Some Engineering and Economic Aspects of Radio Broadcast Coverage

The results of a quantitative study of the major factors affecting radio broadcast coverage are given for a frequency range from 200 to 2000 kilocycles and for transmission conditions covering the range normally experienced in the United States The effects of terrain, frequency, and antenna design in limiting the maximum nighttime service range of broadcast stations are discussed and it is shown that these limits are independent of the station power. The effect of terrain and frequency on the power required to deliver a 0.5-microvolt per meter signal at different distances is then shown in a series of curves, and the effect of atmospheric noise and interference considered. The economic aspects of this coverage are next considered and the power per square mile required is shown and the total costs and costs per square mile are given for the same parameters as before. The economic aspects of the proper balance between transmitter and antenna costs are considered and curves given for the frequency range considered. These studies show that it is economically unsound to attempt to cover large areas from a single station under unfavorable transmission conditions; i.e., high frequencies and high absorption. Also that for limited service areas the use of these high frequencies imposes no material hardships and that the lower frequencies should be reserved for stations of national and regional coverage while the lowest frequencies such as are now in use for broadcasting abroad are primarily suitable only for super-power stations of national coverage.