Skanti TRP 9250 S, Technical Manual

Page: 81 / 227

EARTH CONNECTIONS
Antenna Tuning Unit
As the earth connection of a transmitter is a very important part of the antenna system, it is of the
utmost importance to keep in mind that the earth connection of the Antenna Tuning Unit must have
the lowest possible RF-impedance. Losses in the earth connection will result in a decrease in
radiated power which means that the range of the transmitter will be reduced. In steel ships a 100
x 0.5 mm copper strap as short as possible is connected between the earth terminal at the bottom
of the Antenna Tuning Unit and two or three 1/2" or M12 bolts welded to the superstructure.
Vessels constructed of non-conducting materials must be equipped with a copper earth plate having
a minimum area of 1 square metre mounted below the water line. From a copper earth bolt hard
soldered to the earth plate a 100 x 0.5 mm copper strap is run, preferably uninterrupted to the earth
terminal at the bottom of the Antenna Tuning Unit.
Should it be necessary to break the copper strap,
for example to pass through a deck, two or three
1/2" or M12 bolts should be used for this feed
through.
On wooden ships having a superstructure of
metal, this superstructure should also be
effectively connected to the copper strap by using
stainless steel bolts and preferably pieces of
stainless steel strips between the metal parts.
On fibre glass boats, such as yachts and sailing
boats, it may be difficult to install a sufficiently good
earth. Short copper straps are bolted to
conducting parts on the engine, the keel and other
conducting objects. Many copper straps can be
glued to the inner surface of the hull below the
water line to produce a large capacitance to the
water. It is important that the total area of copper
is large and that the distance between the copper
surface and the water is as small as possible. The
copper straps are connected directly to the ATU.
Transceiver Unit
The Transceiver Unit is preferably grounded separately to the ships metal in the shortest possible
way. A 10 to 16mm sq. ground wire is connected to the ground terminal (cable clamp) at the bottom
of the unit. On vessels with no metallic superstructure the ground connection may be omitted.
fig.11
INSTALLATION EARTH CONNECTIONS
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