Radome: Difference between revisions
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[[File:Navy-Radome.jpg|right|260px|thumbnail| |
[[File:Navy-Radome.jpg|right|260px|thumbnail|Geodesic radomes at the [[Misawa Air Base|Misawa Security Operations Center]], Misawa, Japan]] |
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A '''radome''' (which is a [[portmanteau]] of [[radar]] and [[dome]]) is a structural, weatherproof enclosure that protects a [[microwave]] |
A '''radome''' (which is a [[portmanteau]] of [[radar]] and [[dome]]) is a structural, weatherproof enclosure that protects a [[microwave]] or [[radar]] [[antenna (radio)|antenna]]. The radome is constructed of material that minimally [[Attenuation|attenuates]] the electromagnetic [[signal]] transmitted or received by the antenna. In other words, the radome is [[transparency and translucency|transparent]] to radar or [[radio]] waves. Radomes protect the antenna surfaces from weather and conceal antenna electronic equipment from public view. They also protect nearby personnel from being accidentally struck by quickly rotating antennae. |
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Radomes can be constructed in several shapes |
Radomes can be constructed in several shapes — spherical, [[geodesic dome|geodesic]], planar, etc. — depending on the particular application, using various construction materials, e.g., [[fiberglass]], [[Polytetrafluoroethylene|PTFE]]-coated fabric, etc. |
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When found on fixed-wing [[aircraft]] with forward-looking radar |
When found on fixed-wing [[aircraft]] with forward-looking radar, as are commonly used for object or weather detection,<ref>[http://web.archive.org/web/20090301165418/http://www.asap.co.uk/news/northwest-jet-nose-cone-dented-during-flight-5633156.html example of dented radome]</ref> the [[nose cone]]s often additionally serve as radomes. In case of advanced aircraft systems like [[airborne early warning and control]] (AEW&C), a rotating radome, often called a "rotodome", is mounted on the top of the fuselage for 360-degree coverage. There are newer AEW&C configurations, which instead uses three antenna modules in a triangular configuration inside a radome, usually mounted on top of the fuselage, for 360-degree coverage, such as the Chinese [[KJ-2000]] and Indian [[DRDO AEW&CS|DRDO]] AEW&Cs. |
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On rotary-wing and fixed-wing aircraft using microwave satellite for beyond-line-of-sight communication, radomes often appear as blisters on the fuselage.<ref>[http://www.jenoptik.com/en_30157_mrca_tornado_radome example of helicopter radome]</ref> In addition to protection, radomes also streamline the antenna system, thus reducing [[drag (physics)|drag]]. |
On rotary-wing and fixed-wing aircraft using microwave satellite for beyond-line-of-sight communication, radomes often appear as blisters on the fuselage.<ref>[http://www.jenoptik.com/en_30157_mrca_tornado_radome example of helicopter radome]</ref> In addition to protection, radomes also streamline the antenna system, thus reducing [[drag (physics)|drag]]. |
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==Use== |
==Use== |
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[[File:H2S Radome And Scanner On Halifax.jpg|thumb|260px|right|One of the first radomes |
[[File:H2S Radome And Scanner On Halifax.jpg|thumb|260px|right|One of the first radomes. The radome (top) covers the [[H2S (radar)|H2S radar]] system rotating antenna (bottom) on a [[Handley Page Halifax|Halifax]] bomber]] |
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A radome is often used to prevent ice and [[freezing rain]] from accumulating directly onto the metal surface of |
A radome is often used to prevent ice and [[freezing rain]] from accumulating directly onto the metal surface of antennae. In the case of a spinning radar [[parabolic antenna]], the radome also protects the antenna from debris and rotational irregularities due to wind. Its shape is easily identified by its hardshell, which has strong properties against being damaged. |
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===Stationary antennas=== |
===Stationary antennas=== |
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For stationary antennas, excessive amounts of ice can de-[[Tuner (radio)|tune]] the antenna to the point where its [[electrical impedance|impedance]] at the input [[frequency]] rises drastically, causing the [[standing wave ratio|voltage standing wave ratio]] (VSWR) to rise as well. This reflected power goes back to the [[transmitter]], where it can cause [[Thermal shock|overheating]]. A [[foldback (power supply design)|foldback]] [[electrical network|circuit]] can act to prevent this; however, one drawback of its use is that it causes the station's output power to drop dramatically, reducing its range. |
For stationary antennas, excessive amounts of ice can de-[[Tuner (radio)|tune]] the antenna to the point where its [[electrical impedance|impedance]] at the input [[frequency]] rises drastically, causing the [[standing wave ratio|voltage standing wave ratio]] (VSWR) to rise as well. This reflected power goes back to the [[transmitter]], where it can cause [[Thermal shock|overheating]]. A [[foldback (power supply design)|foldback]] [[electrical network|circuit]] can act to prevent this; however, one drawback of its use is that it causes the station's output power to drop dramatically, reducing its range. A radome avoids that by covering the antenna's exposed parts with a sturdy, weatherproof material, typically fiberglass, keeping debris or ice away from the antenna, thus preventing any serious issues. One of the main driving forces behind the development of fiberglass as a structural material was the need during [[World War II]] for radomes.<ref>[[J.E. Gordon|Gordon, J.E.]], The New Science of Strong Materials: 2nd Edition, Pelican, 1976.</ref> When considering structural load, the use of a radome greatly reduces wind load in both normal and iced conditions. Many tower sites require or prefer the use of radomes for wind loading benefits and for protection from falling ice or debris. |
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| ⚫ | Where radomes might be considered unsightly if near the ground, electric antenna heaters could be used instead. Usually running on [[direct current]], the heaters do not interfere physically or electrically with the [[alternating current]] of the radio [[transmission (telecommunications)|transmission]]. |
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A radome prevents that by covering the antenna's exposed parts with a sturdy, weatherproof material, typically [[fibreglass]], which keeps debris or ice away from the antenna to prevent any serious issues. One of the main driving forces behind the development of fibreglass as a structural material was the need during [[World War II]] for radomes.<ref>[[J.E. Gordon|Gordon, J.E.]], The New Science of Strong Materials: 2nd Edition, Pelican, 1976.</ref> When considering structural load, the use of a radome greatly reduces wind load in both normal and iced conditions. Many tower sites require or prefer the use of radomes for wind loading benefits and for protection from falling ice or debris. |
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| ⚫ | |||
===Radar dishes=== |
===Radar dishes=== |
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For radar dishes, a single, large, ball-shaped dome also protects the rotational mechanism and the [[sensitivity (electronics)|sensitive]] [[electronics]], and is heated in colder climates to prevent icing. |
For radar dishes, a single, large, ball-shaped dome also protects the rotational mechanism and the [[sensitivity (electronics)|sensitive]] [[electronics]], and is heated in colder climates to prevent icing. |
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The [[Menwith Hill]] electronic surveillance base, which includes over 30 radomes, is widely believed to regularly intercept [[satellite]] communications. At Menwith Hill, the radome enclosures have a further use in preventing observers from deducing the direction of the |
The [[RAF Menwith Hill]] electronic surveillance base, which includes over 30 radomes, is widely believed to regularly intercept [[satellite]] communications. At Menwith Hill, the radome enclosures have a further use in preventing observers from deducing the direction of the antennae, and therefore which satellites are being targeted. The same point was also made with respect to the radomes of the [[ECHELON]] facilities. |
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The |
The United States Air Force Aerospace Defense Command operated and maintained dozens of air defense radar stations in the contiguous United States and Alaska during the Cold War. Most of the radars used at these ground stations were protected by rigid or inflatable radomes. The radomes were typically at least {{convert|50|ft|m|abbr=on|order=flip}} in diameter and the radomes were attached to standardized radar tower buildings that housed the radar transmitter, receiver and antenna. Some of these radomes were very large. The CW-620 was a space frame rigid radome with a maximum diameter of {{convert|150|ft|m|order=flip|abbr=on}}, and a height of {{convert|84|ft|m|order=flip|abbr=on}}. This radome consisted of 590 panels, and was designed for winds up to {{convert|150|mph|km/h|order=flip|abbr=on}}. The total radome weight was {{convert|204,400|lb|kg|order=flip|abbr=on}} with a surface area of {{convert|39600|sqft|m2|order=flip|abbr=on}}. The CW-620 radome was designed and constructed by Sperry-Rand Corporation for the Columbus Division of North American Aviation. This radome was originally used for the FPS-35 search radar at Baker Air Force Station, Oregon. When Baker AFS was closed the radome was moved to provide a high-school gymnasium in Payette, Idaho. Pictures and documents are available online at [http://radomes.org/museum radomes.org/museum] for Baker AFS/821st Radar Squadron. |
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===Maritime satellites=== |
===Maritime satellites=== |
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[[File:KNS radomes.jpg|thumb|260px|right|A yacht fitted with small KNS tracking dishes for [[SES Broadband for Maritime]], protected by radomes]] For [[ |
[[File:KNS radomes.jpg|thumb|260px|right|A yacht fitted with small KNS tracking dishes for [[SES Broadband for Maritime]], protected by radomes]] For [[Freight transport|maritime]] [[Communications satellite|satellite communications]] service, radomes are widely used to protect dish antennas which are continually tracking fixed satellites while the ship experiences pitch, roll and yaw movements. Large cruise ships and oil tankers may have radomes over 3 m in diameter covering antennas for broadband transmissions for television, voice, data, and the Internet, while recent developments allow similar services from smaller installations such as the 85 cm motorised dish used in the [[SES Broadband for Maritime]] system. Small private yachts may use radomes as small as 26 cm in diameter for voice and low-speed data. |
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==Alternatives== |
==Alternatives== |
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==Notes== |
==Notes== |
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{{Reflist}} |
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<references/> |
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==External links== |
==External links== |
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Revision as of 23:06, 31 August 2017
 | This article needs additional citations for verification. (September 2011) |
A radome (which is a portmanteau of radar and dome) is a structural, weatherproof enclosure that protects a microwave or radar antenna. The radome is constructed of material that minimally attenuates the electromagnetic signal transmitted or received by the antenna. In other words, the radome is transparent to radar or radio waves. Radomes protect the antenna surfaces from weather and conceal antenna electronic equipment from public view. They also protect nearby personnel from being accidentally struck by quickly rotating antennae.
Radomes can be constructed in several shapes — spherical, geodesic, planar, etc. — depending on the particular application, using various construction materials, e.g., fiberglass, PTFE-coated fabric, etc.
When found on fixed-wing aircraft with forward-looking radar, as are commonly used for object or weather detection,[1] the nose cones often additionally serve as radomes. In case of advanced aircraft systems like airborne early warning and control (AEW&C), a rotating radome, often called a "rotodome", is mounted on the top of the fuselage for 360-degree coverage. There are newer AEW&C configurations, which instead uses three antenna modules in a triangular configuration inside a radome, usually mounted on top of the fuselage, for 360-degree coverage, such as the Chinese KJ-2000 and Indian DRDO AEW&Cs.
On rotary-wing and fixed-wing aircraft using microwave satellite for beyond-line-of-sight communication, radomes often appear as blisters on the fuselage.[2] In addition to protection, radomes also streamline the antenna system, thus reducing drag.
Use
A radome is often used to prevent ice and freezing rain from accumulating directly onto the metal surface of antennae. In the case of a spinning radar parabolic antenna, the radome also protects the antenna from debris and rotational irregularities due to wind. Its shape is easily identified by its hardshell, which has strong properties against being damaged.
Stationary antennas
For stationary antennas, excessive amounts of ice can de-tune the antenna to the point where its impedance at the input frequency rises drastically, causing the voltage standing wave ratio (VSWR) to rise as well. This reflected power goes back to the transmitter, where it can cause overheating. A foldback circuit can act to prevent this; however, one drawback of its use is that it causes the station's output power to drop dramatically, reducing its range. A radome avoids that by covering the antenna's exposed parts with a sturdy, weatherproof material, typically fiberglass, keeping debris or ice away from the antenna, thus preventing any serious issues. One of the main driving forces behind the development of fiberglass as a structural material was the need during World War II for radomes.[3] When considering structural load, the use of a radome greatly reduces wind load in both normal and iced conditions. Many tower sites require or prefer the use of radomes for wind loading benefits and for protection from falling ice or debris.
Where radomes might be considered unsightly if near the ground, electric antenna heaters could be used instead. Usually running on direct current, the heaters do not interfere physically or electrically with the alternating current of the radio transmission.
Radar dishes
For radar dishes, a single, large, ball-shaped dome also protects the rotational mechanism and the sensitive electronics, and is heated in colder climates to prevent icing.
The RAF Menwith Hill electronic surveillance base, which includes over 30 radomes, is widely believed to regularly intercept satellite communications. At Menwith Hill, the radome enclosures have a further use in preventing observers from deducing the direction of the antennae, and therefore which satellites are being targeted. The same point was also made with respect to the radomes of the ECHELON facilities.
The United States Air Force Aerospace Defense Command operated and maintained dozens of air defense radar stations in the contiguous United States and Alaska during the Cold War. Most of the radars used at these ground stations were protected by rigid or inflatable radomes. The radomes were typically at least 15 m (50 ft) in diameter and the radomes were attached to standardized radar tower buildings that housed the radar transmitter, receiver and antenna. Some of these radomes were very large. The CW-620 was a space frame rigid radome with a maximum diameter of 46 m (150 ft), and a height of 26 m (84 ft). This radome consisted of 590 panels, and was designed for winds up to 240 km/h (150 mph). The total radome weight was 92,700 kg (204,400 lb) with a surface area of 3,680 m2 (39,600 sq ft). The CW-620 radome was designed and constructed by Sperry-Rand Corporation for the Columbus Division of North American Aviation. This radome was originally used for the FPS-35 search radar at Baker Air Force Station, Oregon. When Baker AFS was closed the radome was moved to provide a high-school gymnasium in Payette, Idaho. Pictures and documents are available online at radomes.org/museum for Baker AFS/821st Radar Squadron.
Maritime satellites
For maritime satellite communications service, radomes are widely used to protect dish antennas which are continually tracking fixed satellites while the ship experiences pitch, roll and yaw movements. Large cruise ships and oil tankers may have radomes over 3 m in diameter covering antennas for broadband transmissions for television, voice, data, and the Internet, while recent developments allow similar services from smaller installations such as the 85 cm motorised dish used in the SES Broadband for Maritime system. Small private yachts may use radomes as small as 26 cm in diameter for voice and low-speed data.
Alternatives
An active electronically scanned array is a form of radar installation that has no moving parts as such and in ground based installations a radome is not necessary. An example of this is the "pyramid" which replaced the "tourist attraction" golfball-style radome installations at RAF Fylingdales.
Notes
- ^ example of dented radome
- ^ example of helicopter radome
- ^ Gordon, J.E., The New Science of Strong Materials: 2nd Edition, Pelican, 1976.
External links
- Photograph of Mount Hebo while active overlooking Pacific Ocean
