Spectral occupancy on HF NVIS lines in central Europe

As well as being used for long range sky-wave communication, HF can also achieve short range communication by using near vertical incidence skywave (NVIS) propagation. For this mode, power is transmitted upwards and reflected by the ionosphere to give umbrella-like coverage. This mode is particularly important when the terrain does not permit ground wave communication. A measurement programme was initiated in 1995 to measure, analyse, and mathematically model HF spectral occupancy on NVIS communication links in England and in central Europe. The paper presents and discusses work undertaken during the period June 1995 to August 1996