- In general, satellite antennas should be located so that they have a 360° free view for
the satellite at all times. In practice terms this can be difficult to achieve due to
shadow sectors from nearby structures.
- It is recommended for Inmarsat-A , B and F-77 antennas (stabilized directional antennas)
that communication should be maintained with the satellite down to an elevation of minus
5°. For Inmarsat-C (omni-directional antenna) it is recommended that communication should
be maintained with the satellite down to an elevation of minus 5° in the fore and aft
direction and minus 15° in the port and starboard direction.
5.6.2 Satellite communication antenna installation
The following guidelines should be observed in order to fulfil the above
- The antenna should be located at the top of the radar mast; or
- On a pedestal, in the radar mast, or on the top deck so that:
directive antennae; shadows from constructions, especially within a distance of 10 metres,
is maximum 6°;
- for omnidirectional antennas; shadows from constructions,
especially within a distance of 1 metre, is maximum 2°.
- Antennae should be installed in a readily accessible location.
- Satellite antennae should not be located in an area where they can be damaged by heat
- The satellite antenna should not be located on the same plane as the ships" radar
- GNSS antennae should not be located close to or on the same plane as the Inmarsat
- Consideration should be given to installing the Inmarsat antenna on a suitable
(IMO resolutions A.663(16), A.698(17), A.807(19), as amended, A.808(19) and MSC.130 (75)
and Inmarsat Design and Installation Guidelines)
Note: - The mast/or pedestal should be constructed so that vibrations are reduced as much
5.6.3 Safe antenna distances
The following "safe distance" from Inmarsat antennas to other antennas and to the compass
- Distance to the HF antenna should be more than 5 metres.
- Distance to VHF antennas should be more than 4 metres.
- Distance to the magnetic compass should be more than 3 metres. (The installation manual
for the equipment and Inmarsat guidelines)
5.6.4 Inmarsat-C antenna
The antenna should be constructed so as to function up to 15° pitch and roll. In order to
obtain this result, the antenna should be located in such position that no objects or
constructions down to 15° below the horizon are degrading the performance of the
Note: - As it may be difficult to fulfil this recommendation in fore-and-aft, the free
area in this direction may be reduced to 5° below the horizon.
(IMO resolutions A663(16) and A.807(19), as amended)
5.6.5 Calculation of distance to obstructions:
If obstructions such as i.e. mast, funnel etc. is unavoidable, the following guidelines
The distance to the obstruction should be so that the
obstruction only covers a 2° sector.
Note: - In such case the safe distance will be the following: 20 x the diameter of the
obstruction (in metres).
If two Inmarsat-C antennae are installed the vertical distance between them should be at
least 1 metre to eliminate interference.
5.6.6 Antenna cable
The manufacturers specifications regarding total attenuation and maximum DC resistance
(short-circuit in one end) should be complied with. Only double-screened cable should be
5.6.7 Antennas for voluntary radio equipment
Antennas for voluntary radio equipment may be located on deck, provided its use does not
interfere with antennas of mandatory radio equipment. When mobile telephone is installed on
board ships, special attention should be made to the facts that some types of mobile
telephones (especially GSM telephone equipment) may interfere with the ship’s navigational
equipment (especially GNSS) and other electronic equipment.