Just did a quick analysis of the TRK file from my trip last Thursday, and counted 51 contacts - mainly airliners but including a C152, a Cirrus, a Beech 200 ambulance out of Glasgow and an Italian Air Force maritime patrol aircraft - not a bad haul for 30 minutes at 2000' on a quite midweek lunchtime in Central Scotland! I checked that each recorded aircraft was actually in my neck of the woods at the right sort of time using Flight Radar 24, which has given me a lot of confidence that I am looking at broadly the right things.
They are all 1090MHz though, and I would really like to see some 869MHz contacts. I was planning to head over towards Balado today to see if I could bag a glider or two out of Portmoak on the re-broadcast system, but the weather beat me. Maybe later in the week.
I was winging it a bit decoding the TRK file using Excel and a bit of previous experience. Is there a specification for the file's content that I could get a copy of?