I should add that the mast is held in place in the center of the tower by two
ROHN TB-3 thrust bearings, separated 30 inches apart and mounted on plates
inside the tower. There is no conventional rotor inside the tower. I
demonstrated this at my booth in Dayton this year.
Bill Hider, N3RR wrote:
> Dale, It is not a Bozo idea at all!!
> At the top of my 134 foot tower, I run the coax for the 10M Beam, 40M
> beam and 80 M rotatable dipole inside the 18 ft mast, out the top of the
> mast, and attach them to a 1 foot extension angle bracket mounted on the
> mast, down the outside of the mast to the three antennas, two mounted on
> the mast and one on a ringrotor. Also in this coax bundle is a 4
> conductor cable which controls the relays for the 80 M dipole (Force12
> The angle bracket at the top is there so that the coax does not scrape
> (chaf) on the steel mast during rotation. Instead, the coax/control
> cable bundle being attached to the bracket which is attached to the mast,
> turns with the mast and, because of the length of cable used (18 ft
> inside the mast and another 20 feet below the bottom of the mast which
> allows me to lower the mast for access to the upper antennas) it gently
> twists over the 38 feet of cable without any damage. Note that there is
> no chaffing at the bottom of the mast since the additional 20 feet of
> cable/coax drops straight out of the mast, all inside the tower until it
> reaches its first tie-off point on the tower some 20-22 feet below the
> bottom of the mast..
> Why did I do this in the first place? Because my tower is 24 inches/face
> triangular, guyed inches below the ringrotor mounted at the top of the
> tower. It would be extremely difficult and very unreliable to feed the
> 40M beam in the ringrotor cradle otherwise. BTW, the mast is turned by
> using a mast-twister attached to the ringrotor.
> Check out my homepage for fotos and more details:
> Bill, N3RR
> Dale L. Martin wrote:
> > Okay, Steve, you can tell I'm in a Bozo mood tonight....
> > What about this:
> > Run the coax up the bottom and out the top of the mast and down
> > to the antenna? With the appropriate means to prevent chaffing
> > at the top and bottom of the mast, of course. The loop out and
> > down would look strange as heck, but what the heck! We're hams,
> > after-all....we're supposed to be "strange."
> > Or maybe use right-angles and a barrel at the top to cut down the
> > 'loopy' look.
> > :-)
> > 73,
> > dale, kg5u
> > email@example.com
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