Garmin GTX 23 ES Installation Manual - Page 18

2.3.2 Antenna Location Considerations The antenna should be installed in accordance with AC 43.12-2A Chapter 3. Mount Antenna on Bottom of Aircraft Figure 2-1 Antenna Installation Considerations a. The antenna (Garmin P/N 010-10160-00 or equivalent) should be mounted away from major protrusions, such as engine(s), propeller(s), and antenna masts. It should also be as far as practical from landing gear doors, access doors, or other openings that could shadow (block) the signal between the transponder antenna and ATC radar on TCAS. b. The antenna should be mounted vertically on the bottom of the aircraft (Figure 2-1). c. Antenna Separation: DME and TCAS receive signals in the same frequency range that aviation transponders transmit at, so their antennas should be separated from the transponder antenna by as much as feasible. Six feet of separation is a guideline. Radar altimeters (should one be installed on an aircraft with a GTX 23) also have some potential to receive interference from a transponder (the transponders' fourth harmaonic), so it is good practice to separate transponder and radar altimeter antennas by as much as practical also. Avoid mounting the antenna within three feet of the ADF sense antenna or any other communication antenna. d. To prevent RF interference, the antenna must be physically mounted a minimum distance of three feet from the GTX 23. NOTE If the antenna is being installed on a composite aircraft, sufficient ground plane material must be added. Conductive wire mesh, radials, or thin aluminum sheets embedded in the composite material provide the proper ground plane allowing the antenna gain pattern to be maximized for optimum transponder performance. Page 2-2 Revision A GTX 23 Installation Manual 190-00906-01