Radio Channel Characterization by Three Tones

Three radio pilot tones, available on in-service AR6A single sideband radios, have been used to characterize the dispersive nature of radio fading. The paper presents new results on how three tones can be used to determine the delay and amplitude of the second ray and the notch frequency in a two-ray fading model. The model chosen is justified on physical and practical grounds. Measurements on radio hops yield histograms of second ray delay and amplitude. It is found that most of the fading events can be described by the two-ray model. The measurements are compared to distributions, assumed or measured, given in the literature. The experimental technique used lends itself easily to the measurement of other propagation characteristics like the cumulative statistics of single and average tone power and the in-band power difference.