how low can you go VLF FREQUENCY'S

[burts]

Hi
while surfing youtube i found some stuff on receiving very low frequency signals no voice to listen to but interesting and a free program that will amaze you,well i was anyway

YouTube - Software VLF Receiver

 

[burts]

and also

YouTube - Submarine transmissions received in Norway at LA3EQ on VLF

 

[W2NJS]

VLF has been used for many years for long-range underwater radio transmission and reception.