AB7E Antennas
Page 2
Previous Page          Next Page

This 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 was taken.

AB7E Home
Tower and Antenna Project Home
Previous Page          Next Page