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LF: RE: Unwanted LF radiation

To: [email protected]
Subject: LF: RE: Unwanted LF radiation
From: "Gary - G4WGT" <[email protected]>
Date: Fri, 10 Jun 2005 14:01:10 +0100
Delivery-date: Fri, 10 Jun 2005 14:02:53 +0100
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Hi Howard,

In response I can only say that I am Tiscali Broadband on a BT line whilst
activly receiving signals mainly on 136KHz but often tuning 30 KHZ up to 500
KHz & I have not come accross anything like you have described. I can only
asume that the problem you have there is not generated by broadband signals
on BT lines.

I hope this is of some help.

Regards,

Gary - G4WGT - IO83qp

Web : http://myweb.tiscali.co.uk/wgtaylor


-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Howard Aspinall
Sent: 10 June 2005 11:27
To: [email protected]
Subject: LF: Unwanted LF radiation


This might be just a bit off the beaten track for the reflector, despite
being LF orientated,
but I wonder if anyone has any useful observations or information they might
pass on.

Whilst tracking down some noise interference problems, I discovered sizeable
amounts
of wideband RF between 75 and 130 KHz. This manifests itself as
"smooth" noise. It extends outside these frequency parameters well into
long/medium
waveband, and is radiating from the overhead BT telephone drop line.
Broadband
internet RF seems the most likely culprit (there being a null between 130
and 140 KHz),
but we do not have any broadband facility here.

An HP spectrum analyser close coupled to the line (common mode) shows this
signal
level to reach at least 5 mV around 100 KHz.

Tests on BT lines in other areas where broadband is also not installed show
no RF
present other than broadcast stations etc.

Can anyone say if such common mode RF levels on BT lines can be typical, or
might be
expected where no broadband facilities are connected? Are levels I am
finding here
regarded as acceptable? And does anyone know of any regulations, codes of
practice
or technical standards on the subject?

Howard   G3RXH










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