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 acquisition 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. Production of such noise in antennas is analogous to production of shot noise in vacuum tubes. Calculated results indicate that in practical antennas this process is capable of generating noise voltages sufficient to disable lf and mf equipment such as the adf radio compass.