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[TowerTalk] Prosistel Rotors

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Subject: [TowerTalk] Prosistel Rotors
From: (Pete Smith)
Date: Wed Jan 29 14:03:07 2003
At 10:47 AM 1/29/03 -0500, wrote:
>     First, the K-Factor (and Hy-Gain's Effective Moment) are both ESTIMATES
>of rotator capacity.
> >  because it pretends that the whole weight of the antenna is at the 
> turning
>     You lost me. The turning radius is a distance measurement so at what
>point on the turning radius would the weight be?

Well, it sure isn't all the way out at the full radius.  K-factor uses the 
turning radius, which for HF antennas tends to be the circle described by 
the tip of the longest element.  That badly overstates the inertia of any 
practical antenna.  There's virtually NO weight out there.  For example, my 
C-3Es have 18-foot booms, so the farthest from the center of rotation that 
any appreciable weight is located is only 9 feet, but the turning radius is 
19.8 feet.  Big difference!

>     The K-Factor (weight times turning radius) is a more realistic way to
>rate a rotator than the old antenna square footage method since it takes the
>footprint of an antenna into account; it could take more rotator torque to
>turn a small, heavy antenna than one that is big and light.

Well, sure, it's better than THAT, but it's still not very accurate.  If I 
remember my high school physics, any time you rotate a non-uniform body 
around a center, you need to sum the moments of all the masses (distance 
from the center times weight) to get the total inertia.

I think the main effect of the K-factor is to tilt people toward buying 
more rotator than they need, and since Yaesu has such a huge gap in stated 
performance between the G-1000 and the G-2800, that can translate into a 
lot of money (unless people go to Prosistel, RD-1800, AlfaSPID, etc.)  Too 
bad the Yaesu controller is so pretty, and most of those other ones are so 

73, Pete N4ZR
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