Long-Period Fading in Medium-Wave Radio Signals

CONSIDERABLE work has been done on the interpretation of periodic fading observed in continuous-wave radio signals reflected from the ionosphere. Appleton and Beynon 1 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 2 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 3 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.