Models of HF spectral occupancy over a sunspot cycle

A long-term joint UK-Swedish-German project on the measurement and analysis of HF spectral occupancy has been undertaken. This has resulted in an extensive database of spectral occupancy measurements made at four sites in northern Europe, over a complete sunspot cycle. Mathematical models for spectral occupancy have been developed to enable the estimation of future occupancy values. The procedures for measuring and modelling HF spectral occupancy are presented, with final occupancy models for northern Europe, corresponding to stable day and stable night ionospheric conditions.