How to calibrate SDR card ?

SDR cards can be now calibrated using a GPS receiver.This functionality was added sdr driver since the test release version 2019-10-31.

To calibrate SDR card:

stop lte service:

service lte stop

connect the GPS receiver to "GPS" RF port of SDR card.
under /root/trx_sdr/ folder run:

./sdr_util -c 0 gps_cal 30 -s

where:

"30" means 30 seconds of GPS clock acquisition
"-s" is to store the resulting ppm correction to a flash memory on the card

In case of multiple SDR cards. do the same procedure for each SDR card and change the SDR index N "./sdr_util -c N gps_cal 30 -s", with N: 0..numberOfSDRs-1