Evaluation of Signal Mode Characteristics Near the MOF for the Purposes of the Over-the-Horizon Radar

A comparative assessment of the characteristics of the upper and lower rays near the MOF is carried out. The method of oblique sounding of ionosphere by the chirp signals was used and paths of various lengths were used. It is shown that there are frequencies near the MOF which amplitudes of signals of the upper and lower rays are comparable. The difference between the times of group propagation is in the range of ~ 40–460 μs, which corresponds to the range of distances of ~ 15–140 km.