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Hugh, This deep working hydrophone our group developed is based upon "bender" technology such as this "dolphin ear". Some hackers took a unit apart and shared how this was constructed. This particular hydrophone was well to "dip" over the side of tour boats to aid in the listening of whales and works great for this purpose. Problem is, as far as we are concerned, it will flood at 19psi or about 30fsw. This is due to the "o" ring compressing inward from the sides until it is smaller than the piezo unit being used. This breaks the water tight seal and flooding accurs. Look at the PVC hydrophone housing our group came up with in the special projects area of the "PSUB community " page of the psub web site(Other variations are shown to the left) All we have done is enlarge the cavity in which this piezo element operates by using a second "o" ring and a 1 /2" PVC coupler. A simple compression fitting found at any hardware store is used to seal the cable thru way.(add some form of calk or sealant for added reassurance) Small sections of 1 1/2" pvc pipe are conceled behind the "o" rings to prevent them from compressing into a smaller overall diameter and causing the problematic flooding previously discussed. In the depictions of this early unit, plexiglass was used in the making of the back wafer. This was found to crack under stress due to this cable thru hole, so this has been changed to aluminum or other metal. Submarines as it is being rediscovered are ideal passive sonar platforms. This hydrophone seems to be omnidirrectional but work is being conducted to get some dirrectionality from them as a result of its housing, or using baffling plates. Having two such hydrophones mounted on both sides of a submarine in the present configuration, and using some form of stereo comparison could also define a contacts rough location. Be sure to visit "psub community" on the club web site and look at special projects under hydrophones. Jon is soon to add how-to-build instructions and electronic schematics to include the "pinger" circuit also. This hydrophone idea is in its infancy so any added research on anyones part just adds to this mix...jump in! I used both a preamp kit and 7 watt amplifier kit both from allelectronics.com and these worked well together, allthough almost any amplifier would do well. David Bartsch From: hc.fulton@gmail.com To: personal_submersibles@psubs.org Subject: RE: [PSUBS-MAILIST] Hydrophones Date: Sun, 31 Aug 2008 10:01:27 +1200 David, Yes would like to get a hydrophone. Count me in. I got a dolphin ear but it is a bit questionable. How would you rate its performance Hugh
From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of David Bartsch
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