Apparatus comprising: an antenna feed for directing RF signals to and/or from an antenna (30, 110, 315, 320, 350); and coupling means configured to couple a signal from a radiating portion of the antenna (30, 110, 315, 320, 350) and configured to dynamically monitor and/or calibrate the antenna (30, 110, 315, 320, 350), the antenna (30, 110, 315, 320, 350) comprising one or more antenna elements and a ground plane, the coupling means comprising: the ground plane of the antenna; an aperture (120, 325) which passes through the ground plane of the antenna (30, 110, 350); and a conductor (200, 260, 330) for coupling a signal carried by the one or more antenna elements, part of the conductor (200, 260, 330) extending over at least part of the aperture (120, 325), wherein the coupling means is further configured to couple signals from respective radiating portions of a plurality of such antennas (30, 110, 315, 320, 350), the coupling means further comprising a plurality of such apertures (120, 325) spaced apart from the one or more antenna elements of the plurality of antennas, and wherein the conductor (200, 260, 330) is arranged such that respective parts of the conductor (200, 260, 330) extend over at least part of each aperture (120, 325), and wherein the plurality of antennas (30, 110, 315, 320, 350) are arranged as an array comprising one or more rows of antennas (30, 110, 315, 320, 350), and wherein the conductor (200, 260, 330) extends from a first terminal of a connecting port to each of the apertures (120, 325), and wherein the connecting port is configured for connection to measurement and/or calibration equipment and/or to lead off to a transceiver, transmitter and/or receiver circuitry. an antenna feed for directing RF signals to and/or from an antenna (30, 110, 315, 320, 350); and coupling means configured to couple a signal from a radiating portion of the antenna (30, 110, 315, 320, 350) and configured to dynamically monitor and/or calibrate the antenna (30, 110, 315, 320, 350), the antenna (30, 110, 315, 320, 350) comprising one or more antenna elements and a ground plane, the coupling means comprising: the ground plane of the antenna; an aperture (120, 325) which passes through the ground plane of the antenna (30, 110, 350); and a conductor (200, 260, 330) for coupling a signal carried by the one or more antenna elements, part of the conductor (200, 260, 330) extending over at least part of the aperture (120, 325), the ground plane of the antenna; an aperture (120, 325) which passes through the ground plane of the antenna (30, 110, 350); and a conductor (200, 260, 330) for coupling a signal carried by the one or more antenna elements, part of the conductor (200, 260, 330) extending over at least part of the aperture (120, 325), wherein the coupling means is further configured to couple signals from respective radiating portions of a plurality of such antennas (30, 110, 315, 320, 350), the coupling means further comprising a plurality of such apertures (120, 325) spaced apart from the one or more antenna elements of the plurality of antennas, and wherein the conductor (200, 260, 330) is arranged such that respective parts of the conductor (200, 260, 330) extend over at least part of each aperture (120, 325), and wherein the plurality of antennas (30, 110, 315, 320, 350) are arranged as an array comprising one or more rows of antennas (30, 110, 315, 320, 350), and wherein the conductor (200, 260, 330) extends from a first terminal of a connecting port to each of the apertures (120, 325), and wherein the connecting port is configured for connection to measurement and/or calibration equipment and/or to lead off to a transceiver, transmitter and/or receiver circuitry.