Variation of field intensity over irregular terrain within line of sight for the UHF band

Abstract

Late in 1950 the US Federal Communications Commission (FCC) was faced with the problem of having to allocate television (TV) broadcast stations in the ultra high frequency (UHF) band from 300 to 900 mc/s. In order to make an intelligent allocation, some knowledge was necessary of the extent of television service to be expected for these UHF channels. Consequently, a series of statistical studies was made of the available data to derive some empirical propagation formulae and curves upon which the UHF allocation might be based. One of these studies was that of the variation in field intensity over irregular terrain which will be discussed in this paper. Of necessity a great many of the details of the study cannot be included here. Thse who desire these details are referred to the original FCC report. The variation of field intensity over irregular terrain within line of sight for the UHF-band has been studied. The factors which affect these variations and the relative reliability of these factors have been investigated, leading to resultant distributions of field intensity over irregular terrain, as described by figure 9. In addition, this distribution has been compared with that for the VHF band and it has been possible to extrapolate the results to cover the whole UHF television band from 300 to 900 mc/s. by using the distribution of Fig. 9 and correcting for frequency the overall median deviations from a reference [Fig. 11].