Quote:
Originally Posted by Skywave
If it isn't radiation from the mains, then it must be that where you are located there is a strong radiated electro-magnetic field that could be coming from a nearby radio transmitter - or some other source. Perhaps it's coming from a high-voltage street step-down transformer: it's entering your body and re-radiating.
Perhaps, with the aid of a portable transistor radio that shows same problem, a travel around your vicinity - which might be a few miles - might locate said transmission source.
Al.
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Thanks for your comments. So - yes - I will take a portable and go for a wander, weather permitting, this weekend. I do wonder if it is indeed a step down transformer being as my street is supplied from a nearby 3 phase transformer on overhead 11000 lines. Perhaps a combination of the high voltage and the fact the properties will be on different phases is causing the modulation hum.
Clearly the two factors that make this interesting are 1) the higher frequency of the noise, not the usual 50Hz, and 2) the fact that it is only audible on the higher part of the MW band.
Will update next week when I have gone for a walk.