- The U.S. Coast Guard has introduced a four-digit VHF channel numbering scheme, replacing two-digit channel numbers that previously ended with “A.” The new format harmonizes U.S. maritime radio usage with international standards.
- Channels ending in “A” now use the same two-digit number with the prefix “10,” reducing confusion between simplex and duplex channels in maritime communication.
- This update ensures U.S. Coast Guard urgent marine information broadcasts (UMIBs) reach vessels tuned to the correct channels, improving safety for mariners in U.S. waters.
- U.S. regulations require all vessels, including foreign ships in U.S. waters, to use the new four-digit channel numbers to maintain effective communication with the Coast Guard.
The shift to a four-digit channel numbering system for VHF marine radios marks an important modernization in U.S. maritime communication, reports United States Coast Guard. This change replaces the traditional two-digit channels that previously ended in “A” with four-digit numbers. The new system aligns the U.S. with international standards, improving interoperability between domestic and international maritime users. Channels that previously carried an “A” suffix are now prefixed by “10,” signaling simplex channels that transmit on the ship station frequency only, without the need for the former suffix.
Background and Evolution of VHF Channel Regulations
In 2015, the International Telecommunications Union (ITU) updated the VHF maritime frequency regulations, allowing simplex use on channels traditionally reserved for duplex operations. Duplex channels use one frequency for ship stations and a separate one for coast stations, meaning radios on a duplex channel cannot communicate with those on simplex. To prevent confusion, the Federal Communications Commission (FCC) introduced the “A” suffix in 1965 for simplex channels on the ship station frequency. The current four-digit system replaces this with a “10” prefix, ensuring consistent designation of simplex channels.
Coast Guard Communication and Channel 1022
A critical application of the updated scheme is found in Coast Guard operations. The Coast Guard uses VHF channel 1022 (formerly 22A) to transmit urgent marine information broadcasts (UMIBs) to mariners. Radios set to channel 1022 (U.S. mode) operate on 157.1 MHz for both transmitting and receiving, allowing them to receive Coast Guard safety alerts. Conversely, radios set to international channel 22 transmit on 157.1 MHz but listen on 161.7 MHz, which prevents them from receiving these alerts.
Regulatory Compliance for Vessels in U.S. Waters
According to U.S. regulation 33 CFR 26.03(d), bridge-to-bridge radiotelephones on both U.S. and foreign vessels operating in U.S. waters must be capable of operating on the updated VHF channel 22A (157.1 MHz) to ensure compliance with Coast Guard communication standards. This requirement supports safety and clear communication for all maritime vessels within U.S. jurisdiction, reinforcing a unified approach to maritime safety.
This updated VHF channel system, led by the U.S. Coast Guard, ensures that U.S. maritime communication is compatible with international protocols while preserving clear and safe communication in coastal operations.
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Source: United States Coast Guard
