Types of AIS Transceivers

AIS transceivers allow vessels to both receive AIS data and transmit their own position, enhancing visibility and safety on the water. Choosing the right AIS transceiver depends on your vessel type and operational needs.

Class B AIS – Ideal for Recreational & Non-SOLAS Commercial Vessels

Class B AIS transceivers are designed for smaller vessels that want to be visible to others while receiving AIS data from surrounding traffic. They come in two variations:

CSTDMA (Carrier Sense Time-Division Multiple Access)

• Cost-effective option with a 2W transmission power
• Transmits every 30 seconds in normal conditions
• Best suited for recreational boats in low-traffic areas

SOTDMA (Self-Organizing Time-Division Multiple Access) – Also called "Class B+"

• Higher 5W power output for increased range
• Transmits more frequently (5–15 seconds depending on speed)
• More reliable in high-traffic areas like busy harbors and offshore routes
• Recommended for serious offshore cruisers and active boaters who need enhanced visibility

Class A AIS – Required for Commercial Vessels & Large Yachts

Class A AIS transceivers are mandatory for SOLAS commercial vessels and certain passenger vessels. These units:

• Have the highest transmission power (12.5W)
• Transmit every 2-10 seconds, regardless of vessel speed
• Include advanced voyage data and safety features

Important Considerations for Recreational Vessels

While Class A AIS is legally required for many commercial vessels, it is not recommended for recreational boats under approximately 75 feet. Beyond the higher cost and complex installation, having a Class A AIS means your vessel may be treated as a commercial vessel by port captains, harbor masters, and the USCG.

If you install a Class A AIS, you must:

• Update and maintain your vessel’s status (e.g., underway, at anchor)
• Regularly input your destination and ETA
• Report the number of people onboard

Failure to provide accurate updates can lead to inquiries from maritime authorities. For recreational vessels, a Class B SOTDMA (Class B+) AIS offers stronger signals, frequent transmissions, and enhanced visibility without the regulatory burdens.