The Military & Aerospace Electronics take:
8 Jan. 2019 -- ELF radio waves have a proven ability to penetrate deep below water and the ground. In principle, this means that a huge antenna array could be useful in detecting natural resources underground, such as precious metals or fossil fuels. Mining companies already employ ground-penetrating radar and laser imaging systems for similar purposes.
Unfortunately, ELF systems are notoriously inefficient and require large sites. They also only can text-only messages extremely slowly. Since submarines don’t have the space required for their own ELF transmitters, these one-way alerts often simply tell the boat’s crew to get safely into position to receive actual instructions.
Only three oer countries e United States, Russia, and India – have or have had ELF submarine communications sites. The U.S. Navy shut down the last of its arrays in 2004, officially because they were obsolete in light of improvements to very low frequency, or VLF, communications systems.
John Keller, chief editor
Military & Aerospace Electronics
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