Long-period fading in medium-wave radio signals

Abstract

Considerable work has been done on the interpretation of periodic fading observed in continuous-wave radio signals reflected from the ionosphere. Appleton and Beynon observed both slow and fast types of periodic fading in the records of short-wave radio signals which were interpreted by them as due to magneto-ionic origin. Tantry and Khastgir reported long-period fading in the medium-wave records and assumed it to be due to interference of lower trajectory ordinary and extraordinary waves. This interpretation has been confirmed by Satyanarayana and Dharambir Rai by using polarized receiving aerials. The object of the present investigation was to study the periodicity of this slow type of fading in medium-wave records, and compare the observed periodicity with the values obtained from a theoretical calculation of the path-lengths in the ionosphere.