Register Your VHF Radio


The U.S. Coast Guard continues be concerned about the misuse (or lack of use) of VHF radios for distress calling. Many boaters, it seems, don't understand the importance of registering their radio equipment, and how to properly use Digital Selective Calling (DSC) feature. Here we offer a brief overview of the most frequently asked questions regarding DSC. More information can be found at the Coast Guards Navigation Center website,

WHAT IS DSC? DSCs foremost purpose is distress alerting. With the press of a button, users can send a pre-configured distress message to emergency personnel and other DSC-equipped boats in range. The digital message is sent over channel 70 and contains pertinent information about the boat, its Maritime Mobile Service Identity (MMSI) number, owner details, and emergency contact information. When a DSC radio is connected to a GPS, the Mayday includes the boats location. The transmission takes about one-third of a second and is automatically repeated until a rescue authority answers. Because the signal is digital, it has a better chance than a voice call of getting through in rough conditions.

A DSC transmission includes the priority of the call (distress, urgency, safety, routine), who the call is being sent to (all ships or a specific ship/station), and the transmitting boats identity, location, and nature of distress. DSC also allows sailors to use their VHF radios like a cell phone for ship-to-ship and ship-to-shore communications, without interfering with VHF hailing traffic and without the limitations and cost of cell coverage.

WHAT IS AN MMSI NUMBER? All boats operating on the high seas are assigned one nine-digit MMSI for all onboard equipment capable of transmitting and receiving digital signals-including EPIRBs, AIS transponders, DSC-capable VHFs, all INMARSAT satellite terminals, etc.-and that number serves as an identifier for the boat. Once a boat owner registers the vessel with the appropriate agency (the Federal Communications Commission in the U.S.), the boats emergency contact information is linked to the MMSI number, which is then programmed into the onboard electronics. When a distress call is broadcast, the MMSI is included in the message, giving rescue and emergency personnel accurate details of the boat.

The FCC and Coast Guard strongly encourage all boats to apply for an MMSI to enable DSC use in the case of an emergency. With the Coast Guards VHF-based Rescue 21 vessel ID system adding more and more stations, having the ability to send a DSC distress call will greatly increase a boaters chances of rescue.

HOW DO I GET AN MMSI? For recreational boats operating in U.S. waters, boat owners can attain an MMSI through the FCC (888-225-5322, or another approved agency, such as BoatUS (800/563-1536,, or the US Power Squadrons, radios registered through Sea Tow can still be managed through its website (Sea Tow (800-4SEATOW, However, all U.S. flagged commercial boats and those recreational boats operating in international waters must get their MMSI license directly from the FCC. You can start the process online by filing FCC Forms 159 ( and 605 ( If you think your boat may ever be sailing international waters, we suggest getting your MMSI from the FCC. Otherwise, a new MMSI will have to be attained from the FCC and entered into all onboard digital electronics before leaving U.S. waters.

Darrell Nicholson, editor of Practical Sailor, grew up boating on Miami’s Biscayne Bay on everything from prams to Morgan ketches. Two years out of Emory University, after a brief stint as a sportswriter, he set out from Miami aboard a 60-year-old wooden William Atkin ketch named Tosca. For 10 years, he and writer-photographer Theresa Gibbons explored the Caribbean, crossed the Pacific, and cruised Southeast Asia aboard Tosca, working along the way as journalists and documenting their adventures for various travel and sailing publications, including Cruising World, Sail, Sailing, Cruising Helmsman, and Sailing World. Upon his return to land life, Darrell became the associate editor, then senior editor at Cruising World magazine, where he worked for five years. Before taking on the editor’s position at Practical Sailor, Darrell was the editor of Offshore magazine, a boating-lifestyle magazine serving the New England area. Darrell has won multiple awards from Boating Writer’s International, including the Monk Farnham award for editorial excellence. He holds a U.S. Coast Guard 100-ton Master license and has worked as a harbor pilot and skippered a variety of commercial charter boats.



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