David,
After seeing Jon’s presentation at the Conference, really appreciate all of the effort that you have put into this design.
Through all of this, I have not seen formal performance data, only subjective. Application of the sonar equation for typical open saltwater conditions would be useful for us in making judgments of usefulness by providing range and potential signal to noise ratio information. What is the units wattage output into the water?
R/Jay
Respectfully,
Jay K. Jeffries
Andros Is., Bahamas
Talk sense to a fool and he calls you foolish.
- Euripides (484 BC - 406 BC)
From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of David Bartsch
Sent: Monday, August 11, 2008 6:03 AM
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] Convention & Hydrophones
Jon,
Although the home built pinger does not meet the ABS standard for a distres locator, A great use for the one we constructed could be to plant this on a site of interest for later exploitation. The low power consumption would allow it to remain active for long durations. This item could be reaquired once you return to the site and hence used again. As you have tested and can varify, it works quite well in providing an exact location to something.
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
>
>
>
>
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