a radio communications transceiver which operates to transmit radio signals via a transmit antenna and receive radio signals via a receive antenna , wherein said transmit and receive antennas are disposed to provide at least a substantial amount of radio signal isolation therebetween . the radio communications transceiver further includes a cancellation device comprising a first coupler coupled to the transmit antenna and arranged to extract a sample of the transmit signal , a second coupler coupled to the receiver antenna and arranged to extract a sample of the received signal , a correlator fed on first and second inputs with the transmit and the received signal samples respectively , the correlator operating to generate an error signal representative of a correlation of the transmit and received radio signals , which error signal is fed to a modulator which operates to modulate the transmit signal sample , consequent upon the error signal . the modulated transmit signal is fed to the radio receiver via a further coupler , and serves to substantially cancel transmit signals received by the receiver antenna , the cancellation device operating in combination with the disposal of the transmit and receive antennas to effect a desired radio signal separation between the transmit and receive signals .