Your Own Personal DSC Dilemma

By Lenny Rudow

For nine out of 10 boaters, their equipment will fail this simple safety test.

Photo of a US Coast Guard helicopter

What would you say if there was a new emergency distress system that gave the Coast Guard the exact latitude and longitude of any boat in need of help, even when trailered hundreds of miles from its usual launch points, and worked quicker than saying the word "mayday"? If you were to buy this system immediately, you'd be making a smart move. But odds are the system's already on your boat right now. Too bad the chances are just as good that it doesn't work.

We are, of course, talking about DSC (digital selective calling). Any registered VHF radio that has DSC functionality and is interfaced with a GPS will give the Coast Guard your exact location, as well as pertinent data about your boat, at the press of a button. Fixed-mount VHFs have included DSC going back to 1999, so chances are you have the hardware to utilize DSC on your boat right now. And as of this March, FCC regulations were updated to require DSC not only on new radios being manufactured, but also on any radio being sold or installed in the United States. So, what's the problem?

Connection Conundrum

According to USCG Rear Admiral R. E. Day, out of the roughly 100 distress calls the Coast Guard receives each month from DSC-capable radios, a whopping nine out of 10 don't have position information, because those radios haven't been connected to the boat's GPS system.

Pop quiz: Is there a pigtail coming out of the back of your VHF? Is there one coming out of your GPS? The answer to both questions is almost certainly yes. The more important question is, are they connected at this very moment? If your answer to this final question is "no," then you fail the test — along with 90 percent of the other recreational boaters on the water today. The first hurdle we have to overcome to get DSC up and running is the angst and apprehension generated by the mere thought of integrating electronics. "Interconnection between GPS and DSC equipment is not user-friendly for the average recreational boater," noted Rear Admiral Day. And he's correct; to many boaters, the idea of tapping into the maze of wires and plugs behind the helm is overwhelming. Red, green, blue, brown, black, purple, and yellow wires twist and turn in a never-ending web of confusion. To make matters worse, although modern GPS and VHF radios share a common language – NMEA (National Marine Electronics Association) 0183 and/or NMEA 2000 protocols — they don't always share common color-coding. If your GPS was built by manufacturer X and your radio was built by manufacturer Y, the yellows and the greens could mean entirely different things.

Photo of a West Marine VHF radio

The solution? If you're upgrading your electronics anytime soon, the obvious answer is to get both the radio and the GPS from the same manufacturer. Of course, that doesn't help if you don't plan on making any new electronics purchases in the near future. But don't let those different colors deter you. In most cases, you can figure out which wires are the NMEA outputs and inputs, simply by referring to the owner's manual. You didn't save it? In this day and age, you can find the owner's manuals for virtually any unit with a simple Google search.

In the worst-case scenario, you can do some simple experimentation and swap wires until you find the two that talk to each other (see sidebar). Exclude the blacks and the reds, connect the un-shielded grounds, and you'll only need to isolate one additional wire for each unit. And if you've tried all the combinations without any luck, don't give up; many GPS units require you to go into the menu and "tell" them to output the NMEA data stream. Again, use the owner's manual or trial and error to figure out if this is necessary with your unit, and how to do it.

Plug And Play

Standardization and simplification would go a long way toward promoting DSC use in the future. "We're well aware of the problems recreational boaters have when it comes to DSC, particularly with integrating GPS and VHF units," said NMEA President David Hayden. "We're trying to inform both manufacturers and the general public, but part of the problem is that many people buy their electronics online, or at a store where the salesman may not be able to give advice on how to integrate their units. So we've drafted language that specifies color-coding and wiring interconnections, and we've sent them to the Coast Guard. Hopefully, in the near future, the use of these standardizations will be mandated."

Another possible solution would be for VHF manufacturers to integrate GPS into more of the radios they build. Although more and more hand-helds are being manufactured with integrated GPS and DSC functionality (which will be mandated on portable units starting in 2015), this hasn't been the trend with fixed-mount units, even though the cost to do so would be relatively low. There are a handful of exceptions — Standard-Horizon's CPV series, for example — but these are combination units with full-blown chart plotters, not just GPS reception, so they're on the pricey side.

Photo of a GPS-equipped VHF radio


Let's say you've overcome the potential interfacing issues in one way or another, and your units are talking to each other. Good job! But we're not finished just yet. Now you need to register your boat by getting an MMSI (maritime mobile service identity) number. Once you have an MMSI, the USCG will know who you are, the size and type of your boat, and other pertinent information, if you ever call for help. Even though this is a simple process, many boaters fail to get it done and according to Rear Admiral Day, six out of 10 radios with active DSC haven't been properly registered.

Luckily, getting an MMSI is free, fast, and easy, thanks to BoatUS When DSC became widely available to recreational boaters, BoatUS stepped forward and agreed to take on the task of assigning MMSI numbers to recreational boats plying U.S. waters. To get one, all you have to do is go to with the following information: your name and address; two emergency contact names and phone numbers; the number for any cell phones used on your boat; your vessel documentation or state registration number; and your BoatUS member number. Fill out the online forms, and BoatUS will e-mail you an MMSI all your own.

Programming the MMSI number into your radio is a breeze. Depending on the unit (again, see the owner's manual), it usually takes a simple menu choice or two, then you input the number and you're done. Does this whole process sound a lot easier than you thought it would be? It should — when it comes to integration and registration, DSC's bark is a lot worse than its bite. So don't let apprehension stop you from activating DSC on your boat, today. No matter how difficult the job may seem, it's sure to be a whole lot easier than what will come afterwards if you have to say "mayday" on the VHF, and the Coast Guard has to search before they can rescue. 

This article was published in the Summer 2011 issue of Trailering Magazine.

Integration Frustration

Photo of installing a VHF radio with a GPS unit

Integrating the West Marine VHF 550 with a Lowrance HDS 8 on my neighbor's boat should have been a simple job, but the lack of standardization caused problems. First, I had to cut off the plug ends from each wire bundle, as the two manufacturers used males and females that didn't mate. Next, I printed out the owner's manuals found on the manufacturers' websites, and discovered I needed to connect the HDS's orange wire (NMEA out) with the VHF's green wire (NMEA in). Then, I connected the grounds.

Unfortunately, nothing happened. I re-checked all the connections, then went into the HDS's menu and confirmed that the unit was emitting an NMEA 0183 data stream. I noticed that while the printout showed the NMEA out was orange in one diagram, in another it showed yellow. Switching to the yellow wire did the trick — and the VHF immediately began displaying GPS data.

Once the connections were completed and the wires were secured in place, my neighbor got the MMSI number at the web site, and we programmed it into the VHF. The process took a total of an hour-and-a-half, but if the wires were attached to standardized plugs, this could have been completed in 15 minutes. This radio and GPS had been on this boat for over two years, so the cost of activating the system was exactly nothing — but the people on this boat will be forever safer.




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