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[RFI] PC Power Supply Noise

To: rfi@contesting.com
Subject: [RFI] PC Power Supply Noise
From: Roger Parsons <ve3zi@yahoo.com>
Reply-to: ve3zi@rac.ca
Date: Wed, 26 Dec 2007 16:17:49 +0000 (GMT)
List-post: <mailto:rfi@contesting.com>
This will probably not be news to anyone, but may just
be useful.

Just about every desktop PC creates lots of rf birdies
and other nasties. Some comes from the monitor/video
card, but in my experience most is from the computer
power supply. All of the recent supplies that I have
looked inside have pc board spaces for suppression
components which are not fitted. Whilst it would be
possible to fit components in those spaces, they would
have to be properly rated to be safe, and the
component values are unknown.

All the supplies have an IEC connector, and I have
found that in nearly every case, it is possible to
replace this with one with a built-in filter. These
are very commonly available at rallies and electronic
junk outlets for a dollar or two. In my experience
this leads to a complete cure - it is _much_ better
than trying to put toroids round power leads and
similar tricks. (In a few cases there is not enough
clearance between the filter connector body and the
pcb components.)

Obviously it might not be prudent to do this to a
brand name pc under warranty, although as the power
supplies are very cheap one could fit a modified one
instead of the original and change it back in the
event of warranty problems... One should also be aware
that this is a line voltage component, and be sure
that the work is done safely.

73 Roger

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