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Simple underwater wireless communication

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cowboybob

Well-Known Member
Most Helpful Member
Simplest, cheapest and easiest to implement method (and I'm not kidding, although there will be a learning curve):

Both divers with water proof "squealer/buzzers". Use Morse code (or a code of your own making).
 

Externet

Well-Known Member
:happy: Reminds me of the wireless batteryless attention-getters I used for diving :

----> **broken link removed**

Several for $1, disposed when rusted.:rolleyes: No full face mask, no electronics, no waterproofing, no piezoelectrics, no testing, no... ... ...
 

Sean the Nailer

New Member
Wouldn't "bone conducting speakers" fit perfectly here, especially considering the straps holding the mask on? They were by far the best speakers I used, when carrying a radio in 'industry'. Especially with earmuffs, hard-hats, and other PPE. Ina very noisy environment.
 

girishpatil1234

New Member
Yes, modulating the resonant frequency of that particular piezoelectric crystal is necessary.
A piezoelectric crystal has a very narrow range uncapable of emitting or receiving intelligible audio.
One of the ´You need...´ is a pool for testing, not a room.

Go head, keep building your receiver...

For unidirectional communicator, coarse transmitter 'block' diagram:
Voice mic--->preamp--->filtering--->modulator
Throat mic--->preamp--->vox--->oscillator--->power amp--->piezo element
Coarse receiver block diagram:
Piezo--->preamplifier--->filtering--->demodulator--->audio amp--->earphone*

*Forgot that one on the 'You need' list, also waterproof-depthproof.
Dear sir,
Thank you for your response.

Which modulation scheme will suit my requirement?
I will have to design modulation scheme with microcontroller and its associated circuitry and software code.

Thank you
 

Externet

Well-Known Member
If you can program a microcontroller to do modulation, then write several schemes, test them and pick the best.

----> **broken link removed**
 

Tony Stewart

Well-Known Member
Most Helpful Member
FM will improve SNR above the CNR only if the bandwidth of deviation exceeds the signal bandwidth by a large ratio. Since your intended carrier is 40kHz this offers only 2:1 improvement with side band stop margin, which is not much improvement and difficult for a piezo transducer to modulate.

A better utilization of Signal/noise ratio for given bands is VSB or single side band AM , but at the cost of more receiver filter complexity. This is a common method for audio transmissions in the (long wave) LW band for similar reasons. This also happens to be the method used by professional underwater comm. devices. It is also used in TV video for bandwidth and SNR improvement.
 
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