Abstract: Method and apparatus for a duplex communication system wherein a local station transmits a modulated signal at a nominal, fixed frequency f.sub.1 to a remote station which transmits, simultaneously, to the local station, a modulated signal at a nominal, fixed frequency f.sub.2, which frequency f.sub.2 is displaced from frequency f.sub.1, by a frequency .vertline.f.sub.2 =f.sub.1 .vertline. being the intermediate frequency of the receivers at both the first and second stations. Novel transmitter signal suppression is provided in the circuits of the local and remote stations so that a common transmit-receive antenna may be utilized at each station without swamping either receiver's front-end circuits on transmission and optimum conversion gain may be realized on reception.