I know nothing about radio frequencies but what I do know is that Big Harry and Janet were king pins in a field called 'Battlespace Management' when they worked for Nautronics. They told me that VLF was the key to getting information from the databases held in key global locations to submarines on patrol.
That was how the Los Angeles class sub that was sat on the ocean floor monitoring Russian submarines off Murmansk was able to get the sound signature that identified the Kursk and the sound signature of a torpedo fuelled by Hydrogen Peroxide exploding which gave them the reason why the Kursk exploded. The only way to get that at information back to the US securely was for the US sub to go to the nearest Norwegian port and pass the physical recording of all they had heard into the hands of an agent who had a jet waiting to take him back to the US. A copy of the file was sent to Nautronics for Harry, Janet and their team to analyse. That's how I knew what had destroyed the Kursk before the rest of the world.
That triggered me off into going back to read Family Matters for December 2016. Now that
is a forgotten corner....
More.... Janet and Harry's work on battlespace management led them into even more esoteric fields and one was the positioning of the undersea listening posts that listened for the sound signatures of vessels (Including Russian submarines) which also used VLF communications.
This in turn led them into using what they had learned to make what is often called 'Undersea GPS' It is called Nasnet and if you are interested in such things is well worth a coat of looking at.
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