A while back I had installed a doubler plate on the pilot side for a future antenna, in the same location (but opposite) as my transponder antenna which is located on the passenger side, just aft of the baggage compartment bulkhead.
Earlier in the week i was running the coax wiring for antennas, I stubbed one back to this location, so I decided to go ahead and purchase the ADS-B - "IN" antenna (978Mhz) from Delta Pop. I will likely be adding a GDL 39R to compliment my GTX23ES so I have full ADS-B "In" and "out" and be 2020 complient.
I installed the antenna to the doubler plate using a bead of clear sealant and 10-32 lock nuts torqued to 20 in-lbs as specified.
Now i just need to get Stein to add a future GDL-39 wire to my G3X system.