An underground radio communications and personnel tracking system uses a cap-lamp worn by a miner when underground in a mine. A cap-lamp transceiver provides voice and text communication on ultra-low frequency (ULF) to ultra-high frequency (UHF) carrier frequencies and modulation adapted by programming of a software defined radio to making selective and agile radio contacts via through-the-earth, conductor/lifeline, coal seam, tunnel, and ionosphere/earth-surface waveguides for transmission of electromagnetic waves. These waveguides comprise layered earth coal and mineral deposits, and manmade mining complex infrastructures which serendipitously form efficient waveguides. Ultra-Low Frequency F1/F1 repeaters are placed underground in the mine, and providing for extended range of communication of the cap-lamp transceiver with radios and tracking devices above ground of the mine.