Raspberry Pi digital voice VLF Transmitter using EasyDRF via WiNE - through the earth Communications
https://github.com/DazDSP/EasyDRF
http://homepages.ihug.com.au/~daz2002...
this LIVE demo using EasyDRF was run on LINUX using W.I.N.E
LSB VLF ~16kHZ MODULATION/demodulation by Recri Keyer SDR modules
https://github.com/recri/keyer
alsa snd-aloop virtual audio cables were used in this setup to route audio
to & from both EasyDRF digital voice modems
for more examples of 'Through The Earth' Comms setups like these...
see the playlist here:
• DiY 'Through the Earth' Transmitter ...