I can't help but notice that there is an impact on the measured phase error every time the TDOP reported by the LEA-6T changes.  What I don't know is how to characterize the impact.  Is the impact more of a change in the error band, rather than a bias in one direction or the other?  Would a variable dead-band filter be an appropriate response to these changes?  I've experimented with a dead-band filter in the past with mixed results, but I never coupled the width of the dead-band to the TDOP. Bob - AE6RV ----------------------------------------------------------------- AE6RV.com GFS GPSDO list: groups.yahoo.com/neo/groups/GFS-GPSDOs/info