It might be interesting to have Bill, W4AN put his web polling talents
to work on a rotator reliability survey - e.g. what rotator/antenna
combinations have survived (and for how long) and what rotator/antenna
combinations have failed (failure mechanism and failure conditions).
Mike, W4EF
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From: Pete Smith[SMTP:n4zr@contesting.com]
Sent: Tuesday, March 02, 1999 3:46 PM
To: towertalk@contesting.com
Subject: Re:[TowerTalk] Rotator and Antenna Standards
At 09:01 AM 3/2/1999 -0600, Roger Cox wrote:
>
>It has really been interesting reading the discussion on the K-factor and
>Effective Moment on the reflector. While I agree that our EM and Yaesu's
>K-Factor are not perfect, they are much better than the older "square
>footage wind area". The EM rating was developed from what was commonly
>available from all antenna manufacturers - weight and turning radius. It
>would be nice to have a physical model of every Amateur antenna on the
>market so that we could compute the actual wind torque, but this seemed
>unlikely since we also manufactured and sold competitive antenna products.
...
>If someone would like to propose a better specification, that can be
>applied to all antennas with the limited data published by the
>manufacturers, I would consider adding this to our rotator spec's (and
>antenna spec's).
Wouldn't it be a step in the right direction if antenna manufacturers
quoted their own worst-case wind torque numbers at some baseline wind-speed
-- say, a steady 70 mph? Force 12 does this now, presumably on the basis
of some EIA-standard methodology, but even if antenna manufacturers
differed somewhat in how they generated the numbers, it would be better
than the current situation.
By the way, the information you quoted from failure analyses was very
interesting, and tracked with my intuition (which may or may not be a good
sign). Does it follow, from that research, that the absolute worst
situations for rotators are trying to start an array moving against
worst-case wind torque plus inertia; or, alternatively, trying to stop an
array under the same conditions?
73, Pete N4ZR
Loud is good
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