On Sunday, May 6, 2018 at 6:25:25 AM UTC-7, wrote:
My message for a long time has been: If you fly near areas of dense airliners, fast jets and military traffic, just get a transponder, Mode S or used Mode C does not matter... get what you can afford.


This seems logical, but I heard another corner case where might not be so..

I sat in a presentation from our local Approach Control folks. They noted that with the new ADSB ground stations they had better visibility than from their existing radar plus ModeC. Specifically, low and far out. This like it might permit them to route controlled traffic in new places where gliders are, but where a Mode C transponder on the glider might not help.

You need to do a bit more thinking about the flaws in your logic here.

A transponder provides visibility to TCAS and IFF systems in airliners, fast jets and (some) military traffic...

If ATC was about to do this, and direct traffic towards areas where gliders are it is more reason to want to have a transponder.

If in this scenario you also wanted ADS-B out, then a Mode S transponder is the way to go. I hope you spoke up and talked about gliders in the area and what they are or are not equipped with. I'd have possibly also pointed out the Chicago 737-glider NMAC last year as an example....