During the 1980's we had a 120 foot, insulated base tower with an
appropriate radial system. I wanted to improve it's performance and increase
its
bandwidth. I also wanted to add an 11 foot conical monopole to our collection
of antennas.
With the help of friends, we mounted the 14 to 60 MHz conical monopole on
top of the tower. Then we "caged" the tower from top to bottom at 10 feet
in diameter using #12 wire and 10' PVC pipes as spreaders at three levels.
On 160 it was fed as a folded monopole with the tower grounded and it was
below 1.5 to 1 SWR for most all of the band. On 80 where it was voltage fed
as an insulated base, very fat half wave monopole, it was below 1.5 to 1 SWR
for nearly the entire band. The cage doubled the bandwidths.
IMHO, having also worked with using a "cage" as the gamma rod on grounded
towers in several cases, I would say the positive effects are worth the
trouble, Dan. It's hard to predict the results on your inverted "L" but I
would urge you to try it.
BTW, I had a remotely controlled tuner/matcher at the base of that big fat
vertical. It allowed us to switch configurations, tweak the capacitance
and inductance settings and either connect or disconnect the coax up to the
conical monopole on top. I wish we still had that set up.
73, Barry, W9UCW
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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