[aprssig] APRS Antenna Rotator

[Adam Ploessl]

I'm working on a high altitude ballon project and am going to have an ATV
link from the payload.  Has anyone ever used APRS for antenna control
before?   What I have now is 2 rotators, one for vertical and one for
horizontal movement connected to a PC interface.  The system is mounted in a
cargo van that will be following the balloon.  I've seen other ATV links
before but the video quality usually breaks down quite a bit a long
distances so the idea is that the chase van will be nearby bringing down
live video and streaming it back to "mission control" via wireless broadband
link.

The control software takes the APRS telemetry info from the balloon and uses
the van's GPS coordinates and altitude and calculates the vertical angle and
direction of the antenna.  It seems to work ok, but I need to use an
alternate APRS frequency and have a high rate of beacons to make it work
when the van is in motion and the balloon is almost overhead and close to an
urban area.

Has anyone ever done something like this before?  The only other problem I
have is with the rotators, the movement is based on time.  Power is applied
for so many seconds for so many degrees of travel.  It seems after it's been
operating a few hours that needs to be recalibrated.  Anyone know of any
other methods of controlling the rotators or maybe a better type of rotator
to use?  I figured someone might have an idea that tracks satellites.

Thanks,
Adam
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