The real problem in the picture that you paint is that the break point
for center loading is just that, a structural weakness for something
as tall as 60-70 feet. The center loading is in the way for 80 meters.
Perhaps an 80 meter trap at the top of the pipe, continued on to the
top hat wires, made apparently longer by the inductive result of the
trap on 160. This arrangement involves no switching and is consistent
enough a result to be fed into the shack on coax and dealt with by a
tuner.
As always, any minor gains obtained by attention to trap/loading
loading placement will be utterly swamped by your success (or lack of
it) in the radial field.
For starting a new business it's location, location, location. For
success on 160 it's radials, radials, radials.
73, Guy.
On Fri, Jan 29, 2010 at 11:48 PM, Art Trampler <atrampler@att.net> wrote:
> I live on a fairly small lot and use a Hy-Gain AV640 for 40 through 10 and
> currently have no antenna for 80 or 160.
>
>
>
> My backyard is about 90 x 70 but has some ill-placed and ill-shaped trees
> for either wire antennas or a tower.
>
>
>
> So I am thinking of another vertical, but this one ¼ wave with a radial
> field. I would like to get 80 and 160 out of it. I don’t mind having to
> guy it, or even having to pour a concrete base for it.
>
>
>
> My first thought is to use aluminum irrigation pipe as others have, and have
> about 60 to 65 feet of it, an insulator and inductor and high voltage relay,
> and then perhaps 15 to 20 of much smaller aluminum tubing, with a sloping
> capacity hat of four wires going partially down the four top guys. I don’t
> know if I could get away from the relay, and put up a trap instead but am
> wary of using a true trap (coil & capacitor) rather than just a large, high
> Q coil.
>
>
>
> As you can see this idea is full of possibilities and mechanical drawbacks,
> so the question is, is there that much to gain from the center-loaded design
> with capacity hat, versus a switchable tuning network at the base of the
> antenna?
>
>
>
> Your input is appreciated. I am hoping to make this a summer project and
> reward myself with 80 and 160 in the winter.
>
>
>
> 73,
>
> Art
>
>
>
> Art Trampler, KØRO
>
>
>
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>
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