[RFI] RE: Quiet Shack PC Systems?

[kz8e at wt.net]

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.

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.

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.

The idea of taking a radio to the store and listening is a good one.  Also be 
sure that the return policy will allow you to return it if noise is objectional.

These tips won't fix an existing problem but should help if you are in the 
market for a new or used one.

Earl 
N5TU

I'm always intrigued by the photos of other peoples shacks with the PC and
monitor mounted right in among the radio gear.

I have a conventional tower and CRT monitor which creates nasty QRM in my HF
receivers, I also have a laptop with TFT screen which is not too bad but
it's switched mode PSU/Charger is chronic anywhere near my radio.

I'm interested to know how others solve the PC / Radio interface  and
maintain low interference levels.

73, Deni
F5VJC, GM3SKN