Rain Attenuation on Short Radio Paths: Theory, Experiment, and Design

Many characteristics of radio systems above 10 GHz are due to the existence of large attenuation by rain. These characteristics have been discussed at length in a previous publication. 1 The economical design of a system operating at these frequencies requires a knowledge of the incidence of rain attenuation at the location of the system; to be more specific, it requires a procedure for predicting the number of minutes per year that a radio path will be out of service because of excessive rain attenuation. This paper describes such a design procedure and includes data required to design systems in several sections of the country; design examples are also given. The starting point for this design procedure is the theory of attenuation by uniform rainfall 2 and a relationship, derived in Ref. 3, between the attenuation distribution measured on a path and a point rain rate distribution measured near the path. The key result of Ref. 3 is a connection between the theory of attenuation of uniform rain and that of the variable rainfall experienced in practical situations. This connection is, of course, vital to any practical measurement because uniform rain does not usually occur. A conclusion of this work was that the measuring interval used in rain rate measurements has a large 1329