Connecting Garmin GPS to Raymarine VHF DSC Radio

[patrickstickler]

This question, or similar, has probably been asked before, but several minutes of Googling failed to provide a definitive answer.

I would like to feed GPS position data via NMEA from my Garmin 60C GPS to a Raymarine RAY54 VHF DSC radio. I have the Garmin data cable, but the Garmin manual specifies Data In/Out wires while the Raymarine manual specifies GPS +/- wires for the NMEA connection.

Am I correct in assuming that the Garmin 60C 'Data Out' wire connects to the VHF radio 'GPS +' wire? Does the 'GPS -' wire from the radio need also to be connected to ground, or can it be left unconnected (both radio and GPS are already both connected to same ground)?

If my assumptions are incorrect, then how should the GPS be connected to the radio?

Thanks,

Patrick

[KBuckley]

Hi Patrick,

In short the GPS 'data out' goes to the VHF 'GPS +', GPS ground goes to ground, VHF 'GPS -' goes to ground.

Looking at the Garmin GPS60c manual, the 'data out' and 'data in' wires are the '+' signals for each while the power ground wire is the '-' signal. The Raymarine 54 VHF manual shows only 'NMEA in' connections but explicitly shows the polarity. As you suspected, you want to connect the Garmin 'data out' (brown wire) to the 'GPS +' (yellow wire) of the Raymarine 54 VHF and the ground of the Garmin (black) to the Raymarine 54 'GPS -' (green wire). The Garmin black wire will already be grounded if it is being powered from the boat dc distribution so only the Raymarine 54 'GPS -' (green) will need to be tied to ground. If you are running the Garmin off its internal batteries you will need to connect the Garmin ground (black) wire to the Raymarine 'GPS -' (green) wire.

I am basing the colours on what is stated in the manuals I just downloaded for those two units. Hopefully they agree with your manuals.

Ken

[patrickstickler]

Thanks Ken!

[sailingdog]

Yes, Garmin uses the 12 VDC GROUND for their signal ground... if the radio's NMEA in (-) isn't connected to the Garmin's Black Ground wire, it won't work.

Be aware that the Ray54 VHF only has limited DSC capabilities in that it only has NMEA IN, and does not have NMEA out. Better DSC radios have NMEA out as well so that the position of boat's using DSC, like those in an emergency, can show up on your plotter screen.