Hmmm,
Boom length X weight? Not too bad really. Obviously a worst case
approximation, but not so bad.
Assume that the weight is distributed over a square that is the boom
length on each side with the rotator in the center. Longer/heavier
elements will run up the weight, and likely increase the boom length
as well. This will make allowances for the square factor mentioned
earlier.
Times a fixed multiplier, one could calculate a worst case torque that
the antenna would not exceed. Yaesu apparently works the multiplier
into the K factor published for each rotator.
Worst case: Entire weight at ends of the boom. Not physically
possible, since the boom has weight. Take the XM-240 or such. The fact
that large boom weight not at the ends of the boom is offset by the
farther effective distance of some portion of the element weight.
The weight is not the vertical load on the rotator, just something to
multiply the boom length by to get an approximation of a torque.
Either that or establish a standard torque figure that we can get all
antenna manufacturers to agree to publish.
Given the suprememe effort required to get mfrs to abide by any
standards (only the enlightened few seem to understand how this helps
their business...), Yaesu did the next best thing with their K factor.
Gets back to "follow the manufacturer's instructions", doesn't it?
73, Guy
--. .-..
Guy L. Olinger
k2av@qsl.net
Apex, NC, USA
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