Re: VHF Radio - Dual/Tri Watch?
Lets see if I can help here.
Dual watch = You are listening to two channels at the same time. One primary and one secondary. For example, channel 16 and channel 9. If something is broadcast on either channel, you will hear it. If something is being broadcast on both channels, the primary will take over.
Scan = Will run through a continuous loop of all the channels and pause on any channel that has activity on it. There are 2 types of scan, Normal and Priority. Normal does the loop continuously. Priority scans channel, then channel 16 then the next channel then back to 16 and so on.
Your icom manual show it best: