[TowerTalk] Effective moment and K-factor. Was: Yaesu rotators

[Pete Smith]

At 02:52 PM 7/1/2004, K7LXC at aol.com wrote:
>     The bottom line is that they're the SAME and they're just APPROXIMATIONS
>based on the manufacturer's knowledge of the unit.
>
>     This is an improvement over the old square footage capacity when you
>could have antennas with the same square footage but radically different 
>loads on
>the rototor. The only REAL numbers for rotator capacity are starting torque
>and rotating torque; the K Factor/Effective Moment figures translate those
>numbers into recognizable and usable amateur specifications.

Recognizable, usable and conservative, since an antenna built to conform to 
the K-factor would have all its weight at the turning radius.  As far as 
rotator specs, braking torque also matters.  For antenna specs, I very much 
appreciate Force 12's numbers for maximum wind-induced torque as well, 
which gives you a sense of how much braking torque you need.  As someone 
else mentioned, the G-800 and G-1000 have the same rated rotating torque, 
just difference in braking torque.

Perhaps someone could comment on DC vs AC motors so far as starting vs 
rotating torque.  I believe that the Yaesu has a DC motor, and the Hy-Gain 
rotators are all AC.

Something I didn't appreciate, by the way, is how much a swinging gate 
sidemount increases the demands on the rotator, particularly trying to turn 
into the prevailing wind with the gate positioned so that maximum wind 
torque occurs when it has the longest available lever arm to work with -- 
turning my bottom C-3E into the wind, my G-800 often almost stops.


73, Pete N4ZR
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