Hi David,
Sorry, I obviously missed you at Popham. I was unfortunately a bit distracted due to trying to track down the reasons for an electrical failure in my own aircraft on the way down on the Thursday, so was off the stand quite a bit and left early on the Sunday in an unsuccessful attempt to avoid the weather, but have been following this thread with interest. I haven’t commented previously as the others have covered all the relevant points at least as well as I could.
I have been flying with a Trig TT21 emitting Mode-S/ES ADSB (via a different uncertified GPS position source) since Project EVA* was first mooted back in early 2015 (while PilotAware was still in its early development phase) and took part in the Project Eva Trials run up here in Scotland by Trig. I joined PilotAware later that year and, working with Lee as part of the Development Team was instrumental in developing the Mode-S Detection and Alerting System and later, Direct Flarm Integration and ADSB-Out processes using USB to RS232 Serial cables..
Initial testing proved to be extremely reliable and Project EVA confirmed the position reliability and accuracy when using uncertified GPS units as the position source at around 98% - which IIRC was slightly higher than the reported accuracy from comparative certified systems.
Since we first mooted the possibility, literally hundreds (possibly even thousands) of transponder users have gone down this route, with a variety of GPS sources, (though the majority I suspect will be using PAW or Trig’s TN72) with an extremely high success rate, so I would not be in the least concerned about the accuracy of your setup. From what you have already said, it appears to be transmitting a Mode-S/ES as expected and as you have already seen from your Aircrew replays, the signal is displaying the same degree of accuracy as your PilotAware, so will be well within the required parameters. So stop worrying, turn your transponder to ALT (as you are legally required to do) and go flying - then seek out a friendly local PAW user to provide you with the necessary screen grab to prove your SIL/SDA Settings and your local inspector and apply for your Mod.
*The project set up by the CAA and NATS to determine if it was safe to allow the use of uncertified GPS sources to provide ‘ADSB-Out’ via transponders, which eventually led to the issue of CAP1391.
Best Regards
Peter
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