Measurements of the direction of arrival of HF sky wave signals and single site location using a seven element wide aperture (294 m) interferometer array

From measurements of the amplitude and phase of ionospherically propagated HF radio signals received at several spaced antennas, the direction of arrival (DOA) of the signal in both azimuth and elevation can be determined. Furthermore, by combining the DOA with reflection height measurements, the transmitter location can be estimated from a single receiving site. The direction of arrival has been measured for signals received from several European broadcast stations at distances of up to about 1400 km and the position fixes obtained are discussed. The performance of the system was severely affected by multimoded propagation and techniques for recognising periods of single moded propagation, when accurate measurements are to be expected, are described. Good position fixes were obtained when measurements were restricted to these periods provided that accurate height information was available. A period of data is also discussed for which the signal was found to be propagated predominantly by a 2-hop F-region reflection.