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Tvro

Television receive-only, TVRO, big ugly dish (BUD), is a term used in North America to refer to the reception of satellite television from FSS-type satellites, generally on C-band analog; free-to-air and unconnected to a commercial DBS provider. TVRO systems rely on feeds being transmitted unencrypted and using open-standards, which heavily contrasts to DBS systems in the region.

The term is rarely used in recent times due to the general move towards pay television and subscription-based DBS services like DirecTV, Dish Network, Bell TV, and Sky TV, although it is still sometimes used to refer to receiving digital TV "backhaul" feeds from FSS-type satellites.

TVRO was once the sole, and later the main means of consumer satellite reception in the United States, until the mid-1990s and the arrival of services such as PrimeStar, USSB, DirecTV, and Dish Network. While these services are at least theoretically based on open standards (DVB-S, MPEG-2, MPEG-4), the majority of services are encrypted and require proprietary decoder hardware.

Reception of free-to-air satellite signals, generally Ku band Digital Video Broadcasting, for home viewing is still common in Europe, India and Australia, although the TVRO nomenclature was never used there.

Free-to-air satellite signals are also very common in the People's Republic of China, as many rural locations cannot receive cable television and solely rely on satellites to deliver television signals to individual homes.

Big ugly dish

A C-band dish (often given as BUD, for "big ugly dish") is a colloquial name for a TVRO satellite dish used to receive satellite television signals from FSS-type satellites on the microwave C band. BUDs are usually 6½ to 12 feet or two to 3.5 meters in diameter, and have been a source of much consternation (even local zoning disputes) due to their perception as an eyesore. Neighborhoods with restrictive covenants usually prohibit this size of dish, except where such restrictions are illegal.[1]

History

BUDs were originally marketed in the late 1970s, with the earliest dishes being made of solid fiberglass and later models being made of wire mesh and solid steel or aluminum. Fiberglass dishes are most commonly found on low rise commercial buildings, while the wire mesh counterparts are typically found on residential buildings. BUD systems of the time came at a high cost, usually several thousand dollars.

They work by receiving a low-power C-Band (3.7-4.2 GHz) frequency-modulated analog television signal directly from the original distribution satellite — the same signal received by cable-company headends. Because analog channels took up an entire transponder on the satellite, and each satellite had a fixed number of transponders, dishes were usually equipped with a polar mount and actuator to sweep the dish across the horizon to receive channels from multiple satellites. Switching between horizontal and vertical polarization was accomplished by a small electric servo motor which moved a probe inside the feedhorn throat at the command of the receiver (commonly called a "polarotor" setup). Higher-end receivers did this transparently, switching polarization and moving the dish automatically as the user changed channels.

Originally, all channels could be received in the clear (ITC) and free of charge. In 1986, HBO began using the now-obsolete VideoCipher system to encrypt their channels. This met with much protest from owners of big-dish systems, most of which had no other option at the time for receiving such channels. Eventually HBO allowed dish owners to subscribe directly to their service, although at a price much higher ($12.95/month) than what cable subscribers were paying. This led to the 1986 attack on HBO's transponder on Galaxy 1 by Captain Midnight. One by one, all commercial channels followed HBO's lead and began encrypting their channels. Analogue encryption using VideoCipher and VideoCipher II could be defeated, and there was a black market for illegal descramblers. In the mid-1990s, channels began moving their broadcasts to digital TV transmission using DigiCipher scrambling and conditional access.

In addition to encryption, DBS services such as PrimeStar had been reducing the popularity for BUDs since the early 1990s. Signals from DBS satellites (operating in the more recent Ku band) are higher in both frequency and power (due to improvements in the solar panels and energy efficiency of modern satellites) and therefore require much smaller dishes than C band, and the digital signals now used require far less signal strength at the receiver, resulting in a lower cost of entry. Each satellite also can carry up to 32 transponders in the Ku band, but only 24 in the C band, and several digital subchannels can be multiplexed (MCPC) or carried separately (SCPC) on a single transponder. General advancements in noise abatement have also had an effect. However, a consequence of the higher frequency used for DBS services is rain fade where viewers lose signal during a heavy downpour. C-Band's immunity to rain fade is one of the major reasons the BUD is still used as the preferred method for television broadcasters to distribute their signal.

Popularity

BUDs were most popular in rural areas, beyond the broadcast range of most local TV stations. The mountainous terrain of West Virginia, for example, makes reception of over-the-air television broadcasts (especially in the higher UHF frequencies) very difficult. From the 1970s to the early 1990s DBS systems weren't available, and cable TV systems of the time only carried a few channels, resulting in a boom in sales of BUDs in the area, which led to the systems being termed the "West Virginia state flower". The term was regional, known mostly to those living in West Virginia and surrounding areas. Support for BUDs dried up when strong encryption was introduced around 1994. Many long-disconnected BUDs still occupy their original spot. Due to the number of systems in existence, their lack of usefulness, and because many people consider them an eyesore, used BUDs can be purchased for very little money.

Current uses

Most of the free analogue channels that BUDs were built to receive have been taken offline.

As of 2009, there are 23 C-band satellites and 38 Ku/Ka band satellites.[2]

There are over 150 channels for people who want to receive subscription channels on a C-band dish via Motorola's Skyvision.

The dishes themselves can be modified to receive free-to-air and DBS signals. The stock LNBs fitted to typical BUDs will usually need to be replaced with one of a lower noise temperature to receive digital broadcasts. With a suitable replacement LNB (provided there is no warping of the reflector) a BUD can be used to receive free-to-air (FTA) and DBS signals. Several companies market LNBs, LNBFs, and adaptor collars for big-dish systems. For receiving FTA signals the replacement should be capable of dual C/Ku reception with linear polarization, for DBS it will need a high band Ku LNBF using circular polarization. Older mesh dishes with perforations larger than 5mm are inefficient at Ku frequencies, because the smaller wavelengths will pass through them. Solid fiberglass dishes usually contain metal mesh with large-diameter perforations as a reflector and are usually unsuitable for anything other than C band.

Large dishes have higher antenna gain, which can be an advantage when used with DBS signals such as Dish Network and DirecTV, virtually eliminating rain fade. Restored dishes fitted with block upconverters can be used to transmit signals as well. BUDs can still be seen at antenna farms for these reasons, so that video and backhauls can be sent to and from the TV network with which a station is affiliated, without interruption due to inclement weather. BUDs are also still useful for picking-up weak signals at the edge of a satellite's broadcast "footprint" — the area at which a particular satellite is aimed. For this reason, BUDs are helpful in places like Alaska, or parts of the Caribbean.

Modern equivalents

Large Typical uses for these systems include receiving free-to-air and subscription services.

TVRO on Ships

The term TVRO has been in use on ships since it was introduced in the 1980s. One early provider of equipment was SeaTel with its first generation of stabilized satellite antennas that was launched in 1985, the TV-at-Sea 8885 system. Until this time ships had not been able to receive TV signals from satellites due to their rocking motion rendering reception impossible. The SeaTel antenna however was stabilized using electrically driven gyroscopes and thus made it possible to point to the satellite accurately enough, that is to within 2 degrees, in order to receive a signal. The successful implementation of stabilised TVRO systems on ships immediately led to the development of maritime VSAT systems. The second generation of SeaTel TVRO systems came in 1994 and was the 2494 antenna, which got its gyro signal from the ship rather than its own gyros, improving accuracy and reducing maintenance.

As of 2010 SeaTel continues to dominate the market for stabilized TVRO systems and has according to the Comsys group, a market share of 75%. Other established providers of stabilised satellite antennas are Intellian, KNS, Orbit and KVH.

See also

References

External links

  • rec.video.satellite.tvro FAQ
  • Broadcast Engineering (magazine) - Satellite TVRO
  • Part 4
  • C/Ku Band Satellite Systems - Tuning, Tracking...
  • How to set up and align a BUD
  • US satellite TV subscription provider for BUDs
  • Canadian satellite TV subscription provider for BUDs
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