DIY Texting System For Really Underground Radio 98
Gulthek writes "Sixteen-year-old Alexander Kendrick has created a device that allows texting and other data transfer from almost 1000 feet underground. The tech could allow rapid emergency communication with the surface and opens the potential for scientific measurements without the need to continually visit (and disturb) the cave environment." There's some kvetching in the NPR story's comments that it's not the first use of cave radios, but that seems to miss the point.
Underground radio in the 60's (Score:5, Interesting)
I recall reading a story a few years ago about some protesters at Berkely using audio amplifiers to transmit information between their various members and groups. They'd attach the ground lead of the audio output of a 200 watt audio amp to a 10-15' rod pounded into the ground. The positive lead was attached to another, shorter rod, pounded into the ground several feet away. To recieve, they'd switch the wires from the ouput to the input of the audio amp. The claim was that they could send voice as an electrical wave several miles. Don't know how true the story is, but it sounds like it might work.
In central Nebraska, not far from Silver Creek, is a "Survivable Low Frequency Communications System" The wiki writes about it: http://en.wikipedia.org/wiki/Survivable_Low_Frequency_Communications_System/>
"SLFCS single channel, receive only capability is provided at ICBM launch control centers. The single channel operates between 14 kHz and 60 kHz to receive commands from remotely located Combat Operations Center - Transmit/Receive (T/R) sites; this low frequency range is slightly affected by nuclear blasts.". The signal travels along and underneath the ground, i.e., Ground Wave propagation. Because the frequency was close the the 60 Hz power line frequency the two 1 KHz side tones were used to track power line faults.
When I drove by the Sliver Creek antenna and tuned my radio below 550 Khz I could find a hetrodyne signal and listen to the characters being transmitted in 5X5 blocks of characters.
I've sat half way down Aquamole Aven (Score:5, Interesting)
for half an hour with a transmitter waiting for my friends on the surface to radio-locate the position on the surface vertically above me.
The transmitter fits in a 6 inch diameter tube - you'd never get an antenna like the one in the photo down a Yorkshire cave. The one used on the surface is much bigger, though.
The next project is to produce a cheap transmitter that a cave diver can carry into an aven and leave (they don't want to have to hang around), in the hope that once located a dig can be done from the surface directly above.
Here's a links to a UK cave radio web site
http://caves.org.uk/radio/ [caves.org.uk]
Re:This doesn't just apply to caving I expect. (Score:3, Interesting)
The Navy shore VLF/LF transmitter facilities transmit a 50 baud submarine command and control broadcast which is the backbone of the submarine broadcast system.
More at http://www.fas.org/man/dod-101/navy/docs/scmp/part07.htm [fas.org]
Re:This doesn't just apply to caving I expect. (Score:3, Interesting)
Re:This doesn't just apply to caving I expect. (Score:3, Interesting)
This may come as a shock, but some regulations are actually based on chemical reality. In this case, the purpose of "IS" designs of sensors, communication systems, etc, is to restrict the amount of energy in a hazardous area to below the amount that can produce a spark in an explosive hydrogen-air mixture. (I can't remember if it's at LEL or UEL, but WTF - it's still around 20 micro-Joules if I recall correctly). Systems that are designed an installed to IS regulations can be run much more simply than other systems, which we typically called "power" systems. The differences are non-trivial - you need to use single or doubly-armoured cables, solid-walled conduit etc etc. They're a lot more bloody complex to install.
Why would this affect an emergency response system? I hear you ask? Because it is not a good idea to deal with a roof-collapse by turning it into a roof-collapse plus a gas explosion.
You're not the first person to get into confusion about this. The last time I was paying attention, the UK emergency services were being pressurised to use a single, common radio system. A fine and laudable idea, but the fire brigade pointed out that the systems being proposed were not designed to be non-sparking. Un-surprisingly, firefighters did not relish the idea of going into (for example) a gas leak investigation with a radio set that might produce a spark.