A rotatable antenna apparatus comprising: a fixed unit for attachment of the apparatus to an external structure; a rotatable unit mounted on the fixed unit and comprising an antenna assembly and processing circuitry coupled to the antenna assembly for performing signal processing operations; an interface unit coupled to both the fixed unit and the rotatable unit, and through which a cable is routed to provide a wired connection from the fixed unit to the processing circuitry, the interface unit providing a cable housing within which a length of the cable is enclosed in a coiled arrangement; and a control mechanism coupled to said interface unit and arranged to constrain the amount to which the length of the cable is wound and unwound within said cable housing so as to inhibit application of a stretching stress on said cable during rotation of said rotatable unit; wherein: the cable housing comprises a fixed portion and a rotatable portion, the length of the cable being connected to both the fixed portion and the rotatable portion; the control mechanism is arranged to cause the rotatable portion to rotate during rotation of the rotatable unit; the rotatable unit comprises a support for the antenna assembly and the processing circuitry, the rotatable portion being arranged to cooperate with the support so as to rotate as the support is rotated; characterized in that the control mechanism comprises a calibration mechanism to detect a zero reference point at which the length of the cable adopts a first coiled configuration; the support then being rotatable in a predetermined direction up to a specified maximum angle of rotation during which time rotation of the rotatable portion causes the length of the cable to transition from the first coiled configuration to a second coiled configuration, both the first and second coiled configurations being configurations in which the length of the cable is not subjected to said stretching stress. a fixed unit for attachment of the apparatus to an external structure; a rotatable unit mounted on the fixed unit and comprising an antenna assembly and processing circuitry coupled to the antenna assembly for performing signal processing operations; an interface unit coupled to both the fixed unit and the rotatable unit, and through which a cable is routed to provide a wired connection from the fixed unit to the processing circuitry, the interface unit providing a cable housing within which a length of the cable is enclosed in a coiled arrangement; and a control mechanism coupled to said interface unit and arranged to constrain the amount to which the length of the cable is wound and unwound within said cable housing so as to inhibit application of a stretching stress on said cable during rotation of said rotatable unit; the cable housing comprises a fixed portion and a rotatable portion, the length of the cable being connected to both the fixed portion and the rotatable portion; the control mechanism is arranged to cause the rotatable portion to rotate during rotation of the rotatable unit; the rotatable unit comprises a support for the antenna assembly and the processing circuitry, the rotatable portion being arranged to cooperate with the support so as to rotate as the support is rotated; characterized in that the control mechanism comprises a calibration mechanism to detect a zero reference point at which the length of the cable adopts a first coiled configuration; the support then being rotatable in a predetermined direction up to a specified maximum angle of rotation during which time rotation of the rotatable portion causes the length of the cable to transition from the first coiled configuration to a second coiled configuration, both the first and second coiled configurations being configurations in which the length of the cable is not subjected to said stretching stress.