Garmin GI 275 GPS Antenna. The GPS antenna provides a GPS source for the GI 275 for navigation in VFR conditions in class I and II aircraft when no external GPS source is present. In class III and IV aircraft, the GPS antenna provides a backup GPS source in the event of a primary navigator failure. Additionally, the backup GPS source can be used for AHRS alignment and stability.The GPS uses a 96-inch (8-foot) length of RG-316 cable and typically mounts on the glareshield. It is outfitted with a BNC connector as well.