[amsat-bb] Re: inquiry about homebrew az-el systems

[Gus]

Given the shortage of LEO birds, exactly how much antenna do we need to 
rotate?

Hams operate satellite successfully with hand-held antennas, which have 
low wind-loading and are light in weight.

With R/C servos available producing 6½ ft. lb of torque for less than 
150 bucks, I'm surprised a light weight, portable, DC-operated satellite 
system complete with antennas and AZ/EL rotors  hasn't materialized 
before now.

On 02/23/2013 07:59 PM, Samudra Haque wrote:
> Hi, about two years ago, I started a design for a robotics class project of
> a AZ-EL rotator controller system, and a hardware package for the mechanism
> for rotating an antenna in any direction subject to mechanical stops. The
> system would have been able to handle regular and flip modes. I didn't do
> anything more than calculations, and moved on to building a classroom
> instructional robot then.
>
> Lately, as I am setting up (K3GWU, the George Washington University Amateur
> Radio Club and Research Station) I find that the price of az-el systems
> such as G5500 + Yaesu AZ-EL rotors are expensive, and are not typically
> available on an affordable basis on Ebay or eham.net etc. Well, of course,
> expensive is a relative term, for a student hobby organization, it's a lot,
> and I guess for small ham operators it is also moderately expensive.
>
> This may be a frequently asked topic: does any one have experienced with
> (tested) kit designs for AZ-EL rotors that can be made with parts from
>   current suppliers ? I know there are a number of controller designs, but I
> am interested to know if there are any options for suppliers of the
> required gears/motors etc.
>
> I have located several large AC motors / DC motors at my university
> mechanical engineering workshop, but they are not all guaranteed the same
> specs. I now realize if I do embark on a actual design process with my
> model/simulation/hardware, it would be nice to build several of these all
> at once to share the development cost over the production run, and ensure
> those who want a cheap AZ-EL system can get one. Otherwise the production
> cost of one heavy duty system is going to be quite high.
>
> I hope some of you may have suggestions for me, both (+) and (-) or perhaps
> (~) in nature. I thought amsat / amateur radio folks have a common need to
> encourage homebrew activity to keep their brain cells in working condition?
>
> I'm opening this question up to the national US audience, and welcome any
> discussion on the challenges of making the ever-so-important
> azimuth-elevation rotor. I've studied some of the alternatives: Alliance
> U100 and Yaesu G-5500. I think we can do better in 2013. But ideally, to
> allow the wide adoption of AMSAT ground stations, what price point would
> the system have to be to make it worth building ?
>
> 73 de N3RDX
> George Washington University
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-- 
73, de Gus 8P6SM
Barbados, the easternmost isle.