VHF radios serve as marvelous on-water communication tools, allowing boating anglers to send automated maydays in distress situations in the U.S. Coast Guard’s Rescue 21 service areas. You can also privately request and send position data between buddy boats, and privately hail other vessels to arrange voice communications on a pre-determined channel. All three features are made possible via digital selective calling (DSC).
To maximize DSC capabilities, your VHF needs GPS data and a nine-digit maritime mobile service identity (MMSI) number. Some new fixed mount VHF radio now have integrated GPS, including the Cobra 77R GPS, Icom M324G, Raymarine Ray52 and Standard Horizon Matrix GX6000. A number of handheld VHFs also offer DSC with integrated GPS, including the Icom M93D and Standard Horizon HX870
Connect with GPS
For fixed-mount VHFs without built-in GPS, you need to network the radio with a GPS source such as your chart plotter. Some VHFs such as the Icom M506 make this easy with an NMEA 2000 plug-and-play port. If you have a radio that uses an NMEA 0183 connection, networking it with GPS requires some wiring work. With VHFs and GPS units from different brands, figuring out how the NMEA 0183 wires connect can be challenge, but referencing your owner’s manual and calling the company’s technical hotline can help guide the way.
Obtain an MMSI
The easiest way to get an MMSI is to visit BoatUS or Sea Tow. These websites let you obtain, update or transfer a MMSI almost instantly and for free. You will need to fill in your information, emergency contact information and vessel description. Print out a copy for your records and keep it in a secure place.
Enter the Number
Once you have the nine-digit MMSI number, check your owner’s manual for instructions on how to enter it into your VHF. You will need to scroll through the menu to find the correct place to enter the MMSI. Once entered, the number identifies your vessel during routine voice and data communications, and in a DSC distress call, which you can place automatically by pushing the covered red distress key on the VHF control panel. You can also enter your friends’ MMSI numbers in your address list, giving you the ability to communicate privately thanks to the magic of DSC.