R5 SOLID AIS System
INSTALLATION
7000 118-200, C2 Page 18
the voice VHF installations used for main communication to avoid unnecessary
interference.
There should not be more than one antenna on the same level. The AIS VHF
antenna should be mounted directly above or below the ship’s primary VHF
radiotelephone antenna, with no horizontal separation and with a minimum of 2 meters
vertical separation. If it is located on the same level as other antennas, the distance
apart should be at least 10 meters.
The AIS VHF antenna should be installed safely away from interfering high-power
radiating sources like radar and other transmitting radio antennas, preferably at least 3
meters away from and out of the transmitting beam.
3.5.1.3 Clear View of the Horizon
The AIS VHF antenna should be placed in an elevated position that is as free as
possible with a minimum distance of 2 meters in horizontal direction from constructions
made of conductive materials. The antenna should not be installed close to any large
vertical obstruction. The objective for the AIS VHF antenna is to see the horizon freely
through 360 degrees.
3.5.1.4 VHF Antenna Height
The AIS is using VHF radio frequencies, which propagation characteristics are close to
line of sight. The higher the antenna location is, the longer the range will be.
3.5.2 VHF Cabling
The cable should be kept as short as possible to minimize attenuation of the signal.
Double shielded coaxial cable equal or better than RG214 is recommended to minimize
the effects from electromagnetic interference from high power lines, radar or other
radio transmitter cables.
The table below gives recommendation on cables that can be used for the VHF-
antenna connections, the cables used should always be of marine approved type. The
cable attenuation shall be kept as low as possible; a 3 dB loss is the same as cutting
the signal strength in half.
Table 4 – VHF Antenna Cables
Ex: A cable of 40 meter RG 214 has a cable attenuation of 2.8 dB.
3.5.3 VHF Cable Mounting
Coaxial cables should be installed in separate signal cable channels/tubes and at least
10 cm away from power supply cables. Crossing of cables should be done at right
angles (90°).
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