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Re: [TowerTalk] waterproofing big #31 clamp-on choke

Subject: Re: [TowerTalk] waterproofing big #31 clamp-on choke
From: Jim Brown <>
Date: Thu, 29 Jun 2017 13:44:32 -0700
List-post: <>

Thanks for the report. Perhaps your failure was due to moisture trapped within the tape. I've always recommended NOT enclosing the cores, but primarily for reasons of improved dissipation. FWIW, I've never heard of a big multi-core choke overheating on a resonant antenna that isn't badly unbalanced. I HAVE fried a single core bifilar choke under very high duty cycle, legal limit operation that didn't have a second coax choke farther down the line, and another on a dipole that had broken in a storm -- I transmitted high power to it before I realized that. That experience caused me to de-rate those single-core bifilar chokes to about 500W, and to urge the use of a second choke for legal limit. That recommendation is in the latest version of, updated about a year ago.

Having spent 42 years in Chicago and prior years in OH and WV, I fully appreciate issues with cold WX. I would greatly appreciate feedback from those with experience, both positive and negative, with the chokes I've recommended. Please DO include details of the antenna system -- type of antenna (resonant dipole, beam, vertical), feedline used, where the choke was placed, details of the choke, and any of other chokes in the line.

73, Jim K9YC

On 6/29/2017 1:03 PM, Tom Frenaye wrote:
At 01:50 PM 6/29/2017, Jim Brown wrote:
Since I first published this work around 2007, I've yet to receive word of 
problems from moisture, except a single report of cracking from freeze/thaw 
with multiple cores. That's only one report in 9 years.
Jim -

Add me to the list, I've had cores disintegrate over the years.  I use several 
them at the base of my 80 and 160 4-square verticals, wrapped in electrical 
tape to hold them together.   The problem could have been freeze/thaw cycles, 
or heating when one of the verticals detunes when it breaks and I didn't notice 
the problem on the shack end.

I suspect those of us in ice/snow country see it more often than the San Jose 
area does...   Haven't found a good solution yet, I have trouble imaging that 
the addition of a box and associated connectors, caulking and hardware will be 
more reliable over time.

     -- Tom

e-mail:    YCCC  -->
Tom Frenaye, K1KI, P O Box J, West Suffield CT 06093 Phone: 860-668-5444


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