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 (
You proberbly know that atomic subs use very low frequency less than 3 kHz asfair to send to a submarine. Maybe slightly higher frequencies would be ok in this case.
As for acoustic, maybe you could either try to use a modem + waterproofed speaker/mic. If that won't work you might have to implement your own algorithm.
And I guess I'd then have to apply some form of filter to get rid of echoes etc?
Michael
Either use the acoustic "media" as half duplex. Ie wait until sent waves have faded out. Or use the "usual" echo cancelation techniques.
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
and
I do not remember where i picked this one up but; if you use an carrier in the 25 to 35 kHz range and directly AM or FM the carrier and then use about
2 foot (600 mm) dipole antennas you get about 500 to 1000 yards (m) transmission ranges (at 10 W). IIRC there were some experiments done somewhere around Florida in the 1970's-- JosephKK Gegen dummheit kampfen die Gotter Selbst, vergebens. --Schiller
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