That sounds like the power supply is missing the usual common-mode input filter
that switching power supplies nearly always have.
There are companies like corcom that make emi filters for the line. Some of
these filters are integrated with the IEC power connector for the power cord.
If your power supply has enough space to fit one of the combo filter/connectors
in place of the stock connector that might help -- even with your new supply.
This would put the filtering inside the computer chassis which would likely be
better than anything you could put on the power cord alone.
-Bill
[Sent using Blackberry Messaging]
----- Original Message -----
From: topband-bounces@contesting.com <topband-bounces@contesting.com>
To: topband@contesting.com <topband@contesting.com>
Sent: Wed Jul 04 09:10:39 2012
Subject: Topband: Progress with ugly computer noise
Hi,
I have been limping along with a really ugly replacement power supply in
my big computer. It's networked (think of internet tools). I could hear
*nothing* on my radios aside from the racket made by that power supply.
I even found my power supply listed on the internet as an example of
*ugly*. There is no EMI filter at all - just two jumpers where the
filter is supposed to be. The computer had to be turned off to even
think of using a radio.
I have paid for a new, better quality power supply (only $2 more) and
the online tracker suggests it will be in my mailbox any minute..maybe
tomorrow. I got impatient. I have two of those ugly supplies so I took
the filter parts out of one of the dead ones and installed them in this
one. I put the supply in the computer and it made quite a difference!
It's not good enough yet but I am listening to hams on 40 meters while I
am typing this! I couldn't do that before. Next I'll be getting my hands
on some ferrite core materials and looking to see just how far I can
reduce the noise.
I have two laptop computers here, older and newer, and I can barely tell
when I turn either of them on. Neither one talks to my network at the
moment so I will have to correct that. But I have a "target" noise
performance for my PC tower, now. Meanwhile I have the noise knocked
down well enough to try using this computer to help with operations
while on the air. I may be unable to hear the weakest signals but I'll
see how that goes.
73,
Bill KU8H
_______________________________________________
UR RST IS ... ... ..9 QSB QSB - hw? BK
_______________________________________________
UR RST IS ... ... ..9 QSB QSB - hw? BK
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