[amsat-bb] Re: Motor for Yaesu G5500 Azimuth Rotator?

Phil Karn karn at ka9q.net
Fri Feb 24 17:14:08 PST 2012

On 2/24/12 11:58 AM, Joe Fitzgerald wrote:

> Your fans will not be completely happy until your controller runs a
> state-space model of the motor/antenna system, with software that is
> careful to generate acceleration and jerk limited commands such that
> mechanical resonances are not excited.
> With tongue firmly in cheek

What do you mean? That's exactly my plan. 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.

But I think we can do a lot better. It's time to get serious about
moving to the microwave bands. That will require one thing on both the
ground and in space: much tighter antenna pointing. But the payoffs will
be enormous: much smaller and lighter ground antennas that will be
practical for many more hams, much better signal-to-noise ratios, and
much higher bandwidths and data rates.

All this could mean substantial growth for AMSAT. But we'll have to let
go of not only inefficient analog modulation but also the low frequency
bands, especially 2m.

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