Mounted the Trig TT22 Mode S transponder in the floorboard under the starboard mid-cabin cover (opposite side of where the fuel selector valve is located). The transponder comes with a mounting tray that has a single spring-type hold down latch. The mounting tray is pop-riveted on top of a backing plate to the floorboard
The only issue so far with this configuration is that I didn't realize just how long the GRT adapter is, so there is a quick turn required in the wiring harness. It's not shown here, but mounted an adel clamp to a short piece of angle bolted through the tooling hole adjacent to the wiring harness grommeted hole. A slightly better plan would have been to mount the tray angled to match the wiring hole vice parallel to the longeron.
Still need to run the coaxial antenna cable.
The TT22 will provide mode S (extended squitter) and when coupled to a certified GPS (hopefully my 300XL will work) will meet the FAA ADS-B out mandate (due in 2020). ADS-B is tbd, but likely FreeFlight XPRLORER or Radeena SkyRadar D2.
