NMEA 0183 and NMEA 2000

[Debenair]

HELP!

I am installing a digital yacht class B AIS transponder with the combined GPS/VHF aerial.

1) I have a Raymarine A70 plotter, with ST 70 instrument heads and SPX 10 Autopilot, all on the Seatalk ng backbone, but the system/plotter currently sends GPS info to the DSC VHF via 0183 (of course).

2) My VHF is a Navicom 650 RT which presently sends AIS to the plotter via the 0183 protocol over the same wiring.

3)The digital yacht AIS can output AIS and GPS via NMEA2000 [Seatalk ng] which I can hook up to a spare input on a nearby ST 70 head.

4) I can switch off the internal GPS on the plotter--and will need to do so-if I send GPS from the AIS via 2000 or 0183 to the plotter.

5) IF I send GPS from the transponder to the plotter via 2000 will the plotter convert the GPS in 2000 form to 0183 before sending the signal to the radio over the existing wiring, OR will I need to use the available 0183 interface to connect the AIS and the VHF , abolishing the present GPS feed from plotter to radio?

 

[David2452]

If bridging is turned on at the plotter, from memory that is the default then yes it should.

 

[eastlaked]

From memory the Digital Yacht AIS transponder I have has a low speed NMEA 0183 giving GPS position only, and a high speed NMEA 0183 output with AIS and GPS position.

On my yacht:
The low speed is fed to the "older" electronics (GPS position repeater on the chart table for log book updates on the hour).
The high speed 0183 is fed the my C80 (classic) which gives the plotter AIS data and yacht position.

The advantage of connecting it this was was that the slow speed NMEA 0183 devices got GPS position even when the plotter was off. Or more importantly if the plotter is broken, I still get GPS data for DSC VHF etc.

 

[Debenair]

Good answer Eastlaked.
The other option I had considered was to leave the transponder as entirely standalone, with the plotter and DSC VHF talking to each other via the existing 0183 connection.
The only problem I can foresee would be the possible discrepancies between the two GPS positions leading to "doubling" or shadowing of targets on the plotter.