i guess you can "borrow" it from any commercial antennna - like
Cushcruft or Hustler, whoever makes an antenna for 80-40.
On 3/17/07, Rudy Bakalov <r_bakalov@yahoo.com> wrote:
> I have been wondering the same. Is it possible to use commercial traps (or
> homemade for that matter) to disconnect parts of the antenna that are not
> needed for the other bands?
>
> For example, build a T, where the vertical part is 1/4 for 40 m. and the
> horizontal part, which acts as a hat on 80 m, is connected to the vertical
> via a trap for 40 m. On 40 m, the trap will "disconnected" the hat and the
> antenna will act as a normal vertical, while on 80 m the trap will "connect"
> the horizontal part and load the vertical properly for 80 m.
>
> Rudy N2WQ
>
> Alex Malyava <alex.k2bb@gmail.com> wrote:
> there are a few things you can do.
> 1 - use 2-4 wires top hat which is connected through 7MHz LC-filter
> 2 - put a top hat and use remotely controlled matching network to
> switch the bands and match antenna's impedance on each band to 1:1
> 3 - same as #2, more complex matching network which needs no remote
> switching, but you spend some time fine tuning it.
> 4 - same as #2, but choosing properly height of the mast and
> number/length of hat wires you may get an antenna which you can feed
> through simple serial LC network.
>
> I am building 160-80-40 60 feet high vertical using the option #2.
>
> #2 can be found at http://dl2kq.de/ant/3-1.htm. that page is in
> russian, am not sure whether DL2KQ has english version of it, but you
> can look at pictures/schematics.
>
> #3 - bottom part of http://dl2kq.de/ant/kniga/5151.htm
> page, has 80-40 antenna.
>
> #4 - http://dl2kq.de/ant/3-29.htm
>
> On 3/17/07, 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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