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 it...it
resonates at 7.100...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?
73
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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