Although the system demonstrated its utility, further units were not ordered until the fall of 1942, likely due to the increasing tempo of
RAF Bomber Command's night offensives at that time. Production Jagdschloss units were larger than the original prototype, with an antenna wide and tall. New electronics were built for the production units, operating on one of two bands, the A band on 1.2-1.9 m or the B band on 1.9-2.5 m. The first production sets were delivered by
Siemens & Halske at the end of 1943, and when production ended in April 1945 a total of 80 units had been delivered. Jagdschloss units were found to have several "dead spots" due to the antenna being located on an tower. For instance, an aircraft flying at altitude at any range between would be invisible because the direct reflection from the aircraft would interfere with the one reflecting off the ground. This problem was initially solved with the addition of a large wire mesh under the tower, known as
Reflektor-Netz. A more convincing solution to this problem was deployed as
Jagdschloss Michael. Michael added a second antenna on the "back" of the original, operating on a 50 cm wavelength system from
Telefunken (almost certainly adapted from their
Würzburg radar). Range was also increased from the original , which required an improvement in the angular resolution in order to maintain the ability to resolve aircraft. To achieve this, Michael used a new antenna replacing the older 24 m one. The antenna was so large that the mounting had to be re-designed, with the antenna supported by rollers running in a track as opposed to being mounted off a central shaft. Another cm-wavelength experiment was built at Werneuchen, east of Berlin, known as
Jagdschloss Z. This system operated on a 9 cm wavelength, which was very short for the era. The antenna was built up from the center sections of the Würzburg radar's
parabolic dish, stacked vertically to form a single 72-wavelength aperture antenna. Jagdschloss units of all types were optionally fitted with the
Erstling IFF system. Like British IFF units, Erstling fed back its own return upon reception of a Jagdschloss signal. The return signal was slightly delayed, appearing as a second "blip" on the radar screen, allowing the operator to visually identify friendly aircraft. Unlike British systems, Erstling apparently sent back a
morse code signal in return. The FuG25a "Erstling" had two encryption keys inside, each of 10 bits. One called "Reichskennung" and the other "Verbandskennung" (squadron key). A related system,
Jagdhütte (German: "hunting cabin"), is also mentioned in reference to Erstling. This was a reduced version of Jagdschloss without radar receiver, operating only with the IFF Signals from Erstling. This was for control of the Luftwaffe's own night fighters only. Due to the different transmit and receiving frequencies, it was resistant against
Düppel interference. Another optional system for use with Jagdschloss was a remote PPI display known as
Landbriefträger (German: country mailman). This allowed the display from a Jagdschloss site to be sent via
telephone lines to the
flak defenses so they could arrange their attacks locally. Signals from the original Tremmen and the later Werneuchen radars were forwarded to the
flak tower close by the
Berlin Zoo. == Site locations ==