DIY Texting System For Really Underground Radio

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.

Comments

This doesn't just apply to caving I expect.

[Anonymous Coward]

This doesn't just apply to caving, it should work as well for mining no? Range shouldn't be an issue since if it uses radio then relays should be feasible.

Re:This doesn't just apply to caving I expect.

[Darkness404]

Even with low bandwidth, a simple message of "Hey, I'm still alive down here, send help" shouldn't be too hard.

Re:This doesn't just apply to caving I expect.

[electrostatic]

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

Re:This doesn't just apply to caving I expect.

[goldaryn]

Even with low bandwidth, a simple message of "Hey, I'm still alive down here, send help" shouldn't be too hard.

That's what she said.

Yes, my "bandwidth" is "low"

Re:This doesn't just apply to caving I expect.

[SaffronMiner]

No one has yet answered the Coal Mining Location Challenge: http://www.wearablesmartsensors.com/location_challenge.html The is a much harder problem to solve than most people think, as explained at the link. The first thought is always "Use GPS". GPS does not work underground... etc. Range is an issue because Coal absorbs most radio waves. There are also limitations are power due to Intrinsic Safety Regulations.

Re:This doesn't just apply to caving I expect.

[solafide]

There's this thing called marcasite. It is often found with coal deposits, and is extremely flammable at temperature/pressure similar to that at the Earth's surface. Guess what a radio wave potentially exciting marcasite because it's overpowered will do --- it'll set the marcasite on fire, and as a result the whole coal bed. It's _intrinsic_ to coal mining, it's like breaking the gravitational laws --- you shouldn't try it.

Re:This doesn't just apply to caving I expect.

[ndege]

I am giving up the mod points from this thread by posting, but thought you might be interested in something else:

Forget both CW and RTTY. Use PSK31. It uses less RF frequency bandwidth than CW and is a quite common modulation on HF (low frequencies such as 1.838.15 MHz/160meters) right now.

There is also a version that includes error correction: QPSK

Here is a comparison between RTTY and PSK31: http://www.arrl.org/tis/info/HTML/psk31/index.html

PSK31 uses 16 times less transmit power than a CW station.

The difference between a CW filter of 500 Hz and the bandwidth of PSK31 of 31 Hz (10*log(500/31) db = 12 db) is 12 db, which demonstrates that a CW transmitter must transmit 16 times more power than a PSK31 transmitter to achieve the same signal to noise ratio. Therefore, a PSK31 station can operate at 16 times less power than a CW station.

Cite: http://www.larkfield.org/pdf/psk31.pdf

There is also a slower implementation that is less prone to interference; these versions operate at 10 and 5 baud (PSK10 and PSK05, respectively). Seems very slow, but for simple critical communications, there are fast enough.

Here is what PSK31 sounds like: http://en.wikipedia.org/wiki/File:PSK31_sample.ogg

Ran across PSK31 a few months ago and was fascinated by the ingenious insight put forth in the specification.

Just thought you might want to know...

Re:This doesn't just apply to caving I expect.

[RockDoctor]

OK, then the reason for low power is that it's dangerous, not because there is a regulation.

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.

Ultra narrow bandwidth

[stox]

Reduce your bit rate to a few bits per second, even fractional bits per second, and you will be amazed at how far you can get a signal with a minimum of power.

Re:Ultra narrow bandwidth

[pclminion]

By Jove you're right, we'll certainly have no problems aligning the transmitter and receiver through solid rock

The article's more interesting point is buried

[JoshuaZ]

The article also talks about how this could be used by scientists who are investigating or monitoring life in caves and that this could be used to help find useful substances being made by life in the caves. From the article:

But scientists think one of the biggest threats to this emerging source of antibiotics is actually the scientists themselves. In fact, researchers believe the more they visit a cave, the less likely they are to find antibiotics. People contaminate the sensitive cave environment just by being there. Northup thinks that by connecting data recorders to Kendrick's radio, scientists could remotely transmit information about the cave environment. "So a cave radio that allows you to beam data to the surface rather than visiting it in person can be extremely valuable," she says. "It could save the cave."

Frankly, this doesn't seem that likely since to check if something is a useful antibiotic it needs to be tested against actual cultures generally. However, this does have serious potential of helping and of increasing our knowledge base. General medical knowledge and more anti-biotics will likely save far more lives than using the technology just to rescue people who occasionally get trapped in caves.

Underground radio in the 60's

[Jerry]

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.

Finally

[Junior J. Junior III]

No more out of range problems while I'm in my mom's basement.

Cave Rescue

[HarleyCanuck]

"In a 1991 New Mexico cave rescue, it took 170 people four days to save a woman with a broken leg. The rescue team had to lay miles of telephone line in order to stay in touch with the surface." "If they'd had Kendrick's radio, the rescue time may have been cut in half." When we go caving, especially a new one, or a rescue, Who wastes time laying phone wire? Teams are two, each with a different colour string with a wire core for added strength. This way we can follow different pipes simultaneously if its a complex cave. If two can get them out we do. Otherwise one stays one goes back. With all the gear we have who wants to be carrying all this stuff. If it can be made smaller the better. I guess my point is more about the Mexico rescue thing. Cool Idea kid!

Re:Cave Rescue

[Anonymous Coward]

I do cave rescue, so I have some insights.

The first problem is that unless encrypted, radio communications are not secure. We don't necessarily want the press snooping in on radio chatter, which might include things like if the patient has died- then it shows up on the TV news before the family finds out in a less public fashion. That's not very popular with rescuers.

The second problem is that communications aren't always 100% in this fashion; based on the cave radio work that I've been part of, it can be pretty sketchy. We're doing the same things as Alexander- and he's doing great work, no argument- but it's not exactly new stuff. Hard-wire communications aren't always 100%, either, but they tend to be more reliable. Maybe radio will exceed that someday.

The Emily Mobely rescue would probably have taken about 100 hours with radio, same as it did with hard-wire communications. She was in a bad spot when she broke her leg, and Lech is a technically challenging cave- long hauls without a lot of space to work, that kind of thing. Because of Emily, people who have been injured in Lech have "self-rescued." Only a severe, debilitating accident that immobilized a patient would be cause for such a large, intensive rescue as hers.

What am I missing here?

[westlake]

Developed by Los Alamos National Laboratory, the Through-The-Earth Communication system proved capable of sending two-way, very-low-frequency (VLF) voice signals from the surface of the mine to depths exceeding 300 feet at the experimental mine operated by the National Institute for Occupational Safety and Health (NIOSH).

The Through-The-Earth Communication system was developed for the U.S. Department of Energy at Los Alamos National Laboratory's Superconductivity Technology Center with a development team led by David Reagor. The technology has also earned a prestigious R&D 100 Award from R&D magazine.

The system uses VLF electromagnetic radiation in the range of 3 to 30 kilohertz (kHz) and digital audio compression to transmit wireless voice and data signals through the earth. Materials that block higher radio frequency (RF) signals, such as rock, concrete, metal, and high-density ore bodies, do not restrict its signal

Incorporating Sprint/Nextel i325 mobile phones, supported by Raytheon's JPS Communications ACU 1000 cross-band repeaters, the Through-The-Earth Communication system demonstrated its capabilities in the Lake Lynn Mine, which is composed of several long tunnels used for mine safety experiments. The mine consists of nonflammable limestone with a tunnel height of about 10 feet and an overburden of up to 370 feet. Test Of Through-The-Earth Communication System Exceeds Expectations [August 2007]

VLF appeals to radio hobbyists because of its exotic associations with both natural science and submarine warfare. To get started all you really need is a PC and a home-made antenna. Radio Waves Below 22 Hz

I've sat half way down Aquamole Aven

[alanw]

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/

Then what is the point?

[SuperBanana]

Well, what is the point, then?

VLF systems have been in use for decades to communicate with the US Submarine fleet, not because of interference, but because it passes through just about everything and has a very, very wide propagation. Unfortunately, the power levels are so high that people wonder/suspect it's causing nature / health problems for nearby residents.

I mean for fucks' sakes, this stuff was in use by the German navy during WW2- 70 years ago. All this kid did was apply the obvious, and apparently, it's so obvious, someone thought of it 40 years ago. More info:

http://en.wikipedia.org/wiki/Very_low_frequency

Also, the kid didn't implement any sort of retransmission or error correction. That makes it pretty useless for both emergencies (imagine: "person has 3 hours to live" instead of "30 hours") and scientific data collection. It's also pretty standard these days.

Perspective of an actual caver-geek

[Like2Byte]

First. I applaud this guy for making such a neat device. Listening to the story break on NPR this morning was rather captivating. The reporter made the device sound relatively small - something able to fit easily within a single cave-bag after disassembly. After seeing the antenna array, though, I thought my eyes would pop out of my head. There is no *way* a group of cavers are going to carry this contraption around *as it is*. It is certainly a prototype and the device certainly has merit but, for the sake of the device and the caver(s) carrying it, it is hoped (at least by me) that it becomes a lot smaller and still able to transmit/receive with the surface counterpart.

You see, a device as large as the one in the pictures on the webpage would be unwieldy in many, if not most, caves in the US as most US caves are not walking passage. In its current form it would suffer a lot of abuse and probably become submerged in water, covered in cave mud, bumped, sat on, kinked, bent, folded, dropped, hoisted, scraped and buffeted from a normal days wear and tear. If the antenna wire itself became broken trouble would certainly ensue. So, I don't see the current form of cave rescue going away any time soon. (The cave-trip leader has a designated person that did NOT go on the cave trip to call by a certain time. If the trip leader has not called that person by that time a cave rescue is supposed to be carried out.)

Don't get me wrong - this is a very cave-worthy pursuit and many a caver would feel better about having this technology along for the trip - as long as the equipment could withstand the journey. Otherwise, it's just more dead weight.

Second. For the story itself - caving is not 'relatively safe.' It's more along the lines of relatively dangerous. Why? Anyone entering a cave with the attitude of 'relatively safe' is bound to get hurt. Very recently there have been people who went out for a day of caving and came back sans one member. See this story

I didn't know this guy but it seems arrogance killed him. Hate me for it if you have to but he went into a passage where 2 other people had to be rescued from years earlier. It's shameful that the cave owners/grotto overseeing the cave didn't have the foresight or fortitude to prevent future tragedies by closing that passage or making the cavers sign a form detailing that particular passage as off-limits. He died a slow death as hypothermia set in while he was upside down in a passage. He was supposed to be experienced. I heard about his story while he was still alive and I prayed that he could hold on long enough for a solution to extricate him could be found. I'm heartbroken and angry for his needless death.

Thirdly. One part of the radio broadcast that this story didn't relay is a story of the famous (or is it infamous) rescue of Emily Davis Mobley from Lechuguilla Cave very near Carlsbad, New Mexico. I think the broadcast mentioned that this (the Lechuguilla cave rescue) was the reason why he invented this device. (I remind you to see the above paragraph on caving being relatively safe. Still think so?)

You Tube of the rescue: http://www.youtube.com/watch?v=J7I7bXcSWK8
Wikipedia Entry: http://en.wikipedia.org/wiki/Cave_rescue

Fourth. If you want to know more about caving visit Emily's website: http://www.speleobooks.com/

Finally: If you still don't believe me that caving is dangerous just you try cave diving. Near 100% fatality rate where 'accidents' have occurred. The rule of thumb is is something goes wrong while cave diving - you have two minutes to live.

Here's the official website for caving accidents in the Americas - http://www.caves.org/pub/aca/

FYI, There's NO FN WAY you'd get me to cave dive.

The Boy Mechanic

[westlake]

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.

Of course it will work.

Morse used earth conduction to bridge the Susquehanna River in 1842-3. CALLING ALL NATIONS -- 1941

Kids were taking on projects like this in 1913. How To Make A Wireless Telephone

Very Low Frequency (VLF) Stations [2010]
  Ham Radio below 9 kHz [2006?]

Just run a damn cable ...

[BitZtream]

Seriously.

If you're leaving a sensor in a cave or mine to gather data, its going to be there a while. Take a spool of wire with you on the way in and just hard wire the thing for data and power.

Wireless is rarely the right way to do things, especially stationary things.

Re:Living with Mom

[jimbolauski]

Why risk your pasty white skin getting outdoors to text?

What nerd doesn't have wifi and a wifi enabled phone.