[TowerTalk] feedpoint choke for inv L

[john at kk9a.com]

Since I do not have the equipment or expertise to check if a choke is
necessary, I simply wrapped 75 ohm Teflon coax around a few ferrites at my
vertical feed points. This was inexpensive and necessary or not, I have no
feedline radiation concerns.

John KK9A
 

To:	towertalk at contesting.com
Date:	Tue, 20 Nov 2018 05:15:30 -0700

I agree, especially with the last sentence.

Wes  N7WS

On 11/20/2018 4:10 AM, Rob Atkinson wrote:
If the ground system is at or below grade, you don't need a choke.  If
you find you do need one then that means you don't have enough radials
down.  This is an example of ham antenna work where it is useful to
take a look at medium wave broadcast instead of re-inventing the
wheel.  Broadcasters do not have chokes on their feedlines.  That's
because they have a lot of radials and the feedline is (nowadays) coax
under ground.  But even if your feedline is laying on the ground you
can avoid having to fool with a choke provided you have enough
radials, so that the return current to the feedpoint is divided so
much that whatever is on the feedline is insignificant.  And, you need
plenty of radials anyway, if you want to have a decent antenna.  Put
down at least 60 radials and see if you have a problem with RF on your
coax....probably not enough to matter.   Hams are ferrite choke and
balun crazy...use them in many cases where they aren't needed....

73

Rob
K5UJ