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[TowerTalk] 40 meter vertical to 80 meters.

To: TowerTalk Reflector <>
Subject: [TowerTalk] 40 meter vertical to 80 meters.
From: Lee Buller <>
Date: Sat, 17 Mar 2007 10:18:28 -0700 (PDT)
List-post: <>
  Ladies and Gents,,,
  Last year, I build a homebrew 1/4 wave verticle and mounted it on the ground 
with 16 radials underneath it.  I am in the process of adding 16 more radials.  
The antenna is made out of aluminum tubing starting with and 1" 1/4 and going 
down to 3/4".  The length is 32 feet and with 16 radials under 
resonates at least it is flat there...and the MFJ 259 says it has 
imdedance of 55 ohms...R=53-55, X=3-6, Theta is 10 degress,  Works good too.
  What I want to figure out is how to had a "top-hat" to the antenna to bring 
it down to 80 meters.  I know that the MFJ brand of verticals uses a top hat 
loading scheme and I wonder how you calculate or figure out the capacitance one 
would need to build something like this?  Or, is it trial and error?
  In addition, the top of the antenna is fairly small tubing (I am afraid I 
will bend it with to much weight or load) and I need to come down on the 
antenna about 8 feet to install the top hat.  I guess one would have to use 
trial and error to find the right combination of "spokes and Lenghts" to make 
the capacitance hat.  Looking at the Handbook, it does not really have a 
"formula" for such things.
  Anyone have any insite?  Give me a starting point?
  Lee - K0WA

In our day and age it seems that Common Sense is in short supply.  If you don't 
have any Common Sense - get some Common Sense and use it.  If you can't find 
any Common Sense, ask for help from somebody who has some Common Sense.  Is 
Common Sense devine?

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