Characterization of the dynamical response of receivers to fading

The general behaviour of radio receivers with feedback automatic gain control is examined for a range of fading conditions. Mathematical modelling of the a.g.c. system as a non-linear servo-loop goes part of the way to characterizing the dynamical response. It is shown that the characteristics of practical aircraft receivers for u.h.f. voice communications are too complex for representation by simple models and extensive measurements are needed to assess their behaviour under realistic operational conditions. A measurement strategy is formulated and has been applied to several types of radio receiver. It is recommended that dynamical performance clauses be included in receiver specifications.