Clam Lake, Wisconsin
ELF radio signals are not very easy to transmit. In most situations involving radio, the antennas need to be approximately half of the wavelength of the desired signal. As extremely low frequency corresponds to extremely long wavelength, this is a problem when it comes to building a transmitter capable of transmitting ELF signals. The ideal antenna would have to be approximately 1800 kilometers long. The solution to this problem is not easy.
After years of research and experimentation, both the USA and the USSR discovered that it is possible to use part of the Earth's crust as one giant antenna. In Clam Lake, Wisconsin, the USA built a ELF transmission site that worked by sending large amounts of electrical energy into the ground. As the ground conductivity there is extremely low, the current travels through the earth for approximately 52 kilometers before reaching the other electrode that makes up the antennae. This results in using a large part of the Earth as the antenna, enabling the transmission of ELF signals to the entire world.
After years of research and experimentation, both the USA and the USSR discovered that it is possible to use part of the Earth's crust as one giant antenna. In Clam Lake, Wisconsin, the USA built a ELF transmission site that worked by sending large amounts of electrical energy into the ground. As the ground conductivity there is extremely low, the current travels through the earth for approximately 52 kilometers before reaching the other electrode that makes up the antennae. This results in using a large part of the Earth as the antenna, enabling the transmission of ELF signals to the entire world.