W8JI:
>As the antenna is lowered, efficiency takes a big hit and
signal levels at all angles decrease.
Tom, when I decided to put up a high-angle
antenna to complement my 160 vertical, I modeled
a droopy dipole (or large included-angle inverted-V)
over average ground. The optimum height for gain
at 90 degrees TOA was ~100' on 160, or a bit less than
1/4 wavelength. As you lowered the antenna from that
height, gain dropped due to ground losses. As you
raised the antenna above 1/4 wl, the high-angle lobe
began to squash as a new low angle lobe increased.
Like a lot of stuff I see these days, someone
dreams up a fancy name (NVIS) for something that has
been around for eons (i.e. a cloud-warmer antenna).
I bet the Army paid some consulting firm megabucks
for dreaming up the name NVIS. My favorite example is
ADD/ADHD for simple misbehavior. Of course it takes
a PhD in Education to dream up those new terms! ;-)
Little wonder our schools are dumbing down while we
spend their resources for such nonsense.
73, Bill W4ZV
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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