Is My Antenna to Large for My CM-9521? (CM-9521HD)

CM-9521HD Weight Specification
We really do not have a weight specification for the CM-9521A rotator.

  • They were designed for antennas weighing ~15lbs along with a 3ft long upper mast.
    • Like many products, we're sure it was over-designed to handle more, but installing something other than ~15lb antenna and an upper mast longer than 3ft, may shorten the life of the motor.
  • The upper mast clamps can accept from 1" to a 1 7/8" pipe
    • If you are going to run the upper mast through an upper sleeve on a tower, the upper mast must be 1 1/4" in order to rotate true(Centered in the upper mast mount).
      • See Fig 2 on page 5 of the CM-9521A Instruction sheet for an example image. 
    • If you use smaller or larger diameter than 1 1/4" it could seize as it rotates.
    • If you are not going to run the upper mast through a sleeve, then the diameter is not as important.
  • The lower mast clamps can accommodate from 1" up to ~1 7/8" to 2".
  • Also, make certain that you do not have an upper mast over 3ft tall.
    • Too tall of upper mast creates excessive leverage in windy situations and can wear on or damage the thrust bearing assembly and upper mount shim bushing.
    • Your mast could be damaged by high winds if it is longer than 3ft or if the antenna wind load projected area, is larger than 3sq ft.
    • All of Channel Masters outdoor antennas wind load projected area are less than 3 sq ft and can be used with the CM-9521HD rotator systems. 
    • As an example, the antenna with the highest wind load projected area is our CM-4228HD with a wind load projected area of 2.14 sq ft.
    • Our largest ~100 mile log periodic/yagi antennas wind load projected area are less than 2 sq ft.
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