I have a 400kV powerline about a mile away. Twenty years ago it had become
quite noisy - you could see the big glass insulators arcing slightly at
night. After lots of complaints to the National Grid they cleaned the
insulators, and the noise stopped.
The only time there is powerline noise now is when it has been dry for a
while - I guess dirt has built up on the insulators - and THEN there is
light rain - That's when the insulators start arcing. Once there has been
heavy rain, the dirt is washed off, and it's quiet again.
You can tell if it's noise from the powerline if you listen to the noise on
AM - you will hear that is has a VERY loud 50Hz buzz . . . it's not like the
wideband hash you get from Internet Broadband or from some bad Switchmode
PSUs.
Our main source of noise here in Britain is from Internet Broadband, which
is mainly delivered via the old overhead copper telephone wires (which make
great topband antennas, radiating the noise for miles). They have started to
replace these with Fibre Optic Cables . . . so hopefully the noise will be
gone in 5 years!
73 Roger G3YRO
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