On Wed, May 4, 2016 at 6:20 AM, Chuck Dietz <w5prchuck@gmail.com> wrote:
> This was on Eham.net:
>
> 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.
>
Seems to me that K-factor is a better measure than just sqft of wind area.
The OB17-4 would have a
K-factor of (30 ft x 220 lbs) = 6600 foot-pounds. Although the G-2800SDX is
rated for 6870, that's only a
4% margin. I prefer to have at least a 15-20% margin.
I've searched for a list of K-factors for various commercial rotators, but
wasn't able to find anything. Anyone have such a list?
73,
Jerry
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