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Re: [PSUBS-MAILIST] Desert Star Sport



Hi all.

A couple of points.

An echo-sounder, fish finder, etc. as normally installed would require the surface vessel to be almost on-top of the sub. A side scan typically would require the surface boat to always be moving back and forth with the sub broadside in order to image. I think both would have pretty sever operational challenges when trying to track a sub.

The sport/scout do require the receiver to be in the water. As delivered the sonar transducer and display electronics are co-located in the same housing. So, yes you would get wet when attempting to use if from a surface boat.

It would be fairly simple to open up the receiver, disconnect the sonar transducer from the display electronics, connect it to a coax cable, and run the display electronics remotely (like on a pole or in the cabin). This would void the warranty... Remember that the transducer is directional, so if it's rigidly mounted the relative positions of the sub and chase boat would have to stay constant. You could run spirals or something if you lost contact. If you do rigidly mount the receiver I'd get a second one too. That way if you had to send divers or an rov down to the sub you could relocate it easier.

A configuration which would be more like the typical diver application, would be to pinger on a pole off the boat, and the receiver on the sub. The sub could always get back the surface boat without surfacing.

If you want to move up to a "real" tracking system. There are lots. Desert star has an sbl for about $10K, Linkquest was mentioned at $15K for their USBL, then there is sonardyne, tritech, applied acoustics, ORE, ixsea. I think that is everyone. There are companies like Asthtead which rent these systems, which may be an option.

If I had to had to have a fixed budget though I'd get other gear before a nav system I think.

1) Comms, like a OTS phone or something
2) Altimeter/depth sounder on the sub
3) Some imaging sonar, scanning or multibeam if I had the $$
4) Surface beacon (strobe/radio)
5) SBL/USBL acoustic nav system.



On 3/15/2010 12:18 AM, Jon Wallace wrote:

Frank,

Not addressed to me, but I'll throw in my two cents. Most commercial pingers are ultrasonic. The hydrophone that David came up with uses a "sonic" piezo element centered at around 3khz so it would not be resonant to the higher frequency commercial pingers and would not detect them.

The Desert Star scuba pingers provide both direction and range and can be used exactly as you've described. Unfortunately we have never been able to succeed at getting directionality out of the HBH (home-built hydrophone) using 3khz piezo elements, however my experience was that it was very easy to determine range based upon the loudness of the "ping". Therefore, by running a grid-pattern you could "home" in on the pinger by just listening to whether the sound was getting louder or softer. Not the most efficient way of finding an object by any means, however, and similar to what you would have to do with a down-looking sonar or fish finder.

Jon


ShellyDalg@aol.com wrote:
In a message dated 3/14/2010 8:06:39 P.M. Pacific Daylight Time, alanjames@xtra.co.nz writes:

    I have only had experience with cheap fish finders & have
    questions about their reliability,

Hi David and Alan. Gulping air......well, OK.
Now back to the question of finding a sub......
If a sub has a pinger attached, could a surface boat find it with the hydrophone you ( David ) made ? Depending on directionality of the array, a direction for the sub's location should be possible. Maybe then the pilot could motor over in that direction and as the pinger got louder you may be able to tell how close you're getting. At least staying within a pre-set minimum distance. By rotating the pick-up you would know if the surface boat needs to go left or right. Now, if you passed OVER the sub and the pinger signal was now coming from behind the pick-up the pilot would then stop or get out of the way in case the sub was ascending to the surface. Be a bummer to ram your own surface crew. Maybe you could have two pingers with one stronger ( louder ) or more frequent so by listening you'd be able to tell how close you were. What makes a pinger anyway ? Is it just a thing that sends out a sound wave at a set interval ? It seems the pick-up part is the hard piece to make. So the returning signal can be figured how far away it is ( function of time ? ) and what direction it's coming from ( array set-up in degrees ?)
Frank D.





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