Tule Lake Radar Station, California

The footprint of three antenna fields are still discernable at the former Tule Lake Radar Station, in northeastern California. This was the receiving station for a radar system developed by General Electric for the Air Force in the 1980s, which received the reflected signal generated by a transmitting station 115 miles north, near Christmas Valley, Oregon. Both had three antenna fields, covering hundreds of acres. The system was deactivated around 1997, and both sites have been partially remediated. Nearly identical transmitting and receiving facilities were built on the east coast, in Maine, also now closed. The system known as OTH-B (Over-the-Horizon-B), used shortwave radio waves, bouncing off the ionosphere, to detect ships and aircraft. Built as an early-warning system for military defense, the signal was also used by the Border Patrol to track airplanes, and NOAA to track tides and currents.