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Description of the radar set, tactical-technical characteristics

Figure 1: ASR 8

Figure 1: ASR 8 als Trainingsgerät auf einem ASR 4 Turm

frequency: 2 700 - 2 900 MHz
(S band)
pulse repetition time (PRT):
pulse repetition frequency (PRF):
pulsewidth (τ): 0,6 µs
receiving time:
dead time: 700 - 1200 Hz 
peak power: 1.4 MW
average power:
instrumented range: 60 NM (≙ 111 km)
range resolution:
hits per scan:
antenna rotation: 12.5 rpm


The air traffic control radar ASR 8 is a relocatable, solid-state, all-weather radar with dual-channel, frequency diversity, remote operator controls, and a (dual-beam) tower mounted antenna. The military US-designator is AN/GPN-20.

The radar provides controllers with range and azimuth of aircraft within a 60 nautical mile radius of the physical location of the antenna. Radar return information is displayed on radar indicator in the Radar Approach Control (RAPCON) facility and is used to control air traffic within assigned air space. ASR 8 used a klystron as transmitters power amplifier stage with a load of 79 kV and 40A. The two operational frequencies have a minimum separation of 60 MHz.

ASR 8 is the analog precursor to the ASR 9. It is an aging radar system that is obsolete, not logistically supported, do not provide digital inputs to new terminal automation systems, and do not provide a calibrated precipitation intensity product nor any storm motion information.

The USAF used a modified version of the ASR 8 containing as transmitters high power stage a magnetron and the necessary additions; in this system, the magnetron tuning is driven by the AFC.