Hi Steve,
You originally expressed interest in 80 meter antennas so I'm going to
address that in the context of vertical dipoles. Firstly, you left
out some information that matters: How high are your trees? What is
your soil composition? Is it sand? Rocks? Clay? Or black topsoil?
A true vertical dipole will be too tall unless you have a tall tower
or tall trees to hang it off of. Of course anything full sized is
superior to a physically small antenna using coils, stubs, linear
loading with one exception: top capacitive loading. If you have no
way to hang a dipole vertically then I recommend something along the
lines of a monopole with a counterpoise such as my 65 foot vertical.
It is made with fifty feet of 3 inch o.d. tube 1/8 inch wall and a 15
foot aluminum stinger on top. There's one set of guys at 30 feet. It
has to be fed with a ground system of radials, but if you can elevate
yours, or a wire, you can have a sloping counterpoise of just a few
radials that are equal in length and spaced equally from each other.
Think of this as a geometrically modified vertical dipole. The
bottom of the vertical for 80 m. should be at least 20 feet off the
ground. You can lower the height of the driven element by using a
wire or tube capacitance hat. Any of these can be fed with coax and
matched with a L network.
For higher bands I advise studying the vertical dipoles at WWVH and
WWV. They use tower dipoles and sets of sloping wires extending down
and out from the feed points to make the bottom half of their vertical
dipoles simulated cones. You can do something similar without using
towers.
73
Rob
K5UJ
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