An improved fading machine

A fading machine which formerly gave cyclic fading has been modified to give substantially random fading with the amplitude of the signal conforming to the Rayleigh distribution, as with long-distance h.f. radio signals. The fading is obtained by combining six components in random phase. The machine simulates propagation by up to three paths with a spread of up to 2 millisec in path-time delay and caters for dual diversity reception. It has proved to be a valuable tool in laboratory investigations of radiotelegraph equipment.