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AN/FPN-1 (XN-2)

Description of the radar set, tactical-technical characteristics

Figure 1: The height finder as a static display in the former Caspari barracks in Delmenhorst at the end of the 1960s.

frequency: 2 880 MHz
(S band)
9 150 MHz
9 040 MHz
pulse repetition time (PRT):
pulse repetition frequency (PRF): 2 000 Hz
pulsewidth (τ): 0.5 µs
receiving time:
dead time:
peak power: 150 kW35 kW2×35 kW
average power:
instrumented range: 30 NM
(≙ 56 km)
20 NM
(≙ 37 km)
6 NM
(≙ 11 km)
range resolution:
beamwidth: 0.6°0.6°
hits per scan:
antenna rotation: 30 min⁻¹5.75 min⁻¹

AN/FPN-1 (XN-2)

AN/FPN-1 (XN-2) is designed as a fixed ground radar system for airport surveillance, height finding, and for guiding aircraft for safe approach to the airport runway under all conditions of visibility.

Accurate and continuous information regarding the location of incoming aircraft with respect to the predetermined glide path is presented to the operators in the form of azimuth range and elevation data by the radar portion of the equipment. This information is translated by the radar set to lateral and vertical deviation from the selected glide path, and the pilot of the incoming aircraft is instructed verbally as to corrections he must make to keep on the glide path. Through these instructions the pilot is guided to a height of 75 feet or less above the runway and to within 50 ft of the runway’s center line, enabling him to touch down under visual control in the usual manner.

The system consists of four separate radars:

The AN/FPN-1A is similar to the AN/FPN-1 except for component parts.