Navy Seal 
Join Date: Mar 2007
Location: DeLand, FL
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Wow!
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Originally Posted by LukeFF
...I upped the Hydrophone Speed Factor settting all the way to 1, and even at flank speed on the surface I could pick up contacts without any issues. So, I did some more research on the matter, and here's what I've found. First, here are some excerpts from Naval Sonar, NAVPERS 10884, 1953:
JP Sonar (the hydrophone head mounted on the bridge, later replaced during the war by JT):
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The original J-series listening equipment was designed for use on submarines. Most modern listening equipment, such as the JP and JT, is designed for patrol craft, picket boats, and submarines. The JP-series listening equipment is now in use on submarines as a unit of the JT equipment.
The JP is a sonic equipment-that is, it receives audible sounds, amplifies them, and applies them to either headphones, loudspeakers, or a tuning-eye indicator. Because the line hydrophone used with the JP is moderately directional, bearings on the sound sources can be made by use of the tuning-eye indicator. The JP equipment was designed for small surface craft. The JP-1, JP-2, and JP-3 are used on submarines.
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Models JP-1, JP-2, and JP-3 equipments are used on submerged submarines to obtain bearings on other vessels by directional detection of underwater
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WCA Sonar (the balls mounted on the keel):
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When the sonar range to the target is desired, the echo-ranging transducer is trained to the target bearing and a single short ping is emitted. The echo-ranging equipment on a submarine is used most often for navigation and only as required for target ranging.
During World War II, combination sonar equipments that provided ranging, listening, and sounding were installed on submarines. The model WCA is such a combination sonar equipment.
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As shown in figure 14-2, the WCA-2 consists of three systems. One system, the QC-JK, uses the combination sound head for echo ranging and listening. The QC magnetostriction element is used for echo ranging. The JK crystal hydrophone, which is more sensitive than the QC magnetostriction transducer, is used for listening only. The QC and JK units cannot be used simultaneously.
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And from the earlier 1945 manual:
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The WCA system of sonar gear is used for supersonic listening, and also for echo-ranging and depth-sounding. It consists of three main divisions: QB, JK/QC, and NM.
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Sonic listening was covered in the same book and was directly linked to the use of JP Sonar.
That would pretty much solve the issue, right? Well, not quite. From the same manual:
(From the section on "Sound in Water"):
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Propellors generate a wide band of sonic and supersonic frequencies. Consequently, they can be detected with either type of gear.
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And, again from the section on supersonic listening:
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Contact !
Maybe your whole watch will be spent in just routine searching. But at any moment you may pick up enemy propellers.
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So, with all that said, how do we make picking up surfaced sonar contacts realistic without making radar and the watch crew irrelevant? What would really help out is if we could find out what the maximum range was of both the WCA and JP sonar gear. I have found nothing on the web that says what the performance of this gear was. So again, if you have spec sheets on WCA on JP sonar, please let me know or post the data here for all of us to see. It would really help in getting a handle on this matter. So far I can only find referencs to kilocycles, which may or may not be of use. |
Pretty much a repeat and confirmation of the manual we've already looked at. Sounds like one is most likely the source for the other!:p I still think the contact logs are going to be our only source of answers, if they contain enough data. Tater has all that stuff but hasn't been watching these threads, apparently. The answers will come. 
Another emerging (from your exerpt above and my personal knowledge) factor is quite interesting and I haven't thought about it before this. The higher the frequency, the more directional the sound appears. It can be localized with considerably more accuracy than a lower frequency sound.
Familiar example: If the sound is low enough to come out of a subwoofer, when all impression of direction vanishes. It doesn't matter where you put the subwoofer. It matters completely where you put your surround speakers.
Notice above it mentions that the JP/JT sound apparatus is "moderately directional." The QB and QC/JK would be much more precisely directional.
Another factor, which can be illustrated with familiar radio signals. Low frequency sounds, while non-directional carry much further and penetrate more barriers than high frequency sounds. Your AM radio at lower frequency, bounces off the ionosphere and refracts readily around obstacles to give much wider coverage than higher frequency FM signals, which pass right through the ionosphere and reflect off every possible barrier. A GPS satellite signal is so high frequency that the signals will not even pass through the roof of your house. The tradeoff is that the high frequency is part and parcel of its accuracy.
We would expect the same thing with the different sonar signals. JP would be mildly and not so precisely directional. If you really wanted to get a precise bearing it would be from the JB or JC operator. That is, if the higher frequency sound wasn't interfered with. With the sub below the thermal layer, high frequency could be totally gone. But low frequency sounds would penetrate much better, giving much less precise but usable location data. Wouldn't it be great to have a simulation that properly rendered all these nuances?
Last edited by Rockin Robbins; 11-23-07 at 07:17 AM.
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