Low frequency radio wave propagation in the Atlantic and Mediterranean areas

Data from eighteen long range aircraft flights are compared with the wave hop propagation model of Berry, and areas of agreement and disagreement noted. The field strength of low frequency radio waves from transmitting stations in Iceland, Scotland, Morocco, and Greece was measured under daytime and nighttime conditions. The nighttime waves at about 1 mm seem to oscillate with distance more dramatically than the current model predicts. The daytime fields over all-water paths are often in good agreement with theory, but ground conductivity changes and rough terrain effects not contained in available computer models appear to influence the received fields. The unsatisfactory state of mathematical propagation models for this frequency regime is discussed and some areas for improvement recommended.