To solve the problem that, in an SD system in a stationary satellite job of a Ku or Ka band, since an entrance line becomes larger to 50 km to 100 km in a conventional SD system, it is necessary to reduce cost and improvement of diversity effects in the SD system is desired.

A pair of two earth stations disposed at spots separated for about 5 to 10 km in an east-west direction is used. If rainfall attenuation occurs in the sky above one earth station and exceeds a threshold of C/N required in a system, operation is shifted to an SD system mode and line workability is improved. If the rainfall attenuation further increases and cannot be relieved by the SD system, a Sat.D system is driven, signals for the Sat.D system are newly disposed in a satellite repeater, and signal levels of the four signals are detected, compared and determined by a level determination circuit. The earth station is then switched to an earth station with a signal of a highest signal strength and control to receive signals is performed, thereby relieving the considerable rainfall attenuation with synergistic effects of diversity gains of both the Sat.D and SD systems.