Assignment of channel numbers to interleaved channels and simplex operation of duplex channels in the VHF maritime band at 12.5 kHz offsets.   Frequencies are in MHz.  Limited operation on narrowband channels is permitted in ITU-R Appendix S18 as amended by WRC 97, and is allowed in the US on public correspondence channels under 47 CFR 80.371(c)(C) (Third R&O PR Docket 92-257 released 9 July 1998).   Channels and frequencies colored teal will be available in the U.S. for public correspondence.  Channel 228 (red) will available in the U.S. for automatic identification systems (AIS).

A channel plan for simplex use of duplex channels, and 6.25 kHz channels (presently not authorized), is described at the bottom of this page.

This information is adapted from ITU-R Rec. M.1084-2, available from the International Telecommunications Union.
 

Simplex Use of Duplex Channels

For channel number assignments to simplex operation of duplex channels. (This channel numbering sequence is provided as an example.):

NOTE 1 – This method of numbering a duplex channel used for simplex operation is in accordance with the Digital Selective Calling Recommendation ITU-R M.493, Annex 1, Table 13.  Simplex use of certain duplex channels is permitted in ITU WRC-97 modifications to ITU-R Appendix S18, and is also permitted on selected channels used in the United States.

6.25 kHz Narrowband Channels

Extension of channel number assignments for migration to 6.25 kHz channel spacing from the current 25 kHz channel spacing with interleaved 12.5 kHz offset frequencies channels.   6.25 kHz is currently not authorized in the maritime service in either ITU-R or U.S. regulations.  (This channel numbering sequence is provided as an example.):

International VHF Maritime Channels and Frequencies

U.S. VHF Maritime Channels and Frequencies