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Matthew Kanwisher  
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 More options Sep 15 2012, 5:16 pm
From: Matthew Kanwisher <matthew.kanwis...@gmail.com>
Date: Sat, 15 Sep 2012 14:16:31 -0700 (PDT)
Local: Sat, Sep 15 2012 5:16 pm
Subject: Communicating Underwater

Is it possible to have radio transmitters work under water, I haven't been
able to see any readily available devices that do this? Most of the designs
seem to have a wire that goes all the way to the surface for the
communication. If not radio, do any other techniques work over distances of
like a few hundred feet in distance, maybe IR ?

~Matt


 
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Dirk Swart  
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 More options Sep 15 2012, 5:26 pm
From: Dirk Swart <dirk.sw...@wickeddevice.com>
Date: Sat, 15 Sep 2012 17:26:06 -0400
Local: Sat, Sep 15 2012 5:26 pm
Subject: Re: [NYCR:Microcontrollers] Communicating Underwater

This is a very well researched topic, mostly for submarine communication.
Generally, not usefully, unless you are prepared to make concessions of one
kind or another, eg: really, really big transmitters.

Hydrophones work over the distances you mention.
On Sep 15, 2012 5:18 PM, "Matthew Kanwisher" <matthew.kanwis...@gmail.com>
wrote:


 
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c f  
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 More options Sep 15 2012, 5:29 pm
From: c f <christopher.h.fen...@gmail.com>
Date: Sat, 15 Sep 2012 17:29:30 -0400
Local: Sat, Sep 15 2012 5:29 pm
Subject: Re: [NYCR:Microcontrollers] Communicating Underwater

It depends on a lot of factors. Here is a nice short paper on the topic in
regards to amateur radio:
users.tpg.com.au/users/ldbutler/Under*water*_Communication.pdf

Attenutation is higher in salt water than fresh water, for instance (since
it is more conductive), and low frequencies are better than high
frequencies, but you get less bandwidth and can need a bigger antenna. Lots
of trade-offs.

On Sat, Sep 15, 2012 at 5:16 PM, Matthew Kanwisher <


 
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Matthew Kanwisher  
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 More options Sep 15 2012, 6:14 pm
From: Matthew Kanwisher <matthew.kanwis...@gmail.com>
Date: Sat, 15 Sep 2012 15:14:13 -0700 (PDT)
Local: Sat, Sep 15 2012 6:14 pm
Subject: Re: [NYCR:Microcontrollers] Communicating Underwater

Dirk yeah I'm guessing I have to use sound waves instead of radio. I
haven't been able to find a straight answer at what freqs I would need to
transmit, also would it be audible to the human ear? I would rather people
around not to hear a bunch of noise but may be no way around that. I've
heard some speculation about using light for communication but that is
probably a lot harder


 
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raphael  
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 More options Sep 16 2012, 11:17 am
From: raphael <raph...@teuthis.com>
Date: Sun, 16 Sep 2012 11:17:09 -0400
Local: Sun, Sep 16 2012 11:17 am
Subject: Re: [NYCR:Microcontrollers] Communicating Underwater
I really want to hear how you progress! I have some projects that would
require wireless through water too.

I noticed that blue light gets through pretty well. You could do a
modulation scheme like we do with IR, but use blue instead.

Here's the article about EM transmission through water:

http://en.wikipedia.org/wiki/Electromagnetic_absorption_by_water#Visi...

Some hints on data over modulated light:

http://www.instructables.com/id/Nunchuk-controlled-Helicopter/step2/I...

http://jap.hu/electronic/infrared.html

Also, really bright blue LEDs:

http://www.mouser.com/ProductDetail/Lumex/SML-LXL8047USBCTR3/?qs=%2fh...

On 9/15/12 6:14 PM, Matthew Kanwisher wrote:


 
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flink  
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 More options Sep 20 2012, 2:05 pm
From: flink <fl...@crystalwind.com>
Date: Thu, 20 Sep 2012 11:05:18 -0700 (PDT)
Local: Thurs, Sep 20 2012 2:05 pm
Subject: Re: Communicating Underwater

When you want to find out about the newest things in reasonably accessible
underwater stuff, go to the source :-)

http://www.navysbir.com/06_1/1.htm


 
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