Sonar Timeline
1916: Approx. The Allied Anti-Submarine Detection Investigation Committee (ASDIC) develops the first version...a hydrophone hanging over the side of a ship.
1921: Asdic installed on the HMS Antrim was able to detect a shutdown submarine on the bottom at 2000 yards (under optimal conditions).
1931: The U.S. Navy Underwater Sound Group produces the QB echo-ranging SOund Navigation and Ranging (SONAR) effective below 6 knots.
1934: First echo-ranging equipment installed in the American destroyers of DesDiv 20.
1939: West Coast Sound School opened at San Diego Destroyer Base.
1939: Over 165 British destroyers, sloops and trawlers are carrying asdic equipment that can be used at 15 knots. Adopted by the United States, the "Searchlight" operated at 14-22 kilohertz and was effective up to 2,500 yards. This range was reduced by rough or high-salinity seas, underwater temperature inversions and thermo clines. Although sonar was responsible for 68 of the 104 submarine kills in '39 and '40, it was found to be an ineffective area sweep tool.
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