To: <towertalk@contesting.com>
> Date: Mon, 27 Apr 1998 16:29:26 -0500
Hi Lee,
> What are your dipole secrets? The dipole is one of the simplest antennas in
> ham radio. What are your secrets of putting up, tuning, pruning and
> operating from a dipole. Now, don't laugh. I bet there are some pretty
> good comments out there.
No secret, they all work well if you don't stick them in a mess of
other wires..I find they work well even when in droopy V fashion. (An
Inverted V is really a half-Rhombic turned on its side, with the
earth forming the other half. Somehow we started calling droopy
dipoles Invereted V's.)
I've found dipoles and droopy dipoles play much better for DX at 5/8
wl mean height than 1/2 wl, because the pattern is more compressed
and the gain much higher at useful DX takeoff angles.
The ground below the antenna affects performance, and wires parallel
to the antenna help with efficiency (especially if the antenna
height is low).
Thicker elements (especially on the outer end of the element)
provide more bandwidth, and I always use a choke balun. I make the
elements "look thick" by using two thinner wires fanned out a few
feet at the open ends, like a bow tie.
I have an 80 meter dipole (droopy dipole) on my 200 ft 160 meter
tower, and A=B it against a 70 ft vertical. With the dipole at 110 ft
or so there isn't much difference between them in the dipoles
favored direction. When the dipole is at 180 ft it's a few dB better.
> For instance...(Red Herring across the path) what about those guys who
> insist that you must have a half-wave or a multiple thereof of coax on the
> dipole to make it an effective radiator?
Of course the stuff about feedlines needing be a certain length is
non-sense with coaxial or other matched lines.
> Or, how do you get bandwidth on a dipole?
Make it thicker, especially at the ends where the antenna terminates
the E-field.
73, Tom W8JI
w8ji.tom@MCIONE.com
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