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

Michael Mat_62 at charter.net
Sat Feb 23 20:22:04 PST 2013

A few years back I built the SAEBRETrack system shown here 
https://sites.google.com/site/marklhammond/saebrtrack.  It's based 
around a BASIC stamp.  I built the version used to control the OR-360 
rotators but those have become very scarce and worth their weight in 
gold if you can find them. My point is this though, if you open up an 
OR-360 you find a surprisingly small "540" DC motor driving the gear 
train  and direction is controlled by voltage polarity. Positioning is 
by  potentiometer feedback. There are probably better ways to do it than 
a BASIC stamp these days but the concept of driving DC motors to control 
lightweight arrays has crossed my mind a few times as well.
Michael, W4HIJ

On 2/23/2013 9:25 PM, Gus wrote:
> 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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