Automatic Identification System (Ais); General - Standard Horizon GX2200 Owner's Manual

13 AUTOMATIC IDENTIFICATION SYSTEM (AIS)

13.1 GENERAL

The GX2200 does not require a special marine VHF antenna to
receive AIS transmissions. The GX2200 does not transmit AIS
signals, it is NOT recommended to use an antenna dedicated for AIS
operation.
The Automatic Identification System (AIS) is a short range coastal tracking
system. AIS is intended to assist in collision avoidance by seeing positions
and courses of AIS equipped vessels around your vessel.
AIS is mandatory on passenger ships, irrespective of size, all ships 300
gross tonnage and larger engaged on international voyages, cargo ships of
500 gross tonnage and larger not engaged on international voyages.
AIS uses two marine VHF channels. Each ship equipped with an AIS tran-
sponder transmits a packet every few seconds with information about the ship
and its voyage. Radio frequencies: AIS1 = 161.975 MHz, or channel 87B and
AIS2 162.025 MHz , or channel 88B. A stand-alone AIS receiver or the AIS
receiver built in to a Class A or Class B transponder can pick up these radio
signals and translate them into a NMEA data sentence that can be under-
stood by a computer with the proper software or by an AIS-enabled chart plot-
ter.
Classes of AIS:
Class A - 12.5W power output - mandated for use on SOLAS Chapter V
vessels (and others in some countries).
Class B - 2W output - lower cost derivative for leisure and non-SOLAS markets.
The GX2200 is capable of receiving Class A and B transmission with the
internal Dual Channel AIS receiver.
What is the range for AIS receivers?
Since AIS uses similar VHF frequencies as a marine VHF radio, it has

similar radio reception capabilities - which are basically line of sight. This
means the higher your VHF antenna is mounted, the greater the recep-
tion area will be.
Reception from Class A vessels that are 20 or even 30 miles away on open

water is not uncommon as their antennas are mounted high off the water.
Class B transponders use lower power for transmissions, therefore you can

expect Class B vessels to be received when they are 5 to 10 miles away.
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