[TowerTalk] "K" factor gets sillier

[Pete Smith]

At 04:18 PM 7/22/00 -0700, Kurt Andress wrote:
...

>We can't assume that everyone that used a Yaesu rotator properly loaded
>the rotator according to the old "K" factor and we can't assume that all
>of the antennas that were put on these rotators were equal in their
>behavior under wind loading. If you'd seen what I've seen, you'd know
>that there is a disparity between commercially offered antennas on the
>order of a magnitude of 10, with respect to behavior under wind loading.
>It is a huge deal. But, we're not gonna go there till we straighten out
>the much SIMPLER antenna area fiasco.
>

I never read the explanation for the Hy-Gain "effective moment" number, so
I can't comment on that.  And I think I understand the essence of Kurt's
argument, which seems to boil down to "figure out how big antennas will
turn, and specify something less."

My problem, I guess, is that I think we ought to strive for a level of
understanding among hams that leads to a) safe and b) understood
engineering.  My problem with Yaesu's "K-factor" number is that it wasn't
representative of the real world before, and now it's much worse.

To me, it would seem much more rational to come up with a figure such as
"effective inertia = 1/2 x rotating radius x weight of antenna."  Surely it
would be closer to the physical reality to average the rotating radius of
all parts of the antenna (which is what what the "1/2" does) and multiply
times the total weight to come up with an approximation of the total moment
of inertia.  At least that would lead people to a more rational assessment
of their antenna arrays vs their poor brutalized rotators!

Numbers like Yaesu's new K-factor are so disconnected from phyical reality
that they don't help either the buying public or the ham who wants to
understand why things work (or don't).  All they do is impel people toward
buying a bigger rotator than they should require.

I absolutely agree with Kurt that the real load on a rotator is inertia +
wind, and that antennas that generate lots of torque in the wind are to be
avoided.  I just think that we need to look for realism in all the
parameters we consider in building our stations.

73, Pete Smith N4ZR

The World Contest Station Database 
is back up and running at
http://www.qsl.net/n4zr 



--
FAQ on WWW:               http://www.contesting.com/FAQ/towertalk
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com