36 | BoatU.S. Magazine AUGUST | SEPTEMBER 2015
If you ever got into a situation on your boat where you really needed help – if you struck a submerged log and were already ankle deep in water, for example, or if you thought
you might be having a heart attack – and your cell phone was
lying next to your VHF radio, which would you reach for first?
If you thought, even for a moment, that you should grab the
cell phone and dial 911 before using the VHF radio, think again.
Your radio links you not just to other boaters who might be
close enough to come to your assistance but also to the network of towers that make up the Coast Guard’s Rescue 21 system. Conceived two decades ago and rolled out over the last 10
years, the Rescue 21 system was designed to extend VHF cov-
erage to 20 miles offshore and to eliminate coastal coverage
gaps in the old system. The interlocking coverage ranges of
the Rescue 21 towers now blanket over 40,000 miles of coastline, including the entire Atlantic, Pacific, and Gulf coasts of the
continental United States, as well as along the shores of the
Great Lakes, Hawaii, Puerto Rico, and the U.S. Virgin Islands.
Each tower is equipped with direction-finding equipment that
can provide a bearing to your location. If your VHF-radio call is
received by multiple towers, those bearings can be used to triangulate your signal and find you, even if you don’t know your
position. In most cases, Rescue 21 can pinpoint your location in
minutes, all but eliminating search time so that help reaches
you much faster.
But what if you are suffering from a heart attack and
can’t make a VHF call? If your radio is equipped with Digital
Selective Calling (DSC) and has been programmed with an
MMSI (Maritime Mobile Service Identity), all you need to do is
press the distress button. The radio will transmit your 9-digit
DSC radios aboard other boats within VHF range will display
this information and repeat it, so that your emergency signal
effectively multiplies as it fans out from your location. Once
your signal is picked up by Rescue 21 towers, Coast Guard
watch standers can use your MMSI number to identify you,
confirm the emergency, and get details of your boat that will
be helpful in the search-and-rescue effort.
Given the DSC-equipped VHF radio’s technological advantage, plus a track record that includes more than 75,000
Rescue 21 missions, it surprises the U.S. Coast Guard that so
many boaters will still dial 911 instead of using the VHF radio
when things go wrong. Let’s be clear: Even assuming your signal and the call doesn’t get dropped midsentence, cell phone
calls do not automatically reach U.S. Coast Guard rescue-operations centers, and they do not provide those centers
with your current location. Rescue 21 towers can’t detect a cell
phone signal, so they can’t triangulate on your location. When
you call in your emergency using your cell phone, boats in your
area won’t be alerted, and rescue-craft operators can’t directly
communicate with you. If you’re having a medical emergency
and can’t speak, there’s no button to push that will instantly
signal your need for assistance.
So reach for the VHF. But before you do it in an emergency,
get familiar with its capability. One way to do that is by making
boat-to-boat DSC calls to your friends using their MMSIs and
familiarizing yourself with radio talk versus cell phone chatter.
If you don’t have a DSC-equipped VHF, consider upgrading.
BoatU.S. members can get a free MMSI for use in U.S. waters.
Put the phone down. REACH FOR THE RADIO FIRST
Signal is also immediately
picked up by Rescue 21
towers on land, which
determine bearing to the
The emergency signal is
instantly received, displayed,
and repeated by all DSC
radios within range – alowing
nearby vessels to become
Information about the boat in distress,
and its exact position, is rapidly relayed to the Coast Guard, which makes
contact with the crew of the boat and
launches rescue operations.
Distress signal is sent out to
multiple receivers from sinking boat
via their DSC-enabled VHF radio.
Coast Guard station