17
Installation Manual
Saturn Bm
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. Power-
ful 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 enclosed toothed washers and nuts.
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 MCU. The length of the cable can often be more than 40 metres. If
the ground potential level at the two points differ, the current 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 con-
ducting large amounts of current.
If the ground lead from the MCU to the ship’s ground is of lighter gauge,
the MCU will be raised to a different ground potential.
Nera recommends that the antenna cable screen be clamped to ground
at the ship’s deck in such a way that the screen passes through the
grounded clamp before the coaxial cable is terminated locally. This will
confine any noise current caused by potential difference to the cable
screen. This method is far superior to grounding the shield using “pig tail”
ground jumpers. This principle of using shielded cables where the shields
are clamped to ground should be employed as far as possible to all
cables connected to the Saturn satellite terminal.
Below Decks Equipment
The MCU must be provided with a good electrical connection to the
ship’s hull for grounding. This is obtained by using Termination Box
QUFC 911 948 as a common grounding point for MCU, external Power
Supply and Antenna Cable. (See Installation: "
foil/3 cm should not exceed 30 cm. Length of copper foil/10 cm should
not exceed 300 cm. The foil/10 cm should be connected to ship's hull
(deck or roof) by hard-soldering (or screws) to steel.
Mains power/ground
Mains ground is secured to the common grounding point through the
external Power Supply. It is therefore important to use the same mains
branch for additional equipment connected to the MCU (Fax, PC, Printer
etc.).
PLANNING
Grounding considerations
Summary of Contents for Saturn BM Marine
Page 1: ...Saturn Bm Marine Class 2 Installation Manual...
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