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How do I connect my AIS and my VHF?

2013 May 2

Dear Boat Doctor,
I own a Beneteau First 36.7 that I race out of Chicago Yacht Club. I love the boat but I have a slight annoyance with the electronics. When I setup the boat, I decided to go with a Garmin MFD with AIS and an ICOM VHF. AIS is nothing less than a miracle, but I'd love to be able to automatically place a VHF call to an AIS target on the MFD. My radio gets GPS data from the MFD so I know they are connected and talking. Any ideas how to make this work?
Skip Schink
Chicago, Illinois

Dear Skip,
Your problem with AIS radio calls is not uncommon, but unfortunately it is a configuration problem.

The MFD has the necessary data to make the call to the other boat-it really just needs the MMSI number, the unique identifier of the vessel from the AIS. Your radio can make calls based on an MMSI number. The problem is that the MFD and radio don't know how to talk to each other.

In short, the answer is that you need a Garmin radio interfaced with NMEA2000 to the MFD. Electronics from different manufacturers can interface via two different network standards-NMEA0183 and NMEA2000. NMEA0183 has been in use for 20-plus years, and this is the protocol that your radio uses for the GPS data from the MFD. NMEA0183 transmits basic navigation data, but it predates AIS and DSC so it has no ability to transmit that information. NMEA2000 handles more data, but at the time it was developed it did not handle AIS or DSC data. The developers of NMEA2000 were forward thinking enough to allow the protocol to be extensible, if both the sender and receiver agree on the format and semantics of the data. Manufacturers have developed AIS and DSC protocols for NMEA2000, but there is not yet a generally accepted standard among manufacturers for this data.

However, two Garmin devices use the extensibility of NMEA2000 and understand each other in the custom Garmin DSC language.

I'm sorry I can't offer better news, but as you know the AIS data does give you the ability to make calls much easier than in the past. Before AIS you could only hail ships in the distance via position, "Calling the 1,000-footer just south of the Manitou Passage," and they may or may not answer you. With the name and MMSI number, you can hail by name or use the DSC functions on your radio to call via DSC. Just clicking the target would be much easier.