Gus, I like your thinking. Simply put we need to make feedback position sensor with associated motor/motor control stuff.
The motor rpm's and gear ratio are functions of the number of degrees per unit of time, as you say.
One simple solution that I was going to try was a reversible dc gear motor being polarity switched by a dpdt relay, and a three turn pot for position sensing. The pot is 16$US. Per copy. Need two as well as the associated hardware. Scaling the dac on the uP is a nit.
Then again, since we can fiddle with the values in software, so our inputs can be anything (from a hardware standpoint) of reasonable accuracy.
Just thinking, why use gears and gear motors?? Why not a dc motor, bicycle chain and sprockets? The HD bearings for the shaft are $6.95 as I recall, a piece.
Still set on using stock sizes/materials if I can. This would give me a start modelling this stuff with CAD and make it easier to source.
A note regarding your comment on the Arduino. It really does not matter what we use in terms of antenna rotators at this point. I think that if we coherently model the design process, someone in cost reduced circumstances could reproduce whatever we decide with far more basic tools than available to us. The key is that there is a microcontroller with tons of IO attached to a serial port...
Or then again, CO7WT is bit banging the parallel port. Now that's the way to go.
blah, blah, blah,