Propagation parameters for medium frequency signals in a transmission line at different positions within a mine entry

A medium frequency (MF) communication system used in underground coal mines generally couples its electromagnetic signals to existing conductors in a mine entry (tunnel), and exchanges signals with transceivers near the conductors. The conductors act as a transmission line (TL). The propagation characteristics of the TL, which play a major role in determining the performance of an MF communication system, can be affected by a mine environment. This paper compares the measured propagation parameters of a TL in three different positions within a mine entry. This comparison shows that the differences between the electrical properties of local coal and rock close to the TL can influence the propagation characteristics of the TL when in a different position.