comdtinst m2400.1f - US Coast Guard Response Boat-Medium

2.E.2. VHF-AM Frequency 123.1 MHz. The VHF-AM frequency 123.1
MHz is a world-wide SAR on-scene action working freqeuncy.
This frequency was assigned to provide government and
non-government land, mobile and portable radiotelephone
stations a compatible common channel for voice
communications when participating jointly in SAR incidents.
3. VHF-FM Frequency 156.3 MHz. The VHF-FM frequency 156.3
MHz (channel 6) may be used for communications between ship
stations and aircraft stations, using F3E emission, engaged in
coordinated search and rescue operations. When control of the
scene of a SAR incident is under a Coast Guard coast station,
156.3 MHz may be used by ship stations to communicate with
that coast station.