Topband: Caged Inv-L - Pros and Cons ? (Dan Bookwalter)

[W9UCW at aol.com]

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