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Date: Thu, 17 Dec 2009 11:32:33 +0000
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From: Andy Talbot <andy.g4jnt@googlemail.com>
To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: RE: Noise cancelling by using optic transmission of RX 
	signals
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That wouldn't make any difference.  The mount to the metal frame was
non contact, and the outer of the coax forming the counterpoise will
always be the interference injection point as teh rubbish is being
picke dup on th ecoax outer as it feeds its way thuorgh the ducting to
the outside world.    By the time the roofspace itreached, teh actual
localised radiatino is at a moderately low level as its mostly
contined within the metal framed building.

The surest way to counter localised pickup on the coax is to
thoroughly ground the antenna connection using the ground wire
provided to the building frame, then use a common mode choke (a mass
of ferrite rings) to decouple the coax braid.   It worked well-enough
for our HF monitoring purposes.

Andy
www.g4jnt.com

This email has been scanned for damaging side-effects by the health
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2009/12/17 Roelof Bakker <roelof@ndb.demon.nl>:
> Hello Andy,
>
> Have you tried to mount it on a four metre high non metallic pole?
> It probably is still inside the noise field of the building, which drops
> off within a few metres.
>
> 73,
> Roelof Bakker, pa0rdt
>
>
>