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The AN/SPS-55 is a solid state, surface search and navigation radar capable of detecting targets from as close in as 50 yards and out to 50 miles and beyond, with good target resolution.

The radar set uses several signal processing circuits to improve operation under certain prevailing conditions:

  • Fast Time Constant (FTC) circuit - Reduces clutter by displaying only the leading edge of the echo returns.
  • Sensitivity Time Control (STC) circuit - Reduces receiver gain at close-in ranges where clutter is strong, while allowing a gradual return to normal gain at longer ranges where clutter is less.
  • Sector Radiate Capability - Allows the operator to limit radiation to a selectable azimuth segment to minimize interference from other ships' radars or ECM equipment.

Radar Set AN/SPS-55 consists of four major units: antenna group, radar receiver/transmitter, radar set control, and box switch. The system generates two selectable pulse widths. The RF frequency is tunable from 9.05 to 10.0 GHz with a minimum peak power out of 130 kW (measured at the magnetron). The linear array antenna, rotating in azimuth at 16 RPM, forms a beam narrow in azimuth (1.5) and broad in elevation (-10 to +10, centered on the horizon). Return target echoes are amplified and detected by the receiver and applied to a PPI.

The target information can be displayed in either of two modes, a relative mode where zero degrees bearing on the PPI represents the heading of the ship or a true mode where zero degrees bearing.

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