum voltage of 2V2, and the Meiszner, tuned -plate and tuned grid; and ness are directed unerringly to the home charge cannot be lost in consequence of the it is experimentally verified for the first airdrome by the radio direction finder and valve tube. At the next reversal of direc- two. airplanes without pilots, controlled entirely tion a third condenser can be charged to by radio, are already a reality. 3V2, and, if the process is further contin- RECENT APPLICATION OF RADIO The Air Service of the Army, realizing ued, the voltage can be still further mag- TO MILITARY AERONAUTICS. the importance of this newest phase of nified. Thus, if there are five condensers, HE use of radio communication, both radio, has establisht a school for the train- and an original alternate- current voltage of telegraph and telefone, on the mili- ing of personnel to install, operate and 15,00o, the fifth condenser will be charged T tary airplane is perhaps the latest ap- maintain the radio equipment of airplanes to a voltage of Io6,000 volts. If we sup- plication of radio science, increasing ten- at all the flying fields thruout the country. pose the winding W to be disconnected, fold the usefulness of the airplane and al- Radio engineers and operators, as well as then the condensers will endeavor to dis- ready influencing the design of military air- experienced amateurs, may qualify for at- charge thru the valve tubes. In Fig. I craft. Airplanes have been called the eyes tendance at this school upon application to the are five valve tubes in series, and the of the army but eyes without means of in- any army recruiting officer or to the office voltage is distributed between them. The stantly communicating images and impres- of the Chief of Air Service, Washington, discharge voltage thru . each is, there - sions registered upon the retina would find D. C. (Continued on page 75o) www.americanradiohistory.com Radio News for April, 1921 701 Found by Radio By HARRY WELTON

I'VE been "op" aboard this old wagon flash play with my own little D. F. plant with -QST de YOB -S. S. Borderline po- the S. S. Dunkirk for some time and and thereat I rush into my private shack sition unknown bearing by radio 72° off just must spread myself some now. to get a QTE off VCT while the chance Cape Race -engines disabled, require im- My radio cabin is of fairish size lo- is good. Pronto my ol' loop is goin' the mediate assistance." He must be buckin' cated aft on the boat deck and is di- rounds. You see it is located directly ag'in the same conditions as us I reckons vided into the wireless room and my pri- over the mushroom ventilator in the deck as he don't know where he is. I lose no vate "digs." This hookup leaves me more head right over my table and I have a rod time startin' up an' givin' him the "I get or less disconnected from the rest of the running thru this vent attached to the you," then passin' the dope to the ol' man. crush aboard, but there is plenty QRM loop frame and a nice shiny old sewing He tells me this is very vague- meanin' from below and the speaking -tube from machine balance wheel at the bottom for the position -as this helpless one can be the bridge pours out some queer unprint- a turning handle which carries a pointer anywhere on that bearing and we would able things. However, you don't want to and there is a 360° dial right under. VCT have to chase around till we could see him know so much of this old tub, so I'll tell is workin' long and fast so I takes him so I suggests my D. F. again and he laughs you how I managed to get that nifty new several times, to make sure, and get the a little but says "Try your luck." three -stage amplifier what sleeps with me same thing. Now you savvé the idea is- Pretty quick I have YOB on the string now, complete with "A" and "B" batteries where these two bearings -off two differ- and after informin' him "we're coming," n'everything. ent points of land- cross, is the position I request him to pay off some good long cf our ship. I don't bother with the speak- sigs for a coupla minutes which he does When I migrates from radiobug- "toote sweet." I start swingin' my dom to this stage of the game I loop again and have time to check lugs along my trusty old home- the bearing twice before he quits made tuner (no sentiment you Rushin' the news to daddy on the compree -) and V. T. detector cabi- bridge he lays my bearing and this net which I hooked up to a loop guy's bearing off Cape Race down aerial placed on the roof of my on the chart and finds the "fix" "digs" cabin, makin' a fine little di- where this guy is supposed to be at, rection finder which I experiment if the bearings are correct. He's with in my off duty hours. You only some seventy miles from us. see I keep it in here so's to get We have hauled around now to a away from the main gear and thusly course which will bring us out on avoid any arguments between the top of this YOB fella. two armies of microhenries and I hear much parley on the bridge also prevent the grid from leakin' about it bein' some job this chasin' all over the place and maybe spoil thru fog and ice, but they cheer some good message forms; but I up some when the VCE weather have to get my "A" and "B" juice reports come thru which indicate from the "op" room as I never fresh northwest winds. This will have been able since "comin' to sea" lift the fog and sure enough the to scratch up the necessary coin for barometer is rising. Well, we're these valuable acquisitions, altho proceedin' along now with the ice I'm hopin' an' hopin' an' wishin' holding us down to seven knots. you know and savin' hard as a I stay up most all night communi- miser, I don't see any "means" in catin' with our new acquaintance sight yet. And you must admit and every once in a while I take a I'm some optimistic as I also figures bearing off him and find we're on gettin' a coupla' stage amplifier headed his way pretty straight. so's I can work on my D. F. at "all About six hells in the middle hours" instead of as now only watch I goes out on deck for a when close to stations. look around, you know, and find a We were twelve days out from stiff breeze blowing and the fog Glasgow for Halifax running a practically all gone, which I figures norther course which would bring should be some satisfying to the us out fairly close to Cape Race. O. M. The last three days running was I'm sittin' dopy like from then thru thick ice and fog and as we on as 'bout all I can hear is VCT, hadn't had a "shot" at the sun for VCE and VCS workin' now and that time our position was anything then at top speed as they have the but clear- puttin' it mildly. The ether most to themselves in these old man is pacin' the bridge nerv- Now as He Hands a Bunch of "Ps" to VCS I Figure It's Ti me wee hours. Every so often I get ous like as it seems we're pretty I Pull Some Flash Play With My Own Little Direction Find er. a shout from our helpless' friend handy to the banks. I tells him and find we're gettin' closer all the from the way VCE is drilling into time, from the way he's comin' in. my ears we can't be more than a hundred in' tube but hikes up to the bridge personal Pretty soon it's time for mornin' eats and miles off, which doesn't please him any. and hand the of man the news with some when the mate comes down he tells me- About an hour later I'm sittin' very quiet explanation The ginks aboard here have speakin' as if he wasn't believin' all along, listening to the goings on when I get a been kinda handin' me the laugh about my you know -he says : "Well, Sparks, I guess yell from the bridge thru the speakin' tube "experiments" you know and the "om" you're right. I see some smoke about two with orders to get a - radio bearing off frowns a little when he begins to compree points on the port bow which looks about Cape Race. I jams in the main switch, what I'm sayin', but I don't wait to see if twelve miles off -we'll be up to him in less swings over to Boo meters at top speed he believes or not. than two hours." and give VAZ a shout for a QTE. He About five minutes later tho I feel her Breakfast over, we're all on deck watch - comes back right smart with "K." I then swing some to port, and I run along to in' the smoke and by two bells in the first shoots him the sigs and he must be workin' have a peep at the standard compass by watch we're right up close. I won't bore particular fast tonight for it doesn't seem which I see he has hauled her to a more you with the details, but judging from the I have time to ring back to "receiving" southern course, which is some gratifyin' row on decks of both steamers I figures when he comes thru with our bearing. I to me. This will bring us outa reach of they're havin' a hell of a time hookin' 'em finish off with him and shouts the word the banks. up, and as I looked it over when they have on to the old man. Of course we ain't got When I gets back to the works and am finisht I figures they have enough lines on our longitude or latitude so this bearing comfortable again with the fones fittin' to pull the Woolworth Building away. doesn't wisen us up much and as I'm hear - snugly I have just lit a fag for a good After some more bangin', etc., we're in' Sable Island on his smooth musical draw when some geezer starts up on a under way with our tow, makin' about six note O. K. now as he hands a bunch of note which sounds like a cricket's crick knots and gettin' clear of the ice pretty "Ps" to VCS I figures it's time I pull some and disturbs the ether somethin' awful (Continued on page 7io)

www.americanradiohistory.com ,02 Radio News for April, 1921

Two -Step Audiotron Amplifier By FREDERICK J. RUMFORD, E. E.

audiotron amplifier, the reader should have the following parts available: two potentiometers; two rheostats; two audio - tron vacuum tubes; two 18o degree scales; two filament control switches with complete assembly; twenty -six copper or brass binding posts; one panel which will be fully described further on in this ar- ,311111111111,,,11,,,,1,,,1,,,,,11.. ticle. General view With this outfit there are a lot of sta- and dimen- tions that can be heard across the room sions of the from the operating table with the receiv- panel support- ers laid on the table, or again the re- ing the various parts ceivers can have a loud speaking horn of the two - connected to them, causing the signals to stage audio be heard all over the room. Another in- frequency am- is plifier. The teresting fact that it is possible for the panel is sup- experimenter to connect his outfit onto ported by two a loud speaking horn and he can save the brackets. additional expense of purchasing extra telefone receivers. 111111,,,11111,,,11111111.1,1.,.. In making the amplifier, start with the panel, which may be of oak, rubber or bakelite. In this particular instance, oak was used as it can be obtained cheaper than either of the other two A piece of oak suitable for the purpose can be purchased for $1.00 or $1.50, but, of course, those of us who can afford to buy bake- Fiyure lite or rubber will obtain better results. However, the oak will do very nicely. ATWO -STEP audiotron amplifier accompanying The dimensions of the panel in question drawings in order that all are respectively is just the thing for the experi- hook -ups are connected right. Be careful 14/" long, 11/" in width menter who has one or more audio - that the "B" batteries dont get connected or height and /" or %" thick. It is now tron vacuum tubes and a couple of on to the audiotron filament as it would advisable that the next step be the measuring , sets of "B" batteries on hand. Most burn out the tube. Of course, the ex- and drilling of holes. The panel all experimenters have the above appara- perimenter may have ideas as to his own should then be sandpapered to a smooth tus knocking around their shop or labora- hook -ups, but the one already worked finish. After that it is ready to be paint- tory, and if not, it can be purchased at out in this article is really the best that ed or varnisht, just as is preferred. This small cost, when you come to consider can be obtained because most is a matter of judgment. On the panel every in question a the price it takes to buy a two -step am- hook -up conceivable was tried out in the glossy black insulating com- plifier made up. All told, this outfit making up of this outfit. pound was used, which could be highly shouldn't cost more than twenty -five dol- Fig. No. I, represents the general as- polisht. lars. sembly of the front It would be a good idea to have the view of the panel, panel Several have been made up and very showing the wiring which is on the back engraved and have the indentations good results obtained. The outfit is effi- of the panel, illustrated by the thick filled with a white substance which will cientand simple in construction, is easily heavy lines. It also shows the different designate the different articles and their and quickly assembled, and takes but apparata all mounted on the front of the different uses. It will also give the very little space on the operating table. panel. The dimensions are shown by the panel a far nicer appearance and help to It has been the experience of the writer dot and dash lines, and the concealed set the outfit off to better advantage. in the past that the largest number of apparatus is The next step in the construction is the shown by the dotted lines, mounting amateurs use the audiotron vacuum tube also, the brackets assembly, that is if a of the different articles and solely for the purpose of receiving wire- set of brackets is used. The symbols are: their switches, tubes, etc. As will be seen less messages, and for that reason, ex- R, rheostat; P, potentiometer; T.R., tele- in Fig. 1, the correct dimensions are given periments have been conducted along that fone receivers; F.C., for the mounting of the different arti- filament control cles line and a very efficient and simple am- switches; B1, B battery number one; B2, on the front and the back of the plifier has been developed with the use B battery number two; AI, A battery panel. The reader will note that the bat - of two audiotron vacuum tubes. This is No. I for the filament; A2, A battery No. (Continued on page 742) the first amplifier that I have seen using 2 for filament; C, condenser; A.T. auto the audiotron vacuum tubes, as long as transformer or spark coil; and.S, second- I have been in the radio game, and has ary of the receiving transformer. Figure only been fully developed by the spending No. 1 has been drawn to full scale. of considerable time and money in a Fig. No. 2 shows the general wiring laboratory fully equipt for such experi- diagram of the whole outfit connected up 99000) 0000 ments. ready for instant use, including the ex- It would be a good idea to read the ternal hook -ups along with the different Ql description of this article several times symbols designating the different appara- before starting to work on the outfit. It Tr^ tus. In Fig-. 2 the wiring has been made 5. E is of the utmost importance that very as simple as possible and no trouble idipl- particular pains be used in making up should be encountered in making the con- F.nu /e 2 the different parts. nections. Diagram of Connections of the Audio Frequency Careful attention should be paid to the In order to make up the two -step Amplifier Using Audiotron Tubes.

www.americanradiohistory.com Radio News for April, 1921 703 A Synchronous Rotary Gap By WILLIAM SAMBUR

IT has been found difficult by radio ama- r- teurs to introduce the rotary gap in their Synchronous Rotary Gap. set because of their using a spark coil. A k-----2 = - --moi rotary gap, when used with the ordinary vibrator spark coil, produces a very ragged spark instead of the expected pure one. For use with a rotary gap an alternating current of about 500 cycles must be used in order to produce the desired results. I have tested out the ordinary synchroni- For the ham zer, whereby the current is interrupted only, who uses a and have found it to be inefficient. spark coil, here is a This form of synchronizer, instead of inconvenient 8 Reversals of Current terrupting the current, causes it to be re- way to build per Revolution. versed eight times per revolution, and there- a synchronous fore changes it to a true alternating current. rotary gap. On the same The accompanying drawing shows clearly shaft an in- the construction of the device. The two terrupter and separate strips on the commutator are in- the rotor of the gap are sulated from each other. mounted. The interrupter of the spark coil should be short-circuited. Every horizontal slit on 11,,,,,,,,,,,,,,1,,,,,,,,11111111111, the commutator should be in a straight line with a plug of the eight -plug rotary. This arrangement should be adjusted very carefully. A rheostat should be used to regulate the speed of the motor. The transmitting circuit is such as is used for the ordinary rotary. J Ideal Portable Aerial For Vacationists By CLAYTON B. LE GALLEZ

WITH a satisfactory portable aerial, foot lengths of spruce -a wood light but rope and wire can be coiled and the four previously equipt and ready for easy strong -2/" x 21/o" in dimension. Shape spruce sections strapt together for easy, erection on the camping ground, the these pieces in cylindrical form, finishing practical portage or shipment. On reach- radio enthusiast need no longer leave his neatly with sandpaper and paint. Let us ing camp, the site for the pole can now be beloved hobby at home nor spend unneces- call these lengths, sections i, 2, 3 and 4- selected with reference to one's own con- sary time and energy in preliminary me- the bottom section being No. i, the next 2, venience rather than to that of nature (as chanical labor when he shall arrive in camp. the next 3 and the top one No. 4, respec- is not the case when depending on trees or For best results, all ideas should be dis- tively. other natural supports). carded of taking a chance on finding a Fit a brass or iron ferrule 18" long To erect the pole and aerial, slip the suitable tree or on being able to climb safe- tightly about the upper end of sections i lower end of section 2 into the ferrule at ly that tree if found (remembering the and 3, letting it project 9" from the end the upper end of section i and the lower fickleness of weather and wood). of the section. Whittle the lower end of end of 4 into upper end of 3. Lay these Before leaving home, prepare a portable sections 2 and 4 so that they may be in- two 24 -foot lengths parallel to each other pole and aerial, practical and too per cent serted in ferrule. At upper end of section on the ground and side by side so they will efficient, as follows: Procure four twelve- 2 and lower end of section 3, screw on- slide within the iron bands when upright. using wood screws -an iron band shaped Snap the three guy ropes to the top of Brass co//ars --Winy nuf 3 m: as in diagrams and 4 and large enough section 2. Snap the hoisting rope to the to allow two sections to slide freely within. eye on the band at the bottom of section 3, OQ1, Aeria/ wires At lower end of section r, attach con- thread it thru the pulley at the top of sec- 1 venient arrangement for winding and fast- tion 2 and bring it to the halyard fastener ening hoisting rope; a halyard fastener re- at the bottom of section i. Place the brass Sec/4 cesst in pole is excellent. Fasten a pulley collar with the "lead in" first on the brass for the hoisting rope and three eyes for pipe extending from the top of section 4, the guy ropes to the iron band at the top then the four other collars with aerial wires Palley Iran band F/g 2 'Lead in of section 2. (Diagram 3.) Provide each attached and screw down with the wing of the 3 guy ropes with snaps. Also fasten nut to form a connection. an eye to the band at the bottom of sec- Now raise the two lengths in an upright Guy ?apes i rrevveye tion 3 (Diagram 4) for the hoisting rope position, mutually encircled with the iron which should be about 5o feet long and bands. Stretch and fasten the guy ropes ¡Pon band provided with a snap. securely to three tent -pegs driven in the At the top of section 4 (Diagram 2), in- ground. Pulling the hoisting rope, F/9 .3 Fig 4 raise Pu//er sert a length of vs" brass pipe, extending the two combined top sections sec- Nois//n9 /Ó.p until four inches from the end of section and tions 2 and 3 overlap about 21/2 feet. Sec. threaded at the top. In the outfit have a Fasten the hoisting rope securely to the large wing nut to fit this. Procure five halyard fastener. brass collars, each with a center -hole large Attach the lead -in to the set and the `Ferru/e enough to slip over this brass pipe- solder- four aerial wires to the four remaining ing a 5o -foot "lead -in" to one and a 75 -foot tent -pegs by means of the rope already at- Aeria( wire aerial wire to each of the four others. At tached, leaving the wires thus some dis- the ground end of each aerial wire place tance from the ground. This forms an sec I Fg 6 a Ball insulator and six feet of rope. umbrella aerial which has proved most ef- RC wires Provide also in the outfit four 75 -foot ficient for work. Ha/yoiG fasfene g{ Groundound outdoor recessed inpo lengths of No. 12 R. C. wire (to be used On the earth, below each aerial wire, lay for capacity ground) and length Fig 5 an extra a length of the R. C. wire for capacity ig with a connector on the end (Diagram 5) ground, bringing the four together at the When in a Field or at Camp With a Portable for connecting these wires and lastly sever base of the pole, connecting with the pro- Set, This Mast is the Most Convenient Means tent -pegs. vided connector on the extra length of of Supporting an Aerial. With the material thus prepared, the (Continued on page 748)

www.americanradiohistory.com 704 Radio News for April, 1921

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Junior Radio Course The Regenerative Receiver IN the last lesson, the principles of the coupled to the aerial inductance and tuned regenerative circuit was explained, by a variable condenser. The plate circuit which is in itself quite simple. We Aine/i/ying transformer is tuned the same way and a small fixt ca- shall now explain why variometers are pacity shunting the fones is used as a pass - used in the short wave sets instead of by for H. F. oscillations. another type of inductance. The coupling between the grid and plate At first it is necessary to explain the coils G and P being adjustable it is found functioning of a variometer, which con- that the most sensitive regenerative point sists of two coils, one of which can be for spark signals is just before the circuit turned to 18o degrees inside the other. oscillates. The variometer may be compared to an If the circuit is made to generate oscil- ordinary variable inductance, the number lations by sufficient coupling of the grid of turns' of which may be varied at will, and plate coils, undampt waves may be re- but the two distinct advantages of the va- ceived by the beat method already ex- riometer are -the absence of dead end plained. losses caused by the unused part of the in- Figure 3 In this case, where the receiving circuit ductance, and the variation of wave -length II produces oscillations for the reception of a This is the Audio Frequency Regenerative Cir- is which is as continuous as obtained by cuit. Instead of Inductances an Amplifying undampt waves, the method called auto - variable condenser. Transformer is Used. dyne, auto meaning itself and dyne, mean- When the windings of a variometer are ing power ; that is to say which produces in the same direction, the two fields are its own power. is tions. By this process the incoming sig- to added and therefore the wave -length extent and When a separate oscillator is coupled A, Fig. s, and equal nals may be amplified to a great wave re- maximum as shown in if and plate the receiving circuit for undampt to a large inductance. the coupling between the grid circuits is tight enough, the circuit oscillates, producing undampt oscillations which may be used to produce beats for the re-

ception of undampt waves. . Coup/er .Var/ometers, AUDIO FREQUENCY REGENERATIVE ¡I r. CIRCUITS. ..lillilór, On the same principle the audio frequency component of the plate circuit can be amplified as well. In Fig. 3 is shown the hook -up of an audio frequency regenerative circuit. The oscillations induced in the secondary circuit of the receiver are rectified by the V. T. acting as a detector, and then amplified by the amplifying transformer, the secondary of which impresses upon the Figure 4 grid the amplified current. This amplification is repeated many times, giving very Figure 2 good amplification using only one V. T. In Long Wave Receivers the Tuning is Generally Typical Hook -up of a Short Wave Regenerative Made With Fiat Inductances and Variable Con- as a detector and amplifier, as is the case Set Having a Means of Tuning in Both the Grid densers Instead of Variometers. in the regenerative circuit. and Plate Circuit. In fact the impedance of the transformer should When the windings are at right angles, be the same or greater than the inception, the method is called heterodyne; there is no mutual inductance and the ternal resistance of the tube and a condenser about hetero meaning from the outside; the gen- wave -length is shorter and equals about of .002 mf. should shunt the eral meaning is then, power coming from the value of inductance shown in B, Fig. I. secondary winding to provide a Path for in result obtained the H. F. oscillations. the outside. But fact the Then when revolved to 18o degrees, the is the same, i. e., beats are produced which two windings are in opposition to each LONG WAVE REGENERATIVE CIRCUIT. may be rectified by a detector. other;, the total inductance is then mini- ob- For long wave reception, variometers are In the circuit described for long waves, mum and about the same as would be layer or wound coils on fixt inductance in C, Fig. I. not used as the range of wave -lengths is either single bank tained the may be as well, the tuning But all this variation is obtained without too great, and very large variometers espe- used equally cially designed would be necessary to an- effected by variable condensers being very having any unused part of the winding. form of inductance, but For the reasons explained, this form of swer the purpose. sharp with either It is more convenient to use circuits the bank wound, or honeycomb coils, have variable inductance being the most efficient several advantages which have made this for a certain range of wave -length, it has tuned by means of variable condensers as shown in Fig. 4; a part of the grid coil is type of inductances generally adopted for been adopted by most of the manufactur- reception. ers in the construction of regenerative sets. long wave By referring to Fig. 2, it can be seen QUESTIONS FOR THIS LESSON. that the variometers are loosely coupled, I. Explain the principle of the regenera- to I the ,and by referring Fig. of Junior 'MR Trf tive receiver. Course in the March issue of RADIO NEWS, it can be seen that the circuits are practi- 2. Why are variometers generally used cally the same. for short wave reception? Some of the energy in the plate circuit 3. How is it possible to regenerate audio is fed back by induction to the grid cir- frequency oscillations? cuit, and the amplitude of the original grid Figure 1 oscillations is increased. The same process Comparison of the Value of Inductance Obtained 4. Explain the meaning of autodyne and is then repeated, regenerating the oscilla- With a Variometer and An Ordinary Tuning Coil. heterodyne. www.americanradiohistory.com Radio News for April, 1921 705 A Complete Receiving Set for 25 Cents By JOHN D. ADAMS THE one sure way of making a con- up the condenser will not rub on the bench. should be added to the coil. If the signals vert to the wireless art is to have The variable condenser is arranged as are loudest when the condenser is wide open him "listen in" long enough to real- follows : First press down a piece of it is probable that too many turns are being ize that the whole world is wait- paraffined paper and then a sheet of smooth used. The capacity of the condenser itself ing to talk to him, and then lead tinfoil on top of this, working out all the may be reduced considerably by placing an- him to the work bench. Doubtless there wrinkles and bringing the left -hand edge other sheet of paper between the plate and are thousands of lads who look wist- around over the side of the board so that the tinfoil. fully at the supply catalogs, but get no connection may be easily made therewith. We have now only to construct the de- further, feeling that the cost is beyond their The tinfoil should contain an area of from tector, and here more than on any other scant means or that their electrical and 15 to 25 square inches, depending upon how feature depends the strength of the signals. mechanical knowledge is insufficient to cope thin the paper is between the plates. The Do not use a large crystal. Break it up into with the construction of the various con- upper plate consists of a smooth piece of pieces not more than an eighth or a quarter densers, coils and detectors so beautifully heavy tin, the corners and edges of which of an inch, and then test a dozen or more pictured. have been smoothed off. This is to be fas- pieces until a sensitive face is found. To The receiving set illustrated was planned tened down with two screws and is slightly do this the crystal does not have to be for just these boys, the item of expense bent down so that the free edge will stand mounted. Simply put it on any clean metal and the difficulties of construction having about a quarter of an inch from the tinfoil. surface and carefully go over each with a been eliminated. The writer made it com- Cut the latter away for about a quarter of an whisker wire, which may be easily handled plete in one evening and had time to spare. inch from around the screw holes and coat by sticking it in the end of a piece of wood. It was designed to get the boys started in a with shellac. Cover with a piece of shel- A test buzzer will be necessary, and, of practical way, however small, because any lacked paper and press flat. Screw down course, connections must be made in the boy, who is a real boy, who receives a mes- the tin plate, and provide some sort of a usual manner, which is shown in the small sage on apparatus of his own construction screw adjustment so that the distance be- diagram. When a good crystal is found, will no longer be immune to the radio tween the plate and the tinfoil may be solder a brass nut or a short piece bacillus. He may throw of tubing to a piece of sheet the set away in a month brass and fasten to the base, and start after an audion after which pack in the and a bunch of honeycomb piece of galena with tinfoil. coils, but it has served its The essential requirement purpose in making a con- for a beginner in a crystal vert. detector is to have it so ar- In almost every commu- ranged that the entire sur- nity there is one or more face of the crystal may be good amateur stations op- explored quickly. So many erating on 200 meters or detectors have the whisker less, and to receive them is wire on the end of a screw such a simple matter that and are almost worthless the beginner would never because a sensitive spot is suspect it after seeing the no sooner found than lost, usual array of equipment due to a slight wobble of used. One need not be de- the whisker caused by turn- terred by the thot of put- ing the screw further to ad- ting up an elaborate aerial just the tension. If the on poles -a single wire run whisker is about three - from the chimney to the quarters of an inch long garage, or a large loop in the pressure is relatively the attic will answer every unimportant after it is once purpose. gotten to about the right The first thing to do is point. In the design illus- to get a piece of dry three - Boys: Here is a Real Cheap Receiving Set That Can Be Built by the Beginner trated, a light flat spring quarter inch board, four Who Can't Invest Much for a Start in the Game, it mounted on a block with or five inches wide and a single screw which is six or seven long, the exact dimen- altered as desired. set in only fairly tight in order that sions being unimportant. Boil it in The tuning coil in the usual set is here the spring may be moved to or from paraffine, and on the underside press on a replaced with a small coil consisting of fifty the crystal. At right angles to this . is piece of paraffined paper about four by five feet or less of magnet wire. The capacity riveted -a small strip of metal carrying the crystal wire. It will now be seen that inches. On this, build the fixt condenser, of the condenser being unknown, no definite by which consists in all of three sheets of the previous motion and by turning the data can be given for this ; but it is a very tinfoil about two by three inches, with thin latter piece of metal on the rivet, contact simple matter to make a few tests. Take with any point on the may and a heavy pro- crystal readily paraffined paper between any odd length of magnet wire, say number be made. The screw adjustment for pres- tective piece on top. Connections to the 22 or 24, and wind it into a coil about an sure may be added, but is really not essen- tinfoil may be readily made by means of a inch and a half diameter, and the chances tial, as the pressure can be changed by small screw and a washer at each end. are that it will work. If the signals keep bending the flat spring a trifle. Fasten on a small block at each corner, so increasing in strength as the condenser is Four binding posts -two for the fones, that when the board is turned right side screwed down, it means that more turns (Continued on page 730) Dictionary of Technical Terms Used in Radio Resultant Waves -The two wave -lengths raise the pressure of generator during called Rontgen Rays. These rays have produced in oscillating Coupled Circuits, their charge. the power of penetrating opaque sub- owing to mutual inductance between the Rheostat -A variable resistance. stances, whereby, with aid of a fluores- primary and secondary of jigger, being Ring Armature -Also called Gramme Arm- cent screen, hones in a living body are added to and taken from the self- induct- ature. Has its windings wound spirally visible. Also known as X -rays. ance of both circuits at each passage of round an annular ring or cylindrical core. Rotary Convertor-A continuous current an oscillation. Thus both circuits have Risers-Metallic strips attached to one end dynamo provided with slip rings at oppo- two inductances at almost the same time. of commutator bars to which are attached site end of shaft to commutator. Current The closer the inductance coils are to ends of armature windings. supplied to commutator drives machine each other the greater the mutual induct- Rocker -A casting fixed to casing of dy- as a motor. Armature revolving in the ance; therefore, the greater the difference namo or motor and having insulated magnetic field generates A.C., which is between the resultant waves produced. standards for retaining brush holders in collected from the slip rings. Generally See Percentage Coupling. position. It is capable of variation of used on board ship to convert D.C. to Retardation -See Inductance. position. A.C., when it is known as an inverted Ro- Retentivity -The property of retaining Rontgen Rays- Electron discharge from tary Convertor. If it were revolved by magnetism. cathode in a highly exhausted vacuum mechanical means it would generate both Reversible Booster-Booster used in gener- tube is concentrated on to a platinoid A.C. and D.C. simultaneously. ating stations to raise the pressure of plate, which radiates electro- magnetic Rotor -The moving part of an Induction accumulators during discharge, and to pulses of extremely short wave -length, Motor. www.americanradiohistory.com 706 Radio News for April, 1921 Junior Constructor SOME VERY USEFUL ARTICLES. A PORTABLE ANTENNA. It is very likely that many radio experi- An antenna that will not take up much menters are unaware of the great useful room, and can be made to stretch any ness of what is known as the "Bayonet length, can be made from an, old clothes- Socket" line. Under this heading there is line reel. a large variety of sockets, switches and The clothesline is pulled out and cut a fittings that will prove to be of great utility few inches from the reel; the copper wire around the radio room. Perhaps the best is connected to the remaining few inches one is that shown in Figure r, and which f rope. is known as a Double Contact Line Union. The reel is then wound full, and before A few of these properly connected are bet- it is completely wound up, a lead -in is ter than a whole switchboard. soldered to the wire in such a manner that The sketch will show how easy it is to when it is completely wound up the end of change from one tuner to another, at the the lead -in will stick out. same time doing away with lengthy leads, Short lengths of rope are fastened to the more or less inefficient switches and com- end of the insulator, for connecting to plicated wiring. Best of all, however, is rees, etc. The length of the antenna can the ability to change the polarity of the e adjusted by the clog which is on every current instantly. Such an arrangement is .eel. invaluable in oscillating circuits, as all will Contributed by admit. By putting register marks on each DONALD C. ATHERTON. half of all unions as shown at "A" the correct connections are always easily found. A TIME RECORDING DEVICE. The writer, after one trial of these, threw M1111111111111111 away an expensive switchboard and equipt MIN NNW At times it is desirable for the experi- all his instruments with them to the great- menter to have a device that shows the est advantage. Any combination of instru- ú4.1b length of time a certain apparatus is in ments is possible with such an arrange- operation, as for instance a storage battery ment. charging apparatus, to indicate the amount Some doubts were had as to how these of charge. The writer, being in need of would look, but they are so well made and a device of this sort, conceived the follow- finisht that the looks of the instruments are ing simple idea. really enhanced by them, especially if A watch or small clock is secured that bright, clean cord and nickeled terminals fig. jc keeps fairly accurate time. This is fast- are used. It was also found that the ca- ened to a small base. On the base also is pacity effect was quite small, and, due to You Can Easily Make Some Spiderweb Induc- fastened a magnet, as shown in 'the draw- the fact that connectors tances, Using Some old Phonograph Records as ing at A. The armature of the magnet is all the are alike, a Winding Form. there was no change in capacity when the pivoted rather carefully, and a wire C, of circuits about 3o gauge, is soldered to it. The end were switched, unless the leads a hole with the same diameter as the hole were of very unequal length. When it is is bent over so that, when no current is in the center of the record. Then I slotted flowing thru the coil, the wire is resting on the wooden disks as shown in Fig. IA. the dial of the watch, within the dial of the I was now ready to set the disks. I placed a disk on each side of the record and slipt a bolt thru the holes in the center and tightened it (not too tight). The wooden disks were then rotated so that the .42F.1" slots corresponded with each other. Then 1: with a hack -saw I cut the slots in the record using the wooden disks as a guide and supporter so that the record would not snap. (I advise constructors not to attempt to cut the slots in the records without using the wooden disks, for if he does in a short while he will have mother after him for breaking so many records.) The slots being cut the core was ready fig.l for winding. The constructor will have to Here Boys is a Real Idea to Make Quick Con- determine the size and amount of wire to Here is a Practical Device for Closing a Circuit nections. Some Plugs Are Used Instead of ca- at a Certain Time or Measuring Time During Switches. be used in order tc secure the desired Experiments. pacity. Great care must be taken when remembered that such an article costs but winding so as to not break the core by second hand, stopping it when the hand thirty cents, and will do all that two D. P., drawing too tight on the wire. When the hits it. A small adjustable weight is shown D. T. switches will do some idea may be wire is wound the first turn will develop at D. This is for the 'urpose of adjust- had of its benefits. as in Fig IB and the second will develop ing the armature to the different strengths Many uses will be found for other ar- as in Fig. IC, and so on until the desired of current. ticles in this line. The shown number of turns are wound on the core. If the watch happens to have an unbreak- arrangement to in Fig. 3 is much like that shown above, Then the coil is dipt in shellac and left able crystal. a small hole can be drilled but requires permanent fitting for the dry. thru it for the wire. socket. It consists of an ordinary plug and The coils may be then mounted in a small The coil may be either shunt or series ; a nickeled socket with bayonet lock. It will cabinet and coupling secured by opening if shunt, a bell magnet wound with No. 34 be found to be quite useful for wall con- and closing the two sides of the cabinet on or 36 wire will work on voltages up to nections, or on a switchboard, if one is which are fixt the coil. The terminals may about ten volts without undue current con- used. be brot out to binding posts and in this sumption. If series, No. 14 will probably Contributed by L. LONG. manner nearly any circuit used. answer all the requirements of the amateur. Contributed by RAYMOND Contributed by J. COSMAN. ROOF. PHONOGRAPH PLATE SPIDER - WEB INDUCTANCES RUBBER GUYS FOR AERIAL. For the benefit of those who would like /nsulator /nsu/a /o/ My aerial is strung between two high to make their own spiderweb inductance trees, and is about 100 ft. long. To avoid coils I will describe a cheap but efficient the Q4.4011111311111111104 -01111011411-0 swinging of the trees in a heavy wind, way of doing so. I have placed a piece of motor tubing about I secured some old phonograph plates 0/d .c/ores.: Wire 18 inches long between the spreaders and and cut them as shown in Fig. IA in the ,, - the ropes which are i;??p -7-` drawn over branches following manner : Lead in -- of the trees. This tends to keep the aerial into I turned out two pieces of wood A Portable Aerial May Easily be Made of a always steady, and does not allow any un- disks the same diameter as the record and Clothesline Reel. Make One Like This for Your due strain to be put on it. about %" thick. Thru the centers I drilled Portable Set. Contributed by E. H. WALTHER. www.americanradiohistory.com Radio News for April, 1921 707

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HIS Department is conducted for the benefit of our Radio Experimenter. We shall be glad to answer here questions for the benefit of all, but we can only publish such matter of sufficient interest to all. T 1. This Department cannot answer more than three questions for each correspondent. 2. Only one side of the sheet should be written upon; all matter should he typewritten or else written in ink. No attention paid to penciled matter. 3. Sketches, diagrams, etc., must be on separate sheets. This Department does not answer questions by mail free of charge. 4. Our Editors will be glad to answer any letter. at the rate of 25c for each question. If, however, questions entail considerable research work, intricate calculations, patent research, etc., a special charge will be made. Before we answer such questions, correspondents will be informed as to the price charge. You will do the Editor a personal favor if you make your letter as brief as possible.

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AERIAL WAVE- LENGTH. Q. 1. I have a new complete (182) Mr. Earl Moore, of Salina, Radio set consisting of a coupler, Kansas, asks : galena detector, block condenser and Q. 1. What would be the natural pair of Murdock fones, 3,000 ohms, wave -length of a "T" type aerial 15o with a three -wire aerial of 14 gauge feet lJng and about 5o feet high or copper wire, Too feet long and about about 6o feet in all from the ground 3o feet high. My ground is two up to the spread? lightning rods driven in a moist A. 1. The natural wave -length of place. I cannot hear with this set. such an aerial would be about 200 Can you find my trouble? meters if the flat top is made of A. 1. It is difficult to say what is four wires spaced two feet apart. wrong with your set, but if there are Q. 2. Does it make any change in no broken connections, it may be efficiency to use, say 12 wires in the that your crystal is not sensitive or spread instead of four, considering that there is a broken wire in your a t -k.w. installation? In other fones. The best way to test it is to words, does increasing the number use a buzzer. When the buzzer is of wires also increase the range? runnini near your set try to adjust A. 2. Increasing the number of the crystal until you hear the buzz wires in the flat top increases the With Only a Three P. D. T. Switch, a Crystal Detector May in the fones. If you hear the buzz wave-length but does not increase Be Used with a Two -Stage Amplifier or an Audion and One - the trouble is probably in your aerial Step Put in Circuit for Reception of Undampt Waves. the range. circuit ; if not it is for the reasons Q. 3. How would you calibrate a mentioned above. homemade wave -meter when there are no A. 3. No, a "B" battery switch is not nec- standard wave -meters within 25 miles (so essary. SHORT WAVE REGENERATIVE far as I know) and communication has not TO CLUB. SET. been establisht? WANTS JOIN (188) Mr. Homer Hatch, of Plano, Illi- 3. by (184) Mr. James E. Corley, of Pater- A. Wave- meters may be calibrated nois, requests the following information: the Bureau of Standards in Washington. son, N. J., inquires : Q. 1. Could two Z. R. V. We suggest that you write for particulars. Q. 1. Is there a Radio club in Pater- Clapp -Eastham son? variometers and a DeForest army type short wave coupler be used re- FORD SPARK COIL. A. 1. We don't know of any Radio club in a short wave (183) Mr. Walter O. Schwaver, of in Paterson, but if you have some friends generative set similar to that on page 526 of the February issue of RADIO NEWS? Boonton, N. J., wants to know : interested in Radio why not start one? Q. 1. Will it improve the transmission A. T. Yes, this is quite possible and of a Ford spark coil by using a glass plate MOST EFFICIENT RECEIVER. would give good results. condenser and O. T.? (185) Mr. William Perry, of Columbus, Q. 2. What company handles transmit- A. 1. Yes, the use of an oscillating cir- Indiana, asks the following question: ting tubes of Western Electric make and cuit will improve the transmission and can- Q. 1. Which do you consider best, leav- the so- called "U" tube? not be dispensed with according to the ing the price out of consideration, a Para- A. 2. The "U" tubes are sold by the Radio laws of the United States. gon receiver or honeycomb coils? Radio Corporation of America, 233 Broad- Q. 2. If so, how many plates 3" A. s. The former is more efficient for way, New York City. Some Western Elec- and how many sheets of tinfoil will it be wave- lengths up to I,000 meters, but for tric tubes can be had at the Somerville necessary to use? long waves the honeycomb coils have many Radio Co., 102 Heath St., Somerville, 45, A. 2. Each armature should consist of advantages and are the only practical in- Mass. 10 tinfoil sheets 3/" x 2" with a lug for ductances to use. (Continued on page 712) connection. This, will require 20 tinfoil sheets and 21 glass plates. COMPLETE SET HOOK -UP. Q. 3. Is it necessary to use a `B" bat- (186) Mr. J. B. Eccles, of Toledo, Ohio, Ground srvifch tery switch on an amplifier as I do not be- wants to know: lieve any current is being consumed when Q. I. Please advise me the best way to T p the filament is not lit? hook up an outfit composed of second -hand O D Arlington receiving transformer, 2,500- 3,000 v., one galena detector, one small OT Murdock fixt condenser, one set 2,000 ohm fones, one zinc spark gap, one small glass plate condenser, one key, one quarter -inch spark coil, one porcelain base double -pole, double -throw switch, one single -pole, double -throw slate base switch and a test buzzer. A. 1. A hook -up for the instruments you mention appears on this page. You will note that it is necessary to use an oscillation transformer in the transmitting circuit in order to tune your set to a fixt wave -length. Here is the Simplest Hook -up of a C.W. Trans mitter; With Only Two or Three "B" Batteries TEST WITH BUZZER. as H.T. Supply, This Set Has a Very Good (187) Mr. R. C. Brewton, of Hagan, Ga., Complete Hook -up for a Simple Transmitting Range. asks: and Receiving Set.

www.americanradiohistory.com 708 Radio News for April, 1921 News From My Station By G. RIDLEAK, V. T. Chief Radio Eng. Toronto Lunatic Asylum. (Authorized by Fred. A. Burgess, Keeper.)

SINCE the last letter a good many is neither useful nor ornamental and only composed of small pieces of ebonite rod. changes have taken place at my sta- gets in the way. I next removed the iron I" have found these very effective as they so I thot I would put you wise to core and replaced it with a hard rubber prevent the gap from arcing. But the a few of them. one. This, so I am told, reduces Eddie's rotary part of the gap is most unusual. In the first place I have hung up currents to a minimum and also prevents It consists of one of those old-fashioned a new aerial and installed a transmitting hysteria or hysterics or hiccoughs or lawn you have I sprinklers which probably set. Several months ago a sparrow thot- whatever transformers are subject to. all You know has lessly perched on the old aerial and brot once had a transformer that got hysterics seen. the kind. It it crashing to the ground so I decided to while I was sending and jumped out the three arms sticking out horizontally from put up a real good one. It is, I believe, window. The last I saw of it, it was try- a common centre and when you turn on a marvel of modern efficiency, and goes ing to climb a lamp post two blocks down the tap the whole thing revolves and under the name of a "two -wire inverted the street. It probably wanted to get up squirts water all over the place. Well, L." One wire is for sending and the and eat the raisins off the wires; or no, one of these things is the rotor of my other for receiving, thus doing away with it's currents that grow on electric wires, new quenched rotary gap. The source is the necessity . of a change -over switch. isn't it? Or is it figs? I've just forgotten of power the nearest water faucet, Before attempting the erection of the but it doesn't matter. However, let's re- either hot or cold, it doesn't matter. aerial I consulted many eminent authori- turn to my transformer. Several days Since water is the juice consumed by ties on the subject, including Professor after I got it home my wireless room be- this type of gap I naturally use a water B. I. Ologist's treatise called "The An- came infested with rats. I couldn't ima- rheostat to control its speed. The action tenna and its Relation to the Bug." Since gine what mysterious attraction an ozone of the gap is as follows. When a spark I considered myself a radio bug endeavors to jump from a sta- contemplating the erection of tionary to a rotary electrode an antenna, I felt that this book the water squarts it in the eye might prove interesting, but I and thus quenches it. The must say that I was rather dis- more it gets squirted the more appointed. It is a fine book if quenched it is. When it gets you are going to collect bugs squirted too much it becomes but not the least bit of use if positively drenched. When this you are a bug yourself. happens you have to turn the A friend warned me not to tap off for a while and then stretch m<' aerial too tight. He start all over again. said he put up an aerial with In connection with the trans- one end fastened to a chimney, former I am using several coils and stretched it till there was which I believe are called no sag in it. When winter came strangling coils. The purpose the cold caused the wire to con- of these coils is to strangle, tract and pulled the chimney choke, or otherwise kill any cur- down. This sounded like good rents which may be trying to advice so I let my own aerial sneak back into the secondary hang a little slack. You see, it of the transformer after getting is supported at each end by a cold feet from thinking of the large oak tree and I couldn't shower bath awaiting them at bear to think that these patri- the spark gap. These coils con- archs of the forest might be up- sist of a few turns of rope rooted during the first cold snap wound around a piece of stove - we had. An unforeseen diffi- pipe. It doesn't take much. Six culty arose, , tho. One warm feet of good strong hemp soaked afternoon in early spring the in wax will strangle any cur- wire expanded and an old lady rent that ever saw the inside of tript over it and broke her leg. - a condenser. Now she is damming me for As yet ,I have been unable to sewages- excuse me, I mean get my set to work but this is sueing me for damages. probably only due to a loose At first I found it rather dif- connection or some such trivial- ficult to get a good earth con- ity. When I get a little spare nection because the district in time I will go over the connec- which I live is nearly all blue tions carefully and solder them clay. However, I now keep a with a good brand of fish glue. flower pot full of choice earth The Quenched Rotary Spark Discharger Has Two Fizt and Three Rotary If it doesn't work then I guess on my table and Electrodes. When a Spark Endeavors to rump From a Stationary to a I will donate it to the museum operating Eye and Thus Quenches It. ground the set to this. I recent- Rotary Electrode the Water Squirts It In the and turn my attention to some- ly planted some bulbs in the thing more modern, such as earth to see how they would grow but so transformer had for rats but I noticed radiofones or coherers. Till then, I re- far they haven't even started to sprout. that they spent most of their spare time, main, as undampt as ever. When I was making my transmitting and they had lots of it, nibbling the sec - Editor's Note: condenser I naturally felt a little re- ondary of the transformer. Upon investi- Last week our 57th assistant editor went luctant about using castor oil. Doubt- gation it proved that the secondary was to Mr. G. Ridleak's for an interview. less many other fellows have felt the composed of a large number of pies, as- While in the hall, he heard somebody sane about this national beverage. I sorted flavors, and the rats were making holleriner like barefooted devils on a white consulted a doctor, however, and he as- a picnic of them. I immediately removed hot steel plate. sured me that Nujol, besides being as the pies and replaced them with home- Our reporter thought at first that Mr. G. regular as clock work, was quite as effi- made wire pancakes. In attempting to Ridleak was talking into the microfone of cient as castor oil and much more pleas- rats a new Radiofone using "hard" tubes, but ant. If you believe me, try it your- eat these the committed gastronomic when don't I been with introduced into the room, our man self. suicide and haven't bothered saw with great surprise that the well - It might interest you to hear a little them since. known engineer was experimenting with a account of how I made my transformer. Another unique piece of apparatus is new type of cage aerial, composed of steel, I purchased an old ozone transformer and the rotary gap. Due to its peculiar con- paint covered wire, a" in diameter. He carefully removed all the ozone. Spark struction and action I have called it a was inside of the cage and tried to pull the coils should be treated in the same man- "Quenched Rotary Spark Discharger." wires apart without success. Our reporter ner. That is to say, if you buy a Ford It has two stationary and three rotary was then informed that he could not ob- coil you should remove the Ford, as it electrodes. The stationary electrodes are tain the desired interview!!

www.americanradiohistory.com Radio News for April, 1921 709 music, half of the work is done, for they Stuff are almost sure to be stung by the radio Hair Splitting Short Wave Radio Vac- bug. Explain to them how it works and Sometimes we hear some "ham" operator uum Tube Transmitter show them how to hook up a set. If you "splitting the air" with a mile -a- minute gap, get someone interested and started in the but -it's something new to "split hairs" in and Regenerative game you have done some good work for a variocoupler. the Radio community. Don't think, however, that actual frac- receiver with Two - are to be ISI tional parts of human hairs Step Audio frequency found lurking about the coupler shown Test of Insulating Ma- above. Even if they were, they'd be too small to be seen. What we're getting at is Amplifier moulded (Continued from page 693) terial for Radio Use at that the dimensions of this new coupler are accurate to the fractional part 1111111111111,1111111111,11,,,.. , ,,.,1,,,,,,,,1111,11111111111,,,1,,,,,,,,,1,,,,1111111,,,,,,,11,1111,111111j the Bureau of Standards of a hair's breadth. In fact, micrometer circuits. Be sure and place the trans- (Continued from page 682) formers at right angles and wire them carefully so as to prevent "howling." resistivity is the resistance in ohms be- All necessary details and dimensions are tween the ends of a specimen one centi- shown on the drawing, and no amateur meter long by one square centimeter in with ordinary ability should find difficulty cross section. The surface resistivity is the in the construction of this outfit. Standard resistance between tyro sides of a square parts are used thruout. Those who do not and the surface of the material. wish to construct the three units might con- One of the outstanding measurements struct any one as each is complete in itself. made in the radio laboratory of the Bure ", The variometers and the variocoupler may either be constructed, or purchast ready (Continued on page 718) made. Those advertised by Radisco would be suitable. It might be of interest to you fellows to know that I am a Canadian amateur, which, Lieutenants Needed in I hope, will show you that we are not so the Signal Corns years behind the game as some of you imagine. We can't do much in the way of Here is a New Coupler Made of Moulded Com- sending as we are only allowed very short A competitive examination will be held position. The Bearings Are Very Carefully Ad- wave- lengths, my limit being 5o meters, justed, Making Good Contacts and Smooth Run- beginning April 25, 1921, for the filling of ning of the Secondary Coil. How would you like that? But we can re- 2,585 vacancies in the grade of Second ceive, to our heart's content, and some of Lieutenant in the Army, of which vacancies us have very sensitive receptors. I hear 114 are for Signal Corps appointments. measurements show, that in all essential di- POZ, MUU, YN, BZQ, BZL, BZR, and Applicants for appointment in the Signal mensions, the parts for these couplers vary most of the other high power C.W., spark, Corps must fulfill the following conditions: less than .002 of an inch! and fone. "Candidates must be graduates, or mem- That much variation is só close to none bers of the senior class, of educational in- at all that you can take parts from differ- stitutions maintaining four -year courses of ent couplers, assemble them differently, and instruction in electrical engineering and they always fit perfectly. That's a great Get Your Friends physics and conferring the degree of bach- help when you want to replace some part elor of science in these two courses. after years of use. Interested Full particulars relative to the examina- The materials used as a special moulded may by to the (Continued from page 680) tion be obtained writing composition, Formica, and brass. The pri- Commanding Officer of the nearest mili- mary has 12 taps, allowing any combination Signal 111111111111111141111111111111111111111111111111MM11.111111111111111111111111111111111111M 1.111.111,1111111111111111111115 tary post, or direct to the Chief of turns up to 37. No. 22 single cotton - Officer of the Army, Washington, D. C. covered wire is used, thoroly insulated the duty of every ham to recruit some new It is contemplated that successful candi- thruout. amateurs. It is easy to get your friends dates will be announced or appointed, or interested in the fascinating game and if nominated for appointment about two Photograbh by courtesy of the Radio Distr-ibtding you can get them to listen to some radio months after the final examination. Co.

Indoor Aerial and Choke Coil Amplifiers (Continued from page 686)

Choke coils may be substituted for to repeat that I have heard amateur sta- O. K. with choke coils. If the bulbs amplifying transformers very easily with- tions in North Dakota, Nebraska, Kansas, and chokes are kept separated there will out changing the hook -up much. See Texas and New Mexico, as well as a be no squeals. I have mine about six Fig. 2. There is a hook -up in the No- hundred other ninth district stations. inches apart. 2AGE has a four -step vember Q.S.T. for a choke coil 2 -step Another chap in (2BBB) Ridgewood, working which picks up commercial sta- using a separate set of "B" batteries for who uses a choke coil 2 -step is picking tions in California and in Colombia, S. A. each bulb. This is found on page 54. up stuff as far out as South Dakota. The He gets 8th district stations so loud his On the same page is an editor's note con- choke coils are very popular in Ridge- whole fones vibrate. cerning the hook -up, which states that wood and practically all the amplifiers, Consider the cost of choice coils corn - the turns ratio for choice coils was only in a town of 7o amateurs, use choke pared to that of amplifying transformers. one to one. That is probably true, but at coils. Choke coils may be purchased for about the same time I would like to state that The hook -up that I am using Fig. 1, $5.50 or $2 at the most from the nearest my choke coil 2 -step gives sigs about uses choice coils and only one set of "B" garage. If you have some already, so three times as loud as an amplifying batteries and it certainly works fine. It much the better. Amplifying trans- transformer 2 -step by actual test. I is the best amplifier I ever tried and I formers cost from $5 to $7. With choke won't try to tell you why it works, since have tried many. It was originated by coils a I -step costs about $ro including I don't know myself, but I will tell you 2AGF. The one set of "B" batteries the bulb; a 2 -step about $20 including what it does and how to do it. used for all three bulbs is made of flash- bulbs. A 2 -step with amplifying trans- The secondary of an amplifying trans- light batteries soldered together. It formers costs at least $12 more. Then, former will work better as a choke coil gives much better results than amplifying too, if you can get the "ham" next door than when used in its ordinary way. This transformers and it works better than to use his spark coil as a choke coil, there has also been proved by experiment. the hook -ups using three sets of "B" is that much less QRM for you. A However, spark coil secondaries are batteries. All the grid condensers and K.W. may be used the same way-if much better. grid leaks are very necessary as is the in Ridgewood recently fone condenser across the first choke you wish. An amateur I have done quite a little experiment- in on a I -step and coil. If a or fourth step is added, heard 9MT Colorado third ing with amplifiers and this hook -up is honeycomb coils. The one -step used a a very large grid condenser is necessary choke coil. For emphasis I would like on the last bulb. A 4 -step will work (Continued on page 755)

www.americanradiohistory.com 710 Radio News for April, 1921 RADIO COMMUNICATION (Continued from page 679)

spread out on a pond. Something very to- and -fro motion of the air will start the a room. If a note is sung or produced on similar to the ripples would be seen if, in second tuning fork into motion. This can some instrument, a response may be heard some way, the alternations of electric pres- be readily shown with two tuning forks, from one of the strings of the piano or sure could be made visible and a person striking one of the forks, thus producing from a loose portion of a chandelier or were to look down from above on the an- a sound wave. It can be proved that the other resonant object in the room. tenna and the space surrounding it. The An electric wave can produce an effect waves of electric pressure spreading out at a distance in just the same manner. In and successively alternating in direction any electric circuit the moving wave of would look something like the lines shown electric pressure can produce an electric in the upper part of Fig. 5. The waves current alternating with the same frequency spread out in all directions and go to great as the wave. This is also readily illustrated distances. just as the effect of one tuning fork on Now think of what is happening at a another was illustrated. Taking the same distance from the antenna. As the wave electric circuit with its spark gap, which passes any point there is an alternation of was shown before, and allowing an alter- electric pressure going on continuously at nating current to flow in it, it sends out that point. The alternating electric pres- an electric wave which can act on another sure or wave action at that point could be electric circuit entirely disconnected from illustrated by the wavy line of Fig. 3. The the first. The response in the second cir- portions of the wave above the horizontal cuit when a current flows in the first cir- line correspond to the electric pressure in cuit is shown by the fact that an indicating one direction, and the portions below cor- tube in the second circuit lights up when a respond to the electric pressure in the other current flows in the first circuit. direction. This can be understood by In order that this may take place, the thinking again of the ripple on the water. second circuit must be in tune with the Suppose there is a cork or other floating first. That is, it must be arranged to re- object on the surface of the water at a dis- spond to the frequency of alternation pos- tance from the place where the ripple sesst by the first circuit and the wave starts. As the ripple takes place, the cork which it sends out. This is just like what rises and falls, partaking of the to- and -fro happens with the two tuning forks the motion and of the surface of the water. Or Fig. 10. The Upper Line Shows the Variations sound wave. The second tuning fork does consider the sound wave. As the sound of Current Caused by the Voice Along a Tele- not respond to the wave from the first un- wave passes out thru the air, it will set in fone Wire. The Lower Diagram Shows How a less the two Radio Wave is Modulated in Radio Telefone. are in tune. This can be vibration any object which is capable of shown by placing a bit of wax on one of taking up the motion. Suppose, for in- the prongs of the second tuning fork, stance, that a sound wave produced by a second tuning fork is set into vibration changing the pitch of the fork. When the tuning fork passes a second tuning fork by grasping the first with the hand so as first tuning fork is struck under these con- which is in tune with it, that is, having the to prevent its further motion. A sound ditions it can readily be demonstrated that same natural pitch or frequency of vibra- from the second one can then be heard. the second fork does not respond. In the tion as the first tuning fork. Fig. 5a. The The same thing is sometimes illustrated in (Continued on page 735)

..,IMw.w" ,,,,,,e.,m,,,n OSCILLATING AUDIONS FOUND BY RADIO First Annual Amateur (Continued from page 701) Very little has been said about the oscil- ,,,,,,,,,,,,,,,,,,M,.,,..,,, AI,,,,,,,M,,,,,,.,,,,,,,,,,,,,,MM,,,,,,,,,,,l,l,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,.,,.,,,, lating point of the audion. Altho two Show and Convention bulbs may be of the same type, they will (Continued from page 687) well too. The fog has all gone and the not always operate the .,,,,... ,,,,, efficiently under M,,,,,,,,,,,,,,,,,,,,,,,,,, second mate is busy "shootin'" the sun I,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,.,,. now and soon same conditious. Vacuum tubes vary in Armour we have our "exact" position. their characteristics; there are no two alike. Villa Radio Club, Yonkers, N. Y. I'm gettin' the glad hand all round now, Radio Club of the Bronx, Bronx, N. Y. for you see, fellas, this tow means salvage The main trouble with non-oscillating Ridgewood Radio Club, Ridgewood, N. J. money for all aboard and as it is a large V. T. circuits lies in the "B" battery po- The total membership of these Clubs is ship with valuable cargo and we are taking tential. When trying out a new bulb, test 428. him all the way into Halifax, which is now it, using a variable plate voltage, as some The Executive Radio Council was formed five hundred miles off, the money should tubes are very critical, necessitating care- for the purpose of mutual benefit and gen- be considerable. -Oh, yes, the steward is ful adjustment. It may be a "hard" one, eral improvement in amateur operating shovin' up the good eats and plentiful now requiring a high voltage battery, or it may conditions. During its short existence of and I'm "the white- haired boy." he a "soft" tube using under 4o volts. a few months the Council has accomplisht Just three days later we arrive and drop a great deal, has assisted a great many our burden outside The writer had the following experience amateurs George's Island, pro - which proves this statement to be a fact: in the way of a "big brother,' ceedin' to dock ourselves. The old man and has always promoted the advancement rushes up to the office and comes back with He was using a bulb with a "B" battery of the science of amateur radio communi- our mail and the glad news that we go of 4o volts; the circuit did not oscillate. cation whenever possible. The clubs which into dry dock for about six weeks for re- The wiring was thoroly overhauled but was compose the council are the leading ones pairs. That suits us fine, for by that time found to be correctly connected. As a last of the Second Radio Inspection District, this arbitration or whatever board it is will resort 20 volts were added to the plate cir- which includes Southern New York, Long have settled that salvage dope, and sure cuit with no result; 20 more volts and the Island. Staten Island and Northern New enough as we're reposin' calm and peace- tube oscillated, making a total of 8o volts Tersey. ful like in the dry dock about four weeks before this particular audion would oscil- The amateurs of the Second District are later the Capt'n comes down from H. O. late. undoubtedly the most advanced amateurs and passes kale the around. He must be Another vacuum in the world, due in part to the fact of feelin' some grateful to me, for he pats me tube of the same type being located was inserted in the socket ; 8o volts were at the very heart of the radio on the back and shoves me out an extra activity of the world, and so enjoying close ten bucks. found to be high however, the bulb im- Gettin' that tow and those bear- mediately "blueing," proving contact with a practically unlimited amount ings and all. sore put me in right, for the it to be "soft." of first hand information. mate does likewise and pretty soon the rest The potential was reduced to 4o volts and Five the tube oscillated with greater efficiency. commercial radio companies main- come round and by the time it's all over tain their headquarters in the City of New my share is considerable swelled. The of The grid leak is worthy of more attention York and operate stations in or just out- man tells me later on the quiet I can have than is given it by the average amateur, side the city. Three great trans -oceanic the carpenter any time to make that new and it is often overlooked and thot of as radio stations are controlled and operated loop an' rig it tip anywhere anyhow an' all an insignificant detail. from New York. Hundreds of ships are -you know. arriving and leaving the port continually. Well. what do I do with all that kale? Exhaustive tests show that each individ- - ual tube operates with greater efficiency An untold amount of advanced radio ex- bugs-I had them catalogs out like light - perimenting is done by commercial corn - nin' and -well, you know what would when the value of its leak has been deter- it be mined. panies, by colleges and universities within like -I have 'em -that three -stage amplifier the borders of the district. New York is with "A" and "B" juice boxes all new and By shunting the "B" battery and fones the home town of the Institute of Radio they're hooked up to that new loop now with a capacity of .00t3 mf. the strength of Engineers and an untold - the signals surprisingly increased. number of smaller settin' right where the old trusty did the is radio clubs and organizations are also good work. Contributed by IRVING S. SIMPSON. located here. www.americanradiohistory.com Radio News for April, 1921 711

M U DOCK No. 345 THE LATEST ARIOMETERARIOCOUPLER No. 346

No. 345-P Variometer, as illustrated $7.50

No. 345-G Variometer, as illustrated $7.50

No. 346 Variocoupler, as illustrated $8.50

WINDING FORMS ARE "MURDOCK MOULDED"

"THE PRICE IS UNUSUALLY LOW, THE QUALITY IS No. 346 Variocoupler No. 345 Variometer REMARKABLY HIGH" $7.50 SEE THEM AT YOUR DEALERS $8.50 MURDOCK No. 55 MURDOCK RADIO RECEIVERS Variable Condensers

No. 366 -43 Plate $4.75 No. 367 -43 Plate 4.50 No. 368 -23 Plate 4.00 PANEL MOUNT TYPES No. 3660 -43 Plate $4.00 No. 3661 -43 Plate 4.25 No. 3662 -43 Plate 5.00 No. 368o -23 Plate 3.25 No. 3681 -23 Plate 3.5o No. 3682 -23 Plate 4.25 MURDOCK Variable Condensers

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www.americanradiohistory.com 712 Radio News for April, 1921

,,,,,, 1111 ,,,,,,,,,,,,,,,,, 1n11,,,,,,1,,,,,,,,,,,,,,,,,,,11,,,,,,,,11,1,,,,1,,,,,,,,,,111,,,n1111,11111, 10c CHARGES YOUR BATTERY I . " Want to Know "61 e7,wn Cwwe WI HORN F -F BATTERY BOOSTER AN "Old Town" rests as (Continued from Page 707) 'and your station will never be closed because of a battery, Is it not gratifying 11 1,1111111111111111111,1111111111111111111111111111111111111111111111111111111111111111111111111111111111 discharged lightly on the water as to feel that your fila- a sunbeam. The faintest Q. 3. How would tuning variable con- ment battery will aI- to a re- ways be ready when pressure of the paddle gets densers be connected short wave you want it and that generative receiver? you will never have to instant response. It is so A. 3. One should be connected in series give up in disgust steady that rips and white in the aerial circuit, the other as shown in when working a distant station? water can be shot with ease. the diagram on page 527 in the February F -F Battery Boost- number of RADIO NEWS. ers are automatic and There is a built -in operate unattended. strength to every "Old JAR RECTIFIER. Screw plug in lamp socket, snap clips on Town Canoe" that makes it (189) Mr. Donald S. Jones, of Akron, battery terminals and give many years of service. Ohio, asks: see the gravity come up. Q. i. I-Iow can I make a jar rectifier The ammeter shows you just the amount of current Buy the Sponson Model for flowing. Tho full wave of current is rectified thru and what solution is used in the jars? adjustable carton electrodes which maintain a con- the children -it is safer A. i. Full data for of a stant efficiency and last for thousands of hours. Every- the construction thing complete in one compact, self- contained unit. than a rowboat. Write for jar rectifier was given on page 117 of the The F -F Battery Booster is a Magnetic Rectifier for 105 -125 Volt 60 Cycle Alternating Current. catalog. 3,000 canoes in September, 1919, issue of RADIO NEWS. Bantam Type 6 charges 6 Volt Battery at 6 am- Q. 2. Could I use one of these rectifiers Peres $ 45 stock. $67 up from dealer Type 16 charges 6 Volt Battery at S amperes 24 to light an audiotron bulb? Type 166 charges 6 Volt Battery at 12 amperes 32 or factory. A. 2. It is not advisable to use this type Shipping Weights 10, 12. and 15 lbs. rectifier Also Boosters for 12 Volt Batteries OLD TOWN CANOE CO. of to supply the filament current Order from your dealer or Send Check for prompt to an audion bulb. A simple and practical Express Shipment. If via. Parcel Post have remittance 134 Fourth St. include Postage and Insurance Charges. Will also Old Town, Maine, U. S. A. hook -up was publisht on page 447 in the ship C.O.D. Also F -F Battery Boosters for charging 1921, RADIO batteries from Farm Lighting Plants, Direct Current January, issue of NEWS. Circuits and Direct Current Generators. For group charging use the Full Wave, Automatic ADDRESS OF TELEFUNKEN CO. F -F Rotary Rectifier of 100 Volt, 36 cell capacity. Mr. G. Order now or write today for Free Descriptive (i9o) Brown, of Rochester, Bulletin No. 32 or Rotary Bulletin No. 32A N. Y , sends in the following question: Q. T. What is the address of the corn- THE FRANCE MFG. CO., C7 effiveeTlanPfilkll pany in Germany which makes the Tele- funken receiving tube? LEARN ELECTRICIT A. i. The address of the Telefunken Make your successful fu- Co. is S. W. ri, Hallesches Ufer 12 -13, ture a certainty. We Berlin, Germany. teach by practical work and scientific methods un der practical working con BUZZER TRANSMITTER. ditions. Specialists foi 15 years in training young (191) Miss Lucille Rose, of Omaha, men for Nebraska. wants to know: Electrical Engineering Q. i. How far can I send undampt waves with B.S. Degree in 3 Years with an ordinary test buzzer? A place for every student regardless of age A. T. You cannot send undampt waves or education. Up-to-date laboratories-fac - Build Model Planes ulty of 90 experts; individual instruction. Wading River models are exact scale re- with a buzzer. A hook -up for a buzzer "Earn while you learn" system. Low tui- productions of real planes, that's why they transmitter was given on page 540 in the tion; athletics and student activities. Write fly. You can't go wrong with Wading River February issue of RADIO NEWS. The range for latest catalog and full details. New plans and parts. Send 10 cents for new of it depends on input power. term soon starting. 56 page catalogue, showing 25 different SCHOOL OF ENGINEERING or MILWAUKEE models that you can easily build. Q. 2. What is the wave -length of an Dept RN4 373 Broadway, Milwaukee, Wis, 20 feet WADING RIVER MFG. CO. aerial high, 3o feet long, 3o feet Dept. H, 672 Broadway, Brooklyn, N.Y. lead -in, using four strands of No. 14 wire placed I/ feet apart, and of another one, 7o feet long, 3o feet high and 3o feet lead - in, using No. 14 wire, four strands two feet apart? LearnMechamcal A. 2. The wave -length of the 3o -foot aerial is about ioo meters and of the 70- foot one about i5o meters. .D2A Q. 3. Please give a detector hook -up for EARN $35 TO $100 A WEEK an audiotron. Are than this amount? If so my A. 3. Such a hook -up appears on page offer willo lessyou. I offer to give you a horou h, practical training in mechanical drawing by mail, to your spare time, at home, Course in 539 of the February number of RADIO highest quality set of instruments and Deludesrafting equipment. Iguarantee o give you a NEWS. thorough, grander) training that qualifies 4. yyoo for a high salaried position as a profes- Q. How may my wave -length be in- s Draftsman. My graduates are my kmg good with big concerns everywhere: creased in sending with an O. T. ? Should for free book of Information Your in Drafting ". Roy C. Clam, Per.. I increase the number of turns in the pri- ar mary and decrease the number in the sec- Dept. 1436, Columbia School of Drafting, ondary or should I 14th and T Sts., Washington, D. C. decrease the number of turns in the primary and increase those in REEColors E,uhesforBr the secondary or should I increase both? MontlistoPay A. 4. To increase the wave -length of a F Show Card E,SignsWriting Enjoy your 1921 "Ranger" transmitter the at once. Earn money for the number of primary turns Make $10 to $25 dailyI Make Show Cards, Signs, small lYPaints Our of the O. T. should be increased Advertising Posters and Glass Signa Big demand! Plan often f st and then Interesting, profitable profession. Easy to learn in small payment tohelp their boys along. the secondary few weeks by unique, novel method; something new' FACTORY TO RIDER wholesale prices. adjusted until the greatest model factories. eel. intensity is Our wonderful 50- lesson course includes individual orsrands f 4Ranceerrles, obtained in the aerial. This is instruction by correspondence from expert artists; DELIVERED FREE expre, prspax1, fOR shown total cost only $15. Every student given $15 assort- 30 DAYS TRIAL. select bicycle and terms by the antenna H. W. ammeter. suit -cash or easy payment, ment of finest 'Millerine" colors and brushes - that and Q. 5. If T change the power of my send- FREE! SEND NO MONEY -Send name and address lresegmpment,athaifretá,lprices. . and receive complete course and Free outfit. Pay $ Simvply write today for big ing station and increase it do I have to SEND NO MONEY - prices and terms. on arrival and $1 weekly for 12 weeks. Success FREE Ranger Catalog and mar elous get a new license? guaranteed or money refunded. Earn enough first Cycle Company Special A. 5. If you make any change in your week to pay for course. Send TODAY. Dept AIM ChteagoRiderAgents Empire AG Institute. 2050 Amsterdam Ave. Mead station you should inform the Radio in- New York, N. Y. spector of your district just what modifi- Competent and Prompt Professional Attention to cations you intend to make. Brass Binding Posts - 5c each PATENT AND TRADEMARK MATTERS Switch Points, nickle 4c each Expert Services in Radio Inventions LOOSE COUPLER. Battery Rheostats - - - $1.00 Inventor's Adviser, a clothbound library (192) Mr. Paul Rumball, of Beverly, reference book sent free on request. No order for less than 6 Binding Posts or 6 Switch Mass., inquires : Points accepted. William C. Linton Q. 1. Can I use a loose coupler with a All kinds of Wireless Supplies. Patent Attorney and Engineer, Radiotron bulb and what be 932 National Union Bldg., Washington, D. C. would the DREYFUSS SALES CORP. hook -up? 4th Floor. 150.152 Chambers St. New York, N. Y. www.americanradiohistory.com Radio News for April, 1921 713 Wesfnghouse Radio Receiving Equipmen

Type RA Short Wave Tuner Type DA Detector Ampli- Style 307189, 180 -700 Meters fier, Style 307190. 2- Stage, 3 Tubes, Audio Frequency.

THIS high- gradelWestinghouse regenerative tuner, and tube detector -amplifier embody the last ideas of two noted radio engineers, Edwin H. Armstrong and Frank Conrad. This apparatus provides a most efficient set for telegraph and telephone reception °over the amateur and normal ship wave length ranges. Simple in Design -Easy to Operate -Single- Tuning Circuit Highly Efficient

,'..J

Interior View of RA Short Wave Tuner Interior View of DA Detector Amplifier

Our Radio Folder No. 4446 will interest you. Ask your dealer for a copy

Westinghouse Electric & Manufacturing Company EAST PITTSBURGH, PA. Westinghouse

www.americanradiohistory.com 714 Radio News for April, 1921

A. 1. Yes, a Radiotron tube may be used with a loose coupler. The diagram of the PROTECT You a Vacuum Tu BES connections was given on page 539 of the February issue of RADIO NEWS. INDEFINITELY! ANTENNA. (193) Mr. Russ Barringer, of Fremont, Ohio, wants to know: Q. 1. I am figuring on putting up an Sure Protection at Little Cost antenna -four wires, 255 feet long, 65 feet front A few cents invested in the Radeco Safety Fuse at one end, 40 feet at the other and using means the sure protection of an expensive Vacuum two telefone poles for masts. I have on Tube. hand about 1,50o feet of No. to bare copper On the same principle as any fuse the Radeco Safety, toll line wire, but due to the fact that it Fuse protects the bulb against any excessive am- has been in service for some time it has perage. turned a dark greenish color. Would it be advisable to use this wire? A. 1. You can use the wire you have for an aerial providing all the connections are RADECO Safety Fuse carefully soldered. The natural wave- Patent Pending length of the aerial you describe will be Easily applied directly upon the filament terminals of any about 450 meters. standard bulb. Simply clean filament terminal free of solder and composition and slip fuse on. Two fuses -one on each terminal -protects the bulb indefinitely. GRID LEAK. Every radio man in America needs the RADECO (193) Mr. Stuart K. Little, of Kenmore, Safety Fuse. Send certified check or money N. Y., asks: order today. Orders sent post paid. Q. I. Please give the hook -up of a set RADECO Safety Fuses are Unexcelled for C. W. Work with which I can receive Arc and Spark stations and whereby I can change from audion and one -step amplifier to crystal de- RADECO Bindo Post tector and two -step amplifier? A. I. The hook -up for such a set ap- Sizes liInsures 102% Contact. Will not cut 25c pears on this page. the finest wires. Holds firmly lead n g, 1, 1 %, wires S M A L L Q. 2. How can I make a simple grid 14,2 and 2% or terminals. Extreme vibra- Amps. Dimen- tions cannot loosen lock grip of con- 3UC leak? sions % inch tact surfaces. LARGE A. a. A simple grid leak can be made of over all. a piece of stiff cardboard clampt between two binding posts. This cardboard is then darkened from one binding post to the other with a lead pencil, until best results Rotary Quenched Spark Gap 44 V. VARIABLE B" are obtained. $20.00 Postpaid BATTERY $3.60 RADIOTRON BULBS. Include postage on 4 lbs. (194) Complete in handy wooden case and adustable Mr. Reid Cox, of Wallowa, Ore- bronze phosphor The advantages "jiffy" connectors. Better than block batteries gon, sends in these questions : one 4.4 V. unit weakens of a noiseless, -if prematurely, it can be 1. super - efficient emoved and replaced- thereby not impairing total volt- Q. Give a simple diagram for using rotary gap are age, which makes this the best battery value to be had one bulb with 45 volts on the plate now within the at any price. Set of 10 Renewal Units, 44 Volt, $3.10 with reach of all. postpaid. Just the thing for C.W. work. necessary apparatus for transmitting short The casing is distances of cast alumi- with a kev. num with the A. 1. The hook -up for a short range cover machined GROUND WIRE 8c FOOT to make an C. W. set is given on this page; the induc- airtight enclos- $7.00 Per 100 Feet tance should be wound with 36 turns of ure for the ex- No. 4 solid copper-rubber covered -triple braid -in- tremely 1 i g ht elude postage on 20 lbs. per 100 ft, No. 16 D. C. C. wire on a form two inches weight alumi- 100 amp, in num rotor, 600 volt lighting switches, $4 diameter with a tap taken at the 17th with bakelite turn. If an aerial ammeter is used it insulation. Stationary electrodes are of copper with bakelite insulation. The smallest gap motor may be should have a reading scale of o to 0.2 used, but is not supplied with gap. GET YOURS SET AERIAL WIRE lc FOOT amps. TIP AT ONCE, and INCREASE YOUR RADIATION AND RANGE!! 7 strands No. 22 copper-tin plated to prevent oxidation. Q. 2. What is the wave -length Maximum radiation and strength. Include postage on of my -5 lbs. per 100 ft. aerial which is made of four wires 1% feet apart, 15o feet long and 75 feet high at one FILAMENT RHEOSTAT point and 15 feet at the other? For Back or Front of A. 2. It is difficult to say since you do Panel Mounting, d not state the length of the lead -in and ohms, 1% amps., 1 ?6" ground and whether it is dia. an L or T aerial. Roughly, it may be from 16o to 210 meters. $1.75 Postpaid Q. 3. Is it necessary to get good re- Immediate Shipment. sults to have a plate battery control on the new Radiotron detector bulb? Standard VT Socket Honeycomb Coil Adaptor A. 3. It is not absolutely necessary to Improved Contact Type $1.50 per have a plate voltage control for this type pair of tube altho it permits more $1.00 Postpaid Attach to binding post of any variable condenser, critical ad- Copper foil condenser insert R -C coil, making a tuning unit. Two units justment. For complete details about these make a loose coupler, a third makes a tickler coil, 35e p,p one makes a ware,n -'ter. tubes we suggest that you ask for a copy of the Radiotron bulletin from the Radio Corporation America, 630 WASHINGTON ST., of 233 Broadway, RADIO EQUIPMENT CO, Boston, Mass. New York City. RADIOFONE TRANSMITTER. A welcome addition to your library! Send $2.00 today, plus postage for 7 lbs., and your copy (195) Mr. Franklin English, of Berkely, of bound volume No. 1 of Radio Amateur News will come forward by return mail. Calif., wants to know: Experimenter Publishing Company 236a Fulton Street, New York City Q. I. What is the simplest, most efficient and inexpensive Radiofone transmitter that will transmit from five to 25 miles? ! SPECIAL A. 1. For the construction of such a 6V.35 -40A Storage Batteries Radiofone we refer you to page 690 of the Guaranteed 1 year Repairs free OLES June, 1920, issue of RADIO NEWS where full Price $18.75 (SPRUCE) data was given. FOR YOUR WIRELESS Q. 2. Please give a diagram of three - ELJAY BATTERY CO. Furnished and erected at reasonable rates coil honeycomb mounting the primary with 30 N. CICERO AVE., CHICAGO. ILL. J. F..BYRNES 578 Gates Ave. condenser switch on primary, audiotron, Brooklyn,N.Y, (Continued on page 718)

www.americanradiohistory.com 715 Radio News for April, 1921

"A TUBE FOR EVERY NEED"

Radiotrons are now recognized as the amateur's and experimenter's standard for Radio detection, amplification and power work. They are available at established Radio dealers throughout the United States. Scientifically designed and manufactured in the country's largest lamp factories, Radiotrons come to the experimenter with uniform and dependable characteristics.

One of the following tubes is certain to meet your requirements

U. V. 200 U. V. 201 DETECTOR AMPLIFIER $5.00 $6.50

U. V. 202 U. V. 203 U. V. 204 POWER TUBE POWER TUBE POWER TUBE t, 5 -Watt 50 -Watt 250 -Watt $8.00 $30.00 $110.00

The Radio Corporation's tubes are covered by patents dated November 7th, 1905, January 15th, 1907, and February 18th, 1908. as well as by other patents issued and pending. Tubes licensed for amateur and experimental use only. Any other use will constitute an infringement.

Your dealer has Illustrated Bulletins on Radiotrons, or write direct to

SALES DIVISION, COMMERCIAL DEPARTMENT, SUITE 1802

>ee ®° AFa RADIO CORPORATION OF AMERICA 233 BROADWAY III w NEW YORK CITY

i i rrlN ll!! II !! P , .1 I I i ' .1`ìl1 , `11 IIUhülflíIgL

www.americanradiohistory.com 716 Radio News for April, 1921 %///i, 1,%, ,,

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This

RADISCO DEALERS ALBANY, N. Y. CHICAGO, ILL. Shotton Radio Mfg. Chicago Radio Lab. Co. 1316 Carmen Ave. 8 Market St. EUREKA, ILL. ASHEVILLE, N. C. Klaus Radio Co. Hi - Grade Wireless Branch, Peoria, III. Instrument Co. KANSAS CITY. Mo McCreary Radio Sup- ATLANTIC CITY, N. J. ply Paramount R ad io 4th & Delaware Sts. Supply LOS ANGELES. CAL. 518 N. Connecticut The Wireless Shop Ave. 511 W. Washington BI ENVILLE. QUE., S CAN. MONTt. REAL, P. Q., Canadian Radio Mfg C.AN J.'B. Mllier BOSTON. MASS.' 135 Vendome Ave., Atlantic Radio Co. NEW . 88 Broad St. BRUÑSWICI( NEW JERSEY BROOKLYN. N. Y. Geo. N. DeLaplaine Kelly & Phillips 306 George St. and ,.312 Flatbush Ave. 8th & Magnolia Sts. i

www.americanradiohistory.com Radio News for April, 1921 717

i//// 1W,,,,,,,,,,,.,,, .,,,,,,,,,,,,,,/ ACCURATE

HERE'S the new Radisco improved variocoupler -standardized- machine made -accurate, in all essential dimensions, to the .002 part of an inch. First, in design and construction. it sets new standards of mechanical and electrical efficiency. Second, the materials, -special moulded composition, Formica, and brass, -will deliver years of uninterrupted service. Third, it's entirely standardized and machine made. If, after long service, some parts need replacing, you will find that the new parts will vary less than .002 of an inch -a fraction of a hair's breadth. Finally, the price, only $7.50. It's hard to compare prices, because there never was a coupler so well -made, so accurate, so good thru and thru ; but, at least, you have the

satisfaction of knowing that the standardized, machine, quantity production, not only- insures a vastly improved instrument, but also gives you unequalled value per dollar. No printed words can possibly give you the evidence of quality, equal to an examination of this coupler at your Radisco dealer's. But in the meantime. these specifications will indicate the care and valúe that is put into every detail of the construction. The ball and base are special moulded composition, high polished, which cannot warp. The tube is black Formica that will not' Shrink or absorb moisture under any conditions. A treatment of special insulating compound and best grade insulating varnish insures perfect insulation thruout. The hard brass bearings, with phosphor bronze contact springs, are supported by moulded "U- Beam" strips of Bakelite. The shaft projects far enough for panel mounting, and is 3/'16- in diameter, to fit the standard Corwin Dials. The winding consists of No. 22 single cotton -covered wire. Primary is tapped in two groups, -six taps six turns apart and six taps single turns apart. This makes it possible to secure any combination of turns up to 37. Secondary is wound without taps on the moulded ball. This improved coupler is lighter in weight, sturdier, and more efficient than any of the more expensive models that have preceeded it. Your Radisco dealer has a supply now, but it would pay you to see him soon! iParc, antee RADIO DISTRIBUTING COMPANY NEWARK, NEW JERSEY

RADISCO DEALERS NEW ORLEANS, LA. SEATTLE. WASH. Rose Radio Supply Northwest Radio Ser- 604 Gravier St. vice Co. NEWARK, N. .1. 609 Fourth Ave. A. H. Corwin & Co. SCRANTON. PA. 4 West Park St. Shotton Radio Mfg. OMAHA, NEBRASKA Co. 0 -B Radio Supply Co. P. O. Box S 406 Brown Building Branch, 8 Kingsbury PHILADELPHIA, PA. St., Jamestown, Philadelphia School N. Y. of Wireless Teleg- raphy TORONTO, ONT., Broad & Cherry CAN. Sts. The Vimy Supply Co. PROVIDENCE. R. I. Rhode Island Elec. 567 College St. Equip. Co. WASHINGTON. D. C. 45 Washington St. Eastern Radio and PITTSBURGH. PA. Electric Co. Radio Electric Co., 1405 Florida Ave. 3607 Fifth Ave. N. W. PORTLAND, ME. WICHITA. KAN. Atlantic Radio Co. The Cosradio Co. 15 Temple St. 1725 Fairmount Ave.

www.americanradiohistory.com 718 Radio News for April, 1921

(Continued from page 714) WE HAVE THEM WE HAVE THEM. with double filament switch, dampt and un- Uv 200 --UV 201 Preserve the List Below and Order New Tubes New Accessoi ies dampt switch batteries and fones, rheo- UV 202--UV 203 Direct Until New Bulletin is Ready. stat. HAVE YOU NOTICED OUR PHENOMINAL "GREATER BOSTON AMATEURS"! OUR LO- A. 2. You will find this hook -up on page GROWTH? THERE'S A REASON! 909 OF OUR CATION MEANS LOW OVERHEAD AND OUR SHIPMENTS ARE MADE WITHIN 48 HOURS SHOP AT YOUR DISPOSAL MEANS BETTER 462 of the January, 1921, issue of RADIO AND POSTPAID! SERVICE. OPEN FRIDAY NIGHTS 8 TO Ii P. M. NEWS. Q. 3. Give complete data for ' / -k.w. state Chelsea transformer of closed core tyne and .. SORALA if secondary is over primary or at other Variable '- end. use , Condensers A. 3. In a % -k.w. transformer for ,', ` mimanvixes on Ito v. 6o cycle current, the closed iron .$` No. 3 BD 03 zrro SERVICE 54.751, Oenlunry4 be made thin laminated steel i . means that core should of 1\t we'll Day the and have the following dimen- With Dial gg 4. Somerville Radio postage a n d sheeting a No. BD i 1r 4 Laboratory ® ship by return sions : outside, 7h" x 7" ; inside, 434" x $4.23- ß mail! 0006 MFD. C The 3g." ; thickness, I8 ". The primary which With Dial. yopuIarlty e f is wound on one leg, consists of 26o turns e Dial Only. . ' F i ;g nur Type J 70 ® five I Meters has of No. 14 S. C. C. wire wound in lay- I Made of real made possible bake 1 its, larger produo- ers. The secondary, which is wound on the i i1'. 314," a. D i tion, w h 1 ch opposite leg, is made in 16 pies, %" thick A e e urately ..^ with lower raw Moulded - "'" - _ material costa, and wound with 35,438 turns (2,214 turns won't warp. - allows a per pie) of No. 35 D. C. C. This requires about 5.5 40,444 feet. NEW! CHELSEA DIAL INDICATOR, PRICE pounds of wire or Consists of knob and dial moulded in one piece, REDUCTION TO $6.00 The secondary voltage of such a trans- with " or 3/16" uushìug and set screw. on all Ammeters and Milliammetersl former is 15,000 volts. D. C. 0 -3 Ammeters,. Miliammeters, 0 -50, 0 -100, SOMERVILLE DIAL INDICATOR, $2.00 0 -300 and 0 -500 'i.. A Better than Type CSU, 4" D. " bushing eah- Type J 0- 100 Voltmeters CONSTRUCTION OF C. W. TRANS- brations clockwise reading, on upper half of scale. $8.00 Navy knob Type J 0- 500 Voltmeters 16.00 FORMER. RADIOTRON UV 200, $5.00 POSTPAID Type J 0 -1000 Voltmeters 24.00 (196) Mr. Reville L. Swok, of New RADIOTRON UV 201, $6.50 POSTPAID These include external resistances and are of the "Four -page booklet given with each VT." D'Arsonval type. York, requests: CiRln CONP FNSF RS, .0005 and 00025, 25c Double Q. I. Please publish the necessary data VT Socket, Radio Service make $2.50 GENERAL RADIO FLUSH TYPE A.C. HOT WIRE AMMETERS; NEW PRICE $7.75 for the construction of a transformer suit- SORALA S10 VT Ranges, 0-34,, 0-3i, 04, 0 -21 and 0 -5 amperes used able for the radiofone hook -up shown in SOCKET $1.10 for radiation or filament current indication. Question 559 in the I-Want -To -Know col- Spun aluminum shell, umns for February. Mt" x 21" bakellte base, engraved to white, to A. 1. The core of this transformer con- TYPE d e s t g note connections, JX A.C. 0 -I5 VOLTMETER $8.00 sists of No. 27 gauge laminated steel sheet- _ - u n c a e t s urckeled (For power tube filament regulation.) !-, bronze brought out to Dili. 3k" flush -- similar to Type -2- magnetic vane ings, cut to make a core 5" x 5" and Yi." ample connectors. Work- movement-iptvel bearings. Your expensive power she high. Each lamination is 34" wide. Three manship up to Navy will last twice as long with A.C. on filaments and a i standards. Won't warp or using PROPER VOLTAGE. of the legs of the core should be covered .;. m e 1 t. Guaranteed to please you. with six layers of empire cloth and well shellacked. The primary into which the FILAMENT ACME HIGH IMPEDANCE AMP. TRANS. - - $5.00 ACME HEATING TRANSFORMERS impresst Ito volt current is applied con- 75 watt. fully mounted, $12; 22 volt EVEREADY adjustable B Battery $2.00 Unmounted $9 nn sists of 5o turns of No. 14 double cotton 44 volt EVEREADY adjustable B Battery 3.75 150 watt, fully mounted, $16; Unmounted 13.00 covered wire. fila- (The most satisfactory battery on the market!) Bulletin on request. On the other leg the USE A TUNGAR RECTIFIER for charging your ment storage battery secondary should be wound and where it stands, 2 amp. size.. $18.00 ACME 200 WATT CW Maximum sensitivity is obtained from RADA)- TRANSFORMER should consist of to turns of No. I6 D. C. C. TRONS by using a GR "A" battery poten- Unmounted, $16.00- Mounted, $20.00 tiometer, magnet wire. An additional tap is taken for adjusting voltage drop 4.00 Blue print and directions given with each on GR No. 214 7 ohm, 2 amp. panel one rheostat, 3" how to pass 500 M. A. of plate current, with a off at the fifth turn. The secondary, or the diameter 2.50 chemical rectifier. "Simplest thing DOZEN 12e INSULATED in the world, high tension winding, consists of 50o turns BINDING POSTS 1.25 and very inexpensive.' Shipping weight, 20 lbs. Black or Yellow Empire Cloth tubing, per In .01 of No. 28 D. C. C. magnet wire and each layer is 2.3 m. h. HIGH FREQUENCY CHOKE COIL.. 1.00 ACME CHOKE COILS insulated with two layers of em- TRANSMITTING MICA GRID CONDENSER.. 1.00 pire cloth. An additional tap is taken on (.0005 mfd. 1800 volts mounted in Bakelite.) Single Coil, 150 M. A $4.00 25oth Above grid condenser, UNMOUNTED .50 Double Coil, 150 M. A. 6.00 the turn. It is advisable to have each 10,000 ohm VITROHM grid leak, $2.60; 5000 1.75 ohm Single Coll, 500 M. A leg wound separately and then completely Clapp -Eastham 6000 ohm variable resistance 3.00 6.00 UV202 RODIOTRON POWER 'TUBE 5 watt, Double Coil, 500 M. A 8.00 assembled and properly secured by means 350 v. 8.00 W. E. 2IAA 1.000 V. Condenser, I mfd 2.50 of 1203 RADIOTRON POWER TUBE 30 watt, clamping bolts. It will be noted that 1000 v. 30.00 No. 323W WEST. ELEC. TRANSMITTER 4.00 the delivery side the H. T. rectifier, A, B (With mounting bracket, 50c extra.) of 1 204 RADIOTRON POWER TUBE 250 watt, is a C .2000 V. 110.00 ACME SEMI -MOUNTED M O D U L A T I O N shunted with high capacity of the (Operating data given with each tube.) - TRANSFORMER 5.00 order of six mf., and this condenser is used to make the uni- pulsating currents of the SEND YOUR ORDER NEW PRODUCTS -We Have Them FIRST delivery side of the rectifier as much as TO SORALA FOR II APPROVED STANDARD PRODUCTS -We Have Them ALWAYS. nossible a continuous current. Therefore to.help this process and straighten out the REMEMBER ! We Pay the Postage on Orders Less than 10 Lbs. and Ship Direct from Stock. alternating current into a constant current 2 additional choke -coil inductances should SOMERVILLE RADIO LAB WINTERHILL, 45, M SS. be used. The high capacity condenser, C, should be constructed of mica, suitable to withstand a maximum potential of 3,000 volts and the condenser section should be properly clampt and insulated and finally immersed in beeswax compound to elimi- a' °' "4` LONG DISTANCE nate losses as much as possible. As rectifiers ordinary transmitting tubes having Short Wave Receptors equipped their grid and plate connected together are with our NEW MIGNON used. ,e11111,,, ,,,,,,,,,,, ,, 111111111111111111111111111111111111111111111011t11111111111,,,,,1,1111111,,,,r1111111111 VARIOMETERS & VARIO- COUPLERS Test of (nsulating HIGHEST EFFICIENCY AT LOWEST PRICES Materials for Radio Use at the Bureau of Write Today for Literature Standards BUFFALO, N. Y. (Continued from page 710) Mignon System Mfg. Co., U. S. A. of Standards was that of power loss, frequently termed as phase difference of a condenser made of the material. Likewise READ the CLASSIFIED ADVERTISEMENTS on PAGES this test is considered of overshadowing importance. The method . employed con- 756-759. YOU'LL FIND MANY GOOD THINGS THERE. sisted in placing a metal coating on two sides of the panel of insulating material-

www.americanradiohistory.com Radio News for April, 1921 719 A Serious Si gua ''on Menaces the Radio Art By G. K. Thompson * A people plunging into a movie and demand- must be tuned until the very close and Warning If point is A we amateurs ing a seat in the front row orchestra. critical coupling obtained. During the next two years in Radio we make heavily insulated counterpoise or a very, will either break Radio. we could only see that make or Amateur a spectacle of we would low resistance ground connection must we as liberties just such ourselves very If continue at present our be quick to slip into one of those be used, preferably the counterpoise. Com- are is to pre- enough doomed. There but one way meters, 584, 180 and plying these requirements a vent the We must cultivate empty back seats -192 with transmit- fatal climax. finally down to 550 or less. In these days ter employing an Amrad Quenched Gap at once a conscientious respect for our quenched gap will emit very sharp wave, well within laws. Without this respect we of amplifiers and efficient a American transmitters 550 or 175 meter waves are Government regulations. Send for Bul- will fail not only as Radio Experimenters actually just as practicable as 200 meter letin Q -2 which contains the last word on but as Citizens. We must obey the Law. lower wave- quenched gap operation. most waves. Unless we go to those Our Federal radio regulations are the lengths at once we will dig our own graves liberal in the world. They are the simplest, concen- Low Power Sets that with our keys. We must end the most easily complied with regulations tration on 200 meters. The Induction Coil transmitter presents could be imagined and if respected would to the simpest probem of all. To comply with not would Adjust your wave -length according only save our own future but the power of your transmitter. I K.W. the law it must be inductively tuned (use solve many of our own QRM troubles. 34 K.W. about Oscillation Transformer) and employ an let find slightly under Zoo meters; Now us analyze these regulations, Igo meters; % K.W. slightly under 185 approved quenched gap. Send for Bulletin out what we must do to comply with them -2 ? K.W. 175 meters and small in- P which gives operating directions. The see meters; and how our obedience to the law will under 175 meters. If you manufacturers of the Amrad Quenched vastly improve Amateur Radio. duction coil sets have a long antenna you may require a Gap recently reduced the price of the IA License Necessary series condenser. Remember too, that the K.W. model, intended for all classes of In- duction Coils, from $16 to $12. This heavy If you have a transmitting set, no matter use of a counterpoise instead of a con- ductive ground decreases the normal an- cut was made so as to bring the quenched how small, it must be licensed. Radio sta- gap reach and vacuum tenna wave -length. within the of every station tions are now so close together owner as it is the only means of getting tube amplifiers are so common that your Short Wave Reception any distance and a law- abiding wave with signals, no matter how weak, are almost re- The problems incident to shorter wave an induction coil set. In combination with certain to interfere with signals being reception have been well for in the Amrad Induction -3) local provided Coil (Bulletin P ceived at stations from other states. the new receiving unit designs of the Amer- the ?/ K.W. Amrad Quenched Gap has Every time signals from an unlicensed ican of Radio and Research Corporation. covered distances upwards of 200 miles transmitter interfere with the reception Amrad Short Wave Couplers and Vario- regularly. Induction Coil- Quenched Gap interstate messages the law is being broken. meters, for instance, are expressly intended sets will do long distance as a regular you know this you know work If didn't before, for tuning down to 175 meters and below. thing just as soon as general readjustments it now. License your transmitting station. Dielectric and capacity losses, usually ex- of wave- lengths are effected. Minimum Power cessive at the very high frequencies of Speaking of gaps the Amrad Quenched The law plainly says that you must use short wave -lengths, have been eliminated Gap has become famous for its superior only just enough power to maintain com- by use of air cores and single layer coils nerformance in all parts of the country. munication with any given station. Just wound on very thin, porous forms. Amrad The most notable feat was a transcontinen- because nearly everybody breaks this law Tuning Units are the coming designs and tal relay on February 15th when three mes- is no excuse for disobedience. We must all experienced radio men in all parts of the sages were exchanged from Coast to Coast cut down our power for local work. The country have been very quick to grasp this solely by means of Amrad gap stations and most practical method is to use a small fact. Send for Bulletin V. under normal conditions of interference induction coil set on a separate single wire The usual regenerative receiver will not and static. There are now hundreds of antenna. This permits shifting from your tune down to wave -lengths lower than Igo Amrad Quenched Gap enthusiasts, a per- large set to your small set instantly with- meters. We must adapt these receivers to manent Amrad Transcontinental Line has out disturbing adjustments. the new conditions by removing from each been formed and as more amateurs become grid and plate inductance eight to ten turns experienced with quenched gap operation Minimum Wavelength of wire. Do not hesitate to do this; you many phenomenal records will be piled up. General amateur stations employing spark will merely lower the wave -length range Send for latest edition, Bulletin Q. sets which emit waves longer than zoo me- and not reduce the efficiency of your set. Before passing the subject of decrement ters are operating in defiance of the law. it would be unfair to exclude mention of We must stop this practice. An accurate Minimum Decrement C.W. transmission. This provides the Wavemeter, the Amrad, is available at a Here is a great mystery- decrement. means of emitting a legal form of wave low price. If you cannot buy one, borrow Few of us can clearly explain what it but its operation calls for considerable skill one and find out exactly what your wave- means, but no matter. Of more importance and specialized knowledge which the ma- length is. The American Radio and Re- is this fact : Not one amateur transmitter jority of us haven't acquired -yet. C.W. search Corporation was the first Company in two hundred emits a wave of lawful is coming nevertheless and it will have its to produce an accurate wavemeter priced decrement. That's the condition we must field. Meanwhile there is a fortune in- within the reach of all and for a year and face and remedy -and here's how: vested in spark equipment which we can a half has sold the Type D Amrad Wave- In using a rotary gap we must do this : and will use provided we adapt it to the meter at slightly more than actual cost of Reduce the number of studs on the rotor conditions of the hour and operate it in manufacture. The Type D is now discon- to six or less. Make each stud paddle compliance with the law. tinued and supplanted by the new Type E shaped and knife edged. Triple or quad- which tunes from 175 to 34o meters and ruple the speed of rotor; 8,000 r.p.m. is Citizen Radio can be used in a receiving set as an Inter- none too high. Loosen Oscillation Trans- There is a movement on foot to call ference Preventer or as a Variometer. This former coupling far enough so that a sin- Amateur Radio, Citizen Radio. Let us co- new Amrad Wavemeter is an instrument gle, sharp wave is obtained. Use a very operate in this forward, upward step by that you can use all the time and not mere- low resistance ground connection. This is operating our transmitters in strict corn- ly when you wish to tune your transmitter. a large order but unless our transmitters pliance with Federal law, using Minimum Send for Bulletin W -2 which describes the comply with the majority of these require- Power, Legal Wave -lengths, Legal Decre- several uses of this unique instrument. ments the wave emitted will be of exces- ments and genuine American fair play in sive decrement (too broad) and we will everyday communication. Very immediate Re- Adjustments Necessary violate one of the most important Federal and vigorous action must be taken by every In the matter of wave -length many of us regulations. operator and radio club in the land. Get have not only exceeded the legal limit of When using a quenched gap we must be the situation in hand now. And mark this: 200 meters but the majority of us have equally careful. A sufficiently high voltage The only kind of radio that will survive tried to tune our transmitters to exactly transformer must be used. Sufficient re- Amateur Radio is Citizen Radio. Only by 200 meters. This is one of the oddest mis- sistance must be used in the transformer obeying the laws can we deserve the name takes we have made. Imagine a crowd of primary to produce a smooth note. The set Citizen. Advt. `Amrad Sales Division, American Radio and Research Corporation, Medford Hillside, Mass.

www.americanradiohistory.com 720 Radio News for April, 1921

the metal really used being mercury, and the size of the panel tested was .25 by 31 TEL. centimeters (io by 12 inches). Determina- BACK RAY tion was made of the resistance and ca- 5 q 6 4 pacity of the condenser at a radio frequency. The ultimate result is claimed to be the phase difference which is proportional to the product of resistance, capacity and frequency. Accurate and rapid meas- fSZr1°1 urements were made by the use of a vac- 899 BOYLSTON ST. uum tube generator. According to the Bu- 1® reau of Standards, however, it is only re- BOSTON, MASS. cently that precise measurements by the use of a vacuum tube have been possible in radio determinations. A shield for the measuring circuit has enhanced the accuracy and rapidity of the determinations. The study of phase difference yielded interesting observations: The phase difference is essentially constant with frequency. RESULTS However, in some insulating materials the phase difference increases as the wave- If you are interested in studying Commercial Radio, the RE- length is increased, while in others it de- The Eastern Radio Institute should merit creases to a similarly corresponding de- SULTS accomplished by gree. Approximate values of phase differ- your immediate enrollment. ences for various products may be thus expresst : For formica M, 2.8 per cent. ; for bakelite -micarta, 2.3 per cent. ; for bakelite- FOR INSTANCE: dilecto, 2.2 per cent. The high value for The Eastern Radio Institute was founded in 1913 and is formica M, however, was applicable to the six years older than any other Radio and Telegraph output prior to the change in method of now over manufacturing this insulating material. School in New England -We are established ! Strange enough, the tests showed the increase of phase difference in a particular The Eastern Radio Institute moreover has given instruc- sample of formica from three to seven per tion at this date to over 4,000 different students, and has en- cent. after a lapse of six months. Subse- rolled, graduated and placed more Commercial operators than quent investigation proved this change to be an actual one, and when the sample was all other schools in New England combined! We have accom- subjected to a baking process the phase dif- plished things ! ference registered six months before was restored. The observation suggests that the Graduates of The Eastern Radio Institute have actually internal varnish reaction during the manu- secured 90 per cent, 89.9 per cent, 89.8 per cent etc., out of a facture of the materials may not always be carried to completion. Age consequently possible 90 per cent in their Commercial operators first grade varies the nature of the product. examination. We know how to give the student proper training! NEW APPARATUS. The experiments in determining the ef- Successful graduates of the Eastern Radio Institute are fects of voltage at radio frequencies upon found in responsible radio positions all over the world. Why insulating materials have given birth to an entirely new apparatus both for the pro- not be one! It costs no more ! duction of constant high- frequency voltages, for their application to insulation Our latest, illustrated prospectus is free. If you cannot specimens,, and for their measurement. The visit the Institute send for one. Remember our organization method embodies the placing of a specimen with over eight years of continued Results and Success is in a radio circuit with electrodes upon its Send in your enrollment surface in parallel with a condenser and behind every student who enrolls. measuring the voltage required to produce today ! certain effects. For example, such as the F. D. Pitts, appearance of corona, flash over the sur- Director. face, and also puncture of the material, in the event that the latter is desired. Mr. Dellinger of the Radio Communication Section of the Bureau of Standards says: "The flashover and puncture voltages are of very different magnitude at high fre- THERE'S MUSIC IN THE AIR! quencies as compared with other values at Get Your's Now! Order Today! low frequency, for the following reasons: We have had wonderful results with this Very much lower voltages produce these V. T. Short Wave Regenerative Set effects at radio frequencies than at low fre- Which we offer during April and ir_ay at a quencies DISCOUNT OF 10 PER CENT, This i because the dielectric carries a complete except for "A" Battery and considerable dielectric current. This cur- Ground, which we can't send through LEARNERS "HYTONE" rent heats the specimen in virtue of the ab- the mail. sorption phenomenon or dielectric loss in Murdock 2000 Ohm Double Head Set $4.50 the material Radiotron U.V. 200 Detector 5.00 KEY AND BUZZER SETS and soon raises the tempera- V.T. Bakelite Control Panel -Cage Type Rheo 6.00 ture to a point where breakdown occurs. Standard Variable "B" Battery-large size 3 50 Turney 3 Coil Regenerative Tuner 8.00 With Code The effect is then not a puncture or rupture 2- Parkin 0.001 MFD. Variable Condensers 4.00 Grid Leak -Cond. and Phone Condenser .85 Buzzer has silver contacts and two of the low- frequenc,, type at all, so that in- 400 Feet No. 14 Copper Antenna Wire 3.60 tone adjusting screws on top. stead of hundreds or thousands of volts be- OUR PRICE, $31.90 VALUE $35.45 ing required to break down or flash over a Add Parcel Postage for 10 lbs. We insure results PRICE $1.75 specimen, io,00o volts more and furnish guaranteed hook -up that sure brings commonly suf- in the signals and music. Show Dad how you same set with flat spring key $1.25 fice. The most important property is the can save good money. Order today. Immediate Lever keys unmounted 1.00 flashover voltage, as de livery. "Hytone" buzzers .80 this determines whether 10$ Discount on Any of Above Items Lever keys, bakelite base and knob 1.50 there will be a failure of the insulation be- If you send us names and addresses of 5 amateurs All postpaid tween portions of the circuit such as the not in Call Book. Special equipment, binding posts, con- projecting metal post placed on the insu- Pack up all your troubles in a letter and let etc., lating panel." our 12 years' experience solve them for you tacts, made to order. without charge. Prompt deliveries, low prices. for your The apparatus employed for the flashover Send Stamp,. Today Our Latest Bulletin Send in sketches, estimates free. voltage experiments RADIO SUPPLY SERVICE utilized as a source SPECIALISTS IN RECEPTION APPARATUS AJAX ELECTRIC CO. of power a set of six pliotrons, affording AND PARTS Palmer St. Cambridge. 38, Mass. considerable current, the pliotrons being 46 Clinton Place Mt. Vernon, N. Y. operated in parallel. Variable inductances

www.americanradiohistory.com Radio News for April, 1921 721 i MONEY LEARNNOW IS THE TIME WIRELESSTO MAKE BIG Know a Dignified In Shortest Time Uncrowded Profession AT HOME At Lowest Cost The Demand for Good Wireless Operators Far Exceeds the Supply The New York Wireless Institute -America's foremost fastest growing Wireless Institute gives you the best instruments, theory, text books and diagrams available. We will MAKE YOU AN EXPERT WIRELESS OPERA- TOR AT HOME, qualifying you for first grade license, in your spare time, quickly, easily, thoroughly, in shortest possible time at lowest cost. No previous training necessary. Our Home Study Course prepared by Mr. L. R. Krumm, formerly chief Radio Inspector, Bureau Navigation, New York, now in position of greater responsibility with one of the largest commercial Radio Corporations in the United States. Our radio Experts able to impart their practical and technical knowledge to YOU in an easy to- understand way will direct your entire Course. The graded lessons mailed you will prove so fascinating that you will be eager for the next one. The instruments furnished free will make it as easy for you to learn the Code as it was to learn to talk. All you will have to do is to listen. TRAVEL THE WORLD OVER BIG SALARIES A Wireless Operator can visit all parts of the world and receive fine pay and maintenance at the same time. Wireless operators receive salaries from $125 to $200 without travel? There a month and it is only a stepping stone to better posi- Do you prefer a steady position will be many opportunities for you at the numerous tions. There is practically no limit to your earning Wireless or with power. Men who but yesterday were Wireless Opera- land stations or with the Commercial tors are now holding positions as Radio Engineers, the Steamship Companies. Radio Inspectors, Radio Salesmen at salaries up to The New Intercity Wireless Company will need $5,000 a year. hundreds of new operators INSTRUMENTS AND TEXT BOOKS We furnish free to all students, during the Course, the wonderful receiving and sending set exactly as shown in the illustration. This set is not loaned, but given to all students completing the Course. One cell of dry battery all that is required. No additional wiring, aerials, etc., needed. s The wonderful Receiving and Sending Set, Text Books, etc., all become your property upon completing the Course. We also include an up to date and complete course in Wireless Tele- phony, written by our Chief In- structor, Mr. L. R. Krumm. is the celebrated Omnigraph, used by several Departments of the U. S. Government and The transmitter pictured United States and Canada. by the leading Universities, Colleges, Wireless and Technical Schools throughout the learned telegraphy with the Omnigraph. Place the phone to your ear and this remarkable invention Thousands have as though you were receiving them thru the will send you wireless messages, thousands of different ones, the same air from a wireless station hundreds of miles away. United States Government will test you with the Omnigraph -the same model Omnigraph as we furnish When you apply for your license the this. to our students. Ask any United States Radio Inspector to verify POST COURSE TELEPHONY COURSE FREE GRADUATE FREE WIRELESS A month's Post -Graduate Course, if you so desire, at We have incorporated in our institute an up -to -date and one of the largest Wireless Schools in N. Y. City -the Complete Course in Wireless Telephony, written by our Wonder City -the largest port in the World and Head- Chief Instructor, Mr. L. R. Krumm. quarters of every leading Wireless and Steamship Com- This Course is also Furnished FREE pany.

Medina, N. Y., Sea Cliff, L. I., November 28, 1920. December 6, 1920. Endorsed by United States Government Dear Sirs: Sirs: - the Dear - 1 have found the Theory Coure, Received your letter of Decem- by allowing our graduates highest credit of any Wire- Unmigraph Set and Text Books most ber 1, and was very pleased to satisfactory, I think your Wire- leant of the lessons in Wireless less School in first grade license examinations. less Course is the best and easiest to Telephony to be given to the stu- learn for it's interesting from the be- dents of your school. It shows ginning to end, and the way the ques- you do not overlook any phase in U. S. SHIPPING BOARD will testify tions aro written gets you interested at order to furnish the students once. Yours Trued with "up to date dope in the (S. B.) Radio line ". And I am sure it to the great value of our instruction. will be as explicit as your Theory course. of Wireless Telegraphy. r ® Mil ® 0 NIM ® in ® ® ® ® I Milford, Conn., The course is as thorough and Oct. 25, 1920. explicit as one could. ask for and I wouldn't hesitate a moment in NEW YORK WIRELESS INSTITUTE Now York Wireless Institute. of my New York City. recommending it to any Dear Sirs: Radio friends. Dept. 202, 258 Broadway New York City I received- your letter and am very Respectfully yours. glad to tell you completely (Signed) C. D. II Send me, free of charge, your booklet "How to Become satisfied with your course. amIt rrepis an an Expert Wireless Operator," containing full particu- easy way to learn. lars of your Course, including your FREE INSTRU- Thanking you for your kind attention, (Names and address gladly MENT OFFER, I am. Sincerely yours. furnished on application.) Signed J. H. A.. Tr. SEND FOR FREE BOOKLET Name you in any way, send for our booklet "How Without obligating Af r'. to Become an. Expert Wireless Operator "-it is free. Mail the letter do it today. coupon ohposite or postal or -but City or Town

NEW YORK WIRELESS INSTITUTE, 2 weYorkCity d State

www.americanradiohistory.com 722 Radio News for April, 1921

are connected across the plate and grid of the pliotrons set and larger inductances COTO -COIL CO. connected to the ends of these. The radio SELF -SUPPORTING circuit is completed by the connection to ELECTRICAL COIL WINDINGS the ends of these cods of a condenser of Sr WILLARD AVENUE very small capacity. The appearance of PROVIDENCE. R. I. the auto transformer together with series resonance are utilized to produce a large voltage across this condenser. The latter was of special design, enabling it to with- LGcwa./', stand large voltage without failure. To , produce of . a voltage 5o,000 volts at radio ltl/ frequencies with the six pliotrons a condenser of 3o micromicrofarads is employed. This capacity is more than ample for flash- Gt a a/Qe_ t ZÀ1 over tests. - ANALYZATION OF INSULATING MATERIALS. - Q &t.`4-` `,y Cf-ap-e-- More concerning the results of the com- n,e-c .(4v4.ire. ,a-k a. _CO- prehensive tests in analyzing the properties 1- of radio insulating materials: The expen- 0_4 lAvi, cc.z of-- sive grades of products are superior in - coi-a their electrical properties while the reverse a,C- GC Y : ,(,ef obtains with respect to their mechanical a/u- P ct - .l lr o s( e eL LQ 0-u2. strength. The costliness of the materials is determined AAA-4 f o,v by the percentage of phenol U (`-cc l' 9 o-rrctQ_ varnish to paper, the more expensive prod- r ucts having larger percentage to varnish. f .(-(/F_ 6t4/),4 k-4(v)y Insulating materials of the phenol type A7ts were introduced as a substitute for hard ,r,FT rubber. The value of the latter for electrical apparatus is attributable to these fac- 6A1,4-rf.us" d.t , tors, easily machined, has small power loss - a. or phase difference, and extremely high ,t-/C puncture voltage at radio frequencies. Among the objectionable features of rub- j,f4a ( ) ?-w -ZA- ber in this capacity are its tendency to shrink, warp, become brittle, deterioration - .t.ia-S a D-2, .G('zr.c<./ A under the glare of the sun, and its high --8.,---Y/ -+ termal expansivity. The electrical charac- ('4.01,1-cw , y frit tw, ,cto , G teristic of greatest significance is the flash- .; over voltage. However, because it varies fxv6t. -frige.y(, with many properties it is not feasible to assign a particular voltage of flashover to 07-1/4, ci ',e e-tk.GP cui the materials circumscribed by these experiments. Carefully prepared varnish did 14/c<44-(,(1 on,f : - -W-e4 X )( ,(g not enhance the value of one type of in- . sulating material, but the judicious selec- pta.T.t- tta, tion of paper entering into the manufacture of the material appreciably improved the finisht product. The story concludes with -J/a-14-fa t(A_ gf-ef-r, this idea uppermost in the mind.

The Radio Dealer and É the Beginner EMPYREAN (Continued from page 688) VARIABLE CONDENSER tically every American home. With a radio station at every troop headquarters they Consistently Brings In the could deliver a message from the President Long Distance Stations of the United States or any government Designed to meet the most rigid physical and elettrica tests. department to every community -posting it No insulation break -downs; extremely low in public places, giving it to newspapers, energy losses; no short circuits; utilizes the telefoning it over farmers' lines -inside of minimum amount of received energy. an hour or two. Suitable for all classes of Radio Telephone Slowly slowly and Telegraph Work -too -they are grasping the opportunity. Here and there a city or- EXCLUSIVE SEVEN FEATURES ganization is awakening. The only diffi- Show the superiority of this condenser over any other, selling at any where near this price. culty is that radio to (1) Aluminum plates .026 inches thick insuring stability. Plates cannot bend or be- the layman is still a come displaced. mystery. The local scout executive, busy (2) Formica insulation used throughout. Not one particle of moulded insulation with many things, cannot take time to un- entera into their construction. derstand it. The public does not know yet (3) Bearing plates are machined from 3/16 inch grade M. Formica. (4) Finest adjustment is secured with an end block spring which holds the rotary that wireless communication is practical plates in any position. Wear and hard usage will not alter their adjustment. and reliable. Only we who handle it daily (5) All spacers turned from brass stock and accurately guaged before being used. appreciate its progress and its possibilities. (6) Panel mounted type easily on any panel up to 3's inch thickness by drilling What a chance for a live dealer! A very three holes for set screws and shaft, Furnished with screws, knob, pointer, scale, co..necting strip. little publicity would be required to fire (7) The portable type is enclosed in clear glass case with square end pieces of the imagination of the boys. Among the genuine machined Formica with engraved scale. things which could be suggested by dealers PANEL MOUNTING TYPE PRICES PORTABLE TYPES are: A radio mobilization scheme by which 43 plate -.001 Mfd $4.50 43 plate-.001 Mfd 5.75 every scout in town could be called to any Dimensions -2" x 31/4" x 4,4" Dimensions-Pei" z 3g" z 3 *A" designated rendezvous 21 plate -.0005 Mfd 3.65 21 plate -.0005 Mfd. 5.00 inside of an hour Dimensions -2" x 3W' a 3" Dimensions-33.r a 33" z 2?/y" or less; the broadcasting and posting of Weight -2 lbs. Weight-3 lbs. weather reports (Chief Marvin of the 1122 Masonic Temple Building U. S. Weather Bureau has offered to ar- EMPYREAN RADIO COMPANY , CHICAGO, ILLINOIS range for the scouts to receive state fore- casts immediately after they are made up) ; I an emergency communication service for www.americanradiohistory.com Radio News for April, 1921 723

Modulation transformer - - - - $4.50 Type Z.R.V. Variometer has unit Choke coil .8 Henry $3.75 construction with bakelite shell and Amplifying transformer - - - - $4.00 hard wood ball. Has low dielectric All these are mounted as shown in losses and a range of inductance of 1.25 mil henry maximum to .r mil (Illustration exact full size) the illustration and will give you results second to none. henry minimum. Is readily used on Z. R. S. Miniature knife switch is table or mounted on panels. supplied unmounted only, for panel Complete with 3° dial and knob - $6.50 mounting and will harmonize with Without dial or knob $5.75 other fine products of the instru- Variocoupler of same construction - $7.50 ment maker. There is nothing else Complete Regenerative set - - - $38.00 like it on the market. Complete Catalogs Regenerative panel set with detector - $85.00 Double pole, single throw - - - - 80c 6c Stamps Regenerative set detector and 2 Double pole, double throw - - - 90c stage amplifier, combined panel - $140.00

Type ZRL Transformer For use with Rotary Spark Gaps A combination of beauty and convenience. One stage 40o Watts. ire Volts -6o Cycles amplifier has binding posts for connecting two as a two stage amplifier. All binding posts on detector, amplifier Unmounted Price $14.00 and Regenerative set correspond for jumper connection. Mounted on Iron Frame $15.00 The "Cambridge" Rotary Spark Gap Complete Tube Control Detector Panel, Z. R. D. - - - $12.00 with Variable Speed Motor $50.00 One Stage Amplifier Panel, Z. R. A. - - - - $18.00 The "Boston" Key $7.50 Rheostat only $1.20

Z.R.F. Regenerative Receiver consists of two Z.R.V. Variometers and a Coupler of similar construction, together with Grid Condenser and Grid Leak with Bakelite Panel machine engraved. Licensed under Armstrong U. S. Patent No. 1,113,149. This exactly matches our Tube Control and Amplifier panels with which it may be harmoniously used. Its range of wave length is 175 to 600 meters. Price - - $38.00 CLAPP EASTHAM COMPANY 120 Main Street Cambridge, Mass. ALL GOOD DEALERS CARRY OUR PRODUCTS IN STOCK

www.americanradiohistory.com 724 Radio News for April, 1921

use in case of fire, flood or cyclone interfering with wire service; the broadcasting of baseball scores and other news of gen- JUST WHAT YOU WANT eral interest, by arrangement with the local papers. Any town that was not dead from the -0 I 2 neck un would grab a proposition like that Shipped Service as soon as it was understood, provided the goo' practical details were arranged in a way to in v _: and insure success. To encourage progress, contests could be Twenty -four 11 t Satisfaction arranged. These could be based on the reception Hours `aN of the daily amateur broadcasts so Guaranteed transmitted by NAH, or on local broad- ^- casts. A . -- daily local broadcast for begin- 3173 ners could be transmitted at five words psr minute, another at ten words and one NICKEL PLATED SWITCH POINTS DIALS at fifteen words. These messages could be No. 1 x L4 3/16 inch head $ .05 - Chelsea 3" dial with knob 1.00 No. 2 % x 3 inch head ..05 Chelsea 3" dial without knob .75 addresst to individual amateurs. Every No. 3 3/16 x 3/16 inch head boy would listen in if there was a chance No. 4 Switch stop W' high ..0406 FIXED CONDENSERS Grid condenser that the message might be for him. CRYSTAL DETECTOR PARTS Grid leak condenser .50 No. 10 Detector cup .35 Phone condenser .35 In dealing with boy scout organizations No. 20 Mounted Crystal .50 V. T. SOCKETS radio dealers would need to be careful to No. 30 Detector Rod .35 Single No. 40 Detector Stand- .35 V.T. socket 1.10 avoid even the to Double V.T. socket 2.50 appearance of trying SWITCHES AND BINDING POSTS Triple V.T. socket 3.50 commercialize the movement. Boy scouts No. 60 Binding Post .12 are No. 100 Switch Lever, radius 1 .60 TUNING INDUCTANCES organized for public service, not for inch Turner No. 110 Switch Lever, radius 1 inch .60 short wave coils (set) 6.00 private gain. Local organizations are for - No. 130 Switch Lever, radius 1% inches .75 Radsco coils List Arnold coupler (Navy Type, 2500 hidden by their national constitution to CABINETS teloosemeters) 20.00 No. lA Hand Polished Cabinet, fits panel enter into any contract or agreement in- 6" x 9" x %" inside depth 391" 2.00 RHEOSTATS volving the ser "ice of the scouts as such, Paragon 1.75 VACUUM TUBES Reinter 1,25 and also profit to a commercial concern Audiotron (two filaments) 6.00 without the approval of their national coun- U.V. 200 Radiotron (detector) - 5.00 "B" BATTERIES U.V. 201 Radiotron (amplifier) 6.50 Standard 22e Volts. small 1.50 cil. But no objection would be raised Standard 22% Volts, large 2.65 AMPLIFYING TRANSFORMERS Standard 22% Volts, variable 3.50 against a dealer who promoted boy scout Acme (mounted) 5.00 Acme (unmounted) 4.50 NcontrolCONTROL SETS radio with real public spirit even tho his PParagon 6.00 trade were increased thru his becoming VARIABLE CONDENSERS Remler control set 8.00 Chelsea .0006 m f. for panel mounting 4.25 more widely known and thru the increased Chelsea .0011 m.f. for panel mounting 4.75 PHONES Baldwin Superior 8.00 interest in radio. VARIOMETERS AND VARIOCOUPLERS ' 1Tud c Type C 16.50 Variometer (moulded bakelite) 6.25 Murdock 2000 ohms 4.50 INTERESTING PARENTS OF BEGINNERS. Variocoupler (moulded bakelite) 8.50 Murdock 3000 ohms 5.50 The cultivation of the parents of begin- EMPIRE RADIO EQUIPMENT CO. ners would be profitable to the dealer I be- Manufacturers and Distributors of Radio Apparatus lieve. Suppose that after a boy from a 271 West 125th Street New York City well -to -do family had bought a loose - coupler, crystal- detector set the dealer should call his father up, or find a chance to see him, and explain how much better work can be done with audions. Or better yet, invite him in and demonstrate what 82% 90% the set will do. Hiram Maxim became in- Averaged out of a possible terested in radio thru his son and he has Thirteen graduates of the MASSACHUSETTS RADIO been some booster of radio sales. Once get and TELEGRAPH SCHOOL during the Six Weeks' a man and his bov started on radio and examination period between November 1st and Decem- you have a ber 15th, 1920, established this record on their U. S. combination hard to beat for Government Examinations for First Grade Commer- producing sales. The Y. M. C. A. and the Practical course on the application of cial Operator's license. Their average attendance was boy scouts are busy promoting father -and- 5.1 Months. son activities, so the dealer be Vacuum Tubes to all The fact that a new United would right forms of C -W Trans- States Radio In- in line with up -to -date ideals. Further- mission and Recep- spector did the examining, using new and original tion starts Thursday questions unfamiliar to the graduates, speaks all the more, there would be no timorous mother February Tenth. more favorably of our system and methods. sentiment to buck against as there is in To produce Thirteen graduates, who, within the short the case firearms. period averaging a little Over Five Months, obtained of When Mother learns such a high average, is the best way we know of to that a good audion outfit makes the whole convince you of the merits of this school. Results world a party line on which she can listen Count. in to her heart's content she may take up Names, addresses and full data sent on request to anyone. radio herself. 'Why not avail yourself of this service. It costs no more. SEND FOR FREE LITERATURE. A year ano I had an experience which illustrates the good and the poor method MASSACHUSETTS RADIO AND TELEGRAPH SCHOOL of handling beginners. I had started with 18 Boylston Street, Boston, Mass. Tel. Beach 7168 a second -hand loose -coupler, crystal de- R. F. TROP G. R. ENTWISTLE tector set and had reached the point where I was ready to begin building up something better. T called up a leading manufacturer. who also sells direct to the consumer, and stated that I wanted to purchase a few of "EVERYTHING IN RADIO" his units and then add more as I was able. He advised against my plan-altho it was WESTERN RADIO ELECTRIC COMPANY recommended in his advertising. He said: SEND FOR OUR MARCH "You won't have anything unless you get the whole outfit." The fact is that the STOCK BULLETIN AND PRICE LIST units I selected would have constituted a 550 South Flower Street Los Angeles, Cal. much more efficient crystal detector set than I had. and I would soon have purchased the audion units. The result of his argument was that I waited until I had more money and then went to another VACUUM TUBES REPAIRED dealer. This dealer not only made it easy for me RELIABLE I Morb d I Accompan°Order ElAudi trouer I SERVICE to get a first -class, up -to -date outfit, but also offered to give demonstrations where EASTERN VACUUM TUBE LABORATORIES they might attract other customers. Nat- 178 Washington St. Boston, 9, Mass. urally when men become interested in radio thru me I take them to him. www.americanradiohistory.com Radio News for April, 1921 IND

Sheet Materials Magnet Wire Postpaid Price per sq. in. Put up in coils of r/ y, or 1 lb. Less More and shipped postpaid. than than Price per pound 25 sq. 25 sq. C. G. S. S. C. ,Elnamlel Material in. in. Size ,S. Type 104 Panel Switch 46" Dilecto 20 .86 1 26 .72 Bakelite- 2. /3c Sc 22 .96 1.38 .78 Type 121 Rheostat A complete unit for back of panel r/4" " " 5.1/3e 4c 24 1.12 1.56 .86 26 1.36 I.82 .94 mounting. The latest and best ye" Hard rubber 2e I ,/20 Suitable for table or back of in rotary panel switches. Better 44" Hard rubber 4e 3c 28 1.56 2.20 1.06 panel mounting. Has turned alu- looking, more efficient and easier 1/32" white celluloid 11/2c Ic 35 ' 98 2.92 1.12 minum case, convenient binding to mount. Complete with Type 1/16" " " 2e I1/2c 32 2.40 3.88 1.24 posts and 6 ohm resistance unit 116 Dial and 6 contacts $2.25. .010 Spring brass Ic /ze' with all off and all on positions Complete with Type 116 Dial and .015 Spring brasa le '' Long bearing and special designed /c and I I contacts $2.50. .007 Copper lo /c'' Bakelite- Dilecto blade insure smooth running 1/32" Red Fibre lc '/4c positive contact. Only occupies I/16" Red Fibre le /2c' Tubing space 2" in diem. on your panel. Variocoupler Rotor No. 121A with Type 116 Dial I'rices are per lineal inch cut to $2.50. No. 1213 with Knob and Pointer $1.75. Brass Machine Screws A carefully turned hardwood any desired length and shipped form for the secondary coila of postpaid. ound or flat heads. variocouplers, etc. Size is 3v " 3" Outside diam. x 1/16" wall, Z' Prices per dozen postpaid. in diameter and 2" wide. No. ICI 160.; 3%" Outside diam. x I /I6" 'Not less than one dozen sold. Roter $1.00. wall, 18c.; 4" Outside diam. x Size 2 -56 4 -36 6 -32 5 -32 I/l6" wall, 20e. y4 .05 .06 .08 .12 " .06 .07 .09 .13 Type 131 Posts Type 103 Panel Switch .07 .08 .ro .15 Binding Brass Rod, Tube, etc. .12 .18 which is A high grade binding Post for A rotary panel switch ly4 .15 .22 use on panels, etc. Has moulded Prices are per foot, postpaid. Not double pole and double throw .27 composition top with brass collar less than one foot sold nor pieces I. e," will change variable condenser .82 and screw. longer than two feet sent post- from aeries to parallel, etc. 11/4" paid. brass finish 75c. Nickel radius No. 131A small size, suitable for /e"' Round brass rod $.07 finish 85c. Taps and Dies receiving sets, IOc. No. 1318 3/16" Round brass rod .10 large size, suitable for power werk 1/4" Round brass rod .15 These tools are of the highest 20 . State thickness of panel s/s" Round brass rod .75 quality and the dies are of the and whether brass or nickel fin- '/ "Round brass rod .40 round adjustable type. Prices are ish is desired. 1/4"Square brass rod .20 postpaid. 5 /I6 "Sq. tubing. ''V4" Inside .30 Type 14B Rotary,Disk Size Tap Die 3/16" Rd. tubing, ye" inside .15 I /1.6" x 1/4" Rect. brass strip .08 10 -32 25a 90e 116" x The same style rotor as used on 8 -32 25c 91h Type 126 Tube Socket famous belt driven gap, only I /16" x V5" Rect. brass strip .12 our 6 -32 25o 90e brass Made of genuine bakelite dilecto with bakelite center and 4 -36 25c 90c Is and bushing to lit your motor shaft. 2 -56 25e 90e and solid brass. small Size is 4%" diam. and 9/16" convenient for back of panel Switch Contacts thick. This rotor being light mounting. and perfectly balanced will give Heads y4" x % Ne. 126A Audlon Socket 75c. ", Shanks 6 -32 a excellent results on any small Threaded Brass Rod 112A Brass, high speed motor. State size of One foot lengths -6 -32 or 8 -32 Nickel Heads 3/16"3 /16" Bx shaft when ordering. No. 14B thread. Price per length post- 1/4", Shanks 6 -32 x l'o ". 112E Rotary Disk $6.00 102 Panel Switch paid IOe Brass, 21/2c; 112F Nickel. 4e; Type Heads 44" x ", Shanks 6 -32 x 112C / A compound switch consisting of w'. Brass, 3'/2c; 112D two electrically inflependent Hex Brass Nuts Nickel, 5c. Heads 3/16 x ye" mounted with concentric Shanks 6 -32 x %", 112G Brass, switches Prices are per dozen postpaid. 3c; 112H Nickel, 41/2c. knobs. l'/" radius brass finish Not less than one dozen sold. $1.10. Nickel finish $1.25. 2 -56 On 6 -32 6e 4 -36 6c 8 -32 9c Flat Braided Copper Brass Wood Screws Cable Prices are per dozen postpaid. Used for connecting transmitting Not less than one dozen sold. sets making ns ^illation transformers, etc. Price is per foot post- 1 x ;/i" R. H 06 No. l x v" R. H 08 paid. No. 4 x s/4" R. H 10 9/16" wide $ 10 No. 4 x 1" R. H 12 lys" wide 25

Type 5A Var ometer Type 101 Panel Switch Buy from your Type 14A Rotary Gap Made from Wilcox Variometer Our complete A beautiful and efficient rotary dealer or order parts, completely assembled as il- catalog sent for Belt driven, solid balanced rotor switch for general use. Furnished from ad. lustrated, may easily be mounted of special aluminum alloy, large in two sizes. 1" radius brass this on panel if you wish. Wave 5 cents. Stamps steel shaft, long brass bearing, finish 40e. Nickel finish 50e. Prices are postpaid length range in average circuit or coin well quenched. short leading 11/4" radius brass finish 50e. with coils in series about 175-450 spans. clear tone, high efficiency. Nickel finish 602. meters. No. 5A Variometer $8 Price $10.00.

Type 5A Variometer Parts Set No. 1 contains carefully turned wooden parts including winding form. Price $2.50. Set No. 2 contains all parts including 3 inch Type 116 Indi- cating Dial. Price $5.00. Type 1C Variocoupler Parts Set consists of No. 1CI varío- coupler rotor, bake - lite tube for primary, shaft, two No. 101 switches, 14 switch points, 4 binding posts, one No. 116B dial Type 14C Rotary Quenched Gap 0° 90° wire for winding, and instructions for assem- No. Variocoupler Parts, $5.00. This enclosed gap has all the advantages of the bling. ICPI No. 14A with some additional ones all its own. Like Type 116 Indicating Dials an WILCOX Gaps it runs quietly, and it is surpris- SPECIAL OFFER ing how the housing silences the spark. The com- Of polished hard rubber accurately engraved, filled bination makes this gap nearly noiseless. with brilliant white. Furnished complete with knob This is your chance to get a high grade short wave and bushing to fit 3/16 inch shaft. 90° scale 0 -50 regenerative set at about one -quarter the usual price. In addition to this the practically airtight case or 100° scale 0 -100; also 360° 0 -100 scale In 2 inch Mention this ad and we will send two complete sets greatly improves the already excellent quenching size. variosneter parts, one set varie- coupler parts. one qualities making this the ideal rotary gap. bakelite panel 3/16" x 6" x 18 ", all for $17.50, 2 inch diameter $1.25 No. 14C GAP, Postpaid $17.50 3 inch diameter $1.50 Postpaid.

www.americanradiohistory.com 726 Radio News for April, 1921

One acquaintance of mine went to a radio store and, as he was prosperous look- Something New In C. W. Inductances ing, they tried to sell him a $75.00 outfit. The Radio Servi.:e Type 550 C. W. Inductance is He wanted a beginner's set for his own Wound on a slotted bakelite form of 31 turns of use and for some boys to learn with and number g hard drawn copper wire on a 5 inch diam. he did not want to put that much into it. Supplied with three clips making adjustment varia- I took him to the store where I purchased ble to any fraction of a turn. Tunes to 35o meters my outfit and we doped out a set costing and suitable for panel or bench mounting. Mate- $33.00, including the antenna. Then I took rials and workmanship the finest obtainable and the him home and gave him an hour's instruc- price is only $8.50 tion. That evening he called up, as pleased as kid a new If you are to build a C. W. set the a with toy, to tell me that he starting had heard the Arlington time tick, was Radio Service Inductance will start you on the bringing kinds right track or if you already have a C. W. Set in all of traffic and was al- and you are not getting the proper results try ready able to distinguish certain letters. In one of these inductances and you will be sur- less than a month he was ready for an prised at the increased operating efficiency. audion outfit. The first store lost a good customer by trying to oversell him. ASK YOUR DEALER TO SHOW YOU ONE OF THESE INDUCTANCES. IF HE CAN'T SUP- SPARK TRANSMISSION FOR AMATEURS. PLY YOU, WE WILL SHIP YOU ONE POST Beginners PAID. are a good and legitimate market for certain apparatus is becom- 'IIIII;!IIIIII IIIII I IIIIIIIIIIIIII1111111111111111111111111111111I1i which IIIIIIIIIIIIIIIIIIIIIIIII 1 1 1 1 I I I IIIIIIIIIIIIIII1 1IIIIIIIIIIIII I I II' III IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII111111111111IIIIIIIII' ing obsolete. Even tho spark transmission Type S40 Variable Grid Leak becomes commercially obsolete, as navy ex- Helps to increase your signal audibility perts say it will in five years, it is prob- Bakelite Mounted .75 able that beginners will use spark coil transmitters and crystal detectors for dec- = ..._ ades to come, for C.W. apparatus probably Reduced Prices will never be so cheap nor so simple to On Our Products operate. They will continue to be used in S24- Aluminum Socket only $.50 rural districts at least, just as scythes and buggies are used today in spite of all the Slo- Single Tube Socket 1.10 mowing machines and automobiles that S 3- Double Tube Socket 2.5o have been manufactured and sold. The S 4- Triple Tube Socket 3.5o dull seasons in radio can be utilized for starting beginners. A dealer has more 514 -Navy Type Rheostat 2.00 time then. A boy of twelve started in July SII- Complete V.T. Control Panel 6.00 may be far enough along in November to bring in a dozen customers. A group of S22 -Mica Grid Condenser .5o beginners can be organized into a club by All leading dealers or by mail from merely giving the suggestion. An hour of code practice a week with an omnigraph, RADIO SERVICE & in some corner of the store where they MFG. CO. will not be in the way, Lynbrook, L. I. New York will soon develop them into paying customers. The older radio clubs do not take care of the younger beginners. Sometimes they even seem to try to drive them out of radio. When you are up against their QRM this attitude - or homicide-seems quite justifiable, but the fact is that a boy is a most reasonable IS EXPENSIVE APPARATUS MOVING being and will do anything a man suggests SLOWLY IN YOUR STORE, TOO ? if he is sure that the man is an unselfish friend. A dealer. by explaining the evils Most all dealers are making this complaint. And right there is where G. A. Condensers, Detectors, and Amplifiers fit into your line. of interference at the start, could give the beginner an attitude which would be help- LOW RETAIL PRICES AND PROFITABLE DISCOUNTS ful to all concerned. Grid Condenser 35c Another gold mine which dealers have 0.0005 mfd. for the new tubes " ', ]r not yet discovered is the summer camp. Phone Condenser 35c `,. The Y. M. C. A. and the boy scouts are 0.001 mfd. makes the set oscillate ` ¡ rlu,G..., t A,p ,..,, c. P.,y conducting thousands of them, all over the freely `' GRID CONDENSER, 0.0005 in-fa. United States. Most of them lack facili- Grid Leak Condenser 50c mes,e,_' ties for quick communication. They need radio, 0.0005 mfd. and 1 megohm for with scores or hundreds of boys in camp accidents are likely to THESE_CONDENSERS PERMIT A SAVING OF 50 TO 80; OVER OTHER TYPES happen which demand quick assistance from outside. _ ., -\ -- $6.9_5 - iti s 16.95 Most of these camps depend upon the ; chance that some boy will bring an outfit along. Some of them receive press with fair regularity. But very few of the man- agers know that for a few hundred dollars they could install a station which would give them reliable communication with their .f. city headquarters. A dealer who would get that into their heads would pave the ' way for big sales just at the season when ordinary business is dropping off. Inci- fa dentally, he might arrange to send a clerk who was not needed during the summer to a camp to serve as an G. A. DETECTOR, without tube, 2 -STEP AMPLIFIER (4 lb.) $30.95 operator, thus giving (1 lb.) $6.95 3 -STEP AMPLIFIER (6 lb.) 49.95 him a vacation and saving his salary at G. A. AMPLIFIER, without tube, RADIOTRON DETECTOR (1 lb.) 5.00 the same time. (2 lb.) 16.95 RADIOTRON AMPLIFIER (1 lb.) 6.50 DETECTOR and 1- STEP.. (3 lb.) 21.95 G. A. B. G. BATTERY, NAVY DETECTOR and 2- STEP.. (5 lb.) 36.95 SIZE (5 lb.) 2.00 DETECTOR and 3-STEP.. (7 lb.) 51.95 SIGNAL CORPS SIZE (1 lb.) 1.25 SOME OP.! NO OTHER DETECTOR OR AMPLIFIER AT TWICE THE PRICE IS BETTER MADE OF Radio Operator to Amateur: I hear that FINER PARTS. REASON -LARGE PRODUCTION, REASONABLE PROFITS Washington will not send the time signals any more. 570 -N W.184th St. THE GENERAL APPARATUS CO., INC. New York Amateur: Oh ! Why? Operator : Because he is dead. 6 ` By STEPHEN MORTON, Ja.

www.americanradiohistory.com Radio News for April, 1921

,'sODa.___. sA:.:= II ADIOPHON REG U. S PAT. O F F. Interpanel Sets The Most Advanced Idea in Radio Telephone Transmitting and Receiving Apparatus

T11E Deforest RADIOPHONE INTERPANEL Set establishes a new standard of design and efficiency for DeForest Apparatus, and provides the most convenient and all round satisfactory method of purchasing Radio Apparatus yet invented. The INTERPANEL Set consists of a series of panels, each constituting a complete piece of apparatus in itself. and designed to be combined with other panels, thus forming a Set as complete as may be desired, the operating possibilities depending only anon the total number of panels used. The Set for both Telephone and Telegraph Transmission and reception consists of four Panels, as follows Type MT -zoo -A complete short wave Tuner of highest possible efficiency; Type MP -zoo A new Audion Control panel designed especially for tubes of the gaseous type, now Complete Set of Four Units, in Cabinet, each panel sold sepa- considered as standard; r ately for mounting in home constructed cabinet; or completely Type MP -aoo-A one -step Amplifier panel com- assembled in cabinet as shown above. Also for mounting in Hori- in zontal or Vertical Table -style. Complete Set as above, without plete every respect; and batteries or tubes, type MS-I, $189.25 Type OT -3 -A complete Radiophone Transmit- ter, capable of transmitting speech at least 3o miles, and up to Soo miles. (Additional steps of Amplification may he added as desired) Panels are all g inches high; varying widths. Designed for placing side by side, with binding posts in line and convenient to wire. Adaptable to any operating requirement. Panels may be bought individually and mounted in operator's own cabinet; or bought completely mounted in cabinet. Or panels alone may be mounted on table in either horizontal or vertical style.

Horizontal Table -style mounting. 30 Mile Range for the Legs attached to corners of each panel. Any number of panels can be mounted in this style. Ample Telephone Transmitter on space under panels for batteries. A very convenient and inexpensive Average Amateur Aerial. method of mounting. Tests show a 3o mile telephone transmitting range for the Set, which can be exceeded under favorable conditions. Telegraph range from 60 to too miles with unlimited reception possibilities. One 6 -volt storage battery required for all filaments and microphone; Motor -generator, "B" Battery or rectifier supply may be used. This INTERPANEL Set provides the ultimate in RADIOPHONE apparatus; ease and convenience in installation and operation; minimum space, handsome appearance, great efficiency and extreme economy. Vertical Panel-style mounting, without cabinet. Two legs Send Now for Catalog "E" and Prices hold each panel upright. Any number of panels may be Get the full details of this new INTERPANEL idea and joined and mounted this way. get your order placed early.

DEFOREST RADIO TELEPHONE & TELEGRAPH COMPANY Inventors and Manufacturers of High Grade Radio Apparatus 1415 Sedgwick Avenue New York City

www.americanradiohistory.com 728 Radio News for April, 1921

,,,,.,,,,,,,,,,,,11,,,,,,,,,1,,,,,,,,,,,,,1,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,.,,,,,,,,,,,,,,,E ACME A New Universal C. W. Range Receiver APPARATUS (Continued from page 68i) C. W. Power Transformers tapped in the center for use with rectifying devices or for A. C. directly on the plates. A single "A" battery is employed for the lighting of the four filaments. The automatic control, which is effected by the insertion of the telefone plug in the desired jack, prevents any of the filaments from Apparatus that Apparatus lighting until the plug has been inserted that and then only the filaments of the tubes in is guaranteed is guaranteed actual operation are connected in circuit. The jacks are arranged so as to render operative the entire circuit to the point where the plug is placed, by controlling not only the filament current but also the opening and closing of the primary and secondary circuits of the amplifying transformers in 50 watt rating good for twf tubes of 350 volt 50 MA rating each. Filament windings provided. their proper sequence. The special design 200 watt good for four tubes of 550 volt 50 MA rating each, of the telefone plug, furnisht with the set, also 350 volt taps. Filament winding provided. - makes possible the use of a "loud speaker" 500 watt good for two tubes of 1500 volt 150 MA rating each, in connection the step also 1000 volt taps. - with third of am- Filament Heating Transformers Modulation plification. Terminals for the loud speaker _ Transformers 1% Henry Choke Coils. are provided on the upper right -hand cor- This apparatus carried in stock by leading dealers. ner of the panel, which are connected to ACME APPARATUS the third -step amplifier circuit when the COMPANY telefone plug is pusht half way into the 188 Massachusetts Avenue, Cambridge, 3g, Boston, Mass. third -stage jack. The regular head set is Transformer and radio engineers and manufacturers. then automatically thrown out of circuit. The jack, marked "EXT. DET.," permits the bulb circuits to be used in conjunction with other apparatus for test and comparison purposes with the exception that in this CO- OPERATIVE RADIO PURCHASING case the detector Members tube does not function of this association are securing SERVICE at a SAVING by purchasing all their and should be withdrawn from the socket radio needs collectively. You also can secure these savings and with the good service that goes in order to eliminate membership. Stamp brings full details. The following items are indicative of the unnecessary burning large and varied assortment we supply. Remit these list prices and secure the same SERVICE of the filament. our members enjoy. Each of the tubes is provided with its RADIOTRON TUBES, TELEPHONE JACKS own filament control and the automatic ac- UV -200 Gas content detector $ 5.00 Federal closed circuit .85 UV -201 Amplifier tion of the jacks and plug is particularly 6.50 Federal open circuit .70 desirable 17V -202 5 watt transmitter 8.00 Federal two circuit 1.00 in a set of this character, where UV -203 50 watt pliotron 30.00 STORAGE BATTERIES there are a number of tubes to keep ad- UV -204 250 watt pliotron 110.00 justed. Once the RADIOTRON ACCESSORIES. proper filament current Standard receptacle 1.50 has been secured it is not necessary to Grid leaks complete, mounted 1.25 change the position of its control rheostat Grid leak units, .1 to 6 megohms .75 in order to cut off the current. Grid leak holders .50 In connection Audio frequency transformer 5.00 with the detector tube plate Special 50 v' 5.00 circuit a potentiometer has been provided Bt BATBATTERIES for minute regulation of the "B" battery 224 volt, small, flied 1.25 supply. 22% volt, large, fixed 2.60 2272 volt Standard variable 3.50 From the wiring diagram and the photo CONDENSERS of the interior, it will be seen that a num- 41 -C Connecticut .001 encased 6.50 ber of terminals are provided, for the reg- 42 -C Connecticut .001 panel' 6.50 ulation of the No. 1 Chelsea .001 encased 5.00 `B" battery supply, allowing No. 2 Chelsea .0006 encased 4.50 for the greatest possible voltage flexibility No. 3 -BD Chelsea with dial .001 4.75 in the tube circuits with a minimum of No. 4 -BD Chelsea with dial .0006 4.25 supply. It will be seen BARELITE DIALS that the detector- second and . Corwin 3 in. with knob 1.30 third amplifier circuits have Corwin 37A in. with knob 1.70 two, while the first amplifier circuit is fitted Chelsea "true fitting" dial .75 with three such terminals. The pair ad- AUDION CONTROLS jacent to the Fada with automatic cutout 17.50 Endurance 6 v 30 ah special 12.50 detector tube are for the "A" Grebe RORA cabinet 12.50 Marko 6 v 20 -40 ah 14.60 supply. Referring particularly to the photo Grebe RORH cabinet 17.00 Marko 6 v 40 -60 ah 18.00 of the interior, the two outside terminals Marko 6 60 Acme Y -1 new model 10.00 v Ford type 17.10 supply the amplifier' circuits if a bridge is Adams Morgan "Paragon" 6.00 Marko 6 v 80 Ford type 21.60 placed AMPLIFYING TRANSFORMERS HEADPHONES across the pairs adjacent to Arco for panel mounting 5.00 Brandes Superior, new style 8.00 second and third stage tube mountigs. Acme for panel mounting 5.00 Brandes Trans -Atlantic 12.00 The plate voltage of the detector tube is Federal for panel mounting 7.50 Brandes Navy style 1400 determined by the connection made to the MUTUAL PURCHASERS center terminal and that directly to its left. ASSOCIATION 2Ston YORK Dep 8 Considering that three stages of amplification are to be used and voltages of their plate circuits vary progressively as their positions in the circuit. a 4o -volt battery, placed across the outside terminals of the OUR MAIL ORDER SERVICE IS RIGHT three adjacent to the first amplifier tube socket, will deliver that voltage to that We ship same day order is tube. The next set of three terminals received from is especially interesting. A battery con- our large stock of reliable manufacturers nected to the center and right -hand terminals will have its voltage effective on products. the detector circuit alone, but if the remaining terminal is also connected with Get your name on our mailing list. the battery the voltage will be applied to all the amplifier tubes as well. It will, PHILADELPHIA therefore, be apparent that when the am- SCHOOL OF WIRELESS TELEGRAPHY plifier batteries are connected across to the 1002 Parkway Building, Broad and Cherry Streets, Philadelphia, Pa. center terminals a variable voltage on the detector is obtained by connecting from the center terminal to the desired portion www.americanradiohistory.com Radio News for April, 1921 729

Never in the History of Radio Were These Prices Approached Improved Navy Type Receiving Transformer Again 9 5 Improved Arlington Receiving Transformer Again 7 7J Reduced from $27.50 to the startling price of F' $16..7- Reduced from $15.00 to the startling price of0F'a / . Mail 12 cents Substantial Reductions in stamps or coin (not sent otherwise), which on many other radio instruments in our catalog No. 14. Circular with reduced prices and mailed on request. amount you are privileged to deduct on first a large number of new instruments dollar purchase. Revised price list to first edition of catalog, with prevailing prices, "The Greatest Radio Catalog In The World" mailed on request. The Universal Verdict of Tens of Thousands of Radio Amateurs DUCK'S No. 15 BIG 225 PAGE WIRELESS CATALOG. JUST OUT A Veritable Treasure House of Everything Worth While and Dependable in Radio. The largest, most comprehensive, artistic and educational wireless catalog published. The Beacon Light to guide you right in the selection of your radio purchases, and at prices that will command your attention. Every instrument guaranteed with privilege of return if not satisfied. The following prices shall prevail until further notice on the following items in our Catalog No. 14. Concerning our improved type Navy and Arlington Receiving Transformers, our previous reductions were substantial. The prices below show are even lower than pre -war prices and when these instruments did not possess- the existing marked and exclusive features. These instruments can be bought nowhere else. These prices, seemingly unjustified, are subject to advance at any time. We are taking a chance at a reasonable profit on an enormous anticipated quantity production. Model 5BB Navy Type Receiving Transformer; Regular Price, $27.50 Special Price only $16.95 improvement over our former model. Pri- ABIGmary divided into four sections, with three dead end switches, greatly improving selectivity. Secondary divided into three sections, with two dead end switches, eliminating harmonics. The change in the construction of Other Substantial Reductions Ors the guide rod support Items in Catalog No. 14 makes it possible to No. R40 Rec. Set $22.50 obtain a looser coup- No. R41 Rec. Set 38,50 ling It is a wonder- No. R41a Rec. Set 28.50 ful improvement over our old model, both in THORDARSON TRANSFORMERS 40.00 appearance and per- 1 K.W. Type R formance. Y K.W. Type R 28.00 K.W. Type R 22.00 1 K.W. Type RS 30.00 Improved Arlington Receiving Transformer; Regular Price $15.00 20,00 r/,_ K.W. Type RS. New Price, Only $7.75 K.W. Type RS 15.00 25.00 The secondary on our new type Arlington is divided into No. A1792 Thord. Con three sections, with two dead end switches, Nos. 50, 51, 52 .03 eliminating dead end effect and harmonics and Switch Contacts, each giving greater selectivity. The end support is No. 1023 Mica Con .60 2.75 similar to that on our Navy, permitting a looser No. B 670 Det. coupling. The base and pri- No. A862 Det. 2.75 1.50 mary end pieces have a spline No. A1915 Det. to prevent warping or damage No. A367 Murdock Cond. 4.50 9.75 in transit. This feature is No. A1002 Rec. Set also on our Navy. It is a No. A1916 Con. 1,65 2.95 beautifully finished instru No. 61x08A Tuning Coil ment. No. 61x10 Tuning Coil 4.95 No. 14 Aluminum Wire, per lb .90 All Binding Posts reduced 33% %. New Radio Only a few of the Many An excellent Audios Control Instruments in Catalog No. 15 Panel for use with new four - Tron Bulb $5,00 Type C -300 Audio prong and grid Type C -301 Audio Tron Bulb 6.50 bulbs. Grid leak "UV" 200 Radiotron Bulb 5.00 condenser are mounted on rear "UV" 201 Radiotron Bulb 6.50 of panel. New type panel rheo- No. A200 Control Panel 7.50 stat mounted on center of panel. A complete line of new detector regen erative and amplifying sets. The formica panel is attached to Connecticut Variable Condenser.... 6.50 a wood base, upon which is Turney Spider -Web Unit 6.00 mounted the tube receptacle. No. 550 Murdock Socket 1.00 No. 3660 Murdock Condenser 4.00 No. A201 No. 3661 Murdock Condenser 4.25 No. 3662 Murdock Condenser 5.00 No. A200 Panel Detector Sets, less batteries and bulb..$7.50 No. 3680 Murdock Condenser 3.25 No, A201 Cabinet Detector Set, less batteries and bulb..15,00 3,50 No. 3681 Murdock Condenser No. A200 No. 3682 Murdock Condenser 4.25 No. 3664 Murdock Dial Assembly .. 1.25 A complete line of Acme C. W. Apparatus and Tuska C. W. Induc- Send 12 Cents for a copy of tances. Burgess "B" Batteries. Our Big Catalog Today

THE WILLIAM B. DUCK CO., 231 -233 Superior St., Toledo, Ohio

www.americanradiohistory.com 730 Radio News for April, 1921

of the battery. This scheme besides affording great flexibility has distinct advan- DO IT tages because a minimum number of "B" THE EASIEST WAY! batteries are required for a maximum volt - age supply to the total number of tubes in operation. .1'11 When it is desired to place an additional b., f 0 voltage, say 20 V., on the plate of the third , ni stage amplifier tube only, a 20 V. battery f .; is connected to the two terminals at the extreme left. If it is desired to raise the voltage on the two last stages instead of merely on the third stage, the zo V. battery is applied to the next set of terminals, to J the right. Likewise, the three amplifier stages will have their voltages loaded equally if the 20 V. battery be connected in series with the first amplifier battery. From this, it will be seen that any desired com- xt: bination of plate voltages may be obtained. Pilot, graphs and diagram courtesy A. H. Grebe C. R. L. Regenerette & Co.. Inc. And not only that but combine ease and convenience with efficiency. With our C. R. L. Regenerette you can convert your loose coupler into a modern Regenerative Receiver with absolutely no changes in construction. Just modify A Complete Receiving your connections slightly and bring your set up to date. Full instructions supplied for connection and operation. The Price? Set for 25 cents Only $15.00 (Continued from page 705) one for the aerial and one for the ground - CHICAGO RADIO LABORATORY complete the set. As previously mentioned by the title, the 1316 CARMEN AVE., CHICAGO, ILL. cost of constructing this set need not exceed 25 cents for all needed parts. This gap, as can be readily seen from the sketch, is made by a piece of heavy split brass tubing such as a bearing of an automobile engine or like part. Some amateurs will probably find this bearing already in two sections. These sections are mounted on a piece of hard rubber, and separated about a sixty- fourth of an inch. 4. This is done by placing a very small strip of celluloid between the two halves. To the one on the right is fastened a length of No. 4 copper wire. The other one is fastened to the earth wire, which is made of a piece of No. 4 galvanized -iron wire, which in turn is joined to a 10 foot length of iron pipe driven into the ground. The A wires are joined B N to the pieces G of brass by means of fairly strong rivets. The whole is placed in a water -tight box, and the lead - in and earth passing out thru porcelain PRICES HIT BOTTOM insulators. The copper wire, which by the way should be of the insulated kind, is held Reduced by two strong cleat insulators to the top of From iTo a pole about 7 ft. long, driven in the ground. Arnold V.T. Control . . $21.00 $19.50 To avoid the possibility of water running Arnold Loose Coupler, (Navy Type) . 25.00 20.00 down the aerial, and thence over to the Thordarson . Transformers, % KW 27.00 22.00 box, thus causing leakage, I placed a ten " " N KW . 33.00 28.00 cent funnel 4 1 over the wire, point upwards, " 1 KW . 45.00 40.00 and filled in the top of the funnel with Watch for announcement next month pitch. At the extreme top of the copper wire there is fastened a C.E. 3339 "Electro" connector, from which one wire goes up to DAVID KILLOCK COMPANY the top of the house to the lightning switch 57 MURRAY STREET NEW YORK CITY and the other three to the aerial, which is 40 ft. above the ground. Construction of VACUUM TUBE CONTROL UNIT Type MW Transformers (Continued from page 693) Adaptable to any modern hook -up. Best appearing and highest type Vacuum Control Unit at the price of the in the market. secondary is slightly lower than the primary we divide the volts into the watt- Grained formica panel, Grid condenser and age of secondary, considering it the same, 51/2" x 6h ", lettered in leak mounted in back and get slightly less than 5o for the maxi- white, graduated rheostat of panel and so wired mum amperage. Consulting the table we dial, variable plate con- that it can be adapted find that the smallest wire which will carry trol. Tube socket (stand- to any modern hook- this amperage safely is No. 8 B. & S., cot- ard 4 prong). up. Price $10 ton covered. By the above process one can WRITE for descriptive Booklet MW. Sent free on request. Parcel pest prepaid in U. 5. readily find the dimensions of a trans- Immediate shipment former. THE MIDWEST RADIO COMPANY, CINCINNATI, OHIO Tn building the transformer it is usually DEPT. A 3423 DURY AVENUE considered best to make the coils and "build" the col;: in them. The primary WHETHER YOU ARE IN THE MARKET TO BUY OR SELL, THE winding is divided into two equal sections CLASSIFIED COLUMNS OF RADIO NEWS WILL GET RESULTS FOR and one section put on each "leg" of the YOU. TRY THEM. transformer; the secondary is fixt the same way.

www.americanradiohistory.com Radio News for April, 1921 731 RADIO APPARATUS Distributors of Reliable Radio Apparatus to Schools, Colleges and Experimenters All Over the World !

"PITTSCO" "SPECIAL" The sign of service and Our New Catalog No. 22 prompt delivery. is just out.

Why not let us prove it ! Insist upon your copy !

AMRAD APPARATUS No. UCV -1500, .0015 MF. variable condenser THORDARSON APPARATUS on unit panel 13.95 Type A. VT detector in cabinet $15.00 No. T -1 Type It r/4 K.W. power transformer. 14.95 21.00 No. CV -1500, .0015 M.F. variable condenser, No. T -2 Type R K.W. power 22.00 " " One -step amplifier unmounted 13.90 1 transformer 1 34.50 No. T -8 8 -point rotor 5.00 " " VT detector and step No. CV -500A, .0005 M.F. variable condenser, " " VT two -step amplifier 39.50 without knob and pointer 3.95 No. T -16 16 -point rotor 5.00 No. G -1 1 K.W. quench gap 41.50 No. CS -1502, .0015 M.F. bridging condenser, F. D. Pitta Co.. Boston, Mass. No. G -2 3 KW, quench gap 24.50 in cabinet 5.95 No. A -2 K.W. Quench gap resistance 5.95 No. CS -3002, .003 M.F. bridging condenser, in r/a cabinet 5,95 No. G -3 r/a KW. quench gap 12.00 MISCELLANEOUS APPARATUS No. US -400 2 -point Audion, Ultra Audion switch Type D Varlometer in cabinet 14.50 on unit panel 1.95 HOYT jeweled bearing 0 -3 amps., flush mount- 17.50 ing D. C. A " " Vario- coupler in cabinet No. 1 Small variometer tube .25 ammeters, 3" dia. splendid value 6.95 " E Crystal receiving set 23.50 F. D. Pitts Co., Boston, Mass. Amrad Lightning switches 100 Amp 9.85 'CUSKA ticklers, in cabinet, will make any circuit regenerate 6.95 F. D. Pitts Co., Boston, Mass. GREBE APPARATUS No. PDA, 4" 0 -100 bakelite dials 3.00 WIRELESS SPECIALTY, eaton ocsillators, in ACME APPARATUS beautiful oak cabinet 13.95 No. PDR, 4" 0 -50 bakelite dials 2.75 No. 1.-1 1/2 K.W. trans., bakelite panel type 30.00 No. PDC, 3" 0 -100 bakelite dials 2.50 RADIO APPARATUS, 3500 meter couplers No. M -2 Oil condenser .0035 M.F. Self-heating, mahogany thruout Gets NAA fine 24.95 good value 29.00 No. PDD, 3" 0 -50 bakelite dials 2.25 Mass. No. PSA Switch arm .95 STERLING voltmeters, 3" diameter. 0 -50 N.P F. D. Pitts Co., Boston, front of board mounting. Just the thing for No. ROBA VT control cabinet 12.50 "B" batteries 2.95 BUNNELL APPARATUS No. RORZ 4 tube mount, ideal for radiophones 11.95 CENTURY.induction motors 1 /10 H.P.., R.P.M , No. B -1 Thee slide tuner, 2000 meters. A F. D. Pitts Co., Boston, Mass. 1750, runs on 110 or 220, just the thing for Dandy 4.05 Benwood or Bell gap 29.95 No. 7751 Mascot spark gap, 1 K.W. size, heavy KILBOURNE AND CLARK APPARATUS duty 2.95 COUCH Yankee well phones, ideal between house No. K -1 r/s K.W. power trans., mounted 9 95 and radio per pair No. 8854 Jove crystal detector 2.00 shack, 11.95 No. K -2 r/s KW. power trans., unmounted 7.95 F. D. Pitts Co., Boston, Mass. PITTSCO heavy 3 ft. double telephone cords. No. K -3 Change -over switch, bakelite base, ideal connectors. While they last .19 very rugged 4.95 CLAPP- EASTHAM APPARATUS No. K -4 Band key. A beauty 3.95 TECO Honey-comb coil stands, mounts two Mur- dock var. condensers, using Honey -comb coil No. 652 Large oscillation transformer, 1 K.W. F. D. Pitts Co.. Boston, Mass. size. Splendid value 17.50 adapters, one of which is movable for coupling, stands only (makes splendid coupler) 1.95 Na. ZRL 409 Watt power transformer, unmounted type 12.95 INTERNATIONAL RADIO APPARATUS WAYNE 50 watt, bell ringing transformers. 20 No. RTD -102A VT control panel 13.95 4 30 No. 651 Oscillation trans., suitable up to 1 K.W 14.95 voltage variations, to volts 4.95 No. RTA -104A 1 step amplifier 23.95 No. F-656 Large plain spark gap, marble base, HAYWARD rotary spark gap, operates on 6 volt heavy points 3.75 No. TXL -100A Oscillation transformer up to battery, or on 110 volt thnt step down trans. No. Z -5002, 10 Step variable inductor 13.95 1 K.W. 14.95 Can be used up to r/z K.W 9.95 No. F -659 Type D variometer coupler, 1500 F. D. Pitts Co., Boston, Mass. SLEEPERS Radio Experimenters' Handbook. All meters 12.95 the new apparatus illustrated and described .95 FIRTH APPARATUS F. D. Pitts Co., Boston. Mass. DE FOREST Amateur's Handbook. "How to Type C Baldwin telephones 16.50 Set Up a Wireless Station" .10 DE FOREST APPARATUS Type E Baldwin telephones 20.00 PITTSCO No. 22 and 24 specially insulated No. LL -300 Litz coils 1.96 Type F Baldwin telephones 21.00 magnet wire, great for variometers, etc. While No. LL -750 Litz coils 2.75 Baldwin head band only 1.75 it lasts, per lb 1.19 No. LL -1000 Litz coils 2.95 F. D. Pitts Co... Boston. Mass. F. D. Pitts Co., Boston, Mass.

Important! Our new catalogue No. 22 illustrating, describing and pricing our immense stock of radio apparatus sent upon receipt of io cents. Insist upon receiving your copy! "Over loo Pages, Over 15o Illustrations, Over 600 Items."

Pittsco service reaches all over the world ! Why not let it reach you !

F. D. PITTS CO., Inc. 12 Park Square Dept. C Boston, Mass., U. S. A. Cable address "PITTSCO" Boston

www.americanradiohistory.com 732 Radio News for April, 1921

JIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIillllll IIIIIIIIIIIIIIIIIIIIIIII IIIIIIIIIIiIIIIiIIIiiIIIIiIIIIIIIIIIIIIIIIiIIIIIIIIIIIIIIIIIIIIiiIIIIIIIIIIIIiIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIUII°= In winding the coils it is best to wind them on a form similar to the one shown in Fig. 1, first winding one turn of "em- KLAUS pire cloth" or some other insulation on it "13" BA i 1 ERIES KLAUS and putting a little shellac on the next turn D D so it will not unroll when the form is re- I moved. Now wind the primary on and One More KLAUS Specialty ó shellac it. After this wind on a few turns of empire cloth and then wind on the secondary. Shellac this well and tape the Consider these facts before buying your "B" Batteries whole think. It should be baked after this if possible. Klaus No. 5763 Radio Battery -size 2iy% i Klaus No. 5766 Radio Battery-3 s 6% s 4 When both coils are complete lay them 3%s x 2 inches. Initial voltage 221/2. In inches. Initial voltage 22 %. Operating under the in actual tests, when operating thru resistance t h e same conditions as above this battery de- E. on the bench and assemble core equal to amateur vacuum tubes, this battery livered upwards of 2400 hours' continuous them, putting three laminations first one gave 450 hours' continuous service before service. After reaching 17 volts it can be 7-2 reaching its cut -off point of 17 volts. connected in series with another battery and way and then the other, as can be seen in _ use d until run down to 12 volts, E- Fig. 2. Price $2.25 Price $3.50 After the transformer is completed it S should be supported by four wooden blocks placed under the corners and secured to a WATCH THIS SPACE FOR OTHER ANNOUNCEMENTS board. The blocks should be high enough to prevent the coils from coming in contact with the board, or sides of a box, should it be mounted in one. Order direct or If a transformer is constructed for the thru your dealer purpose of charging storage batteries using a Tungar, it will be necessary to figure out the voltage the bulb requires and take a tap off at that point in the winding. Then wind the required number of turns to give KLAUS RADIO COMPANY the required voltage. The tap on the Tun- E gar forms the other terminal. EUREKA, ILLINOIS Size of With Other wire, rubber. insula-

.,,.,,IIIIIIIIIIIIIIIIIIIIIIIIIIII IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIAIIIIIIIIIIIIIIIIIIIIIIIII B. & S. tions. IS 3 5 Maximum num- r6 6 io ber of amperes 54 15 20 a wire will I2 20 25. carry. Approved The Back Mounted Rheostat- Io 25 30 by underwriters. S 35 50 6 50 70 5 55 8o 4 70 90 3 So loo 2 90 125 J TOO 150 O 125 200 00 150 225 COG 175 275

An [deal Receiving Set Type R. G. I. for Short and Long already on a Bakelite panel -can be mounted upon any panel Wave - Lengths in a very short time and without adjustments. Complete with large knob, shaft, pointer, brass bushing and nickel plated (Continued from page 692) screws for supporting it to the panel.

Price $1.25 frequency coupling exclusively or both in weight 6 oz. combination to obtain certain desired re- Our new Loose -leaf catalog for 10c sults. At any rate, no amateur after having once used this form of selective amplification would want to do without it. A The Marshall - Gerken Co. certain amount of leeway is also given with 24 Radio Bldg. Toledo, Ohio this arrangement and the "experimental bug" gratified. Nobody seems to be altogether without this contagious bug any- way. The other apparatus used in connection with the receiving set, condensers and va- YOUR CHANCE riometers, are all of the standard type and design and no detailed description need be SPECIAL DON'T FAIL given here. Every radio enthusiast will We have just received a large shipment of To get our new catalogue. Sent on receipt of follow his own type of construction. No. 14 pure solid copper aerial wire. We IOc. This amount deducted from your first are offering this wire for a limited time only order. A short description should be given of at this price. "We will surprise You." the primary and secondary coil design. The Remember -this is real solid copper wire, Testedt d G 1 packed in primary coil P and PL, Plate 2, is wound guaranteed. sealed container, per box 25e. on á cardboard tube 4" by 9" outside di- Per 100 Ft 58c RT S Tested Silicon, per box 25e mension. For two inches on the left end Per 1000 Ft $5.50 DEALERS (see Plate 3 dotted outline). One layer of Wire Shipped by Express. Write for our Tested Mineral Proposition. No. 24 S. C. C. wire is wound up' to within ORDER YOUR AERIAL WIRE AT ONCE %" from the end. This forms the short wave coil P. Switch contacts X. divide this Radio Testing Station, Binghamton, N. Y. coil into equal number` of túrns. The right end of the cardboard tube is wound with 2 lavers of No. 24 S. C. C. wire using the Insure your copy reaching you each month. Subscribe to Radio well -known bank method of winding. The News- wire should cover 5 %" of the tube and is $2.00 a year. - Experimenter Pub. Co.. 236 -A Fulton St., N. Y. C. also wound to within ps" from the end,

www.americanradiohistory.com Radio News for April, 1921 733 thus leaving a clearance of %" between coil windings. The latter coil is the long wave or loading coil PL. Both coils should be wound in the same direction around the PROUDFOOT SPECIALS of tube. Five taps are taken off each layer Vacuum Detector Cabinet, 7T/, "x54" $12.50 the PL coil, one at the ends and 3 at equal Amplifier Cabinet, 7 % "x5 %" 18.00 One -Stage Amplifier, 7 % "x8 25.00 intervals within the winding and brot out Detector and /" 35.00 to switch Y. The secondary coils S and Detector and Two -Stage Amplifier, 7% "x9" Regenerative Set, 7% "x14" 35.00 SL are of the ball variometer type. The Regenerative Set with Detector and One -Stage Amplifier, 7% "x18" 45.00 shown markt "sec sh" dials on Plate 3 are THESE INSTRIIMENTS HAVE:- Panels of 3/16" bakelite; boxes with waxed oak finish, and "sec L" for short and long wave- hinged covers, no ugly hooks, special spring ball clasp; black oxidized binding posts; special lengths respectively. The coil for short design transformer; 5- stages of amplification, no howling; fixed condenser in grid circuit; wave -lengths S is wound with No. 26 VT sockets highly polished lacquered brass, parts all machined. of can S. C. C. wire and the one for long wave- ALL instruments 5 inches in depth and wired so that as many stages amplification lengths SL two layers of No. 28 be added as desired. with and amplifiers can be added by connecting C. are the same Wiring of regenerative set such that detector S. C. wire. Both coils of binding posts directly opposite. NO LOOSE CONNECTION ENDS. Detectors and amplifiers size and general overall dimension. They all have standard nickel jacks. ONE PLUG IS SUPPLIED WITH EACH INSTRUMENT are 3V" in diameter so as to permit free ORDERED. rotary movement within the cardboard tube ALL INSTRUMENTS ABSOLUTELY GUARANTEED. of the primary coils. The connections to be made to the various contacts points are G. M. PROUDFOOT, 361 E. Ohio St., Chicago, III. clearly shown on Plate 2.

14-5 ct, - IS i HERE IT THAT NEW « ,, CW" VARIABLE NOW YOU CAN SHOVE UP r >v YOUR PLATE VOLTAGE A "WIRELESS SHOP" PRODUCT -"NUF SED" THAT MEANS QUALITY There has been a growing demand for a Variable Condenser which could be used on CW sets without breaking down when you shove up the plate voltage. Receiving condensers are entirely unsatisfactory for this work, and we have now developed a "NEW CW VARIABLE CONDENSER," designed for just this work. The plates are widely spaced, and the construction is heavy. Only the hest of materials and workmanship are put into these instruments, and you can't go wrong in using "WIRELESS SHOP" condensers exclusively, as they are fully guaranteed to give entire satisfaction, or we will cheerfully refund your money. What more could you ask ? PRICES No. 1500 15 plate, approximately .0004 m.f. max. capacity $6.00 No. 2500 25 plate, approximately .0006 m.f. max. capacity 7.5o No. 3500 35 plate, approximately .0008 m.f. max. capacity 9.00 Prices include knob and pointer and mounting screws. A metal dial will be furnished instead of the pointer at 75c extra, or a high grade moulded Bakelite knob and dial, with graduations finely engraved and filled in with white at $I.00 extra. Postal charges and insurance must be included in remittance. Insurance charges on any of the CW condensers is only 5c. Our new bulletin on all "WIRELESS SHOP" variable condensers is just off the press, and is yours for the asking. 111Wil Well -- 143-za A. J, E D G C O M B ..°

511 WEST WASHINGTON STREET LOS ANGELES, CAL.

www.americanradiohistory.com 734 Radio News for April, 1921

No dimensions have been given for outside dials shown in front of panel, Plate 3- BURGESS The drawing, as made to scale, has dials "B" BATTERIES of approximately 3" in diameter and these seem to be of the desirable size. Uniform- ARE ity and good appearance will be the gov- THE NOISELESS KIND - erning points. made with and without taps BAD TEMPER! First Rectifier : -"I can't seem to satisfy Send for my friends, the transformer and the re- catalogue giving sizes and prices actance." Second Rectifier :-"How so ?" First Rectifier : -"Why, the reactance BURGESS BATTERY says he can't take alternating currents with- COMPANY out choking, Harris Trust Building CHICAGO and the transformer can't stand currents direct, so no matter what I do one or the other is always down on me," By C. w. HALLIGAN.

A RAY-DI-CO "QUALITY" SYNCHRONOUS Canadian Radio Experimenters Lateral Wound Coils. GAP WILL PUT YOU IN THE DX CLASS Turns App. Wave -Length Price 25 130- 375 $0.55 Clear steady signals. Clean cut tone. 40 225- 575 .60 Constant time intervals between dis- 75 240- 740 .70 charges of equal amplitude. Puts the 100 460- 1480 .80 current where it belongs in the antenna, 175 750- 2400 1.00 Extra large sparking surfaces Vs" by 1" 325 1375- 4500 1.25 accurately spaced upon a 9" Grade XX 550 2250- 7700 1.50 Bakelite Rotor. Design of revolving elec- 750 3000 -11200 1.75 trodes provides a decided air blast giving 1200 6000 -20000 2.50 a quenching effect. Extreme shortness of conductors in rotor allows use of larger Special Sizes to order condensers, 480 discharges per second. Special discount to dealers Permits extremely low decrement. Motor Plugs and Bands with screws for single phase, Synchronous type, speed of coils .75 1800 R.P.M., 1/6 H.P., 110 volts, 60 cycle, C.W. Inductances 2.00 net weight 35 lb F.C.B. Chicago, $85,00. C.W. Inductances 7.50 Rotors built order. Transmitters for radio purposes 3.50 to Vario- Couplers and Variometers 4.25 RAY - DI - CO Send 5c for 20 page catalogue (Ray- Dee -Ho) J. M. PAQUIN 2653A N. Clark St. CHICAGO, ILL. The Electrical Shop RADIO 9AG 787 Queen St., West, Toronto, Ont. PARAGON MEANS "A PERFECT MODEL OF EXCELLENCE" AND IT IS FOUND ONLY ON RHEOSTATS CONDENSERS DETECTORS SWITCHES RECEIVERS VARIOMETERS KNOBS AND OTHER V. T. CONTROLS DIALS SOCKETS SPECIALTIES Manufactured by r ADAMS -MORGAN CO. -

1 No. 70 Paragon V. T. Control ;IIflll tt "_á A compact control panel consisting of a standard socket, rheostat, grid condenser, grid leak and nine binding posts mounted on a moulded con - ...> densite panel. Polished nickel metal parts. A high -grade inexpensive in- ue` strument that will do as good work as the highest priced cabinet. f. Price - - - $6.00

- No. 25 Paragon Rheostat For either panel or table mounting. Moulded condensite base. Resistance six \\ ohms. Smooth operation. Capacity 1% amperes, The highest grade rheostat on the market. Price - - - $1.75 MOST ENTERPRISING DEALERS CARRY PARAGON , PRODUCTS AS REGULAR STOCK. c.--) r y Illustrated Bulletins will be mailed upon receipt of a two cent stamp. Send us your dealers name. ADAMS -MORGAN CO. UPPER MONTCLAIR NEW JERSEY

www.americanradiohistory.com Radio News for April, 1921 735

2 s Radio Communication (Continued from page 71o) Standardized ,,,,,,,,,,,11,1,1111,,,,111111111111111111111111111111111,/1,11111111111111,111111111111111111111111111,1111111111111111 same way the electrical arrangements in the receiving circuit which are used to receive radio waves must be such that that receiv- ÚNIT Cabinets ing circuit is electrically in tune with the radio wave. By this means the radio re- EACH ABC Unit is complete in itself for its particular purpose. Yet the series ceiving circuit can pick out the particular is so designed that any combination of units works as if it were a single set. wave which it is desired to receive and not The photograph below shows three of the units -the Receiving set, the VT De- tector, and the Two -step Amplifierhooked up together into an efficient, smooth - be affected by other waves. This is for- working combination, tunate because otherwise the interference between different radio messages would be hopeless. It would be just as tho every sound wave which passed thru the air set absolutely everything which it touched into vibration. As has been mentioned the frequency of alternation of radio waves is very high, so high, in fact, that a sound wave of such frequencies could not be heard. Suppose for instance, that an ordinary telefone receiver was placed in the circuit which is receiving a radio wave. The electric currents of the same frequency as the wave frequency tend to cause motions of the Receiving Set or Radio Re- VT Detector. Simply hook Two -Step Amplifier. Adds telefone receiver diafram. These motions ceiver. Complete in itself. up this detector to your ABC two stages of radio amplifi- are, however, of such great frequency that Equipped with selected ga- receiving unit, disconnect the cation to any previous com- is produced. In order to lena crystal detector, and crystal detector, and the set bination of units, making a no audible sound three Bi- Lateral Coils. Price, is ready for operation. Price smooth -working, long range permit the radio wave to be received and $24.50. (less tube), $10.5o. set. Price (less tubes), $45. transformed into a sound it is therefore necessary to break up the radio wave in some manner. This is done in radio telegraphy by interrupting the wave completely NOW -add to your range so that it consists not of a single regular series of alternations but of a succession gradually -discard nothing! of groups of such alternations, that is, in- ABC Units solve the problem of starting off with a small investment, and grad- shown in ually increasing your range without discarding a nickel's worth of apparatus as stead of the continuous wave you go along. Start with the receiving unit (complete in itself). Then you can gradually build up your station to include a VT Detector and three stages of radio amplification. Yet, every new combination of units, as you go along is guaranteed to give satisfactory, dependable performance. u to J Finally, when you have secured the complete system, yea have a commercial- grade station- equipped to receive all classes of signals; damped or undamped, r code or radio phone, on all known wave -lengths.

J V J J I The combination shown unit This Diagram Shows a Continuous Wave and here is the receiving Form (described above), and i the Same Interrupted so as to "Trains. the combined VT Detec- tor and one-step amplifier. Further amplification Fig. 3 we use the interrupted wave or group can be secured by adding of waves illustrated in Fig. 4. The fre- a one or two -step ampli- quency of the interruptions or of the fier at any time. Price of is frequency which the combined Detector groups of waves the and one -step (less tubes). ! ?: VT DETECT. can be heard. $37 -50. There is another thing that is to be taken into account before it becomes possible to "Rer't .sl'- translate the received radio current into a heard. When one of the ABC Units are standardized in design, and Every part, even the least important sound that can be produced by automatic, machine methods, 2nd binding post is standardized. and groups of alternations acts on the tele- down to the smallest switch point. made by unvarying, automatic machines. You can always buy replacement that are fone receiver it causes no motion of In addition to the progressive, "building up" parts of feature, this standardization offers three dis- identical with the original. the diafram because each variation tinct advantages: 3rdStandardized quantity production in the current in one direction is imme- the ABC factory, (the only one of 1StYou can invest in a receiving unit, its kind in the world), has brought about diately followed by the current in the with perfect confidence that the other economies previously impossible in radio aP- so that the resulting ef- units, In the same standard design, ready to paratus. That's why we can sell 'Profes- opposite direction hook on, will be ready for you whenever sional Radio Equipment at Amateur Prices", fect of the group of waves upon the tele- you want them. We took three years of re- and at the same time back up every ABC no motion at all. search to make ABC Units right, and the de- instrument with our unequalled guarantee, fone receiver diafram is sign will remain unchanged in all essentials. "Your Money's Worth or Your Money Back!" It is therefore necessary, in order to convert the current into a sound, to use something else with the telefone receiver. This Professional Radio Gquipment at Jfmateur Prices something else must be such as to make the in current flow thru the telefone receiver )4 only one direction. It must allow the elec- WIRELESS E Q UIPMENT CO.V.GPoee, " it in one direc- ,,de` tric current to flow thru 188 GREENWICH ST. NEW YORK CITY , tion ànd stop current which tries to flow thru it in the opposite direction; that is, it must be some sort of electric valve. The t Wireless Equipment Co., Ine., effect of such an electric valve may per- Dealers- Amateurs- 188 Greenwich St., New York. haps be understood more clearly by taking I enclose one nickel, Send me by a sheet of paper and placing it upon Fig. 4 The ABC line includes The ABC new folder, describes, return mail your new ABC folder. a complete assortment in detail, the five ABC unit cabi- so as to block out the lower half of the radio apparatus, nets, the ABC variable conden- the upper of sers, the ABC small parts, Bi- Name waves shown. This leaves only both assembled and Lateral Coils, the Vibratone, Jr. a halves of the little groups of waves and unassembled. It is Transmitter, eta, etc. Slip this Address fast selling, profitable coupon and a nickel into an this is exactly what the electric valve does. line, that makes good envelope NOW! and your copy I It results that successive impulses of cur- Write for discounts. will come by return maiL I City State rent flow thru the telefone receiver and all

www.americanradiohistory.com 736 Radio News for April, 1921

of these tiny impulses in any one group add their effects together and produce a motion out of the telefone diafram. The Let's Go ! interval between one group and the next -the chief battle slogan of the American Army in the World War. The slogan permits the motion of the telefone diafram that typified the American fighting spirit -that gave enthusiasm at the right to subside and this intermittent motion moment. causes what is heard as a note in the re- Let's go! -the same spirit permeates American business to -day. ceiver. A number to Let's go! -in the FADA shop means the extension of my personal of devices are used per- service form the electric valve action which has- to every radio amateur. It means that if you want the very best in completed instruments or only a piece been mentioned. The most interesting and of bakelite cut to your special size that you will be most served courteously, economically and promptly. Panel effective device of this kind is the engraving is a particu- electron tube. The electron tube is a very lar feature. Estimates will be cheerfully given on any experimental or machine work. simple device which looks more like an ordinary incandescent lamp bulb than any- Send nie your order for any parts listed below or for any piece thing else. Your attention is particularly of apparatus made, and know at invited to the principles it first hand my upon which op- what "Let's. go" means to you. erates since this is the most important of Engraving, per letter $ .09 FADA Mica Condensers made of Bakelite Mounted Galena %% the apparata used in radio. While experi- Crystals .50 and copper foil carefully tested, ca- menting in FADA Binding Post .16 pacities 0.00025, 0.0005 and 0.001 mfd. 85c the development of the incan- FADA Crystal Detector 3.00 Genuine Grade XX Bakelite cut with descent lamp Edison made the discovery Radiotron UV -200 Tubes 5.00 square edges to your size per square inch, that an electric current could be made to in. thick 2c; 3/16 in. thick 3c.; 4 in. flow Radiotron UV.201 Tubes 6.50 thick 4c. in the empty space inside the bulb General Radio Socket 1,75 Federal Automatic Phone Jacks light near the hot filament. If a middle plate is Four FADA instruments with auto- your filaments nlaced inside incandescent matic filament control with the insertion of phone an lamp bulb that have plug. The most modern instruments use near the filament if not been equaled by any compari- them. and by means of son. a wire thru the glass this middle plate Set of 2 for Detector and 1 -stage Audion Control Panel $17,50 Amplifier $2.70 is connected by wire thru a battery and an Detector and 1 Amplifier 45.00 Set of 3 for 2 -stage Amplifier 3,55 indicating instrument to the filament, a cur- Detector and 2 Amplifiers 65.00 Set of 3 for Detector and 2 -stage Two Stage Amplifier 50.00 rent will flow as indicated by the instru- Amplifier 4,20 ment. A current in Progressive dealers stock is flowing the wire and FADA apparatus also flowing across the empty space be- Frank A. D. Andrea, 1882 -A Jerome Avenue, New York City tween the filament and the plate. By much patient scientific research, scientists have found out that this current taking place in the lamp consists of the flow of a stream of very small electric particles called elec- A Save Time and Money A trons. These electrons are shot out into A ACE By Forwarding Your Mail Orders ACE E to Us E Furring couper Our Central Location Makes It Possible for You to Do So

ANTENNA MATERIAL CRYSTAL RECEIVER $23.50 Ramoso Spreaders CRYSTAL DETECTOR 2.80 8 ft. lengths $1.00 RECEIVERS 12 ft. lengths 2.25 Baldwin Navy 16 ft. lengths 16.50 3.00 Brandee Superior 8.00 7 -22 Std. Wire, per ft 01Y4 Murdock 55 -3000 10" Electrose 5.50 .75 Murdock 55 -2000 4.50 Ball type Electrose .35 STORAGE BATTERY AMPLIFYING TRANSFORMER Marko 6V 40A GAP 16.25 Acme Semi -mounted 5.00 Marko 4V 40A .CAP 10.75 . Nieves.0 R/,eósMl ANTI- CAPACITY SWITCH 2.80 ANTENNA VACUUM TUBES Fig. 7. SWITCH 4.50 E. R. Detector 6.00 This Diagram Shows How a Vacuum LIGHTNING SWITCH 4.50 Amplifier Tube is Used in a Receiving Circuit to Rectify BURGESS B. BATTERIES 7.00 Ex. Hard Transmitter 7.50 Wave Trains and Transform Them Into Audible 22'/ V -1200 hrs. 3.50 Radiotron Detector 41/4V- 200 hrs. 5.00 Sounds. .40 ACE VT SOCKET 1.50 CONDENSERS -VARIABLE WIXICO MOUNTING Connecticut .001 6.50 For D -L or H -C Coils C -E Bal. with dial 9.50 Table Type 8.00 the surrounding space in all directions by C -E .0006 with dial 7.50 Panel Type 6.00 Murdock mtd. .001 the hot filament. The electrons may be 4.75 VARIOMETERS Murdock Interior 001 4.25 Amrad said to fill the bulb like a Murdock A005 mtd 4.00 Mounted 14.50 vapor. They G -E with dial 6.50 move at random in all INSTRUCTION BOOKS Radlsco with dial 8.50 directions unless Experimenter's Manual 2.25 Klithen mtd. in cab. 9.00 there is an electric force to make them move Practical Radio Tel. 2.25 WAVEMETER in some particular direction. The battery Audel's Easy Lessons .50 Amrad 8.50 the MAIL ORDERS RECEIVE PROMPT ATTENTION. connected in circuit outside the bulb SEND IN 3e STAMPS FOR CATALOG supplies an electric force which acts between the filament and plate and makes the THE PRECISION EQUIPMENT CO. electrons move from the filament to the 2437 -2439 Gilbert Avenue plate. If the battery is disconnected, there Dept. A Cincinnati, Ohio is no current, and as many electrons as "You May Pay More But You Can't Buy Better." strike the plate fall off again into the bulb. The current depends on the number and speed of the electrons. The battery is what gives them their speed in the INSTRUMENTS direction £tlament to plate. The bat- Always Reliable tery performs much the same action as Bunnell a steam pump would if the bulb were a room into and out of which steam pipes JOVE DETECTOR were connected. If the pump were discon- Handiest, Handsomest, Best nected, there would be no flow of steam Sample by Mail, $2.00 and when the pump is connected, steam is made to flow into and out of the room and Tested Galena Crystal, 25c thru the pipe. We are distributors of the Standard Electric Novelty Co..' Type B "Cyclone' Audion Batteries. The point of all this is that the electron Also of De Forest and all the leading manufacturers flow in the bulb has a valve action. The of High Class Wireless Apparatus. Send stamp (MEGAN PATENT) for electrons are emitted by the very hot fila- new edition 42RN Catalog. ment and can be made to flow toward the plate by connecting a battery in the proper J. H. BUNNELL & CO., 32 Park Place, New York direction. If the connections of the battery are reversed however, no current will flow because there is no such emission of Insure your reaching electrons from the plate which is cold. The copy you each month. Subscribe to Radio News -$2.oe electric force produced by in a year. Experimenter Co., 236 -A N. the battery Pub. Fulton St., Y. C. this case has nothing to work on and can

www.americanradiohistory.com Radio News for April, 1921 737 do nothing except prevent the flow of electrons out of the filament to the plate. It should be clearly understood before going further that the action of the electron tube THE thus depends upon the fact that an electric force can be applied in one direction which causes an electric current from the filament to the plate, but that if this electric force WORLD'S TUNER MARKET is reversed no current flows. The device gives exactly the electric valve action Y N - France -P O Z - Germany - I D O - Italy. Read in the U. S. with needed in order to make the incom- one bulb and single wire aerial 25 ft. high by 4o ft. long. Read unsolicited ing radio signals produce sound in a testimonials and note we always give names. Verify these -we will accept telefone receiver. Suppose that the bulb then. is connected up to a radio receiving your decision circuit in place of the battery. Suppose TUNERS wound with involute coils have lived to see all others also that the indicating instrument is re- TRESCO placed by a telefone receiver. This is funny wound coils die a natural death. shown in Fig. 7. The pulses of current in the radio receiving circuit similar to those COMPLETE -NO LOADING COILS NEEDED of Fig. 4 produce electric force inside the filament and the plate bulb between the $10.00 add P. P. Type B.S. which alternates in direction just as the 5000 to 20000 M pulses of current do. On account of the ryoo to 5000 M 10.00 add P. P. Type A.S. valve action, current can flow thru the 200 to 700 M ro.00 add P. P. Type C.S. bulb only in one direction and consequently the pulses of electric force in one direction Coils of either for panels $6.00 plus P. P. only are effective. As a result, pulses of current flow thru the telefone receiver in groups, the pulses being all in one direction. This causes a note in the telefone receiver, as already explained. Hook 'Er To Yer Bulb It might seem that these small electric particles, called electrons, are very remote from any practical use. The study of elec- 200M -P. R. L TUNER trons has in fact been advanced by purely Something new, using a variocoupler wound with %" copper strip. Very efficient and also including our special Wives from Antenna,from above.- . selective, variometer. Just as efficient as any Para- gon. Weight 5 lbs. Price, $25.00-add P.P.

KNOCKED DOWN PANEL Set it up, save money. Consists of Formica Panel - drilled ready for parts, I Rheostat-one II Plate condenser, H.V. switches, points, base and necessary binding Posts. V.T. socket $I.00 extra. Shipping weight, 4 lbs. Price, $8.00. Add Parcel Post.

Waves from Antenna.

ELLIPTIC VARIOMETER Embodying a new principle. Most efficient made. Same as used by us in our P.R.L. Tuners. Shipping weight 3 lbs. Fig. 5. This Diagram Shows How the Electric Price, $5.00. Mounted in hard wood fin- Waves Are Radiated From an Aerial into Space. ished case, formica top, binding posts, scale. Complete, $7.50. Add Parcel post. scientific research not at all connected with any applications. By means of the electron tube, however, very practicable use RHEOSTAT indeed is made of electrons and their im- pan- Sci- Smoothest running that's made for portance is recognized commercially. els. Auto stop that prevents burning out entific research work which has been done radio filament. Weight I lb. Price, $1.75. Add in this connection has revolutionized parcel post. and provided a means for great improve- 011100111111IIIIIpll,fiiili ments in ordinary wire telefony and also KNOCKED in other uses of electricity. An improvement in this electron device DOWN can be made which very greatly extends its CONDENSERS power and usefulness. As shown in Fig. 8 Assemble and save a grid of very fine wire can be placed in money. the tube between the filament and the plate. The grid is placed closer to the filament II Plate $1.80 than to the plate. The electrons which are 2I Plate 2.25 emitted by the filament can move freely 41 Plate 3.2o between the grid wires. If by means of a Add P. P battery or something else an electric force and the is established between the filament 10 catalog full of dope. grid, this electric force causes electrons to cents brings complete move away from the filament toward the plate and since the grid is placed much closer to the filament the electric force Iowa makes the electrons move much faster than TRESCO, Davenport, the saane electric force between the filament

www.americanradiohistory.com 738 Radio News for April, 1921

and the plate would. Very few of the electrons are taken by the grid and a very small current thus goes thru the wire con- Keeping Pace with New nected to the grid. Thus a very small current to the grid controls the flow of a much Tube Developments larger current to the plate. Hence a larger current can be taken out of the tube than The new amplifying tubes are out and they are fine. is put into it. A small electric force acts But are you getting the most out of your tube? A com- between large plete amplifier is more than a mere assembly of parts. It grid and filament causing a consists first of the selection of units of correct electrical electron flow from filament to plate. There characteristics. An amplifying transformer must be more results a relatively large flow of current in than a coil of wire and a core. It must have incorpor- the apparatus connected outside the tube ated in it the results of engineering skill. ln our Type 231A amplifying transformer we have produced an in- between the plate and filament. This de- stmument designed specifically for the new Radiotron tubes. The design is right, vice is commonly called an tube. ance is right the appear- electron and the price is right. Send for free Bulletin 007N on the operation of ampli- It magnifies or amplifies electric currents. fying transformers and completely describing this instrument. It accomplishes the control of a large PRICE amount of power by a small power. This COMPLETELY MOUNTED $5.00 is just the same thing that a gun does- TRANSMITTING TUBE RHEOSTAT pressing the trigger several times in a re- peating pistol is like the action of the tube The new five watt Radiofron tubes require a filament current of 2.35 amperes. We have added to our already with successive pulses of electric force. complete line of Type 214 receiving tube rheostats a 2 -ohm The grid corresponds to the trigger and transmitting tube rheostat which will carry 2.5 amperes. the plate to the gun barrel. This resistance is sufficient to regulate the new tubes on as high as a 12 volt supply source. This rheostat does A number of forms of electron tubes as not run hot and may accordingly be mounted inside of used today are shown in Fig. 9. They are enclosed transmitting cabinets where space is often very used to receive radio waves and make sig- limited. Like our receiving tube rheostats and grid nals just as the simpler device shown in biasing potentiometers, it is made in two styles, 214A for back of panel mounting and 214B for surface mounting. Fig. 7 does and they amplify the signal as If you have not already received bulletin 904N, request well as make it audible. On account of the it when you send for Bulletin 907N. control of the plate current by a smaller PRICE $2.50 grid current, the electron tube makes possible very wonderful feats. It is worth GENERAL RADIO COMPANY while to note the explanation quite care- Massachusetts Avenue and Windsor Street, Cambridge, 39 Massachusetts fully as it soil he shown presently that this explanation contains all the most important features of radio telefony. ALL RADIO PARTS FOR THE AMATEUR SPECIALS "B" Batteries, $l.00 each. Trench Set Panels, 5oc. each. Variocouplers, 600 Meters, $5.00, $7.00 and $8.00. Variometers, $4.5o ; Others at $7.00 and $7.50 Grid Leaks and Condensers, 35c. each. Variable Grid Leaks, 75c. each. PHONES REGENERATIVE SETS Fig. 8. This is the Type of Vacuum Tube Ac- Western Electric, $14.00 each Signal tually in Use. The Grid is Generally Given the Electric, $35.00 Shape of a Spiral Wound Around the Filament. Baldwin, $16.50, $20.00, $21.00 each Grebe, $65.00 Brandes, $8.00 each Tuska, $65.00 Murdock, $4.50, $5.5o each Paragon RA Ten, $85.00 It is perfectly possible and quite easy to take the magnified output from an electron tube and pass it into a second electron We give 10% Discount to all Radio Clubs. tube, using that to make a still further am- Send for Price plification of the current. Using one tube List. after another in this way, we obtain what is called an amplifier. Three tubes joined AMERICAN ELECTRO together in this way are shown in Fig. 6 TECHNICAL APPLIANCE CO. and the process can be repeated several 235 times using a number of tubes. The cur- Fulton Street Dept. R NEW YORK rent is increased by each tube and handed on to the next without any change or distortion of the current even tho it passes thru several stages. A demonstration amplifier is shown in WIRELESS MANUAL M12 Fig. 6. A buzzer is connected between You should have it I RËFs even if only super- TELEGRAPHY Containing as does grid and filament of the first tube. Ar- ficially interested. Around about you it a fund of valu- every I able information not generally day you read of some marvelous occur- contained rangements are provided so that a telefone rence in which wireless in a catalogue, it approaches nearer a played a distin- text book in the fascinating field of wire- receiver may be inserted in the buzzer cir- guished part. It may not be entirely clear less telegraphy. No expense has been to you. The Manual will explain it. To spared to make it accurate cuit or in the plate circuit of any tube. the student of Wireless Telegraphy, the and reliable. Manual contains much that is indispens- No Wireless Experimenter Should When the telefone receiver is connected able to a proper understanding of the art. be Without the Mesco Wireless directly in the buzzer circuit a feeble sound It contains 200 pages, fully illustrating Manual. We ask 25 cents (25e) is heard; when connected in the plate cir- and describing the many instruments used for it-give you a coupon receipt in Rgdio. 45 pages cover general instruc- which can be cuit of the first tube a considerably louder tions, diagrams, station calls, tablee, applied on any fu- codes and other information. ture order. sound is heard and still louder in the sec- The book is printed on highly finished Send your name and address now, and ond and much louder in the third. A front paper with a two -color cover and meas- get one of the most complete, comprehen- view of an actual amplifier as used in radio ures 9 x 5% inches. sive and reliable wireless books published. work is shown in Fig. lib. MANHATTAN ELECTRICAL SUPPLY CO. INC. The amplifier is of the greatest impor- 17 Park Place 114 S. Wells St. 1106 Pine St. 604 Mission St. tance both in radio and in long distance New York Chicago St. Louis San Francisco wire telefony. It reduces the amount of power that must be used in a radio trans- A welcome addition to your library! Send $2.00 today, plus postage for 7 lbs., and mitting station because of bound your copy when an amplifier volume No. 1 of Radio Amateur News will come forward by return mail. is used in a receiving station, can Experimenter Publishing Company 236a Fulton Street, New York City signals be received which are far too feeble to he www.americanradiohistory.com Radio News for April, 1921 39

The photograph shows the U. S. Army Transport Sheridan steaming through San Fran- cisco's Golden Gate. Because such ships require the most efficient and most dependable apparatus, the Sheridan and all other Pacific Coast U. S. A. Transports are equipped with A -P Electron Relays. The Transport Service has adopted the Electron -Relay as its standard receiving tube. Use the tube the army uses. One of the largest radio dealers in the North- A letter from the Radio Section of the Bureau west (name on request) writes :-"You may be of Standards furnishes further proof :- "These interested to know that after trying the new , .. . tubes (Electron Relays are very good detectors, and the new .. tubes, the amateurs are con- far superior to any of the tubes with which we vinced that there is no satisfactory substitute have made comparisons." Far superior to "any" for the `E. R.'" -Notice that. Use the tube the Army uses-use A -P tubes for efficiency. Licensed by the Radio Corporation of America under De Forest Audion and Fleming patents, for amateur and experimental use in radio communication. AND for the best book on RADIO ask your dealer for "ELEMENTS OF RADIO TELEGRAPHY" by Lieut. Ellery W. Stone, U.S.N.; or order from- CO. PACIFIC RADIO SUPPLIES CO. The A -P Electron Relay ATLANTIC RADIO SUPPLIES -Price $6- equipped 8 KIRK PLACE -NEWARK -NEW JERSEY 638 MISSION ST. -SAN FRANCISCO -CAL. with the SHAW standard, condensite, four - Distributors for Moorhead Laboratories, Inc. -Manufacturers of prong base. The A -P Electron Relay

THE THIRD EDITION OF THE CONSOLIDATED RADIO CALL BOOK Very Greatly Enlarged 192 pages. 32 pages more than 2nd edition, better paper, stiff covers, etc. Some of the special information contained in the new book: Radio rate sheet (charges to and from vessels, etc.); Cable rates; Table for finding cable charges to various points; Weather reports and hydro - graphic reports of the world; Time signal section of the world; American radio compass stations; French 'radio compass stations; British radio compass stations; Canadian radio compass stations; General information section; International abbreviations; High power radio stations of the world; Press schedules of spark stations. The Consolidated Radio Call Book is the only book in print officially listing all the Radio calls as issued by the Bureau of Commerce. Every vessel and land station in the world is represented and listed alpha- betically, according to names of vessels or land stations, and according to call letters; Revision of American coastal stations under U. S. Naval control, and their new calls. Every New Amateur Call Is Listed SPECIAL- Wireless Map of the World in Colors Given Free With Each Copy Price $1.50 Prepaid Either Direct from us or for sale by the following responsible Dealers:

American Electro Tech. Appliance Co..'Iew Lehigh Radio Co., Bethlehem, Pa. Radio Electric Co., Pittsburgh, Pa. York City Linie Electrical Supply Co., St. Louis. Mo. Radio Equipment Co., Boston, Mass. American Hardware Stores, Bridgeport, Conn. McCarthy Bros. & Ford, Buffalo, N. Y. Radioelectric Shop, Clëveland, Ohio Atlantic Radio Co.. Boston, Mass. McClurg & Co., A. C., Chicago, III. Ray- Di -Co., Chicago Ill. Bamberger & Co, L., Newark, N. J. Manhattan Electric Supply Co., New York, Chicago Reuter Electric Co.. Cincinnati, Ohio Benwood Specialty Co., St. Louis, Mo. Meter Eleetriealt Construction Co. Oshkosh, Wis. Riverside Laboratory, Milwaukee, Wis. Brode Electric Ca, Los Angeles. Cal. Meyberg Co., Leo San Francisco, C'aL Rose Radio Supply. New Orleans. La. Bunnell & Co., J. H. New York City Mohawk Electrical Supply Co., Syracuse, N. Y. Saunders Co., Geo. S. Boston, Mass. California Electric Co.. San Francisco, New Era Shop, Milwaukee, Wis. Schmidt & Co., Rudolph, Rochester, N. Y. Cation. Neill & Co., Cal. Newman -Stern Co., Cleveland, Ohio Sears, Roebuck & Co., Chicago, Ill. Central Radio Co., Independence, Mo. Nola Radio Co., New Orleans; La. Service Radio School, Washington. D. C. Chicago Radio Apparatus Co.. Mileage, Ill. Noll & Cb.. E. P., Philadelphia, Pa. Shaffers', Norfolk, Va. Continental Radio & Electric Corp., New York City Northwest Radio Service Co., Seattle. Wash. Shotton Radio Mfg. Co., Scranton, Pa. Cutting & Washington Radio Corp.. New York City N. S. W. Bookstall Co., Sydney, Australia Sarnia. Ont.. Canada Detroit Radio Laboratories, Detroit, Mich. Patent Electric Co.. New York City N C. City, N. J. Smith Novotoy Electric, Inc., Charlotte, Dewey Sporting Goods Co. , Milwaukee, Wis. Paramount Radio Supply So., Atlantic Southern Electrical Supply Co., San Diego, Cal. Doubleday -Hill Electric Co., Pittsburgh, Pa. Parks, Henry Francis, Butte, Mont. United Radio Telegraphers' Assoc., Baltimore, Md. Electro Importing Co.. New York City Pearlman's Hook Shop, Washington, D. C. Western Radio Electric Co Los Angeles, Cal. Findley Electric Co., Minneapolis, Minn. Penn Radio Anparatus Reading, Pa. Whitall Electric Co., Westerly, R. I. Fuller Co.. W.. Boston. Mass. Pennsylvania Marconi Wireless School. Seth Pa. White Co.. The, Columbus. Ga. Curd & Co.. Wm. London. Canada Philadelphia, White & Rover Co., Washington, D. C. Lilco Wireless Supply Co., Marion, 111. Philadelphia School of Wireless Telegraphy. williemson FaOotrie Co.., H. E. Seattle. Wash, Holt Electric Utilities Co.. Jacksonville. Fla. Philadelphia Pa. Wilmington Electrical Specialty Co.. Wilmington, Del. Jenkins. Lester T.. New Bedford. Mass. Piedmont, Electric Co., Asheville, N. C. Minn. Wireless Mfg. Co. Canton. Ohio Katzenbach & Co . F. S., Trenton, N. J. Pioneer Electric Co., St. Paul, Wireless Press. New York City Kendall Co., W. D. Worcester. Mass. Pitts Co.. F. D.. Boston, Mass, DL Young & McCombs. Rock Island, nl, Killoch Co.. David, New York City Post Office News Co . Chicago, Vno Men's Christian Assoc., Los Angeles, Cal. Kluge. Arno A.. Los Angeles. Cal. Precision Equipment Co.. Cincinnati. shin r'n. 7,amoiski Co., Jos. M.. Baltimore, Md. Krause & co A. F.. Detroit.. Mich. fli,u,ntin., , Newark, N. J. Consolidated Radio Call Book Co., Inc., 41Park Row, New York City

www.americanradiohistory.com 740 Radio News for April, 1921

received without an amplifier. By means of amplifiers to which were connected loud - TWO GOOD AUDION CONTROLS speaking telefones, demonstrations have been given in which an airplane more than a mile away in the air addresst large crowds in the streets of New York. One of President Wilson's speeches in the West was spoken into a telefone apparatus and amplifiers were used to make it fully audible to all persons in a very large crowd. The large announcers used in railway stations now make use of amplifiers. By means of amplifiers, submarine vessels can receive radio messages when entirely submerged. It is an interesting fact that an amplifier can be made so powerful that no input current at all is required. This does not mean that it is a perpetual motion machine, because the power to operate it must be supplied by the battery that is connected in the plate circuit of the tubes. It TYPE "D" does mean, however, In addition to permitting you a fine adjustment of that the electron tube There are many audion control units BUT-Do both plate and filament voltages this Unit makes the can be used to generate alternating currents they all provide a good means of adjusting the plate signals over 25 times as loud. A REAL Instrument as well as to receive voltage as well as the filament? This Unit provides at a price which you can afford to pay. Equipped and amplify them. both and both well. Can be used with any type with plugs and jacks for connecting the phones to Thus receiving tube made. Cabinet of selected oak with the desired stage. Cabinet of oak "Early English" far we have discusst only signals beautiful "Early English" finish. finish. such as are used in telegraphy. The voice Price $15.00 Price $35.00 can be transmitted and received by the same Without Cabinet 12.00 Without Cabinet 32.50 apparatus Eveready 45 Volt Tapped B Battery $5.00 Electron Relays $6.00 and principles. The human voice Small Size Non -Tapped 2.25 Amplifier -0soil atom 7.00 produces sound waves which cause air vi- Catalog sent upon receipt of IOc. which will be refunded on your first brations of an irregular character. Such $1.00 purchase from us. It will pay you to get it. a wave may be roughly illustrated as in Fig. so. The variations in the wave are 1103 SOUTH THIRD STREET, much EVANSVILLE RADIO LABORATORY 9 EVANSVILLE, INDIANA slower than the alternations of current used in radio. It is possible to make i a radio wave carry a voice wave, and when this voice -modulated wave is received it can be passed thru a telefone receiver and the voice hear just as the radio telegraph signals are heard. The principle is that instead of breaking un the continuous wave of Fig. 3 by interrupting it, as in Fig. 4, it REMLER No. 93 A BATTERY is caused to vary in accordance with the - voice wave and these variations can be made audible. The way in which the voice POTENTIOMETER wave is superimposed upon the radio wave Increases is illustrated in Fig. io. The alternations detector sensitivenes of the radio wave are shown by the full and signal audibility. lines and the dotted boundary lines show that the HE plate voltage of any detector tube must be care- intensity of the wave has been fully adjusted for maximum sensitiveness and signal made to vary in accordance with the sound audibility. Potentiometer control provides close ad- Pat. Applied For. justmentr with ease of operation. This new Bender wave produced by the voice. This wave Unit with metal inserts provides positive definite electrical can be received in exactly the same way as No. 93- Remler A- Battery Potentiometer contact and eliminates the uncertainty of carbon to any in Unit only, with studs for graphite contact This Remler Unit Is not brittle and wave ordinary radio telegraphy-no is connected across the A- Battery to control the plate special apparatus panel mounting .75c potential over a six volt range by half -volt steps. Cir- is required for receiving No. 94-Remler Rotary Lever Switch cuit diagram furnished with each unit. radio telefony. The voice at the transmit- for ting use with No. 93.45c "Apparatus that Radiates Quality." station is heard very clearly. It can Unit be made as loud as desired at the receiving station just as radio telegraph signals cari REMLER RADIO MFG. COMPANY be by the use of amplifiers. E. T. OIINNINGHAM, Sales Mgr. The radio wave 163 Sutter Street San Francisco is really modulated or molded just as a phonograph record is molded by a sound wave. The means by which this modulation is accomplisht is the electron tube. If the telefone receiver is replaced by any kind of generator of radio current, then if a person speaks into a telefone transmitter connected between the, grid and the filament of the tube QUALITY RADIO the variations caused by the sound of the person's voice are impresst upon the radio EQUIPMENT current in the plate circuit and a modulated radio wave as in Fig. io is produced. RADIO MAGNAVOX RADIOTRON U. V. 200 A small radio telefone transmitting outfit The latest developmetìt in An excellent new super - which is used for demonstration and ex- sound amplifiers; con - sensitive detector and perimental purposes structed on a patent pro- tone frequency amplifier; at the Bureau of tected electro - dynamic constructed especially for Standards is shown in Fig. 12. Music is principle. Can be used amateur and experimental readily transmitted out into space by playing with excellent results stations. Will operate the music into a telefone transmitter. A with 2 to 4 dry cells. from one standard plate phonograph battery. may be used as shown in Fig 12. The telefone transmitter is connected Full supply of quality Vacuum Tubes, to the radio telefone apparatus upon which Controls and Parts. Special Dealer's the electron tubes may be seen. offer. Mail orders filled promptly. A receiving outfit usable in demonstra- Write for Radio Catalog No. 2. tions is shown in Fig. 14. The receiving circuit or antenna is entirely contained within the frame shown in the picture and electron tube used as a detector and am- DOUBLEDAY- HILL ELECTRIC CO. plifier and the loud- speaking telefone re- I715 TWELFTH ST., N. W. 719 -21 LIBERTY AVE. ceiver are all visible. A much more com- WASHINGTON, D. C. Radio Dept.Desk B pact radio receiving outfit is shown in PITTSBURGH, PA. Fig. 13. The box encloses the electron tubes, the receiving antenna and all neces- www.americanradiohistory.com Radio News for April, 1921 711

SEMI - COMPLETED RADIO EQUIPMENT The progressive amateur of today does his own construction. Supply houses sell more parts than finished instruments. Given the tools and facilities of radio manufacturers most amateurs could easily duplicate the work of the best constructors. Such equipment is, however, seldom available. Even the largest manufacturers cannot do all their own work. Many place orders with assembling companies having facilities for drilling, assembling, engraving, machining, etc. In such cases all the manufacturer does is to wire the circuits in accordance with his ideas. You probably have circuit data and ideas that you know are superior to those of many manu- our STANDARD ASSENOUNG facturers. If so you can apply them to COMPANY fully assembled unwit'ed instruments or you 19 BNIPCe Si.. N.v. AEAIAI INcuc, can wire in accordance with blueprints of the best circuits. Such prints are supplied with each of our instruments. By doing this part of your work you can have machine made instruments quite as cheaply as you could purchase panels, parts and have the larger drilling and engraving done. Front View Back View wired and tested, the Our radiophone illustrated here consists of tube receptacles, engraved bakelite panel. Completely modulation transformer, indicating meter, price is $i5o including cabinet. Unwired but exactly control rheostats, are included. key switches, wave switch, triple coil variocoupler, micro- as illustrated $So. No tubes or batteries -finished instruments, 6 volt to 500 volt transformer and other neces- Details on our other finished and semi phone, ICW Receivers, sary equipment for a CW telegraph or which include Regenerative Jewellers' Receiv- telephone transmitter and an ICW tele- Model 1 Radiophone Detectors, Amplifiers, graph transmitter. The equipment is of (as illustrated) ers, Utility Receivers, etc., will be sent an In cabinet, without tubes, $150 you on receipt of stamp. the best quality neatly assembled on Unwired and without tubes.. 80

STANDARD ASSEMBLING CO., 19 Bridge Street, NEW YORK CITY

THE TURNEY SPIDER - Illustration WEB INDUCTANCE shores front A compact, efficient short wave of cabinet removed coil set Patent Pending Dimensions, IMF 4'/z x 5 13/

l Iule., (5400 Price Now $8.00 1cters The Best $8.00 Worth of Radio You Ever Saw. WHAT WE CLAIM- Practically no magnetic leakage, which means more mutual inductance and stronger signals. Less distributed capacity than any form of 2 lattice winding which means finer tuning. Occupies much less space than any other 3 form of winding.

PACIFIC COAST AGENTS HERROLD LABORATORIES SAN JOSE CALIF.

Ask Your Dealer to Show You ONE or send us $8.00 plus postage and we will ship same day order is received. RADIO MES, LÁbOratories,lnc. NEW YORK

www.americanradiohistory.com 742 Radio News for April, 1921

sary apparatus connected to the horn which projects from the box. This is actually a HERE'S GOOD NEWS! satisfactory receiving set for demonstration and other purposes. It suggests the possibilities of the future. Radio sets of small enough size to use in any ordinary room or in moving vehicles can easily be made even now. By means of electron tubes, radio telefone messages were successfully transmitted five years ago over a distance of 5,000 miles. Concerts are already being sent out by radio and are receivable by anyone who has an ordinary receiving set. This result has been accomplisht by patient research, RED - HEAD N $000 scientific study and progressive engineering. RADIO PHONES w Wpp,p In Bellamy's "Looking Backward" describing conditions 1921 Model 3000 Ohms in the year 2,000 an arrange- Incomparably ment is the World's Greatest Phone Value, described by which people receive Guaranteed identically the same head -set as music in their houses any time desired by previously sold for $12.50. Increased production :'/%%////%///O////%% simply connecting a certain electrical in- and decreased manufacturing costs make the % strument. In this particular the dreams of new low price possible, j EXQUISITELY SENSITIVE the prophet have been anticipated by eighty i RUGGED /!//%iY///iY/ years. AND STURDY iii/1 Aluminum backs, military type head -band, Bake- IT is just as easy lite ear caps, strain loops and posts, extra thin to specify diaphragm, superb workmanship, beautiful ap- "Corwins" when buying pearance, 3,000 ohms resistance -these are a few dials, of the features which have made Red -Heads a and it implies that Two -Step Audiotron triumph in radio phone building. you have quality appar- Amplifier Send us $8.00 for Red -Heads today. You take atus no risk. If Red -Heads do not satisfy we will throughout. Dealers (Continued refund your money. 3 from page 702) acquire respect for those EIGHT DOLLARS, COMPLETE, PREPAID who specify good Furnished with braid covered military type or genuine makes of phosphor -bronze split head -band. Illustration shows radio goods. tery binding posts have been placed suffi- phosphor- bronze type. ciently far apart to eliminate all possible Price subject to change without notice. 3" Dial, 75c-with knob, $1.30 Be sure to stock the new Red Head Phones. chance of causing a short circuit. In the DEALERS Be prepared for the big demand, 3h" Dial, $1.00 -with knob, $1.70 mounting of the apparatus the utmost THE NEWMAN At all Radisco agencies, care should be taken all -STERN CO. and other reliable dealers, that connections Newman -Stern Bldg. Cleveland, O. or sent postpaid anywhere are made as per drawing. If they are Write for Free Catalogue. not, the experimenter is storing up a lot A. H. CORWIN & CO. of trouble for himself in the future when 4 West Park St., Newark, N. J. he least expects it. As will also be noted The Smallest on Fig. No. I, this is essentially two audiotron detector circuits connected in Audion Control cascade by the means of using a one to one step iron core coil with a high re- Panel Made sistance, or in other words an auto transformer. No. A0 -5. Equipped with a socket. rheostat, eight A %" or %" spark coil would do the binding posts and a grid trick very nicely, but only the secondary of leak condenser mounted on a hand engraved hard the coil should be used and care should rubber panel. size 4,/z" x 2'',4 ". Price $6.50 be taken to see that the vibrator is At your nearest dealer or screwed down firmly to the core. Of from the course, if a person has the means of removing the primary of the spark coil WORTH RADIO CO. without injury to the secondary, he can 1843 East 12th St. BROOKLYN, N. Y. readily do so, but it is not absolutely necessary that this be done. If it is not done, one should not forget to leave Grid Condensers Selling the primary leads open. This is abso- Like Hot Cakes THE RHEOSOC lutely necessary. As a matter of fact, most any winding an Combination Rheostat and Socket. with iron core Prepaid Prepaid For back panel mounting. having a resistance of between 6,000 and 25 cents 25 cents BAKELITE throughout. 7,000 ohms will do very well. Type A 9 ohm 1.2 Amp. The two audiotron vacuum tubes Hermetically 100% Type B 6 ohm 1.8 Amp. Price $2.50 should be adjusted, as in the case of using Sealed Efficiency With Radiotron 11V200, $7. the audiotron vacuum tube detector, thereby getting the maximum Prices must go down. We are the first Postage EXTRA- Loose -Leaf Catalog Sc sensitive- to start the ball rolling. Selling these ness. After the outfit is once adjusted, condensers faster than we can turn them A. K. LAING, RADIO SUPPLIES there will be no further need of adjust- out. Everybody satisfied. Pelham Manor, N.Y. ment which will, of course, save a considerable amount of time. Crescent City Radio Company The reader can purchase a one to one P. O. Box 1104 New Orleans, La. step two circuit iron core coupling transformer, which will permit the use of the one battery for the lighting of the two Battery Charging Pais WHO filaments on the audiotron vacuum tubes. 51500 to 53000 a Year D \. Such a transformer can be readily pur- GET AN 113 CHARGER Small each payment starts yo,, in big, MASTERED CONTINENTAL chased at a small cost at most any of eses chrcharging ging business. Longa the reliable Radio supply houses. By on balance. Money-back CODE IN ONE HOUR BY guarantee. Write TODAY for r liberal prop "timon. having one of these transformers, the HOBART BROTHERS COMPANY USING DODGE SHORT Box N47, Troy, Chia cost on the lighting of the filaments j _:._, CUT 50 CENT within the two audiotron vacuum Small Cash Pagment-Balance` Easy Terms METHOD tubes can be saved. The experimenter is ready to do the wiring on the back of the panel. Par- WHO ticular attention should be paid to the SHELLAC wiring and hook -ups as shown in Fig. Ask DODGE, Box 200 2. I would suggest that No. 16 rubber Red Triangle Brand covered wire be used on the panel wir- For Radio Work - 50e, 14 pt., Post Pd. Mamaroneck, N. Y. ing, and have the wiring bridged. Also Shellac Co. of New York (Continued on page 744) Agents Wanted 30 Park Place, N. Y.

www.americanradiohistory.com 743 Radio News for April, 1921

' `HE RAD It MA NAV( X

THE RADIO MAGNAVOX when used with a suitable amplifier, will give forth signals of far greater volume than any other receiver and radiophone music may be used for dancing. THE RADIO MAGNAVOX does away with a continuous watch, allowing the operator to hear what is going on at his station while in another part of the house. THE RADIO MAGNAVOX is manufactured under the same patents and on the same electrodynamic principle as the Magnavox Radio Tele- megafone, and will reproduce signals with the same volume. THE RADIO MAGNAVOX is supplied without means of varying the field current. If six volts from a storage or dry battery are applied to the field windings the field becomes saturated and maximum reproduc- tion is obtained. It is not necessary that the field be saturated for the reception of the average Radio signals. Therefore, we recommend that a variable resistance be placed in the field circuit and no more current be used than is necessary to hear the signals at a good volume. This rheostat may be approximately 8 to 12 ohms resistance, resembling a vacuum tube filament resistance. Price $45 at your Dealers If he cannot supply you send remittance direct to the Magnavox Company, Oakland, California and receive prompt shipment There is still opportunity for more live radio dealers to handle this line, as well as our transmitter tone arm and hand transmitter for Radiofones.

SPEAKING OF SOCKETS "SERVIMUS " When our Government with all its experience and unlimited facilities, sets to work designing a piece of radio apparatus, you can be certain that said piece of apparatus is the last word. Such is the case with our single, double and triple vacuum tube sockets. They Type WI -182A Socket are "EVENTUAL" apparatus. Each socket has a spun aluminum shell that is accurately machined; the tubes fit snugly but do not have to be forced into of filament terminals coming in contact with the spring contactors ; and there is no danger the contact with the high voltage of the plate battery. Several features at once distinguish this socket from the many inferior devices now on the market. Type 18íA Single "Eventual" Socket. Price $2.00 Type 182A Double "Eventual" Socket. Price 3.90 Type 183A Triple "Eventual" Socket. Price 5.8o Bulletin IoR describing the above and other WICONY "EVENTUAL" apparatus will be sent you on receipt of five cents in stamps. Dealers -deal with us. Amateurs -deal with your dealer. Sole Distributors for Wicony Complete Line Pacent Plugs Standard VT Batteries Dubilier Condensers Rawson Meters Seibt Condensers Special Distributors of Brandes Headsets. PACENT ELECTRIC COMPANY, Inc. LOUIS GERARD PACENT, President 150 NASSAU STREET Telephone Beekman 5810 NEW YORK CITY

www.americanradiohistory.com 744 Radio News for April, 1921

(Continued page from 742) t11111111111111111111111111111111111111 I I 1111 l f l l I f 11. PLATE BATTERIES! have the wiring kept from resting on Give Your Bulb a Chance! the back of the panel. This can be done by giving the covering on the wire a Economy Radioplate Batteries are coat of some good Ú MARK'S= insulating compound UTICA1áCADFMY genuine lighting flashlight batteries and letting it stand until is soldered it it dry. A together with 1/4-inch brass good method of placing this wiring is to SÇHOOL= strip connectors which also serve as plot out the different wires and the way OI taps. We are proud of having put this you would like to have them run. Cut battery on the market. It represents and peel them to the required sizes, and NEW YORK BOSTON our effort to give you Maximum then put the compound on them, and Battery Quality just Offers a thorough course in for your money. before they are dried, bound them into all branches of wireless teleg- Two sizes. you know best if you need the shape desired. Now, that the ama- raphy. Radio Operators earn either or both. teur has advanced so far, he has prefer- at the start 3125.00 per month, and first class board, etc., free. Ersco No. 503 22% Volts, Price $2.00 ence as to the mounting of the panel assembly complete upon the Our school prepares you for Ersco No. 803 36 Volts, Price $3.20 brackets or your license in three to four Made for Long Life making a cabinet and securing the panel months. Positions and Heavy Duty. upon guaranteed "Always Something Doing" with the front of the cabinet by means to first grade licensed opera- Ersco Batteries on of a number of wood screws. If he de- tors. your plate. cides Day and evening classes. Don't forget our Black Fiber Panels. to use brackets, I will explain how they are made. These brackets are made The leading Nautical School in Paragon size 7 x 20 x % inches, price of W" angle irons and drilled so to U. S. A. Established 0804. $6.00 or cut to any reasonable size at as allow 2% cents per for the passing thru of four machine screws, CAPTAIN F. E. UTTMARK, Principal square inch. two to a side from the Make a one -step front of the panel, amplifier complete for and having a nut fasten the Write, call or phone for illustrated $22. You need I onto back, thus Paragon Moulded VT holding the panel firmly upon the brackets booklet. Control Panel (has socket, rheostat, itself. These screws grid condenser and leak can be four machine all on a base screws, 4" in diameter, and 1" in 8 STATE ST., NEW YORK, N. Y. about 5 3 length, by inches), price $6; r VT, with whatever thread the experimenter price $7; I Facing Battery Park. N. P. amplifying transformer, desires. That is price $5; left to his own judg- and 2 Ersco Radioplate Bat- ment. To mount the in Telephone, Bowling Green 8079 teries No. 503, price panel cabinet $4. Total $22. form, procure a sufficient amount of oak We will supply these parts separ- wood to make a cabinet sufficiently large UTTMARK'S for Nautical Education ately or altogether at the prices enough listed. on the outside so that the panel can be 9111111111111IIII11111I1111I1111IlllIItI11111I1111IIIrr Ire ship parcel post paid anywhere mounted firmly and set snugly rn the United States. upon the front of the cabinet. Make the Mail orders should be accompanied cabinet large enough to place the "B" by remittance. Reference, Mer- batteries in the back of it; also make a LOOK AT THIS chants and Manufacturers Nation- cover to set on the AUTOMATIC FILAMENT CONTROL. al Bank, Newark, N. J. front of the panel Three jacks for the automatic control of assembly. which will cover the whole detector and two stages of amplification ECONOMY RADIO SUPPLIES CO. outfit and keep dust or dirt from getting or any combination of three tubes. Great- 232 Sanford Street East Orange, N. J. on the instruments. est convenience yet. big saver of battery. Complete with blue print of connections "Always Something Doing" It will also give the amplifier a much and plug. Limited quantity. Post paid neater appearance and it will be easier to $5,00. handle. PHONE CORDS. One of the best cords The binding posts can be either copper you have ever used. Closely woven over or brass and rubber insulation. Regular government there are twenty -six of them. standard. Our price while they last, BACK TO OLD PRICES They are I 4" in length and ?/" in diam- 50c post paid. Specify style tips wanted, eter. The thread size is left to the build- regular, spade or for W. E. Fones, or ers judgment. is mention fone used. PARKIN RHEOSTAT It advisable to use plain brass washers on the front and the FAHNESTOCK CONNECTOR BLOCK. back of the panel. For connecting fones to tuner. Mounted 5000 sold last year The on Bakelite block 17,4 by 2t;" which at $1.00 potentiometers used have a re- can be screwed on the table. This block sistance of 400 ohms and are the kind that insures good firm positive contact at all are mounted times which is quickly and easily made. NOW REDUCED TO on the back of the panel. Specially priced at 25c post It is also advisable paid. to have spacers go STANDARD PLUGS, These plugs fit the over the screws that hold the poten- jacks usually used for connecting fones 75c tiometers to the back of the panel to to detector and amplifier units or various keep the potentiometers from coming in other circuits. Price 50c. contact with the panel proper. There CHICAGO RADIO SHOP Due to the general drop in the prices of should be a pointer 326 River Street Chicago, 111. raw material and to our large production, and scale to go with we have been able to reduce all our prices each one of these potentiometers and the to their pre -war level, and in some cases scales can be either brass or celluloid even lower. with readings up to i8o degrees. New Catalog No. 5, listing our complete The rheostats can be of the ordinary Miniature line, sent free. battery kind Here are a few of the items: with a resistance of from No. Postpaid to to 15 ohms. They are mounted as Rheostat 31 Audion panel with rheostat and B shown in Fig. 1. battery switch $3.00 The filament 43 45 volt large B battery 5.00 control switches are for 50 PARKIN .001 mf. variable conden- the purpose of burning either filament of Something ser, unit only 1.50 the audiotron vacuum tube. The con- 51 PARKIN .001 mf. V.C. with knob tacts of these filament control switches New for and pointer 2.00 are 1%" 52 PARKIN .001 mf. V.C. with knob long with a head on them %" and 3" dial 2.50 in diameter and %" long. There are six 53 PARKIN molded bakelite fixed contacts in all. The switch blade knobs $1.25 condenser .70 are I%" in UV 200 New Radiotron vacuum tube 5.00 diameter and 1%" in length, made of a composition of rubber with a Detroit Radio Laboratories, Inc. DEALERS-If you are not on our mailing shank I%" long, list, write for new catalog and discounts. and %" in diameter. 3661 Gratiot Ave. DETROIT, MICH. They may be either copper or brass. The PARKIN MFG. CO., San Rafael, Calif end of this shank is threaded and has a nut fastened onto it, which holds it fast to the back of the panel. The switches TELEGRAPHY swing in a radius of x% ". Two small (Both Morse and Wireless, and RAILWAY ACCOUNTING nails can taught thoroughly and quickly. Big salames now paid A COMPLETE TUNER be used as switch stops so that Great opportunities for advancement. Oldest and largest the switch blades achool established 46 years. Endorsed by Telegraph, Rail and Audion Detector that gets everything from 150 to won't run off the switch way. Radio, and Government officials. Expenses low 000 meters. All enclosed in walnut finished cabinet contacts. opportunities to earn large portion. Catalog free. with bakelite 40 panel and colt B. battery. MIDGE'S Price $35.00 Little copper terminals should be sol- INSTITUTE D Street. Valaenme.eee. VARIABLE B. BATTERIES dered to the five leads on the - 22V, volt $2.50 45 volt 55.00 two audio a., 3.500 -meter loose couplers $9.00 up tron vacuum tubes. This will eliminate PI EONS PAY y'a`Sef1 very little space Postage extra. Circular for stamp any possible chance of the tubes required. Build their own nests. ed their own getting yqung. Very business. Get your start Jeffery, Crawford Co., 2173 Hillger Ave., Detroit, Mich. loose from the binding posts, and falling rn few toga pairs. wTlte waxy ref Isu (Continued on page 755) Pigeon Supply House, Hanover. Pa. www.americanradiohistory.com Radio News for April, 1921 745

THE BENWOOD "SUPER" ROTARY DISC. again we have SOMETHING NEW

Lighter than the old style BENWOOD discs and yet has the same wide sparking surface. The teeth are longer and far more accurate than has ever been produced before. Co replete disc weighs only one -half pound when fully made up. Is of ample size for any i KW installation and yet is so light and evenly balanced that the smallest fractional high speed motor will run it with ease.

DIMENSIONS:- Diameter, 6 inches - width, 3 -4inch - weight, 1 -2 pound Is complete with black fibre center and heavy brass bushing with set screw for fastening to the motor shaft. This is the identical disc that is furnished with the New "SUPER BENWOOD" rotary quenched spark gap. As shown by the cut these discs are furnished in 4, 6, 8, 12 and i6 points at no extra charge, merely specify which type you desire. Drilled to fit any sized motor shaft, just designate the size of the shaft on your motor. Each bushing is drilled twice and then reamed to the size desired, thus assuring the purchaser of the utmost accuracy. ONLY $7.00 EACH Specify size of motor shaft. The Benwood Co., Inc., 1300 Olive St., St. Louis, Mo.

WANTED FOR CASH Used Radio Apparatus of AU Standard Makes Our used wireless apparatus department, connected with our local retail store at 233 Fulton Street, New York City, is anxious to buy any radio instruments you may have for sale. These goods are for our New York customers only-we sell no used radio apparatus by mail. But we do have a tremendous call at our store for fine class goods and we will be glad to hear from you if you have any that you would like to dispose of. WE PAY CASH for all such merchandise that we buy, and this If you have friends who wish to dispose of is an invitation extended to the radio fraternity such apparatus, show them this advertisement. to sell us their radio apparatus for which they Also please note that your letter must state in have no further use. Write us in your first let- just what condition the instruments are and ter what make apparatus you have to sell, and that no goods must be sent to us unless we send your lowest spot cash price. It must be under - you a written order to do so. stood that all transportation is to be paid for by We invite amateurs residing in New írork or you. All goods to be sent to us prepaid either vicinity to call at our store and inspect the used by parcelpost, express, or freight.- radio apparatus which will be placed on sale We can use only standard apparatus, no ob- shortly after this advertisement appears. scure instruments or home -made apparatus can be considered in any event. Address all letters to Used Apparatus Department ELECTRO IMPORTING COMPANY (Established 1904) 231 Fulton Street New York City

www.americanradiohistory.com Radio News for April, 1921 YOU JUST LISTEN AND LEARN Notes on Quenched . - -- 6 Gap Transmitters Double (Continued from page 689) MAGNET WIRE Faced MARCONI VICTOR 11111111,1111111111,1111111111111m,,,,,,,,,,iiii,,,,i,,,,i,,,,,,,,,,,, Rec- COURSE . We are prepared to furnish best ords, IN WIRELESS TELEGRAPHY sary, for the power 12 can be varied by vary- grade magnet wire on % and % lb. Will give you the practice ing the number of gaps in Les- in code work you need to use. (Specific- spools at the following revised sons, get a high rating when you ally the power varies as the square of the prices: With go up for exams. number of gaps, for it varies as the square In- Just what you need to of the condenser voltage, PRICE % struc - and the voltage PER LB. SPOOL develop your speed in re- used varies tion ceiving. Everything cov- approximately as the number of Single Double Single Man- ered from alphabet to Press gaps.) For low power the gap short -cir- B &SGa. Cotton Cotton Silk Enameled ual, with interference and ten cuiting device is useful, and it might be so No. 22 $0.56 $0.68 $0.62 $0.45 Price letter code words. designed in the radio No. 24 .60 .77 .67 .47 $6.00 "They're set, that it automatically inserts the necessary amount re- No. 26 .65 .88 .71 .49 great." of No. 28 .75 1.10 .85 .52 actance in the primary of the transformer No. 30 .85 1.24 .97 .53 to reduce the secondary sparking voltage. No. 32 1.15 ,55 Finally gaps should be designed with a No. 34 1.52 .59 view to easy assembly. The writer has seen No, 36 1,77 .69 gaps designed where the surfaces were as- Price on .4 lb. spools double above list. sembled by bolting together with five or six All prices are net and include cost of bolts passing thru holes which had to be spool and delivery charges via Parcel fitted Post to any Post Office address in the with an equal number of fibre sepa- United States; safe delivery guaranteed. rators ! One bolt for each gap with one insulator is quite sufficient. Send for Circular 21 -A giving prices on other sizes, insulations and quantities of Magnet Wire. This circular lists "WIRE FOR EVERY WIRELESS PUR- Conduction of Electrici- POSE." tY Thru Vacuum Send and KEYSTONE WIRE COMPANY for our book Gases With Applica- P. 0. Box 120 SCRANTON, PA. catalog. tions to Design of WIRELESS PRESS, Inc. Radio Apparatus 326a Broadway NEW YORK (Continued from page 694) ,,,,,,,,,,,,,,,,,,,,,,,,,,.,,,.,,,,,,,,,,11,,,,,,,1,,,,,,,,,,,,,1,1,1,,,,,,,,,,,,,,,,,,,,,,, M ,,, .,,,,,.,,,,,,,,,,,,_ Canadian Amateurs both signs are present at the metal surface. If two platinum electrodes are immersed BUY in CANADA and save $$$$$$ SIXES & SEVENS in a vessel containing gas and heated to a red, Here are a few additions to our Save time and freight by getting your ap- bright current from a battery will pass paratus from us. We carry full AMRAD between them. If now a cold metal plate stock Variometers and V ariocoup- and RADISCO stocks. Order from theft be placed between the two hot ones, the catalogs. Also DeFOREST. TRESCO, lers. MURDOCK, THORADSON current will be completely stopt and will and others. not recommence until the middle plate Transmitters for Wireless Tele- A -P Amplifier Tubes $7.00 reaches A -P Detector Tubes 6.00 the ionizing temperature. The rea- phone $2.50 Federal Transformers 7.50 son for this is that the cold plate dis- Transmitters, Spoon type 7.25 Tube Bases 1.00 charges the ions that were carrying the Grid Condensers .30 current and continues to do so until it gets Rheostats 1.50 Brown's Famous Receivers 2 -Stage Amplifiers 40.00 hot enough to form ions itself. 45 -Volt B Batteries 5.00 TEE ELECTRIC SPARK, 4000 Ohm with cord $19.25 8000 Ohm with cord 20.5o NORTHWEST RADIO'SERVICE CO. When a small potential difference is im- 6og Fourth Ave., Seattle, Wash. presst on two electrodes in air a very small Shipping weight 2 lbs. current will flow which will be proportional Send for our list .05c to the voltage. As the voltage is increased The Midget "FIVE-IN-ONE" Slide Role the current will increase in proportion THE VIMY SUPPLY is a combination Mannheim, Log - for CO. Log, Add and Subtract, Polyphase a short while only, and then will assume 567 College Street TORONTO, and Binary Slide Rule. It will ONT. instantly add, subtract, multiply nearly a steady value over a wide range of and divide any combination in- voltage changes. volving whole numbers, fractions, This steady value, A in decimals and mixed numbers. Fig. 1, is the saturation current. As the Gives every possible root and voltage r('C. power of every quantity. The is still further increased, a point graduations are printed on metal is reached at which the current again be- W. APPARATUS coated with white celluloid and gins to rise, at first are grease and waterproof. While slowly, then very rap- We have for immediate shipment a complete it is the most versatile calculator idly as the sparking voltage is reached. line of C. W. Apparatus and parts. If you are ever invented, its operation is simple and easily under- in the market for any type of Radio Apparatus stood. Diameter 4 ". The saturation current is the value of cur- you should have our Bulletin No. 12. Price with 16 -page Instruction Book, $1.50. Leather- rent when all of the ions in the field be- Carbon Grain Transmitters very best, ette carrying case 50e extra. Catalog free. nickel plated - $1.45 money tween the two electrodes are acting as car- Power Tubes-Radiotron U.V. 202, you a °°°` Gilson Slide Role Co., Price 8.00 are not satisfied. Niles, Mish. riers. Then in order that the current may Modulation Transformers Price 4.40 I and 2 Mfd. Condensers Price 1.23 increase past point A, Fig. 1, additional C. W. Transformer Core for making your own C. W. H. P.,110 volts, ions Transformer -250 Watt Size I must be created is some way. This Price 5.95 A. C., 60 cycle, is accounted for as follows. We can quote prices on any special apparatus. single phase, As the voltage between the two electrodes increases, Send 2 red stamps for our complete 4 1750 R. P. M. ÖRS the force acting to attract the ions in the list of Radio Apparatus LARGE QUANTITIES NEW WASHING MACHINE MOTORS field increases correspondingly, and the EASTERN RADIO & ELECTRIC CO. ions travel with greater speed toward the 1405 Florida Avenue Washington, D. C. M.ilS5Nw11wM"e,v1e. electrodes. When they collide with other .75 ions Each and molecules while on their way to J 2 the electrodes, greater forces take place in the CHAS. H. JOHNSTON -fV Bei lO W. E,PiUsburgb, Ps, collisions and new ions are formed, the number of new ions increasing with For Various Reasons - the voltage. Finally with large voltage their speed becomes so great as to result in al- P articular RADIO CLUB PINS most a complete breakdown of all the mole- R adio cules in the field. At this stage the spark A mateur Special folder of designs and prices - B passes. C in addition to regular school pin and The sparking voltage, ustomers ring catalog free on request. Be sure which is defined O rder from to see these new numbers which will as the lowest voltage that will cause a us. put new life in your club spark to pass between two given electrodes, PENN RADIO APPARATUS CO., Inc. Metal Arts Co Dept. il, Rochester, N. Y. depends upon many factors, among them Box 110 Reading, Pa, being the shape of the electrodes, the dis- www.americanradiohistory.com Radio News for April, 1921 747 Another Grebe Triumph! 150 -3000 Meters After much experimental work, we have succeeded in adopting the Arm- strong Regenerative circuit to a receiver having a wavelength range of 150 -3000

meters. The result is the .

TYPE CR -5 REGENERATIVE RECEIVER This is a complete receiver. The only additional equipment needed are 'phones, batteries and a detector tube. Included in its range are amateur, navy and corn merciai wave -lengths, special land stations, ship CvV stations, navy low -wave arcs, all radio 'phone work and "Time." In operation, it is the last word in simplicity. Ask to see it at your dealers' today. GREBE RADIO apparatus is licensed under the original Armstrong and Marconi patents. Bunnell & Co., J. H., New York City. Kelly and Phillips, Brooklyn, N. Y. Central Radio Institute, Independence, Mo. Klaus Radio Company, Eureka, Ill. Continental Radio and Electric Corp., New York. Manhattan Electrical Supply Co., New York, Chicago, St. Louis. Detroit Electric Co., Detroit, Mich. Leo. J. Meyberg Co., San Francisco, Cal. Doubleday -Hill Electric Co., Pittsburgh, Pa. Newman -Stern Co.,, Cleveland, Ohio. Electrical Specialty Co., Columbus, Ohio. F. D. Pitts Co., Inc., Boston, Mass. Bolt Electric Utilities Co., Jacksonville, Fla. Philadelphia School of Wireless Telegraphy, Phladelphia, Pa. Hurlburt Still Electrical Co., Houston, Texas. Western Radio Electric Co., Los Angeles, Cal. A. H. GREBE & CO., Inc., 72 Van Wyck Blvd., Richmond Hill, N. Y.

" SHRAMCO SPECIALTIES " Large Stock Immediate Shipment No. 90- Shramco Reo, 6 ohm, Panel Type Rheostat, each $2.00 602 No. 60- Shramco Oscillation Transformer, with four shielded clips, each 10.00 No. 61- Shramco Shielded Oscillation Transformer Clip, each .30 BRASS SWITCH POINTS Doz. 50 100 No. 626 -1/2" dia. x %" high, with brass screw $ .30 $1.10 $2.00 No. 627-1/2" dia. x /" high, with 1" threaded shank fitted wth nut and washer .36 1.25 2.25 No. 628 -1/2" dia, x /" high, with brass screw .30 1.00 1.75 No. 630 -1/2" dia. x %" high, with yz" threaded shank fitted with nut and washer .36 1.25 2.25 COMPOSITION KNOBS-We Carry 15 Other Styles Ea. Doz. No. 602-1" dia. with 8 -32 brass bushing $ .08 $ .85 No. 618 -1" dia, with 8 -32 brass shank 1" long .10 1.10 No. 606-11/2" dia. as used on No. 750 Switch .15 1.65 7H BINDING POSTS No. 800-Panel Type, complete as shown .10 1.10 No. 600-1/2" Brass Type with brass screw and washer .00 .65 PANEL SWITCHES Each No. 750-Bushing Type, 11/2" Radius as shown, each .75 No. 751 -Brass Finish, 1h" Radius, each 40 No. 530 -N, P. Finish, bushing type, 1" Radius, each .60 800 VACUUM TUBES, ETC. No, 180-Electron Relay Detector Tube, each 6.00 No. 181- Moorehead Amplifier Tube, each 7.00 [-:;) No. 165 -V, T. Socket for 4 -prong base tubes, each 1.00 [ij No. 101 Leak and Grid Condenser combined, each .50 i -Grid 628 626 627 No, 102 -Grid Condenser, .0005 Mfd each .35 Postage on above extra. Send 5c in stamps for our Catalog K showing complete line of high grade apparatus. SHOTTON RADIO MANUFACTURING CO. SCRANTON, PENNSYLVANIA 191

www.americanradiohistory.com 748 Radio News for April, 1921

tance between the electrodes, the atmos- pheric pressure, the humidity or amount LOOK AT THIS of moisture in the air, and the amount of light that is admitted to the sparking space. The sharper the electrodes the lower the RHAMSTINE * sparking voltage. The sparking voltage varies almost directly as the pressure, and the Radio Products IN1XIç° sparking voltage increases with the distance between the electrodes, altho the relation is not a linear one. Sparks will pass COIL at a lower voltage in daylight than in the - MOUNTINGS (Pat. applied for.) dark. This is because the light helps some Cheapest-®u ickest Simplest --Durable -Anti- in creating ions. C'apacity-No Moving Parts-Adjustable Coils Whenever a spark passes between two Locked in Place-No Wires. Solves the lattice coil problem for amateurs. electrodes it is accompanied by a loud Coils changed in half time. crackling sound. This sound Coils lock in mounting when swung to vary is due to the coupling. Handle on coil strap provides most pressure of the spark. The ions in the field PLUG. and JACK convenient means of operating coils. of AS metal parts brass nickel plated; Formica the electrodes acquire considerable ki- Complete - $1.50 Postage - 4c panel, hardwood base. netic energy. Pressure is proportional to PLUG ONLY, 75e; JACK 85c WRITE FOR PARTICULARS the kinetic energy per unit volume. The ONLY, Table Type Mounting $8.00 actual volume of the spark is very small, Ask your dealer for this high- grade, Panel Type Mounting 6.00 so that the ratio of kinetic energy to vol- nickel plated plug and jack. Cords Plug Complete with Handle and strap.. .70 ume will be high, and therefore the pres- easily attached to plug connection. Con- Above does not include coils. Plugs fit sure. Pressures of over too atmospheres tacts automatically connect transformer. only WIXICO Mounting but are sold Eliminates binding posts and switches. separately if desired. have been measured in some sparks in air. If your dealer cannot supply you, order direct. Immediate shipment. Discount to Dealers. Ideal Portable Aerial DEALERS WANTED EVERYWHERE for Vacationists J. THOS. RHAMSTINE* (Continued from page 703) 2152 E. Lamed St. Detroit, Mich. R. C. wire and running the latter length to the set. *Radio Plugs and Jacks. This aerial, designed by the writer, was used with great success for several years by the Albany Signal Corps and it can be unpackt, joined, hoisted and the set attached ready for use in three minutes. Dismantling is equally easy, consisting of BAKELITE disconnecting the set, unfastening the hoist - CUT THE ing rope, letting down the top sections, loosening the guy ropes, unsnapping the SIZE YOU WANT IT THE AMOLECCO CO. ropes, unscrewing the wing nut and slip- ping off the brass collars, " thick 2c per sq. inch CINCINNATI, O. pulling section 2 ,î;" thick 3c per sq. inch from l and 4 from 3, coiling ropes and %" thick 4c per sq. inch wires and strapping sections together. Of example: 6X10X2c = 60" X 3c = $1.80 all the portable aerials I have tried, I con- postpaid. sider this "the only one" for its practicabil- Send for price list of all ity and general utility. I recommend it to Radio Supplies & Parts the trial of all enthusiastic radio vacation - Agents for Grebe, Bunnell, Federal, ists. Acme, Murdock, etc. DETROIT ELECTRIC CO. (Est.1886) Continuous Wave 434 Shelby St., Detroit, Mich. Multi -Stage Receiving Circuits (Continued from page 690) the third V.T. The beats produced are RADIOTRONS! rectified by DUPLEX the last valve, whose filament The EFFICIENT vacuum tubes. De- SENDING GAP RECEIVING current may be independently varied by signed specifically for the amateur. They means Ra. give unusual results in standard amateur An air tight micrometer gap which makes of regenerative it possible to "Break" as on a land telegraph Various modifications of this circuit are circuits. wire. You can hear the man you are work- Radiotron U.V. 200 (Detector and ing with through your own sending, Abso- possible. For example, the condenser C3 amplifier) $5.00 lutely safe and automatic -no relays on con- may be connected across R, if desired. In- Radiotron U.V. 201 (Pliotron type) 6,50 tacts. Just the thing for remote control itial tuning -in to signals may be facilitated To get RESULTS that COUNT you system. Full instructions. Price $6.00. Add by making the first V.T. oscillate and ad- should use the new RADIOTRONS. We postage for 1 lb. Request Bulletin 109, can make immediate shipment. which describes this instrument. justing C1 and L, till the beat note is heard F. M. Doolittle Co. the coupling between R, and the inductance Independent Radio Supply Co. 817 Chapel Street in the anode circuit of the second valve is 1426 S. Clifton Pk. Ave Chicago, Ill, New Haven, Conn. made less than that required for self- oscil- Write for Particulars on the New lation. Transmitting Tubes The second figure shows a four -valve re- Franklin "A" Battery ANNOUNCEMENT ANNOUNCEMENT 60 Amp. Hour $12.50 3 Year Guarantee H. F. PARKER & CO. THE KARLOWA RADIO CORP. Baltimore Maryland STOCK ROOMS, 5TH FLOOR BEST BLDG. MAIN OFFICE, 611 BEST BLDG., ROCK ISLAND, ILL.

Announcing Used APPARATUS DEPT. HAS PURCHASED THE ENTIRE RADIO BUSINESS OF Write for cur complete list of bargains in new THE YOUNG & McCOMBS CO., OF ROCK apparatus as well as used apparatus. Absolutely ISLAND, ILL. everything from crystal sets to complete C -W phone The new organization solicits your orders as they have heretofore been placed with the old company. A transmitters, including bulbs, batteries, sockets, new catalog is in preparation, and until it is issued, you are requested to make your selections from Catalog B rheostats, grid condensers. and Supplements of the former Young & McCombs Co. Immediate deliveries are guaranteed on all Items. Address Write for particulars. all orders and correspondence to WESTCHESTER RADIO SERVICE THE KARLOWA RADIO CORPORATION 253 SO. B'WAY YONKERS, NEW YORK 611 BEST BUILDING ROCK ISLAND, ILL.

www.americanradiohistory.com Radio News for April, 1921 749

STOP! LOOK! and ACT / A Pliotron V.T. Amplifier, U.V. 201, $6.50, or an A.P Navy F°R Type V.T. Amplifier, $7.00, will be given FREE with each Radio Magnavox purchased from us, not later than June 30th. THE RADIO MAGNAVOX The latest development of the Magnavox Company THE RADIO MAGNAVOX THE RADIO MAGNAVOX when used with a suitable amplifier will is manufactured under the same patents give forth signals of far greater volume and on the same electrodynamic prin- than any other receiver. ciple as the MAGNAVOX Radio Tele- megaf one. THE RADIO MAGNAVOX will allow you to have your friends THE RADIO MAGNAVOX listen to all incoming signals without will reproduce signals with the same the necessity for additional apparatus. volume as the Radio Telemegafone. THE RADIO MAGNAVOX THE RADIO MAGNAVOX will reproduce radiophone speech, or can be operated on 2, 3, or 4 dry cells music to such a degree that it may be with wonderful results. A six volt stor- used for dancing if sufficient amplifica- age battery with rheostat is recom- tion is available. mended for continuous operation. QST THE RADIO MAGNAVOX WDNT U LIKE TO HR SIGS does away with a continuous watch, al- QSA lowing the operator to hear what is go- ALL OVER YR HOUSE ? ing on at his station while in another The Price is within reach of all part of the house. You need it in your station. $45.00 THE KEHLER RADIO LABORATORIES Dept. R, ABILENE, KANSAS

NOTICE AMATEURS ! NOTICE Our entire stock of Radio Apparatus must be sold at once. io% flat slash in prices. First come first served. Order now if you wish to take advantage of this offer. Our stock is limited. Only orders accompanied by money orders honored. SOME OF THE NEW PRICES Transmitting Receiving Thordarson 1 K.W. transformer $40.50 C. R. L. Paragon regenerative $58.50 Thordarson % K.W. transformer 24.30 C. R. L.-A -G -N -2 94.50 Grebe C -R -2 regenerative 45.90 Thordarson % K.W. transformer 15.30 All other Grebe and Chicago Radio Lab. appara- Thordarson Oscillation xo.8o transformer tus at xo %o off List. Benwood super rotary gap 22.5o Deforest panel units io% off. Benwood Discs, 4- 8 -12 -16 point 7.20 Honey Comb Coils, any size, ro% off. Amrad 1 K.W. quenched gap 37.35 Deforest tube sockets 1.35 Amrad % K.W. quenched gap 22.05 Paragon rheostats 1.57 Amrad % K.W. quenched gap xo.8o Magnavox loud speaker, large size 99.00 Amrad r K.W. Resistance 9.00 Magnavox loud speaker, small size 81.00 Amrad % K.W. Resistance 5.85. A -P Electron Relay tubes 5.40 Amrad % K.W. Resistance A P V -T amplifier tubes 6.3o 2.7o A -P Transmitter tubes 6.75 r K.W. Dubilier mica condenser 40.50 Radiotrons U -V -too 4.50 K.W. Dubilier mica condenser 27.0o All types of Phones -Baldwin, Brownlie, Liberty, 1/4 K.W. Dubilier mica condenser x7.10 Brandies and Murdock, at 1o% off list price. If your wants are not listed here write us and we will give you prices on whatever you want. Everything goes at 10% discount

The American Radio Sales and Service Company GREAT AMERICAN BUILDING, MANSFIELD, OHIO

www.americanradiohistory.com 750 Radio News for April, 1921

ceiver, which works on the same principle as Fig. 7. The first valve lessens the resistance of the aerial circuit and reinforces BALDWIN PHONES the incoming continuous waves which are amplified by the first and second valves, heterodyned by the third and rectified by Special Reduction the fourth. An interesting feature of this The TJ. S. Nary, the British, French and sev- arrangement is that it as The eral other European Governments, in addition to acts a limiter. most professional operators, have adopted BALD - third valve produces oscillations of fixed WIN PHONES as their standard of electromag- netic receiver excellence. amplitude, so that incoming signals which The reason for this preference is apparent. Ex- are of greater amplitude (when they reach ceptional sensitiveness combined with ruggedness gives BALDWIN PHONES their popularity. The the third valve) than the oscillations taking diaphram is made of the finest Quality selected place mica with the force concentrated at the exact there will not produce signals in pro- center as in high grade phonograph reproducers. THE "ILLINOIS" VARIABLE CONDENSER portion to their amplitude. When the am- This feature is highly important in the reception plitude of radiophone music. The Condenser with "Star Spring" Tension of the local oscillations is greater The small armature is pivoted and designed to MADE RIGHT - STAYS RIGHT than the amplitude of the incoming oscil- act as a fulcrum when connected to the diaphram by a small link. There is no tension or spring- Hard Rolled Aluminum Plates lations, the signal strength is dependent on ing of metal as in ordinary receivers. Four pole the strength of the incoming oscillations. pieces of a single solenoid act upon both sides of These condensers are made by a watch me- a highly balanced armature. chanic schooled in accurate workmanship When, however, the local oscillations are Signals that cannot be heard with the best and who can't get over the habit of criti- signal is types of ordinary receivers become easily read- the weaker, the strength indepen- able with the BALDWIN PHONE'S. cal inspection. dent of the amplitude of the incoming oscil- Three Styles; No. 1, Panel; No. 2, Open lations. By taking advantage of this fact, Original Type "C" $15.50 Type as shown; No. 3, Fully Encased.. Anti - Regular Price 16.60 Profiteer. Less than pre -war, prices. Fully we can use the third valve as a limiting de- Improved Type "E" 19.00 assembled and tested. vice to prevent very strong signals from Regular Price 20,00 Style No. 1 No. 2 No. Money back U 3 not satisfEd. completely interfering with weaker ones. Lighter Type "F" 20.00 67 Plates, $7.00 j $ Just return con- Regular Price 21.00 43 3.50 4.50 4.75 denser within 10 23 2.75 3.75 4.00 days by insured All types are supplied with the standard Bald- 13 " 2.25 3.25 3.50 Parcel Post. win self - adjusting, self -locking headband which is most comfortable to wear. With Style No. 1, we wi 1, if desired, fur. The H. C. of L. and These BAT,T)WIN MICA DIAPHBAM AMPLI- nish 3 inch Dial with', large knob, instead FYLNO TIIT.EPHONES, which are shipped direct of Scale and Pointer. to us from John Firth & Co., Inc., are absolutely Burned Out Ampiifving guaranteed to prove fully satisfactory. Extra Price 75 cents. Sent Prepaid on Receipt of Price. Transformers The Kehler Radio Laboratories Except: Pacific States, Alaska, Hawaii, Phil- (Continued from page 697) ippines and Canal Zone, add 10e. Canada 901 West First St., Dept. R, Abilene, Kansas

add 25c. 1111111 111 1 1 1,11,,.111,.11111111111.,1111111111111.111111.1111111.,111111111111 1 1 11111 1 1,1, 11111 11111 lll,,, Foreign Orders other than Canada not so- licited. In closing I would like to add that one Kindly note: We issue no Catalog, and of my students thot the hook -up so satis- make no "trade discounts." We set our factory that he suggested I tell no one prices at the lowest limit, and leave the until he had had time fo go around and "middle man" out for the sole benefit of the "consumer." buy up all the otherwise. -useless amplifying in G. F. JOHNSON transformers the City of Honolulu! 625 Black Ave. Springfield, Ill. Radio Digest APPARATUS and SUPPLIES TUSKA C. W. INDUCTANCE (Continued from page zoo) III ,,,,1,,,,,,,,,1.,,,,,,11,,,,,,,1,,,,,1,,,,111,1,,,,1111,,,,1,1,,,11111,,,,,u11,,,,,,,,,,,,,,,,,,,,w,,,,,,16, ROSE RADIO SUPPLY Type 181 fore, comparatively low. If current is 604 Gravier St., New Orleans, La. Unmounted taken from the last of the condensers, it is Send 10c for Latest Catalog PRICE immediately recharged by the winding W. $5 and this takes place thru the agency of the other condenser; thus the sizes of the condensers vary, and the ones with the highest voltage are the smallest, and the LEARN WIRELESS one next the winding will be the largest. at the largest radio school In Fig. I it is assumed that high -voltage in the Central States. Modern complete equipment. valve tubes are used with cathodes which Experienced instructors. Dor- are heated with current from an external mitory In connection. Stu- dents may earn expenses if source. The heating terminals are shown necessary. Write today for Use a Tusk& O. W. Inductance in your R_ R catalogue and full informa- new tube set. Bend your tion. dealer's name CENTRAL RADIO and 5 cents for our illustrated C. W. SCHOOL Booklet. If2 Indepsndeeee. Me N THE C. D. TUSKA COMPANY HARTFORD, 3 - CONN. NECTIGUT RADIO EQUIPMENT Variable Condseners, Transmit- ters, Head Bands, Panel Announcing New Location Switches, Etc, Connecticut Tel. & Elec. Co Meriden, Conn. REYNOLDS RADIO SPECIALTY CO. a a ld b. The anodes are shown at A. 613 -19th STREET Oé course, any other kind of electric valve STANDARD RADIO EQUIPMENT DENVER, COLORADO can be used, if it is capable of withstand- AGENTS FOR ing the voltage, MURDOCK FEDERAL TEL. OUR NEW LOCATION WILL ENABLE or even mechanical com- BRANDES AMERICAN RADIO US TO CARRY A COMPLETE mutators. In the latter case we should BURGESS AUDIO TRON. STOCK GREBE CHICAGO RADIO LAB. OF THE LEADING MAKES OF RADIO have a number of rotating contact pieces, BENWOOD SPEC. DUBILIER GOODS. mounted on one spindle. This would be- DE- FOREST TRESCO AND OTHERS come somewhat U. of I. SUPPLY STORE, Inc. Inquire about our new Reynrad Short- similar to Delon's method, 627.29.31 SOUTH WRIGHT STREET wave Coils, tho it would be simpler, and would not CHAMPAIGN, ILLINOIS Enclose 6c in stamps for our Catalog and require such a high alternate- current volt- Bulletins. age. The advantage of the new system lies FOR ONE MONTH ONLY You can be quickly cured, if you specially in the low cost of the apparatus. In order to introduce the Radeq Control If a small amount is required, Panel to the Amateur, we offer these panels of current complete with tube and B battery for $15. the condensers can be small and cheap. Add parcel post charges for four pounds. STAMMER Leyden jars are quite sufficient. The valve Radio Equipment designed to use apparatus Bend 10 cents for 288 -page book on Stammering and tubes are not very expensive. The low you have on hand. Send specifications for Stuttering, `Its Cause and Cure." It tells how I estimate. cured myself after stammering 20 yrs. B. N. Bogue, voltage of the alternate current is a great 869 Bogue Bldg., 1147 N. III. St., Indianapolis. convenience. Under suitable conditions, A. C. PENFIELD Conneautville, Pa. www.americanradiohistory.com Radio News for April, 192.1 751

BALDWIN PHONES ELDREDGE METERS BROWNLIE PHONES More World's Records. Each one has hand -calibrated, individually - in signal Distinguished by Can be instantly adjusted for changes On Feb. 11 and 12, 5XB (Agricultural and engraved scale dimensions. strength and pitch. Adjustable feature makes Mechanical College of Texas), successfully sent their high polish nickel finish, unvarying accu- and selective of all racy over 25 years of service, and the rea- them the most sensitive radio -phone messages to 2ZL (J. O. Smith, of metal diaphragm telephones. Lynbrook, L. L) sonable prices. As usual. Baldwin Phones were on hand to bring in is directly under the the signals, strong, clear and true. First in H.D. Radio Frequency Ammeters Single solenoid core Selvage's 3300 spark reception, then in the trans- and Milli-ammeters $7.00 exact center of the diaphragm. Eight sensitive continental relay, Jan. 18, now in this 1000 mile radio- (Model Shown) springs for support, allow the diaphragm to phone reception, Baldys are demonstrating the super- Advance "Midget" Ammeters and Voltmet- vibrate thruout its entire area. sensitive action of their amplifying mechanism and 12 AC and DC, $8.00 genuine mica diaphragm. ers, ranges, weight, rugged, Model S-D, specially designed for 60 cycle One model, 2,000 ohms, light Original Type "C" $16.50 transformer primary circuits. equipped with Improved Baldwin type head- Improved Type "E" 20.00 band. Price $12.50. Type "F" 21.00 Voltmeters, $10.00; Ammeters, $9.50. Ask your dealer for booklets describing any of the above Fir h Specialties. If he lacks a supply write, mentioning his naine and address, direct to JOHN FIRTH & COMPANY, Inc., 18 Broadway, New York

Are You Getting Radio Phone Concerts? This Tuner Gets Them Fine This new Short Wave Regenerative Tuner when used with an audion or vacuum tube detector, a fixed condenser, a headset, and 75 ft. aerial brings in wonderful results from 200 -600 meter stations, including radio phone stations. This tuner has a variable primary, a variable secondary, and a variable tickler coil and has many tuning advantages not possible with fixed inductances. It is the biggest value ever offered for only $18.00. Finished in quartered oak cabinet and hard rubber panel. It is very selective and efficient. It does not require a variable condenser for 200 meter stations, while many other tuners require two and three variable condensers for best results. Lyle Halstead, R.D. 5, Auburn, N. Y., says: "I am getting fine Can You Hear POZ, YN and the Other Big Stations? results from amateur, commercial and radio phone stations with only one audion detector. Your Short Wave Tuner does all you it and more." Can You Tune Out the Unwanted Stations ? claim for This Long Wave Regenerative Tuner is in a class by itself. The amplifi- $34.50 cation of signals is wonderful. It brings in Arlington time signals as clear as a whistle. Its tuning range includes all of the big trans -Atlantic stations and it gets them too. The peculiar construction and placing of the inductances and couplings enable you to tune in the station you want to read, without interference from other stations. Price in quartered oak cabinet...... $34.50 Price with hard rubber panel...... 40.00 Mr. Carl Woese, President of Radio Club, 8o2 McBride St., Syracuse, N. Y., says: "Your New Long Wave Tuner is a knockout. Believe me, it works O.K. My aerial is only 75 ft. long. I have heard XDA and NAA very loud, and also have heard POZ and YN with only one bulb. Hear NFF, NDD and WSO all over room with one bulb. With two -step amplifier have heard POZ loo ft. from phones. With loud speaker, consisting of I Baldwin phone clamped onto it and same out of window, my father went half of block away and heard TIFF and WSO. Could hear all through house, even down cellar. Your Tuner sure has the wallop, and I never heard one like it. If anybody don't believe it, scud them over to see me and I will show them a thing or two." Send a 2 -cent stamp for bulletins COLBY'S TELEGRAPH SCHOOL, Auburn, N. Y.

www.americanradiohistory.com 752 Radio News for April, 1921

ordinary transformers can be used. The accumulators that are necessary for heating the cathodes are the only external acces- The s 1 sory. By adjusting the original alternate - g y current voltage any desired voltage on direct current can be produced, or if the voltage is taken from different condensers, -. Esco then, again, different voltages with direct current are possible. The high- tension valve tubes protect the arrangement against overloads, as they do not allow more cur- . + Re rent to pass than that which corresponds to their saturation point. When not in use it can be safely handled. The maximum voltage is not developed in the winding, but in ii;** one of the condensers; this is an advan- THE SET tage, inasmuch as a breakdown in the M winding might be difficult to repair under THE VARIO METER` A Wonderful Success many conditions, whereas a condenser or - valve tube might conceivably be repaired We again wish to call to the attention of the amateurs the ESCO regen- without great difficulty. In any case, the erative receiver. Responses from our first announcement of this set have over- cheapness of condensers and valve tubes whelmed as well as gratified us. They serve only to convince us the more that makes it possible to keep a few in stock. we have the most phenomenal success ever attained in regenerative instruments. The condensers are very easily and quickly Orders upon orders for this outfit have piled up and have just as quickly been charged, so that the direct -current voltage filled. We have built a large number of these sets in anticipation of just such is at once available, and remains substan- a rush and are prepared to ship your order upon the day it is received. Price tially constant. Its constancy depends on of the set is $50.00, f. o. b, Columbus, Ohio, or Philadelphia, Pa. Shipping that of the alternate- current supply. weight is Ii pounds. The defects of the system are, in the Because of the demand by many amateurs who wish to build their own first place, that it gives very little current. equipment we have decided to market the variometers and couplers as used in If a large current is necessary, the capaci- the ESCO set separately. The variometer as shown above complete with dial ties must be great, and the apparatus be- will sell for $9.50. Without the dial the price will be $8.50. The vario-coupler comes expensive; but this case is not com- which is practically the same as the variometer with the exception that the mon. Usually a small current suffices. A primary is tapped is priced at $10.00 complete with dial. Without the the further disadvantage is the high tension dial to which price will be $9.00. Shipping weight on either instrument is 2 pounds. Order the valve tubes and condensers direct from us or through your nearest dealer. are continuously exposed. The insulation DEALERS FOR must, therefore, be very carefully designed. WRITE OUR PROPOSITION. Insulation of this sort is not impossible in the present state of our knowledge, but there are, obviously, limitations due to radiation into the air. The device is de- Esco Dials -Plugs and Jacks scribed in the German patent No. 310,356, l i which is the property of the Siemens "5ó äö j'.. a Schuckert works. *Abstract of an article in the "Elektrotech- nische Zeitschrift," No. 28, 1919. , Aeroplanes and Radio-

ii Goniometer - (Continued from page 683) VIIIIIIIIIfl[!Iv 1 111`: '; .tea say but "Huh?" when anybody speaks to them in words of more than one syllable. By the way, "goniometer" means : "An Our dials are of black polished condensite and are 3 jches in diameter with instrument for measuring angles." A radio - beveled edges. Dials are of an inch thick and are graduated from zero to goniometer, technically, is an instrument loo. Graduations are filled with a brilliant white compound which will not for measuring angles by means of radio. crack or flake. The Postoffice Department has announced Plain dial $0.80 that radio direction finders, including field Dial with small knob 1.10 Dial with large knob 1.50 marking devices, are to be used by mail - Shipping weight on any of above 8 ounces. planes in making landings in fog, clouds, rain or snow. A non -magnetic non -gyro- scopic compass has been devised also. This The cut alongside illustrates a plug and will overcome the unreliability of the mag- -'1' jack which has been on the market for only netic compass. Whatever improvements a short time but have already acquired an may have been made, it is probable that the enviable following. With their use many new direction finders, or radiogoniometers, practical connections can be affected. Phone will utilize the same general principles as and amplifier connections are quickly made that described above. These principles can !IA -- - in multi-stage circuits. The upper and lower be studied at first hand by any boy who contacts complete a single circuit thru the has or will make a receiving set and con- I` phones, when removal of the plug automatic- nect it with a loop antenna which can be ally connects the amplifying transformer. Jack and plug are nickel -plated and turned to meet the advancing radio waves very attractive in appearance. at any angle.

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1. 1 1 1 . . 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 _ 1.. 1. . . 1 1 1 Plug only $0.75 ...... 111111111111111111111111111111111111111ll l l l. I l. l l l l l l.,, l ,.. Jack only .85 Plug and jack complete 1.50 Shipping weight 4 ounces, Awards of the $100 Portable Radio Prize Send 15c for our large illustrated catalogue with supplement. This amount will be refunded on your first order for $1.50 or over. High Contest printing costs makes free distribution impossible. (Continued from page 684)

sheets of tinfoil, 7" by r,/ ", separated by Electrical Specialty Company waxed paper, is rolled into a small bundle, wrapt with tape and shunted across the Dept. R -48-50 So. Front St. Dept. R., zo N. gth St. fones. Columbus, Ohio Philadelphia, Pa. A schematic diagram of the hook -up is given in Fig. 3.

www.americanradiohistory.com Radio News for April, 1921 753

REMLER TYPE 330 VACUUM TUBE CONTROL PANEL FOR THE NEW TYPE C -300 DETECTOR TUBE Maximum Value and Quality Through Quantity Production

THESE SPECIFICATIONS SPEAK FOR THEMSELVES Genuine bakelite, highly polished, 5" x y % ". White filled engraving. Special smooth running rheostat back mounted. All bakelite VT socket. The new Remler positive metal contact potentiometer for controlling plate voltage. Variable grid leak. Fixed grid condenser. Busbar wiring. Hard- wood base. All metal parts polished nickel Price $8.00 DEALERS: Send for our trade proposition on Remler Apparatus. "Apparatus that Radiates Quality" REMLER RADIO MFG. COMPANY 163 Sutter Street, San Francisco, Cal.

u S s ìt íg Condenser - leo No. CHELSEA

3 1 Variable Condensers

II ' 0' (Die -Cast Type) ^,.. X00 00 / No. I. -.0011 m. f. mounted $5.00 \ no z. -.e006 m. t. mounted 4.50 i bP f0 No. 3.-.0011 m. f. unmounted 4.75 o ftgg o m. without a No. 3. -.0011 f. unmounted, ` C dial 4.35 ELK - ro ç No. 4.-.0006 m. f. unmounted 4.25 +Qtr. No. 4. -.e006 m. f. unmounted, without r"-.- '¡ \ O dial 3.85 p6, _ ,r Top, bottom and knob are genuine p2 bakelite, shaft of steel running in bronze °//j% o, o. movable ii o bearings, adjustable tension on I / plates, large bakelite dial reading in hundredths, high capacity, amply sep- ` /ik/1 orated and accurately spaced plates. BAKELITE DIAL NO, 41. Unmounted types will fit any panel "CHELSEA" ` and are equipped with counterweight. / The Chelsea dials are made of genuine a` Purchase from your dealer; if he does bakelite, beautifully finished, and bear a it, send to us, not carry 100 division semi -circular scale. The dial is h inches in diameter, , f`f >' inch thick, with a long, sloping, easily Jf/ VARIABLE GRID LEAK !/ 1`64 Chelsea bakelite dials run e f read marking. Permits the selection of the proper leak re- true and will not warp. the type of tube, cr its sistance regardless of The complete dial and knob is made to use as detector, amplifier or oscillator. Ten a fit either 3/16, ?. or 5/16 inch shaft. Spec - steps give a range from I2 to me g ohms. ,_ ify size when ordering, otherwise the Vs Genuine bakelite base and knob. 5 ai inch hole will be furnished. All our apparatus embodies the highest de- `' gree electrical Chelsea dials are beautiful in appear - of mechanical construction, and durable efficiency, and good appearance. ance, low in price, accurate VARIABLE EAlO !E in service, unexcelled by any, at any Purchase Chelsea Apparatus from price. PRICE $3.00 your dealer Dial and knob complete 1.00 NEW MARCH BULLETIN SENT UPON REQUEST Purchase from your dealer.

Chelsea, Mass. CHELSEA RADIO CO., 11 Fifth Street, Manufacturers of Radio Apparatus and Moulders of Bakelite

www.americanradiohistory.com 754 Radio News for April, 1921

WJCioiJIUnAAs/JlU;IMMIIUVVA SPECIAL PREMIUM OFFER With a Year's Subscription to Radio News or Science and Invention (Electrical Experimenter)

Offer A REG. PRICE Offer C Science and Invention $3.00 Science and Invention (Electrical Experimenter) (Electrical Experimenter) / \ THE HOWARD for one (1) year with WHY OF for one (1) year with THOUSAND AND DNÉ RADO APPARATUS The How and Why $1.75 A Thousand and FORMULAS , ' J of Radio Apparatus One Formulas 1' I6u1H1C $4.75 DERH BA I SPECIAL PRICE OFFER, A or C, $3.75

Offer B REG. PRICE Offer D Radio News $2.00 Radio News for one (1) year with for one (1) year with FAP rii;0Ä ÌE The How and Why $1.75 A Thousand and This newest of Radio of works, bound in flexible Radio Apparatus $3.75 One Formulas A Laboratory Hand- velum and hand sewed, book for the Experi- has 160 pages. Size of SPECIAL PRICE OFFER, B or D, $2.75 menter. Bound in flexi- book 6 x 9 inches. ble velum. 160 pages. Size 6 x 9 inches. Offer E REG. PRICE Offer G

and IIII Science Invention HINDI I ill $3.00 I I Science and Invention IIIIB I dl InN (Electrical Experimenter) (Electrical Experimenter) ',EXPERIMENT` for one (1) year with for one (1) year with L, t! EËónÚRSE" Wireless Course in 20 $1.25 Experimental ...ill, Lessons ` SAEBNSBÀCK1fl p $4.25 Electricity Course rWSECORIu WI GéRHSEIAfK I

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I DÍF%P PINENEE9PP9Há86CÓJIy Wireless Course in 20 $1.25 Expe =- -imental Lessons IIIIIIIIiIIIGIh111IIIIiVIlü111NIIIlIll $3.25 Electricity Course Book is bound in Book is bound in flexible flexible Velum; Velum; has 160 pp. Size SPECIAL PRICE OFFER, F or H, $2.50 has 160 pp. 7 x 12 Size inches. 5 x 9 in. Offer K Reg. Price Special Price to you HOW TO MAKE Science and Invention $3.00 DESIGN.MCONSTRUCTION HOW TO MAKE WIRELESS (Electrical Experimenter) A0000N AMPLIFYING TRANSFORMERS WIRELESS RECEIVING APPARATUS RD RADIO CONSTRUCTORS for one (1) year with SENDING APPARATUS '.t0 es T90 luusua1o115 Design and Construction of

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Printed on heavy Book has 100 Book has 100 Offer L paper, paper pages. Size 5 x 7 pages. Size 5 x 7 bound. Size 5 x 7 inches. 88 illustra- inches. 90 illustra- Radio News $2.00 inches. Fully illus- tions. Paper cover tions. Paper bound, for one (1) year with $2.25 trated. The latest printed in t w o in two colors.. book out. colors. Same Books as Offer (K) .95 $2.95 EXPERIMENTER PUBLISHING COMPANY, Inc. 236 -A Fulton Street, New York City, N. Y. Dear Sir : I accept your offer Enclosed find $ in payment of premium and one year subscription. Name Address Town State R.N. 3 -21 íìÌi1

www.americanradiohistory.com Radio News for April, 1921 755

With this set connected to the aerial previously described, erected to a height of forty feet, Great Lakes (NAJ) came in loud enough to be heard six inches from the fones. NUR, and a number of ships on Lake Michigan have also been heard, not to mention "Hams." Altogether it cost me exactly $2.00 to construct, and I think I am well repaid for my time and trouble, by the results I am obtaining. Learn Telegraphy WILLIAM F. MARQUARDT, 4740 N. Ashland Ave., Chicago, Ill. Wireless or Morse) ,,,,,,,1,1,11,,,,,,,,,,,,,,1,,,11,,,1111111,1,1111,,,1,,,,,,,,,,,1,1,11111,,,1,,,,11,111111111,,,111111,,,,,, ,,,,,, ,1,1,1,,,111,11, The EASIEST, QUICKEST, Two- Step Audiotron CHEAPEST WAY Amplifier (Continued froid page 744) AT HOME ,,,,,, ,,,,,,,, ,,,,,,,,,,,,,,,,,,, and breaking, which would sure enough In Half the Usual Time be a calamity in these days of high prices. Telefone receivers of 2,000 or 3,000 ohm ones should be used. The receivers can WITH THE OMNIGRAPH be placed in a small cigar box with a "Just Listen -The Omnigraph will do the teaching" hole at the top sufficiently large enough for the placing of a horn, and signals will The Omnigraph is an Automatic Transmitter that teaches you both the be heard all over the room. Be sure the Wireless and Morse Codes, at home, without any diaframs are facing up toward the hole expense except the where the horn is placed in the box. cost of the machine itself. Merely connect to battery and your Buzzer, The condenser used is of the variable or Buzzer and Head Phones, or to your Sounder and the Omnigraph type, .0005 or .0002 ; in fact, the ordinary will send unlimited messages by the hour, at any speed you desire. receiving variable condenser will do the trick very nicely. The condenser should USED BY THE U. S. be connected on to the posts marked Con. GOVERNMENT A grid leak should be used in series or The Omnigraph is used by the shunted across the variable condenser Government in testing all appli- /i (I megohm). A simple grid leak can be cants applying for a Radio / made by taking a piece of stout drawing License. It is also used exten- / paper and drawing a heavy line upon it / sively by the large Universities, / with india ink the length of the line to --n Colleges and Telegraph Schools be regulated to the reaching of the de- throughout the Country for / sired results. teaching Wireless and Morse. / The other different outside apparata Hundreds of the Army's skilled / are connected onto the posts marked for operators who served during the / them such as TR, telefone receivers; Bi, war learned with the Omnigraph. / B battery number one; 132, B battery / number two; Al, A battery number one; Let The OMNIORAPH Teach You / A2, A battery number two; AT auto Wireless / For a few dollars you can have a complete You'll be surprised how quickly you will attain / transformer, and S is to connect onto outfit that will make you an experienced speed. Even if you are already an operator / the secondary of the receiving trans- operator in the shortest possible time. No the Omnigraph will help you. It will make former. hard, laborious work-just learn by listening. you more proficient, more accurate and more / The Omnigraph is adjustable so you can start confident. Thousands of Omnigraphs are in receiving messages slowly, gradually increas- use today and thousands of operators owe Indoor Aerial and Choke ing the speed as you become proficient. their -success to them. Write for Free Catalog Coil I The Omnigraph Mfg. Co. Amplifiers Send for a catalog today, showing the 3 differ- 26 F Cortlandt St., ent models, $14 to $30. Every Omnigraph (Continued I from page 709) is sold with the absolute guarantee that you New York City must be satisfied your money back for II 1111111111111111111,1111111111111111111,111111111111111111111111111111filii3tiimiinewilitil,,,. or the Gentlemen:- asking. Mail the coupon today -the catalog honeycomb coils. I don't know whether will come to you by return mail. As per your ad in RADIO News please mall you have QRM but we certainly do have me your free catalog of Omnigraphs. it up near New York. I can copy stuff on my honeycomb coils when nearby re- The Omnigraph Mfg. Co. Name generative sets are jammed by QRM. 26 F. Cortlandt St., New York City Address That has happened time after time. One yç relay station in our town, who uses a Y.11.14.10e%V~CCCWCC0.'XSMICNJOCMSI City State regenerative set, had to ask for a QTA five times. I copied the message easily the first time with very wide coupling. THE WIZARD " B " BATTERY There is generally so much QRM that I have to put the primary coil almost at Attention Amateurs right angles to the secondary to get rid 15,, of it. Honeycomb coils pick up far dis- OFF LIST PRICES tant stations QSA List Price with very wide cou- No. 1623 Small B Battery, 22% volts $1.50 pling when a regenerative will not. I picked up 52A in New Mexico with my No. 1625 Large B Battery, 22% volts 2.50 primary coil almost at right angles to the No. 1625 Variable B Battery, 11/2 to 221/2 volts 3.5o secondary. I would like to see a regenerative set which would do that with The above batteries are manufactured according to government the coils in a similar relation. To my specifications. Sent free of parcel post charges. Money back If not satisfactory. mind it is worth while sacrificing a little signal strength for the great amount of 1315 42ND STREET selectiveness. Everybody seems to think DEPT. R. BROOKLYN, N. Y. that regenerative sets are much better than honeycomb sets. That is not true in our town. My honeycomb Add to your Salary-Make extra Pin Money. set has got MONEY for You Start a lucrative business of your own. better distance than any of the regen- Spend an hour each day taking subscriptions for the "Radio News." We'll pay you well and you'll erative sets with outdoor aerials. Think enjoy tie work. Write for full particulars. Circulation Dept., RADIO NEWS, 236A Fulton St., it over. New York City,

www.americanradiohistory.com 756 Radio News for April, 1921

Jlvl-1!aw1CLCVw!VJ.IpJ!lvAmmw:Ú:;Ú!Gm0.%A%L\%",:m.mmt\%1.m1f mmA%LVm!u WJmLV:A%" ;".0).,\%LVJm!tJJ0)..pAAÇ!:Ú:.w.m":l\l_,,...wd.m:"^' OPPORTUNITY AD -LETS Follow these advertisements every month. Reliable advertisers from all over the country offer you their most attractive specials in these columns. Classified advertising rate six cents a word for each insertion. Ten per cent discount for 6 issues, 20 per cent discount for 12 issues. Name and address must be included at the above rate. Cash should accompany all classified advertisements unless placed by an accredited advertising agency. No advertisement for less than 10 words accepted. Objectionable or misleading advertisements not accepted. Advertisements for the June issue must reach us not later than May lo. THE CIRCULATION OF RADIO NEWS IS OVER 40,000 : EXPERIMENTER PUBLISHING CO. INC., 233 and 230,1Pulton Street, New York, N. Y. ; íllrrarMtraiYel!YaMlA1Y!%il1!i11!ñ11Ìilfratrih!Oki!Yí\1(ri (

Automobile Accessories. Books. Chemistry Autoists- "Saviorgas "; easily mixed. Saves gas. The Amateur Electrician- Pocket size, 20e, Chemistry -Learn qualitative analysis by the Decarbonizer. Recipe, lOc coin. Hawthorne Co., coin. Joe Tillberg, Proctor, Vermont. modern simplified chart method, U. S. $1; foreign Roslyn, Wash. countries $2. Technical Charts, Dept. C-2, 1038 Auto Motors Supplies -Buick, Michigan, Stod- "Ten Days " -Stories from Boccaccio's "Decam- W. Chicago Ave., Chicago, Ill. eron"; best you ever read; 35c postpaid. Martin, Sell chemicals, chemical, electrical, high dard- Dayton, E. M. F., Cadillac, Overland, Con- Box Will tinental and Buda Motors. All types, $50 each 67, Pontiac, Michigan. frequency and wireless apparatus. Send 5 cents. Karl Peterson, Weldon, Ill. and up. New Dixie magnetos, $20; Splitdorf high Safe and Vault Opening Secrets-How to open tension magnetos, $10; Kellog pumps $3.50; Auto - 22 different makes. How to work out systems to Lite generators, new, $10; air gauges, 65c; Remy open any safe or vault, combination etc. Correspondence Courses. ignition coils, new $3; electric and gas head- setting, etc. Former price $25; your copy $5 postpaid. J. lamps, coils, distributor heads, air compressors, Hartmann, Desk C, 913 21st Street, Rock Island, Dollars Saved. All kinds of used correspond- Write for catalog. Motor Sales Dept., 16 West Illinois. ence courses sold. (Courses bought). Lee Moun- End, Pittsburgh, Pa. tain, Pisgah, Alabama. We Buy and Sell back issues of Radio Amateur ,,,,,1.,,,,,l,. 11111.,,,..,.mu.,.. ,mu.,,mameownru,,wnmom Motor Engines and Dynamos. News and Electrical Experimenter. Boston Maga- zine Exchange, 109 Mountfort St., Boston, Mass. For Advertisers. Special Garage Motors- Manufactured by the Advertise in 100 Magazines. Words 9c each; General Electric Co.: 1 H.P., $78.50; 2 H.P., $110; three times 18e each. Concordia Magazine, 9A York, Penna. 3 H.P., $128.50; 5 H.P., $166.50. All sizes botti e.,..,.,.,,11.,1111111111111113111113,1113333131,111111111111111.11111111111111111133111131 Water, 13111131.1,13111111111111111 11 1111 13111t single and polyphase motors for immediate deliv- Don't Wait for Business.- Advertise and get ery. Special charging generators, all voitagea. it. We will help you. Jacobus Service, 41 Bruen, Write for catalog. Motor Sales, Dept. 16, West Roseburg, Ore., Irvington, N .J. End, Pittsburgh, Pa. Jan. 26, 1921. For Inventors. Motorcycles -Bicycles. RADIO NEWS PUB. Co., Dear Sirs: Model Making by experts. Satisfaction assured. Don't Buy a bicycle motor attachment until you I put an ad in RADIO NEws, January Scillitoe, 15 Frankfort St., New York City. get our catalog and prices. Shaw Mfg. Co., Dept. issue, 1921, and one day I received a lette, 1604, Galesburg, Kans. from a boy that had read the ad and in Health. Used Parts for all motorcycles. Schuck Cycle two days I had received five letters in re- Co., 1922 Westlake, Seattle, Wash. gard to the ad. Also, these letters all Pyorrhea (Riggs disease- bleeding or swollen came RADIO have ...... ,.....:.,...W..vr.,..,.»,,,a..w ...... Wi.,illii11111.331: 133 before the News had reached gums)- hundreds been helped by "Pyorrdent" our city. the successful home pyorrhea treatment. Puri- Agents Wanted. After this, if I ever want to sell any- fying, healing, preventative. Full month's treat- thing, I'll put an ad in RAmo NEWS. ment, consisting- of a very beneficial massage Big Money and fast sales. Every owner buys paste and an antiseptic tooth -cleansing paste to be gold initials for his auto. You charge $1.50; My motto is "It pays to advertise in used in place of your ordinary dentrifice, to- make $1.35. Ten orders daily easy. Write for RADIO NEWS. gether with full directions for treatment. $1 particulars and free samples. American Mono- Yours truly, postpaid. Or write for free booklet "R." Pyorr- gram Co., Dept. 133, East Orange, N. J. Box 1055 (Signed) EARL PATTERSON. dent Mfg. Co., 439 Seventh St., Brooklyn, N. Y. Make Big Money-Sell soldering solution; no Tobacco or Snuff Habit Cured or no pay; $1 acid. Better than paste. Sample 25c. F. Kossatz, if cured. Remedy sent on trial. Superba Co., SB, Baltimore, Md. Fifth Ave., New Rochelle, N. Y. .11111111111111111111111111111111111111111111131111111111111111111111111111311113311111111113=1111.11113110.1ffilmammillim Help Wanted. Patent Attorneys. Mailing Lists. Canadian Lists of automobile owners, agents, Detectives Earn Big Money. Excellent oppor- Patents -Send for free book. Contains valuable garages, repairers, dealers, $3 per 1,000. Lasnier tunity. Travel. Great demand everywhere. Fas- information for inventors. Send sketch of your Agency, Bathurst, N. B., Canada. cinating work. Experience unnecessary. Particu- invention for free opinion of its patentable nature. lars free. Write, American Detective System, Prompt service. Twenty years' experience. Tal- 1968 Broadway, New York, N Y. bert & Talbert 4927 Talbert Bldg., Washington, Moving Pictures. Be a Mirror Expert. $3 -$10 a day; spare time D. C. Jazz Movie Portraits, patented, $1.60. Machine home at first; no capital; we train, start you rights selling. Cenama or Western portraits, 90c making and silvering mirrors, French method. Patents Secured -Prompt service. Avoid dan- set. Samples and list 25c. Tec-Art, 412 Temple, Free prospectus. W. R. Derr, Pres., 579 Decatur gerous delays. Send for our "Record of Inven- Los Angeles, Cal. St., Brooklyn, tion" form and free book telling How to Obtain N. Y. a Patent. Send sketch or model for examination. Big Money made silvering mirrors, auto head- Preliminary advice without charge. Highest ref- News Correspondents lights, refinishing metals. Free outfits. Write for erence. Write today. J. L. Jackson & Co., 133 Earn $25 Weekly, spare time, writing for news- particulars. B. Decie Laboratories, 286 Fifth Ouray Bldg., Washington, D. C. papers, magazines. Experience unnecessary; de- Avenue, New York. Millions Spent Annually for ideas. Hundreds tails free. Press Syndicate, 566 St. Louis. Mo. Young Men! -Train now for wireless or rail- now wanted! Patent yours and profit! Write way operator or station agent. Largest and only today for free books -tell how to protect yourself, Novelties. officially endorsed school in Canada. Correspond- how to invent, ideas wanted, how we help you ence and resident courses. Free book R explains. sell, etc. 301 Patent Dept., American Industries, Genuine Indian Baskets. -Wholesale catalogue. Write Cassan's Wireless School, Toronto. Inc., Washington, D. C. Marion Gilhams, Highland Springs, California. Earn $25 Weekly, spare time, writing for news- Mr. Inventor! Investigate the possibilities of Phonographs. papers, magazines. Experience unnecessary; de- your own patent. $40 to $100. We tails free. Press Syndicate, 5665, St. Louis, Mo. obtaining Save prepare drawings, specifications and claims you file. Build Phonographs; knocked down cabinets, $2. Wanted-Radio instructor to take charge of Quicker action. Let us explain. Enclose stamp. Catalogue, suggestions on cabinet parts, drawings, school, A -1 man preferably with teaching experi- The Plan Bureau, 1929 McCausland Ave., St. dimensions, and instructions, 65c postpaid. Port- ence and college education. Box 100, RADIO NEws. Louis, Mo. land Phonograph Supply Works, 48 N. 15th St., Portland, Ore. E. T. Brandenburg (former patent expert, Ord- Business Opportunities. nance Division. War Department), Attorney -at -law Build Your Own Phonograph. Big Saving. Blue prints, parts price list. instructions free. Earn $50 $75 and Solicitor of Patents, 927 Loan and Trust Bldg., to per week tuning and repairing D. and Associated Phonograph Co., Dept. R -N, Cincin- pianos. We teach you to be an expert. Chicago Washington, C. Send sketch description, nati School of Piano River Forest, or model of your invention for careful investiga- Tuning, Ill. tion at Patent Office and unbiased report as to You to Sell Build a genuine Choraleon phonograph and save If Want or exchange your farm, patentability. over half. Fine profits building and selling. We unimproved land, city property or patent, write furnish motors, tone arms and necessary parts. me. John J. Black, 194th St., Chippewa Falls, Competent and. Prompt professional attention to Wis. Send for our catalog and free blueprint offer. patent and trademark matters. Expert service in Choraleon Phonograph Co., 421 15th St., Elkhart, Substantial Manufacturing Corporation wants radio inventions. "Inventor's Adviser," a cloth- Indiana. capable men to establish branch and manage sales- bound library reference book sent free on request. 1311.1411111111111 118133menntr 1333331113311133 llllllll men; $300 to $2,000 necessary. Will allow ex- William C. Linton, Patent Attorney and Engineer. Postcards and penses to Baltimore as explained. Address Mr. 932 National Union Building, Washington, D. C. Pictures Clemmer, 603 N. Eutaw St., Baltimore, Md. Pictures-"Beach Beauties." Samples 20e. Sell our portable battery charges to wireless Patents For Sale. Lucky elephant charm, ivory, 35c. Catalogue 4c. operators, car owners, garages, etc. Average re- Taylor, Box 1374, St. Louis. charge cost ten cents. Price $15 and up. At- Stump Puller, Patent No. 1298372; outright Two Dimes brings ten San Diego views which taches to any lamp socket. Harkleroad Co., 1240 sale or rights to manufacture on royalty basis. you may return here for mailing. "Fun." First National Bank Building, Chicago. T. H. Monk, 812 Gaskin Ave., Douglas, Ga. "Christies," 2321 5th, San Diego, Calif. www.americanradiohistory.com Radio News for April, 1921 757

(Continued from page 766) (Wireless continued) (Wireless continued) Printing. Build Your Own Regenerative- Seamless, gray Our Special for this Month -This month we are cardboard tubes of highest quality for winding making a special offer on Chelsea apparatus, and Labels, 60e per 1,000 up. Irvin J. Wolf, Sta- forms. Variometer 37/8x2 in. and 47/13x2% in., per for one month we are making an offer of 5% less Philadelphia. in. and 47/gx4yz in., than list prices and all goods fully guaranteed and tion E, set 25c. Variocoupler, 37Ax2 We run specialists. per set 35c. 3,500 meter loose coupler tubes 3%x will be shipped by insured parcel post paid. Everything Printed.-Long handle all the best grades of radio apparatus and Samples. Quality Printery, Marietta, Ohio. 7 in. and 3%x7 in., per set 45c. 6,000 meter 37/8x7 in. and 4%x7 in. per set tiUc. practically make shipment the same day the order card - loose coupler 100 Cards, business, professional or social; in., 35e each. 37/8x14 in., is received. Radio Mail Order Supply Co., 533 Agents wanted. G. B. Pratt, Loading coils 3%x14 case free; 75 cents. 40e each. 4%x14 in., 50e each. Order today. West End Avenue, New 'York City. 68 Madison St., Cortland, New York. 1...11 We'll ship them right off, postpaid. The Taylor . . 1 1 1 111111...1111111111111111...1.11111..11,,,,,,,,,,,,,.,.,...,.,..,.,,,...... 11 ... . Box 1043B, Lowell, Mass. Radio Phonists' Attention-High voltage gener- . Co., ators. We supply motor generator units in vari- Hire. Scenery for Stop Look! and Act! New, $5. Radiotron detec- ous capacities especially designed for radio phone and insured. New - Collapsible Scenery for all plays. Amelia tors at $4.25 each postpaid work. Low powered rotary converters, dynamo Philadelphia, Pa. $6.50 radiotron amplifiers at $5.75 each postpaid tors. fractional H.P. motors, storage batteries. Grain, and insured. These are the new genuine super- Various types of meters, condensers, spark gap sensitive radiotron V.T.'s manufactured in the rotors. The new synchronous spark gap. Get ac- Song. Writers. great works of the General Electric Co. and are quainted with our service. Ray- di -co. 2653A, N. the result of research work by the foremost Clark St., Chicago, Ill. Song Writers !-Learn of the public's demand vacuum tube experts in the United States. Each for songs suitable for dancing and the oppor- and every tube is guaranteed to arrive in perfect Variometers -You can now have as many as tunities greatly changed conditions offer new writ- condition. The Kehler Radio Laboratories, Dept. you need. We furnish you precision variometer ers, obtainable only in our "Song Writers' Man- Abilene, Kansas. coils ready made, you make the other parts easy. for R, ual and Guide, sent free. Submit your ideas parts. Write J. Donnelly, These coils are something new. The dielectric and advice. We For Sale- Wireless 10e songs at once for free criticism 107 Talmadge St., Poughkeepsie, N. Y. losses are less than half present coils. Send revise poems, compose music, secure copyright and for blueprint instructions and colored circular. facilitate free publication or outright sale of Remarkable Bargains -Used radio apparatus. Precision Radio Equipment Co., 120 Christie St., 319 Gaiety Bldg., Amateurs in Missouri and bordering states send songs. Knickerbocker Studios, Missouri. Ridgefield Park. N. J. New York. for list. Central Radio, Independence, 1.1111.101111111111I.m11111.11111111111...1/.11111..1.,....1,,.1111,..,.11ll,,,,,,,,,.,,..,,,,,,. Make Your Station Look Alive -Show a set of Rewire Your Present Set and hear Hawaiian high -class warning signs. Five wordings- Danger, and German stations with a single bulb. Are you Stammering. High Voltage, Do not touch the instruments, satisfied with your receiving set? Would you like Please be quiet while operator is receiving, Gov- to build one that will receive over 6,000 miles on St- Stu -t -t- tering and Stammering cured at radio booklet free. Walter McDon- ernment licensed radio station, Experimental a single bulb and quit experimenting? One that home. Instructive 2 for 25e. All 5 for equal of any regardless of claims or 121 Potomac Bank Bldg., Washington, D. C. laboratory, No admittance. will be the nell, 50e. Postpaid. The Taylor Company, Box 1043b, price? Using the instruments you now have you Stammerers -My simple and natural method Lowell, Mass. will be able to duplicate the long distance records will correct your impediments. Instruction indi- you read about every day. Get our simple diagram Samuel I. Robbins, 246 Huntington Ave., Central Radio Company (Incorporated), Inde- vidual. heart of a complete short and long wave receiver, 175 Boston. pendence, Missouri. (Nine miles from the to 20,000 meters, with which we read Honolulu. of Kansas City.) California, German, South American. French and Stamps and Coins. Your Call Letters in handsome gold, black - English stations, and practically all the high - bordered letters 3 inches high. A wonderful ad- powered foreign and domestic stations, amateurs 100 Different Stamps, Nicaragua, Salvador, Vic- dition to your station. Any call letters on 8x10 as far west as New Mexico and numerous tele- toria, Brazil, Chile, large pictorial French Colo- in. glass sign for $1.50 postpaid. Your naine on phone and musical concerts come in good. Dia- nies, etc., album with perforation gauge, only 10e the sign also in one inch high gold letters at 10e gram and complete instructions, leaving nothing silver. Stamp collections and accumulations bought. per letter extra. You want one so order today. to guess about will be promptly mailed for 50 Clarence Gibbs, 8932 Juniper, Los Angeles, Calif. The Taylor Co., Box 1043B, Lowell, Mass. cents in coin or stamps. Wire a set up and quit 500 Different Stamps, $1.40; 200, 30c.; 100, Lightning Service to Central West amateurs. wasting good money. Virginia Novelty Co., Mar - 13e.; approvals. Michaels, 5600 Prairie, Chicago. Immense stocks, all leading makes. Catalog free. tinsburg, West Virginia. Central Radio Co., Independence, Missouri. California Gold Quarter size and Colombia Blue Prints -Twelve proven receiving circuits, nickel coin 30e; Italy 10 Centimes and catalog Make Your variable condensers 1/32 aluminum City, Mo. each on separate sheet, all for 40e. Ten proven 10e. Homer Shultz, King plates, 4c. Write for particulars. Gravenstede, radio phone and two combination VT hookups for S4 Hancock Ave., Jersey City. transmitting, 50c. Wireless code on large blue Telegraphy. Want Something Quick? -Order from Central print 25c. The Plan Bureau, 1929 McCausland Radio. Ave., St. Louis, Mo. Telegraphy (both Morse and Wireless) and Amateurs' Attention! -New wind and weather Railway Accounting taught quickly. Tremendous code chart, neatly arranged on blue print, 10c coin. Radio Phonists' Attention -Money refunded it demand. Big salaries. Great opportunities. Old- E. H. Cummings, 18 Richard St., Auburn, R. I. no results are obtained, using my circuit. Com- est and largest school; established 46 years. All plete radiophone outfit, transmits 15 miles clear- expenses low -can earn large part. Catalog free. Wireless Receiving Station Free with our prac- ly. Results are positively guaranteed. operated Dodge's Institute, M. St., Valparaiso, Ind. tical new home study course. Write for informa- on 1 "B" battery. Initial cost low, only $17.40 1, ,lll 1111111..1.111111111 111.1. 1.1111...... 1.1,,..1..,11111111111.....11.11111111.1111..11111111111111111111111 tion. Central Radio School, Independence, Mo. to construct, upkeep extremely low. Exactly what Wanted to Buy Radio Equipment of all kinds. Agents for Mur- you have been looking for. Have convincing tes- dock, DeForest, Signal, Tresco, Cunningham and timonials from well-known amateurs, praising the circuit highly. Send only $1 for blue prints and You Can Raise Cash by mailing us any old, many other lines. Write for pamphlet describing platinum, broken our Torode rotary spark gap. Garver Hardware working direction. H. D. Selvage, 1096 Clinton broken jewelry, diamonds, Ave., Dept. R, Irvington. N. J. watches, false teeth, bracelets, old gold, silver, sil- Co., Des Moines, Iowa. ver plate, magneto points, platinum wire, contact Central Radio -For lightning service. We Jack to Make One and break one circuit, with points or crucibles, mercury and all valuables. Listen Fellows -We make sets to specifications, plug, 70e; jack to make one and break two cir- pay the highest prices in spot cash by return mail expert workmanship. Fair prices. Audion sockets cuits, with plug, 90e; jack to make two and breale and will return your goods in ten days if you're 65c postpaid. No stamps accepted.. Kenny Radio two circuits, with plug, $1.25. The 90e and $1.25 not satisfied. The Ohio Smelting & Refining Co., Laboratories, R. F. D. No. 2, Elizabeth, N. J. jacks have platinum contacts. Heavy brass binn- Bldg., Cleveland, Ohio. 207 Lennox Special Sale of Parts for radio apparatus. In ing posts, each, 7c; 2000 volt mica. condensers, order to liquidate a large stock we are offering at 32 mfd. cap, each, $1.10; .025 mfd. cap, each, 30e. Wireless. practically half price the following sets of com- Litz wire 25 -32 per ft., lc; short wave regenerative plete units ready for assembly. This is an ex- receiving set, good construction and very efficient, Slab Inductances -Set of eight, tuning with .001 cellent opportunity to make a start in wireless. each $18.50. Postage extra on all goods. Haupt MF condenser from 300 to 30,000 meters. For- We have the following ready for immediate ship- Electric Supply Co., 2442 Ogden Ave., Chicago, Ill. ward money orders, $4.50, made payable at Atlantic ment, by parcel post prepaid, on receipt of re- Road Brixton to Perry 9 Jelf Road Brixton, Lon- mittance: receiving tuner, 60e; loose coupler, Ammeters, new, read 5 amperes charge and dis- don, England, and secure a set post free by return. 2,000 meter, $2; variable condenser, .005 Mf., $3; charge, $1. Postpaid. The Recto Mfg. Co., Inc., 23 W. Third St., Cincinnati, Ohio. Radiosts -10% reduction on Murdock and Clapp - crystal detector, 70e; No. 14 antenna wire, 100 Eastham apparatus. Turney spider -web coils, $5; ft coil, 60e; transmitting helix, $2; TA in. spark 10 (complete assembled). $3.50; zinc spark gap Audion Detector and Amplifier, V.T., 50 cents. copper aerial wire, 100 feet, 60e; Rayolite "B" coil Honeycomb coil mountings, 25 cents. Back mount- & rotary gap, with polished bakelite base. 70e; hand key, 50c; batteries, $3.25; Young McCombs ed rheostats, 40 dents. Composition for $14; radiotrons, $4.75; Wets grid condenser, 20e; K.W. radio transformer, $11.25; 1,000 ohm head molding aouble, your own knobs, panels. etc. 35c pound. Send galena, per crystal, 15e. Wireless Experimental phones, single, $2; 2,000 ohm head phones, Palmers Testing Station, Stuart St., Binghamton, N. Y. $3.75; strain insulators, 12c each; filament rheo- stamp for particulars. Electrical Equip- stat, 8 ohms, $1.75; set of tools consisting of ment Co., Palmers, Minn. Laboratory Necessity-Plug type bridge for pliers, large and small screw drivers. 25c; no measuring resistance and capacity, 38 coils, 10 orders immediately. Kilbourne The How and Why of Radio Apparatus, by catalogues. Send H. W. Secor, E. E. This newest book on radio to 4,000 ohms, hard rubber top, mahogany cabinet, & Clark Mfg. Co.. Seattle, Wash. few at matters fulfills a distinct gap in wireless litera- blue printed instructions furnished; left transmit. Our book- less than price of wire or plugs alone, $6.50. Fol- Get a License before you ture in that, while the treatment is made as under- mica condenser... let, "Amateur Licenses and How to Get Them" standable and as free from mathematics as possi- lowing brand new: 0.32 mfd. know. Postpaid 15e. puncture proof to 1,400 volts, heavy brass mount- tells you all you need to ble, it at the same time incorporates a wealth of Order at once, limited supply. First come, first technique and instruction for the Radio Amateur ing clamp, 85c. Fahnestock connection blocks, 20c; Hazel - hard rubber encased, 30 ohm, electromagnets, %;s.. served. Philadelphia Radio Supply, 5714 the Radio Operator -the Installation and Designing You pay postage. Western Instrument Repair, Avenue, Philadelphia. Expert -as well as teachers an students of the 314 N. Fairfield, Chicago, Ill. Pre -War Prices- Variocouplers wound on Bake- subject in general. A very broad field has been Loud Talkers-To those who want an efficient, lite tubes, $5.25; variometers, inside windings, covered by the author, at the same time giving a neat and inexpensive loud talker, one receiver and $4.25, assembled for panel mounting; oak cabi- great deal of information not found in other text fill Three feet long, nets with bakelite panels 5x5x6 in., $2.25; hard- books. If you are engaged in any branch of the our horn will the want. Radio or allied arts at all, you will surely need tapers from 15 in. to 34 in. diameter. Hard lac- wood rotars. centered, 0.70. All parts craried in quered, black enamel, inside and out, ornamenten stock for regenerative sets. Meade Bakelite Radio this latest contribution to radio literature, which is Packed, crated, in- Apparatus, 975 Putnam Ave., Brooklyn, N. Y. destined to be found on every radio man's book with two neat gold bands. shelf before long. This newest of Radio Works, sured and postpaid anywhere for $2.50. To in- Storage "B" Batteries-Fellows end your B sure prompt shipments same day order is received, cloth bound in Velum de luxe, Gold stampt and battery troubles. Our new alkaline storage B Hand Sewed, has 160 pages. Size of book 6x9 send only money orders to "Loud Talkers," Box batteries which are equipped with switches giving 18, W, Brooklyn, N. Y. inches. "The How and Why of Radio Apparatus," Station one cell control and rectifiers for charging will postpaid, $1.75. Experimenter Publishing Co., Stop! Look! and Think! 5 to 30% discount on last indefinitely. Thirty -two volts, $8; 50 volts, Book Dept., 236A Fulton St.. New York City. new well -known regenerative sets, vacuum tubes, $10; 70 volts, $12. Pictures and further infor- power tubes, radiophones and accessories. The mation upon request. L. W. Kimley, 290 Winslow Kehler Radio Laboratories, Dept. R, Abilene, Kans. Ave.. Buffalo, N. Y. (Continued on page 75g)

www.americanradiohistory.com 758 Radio News for April, 1921

(Continued from page 757) (Exchange continued) (Exchange continued). Electrical Supplies and Appliances. DeForest receiving set complete, 3 stage ampli- Sale -5 W. E. V.T. -l's, W. E. V.T. 2, 12 -90 fier, paragon regenerative, new; enormous sacrifice; Willard storage battery and 2 6 -90's Chambers ro- Electricians -Wiremen, linemen, send your write. name and address for descriptive literature of our Charles Ettl, Leonia, N. J. tary; Veniier rotary, oscillation transformer Mar- modern blue print chart method of electrical wir- Used Apparatus- That's us; look! V.T. sockets coni jar; 3 pair 2,000 ohm fones; 2 audiotrons; ing. Over 350 practical diagrams. Electrical Wir- 90e, rheostats $1.50, panels 6 %x7, $1.10; control large Universal motor, keys, dial; all A-1 shape; ing Diagram Co., Box C -173, Altoona, Pa. panels $6.75, 6 in. bakelite disc 45c. double V.2. cheap. Walleze, 234 Vine St., Milton, Pa. De- sockets $2.25, triple V.T. sockets $2.90, knobs 1% For Sale -Complete receiving set for spark re- Sulphating methods are guarded as trade in. 19c. The secrets, yet sulphation causes 90 per cent of all above is only a few bargains. Get ception. F. Kahmer, 1639 W. Lanvale St., Bal- storage our list. Newark Wireless Exchange, 87 Halsey timore, Md. batteries to be discarded. $1 brings my St., Newark, N. J. guaranteed methods. Secure your A batteries this For Sale-% K.W. transmitting set, $25; 1 way. Eugene F. Grossman, electric starter ex- Will Buy Amrad receiving units and sell Kodak. DeForest P. 500 audion control panel, with cabi- pert, 14 E. Read St., Baltimore, Md. Myron Jacoby, Brentwood, Maryland. net and "B" batteries, $15 Wardell Smith, 191 Storage Batteries for automobiles. We furnish For Sale- Receiving apparatus. Am selling out. Alexander Ave., Upper Montclair, N. J. Phone all parts and moulds for making them. Sample Write for list. D. B. Roberts, 1621 Kensington 4361. plate, 40c. Foreign countries, 50c. Windsor Blvd., Ft. Wayne, Indiana. Bargain- Detector and one -step amplifier in Specialty Co.. 5419 Windsor Ave., Chicago, Ill. For Sale-325 feet copper wire, 500 volt ground cabinet, with phones, "B" batteries and brand new Rebuilt starting storage batteries in good con- switch, 300 ohm phones, % dozen insulators, bulbs, $55. Isadore Wolf, 1529 Evergreen Ave., dition, 6 volt 60 ampere, $15 brings it home fully wall insulator, 1 anchor gap, 1 plier. $10 takes Chicago, Ill. charged. Myer Myerson, 1832 S. 5th St., Phila- everything. H. W. Johnson, Hurley, Wis., Box Bargain -For sale, large oak cabinet chemical delphia, Pa. 751. set, 40 reagents, glass tubing, etc; all for $20. For Sale -Wireless instruments cheap. Janitor, Write B. G. Firth, 1109 Broad St., Newark, N. J. Exchange. 567 Amsterdam Ave., New York City. For Sale- Duo -lateral coils, one each, numbers New Casting form No. 21, $4; sounder $1.50. 60, 150, 600; two each numbers 250, 500, 1000, Exchange- Edison Ambrola phonograph with 80 Hermann Rosenkranz, 781 Grant Boulder, Colo. 1500; unit panels, crystal detector "A" battery switch and telephone records, for receiving set with audion detector, For Sale- Mignon RW3 undamped receiver with jack; 15% off prices in De- or sell $50. Albert Brown, R. No. 4, Greenwich, Forest catalogue "D ". L. Vexler, 70 Lyons Ave., tube, perfect, $50; Duck's No. 16 hydro- electric Newark, N. J. N. Y. generator, $10. Might consider trade outside radio Genuine "Jupiter" aerial wire now back to line. F. H. Ransford Dalton. Massachusetts. For Sale- Cheap; radio, electrical and chemical the old price of 1 cent per foot, $9 per thousand. apparatus. Call at Leons, Inc., 28 West 46th St., For Sale -One No. 5 B. B. Duck's louse coup- and ask for Vincent Ingrassia. Seven strands No. 22 solid copper. 100% con- ler, $15; 1 home-made auction control cabinet, ductivity. No C. O. D's. 15 lbs. per 1,000 feet. complete with bulb and "B" battery, $15. Ralph Regenerative short wave, complete, bargain, $65. Send postage. Lee A. Bates, 8 Moen St., Worces- Reed, 315 Fifth St. S. East, Watertown, So. Dak. 2 -inch spark transmitter, $9; Blitzen 43- plate, $4. ter, Mass. Burgess, Closter, N. J. For Sale -1 K.W. sending set, $60; same re- Bargain -Selling out; 1 K.W. transmitter with ceiving apparatus. Write for list. D. Meirowne, Selling Out -3,000 meter loose coupler, audion, a record, complete, $60; paragon regenerative, $15; Pittsfield, Mass. one -step amplifier and other instruments. Bar- Brandes superior phones, new, $5; also miscel- gains. Write V. S. Scott, Sidney, Harken! Harken! Complete 2,000 mile wire Ohio. laneous parts. Barrett, 222 N. Dunn St., Bloom- For Sale -Electro radioson ington, Indiana. less receiver, with auction, loading coils, phone, "'n' detector and poten- everything " -$30 takes it. Reason -former own- tiometer, $5; Duck 1500 meter loose coupler, $4; For Sale -DeForest unit panel outfit; TJcv 1503 er dead. Edward Miller, Woodsville, N. H. Brandes Superior phones, $4; DeForest "A" bat- Vernier condenser; U100 variable grid condenser tery switch and telephone jack panel and double and grid leak; Ulc 400 triple coil mounting; U300 Receiving transformer and cabinet, $10. Send inductance coil panel, $5. for details. Martinelli, 213 Money orders only. "A" battery switch and phone connections; Uf Summit Ave., West Sent prepaid. Earle Hadley, Bristol, N. H. 100 400, 2uu, Hoboken, N. J. 200 rheostat; Ur socket; coils 300, Beautiful Receiver in three oak cabinets, De- 100, 75; price $30 including cabinet. John Burke, Bargains- Receiving set, 500 to 12,000 mete,:., Forest T -200 tuner honeycombs, audion cabinet, Geldart St., Valley Falls, R. I. in cabinet 9x12x6 with batteries, but without bulb, "Ace" B 2 -step amplifier in cabinet, Brandes For Sale -Turney, spider -web unit, $5. Alvan $38.50; regenerative set for amateur commercial phones, 1 A. P. tube, 2 radiotrons, 80 feet an- Dean, Brocton, N. Y. reception, $18.50; 15 amp. ammeter $5; Ford coil, tenna, grounds, wire, insulators, "B" batteries, Sell-Transmitting and receiving apparatus, list $1; polar cub fan, $3.50; 2- battery bicycle light, Presto-lite "A" battery, used two weeks, perfect on request; write. Floyd Daisey, Cape Charles, $1.50; new .22 takedown rifle, $5; hunting knife, condition, cost $250. Complete for $175. L. Virginia. $1.25; 3 pocket flashlights, 55c each. Robert Leh- Weiner, Bicknell, Indiana. mann, 408 Hastings, Grand Rapids, Mich. For Sale -% K.W. Thordarson Type R trans- Sell- Motors, power and fan; 10 pounds double former, Thordarson oil condenser, Murdock os- Sale or Trade -Three new Clapp -E. amplifying cotton covered magnet wire, Crystaloi type "AA" cillation transformer, and Bunnel key, sell ail transformers, $10; one new General Electric type detector, loading . coil 36x6, loading coil 36x4 in.; for $55, you pay express; Meteor phones, cost S -1 electric range. Want good transmitting set. generators, D.C.; small gasoline engine. Write $9.19, sell for $6.50. W. Cooley, 1831A State St., C. W. Williams, Cave City, Ry. for information. Dwight Wiard, Carrollton, Ohio. Sell Cheap -Mesco coil navy quenched Granite City, Ill. gaps, in- Let's Swap! Buy! Sell!t.Whatd'ye . got? $20 Baldwins, $14- Wireless shop condensers sulators, other articles. Stamp for list. Winkler, Whatd'ye want? Forward price, description and cheap. Everything new. Harold Jones, Ferndale, 1332 First Ave., New York. quarter for listing, including year's subscription, Wash. For Sale -New, never been used, $3.25 and Swap Bulletin, New York -Detroit- Wichita Falls, $4.25 and postage; 2 Tresco assembled Texas. For Sale -8 panel DeForest set includes two - condensers, step amplifier, honeycomb coils 150 -2500 meters, .001 Mfd. and .0005 Mfd. L. R. Smith, Kenner - Swap! -$85 library for radio apparatus. Mean $67. W. Cooley, 1831A State St., Granite City, dell, Pa. business or don't answer. Melvin R. Scott, Ala- mogordo, N. Illinois. Bargain -Complete panel receiver, less tube, $25. Mex. Sell % K.W. transformer coil $5; 1 K.W. Herman Seikel, Dover, Ohio For Sale-New typewriter, brass spark plugs, condenser, $6; 1 K.W. rotary, $11; Helix, $3; key, tire protectors, automobile trailer. G. A. Loffel- Sell- Regenerative tuner, $30; 14 in. coil, $5; macher, $1.50. Hartwig, 4430 Princeton, Chicago, Ill. condenser for same, $1; flanged gap, $1; heavy Fairfax, Minn. Sell-Never used Jewel meters, 500 V. at $15; antenna switch, $2.50; Murdock O T., $3.75; key, Burned Out V.T.'s. -Have fifteen burned out 100 M.A. at $6; 5 A. at $6 G. R. 2.5 A.H.W. $1; wireless key, $2.50; Bunnel 150 ohm relay, $5. V.T.'s, mostly transmitters; make offer. Joseph ammeter $7. E. Hamalaine, General Delivery, Books, etc. P. Schroeder, Wayland Hall, Beaver Fairhall, Jr., Electrical Machine Shop, Danville, Hibbing, Minn. Dam, Wis. Radio SAYE. Illinois. For Sale -Meccano construction sets cheap, $15. Exchange- Wheatstone bridge for small lathe. For Sale-4 in. spark coil with electrolytic in- Johnson hockey skates, size 9, $8. Maurice Hair, A. Senecal, 437 53d St., Moline, Ill. terrupter gives 4% in. spark, $12; 1?/ spark coil 4734 Congress St., Chicago, Ill. Bargain-New navy coupler, 15,000 meters, $18. with electrolytic interrupter, $7; $5 tel- radion de- Gordon Sargent, 126 Perry Bedford tector, $2.50; $37 type X Clapp -Eastham loose- For Sale-DeForest 15 panel 150 -25000 meter re- St., New coupler, $24. Money ceiver, corn., $100; and 2 -stage amplifier, $50; Mass. talks. Randolph Froehlig, 779 Sixth St., Milwaukee, Wis. Magnavox radio telemegafone, $60; 1 K.W. Bargain transmitter, comp., $50; radiophone, $40. Lots -Five dial omnigraph with extra dials, Complete Wireless receiving set for sale. Con- others, etc. Write for list and particulars. Hahn's $12; Grebe CR4, $45; Mignon BD1 audion contains receivers, receiving transformer, fixed con- Radio Station, Hamburg, Pa. trol, $18; Blitzen, Murdock 43 plate variable, $4 denser, variable condenser, audion panel with B each; Hammond typewriter, $12; two sets of typ,., batteries and aerial. Price $45. Delivered. Jack For Sale -Short wave regenerative receiver, $15; $35. Everything in excellent condition. Wanted Palmer, Ashville, detector, two-step amplifier, two audiotron bulbs, Magnavox. N. Y. Write, phone or call 2HK. For Sale no transformers, $30; large .002 rotary variable For -Complete new audion set. Write condenser, $10; rotary gap, 30 cycle motor, $15; Sale -Smith Premier typewriter, double key- J. Miller, 3227 Abell Ave Baltimore, Md. large oscillation transformer, $15; marble switchboard, good condition, $20. Rollin H. Stewart, 3023 Boulevard Place, Indianapolis, Ind. For Sale -V.T., 45 volt B battery, rotor motor board and switches, $15; 30 -cycle 1 K.W. closed and some more radio goods. New cost $50. Will core transformer. No junk. Ralph Haynes, 615 For Sale-$35, or trade for smaller one, large sell for $25. Bargain. E. L. Forslund, Madrid, Woodlawn Ave., Canon City, Colorado. 1 to 5 kilowatt transformer. Write, Francis Mc- Iowa. Kee, For Sale or Exchange -Wireless receiving set Weiser, Idaho. Swap or Sell -Amplifone as described in Decem- (value $300), for late model motorcycle. A. Pair Brandies Superior phones, complete, $4; ber issue, page 567, will sell for $15, or 2 in. trans- Greenberg, R. 2, Hackensack, N. J. 8 unmounted Universal (honeycomb) coils, 180 to former coil or rotary gap. R. Fangaroli, 40 Bed- For Sale-Slightly used audion panel, $5; am- 4500 meters, $3.75. Add postage on one pound. ford St., New York City. plifier, $10. J. Francis, 5230 Superior Ave., Cleve- H. Butterworth, 331 Quincy St., Brooklyn, N. Y. For Sale- Regenerative set. $18; money order land, Ohio. For Sale or Exchange-Good % H.P. General gets it. Theodore Heinemeyer, 310 Chilton St., Regenerative Units, variocouplers wound on Electric D.C. motor. Paul Bietton, 6195 McMillan, Elizabeth N. J. Detroit, Mich. bakélite tubes $5.25; variometers, $4.25, inside 600 Meter Regenerative Outfit and 2 -step winding; oak cabinets with bakelite panel, 5x5x6 am- For Sale -1 K.W. Type R Thordarson, $20; plifier and detector, Grebe mounted on single bake - in., $2.26; other sizes at proportionate prices; bake- plate glass oil condenser, $15; "Hyrad" rotary lite panel with battery test voltmeter, with two lite tubes and panels carried in stock. Meade gap mounted, $15; 1 K.W. oscillation transformer, amplifier bulbs (A -P); first offer $85; phone Bakelite & Radio Apparatus, 975 Putnam Ave., $4; a set with a record; Brandes phones, $5, ( Mesco), $5. W. D. Cleary, 4 Agate Court, Brooklyn, N. Y. new. Wanted: Tungar rectifier, half list price. Brooklyn, N. Y. Barrett. 222 N. Sale -R. B. D. 8 Mignon detector, R. C. 2 Dunn St., Bloomington. Indiana. For Sale- Murdock phones and variable con- Mignon receiving set; Brandes Superior phones, Regenerative 200 -20,000 meter receiving set with denser. Write. Einer Carlson, Comfrey, Minn. 550 feet seven strand copper aerial wire. Fine two -step amplifier. Audiotron detector and adapt- condition. How much am I offered? Eric Fin- For Sale -% k.w. Packard, $12. Daryl Mc- er. Radiotron 201 amplifier. Send stamps for Clung, 1221 -9th Ave., Huntington, W. Va. ney, Uhrichsville, Ohio. description and photograph. Bargain. C. F. Allen, Box 1504, Providence, R. I. For Sale -Four bulb C.W. radiofone set, send For Sale-New DeForest 6 unit panel set, stamp including 8 honeycomb coils, $38. Write for description and price. H. Becker. 3405 for For Sale- 20,000 meter loose coupler, $16; Itaska St., St. Louis, Mo. particulars. Francis Furlong, 733 N. River St., radioson detector, $3.50; vest pocket kodak, $5. Ypsilanti, Mich. Robert Onstott, Sharpsville, Pa. (Continued on Pape 769)

www.americanradiohistory.com 759 Radio News for April, 1921

(Continued from page 758) (Exchange continued) Receiving Set-First class, at an attractive price. They know how A. F. McAllister, 1825 Monterey Ave., Chicago, Illinois. ONE important reason for the ac- send out your order within a few receive it, at the Bargain -Audion cabinet with tube, $10; de- curacy and speed, which is mak- hours after we -and A. Krauss, time fill it correctly and ship tector and amplifier units made. R. ing Mail Order Service fa- same 4936 W. 12th St., Philadelphia, Pa. Corwin it carefully. mous, is that real radio men actually For Sale- Complete wireless set, list free; en- Send in your order for any item close stamp. Rollin H. Stewart, 3023 Boulevard ship your order. listed below, and expect the same Place Indianapolis, Ind. Their own thoro knowledge of radio, courtesy, accuracy and speed that Swap- Complete set Hawkins' Guides and Har- combined with our up -to -date stock have delighted thousands of other pers' electrical books for 1 -step amplifier. D. Hy- keeping system makes it possible to amateurs. man, 51 Sheldon St., Springfield, Mass. Sale -Clapp- Eastham set of regenerative instruments, $15; tron panel, $4; violet ray machine, Universal -Coil Mounting Plugs $10; also B batteries Write R. G. Schlegel, 1115 Pittsburgh, Pa. Anyone can easily make smooth -running mountings with N. Negley Ave.. these plugs. No bending, no filing, -they are made to fit Bargains -Audion cabinet with one -stage of am- exactly in the first place. Suitable for Radisco and all plification, phones, switches, wireless keys, spark coils and other instruments too numerous to men- hand -wound coils. A few minutes' work with these plugs tion. Send 2 cents stamp for list and prices. will save you dollars that can be put into better apparatus. 114, Lake Como, N. J. Harold Hurley, Box Price, 80 cents, postpaid Sale by lAE -One kilowatt spark transmitter comprising Acme, Dubilier, Benwood, Clapp -East- ham instruments. None separately. Sell complete New Radisco Vario- Coupler nominal price. Prefer local customer bitt all at St., Described on the center page spread of this issue, now in stock. It's an extremely efficient inquiries answered. Young, 294 Ashmont instrument, accurate to the .002 part of an inch! Dorchester, Mass. Price, $7.50 postpaid Choice Chamois Skins- Excellent for polishing and cleaning in the laboratory and home. Guaran- teed washable. Large skin $1; % skin 60e. We VARIABLE CONDENSERS VACUUM TUBES opportunity Relay 6.00 are importers and offer an exceptional A. R. Co., .001 $6.25 Electron to agents. A Boucher, 23 Kimball, Bradford, Mass. VT Amplifier, 1 lb 7.00 A. R. Co., .0005 5.00 VT Extra Hard 7.50 Clapp -Eastham With No. 67 Dial add $1.00. Sell -Marko 4-60, $6.50; 2.0006 AMPLIFYING TRANSFORMERS $6 each; audiotron cabinet, $8; trans - Murdock 866 4.75 condensers 1 5.00 extra. E. Howard, 218 E. 188th St., Murdock 367 4.75 A. R. Co., lb. portation Federal, 1 lb. 7.50 New York City. Murdock 368 8.75 Clapp - Eastham 800 7.50 JACKS AND PLUGS Omnigraph Dials and wireless receiving appara- Clapp -Eastham 800A 9.50 Federal Closed Circuit 85 tus for sale cheap. A Hersde, Burlington, Ont. Clapp -Eastham 800B 11.50 Federal Open Circuit .70 For Sale- Chambers loose coupler, Duck navy Complete with dial. Federal Double Circuit 1.00 set, $10. Five con- Shipping weight One Pound Federal Plug 2.00 coupler, $12 each. Arlington Postpaid. densers, two switches, Murdock phones. Write, GRID CONDENSERS ALL RADISCO COILS James B. Rich, Hobart, N. Y. Radisco, Postage 3 cents .35 For Sale -1 variocoupler, $10; in excellent con- ANTENNA SWITCHES ROTARY SWITCHES Carl Staugaard, 4531 N. Clapp -Eastham, No. 19 1.00 dition and tunes good. Murdock, 3 lbs. 4.50 .85 St., Chicago, Ill. Clapp- Eastham, No. 19A Rockwell Clapp -Eastham, 10 lbs 12.50 Our Own, No. 1 .40 First For Sale -My valuable stamp collection. OSCILLATION TRANSFORMERS Our Own, No .2 .55 $3.80 gets it. Clark B. Rice, Jr., 645 Mills Ave., Postage .05 Baton Rouge, La. Murdock No. 424, 5 lbs 5.00 CORWIN DIALS Will Exchange one 4x5 Serco plate camera for RADIO CRAFT PRODUCTS No. 66, 3" .75 or receiving trans- 15.00 No. 67, 3" with knob 1.80 enclosed variable condenser Detector 1.00 former. Alvin Schaub, Provemont, Mich. Two Step Amplifier 50.00 No. 68, 37%"' 45.00 No. 69, 3y¢" with knob 1.70 real money maker, indispen- Detector and 1 step Postpaid. Found At Last-A Detector and 2 step 70.00 sable to telephone users. Sells for 25c; costs 1 Postage paid. RECEIVERS cent to make. For particulars write That Lab, at Murdock No. 55, 2000 ohm 4.50 Baton Rouge, La., 645 Mills Ave. "B" BATTERIES Murdock, No. 55, 8000 ohm 5.60 Radisco No. 1, 2 lbs 1.50 Brandes Superior 7.00 Must Sell 6 volt, 120 ampere hour Willard Baldwin C. 16.50 battery. Bargain, $12. Geo. Tcter, Sheri. Radisco No. 5, 5 lbs. 2.65 storage Eveready Storage battery prices on Baldwin E, improved 20.00 dan, Indiana. application. Brownlie, New 12.50 The How and Why of Radio Apparatus, by H. Shipping weight 2 Pounds W. Secor, E. E. This newest book on radio mat- TUSRA C. W. APPARATUS CONTACT POINTS ters fulfills a distinct gap in wireless literature 181 Coil, 2 lbs. 7.50 CP -No. 1 Brass, dozen .25 in that, while the treatment is made as under- 182 Coil, 2 lbs. 10.00 CP-4 Brass, dozen .85 standable and as free from mathematics as 183 Coil, 3 lbs. 12.50 CP-5, Nickel Plated, dozen .45 possible, it at the same time incorporates a wealth 170 FM., 8 lbs. 16.00 Postpaid. of technique and instruction for the Radio Amu All apparatus not listed must be teur -the Radio Operator -the Installation and orders for as postpaid Designing Expert -as well as teachers and stu- accompanied by p ostage charges. dents of the subject in general. A very broad field has been covered by the author, at the same time giving a great deal of information not found in A. H. CORWIN & COMPANY other text books. If you are engaged in any branch of the Radio or allied arts at all you will Dept. B2 4 West Pa rk Street, Newark, N. J. surely need titis latest contribution to radio literature, which is destined to be found on every radio man's book shelf before long. This newest of Radio Works, cloth bound in Vellum de Luxe, Gold Stamped and Hand Sewed, Iras 160 pages. Size of book 8x9 inches. The How and Why of Write to our nearest branch for Radio Apparatus, Postpaid $1.75. Experimenter Book Dept. 236 -A Fulton St., Canadian Publishing Co., New York City. Price List "B" of Radio Apparatus, Just Off the Press- Design and Construction Supplies and Publications. of Audion Amplifying Transformers (Radio and Amateurs Audio-Frequency Types). By Edward T. Jones late Associate Editor Radio Amateur News. The transformers shown in this book have never been described in print before and have usually been Scientific Experimenter Limited considered a manufacturer's secret. The designs are very rugged and simple. A book that every Dominion Bldg., Confederation Life Bldg., 93 King St., E., radio "bug" should have. Written so you will Vancouver, B. C. Winnipeg, Man. Toronto. Ont. understand every word. Price 25c postpaid. Ex- Vaughan Electric Ga., Board Book Dept., 236 -A Arcade Bldg., of Trade, perimenter Publishing Co., Halifax, N. S. 94 Germain Street St. John's, N'fl'd Fulton St., New York City. St. John, N. B. Show Rooms, Electricity Course in 20 Lessons. Head Office, QUEBEC Experimental 11 St. Sacrament St. MONTREAL, 83 McGill College Avenue By S. Gernsback and H. W. Secor, E. E. t course of the theory and practice of Electricity for the Experimenter. New experiments are described and explained and nearly every ap- Add to your Salary-Make extra Pin Money. plication of Electricity in modern life is given. MONEY f o r You Start a lucrative business of your own. 160 pages -400 illustration. Flexible cloth cover, Spend an hour each day taking subscriptions for the "Radio News." We'll pay you well and you'll 75c postpaid. Stiff cloth cover, $1.25 postpaid. enjoy the work. Write for full particulars. Circulation Dept., RADIO NEWS, 296A Fulton St., Experimenter Publishing Co., Book Dept., 986 -A New York City. Fulton St., New York.

www.americanradiohistory.com 760 Radio News for April, 1921

"ATLANTIC RADIO" UL ETIN

T -A -W HOT WIRE Use the "EVEREADY" AMMETERS Six "I" G 60 "A" 0 -1, 0 -212, 0 -5 BATTERY A FEW LEFT AT 6 Volt An Exceptional 5 Opportunity 60 Ampere Hour Capacity GUARANTEE -18 MONTHS

Radiotron UV 200 $5.00 CHELSEA VARIABLE Radiotron UV 201 6.50 Paragon V. T. CONDENSERS Control 6.00 No. i -.00ir m.f. mounted $5.00 Paragon 6 ohm Rheostat 1.75 No. 2 -.0006 m.f. mounted 4.50 Radisco "B" Battery (small) 1.50 Radisco `B" Battery (large) No. 3 B. D..00rr m.f. unmounted 4.75 2.65 No. 4 B.D. .0006 m.f. unmounted 4.25 G. E. Variometer 6.50 Radisco Grid G. E. Variocoupler Condenser .0005 m.f .35 7.50 G. R. Grid Condenser .0005 m.f .25 "ZRF" Regenerative Set 38.0o Murdock Variometer, Turney Spider -Web Inductance 6.00 complete with "Ajax" Buzzer Practice Set 1.75 wood panel, dial and knob 7.50 0-0 "Ajax" High Tone Buzzer Murdock Variocoupler, complete .50 with panel and 6 -point switch 8.50 `RADIOTRON" EVERYTHING FOR THE Murdock No. 366 V. Condenser 4.75 Interior only 4.25 UV-202 AMATEUR Murdock No. 367 V. Condenser, A FIVE -WATT TRANSMIT- We carry at all times a complete transparent case 4.75 TING TUBE; FILAMENT line of the best in Radio Equipment. Murdock No. 368 V. CURRENT 2.35A, AT 7.5V. Condenser 3.75 PLATE VOLTAGE, 350 V. Interior only 3.25 NOW READY FOR DIS- Our service department will Murdock No. 55 Telephone Headset, TRIBUTION. cheerfully answer your questions or 2000 ohms 4.50 give you advice -this service is Murdock No. 55 Telephone Headset, Price, $8.00 each FREE. 3000 ohms Include Postage on 1 5.50 Pound Let us solve your problems! C. W. EQUIPMENT

"National" Rheostat, back mt'd, 6 Acme C.W. Power Transformers ampere current carrying capacity $5.50 200 watt mt'd, $20.00; unmt'd 5 lbs. 16.00 Tuska Inductance Type 181 (capac- 5o watt mt'd, $15.00; unmt'd 5 lbs. 12.00 ity feed -back circuit 2 lbs. 7.5o Acme Choke Coil, 500 MA capacity 3 lbs. 6.00 Tuska Inductance Type 182 (split - Acme Choke Coil, 15o MA capacitY 3 lbs. 4.00 filament type feed -back 2 lbs. 10.00 Acme Type A -3 Modulation Trans- Tuska Inductance Type 183 (grid- former 2 lbs. 7.00 tickler feed -back) 2 lbs. 12,5o Acme Filament Transformers, fully Tuska Filter, Type 170 3 lbs. 16.00 mounted, 5o watt 2 lbs 12.00 Weston Model 301 milliammeter Acme Filament transformers, core (plate meter o- iooma) 2 lbs. 8.50 and coils assembled, 5o watt. . 2 lbs. g.00 Acme Filament Weston Model 301 ammeter o -5A 2 lbs. 8.5o Transformers, fully mounted, 15o G.R. Hot Wire Ammeter, o o -i, watt 2 lbs. 16.00 -/, Acme Filament transformers, core 0 -2 1/2, o -5A . 2 lbs. 7.75 and coils assembled, 150 watt 2 Ibs. 13.00 G. R. Tube Socket 1 lb. 1.75 W.E. Microphone, with bracket 2 lbs. 4.05 "Eldredge" 6o -A.C. Ammeter, o -IoA.2 lbs. 9.5o Connecticut Microphone 2 lbs. 3.95 "Hoyt" Flush, Black, A.C. Volt- Connecticut Microphone, with long meter o -15V 2 lbs. 8.00 arm 3 lbs. 4.25 ATLANTIC RADIO COMPANY, Inc. 88 Broad Street Branch: 15 Temple St. Boston 9, Mass. REQUEST "BULLETIN 14" Portland, Me.

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Just what you need to know to succeed in ELECTRICITY EVERY electrician, every engineer, every mechanic should know READ THIS PARTIAL LIST OF CONTENTS instructive books, which give in Contains 348 pages, 388 illustrations. Electrical about these wonderfully helpful No. 1 signs and symbols-static and current electricity plain words a complete working knowledge of electrical engi- -primary cells -conductors and Insula tors- resistance and conductivity- magnetism -induction coils- lynamo principles neering in all its phases. -classes of dynamos-armatures--windings-commutation- brushes, etc. You run into some new electrical problem almost every day. The Contains 348 pages, 394 illustrations. Motor in your every day work is in No. 2 principles -armature reaction-motorn -motor startin - information you need to help you calculations-brake horsepower -selection and installation of dynamo and motors -galvanometers-standard cells -current measurement resistance measurement - voltmeters - watt- meters -watt -hour meters-operation of dynamos-operation of motors. etc: Contains 300 pages, 423 illustrations. Distribu- No 3 tion systems -wires and wire calculations-inside, outside and underground wiring -sign flashers- light- ning protection -rectifiers -- storage battery systems. etc. Contains 270 pages, 379 Illustrations. Alternat- HAWKINS current dia- No. 4 ing current principles -alternating grams =the power factor -alternator principles- alternator GUIDES etc. ELECTRICALfinger ends. They cover every imaginable construction- windings, These books place electricity at your Contains 320 pages, 614 illustrations. A. C. Motors principle, theory, problem, trouble, and way of doing things electrically. No 5 -synchronous motor principles -A. subject, a and induction Every subject is indexed so that you can turn right to it. They are study course C. commutator motors -induction motors. transformers; losses, and a reference guide in one, written in plain every day language-no wasted words construction, connections, tests -- converters -rectifiers, etc. what you need to know -chock full of up-to- the -minute electrical knowledge. Contains 298 pages, 472 illustrations. Alternating -only engineering. They will help you in NO. 6 current systems -switching devices -circuit break- The guides are a complete course in electrical -regulating devices day's electrical work. You can't ask an electrical question that ers-relays- lightning protector apparatus every uccall of the -synchronous condensers -indicating . devices-meters -power Hawkins Guides can't answer. factor indicators-wave form measurement- switch boards, etc. 379 illustrations. Alternat- ^% Contains 316 pages, NO . 'Sng current, wiring power stations - turbines E -Size Flexible Covers management, selection, location, erection, testing, running. Pocket care and repair-telephones, etc. The books are small enough to slip into your coat Contains 332 pages, 436 illustrations. Telegraph pocket -handsomely bound in flexible black covers. No. 8 -- simultaneous telegraphy and telephony-wire- You can carry each volume with you until you have less - electric bells - electric lighting - photometry, eta. What Electrical Men Say mastered its contents. 3,500 pages of actual information Contains 322 pages, 627 íllus.. atlons. Elec- Helped Him Make Good and 4,700 illustrations. Once you see these books and No. 9 tric railways-electric locomotives -ear light- put them Into actual use you will never again want to be ing-trolley car operation- miscellaneous applications - "lt is only right for me to recom- motion pictures engine ignition -automobile self - mend highly the Hawkins Guides, for without them. Try 1t at our expense. -gas assist- starters and lighting systems. electrie vehicles, eta they have been of the greatest Contains $13 pages, 599 illustrations, ance to me in placing me in my NO. 10 Elevators -cranes -pumps-air com- present position as Superintendent of heating-electric welding- Construction Department of one of prsoldering ssolor and brazing - industrial electro- AUDEL Ohio's largest Electrical Companies. NO MONEY lysis- electro plating - electro- I would like to see every man have a SEND look -rays, etc. & CO. set of Hawkins Guides." It will cost you nothing to receive these books -to -X '72 Fifth Ave. Knecht, Columbus, Ohio. them over -ask them all the questions you can think of Also a complete 126 -page ready Geo. -use them in your work-study them-pick up some reference index of the complete New York, N.Y. In the Naval Electrical Dept. lnformatioh that will increase your earning ability. We library. This index has been will ship you the entire set of 10 volumes entirely FREE. planned render S please submit me for "The Hawkins Guides are great This is a sign of our confidence in the guides. Pure to easily ac- Hawkins help to me in the Naval Electrical gold does not object to being tested. Keep them for cessible all the vast infor- examination Department, which they cover very seven days and if you db not decide that you can't get mation contained in the Electrical Guides (price thoroughly." C. 1. Cornell. along without them, return them to us and owe us 10 guides. Si each). Ship at once, pre - U. S. Receiving Ship, Brooklyn, N. Y. nothing. electrical ® There are over 13,- paid, the 10 numbers. If satis- When you decide to keep them you only have to pay Superintendent $1.00 down and remit the balance of $9.00 on the easy 500 cross refer- factory I agree to send you $1 "I am now superintendent of the payment of $1.00 a month till paid for. ences. You find within seven days and to further Hydro - Electric Systems, will you want Dunnville Use this coupon to get the books. It pay you what $1 each month until paid. and Hawkins Guides were a great many times over to know In- mail you help to me in holding down a responsible position." stantly. W. B. Swartz. Dunnville, Ontario. THEO. AUDEL & CO. Signature. Wireless Operators Occupation 'T have worked wireless for ten 72 Fifth Ave. New York, N. Y. years -but I wish I had these books years ago. as they have saved me a Employed by great deal of trouble." H. Marshall. Steamer M & B No. 2, Ahlr Residence Walker/111e. Ont. N., Reference ...... R. April

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