Sonar Equipment

Sonar Equipment
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. 1941: Summer. A British invention, the Attack Teacher was installed in Portland, Maine for training destroyer sailors in ASW tactics. 1941: October. Bathythermograph introduced to the Fleet. 1942: The "Q-attachment" is fielded. It enables the sonar to detect the new deep-diving submarines that can operate below the searchlight's detection cone. It operates at 38 1/2 kilohertz to a range of 1,200 yards. 1943: The "Type 147" sonar called "Sword" fielded that allows tracking of the deep-diving submarines. It operated at 50 kilohertz and was effective out to 1,000 yards. It could provide depth and targeting information to the British "squid", an ASW rocket propelled depth charge.
A cut-a-way of the retractable sonar "pod". The pod was constructed of either stainless steel or some type of synthetic material such as fiberglass and protected the transducer from passing water. The entire pod is full of salt water so the transducer can transmit & receive its pulse. When "pinging", the transducer is turned incrementally with the control rod. In early models the transducer was turned manually.
*This* picture is worth TEN thousand words! It shows the detection areas and capabilities of the three different asdic models. The "searchlight" was the first development, followed by the "Q" attachment, and finally the Type 147 or "Sword". The "Q" allowed the hunter to continue tracking deep-diving U-boats as they got closer, something the early searchlight could not do. The Type 147 Sword added lateral tracking of deep-divers, which permitted last-second targeting adjustments.
Sonar, or "Asdic" as our British allies called it, was one of the greatest innovations of WW2. A British invention, sonar was theorized as early as WW 1 but was not technologically possible until November 1941, when it was first installed on British Destroyers. These early sonars had a "searchlight" beam, cone-shaped much like a flashlight's beam. Targets that fell within the search beam reflected the "ping" of the transducer back to the ship. Based on the amount of time needed to return the ping, the sonar could calculate the target's range. These early sonars had several shortcomings. First was the 2500 yard maximum range, requiring escorts to be less than 5000 yards apart to obtain overlapping coverage. Second was the narrow beam, measuring only 16 degrees. This was akin to searching a very large dark room with a tiny penlight while wearing blinders. Third, the sonar beam had to be aimed below surface level because surface waves and noise disrupted the beam, producing false "hits." This allowed surfaced submarines to remain undetected until later when surface radar was fielded. Fourth, the early sonar could not determine depth, a critical piece of information when setting pressure fuzes on the depth charges. Fourth, the sonar worked best at very slow speeds, providing the enemy of both advanced notification with the active pining and a slow-moving easy target. Finally, while the searchlight could traverse about 360 degrees (minus the area around the noisy propellers), it could not move vertically. Once the beam passed over the target submarine, the searching vessel's sonar lost contact. The transducer (the thing that transmitted & received the pings) could not be exposed directly to the passing ocean because it caused enough noise to make it useless. The solution was to suspend it in a "pod" below the vessel. The pod was full of salt water which allowed the transducer to "see" without reducing its effectiveness. The "pod" on DEs was retractable. Three of the photographs to the right are views of a sonar's transducer "pod" that hung beneath the ship. This pod is on the USS Kidd and is one of the earlier versions and is non-retractable. Destroyer Escorts were equipped with the later QC-Series Searchlight Sonar, usually the QCS. The retractable magnetostrictive transducer was in a streamlined dome located 25 feet aft of the bow. The QCS was equipped with a Bearing Deviation Indicator that permitted the sonar operator to detect target bearing changes. The echo rangefinder station also had a sonar transmitter and echo amplification unit and attack plotter. In mid-1944 the U.S. obtained 85 British model 147B asdic units. These were the most technologically advanced sonars used by U.S. warships in WW2. Fifty of the units were installed on ships in the Pacific fleet, including some of the DEs.	AN/UQN-1E Sounding Set, Sonar.
AM-1011/SQS-4, Amplifier, Audio Frequency, a unit of sonar set AN/SQS-4 Manufactured by: Sangamo Electric Company, Springfield, Illinois Contract Number and Date: NObsr-71071 Note: This component is located in the sound room in the bottom of the ship near the transducer pod.
R-613/SQS-4, Receiver-Scanner, Sonar, a unit of sonar set AN/SQS-4 Manufactured by: Sangamo Electric Company, Springfield, Illinois Contract Number and Date: NObsr-71071 Note: This component is located in the sound room in the bottom of the ship near the transducer pod.	No photo available but is a large gray box almost identical to AM-1011/SQS-4 above.
CV-312/SQ, Converter, Signal Data, a unit of sonar set AN/SQS-4 Manufactured by: Sangamo Electric Company, Springfield, Illinois Contract Number and Date: NObsr-71071 Note: This component is located in the sound room in the bottom of the ship near the transducer pod.	No photo available but is a large gray box almost identical to AM-1011/SQS-4 above.
Computer, Mark 59, Mod. 10 Weight: 448 pounds Manufactured by: ARMA, Garden City, New York Note: The two-axis sonar stabilization module at the right attaches to the left side of the computer in the top photo. The top window is marked "Dir.(ection) Train". The Second window from the top is marked "Sonar Train." The third window from the top is empty. The bottom window is marked "Sonar Depression." Note: These components are located in the sound room in the bottom of the ship near the transducer pod.
RT-158B/UQC-1, Sonar Receiver-Transmitter, a component of sonar set AN/UQC-1B Manufactured by: Pacific Division, Bendix Aviation Corporation, North Hollywood, California Contract Number: NObsr-52275 Note: This component is located in the sound room in the bottom of the ship near the transducer pod. The UQC-1 was the underwater telephone. It used a simple superheterodyne Receiver-Transmitter operating at 8 and 12 kHz. Mikes and audio amplifiers were located in sonar and on the bridge. Courtesy of Locke Wilde.
AN/SQS-31, Sonar Detecting-Ranging Set Manufactured by: Sangamo Electric Company, Springfield, Illinois Contract Number: NObsr-71071
CAN-55134-B, Chemical Recorder Manufactured by: Unknown Contract Number: Unknown The chemical attack recorder registered the echoes sent to it by the sonar equipment. The echoes were registered on thermal sensitive paper, and the recorder then acted as a mechanical computation device, calculating the target depth changes and determining when depth charges should be dropped. Frequently, the attack recorder operator would issue the command to initiate a depth charge attack with the sound powered phone connection to the depth charge racks and K-gun operators.
CRP-55ABC-3, Range and Train Indicator, a unit of model SG-1 Radar Equipment Weight: 490 pounds Manufactured by: Raytheon Manufacturing Company, Waltham, MA Contract Number: NXss-33776
IP-236/SQ, Azimuth and Range Indicator, a unit of sonar set AN/SQS-4 Manufactured by: Sangamo Electric Company, Springfield, Illinois Contract Number: NObsr-71071
Mk 5, Mod 2 Attack Director Weight: 740 pounds Manufactured by: Control Engineering Corporation, Norwood, MA Note: The Attack Director belongs in Sonar control. It is the fire control computer for the hedgehogs and the depth charges. It has nothing whatsoever to do with surface or anti-air gunnery. The analog computer solved the fire control problem and could fire the weapons automatically if that mode of operation were chosen by the ASW officer. It was hard-wired into the sonar set and could also take over the sonar so as to keep the sonar beam on the sub during the attack. The sonar operator would then watch the PPI carefully to ensure that sub maneuvers didn't throw off the attack director. He could aid the computer back on the sub with the 'aided track' mode. Courtesy of Locke Wilde, retired "Mustang" Officer that worked his way up through the ranks as a Chief Sonar Technician.
T Mark 6 Control Panel Weight: 130 pounds Manufactured by: Food Machinery and Chemical Corporation, John Bean Division BuShips Contract: NObs-66887 SNSN: S-17-P-20150-2500
Sonar Transducer Control Panel Manufactured by: Unknown Contract Number: Unknown Note: The sonar transducer control panel is actually the top portion of the AN/SQS-4 sonar control console. You can see the transmitter/pulse and fire control controls on the faceplate. This was where the sonar operator sat. It was colloquially called the sonar 'stack'. Courtesy of Locke Wilde.