<html><head><style type="text/css"><!-- DIV {margin:0px;} --></style></head><body><div style="font-size: 13px;color: rgb(0, 0, 0);font-family: arial, sans-serif;"><div><br></div>Hi Brian,<div><br></div><div>I'd research it a few years ago. :)</div><div>An interesting related topic, certain governments have "radios" (more like pagers) that use low frequencies radio waves (like kilometers long wave length) to penetrate 100s of meters to send instructions to military subs. However these are very low bandwidth, like a few characters of a minute (or something like that).</div><div><br></div><div>How much data are you looking to transfer?</div><div><br></div><div>Alternative idea:</div><div>You could also use light to communicate with the remote computer (kind of like IR remote controls, but using a blue/green light for water penetration).</div><div><br></div><div>Related project I was playing with:</div><div>This last weekend I was working on using vision processing (on a tiny embedded computer with a camera) to identify and decode Morse code messages. Essentially a camera which is pointing at 1 or more LEDs which are blinking Morse code messages. The camera sees the LEDs turning on and off, then tries to decode the messages. It should be able to decode multiple different Morse code sources at the same time.</div><div><br></div><div>I just picked Morse code because, hey it's Morse code. It doesn't give a particularly high bandwidth (characters per minute), and I'm sure I could create a faster protocol. Although the ultimate limit with this approach is the FPS of the camera, which will limit it how short of a flash I could reliably detect.</div><div><br></div><div>The use case I was exploring is having multiple underwater vehicles, each with a bright blue/green LED and a camera. They should be able identify each other and send short messages. Each vehicle would have a unique ID (e.g. 3 digit ID like "S01", "S04", etc.) which they would prefix their messages with. The other vehicles would receive the ID and message if it was with in visual range and the viewing angle of the camera (a fisheye lens should improve the view angle a lot). I was kind of excited I was able to get it working in a "lab"/bench-top environment after tinkering with it for a few hours.</div><div><br></div><div>Cheers,</div><div> Ian.</div><div><br><blockquote style="padding-left: 5px; margin-left: 0px; border-left: #0000ff 2px solid; font-weight: normal; font-style: normal; text-decoration: none; font-size: 10pt; font-family: arial,sans-serif; color: black;">-----Original Message-----
<br>From: Brian Cox via Personal_Submersibles <personal_submersibles@psubs.org>
<br>Sent: May 20, 2019 2:01 PM
<br>To: Personal Submersibles General Discussion <personal_submersibles@psubs.org>
<br>Subject: Re: [PSUBS-MAILIST] Wifi signals
<br><br><div style="font-family:Arial, sans-serif; font-size:10pt;"><font size="2">Ian,</font><div><font size="2"> I was thinking about gathering data from a remote computer sitting on the ocean floor .</font></div><div><font size="2"><br></font></div><div><font size="2"><br></font></div><div><font size="2">BTW, how the heck do you know that !</font></div><div><font size="2"><br></font></div><div><font size="2">Thanks,</font></div><div><font size="2"><br></font></div><div><font size="2">Brian<br></font><br><br><span style="font-size: 10pt;">--- personal_submersibles@psubs.org wrote:</span><br><br><span style="font-size: 10pt;">From: irox via Personal_Submersibles <personal_submersibles@psubs.org></span><br><span style="font-size: 10pt;">To: Personal Submersibles General Discussion <personal_submersibles@psubs.org>, PSubs <personal_submersibles@psubs.org></span><br><span style="font-size: 10pt;">Subject: Re: [PSUBS-MAILIST] Wifi signals</span><br><span style="font-size: 10pt;">Date: Mon, 20 May 2019 13:51:39 -0700 (GMT-07:00)</span><br><br><div style="font-size: 13px; color: rgb(0, 0, 0); font-family: arial, sans-serif;"><br>Hi Brian,<div><br></div><div>this should work providing the transceivers are within 1/4 wave length of each other (after that it may work, but results will degrade the further apart they are, probably with the signal being unusable after a wavelength or few).</div><div><br></div><div>For 2.45GHz Wifi signal, the wave length will be 122.45 mm (so 1/4 wavelength will be ~30mm)</div><div>For 900MHz Wifi signal, the wave length will be 333mm (so 1/4 wavelength will be ~83mm)</div><div><br></div><div>Cheers,</div><div> Ian.</div><div><br></div><div><br></div><div><blockquote style="padding-left: 5px; margin-left: 0px; border-left: #0000ff 2px solid; font-weight: normal; font-style: normal; text-decoration: none; font-size: 10pt; font-family: arial,sans-serif; color: black;">-----Original Message-----
<br>From: Brian Cox via Personal_Submersibles
<br>Sent: May 20, 2019 1:10 PM
<br>To: PSubs
<br>Subject: [PSUBS-MAILIST] Wifi signals
<br><br><div style="font-family:Arial, sans-serif; font-size:10pt;"><font size="2" style="font-family: Arial, sans-serif;">Hi everybody,</font><div style=""><font size="2" style=""><font face="Arial, sans-serif"> Has anyone experimented with wifi under water ( saltwater) where the transceivers are directly next to each other and only separated by an acrylic window ?</font></font></div><div style=""><font size="2" style=""><font face="Arial, sans-serif"><br></font></font></div><div style=""><font size="2" style=""><font face="Arial, sans-serif">Brian</font></font></div><div style=""><font size="2" style=""><font face="Arial, sans-serif"><br></font></font></div><div style=""><font size="2" style=""><font face="Arial, sans-serif"><br></font></font></div></div>
</blockquote></div></div><span style="font-size: 10pt;">
_______________________________________________
Personal_Submersibles mailing list
</span><a href="/eonapps/ft/wm/page/compose?send_to=Personal_Submersibles%40psubs.org" style="font-size: 10pt;">Personal_Submersibles@psubs.org</a>
<a href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" style="font-size: 10pt;">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a>
</div></div></personal_submersibles@psubs.org></personal_submersibles@psubs.org></blockquote></div></div></body></html>