Radio Altimeter Ln.28330-1 Funkhöhenmesser AFN101A

This is an authentic WWII-era German Funkhöhenmesser AFN101A, Ln.28830-1, or Radio Altimeter as used in various aircraft of the Luftwaffe such as the Heinkel He 219 Uhu night fighter, the Dornier Do 335 V Pfeil fighter, Junkers Ju 88 bomber, and Messerschmitt Bf 110 fighter.

The radio altimeter was a component of the FuG 101a system used to accurately measure height above ground.  The device has a selectable range, 0-150m and 0-750m, which is changed by turning the lower center knob left or right.  The radio altimeter would be connected to a power supply and to antenna mounted underneath the wing or fuselage. A transmitting antenna would send a short wave signal towards the ground, where it would be reflected back to the aircraft's receiving antenna, thus measuring the distance to ground.  The system was particularly useful in measuring height over water, mountainous terrain, and during blind flight and landings.  The center knob also pulls out and turns to adjust for accuracy. 

This instrument is in very good condition given its age. The knob turns as it should and the markings are clear and precise.