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

Robert C. Campbell kb3pmr at gmail.com
Sat Mar 2 02:55:49 PST 2013

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
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

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