[TowerTalk] Feed Point Choke Question

[Jim Brown]

On 11/7/2020 11:04 AM, Tom Osborne Sr. wrote:
> One thing I have wondered.  I saw sometime back, that taping the coil of
> coax to the boom of the antenna hurts the function of the coil.  Is it
> better to just let the coil hang down, maybe from a line or something,
> instead of taping it to the boom?  73

Hi Tom,

First, a coil of coax with no ferrite core is a lousy choke. Second, 
yes, capacitive coupling between the coax and the boom on both sides of 
the choke de-tunes and defeats the choke. There's a photo in 
http://k9yc.com/ChokesVHF.pdf showing what I asked Hector, XE2K, to do 
when he rigged my new 6M antenna. There are two half-sections of PVC 
conduit between the chokes and the boom. The coax is a very low loss 
PTFE version deigned for use in plenums. He developed a different method 
to rig the choke on my SteppIR.

73, Jim K9YC