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RE: hf noise from monitor



True, the most probable place you will pick up noise is from poorly or
unshielded cables. But just buying a flat panel display won't guarantee
a quiet receiver!  If you choose a digital flat panel, you might be in
for a big surprise.  Also, most things nowadays come with switching
power supplies, even when they look like a harmless wall wart.
Switching supplies are notorious for being dirty.  And most computers
you buy now only meet Class-C certification, or otherwise, no shielding.
I have numerous SGI's and am amazed at how well they are shielded; they
meet Class-A (even that doesn't guarantee zero emissions).  They're so
good in fact I wouldn't doubt they could pass a military Tempest
certification.  But you get what you pay for.  It's often impossible to
peer into a cable to see how it's shielded.  Stay with known brands that
have a reputation for quality, or roll your own with quality cables and
shielded connectors.  For difficult problems, you can also try lead or
copper tape for inside computer cases and such.

73's
Ray - WB3ABN
Kingston, WA

-----Original Message-----
From: owner-AMSAT-BB@AMSAT.Org [mailto:owner-AMSAT-BB@AMSAT.Org] On
Behalf Of Elec Dep
Sent: Wednesday, February 12, 2003 12:26
To: amsat-bb
Subject: Re: [amsat-bb] hf noise from monitor

...the most suspicious point for noise generation is the cable, between
VGA
card and monitor.
I've reduced dramatically the noise by decreasing the length of this
cable,
as short as possible.
That is not easy sometimes, this cable has several inter-connections.
Keep
in mind, if you have
this cable very close to your Antenna RG cable, that is also a reason
for
noise.
 Try also to put ferrite beads on the same cable, sometimes are very
helpfully for the noise reduction.

KC2JO is right 100% ... "refresh rate" is very important for
noise-generation.

 Finally, I've found some monitors are extremely noisy-devices, probably
they are
without enough shields inside !  Nowadays, a TFT monitor is the best
choise
for our
shacks.

     Regards
        Mat
Matronics Electronics Dep.

----- Original Message -----
From: "John Taylor, K0QH" <kc2jo@brick.net>
To: "Phil" <phil@spiderweb.com.au>; <amsat-bb@AMSAT.Org>
Sent: Wednesday, February 12, 2003 9:31 PM
Subject: Re: [amsat-bb] hf noise from monitor


> I cured my noise problem on 40 meters by changing the refresh rate
under
> display props.
> John
> ----- Original Message -----
> From: Phil <phil@spiderweb.com.au>
> To: <amsat-bb@amsat.org>
> Sent: Sunday, February 09, 2003 6:55 PM
> Subject: Re: [amsat-bb] hf noise from monitor
>
>
> > On Sat, 8 Feb 2003 10:58 pm, nick pugh wrote:
> > > I have ask on the bb before but no joy. I am getting from
interference
> on
> > > 20m from my monitor and have been unable to get it out.
> > >
> >
> > I'm sure that this is a common problem. My monitor caused
interference
to
> ALL
> > bands. I bought an LCD monitor; no RF noise and excellent video.
> >
> > --
> > Regards,
> > Phil
> > phil@spiderweb.com.au
> >
> >
> > ----
> > Sent via amsat-bb@amsat.org. Opinions expressed are those of the
author.
> > Not an AMSAT member? Join now to support the amateur satellite
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> >
>
> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are those of the
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----
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