Back-scatter sounding: an aid to radio propagation studies

An historical account is given of investigations of back-scatter, and the evidence indicating the ground as the source is discussed. By means of the radar equation the echo intensity is calculated, and the effects of layer curvature and thickness are indicated. The marked seasonal variations in the echo patterns observed at Slough are discussed. Back-scattering after two or more ionospheric reflections is also considered, while very long distance scattering, sometimes with no intermediate ground reflection, is reported. Tests are described which show that, although good accuracy in skip distance measurement is possible, errors may be high if aerials with a large beamwidth are used. The utility of the rotating-aerial back-scatter sounder with plan position indicator for study of propagation over a wide area is stressed and some samples of records obtained with such an instrument are given.