Re Bookworm’s question, what to do if a non-azimuth alert is received on PCAS (MRX) – cut and pasted from an earlier document:
“I had a near approach by a powered aircraft which came up from behind me, detectable only by PCAS (a transponder detector even more compact that Flarm, which I also have.) Not being able to see it, or anything else in the forward visible arc, I did a turn and watched it go by. It was close-ish, but probably never on an actual collision course, and plenty of room for my turn. But suppose it had been on a collision course, with the pilot’s head down? Would you rather have no alert, or get one? I was glad I got one.”
Chris N