VHF Channel 13

VHF Channel 13 (156.65 MHz) — the bridge-to-bridge channel for navigational coordination, used for primary collision-avoidance communication between vessels in the United States, Mexico, parts of Canada, and several Asian and European waters. ITU Radio Regulations Appendix 18 designates the channel for inter-ship safety navigation; USCG 33 CFR 26 makes Ch.13 watch mandatory for many US-port-bound vessels. Ch.13 is used for one-whistle / two-whistle passing arrangements, anchorage coordination, and traffic-pattern queries — distinct from Ch.16, which is reserved for distress alerting and initial calling.