Re: Acoustic Modem For A Hobby AUV


Michael wrote:
Hi,

I'm building an AUV for hobby use, however I'm having trouble whe it comes
to communications. So far I've considered sending DTMF tones through 2, 2
way radios, and encoding sets of numbers on R/C equipment but neither will
travel/penetrate far enough (<3m).

It needs to be a duplex system capable of transmitting 32 on/off comands and
8 values (0-255) through about 100m of water.

So far I've found lots acoutic modems except they are more for industrial
use and so are rather high-spec compared to what I need.

So, can you guys suggest where to start (happy to learn any new skills I
have to) or if you can think of a better method I'm open to ideas,

I did an audio system that worked in excess of 4000 feet. You could
adapt it for data quite well.

Get a matched pair of 40Khz underwater transducers.

Send baseband async ascii in narrow band fm at 40Khz.

Decode with standard PLL fm detector at the reciever.

Turn off transmitter when done to allow communication in the reverse
direction.

Data blocks you send should have some kind of error detection
(checksum). Since you are running both directions, you can do
re-transmissions in case of error.

Luhan

.