Towertalk
[Top] [All Lists]

Re: [TowerTalk] Feedline (choke) question

To: Rob Katz <rob.katz@worldlegacy.com>
Subject: Re: [TowerTalk] Feedline (choke) question
From: Jack Brindle via TowerTalk <towertalk@contesting.com>
Reply-to: Jack Brindle <jackbrindle@me.com>
Date: Sat, 27 Sep 2025 12:43:56 -0500
List-post: <mailto:towertalk@contesting.com>
That is worth trying. Very interesting web site as well - lots of info about 
knots.

Thanks!
73,
Jack, W6FB

> On Sep 27, 2025, at 10:29 AM, Rob Katz <rob.katz@worldlegacy.com> wrote:
> 
> Jack,
> 
> Here’s an alternative to severing your coax to install a Kellum grip.  You 
> can use some rope with a whipping knot to provide the same function as a grip 
> (I use 3/16” black Dacron rope).  I’ve used these knots for decades on 50-75’ 
> of BuryFlex and hardline hanging down to the ground, with no slipping at all. 
>  I’m careful to lay the wraps as tightly as possible, and then the weight of 
> the coax provides the final tightening of the knot.
> 
> https://www.netknots.com/rope_knots/common-whipping
> 
> 73,
>    Rob K4OV
> 
> On Sept 26, 2025, at 5:21 PM, Jack Brindle <jackbrindle@me.com> wrote:
> Brian;
> 
> Last spring I replaced the coax on my A3S-JK with a new (and longer) length 
> of 
> Bury-Flex. I did a great job of soldering on the PL-259s.  It wasn’t until I 
> had it connected to the choke and fully wx sealed that I realized I forgot to 
> install the Kellum Grip. I have spent quite a while trying to figure out how 
> to 
> slide one over the PL-259 to no avail. I will shortly go out to the tower 
> base, 
> cut off the bottom PL-259, slide on the Kellum Grip, then re-install a new 
> PL-259. But not in 95+ degree heat we are still having.
> 
> I have found that the one antenna type that absolutely must have a choke is a 
> vertical. Without it the coax will provide a return for the current (no 
> matter 
> how many radials) and give all sorts of problems. If I were to put one of 
> those 
> up (K9YC-style with tall trees holding up the antenna at over 100 feet), and 
> forgot to add the choke, I guarantee that I would be out winding the coax 
> (with 
> installed PL-259) through the toroid to get the results I need. Jim’s method 
> of 
> installing verticals is to use a single piece of coax, remove the jacket and 
> shield for 1/4-wave to form the top portion of a dipole, then add a choke 
> 1/4-wave down from the “feed” point. No connectors needed until it gets down 
> to 
> the shack entry. Large toroids are very useful here. Having said that, I am 
> pretty sure Jim placed connectors at the lower end of the dipole.
> 
> But, I wonder, how important is it to have a choke at every current node? 
> Having one at the antenna feed is important, and perhaps at the shack entry 
> point. But does the modeling really show that we need them in-between?
> 
> 73,
> Jack, W6FB
> 
> 
> > On Sep 26, 2025, at 4:08 PM, Brian Beezley <k6sti@att.net> wrote:
> > 
> > "Why sever the connector? If we are talking about RG-213 size coax, that is 
> > .405 inches in diameter."
> > 
> > 
> > Sever the coax. I assumed the desired spot was far from the shack and it 
> > would be too much trouble to fetch the end of the coax and then wind the 
> > whole length several times through a large core. But maybe not! And maybe 
> > installing connectors isn't that much trouble for someone good at it (I'm 
> > not). I'd just want to be sure I had the right spot first.
> > 
> > A quick model of the two-wire current shunt didn't look that promising, at 
> > least for the initial geometry I picked. I'm not sure the idea is worth 
> > pursuing.
> > 
> > Brian
> > 
> > _______________________________________________
> > 
> 
> - -
> <WorldLegacy logo swooshes 25%.png>
> Rob Katz, Director
> rob.katz@WorldLegacy.com
> 
> 
> 
> 

_______________________________________________



_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
<Prev in Thread] Current Thread [Next in Thread>