While flying with a another pilot a few days ago, we were following another aircraft. It did not show up on AvareX. I had the "small" setting. The other pilot had ForeFlight, and that aircraft did show up. We were both connected to the same Stratux.
I have flown the aircraft that was in the pattern with us. The nav light needs to be on for the ADSB out to work. I was able to see that the nav lights on the other airplane were off, so no ADSB out.
I can only assume that ForeFlight was seeing that aircraft via TIS-B.
Does AvareX show TIS-B aircraft?