FEB. 15 15C NR4 ANALYZED 1930 Per Copy STABILITY of NON -REACTIVE AF

FEB. 15 15c NR4 ANALYZED 1930 Per Copy STABILITY OF NON -REACTIVE AF

SCREEN GRID TUBES REG. U.S. PAT. UFF. COMPARED WITH OTHERS

OVERALL TESTS

412th Consecutive Issue EIGHTH YEAR FOR CIRCUITS New Detector System for Non -Reactive Audio

RADIO WORLD, publisbed by Hennessy Radio Publications Corporation. Roland Burke Hennessy, editor; Herman Bernard, managing editor and business manager, all of 145 West 45th Street, New York, N. Y.

www.americanradiohistory.com RADIO WORLD February 15, 1930 High Impedance Audio Transformers

Audio frequency coupling transformers with high impedance primaries and secondaries are made in ipj two models and two ratios of each model. At left is the "Gold Bond" shielded type, at tight the "Uni- versal" unshielded type for subpanel mounting, overall height 2g". The ratios are 1 -to -3 and 1 -to -5, primary to secondary. The shielded "Gold Bond" model has 4,000 turns on the primary, so the 1 -to -3 model has 12,000 secondary turns and the 1 -to -5 model 20,000 secondary turns. Ex- treme compactness and neatness prevail. The "Universal" Excellent reproduction of tonal values as supplied by model for subpanel of mounting has 3,200 the detector or first audio tube is assured by use primary turns. either of the transformers. The "Universal" model illus- Laminations in both trated above, is excellent for replacement purposes. A single stretch of copper wire without soldered are of best silicon Even on this model high plate voltages may be used, connections of in-between joints is used on each steel in a strong with consequent high plate currents, due to the relatively winding of both transformers. The "Gold Bond" steel frame. The coils model is illustrated. in both are vacuum large diameter of wire used. impregnated and GB -1-3 I -3 for 1 -to -3 ratio Order Cat. for -to ratio therefore moisture - Order Cat. UVS-1-3 Order Cat. GB -I-5 for 1 -to -5 ratio $ 1.50 each proof. Order Cat. UVS-1-5 for 1 -to -5 ratio $1.13 each GUARANTY RADIO GOODS Co., 143 West 45th Street, New York City FIVE-DAY MONEY -BACK GUARANTY!-C. O. D. ORDERS ACCEPTED.

USE %" Extension Shaft Here is a handy aid to Aristocrat Floor Speaker salvaging condensers and coils hare LYNC that )4" diam- With Molded Wood Horn of 0 ft. $12.00 eter shafts not long enough tone travel (exponential type) with RESISTORS for your purpose. Fits on baffle and horn motor built In. 5j4" shaft and provides %" Extraordinary bargain. for new Loftin -White Set and Amplifier, auto- extension, still at 14". mobile radio sets, and new 245 resistance - Price 10e net. coupled amplifier. Write for catalog and 40- RADIO WORLD page booklet. 145 W. 45 St., N. Y. City LYNCH MFG. CO., Inc., 1775 B'way, N. Y. CONE RADIO AND OTHER ASSEMBLY TECHNICAL BOOKS WITH DOUBLE At a Glance MAGNET UNIT RADIO "Audio Power Amplifiers," by Anderson and $4.95 Bernard $3.50 "Elements of Radio Communication," by Morecroft 3.00 IIIIIIIIÌIÍ_IÌÌIIIÌIjII 'Foothold on Radio, A," by Anderson and Bernard 1001.00 Mathematics of Radio," by Rider "Practical Radio," by Moyer & Wostrel 250 "practical Radio Construction and Repairing," by Moyer & Wostrel "Principles of Radio Communication," by Morecroft "Radio Blueprint Library"-AC Hook-ups .35 "Radio Cyclopedia," by Drake 0.00 "Radio Receiving Tubes," by Moyer & Wostrel 2.50 "Superheterodyne Construction and Operation," by Lacault "Thermionic Vacuum Tube, The," by Van der Bill 5.00 osa excellent magnettc type speaker for installa- The speaker cabinet la walnut 33" "Trouble Shooter's Manual," by Rider 3.50 tion in any cabinet. The unit is a finish, high, double -magnet 241/2 ' wide, 175/" deep, with carved legs. Paratone, with two magnet coils, for utmost Golden cloth grille covers front opening. Built TELEVISION sensitivity. Each horseshoe magnet is %" thick. inside is No. 595 molded wood The coils forever horn with baffle 3.00 magnet are protected against and No. 203 driving motor unit that stands 250 "A B C of Television," by Yates dust and other foreign, injurious substances, by volts without filtration. Horn and motor re- special bakelite housings. The pin Is reverse movable. Table alone is worth price asked. drive. The cone frame is metal. The 0" cone AVIATION Is specially treated buckram. Shipped C.O.D. if desired. "A B C of Aviation," by Maj. Page 1.01. and Meterology," by All assembled, with long cord, ready "Aerial Navigation 406 to play, Shipping weight 4 lbs l9w5 Acoustical Engineering Associates Capt. Yancy .. Guide," by Maj. Page 4.00 (Cat. CAS) Net .... 143 WEST 45th STREET NEW YORK CITY "Everybody's Aviation "Ford Model 'A' Car." Its Construction, Oper- The unit alone (cord Included) II ation and Repair-by Maj. Page will operate any type sounding sur- "Modern Aircraft," by Maj. Page 5.00 face, including paper, cloth, wood, etr A PLEASE GIVE. US TWO WEEKS "Modern Aviation Engines," by Maj. Page 9.00 Shipping weight t iha. (Cat. UM $ L 9 Net for changing your address, showing new 5 renewal expiration date, etc. Subscrip- RADIO WORLD tion orders are arriving in such larga Guaranty Radio Goods Co. 145 West 45th Street numbers that it takes two weeks to N. Y. 145 45th St., New York City effectuate the change. New York, West RADIO WORLD, Broadway) 145 West 45th St., N. Y. City. (Just East of

www.americanradiohistory.com February 15, 1930 RADIO WORLD 3 Attention... Highest Grade Key Tubes at Radio Service Men

is compiling an international list of names of qualified service men throughout the Defiant /Radio(Faft United States and Canada, as well as in ($rofessional Servicremao-Radiotrician foreign countries. This list, which RADIO -CRAFT is trying to make the most complete one in the world, will be a connecting link Prices: radio service man. between the radio manufacturer and the RADIO -CRAFT is continuously being solicited by radio manufacturers Screen Grid Tubes for the names of competent service men; and it is for this purpose only that this list is being compiled. There is no charge for this service 224 at $1.43 to either radio service men or radio manufacturers. We are asking every reader of this magazine who is a professional 222 at 1.88 service man to fill out the blank printed below or (if he prefers not to cut the page of this magazine) to put the same information on his letterhead or that of his firm, and send it in to RADIO -CRAFT. The data Power Tubes thus obtained will be arranged in systematic form and will constitute an official list of radio service men, throughout the United States and for- 245 at 1.28 eign countries, available to radio manufacturers. This list makes possible increased cooperation for the benefit of the industry and all concerned 112A at .78 in the betterment of the radio trade. 171A at .78

Other Tubes MEN' York, N. Y 'List I OF SERVICE National Lei. 98 park Place, of your below: .90 NATIONAL/oL CRAFT' files 227 at c/o RADIO as set forth the undersigned are .68 Please enter My qualifications 226 at Service Men.(State) of Radio print) (City) . 280 at 1.13 Name (please so state) please for self, 201A at .53 Address Address in business and (If ' Firm Name Construction? in Radio The above constitute the nine most popu- Experience lar tubes used in radio today. Despite the Years'Year EX' Makes?) severely low prices the Key tubes are firsts ...... What of the very first quality. Besides, there is Servicing a five-day money -back guaranty! The above tubes are manufactured under years in licenses granted by the RCA and its Agency . affiliated companies. You All prices are net and represent extreme .... Recommend? discount already deducted. Institutions Tubes Do Y (What SpeCFollowing 228 HIGH -GAIN DETECTOR What Work from Builder Taken Radio . Increase The sensitivity of modern AC - Custom in operated circuits by substituting the new Courses ... 228 AC high mu tube (large amplification), Study for the 227 tube otherwise used as detector Makes in up - to - date circuits. The result Following is immediately obvious in the greatly in- in Servicing creased volume. Then the weak, distant Specialized stations come in stronger and tone quality is improved. Simply substitute the 228 You Own? for the 227 in the detector socket only. Equipment No wiring change of any kind is required. Testing Price, 51.88. What Professions? Trades or GUARANTY RADIO GOODS CO., 143 West What Other 45th St., N. Y. City. (Just East of Broadway). Other Qualifications? Enclosed please find $ for which ship and at once tubes marked below: Educational high mu. E 228 AC $1.88 ' ' (Signed) 0 224 AC screen grid $1.43 245 AC power tube 81.28 Comments 228 AC amplifier (RW 215) 227 AC det.-amp. .90 280 AC rectifier 51.13 D 222 battery screen arid 88 D II2A power tube SI .78 D 171A power tube .79 201A battery tube .53 Matched pair of 245s for push-pull (for SEPARATE TESTER COMBINATION both) $2.58 Matched pair 171As fer AC push-pull (fer in neat black both) 51.80 Consists of two -meter assembly Matched pair of I12As for push-pull (for metal case, with an external high resistance both) 51.80 meter. The two meters in the case read (a) 0-20, 0-100 milliamperes; (b) 0-10 volts, AC or DC, same meter reads both. The ex- Name ternal high resistance meter reads 0-600 volts, AC or DC (same meter reads both). Thus Address you can test any plate current up to 100 ma., any filament voltage, AC or DC, up to 10 V., or line voltage or other City State and any plate voltage, AC or DC voltage, up to 600 volts. Five -prong 4 -prong adapter Put cross here If C. O. D. shipment Is de- plug, screen grid cable, and sired. included. Order Cat. ST -COMB @ $11.01 Canadian remittance must be by postal or ex- 2-meter-600 cable plugs, M6005 @@ $4.95 press money o -der. AC-DC meters N. 5 -Day money -back guaranty Guaranty Radio Goods Co., 143 West 45th St., Y. City

www.americanradiohistory.com 4 RADIO WORLD February 15, 1930

"AUDIO POWER AMPLIFIERS" By J. E. ANDERSON and HERMAN BERNARD The First and Only Book on This Important Subject-just Out

T N radio receivers, separate audio amplifiers, talking movies, public address systems and the like, the power amplifier stands out as of predominating importance, therefore a full and authentic knowledge of these systems is imperative to every technician. "Audio Power Amplifiers" is the book that presents this subject thoroughly. The authors are J. E. Anderson, M.A., former instructor in physics, University of Wisconsin, former Western Electric engineer, and for the last three years technical editor of "Radio World." Herman Bernard, LL.B., managing editor of "Radio World." They have gathered together the far-flung branches of their chosen subject, treated them judiciously and authoritatively, and produced a volume that will clear up the mysteries that have perplexed many. What are the essentials to the reproduction of true tone values? What coupling media should be used? What tubes? How should voltages be adJusted? These are only tour out of 1.400 questions raised and solved in "Audio Power Amplifiers." The book begins with an elementary exposition of the historical development and circuit constitution of audio amplifiers and sources or powering them. From this simple start It quickly proceeds to a well considered exposition of circuit laws, Including Ohm's laws and Kirchhoff's laws. The determination of resistance values to produce required voltages Is carefully expounded. All types of power amplifiers are used as examples: AC. DC. battery operated and composite. But the book treats of AC power amplifiers most generously, due to the superior importance of such Dower ampli tiers commercially. Rectification theory and practice In all the applied branches, grid bias methods and effects, push-pull principles, power detection. reproduction of recordings and methods of measurements and testing are set forth. And besides there is a chapter on the subject of motorboating, with which one of the authors la probably better familiar than any other textbook author. Then, too. there is a chapter on tubes, with essential curves and a full list of to bias of tube data. Every tube that will be used In an audio amplifier -therefore virtually all tubes-is clearly diagnosed, classified and tabulatedi These data on tubes should be at every radio engin- Amplifiers," eer's hand. "Audio Power "Audio Power Amplifiers" Is a book for those who know someth Ina about radio. It Is not for novices-not by a mile. But 193 pages, 147 Illustrations; the engineers of manufacturers of radio receivers, power amplifiers, sound installations in theatres. public address systems and Maroon Cloth Bound Cover, will welcome this book. Engineers-even chief eng sneers-of the Bell Telephone Laboratories. Radio Corporation phonograph pickups needn't be afraid won't Lettering in gold. Price, of America. Westinghouse Electric & Mfg. Co.. Western Electric, Photophone, Vltaphone and the Ilke they use. learn something from this little book. these Table of The book consists of 193 pages in type the size used in printing What Is Not words, known as 8 point, and therefore a great deal of text is contained in As Well As Contents these 193 pages, and the book is small enough to be carried conveniently in the side pocket of a sack coat. It was purposely printed that way because What Is Page will want to consult this precious busy engineers and other experimenters OMETIMES is is Chapter I volume while riding in conveyances, as well as when in the laboratory, and more important to General Prin- was therefore desirable. expose o fallacy than compactness merely to state the fact. ciples 1 The edition is strictly limited to 1,000, and the publishers recognize that A crop of technical weeds Chapter II the field of distribution is necessarily small, hence the price is $3.50. Those has grown into the garden Circuit Laws 20 a volume is of any value would not be without it at any price. of audio amplification, to whom such and the authors have gone Chapter III The device of presenting no more information or greater number of to the pains of exposing Principles of illustrations, but of using larger type, and thicker and often cheaper paper, these. 35 a was purposely avoided. The paper is finest The book "Audio Power Rectification to present bulkier appearance, Amplifiers" is free from Chapter IV super stock and the size of the page is 5 x 8". traditional errors, except in citing them as falla- Practical cious conclusions. Each Voltage Ad- Detailed Exposition of Chapter Contents attack on a fallacy ú justments 62 Chapter I. General Principles, analyzes the four types of power amplifiers, AC, DC, abundantly supported by Chapter V battery -operated and composite, illustrates them in functional blocks and schematic diagrams, proof of the REAL facts. media are illustrated and As an example, take the Methods of and treats each branch in clear textual exposition. Audio coupling theory that motorboating discussed as to form and performance: transformer, resistance -resistance, impedance -impedance, Obtaining and non -reactive. is due to grid blocking. impedance -resistance, resistance-autotransformer, autotransformer-resistance The authors say: "Many Grid Bias 72 Pushpull forme are illustrated, alsr speaker coupling devices. Simple audio ampifiers are explanations for this Methods of connection for best results are stressed. os- Chapter VI illustrated and analyzed. cillatory condition (motor - form Principles o f Chapter II. Circuit Laws, expounds and applies Ohm's laws and their special boating) have been made, known as Kirchhoff's laws. Direction of current flew in tube circuits is revealed in connection some of which are wholly Push - Pull with the application of these laws to several circuits, including a DC 110 -volt A, B and C untenable. One of these Amplifier 90 supply, and series and parallel filaments in general. Special diagrams are published for is that the oscillation is Chapter VII Ohm's and Kirchhoff's laws. due to blocking of the Chapter IiI. Principles of Rectification, expounds the vacuum tube, both filament and grids of the amplifiers Oscillation in gaseous types, electrolytic and contact rectifiers, and explains why and how they work. If blocking of the Audio Amp- with current flow and voltage derivation grid were the cause of Full -wave and half -wave rectification are treated, phenomenon, lifiers 98 analysis. Regulation curves for the 280 tube are given. Voltage division, filtration and the the wave and dissected. form of the oscillation Chapter VIII stabilization are fully illustrated would be very irregular, Chapter IV. Practical Voltage Adjustments, gives the experimental use of the theoretical but an oscillogroph shows Characteris- knowledge previously imparted. Determination of resistance values is carefully revealed. that it is very nearly of t i c s of Chapter V. Methods of Obtaining Grid Bias, enumerates shows and compares them. a sinusoidal form." Tubes 118 defines the relationship, with Then follows an exposi- Chapter VI. Principles of Push -Pull Amplifier, push-pull tion of motorboating, and Chapter IX keys to the attainment of desired electrical symmetry. oscillation at other fre- Reproduction Chapter VII, Oscillation in Audio Amplifiers, deals with motorboating and oscillation at fuencies, with expressions of Record- higher audio frequencies, explaining why it is present, stating remedies and giving or (.redetermining the in- expressions for predetermination of regions of instability. The trouble is definitely assigned stability or stability of ings 151 to the feedback through common impedance of load reactors and B supply, and in some audio circuits. Chapter X special instances to the load's relationship to the C bias derivation as well. The feedback Power Detec- is shown as negative or positive and the results stated. tion 161 Chapter VIII, Characteristics of Tubes, tells how to run curves on tubes, how to build and use a vacuum tube voltmeter, discusses hum in tubes with AC on the filament or heater, and presents families of curves, plate voltage- Chapter XI plate current, tor the 240, 220, 201A, 112A, 171A, 227 and 245, with load lines. Also, plate -screen current character- Practical istics of the 224, at five different control grid biases, at platevoltages 0.250. Then Table I gives the Average Character- istics of Amplifier and Detector Tubes 220, 200A, 201A, 112A, 171A, 222, 240, 226, 227, 224, 245, 210 and 250, stating use, Power filament voltage, current, and resistance, Det. B volts, Amplifier B volts, grid bias for amplification and detector, Amplifica- plate current, plate AC resistance, mutual conductance, mu, maximum undistorted power output, physical size. tion 121 There is a composite table (II) of characteristics of Rectifier and Voltage Regulator Tubes, and individual tables, giving Chapter XII grid voltage, plate current characteristics over full useful voltage ranges for the 220, 201A, 112A, 171A, 222, 240, 227, Measure- 245 and 224. ments a n d Chapter IX, Reproduction of Recordings, states coupling methods and shows circuits for best connections. Testing 183 Chapter X, Power Detection, explains what it is, when it should be used, and how to use it. A rectifying detector, designed by one of the authors, is expounded also. Chapter XI, Practical Power Amplifier, gives AC circuits and shows the design of in Now! a sound reproduction system for theatres. A page is devoted to power amplifier symbols. r Send This Coupon Chapter XII, Measurements and Testing, discloses methods of qualitative and Hennessy Radio PublicatioM Corporation, quantitative analysis of power amplifier performance. A scale illustrates the audio 145 West 45th Street. New York, N. Y. frequencies in comparison with the ranges of voice and musical instruments. A beat (Just East of Broadway). note oscillator is described. Thirteen causes of hum, with remedies, are stated, also Please send at once postpaid copies of the estimation of power required for output and preliminary tubes. "Audio Power Amplifiers," by J. E. Anderson and Herman Bernard, for which please find enclosed 53.50 You may safely order "Audio Power Amplifiers," either per CDDy. enclosing your O Please send copies C.O.D. I will pay remittance or ordering the book mailed C.O.D. Examine it for five days. 53.50 plus Post Office charges. If you are not completely satisfied with it for any reason, or for no reason, send it back in five days with a letter asking for a refund. A check Name refunding the purchase price will be sent to you immediately. We can not send the book on approval, without payment before receipt, so please Address do not ask us to do so. Bits Stata

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RADIO WORLD, owned and published by Hennessy Radio Publications Corporation, 145 West 45th Street, New York, N. Y. Roland Burke Hennessy, president and treasurer, 145 West 45th Street, New York, N. Y.; M. B. Hennessy, vice-president, 145 West 45th Street, New York, N. Y.; Herman Bernard, secretary, 145 West 45th Street, New York, N. Y. Roland Burke Hennessy, editor; Herman Bernard, business manager and managing editor; J. E. Anderson, technical editor. Carrier Intensity Detector New System Utilizes Instability in Non -Reactive Audio By Herman Bernard Managing Editor

THE NR4, first published in the February 1st issue, is shown this week in a slightly changed form. Instead of the detector biasing resistor, R2, of 20,000 ohms, being connected directly to negative, it is connected to the second tap on the voltage divider. The screen grid voltage on the detector tube is lifted a little, so that the connection is made to the fifth tap. Otherwise the diagram is the same. The object of suggesting the change is that, although the volume is a little less, the selectivity is considerably increased, and the circuit works without any "thickness" of tuning. Such "thickness" is due to attenuation of power tube plate current. While only a little plate current is necessary in this circuit for the power tube, the diagram as shown this week produces a flow of 22 milliamperes and permits an effective pate voltage of 250 on the power tube, at maximum signal input. The applied voltage on this plate is some 12 volts more, the difference being due to the voltage drop in the 500 ohms DC resistance of the speaker winding. INSTABILITY ANALYSIS No output filter is needed under either method of connection, the one on next page or the one republished from the February 1st issue. None is needed, as the current is only 22 milliamperes on the loudest signal and rises to 30 milliamperes at 190 volts at no signal. The comparative instability should be judged preferably on the POWER TUBE basis of current at no signal and current at loudest receivable (5) FILAMENT CENTER signal. This is 30 as compared with 22 milliamperes, or about 33 1/3 per cent. The weakest station will create a situation about equal to a no-signal condition. ;-1 -I 1-I=P This instability aspect has worried some inquirers, but I. there is nothing to worry about. It is merely a reciprocal 1 current -voltage conditio'n that does not adversely affect the I I ¡(j practical operation of the circuit at radio or audio frequencies. In fact, it helps to depress large differences in volume. 1111111111111111.1.11011 The audio channel is non -reactive, which means that it is free from the phase displacement of current and voltage caused 1-1-1-1-1-1-1-1-1 !'l-'l. by condensers and coils, hence free from frequency distortion. This is relative non -reactance, since bypass and filter con- I I 1 I densers are used in the B supply and adjuncts. But no isolating Hi da r condenser is used in the audio circuit, and no coil. iii The reactive effect on the audio coupling form by the presence of the bypass =i Mi and filter condensers is small. Their effect on the filtration (i)(Z) (3) liZZ of the B supply is relatively large. FIG. 1 NEW DETECTOR FORM ANNOUNCED THE NR4, WITH DETECTOR BIASING RESISTOR RE- THE VOLTAGE DIVIDER, At expense of volume the circuit shown TURNED TO NEGATIVE OF the can be made AS SHOWN IN FEBRUARY IST ISSUE. THE TWO ILLUS- as selective as desired. It is possible to achieve the utmost in BE READ TOGETHER faithful selectivity, by close arrangement of detector screen STRATIONS SHOULD grid and negative bias voltages, in a manner to cause the car- ments. How to try it with this circuit in modified form I rier intensity to govern the operating point. The screen voltage describe elsewhere in this issue. is then only slightly less than the plate voltage. This results in Now, since the non -reactive audio channel is made highly an entirely new form of detection, which makes detection unstable as to power tube plate voltage and plate current, an impossible except at resonance. Hence there is no incidental example chosen for first mention because these values are sus- detection and no possibility of detection of interfering signals, ceptible of easy measurement, it follows that the effective as the intensity of the carrier would have to reach a predeter- detector plate voltage is unstable. By taking the detector bias mined level, and nothing except the intended frequency could off the voltage divider entirely-the NR4 now takes it partly produce that level. At the present writing the system is not off the divider-the carrier intensity will make the consequent recommended for general use, but is suggested for experi- current changes through the biasing section used for the

www.americanradiohistory.com 6 RADIO WORLD February 15, 1930 Performance of NR4, w Voltages and Currents Given, Also Voltage and Current Values in the NR 4 THE VOLTAGE and current measurements obtained on the NR4 when hooked up according to the diagram, Fig. 2, as published at left, with 110 volt AC input, were as follows: RF Tube, 224 Heater voltage, 2.5 volts AC. Negative bias, 4 volts. Screen grid voltage, 100 volts. Screen grid current, 1 milliampere. Applied plate voltage, 190 volts. Effective plate voltage, 190 volts. Plate current, 4 milliamperes. Detector, 224 Heater voltage, 2.5 volts AC. Negative bias, 5 volts. Screen grid voltage, 24 volts. Screen grid current, 83 microamperes. Applied plate voltage, 180 volts. FIG. 2 Effective plate voltage, 119 volts. THE NR4, USING THE SAME PARTS AS PREVIOUSLY, Plate current, 27 microamperes. BUT WITH DETECTOR BIASING RESISTOR R2 RE- TURNED TO A POSITIVE POINT ON THE VOLTAGE Power Tube, 245 DIVIDER, WITH SCREEN VOLTAGE RAISED A LITTLE. Filament voltage, 2.5 volts AC. Applied plate voltage, 262 volts. Effective plate voltage on loudest stations (depends on drop detector effective in changing the bias. Hence a point is in speaker winding), 250 volts. selected that requires a certain value of carrier intensity to Negative bias, 56 volts. make the detector plate current high enough to enable opera- Plate current, on loudest station, 22 milliamperes. tion at the critical point of bias for detection. Since negative grid -bias detection is used, the higher the signal intensity or Voltage Divider carrier strength, the higher the current flowing through the Total voltage (across extremes), 400 volts. plate -load resistor, the greater the drop in this resistor, the higher the negative bias on the power tube, as this bias is the drop in the resistor, the smaller the plate current in the power tube, and the smaller the current through the section of the voltage divider used for detector biasing. fact, an enormously long aerial could be used. I tried 350 feet, at an elevation of 182 feet from ground, with a good LIMITED SENSITIVITY ground as well, and found it impossible to pick up any inter- The shortcoming of this system of detection, aside from ference, using only one tuned circuit. Selectivity was independ- is fact a simple tuner only about ent of aerial length. In fact, the tuned circuit was connected its instability, the that with and a condition half a dozen stations can be tuned in, even in New York City, directly to aerial ground, that usually makes since a certain magnitude of carrier is required to bring about separation of stations impossible, and yet the nine stations avoid obtainable under those conditions came in without any cross- detection and anything less than this magnitude will talk. reception of the station by causing the tube not to detect QUALITY but to amplify, or be "dead" so that no plate current changes OF SELECTION are produced. This is just the opposite to an automatic volume The circuit could be resonant at only one frequency at a control feature, since only loud stations are received at all. time, hence could detect only one carrier at a time. The usual Use of more radio frequency amplification, preferably with considerations of inadequate exclusion by one tuned circuit do an RF automatic. volume control, would enable enough ampli- not apply, nor is it possible to cut side bands by using one tude to enlarge greatly the number of stations receivable. tuned circuit. Sideband cutting arises from cascaded tuned As was stated, detection will be confined solely to resonance. circuits and from regeneration, but neither was used. The Hence one tuned circuit would be enough. The radio fre- phenomenon of the carrier intensity alone being made to deter- quency amplification could be untuned, as selectivity is not ad- mine detection made it absolutely necessary to achieve resonance versely affected by absence of tuning antecedent stages. In to be able to hear anything, and the moment you were off resonance you were out of the detecting region and heard nothing whatsoever. Hence you can not possibly pick up more than one station at a time. LIST OF PARTS The so-called incredible selectivity of a single tuned circuit L1L2, Cl-Bernard antenna tuner assembly, including link, coil, feeding the detector of a non -reactive audio channel arises from condenser. Cat. BT -L -AC. the relatively high negative bias used for detection, obtainable L3L4, C2-Bernard interstage tuner assembly, including link, in any way, since that increases the input impedance, but a coil, condenser. Cat. BT -R -AC. simple tuned circuit feeding the detector-radio frequency Rv-Volume control, 0-500,000 ohm Electrad Tonatrol potentio- amplification omitted-under best conditions brings in eight meter. stations in New York City with good separation if the stations R1-800 ohm Electrad resistance strip. themselves have good channel separation. This is loudspeaker R2-20,000 ohm resistor leak with mounting (0.02 meg.). operation. Yet the performance can be repeated under the R3-0.5 meg. Lynch resistor leak with mounting. same detector biasing conditions with two transformer audio R4-Multi-Tap Voltage Divider. steps connected in the usual manner. C3-.01 mfd. condenser. But when the detector is worked at its most critical bias C4, C5, C6, C7, C8, C1l-Six 1 mfd. 200 volts. DC. condition, obtainable by accurate apportionment of screen, C9, CIO-Two 1 mfd. 1,000 volt DC. plate, and control grid voltages, the selectivity may well be RFC-Shielded RF choke, 50 millihenrys. such as to occasion incredulity. But the instability is of a high T1-Polo filament -plate supply. Cat. PFPS. order. Ch-Polo single choke. Cat. PSC. Ant., Gnd., Sp(-), Sp(+)-Four binding posts. FEATURES OF FIG. 2 AC switch with 12 ft. AC cable. SW-One pendant is 2, (91/2 x 15"). The apportionment of voltages such, in Fig. as to make Drilled metal subpanel with sockets affixed the circuit somewhat of the automatic volume control type, Subpanel and front panel insulators. while the selectivity increase over the circuit, as previously Two dials. shown, is on account of some carrier intensity detection. A compromise was struck, which left the automatic volume con-

www.americanradiohistory.com February 15, 1930 RADIO WORLD 7 ith N on-Reactive Audio Method of Achieving Good Selectivity

is 14 t3 12 tt i=Ï I ' Ï How to Adopt NR 4

k 1 1 I i1 to the New Detector THE CARRIER intensity detection system depends on the 111 011 most unstable condition of the non -reactive circuit, whereby even so small a difference as the voltage drop across the a a d 3 a a plate load resistor due to the carrier current puts the detector at a detecting point. i11 1 1 1 I I 1 I! i i ! To try this method in modified form on the NR4, connect cathode of detector i 23 4 5 6 1 8 9 101 to the second lug (2) on the voltage detector, and detector screen grid to the third lug (3). Remove R2. The selectivity condition that absolutely blots out the strongest FIG. 3 station if either dial is turned just a trifle does not prevail, as VOLTAGE DIVIDER CONNECTIONS CORRESPONDING the detection does not depend exclusively on the carrier in- TO THOSE IN FIG. 2 tensity. To make this condition prevail would require voltage adjustments not obtainable directly from the present voltage trol feature predominating. The circuit was gaited to a medium divider. However, the potentiometer could be placed from the loud station, so stronger ones came in no louder, weaker ones third lug to the fourth, with screen grid lead to the midtap, coming in louder than in other systems, due to the reduced and the arm moved until the desired condition prevails. 245 plate resistance as the detector bias receded. When working thus the circuit will tune out the strongest The automatic volume control is due to the use of part of local in less than one division of any dial, even if you use only the voltage divider, if only 50 ohms, through which 44 milliam- one tuned circuit. Hence it is so selective a station that other- peres flow at resonance with a station of selected original wise comes in "all over the dial," actually will be "hard to find" intensity. The 44 milliamperes represent the total drain, includ- when tuning the carrier intensity detector. ing all screens and plates of all three tubes, and voltage divider It is interesting to' experiment with this detector. It need not bleeder. The bleeder current alone is 24 milliamperes. The be used permanently with the NR4. modulated current is preponderating through the voltage divider, on weak signals, when the 44 milliamperes rise to 55 milliamperes, so the automatic volume control is most effective where needed most, as a sort of booster. The best of such detector, so that step-up ratio is established. By use of the controls are only partly effective. Bernard tuners full coverage of the wavelength band is assured, besides high gain is established at the low frequencies (high BIAS IS 5 VOLTS NEGATIVE wavelengths). The The reason for the existence moving coils are physically connected to the condenser of the automatic volume control shafts and may be pushed around to any relative position with when part of the voltage divider is used for biasing the detector the fingers. Turn was fully explained in last the condensers so that the plates are entirely week's issue, February 8th. enmeshed. Then see that both dynamic coils are parallel with In the NR4, as diagrammed now, the bias is 5 volts negative the fixed winding. when the total current through the biasing is 44 mil- section It is necessary that the variometer effect be obtained in the liamperes, the detector screen-grid voltage 24 volts, the applied right detector plate direction, so that the dynamic coils aid the fixed seg- voltage 180 volts. ments when the condenser plates are totally enmeshed, and The detector plate current is too small to be measured on oppose at the other extreme. usual meters, but the total of the detector plate and screen currents through the 20,000-ohm resistor and the 50 -ohm sec- BALANCING DIAL SETTINGS tion of the voltage divider was .00014 milliampere. Through 20,000 ohms, therefore, the drop was 2.8 volts. The 44 milliam- You may find that you get widely diverse dial settings, and peres through the 50 -ohm section produced a drop of 2.2 volts, other complications, but all are easily remedied when you bear in hence the negative bias on the detector was the sum of the two, mind that the dynamic coils can be in only one correct position or 5 volts. at full capacity of the condenser, and that correct position alone The bias on the power tube is the drop in the plate load brings in the very highest wavelength stations. When either resistor, not measurable except with a vacuum tube voltmeter, moving coil is wrongly placed, 526 meters is as high as you can for that alone draws no current from the measured circuit, and tune with that circuit, otherwise 550 meters is the highest. all other devices would draw more current than what flowed You can reach down to the lowest wavelength, no matter if the through the plate resistor. A voltmeter of 20,000 ohms resist- dynamic coils are rightly or wrongly positioned, but when ance per volt would be only 50 per cent accurate. wrongly, 200 meters comes in far too high up on the dial. So straighten out. 245 AS this VACUUM TUBE VOLTMETER But still the circuits will not tune in step. To accomplish The bias is obtained by measuring the resistance of the plate this it is necessary to add fixed capacity across the first tuning resistor. It is rated at 0.5 meg., and was actually so close as condenser. An equalizing condenser of 80 mmfd. will just about to justify the use of the 500,000 ohms for computation. With do it, but sometimes not, so add an extra 80 mmfd. condenser. 250 volts on the plate of the 245 power tube, and with 22 milli- Use one equalizer at full capacity and adjust the other so that amperes of plate current, from calibration of the 245 it was at some low wavelengths, around 300 meters, the dials read known that the negative bias was 56 volts. This, indeed, is together. Remember both equalizers are across the same tuning using the 245 itself as a vacuum tube voltmeter, whereby we condenser. know the drop in the plate resistor of 500,000 ohms to have As for tone quality, you will find it as good as you have ever 56 volts. By Ohm's law, which is never wrong, we can now de- heard, probably better. termine the current through the plate resistor. The current is CURE FOR ANY SQUEALS the voltage divided by the resistance, or 56 volts divided by 500,000 ohms, equals .0001102 ampere, or about 110 microamperes. Regarding hum, there is some hum, not objectionable when As for other aspects of the circuit : The Bernard tuners are the program is heard, and a compliment to the circuit for its used, and these have a moving coil in series with a fixed wind- fine low -note reproduction. ing, the total comprising the tuned winding. In the antenna The circuit may squeal at the very low wavelengths, but the stage the primary is a small winding in the antenna -ground volume control should take care of this. If not, use a 3,000 circuit, while the secondary is tuned and has the dynamic coil ohm grid suppressor from control grid of the RF tube to the in it. INTERSTAGE COIL DIFFERENT The interstage coil is of different construction, with three forms instead of two. The outside form consists of the fixed Special Non -Reaction Service part of the tuned winding. The dynamic coil, the remainder IF you have any questions to ask about non -reactive of the tuned winding, is on the moving form. In this instance circuits, address Non -Reactive Editor, RADIO WORLD, the combination constitutes the primary, not the secondary, as 145 West 45th Street, N. Y. City. You will get some reac- the plate circuit is tuned, which is the best method of obtaining tion. Tabulate questions so answers can be written next high amplification from the screen grid tube. The third form, to them. inside, contains a large winding used as pickup coil to the

www.americanradiohistory.com RADIO WORLD February 15, 1930 Conversion of AC Compact Same Tuner Used, Audio Change Easily Made

PLATE VOLTAGE APPLIED Two Curves Exemplify D Carrier Intensity Detector A peculiar effect may be brought about when using non - reactive amplifiers in which the first tube is a grid bias detector of the screen grid type. The operating grid bias is obtained from a drop in a resistor, and this drop depends on the plate current flowing through the resistor. The plate current in turn depends on the intensity of the signal that is impressed on the grid of the detector. For a certain signal intensity there may not be any detection at all but as the intensity increases detection begins. REFERENCE TO CURVES An explanation of the phenomenon can be made simply by referring to curves giving the relation between the grid voltage and the plate circuit. In Fig. 4 are two such curves, for two different screen voltages and the same applied plate voltage. The ordinates (vertical) in these curves are actually the drops in the plate load resistance, but are equivalent to plate current since the plate load resistance is constant. Suppose the starting grid bias of the detector tube is adjusted so that the plate current is zero. This would mean that the A2 starting operating point would be to the left of the bends Al and A2 in the curves. For the sake of definiteness let us con- fine our attention td curve No. 1, which is for the higher screen GRIP VOLTAGE + voltage. The starting grid bias would then be considerably greater than that which gives the plate current indicated at Al. FIG. 4 The starting operating point is to the left of the point where CURVES SHOWING THE RELATION BETWEEN THE the curve touches the horizontal axis. GRID BIAS AND THE PLATE CURRENT, OR THE VOLTAGE DROP IN THE PLATE LOAD RESISTANCE, OF BEST DETECTING POINT A SCREEN GRID TUBE FOR TWO DIFFERENT SCREEN Best detection occurs when the bias is such that the operating VOLTAGES. THE POINTS OF GREATEST DETECTING point is where the curvature or bend is greatest, that is, in the EFFICIENCY ARE Al AND A2. vicinity of Al. While the signal voltage is weak the positive swing of the voltage wave does not enter that region of the stator of the tuning condenser, the coil being connected to the curve where plate current is shown but remains all the time stator, not to the grid itself. where the current is zero. But as the signal voltage increases In New York City the circuit tunes in all locals, some 28 the positive loops of the voltage wave will encroach on the stations, about 20 on the air at the same time, without inter- curved portion of curve No. 1. ference. It did not get much distance, but this may be because As soon as any plate current at all flows this current will I operated the circuit only with knobs, not dials. Not including change that grid bias on the power tube, making it more nega- the rectifier, this is a three tube circuit, and as such it is the tive. The plate current in the power tube decreases, and since best three tube circuit so far developed. this current flows through the grid bias resistor for the detector, The volume on local stations is all -sufficient for speaker the grid bias decreases. That is to say, the actual operating operation, and the volume control is necessary on some stations. point on the detector grid bias, plate current curve moves to the right, and it moves into the region of the curve where the detection efficiency is higher. How to Convert Compact SCREEN VOLTAGE CHANGES SIMILARLY The screen voltage also changes in the same direction as the to the New NR4 Circuit bias so that the curve as a whole moves toward the right. This resembling those in the AC model makes the point of highest detection efficiency recede from the The NR4 uses parts closely bias the less of the HB Compact. It is recommended that the Compact be grid and makes change abrupt. However, the the NR4. The Mershon would be connected operating point moves faster as a result of the grid bias change, changed over to and as the signal voltage increases the point 18 as C10, 18 mfd. as C8, 8 mfd. as C4, and 8 mfd. as operating over- with mfd. takes the point of highest detecting efficiency. C5. The two chokes in the Polo block would be left united, at the midsection, to constitute the single There is an important and practical effect of this operation. without capacity a signal to be detected at all, and is C9, 1 mfd., 1,000 volts, R2, It takes strong that signal choke Ch by series connection. very efficiently. Signals off resonances will 20,000 ohms, RFC, 50 millihenrys, R3, 0.5 meg., Rl, 800 ohms, detected not be mfd, would be required. The present potentiometer detected. The result is that the circuit is highly selective. The C3, .01 selectivity is enhanced by the fact that the operating point is for Rv. C6 and Cll at 1 mfd., 200 volts, would could be used sufficiently negative to preclude the flow of any grid current. be required, too. The original voltage divider affords adequate taps.

Pointers Are Given On Aerial Location The following pointers on aerials are made by E. T. Cunning- metallic objects also are sources of disturbance, and good height ham, Inc.: for the aerial is recommended when roofs are made of tin, It is advised that location of the set within the room and the copper, or metal alloys of any kind. route of the aerial lead-in should not be determined until the Short aerials often prove more satisfactory, for both local and exact position of all other electrical wiring in the room and close distant reception, than long aerials, it is stated by a Cunning- by is located. Cable lead-ins of high voltage, supplying electrical ham engineer. power for neighboring households, should be especially deter- This is frequently true with screen grid receivers, whose high mined in apartment houses, it is declared. amplification ability compensates for the reduction in the aerial wiring is traced, the aerial lead-in should length. Greater selectivity and less interference is achieved by After such electrical adding to the be so placed that it is farthest away from them. shortening the aerial, thus set's ability to "tune Similarly, the aerial itself should be placed as far away from in" distant stations, as well as increasing the enjoyment of the power wires on the roof as possible. Metal roofs and other listener to the actual program.

www.americanradiohistory.com te ebruary 15, 1930 RADIO WORLD 9 New Loftin -White Kit Electrad's Assembly Provides Strong Output from 245

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i/j+i`,CCC1 iCCCCCCC, :CCCCCGC: :CCCOÓC; FIG. I o THE DIAGRAM OF THE ELECTRAD LOFTIN-WHITE AMPLI- FIER WHICH IS OBTAINABLE IN KIT FORM. THE POWER UNITS CONTAIN TWO 2.5 VOLT WINDINGS AND ONE FIVE VOLT WINDING. THEY ALSO CONTAIN A HIGH VOLTAGE, CENTER -TAPPED WINDING FOR THE FULL WAVE RECTIFIER. THE VARIOUS RESISTANCES HAVE BEEN SPECIALLY MADE FOR THIS CIRCUIT. FIG. 2 ACHARACTERISTIC of the Loftin -White amplifier which THE PLAN OF THE ELECTRAD LOFTIN-WHITE makes this circuit so attractive to radio fans is its sim- AMPLIFIER SHOWING THE POSITIONS OF THE plicity. The Electrad amplifier built according td the POWER BLOCK, THE CONDENSER BLOCK AND findings of Loftin and White is no exception to the rule of sim- plicity, as can be seen from the pictures and drawings herewith. THE THREE SOCKETS All the by-pass condensers required in the circuit are contained in a single block, likewise all the filament and power windings vinced theoretically that there is anything superior about it are contained in another block. change their mind when they have heard its performance. No On the front there are four binding posts, two for input and two one is skeptical after a demonstration. for output. At the back there is one binding post for the ground The illustrated device was built up from the official Loftin - connection and a knob controlling the hum -bucking adjustment. White kit put out by Electrad, Inc., of 175 Varick Street, New It is really surprising that such a simple and inexpensive cir- York City, of which Arthur Moss is the head. The amplifier cuit should give such splendid results, and many fans not con - may be used after a tuner or after a phonograph pickup.

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280 245 224 C lOUTPUT INPUT FIG 4 A VIEW OF TE UNDER SIDE OF THE SUB -PANEL OF FIG. 3 THE ELECTRAD LOFTIN-WHITE AMPLIFIER WHICH FRONT VIEW OF THE ASSEMBLED ELECTRAD LOFTIN- SHOWS THE POSITIONS OF THE VARIOUS RESIS- WHITE AMPLIFIER WITH THE THREE TUBES IN TANCES AND POTENTIOMETERS. THE DESIGNATIONS POSITION. CORRESPOND WITH THOSE IN FIG. 1

www.americanradiohistory.com 10 RADIO WORLD February 15, 1930 Stability and Instability Slight Wiring Changes Produce Large Diff By J. E. Technical

FIG. 1 FIG. 2 THIS NON -REACTIVE AMPLIFIER IS RELATIVELY UN- THE STABLE BECAUSE THE BIAS RESISTOR IS PLACED SO GRID BIAS RESISTOR IN THIS CIRCUIT IS THAT TUBE IS PLACED SO THAT THE CIRCUIT IS RELATIVELY THE FEED BACK FROM THE POWER STABLE. FEED BACK FROM THE POWER TUBE DOES IN PHASE. NOT OCCUR. THAT non -reactive differently than other amplifiers behave the voltage supply is in the current types of circuit is one of the first things that experimenters not perfect. But the change discover. They notice, for example, that the plate current through R3 will be small and can be neglected. Not so the in the power tube undergoes wide and seemingly erratic changes increase in the current through Rl and R2. This increase is of when the adjustments of the voltages on the tube or tubes the first magnitude and may in fact be many times greater ahead are changed by small amounts. Or it may be that the than the current that flows steadily through this resistance. plate current in the power tube will drop to almost zero and Since the current through Rl increases as a result of our remain at this value for large changes in the voltages on the assumed change in the bias of the first tube, the voltage drop other tube. in R1 also increases. Hence the circuit is unstable. That is to in the power tube say, the change we introduced at first results in a still greater These fluctuations, or lack of fluctuations, we plate current are not erratic at all. They are normal and should change in the voltage in the same direction. Had started be expected. The adjustment of the tube or tubes ahead of the with a decrease in the bias of the first tube we would have power tube should be made so that the changes in the plate reached the same conclusion, that is, that the resulting change current of power tube occur in the right way when changes are in R1 is in the same direction as the change introduced. made in the grid bias of the tube ahead. This reflected change really amounts to regeneration, and the If the plate current in the power tube does not change at all circuit amplifies more than it would have done had not Rl been for relatively large changes in the grid bias of the tube ahead connected so as to result in a cumulative change. Whether or there can be no amplification and obviously the adjustment is not the instability is great enough to start oscillation depends wrong. The condition that no change in the plate current of entirely on the amplification. If the circuit is such as to create the power tube occurs for large changes in the grid bias of the oscillation, the circuit is unstable in fact, but if it is such as first tube occurs usually when the screen voltage on the first only to increase the amplification, the circuit is only potentially tube is too large, and may not take place at all when the screen unstable. voltage is low. COUNTERACTING EFFECT OF SCREEN VOLTAGE STABILITY OF NON -REACTIVE CIRCUITS In the above reasoning we neglected the effect of the change The behavior of the power tube plate current is indicative of in the screen voltage. Since this voltage increases with the the behavior of the plate current in the first tube. Usually increase in the current through R2, or decreases in phase with the plate current in the first tube is so small that it cannot be it, as the case might be, we have to consider its effect. The measured with instruments ordinarily used for measuring plate increase in the screen voltage tends to increase the plate cur- current. Indeed, they may be so small that they cannot even rent in the first tube when the bias tends fr.) decrease. Fence be detected with these instruments. They can only be detected the change in the screen grid voltage tends to stabilize the by their effects on the plate current in the power tube. circuit. The effect of the grid voltage, however, is greater than The adjustments of the voltages on the first tube have a great the effect of the screen voltage, or else there would be no ampli- deal to do with the stability of the amplifier, or the lack of fication in the circuit. stability, as the case may be. For that reason it is worth while There is also a change in the plate voltage applied to the first to examine a circuit critically with a view of finding its state tube, and this change also is such as to reduce the instability. of stability. The voltage is increased when plate current in the first tube is Consider first the circuit in Fig. 1. This consists of two tubes, decreased. While there are two opposing factors tending to an AC screen grid tube and a 245 power tube. The total voltage stabilize the circuit, the effect of the grid bias changes is much available is connected across the three resistances Rl, R2 and the greater, thus leaving the circuit unstable, actually or R3 in series. The signal voltage impressed on this circuit is potentially. assumed to be E, applied where indicated. What is the state of stability in this circuit? Suppose there CONNECTION FOR STABILITY is an increase in the bias on the first tube. This increase may be due to a suitable change in E or to an increased drop in the resistance Rl. What is the effect of this change in the grid Now let us consider the circuit in Fig. 2. This is the same and particularly what is the effect on as that in Fig. I with the exception that R1 is connected so voltage of the first tube, currents of the first tube flow the drop in the resistance Rl? Does the assumed increase in that only the screen and plate the bias increase the drop in Rl still further or does it decrease through it. This change in the circuit, simple though it may be, change results in an increase in the drop in has a great effect on its performance. it? If the assumed before, that there is an increase in the bias circuit is unstable and if it results in a decrease the Let us assume, as Rl the on the grid of the first tube. The increase in the bias causes a circuit is stable. decrease in the plate current through R4, which in turn causes an increase in the plate current of the power tubes. There is a THE CUMULATIVE EFFECT negligible change, a decrease, in the voltage drop in R3, and there is a large increase in the drop in R2 due to the fact that We have assumed that the grid voltage on the first tube be- the increased plate current from the power tube flows through it. that is, that the bias is increased. This The first effect of the increase in the voltage drop in R2 is to comes more negative, voltage on the tube. This tends to increase in the bias results in a decrea >e in the plate current increase the screen grid results in a decrease in the voltage increase the plate voltage in the tube and hence to counteract through R4, which in turn the grid bias. It, therefore appears drop in the resistance, and hence a decrease in the bias on the the effect in the change in the bias of the power tube results that this circuit is stable. However, we have to investigate the second tube. This decrease in might occur in the drop in Rl. in an increase in the plate current of that tube. The increased effect of any changes that Rl and R2 but not through R3. Indeed, In a screen grid tube the sum of the screen and the plate current flows through for as one goes up the other the current through R3 decreases if the voltage regulation of currents is very nearly constant,

www.americanradiohistory.com February 15, 1930 RADIO WORLD 11 Non -Reactive Circuits erence in Results, Including Regeneration Anderson Editor

FIG. 3 BY SUITABLY CHOOSING THE GRID BIAS RESISTORS RO AND Rl THIS CIRCUIT CAN BE MADE NEUTRAL IN SO FAR AS FEED BACK IS CONCERNED. FIG. 4 down when the grid voltage on the tube changes. However, if THIS the tube is adjusted for amplification, the plate current exceeds IS THE PUSH-PULL VERSION OF THE CIRCUIT IN FIG. 1. the screen grid current and any changes in the plate current IF IT IS NOT SYMMETRICAL IT IS UN- will be larger STABLE TO SIGNAL VOLTAGES. IT IS ALWAYS UN- than the corresponding changes in the screen STABLE circuit. Since both the plate and the screen currents flow TO DC VOLTAGE CHANGES IN THE SUPPLY. through R1, the change in the voltage drop in Rl will be due to the change in the plate current. As the plate current decreases, divided by 42 milliamperes from which to determine Rl. We the change in the drop in Rl will be a decrease, or in the direc- get nearly 18 ohms. Multiplying this by 6,400 we obtain 115,200 tion opposite to the grid voltage change that produced it. This for Ro. Thus the order of magnitudes of the two resistors is is degeneration and again we conclude that the circuit is stable. 20 for Rl and 100,000 for Ro'. Exact adjustment in any case Indeed, this circuit may be so stable that it will not amplify well. can be effected by making Ro fixed and Rl variable.

COMPROMISE POSSIBLE EFFECT OF BY-PASSING

We thus conclude that the circuits in Fig. 1 and Fig. 2 are A by-pass condenser across any resistance such as R1 or Ro totally different although they look almost identical. will tend to reduce the feed back, whether it causes regeneration In a good amplifier we want neither regeneration nor degenera- or degeneration. For that reason a condenser should always be tion. Or if we want regeneration we only want a little of it so used. But if a condenser across R1 in Fig. 1 is to be effective that the circuit will not break into oscillation. Is it possible to at the low and middle audio frequencies it must have a very arrange the circuit so that we can enjoy this happy compromise? high capacity. Indeed, it would have to be unreasonably high The fact that one of the circuits is stable and the other if it is to prevent feed buck at the lowest audio frequencies. unstable suggests a simple arrangement which will effect the The reason for this is that the resistance is small. compromise. If we combine the two as we have done in Fig. 3, A resistance across R1 in Fig. 2, or across Ro in Fig. 3, resistance Ro will make the circuit stable and resistance Rl would not have to be so large because the resistance is higher. will make it unstable. The two together will make it neutral, It would be very easy to nullify the effect of the balance estab- or feebly regenerative or degenerative, according to the rela- lished between Ro and Rl in Fig. 3 by connecting condensers tive values of Rl and Rd. of improper values. If condensers are used their impedances It is not a simple matter to calculate the relative values of should be proportional to the resistors, or their capacities should these two resistors which will result in the neutralizing adjust- be inversely proportional to them. For example, if the con- ment, because we do not know what the current changes in the denser across Rl is 8 mfd. that across Ro should be only .0016 two will be for a given change in the grid voltage. The best mfd. If this proportion is not maintained the advantage gained that can be done is to give the result in general terms. Suppose by balancing would be lost and it would be better to use Rl id is the change in the signal current through Ro and it the alone and then connect an electrolytic condenser across it. change in the signal current through Rl due to a given change in the grid voltage E. Then in order that there should be no STABILITY OF PUSH-PULL CIRCUITS net change in the feedback, either positive or negative, Rojo should be equal to Rli1. But this equation is of little help since What has been said of the single -sided amplifiers in Figs. 1 we do not know the values of the current changes. Experi- and 2 applies with almost equal force to push-pull amplifiers mentally the adjustment could be made exactly on a given cir- of the same types. If the push-pull amplifiers could be made cuit, but it would ngt be simple. The experiment would be based exactly symmetrical this statement would not be true because on the scheme used in determining the amplification factor of there could then be no feed back one way or the other. But a tube. no amplifier can be made exactly symmetrical, due to differences APPROXIMATE SOLUTION in tubes and resistors. Any such amplifier is to some 'extent single -sided, that is, stronger on one side than on the other. (Continued on next page) But by making certain reasonable assumptions we might arrive at a solution which gives the order of magnitudes of the two resistances. Let us first assume that the changes in the current are proportional to the steady plate currents, which may or may not be justified. Next let us assume that through Rl only the plate current of the power tube flows and through Ro only the plate current of the first tube. This assumption is not far from the truth in view of the relative values of the currents. The plate current in the first tube will he about 50 microamperes and that in the power tube about 32 milliamperes. If we put these two currents in the formula we arrive at the conclusion that Ro should be 6.400 times greater than Rl. But how large should either be? This we can settle by using the required bias on the first tube, which should be 1.5 volts, half of which is dropped in RI and the other half in Ro. At this point we have to use a different current through Rl, for we can no longer assume that the plate current of the power tube alone flows through it. For bias purposes the cur- FIG. 5 rent through RI will be the 32 milliamperes of the power tube THIS IS THE PUSH-PULL VERSION OF THE CIRCUIT plus the current through R3. We may adjust the current so IN FIG. 2. IT IS RELATIVELY STABLE BOTH AS TO that the total is 42 milliamperes. Hence we have .75 volts SIGNAL AND SUPPLY VOLTAGES.

www.americanradiohistory.com 12 RADIO WORLD February 15, 1930 Results with Screen Grid T Gang Tuning One Reason for Same Number of SG By Edward

LIST OF PARTS Ch-Five 50 millihenry choke coils. T-Two radio frequency transformers such as Screen Grid Coil Co. SGSS. C-Seven .1 mfd. by-pass condensers. Cl-Two .0005 mfd. tuning condensers. C2-One 2 mfd. condenser, low voltage rating. C3-One .00025 mfd. condenser. C4-One .01 mfd. mica type condenser. CS-Five 2 mfd. or larger by-pass condenser, 400 volt rating. C6-One 4 mfd. by-pass condenser, or larger. Rl-One 150 ohm resistor, 10 milliampere capacity or more. FIG. 1 R2-One Electrad 5,000 ohm potentiometer. THIS RECEIVER COMBINES ORDINARY RESIST- R3-One 7,000 ohm fixed resistor. ANCE COUPLING WITH NON -REACTIVE COUPLING R4-One Electrad 2,000 ohm resistor. TO GAIN MANY ADVANTAGES. R5-One Electrad 25,000 ohm resistor. R6-One Lynch .1 megohm metallized resistor with mounting. IF screen grid tubes are so much superior to three -element R7-One Lynch one megohm resistor with mounting. tubes, why is it necessary to use more of them in modern R8-One 25 ohm resistor, 60 milliampere capacity. receivers than are used in circuits using three -element tubes R9R1O-One 2,000 ohm potentiometer, 60 milliampere capacity. exclusively? This question has been asked many times and Rl]-One 25,000 ohm potentiometer. in many quarters, and it does seem a reasonable question to ask. R12-One Lynch .5 megohm resistor with mounting. The answer to this question is that it is not necessary to use R13-One 15,000 ohm resistor. more screen grid tubes than three -element tubes if we are Four five prong sockets. satisfied with the same sensitivity, or if we are content with One four prong socket. double tuning controls. A power supply giving at least 400 volts and 60 milliamperes and We have seen many receivers incorporating four and more at least two 2.5 volt windings. screen grid tubes which did not do as well, either in sensitivity [The current which any of these resistors will carry will be or selectivity, as circuits incorporating three -element tubes less than 10 milliamperes, except those otherwise listed.] throughout. But comparisons of this kind are misleading as they are fair neither to the screen grid nor the three -element fair it is necessary to tube receivers. To make a comparison of all the conditions into consideration and to weigh their must intercept any electric line force running from any part take of one stage to any part of another stage, considering only those relative importance. parts which are at a high potential. Since the lines of force GANG TUNING DIFFICULT may be curved, it is best to make the shield larger than the geometrical dimensions would call for. When many tuned circuits are controlled by a single knob there is often a great loss in selectivity, and as a result of this, USE OF LARGE COILS also a great loss in sensitivity. More tuned circuits and more tubes are necessary to overcome the effects of lack As there are only two tuned circuits in the receiver illustrated amplifier in Fig. 1, we not use of very small coils. of tracking of the tuned circuits. But single control is a great are limited to the convenience and most persons prefer single tuning control. The DX records made in the early days of broadcasting with receivers using one or two radio frequency tubes, including the detector, were largely the result of well -controlled regeneration, but extremely accurate tuning also was responsible. If a receiver has two tuners now, both controlled by the same knob, and Stability of Non - if there is no regeneration, it is quite likely that the set will not break records. (Continued from If the two tuned circuits in the receiver are accurately tuned, Insofar as it is unsymmetrical it may be either stable or and if there are no great losses in the tuning coils, a receiver unstable. incorporating two screen grid tubes ahead of the detector will Let us consider for a moment the circuit in Fig. 4, which is be sensitive enough for all average use. Much, however, will the push-pull version of that in Fig. 1. Suppose there is a dis- depend on the coils used and how they are used. They must turbance in the voltage crop in Rl in Fig. 4 tending to increase not be shielded too well, because if they are the eddy current the voltage drop. The plate currents of both screen grid tubes losses will be excessive. will be decreased and those in both power tubes will be increased. Hence the current through Rl, and consequently the drop, will PRECAUTIONS AGAINST LOSSES be increased. This circuit is therefore unstable even when perfectly symmetrical, but only disturbances in the bias resistor, If we put the coils inside small shields, as must be done for to circuits and many screen grid or DC voltage supply. space reasons when many tuned Suppose there is a change in the current through both resis- tubes are used, there will be so much loss in the shields that If, however, we tances marked R4. This change will make the grid of one selectivity and sensitivity are heavily taxed. input tube more negative and that of the other less negative by allow much room between the shielding and the coils both will as in the circuit the same amount. The two plate currents will change cor- be good. When only two tuning coils are used, respondingly. So will the plate currents in the power tubes. in Fig. 1, it is possible to mount the coils, without resort to coupling between them. To One will admit more current and the other less by the same shielding, so there is no inductive amount. There will be no change in the drop in Rl. Hence the do so we place them electrically at right angles, or so that the angles. The circuit is stahle insofar as the signal voltage is concerned. field of one coil cuts that of the other at right There will be cumulative changes due to disturbances in the simplest way of doing this is to make their axes perpendicular of the two plate supply, but these are proportional and are not likely to to each other and place them so that the centers upset the adjustment of the amplifier. coils lie on the same horizontal line. It is possible to place three coils so that they are mutually perpendicular but no more. UNBALANCED INTENSIFIED When the coils have been placed so that there is no mutual inductance between any two there is no need at all for shield- If, however, the two sides of the amplifier are not equal as to ing so far as the magnetic fields go. But there would still amplification and if the tubes are not equal as to mutual con- have to be some shielding against electric coupling. This shield- ductances, the inequalities will be intensified and cause a greater ing would not have to surround the coils, but only separate the unbalance of the circuit. We conclude that this amplifier is not parts of one stage from the parts of another. A sheet of the best, just as we concluded in connection with the circuit in aluminum or other good conductor of electricity is all that Fig. 1. would be required, provided that this sheet is connected to Let us see how the circuit in Fig. 5 behaves to changes in ground. supply and signal voltages. It will be noted that this is the In placing the sheet shield it should be remembered that it push-pull version of the circuit in Fig. 2.

www.americanradiohistory.com February 15, 1930 RADIO WORLD 13 ubes Compared with Others Valves with No Greater Sensitivity or Selectivity Foote Harrison

224 224 224 221 224 2

MFD

2.5 V.

280 5V. Eli 25180 1855.0 MIGN »LAUr I.000V.

Ç COMMON INPUT A SPLENDID VOLUME CONTROL IS PROVIDED IN THIS RECEIVER IN THE FORM OF A HALF MEGOHM POTENTIOMETER IN THE GRID CIRCUIT OF THE FIRST TUBE. THOROUGH FILTERING IS PROVIDED FOR THE NON -REACTIVE AUDIO AMPLIFIER. Diameters as large as three inches can well be used, although a difficult task as it requires not only an adjustment of the somewhat smaller coils will work out all right. distributed capacity in each circuit but also of the inductance When building a receiver of this simple type it is strongly of each coil. recommended that the condensers be tuned separately. If they It may be worth while to give a few practical suggestions must be put on one control there should be a good sized trim- on the adjustment of tuned circuits. Suppose there is a mer, available from the panel, across one of them. Whether trimmer condenser across each tuning condenser and further this trimmer should be put across the first or the second Cl suppose that the main condensers are connected to the same depends on the inductances of the coils and the distributed shaft. Let a short-wave station, near the 200 -meter limit, be capacity in the two tuned circuits. It will only take a few tuned in. Adjust the trimmers until the station selected comes minutes to determine where it should be in any particular case. in loudest. Note the settings of the trimmer condensers. Now go to the other end of the dial and in the same manner tune ADJUSTMENT OF CIRCUITS in a long-wave station. The trimmer condensers will now undoubtedly have different adjustments. It cannot be emphasized too strongly that common control Note particularly which tuned circuit required the greater of two or more tuned circuits is not consistent with selectivity change in the trimmer condenser. For example, the second unless every tuned circuit has been adjusted so and sensitivity tuned circuit in a receiver like that in Fig. 1 may require that that it is exactly alike every other. The adjustment is usually the trimmer condenser be fully meshed at 550 kc., while the first requires only that it be half meshed. This may mean that the inductance in the second tuned circuit is too small and that a turn or two should be added. Or it may mean that the first coil is too large and that a turn or two should be removed from that. Whether it means the one or the other must be Reactive Audio determined from the position on the dial that the high wave station comes in. If it comes in well below 100 on the dial page 11) turns should be removed from the first. If it is very close to If the drop in Ro increases for any reason there will be nd the 100 mark it is safest to add a turn or two to the second. feed back from the power tubes because the plate currents from If the trimmer condensers should show the reverse situation, those tubes do not flow through the resistance. But the plate the above directions should also be reversed. currents as well as the screen currents of the first two tubes THE AUDIO SYSTEM will flow through it, and the net current will flow in such direc- is is far as The audio system in the circuit above a bit unusual. Be- tion as to decrease the change. The circuit stable as and the first audio amplifier the coupler changes in the drop in Ro are concerned. tween the detector R4 is the ordinary resistance with stopping condenser. That be- Now suppose a signal voltage is impressed on the two power is popularized resistances. Let the voltage impressed on the upper tube be tween the first audio tube and the that slightly larger than that impressed on the lower. Each signal by Loftin and White. tube, but since the There are several reasons for the choice of this type of will feed back and reduce the input on that is voltage is not so high is larger this will be coupling. The first that the required signal impressed on the upper tube the if non -reactive coupling were used throughout. decreased the more. Moreover, since this is greater it will as it would be tubes, and therefore The second is that the circuit is more easily adjusted. The determine the feedback direction for both is not impaired. Fourth, amplification at zero the signal input to the lower tube will be augmented while that third, quality be frequency is eliminated except after the stopping condenser. of the upper will be decreased. Hence the inequality will in the plate current in the detector due to in in Fig. 5 Fifth, the change decreased. Here is another point which the circuit changes in signal level does not upset the adjustment of the is superior to that in Fig. 4. voltages in the non -reactive portion of the amplifier. Sixth, Since the feed back in the circuit of Fig. 4 is opposite to any difference in the input voltages the audio amplification is greatly increased. Seventh, the detect- that in Fig. 5, it follows that ing efficiency is not impaired, but rather enhanced. Eighth, less on the two tubes in Fig. 4 will be intensified. radio frequency amplification is needed to obtain a given output NOT ALL ADVANTAGE than when only one audio tube is used. A possible disadvantage is that under certain conditions the But the circuit in Fig. 5 does not have all the advantages and circuit may motorboat. The reason for this is that the detector that in Fig. 4 all the disadvantages. When Ro in Fig. 5 is large and the power tube have a common impedance in the B supply. enough to give the proper bias, the reverse feed back will be sc The feedback through this impedance is such as to increase the large that the amplification is reduced greatly. This reduction, signal. This effect, however, is minimized by the parallel con- however, need not be appreciable except at the lowest audio nection of the plates, or by the use of separate voltage dividers. frequencies, because a by-pass condenser of usual values will be Si -ice R13 must be a rather high resistance, very Iittle feedback effective in preventing any feed back at the more essential audio can occur and the danger of motorboating is not great. If it notes. A little reverse feedback at the sub -audible notes is should occur it can be stopped by a condenser of large value. advantageous in that it prevents disturbances in the voltage This condenser should be placed either across R5 or across both adjustments. R5 and R4, and it should preferably be an electrolytic.

www.americanradiohistory.com 14 RADIO WORLD February 15, 1930 Overall Measurements Two Oscillators and Vacuum Tube Volt By Captain Peter Contributing

;L i1í -A

DETECTOR

B- +Bi +B1 FIRST OSCILLATOR VACUUM TUBE VOLTMETER A SUGGESTED ARRANGEMENT FOR MEASURING THE OVERALL AMPLIFICATION, THE SELECTIVITY, AND THE AUDIO FREQUENCY CHARACTERISTIC OF RADIO RECEIVERS.

VARIOUS methods for measuring the overall amplification The amplification in the audio circuit is involved because the of a radio receiver have been described but nearly all are beat note is amplified before it is impressed on the vacuum tube complex and not readily applicable in places where only a voltmeter. Hence the device not only measures the radio fre- limited equipment is available. quency amplification but also the audio frequency amplification, The method which is about to be described seems to be and the detecting efficiency as well. simple enough td fall within the scope of all experimentally inclined fans and is capable not only of measuring the overall MEASURING THE SELECTIVITY amplification of receivers but also of measuring the selectivity and the quality of the audio amplifier. As far as is known to the The selectivity of the circuit can be measured by detuning the writer the method has never been described before, although in receiver by known amounts and measuring the audio frequency the January issue of the Proceedings of the Institute of Radio output at each setting. In order to accomplish this with fair Engineers Suits describes a method of measuring harmonic con- accuracy it is necessary that the tuning dial of the receiver tents of alternating current and voltage waves by a method be calibrated. It may be that this calibration is not accurate which is based on a similar idea. enough for measurement purposes or that it can not be cali- The principle of the method is as follows: brated accurately enough. In that case another method would A radio frequency voltage of constant, though not neces- have to be used. When the tuning of the radio amplifier is sarily known, intensity is introduced into the grid circuit of the changed for this purpose it is essential that this change does detector tube in the receiver to be tested. The frequency of not in any way change the frequency of either of the two this voltage is adjusted until it beats at a suitable audio fre- radio voltages involved. quency with an unmodulated radio frequency introduced into In case it is not practical to detune the radio amplifier the the receiver in the usual manner. This signal voltage may be same effect can be achieved by leaving the tuner where a given derived from a local broadcast station during moments the car- signal comes in loudest and then change the frequencies of rier is not modúlated or it may be introduced by a separate both radio voltages impressed on the detector. This can be local oscillator. It is preferable to use two local oscillators, one accomplished easily if the two oscillators used are calibrated in cpupled to the input of the receiver and the other to the kilocycles. The two frequencies should be changed so that the detector grid. audio frequency beat remains constant, since a change in the The beat frequency generated in the detector is impressed on audio frequency might lead to spurious results due to differences the audio amplifier without any special connections, and the in the amplification at different audid frequencies. It is rela- amplified beat voltage is measured at the output by means of tively simple to pick out an audio frequency of say 1,000 cycles a vacuum tube voltmeter. and adjust to that every time. As a guide a tuning fork or a Helmholtz resonator may be used, or even a given note on a PROPORTIONAL TO SIGNAL piano. The 400 cycle note is often used as standard of reference. The intensity of the beat note produced is proportional to the MEASURING AUDIO AMPLIFICATION local oscillation introduced at the detector and also to the signal voltage as it arrives to the detector from the radio frequency The measurement of the amplification at audio frequencies, and amplifier. This proportionality assumes that the detector hence the quality, is suggested in the preceding paragraph. When operates on the square law of detection, an assumption which is this is to be done the radio frequency impressed on the radio usually justified. frequency amplifier is left unchanged and only that introduced If the voltage introduced by the local oscillator directly into directly on the grid of the detector is changed by known the detector is kept constant in magnitude, the heat note pro- amounts. Here again the method calls for a calibrated oscillator, duced will be proportional td the signal voltage from the ampli- calibrated in kilocycles or fractions thereof at low frequencies. fier. Now if the signal impressed on the input of the radio fre- When the frequency of the second oscillator is changed the quency amplifier is also constant the beat note will be propor- amplification in the audio amplifier will change because the tional to the amplification at radio frequency. If the signal is audio frequency is changed. The output at any audio frequency derived from a local station the intensity will be constant, since can be measured with the vacuum tube voltmeter. Since the in- fading effects will not be appreciable, and also since the fre- tensities of the two radio frequencies are constant and since quency will not vary enough to detune the amplifier to an ap- the tuning of the receiver is not changed, any changes in the preciable extent. The trouble with using a local station as a readings of the voltmeter must be due to changes in the ampli- source is that it does not remain unmodulated for long periods, fication in the audio circuit. and there may not be sufficient time to take a reading. If a The vacuum tube voltmeter may be connected at one of sev- local oscillator is used for supplying the signal the intensity can eral different points, depending how much of the audio system be maintained reasonably constant for long periods. it is desired to include in the test. For example, it may be con-

www.americanradiohistory.com 16 RADIO WORLD February 15, 1930 i February 15, 1930 RADIO WORLD 17

NEW CONDENSER Filling Graf With Stock He Got at $1,500 Screen Grid Tubes TERMS EXPIRE Tube Gas Long Job Widen Day Range Dirigibles, such as the Graf Zeppelin, Grew to $3,071,897 "Daytime reception has been materially WBAL cannot fly without gas, and radio tubes benefited by newest type receivers using MIKE AT cannot work with gas. As much care is screen grid tubes," reports Alfred H. FOR ALL FIVE devoted to getting the gas out of a tube Another Kolster executive who made a bi g profit on stock transactions was Maurice C. Grebe, who has been in touch with sta- as to keeping it in the Zeppelin. The Rypinski, who was general sales manager, a p osition he accepted with C. Brandes, Inc., in tions throughout the country. vacuum in the modern radio tube is well 1922whl ch co rPoranon was bought out by th e Kolster Radio Corporation. Mr. Rypinski is Judith C. Waller, director of WMAQ, NON -POLARIZED nigh perfect, according to Walter Krahl, now radio department manager of the Westinghouse Electric and Manufacturing Company. Chicago, declares that the daytime range chief engineer of the Arcturus Radio He testified before John A. Bernhard, speci al master in chancery, at a hearing in Newark, of that station has been very widely ex- ON THE BOARD Baltimore, Md. Tube Company, of Newark, N. J. N. J., in an investigation of whether any one h ad "rigged the market" for Kolster stock, as tended and that reception is reported as WBAL is using a new type of con- "Assuming that the residual gas in a charged by Albert Schwartz, a lawyer of Pat eon, N. J., himself a holder of 400 shares of far away as New Orleans, Texas, Okla- designed by Gerald W. Kolster stock. Mr. Rypinski denied, as had ery W. Stone, president, and Rudolph Spreckels, homa, the Dakotas, and in Washington. denser microphone good radio tube were all hydrogen," says Saskatchewan. An Cooke, chief engineer. This microphone Mr. Krahl, "it would require 167,000,000,- chairman of the board, participation in any of or the short sale of any Kolster stock. The highly sensitive receivers thus amendment to the radio law n_akes has been in 000,000 tubes to supply enough gas to fill Mr. Stone had testified to making a profit .f $698,000 on Kolster stock, and Mr. Spreckles, made it possible for hundreds of thou- the terms of the present Radio Commis- e x p e rimental the gas bags on the Graf Zeppelin. A the sugar magnate, had made large sales, too, y his own testimony, which did not reveal the sands of persons living a considerable sioners expire on February 23rd. Presi- use at this sta- few years ago, before we perfected our profit. distance from broadcast stations td re- dent Hoover has not disclosed what tion for about evacuating systems, only half this num- For $1,500 Rypinski bought 30 per cent. of the Brandes stock in 1922, an opportunity ceive programs during daylight hours. changes, if any, he will make, but there a year. Dupli- ber of tubes would have been required. offered to him if he would accept the sales management. The money was a "nominal" amount In agricultural sections, the information is a general impres- cates have "An idea of how many tubes are repre- for the stock, he declared. received in these programs, as well as the sion that reappoint- been con- sented by the number 167,000,000,000,000," He remained in the position during and after ownership changes, including the Federal entertainment, is much desired, and en- ments will be the structed in the concludes Mr. Krahl, "will be more Brandes regime, and in 1929 disposed of his last holdings, in Kolster, by open market sale, thusiastic letters have ocen forwarded order of the day. Of WBAL shops tangibly appreciated when it is mentioned whereupon he was able to figure his profit from $1,500 as $3,070,397, but- to the stations as a result. the Commissioners, and are used that this represents the world's produc- There was the Federal income tax! C. W. Horn, Chief Engineer of the almost exclu- tion for about three million years! Each And the net profit, tax deducted, was only $934,326. National Broadcasting Company, says that sively at this year we leave about one cubic foot of gas Frederic Dietrich, vice-president of Kolster and also a director thereof, made $2,021,219 the screen grid tubes have enabled the station. Moist divided among all the tubes made on net profit on $1,200 invested in 1912, he himself testified. His gross profit was $6,248,265, he manufacturers to design more selective or humid earth." said. The 1912 purchase brought him control of the Brandes corporation. It was from Mr. receivers. He terms this feature of weather has no Dietrich that Mr. Rypinski got 30% of Mr. D ietrich's holdings for the nominal $1,500. Mr. selectivity a paramount factor in achiev- effect on the Dietrich, who never participated as an executive of Kolster, despite his title, held only pre- ing the superior results in reception which efficiency or operation of these micro- ferred stock. Like Mr. Spreckles, he is a heavy creditor of the Kolster Corporation, which is are now so common. phones, says WBAL. in the hands of three co -receivers, and has indorsed heavy notes. He puts the amount owed Under Mr. Cooke's direction, special him on Kolster notes at $700,000 and the amount of Kolster paper he endorsed at $1,200,000. circuits have been installed in WBAL's studios to permit the operation of two TRADE EXHIBIT condenser microphones in each studio and also one in the announcer's booth. The TUBE MARKET Ira E. Robinson microphones themselves are very different New NBC Artists Service from the usual type of condenser micro- GOES TO EAST phone and are like no others being used today. Plans are maturing for the annual CONCENTRATING Use Push -Pull radio industry events, the convention and Signs Up Noted Talent They employ the push-pull principle of trade show of the Radio Manufacturers Creation of a new NBC Artists Service and the signing of a number of the foremost stars Competitive lines in the radio tube field Chas. McK. Saltzman operation in that the vibrating diaphragm Association at Atlantic City, week of June of the concert and operatic world were announced by M. H. Aylesworth, president of the Na- are being drawn now for the sharpest 2. More than 30,000 persons connected contest in two are appointees of of the microphone is provided with two tional Broadcasting Company. the history of the industry, President fixed plates forming the condenser of the with or interested in radio manufactur- Schuman-Heink, Werrenrath, Lauri -Volpi, Walter Damrosch, Josef Lhevinne, Mischa Levitzki, said Paul P. Huffard, newly elected pres- Hoover. ing and radio merchandising attended Paul Kochanski and Hallie Stiles are under contract and will make personal appearances ident of National Carbon Company. They are Maj.-Gen. instrument, one of the plates being per- Charles McK. Saltz- forated in a special manner to permit the this event last year. throughout America next season under the auspices of the new organization. "The industry finds itself in the same This is the first time that the show The NBC Artists Service enlarges the scope of the concert activities begun by the National condition that confronted the automotive man, Middle Western passage of the sound wave energy to States, D. L. the diaphragm and cause the diaphragm and convention, the largest industrial Broadcasting Company about a year ago under the direction of George Engles. The Service will industry in its early years," he said. and W. gathering in the United States, has been absorb all present concert and managerial activities of the National Broadcasting "From a position in which a good portion Starbuck, for New to vibrate in accordance with the sound. and Con- York and No polarizing voltages are used with held in the East. For three years the cert Bureau, which name will be discontinued. of the annual production came from a New Eng- events have been held in Chicago. The NBC also is sponsoring the expansion of the Civic Concert Service, now in number of scattered manufacturers, the land. this instrument and no audio amplifiers are Chicago. The used. The usual polarizing and amplifying There will be national gatherings of to include the entire country. automotive industry has evolved to a stage other Commis- affiliated radio industry organizations, the The function of this organization is to wild up permanent audiences throughout where the bulk of production comes sioners are Ira E. W. ll. system is replaced with a simple radio the Robinson, L,. Dcarbucu frequency system giving complete free- National Federation of Radio Associa- country by means of membership subscriptions' extending over a period of five years. At from a very few concerns. This is ex- Southwest tions, the Radio Wholesalers Association, present 1157 cities are operating on this plan, Peach with annual memberships actly the stage at which, in our opinion, chairman; Harold A. Lafount, Western dom from distortion, according to WABC, ranging from 1,000 States, and thus insuring that the electrical out- the organizations of radio dealers and to 3,800. The same system will now be ma available throughout the eastern states as well the radio tube industry will have ar- and Eugene O. Sykes, Southern jobbers, and other radio organizations. as the west, according to Engles. New York headquarters has been established at the National rived by the end of 1930. The handwrit- States. put of the microphone is exactly in ac- It is regarded cordance with the vibration of the di- The show, convention and banquet will Broadcasting Company Building. ing is definitely on the wall and should as certain that four of aphragm. he held in the new mammoth civic audi- Engles explained that the new NBC Art sts Service will continue to represent more than not be disregarded. the Commissioners, excepting Mr. Robin- "National Carbon Company, through son, will be reappointed, but many believe Silent Background torium on the boardwalk. 200 artists now under contract to the National Broadcasting and Concert Bureau, whose activ- The very latest in modern radio will ities in radio, talking pictures, vaudeville and concert have become an important factor in the its Eveready Raytheon Tube division, is Mr. Robinson will not only be continued as The use of these microphones results be exhibited. The latest in receiving sets, entertainment field. definitely in the tube business to stay. a Commissioner but also as chairman. in a silent background for the reproduced tubes, loudspeakers, parts, cabinets, ac- With 40,000,000 radio listeners estimated Contrary reports circulated earlier cited music, especially valuable for broadcast- cessories, etc., will be displayed by about today in the United States, the tube the possibility of Mr. Robinson being ing in large auditoriums where high am- 300 of the leading radio manufacturers, market offers one of the greatest replace- passed over entirely, some one else ap- plification is necessary properly to repro- all members of the RMA, but only for the ment markets available to industry. It pointed to the Commissionership, and duce the sound. trade. The radio exhibition will not he Two Foreign Programs Heard is destined to grow from year to year. Maj.-Gen. Saltzman, former Signal Corps "WABL's listeners may have noticed open to the public. "As a result of our withdrawal from the chief, made chairman. the high quality of organ pick-ups from glutted radio receiving set field, our the Peabody Conservatory of Music in company has fortunately taken itself out Baltimore during the recitals on Thursday Over Chains in One Afternoon of a competitive position with all set evenings and also during the Evening Two Stations Ask makers. Two European broadcasts were relayed throughout the United States by the National Broad- "National Carbon Company, in addi- Reveries programs on Sunday nights," casting recently. says an announcement by the station. For Increased Power Company tion to extensive manufacturing resources, "Prior to the use of these microphones The first was a special program from Holland, where Dutch program experts offered enjoys the advantage of possessing the Washington. special musical features for American listeners. The second was another topical review from largest force of salesmen contacting the the reproduction of these programs was the scene of the London Naval Arms always somewhat marred, but it is felt WLBW, operated by the Radio Wire Conference, continuing NBC's weekly service for Amer- tube distributors of America. This sales that the quality obtained with this new program Corporation of America, former- ican audiences on this event. force consists df more than 200 men, oper- type of condenser instrument has per- ly the Petroleum Telephone Co., of Oil As an additional feature of the Holland program, the music was prefaced by a short talk ating nationally. In our Eveready Ray- City, Pa., 500 watts night, 1,000 watts day, by William Hard, who was heard as NBC's official observer at the naval parley during the theon tube division this year we are mitted the broadcasting of the deep bass Holland, tones as well as the flute -like tones of asked an increase to 1,000 watts day and opening days. Hard was now in Eindhoven, en route for other parts of Europe before confirming our own confidence in the the small pipes of the great organ with night on the 1,260 -kilocycle channel. returning to the United States. future of the tube business itself by sup- The Dutch program was heard in country through all combined the a faithfulness and realty that leaves little Change in wave length and increase in this networks of porting our dealers with the largest ad- to be desired." power from 100 to 500 watts was sought NBC, at 1 P. M., Eastern Standard Time. By special arrangement, WOR also was linked vertising appropriation being devoted td Cooke has been chief engineer of WABL by KMJ, of Fresno, Calif., operated by with WEAF and WJZ in the New York area. any single product of National Carbon i ever since the station was planned, early the Fresno "Bee." The station now oper- England was heard at 4:20 P. M., S. S. T. The voice was that of Vernon Bartlett, official Company, Inc." the British Broadcasting and WOR in New York in the Summer of 1925. He is a John Hop- ates do 580 kilocycles and desires a change commentator of Corporation. WJZ headed Most tube makers are finding the going kins School of Engineering graduate. to 1,210 kilocycles. the NBC network for this feature. tough indeed just now. Eugene O. Sykes Harold A. Lafount

www.americanradiohistory.com February 15, 1930 RADIO WORLD 15 of Receiver Performance meter Test Selectivity, Gain and Quality F. O'Rourke Editor fleeted across the input to the power tube or across the loud- pendent batteries. Howeverif very large by-pass condensers speaker. If the effects of the loudspeaker are not desired a are connected across the plate return leads one battery will suitable non -reactive resistance can be connected in place of the serve both tubes without any trouble. Only one by-pass con- speaker and the voltmeter connected across this resistance. denser, C2, is shown, and this is connected across the grid bias It may be desired to study the effects of baffle boards of dif- resistance of the voltmeter tube. Two microfarads will be large ferent sizes or of a single baffle board at different frequencies. enough for this condenser. The grid bias resistance should be Again, it may be desired to study the effects of open windows so large that the tube will operate as a grid bias detector. It and various sound -absorbing surfaces in the room. Suitable is preferable to use a battery for bias. This battery should be conditions can be arranged in any case very simply. The vacuum connected between the same point as the resistor and in place of tube voltmeter in these cases should be connected across the it. speaker. The input terminals of the vacuum tube voltmeter should be ARRANGEMENT OF TESTER connected across the points the voltage between which it is desired to measure, for example, across the loudspeaker term- 1 herewith shows the essentials of the circuit. The tube Fig. inals. The M in plate circuit of the tube should be td the left is the detector tube in the receiver to be tested. It is meter the made with a a sensitive milliammeter, say an instrument of 0-1 milliampere transferred to the test circuit and connections are a The value re- suitable cable. It will be noted that the detector tube and tilt sensitivity, or better microammeter. of the for the coupling sistance R3 depends on the particular tube used, on the bias rest of the tester are entirely independent except selected, on the sensitivity of the meter and on the plate volt- between the coils L and L2. This independence is maintained tube. in order that the test circuit should have as little influence on age applied to the 171A the receiver as possible. The same tube is plugged into the re- LIMITING VOLTAGES ceiver detector socket and the only reason for transferring it is to introduce the coil L2 in the grid circuit. If a high plate voltage is used the range of the voltmeter will Now this coil will have a slight detuning effect on the last be greater and then the resistance R3 should have a high value. tuned circuit. This should be compensated for when the change- It is not essential that the vacuum tube voltmeter have as wide over is made. a range as the voltages that may be encountered in ordinary re- Loose coupling between the oscillator LC and the detector ception because the voltage of the beat note may be adjusted is essential because if the coupling is close the effect of the to almost any desired level either by adjusting the radio fre- oscillator on the tuning characteristic may be so great that quency voltage impressed on the receiver or by adjusting the compensation for it may not be possible, and also because if radio frequency voltage introduced directly into the grid cir- the coupling is not loose it may be impossible to secure very cuit of the detector, that is, by adjusting the coupling between low audio frequency beat notes. coils L and L2. It might be stated that the audio voltages encountered in a EFFECT OF TRANSFERRING TUBE radio receiver across the loudspeaker may be as high as 150 volts. It will be noted that when the detector tube shown in the There is no reason why voltages higher than 5 volts should figure is plugged into the detector socket in the set the grid be used while testing the circuit for amplification and selectivity. up last tuned circuit, only introducing the coils The only reason for using high voltages would be to test the lead picks the of a is L2 in the lead between the tuned circuit and the grid. The effects overloading, use to which the circuit not adaptable. cathode lead picks up the corresponding lead without any change Hence the vacuum tube voltmeter need only have a moderate at all, in length of the leads. Likewise the heater range, which can be obtained by using a plate voltage of the except the for the a grid or circuit is picked up. The plate lead is also picked up without usual values tube and voltage about twice of the leads. three times the usual values. change other than a lengthening For the details of construction and calibration of the vacuum The second oscillator, that shown in Fig. 1, is of the ordinary range should tube voltmeter the reader is referred to articles specially treat- type used in Super -heterodynes and its tuning ing be the same as that of the tuned circuits in the receiver. Thus this subject. the inductance of L should be 160 microhenries when the con- CONSTRUCTION OF OSCILLATORS .0005 mfd. Ll is the usual tickler denser C has a capacity of Those who wish td try the method of measuring the overall coil, which may or may not be of the rotable type. The pickup amplification should start by constructing two equal oscillator coil L2 should be small and it should be mounted so that it be rotated respect to coil L. Half a dozen turns on a circuits, one entirely independent of the other and both shielded. can with The tuning condenser in each should be a .0005 mfd. The tuning one inch diameter will suffice. coils should be wo'und for the condensers used and may be those Condenser C should be provided with a dial having a real dial with many divisions. The dial in Super -heterodyne receivers to generate the local frequency. vernier or with a very large is the variable coupling between the should also be mounted directly on the shaft of the condenser An important feature be no backlash or lost motion to upset the oscillator inductance and the pick-up coil. Many Super -hetero- so that there can dyne oscillator coils are constructed so that the pickup coupling calibration. zero to a maximum The calibration can be accomplished accurately by comparing can be adjusted from depending on the with the frequencies of broadcast geometry of the assembly. There is no need for a higher plate the oscillations generated on than 45 volts. stations. With a very small antenna, coupled extremely loosely, voltage either tube it is possible to pick up the squeal of nearly every broadcast station in the country, even if the work is done at one ex treme of the country. It may be difficult to identify all stations and thus to locate the frequency on the dial, but this work can Fixed and Ballast be disposed of by plotting a curve of frequency against dial settings. A few stations will be recognized easily, and they will Controls Compared be well distributed over the dial. Weaker squeals of remote stations can be located by reference to the other and louder A line ballast, according to Charles Golenpaul, of the Claro - squeals. stat Manufacturing Company of Brooklyn, N. Y., is an auto- The first oscillator, not shown, which is to replace the broad- matic line voltage compensator which, as a ballast, throws cast station, should be just like that shown and it should be more or less resistance in series with the power transformer of calibrated in the same way. After one of them has been cali- the all -electric radio set, to allow for the increased or lowered brated against broadcast stations the other oscillator can be line voltage. calibrated against the first. When the line voltage is exceedingly low, such as below 100, the radio set can still function at full efficiency, since the design THE VACUUM TUBE VOLTMETER of the power transformer allows for operation on a voltage as There are many kinds of vacuum tube voltmeter which will lowas 85, while the ballast makes up the difference between measure AC voltages. Many have been described in RADIO that and the line at all times. in a plug or WORLD. circuit of a simple meter of this type is shown in "The fixed resistor type, usually the, form of The a fixed resis- Fig. 1, using a 171A tube. This tube is especially suitable because similar attachment, on the other hand, is simply it has a low amplification factor and a high emission. The low tance value designed to cut down the line voltage," he added. amplification factor makes it possible to cover a wide range "It introduces the same resistance into the circuit at all times. of voltages and the high emission insures constancy of the When the line voltage is high, the resistor serves to safeguard calibration. the tubes, filter condensers and other components ; but when While the circuit shows that the same plate battery is used the line voltage is low, there is no means of increasing it by for both the oscillator and th.. voltmeter it is best to use inde- edu ;ng the 25-0'hm resistance."

www.americanradiohistory.com 18 RADIO WORLD February 15, 1930

RMA ALL WET College Girls LICENSES RING Swim to Music Saratoga Springs, N. Y. Skidmore College has adopted "musical ON PENTODES, swimming." Miss Margaret Bridgman, dean, WITH BANS ON thinks the idea of examination week as a time of terror and worry is out of date. With midyear examinations approaching, she IS CECO REPLY called on the departments of psychology and physical education to devise ways of saving VESTED RIGHTS The official statement of the Radio Skidmore girls from headaches and "nerves." Manufacturers Association, stating there A substitute for midnight oil, wet towels found Washington. was nothing new in the pentode an- and pots of coffee was sought. It was What will be done about WMAK, Buf- nounced by Ceco Manufacturing Co'., of in a combination of music and physical ex- falo, N. Y., now on 900 kc, which frequency Providence, R. I., and that no improve- ercise. Every day the organ played soft is tentatively intended for a new station, ment in performance can be obtained music in the chapel, a series of piano recitals owned by the Buffalo "Evening News" with pentodes that can not be had with was arranged, and the students encouraged will not be clear at least until the impend- present tubes, brought a blasting retort to skate on the college rink. But most of all, ing reallocation. Forty major changes are from Ernest Kauer, president of Ceco. every girl is urged to calm her nerves and to be made in the broadcasting structure, Mr. Kauer characterized the RMA state- sustain her strength by "musical swim- and WMAK may find itself in another ment as "ill-advised propaganda," and ming." channel on limited time. said that failure even to consult Ceco, an A loudspeaker was installed directly above It is intended that the "News" station RMA member, showed that "some one the swimming pool. Market reports and shall have full time. The construction was bent on putting something over solemn speeches are tuned out, but every va- permit says so, but that is not inevitably quickly." riety of music tuned in. Loudspeakers have controlling. been used on many beaches, but the music What the Elements Are scarcely reached the waters. In the Skid- WMAK Gets Temporary Aid more pool the students practice "musical The tube, he said, is not the same as swimming" by stroking rhythmically with Meanwhile, by a recent Commission the European one with which the RMA the music. They find the livelier tunes great order, WMAK got a 90 -day license for statement compared it. fun, while music in the waltz tempo is 900 kc on part time as did WFBL, Syra- The pentode is a five -element tube, dif- found by the psychology instructors watch- cuse, N. Y. WMAK was charged by the fering from the screen grid tube because ing the experiment to be particularly sooth- "News" with being owned by a corpora- of a second screen. The elements are ing to tired nerves. tion that had a monopoly of Buffalo cathode, plate, control grid, screen grid stations. Each license contains this clause: around the plate and screen grid between "This license is only temporary, and is cathode and control grid. Contact to the not to be taken as a finding of public con- fifth element is made to a binding post venience, interest or necessity. It is issued on the side of the base. Otherwise the merely ad interim until such time as the tube looks like a 224. LINE VOLTAGE Buffalo Evening News is entitled to license So far only an AC model is announced, on a construction permit heretofore issued and it is intended for radio frequency to it if that be within the terms of this amplification. temporary license. Nor is this license to SURVEY STARTS be taken as any reversal of the judgment Paragraph Cited of the Commission whereby the frequency A nation-wide survey is being made by of 900 kilocycles has been assigned for In his reply Mr. Kauer refers to the the Allied Engineering Institute, at the in- license to the Buffalo Evening News on "introductory paragraph" of the RMA stance of a group of radio manufacturers. the aforesaid construction permit." report. This paragraph read: The purpose is to obtain authentic data on "To advise the radio public and industry voltage conditions in every town and city Claim Always Lost correctly and authoritatively regarding the of the United States, so that radio set manu- 'new' pentode radio tube, the Radio Man- receivers Clauses such as these are intended to facturers will be able to furnish make it plain stations nothing ufacturers Association, comprises all im- adaptable to the voltage conditions of each to that even portant manufacturers, today issued a particular locality. approaching a "vested right" goes with a statement regarding the pentode. It was license. In several court contests with the Those who have experienced imperfect Board, declared neither new nor revolutionary. radio reception such as under -volume, fading, stations have claimed a "vested No improvement in performance can be right." WGY, Schenectady, N. Y., was sudden blasts of volume, tube burn -outs and first obtained with pentodes that cannot be distortion, are asked to write to the Allied with this claim, put forth by Charles had with present tubes, the official state- Evans Hughes, then WGY's counsel. Mr. Engineering Institute, Suite 429, 30 Church long a ment declared, and it is unlikely that pen- of the con- Hughes likened occupancy of par- Street, New York City, telling ticular frequency as equivalent to a trade todes will replace present tubes this ditions of radio reception in their vicinity. year." AC meters can be of assist- mark. Those who have No "vested right" claim by a station has Reply to RMA ance if they will send in a record of the line voltage readings at several different times of been sustained by a court. Mr. Kauer's statement, released by his the day. For example, in most cities the company's publicity representatives, was voltage is higher during the clay than in the as follows, in full: evening Manufacturers Aid "From Fred Baer & Associates, 366 Madison Avenue, New York City. are identical, whereas they are different Aero -Radio Study "KAUER ANSWERS types of tubes. The Radio Manufacturers Association, "RMA CRITICISM Cites Foolish Haste comprising virtually all radio makers, is "OF AC PENTODE "'To deny that Ceco's development is cooperating with the Federal Govern- an advance in the radio art is as futile ment in the application of radio to aero- "The 'news release' issued last week by as was the attempt of automobile manu- nautics. Dr. Lewis M. Hull, of Boonton, the Radio Manufacturers Association in facturers who tried to delay the use of New Jersey, who has done considerable connection with the AC pentode tube four wheel brakes or balloon tires. aero -radio development, has been ap- caused Ernest Kauer, president of Ceco "'Little if any thought was given to pointed by H. B. Richmond, president of Manufacturing Co., Providence, R. I., to that news release before it was issued. the Radio Manufacturers Association, on make the following comment: The fact that Ceco, as the pioneer in the the Aeronautical Radio Research Commit- "'I consider that news release an ill- development of the AC pentode tube for tee just formed by the Department of advised piece of propaganda. It can have its practical application here, and as a Commerce. Harry H. Blee, of the De. no good effect on the radio industry. Its member of the RMA, was not consulted, partment's Aeronautical Branch is chair- introductory paragraph is not supported shows that someone in the organization man. by the facts brought to its support. The was bent on putting something over Other members include Dr. J. H. Del- body of the statement, when analyzed, quickly. As I see it, all they achieved linger, of the Bureau of Standards ; Her- really supports the claims of Ceco's engi- was a foolish haste. They did nothing bert Hoover, Jr., of the Aeronautical neers. constructive, unless the distribution of Chamber of Commerce, Army, Navy and "'Whoever in the RMA caused this misinformation can be called constructive. other experts. The committee will study statement to be issued made no effort to "'Tests in laboratories other than our radio problems in aeronautics and com- secure our pentode tubes for testing. o'wn show that the AC pentode as devel- pile information to assist in developing They have gone on the assumption that oped by Ceco will do all that we claim the important application of radio to aero- the European pentode and our pentode for it.'" nautics.

www.americanradiohistory.com February 15, 1930 RADIO WORLD 1')

WORLD SIGNALS More Stations Seek MAXIM PLEADS Short -Wave Permit A few broadcasting stations, such as FOSTER STUDY KDKA, WGY and WABC, have maintain- WITH SENATORS ed simultaneous short wave transmitters, but the list is about to grow considerably. Activity in this direction followed the repeated successes of the National Broadcast- OF TIME GAP ing Company in sending relayed European FOR AMATEURS Will the development programs into American homes. of international WOR, Newark, N. J., which is to be Washington. broadcasting put stations on a twenty- Hiram Percy Maxim, president of four -hour -a owned as of record by the Bamberger de- the -day basis of service? partment store in Newark, N. J., is erect- American Radio Relay League, consisting Principal events throughout the world of 17,000 amateurs, already ing a short-wave transmitter. appearing before the are being relayed, thanks to the The Voice of Brooklyn, Inc., has applied Senate Committee on Interstate Corn efficiency of short waves, high power, and merce, improved for a construction permit on 2,800 kc., 500 asked that in working out the transmitting and receiving ap- watts. Other applications are pending. Couzens bill for a communication com- paratus. What happens in one country all mission, asked the be may be Stations want their programs heard that amateurs tuned in by listeners in another, over the world now. "protected, encouraged and adequately even at the far ends of the earth. provided for," a condition that, he added, It is the time factor that intervenes. does not exist today. That was dramatically conveyed to mil- He urged that the new avenues of com- lions in the United States and Canada by munication which doubtlessly will be the address of King George opening the opened by their research be not entirely London Naval Conference. To New taken away from them for the use of Yorkers that meant listening in at 6 SIGNALS FROM commerce and industry, but that they be a. m., in California at 3 a. m. allowed sufficient room in which to main- The Song Paralleled tain their own experimental networks, And when it's Wednesday in the always available to the Nation in emer- U. S. A. it's Thursday in New Zealand. OVERSEA GAIN gency, and serving as a training school Time changes with each 15 degrees of for radio operators. longitude and the world is divided into The first network rebroadcast of a pro- Cites 1912 Legal Safeguard 24 zones for the purpose of recording gram originating across the Atlantic took time. place a year ago. The National Broadcast- In 1912, Mr. Maxim pointed out, Con- This becomes a vital consideration in ing Company, with less than three hours no- gress specifically provided that there international broadcasting, the era of tice, successfully picked up and rebroadcast should be amateurs and it allocated which is to now beginning. a symphony concert from London through them waves below 200 meters (1,500 kilo- That is why all those interested in a network of thirty associated . stations. cycles). broadcast reception are recalling their In July, 1929, Thanksgiving Services for "They were considered in the `useless study of this time division their gram- the recovery of King George of England, waves' at that time," lie explained, "but mar school days, never figuring that they held in Westminister Abbey, London, were there was room enough would interest in and the amateurs have very much the way rebroadcast through the NBC network. The set about seeing what could be done with it operates. Now traveling and radio same morning a them. It bring the into the limelight. program originating in Syd- was an historic occasion in the topic We ney, Australia, was picked up and went on art of radio communication, for it marked remember that the meridian of longitude the American network the birth of shortwave radio." which runs through the little town pf Later came the broadcast description of the "This legislative act," he declared, "was Greenwich, England, is the starting point, Schneider cup races. one of the wisest steps a so that international time is expressed in Congress ever In October American listeners heard a took, and I submit that if it is wisdom to terms of Greenwich Mean Time ,(G. M. program from Holland and before judge of the future by T.) Traveling 180 degrees away, east to just the past, then we Christmas there came a program from Ger- here today may safely assert that it will west, a day is actually lost at the Interna- man studios. Christmas Day further the art of tional Date Line; a day is gained in the shattered all communication during previous records for programs from Hol- the 18 years to come just as much as it opposite direction' . land, Germany and England went on the air furthered the art of radio communication Told in Book in rapid succession. during the 18 years that have passed, if In order that we might hear reports of New Year's Eve brought more programs the Senate Committee on Interstate the Naval Conference at customary hours, from abroad. Then, when the Naval Par- Commerce, in working out the details of speakers appear before the microphone ley opened in London the morning of Janu- Senate bill for a Federal commission on in the early morning, or after midnight, ary 21st, radio outdid itself. The voice of communications see to it that our radio in London. This is convenient from the King George opening the parley and the amateurs are protected, encouraged and viewpoint of the invisible audience in the addresses of the delegation chief from the adequately provided for." North American Continent, but such a United States, England, France, Italy and For the 1,500 -kilocycle limit of the days process could hardly apply except on Japan were heard. Secretary of State Stirn - after the World War, amateurs have made occasions of exceptional importance and son, who had never addressed an American possible regular commercial operations on certainly not in the relaying of an actual network audience as a cabinet member, was frequencies up to 23,000 kilocycles, and are news event as it occurs. heard from London. now experimenting with excellent results If Australian programs are to' be car- beyond that limit and in the "ultra -high" ried to the United States, they would be frequencies, Mr. Maxim said. best heard in the East from 4 to 6 a. m. At these periods the experimental pro- New Corporations Crowded Beyond Endurance grams from 2ME, Sydney, for example, Finally, have been picked up by WGY in Stitt Radio Studio-Atty. H. A. Kulowski, Buffalo, he said, at the International Schenectady. N. Y. Radio Conference of 1927, and despite Bamberger Broadcasting Service, Inc. - Attys. the efforts of American delegates, the These points are brought out by Eric Pitney, Hardin & Skinner, Newark, N. J. American Palmer, Jr., in his new book entitled, Brandywine Radio Shop, Inc.-Atty. Edward T. amateur "was all but sacrificed." "Riding the Air Waves," published by Varley, Wilmington, Del. He continued : "All that was left of the Radio Mart-Atty. D. B. Williams, 521 Fifth Liveright, Inc., dealing with the Ave., territory the amateur had so brilliantly Horace New York, N. Y. chiseled out of the solid adventures of the youthful owner of Catrons radio-Atty. M. Annis, 1,560 Broadway, were extremely Amateur Station W2ATZ and covering New York, N. Y. narrow bands around 160, 80, 40 and 20 the latest phases of short wave relays. Winthrop Radio Co.-Atty. S. M. Rivelson, 38 meters. Here we find him today, more Park Row, New York, N. Y. than 17,000 in The author is the son of Eric Palmer, Locust Radio Co.-Atty. G. Voigt, Jamaica, number, crowded beyond all representative of Queens, New York. conception and almost beyond endurance, formerly publicity Bernardsville-Atty. W. Freed -Eiseman and of the Radio World's Griffiths, Inc., Eddy suffering from what he feels is injustice Heath, Somerville, N. J. and ingratitude and in constant danger of Fair, and more recently an executive of Vaco Radio Corp.-Atty. O. L. Landman, 26 a Western radio chain. Court St., Brooklyn, N. Y. losing even the little that he still retains." more, Md. Declaring that both the Federal Radio Leroy Flippen, 912 W. 13th St., Oklahoma City, Commission Okla. and the Department of Com- GILBERT NOW WITH PILOT F. W. C. Baines, Box 1058, Saskatoon, Sask., merce have recognized the position of the Charles Gilbert has become affiliated Can. amateurs, Mr. Maxim said, according to B. A. Dwojakowski, 991 Canfield, E., Detroit, with the Pilot Radio & Tube Corporation, Mich. "The United States Daily," his organiza- of Brooklyn, N. Y., as vice-president in Sol. Weber, 836 Mt. Prospect Ave., Newark, tion would he "very well satisfied if the of merchandising. He was a close N. J. Government communications commissions charge B. T. Stubbs. Box 86. Rosebud. Tex. business associate of Dr. Lee DeForest. Charles F. KKirkland. 4432 W. 10th Ave., of the future deal with us as fairly as have More recently he was with Kolster. Gary, Ind. the existing agencies."

www.americanradiohistory.com 20 RADIO WORLD February 15, 1930 1929 NBC TAKES IN Summary of MIKE IS MADE Report on NBC Broadcasting has been called "the fast- est growing industry." Here is what hap- WITH $15,000,000 pened to the National Broadcasting Com- AMAZING pany during 1929 according to the annual report of M. H. Aylesworth, president of the company, submitted to the Advisory NO PROFIT Council of the organization. PRECISION FEAT AT Fourteen stations were added to the na- in manu- Company tional network, including one Canadian An amazing example of precision The National Broadcasting The network now includes 73 facturing is illustrated in the new type nu- became, in fact, an international broad- station. its net- stations. crophone manufactured by the Western Elec- casting Organization, increased revenue of the NBC in 1929 tric Company for sound picture apparatus work facilities more than twenty per cent Gross in 1929, totalled more than $15,000,000. There and radio broadcasting. and nearly doubled its personnel were no profits. The condenser type microphone was de- according to the annual report to the most sensitive and by M. H. Ayles- Fifty-four hundred miles of wire were veloped to provide the Advisory Council made NBC System, bringing the faithful method of picking up all kinds of worth, president of the NBC. added to the annual meeting total to 32,500 miles of wire lines. sound ranging from the highest soprano Those present at the than one million letters from lis- notes to the low boom of a bass drum, and of the Advisory Council held in the Na- More Building, teners were received in the year. to reproduce them with utmost fidelity. tional Broadcasting Company was in- must pass 46 mechanical New York, included The personnel of the NBC Each transmitter 711 Fifth Avenue, 558 td 917 in 1929. and electrical inspections before being ac- Charles Evans Hughes, Elihu Root, Owen creased from Davis, William Green, Sixty hours of programs a week were cepted as a finished product. The insulation, D. Young, John W. regular schedule of broad- for example, must show a resistance of at Paul D. Cravath, Gen. James G. Harbord, added to the Mrs. John D. Sher- casts from the key stations oI the net- least 80,003,000,000 ohms, the natural fre- Walter Damrosch, quency of the diaphragm is required to be man, Francis D. Farrell, Morgan J. work. S. MacFarland. The President of the United States between 5,000 and 5,050 cycles a second and O'Brien and Dr. Chas. times through a national the back plate of the condenser must be with- "In 1929 our gross income was approxi- spoke thirteen which was de- network. There were twenty-seven ad- in .00008 inches of a true plane. mately $15,000,000, all of members, twenty-eight voted to service to the radio audience," dresses by cabinet Assembled Under Microscope "There was no senators were heard and twelve members said Mr. Aylesworth. made addresses. The test which determines the last factor profit. One hundred and ninety-nine of the lower house facilities during the Virtually the entire population of the is made by utilizing certain laws of physics clients used NBC can be entertained or in- regarding the interference of light waves It 1929 as compared with ninety-six United States year formed by one program in the same hour. is almost impossible for the layman to under- during 1928." stand such a degree of accuracy. Democracy Realized The assembly and inspection of the microphone are done in an air conditioned room "Nothing comparable to network broad- is supplied a tem- of which with air at constant casting as a means to the realization perature of 70 degrees Fahrenheit and a con- our democratic ideals in national cultural stant humidity of less than 40 per cent. Be- development has ever before existed," Mr. NEGRO STATION has al- tween operations all piece parts are kept in Aylesworth said. "Our population jars in which a supply of calcium chloride ready reached a figure that would have absorbs all moisture. The intricate assembly been almost certain to have brought dis- he operations are carried out in dust -proof integration a hundred years ago," 15 REQUESTED boxes under a low power binocular micro- added in pointing out the service radio a mass -con- scope which magnifies the object being as- has rendered in developing Washington. sembled to 16 times its actual size. sciousness of a common national ideal. "A voice for the Negro" was asked by Radio broadcasting already is bringing William J. Thompkins, who appeared be- Frequency Tested in marketing about revolutionary changes fore the Federal Radio Commission on an In the first assembly operation a duralumin methods, the report continued. It gives application by the Kansas City "Amer- avail- diaphragm only a thousandth of an inch thick the farmer all of the information ican" for a 250 -watt license to broadcast is mounted in a shell with a ring which can able to the buyer of his products and on 1,120 kilocycle. The Negro newspaper, places him be adjusted to stretch the diaphragm. An for the first time in history of which Thompkins is managing editor, oscillograph is used to determine that the on an equal footing with the buyer, Mr. asserts there are no stations licensed to An hour at noon diaphragm has been stretched so that its Aylesworth pointed out. any Negro or Negro organization. natural frequency is between 5,000 and 5,050 six days a week is devoted by the NBC Thompkins told the Commission: "We to farmers cycles per second. in supplying this information hope to stimulate interracial interests, of- The diaphragm and the backplate, which and producers. fering America's only distinctive music- the spir- as already mentioned, is lapped to within the Negro folklore, exemplifying .00008 inches of a true plane, are then thor- Suggests a Contest itual life of the Negro in sermons, and conception of oughly cleaned under a microscope. A du- A national oratorical contest to train demonstrating the Negro's ralumin spacer of from .001 to .0012 inches, young speakers in the technique of patriotism and Americanism." placed between the backplate and the dia- microphone oratory was suggested in the One of the reasons for the station, said phragm, insures the proper capacity of the report. the witness, is for the uplifting and edu- people condenser. This assembly is then sealed with Relief of the "traffic jam" on the air cating of the Negro, and to give hot wax. The condenser is sealed off from is hoped for through development of syn- "the Negro viewpoint." the outside air by means of a thin mem- chronized broadcasting which means the The application filed by the newspaper brane, air exhausted and the space is by a Representatives the is employment of a single wavelength was for unlimited time. filled with nitrogen. This prevents any number of stations broadcasting the same of WISN, Milwaukee, Wis., and KTRA. said. to change in atmospheric pressure from affect- program at the same time, the report Houston, Tex., asked leave to object ing the capacity of the condenser. NBC engineers have been conducting ex- the assignment. periments in this work for the past year. The NBC now is definitely engaged in international broadcasting, Mr. Ayles- ef Set Manufacturers worth stated. "Old Man Donaldson, That present radio facilities, had they Veteran, Dead Buy 87% of Resistors been available in 1914, probably would War From International Resistance Company War, was pointed "Old Man Donaldson" is dead. Colonel have averted the World There are very few radio parts, other than out in the report which sees the micro- C. T. Davis, pioneer radio writer and cannon in the settlement author, died at his home, 100 East 55tn basic materials such as wire, metal, bakelite, phone replacing etc., that are produced nowadays by radio of international disputes. Street, New York City, after prolonged ill health. Although he had been partly manufacturers. Probably the three items disabled by his illness, Colonel Davis con- which are produced in the greatest quantity FOR THE WEEK tinued to be active until a few days before by radio manufacturers are volume controls, A THOUGHT resistors and fixed condensers, and a statis- an awful thing! the end. His last work was in adapting ]^ OVE! Love! It's for in tical survey showed that 87 per cent of the Proof? List to the crooners sing several short stories presentation Collier's Radio Hour. resistors used by radio manufacturers are J Syncopated wails that ring purchased and that it is impossible for the and bring Colonel Davis, an Englishman by birth, Through the microphone as a profession radio set manufacturer himself to produce Heartaches, earaches-ting-a-ling! did not take up drama wing!) until after the war. He was a captain at his own resistors at a cost approaching that. (See-our brains have taken War. which he may purchase them for. Gee! Hut love is an awful thing! the front in the World

www.americanradiohistory.com Fein uary 15, 1930 RADIO WORLD 21

BAR TO DISCUSS Solution Proposed HIGHER QUALITY for Iowa Dispute Washington Adjustment of the Iowa broadcasting NEED TO AMEND problem by establishment of a new com- CITED TO MAKE pany which would own and operate the two large stations of that State, WHO at Des Moines, and WOC at Davenport, is proposed in an application filed with the LEGISLATION Federal Radio Commission by the Central 1930 BEST YEAR Broadcasting Co., of Des Moines, the new Washington corporation. Officials of twenty-seven broadcasting The American Bar Association, through The two stations would be synchronized by stations, located in representative sections its committee on communications, will dis- wire to give a continuous program to listen- of the country, are unanimous in agreeing cuss four aspects of radio legislation at its ers in the territory, Dr. Frank W. Elliott, that 1930 will bring a substantial increase in meeting February 20th, called by Louis G. of Davenport, who is vice-president in radio's popularity, giving interesting and Caldwell, committee chairman. Mr. Cald- charge of operation of the company, told varied reasons as the basis for their opin- well was general counsel of the Federal the Commission. ions, in answer to a questionnaire forwarded Radio Commission. He listed the topics Since the reallocation of November 11th, by George K. Throckmorton, executive vice- as follows: 1928, the two stations have been forced to president and general manager of E. T. " 1. Need for amendments to radio act divide time on the 1,000 -kilocycle channel, Cunningham, Inc., radio tube company. of 1927. says "The United States Daily." "What phases," asked Mr. Throckmorton, "2. The Couzens bill to establish a com- Dr. Elliott said an application shortly will "will be the most important in effecting ra- mission on communications (S. 6). be filed for authority to erect a station using dio's expansion during the coming year?" ''3. Miscellaneous bills concerning radio the maximum power of 50,000 watts. Then, The majority of these officials are agreed and other forms of electrical communica- he said, the plan is to reduce one of the that three factors-namely, the betterment tion now pending or proposed in Con- stations to a regional status and maintain of receiving and broadcasting facilities and gress. the 50,000 watt transmitter as a national the higher standard of programs-are the he "4. Problems of State and municipal station. These developments, however, foundation upon which radio is to build a, regulation of radio and other forms of explained, are subject to Commission ap- still greater public following. electrical communication." proval. The new company is capitalized at $500,- Attracts High Class Talent Members of Congress Invited 000. The Bankers Life Company, of Des has operated At the same time, many other reasons Moines, which heretofore are cited as additional effecting The invitations sent out by Mr. Caldwell WHO, has sold its interests to the new com- factors by contained the following: officials of individual stations. For instance, pany. The Palmer School of Chiropractic, as reported from WOR, "Members of Congress (and particularly has operated the Davenport station, of Newark, N. J., which radio's popularity will increase in 1930 be- members of the Senate Committee on In- it was stated, will sell out to the new cor- terstate Commerce and the House Commit- new cause "resistance of high class talent to ra- poration in exchange for its stock The dio has broken down." tee on Merchant Marine and Fisheries), corporation is entirely devoted to broadcast- members of the Federal Radio Commission From WOW, Omaha, comes the comment ing, and has other plans for expansion, Dr. that "irresistible and lawyers of its legal division, members informed members of the Commis- programs and news fea- Elliott tures" are winning new fans, and an official of the American Section of the International sion. Committee on Wireless Telegraphy, repre- of WWNC, Asheville, N. C., adds the sa- sentatives of the various branches of the lient point that "the plug -into -light -socket radio industry and, generally, all lawyers receiver has answered the demand for a interested in the law of electrical communi- set that requires little, if any, attention." cations are cordially invited to attend, to WLBW, Oil City, Pa., includes "more in- participate in the discussion, and to submit SQUIER WANTS terest" to the "more sets-better programs recommendations." -better reception"- list. Robinson To Open Session Good Taste Better The meeting will be opened by Chairman PHONED MUSIC An official of WMAQ, Chicago, amplifies Ira E. Robinson, of the Federal Radio Com- his statement by declaring that "increasing mission, who will welcome the committee Washington. understanding on the part of program spon- members and discuss some of the legal as- Testifying before the Senate Committee in sors as to good taste in announcements, con- pects of radio. charge of the Couzens' bill for the creation stant competition and the natural develop- of a Federal Communications Commission, ment of the means for better programs are General George O. Squier, retired, expressed bringing, in turn, greater popularity." the opinion that the Bell system should be An interesting point is stressed by an AC Sets Outsell required to utilize its extensive wire system official of WDSU, New Orleans, La., on -to -1 for broadcasting entertainment by the wire his observation that "radio has not reached Others by 30 radio system to telephone subscribers at a saturation point of interest." Washington. nominal monthly rate, thus permitting the From WNAX, Yankton, S. D., comes a AC sets outsell battery -operated sets use of every telephone line for 16 hours a specific estimate that radio's popularity will in New York City 30 -to -1, according to day instead of the present average of 18 min- increase by twenty-five per cent during the reports obtained for the third quarter of utes per day. coming year. The assertion that "more brains 1929 from more than fifty dealers by the This method of entertainment distribution are going into broadcasting" is a supple- Electric Division of the Department of would eliminate advertising as well as all mentary bit of advice from an official of Commerce. The figures were 4,054 and kinds of interference to which space radio KFBB, Great Falls, Mont. 135. The combined price was $925,995, is subject, according to Gen. Squier. He Necessity, Not or an average of $221 per set. also pointed out that at the present time a Luxury In the entire country during the same the space radio facilities are already satu- The fact that radio may be classified as a period showed that more than 6,000 deal- rated. "necessity" and not a "luxury" is emphasiz- ers sold a 'total of about 8,000 battery - General Squier claims that by means of the ed in the answers from several stations. operated sets and 133,000 electric sets, the monophone, one of his many inventions in KOMO, Seattle, Wash., pictures radio as total sales of both being $21,662,874. carrier telephony or wire radio, the entertain- "taking its place with the automobile as a ment could be broadcast to every home with- family necessity," while an official of KFRC. out any interference with the ordinary con- San Francisco, uses another illustration in LITERATURE WANTED saying radio R. C. Smith, 2413 Clark Ave., Parsons, KKans. versational use of the telephone. The pro- that the set "is regarded al- Oliver F. Klein, 783 39th St., Milwaukee. grams would be broadcast over the wire sys- most as necesary in the American home as Wis. the kitchen stove." W. M. Horn, Leon, Iowa. tem by means of high frequency currents A. R. Wapple, 807 College St., Georgetown. which are far above the audible limit and Texas. above those frequencies used in telephony. Delmar Lesswing. 403 Herman St., Buffa:o. N. Y. The monophone attached to the telephone 4,500,000 Receivers J. C. Black, Box 410, Temple, Tex. receiver would convert the modulated high C. A. Turner, 1002 N. Washington, Enid, Okla. frequency current into audible signals in the Sheldon Drennan, Asheville Sch., Asheville, in Use Held Obsolete N. C. same manner that the radio receiver converts E. L. Selander, 370 E. 7th St.. Winona. Minn. the modulated radio waves. He also pointed According to statistics just compiled, out L. L. Proctor. 13454 Anglin. Detroit, Mich. out that an entire city could he served sat- of the 11,500,000 radio receivers in this Peter T. Lang. Victoria, Kans. Cadilek Radio, 427 E. 75th St.. N. Y. City. isfactorily with a few watts of power and country approximately 4,500,000 are of obso- Jerome E. Hacker, 6602 Barton Ave., Holly- it would no longer be necessary to use lete design. If radio manufacturers are cor- wood. Calif. enormous power such as is now required for rect in their opinion, however, millions of P. Glaum. 7144 Theodore St.. Phila., Pa. Anton Bisk. Ladysmith. Wis. snace broadcasting in order to overcome these obsolete receivers will be replaced by Joseph E. Callahan, 1301 Holbrook St., Balti- natural and man-made electrical disturbances. the new sets this year.

www.americanradiohistory.com 77 RADIO WORLD February 15, 1930

RADIO ACT VOID, Police Radio for WMCA FIGHTS Three More Cities Washington. Amateurs must not disclose the mes- WGBS "BERTH" HIGHEST COURT sages they overhear. Against regulations. Always has been. But now more so' than evr, because dulice departments are sea ing voice modulated short waves fromm NEW WAVE TOLD DY WNYC headquarters to patrol motors equipped ON with special tuners. Washington. Washington. Detroit has radio crime detection. Chi - assign- As an outgrowth of the unsuccessful Having been denied exclusive cago is putting in a system. Now three attempts of WMCA and WNYC in New ment to 570 kc, 526 meters, by the Federal more cities are in the same class, even York and having lost its City to obtain full-time assignments, Radio Commission, licensed: WMCA, which shares 570 kc (526 meters) appeal to the Circuit Court of Appeals, Cincinnati, Ohio, WKDU, 1,712 kc, 500 with WNYC, protested to the Federal WNYC, owned and run by the City of watts. the Radio Commission against the recent New York, has attempted to get Youngstown, Ohio, (no call yet) 2,416 assignment to WGBS, also of New York Supreme Court to review the lower court's kc, 500 watts. it. The City, to 600 kc (500 meters), full time. finding, and finally reverse Pasadena, Calif., KGJX, 1,712, 2,416, The 600 kc frequency had not been used municipality makes the assertion that the 2,462 kc, 250 watts. in is un- New York City. WMCA asserts that radio act, in at least two respects, eeryone was told and believed there constitutional and that Congress has no were too many full-time broadcasting sta- power to regulate broadcasting. the control of the transmission of com- wave with tions with studio's in the metropolitan area, WNYC is sharing the merciai messages or intelligence by wire- operating with high power ih a congested WMCA, and the two stations have been less between shore and ship stations, or of district. at loggerheads for a couple of years. signals between shins on the high seas for WGBS Wave Temporary Occasionally the strife resulted in both the protection of life and property. This stations, both in New York City, being on is plainly evidenced by the provisions of WGBS formerly had its studio in the the air at the same time. WNYC, prior the act of 1910 quoted above as well as by Gimbel Bros. department store, but was to the reallocation of November 11th, 1928, the provisions of the act of 1912. sold to the General Broadcasting System, occupied the channel exclusively. "The latter act specially refers to 'corn - of which Dailey Paskman, former man- Arthur J. W. Hilly, corporation counsel merciai intercourse.' There is nothing in ager of WGBS in the Gimbel store, was of the city, and a boyhood friend of either of the acts to indicate an intent o'n head. Now the studio is in the Hotel Mayor James J. Walker, argues in the the part of Congress (and this is made Lincoln while the transmitter is about brief that the radio act of 1927 in so far further apparent by the above quotation eight miles away, in Astoria, across the as it terminated all existing broadcasting from the report of the committee which East River. licenses or rights without notice and a considered the act of 1912) to regulate WNYC is owned and operated by the hearing and without compensation "vio- broadcasting nor that broadcasting was City of New York, and has a separate lates the Fifth Amendment of the Federal even contemplated at that time." fight on the Commission, in a Supreme Constitution and is invalid and void." Court motion aimed to gain an exclu- Commerce or no Commerce? sive wave. Arbitrariness Alleged It is argued also that broadcasting is not Orestes H. Caldwell, formerly a member It is contended further in the brief that "commerce." The brief points out that in of the Federal Radio Commission, in a section 89 of the radio act in so far as it the only case arising under the radio act recent speech said that political consid- provides that allocations shall be charged in which this question was raised at erations were actuating the assignment of to the State, district or territory wherein length, the United States v. American frequencies and power. It was inferred the studio of the station is located and not Bond and Mortgage Company, the court he had reference in particular to the as- where the transmitter is located is "un- held that broadcasting was interstate signment of an exclusive wave to WGBS. reasonable, invalid and void." commerce. At the Coimission it was pointed out Other points raised in the summary of Discussing the commerce clause, the that the WGBS assignment was only tem- argument follow: petition states that in decisions construing porary, and was being made the basis "The reallocation orders of the Radio the powers of Congress under it, "there of a study of conditions in the New York Commission which deprive petitioner of runs the basic idea of tangibility, if not area. the unlimited use of its established fre- o'f the thing transported, certainly of the New Set -Up Soon quency were made without giving peti- means by which it is transported. In the As a reallocation is impending, involv- tioner notice and an opportunity to be case of the railroad there is the train run - ing forty major changes, some of these heard and are therefore in violation of ping from one State into another or the are expected to involve stations with the Fifth Amendment of the Federal track over which the train runs ; in the studios in New York City. Some such sta- Constitution. case of the telephone and telegraph there tions have transmitters in New Jersey. "The procedure adopted and followed by is the wire and the pole or conduit which The Radio Corporation of America has the Radio Commission which resulted in conducts the wire. asked the commission assign a td certain the denial of petitioner's application for Not Common Carriers experimental licenses to the R. C. A. Vic- modification of the reallocation ordered tor Company, Inc., including Station unreasonable and violative "In radio broadcasting, however, there is was arbitrary, no physical tangible connection between W2XW in New York City, W2XN in the of law. the sending and receiving station, but Bronx, W2XCI at New York City and Calls Action Unlawful W2XAJ at Yonkers. Radio more important than this there is the "The reallocation orders of the intent, or purpose to establish communica- Commission in so' far as they compel the indi- its broad tion between one o'r more particular petitioner to surrender half of viduals; there is nothing transported from casting time are an unlawful hindrance of Slump Called "Over" the sender to the receiver that the sender Cambridge, Mass. and interference with the exercise of peti- was under any duty or obligation to send tioner's governmental and municipal func- The recent depression in the radio in- or that the receiver had any right to dustry appears to have passed and Janu- tions. In no event could the exercise of receive. such functions be 'interstate commerce.' ary radio sales showed marked improve- is nothing over which Congress ment, according to H. B. Richmond, of "The findings o'f the Radio Commission could exercise control under the commerce which resulted in the denial of petitioner's this city, president of the Radio Manu- clause. The generating or transmitting facturers Association, comprising all im- application for modifications of the reallo stationary and local, upon evi machine itself being portant radio manufacturers. cation orders were not based is certainly not subject to Federal control. dence adduced at any hearing and the "The radio industry apparently has upon The same may be said of the receiving turned a corner and is now on the up- determination of the Commission apparatus. It, too, is local, complete in such findings were violative of the Fifth grade," said Mr. Richmond. "Sales of itself and disconnected from any physical all radid products in January showed a Amendment of the Federal Constitution." conducting medium. Arguing that Congress "has no power marked improvement over December and under the commerce clause o'f the Federal Second Case in Highest Court November. From parts and accessory Constitution to regulate broadcasting," the "The fact that broadcasting stations are manufacturers, as well as receiving set petitioners pointed out that the interstate not 'common carriers' and could not be manufacturers, come general reports of commerce act,, and the radio act of 1912, made such even under the doctrine of the decided improvement in their January specified that Congress should control pipe line cases would seem to be con - business. transmission of "commercial messages or clusive on the point now argued." "Broadcasting is also . at its peak, and that there This is the second case involving the domestic as well as the new regular in- intelligence by wireless," The heavyweight is nothing in the acts to regulate broad- radio act to come before the United States ternational broadcast. casting. Supreme Court. The first was the suc - pugilistic contest, scheduled in February, "Both of these acts by express words cessful suit of WGY, Schenectady, N. Y., is another large sales stimulus in pros- and unmistakable intent were directed to to retain full time on 970 kc. pect "

www.americanradiohistory.com February 15, 1930 RADIO WORLD 23 TREATMENT OF Forum AUDITIONS FOR WCFL BV BOARD ALL, NEW PLAN Wants Technical Stuff Positively ISEE in the February 1st edition that Jo'seph Henkin, Sioux Falls, S. D., re- AMAZES LABOR quests that you cut out the technical TRIED BY WLW stuff, stating that "the time is past when Washington. the public is interested in how to build Cincinnati, O. Edward N. Nockels, secretary of the a set." Personal invitations to visit the Crosley Chicago Federation of Labor, and man- Well Joe is sidetracked. He should come broadcasting studios for auditions that will ager of WCFL, Chicago, who appeared to Chicago where on Saturdays and often determine their suitability for radio appear- on behalf of the American Federation of on other days home builders and set ance on WLW and WSAI have been sent to Labor, told the Senate committee con- builders are lined up two and three deep, musicians and entertainers in Cincinnati and sidering the Couzens bill he supported the clamoring for clerks to take their money environs. views of Hope Thompson, counsel for the for parts. Joe may be an announcer of a Others will be invited as their names are Federation, respecting broadcasting, as broadcasting station, but he admits his brought to the attention of station officials, expressed before the committee. He ad- ignorance of conditions when he states Ford Billings, director of broadcasting, said. vocated a communications commission, as the ready -built sets are better than any- "To a great percentage of those entertain- proposed in the Couzens bill, declaring thing that can be built by an amateur. ers and musicians who have never made any that the past few years have demonstrated The ready -built sets often look better, but attempts to get into broadcasting, the busi- that the Federal Radio Commission has the ones that get the results are nine ness probably seems a closed field, open only dealt with the radio problem inefficiently. times out o'f ten, built by amateurs. He to those who got in when the art was `young' Mr. Nockels declared that organized should listen to the DX program over or to those who know someone with a 'pull' labor had not been treated justly by the WMAQ every Friday night where the at the stations," he continued. Radio Commission in allocation of broad- records of the amateurs conclusively de- casting facilities. Its single station, WCFL, monstrate who make the best set-not Constant Need of Variety he said, operates daylight hours only, with the best furniture. magazine along the pres- 1,500 watts power, whereas he said that Keep up your "Radio entertainment as we see it is by the "radio trust own and operate some 11 ent lines. I buy all the leading radio magazines, when they cut out the no means a closed corporation. Constant stations with an aggregate of about 230,000 but need of variety demands an unending pro- watts of power, and are granted the ex- stuff that interests the amateur they cut new me out. cession of new talent that will bring clusive use of 6 or 7 out of the 90 available types of amusement, new interpretations, and channels in the United States." A. J. L. WALKUP. Chicago, Ill. other novelties for the radio audience." Too Much Entertainment * * * Ideas for programs are as vitally needed as are entertainers, musicians and actors, By means o'f chain hookups, moreover, No, Not to Henkin Billings said, expressing a willingness to con- he declared, "the stations owned by the sult with any writer or producer who has a radio trust tie into their control some 100 IN reply to Joseph Henkin's letter in thoroughly organized idea for a group of or more of the leading radio broadcasting the February 1st issue, I have this to programs or even for a single production. stations in the United States-practically say: "There is just as much chance for the all of these which have more than a local NO! NO! 'free lance' radio writer as for the 'free service range." Dear operator, You'd better have a little lance' in the magazine or newspaper field," He said that Congress should require experimenter's blood innoculated into he said. "While we employ a large staff that radio be used for something more you, a little of the radio amateur's prin- of continuity writers to prepare our pro- than entertainment and amusement. "How- ciple, respect for the enlightenment of grams, we also purchase some of our best ever entertaining and amusing the average the public in quality in radio and for the continuities from writers who never come program may be," he declared, "it is cer- encouragement and education of the boy near the studios but who know exactly the tainly not in the public interest that this just beginning in radio. There is noth- sort of material we can use." new means of communication should be ing wrong with RADIO WORLD and I hope monopolized for entertainment, amuse- it has more dope for the set builder. Wants Workable Ideas ment and advertising." For the sake of the boys who now depend on magazines to develop their ideas, Stresses Education they are more valuable to the country "Here again, our chief demand is only at large than the listener, and must be that the idea be presented to us in a work- Some of the facilities, he suggested, encouraged to continue. able plan and not merely as a nebulous sug- should be apportioned among stations Self -trained men all boost the beginner. gestion. The writer who listens to radio under restrictions requiring that a sub- I'm one and I feel thankful that some programs from all over the country with stantial part of the time be devoted to magazines are interested in beginners. I the idea of building new programs from an education. don't know where your idea originated, original angle should be no more of a rarity About 60 broadcasting stations are oper- but I hope that you will change your than the writer who studies magazines on a ated by manufacturers and dealers in radio mind. I'm telling you indirectly why newsstand with the idea of discovering new supplies, while some 25 or 30 great metro- RADIO WORLD should publish dope for the markets for his stories or articles." out that the tremendous politan newspapers have been granted set builder and beginner ! And in closing Billings pointed licenses for other stations, he said. Some I wish you would have read the Com- increase of sponsored programs is originating 350 licenses have been issued, according mandments and Don'ts! for operators a new demand for extraordinary features to "The United States Daily," to various and experimenters in different issues of not duplicated on other programs. private business concerns, entirely local in the QST. I know you'll feel differently. character, while 40 churches, about 70 RADIO WORLD has plenty of news of events educational institutions, and 30 local cham- and markets, monopolies, Senate bills, etc. PALMER JOINS TOBE STAFF bers of commerce hold broadcasting -The experimenter and listener are both George E. Palmer, general sales manager licenses. served. re- An "astounding and well-nigh unbe- FRANCIS WALCZAK, of the Dubilier Condenser Corporation, lievable fact," he said, "is signed to go with Tobe Deutschmann as that organized Elwood City, Pa. vice-president in charge of the condenser labor, with 4,000,000 members and corn- * * * nrising with their families almost a fifth division. of the entire population of the country, Sets That Do Things has asked the Radio Commission for just OUR Forum contained a letter writ- one channel of the 90 available, together ten by Mr. Henkin advising you to would put out an announcement for with ample power and adequate time of discontinue technical articles. I listeners to reply to that very few factory operation, and have been denied it." disagree with him, as your magazine is sets a few hundred miles away from his about the only one that is left on the station will receive KSOO when KMOX YANOCHOWSKI HEADS KELLOGG market frcyn which technical and experi- and KSL are both going, and if they do, mental data can be obtained, and I do how can they expect to receive KSFG or The Kellogg Switchboard & Supply Com- not believe there are any of us who have WPG? It has always been up to the pany, radio manufacturers of Chicago, an- real radio sets who have not used several home constructor and experimenter to nounced the election of G. A. Yanochowski of your articles to our benefit. solve these things as I have not yet seen as president, succeeding W. L. Jacoby, who On my particular home-made set, any factory -built sets that will do what died recently. Mr. Yanochowski has been KMOX is on 30: WPG on 29% : KSOO is required. associated with the Kellogg Company for on 29: KFSG on 28/ : KSL on 28: and I A. G. NUTTING, the past fifteen years. am of the opinion that if Mr. Henkin Livingston, Mont.

www.americanradiohistory.com 24 R :A I) T C) \L" C) l: L D February 15, 1930 v, A Substantial FourGang Condenser For .95 $

A FOUR - GANG CO11- denser of good, sturdy construction J and reliable performance fits into the most popular tuning requirement of the day. It serves its purpose well with the "/14 most popular screen grid designs, which call for four tuned stages, including the detector input. Ordinarily a good condenser of this type costs, at the best discount you can contrive to get, about twice as much as is charged for the one illustrated and even then the trim- ming condensers are not included. The question then arises, has quality been sacrificed to meet a price? As a reply, read the twenty-six points of advantage. The first consideration was to build quality into the condenser. Points of The reason for the low price is that the condenser was manufactured in very large quantities and is sold to the consumer with only one handling between factory and him, Advantage! at a price only 10% above the cost of production. are HE desirability and dependability of this condenser All claims are backed up by our guaranty- 7 attested by the following roster of features: MONEY BACK IF IN FIVE DAYS AFTER ( 1)-Rigid steel frame. RECEIPT OF CONDENSER YOU ARE NOT ( 2)-Accurate mechanical alignment. steel shaft. COMPLETELY SATISFIED. ( 3)-Single and at the center. ( 4)-Shaft supported at both ends rotor and stator plates. ( 5)-Accurate spacing of The Capacity is .00035 mfd. for each sec- made of aluminum of uniform thickness. ( 6)-Plates other and from external conductors. this condenser in any ( plates shielded from each tion. We haven't 7)-Stator built-in adjustable trimmer condenser. ( 8)-Each section provided with a 4,c, capacity. The price is net to \ other ( 9)-Steel spring bearings. ;.,4* all, no matter what quantity. (10)-Adjustable tension on bearings. removable. C. D. (11)-Shaft and rotor plates A ri 4,e s~\ Order one shipped O. (12)-Low minimum capacity in each section. loss insulation between stator and rotor plates. 44s e 408/0 -, (13)-Low 444n%/O r t °O (14)-Common rotor connection to steel frame. ./ .. N. two set screws. 1 ±5 res 4, 4,.`04, (15)-Each rotor attached to common shaft with 4 '4,N '' 'y., 5 -DAY equality of all condenser sections at all settings. 4, %/iI''0..' (16)-Exact 4. p : `/ \ MONEY -BACK (17)-Side and bottom mounting provisions. 4,,,o. /4 (18)-Straight line wavelength shape of plates. ti °é; a Y \ \ GUARANTY (19)-Brass soldering lug for each condenser stator section. (20)-Capacity increases with counter clockwise rotation of shaft. 4,/4 .00035 mfd. - er (21)-Capacity of each section, \ (22)-Plates cannot short. \ shaft. 4 ,446/. (23)-Easy turning \ (24)-Will last a lifetime. (25)-Eleven rotor and eleven stator plates in each section. .4" (26)-Weight (condenser alone), 354 lbs. wr \

www.americanradiohistory.com February 15, 1930 RADIO WORLD 23

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The three -meter assembly, In the crackle - Illustration above 1 upper Ielt. wIth brown finish carrying case, with slip-on -III Multiplior. tip; below It. J-108 Multiplier with tip; flues, left to Is 2/3 scale. conforms U V socket to In The handle is genuine right, 1-19, UX plus; J-20, conforme UX tester seeket te cover place. 199 lobe: 1-24, leather. The buckled strap holds the UV to test Kellogg and oto style Arcturus tubes. cover on. Makes All Necessary Tests in a Jiffy and Simplifies Service Work! speech amplifier or sound THE new Jiffy Teeter, J -245-X, is a complete servicing outfit. It WHEN servicing a radio set, power amplifier, consists of a three -meter assembly In s metal case. with slip -0a reproduction or recording e9utpment, the circuits and voltages are almost cover and a table plug. Thora ara ten adapters. It is vital te inaccessible, unless a plug-in tester is used. have the complete outfit so you can meet any emergency. of: With this outfit you plug the cable into vacated socket of a receiver, The Jiffy 245-X plugs in and does everything you want done. It consists putting the removed tube in the tester, and using the receiver's power (1)-The encased three -meter assembly with 4 -prong (UX) and 5 -prong for making these tests: plate current, up to 100 milliamperes; plats (UY) sockets built in; changeover switch built in, from 0-20 to 0-100 ma.; voltage up to 300 volts; filament or heater voltage (AC or DC), aP tipped ends of Lo 10 volts. ten vari -colored jacks, five of them to receive the vari -colored Each meter may be used Independently. One of the adapters-a pair the plug cable; grid push_bütton, that when pushed in connects grid direct of teat leads, one red, the other black, with tip lack terminsls-serves to the cathode for 224 and 227 tubes, to note change in plate current, and thus this purpose. Multiplier 3-108 extends the range of the DC voltameter aborts the signal input. to 600 volts, but this reading must be obtained independently, as mast readings on the 0-80 scale of the DC voltmeter. Independent reading (2) -4 -prong adapter for 5 -prong plug of cable. of the AC voltmeter for line of voltage is necessary; also to woe 0-140 grid tubes. stele while Multiplier 3-111 extends the AC scale to 680 volts for reading (3)-Screen grid cable for testing screen power transformer secondaries. for individual use of meters. (4)-Pair of Test Leads The other adapters permit the testing of special receiver tubes, so that (5)-J-106 Multiplier, to make 0-300 DC read 0.600. tests may be made. in ell, of 22 different tubes: 201A, 20eA, 0-560. 17X199. 17V199, 120, 240. 171, 171A. 112, 112A, 245, 224. 222, 228, (6)-J-111 Multiplier, to make 0-140 AC read 280, 281, 227. 226, 210. (7)-Two jack tips to facilitate connection of multipliers to jacks in tester. 250, Kellogg tubes and old style Aretarue tubes. (8), (9), (10)-Three adapters so UV199 and Kellogg tubes may be tested. GUARANTY RADIO GOODS CO. (11)-Illumination Tester. 143West 45th Street, Just East of Broadway, The illumination tester will disclose continuities and opens and also the N. Y. City. a and fits in your vest 1 Please send polarity of DC hcuse mains. It is as handy as pencil me on 5 -day money -back guaranty your J-245-X Jiffy in a Tester, complete, with 10 pocket. It works on voltages from 100 to 400. There are two electrodes 1 all adapters, and with illuminated Teeter On AC both electrodes light. On FREE with each order. Also send instruction sheet, tube Neon lamp in the top of the instrument. and rectifier tube data sheet DC only one lights, and that one is negative of the line, the light being on testing information. Hence illuminator shows whether tested source Enclosed please find 315.82 remittance. Ship at your expense- [Canadian the same side as the lead. the must be P.O. or Express M.O.] is AC or DC, and if DC, which aide is negative. Please ship C. O. D. @ 315.82 cartage Even the output of the speaker cord will show a light. plus and P.O. fee. Also, the device will test which fuses are blown in fused house lines, AC or NAME DC. Besides it tests ignition of spark plugs of automobiles, boats and airplanes, ADDRESS faulty or weak spark plugs. also CITY Just flash on the illumination tester momentarily. It will last about 4,000 STATE flashes. S -DAY MONEY -BACK GUARANTY

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La-ut Model National Velvet -B, Type 8180, te handsome crackle finiab black metal easing, for au with sate up to and including six tubes. Input 105-120 volts AC, $0 to 60 cycles. Output. 181 mite maximum at 95 milliamperes. Three variable Here is a 0-1 milliamineter, accurate m.tput Intermediate voltages. (Der.. RF. Ar'l. Eliminator has excellent filter system te eliminate to plus or minus 1% clearly legible to bum. ineluding 30 henry choke and It mft Berthan condenser No motorboatingI two -one hundredths of a milliampere (Eliminator Licensed under patent. of the Radi, at any reading (20 microamperes). Corporation of America and associated eompanlea.) This expertly made precision instru- Guaranty Radio Goofs Co. ment is offered at the lowest price so 143 W. 45TH STREET Modernize the appearance of your receiver by installing (Just East et Broadway) far for a 0-1 ma. Order Cat. FO -1 the brilliant new National dial. with color wheel built in, NEW YORK CITY ao that as you turn the dial knob one color after another at $5.95. C. O. D. orders accepted. floods the screen en whic5 the dial numbers ere read. On this screen the numbers are projected, so that you get the same dial reading from any position of the eye. This I. lust what DX hunters want-laboratory precision of dial RADIO WORLD Guaranty Radio Goods Co. reading. The escutcheon is of modernistic design. The Velvet and "RADIO NEWS" 143 West 45th Street, Vernier mechanism drives the drum superbly. Order today Remit with order and we pay cartage New York City Shipments day following receipt of order. BOTH FOR ONE YEAR ®. 7 .00 GUARANTY RADIO GOODS CO.. 149 W. 45th St., N. Y. City (Just E. of 13' way) You can obtain the two leading radio techrleal mama Enclosed please find $3.13 for which please send me sines that eater to experimenters, service men and etedente, dial marked below: the fini and only national radio weekly and the 1etglaa HC6. National modernistic drum dial, with color monthly, for one year each, at saving of $1.00. The AERIAL TUNER Cat. regular mall subscription rate for Radio World far tae wheel built In, pilot bracket, 6 -colt pilot lamp for year, a new and fascinating copy each week far 51 week», storage battery or A eliminator sets; hardware; lnatrue- i. $6.00. Send in $1.00 extra, get "Radio News" do Improves Your Reception tiens $3.13 for year-a new issue each month for twelve Bertha Cat. HC2%, same as above, but with 2% -volt Total, 54 Issues for $7.00. AC pilot lamp 3.13 D If renewing Radio World subscription, put 'MU Order C.O.D. and I pay cartage. square. RADIO WORLD, 145 West 45th Street. New York, N. Y.

NAME

ADDRESS

CITY STATE Hi Q 30 Remove aerial lead from set. Connect aerial laatead to one of the binding poets of the Aerial Tuner Connect the other binding poet of the Wholesale Aerial Tuner to antenna post of your set. Then Dove the lever of the Aerial Tuner until any weak station comes in loudest. The lever need not be moved for every different frequency tuned in. Prices! The Aerial Tuner acts as an antenna loading coil and puts the antenna's frequency at any frequency in the broadcast band that you desire Write or wire! to build up. Price, 85c. GUARANTY RADIO GOODS CO. 143 West 45th Street Guaranty Radio Goods Co. New York City (Just East of Broadway) 143 West 45th St., GUARANTY RADIO GOODS CO. imifflionsmonaromboussionlormodusso New York City 143 West 45th Street, New York, N. Y. Quick Action Classified Ads Radio World's Speedy Medium for Enterprise and Sales 10 cents a word - 10 words minimum - Cash with Order Batteries RADIO PARTS-Western set builders com- ARISTOCRAT FLOOR SPEAKER-With Mold- DISTON ELIMINATORS $6.95. Edison in. Great $1.95. Audio Transformers 95c. Western Electric pare our prices with eastern houses. ed Wood Horn and Horn Motor built list sets MAIL ORDER RADIO, Box 1110, Portland, Ore. $14.01). Acoustical Engineering Associates, Amplifier $14.00. Get our big bargain value. Radio Shop, Richmond, 143 W. 45th St., N. Y. C. and Darts. Quality Indiana. PATENTS POLO 245 POWER SUPPLY. Read all about PATENTS pending sold to Mfrs. You pay for page of this issue. Polo Engineering results only. W. Nestle. 852 Belmont, Chicago. it on another Equipments. Star, 111 W. Laboratories, 57 Dey St., N. Y. City. BERNARD Tuning 28th St., Indianapolis, Ind. OUTDOOR WORK-Get outdoor government job; "EVERYBODY'S AVIATION GUIDE." By Maj. $1680 year. Patrol forests; protect game. Write by for details. Bradley Inst., All, Denver, Colo. Pagé. $2 postpaid. Also "Modern Aircraft" TWO FOR ONE. Radio World for 52 weeks and same author. $5. postpaid. Radio World, 145 W. at the combination Radio News twelve months "A B C OF AVIATION." By Maj. Pagé. $1.00 45th St.. N. Y. City. 145 W. 45th St., N. Y. rate of $7. Radio World, postpaid. Radio World, 145 W. 45th St.. N. Y. BE SURE TO READ the advertisement on City. another page of this issue about the HB Compact WORLD'S BEST AVIATION BOOKS: "A B C Radio Goods Co., 143 W. 45th St. Engines," "AUDIO POWER AMPLIFIERS," by J. E. Guaranty of Aviation," $1.00; "Modern Aviation Anderson and Herman Bernard, the first and only N. Y. City. $9.00 postpaid. Both by Maj. Pagé. "Aerial By Yancey. book on the subject. $3.50. Hennessy Radio Pub- Navigation and Meteorology," Capt. 145 "MATHEMATICS OF RADIO. "-A great help 145 11. 45th St., lications Corporation, West 45th St., N. Y. $4.00 postpaid. Radio World, City. to everybody interested in radio. $2 postpaid. N. Y. City. Radio World, 145 W. 45th St.. N. Y. City. www.americanradiohistory.com February 15, 1930 RADIO WORLD 27 1111111111111I1111111111111111111111111111111111111111111111111111111111.1111111111111111111111111111111111111111111111[ 11111111111111111111111111111111111IIII11111111111111111 Highest Grade Speakers at Lowest Prices! TEM°PL.nE FAoR0RAoNiiD

11101111101111111111311111111I. I ii zIIIII11IIIIIIIniIIII1IÍIRIIIIIInt

Farrand Inductor Chassis, consisting of the unit, cone, spider, bracket, assembled, but not in a cabinet.

Model 6-G, 10" extreme diameter of cone front rim $8.00

Model 10-G, 12" extreme diameter of cone Temple AC Dynamic Model ío, in a beautiful cabinet. front rim $ 10.00 The speaker chassis is one of the finest made. There are an output transformer and dry rectifier built in. Model 10 -G -PP for connection to push- The cabinet has decorated walnut front and back, with carved pull, requiring no output device, because grille ornament. An AC switch is accessible underneath cabinet. unit is constructed as a center tapped Rear is removable for adjustment of resistor knob to match output impedance. Center tap is yellow the impedance of your receiver's output tube. Connect plugged and goes to B+. Tipped cords go direct AC cable :o 110 volts AC, 50 to 60 cycles, and connect tipped to plates. Outside diameter 12" $11.00 cords to speaker post of receiver. This remarkable $1 .34 Cat. TEM-1& at only speaker Brookfield cabinet, No. 10 or No. 6 for those speakers, $6.50 R -O -L -A Rola Model D-10 dynamic chassis, less cabinet, for 110 volts 50- 60 cycles AC. Dry rectifier and output transformer built in. The fine workmanship of this chassis is shown in the illustrations of the front and rear views. Extreme diameter of rim 9 inches but baffles with cutouts down to 7 inches may be used. This is the biggest dynamic chassis bargain we have ever offered and enables you at low price to obtain one of the best chasses made. Tone is most excellent. Order Cat. No. RO -10 at

Front view of the Rola chassis. Holes are 1 34 provided for attachment to your own baffle. Si The rim is protected by a lining of Rear view of the felt. The Rota chassis voice coil (center) is firmly mounted.

Acoustical Engineering Associates The Temple, Rola and Farrand speakers are highly recommended by us 143 West 45th Street, New York City. (Just East of Broadway) for true tone and high volume. They are extremely Gentlemen: Enclosed please find money order D check sensitive as well. for f for which please send me at once The chasses (Farrand and Viola) will work without a baffle, but it is One Model 6-O Farrand Inductor 88.00 preferable to provide one. The Temple One Model 10-6 Farrand Inductor 10.00 requires no extra baffle, as One Model 10-13 -PP Farrand Inductor 11.00 the cabinet is itself a baffle box. One Model 10 Brookfield cabinet 8.50 One Model 8 Brookfield cabinet 8.60 All three speakers are sold in factory -sealed cartons. Immediate de- One TEM-10 Temple Dynamic in cabinet 15.34 One RO -10 Rola dynamic chassis 11.34 livery. For C. O D. shipment put cross here Model 10 -G -PP Farrand may be used in push-pull without any output Name device. Connect yellow lead to B+, tipped leads to power tube plates. Address May s be used on ngle ottp,:it by ignoring yellow lead. City State [Prepaid orders shipped same day as received. Canadian remittance must be by postal or express money order.] 1111111111111111111111111111111111111111111I111111111111111111111111111111111111111111111111111111111111111111 1111111111 :llliII111111111111111111111111111111111111111111111111

www.americanradiohistory.com 28 RADIO WORLD February 15, 1930 0.60,0300 High Gain HIGH RESISTANCE DC VOLTMETER at Low Cost With three 28" tipped leads built in A portable type, high mistime* meter, 2'/a" outside diameter, for close reading of direct current voltages up to 60 volts, and fee HB44 reading DC voltages up te 300 - - - $45.59 volta. 'Three sari -colored 28" In- sulated leads, with jack tips, are built In. Black Is minus, yellow 13 CO volts maximum and red L 300 volta maximum. These voltages are marked at the meter outlets. Cat. J-246. Net price. $2.28. J-246 Voltmeter, for measuring all direct Multiplier, with Jack terminals, current voltage.. In- to insreaae range 0-300 range te cluding B elimina- trr.. 0.80. 0-300 0.600. Cat. J-108JT (with Jack (double range). terminals), net price, 91.1$. GUARANTY RADIO GOODS CO. 143 West 45th St., N. Y. City MICROPHONE

The H B44, assembled. presents In compact farm, en 171/4 a 111/4" stool chassis, completely AC operated shielded roeelver, usino four 224 screen grid tubes, one 227, two 245s in push-pull, and 280 rectifier, eight tubes all told. Here lb the eircult LIGHTERS that will bring 'em In from all ever the country-and at a price you eau afford- $45.59- This price Includes EVERYTHING except sneaker, cabinet and tubes. for cigars or cigarettes, with button switch at top. Press the switch and It's the Real Thing! light up 1

(a) Three stages of tuned R.F., using 224 screen grid tubes. (b) Tuned input to 224 power detector. (e) Audio, consisting of first stage resistance coupled, second stage 245s in push-pull (d) Four totally shielded R.F. coils. (0) A chassis all drilled for necessary parts. (I) A four gang condenser, guaranteed accurate, with equalizing condensers built in. (g) 01 mfd. of filter and bypass capacity. (h) Thirteen different fixed voltages available from the output. (1) Single dial control. Model A lighter, microphone design, with 5 -ft. AC cable and LIST OF PARTS FOR THE HB44 plug. Works on 110 volta, AC D SL1, SL2, SL3, SL4-Four stage individually shielded coil cascade any frequency and on direct cur- for .00035 mid. (Four Cat. SH -3 of Screen Grid Coil Co.) $ 3.80 rent. Price $1.911 D Cl, C2, C3, C4-One four gang .00035 mfd. condenser with equalizers El, E2, E3, E4 built in 3.95 D CS-One .01 mfd. mica condenser .35 D CO, C7, C13, C14-Four 1 mfd. 200 volt DC bypass condensers 2.00 D CB--One 1 mfd. SSO volt AC filter condenser .85 D C9, C10, C11, C12-One Mershon, consisting of four condensers, two of 8 mid. and two of 18 mfd. with bracket (Cat. Q-2-8, 2-18-B). 5.15 D RI-One Electrad 25,000 ohm potentiometer with knob and two insulators 1.80 R2 --One 50,000 ohm Lynch metallized resistor (.05 meg.), with mounting .45 D R3-One Lynch 5.0 meg. metallized grid leak, with mounting .40 SR4-One 5,000 ohm resistor with mounting .50 VD-One Multi -Tap Voltage Divider, 13,850 ohms, 14 taps 3.95 D Ti-One push-pull input transformer 2.50 Model B lighter, microphone de- OPC-One center -tapped output choke 2.50 sign, on tray, with 5 -ft AC cable D T2-One Polo filament -plate supply (Cat. PFPS) 7.50 and plug. Works on 110 volt D Ch-One double filter choke coil, 30 henrys each section, 100 ma 3.71 AC, any frequency, and on direct AC switch with 12 ft. cable .8s current. Exactly the same lighter D SW-One pendant as D PL-One 2.5 volt pilot lamp and bracket .70 the other, only tray is added. D Speaker (+), (-), Ant., Gnd.-Four binding posts with insulators. .40 Price $1.50 Humdinger, 30 ohms .50 D One Clarostat lighter Is 171/2" x with five UY and three UX sockets 3.00 This instantaneous. Hold button dowa One subpanel 111/2', only long enough to light a cigar or cigarette. O One vernier dial .50 The two models are furnished in attractive Four National grid clips .24 sprayed finish. Both are very For D Hardware .24 compact! instance, the tray is only 4V2" in diameter. cabinet, tubes and speaker) Use these lighters in your home and for D All parts (less $45.59 holiday gifts. D Tubes: four 224, one 227, two 245, one 280 9.51 he heater element is renewable. Price 35 cents.

RADIO WORLD. 145 West 45th St.. IN. Y. City RADIO GOODS CO.. GUARANTY D Please Bend me Model A Microphone Lighter at 143 West 45th Street, New York. N. Y. 81.00 (Just East of Broadway.) Please send me Model B at $1.50. Enclosed 1s remittance [Canadian muet be P.O. or ex- Please ship all parts for H B44 64 $45.59 press money order. ] D Eight tubes for HB44 9.51 Ship C. O. D. Please ship C.O.D. Enclosed find $ remittance. (Canadian must be P. 0. or Express M. O.) Nano

Address,

NAM E City state

ADDRESS MORECROFT wrote a great book when he turned out "Principles of Radio Communication." Second edition now ready. Price $7.50. Radio World, 145 W. 45th St., N. Y. City. CITY STATE

FIVE DAY MONEY -BACK GUARANTY "AERIAL NAVIGATION and METEOROLOGY." By Capt. Yancey. $4.00 postpaid. Radio World, 145 W. 45th St., N. Y. City.

www.americanradiohistory.com February 15, 1930 RADIO WORLD 29

e p O ih? r4ua aaa 37. O D BOOK SERVICE AS the first and only national radio weekly, now in its eighth year, RADIO WORLD publishes the most timely, up-to-date news of radio circuits and events in the set -building and broadcasting fields. Tech- nical accuracy second to none. Get a copy at your news-stand today, 15c. RADIO WORLD advises im- partially on all radio topics, including what text books to buy, and helps you to read the books Properly. Every book advertised on this page is essential to your radio library. Five New Volumes Offer Short - Cut to Knowledge! MORECROFT ANDERSON and BERNARD "Elements of Radio Communication" "Power Amplifiers" The latest book by Prof. John H. Morecroft, of the Here is the first book to be published on the subject of "Power Engineering Department of Now is certain to a void in radio Columbia Amplifiers." printing, It fill University, and past literature. The whole subject is fully covered in a masterful president of the Institute of theoretical discussion of audio amplifiers and power supplies. Radio Engineers, is his "Ele- supplemented by constructional chapters, with complete wiring ments of Radio Communica- diagrams and specification of parts. Learn while you build! a book for the novice tion," J. E. Anderson, M. A., technical editor of RADIO WORLD, and POWER AMPLIFIERS I to enjoy. We regard this as Herman Bernard, LL. B., managing editor of RADIO WORLD, the best elementary book to both of the Institute of Radio Engineers, have explained fully the inform you authoritatively on phenomena of power amplifiers. Learn all about motorboating the technical phases of radio and its cures, push-pull theory and practice, grid bias methods in plain language, without and effects, vacuum tubes in audio circuits, AC and battery type requirement of mathematical AF amplifiers, phase relationships, common impedance, filter knowledge. The book is a systems, by-pass condenser effects, necessities for tone quality, course on the ele- complete values of coupling constants, and a host of other topics associated ments of radio, containing with power amplification, including speech amplifiers and "talkie" much material never before installations. published. It has 226 pages. 170 illustrations and a com- More than 200 pages and more than 100 illustrations are devoted plete index. Just out, it is to an analysis of this outstanding radio subject. "Power Ampli- the book of the year in radio. fiers" is authoritative, original and comprehensive. It is free Cloth bound. Order Cat. ME from the traditional errors that have crept into this subject. The H $3.00 theoretical part of the book can be understood by most novices, while the constructional part, that capitalizes the previously im- By the same author: "Prin- parted knowledge, is thoroughly understandable by anybody. ciples of Radio Communica- There is virtually no mathematics in the book. Cloth bound. tion," second (new) edition. Order Cat. PAM @ $3.50 This book is for adva,ced students. It is the standard of excellence in its field. It covers much the same ground as the later book, only much more fully and more technically. Contains 1,001 pages, 831 illustra- RIDER tions. Cloth bound. Order Cat. MP © $7.50 "Service Man's Manual" MOYER and WOSTREL Two new books by John F. Rider, R. E., ',Member, Institute of Radio Engineers, constitute the series grouped by him tinder the heading "Service Man's Manual." l'art I is "Mathematics of Radio." "Radio Receiving Tubes" Part II is "Trouble Shooter's Manual." The need for an elementary book on radio tubes that answers The value of one of these books is more than doubled by the possession of the other. all the important questions has been filled by James A. Moyer, Director of University Extension, Massachusetts Department of "The Mathematics of Radio," 128 pages. 81/zx11", 119 illustrations, bridges the gap between the Education, and ,John F. Wostrel, Instructor in Radio Engineer- novice and the college professor. It gives a theoretical background so necessary for a proper under- ing, Division of University Extension, Massachusetts Department standing of radio and audio circuits and their servicing. Flexible cover. Order Cat. MOR H..,,$2.00 of Education. The first comprehensive volume devoted exclusively to the topic uppermost In every service man's This new book is a complete discussion of tube principles, mend is "Trouble Shooter's Manual," just published. It is not only a treatise for service men, telling functions and uses, thoroughly up-to-date. In this book the them how to overcome their most serious problems, and fully diagramming the solutions, but it is a essential principles underlying the operation of vacuum tubes course in how to become a service man. It gives all the details of servicing as they have never been are explained in as non -technical a manner as is consistent with given before. Finding the right mode of attack, applying the remedy promptly and obtaining the accuracy. The book covers the construction, action, reactivation, actual factory -drawn diagrams of receivers always have been a big load on the service man's chest. testing and use of vacuum tubes as well as specifications for But no more. Rider, expert on trouble shooting, has producd the outstanding volume on servicing, vacuum tubes and applications for distant control of industrial and has taken the load off the service man's chest! processes and precision measurements. 297 pages, cloth bound. Order Cat. MWT @ $2.50 This book le worth hundreds of dollars to any one tcho shoota trouble in receivers-whether they be By the same authors: factory -made, custom-built cr home-.made receiee*s. The home experimenter, the radio engineer, the 'Practical Radio," including the testing of radio receiving custom set -builder, the teacher, the student-all will find this new book immensely informatire and sseetPR376Qpages, 223 illustrations. Cloth bound. Order absolutely authoritative. $C 6t. "Practical Radio Construction and Repairing," 319 pages, a MORE THAN 100 WIRING DIAGRAMS OF RECEIVERS MADE BY MORE THAN FORTY companion volume. Order Cat. MWPRC R $2.00 DIFFERENT SET MANUFACTURERS ARE PUBLISHED IN THIS BOOK, INCLUDING OLD [NOTE: The standard book on tubes for advanced students is MODELS AND LATEST MODELS! RCA, ATWATER KENT, CROSLEY, MAJESTIC, ZENITH. "The Thermionie Vacuum Tube," by Hendrik Van der Bijl. STROMBERG CARLSON, KOLSTER, FEDERAL, FADA, Etc. 240 pages, size li'Ftx11"; 200 illus- Order Cat. VDB @ $5.001 trations. Imitation leather cover. Order Cat. TSnt C $'i 50 Read Radio World Every Week RADIO WORLD will help you in your radio work, so you will be able to use meters onset valuably. Keel( breast of new circuits, intimate details on perfecting existing sets, get inside track on sensitivity, distance eception, tonal quality, and news of radio, technical and non -technical. Enjoy the writings of McMurdo Silver. . E. Anderson, Herman Bernard, John F. Rider and a host of other radio engineers in RADIO WORLD. You can find no magazine that better caters to your needs than RADIO WORLD. Short waves? RADIO WORLD will tell you all about them. Extremely sensitive broadcast receivers? Their construction and peration are fully discussed with confident regularity. Power supplies--posh-pull or otherwise? AC re- eivers? Screen grid tubes? Large receivers that give a super -abundance of performance-small, economical eceivers that give performance out of all comparison to their size? Are you interested in these? Then you're Ii nterestd in RADIO WORLD. See the list of nine meters at left. Obtain one or more of these meters free. by sending in $1 for 8 -weeks' subscription, entitling you to one meter; $2 for 16 weeks, entitling you to two meters; $3 for lit weeks, entitling you to three meters; $4 for 35 weeks, entitling you to four meters; $5 for 44 weeks, entitling you to 5 meters; $6 for 52 weeks, entitling you to six meters. Present RADIO WORLD mail subscribers may renew their subscription under this remarkably generous offer. I'ut a cross in square.

Gentlemen: Enclosed find $ for RADIO WORLD which please send items checked on coupon., (R -10) 145 W. 451h St.. N. Y. City-Published Weekly. All Newsstands, 15c per copy-$3, six months-$6 a year

D CAT. ME @ ,. $3.00 [I CAT 326 Name 0-6 Voltmeter D.0 Cat. 326 CAT. MP @ .. $7.50 CAT '07 D 0-50 Voltmeter D.0 Cat. 337 CAT. PAM @...... $3.50 D CAT 23 D 6 -Volt Charge Tester D.C Cat. 23 CAT. MWT H...... $2.50 D DAT 338 D 0-10 Amperes D.0 Cat. 338 D CAT. MWPR Hu..,. $2.50 D CAT 325 Address D 0-25 Milliamperes D.0 Cat. 325 CAT. MWPRC H... $2.00 D CAT 350 D 0.50 Milliamperes D.0 Cat. 350 CAT. MOR H...... $2.00 CAT 390 0-100 Milliamperes D.0 Cat. 390 CAT. TSM H.. ... ,. $3.50 CAT 399 D 0-300 Milliamperes D.0 Cat. 399 CAT. VDB H $5.00 CAT 394 City State D 0-400 Milliamperes D.0 Cat. 394

RADIO WORLD. a weekly paper published by Hennessy Radio Publications Corporation, from Publication Office, 145 West 45th Street, New York, N. Y. Vol. XVI, No. 22. Whole No. 412. February 15th, 1930. 15c per copy, $6.00 per year. [Entered as second-class matter, March, 1922, at the Post Office at New York, N. Y., under act of March, 1879.] Roland Burke Hennessy, president and treasurer; M. B. Hennessy, vice-president; Herman Bernardi. businessmanager and managing editor; J. E. Anderson, technical editor.

www.americanradiohistory.com 30 KAllIO WORLD February 15, 1930

Efficient Coils for Standard Circuits at Lowest Prices ANTENNA COUPLER BERNARD TUNERS Bernard Tuner BT5A for .0005 mfd. for antenna coupling, the Primary being fixed and the secondary tuned. This coil is used as input to the first screen grid radio frequency tube. Secondary has moving coil. Cat. No. BT3A for .00035 mfd. ..$1.35 Bernard Tuner RT5B for .0005 mr;. for working out of a screen grid tube, tuned primary, un - t u n e d secondary. Primary has moving coll. Cet. No. BT5A-51.55 Cat. BT 3B for Cat. No. BT5B-$i.35 Cat. Na. VA5-50.85 FOR .0005 MFD. CONDENSERS .00035 mfd. ..31.35 FOR .0005 MFD. CONDENSER FOR .0005 MFD. CONDENSER Moving primary and fixed secondary, for antenna coupling. Serves as volume control Cat. No. VA3 for .00035 mfd. $0.98 DIAMOND PAIR SG TRANSFORMER Cat. No. RF5-$0.00 FOR .0005 MFD. CONDEN- SER Antenna coil for a n standard circuit, and one of the two coils constituting the Diamond Pair. Cat. No. RF3 for .00035.00.85 Cat. No. SGT5-S0.05 FOR .0005 MFD. CONDEN- SER Interstage 3 -circuit coil for any hookup where an un - 1s in the Cat. No. RF5-$0.00 tuned primary plate circuit of a screen grid tube. FOR .0005 MFD. CONDENSER SGT3 for .00035 mfd...00.90 Order the Diamond Pair, Cat. DP5 for .0005 mfd. at $1.45 Cat. No. SGT5-$0.85 Order the Diamond Pair, Cat. DP3 for 00035 FOR .0005 MFD. CONDENSER mfd. at $1.05 I Thee same coils are for AC or battery Cat. Ne. SGSS-$0.80 Notº: FOR .0005 MFD. CONDENSER circit.I Interstage radio frequency transformer, to work out of a acreen grid tube, primary un - tuned. STANDARD TUNER Cat. No. 6063 for .00035 mfd. $0.85 FL4 $0.30 The standard three -circuit tuner is used with Flexible in- primary in the plate circuit of any RF tube, AC auleted coupler or battery type, excepting only screen grid tube. for uniting coil For .0005 mfd. order T5 at $0.85 - o r condenser -Coll - Cowan,. Semen- Grid order Cat. T3 at $0.90 143 West 45th Street. shafts. For .00035 New York, N. Y. (lust East of Broadway.) Order Cat FL9 All coils have 2 ',h" diameter, except the shielded at $0.30 coil, which is wound on 1%". Enclosed please find $ for which Equalizing eon - The coils are wound by machine on a bakeilte please send at once the following parts: denser, 80 form, and the tuned windings have identical in- mmfd., for con - for a capacity condenser, 1. e.. at $ ductance given CI Cat. No. eroas .0005 mfd. or .00035 mfd. Full coverage of the D Cat. No. at $ any tuning con- wive uand is assured. denser w h e r e y Cat. No. at S All coils with a moving coil have single hole so e 1s for mounting fixture. All others have base ship C. O. D. sorted to, sor for panel prim mounting provision. The coils should be used inde- connection lugs at bottom, to shorten leads. Nama pendently tuned with circuits to make Only the Bernard Tuners have a shaft extend- Address dials track. ing from rear. This feature is necesary so that Order Cat. EQ80 physical coupling to tuning condenser shaft may link. City State at $0.35 be accomplished by the insulated

LOOK AT YOUR WRAPPER ARISTOCRAT FLOOR SPEAKER FULL EXPOSITION OF You will see by the date thereon when With Molded Wood Horn and Horn HB COMPACT, BATTERY MODEL built in. Good value. $12.00. your subscription for Radio World ex- Motor Complete details on 143 the theory and conatructlm of the pires. If the subscription is about to run Acoustical Engineering Associates, W. HB Compact were published ln a four-part article ie 45th St., N. Y. C. Radio World, written by Herman Bernard, designer of tea out, please send us renewal so that you circuit and inventor of the Bernard Dynamic Tuners used will not miss any copies. Subscription 'n the circuit. Full details on how to wind your own Mts. Full-sized pictorial diagram of the wiring. Order the Department, RADIO WORLD, 145 West MICROPHONE LIGHTERS August 24th, 31st, September fth and 14th Lsues, Ies- 45th St., N. Y. City. For cigars or cigarettes, with button RADIO WORLD. 145 West 45th Street. New York, N. T. switch at top. Press switch, and lighter acts instantaneously. $1.00. Model B "A B of TELEVISION and all about it in C $1.50. 145 Television," by Raymond Francis Yates. $3 post- lighter on tray, Radio World, paid. Radio World, 145 W. 45th St., N. Y. City. W. 45th St., N. Y. C. SUBSCRIBERS! FILL OUT AND MAIL NOW Look at the Expiration Date on Your SUBSCRIPTION BLANK Wrapper Please look at the subscription date stamped on your last wrap- RADIO WORLD per, and if that date indicates RADIO WORLD 145 West 45th Street, New York City that your subscription is about to expire, please send remit- Please send me RADIO WORLD for months, for which tance to cover your renewal. In this way you will get your SUBSCRIPTION RATES: please find enclosed copies without interruption and Single Copy $ .15 keep your file complete. Three Months 1.50 SUBSCRIPTION DEPARTMENT Six Months 3.00 One Year, 52 Issues 6.00 RADIO WORLD $1.00 a Year for Foreign Add 145 WEST 45TH Postage; 50c for Canadian Post. ST.. N. Y. CITY age.

www.americanradiohistory.com February 15, 1930 RADIO WORLD Non.Reactive Audio with Tuner! NR -4 The Remarkable Non -Reactive Circuit designed by Herman Bernard, using the newly popular audio channel for AC operation. Speaker operation on four tubes, including rectifier. Ll, L2, Cl-One Bernard antenna coil, .00035 mid. condenser, link, Cat. BT -L -AC $3.00 L3, IA, C2-One Bernard interatage tuner, with .00035 mfd. condenser, link, Cat. BT -R -AC 3.00 C3-One .01 mfd. condenser ..35 C4, C5, C6, C7, C8, C9, C12-Seven 1 mfd condensers, low voltage 3.50 C9, C10-Two 1 mid. filter condensers, 550 v A.C. r.m.s 1,000 volts D.0 2.00 Rv (vol. control)-One Electrad Tonatrol pot (500,000 ohms) 1.50 R1-One Electrad 800 ohm biasing resistor strip .20 R2-One .02 meg. (20,000 ohms) resistor with mounting .55 R3-One Lynch 0.5 meg. metallized resistor with mounting .50 Layout of the NR -4, using a steel chassis, 15" wide x 9/a" deep. The R4-One Multi -Tap Voltage Divider, with volume control (not shown) is at center. For installation dials replace brackets, Cat. MTVD 3.95 the illustrated knobs. Tl-One Polo filament -plate supply, (50-60 cycle), Cat. PFPS 7.50 Ch-One single Polo B filter choke, Cat. PSC 2.50 RFC-One shielded radio frequency choke, 50 millihenries .50 SW-One pendant AC switch with 12 foot cable 1.12 Ant., Gnd., Speaker-Four binding posts .40 One steel chassis 15" wide by 954' deep, with sockets affixed 3.50 Two dials. 100 to 0 1.00 Insulators (four for subpanel, three for front panel) .22

$35.29 Tubes: Two 224, one 245, one 280 $5.27 Construction Advice. In building the NE -4, insulate the right-hand condenser from the chassis, as it tunes the SG plate circuit, and ground the chassis, also POLO connecting ground and [r.a [eR6,ttc[ negative of the B sup- t[nre[ T.P. Mee a [o ply. Then, to have both condensers equally ele- vated, insulate the left- hand one, but connect its frame to sub - panel by a lead soldered to a lug fastened to sub - The NR -4 circuit diagram, with numbers designating voltage divider panel. taps, corresponding to illustration below.

Multi -Tap I'olo 245 Filament Plate Sup- ply (less chokes) has four windings, all save primary center - 15 14 1.3 12 11 tapped (red), is 41" wide, 5" Voltage Divider high, 4" front to back. Weight, 9 lbs. Filament windings, 2.5 v. at 12 amps., 2.5 v. at 3 amps. For non -reactive audio circuits, (for 245 filaments), 5 v. at 2 instead of using variable resist- amps. for 280 rectifier, and 724 ors you may more conveniently v. @ 80 m.a., center -tapped. use a voltage divider with numer- Order Cat. PFPS (a1 $7.50. ous taps. Used as in the NR -4 [For 25 cycles order Cat. it will not get hot-barely tepid PFPS-25 Q $12.00.] after 10 hours continuous opera- [For 40 cycles order Cat. tion-because it will stand 125 PFPS-40 (cÀ $10.00.1 milliamperes! The conservative rating, actual use, is 50 watts. Two rugged, expertly engineered wire -wound, enamelled resistors, Headquarters mounted in series, one atop the other, with fourteen useful lugs, We are headquarters for providing all necessary choice of information and advice on voltages without the uncertainty non -reactive audio amplifiers of adjustable variable resistance. and ttiners therefor. Write us your questions, Voltage or tele- The Multl-Tap Divider Multi -Tap Voltage Divider, showing where to connect the Bads for phone BARclay 8659. Tele- has a total resistance value of plate and 13,850 ohms, in the following screen voltages in connection with circuit diagram above. graphed inquiries answered steps: 3,000, 4,500, 2,000, 800, same day as received. All 700, 600, 550, 500, 450, 400, 200, orders promptly filled. Five- 100 and 50 ohms. With the zero day money -back guaranty on voltage lug (at lower left) the everything. Square deal is total number of useful lugs Is our motto. fourteen. The resistance stated are those between respective lugs and are to be added together to constitute 13,850 ohms total. Extreme care has been exercised In the manufacture of the Multi -Tap Voltage Divider. It is mounted on brackets insulated from the resistance wire. Please Use This Coupon The Multi -Tap Voltage Divider is useful in all circuits, including push-pull and single - laynxon Laboratories, sided ones, where the current rating of 125 milliamperes is not seriously exceeded and the I57 Dey Street, N. Y. City. maximum voltage is not moro than 400 volts. If good ventilation is provided, this rating Walter J. McCord, Chief Engineer. may be exceeded 15 per cent. Please ship at once C. O. D. tested parts for NR -4 as advertised. attaching a list of these I am The expertness of design and construction will be recognized by those whose knowledge parts desired. teaches them to appreciate finely made. D All parts are desired, as Indicated by cross parts sentence. in square at left of this When the Multi -Tap Voltage Divider is placed across the filtered output of a B supply which serves a receiver, the voltages are in proportion to the current flowing through the Name various resistances. Sample voltages are 300, 180, 120, 75, 50, 40, 35, 30, 25. 16, 10, 6 and 3. By making suitable connection of grid returns the lower voltages may be used for IAddress negative bias or even for positive voltage on the plates. Order Cat. MTVD at $3.95. City State S -DAY MONEY -BACK GUARANTY

www.americanradiohistory.com RADIO WORLD February 15, 1930 The Most Fascinating Radio Book of the year! FR EE thN EW RADIO NEWS

THE thrill of the Short Waves! It's like the stand intelligently the conditions under which it is invention of radio all over again. If you've accomplished and how to get the most out of your ever decoded messages straight from South Short Wave work. Here's the Manual that gives you Africa or Australia-if you've ever known the kick the complete and latest dope-just the book you of getting Europe or Little America direct-if want! you've ever had S.W. chats with friends hundreds of miles away, then you know what we mean. Why It's Yours FREE The Short Waves are opening up a tremendous new field of amazing possibilities. An entirely new RADIO NEWS has many thousands more readers world of experimenting, of thrills, of new ex- than any other radio magazine. But we feel there periences with these miraculous S.W: s lies ahead. are still a few of you radio men who have been so Because you and thousands of other radio men close to your work that you don't realize what you want to keep posted on all the latest wrinkles on are missing. Short Waves, the Technical Staff of RADIO NEWS That's why, although we will sell thousands of has especially prepared a complete new SHORT these SHORT WAVE MANUALS for a substantial WAVE MANUAL-so up-to-the-minute that, even price, for a limited time you can have a copy entirely as this is being written, complete proofs have not FREE as an inducement to try RADIO NEWS. yet come from the printer. Here's the magazine that tells you all about the Crowded with chapters especially written by that newest receivers, all about the latest discoveries in foremost Short Wave authority, Lieut. W. H. Wen- servicing and handling radio parts and sets-and strom, this volume represents the last word in then goes beyond all that to give you the vital radio authentic Short Wave data. You will be fascinated news of the whole world in a terse, business- with such chapters as: like way that demands reading by every man whose interest lies in radio. Breaking into Amateur Transmitting If the Federal Radio Commission makes a new S -W Transmitter for the Average Home and Purse improved A Portable S -W Transmitter and Multiwave Receiver ruling-if an Austrian inventor designs an For Real Thrills Get Down in the Amateur Wave Bands tube-if a new discovery in television occurs in Ready for a Short -Wave Chat Greece or even Patagonia, you'll find it all explained Getting the Most from Your S -W Transmitter in RADIO NEWS. Some Experiments on Ultra -High Frequencies radio Short -Wave Stations of the World That is why we say with emphasis-if it's news, it's in RADIO NEWS. Here's the magazine It is one thing to pound the key of a short-wave for the man who wants to see with modern vision transmitter and hope to high heaven that your sig- the future trends and developments of radio's rapid nals are "getting out." It is another thing to under - progress. Mail Coupon Before It's Too Late -1 Send for Your FREE S.W Book NOW! The NEW RADIO NEWS, Dept. 215-RW. 1LACKINNON-FLY PUBLICATIONS, Inc., To introduce the NEW RADIO NEWS to you, we 381 Fourth Avenue, New York, N. Y. Gentlemen: Send me. ENTIRELY FREE, postpaid. the neu, will send you the next Eleven Big Numbers, almost 1930 SHORT WAVE MANUAL, and enter my subscription for a full year subscription, for only $2-and will ship the next Eleven Big Issues of the NEW RADIO NEWS at oni:, $2 which I enclose (regular newsstand price $2.75). I understand you the new 1930 SHORT WAVE MANUAL, post- you will cheerfully refund my $2 and I may keep the S.W. MAN after reading the first issue. paid, ENTIRELY FREE! You save 75t on the UAL if I am not perfectly satisfied newsstand price of RADIO NEWS and get this in- Name valuable S.W. volume without cost! Risk nothing. Address Mail coupon TODAY- ('ity & State Are you a Serviceman? Engineer? Dealer E? Experimenter E? Present subscription will be extended from expiration.