Oddly it may surprise you to learn that the Germans had developed an
effective ELF system. It was found that Extreme Low Frequency radio
waves (approx 28000 metres in this case ) were able to penetrate the
upper layers of the ocean.
the antennae was sighted at magdeburg. If equipped with
appropriate recievers uboats could while the transmitter was
working. recieve radio transmissions down to about 50 ft.
M
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