First we'll cover what sync options are available. Below is a list of syncronizaiton options:
GPS: Synchronization timing is received via the AP’s connected GPS antenna. Co-located or in-range APs receiving synchronization via GPS or CMM transmits and receives at the same time, thereby reducing self-interference.
CMM: Synchronization timing is received via the AP’s Ethernet port via a connected Cambium Cluster Management Module (CMM). Co-located or in-range APs receiving synchronization via GPS or CMM will transmit and receive at the same time, thereby reducing self-interference. For more information on CMM configuration, refer to the PMP Synchronization Solutions User Guide.
Internal: Synchronization timing is generated by the AP and the timingis not based on GPS pulses.
Within the radio configuration page you need to configure the parameter Synchronization Source:
This parameter defines the timing source for the device which can be GPS-based or internally generated. Select GPS if the AP will receive synchronization pulses from a connected GPS antenna. Select CMM if the device will receive GPS synchronization pulses from a co-located Cambium Cluster Management Module (see PMP Synchronization Solutions User Guide). Select Internal if no GPS synchronization source is available (in this mode, transmission between co-located devices will create radio interference). If Flexible is chosen as the DL/UL Ratio, then this parameter will be greyed out.