I built one right after the article appeared in QST. I live in
the country with no close neighbors and had practically no noise to begin
with. So I didn't notice a difference in reception, and I didn't keep it
long. At that time the only RX antenna I had was a 160M dipole a 50 feet.
This antenna should be very subject to feed system errors, surroundings, and
local noise sources. The reason this happens is this antenna "fights" the
earth reflection and itself with the small remainder the useful signal.
1.) The horizontal sections do not respond well because earth is cancelling
the primary response. There is very little horizontal component of electric
field, because earth shorts the horizontal component. The dominant allowed
horizontal response is straight up to the sky.
2.) The out of phase element coupling and close spacing cancels radiation at
all angles, but has the least cancellation along the horizon. This forces a
null in the highest response direction, straight up.
3.) What remains is an exceptionally low signal response between those two
nulls, the null along earth caused by earth conductivity and the null
straight up caused by out-of-phase elements.
The result is that a model, where the earth is ideally perfectly homogeneous
and the area is clear, shows an excellent local noise groundwave null. The
antenna, however, is so insensitive that any small errors have a large
effect on results. Many of these errors are beyond control of the builder,
because they would involve soil characteristics and coupling to anything
around the antenna.
When an antenna has very low response, it does not want to respond to any
signals, it becomes extremely sensitive to things that unbalance the system.
Its function is also dependent on local dominant noise propagating from
somewhat distant groundwave sources, because it nulls groundwave to get rid
of noise.
This is why there will always be a very mixed review of results, and why
having it work at one place does not mean it will work some other place even
when EXACTLY duplicated.
73 Tom
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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