Factors Affecting Spacing of Radio Terminals in a UHF Link

Measurements made by Central Radio Propagation Laboratory and others have established the feasibility of producing uhf fields at long distances which are sufficiently strong and consistent to be usable for communication purposes. This paper assembles the results of several investigators of the field strength-distance relation and shows that these results are in reasonable agreement in a range of about 75 to 250 miles. Statistical variations from the median due to fading are discussed. Graphical means are developed to facilitate the determination of the signal-to-noise ratio at the receiver for various ranges of distance, antenna gain, frequency, transmitter power, bandwidth, and receiver noise figure. Diversity systems are explored briefly. Estimates are made of the effect of the medium upon the antenna gain and the maximum bandwidth.