[PSUBS-MAILIST] passive sonar

Sat May 18 14:56:27 EDT 2019

I bought a cheap depth sounder/fish finder that I thought I would mount up
front facing horizontal and my thought would be that if I were trying to
locate a wreck or an atoll that was out of visibility, assuming that the
bottom was relatively flat, I could rotate 360 degrees and look for a depth
that was showing close. I would probably have to rotate very slowly for it
to show but I figured for the price, it was worth trying. I spoke with
Garmin who built it and they weren't sure it would work in that capacity as
the signal comes out as a cone and if I was close to the bottom, I might be
picking up the bottom right away? The did sell much more expensive forward
looking sonars for yachts but trying to keep my costs down per wife. I will
probably take it down to the dock and clip the transponder to a stick and
hold it horizontal just underwater and see how it does. I'll let ya know
the results when I do.
Rick

On Sat, May 18, 2019 at 7:26 AM Brian Cox via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Tim,
>                        Yes that's the idea.   On my Garmin depth finder
> there is an optional screen which is simply stationary screen and then
> there is the screen that is moving , which gives you a "history" of the
> last few seconds of scanning .  But it would be interesting to play around
> with the detect ability of something like that.   Not sure how practical it
> would ultimately be.
>
> Brian
>
>
>
> --- personal_submersibles at psubs.org wrote:
>
> From: T Novak via Personal_Submersibles <personal_submersibles at psubs.org>
> To: "'Personal Submersibles General Discussion'" <
> personal_submersibles at psubs.org>
> Subject: Re: [PSUBS-MAILIST] passive sonar
> Date: Sat, 18 May 2019 07:15:35 -0700
>
> Brian,
>
> What are you trying to do with the "passive sonar" that you are
> considering? Are you wanting to make your submarine more easily detectable
> by a surface boat with a depth sounder?
>
> Tim
>
>
>
> *From:* Personal_Submersibles [mailto:
> personal_submersibles-bounces at psubs.org] *On Behalf Of *Brian Cox via
> Personal_Submersibles
> *Sent:* Friday, May 17, 2019 8:35 PM
> *To:* PSubs <personal_submersibles at psubs.org>
> *Subject:* [PSUBS-MAILIST] passive sonar
>
>
>
>         I've been thinking about some sort of pinger locator for my sub.
> I may get a commercially available one just as an extra safety measure, but
> in the mean time I was playing around with my depth finder on my sailboat
> .  I was thinking if I had a rotating disk that would be a little higher
> than the sub the changing surface exposure to the sonar waves would appear
> on the depth finder as a recurring blip .  I tried it with a radar
> reflector that I have, I tied it to a line and located it just below my
> transducer, I was able to move it around and observe the display on the
> screen.   Since the radar reflector ( used on boats so big ships can see
> you) has all these sides to it, as I moved it around it would show up
> intermittently since the sound wave sometimes would not bounce back.  I
> think a flat surface rotated so only the edge is showing and then a large
> surface was showing at a regular intervals could work as an indicator.   I
> might be especially valuable if you were blending into the bottom so much
> as to not be detectable .  That way someone with just an ordinary depth
> finder could detect you.
>
>
>
> Brian
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