Abstract: In a radar antenna system comprising antenna elements arranged in an active array, the elements are located in predetermined groups such that an individual group can be selected electronically from within the whole array aperture, the said selection being effected by variable attenuator means. This produces a phase difference between direct and multipath reflections so that the radar information from a direct reflection can be distinguished from multipath information.

Abstract: A torsional vibration damper, for example a twin mass flywheel (10), has an input element (11) and an output element (12) which are relatively rotatable against the action of a damping means which includes a plurality of linkages (40). Each linkage includes a plurality of interconnected links (41, 42), at least one of which is flexible in an axial sense relative to the remainder of the damper to accommodate forces applied to the flexible link as a result of relative tilting of the damper elements (11, 12) during use of the damper. Various designs of generally radially extending flexible bob weight links (41) and additional connecting links (42) are disclosed.