In article ml50d.17720$aW5.7105@fed1read07,
"Craig Buck" wrote:

With linear loading, you can get up a lot of wire in a small space. Take a
look at
http://hamgate.sunyerie.edu/~larc/su...inverted_v.htm for
an example of a 160 meter inverted vee in a 40 foot yard!

If you want multi band operation, put up as much wire as you can and feed it
with ladder line to a 1:1 balun to a short piece of coax to a tuner.

Feed it at the top so the maximum current is up high.

If an inverted L works for your lot, try feeding it at the top middle
instead of the bottom end and using the linear loading technique to make
each leg longer. According to Cebik if you can get 3/8s wavelength, you are
very close to the full performance of a half wave. Feeding at the top
middle does not require a radial field to work.
--
Radio K4ia
Craig "Buck"
Fredericksburg, VA USA
FISTS 6702 cc 788 Diamond 64
[snip]

Some nice suggestions, there, especially the point about keeping the
maximum current area of the antenna as high as possible.

The antenna can be end-fed (high impedance), off-center fed (moderate
impedance) and center-fed (low impedance). With a good antenna tuner, I
don't s'pose it much matters about impedance, as long as the varying
amounts fall within the tuner's range.

It was a revelation to me to realize that a half-wave length of wire
doesn't really care where it is fed: end, off-center, or mid-point. The
high-current portion will be in the middle and the high-voltage points
will be at the ends, regardless of where the feed point is located, as
long as the wire is resonant at the operating frequency.

Linear loading is effective, but as more wire is tightly folded back
from the ends, the more narrow the 'bandwidth' becomes, limiting the
tuneable range. This would also pretty much kill the multi-band utility
of the antenna.

I use a 130-foot ladderline fed dipole, center-fed. In a location like
yours, I'd keep as much of the center portion of the antenna as high and
level as possible, and then at each far end I'd fold them down and to
the side, and then back along the fence toward to the center as far as
needed, clipping the wire to stand-off insulators and keeping them up
out of reach of curious fingers. The radiation from the end portions is
less, and is a practical compromise for 80 meters and up.

For 160 meter operation, I use "clip on" extensions that run along my
perimeter fence on both sides, and they make a sort of "Z" in respect to
the main antenna. This works very well, letting the center part of the
dipole radiate up high, while providing enough physical wavelength to
allow tuning.

All of this is a compromise, of course, but it's practical and effective.

I suspect that the performance of the "all band" antenna is somewhat
less effective on 20 meters up .. but this is a much more approachable
situation. I've acquired an end-fed trapped half-wave vertical for 20
thru 10 meters that is only 17 feet in length. I plan to mount it on a
mast alongside the house. I suspect that the radiation pattern on 20
meters and up from this "vertical halfwave" will be much more evenly
distributed and predictable than the multi-node variations of the
tuneable dipole. Between the two antennas, one should be pretty well
covered, given the space restrictions.

Gray K7VGW

--
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"Those who figure that freedom is maintained by putting a .50 caliber slug
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