I had quite a bit of monitor noise problems, mostly on
20 meters, but after I made a few changes, its pretty
much gone. I found that a great deal of the monitor
noise was being picked up by the coiled keyboard
cable! I put chokes on it where it goes into the
keyboard and that helped. I also reorganized the
grounding system. At first I had the ground
connection going to the antenna tuner. From there I
had a short jumper to the transceiver. Now the ground
wire connects directly to the power supply negative
lead. From there I have a short jumper to the
transceiver chassis ground. I also removed the line
ground lead from the ac cord going to the outlet on
the monitor and the PC. Then I ran a separate wire
from the outlet ground directly to the CASE of the PC.
I have very little monitor noise now.
--- John - G3JAG <patents@dx0man.prestel.co.uk> wrote:
>
> Seems I'm not the only one to have PC noise
> problems.
>
> Sounds like you do not have a screened cable. Or if
> you do, the noise
> is apparently on the screening braid. Have you tried
> disconnecting the
> screening braid at one end only of the cable, so you
> do not have an
> earth loop ?? I have never had much luck with
> ferrites, even though I
> have them on most of my PC leads. I also have a
> small stock of ferrite
> sleeves that were used on commercial data cables.
> Unfortunately, the
> makers code numbers give no clue as to the RF
> performance, and I cannot
> detect any useful effect from using them. They look
> good ...
>
> Most of my noise problems came from the monitor,
> which is necessarily
> close to the rig (very small shack). The only
> solution (not 100%
> effective on 30m) has been to acquire a fully metal
> jacketed
> surplus monitor designed for use in very close
> proximity (stacked
> sideways and vertically) with other monitors. Well
> worth the $75 I paid
> for it.
>
> Another prolific noise source may be the PC AC power
> supply outlet which
> supplies the monitor. Some (usually older) rice box
> PSUs come with
> minimal to zero filtering. Properly filtered outlets
> nake a big
> difference..
>
> John G3JAG
>
> On 18-Dec-99 Anthony Bowyer wrote:
> >
> >
> > If, while tuning your Pegasus, you've heard a
> > strange signal that sounds like a child's ray gun
> or a
> > sound effect from a bad sci-fi movie, I found out
> what
> > it is. I initially thought it was a birdie, but I
> > found out that it's a signal being generated from
> the
> > RS-232 port in the PC that connects to the
> Pegasus. I
> > put a couple of split ferrite chokes on each end
> of
> > the cable and that attenuated the signal, but not
> as
> > much as I'd like. Like most newer motherboards,
> the
> > serial ports are on the motherboard. In my case,
> there
> > are headers on the board, and a piece of ribbon
> cable
> > connects the header to the RS-232 connectors
> mounted
> > on the back of the case. I wound as much of the
> ribbon
> > cable as i could around a toridal core, about 3/4"
> in
> > diameter (they came from old diskless
> workstations, so
> > I'm not sure of their characteristics), and that
> > attenuated about 98% of the signal. I can only
> hear it
> > very-very faintly on a few freqs when there are no
> > signals.
> > __________________________________________________
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> ----------------------------------
> E-Mail: John - G3JAG <patents@dx0man.prestel.co.uk>
To: <tentec@contesting.com>
> Date: 18-Dec-99
> Time: 15:20:41
>
> This message was sent by XFMail
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