Mount The Gps Antenna - Saab R5 SUPREME AIS Operation & Installation Manual

3.11 Mount the GPS Antenna

The R5 SUPREME shall be connected to a GPS antenna type MA-700, AT575-68 or a combined
AC Marine GPS/VHF antenna. 5V DC is supplied through the antenna lead for the antenna
preamplifier.
If the combined AC Marine GPS/VHF antenna is used the diplexer unit shall be installed in an
indoors environment.
Attention should be paid to the location and installation of the different antennas on the ship in
order to obtain the best possible efficiency. Special attention should be paid to the installation of
mandatory antennas like the AIS antennas.
So, installation of the GPS antenna is a crucial part of the system installation. How and where
you install your GPS antenna and cable will greatly affect its sensing efficiency.
3.11.1 GPS Antenna Location
The GPS antenna must be installed where it has a clear view of the sky. The objective is to
see the horizon freely through 360 degrees with a vertical observation of 5 to 90 degrees
above the horizon. Small diameter obstructions, such as masts and booms do not seriously
degrade signal reception, but such objects should not eclipse more than a few degrees of any
given bearing. Do not mount the antenna in the top of a mast or tower, as this may degrade
the COG and SOG readings.
Locate the GPS antenna at least 3 meters away from and out of the transmitting beam of high-
power transmitters such as S-Band Radar (typically 15° vertically from the array‟s centre
point) and/or Inmarsat systems (A, B, C, or M; typically 10º from the array‟s centre point in
any of the possible transmitting directions).
Locate the GPS antenna at least 3 meters away from HF or VHF radios or their antennas. This
includes the ship‟s own AIS VHF antenna if it is designed and installed separately.
3.11.2 GPS Cabling
The gain of the GPS antenna built-in pre-amplifier shall match the cable attenuation. The
resulting installation gain (pre-amplifier gain minus cable attenuation) shall be within 0 to 26
dB. A minimum value of 10 dB is recommended for optimum performance.
Double shielded coaxial cable is recommended. The coaxial cable should be routed directly
between the GPS antenna and the R5 SUPREME Transponder‟s GPS connector in order to
reduce electromagnetic interference effects. The cable should not be installed close to high-
power lines, such as radar or radio-transmitter lines or the AIS VHF antenna cable. A
separation of 1 meter or more is recommended to avoid interference due to RF-coupling.
Crossing of antenna cables should be done at 90 degrees to minimise magnetic field coupling.
The table below gives recommendation on cables that can be used for the Transponder GPS-
antenna connections. Due to the high frequency it‟s important that the attenuation in the cable
is low for the specific frequency (1.5 GHz).
7000 118-300, A3
R5
INSTALLATION
Page 22
SUPREME AIS System