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Computer image processing methods have been widely used in various fi elds. Currently, one of the topical scientifi c objectives is an image processing aimed at extracting data on the object under study. In particular, it is crucial to extract data on the parameters of multi-dimensional HF ionospheric radio communication channels from the ionogram images obtained by ionospheric sounding [01-03]. However, these images are contaminated with noise and radio frequency interferences (RFI) stem from other users. Furthermore, the useful signal and interference signal are stochastic processes. Thus, it is crucial to fi lter ionogram image. In this case, the fi ltered image represents the useful signal. We have assumed that it will allow to apply the algorithms of automatically determining the parameters of HF communication channels. We shall note that theoretical studies were enhanced with the results obtained in studies of ionogram fi ltering by various authors [04-06]. In this study we applied computer fi ltering methods including whitening, median equalization as well as threshold method. The originality of the research is to develop an algorithm that can be automatically applied to an ionogram. The algorithm is aimed at determining signal-to-noise ratio in radio channels of HF range and adequate for choosing an optimum channel.

Computer filtering of images of ionograms of HF ionospheric radio communication paths and an algorithm for determining signal-to-noise ratio