[TowerTalk] "K" factor gets sillier

[Stan or Patricia Griffiths]

Hi Pete,

My comments are interspersed below:

Pete Smith wrote:

> Imagine my amusement to discover that Yaesu now defines the K factor to
> mean the product of the antenna weight and turning radius, PLUS the weight
> of the mast (or a share of the mast in the case of multiple antennas) times
> the turning radius!

My understanding of "K Factor" is that it is supposed to be a measure of a
rotator's ability to handle starting and braking torque loads as well as
rotator torque loads due to wind gusts.  So, if you are going to compare a
rotator's K factor to your antenna configuration, you need to consider every
bit of mass that the rotator is expect to turn and/or stop by braking.  Whether
or not it is appropriate to include the mast can be answered by answering the
following question:  "Is the mast being rotated and/or braked by the rotator?"
Well . . . obviously YES it is, so it should be included.  If it is a long
mast, the mass is significant, but the radius will always be small compared to
the antennas themselves.  Whether the product of mast mass times radius is
large enough to impact the comparison of your antenna system to the K factor of
the rotator is open for discussion, ie: it depends on HOW large it actually is.

> Then just to gild the lily, they recommend that you not exceed 60 percent
> of the allowable K factor for a given rotator,

I don't really understand why it is acceptable to exceed the K factor at all.
I would think that a good definition of K factor would mean that you don't
exceed it, at all, ever.  If exceeding it by 60% is OK, why don't we just make
all K factors 60% larger in the first place . . .  ? ?

> and they caution that even
> if you use a thrust bearing, you still have to count the mast weight in
> your calculation!

For this concept, you have to go back the the original question:  "Is the mast
being rotated and/or braked by the rotator?"  Well . . . yes, it is.  Having a
thrust bearing in place does not affect the fact that the mast is still being
rotated and braked by the rotator.  Therefore, its mass and radius must still
be considered when comparing your antenna system for K factor compatibility
with a rotator.

> This K factor thing gets further and further from physical reality, and
> looks more and more like CYA/marketing of bigger rotators!

Other than the 60% fudge factor, it seems a little more "real" to me if the
mast is included in the calculations.  I would think if the manufacturer's
intent was to get you to buy a bigger rotator, they would never suggest you
could exceed the K factor by any amount, let alone 60%.

>
> 73, Pete Smith N4ZR

Stan  w7ni@teleport.com




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