At 03:16 PM 3/29/05, you wrote:
>--- N�ATH <[EMAIL PROTECTED]> wrote:
> >
> > Not quite on topic - But I can send any one who
> > would like it a picture of a Rohn 25
> > with the top neck twisted out of it because of such
> > an antenna mounted on the top neck.
> > Please mount these on one of the top legs or if
> > center mounting, mount on a piece of
> > pipe that is stabilized mechanically further down
> > inside the tower so that the top neck
> > can not flex as it will come out - sooner or later.
> > These antennas don't work very well
> > hanging beside the tower by the feedline. And they
> > don't hang there very long either.
> > This picture is at 110 foot - Sheriffs installation
> > by professionals'
> >
>I don't have any pix but we had one twist off about 20
>years ago. It was a 4 bay dipole antenna for 146 mhz.
>It was on top of a 100 foot tower and a hill about 400
>feet haat. Replaced it with a station master.
>Getting ready to replace the SM with another dipole
>aray. Thinking of mounting it where the bottom of the
>antenna is about 10 feet below the top of the tower
>and putting a bracket at the top. This will leave
>about 10 feet sticking out of the top of the tower.
>
>Probably will set the lower dipole and the next one up
>at tight angles to the tower, one in each direction
>and the two at the top at right angles to thoes.
>Hopefully this will give up an omni directional
>patern.
Years ago I saw a weird situation - a pair of 4-bays
on opposite sides of the tower, fed by a KLM 2-port
power splitter. Later at a different site I saw a custom
pattern engineered with a 4-port splitter and 4 beam
antennas.
How they kept them from interacting and screwing up
the pattern I'll never know...
In your case you might be able to mount the dipoles
to the tower leg itself, perhaps with some magic
distances to get an omni pattern. This would leave
the top of the tower bare ... let the tower itself be
the lightning rod.
I'd measure the tower face and make up a drawing
showing the 4 sides (or 3 sides?) of the tower, and
your mounting concept. Then contact the engineer
at the antenna company (via email or phone) and fax
the drawing to him and get his ideas.
Mike WA6ILQ
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