Underwater Wireless Alert Help

hi there..

there are two ways to develop your device for communication.. one can be using acoustics and the other one can be by light- optical communication!

There are sensor networks using optical wireless communication. They work on the concept called- LIDAR- light detection and ranging. refer to some IEEE papers on that topic.

Another field is acoustics i.e acoustic wireless networking. Sound waves can travel really good amount of distances compared to terrestrially used electro-magnetic waves , however,certain factors like limited bandwidth, specific protocols, refractive paths and multipaths taken by sound waves , low speed of these waves make the process difficult...

try designing your device that can actually minimize these losses...

hope this helped!

all the best.

Back in the day I worked on a system called ELF - extremely low frequency radio, broadcasting at about 50Hz. It's only ELF radio that can propagate under water for long distances. For relatively small distances the frequency can go up.

http://www.qsl.net/vk5br/UwaterComms.htm

Ocean Reef systems use ultrasonic sound.

http://www.oceanreefgroup.com/

Thank you both for your quick responses!

I will investigate both these avenues tomorrow and see where they lead. If you have any other thoughts or comments please leave more!

I think the range that I am aiming for is no more than 50m, so I am assuming that in terms of underwater networks that is relatively short? potentially meaning i can use some higher frequencies.

once again thanks, and keep em' comin :P

Joel

For that distance could you use modulated ultrasound?

Chas

Thanks,

That seems like a good idea. Do you think it would still be appropriate if I just want to send an activation signal rather than an audible sound message?

Joel

Modulated ultrasonics is used in modern submarines. It's called a Gertrude. It's basically an audio (voice) signal riding on an ultrasonic carrier wave using FM modulation. I think 50 meters is easily achieved if you use an ultrasonic transducer with enough power.

Joel, May be of some use, would appreciate a call as I have done some design and functionality for this device already.01268 442147 eves. 07957 817355 .

Will call you back if ness'.

Best Regards.

Lez T.

Edit landline phone number

01268 442140.

Lez

hi..

the modulation of ultrasound waves is done by modulating it with the ultrasound acoustic modulating frequency using the binary frequency shift keying. you will need a transmitter of course, from where you ll send the signals , these signals must be first encoded and then modulated. these modulated - encoded signal then travel and reach the receiver which must be equipped with decoder and a demodulating device.. the receiver could have a hydrophone and a pre-amplifier to raise the level of your received signal..

Thanks for your response,

As technical as it was I think I understand the principle. Are there many products that use this type of system already? I think knowing the size and potential cost of such a set up will certainly help me to start adapting the technology to my current concepts.

Joel

What if you Use Cell phones on an appropiate enclosure ?

Best regards ( faraon34@hotmail.com )