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
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
HREF="http://www.ChampionRadio.com";>
www.ChampionRadio.com</A>
-----
FAQ on WWW: http://www.contesting.com/FAQ/towertalk
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
|