I’m using a Garmin GTX 45R as my transponder. The unit provides ADS-B in/out and can stream ADS-B in data to connected devices over Bluetooth (ForeFlight, etc.).
For Bluetooth connectivity, Garmin recommends that the unit be oriented such that the front of the device faces the cabin of the aircraft.
The unit is installed with a tray that allows the device to be removed without disconnecting the wiring harness.
I chose to mount this horizontally underneath the subpanel so that the unit can be removed by lowering the forward part of the tray, then sliding it out under the panel.
I made a support rail that parallels the rails that I am using to support a forward battery. Like those rails, this rail is secured to the flange of the sub-panel with a #6 screw, allowing it to be removed.
The tray in the pictures is a 3D-printed mockup (I didn’t print the top part of the tray as it was easier to print it this way). The actual tray is a sleeve.
I made hangers from .063 that attach the tray to the rails. The rear hangers will be riveted to the rails. The tray is secured with a single screw at the rear allowing it to be pivoted around this point.
The forward hangers are attached to the rails with #6 screws. The hangers will first be secured to the tray, then mounted to the rails. This allows the tray to be dropped at the front by removing the rail attachment screws. The unit can then be slid forward out of the tray.
