I am using a Digital VT320 terminal in the packet dx-cluster link.
The problem was very bad on 80/160 meters. So I decided to put .01
capacitors from each of the
key wires (keys to printed circuit into the keyboard) to ground. Wow ! it's
fine now on 160.
Next day I called a friend on 20 and :-(
The RFI shifted from 160 to 20 m. That all after install a lot of C's...
Certainly the keys and its wiring (all flat cable) are the "antennas".
73
Egon Boehm
PY2BW
mailto:egon@virtual-net.com.br
----------
> rfi-digest Wednesday, January 28 1998 Volume 01 : Number
016
> Can anyone recommend a computer keyboard that is RFI resistant,
> >Can anyone recommend a computer keyboard that is RFI resistant,
> >preferably a compact type? I have applied ferrite toroids to both ends
> >of the keyboard cable just in case the cable was acting as an antenna
> >but this did not correct the problem. Un plugging the key board clears
> >the problem. Whenever I transmit on 80 or sometimes 40 meters the
> >computer genetates all kinds of strange characters, etc. on the screen.
>
> Unfortunately, I can't tell you which keyboards are okay; hams don't call
> ARRL HQ and tell us that they are NOT intefering with their computers.
:-)
> At W1AW, they currently have Gateway 2000 computers; their keyboards
seem
> immune, although I must admit that our antennas are located up in the air
a
> bit. :-)
>
> I note that you had tried ferrite material, but the single clamp-on beads
> are really not enough for 80 or 40 meters. Get some FT-140-43 ferrite
cores
> (Amidon, Palomar, etc), or other cores you KNOW to be ferrite that will
work
> in the HF range and warp about 10 turns of the keyboard cable onto a
ferrite
> core, at both ends of the cable. This SHOULD make a significant
difference,
> at least in the power theshold that causes the problem. If you find it
goes
> from 15 watts to 95 watts, for example, you are on the right track.
>
> If it makes no difference, it may be the wiring in the keyboard itself
that
> is causing the problem. (This could also be true if it goes from 15 watts
to
> 50 watts, as an example: the problem could have a 15 watt threshold on
the
> cable pickup and a 50-watt threshold on direct pickup.) If it IS the
> keyboard, the easiest solution is to try another. You could also TRY
some
> of the EMI shielding sprays available, trying to get a good shield inside
at
> least most of the keyboard. You could also try a shielded keyboard
cable,
> grounded at either the computer or the keyboard end, or both. Flat
1/2-inch
> braided strap is usually hollow and can be used to shield your existing
> cable.
>
> If you do try sprays, try to ensure that both halves of the keyboard case
> will be electrically connected to each other and to the keyboard-cable
> shield. And remember, these sprays are conductive paint; if the surface
> being sprayed is not clean and compatible with the spray, the paint could
> flake off later, putting bits of metal flakes inside the keyboard. The
> gibberish on the screen will probably return.
>
> Radio Frequency Interference has a chapter on computer RFI.
>
> 73 from ARRL HQ,
> Ed Hare, W1RFI
> ARRL Lab
>
> - --
> Submissions: rfi@contesting.com
> Administrative requests: rfi-REQUEST@contesting.com
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> Questions: owner-rfi@contesting.com
>
> ------------------------------
>
To: <rfi@contesting.com>
> Date: Wed, 28 Jan 1998 22:49:43 -0500
> From: "Richie" <aa2mf@earthcom.net>
> Subject: Re: [RFI] computer keyboard
>
> - ----------
> > From: Richie <aa2mf@earthcom.net>
> > To: David Pugatch <dp@sj.bigger.net>
> > Subject: Re: [RFI] computer keyboard
To: <rfi@contesting.com>
> > Date: Wednesday, January 28, 1998 10:48 PM
> >
> >
> > Jan.28,1998
> > Dave, I find the IBM Spacer Saver keyboard dose the job very well for
> me.
> > I get them at the local computer shows for around $20. My station and
> > antenna farm are all located within my 25ft x 44ft back yard. I
> sometimes
> > have to use my amp on 160, 80 and 40 and I find the computers are RF
> > free. I can't say how well these keyboards will work above 40 under
high
> > power conditions becouse I do not operate that way.
> > Rich/AA2MF
> > ----------
> > > From: David Pugatch <dp@sj.bigger.net>
> > > To: rfi@contesting.com
> > > Subject: [RFI] computer keyboard
To: <rfi@contesting.com>
> > > Date: Wednesday, January 28, 1998 5:29 PM
> > >
> > > Can anyone recommend a computer keyboard that is RFI resistant,
> > > preferably a compact type? I have applied ferrite toroids to both
ends
> > > of the keyboard cable just in case the cable was acting as an antenna
> > > but this did not correct the problem. Un plugging the key board
clears
> > > the problem. Whenever I transmit on 80 or sometimes 40 meters the
> > > computer genetates all kinds of strange characters, etc. on the
screen.
> > >
> > > 73 and tnx. Dave, KI6WF..
> > >
> > >
> > >
> > > --
> > > Submissions: rfi@contesting.com
> > > Administrative requests: rfi-REQUEST@contesting.com
> > > WWW: http://www.contesting.com/rfi-faq.html
> > > Questions: owner-rfi@contesting.com
>
> - --
> Submissions: rfi@contesting.com
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> WWW: http://www.contesting.com/rfi-faq.html
> Questions: owner-rfi@contesting.com
>
> ------------------------------
>
> End of rfi-digest V1 #16
> ************************
>
>
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