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RE: Antenna Mounting Masts / Poles Strength



Gary "Joe" Mayfield[SMTP:ka0yos@AMSAT.Org] asked (in part):

> I'm sure this will sound absolutely insane, but I am going to attempt to
> build a mast that sticks 20 feet above the ground with no guys.  On top
> of this mast I intend to mount a rotor, yagis for VHF and UHF, as well L
> band and S band antennas (some time in the future).  I hope to pin /
> hinge this mast so it will fold over allowing me to work on it near the
> ground.  The current plan is to install a pair of 10 ten foot masts in the
> ground and then mount the 20 footer between them.

You're not describing a mast, you're describing a tubular tower!  Either
that or you are insane (to you your word for it).  I'm gathering from your
description that you want to have the two 10 foot masts spaced a short
distance apart with a pivot pin between them at the top and that will pass
through 20 foot mast that's holding up the antennas.  The bottom of the 20
foot mast would be between the 10 foot masts just above the ground (and
pined there)  when it's all up.  To lower, pull the bottom pin and pivot the
20 foot mast over (likely with a winch).  Do I have the description right?

If that's what you're doing, it would need to be quite massive to have
decent stability.  Sorry I'm not a mechanical engineer so I can't tell you
really how massive.  I can tell you how my satellite antennas are mounted,
and that they move a lot more than I would like.  They will be moved to a
tower when I get it up later this spring (I hope).

What I am running currently is the KLM 22 element CP on 2M and 40 element CP
on 430 antenna pair mounted on a 10 foot crossarm through a Yaesu G-5500
El/Az rotor.  The rotor is mounted on the bottom 3 sections of a Radio Shack
4 section mast.  The mast lower section is sitting on (and pinned to) a post
sitting in concrete in the ground and is clamped to the roof overhang just
below the top of the bottom section.  The middle section is almost fully
extended and it is pinned to the bottom section a foot or so below the top
of the bottom section and it's clamped to the roof at about the midpoint
(about 14 feet above ground).  The top section is extended only 3 or 4 feet
above the top of the middle section and is pinned to the middle section near
the top of the middle section and near the bottom of the top section.  If
you followed the description right, the top section is mostly surrounded and
attached to the middle section and the top clamp is just below the bottom of
the third section.

I get nervous every time I'm outside watching the computer move the
antennas, and every time the wind blows real hard.

73
-------------------------
Jim Walls - K6CCC
k6ccc@amsat.org
http://home.earthlink.net/~k6ccc
Ofc:  626-302-8515    FAX:  626-302-9999
Res:  626-914-4641
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