Through-the-earth mine communications

Last updated

Through-the-Earth (TTE) signalling is a type of radio signalling used in mines and caves that uses low-frequency waves to penetrate dirt and rock, which are opaque to higher-frequency conventional radio signals.

Contents

In mining, these lower-frequency signals can be relayed underground through various antennas, repeater or mesh configurations, but communication is restricted to line of sight to these antenna and repeaters systems.

Overview

Radio communication within caves is problematic because rock is a conductor and therefore absorbs radio waves. Ordinary radios typically have a very short range within caves. Low frequency (LF) or very low frequency (VLF) radio with single-sideband modulation is more commonly used today.

Through-the-Earth transmission can overcome these restrictions by using ultra-low frequency (300–3000 Hz) signals, which can travel through several hundred feet of rock strata. The antenna cable can be located on the surface only at a mine site, and provide signal coverage to the mine. The antenna may be placed in a "loop" formation around the perimeter of the mine site (or wherever coverage is needed) for systems using magnetic fields to carry signals. Systems that use electric fields as the signal carrier are not subject to this limitation. Transmissions propagate through rock strata which is used as the medium to carry the ultra-low-frequency signals. This is important in mining applications, particularly after any significant incident, such as fire or explosion, which would destroy much of the fixed communication infrastructure underground.

If the terrain makes a loop surface antenna impractical to install, then the antenna can be installed underground or a non-magnetic field type carrier may be used. But because the signal travels through rock, the antenna does not need to run into all parts of the mine to achieve mine wide signal coverage, thus minimizing the risk of damage during an incident.[ citation needed ]

Cave radios

Portable magnetic-loop cave radios have been used by cavers for two-way communication and cave surveying since the 1960s. [1] In a typical setup the transmitting loop, consisting of many turns of copper wire, is oriented horizontally within the cave using a spirit level, and driven at a few kHz. Though such a small antenna is a very poor radiator of propagating radio waves at this low frequency, its local AC magnetic field is strong enough to be detected by a similar receiving antenna up to a few hundred meters (yards) away. The received signal's strength and its dependence on orientation of the receiving coil yields approximate distance and directional information.

Early models were called "speleophones"—examples include Bob Mackin's "Molefone". The Molefone is called "one of the first practical cave radios," though it is no longer manufactured. [2] Other popular LF/VLF radios include the HeyPhone, [3] Nicola System [4] [5] and Cave-Link. [6] HeyPhone and Nicola operate single (upper) sideband on 87 kHz in the LF band, while Cave-Link uses different frequencies between 20-140 kHz depending on the expected distance at 30 W power. [7]

Systems like Molefone and HeyPhone operate as single-sideband (USB) 87 kHz radio with earthed electrodes of 25–100 metres (80' to 330') length. [8] Design for HeyPhone system is openly available. [9] European Cave Rescue Association (ECRA) maintains a list of systems scalable and reliable enough to be used for cave rescue operations. As of April 2023 the catalogue lists CaveLink (Germany), Nicola (Great Britain), µHeyPhone (Great Britain) and Pimprenelle (France) as operational wireless systems. [10]

Personal emergency device

There are several systems that have been recently developed. One system is known as the PED System, where PED is an acronym for personal emergency device. [11] Initially developed after a mining disaster in Australia at Moura No. 4 Coal Mine in 1986, [12] and further developed after the Moura No. 2 Coal Mine explosion in 1994 [13] where the need for a communication system to survive major incidents underground was identified in the inquiries into the disasters.

PED is a one-way text paging device, with wide use in Australia, as well as installations in the United States, China, Canada, Mongolia, Chile, Tanzania, and Sweden. [14] Australian company MST Global (formerly Mine Site Technologies) began the development of PED in 1987, and it became commercially available and Mine Safety & Health Administration (MSHA) approved in 1991. [14] The best documented use of PED during a mine emergency is from the Willow Creek Mine Fire in 1998 in Utah, where it was able to quickly alert miners underground of the need to evacuate before toxic fumes from the fire filled the mine. Reports of this use can be seen on the MSHA website. [15] [16]

Development

Emerging technologies have recently been developed such as the Rescue Dog Emergency Through the Earth Communication System [17] developed by E-Spectrum Technologies. The Rescue Dog is a two-way extended-range portable through-the-Earth solution that was developed in the US in cooperation with The National Institute for Occupational Safety and Health (or NIOSH) [18] which does not rely on large loop surface antennas for signal transmission. New non-portable systems have also been developed by companies such as Lockheed Martin for use in emergency chambers to provide post-accident, two-way, emergency voice and text communications independent of surface or in-mine infrastructure.

New technologies

A new wireless "Miner Lifeline" telecommunication technology is being tested in 2012 at the West Virginia Robinson Run mine (recent production 6,000,000 short tons (5,400,000 t) per year of coal using 600 miners). The system supports voice, text, or SOS sent on a "bubble" of magnetic waves, and "can move more than 1,500 feet (460 m) up or down and 2,000 feet (610 m) laterally, arriving in less than a minute." [19]

The Israeli company Maxtech [20] has developed a software system that automates the optimal organization of a set of limited-range communications devices, using any mixture of types of communication (through-the-earth radio, line-of-sight radio or optical, etc.). This system was used in the Tham Luang cave rescue. [21]

Sybet developed an underground communication network system based on a large number of autonomous, portable transceiver nodes (BatNode) which operate in mesh architecture, forwarding voice calls over long distance with no radio connection between the end stations, as long as the BatNodes can see their neighbours. [22]

See also

Related Research Articles

<span class="mw-page-title-main">Amplitude modulation</span> Radio modulation via wave amplitude

Amplitude modulation (AM) is a modulation technique used in electronic communication, most commonly for transmitting messages with a radio wave. In amplitude modulation, the amplitude of the wave is varied in proportion to that of the message signal, such as an audio signal. This technique contrasts with angle modulation, in which either the frequency of the carrier wave is varied, as in frequency modulation, or its phase, as in phase modulation.

Ground waves are radio waves propagating parallel to and adjacent to the surface of the Earth, following the curvature of the Earth beyond the visible horizon. This radiation is known as Norton surface wave, or more properly Norton ground wave, because ground waves in radio propagation are not confined to the surface.

<span class="mw-page-title-main">Radio wave</span> Type of electromagnetic radiation

Radio waves are a type of electromagnetic radiation with the longest wavelengths in the electromagnetic spectrum, typically with frequencies of 300 gigahertz (GHz) and below. At 300 GHz, the corresponding wavelength is 1mm, which is shorter than the diameter of a grain of rice. At 30 Hz the corresponding wavelength is ~10,000 kilometers, which is longer than the radius of the Earth. Wavelength of a radio wave is inversely proportional to its frequency, because its velocity is constant. Like all electromagnetic waves, radio waves in a vacuum travel at the speed of light, and in the Earth's atmosphere at a slightly slower speed. Radio waves are generated by charged particles undergoing acceleration, such as time-varying electric currents. Naturally occurring radio waves are emitted by lightning and astronomical objects, and are part of the blackbody radiation emitted by all warm objects.

<span class="mw-page-title-main">Very low frequency</span> The range 3–30 kHz of the electromagnetic spectrum

Very low frequency or VLF is the ITU designation for radio frequencies (RF) in the range of 3–30 kHz, corresponding to wavelengths from 100 to 10 km, respectively. The band is also known as the myriameter band or myriameter wave as the wavelengths range from one to ten myriameters. Due to its limited bandwidth, audio (voice) transmission is highly impractical in this band, and therefore only low data rate coded signals are used. The VLF band is used for a few radio navigation services, government time radio stations and for secure military communication. Since VLF waves can penetrate at least 40 meters (131 ft) into saltwater, they are used for military communication with submarines.

Low frequency (LF) is the ITU designation for radio frequencies (RF) in the range of 30–300 kHz. Since its wavelengths range from 10–1 km, respectively, it is also known as the kilometre band or kilometre wave.

<span class="mw-page-title-main">Medium frequency</span> The range 300-3000 kHz of the electromagnetic spectrum

Medium frequency (MF) is the ITU designation for radio frequencies (RF) in the range of 300 kilohertz (kHz) to 3 megahertz (MHz). Part of this band is the medium wave (MW) AM broadcast band. The MF band is also known as the hectometer band as the wavelengths range from ten to one hectometers. Frequencies immediately below MF are denoted as low frequency (LF), while the first band of higher frequencies is known as high frequency (HF). MF is mostly used for AM radio broadcasting, navigational radio beacons, maritime ship-to-shore communication, and transoceanic air traffic control.

<span class="mw-page-title-main">Whistler (radio)</span> Very low frequency EM waves generated by lightning

A whistler is a very low frequency (VLF) electromagnetic (radio) wave generated by lightning. Frequencies of terrestrial whistlers are 1 kHz to 30 kHz, with maximum frequencies usually at 3 kHz to 5 kHz. Although they are electromagnetic waves, they occur at audio frequencies, and can be converted to audio using a suitable receiver. They are produced by lightning strikes where the impulse travels along the Earth's magnetic field lines from one hemisphere to the other. They undergo dispersion of several kHz due to the slower velocity of the lower frequencies through the plasma environments of the ionosphere and magnetosphere. Thus they are perceived as a descending tone which can last for a few seconds. The study of whistlers categorizes them into Pure Note, Diffuse, 2-Hop, and Echo Train types.

<span class="mw-page-title-main">High frequency</span> The range 3-30 MHz of the electromagnetic spectrum

High frequency (HF) is the ITU designation for the range of radio frequency electromagnetic waves between 3 and 30 megahertz (MHz). It is also known as the decameter band or decameter wave as its wavelengths range from one to ten decameters. Frequencies immediately below HF are denoted medium frequency (MF), while the next band of higher frequencies is known as the very high frequency (VHF) band. The HF band is a major part of the shortwave band of frequencies, so communication at these frequencies is often called shortwave radio. Because radio waves in this band can be reflected back to Earth by the ionosphere layer in the atmosphere – a method known as "skip" or "skywave" propagation – these frequencies are suitable for long-distance communication across intercontinental distances and for mountainous terrains which prevent line-of-sight communications. The band is used by international shortwave broadcasting stations (3.95–25.82 MHz), aviation communication, government time stations, weather stations, amateur radio and citizens band services, among other uses.

<span class="mw-page-title-main">Extremely low frequency</span> The range 3-30 Hz of the electromagnetic spectrum

Extremely low frequency (ELF) is the ITU designation for electromagnetic radiation with frequencies from 3 to 30 Hz, and corresponding wavelengths of 100,000 to 10,000 kilometers, respectively. In atmospheric science, an alternative definition is usually given, from 3 Hz to 3 kHz. In the related magnetosphere science, the lower-frequency electromagnetic oscillations are considered to lie in the ULF range, which is thus also defined differently from the ITU radio bands.

<span class="mw-page-title-main">Ultra low frequency</span> Range 300-3000 Hz of the electromagnetic spectrum

Ultra low frequency (ULF) is the ITU designation for the frequency range of electromagnetic waves between 300 hertz and 3 kilohertz, corresponding to wavelengths between 1,000 to 100 km. In magnetosphere science and seismology, alternative definitions are usually given, including ranges from 1 mHz to 100 Hz, 1 mHz to 1 Hz, and 10 mHz to 10 Hz.

Super low frequency (SLF) is the ITU designation for electromagnetic waves in the frequency range between 30 hertz and 300 hertz. They have corresponding wavelengths of 10,000 to 1,000 kilometers. This frequency range includes the frequencies of AC power grids. Another conflicting designation which includes this frequency range is Extremely Low Frequency (ELF), which in some contexts refers to all frequencies up to 300 hertz.

Communication with submarines is a field within military communications that presents technical challenges and requires specialized technology. Because radio waves do not travel well through good electrical conductors like salt water, submerged submarines are cut off from radio communication with their command authorities at ordinary radio frequencies. Submarines can surface and raise an antenna above the sea level, or float a tethered buoy carrying an antenna, then use ordinary radio transmissions; however, this makes them vulnerable to detection by anti-submarine warfare forces.

<span class="mw-page-title-main">Rugby Radio Station</span> British government radio transmission facility

Rugby Radio Station was a large British government radio transmission facility just east of the Hillmorton area of the town of Rugby, Warwickshire in England. The site straddled the A5 trunk road, with most of it in Warwickshire, and part on the other side of the A5 in Northamptonshire. First opened in 1926, at its height in the 1950s it was the largest radio transmitting station in the world, with a total of 57 radio transmitters, covering an area of 1,600 acres (650 ha). Traffic slowly dwindled from the 1980s onwards, and the site was closed between 2003 and 2007.

<span class="mw-page-title-main">Grimeton Radio Station</span> Historic Swedish wireless telegraphy station

Grimeton Radio Station in southern Sweden, close to Varberg in Halland, is an early longwave transatlantic wireless telegraphy station built in 1922–1924, that has been preserved as a historical site. From the 1920s through the 1940s it was used to transmit telegram traffic by Morse code to North America and other countries, and during World War II was Sweden's only telecommunication link with the rest of the world. It is the only remaining example of an early pre-electronic radio transmitter technology called an Alexanderson alternator. It was added to the UNESCO World Heritage List in 2004, with the statement: "Grimeton Radio Station, Varberg is an outstanding monument representing the process of development of communication technology in the period following the First World War." The radio station is also an anchor site for the European Route of Industrial Heritage. The transmitter is still in operational condition, and each year on a day called Alexanderson Day is started up and transmits brief Morse code test transmissions, which can be received all over Europe.

<span class="mw-page-title-main">Leaky feeder</span> Communications system used in underground mining and tunnel environments

A leaky feeder is a communications system used in underground mining and other tunnel environments. Manufacturers and cabling professionals use the term "radiating cable" as this implies that the cable is designed to radiate: something that coaxial cable is not generally supposed to do.

<span class="mw-page-title-main">2182 kHz</span> Radio distress frequency

2182 kHz is a radio frequency designed exclusively for distress calls and related calling operations in the maritime service.

<span class="mw-page-title-main">Umbrella antenna</span>

An umbrella antenna is a capacitively top-loaded wire monopole antenna, consisting in most cases of a mast fed at the ground end, to which a number of radial wires are connected at the top, sloping downwards. One side of the feedline supplying power from the transmitter is connected to the mast, and the other side to a ground (Earthing) system of radial wires buried in the earth under the antenna. They are used as transmitting antennas below 1 MHz, in the MF, LF and particularly the VLF bands, at frequencies sufficiently low that it is impractical or infeasible to build a full size quarter-wave monopole antenna. The outer end of each radial wire, sloping down from the top of the antenna, is connected by an insulator to a supporting rope or cable anchored to the ground; the radial wires can also support the mast as guy wires. The radial wires make the antenna look like the wire frame of a giant umbrella hence the name.

<span class="mw-page-title-main">Ground dipole</span> Radio antenna that radiates extremely low frequency electromagnetic waves

In radio communication, a ground dipole, also referred to as an earth dipole antenna, transmission line antenna, and in technical literature as a horizontal electric dipole (HED), is a huge, specialized type of radio antenna that radiates extremely low frequency (ELF) electromagnetic waves. It is the only type of transmitting antenna that can radiate practical amounts of power in the frequency range of 3 Hz to 3 kHz, commonly called ELF waves. A ground dipole consists of two ground electrodes buried in the earth, separated by tens to hundreds of kilometers, linked by overhead transmission lines to a power plant transmitter located between them. Alternating current electricity flows in a giant loop between the electrodes through the ground, radiating ELF waves, so the ground is part of the antenna. To be most effective, ground dipoles must be located over certain types of underground rock formations. The idea was proposed by U.S. Dept. of Defense physicist Nicholas Christofilos in 1959.

<span class="mw-page-title-main">Radio</span> Technology of using radio waves to carry information

Radio is the technology of communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates the waves. They are received by another antenna connected to a radio receiver. In addition to communication, radio is used for radar, radio navigation, remote control, remote sensing, and other applications.

Waves (<i>Juno</i>) Experiment on the Juno spacecraft to study radio and plasma waves

Waves is an experiment on the Juno spacecraft to study radio and plasma waves. It is part of collection of various types of instruments and experiments on the spacecraft; Waves is oriented towards understanding fields and particles in Jupiter's magnetosphere. Waves is on board the uncrewed Juno spacecraft, which was launched in 2011 and arrived at Jupiter in the summer of 2016. The major focus of study for Waves is Jupiter's magnetosphere, which if could be seen from Earth would be about twice the size of a full moon. It has a tear drop shape, and that tail extends away from the Sun by at least 5 AU. The Waves instrument is designed to help understand the interaction between Jupiter's atmosphere, its magnetic field, its magnetosphere, and to understand Jupiter's auroras. It is designed to detect radio frequencies from 50 Hz up to 40,000,000 Hz (40 MHz), and magnetic fields from 50 Hz to 20,000 Hz (20 kHz). It has two main sensors a dipole antenna and a magnetic search coil. The dipole antenna has two whip antenna's that extend 2.8 meters and they are attached to the main body of the spacecraft. This sensor has been compared to a rabbit ears set-top TV antenna. The search coil is overall a mu metal rod 15 cm (6 in) length with a fine copper wire wound 10,000 times around it. There are also two frequency receivers that each cover certain bands. Data handling is done by two radiation hardened systems on a chip. The data handling units are located inside the Juno Radiation Vault. Waves was allocated 410 Mbits of data per science orbit.

References

  1. ↑ David Gibson, "Cave Radiolocation" ISBN   978-1-4457-7105-2
  2. ↑ Beford, Mike (2012). "A Directory of Cave Radio Designs". CREG Journal Archive.
  3. ↑ "HeyPhone Home Page". bcra.org.uk.
  4. ↑ Gibson, David (2010). Cave Radiolocation. Lulu.com. p. 73. ISBN   978-1445771052.
  5. ↑ "Systeme Nicola Mk2" (PDF).
  6. ↑ "Home". www.cavelink.com. Retrieved 2023-09-08.
  7. ↑ "VLF-Übermittlungssystem für die Höhlenforschung Cave-Link V2.1x" (PDF).
  8. ↑ "HeyPhone Introduction". bcra.org.uk. Retrieved 2020-01-14.
  9. ↑ "HeyPhone Documentation". bcra.org.uk. Retrieved 2020-01-14.
  10. ↑ "Communications Catalogue - ECRA - European Cave Rescue Association". 2023-04-25. Retrieved 2024-01-10.
  11. ↑ "Mine Safety and Health Administration (MSHA) - Emergency Communication and Tracking Committee - Underground Communication and Tracking Systems - Description of MSHA Approved Technologies" (PDF). US Mine Safety and Health Administration. 2007. Retrieved 2012-09-30.
  12. ↑ "Department of Mines and Energy - Moura No 4". Archived from the original on 2008-07-25. Retrieved 2009-01-20.
  13. ↑ "Department of Mines and Energy - Moura No 2". Archived from the original on 2008-07-25. Retrieved 2009-01-20.
  14. 1 2 "Archived copy" (PDF). Archived from the original (PDF) on 2013-03-11. Retrieved 2012-02-07.{{cite web}}: CS1 maint: archived copy as title (link)
  15. ↑ "Archived copy". Archived from the original on 2009-01-17. Retrieved 2009-01-20.{{cite web}}: CS1 maint: archived copy as title (link)
  16. ↑ http://www.msha.gov/disasterhistory/WCREEK/WCREEK.HTM
  17. ↑ https://dl.dropbox.com/u/34622965/Rescue%20Dog%20Web%20Brochure.pdf [ dead link ]
  18. ↑ http://www.homeandsmallbusinessnetwork.info/niosh/mining/mineract/contracts/200-2008-26818.htm [ dead link ]
  19. ↑ Rizzo, Johnna (May 2012). "Miner Lifeline". National Geographic. 221 (5): 37.
  20. ↑ "Maxtech Networks" . Retrieved 2020-09-27.
  21. ↑ Orr Hirschauge (2018-07-03). "Direct Radio Contact with Stranded Thai Group Still Unattained, Israeli Technology Vendor Says". Ctech. Retrieved 2020-09-27.
  22. ↑ "BATNODE – Sybet" (in Polish). Retrieved 2023-09-20.

Further reading

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.