In a message dated 97-01-03 14:51:49 EST, you write:
>>The
>>Effective Moment/K-Factor of the TH11DX (weight times turning radius) is
>>1936; the G800 is rated at 1299 ft-lbs and the Ham IV is 2800 ft-lbs.
>
>Is the 1936 ft-lbs actually the published weight of the antenna times the
>published turning radius?? If so, this sounds grossly extreme and
>incorrect. That would be putting the entire weight of the antenna at the
>end of an arm the length of the turning radius. Is this a published moment,
>instead??
>
Chadster --
The 1936 is correcto mundo and right out of the Hy-Gain catalog. Why
would it be gross and extreme? You're not looking at this from the
perspective of the rotator; it has to swing an antenna that weighs X and has
a moment of Y. It's Effective MOMENT, remember? All of the rotator
manufacturers are using this kind of a measurement for rotator capacity now
instead of just a square foot load. You can imagine two antennas with the
same square footage but radically different moments on the rotator. The
rotators are capable of turning things of a certain SIZE and square footage
doesn't tell the whole story.
>Think of a rotatable "wire" 40M dipole with a 10 lb chunk of lead in the
>center. Turning radius of 33 ft times 10 lbs (negligible wire weight), for
>330 ft-lbs. Incorrect. Virtually 0 ft-lbs because all the weight is at
>the center.
Actually I think that the ft-lbs would equal zero; no feet, remember,
because it's all on the mast (10 lbs times zero feet = zero).
>
>Now, split that lead weight in two and put them at the ends of the dipole.
>Here, the correct moment is indeed 330 ft-lbs.
Correcto mundo, Senor. Since we're estimating, now you have to add that
to the 1936 ft-lbs of the TH11 to give you the real final load on the
rotator. And obviously it doesn't change things significantly so the rotator
recommendations remain the same.
73, Steve K7LXC
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