What are ELF radio waves used for?
Extremely low frequency (ELF) electromagnetic waves are currently the lowest frequency waves used routinely for wireless communication.
What frequency do submarines use?
Very Low Frequency (VLF) communications transmitters use digital signals to communicate with submerged submarines on at frequencies of 3-30 kHz. The eighteen Trident submarines constitute about half the US strategic nuclear capability.
How do Trident submarines communicate?
VLF radio waves (3–30 kHz) can penetrate seawater to a few tens of meters and a submarine at shallow depth can use them to communicate. If two-way communication is needed, the boat must ascend nearer to the surface and raise an antenna mast to communicate on higher frequencies, usually HF and above.
Is ELF radiation hazardous?
It’s not clear that exposure to ELF radiation is harmful, but there are things you can do to lower your exposure if you are concerned. Your exposure is based on the strength of the ELF radiation coming from each source, how close you are to each, and how long you spend in the field.
What is a Gertrude phone?
The underwater telephone, also known as UQC, AN/WQC-2, or Gertrude, was developed by the U.S. Navy in 1945. The UQC underwater telephone is used on all manned submersibles and many Naval surface ships in operation.
What’s the highest frequency a human can hear?
to 20 kHz
Humans can detect sounds in a frequency range from about 20 Hz to 20 kHz. (Human infants can actually hear frequencies slightly higher than 20 kHz, but lose some high-frequency sensitivity as they mature; the upper limit in average adults is often closer to 15–17 kHz.)
Where are the ELF transmitters in Project Sanguine?
Project Sanguine. A smaller, less hardened system consisting of two linked ELF transmitters located at Clam Lake, Wisconsin and Republic, Michigan was built beginning in 1982 and operated from 1989 until 2004. The system transmitted at a frequency of 76 Hz. At ELF frequencies the bandwidth of the transmission is very small,…
How many Watts Does a ELF transmitter generate?
At their full input power of 2.6 MW, both US ELF transmitters working together only generated about 8 watts of ELF radiation. This weak signal was able to reach submarines over half the globe only because of the extremely low attenuation of ELF waves of 1–2 dB per 1000 kilometers.
Where are the ELF transmitters in the US Navy?
Map showing location of the US Navy ELF transmitters. The red lines show the paths of the ground dipole antennas. The Clam Lake facility (left) had two crossed 14 mi. ground dipoles. The Republic facility had two 14 mi. dipoles oriented east–west, and one 28 mi. dipole oriented north–south.
Why are ELF signals used for submarine communication?
Generally, ELF signals have been used to order a submarine to rise to a shallow depth where it could receive some other form of communication. One of the difficulties posed when broadcasting in the ELF frequency range is antenna size, because the length of the antenna must be at least a substantial fraction of the length of the waves.