Reg Edwards wrote:

"Ian White GM3SEK" wrote
Reg Edwards wrote:
Radiation from the feedline is usually the least of one's problems.

99 % of RFI is due to radiation from the very nearby antenna.


That's rubbish - have you ever *measured* the RF currents in your
station wiring?

==========================================

No, but I HAVE measured RF current in the antenna - from where most
RFI originates.

Can't you see the circularity of your own 'logic'? If you haven't
measured common-mode RF current in the feedline as well, you don't
actually have a clue where the interference is originating. All you have
is an unsubstantiated opinion.


Have you ever run 400 watts from an 80 meter 1/2-wave dipole a few
feet above your roof and not far from the TV aerial?

I'm not disputing that RFI very often originates from the antenna - of
course it does (and the question you pose is a set-up, designed to make
*sure* it does).

What I object to is your sweeping generalization that "99 % of RFI is
due to radiation from the very nearby antenna." When absolute nonsense
is delivered with absolute confidence, some unfortunate beginner might
actually believe it.

However, since you asked...

In a typical small British back garden, I have been forced to do
something very similar to what you describe. Sure enough, it caused RFI,
but the interference was *not* due to my antenna! It was entirely
mains-borne, and only to the two neighbours (not the closest) who were
connected to the same phase as ourselves. The cause of the interference
was that a substantial fraction of my RF ground current was going into
the mains ground. Once I'd cleaned up my act and stopped injecting RF
current into the mains, the interference stopped too.

The high field strength from my antenna wasn't a problem at all, and the
neighbours continued to watch their TVs until I took the antenna down.

That's how it was in that one particular case.... but unlike you, I'm
not claiming it represents 99% of anything.

With RFI, the only safe generalization is to keep your mind open to
*all* possibilities.


--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek