Emergency and operational low and medium frequency band radio communications system for underground mines

A minewide low and medium-frequency radio system has been developed and installed in coal and metalliferous mines. The radio system utilizes two robust radio signal transmission modes to establish underground radio coverage areas. The seam transmission mode occurs when layers in the ground form a natural waveguide. The conductor transmission line mode waveguide occurs when electrical conductors, such as AC power distribution cables, are in place in mine passageways. The author describes the development history of MF band technology during the past five decades in South Africa, Europe, and the United States. How EM wave theory guided the design and development of the conductor transmission line repeater network and associated mobile radio equipment is discussed. The safety and cost reduction benefits of a practical radio system are also described