The influence of focusing on the apparent reflection coefficient of theFregion

The apparent reflection coefficients of the ionosphere for high frequency radio waves have been studied using vertical incidence pulse amplitude data obtained at Prince Rupert. The F-layer first-hop reflection coefficient increases in magnitude as the degree of spread F increases. This increase in magnitude can be explained by focusing of the energy scattered from an irregular surface or by propagation of the energy along field-aligned ducts. Revised methods for obtaining calibration constants for ionospheric absorption measurements are required.