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VHF255S INTRODUCTION
The Humminbird® VHF255S represents state-of-the-art high tech VHF radio engineering,
and is skillfully designed and constructed with the finest components. It is constructed
to commercial- grade standards to give you clear, reliable communication.
HOW VHF RADIO WORKS
The most popular method of communicating with other boats is via very high frequency
(VHF) radio. In technical terms, this is similar to the way that commercial radio stations
transmit. VHF equipment is relatively simple, and can therefore be compact and low cost.
To ensure that maritime users do not cause interference for other radio users, a part of
the radio spectrum has been allocated specifically to this group of users. These reserved
frequencies have been numbered, for example, Channel 16 (usually abbreviated Ch16)
actually refers to a frequency of 156.800 mHz.
Because radio does not recognize geographic or political boundaries, and to make sure
that boats traveling on international voyages can always communicate, the VHF marine
band is the same worldwide. There are 55 international marine channels, a similar
number of private channels (allocated on a local basis to commercial organizations) and
some other unique national channels.
The United States and Canada employ a slightly different application of marine
channels, using the same frequency but allocating more simplex (one-way) rather than
duplex (two-way) channels.
National channels include WX (weather) channels in the U.S., fishing channels in
Norway and the marina channels M and M2 in the U.K. To make sure that your radio is
fitted with the correct local channels, be sure to purchase type-approved equipment for
the country of intended use.