The mapping of HF spectral occupancy over northern Europe

Since 1982, a long term programme has been undertaken to measure and analyse spectral occupancy across the whole HF band 1.6-30 MHz. The aim of the work is to provide experimental data and mathematical models, showing how occupancy varies with frequency, time, bandwidth, threshold level, type of user allocation, antenna, and geographical location. Measurements of spectral occupancy were initially made twice yearly, approximately at the times of the winter and summer solstices. Such systematic measurements have been made since 1982. From 1982 to 1989, the measurement site was RSRE Pershore, Worcestershire, a rural site in central England. In 1989, a dedicated and continuously operating measurement system was installed at the Radiocommunications Agency monitoring site, at Baldock, Hertfordshire. In 1990, an identical measurement system was set up at Linkoping, and an agreement made for the simultaneous operation of the two sites, and data exchange. In 1993 a third system was installed at the antenna site of Rohde and Schwarz near Munich. These three sites are approximately at the corners of an equilateral triangle of side length equal to 1000 km, and they provide effective measurement of spectral occupancy over northern Europe. Experimental results from the three measurement sites have been combined into a single model which is able to estimate occupancy for a defined latitude and longitude. The region covered is that enclosed by the triangle defining the positions of the sites, and also includes reasonable extrapolations outside this area, say for a few hundred kilometers.