A Study of Phase Fading of Ionospheric Reflections

Abstract

Pulsed 2·28 Mc/s radio waves were transmitted imd measurements were made on the first-hop, vertically-incident reflections from the ionosphere. A method of continuously recording the changes of phase difference between the signals at two aerials is described. The general features of the records are described and it is shown that the quasi-periodic type of fading can be explained in terms of two component rays being reflected from two reflecting areas of the ionosphere and interfering at the receiving aerials. The horizontal separation of the two regions is about 50 km in the case analysed. The direction of arrival of the radio waves, the velocity of the amplitude pattern over the ground, and the statistical distribution of the phase difference are also discussed for this type of fading.