www.radartutorial.eu www.radartutorial.eu Card Index of Radar Sets - Air Defense Radar


Description of the radar set, tactical-technical characteristics
frequency: X-Band
pulse repetition time (PRT):
pulse repetition frequency (PRF): 8800 Hz
pulsewidth (τ): 1 µs
receive time:
dead time:
peak power:
average power:
instrumented range:
range resolution:
accuracy: 0.1%; 0.1°
hits per scan:
antenna rotation:


The AN/APN-81 was operating in X-Band pulsed Doppler radar dedicated as radar front end for use in the Doppler navigation equipment AN/APN-66. This Doppler navigation equipment was intended for use in long-range bombers (e.g.: on SM-62 missiles, and B-47). It was operational since 1954.

In the AN/APN-66 equipment, one-microsecond radar pulses are transmitted on four beams formed by flush-mounted linear array antennas symmetrically oriented width respect to fore-aft and right-left axes of the aircraft and directed downward at an angle of 20° with respect to the vertical. The antenna array is gyro-stabilized, and its servo system ensures that the antenna system is aligned along the ground-based course of the aircraft. The Doppler shift in frequency between the signals received on one single pair of antennas is then a measure of the ground speed of the aircraft. The difference in Doppler frequency between left and right beams is a measure of the aircrafts drift.