AN/TPS-71 ROTHR (Relocatable Over-the-Horizon Radar) is a US Naval system capable of monitoring activity in a 64° wedge shaped area at ranges between 500 NM and 1600 NM. The AN/TPS-71 is deployed at stations in Virginia, Puerto Rico and Texas.
Traditionally used for early warning surveillance during the first half of the Cold War OTH (Over-the-Horizon) radar systems were phased out with the emergence of airborne early warning systems that were higher resolution and more accurate but also expensive to operate and maintain. Since the close of the Cold War OTH radar systems regained popularity due to their lower price tag and wide area of coverage, they were notably used by the US for drug traffic detection and interdiction operations. In the 21st century OTH radar remains relevant due to its ability to detect the operation of low-visibility and stealth vehicles. Most stealth technology is geared towards defeating X and Ku band radar detection but is less effective in preventing detection in the HF and VHF bands utilized by OTH radar. OTH technology has also proven effective in detecting emerging threats like hyper-sonic missile technology.