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All outdoor connectors on the coaxial cables should be fitted with preventive isolation, such as
shrink-stocking with silicone to protect the antenna cable against water penetration. Coaxial
cables should be installed in separate signal cable channels/tubes, and at least 10 cm away from
any power supply cables. Crossing of cables should take place at right angles (90°). Coaxial
cables should not be exposed to sharp bends, which may lead to changes to the characteristic
impedance of the cable. The minimum bend radius should be 5 times the cables outside
diameter.
Grounding
Coaxial down-leads must be used for all receiving antennas, and the coaxial screen should be
connected to the ground at one end.
GNSS Antenna installation
A Class A AIS must be connected to a GNSS antenna.
Location
The GNSS antenna must be installed where it has a clear view of the sky, so that it accesses the
horizon freely through 360°, with a vertical observation of 5 to 90 degrees above the horizon.
Small diameter obstructions, such as masts and booms, do not seriously impair signal reception,
but such objects must not eclipse more than a few degrees of any given bearing.
The antenna must be located at least three meters away from, and out of the transmitting beam
of high-power transmitters (S-Band Radar and/or Inmarsat systems). This includes the ship's
own AIS VHF antenna, if it is designed and installed separately.
Cabling
To achieve optimum performance, the gain of the antenna pre-amplifier should match the cable
attenuation. The resulting installation gain:
pre-amplifier gain - cable attenuation = max 18dB.
Attention not to overload the GPS receiver! This could damage the internal GPS.
RG214 at GPS attenuation per meter of app. 0,35 dB/m (45m = 15,75dB)
GPS frequency app. 1,2GHz
The coaxial cable between the antenna and the AIS ship borne station connector should be
routed directly, in order to reduce electromagnetic interference. The cable should not be installed
close to high-power lines, such as radar or radio-transmitter lines, or near the AIS VHF antenna
cable. A space of one meter or more is recommended in order to avoid degradation due to RF-
coupling. Crossing of antenna cables should take place at 90 degrees, to minimize magnetic field
coupling.
Antenna Layout
The position of the VHF und GNSS – antennas must be added to the existing antenna layout of
the vessel.
7
Installation Manual
Y1-03-0219 Rev. A
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