Using VLF receiver as a RX part and it connect to earth dipole antenna ( 20...24m between ground spikes ). TX part consists of FM radio ( audio source ) and A class audio amplifier with earth dipole antenna ( about 70m between ground spikes )... TX part transmitts audio freqencies in to ground and it make ground currents... it can receive 110...160m away... about 300m signals is weak and only morse code can detect...
In this video between RX and TX about 110m

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