Switching power supplies tend to put out broadband noise from about 150kHz
to
approximately 5MHz. Any number of design errors can cause this - recovery
diodes
breaking down as they switch, high/low MOSFETs both on at the same time for
an instant,
poor PCB layout.
Copper tape, and ferrite beads are about the only cure.
N6RCE
-----Original Message-----
From: tentec-bounces@contesting.com [mailto:tentec-bounces@contesting.com]
On Behalf Of wb5jnc@juno.com
Sent: Wednesday, June 11, 2003 7:52 AM
To: tentec@contesting.com
Subject: [TenTec] RFI update
Greetings all,
About a month ago I posted a message about an intermittent RFI problem on
the AM BC band and 160M (which shows up spaced at approximately 138 KHz
intervals). I had continued to try to track it down as time/WX permitted and
had narrowed it down to my house and the neighbor behind me. Yesterday the
neighbor's jr. op was out mowing the lawn so I went over and talked to him
after he finished. It turns out that he came home from college about the
time the RFI started. He brought his clone computer home that they had
bought for him last fall when he went off to school and started using it
here. I have checked from their QTH and the RFI seems to disappear
completely with unplugging it -- now I need to get on the landline with him
and check from my QTH. I had him unplug it as a secondary test because when
it was on it _completely_ wiped out the AM radio in the hall outside his
room with broadband noise! (BTW the computer is an "Alaska" brand: PS says
"Made in China" as to be expecte!
d.)
Does this sound like it could be the culprit, and if so, what's the best way
to get it resolved? (The family is very cooperative and the system is less
than 1 yr. old, so the question would seem to come down to whether the
dealer or the manufacturer is responsible if I can prove that this system is
the source of the RFI.)
TNX/73, Al
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