Variation of HF spectral occupancy with azimuth in the UK

In 1995, UMIST with the support of DRA (Malvern) initiated the measurement of the azimuthal distribution of HF spectral occupancy in southern England, using a sloping vee antenna array installed at Cobbett Hill Radio Station, near Farnborough, UK. A description of this programme of work is given, together with examples of preliminary mathematical models for the azimuthal distribution of occupancy.