nbr wrote in message . ..
On Sun, 27 Jul 2003 19:19:26 -0500, nbr
wrote:

I've put up an inverted-L, which consists of approx. 135' horizontal
leg, and approx. 70' vertical leg. I can shorten the overall length of
the antenna, but cannot lengthen it. There are about 4 ground rods
within about 10' of the base ofthe vertical element, plus about 25
square feet of chickenn wire to serve as a ground plane. I can feed
the antenna right at ground level, or can arrange to feed it up to
6-10' above ground. There is about 120' of buried coax to the shack,
which must feed this antenna. I'd like to use this inverted-L on
160-10M (will settle for 80-10M).
1) How to feed the antenna and be able to run legal limit, all bands?
Current or voltage balun? Won't a balun disspiate power and decrease
efficiency? WIll a balun at ground level increase ground losses?
2) How is the inverted-L said to be a vertically polarized antenna,
when a major portion of its radiating element is horizontal?
3) For Field Day we added another vertical leg to this antenna to make
it into a half-square, and had decent results on 40M/20M. How is the
half-square described as "two verticals in phase", when again, there
is a major part of the antenna (the so-called "phasing element") which
is horizontal?
Thanks and 73
Dan (K0DAN)


Thanks for the recent comments on my previous post. They have been
interesting and informative.

The "antenna voodoo" is still bothering me about the theory of some of
these antennas (e.g. inverted-L, half-square, etc.). I understand that
the horizontal leg of the "L" is considered an "inductor at the top of
the vertical" element, but why not the reverse?

Myself, I tend to consider it capacitance rather than inductance. IE:
one leg of a top hat.

Why is this not a
"bent horizontal" with segments which radiate both in the horizontal
and vertical planes?

In a way it is, but the vertical radiation overshadows the horizontal
when using a 1/4 wave long inv L. Maximum current is at the base if
you are feeding it at the base. The thing with your antenna is it's
longer than a 1/4 wave on even 160 meters. So you will have more
radiation from the horizontal wire than you would a shorter antenna.
But on some bands, this may not be a bad thing. To run on 160m with
power, it's fairly simple. Use a big variable cap in series at the
base to tune out the reactance. The match should be usable. And the
antenna will work well for mid range use. Better close in than the 1/4
wave L. The max current point is well up the vertical part from the
base, and ground losses are reduced. But it might not be as simple on
the other bands. You almost need a tuner at the base. A simple L
network should do the job. It would be much simpler for all band use
if you had a 135 ft center fed dipole fed with ladder line to a tuner
in the shack. The overall performance on most bands would be better.
If your run of coax to the antenna were real short, and you used good
fat coax, you could tune the L with a good tuner at the shack and have
a usable signal. But I think you said you had 120 ft. Thats a bit long
for very high SWR use. And being it's buried, the expected likely
common mode currents that could be usefully radiated, will be wasted
heating earthworms...:/ MK