Which frequency range is used for one-way communication to submarines?

The Extremely Low Frequency (ELF) range is utilized for one-way communication to submarines primarily due to its unique propagation characteristics. ELF signals can penetrate deep underwater, allowing communication with submarines that are submerged at significant depths where higher frequency signals would be attenuated and unable to reach.

Submarines often operate at depths where conventional radio frequencies simply cannot penetrate effectively, making ELF a vital option for sustaining communication. In addition to penetrative capabilities, ELF waves can travel vast distances, which is crucial for maintaining contact with submerged vessels over large ocean areas.

This method of communication is strategic, allowing for the sending of crucial messages without needing the submarine to surface, thus maintaining stealth and security during operations.