Long-term measurements of occupancy in the HF band 1.5-30 MHz

The HF band is heavily congested, particularly in Europe, but remains an important communications medium. A review of occupancy measurements performed over a period of years is presented, with the models which have been generated from the data. Use of the models is discussed. Since 1982, the UK MOD through DRA Malvern in conjunction with the University of Manchester Institute of Science and Technology, UMIST, has undertaken a continuous experiment to measure the interference in the HF part of the radio frequency spectrum. The objective of this long-term study was to look for aspects of statistically predictable structure in the man-made occupancy of the band, consisting of myriad signals arriving by both relatively-local groundwave propagation and from very long ranges by sky-wave paths; such information would then be made available to guide the design of modems and to aid frequency allocation and planning