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M.G.BREEZE B.ENG.ELECT. wrote: > > My name is Mick Breeze. I am a final year degree student currently > researching underwater radio communications. I would be interested > to hear from anyone who is knowlegdeable on the subject with a view > to future correspondence. At the moment I'm just looking at the > viability of a radio system and how this may be better than an > ultrasonic system. I reckon that if I am designing a system for > sport divers then a working depth of 50m should be enough, but what > would a reasonable range be, that is diver to diver range and diver > to boat range. If anyone thiinks they can be of any help, please > mail me. > > Cheers, Mick Breeze > -- Mick, I'm very interested in knowing how far along your research might be. I work in wireless - cellular networks, wireless data, that sort of thing. I got my training in wireless as a submarine radio technician in the US Navy. I remember the subs were all fitted with bouyant long wire or bouy type antennas that would allow them to receive broadcast traffic. (floating wire antennas was technology developed by the german U-boat Navy and I believe *borrowed* by the brits or US later on) I'm not sure who takes the credit for developing the bouy type antennas - basically a sealed, bouyant shell housing VLF/LF loops and phasing circuitry streamed on a long cable from a submarine at depth. I recall that the lower limit for the VLF/LF devices to achieve reliable reception was something like 40' to 60' (13m to 18m) - RF just doesn't propagate through water very well. Those frequencies that _do_ propagate through a medium as dense as water - particularly at typical tech dive depths, are so low as to require impractically large antennas...by way of example, the ELF broadcast used by the submarine Navy (a very long range, reliable, but terribly slow (in terms of rate of data you are able to transmit - frequency of the carrier is inversely proportional to the rate of data you are able to modulate onto it) uses earth itself as its antenna - very long wavelength. So. You are working on this technology. I'm not naysaying it - I'm just very interested in feasability and work-arounds. Some questions I have: What RF band<s> are you considering? Polarization of transceiver antennas - isn't scatter a bitch? As to an RF system being _better_ than an ultrasonci system, consider that RF propagates (at most frequencies) very poorly, while sound energy propagates extremely well. It appears to me that ultrasonic has the advantage here, hands down. OTOH, if you are able to develop some- thing useful, for very short range comms, a tactical network for example security would very probably be a benefit - signal attenuation at all but the shortest distances would be so great that the likelihood of eavesdropping would be very low. I wish you luck and great success in your studies. Please keep me posted on your progress. Best regards, Drew Mooney Wanna Bubba Wanna Stroke -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send list subscription requests to `techdiver-request@aquanaut.com'.
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