Determination of maximum usable frequencies based on frequency characteristics of sporadic layer obtained by vertical sounding

It is analyzed determining methods and calculation techniques of MEs coefficient - converting the frequency characteristics of Es-layer by vertical sounding (VS) to maximum usable frequencies (MUF) of Es layer at oblique incidence (OI). Correction coefficient K, caused by the difference in technical provision of ionosonde and radio-line, and depending on the choice of threshold detection of Es-signal amplitude, introduces for determining of MUF Es. Revealed changes of correction coefficient from the type of Es-layer. For signal level appropriate to -30 dB, correction coefficient K for type c of Es layer equal 1.31, f type - 2.15, l type - 1.54, h type - 1.38. It is explained not only by geometrical factors, but also by changes in Es-layer structure, depending on the height of its location, and the magnitude of background ionization, which leads to daily changes of correction coefficient at fixed levels of Es-layer reflection coefficient. Changes in K coefficient during the day are considerable, since its value from night to day reduced by 1.3 times on Moscow-Kazan line. When the sensitivity of ionosphere station and radio-line are close, the value of K coefficient should not be significantly different from unit. This situation was checked by probing at sliding frequency on the Moscow-Kazan line. Found that at approximately same power of VS and OI stations the experimental distribution of K coefficient with standart deviation of 0.14, the same as calculation obtained by simulation modeling based on cloud model layer with parameters obtained from temporal variations of frequency fbEs.