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Jon, I agree. There is only so much from shallow water we can do. David Bartsch > From: jonw@psubs.org > To: personal_submersibles@psubs.org > Subject: RE: [PSUBS-MAILIST] Convention & Hydrophones > Date: Tue, 5 Aug 2008 18:36:26 -0400 > > > From a hydrophone perspective, I think we need some testing to be done by > those who have submersibles. There's only so much testing one can do on the > surface from a kayak (in my case). I think we've done a good job of proving > that hydrophones can be made very inexpensively from common parts, and that > they are surprisingly sensitive. The issue we need to deal with now is > directionality. Someone told me that a sub acts as a pretty good listening > device all on its own, and that you can hear distant objects quite well. I > think someone with a divable sub could, with just a few field tests, make a > determination if the omni-headphones we've created add any value for > identifying surface traffic. Lynn Darnell had a theory in terms of a > "stereo" hydrophone to provide directionality. JimK suggested using a > housing such as a steel pipe, and somebody else mentioned using a funnel > type object (made of metal) to act as a collector. To date, only shallow > testing has been performed (50 foot depth or less) and we are likely to see > different results in deeper water of 350 feet just due to the way the sound > waves bounce around. So there's still alot of experimentation that can be > done in this area. I'll be putting the hydrophone and pinger slides up on > the website soon so people can build them for themselves. I also have a > number of hydrophones available that I can ship to people who want to test > them. > > In regards to the acoustic pinger, Andy is correct that ABS has specs for > them and the homebuilt 3.2khz buzzer piezo doesn't meet those standards. If > I remember correctly the ABS standards call for a 37 khz (maybe 37.5 khz) > transmitter and that it be active throughout the entire dive for tracking > purposes. Since it is ultrasonic, it doesn't bother the pilot. I know the > Desert Star homing beacon operates at 72.5 khz based upon the SPORT > documentation. Anyone remember Lee's last name, from the convention. He is > an electronics guru and showed interest in the ABS specification for the > pinger and suggested he could probably come up with a schematic to build > one. The homebuilt pinger is inexpensive and easy to build, so from that > perspective it might be able to find use as a supplemental device, but a > device that meets ABS standards should take priority. > > Andy, from Desert Star, stayed with us the entire weekend and participated > in all our events. It was great having him there both as a DSS rep and as a > friend. Put a lobster and some steamers in front of him and he'll talk all > night about underwater acoustics. :) > > Jon > > > > > ************************************************************************ > ************************************************************************ > ************************************************************************ > The personal submersibles mailing list complies with the US Federal > CAN-SPAM Act of 2003. Your email address appears in our database > because either you, or someone you know, requested you receive messages > from our organization. > > If you want to be removed from this mailing list simply click on the > link below or send a blank email message to: > removeme-personal_submersibles@psubs.org > > Removal of your email address from this mailing list occurs by an > automated process and should be complete within five minutes of > our server receiving your request. > > PSUBS.ORG > PO Box 53 > Weare, NH 03281 > 603-529-1100 > ************************************************************************ > ************************************************************************ > ************************************************************************ > Get more from your digital life. Find out how. |