[TenTec] RFI Problem

[Patrick A. Thompson Sr.]

For what its worth...

I've been struggling with computer noise for some time now.  I have one
extremely noisy computer and two others in the shack that make very little
RF hash.  I already have an LCD monitor. The noisy computer starts radiating
as soon as the power plug goes in the wall because of the "wake-on-lan"
feature that isn't needed in a home environment. RF hash extends from the
standard broadcast band as high as 2 meters at S meter strengths of 20 over
9 or more depending on which antenna I'm using.  I've even seen low level
trash drifting upward through the picture on TV VHF channel 2 and 3.  This
is of course my fastest and most capable computer so its the one you would
want to use.

I've tried various clamp-on ferrite devices on the power cord, vga cable,
Ethernet, and internal to the box etc. with no real improvement.  Small caps
to ground at the motherboard DC connection made no difference.

I did note that pulling the power cable from the power supply to the
motherboard ended the hash so I erroneously concluded that the motherboard
was the source of the noise. Voltage was still present on the cable when
removed from the PC motherboard so I assumed the supply was still operating.
Some supplies will shut down at no load so I've read.

So yesterday because of the write-ups from various folks on this list I
bought one of Radio Shacks filtered power strips to replace my existing
strip.  $29.95 with colored LED's to look at. Initially I thought there was
no improvement but quick comparisons by plugging first into the RS strip and
then into an ordinary strip tuned to a noise peak near 7 MHz showed S9 or so
compared to S1 with the RS strip.

Down on the bench now I have a Corcom filter salvaged from a defunct piece
of equipment mated to the 3 pin power plug clipped from an old power cord.
This filter was part of the AC input assembly and included a 3AG style line
fuse.  When the RTV I potted the thing in dries I'll try it right at the
back of the computer. This won't require any modification inside the
computers box and it might help radiation from the power cord to the strip.
The line filter should have been incorporated into the power supply before
it left the factory.

I've also bought off EBay a couple of Corcom filters for further
experimentation. You are too late, I bought-it-now! (There are others still
for sale or look in your collection of recent boatanchors.)

DISCLAIMER: I don't work for or have a monetary interest in Radio Shack or
EBay. (I do contribute to their bottom line on occasion!)

Pat
wa4tuk



> -----Original Message-----
> From: tentec-admin@contesting.com [mailto:tentec-admin@contesting.com]On
> Behalf Of Paul (ve1dy)
> Sent: Thursday, December 05, 2002 7:31 PM
> To: Bill; Tentec Reflector
> Subject: Re: [TenTec] RFI Problem
>
>
> Hi Bill...
>
> The Corcom filter really worked for me.
>
> I wrote a little page about it on my web site at
> http://www3.ns.sympatico.ca/ppike/Filter.html
>
> This may not be the answer for everyone, but it sure worked for me, and
> by the sounds of it, for others as well.
>
> 73, Paul (VE1DY)
> Halifax, NS
>
> ps... love my 516!
>
>
> --- Bill <fla.pi@verizon.net> wrote:
> > I have always tried to keep my ham radio separate from my computer
> > because I play on my radio and work on the computer.
> >
> > Since putting a computer near my radio I have noticed that my
> > computer monitor is providing RFI for my ham rig.
> >
> > I know its the monitor. The pitch and intensity of the RFI changes as
> > I change images on the monitor.
> >
> > Monitor is a 19" Compaq, rig is a Ten Tec Delta II.
> >
> > Any advice?
> >
> > Bill
> >
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