Abstract. The use of short-wave radio communication range for the transmission of messages is of vital importance for the life of the state. In recent years, the opinion has been repeatedly expressed that highly efficient communication means will oust HF radio communication from the general communication system. However, not a single country in the world is raising the issue of eliminating HF radio communications. The shortwave communication system has retained its importance not only as an auxiliary tool for mobile communications services, but also as an essential auxiliary tool for the fixed network.
Key words: ionosphere, short waves, day and night.