Radio Propagation Measurements In Coal Mines At UHF And VLF

Radio propagation measurements were conducted in a coal mine at UHF (200 to 1000 MHz) and VLF (1 to 50 kHz) to characterize the transmission loss of intra-mine paths. The basic experimental parameters included frequency, polarization, path orientation and distance. Further tests evaluated the performance of roof-bolt vs. loop antennas at VLF and parasitic reflectors at UHF. Measurement results are summarized in a series of transmission loss curves. Examples are presented to show the use of these curves in predicting the performance of radio communication systems in mines.