hangflyer
I would like to suggest a test, please. One of the explanations suggests that there is no external noise, and that the white noise you hear is just the normal internal radio mixer noise heard when the received signal gets very weak and the agc (automatic gain control) turns up the radio gain.
Would it be possible to check reception on a distant station and see if the noise level comes up and whether it sounds the same? To one side and using each receiver in turn.
Many thanks, Mike.