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[TowerTalk] 25 mtr. tower insulator

Subject: [TowerTalk] 25 mtr. tower insulator
From: Nick Pair <>
Date: Mon, 17 Jul 2006 10:05:05 -0700 (PDT)
List-post: <>
A quick suggestion, why insulate at all. You can shunt feed each tower and have 
the benefits of a DC grounded antenna. Adjusting the height and the spacing of 
the shunt arm along with a series capacitor will give you a perfect match at 
your favorite frequency. Multiple  shunt arms will give you several bands too. 
This also gets around the problem of calculating the top loading the antennas 
on top present. The top loading and your 25 mtr. towers will give you somewhere 
around a 3/8 electrical wave length radiator for each of your four square. This 
would make a great system where all elements are phase fed. If you chose to use 
the parasitic method it will require a bit more work to get reflectors to play 
right but still doable.
  If you are still set on insulated, the two methods I have seen are to put a 
taper to point  section on bottom with a commercial "keg" type insulator or two 
base on stubs out of base slab and one on bottom of tower assembly, 
with three or six smaller insulators between plates. 
  If you want to use a fix it and forget it type of series capacitor, I have 
several methods of doing this without a commercial assembly being required.
  Whatever you do, you will need insulated guys(i.e. philstrand or equal) or 
carefully broken up with insulators if conductive.
   Good luck, you have quite a project going there !

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