To attain a speech with excellent quality without the need for mechanically changing an antenna direction by controlling the directivity of antenna so that a direction of the antenna providing the gain is not directed to a ground surface with a high antenna noise temperature in the case that a portable satellite telephone terminal is used with a tilt during the speech.

The directivity of antenna forming a null point in a direction of +60 degrees or -60 degrees is realized by selecting a phase shifter 12a connected to a 1st antenna 11a or a phase shifter 12b connected to a 2nd antenna 11b so as to select the antenna directivity at which a signal to noise ratio measurement means 14 discriminates best a signal synthesized by a signal synthesis means 13.