Re: [NYCR:Microcontrollers] Communicating Underwater

[Dirk Swart]

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....@gmail.com> wrote:

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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[c f]

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/Underwater_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.

[Matthew Kanwisher]

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]

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#Visible_radiation_.28VIS.29

Some hints on data over modulated light:

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

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


Also, really bright blue LEDs:

http://www.mouser.com/ProductDetail/Lumex/SML-LXL8047USBCTR3/?qs=%2fha2pyFadugxIZbYLo8qm2x6WqhaBGMQOiQ706%2fB%2fR0%3d

On 9/15/12 6:14 PM, Matthew Kanwisher wrote:
> 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
>
> On Saturday, September 15, 2012 5:29:33 PM UTC-4, chris fenton wrote:
>
> 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

> <http://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
> <matthew....@gmail.com <javascript:>> wrote:
>
> 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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