Features of Forecasting the Operation of Ionospheric Radio Lines in Upper Rays Modes

The frequency dependence of transmitted information qualitative indicators is analyzed on the example of two meridional radio links: single-hop (~2600 km) and dominant two-hop (~5100 km) for basic modes of radio wave propagation in the ionosphere. It is shown that the presence of highly efficient receiving-transmitting antennas in a radio communication system leads to the need to take the existence of a priori energetically extremely weak modes into account in the problem of radio path specification statement. In this case, we consider those formed exclusively by the mechanism of radiation transfer along the upper-angles ray trajectories in the ionospheric propagation of radio waves. If the angles of departure and arrival for such modes and the directions of the main lobes of the antenna patterns at the end points of the radio path coincide, the signal-to-noise ratio for the wave field can reach the required threshold value and ensure the successful operation of the radio communication system. This may expand the upper frequency limit for the passage of radio waves in the transition regions of jump propagation of radio waves in the ionosphere; it should be taken into account in forecasting the operation of ionospheric radio links.