Sperry Marine NAVIKNOT 600 SD, Operation, Installation And Service Manual

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NAVIKNOT 600 SD 056353/J
Mechanical Installation 5-1
Chapter 5: Installation
5.1 Mechanical Installation
Antenna Unit
The NAVIKNOT 600 series satellite speed logs determine ship’s heading
by comparing the phase differences of the GPS carrier signal arriving at
two GPS antennas (bow/stern or stbd./port antennas), mounted on a
beam-shaped support.
Therefore, it is critical for the function of the NAVIKNOT 600 SD that the
antenna unit is installed at the best possible location.
The two main factors which may degrade the performance of the anten-
nas are shadowing of the GPS signals and multipath reflections. Inter-
ference from nearby transmitting devices may also disturb the reception
of the GPS signals.
Ideally, the antenna unit should be mounted above all superstructures,
so that both antennas have an unobstructed all-round view of the sky
over a range of ± 80° from the vertical.
Figure 5-1:
Antenna unit
field of view
The unit should be clear of reflections from masts, out of the path of
RADAR beams and out of the range of any object that may shadow or
interfere with the reception of GPS signals. The optimum mounting
location of the antenna unit would therefore be the top of the main
mast, above all other structures.
Figure 5-2:
Optimum antenna
location
In most cases, however, it will not be possible to mount the antenna unit
at an optimum location. It may be particularly difficult to maintain the
required distances to the antennas of safety-relevant communication
devices, such as Inmarsat-C or other GMDSS equipment.
80°
80°
80°
80°
80°
80°
80°
80°
RADAR RADA
Satellite Antenna Unit
VHF, MF, other Radio
Inmarsat