If you already have an MMSI number registered to a fixed mount VHF on a boat you can use that same number for your handheld. Otherwise you'll need a number just for the handheld, however I don't know how that can be done without a boat registration as the number is assigned to the boat, not the device itself.
Several radios include a built-in GPS receiver, which you can use for navigation, providing your Lat/Lon position and allowing you to navigate to stored waypoints. These VHF/GPS combo handhelds include Digital Selective Calling (DSC), which functions as a sort of VHF-frequency emergency beacon. Just push and hold down the red DISTRESS button on your handheld VHF radio, and it sends an automated digital distress message to the Coast Guard and all other DSC radio-equipped vessels. Rescuers instantly know who you are, where you are (using GPS coordinates), the name of your boat and the phone numbers of your emergency contacts.
DSC also provides non-emergency capabilities, allowing you to communicate individually with another boat or group of boats using MMSI numbers. You can send and receive each other’s positions as well, if your radio and the other vessel’s radio are interfaced to GPS. While we’re excited by the promise of these features, we actually haven’t heard of many of our customers using them, and the user-interfaces of the radios can make the more complicated features challenging to use.
To get the safety benefits of DSC you must obtain your nine-digit MMSI number. We recently purchased a Standard HX870, and it took about ten minutes to go on the BoatU.S. web site and register our new DSC radio. We logged onto
https://www.boatus.com/mmsi and followed the instructions. The registration is free, and by registering your beacon, you’ll be prepared in an emergency.
https://www.westmarine.com/WestAdvis...Handheld-Radio