There is no way to minimize the twisting of a rotating tower, unless you
mount the rotator midway up the tower and use a star guy under the bearing.
3 element 40m beams can vary significantly in size. A full sized one will
put a lot of torque on a tower. K4JA lost an AB105 rotating tower with two
full sized 40m beams when a hurricane caused it to violently twist. The
same towers with smaller antennas all survived.
Subject: [TowerTalk] Rotating tower
From: Art K6XT <firstname.lastname@example.org>
Date: Thu, 18 Aug 2011 18:51:22 -0600
I've started construction of a 150 ft Rohn 45 rotating tower using K0XG
base and four rings, top ring at 140 ft. Just above the top ring will be
a 3L40 and possibly a small 20 above that, like 3L.
I'd be very interested in any experience or anecdotes on projects like
this using R45. That tower was selected because I already own it. My
area has the potential for icing. The ice I've seen is very light,
nothing like back east or in EU. But I suppose its possible. Not too
windy, the strongest seem to peak out around 70mph and that's rare.
One issue I see is, there are no torque bars on the tower. All its
torque is transmitted to the rotator on the ground. K0XG's rings do have
torque bars but that doesn't help the tower.
The general plot is to add antennas down the tower above the guy rings.
Second 3L20, a shorty 40 Hygain, 10 and 15M.
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