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Here Comes Class B, Part 2!

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Photo by Ben Ellison

Now Class B-equipped Gizmo shows up on ship AIS displays and Web viewers like this.

I've never been more pleased to write this column. If you read the original "Here Comes Class B" in the March 2007 issue, you'll recall my cautious optimism about the then untried yacht version of the proven Automatic Identity System (AIS) collision-avoidance technology. Then I actually tested a Class B transponder during an offshore trip from Bermuda to Maine, and became a complete believer, as evidenced in my review of the nifty ACR Nauticast B in September 2007 and innumerable blog posts. But I had to put the ACR into "silent mode"—just listening, not transmitting—before we entered U.S. waters, and wasn't able to fully test it again for 17 months.

That was a dark period for safety-minded American boaters anxious to add Class B visibility to their commercial-shipping encounters—not to mention the many manufacturers anxious to serve them. But when the FCC commissioners finally issued their AIS ruling in September, even harsh critics like me agreed that they'd done good work. In terms of an important side issue involving the two VHF frequencies that all AIS devices share, the commission recognized that the technology will expand in many valuable directions. Satellite AIS monitoring, AIS transmitted tidal current data, and AIS liferaft aids are all in testing, and ideas ranging from AIS EPIRBS to AIS marina info are in the hopper. In terms of Class B, the FCC added a level of regulation that makes sense and will only be a minor impediment to its wide adoption.

Before I get into the specifics, let's note a silver lining to the FCC's protracted deliberations. Within weeks of its decision, U.S. boaters had a wide choice of Class B models to choose from, several already proven abroad and all certified to European, USCG, and FCC standards. Today inventory is ready to ship, and operators, as they say, are standing by. And once you install Class B on your vessel, it will join an AIS universe that's already fully populated with the ocean-going ships mandated to carry Class A transponders; all their deadlines are past.

As you may know, there are many Web sites that plot AIS targets using coastal receivers. My current favorite is the "pro" viewer at because it counts the various types of AIS in sight and can also replay a day's target history (great for testing). Siitech's network only covers roughly 30 percent of the U.S. coast, but I can sometimes see 2,000 to 3,000 Class A transponders in action, mostly on ships but also on some yachts either big enough to require one or smart enough to carrying one voluntarily (which is perfectly legal). It's been a kick to sometimes return from testing and see that the only Class B visible via Siitech in the United States that morning had been my boat Gizmo.

But that situation is going to change fast, I think. One reason—trivial in a way, but real—is that very charge I get knowing my little boat is not only showing up on the Web but the displays of ships running up the bay and the smaller vessels that have installed AIS receivers over the last few years. Want to be a player in Newport, Rhode Island, Miami, or San Francisco? You too can join the megas on all those AIS screens. (And secretive fishermen shouldn't fret; most every Class B AIS can easily go into silent mode when desired.)


Photo by Ben Ellison

The ACR Nauticast B is a compact transponder with a good antenna, status LEDs, and versatile data cabling.

Of course the real value is when you tangle with Class A vessels, or other Class Bs, in limited visibility. Yacht-level MFDs and charting programs are getting better and better at displaying AIS data and helping you make good use of it. And on top of all that, the USCG is planning to mandate AIS, A or B, on some 14,000 to 17,000 more U.S. commercial vessels, mostly tugs, ferries, and fishing craft that in many cases happen to be the same busy coastal passagemakers that occasionally cause rules-of-the-road heartburn.

Equipping a yacht with Class B will not break the bank. The two basic, though thoroughly competent, units I've been testing recently—that trusty ACR Nauticast B (see and a Digital Yacht AIT250 (see page 40)—both sell for about $900 including both GPS and tuned-for-AIS VHF antennas along with breakout cables able to feed plotter or PC or both via NMEA 0183. On the following pages you'll find more sophisticated Class Bs. In most cases a do-it-yourself installation is possible, but inputting the so-called "static data" needed to make a transponder meaningful cannot be done by a user. That's where the FCC stepped in. Due to the bad data—like vessels with a plotted beam greater than their length, and worse—that got into some Class A transponders during the rush to meet mandates, and probably due to the USCG's use of AIS as part of its MDA (Marine Domain Awareness) security program, the government has gotten dead serious about AIS data validity. While thankfully they did not impose a licensing requirement on Class B installers, a serious fine can be levied against an AIS user broadcasting inaccurate data. It's not hard to get it right, but do get it right.

The main thing you need is a vessel MMSI number, which may already be programmed into your DSC VHF (they should be the same, and will work together very nicely eventually, as explained in the Simrad entry on page 38). If you never intend to cruise outside U.S. waters you can get a free MMSI from BoatU.S. or other providers; Shine Micro (see "How's Your 'Q'?" September 2008) can even provide one already programmed into its Class B transponder. Otherwise, get your MMSI with an FCC Station License, which will include a call sign as well. Your local or online data installer will also need your vessel name exactly as it reads on your topsides and on your MMSI registration, along with its dimensions as measured from the intended GPS antenna location, and as shown on the Digital Yacht Class B installation screen above.

Of course there are a few installation subtleties, like how to integrate a Class B so your current GPS becomes an automatic backup. And there are still some operational niggles, like the fact that some old Class A transponders will only see a B's MMSI and position, not the vessel name. My blog covers all sorts of AIS-related issues like these, and it, along with the various articles mentioned, are all available at But I've stopped writing about how valuable Class B AIS promises to be; it's really, truly here.

This article originally appeared in the January 2009 issue of Power & Motoryacht magazine.