Microwave radio in mines and tunnels

A set of experiments was carried out to characterise the propagation of microwaves in mines over the wide range of frequencies from 400 MHz to 24 GHz. The aim of the work was to reexamine whether a viable microwave communication system for a mine could be developed without resort to leaky feeders. The paper confirms the difficulty of propagating past obstacles and round corners, but describes some results which indicate that a workable system is possible using active repeaters at appropriate sites.