Rotators – by Dan, N5AR


The mast clamp on some rotators is a fixed part on the main rotator body. On others it is bolted to the main body and may be moved in its attachment point to the rotator body. This includes the Yaesu, M Squared and many other rotators.

Most tower installations use 1 or 2 thrust bearings on the tower which establish the mast axis of rotation. The sequence of tightening the bolts on the mast clamp, the clamp to rotator attachment, and the rotator to mounting plate is important to attain a non binding system. Pete, N4ZR described the proper tightening sequence perfectly on Tower Talk so I will just quote him directly.

A trick that takes advantage of the Yaesu mast clamp’s centering capabilities – Tighten the mast clamp on the mast first, with all the other bolts loose; then tighten the bolts that hold the clamp to the top of the rotator, using the index marks on the rotator case to get it centered; finally, tighten the bolts that hold the rotator to the shelf. The shelf holes have enough adjusting room to take up normal amounts of misalignment.

73, Pete N4ZR

If your rotator has a mast clamp which is part of the rotator body, you must shim the mast clamp until the mast center of rotation is the same as the rotators before mounting the rotator.

73, Dan, N5AR