Communicating with a submerged submarine is a harder problem than controlling an aircraft or surface vessel. Very-low-frequency transmissions reach submarines but have limited penetration and bandwidth. The VLF operators named in the discussion are Norway, France, the United States, Russia, Britain, Germany, Australia, Pakistan, and India. Extremely-low-frequency systems can reach operating depths of hundreds of metres, yet their antennas are enormous and depend on suitable geology. Only a small group of states has built such infrastructure, and some systems are uncertain or no longer active. Their data rates are measured in bits per second and messages often require error correction. Britain has VLF infrastructure rather than ELF; the frequencies given here are 3 to 30 kHz for VLF and 3 to 300 Hz for ELF. These links can tell a submarine to rise to a depth where it can receive a richer transmission, but they cannot provide continuous high-bandwidth remote control. The same constraint sharply limits concepts for globally operated uncrewed underwater vehicles.
Notable Point · 2:33:34-2:43:14
VLF and ELF links for submerged submarines
VLF and ELF signals can reach submerged boats, but immense antennas and bit-per-second data rates rule out continuous high-bandwidth control.