Yep the GroupID had been changed to S for some reason now reset to PAWGRP
Nothing wrong with changing the GroupID - that is the purpose
I was being a bit lazy when post processing the data, there is better instrumentation in the trk file to indicate the type of transmission, so I corrected to use that information. FYI the $PAWRT field indicates the sources of data
C,S,A,P,F
ModeC, ModeS, ADS-B, P3I, Flarm - respectively
Thx
Lee