below 22 khz
http://www.vlf.it/
I remember just post a link to software to take computer sound card and plug
http://www.rtl-sdr.com/receiving-vlf-pc-sound-card-miniwhip-antenna-saqrx/
http://www.vlf.it/
I remember just post a link to software to take computer sound card and plug
http://www.rtl-sdr.com/receiving-vlf-pc-sound-card-miniwhip-antenna-saqrx/