[TowerTalk] Feedline (choke) question

[Steve Harrison]

I've been using that technique to suspend coax since the mid-'60s, soon 
after I got my Novice. Never had one slip, but I've had cheap RG-58 coax 
pull apart right under the knot, and cheap RG-8 stretch enough to 
emulate RG-59!

Steve, K0XP


On 9/27/2025 10:43 AM, Jack Brindle via TowerTalk wrote:
> 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 at 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 at 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 at 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 at WorldLegacy.com
>>
>>
>>
>>
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