A recently derived attenuation function for multiple knife‐edge diffraction is described, and some example calculations are presented. The function, in the form of a multiple integral, is transformed into a series representation which is amenable to computer implementation. A program has been written to compute the attenuation over propagation paths containing up to a maximum of 10 knife‐edges. Attenuation curves for three example paths are presented showing the effects of multiple knife‐edges on the received signal. A means of estimating the statistical distribution of attenuation for a given path from statistical knowledge of the atmospheric surface refractivity is suggested.

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Expressions to model the sky wave propagation conditions that occur in a HF communication link are presented. The model is intended not only for narrowband applications but also for wideband systems such as those using spread spectrum techniques. A discussion of the background leading to the present development effort is followed by a description of the method used to derive the model transfer function. Analytic expressions for the impulse response and the scattering function are given, and the introduction of random processes into the model is described. Comparisons of scattering functions from the model and from measurements are shown for spread‐F conditions ranging from mild to intense and for both an auroral path and a midlatitude path.