Precipitation particle impact noise in aircraft antennas

It has been found that precipitation static noise is produced in antennas under plastic surfaces, even though these surfaces are covered by conductive films. In this paper the noise is shown to be due to a noise producing mechanism associated with the aquisition of charge by individual precipitation particles upon impact in the antenna field region. The existence of such a mechanism is demonstrated theoretically and substantiated by experiment. The production of such noise in antennas is analogous to the production of shot noise in vacuum tubes. Calculated results indicate that in practical antennas this process is capable of generating noise voltages of several hundred microvolts at a frequency of 500 kilocycles and a bandwidth of 3 kilocycles, while at lower frequencies the noise is even higher.