Prudent frequency management through accurate prediction of skywave field strengths

A nonexhaustive chronological summary of the advances made in MF skywave propagation studies is presented with emphasis on progress made in the United States. A qualitative analysis of the documented methods for calculating skywave field strengths and a quantitative comparison of selected methods with measured data are also included. Methods compared include the FCC clear-channel curves (the method for ITU Region 2), the Cairo North-South curve (the official method for the Asian part of Region 3), and the J.C.H. Wang (1985) method (the proposed modified FCC method). Field-strength values calculated by using these methods are compared with data collected in different parts of the world