Satellite dish
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A satellite dish is a dish-shaped type of
History
Parabolic antennas referred to as "dish" antennas had been in use long before satellite television. The term satellite dish was coined in 1978 during the beginning of the satellite television industry, and came to refer to dish antennas that send and/or receive signals from communications satellites. Taylor Howard of San Andreas, California, adapted an ex-military dish in 1976 and became the first person to receive satellite television signals using it.[1]
The first satellite television dishes were built to receive signals on the
Satellite dishes made of
In the early 1990s, four large American cable companies founded
Principle of operation
The
The theoretical gain (
With lower frequencies, C-band for example, dish designers have a wider choice of materials. The large size of dish required for lower frequencies led to the dishes being constructed from metal mesh on a metal framework. At higher frequencies, mesh type designs are rarer though some designs have used a solid dish with perforations.
A common misconception is that the
Modern dishes intended for home television use are generally 43 cm (18 in) to 80 cm (31 in) in diameter, and are fixed in one position, for Ku-band reception from one orbital position. Prior to the existence of direct broadcast satellite services, home users would generally have a motorised C-band dish of up to 3 m in diameter for reception of channels from different satellites. Overly small dishes can still cause problems, however, including rain fade and interference from adjacent satellites.
Europe
In
Systems design
In a single receiver residential installation there is a single
Satellite finder
A satellite finder (or sat finder) is a satellite field strength meter used to accurately point satellite dishes at communications satellites in geostationary orbit.[14][15][16] Professional satellite finder meters allow better dish alignment and provide received signal parameter values as well.
Types
Motor-driven dish
A dish that is mounted on a pole and driven by a
Motor-driven dishes come in a variety of sizes, but a dish of at least 120 centimetres (47 in) is required to receive signals from distant satellites which are intended to serve other areas.[citation needed]
With DiSEqC and USALS, the satellite dish will automatically aim itself at one of sixteen satellites programmed in previously when pressing one of the channel buttons on the remote.[citation needed] Motor-driven satellite dishes using USALS can detect other satellites in a constellation after one has been found and aimed at.[citation needed]
Most receivers sold at present[when?] are compatible with USALS and DiSEqC 1.0 and 1.2.
Multi-satellite
Every standard-size dish enables simultaneous reception from multiple different satellite positions without re-positioning the dish, just by adding additional LNB or using special duo LNB, or triple- or four-feed monoblock LNB.
However, some designs much more effectively optimize simultaneous reception from multiple different satellite positions without re-positioning the dish. The vertical axis operates as an off-axis concave parabolic concave hyperbolic[clarification needed] Cassegrain reflector, while the horizontal axis operates as a concave convex[clarification needed] Cassegrain. The spot from the main dish wanders across the secondary, which corrects astigmatism by its varying curvature. The elliptic aperture of the primary is designed to fit the deformed illumination by the horns. Due to double spill-over, this makes more sense for a large dish.
Switching between satellites is possible by using DiSEqC switches added to a satellite installation, or built-in Duo LNBs or Monoblock LNBs.
Most receivers sold presently[when?] are compatible with at least DiSEqC 1.0, which can switch automatically between 4 satellites (all of contemporary Monoblock LNBs) as the user changes channels using the remote control.
DiSEqC 1.1 allows for switching automatically between 16 satellite positions or more (through cascading switches).
Motor-driven dishes assure better optimal focusing for the given dish size; LNB is always in central alignment with the broadcasting satellite, but DiSEqC switches are faster than DiSEqC motors as no physical movement is required.[citation needed]
VSAT
A common type of dish is the
Homemade dishes
Any metal surface which concentrates a significant fraction of the reflected microwaves at a focus can be used as a dish antenna, at a lower
Others
- Individual dishes serving one dwelling: Direct to Home (DTH).
- Collective dishes, shared by several dwellings: satellite master antenna television (SMATV) or communal antenna broadcast distribution (CABD).
- Automatic Tracking Satellite Dish
Gallery
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General Electric satellite dish for DirecTV satellite television.
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Sky "minidish".
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Satellite dishes installed on an apartment complex.
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The back side of an old C-band satellite dish showing the pole, mount, motor, and structure of the dish.
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Satellite dishes above CCTV Headquarters.
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A WWE HD satellite truck in a parking lot.
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Satellite dish at a hut in East Timor
See also
- USALS = Universal Satellites Automatic Location System
- DiSEqC = Digital Satellite Equipment Control
- SAT>IP end user consumer equipment that can switch different ip streams from different SAT>IP servers and facilitates selection of reception from different satellites
- Satellite television
- Set-top box
- Parabolic reflector
- Low-noise block converter
- Automatic Tracking Satellite Dish
- Starlink Dish
References
- New York Times. Retrieved 19 July 2014.
- ISBN 9780879728212. Retrieved 1 July 2014.
- ^ Giarrusso, Michael (28 July 1996). "Tiny Satellite Dishes Sprout in Rural Areas". Los Angeles Times. Los Angeles. Retrieved 1 July 2014.
- ^ Nye, Doug (14 January 1990). "SATELLITE DISHES SURVIVE GREAT SCRAMBLE OF 1980S". Deseret News. Salt Lake City: Deseret News. Retrieved 30 June 2014.
- Baltimore, MD: The Baltimore Sun. Retrieved 1 July 2014.
- ^ a b Somerfield, Harry (30 September 1990). "Satellite dishes getting smaller, sharper in future". The Tuscaloosa News. Tuscaloosa, Alabama. Retrieved 7 August 2014.
- ^ a b "ASTRA 1A Satellite details 1988-109B NORAD 19688". N2YO. 9 July 2014. Retrieved 12 July 2014.
- ^ a b Barber, Dave (18 August 1995). "500,000 families already made PRIMESTAR their choice in satellite TV". Bangor Daily News. Bangor, Maine. Retrieved 7 August 2014.
- ISBN 978-0-240-81475-9.
- ^ Evangelista, Benny (10 November 2003). "Satellite TV in the car, on the move / New technology makes dish receivers small enough to fit atop an SUV". San Francisco Chronicle. San Francisco. Retrieved 7 August 2014.
- ^ "Rain fade: satellite TV signal and adverse weather". Dish-cable.com. 2010. Retrieved 16 July 2014.
- ^ "Team develops in-car satellite TV". University of Waterloo. 2006-05-06. Archived from the original on May 14, 2006. Retrieved 2008-04-29.
- ^ "News 24 STILL gets an F for physics". Retrieved 2008-04-29.
- ^ "How to use a signal meter correctly - Satellite for caravans".
- ^ Murray, Richard. "How to use a sat 'finder'".[permanent dead link]
- ^ "SATELLITE FINDER METER - Winegard" (PDF).