[TowerTalk] decoupling RF from control lines

[Jim Brown]

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.

http://audiosystemsgroup.com/SAC0305Ferrites.pdf

Also look at the material in the link below on "the pin 1 problem." 

http://audiosystemsgroup.com/Ferrites-Ham.pdf 

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. 

Jim K9YC