On Friday, June 7, 2019 at 8:20:22 AM UTC-5, son_of_flubber wrote:
On Thursday, June 6, 2019 at 7:53:51 PM UTC-4, wrote:
it occurred to me, that the previous day I had obtained a free FAA report on my adsb/transponder in flight, which was satisfactory.

In another thread, a 'known to be knowledgeable person' said that the obligatory 'transponder check' tests things that are not tested by the Public ADS-B Performance Report.

On a related note, does ADS-B out report the GPS altitude, the pressure altitude reported by the transponder or both? I assume that a Mode-S transponder is still talking to TCAS systems and not using GPS altitude. What happens when the pressure altitude from the transponder disagrees with the GPS altitude? Would this allow the transponder to detect a blocked static port or bum pressure sensor?

My 'transponder check' was done inside a metal hangar building, so there was no GPS altitude available to compare to the pressure sensor altitude.

At Chicago Glider Club, every club and most private gliders have transponders. We all take the test together every 2 years and the charge has been $100. The avionics shop comes out to our field with 2 technicians and 2 test rigs and they do about 20 gliders and power (tow) planes in a couple of hours. See if you can negotiate such a deal, the cost should come down. Also, insist for them to do a VFR test that does NOT include to take the altimeter to 10,000' and to calibrate it.