Underground Radio Communication

communication between two or more points by means of radio-wave propagation through the earth. The communication points are often located at great depths— in mines, tunnels, underground bunkers, and wells.

Radio waves transmitted from the antennas of such underground systems are propagated through rocks having a high electrical resistance, such as beds of rock salt or basalt, that are topped by a stratum of sedimentary rock with good electrical conductivity. Such systems are well protected against all forms of atmospheric and industrial interference and may have a signal-to-noise ratio at the receiver input that is substantially higher than that of similar aboveground systems. In addition, the conditions for radio-wave propagation in such a system are highly stable; they are practically independent of the time of day, the season, ionospheric conditions, and other factors. When antennas are used at shallow depths, the major portion of the transmission sion path between transmitter and receiver is through the atmosphere; the properties of such systems differ little from those of similar aboveground systems.

Radio waves used in underground radio communication range from myriametric to decametric wavelengths.