Sunfish:
WHy did I have to spend $3500 for a mode S transponder
Because TCAS will pick up your mode S. As far as avoiding heavy metal goes, that was the best investment you could have ever made.
To put it another way, I can see old mate in his Jizzler 700 with his skyecho. I can't see the RPT Airbus inbound because he doesnt transmit ADSB (?). The Airbus can't see me unless we get close enough for her TCAS to generate an RA because she doesnt have ADSB - in, the Airbus also can't see Old Mate and AsA can't see any of us because there is no radar down low and it isn't even looking at ADSB at all?
I may not be reading this right, but if you have ADS-B in, you'll see the A320 because we all have ADS-B out (IFR requirement since 2020(?) and you'll see the Jab if fitted with that gadget.
Likewise, if the A320 has ADS-B In, they will see other ADS-B Out aircraft.