I was under the impression that the Buddy Phone type systems used sound waves in water as the transmission medium. I spent some time looking at the Ocean Technology product pages, and they describe things like 'transducers' rather than 'antennas'. They look like ultrasonic hydrophones, not antennas. Still pretty nifty technology...and I don't think the FCC regulates acoustic pressure wave bands, even if they regulate the same electromagnetic wave frequencies ..... 73 Jon AF7TS
The common underwater diver comm units are ultrasound. They use acoustic wave at around 20 kHz~40 kHz SSB (common freq 32.768 kHz Upper SideBand). Power levels are about 1/2 watt or so for the diver mask and about 5 watts for the surface unit. They have an effective range of less than 1500 feet (sometimes much less). The ultrasonic dive comm unit is not electromagnetic radio communications. It uses piezoelectric transducers (a metal-plated ceramic crystal slug) to convert ultrasonic acoustic waves to electronic signals and vice-versa. The dive comm unit is an "ssb radio transceiver", but in place of the antennas, are the piezo transducers instead. You could call it a hydrophone system, but usually hydrophones are commonly acoustic baseband, like a waterproof speaker and microphone with normal audio. Some types of hydrophones can cover the infrasound and ultrasound range, and are usually set up with baseband audio gear. The main reason acoustic waves are utilized for diving is because low power HF/VHF/UHF radio has a very limited distance in salt water. Effective antennas for ELF/LF/MF underwater are too bulky for divers, and the transmit antennas are so inefficient that they would require too much transmit power. Perhaps the use of piezoelectric-transducer-coupled-magnets could make a better magnetic field antenna for this AMEBA purpose.
It's QUITE Newsworthy. Thanks for posting it. I have experimented with reception along some of these lines. You can find those experiments if you search my callsign, W8LV on eham.net. I appreciate hearing from anyone who is also working on the lower frequencies. 73 and All the Best! DE Bill W8LV
