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

To: K7LXC@aol.com, TexasRF@aol.com, ab2os@att.net,towertalk@contesting.com
Subject: Re: [TowerTalk] Effective moment and K-factor. Was: Yaesu rotators
From: Pete Smith <n4zr@contesting.com>
Date: Fri, 02 Jul 2004 03:53:56 -0400
List-post: <mailto:towertalk@contesting.com>
At 02:52 PM 7/1/2004, K7LXC@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
The World HF Contest Station Database
was updated on June 5, 2004
2728 contest stations at
www.pvrc.org/WCSD/WCSDsearch.htm


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