Originally Posted by RichH
Not compulsory if you dont have a 'required' license --- ie.: vessel engaged in 'commerce'.
In general, any vessel
equipped with a VHF marine radiotelephone (whether voluntarily or required to) must maintain a watch on channel 16 (156.800 MHz) whenever the radiotelephone is not being used to communicate.
Source: FCC 47 CFR §§ 80.148, 80.310, NTIA Manual 188.8.131.52.c(2)(e), ITU RR 31.17, 33.18, AP13 §25.2