The AN/SQS-23 (with hull mounted dome seen on USS New DD818 on 22 Dec. 1964 above) was a long range, low frequency, azimuth-scanning type of search and attack sonar used for search, search-analyze, attack-RDT (Rotated Directional Transmission), attack-SDT (Steered Directional Transmission) and hand-key applications. RDT allowed for sound energy to be concentrated into a narrow sector while omnidirectional search continued. SDT utilized a non-rotating beam used to examine and classify contacts omnidirectional search progressed. In theory, the system had a 360 degree scan coverage however the baffles astern limited this coverage to 300 degrees. A rubber baffle was fitted to the dome aft to minimize noise from machinery, props, etc.
Beam Width: 9.25x 9.25 deg; could be varied and widened vertically.
Scan Coverage: 360 degree omnidirectional.
Range Scales: 1000, 2500, 5000, 10000, 20000, and 40000 yds.
Power/Frequency: 60kW/4.5, 5 and 5.5 kc.
Pulse Length/Repetition: 5, 30, and 120 us./150 cps.