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18-533: The initial production version, the Sapfir-23L (L - Lyogkiy or lightweight) pulse radar was first carried on the MiG-23 Edition 1971. Using a twist- Cassegrain antenna 800 mm (31 in) in diameter, it used a continuous-wave target illuminator channel to provide guidance for the semi-active radar homing (SARH) R-23R missile. However, as an interim variant it was considered unreliable and lacked

36-478: A fighter-sized target at high altitude, reduced to 25km in look-down mode. An improved version of the Sapfir-23ML with better range, reliability, ECCM and the capability to guide the updated R-24R/T air-to-air missiles. It also had a frequency spacing feature that prevented multiple radars from interfering with each other's operation, allowing for group-search patterns to be conducted. A downgraded version of

54-417: Is a paraboloid , while the shape of the convex secondary reflector is a hyperboloid . The geometrical condition for radiating a collimated, plane wave beam is that the feed antenna is located at the far focus of the hyperboloid, while the focus of the primary reflector coincides with the near focus of the hyperboloid. Usually the secondary reflector and the feed antenna are located on the central axis of

72-584: Is mounted at or behind the surface of the concave main parabolic reflector dish and is aimed at a smaller convex secondary reflector suspended in front of the primary reflector. The beam of radio waves from the feed illuminates the secondary reflector, which reflects it back to the main reflector dish, which reflects it forward again to form the desired beam . The Cassegrain design is widely used in parabolic antennas, particularly in large antennas such as those in satellite ground stations , radio telescopes , and communication satellites . The primary reflector

90-470: Is mounted suspended in front of the dish at the focus, pointed back toward the dish. The Cassegrain is a more complex design, but in certain applications it has advantages over front feed that can justify its increased complexity: A disadvantage of the Cassegrain is that the feed horn(s) must have a narrower beamwidth (higher gain ) to focus its radiation on the smaller secondary reflector, instead of

108-410: Is used in very large steerable radio telescopes and satellite ground antennas, where the feed electronics are too complicated and bulky, or requires too much maintenance and alterations, to locate on the dish; for example those using cryogenically cooled amplifiers. The beam of incoming radio waves from the secondary reflector is reflected by additional mirrors in a long twisting path through the axes of

126-654: The altazimuth mount , so the antenna can be steered without interrupting the beam, and then down through the antenna tower to a feed building at ground level. The Cassegrain antenna design was adapted from the Cassegrain telescope , a type of reflecting telescope developed around 1672 and attributed to French Province England priest Laurent Cassegrain . The first Cassegrain antenna was invented and patented by Cochrane and Whitehead at Elliot Bros in Borehamwood, England, in 1952. The patent, British Patent Number 700868,

144-520: The 1960s. The technology was reportedly taken from the F-4J AN/AWG-10 radars captured in Vietnam in 1967. The Sapfir-23D had a detection range of approximately 45km against a high-flying, fighter-sized target. All Sapfir-23Ds were eventually updated to the definitive Sapfir-23D-III during field upgrades. The definitive version of the first-generation Sapfir-23s, all MiG-23Ms were fitted with

162-672: The N003 carried on MiG-23MLDs exported to Syria. It was also carried on export versions of the MiG-23ML. The N003E had no ability to detect or track targets in a tail-chase engagement, relying on the fighter's IRST instead. It's field of scan was +/- 30° to either side of the fighter's nose and +/- 6° in elevation. The ultimate version of the RP-23, the N008 was carried on the MiG-23MLD used by

180-467: The Sapfir-23D-III carried on the export-specific MiG-23MF. Those which were sold to Third World clients had downgraded performance and lacked electronic counter-countermeasures (ECCM). Equipping the newer MiG-23ML, the Sapfir-23ML was an improvement upon the Sapfir-23D-III, being more reliable and with superior look-down/shoot-down capability. It had a maximum detection range of 65km against

198-525: The Sapfir-23D-III starting in 1975. Working in the 3cm wavelength and with a carrier frequency of about 9 GHz , it had a detection range of about 45km against a high-altitude fighter-sized aircraft during a head-on engagement , and between 10 and 20km in look-down mode during a tail-chase engagement . Against bomber-size targets these ranges were 55km and 15 to 20km respectively. However, in look-down/shoot-down mode targets flying slower than 60 km/h (37 mph) would not be detected. A re-designation of

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216-460: The VVS. Weighing 360 kg (790 lb), it had an average emitting power of 1 KW and peak output of 60 kW . It featured improved detection range, reliability, ECCM, look-down/shoot-down over rough terrain, and a close air combat mode with vertical-scan capability. Search range against high-altitude targets was 75km for a bomber-sized target and 52km for a fighter-sized target; in look-down mode it

234-401: The dish. However, in offset Cassegrain configurations, the primary dish reflector is asymmetric, and its focus, and the secondary reflector, are located to one side of the dish, so that the secondary reflector does not partially obstruct the beam. This design is an alternative to the most common parabolic antenna design, called "front feed" or "prime focus", in which the feed antenna itself

252-455: The look-down/shoot-down capability of later Sapfir radars; it could only guide missiles onto targets flying above 1,000 m (3,300 ft). Equipping the MiG-23M, the improved Sapfir-23D had look-down/shoot-down capability and could guide both R-23R and R-23T missiles. It was not a true Doppler radar but used the less effective "envelope detection" technique common to Western radars of

270-470: The search area. This derivative of the Sapfir-23ML was designed specifically for the MiG-23P interceptor , although initial models were unreliable and required additional maintenance. It had slightly improved look-down/shoot-down, including against cruise missiles . Cassegrain antenna In telecommunications and radar , a Cassegrain antenna is a parabolic antenna in which the feed antenna

288-444: The wider primary reflector as in front-fed dishes. The angular width the secondary reflector subtends at the feed horn is typically 10–15°, as opposed to 120–180° the main reflector subtends in a front-fed dish. Therefore, the feed horn must be longer for a given wavelength. A beam waveguide antenna is a type of complicated Cassegrain antenna with a long radio wave path to allow the feed electronics to be located at ground level. It

306-460: Was 23km for both target types, except for fighter-sized targets in a head-on engagements in which case it was 14km. Tracking range against high-altitude targets was 52km for bomber-sized and 39km for fighter-sized targets; in look-down mode it was 23km for bombers, while for fighter-sized targets it was 15km in tail-chase or 9km in head-on engagements. The scan field was limited to 60° x 6°, although it could be steered up to 60° left and right to expand

324-533: Was subsequently challenged in court, but prevailed. The Voyager 1 spacecraft launched in 1977 is, as of September 2024 , 24.6 billion kilometers from Earth, the furthest manmade object in space, and it's 3.7 meter S and X-band Cassegrain antenna (picture below) is still able to communicate with ground stations. Antenna feed Too Many Requests If you report this error to the Wikimedia System Administrators, please include

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