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GSS6400, GSS6425: Why does my receiver reject the recorded signal during playback?

  • GSS6400
  • GSS6425
  • Normally the carrier phase of a GNSS signal is derived from the transmitting satellite's highly stable atomic clock.
  • This wave comes to the Earth and is picked up by a receiver with a relatively low grade TCXO.
  • The receiver however knows this and has a model built in that allows the carrier phase to be recovered.
  • With the GSS64xx product the carrier phase is recorded using a TXCO but is then played back using an OCXO
    • This helps minimise any further degradation in carrier phase reproduction
  • However the receiver connected to the GSS64xx output will still be using its TCXO (and model) to recover the carrier phase.
  • If the receiver filter used to 'analyse' the carrier phase is set very tightly then it is possible that the receiver perceives the carrier phase measurements to be too 'degraded' / outside 'expected' ranges
    • Possibly as a result of the two TCXO’s involved in recording the signal and then receiving the recorded signal?
  • The receiver therefore rejects the carrier phase observations at most of the epochs and this can potentially lead to signal dropouts.
  • If the receiver rejects one signal type more than another it may be due to different filtering 'rules' / 'techniques' being applied to the different signals
    • For example, the receiver may be more stringent with the GPS carrier phase measurements than for the GLONASS measurements?
  • Contact the receiver manufacturer to determine if it is possible to change the filter setting or reduce / disable ‘carrier smoothing’. 

Product : General Navigation,GNSS,GSS6400,GSS6425