Neptun (radar)

Neptun (Neptune) was the code name of a series of low-to-mid-VHF band airborne intercept radar devices developed by Germany in World War II and used as active targeting devices in several types of aircraft. They were usually combined with a "backwards warning device", indicated by the addition of the letters "V/R" Vorwärts/Rückwärts, meaning Forward/Backward). Working in the metre range, Neptun was meant as a stop-gap until scheduled SHF-band devices became available (for instance the FuG 240/E cavity magnetron-based FuG 240 Berlin AI radar).

Transceiving antennas used for Neptun on twin-engined night fighters usually used a Hirschgeweih (stag's antlers) eight-dipole array with shorter elements than the previous 90 MHz SN-2 radar had used or as an experimental fitment, the 90°-crossed twin-element set Yagi based Morgenstern single-mast-mounted array.

Variants
FuG 216: Experimental series to plan the further development. Installed in Fw 190 A-6/R11 and Bf 109 G-6 The aircraft were used by NJGr 10 until March 1944, after which some machines of 6./JG 300 (Kommando Plöger) were equipped.
 * Manufacturer: Flugfunkforschungsinstitut Oberpfaffenhofen (FFO, German for airborne radio research institut in Bavaria)
 * R1 version (backwards warning device)
 * Frequency: 182MHz
 * Power: 1.0kW
 * Transmitting and receiving antennas each consist of twin dipoles, mounted under and above the wings, respectively
 * Single display device with distance readout


 * V version (for single engined night fighters)
 * Frequency: 125MHz
 * Power: 1.2kW
 * Range: 500 to 3,500m
 * Antennas in the form of spikes or (Fw 190) as "antlers" on right and left wings

FuG 217: Installed mainly in Ju 88 G-6, only a few Bf 110 G-4, He 219 or Me 262 received the Neptun. It could be combined with the additional Elfe device to automatically measure the target distance and fire the guns at a set range.
 * Manufacturer: FFO
 * R2 version (backward warning device)
 * J2 version (for single-engined night fighters)
 * Ausführung V/R (combined night fighter and backward warning device for two-engined fighters)
 * Two switchable frequencies: 158 and 187MHz
 * Search angle: 120°
 * Range: 400 –
 * Spike or "antler" antennas

FuG 218: mass-produced
 * Manufacturer: Siemens / FFO
 * R3 version (backward warning device)
 * J3 version (for single-engined night-fighters)
 * V/R version (combined night fighter and backward warning device for two-engined fighters)


 * Six switchable frequencies: 158 to 187MHz
 * Search angle: 120°
 * Range: 120 –
 * Weight: 50 kg
 * R3 and J3 with spike antennas and V/R with "antler" antennas.


 * G/R version (combined night fighter and backward warning device for two-engined fighters)
 * Only one single device built, replacing the 2kW transmitter with a 30kW transmitter. Range increased to up to 10 km. This device was intended for the Dornier Do 335. "Antler" antennas.