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.
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