Garmin 172C <----nmea0183---> Icom M603 VHF

simonl · 23 August 2017, 01:33

I am trying to make the red button on my VHF a bit smarter in case it's ever pressed, by linking the output of the chart plotter to the VHF. As a secondary measure I'm hoping I can also receive DSC info into the plotter too, but this is much less important.

Just concentrating on the important one, I have:-

- plotter green NMEA OUT (Com 2 TX) ----->>----- NMEA IN+ on VHF Red RCA/phono plug centre pin

- plotter black connected to 0V and connected to NMEA IN- on VHF red RCA/phono plug shield.

On both the plotter & the VHF (which are both supposedly NMEA0183 V3.01) they seem to share a common 0V with the power rail, rather than have a balanced line. More RS232 than RS422. This seems to fly in the face of them being 3.01 compatible.

Rather than trying to boil the ocean over how they should work, can anyone shed any light on why it doesn't seem to work?

Both ports on the 172C plotter set at NMEA in / NMEA out @4800 baud.
DSC tab enabled on the 172C

I had a quick peep with a voltmeter & saw no AC volts coming from the GPS.

Any pointers much appreciated. Probably something obvious, but just can't see it

Erin · 24 August 2017, 16:27

Your wiring looks correct. The only thing I seem to remember is that there is a setting hidden in the Icom to turn on the 'receive GPS data' option. Might be that

ajstars · 24 August 2017, 17:50

I have a similar problem with AIS signals not being picked up by my radio and it's driving me nuts!

TEK89 · 24 August 2017, 19:08

Hi!

Try port1 on the garmin. Might be that port2 is broken.

You can measure the NMEA Out+ and Out- wires and see 0-6 volts "flashing" on voltmeter.

If you have something connected already to port1 just divide the signal.

simonl · 24 August 2017, 19:14

Things I've googled, found, and already done prior to posting, that might be of sue to others are

put an MMSI into the VHF
turned DSC on the Plotter (DSC tab)
turned NMEA on on the VHF (or similar, can't remember exactly)

TEK89 · 29 August 2017, 15:19

If you do not get it to work, just by some cheap nmea0183 gps antenna suchs as digital yacht 150 and fix it on a rail. As said sometimes different brands just do not connect via 0183.... Thank god all new equipment mainly comes with nmea2000...