Possibility Evaluation of the DRM NVIS Broadcasting Time Extension through Extraordinary Wave

The use of Near Vertical Incidence Skywave (NVIS) in the lower part of the HF range makes it possible to organize radio communication and broadcasting at distances from 50 to 500 km in the absence of radio shadow zones in mountainous conditions. However, with minimal solar activity at night, the F2 layer critical frequency falls below the 4 MHz band allocated for broadcasting. Under these conditions, an extraordinary wave can be used, which is capable of being reflected at higher frequencies. The use of an extraordinary wave makes it possible to expand the time interval available for broadcasting under these conditions by an additional 4 - 5 hours. Conducted theoretical studies have shown that when used for broadcasting in years with minimum solar activity, as well as in northern latitudes in winter at night, when the critical reflection frequency f
0
F2 for the ordinary wave drops below 4 MHz (f
0
E<1MHz), the extraordinary wave in the 4 MHz band may be successfully reflected. This is accompanied by additional losses ranging from 3 to 8 dB. These losses are not critical compared to the absence of broadcasting at all, and can be easily compensated by increasing the transmitter power.