Results 21 - 25 of 25

• Antenna Design & Coupling Studies at Medium Frequency for lmproved Coal Mine Communications
  9/1/1978 - Contract reports
  This report covers antenna design, analysis, and development work suited for use with a wireless radio communication system operating at medium frequency. The work includes the test and evaluation of prototype vehicular antennas developed during the pro...
• 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...
• 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 ...
• Magnetic Field Strength Mapping of the Helvetia Coal Co. Lucerne No. 8 Mine at Medium Frequency
  9/1/1977 - Contract reports
  This report describes magnetic field measurements in the Helvetia Coal Co. Lucene No. 8 Mine for purposes of deriving a mapping of the magnetic field strength covering the major haulageways which contain conductors.
• 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.