HADR

The HADR (Hughes Air Defense Radar), also designated HR-3000 by the manufacturer, evolved from the AN/SPS-52 ship radar. It utilized two stacked phased array antennas from its predecessor, with the serpentine feed repositioned behind the antenna plane. To achieve its maximum instrumented range of 240 nautical miles, an amplitron power amplifier was added downstream of the existing traveling wave tube (TWT) amplifier, which then functioned as a preamplifier. For close-range and high-altitude operations, the amplitron is deactivated, and the radar operates solely with the TWT. The HADR's software incorporated a unique "data mile" constant, derived similarly to the radar mile but using 6,000 feet instead of 1,852 meters as its reference. Until 2006, the radar used the Siemens 1990 D14 secondary radar; since 2007, it has been upgraded to the Mode S-capable MSSR 2000 I. Germany operates four HADR air defense radars, all slated for replacement by the Hensoldt "Hughes Air Defence Radar Nachfolgesystem" (HADR-NF) program.

radartutorial.eu: https://www.radartutorial.eu/19.kartei/02.surv/karte003.en.html