R&D Report 1985-02 : An electronically-steerable active receiving array for h.f. A.P. Robinson The array described offers advantages over the directional aerials commonly used for monitoring at h.f.. It is compact and can be steered electronically in any direction. A steerable null may be placed in the radiation pattern. Active elements are used so that the effects of mutual coupling are negligible. The array comprises eight short, vertical monopoles in a line, the outputs of which are passed through variable delay lines, and summed. The systems is highly linear and has a large dynamic range. The delay lines comprise nine binary steps and are controlled by a microprocessor to give the desired patterns in response to the control settings. The array has proved a useful addition to the aerial systems at the BBC Monitoring Station.