US Coast wrote:Radio Watchkeeping Regulations
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 220.127.116.11.c(2)(e), ITU RR 31.18, 52.244
The cited sources in 47 CFR Part 80 are shown below. In general, the actual regulations provide the best information about what the regulations requires, and interpretations or summaries of them on websites should be considered secondary sources.
The cited part 80.148 applies only to compulsory-equipped vessels:
§ 80.148 Watch on 156.8 MHz (Channel 16).
Each compulsory vessel, while underway, must maintain a watch for radiotelephone distress calls on 156.800 MHz [Channel 16] whenever such station is not being used for exchanging communications. For GMDSS ships, 156.525 MHz [Channel 70] is the calling frequency for distress, safety, and general communications using digital selective calling and the watch on 156.800 MHz is provided so that ships not fitted with DSC will be able to call GMDSS ships, thus providing a link between GMDSS and non-GMDSS compliant ships. The watch on 156.800 MHz is not required:
(a) Where a ship station is operating only with handheld bridge-to-bridge VHF radio equipment under § 80.143(c) of this part; or
(b) For vessels subject to the Bridge-to-Bridge Act and participating in a Vessel Traffic Service (VTS) system when the watch is maintained on both the bridge-to-bridge frequency and a separately assigned VTS frequency.
The cited part 80.310 applies to voluntarily-equipped vessels:
§ 80.310 Watch required by voluntary vessels.
Voluntary vessels not equipped with DSC must maintain a watch on 2182 kHz and on 156.800 MHz (Channel 16) whenever the vessel is underway and the radio is not being used to communicate. Noncommercial vessels, such as recreational boats, may alternatively maintain a watch on 156.450 MHz (Channel 9) in lieu of VHF Channel 16 for call and reply purposes. Voluntary vessels equipped with VHF-DSC equipment must maintain a watch on 2182 kHz and on either 156.525 MHz (Channel 70) or VHF Channel 16 aurally whenever the vessel is underway and the radio is not being used to communicate. Voluntary vessels equipped with MF-HF DSC equipment must have the radio turned on and set to an appropriate DSC distress calling channel or one of the radiotelephone distress channels whenever the vessel is underway and the radio is not being used to communicate. Voluntary vessels equipped with a GMDSS-approved Inmarsat system must have the unit turned on and set to receive calls whenever the vessel is underway and the radio is not being used to communicate.
Note that the references to 2182-kHz is for the medium frequency marine band, and for recreational vessel practically none are today equipped with a radio for that marine band. The USCG themselves announced they would no longer maintain a watch on 2182-kHz after August 1, 2013., so this section of 47 CFR Part 80 seems to be a bit out of date. See:
https://www.federalregister.gov/documen ... -selective
Maintaining a radio watch on Channel 16 is always a good idea, but if you have a DSC radio you are no longer required to keep a watch on Channel 16 if you are operating in what is known as a GMDSS SEA AREA 1. That generally means the coastal waters of the United States out to about 20-miles to sea, which is the area that will be covered by DSC shore stations at USCG facilities. If you are outside of GMDSS SEA AREA 1 you must still maintain a radio watch on Channel 16 even if also monitoring with a DSC radio.
For more about what constitutes GMDS SEA AREA 1 in the USA, see
For more about relief from Channel 16 radio watch, see
In regard to the Great Lakes, the formal announcement of declaration of GMDSS SEA AREA 1 contained this notice:
While not related to Sea Area A1, the Coast Guard would like to inform mariners that the Rescue 21 System also provides VHF Coast Stations along the Great Lakes so that continuous DSC alerting is available within 20 nautical miles offshore from more than 90 percent of U.S. locations along the Great Lakes. The Coast Guard is also building Rescue 21 facilities along the Western Rivers and in Alaska.
As noted above, the current 47 CFR Part 80 regulations allow voluntary-equipped vessels to be exempt from the Channel 16 radio watch if they have a DSC radio and are monitoring the DSC channel (Channel 70 or 156.525-MHz).