DSC VHF’s

May 12, 2015
By: Bill Jennings
Originally posted May 1, 2012
The Importance Of Being Connected

Unfortunately, boating emergencies do happen every day and statistics prove they could happen to you. The difference between a safe return and a tragic event can come down to having clear communications with an appropriate Search and Rescue (SAR) operation so that you can be found quickly. The latest advancement in marine communications ensures such a connection. It is called “DSC” and has been designed to be used on all types and sizes of boats, worldwide.
Digital Selective Communication, or DSC, is a unique feature that in recent years has been mandated into fixed VHF radios. This global marine communication system allows your VHF to send and receive digital messages on channel 70, the VHF frequency that is dedicated to DSC calls. There are several important applications for DSC on your boat. The most important is the ability to send a distress signal by lifting the tiny cover on your VHF radio and pressing the red button for at least three seconds.  Your distress signal will be sent to the Coast Guard as well as vessels in your vicinity that are also equipped with VHF -DSC.  You may comment that even using the maximum VHF transmission power of 25 watts, your range between small boat antennas is only about 9 kilometers, but you have to remember that with the large antennas used by Coast Guard and their relay system, this range is greatly extended. And don’t forget that your VHF antenna has a vertical polarization, meaning it must be in a vertical position to work efficiently.
A DSC emergency call is repeated automatically, so once you push your emergency button, you can take care of business onboard or abandon our boat, knowing that the proper authorities have been notified. The repetition of your DSC signal allows SAR to triangulate your approximate position.
For an even more effective response you can connect your radio to a GPS.  This allows your distress call to automatically include your present longitude and latitude. To hook up your VHF-DSC radio to your GPS, first refer to the GPS and VHF operator manuals to ensure the settings between the two units are compatible, then purchase the required length of DSC cable to connect the them.  It’s really that simple.
Despite the many advantages of DSC, many VHF owners do not use it, or simply do not understand it.  Making the system operational on your VHF-DSC radio is really quite simple.  Apply for your own worldwide Maritime Mobile Service Identity number, (MMSI), by completing a form available at most electronics dealers, the “Industry Canada” website, or the Canadian Power Squadron. MMSI numbers are all 9 digits, with the first three being your country of origin. The application form includes straight forward information about you and your boat. The completed form is forwarded to a Rescue Coordination Center, (RCC).  Once registered, the applicable search and rescue center for your emergency can access all the important details on your boat as soon as they receive your DSC signal.
As previously noted, DSC also offers other very practical communication features. For example, you can establish voice communication with other boats with DSC by dialing their MMSI number into your VHF. The VHF for the boater you are calling will ring and automatically switch to the transmitter’s channel. At this point the two boaters can carry on a normal VHF radio conversation, without using channel 16. This call system is also designed to work when calling harbours, marinas, locks and bridges.
“Position Polling” is another DSC feature that allows another boat or land station to automatically connect to your radio to obtain your GPS position.   As a side note, you no longer require a radio station license for your boat to operate a VHF, providing it is within Canadian waters.
So DSC can prove reassuring to family members at home and useful to other boats you may be cruising with.  Perhaps it may be time to upgrade the VHF radio on your boat to one of the new models that include DSC.  The price of a new radio will pale in comparison to simply knowing that you may well be avoiding a tragic event, by being well connected.