[TowerTalk] waterproofing big #31 clamp-on choke

[Jim Brown]

Hi Dave,

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. For 
a permanent installation, I strongly recommend a stack of toroids rather 
than a clamp-on. Also, for low to medium power (up to about 500W), 
consider one of the bifilar chokes.

73, Jim K9YC

On 6/29/2017 10:30 AM, Dave Clemons wrote:
> I have read Jim Brown's RFI-Ham.pdf (K9YC.com).  In chapter 7 ("K9YC's 
> Choke Cookbook") he gives specifications for number of coax turns 
> using a big #31 ferrite clamp-on.  I have built one of these, and it 
> will be installed at the feed point of a 40m sloper.  Has anyone done 
> this, and if so, how did you waterproof the clamp-on? I would imagine 
> that ice will pretty quickly destroy the ferrite clamp-on.  I would 
> prefer not to have to use an enclosure due to the added weight it will 
> bring to the sloper.  I think that the expandable urethane based spray 
> foam sold in hardware stores, and used on RVs as well might be my best 
> bet, but I'd like to hear if others have tackled this problem.