“…are advised to navigate with extreme caution. Coast Guard Sector Seattle out.”

Wait…what? I missed the first part. What’s the problem? Where’s the problem? Should I care?

I hate that feeling. It seems that every time I get a slip assignment from a harbormaster, I forget it within five seconds. Or I hear the tail end of a transmission on the vessel traffic channel, and I’m not sure if they said that 20-knot container ship is inbound or outbound, which matters because I’m about to cross the lanes! I sure wish I could just listen to that last transmission once more, know what I mean?

The product developers at Cobra know what I mean, and they offer an innovative feature on some VHF models that should help. It’s called Rewind-Say-Again, and it uses a digital voice recorder to play back the last call received.

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Here at Navagear, we’ve got a time-honored tradition of being confused about MMSI numbers. Let’s continue, shall we?

For those just joining, MMSI stands for Maritime Mobile Service Identity, and it’s a unique number assigned to your vessel for identification purposes within digital communication  protocols such as DSC (Digital Selective Calling, a feature included on virtually all new VHF and SSB radios) and AIS (Automated Identification System, in use by large commercial vessels and some recreational craft).

Oh wait…did I just say that MMSI numbers were assigned to vessels? That’s NOT entirely accurate. There are MMSI numbers assigned to ground stations, and groups of vessels, for instance.

And in the United Kingdom, apparently, there are MMSI numbers assigned to the new DSC-equipped handheld VHF radios. In fact, the UK Radiocommunications Agency has been quite clear about this:

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I finally got an opportunity to confirm that my recently installed Raymarine Ray49 DSC-enabled, two-way-NMEA, VHF radio is working correctly. For those just joining us, you can read about my first impressions of the radio itself and my crazy NMEA wiring scheme.

Anyway, once I got it all hooked up a few weeks ago, everything appeared to be working fine. Everything, that is, except NMEA data from the VHF to my Raymarine C-80. This sort of data is pretty infrequent, so I was not able to test that it was working until yesterday. I got some help from Captain Mac Lamay aboard Island Ranger. I sent DSC position requests to Island Ranger to conduct this test.

And it works! When the Ray49 VHF radio receives a vessel position message over DSC, it forwards it (via the AIS) to the chartplotter, which displays a dialogue like this:

At this point, you’ve got three options: place a waypoint, begin navigating toward the coordinates, or clear the message and ignore it.

If I were to see this dialogue box associated with a distress call, here’s what I would do:

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I got my Raymarine Ray49 DSC VHF radio wired up. The NMEA routing got too complicated for me to keep track of it in my head, so I had to draw a diagram.

[Note: Yes, I mistakenly used the electrical symbol for "battery" or "power source" when I meant "ground", for the yellow wire out of the AIS. I knew what I meant, so leave me alone about it!]

Actually, once I drew the diagram, it was pretty straightforward! Regular readers may recall that I’ve been attempting to get all this data moved hither and yon without resorting to an NMEA multiplexer. See my earlier posts here and here.

The diagram demonstrates the physical infrastructure that…

• Gets GPS coordinates from the chartplotter into the Ray49 (via the autopilot’s built-in SeaTalk-to-NMEA converter)
• Gets DCS messages to the AIS receiver.
• Gets AIS data (plus DSC messages) into my chartplotter.

It all APPEARS to be working, but I was unable to confirm that

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The Ray49 is Raymarine’s new compact DSC-enabled VHF radio. I wanted one because I want position data received over DSC to appear on my chartplotter, and my current Ray54 can’t generate outgoing NMEA data.

So I’ve got a Ray49, and I’m thinking about how I’ll install it. If you’ve been keeping track at all, you might be aware that I’ve used just about every available route to move NMEA data between components on Two Lucky Fish. For this project, I’ll PROBABLY use the other pair of NMEA wires that go into my autopilot…those wires are just sitting there at the current time.

The big question: will the autopilot forward any and all incoming NMEA data, or only those it knows how to “transcribe” into SeaTalk? The documentation implies that the autopilot might be picky about what it forwards. We shall see.

In the meantime, I’ve been reading the manual in detail. This is a nice little radio, with several minor software and hardware enhancements that should make it easier to use.

But you know me…once I start to visualize the scenarios, I always have to jump ahead to the NEXT cool feature. The one they didn’t include. Which is this:

The manual provides no indication that the Ray49 can initiate a station-to-station DSC call when requested by an external device. You can only initiate a call using the buttons and knobs on the Ray49.

Why is this a problem? Because now I’ve got AIS! I can imagine all sorts of legitimate vessel safety scenarios in which it would be prudent for me to contact the bridge of a commercial vessel transmitting AIS telemetry. Perhaps I want to clarify its intentions or something. It probably wouldn’t happen very often, but…

Wouldn’t it be cool if I could move my chartplotter’s cursor over an AIS-broadcasting vessel and push a button to initiate a DSC call? Doesn’t that make sense? Isn’t that a heck of a lot safer than having me spend the next two minutes manually entering the MMSI number off the chartplotter into my VHF radio?

And if Class B AIS is ever approved, I can imagine scenarios where I might want to chat with another small vessel about navigational conditions or something, and shouldn’t I be able to just mouse-over and click to hail them over DSC?

Well, I think I should be able to do that. So there!

We interrupt our recent policy punditry for some GEAR AND GADGET news…whodathunkit, eh?

Our colleague Captain Richard Rodriguez is debuting a new feature on his BitterEnd blog today:

Tomorrow, Thursday, May 1, 2008 begins my summer Vessel Assist season. I will be using a Spot GPS Tracker this year.

TRACK PROGRESS: Also known as SPOTcasting^SM, this feature allows friends and family to follow my progress in real time. I’ll actually use it for the first time on my trip from Anacortes to Friday Harbor aboard Diligence. I’ll be underway between 08:00 and 09:00 local. The trip will take about 3.5 hours.

And there’s a new link featured prominently on the blog:
“Click here to follow me on SPOT.“

It’ll be really interesting to see how SPOT performs in the real world. Thanks for the opportunity, Richard!

(With apologies to Lewis Carroll.)

`Twas brillig, and the slithy toves
Did gyre and gimble in the wabe:
All MMSI were the borogoves,
And the mome raths outgrabe.

I’ve written lots (here and here, particularly) about MMSI—the Marine Mobile Service Identity numbers programmed into our DSC radios and AIS transceivers.

I’m also waiting eagerly for news about FCC approval for Class B AIS in the United States.

But right this minute, I’ve got a new VHF radio to install aboard Two Lucky Fish; it’s a Raymarine Ray49 with two-way NMEA messaging, which should allow incoming DSC calls (such as distress calls) to appear directly on my chartplotter. Recall my disappointment when I confirmed that my Ray54 could not send position data to my chartplotter.

So I’m going to hook it up, and I’m going to program it with my BoatUS-provided MMSI number.

Or am I?

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There’s some ongoing discussion and trouble-shooting in the comments of recent posts in this series…take a look here, especially. Good stuff.

If you’re a gadget-obsessed boating geek, I mean!

Meanwhile, I wanted to report on some antenna testing I conducted. I’ve got two antennas (or antennae, if you prefer) mounted on the cabin top of my C-Dory. I was able to change them back and forth on my AIS receiver, and then wait several minutes to see how many targets appeared. Here are the results of that test, conducted while tied up inside the breakwater at Edmonds Marina. A cheap, bottom-of-the-line eight-foot antenna with 6db gain picks up target up to about 15-20 miles away.

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Remember my various issues with my Ray54 VHF radio? It’s a good radio, and I like the compact size. But it does have its idiosyncrasies. The only feature I really miss, though, is NMEA output, which would allow me to see incoming DSC calls right on my C-80 chartplotter.

At my last writing, I figured I would have to go with another manufacturer. Other Raymarine radios have NMEA output, but they were all larger, and I don’t want a big radio on my small boat. This morning, though, I noticed a new item on the Raymarine website…

The new Ray49 DSC VHF Radio is a compact VHF Radio with NMEA 0183 output for chartplotter position polling and Class D Digital Select Calling. 

Raymarine’s most compact VHF radio to date, the Ray49 does everything I want, and it’s actually smaller than my Ray54. It’s available in gray or white.

Hey, this just might be the radio for me!

Ask Jack Rabbit directs our attention to a new document "that describes in detail the Digital Selective Calling (DSC) system for VHF and SSB radios, and its use in Search & Rescue areas around the world." Hey, that sounds handy.

The document, written by Walter Paul, was published in late February by the Cruising Club of America. It includes an updated Rescue 21 rollout schedule. We’ve discussed Rescue 21 before.

This got me looking around for other information about Rescue 21 deployment scheduling. And looky here: BoatUS has a recent update, too.

But the "horse’s mouth", of course, is the US Coast Guard. They’ve even got a map that shows current Rescue 21 coverage: