![]() ![]() These systems can detect objects beyond a hundred kilometers away from modest, conventional radar stations. The Ionosphere is a region in Earth’s upper atmosphere between 80 and 600 kilometers high where Extreme UltraViolet (EUV) and x-ray solar radiation ionize the atoms and molecules, producing a layer of electrons. The most frequent techniques are shortwave systems that refract their signals off the ionosphere for long-range detection, and surface wave systems, which use low frequency radio waves that diffract to follow the curvature of the Earth beyond the horizon. OTH radars employ various techniques to see well beyond the limit of traditional radar systems. Siting an antenna on a high mountain might improve the range somewhat however, line-of-sight ranges beyond a few hundred kilometers are generally impossible to achieve. Because of the shape of the Earth, radar systems’ detection ranges are restricted to things on their horizon (usually referred to as “line of sight” since the aircraft must be at least theoretically visible to a person at the location and elevation of the radar transmitter. ![]() Most radars, which employ microwaves, generate radio waves in straight lines. Over-the-horizon radar operates in high-frequency(HF) range from 5 to 30 MHz.īeginning in the 1950s and 1960s, several OTH radar systems were utilized as part of early warning radars, but these have mostly been supplanted by airborne early warning systems. Over-the-horizon radar (OTH), sometimes referred to beyond the horizon (BTH), is a form of radar technology with the capacity to detect objects at long distances, often hundreds to thousands of kilometers, beyond the radar horizon. They’re also used in commercial and military ships for navigation and surveillance. Extremely useful for militaries in providing protection and intel gathering. Over-the-Horizon (OTH) radars are very powerful and are usually utilized as early warning and threat detection tools. Now a days over-the-horizon radar (OTH) is very common among developed countries with systems located in the United States, China, Russia, UK, Australia, Canada, Germany, France, Brazil, etc. In today’s world it’s radar ranges have been expanded to over thousands of miles away from the transmitter. During the late 1960s, SRI took over this advancement from Stanford and transformed radio waves’ use to detect distant things. Stanford University’s wide-aperture research facility, laid the groundwork for developing radar that can see over the horizon. The ability to see things outside of the radar horizon was a problem and a scientific mystery that SRI International helped solve, resulting in the invention of over-the-horizon radars (OTHR). Interference and dispersion caused by weather, atmospheric conditions, or other radio waves might also limit how far radar signals may travel and result in false-positive identifications.Īt the very best, radar was only capable of detecting objects only to the line-of-sight horizon. Radio waves move in a straight line and require a clear line of sight between the antenna and the object being detected. While this feature is quite useful, it had several drawbacks. ![]() The distance to an object is determined by the time difference between the pulse transmission and the echo’s arrival. Echoes from any objects in the signal’s path are detected by a receiver. OVER THE HORIZON SERIESA transmitter sends a series of short bursts from an antenna toward a predetermined spot. Radars in their simplest form, use radio signals to determine the location of moving targets. ![]()
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