The results of the dispersion analysis of the spaced receiver records of fading for an equatorial station in the Indian zone are discussed. It is shown that the apparent drift speed increases almost linearly with the frequency of fading in all the cases studied for both the E and F regions. The dispersion of drift speed is larger for the F region than for the E region in general. Furthermore, the F region shows a larger dispersion during the daytime whereas it is of the same order in the day and nighttimes for the E region. The drift speed corresponding to the highest Fourier frequency present in a particular record is found to be close to the apparent drift speed Va as determined from the shift of the peak of cross correllograms while the total frequency spread of the speed is linearly related to the random drift speed Vc derived by the full correlation analysis.

Several possible causes of dispersion in the ionosphere such as gravity waves, independently moving reflecting screens, height gradient of the horizontal drift and size of irregularities, the dispersive nature of the vertical drift velocity, and the variability of the drift during the course of record are discussed. Interference of the signals reflected from two or more highly aspect-sensitive areas in the ionosphere is suggested as a possible mechanism resulting in the positive and linear dispersion observed on the ground at an equatorial station.