Forward scatter from rain

The forward scatter of radio waves from rain has been observed over a 90-mile, 2720-mc path. The observations support the assumption of omnidirectional scattering from rain. On this link rain scatter may exceed the normal tropospheric scatter signal by 15 db. This latter signal may itself be increased by the presence of thunderstorms in the vicinity. Signal level distribution during rain and no-rain conditions are presented. Among the effects of rain on a tropospheric scatter link are the increased fading rate and decreased bandwidth. The fading rate may increase by a factor of ten or more, and pulse-to-pulse fluctuations have been observed at a pulse repetition frequency of 600 pulses per second. Evidence for a decreased bandwidth is presented in the form of pulse photographs. The
1.5-\mu
sec pulse is commonly broadened to 3 or
4 \mu
sec and on occasions to lengths in excess of
20 \mu
sec.