[TowerTalk] ferrite clip-ons & OCF dipoles

[Jim Jarvis]

OK...this to some degree repeats a thread from two years
ago, but I'm looking for validation of my thinking on
feedline treatment for an Off Center Fed dipole...in this
case known as a Carolina Windom.  I'll skip antenna details.
Suffice it to say that there is current on the outside of
the feedline, which is problematic at high power.

The antenna is intended for quick-deploy, quick removal,
for portable, emergency or relocation purposes. Within reason,
absolute efficiency is secondary to easy of installation.
In the intended application, the budget is ONE wire, and even
open wire line has too big a visible cross section to be tolerable.
i.e. you can't change the conditions.

In the typical installation, the antenna is 50-75' in the air. Coax runs
vertically to ground, where the shield ties to a ground rod.  Added rg213
runs on ground, to the point of house entrance, where another ground rod
is used, before the entry.

I have ample inventory of type 73 ferrite clip ons, for both 1/4 and 1/2"
coax.
(legend: "=" is a ferrite, "-" is coax, G is ground rod)

That should set the stage.  So...here's the question:

In the past I've done this:

ANT --------======G======----------------------======G======---stn

This worked ok, but it seems to me it would be more effective if it were:

ANT  --------------G============---------------G============---stn

That is,  let current on the outside of the coax go to ground without
attenuation...and use those ferrites on the downstream side.  (Although
the system worked, I never measured temperatures on the respective ferrite
groupings after key-down @ 1kw.)

Your thoughts?  Please restrict comments to the ferrite choke topic.
Tnx.

n2ea
jimjarvis at ieee.org