====== DBBC Calibration ======
  * Apply a tone of 764 MHz at -15 dBm to one input 1 of all four CoMos
  * Use dbbc_config_file_104_calibration.txt
  * Set dbbcifa/b/c/d=3,agc,1 (i.e. input 3, filter 1)
  * Once gains have stabilised, turn off the agc loop with dbbc=dbbcgain=all,man
  * Run "calibration" in DBBC Control
  * dbbc=dbbcgain=all,agc
  * The results are written to  C:\ as yyyy-ddddThhmmss-calib.txt
  * The file has 5 columns: phase, CoMo A/B/C/D value. Pick the phase at the null past the first peak.