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Re: LF: Mike's "ADSL problem"

To: [email protected]
Subject: Re: LF: Mike's "ADSL problem"
From: "Dave Sergeant" <[email protected]>
Date: Mon, 18 Jun 2007 06:43:49 +0100
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On 17 Jun 2007 at 22:14, Alan Melia wrote:

> I have neighbours either side with broadband and I am not aware of any
> problems on 500k, but what I did notice was a horrendous noise in the
> middle of the band when the video recorder was sitting on timed record
> and the TV was switched to AV. I often do this to avoid missing
> programs or missing them due to a phone call in the middle. It would
> seem that whilst not receiving a signal, but producing a raster (blank
> screen with an "AV" legend) there is a large comb of frequencies at
> about 502. I am guessing that without a signal to lock it, the line
> oscillator free-runs a little above 15.625kHz. Putting my TV on
> standby or OFF kills the noise.

Alan, those sorts of problems are certainly due to dodgey switch mode 
psus in equipment and fairly common. You and Mike should be looking 
in that direction and not blaming ADSL. I would not expect problems 
from ADSL as it is a balanced system and should not radiate very far 
at all. You would only get any radiation if there is a dodgey 
telephone connection somewhere, say in the overhead lines, where the 
twin pairs have been accidentally split between two separate pairs so 
the two lines do not run parallel - very rare but has been known to 
happen. It most certainly will not be a dodgey ADSL filter as the 
broadband signal is not filtered at all in those, only the telephone 
side is filtered (and I doubt whether they ever fail despite all the 
suggestions to change them when you have a fault, as passive devices 
there is nothing inside them to fail...).

So look very seriously at those smpsu's, wallwarts etc.

73 Dave G3YMC

http://www.davesergeant.com



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