Sweep frequency propagation on an 8,000 km transequatorial north south path

Two prediction improvements are suggested according to sweep frequency observations between Tsumeb, South West Africa and West Germany. In summer daytime the observed MOF is up to a factor of two higher than the predicted MUF. This error can be reduced to a factor of 1.2 if an Es-transmission factor of 7 is applied instead of a factor of 5 which had been used hitherto. In the existing predictions for long distance medium wave propagation only E-layer reflections are taken into account. In contrast to this assumption strong F-layer reflections have been observed. The median F-layer LOF was 1.3 MHz after midnight. At these low frequencies, signals reflected at the E-layer were quite often weaker than the signals reflected at the F-layer.