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Andrew, I am also developing a system that does not transmit at all until the need presents itself. We wish to explore the under sea environment, not show a serious presence. The system works as follows: During submarine operations, this distress pinger is vertually silent. A timing circuit counts down for a preset period of time prior to which a small audible alarm is triggered. ( I am toying with twenty minutes) The pressing of an alarm timer "reset" button will start this timing cycle back to its starting point. If during the deployment, should the submarine operator becomes unable to reset this circuit, this pinger will begin to transmit without the need for further operator intervention and will continue to transmit until either turned off or becomes depleted of its supplied power. (Several days later) In this way, this distress pinger would not interfere with the local aquatic life nor distract the operator from hearing any other submarine operations He is performing. This set up may seem complicated to employ, but it is actually quite simple to both make and use. David Bartsch > Date: Tue, 5 Aug 2008 06:20:09 -0700 > From: ag@desertstar.com > To: personal_submersibles@psubs.org > Subject: RE: [PSUBS-MAILIST] Convention & Hydrophones > > David, > > I thought the testing went well. Yes it was a bit wet, but luckily these devices are made for underwater use :) > > We were certainly able to roughly evaluate the performance of the various hydrophone designs and could detect the > home built pinger. It would have been nice to be able to perform some more rigorous testing, but I think demonstration and > basic proof of concept goals were met. > > I liked seeing the low cost housing designs, I thought they were particularly neat using almost no machining and easily obtainable parts. > > I would suggest that nailing down a set of desired specs would be a good idea. For example, on the pinger audio frequencies are nice, but they will drive the sub operator nuts if the pinger is active throughout the op. Also, ABS specs out certain parameters such as frequency and pulse length which may be important if you ever need the navy to come looking for you. > > As an aside, the entire convention was really fun. I would strongly recommend anyone with an interest in submersibles to > attend, if only to share sea stories. I think you would be amazed at the various tidbits that can be picked up not only from the > presentations but also from just talking to all the people who showed up. > > -a > > > > -----Original message----- > From: David Bartsch dbartsch2236@hotmail.com > Date: Tue, 05 Aug 2008 08:50:37 -0700 > To: personal_submersibles@psubs.org > Subject: RE: [PSUBS-MAILIST] Convention > > > > > Jim, > > > > The military used hydrophones formed in a circle. Since sound propogates from a single point of origin, it expands from this point in an ever enlarging circle. These sound waves would eventually encounter this hydrophone array and strike specific hydrophones in a set given order as it continues to pass thru this array. The military having almost endless resources had the ability to determine the bearing to the point of this sounds origin by this sequence of detections and hence where it came from. > > Dealing with Psubs, we have limited space, limited funds, and the need for exact contact bearing of detection is not critical. > > I too am at a loss as to the lack of bearing accuracy now being shown from these later units. The initial "dolphin ear" hydrophone had almost no side detection capability and the level of detection increased as the source became closer to ninty degrees from the piezo elements mounting surface. It was bi-dirrection as back side detections were also part of its beam pattern. > > I need to go back and redesign this unit so as to regain its dirrectionality (Is there such a word?) > > Where is your location, and do you feel like participating in this road of discovery? Your input, testing, and evaluations would be a great asset to us all. > > Do you have a working sub or one under construction? Are there lakes, ponds, or other bodies of water nearby for testing? > > > > David Bartsch > > > > > > > > From: kocpnt@tds.netTo: personal_submersibles@psubs.orgSubject: Re: [PSUBS-MAILIST] ConventionDate: Mon, 4 Aug 2008 21:02:13 -0500 > > > > > > > > Hi David, > > > > I think that the underwater hydrophone testing went well. The results were not as good as hoped for from a directional standpoint. I brought up that if we used some of the same components and made the tube from steel or some othe dense material, I think that directionality will be improved. This is just a guess. Perhaps the opposite is also true, you could use the similar tube and some insulation to soften the reaction of the outside diameter of the tube and allow the acrylic front take a higher percentage of the feedback. I feel as if one or the other of these approaches are worth testing for positive directional results. > > > > Best Regards, > > > > Jim K > > > > ----- Original Message ----- > > From: David Bartsch > > To: personal_submersibles@psubs.org > > Sent: Monday, August 04, 2008 5:45 PM > > Subject: RE: [PSUBS-MAILIST] Convention > > Jim, It is my understanding that the weather played against us when it came to the underwater passive hydrophone and pinger presentations. Of what you were able to participate in, what are your thoughts and reactions on this presentation? David Bartsch > > > > From: kocpnt@tds.netTo: personal_submersibles@psubs.orgSubject: [PSUBS-MAILIST] ConventionDate: Mon, 4 Aug 2008 05:29:08 -0500 > > > > > > Hi All, > > > > Having just returned from the comvention, I would like to thank Jon & Ray for all the effort to put together a fine meeting. I learned a lot and met some more great people. Also thanks to all presenters, who added to my personal knowlwdge base. > > > > Thanks again, > > > > Jim K > > > > Get more from your digital life. 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