Experimental Study of the Nonstationarity of an Oblique Ionospheric Sounding Signal on a Mid-Latitude HF Radiopath

We consider issues relating to the nonstationarity of an oblique ionospheric sounding signal. Experimental data obtained with the Doppler goniometric facility of the Kazan State University are used. The equipment, methods of measurement, and the algorithms used for analysis of the experimental data are described. Typical coherence ranges of an ionospheric signal measured in the daytime at different frequencies on the Moscow – Kazan path are presented. Diurnal variations in the coherence range and the diurnal mean distributions of the Doppler shift and its drift velocity are analyzed. The relative contribution of short- and long-period variations to the signal distortions is examined using wavelet transform.