PR Sep 1925 .Pdf

with which is combined `the Wireless Age Edited by KENDALL BANNING

Opedistisr WO pages ofiniacticaliusefta and alagtotitativeinformaeon for the Itpdio Antatestr and the Ilvoadcast Listener

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FOUNDED 1911 CONTENTS for SEPTEMBER, 1925 VOLUME (('ozvr design by Frank B. Masters) VIII NUMBER 3 The Nlan Who First Found a Use fur Ionization in Radio FRONTISPIECE Ilow the Air Affects Radio E E Free . . Page 199 How Radio Dead-spots are Found by a Wandering Broadcasting Station / O. Perrine 207 When You 'rum Your Dials. Jacques Avon 212 \Ien Who Made . 218 gth I nstallincnt Useful Charts for Amateurs t. Todd, Jr. 221 Simple -How-to-Build- Articles for Beginners Laurence M. Cockaday.. 227 Ni). 11 : An Antli0-frequency Anudnier fr AC The At( nu Bragg 232 .1rtiile Nio. 2: The Nature iif (ial...... The Diary of a Radio Fan 1) R. Patterson 237 Ilandv Tools fur Radio Fans 239 Nii. 0: The lackknift. "What Set Shall I Buy ' Thc Tcchn ica/ tat T 240 4th 111st:dime-lit I roW to Cret the NI, )st Out i if Yi )ur Read v-inade Receiver (;ordc),: Taylor 244 \. The Freed-Pisumann Nuutr,n1\ fly Call Letters That I lave a Past .. ..LwaTence .4. Corridon 255

Riding to Riches by Radio...... Ralph E. Renaud 256 Part 11 Listening liorn to Det,ct Aircraft 261 DLI,ARTNIENTs In the Exper-j.menter's Laboratory The Technical /aft. 262 'rite Broadcast Listener Raymond Francis l'ates.. 272 What's New in Radio Apparatus The Technical S'talf 276 In the World's Lai)oratories E E. Free 280 What Readers Ask Laurence M. Cockaday... 288 Broadcasts J Andrew ll'hite 294 \ Loa. \ Ill SEPTEMBER, 1925 NUMBER 3 tox Popular Radio, Inc., (27 \Vest 43rd St., New York. N. Y.. telephone num- . Chickeling I91ir,: Douglas IL Cooke. President and Treasurer; Kendall Banning, Vice-Pres- ident; Eatrence M. Cockaday, Secretary; Joseph T. Cooney. Asst. Treasurer. Price 25 cents a copy; subscription $3.00 a year in the U. S., Canada and all countries within the domestic postal zon,-; else%s here .$3.50 a Year, payable in advance. The International News Company, Ltd., No. 5 Bream's Bldg., London. E. C. 4, sole distributors in England. Entered as second class matter April 7, 1922, at the Post Office at New York. N. Y.. under the act of March 3, 1879. Copy- right, 1)25, and title registered as a trade-mark by Popular Radio, Inc. Copyright in Great Britain by Popular Radio, Inc.. 6 Henrietta St., Covent Garden, W. C., London, England. Printed in U. S. A. LAURENCE M. COCK.ADAY. Technical Editor E. F. 1.10,21-2. Ph.D.. Contributin.4 Editor JOHN \. L. HOGAN. Contributing Editor

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www.americanradiohistory.com PAGES WITH THE EDITOR

Radio Corporation ut America "NO COMBINATION COULD BE MORE IDEAL TION TH. \ \' THE COMBINA- OF THE WIRELESS AGE WITH POP('LAR RADIO" ft'ith this issue THE WIRELESS AGE, the oldest radio magazine in the United States, is consolidated with POPULAR RADIO. Cllr. J. Andrew White, for ten years the Popular editor of THE WIRELESS AGE and known the country, to radio fans throughout takes this occasion to welcome his former readers growing army of readers to the large and of POPCL \R RADIO. The Editor takes pleasure in calling upon his friend lIr. 1f'hite for a few remarks! The Dean 's Declamation ALTHOUGH the surroundings are unfa- as often as we would have liked miliar, looking up from this page to; but as years into rolled by and the same familiar names kept the eyes of old friends gives me the comfort- repeating themselves able feeling on the subscription lists of having strayed into the hearth - there was no resisting side circle after being far the feeling that we were afield for a time. welded into one large but never cumbersome If home is where the heart is, then I have family. never gone away ; for nothing is dearer in the memories I have stored up than the many AND now this move into a new community, happy years when it was my good fortune to where there will be more room for the growth guide and govern feeble footsteps into radio of the true ideals and high purposes that served for a host of loyal followers of that brave little so well in cottage days and made the mansion pioneer publication, The Wireless Age. possible. * * * GOOD neighbors, these POPULAR RADIO folk! IT is a very easy thing to be sentimental They looked like it about old at the beginning and they associations, and it doesn't embarrass have proved it since. A happy me a bit to say that on an occasion culmination like this of the romance in radio, that is the there is no little emotion welling up way I within see it ; the words consolidation and combina- me. tion seem too * * * cold. As an Editor, there were thousands among POPULAR RADIO and The Wireless Age have my readers I counted as my friends. We wrote always had so much in common, to each interests and other, we met occasionally ; neither, (Continued on page 6) 4

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www.americanradiohistory.com PAGES WITH THE EDITOR (Continued from page 4) aims identical - I simply can't picture their If you are in Atlanta coining together in the light just let me know and I of anything as xvill try to show you a good time." stiff and formal as is suggested by the phrase, -MORRIS DORSEY, Atlanta, Ga. a merging of corporate property. No, it may 1 e whimsical, but I see that first born brain- ON page 68 of POPULAR RADIO for child wedded to the big boy next door, appeared July and some data concerning the Type C hordes of friends welcoming the new com- receiver of the Standard munion of interest. Radio and Electric Company. But the picture that accompanied it, as well as the title, applied to the Stand - I LIKE the idea of these two magazines as ardyne receiver ruade by the Standard one. No combination Corporation Radio could be more ideal. -an entirely different concern with * * * a name that is somewhat similar. The Am concerning data I proud of the mutual respect in which the Standardyne receiver, accom- the staffs of each have held each other, and in panied by a picture of the set, appears every present in the way I look for the readers to cone out installment of the "What Set Shall I ahead in the newer, bigger and better maga- Buy" series. zne resulting from a fusion of interests iden- * * * tical in purpose but characteristically indi- To the cynics who insist that the broadcast- vidual. ing of an event adversely affects the tendance, pa'd at- * * * the extraordinary success of the PERSONALLY, I feel more than a tinge of outdoor concerts given at the Lewisohn regret that I can have no hand in fashioning Stadium in New York by the Philharmonic Orchestra the new periodical ; it is a task worthy conies as both a refutation of any rebuke. and a man's finest effort ; but fate eased the editorial blue pencil out of my fingers some two years * * * ago, and it looks that it might UNTIL the first of these great concerts be for all broadcast were time, for the growing pains of infant broad- (an event that was initiated by casting allow of no digressions into the pleas- POPULAR RADIO on August 11, 1922), the paid ant paths of journalism. attendance at these concerts averaged between 6,000 * * and 7,000. As soon as the concerts * broadcast, were So I shall stand aside and envy Kendall the attendance jumped conspicuously Banning-who unquestionably -reaching the record figure of 20,000. will do a better * * * job than anyone else could, anyhow. To him, success. To you, congratulations. THAT is why the Philharmonic concerts are now broadcast regularly * * three times a * week through WJZ. FoR myself, it is but a step back to the ranks The reason is obvious. of interested readers, It pays. whence I carne, just for * * * an occasion which seemed to call for a verbal handshake all around. WITH this issue POPULAR RADIO welcomes to its subscription list the subscribers of The * * * Wireless Age -whose unexpired GLAD to have subscrip -, been with you for these few tions will be filled by this magazine. minutes -73s for now and all time. * * * Jr. ANDREW WHITE As POPULAR RADIO costs $3.00 a year, and * * * as The Wireless Age cost $2.50 a year, an ad- BUT the Editor has no intention of letting justment on all unexpired subscriptions to Mr. White slip off the editorial harness quite the latter magazine will be made on a pro so easily. Since Mr. White wrote the above rata basis. Thus, any subscriber who has a he has accepted the Editor's invitation to con- s'x months' unexpired term on The Wireless duct ' the "Broadcasts" department of this Age will receive POPULAR - -RADIO for five magazine -a department that will give him issues. And subscribers to POPULAR RADIO the opportunity of keeping our readers in- who have also subscribed to The Wireless formed of the progress of radio throughout Age will have their subscriptions extended the world. proportionately. * * * * * * So if you turn to page 294 of this issue, THE consolidation of these two subscrip- you will find Mr. White's department, written tion lists gives POPULAR RADIO far and away in his own characteristic vein -and illustrated the largest subscripitori of any radio maga- with a portrait of the "Major" (as he is zine in this country, according to the last popularly known) at the head! available figures of the Audit Bureau of * * * Circulation. HLRE is a letter that makes the Editor appreciate the disadvantages of being confined in an editorial sanctum in New a York: "You amottla may be sure that I am not going to miss a single number of POPULAR RADIo. It is the only radio magazine that thinks of the reader first. Editor, POPULARPULAR RADIO 6

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ARCTIC t THE MACMILLAN ASSOCIATION Since 1915- Standard for all sets Types C -301A M39 C : -300 BULDwO. psTOw. -299 C 910 TREMJNT C -11 : C -12 1925 April 19th, In the Orange and Blue Carton In that Jr.. white and Mr. E. F. McDonald, silent Northland Avenue, with 332 S. Michigan its glistening Illinois. ice, driving blizzards ChiL`ago, and endless, relent- less cold, Cunning- My dear Gene: ham Radio Tubes much success and deliver the I have had so same ef- in my ficient, well- rounded the Cunningham tubes long life with service that makes such favorable reports them valued so high- and I have heard set, United ly in the shelter of tour throughout the during my lecture the American home. we should have decided that States, that I with Cunningham receiv- MacMillan's equip the Expedition choice ing tubes exclusively. may well be arrange You will therefore please order, yours tubes, per attached to purchase these in time to the Bowdoin and have it shipped the sailing at Wiscasset. for the tests before Sincerely yours, r

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www.americanradiohistory.com The Progressive Policy of POPULAR RADIO is Serving the Interests of Science

"POPULAR RADIO, one of the first magazines in the broadcast ' field, has kept abreast of the extremely rapid development of this science in a manner that reflects much credit upon its editorial direction. The progressive policy of this magawine in giving publicity to developments in the radio field which will affect the future of the science is particularly commendable."

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www.americanradiohistory.com Courtesy of Mr. H. P. Don1é The Man Who First Found a Use for Ionization in Radio THE sodion detector tube, invented by Harold P. Donlé, operates by virtue of a swarm of ionized atoms which it contains. Other ionized atoms, formed from the gases of the air, are now believed to be of great importance in the transmission of radio waves through the upper levels of the atmosphere.

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VOLUME VIII SEPTEMBER, 1925 NUMBER 3

How the Air Affects Radio Theories of the transmission of radio waves have created much argument among radio engineers. Contro- versies" over the Heaviside Layer are still fresh in everyone's memory. During the past twelve months some new theories Of great interest have been formu- lated; among the important factors are the atoms and electrons of the air and the magnetic field of the earth.

By E. E. FREE

IF a fish at the bottom of the sea knew more exact, but, in any case, the air how to build himself a radio trans- gets into it. mitter we might expect his broadcasts Does this air through which we must to be hampered somewhat by the fact do our broadcasting affect radio in any that above and around his apparatus way? A year ago most enginéers would there lay a vast ocean of s_ alty watet probably have answered no, except as through which radio waves could not the upper levels of the atmosphere be- be expected to move with complete free- came involved in the supposed phenom- dom. Indeed, we know from the experi- ena of the Heaviside Layer. ence of the man -made fishes which we Now we are far less sure. It appears call . submarines that the ocean of water that the atoms and electrons of the air really does hamper the progress of radio do have some rather important effects waves. . on the propagation of radio waves. Not We forget, however, that all our or- only is the difference in transmission be- dinary broadcasting takes place at the tween day and night now ascribed to very bottom of another great ocean; effects in which these atoms play a con- the ocean of air that surrounds the earth trolling part, but such things as fading, and in the depths of which we live. The the deviation of the apparent direction radio waves with which we work do not of radio waves and other anomalies of move in a vacuum or in pure ether. transmission are now believed to be af- They move in the air. "On the air" and fected quite materially by things that "on the ether" are used popularly as happen to the particles of the air. synonymous terms. "Through the air" The work which has led to these ideas and "by means of the ether" would be began with the attempt to define more 199

www.americanradiohistory.com 200 POPULAR RADIO exactly and surely the nature of the fa- This idea of two waves helped greatly mous Heaviside Layer. This laver was in explaining some of the phenomena of supposed, you remember, to consist of fading and of daytime absorption stratum but it a of very thin air, high up still left us essentially without an under- above the earth and possessed of a con- standing of what actually happened siderable to electric conductivity. It acted, the upper wave -the one in the supposed the physicists thought, as a sort of Heaviside Layer -or of why mirror the two for the radio waves, forcing them waves split off from each other and to travel around the curvature of the sought their different paths through earth instead of moving off in straight space. It is in attacking these proble'rns lines into space. that we come to the effects of the atoms There were two theories of long -dis- and electrons in the air. tance radio transmission. One was this As long ago as 1912 the distinguished Heaviside Layer theory. The other and English physicist and radio expert, Dr. opposing theory was the Gliding Wave W. H. Eccles, had suggested that the theory. It assumed that the waves trav- conductivity of the Heaviside Layer eled along the surface of the ground in might be caused by "ions" in the upper much the same way in which the waves air. An ion is a particle of matter which of "wired radio" travel along the copper carries an electric charge. Most atoms wire that guides them. Arguments be- are electrically neutral. But once in a tween the advocates of these two theories while an atom may pick up an extra were rife up until about two years ago.* electron or may lose one of its own elec- Gradually it became apparent that trons. This gives it a charge; negative both of these theories might be right. in one case, positive in the other. It A radio wave moving outward from a becomes a negative or a positive ion. transmitting antenna seems to be split Many of these charged ions might into at least two parts. One of these parts exist, Dr. Eccles thought, in the upper moves upward into the upper levels of part of our atmosphere. Being charged, the atmosphere and travels along some- they might serve to carry electric cur- thing, perhaps a Heaviside Layer, which rents, just as do the similar ions which exists there to provide a path for the exist in the solutions used in storage waves. The other part of the wave moves batteries. Thus the Heaviside Layer outward along the surface of the ground would be rendered conducting and would (or of the water) just as the Gliding have the property of reflecting radio Wave theory assumed that it did. wáves. This ionic idea lay, rather vague- Actual experiments carried out in Eng- ly, at the bottom of most of the reasoning land on December 1 1 , 1924, and repeated about the Heaviside Layer. on February 17, 1925, resulted in a On October 27, 1924, Sir Joseph virtual proof of this two -path trans- Larmor, one of England's greatest math- mission. Still more convincing evidence ematical physicists, read before the Cam- was obtained by Mr. Greenleaf W. bridge Philosophical Society an import- Pickard and his collaborators in their ant contribution to radio theory. He radio investigations during the eclipse of took this vague idea of ions in the upper the sun on January 24, 19254 air and gave it precise and definite *See the papers by Dr. Elihu Thompson, Sir Oliver meaning. He showed just how these ions Lodge, General George O. Squier and Professor R. A. Fessenden in POPULAR RADIO for December, 1922, and would react on the waves and how they January, March and November, 1923. could produce the bendings and absorp- f "Local Reflection of Wireless Waves from the Upper A'mosphere," by E. V. Appleton and M. A. F. Barnett. tions of the waves which we know to Nature (London), vol. 115, pages 333 -334 (March 7, 1925). occur.* $ "The Effect of the Solar Eclipse of January 24, 1925, on Radio Reception," by Greenleaf W. Pickard. Read before the Institute of Radio Engineers, New York City, April 1, *Larmor's 1925. To be paper was published, in abstract, in Nature published in the Proceedings of that Institute. (London), vol. 114, pages 650 -651 (November See also the summary note in POPULAR 1, 1924) and RADIO for July in full in the Philosophical Magazine (London), vol. 48, 1925, pages 85-86. pages 1025 -1036 (December, 1924).

www.americanradiohistory.com HOW THE AIR AFFECTS RADIO 201

Brown Brothers A GOOD DETECTOR OF AIR IONS The familiar gold leaf electroscope will serve very well to detect ionization in the air. The thin gold leaf, just visible to the left of the downward projection inside the glass case, stands out from the projection because it is repelled by the electric charge. In ionized air the ions rapidly carry this charge away, so that the gold leaf falls against the projection.

To see just why these ideas of ions nitrogen gas; approximately twenty per are so important for radio theory we cent is oxygen gas. There are very small must examine a little more closely the amounts of other gases; argon, carbon nature of the air. At the surface of the dioxide, hydrogen, helium, neon and earth -that is, on the bottom of the air others. The atoms of all these gases are ocean -the air has a pressure of about relatively free. They move about rap- fourteen and one -half pounds on each idly in a vast cloud, like a swarm of square inch of surface. bees. A cubic foot of air weighs a little over As one goes up above the surface of one ounce. Approximately eighty per the earth the air becomes thinner and cent of this air, by volume, consists of thinner. At a height of seven miles,

www.americanradiohistory.com 202 POPULAR RADIO

which is approximately the record for a in thinking about atomic dimensions. man in an airplane, the pressure and Imagine a cubic inch of air, cut out density of the air are only about one - of the atmosphere somehow and con- fourth of their values on the surface of tained in a small glass box. Imagine, now, the earth. At fifteen to twenty miles, that some obliging magician enlarges which heights have been explored to this small block of air for you, atoms some slight extent by means of recording and all , until it is a hundred million instruments sent up on balloons, the times as large as in its normal state. density of the air is less than a twentieth The glass box holding the air will now of its value at the surface. At a height be a little more than fifteen hundred of fifty miles there is prcbably only miles square. Set down on the United about one one- hundred -thousandth as States it would reach from New York to much air as we are accustomed to. But Denver and from the Canadian bound- even up as high as three hundred miles, ary to the southern tip of Texas. Of and possibly even higher, there are still course, it would reach up into the sky a few scattered atoms of the various the same distance of fifteen hundred gases. miles. To get an idea of how the air affects Now suppose you investigate the in- radio we must think of it as a vast as- terior of this swollen cubic inch of air. semblage of individual atoms. Let us If your eyes are quick enough you will make use once more of the idea of see the rapidly moving atoms of nitrogen enlargement which is so convenient and oxygen and other gases in the air.

Browa Brothers HOW IONS STOP WAVES If a water wave entered this mass of floating logs, each log would be swung up and down by the wave. The logs would rub together and thus use up energy. This would absorb the energy of the wave. Just so, the swinging ions in the air may hit together and use up the energy of the radio waves, as is described in this article.

www.americanradiohistory.com HOW "11 I F. AIR .1 F 1 ECTS RADIO 203

WPUcÌnRhOII+P TWO ANTENNAS FOR TESTS OF WAVE TRANSMISSION !Pork with this short -wave experimental station of KDKA, near Pittsburgh, is reported to have led already to significant new data concerning the effect of atmospheric conditions on waves of different wavelengths. The horizontal cages on the tops of the masts constitute one antenna. The other one is the vertical rod visible just beyond the house.

Each of these atoms consists, you re- collisions will be about thirty -three feet. member, of a few electrons revolving The number of atoms in even so small around a central nucleus, much as the a bit of air is a'most incomprehensible. planets of our solar system revolve In ordinary air some of the atoms are around the sun. On the scale of enlarge- attached to each other, two by two, to ment which we have adopted each of form what chemists call molecules. these solar -system groups constituting Ignoring this, and counting each such an oxygen atom will be about one inch molecule only as a single atom, the across. Each nitrogen atom will be a number of individual particles in one trifle larger. cubic inch of ordinary air is expressed by All these atomic systems will be flying the figure 440,000,000,000,000,000,000. about inside the glass box very rapidly Imagine all of the atoms in our en- indeed. They collide with each other larged cubic inch of air piled up on the every moment. Others collide with the ground, like billiard balls. They would glass walls of the container that holds cover the whole United States to a them. On the average, in our enlarged depth of nearly three hundred feet. model of a cubic inch of air, the atoms Even if the atoms were only as large as will be about twenty -three feet apart. peas, there would be enough of them to Each one will collide with another one cover our country up to the chin of a many times a second. The average moderately tall man. distance of travel of an atom between All this applies to a cubic inch of air at

www.americanradiohistory.com 204 POPULAR RADIO the earth's surface. As one goes up about two thousand feet higher and higher apart instead of in the atmosphere the twenty -three feet apart. At atoms remain individually higher levels of the same the atoms would be scarcer still. size but the number of them in a cubic But our interest is not so much in the inch decreases greatly. At a height of ordinary air atoms fifty as it is in the few of miles, which is about where the them which are electrically chief radio phenomena charged or probably occur, "ionized." Sir Joseph Larmor the number of atoms estimated (or molecules) in a that at a height of fifty miles there might cubic inch is probably about i ,000,000,- be one charged 000,000,00o; atom -one "ion" -for still a very large number each Io0,000,000,000,000 neutral but vastly less atoms. than are present in one There are also a few cubic inch free electrons, of air near the ground. On the electrons that are flying about same scale of enlargement by them- which we have selves without being attached to atoms been using, the one -inch atoms of this at all. upper air would he, on the average, It is these charged ions and free elec-

A drawing made for POPULAR RADIO by Arthur Merrick ONE WAY TO CONVERT AN ATOM INTO AN ION This diagram shows how a speeding electron may hit an atom of carbon and knock out one of the atomic electrons. This atom, then, minus one of its full complement of electrons, will he an ion. It will have a positive charge, the charge on the atomic nucleus being no longer neutralized in full by the outer e.'ectrons.

www.americanradiohistory.com 110W)W T II E.1I It _\ hEC;T 5 RADIO

Brown Brothers SHOOTING STARS TELL MUCH ABOUT THE UPPER AIR This picture shows the track of a shooting star that happened to cross the field of the telescope while a star held aS being photographed. Shooting stars are small solid bodies that encounter the earth and are heated by friction with the air. Observations of them have proved that there is still some air as high as three hundred miles above the earth.

Irons which effect the radio waves. wave may have a reaction on the wave A radio wave represents electric and itself. To lift and drop the floating stick magnetic force. If it hits against a on the ocean may absorb some energy. charged particle, such as an ion or an That may take away a little of the electron, the wave tends to make the energy of the water wave. Similarly, if particle move. A single ion or a single the ions or electrons in the air absorb electron is swung backward and forward some of the energy of the radio wave by the wave in exact time with the fre- that may slow up the wave or deplete its quency of the wave. energy. A five- hundred meter wave, for ex- There is at least one way in which this ample, has a frequency of boo kilocycles, really does happen when radio waves which means 600,000 alternations of traverse the air. This is by collision of force each second. Such a wave will the swinging ions with other ions or with swing an ion back and forth 600,000 ordinary uncharged atoms. Such colli- times a second. It is much as though a sions absorb energy. The energy must water wave on the ocean came along and come from the thing which started the swung a floating stick upward and swings, namely from the radio wave. In downward in time with the successive the lower part of the air the atoms are crests and troughs of the wave. - very close together. An ion, swinging in But the important thing about this is response to a passing radio wave, is that the swing of the ion in time with the practically sure to hit many ofher atoms

www.americanradiohistory.com 206 POPULAR RADIO during even a single back -and -forth Drs. H. W. Nichols and J. C. Schelleng, swing. That is why the absorption of have calculated some of the effects of energy from radio waves is so great in the this terrestrial magnetic field on the lower part of the atmosphere. The wave vibrating electrons of the upper air and, is wasting its energy in bumping the through them, on the propagation of swinging ions against the neutral atoms radio waves.* It appears that the effects of the air. are considerable; amounting, on certain In the upper part of the air the ions probable assumptions, to a sufficient and atoms are much farther apart. When cause of fading, as well as an explanation the ions swing in response to a passing of some of the mysterious alterations of wave they have a much lesser chance of direction which radio waves so frequently hitting something and losing energy. exhibit when they have travelled con- Accordingly the loss of wave strength by siderable distances. There is a proba- such ionic absorption is much less. At a bility, also, that a magnetic effect is the high enough level it is virtually zero. chief factor in dividing the original wave This matter of energy absorption is into the two or more parts which follow but one of the efTects of air particles on different paths. the wave. In the higher parts of the Further complexities are introduced atmosphere, where the Heaviside Layer by the fact that both the magnetic field is supposed to be, freè electrons are sup- of the earth and the number of ions in a posed to be even more effective than the cubic inch of air may vary from hour to ions. These electrons may actually assist hour. For example, sunlight increases the the passage of the wave. They can make number of ions. That is probably why it move faster. That is one reason why radio transmission is better at night than the wave is bent around to follow the in the daytime. When these new ideas of curvature of the earth. the reactions between radio waves and Other effects of the swinging ions and the charged particles in the air shall have electrons are due to the reaction between been worked out in detail we will be able the particles and the magnetic field of it is already evident, to understand the the earth. Like all moving electric day -by -day vagaries of radio much more charges, an electron which is set swing- completely than ever before. ing by a radio wave will be affected by any *This work will be described in detail by Drs. Nichols magnetic field. It is swinging in just and Schelleng in an article in an early issue of POPULAR such a field, the field RADIO. The mathematical theory has been set forth in due to the earth's "Propagation of Electric Waves Over the Earth," by magnetism. Two American Nichols and Schelleng. Bell System Technical Journal (New physicists, York), vol. 4, pages 215 -234 (April, 1925).

The Effect of Earth Magnetism on Radio Waves IT is now believed that the magnetic field of the earth -the same field which keeps the magnetic compass pointing toward the North - has marked effects on the ions and electrons of the air, and through them on the propagation of radio waves. This theory has been worked out by Dr. H. W. Nichols and Dr. J. C. Schelleng, who will themselves describe their conclusions in an important article in the next issue of POPULAR RADIO.

www.americanradiohistory.com A. T. & T. Co. THE MOBILE RECEIVING SET USED IN THE TESTS In order to determine the electromagnetic field strength at various places around a city. measurements are taken in small areas. This data rs then plotted on a map of the city which will show approximately where the good locations for transmitting and receiving are.

HOW R9DI0 DEAD -SPOTS ARE FOUND BY A Wandering Broadcasting Station Recent tests that are of great value to the radio fan in improving reception in places where receiving is difficult or at some seasons almost impossible.

By J. O. PERRI NE

fading of radio signals, differ - For the past three years radio trans- RAPIDences in day and night transmission mission and distribution measurements and geographical distribution, are peculi- have been made in three fields, trans- arities of radio transmission known to oceanic, ship -to -shore and broadcasting. almost every enthusiast. In POPULAR RADIO of March, 1924 "Just how are radio waves distributed the diurnal and seasonal variations of about a broadcasting station" is often a signal intensity and noise revealed by topic of discussion among the radio fans. transatlantic tests were reported. The All of these questions are receiving present article is concerned with the dis- effective answers through extensive ether tribution over city districts of radio surveys.* waves from broadcasting stations. All of the work of radio transmission measurement has been made possible by * Carried on by the engineers of the American Telephone and Telegraph Company and the Bell design of practical and portable ap- Telephone Laboratories. the 207

www.americanradiohistory.com 208 POPULAR RADIO

paratus by means of which the intensity set, mounted in an automobile, it was of received signals can be accurately possible to take measurements for many measured. The receiving set is pro- points in all directions and at distances vided with a carefully shielded local os- varying from a few blocks to about 50 cillator associated with the loop antenna, miles in the territory surrounding Sta- through a calibrated potentiometer. This tion 2XY, 24 Walker St., New York system makes it possible to compare the City, and Station WCAP, 725 13th St., received antenna current with similar N. W., Washington, D. C. The points current from the local oscillator and by at which the field strength was the same calculation obtain the value of field were spotted on a map or airplane pic- strength in microvolts ; per meter field ture and connected by a line ; "signal strength being a measure of signal contour lines" they might be called. power. The comparisons are made The size and location of dead spots, through the agency of a micro ammeter indicated in the accompanying chart by at the output of the receiving set, and the closed curves, and the manner in by this method the human ear is en- which field strengths decrease in differ- tirely eliminated in the actual recording ent directions, were disclosed. In regions of data. where the contour lines are close to- Using this specially designed receiving gether, the signal intensity is decreasing

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RADIO FIELD STRENGTH Pocomoke Gy CONTOUR MAP OF VASHINGTON D.C. AND VICINITY

Scale d m.au II A. T. & T. Co. HOW THE RADIO FIELD STRENGTH AROUND WASHINGTON IS PICTURED The distortion is less marked around the transmitting station than in New York. The effect of Chesapeake Bay to the north awl south is noticeable. At locations five miles away from station WCAP, a difference of one mile makes a difference of two units of field strength. At places 50 miles away, a difference of five miles makes a difference in field strength of only one unit.

www.americanradiohistory.com A WANDERING BROADCASTING STATION 209

A. T. & T. Co. THE "GYPSY" STATTON 2NBr This picture shows the truck that carries the ?OU -watt transmitter. Alongside il is the portable antenna from which test signals are sent that tell the engineers at the receiving end the quality of the location for transmitting. rapidly with the increased distance. An and the atmosphere, relight be expressed inspection of the accompanying chart in Simple mathematical form. The many will also show that at distances close to widely varying factors revealed ht the the broadcasting station one may expect great irregularity of the contour lines signal intensity to decrease much more make it appear that a transmission for- rapidly with distance than at great dis- mula cannot be readily set up to properly tances away. In this way, the chaotic account for all of them. Iíowever, array of qualitative impressions about through charts and data presented in this radio wave distribution have been re- article the reader can obtain a good pic- placed by actual quantitative measure- ture of how water, dry land. hills, val- ments. leys and steel buildings affect radio Aside from the general interest de- transmission and gain insight into the rived from an examination of the curves, allowances which radio engineers must they also make possible some analysis of make in their problems. The work of radio transmission problems. Messrs. Bown and Gillett here being re- If the surface of the earth were flat ported disclosed the following salient and of uniform electrical characteristics, points: due to the decrease in signal intensity, First: The radio attenuation over different the spreading out of the waves and the kinds of earth surface vary widely. It is low absorption of the waves by the earth for sea water and for flat, moist ground. For

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THE INTERIOR OF THE TRUCK On the right, banging from the side of the truck, are the wires antenna, and and gut's for the Belo o them is the collapsible antenna mast. On the telephone left is the radio- transmitter, the generator and the control panels. dry ground the attenuation is relatively much various sorts on the greater. In the case of closely built cities surface of the earth filled with steel buildings, the local attenua- and not from changes in atmospheric con- tion may be enormous. dition. A fraction Second: Sudden changes of the radiated energy in land elevation is subtracted and large masses of conducting material cast from the outgoing waves on radio shadows which may be very heavy in account of the variable character of the extreme cases. earth's surface. This energy is Third: Shadows cause local dead spots; but trans- usually within a relatively short distance be- formed into heat and therefore is lost yond the shadow is wiped out by refraction to radio uses. or diffraction. Hence the topographical character of the earth's surface, together It can he appropriately pointed out at with the presence of man -made build- this point that in the results enumerated ings, are the main factors concerned. above, the diminution of signal intensity Differences in day and night transmis- results almost entirely by obstructions of sion are not outstanding for a resident

www.americanradiohistory.com A WANDERING BROADCASTING STATION 211 or near -resident of New York City; One of the accompanying photographs actual geographical location is a point shows the interior of the truck with the of more importance. panels of the transmitting set, and on Ship -to -shore tests have shown that the left hand the receiving set. Gov- the absorbing effect of sea water re- ernment regulations require that every mains quite constant. The great differ- coastal transmitting station be equipped ences experienced in this case are due to for listening on 600 meters, the wave- wide differences in atmospheric absorp- length at which ship distress signals are tion during the day and night. On some generally sent out. In operating this occasions it requires 10,000 times more portable transmitting station, it is cus- power to "get through" as well during tomary to listen continuously on 600 the worst clay as during the best night. meters, since the messages from the If the decrease in signal power re- truck are sent out on another wave- sulted only from the fact that the waves length. spread out in continuously enlarging This traveling transmitting station is hemispheres with no absorption effects known as 2XBE and undoubtedly many operative, then "the inversely as the of the radio audience in the past have square of the distance law" would ap- heard these call letters on the air. I f so, ply. Records show that during the best they will understand that telephone engi- night conditions the signal power on neers are on the job seeking to achieve some occasions seems to follow the in- their objective; to eliminate dead spots verse square law. Provided no directive and to enable each individual in the radio effects were present, this might be inter- audience to receive broadcast programs preted as meaning that on these occa- under the best possible conditions of sions both the water surface and the clearness and loudness. atmosphere were non- absorbing. It is thinkable that to obtain a more It was early recognized that the best complete picture of radio transmission. be and most comprehensive understanding signal intensity measurements might In addi- of radio wave distribution, as far as taken in more than one plane. for the broadcasting is concerned, would be ob- tion to obtaining contour lines tained by slaking the transmitting station earth's surface, lines in planes parallel give portable as well as the receiving station. and perpendicular thereto might the Consequently telephone engineers have valuable information. In this study be effectively designed a traveling transmitting station. airplane and dirigible might This has been constructed by the \Vest - used. By having a great airship circle ern Electric Company, using a White over a broadcasting station at varying experi- truck as the conveyor. The truck is of heights and distances, additional would a special type used extensively in tele- mental data of great importance phone work for pulling cables through perhaps be made available. If measure- underground conduits and through the ments for high altitudes were thus ob- dis- long chains of supporting rings used for tained, one might be better able to Heavi- aerial cable suspension. cuss the existence of the so- called The mobile transmitter is rated at 500 side layer, that electrically conducting watts output and employs vacuum tubes sheet of rarefied air supposed to exist using a plate potential of 1,500 volts. above the earth's surface.

How to Eliminate the "B" Battery article In a near future issue of POPULAR RADIO will appear a constructional of widespread value to broadcast listeners. that represents the latest product of the POPULAR RADIO LABORATORY.

www.americanradiohistory.com THE OPERATOR SHOULD KNOW WHAT EACH ADJUSTMENT MEANS I!'h,u tuninq o uhire complicated type of receiver, it is ess, nliai that the what hattt-us with each operator I'"''"'` adjustment and just what each one is for; other- ;cis,' he cannot obtain the lest results. When ou Turn Your Dials Few broadcast listeners actually know what is going on inside their radio receivers when they "twist the knobs." This article tells them just what happens. An understanding of these details will help you to tune in!

By TACO> LS AVON

IT is one thing idly to turn a knob sary to understand thoroughly what hap - on a receiving set and another pens when we do turn a knob. We must thing- to tune a receiving set in a prac- know what is going on behind tical, scientific manner. the scenes. Secondly we must know that To some radio fans "knobs" are simply the knobs are set upon their shafts in wheels to be turned when one wishes to such a way that we are informed of the listen to a broadcasting station, and they exact position of the instruments (to depend largely upon the "Be- Gosh -and- which they are attached) when a par- Be -Gad" principle of bringing about the ticular portion of the scale is reached. desired results. The first device to consider is; perhaps, A tuning knob is more than a mere the variable condenser, as this is by far handle. It is a key with which we are the simplest. enabled to open up the doors of the Most of us know that a variable con- wavelength channels which we may want denser is at maximum capacity when all to use. Some fans think that the num- of its plates are interleaved, when the bers on a dial are placed there to aid movable plates are entirely sandwiched their memory. Perhaps they are-hut between the stationary plates. When this is not the only function they have. setting the knob initially on the shaft, Before we can hope to tune a radio set the condenser should he brought to the way it should be tuned, it is neces- maximum capacity as just described. 212

www.americanradiohistory.com WHEN YOU TURN YOUR DIALS 21

50 /00

THE DIAL SETTING OF A CONDENSER MAXIMUM INDUCTANCE FIGURE 1: The dial and the condenser (at the left of the above diagram) show the relation. between a dial setting of 50 and the position of the rotor plates of a variable condenser. In this position they are half -way meshed. At the right the corresponding setting of the rotor plates is shown as fully meshed with a dial setting of 100.

Then the dial is moved to a point where the 100 mark will be directly opposite the adjusting line marked on the panel. away from this FIGURE 2A: The t'zoo coils of the variorneter As the knob is turned when turned at 100 on the dial have a 'maxi- position clown the scale until 50 is mum inductance. the condenser plates will be half- reached INOUCTANCE AT NAL F VALUE way interleaved. But, of course, this does not mean that the condenser is at exactly half capacity. This will depend upon the capacity curve of the particular condenser used. However, if a curve is supplied with the condenser (and some manufacturers are willing to do this) the dial attached to the knob can be calibrated so as to give an accurate indication of the capacity of the condenser, in at any point. micro -microfarads, coil is at right wants to create a FIGURE 2B: When the rotating The radio fan, who angles at a corresponding dial setting of .50, the professional appearance while he is work- inductance is a medium 7'alne. in the presence of ing over his set M/N/MUM /NOl/CTANCE friends, should never be seen turning his dials around onto the unmarked portion of the dial beyond the 100 mark. This is ridiculous from the standpoint of the radio expert. When we reach the unmarked edge of the dial we are going through the same cycle of operations that we go through on the marked half, save that in the latter case we have little or no notion as to the relative positions of plates of the condenser at any par- the the dial setting is at zero, a con- FIGURE 2C : When ticular setting of the dial. As the two coils oppose each other and the in- denser can be brought from maximum to ductance is a minimum.

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THE DIAL SETTING OF A VARIO\IETER 1 luxr. 3 : 7 his diagram shw,cs tat tht left)) tht' corresponding st'ttinge' for the rwriont,7t'r as sho n iu higtu t s 2h and 2.-1 respectively. minimum capacity within the marked push iotn shown at _A. I f, however, one space of the dial, it is unnece-,sary tu gu coil is rotated on its axis until it has between the 0 and 100 limit, un the un- passed through 180 degrees correspond- marked portion of the dial. ing to the 100 mark on the dial, two The second instrument of importance, coils will present little or no inductance, that is usually controlled by a knob and providing they are close enough to each dial, is the \ ariulneter. other to bring about an inductive rela- Here we are confronted with a prob- tionship. Any position between these lenl essential' different from that of the two extremes will result in placing a condenser, for we are controlling the certain amount of inductance in the cir- second property of all electric circuit, cuit. inductance. Unlike some of the other instruments Inductance is, of course, cuntrulled by used in radio, the variunleter may be ro- several different instruments, hut the tated in either direction with the re- vartunleter i, une ul the must important, sult that the same increase or decrease in for the adjustment obtained by ntrans inductive relationship between the coils of this instrument is cuntinuuu,ly vari- is uhtained. able. From tile diagram it will be seen that The operation of the variunleter will what we actually do when we rotate one be better understood by reference to of the coils through 180 degrees is to Figure 2. 1 f we have two coils of wire change the direction of the current flow- wound in the same direction maximum ing through it. hence, if there is ex- inductance will be ul,taine i when they actly the sane amount of wire in each are placed in inductive relation in the coil -tile stationary and the movable one

THE DIAL SETTING OF A VARIOCOUPLER FIGURE 4: At the left, corresponding to a dial setting of zero, the secondary coil (or tickler) is at right angles to the primary coil that gives minimum coupling. At the right is shown a dial setting of 100 with both coils in inductive relation whereby maximum coupling is obtained. This is true only of the 180 degree variocoupler.

www.americanradiohistory.com WHEN YOU TURN YOL;R UIAI_S ?15

THE DIAL SETTING i\ RELATION TO THE 90 DEGREE. \ RIOCOUPLER Firi!RE 5: At the left is shown the position of ti,' rot,,i' for a dial setting/ of zero; this gives minimum coupling between the f 'n coils. ii'WI this tçpc of coupling the maximum inductive relation is obtained 'li,-i, the dial is set at 1. l f it were re-'oh-etl tu Um the Minimum coup /inns 7.. ould be again obtained.

-the two coils will theoretically repre- setting of the dial will represent approxi- sent no inductance when they arc entire- mately 30 percent of the total inductance ly opposed to each other,* while their of the coils. inductances will be added when the cur- The 180 -degree coupler operates in a rent is flowing through them in the sanie fashion similar to that of the ordinary direction. To set the dial properly, we variocoupler. That is, minimum coupling first turn the variometer to a position will be obtained when the coils are at of maximum inductance. This can he right angles to each other. We can determined by tracing the coil connec- understand this relationship when we tions through to see that the current is recall that we get maximum magnetic - flowing in one direction. Otherwise one coupling between two coils carrying elec- will have to guess which position to set tric currents when their axes are in line the dial in. When this point is reached, with each other. 1 f we place them at the dial is put on the shaft so that its right angles to each other the coupling 100 degree mark will he at the line on is reduced to a minimum because their the panel. With this arrangement a 50 electromagnetic fields are at right angles. When the 180 -degree variocoupler is 'Actually there will he some slight inductance left, as the coupling never is close enough to produce brought to the position indicated in Fig- zero inductance. ure 4, the dial is set at zero degrees indicating minimum coupling. From this STATION CONDENSER VARIOMETER CONDENSER point there will he a gradual increase in WOBX / 5 /9 33 coupling to a maximum as the dial is WPbW 26 32 42 slowly turned to 100. 4 48 KOKA 33 / The next instrument of importance, W4'16 34 43 49 that is controlled by the motion of a WBZ 3 7 46 5/ dial, is the type of variocoupler illus- WHN 4 2 52 55 WaY 45 56 58 trated in Figure 5. WO? 49 6/ 6/ Here we have an ordinary coil of wire WJZ 57 67 70 with a rotatable member that carries an- WEAF 62 72 77 other coil arranged near it. This vario- WNYC 67 76 84 coupler, although mechanically different K50 6 9 78 8 7 from the variocoupler previously described, is closely related to it GOOD TYPE OF TUNING LOG FOR and oper- EVERY SET -OWNER TO KEEP ates on the same principle. However, FIGURE 6: This table shows a sample log for the rotor operates through an angle of making a record of the settings of the in- only 90 degrees if it is provided with struments for given stations so that they may be readily found again. a stop (which it should be, for there

www.americanradiohistory.com 216 POPULAR RADIO

... w.ww..ww.. NYiiT .w... ii/q C ' It!!NU NYN.N,M N/NWNrNNN=.Y..rN '-. NC... W..YYp'rW.Y...N.,trN:: 550 YYN.I..NpWiNNY.N.NNÁpi,iiüiN rr .:YgnC..N.MI MM MM NNÑ 500 :.CCNW.i.YY.Yi,YL:.:BGCC:.ii-. : .. NC.I,.....Yr..YY -ppii..Y_NrYi.ISNiiúúiI.Ñlp AN\Ñ:.w r) 450 iiiiNrNNÑ.N...NN..\Ñ ÑÑN Y YM 6. T:pii ::"w i==::óETr:íNii':ipiNnúp NN Cr-- ;::ÄCYVN Nr N 7 400 :i'.pO...ii::i.....iir.Ci. \ ..róN C..N;;.uiiúq NÑr LL.Y.rNNNNMÑN YNpNWp. 350 NYYNmm¡:N ...I i iiiY iiiNÓN N .30G` :TAMé.NN::: :° i . .. : :° .:C::: :. BNNY:Y:YVY:.:..T :: T::C.: 250 NWNN/N:NN.N NMN . . N n/Np N W.NNNYNNr! NNNY pjN r-i-- r Ñi C..éNÑMN¡ :NNY/iiiiúü i 0 /0 20 30 40 50 60 70 90 /00 CaYOFN5&e 5f777/Y6 A SAMPLE TUNING CURVE FOR A RECEIVER I iL l RE 7: This chart shows how a single- control receiver might be charted to enable the setting of the tuning dial for any given wavelength. For instance, the setting for the wavelength of 350 meters, which is shown at the left -hand vertical scale, would correspond to 50 on the condenser dial. A wavelength of 4.50 meters would correspond to a dial setting of approximately 70. A glance at this chart mill reveal the method employed. is no practical reason why it should be also important. Too many radio fans allowed to turn in a complete circle). have the mistaken idea that no vacuum When the rotor is in such position tube is operating at maximum efficiency that its sides are horizontal there is maxi- unless the filament is at full. brightness. mum inductive coupling between it and Some of them seem to think that a the primary coil. With this data avail- vacuum tube is an electric light. This able the fan should have no trouble in idea leads to distorted reception, general setting his dial in such a way as to have circuit troubles and a heavy drain on an approximate idea of the coupling in the pocketbook for "A" and "B" bat- the circuit when the dial is at any one teries and for burned out vacuum tubes. particular position. The only difference Nor should one attempt to regulate the between these two types is that the first current passing through the vacuum tube type takes one -half revolution of the by depending upon the brightness of the dial to go from minimum to maximum filament as an indication. Visual indi- coupling while the latter type takes only cations of this nature cannot be relied one -quarter revolution. upon, nor can one return to that particu- The matter of knobs, for rheostats, is lar position on the rheostat where best

www.americanradiohistory.com WHEN YOU TURN YOUR DIALS 217 results are obtained by merely trying to nearly always bring the desired results. bring the filament to a certain point of One exceptionally clever method of incandescence. It is much better to use tuning is that which uses a curve similar a small ammeter which will tell how to that shown in Figure 7. This result much current the filaments are passing, can be obtained by so arranging the con- or a voltmeter which will tell the proper stants of the coils and capacities that voltage across the filaments. the two tuning condensers have the sanie With so many broadcasting stations setting for any particular wavelength. in operation, it is difficult to remember Of course, the condensers could be the tuning dial settings for each one mounted on the sanie shaft with a single unless one has an exceptionally good knob, which would bring about the sane memory. Of course, it is possible to results. It will be seen, however, that make up a chart like the one shown it would be practically impossible to in Figure 6. Reference to this chart bring about this result unless both the any moment will show just where condensers were working in unison in the station can be found on the tuning this fashion. It will be a simple matter apparatus dials. This saves time and to use this type of chart with some of trouble, and if the condensers have the simplified single -control sets that verniers such an approximate setting will are now coming into general use.

RADIO PLAYS A PART IN A BALLOON RACE When these two aeronauts set forth from, St. Joseph, Mo., on May 1 in the Army balloon S -14, they carried radio receiving sets with them -largely in order to obtain advance information about weather conditions.

www.americanradiohistory.com Ihe MEN WHO 9th Installment

The Scientist Who Added a "C" Battery to the Receiving Circuit ONE of the men responsible for the radio successes of the United States A'avy was FRITZ LOWENSTEIN. He studied, especially, the effects of controlling the grid potential by a biasing voltage. One of his inventions is that of adding a "C" battery to the receiving circuit.

An Authority on the Radio Control of Machinery

JOHN HAYS HAMMOND, JR., SOIL of the distinguished engineer of the same name, has devoted his active life to radio experimentation. In his private laboratory at Gloucester, :Vass., he perfected, before the war, devices for the control of unmanned ships, torpedoes and other craft by radio signals. Mr. Ham- mond is the inventor, also, of the system of Preventing radio interference by means of double modulation -a system now in use by the Radio Corporation of America. lnternaUon,1 _..._ =Vë 77711 {

The Inventor of the Langmuir Vacuum Pump DR. IRVING LANGMUIR, distinguished physicist and research worker in the Schenectady laboratories of the General Electric Company, is known in radio for his work on the space charge inside vacuum tubes and for his perfection of the thoriated filament, which filament has a much greater electron emission than can be obtained with ordinary tungsten wire. Dr. Langmuir is also the inventor of the Lang - muir mercury -vapor pump, a device for attain- ing very high degrees of vacuum in vacuum tubes or other apparatus. General Electric 218

www.americanradiohistory.com MADE RADIO The Creator of the Grimes Inverse Duplex System GRIMES is the inventor of the "in- DAVIDverse" method of employing the reflex principle, of which the well -known "Grimes inverse duplex" circuit is an illustration. By this principle the one of a succession of amplifier tubes which has the smallest radio -frequency load is made to carry the largest audio - frequency load, thus equalizing the work of the tubes.

The First Scientist to Send Pictures by Radio IN inventive circles C. FRANCIS JENKINS is known as the man who perfected the first adequate motion- picture projector as well as many other inventions. Turning his attention to radio, .11r. Jenkins devised the first successful apparatus for transmitting pictures by radio. He is now at work on the problem of the radio transmission of motion pictures, a step toward radiovision. From a photograph made for POPULAR RADIO

The Inventor of the Reinartz Receiver JOHN L. REINARTZ is one of the best known of American radio amateurs. His modification of the fundamental Hartley circuit has been built and used by thousands of amateurs. This "Reinartz receiver" is now proving especially successful in work with the new short waves, below one hundred meters in wavelength. Mr. Reinartz is now with the Mac - Millan expedition in the Arctic. Underwood & Underwood 219

www.americanradiohistory.com 220 POPULAR RADIO

r:-t . i: .1:1:.:i::= .ï rrr^,:üiis,i aimrí. =;íj.í. =o:In//,ihi4i.::1f;i a=,ydi?:_::-,:::_ : ...... W... =1. ...:,.:: ::. 1:..s :..._ : 1 // =... üTRE1 // Eu:. 0,17%-rid :x77,z::::.:::.__ :96. :M1L JOY ::111 FOR DETER MINING THE CAPACITY OF AN ANTENNA FIGURE I : This chart of curves shows the variation of capacity in an antenna with the variation of antenna height and length. The uneven portion of the curves of the 100 foot to 300 foot antenna is due to the capacity of the lead -in wire.

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::::: M..._ 1 u Mr, 7,7 ¡rr,: W ,` .rj.4 :: :...: 1CC ' r.:TgO .: 14::: u.....:: C :1»:: rim ammo :9r,,.,,., ... INIMMESSM _ :::::::: : :o : ::: i .%%riir/*rerr»r.rwr.r»ira .. ` :o i.o i rr /.ir .,n,9Lr..wi,%naor Trir,i :r 1r..icr nr. Pr;r-,T, ,,,. .. r17h94!+h St ..... __..:. :..9T=.1 :':: :.:...... :INIJ _ :.u.. P...... : u ... :: . r :,,.iio u r..i. n: i: ïiiiä / v 1 :k i:1 : : 1 f,:,:°R:/!R: . :i 1

FOR DETERMINING THE LEAD -IN CAPACITY FIGURE 2: The variation in capacity for straight vertical' lead -in wires of varying heights is illustrated on this chart.

www.americanradiohistory.com Useful Charts for Amateurs Authoritative information tables for the guidance of experimenters who design or build radio receiving sets

l;y T.IEUT. C. C. "l'O1)l), JR., U. S. N.

AS a rule, most amateurs get their the amateur attempts to apply the in- hook -ups from friends, or from formation to his particular needs. popular literature on the subject. This The curves accompanying this article information, while good, is as a rule in- have been prepared to furnish the incomplete as far as the individual is formation necessary to amateurs in concerned, and there are generally a building radio sets, and at the same time number of points left in doubt when to present this information in the

' i 1 CC gggC '::::'::: L::L :: ' .:::L:= ...... u...... : ' II Im 111 11 : : g g L _ ::"Lg g11LL. .:LION . . 1111111 g::gG 11111 11111M1111111111...:::: Ill 11 1:9: gg :6Lg.::LL'L:. g:::g:.. ::.Onr allr% ..1 ... g.11..gg.. r,3 ! ... . i_... in L:nL. 3 .. diyr ...... n:gLg':: g ag.::g L.= ..i ..n.....=.nn..C..:..gg r d ... .L:g:'lg i ..iC: g Ill 'Pal ::: ...... CLLL::'::.' ::°:' : :':: iiL " : , ....:... g...... :g. .L :pL..L. a : LL=:::g i 'i'g:g1 'g L: g:C!Li...... ggggLg .rA...i..u...LLL....:L.C":: :ï i:::::::L .:L 'TIM:...... u p:L:! G...... /.. -i/ / . .NN . .,.i..L:.... . :.... a...:.::='g°Egg...... 1.. gN: . : g:...N , ::..n.g': :. ..._...... g9 3.. 9 :g ::" 1 '¡ CiiG::'::'°L:L:':' L. L. : ,.n g:g ! IPLiaa ::' ..... L..:L'L::: ii .... lL::=:L'EL:°:: ::: : '::"é: : ': '. " . ï . "MUM ....:...... 1L...... :. .. °L _ .. L 1 . .. . .:..: 6dC :: : . LL :l ns..rEi:LL:::::L:::Lg:::iii:Giiíìi`ijiiiGL:.GiiiiG.'üL... N..... iiigiii 1 A .. n ..ggg ::g: . . V...... : ' ::iL. rQ oé ... : d i.iGi=: , ...... L...... g gg : .V/i , /...... i .ii ui.../. :..... ::i. L: .....i.....:..... i'iig:ggi.L i l .. Giñ:::L'gL::i:::L:u::...... i:::::i:LL:::::L:LL::Lg 'lii::iR°ú':Li iaaïúLL:::°Ln.N..úLl t L r,.....L...... =iiiiiL ::pgL:'gg::.:::'iï ..... r . ...1 "::::ï:::g'Gi ' g g ...... í .fi...... Lg:.n.. L : ... :L: _.. : .... : : .n...... g. -...... n g..un.. :".%." + ...... r...... 492909 :L: í..í' ...... !pL::L..1i9n...... l...n...n.. r""%3áL"Gú,,'i ....o s!e-iíe..pCi. T ii.'g...N orni I/, i. Ct! .. ri..r.n....i.. íi1...... :':'gLr.r1 /! / f_l!!..12- ...... n Ci suv`-- . sf 60 ..'..Ginig: ..n.. g n'....n = n". ' n i..i....L'..-...... {...... ,=..g...t i ..... N.... L ...g.g. .::g: i.r=...... I... 1. rr ...._-.LS...... :L::::L.:L::::::::::::gi '_ ..u...... r'.....:.r...... r..C...... w:...... /,..1 er /iG...... 1. . ..uL:... : ...... ir,...r...... ':::gg'g L:. .h;...... r.....::::g....,,,, ./, .l..g 1...... n....r/...... n:.....N.NN...r/...... Ln.uLi:..ui.ï .. I/Ai tm ... / Ginm. ::: :i::::::::ii::::ïT::ï °p :L::::::N:ï :L::::::i:::L.i::i i:-:i::::ii:::i%iii:::i L.l:..gg... .g..1...L.m . t .N.....i../...... :.1...... :LL .. mu ...... r...... ":_1. :B :g.' :g':'L :.....:g .. L g ...... /...... _,...... g==3 ...1. L 6 :: . g L ggggggL ggg.'. p. i piiiIIllhI!1UÌ111.' ...... C:::::::G:::°:::::::: _G...iüi::.. íiiiiüi . io...: . ig ..pr1.. rpm ... ap 1! .i ./NpNy pips .NNp.. r.1.li... J..:Ii, .I1...r/l' . N./ i .ri i i7,I.n ii,,4..: .rid'L^....ii/tG..7/...:..0 .g .....i...... 70...... m.i.dL i:íi ...N...r,..../r.rl1..... 1.....i...... i .u. g1.1=. l. '-U..:p _ ...... r...... r.g. LL ..T f:..L...:g' i 7.. 1r 7 r7 7.r,...... ' ...... ui iw i,% .%.iA., /JÍlT1N/, :r. :.....1.. .. w...... /...... ui ...... :::::::::::'.L:.::L:L::::':::::::::::L:::::::::::::::::::::::L:::::.:::L:L:::L:::B: i'uLiI FOR DETERMINING TOTAL ANTENNA CIRCUIT CAPACITY FIGURE 3: This chart shows the average capacity for the combined antenna circuit when using condensers of different sizes. The values are given for the mid position of each of the condensers. 221

www.americanradiohistory.com 222 POPULAR RADIO simplest and most convenient form for Let us work out amateur use. a typical design to illustrate the use of the curves: The curves are based on formulas to The first consideration, in the design be found in the circular of the Bureau of radio receiving sets, is the space of Standards, Number 74 (issue of available for the location of the antenna. March, 1918) and on a formula for the The single wire (No. 14 B. & S. gauge inductance of coils which was developed copper wire) is generally the most satis- by Dr. L. A. Hazeltine, of Stevens In- factory for amateur use. Let it be as- stitute. The curves are not intended to sumed that there is available a 50 to furnish exact data, but will furnish in- 100 foot formation span, 30 feet high, where an far superior to "guesses," antenna can and they be strung, and that the lead - will eliminate a large amount in is 30 feet of experimental long, practically vertical. work on the part of The second consideration the amateur. is the type of set to he built. A radio set, like any

. + . miivaí...wi

...... s...... rc ro-v 7a. 'Ardi . ....ua....uu..aaí.

u...... a...... iúiiiiilium ...... aa.a....=üii=iiii=...is ...... o . .. . . s .....u...... n ...... a:...... a i... a ::::::: ...... ,ñ: :.::..a 111:11.111...... _ ...... e . //ria 7...... s...,..- ..1...... :'.a ...... ii. .r ..a...... u...... u...... ri....ra ...... w...... i .iiiüiiiiiiiiiiiiiiiiiiiiiiiii mani:l.a ...... FOR DETERMINING THE INDUCTANCE AND CAPACITY FIGURE 4: this FOR LONG WAVES In chart is shown a series of curves ity so that the experimenter for condensers of various capac- may choose the proper inductance for his S -ec rued wavelength range. (For û'aî'í coils to cover leng.!rs beloîi' 00 meters consult Figure 5.)

www.americanradiohistory.com USEFL;L CHARTS FOR AMATEURS 223 mC.. ... 11--T : f- Cuai 500

TOML Cg'CU/T //DÚ'CTA/YC,E5

`V. \\-ES FOR DETERMINING INDUCTANCE AND CAPACITY FOR SHORT in Figure 4, except FIGURE 5: This chart gives the same kind of information as that acrd, therefore, that the wavelength range is lower than shown in the preceding chart be determined. ct more accurate value of inductance may with detector other piece of apparatus, will work best Grid condensers for use about .00025 micro - if designed for a particular duty. It tubes are usually leaks of about 1 or 2 is, therefore, unwise to try to design a farads. Grid receiving set to work over too great a megohms are found best. should be range of wavelengths. It is better to The rest of the equipment design the coils of a set to a particular of reliable manufacture. Figure 1 shows band of wavelengths, and to have sev- An examination of height of 30 feet eral sets of coils to cover the entire that for an antenna the combined range of wavelengths in which the ama- and a length of 50 feet, capacity will be teur is interested. This last feature antenna and lead -in would lead to the choice of a 3- circuit about .00015 microfarads. be consulted unless set, having a primary or antenna in- Figure 2 need not the lead -in is longer or shorter than the ductance coil ; a secondary inductance If the length of and a plate -circuit or tickler coil. height of the antenna. coil, the antenna This naturally suggests some form of the lead -in differs from should he coil easily wound, small in size, and ef- height, the antenna capacity of the lead -in ficient. The pancake form of coil an- corrected by the amount to this differ- swers these requirements; consequently capacity corresponding : if the length of the pancake coils of 2/ -inch inside diam- ence. For examp'.e of 30 feet, be chosen. lead -in were 10 feet, instead eter may to The necessary condensers «,ill be one .00004 microfarads (corresponding 20 feet in Figure 2) should be sub- 43 -plate variable ; one 23 -plate variable, microfarads to ob- and one .001 microfarad fixed con- tracted from .00015 antenna capacity. ; together with the grid leaks and tain the denser microfarads condensers recommended by the manu- With the value of .00015 curve in facturer of the vacuum tubes. and the 43 -plate condenser

www.americanradiohistory.com 224 POPULAR RADIO

Figure 3 it will be found that the an- microhenrys. As a total of tenna- circuit 370 micro- capacity is equal to about henrys is required for a wavelength .00011 microfarads. of 375 meters, and it was found that the Let it be assumed that it is desired antenna would furnish 16 microhenrys, to design the receiving set for an aver- the primary inductance coil should be age wavelength of 375 meters. With wound for an inductance of 370 -16, or a wavelength of 375 meters and a circuit 354 microhenrys. capacity of .00011 it is found that From Figure 7 it is found (from Figure that a pan- 5) the primary circuit cake coil of 2/ -inch inside (antenna diameter circuit) should have an induc- and 56 turns will give an inductance of tance of 370 microhenrys. 354 microhenrys. Figure 5 should be used for greater The secondary circuit is wavelengths to use a 23- than covered by Figure 4. plate variable condenser, the maximum The combined length of the antenna capacity of which is usually about .0005 and lead -in is 50 feet plus 30 feet, or microfarads. In mid- position the con- 80 feet. From Figure 6 it is found denser is assumed to have a capacity of that the antenna inductance is about 16 .00025 microfarads. The secondary cir-

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FOR DETERMINING ANTENNA INDUCTANCE FIGURE 6: This chart gives the variation of antenna inductance in microhenrys the combined with lengths of the antenna and the lead -in in feet. From it the experimenter may determine the inductance of his antenna system.

www.americanradiohistory.com USEFUL CHARTS FOR AMATEURS 225

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L::VHC w::.:i::::NONOMN.GNMN pÑmNOCl MI-- . f-C C;M..r iMii:im..iG:f./NOi:.NOCmMmNONNm. íi::NO:...iNM1rMN.NO f j_,_' +, nM..NOMNUa m Mmp. MMM { rNOC.MMUnnMaGC:M:MMaaM:C -. 1 - N4' r M.nNONNm MpM.mmm -r-1-, 1-1- NO MÑCM::NONO.MrMM::q áim.úMUau ' 'rt-;-. : f-- MENEM= A - M.'::::ú ,MU -t , ` - l; Il! Mn.Nm.NOmM.NNC_mNO pC~;T:-.r wane" .. Ñ -= MMM { , Z p. ..NOaC.M..Mm.CNMM:Má::::CMMiNMmM:.mM.mMU. !y m

i :-+ .'-1 ¡{ F Nb7..ro9cMCUl..n::N:C:CpMMa uu...M..NOMmmMnCM.NO.wNOC:..MMMGMM MMH MMCO.úH.CC IIw`M.miMU,. ..rr/p, MU.MUm.m..mm.MUMUMn.MUNOMUMUnNO[gMM: MmMWMMIIm.mmMMMCC ' f v.u.aN CC.::..MCCC.nM .. TII. CMmMMNOmNO:M0MMMMMMmmM.MMM.RMM u:CGNOmNOMNNOYG:CCMMp.MMmN..N MmMmmMM.mmM f M..MC.CaCBÑB.MY.gMMMMMMmMm.MM . iCÿn.r/.1~` Ú: i MUNO..Mm.MM.M.MMMl./.NO..M-N°H1Mm.M.Mm.NMM v. mNMNOMMUNO..A.NMNONMI,,-,//',RIT777.7 O 7Z-774 cm: M.MM.Á..7Li.,Lp7ÌpC ::. :NrCCpMCMMMMMCIM.pm . NO. mu. .MmM.nM 1 G...C..iMüti=:P%_-'Míi.0 IMi .M.MaCaCMMMNO;.MM:pilr.M.m:lMMM'tl,.M.:MYMM Mr..Bu° -- fNi M..MNNN. .CMÑM IMMMM -I IIMmmMUNM MmMNmN.Nm..mm.MpNONO 1 1MN./. Im.._maeMNC[IIM.M%IiC..MI,LIIMMI iriMNI(// / CCCCN1I.CCH.m..NO.MMMMU::MMM.MmM'.m.MGÑNMM'MM MM.CMMMMu M I ...MM.NNM.MCCmMMMMU1,%Ur!rNA.r/ArNOrLA/M.MU. CM .MCm..if.i/r.+vr-...vr/7IINNOMUM.MMMMM N..N. MNm II. pNO.C.MI M.MMMNH:M..HC.n.::.::::CCNOMMNnNMMMCCLMCMNr..MMmMC MM MMMMMMiMNMMMM.tll FOR DETERMINING THE INDUCTANCE VALUE OF PANCAKE COILS FIGURE 7: This chart gives the inductance value for pancake coils made with No. 22 BCC wire with an inside diameter of 2/ inches. The values are given for coils containing approximately 10 to 120 turns.

__ :C: a:: i a i i ii C i :: i i 1 , :: Ii 1 i :n 1162-1a : : :% YC ó' : W , :GG:::y 1 i:i : G M .,,3 I. ....mum. iNM.N G nMa.: a I.w'1M ruii :..:...L..,"...... ::::::G:.: :: G:: :GG:°:=.Ma ni:. 1.rn:7M:. : . . i iii.M M.pL M. ::::i:::: :G .MM r. :viiG: :l . i!r ::Gr=u aaari i 77 C1iC :: ..mi..:i.. M:Ç=Lr.a.07e.::.Y :': :i :: y Ga 1 :r. : ' .: G. M.:Miu¡maw i:.mi : n N 1 G::: a n u 1:: Mr: n q C ,ruiii::g. r ' ii =.. i r,... C C: . . : . . r C C =C1i : .Q. l: 0 : . i.=:: 5a _ GE : . . :iG n::::G:: :a... ' ra as. : 0ffg G::.: : :. éiB! .. r6NOi.. Gu i M r ii:me:i:::iGl:'6 i=%aiiiif M á i:CiÇ:GG: ' . CeC..G.G. .w:::..:tliii::M .::i!' : =':i iD: : ei1= Y 1íl 1 1 ::CIiiti.. i:eG:iii iw4:r.iMi=iiC:Mp1Q ,C . i 9i := i ñ C .Mi::: ::i ,0..4ï 0a M.; ç = :: 1:M 1 M ..gé :: : : G. ,--00,.,.... e. a M. .0 ii %w.S jj .. -á. v .ilia n G; G : I:::.a e0 : a= 1 :::iGi : 1 P1:.i..)`i,.i,Ri.:r iioiCiG a:i:.M 14111111161111::=:: i: .... i9;"14044040:1011:111.111 kitormyrallid 1:iG: : :d! 0111111111 a:i G=: i 7Cr '..., P. C::r i 44 r4 r r93H u "u- 11 Gïií. w6 1 rp:'i; .pG!=yn:NO çii li : % !ÿ1 ,,C C: Lr .T E.;O r-:.: sr. ii ::i,ij,,0ç r :i GI::E:CG C::::. I.1:$ iG GI :MC.MiG :GiAMis G:Q: G ï. Gurs y Gr : =ii ::-i:: I:11111:1 :sii ....:G M -i := r ;r;:r;:; i C:3CCii ,7;a ::i: _ ::v;: ;;= 6 ... . i....:i GiM.i::r:G.i °'iGía ;: : g1M. M::é?,rGEr=: : : M GM i:b:M::iGMU IA G.::ni:NOI:ú: r :::i17,35 íriíijiiii1Mrii:G:. ::u:ï G:::::íi: 6ss::s:a:s:sszea:MrM:C.::Gsssssss ::ssss :iss9ssssas::ssssBs:ss. FOR DETERMINING THE COIL AND CONDENSER SIZES FOR VARIOUS WAVELENGTHS FIGURE 8: This chart tells the size of coil to use shunted by the proper size condenser for a given wavelength range. It is valuable in determining proper con- stants for secondary and tickler circuits.

www.americanradiohistory.com 226 l'Ol'C1..\K R.\I)ll) cuit is to work on 375 meters wave- "l'lte results of this hypothetical de- length, so from Figure 8 with a wave- ign arc as follows: length of 375 meters and a capacity of No. .00025 microfarads it Antenna length 50 feet 14 is found that a B. Antenna height 30 feet & S. gauge pancake coil of 2/ -inch inside diameter copper Antenna lead -in 30 feet l with 38 turns is required. l wire Antenna capacity It is decided to use a .001 microfarad 00015 microfarads Antenna inductance ... 16 microhenrys fixed condenser as a by -pass condenser Antenna circuit capacity 00011 mfd. around the telephones or the Secondary circuit capacity 00025 mfd. primary Plate of the first -stage amplifying circuit capacity 001 mfd. transfor- Primary (Antenna) circuit I mer. From Figure 8 with a wavelength inductance coil 56 turns I ZSicíech of 375 meters and a capacity of .001 Secondary circuit inductance coil 38 turns microfarads it is found that a pancake Plate- circuit (tickler) in- pancake»zete coil of 2'A-inch inside diameter with ductance coil 18 turns 18 turns is required for the plate cir- The hook -up to use with this arrange- cuit or tickler coil. ment of coils is shown in Figure 9.

611 w

GC 2

111 11 Ilololl Iillef- r7 É 222 I! B4S 90 l!

FIGURE 9: A circuit for a triple -coil receiver with one -stage of radio -frequency amplification.

What Makes a "Low -loss" Coil? RADIO fans and experimenters usually connect the tern, "low - loss" coil with some sort of multi- layer coil which contains no dielectric supporting material. Some interesting facts that show this is not the case will be presented in an article in the next issue of POPULAR RADIO -for October.

www.americanradiohistory.com THE REAR VIEWV OF THE AMPLIFIER of the hook-up. FIGURE 1 : Study this view in connection with the picture diagram Figure 2. The locatio1i and connecting points of each .cire appear clearly and connection you may determine lust 11 to bend the ires to get the shortest ,:th the proper clearance. Simple "How-to-Build" Articles for Beginners No. 11 How to build a two -stage audio -frequency amplifier for AC tubes By LAURENCE M. COCKADAY

COST OF PARTS : A of more tila!! S23.00ß.(i(7

HERE ARE THE ITEMS You \V ILL NEED-- - A and B- Precise audio- frequency trans- circuit jack ; formers, No. 285; G- Hard rubber panel, 7 inches by 14 inches; 14 inch C and D- Kellogg sockets; I- I- Ilardwood cabinet for 7 by E- Brooklyn Metal Stamping Corp. single- panel ; circuit jack; I- Baseboard, 121/2 inches by 61/2 inches; F- Brooklyn Metal Stamping Corp. double- 6 -Eby binding posts.

for T11E eleventh instrument to be de- transformer -coupled amplification scribed in this series of simple use with the new McCullough AC tubes. "how -to-build" articles is a vacuum -tube This unit will be found efficient when amplifier that comprises two stages of used with any of the preceding units and 227

www.americanradiohistory.com 22S l'U1't' R.11)1(

tuucrs described in this series or where - Take the list of parts (given at ever a two -stage, audio-frequency the ampli- beginning of the article) to your radio fier of the usual type is satisfactory. dealer and ask him to supply you with This particular unit was built in the thew. POPULAR RADIO LABORATQ1 y for the lfter you have obtained all of them, purpose of supplying- the beginner with find a satisfactory table or bench on details of an efficient amplifier that which to work and lay out the parts on utilizes the new .1(' tubes and fur ac- the baseboard as shown in F igure, 1 and quainting hmi with its operation.

_ ®3

THE "PICTURE DIAGRAM" OF THE HOOK -UP FrcvRE 2: The illustration placed shows the exact manner in which the instruments on the panel and baseboard and how are The upper rectangle the wires run in relation to them. shows the hack of the panel, and the lower baseboard. All the parts are lettered one shows the to correspond with the designations in the text and in the list of parts.

www.americanradiohistory.com SIMPLE "IIO\V-- TO- HLILI)" ARTICLES FOR BEGINNERS 229

3% ->-}- 2"' 'r /4- THE PANEL LAYOUT FIGURE 3: This drawing gives the dimensions for the front panel and the correct spacing from center to center for the holes that are used to mount the instruments and the binding posts as well as the holes for attaching the panel to the cabinet.

/3" /54- THE DIMENSIONS FOR THE CABINET FI ;VRE 4: This diagram- (which. contains the top, front, and side measurements for the 2uahtut cabinet) may be turned over for construction to a competent cabinet maker who can build it from these directions exactly the right si. e for the panel.

www.americanradiohistory.com 30 POPULAR RADIO

/NPUT F,POM PLATE 0/ drilled. To minimize the possibility of spoiling the looks of the panel by making scratches in the wrong place, cut out a piece of paper the exact size of the panel. The position for the holes should then /NP/i7" FiPOM Bf o2 be marked on this using the dimensions given in the panel drawing in Figure 3. This is then used as a template by holding it on the panel carefully and punching through it with a sharp instrument of some kind at the required points. The dimensions of the holes have not been given, but the builder may readily determine the size of drill to use by noting the size of the jack nuts and the binding - post screws. After the panel is drilled it should be fastened to the baseboard with one -inch nickel -plated screws. Flat-head screws should be used and the holes in the panel should be countersunk to make a neat job. The holes which require counter- sinking have a double ring drawn around them in Figure 3. The 4.5 -volt "C" battery should be 5 fastened to the base with a brass strip bent and fastened with two small wood screws as shown in Figure 1. This battery will last almost as long in the set as when it is not in use, due to the very light drain on it. It may readily be replaced, when necessary, by removing The brass retaining STEP strip J, and discon- OOWN necting the TKA/YSFORMER two leads to the battery. You are now ready HOW TO HOOK UP THE BATTERIES to wire the set and AND THE TRANSFORMER should have no difficulty if the picture FIGURE 5: This drawing prevents you from diagram is carefully followed. All parts making mistakes in making connections from are lettered with their designating letters the batteries and the step -down transformer to used in the parts the terminals of the amplifier. If you follow required list and this these instructions the unit will be hooked up eliminates the possibility of a mistake. correctly because the binding posts shown in When the wiring has been the picture wiring completed diagram are marked with the set should be designating numbers that correspond with the fastened into a cabinet numbers given here. of the sizes shown in Figure 4. Figure 5 shows how the batteries The grid and post G of the sockets should the transformer should be connected be located immediately to below the G post the completed set. Although the binding on the transformer as shown. Only posts have been placed so as to simplify two screws on diagonal corners of the connections to any of the preceding units sockets and transformers need be used to described in this series, they also cor- fasten them to the baseboard. respond to those used on most stand- The panel should then be laid out and ard tuning units. Having the two step-

www.americanradiohistory.com SIMPLE "HOW-TO-BUILD- _ARTICLES FOR BEGINNERS 231 down transformer lead, ( corresponding- ament type tube the heater coils should to the usual "A" battery leads) at the left he run at as low a voltage as possible of the panel makes it possible to connect consistent with good reproduction and these two to the preceding unit when the volume. so as to insure long life. latter is also designed to use : \C tubes of In adjusting the filament circuit make this type. This minimizes induction from changes slowly as there is a time lag of long leads carrying alternating current. some ten or fifteen seconds before vari- Two flexible leads made of ordinary ations in the applied voltage cause much lamp cord (or similar wire) should be of a change in the electron emission. run from the two bottom binding posts Where this unit is to he used with a to the heater terminals on top of the tubes tuner- already using the AC tube,, care as shown in Figures 1 and 2. To make should be taken to see that the same fila- these leads readily remoyahlc four fric- ment lead is connected to the "U" in the tion clips of the type designed for these toner as in the amplifier. The fifth post tubes should be soldered to the two leads. from the top is connected to the "1:1-" These tubes operate best with from and this post should connect to the post 3.25 to 4 volts on the heater circuit and which goes to the filament and "11-- a small step -down transformer designed of the preceding unit. This precaution for this special use should he employed will prevent a short -circuit through the to supply this current. Care must be common "B -" connection. Where a tal

THE PANEL ARRANGEMENT FOR THE :\1°JPLIFTER FIGURE 6: This picture shows the front view of the paner installed in the cabinet. The only instruments on the front arc the two jack which connect to the fr,dt and second stages of amplification and the row of binding posts at the left.

www.americanradiohistory.com ;H. s- Ne:. 2 Li_$t`G ) B, S (72:.3

;HYDROGEN MEf.7üM

( 7) AI. Lb 0:1:6

T i 411[ e C? i7 i U M luT A 6) Ctt7'(?.t3;7 Aì$

; ,t$. 1jií, << , 'Y,, .'f PFtO:et'iORUB BLit P1-11,1 R C Hi.,d7 REN i; PCST.ß1Stii C THE PROBABLE NUMBER AND ARRANGEMENT OF ELECTRONS IN THE ATOMS OF VARIOUS ELEMENTS FIGURE 1: The first model shows an atom of hydrogen, which consists of a positive nucleus and only one electron; the last model shows the calcium atom, which contains a positive nucleus surrounded by twenty electrons. The ATOM ARTICLE No. 2: TIIE NATURE OF GASES In this article the author reveals in simple, everyday language some more of the little -known facts about the atom -that little understood particle that plays such an important part in radio -and the laws that govern electrons in the various combinations that make up the various elements. By SIR WILLIAM BRAGG, K.B.E., D.Sc., F.R.S., M.R.I.

IN the first article it was shown that surrounded by negatively charged satel- the behavior of the helium atom, lites which we call electrons. The posi-

which was expelled by the radium atom tive charge of the atom is invariable : its at the moment of its disintegration, ne- amount determines the number of elec- cessitated a new conception of the struc- trons which it can attach to itself. A "six - ture of an atom. electron" atom, for example, has a nucleus The helium atom passes through the charged with positive electricity equal hundreds of thousands of atoms of all to six of the standard units of electricity sorts which it may meet in its brief career. in nature -there is only one standard mag- Starting at the rate of 100,000 miles a nitude. It can attach to itself six elec- second, it travels in a straight line, until its trons, for every electron has one standard energy is used up in the encounters with unit of the negative electricity which is the atoms it meets. This and other effects the antithesis of the positive. observed in the movement make us believe The atom as a whole is electrically neu- that each atom is like a minute solar sys- tral. The behavior of the "six- electron" tem, in which the sun is replaced by a atom is, for all practical purposes, entirely nucleus charged with positive electricity, determined by the fact that the nucleus 232

www.americanradiohistory.com THE ATOM 233 is a "six- electron" nucleus. It is what we of the name is obscure. Most of the call carbon. When the atoms of carbon names are well known and time -honored, are arranged in a certain way, they form and are not likely to be abandoned. Actu- diamond ; a second arrangement gives ally each kind of atom is identified with ; graphite, and black lead carbon is the a certain number, as already explained ; most important constituent of the animal so that the number is a perfectly sufficient body and of all organic substances, of description. Some of the atoms have not coal, of fats, oils, petrol and a vast variety yet been met with; for example. number of well -known materials. But, though it 43. A few months ago there was great plays so great a part, all its properties interest in the discovery of number and uses depend on its possessing a six - 72 ; it is generally agreed that it shall electron nucleus. A "seven" or a "nine," be called "hafnium," the name being- or any other number gives totally differ- derived from the old Latin naine of ent properties, and, in fact, makes a new Copenhagen, where its existence was substance. The former is nitrogen, and proved. the latter fluorine. In the first of the figures on the oppo- Atoms are found with almost every site page a set of models is shown ( higure number of charges on the nucleus, from 1). These are to represent, roughly, a the "one- electron" atom which we call probable feature of the arrangement of hydrogen, to the "ninety -two" electron, the electrons in each of the first twenty which is called uranium. Every atom has atoms. Whether the electrons are in its name : a name generally given by the movement or not, and what is the char- discoverer as indicating some special prop- acter of any movement they possess, is for erty which it possesses ; or it may have the present of no importance. The point been discovered so long ago that the origin that is meant to be illustrated is an un-

xs ih sl'rip is beni' icurvoar,ls by the cgqntinuous

baa-dmenl"aF The billiard I balls, so balloon ïsdis%nded by Fbe molecular bombardment of the las.

HOW MOLECULES OF GAS "BOMBARD" A CONTAINER FIGURE 2: This drawing shows, by analogy, how a gas expands the silken envelope of a balloon by bombardment; the tiny molecules of gas act on the envelope separately, just as the billiard balls do, in bending the strip outward.

www.americanradiohistory.com I P(1PUL_-1R RAll10

An old experi Faraday's showin of a chimney.

LABORATORY EXPERIMENTS THAT ILLUSTRATE PHYSICAL LAWS I'IGU'RES 3 and 4: The figure on the left shows the action of a chimney in guiding the molecule of gas through a tube to the flame. Figure 4 (on the right) illustrates the fact that a feather and a coin, although of different rises and weights, fall at exactly the same rates of speed in a :'acuuuu. doubted arrangement in gnmps, to some A fter that a third group appears, which extent concentric about the nucleus. Thus grows until it also has eight members ; and the first, hydrogen, has one electron ; the after that appears a fourth. We need not second, helium, has two. These electrons go further, because the rules of the fur- are more closely associated with the nu- ther formations are of a similar character, cleus than any of the others that are to be and we wish to avoid the complication of added as we go to higher numbers. The detail. nucleus of lithium can attach three elec- All these facts are illustrated by the trons to itself. Two of these are closely models. For instance, aluminum has a associated with the nucleus just like those "thirteen- electron" nucleus, and the thir- of helium ; the third is further away, and teen electrons which it can attach to itself is not to be classed with the first two. are so arranged that there are two close to As we go along the line and add one the nucleus, eight in the next group, and electron after another -the positive charge three in the next. on the nucleus growing steadily -the new The forces exerted by one atom on an- electrons are to be classed with the third other, when the two are brought close to- electron of lithium. The two inside mem- gether, are very complicated in character, bers are present in all of them ; but an and are imperfectly understood. If more outer shell is being formed. This goes on were known, the models might be more until the number in the new class is eight. exactly constructed. No doubt they de-

www.americanradiohistory.com THE ATOM 235 pend on the way the atoms are presented With the help of Ramsay he proved the to each other, just as -to take a simple existence of a new gas in the air, which example -a magnet can be made to at- was the number eighteen shown in our tract another magnet according to the models. The proportion in the atmos- way their poles are brought together. We phere is quite considerable. The air in know that atoms do attach themselves to the theater Of the Royal Institution weighs one another, and that the forces are very about three quarters of a ton ; of this different for different members and ar- about eighteen pounds is composed of the rangement of electrons, and depend on new gas. Such a proportion would easily that arrangement. For example, fluorine, have been discovered long ago i f the new which has two electrons in the first group element had been willing to enter into and seven in the second, has properties combination with any other. The dis- very similar to those of chlorine, which coverers named the element "argon," the has two in the first, eight in the second, lazy one, because of its unwillingness to and seven in the third. In both cases the associate itself with other atoms. It is outside group, that which presents itself rather, however, unsociable than lazy ; its to the outside world, is an arrangement of physical movements are as quick as those seven. of any other atoms of the sanie weight. A certain number of the atoms have The discovery of argon was quickly singularly feeble attractions for any other followed by the discovery of others like it. atoms, whether like or unlike themselves. The two -electron, helium, was found in These are numbers 2, 10, 18, 36, 54, 86. certain minerals ; its existence in the sun They are, we may say, the "unsociable was already known. Neon (10), the atoms," because they never combine with "new" gas ; krypton (36), the "hidden" others, they take very little part in the gas ; xenon (54) , the "stranger," and the affairs of the world. They were, in con- radium emanation (86) are all very rare. sequence, overlooked until a few years All these are gases, which is to be ex- ago. The late Lord Rayleigh found that, pected. Their atoms are in movement, after the oxygen had been removed from and are each on their own, there being so a sample of air, and every other known little tendency to associate. Only when gas which might be contained as a small the temperature is greatly reduced do they impurity, the remainder did not, as he ex- liquefy, especially those that are light. pected, exactly resemble the pure nitro- They are excellent examples of the na- gen which he prepared in the usual ways. ture of a gas ; of the state in which

AN EXPERIMENT WITH MAN -MADE FOG FIGURE 5: A dense fog may be formed in a tube by moisture settling on the innumerable small particles in the air.

www.americanradiohistory.com 2 "h l't t1'l LAR RADIO

I urroughs and Watts were kind enough to make a special table of small size and having no pockets. A number of balls moving on the table represent the atoms of a gas -like argon ; the cushions represent the walls of a containing vessel. The only defect is that the balls, when set moving, soon come to rest, whereas the atoms of the gas are always on the move. But the table and balls may still be used to illustrate the main properties of a gas. The pressure of a gas on its containing vessel is illustrated by the continual bombardment of the cushions by the moving balls ; a thin strip forming a false cushion is bent outwards just as a balloon is dis-

tended by its gas ( Figure 2) . If, again, a loose cushion is pushed in the balls are made to move more quickly. Just so, when the piston is driven into a cylinder, the atoms or molecules of the gas move more quickly. In other words, the gas is heated, as every one has realized who has felt the bicycle pump grow warm with use. If the gas is allowed to expand sud-

denly, it is chilled ; so, if the false cushion is withdrawn, the balls that strike it lose 110W SOUND WAVES ARE PRODUCED some of their speed. In the same way, FIGURE 6: This picture of a laboratory set -up the hands are drawn back while catching sh,,Ws hntC the atoms of a in gas are set »lotion a ball, so that the ball can be brought to by contact with .z ibrution; a pith ball is hurled az ay when it comes in contact with a vibrating rest. If damp air is allowed to expand tuning fork. suddenly, the chill may produce a fog. The apparatus that is shown in the figure movement overcomes attraction. There is designed to show the effect (Figure 5) . are many other well -known substances If the air is clean, though damp, the ex-

which are usually met with as gases, oxy- pansion produces a light mist ; but if the gen, hydrogen, nitrogen, and so on. But air of the lecture -room is drawn into the in these cases we have examples of mole- tube, the expansion produces a sample of cule building which will be considered London fog. more carefully later. In each case atoms The pressure of the atmosphere is much have combined in pairs ; and the pair forms greater than may naturally be supposed. a contented combination, somewhat un- Its flexibility, due to the independence willing to join up with other atoms, and of the separate atoms, is so great that its therefore maintaining an independent ex- massiveness is overlooked. The pressure istence like argon. on the exterior of the human body is more The properties of a gas are readily un- than ten tons. The body would collapse derstood if its nature is borne in mind. were it not that gases and liquids within ft is convenient to take the analogy of a are exerting the same pressure outwards, billiard table. For these lectures, Messrs. so as to counter the pressure of the air.

www.americanradiohistory.com Paths; The Diary of a Radio Fan By D. R. PATTERSON

Dec. 20. -The papers say you can idea o f all children that they can do hear music and bedtime stories with a anything better than their parents, tried little box affair connected to telephones it. And purely by luck he got some on the head, like a telephone operator. nice music going. This should be good

Oh, well ! Just another fad. stuff. Dec. 22. -Bill Parker says this radio June 4. -Bill Parker says the new stuff is good. Says he can almost dis- idea of vacuum bottles instead {)f tinguish the words on a set he made crystals is better, but you have to use himself. Think I'll get one for son storage tanks -or was it storage bat- Gordon. teries? Will go over and see what his Dec. 23.- Hooked up a radio set to new idea works like when he gets it clothes lines tonight after Gordon had going, just so I can tell the young son gone to bed. You have to monkey about it. I have no interest in it myself. around with a little curly wire dinkus June 10. -Heard some great stuff at the clerk told me was a cat's something - Parker's tonight. Must get Gordon a or- other. Then you connect the clothes set like Bill's. Son must be kept up -to- line to a water pipe or something, and date. a condenser (or was it a crystal ?) has July 12. -Tried all evening to hear to be touched by the curly wire vario- something on new outfit ; phoned a chap coupler. Maybe I've got it wrong. who sold it and he showed me where

Dec. 24. -The darned thing works ! I'd forgotten to put the vacuum tube Late tonight, after Parker fixed the in place. Stayed up till three A.M. wires up right and Friend Wife was in listening to dots and dashes. bed, I heard a chap saying, in the ear July 13.--Must teach Gordon the phones : "This is Station BVD broad- Morse code so he can read the messages casting-" Later on I heard some dots in the air. Dug up a code in the en- and dashes. It will be great sport for cyclopedia. Copied message I heard

Gordon. like this : "AXGP dnm 64k hsd mnli." Dec. 26. -Tried all day yesterday to Must have been some operator outside hear something on the radio but had no the three mile limit. Maybe I didn't luck. Son Gordon, who has the modern get it right myself. 237

www.americanradiohistory.com 238 POPULAR RADIO

Aug. 29. -Had a lot of trouble on Heard sixteen different stations tonight ; Monday -that is, Gordon did -until heard a lecture on shoemaking and one Bill Parker discovered it was the wash- on curing hay fever. Friend wife says ing on the line. Friend Wife will have you wouldn't go to those lectures in a to hang the washing in the cellar. hall. Isn't that just like a woman? Sept. 1.- Parker helped me to put up May 15.- Bought a new book which an aerial wire from chimney to a tree, shows that all my trouble was on ac- so it won't interfere with washing any count of the aerial. Took it down. more. Now hear stations in the west Building a set myself on plans in the but can't get southern ones. book. Nov. 5.- Gordon wants to know why May 16. -Took the day off to finish he can't work the set himself. Says I set. Got tangled up with the coils of oughtn't to want to listen to what wire and also bust the black panel. Hoppity Rabbit did to Phewie Skunk. Finally hired a young radio enthusiast I don't like fussing with the darned to finish it for me. Didn't cost much radio but have to get it running for the more than a factory built set. sake of the kids. May 17. -Now using new set with Jan. 8.- Parker says aerial is in bedspring instead of outside aerial. wrong direction. Took it down and With a loop hung on a miniature "Stop, put it up on another tree. Now hear Look and Listen" sign can hear western southern stations but no westerners. and southern stations now, but not very Jan. 20.- Gordon is now using the well. No wonder the other set wouldn't old crystal set all himself, while I keep work. on experimenting with the big one until May 20. -This new outfit is too com- I get it working right for him. Heard plicated to bother with. Gave it to three concerts tonight ; got to bed Gordon and hooked up the old crystal earlier, two A.M. Willing to lose a set. No batteries to bother about. little sleep for the sake of the children. July 25. -Off the radio for life. Had Mar. 3. -Got a new book which says the boss in to hear the thing tonight and a variable condenser is no good. Gave couldn't make it work. Boss wonders the old set to Gordon. why I stay off work to monkey with it. Mar. 4.- Bought a new set, regenera- After he left, young Gordon tuned in tive variocoupler and variometers. Was Cuba on his set, just by chance. telling the boys at the office how to Sept. 8. -The reflex is the thing ! No work it, and those big words came in more regenerative radio frequency for fine. (Memo : find out what those words me. This new book says the sound mean.) goes in the vacuum tube and out, then Mar. 15. -Tried for an hour to get dashes through it a few times more, a station ; gave it up. Put set away in picking up more sound each trip, with the attic. a final run through a crystal. Have to Mar. 30. -Saw a good program in look up the prices of these sets. the paper tonight which was to be put Oct. 10.- Friend Wife wants to in the air by station IOU. Some day I know why we didn't buy a flivver in- may dig up that set and see if it works. stead of spending all the cash on radio April 24. -Bill Parker has a copy of sets. No interest in science, these POPULAR RADIO that shows all the new women. radio stunts. No wonder my set Oct. 25. -Too much work getting wouldn't work ! Bill showed me where new set working. Son objects to tak- I was wrong, and we stayed up till ing any more sets. I took back his old three A.M. tuning in different stuff. crystal set and bought him a tricycle. Apr. 18. -This radio is great dope! The crystal is the thing for me !

www.americanradiohistory.com Handy Tools for Radio Fans: No. 6

From a photograph made for POPULAR RADIO THE JACKKNIFE

Useful for waking connections

IT is almost impossible to put up a set, install an antenna, and make connections to batteries, without the use of a knife, yet this tool is often overlooked in the radio fan's kit. For scraping the insulation from wire that is to be used for connections and for cleaning up the ends of wires that are to be soldered, the jackknife is invaluable. It should contain one large "husky" blade and at least one other smaller blade. There are some knives that are also provided with a small screw- driver blade.

The preceding suggestions in this series were SIDE- CUTTING PLIERS, SCREW- DRIVERS, TIDE HYDROMETER, THE BATTERY- TESTING VOLTMETER and T FILE.

239

www.americanradiohistory.com "What Set Shall I Buy?" 1th Installment For the guidance of readers who want specific and authoritative information concerning the best of the ready -made receivers that are now on the market, this feature will be published monthly until all of the receivers that have passed the tests of the POPULAR RADIO LABORATORY have been included The Standardyne Receiver MANUFACTURER'S NAME; Standard Radio Cor- DV -3, DV -2

poration DETECTOR TUBE ; same MODEL ; Standardyne AUDIO TUBES ; same NUMBER OF TUBES; five TYPE OF "A" BATTERY ; 4% Volt dry cells for 199 TYPE OF TUNING ; tuned -radio -frequency with or similar tubes; 6 volt storage for other a variable -reactance control that gives the tubes receiver practically a straight line regenera- TYPE OF "B" BATTERY ; 90 to 100 volt dry or tion or tendency toward oscillation curve storage "B" Battery DETECTOR "B" VOLTAGE ; TYPE OF DETECTOR ; vacuum tube 22% to 45 volts WAVELENGTH RANGE ; 190 RANGE ON PHONES; 3,000 miles to 575 meters NUMBER OF TUNING CONTROLS; 3 individual RANGE ON LOUDSPEAKER; 3,000 miles variable condensers, detector and audio on COST, COMPLETE ; with cabinet, $60.00; with one rheostat; radio on another all accessories, $90.00 to $150.00 "A" BATTERY CURRENT USED; 3 amperes with ANTENNA RECOMMENDED; antenna about room dry -cell tubes, 114 amperes with 201 -a tubes or outside antenna about 100 feet long "B" BATTERY CURRENT USED ; 15 to 25 milli- KIND OF TUBES FOR R. F. ; UV -199, 201 -a, amperes, depending on tubes used

THE COMPLETE RECEIVER IN A CABINET This picture shows the "Standardyne" receiver mounted in a cabinet that contains batteries and loudspeaker. The dials A are the three tuning coils; B are the two rheostats; C and D are the loudspeaker and phone jacks for plugging in. 240

www.americanradiohistory.com I ?" 1 "WHAT SET SHALL BUY , 1

Trirdyn Receiver

m t'RER'S NAME; Crosley Radio Corp. DETECTOR TUBE; UV -200, C -300, WD-12, C -12, ,N.\NIE; Trirdyn UV -199, or C -299 HER OF TUBES; three AUDIO TUBES; UV- 201 -a, C- 301 -a, WD -12, C -12, -199, OF TUNING; tuned R. F. combined with UV or C -299. regenerative detector, and reflex amplification TYPE OF "A" BATTERY ; to Suit tubes "B" I'm,: OF DETECTOR; vacuum tube TYPE OF BATTERY ; 90 Volts I'ANGE ON PHONES; 1,000 to 1,500 miles DETECTOR "B" VOLTAGE ; 22/ Volts (CANGE ON LOUDSPEAKER; 1,000 tO 1,500 miles WAVELENGTH RANGE; 180 to 575 meters POST COMPLETE; $65.00 NUMBER OF TUNING CONTROLS; two ANTENNA RECOMMENDED; outdoor "A" AND "B" BATTERY CURRENT USED; depends KIND OF TUBES FOR R. F.; UV- 201 -a. C- 301 -a, on tubes used WD -12, C -12, UV -199, or C -299

Melco Five Receiver

\IANITFACTURER'S NAME; Amsco Products, Inc. KIND OF TUBES FOR R. F.; UV -201 -a or C -301 -a ,AJODEI, NAME; 1\lelco five DETECTOR TUBE ; UV -201 -a or C -301 -a

vUMBER OF TUBES ; five AUDIO TUBES ; 201 -A or 301 -A CYPE OF TUNING; variometer- inductance TYPE OF "A" BATTERY; Exide 100 amperes CYPE OF DETECTOR; vacuum tube TYPE OF "B" BATTERY ; Burgess 45 -volt

ZANGE ON PHONES ; coast to coast DETECTOR "B" VOLTAGE ; 45 Volts

ZANGE ON LOUDSPEAKER ; coast to coast WAVELENGTH RANGE; 200 to 600 meters COST ; $165.00 without accessories NUMBER OF TUNING CONTROLS; three ANTENNA RECOMMENDED; 20 to 25 feet indoor "A" BATTERY CURRENT USED ; 11/4 amperes or 60 to 75 feet outdoor "B" BATTERY CURRENT USED; 10 to 15 milliamperes

www.americanradiohistory.com 242 POPULAR RADIO

Neutro -Junior Receiver MANIFACTURER'S NAME; F. \. 1). Andrea, DETECTOR TUBE; UV- 20l -a, C- 301 -a, UV -200, Inc. C -300 a; MODEL NAME; 195 -A Neutro- Junior AUDIO TUBES ; UV- 201 -a, C -301 -a Nu M131-.12 OF TUBES; three TYPE OF "A" BATTERY ; 6 volts TVI'E OF TUNING; nentrodyne TYPE OF "B" BATTERY ; 90 volts

TYPE OF DETECTOR ; tube DETECTOR "B" VOLTAGE ; 22% Volts RANGE ON PHONES; 500 to 1,000 miles WAVELENGTH RANGE; 200 -600 meters RANGE ON LOUDSPEAKER; up to 500 miles NUMBER OF TUNING CONTROLS; three Cosy ; approximately $110.00 "A" BATTERY CURRENT USED ; 3 ampere ANTENNA RECOMMENDED; single wire, 60 feet "B" BATTERY CURRENT USED; approximately Ki ND of TUBES FOR R. F.; UV- 201 -a, C -301 -a 10 milliamperes

The Logodyne "Big Five" MANUFACTURER'S NAME ; Kodel Radio Corp. KIND OF TUBES FOR R. F.; 201 -a MODEL NAME ; Logodyne "Big Five" DETECTOR AND AUDIO TUBES; 201 -a NUMBER OF TUBES ; five TYPE OF "A" BATTERY; storage TYPE OF TUNING; tuned- radio -frequency TYPE OF "B" BATTERY ; 90 volt dry cell TYPE OF DETECTOR ; vacuum tube DETECTOR "B" VOLTAGE; 22/ to 45 volts RANGE ON PHONES ; 1,000 miles WAVELENGTH RANGE; 200 to 550 meters RANGE ON LOUDSPEAKER ; 1,000 miles NUMBER OF TUNING CONTROLS; three COST, COMPLETE ; approximately $125.00 "A" BATTERY CURRENT USED; 1.25 amperes _ANTENNA RECOMMENDED; single wire "B" BATTERY CURRENT USED; 20 milliamperes

www.americanradiohistory.com "WHAT SET SHALL I BUY ?" 2 -

Howard Neutrodyne Receiver

MANUFACTURER'S NAME; Howard Mfg. Co., KIND OF TUBES FOR R. F.; UV -201 -a or C -301 -a Inc. DETECTOR TUBE; UV -201 -a or C -301 -a

MODEL ; models A, B and C AUDIO TUBES ; UV- 201 -a or C -301 -a

NUMBER OF TUBES; five TYPE OF "A" BATTERY ; 6 -volt storage

TYPE OF TUNING; three dial neutrodyne TYPE OF "B" BATTERY ; 90 -volt dry or storage TYPE OF DETECTOR; UV -201 -a or C -301 -a DETECTOR "B" VOLTAGE; 45 volts

RANGE ON PHONES ; coast to coast WAVELENGTH RANGE; 200 -600 meters

RANGE ON LOUDSPEAKER ; coast to coast NUMBER OF TUNING CONTROLS ; three

COST COMPLETE; $200.00 "A" BATTERY CURRENT USED ; PA ampere ANTENNA RECOMMENDED: 50 feet single wire "B" BATTERY CURRENT USED; 12 milliamperes

No. 100 Neutrodyne Receiver

MANUFACTURER'S NAME; Wm. J. Murdock CO. DETECTOR TUBE ; 201 -a Radiotrons

MODEL NAME; No. 100 Neutrodyne AUDIO TUBES ; UV -201 -a Radiotrons

NUMBER OF TUBES ; five TYPE OF "A" BATTERY : storage

TYPE OF TUNING; 3 dial neutrodyne TYPE OF "B" BATTERY ; regular TYPE OF DETECTOR; vacuum tube DETECTOR "B" VOLTAGE; 22/ volts RANGE ON PHONES; 3,000 miles WAVELENGTH RANGE; 150 to 650 meters

RANGE ON LOUDSPEAKER; 1,500 miles NUMBER OF TUNING CONTROLS ; three COST; $100.00 with loudspeaker but without "A" BATTERY CURRENT USED; 1 1 amperes batteries or tubes "B" BATTERY CURRENT USED; 10 to 15 milli- ANTENNA RECOMMENDED; 60 to 100 feet amperes KIND OF TUBES FOR R. F.; UV -201 -a Radiotrons

www.americanradiohistory.com N

IRFC2 1772 iPFC3

J J

C5 o O çiPOl/NO A- F + C1- B- THE WIRING DIAGRAM OF THE COMPLETE RECEIVER The hook -up for the Freed- Eisenl,tnn receiver. The designating letters shown in this diagram are as follows: RFC 1- Antenna coupling coil; R1 and R2- Filament rheostats; RFC 2 and RFC 3 -Tuned radio -frequency SI- Battery switch; coupling coils, (neutrufornter) ; S2- Amplifier jack switch; VC1, VC..? and VC3- Variable condensers; R3- Grid -leak resistance; VTI, VT2, VT3, VT4 and VT5-UV-201-a J- Loudspeaker or phone jack ; (. -301 r -a vacuum tubes; AFT1 and AFT2- Audio -frequency am- Cl. C2, C3, C4 and C5 -Mica fixed con - plifying transformers; densers; H 1 and H2-Neutralizing condensers.

HOW TO GET THE MOST OUT OF FOUR READY- MADE RECEIVER

Nu. 8: THE FREED- EISEMANN REC1:1\ R This .verlt'S of articles explains the theory, operation, men?' (llldand care of standard receiving sets

This suri, , does not indorse the product of any manufacturer or make cuunparisctns between receivers. The sets already described include: No. 1, the Eagle Neutrodvne; No. 2, the Radiola Superheterodyne; No. 3, the M elco Supreme; No. 4, the Crosley Trirdyn; No. 5, the De Forest Reflex; No. 6, the Atwater Kent; No. 7, the Grebe Synchrophase.

By S. GORDON TAYLOR

1 IE -r Freed -Eisemann receiver, model oscillation in the radio -frequency am- 1 NR 20, is of the tuned radio -fre- plifier is employed in this set. In view of quency type and makes use of five the fact that two other receivers which vacuum tubes. employ the neutrodyne principle have The neutrodyne method of preventing already been described in this series of 244

www.americanradiohistory.com HOW TO USE YOUR READY -MADE RECEIVER ;

in rear wall articles, it will not be necessary to repeat through holes provided the ; posts the theory of operation nor to again of the cabinet connections to these rear of the describe the course of the signal through are made from the outside the receiver and the action of the individ- cabinet. ual parts.* The Antenna and Ground Receiver Construction of the The antenna for use with this re- This receiver is designed for home ceiver may be anything from a short the picture mould- use ; it is not designed for use as a port- wire stretched along able. The cabinet is of mahogany and ing of one or more rooms, to a regular is a massive and ornamental affair. The outdoor antenna up to 100 feet in length. top raises up to permit access to the in- For local reception a short outdoor an- side for the purpose of inserting the tenna or even an indoor antenna will give vacuum tubes and other parts. In ad- results practically equal to those obtained dition there is a front door that covers with the larger outdoor type. For re- the entire panel. This panel is lowered ception from (listant stations, however, to permit access to the tuning dials and the longer antenna will he found best. other panel controls. When the receiver Such an antenna is illustrated in Figure is not in use the f rout (loor may be 1. closed, thus concealing all of tlfe tuning To find out which is the best ground controls and at the same time protecting connection in any particular location, try them from dust. all that are within convenient reach of is The receiver itself is mounted entirely the receiver. The cold water pipe on the panel and is completely assembled usually best, but hot water pipes, radia- and wired before being placed in the tors -or pumps will in many cases serve cabinet. The binding posts for connec- equally well. If none of these are avail- tions to the batteries and other parts are able, a pipe driven several feet into a of mounted on long shafts which extend out fairly moist earth will do. or coil copper wire suspended in the water of a *Readers who want this information are referred well. to the articles of this series which appeared in POPULAR RADIO for December 1924 and August 1925, The antenna should be well insulated

www.americanradiohistory.com 246 POPULAR RADIO

from its supports and the lead -in wire should 1)V2. "Soft" detector tubes, such as the either be a continuation of the an- U V -200 tenna or the C -300 cannot be used, wire or else securely soldered to nor can power the antenna amplifier tubes such as wire, to prevent corrosion at the VT2 or 216 the joint. Before -a be used. These limita- making the actual in- tions are due to the fact stallation of the outdoor that the rheostats antenna it is ad- incorporated in the receiver visable to make inquiries have insuffi- as to the re- cient current carrying capacity for quirements of the local rules of the fire these tubes, underwriters. which require comparatively These require the use of high filament current. a lightning arrester with an outdoor antenna and sometimes require that the What Batteries to Use arrester he installed on the outside of the house with a ground connection For lighting the filaments of the vac- f rum the uum arrester to a point outside tubes, a six volt storage battery is of the house. required, "these requirements vary in different preferably with a capacity of lo- not less calities, but in any case the desired than 60 ampere hours. The fil- in- ament current formation may he obtained frrnn the consumption of the re- local fire insurance agents. ceiver is approximately' 14 amperes an hour when all five tubes are in use. This means The Tubes That Arc Used that, in theory, with a 60 ampere hour battery The Freed- the receiver can be operated Eisemann receiver is de- for close signed to 50 hours from a single charge for the use of the 201 -a type tubes of the in battery. Actually it is not ad- all five sockets. These may be either visable to keep the battery in use until it UV- 201 -a, C -301 -a or the De Forest is completely discharged, as a total dis-

/NSUL HTOeS - ' \ \\\\ WALL OF1-101/5E - ANTENNA /EAD -/N W/RE CONNECT/ON TOiPECE/VEe POLE De OTHEe PO,PGELA/N BUSH /Na ANTENNA -SUPPORT 1.1111 L/GHTN/NG ARRESTOR \------.\\. COLDWi9TEPP/PE

.l i ( 'OUNO CONNE C T if N ,PECpvE-e

OUTS/OEG.PODNO CONNECT/ON -

HOW TO ERECT AND BRING IN YOUR ANTENNA FIGURE 1: This LEAD shows how the antenna should be erected to the antenna and anchored and how the lead -in is attached near the window. From the insulator outside lead passes through a porcelain tube the house the or bushing that is set in a hole bored through window shaft. the

www.americanradiohistory.com HOW TO USE YOUR READY-MADE RECEIVER 2-17

From .1 photograph made Ior I'1u,1'1.AR RAOtt) THE AUTHOR EXPERT IEN'l'ING WITH THE, RECEiVI'.b on type, yi the set had been installed in the laboratory it was carefully tested different After in thi aerials and different types of loudspeakers to determine the (lat.' that has been written u/' from his ser. article to enable the prospective user to iel the most pr, rtieal benefit The state charge is harmful to the battery. \\itlt the battery is fully discharged. Lew between such a battery the receiver should be used of charge should always lie and only about 40 hours before recharging maximum and 1.185 for lest results the battery. the battery ; this means that the battery prolonged life of should be recharged every ten days if To provide the high voltagc plate sup - may the receiver is used four hours a day. ply "1 batteries arc necessary and The advantage of using a battery with lie of either the dry -cell or the storage higher ampere hour capacity is therefore type. The first cost of the former- is evident. A 100 ampere hour battery is lower but the storage batteries will be the probably the most practical size. cheapest in the long run. because instead The storage battery requires little care of throwing them away when they be- other than occasional recharging. Every come run down, they can he recharged month or two it will be necessary to add a for a few cents. Thus the life of storage little distilled water to each of the three "B" batteries is figured in yeaN rather cells of the battery to keep the level of than weeks or months. the electrolyte above the tops of the If dry -cell "B" batteries are used they plates. It is never necessary to add acid. should he either the "large" size or the A check is kept on the state of charge extra large "heavy duty" type. The of the battery by means of a hydrometer. "heavy duty" type are More CC( nontical This little instrument shows the specific as shown in the accotnpanvng tabulation. gravity of the electrolyte and therefore While their first cost is some higher, their indicates the amount of charge in the bat- life is much greater. tery because the specific gravity fluctu- In any event, the total required "l;" ates in a known proportion with the battery voltage is 90. In the case of dry- charge and discharge of the battery. cell batteries this will mean two of the 45 When the battery is fully charged the volt blocks while in the case of the stor- hydrometer should read approximately age "B" batteries, which arc usually 1,285, and will drop to about 1,150 when made in 24 volt blocks, four will he

www.americanradiohistory.com 248 POPULAR RADIO

needed. In this latter case the total volt- rent drain on the "C" battery itself age will be approximately 96, is which is almost zero and its life is therefore great close enough. -usually somewhere Some in the neighbor- owners may wish to equip their hood of a year. The receivers economy effected with a "B" battery eliminator through the use of in place a "C" battery with of the "B" batteries. In such a the Freed- Eisemann receiver case the is shown in eliminator should be purchased the accompanying tables. with the understanding that the price will be refunded if the eliminator fails to How to Operate the Receiver function properly during an actual trial In putting the receiver into at the home of the purchaser. operation, connections are first made from Provision is also made for the re- the use of ceiver to the antenna, ground, batteries a so called "C" battery. This is a small and loudspeaker dry -cell as shown in Figure 2. battery of 4/ volts and is used Be sure that to provide connections are made ex- the proper grid bias to the actly as shown, audio amplifier otherwise there will be tubes, thus serving two trouble- especially if most useful purposes: the "A" battery First, by main- connections from the taining the receiver are con- tube at the proper bias, which nected to the "B" battery tends to improve instead of the tone quality and vol- "A" battery. The ume; Second, penalty may be one by prolonging the life of or more tubes ruined. the "B" batteries, because the "ß" bat- The filament supply current from the tery current drain is reduced through "A" battery is then turned on. This is the action of the "C" battery. The cur- accomplished by first pulling out' the

/FAN T E N YA / /S LE 5S THA /Y /F/ON6ANTENNA /00 FEET, CON/YECTTO /5!/SED, CO/YNECT TO

iPEAR OFPANEL=

"óATTEeY ? ;9 "Bi9TTERY THE BATTERY HOOK -UP FIGURE 2: How to connect the "A," "B" and "C" batteries to the rear of the Check up before actually using the set receiver. to make positive that you have the terminals connected exactly as shown in this diagram; then you will have no trouble with burned out tubes.

www.americanradiohistory.com HOW TO USE YOUR READY -MADE RECEIVER 249

THE PANEL VIEW OF THE RECEIVER The three principal This pit are shows the set with the front flap let down as in operation. controls are VCl, 1'C2 and VC3 while the rheostats RI and R2 control the volume and quality. knob of the battery switch in the lower the beginning of this article and should right hand corner of the panel, and then correspond very closely with those of any turning the knobs of the two rheostats in other Freed -Eisemann receiver of this a clockwise direction to about 40 on their type. At least this is true of the settings dials. Now insert each of the five tubes of the second and third dials. The set- in the first socket to make sure each lights ting of the first will vary according to properly. the antenna used. The next step is to insert the five tubes It is advisable to first try tuning in a in their proper sockets. Place them in local station which is known to be "on their sockets so that the pin on the side the air" at the time. Find its dial settings of the tube slips down in the slot provided on the chart, or the dial settings of an- in the side of the socket. Then press other station operating on the same or down as far as possible and turn tube to near wavelength. When it is heard read- the right as far as it will go. Thus it is just each of the three dials until the great- securely locked in place. The rheostat est volume of sound is obtained. This knobs are then turned up to about 70. setting will be the proper one for that sta- Now the tubes should all light up, pro- tion. If the station is not heard at all, vided the knob of the "amplification" even after considerable "feeling around" switch is pulled out, and all is in readi- with the dials, it is evidence that some- ness to tune in the broadcasting stations. thing is wrong in the connections to the If the "amplification" knob is in only batteries, or in the tubes, and they should four of the tubes will light. By referring he checked over carefully. to the chart near the end of this article Assuming that the first station lias the approximate settings of the three been successfully tuned in, it is well to large dials for a number of broadcasting repeat the operation on a number of sta- stations will be found. These readings tions until the method of tuning becomes were made with the receiver shown at familiar. Be sure and keep a record of

www.americanradiohistory.com 250 POPULAR RADIO the dial settings at which each station is ing the "volume tuned in so control" dial in an that the same station may be anti -clockwise direction tuned in again if desired, until the volume without the ne- is reduced to the proper point. cessity for hunting around. By following the former plan the Now for a little last tube is investigation of the automatically cut other controls out of the circuit and -and a word or two of ad- its filament extinguished. vice regarding them. The drain through the rheostat (R2) is thus re- Under ordinary conditions this receiver duced and this rheostat should be turned will deliver more than ample volume of back (anti -clockwise) sound about 20 degrees in the case of reception from local on its dial. The stations. best plan for ordinary If it is operated at full blast on use, however, the locals is to leave the "amplifica- the tone quality will be sacrificed tion" knob pulled because out and to control the the average loudspeaker cannot volume by handle means of the volume control such volume satisfactorily, espe- dial. This provides cially if it be a smooth regulation operated in a small room of volume to just with the the degree desired and acoustic qualities of the average results in room. just as economical operation Secondly too great volume is un- so far comfortable as "B" battery consumption is to the ear of those who may concerned not -and this is the largest item be used to listening to the receiver. of upkeep The upkeep cost -as would result from cost of the receiver can be using the "amplification" greatly reduced knob to reduce by keeping the volume the volume. at a point where it is comfortably au- When the receiver is to dible. In the case of local reception be turned off this it is necessary only to push in is accomplished by pushing the "ampli- the knob fication" marked "battery." The rheostats knob all the way in, or by turn- may be left in their regular operating position TO ;9 "BATTEATCON/YECT/DNS OFiPECEivE,e

1/4-AsJ f/OUSECIRkENT,SUPPLY-APECTCURWNT 7.9 "BATTERY + ," (S- O O /00`YATT TU/Y65TENLMlPS, OR 32 CA/ YOL EPO f DIS E P C9 PB O N L 9 Yl P 5

0 , dr) IC:) (I? dr) (jr) HOW TO CHARGE THE BATTERIES WITH This DIRECT CURRENT diagram shows the proper connections for charging volt direct -current lighting the storage "A" battery from 110 lines. If you have alternating current your should be connected as shown in home, the battery in any of the preceding articles of this series.

www.americanradiohistory.com RECEIVER 2' 1 HOW TU l f . YOUR READY -MADE

\I L IER\ I:. \'l'H V I LW OF THE RECEIVER FRO \ the general construction features of the Freed -Eisemann Neutrodyne This picture giro are clearly shown as receiver as viewed from below. The mounting and spacing of the coils well as the method of supporting the sub -panel.

a comfortable degree because the battery switch cuts off the duce the volume to entire receiver from the "A" battery cir- for use with the headphones. rheostat dials (R1 cuit. Also, when the '' ;A" battery is dis- In any case the two kept at as low a set- connected by means of this switch the and R2) should be with good vol- "B" batteries are in effect cut off also, as ting as possible, consistent no current can flow from the `B" battery ume. of both the "B" unless the tube filaments are lighted. In this way the lives tube filaments The loudspeaker may be connected to batteries and the vacuum and the "A" a phone plug and plugged into the jack at will be greatly prolonged longer service the center of the lower edge of the panel, battery will give somewhat although this last is or it may be connected without a plug to on a single charge, owner has a battery the two binding posts that are provided not important if the for this purpose at the back of the re- charger. effects economy of ceiver. Results are the same in either Another item that battery. case. If desired, the headphones may be operation is the little "C" is and lasts plugged into the jack whether or not the While this battery small on the entire loudspeaker is connected at the back of for a long time its influence tone qual- the receiver. This is a convenience as it receiver is marked. It affects life mate- is sometimes desirable to use headphones ity, volume and "B" battery table showing in tuning in distant stations. When this rially. The accompanying life of "B" batteries is done, however, the "amplification" the approximate the "C" bat- knob should be pushed all the way in and demonstrates the effect of of the the "volume control" knob will probably tery on the economical operation the life have to be turned back somewhat to re- receiver. It will be noted that

www.americanradiohistory.com 252 POPULAR RADIO of the "B'' batteries increases with in- tenna" binding post. Thus connected, creased voltage of the "C" battery; there- there will be ample selectivity. fore it is most economical to use If the antenna be only 60 or 70 feet the full 4/ volts of the "C" battery. in length there will probably never be Oil the other hand the best tone occasion to use the "long antenna" con- duality is frequently obtained with only nection. Best results are obtained with 1V, or possibly 3 volts of "C" battery. the antenna connected to the "short an- It is further up to the owner to experi- tenna" terminal, provided it is found that ment a little to determine whether 1 1, 3 selectivity is satisfactory in this case. or 4/ volts of "C" battery give the most satisfactory results. Indeed the tone Charting time Receiver quality without any "C" battery at all Under the head of "How to operate the may prove more desirable than the receiver" it was suggested that a record greater volume and economy obtained of the dial settings for each broadcasting- when the "L" battery is used. station be kept, in order that the same stations may he tuned in again at will Seleetk,ity without the necessity of hunting around When an antenna 100 feet in length is for them. used, and is connected to the binding It is well to keep this record in a con- post at the back of the receiver marked venient form so that it constitutes a tun- "short antenna." it may he found that ing chart. An approximate chart is two stations separated less than 10 meters shown on page 253. A better form of apart in wavelength will interfere with record, however, is one which lists the each other, especially if one is a powerful actual settings of each of the three dials, local station. In that case the antenna as the settings may be different. should be connected to the "long an- It is advisable to jot down the settings

VIEW OF THE SET FROM THE REAR In this picture the reader may clearly see the method of shielding the three tuning units, VCI, VC2 and VC3 and also the arrangement of the sockets and the transformers, which are mounted directly upon the top of the sub -panel. The designations of the various parts are the same as shown in the other diagrams, in the list of parts and in the text.

www.americanradiohistory.com HMV TO USE YOUR READY-MA DE RECEIV-I',R 23

_ . /00 NuNwn ON O nnNNnNwi'n w. w% NNw T ' 1 1 r pN n : iiiñiwiiinu i:i.:: . NiiN tI i' iiii MIES i jHÚ ii L i iiiiiiÚHiiiiii riNNiN H ENE= u MBEúN NwNn11 N uNN ` MEMO_ /:I/Nw qnnNN iiui',.4111111 -- nHÑiiiiHÚ N 60 NNnun pNNtN ÚÚqiiiiifpwggqNnw. :d :N;NiúiNNÓwn' ÑÁi i:iiiÓiiniii. pWNiiiwn 1N N N 81Nn Nn Ll pn.TiÚiÇÚÚiiiÚ wnniHN ÚH HíNñ NwN_N punqNn niN N 40 on eNe__iYYii:. _1I NiiiN'u1°iiNNCiNpsäiii t n NM .ÚÚNN:11111111 /Ma G_ii .í ?T NwNNNnnN n iÚÚÚiiHÚÚÚÚÚppÚ ¡y±n ÚwÚÚÚÚÚÚÚÚÚÚHNNppwqq u I i ÚNAN Ì NNNiCw !:NÚÚN.. f , - 20 NÚNnN NwNNOwÑqÑN i n Ú H I !i:NNnNnNÚiiÚÚ NÑ ÚNw =mom sin= NNNNNNnw :: " ran= tY NE

+ . [ o NN I 200 250 800 850 400 450 500 550 600 WA lE L ENaT H -/YI E TE# 5

:A TUNING CHART FOR THE RECEIVER This gives Ille approximate setting for the three dials, ICI, I-C_? and IFC3 for tuning in the varions wavelengths used in broadcasting. The first dial setting may be a little higher or a little loger Ihan shown in this curve on account of the varying lengths of antenna that may be used with the receiver; however, the setting given above will be approximate for all three dials.

APPROXIMATE "B" BATTERY LIFE OF THE FREED- EISEMAN\ \R 20 RECEIVER "LARGE" BATTERIES "HEAVY DUTY" BATTERIES \"r:RÁ(;E HOURS K PER DAY ,? .a 2 hours- 3 hours , 4 hours 2 hours hours hours

No. "C" battery 68 (lays 38 days 20 days 147 days S4 days 52 (lays 26 96 ,r ,; 46 " 164 " 60 " 1 1 volt "("' Sl 3 volt "C" 91 " i/ 3 1 179 " 107 68 " 41:"2 volt 107 63 " 39 " 203 " 123 " 81 "

.. .. Measurements made with 9(1 colts of B' Latter, varying C' hatters voltage from a to 4 I _, ":nn ¡rlificatur,u ssu'itch pulled out and both rheostats set at 70.

Same c nnlition, as in Table 1 except with the -Amplification'. switch pushed in. LARGE" BATTERIES -HEAVY DUTY" BATTERIES AVERAGE HOUR.; USE PER DAY 2 hour s i Goure ! hours 2 hours 3 hours hours

99 59 34 days 190 days 114 (days 73 days No. "C" battery clays days 123 11., volt "C" 107 " 63 " .39 - " 203 81 " 43 215 130 " 88 " 3 N olt 'C"C.,, 115 " 69 " " 41 > volt 130 " 77 " 51 " 237 148 " 100 "

Inasmuch as the cost of "B" battery replacement is practically the entire upkeep cost of the receiver, the above' tables 'n'ill be of interest. The conclusion to be drawn from the tables is: To attain maximum economy, use 41/2 volts of "C" battery and keep the "amplification" switch pushed in wherever this will provide sufficient volumr. .'l /so, don't start the receiver going early each evening and leave it going until bedtime unless someone is actually listening.

www.americanradiohistory.com 2;-4 POPULAR RADIO for each station as it is tuned in for the stations are tuned in for the first time, in first time. After this has been clone for order that the dial settings of these new a few evenings a new record should be stations may be entered in their proper made listing all the stations that have place on the record. been recorded in some convenient order. The important item is to note the dial This may take the form of a list arranged settings for every station received. Other- alphabetically according to station calls, wise, when it is desired to listen in on the or it may list the stations in the order of program of one particular station, several their wavelengths with the highest wave- minutes may be spent in trying to locate length stations first. If one is not fa- it on the dials. This in itself does not miliar with the wavelengths of the differ- seem a serious matter but every operator ent stations, or if someone other than of a receiver knows the embarrassment the maker of the record will llave oc- of having to "fish around" in front of casion to use it, the alphabetical arrange- company, when one of the guests asks to ment will probably be best ; one can easily hear some particular distant station. If determine which form is most suitable to the operator can, by referring to his tun- his needs. ing chart, set the dials immediately for A fter this list has been made up it will the desired station it is much more plea - need to he revised occasionally as new sant for everyone concerned.

A UNIQUE USE OF RADIO IN THE BUSINESS OFFICE Henry Ford maintains the largest private radio system in the country. His station at Dearborn, Mich., is in constant communication with six of his plants and his four lake ships. Communicating in private code, Ford is said to be able to save large sums yearly. In each of his stations are installed electric typewriters which transmit the messages to other reproducing typewriters in the various plants.

www.americanradiohistory.com Call Letters That Have a Past

By LAWRENCE A. COkI:IDON

Call letters that were originally assigned to ships that have met disaster are seldom re- assigned to other ships, in deference to the superstitions of seamen. They are, however, 110îl' assigned to lnoadcasting stations. For example:

KJ S, now assigned to the Bible Institute of Los Angeles, was formerly used by the steamer North Star in transmitting an important message when on a foggy morning in August, 1919, a call for immediate assistance was sent out by the radio operator of the vessel. Radio played an important role in the rescue of all of the 348 persons on hoard.

\WSB, now assigned to the station of the Atlanta Journal, was formerly assigned to the steamer Francis H. Leggett which foundered off the Oregon coast on September 18, 1914, with 67 persons on board, two of whom were lost. After this wreck the call signal was re- assigned to the steamer Firzc'ood which burned off the coast of Peru on December 18, 1919, with 28 persons on board, none of whom were lost.

\VHN, now used by the station of Loevy's Theatre, New York City, was at one time assigned to the steamer Hanalei which was wrecked. It was later used by the steamer Santa Isabel which was sold to citizens of Chile. When a vessel is sold to a foreign country, the country to which it is sold assigns its own letters to the vessel's station.

KLZ, Reynolds Radio Co., Denver, Col., was the call of the steamer Speedwell in 1920. KLZ and SOS were an important combination of signals on September 29 of that year \vhen the Speedwell was caught in a tropical hurricane in the Gulf of Mexico. This storm was so severe that after the distress call and position of the vessel were sent out the en- gine room became flooded, the dynamo ceased to work and the sea carried away the whole after -deck, taking with it the storage batteries which were necessary to operate the radio station. This catastrophe caused the loss of nine lives, including the captain, mate, and two women passengers, out of 25 persons on hoard.

KGB, now assigned to the Tacoma Daily Ledger, was at one time used by the steam screw D. .\'. Lucl,'enbach which was sunk by a sub- marine about 100 miles off the French coast on December 27, 1917. WGR, Federal Telephone Manufacturing Co., Buffalo, N. Y., was used by the passenger steamer Governor prior to its assignment to the broadcasting station. The Governor was sunk in a collision with the freighter ft -est Hartland in April, 1921. Eight lives were lost. No doubt some old - titne operators recollect when \V /GR was heard up and down the Pacific coast.

\W\%VJ was once the call of the steamer Peru: it is now used by the Detroit News station. The Peru was transferred to the French flag, causing the cancellation of the call letters of the United States. KLS, now assigned to the Oakland Tribune, was formerly assigned to the steamer Kermanshah which was transferred to the Hungarian flag. KNX, Los Angeles Evening Express, was formerly used by the vessel ,Susana which was sold to citizens of Italy. KOB, New Mexico College of Agriculture and Mechanic Arts, State College, New Mexico, was used by the steamer Princess Anne up to the time she stranded on Rockaway Shoals, Long Island, February 6, 1920, with 106 persons on board none of whom were lost. The Princess broke in two and the cargo, valued at $500,000, was practically a total loss.

KRE, Berkeley Gazette, Berkeley, Cal., was at . one time assigned to the steam screw Florence H. which was blown up by an internal explosion in Quiberon Bay, France, April 17, 1918, causing the loss of 45 lives out of 77 on board. 2S5

www.americanradiohistory.com M

R. Winters INVENTIONS BY PUBLIC OFFICIALS MAY BECOME PUBLIC PROPERTY The value of stock in radio enterprises that are based upon inventions and patents of men who were in the Government's employ are vitally affected by the recent court decision against Major General George O. Saltier, whose ", erred wireless" patents have been declared public property. Riding to Riches by Radio PART II flow much are the radio stocks that you own -or that you are thinking of buying- really worth? On what factors do their values depend? What is their value likely to be? In this series of two articles the author points out some of the points that every investor or prospective investor should consider before he buys. By RALPH E. RENAUD

THE quickest wad- is to purchase the includes the average earnings over a offered certificates, take them to reasonable period, the progression of your bank and ask how much they will earnings in proportion to the outstand- lend you on them. But this is expensive ing capital, the current asset posi- and may subject you to insult. On the tion, the latest available balance sheet surface, at least, the proper examination and the relation of the funded debt to of radio stocks does not differ from that the capital stock. Then there is the ques- suitable to any proposed investment. tion of management -how much brains, Perhaps the Golden Rule is : Don't be- how much honesty and what sort of repu- lieve the salesman. After that the first tations are back of the enterprise ? Mar- consideration should be the general fi- ketability is also a factor in the radio field nancial position of the company. This where changes have been so rapid. 256

www.americanradiohistory.com RIDING TO RICHES BY RADIO 257

Inventory is an item decidedly worth is necessary to go back a little way for a considering. A company which manufac- running start. Before the United States tures more sets than it can sell is to be entered the war wireless communication avoided. These extra sets, above the pre- in this country was controlled chiefly by vailing market, may be carried as surplus the Marconi Company, a British concern. or current assets, but they almost invari- The Marconi Company, it is claimed, could ably mean loss. The only way to move not give efficient service because of faulty such current assets is through sales, and apparatus at both ends. It used the Flem- in view of the fact that sales failure ing, or two electrode tube, but required caused the accumulation the prospect is to perfect its service at least two things usually and obviously pretty poor. Per- which it never succeeded in getting -a haps nothing except yesterday's news- three electrode vacuum tube, based on paper becomes obsolete more quickly than De Forest patents then controlled by the today's radio set. Even eggs keep better American Telephone and Telegraph Com- in storage. pany, and the Alexanderson alternator, When you have settled all these points developed and controlled by the General to your satisfaction and are about to Electric Company. reach down into your pocket, stop one `When the United States entered the moment more. Consider the patent as- war the government took over the Mar- pect of the stock. Ask yourself these coni stations and appealed to all manufac- to disregard patent rights for the questions : turers period of the conflict. Under the govern- 1. What patents does the company control or under what patents are they licensed? ment guarantee of protection efficient 2. How basic are these patents? radio apparatus was manufactured and to conduct scien- 3. Is the company equipped many improvements perfected. All pat- tific research and thus build up its patent structure? ents were, in effect, scrambled, and to this in- 4. Am I about to buy a radio patent day they have never been satisfactorily fringement suit? unscrambled. Don't flatter yourself that you will ever After the war the British Marconi Com- be able to answer all these questions defi- pany naturally sought to buy the rights nitely or even approximately. The radio to the Alexanderson alternator. Their experts themselves, the boys who get a advances were smiled upon. At this junc- hundred dollars a day to contradict each ture Admiral Bullard stepped in with another on the witness stand, can't answer other patriotic appeal to the General Eec- them. The courts thus far have spoken tric Company not to make it possible for obscurely and with many voices. Can- American radio communication to fall didly, the patent situation is a mess. wholly into the hand of foreign interests. But unfortunately for the buyer of That appeal was the genesis of the radio stocks this patent situation must Radio Corporation of America, the child govern the future of his investment for of the General Electric. In 1919 all two reasons. A patent is the most con- rights and physical assets of the Marconi venient nozzle in the world through Wireless Company of America passed to which to pour water into a stock. And the new corporation, a strictly American the patents under which any company organization, which thus started with con- operates may turn out any minute to be trol of both the Marconi and General valueless or void. Nevertheless, in this Electric patents. Within two years labyrinth of patent litigation there are cer- thereafter, in one way or another, it tain signposts which may serve to guide acquired the radio patent rights of the the investor toward peace and profit. American Telephone and Telegraph, the For the layman to grasp even the first Wireless 'Specialty Apparatus, the Federal syllable of the patent crossword puzzle it Telegraph Company, the Western Elec-

www.americanradiohistory.com 258 POPULAR RADIO

t ric Company, the United Fruit Company, Anyone might think all this consolida- the Radio Engineering Company of New tion, as in the case of the steel industry, York, and the Westinghouse Electric and night have tended to clarify and \lanufacturing stabilize Company which, as far conditions. Far from it. Despite the fact hack as 1920, had developed radio. receiv- that the Radio Corporation controls 2,000 ing sets but couldn't sell them because the patents there are thousands more which Radio Corporation controlled the vacuum it sloes not control And always there are tubes. new ones. At this moment 2,247 radio The chief elements in this combination, patents are pending. In addition there are of course, are the General Electric, West - all the government patents, many foreign inghouse and the American Telephone & patents and the German patents seized Telegraph Co. Agreements of the Radio during the war. Corporation with the General Electric run The legal confusion may be gauged by to 1947, with Westinghouse to 1945 and the present anomalous position, of the with A. T. & T. only until 1929. Under Armstrong regenerative system, a basic these agreements the Radio Corporation circuit used in the bulk of modern sets. of America accepts 60 percent of its manu - Lee De Forest has attacked it repeatedly -factures exclusively from General Elec- as an infringement on prior patents of tric and 40 percent from Westinghouse. his own. One court has decided for the Through its various connections it is said Radio Corporation. Another court in a to control the rights to something like different district has held for De Forest. 2,000 patents, among them the highly im- The Court of Appeals has ruled for Radio portant Armstrong l'egenerator and the Corporation and De Forest is attacking F I essenden Ieterodvne. on another angle in still a different court.

From a photograph made for POPI'I.AR RADIO A COMPANY THAT PLAYED A CONSPTCUOUS PART ON THE CURB During the first four months of this year (1925) the stock values Condenser & Radio Corporation of the Dubilier (one room in whose factory is pictured above) fluctuated between 127/8 and 35/. Stocks in other companies varied between 2 and 1734. How may the causes be ascertained -and anticipated?

www.americanradiohistory.com RIDING TO RICHES BY RADIO 259

It will be fully two years before the United States has adjudicated the main patents in dispute. Big issues in the radio industry are at stake. Radio Corporation, for example, is suing Hazeltine on the ground that the neutrodyne is an infringement on the Rice and Hartley patents which are held the pioneer inventions in the field of controlled regeneration. The Alexanderson tuned -radio -frequency is just about to be litigated. In fact, there are now approximately twenty big radio patent suits of which six are of the most vital importance. The recent decision against Major Gen- eral George O. Squier, refusing him the fruits of his wired wireless invention, largely because it was perfected through the expenditure of government funds, has also precipitated the fat into the fire with a sickening sizzle. Every radio inventor who was in public service, during the war, Kadel & Herbert and there were many, now fears his pat- MILLIONS ARE INVESTED IN RADIO ents may have become public property. IN THE UNITED STATES If you want to find out something of the value of The Latour patents have also risen to add the particular stock that you own, bring the stock another element of confusion to the pre- certificates to a bank -and find out how much the vailing madhouse atmosphere. bank will lend you on them. (The above picture was made in the plant of a concern that manufac- Dr. Marius C. A. Latour, a French tures radio parts.) scientist, formerly in the employ of the General Electric Company, recently vis- fragments will be many fly -by- nights and ited us with the glad tidings that there pirates who have worked the stock gaine was scarcely a receiving set in use here to the limit. Unhappily, some legitimate which did not infringe some of his eighty enterprises will also suffer. basic patents. The Radio Corporation But let us reason together. It isn't all thought they had exclusive rights to these, hopeless. Radio will continue to develop but Professor Latour differed. Finally, despite the patent confusion and the in- after long negotiations, four non- exclusive dustrial slump. Safety for the investor licenses were issued to the American Tele- seems to lie inevitably with the big fel- phone and Telegraph Company, the Pos- lows, those which have the means to build tal Telegraph Company (purely for wire up a broad patent structure, to defend it, use), the Radio Corporation and the and to prosecute extensive research. Freed -Eisemann Company. It now devel- Research, indeed, is the key to the fu- ops that the Hazeltine Corporation has ture of radio. Systematic invention, as bought control of the Latour corporation against empirical experiment, is almost and threatens suits against all unlicensed bound to win. It is the laboratory against users of the Latour devices. the work bench. Of course, outsiders will Obviously those who have really put continue to invent, just as Professor Haz- constructive effort into radio development eltine (lid with his amazing mathematical will use the courts to maintain their rights. formulas, but even there a scientist was at A lot of patent claims are bound to blow work. Amateur experiment is interesting, up in the next two years, and among the but it is also disorganized and sometimes

www.americanradiohistory.com 260 POPULAR RADIO

incompetent. The cleverest of the ama- web of great government stations. A teurs are pretty sure to find their way plotted chart showing a curve of radio into somebody's research laboratory. set sales and another curve of returns It is through research that what looks from radio communication reveals some to be the next great step in radio will have interesting trends. The curve for set been taken. sales is like the trajectory of a shell it Now they are talking super- regenera- mounts spectacularly until recent months tion which enables us to make one tube do when the upward angle begins to diminish the work of three. It is true that no com- appreciably. The curve for radio commercial super -regenerative sets have vet munication, though flatter. doesn't dimin- been manufactured and sold. But the ish at all. It has remained steadily up- problem is an engineering one which is ward. Where will the two lines be ten bound to be solved. The new thorium fila- years hence ? Will they, like Einstein's ment tubes which use less current because parallel lines, meet each other at infinity, their electronic efficiency is heightened, or will the set sales curve acquire a new new methods of more efficiently exhaust- energy ? Few people realize that already ing these tubes are likewise the result of twenty percent of the total telegraphic research. Clearly, the organizations which communication with Europe is handled by cannot produce these improvements are radio. going to be left either without anything American Telephone and Telegraph is tor sell or will be forced to sell their obso- the most powerful agent of communica- lete produce at a price too low to guar- tion in the United States today. The antee profit. agreements between A. T. & T. and Other factors, too, now dimly moving Radio Corporation only run until 1929. beind the continuous curtain of time, 1 f the telephone company, with its superb will influence radio as a business and as patent structure, ever decides to enter the an investment. There is, for example, the field of radio, either in communication or gradual shaping of public opinion, reset making, present estimates of the indus- flected in Congress, toward the great pub- try will have to be revised. just now A. T. lic utility group of industries. Will it be & T. understands telephonic radio trans- actively inimical, inclined to regulation, mission perhaps better than any other or merely passive ? The Radio Corpora- group and maintains what the public re- tion, summoned into being, or at least god - gards as some of the most efficient of the mothered by one branch of the govern- broadcasting stations. As the advance ment, is now being examined as a mo- of radio is inextricably interwoven with nopoly in restraint of trade by another the improvement and limitation of broad- branch of the government, the Federal casting this may or niay not be signifi- Trade Commission. Is this a symptom ? cant. Or is the change in character within the But enough has been revealed here to Commission itself and the postponement show that the purchase of radio stock isn't of the present proceedings the vital symp- quite so simple as it is made to seem. I tom ? am serenely aware that nothing I have Then there is the matter of radio com- said will check you if you have the bug. munication or radio telegraphy. There But if you have read this far you may is no question of competition here. Radio at least be able to do a little blooping with Corporation controls it absolutely so far the salesman before you sign on the dotted as private enterprise may, in face of the line.

How to Cut Down Interference in Reception A helpful and essentially practical article on this timely topic will appear in POPULAR RADIO next month-written by the well- known expert, John V. L. Hogan.

www.americanradiohistory.com LISTENING HORNS TO DETECT AIRCRAFT 261

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Listening Horns to Detect Aircraft The United States Army has developed this ingenious listening device to detect the approach and position of hostile aircraft by means of the noise of the motors: The horns are designed on the so- called "exponential" equation, also used in designing some t \'pes of loudspeaker horns. One pair of horns follows the elevation of the sound, the other pair follows the sound around a horizontal circle. One operator controls each pair. The combined setting shows both the direction of the aircraft and its elevation angle. Corrections must be made, however, for the relatively slow speed of sound and for the "drift" caused by wind. The sensitivity of the horns could be increased, no doubt, by attaching microphones and audio - frequency amplifiers instead of the ear tubes.

www.americanradiohistory.com IN THE EXPERIMENTER'S LABORATORY

Operating a Loop Receiver Near might decrease the efficiency of the receiver or an Outdoor transmitter that is being wired up. Antenna When soldering leads to taps on an induc- MANY radio experimenters who have pre- tance be sure that the silk or cotton covering viously operated sets on the ordinary outdoor on the wire is first scraped back out of the way antenna have finally built a loop receiver and before the soldering flux or paste is applied. installed it on their radio table or bench and This will prevent the hot flux or paste from found that its selectivity is not what they running up along the insulation and causing expected. This, in many cases, is due to the a short -circuited or partly short- circuited turn fact that when the outdoor antenna lead -in wire in the coil. runs near the loop antenna it gives too great a pick -up for the ultra- sensitive loop receiver, "Straightline Frequency" causing lack of selectivity. A loop receiver should be operated at least fifteen feet distant Condensers from the lead -in wire to be of the required selectiveness. THE latest development in condensers that seems to overshadow, at present, If you want to test out the loop receiver to the "low -loss find its true selectivity, theme" is "straightline frequency." it is always best to Condensers, to date, are curl up the lead -in wire and leave the out- constructed so that door antenna as the dial setting is varied the capacity will ungrounded. In this way its vary proportionately effect of energizing the loop will be negligible and the area of the and the true directional meshed plates will vary uniformly. But, it characteristics of the has been loop antenna may be employed. determined, that, as the wavelengths of the broadcasting stations are allocated according to frequencies, the old type of con- Tubes for Resistance- denser normally known as the "straightline- coupled capacity type, crowds the low -wave stations Amplification too closely. Frequency is figured from the formula THERE are some new tubes now being placed on the market for use with resistance -coupled 1 ,000,000 1 59,154 amplifiers. These tubes have a higher "mu" and thus will enable the user to obtain greater 22.7r 1 LC 1 LC 1 amplification when used with this type of amplifier. They run in amplification with a where f = frequency in cycles per second, ratio of about 20 to 8, which is about two C = capacity in microfarads, and L = induc- and one -half times that obtained with the tance in microhenries. In this case we may standard tubes. regard the inductance, L, as unity and therefore not it in the formula, 159,154 Soldering Connections so that T = 2 I C WHEN soldering the wires in a receiving set, the experimenter should always be careful Therefore, it will be seen that to use soldering flux or paste sparingly, the frequency wiping will vary inversely as the square of the ca- off each joint after the connection has been pacity. In made, a condenser this means that in to be sure that no superfluous paste or order to space the frequencies liquid is left on the joint of the stations or on the insulation evenly over the dial the meshed condenser surrounding the joint. This will prevent cor- plates must rosion of the vary as the square of their areas. joint itself and will also prevent Thus, if at a frequency leakage across any insulating materials, of 1,250,000 cycles which (240 meters), the included area of all the 262

www.americanradiohistory.com IN THE EXPERIMENTER'S LABORATORY 263

THE ROTOR PLATE DESIGN FOR STRAIGHTLIN E- FREQUENCY CONDENSERS con- ] iGuur: 1 : Here are shown two new types of straightlin,e- frequency variable densers. The condenser on the left contains also a compensating plate that forms a shunt capacity across the condenser which can be varied. This enables the condenser to be set so that it will give a straight -line -frequency curve with alrhost any type of tuning coil. condenser plates is figured to be 6 square Such a condenser would be just the thing inches, then, at half that frequency, 625,000 for spacing the frequencies evenly over the cycles (480 meters), the included area of the dial, but as soon as the condenser is coupled meshed plates would have to be 36 square in a radio set to some part of the circuit, then inches and so on. the distributed capacity of the coils connected Neglecting all other capacities outside the with it (and even the connections to a slight condenser such as distributed capacity of coils degree) will affect the capacity of the condenser the shape of such a plate would be as shown and likewise the straight -line- frequency char- in Figure 1. The curves for this condenser acteristic. Laboratory tests and experiments are shown in Figure 2. have shown that ordinary coils coupled to the 5ÁJ .. . C.:Eatl:: Ñ :WWWC.° atltlN tlW W MN Y :°.WMCtltlY:C 400 CC::

ME= YMW =MOMRi 300 .WtlNpWWYtltltlYtlW WWYitlWl. VC1%>fpNWtlNWTMpWCÑf--177... é C YWWN:.tltl tlY 1. WW MEN tlNMrMíj/a^NN.YYY\Z!/[47YtlYWYtltltl 11 a V VF't71YYY IIIN Y._ M.WN M._ [. J7Y Y m:::::....Y YY w YtlY5Y.,PJ'Ntl WNY2ïilr'W Y tl i Itl.1'W 200 tlWirMNiM ' /./' //f-11Atl. vYYN M+[!'/l YitlNtl/T.1 LI2M YYC / r..Y^-rrM., YBw/4 Yr d':./! T, fd' tlN Y .. N 111 YWWMW Ntltl úarEsi.rii, tlld,J' A fi . 1T tl MONO L.A .ì Y WMOMWNMO I . W +- MNNYMMMW NWWÑ /00 MSsONWpp Y B ti^ MWWtltl YONtlrtlM-tltl pNM-Ytlìw-' WWWtlWtltl0YY' _ .tlANtlY é + . . F . . . . .NWWtltlYWWNNM^ A=MV .. WWtNNCY-.NONMrMYYpNtltl otl pYN/MMitl Ntl N MMMOYYM..-- NYYM . tlYY i°-LYMiGBYWYN---tl YNTiMYYtlG1 O NN N tl iGMMNNMMMM1tlMWl tlNYtltlW -. T '_i--., . . . ..- .. /W P/AL SETT/N6 EVALUATED CONDENSER CHARACTERISTICS IN CHART FORM FIGURE 2: These curves show the characteristics of the left -hand condenser shown in Figure 1. The lower capacity curve marked "condenser alone," shows the continuing various values of capacity with dial setting. This gives the frequency curve shown under the heading "frequency- condenser alone." It will be noted that this curve has a slight curve characteristic. To snake it a straightline, a shunt capacity must be added as shown in the top capacity curve. This gives the straight - line- frequency curve which is marked on the chart "frequency- with shunt capacity." In this way the condenser with the compensating plate can be adjusted so that it will give a straight -line- frequency characteristic with any type of coil.

www.americanradiohistory.com POPULAR RADIO

THE TWO PREVIOUS TYPES OF VARIABLE CONDENSERS FIGURE 3: The condenser "A" is a straightline -capacity condenser in which the capacity varies directly as the dial setting. The condenser "B" is a straight -line- wavelength condenser which is supposed to prevent crowding at the lower wavelengths. condenser vary up to approximately .000025 in frequency. This plate can be so adjusted microfarads in distributed capacity. Coils as to compensate for the distributed capacity with a small number of turns may have .000005 of the coil in the circuit. microfarads distributed capacity. One manu- To design a straightline frequency condens- facturer of the new type of condenser, in er properly a capacity curve for a condenser order to offset this effect, adds an extra end of the desired capacity should be drawn first, plate, which has the appearance of the old ignoring coil capacities. time vernier. He has so figured his condenser Then a second curve should be drawn, de- that when the end plate is fully meshed the ducting a certain amount resultant of capacity corre- readi igs are absolutely straightline spond'ng to the distributed capacity of the 250 ,__: ; 300x'1 --;i¡ _:_...... , /.í T -r3 .arv in/-u// 200 M M/PAeW'.i W-p- WMN 2500! 1 ' .. iíiúM/p21óóBú / ONd ...... iYOm ppY.Yj I//1111111111111N..W/MH/M/NW/% 20,00! {OYUNYWW OÑ°/ *. -- ...... /...... -..OMO /i11L - ®eOY®fMNN/ w ;TF !!wiNUáuöuou/uiü -aouW/i .--..-m--//uu umo/ mdé n -___uuwiúoau uü

0 5,000 /0 20 40 50 60 70 /00 O/AL SETT//Y WAVELENGTH AND CAPACITY CURVES FOR THE STRAIGHT -LINE- WAVELENGTH CONDENSER FIGURE 4: A study of the above capacity curves and its corresponding wavelength shows that this condenser although it does distribute the lower wavelength slightly over the dial, is not as effective as the straight -line- frequency condensers for this purpose.

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4Z 6C pNNNNill mÚILL NNNNNMHY 300 W rr.r.M./W- er N NrN YiN V .NÑlnW .rN NrrNit NNpNN.. N.. aC ~NN Z00 rÑNNNN::NNu.uNNN .N.r NNNNNNN N..N NNYN NNNN NYN óNN.Y.Nw .MVNrNNNpN . -r N°\iNNNNNYN YU=i.N.-°..! . NNNNNuuNNNN /00 - rrrN.WrÖ~rrrppN.N.NN NNpNNNrYNNN WW N.rNNNNN..rruNNU N Nr.NÑN Ouwu_w-- NN L NNWNNNNiÑÜiNNrúi NN.MN .N NN Ns ri.rä. NpiiiiiúNw rpiNNiiñou Á.NNN.:.pp MiNNNtllöpNNriNA u: u.ÓNNNNÓN.pNN..Np..iy NNONNN..NN.N....NN WNN.NN N o rMNÓNNNNÓ.Ó Nr0NNÓCW.N NrrNNNNrr rNrrNrNrr 0 0 /0 20 30 40 50 60 70 80 /00 D/AL SET TING IDEAL CHARACTERISTICS FOR THE STRAIGHT -LINE- FREQUENCY VARIABLE CONDENSER FIGURE 5: This curve gives the data for the proper capacity settings against dial settings in order to have an ideal straight -line- frequency condenser. The capacity as denoted in the lower curve includes both the capacity of the condenser and the distributed capacity of the coil. To find the correct capacity to be incorporated in the condenser, the distributed capacity of the coil must subtract all along the line. coil to be used, say .000025 microfarads, from diation. Many fans seem to be under the the first curve. impression that a receiver which contains one This will then give the actual capacities of or more stages of radio frequency amplifica- the condenser at various dial settings. tion cannot radiate. On the other hand, The truth of the whole matter is this ; there is another faction which labors under there is really no such thing as a straight the belief that any receiver which squeals also line -frequency condenser, except when con- radiates. sidered in connection with a particular type Both of these impressions are wrong. and size of coil. Many of the receivers which include one -MORRIS M. SILVER or more stages of radio frequency amplification radiate as freely as the "single circuit" type. On the other hand some regenerative Single- circuit Receivers receivers which whistle freely when tuned in an oscillating condition will not ra- IT is recommended that single- circuit re- while is, those circuits in which the diate. ceivers (that It is any receiver which is ca- input circuit to the tube is also a conductive true that circuit), should not be pable of oscillation is capable of radiating. part of the antenna in some types of receivers this used in crowded areas where receivers are However, radiation is possible only from the coils of located closer than half a mile apart. These there- if they are of the regenerative the receiver -not from the antenna -and simple receivers, is only a few feet from the type, will cause great disturbance in neighbor- fore effective a wave in the receiver. ing sets because they radiate In the case of the Four -circuit receiver, for same manner that the broadcasting stations made to deter- waves are of smaller instance, a test was recently do, except that the mine its radiation qualities. In the test two intensity. other sensitive receivers were used, and two These simple circuits have been found to antennas. The Four -circuit receiver was con- in the country be useful in portable sets used nected up to one antenna and put into regular or in any place where neighboring receivers room a tuned radio but in operation. In the same are not closer than half a mile or so, frequency receiver loop was set up and also the city their use should be prohibited by put into operation. When the Four- circuit mutual consent of all radio users. receiver was made to oscillate, the oscillations were picked up faintly with the other Radiation or So Called receiver but -and this is important -the oscillation was picked up equally well whether "Re- radiation" the antenna was connected to the Four -circuit THERE seems to be considerable misun- receiver or not. derstanding regarding the question of ra- This proved that the slight radiation no-

www.americanradiohistory.com 66 1)( IPL'l..-R IZADIO

COVPE/YSE# TO BE TESTED loop. But it does not follow that all super - o heterodynes radiate. Where the first tube is used as a stage of non- oscillating radio frequency amplification there is little danger of radiation. Or a balancing coil arrangement may be used, as in the Pressley Superhetero- dyne, which will prevent interference to other receivers. The real trouble makers among the superheterodynes are those which have the oscillator coupled directly to the grid circuit of the first tube. A receiver will not radiate if the first tube FIGuRI. 6: This simple circuit shows the man- sloes not oscillate, and there is no oscillating ner of connecting o condenser with dry cell circuit coupled to the antenna circuit or the and busser for testing of short -circuits. antenna coupler. Moreover, even if the first tube (loes oscillate, there will be no radiation ticeel was coming from the receiver direct, providing the coupling between the grid cir- rather than through the antenna. cuit of the first tube and the antenna is suf- Next. the loop receiver was moved into the ficiently loose. In many regenerative receivers next room and another test made. This the coupling between antenna and regenerative time no radiation could he picked up from detector cannot be made sufficiently loose to the I. our-circuit. with or without an antenna. prevent radiation and at the same time pro- Finall , a third receiver was connected to vide satisfactory reception. The Four -circuit an antenna which ran almost parallel with the receiver works best with extremely loose coup- one ronnerted to the Four -circuit, and about ling, the coupling consisting of the single turn 15 feet distant from the latter. When both which is wound around the stabilizer receivers coil. It were put in operation, absolutely no is this extremely loose coupling that prevents interference was noticed in the other receiver, it from radiating. although the Four- circuit set was oscillating -S. GORDON TAYLOR continuously. This gave conclusive evidence that the Four - circuit receiver sloes not radiate, in spite of Shooting Trouble in Condensers the fact that it can be made to oscillate, es- WHEN trouble is encountered in pecially on the lower wavelengths. a radio receiver it is frequently desired to test the The fact that a receiver is used with a loop fixed and variable condensers to make sure rather than with an outdoor antenna does not they are O. K. prevent it from radiating. Many super - There are two main possibilities heterodynes cause considerable of trouble interference to in condensers, i.e.: short -circuit between plates neighboring receivers, even when operated on a and poor internal connections.

Corv©E/YSEh' UAW Tar HOW THE BUZZER TEST LOOKS FIGURE 7: This shows the set -up diagramed in Figure 6 for testing fixed condensers to find out if they are short -circuited or not. If the buzzer operates, the insulation in the condenser is broken do7un and it is useless.

www.americanradiohistory.com IN THE EXPERIMENTER'S LABORATORY 267

connects the phones across the condenser, al- lowing the charge to leak off through the CON0fN56R AlBf 7137ED phones, making another click. To sum up : a condenser is short circuited if a click is heard every time the battery circuit is connected, provided the circuit is disconnected and reconnected rapidly. The cur- up in RPYCELC rent is then not stored the condenser but flows right through. If no click is heard at all, there is a poor connection inside the condenser which does not permit the current to flow into the condenser, and therefore the condenser can neither charge nor discharge. FIGURE 8: The wiring diagram for testing cases to leakage. Due care must be exercised in all condensers for prevent any leakage path across the condenser for instance, as hold- circuit in while it is charged, such, The test for a complete short either ing the finger across both ends of the con- fixed or variable condensers is simple. It is is done the condenser in denser during the test. If this necessary only to connect the condenser will discharge as quickly as it is series with a battery and buzzer as shown in of the test will operates it is charged and the effectiveness Figures 6 and 7. If the buzzer be spoiled. complete short. If it does an indication of a -S. GORDON TAYLOR not operate, however, there is no complete short. This test does not show a partial short -circuit. In making such a test the condenser must, of course, be disconnected from An Oscillating Wavemeter the receiver. There is a single test for both of these THE PARTS USED IN THE OSCILLATING defects in the ordinary small condensers used WAVErIETER- in radio receivers. This test is simple but, nevertheless, some care will have to be exer- A- 4/ volt "C" battery, Eveready type No. cised to make it effective. When a direct 771 ; current, as from a 1/ volt battery, is allowed B -Small size 221/2 volt "B" battery, Eve - to flow through a circuit in which a ready type No. 763 ; series condenser is connected, the current will flow for only a fraction of a second, or until the condenser becomes charged. If phones are in the circuit during that time, the mo- mentary current flow will result in a single audible click in the phones. Even if the circuit is broken and immediately connected again, there will be no further current flow in the circuit. If current does flow it indicates a defective condenser. Such a test circuit is shown in Figure 8. If a path is provided from one side of the condenser to the other, without the battery in the circuit, there will be another flow of current while the condenser discharges the energy which it has stored up. If the finger is placed across the two ends of the condenser, for instance, this energy will flow through the finger. Or if the phones are connected directly across the condenser the energy will flow through the phones, resulting in another audible click. This is a sure sign of a good condenser. Perhaps the surest way to make this test, to avoid any undesirable leakage path, is shown in Figure 9. Connect one phone tip to the negative side of a dry -cell and hold the other phone tip against one end of the condenser with the fingers (being sure that the fingers do not touch the other end of the condenser). Now tap this other end of the condenser against the positive pole of the battery. At the first tap there should be a comparatively faint click. At the FIGURE 9: The author is here shozc'n using a second tap there should be no click because the set -up diagramed in Figure 8 for testing the condenser was charged at the first contact. ordinary fixed condenser for leakage. If more Now touch this end of the condenser to the than one click is heard the condenser is negative pole of the battery. In effect this defective.

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+ "a`zzv

Iu Á4Jv j THE AWIRING 1)IAGR:A\I l'OR THE NEW OSCILLATING \VAV'EMETER l0: This diagram rires the hook, -up for the wCa7.'erneter. All the swnhols the coils, enudeusers and other instruments hear designating letters which are used in the list of parts and throughout the text and illustrations.

C- Cardwell .0005 nufd. variable condenser-, \'- Accuratnne vernier dial, 4 inch diameter ; 21 plate ; N I--General radio inductance coil No. 277A, 1) -N a -ald No. 499 socket for U V-199 tube, without plugs ; equipped with Na -ald panel mounting No. N2 -- General radio inductance coil No. 277B, 461) ; without plugs: JI, J2 and J3-- General Radio coil mounting X3- General radio inductance coil No. 277C, jacks, No. 274J ; without plugs; P -12 General Radio coil contact plugs, type X4- Gcncral radio inductance coil No. 277E, 274P (3 used with each coil ). without plugs;

R- General Instrument 30 ohm rheostat ; 1 composition panel, 7 inches he 10 inches; S -- Benjamin Battery switch ; 4 Eby binding posts;

THE FRONT VIEW OF THE OSCILLATING WAVEMETER AND ONE OF THE COILS FIGURE 11: This picture gives from an idea of how the wavemeter looks when viewed the front. As all the parts and accessories are the prosheetive operator marked with designating letters, will have no trouble in locating the various controls are explained in the test. In operation as they any one of the four coils nnaiv he used by plugging into the three jacks, J1, J? and J3.

www.americanradiohistory.com IN THE EXPERIMENTER'S LABORATORY 269

THE INSIDE VIEW OF THE OSCILLATING \VÀVEMETER hu.tíw 12: This gives the general arrangement of the instrument fastened I Ihr panel and shows how the two batteries are attached to the cabinet. It also show's the hole which is made in the top of the cabinet for inserting the i-acuum tube.

Lumber, screws, strap brass --18 inches by Four coils are used, and they cover the inch by 3/32 inch. wavebands as follows : X 1-33 to 100 meters X2 -65 to 206 meters ONE of the most important pieces of X3 -127 to 398 meters to 602 meters equipment that a radio experimenter can have X4 -194 is an oscillator wavemeter such as the one to As will he noticed this set of four coils he described below. This instrument serves covers all of he broadcast band and also the not only as an accurate and precise reading amateur 150 -200 and 75 -85 and 37 -42 meter wavemeter, hut also as a standard for meas- bands. uring capacities, inductance and other details. It is best to use only .the upper part of the In making your own coils, this instrument oscillator dial -from 30 to 180 if accurate enables you to tell the exact waveband the readings are desired. changes coil will cover ; it also enables you to measure It is extremely important that no the capacity of small fixed condensers, the he made in the oscillator after it is once cali- maximum capacity of variable condensers and brated, otherwise recalibration will be neces- your antenna capacity. sary. Even the position of the batteries in With it it is possible to tell in an instant relation to the oscillator must remain fixed. the wavelength of a broadcasting station to It is for that reason that the batteries are which your receiver is tuned. attached directly to the case of the oscillator, This article is confined to the construction as shown in Figure 2. Va-iations in rheo- and operating directions for the oscillator used stat setting or battery voltage will, however, setting, and as as a wavemeter ; in a later issue more data have little effect on the dial will he given on the use of this instrument for a rule the use of a different tube of the sanie measuring condenser capacities and coils. type as the one used when the oscillator is The circuit used in the oscillator is a modifi- calibrated will not materially affect the cali- cation of the Hartley Circuit ; it is shown in bration. It is well to always use the same Figure 10. tube, thus eliminating any possible chance of The coils are fixed and are connected into variation from the calibration. the circuit by a plug arrangement which pro- There are several ways of calibrating the vides a simple and satisfactory way of chang- oscillator. The first and best way is to cali- ing coils for different wavebands. brate it by means of a standard oscillator - The construction of the oscillator is clear if the use of one can be obtained. The next from the illustrations. It will be noted that best plan is to listen in on the standard fre- the coil, tube and "B" battery are placed well quency signals sent out from the Bureau of away from the dial for the purpose of elimi- Standards in Washington. These are sent out nating body capacity. It is for the same rea- on the 5th and 20th of every month, beginning son that the variable condenser is shunted at 10 P.M. Each evening a band of fre- across only one half of the coil rather than quencies is covered. One evening, for in- across the entire coil. stance, the band from 545 meters down to

www.americanradiohistory.com 270 POPULAR I:ADIO

200 meters is covered ; the next transmission both vertical and horizontal, dividing each night the band from 200 to 100 meters is cov- square inch into 400 small squares. The size ered. The schedule of transmissions may be of the ruled form should be not less than 6% obtained from the Radio Bulletin issued inches by 9% inches. This is a standard size monthly by the Government Printing Office; it which can be obtained at most draughtsmen's may be purchased for five cents a copy. supply stores. The third and most usual methcd of cali- The left hand margin of the sheet is marked brating the oscillator is to use the wave- off to correspond with the dial, the bottom lengths of broadcasting stations. line being marked 30 and the top line 180, To do this a number of broadcasting sta- if the above size paper is used. Every tenth tions, ranging from the lower to the upper line is marked, the tenth from the bottom wavelengths, are tuned in on any type of marked 40, the twentieth 50, and so on. This ordinary receiver. When a station has been applies in cases where a 180 degree dial is tuned in the oscillator is placed about three used on the oscillator. If a 100 degree dial feet from the receiver, the oscillator tube is is used the bottom line may be marked 0, the lighted and the dial rotated until the familiar tenth line 10, and so on. heterodyne whistle is heard as the oscillator The bottom margin is marked with wave- is tuned to resonance with the receiver (and lengths. Where the coil being calibrated is therefore also with the transmitter of the one which covers the broadcasting waveband broadcasting station). As the wavelength of the left -hand line is marked 200 and the right - the broadcasting station is approached on the hand line 600. Then every vertical line rep- oscillator dial the whistle will first he high resents 2 meters and every tenth line is pitched. As the dial is turned further the marked accordingly. whistle will become lower until it is no longer To spot the calibration points, find the in- audible. At this point the oscillator is in tersection of the dial setting and the wave- exact resonance with the broadcasting sta- length. For instance, the eightieth line from tion. If the dial is turned too far the note the left represents 360 meters. If a reading once more rises, an indication that the dial has been taken on a 360 meter station the has been turned too far. eightieth line is followed up to where it inter- When the oscillator has been tuned to reso- sects the horizontal line corresponding with nance in this manner make a note of the read- the oscillator dial setting for that station. At ing of its dial, together with the wavelength this intersection a dot is made, and all of of the broadcasting station. Now repeat this the other calibration points are marked in the operation on different stations, obtaining a same way. After they are all marked in, goodly number of calibration points. connect them together with a line and the The method of calibrating the smaller coils "curve" will be completed. Such a set of by the harmonics of the higher wavelengths curves is shown in Figure 5. will be explained in a later issue. The method of using the oscillator and To make up the calibration "curve" or chart, the "curve" is simple. Suppose a broadcast- a piece of cross-section paper will be helpful, ing station is tuned in on a receiver (not preferably the style with 20 lines to the inch, necessarily the sanie receiver used in obtaining

CO/L TERM /1VAL5

FIGURE 13: Two of the coils and the method of mounting provided plugs on the cross strip on the coil form. Four holes will be found in the cross strip but only three of thent are used. In the left -hand picture, the first plug on the left is connected to the front end of the coil; the second one is connected tap and to the center the third right -hand plug is connected to the rear end of the coil. The two inner coil terminals arc connected together with a piece of wire as shown.

www.americanradiohistory.com IN THE EXPERIMENTER'S LABORATORY 2 7 1

if4Y8 EN67M- Mort-450/i X-3) 400 Kt di _,r, 120 24o 160 180 sen MO NO ,%0 .iß0 ;

t °G44, rlaiii p :04.11411_1111. li e: i /70 4 !}:gFeeei é ,1iimilii ii lii l iitf E60 t: t A 4ii Nga tai 450 ; 611P ïg 3 g 11[triiit@ i e MO 101P WEIe i I@aE11"= g,tiimh attiti.i it1 ltiii!i .:a i 3:: eT ! /30 11111611111110111111111111111111 :l ! F" /20 i!i i i i pöFi °i g t i idq sittüuiii.iiElllliii ei iimp , :i l 'ti ii3 !li i { ai,r ilsiaEisi's tti i I _i' .t i : . =ee13!&el ISS:êe ssi eea::::;; : ! i" a s.::i ' ilai F EIIi iE' I.. Iihtl e..Ii :saiR aF E!i ' t e E I E is' iIi se: aai le iFs:. e s s i t :Fi ' IIis.: set::.! i. Iiai :sisai:i=i ittt E isi:a e s i.. :. EF.!! e.s..iel i. ir ii wigteEi:.is:.tstiitei s ae e!e i i..1111111111111111114 EtiiiflatEil Ee °e e , s ,. Ytiti ijj F i! e0 i;liiil:it t°a ï,É,ai; °üf eial!,,tiiE'Eii¡Ii WIiEietitla£iiiitii:iiF 9F fi sr.eeeseee:a»ees:r.:stE(((((((((((((((i((Hitli3ittiiiliiE!!Eltiéti!!

a0 460 480 500 .5c r0 xv .Fo.X 600 ISO 800 810 340 360 380 400 420 440 WAVELEIi6TH- METERS (COIL X-4) A SAMPLE TUNING CHART tuning curves Were grade for coils, FIGURE 14 : This diagram shows how 'two the kind of chart which the author tells hot' to make in the X4 and X3. This is the article. bVith one of these charts and the oscillator described, text of his signal that he picks experimenter is able to tell the wavelength of any incoming up with his receiver. the calibration points) and it is desired to A Power Tube in the Last Stage know what station it is, or what the wave- of Audio length is. The oscillator is turned on and its is dial rotated very slowly until the whistle to use a power tube, of the oscillator is IT is often advisable heard. The dial setting such as the VT -2 or the 216 -a tube, in the noted. Referring to the "curve" the horizon- amplification. is fol- last stage of audio-f requency tal line representing this dial setting help considerably in getting the "curve." This will usually lowed across until it intersects better quality from the receiver, especially if The vertical line nearest this point of inter- radio- frequency amplification wavelength. the receiver uses section represents the desired ahead of the detector. in the illustration can The cabinet shown If a power tube is used, be sure that the be easily made. Its inside dimensions are has sufficient current carrying inches deep. A last rheostat 6 inches by 9 inches by 3/ capacity for the tube you use. If it has not, small shelf is mounted on one side for the and the proper rheostat is bent to it should be changed batteries and a piece of strap brass installed. In the case of Amperite filament is screwed on to the side fit the batteries and adjusters, the ordinary type No. 1 -a (which of the cabinet. A threaded rod is provided -a type tubes) should he bracket to tighten is used w:th the 201 at the center of the brass Amperite No. 1 substituted. them securely taken out and an it against the batteries, holding This latter type will accommodate the so- in place. tube. -s. GORDON TAYLOR called pov.'cr

"How to Compare Losses in Condensers" every Useful information -based on laboratory experiments -that RADIO next month. radio amateur should have, will appear in POPULAR for

www.americanradiohistory.com Barratt's. London AN ENGLISH "RADIO CARAVAN" THAT COMMUNICATED WITH AMERICA An enterprising and inventive English radio experimenter recently succeeded in communicating vwtlt alnat.'urs across the Atlantic ment by using a transmitting equip- which obtained its power from the rear wheel of end of the car was belted his motor car. The rear to a high voltage generator which supplied the current to the plates of the vacuum tubes employed. The BROADCAST LISTENER Comments on radio programs, methods and technique -from the point of view of the average fan By RAYMOND FRANCIS YATES

Why German heart of Programs in ours for the worst- sounding, beer - drinking German band that America? red ever inflated its cheeks. Our argument is, "Ladies THE Gentlemen and artful publicity department of the of the radiophone audience," that Radio Corporation of America probably the exchange of foreign programs can be thought it ing noth- was dropping a great big bombshell bi-t an amusing experiment made to order when it announced that the German broadcast- for the publicity departments ing station of the various was going to export its programs corporations concerned. As a diversion to America and a night for that they were going to be or two, it receives our very official rebroadcast here. The announcement was O.K., but technical radio is not received tend ready to ex- coolly in our department, however, this into a lasting performance of a really for, while we anticipate the day when the en- meritorious nature. tertainment of the nations of the world will mix and blend in the great amphitheater of Something the ether, we are, for the time being at least, Novel on a Program perfectly satisfied with the American -made WHEN our field department product. This decision is not the wired us from result of Cincinnati that the Crosley station had installed a patriotism so intolerant that it cannot condone a new feature, the thought of music from we were all aflutter. Any studio the Deutschland. manager who is caught doing As a matter of fact, there is a place in this a little thinking big in an effort to inject fresh blood into the fast 272

www.americanradiohistory.com THE BROADCAST LISTENER 273 hardening veins of the art, will find the full with clumsy paragraphs very similar to the power of this department squarely behind him. present run, Mrs. Marie Hemstreet contributed We don't care if it is the simple trick of a little poem that we liked a great deal because permitting a pig to squeal into the micro- it pleasantly expressed sentiments of our own phone ; as long as a pig has never squealed concerning the constant reference made by an- into a microphone before (and we really don't nouncers to the "invisible guests." One is know why pigs have never been permitted to very uncomfortably reminded of a spiritual squeal into microphones), we shall be back seance because that is really the only place you of the pig -squealing movement heart and soul. would expect friends in the proto- plasmic The trouble with radio (or one of the troubles realm. Mrs. Hemstreet objects with poetry : at least) is that studio managers are not ex- perimentally inclined. When KDKA broad- There is one thing I hate to be called, cast its first program; it set down a pattern that Against it I boldly protest; has been followed ever since. It gives inc a shiver, WLW is using a novel method to present A chill on the liver, the daily news, and while it may not be very To be hailed as "invisible guest." exciting as excitement is measured in these days of petting parties and uncovered feminine It's hard to imagine the ether, knees, it is pretty good for so young and yet As crawling with bodiless hosts, so mossy a thing as radio broadcasting. WLW But it gives me the creeps, mixes news items with music, reading a piece When a voice from the deeps, of news and then playing an appropriate (or Seeks to claim me as one of the ghosts. as near appropriate as possible) selection. Al- though the brief wire of our Cincinnati at- When you call me "dear friend" or tache does not so state, we presume when a "dear fan," news item concerning the K.O. of a pugilist I'll tune in with fervor and zest, is read, that the orchestra lapses into the But somehow I quiver, plaintive strains of "I Dreamt I Dwelt in And cannot but shiver, Marble Halls." This may be a little far- When hailed as "invisible guest." fetched, but it is the best example we can think of at this time. This Month's Cake Is Awarded * * * CONTINUING our practice of including one The "Invisible Guest" little puff of simon -pure praise each month, we at LONG years ago, when we were annoying wish to lay a wreath the door of the the readers of the New York Herald - Tribune Eveready Entertainers. The nice thing about

Kadel & Herbert HOW A STATE'S PRISON INMATE EVADES THE LONELINESS OF CELL LIFE Radio is a magic fluid that seeps into every crevice of human life -even through prison walls. Here is a Sing Sing prisoner manipulating a curious radio set built by himself.

www.americanradiohistory.com 274 POPULAR RADIO

the Eveready Entertainers is the delightfully ness, one finds in much of it kernels of real reckless way in which they abuse the most subtle humor. To say that one was dining sacred traditons of the art, for the habitual with a big rubber man from the Turkish listener of WEAR, WSAI, WEEI, WJAR, Baths or that one went to the theater with WOC and WEAF must feel with us that a large collar man from Great Neck or that Eveready entertainment is unusually good to the evening was spent with a big locksmith the point of being actually satisfying. It man from Key West is, to our way of think- seems that a perfectly appalling amount of ing, a pretty steamy line of talk. All of which thought and painstaking effort has been put goes to show how easily a man like Richman into the construction of these weekly events. can take on customers like us. They should be a great inspiration to the hundreds of studio directors with heads filled Talky Announcers with ground -up corn cobs. * * * SOME day when we are under a little less A Real Nut Comedian social pressure, we are going to look up the on the Air WEAF, WJZ, WJY, KDKA, WMAQ and WHILE we are at it, we may as well add WFI programs of a year back and publish another dash of parsley to this unpalatable them with the programs of the present time. dish of arid hokum. We wish, in this case, This would be, perhaps, the most effective to extol Harry Richman, who is perhaps the way of saying that radio is hog -tied to the most outlandishly foolish man on the air. To hitching posts of broadcast tradition and that say that he is the most outlandishly foolish the majority of our impresarios and entre- man on the air is saying a pretty large mouth- preneurs are at the very end of their wits. If ful, too, when we stop to think things over. you changed the date on any one of these Yet with all of his downright foolishment, he program cards, it would be just about all you is a powerfully funny man, and the weak old would have to do to bring them right up to thing that runs this department has been a the minute as the classiest and newest means subscriber of his since the second night he of cooking up a batch of entertainment for came to the air through WHN -yes, it's a the yokels "out there." little over a year ago now. With the precious few announcers that we It takes a good man to he so foolish that have who know how to carry on an intelli- he is funny. Most of the super -nutty come- gent, connected conversation free from "ands" dians are just foolish without being funny, and "buts," we often wonder if the bare which is a most pathetic status. While Harry announcement of the station, the number and the Richm-an unloads many scuttles of utter crazi- artist would not be the wisest course to

F. M. Delano, Paris THE ALUMINUM LOUDSPEAKER SPEAKS This gigantic loudspeaker, which u'as set up on the grounds in Germany, of the Leipsig Fair consumed approximately one horse -power of electric current, which was sufficient to send the sound waves scurrying over loudspeaker the entire exhibition. This operates with a thin aluminum ribbon pulled taut between the poles of a powerful electromagnet.

www.americanradiohistory.com FIVE POINTERS FOR REDUCING STATIC 275 follow. Surely that would be better than listening to a long line of grammatical goulash, which, after all, is simply designed to say, "This is station BXW, Buffalo, N. Y. John Jones will play `Home Sweet Home' on the harmonica." It is certainly amusing to hear some of the patter that is offered as intelligent comment by talky announcers. There is one chap in New York (we'd hate to mention his name because he took us out to lunch one day, poor devil ; we're pretty decent after all, aren't we who offers the rarest bit of irrelevant matter that you would care to listen to every time he approaches the microphone. He is perhaps the most capable oratorical kaleido- scope that has ever faced a microphone. The photographic rhapsody of a Pathé news reel is an example of unblemished harmony when compared to the thoughts commented upon by this young man in the course of a single minute. Metaphysics, baseball, music, pancakes, flowers, race horses, subways and hardware are some of the subjects that you might find little rhetorical grab -bags in any one of the Underwood & Underwood that he injects into the program at the end of each studio feature. A BROADCAST ARTIST WINS A We don't mind being announced at in the FORTUNE conventional manner by men like Milton Cross So gentle and soothing was the .jazz sym- (WJZ) or Thomas Cowan (WNYC), but we phony music played by Paul Ash that a kind- are awfully sensitive to the intellectual white hearted old lady of Olathe, Kansas, remem- wash peddled by the average young man who, bered him to the extent of $66,500 in her by some dirty trick of fate, has found himself will. This is the first case on record where in a radio studio. a man has been rewarded in the will of one

And that's that ! of his radio listeners.

Five Pointers for Reducing Static

NEARBY signals, when we have the ad- erful signals by means of the head -set, with- 1: vantage of a relatively high signal level as out amplification of any kind. compared with the static level, are fairly free from static. Good reception is therefore as- . LOUDSPEAKER reproduction often may be sured from nearby broadcasting stations, es- 4 improved in summertime reception by pecially today when many of the broadcasters bridging a small fixed condenser across the have gone to higher powers so as to insure loudspeaker terminals. The capacity of such proper reception of programs under all con- a condenser obviously must vary from one type ditions. of loudspeaker to another, but a little experimentation with several sizes of small fixed THE most effective way of reducing static condensers must soon disclose the proper value 2. is to select a powerful radio signal -which for a loudspeaker. usually means a local station. Ordinarily, there will be no static interference in the first IT is hardly necessary to go to the trouble place ; but if the background is scratchy and 5. of installing a shorter antenna for summer- blurred as the result of intense static, the out- time operation,, although the radio listener will put volume of the set can be cut down until obtain interesting results by trying out various the background noises are reduced to the van- kinds of antennas. After all, the only result ishing point. Obviously, the signal volume of a short antenna or an indoor antenna is is also reduced, but if it is sufficiently power- that the amount of energy intercepted is no- ful to begin with, there is ample opportunity ticeably less than with a full -sized antenna ; for reducing it and still have left sufficient hence the static level falls and with it falls volume at the end. the signal level. If the static level is below the signal level to begin with, this matter of 3. WHEN static interference is excessively should be dropping the initial values to lower levels mu-t troublesome, the amplification bring the low static down below the thresh- cut down to one stage. In the event that static troublesome old of audibility. At best it is an illusion, interference is overwhelmingly though to some it is highly pleasing. (such as with an approaching thunderstorm) ALFRED N. GOLDSMITH it is still possible to listen to sufficiently pow- -DR.

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THIS department is conducted by POPULAR RADIO LABORATORY for the purpose of keeping the radio experimenter and the broadcast listener informed concerning approved the ne'w'est inventions and the developments in radio equipment. Only such apparatus as lias been tested and endorsed by the Laboratory is noted in these columns.

AERI-\I.s CRY ST. \I. I)ETECTORS Super -.Sensitive Onnti- Directional a,rial: Portable Globe .Aerial Oscillafor'uer; Uscillafurntcr Co. (2o. Detector stand; Pacent Electric Co., Inc. AUDIO -FREQUENCY "DeaU, Valley" crystal; Pacific TRANS FM: \I ¡ k5 Radio Specialty Co. Parent audiofornters; Pacent Electric Inc. Peerless Vein- ('. "Death Valley" permatect; Pacific Radio Spe- attilio: L Pecrlca I: lin Corp. cialty Co. Precise audio -frequency transformer: l'reci., \Ifg. Co. De -Tec -Tone crystal detector; Pyramid Products Co. Precise push -pull transt"rmers: l'reci.c :Alfg. Co. lain Pvrz;nia' crystal; Pyramid Products Co. "HegeIog" audio- fretitle)! y transformer; l'remi. r Electric ((/il-chisl;er; Rep Radio Co. Co. Roll-O crystal; Roll-0 "Recept'-ad' audio- fre /netcy transformer I:ailiii Crystal Co. Receptor Co. R -( -F semi-fixed detector; R -U -F Products Co. It -1' -F rough Reliable audio -frequency transformer; Ri-liable wonder crystal; R -U -F Products Parts Mfg. Co. Co. Rusonite fixed detector; Rusonite Products "Rhamstine" audio -frequency transformer; I. Corp. Thomas Rhamstine. "Rubicon" audio- frequency transformer clu m a, Co. Duplex (push -pull) transformer; Rubicon Co. DIALS (7t-a- rernit'' tuning control; Phoenix Radio B- \TTERIES Corp. Prest- O -Lite batteries; l'rest -t) Lite (' ., Inc. "flemco" dials; Geo. Richards & Co., Inc. Jumbo battery; Primary M fg. Grp '' Rebat" rechargeable wet "B" batteries: Radio Rebat Co. GRID -LEAKS BATTERY CHARGERS AND RECTIFIERS AND RESISTANCES Cartridge resistances; "Rhamstine" "B" rectifier; J. Thomas Rham- Pacent Electric Co., Inc. stipe. Grid -leak and condenser; Pfanstiehl Co. N'onais,- roriable grid -lead; Radio Battery chargers; P. C. Rumbold Inc. Foundation,

TILE DIAL WITHOUT A SET -SCREW Name of instrument: Knob and dial. Description: This knob and dial unit is made in two pieces and is attached to the shaft of a tuning instrument by means of a threaded chuck. The dial itself is placed over the shaft in the right position and then the small knob is screwed up tight causing the chuck to pinch on the shaft, thus 'making a secure and self- centered fit. Usage: As a dial for tuning a radio- frequency circuit. Outstanding features: Neat appearance. Clear vision of the numerals. Self- center- ing. No set -screws. A dial made in two parts that is self -centered. No wobbling. .Maker: Waterbury Button Co.

276

www.americanradiohistory.com WHAT'S NEW IN RADIO APPARATUS 277 -

HEADPHONES "Pacent" headsets; Pacent Electric Co., Inc. "Perfectone" phone; Perfectone Radio Corp. "Randolph" special headphone; Randolph Radio Corp. "Royalfone" headset; Royal Electrical Labora- tories. JACKS Pacent jacks; Pacent Electric Co., Inc. KITS Ultradyne kit; Phoenix Radio Corp. Pink -A -Tone superheterodyne kit; Pinkerton Radio Corp. "Vir Bren" kit; Radio Instrument Co. - "Raven" superheterodyne kit; Raven Radio, Inc. "Rubicon" kit; Rubicon Co. LIGHTNING ARRESTERS Anchor lightning arrester; Radio Receptor Co. LOOPS A low, capacity is obtain-ed between terminals. "Paths" Curtentcnna; Pattie Phonograph & Radio Corp. "Pollard" loop; Pollard Bros. AN EFFICIENT VACUUM -TUBE SOCKET Collapsible loop aerial; Radio Association of America Name of instrument: Vacuum -tube socket. Duo- Spiral folding loop; Radio Units, Inc. Description: This instrument is about as sim- "Hemco" loop aerial; Geo. Rchards & Co., Inc. ple as it is possible for it to be. The "Ritter" loop aerial; Ritter Radio Corp. contact pieces are attached to the skele- ton insulator hase by screws which can be used for fastening connecting wires. The contact, however, is also brought out in a single piece which is available for soldering. The tubular support for the. vacuum tube contains a unique flap for applying pressure on the side of the tube and thus holding it secure in r s[e.np. the socket. The four eyelets are in- No.1600,,... '...,....,« o stalled in the base for mounting. Usage: As a holder for vacuum tubes in a receiving set. Outstanding features: Light weight. Good contact. Low capacity between terminals. High insulation. Neat appearance. Maker: Leich Electric Co.

LOUDSPEAKERS "O'Neil" audiphone; O'Neil Mfg. Co. An automatic switch that prevents circuits. "Pattie" loudspeaker; Pathe Phonograph & short- Radio Corp. " Perfectone" loudspeaker; Perfectone Radio A BATTERY Ccrp. CIRCUIT BREAKER "Radiola" loudspeaker; Radio Corporation of Naine of instrument: Circuit breaker. America Radio lase: Radio Vase Co. Description: A protective switch enclosed in American Bell loudspeaker; Randolph Radio a neat metal container for mounting near Corp. the storage battery of a receiving set, "Thorola" loudspeaker; Reichmann Co. "Thorophone" loudspeaker; Reichmann Co. to protect the battery and the set against "Remo" Trumpet; Remo Corporation short -circuits. The breaker may be set " Remola" recreator; Remo Corp. in operation by "Royalfone" loudspeaker; Royal Electrical Lab- pressing one of the small oratories buttons. The other one if pressed will re- lease thé switch and open the circuit. If a MISCELLANEOUS ACCESSORIES short -circuit occurs the switch auto- Radio wall map; Ozarka, Inc. matically Peerless Twin -audio amplifier; Peerless Radio opens and stays open until it Corp. is reset by the operator. The mechan- "Nodust" cleaner; Peiffer & Co. ism may be set to open at a load of "PRSH" A. C. leads; Pittsburgh Radio Supply three or House four times that drawn by the Standard adjustable aerial base; Pomona Hard- filaments of the vacuum tubes in the ware Co. receiver. Panel engraving machine; H. P. Preis Sr Co. Usage: As a protective switch "Precise" No. 1,600 protector (circuit breaker); against short - Precise Mfg. Corp. circuits in a radio installation. Filtoformer; Precise Mfg. Co. Outstanding features: Absolute protection. Coil plug receptacle; Pacent Electric Co., Inc. Small size. Ease of setting. Jack name plates; Pacent Electric Co.. Inc. Maker: Precise Quinby radio frames; Quinby Radio Frame Corp. Mfg. Corp. "Radeco" safety fuses; Radio Equipment Co.

www.americanradiohistory.com 278 POPULAR RADIO "I'ir Brem" input transformer; Radio Instrument Co. "Reliable" radio -frequency transformer; Reliable Parts Mfg. Co. Intermediate-frequency transformer; Reliable Radio Mfg. Co. Intermediate- frequency transformer; Reviler Radio M fg. Co. "Rubicon" radio -frequency transformer; Rubicon Co. Tuned stage transformer; Remler Radio Mfg. Co. RECEI \'ING SETS " Operadio" receiver; Operadio Corp. Low -wave receiving set (for amateurs); Ott A small condenser provided with an adjusting Radio, Inc. screw that is a great in neutralizing a " Ozarka" portable receiver; Ozarka, Inc. aid "Os.arka" 4 -tube set; Ozarka, Inc. receiver. ".Minute Man" receiving set; Pathe Phonograph & Radio Corp. A SMALL .A1)JUST.AISLE CONDENSER Name of instrument: Small variable condenser. f)escuiplion: The two plates which form part of this condenser are mounted inside of the neat hakelite container directly on the two screw terminals shown and also serve as binding -post terminals. The adjustable screw in the center when turned in a clockwise direction depresses one of the plates, thus decreasing the distance between them and increasing the capacity. I sage: In any part of an electric circuit where a very small variable condenser is necessary. Outstanding features: Small size. Electrical efficiency. Exactness of manufacture. Ease of adjustment. Neat appearance. shaker: X -L Radio Laboratories.

heur-a-Radio ; Radio Appliance Co.. Inc. 1 y-T -II ;cruicr crrntrr,l; Radio CH it . Ihm Rajah " Snap tcrn,inals,- Raial, .\uto Supply Co. /.'ajalr" radialor ground; Rajah .Auto Suppl Co. (io/dahiskc,': Rep Radio Co. PANELS Pa ne/ vte radio panels; Panclyte Board Co.. Inn. insu/inc radio panels; Radio Panel \ l'art, Corp PHONE PLUGS Plugs; Pacent Electric C.... Inc. Poly plug; Poly met \Ifg. Corp. PHONOGRAPH ATTACHMENTS This loop is jointed in fi -re places, which permits Phonograph attachment: Perfectone Radi,. Carl.. folding into Thorola" phonograph attachment: Reichm,nrti a very compact unit. Co. h'h,unstine" rictoph (MC : T. Thomam Rhanmtine .A COT.L. \PSIBLE LOOP "Rhamstine" needlephone: T. Thomas Rhanistinr Royalfonc" unit: Royal Electrical Laboratoric- -lame of instrument: Loop antenna. POTENTIOMETERS Description: .1 portable loop with a unique folding feature. .Yo. 88 potentiometer; Pacent Electric Co.. Inc. The wooden strips "Premier'' potentiometers: Premier Electric Co. which support the five slotted insulator PO'.VER AMPLIFIERS rods are hinged so that they may be folded up. "Radio/a- balanced an,p/iticr tpush- pal/,; Radi., The two upper sections thus Corporation of America. may be inverted and the two lower sec- RADIO CABINETS tions may be closed up vertically, reducing the over -all "Camp ?bell" radio cabinet; Perkins- Campbell Co. dimensions to a small Radio cabinets (desk style); l'eters Electric space for packing. The wires, however, Cabinet Co. remain taut ill any position "Robbins" radio desk ; Robbins Woodworking of the outer Co. frame. The loop itself may be revolved RAhIO FREQUENCY TRANSFORMERS on a fixed base. l'ltrafornu'r; Phoenix Radio Corp. Usage: As a pick-up Pink -A -Tone device for a radio - transformer; Pinkerton Radio Corp. f requency receiver. Super- ntultiformer; Precise Mfg. Co. Outstanding Precision radio -frequency transformer; Precision features: Portability. Neat work- "i'irCoil Co., Inc. manship. Good appearance. Variable Bren" radio -frequency transformers; Radio inductance. Directional Instrument Co. .Maker: efficiency. Aalco Radio Laboratories, Inc.

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CONDUCTED BY DR. E. E. FREE The Ether and the Soul of the body and of matter. The present connection of life with matter is probably, Sir SIR OLIVER LODGE is one of the world's mos ()liver thinks, neither permanent nor direct. competent and sensible scientific investigators The real medium of the life force is ether. He is also, as newspaper readers well know Undeniably these speculations are interest- one of the few scientific men who have ac- ing. Sir Oliver always contrives to be that. cepted the beliefs of the spiritualists. He not Whether, in the present state of knowledge, only admits a possibility that there exist non- they get us much farther in the progress of material forces and actions and even beings, but thinking, is another question. The ether itself he believes all these things to be facts. He has is, admittedly, utterly mysterious. The life - devoted much work to the field of psychic re- force or soul or whatever you want to call it search. He is convinced that human person- is equally mysterious. It does not seem so alities survive after the dissolution which we very useful, therefore, to equate the two mys- call death. teries. Unusual interest attaches, therefore, to a Still, most people demand to be allowed to recent radio address made by Sir Oliver from think about the soul. They might as well 2L0, in London, in which he suggests that the think about an etheric soul as any other kind. mysterious ether, about which there has been No one can say that they are wrong -or right. so much argument, may be the seat of psychic forces and entities as well as the medium for the transmission of radio waves and of light.* It is possible, Sir Oliver thinks, that life may New Antenna System Reduces be connected much more intimately and per - manently with the ether than with matter. Static The ether has "perfect properties." No en- AN ingenious application of two loop an- ergy is lost when light (for example) traverses tennas to the problems of directive recep- it. Matter, on the other hand, is liable to de- tion and of static reduction has been per- terioration. Energy is lost in it and by it. fected by Mr. H. T. Friis of the Bell Telephone Matter becomes the seat of the mysterious Laboratories and was described by him re- forces which we call life. Matter becomes cently before the Institute of Radio Engi- "animated." The question arises, can ether be neers, in New York City.* animated too? The device consists of a long structure, like All force, Sir Oliver continued, is exerted the movable part of a rotating drawbridge. through the ether. It is the medium of such It rotatess, too, life just as the drawbridge does, attributes as minci and memory. These but on wheels at the two ends instead of on a attributes belong to the part of the universe central pivot. At the two ends of the structure which is unseen. If they have contacts with are the two loops, physical the length of the "bridge" things at all, those contacts are pre- being such that these loops are distant from sumably through the ether. Our material bod- each other ies are transient. just 1/12 of the wavelength that is They wear out. Mind, too to be received. For example, may need a vehicle, one that is independent for receiving a 600 -meter wave, the length of the bridge between the *The address was the last of a series of seven broad- two loops is 50 meters, approxi- cast by Sir Oliver under the title "Ether and mately 150 feet. Reality." It was delivered on March 31, 1925, and was reported in the London press and in Nature *Mr. Friis' paper was presented (London), vol. 115, page 505 (April 4, 1925). In stitute before the In- another in of Radio Engineers on May 6, 1925. It was address Christ Church, London, on March reported in the Radio 12, 1925, Sir Oliver expressed somewhat the same Section of the New York Herald -Tribune on May 10, 1925. The facts given ideas. This address is reported in the Chemical here are taken from News (London), vol. 130, page 199 (March 27, 1925). a statement issued by the Bell Telephone Laboratories, Inc., New York City. 280

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The operation of the apparatus depends on lying in the opposite semicircle. The ordinary the fact that radio waves need time to move directional loops are much less effective than through space. If one end of the bridge is this, since they receive reasonably well from pointed directly toward the transmitting sta- any direction except those within a narrow tion the loop at that end of the bridge will angle nearly perpendicular to the plane of receive the wave first. The loop at the other the loop. end of the bridge receives the wave a little This is why Mr. Friis' device is so effective later. If the two loops are 1/12 wavelength in reducing static. Most of the static is di- apart this will mean that the received wave in rectional. If the bridge is pointed in any direc- the second loop will be 1/12 later in phase than tion in the semicircle opposite to the direction the wave in the first loop. Expressed in the of the static, the static will be canceled out usual fashion, this means that the second wave and will not be heard. Any desired signal will he 30 degrees out of phase with the first. coming from the proper semicircle will he The next step is to shift this phase differ- heard unimpaired. In the actual set -up used ence still further by means of a phase- changer by Mr. Friis a superheterodyne receiver was attached to the receiver. It is shifted, in fact, employed, and the precise tuning of this re- 150 degrees, which makes it just 180 degrees ceiver enabled a still further reduction of the out. This means that the wave coming from static. that direction will actuate the two loops in The chief disadvantage of the apparatus is exactly opposite fashion. They will cancel the length, cost and cumbersomeness of the each other. Nothing will be heard in the removable bridge carrying the two loops. But ceiver. doubtless this can be reduced. One thinks, But consider a wave coming from the oppo- for example, of a pair of very light loops site direction. This wave will encounter the mounted on the two ends of a long pole or a two loops in the reverse order. The 30- degree duralumin girder and balanced on the top phase lag will apply in the reverse direction of a tall vertical pole, like the weathercock to the 150 -degree phase difference produced on a steeple. by the phase changer. Accordingly, the net, or resultant, difference in phase between the two loops will be 120 degrees, instead of 180 degrees. This means, as any electrical engi- Earth Conductivity Affects In- neer will tell you, that the signal strength clination of Radio Wave is not canceled. In fact, it is left unimpaired. The two loops function as though they were MosT of the modern theories of radio a single loop or any other satisfactory type of transmission assume that one component of antenna. the wave arriving at a distant receiving The net effect is, then, that signals coming station has reached there by some path high toward one end of the bridge are received per- up in the air, as, for example, along the sup- fectly, while signals approaching toward the posed Heaviside Layer. If this be true this other end of the bridge are not received at component of the wave ought to arrive at the all. This gives us a directional antenna which receiver with a downward inclination, its wave - will receive from any direction lying in one front being not quite perpendicular to the sur- semicircle and not at all from any direction face of the ground. A mechanical analogy i;

Bell Telephone Laboratories A NEW ANTENNA SYSTEM FOR DIRECTIVE RECEPTION bridge, having loop antennas at both of its ends, has been built by Mr. H. T. This rotating system Friis to obtain more complete directive reception as well as to reduce static. The receives signals from any direction in one semicircle, but from no direction in the opposite semicircle.

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land showed values between 6 x 108 and 4.7 x 10" electrostatic units. The higher of these values is equivalent, roughly, to 800 ohms resistance per cubic inch of soil. The measurements were made at radio frequencies, by observing the forward tilt of waves from a nearby transmitter. These conductivities are relatively high for materials of the insulator class and this is ascribed to the fact that the soil and rocks of England are prevailingly moist. This suggests a possible research for radio engineers %vho happen to be located in some of the American desert regions. In large parts of California, Nevada, Arizona and other west-. ern states the soil is almost waterless. Its conductivity is probably far lower than the values found by Dr. Smith -Rose and Mr. Barfield in England. The repetition of these experiments in some such locality might yield very useful information about the actual paths of radio waves close to the earth. The research is not to be recommended, however, to the amateur or to any one except a well -trained and experienced radio engineer. The necessary technique involves the determi-

1)r- R. L. Smith -Rose MEASURING ELECTRIC FIELDS This straight -wire antenna, or "Hertzian rod," was used by Dr. Smith -Rose to determine the direction of the electric field of an arriving radio wave.

the artillery shell which is fired at a high angle of elevation, reaches the higher levels of the atmosphere during its flight, and finally arrives at its target along a downward- pointing path as though it were falling obliquely from the clouts. The well-known English radio engineers, Dr. Smith -Rose and Mr. Barfield, have now attempted to verify this theory by a direct test of the inclination of the wavefront arriving at a receiving station.* This proved to be impossible practically because of the relatively high conductivity of the earth's surface. For a perfectly -conducting earth the electric force is always vertical and the magnetic force always horizontal regardless of the real inclination of the wavefront of the arriving wave. Experimental tests of the actual conductivity Dr. R. L. Smith of the earth at a number of localities ill Eng- -Rose THE TILTING *"On the Determination LOOP of the Direction of the This device Forces in Wireless Waves at the Earth's Surface,'' determined the direction of the magnetic by R. L. Smith -Rose. Ph.D., field of the arriving Proceedings and R. H. Barfield. wave. The intensity of the of the Royal Society (London). Series A, signal varied with the position vol. 107, pages 587 -601 (March 2, 1925 . of the loop relative to the wave.

www.americanradiohistory.com IN THE Wr)RLD'S LAßORATORIES 283

Dr. R. L. smith -Roar! THE COMPLETE APPARATUS FOR MEASURING WAVE INCLINATION combines the Hertzian rod This portable apparatus, being operated by Dr. Smith -Rose, appa- and the tilting magnetic loop shown on the preceding page. Measurements with this ratus led to a determination of the prevailing electrical conductivity of the soil in Eng hitul. nation of the direction of the electrostatic field and will acquire a thin film of the respective a straight, sin- sulphide, which film is then quite efficient as a by a Hertzian rod -practically used gle antenna the inclination of which can detector. It works best, he reports, when -wire Similar effects may he varied -and the exploring of the electro- with an applied potential. a tilting loop. be obtained with oxide filins on copper or magnetic field by means of forms natu- Both of these pieces of apparatus will work brass. The mere tarnish which experts, who rally in the air on brass articles and which usefully only in the hands of oxides and sul- know exactly what they are about. consists, usually, of mixed phides of copper and zinc, will serve quite well for radio detection. These film detectors are worthy of more at- Surface Films as Radio Detectors tention from experimenters than they seem to have had hitherto. WIIATEVER be the secret of the detecting action of a crystal, it is reasonably certain that this action is accomplished within a thin film, possibly some scores of atoms deep, on the How to Repair a Broken Lead surface of the crystal. The main body of the crystal serves merely to support this surface Wire film. It has no more to do with the detecting of a house has -A IIiNT of real v-able for those Nvbo experi- action than the main structure is contained in a on its roof. ment with vacuum tubes to do with the paint Mr. D. A. Wells of the Uni- Why not make use, then, of a mere film of recent note by sulphide (which is versity of Cincinnati.* When one of the line crystal material, of lead glass of an ex- or of silver sulphide or of wires that enters through the the same as galena] is broken off outside the glass, something else? That this can he done with perimental tube by Mr. James as is all too frequently the case, it is usually considerable success is claimed tube away. work on various phases of believed necessary to throw the Strachan,* whose wire to the tiny projecting crystal detection is already familiar to readers Soldering a new point of metal is ordinarily a hopeless task. of this department. he reports, a contact consist- Mr. Strachan reports, for example, that a Mr. Wells uses, a piece of ing of a drop of metallic mercury. First he piece of lead, a piece of silver or wire to moist sulphuretted cleans the broken, projecting point of the copper niay be exposed Then he places a hydrogen gas (which is the gas of rotten eggs) with a drop of nitric acid. -off Lead -in Wires," Single -Point * ";Method of Repairing Broken * "Some Interesting Experiments with of the Optical Society of Wireless I rorl ? he D. A. Wells, Journal Detectors," by James Strachan. Wis.), vol. 10, pages 615 -616 (London), vol. 15, pages 200-202 (November 12, Inerica (Menasha, 1924). (May, 1925).

www.americanradiohistory.com 284 POPULAR RADIO

drop of mercury on it. Next he (lips the end cillor M. Baumler, of the German Government of a clean copper wire into this mercury. The Telegraph Service, for the cities of Berlin copper wire must be held in place mechanically and Hamburg.* by a strip of tape around the tube or in some As was expected, Herr Bäumler found deter- other way. Electrically, the mercury contact is minable irregularities in the strength of the good enough. Many a damaged experimental fields in different directions from the trans- tube can be saved in this way, thus avoiding mitter. Perhaps the most interesting feature the blowing and pumping of a new tube. disclosed by the map of Berlin is the fact that transmission was better over the famous Tier - Radio Wave Absorption garten park than in directions where the city by is closely built up. Buildings are evidently Berlin Houses more absorptive than trees, at least under the conditions of these tests. OVER a year ago the engineers of \VEAF As was the case in New York, made a series of measurements no actual of the strength "dead spots" were found. hear less of signals from their station at numerous We of points these supposed (lead spots nowadays in the on and near Manhattan Island and pre- United London pared a map showing States, but is going through in most interesting fash- an epidemic of them. The London broadcast- ion just how the signals were affected by the two rivers and by the blocks of tall steel build- 'The results are reported in "Elektrische Nach- ings in the downtown and the Forty- second richten- Technik," vol. 1, part 5, published by the Street districts of the city. A similar inves- \ \'iedemannsche Buchhandlung, Berlin, and are ab- stracted (in German) ill Der Funker (Berlin), vol. 4, tigation has now been made by Postal Coun- pages 17 -19 (February, 1925).

P?Vlittt C.179,01o,

Redrawn from "Der Funker" HOW THE CITY OF BERLIN AFFECTED RADIO WAVES The black dot at the center shows the location of the transmitter at Voxhaus. The indicates a uniform distance from this transmitter. circle which The other line connects points at the sanie signal strength was found. Note that westnorthwest, the transmission is good toward the over the great park marked " Tiergarten."

www.americanradiohistory.com IN THE WORLD'S LABORATORIES 285

From a photograph made for Pop. i..\k RADIO HOW DEAF STUDENTS CAN LEARN TELEGRAPHY The "touch receiver" invented by Mr. Jakosky and his associates is worn by the man at the right. Mr. Jakosky himself is at the key. At his left are Dr. McConnell, of the Bureau of Mines, and Mr. Ingel of the Western Pennsylvania School for the Deaf. The type of receiver designed for reception by the finger tips may be seen on the table. ing station, 2L0, was moved recently to a Receiving Radio Code by Touch new location. Since then there has been much complaint that the southeastern portion of the AMONG professions lately made available city is so shielded that the programs cannot to deaf persons is, curiously enough, the be received. profession of telegraph operator. This has been done by the perfection of a code receiver which operates by touch instead of by hear- ing. The device can be applied to radio code Long Waves Also for MacMillan as well as to the Morse code of land telegraph lines. There is no reason, therefore, THE MacMillan Arctic Expedition, which why deaf persons cannot now enjoy code con- sailed recently for its winter vigil in the north, versations by radio or even, it may be possible, was originally designed to be equipped only seek employment as commercial radio oper- with short -wave radio, the experiences of the ators. last expedition having convinced the officials The new touch receiver has been devised by of the American Radio Relay League that Mr. J. J. Jakosky, well -known radio engineer the best results would he attained with waves of the United States Bureau of Mines, in co- shorter than one hundred meters. operation with Dr. ,W. J. McConnell, a surgeon But this is not to be. The United States of the Bureau of Mines, and Mr. Truman L. Navy is contributing to the expedition some Ingle, Principal in the Western Pennsylvania airplanes and equipment together with fliers School for the Deaf.* Two forms have been to operate them. The Navy insisted that the ; one operating through the finger -wave radio perfected expedition carry regulation long tips, the other by means of a small plate held apparatus, it being the Government opinion as the telephone receivers were more against the temple, that these more usual wavelengths worn by switchboard operators are held against surely dependable than the newer short ones. to be the ear. And so, i f newspaper reports are In both cases the line is actuated with ordi- be equipped with trusted, the expedition will nary 60 -cycle alternating current. Attached both short -wave and long -wave transmitters to the "sounder" or receiving device on this and receivers. Assuming that space for both is available, this is an admirable outcome. The expedition should come back with much data *"Telegraphy for the Deaf," by J. J. Jakosky, W. advocates J. McConnell and Truman L. Ingle, a pamphlet pertinent to the controversy between printed by the Class in Printing at The Western of shortwaves and low ,power and advocates Pennsylvania School for the Deaf, Englewood, Pitts of long waves and high power. burgh. Penna.. 1925. 7 pages.

www.americanradiohistory.com 286 POPULAR RADIO line is a vibrating armature designed to re- pounced at the recent meeting of the National spond by vigorous vibration to this 60 -cycle Academy of Sciences in Washington and con- current. In the finger -tip apparatus this arma- stitute some of the most important scientific ture is attached to a small metal plate against data that we are likely to acquire this year. which the lingers are placed. In the head -hand One of the experiments was devised by the form of the apparatus a similar metal plate sanie Professor Albert A. Michelson who presses against the skin of the temple. helped conduct the original Michelson -Morley Pressing the key at the sending end of the experiment. In a field some ten miles west of line sends the alternating current into the re- Chicago, Professor \lichelson built a square of ceiver, sets the vibrating plate into motion and iron pipe approximately one mile on a side. He makes the quivering of this plate perceptible to pumped most of the air out of this pipe so that the deaf "listener" at the receiving end. Dots and accidental variations of the temperature or clashes are distinguishable by length, just as in pressure of the air inside the pipe would not the usual audible receivers. Weak impulses from affect the experiment. Then he sent two light long lines are fed into relays and converted rays around the square of pipe; one ray in one into the alternating- current local signal, just direction, the other in the opposite direction. as telegraph signals are now reinforced by Meanwhile the earth was revolving, carrying using direct -current relays. Radio signals may the pipe square with it. The light ray that be converted and made sensible to touch in moved in one direction through the pipe was the same way. moving, on the average, with the rotation of the earth. The ray in the opposite direction was moving against the earth's motion. Ac- Two Important Experiments on cordingly any "ether drift" should " causé one ray to complete the circuit a trifle faster the Ether and Relativity than the other one. THE famous Einstein theory was developed, A long series of very exact measurements you remember, partly from a remarkalde ex- was carried out. No ether drift was detected. periment known as the \lichelson -\I,r ley ex- The result agrees, therefore, with that of the periment. This experiment had for its object earlier \lichelson \lorley experiment and is the detection of any possible motion of the consistent with the Einstein theory of rela- earth with relation to the ether, this being as- tivity.* cribable, of course, to the.motion of the earth in The other experiment was carried out by its orbit or to its rotation on- its axis. Professor Dayton C. Miller, of the Casé School The experiment failed. No drift of ether of Applied Science, of Cleveland. Hé too re- through or past the earth was detected. There peated an experiment essentially similar to the Michelson -Morley experiment, but he.díd it on three .explanations: ( 11 that were possible Mt. tlié're is no ether, (2) that an ether exists but top of Wilson, in California, where the great astronomical observatory is --situated. moves with the earth, 13 ) that the motion of the earth relative to the ether is exactly coni- His results are absolutely contrary to-thóse of pensated, by a contraction of matter in this Professor Miehelsón. He finds a drifts-of the direction, just as a wind blowing against a gas-- filled balloon will cause it to contract a little The results were announced tentatively at a lec- pressure. The ture in Chicago on January 8, 1925, this lecture in the direction of the wind being since printed in the University Record, Uni- Einstein theory is consistent with either the versity of Chicago, vol. 11, pages 136.153 (April, first explanation or the third. 1925). Details of the results are given in "The experimenters have carried out Effect of the Earth's Rotation on the Velocity of Two recent Light," by A. A. Michelson, Henry G. Gale and tests essentially analogous to the famous Fred Pearson, Astrophysical Journal (Chicago), Michelson- Morley one. The results were an- vol. 61, pages 137.145 (April, 1925).

1011,

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LUSSEV'S OSLILLATING CRYSTAL USED AS AN AMPLIFIER When the voltage drop across the oscillating crystal is adjusted to exactly the right value the crystal can operate as a "negative resistance," thus causing some amplification of the signal heard in the telephones connected to the detecting crystal.

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Rouen N. Moulton AMERICA'S GREATEST EXPERT ON ETHER WAVES Professor Albert A. Michelson completed recently the most accurate measurement ever made of the speei of light. His experiment on ether -drift is described in the text. In addition, Professor Michelson has done much other important work with light rays, including the perfection of the interferometer method of measuring the sizes of the stars. earth relative to the ether equaling approxi- that it is notably shaken. That theory is sup- mately ten kilometers per second. More sig- ported in any event, by a vast amount of other nificant still, this drift varies in amount in evidence. But neither is it possible to say that just the way it should at different times of the the real existence of an ether is disapproved. If clay and the year, corresponding with the chang- Professor Miller's results stand the tests of ing direction of motion of the particular point criticism and repetition they will furnsh strong on the earth where the experiment was con - evidence for the reality of an ether through ducted.t which our earth sails along like a bullet through This leaves us confronting a sharp contra- the air. diction between two experiments which should In the report referred to Dr. Slosson makes Iave come out the same. It is too soon to say the interesting suggestion that the difference that the Einstein theory is disproved or even between the results of Professor Michelson at Chicago and those of Professor Miller at Mt. tProfessor Miller's data have not yet been published in detail. They were reported orally to the Wilson may be due to the greater altitude of National Academy of Sciences, in session at Wash- the latter station. Close to the earth's surface ington, D. ('., on April 28, 1925. Brief accounts the ether may be dragged along, he thinks, by by Dr. E. E. Slosson, of Science Service, appear in Higher up Science (Lancaster, Pa.) vol. 61, number 1584, (May the motion of the ground. this 8, 1925) and number 1586 (May 15, 1925). dragging effect may be less complete.

In POPULAR RADIO for October, "How to Build the New Single Control Supenceterod\'ne Receiver" -tile latest development of 411 J. L. McLaughlin in the POPULAR RADIO LABORATORY.

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C2- Rathbun The Browning -Drake Receiver three -plate vernier condenser ; C3 -mica fixed condenser, .001 mfd.; QUESTION : Will YOU kindly give me C4- bypass condenser, 1 mfd.; the proper circuit for wiring up the R 1 -fixed resistance, 25 ohms; R2- filament rheostat, 20 ohms; Browning -Drake receiver? R3- filament rheostat, 10 ohms; R. E. WILLIAMS GC -grid condenser, .00025 mfd.; GL- variable grid-leak; ANSWER: In Figure 1 you will find the J1- double- circuit jack; circuit for this receiver. The parts you will J2- single- circuit jack, filament -lighting type; need for this set are the following: AFT1 and AFT2- audio- frequency ampli- L1, L2, L3 and L4- inductances which com- fying transformers. prise part of the National llcenaformer Three standard sockets should be used for kit ; the last three tubes and one 199 type of VCi and VC2- variable condensers, .00035 socket for the first two. The first tube may mfd. and .0005 mfd. respectively which be either a C -299 or a UV -199 tube -this is the also comprise part of the above mentioned reason for the extra resistance, RI. The three kit ; other tubes should be either UV -201 -a or Cl -mica fixed condenser, .0001 mfd.; C -301 -a tubes.

IL3 1/C2

VC/

www.americanradiohistory.com WHAT READERS ASK 289

All the tuning is done with the two condens- about 55 percent of the capacity of your ers, VC1 and VC2 while regeneration is con- condensers. Therefore by using condensers trolled by revolving the small knob which is of lower maximum capacity you discard the connected to the tickler coil, L4. unused portion of your present condensers, in this way making practically the entire dial range useful. Condenser Capacity Difficulty would be encountered in removing turns from the coils because the turn ratio be- QUESTION : I have recently constructed tween the primary and secondary coils is care- a 5 -tube receiver with two stages of tuned fully proportioned to prevent oscillation. If radio turns were removed from the secondary wind- -frequency amplification but find ings (which are tuned by the variable con- that the entire broadcasting waveband densers) this ratio would be changed and you lies between 5 and 60 on the dials. The would find difficulty in controlling oscillation in the radio -frequency amplifier. tuned circuits consist of coils taken from an old neutrodyne receiver shunted by Voltmeter for Storage Battery variable condensers of .0005 mfd. ca- Testing pacity (23 plate). The broadcasting sta- QUESTION : My storage battery is lo- tions come so close together on the dials, cated in a cabinet and must be removed especially the lower wave stations, that from the cabinet whenever I test it with it is almost impossible to separate them. the hydrometer. Could I install a meter I understand that this situation can be on the radio set which would tell the con- remedied either by using smaller capac- dition of the storage battery and thus ity variable condensers or by removing save moving the battery around ? some of the turns from the coils. Which B. MONTGOMERY would you advise ? ANSWER : A small panel mounting volt- MILTON GLASSBURG meter with a range of from 7 to 10 volts will give a good indication of the condition of your ANSWER: Either of the plans you suggest storage battery. The meter should be con- may be followed. However, the better plan nected across the "A" battery terminals of would be to leave the coils as they are and your set and readings should be taken with replace the variable condensers. If you use the tubes in the set burning. The ordinary .00035 mf d. condenser (17 plate) the broad- 6 volt acid type of battery should read about cast band will be spread out to cover approxi- 6.6 volts whet: first charged and it should be mately from 5 to 90 degrees on your dials. recharged when the voltmeter reading falls Roughly speaking, you are now using only off to 5.4 volts.

THE BROWNING-DRAKE CIRCUIT FIGURE 1: This popular circuit consists of one stage of neutralized tuned radio frequency, a regenerative detector circuit and the customary two stages of audio frequency amplification.

AFr AFT2 n- 2

J C4zli -1E-

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L2 ii G C, 612

VCZ

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d = /35v A Novel Audio -frequency Ampli- New McCullough AC Tube and fier Added to the Three -circuit Regeneration Honeycomb Set OUESTION : Is the new McCullough QUESTION: I want to add two stages _\(tube adaptable to a regenerative cir- of resistance- coupled amplification and cuit ? one stage of transformer -coupled ampli- PATRICK L. NEWSAND fication to my single -tube regenerative receiver which consists of three honeycomb ANSWER: Yes; satisfactory result has been coils and two I obtained with the new AC tube in various condensers. want to use regenerative the transformer -coupled circuits. However, caution must stage last. Will he exercised to keep the detector tube from you show me how to do it ? an oscillating condition because the moment the detector R.1L1'11 ITIA11N tube oscillates the AC hum will immediately become apparent. ANSWER : The circuit diagram for this addition to your receiver is shown in Figure 2. The coils L1, L2 and L3 comprise the triple AC Tubes on Direct Current coil set which you already have. The other parts that are necessary are given in the fol- OUESTION : I have direct instead of lowing list : alternating current in my house but would VC1 and VC2- variable condensers, .0005 mfd.; like to use the new McCullough AC tube C- bypass condenser, .006 mfd.; instead of the usual "A" battery. I have GC2 and G(3 -grid condensers, .006 mfd.; a five -tube radio -frequency set. Can this R5, R6 and GL3-- coupling resistances, A. megohm; be done? GL2- coupling resistances, megohm ; HARRY H. NORTINGTON GC1 -grid condenser, .00025 mfd.; GL1 -grid -leak, 2 megohms ; ANSWER : These tubes may be used on R1, R2, R3 and R4- filament rheostats; direct as well as alternating single- circuit jack; current. The ap- J- plied voltage must be between 3.25 and 4 volts AFT -audio -frequency amplifier transformer. for best operation, however. Use any make of standard This means that hard vacuum the 110 DC must he reduced to this value. tubes throughout. The tuning is accomplished In an alternating with the two condensers, current circuit this may be VC1 and VC2 and done economically with a the coupling is varied by moving transformer, but this coil L1 device cannot be used with direct current. To away from coil L2. The radiation is con- reduce the voltage trolled by moving coil L3 applied, a series resistance, closer to or farther capable of carrying in away from coil L2. this case approximately five amperes, must be used. This is poor

www.americanradiohistory.com 1 WHAT READERS ASK 291

A HONEYCOMB CIRCUIT WITH COMBINATION AMPLIFIER FIGURE 2: The amplifier added to this honeycomb circuit consists of two stages of resistance - coupled and one stage of transformer- coupled audio frequency amplification. It is different in that the transformer- coupled stage is placed last.

Gc3 AFT f .j aL3

-C'-.4pV l J T l

economy as only about 4 percent of the energy ANSWER : A 20 -ohm rheostat is suitable for is used in the tube; the rest is dissipated in a single 201 -a tube or even for two such tubes. the resistance. This load will correspond However, when several tube filaments are roughly to that of a flatiron. operated in parallel through one rheostat the The easiest way to make a resistance is to current passing through the rheostat is the fasten five porcelain sockets to a board and sum of the current requirements of the sev- connect all of them in parallel. One wire, eral tubes. In the case of five 201 -a tubes connecting all the terminals on one side, should the total current drain is about 1/ amperes go to the plug and another wire connecting the and the average 20 ohm rheostat has a current remaining terminals on the other side should carrying capacity of only / ampere. It is go to the "A" battery terminal on the set. The therefore evident that the rheostat was heavily second plug terminal should go to the other overloaded in the case you mention. "A" battery post. (For details of the connec- Following are the rheostat resistances re- tions for the filaments see page 511 of the quired for various types of tubes : June 1925 issue.) Four 100 -watt lamps (or 1 -201 -a tube, 20 ohms ; a combination giving the equivalent) should 2 -201 -a tubes in parallel, 20 ohms ; be inserted in the first four sockets. Lamps 3 or 4 -201 -a tubes in parallel, 6 ohms; varying from 25 to 100 watts should be in- 5 to 8 -201 -a tubes in parallel, 2 ohms ; serted in the last to get the proper resistance. 1 -UV -200 tube, 6 ohms ; Use the lowest possible wattage consistent with 1 --199 tube, 50 ohms; good reception. 2-199 tubes in parallel, 30 ohms ; 3 to 5 -199 tubes in parallel, 20 ohms ; 6 to 8-199 tubes in parallel, 6 ohms. What Size Rheostat? When two or more tubes are used in parallel and operate through a single rheostat less QUESTION : With rheostats of so many resistance is required than when only a single market, how tube is drawing through the rheostat. For- different resistances on the tunately, it is also true that the lower resist- am I to determine which to use with the ance rheostats have a greater current carrying different tubes ? In one receiver I con- capacity than those of higher resistance. Therefore, the low resistance rheostats are structed recently I used a 20 -ohm rheo- suitable for several tubes in parallel, not only stat to control the filaments of five 201 -a in resistance but also in their current carrying tubes, as I understood this to be the capacity. proper resistance to use with this type of tube. However, upon putting the set into operation the rheostat became very The Oscillating Receiver hot and in a short time burned out. Why QUESTION : At irregular intervals my was this, and what type of rheostat should receiving set squeals to such an extent I have used in this case? that reception is almost entirely blotted HERMAN SCHWENK out. These noises, I have been told, are

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caused by other receiving sets in my vi- VAR-variometer; RFT- neutrodyne ; cinity. I would like to know if there is coupling unit CI -mica fixed condenser, .00015 mfd.; any attachment which could he applied to C2- neutradon condenser ; my set that would filter out these squeals ? R1 and R2- filament rheostats, 20 ohms; J- single -circuit jack ; A. B. CLAN-Tux llET- crwstal detector; .\FT- audio -f requency amplifying trans- ANSWER : There is no such device for eliminating the squeals former. caused by your neigh- All the tuning of bors. Each operator of a receiving this receiver is done with set should the variometer, VAR. see that his own set never oscillates as he The neutradon con- owes that much to the general radio public. denser, C2, should he adjusted by placing a small piece paper The scheme for elimination of oscillation is of over one of the filament to tune in the signal first and then increase terminals of the first tube and inserting it in regeneration to strengthen the signal. the socket so that it will not light. Then, the condenser, C2, is adjusted until the signals are reduced to as low a value as possible. When One Stage this is done the receiver is neutralized and the Neutralized Radio- first tube cannot oscillate or cause radiation. frequency, Crystal Detector The crystal detector will have to be adjusted for suitable sensitivity before this can be done, and One Stage of Audio however. Use two C- 301 -a QUESTION : I have a single or UV -201 -a or any other -tube re- standard make of ,' i ampere hard tube for ceiver which is regenerative that employs this set. a variometer with a fixed condenser in the antenna circuit. I would like to add one How to Eliminate Microphonic stage of radio to this receiver, a crystal Noises detector and one stage of audio, so that QUESTION : To what it will operate a loudspeaker. The one are microphonic noises due and how can stage of radio I would like to have neu- they he eliminated ? tralized like in a neutrodvue. JOHN CiILLIES T. l' . I i.\ ER Axs\VER: Microphonic ANS\vi_R: In Figure noises are some- 3 we have drawn a times due to vibrating elements in a tube. hook -up for the final design of your receiver. This condition The is sometimes overcome by put- parts Cott will need in rebuilding this set, ting in a non- microphonic cushion including the ones socket, or you already have, are the by putting rubber cushions under the four cor- following: ners of the receiver.

RFT OEr

+ - - + -Melt 'I'i0,'f A., a..6z v

A SENSITIVE TWO -TUBE CIRCUIT FIGURE 3: This diagram shows how to change a single tube regenerative circuit non -radiating set. The stage of audio frequency over to a amplification requires one additional tube.

www.americanradiohistory.com WHAT READERS ASK 2)

A CIRCUIT FOR THE SHORT WAVES FIGURE 4: The single tube circuit in this diagram is satisfactory for the experimenter who is bent upon receiving the short-wave C.W. stations. The number of such stations is steadily increasing.

and L4 consists of 150 turns of wire wound A Novel Short -wave on a one inch tube. Regenerative Receiver All the tuning is done with VC1 as far as wavelength is concerned and regeneration is QUESTION : Please give me a diagram controlled with condenser VC2. Coils L1, L2 showing a form of short -wave receiver and L3 may be experimented with for increasing or decreasing the wavelength range of this that employs a condenser for controlling type of receiver. regeneration. I want to use this receiver for C.W. signals. TAIT LAURENCE The Principle of Modulation

a : ANSWER : In higure 4 you will find cir- QUESTION What is meant by "modu- cuit diagram for a regenerative receiver em- lation ?'' I have often heard the word but The parts you will need ploying one tube. be in a popu- for this set are the following: it seems never to explained LI and L2- single -layer solenoid coils tapped lar way. in the center; A. ANIERo L3- single -layer solenoid coil ; single -layer solenoid coil ; L4- into VC1 and VC2 -variable condensers, .00025 ANSWER : When the announcer talks the microphone the carbon granules which mfd.: in GC condenser, .00025 mfd., compose part of the microphone vibrate -grid voice frequency. This GL- variable grid -leak ; accordance with the R- rheostat, 20 ohms; vibration in turn varies the resistance of the circuit of the microphone and causes rapid TEL -telephones. -wave Coils LI, L2 and L3 are wound with about changes in the amplitude of the carrier the thickness of one wire current. This variation then comes into our No. 22 wire spaced The 31/2 inches in diameter. Coil Ll receiving set as the announcer's voice. on a tube place in the consists of 10 turns of wire; L2 consists of change of amplitude that takes is called "modulation." 6 turns of wire; L3 consists of 4 turns of wire carrier wave

www.americanradiohistory.com CONDUCTED BY J. ANDREW WHITE IN this department the Dean of Broadcasters -whose voice is known to millions of broadcast listeners- records items of interest and aulne to all radio fans cz yrywhere.

Stopping Bad Radio Manners by radio stations to enable the distant Siberian Injunction peasant to get advice on his farming problems direct from the agricultural colleges in Euro- KKEEP it clean has been the one thing pean Russia. The latest inventory discloses broadcast station directors have been very the fact that there are forty -three transmitters particular about from the beginning. It is and 282 receivers scattered throughout the ter- gratifying see to how ably the courts supported ritory of the Soviet Union ; fifty new receiving this policy in reviewing one of the first and stations are to be built. Incidentally, sets and one of the most important slips, a series of so- parts manufacture has been turned over to a called "health talks" which waved themselves State syndicate. off the antenna of WEBH on the roof of the * Hotel Majestic, in New York An injunction was granted the hotel people to "pull the How to Check Up on switch" on programs which do not measure Wavelengths up to the reputation of refinement the hotel Ir it interests enjoys. The case developed, incidentally, that you to scratch on your dials the health the place where definite wavelengths are to talker had been convicted ten years heard, be ago on a charge of maintaining rather than work with a station log and a nuisance, arbitrary numerals, you which seems to remove any chance of an alibi may listen in twice a on the part of the radio month to radio signals of definitely announced concern which leased frequencies transmitted the space. Personally, I am not familiar with by the Bureau of any previous dereliction Standards from Washington and California. of duty as flagrant All the as this; it is customary to require manuscript dope on how to receive and utilize this copies service is given in Bureau of talks in advance; and this is as it of Standards Letter should be. Circular No. 92. It's free. Write Bureau to the * * * of Standards, Washington, D. C. Yes, but * * * Who [Pants to Listen in "Radio on Lawmakers? Sport" as Played by WHEN the question of broadcasting the pro- Fritzie ceedings of both houses of Parliament THEY call broadcasting "radio came up Germany, sport" in in England recently, the Prime Minister ad- which in itself is just about as inter- vised setting up a committee to report esting as the fact that in two years matter. on the subscribers as many Whereupon spokesmen for the Brit- have been gained for the - ish wave ether public at lave facetiously suggested a ple- variety as have lined up for the Govern- becite to determine whether listeners them- ment's wire telephone in forty years. Radioing selves favored an additional burden of tedious started out as a state monopoly, but the advo- political speeches. Which is somewhat cates of unrestricted development like our argument whose main own situation ; the supply of oratory was the growth of halls in the radio in the of Congress seems still to be far in ex- United States, did succeed in getting across cess of the a compromise demand for its propagation. and all wavelengths up to 800 * * * meters are released by permit companies. to broadcasting Radio Net Spreads But the Government holds ma- f Over jority control and title to the apparatus. There Soviet Russia are now nine of these companies operating same number the THE of stations ; also Soviet is figuring on erecting nine new sub- a total of five stations, with three more to come. Every 294

www.americanradiohistory.com BROADCASTS 295 listener must have a post office permit, which Linking the Telephone to Radio marks a month, local postmen tak- costs two a radio ing care of the collections from the 714,352 IN Hawaii they are planning to use registered subscribers. The latest move is to system between several central exchanges of a the power from 1,500 watts to 8,000 local telephone company. Central will be called hop up phone, and if the and 10,000 watts and inject more variety in in the usual way from any programs which have had a preponderance of call is for one of the other islands the voice intellectual and educational features. * l New Record in Sales of Radio Apparatus EIGHT million dollars is the estimated total value of America's exports of radio apparatus when the year shall have come to an end. Very close to half that amount was shipped abroad in the first five months of the year, the total for the period and the monthly average showing respective increases of 123 percent and 130 percent, on which basis all existing records should be broken. * * * Radio Waves 2,200 Feet Below the Earth ANY question remaining that radio waves penetrate to great depths into the earth seems to be pretty well answered by the success of Meade W. Powel, an amateur of Warren, Ariz., in picking up a distant naval station while 2,200 feet below the earth's surface. He had no success with bare copper wire nor with a loop, but when he tied 100 feet of lead -covered No. 14 copper wire cable strung along the mine gallery midway between the roof and the floor, NPL, 400 miles distant, came in on a three -tube regenerative outfit, although a five -tube radio frequency set wouldn't percolate at all. Maybe it was freak reception, but the experiment is interesting because no means has yet been devised for two -way communication of a continuous order in the interest of saving lives and keeping in touch with entombed miners when a disaster takes place. The main problem, of course, is to overcome the rapid deterioration due to damp- ness, which breaks down insulation. * * * The Broadcasting Stations of the World EVERYBODY knows that the United States leads in the number of stations transmitting news and entertainment, in fact that we have more stations than all the other forty -one countries added together, and there are those who think that this is not an unmixed blessing. But it is surprising to lea,.. that Canada holds second place with eighty -three stations ; then Russia, with forty -three ; and Cuba fourth with Mexi- thirty -eight stations. Great Britain and Pacific & Atlantic co are tied for fifth place with twenty each. share WHERE THE "RED PROPAGANDA" France and Germany, eighteen apiece, COMES FROM sixth place. Then comes .Australia with sixteen, and Argentina with thirteen. From this The famous antenna tower of Shablovka at figure downward the numbers decrease rapidly, ?Moscow, which the Soviet Government of six small nations bringing up the rear, each, Russia has made the center of its broad- with a single broadcaster. casting activities.

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will hop across the water on a wavelength between 66 and 70 meters and be connected What the Austrian Fan Likes Best up at the other end with the phone of subscriber the THOSE straw vote things, as to listeners' pro- in the usual manner. Experiment- gram preferences, of ally, this has been which we have had a done often ; there doesn't plentiful sufficiency, have seem to be any reason now invaded Austria why such communica- where broadcasting is a tender infant tion cannot be maintained commercially. not yet We a full year in existence. The publication which will find out, anyhow, because they are alive conducted in Honolulu; the feature required the first three I recall that one of the earliest choices to indicate positive interest. of the automatic calling disc telephones And the worked there Viennese picked them in this order: concerts, itself out to familiar practicality. time signals and financial talks ! Education nosed out humor, operas beat out plays, daily Il'hat the Broadcasting of Adver- news was preferred to dance music -a lot of tisinJ things cropped up that seemed hard to recon- is Doing to One Station cile with America's radio sophistication, not- IN ably that the tailenders included sports the city of Durban in South A frica the sermons. and listeners won't stand for But there are some 50,000 receiving advertisements mixed sets in the country under up in the programs. They went on a license system with strike re- the individual paying a fee cently when advertising appeared along with of from 15,000 the entertainment to 30,000 crowns a year for the privilege aoci made known their wishes tuning -in, of very effectively by refusing so the Austrians must like what they to pay the license have been getting since fee which is required of set owners. Initially, last October. the audience was 500 persons ; now there are only 200 licensees, and it looks as if the station If hat If ill the Author will have to run at a heavy loss. In an effort and Com- to recoup, the directors of the station agreed poser Make Out of Radio? to leave off mentioning advertisers on the air ATLANTIC CITY saw the but to publish them in official programs, first annual conven- tribution dis- tion of the Radio Manufacturers Association of which immediately went into a recently slump. The scheme and a major topic of discussion was was then tried of selling the adjustment of differences programs only to those who gave which have arisen naine their full between station owners and the American and address on special blanks. This idea ciety of So- was successful only Composers, Authors and Publishers; in increasing the ire of a committee was the listeners, and at last reports apopinted with a view toward programs the sale of reconciliation of these differences. had fallen almost to zero. little known Although to the public, this clash of inter-

F. M. Detail( RADIO RECEPTION AT A MILE A MINUTE J. L. lllenars, the well -known French Portable amateur, recently experimented set on a French sleeping car, with this and using hooking it up to the train lighting the heating pipe as a ground. system France, He picked up stations Spain, Germany and Wales, in England, while traveling 60 miles an hour.

www.americanradiohistory.com BROADCASTS 297

Pacific & Atlantic SOUND WAVES THAT ARE HEARD BY THE HANDS of Unique experiments are being made by Dr. Robert H. Gault, professor psy- University, in conveying language to the deaf by means chology at Northwestern vibrations of telephone receivers that are held in the palms of the hands; the enable the subjects to "hear" words spoken into the transmitter. night -when the radio fan ests, which has been active for several years, perhaps better, the problems will be able to hear programs broadcast while presents one of the most absorbing he with which the industry he is asleep. And hear them as often as in broadcasting ethics what, in Germany, is has been confronted. The station owners are wants, repeated by suitable known as the talking wire. The idea is, that practically united in agreeing that attached to reward and compensation is due the men who you set the recording instrument, the radio receiver, and speech, music, and write the nation's songs ; but they can't see the which run all other sounds are permanently retained on point of accepting license contracts spools. and leaving the future wide thin steel wire running between two for one year only being registered through open for charging whatever fee the traffic will tonal differentiations is guilty of charg- the reactions of a small electromagnet. Eight- bear. Already, the Society are said to a certain price and insisting een years of laboratory research ing one station of this apparatus. that, for the same privileges, another station be behind the achievement royalty figure. The which is accredited to Dr. Kurt Stille, hut pay a great deal higher it looks seems to vary from $250 a year to ten from the incomplete advance reports figure merely a modification of the times that amount, and the most recent de- as if the device is as I know, no machine invented some years ago by Waldemar mands run even higher. So far an in the country is making Poulsen, a Danish scientist, who produced broadcasting station was simplicity money today; how many will continue in exist- electromagnetic recorder that burden, the itself and certainly worked well, but struck ence under an additional financial was which cannot even be anticipated, is a the snag of too high cost when an attempt size of I f .the It is a question that right- made to introduce it commercially. pretty question. market is wide fully belongs to the public, the listeners, whose price is right this time, the in the forth- enough. Yes, I want one, too! entertainment must predominate * coming attempt to place the interest of the broadcasters and the music publishers on a The Don Is Stirred by working basis. * * * Radio Waves Broadcast Programs on a WHILE Spanish playwrights and composers have been seeking relief from unauthorized Wire Spool broadcasting of their works, public interest in up by SOMEWHAT closer at hand is the day -or radio throughout Spain has been stirred

www.americanradiohistory.com 29 I'OI'L'L.1R R:1IIO

the addition of two stations in Balboa, dupli- compass employed while the Texas cating the situation in the vicinity of Madrid, is using where its radio apparatus. In like fashion, when another pair serves. Power three times the Shenandoah as great as the earlier transmits, it will enable the ones, incidentally, has Texas to locate the big balloon and been provided for the station just completed steer clear. at Seville. * What Programs Do the Farmers The Irish Still Squabbling Over Want? Their One Proposed Station THE farmer is to get what he wants in the way of programs. Questionnaires are to be THE Irish haven't gotten around placed in the hands of 850,000 tillers Over to it yet. of the soil a year ago the Dail disposed of legal dif- as part of the program for conducting a survey ficulties by and called for plans for a broadcasting the National harm Radio Council in co- station that would be the Free State's very operation with thirty farm magazines. own. The vious Pre- optimists who bought their sets a radio surveys have confined themselves year ago are to determination becoming a bit fretful, but the of the number and nature of Dail has not acted on the plan nor consid- the receiving sets in the rural sections; ered it in will this one any way. deal exclusively with preferences in * gram material. pro- Locating * Vessels by Radio One Public Service Engineer Compass Kills "flnticipated Static" WHETHER or not the radio compass is of COMPLAINTS by residents value to airships while aloft is of Orange, N. J. lem the latest prob- that "artificial static" was the Navy has undertaken to solve. The mutilating broad- dirigible Shenandoah, cast programs to the point of distorted engaged in a game of perings, resulted whis- hide and seek with the battleship in the declaration by the Texas, is chief engineer of the municipal the interesting form given to the test. The lighting plant ship being given that radio is no longer a novelty but loo miles start at sea upon sity, and forthwith a neces- a course unknown to the airmen, an order was given for in- the only stallation of choke coils means of spotting- the essel will be to overcome the an- the radio noyance caused by arcing brushes.

Pacific & Atlantic` RADIO PLAYS A PART IN THE "EVOLUTION For the first TRIAL" IN TENNESSEE time in the history of American criminal trial were broadcast jurisprudence, the proceedings of Dayton, from a courtroom when of a was prosecuted John T. Scopes, a teacher for teaching scientific theories lVGN of Chicago of evolution. Station broadcast the event.

www.americanradiohistory.com () The Best in Radio Equipment

Now- The Jewett Receiver reception. Again Jewett leads the way to new and better radio First the Superspeaker -Now the Jewett Receiver. more startlingly so in Different -Yes, fundamentally so in design -Even performance. -made noises entirely eliminated - scqueals, whistles and other self - Distortion, Top efficiency insured by a new and exclusive- method of audio amplification. at all points on the dial from i go to óoo meters. its natural tones. Music as it is actually played -the human voice in richest, handsomest And with it all -the Jewett Receiver is beautiful -the 'recëiver you have ever seen. hopes for radio reception The Receiver that meets and exceeds your fondest & PHONOGRAPHorCIOMP JEWETT RADIO PT, MICHIGANNY 5668 TELEGRAPH ROAD e Michigan Factories; Allegan, Michigan e Pontiac, Export Sales Office: In.Canada 116 Broad Street, New York City Walkerville, Ontario . Jewett Radio-Phonographs, Ltd.,

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www.americanradiohistory.com The Best in Radio Equipment

No. 486 Eveready Layerbilt "B" Battery. 45 volts. Length, 8 3/16 inches. Width, 4 7/16 inches. Height, 7 3/16 inches. Weight, 1414 pounds. Price, $5.50. The greatest improvement ABSOLUTELY new in construc- of zinc plate and the quantity tion- perfected through years of active chemicals to which of research, the new Eveready the plate is exposed. Layerhilt "B" Battery is as superior After the most rigid labora- to the old type as a tory tube set is to a crystal, tests, more than 30,000 of these new Eveready Layer - Heretofore, all dry "B" bilt "B" Batteries Batteries were manu- have been made up factured and tested by use of cylindrical cells -no one under actual home receiving knew how to make them any conditions. These tests proved other way. The new Ever- that this new battery is far eady Layerbilt is made of flat superior to the layers famous Ever - of current -producing eady Heavy -duty Battery No. elements compressed one 770, which up against to now we have another, so that every ranked as the longest lived cubic inch inside the battery "B" Battery obtainable. case is completely filled with electricity- producing On 4 -tube sets, 16 mil drain, material. it lasts 35 Layer- building heightens % longer. effi- On 5 -tube ciency by increasing sets, 20 mil drain, the area it lasts 38 % longer.

AB apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Ra'!io Equipment 11

It's all battery. With every cubic in, h packed to capacity, it contains about 30 per cent more electricity- producing material. All chance of loose or broken connections avoided by contact of full area of carbon plate against zinc plate. The scientifically correct construction. ever made in "B" Batteries On 6 -tube sets, 24 mil drain, lieve, by far the most econom- it lasts 41 % longer. ical source of "B" current On 8 -tube sets, 30 mil drain, obtainable. it lasts 52 % longer. Manufactured and guaranteed by The new Layerbilt principle NATIONAL CARBON Co., Inc. is such an enormous stride for- New York San Francisco Canadian National Carbon Co., Limited ward in radio battery economy Toronto, Ontario that we will bring out new EVEREADY HOUR EVERY TUESDAY at 8 P. M. sizes and numbers in this (Eastern Standard 7'ime) Beginning September 29th, 9 P. M. Layerbilt form as fast as new (Eastern Standard Time) For real radio enjoyment, tune in the machinery is installed. For eady Group." Broadcast through stai WEAF New York only the extra - WIAR Providence WSAI Cincinnati the present, WEEI Boston WWJ Detroit size will be W FI Philadelphia wcco ¡( Minneapoli large 45 -volt WGR Buffalo l St. Paul available. WCAE Pittsburgh WOG Davenport Buy this new Eveready Lay- erbilt No. 486 for heavy drain service. It far exceeds the performance for which Eveready Radio Batteries always have Radio Batteries been famous and is, we be- -they last longer

POPULAR RADIO LABORATORY All apparatus advertised in this magazine has been tested and approved by

www.americanradiohistory.com 12 The Best in Radio Equipment THE BIG LITTLE

The biggest of all the little things -THE DAVEN GRID LEAK

THE discriminating owner of a radio set demands three things: (1) Volume on the weakest signal, (2) Tone quality that makes criticism The Daven Super Amplifier with all impossible labor of assembly eliminated $15.00 and excuses or qualifica- tions unnecessary, (3) Both volume and freedom from distortion. The last is today's problem. We can get volume. We can get quality. There is only one way to get both. Eliminate the distortion from which no circuit employing trans- Tho Daven 3 -Tube Amplifier Kit, com- former coupled audio amplification plete except for sockets and tubes $9.00 is free. If a transformer will not amplify over -tones and under -tones alike at all frequencies, do away with the transformer. We must get i The Resistor Manual rid of rushing, blowing, A practical handbook frying noises. on Resistance Coupled Amplification. Atvour The Daven dealer's 25c. By mail Radio Corporation have made postpaid 33e. this possible in their development of Resis- tance Coupled Amplifiers. If you will couple GWEN up Daven precision -built resistances and USE THIS FREE COUPON mountings DAVEN RADIO CORPORATION under the direction of Daven en- 150.160 Summit Street. Newark, New Jersey gineers, you will know radio at its Please send me the following on Resistance best. Coupled Amplification : - Check one. DAVEN PRODUCTS ARE SOLD Resistor Manual. 25c is enclosed. 1 Complete catalogue (free ) "....67A; J[/te Name Address f*AV N A 10 For dealers: Send your letterhead or card. or this coupon and we tvil[ have our nearest distributor communicate with you. NEWARK Reg. U. S.

All apparatus advertised in this Mugu cr) ;(' has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com Tl r /;e.tit in Kadin J /ui fame?? t THINGS OF RADIO

The DAVEN LEAKANDENSER -the combination grid leak and grid condenser Daven bulletins are the A. B. C. of resistance coupled amplification. Write for bulletin on the Daven "big little thing" in which you are most interested, or get the Resistor Manual, a practical

handbook for radio designers and builders. Clip Mounting No.50 -for single Resistor, Grid Leakor Dealers who do not handle the Manual are in- Ballast $.35 each vited to send for free sample. E are able to announce two new Daven products at this time. The Daven Leakan- denser is a combination of a grid leak of Daven of value, and a grid con- permanent constancy Resisto- Coupler No. 42- of The first and most popular denser of fixed capacity, correct for all makes resistance coupling unit. detector tubes. It is mounted in a new snap fast- With condenser - - $1.50 ener that does not permit it to shake out. Pre- cision- built, simple, effective, sturdy and very handsome. Price $1.00 each. The new Daven High MU Tube increases the to Daven Ballast Resistors for amplification of the Daven Super Amplifier use with amplifying tubes in place of rheostats. Four equal or exceed that obtainable with transformers. types, without mounting. $.;5 each 6 volt, ? ' ampere -$4.00 each. The Daven Power Tube Type MU -6 for the last, or output stage -$5.00 each. ONLY BY GOOD DEALERS

The new Daven Tube MU IO 20 recommended for use with the Daven Super Am- t pecial1sfs plifiers. Pat. Off. NEW JERSEY

been tested and approved by POPULAR RADIO LABORATORY AU apparatus advertised in this magazine Izas

www.americanradiohistory.com 14 The Best in Radio Equipment

Solved! The space problem of the straight -line frequency condenser. Half a Heart is The new the secret. AMSCO Allocating Condenser is ingeniously designed to save room in the cabinet -yet Half a Heart is spreads the stations evenly around the dial, the shape of the rotor plates. according to frequency. Greatly improves the selectivityof the set -and simplifies tuning. Half a Heart is Three sizes -Single or Siamese. the new symbol for efficientS.L. Ask your dealer -or write Dept. D F. variable condensers. AMSCO PRODUCTS, INC. Broome and Lafayette Streets, New York City MAKERS OF MELCO SUPREME RADIO RECEIVERS EMMMMIIIIIMIMIMIMMIMMIMIMIEmmmmmo

All apparatus advertised in this magazine lias been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 15

tressFamenVIIMMEI

PR.ODUCT ARPE SPECIFIED ;Y STROMEERG-CARLSON FREED- EISEN/ANN PRIESS RADIO sa

Set builders who strive for electrical and mechanical perfection inevitably come to AMSCO. Look behind the panel of the finest sets, and you will find the AMSCO trademark, the sign of engineered radio parts. Standardize NEW -The Amsco on AMSCO Condensers, Vernier Dials, Rheo- Vernier Dial -at Sockets and Binding a popular Price . stats, Potentiometers, The right ratio for Posts -each the best that can be made, and precision tuning. made to match each other. Ask your dealer -or write Dept. D AMSCO PRODUCTS, INC. Broome and Lafayette Streets, New York City MAKERS OF MELCO SUPREME RADIO RECEIVERS

Al! apparattts advertised in this magazine Ita been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 16 The Best in Radio Equipment

CISCHOW NEW YORK PATENT PENWICr

mec cal G MA rz`ncl`al ar11. 1 rf_ cCl e; «I eLr rr: ét;er Aekre "Norr. used r,rz D/}'5 8ackl'a.sh-backlash- Peaïiy rs responsible e chalkle nge ihe maker o,f _11yy Met. 47/ Liiarrs tv Grove fus has No Backlash, urtevrz Ate onitj dia L Lvhích enables .you, alte ci pick. up stcLtiong u..uatty missed, e . ormance RATIO 10 Uto i Jive ortLti día L wtLlt Ellis ratio Veda*. r C, less mad- GEE -1.1 .' h I _ wilt actually iYrtProve. the Per-I-ormance of yoLLt" / \

5 West 5IstSt

--- Xle alread.y. great demand for GEE -HAW DIALS' makes it advisable to WPM, 4ONCE f r jr). or atton.

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment t 7

UbTR71-LOWL 055 CONDENSER _ } ; _ _ - _ .. = ---1I = ác_ - =_ - w

---)---7fmllSill ,w

^ Quick,positive tuning Cutlase Stator Plate exclusive. any station, Iv an Ultra SPEED- ability to turn directly to Lowtos, feature to tune -in instantly and get your station without interference from broadcasting on similar wave - feature of the Ultra - A guarantee lengths-is the outstanding of satisfaction Lowloss Condenser. and Lacault ofknown wavelength located on the dial, all design With one station Cutlass stator i,t hers can be found instantly. Special design of stations evenly over the dial -each degree on a plates distributes difference 100 degree dial represents approximately 3% meters in wavelengths. common in other condensers are reduced in In addition, losses small strip the Ultra -Lowloss to a minimum by use of only one by the small amount of high resistance metal in of insulation, mounting of the field and frame, and by a special nlonoblock plates. Designed by R. E. Lacault, E. E., fixed and movable Ultra -Vernier originator of the famous Ultradyne receiver and tuning controls. At your dealer's; otherwise send purchase ZILTR11 WRf.IER be postpaid. TUNING CONTROL price and you will supplied

Simplifies radio tuning. Pencil record a station on the dial -thereafter, simply turn the finder to your pencil mark and you get that station instantly. Easy- tUJTR7I-LOWLOßB quick to mount. Eliminates fumbling, guessing. A single vernier control, gear ratio 20 to 1. Furnished clockwise or DENSER anti -clockwise in gold or silver finish. CON SILVER, $2.50 GOLD, $3.50 25t1i Street, New York City PHENIX RADIO CORPORATION 116 E. i and approved by POPULAR RADIO LABORATOR Y All apparatus advertised in this magazine has been tested

www.americanradiohistory.com The Best in Radio Equipment Wonderful Volume with Clearness AMPL- TONE

Announcing the NEW $80 Five Tube $300 Phonograph makers have spent years perfecting the acoustic properties of their phonographs. Use an AMPL -TONE Unit and make a real Loud Speaker in an instant or use it in your horn and get better results. After all, speakers are as good as their unit We make a real unit at a real price. Money g'adly re- turned if you are not entirely satisfied. SUPER- SELECTOR The UNION FABRIC CO. DERBY, CONN. G l: A t I NE tri umph! Combined resistance and transformer Makers of the Excellent French AMPL -TONE Headset coupl,ng; hence Please send me an AMPL -TONE marvelous el:I ri ty of tone. Control of se- Unit for which I ltct:vity enclose $3.00 -a distinct departure, an ELKAY Name. invention -of extreme importance to those clos: to I3. C. centers. Address State Complete control of oscillation. R. F. device t hat permits the saine smooth operation on the low wave lengths as on the high. Except _on- l I v handsome cabinet work. Also built for 4 tubes at $70.00. Write for folder. Amateur set builders, write for profit - able kit offer on ELKAY sets. TO T111' TRADE -Write for exclusive territory today, while still available.

"zv 1,,. V.R,oT sEORMER

RE55!TnhCE H4 NTnBi S1.411N

GiLANTENT CONTROL JaCn

00V017 CiRCU1T REGISTERED _ÿ -` INFRINGEMENTS RESIST U.$.PATENTS OFFICE v5GOROUSLY PROSECUTED c BCes GUARANTEED RES L N. R, E4 FOR A Oi0 TUBES LIFE! vU0I0 BE Tu OE ELTTAT DETECTOR Folds to any position -Wires wOO TRqM1S1 CANER always taut The newest addition to the line of quality Radio Accessories. Made of the highest grade materials throughout in a new and masterly The Langbein- Kaufman tions: design. Specifica- Radio Company Length, 24 inches, Normal Ht., 30 inches, Wavelength range 120 to 600 meters. 511 Chapel St., Dept. P New Haven, Conn. The "AALCO" Is different both in appearance and find that this operation. You will An L K Product new loop adds to the performance of your set. If your Dealer cannot supply you send fflimon===ists order, and we will ship direct. money TUNERS JO BB ERS : Write for our proposition ]E]LKAY,_ AALCO RADIO LABS. 6336 Cottage Grove Avenue CHICAGO

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio I':qui /orient

charge it -. while gou sleep Last thing at night- concert over -time to lock up. Ra- dio battery low? Just clip on the Tungar, and plug it in. Or if you connect up the Tungar permanent] y,just throw a switch. Charge the battery while you sleep. The Tungar is simple -make3 no disturbing noise. And the low cost of Tungar recharging cuts battery upkeep to next to nothing. It means top notch performance - clear, full -volumed reception -all the time!

The Tungar is a G -E product developed in the great Research Laboratories of General Electric. The new Tungar charges radio "A" and "B" batteries, and auto batteries. I BATT E RY C HA RCà ERI Two ampere size (East of Neta0/ the Rockies) . . . $18.00 Tungar -a registered trademark -is found only 60 cycles -110 volts on the genuine. Look for it on the name plate. Merchandise Division General Electric Corrrpanjl, Bridgeport, Conn. GENE AL ELECT

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 20 The Best in Radio Equipment

v\r

LORENZE I IIIJirMODIFIEDEFFICIENT RADIO COILS I I Require I A Specialized Organization for Economical Production We make Coils only. Our entire resources are devoted to Radio Coils. Cive Me a For that reason we are able to render Radio Set Manufacturers an un- equaled coil service. Regardless of your own facilities you FIBROC- will undoubtedly find this service BAKELITE profitable to you. Ask us for estimates and samples. PANEL-Every Time !

Believe lie, when I sink good hard earned east, in efficient parts I ale not di going to skimp when it comes to a panel. _II 107W Canton St. Hoston .Mass. (;ive lee the best every time -a panel , that I eau drill and cut without chipping or feathering -a panel that engraves cleanly and with a finish that will make my set show up like a million -that's a PROFESSIONAL F113ROC- 13A KELITE panel and I know for I've tried 'ein all. and for winding SET BUILDERS! coils, l'ihroe tubes rate just as high as the panels-you just can't heat them. and dealers who build sets Fibroc- Bakelite Features WE will shortly begin a series of newspaper ad- High dielectric strength assuring louez4 vertisements, featuring dielectric losses. G'r(ai'cosily strength. the work ll'ill not warp, crack, chip, feather or of individuals and dealers who cold flow. Easily worked. Readily engraved. In black, high polish or mat builds sets using Cardwell Con- finish; mahogany,' circassian walnut densers. or natural finish. Standard sizes each packed in individual envelope. If you build to specification or Ç from original design, it will be All Good Radio Dealers Have or Can Get to your interest to communicate FIB ROC-BAKELITE PANELS with us immediately. Ask for details of plan. Be sure Fibroc Insulation Co to give name of your jobber. 257 Lincoln Ave. ALLEN D. CARDWELL Valparaiso, Indiana MANUFACTURING CORP. 81 Prospect Street, Brooklyn, N. Y.

All apparatus advertised in this magazine Izas been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment ' RODYNE 1roido/ 'Receiver

A New and Is etter Receiver The TORODYNE is the newest AINSWORTH Receiver. It is one of the few really new developments of the season. Be sure to see it before placing your order. What is the TORODYNE? Appearance I-eauty that makes is a five -tube, tuned The TORODY \L has a refined The TORODYNE it very attractive. The panel is engraved in silve radio frequency receiver employing Tor- by a patented process. Pointers on Bakelit, oidal (doughnut -type) transformers. The knobs. operate over a scale engraved on the panel entire arrangement is one of beauty, sim- The cabinet is .Adam brown mahogany. plicity and refinement. Simplicity Very easy to tune and logable. A silver engraved Why is it Better? sub panel on the inside leaves only the three con- Largely through the use of Toroidal transformers. densers and five tube sockets visible. All termi- connec- which give it : nals arc correctly marked to insure correct in the cabinet Selectivity due to the fact that these tions. Ample space is provided 1. Greater for necessary "B and "C. batteries. coils do not pick up outside interference. Only the picked the signal to which the set is tuned can be The TORODYNE will give greater satisfaction up. than any other set in its class. Ask your dealer 2. More Volume by eliminating coupling. Greater for a demonstration. You will be sold on it amplification is thus secured without oscillations. immediately. in 3. Distance. The greater amplification brings which naturally distant stations with more volume, PRICE ( without accessories) $100.00 increases the range. the 4. Superior Tone Quality is secured through The Ainsworth Radio Company and foreign noises by elimination of distortion Street Cincinnati, Ohio preventing stray feed -backs. 308 Main and approved by POPULAR RADIO LABORATORY All apparatus advertised in this magazine has teen tested

www.americanradiohistory.com 22 The Best in Radio Equipment

here's This IS the Best sharp tuning Variable Resistance \\ with a Universal for you! III °NO Range t C THE NEW PACENT LA R,O5TA7 MICRO VERN can be used in ANY circuit The Clarostat connected across the secondary of the former eliminates last trans. any possibility of distortion thru uneven am- iifi cation of sound frequencies, as adjusting the amplifier Clarostat bringe the circuit into a state where distortion caused by slit transformers is eliminated entirely. WHAT THEY THINK ABOUT CLAROSTAT I temporarily shunted the Clarostat across the secondary of that rusty old transformer -and let me tell you, distorsion I've tried every o.her remover on that set, but the Clarostat beats them all. Signed: HARRY A. HENHAW 2o6 West r4th St.. New York City Price $2.25 AMERICAN MECHANICAL LABORATORIES, INC. 285 -287 N. 6th St. Dept. P.R. Brooklyn, N. Y.

"How to Build Your The Greatest of Vernier Dials Radio Receiver" II IMPROVES tuning with any condenser- As a special especially the Pacent Straight -Line Fre- inducement for you to send in your quency. subscription Note these special Microvern during the month of August you may features: have a copy of "How to Build Your Radio Receiver," Most practical ratio -5 to I. the most complete Proper size -4%" diameter. and authoritative collection of ma- Absolutely noiseless in operation. terial on Receiver Construction Positively no back -lash. yet published in book form, which gives Exclusive " Radiofile" feature simplifies logging. all working details, lists of parts Direct reading in wavelength and frequency. required, complete Provides an electrostatic shield. hook -ups and circuit diagrams. Write today for prices and full details. (See page 84.) PACENT ELECTRIC COMPANY, Inc. and 91 Seventh Avenue, New York City Washington Birmingham Detroit Chicago Jacksonville San Francisr Popular Radio Buffalo Boston St. Louis Minneapolis Philadelphia Pittsburgh with which is combined Canadian Licensees: While . Radio. Ltd Hamilton (lnl. The Wireless Age for 7 Months BOTH for only $2.00 Pacent POPULAR RADIO RADIO Department 97 ESSENTIALS 627 West 43d Street New York City

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment ,;

$2 5 SAAL SIPIEÀ1KIEIR. YOU need no longer. object unbroken enlargement of to loud speakers because of sound. The neck is of alu- theirharshness. Hear the Saal minum, a porous and non- Soft Speaker at your dealer's. vibrant metal with no tinny The Saal has no blare, no ring. The bell is of genuine blast, no metallic ring. It is Bakelite, the most perfect and not a trumpet. It is a faithful resonant of all radio materials. SAAL Jr. reproducer of radio programs. There is no wood, no tin, no The same in every respect as composition. It has nothing the Saal Soft Speaker except it is It combines volume with a smaller. Measures 18`/= inches the to warp, crack or deteriorate. instead of 21% inches in height. velvet tone. It removes objection to loud speakers. It will last indefinitely. $20 The Saal is properly con- The basis of Saal volume structed for the accurate repro- with tone quality is the reproduction of sound. It is not ducing unit described to the straight- necked like a trumpet. left. In appearance the Saal, The goose -neck is curved like with its large black bell, black a saxophone, the most melo- stippled throat and graceful dious of all instruments. From lines, is the aristocrat of horns. The Saal Soft Speaker Unit is of the floating armature type the reproducing unit to the Also furnished with a brown exclusive with the most expensive reproducers. It automatic- edge of the bell is one un- bell and gold or silver stippled ally maintains its tone with any even, throat at $5 extra. volume, and cannot be harmed broken taper -one by the loudest receiver. It will not break down with the longest or most constant use. All metal construction -no rubber gaskets. Used as standard equipment by many leading manu- IE facturers of fine radio receivers SANAILcf(g IP EA K in built -in reproducers. VOLUME W I T H T O N E QUALITY Manufactured and guaranteed by H. G. SAAL COMPANY, 1800 Montrose Ave., Chicago, Ill.

All apparatus advertised in this magazine has been tested and approved by POiCLAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment Announcing CELCO D, e.bl3 "D" Intermediate Frequency Transformers The 11-art of the Super- Heterodyne is its Intermediate Ere yuency Transformers, therefore, the set is no better than the transformers therein. 'l'o be properly suited to this application they should be capable of Maximum Amplification and Ex- treme Selectivity without sacrificing Definition or Quality of iteproductiun. C'ELC't t transformers are of the Air Core type, Matched and Peaked Uniformly and Exactly, 1producing a uniform com- posite curve, one of the essentials of Quality Reception. They will give Superior results in the Pressley or Super -Auto- dyne, the Ultradyne, the Tropadyne or the straight Super - Heterodyne circuits. Volume Super - Selectivity Quality Reception CELCO Indicating Battery Switch There need be no more annoyance over tubes burning all night with a (' ('leo Battery Switch J your set. The jeweled pilot light emits a soft golden glow that makes It as hard to forget turn off as it is easy to turn on. Simple to install -only two holes to be drilled in panel, ,ue for pilot light and one for switch. Agent Representatives wanted CENTRAL ENGINEERING LABORATORIES Some Good Territory Still Open CHICAGO, ILL.

a TOWN CRIER Radios/losilleaufl Speaker Since binding posts cost so little and mean so much, why not You will be delighted with the gorgeous treat your set to the best? colors ... the handsome, stippled finish, and the novel design of the Town Crier - Practically any dealer can show the Speaker with the voice that thrills. you why EBY Quality Posts Ask your dealer to show you a Town Crier are preferred by most Speaker. Write today for beautifully expert illustrated circular describing the Golden set -builders. Polychrome and Green Polychrome in odds. List Price $17.50 West of the Rockies $18.50 GALE RADIO LABS. 2512 Irving Park Blvd. CHICAGO All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com b The Best in Radio Equipment

9/e Qnswer to the Question - "HOW GOOD CAN A RADIO TUBE REALLY BE MADE 9"

SYLVANIA. tubes are not made simply to sell but, first of all, to perform. If you have had experience with tubes of questionable quality, this simple statement of a fact will go far in accounting to you for the big difference in quality of tone, sensitivity and volume that you will notice immediately you install Sylvanias in your receiving set.

The fundamental reason for the extra measure of performance that Sylvania tubes deliver is easily understood when you consider the attitude of the makers to their product. They know beyond any question of doubt that the future of radio depends on how good its equipment is made -not how cheap.

Sylvania tubes are made by a close knit organization that has been identified with the manufa&ure of superior quality eleErical produés for many year,. You are invited to investigate its responsibility through any of the commercial agencies.

To demonstrate to yourself how good a radio tube really can be made, compare Sylvania performance with that of any other tube you may hold in high esteem.

We Invite Dealers -who recognize the relationship of quality to profits to ask us about the Sylvania franchise and the better business building plan. It will he worth your while to inve,- tigate regardless of present connections.

Types: S 01 -A, S 99 Large Base, S 99 Small Bose

SYLVANIA PRODUCTS CO,

Emporium, IP a o

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 26 The Best in Radio Equipment

Aso Ora NEW A single control tuning element for two - control sets! With a vernier that allows a variation between the two circuits of fifteen points on a 100 point dial! Can be easily applied to SUPERHETRODYNES BROWNING-DRAKE ROBERTS HARKNESS or any set employing two tuning controls. RIMM Concert reproduces Details on request all the tones, from high of HANSCOM RADIO DEVICES violin to low of organ, with perfect Woonsocket Rhode Island fidelity. Easily accessible adjustment permits control of tone and volume. Volconite horn eliminates scratchy overtones and noises.

TRIIVIM Superior Reproducers HEADSETS Professional - - $5.50 Dependable - - - 4.40 PHONODAPTERS Giant Unit - - $10.00 Little Wonder - 4.50 SPEAKERS Home Speaker - $10.00 Entertainer - - 17.50 Cabinette - - - 17.50 No. 248 Concert - - - 25.00 E -5841 Chello - - - 30.00 Underwriters ADD. "Little Joe" Lightning Arrester Especially designed for Radio Work. Made of Porcelain, small, neat rugged RAIrITWIT%MANUFACTSRING and serviceable. Can be suspended CAMPAN on antenna or fastened to wall. 24 So. Clinton St. Ask Your Dealer CHICAGO J. S.A. M'f'd by CIRCLE F MFG. CO. Trenton, New Jersey UM

All apparatus advertised in this .magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 27

Send for your free copy Ward's New Radio Catalogue The best radio experts made this cata- a radio log for recording stations. It is a logue. It is one of the very best and complete radio manual - sent -entirely free! most complete books on Radio ever Ward's is Headquarters published. for Radio Its 52 fully illustrated pages are sim- And best of all, the catalogue offers you everything new in Radio at a big saving ply invaluable to everyone interested in in price. radio. And one copy is to be yours Free At Ward's, everything for Radio is sold - merely for the asking! without the usual "Radio Profits." Thou- It shows guaranteed Radio sets, one tube sands of pleased customers write us of sets that give remarkable results, and sets their constant delight with Ward's Radio of every variety up to Ward's new five - products. tube one -dial control. Think of tuning in Our 53 year old Policy one station after another by turning a For 53 years we have sold only quality mer- single dial! chandise under a Golden Rule Policy. You It shows guaranteed, tested parts, bat- can rely absolutely upon the quality of teries, cabinets, contains a list of stations, everything shown in this Radio Catalogue. Be sure and ask for Radio Catalogue No 38 -R Montgomery Ward &Co The Oldest Mail Order House is Today the Most Progressive Baltimore Chicago Kansas City St. Paul Portland, Ore. Oakland, Calif. Ft. Worth

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 28 The Best in Radio Equipment

NAVY MODEL C -10 Super - Heterodyne For any Circuit The Highest Class Receiver in the World Prompt shipment can he Wave length range 50 -600 meters with removable Coils. made on tested, standard Panel Dimensions 28 3/16 in. x 8 in. x 1/4 in. apparatus of the follow- Only two major tuning adjustments. ing manufacture : Total amplification almost 2,000,000 times. E. 1. S., Inc. A high powered 10 -tube Broadcast Receiver capable of receiving General Radio 3,000 Willard over miles under favorable conditions, and having a degree Benjamin Electric of selectivity far in advance of others. Allen Cardwell We believe the Navy Model C -10 represents final superiority Dubilier Formica over any receiver now Western Magnavox being manufactured or even contemplated for broadcast reception. Jewell Amer Tran Attractive illustrated literature gladly mailed upon Western Electric request. Write direct to Radio Corporation Music Master Acme NORDEN- HAUCK, INC. Cutler Hammer Frost Engineers Federal Kellogg 1617 Chestnut Street, Philadelphia, Penna. Chart your Radio "Take No Chances -Use Como" EXPLOITS ! COMO DUPLEX The World's Standard Push Pull Transformer

T this marvelous new help for radio explorers -a heauti- C[J ful Air Map, printed in three colors, every station clearly PRICE $12.50 marked per pair and 'rime zones outlined! Size, 22{ x 34 inches For maximum volume I here s no limit to the amusing ways you can without distortion use What Prominent Writers on Radio COLLIER'S NEW RADIO MAP Subjects say About Como. of the U. S. and CANADA Lewis B. Hagerman, Technical Editor, Chicago Post: "Actual Tests show this \\ eh its help you can find instantly how far away any station superior transformer to be far If you use a directional aerial, you to any others of similar makes." can point the loop ex- R. J. Robbins, New York Sun: "After actly toward the station you want- Also outlines the radio di ',- of consideration tricts, and gives an alphabetical several well -known mak es of push pull transformers list of all stations and their which are available 'COMO operators. most satisfactory." DUPLEX' was selected as Thousands already sold_ Get yours today! At your news stand C. White, Radio or radio dealer's, World: "'COMO DUPLEX' is infi- only 25 cents -or just maul us a quarter. nitely superior - most other push pull transformers seem to be ordinary transformers with a center tap '. F. Collier & Son Company brought out as a makeshift." 244 Park Avcntle, New York ('ity E. P. Gordon, Open Road: fication "A system of audio- ampli- Enclosed Please find twenty -five cents for your new Radio Map which is becoming increa singly popular. Its use of l'. S. and Canada. will give surprising results in b oth qualityand volume, and is thoroughly recommended by Name this department." .. - --- NEED WE SAY MORE? Address COMO APPARATUS COMPANY 3424-RMC-M i Manchester, New Hampshire L------1 For Sale at Leading Dealers All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 19 U N I P O W E R -the latest sensation in Radio! rTO longer is it necessary for you to put up d with the cost and inconvenience of orerat ing your set on dry "A" batteries -or the bo;:hcr of charging a storage battery every week or so! No longer need your "A" batteries fail when you want them most. And that today is the most frequent cause of poor radio recoption. You can now equip your set with Uniresw er and have the thrill of continuous, unfailing A" power always of the highest quality and refinement, always at full voltage. What Unipower Is Unipower is a single compact "A" power unit that fits inside most radio cabinets. It takes the place of separate storage battery and charging units. Unipower comes to you completely wired and assembled -all you have to do is connect two wires to your set and plug in on your house current. A unique feature of Unipower is the master - control switch that governs the operation of your entire set. When the switch is ON, Unipower feeds your set rich, quiet power, with neither hum nor noise. When the switch is OFF, Uni- power automatically replenishes itself from your house current. Until you use Unipower, you will never know how easily, perfectly and economically your set can be operated. Never again will you go back to dry cells -or bother with a storage battery and charger. The nearest radio dealer can supply you with Unipower is quickly and easily Unipower. . installed. Fits comf ri ! iv inside most set cabinets. t fi};- i. .;;1. GOULD STORAGE BATTERY CO., Inc. w 250 Park Avenue New York

The first cost is the last ! Unipower's initial cost is moderate -and the first cost is the last. Unipower has no tubes, bulbs, lamps or working parts that require frequent or expensive replacement. Unipower is equipped with an exclusive Balkite charger of special design. Unipower operates from alternating current, tro-12,5 V -6o cycle. It is supplied in two types. The 4 Volt type is for sets using U V 199 tubes or equivalent and retails for $35oo. The 6 Volt type is for sets using U V 20VA tubes or equivalent and retails for $40.00. West of the Rockies, prices are slightly higher. nipower Ofwhen its on On when its off

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 30 The Best in Radio Equipment Premier "Blue Ribbon" Battery Cable insures the right hook -up

Get a PREMIER 5 -Wire Battery Cable. Keeps wires neatly concealed, untangled and out of the way. Five different colored wires insure proper battery and set connections. With a flip of your finger you can unhook "A" battery and hook on charger.

No. 23 pictured) in addition In attractive carton, $1.00 to ita une as a fi" battery instrument is being used extensively for "A" battery testing in place of hydrom- At your eters. dealer's -or write CRESCENT BRAID CO., Inc. Test accurately Providence, R. I. "' Makers of Premier "Blue Ribbon" Extension Cords, Premier, Jr. Extension Cords and Phone and safely Cords for headsets and loud speakers. There's no substitute for high resistance in a voltmeter for testing radio batteries, tube voltage, or experimental work. 60 Ohms per volt is the Nagel standard, assuring accurate readings and safety against battery drainage Knowledge of under touch contact Radio is not required or continuous to obtain service. See your dealer or write The results perfect W. G. Nagel Electric Co., 513 Hamil- with the ton Street, Toledo, Ohio. LIBERTY Seale If you own u "Super -Het" you can test your "A" and "B" batteries with one instrument -the Nagel No 62 Voltammeter.

l;/' il anufac /ur,'rs O` DRY CELL TESTERS -AMMETERS Manufactured by HIGH-RESISTANCE VOLTMETERS oria VOLTAMMETERS BAKELITE LIBERTY HOT MOULDED INSULATIONS TRANSFORMER CO., INC. 123 North Sangamon St., CHICAGO, ILL.

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment

GRAND CENTRAL PALACE urbiI : ------,. .4rar -A,, 2,.I _.J e I(t u' - I.tílMli1/

'1,f 4th !Annual NATIONAL RADIO EXPOSITION Grand Central Palace, New York September 12th o 19th incl.

- --the fourth successive national exposition representing all the leading manufacturers of the radio industry; --the only great radio exposition of 1923 to be held in the metropolitan center of New York; -the greatest spectacle of the year in the scientific, industrial and business progress of radio!

Business Office HAROLD BOLSTER. Directo, AMERICAN RADIO EXPOSITION WCo, J. C. JOHNSON General Manan 522 Fifth Avenue. New York

v 1 ',`I 1fJ, N` lory 911arN 11)`

I y I n 6 ,I a . A

r ß y er.Better adio 4th ANNUAL NATIONAL RADIO EXPOSITION Grand Central Palace Jptember 12th to 1914

RADIO LABORATORY All apparatus advertised in titis magazine has been tested and approved by POPULAR

www.americanradiohistory.com 1he liest in i!udto Lgutpment Back of Each Instrument The assurance of reliable operation, which you have always felt when buy - ing an ALL -AMERICAN Transformer, is now increased by a knowledge that it is the product of one of the largest and most completely equipped factories in America devoted exclusively to radio products.

The RADIO KEY BOOK -new edition -is a practical enjoy modern handbook for all who wish to radio at its best. Send 10 cents -coin or stamps -for the KEY BOOK. ALL -AMERICAN RADIO CORP., E. N. RAULAND, Pres., 4211 Belmont Ave., Chicago ALIAMER C Largest Selling Transformers in theAN World

mm')uununnuumnu' Insure Your Tubes WI : ::¡?':4`ri?1t!¡ BY CONSISTENT USE OF ,tL;'(,`:ri :tki,' :ili i. RT04 $1150 TUBE ERÇ Brings Back L -ASHER Bad Tubes

Developed by an organization of long experience in the n:unufacture of electrical instruments. CORRECT ENGINEERING UTMOST SIMPLICITY OF OPERATION One model for D.C. or A.C. -Any number of cycles Filament does not cool for an instant during flashing. -Re- sults will exceed your expectations. Cannot be burned out. -Fully guaranteed. -For tubes- with thoriatedfila- ments: types 201 -A and 199 only. Òriginakors nndW,rhhs'LirucsrAfuiú='jc Send for pamphlet " Sore A Iµclunrr. Life" of Sell Fh.,inu Sold,r : BURTON & ROGERS MFG. COMPANY I'ÒUR D8A7.112 CAN SUPPLY YlilJ i 755 Boylston Street, Boston, Mass.

All apparatus advertise! in this magazine lias been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment

(2Jou may escape the collection f,OZARKASERVICE but not the need o HE satisfaction you re- but -that isn't enough- compare We Have Openings for ceive from your radio the service behind each one. More Ozarka Factory depends not on what it does Any Ozarka factory representative will set up an Ozarka in your home Representatives night - once in a while -but will not even operate it him- Incorporated, is now enter after -he OZARKAing its 4th year. From a beginning after night and month self, but will depend for his sale on with one engineer. one stenographer, month. Whether you grin what you yourself do. If you, by one salesman -our present president, own operating, do not bring the Ozarka organization has grown to or cuss depends on the serv- your over 3100 people. There must be some ice behind your radio. in the distance, the volume awl good reason for this growth. tone, you expect a radio to give, Ozarka instruments have made good - Ozarka radio instruments then you do not buy the Ozarka. they have more than met competition. do buy it, you can rest as- Ozarka representatives have made are only sold by trained fac- If you good not only because Ozarka instru sured, no matter what happens, a ments were right, but because they tory representatives, men competent service man is at your have been willing to learn what Ozarka in No Ozarka rep- engineers were willing and capable to who not only specialize call at all times. teach them -Ozarka unusual sales- radio but sell and service resentative can sell Ozarka Instru- manship and Ozarka service. 3,100 of these ments without giving Ozarka serv- Radio offers a wonderful opportunity Ozarkas only. ice. You are entitled to such serv- to men who are willing to start at the men, trained directly under it! bottom and build. You need not know ice-demand salemanship, but will you learn what Ozarka engineers consti- we will gladly teach you? You may un- That is why our book, "Ozarka not know radio, but we can and will tute a service force, Instruments No. 200," describing teach you if you will do your part. elsewhere in radio should be of With such knowledge and willingness equalled all models of Ozarka to work, it doesn't seem possible that today. particular interest to you. This you cannot make good. Sign the cou- you buy a radio you'll com- book and the name of the Ozarka pon below, don't fail to give the name When you, will be of your county. Better still write a let- pare appearance, tone, volume and representative near ter, tell us about yourself and attach selectivity by having various in- sent immediately at your request. coupon. If interested in our salesman's struments set up in your own home Please give name of your county. plan ask for "Ozarka Plan No. 100." INca RPORHIED 117 Austin and La Salle Streets 117 Austin and La Salle Streets Chicago, Illinois Chicago. Illinois 1 Gentlemen: I am greatly interested in the FREE BOOK Gentlemen: Without obligation send hook "Ozarks In- "The Ozarka Plan" whereby I can sell your radio Instru- struments No. 200" and name of Ozarka representative. ments. Name Name YOU'LL KNOW Address City Address City THE MAN BY County State County State THIS BUTTON! LABORATORY All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO

www.americanradiohistory.com 34 The 1]est in Radio Equipment New and Improved

APPROVED _

ASS us Rs, Orr 50

Authorized Cockaday Coil! A PIONEER No more loose winding- special new feature holds coil windings fast. Built throughout of moulded hard rubber. not affected by atmospheric conditions. k\ound with No. IS 1). S. C. copper wire. The only coil specified by I.. M. Cockaday in his LEADER New Four Circuit Tuner with Resistance Coupled Amplification because it meets all his specifications. Described in October POpt'LAH RAnto as. Cockaday Precision ('oil. Hundreds have substituted this AmerTrans quality, coil for those of inferior make and are amazed continue at the unproved reception, selectivity from month to month as D X results. and general At your dealers, otherwise send purchase one of the best selling price and you will be supplied postpaid In Canada $7.75. Canadian Distributor, Perkins, Ltd. audio transformers. Montreal-Toronto- Winnipeg PRECISION COIL CO., Inc. There is ample volume, 209 -B Centre St., New York City and the "tone- keen" char. i acteristic of AmerTrans furnishes a pleasant, distinct reception value- - most appreciated by the critical listener. In fact, there is no more efficient

and permanent working Model SR 5 part in any set than a pair of AmerTrans. ,Radio at its best - With the Simplex SR 5 Receiver. you get pure Buy Amer Trans by the Pair! tone and full volume. A good distance getter. Extremely selective. Very simple to operate. from an I landsome hand - rubbed mahogany cabinet. Authorized AmerTran Dealer Dust-proof; wiring and coils concealed beneath sub -base. They are made in two types, one quality -AF6, ratio 5:1 and AF7, ratio 3V):1. Price SIMPLEX SR5 $57 either model, $7.00. The great popularity cf Simples products has AMERICAN TRANSFORMER caused our name to be widely copied. Be sre COMPANY you get the genuine products made by the original manufacturers of Simpler Radio products. 175 Emmet St., Newark, N. J. If your dealer cannot supply ;you, "Transformer builders for over 24 years" write direct. SIMPLEX RADIO COMPANY Main and Rector Sts. L_M-anayunk, Phila., Pa.

All apparatus advertised in this magazine has been tested and approved by PCPUI.AR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment GENERAL RADIO /Rheostots end Sockets mean higher tube efficiency

Type 301 Type 214 6, 10 and 30 Ohms 2, 7, 20 Price $125 and 50 Ohms Price $225 General Radio Rheostats Are Smooth Running and Uniform

THERE is only one way to operate tubes at their peak of efficiency -by the use of properly designed rheostats and sockets. In building your set, remember that vacuum tubes are important factors Type 15 6 in successful radio reception, and require rheostats For all standard base which provide a gradual and uniform resistance con tubes. A positive wiping contact is made to the trol over the filament. side of the tube prongs by double spring termin- General Radio Rheostats are smooth running, uni- als. These terminals hold of very minute variations. Many the tube firmly and pre- form, and capable vent vibrations. of the well -known manufacturers of receiving sets have Price $ 100 chosen General Radio Rheostats and Sockets as standard equipment because of their high efficiency in tube operation. Why not use them in the next set you build, and get more out of your tubes? Sold at all good radio stores Write for New Radio Catalog 920 The red cartons with the General Radio Type 299 label are your unfailing assurance For UV -199 Tubes. This of satisfaction. socket is a particularly high - grade socket of moulded bakelite. Con- tact is made to tube prong s by phosphor bronze terminals with double leaf C blades. Price 50C. TYPE 001 GENERAL RADiO C. RHEOSTAT 10 OMM] 1 AMP Cambridge, Mass. PRICu 01.25

approved b.- 'oI'I'LAR RADIO LABORATORY All apparatus advertised in this magazine has been tested and

www.americanradiohistory.com 11

3G The Best in Radio Equipment

INDUSTRIAL RESEARCH EN INEERS Scientific Research for Radio Manufacturers Radio Manufacturers are constantly faced with scientific problems due to the discovery of new principles and the necessity for keeping their product in the front rank in Radio's rapid advance. Kalmus, Comstock & Wescott, Inc., offers to the Radio Industry resources, equipment, and trained scientific skill necessary to solve these problems. We maintain a staff of highly trained scientists and engineers with years of practical experience in the various fields of industrial research. Our Laboratories, personnel and experience are available to Radio Manufacturers for a reasonable compensation. It will pay you to write for complete information. KALMUS, COMSTOCK&WESCOTT Inc. Industri al Research Engineers. 110 /114 BROOKLINE AVE . BOSTON. MASSACHUSETTS 57ppAG

"B" ELIMINATOR SIMPLICITY PERMANENT ALKALINE STORAGE The BATTERY RECEPTION Red Stripe KIC-0 MULTI.POW ER UNITS operate A Radio Guide Line from your lighting line end eliminate the For your protection, replacing of dry cell "B" batteries throughout the center of every Dilecto radio panel is a usually saving their cost in the first sia Red Stripe. You can see it along the edge of every to twelve months of service on Neutro panel. dyne and Super Heterodyne sets. If you buy or build a set Look for the Red Stripe -and you'll be sure of the finest, strongest radio panel that can be made. Dilecto is a Phenolic condensation material. THE CONTINENTAL FIBRE COMPANY Factory: Newark, Guaranteed Two Years Delaware PRICES Service on Dilecto, Conite, Contez Vulcanized and MULTI -POWER UNITS Fibre from: New York, (Complete) 250 Park Ave. Chicago, Wrigley Bldg. San Francisco, 75 Fremont St. 90 Volt MX.. $26.50 Los Angeles, 307 S. Hill St. Seattle, 1041 Sixth Ave., South Pittsburgh, Farmers Bank Bldg. P ower -E conomy -P erformance Shipped charged and ready to use. No costly bulbs! No acid turves! Unita for 110 volt A. C., D. C. or farm plants. Write for special offer! Distributors! Everybody! Kimley Electric Company, 2667 Inc. Main Street Buffalo, N. Y. fled A, All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com It's mahogany to the eye- but in fact in 73ahelzte

So perfectly is the grain and color of mahogany and walnut reproduced in these Bakelite Radio Panels. that the eye cannot distinguish them from the natural woods. By using a Bakelite Panel that matches the wood in the cabinet, your finished set will be far more handsome than if a plain panel is used. Rigid and strong, Bakelite Panels support the weight of heavy instruments without sagging. They will not compress, or cold -flow, under pressure of binding screws. Because of their resistance to extremes of heat, cold and moisture, they will not warp nor split. These properties and their insulation value, color and finish are permanent. Be sure to ask your dealer to show you these wood finish Bakelite Panels -obtainable under any of the following trade -names:

n. tvacs a» CELORON Dilecto

Spauldin F i b r o c Mícarta

A Bakelite Panel on a set is an indication that the manufacturer has used the best. Write for Booklet 28 BAKELITE CORPORATION 247 Park Avenue, New York, N. Y. Chicago Office: 636 West 22d Street

and New York Radio Shows J Visit our booth at the Chicago t.kei, de ark can be BAKELITE twnt only on products is the realstered trade made from materials by the murkfor the phenol manufactured product Bakelite Corporation matenal under pat. It K the only is owned by the which may thia fncrai beat Bakelite Cor tino. famous mark of excel. lama. i ELI I r THE MATERIAL OF A THOUSAND USES has been tested and apprl: i by POPULAR RADIO LABORATORY .4 it apparatus advertised in this magazine

www.americanradiohistory.com 38 The Best in Radio Equipment

SET OWNERS: Crowe markers are carried in stock by leading dealers.

Jobbers and Manufacturers Crowe Metal are invited to write for Cable samples Markers and Every set owner and radio prices. manufacturer will appreciate the safety and convenience afforded by these markers. Supplied in all standard marking-s. Special requirements of set manufacturers made to order. CROWE Quickly NAME PLATE and easily ¿S MANUFACTURING CO. attached with a pair of 1749 Grace Street CHICAGO ordinary pliers. SICKLES DIAMOND -WEAVE COILS Patented Aug. 21, 1923

Sickles Coil Set No 24 for Itruwning -Drake For Browning- Drake, Roberts, Craig, Circuit. Price $7.50. and Hoyt Circuits sickles Coils for the famous Browning An -Drake Circuit are the entirely new system of latest Sickles achievement in efficient design for a particular use. Radio Reception They are priced at $7.50 a set. The New Stapes Diamond - Weave Coils hare been No. 18A Coils for any Roberts Circuit are absolutely spectled for use in the Hoyt System of .' ignal standard equipment. They are priced at $8.00 per set. Augmentation, by the inventor, Francis I?. Hoyt. Coil We have a limited Set No. 20. at $4.50, is for use specifically with number of blue printed copies Reflex the New of Mr. Hoyt's original laboratory notes on this Receiver designed by Albert G. Craig using the Sodion new system of radio reception, together with nine detector. circuit sketches, which will be sent free to you Coils for the Hoyt upon receipt of this coupon and four cents for Circuit at $10.00 a set, for the Knock- postage. out Reflex Circuit at $4.00 a pair, and the Tuned Radio Fre- quency coils at $2.00 each are other standard Sickles Coils. We The F. W. Sickles Co. manufacture also for manufacturers' special requirements. Springfield, Mass. Please send information of Hoyt System Send for descriptive catalog Name

Address I The F. W. Sickles Co. 13.1 Union Street Popular Radio SPRINGFIELD, MASS.

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment

The Gold Standard

VERY INDUSTRY has its pioneers whose achievements blaze the trail and establish FERGUSON SIX Console Model the standards. Ferguson, actuated by the desire "The Gold Standard of Radio Re- to build fewer and better receivers, attained ceivers" built into a graceful cabinet, finished in the choicest genuine wal- early distinction in the radio industry. nut, with spacious compartments for batteries, charger, etc. The loudspeak- The high notes of a coloratura soprano ; the er, of special - design, employs the Amplion unit. rich, mellow tones of a bass horn reach your Price, $290 living room with crystal clearness and life -like (Accessories extra) tone fidelity through the Ferguson Six. To examine the graceful craftsmanship of this Receiver; to experience its easy, thoroughly dependable operation is to know why it ha s been called "The Gold Standard of Radio Receivers." Have your Ferguson Dealer give you a com- parative test, or write us.

'FERGUSON SIX Cabinet Model J. B. FERGUSON, INC. The Ferguson Six employs two stages ST. NEW YORK, N.Y. of balanced tuned radio frequency, 41 EAST 42ND oscillating detector (non -radiating).

and three stages of perfectly matched . audio frequency. The De Luxe cabinet, with "B" battery compartments, may be had in either high -light walnut or mahogany. Price, $180 (Accessories extra) usor1 B. INCORPORATED r7h0 Gold Siandczrd ?Radio Receivers

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 40 The Best in Radio Equipment

The Nu-Way Snap Terminal ACME WI RE Makes a Perfect Binding Post RADIO PRODUCTS

The New CELATSITE Flexible stranded (vire for "point to point" ant sub -panel wiring- latest 14 ACME method of wiring sets. 5 colors, black. yellow, .: °" fEIATSITE green, red and brown, 'l'Ire Stud twit I the lettered gt t rd is fastened to one for each circuit. the set the same as the regular binding post. The Connector, to which the wire is fastened ,x;'/ . (by closing down the lug) is marked the same as the guard. Simply snap it to the Stud. 'Flic Bronze Spring in the Connector compresses the C'onnec'tor and Stud together, making a x The Original Celatsite perfect contact. Wire With the Multi- Connector more than one wire ('elat;ìt,' k a oraied copper bals bar can be attached to the wire wuti a non- in/lantntable "spa- sane place as when ghetti" insilation in live colors. Sup- slaking phone or battery connections. plied in 30 -inch lengths. THE HATHEWAY MFG. CO. Flexible Varnished Bridgeport, Conn. Radio Division

"Spaghetti" E ACME A perfect ei, !labos tube for all dan- CELATSITE ger pouris in set wiring. ('rots little - WIRE more und is worth a lot mure than the cheaper substitutes offered. Black, yellow, red, green, brown: for wires No. 10 to No. 15. 30 -inch lengths. Enameled An- ACME tenna (Stranded) The Mist outdoor antenna you can put up. 7 .strands of enameled copper wire: maximum surface for reception. ltname'lIng prevents corrosion and conse- quent weak signals. 100, 150 or 200 foot coils, boxed. Have you met Loop Antenna Wire V'on can nia' :,' a good loop with Acne' wire made of 05 strands line copper wire, green silk covered. Flexible: non -stretching. neat. Celatsite Battery Mayo Cable Reg. U. S. Pat. Office. For connecting A and II Itat tories (or current supply) to radio set. MA TUNER will end those Silk braid covering 5 flexible "interference blues." A - set built Celatsite wires with -5 feet long - the MAJOR TUNER gets only a different color for each one station at a time -the one you terminal. Pre- want vents messy wiring and "blown" tubes. to get and no other. Send for Folder I\ IA J OR TUNER is the most advanced THE ACME WIRE COMPANY form of three circuit Low -Loss tuner. Dept. P New Haven, Conn. It is packed with complete picture wir- Also makers of One enameled magnet wire and coil ing diagrams and full instructions. for Audio Transformers, Battery chargers, "B" Battery Eliminators. (If your dealer cannot supply you, write us.) A ...... _... s- 41 -- Raes. - saw - - BEL -TONE RADIO CO. 161 Jamaica Ave., Brooklyn, N. Y.

All apparatus advertised in this Magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 41

11NNOUNCING eyVewnroders of U.S.TOOL CONDENSERS

new models U. S. Tool l'onndeuscrs THEembody the latest refinements made possible by the combined skill of our lare- staff of engineers. l S. Tool Condensers have always been good condensers. The new models are better condensers. When the best condensers arc made, tr. S. Tool will make them. Model 8 An efficient condenser made with new and patented one -piece stator, guaranteed to give sharp tuning at the lower broadcasting wave lengths Capacity. Max 00025, Min. 0000076. $2.70 Max 00030, Min. 000008. 2.85 Max 00035, Min. .0000080. 2.95 Max 00050, Min. .000011. 3.75

Model 9 Same as Model S, but with Vernier and Kurz -Kasch Dial. Capacity, Max. .00025, Min. 0000076, $3.75 Max. 00030. Min 000008. 3.85 Max. .00035. Min. 0000086, 4.10 Max. .00050, Min. .000011, 4.75

MULTIPLE CONDENSER For Single Control $ Receivers

You can now build a single control receiver with two or three units of U. Made under S. Tool Condensers. The sanie Hogan Pat. but greater simplicity. One dial efficiency, stations at No. 1.014,002 /tables any novice to tune in Jan. 9, 1912 will. SEE THESE NEW MODELS AT YOUR DEALER'S Write for Booklet U. STOOL CO ,Il1jC. AMPERE, N. J

tested and approved by POPULAR RADIO LABORATORY .411 apparatrrc advertised in this magazine has been

www.americanradiohistory.com 42 The Best in Radio Equipment 0 Hoyt Meters Insure Reliable Radio Reception

CLIP THIS COUPON This is Hoyt Meter Type 17 Burton- Rogers Co. 26 Brighton Ave. Used for keeping just the Boston proper voltage on the tube filaments Please send me your -a critical value book HOYT METERS in set operation. Case 2" FOR RADIO. in diameter. Draws so My dealer's name is .. little current that it may be left continuously in circuit. HOYT builds a complete line of RADIO METERS Name of all sizes and types. Send for our book HOYT METERS FOR lt:1DIO. Address Use coupon opposite BURTON - ROGERS CO. 26 Brighton Ave. National Distributors Boston, Mass.

Loud Speaker of Distinctive Beauty

GENEROUS The AEROVOX PROPORTIONS process insures electrical contact with the entire surface of end Natural Tones With Volume plates. This prevents leakage. Other makes depend on eyelet contact only. Convince yourself by trying it. A Reproducer that Satisfies. Large size unit. Aluminum Sound Column. Hand- IMPREGNATION with our secret for- some pyralin bell. Convenient adjuster. mula (patent pending) predetermines and controls capacities. Result -capacities No. 205B Polished Black Flare . $22.50 are No. 205D Mahogany Tinted exact. Flare $25.00 Endorsed No. 205P Mother -of -pearl Flare . $30.00 by Radio News, Popular Radio, Popular Science, and Professor Wheeler of Yale. Approved and used by over 100 ail/Berk= 6'kdrk set manufacturers. Made in an capacities. Write for particulars Company of complete line including Resistoformers, State and Rheostats and Grid Leaks. 64th Streets Chicago Chicago Office: 53 W. Jackson Boulevard AEROVOX WIRELESS CORPORATION 491 Broome Street New York City All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment SELECT[VITY THE OBEDIENT SLAVE TO /]//lam YOUR DESIRES

é Just as the skillful , 'il fingers of a trained mu- t . fÍ , ,. / ' sician select and control the sensitive, vibrant strings of a harp -so, too, do you, who operate an APEX Radio Receiving Set, select and control the sound waves wafted through the air. Stations thousands of miles away, or powerful near stations can be entirely and Upon request, we instantly isolated from interference. This degree of finer selectivity is not the only we will gladly mail triumph achieved by APEX scientific engineering you descriptive principles. Full volume, wider range. greater folder. clarity have been acquired and are enthroned in a setting of exquisite beauty of design and finish that place APEX Cabinetsin the highest ranks of the finest furniture. Only a dependable merchant is given the APEX dealer franchise. Your APEX dealer will gladly make a persona! demonstration of APEX Quality Radio Apparatus. APEX ELECTRIC MFG. CO. 1410 W. 59th St., Dept. 902 CHICAGO Also makers of the famous APEX Vernier Dials and APEX Rheostats, which are sold by every good dealer in Radio.

Apex Baby Apex Super Five Quality Radio Apparatus Grand Console Price $95 Price $22S without accessories

Apex Console Entertainer Price $27.50

Apex Utility Apex Apex De Luxe Radio Table Price $135 Entertainer Price $75 Price $22.50 Prices West of Rockies slightly higher. Canadian prices approximately 40% higher

by POPULAR RADIO LABORATORY All apparatus advertised in this magazine has been tested and approved

www.americanradiohistory.com 44 The Best in Radio Equipment

AllEll -4=11.- /111111L. -Uses the full - AC.currenFnotha/fofil/ wAVE Save Time and Money by Charging Your Battery with the Fu Charger \VINE NO more interrupted programs, lost stations, "muddy" reception.... FUL -WAVE charges batteries BETTER and QUICKER than ordinary chargers because it uses the FULL electric wave. The "A -B" model charges A and B batteries AT THE SAME TIME. No wet chemicals in FUL- WAVE, no water, no acids, NO ADJUSTMENTS. Model "A" -for radio "A" Batteries only $18.00 It is factory SEALED and absolutely guaranteed. SIMPLE TO OPERATE, JUST PLUG M .del "A-B"---for charging "A" and IN YOUR ELECTRIC SOCKET "B" Batteries SEPARATELY or to charge BOTH AT THE SAME TIME $22.00¡ SOLD BY THE BETTER CLASS OF DEALERS Write for `, took let LIBERTY ELECTRIC CORP O/NEWYORK- 342 MadisonAve..NewYork CARTER New "IMP" Rheostat (Pat. Pend. ) DUPLEX STANDARD "None better made" Conform to Bureau of Standards specifica- $1.00. tions Rugged con - struction assures per - nement alignment.

DUPLEX MATCHED CONDENSERS Half Size. ALWAYS ONLY ONE 6 ohms and 25 ohms READ 4w3¡° NUMBER ALIKE Smallest the stat made. Diameter 1% in. TO LOG t Projects but 8 inch back of panel. Single Or eliminate logging -Dial by call letters or nave hole mounting. Cc mplete with pointer lengths Specially tested and -guaranteed.ed. ;\I;rtclied. packed and knob. New exclusive Carter method of sealed, to remain unopened until use I Literature on request. c Intact. Positive, smooth, silent. Same DUPLEX CONDENSER & RADIO CORPORATION Carter high quality and standard of SO Flatbush Ave. Extension. Brooklyn. N. Y. workmanship. See one at your dealer's today. Write for information on other Carter orig- DUPLEX JUNIOR inal Radio products. "Best at the price" Any dealer can supply A rood, low - priced condenser. Die -cast rotor. In Canada -Carter Radio Co., Bakelite insulation. Ltd., Toronto Many other features.

_?ll apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 45

EVERY PRECISE INSTRUMENT IS A LABORATORY PRODUCT Announcing Two New Precise Instruments The Syncrodenser Like a pure straight -line frequency condenser, the Svncrodenser spaces the lower wavelength stations evenly over the first half of the dial from 0 to 50. It does not, however, start at that point to crowd the higher wavelength stations together over the last half of the dial, from 50 to 100. This is because the Syncrodenser is a scientific combination of straight -line frequency, where it is vital, with straight -line capacity where that is superior. The practical manner in which the Syncrodenser actually separates stations over this entire broadcast waveband marks a new era in condenser design. Unusual design and great strength permit the Syncrodenser to be mounted on panel or subpanel in any conceivable position, Made in two styles. The 750 type has extremely high minimum to maximum capacity ratio for use where a great frequency PRICES range is desired. The 750L is designed to cover the same fre- .00035 Cap. $4.00 quency range as the average condenser of approximate capacity .0005 Cap. $4.50 using the same coil. No. 480 Super-size Audio Transformer The need for faithful reproduction of all forms of broadcasting caused this Precise super -size audio transformer to be designed. It reproduces with absolute fidelity the true richness of the original creation as broadcasted, with magnificent amplification. The core and windings are unusually large and designed to withstand great overload. Compactly housed to permit subpanel mounting. transformers in the complete Made in two ratios, 5 to 1 and 21 %- to 1 The other audio Price for either ratio, $7.50 Precise line are the original No. 285 (41/2 to 1) at $5. Eclipse (2% to 1) at $4. Comet (31/2 to 1) The BRANCHES $3.25. Push Pull No. 800 -801 $11 per pair. 105 Park Ave., East Orange, N. J. radio 53 W. Jackson Blvd., Chicago, 111. Super -Multiformer is four matched 821 Market St.. San Francisco, Cal. Precise 454 Builder's Exchange, frequency transformers in one unit, $20. Precise Minneapolis, Minn. Filtoformer radio frequency choke coil and bypass and CANADIAN DISTRIBUTORS condenser with inductance of 200 millihenries Perkins Electric Ltd. .006 m.f.d. is $4.50. Toronto, Montreal, Winnipeg PRECISE MANUFACTURING CORPORATION ROCHESTER, N. Y.

been tested and approved by POPULAR RADIO LABORATORY AU apparatus advertised in this magazine has

www.americanradiohistory.com The Best in Radio Equipment Fast, Safe, Noiseless * ,f $ 14 List (without bulbs) East of the Rockies $22.00 COMPLETE WITH 2 BULBS EAST OF ROCKIES RADIO Storage "B" Battery 12 Cells 24 volts Lasts Indefinitely -Pays for Itself performance unheard atta negligibletcost. The NEW Leading and listed as Standard by Radio Authorities, Including Sul. Inst. Standards, Pop. Radio Laboratories, Pop. portant Radio News Lab., Lefax, Inc., and other im- institutions. Equipped with Solid Rubber Case. ance against acid and leakage. Extra an 'naur- Srugged plates. Order yours today! heavy glass jars. Heavy, END NO Just state number of batteries MONEY wanted and we will ship day Pay expressman series BULB, after exxamining batter es. lcent discount TWIN rush for with order. Mail your order now! WORLD BATTERY COMPANY 1219 So. Wabash Ave., Dept. 77 Chicago, 111. Makers of the Famous World Radio Storage Price, 0 -roll. 100 Amp. 'A' Batter( $11.25: 120 Amp. $13.25; 140 Amp. $14.00 All Equipped with Solid Rubber Case

IINDYÇRARGR FOR Wo rl RADIO STORAGE BATTERIES flDliAWEAF' . s i 5f . This improved charger is abso- slUs`Of J?_? : iF]'13:ts]] lutely noiseless with double the speed of the ordinary bulb charger. Yet there is no danger of this charger over -charging your battery or becoming over- heated. It is safe and dependable. This means when you hook up the new Twin gull) Patent HANDY to your battery, you April can forget about it, with assur- 21 -25 Other ance that when you return a Patents full charged battery awaits you. Pending Uses Full Wave feared 80 to Y The new Twin Bulb HANDY Charger employs the advanced "Push - Pull" principle using both halves of the AC Adaptable to coarse or fine tuning, wave, thus providing a faster, more eco- the infinite precision of the Accura. nomical charge. It will charge all "A" tune brings in all stations storage within the batteries from 2 to 12 volts at a scope of your set clearly, strongly, and speed of from 4 to 5 amperes per hour; with little effort on your part. Easily also "B" storage batteries from 24 to 120 substituted in a few minutes for or. volts. And remember that the new Twin dinary dials without alteration of your Bulb HANDY has beauty as well as effi- set. An essential accessory. ciency. It harmonizes with the most luxuriously furnished home. Write for descriptive folder Ask your dealer about this outstand- MYDAR RADIO CO. ing new charger. 5 CAMPBELL ST., NEWARK, N.J.

QC VAT E CCLRATUNE 4337 Duncan Ave., 4 cos .e 4a u s 1.r C+r

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipnrertt ; NIÌVER$AL PLI 0.6 The Only Set 'Hutt 7'rrrre. All ll u re 1,( myths ll /thin 1)i.arrrrrr- Burry, 35 To 3600 METERS

3AR Melbourne 480 -WGY I09 -2FL Sydney 770 -WKAQ San Juan 360 -2BL Sydney 350 -PCFF Amsterdam 2000 Karachi - Bombay - KOP - WGY 1660 -6KW Tuinucu 340 - Bankok -NSF Hilversum I050 -WLW -KDKA 64 KYW -5NO New Castle 400

UK10N ß': Aj!!t__ 14 T ; -- . .,hett ..-..-- " _ --.. t, JUL 1 1925 ' r...-..."*"-' ri 3 r,,-,... ,n2 3 ; `r;'r; (Ciruit J .i ¡c Ir ú ' :;061, r..i A ET`s N .. cr _ iC, To CpLLECT 1 rll.0 Cr:" 1.1 r Cri 0 ,J .. c¡r . .,. ` , il[ Çr p .+,,..Ir ..( 1[ q Ala.r rii.'vl, `[ usl. F C '"( F 'Crli IIY h. (r IiAì ;iti , ..(ii iC(4t5 O VF MR( r AC r I4C FCELY ollt Alu"rIT I`ii T (cE ilA `Olrrl I``(ilicl I.Tritll,r' W,. TMI$ r.l'.. L:CLLC'`T fTCF 1..RTfcL1A ultl _ 14 ic,,'.".-: rrt T TIVC iN.C, REBROADCAST ( írEcY ,..Ir .. ._ I.000UPIIÇi.íO '4'N( W.11.4 , F.1'.T FiF TICVLIFLY l'. T VARICS L(IcGE.'. FI C C IrFIC1 L. SylllS IN mUTN I:- CFC iTI('S

WOC -CYL Mexico City 5I0 -2FC Sydney 1100- KFI -PA5 Amsterdam 1050-Vienna- Colombo- WWJ -WCX Lakehurst 80 -ICE Rome 470 -5PY Plymouth 330 -Voxhaus 430 -CNRC Calgary 440 - Madras - Stuttgart 437 BAV Brussels 1 I00 -6FL Sheffield 303 -WGY 38 -PCGG Hague 1050-Otchiski -KG \V -CFAC 430 -CHXC Ot- tawa-EBX Cartagena -NAA 2500 -PCMM Ymuiden 1050 -SBR Brussels 262 -KHJ -LOX Palermo 375 -OXE Lyngby 2400- KOA -2SB Sydney -OKP Kbely 1l50 -2BE Belfast 435- KGO -YN Lyons 470 -1 Nice 360 -FL Eiffel Tower 2600 -PTT Paris 450 -5XX Chelmsford 1600 -LOZ Monte Grande 425 -2LS Leeds 346 -5MA Ade- laide 850 -2L0 London 365 -PWX Havana 400 -RAS Vladivostok -WMBF -CJCM Mont Joli -LOR Buenos Aires 400 -LP Berlin 2370 -VTR Rangoon

3L0 Melbourne 6VL Liverpool 1720 318 6BM Bourne- HBI Geneva mouth 385 1100 5WA Cardiff KDKA 64 350 POZ Berlin PRG Prague 2800 1800 2EH Edinburgh 2ZY Manches- 325 ter 375 5IT Birming- HB2 Lausanne 850 ham 475 JJC Funabashi Munich 485 JSB Chemulpo Leipzig 452 3FL Mel- 2BD Aberdeen bourne 400 495

THE NEW UNIVERSAL PLIO -6 and 3 Stages Distortionless Radio Six tube, 2 Stages Non -Regenerative Tuned Radio Frequency Amplification, Detector i Amplification. Receiving range from 1,000 to 12.000 miles depending upon location, station transmitting, wave -length received and other variable factors FULL DETAILS NOW AVAILABLE FROM MANUFACTURERS COLDÉ,NI-LE';ÚTZ INC. 476 BROADWAY NEW YORK CITY CABLES "EXPERINFO" NEW YORK r Manufactured under Hogan Patent 1.014,002 -Other Patents Pending by POPULAR RADIO LABORATORY 11 apparatus advertised in this magazine has been tested and approved

www.americanradiohistory.com 48 The Best in Radio Equipment A NIEW HI -MU TUBE The HI- CONSTRON Tube Model 10 1 A A CLEAR TRON PRODUCT For Resistance Coupled Amplifiers The Hi Constron is a Hi flu tube with an amplification c,,n.,tant of 20 that has been especially designed for Resistance Coupled Amplifiers. The Hi- Constron was the first Hi -Mu tube offered for sale to the general public and is the result of years of research work.

Others may imitate the Ili - Constron as to its appearance its quality. but none surpass List Price $3.00 We also manufacture CT 201A CT 199 Standard Base CT 199 Small Base CT 100 Rectron for B Battery Eliminators LIST PRICE $2.50 CLEARTRON VACUUM TUBE COMPANY 28 West 44th St., New York, N. Y. Factory - - - - West New York, N. J.

New AIR COOLED Rheostat BROADCASTS 0./..n..r.mi Air Bakelite I BOOKLET Cooled Base RAD IO Cod , BLNS Coil Adjustable Exposed on _114 soy, TAti Contact All Sides Sliding No Vernier Lever Required FOR "FANS" FOR "HAMS" OUR new 64 -page Radio NEW 32 -page booklet of Operates without appreciable temperature rise and at Catalog including all the army and navy transmit- constant coefficient of conductivity. The many turns, best and latest Kits, Parts ting apparatus and miscella- with an unusually long contact surface permits fila- neous specials for "hams" ment voltage to be built up slowly and held at just and Accessories for broadcast such as W. E. Choke the right point to facilitate tuning receiving sets. Lowest prices and develop perfect Coils, Generators, Resistance reproduction. Quarter inch shaft fits same size hole in the country! Boxes, etc. as jack and requires a single nut mounting. More than 1,000,000 fans and hams make our store At the best radio dealers Dial, l their headquarters -get these books and find out why 25e extra. $ . 357 Write for either or both 509 Dept. South P R 6 State Chicago Street Ill. YAXLEY MFG. CO. Dept. P 217 N. Desplaines St., Chicago, Ill.

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment t9

"How I Located My Trouble"

A Massachusetts radio enthusiast tells of a happy discovery that finally solved his difficulties.

figure out what was wrong "I was pretty nearly convinced I'd have to get "I COULDN'T some high -priced installation man to come out to with my radio set" states a Fitchburg my home and set me right, %Olen purely by chance whose experience is interest- I happened to pick up a copy of PorLAR business man and thumbing through its pages I found the very ing because it shows how one simple little answer to my problems! adjustment. will sometimes make such an "There in black and white, diagrammed and explained, was a simple, practical suggestion amazing improvement in results. that turned the trick for me." had erected my antenna in just the "I Way to Get Results my different The One Best right way, had connected up Many other radio enthusiasts, to(,, who want parts with the greatest care, had added to get the most out of their sets have found in designed to bring POPULAR RADIO many an idea and practical sug- improvements that were gestion that has made a world of difference in my apparatus to the highest possible per- their enjoyment of this fascinating pastime, and saved them hoars of experiment and costly error. fection," he continues. If you don't already subscribe to POPt TAR ItADto "I spent a good many hours talking over (with which is combined The Wireless Age), don't the magazine experts. I miss this opportunity of getting my problems with dealers and regularly at your permanent address. followed one suggestion after another. But still the same old trouble!" Your Questions Answered FREE! any questions Do You Have This Trouble? Then, too, as a regular subscriber, to ask of the Technical Editor will be I wanted to you wish "In spite of all my efforts, when answered free of charge. This is one of the most hear some particularly interesting broadcasting features of POPULAR RADIO'S service, and in; I found valuable program, other stations kept breaking is the same service for which non -subscribers pity difficulty in getting long distance points; and asked, and they say it's per- 50 cents for each question intermittent squeals, whistles and howls would what they pay. Yet you can get my dials. worth many times sist, no matter how I tuned or adjusted this same added service absolutely ,free. -- The Coupon Entitles You to This Service r POPULAR RADIO, Dept. 98A, the attached coupon I I 627 West 43d Street, New York City. Simply till out and mail will start with the very 1 1 today your subscription Please put me down for a year's subscription to to put up RADIO, beginning with the October issue. next issue. If you have some problem I POPULAR I I am enclosing $3.00 in full payment which also en- to our Technical Editor now, send in your question Question and Answer I I titles me to free use of your with the coupon and he will be glad to straighten year. I Department for a full you out. This is a privilege to which all subscribers I to take full advantage Name are entitled, and we want you tI of it. Address But do not delay sending in your subscription. II I Get POPULAR RADIO now, and don't risk missing any 1 of the helpful and practical suggestions that are tI o for Canada. Foreign countries (ti extra I coming in future issues. It I 25 cents postage extra.)

RADIO LABORATORY All apparatus advertised in this magazine has been tested and approved by POPULAR

www.americanradiohistory.com 50 The Best in Radio Equipment

Our MARVEL Cabinet

Made to take 14 sizes of panels This is only one of our 1925 -26 models. You ought to see the other models including B Battery types, also Loud Nocturne Speaker types. Miracle of science - this flight of Free circular mailed on request. music through the air! Into your All sold at factory to user prices. home it comes, from hundreds of miles away. It speaks a universal language, straight to your heart. UTILITY CABINET CO. And not less a miracle is that Waukesha, Wis. magic building up of tonal power 'Phone 721 -still preserving every mood of the artist -until the room is filled. This is the supreme achievement of Rauland- Lyric. Daeloed 1 rR. 6:4ácazell

Rauland -Lyric is a laboratory - -no anel grade audio transformer de- P signed especially for music lovers. The price is nine dollars. -no dials Descriptive circular with amplification curve will be mailed on request. All -American Radio Corporation, 4201 Bel- -loudspeaker mont Ave., Chicago. 6 tubes-Cornplefely Wired-

AN - AMER je TFAÚE MHfìK LTINDXPE TRANSFORMER MODaEL 1,-3 The Choice of Noted Music Critics Outfpr` 1'o --'W ile for del`á`rIS Alm PHE.NIX }..ADIO CORP. 116 EAST 25 STREET V. Y. C.

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 51 PRE -SEASON REDUCTIONS 30 Days Only Before the regular Fall Season begins you may subscribe for your favorite magazines at greatly reduced rates, $5.00 AKE any selection you POPULAR RADIO subscriptions wish from the following Additional one year gift subscriptions only $2.50 lt st, to be sent to different addresses if desired. Remit 'Judge `Cosmopolitan Film Fun only the amount shown in the 'Popular Radio "Good Housekeeping J edge Popular 3adio *Popular Radio Reg. right -hand column, if more Sift') g0.99 For $5.50 Pa",. S10.00 Reg. than I or $7.75 For.... $7.25 one magazine is ordered. All quotations cover twelve issues to the year unless otherwise specified. Pictorial Review McCall's Judge POPULAR RADIO may be added to any Modern Priscilla Popular Radio "Film Fun Popular Radio *Wit of the World combination of right -hand figures at $4.00 Reg. $2..50 for $0.50 Reg. $5.25 Por $3.50 $10.00 Reg. each yearly subscription. For For $7.00 American Magazine reg.$2.50 for $2.50 Atlantic Monthly " 4.00 " 4.00 'American Magazine Baseball Magazine " 2.00 " 1.75 Today's Housewife Century Magazine *Woman's Home Success " 5.00 " 4.00 McCall's Companion Christian Herald (52 issues) " 2.00 " 1.50 Popular Radio Collier's Popular Radio Popular Radio Weekly (52 issues) .. " 2.00 " 1.75 ;.+:5.50 Reg. Cosmopolitan Magazine $4.50 ¡lea. $7.00 Peg. For $4.00 For $3.90 (Hearst International) " 3.00 3.00 For . . . $5.75 Delineator " 2.00 1.50 Designer " 1.50 id 1.10 Combinations starred *) must go to one address. Etude (Music Magazine) " 2.00 66 1.75 Excella " 2.50 66 2.00 Field and Stream " 2.50 64 2.25 Now before the publishing business is in the full swing of the Film Fun " 2.00 1.85 Fall rush, is the time to send in your Forbes Magazine (24 issues) " 5.00 4.50 annual subscriptions and GO Golden Book " 4.00 2.75 save money on your magazine purchases for the entire year. Good Housekeeping " 3.00 3.00 Harper's Bazar " 4.00 4.00 This page represents an opportunity for you to secure your entire Harper's Magazine " 4.00 3.50 season's reading at a substantial cash saving over regular rates. Ilouse and Garden " 3.50 3.25 House Beautiful " 3.00 66 2.75 The special combinations above and the representative list at the 44. Judge (52 issues) " 5.00 4.25 side should cover all the magazines you are accustomed to read. *Ladies' Home Journal " 1.00 66 1.00 But if any of your favorites are missing, let us quote prices. You McCall's Magazine " 1.00 46 1.00 Modern Priscilla " 2.00 1.75 will find our rates as low or lower than you can get anywhere else. 66 Outlook (52 issues) " 5.00 4.50 As of can be sent to different addresses, People's Home Journal " 1.00 .80 most these combinations l'ictorial Review " 1.50 1.50 you will find that your friends and neighbors will be glad to have Popular Radio.. " 3.00 2.50 you forward their order with your own that they may take ad- Popular Science Monthly " 2.50 2.50 Q. S. T " 2.00 64 1.85 vantage of these very low prices. Radio " 2.50 61 2.00 of these magazines have not yet Radio Broadcast " 4.00 3.50 If your subscriptions for any Radio Digest (52 issues) " 5.00 4.50 expired, your present order will be entered as an extension. Radio News " 2.50 2.25 Review of Reviews " 4.00 66 2.75 So fill out the coupon below and mail it promptly. Magazine *Saturday Evening Post " 2.00 2.00 prices change so rapidly that these rates cannot be guaranteed for Science anal Invention " 2'50 2.25 Snappy Stories (24 issues) " 4.00 66 3.50 more days. 61 than thirty Success- . 2.50 1.50 Sunset Magazine " 2.50 64 2.00 Theatre Magazine " 4.00 3.75 POPULAR RADIO Today's Housewife " .50 .40 Vogue (24 issuest " 5.00 4.50 627 West 43d Street, New York City, N. Y. Wit of the World ' 3.00 2.50 Woman's Horne Companion " 1.50 66 1.50 12 World's Work ... " 4 00 3.50 For Boys and Girls POPULAR RADIO, Dept. 92, West 43d Street, American Boy. , reg. $2.00for $2.00 627 American New York City, N. Y. Girl " 1.50 " 1.40 Enclosed remittance of $ is payment in full for the Boys' Life " 2.00 " 1.75 magazines ordered on the attach_d list. Child Life " 3.00 " 2.50 Every Child's Magazine " 1.50 " 1.25 Every Girl's (10 issues) " 1.00 " .95 Nanne l:veryland (10 issus) " 1.50 " 1.40 John Martin's Book " 4.00 " 3.50 Junior Home Magazine f° 2.50 " 2.10 Street and Number Kindergarten- Primary (5 issues) " .75 " .70 Little Folks " 2.00 " 1.50 State St. Nicholas " 4.00 " 3.50 City Youth's Companion (52 issues) " 2.00 " 2.00 stark R art; r (If not a NEW subscription, please *These magazines do not club but may be the game of the magazine, to indicate REA'EII".l i..) added to any combination at the price shown. Prices for Canada and foreign countries will be quoted on request.

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com l'ue Be\t in Radio Equipment

ZY.

A. 't,_ EDITORS are no- O-- Cl ..- toriously "hard - boiled." Before they t go ,r:p,, nsQi Dtst`i into ecstasies over RaS1aUtt'YReeelvy a circuit, it must re- a: S ally be excepticnal. Albe Nicer wi h . p1i$11t You ee is ., can draw your 1W aFa o w n conclusions p BecSe°/ DX 'theBÿd Toas sca e from the fact that a to Seectéa%Sa^ the Rasla Reflex was Í01oU??Ç S;jO>>xl;taft e editorially boosted by The N. Y. Sun and by many others. Write at once for FREE picture diagram Davidson Radio Corp. Dept. "A" 222 Fulton St. NEW YORK CITY

tRASLA REFLEX {4

12- Cell -24 Volt Storage 'B' Battery Positively given free with each purchase of a WORLD A" Storage Battery. You must send this ad. with your order. WORLD Batteries are famous for their guaranteed quality and service. Backed by years of successful manufacture and thousands of satisfied users. Enu'pped with Solid Rubber Case, un insurance against acid and leakage. You save 60 per cent and get a 2 -Year Guarantee Bond in Writing WORLD Battery owners "tell their No More Bunching friends." That's our best proof of performance. Send your order in today. Solid Rubber Casé Radio Batteries of Stations

ti . -Volt. 100 -Amperes . . . . $11.25 Open tuning on low wave lengths, either right -hand 6-Volt. 120-Amperes . . . . 13.25 ti -Volt, 140- Amperes . 14.00 or left -hand dialing, is assured by the new exclusive Solid Rubber Case Auto Batteries plate shape of the 6 -Volt. 11 -Plate ...... Approved and Listed $11.25 as 6 13 -Plate . . . Standard by Leading -Volt, ...... 13.25 12 -Volt. 7-Plate . . . Authorities 16.00 includingRadioNewsLab- Just state battery SEND NO MONEY wanted and oratories Popular Sci- we will ship day order is re- ence Institute of Stand- ceived, by Express C. O. D. subject to your ex- ards, Popular Radio Lab- CHELTEN amination on arrival. FREE ß" Battery in- oratories, Radio Broad- cluded. Extra Offer: 6 per cent discount for cast Laboratories, Radio cash in full with order. Buy now and get a w the Home. and Lefax, guaranteed battery at 60 per cent saving to you. Inc. Variable Condenser Brase Plates Al uu Plate - WORLD BATTERY COMPANY 13-plate undo 1219 So. Wabash Ave., Dept. 3 CHICAGO, ILL. .00025 $4.10 $3.25 19 -plate .00035 4.25 3.35 For 25 -plate .0005 AUTO 4.50 3.50 World and At Your Dealers or Direct by Mall STORAGE BATTERIES RADIO Chelten Electric Co. , I911íf:Cri : f it 71`. . r-.ZIit" &ZUtL 1170J1óälftl'1 Philadelphia

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 53

Now You Can Test and Renew Tubes! -tell their exact condition -- reactivate them to full efficiency -match them in the set, uniformly

Tube Reacefrator It is now possible to know the exact condition of your tubes, and to renew the worn -out filaments. All of which requires

Tube but a few moments of your time. Tester Sterling Tube Reactivator This device will reactivate the filaments of UV -201A, C -301A, UV -199 and C -299 v .cuum tubes, so that you are able t.' use your tubes long after they have given the usual amount of service. The process may be repeated t'me after time. An exclusive feature of the Sterling Reactivator is that it includes a filament emission meter .which shows in- The Complete stantly whether the tube needs reactivation and tells Sterling exactly how efficient the tube is after treatment. Tubes Radio Line c he maintained at high efficiency and matched in the set. l :..> reactivator will pay for itself in a very few months. Pocket Meters and Panel -60 cycle) $12.50 (25 -40 cycle) $14.00 Meters Price (50 "A" and "B" Battery Sterling Tube Tester Chargers In less than half a minute you can test the plate find the defective tube, or Tube Testers current of a tube and tubes if any, in your set. A convenient chart furnished with the e tells at a glance whether a tube is good, fair or Tube Reactivators instruments poor. This tester is also helpful t , locate transformer. wiring and socket troubles. Price $8.50 Rheostats See a good dealer or write us direct Microcondensers Audio and Radio Fre- quency Transformers

Radio Equipment THE STERLING MANUFACTURING COMPANY 2831 -53 Prospect Ave. Cleveland, Ohio Electrical Manufacturers since 1906

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment el Another JO: Achievement! Why $5.00 Set Manufacturers are per Standardizing on D X L set Condensers the New Single End Plate Model C . . PRECISION When the enginet'- t mane it manufact irrrs R. F. COUPLING UNIT in all of 1. - parts the country specify 1) X Con May be used as a transformer for coupling two tubes in a densers for the new Sets -when they select D X L circuit as a radio frequency amplifier. Designed for present broadcast range in conjunction with a standard .000s mfd. from the hundreds offered them it means they ariable condenser. The coupler consists of a compact are satisfied with the sound. sensible principles of primary. winding to be connected to plate circuit of one ,tie and a split secondary winding, half on each side of design upon which D X L Condensers are b.oit. primary, to be shunted with the tuning condenser and ': uected in grid circuit of following tube. Light, yet sturdy and rigid yet a au wound type, the most efficient coil winding, special -Simple, mar- sign prevents windings becoming loose at any time. vel of precise workmanship -Instant admiration The design is such that an amplifier built with this appara- is won for Model C--just one end plate yet any tus makes possible extremely sharp tuning with maximum engineer will vouch for its absolute rigidity. signal strength and stability of operation. Made by the makers of the famous Cockaday Coil. At your dealers, otherwise send purchase price, and Like all D X L Straight Line Condensers Model you will be supplied postpaid C is guaranteed to ru ri true to specifications and careful workmanship in every single shipment. Precision Coil Company, Inc. 209 -B Centre St., New York City Buy D X L with perfect confidence.

Samples to rep- Deliveries thru- utable ma n u - out season guar- LO W fact urers shipped anteed with ac- instantly. ceptance of order. 5t0itati LOSS Interference Eliminator What Every Radio Owner Needs Tested and approved by the Popular Radio Laboratory Over 36,000 Sold First 6 Weeks. Now you can select stations at will, cut out interference and undesired stations -rune in loud and clear. Wonderful results with tube or crystal sets of any make using any kind of aerial except loop antenna. Reduces Static Postpaid Amazing satisfaction. Better reception guaranteed or your money Individual Set Builders cheerfully refunded. D X 1. Condensers will make your set perform Select Stations At Will ai maximum. Ideal for low wave lengths. De- Put till, into i I erenre eliminator on yo ar set- that's the and prices on request. test -no tools - attached in two minutes tu aerial. Doesn't disturb present log. Directions easy to follow. No additional tubes or batteries. Two big banks testify to our reliability. Order today -dollar bill will do-we take the risk -money back if you say so. TRADE MARK STEINITE LABORATORIES Man ufacturers 134 Radio Building, ATCHISON, KANSAS Write for complete radio literature -it's FREE. Steinite sharp tuning summer sets. Most beautiful and least ex- RADIO CORPORATION pensive radio sets in America. 5767 Stanton Ave., Detroit, Mich. d4 rite today for full Jobbers- Dealers: description and prices

- s - - BIM Stinite nationally known popular price radio sets, inter- 1 a,NM' 111M1 (creme eliminator, cod long distance crystals. I _ >

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment

The Six Point Pressure Condenser The "Electrad" Certified Fixed A Foe to Mica Condenser is a revelation in accuracy and design. Ingenious, Old Man Static rigid binding and firm riveting This demon tormentor with fastens parts securely at six his rattles and hammers- different points insuring positive This outlaw of the ether. electrical contact. Impervious -will be a stranger in your home when you use the "Electrad" Lamp Socket Antenna. to temperature and climatic vari- Plugs in at any electric light socket, replaces ations. Exerts even pressure outdoor or indoor aerials. Reduces inter- upon the largest possible surface ference, a distance getter. -can't work loose. Binding Price 75c. At Most Good Dealers strap and soldering lug in one together with other handy "Electrad" piece. Accuracy an d quietness Radio Accessories- Variohms. Audi - assured always. Value guaran- ohms and Lightning Arresters. teed to remain within 10% of calibration. Standard capacities, 3 types. Licensed under Pat. No. 1,181,623, May 2, 1916 and applications pending. Price 30c. to 75c. in sealed dust and moisture proof packages. "ELECTRAD" LEAD -IN Also Type G S with grid leak Price 40c. Fits under locked brackets and specially designed windows. No holes arms for direct connection to to bore. Extra waterproofing. socket terminal. Meets the quality standard set by "Electrad" - there is a difference.

ELECTRAD INC. 428 Broadway, New York City

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com Tite Best in Radio Equipment

IN 50 U. S. A. CARBORUNDUM DETECTOR FROM YO uR DEALER OR DIRECT PATS, PFNIA NG l NO NEED TO HUNT FOR THE SENSITIVE SPOT The Carborundum Detector Unit is Fixed- Permanent the first moment you hook up the Carborundum Detector FROMUnit in your Reflex or Crystal Set you get a positive sensitivity that is permanent. 1 There are no adjustments. This is one Detector Unit that retains its sensitivity indefinitely It will not burn out. 9 The Carborundum Detector Unit comes to you laboratory tested and it's made with a special Carborundum created for Radio use. 1 It will give you clear, true, tones- increased selectivity- greater volume and distance. Sold under a Guarantee by All Dealers MADE ONLY BY THE CARBORUNDUM COMPANY, NIAGARA FALLS, N.Y. New York, Chicago, Boston, Philadelphia, Cleveland, Detroit, Cincinnati, Pittsburgh, Milwaukee, Grand Rapids Çarborundum Detector Unit

CRISS-CROSS LOMBARDI THE COUNTRY WITH

VriuuirSTUBE

SOMETHING decidedly new, different and better has been perfected in radio. Interesting information is ready for you. Write us at once. STRAIGHT LINE CONDENSERS PREMIER ELECTRIC CO. (Wavelength or frequency rotor plates) No Backlash- Geared Vernier -Pat. Pending Dept. K19, 1800 Grace St., Chicago, 111. Separates the Short Wave Stations In Multiple or Single Units o4ouoaauoao.aoaouaoo.oaouoouaua0004oaououuuuaoau0004o0oaouuoaoaao Iligh Electrical and Mechanical Precision PREMIER ELECTRIC CO., Adjustable Ball and Taper Bearings Dept. K19, 1800 Grace St., Chicago, Ill. Watchspring Pigtail on Rotor Send me immediately full information about the New Premier Recommended in AUGUST POPULAR RADIO Ensemble. This does not obligate me. For use in Craig Tuned Radio Frequency Set Name FOR HOME SET BUILDERS Address LOMBARDI RADIO MFG. CO. 67 Minerva Ave., Derby, Conn. City State Multiple Condensers Licensed Under Hogan Patent

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 57

"THE PERFECT PANEL'

Authoritative laboratory tests disclose electrical qualities and advantages in metal panels, not obtainable in any of the com- monly employed paneling materials. Losses are reduced to a negligible factor, and "body capacity" effects--so disturbing to set owners when tuning-are eliminated. These, coupled with many other equally important manufacturing advantages, are now available to builders of quality receiving sets in Crowe etched bronze and brass panels. Crowe panels are supplied ready to assemble fully engraved with any desired wording, decorative or trademark design, accurately sheared to size, and completely machined with holes pierced and countersunk if required. Crowe panels will not break, split or warp. They are produced in a wealth of beautiful finishes-mahogany and walnut grainings, deep black and velvety brown Morocco effects, and other rich and pleasing patterns which cannot be duplicated in any other pant I material. Set manufacturers and radio engineers arc invited to write us for a report of laboratory tests on metal panels by Professor R. S. Glasgow, Department of Electrical Engineering, Washington (in ilcrl iv.

CROWE NAME PLATE ,S.," MANt'FACTURING CO. 1749 Grace Street CHICAGO

..... ?

-f/Cr7 _,;7';:, 7,01

Products for Nearly a Quarter Century Producers of Name Plates and Etched

RADIO LABORATORY All apparatus advertised in this magazine has been tested and approved by POPULAR

www.americanradiohistory.com 58 The Best in Radio Equipment Sangamo Mica Condensers

"SEE THE RATHBUN has a complete SAN GAMO EXHIBIT practical solution of the AT THE NATIONAL Straight Line Frequency RADIO EXPOSITION, CHICAGO, Problem. No existing THE REEK OF SEPTEMBER apparatus is similar to 28th." this invention in theory or universal application. Watch for the Nothing will change announcement story in the next issue of their accuracy this and other radio HAT'S wrong with my set ?," asks publications. W many a puzzled builder, forgetting that inaccurate fixed condensers throw the whole circuit out of electrical balance. RATHBUN MANUFACTURING CO.,Inc. Jamestown New York Perhaps this is your trouble. With San- gamo Mica Condensers you can he sure of dependable accuracy no matter how severely they are used. For here is a condenser that is guaranteed to he accurate within io per cent of marked capacity, and to sustain that accuracy under all conditions of service. It is solidly molded in smooth brown bakelite; impervious to t,MEWD'lil IÍD,,, m,.'°I moisture, acid fumes or salt air.

Even boiling and freezing will not injure $12.00 and up Adjustment (\{`Í a Sangamo Mica Vr Alfred Graham 'at rear for Condenser. Soldering has & Co., London, "tuning" unit Eng., Patentees t0 your net 04, no effect upon the capacity; heavy surges +._ of 4, current in special uses will not break it down. Its great mechanical strength Test it for "Selectivity" 40,, gives protec- against any other loud speakers tion against shipping or cracking even if Hear The Amplion in comparison; let dropped on laard cement. Approved by all your ears tell you why this creation of nationally recognized radio laboratories. the actual originators and oldest makers of loud speakers leads in sales First class radio dealers have throughout the world. Not only is The Í SANGAMO Amplion supremeforclarity, realistic tone and Sangamo Mica Condensers tong distance volume. It alsp has "selectivity-- Accurate in stock - or can quickly the ability to separate distinctly the different Radió Parts obtain them for you. Insist! instruments in an orchestra, or the various voices in a quartet, instead of jumblingthem together. Interesting Amplion literature will Sangamo Electric Company explain why. Write for it and dealer's name. 13zo -8 Springfield, Illinois RADIO DIVISION, 50 Church Street, New York AMPLION SALES OFFICES -PRINCIPAL CITIES 1he?ÏJorldsStandarcl ,Cud Speaker For Canada Sangamo Electric Co. Canada, - of Ltd., Toronto. THE AMPLION CORPORATION OF AMERICA For Europe -- British Sangamo Co., Ponders End, Middlesex, Eng. Executive Offices: For Far East Engineering Co., Osaka, Japan Suite, X, e80 Madison Ave., New York City -Ashida Canadian Distributors: Burndept of Canada, Ltd., Toronto

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com TLe Best in Radio Equipment

Amazing new receiver NOW anyone can build it in an amazingly short time this new easy way. Experts assemble it at factory. You simply wire. Note revolutionary new principle it contains. NC) excuse now for not having a 3. Increased selectivity. Circloids 1 fine radio. At a surprisingly low have absolutely no pick -up qualities cost, too. For a remarkable plan is of their own. Only signals flowing in showing thousands a new way to build the antenna circuit are built up. their own. It is so easy that anyone can do it in an hour's time. So fasci- 4. Finer tone quality. The self - nating that many continue to build enclosed field positively prevents stray them for others. No wire bending or feed -backs between coils. Hence no soldering. Merely attach a few ready - blurring or distortion. Tones are cut, flexible eyeletted leads, and the crystal clear. job is done. Circloids are sold singly and in sets And in addition to the fun and pride of three; also in kits containing three of building your own, the finished re- Circloids and three .00035 condensers. ceiver actually contains a phenomenal feature not yet found in the most Write for free information on kit -- expensive sets; that brings results also book otherwise impossible. See how a few minutes of fun «ill This feature follows the discovery give you the newest and most nearly of a new inductance principle that perfected set known to radio science. overcomes many vital weaknesses of Examine it at any Erla dealer's, or present day sets. It is based on an send the coupon for full information, entirely new type coil -the Erla *Bal- illustrations and diagrams contained loon *Circloid. in the remarkable new book, "Better Circloids are the backbone of the Radio Reception," describing the sen- Erla kit and are largely responsible sational new Circloid principle. En- for the striking improvements this kit close 10e for mailing and postage on alone offers. Note these four advan- book. tages in particular: *Trade Mark Registered. 1. Greater distance. Circloids have Electrical Research no measurable external field to affect Laboratories, adjacent coils or wiring circuits. This 2500 Cottage Grove Ave. makes possible higher amplification in Dept. 119 each stage, with increased sensitivity Chicago, U.S.A. and greater range. Send me free information on kit. Enclose This sign identifies au- 2. More volume. Higher r. f. am- 10c for postage for book, thorizedErladistributors. "Better Radio Recep- All are equipped to give plification enables Circloids to bring complete radio service. in distant stations scarcely audible in tion." ordinary sets with volume enough on Name the loud speaker to fill an auditorium. Address Dealers- Exclusive franchises are available to high class dealers in localities still City State open. Write or wire immediately. All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 60 The Best in Radio Equipment

Parts for a Thousand and One Hookups 1111111 Always Obtainable at Morisons ! ! ! And you will also get - Morison service, expert advice, high quality, fair prices COCKADAY'S 8 -TUBE TOWN AND COUNTRY RECEIVER McCULLOUGH SUPER -REFLEX RECEIVER (See May Popular Radio) AC 5 -TUBE RECEIVER (See January Popular Radio) Remler Variable Condenser .00035 $6.00 (See June Popular Radio) Amaco 20 -Ohm Rheostat 1.25 1 General Instrument Low - Loss Arnsco 400 -Ohm Potentiometer 1.50 1 General Radio Variometer No Condenser 'isolantite insula- Cutler- Hammer Battery Switches ea. 60 1.20 260 $5.00 $5.00 tion, .0005 unid. Adams Jack No. 602 .70 2 Precision R. F. Coupling Units 5.00 501 .60 1 General Instrument Low -Loss Adams Jack No. 2 .0005 Condenser IisolantRC insula- Dubilier .00025 -601 -t1 Condenser .45 Hammarlund 10.00 tion..001 infd 6.50 Dubilier .00025 -601 Condenser .95 5 Federal Sockets No. 16, 1.20 ea. 6.00 Daven 4 mea. Resistance .b0 1 (General Audio 1 Set of 4 Matched Haynes -Griffin ltadio Trans- Intermediate Tianstornters 20.00 6 Benjamin No. 199 Sockets ea. $1.00 6.00 former No. 285 7.00 3 ea. 4.00 12.00 3.50 Dubilier Duratrana 1 Daven Mtg. No. 41 1 Precision Autodyne Coupler 2 Parent Audioformers No. 26 ea. 6.00 10.00 1.00 . I Karas -Harmonic Audio- Frequency 9 Eby Binding Posts ea. .15 1.35 2 Dubilier .006 Cond. No. 601 transformer 7.00 7 x 18 Radios Panel 2.26 ea. .75 1.50 1 Amplex Grid- denser .0005 mfd 1.25 Brass Strip for Brackets .15 1 Daven Resistor .25 Meg .50 liard Rubber Strip 1 x 9 ins .26 . 1 Benjamin Cle -ra -tone Socket 1.00 1 Daven Itesistor 4. Meg .50 Baseboard 7 x 16 3 -4 .60 7 Federal Sockets No. 16 .ea. $1.20 8.40 Dixie Assortment of Screws, etc .50 1 Daven Resistor .5 Meg .50 1 Percent Double Circuit Jack .60 16 Lengths Bus Bar ea. .02 .90 1 Dubilier Condenser .00025 No. 1 Pacent Single Circuit Jack .50 7 x 18 Cabinet 7.50 601 -G .45 Hole 0 -6 Voltmeter 3.00 2 Na -ald 4 inch Dials No. 3043.ea..75 1.50 Hoyt Bezel 1 Dubilier Condenser .00015 No 1 Amero 2 Ohm Rheostat 1.35 $55.95 601 .35 1 Amaco Potentiometer 400 Ohms 1.50 1 Dubilier Condenser .0001 No 2 Daven Resisto coupler mountings 601 .35 ea. $1.00 2.00 McCullough AC Tubes 1 Pacent Jack No. 61 S. C .50 1 Daven Grid -leak Mounting .35 1 Radion Panel 7 x 24 3.00 2 Daven Resistor .5 Megohms.ea.50 LOO $6.00 each 1 Baseboard 9 ié x 22 % . 75 1 haven Resistor 5 Megohrns .50 get 1 Antenna Binding Post Strip . 15 1 Daven Resistor .005 Megohm 1,00 Ask for any Parts you can't 1 Battery Binding Post Strip .25 2 Daven Resistor .25 Megohm. ea. 50 1.00 WHOLESALE RETAIL 1 Cabinet 7 x 24 12.50 1 Radion Panel 7x24 ins 3.00 3 4 inch Kurz Kash Dials 3 00 2 .0001 N. Y. Coil Mica Condensers 1 Dongan Transformer ti 1111 ea. 35 .70 A. C. Leads 1.50 4 .006 N. Y. Coil Mica Condensers ea. 76 3.00 $115 1 .00025 N.Y. Coil Mica Condenser .S0 with Grid -leak Mounting .45 1 Duratran Radio-FrequencyTrans- O1%ISO Establish connections with former 4.00 1 Walbert A Battery Switch .60 Morison now before the fall 1 Baseboard 9 3 -8 x 22 3 -4 x 1 -2 ins 75 rush begins. C O D Mail Or- . 1 Connection Block I x 9 x 3 -16 ins 25 Electrical supply C Inc 7 Eby Binding Posts ea. .15 1.05 ders filled promptly. Material for making brackets .25 hil1 Kurach Tuned Loop 16.50 1 Mahogany Cabinet L' .51[ $10:1.9u 15 East 40th Street, New York City WRITE TODAY! s s _ _ _ A_ 1_-.II1

Our By -Pass Condensers Will Improve Your Prod- uct and Save You Money Capacities .006 to 5 Mfd. You'll Like Our Mica Fixed Condensers This Duplex Need No Comment- One cabinet - Any panel size, 7x26, 7x24, 7x21 or 7x18 ". Depth 10". Room for all dry batteries. Either straight or sloping panel -grooves, no screws. Solid mahogany. Latest lacquer hand - rubbed finish. Entire lid raises. Full length piano hinge. Folding lid supports. Felt covered feet Extra %" mounting board. has for years their quality been the The new Blandin Console is ready for standard of comparison. you. Write for Duplex and Console illustrated "Not to investigate is to lose money." price lists. Dealers, write your jobber.

NEW YORK COIL CO. Built by 338 Pearl St. New York City BLANDIN

Pacific Coast Representative: Marshank Sales Co. (Radio Cabinets 1500 -16th St. j 926 Ins. Exch. Bldg., Los Angeles, Calif. Racine, Wis.

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 6I Tuning Marvelously Simplified with KARAS ORTHOMEJRIC Condensers The condenser that brings in KDKA where it belongs - at 53 on the dial. Remember, 52 of the 100 wavelengths must come in below KDKA- !OM

mpinmlnuininnininuuapihT rlunminnnnmiill/ EMI

0 10 20 30 40 50 60 /0 80 90 100

6 AVH NGRIS WAYff Spreads Stations 194/4 (_0.+.1 Evenly D.READps p ó Over the Dial aos, No 4 - Crowding Whatever The Karas Orthometric Condenser positively separates all ad- t joining wave lengths by EQUAL distances on the dial. giving Ordinary Condenser Arrangement of Wavelengths full benefit of the 10 Kilocycle frequency separation fixed by Ordinary straight capacity condensers crowd 70 the Government. of the 100 wavelengths into the first 30 points of the dial. Ordinary condensers jam 70 on the 100 Government allotted wavelengths into the first 30 points of the dial -even straight - WAY[7 line- wavelength :00 1V1-47 7 condensers crowd 57 of them below 30. S f'H With Karas Orthometrics each point of the dial corresponds 40 l0'.S exactly to one of the 100 allotted wave lengths. The result is 2v` 50 60 READINC Fy ge p ow. )O marvelous simplicity in tuning - better, clearer reception. B il 0 O The Karas Orthometric is a "job" that will delight the eye of (DÚ ti _ r 0 the mechanical critic. Made entirely of brass -frame die stamped, MW not cast. Every joint soldered. Grounded frame and rotor. _ O Adjustable cone bearings. Spring copper pigtail. Straight Line Wavelength CondenserArrangement Even with the recent straightline -wavelength condensers 57 of the 100 wavelengths are crowded If Your Dealer is Not Yet Supplied into the first 30 points of the dial. 1GTSSwAÚCx 0,6' ,O Order On this Coupon! `ßa0 We are supplying dealers and jobbers as fast as our factory SD REAObv0 ?Ó output permits. If your dealer is not yet supplied, order ,)O Q\A direct on the coupon. Send no money. Simply pay the sr o s, postman on delivery. Order today! i O o o o 9 Money - KARAS ELECTRIC CO., KARAS oRTHOMErRlc CONDENSER Arrangement Back 4037 No. Rockwell Street, Chicago on of Wavelengths Dial Guarantee! Please send me.. Karas Orthometric Condensers. Conden- The New Scientific Karas Orthometric KARAS Ortho- size indicated below. I will pay the postman $.... , sers insure absolutely equal separation on the metric Con - plus postage, on delivery. This order is subject to dial, of all wavelengths throughout the entire densers are your 30 day Money -Back Guarantee. broadcasting range. positively guaranteed to give you thorough Size wanted satisfaction. Sizes and Prices Any time with- Name 00 in 30 days they 23 plate .0 0 0 5 , Mfd., $7 may be re- Address 17 plate .00037, Mfd., . . . 6.75 turned for full .00025, Mfd., . . . 6.50 refund. Dealer's name 11 plate If you send cash with order, we'll send Condensers postpaid.

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LAI;OR A_TORV

www.americanradiohistory.com The Best in Radio Equipment VEBY "HAMMARLUND, JR." Resistance - Coupled The Midget Condenser Amplifier of Many Uses as

Three Stage Resistance Coupled Amplifier Built with VEBY Resistance Coupler No. 104. VEBY Resistors are responsible for the un- matched tone quality of the VEBY amplifier. High resistance in plate circuit of three tubes prolongs B- battery life. An unique and original mechanical asse 1 bly results in a neat, compact and efficient amplifier ready to operate. VEBY 3 -Stage Amplifier..... $10.00 TA surprises mane radio fans and dealers, VEBY Resistance Coupler No. 104 1.25 I and even some technical experts when they Manufactured by learn that " Hammarlund, Jr." is more than just a small vernier condenser for fine tuning. VEBY RADIO COMPANY It is ideal as a vernier, of course, but it Makers of has other even greater advantages. For QUALITY RADIO RESISTORS example, you can use it for capacity antenna 141 Washington St. Newark, N. J. coupling to increase selectivity; capacity regeneration control; adding regeneration to the superheterodyne loop; neutralizing oscillations in radio -frequency tubes; vernier control of regeneration in a tickler coil; control of tone in a loud speaker; balancing ALMOS T multiple circuits individually, or for one - TOO GOOD dial control; and in numerous other ways. TO BE TRUE Remember, "Hammarlund, Jr." is unlike any midget condenser you ever saw. It is a laboratory product, designed and built with all the care and precision that have brought X -L VARIO DENSERS fame to other Hammarlund products. You will like it. SPECIFIED BY ALBERT G. CRAIG For Easier Balance and Tuning Minimum Capacity. .000004 More Stability Maximum Capacity, .000032 Greater Distance Volume and Clarity Price $1.50 including Bakelite Knob. IN HIS Standard shaft, permits use of dial. FIVE TUBE RADIO FREQUENCY RECEIVER is With Simplified Control FOR SALE BY THE BETTER RADIO DEALERS ENDORSED BY LAURENCE M. COCKADAY Would you like to have a circular showing MODEL N- Capacity range 1.8 to 20 micro -micro -farads, diagrams of various uses? ask it. for balance in Roberts two tube, Browning- Drake, McMurdo Just for Silver's Knockout, Neutrodyne and tuned radio frequency circuits. Price $1.00 HAMMARLUND MANUFACTURING CO. MODEL G -Two capacity ranges, .00010 to .00055 and .0003 to .0015 Microtarads, for the Cockaday circuits, filter 424 -438 West 33rd Street, New York and Intermediate frequency tuning in super -heterodyne and positive in Export Offices: 375 Broadway, A'<_r York grid bias all sets. Price $1.50 X -L RADIO LABORATORIES 3-0^c., B.ettarc, TZa.d,i,o- 2422 Lincoln Ave. CHICAGO Positively Necessary for ammarlundPREC/S/ON Super -Hetero- CONDENSER dyne Copyright March 17, 1925 Filter Tuning

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 6,; New Reproducer That Improves "Tone Clarity" «,:., Thàt01 u rtette9' The Kellogg Symphony Reproducer ,_Q brings the artist into your very room -so Ems Noté/ Clear realistic is its reproduction. Perfect Alimony! Piano music, the most difficult to re- produce, sounds so natural that you Kellogg Symphony Reproducer are completely carried away by its beauty. $20.00 Vocal selections retain all the tone colorings of the artist. Orchestra music is a revelation, each instrument can be heard, clear and true. Radio fans, dealers, musicians, artists, engineers, all unite in endorsing the Kellogg Symphony Reproducer. The Kellogg Symphony Reproducer uses the Kellogg unit with the mag- netically controlled diaphragm. An exclusive feature. The Kellogg unit with an adapter makes a wonderful loud speaker of any phonograph. See a radio dealer today. Let him demonstrate this remarkable instrument.

Unit with phonograph stand Kellogg unit with cord in position $7.50 $6.90 DEALERS: Write for special proposition immediately Kellogg Switchboard & Supply Company 1066 W. Adams Street CHICAGO, ILL.

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Rest in Radio Equipment Build / Mr. Craig's 5 Tube Set 95', AIR Dielectric which specifies Dopeless, Air -spaced AERO -COILS Windings (See August POPULAR RADIO) Ilen In the i ircult -and here is the coil which makes possible the amazing results of which the circuit, is capable. AI

AERO PRODUCTS, INC. 217 N. Des Plaines St. Chicago, Ill. Below 200 Successors to Above 550 Meters Henninger Radio Mfg. Co. with a good Pacific Coast Representative .00035 condenser S. A. WINSOR 1221 W. 16th St., Los Angeles

FREE SIMPLIFIED BLUEPRINTS FREE YOU CAN HAVE YOUR CHOICE OF ANY ONE OF SEVEN SETS You can lithe your chulce of any one of sewn POPULAR RADIO SIM/Al- Set No. 7- - "Craig lied Blueprints with your new or renewal subscription for l'oetmnit 4 -Tube Reflex Receiver with Sodion Detector Tube" as described In February, 1925, POPULAR ItADtt), with which IS uoihlned 'i'ls IV in l .es Ape, accompanied by RADIO. recut bailee of $3.00. 'These Blueprints will maize it possible for you to build a tested Mull approved set, while POPULAR ltADlo for 12 Set No. S- "Cockaday Improved DX Regenerative months will keep you in touch with the progress being made in Receiver" (four tubes, dlstortionless automatic filament radio. control) as described In March, 1925, POPULAR RADIO. Set No. You, its it reader of Poirrl.Art RADIO, with which Is combined 9 "The Portable' Town and country Receiver" 7'ite (sir tubes. three stages of transformer IVirrl- t.s.4g'. know the tinily ent:rtaining, interest inc and instruc- frequency -sou pled. radio- t lye articles that are published ampllncat,ion, loop antenna) as described in .'ach month. Every Issue sonic new May, 1925, item Is sure to attract your attention. \Ve promise that through- POPULAR RADIO, out the coming months l'upt LAtt ItAnio will hold more and more Set No 10- -"Th,' 5 -T+Nr A -C Recover" (five A -C tithes, of interest for Radio leans. two stages of toned- radio -frequency amplifcation) as described in June, Ease, Economy and Accuracy in Construction 1025, issue of POPULAR RADIO. Set No. 11 -5 -Tube Tuned Radio- Frequency Receiver Simplified Blueprints were prepared tauter the personal supervision with .411101Ji -I Control, as described in August, 1925, of Laurence 11. ('Ob kattay. They make It possible for anyone, POPULAR RADIO. without previous knowledge of radio, to construct a highly efficient Use coupon below; indicate which radio receiver. Each set of Blueprints consists of 3 prints as follows. set of Blueprints you want. Panel Pattern POPULAR RADIO This Blueprint Is the EXACT size of the actual set. So accurate Dept. 99 that you need nu'r: lv lay It on your panel and drill as indicated. 627 West 43rd Street New You can readily appreciate the convenience of this Blueprint. No York City scaling or measuring to do, no danger of ruining the panel through faulty calculation. POPO 1, %n its 1)1 0, Dopt. 90 Instrument Layout tí27 Wust 43rd Street, New York City Dery again you have I P:nciosed is wry remittance of $ an actual size print of each instrument and scription, in full payment for sub - binding post and its exact io"atiori both on the panel and within with Blueprints as checked below, yREE. the cabinet. Even the cabinet structure is clearly shown. Sot No. 4- Cookaday Four - Set No. 8- Cockaday Im- c ireuit Tuner proved DX Re- Wiring Diagram with Resistance- generative Re- coupled The unusual feature of this Blueprint is that It Is an actual size Amplifier. oeivor. picture diagram of the finished Set No. 6- Cookaday 8 -Tube s.tt. Each Instrument and other Super -heterodyne Set No. 0- "The P o r table parts appear In (out size and the wires are so clearly traced from one Town and Coun- contact to another that you can connect Reflex Receiver. all terminals accurately Set No. 7 try Receiver." without even knowing how to read a hook -up diagram. -Craig 4-Tube Re- flex Receiver with D Set No. 10 -"The 5 -Tube Set No. 4- "Cocltadatt Four- eircutt Tante with Rests - Sodion Detector A-C Receiver." tance- eoupled Amplifier" (five tnbc9. distortionless, Tube. two dials, automatic vacuum tube control) as de- Set No. 11 -5 -Tube Tuned Radio -Frequency Receiver with scribed in October, 1924, POPULAIt RADIO, Simplified Control. Set No. 0 -' Cockaday 8 -Tube Super- heterodyne Reflex' Name Receiver" as described in January, 1925, POPULAR RADIO. Street City State

411 apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 65 1i "WiRI..ii.rW/l./l/l/l/l/l/l/l/l/l/l/l/l/l/l/lA/l/l/l./l/ .\rol NMI e.lrArArAr.Ar.Ar.l r.1r.Ar.1,.A,.Ae.\r.Ar.A/.A/.ArArA10Ar.Ar.Ar.lr.Ar\r.\r.\r.ll/l//l./ r1 r.\ Ìi1 .i. Ì i\ .i.1/01 4 /.\ , o\ ION.i. i .:. ei el ION ,.I.:: .:. ;;l, rl:: The Kurz -Kasch Aristocrat . :: .:. l./,., Wee Dials and Knobs :; .:. o\ rl.:. r.t. :: .:. ../ á i:I .:.,.1 dea r.l ro\.s1 .:. ili . :. i:é .:. é ii .i.r1 r.A WON i:á .:. %AP urea iS rl.:. r.\.:. .:. .éi .:.ifOw i:,.A .:: .:.ION \ .:.Wed iY .:. i: ION i:i l/ IMP :: The Choice of the Leading ;:: :I;:: l/:: . :. Set Manufacturers ::: .:. ;:: . :. Last season over two hundred markings have all combined to of the leading radio manufac- make these products the leader. :i iIAN turers equipped their products i: li See -The New Aristocrat NOVO i:s with Kurz -Kasch Dials. 'r: .:. These manufacturers had the E -Z- TOON l/ "The Key to Simplified Tuning" %i\ world to choose from -they S: r.\ . chose "the best " -Kurz -Kasch This has a 50 to 1 Vernier that O. .:. Aristocrat. makes possible that close tuning i:w r.Aá The exclusive patented split so desirable and necessary to ,1. :: r.\.i. bushing which not only holds separate stations. i::l/ the dial tight on the shaft but Write for illustrated folder on .:. W.\ .:., assures perfect alignment. complete line. . :: /:i The beautiful lustrous finish - Your dealer will gladly show :i i:a the exquisite perfection of the you these Kurz -Kasch products. l/': r.\.:. .:. l/i: :; THE KURZ -KASCH COMPANY : .:: r.\ The Largest Exclusive Moulders of Bakelite ::: rolo::. Main Office and Factory - - - - DAYTON, OHIO , \/l/l/l/l/l/l/l/l/l/l/l/l/l/l/l/l/l/l/l/l/l/l/l/l/l/l/l/l/l/l/l/l/if::. r\é Muff1 (Mg e\e.1 r.\r.Ae.Ar.\e.Ar.\r.Ar\r.\e.\ro\rAr.\r.1 r.Ar1 r.\r.Ar.\r.Ar.1 torr.\ r.\r.\r\r.ar.1 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 66 The Best in Radio Equipment

Q_Arnnouncing- `115eZliilson' 3" ® at_ --e=

"The Wonder of Niagara" ARAGAIN This new unit will be welcomed by all set RADIO RECEIVER owners, who are looking for a device which will eliminate all "B" battery troubles. It The Set of Satisfaction is guaranteed not to set up the slightest hum in Combining extreme selectivity and exceptional tonal receiver. quality with ample undistorted volume, easily the trolled. con- It supplies uniform voltage at all times thus $180.00 f. o. b. Niagara falls insuring better reception. Nothing to adjust. Some territory still open No moving parts to break or get out of order. No AUTOMETAL CORPORATION acid to spill. No voltmeter or hydrom- 311 Falls eter necessary. Will not affect your neigh- St. NIAGARA FALLS, N. Y. bor's set. Requires no attention whatever, except to switch it on or off as you want to use your receiver. It fits all sets. In handsome, walnut case. Price $35. Write direct, if your dealer cannot supply you. 'The Andrews

The coil of ideal characteristics. Has exceptionally high ratio of inductance to resistance. Losses are negligible. Gives maximum range and volume with entire freedom from distortion. Increases selectivity and greatly improves tone quality. Used in the famous Andrews DERESNA- DYNE Receiver. Can be Pats Pend. used in most standard hookups. Price $3.00. Get blueprints of tested hook -ups specifying this coil from your dealer or write direct.

DuceSpira 15 `lding k}op

Handsomely finished in silver AMPP' TE and mahogany. The "SelfAdjusting" Neat and compact. An Rheostat ornament to your set - AMPERITE controls the flow of current through not an eyesore. Folds the tubes automatically just as the heart controls readily and can be used the flow of blood through anywhere. the body. Does away Has silvered with hand rheostats and filament meters. Elimi- dial graduated in degrees. nates guessing and all tube worry. Prolongs tube Even if you have an out- life. Lowers set cost. Proved side and adopted by more aerial, you will have than 50 set manufacturers. For perfect filament con- many occasions to use a trol you must use AMPERITE. $1.10everywhere. DUO- SPIRAL. It will reduce static and help to cut out undesired stations. RADIALL COMPANY There is a special model for every circuit. Write Dept. P. R.12, 50 Franklin Street, New York, N. Y. direct, if your dealer cannot supply you. Write for FREE Maiie Units Enc® Hook -ups 1301 First Avenue Maywood, Ill. Perkins Electric Ltd., Montreal Toronto Winnipeg the "S ELF ADJUSTING "Rheostat All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com Padr l.lttrpmr°siì L

announcing the BalkiteTnckle Charger at $10 and the new Balkite"B"ae $35 The Balkite Battery Charger is today the most popular charger on the market. It is the only charger corr,monly used while the set is in operation. Balkite "B "II is also well ;1. S. I'atent U.S. Patent known. It replaces "B" batteries entirely and May27. 1924 supplies plate current from the light socket. We now announce the Balkite Trickle Charger at $10. This low -rate charger is especially adapted to use with sets of rela- Balkite tively low "A" current requirements -dry Trickle Charger cell sets and storage battery sets with few Balkite "B" Charges both 4 and 6 volt tubes. Owners of dry cell sets can now make Radio "A" batteries. Will Eliminates "B" batteries. furnish more current than a very compact and economical installation Supplies plate current is used by 6 dry cell tubes, a from the light socket. Op- if used only while the set with a Balkite Trickle Charger and low erates with either storag° is in operation. If allowed capacity storage battery of the type offered battery or dry cell tubes. to "trickle" charge con fall. Keeps "B" circuit always tinuously will also furnish by battery manufacturers this operating at enough current for 8 stor- maximum ef- age battery tubes. Size 5% We also announce the new Balkite "B" ficiency. Requires no attention other than adding in. long, 2 in. wide, 5 in. sets of high. Operates from 110- at $35. This new model will serve water about once a year. 120 AC 60 cycle current. five tubes and less. It fits in your present Will serve any set of 5 Manufacturers are of- tubes or less. Occupies fering switches which "B" battery compartment. about same space as 45 turn on Balkite "B" and volt dry "B" battery. Op- turn off the charger when erates from 110 -120 AC you turn on your set. Noiseless-No bulbs -Permanent This makes the current 60 cycle current. supply for both circuits All Balkite Radio PowerUnits are entirely Trice $35 automatic. no mov- Trice $10 noiseless in operation. They have West of Rockies, $10.50 ing parts, no bulbs, and nothing to adjust, or get out of order. Each is a perma- U.S. break Patent with nothing to Mny 27. nent piece of equipment 1924 replace. They require no other attention than the infrequent addition of water. They require no changes or additions to your set. They are guaranteed to give satisfaction. Balkite ttB" II by Sanie as the new Balkite Manufactured "B" but will fit any set FANSTEEI. PRODUCTS COMPANY, Inc. including those of 10 Balkite North Chicago, Illinois tubes or more. Operates from 110.120 AC 60 cy- Battery Charger clecurrent.Special model The most popular battery FAN TE E L for 50 cycles. charger on the market. It can be used while the ra- Price $55 dio set is in operation. Charging rate 2.5 amperes. Operates from 110- Tested and Listed as 120 AC 60 cycle current. 50 al kite by Special model for Standard cycles. Underwriters' Trice $19.50 RgdioPower Units Laboratories West of Rockies, $20 TRICKLE CHARGER BALKITE "B" BALKITE "B" Il BALKITE BATTERY CHARGER BALKITE

and approved by POPULAR RADIO LABORATORY All apparatus advertised in this magazine has been tested

www.americanradiohistory.com =2.50 1 1[ 1 1 t' t

"a good tube Jor u good set" a b.t,_ 1,ti 'Me \l.\(r\-\11:1\ are built Hith h oI IIt' KOHL.; the i,lCti,iton ,ot u tint. \\ All, h alit' ILL ,. it{ .tl,,,,_1t In)) Crlt'ti Itt.,,t .l, t,lrCltlll\ bi'Itlrt' tht, _ttt but thct It'.l\C the I,lctUr\. 1V11 call v.hat .1 Últlttelk r l}lc luclh r,i want till \l.klr\_11-kt\ a1td lli.tllul_lt,!!c' ;;t-t nito:-,t t tilt' and I. he brct uUt

111.11.1' I \,,LIE x l Connewey Electric Laboratories, hlaguatron Building, Hoboken, N. J. MACMATRONS

Something New EyEarirli Hornig Glass Insulated Terminal Strips " BARGAIN PRICES Just (wt uSthe { Dress- btgltadioCwtotog &Guide brimful of latest ideas, over WO newest hook - ups with illustrations -all free. Shows savings 2 connections S .50 Each includes a as high as 5U''Q un standard guaranteed radio 3 connections .65 harts, seta, kits. Mesure to get this thrifty hook glass tube, two 4 connections 6u le -fore you buy. It buta money in your pocket. mounting brack- Unusual? nn _o when you it. S connections 95 let Also ¡.Isaac' mend tutrloe of i . Lo fri -ti 1 R rit,- today 6 connections l.lu ets and all necessary machine 7 connections 1.25 screws and nuts rii BARAW I K COMPANY S connections 1.40 - 102. 109 5. Canes St., Chruao, U. 5. A. Au I t)11 1141(4.8 ON Al I'.., (.2i_,_ ;,..... K.,1i,r I' r, u.,., Set. .e J,.,.i.l,J ui 11)1'1'1 It k 11.)1(), Cuullctc. $59 50 C'1uru>trklad. ç -tutrc t. ( . kr.rivc'r 47 50 l l',lada) ti-tube SuF,eiherrud)'me C,..I...d.,- ,-tubr 74 50 0 G O O Ciicuit . 67 00 l'ut.c I+ 4- ouiuK I)rale 35 00 O 0 0 g $.s, `,, ', u,.dy-ur-krtmlrr parte 52 50

11 ! I .i Itadvttr Kit with all parts 59 50 ç f,.! It,,,;,r Tully Nanirlcs> ll Genuine Low- Hornig Glass 42 50 Panels > I and Cabinets I' uprrhrtr,rdy-nt' Kit, Grnuinr Sangatnu pea 1%111, S.,fety B 1 ..,r t . l' -t, .1, i l 69 50 Ask for our Bulletns Parts all exactly as specified and of same brands or equal quality A. W. HORNIG brands as in original specifications. 3921 Dickens Avenue, Chicago, IU. Tel Spuldlns THE BARAWIK COMPANY 3156 102 -103 S. Canal St., Dept. PR., Chicago, Hl.

All apparatus advertised in this mal;asine huy been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 69

You Need Quality in the Base Panel use of a base panel makes possible shorter, neater and more effi- THEcient wiring. But the panel must be an insulator of the first VERI.CHROME PANELS It must be free from any By the purchase of a con- quality that will not deteriorate with time. trolling interest in the Veri- tendency to absorb water to function properly in damp, humid weather. Chrome laboratories, the It must not warp or distort, disturbing the angle of the coils and the financial and production re- arrangement of the apparatus. sources of the Formica Insula- tion Company have been are sure of getting all of those placed behind this remarkable There is one panel material in which you new process for decorating essential qualities -and that is Formica. radio panels. Elaborate decorations can be produced For years it has been accepted by the vast majority of leading radio much more rapidly and more manufacturers, as mechanically and electrically the best available economically than by engrav- material for radio panels. It also is the most handsome, and its finish ing. Decorations designed by crack or lose its lustre with the leading American artists is entirely permanent. It does not check, are offered. Tuning scales time. may be marked directly on the panel eliminating the Formica is evidence of quality, durability and genuine worth in any standard dial and substituting pointers instead. The reduc- radio apparatus. tion in cost is large. Write for prices on complete panels Dealers: Home set builders who want the best results finished in this way in quan- want Formica. It has been for years a highly profitable tity. line for thousands of dealers. THE FORMICA INSULATION COMPANY 4641 Spring Grove Avenue, Cincinnati, Ohio and all the leading set Formica has high mechanical strength Formica is used by nearly 5 in use. 1 makers -and has for years been used by will not break more set makers than any other ma- Formica will not sag from heat or cold flow terial. 6 under pressure. It retains its dimensions. Everything you fasten to it stays tight and Formica is unaffected by weather and time precisely where you put it. 2 lasts forever. -it P7 Formica panels are sold in neat craft paper Formica in appearance is the finest of all envelopes which assure you that you are 3 panel materials and always remains so. getting the genuine. approved of every kind Formica is one of the most widely Formica's electrical qualities Q materials in radio. 4 far exceed any possible requirement. SALES OFFICES Minn. New York, N. Y. 1026 Second Avenue Minneapolis, 50 Church Street Ill. 725 Bulletin Bldg Philadelphia, Pa. 9 South Clinton St Chicago, Baltimore, Md. Bldg. Cleveland, Ohio 708 Title Building 516 Caxton N. Y. 585 Mission Street San Francisco, Cal. 327 Cutler Bldg Rochester, Building Toledo, Ohio Avenue Pittsburg, Pa. 419 Ohio 422 First Boston, Mass. 309 Plymouth Bldg. .. New Haven, Conn. 6 Beacon Street Whitney Central Bldg. New Orleans, La. 55 Calle Obispo Habana, Cuba

Hear the Formica Or- chestra over W L W every Tuesday evening from 9 to 10 Central ORM C Standard Time. Made from Anhydrous Bakelite ®ski SHEETS TUBES s

tested and approved by POPULAR RADIO LABORATORY All apparatus advertised in this magazine has been

www.americanradiohistory.com 0 ' The Best in Radio Equipment

Elmo N. Pickerel], Chief Radio Officer, S. S. Leviathan - a former Radio Insti- " WINDHAM " tute of America man. WIRE FORMER (Patent Pending) A complete íi# and handy tool f o r electricians, radio set builders and mechanics. It will accurately form loops or eyes for No. 4, 6, 8 and Radio 10 screws, slake easy radius and sharp right angle bends, has flat Needs Men jaws and wire cutters. "We can't get radio operators fast This tool is made of the enough," said a big man in a company best quality steel, that drop- employs thousands of operators, ped forged and care- mechanics, repairmen and executives. fully tempered in oil. The tremendous expansion of the radio industry is daily creating new Price $1.25 Each vacancies for operators and causing Manufactured by rapid promotions right up the line. THE GOYER COMPANY Your Chance is Here Willimantic Connecticut Prepare yourself for a pleasant and profitable life career in radio. In the past sixteen years the Radio Institute of America, (directed by the Radio Corporation of America) has turned out 7,000 finished operators -with U. S. Government Licenses -men who have met with marked success in radio. Study at Home Don't let your present employment interfere with your ultimate future. Absolutely warranted to Study radio in spare time. The Radio protect your set from light- Institute of ning, with a guarantee to America offers the finest pay and most up -to you $100 or repair -date instruction given your set, should it be anywhere. The coupon will bring damaged through any complete information. fault of the FIL -KO- ARRESTER. Radio Institute of America Listed as standard under the (formerly Marconi re- examination service of Na- Institute) tional Board of Fire Under- 322A Broadway Established in 1909 New York writers. If your dealer has none send his with remìllanee name 1 CUT HERE ------) to Dept. PR -9Z5 Radio Institute of America DX Instrument I 322A Broadway, Co. N ew York City Harrisburg, Pa. I Please send me full inf about your Home Study Course of radio instruction. I I am interested in the complete course, including instruction. code I am interested in the technical course, without instruction. code Name Address

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 71 This special insulation made to order for radio - -now built into a line of low -loss parts THE first choice of thousands of successful set builders is Radion Panels -made of Radion, the insulating material built to order by our engineers for radio exclusively. Now we announce new developments in radio parts made of this perfect insulation that practically reduces losses in reception to a minimum. These parts have the wonderful Radion finish, smooth and high -polished. This finish eliminates those losses caused by moisture gathering on the surface of ordinary insulation, causing leakage paths. The high- resistant characteristics found only in Radion Panels also mark these new parts. You can now get Radion Sockets, Radion Dials, the new Radion Loud Speaker Horn, Radion Tubing, Radion Binding Post Strips, Insulators, etc. And, of course, Radion Panels (made in The Radion Built -in Horn Mahoganite) come cut in standard takes up small space in the black and cabinet and gives clear, sizes for whatever set you wish to build. rounded tones. Ask your dealer to show you these new Radion parts. Practically every radio store carries Radion Panels and will gladly get any of the new Radion Parts if it hasn't them in stock. Send for Booklet, "Building Your Own Set' MANY set builders have written us that our booklet, "Building Your Own Set," is the most practical and helpful they have seen. It gives wiring diagrams, front and rear views, shows new set with slanting panel, sets the Radion Built -in Horn, list of parts and direction with the The new No. 10 1 -inch Radion for building popular circuits. Mailed for 10c. Send built to Close - Tuning Dial, today. conform to the fingers. We be- coupon lieve it is the most beautiful RUBBER COMPANY dial yet designed. AMERICAN HARD Dept. B9 11 Mercer St. New York City AMERICAN HARD RUBBER COMPANY Dept. B9 11 Mercer Street New York City Please send me your booklet, "Building Your Own Set," IRAD1ON for which I enclose 10 cents in stamps. Tie Supreme Insulation .Vainc, Made to Order for Radio Purposes Exclusively Address - - - - has been tested and approved by"POPULAR RADIO LABORATORY AU apparatus advertised in this magazine

www.americanradiohistory.com The Best in Radio Equipment

First in the Field Specializing in Cockaday Kits 303 Atkins Ave. . HAMMER RADIO CO , Brooklyn, New York Cockaday Sets Now Made Easier to Build by Our New "Ready -to -Wire" Plan 50% of Your Time, Work and Worry All you need SAVED! do is to connect bus -bar according to diagram, solder These Kits are sent to you completely and your set is finished. bakelite panel, mounted, and assembled on a Veneered Mahogany baseboard drilled and engraved; in a solid Mahogany Cabinet. Genuine parts and genuine specified by Mr. L. M. Cockaday. COMPARE OUR OFFER. used as listed below; exactly as 5 Tube New A C Receiver TUBE NEW COCKADAY General Radio Variorneter, No. 269 SUPERHETERODYNE 2 "Precision" R. F. Coupling Units 8 REFLEX RECEIVER KIT 2 Hammariund condensers, .0005 mfd. I General Instrument .0005 1 Daven Grid -leak Mounting ..$ 35 3 Kurz -Kasch 4 inch dials Condenser (Isolantite In- sulation) 2 Daven Resisto - Coupler 5 Federal Sockets, No. 16 $5.50 Mountings 2.50 1 General Instrument General Radio A. F. Transformer, No. 285 .001 2 Daven Resistors .5 Megohms 100 Condenser (Isolantite In- I Daven Resistor Dont_,an Special Step -Down Transformer, Type B sulation). 5. Megolims. So Daven 6.00 1 Daven Resistor .005 Megoluu- 100 Resisto- Coupler I Haynes mountings - Griffin input trans- 2 Daven Resistors .25 2 Dubilier Mica, former (new Megohut- I 00 fixed condenser, .006 mfd. type) 5.00 2 New York Mica Condenses, 3 Haynes Griffin ea. Daven resistor, % megohm, intermediate .0001 70 !6 megohm transformers Mfd Daven grid -leak, 4 megohms (new type) .. I5.00 4 New York Mica Condensers 1 Precision Autodyne Dubilier Coupler 3.50 .006 Mfd... 3.00 fixed condenser, .00025 mfd. -clips I Karas Harmonik Audio Fre- 1 New York Mim Dubilier Mica fixed condenser, .00015 fluency Transformer Condenser rnfd. 7.00 .00025 with clips...... 45 Dubilier Mica fixed I Amplex Grid -Denser .0005 condenser, .0001 mfd. 1.25 1 Duratran Radio Frequency I Benjamin Pacent single circuit jack Cle -ra -tone Socket t.00 Transformer... 4.00 7 Federal Sockets No. Genuine Bakelite Panel Drilled 16...... 8.40 1 Walbert "A" Battery Switch .50 and Engraved 7 x 24" 1 Parent Double Jack... .60 7 Eby Binding Veneered Baseboard Posts . 1.40 1 l'acent Single Jack .50 1 Sub -Panel 1 x 9 Genuine Antenna Binding Post Strip 2 Na -AId 4 inch Dials... 1.50 Bakelite .15 Battery Binding I Anrsco Rheostat 2 Post Strip, small brass brackets. A C Ohms.... I 35 1 Baseboard (Hardwood) .35 I Anise() ..... Leads, Binding 14,sts. etc. Potentiometer 4110 Genuine Bakelite Panel, Drilled Ohms I SO READY -TO and Engraved.... 3 00 -WIRE KIT PRICE, . $52.50 UNASSEMBLED KIT PRICE, Write Us READY -TO -WIRE KIT PRICE X50 WIRED COMPLETE In Genuine Mahogany $74 Cabinet, Includingcluding Don $ WIRED COMPLETE gai Transformer and S McCullough A C Tubes HOGANY CAR, 00 W INCLUDING NORACH LOOP.. ET: $110 McCullough A C Radio Tubes in Stock COCKADAY'S Authorized ANTENNA COUPLER for the 8 Tube Super -flet for use $2.00 WRITE FOR CIRCULAR with outdoor aerial about these Parts and Kits. Also for Free Radio Catalog Transportation Prepaid. One -third must accompany all C. 0. D. orders. Not insured unless insurance charges included

FILTER

Want to make big, easy money? Learn how to install, operate, repair. construct CONDENSERS and sell Radios. Write now for facts about the amazing opportunities for Another remarkable Radio experts, and our special offer of a FREE 1000 -mile receiving set, and how example of Deutsch - you can quickly train at home by mail_ mann technical and Be a Radio Expert No previous experience necessary. Anyone scientific with ordinary education can now learn Radio skill quickly under our simplified home -study plan. We need men right now to represent our Condenser illustrated is Association. Be the Radio expert in your used neighborhood. Get your share of the big in connection with profits. Hundreds about you want Radios and "B" battery eliminators advice how to operate. You can earn enough -is light, durable, and in- money right from the start to pay for course. expensive. This marvel removes disturbing noises Nothing difficult about it. and in addition greatly increases the efficiency of Low cost and easy terms. sets so equipped. Each condenser is tested to show a resistance from 125 -150 megohms, and withstands a breakdown test of 750 volts D.C. One of a complete line of quality condensers of FREE all types for transmission or reception. 1,000 -MILE Manufacturers, manufacturers agents, and job - bers write for details. Receiving Set Don't miss this big special offer to supply FREE all parts necessary to construct a high -grade 1000 -mile receiving set. You can TOBE DEUTSCHMANN sell this set alone for practically the entire C. cost of the course. Send for the facts now. CORNHILL BOSTON Find out all about this big -pay field. Address Radio Association of America 4513 Ravenswood Ave., Dept. 59 Chicago, III. All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment VitalPdrts ofleading Radio Sets Nowhere is the axiom "an article is no better than the parts it contains" more true than in the radio world. So it is not surprising that leading manufacturers of radio sets choose the accessories for their hookups only after gaining a full technical knowledge of their make -up and the results they give. In full consideration of this, the choice of Benjamin Radio Products, above all others, by the manufacturers of many of the finest modern radio sets, bespeaks eloquently of their worth as practical radio parts made by one of the oldest manufacturers of electrical goods. Each has been made a super radio part -to secure for the owner of the set the purest, loudest and clearest radio signals possible. Used together, their total efficiency spells the acme of selectivity, tuning range, the elimination of disturbance and distortion, and the reduction of radio losses. And, the logical total of these many worthy features is "Better Radio."

120-128 S. Sangamon Benjamin St., Chicago / 241 W. 17th Street New York Electric 448 Bryant Street San Francisco Mf¡g Co. Manufactured in Cenada b; the Benjamin Electnc Mfg. Co. of Canada, Ltd., Toronto, Ontar,o

BENJAMIN Tuned Radio Frequency Transformers Low Resistance - Low Distributed Capacity Wires are space wound, adjacent coils are parallel, air insulated and so separated that while capacity is reduced to a minimum, inductance is maintained at a high point of efficiency. Greater Tuning Range - Greater Selectivity These coils are very uniform, both in inductance and distributed capacity, so that if desired they may be geared for single control of the three tuned stages. A minimum amount of material is used in the field of the coil, and an anti -capacity cement is used only where the wires cross. Coils are coupled so as to reduce capacity coupling to a minimum. Green double silk covering provides high insulation and gives a fine appearance to the coiL Benjamin Benjamin Cle -Ra -Tone Sockets Low -Loss, Long -Range Condensers Benjamin Cle -Ra -Tone Sockets prevent the transmission of positive control of minute changes in condenser deli- Definite and outside vibrations into microphonic disturbances. Four capacity. By the use of cutaway plates this condenser spreads cately adjusted double springs support the socket -"float" it the broadcast frequencies over the lower end of the dial and in this way eliminates the bunching of stations within a few above the base -and absorb all jars and shocks. An absolute degrees. This cutaway feature aids in obtaining sharp tuning necessity in portable sets. Used by leading manufacturers by making tuning easier. Minimum insulation is used and leakage must go through long paths outside of strongest field. and recommended by radio engineers in their most popular Unpolished silver plate finish. Small size of condenser hookups. There are no rubber parts to deteriorate. Bake- makes it adaptable to any set, regardless of crowding of lite is used wherever possible to in- apparatus on sub - panel. Friction disc sure sturdiness, long life and high in- on rotor shaft adjusts sulation. Handy lugs make soldering tuning tension with- easy. Stiff bus wiring does not affect out throwing rotor plates out of align- the flexibility of the Cle -Ra -Tone ment. Drilling tem- springs. Furnished also in plate furnished with gangs on Bakelite sub-panels each condenser. Made in three sizes: for compact set building, as when mounted on Benjamin 13 plate for .00025 Mfd. brackets there is plenty of 17 plate for space underneath for .00035 Mfd. mounting accessory 25 plate for equipment. .0005 Mfd SPRING SUSPENOCD SHOCK ABSORBING 1

and approved by POPULAR RADIO LABORATORY All apparatus advertised in this magazine has been tested

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THE TUBE WITH A SENSIBLE GUARANTEE BLUEPRINTS FREE! The Improved Cockaday DX Regenera... tive Receiver. Portable Town and Country Receiver. 5 -Tube AC Receiver. 5 -Tube Tuned Radio -Frequency Receiver with Simplified Control. The POPULAR RADIO (with which is combined The Wireless .lge) TECHNICAL LABORATORY has prepared complete sets of Blueprints for the four Recei "ers named above. Each set consists of three Blueprints as follows: A -Panel Pattern (actual size), B- Instrument Layout (actual size), C- Picture Diagram (all parts actual size) showing all wire connections. The Improved Cockaday DX Regenerative Receiver (Set No. 8), 4- tubes, distortionless, automatic filament cuts down tuning controls and at the same time embodies features that eliminate the trouble experienced with this type of Receiver. This is one of the most reasonable sets to build. The Portable Town and Country Receiver (Set No. 9), 6- tubes, three stages of transformer -coupled, radio- frequency amplification, with loop antenna, is a single control set for all- around home use, besides embracing a portable feature that makes it an unburdensome companion for the camp, cruise or motor tour. The 5 -Tube AC Receiver (Set No. 10) with 5 "McCullough" AC Tubes, two stages of tuned radio- frequency amplification, operates directly from a special step -down transformer, which can be plugged into an AC lighting socket. There is abso- Ai Supertron to your dealer and lutely no hum produced and no "A" battery is used. The watch him smile-notice how Receiver contains only three dials and can be logged. The 5 -Tube Radio -Frequency (Set No. 1 1) different he will serve yo 1. So con- is a set particularly recommended because it will not radiate even though it fident. Ile will make s Ire that the uses regeneration. Operation has been simplified by using a minimum of panel n Imber on controls. A special type of amplification the t Ibe corresponds has been used to give distortionless reproduction. w th the number on the guarantee Any one of these sets of Blueprints will be mailed promptly, absolutely free ce tilicate . . Ah! If he of charge, if you will send us one annual d. es not scription sub- smile for POPULAR RADIO, with which is combined The -If he is not confident. or Wireless age, accompanied by a remittance of $3, the regular says ' try this, it's just as g. od," subscription price. The subscription may be new or renewal -and for a limited then y lu time will include REE any set of Blue- must insist on Supertron prints described on page 86. Only one set of Blueprints -yo it dealer is obligated to you in will be allowed with your own subscription. c inside ation of your patronage. Two sets of Blueprints for 2 annual subscriptions with 0000 remittance of $6; three sets of Blueprints for 3 annual sub- Genuine Supertrons scriptions and remittance of $9; all four for 4 annual sub- are serial U. S. A $ao., scriptions and remittance of $12. numbered for your protection. Canada $2.7, You know how helpful, interesting and practical POPULAR AT ALL GOOD RADIO is. You fully appreciate that at $3 a year it is a real DEALERS bargain. Consequently you should find it easy to convince one, two or three friends of the unusual value offered when SUPERTRON MFG. CO., any one of these four sets of Blueprints is included free 222 -228 Washington St., with their twelve month order at the regular price of the magazine alone. So get busy today and see if you can't Hoboken, N. J. mail the coupon for your Blueprints tomorrow. Export Division, 22!) Broadway, New York City. Factory Branches POPULAR RADIO Throughout the United States 627 West 43d Street - - New York City 00.)00)00000>>>4O 000000000000 0000000090000 00000000004.,00004444Y4 Distributors POPULAR RADIO, Dept. 93, 627 West 43d Street, New York Fireside Radio Set Co Chicago M. Baker& Son Syracuse City. Yahr& Lange Drug Co .. Milwaukee M. H Johnson Electric Co....Utica Enclosed is my remittance $ The Roycraft Co...... Minneapolis of covering annual sub- Hin' dill Electric Co Troy scriptions for POPULAR RADIO with which is combinedThe Sorenson Lamp Co Des Moines American l'honograph Co...Albany Age. Wireless Hippee- Staten Auto Des Moines Rosen Talking Machine Co.. Boston Additional names on sheet attached. Kindly send me the Urr Bros Cedar Rapids Balt. Hub Wheel & Mfg.. Baltimore following sets of Blueprints: Radio Dealers Sup San Francisco Cycle Auto Supply Co Buffalo E Set 8 Western Light & Fix Los Angeles H. D. Taylor Co Buffalo No. -The Improved Cockaday DX Regenerative Franklin Elec. Sup. Co Phila. Hamburg Bros Pittsburg Receiver. Keystone Radio Dist. Co Phila. Reynolds Radio Co Denver Allentown Radio Dist. Co Allentown Burr -Fowler Syracuse Set No. g- Portable Town and Country Receiver. (ìoodlin Auto Sup. Co...gtouth Bend Ed. J. Goetz Co Cincinnati Fort Wayne Iron Store.. Ft. Wayne Elgin Radio Corp Elgin Set No. ro-s -Tube AC Receiver Swanson Electric Co Evansville Set No. r r -s -Tube Tuned Radio -Frequency Receiver with Exhibiting at National Radio Exposition Simplified Control. Grand Central Palace, Sept. 12 -19 Name Addreso City State SU f'E RT R ON. (No extra charge for Canada. Foreign countries so cents, magazine postage A S fi R i A l NUMBER G U A R A N T E E extra.)

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment

Ina Haw Tim %IRETON REG U S PAT OFF

To be both Rich ind Beautiful is an accomplish- ment. The new Timbretone is just that. Two years ago we inaugurated a speaker made on the principle of the violin with a small horn. We now announce a cabinet type -only 4 inches high, to be placed on top or bottom of your present set and -harmonize without obtrusiveness.

It is a welcome innovation for those who have a set and desire the "console" feature without the resultant high cost. It is the "Baby Grand- of Radio. List price in United States (east of Mississippi river), $30.00. Dealers and jobbers -write for advance information.

Made in Hoosick Falls, N. Y. by the TIMBRETONE MFG. CO.

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 7O The Best in Radio Equipment A RADIO CABINET OF BEAUTY AND ELEGANCE DIRECT TO YOU AT LOWEST COST Lid splined both end to prevent warping. Nickeled piano hinge. Nickeled lid support of artistic design. Anti -vibration cushion feet (not visible in cut). Edges of lid moulded to match bottom. Shipped securely packed in strong carton. Prompt shipment. Hardwood, Rubbed Solid Black Mahogany American Finish Walnut 7x18x7'2 or 10 in. deep $3.50 $5.00 7x24x712 or 10 in. sleep 4.00 5.50 7x26x732 or 10 in deep 4.75 6.25 7x28x7!2 or 10 in. deep 5.50 7.00 7x30x7'2 or 10 in. deep 6.00 8.00 c'As11 WITH ORDER or C. O. D. if 'a of price is sent with order. Prices F. O. B. Hickory, N. C. Order express shipment, often cheaper than mail and much safer from damage. FREE WITH EACH CABINET a glued -up stock non- warping i2- inch BASEBOARD. Free Catalogue. THE SOUTHERN TOY COMPANY, INC. Dept. P. HICKORY, NORTH CAROLINA BROADCAST LISTENERS THE POPULAR RADIO ATLAS AND LOG will give you a list of all the NEW Broadcasting Stations with wavelengths and other necessary information

O receive the full benefit of your set you should have articles of interest to Radio Fans. With POPULAR RADIO a complete log of the principal broadcasting stations and the "POPULAR RADio International Radio Atlas and T and a convenient place to note your dial readings when Log" you will have available the two most useful adjuncts you "pick -up" any of them. to full enjoyment of your radio receiver. A Complete Atlas and Station Log SPECIAL FREE OFFER The "POPULAR RADIO International Radio Atlas and Log" will supply you with full information regarding broadcast- You may have a copy of the "POPULAR RADIO Inter- ing stations of the United States and Canada. national Radio Atlas and Log" free, with POPULAR RADIO This most useful and practical Atlas, consists of 16 pages, for (8) eight months size 12" x 15" printed on good paper, from clear type in two For Only $2.00 colors and contains a complete series of double page maps, Pin $2.00 in bills to the coupon below. including -The World -The United States- Canada- North and South America, showing location of principal If you are a subscriber to either POPULAR RADIO or The broadcasting, leading commercial and governmental radio Wireless A ge, your subscription will be extended eight months. stations. In addition these maps show time zones and Radio Districts with Headquarters and also the district ------zoning of the American Radio Relay League. Date a list of all Ur ted There is also included in this Atlas POPULAR RADIO, Dept. 92, States and Canadian stations, alphabetically arranged, 627 West York City. wave lengths, kilocycles, ownership and 43d St., New giving signals, Enclosed is my remittance of $2.00 for which you are to other important data, with space for logging three dial outer my subscription (extend my subscription) for (8) eight readings. months for POPULAR RADIO and send FREE a copy of the The Leading Radio Monthly .POPULAR RADIO International Radio Atlas and Log." In POPULAR RADIO, with which is combined The Wireless Age, each month you will find the very latest news of the Name field with many interesting and instructive radio entertaining, Address POPULAR RADIO City State 627 West 43d Street New York City

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

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A EFFICIENCY On Long or Short Waves For 2 to 60 meter receivers, such as which fits a tube for both types are being built at the Brightson Labora- reception. tories to communicate with \\NP, the McMillan expedition, the tubes must 10 Day Return Privilege be dependable. They must be well Lnlc-s True Blue Tubes prove c matched, noiseless, and have a high int r- amplification constant. changeably uniform. noiseless, cryq.rl Ordinary un- clear in tone and the handsomc.t, iform tubes cannot be expected to finest quality work efficiently on such short wave- tubes you have ever used. you can return them in ten days lengths. for refund. Brightson True Blue Tubes have been developed with characteristics making 60 Day Guarantee them more efficient on low wavelengths Whether you buy one True Blue Tube than any other tube available or a set of three, to the amateur. Constant short -wave five, six or night experimentation in a safety case, each individual tube in the Brightson is covered by its Laboratories has shown the possibility own Brightson guarantee. If within 60 days a mechanical of making a tube, which, while more defect prevents efficient than any True Blue "l-ube ordinary tubes on broad- from operating perfectly, you can re- cast wave -lengths, is also more efficient turn it for replacement. on extremely low wavelengths. A mutual conductance value, efficient on If your dealer does not stock True very low wave -lengths. will not func- Blue Tubes write us direct. Prices, 6 tion properly on high -powered low volt type "Power Plus- for

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com /b The Best in Radio Equipment ICtSI By WESTON CONCERNING J Radio Voltmeter BURGESS BATTERIES The unique position of esteem and confidence occupied by Burgess Radio Batteries is a natural devel- Model 506 opment for panel of the conservative policy mounting, which has characterized the manu- 2 inch diameter. facture, advertising and sale of Single scale. Burgess products. Of interest, perhaps, to the thinking battery buyer is the fact that no Burgess product is advertised or sold until its merit has been proven, No guess at battery and tube voltages or tuning conditions with a Weston Radio not only by our own Panel Voltmeter. rigid tests, but also those You are sure at every instant of just how effi- of the foremost radio engineers, manufactur- ciently, safely and economically your set is operating. Get the facts of radio reception. See it at ers and experimenters in the country. your dealers. Send for the booklet: Radio Instruments." "Weston Through friendly criticism and suggestions, Weston Electrical Instrument together with extensive research and engin- Corporation 115 Weston Avenue, Newark, eering by the C. F. Burgess Laboratories the N. J. efficiency of Burgess Batteries has increased STANDARD THE WORLD OVER to a degree which we believe is not equalled elsewhere. WESTON 9'nurrl'I. stn(i' /SSS c4sk crny `Radio Engineer BURGESS BATTERY COMPANY ENGINEERS DRY BATTERIES - MANUFACTURERS FLASHLIGHT - RADIO - IGNITION - TELEPHONE GENERAL SALES OFFICE: HARRIS TRUST BLDG.. CHICAGO MAKE MONEY LABORATORIES AND WORKS: MADISON. WISCONSIN BRANCHES Right now, there is an opportunity in your locality NEW YORK to profitably BOSTON KANSAS CITY MINNEAPOLIS devote your spare time or all your WASHINGTON time to PITTSBURGH ST.LOUI$ a pleasant, easy and profitable business - IN CANADA one that does not require any training or capital. PLANTS: NIAGARA FALLS AND WINNIPEG The publishers of POPULAR RADIO, with which is FUInb1InC(l THE eRMICHES: TORONTO MONTREAL ST. JOHN WIRELESS AGE, offer you an opportunity to become their local representative to take care of expiring subscriptions and new subscriptions for POPULAR RADIO and the four other popular magazines that they publish. SALARY AND COMMISSION All material will be furnished you free of charge and you will be paid an attractive commission salary. and Mail coupon for full particulars to POPULAR RADIO 627 West 43d ST. NEW YORK CITY

POPULAR RADIO, Dept. 96, 627 W. 43d St., New York City Send me full particulars regarding your salary and commission offer to local representatives.

Name

Address

All apparatus advertised in /Iris magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipmeni 79 B-T Tandem Condensers 1

B -T Tandem Condensers provide the essential elements of balance required to make this type of unit a success. Design and craftsmanship show the usual conclusive evidence of B -T's sense of obligation to the purchaser. LD -13 (.00025 M. F.) $9.00 LD -17 (.00035 M. F.) $9.50

The B -T "Counterphase" Circuit

The new B -T "Counterphase" circuit (covered by U. S. Patents) employs the "Torostyle" Transformer. The combined results exceed anything we have ever done before. (Described in "Better Tuning. ") .7OROSTYLE' FOR EASY VI RING B -T Resistances The highest grade Non -Inductive Variable High Resistances, Potentiometers and Modulators are now, under license, in the B -T line. Stepless -Noiseless- Stable. All sizes $2.00. Straight Line Frequency vs. Wave Length Three articles so far noted on Straight Line Frequency Con- densers in national magazines, omit or evade the most important considerations. We build both kinds and tell both sides. "Better Tuning" 8th edition tells the whole story. Issued bi- monthly. Copy 10c. Per year 50c. Bremer -Tully Mfg. Co. 532 South Canal St. Chicago, Ill.

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 60 The Best in Radio Equipment New Tubes from Old! Just think, now you can take your old, run -down tubes -tubes you formerly threw away -and give them the same snap and pep they originally had. That's what the Rhamstine* Tube BOOSTER will do for you, whether you use 201 -A or 199 type tubes. Works on any alternating current of 110 to 120 volts, 50 to 133 cycles- the ordinary electric light circuit. You can soon pay for it by boosting tubes for your friends and neighbors. Check the coupon below, pay on delivery. Better Than "B" Batteries Silky smooth reception free from the annoyance of run -down batteries- that's Rhamstine * what you'll get when you use the Rham- Tube Booster stine* 'B" RECTIFIER for your source of B- power. Operates on any electric light circuit of 110 volts AC, 60 cycles. Detector Only '6 voltage range from 0 to 50; amplifier 0 to 110. Use it on any tube set. Check the coupon below, pay on delivery and try - - out the "B" RECTIFIER for five days. If you ------are not entirely satisfied, return and THOS. RHAMSTINE* Rhamstine* B RECTIFIER it Rham- (Woodbridge at Beaubien, (9) Without stine* will refund your money. Mail the Detroit. Mich. Tube coupon now -before you forget. Please send me your ( ) Tube Only $25 4.0 BOOSTER at 86. ( ) B" RECTIFIER at 825 by express C. O. D. subject to inspection. If I am not entirely satisfied with the "B" J. THOS. RHAMSTINE * RECTIFIER I will return it to you i.t five ays and receive a refund of the full purchase Woodbridge at Beaubien prdice. Detroit, Michigan "NAME i ADDRF_ti,,,

TELL YOU LET COCKADAY THE ANSWER I'OPCI. ut It &Dto maintains for the benefit of its readers a subject, writing on one side of the paper only, and enclose a Technical Service Bureau and I.aboratory, under the per- self -addressed and stamped envelope. sonal supervision of Laurence M. Cockaday which will, It is possible that your individual problem has been covered without charge, answer by personal letter any question, in an issue of POPULAR RADIO, and so as an aid to you we problem or request for information submitted by a sub- endeavor to keep a supply of back numbers in stock. The scriber. This service is, however, also available to readers, condensed index below gives a few of the subjects that have other than subscribers, at the very nominal rate of 50 cents appeared recently, look this list over and if the information the inquiry. you want is covered, we will be pleased to supply back In writing please confine your questions to one general numbers at 35e. a copy. October, 1924 February, 1925 May, 1925 -How to Build the (Cockaday) Four Circuit -How to Get on a Radio Program. -Factors That Affect Antenna Capacity. Tuner with a Resistance -coupled Am- - A Loudspeaker for a Crystal Set. -How to Wire Your Home to Have Radio plifier. - How to Build a 4 -tube Reflex Receiver in Every Room. -How to Select a Readv -made Receiver. with the New Sodion Detector. -Handy Tools for Radio Fans, The Hydrom- -How to Build a Detector -amplifier. - Cockaday Article for Beginners. eter. -A Radio Set to Pack in 1 our Suitcase. -How to Build the "Portable Town and -Harnessing the Radio and the Movie. March, 1925 Country Receiver." -How to Build the Improved DX Regenera- June, 1925 November, 1924 tive Receiver. -New Development in Vacuum Tubes. -How to Locate Interference from Power -Factors that Govern the Capacity of -How to Build a Five -tube A-C Receiver. I.ines. Condensers. -How to Draw Up Your Own Tuning -Cockaday Article for Beginners. -What "Induction" Means to Your Set. Chart. -How to Build a Low -loss Tuner for Short- -A Five Meter Vacuum -tube Transmitter -Watt's Law in a Nutshell. wave Reception. and Receiver. -"What Set Shall I Buy?" -The New Type of Superheterodyne. April, 1925 First Installment. December, 1924 -Single Control Receivers. July, 1925 now to Build a Non -radiating 7 -tube -How to Improve Broadcast Reception, VI: -The Best 101 Hook -ups. Superheterodyne Receiver. Increasing the Selecting Power of Your -"What Set Shall I Buy?" - Cockaday Article for Beginners. Receiver. Second Installment. --How to Get the Most Out of Your Ready - -How to get the Most out of Your Ready - -Broadcast Stations in the United States. made Receiver. made Receiver. What's New in Radio Apparatus. -Quartz Crystal as a New Wavelength - Standard. August, 1925 January, 1925 -"Motion Pictures" by Ether Waves. Ilow to Build the Cockaday 8-tube Super- -A New Type of Hornless Loudspeaker. heterodyne Reflex Receiver. --Row to Build a 5 -Tube Radio- Frequency How to Improve Broadcast Reception. Set with Simplified Control. Cockaday Article for Beginners. -- Trouble Shooting. -Hints for Amateurs. 627 West 43d Street Dept. 98 New York City

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment

KINGIPI RADIO

Lute King Five Broadcast Receiver gives you all the joys of Radio- music, adventure, sport, education -every note of music in its full natural tone, each spoken word clear and distinct. You get it easily and surely, nothing is left to chance. The King Five Broad. The King Five Broadcast Receiver gives you the cast Receiver meets one station you are seeking and no other -its selec- Fifteen years of spec. every taste with three ialized work in Radio, tivity is remarkable. beautiful models - plus twenty years ex- employed has the approval of emi- Plain Table Type. The circuit perience in the manu- Built.in Reproducer. nent engineers as well as the endorsement of public facture of quality pre. Magnificent Console. demand. It can be operated by anyone regardless of cision products is Offered in Mahogany age or knowledge of radio. When a station is once behind our guarantee the King Five and Walnut. received at a certain dial setting, it can always he that Broadcast Receiver brought in at the same point on the dial. will give you the very on the King No need for repairs or adjustments hest of radio reception Five Broadcast Receiver. It is built for dependable - "King in Radio.' reception. Beauty is combined with excellence of reception. The cabinets are attractive in design, artistic in every line. The wood is carefully selected -the quality of workmanship unsurha.sed.

Let us send you i booklet, "King in Radio" KING QUALITY PRODUCTS, Inc. BUFFALO, N. Y. BRANCHES: CHICAGO- KANSAS CITY- BRIDC ;EBCIRO. ONT.

JOBBERS AND DEALERS The "King In Radio" sales franchise is a valuable asset. The line is complete. The name has always stood for quality. Write for full particulars. MODEL 30

by POPULAR RADIO LABORATO.n. 416 apparatus advertised in this magazine has been tested and approved

www.americanradiohistory.com The Best in Radio Equipment FREE Build Your Set PARTS with for the new A -C RECEIVERS Quality Parts READ THIS UNIQUE OFFER IF you want to build your own set, here is your opportunity to secure FREE all the parts you need for this new 5- For Tube A -C Receiver. Call on all your radio friends, and on anyone who has a set and tell them of the many special Fine Reception features of POPULAR RADIO. These liberal offers will make it possible for you to secure Choose This an order from every one you call upon. For each subscription with remittance you send us you will receive credits as Audio Transformer per the following settle: POPULAR RADIO Here is one of Dungan's 4 Months.. for" $1.00 counts 16 credits most popular Audio Trans- 6 " " 1.50 ' Y5 .. formers. 8 2.00 " 33 .. Sturdy, perfectly 12 " balanced and assuring the 3.00 " 50 " greatest possible Type S 24 ' 5.00 " 75 " amplifica- Handsome Mountings Send us the full tion with practically no dis- Ratios 2 -1, 3'_ -i and 6 -I amount collected with names and addresses tortion, this handsome Type List $4 $3 $3.75 of subscribers and tell us the parts your credits entitle you to S Audio will get the best and we will send them to you. If the subscriptions you performance from your set. secure do not give you enough credits for the parts you want, we will allow you to purchase credits at the rate of 3 cents Suited to all hook -ups and each. designed particularly for low Example: With (5) five I -year subscriptions (250 credits) and 30 cents additional in cash you may have a wave reception. General Radio We build 35 types of Audio variometer, No. 269 and a set of 'PRSH" Transformers. Thousands A -C leads for which you need 260 credits. are in use today as the supply If the parts you want are not listed on this page, we are 38 set manufacturers with prepared to supply them. Let us know what you want and transformers. we will tell you how many credits you will need. On page 86 are described POPULAR RADIO'S Simplified Voltmeters That Blueprints. You can have any set of prints you want for only 44 credits. You may also secure a copy of "How to Type N Panel Mnuntmgs Nìek, Build Your Radio Receiver" described on page 84 for 60 Are Accurate Finish. Black bezel Clamp Mounting credits Range O -7, 0 -50, and 0 -100 Volts Leading Set Manu- List $1.75 $1.75 $2.00 facturers are equipping their sets with panel - mounted voltmeters for CREDITS Needed for Parts Required for they know that efficient 5 reception depends on the New -Tube A -C Receiver correct tube and B- (Described and illustrated in POPULAR RADIO Battery voltage. By for June, 1925) all means equip your set with a 1)ongan Quantity Item Credits Voltmeter and keep 1- General Radio variometer, No. 269 200 performance up to par 1- General Radio a.f. transformer, No. 285 280 all the time. 2- "Precision" r.f. coupling units (per pair) ® 200 400 Dongan builds 5 2- Hammarlund variable condensers, .0005 mfd. types of \'olirneters- (0 200 400 each one is accurate 3- Kurz -Kasch 4' dials C. 40 120 over the entire range of 5- Federal sockets, No. 16 C 48 241) scale. You get definite 1- Dongan special step -down transformer Type B 240 readings from these 1 pre- Type F -Daven reslsto- coupler mounting 40 cision instruments. Portable 1 Handsome Black Finish -Daven resistor, 1/2" megohm 20 Range n.7, 0-50. and 0 -100 Volts 1 -Daven resistor, 1/ megohm. 20 List $1.50 $1.50 $1.75 1 -Daven grid -leak, 4 megohm 20 2- Dubilier mica fixed condensers, .006 mfd. t

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment PYREX INSULATION

WHEN you overhaul your antenna for the approaching season of real reception, consider the small cost of replacing your present insulators with PYREX Broadcast Insulators and forever forgetting insulator troubles and energy losses,

A Pair of PYREX Insulators (45c each) is a Low Premium for Insuring Reception PYREX Insulation is used on the antennae of the "Bowdoin ", "Peary ", and the planes of the Navy- MacMillan Arctic Expedition. PYREX is used on the ice patrol cutters of the Coast Guard Service. PYREX is used by the Navy, Lighthouse Service, Air Mail and Signal Corps. PYREX is used by many of the class "B" Broad- casting Stations. PYREX is used by people who demand results. When You Buy PYREX Insulators, Look for the Trade -mark PYREX All Good Dealers Sell PYREX CORNING GLASS WORKS INDUSTRIAL DIVISION CORNING NEW YORK World's Largest Makers of Technical Glassware

Al apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment Instruction Book and Radio Manual FREE with

with which is combined The Wireless Age In "How to Build Your Radio Receiver" you will Build Your Own find complete constructional diagrams, specifications, photographs and instructions for building Aside from the feature of ,..,n ,niy, then is t!: tïirill the following sets. Each has been selected as repre- and satisfaction that cosies from building your own resentative of its circuit because in laboratory testa ceiving set. Instead of being -t mere "dial- twister" you it proved the best for distance, selectivity, tone will necessarily have a very definite basic knowledge of volume, simplicity of construction, ease in tuning, what radio is all about after constructing a set. reliability and all -around satisfaction. Thousands of sets have never been constructed be- A $5 CRYSTAL SET cause of the atmosphere of mystery that has enveloped The simplest up -to -date set for local broadcast reception. Approxi- the whole subject of radio. Kendall Banning, Editor, mate range. 15 mules, though distances up to 400 miles are not and Laurence M. Cockaday, Technical Editor of extraordinary. Gives clear signals on headset without distortion. POPULAR RADIO, through their close contact with the No operating cost whatever. great radio public sensed this and compiled a book that THE HAYNES SINGLE TUBE RECEIVER will convince the veriest beginner that technical training An efficient set that may be made by a novice at an approximate is not essential. If you have a little time to devote to a cost of only $15 for parts. Simple to tune, selective, good audi- most fascinating pastime, send for a copy of "Ilow to bility. Long distance range up to 1,000 miles on earphones. and liscover how simple Mix -volt storage battery and 22'6 -volt "B" battery required, or Build Your Radio Receiver" for and dry cell tubes. and easy set building really is. This famous book has may be adapted dry cells made it so. A TWO -STAGE AUDIO -FREQUENCY AMPLIFIER This instrument may be added to any set, crystal or tube, to Free Advisory Service strengthen the received signals, so that they will operate a loud - well spraker. It is easy to construct, efficient and inexpensive, costing POPULAR RADIO is full of helpful suggestions as only SI 5 for parr. Operates on the same "A" battery that is used as instructive and entertaining articles on radio and on cite vacuum -tube detector unit. is supple- allied scientific phenomena. This information 4- CIRCUIT TUNER mented by an advisory service that is free to all sub- THE COCKADAY scribers. Any problem you encounter that is not A 3 -tube set, famous for its high selectivity and beautiful tone. will be answered by o neat and compact that it may be kept in a bureau drawer. Cost answered in the book or magazine of parts about $40. Receiving range approximately 1,500 miles on personal letter if you will submit it to the Technical a loud -speaker. Operates on a 6 -volt storage battery and two Service Bureau. For this purpose a big modern, labora- 45 -n,lt "B" batteries, or may be adapted to dry cells and dry tory with a trained staff of investigators under Mr. cell tube. is always at your service. Cockaday's personal direction A 5 -TUBE TUNED RADIO- FREQUENCY RECEIVER Two stages of tuned radio- frequency amp:ification, detector, and A Combination two stages of audio -frequency amplification are here employed so Valuable that the possibility of "oscillation and re- radiation" is eliminated. For the next thirty days we will give you a copy of 1 he set can be operated on a loop antenna and may be built at a "How to Build Your Radio Receiver," FREE and enroll cost of only $90 for parts. Six -volt storage battery and two 45- of the Technical Service Bureau voft "B "batteries required. Range about 1,000 miles on loop or you for all privileges and 2,500 to 3,000 miles on an outdoor antenna. at no further expense, on receipt of your remittance of indoor antenna $3.0(1 in payment for a 12 months' subscription for THE "IMPROVED" COCKADAY 4- CIRCUIT TUNER POPULAR RADIO. (As an alternative offer, if you wish Probably the most important cont ribution yet made to the equip- the combination with PO1vLAR RADIO for 7 months ment of the radio fan. A compact 5 -tube set with a receiving ranee event, you run absolutely of over 3,000 miles. Cost of parts about $95. Wave length only -send but S2.001. In any and power in full if you are not mire than r.ince from 150 to 675 meters. Automatic tuning no risk as we will refund amplification. Maximum volume of sound, excellent reproduction satisfied with your purchase. and no interference. Requires a 6 -volt "A" battery, three 45 -volt "B" batteries, one 223.1 -volt "B" battery and a 9 -volt "C" battery. THE REGENERATIVE SUPER -HETERODYNE RE- POPULAR RADIO Dept. 95. Offer expires CEIVER Sept. 20, 1925 627 West 43d Street, More sensitive, more selective and more simple to tune than any New York City. other 6 -tube receiver yet developed. A three-section 6 -tube set Enclosed remittance of 513.00 is payment in full for a 52 employing the Haynes Single Tube Receiver as tuner. May be months' subscription for POPULAR RADIO und corn- of "Ilse, I further extended to a four -section, 8 -tube set by the addition of to Build Your Radio Receiver" FREE. the two -stage audio -frequency amplifier. The cost of parts I approximates $100. Ranee of 3,000 to 4,000 miles on a loud- Naine speaker. Has been called the "Rolls- Royce" of radio receivers. Address I City State Check here and remit $2.00 if you prefer PoprLAR POPULAR RADIO RADIO for 7 months only in combination with "How to I I 1 627 West 43d Street, New York City Build Your Radio Receiver." '

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment

Dimensions Weight: in. x in. x 4 ,', 1O; ; in. 12 Pounds Unfailing "B" Power Direct from your lighting socket

ELECTRiCALPOM PRODUCTS OF MER1 :' it 19 Battery Eliminator Write to your nearest distributor or direct for details. These distributors have approved the Epom "B" Battery Eliminator

NEW YORK, N.Y., E. 13. Latham & Co. CHICAGO, Commonwealth Edison Co. NEW YOR.K, Sibley- Pitman Elec. Co. INDIA NAPOLIS, Indianapolis Elec. NEWA R N, Tri -City Electric Co. Supply Co. BOSTON, Pettinuiell Andrews Co. CINCI N NATI, Post -Glover Elec. Co. BA LTI MORE. Southern Electric Co. KANS:XS CITY, B -R. Electric Co. RICHM(1ND, Southern Electric Co. COLUMBUS, Erner & Hopkins PHILADELPHIA, F. H. Stewart Elec- MII.W'AUNEE, J. Andrae & Sons Co. trical Co. ATLANTA, Carter Electric Co. PITTSBURGH, Union Electric Co CLEVELAND, Erner Electric Co. HARTFORD, So. New England Elec. C, DETROIT, Electrical Specialties Co. EPOM CORPORATION (Dept. P. R.) 114 East 47th Street, New York City

All apparatus advertised in this inaAafine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 6 The Best in Radio Equipment

ANYONE CAN BUILD A SET WITH SIMPLIFIED BLUEPRINTS AURENCE M. COCKADAY has personally supervised the preparation of Simplified Blueprints of seven of POPULAR RADIO'S most popular circuits. Each set consists of three separate Actual Size Blueprints; first a Panel Pattern; second, an Instrument Layout; and third, a Picture Wiring Diagram all simplified in the fullest sense of the word because The Panel Pattern can be laid on the panel and all holes drilled as indicated. No scaling to do and so accurate there is no danger of ruining the panel through faulty calculation. The Instrument Layout placed on the sub -base permits you to indicate by pinpricks the exact location of every screw. The Picture Wiring Diagram gives every instrument in exact size and position with every wire clearly indicated from one contact to the other. With no knowledge of radio symbols you can assemble every part and complete your wiring with no chance of error. Priced at $1.10 per Set of Three Prints Set No. 4 -"Coc1 aduy Four -Circuit Tuner with regeneration dial, short or long indoor or outdoor Resistance -Coupled .1m Ifier" (five tubes, dis - antenna, resistance coupled amplification as de- tortionlcss, two dials, automatic vacuum tube scribed in March 1925 issue of POPULAR RADIO.) control, as described in the October 1924 issue of Set No. 9 - "Portable Town and Country Re- POPULAR RADIO). ceiver" (six tubes, three stages of transformer, Set No. (i- "The Cocicaday 8 -tube Superhetero- coupled, radio- frequency amplification, loop an- dyne Reflex Receiver" (eight tubes, two tuning dials, tenna, tuned by variable condenser as described loop, non- radiating, distortionless, as described in May 1925 issue of POPULAR RADIO.) in January 1925 issue of POPULAR RADIO). Set No. 10 -"5 -Tube A -C Receiver" (five "Mc- Set No. 7- "The Craig 4-Tube Reflex Receiver with Cullough" A-C tubes, two stages of tuned radio the New Sodion Detector" (four tubes, two tuning frequency amplification, as described in June dials, short antenna, non -radiating as described 1925 issue of POPULAR RADIO). in February 1925 issue of POPULAR RADIO). Set No. 11 -"5 -Tube Tuned Radio- Frequency Set No. 8 -"The Improved Cocl;aday DX Regen- Receiver with Simplified Control" (as described erative Receiver" (four tubes, one tuning dial. one in August 1925 issue of POPULAR RADIO). Full constructional and parts details for these Receiving Sets will be found in the issue of POPULAR RADIO indicated. Back issues of POPULAR RADIO will be furnished at the rate of 35c a copy

627 West 43d Street Dept. 94 New York City ------hI I POPULAR RADIO, Inc., Dept. 94 1 627 West 43d St., New York City Date I I Enclosed is my remittance of S for which kindly send me Blueprint Set (s) I I consisting of Panel Pattern, Instrument Lay out and Wiring Diagram as checked below: I DEALERS Set Number 4 Set Number 8 Set Number 6 Set Number 9 Write for terms Set Number 7 Set Number 10 Set No. 11 on these fast sell - I i n g Blueprints. Name I An attractive Dis- I Address play Chart free ICty State ------J with orders. All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 57

There are many improvements in the new Prest -O -Lite Battery IN THIS new battery you'll find all the good points and sides of the cell connectors. and high quality preserving the original that have made Prest -O -Lite an fine finished appearance at all unfailing aid to times and giving protec- better radio. And in addition there tion against accidental short circuits. are many important refinements and improvements No effort has been spared to that make it the most make this a battery attractive, most convenient you will be proud to own. Yet, battery you can buy. like the rest of the Prest -O -Lite line, it is priced to offer you the biggest This new battery has a beautiful stippled finish hard value of the day. Ask your dealer to show you rubber case that blends with any furnishings. this The battery and the Prest -O -Lite Chart that helps you case is molded in one piece, giving sturdy, leak -proof select the right strength. battery for your set. Or write Indian- apolis for a copy of our interesting handbook To make the battery convenient to carry, on the handle radio storage batteries and how to charge them. has been given a comfortable rubber grip. The oversize terminal nuts on the binding posts are THE PREST- O LITE CO., INC. easy to turn and insure perfect contacts. INDIANAPOLIS, IND. New York San Francisco Novel rubber insulators completely cover the In tops Canada: PrestO-Litc Company of Canada, Ltd., Toronto, Ont.

44. All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

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HETORUS -The Final Achievement! A NEW AND IMPROVED TYPE OF TUNED R. F. TRANSFORMER WITH ISOLATED FIELD COILS It does three things: 1. Increases selectivity for precise tuning. 2. Improves tone and volume of distant stations. 3. Reduces static and interference to a minimum.

Because: The Hetorus Coil has no pick -up quality of its own and amplifies only the signals to which the antenna is tuned. Being "fieldless" there can be no interaction either between the coils themselves or adjacent apparatus. They can therefore be mounted in any position or angle.

This is a completely equipt 5 -tube Whether you give your present set the tuned R. F. Receiver using Hetorus advantage of this latest forward step in radio or build a new Coils. It is giving re- receiver, phenomenal Hetorus Coils will afford you results sults equal or superior to any 5 -tube in keeping with the best radio de- receiver on the market. velopments of 1926. Write at once for free information on this outstanding sensation. CHAS. A. BRANSTON, Inc. 811 Main Street, - - - - Buffalo, N. Y.

A Dollar Bill Around the Coupon Below Will Bring Popular Radio for 5 Months

We want more subscriptions, and so we will enter your subscription for 5 months, if you will fill out the coupon below, wrap a $1.00 bill around it and mail it to us promptly. This offer should interest the casual reader, the newcomer into the ranks of radio fans and all POPULAR RADIO readers who are not now subscribers. This offer is only open to new subscribers.

DO YOU WANT TO BUILD A SET ? You will get more out of Radio when you build your own set. POPULAR RADIO has made it possible for the beginner, with no previous knowledge of radio, to build any type of receiving set desired with the assur- auce of getting perfect results.

"HOW TO BUILD YOUR RADIO RECEIVER" POPULAR RADIO, Dept. 97A The most complete and authoritative collection of mate- 1 627 West 43rd Street, New York City. rial on Receiver Construction yet published in book form. All working details given; lists of parts required; complete Enclosed is remittance of $... , as payment, in hook -ups and circuit diagrams. (See page 44.) full, of subscription offer for POPULAR RADIO as checked below. TUNE -IN ON ONE OF THESE 5 months for $1.00 You may have a copy of "How to Build Your Radio (new subscription only). Receiver" FREE with a 7 months' subscription to POP- 7 months and "I-Iow to Build Your Radio ULAR RADIO for $2.00. Or your subscription for Receiver" for $2.00. I'OPI'LAR RADIO for 12 month; and your copy of 12 months and "How to Build Your Radio "How to Build Your Radio Receiver" both for $3.00. Receiver" for $3.00. 12 months and Set of "Simplified Blueprints" SIMPLIFIED BLUEPRINTS No. .... for $3.00. POPULAR RADIO'S latest aid to receiving set build- 24 months for $5.00. ers show in ACTUAL SIZE every detail of the construction of 7 popular sets. (See page 86.) Subscribe to POPULAR RADIO for 12 months and I NAME you may have your choice of any one set of Simplified Blueprints, at the regular subscription price of $3.00. ADDRESS POPULAR RADIO 627 West 43d Street New York City I CITY STATE

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

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- ALB. èveloped ne ¡truéhio VERNI tts Straigh inc Data quency cha ny semi - cula ;wily installe te condenser. oncent-r.ic mounting more crowding of stations at - wa Takes standard The S LF VERNIER DI separat s shaft -projection ow wave -lengths jus easily No friction aat ounting (no hi v=° -i ' ! s. ppage The sue: n ingenious mec anism 5. H vy gears .:. (sm #h action) contained in the knob gives small inc ases in 6. All b kelite capacity at low wavelengths and progressively knob greater increases at higher wave;,.kngths while 7. Nickeled- si dial (not plated) knob and pointer revolve at,_ itniform speeds. 8. Precision grad- uations ! nndard 12 -to -1 JVIER DIAL giving SLF 9. Hairline pointer characterises ícs to any ordinary condenser. Write for prices. JOBBERS AND DEALERS: Deliveries September 10th. Orders filled in rotation as received. Catalog copy and cuts ready August 15th WALBERT MANUFACTURING COMPANY 923 Wrightwood Avenue, Chicago, U .S.A

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORX

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Use Allen- Bradley Perfect Radio Devices for maximum selectivity and noiseless control i - Bradleystat - Noiseless Rheostat for ALL radio tubes. 2- Bradleysw itch -Compact Switch for receiving sets. 3 - Bradleydenser -Low Loss Condenser for sharp tuning. 7 4- Bradleyometer- Perfect Potentiometer for all circuits. ALLEN -BRADLEY CO., 276 Greenfield Ave., Milwaukee, Wis, 5- Bradleyohm- Adjustable Resistor of every application. Please send me your latest literature on the complete Allen-Bradley 6- Bradleyleak- Adjustable Grid Leak for highest efficiency. line of Radio Devices. 7- Bradleyunit -Fixed Resistor for Resistance Amplifiers. Name 8 - Bradleynier - Vernier Knob, easily attached to any set. Address

All apparatus advertised in this magazine lias been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com Crosley Radio ideas 1926 With these improvements Powel Crosley Jr., makes his greatest stride forward in the development of radio The Super -Trirdyn for the millions. Special

.r-

The famous Crosley Trirdyn circuit -3 tubes doing the work of 5-greatly improved - mechanical refinements - finer and richer designs and finishes. New Crosley designed low loss Vernier condenser -new worm rotary type tickler control. Wiring concealed under sub -panel. In this model all dry batteries are contained in the cabinet. Price quoted is without accessories. Super-Trirdyn Special with matched console table and Musicone De Luxe $112.50. Table separate $25.00. vik

The Super -Trirdyn Regular Croslev Trirdvns have hecn the marvel iif the rads, a aid Tuned radio frequency combined with Armstrong regenerat it and reflex amplification do in 3 tubes what 5 do in other sets do radia- of solid mahog- t ion. This model is a simple, richly finished cabinet any. Price is without accessories. . Add 10% to Prices West of Rocky Mountains

The Crosley "Pup" New 2 Tube 51 New 3 Tube 52 The Musicones regener- Improved popular Crosley Another popular (:rosley The first loud speaker to A genuine Armstrong repro duce the Jul! tonal range ative double circuit receiver 2 tube No.5I Special De Luxe. model -the 3 tube 52 Special circuit New Crosley De Luxe. Redesigned with of voice or instrument with- for $9.75. A refinement of Double Superior to the one tube set with which Vernier condensers; worm new Crosley Vernier con- out distortion. rotary type tickler; cabinet densers, rotary type tickler all others regardless of cost. Leonard Weeks, of Minot, will prove this. N. D., heard the MacMillan will hold necessary dry bat- and beautifully finished cabi- Investigation teries. Price with - net. Price with- A 50 Rapidly replacing other types polar expedition while the $23,50 t ] 500,000 use by listened in out accessories G out accessories... 33GG of speakers. in rest of the world Jan. 1st. Crosley developed vain. One dry battery - unit secret of its remark- one B battery, tube, able success. $17.50. De phones and antenna only Luxe model, accessories need- $9.75 mahogany $27.50G ed. Price with- I out accessories.. cabinet ..

THE CROSLEY RADIO CORPORATION :: Cincinnati, Ohio PRESS OF WILLIAM GREEN, NEW YORK

www.americanradiohistory.comN li Icon now has the new RCA Tube sßecially designed Right in your electric light wires lies all the current you need to keep your radio set at the peak of efficiency. A Super- Ducon,which now has the advantage of a specially designed RCA tube, Rectron UV -196, delivers rent a steady cur- of just the right voltage - always constant- always silent. It takes the place of "B" batteries. Less trouble -lower keep up- -and better radio reception always -with a Dubilier Super -Ducon. Just plug it in on the house current. Tested and listed by the National Board of Fire Underwriters. Write for descriptive bulletin, 238th St. and Bronx Boulevard. Dubilier CONDENSER AND RADIO CORPORATION

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