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Nomadic
HF Antennas:
The Screwdriver Antenna
and the Chevrolet P30-Based Motorhome |
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Editor's
note: This
is the first in a series of articles from Steve Crouch, NO7V,
about installing ham antennas on various vehicles. Subsequent
articles will cover a different motor home with a chassis that
is harder to get to, and also his Saturn. Pictues supplied
by Pete Rodabaugh, W7PR.
 or
those of you unfamiliar with the term, a screw-driver antenna
is simply a motorized coil tuning device using the motor from
an electric screwdriver to run the coil in and out of a metal
tube to change resonant frequency.
The P-30 chassis, used for many different brands of motorhome,
yields a fairly simple installation challenge since the frame
is exposed and thus accessible for cable installation.
For my BB3 screwdriver antenna installation, I used a standard
"L" clamp bracket attached to a rear ladder tube.
The top of the base tube should be at roof level so that as the
coil is raised, it will be above the roof. They can be
mounted on a bumper or the rear hitch but that would not be as
effective.
 he
1988 36' Shasta Roadmaster Class A motorhome I installed mine
on had a one-piece alumi-num roof so it made a great ground plane.
If yours doesn't, just make sure you have a solid connection
to the metal super- |
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A typical
mobile screwdriver antenna. The remote tuning lower section is
below, and a 5 foot top whip is above it. As it tunes lower in
frequency the lower section length |
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A view
of the internal resonator portion with the outer PVC tube removed.
The coil moves up and down in the outer tube when tuning down
or up frequency. The top whip is attached in this view, using
a quick disconnect. |
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