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Placing analog telephones (option)
UP
Analog 2-wire telephones can be installed anywhere onboard the
vessel.
The analog telephone DBAR104001/888 (option) should be installed
on a bulkhead.
1.7
Grounding Considerations
A successful installation of a maritime satellite terminal must take into account the noisy
environment in which the equipment shall operate.
Electrical noise
The electrical environment on board a ship is usually quite noisy. Powerful electrical
installations cause voltage variations and transients, as well as low and high frequency
noise. Radio and radar equipment radiate radio frequency signals which frequently
impregnate cables on board with unwanted interference.
Ground plane
Most ships have a steel hull. One should think that the steel construction of the ship would
constitute a good ground plane. This is often not quite true. Rust, other forms of corrosion,
paint and grease, often prevent a good ground connection. A consequence of this is that
high energy power distribution on board a ship can cause significant ground potential
differences.
Antenna unit
Adequate grounding of the antenna unit depends on the fastening bolts making good
contact with the top flange of the mast. This is obtained by removing paint and using
supplied washers and nuts and running a ground wire (local supply) between an antenna
fixing stud on the antenna unit and a ground stud (local supply) bolted to the mast. Coat the
antenna fixing stud and ground stud with silicon sealant. For details, see page 17.
Antenna cable
The antenna coaxial cable normally has a solid or meshed metal screen which must be
terminated to ground both at the antenna pedestal and at the communication unit. The
supplied cable is 25 meters; lengths of 50 m and 140 m are optionally available. If the
ground potential level at the two points differ, the communication unit passing through the
screen of the coaxial cable can be quite strong. The antenna cable screen constitutes a
heavy gauge wire, which is capable of conducting large amounts of current.
Below deck equipment
The communication unit must be provided with a good electrical connection to the ship's
hull for grounding. This is obtained with the supplied ground wire. "Location and grounding
of units" on page 18.
13
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