Design of FM radio relay systems for multi-channel telephone service

The discussion which follows leads to a set of simultaneous equations relating system parameters to channel capacity and performance minima, and to their solution. Largely due to the characteristic distribution of fading probabilities, the optimum system is not very sharply defined. It is also observed that nature, in a lapse of perversity, arranged for microwave fading probabilities which do not very closely match the performance expectations of the telephone user! Hence, a truly optimum FM system for long haul service is not quite within the reach of the designer. In order to avoid somewhat prolonged algebraic detours in the text of the argument, equations relating the detection threshold and channel signal-to-noise ratios (SNRs) to system parameters are derived in an appendix.