Seiwa Si-Tex MDA3 - Manual (Page 6)

About your AIS antenna splitter
Page 3
2 About your AIS antenna splitter
2.1 About AIS
The marine Automatic Identification System (AIS) is a location and vessel information reporting system. It allows vessels equipped with AIS to
automatically and dynamically share and regularly update their position, speed, course and other information such as vessel identity with
similarly equipped vessels. Position is derived from the Global Positioning System (GPS) and communication between vessels is by Very High
Frequency (VHF) digital transmissions.
There are a number of types of AIS device as follows:
•
Class A transceivers. These are similar to class B transceivers but are designed to be fitted to large vessels such as cargo ships and
large passenger vessels. Class A transceivers transmit at a higher VHF signal power than class B transceivers and therefore can be
received by more distant vessels, and also transmit more frequently. Class A transceivers are mandatory on all vessels over 300 gross
tonnes on international voyages and certain types of passenger vessels under the SOLAS mandate.
• Class B transceivers. Similar to class A transceivers in many ways, but are normally lower cost due to the less stringent performance
requirements. Class B transceivers transmit at a lower power and at a lower reporting rate than class A transceivers.
• AIS base stations. AIS base stations are used by Vessel Traffic Systems to monitor and control the transmissions of AIS
transceivers.
• Aids to Navigation (AtoN) transceivers. AtoNs are transceivers mounted on buoys or other hazards to shipping which transmit
details of their location to the surrounding vessels.
• AIS receivers. AIS receivers will generally receive transmissions from class A transceivers, class B transceivers, AtoNs and AIS base
stations but do not transmit any information about the vessel on which they are installed.
Because VHF radios and AIS devices operate within the same frequency range and therefore require the same type of VHF antenna it
is possible to utilise a single VHF antenna for both devices by using an AIS antenna splitter.
This AIS antenna splitter is designed to work primarily with AIS class B transceivers, although it will operate equally well with AIS
receivers.
It is not recommended to use this AIS antenna splitter with Class A transceivers, Aids to Navigation transceivers or
AIS base stations.
!