What's going to keep the snow off the top hat / switch /
top of vertical?
You really don't need a roller inductor at the base, just
switch a fixed inductor (which you pretune). If you don't
like inductive loading, tune the vertical for 80M CW and
switch in a fixed series capacitor for the SSB portion of
the band.
Tom N4KG
On Wed, 18 Jul 2001 21:54:22 -0500 "Ford Peterson" <ford@cmgate.com>
writes:
>
> 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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