Phase or amplitude compensation for beam-former Apparatus for an antenna with a plurality of antenna elements, the antenna providing a radiation pattern including one or more beams and the apparatus comprising: a digital beam-former for digitally weighting component signals corresponding to the one or more beams with respective beam-forming weights to provide each component signals of a beam with a phase relationship and amplitude relationship to other component signals of the same beam; and a processing arrangement for processing signal for the beam-former or for processing signals received from the beam-former; the apparatus further comprising compensation means for compensating for at least one out of phase and amplitude distortions between component signals associated with the same frequency channel and related to the same beam arising in the processing arrangement.