The default positioning datum used in the 4380A is WGS84, however, the system is
capable of using the NAD-83 datum. Ensure that any manually entered position is using
the correct datum by using the settings gps:datum command.
• Is the GNSS antenna cable connected at both ends and undamaged?
The antenna cable may have failed due to exposure to the weather, kinking, or bending.
Inspect the antenna cable and correct any issues and replace any cables that appear to
be weathered. Also, check the antenna cable connectors to make sure that they are
properly affixed to the cable ends and that the connectors are properly threaded onto
the connectors at both ends. If a lightning protection device has been installed in the RF
and DC path, ensure that the device has not failed and is not open (no continuity).
• Is there some other source of radio frequency energy located close to the GNSS
antenna?
Nearby sources of radio frequency (RF) radiation, especially those that operate near the
L-band frequencies used by GNSS satellites, can sometimes cause problems with
reception of the extremely low power GNSS signals at the GNSS antenna. It’s best to
mount the GNSS antenna well away from other sources of RF radiation to reduce the
likelihood of interference.
• Is the GNSS antenna setting in the 4380A set to manual position mode?
If the operator enters the manual position incorrectly, the system will indicate it is
tracking satellites in the status output, however the system may show the gnss status as
“not tracking” both in the status results and on the front panel. To correct this problem,
ensure that the position is entered correctly. If this does not work, set the unit to the
auto position mode and re-survey the antenna position.
Q13: How do I determine the position of my GNSS antenna?
A13: The 4380A offers three different modes for determining the antenna position and
determining receiver operation: Dynamic, Auto, and Manual. The Dynamic mode is typically
used for systems located on mobile platforms. The system default mode is Dynamic. Users at
static locations should change this to Auto or Manual based on the information provided below.
The Auto mode is recommended for static locations where the antenna location has not been
surveyed. When using the Auto mode, the 4380A will automatically determine the location of
its antenna. It does this by averaging its calculated position solutions over a period specified by
the auto_hours parameter. The factory default for the position period is 12 hours. It is
recommended that the auto positioning period should be set to at least 4 hours. Once the
position_period expires, the 4380A will enter the fixed position mode (status
gnss:position:fixed
). Fixing the antenna position reduces the noise of the GNSS
measurements and increases the frequency stability of the timing outputs.
© 2016 Microsemi Corporation. All rights reserved. SyncSystem 4380A FAQs Version 1.0 (22 Feb 2016)
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