Variety radio directory (1937)

FEDERAL RADIO REGULATION— Continued Europe has experimented with channel widths of less than 10 kc. for broadcasting with disastrous results by way of interference. A width of 10 kc. is the least that is consistent with any degree of fidelity of reproduction of sounds : a 15 kc. width would constitute a great improvement, particularly for the faithful rendering of music. The third legislative task, with particular reference to broadcasting, is to classify channels as to number of stations permitted on each channel, restrictions on power used, and distance separations between stations on the same or adjacent channels. At this point, we must note that, by agreement with Canada, 6 of the 96 channels are allocated to exclusive use by Canada, leaving 90 which may be dealt with by the Commission. Some of the 90 are, by the same agreement, subject to shared use with Canada, but it would complicate this discussion unduly if we were to pause to consider these shared channels. The Commission's regulations divide the 90 channels in the broadcast band into four major classes, as follows : 1. CLEAR CHANNELS. The Commission's regulations designate 40 of the 90 channels as clear channels. A clear channel is a channel on which only one station in the United States (and, in principle, in the entire continent of North America) operates at nighttime, such station to operate with substantial power. Two or more stations may operate on these channels in the daytime, if sufficiently separated, since the interference range of radio waves by day is much less than at night. The minimum power of clear channel stations, under the Commission's regulations, is 5 kilowatts (abbreviated "kw.") and the maximum is 50 kw. Clear channel stations operating with high power are, in a general way, the only method of assuring broadcast reception to rural and remote areas, that is, regions which are not within the immediate vicinity of a broadcast station. The moment two or more stations are permitted to operate on the same channel after sunset, each station severely limits the service rendered by the other, by interference. 2. HIGH POWER REGIONAL CHANNELS. The Commission's regulations designate 4 of the 90 channels as high power regional channels. Two or more stations may be licensed to operate simultaneously on these channels, with a power of not less than 5 kw. As the word "regional" suggests, these stations are designed to serve limited regions, each of them restricting the service areas of others on the same channel by interference, particularly at night. 3. REGIONAL CHANNELS. Of the 90 channels, 40 are designated as regional, with nighttime power ranging from 1 kilowatt down to 250 watts and with daytime power up to a maximum of 5 kw. On these channels several stations (from 3 to 6 or 7) are permitted to operate simultaneously at night, each of them being severely restricted by the others but still capable of rendering service over an area equivalent to a fairly large city and its immediate environs. 4. LOCAL CHANNELS. The remaining 6 channels are designated as local, with nighttime power not in excess of 100 watts and daytime power not in excess of 250 watts. A large number of such stations (about 50) are assigned to each such channel and, needless to say, each of them serves a comparatively small area, roughly corresponding to a smaller city or town. All told, there are, at present writing, 704 broadcast stations authorized by the Commission, of which 100 are on clear channels, 9 on high power regional channels, 274 on regional channels, 317 on local channels, and 4 are called "special broadcast stations" in the band 1500-1600 kc. These totals are somewhat deceptive since in a number of instances two or more stations divide time 278