Radio Broadcast (Nov 1926-Apr 1927)

460 RADIO BROADCAST MARCH, 1927 recently and, for an entire day, to question its inventor as to its functioning. Dr. E. F. W. Alexanderson, the wellknown General Electric research engineer, has concentrated on the problem of picture transmission during the last few months with a view to developing simple apparatus within reach of large numbers, rather than looking toward a revolution of method. Alexanderson's extraordinary record in the radio field is characterized by his ability to get down to simple basic principles. He was the first to apply the vacuum tube to tuned radio-frequency amplification; the first to use it for transmission of radio telephony; the first to develop a practical source of high-frequency energy for radio telegraphy and telephony; and the first to analyze the polarization of short waves. His recent announcement of his work with radio photography and television cameonlyaftera longperiod of experiment. While chief engineer of the Radio Corporation of America, his attention was focused on the problem by a speech of Owen D. Young, forecasting the transmission of the entire page of a newspaper by radio photography rather than the laborious word by word system. As a result of this remark, Alexanderson concentrated his attention on the subject, and it was he who afterward took steps to organize the development of the transoceanic photoradio service which has since become known through the work of Captain R. H. Ranger. During the last few months, Doctor Alexanderson has concerned himself with simplification and improvement of the apparatus, and the discovery of newer, simpler, and more rapid instruments of transmission and reception. Some of the photographs reproduced on these pages are samples of the success which has already attended his efforts. It has required twenty minutes heretofore to transmit a good 4 x 5-inch photograph, but those shown herewith were transmitted at the rate of sixteen square inches a minute. The reproducing apparatus used in making these photographs comprises a standard General Electric oscillograph with some adaptations for controli'ng a beam of light according to the intensity of the received radio signal. This light is flashed upon a revolving cylinder which is synchronized with the transmitting equipment. On the revolving cylinder is a sensitive photographic paper which makes a print according to the intensity of the light flashed upon it. The design of the receiving apparatus is relatively simple. A synchronous motor, which may be powered from the sixty-cycle power line, revolves a cylinder of a certain diameter which moves, at the same time, from side to side along a threaded shaft. The rotating and side to side motion thus permits a single beam of light, fixed in direction, to cover systematically the entire surface of the paper upon which the print is to be made. This light-sensitive paper is, of course affixed to the revolving drum. The intensity of the beam of light is controlled by a shutter actuated by a received radio signal. An expensive laboratory oscillograph is not essential; a cruder device, consisting essentially of a telephone receiver J) ojy ONE OF THE ADVANTAGES OF THE PHOTORADIO SYSTEM Is its accuracy in the transmission of signatures, as is shown in this example. Reading from top to bottom, the signatures shown in this photograph are of: Edgar H. Felix, the author of this article; Willis K. Wing, editor of Radio Broadcast; Carl Dreher, chief engineer of wjz; W. T. Meenam, W. J. Purcell, Barrington S. Havens, and Guy Bartlett, of the General Electric Company; Kolin Hager, chief announcer of wgy; and Harry Sadenwater, chief engineer of the General Electric Company's broadcasting stations, wgy, koa, and kgo and simple shutter will serve the experimenter. With apparatus reduced to these simple terms, the amateur experimenter has not long to wait for his embarkation in this new branch of the radio hobby. alexanderson's television experiments IE development of this simplified HTHI •I rri reproducing equipment is only preliminary to the problem which is engaging Dr. Alexanderson's attention. Instead of producing a photographic print in two minutes, Dr. Alexanderson is seeking to solve the problem of television. Television enables the observer to sec what is taking place at the point of transmission without entailing the making of photographic prints. Motion pictures are a form of recording and reproducing motion but, instead of the medium of a film for the purpose, television uses an electric system capable of transmission over long distances. Television has the same relation to radio photography as motion pictures have to still prints. Transmitting a good 4 x 5-inch still picture in a little more than a minute may seem like a long step toward the attainment of television. With true television, however, sixteen complete pictures must be transmitted a second in order to give the eye the impression of continuous motion. That means speeding up the process very considerably. Doubling the speed of almost any mechanical or electrical system is task enough for any engineer, but to step up a delicate and accurate process almost two thousand times is a problem of tremendous magnitude. Even the feat of tenfolding the earlier speed of transmission, which Doctor Alexanderson has already accomplished, is a remarkable tribute to what may be achieved by ingenious mechanical and electrical refinement. Clearly something radical is necessary to make the system work the two thousand times faster necessary for television. It is recognition of this fact which has led many experimenters in radio photography to await a new and radical invention before pronouncing television as a forthcoming certainty. Alexanderson works on the theory of using what science has already made available rather than waiting for revolutionary means and methods which may never come. He does not believe in speeding a machine far beyond its normal capacity, for that makes neither for safety nor reliability. Instead, it is characteristic of his research methods to find ways and means of dividing the work involved by new and ingenious methods so that it falls within the capabilities of existing systems. The Alexanderson system of transoceanic telegraphy, for example, was invented on that principle. In order to get the required signal strength, he divided up the antenna in a multiplicity of units with the result that the local losses in the ground were reduced to one-tenth. Thus the high-power telegraph stations of the Radio Corporation, using the Alexanderson 200-kw. alternator, are giving a signal strength that with older methods would have required 2000 kw.