On Tue, 16 Aug 2005 08:36:18 -0400, Pete Smith wrote:
>I'm thinking that an RF choke in series and bypass cap to
>ground on each line would help.
Pete -- take a look at the following link, which is an applications
note I wrote for audio system RF suppression. The chokes described
would work quite nicely to suppress common mode current on those
cables. Simply use the data (curves) and guidelines to tell you how
many turns to use for the frequencies where you are having problems.
Also look at the material in the link below on "the pin 1 problem."
You might also need capacitors, but probably a lot smaller ones.
Another point. Twisting can be just as important as shielding in
rejecting interference. If you aren't already doing so, and if the
right choke doesn't fix it, my next move would be to use cable that
uses a twisted pair for each signal circuit.
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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