What the heck is "K-factor"?
In addition to windload and torque ratings, Yaesu also offers a specification called "K-factor," which is derrived by multiplying the turning radius of the antenna (in feet) by the weight of the antenna (in pounds). Add the K-factor of each antenna on the mast together for your total system K-factor. The resulting number (in foot-pounds) must be less than the K-factor rating for the rotator.
For example, the Hygain TH-11DXS has a 12.5 square foot windload. The Yaesu G-800DXA rotator will handle up to 21.5 square feet. But, when you multiply the antenna's turning radius, which is 22 feet, by the weight of the antenna, you get a K-factor of 1,936 foot-pounds. So, although the windload rating of the rotator would seem to indicate that it will handle the antenna, the K-factor of the antenna is greater than what the rotator will handle (1,302 foot-pounds). If we look at the K-factor rating of the Yaesu G-1000DXA, we see that it is 1,663 foot-pounds, so it's not even the correct choice. At this point we would need to use a G-2800SDX, which will handle a K-factor of up to 6,870 foot-pounds, which is obviously much sturdier than what we really need.
Yaesu rotators are great. They offer great features and reasonable prices, but you really have to understand how K-factor determines how the rotator will perform. K-factor: Learn it, love it, live it. Your rotator will thank you for it.
