<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=utf-8"><meta name=Generator content="Microsoft Word 15 (filtered medium)"><style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman",serif;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:#0563C1;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:#954F72;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal-reply;
font-family:"Calibri",sans-serif;
color:#1F497D;}
.MsoChpDefault
{mso-style-type:export-only;
font-family:"Calibri",sans-serif;
mso-fareast-language:EN-US;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]--></head><body lang=EN-CA link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US'>Brian,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US'>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?<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US'>Tim<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><b><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri",sans-serif'>From:</span></b><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri",sans-serif'> Personal_Submersibles [mailto:personal_submersibles-bounces@psubs.org] <b>On Behalf Of </b>Brian Cox via Personal_Submersibles<br><b>Sent:</b> Friday, May 17, 2019 8:35 PM<br><b>To:</b> PSubs <personal_submersibles@psubs.org><br><b>Subject:</b> [PSUBS-MAILIST] passive sonar<o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal><span style='font-size:13.5pt;font-family:"Arial",sans-serif'> 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. </span><span style='font-size:10.0pt;font-family:"Arial",sans-serif'><o:p></o:p></span></p><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial",sans-serif'><o:p> </o:p></span></p></div><div><p class=MsoNormal><span style='font-size:13.5pt;font-family:"Arial",sans-serif'>Brian </span><span style='font-size:10.0pt;font-family:"Arial",sans-serif'> <o:p></o:p></span></p></div></div></div></body></html>