Group DSC Primer for Fleets, Racing and Safety: Group Calls on your VHF or SSB
A proposal for the Ocean Cruising Club to choose a group MMSI for DSC Calling.
A new use for Digital Selective Calling
DSC can be used to contact another boat, and alert them to the call with a loud sound just like receiving a telephone call, on your VHF. For sailing in a fleet, you can set your radio to be part of this “group” to send and receive alerts intended for any and all boats in a fleet of vessels. Thus, fleet announcements can alert and notify simultaneously every vessel racing. A boat with a man overboard or emergency situation can immediately notify every racing vessel in VHF range.
The DSC Basics
Every DSC-capable VHF should be connected to a GPS and be programmed with the vessel’s MMSI number. The MMSI (“Maritime Mobile Service Identity”) is a unique number, like a phone number, and can be obtained from your national registrar (FCC in the US) or, for US use only, from BoatUS or others. The FCC license has a fee and may be used for individual and group calls, and may be used internationally. The BoatUS MMSI is free, cannot be used for international travel, can be used to make group calls, and cannot be used to generate a new group MMSI. Only one MMSI number should be used on all equipment used on a boat (VHF, SSB, VHF handhelds, AIS, AIS emergency beacons). The FCC in the United States does not allow a user to change an AIS MMSI: if a change is desired, it must be done by an authorized dealer. If you ever decide to travel out of the US, it would be wise to obtain an FCC MMSI for the boat, rather than send the AIS unit back to the dealer. An FCC issued MMSI is also listed in the international database provided to international rescue groups, while a BoatUS MMSI is not. Since an MMSI stays with a boat when it is sold, it is wise to have an FCC MMSI, so that the boat can be sailed in foreign waters, after the sale, without changing the MMSI entered into electronics at the dealer or manufacturer.
If you are racing or traveling internationally, you should have an FCC issued license and MMSI. You should check that this MMSI is in the international database for safety.
The MMSI identifies your vessel when making or receiving a DSC call, whether it’s an emergency transmission or just a normal contact. VHF radios have directories that allow users to store commonly-called MMSI’s for ease of use. Some older radios do not have a separate group directory; newer ones do.
Procedures vary for placing DSC calls, depending on the VHF model, but all include selecting the MMSI of the recipient, specifying the nature of the call and sometimes the working channel, and initiating the transmission. The recipient will hear an alert tone on their radio and depending on radio model and nature of call, the radio may switch to the appropriate channel to complete the traffic. Some radios require accepting and acknowledging a DSC call before switching to the channel proposed by the caller, by pushing a button on the microphone. Please see your radio’s instructions.
About Groups
It is now possible to create groups and to contact all group members at once. This is very simple to do. If you add a “group MMSI” into your group directory, then calls transmitted to that group will cause your radio to respond and change to the working channel. For a racing fleet, this may be a huge convenience and safety benefit. No separate license, fee or special programming is required. Having a group MMSI entered into the radios of all vessels in a racing fleet, will enable newer AIS locator beacons with a group DSC call feature (like the MOB1) to call and notify any rating vessel in VHF range.
Group MMSI
Every DSC radio has a directory to enter the MMSI numbers for boats that are called frequently, and newer radios have a separate directory for group MMSI numbers. One does not need to change your MMSI or a get a separate license to use group MMSI calling. Group calls allow radio calling to all members of a group that have the group MMSI call entered into the group directory.
There is no formal program for issuing Group MMSIs. A Coast Guard site explains how you may generate your own legal one. Simply put, you take an existing MMSI, knock the zero off the end and add a zero to the front, so 123456780 would become 012345678.
When you add this number to your VHF radio group directory, the radio will become part of that group. Calls placed to the group will now be received by all members within range (usually about 25 nm) including YOUR radio.
Benefits of groups
Boat-to-boat VHF DSC group calling creates significant day-to-day benefits.
1. VHF radios now have an “extra set of ears” on watch, listening for calls from the group(s) you’re affiliated with. You can leave the radio on VHF 16 as required and still not miss those fleet calls.
2. Yachts racing can provide quick mutual support, for alerts and emergencies. This semi-private multi-party conference call is a perfect solution for a race. This allows allow quick, nearby support, advice or assistance from other racers. The advantage of this on a race would be that a group call would ring on every boat on the race within VHF range and switch everyone's radio, when acknowledged, to a group working frequency.
Some additional DSC items for Emergencies and Urgency
There are some USCG numbers you may wish to have in your radio for emergencies. Program these into your INDIVIDUAL, and not group, directory unless you want to be listening in on group Coast Guard calls.
Ship Group. The U.S. Coast Guard group ship station call identity is 036699999. Calls to all U.S Coast Guard ships within VHF range can be made by entering 036699999 in the INDIVIDUAL directory and then placing a DSC call.
Shore Group. The U.S. Coast Guard DSC group coast station identity is 003669999 (note the two zeroes. A call goes to USCG only). Calls to all Coast Guard coast stations within VHF range can be made by entering 003669999 in the INDIVIDUAL directory and then placing a DSC call. This will allow discussions of a routine, Securite or Pan-Pan nature to take place with the Coast Guard easily before a situation becomes a Mayday.
Some radios do not allow entry of a group number in the individual directory. I could not enter the CG ships MMSI in the individual directory in the ICOM 92d, but I was able to enter both CG ships and the Coast Guard into the individual calling directory of a Vertex Standard GX2100. Interestingly, I was able to enter the group CG MMSI into the individual directory of the ICOM 92d.
One can call a group from the group directory. The Coast Guard should be entered and called from the individual directory, since one does not want to receive all Coast Guard group traffic. It is helpful to enter the ship's MMSI into the individual directory of all of the ship's radios and handhelds. With this, one can call to or from the vessel and the dinghy (especially when the outboard stops and before you float out to sea!)
Your local district. A complete list of USCG MMSI group numbers for local sectors and groups can be found at
http://www.uscg.mil/acquisition/rescue21/dsc.asp Having your local number programmed in may be helpful in reaching them in an urgent situation.
A group MMSI is easy to implement for any ocean race. A boat Inspector can simply look in the group directory of the main VHF. There is no cost to this implementation or inspection, and it adds greatly to the safety and ease of communications of the race.
I propose that we chose a group MMSI for our Ocean Cruising Club. Group calls could be made to contact any other OCC boat in an emergency, for any kind of help or AIS, and to make contact with any other OCC boat in a harbor for any social occasion.
I also believe that adding an OCC group MMSI will spread the use and general education in the use of MMSI group calling to the general boating public, and we will lead the way in furthering safety at sea. I propose we use the present Commodore’s MMSI to generate a permanent Ocean Cruising Club group MMSI.
By Charles L. Starke MD FACP
s/v Dawnpiper