Determination of sporadic E radio wave propagation parameters based on vertical and oblique sounding

Sporadic E layer is often determined for HF radio communication. We have to deal with oblique radiowave propagation in the radio practice. The limiting frequencies at oblique propagation depend heavily on the transmitter power and the receiver sensitivity. The reason for this, as in the case of vertical propagation, is the dependence of Es reflection coefficient, ρEs (reflection loss R(dB)), on Es operation frequencies. This paper describes the characteristics of HF Es propagation in relation to foEs obtained from ionospheric vertical observations. It was found that characteristics of Es propagation depend on the type and height of the Es layer. Also the foEs diurnal variation at definite R(dB) was detected. This investigation allows improving the prediction of limiting frequencies for HF radio propagation.