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Thread: Do you know what an MMSI is (for VHF radios)?

  1. #1

    Default Do you know what an MMSI is (for VHF radios)?

    This questions came up on another boating newsgroup I participate in.

    First of all, you need to have a VHF radio that has the DSC (Digital Selective Calling) feature. A radio with the DSC feature, if set up properly, will allow you to push one button on the radio which sends out a distress call. Other boaters (and eventually the Coast Guard will be set up for this) with DSC-compatible radios will receive an alarm on their radios and their radios will show your lat/lon AND, if their gps is connected to their radio, will also show your location on their gps. They can then hit the "go to" button on their gps and head your way.

    From what I've been reading, too many people (myself included until I read up on it) don't understand how all this works, and its advantages. They also don't know that you need to get (it's free) an MMSI (Meritime Mobile Service Identity) number that you'll need to program into your radio before all of this will work.

    The MMSI numbers cost you nothing. Information about DSC, and to get your MMSI, you can go here

    Another good use of this system is that if you have a buddy's MMSI number, you can call his radio directly (don't have to hail him on 16 and then switch to another channel to talk). Once he picks up, you're on a regular channel and your conversation can be heard by others as usual. Also, when you call him, your lat/lon will show up on his radio and your position will show up on his gps.

    My radio is about 5 years old and isn't DSC compatible. I bought a new one and got it in the mail yesterday and will use it beginning next season. The cost was only $139, but there are less expensive ones with DSC.

    So how many of you are set up with this system, and how many have used it?

  2. #2
    Member akdeweyj's Avatar
    Join Date
    Mar 2007


    There is no coverage for Alaska waters yet!

  3. #3


    Quote Originally Posted by akdeweyj View Post
    There is no coverage for Alaska waters yet!
    No coverage by USCG estimated until 2011, but other boaters (with DSC radios) will pick it up. Plus, according to the link I provided, commercial ships are required to monitor DSC for distress calls and have relayed maydays to the Coast Guard.

    I believe that channel 16 should be your first choice. But then if you have to abandon ship you push the DSC button and it continues to send out a mayday even after you've left the boat.

  4. #4
    Member AKBighorn's Avatar
    Join Date
    Jul 2006


    I have it setup but haven't spent the time to see how it all actually works. It's one of those things I planned on doing and for some reason every time I got in the boat all I could think about was fishing

    After talking with people in the CG and the Aux CG it may or may not happen then. Apparently we are pretty low on the list in getting this new tech. in AK. Also seems like I was told that with the changes that have happened in the last few years with the CG's responsibilities the money just isn't there at this time.

    I was dissappointed after researching this very subject and buying my radio that the tech. isn't here. However as I understand it you are correct that if in range anyone else that has it will recieve your info in the event of an emergency.

  5. #5
    Member GOT TOYS's Avatar
    Join Date
    Apr 2006

    Default DSC

    It's a free technology I wouldn't be without. I like to "ping" my buddies to find out where they are. If you are in VHF range, an icon shows up on your plotter showing their exact location. Sweet. Even though the CG may not yet monitor it, other boats out there have it, and they all will receive your SOS with the push of a button on your VHF. I always give a briefing to new people on my boat, and it includes pushing the red button on the VHF if things go really bad. It will broadcast your exact position to all boats with MMSI/DSC setup, and put the icon on their plotter. I wish everyone would get their number and get it set up. It would make boating safer for us all. All it requires is connecting a couple wires between your DSC-capable VHF and your GPS, and going to BoatUS to get registered. They give you a number. You can give that number to your buddies, and they can "ping" you individually. It's also a good way to let them know where the hot spot is without broadcasting it to everyone.
    As simple as it is, I'd like to think the CG has it already on their boats, though maybe not officially. A full-blown version and the CG would know your name, the name and size and color of vessel, phone numbers, etc. It sure would save a lot of time on bradcasting coordinates. Maybe Mike can let us know his 2 cents.

  6. #6
    Join Date
    Sep 2006
    Douglas Island

    Default DSC radios

    Digital Selective Calling (DSC) is part of the GMDSS program (aka Rescue 21 for the CG)....DSC is essentially "stand-alone" technology that works best when integrated into other systems (such as GPS, etc.). All you really need is two DSC-equipped VHF radios (with programmed MMSI numbers) and you can take advantage of DSC. It works, I've tried it. The problem is that one of the reasons to get a functional DSC radio is the enhanced rescue benefits it provides....only the Coast Guard doesn't have the hardware systems yet. I wish it was as simple as us going out and buying DSC VHF radios for all of our boats, but it isn't that easy. Let me explain: The CG utilizes 'high sites' systems designed and usually located on mountain tops (look closely, you might be able to see the tower on Mt. Robert Barron on Admiralty Island). These systems allow the CG Command Centers to talk to boaters (usually during emergencies!) in Chatham Strait from downtown Juneau...try that from your boat-you can't talk that far because VHF is essentially line-of-sight. The necessary hardware for the CG to utilize DSC isn't just an off-the-shelf VHF radio; it's a custom-built electronic console that's been engineered to meet specific demands. They're quite expensive as you might imagine.

    The Rescue 21 project was designed to upgrade all the coastal stations with DSC (and quite a bit more) capabilities. Alaska was scheduled to be last on the list...(surprise!)...and, the project ran behind schedule and the money ran low. Plus, the 'lower 48' engineers didn't really design a system that would work for Alaska. The result was that the Alaska Coast Guard requested that we have more ownership of the project in Alaska to help guarantee functionality. We recently opened a "Rescue 21" shop in Juneau....sorry, no time lines yet.

    The bottom line for boaters is this: Go ahead and get a MMSI number for your VHF radio, program your radio and use it with other boaters. You'll be able to take advantage of the technology now, especially if you have your radio connected with your GPS/chart plotter. Contact the CG with emergencies just like you have in the past; on Channel 16 with a Mayday or cell phone with *CG. When we get full DSC functionality, the CG will be able to "see" you when you press the red button on your DSC radio...right now, only other DSC-equipped vessels (in your range - line of sight) will hear it.

    The (linked) brochure is a bit dated, but much of the information is still good, just remember that the CG in Alaska does not yet have Digital Selective Calling capability, but we will eventually. Call or PM me if you have specific questions or post and I'll try and answer them as I can. Mike 463-2297

  7. #7

    Default ACR Terrafix 406 GPS PLB

    I just ordered one of these. It is waterproof and floats. I transmits GPS coordinates and user I.D. info via satelitte to resuce network. I plan to wear it on my life vest 100% of the time. My understanding is this is the single most reliable method of rescue communications available. One would certainly also transmit mayday on VHF 16 if your boat didn't sink before you could do so.....I also carry a submersible handheld VHF in float bag (so it does not pull my skinny body down in the waterr), and three individually vacuum sealed hand held flares on my life jacket 100% of the time. I figure if you have a fast disaster, it will be all you can do to get people overboard, grab your ditch bag, and get in a life raft if you have it.


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