Description of the radar set, tactical-technical characteristics
Figure 1: AN/APS-20 fitted to the TBM-3W
|frequency:||2 860 … 2 880 MHz
|pulse repetition time (PRT):|
|pulse repetition frequency (PRF):||300 Hz|
|pulsewidth (τ):||2 µs|
|peak power:||1 MW|
|instrumented range:||250 NM (≙ 460 km)|
|hits per scan:|
|antenna rotation:||6 or 3 min⁻¹|
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.