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Sandman: As i understand it, entering a group MMSI number in the part of you radio for doing that, will not affect your personal MMSI number at all.
Everyone: You can get your MMSI number online for free at BOATUS.com.
All that's involved in setting up a "group", is for every member of the group to input the GROUP MMSI number into their radio. It is entered on a screen specifically for group numbers. You don't do anthing to your personal MMSI number to do this. I think, actually, that group members could use any number to set up a group, as long as its first digit is a zero. They just all have to use the same group number for the group DSC funtion of our radios to work. The USCG explanation said that to pick a GROUP MMSI number, all you do is take any personal MMSI number in the group and put a zero in front of it and drop its last digit. So, 336234567, would become a group number of 033623456, and all members would enter 033623456 into their respective radio's group MMSI number set-up.
As I understand it, any radio that is turned on and within range, that has that GROUP MMSI number set up, will respond whenever any radio in the group that also has that group number set up, sends a msg using the group DSC function (DSC is Digital Selective Calling). When a group DSC msg is sent, two things happen: 1. All radios with the group MMSI number will first automatically switch to the channel the sender has selected for his group DSC call, and 2. all members (a "member" is defined as anyone with that specific GROUP MMSI number set up on the radio), can then communicate with each other just as if they were making a conference call on telephones.
So, suppose five S-B members who are using the same S-B GROUP MMSI number are out one day and one of them gets into fish. If he wants to (A BIGGGG ASSUMPTION!!!), he could make a GROUP DSC call and all the other four would automatically switch to that channel and receive his message. The other four could call back and they would all be on the same channel for a certain amount of time. After some delay, if there is no further calling on that channel, all their radios would automatically jump back to the channels they were on when the group DSC call was first made (although I am a little unsure about this part).
I also THINK the call automatically sends lat-long info to all group members, as long as the sender has a GPS NMEA connection and the GPS is turned on.
The DSC funtion of radios is set up to send at least four types of DSC calls: individual, group, all ships and maritel telephone, in addition to the distress calls. Without getting into all of the options, if you selected "individual" for a DSC call, then only that individual's radio would switch to your selected channel. For a group call, all members of the group would automatically jump to that channel. In both cases, the receiving radios would display the caller's lat-long and some other stuff.
Radios have built-in timing protocals for handling DSC messages. Certain things happen, for example, when you make a DSC call and no one in the group is up and operating. Certain time delays go into effect and certain msgs show up on the sender's radio telling him there's no one around, basically, and the radio jumps back to the previous channel.
I think a good idea would be for a group of interested S-B members to identify themselves to each other, and then we'll create a GROUP MMSI number among us. Then each of us will enter that number as our GROUP MMSI number for the GROUP DSC calling feature in our respective radios. Then, whenever we get into the water, we'll just give it a try and see what happens.
Whadyathink?
BTW, I hope everything I've said here is accurate. Obviously, anyone interested in using the GROUP DSC calling feature of their radio should READ THE OWNER'S MANUAL to see how it works.
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