Extraordinary Wave NVIS Propagation at 5MHz

摘要

In amateur circles, a measure of NVIS communications likelihood is the ordinary wave critical frequency foF2 exceeding the operating frequency. Analysis of the 5MHz beacon data has shown that for the UK, the extraordinary wave critical frequency fxF2 (or fxl as obtained from modern ionosondes) is a much better indicator since it is about 0.7MHz higher. Using foF2 may suggest the 5MHz band to be closed, but fxl and actual conditions show it otherwise.