To realize the function property of a frequency division duplex system by receiving a frequency in a first frequency band at a regular mode, receiving the frequency in a second frequency band at an acquisition operation mode, transmitting the frequency in a third frequency band at a regular operation mode and transmitting the frequency in the second frequency band at the acquisition operation mode.

A duplex mode transmitter/receiver 200 contains a walkie/ talkie(WT) module 280, generates a W-T mode transmission signal in an intermediate frequency band and takes out an audio signal from an RF signal received during a W-T mode. The duplex mode receiver/transmitter 200 uses a duplexer 220, an antenna 23, a reference originator 210, an input audio amplifier 204, a transmission amplifier 216, an RF amplifier 232 and an output audio amplifier 242 at a regular mode and the W-T operation mode. The function of a radio machine for transmission/reception can effectively be realized by reducing the necessary number of components.