Re[2]: [TowerTalk] HF2-V Doorknob Capacitor Failures

[Bob Otto]

I'm not sure, but I believe RTV is a petroleum based product.  We used
to use it on aircraft engine to seal all kinds of things.  One thing I
do know, it has a shelf life, and cannot be shipped by air without
special permits (that's why I THINK it's petroleum based).  If I'm
right, this means it may not be the best product to use in your
application.

I've used the GE silicone material (clear, 50 year guarantee) you buy
at Home Depot, etc., for all kinds of projects and have never had a
moisture or UV failure. I used it to coat my cable connections and
they never leaked in years of use.  I also used it to seal the open
ends of the cable connections to my antennas. I've even used it to
coat the area between the bolt head and wire for grounds -- it
completely seals it and keeps the connection from corroding over time.
The stuff isn't cheap, and makes on ugly connection <G>, but it works
and has had no chemical or electrical impact on anything I've ever
used it on. It sticks to most anything, but is a bit difficult to get
off if you need to repair something. You darned near have to cut it
off with a knife. I've tried some other silicone products, but none
have worked nearly as well as the GE silicone material.

73's from.......

Bob Otto
N8NGA@one.net
Cincinnati, Ohio

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Friday, September 22, 2000, 9:08:28 PM, you wrote:


K> Hi Bill, there is another product similar to RTV in appearance and is
K> silicone based, but made especially for HV ( and I meanHHv) dielectric. I
K> used to have a 1 pound can of it somewhere, and if I can find it, will give
K> more detail. We used it to pot 15KV solid-state powersupplies. Meanwhile I
K> wonder what Q-Dope or Glyptol would do outside? I'll run a test this winter,
K> as I use Q-Dope on torroids so there is some handy.
K> I've always wondered about leaving that capacitor open to freeze-thaw cycles
K> too.
K> In my opinion, the HF2V is as good as a "multiband " vertical can get
K> otherwise.

Geo>>K0FF
K> ---Original Message-----
K> From: Bill Jackson <k9rz@radiks.net>
K> To: towertalk@contesting.com <towertalk@contesting.com>
K> Date: Friday, September 22, 2000 6:13 PM
K> Subject: [TowerTalk] HF2-V Doorknob Capacitor Failures


>>
>>Towertalkians,
>>
>>I have a Butternut HF2-V 80/40m vertical that has served me well for over
K> 10
>>years.  The only problem I have experienced is the periodic failure of the
K> 200
>>pF, 10 kV, door knob capacitor on the 80m coil assembly.  I have had to
K> replace
>>this cap about every 3 years or so.  The failure mode is usually rather
>>spectacular, occurring with a loud bang and pieces of the capacitor ending
K> up
>>several feet from the antenna. It appears that maybe moisture is getting
K> into
>>the capacitor causing a flash over which ends up destroying the cap.
>>
>>I have thought about using some type of sealer on the ends of the cap to
K> prevent
>>the moisture from getting in.  I am hesitant about this as I don't want to
>>affect the electrical characteristics of the cap.  Has anyone done this
K> before
>>with any success and if so, what type of sealer did you use?  Someone
K> suggested
>>using RTV, but having learned from towertalk about the acidic properties of
K> RTV
>>type sealant, this doesn't sound like a very good idea.
>>
>>Any thoughts?
>>
>>Thanks in advance.
>>
>>Bill - K9RZ
>>
>>
>>
>>--
>>FAQ on WWW:               http://www.contesting.com/FAQ/towertalk
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>>


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