PURPOSE: To reduce erroneous compensation of an AFC circuit provided to the reception part of a ground station, by transmitting a pilot signal from a pseudo mobile station at a frequency shifted intentionally by as much as the frequency of a receiving local oscillator varies.

CONSTITUTION: The extent of variation in frequency for transmission from a satellite to a point B is obtained as the sum of the variation ΔfMr1 of a voltage- controlled oscillator VCO19 and the variation ΔfMrP of a signal generator 21. When each mobile station receives a signal with said variation extent, the variation extents of frequency converters 27 and 29 are added together at the input point C of an AFC circuit 32, so the extent of frequency variation at a point D is the sum of the variation extent at a point B and the variation extent ΔfMi2 of a VCO30. On the other hand, the extent of frequency variation at a point E of a pseudo mobile station is the same with the point B. Therefore, the difference between the extent of frequency variation of a pilot signal transmitted from the pseudo mobile station and that of a signal transmitted from a mobile station is equal to the variation ΔfMi2 of the VCO30, so errors in the frequency variation of an AFC circuit 12 are reduced.