The effects of dry snow on reflector antennas

Fading due to snow accretion on the reflector antenna is a major problem in satellite communication in Finland and other northern countries. Dry snow may stay on antennas for many days or even weeks, if the temperature is below 0°C, making fading events longer. Dielectric losses of dry snow are very small and can be normally discounted, but asymmetrically gathered dry snow tilts and distorts the antenna beam due to the different phase delays of the different wave paths. Theoretically, the worst case would be a dry snow layer on the lower half of the reflector causing a phase delay of 180°, when the signal entirely disappears from line of sight. The author expands research in this neglected area. The measured radiation patterns of a 1.8 m reflector antenna are presented for three cases of a parabolic reflector partially covered by dry snow. The measurements were made at 20 GHz in one case and simultaneously at 20 and 30 GHz in two cases