Re: [amsat-bb] G-5500

[Jim.Walls@xxxxxxx]

"Ben" <b-fisher@uiuc.edu> said:
> I just bought a G-5500. I don't have it up yet, but I did study the
> schematic. There is no provision for speed control.

Correct

> I suspect these things are poor auto trackers. In order to stay fixed
> on a moving target it would become necessary to pulse the motors.
> I can see where these things would exhibit jerky motion.

We're not trying to track airplanes overflying at 1000 feet.  Even low
earth orbit satellites don't move across the sky fast enough to be a
problem.  With the antennas that us hams are using for 2M and 430, pointing
only needs to be within about 10 degrees for really large arrays and with
small yagis that figure is more like 30 to 45 degrees.  At S-band it starts
getting picky and the guys running big dishes need better directional
control than the G-5500 will provide, but I can't imagine anyone trying to
point a 10 foot dish with a G-5500 from a mechanical standpoint.  Most of
the tracking programs will correct the antenna pointing when the satellite
is more that some number of degrees from the antenna pointing.  So yes, the
antenna moves a few degrees and then stop for a while.

> I've thought about designing a better system using servos or stepper
> motors with optical encoders for position feed back. With the proper
> software interface it would be easy to track a satellite with a
> smooth motion of the antenna system. I'm sure its already be done but
> by who?

It's been done for larger arrays, but not worth the effort (especially
since you already have the G-5500).  The G-5500 is generally considered to
be the standard by which all other El/Az rotors are compared.

73
-----------------------
Jim Walls - K6CCC
k6ccc@amsat.org
Mobile Radio Operations
Southern California Edison Co.
Ofc:   626-302-8515   -   PAX   28-515
FAX:   626-302-7501   -   PAX   27-501



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