Results 301 - 310 of 331

• Detection of Trapped Miner Electromagnetic Signals Above Coal Mines
  7/1/1980 - Contract reports
  This report assesses the expected detectability, on the surface above mines, of electromagnetic signals produced in the 630- to 3,030-hz frequency band by a rescue transmitter activated by miners trapped underground. The implications of the results and ...
• An Evaluation of Leaky Feeder Communication in Underground Mines
  6/1/1980 - Contract reports
  The objective of this project was to develop technical data and evaluate performance and utility of leaky feeder communications systems currently used in U.S. underground mines.
• Electromagnetic Location Systems for Metal/Non Metal Mines
  1/15/1979 - Contract reports
  Characteristics of metal-nonmetal mines were evaluated to determine the suitability of applying the Bureau of Mines electromagnetic (em) location system to locating trapped miners.
• Improved Rail Haulage Communications
  10/1/1978 - Conference papers
  An analysis is made of the trolley line as a communications line, and methods of improving its characteristics are discussed.
• Medium-Frequency Propagation in Coal Mines
  8/1/1978 - Conference papers
  Medium-frequency (MF) waves can propagate in a coal seam, bounded above and below by conducting rock, in an approximate transverse electro-magnetic (TEM) transmission-line mode with the electric field vertical and the magnetic field horizontal. The theo...
• Underground Mine Communications
  1/1/1978 - Peer reviewed journal articles
  Extensive analysis of mine-communications systems has identified specific areas, in particular the excessive times required to locate key personnel underground, the inadequacy of existing phone systems in terms of capacity and privacy and the inability ...
• Electromagnetic Propagation in Low Coal Mines at Medium Frequencies
  1/1/1978 - Contract reports
  This report covers magnetic field strength measurements versus range and frequency in low to medium coal mines. Both quasi-conductor-free and conductor-proximity areas were investigated.
• Transmit Antennas for Portable VLF to MF Wireless Mine Communications
  9/1/1977 - Contract reports
  An investigation was made of the feasibility of developing compact transmit antennas and/or other means to efficiently couple VLF to MF band radio energy between portable wireless communication units in coal mines. The completely wireless communication ...
• Propagation of EM Signals in Underground Mines
  1/1/1977 - Conference papers
  This report is a comprehensive summary of the results of the propagation measurements program conducted for the Bureau of Mines.
• Underground Mine Communications (in Four Parts): 4. Section-to-Place Communications
  1/1/1977 - Information Circulars
  This Bureau of Mines report on underground mine communications addresses methods and equipment to meet the communication requirements of working sections and places of coal and metal-nonmetal mines. A review of the status of trapped miner detection is a...