Abstract: A communications system including a first channel adapted to receive data on a first carrier and a second channel adapted to receive data on a second carrier having a frequency substantially equal to the frequency of the first carrier and polarized approximately orthogonal thereto and wherein degradation in the orthogonality occurs during transmission so that portions of the first carrier appear in the second channel and portions of the second carrier appear in the first channel, a summing device in each channel and apparatus for coupling a portion of the output signal from the summing device in one channel to the input of the summing device in the other channel, in the correct phase relationship and amplitude, so as to cancel the portion of the second carrier appearing in the first channel and the portion of the first carrier appearing in the second channel.