[TowerTalk] Folded dipole
WA3GIN
wa3gin at comcast.net
Tue Aug 25 15:45:50 PDT 2009
OK,
I don't use EZNEC...I guess its too EZ.
I have installed a NVIS 40m dipole at 15ft above the sandy loam soil where
I live. I also have a 40m dipole aboutg 300ft away at 65ft and also a 1/4
wave cage vertical on 40m.
Back in the old days when we had sun spots tand conditions that supported
high angle radiation the NVIS would blow away the dipole at 65ft anywhere
within 0-250 miles. Out past 400 miles the dipole was the clear winner in
comparison testing and held that lead out to about 1500-2000 miles when the
ground mounted cage vertical on 40m then started to pull ahead of the dipole
at 65ft. As the sun spot cycle continued to decline the usefulness of the
NVIS has become less and less. I guess the signals just go straight up and
not much signal gets reflected back. Seems like if you till the take-off
angle a bit more signal gets reflected.
I wonder if EZNEC has a parameter to simulate the conditions of the
inonousphere? Seems that might be a really useful element to the equation
for folks that prefer to model antennas before the build them and play with
them.
Just my subjective opinion and experience of one.
73,
dave
wa3gin
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These days however the conditions do not favor an NVIS on 40m....
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