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Here are the test results (the second email attached) from July 18th, 2008 of that six hydrophone array to give an idea of ranges achieved. I noticed that I was using a 7 watt amplifier at the time and we now use 18 watt so our ranges should be even further. David Bartsch From: dbartsch2236@hotmail.com To: l_nierth@hotmail.com Subject: FW: In-water tests are in Date: Sun, 27 Jul 2008 07:00:32 -0400 Larry, After evaluating the testing results of my in-water tests of the sonar array and new hydrophone, I reported to the group leader my findings...here is what my boys and I discovered... The convention for this group is from the 31st of this month to the third of August. Passive sonar will be one of the topics of discussion...I have done my best in aiding these gents into not having an accident...I hope this work and research is well recieved! David Bartsch From: dbartsch2236@hotmail.com To: jon@psubs.org; sjpearceqld@bigpond.com Subject: In-water tests are in Date: Fri, 18 Jul 2008 16:04:13 -0400 Jon and Stephen, I just got back from the in-water testing of both the hydrophone and six hydrophone array and wish to report my findings. We (My two boys and I) tested the new hydrophone (PVC with metal back plate) as it was mounted on a ten foot aluminum conduit section. This was easy to deploy athough some care was needed to avoid any contact with the sides of our boat. I used a large speaker as I did not want to seemingly exclude my sons with the use of headphones at first. The electronics I used proved very useful (a single 741 op amp in series with a 7 watt mono amplifier both kits were from all electronics) The humm I heard early on was in fact 60 cycle related...My wife called on my cell phone during testing and man did that play a number on us! Early on in the testing we picked up on a radio station as you did Jon...remember, these electronics lack an enclosure at this point. We were able to clearly hear the spillway near the earthen dam. A small two hull boat passed us on the way back to the docks on trolling motor power...It was easily heard and was 800 feet at its CPA (closest point of approach) The individual blades could be heard as each sliced into the water. Also, a small hum from the electric motor itself. I tried to determine any dirrectionality with this single hydrophone, but as Jon found out, the beam pattern is quite wide being practically the full 180 degrees of the piezo mounting surface. We later picked up a small boat with an outboard gas engine at 2000 feet verified with visual and it could easily be heard as well. The inside workings of the engine as well! At this point, we shifted our testing to the six hydrophone array. 277 ping pong balls displace quite a bit of water! I fought this and eventually forced into proper position so as to hear all around even under our boat and locked it into place. With a small pointer at the end of the mounting rod, even though we could no longer see this array, we new in what dirrection it was facing. The hydrophone selector unit was faced forward as was this array so that the dirrection selected was simular to the array orientation. I like a no brainer from time to time to rest my brain! I simply steared in the dirrection I wanted to hear and it was automatically selected by the HSU. This portion worked great! The ping pong balls did aid in isolating each hydrophone one from another, but a poured in air filled substance would better have conformed to the small stainless dog bowls within which each of these hydrophones were mounted. This would have even better channeled the sound into each phone. Moving along...as boats passed at some distance, by training in the dirrection of these boats, you could determine by the amplitude of the recieved sound, the dirrection of these contacts within the sixty degrees assigned to each hydrophone. By placing a boat between two hydrophones, I found it not to be as accurate as I had hoped. Each piezo element is not created alike and it took a small amount of time for the electronics to stabilze for comparisons between two different hydrophones. By the time you have a clear perception as to the signal present at the newly selected hydrophone, you may have lost your reference as to the level from the previous one. (perhaps the use of a visual bar graph display as Stephen is developing would be a better way of accomplishing this) The switches used in the HSU caused some switch bounce clicks as each hydrophone input was selected or removed. The next array should use stator brushes so as to remove this sudden shock to the electronics. In this way, perhaps less time would be needed for the signal to be stabilized for comparisons. So, at this point, the accuracy can be silidly established to be within the 60 degrees of each hydrophones area of assigned coverage. I feel that additional hydrophones in this array would not greatly improve this accuracy unless this visual display was also incorporated as well. Perhaps it is as Dan H. suggested that a single hydrophone placed at a given dirrection would be the best application when it comes to psubs. You could determine the dirrection to a given contact by simply stearing your boat and in doing this free your hands up for other multitasking functions. It is only with visual aids such as Stephen is working on that a clearer bearing accuracy can be achieved. On the HSU, I installed the ability to select all six hydrophone and thereby have a full 360 degree of coverage. This feature worked very well also! This was done with simple toggle switches and I would add this feature again and turn to trainable mode when needed. So, on small bass/John boats, the range of detection should be around 1/2 mile (less if trolling on electric) It may be that underwater communications and distress submarine pinger locator will turn out to be the most practical application of this set up. Testing on larger vessels is definately needed. As Jon has pointed out, collision avoidance with passive hydrophones is not fool proof but should be taken as another tool available that when properly used, could reduce the risk of collision in most instances. David Bartsch Stay in touch when you're away with Windows Live Messenger. IM anytime you're online. Stay in touch when you're away with Windows Live Messenger. IM anytime you're online. |