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Mining Publication: Medium-Frequency Propagation in Coal Mines

NOTE: This page is archived for historical purposes and is no longer being maintained or updated. Contact NIOSH Mining if you need an accessible version.

Original creation date: August 1978

Image of publication Medium-Frequency Propagation in Coal Mines

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 theory of this coal seam mode is applied to recent MF data for a number of mines in order to classify the propagation characteristic of the mines in a simple way. When conductors such as rails, trolleylines, or power cables are present in the vicinity of the measurement path, it is found that the magnetic field versus range plots have two distinct regions with very different slopes. This effect is attributed to coupling of the cylindrically spreading coal seam mode to a low-attenuation conductor guided mode. As a result, voice communications range between mobile transmitters can extend several thousand meters. The use of MF for mine communications is discussed.

Authors: HK Sacks, RL Chufo

Conference Paper - August 1978

NIOSHTIC2 Number: 20032395

Proceedings of the Fourth WVU Conference on Coal Mine Electrotechnology, Aldridge-MD, ed. Morgantown, WV, Aug 2-4, 1978, 1978 Aug; :27-1-27-12