Mutual Interference Between Surface And Satellite Communication Systems November 1961 By William J Hartman And Martin T Decker Nbs Technical Note 126

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Estimates of the mutual interference expected to occur between the ground terminals of space communications systems and surface point-to-point systems are presented in a fashion suitable for engineering applications. These estimates are obtained from recently developed methods for predicting the transmission loss over tropospheric paths in terms of parameters such as a geographic separation, elevation angle of the antenna, antenna patterns, and frequency. It is concluded that these systems can share the same frequency assignment under suitable conditions.

Estimates of the mutual interference expected to occur between the ground terminals of space communications systems and surface point-to-point systems are presented in a fashion suitable for engineering applications. These estimates are obtained from recently developed methods for predicting the transmission loss over tropospheric paths in terms of parameters such as a geographic separation, elevation angle of the antenna, antenna patterns, and frequency. It is concluded that these systems can share the same frequency assignment under suitable conditions.

High gain antennas, sensitive receivers and high power transmitters which are used at the earth stations of space communications systems complicate the problem of sharing frequencies with other surface services. However, because of the dependence of beyond-the-horizon tropospheric propagation on the scattering angle, it is possible to offset the gain of the terminal antenna by elevating the beam. Early studies of frequency-sharing assumed that the beam of the earth station was elevated 'sufficiently' to increase the transmission loss to that which would be obtained if the actual antenna were replaced by an isotropic antenna. This paper studies the question of what constitutes a 'sufficient' elevation angle, as described above, for the particular conditions of a smooth earth, 30-foot antenna heights and several combinations of antenna sizes. Some results are also given when there is an elevated horizon at the earth terminal end of the path.

Predictions are made of the coverage to be expected from a network of airborne television transmitters operating in the UHF television band. Various system performance and interference conditions are assumed. The results are presented in a series of graphs with probability of service as a function of receiving location and in terms of the total effective area of a station or network of stations. System requirements for a coverage approaching 100% of a large area are indicated.

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