C-Nav Hardware Reference Guide
84
Intermittent GPS Loss
When GNSS lock is intermittent, the antenna cable may be disconnected or loose. Check that
all connections are secured properly. Protect the cable/antenna connection with a weather-
sealant tape such as Coax-seal. If the sealant tape is not properly placed, water may enter the
cable connection and cause intermittent loss of power or data communication link.
If the antenna is connected properly, ensure that it is mounted on the highest point so that no
GNSS signals are blocked. Depending on the location of the C-Nav GNSS antenna, the
satellites and possible obstructions, one or more satellites may be blocked. The C-Nav GNSS
receiver must be mounted so that it has a clear view of the sky. It should be on the center-line of
the vessel, and away from any sources of interference such as electric motors, radar antennas,
L-band communication antennas, cellular radio telephone antennas, radio voice or data
communication towers or satcom domes. If the C-Nav GNSS antenna location seems fine,
check the GNSS configuration parameters. If they are set to extreme levels, the C-Nav GNSS
receiver could ignore valid satellite data.
Power Lines and Strong Magnetic Fields
In North America, the energy from electrical power lines is 60 Hz (50 Hz in Europe). The
harmonic energy falls off rapidly as the frequency increases. Thus, power lines have very little
effect on the GNSS signal. However, noise radiation from power lines may cause interference to
the GNSS and L-Band signal corrections. The interference, if any, is usually localized, up to a
half mile from the power line.
While strong magnetic fields have no effect on GNSS signals, some computers and other
electronic equipment radiate electromagnetic energy that can interfere with C-Nav GNSS
antennas or with the corrections data link. If you suspect interference from a local magnetic
field, move the C-Nav GNSS receiver away from any electronics while observing the C-Nav
GNSS receiver’s output.
Checking for Cable Failure
To check a C-Nav GNSS receiver’s interconnect cable for a short, use an ohmmeter. The
resistance of a good cable between any of the conductors is infinite and the resistance between
each end of the same conductor is near zero. If the interconnect cable is defective, contact C-
Nav Support.
C-Nav Corrections Availability
Radio signals from geo-stationary communication satellites that broadcast the C-Nav signals
occasionally get blocked or encounter interference. If you are outside of the range of these
broadcasts or have local RF interference from power lines or high power radio transmitters, you
may not receive the C-Nav corrections. High voltage power lines can be a severe source of
noise, particularly if there is a leaky insulator or other source of corona discharge.
The ionosphere can also cause loss of signal especially along the geomagnetic equator of the
earth. The 11-year solar cycle can interfere with L-band transmitted correction signals, as can
instances where the sun is directly in line with the view of a geo-stationary communications
satellite. Often, simply selecting another L-band communication satellite will resolve the
reception of the C-Nav corrections for the period of the ionospheric disturbance.
Summary of Contents for IALA
Page 1: ...DGNSS Systems Hardware Guide www cnavgnss com...
Page 20: ...C Nav Hardware Reference Guide 20 Figure 2 3 C Nav Antenna Mounting Pole Dimensions...
Page 65: ...C Nav Hardware Reference Guide 65 Model No 3402 17 0070 Specifications...
Page 67: ...C Nav Hardware Reference Guide 67 Huber Suhner Lightning Protector Mounting Instructions...
Page 68: ...C Nav Hardware Reference Guide 68...
Page 69: ...C Nav Hardware Reference Guide 69 MOXA Converters TCC 80I TCC 80I Specifications...
Page 72: ...C Nav Hardware Reference Guide 72 Times Microwave LMR400 Coaxial Cable LMR400 Specifications...
