A friend of mine is working to fix an RFI problem at the University of
Texas club station, N5XU. He's hooked up a digital voice keyer (DVK) PC
card to a TS-850 and it's picking up RF. Any comments would be
appreciated.
Robert K5PI
........................................................................
....................................
I built a new cable to connect the W9XT DVK to the TS-850SAT (our old
cable has 4-pin mic connectors on it) and it works, but it's picking up RF,
like the packet cable was. This new cable is really two 4-conductor cables
spiral-wrapped together I have the shields of both cables and the D-shell
at
the computer end all tied together. The two cables' shields are not
connected
to either of the mic connectors at the other end.
Y'all may not know the answers, but...
1) What should I do with the cable shields? Did I do right? Or should
they
"float" free of both the computer ground and the radio ground?
2) If I put ferrites on the cable, do you suggest putting them near the
computer end or the radio end?
3) Any other ideas?
I'm trying to get as much of the station in top shape for the contest
season as I can.
........................................................................
.........................................
So, I played around with the TS-850SAT and the cable for the W9XT DVK
card
some tonight. I had some Radio Shack ferrites (4) lying around (they've
been
quite succesful in defeating the RFI our computers face) but as near as I
can
tell, even four of these ferrite donuts do nothing for this problem, either
near the radio or near the computer. Which is really disappointing, as
they
work really well on the computer cables. I tried disconnecting the cable
grounds from each other and the connector shields, and that didn't seem to
make any difference.
I connected the radio ground to the case of the PC in question, and
that
actually cut down the RFI a lot - by about 65-70% is my guess. But it
didn't
eliminate it completely. Is this a clue? Should I try connecting the
cable
grounds to the PC ground via the connector again (which would require
soldering, which I'm not going to do tonight, but might try if it seems
promising?)
This is by far the most difficult RFI problem I've ever seen at N5XU.
And all of this is at low power, BTW. Plug the microphone directly into
the
radio, and the problem goes away _completely_.
--
--
Submissions: rfi@contesting.com
Administrative requests: rfi-REQUEST@contesting.com
WWW: http://www.contesting.com/rfi-faq.html
Questions: owner-rfi@contesting.com
|