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LF: Re: LF broadband QRN?

To: [email protected]
Subject: LF: Re: LF broadband QRN?
From: "mike.dennison" <[email protected]>
Date: Thu, 6 Mar 2003 15:34:05 -0000
References: <[email protected]>
Reply-to: [email protected]
Sender: <[email protected]>
Since the 73kHz tests on Tuesday I have been monitoring at several times a
day and find a consistent and steady  noise-level that is about 20dB below
the signal at 138.8kHz, and about 6dB below the one at 75kHz. Its a mains
type of buzz, beating at times with itself.  Like most I have had this in
the past and put it down to RFI from switched-mode PSUs, however, it was
only sporadic in the past so I am wondering if it's something new.  It
seems
to be all the way up the LF band to just below the LW broadcast band (but
that cut-off could be a function of my aerial's resonance set at 73kHz).

The only thoughts that I have is ADSL or signalling on the HV underground
cable somewhere beneath my garden.

  How far away do TV's etc need to be before they cause problems, or
is it more caused by the interference conducting itself along the mains
cabling, etc.
Any thoughts?

73 John, G3WKL

I don't have ADSL, but I (and several of my neighbours) have cable modems
supplied by NTL running between 128kb and 1Mb. My modem, and the unscreened
switch/gateway for my small network are both in the shack and only a couple
of metres from the antenna. I do not experience any problems to/from either
on LF.

My main noise sources are TVs, video recorders and computer games. These
seem to be within a few metres of my house. I fixed the QRM from my own TV
by using a braid breaker.

I have found QRM radiated by power lines (and once a telephone line) whilst
out portable, but have not located the source.

Mike, G3XDV
http://www.lf.thersgb.net
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