Ted,
The inverted L will have some horizontally polarized radiation. The
other top loaded verticals should have only vertically polarized
radiation - assuming that the top loading is symmetrical, whether that
be a capacity hat or a T wire.
In general, the vertically polarized radiation will be at a lower angle
than horizontally polarized, but that all depends on the ground
conductivity and your radial system. A radial system of 64 radials is
good if your ground conductivity is decent, but if you are in an area
where ground conductivity is poor, you may have better luck with
horizontal antennas or an inverted Vee - the higher the better.
So the answer is "it all depends". If you do not have a wonderful
ground screen, a vertical may perform worse than a horizontal antenna
because a lot of your RF goes into "heating the worms".
73,
Don W3FPR
On 2/27/2017 6:13 PM, Dauer, Edward wrote:
A question that’s admittedly a bit OT – though if I need a pretext, the rig to
be used is a K3 . . .
I have been reading through the usual texts about vertical antennas for 80
meters, to replace the half wave dipole I now have and the Vee I had but didn’t
like. But I have not yet found the answer to one question I am thinking about:
The advantages or disadvantages of an inverted L compared to other variations
of the top-loaded vertical.
Assume a 40-foot ground-mounted vertical section made with wire running up a
fiberglass mast. There could be a remote tuner or balun at the base if it’s
needed. The top of the vertical section would be guyed with four lines more or
less parallel to the earth extending from the top tip of the vertical section
to four suitably located trees. That physical configuration offers three kinds
of options.
One is an inverted L. One of the four guy lines would be a wire making the L
and long enough to have the overall antenna resonate, with nonconductive line
from there to the tree. The other three guy lines would be nonconductive for
their entire length.
Another would be the classic top-loaded “T” vertical. Two opposing guy lines
would be equal-length wire out far enough to achieve resonance, with the other
two nonconductive for their entire length.
A third would be something closer to a capacity hat. All four of the guy lines
would start at the tip as wires, of equal length and just long enough to effect
resonance, with nonconductive rope from there to each of the four trees. This
variation might also have a square loop connecting the distal ends of the four
top wires.
If the goal is to have the highest efficiency and the lowest net radiation
angle, and if the height of the vertical section is fixed and the radial system
is the same for each choice, does it matter which of those three or four
options is chosen? And if it does, how come?
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