The many thousands KVs developed at the edge of a vertical aren't
manageable other than with a big glass or porcelain insulator and a
knife contactor, just likewise it's used to sectionalize along high
voltage power lines.
To me, the phisical hat removal doesn't appear as a practical and
easily manageable solution.
73,
Mauri I4JMY
> ---------- Initial message -----------
>
> From : owner-towertalk@contesting.com
> To : <towertalk@contesting.com>
> Cc :
> Date : Wed, 18 Jul 2001 21:54:22 -0500
> Subject : [TowerTalk] Top Hat Switch (mercury)
>
>
> Many people have responded to my previous post. All responses were
quite
> valid and appreciated--thank you. The consensus was to simply cut it
for 75
> meters and base load it with a variable inductor arrangement (or
variations
> on that theme).
>
> My quest for a top hat switch continues. Why? Because the thing
models
> like it will play great!
>
> I'm building an 80/40 open sleeve vertical. It will tune all of 40
at < 1.6
> or so. It will tune all of 80 / 75 if I can get this hat on and off
the
> tower. The base loading is the most commonly used and possibly the
easiest
> to fabricate. I live in Minnesota and the base will be 5' or 6'
under the
> snow in just 6 months. Making a tunable roller inductor arrangement
that
> will work in this environment is no simple task either...
>
> How about this option....
>
> Mount a mercury tip switch at the top of the tower in a box on a cam-
like
> rotary arrangement (still designing that) and activate a latching
> arrangement using some 1/8" Stainless cable running up the middle of
the
> pipe from the base of the tower. I have these little 12 v solinoids
that
> will pull several pounds about 1/2". These are details I will work
out in
> the shop. My question is, have I simply created a very complicated
> mercury vapor lamp?
>
> The mercury switch is a vacuum. The leads are about 1/4" apart as
they
> escape the envelope. At 21 volts per thousanth of an inch (handbook
#), a
> 1/4" gap should handle many KV. (I only run 1KW max here at this
time ~~
> 3KV). I know nothing about the conductivity of mercury. For all I
know it
> will explode in this environment! A buddy of mine said "Hook it up
and
> watch it. If it looks like a strobe light mounted on your tower, you
better
> shut it down."
>
> I think I can master the mechanical stuff. What about the switch?
Anybody
> venture a guess as to how it will behave to RF as a top hat switch on
my 1/4
> wave monopole?
>
> Ford-N0FP
> ford@cmgate.com
>
>
>
>
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>
List Sponsor: Are you thinking about installing a tower this summer? Call us
for information on our fabulous Trylon Titan self-supporting towers - up to
96-feet for less than $2000! at 888-833-3104 <A
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