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AN/APS-20

Description of the radar set, tactical-technical characteristics

Figure 1: AN/APS-20 fitted to the TBM-3W

Figure 1: AN/APS-20 fitted to the TBM-3W

Specifications
frequency: 2 860 … 2 880 MHz
(S-Band)
pulse repetition time (PRT):
pulse repetition frequency (PRF): 300 Hz
pulsewidth (τ): 2 µs
receive time:
dead time:
peak power: 1 MW
average power:
instrumented range: 250 NM (≙ 460 km)
range resolution:
accuracy:
beamwidth:
hits per scan:
antenna rotation: 6 or 3 min⁻¹
MTBCF:
MTTR:

AN/APS-20

The AN/APS-20 was an operating in S-Band surface search radar for airborne early warning (AEW). It was complemented by the AN/APX-13 Identification Friend of Foe (IFF) system.

The transmitter used a magnetron. The AN/APS-20 has a number of special circuits for the suppression of Seeclutter and other sources of noise. The IF-frequency was 30 MHz with a bandwidth of 1.5 MHz and an amplifier noise figure of 2.5 dB. It had a PPI-scope with a 12 inch cathode ray tube with a long-persistence phosphor. The eight-foot antenna was installed in a large circular radome mounted in the underbelly position just behind the nose wheeldoors.

The AN/APS-20 was initially developed during WWII but did not enter operational service until 1946. The radar as fitted to the TBM-3W and PB-1W became the mainstay of AEW aircraft developments following World War Two. Modifications were AN/APS-20B, AN/APS-20E, and AN/APS-20F with up to 2 MW pulse power. AN/APS-20 was replaced since 1956 by the AN/APS-95 and AN/APS-103 but some sets were operational up to 1978.