[Antennas] OCF Long-wire with movable feed point

[Joe Mayenschein]

This antenna was in a recent magazine less than I'd think two years ago, Built exactly as you describe
with the folded dipole setup and pully system. The author IIRC didn't talk much about radiation patterns
as much as it would match impedance's to any frequency. And he had one of the pulleys remotely motorized
from the shack.

Pretty cool idea I thought.

Joe

Terry O'Neill wrote:

> I was reading an old 73 Magazine, (May, 69')  when I saw an article
> discussing Off Center Fed longwires.  The article examines directivity
> pattern of a 3.5 wavelength longwire. Article shows how the radtiation
> pattern changes depending on where the feed line is placed along the
> length of the antenna to achieve a steerable pattern. This article was
> written before antenna modeling programs were invented and I assume the
> author's (W2EEY) results were experimental, although he doesn't say.
>
> Per the ARRL Antenna book, a 3.5 wl longwire has about 3db gain over a
> dipole.
>
> I have a long narrow lot with several tall trees where 3.5 wavelengths
> on 40 meters (about 475 feet @ 7.2mhz per the Antenna book) would be
> feasable.
>
> What if one was to erect a folded doublet, 455 long, fed with open wire
> to a  tuner ? Further, what if one were to arrange the wire of the
> folded doublet in a continuous loop around pulleys, so that you could
> move the feedpoint where you wanted it along the length of the doublet
> like this:
>
> xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>
> x
> x
> x    x
> x
> x
> x    x                     x
> x
> x    x
> xxxxxxxxxxxxxxxxxxxxxxxxxx
> xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>                          x            x
>
>                          x            x
>
>                          x            x
>
>                          x            x
>
>                          x            x
>
> The result should be a 3 dbd gain antenna (on 40) with steerable
> pattern. Further, on 20 meters, 455 feet is approximately 7 wl, which
> would theoretically yield about 5.5 dbd. The gain would increase with
> frequency to about 8 dbd @ 10 meters.
>
> Per the Antenna Book, take-off angle also decreases with wavelength, so
> it should be a good DX antenna.
>
> It would seem to be a cheap alternative to a beam if a person had the
> room.
>
> Has anyone built and or modeled this antenna? If so, I would be curious
> as to the results.
>
>  Match
>  Box
>
>  Rig
>
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