Hello All,
I have had very good success building end-fed, 1/2-wave verticals (zepps)
from wire and ladderline. They are, essentially, j-pole antennas. The
radiator is cut for 1/2 wave from a piece of 14 gauge copper wire. The 1/4
wave matching stub is simply a section of ladderline, shorted at the bottom,
with one of its upper ends attached to the radiator. The resulting,
composite wire structure forms the "J", with an overall length slightly
shorter than 3/4 wave.
A 50 ohm feed point can usually be found near the bottom of the stub. Add
a several-turn choke balun, an insulator, a rope, and single, high tree limb
(or sky-rope between trees with a pulley), and you will be very pleasantly
surprised.
I have constructed one for 10m, and one for 20m. I worked many countries
with the 20m version. I can provide construction dimensions for those
interested. There's no argument about the nice pattern from a vertical 1/2
wave, even if it does "radiate equally poorly in all directions"! <*grin*>.
These are the easiest antennas to put up if you have trees. A single rope
pulls them up in the air. No *RADIALS* required! In comparison tests with a
160m dipole up 55 feet, the zepps, at approximately the same height, were
consistently as good or within a few db of the dipole, and sometimes, better
(the dipole's patern is spikey on 10m).
The 1/4 wave matching stub doesn't have to hang vertically in line below
the radiator. It can come off sideways to conserve overall height.
I have found that these zepps can be used with a tuner at frequencies below
that band they are cut for, but not above. The 10m zepp worked pretty well
on 12 and 15, but the 20m one didn't. They will also detune slightly (lower
resonant frequency) in wet weather.
Ok, grab your wire, and smoke some solder! Have fun!
--... Mark - N1LO...--
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