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Mining Contract: Through-the-Earth Communication Antenna Feasibility Demonstration
Keywords: Antennas Through-the-earth communications systems
This page is archived for historical purposes and is no longer being maintained or updated.
Contract #
200-2014-58688Start Date
9/1/2014End Date
8/31/2015Research Concept
New antenna configurations are needed to improve performance and utility of through-the-earth (TTE) communications systems once deployed in underground coal mines. One concept is a small form factor antenna housed in an explosion-proof enclosure. Such an antenna would allow the underground transmission power to exceed the intrinsic safety limits of an open loop antenna. This new design is anticipated to maintain or improve the performance of an existing communication system while affording portability and increased potential to survive an emergency event.Topic Area
Emergency Communications and Tracking
Contract Status & Impact
This contract is complete. To receive a copy of the final report, send a request to mining@cdc.gov.
The most capable magnetic TTE fully wireless two-way voice and data radio systems offer communication ranges in excess of 1,000 feet. These systems employ large loop antennas to provide the necessary magnetic field strength (moment) while limiting energy at the coil terminals to intrinsically safe levels so that the communication systems may continue to operate even if contaminants in the mine atmosphere approach or exceed explosive levels. The strength of the magnetic moment is a function of area enclosed by a length of wire and the current that flows through it. Unfortunately, the resulting loop antenna length (on the order of hundreds of feet) makes these antennas cumbersome to deploy and vulnerable to damage under both routine and emergency underground conditions.
Raytheon UTD was contracted to leverage prior research and existing technology to conduct a feasibility demonstration of a compact Very Low Frequency (VLF) transmitting antenna. The goal of this research project was to design and build a novel, compact VLF magnetic antenna deployed in a volume of less than 5 ft3 (approximately a cube 20 inches on a side) to support communications through overburden to ranges in excess of 1,000 feet. The design was based on the Hitachi FINEMET® nanocrystalline alloy toroidal cores. The unique combination of low loss and high saturation flux density of this material allows higher performance levels than previously possible with conventional ferromagnetic materials. Since the VLF signal has very low loss when penetrating a metal enclosure, it could be housed in an MSHA-approved explosion-proof enclosure. Therefore the power would not be limited to the intrinsically safe levels of conventional systems.
Testing was conducted with an 80-core antenna in open air and inside a simulated explosion-proof enclosure at an underground mine. The enclosure was built out of mild steel plates of 0.25” thickness and approximately 18” X 16” X 2”. The testing showed that an enclosure greater than 30 ft3 (20” X 20” X 10’) may be required to achieve a TTE communication range of 1,000.
See Also
Adaptive-Noise-Cancellation Techniques for Through-the-Earth Electromagnetics: Volume III
Apparent Earth Conductivity Over Coal Mines as Estimated from Through-the-Earth Electromagnetic Transmission Tests
One-Way Fire Warning Alarm System for Underground Mines
Propagation of EM Signals in Underground Mines
Theoretical Noise and Propagation Models for Through-the-earth Communication
Through-the-earth Communications Technologies Available
Through-The-Earth Wireless Real-Time Two-Way Voice Communications
Two-Way, Through-the-Earth Emergency Communication System for Trapped Miners and the Surface
Ultra-Low Frequency Through-the-Earth Communication Technology
Vertical Magnetic Noise in the Voice Frequency Band Within and Above Coal Mines
Page last reviewed: July 18, 2016
Page last updated: November 20, 2015
Content source: National Institute for Occupational Safety and Health, Mining Program
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