• Channel 70 is reserved for Digital Selective
Calling signaling.
• Separate working channels are allocated
for commercial use.
• In some Coast Guard districts, Channel
09 has been designated as the recreational
boating calling channel. Check with local
boaters, marina operators, launch ramp
supervisors, or boating law enforcement
officials in the area where you plan to
operate your boat to learn what channel
to use for calling and monitoring for
urgent marine information.
• Commercial vessels must have VHF
radios and must continuously monitor
Channels 16 and 13 (bridge-to-bridge).
Recreational boaters can monitor Channel
13 and communicate with commercial
vessels on that channel to explain or
inquire about the vessels’ intentions.
Digital Selective Calling
With everyone using the calling channel,
that channel has become quite busy. Now,
all new fixed-mount radios must have a
special signaling feature called Digital Selective
Calling (DSC) that relieves the load
on Channel 16. This section will help you
understand what it is and how to use it.
• Each DSC radio (Figure 12-3) should be
registered and receive a Maritime Mobile
Service Identity (MMSI) number. This
ensures that should you need to put out a
distress call, authorities will know the vessel
making the call.
• You program your MMSI into your radio.
• Your MMSI is transmitted with every
DSC call.
• The owner’s information is kept on file
and is available to the Coast Guard in
supporting a rescue.
• DSC radios are equipped with a DSC distress
button that automatically sends out
a coded digital distress signal to emergency
rescue authorities (i.e., USCG).
• The DSC distress channel is currently
Section 12: Communications Afloat 137
being monitored by commercial ships
and other vessels equipped with DSC
radios. A DSC call includes your MMSI
number and your coordinates if your
radio is connected to a GPS.
• Digital Selective Calling is part of treaty
arrangements among all seagoing nations
to improve maritime distress communications.
• DSC radios also allow boaters to call all ships
for distress, call selectively to single ship or
shore station, or call a group of ships.
DSC Operation
• DSC uses VHF Channel 70 as its distress
channel. This channel is now digital only
and must not be used for voice communications
(Figure 12-4).
• When the DSC distress channel is
initiated by lifting the red cover and
pressing the “Distress” button on the
radio (red button), the USCG and all
DSC-equipped radios are automatically
signaled with the distress call
(loud alarm).
• All DSC-equipped radios are automatically
switched to Channel 16 for
voice communication.
• When receiving a DSC call, wait for
the Coast Guard to respond; if they
do not, you acknowledge the call and
be prepared to attempt contact with
the Coast Guard. You may be closer
and can be heard when the boat in
distress may not.
• Some DSC radios allow you to enter a
code for the nature of the distress, which
also will be transmitted once you press
the button.
48
49
50
51
52
53
54
55
56
57
58
Figure 12-3. DSC radio
59
60
61
62
63
64
65
Operator Tip
It is important to
to
have pencil and
and
paper near your
your
radio station to
to
record critical items
items
such as the position,
number of persons
persons
in in the vessel, and
and
nature of the distress.
This facilitates accuracy
when responding
to the call, and
and
when needed, relaying
accurate information.