I just converted a 40 meter aluminum vertical (33') to an 80 meter
vertical. I attached about 33 feet of #12 wire to the top of the
aluminum whip, and then hoisted the wire over the top of a nearby
60' tree. I had to trim it a few times to get it right where I
wanted it. With a good choke balun on the feedline, and (currently)
about 32 radials, the antenna is now starting to play. I'm getting
more QSOs out of this piece of aluminum on 80 meters than I ever
got out of it on 40 meters.
73
-Kirk K4RO
On Sat, Mar 17, 2007 at 10:18:28AM -0700, Lee Buller wrote:
>
> 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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