The AIS data transmission is designed to exchange information automatically over line-of-sight VHF-FM. Where does this occur?

• A. Internet cloud only
• B. Line-of-sight VHF-FM band
• C. Through satellite
• D. Via HF radio

Answer: (B)

The main idea is that AIS uses a short-range marine radio link to automatically share vessel data. It transmits digital information over the VHF-FM marine band, specifically designed for line-of-sight propagation between ships and shore stations. Because the signal travels only as far as the radio horizon allows, the practical range is tens of nautical miles, limited by antenna height and power, which is why AIS is described as line-of-sight VHF-FM communication. This is different from internet-based exchange, which would require network access, or long-range options like satellite or HF radio. While satellite AIS exists as an augmentation, the standard system relies on the VHF line-of-sight band for automatic data exchange.