is the fixture I built to hoist up the antennas. It was intended to be clamped to
the mast, and in combination with a similar pulley near the antenna the
mechanical advantage should have been 4:1 less mechanical friction.
It turned out that the mechanical friction of these strong but
cheap brass pulleys was greater than I anticipated, and the effort
required to hoist up the antennas (especially the tribander) was
substantial. I was able to do it without a winch, but before I do
something like this again I will invest in some decent pulleys.
I wanted the 40m antenna to
go up near the top of the mast, and the tribander to go below it just
above the tower. Since I am way
to chicken to climb an extended mast using clamp-on mast steps, I
decided to start with the mast mostly nested inside the tower, attach
the 40m antenna to the mast, crank up the mast high enough to clear the
rotator, install the rotator, drop the mast down into the rotator, and
then install the ribander on the mast.
This is the
fixture I built to crank up the mast. The idea was for it to sit
on the intermediate thrust bearing shelf (which doesn't have a thrust
bearing since it is only there to keep the mast positioned when the
rotator is not in place) and straddle the mast. The combination
of the mast and the 40 antenna weighed almost 200 pounds, so I went
with a worm drive winch with a claimed capability of 2000 pounds.
However ... I tried to cut corners and bought the winch from
Harbor Freight, and even though the description said that it had
hardened steel gears the damn thing almost ground the teeth off the
large shaft gear before I weas finished with it. I managed to
make it work, buit I literally had to liberally grease the teeth of the
shaft gear every turn in order for them to survive the task. The
design concept was good but my execution was flawed. I have
since found a much better worm drive winch from a reputable source that
is essentially the same size, and I will for sure buy it before ever
using this fixture again.
This is the boom-to-mast plate, and it is essentially the same for
both the OB2-40 and the OB16-3. The feedpoint for both antennas
is far enough out on the boom that I wouldn't be able to reach them
from the tower, so I added this simple little bulkhead to both antennas
for a bit of extra protection from feedline damage if the rotator loops
should somehow get entangled. Hopefully the loop portion would
break before pulling the portion of the feedline that goes out to the
feedpoint. It's possibly a dumb idea, but I thought it might be
worth a try.
Here is the OB2-40 raised and secured to the mast. The
raising arm and rope can be seen clearly, and if you look closely you
can also see the mast raisng fixture sitting on the intermediate shelf.
The tag lines were handled by my wife and son, without whose help
I never would have been able to get these antennas up. I cut them
loose (the tag lines, not my wife and son) shortly after this picture
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