Radio interference reduction and spectrum utilization of VHF FM Net equipment in a mobile environment

Spectrum conservation and interference reduction are not mutually complementary in a field area complex. Spectrum economy implies minimum utilization of RF channels, whereas interference-free operation requires an extensive number of channels. A certain minimum level of interference is tolerable in practice. Therefore, it follows that a system designer achieves realistic spectrum economies by designing the frequency assignment plan for a “calculated risk” level of interference. Frequency assigners have, in fact, been doing just this sort of thing on a “rule of thumb” basis. An evaluation is made of what the use of such a practical rule means in terms of the probability of interference. The analysis is based on a statistical propagation model called “Universal Terrain.” A procedure is established for conserving spectrum when unlike combinations of equipment are employed. Curves of propagation loss and interference statistics are presented.