Radio Broadcast (May 1928-Apr 1929)

AUG -6 1928 i Cl B 7 9 »i 6 « 1 RADIO BROADCAST AUGUST, 1928 Willis Kingsley Wing, Editor Keith Henney Edgar H. Felix Director of the Laboratory Contributing Editor Vol. XIII. No. 4 CONTEXTS Cover Design ' From a Design by Harvey Hop\ins Dunn Frontispiece Radio Brings the Stoc\ Exchange to the Wilderness R. P. Clar\son Joseph Morgan ' Robert Burnham An Editorial Interpretation Caldwell Hits Straight from the Shoulder Amateurs in the Ten-Meter Band Here and There What Can We See by Radio? All About Loud Speakers ' ' ' A Dual Control A.C. Receiver The March of Radio ' * * < The War on the Short Waves Struggles of the British Imperial System The Mackay-R.C.A. Struggle The Commission Announces Its Short-Wave Policy Building the D.C. Lab Receiver "Strays" from the Laboratory ■ Keeping R.F. Current out of the Audio The Short-Wave Market ll5ink or Swim" Tube Testing Line Voltage Variations A.C. Screen-Grid Tubes A Screen-Grid ShortWave Receiver ' "Radio Broadcast's" Home Study Sheets Keith Henney "Strays" from other Laboratories Making D.C. Sets Comfortable Loud Speaker Tests Recent Articles of Interest Howard Barclay No. 3. Testing Vaccum Tubes No. 4. Ohm's Law What "Pick-Up" Shall I Buy? Adding Regeneration to Any Set What About the 5-Meter Band? "Our Readers Suggest " Increasing the Output Voltage of B-Power Units Cleaning Corroded Battery Terminals New Use for a Block Filter Condenser Simplified Plate Rectification Parallel Plate Feed An Extra R. F. Stage for Any Receiver As the Broadcaster Sees It David Grimes Herbert Grove R. S. Kruse Some More on Balanced Speakers A Milliampere Meter Protector and Multiplier Tinning Wires Emergency Battery Connections The Laboratory Staff Carl Dreher Broadcast Frequency Characteristics Low Voltages Are Dangerous Commercial Radio Publications: Radio Equipment" "Aircraft "Radio Broadcast's" Service Data Sheets on Manufactured Re ceivers No. 5 The Fada . No. 6. The Federal Ortho-sonic Seven-Tube Receiver Is the Highbrow Entitled to a Program of His Own? The Listener's Pomt of View John Wtf/Z<JCe Operating the National Screen-Grid Five James Millen New Apparatus Useful Information on New Products Manufacturers1 Booklets Radio Broadcast's Laboratory Information Sheets No. 200. Selectivity No. aio. Protecting the Rectifier Tube No. in. Soldering Irons No. 212. Equalizers Letter from Readers No. 213. Frequency Characteristic of a SevenMile Cable No. 214. Measuring Instruments No. 215. The Hi-QSix No. 216. The Circuit of the Hi-Q Six The contents of this magazine is indexed in The Readers' Guide to Periodical Literature, which is on file at all public libraries. 184 185 l88 I92 195 199 201 203 205 207 2IO 212 215 217 219 221 223 225 227 228 23o 23 1 AMONG OTHER THINGS. . TELEVISION, for the moment, appears to be drawing perhaps more than its just share of attention. Our leading article in the July number explained some of the most serious limitations of television systems and pointed out the greatest obstacles which are yet to be overcome. In this issue, Mr. Clarkson discusses the results which can be had from some of the systems which may be before the public. If Radio Broadcast does not rush into print with "constructional" articles on television sets, our readers may forgive us. We strongly doubt that even the most enthusiastic of experimenters will be content with the results he can achieve from the transmissions now taking place. Television, we fear, is now rather a glittering idea than an accomplished fact. As the apparatus made available to the experimenter improves, we shall publish instructions on how to use it. It should be noted that the transmission of television signals on broadcast frequencies now seems to offer definite limitations in quality. The short waves — already nearly overcrowded with other services — offer the only possibility, both in still and motion picture transmissions, for improved quality (unless some new system is developed), and it is our belief that they should be employed at the start of our technical gropings in this field. ONE hears the argument that if only the experimenter is permitted to investigate television — and still picture transmission— the play of his ideas will hasten the day when seeing ■ by radio at a distance is general. It is certain that almost everyone, except those who are technically informed, feels that radio motion pictures, in sufficient detail and size to be comparable with good fidelity and volume in broadcast re ception, are shortly to be attained. Attained in some mysterious way, like the radio transmission of power, for example. Television apparatus thus far shown is little more than a laboratory toy, remarkable perhaps, but still a toy. And, while the tightly closed doors of large laboratories may even now contain experimental secrets which will in time smooth the way, so far as the published facts go, television is still a laboratory matter. THE Trade Show recently concluded at Chicago offered nothing startling. The complete sets presented showed some features of interesting design — a six-tube battery operated set consuming 8 mA. in plate current, for example. There was no great stir over automatic or semi-automatic tuning control as offered in some receivers. The parts and accessories presented were of better design and were lower in price. It is quite apparent that the set builder in the coming season can choose from highly satisfactory apparatus, can assemble it at a low cost, and the result will be not only a good-looking set of fine performance, but one which will compare favorably in cost with completely assembled sets. Every maker, it seems, has a dynamic type loud speaker, many of which are excellent. A REGRETTABLE error occurred on page 128 of the July number of Radio Broadcast, in the article, "What Hope for Real Television?" The captions for the two diagrams on this page were reversed. The diagram at the upper left is the Clarkson television camera, and that at the lower right the television projector. — Willis Kingsley Wing. 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Everitt, Vice-President Russell Doubleday, Secretary John J. Hessian, Treasurer Lillian A. Comstock, Asst't Secretary L. J. McNaughton, Asst't Treasurer Copyright, 1928, in the United States, l\ewfoundland. Great Britain, Canada, and other countries by Doubleday, Doran & Company, Inc. All rights reserved. TERMS: S4.00 a year; single copies 3? cents. l82