An investigation of HF direction-finding accuracy on the Churchill-Ottawa auroral zone path

The CRC HF Direction-Finding Array, consisting of a 1181 meter by 236 meter cross, was used to make angle-of-arrival measurements on HF waves propagated over a 1900 km path from Churchill, Manitoba to Ottawa, in May, 1976. This path is of interest because much of it is in the auroral zone where conditions are generally more disturbed than at lower latitudes. Swept-frequency transmissions allowed the investigation of the variations in angle of arrival of individual propagation modes, while fixed-frequency transmissions permitted a test of two azimuth-estimation schemes. One of these used a phase-front planarity test and averaging of azimuths over relatively frequent samples, while the other was based on the separation of modes by Doppler processing. The former technique was found to provide slightly better accuracy than the latter on this path and both compared well in accuracy with estimates from separated modes using swept-frequency data.