The transmission of messages is a complex process, which is largely determined by the properties of the radio channel used. Decameter radio channels are the most difficult for organizing communication, since the ionospheric propagation of radio waves is associated with their significant attenuation, due to the significant length of the paths, as well as the presence of Rayleigh fading in the channel. However, the possibility of transmitting information over long distances without serious resource costs stimulates further research to improve the reliability of decameter radio communication. In this paper, we investigate the possibility of increasing the noise immunity of frequency-shift keying transmissions of decameter radio channels in conditions of unintentional interference due to the use of broadband signals. An analytical expression of the dependence of the probability of a bit error on the level of the ratio of the peak signal power to the peak interference power is considered; a graph of this dependence is presented. It is shown that the plot is consistent with the overall noise immunity estimate for Rayleigh fading channels using double FSK signals. The rationality of methods for obtaining the required reception quality in decameter radio channels is analyzed. It is shown that the most rational direction for increasing the noise immunity of FM-2 transmissions in decameter radio channels with Rayleigh fading in conditions of unintended interference is the use of broadband signals. In this case, for expansion, it is advisable to choose a value kf = 7, which makes it possible to increase the noise immunity by 9 dB. The conclusions are illustrated by graphs.
NCREASING IMMUNITY OF DECAMETER RADIO CHANNEL TRANSMISSIONS UNDER UNINTENDED INTERFERENCE
