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ridgewayranger · 07-19-05, 03:41 PM

I was quite surprised to read that these sonars were American. Iwas a sonar operator back in 1948 using both sets in British ships. It was not possible to estimate depth with 144, due to the beam shape, and of course increased diving depths meant boats could be below the main beam, but the addition of a second set with less range but with a flat wedge shaped beam known as "Q" and mounted below the main oscillator at an angle allowed for the detection at greater depths and made it possible to estimate depth when the echo moved from one beam into the other.The type 147 was a depth predicting set designed to overcome the 144 limitation. It was never very successful. Basically it tilted back and depth was worked out trigonometrically, based on angle of tilt and horizontal range. The only time I ever knew it to work was in the simulator. As far as I know, the Americans concentrated on the omnidirectional set while the rest of us used the rotatable narrow beam, similar to radar. Detection was problematical over 2000 yards except in perfect conditions. Another limitation ( still is) was speed. Over about 12 knots background water noise masked everything else, and there was the risk of damaging the underwater dome, which had to be raised before speed could be increased. Hope this explains some of the real limitations of submarine detection in WW2.
Jim O
Ex.TASI, Royal Navy.

07-19-05, 03:41 PM	#2
ridgewayranger Frogman Join Date: Jul 2005 Location: Ipswich, England Posts: 302 Downloads: 281 Uploads: 0	Sonar Type 144/147 I was quite surprised to read that these sonars were American. Iwas a sonar operator back in 1948 using both sets in British ships. It was not possible to estimate depth with 144, due to the beam shape, and of course increased diving depths meant boats could be below the main beam, but the addition of a second set with less range but with a flat wedge shaped beam known as "Q" and mounted below the main oscillator at an angle allowed for the detection at greater depths and made it possible to estimate depth when the echo moved from one beam into the other.The type 147 was a depth predicting set designed to overcome the 144 limitation. It was never very successful. Basically it tilted back and depth was worked out trigonometrically, based on angle of tilt and horizontal range. The only time I ever knew it to work was in the simulator. As far as I know, the Americans concentrated on the omnidirectional set while the rest of us used the rotatable narrow beam, similar to radar. Detection was problematical over 2000 yards except in perfect conditions. Another limitation ( still is) was speed. Over about 12 knots background water noise masked everything else, and there was the risk of damaging the underwater dome, which had to be raised before speed could be increased. Hope this explains some of the real limitations of submarine detection in WW2. Jim O Ex.TASI, Royal Navy.