NorthStar 961 Install Manual page 48

SECTION TWO - Installation
Table 2: Troubleshooting the installation (continued)
Symptom
Interference
Electrical, magnetic, or radio frequency (RF)
energy is interfering with the reliable
operation of the system, as shown by high
DGPS STATUS
levels of noise on the
screen.
GPS
The head and processor power up, but poor
GPS SNR readings are obtained even after
running the system for several minutes.
Page 38
Possible solutions/reasons
•
Turn off power to each and all of the vessel's other
instruments and systems, one at a time, to isolate the source
of the interference.
•
Try to eliminate the noise through earth grounding or RF
filtering techniques, as appropriate to the type of noise
encountered.
•
Check that you have the proper length of cable and that all
connections are clean and secure.
•
Verify the quality of the antenna location (the antenna should
have a clear view of the sky). For the correct antenna
placement, see Figure 5 on page 16.
•
See Table 3, "Troubleshooting the GPS/DGPS antenna
installation," on page 39.
Troubleshooting the GPS/DGPS antenna installation
In the following table, the Northstar AN150 refers to the 12-dB GPS
antenna, the Northstar 8410 coupler with whip antenna refers to the
beacon receiver whip-type (E-field) antenna, and the Northstar AN205-P
refers to the combination GPS/DGPS loop antenna with splitter.
Whenever possible, the best and most efficient way to troubleshoot is to
use a known-good set of cables, a splitter for combination antennas, and
working antennas as spares for swapping.
Concerns for the AN205-P that aren't explained in the GPS/
DGPS antenna troubleshooting table below include the fact
that mounting a loop-type antenna in close proximity to a
radome (radar-set antenna) can cause signal degradation or a
complete loss of the beacon signal. The klystron or magnetron
contained in the radar antenna produces a very dense
magnetic field whether or not the radar set is turned on. These
magnetic field effects are also present during the operation of
the servo motors located on gyro-stabilized TV or INMARSAT
communications dish platforms. Checks for signal degradation
should be performed before finalizing the installation.
NOTE:
961/962 INSTALLATION MANUAL Revision A