One of the sessions for the Utah Coal Mine Safety Conference held recently concerned new technology for underground communication with the surface. Marshall Radio Telemetry is a company based in Salt Lake City. They are dedicated to the design and production of premium telemetry equipment for tracking and communication.
Kevin Harcourt spoke to the audience at the conference. He said their radio tracking system was used to locate a hunting dog wearing a radio tracking collar that went into a cave and never came out. Using a hand held telemetry receiver, the dog's owner was able to exactly pin point the dog's location from above ground. After three days of digging and the help of a drilling rig, rescuers punched through the rock and rescued the dog. Their tracking systems have also been used to keep track of wandering boy scouts on wilderness camps. Recently a research team from Marshall has been in Carbon, Emery and Sevier counties testing their equipment. They have visited Consol, Dugout, Westridge, Bear Canyon and Skyline mines. In the aftermath of the Crandall Canyon mine disaster, MSHA has mandated mining companies to install equipment for tracking and communicating through the Earth with coal miners. The problem has been the technology hasn't been there to do what MSHA has requested.
David Marshall said they had a great time visiting the coal mines in the area. He couldn't believe the darkness of the mines and he commented, "You must feel like you are leaving all communication behind when you enter the coal mine. With our technology, we hope to bring that communication back. He said it is a myth that radio waves will not travel through rock. They travel shorter distances underground than they would through the air, but they always can penetrate some distance. Marshall said they have met with success in their testing and have achieved two-way voice communications through thousands of feet of rock in Utah mines. "This is a breakthrough. We have spent 10 years working on equipment small in size but powerful enough to send radio waves long distances," Marshall said. "Our very small (10 grams) radio transmitters are capable of sending a signal 360 miles and yet are able to transmit a signal for up to two weeks. But, it's not an ordinary radio system. Marshall mentioned that above ground the system has been used with tracking falcons. NASA has even called Marshall Radio Telemetry to ask if their system could be used to track equipment on the moon or Mars. Currently the military is buying their tracking devices to track their unmanned aerial vehicles. Marshall Radio has its tracking equipment currently in use worldwide, including Afghanistan and Iraq. Marshall said he has been interested in radio communication since he was a child. He became a HAM radio operator at age 14. He said radio waves can go through almost anything, but metal and salt water. "With a lower frequency it's easier to go through solid material. We go down in frequency until the radio signal gets through. There were experiments in 1922 and they said it's not possible for signal to pass through solid rock. I have done extensive research on their findings and other reports. While searching the internet I found more than 300 papers written on the subject which I have reviewed. Currently there are more than 80 companies interested in this technology and working on it," said Marshall.
Marshall explained frequencies and said a normal radio communications frequency would be a million or more vibrations per second. A cell phone operates between 800-1,900 million vibrations per second. In the mining world, the vibrations need to be reduced from millions to thousands of vibrations per second or less, which is really slow, but in this manner the sound of a human voice can be transmitted down into the earth, as well as from inside the earth to the surface. "As a result of these tests we've conducted, we know we can go down to the depths required by coal mines," said Marshall.
Marshall said the human ear will be able to pick up these sounds. He said there is no limit on how low in frequency you can go and how far you can penetrate the earth with these kinds of radio waves. He said there are several problems with such low frequencies. One is that there is a lot of noise underground, it is difficult to get the signal through with all the interference. Nature itself is noisy and there are atmospheric disturbances when broadcasting on such a low frequency. At low frequencies, disturbances from lightning discharges even become a problem. "You can hear lightning strikes from thousands of miles away," said Marshall. "There are some difficult challenges as you go to lower and lower frequencies. The challenge is to be able to put information on the radio signal. To transmit a human voice you need a band width between 400-3,000 cycles per second. The voice is still understandable at 2,000 cycles per second. Any lower than that and the words become indistinguishable. So the question is how do you convey a voice on a signal that is lower in frequency than the voices own frequency? You can take a single radio wave and put in a certain amount of modulation and you can convey information. Like, Morse code, there is a limit to how much information you can pack into one signal. You can try to communicate non-vocal information. Like, having a coded signal that means 'I'm alive.' But, As you go deeper and decrease the cycles per second, then the ability to send many such coded messages or text or voice information continues to go down. And, the abilitiy to decipher the information also diminishes," said Marshall.
Marshall explained an existing magnetic wave system that goes through the earth, but the information is so slow and it takes minutes to transport a simple message. These are the problems that the industry has faced. "But, to the extent that you can separate the signal from all the noise you can pick up signals further underground. "We use powerful microchips with a special kind of new signal processing software to achieve this goal. To separate the noise from the signal underground, and then reconstruct the voice, requires billions of calculations per second. This is what enables our technology to transmit fast information including voice or digital signals and still be able to dig them out of the horrendous noise deep within the earth," said Marshall.
"Life is without price. We got into the business to see if there was anything we could do to help. We have tested our product in caves and we went into the silver mine tunnels in Park City. "At the first coal mine test at Consol mine near Emery, we had two way communication from the surface to the coal seam at a depth of 400 feet. In the Dugout mine we had communication to a depth of 5,800 feet from outside the mine into the mine along the coal seam. Transportation of signal has to do with the nature of the materials also, the dryer the material the easier it is to transmit the signal. We tested at West Ridge, Skyline and Bear Canyon. In one of our experiments, at the Bear Canyon Mine, at a depth of 1,400 feet we picked up a signal, from the surface to the coal seam. The radio signal was strong and at that depth we could have sent a voice. "We have been researching and now we are ready to move to the next step. Our belief is that we can build a practical two-way communication system today which will work at depths not more than 2,000 feet. It already does work. We would set up base stations in the mine. A small amount of equipment would be contained within a box. We plan later to have a mobile system that can be moved as workers move within the mine or with mine vehicles. A hand-held system, similar to a walkie-talkie is also being considered," said Marshall.
Marshall questioned the mine companies present and asked if they developed such a system would the companies be interested in it.
The question was asked as to where the underground equipment has to be in relation to the equipment above ground. Marshall said for a depth of 1,000 feet then the radio on the surface area would need to be in the 5,000 foot range. Marshall said some companies have asked if the system could be used for day to day communication. Marshall said it is less practical as a day to day system. For day to day use, they believe they can create a horizontal system, that would transmit along a coal seam for miles as well as vertically. When transmitting horizontally, the radio signals go straight through the coal pillars and solid rock and coal rather than going through the air down tunnel as some other short range systems do. The question was asked about tracking devices for miners. Marshall said with a tracking device worn by a miner they can get a pretty good idea of where the miner is in the mine, but it won't give a pinpoint location. But it is possible to tie in with other systems already on the market today which read computer chips as a miner walks by a certain location and you can tell when a miner has passed into a certain area of the mine. Such information can be relayed to the surface with the Marshall system.
Currently none of the technology available for mines is truly through the earth (wireless). MSHA has mandated wireless systems for the mines, but these products aren't on the market yet, or if they are they do not provide two way voice communication after an emergency as required by the requlations. Marshall was asked about the cost of their system. He said the cost hasn't been determined yet, but he expects it will be cheaper than some of the systems out there today. Marshall said he doesn't know yet, when their product will be available, but expect a system for use in coal mines to be ready within the next two years.
The mining companies said they are very interested in the product. Their problem is they are being mandated to have this equipment in their mines, but this two way communication isn't available yet. When new regulations came out on June 15 the mines were instructed to have this type of equipment. If the new system could be developed within a year, the mines could put it to use if not they are being required to have something in place. One mining official said, "MSHA is putting the heat on mines to get a system."
It was mentioned that Congressman Matheson helped pass legislation to require better communications at mines. It was wondered whether he could be contacted to slow this down, until the wireless equipment is available. MSHA is being instructed by Congress to move ahead with communication systems for mines. Garth Nielsen, is the director of the Office of Coal Mine Safety and he closed the conference by asking miners and companies to use the technology as it becomes available. "Use your minds and try to come up with new things to help keep our miners safer," said Nielsen.