For R5700/R5750 device with an embedded GNSS module, the timestamp received in the VRT captured packets (data or context) and the clock system are affected by the following setup options, controllable through the SCPI commands.
The 10 MHz reference clock source can be changed via :SOURce:REFerence:PLL command with GNSS, INT (internal) or EXT (external) options.
The on-board RTC (real time clock), the internal clock system and the VRT data packet’s timestamp synchronization is influenced by :SOURce:REFerence:PPS command (options GNSS or EXT). If the GNSS option is selected with the GNSS module enabled but a GPS fix has not been obtained (:GNSS:REF? query did not return GNSS), the internal reference clock source will be used until a fix is obtained.
For both the reference source and the PPS, the GNSS option is the default setup.
The time sync can also be optionally influenced by:
:SYSTem:TIME command (sending this command would disabled the NTP option setup by the following command), or
:SYSTEM:TIME:SYNC NTP option, once or continuously.
However, ":SYSTEM:TIME:SYNC NTP,continous" is needed if precise time synchronization to global time is required.
The change option provided through these last two commands is similarly made available through the device's web-admin console.
Refer to ThinkRF R5700/R5750 Programmer's Guide for the details of the SCPI commands mentioned.