On 1/14/2013 9:01 AM, Larry wrote:
Something like a Ham IV, for example, does not ramp nor does it coast
all that well.
I would strongly disagree about the coasting as they offer very little
turning resistance. Put a wrench on it and you can turn any of them by
hand. Turn a big tri-bander and it will coast quite a few degrees if you
don't use the brake. Release the brake and any of the ham series
including the tail Twister make good weather vanes. They are after all
just a tiny (cheap) motor with a huge gear ratio that consists of spur
gears that offer little resistance. They are a good, economical way of
turning "relatively" small antenna systems
I went through several of them on windy days with the big array. They'd
turn it or hold it BUT.... Release the brake on a windy day and kiss
the rotator good by when trying to stop the rotation.
It was difficult to imagine that array turning that fast. Course the
wind was well over 30 mph.
http://www.rogerhalstead.com/ham_files/Tower29.htm which I've shown
before. Trying to turn that with any of the Ham series was a bit naive.
(I've shown it before)
If you are turning an antenna with a long boom and/or
elements there can be a fair amount of torsion when starting or
stopping.
With the large antennas I much prefer a big rotator with double worm
gears or a prop pitch motor with a controller that ramps up and down
When putting that much money in a big antenna and tower I prefer not to
scrimp on the rotator and the big ones are only about 50% more than the TT.
73
Roger (K8RI)
Without something like the GA-3000 or the ramping the rotator
and/or tower has to handle the torsion. The GA-3000 presumably would
ease the torsion effects on the rotator and tower. A bigger rotator can
help but it will most likely just transfer the torsion directly to the
tower. With the GA-3000 there might be a tendency for wobble or
oscillation under high wind situations as Roger pointed out.
It has been a while since I read Leeson's book on this subject.
73, Larry W6NWS
-----Original Message----- From: john@kk9a.com
Sent: Monday, January 14, 2013 7:17 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] any source for a GA-3000 ???
Green Heron Controllers do a very nice job of ramping!
John KK9A
To: <towertalk@contesting.com>
Subject: Re: [TowerTalk] any source for a GA-3000 ???
From: "Larry" <lknain@nc.rr.com>
Date: Mon, 14 Jan 2013 04:56:20 -0500
It is probably most useful with large antennas/arrays unless you ramp up
and down the rotational speed.
73, Larry W6NWS
-----Original Message----- From: john@kk9a.com
Sent: Sunday, January 13, 2013 10:10 PM
To: TOWERTALK@contesting.com
Subject: Re: [TowerTalk] any source for a GA-3000 ???
I think it is unnecessary of you use a strong enough rotator.
To:<towertalk@contesting.com>
Subject:Re: [TowerTalk] any source for a GA-3000 ???
From:"Larry" <lknain@nc.rr.com>
Reply-to:Larry <w6nws@arrl.net>
Date:Sun, 13 Jan 2013 20:49:07 -0500
List-post:<towertalk@contesting.com">mailto:towertalk@contesting.com>
I think it roughly equivalent to Leeson's book recommendation except
that
Leeson used a BMW part. Or was it Lawson's book?
73, Larry W6NWS
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