Description of the radar set, tactical-technical characteristics
|pulse repetition time (PRT):|
|pulse repetition frequency (PRF):||8800 Hz|
|pulsewidth (τ):||1 µs|
|hits per scan:|
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.
- W. E. Frye, E. V. Stearns, ''Survey of Self-contained Navigation Systems'', RM-756-1, 26 December 1951, Revised 20 May 1952 (online)