Directional Measurement of HF Spectrum Occupancy

Results concerning spectrum occupancy in HF range as function of the direction of signals arrival are reported. In addition to time and frequency, the influence of the spatial dependence on spectrum occupancy is analyzed. Spectrum occupancy is computed using an energy detection criterion. Parallel measurements of HF signals have been made using software defined radio equipment, a reference omnidirectional broadband antenna and two type of HF directional antennas. Measurements results prove that directional antenna can bring additional gain in terms of spectrum occupancy data and can offer more free frequency bands for an opportunistic transmission in an emergency communications system.