An FME (For Mobile Equipment) RF adapter is a type of coaxial RF connector designed primarily for mobile communication applications in vehicles. These adapters were used to link RF equipment that possess different types of connectors.
The FME connector is characterised by its relatively small size and a threaded interface. The male connector features an inner pin and an internally threaded shell, while the female connector has a central socket surrounded by a plastic sheath and an unusual spinning nut with an external thread.
FME RF adapters were once common in UHF communications, particularly in vehicle-mounted mobile antennas and mobile communication equipment. Over the last decade they have fallen out of favor due to their relatively poor electrical performance, especially in higher frequency applications. This makes them less suitable for modern mobile communication systems, which often operate at higher frequencies and require low signal loss. They have widely been replaced by the more compact and higher performing SMA connector.