[PSUBS-MAILIST] Blue Robotics Sonar

[Jon Wallace via Personal_Submersibles]

I believe it is because air molecules are not dense enough to carry the ultrasonic wave and so it is reflected back as if it were the "bottom".  No different than an ultrasound on the human body, it requires a "grease" between the skin and ultrasound wand so there are no air gaps.
Fiberglass is dense enough to pass the ultrasonic wave but there can't be any air bubbles in the area of the transducer.See http://www.raymarine.com/view/?id=199

      From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
 To: Jon Wallace via Personal_Submersibles <personal_submersibles at psubs.org> 
 Sent: Tuesday, February 5, 2019 2:17 PM
 Subject: Re: [PSUBS-MAILIST] Blue Robotics Sonar
   
 It just doesn't make sense to me?  I thought the sound had to hit a more dense material than air to bounce back.  it is great if it works- I will have to give it a try when the ice melts.Hank
    On Tuesday, February 5, 2019, 8:46:00 AM MST, Jon Wallace via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  
 
 Pretty sure the beam reflects off the water surface.

      From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
 To: Brian Hughes via Personal_Submersibles <personal_submersibles at psubs.org> 
 Sent: Friday, February 1, 2019 10:54 AM
 Subject: Re: [PSUBS-MAILIST] Blue Robotics Sonar
  
 Brian, Have you tested the Hummingbird pointing strait up?  I didn't think that would work because there is nothing for it to bounce back against.Hank
    On Friday, February 1, 2019, 7:44:42 AM MST, Brian Hughes via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  
 
  In the original configuration of Harold, Maynard attached a transducer to the front of the starboard side thruster. I assume he did so as a way to easily shift direction, up to get depth bouncing off surface, spin the thruster down for depth, forward for collision avoidance.

Here's the upgrade:

1) transducer always pointed up for a Humminbird HDR 650. Basically a digital depth gauge. Small and accurate. Works well.

2) Raymarine Dragonfly 4 Pro aimed down to give depth below and detailed image of what's under me. Amazing little CHIRP sounder.

3) still debating on what to aim forward. Currently have an Interphase forward scanning sonar, but not real impressed with it. Older technology that works. Sort of.

Brian


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