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Re: [RFI] RE: Quiet Shack PC Systems?

To: kz8e@wt.net, rfi@contesting.com
Subject: Re: [RFI] RE: Quiet Shack PC Systems?
From: Pete Smith <n4zr@contesting.com>
Date: Thu, 18 Mar 2004 16:43:38 -0500
List-post: <mailto:rfi@contesting.com>
A couple of comments interspersed in this excellent message

At 02:20 PM 3/18/04, kz8e@wt.net wrote:

Deni,

There is no cut and dried way to eliminate all the interference. It would even
be incorrect to say that CRTs are the worse offenders. I would usually vote on
s SMPS as being the worst offender since the noise is usually wideband and the
harmonics are every 50 to 200 kHz . Damaging enough to take out a whole band.


Anyway here are a few simple things to do:

Stay away from the roll your own "mom and pop" computer specials. These are
usually heavily cost reduced. The power supply filters are almost always
thrifted out of them because designers know that emc suppression components can
be left out with no performance hit except for in the radio bands but most
people won't notice.


If you have one of these, you can buy replacement power input connectors from Mouser et al that have built-in EMC filtering, probably better than the stock components that were left out.


Most computer companies have two lines of computer products. One is commercial
and is typified by a longer warranty and higher price while the other is a
consumer line typified by the opposite. The consumer line is made to be sold
to the general public and has features aimed for that group. If I relied on my
computer for my income it would be a commercial line model. Compaq's
commercial line models were the Evo, Armada, and Deskpro while the consumer
line was Presario (I'm sorrio). Anyway the bottom line is the commercial line
is tried and tested and goes to a more demanding customer (coporate IT
departments) with stringent requirements. The consumer line is made for the
less demanding user.

Yes, but be sure that the computer has FCC certification for class B, not class A.



I ran a shack that had 6 computers (all commercial lines)in it and only one
flat panel monitor showed interference to an antenna on tower 1 50 feet above
the shack but not to antennas on tower 2 that was 100 feet away and 100 feet up.

I'm on my second flat panel LCD display -- a generic Circuit City item -- and find it absolutely quiet -- though my antennas are 250 feet away. The CRTs they replaced were not quiet, particularly on 15 and 10. The SONY display I replaced last also got into my microphone audio, apparently some sort of magnetic field coupling to the cable. Quiet is bliss!


73, Pete N4ZR
2671 calls now in the
World HF Contest Station Database
at www.pvrc.org/wcsd/wcsdsearch.htm


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