The propagation of metre radio waves beyond the normal horizon. Part 2: Experimental investigations at frequencies of 90 and 45 Mc/s

Measurements of radio field strength at frequencies of 90 and 45 Mc/s over distances such that direct transmission from the sender to the receiver was impossible are described. Two paths, of lengths 110 and 270 km, have been investigated at 90 Mc/s, and one, of length 160 km, at 45 Mc/s. The statistical distribution of quasi-peak field strengths as a function of time over these paths has been determined, and it is shown that signals considerably in excess of values corresponding to standard atmospheric refraction often occur. An attempt is made to interpret the observed field strengths in terms of the meteorological data obtained from the routine radio-sonde ascents made by the Meteorological Office, and some degree of correlation has been obtained. An indication is given of the bearing of the measurements on the planning of v.h.f. broadcasting and communication services.