GPS Sync Loss Troubleshooting First Steps

To troubleshoot a loss of GPS sync, perform the following steps:

1 If the AP is configured to receive synchronization via CMM (via the AP's Ethernet Port), visually inspect the CMM GPS Master LED to verify that the CMM is receiving GPS sync from its antenna.  Alternatively, log in to the CMM web management interface and check the value of SYNC Pulse Status (located in Home > Sync Status) to verify that the CMM is properly receiving sync via its attached GPS antenna (see PMP Synchronization Solutions User Guide).

If the CMM is not receiving GPS sync via the connected GPS antenna, verify that the cables from the CMM to the network switch are at most 30 Ft (shielded) or 10 Ft (unshielded) and that the network switch is not PoE (802.3af) capable.  Doublecheck cable condition and quality of terminal connections.  The GPS antennarequires a good view of the sky, and should not be mounted at the highest point of the tower. For best satellite tracking results a clear vew of the southern horizon is required. 

2 If the CMM is receiving GPS synchronization pulses properly but the ePMP AP has no sync, verify that the AP’s Synchronization Source is set to "CMM3" or "CMM4"  and that the AP’s network connections to the CMM are sound.  AP-to-CMM connections may be verified in the CMM web management interface.

3 If the AP is configured to receive synchronization via its internal GPS module and an external GPS antenna but no GPS signaling is received, verify the cabling from the AP to the GPS antenna, and verify that the AP’s Synchronization Source is set to GPS.  As mentioned above, the GPS antennarequires a good view of the sky, and should not be mounted at the highest point of the tower. For best satellite tracking results a clear vew of the southern horizon is required.  If no satellites are listed on the AP web management GUI (under Monitor > GPS) the GPS antenna may need to be repositioned.

Via the AP web management interface, navigate to Monitor > GPS and verify that GPS Firmware version is AXN_1.51_2838. If the AP is configured wtih a different version, please see  How do I upgrade the ePMP onboard GPS chip firmware.  

If the GPS Firmware Version under MonitorGPS  shows “NOT AVAILABLE”, it means that the on-board GPS chip has locked up. A power cycle of the ePMP unit is required to restore the connectivity to the chip before performing the GPS firmware upgrade.

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