"This report covers magnetic field strength measurements versus range and frequency in low to medium coal mines. Both quasi-conductor- free and conductor-proximity areas were investigated. The program covered five mines, four seams, six measurement sets, and three geographic areas. The results are summarized in terms of maximum communication range expected per seam and noise condition. Scatter gain is further explored as a simple measure of energy coupled to conductors." - NIOSHTIC-2 NIOSHTIC no. 10002377

National Institute for Occupational Safety and Health