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Marine VHF Radios, Generally Speaking. To help boaters communicate when with out sailing with; Marinas, other boaters,
requests for
Check out our Marine Weather Channel webpage Although cell phones have been used, they only make direct calls and they are
private calls and thus
Operation:
Rules and Regulations?:
Licensing:
Transmit Power, Distance, and Antenna:
DSC-Digital Selective Calling & GPS:
When the emergency button is pressed on your DSC radio, both your MMSI# and your GPS location are transmitted in one second. When the Coast Guard Station hear your call electronically, it is displayed on their computer screen with your immediate location and your MMSI#. Overlaid on the screen can be the areas water current, wind factors, shoreline, so the Coast Guard can also plot an additional drift pattern circle of where your disabled vessel could end up to aid in the rescue search. There is also a belief that they can also force a poll or resend of your DSC's GPS location to also reconfirm and to additionally find your location. In accessing your MMSI number the Coast Guard can additionally find all your submitted emergency info such as your name, address, family, boat type and boat info, to aid in the rescue and who to contact. One can make DSC calls to other boaters and find out their position, when you are on a voice channel your DSC radio can alert you to incoming DSC calls and logs them. There are also preconfigured DSC messages that you can select to be sent out in your DSC call. Upon receiving DSC you can briefly respond to it and then go to a voice channel and further communicate more with them. Sailing Clubs can also have a group MMSI# that when any messages are directed to the group MMSI, it will also be received by all ships within that group. AIS-Automatied Identification:
Marine Radio Channel Modes: A/B/I
Note: Only on those channels with different modes eg: 21A, 21B, they may not be able to cross-communicate with each other as they use a different frequencies. The Emergency Channel 16, Hailing Channel 9, and Marina Channel 68, are the same, regardless of modes. The following list gives a "general description" of some the radio channels, frequencies, and usage.
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assistance, and for
Marine Safety with Coast Guard
units, the Marine VHF Radio is the authorized and preferred device to use. Using
VHF Marine radios also alerts other boaters close by to the dangers and hazards
encountered and will
involve them to respond for calls of assistance until Coast Guard rescue units can
arrive. As the general rule of the sea is that all boaters are required to
respond or assist to calls of help. Some of the newer Marine Radios have extra
Marine Weather Channels to receive or listen to continuous weather and
safety broadcasts for your area. Its a good idea to listen to these broadcasts
before sailing as they are "customized" just for boaters on the waters.
hamper
rescues as other boaters and rescue units cannot hear or make contact with you.
Cell Phones have an Achilles Heel or weakness as; the poor transmit power of the
phone (short range), height of the terrain, remoteness, and lack of cell towers.
Cell towers are configured for high use demands and hence are mostly used for
homes and highway usage designed to point and only operate for those directions.
The Citizen Bands (CB) Public Radios of the late 1970's in which every trucker
on the road and every kid in town had one are also not acceptable for marine
use, even though they cover more range than that of a cell phone.
products.
One should have "two" radios; a primary fixed station and secondary
portable battery handheld unit for backups. Small Sailboats can encounter
scenarios that when the mast that the antenna is mounted to, is laid down on
the boat (eg: trailering) can render the radio more or less useless. The
antenna or cable can also become damaged in this process or the antenna
could be damaged from high winds en route trailering on the highway. Some
small sailboats when rafted all together can rock or sway back and forth
with the top of the masts colliding from the big waves of large power
boaters racing close by. Larger Sailboats also have dinghy's to access the
shoreline and usually bring their portables with them.
preferred
to use the lower power settings for short distance communications. This also
helps out small handheld radios in prolonging the battery life. But in;
hilly terrain, far from shore, or in an emergency, the highest power setting
is the best one to use. Most radios have Low/Medium/High power settings of
1/5/25 watts and more power helps for longer distances. Some radio channels
are designated to use lower power levels to limit interference when sharing
with others.
can
predetermine the antenna style to be used. Some antennas are designed to be
extra long in length to overcome low mounting heights and can be folded down
(hinged) on deck to pass under low bridges or when trailering. Due to the
curvature of the earth, an antenna on a boat mounted 12 feet above sea level
has a line of sight about 5 nautical miles, thus two boats set far apart
could talk to each at 10 nautical miles with the higher transmit power
increasing range. Coast Guard stations have their shore based antennas
mounted extremely high up on high radio towers to give extra range of 60
nautical miles (110 km), and can have multiple towers along the shoreline
all connected via phones lines back to the station to increase the coverage
area.
low
height by being quite tall or long in length 8-10 feet, and have a small
wire continuously being wrapped around a fiberglass rod, and they also have
a hinge point at the base to allow the antenna to be laid down flat on deck
for low bridges or when the boat in on the trailer. Sailboats usually mount
their antennas high up on the top of their masts and hence the antenna needs
not to be physically as long and must be far lighter in weight. They also
have small wire coil built-in the base of the antenna to reduce the length
of the antenna before the single wire whip, as with the extra height they
all ready have more range/distance.
type
of coax cable being used, and how many splices/connectors are in between the
radio and antenna, all combined together can weaken the transmit signal by
up to 3 watts. Being an emergency device and wanting to be heard this is
very important. Additionally the gain of the antenna (narrow, medium, or
wide beam) that can focus the signal for more distance can have an effect,
but the type of boat that it is to be used upon can pre-determine that
selection. For example having a narrow beam antenna high up on a sailboat's
mast when the boat is swinging or heeling can point some of the signal into
the sky rather than across the water equally. 
electronically
only on the designated DSC channel 70, and these calls do not use the
microphone. Its easier to understand if one can think of the concept, that
your radio now has two separate radios built in to one, "one for voice
calls" and "one for electronic calls" but both listening for calls at the
same time. These Electronic DSC calls are faster to send and can travel 20%
farther and hundreds of calls can share the same channel far more
efficiently. Overall DSC is great for making emergency calls, for example;
when a ship is sinking taking on water fast, and is seconds away from the
ship batteries to be flooded, just press the Emergency Button and in just
one second your MMSI# and GPS position are transmitted. 
