[PSUBS-MAILIST] passive sonar

[Alan via Personal_Submersibles]

Hi Brian,
the fish finders work like a car head light, so it would be hard to locate a 
submarine that was outside it's cone of detection even if you moved it
around. If for instance you were 500 yards away & 100ft deep it would 
probably be out of range & impossible to differentiate from anything else.
Alan

> On 18/05/2019, at 3:34 PM, Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
>         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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