Comar Systems CSB200 Installation And Instruction Manual page 7

CSB200 Class B AIS
GPS Antenna
The GPS antenna used must be of the active type (i.e. it should
incorporate an LNA) and must be suitable for marine shipboard
applications (index of protection, ruggedness, means of mounting, etc.).
An antenna should be selected with a gain (in dB) depending on the
length of cable between the antenna and the AIS unit; after subtraction of
cable and connector losses a minimum total gain of 25 dB should be
available at the CSB200 unit GPS antenna connector.
The GPS antenna to be used for AIS use must be a dedicated antenna,
i.e. not shared with any other GPS receiver.
Installation of the GPS antenna is critical for the performance of the built
in GPS receiver which is used for timing of the transmitted time slots and
for the supply of navigational information should the main navigational
GPS fail. We strongly recommend that:
1. The GPS antenna is mounted in an elevated position and free of
shadow effect from the ship's superstructure.
2. The GPS antenna has a free view through 360 degrees with a
vertical angle of 5 to 90 degrees above the horizon.
3. As the received GPS signal is very sensitive to noise and
interference generated by other onboard transmitters, ensure that
the GNSS antenna is placed as far away as possible from radar,
Inmarsat and Iridium transmitters and ensure the GPS antenna is
free from direct view of the radar and the Inmarsat beam.
4. It is also important that the MF/HF and other VHF transmitter
antennas are kept as far away as possible from the GNSS antenna.
It is good practice never to install a GNSS antenna within a radius of
5 meters from these antennas.
VHF antenna for AIS use
The VHF antenna employed for AIS use:

Must be a dedicated antenna, i.e. not shared with any other VHF
transmitter/receiver.

Must be suitable for marine shipboard applications (index of
protection, ruggedness, means of mounting, etc.)

Should be omni-directional and vertically polarised with unity gain
(0 dB) with a bandwidth sufficient to maintain
the frequency range 156 – 163 MHz. As a minimum the 3dB
R4.0 7
VSWR <1.5
over