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

[Robert C. Campbell]

Unless we want lightning fast antenna rotation, we're going to need some
sort of gearbox with virtually any motor we're likely to find. We could
gear the drive to a simpler pot as well.

Gus,  I used a pulse width modulator to slow my DC motor down with out
having to loose a lot of power. This eliminated the resistor and the motor
ran cooler. Mine cost $80.00 usd out of Canada but I understand that they
are nothing more then modified fluorescent light dimmers.
My thought would be to count the pulses instead of a pot. I think we will
be stuck with gear motors if the goal is to go small and have lots of
torque.
Even with the PWM mine was a gear motor but it beats a big restive load
hands down.

I would like to move away from stops and find another way to establish
0~360az and 0~90/180ex indication so as to enable continuous rotation to do
 continuous sky scan or search and rescue with out having to wind up and
damage my coax. I am not sure what battle ship radar uses for constant
rotation but that would be the ticket.


Bob Campbell
KB3PMR