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Technical information

At the 2012 ITU World Radio Conference (WRC) changes were made to the International Radio Regulations in regards to the allocation of VHF frequencies for maritime use. These changes, directed by the International Maritime Organization (IMO), provide more radio spectrum for automatic identification system (AIS) signals and VHF data exchange system (VDES) signals.

AIS frequencies in some maritime areas are almost at their capacity due to the number of ships using AIS signals (giving ship position information). At present VDES messaging services are carried on the same frequencies as AIS information.

To improve the reliability and robustness of both AIS and VDES signals, the ITU decided to allocate additional dedicated frequencies to VDES signals. This will allow VDES and AIS information to be carried on separate frequencies.

The changes made by the ITU come into force on 1 January 2017. These changes will allow vessels to operate additional VDES and AIS services anywhere in the world. As a consequence, the following maritime channels are no longer used for maritime repeater use:

MM19 MM20 MM21 MM22 MM23 MM24 MM25 MM26 MM78
MM79 MM80 MM81 MM82 MM83 MM84 MM85 MM86  


To ensure continued coverage, RSM used as wide a range of channels as possible, therefore the channel numbers may not be in logical numbering blocks as they were previously. Transmitters have not changed location and coverage has not been affected.

Detailed information about the affected channels is available in the following documents.


As a consequence of the updated maritime channels, there are no new MM repeater channels available in the North Island and the Cook Strait area. There are channels available in the lower South Island, but any proposed assignments must be cleared with RSM.