Radio Broadcast (May-Oct 1922)

192 Radio Broadcast discouraged; it is quite evident to any one that the use of one "channel" in the ether for conversation between two individuals is entirely out of the question unless such communication is impossible by any other means. Thus point-to-point communication by radio must be allowed only for shore-to-ship, to light-ship, or to isolated islands, etc. The granting of licenses to companies organized for commercial radio traffic between cities should not be permitted. It is to be pointed out that if such procedure had been followed during the last few years, it would not have been necessary to get out injunctions to prevent such interference as was caused by the operation of the Intercity Radio station in New York City. Such unnecessary use of radio always impedes its progress for the financial benefit of a few men more interested in their own fortunes than in that of the radio art. Wire telegraphy and telephony furnish ample means of communication for commercial traffic, in fact, it seems likely that if inquiry were made it would be found that much of the "radio" traffic of such companies is sent over lines leased from the wire companies. HOW MANY SIMULTANEOUS BROADCASTS ARE POSSIBLE? IT WILL be seen that for private and public broadcasting the committee recommends three bands of frequencies, rather widely separated. Public broadcasting, such as might be done by a University carrying on extension work or the free lectures sent out by city departments, have wave lengths from 1050 meters to 1500 meters; this range should permit the simultaneous transmission of about eight messages without undue interference. In estimating how many simultaneous messages are possible (or how many "channels" are available) it is assumed that the receiving set is a good one of the type using vacuum tube and regenerative connection. For private and toll broadcasting, the band from 285 meters to 485 meters is assigned; it will be remembered that at present all private broadcasting is done on a wavelength of 360 meters. The frequency range permitted for broadcasting of this kind in which we are especially interested is therefore from about 600,000 to about 1,000,000 cycles per second, a range of 400,000 cycles. How many separate channels are there available in this frequency range? It must depend very largely upon the quality of the receiving set used and upon the skill of the operator in adjusting it, but with the average receiving set sold to-day it seems that there may be ten or fifteen channels; if all the receivers in use were of the better types and in the hands of skilled operators, probably twenty or thirty channels would be available, but of course, such is not the case. Probably there will be not more than eight useful channels in this range of frequencies. The question must be indeterminate to a considerable degree because of the possibility of large differences in the various signal strengths. If, for example, two stations of equal power were transmitting from New York and were being received fifty miles away, both would be of equal strength, and it would be possible to adjust the receiving sets for no interference with two wavelengths as close together perhaps as 300 and 310 meters. But if one of the transmitting stations was within a few miles of the receiving set, and the other fifty miles away, then, in order to hear the distant station without interference from the nearby station a wavelength difference of 30 meters or more would be necessary. Private and toll broadcasting are also allowed another frequency band from 100 meters to 1 50 meters; although this is a comparatively narrow band, there are several channels possible because of the large difference in frequency of the two limits, namely 1,000,000 cycles. It is quite likely that there are twenty more channels available here for good receiving sets and five to ten with ordinary sets. It must be pointed out, however, that practically none of the receiving sets which have been supplied to the public so far will be much good for receiving these low wavelength signals; most of them cannot tune for a signal of such low wavelength and those that can are very inefficient for such high frequencies. WHAT KIND OF BROADCASTING IS COMING? IN THE range of wavelengths, 285 to 485 meters there will be about eight channels available. For what are these eight channels going to be used? We do not need to consider the possibility of broadcasting lectures or other educational talks because for such work a special frequency band has been allowed, offering, for the present at least, plenty of channels for such traffic. It appears then, that for entertainment and toll purposes there are eight channels available. This seems a lot;