On 2/24/2012 8:14 PM, Phil Karn wrote:
Fortunately, the problem of tracking a LEO satellite with a deadband of 5-10 degrees is a very non-demanding problem. That's why most hams are still doing it with primitive, bang-bang control.
I had occasion to install a Pro-sis-tel rotor for a nearby ham a while back. I beleve they presently ship with DC motors, but early models had a little (by industrial standards) three phase motor .. I think 1/8th horsepower. I did not have a chance to reverse engineer their controller, but it was not particularly sophisticated. They simply pulsed 60Hz AC from a 24V transformer when they wanted to accelerate or slow down. I am not exactly sure how they generated torque since there was no evidence that they did anything to shift the phase of the three windings. Of course my imagination started thinking about using industrial variable speed drives with it. The long cable from the shack to the tower is a concern ... most industrial drives specify a length limit to to the motor in an effort to minimize reactance. I suppose you could put the power electronics at the rotor, but lightning concerns give me pause.
-Joe _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
