Medium-Frequency Sky Wave Propagation in Middle and Low Latitudes

Frequency assignments to particular broadcasting stations within the range 150-1500 kHz are now made on the basis of empirically derived sky wave propagation curves that are used to determine the service and interference field strengths of these stations. Using the concept of propagation loss, a detailed comparison is presented between two series of propagation curves used for this purpose in the United States and in Europe. Serious differences are shown to exist even though both series are based on extensive measurements taken in similar middle latitude areas. Using all the available data and guided by the theory of medium-frequency ionospheric propagation, a new series of sky wave propagation curves is derived which shows a different frequency dependence factor; these new curves are believed to be more applicable in middle latitude areas than either of the present series.