PURPOSE: To irradiate a radio wave in response to the service area of information by moving a radio wave absorbing body and controlling a radio irradiation effective area so as to vary the radio wave irradiating area.

CONSTITUTION: The radio wave absorbing body 8 made of ferrite or the like, a gear 9 to move the absorbing body 8 and a supporting part for the gear 9 and the absorbing body 8 are added to a reflector 5, an antenna pedestal 6 and a satellite main body 7. The supporting part 10 is fixed to the root of the reflector 5 and independent of the direction control of the antenna. Further, the control signal line of the gear 9 is installed along the supporting part 10. The absorbing body 8 is moved vertically, that is, in radial direction viewed from the center of the reflector 5 by the turning of the gear 9. The radio wave absorbing body 8 is moved by turning the gear 9 so as to obtain an effective antenna diameter corresponding to a desired beam half band width.