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

[Pete Smith <n4zr@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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