SIMULTANEOUS CONSIDERATION OF FAST AND SLOW FADING ON SW COMMUNICATION LINKS.

It is well known that reception of short waves is always accompanied by fast and slow fading. Slow fading is caused by changes of the state of the ionosphere due to various factors and its quasi-period is usually longer than 10 minutes. The distribution of slow fading is almost log-normal. Fast fading, caused by multipath field structure at the receiving site, is superimposed on the slow fading. As a rule, the distribution of fast fading is Rayleigh and only in some cases is it described by more complicated functions. A method of simultaneously considering fast and slow fading is proposed for fading distributions most frequently encountered in practical situations. This paper proposes a justified method for calculating the power safety margin required to overcome fading. Until now this margin has been calculated separately for fast and slow fadings, which resulted in an excessive increase in the transmitter power.