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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