A system for measuring through-the-earth radio propagation

A measurement system used in through-the-earth magnetic field signal attenuation measurements is described. In addition, an associated calibration system for determining the magnetic antenna factor of a receive antenna is also described. Attenuation data at frequencies ranging from 300 to 3000 Hz was collected at an active coal mine with 201 m of overburden using the system. Results suggest that the data collected fits existing analytical models. Use of this system assists researchers by validating Through-the-earth (TTE) models and increases our understanding of the performance limitations of TTE systems.