OBSERVATIONS OF THE DIRECTIONAL CHARACTERISTICS OF IONOSPHERICALLY PROPAGATED HF RADIO CHANNEL SOUNDING SIGNALS OVER 2 HIGH-LATITUDE PATHS

The author presents measurements of the directional characteristics of the Doppler and time delay components of a pulsed channel sounding si gnal received over two high latitude paths. A variation in bearing wit h Doppler frequency was frequently evident, an effect attributed to Do ppler shifts imposed on the signal when scattered from ionospheric irr egularities drifting across the reflection points. For a transauroral path, for which the ionospheric reflection points were subauroral, sta ndard deviations of up to similar to 2.5 degrees were observed in the azimuthal power distribution of the received energy. Much greater dist urbances with azimuthal standard deviations of up to similar to 35 deg rees were recorded on signals received over a path contained entirely within the polar cap path.