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Rotating Tower

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Subject: Rotating Tower
From: (David & Barbara Leeson)
Date: Wed, 12 Jun 96 19:56 EST
I have one RTS rotating tower and one with a TIC ring rotator.  I'm
satisfied with both.

Re the RTS setup, I would recommend using at least two ring bearings
(my setup has only one above the rotator, and it would fall if one guy
failed - however, it has survivied 134 mi/h fastest mile winds).  I
plan to switch to double guys on the ring bearing.  If you order the
RTS setup, you might want to see if you can talk Dick into drilling
drain holes in the tower leg stubs in the base bearing, so the legs
can drain more easily than just hoping they will drain at the circum-
ference of the stubs.  Otherwise all first class.

As a practical matter, there is a good-news/bad-news element of the
rotating tower choice.  The antennas are always in the same relative
position to each other, so you don't get odd effects of resonant booms
or the like when antennas are in different directions.  On the other
hand, most contesters find they benefit more from being able to "spray"
in two directions at once, and the rotating tower doesn't do this readily.

If you go the RTS route, I would give serious consideration to putting the
rotator at the ground level, even though that adds to the cost of the
ring bearings.  This gives you guying redundancy, so you can sleep at
night.  There's no question about the generous engineering margins on
the ring bearings, but they are really heavy to wrestle on the tower
and tough to climb around or stand in when working.  As a last caution
(don't laugh, it happens!), the ring bearings are easy to bang your
front teeth on if you aren't careful.  And they are SOLID STEEL, so 
guess what would give way.

The TIC rotator is not as conservative in it's engineering, but mine
has worked well.  I have two motors, and short them for braking when
not rotating.  The offset is a bit of an additional wind problem, but
the 50' boom hasn't been a problem.  The ring rotator is also hard to
climb around, so outfit your belt with auxiliary Gorilla Hooks (I use
aircraft control cable, NICO clamps installed with proper tool, and 
REI spring-release caribiners, one on each side of the belt in the D-
loops, in addition to the standard halyard).

For the future, I'm giving more thought to fixed antennas (that is,
to orienting the towers at installation to get the sides aimed in the
right directions for EU, JA and US), as well as simple side mounts
without the extensions to get 120 degree rotation.  The problem to be
solved for that setup is a simple limit switch arrangement, but the
bearings and rotators are simpler and I just don't think the need is
there on side mount antennas for any more rotating range.  There is
an N2TR side mount used at, for example, the W2SX/1 VHF setups that is
simple and inexpensive.  It is essentially two crossed aluminum or 
galvanized steel angles, bolted to adjacent sides of the tower, crossing
at the apex tower leg and continuing so as to mount a rotator plate or
mast bearing.  One angle is mounted with the vertical face down, the
other with the vertical face up, they are bolted at the overlap.

You can sketch this to see how it would work.

73 de Dave, W6QHS

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