Due to the short distance in water (less than 3km) and the availability of required power density, wouldn't a full duplex ultrasonic comm link be more effective/durable/predictable? I wouldn't cont on LF radio, or even ELF in that circumstance. Too many variables.
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The reason the HeyPhone was used is that we spend many hours doing practice rescue scenarios in the British cave rescue groups using this equipment. The radios are tried and tested in many cave environments. We know they work and don't fail in the muddy wet conditions.
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Wait i thought they used some radios by an Israeli firm. Let me see if i can find the video...
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Okay i have other reputed and independent resources which can confirm that heyphones were used extensively.
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This old cave-rescue radio is really cool. It's a niche application that would not be well served otherwise. We could update the tech, but that might not make it more usable. Well done heyphone.
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Jeez you could darn near use a LM555 as a Local osc at that low of a freq . toss in a LM602 mixer and volla .
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It's not high date rate, and doesn't need to be. When I last looked at CREG they had moved on from 555s, but the band's were comparable. The electronics went over my head in the 1980s.
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I've heard briefly about this a long time ago! Thanks for the heads up, gonna do some reading
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We did a 8.97khz experiment using ground rods and a 1000w audio amplifier! Things get very interesting when you drop into Lower LF and VLF. Not to mention the ELF submarine communications at 70-90Hz range! Of course SSB is not possible!
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@ppapadeas since you are an open hardware/ham radio/diver I think that would be nice to check out with our cave dwelling friend@Konstantina_P
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I came across this and just read it to a local net. Hams agree--very cool!
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My dad and his brother used to do this for fun ages ago. Maybe the 50’s.
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Are you a ham?
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This is awesome!
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There is a counter-part to this. I don't know for certain, but I suspect that a major factor in the cas-evac was that the Navy divers had diver-diver comms. That is rare, very non-standard kit.
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