Effect of Oblate Raindrops on Attenuation at 30.9 GHz


  • R. A. Semplak


An experiment that measures the difference in attenuation of horizontally and vertically polarized fields propagating along a 1.89-km path at 30.9 GHz is discussed. For a rain-induced fade of 18.5 db/km, differences between attenuations in horizontal and vertical polarizations as large as 3 db/km have been observed. There is good agreement when these microwave measurements are compared with calculations based on raindrop shapes that were measured visually by an independent investigator. From the data, we conclude that there are significant differences between attenuations in these polarizations for rain-induced fades and that we should think in terms of an effective rain rate for vertical polarization that is less than that measured by rain gages.