Influence of an atomspheric duct on microwave fading

The results of continuous observation of a duct carried out utilizing a tower 312 meters high are presented together with those of measurements of microwave fading conducted simultaneously. The variation of duct height with time, as well as the influence of the duct on fading for a horizontal and an oblique propagation path, are investigated in detail. A ray-theoretical analysis is given, indicating that fading may be attributed to the divergence or the convergence of radio waves and to the interference of two or more rays, caused by existence of a duct, or, more generally, of nonlinear -profile. A comparison of calculation with experimental results shows that many of the characteristics of microwave fading are well explained by means of this interpretation.