VHF DSC Radio
Digital Selective Radio
What is Digital Selective Radio?
It is a feature which has been added to all VHF radios manufactured after June of 1999. DSC equipped VHF radios are all capable of these features or capabilities:
| • | A one button distress call which can be used in a Mayday emergency** |
| • | Automatically repeat the distress call until an acknowledgement is received |
| • | Privately hail another DSC equipped radio (channel 70) |
| • | Automatically transmits your registered MMSI number during the above situations |
| • | If connected to a GPS, will transmit your coordinates during the above situations |
**When you, a passenger or a member of your crew or your boat are in 'grave and Imminent Danger' it is time to call in a Mayday.
What does MMSI mean?
MMSI is an acronym for Maritime Mobile Service identity. It is a nine digit code assigned to each vessel which is unique to that vessel. The FCC and the U.S. Coast Guard maintain a database of all the assigned MMSI numbers which includes descriptions of the vessels. The use of the database is restricted.
Each device on your vessel which is capable of transmitting (other than radar) must have the vessel's MMSI number programmed in to it. This includes your DSC equipped VHF radio, EPIRB, AIS transceiver, and SSB (Single Sideband). You mat NOT use your DSC equipped VHF radio until you have registered and programmed your MMSI number.
Each device on your vessel which is capable of transmitting (other than radar) must have the vessel's MMSI number programmed in to it. This includes your DSC equipped VHF radio, EPIRB, AIS transceiver, and SSB (Single Sideband). You mat NOT use your DSC equipped VHF radio until you have registered and programmed your MMSI number.
How do I get my MMSI number?
This will come as a surprise to you, it did to us. You radio's instructions and all over the internet it says you can get a MMSI number FREE from the US Power Squadron, Boat US, SeaTow and more. And you can, unless you ever intend to sail in International or Foreign waters. I'll repeat in larger letters:
Do not register your vessel's MMSI number with anyone but the FCC or the US Coast Guard if you intend to sail in International waters or foreign waters.
Further, if you intend to travel in International or Foreign waters, you need a station license for your VHF radio, and each crew member who will operate the VHF radio needs an operators license.
"The Role of Boat U.S.:
BoatU.S. has been authorized by both the Federal Communications Commission and the U.S. Coast Guard to assign MMSI numbers to vessels with DSC capable radios that are not required by law to carry a radio, and do not make international voyages or communications. BoatU.S. is responsible for relaying the MMSI registration information to the U.S. Coast Guard for search and rescue purposes.
The BoatU.S. MMSI Service is limited by agreement to registering recreational vessels only - those not otherwise required to have an FCC ship station license (also called "voluntarily equipped".) Vessels required to carry a radio on board are "compulsory equipped" and therefore FCC licensed and should obtain an MMSI from the FCC."
BoatU.S. has been authorized by both the Federal Communications Commission and the U.S. Coast Guard to assign MMSI numbers to vessels with DSC capable radios that are not required by law to carry a radio, and do not make international voyages or communications. BoatU.S. is responsible for relaying the MMSI registration information to the U.S. Coast Guard for search and rescue purposes.
The BoatU.S. MMSI Service is limited by agreement to registering recreational vessels only - those not otherwise required to have an FCC ship station license (also called "voluntarily equipped".) Vessels required to carry a radio on board are "compulsory equipped" and therefore FCC licensed and should obtain an MMSI from the FCC."
The below is quoted directly from the Boat U.S. website:
"US Coast Guard Sea Implementation of Areas A1 (VHF)
Currently, the USCG is implementing GMDSS in Sea Area A1.One element of the USCG National Distress and Response System Modernization Project, is called "Rescue 21", which updates the USCG VHF distress system to include DSC capability & direction finding capabilities.
**The Coast Guard can't reliably receive VHF DSC distress calls where Rescue 21 has not been installed."
Currently, the USCG is implementing GMDSS in Sea Area A1.One element of the USCG National Distress and Response System Modernization Project, is called "Rescue 21", which updates the USCG VHF distress system to include DSC capability & direction finding capabilities.
**The Coast Guard can't reliably receive VHF DSC distress calls where Rescue 21 has not been installed."
The below is quoted directly from the Coast Guard website:
Where has Rescue 21 been installed - and where not?
Because this is constantly changing information, here's the Coast Guard's info in PDF form:
As of this writing (September 2010) the East Coast and the Gulf Coast are operational, Most of the West Coast is covered (all but Los Angeles and Long Beach). The Great Lakes and Hawaii should be covered in 2011. The Western Rivers in 2012 and Alaska by 2017.
How do I call someone using DSC?
You first need to program in the vessel's MMSI number into your radio. Then you need to select an open channel. Then you need to turn to channel 70.
We can't help you after that. Because different brands and models of radios operate differently, you will need to read the instruction manual which came with your VHF radio. Sorry.
There are a several controls on different models of VHF radios to program in the MMSI numbers. Some are easy, some not so much. The higher end models in some brands have a keypad which makes it easier. Some use a control knob which makes it a little quicker to scan through each digit. Some you have to use an up and down arrow. Not so easy. You get what you pay for here.
We can't help you after that. Because different brands and models of radios operate differently, you will need to read the instruction manual which came with your VHF radio. Sorry.
There are a several controls on different models of VHF radios to program in the MMSI numbers. Some are easy, some not so much. The higher end models in some brands have a keypad which makes it easier. Some use a control knob which makes it a little quicker to scan through each digit. Some you have to use an up and down arrow. Not so easy. You get what you pay for here.
Okay, I've got my MMSI number. What now?
You need to get out your instruction manual and program the MMSI number into your VHF radio. Bear this in mind though: BE VERY CAREFUL! Check each step as you do it. This is because, with many, if not most DSC VHF radios, you can only program the MMSI number twice. (Some only once!) That means if you screw up twice, you need to send the radio back in to the manufacturer and have them re-program it.
If you buy a boat, and the previous owner programmed his MMSI number into it, you will most likely have only one chance to program in your MMSI number. And if he screwed up, you'll have to send it in. We can find no reason for this programming limitation to have been implemented.
I need to connect my GPS to my DSC VHF radio. Why isn't it built in?
(And why am I speaking in initials?)
We asked that very question at the ICOM booth at the Annapolis boat show (October 2010). We were told that most VHF radios are built in to a dashboard or a navigation station and that therefore, an internal GPS antenna would have too much interference. Many handheld VHF radios have built in GPS, but, at this writing, most manufacturers have no plans to implement internal GPS in their mounted VHF radios.
It shouldn't be terribly difficult to connect your GPS to your VHF radio, even though there are no industry standard plug / socket specifications. Your radio most likely came with an accessory plug which will connect into the accessory socket. The other end just has a bunch of colored wires hanging out.
These wires will be explained in your manual, but will probably include connections for Power and Ground; External speaker, PA speaker GPS Data in. You may use crimped butt connectors to fasten them together. But what we did was connect each to a terminal block with a spade connector.
What else do I need to know about DSC VHF radio?
You can probably find out everything you should know on this page and in your radio's instruction manual. However, there is a lot more information, if you're curious, on the Coast Guard Website.
United States Coast Guard
Digital Selective Calling
One other thing you need to know, involves the FIPS (Federal Information Processing System) as it relates to SAME (Specific Area Message Encoding) weather alerts. You program into your VHF radio your local area SAME number and if there is a weather alert for your local area, your radio will alert you. Again, read your instruction manual.
One word of caution - if you are traveling out of your SAME area, you will either need to reprogram every day you travel, or turn the feature off so it doesn't drive you buggy with alerts for an area other than where you are.
Here's where you can get the FIPS SAME code for your area:
NWR Specific Area Message Encoding
There were some wires we didn't use - like the PA speaker, but we connected it to the terminal block and labeled it anyway, so that if we decide to get one in the future, it's ready to install. Connect your other components to the corresponding terminal on the other side and you're all set. The advantage to this is that if and when you change components, you don't need to reconnect everything, only the affected wires.
Terminal Block
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