[TowerTalk] any source for a GA-3000 ???

[K8RI]

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 at kk9a.com
> Sent: Monday, January 14, 2013 7:17 AM
> To: towertalk at 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 at contesting.com>
> Subject: Re: [TowerTalk] any source for a GA-3000 ???
> From: "Larry" <lknain at 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 at kk9a.com
> Sent: Sunday, January 13, 2013 10:10 PM
> To: TOWERTALK at 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 at contesting.com>
> Subject:Re: [TowerTalk] any source for a GA-3000 ???
> From:"Larry" <lknain at nc.rr.com>
> Reply-to:Larry <w6nws at arrl.net>
> Date:Sun, 13 Jan 2013 20:49:07 -0500
> List-post:<towertalk at contesting.com">mailto:towertalk at 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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