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The outage time on short radio paths at frequencies above 10 GHz can be estimated from distributions of point rain rates derived from U. S. Weather Service rain gauge charts. In this paper, a previous theory is extended to include the effects of path length and frequency. Experimental corroboration is presented for three locations on the east coast of the United States, and the design of short radio paths is illustrated by examples. One‐minute rain rate distributions for 20 locations are also included.

Transmission over line‐of‐sight microwave radio paths is analyzed with the aid of a piece‐wise linear approximation of the atmospheric index of refraction. The simple model is adequate; it predicts published experimental results. A short path is defined on which no deep fading can occur and the maximum length of such a path is estimated from measured data for New Jersey. Expressions are presented for the worst‐case amplitude‐frequency response and for the maximum echo delay for short paths. It is shown that if the normal Fresnel‐zone clearance is maintained on short paths, no fading will occur due to substandard conditions of propagation. W. T. Barnett's result is also predicted from this model: the distribution of attenuation on long paths is a function of L3/Λ where L is the path length and Λ is the free space wavelength. The distribution of deep fades on long paths is predicted by this model to have the same slope as the Rayleigh distribution, the slope normally found in measurements of attenuation distributions on long paths.

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This paper describes the application of the rain attenuation theory of Ryde and Ryde to the design of Radio Systems. It shows that an upper bound on the outage time due to rain attenuation can be computed from a measured point rain rate distribution. The paper also describes a suitable rain gauge.