[TowerTalk] decoupling RF from control lines

[Jim Lux]

At 05:36 AM 8/16/2005, Pete Smith wrote:
>I am dealing with some pesky rf in control lines to a remote antenna 
>switch.  I'm thinking that an RF choke in series and bypass cap to ground 
>on each line would help.  My question -- are .1 mfd and 100 uh appropriate 
>values for good performance down to 160 meters, or if not, what would be?
>
>73, Pete N4ZR



Of more interest might be what the properties of those capacitors and 
inductors are at HF frequencies.  I assume you're not using microwave 
chip-caps, for instance, so that 0.1 uF cap might well look very different 
at 14 MHz.

You might take a look at some commercial filter feedthroughs (like those 
from Spectrum Control).  If you can find them surplus, it might even be 
cheaper.  In any case, they have catalog data which you can use to evaluate 
them.