Furuno Inmarsat FleetBroadband FELCOM251 Installation Manual page 16

2.2.3 Interference
Overview
The antenna must be mounted as far away as possible from the ship's radar and high
power radio transmitters (including other Inmarsat based systems), because they may
compromise the antenna performance. RF emission from radars might actually dam-
age the antenna.
The FleetBroadband antenna itself may also interfere with other radio systems. There
are some Inmarsat systems and GPS receivers with poor frequency discrimination
which are vulnerable to the radiation generated by the FleetBroadband antennas.
Radar
It is difficult to give exact guidelines for the minimum distance between a radar and the
antenna because radar power, radiation pattern, frequency and pulse length/shape
vary from radar to radar. Further, the antenna is typically placed in the near field of the
radar antenna and reflections from masts, decks and other items in the vicinity of the
radar are different from ship to ship.
However, it is possible to give a few guidelines:
Since a radar radiates a fan beam with a horizontal beam width of a few degrees and
a vertical beam width of up to +/- 15°, the worst interference can be avoided by mount-
ing the antenna at a different level – meaning that the antenna is installed minimum
15° above or below the radar antenna. Due to near field effects the benefit of this ver-
tical separation could be reduced at short distances (below approximately 10 m) be-
tween radar antenna and the FleetBroadband antenna. Therefore it is recommended
to ensure as much vertical separation as possible when the FleetBroadband antenna
has to be placed close to a radar antenna.
RADAR
d
2. INSTALLING THE SYSTEM
Min. 15°
Min. 15°
2-3