Experimental Study of Single-Mode Propagation Ranges of Short Waves on Mid-Latitude Radio Paths of Various Lengths

Paper presents the findings of experimental research into the single-mode propagation of HF radio waves over long-haul paths by analyzing frequency range where single-mode propagation exists. The influence of various geophysical factors on single-mode propagation range was thoroughly studied. The analysis of the possibilities of the operation of narrowband (3 kHz) and wideband (1 MHz) communication systems in that frequency range is presented.