Fading of shortwave radio signals in the tropical zone

The amplitude fluctuation of a received signal is commonly known as fading. It varies from place to place and has some distinctive characteristics in the tropical zone. Due to its inherent properties, i.e. time variation of received amplitude, fading plays an important part in the planning of a shortwave broadcasting service. The paper first discusses the various types of fading and their possible causes of occurrence. Then the different amplitude probability distributions of a randomly fading signal are described. This is followed by a discussion of special types of fading encountered in the tropical region. Finally, fading allowances to be provided for planning broadcasting services in the tropical region are considered.