Application of permutation frequency modulation signals manipulated with a constant weight code to increase the noise immunity of decameter radio communications

Introduction: The operation of radio lines in the decameter range, as a rule, occurs in a complex interference environment, characterized by the presence of fast and slow fading. Therefore, one of the most relevant areas of research in this subject area is the development of new technical solutions aimed at improving the noise immunity of reception. Purpose: Development of signals with permuted frequency modulation that allow detecting single errors at the physical level by selecting combinations of subcarriers of each character in accordance with the alphabet of the code with a constant weight. Results: Theoretical aspects of formationof the permutation signals with frequency modulation, the choice manipulating code to select subcarriers within a signal symbol, presents an analytical approach for the derivation of the generalized expression evaluation of noise immunity of the developed signals of permutation modulation in a channel with variable parameters in incoherent processing, we obtained the estimation of the values of probability of bit error for new signals in comparison with the known results. Practical relevance: The developed signal with permuted frequency modulation is proposed to be used in decameter radio communication systems operating in a narrow frequency band in the ionospheric channel. Discussion: Further research is associated with optimization of decision-making procedures for demodulating the developed signals, as well as the search for effective ways to encode signals with permuted frequency modulation at the physical level, allowing to increase the data transfer rate while maintaining the noise immunity of reception.