VHF Radios - updated May 2009
by Chuck Husick
A handheld VHF radio
can serve as the primary communication device on smaller boats as well
as a back-up for a fixed mount transceiver. The use of large scale integrated
circuits and microprocessors makes it possible for even the smallest of
these radios to provide virtually all of the capabilities and features
of conventional radios. The major differences between the hand-helds and
fixed mount radios are maximum transmitter power output and the non availability
of digital selective calling in the handheld sets. Virtually all of these
radios operate on all allowable transmit and receive channels, including
all NOAA weather channels.
As with all marine
VHF transceivers, handhelds must provide a 1 watt transmit power selection
in addition to whatever higher power may be available (usually 3-6 watts).
The general considerations that govern the choice of a fixed mount VHF
set apply to a handheld radio. The receiver is the most costly part of
the radio and its ability to separate the signal you need to hear from
interfering signals may determine the radio's worth. Transmit power is
a secondary consideration. Remember, communication on the marine VHF band
is essentially line of sight. Unless the radio is connected to a fixed
antenna, mounted at some height above the water, the one watt low power
setting will usually be all you need for clear communication. The Rescue 21 VHF/DSC communication system now being completed is designed to provide reliable communication with a 1 watt radio, 1 meter above the water, at a distance of up to 20 nautical miles from shore. Further,
unless the radio is connected to an external power source it will be drawing
energy from its internal battery. Battery life is greatly extended by
using the low power setting.
Connecting a handheld
radio to the boat's fix mount antenna can be very worthwhile. The fixed
mount antenna is a more efficient means for radiating transmitter power
than the necessarily small antenna on the radio. The added height of the
fixed mount antenna will increase the "radio horizon", the distance
over which you will be able to establish reliable communication. The antenna
on many handhelds plug into an RF connector on the top of the set. With
the antenna removed a coaxial cable connected to a fixed mount antenna
can be plugged into the radio. If you elect to use this option be sure
to secure the normal antenna to the radio so that it will be immediately
available when it is necessary to use the set without the fixed antenna.
As noted, all VHF
radios are vital safety devices. Carrying a hand-held in addition to a
fixed mount set provides a valuable degree of additional security. The
hand-held may be a critical device in an emergency. Buying a high quality
model that is waterproof (submersible) can provide a possibly critical
degree of assurance that it will work when needed. Buying a radio capable
of using standard alkaline cells as an option to the normal rechargeable
Lithium-ion or other rechargeable battery can be a very desirable choice.
It is difficult to ascertain the state of charge of a rechargable battery which may
become depleted just when it is needed most. Alkaline cells can be stored
on board for a number of years with little or no loss of stored energy.
Choosing a fully waterproof set capable of operating from alkaline cells
is an obvious choice for a radio to be included in an abandon ship bag
or in a liferaft. (Any battery or battery operated device included in
a life raft container must be carefully packaged to ensure that the raft
is protected from damage in the event a cell leaks its caustic active
Recent developments in electronics technology make it possible for some manufacturers to offer handheld radios with integral GPS receivers and DSC hailing capability. Properly programmed with the vessel's MMSI these radios can transmit a digitally encoded automatic MAYDAY signal in the event of a life threatening emergency.
Many of today's handheld radios are waterproof and some will float if accidentally dropped overboard. Some models include a BlueTooth communication function allowing use of any number of BlueTooth communication devices.