[RFI] RE: Quiet Shack PC Systems?

[Pete Smith]

A couple of comments interspersed in this excellent message

At 02:20 PM 3/18/04, kz8e at 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
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