Did you know it will send an alert to all DSC equipped boats around you in case of trouble?

Quick Tips:

  1. Connect your VHF Radio equipped to a GPS signal on your boat.
  2. Register for an MMSI number. For use in Canadian (International) waters register through the FCC, US waters register through BoatUS. URLs below.
  3. Brief your crew. The DSC DISTRESS button will alert Coast Guard and surrounding boats of your problem and location.
  4. Test your system with a call to the nationwide Coast Guard MMSI number, 003669999. See below for more information.
  5. Use DSC to communicate on flotilla cruises or directly with friends.

According to industry sources, fewer than 10% of marine VHF radios have a working DISTRESS DSC button. Why? Most VHF radio owners have not bothered to register for an MMSI number and enter it into their VHF radio (full disclosure: I was one of them several years ago. I kept putting it off…) And they have not connected the VHF radio to a GPS signal on the boat. It is not that difficult, or expensive if a marine electronics shop does it. If this is you, not only is DSC essential for summoning emergency help, it allows you to hear other boats in trouble, and it can be handy to call friends, or make general announcements to other vessels.


This Standard Horizon VHF has a GPS receiver built in.

If you are one of the 90%, imagine this:
You are incapacitated on your boat, or in the water. One of your crew or family runs to the VHF, sees the red DISTRESS button, presses the button, but nothing happens. Unfortunately, they do not even know nothing happened. They can call for help on VHF 16, but they might not know how to operate the GPS to provide a position to the Coast Guard.

The distress function on a DSC radio works in conjunction with the Coast Guard’s Rescue 21 system. When the distress button is pushed, a DSC message containing your vessel’s MMSI (Maritime Mobile Service Identity) number and position is sent. The Coast Guard receives this information and can quickly correlate your MMSI number with additional information about your boat contained in the MMSI registry. Moreover, nearby boats equipped with DSC radios will receive an alarm for a nearby vessel in trouble. If the VHF radio is interfaced to a chartplotter the distress signal will appear as a marker on their chartplotter, making it easy for them to render assistance. In our frigid waters, time is critical, and the DSC system can bring help faster from nearby boats and the Coast Guard.

The heart of this system is a capability that has been built into every marine radio sold for the last 15 years called Digital Selective Calling, or DSC. VHF radios with DSC all are equipped with a red DISTRESS button to summon help and provide location information. During the last 10 years the US Coast Guard completed the national roll-out of a new system called Rescue 21 to incorporate DSC and MMSI information into its Search and Rescue System. This system is now operational along the entire coastline of the US. Alaska and many of the major rivers are in the process of deployment and should be online by 2017.

After you enter the MMSI number for your vessel into the radio you become part of the system. Your radio silently “listens” to VHF 70 for a digital signal. There are several types of programmed signals and associated tones for: distress, urgency, safety, routine, position send, position receive, and group calls.

For distress calls the tone is loud and shrieking. It will get your attention and all on your boat. The first time it might be difficult to isolate the tone and where it is coming from. Just touch any button on your radio to silence the tone. Listen and you will hear more about the nature of the call. The coordinates of the stricken vessel will appear on your radio. Some radios plot course to and distance of the distressed vessel and display it on the VHF radio and the chartplotter.

Dive into the manual for your VHF radio and you will see that there are many capabilities built into the DSC system. While the interface to use them may be a bit cumbersome, once you learn them you can really utilize the capability of your VHF radio.

Maintain a list of MMSI numbers for your friends, yacht club, and type club members. At the Waggoner Guide, we encourage yacht clubs and type clubs to add MMSI numbers to their membership roster books. It is a great way to keep in touch.

If you don’t have an MMSI number, get one. There are two options for U.S. boaters. Best is to register in the international database with the FCC. The FCC website allows you to register for a Ship Station License and obtain an MMSI number with a single application. This is required by law for vessels traveling in international waters including Canada. A fee is involved and the web site is hard to follow. Be sure to fill out Main Form 605 and Schedule B. Also, Form 159 for remittance.

Start the process here by registering with the FCC: http://wireless.fcc.gov/uls/index.htm?job=about_getting_started
Don’t be afraid to call their help line at 1-888-CALL-FCC. They are used to getting calls requesting help.

Boaters can also register with BoatUS, though this is not an international database. There is no charge for registering with BoatUS, though it is not legal for international travel. Some have pointed out that this is not enforced and at this time BoatUS is lobbying the FCC and authorities to drop the Ship Station License  requirement for recreational vessels.

For Canadian boaters, register for your MMSI at: http://www.ic.gc.ca/eic/site/smt-gst.nsf/eng/sf08138.html.

Some think DSC is a private digital channel capability. This is not true. Think of DSC more as a private hailing channel. For instance, others can’t hear you hailing the vessel Searaven. However, upon switching to a working channel, all conversation is open for all to hear.

Increasingly, radio manufacturers are incorporating GPS receivers directly into new VHF radios to eliminate the need for interfacing with an external GPS. This simplifies installation and adds little cost. Standard Horizon has several fixed mount VHF receivers with GPS built-in. They even have the model HX851 handheld VHF radio equipped with GPS and DSC, perfect for use with the tender.


The portable Standard Horizon HX851 has DSC built in.

We have added this very capable handheld radio to our boats for the 2014 season. It’s an ideal radio for the dinghy. With GPS you can set a waypoint for your anchored boat. Or, thanks to the DSC capability you can send a position request to the dinghy’s handheld radio to learn its location. With the handheld you can send a position request to the mothership to learn where the boat is. And of course, if you run into a problem, you can use the red DISTRESS button on the handheld to alert nearby boats and the Coast Guard of an emergency. The radio floats and is waterproof. It even has a strobe in case the radio is dropped into the water at night (or you are in the water at night). Icom’s M92D handheld VHF has similar capabilities.

DSC on your VHF radio offers a lot of interesting capabilities that you probably already have on your boat and could be critical in an emergency. Get your VHF connected to your GPS, or purchase one of the new VHF radios that have GPS built-in. Register your radio with your vessel’s MMSI number. Learn how to use the DSC features and give them a try.

Mark Bunzel

Learn more at:
BoatUS Tutorial on DSC: http://www.boatus.com/foundation/dsc/player.html
BoatUS FAQs on MMSI:  http://www.boatus.com/mmsi/MM1.htm#q10
Standard Horizon: http://www.standardhorizon.com/

Courtesy of BoatUS:

To Test Your DSC System
To run a test call the nationwide Coast Guard MMSI number, 003669999.  Enter this number into your radio’s calling memory and select the “Test Call” option from the radio’s list of individual DSC calls, you can then press the “call” or “enter” key.  Your radio will silently hail the Coast Guard with a digital signal on channel 70.  If everything is working properly, your radio will almost immediately receive the Coast Guard’s acknowledgement of your call, providing assurance that both your radio and the Rescue 21 system are operating properly. You must be boating in an area served by Rescue 21 to use this test.  Alternatively you may also use the DSC function to privately hail another boater’s MMSI number so that they can verify what MMSI came up on their ID. The DSC functions do not work at all until an MMSI number is entered into your VHF radio. If connected to a GPS, the signal will also provide your exact coordinates. TowBoatUS Captains with DSC radios will do a radio check with you if requested.
Register with FCC or BoatUS?
While Canada is considered “international waters” which calls for an FCC Ship Station License, it is our understanding that Canada is not enforcing US regulations. Canada has also de-licensed recreational boaters. That does not mean they can not or will not require it if given reason to do so. If you proceed to operate in the shared waters without license you do so at your own risk.  Under international treaties to which the US is a party, you are required to have an FCC license to transmit your radio in a foreign port. It is recommended for Mexico, Bahamas and the Caribbean etc. BoatUS and the GMDSS Task Force are working to have the FCC lift the rule for Canada and the Bahamas. Also, the U.S. & Canadian Coast Guard are working together to respond to any distresses in the border waters.

Using the DSC System
IF YOU HEAR A DSC DISTRESS CALL. Shut the radio alarm off by pressing 
any button on your radio. Write down the MMSI and position information showing 
on your radio display screen. Wait 3-5 minutes for an authority to answer the call. 
If no other station replies attempt to verbally relay the MMSI and position 
information to USCG. Contact the station in distress if no one else does and go to 
their rescue, if you are able to do so. 

Get on the VHF Distress, Safety and Calling Frequency (VHF Ch-16) or SSB 
Safety and Hailing Frequency (4125 kHz, USB) and make an all stations 
announcement to cancel the DSC Distress Call. 

of this form should be filled out with boat description ahead of time and posted 
near each fixed DSC VHF Radio on board. This form can be filled out and used as a script when issuing voice MAYDAY Calls. 

Reprinted from with permission from theThe Official Program of the US Sailing Safety at Sea Seminars. Consider printing and posting this at your helm and brief your crew on its use in an emergency.

Post this form by each permanently installed radio equipped with DSC
Fill in Items 5, 6, 11 and 13 prior to getting underway. 


1. Make certain your radio and GPS are turned on and the radio is on High Power. 
2. Send DSC Distress Call – press Red Distress Button for 5 seconds. Wait for a DSC 
Distress Acknowledgement then shift to VHF Ch 16 or SSB 4125 kHz (USB) for voice instructions. 
3. If no DSC Acknowledgement is received Select VHF Ch 16  
4. Press microphone button and say: “MAYDAY – MAYDAY – MAYDAY” 
5. Say: “This is (Your boat name, MMSI or Call Sign)” 
6. Repeat once: “MAYDAY (Your boat name)” 
7. Tell where you are: 
a. Latitude and longitude 
b. Navigation Aids or Landmarks nearby 
c. Direction and distance to a Prominent Landmark 
8. State the nature of your distress and the kind of assistance required:  
9. Give the number of people aboard and condition of any injured 
10. Estimate present seaworthiness of your boat. 
11. If time allows – Briefly describe your boat: 
a. Type – (Sail or Power) 
b. Length in feet- 
c. Hull color- 
d. Trim color- 
e. Masts- 
f. Other Identifying Info- 
12. Say: “I will be listening on Channel 16 ” 
13. Say: “This is (Your Boat Name, MMSI or Call Sign) OVER” 
14. Release microphone button and Listen for an Answer. 
16. If you do not receive an answer Repeat Call beginning at Item 3. 
17. If no answer again Check to see if radio is turned on and VHF is on CH 16, high power.

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