I have 60 ft tower with a C31XR placed 1.5 ft above the tower and a EF240s 6
ft above it (rotated 90 degrees to the C31XR). For a variety of reasons I
ran a steel torque tube from 3 ft above the tower base up through the center
of the tower and through 12 ft of 2" steel mast. The torque tube is
positioned using wooden guide bearings spaced equally along the tower and a
centering bearing situated approximately 4 ft below the top of the tower.
The torque tube was spot welded to the mast ... 3 holes were drilled around
the circumference every 24" inches and the torque tube was welded to the
mast through the holes. This secured the torque tube firmly to the mast and
it had the additional advantage of increasing the mast's moment of inertia.
The rotator is mounted on a rotator plate at the lower end of the torque
tube and the antennas are located at the other what essentially is a steel
spring ... the torque tube plus mast. This setup not only brings the rotator
down to the ground where it can be serviced easily at -40C but if my physics
is correct the torque tube acts as a pretty good absorber of wind energy
shocks and delivers the force nearer to the base of the tower.
If I insulate the rotator from the tower, can I consider the torque tube
that runs up to through the thrust bearing and is electrically connected to
the tower there and the tower itself as a folded unipole? Can I use this to
my advantage on 80 and 160?
Sylvan Katz, VE5ZX
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