Still chasing bad FAA ADSB flight tests. Have checked set ups, metered out wires, etc. Jason thinks it might be the GTX 45R box. He called Garmin and they suggested several things to check. I knew I had a blade type antenna, but could not find documentation as to brand/model in my build log. Have to take out 1/2 the interior and both front seats to get to the antenna mounting. So, I ordered a new Comant CI 105 from ACS in case. (on the Garmin "approved" list. New one is serial # 85283
Turns out that the existing antenna was in fact a CI 105 as required. Installed the new one anyway.
