I have had a fair amount of experience swapping rotators. At one point
Hygain/MFJ had a pot problem; mine were wearing out in roughly a year. What I
did was procure a 2nd "hot swap" rotator so that I could do a replacement in a
single tower climb.
I place my masts about 1/4" above the rotator bell so that when it is time to
swap all I need to do is remove the bottom and clamp bolts and tip the HamIV
out. The new one is tipped into place, bolts connected and I am ready to go in
about an hour.
The key is to clamp the mast at the thrust bearing ( I used a muffler clamp) so
that the weight of the mast and antennas is held off the rotator. Once the new
rotator is in place and clamped to the mast (with the 1/4" clearance) I loosen
a set screw in the thrust bearing so that full weight of the mast/antenna is
borne by the rotator. I immediately retighten the thrust bearing .
When I first started this I used a home made two leg clamp to stabilize the
mast in the tower, but I ultimately abandoned it because I could swap the
rotators so quickly that I never had a problem with the mast tipping out of
This was all with a 3el/40 SteppIR on a 10' Rohn mast. I finally got sick of
HamIV and put in a Yaesu 2800; I haven't had a problem in over 10 years now. I
still installed the mast on my 2800 with a 1/4" of clearance though.
Keith - AC9S
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