What AIS provides
AIS can receive information transmitted by equipped vessels and stations, including identity, position, course and speed. A display can plot these targets alongside your own position.
Receiving is not transmitting
An AIS receiver only displays messages it receives; it does not make your boat visible to others. The antenna, installation, range and interference all affect reception.
Not every boat appears
Not every vessel transmits AIS, and data can be incorrect or outdated. Maintain a visual lookout and use all other available means.
Receiver and transponder are different
A receiver listens to AIS messages and presents them on a compatible display. A transponder can also transmit the vessel’s own data when correctly installed and configured. If you want other vessels to see you on AIS, ask specifically about transmission, configuration and local requirements; an SDR reception kit does not provide that function.
Why a position may appear before a name
Dynamic data such as position, course and speed and static data such as name and dimensions are sent in different messages. Position can arrive before the name, and some messages may be lost because of coverage or interference. Check the age of the last update and corroborate uncertain targets using other means.
A practical reception check
In port, compare displayed targets with equipped vessels nearby, inspect connections and observe whether reception changes when other electrical equipment is switched on. A missing target does not prove a fault: the vessel may not transmit, may be out of range or obscured. An empty list does not mean the water is clear of traffic.