Introduction to Marine Radios
Cell phones and satellite communications
on shore (a mode called duplex communica-
gear have become commonplace on yachts
tions). Both, or all, stations use the same fre-
and small workboats, leading many captains
quency for transmitting and receiving. High
to rely less on radios for basic communica-
Frequency channels on a single-sideband
tions. However, VHF and SSB radios remain
radio allow duplex communication by using
a critical component of safety and commu-
different frequencies for transmitting and re-
nications on a cruising boat. These radios are
ceiving. The International Telecommunica-
part of a worldwide safety-at-sea network,
tions Union designates these channels, which
and remain the primary means of skippers
are often referred to as ITU channels.
and crews communicating with one another.
In addition, a wealth of information is avail-
Radio Usage and Operating Rules
able via radio at a fraction of the cost of a
All marine radios in the U.S. are subject to
satellite hookup.
operating rules set by the FCC. Many of these
Radio Bands: VHF, HF, MF
rules are poorly understood and largely un-
enforced. What follows are general guidelines
The frequency of radio waves is measured
and the primary rules associated with radio
in hertz (Hz)—cycles per second—the same
use. Supplement these with common sense
as audio waves and electrical power. For ra-
and good manners. More details are provided
dio, however, the numbers are so large that
for each radio band: VHF, HF and MF.
the units are kilohertz (kHz), megahertz
Permitted Transmissions: Marine radio is
(MHz), and gigahertz (GHz), for respective
not a chat forum. Personal and social conver-
adio
values of a thousand, a million, and a billion
sations are not permitted. Ordinary contacts
times per hertz.
must relate to the needs of the vessel, such as
The radio frequency spectrum is divided
ine R
navigational information, obtaining supplies
into bands from Extremely Low Frequency
and services, and so forth. Avoid using the
ar
(ELF), below 3 kHz, up to Super High Fre-
radio to discuss to chat about who landed
M
quency (SHF), which is 3 GHz to 30 GHz.
the biggest fish, or where to meet for dinner.
The radio bands of greatest interest to
Calling and Working Channels: Separate
mariners are the VHF (30-300 MHz), the
calling and working channels ensure the
MF (300 kHz–3 MHz) and HF (3-30 MHz)
maximum number of stations are listening
bands. Almost all communications require-
on the calling channel in the event of a dis-
ments will normally be met within these
tress call, yet allow for the minimum amount omms
three areas of the radio spectrum. Lower
of traffic on the channel so that it will be
C
frequencies may be used for navigation and
clear to hear a distress call. Upon establish-
higher frequencies for navigation and com-
ing contact on a calling channel, stations
munication satellites.
must immediately shift to an appropriate
VHF frequencies are arranged into op-
working channel—no communications, no
erating channels, and all VHF radios are
matter how brief, are permitted on the call-
manufactured to dial through the various
ing channel. This does not apply, however, to
channels, rather than tune in actual frequen-
distress traffic.
cies. Use of MF and HF frequencies requires
In U.S. waters, every power-driven vessel
a marine single-sideband radio. Most of
of 20m length or greater; every vessel of 100
these too are pre-programmed with channels
tons and upward carrying one or more pas-
designated by the International Telecommu-
sengers for hire; every towing vessel of 26 ft
nications Union.
length or greater; and every dredge and float-
Modes of Operation
ing plant near a channel or fairway, must
maintain a watch on both VHF 13 and 16
On the VHF band, most communications
while the vessel is underway. These rules ap-
are in the simplex mode, where only one sta-
ply to all foreign vessels, recreational vessels,
tion can transmit at a time. The other party
federal government and military vessels, as
can only listen and wait for its turn to trans-
well as commercial vessels, operating within
mit. You cannot interrupt the person speak-
U.S. territorial waters.
ing as you can in an ordinary telephone call
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