I'm putting together some programs that use the serial port capability
of the HP-50G graphing calculator.

They're going to be incorporated in the astronomy and satellite
prediction stuff on http://members.cox.net/above, and posted to
www.hpcalc.org. The added features will be geared to amateur radio
satellite and APRS operations.

1) Grab time and position from a GPS receiver using 4800 baud NMEA
format.
2) Trigger an APRS transmitter when an appropriate satellite is
visible.
2a) Turn the APRS transmitter _off_ when the satellite goes below the
horizon.

(2 and 2a) are done via alarms on the HP-50G.

I'm open to suggestions. It should be posted after some testing.