Keywords: AIS, marine GNSS, marine antenna, marine traffic, boating, fishing, port monitoring, environmental conservation
Real-time information about the movement and identity of other ships in the vicinity is critical for at-sea navigators to make decisions in advance in order to avoid collision with other ships and dangers. Historically, visual observation, audio exchanges (i.e. whistle, horns, and VHF radio), and radar or Automatic Radar Plotting Aid were used, but the integration of AIS has vastly augmented capabilities.
AIS technology, immune to weather or radar related conditions, has been widely used to improve safety at sea, avoid collisions among large vessels, consolidate navigational information, effectively track and monitor activities of fishing fleets, and provide information and enhance awareness of available resources even if the signal range is limited to VHF radio range.
The most important factor is the VHF antenna connected to the AIS system, including the antenna itself, the cable, the connector and the location of the antenna.. The VHF-coverage range of AIS is similar to other VHF applications and will essentially depend on the transmission power and height of the VHF antenna mounting. Since its propagation is slightly better than that of radar, due to the longer wavelength, it can navigate around bends and behind islands if the land masses are not too high. Under optimal conditions the AIS range can stretch to 30-50 nm for a class A device sending with 12.5W. A typical class B range (2W) would be 6-9 nm, even more depending on position and installation of the VHF-antenna.
AIS uses two frequencies to send and receive AIS messages (161.975 & 162.025 MHz), there are actually two additional transmit-only channels (156.775 & 156.825 MHz) used by Class B SOTDMA and Class A transponders for long range message 27 AIS broadcasts intended for reception by AIS satellites and other long range receiving stations. In addition, AIS transponders listen for digital management messages on the DSC channel 70 (156.525 MHz). Standard VHF radio channels range from 156.050 MHz to 157.425 MHz. For example, VHF channel 16 uses 156.800 MHz. Knowing the range of frequencies used is important as you select your VHF antenna, especially if you plan to use an AIS/VHF antenna splitter.
Unictron offers a range of Marine Automatic Identification (AIS) products including AIS transponders, receivers, and marine antennas for remote monitoring and satcom. We offer high efficiency marine-specific antennas encompassing the SATCOM bands(1616-1626.5MHz) in IP67 rated housing, as well as ultra durable, low-profile MIMO antennas with combo GNSS, LTE MIMO and L band(1621MHz). For LPWA (Low Power Wide Area), a long range connection is often necessary, so an antenna with 8dBi at either 868MHz or 915MHz, housed in a robust, all-weather casing is optimal. Marine applications range from sea-skimming UAV drones, coastal monitoring, ship surveying, and surveillance for large marine traffic and intelligence information providers to private boating, fishing and yacht industries.
- AIS 100 & AIS 700
- EG 20, GM 44