File:Clam Lake ELF.jpg

Summary
Description English: An aerial view of the U.S. Navy's Clam Lake Extremely Low Frequency (ELF) radio transmitter facility. This transmitted ELF radio signals at a frequency of 76 Hz to communicate with submerged nuclear submarines around the world. The transmitter powered two perpendicular "ground dipole" antennas each consisting of a 14 mile transmission line grounded at each end. Sections of the transmission lines can be seen passing through the forest at lower left. The transmission lines were driven with a current of about 300 amps, which flowed deep in the ground between the ends of the lines, in a huge loop. The input power to the antennas was about 1 megawatt, and they radiated about 2 watts of ELF radiation. The Clam Lake facility became operational in 1985 and was shut down in 2004. This photo was taken in 1982 before it became operational, when it was known as the Wisconsin Test Facility. https://en.wikipedia.org/wiki/File:Clam_Lake_ELF.jpg Location: Clam Lake, Wisconsin (WI) UNITED STATES OF AMERICA (USA) Date	Shot: 1 Feb 1982 Source	ID:DNSC8203911 Author	Service Depicted: Navy Permission (Reusing this file) Public domain	This file is a work of a sailor or employee of the U.S. Navy, taken or made as part of that person's official duties. As a work of the U.S. federal government, the image is in the public domain in the United States. Seal of the United States Department of the Navy.svg This file has been identified as being free of known restrictions under copyright law, including all related and neighboring rights.