Yeah, that's what I figure, too. I should have mentioned that even though
the rig is a mobile unit, I'm using it as a base station from my basement
suite, so the antenna doesn't need to be capable of being mounted on a
vehicle. Given that new piece of info, doesn't it make more sense for me to
make a simple, 2-wire dipole temporary antenna than a ground plane? Or are
there some reasons why ground plane antennas are better than dipoles?

Getting best performance (pattern) out of a 2-wire dipole usually
requires that you bring the feedline out in a perpendicular fashion
for some distance before you turn it in a downwards direction. This
may or may not be convenient.

You'll also need ways of tensioning or supporting the wires to keep
the dipole fairly straight and vertical, and this also may be somewhat
inconvenient. You'll either need to hang the upper wire from a
support above it, and hang a weight of some sort down below the bottom
wire to keep the antenna taut and keep it from swinging in the wind,
or use fiberglass rods or something like that to support the wires.
In either case, you'll have to have a non-metallic support structure,
and keep the antenna a reasonable distance away from any metal-bearing
portions of the structure (pipes, stucco walls containing chicken
wire, etc.).

A quarter-wave ground plane can be made quite simply from three to
five pieces of copper wire and an SO-239 connector. The
feedline comes down the bottom, and if the feedline is sufficiently
stiff you can probably support the whole antenna just by using plastic
tie-wraps to lash the feedline to a vent pipe on your roof and letting
the feedline bear the (very modest) weight of the antenna. You won't
need an overhead support, you won't need any sort of balun (loop or
otherwise).

The gain pattern of a center-fed half-wave vertical dipole, and a
quarter-wave monopole with two to four radials drooped downwards at 45
degrees, are very very similar. See

http://www.cebik.com/gp/58-2.html

and take a look at the second chart of the radiation patterns - it
compares a vertical dipole with two ground-plane antennas (horizontal
and drooped radials). "In practical terms, the low-angle lobes of
the dipole and the 45° sloping-radial monopole overlap, with the
90°-radial monopole slightly weaker."

So, basically, I think you'll get equivalent performance from a
monopole with a ground plane, and will find the mechanical
arrangements rather easier to manage.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
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