Bob wrote:

I have a new DSC VHF marine radio with a + & - input for a GPS in NMEA
format. I have my Garmin MAP76 outputting in Garmin format on RS232 to an
older laptop running Mapsource on my boat as a chart plotter. I would like
to get the required signal to the radio - any ideas or suggestions ?
Thanks, Bob
I do not recall if your Mapsource software requires a data in Garmin format
or not. If it does not, you can select a NEMA out on your Garmin GPSMAP76
and on your Mapsource software. Then you can do some cable surgery and
make what amounts to a serial Tee connection. The other end of the Tee
would connect to your radio. Generally you can get away with this since
most serial devices don't drag down the 5 volt signal signficantly.

NEMA offers a variety of information on postion, satellite info but does not
have the provision to handle stored waypoints. The more I think about it
the more I suspect NEMA may not be supported with your Mapsource software.

If we assume that your Mapsource can only accept Garmin data, then things
become more complicated. If you have a second serial port on your laptop,
you can install a low level driver to convert serial data in a Garmin
format to a NEMA format and output it on the second serial port. Several
years ago I saw a freeware window95 program that would do conversion in
real time but I do not know if it even exists anymore.