Technical services for mine communications research. Propagation of radio waves in coal mines.
Lagace RL; Cohen ML; Emslie AG; Spencer RH
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, Contract - H0346045 1975 Oct; :1-187
Theoretical analyses of radio wave propagation in coal mines are performed and performance estimates are made for several wireless mine communication applications. A theoretical model and formulas were developed to account for the unexpectedly favorable signal propagation behavior observed at lf-mf frequencies in a conductor- free area of a particular coal mine. This model is based on a dipolar, cylindrical, tem mode of propagation within a low- conductivity horizontal coal seam in which the presence of the tunnels can be ignored, and which is bounded top and bottom by high- conductivity rock. Lastly, a transmission line analysis is performed to characterize the behavior and performance of an lf band hoist shaft communication system in which the steel hoist rope and the surrounding rock wall form a coaxial transmission line that is terminated resistively at one end by the sheave wheel structure, capacitively at the other end by the hoist cage, and to which the signals are inductively coupled by toroidal hoist rope couplers.
Attenuation; Coal mines; Low frequencies; Medium frequencies; Mine haulage; Mine shafts; Mining equipment; Radio transmission; Telephone systems; Through the earth transmission; Transmission loss; Tunnels; Ultrahigh frequencies
CP; Final Contract Report
NTIS Accession No.
OFR 46-77; Contract-H0346045
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, Contract - H0346045
Arthur D. Little, Inc.