The reception of substantially noise-free u.h.f. television signals over long-distance paths

The factors involved in receiving u.h.f. television transmissions with tolerable noise impairment at ranges exceeding 60 miles are discussed in the light of available and practicable aerial and pre-amplifier techniques, and of the path attenuation. It has proved feasible to use varactor parametric amplifiers fed from aerial arrays of 24 dB forward gain, and this has made it possible to obtain adequate reception at up to 90 miles at some selected sites where the path attenuation does not exceed 180 dB. Comparison of calculated and measured path attenuations indicates that, where the receiving site is free from local obstructions, the path attenuation calculated on diffraction theory does give a close approximation to the highest measured path attenuations. Field-strength recordings show the largest fading amplitudes during the hours before noon, with a significant decrease in fading amplitude towards the television programme hours of the afternoon and evening.