On Thu, 05 May 2016 11:17:09 -0700, herbkilian wrote:

Here at Chicago Glider Club we have the dubious distinction of flying
right under the approach path into Midway airport. I have looked at
SouthWest planes coming through from all angles, including head-on.
Flying with a C-mode transponder helps a lot, Approach will guide the
big iron around us although I'm sometimes wondering about the spacing.
My PFlarm will indicate through the FlarmView display a blue dot around
my position that is blinking ONLY when a SW or bigger commercial plane
(equipped with TCAS?) is coming through. Could there be a connection
such that the transponder when interrogated by a TCAS responds in a way
that is picked up by PFlarm? What else might the blue blinking dot
mean?
Please enlighten me.
Herb, J7

In bench testing, I've seen PCAS targets create flashing blue rings,
decreasing in diameter as the target approaches, and then the small blue
ring is replaced with the blue blinking dot as the target is overhead.
The dot is bigger than a small blue ring, so I assume that's just to make
it more visible. The beeper is not going off, so PF doesn't think
there's an imminent collision threat. Are you not seeing the blue rings
before the blue dot? If you're not, then there's some configuration
issue that needs to be fixed.

The bigger question is how well your PF is handling your Mode C
transponder? It has trouble filtering out your own transmissions, may
want to consider upgrading to Mode S for best results. I assume you have
Aggressive filtering selected, and you are receiving Mode C?