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[RFI] RFI on voice keyer cable

To: <rfi@contesting.com>
Subject: [RFI] RFI on voice keyer cable
From: EDWARDS, EDDIE J" <eedwards@oppd.com (EDWARDS, EDDIE J)
Date: Thu, 7 Oct 1999 16:22:31 -0500
> -----Original Message-----
> From: Robert Brandon [SMTP:rbrandon@austin.ibm.com]
> 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.
> ........................................................................  
>   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.
> 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?
        [Ed-K0iL]  I've heard that grounding at one end or the other is OK
or even desirable, but at not both ends.  So it appears you're OK here.  I'd
guess the computer end would be better since it has a signal ground on the
DB connector.

> 2) If I put ferrites on the cable, do you suggest putting them near the
>    computer end or the radio end?
        [Ed-K0iL]  If you're getting audio detection in the computer board
audio, place the ferrites as close to computer, but you may have to
experiment to determine which end gives the best results.
> 3) Any other ideas?
        [Ed-K0iL]  How about trying an 8-conductor shielded cable instead of
the 2 separate cables?  might reduce any possible interaction to have it all
in one cable with twisted pairs.  

        GL & 73,
        de ed -K0iL


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