Extended UK models for high frequency spectral occupancy

Since 1982, a programme of research has undertaken the measurement, analysis, and mathematical modelling of occupancy across the entire high frequency (HF) spectrum at the times of the solstices, and this work has been published. Since the establishment of an automated, remotely controlled UK measurement system in 1989, occupancy measurements have been made at nominally fortnightly intervals. The authors present mathematical models based on these frequent measurements made during the period 1990 to 1997, when the 12-month moving average sunspot number varied from about 160 to 10. The models incorporate the parameters field strength threshold, frequency, measurement bandwidth, sunspot number and week of year