Standard Horizon HX-870 - Manual (Page 122)

Page 122 HX870
18 CHANNEL ASSIGNMENTS
Tables on the following columns list the VHF Marine Channel assignments for
U.S.A. and International use. Below are listed some data about the charts.
1. VTS. Where indicated, these channels are part of the U.S. Coast Guard’s
Vessel Traffic System.
2. Alpha channel numbers, that is, channel numbers followed by the letter A
(such as Channel 07 A) are simplex channels on the U.S.A. or Canadian
channel assignments whose counterparts in the International assignments
are duplex channels. International channels do not use “alpha” numbers. If
you call the Coast Guard on Channel 16, they will sometimes ask you to “go
to channel 22 Alpha”. This is a channel assigned to U.S.A, and Canadian
Coast Guards for handling distress and other calls. If your radio is set for
International operation you will go to Channel 22 instead of 22A, and will
not be able to communicate with the Coast Guard. To use Channel 22 A,
your radio must be set for USA or Canada operation, usually by a U/I/C
(USA/International/Canada) control or combination of controls. Channel
22 (without an “A”) is an International duplex channel for port operations.
Some radios indicate an “A” adjacent to the alpha channels on the display;
on others “alpha” is not indicated but the proper channel is selected based
on the U/I/C setting.
3. Bridge-to-Bridge channels (for example, Channel 13) are for use by bridge
operators on inter-coastal waterways and rivers. It is also used by marine
vessels in the vicinity of these bridges for navigation and for communicating
with the bridge operators. Note that a limit of 1 Watt is specified for these
channels.
4. The S/D column on the chart indicates either S (simplex) or D (duplex).
Simplex means transmitting and receiving on the same frequency. Only
one party at a time can talk, unlike a telephone. Be sure to say “over” and
release your microphone push-to-talk switch at the end of each transmis-
sion. Duplex operation involves the use of one frequency for transmitting
and a separate frequency for receiving. On channels specified as duplex on
the charts, correct mode of operation is established automatically by your
radio when you select a channel; you cannot change the mode. And you
still must release the push-to-talk switch after each transmission in order
to listen to the radio.
5. Channels normally used by recreational boaters are those that include the
term “non-commercial” in the Channel Use column of the chart. Some
of these are shared with other users and some are used only in certain
geographic regions.