I bought an AIS receiver recently, and tried to connect it to the chart plotter, without success.
The instructions weren't really clear, especially with the data cables - which wire goes where.

I found nswsailor's post from 10 years ago, but Seabreeze won't let me add to such an old page: www.seabreeze.com.au/forums/Sailing/General/Connecting-a-VHF-Chart-Plotter-and-AIS-Receiver?page=1
NSWsailor's original schematic

Anyway, I followed his hand-drawn schematic (except for connecting a DSC-equipped VHF radio to these other 2. )
The part I wanted to quote was the bottom part of his first post, with the schematic diagram. From the AIS to the Chart plotter he connected brown AIS wire to blue CP wire, and a blue AIS wire to the brown CP wire. I did the same, and the AIS was flashing orange occasionally, indicating that a signal was received, but it didn't shop up on the CP.

Last night I connected the blue wire to the blue wire and the brown wire to the brown wire and, bingo, it shows up on the CP.



Just a mix-up on the data wires. BTW the brown wire has the label P1RXD and the blue CP wire has the label P1TXD. On the AIS receiver (in the instruction book) the brown wire is called Transmit + / NMEA0183 port 1 TX+ and the blue wire is called Transmit - or NMEA0183 port 1 TX- One version in the book, one version in the PDF book.

Good work Phil! How good is that magic moment when the data starts flowing?

It's magic.
I tried it a few months ago, no results. Then about 3 weeks ago and my original cable to the CP wasn't supplying power. So I cut back the plug and wires, but nothing. Had I short-circuited the chart plotter? So I bought a new data/power cable and then the CP worked again. Phew! Then some research here and online, then swapping over the data blue & brown wires.

I was thinking: is there a signal shadow here? Was my 30cm VHF cable big enough? Was I too far away? Were the cables correct? Etc. Just as well I live on a hill, overlooking the bay somewhat, 16 km inland.

Phill,
That took me weeks to work out and a chance comment by a technician in Sydney gave me that moment of clarity as to what should be happening. The wires needed to be connected in such a way for the data packages to be seen separately by the units downstream of the AIS receiver.
The difference in the wire colour maybe because of the different plotters we have.
My setup is still working on SEAKA but I have added a Lawrence sounder with an inwater transducer which has opened up a whole new world underwater, especially the fish!
Phil.

Hiya Phil,
NMEA has two types of devices, V1 and V2.
- V1 is dumb, it's a single TX (or RX) wire and a ground.
- V2 is smarter, it uses 2 wires and no ground.
The Garmin GPSMAP is a V1 device. The other two are V2 devices.

There are two simple rules when going between the two. For a:
- V2 Talker to a V1 Listener (GME to Garmin)....wire the + port to the Input port, and the - to the ground port;
- V1 Talker to a V2 Listener (Garmin to Raymarine)....wire the Output port to the + port , and the ground to the - port.

Here's a simple wiring diagram showing the correct way to wire between V1 and V2.
Hope this helps!


On yours, you should disconnect the blue wire (GME AIS Receiver) from the Blue wire (Garmin GPSMAP). The reason is:
The Blue wire on the GPSMAP is transmitting NMEA strings.
The Blue wire on the GME AIS is also transmitting NMEA strings. (This is the same signal as the GME Brown wire, just 180 degrees out of phase).
That's two transmitters talking at each other. Just connect the GME blue wire to the GPSMAP black wire and you da man!