Underground Radio Broadcasts New Possibilities

December 2007
By Henry S. Kenyon

Developed by the Los Alamos National Laboratory and marketed by Vital Alert Technologies Incorporated, the Through-The-Earth communications system allows miners, first responders and other personnel to transmit voice and data through hundreds of feet of rock, concrete, metal and debris.
System peers through the earth to allow rescuers to contact personnel in deep mines, buildings and subways

First responders have historically had great difficulty communicating with each other and with survivors during operations in mines and very large buildings. A radio technology developed by a U.S. government research laboratory allows rescuers to exchange voice or text messages through hundreds of feet of rock, concrete or debris. Commercial products based on the radio system are preparing to enter the market.

The underground radio (UGR) system originated to meet the needs of the U.S. mining industry, explains David Reagor, project leader for the underground communications project at the Los Alamos National Laboratory, New Mexico. He notes that major mine accidents such as the recent Sago Mine disaster in West Virginia and terrorist incidents such as the London subway bombings all illustrate the need for reliable underground communications.

A common feature of these events is the inability of rescuers to coordinate operations properly because of limited communications and an inability to alert workers or other personnel during the event itself. In mine accidents, many workers often do not receive an alert in time to evacuate. In very large mines, personnel are often unable to observe problems early enough to take corrective action. “The same drivers were present 10, 20 and 30 years ago. These accidents are greatly magnified by lack of communication,” Reagor maintains.

Reagor began developing UGR technology in 1996. He shares that in the early days, he worked with a very small budget until the U.S. Energy Department began providing funding in the late 1990s. The technology is built around the small, powerful processors used in cell phones. Modern handheld communications devices use digital signal processors to convert voice communications into bits. “We are using similar technologies developed in the cell phone world—concepts such as digital audio, data compression and radio-on-a-chip,” he says.

These radios on chips are included in small handheld UGR devices. Reagor adds that the opportunity to develop these systems emerged from the revolution in digital processors in the 1980s and 1990s. “We just came in on the end of that [revolution] and applied the results to a product,” he says.

A major difficulty in sending radio signals through earth and rock is that very low frequencies are required. Reagor explains that a typical AM radio station produces signals at one megahertz, or 1 million cycles per second. But the frequencies necessary to pass through dirt and rock must travel at least 30 kilohertz, or 30,000 cycles per second, or less.

The Through-The-Earth Communication system sends very low frequency (VLF) voice signals from the surface to depths of more than 300 feet vertically and through 550 horizontal feet of soil and rock. The radio transmits the signals in the 3- to 30-kilohertz range and uses digital audio compression technology to send wireless voice and data messages.

The VLF system developed by Los Alamos communicates from a surface location to underground receivers. Reagor notes that parts of this capability, such as a basic text messaging system, have been available for several years. The most recent addition is the ability to network the radio to a number of small personal communications devices.

Reagor says that a typical 900-megahertz radio will send its signals down a tunnel very efficiently, but these high frequency transmissions will not travel through the earth. This is where the Through-The-Earth radio works to connect the surface to the underground world.

Digital compression techniques allowed Los Alamos researchers to transmit enough data for audio communications, Reagor says. UGR technology with digital compression was recently tested in an underground facility in Pennsylvania. The system used a surface-based antenna 12 meters in diameter to transmit messages between above-ground personnel using Sprint i325 radios and similarly equipped individuals deep in the mine. He notes that in its current configuration, the UGR system’s transmitter is relatively large, but the workers themselves carry small handheld units.

The tests demonstrated that radio communications can pass down tunnels and through rock and soil with cell phone type equipment. The UGR equipment transmitted signals from the tunnel, through the surrounding rock to the surface. Reagor explains that once the signal reaches the surface, it can be converted into any other type of radio coverage. The UGR radios also can be deployed in an emergency.

The handsets and radio system are being marketed through a Los Alamos-based commercial firm called Vital Alert Technologies Incorporated. Reagor explains that Los Alamos does not have the resources or the legal clearance to create products. After government laboratories such as Los Alamos conduct their research and acquire patents for their inventions, the patents are licensed to private firms. Los Alamos also provides assistance to Vital Alert to help improve the technology or to help develop the product.

Vital Alert is developing and preparing to market several systems based on the Through-The-Earth technology, the Canary 1 and 2 Mine Messenger systems and an emergency broadcast network capability for urban areas. The Canary 2 Mine Messenger System is designed as a pre- and post-emergency warning, evacuation and rescue system for miners that transmits and receives text and two-way digital voice communications. According to Joe Miller, Vital Alert’s president and chief executive officer, the device’s VLF signal cannot be blocked by high density ore, concrete metal, rock, earth, debris or dust.

Miller notes that he had developed an underground emergency notification system for miners in the 1980s, prior to working with Los Alamos. The original Canary 1 pager system was developed as part of a project with the U.S. Bureau of Mines in the late 1980s and early 1990s. He explains that it was successfully tested in a working mine. However, before the technology could be used widely, the Bureau of Mines was closed in 1996, which ended the beta site testing. “It was bad timing for us,” Miller says.

The Canary 1 is a basic pager version of the technology that sends miners text message alerts. The Through-The-Earth pager sends emergency evacuation and operational work-related messages that are displayed on the device’s 32-character liquid crystal display. The entire system consists of one or more transmitters, a wire loop antenna and a computer with proprietary operating software. Miners are alerted to incoming messages via a loud buzzer in the integrated receiver/battery unit and by flashing cap lamps powered by the unit.

The more sophisticated Canary 2 system uses the Los Alamos unmodulated VLF radio technology for voice and data transmissions. Miller says that the system interoperates with most radio handsets and that it vertically integrates with and leverages the capabilities of existing communications systems. The system’s transmitter boxes also can serve as radio frequency links.

Vital Alert is developing an emergency broadcast network capability for use in urban applications such as subway systems, skyscrapers, airports, refineries, power plants, tunnels and large commercial and industrial structures as well as for use by marine and port security.

An emergency broadcasting capability would be especially useful to support operations in large underground mass transit systems, Reagor says. During the terrorist attacks in the London subway, he notes that first responders faced difficulties communicating because the built-in underground radio system was damaged or overwhelmed. “They couldn’t communicate with rescuers very well because of limitations to the current technology,” he says.

But the UGR technology also is useful for coordinating rescue operations in large structures such as the WorldTradeCenter. Reagor cites reports noting that radio signals do not travel very well in large buildings. Skyscrapers and other very large buildings have internal antennas or cables to allow signals to travel inside. But if the antenna or cable is broken, as happened in the WorldTradeCenter, rescuers have no communications. He adds that many firefighters died in the event because they did not get the evacuation notice in time. “These are very serious issues for people outside of the mining industry,” he says.

Web Resources
Los Alamos National Laboratory: www.lanl.gov
U.S. Energy Department: www.energy.gov