Rain attenuation measurements using the equivalent-distance model

Five years of slant-path-attenuation and point-rain-rate measurements in Sweden have been used to estimate the prediction accuracy of a simple equivalent-distance model. Radiometer attenuation data at 11.4 and 14.0 GHz, obtained at 21° elevation and rain-rate data from a tipping-bucket-type rain gauge have been used. The long-term predication error is estimated to be within a few tenths of a dB, giving strong support to the usefulness of the method. The equivalent distance is found to be frequency independent over the range 11¿14 GHz at least, and consequently frequency scaling of attenuation data, using the theoretical specific attenuation, is proposed.