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[TowerTalk] Top Hat Switch

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Subject: [TowerTalk] Top Hat Switch
From: (Ford Peterson)
Date: Mon, 16 Jul 2001 19:15:56 -0500
I'm building a full sized, base fed (insulated), 80 meter vertical antenna.
The design I am playing with uses a top hat to tune the lower portion of 80.
Removing the top hat tunes about 3850 or so.  This arrangement will give me
access to all the band without reactive elements at the base of the tower.

I am looking for ideas.  The top hat is two pieces of 1/2" copper pipe cut
to 4' and mounted as an X shape.  I want to be able to switch this in and
out using a bias tee on the feedline.  The trouble is the switch.  I suspect
that there are substantial voltages at this point of the antenna (duh!) and
am concerned about flashover.  A latching relay would work best but I may
have to fabricate something in the shop to accomplish this.  Near as I can
figure, there is no such thing as a HP latching relay (MSC, Newark, etc.).

Perhaps I don't understand the problem.  The potential accross the switch is
the difference between the top of the radiator and the hat, which by itself
has very little capacitance.  Will any relay do in this mode?

I can't be re-inventing the wheel here.  Anybody else tried this?  What
worked for the switch?


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