At least some some (Nasa AIS engine and Euronav AI300/Nobeltec SLR-200) AIS
receivers
can receive GPS data at 4800bps from a GPS and add the AIS data (NMEA
sentece VDM).
The sum (GPS+AIS) is then outputed at 38.400bps throug a single output, no
need for a multiplexer.

Regards,
TomS

"Patrick Harman" wrote in message
k.net...
I want to combine my GPS (4,800 baud) with my AIS engine (38,400) so I have
one RS-232 output to put into my laptop computer loaded with Coastal
Explorer navigation software.

Any advice on what works?

Pat Harman
M/V Meriwether