International projectionist (Jan-Dec 1939)

Mr. Projectionist: Knowing that the TRANSVERTER maintains its efficiency uniformly year after year . . . why even consider other equipment that requires nearly total replacement within five years? Sold through The National Theatre Supply Co.; In Canada, General Supply Co.; or write y'ujhjf\9nlwsity Theatre us THE HERTNER 12692 Elm wood Avenue ELECTRIC CO. Cleveland, Ohio, U. S. A. Exclusive Manufacturers of the Transverter TELEVISION'S ROAD AHEAD (Continued from page 17) of many reflectors in the form of tall buildings, the problem is serious indeed. The usual solution is to use a directional antenna which will discriminate against the undesired signal. Horizontal polarization of the radiated signal has been found to improve the signalto-noise ratio at television carrier frequencies, and its use will therefore probably become a standard practice. • Network Problems Some of the problems connected with the chain distribution of television programs may now be considered. There are two general methods which have been used to transmit television programs from a key transmitter to a distant transmitter. These are the use of (1) The radio relay or (2) The coaxial (or other) high-fidelity cable relay. Whichever method is used, the relay stations must be sufficiently close together so that non-fading, noise-free signals are received at each repeater location. It has been found that relay stations must be located from 30 to 70 miles apart, the exact distance depending on noise conditions and (in the case of the radio relay) on the topography of the landscape. It has been customary to operate radio relays at wavelengths of two meters or less. Each relay station, of whichever type, must reproduce the incoming signal with the highest fidelity, having neither amplitude, frequency, nor phase distortion. In other words, the picture must not 24 be degraded in passing through the relays. • Major Problem is Cost It is not surprising that the great problem in the relaying of television signals is cost. The cost-per-mile of a coaxial cable required to handle the exceedingly wide frequency bands of television programs is, at the present time, many times as great as the cost of corresponding networks used in sound broadcasting, both as regards initial cost and maintenance. If radio relaying is used, the cost of the relay transmitters required is obviously very great. However, the coming years are likely to bring great reductions in the costs of both methods of relaying, particularly the coaxial cable. This paper has been an effort to point out the fact that many problems still must be solved before fully satisfying television pictures will be available in the home. However, it is not to be construed that the commercial introduction of television will await a solution to these problems. Undoubtedly television will be commercialized in the near future and the problems will be solved as time passes — much the same, for instance, as was the case in the motion picture industry. One fact is very clear, that the further development of television must come largely through findings in the field, that is, by actual trial. Discussion: Mr. McNabb: Referring to the reproductions of a British picture and an American picture, the line structure was quite evident in the British picture, but the contrast seemed a little better. Is the contrast better in the British picture due to the method of transmission, or is the transmission of direct current along with the signal better than the American method of adding the d.c. at the receiving end? Mr. Kaar: There is no essential difference in the method of transmission in England and here. The only difference is the means of synchronization. As far as contrast and detail are concerned, there should be no difference between the two systems except for the possible fact that we have 441 lines whereas they have 405. It is possible to photograph any kind of picture from the front of a picture tube and we can so adjust focus and contrast as to make the line structure visible on an American picture. As a matter of fact, neither of these pictures is a good example because they have both been degraded by photographic processes in the original photograph, the enlargement, the negative, and the lenses, so in order to compare the two fairly the originals should actually be seen. Our pictures are somewhat better than the British pictures. Mr. Finn: In the choice of repeaters, Mr. Kaar suggested that the choice as between coaxial cables and straight etherization of a program is very close. Is it your suggestion that the coaxial cable be used, over hill and dale for thirty or sixty miles, $i£?mie SMS PROJECTIONIST "JdOHiveit&i evet weau out, "you, can -vefweif <8uy i^tmn Ae&mceu ^ f&. STANDARD EQUIPMENT for .BETTER PROJECTION NATIONAL THEATRE SUPPLY COMPANY INTERNATIONAL PROJECTIONIST