more at http://quickfound.net/links/military_news_and_links.html Shows how different radar targets are differentiated by output sound. "THE AUDIO RETURNS PICKED UP BY AN/TPS-25 FROM: WALKING PERSONNEL, LIGHT AND HEAVY WHEELED VEHICLE, VEHICLE DISPERSION MANEUVER, TRACKED VEHICLE, AND TANKS." US Army Training Film TF6-3184 Reupload of a previously uploaded film, in one piece instead of multiple parts. Public domain film from the National Archives, slightly cropped to remove uneven edges, with the aspect ratio corrected, and mild video noise reduction applied. The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and equalization (the resulting sound, though not perfect, is far less noisy than the original). Comment by qawwss2000 The ANTPS-25 that we used on the korean DMZ must have been an improvement because the sounds were alot easier to distinguish than what was heard in this film. The radar picks up the combined movement of spinning metal parts on each vehicle. Light vehicles have a higher pitch. You can hear every change of velocity when the driver changes gears, uses the clutch and presses the accelerator. A moving leg has a 'whup' sound, so a walker sounds like 'whup, whup whup' at a walking cadence. See it's use on the korean DMZ - replace the dot with a period and delete spaces to fix the address... tinyurl dot com/ANTPS-25RadarIn1974 http://creativecommons.org/licenses/by-sa/3.0/ http://en.wikipedia.org/wiki/Radar Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio waves or microwaves which bounce off any object in their path. The object returns a tiny part of the wave's energy to a dish or antenna which is usually located at the same site as the transmitter. Radar was secretly developed by several nations before and during World War II. The term RADAR was coined in 1941 by the United States Navy as an acronym for radio detection and ranging... The modern uses of radar are highly diverse, including air traffic control, radar astronomy, air-defense systems, antimissile systems; marine radars to locate landmarks and other ships; aircraft anticollision systems; ocean surveillance systems, outer space surveillance and rendezvous systems; meteorological precipitation monitoring; altimetry and flight control systems; guided missile target locating systems; and ground-penetrating radar for geological observations. High tech radar systems are associated with digital signal processing and are capable of extracting objects from very high noise levels. Other systems similar to radar have been used in other parts of the electromagnetic spectrum. One example is "lidar", which uses visible light from lasers rather than radio waves.... A radar system has a transmitter that emits radio waves called radar signals in predetermined directions. When these come into contact with an object they are usually reflected or scattered in many directions. Radar signals are reflected especially well by materials of considerable electrical conductivity—especially by most metals, by seawater, by wet land, and by wetlands. Some of these make the use of radar altimeters possible. The radar signals that are reflected back towards the transmitter are the desirable ones that make radar work. If the object is moving either closer or farther away, there is a slight change in the frequency of the radio waves, caused by the Doppler effect. Radar receivers are usually, but not always, in the same location as the transmitter. Although the reflected radar signals captured by the receiving antenna are usually very weak, these signals can be strengthened by electronic amplifiers. More sophisticated methods of signal processing are also used in order to recover useful radar signals. The weak absorption of radio waves by the medium through which it passes is what enables radar sets to detect objects at relatively long ranges—ranges at which other electromagnetic wavelengths, such as visible light, infrared light, and ultraviolet light, are too strongly attenuated. Such things as fog, clouds, rain, falling snow, and sleet that block visible light are usually transparent to radio waves. Certain radio frequencies that are absorbed or scattered by water vapor, raindrops, or atmospheric gases (especially oxygen) are avoided in designing radars except when detection of these is intended. Radar relies on its own transmissions rather than light from the Sun or the Moon, or from electromagnetic waves emitted by the objects themselves, such as infrared wavelengths (heat). This process of directing artificial radio waves towards objects is called illumination, although radio waves are invisible to the human eye or cameras...

• published: 09 Nov 2014
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