Continuous watch on VHF CH 16 is necessary whilst at sea. It may also be necessary to monitor another VHF channel at the same time. For example, a port and harbour operations channel. Selecting Dual Watch by "DW" or D/W" control allows the radio to monitor the working channel and VHF CH 16 alternately.

It is recommended whilst at sea that a continuous watch be maintained on VHF CH 13 used for Boat to Boat Navigational Safety. You may also wish to maintain a continuous radio watch on a port and harbour operations channel, for example, VHF CH 12 when sailing in and out of a particular port. So, for example, a small boat crossing the English Channel from France to the UK may wish to maintain a continuous watch on VHF CH 16 and VHF CH 13 whilst crossing the traffic separation zones and VHF CH 16 and VHF CH 12 as she approaches Southampton port.

Practice on VHF radio simulator

To switch to Dual Watch, select the working channel and then press the D/W key. D/W appears on the display and the channel switches between the chosen channel and VHF CH 16. If a transmission is received on either of the channels, Dual Watch is disabled and the receiver stays on the channel on which the transmission is being made. To exit Dual Watch press 16 key, D/W key, or C key.