My 160m inverted vee hangs from the top of a 24' mast. The latter sits
on top of a 125' 25G tower. There is a mast (from rotator) sticking up
about 5' through the thrust bearing on top. A Hy-Gain 155CA beam is on
that mast, just above the thrust bearing. The 24' mast rests on the
Hy-Gain boom to mast bracket and is sleeved over the rotator mast for
about 4 feet. (The 24' mast does not go into the tower.) To install
that, not only did the entire 24' mast have to clear the top of the
tower, but it had to go 5 feet higher to clear the rotating mast that it
had to slide over. No problem for a regular 12' Rohn gin pole....
All you need is a counter weight. With a counterweight and a 25' rope
dangling from the bottom of the 24' mast, I was able to tie the gin pole
rope only 6' from the bottom of the 24' mast. There was 18' of
free-swinging aluminum mast above the gin pole rope tie-off, 6 feet of
mast below, 25' of rope hanging down and then a hefty counterweight.
With that set up there was no way the mast is going to point any other
direction than straight up. It was actually pretty easy to do and I did
the same procedure when I had to remove/re-install the mast for
maintenance on the pulley at top. The only real problem was my ground
person who whined about hauling up the heavy counterweight. Of course,
I had to stand on top of the thrust bearing plate (or the boom) to reach
that high, but that's why I buy flat tops instead of taper tops.
Personally, installing this mast feels a lot safer than wobbling around
on 2 or 3 unguyed sticks of 25G while the section with the guy wires
comes up the side. Of course, we checked out all the weight and balance
several times before hoisting the thing up.
For those interested, the 24' mast is not secured. The 5' of mast
inside holds it upright and the weight of the inverted vee keeps it
pressing down on the boom to mast mount. The 24' mast will ocassionally
wind up a half turn of top rope as the rotator turns, but any breeze
unwinds it right away and there has never been a problem there. The
mast is wearing down a bit, and also eating into the boom to mast
mount. But it has been up there for at least 15 years and the wear is
maybe 1/8" on the mast and less on the mount. I will wear out before it
does. Getting the 160m antenna up above the beam and away from all the
metal of the tower and guy wires really seemed to help the signal more
than expected from just an increase in height.
Dan KL7Y
|