Cable television
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"Cable TV" redirects here. For the Hong Kong-based cable television network, see Cable TV Hong Kong.
"Premium TV" redirects here. For other uses, see Premium TV (disambiguation).
Coaxial cable is often used to transmit cable television into the house. The RG-59 comes from an obsolete military term Radio Grade, the number following refers to the grade of the cable.Cable television is a system of providing television to consumers via radio frequency signals transmitted to televisions through fixed optical fibers or coaxial cables as opposed to the over-the-air method used in traditional television broadcasting (via radio waves) in which a television antenna is required. FM radio programming, high-speed Internet, telephony, and similar non-television services may also be provided.
The abbreviation CATV was often used to mean "Cable TV". It originally stood for Community Antenna Television, from cable television's origins in 1948: in areas where over-the-air reception was limited by mountainous terrain, large "community antennas" were constructed, and cable was run from them to individual homes.
It is most commonplace in North America, Europe, Australia and East Asia, though it is present in many other countries, mainly in South America and the Middle East. Cable TV has had little success in Africa, as it is not cost-effective to lay cables in sparsely populated areas. So-called "wireless cable" or microwave-based systems are used instead.
Contents [hide]
1 Cable television deployments
1.1 Asia
1.1.1 Mongolia
1.1.2 Taiwan
1.1.3 China (Mainland)
1.1.4 Hong Kong
1.1.5 India
1.1.6 Indonesia
1.1.7 Israel
1.1.8 South Korea
1.1.9 Malaysia
1.1.10 Maldives
1.1.11 Philippines
1.1.12 Singapore
1.1.13 Sri Lanka
1.1.14 Thailand
1.2 Europe
1.2.1 Belgium
1.2.2 Cyprus
1.2.3 Czech Republic
1.2.4 Greece
1.2.5 Italy
1.2.6 Macedonia
1.2.7 Latvia
1.2.8 Romania
1.2.9 Republic of Ireland
1.2.10 Switzerland
1.2.11 United Kingdom
1.3 North America
1.3.1 Canada
1.3.2 Caribbean
1.3.3 Mexico
1.3.4 United States
1.4 Oceania
1.4.1 Australia
1.4.2 New Zealand
1.5 South America
1.5.1 Argentina
1.5.2 Brazil
1.5.3 Ecuador
2 Other cable-based services
3 Consumer issues
4 See also
5 References
6 External links
[edit] Cable television deployments
[edit] Asia
[edit] Mongolia
There are several cable tv providers in Mongolia, main of which are "SuperVision", "Hiimori" and "Sansar CATV". All three cover approximately 10 national channels and plus above 40 foreign channels, such as CNN, BBC, NHK etc.. Among them "SuperVision" is known for its superior quality and give much more interesting channels, as National Geographic, Discovery, whereas "Sansar" and "Hiimori" and other smaller companies full their channel list with Chinese and Indian channels.
[edit] Taiwan
See also: Television in the Republic of China and Digital television in Taiwan
Taiwan currently has more than 80 cable television channels. Taiwan's main cable provider is Chunghua Telecom (中華電信).
[edit] China (Mainland)
See also: Television in the People's Republic of China and Digital television in China
Cable television in the usual transmission method in all urban areas of mainland China - television aerials are an extremely rare sight. Cable systems usually carry all the CCTV channels in Mandarin, plus all the channels of municipal, provincial or regional station in question (such stations are listed here).
[edit] Hong Kong
See also: Television in Hong Kong and Digital Television in Hong Kong
Only one traditional cable provider operates in Hong Kong, i-Cable Communications Limited (branded as "CableTV"). Another three operators offer pay-TV via DSL and Ethernet, which are now Broadband TV (PCCW), HKBN Digital TV and TVB PayVision.
Many people in Hong Kong subscribe to satellite TV services like STAR TV.
[edit] India
India has over 130 million homes with television sets, of which nearly 71 million have access to cable TV. The overall Cable TV market is growing at a robust 8-10%.[1] The cable TV industry exploded in the early 1990s when the broadcast industry was liberalized, and saw the entry of many foreign players like Rupert Murdoch's Star TV Network in 1991, MTV, and others. The emergence and notification of the HDVSL standard as a home grown Indian digital cable standard is likely to open an era of interactivity on cable networks.
Sun TV (India) was launched in 1992 as the first private channel in South India. Today it has 20 television channels in the four South Indian languages - Kannada, Malayalam, Tamil and Telugu. Channels of the Sun TV network are also available outside of India. Recently Sun TV launched a DTH service.
The Raj Television Network was started in 1994 and continues to be an important player in the South Indian cable TV provider space.
[edit] Indonesia
Kabelvision was the first cable television operator which started its operation in 1995. In 2006, its holding company launches Digital 1, the latest cable television operator that requires a digital setup box to be installed. Some of Kabelvision network was later converted to Digital 1. In 2007, the holding company of the two cable television operator rebranded the two services as First Media home cable which incorporates Digital 1 technology. The company is owned by Lippo Group PART OF BDM SOLUTIONS BANGALORE INDIA. The company now operates under the Firstmedia brand www.firstmedia.com
[edit] Israel
Main article: Hot (Israel)
[edit] South Korea
There are many cable operators in South Korea, such as Tbroad, C&M, and CJ. The cable TV subscriber is approximately 14 million. The cable operator provides TPS to its subscribers.
[edit] Malaysia
Mega TV was launched in 1996 by TV3 as the only cable television service. However, it failed to expand its content, and so, had to close down in 2001, and was replaced by its competitor, the satellite television network Astro.
[edit] Maldives
There over 100 cable TV operators across the country. As the population of the Maldives is separated across around 200 inhabited islands, there is a cable TV operator for nearly every island. Media Net Pvt. Ltd. is the country's largest cable TV operator. Media Net is a Male-based cable TV operator that provides cable and MMDS service to five islands near Male. Media Net holds the license of distribution for 41 channels and distributes channels to nearly all the operators of the country. In Maldives, cable TV subscribers can get most premium channels available in Asia.
[edit] Philippines
In Metro Manila, SkyCable and Global Destiny are the primary cable operators. SkyCable also has provincial affiliates, which carry the former's brand and programming may vary from the one provided in Metro Manila.
In 2006, digital cable was launched. This not only made additional channels possible but also pre-paid cable service. Both companies also offer cable internet where cable television is bundled either free or at a discount.
Besides cable, direct-to-home satellite is offered through Dream Television and has pre-paid variants as well.
[edit] Singapore
StarHub TV is the sole cable television operator in Singapore, where private ownership of satellite dishes is banned. StarHub Cable Vision was formed as a result of a merger between StarHub and Singapore Cable Vision on 15 May 2002. The latter first began broadcasting as a terrestrial pay-television operator in 1992 as the first cable network was not completed until 1995. Around 15% of households and offices in Singapore are connected to the StarHub network.
[edit] Sri Lanka
Lanka Broadband Networks pay television broadcaster using cable networks to serve 10,000 customers.
Southern Broadband Networks (Pvt) Ltd television broadcaster using cable networks
[edit] Thailand
TrueVisions[2] is the only exclusive CATV in Thailand, formerly known as UBC (United Broadcasting Corporation). True Visions is a subsidiary of True[3], provides CATV only in Bangkok area while operate DSTV (Digital Satellite TV) outside Bangkok.
[edit] Europe
According the European Audiovisual Observatory, there were 58 million cable households in the European Union as of 31 December 2004, i.e. a rate of penetration of 32 % of the television households. 5.7 millions were connected to digital networks.
[edit] Belgium
Main article: Television in Belgium
Belgium is the second most dense cabled country in the world after the Netherlands with over 99% of all households connected to cable television networks. The first networks were built in 1960 in Namur and the Liege region. In 1972, cable television was deployed nationwide as a measure made by the government to eliminate the millions of antennas. Currently most cable companies are active on the triple-play market, offering television, telephone and internet services. Currently the analogue services are phased out to make way for digital television services and high definition television.
[edit] Cyprus
Cablenet in Cyprus offers cable television and cable internet through a Hybrid fibre-coaxial network in a few areas of big cities, mainly the capital Nicosia.
[edit] Czech Republic
See also: Television in the Czech Republic
The major cable operator is UPC Czech Republic.
[edit] Greece
Since 2006, 2 companies distribute cable television in Greece. Those companies are Vivodi and On telecoms. Cable television in Greece provides public, private, and some satellite and local channels. Greek cable tv also includes video on demand (VOD) and both distributors also provide triple play. The service is based on IPTV over ADSL2+ and only available in Athens.
[edit] Italy
See also: Television in Italy
In the 60's the public television network RAI was a monopolist and the only authorized to broadcast in Italy, so were tested the first systems television broadcasting on coaxial cable. Afterwards was approved a new law to regulate and allow the cable broadcasting but with many limitations [4] : only one cable system for every city and only one TV channel for each system.
[edit] Macedonia
Macedonia has consolidated its 15 cable channels into a single provider called LynxTV. HDTV in Macedonia is expected in the beginning of 2009. The penetration for cable television in Macedonia is high rated with 67% of all households. The Macedonian Broadcasting Council gave a warning to Telekabel and CableTEL to remove the Serbian and Bulgarian subtitles of the foreign channels and to add Macedonian subtitles. Till the end of July more than 6 foreign channels will be transmitted with Macedonian subtitle. The internet which is offered from the cable providers is fast and cheap. The cable tax is also very cheap and it costs 350 denars or 5 euros.
[edit] Latvia
IZZI, Baltcom TV, Livas and Lattelecom is largest cable operators in Latvia.
[edit] Romania
See also: Television in Romania
Romania has very high penetration rates for cable television in Europe, with over 79% of all households watching television through a CATV network in 2007.[5] The market is extremely dynamic, and dominated by two giant companies - Romanian based RCS&RDS and U.S. based UPC-Astral.
[edit] Republic of Ireland
Main article: Cable television in the Republic of Ireland
[edit] Switzerland
See also: Television in Switzerland
A vast majority of the country is covered by cable networks; the major cable operators are Naxoo, Teleclub and Cablecom.
In 2007 the OFCOM applied a must-carry regulation, requiring the local cable companies to transmit all the SRG SSR network stations and the following foreign channels: arte, 3sat, Euronews, TV5MONDE, ARD, ORF1, France 2, Rai Uno
[edit] United Kingdom
It has been suggested that this section be split into a new article. (Discuss)
When the infant BBC Television service was started in 1932, Rediffusion, which had supplied cable radio services since 1928, started providng "Pipe TV" to its customers who had difficulties tuning into the weak TV broadcast signal.
The service was suspended during World War II, and when it was re-established in June 1946, it had only one transmitter, at Alexandra Palace, which served the London area. From the end of 1949, new transmitters were steadily opened to serve other major conurbations, and then smaller areas of population. The areas on the fringes of the transmitter coverage provided an opportunity for Rediffusion and other commercial companies to expand cable systems to enlarge the viewing audience for the one BBC television channel which then existed. The first was in Gloucester in 1950 and the process gathered pace over the next few years, especially after a second television channel, ITV, was launched in 1955 to compete with the BBC. By the late 1970s, two and a half million British homes received their television service via cable.
By law, these cable systems were restricted to the relay of the public broadcast channels, which meant that as the transmitter network became more comprehensive the incentive to subscribe to cable was reduced and they began to lose customers. In 1982, a radical liberalisation of the law on cable was proposed by the Information Technology Advisory Panel, for the sake of promoting a new generation of broadband cable systems leading to the wired society. After setting up and receiving the conclusions of the Hunt Inquiry into Cable Expansion and Broadcasting Policy, the Government decided to proceed with liberalisation and two pieces of legislation: the Cable and Broadcasting Act and the Telecommunications Act, were enacted in 1984.
The result was that cable systems were permitted to carry as many new television channels as they liked, as well as providing a telephone service and interactive services of many kinds (as since made familiar by the Internet). To maintain the momentum of the perceived commercial interest in this new investment opportunity, in 1983 the Government itself granted eleven interim franchises for new broadband systems each covering a community of up to around 100,000 homes, but the competitive franchising process was otherwise left to the new regulatory body, the Cable Authority, which took on its powers from 1 January 1985.
The franchising process proceeded steadily, but the actual construction of new systems was slow, as doubts about an adequate payback from the substantial investment persisted. By the end of 1990 almost 15 million homes had been included in franchised areas, but only 828,000 of these had been passed by broadband cable and only 149,000 were actually subscribing. Thereafter, however, construction accelerated and take-up steadily improved.
The first new television channels launched for carriage on cable systems (going live in March 1984) were Sky Channel, Screensport, Music Box and TEN - the Movie Channel. Others followed, some were merged or closed down, but the range expanded. A similar flux was seen among the operators of cable systems: franchises were granted to a host of different companies, but a process of consolidation saw the growth of large multiple system operators, until by early in the 2000s virtually the whole industry was in the hands of two companies, NTL and Telewest.
In 2005 it was announced that NTL and Telewest would merge, after a period of co-operation in the preceding few years. This merger was completed on 3 March 2006 with the company being named ntl Incorporated. For the time being the two brand names and services were marketed separately. However, following NTL's acquisition of Virgin Mobile, the NTL and Telewest services were rebranded Virgin Media on 2007-02-08 creating a single cable operator covering more than 95% of the UK cable market.
There are a small number of other surviving cable television companies in the UK outside of NTL including WightCable (Isle of Wight) and Smallworld (Ayrshire, Carlisle and Lancashire).
Cable TV faces intense competition from British Sky Broadcasting's Sky Digital satellite television service. Most channels are carried on both platforms. However, cable often lacks "interactive" features (e.g. text services, and extra video-screens), especially on BSkyB owned channels, and the satellite platform lacks services requiring high degrees of two-way communication, such as true video on demand.
However, subscription-funded digital terrestrial television proved less of a competitive threat. The first system, ITV Digital, went into liquidation in 2002. Top Up TV later replaced it, however this service is shrinking as the DVB-T multiplex owners are finding FTA broadcasting more profitable.
Another potential source of competition in the future will be TV over broadband internet connections; this is known as IPTV. Some IPTV services are currently available in London, while services operated in Hull ceased in April 2006. As the speed and availability of broadband connections increase, more TV content can be delivered using protocols such as IPTV. However, its impact on the market is yet to be measured, as is consumer attitude toward watching TV programmes on computers instead of television sets. At the end of 2006, BT (the UK's former state owned monopoly phone company) started offering BT Vision, which combines the digital free-to-air standard Freeview through an aerial, and on-demand IPTV, delivered over a BT Broadband connection through the Vision set-top box (BT have chosen to deploy Microsofts Mediaroom platform for this.)
[edit] North America
[edit] Canada
Main article: Multichannel television in Canada
[edit] Caribbean
Main article: List of Caribbean television channels
The Caribbean region has a variety of single island cable television companies. The largest multi-island provider in the region however is Columbus Communications, which currently has operations in Jamaica, The Bahamas, and Trinidad and Tobago. The company also owns the ARCOS undersea fiber optics network spanning 20 countries in the Caribbean, Central America, and South America.
[edit] Mexico
The first cable system started to operate in the early 1960s in Monterrey, as a CATV service (an antenna at the top of the Loma Larga, which could get TV signals from South Texas). Most of the other major cities didn't develop cable systems until the late 1980s, due to government censorship. By 1989, the industry had had a major impulse with the founding of Multivisión—a MMDS system who started to develop its own channels in Spanish—and the later development of companies such as Cablemas and Megacable.
Over the past few years, many US networks have started to develop content for the Latin American market, such as CNN en Español, MTV, Cartoon Network, Disney Channel, Nickelodeon, and others. The country also has a DTH service called SKY (Televisa & News Corp. owned). Recently DirecTV merged with Sky. The dominant company nowadays is Megacable and Grupo HEVI.[6]
[edit] United States
The large majority of American television viewers get their signal from CATV.
Main article: Cable television in the United States
[edit] Oceania
[edit] Australia
Cable television services have been available in Australia since 1991 or 1992, with Galaxy TV being the first. It became insolvent in 1997, due to decreasing popularity with the launching of Foxtel and Austar in May 1995, two cable services that offered more variety than Galaxy TV. Foxtel immediately commenced in supplying programming to Galaxy's subscribers on an interim basis. In 1999 Foxtel was able to significantly boost its customer base by acquiring Galaxy TV's subscribers from the Australis Media liquidator and commenced offering its services on a satellite television platform. There are currently two major and four minor cable television providers in Australia - Foxtel and Optus TV. Minor providers include Austar, TransACT, and Neighbourhood Cable, which only operate in limited areas.
Inside the capital cities, cable is the more predominant form of pay television distribution. In regional areas or in new or outskirted areas of cities, satellite is far more common.
Due to its history, financial backing and market dominance, most local versions of channels are either owned directly by Foxtel and Austar or through related companies.
In terms of coverage, Foxtel's cable network covers parts of Sydney, Melbourne, Brisbane, Adelaide, and Perth. Optus's network covers small parts of Sydney, Melbourne, and Brisbane, though its restrictive subscription rules means that many people living in apartments or confined living areas may be unable to be connected.
Austar is available by satellite in most of regional and rural Australia, but does have a small cable network in the city of Darwin. TransACT is only available in the city of Canberra, where a custom cable network was developed. A similar situation used to exist in Perth where a small area was covered by Bright Telecommunications (however they closed down after lack of funding) as well in parts of Geelong, Ballarat and Mildura that are reached by Neighbourhood Cable.
[edit] New Zealand
TelstraClear operates a cable television network in Wellington, Kapiti and Christchurch. Customers can subscribe to plans incorporating between 25 and 95 channels. Most content is offered on behalf of Sky Network Television, however, some channels such as TBN, Discovery Travel & Living and Deutsche Welle are broadcast exclusively through TelstraClear.
[edit] South America
[edit] Argentina
Cable television had its origins in the 1960s, when a CATV service started to operate in Junín, Buenos Aires.
In the 1980s cable operators started operations in the absence of local regulations. Those earlier operators started a merged process which evolved toward the merge of Cablevision and Multicanal, the two biggest cable companies. The resultant company, named Cablevision, is owned by Grupo Clarin, the biggest newspaper in Argentina, who is also the owner of LS85-TV (the highest-rated TV station in Buenos Aires) TyC the owner of the monopoly of the soccer TV broadcast right, thus turning into the dominant player.
Some small TV cable companies are operating, but the tendency now is that Cablevision will dominate this market in the future. Telecom Operator, Telefonica and Telecom, the monopoly in the fixed-cellular market is lobbying for opening the market towards the triple play. The Government is opening a window to allow the cable operators to enter in the telephony and extend internet coverage, before fully deregulating this market.
In order to operate as a cable company in Argentina, a license from Comfer is required. This license is very difficult to get.
[edit] Brazil
Cable television is distributed in Brazil by various companies, it is:
All Brazil and São Paulo Digital TV
NET Cable TV (Organizações Globo)
NET Digital TV (Organizações Globo)
Globo SAT (Organizações Globo)
SKY(***) (The DirecTV Group)
DirecTV(***) (The DirecTV Group)
Only in São Paulo
TVA Cable (Abril Group Viacom)
TVA Digital (Abril Group Viacom)
VocêTV (Telefônica Digital TV LTDA)
Vivax Cable TV (Organizações Globo LTDA)
Alphaville Cable TV (Silvio Santos Group LTDA)
Assis
TvCassis
(***)SKY and DirecTV are together since 2007.
[edit] Ecuador
The dominant company nowadays is Grupo TVCable.[7]
[edit] Other cable-based services
Coaxial cables are capable of bi-directional carriage of signals as well as the transmission of large amounts of data. Cable television signals use only a portion of the bandwidth[8] available over coaxial lines. This leaves plenty of space available for other digital services such as broadband internet and cable telephony.
Broadband internet is achieved over coaxial cable by using cable modems to convert the network data into a type of digital signal that can be transferred over coaxial cable. One problem with some cable systems is the older amplifiers placed along the cable routes are unidirectional thus in order to allow for uploading of data the customer would need to use an analog telephone modem to provide for the upstream connection. This limited the upstream speed to 31.2k and prevented the always-on convenience broadband internet typically provides. Many large cable systems have upgraded or are upgrading their equipment to allow for bi-directional signals, thus allowing for greater upload speed and always-on convenience, though these upgrades are expensive.
In North America, Australia and Europe many cable operators have already introduced cable telephone service, which operates just like existing fixed line operators. This service involves installing a special telephone interface at the customer's premises that converts the analog signals from the customer's in-home wiring into a digital signal, which is then sent on the local loop (replacing the analog last mile, or POTS) to the company's switching center, where it is connected to the PSTN. The biggest obstacle to cable telephone service is the need for nearly 100% reliable service for emergency calls. One of the standards available for digital cable telephony, PacketCable, seems to be the most promising and able to work with the Quality of Service demands of traditional analog POTS service. The biggest advantage to digital cable telephone service is similar to the advantage of digital cable TV, namely that data can be compressed, resulting in much less bandwidth used than a dedicated analog circuit-switched service. Other advantages include better voice quality and integration to a VoIP network providing cheap or unlimited nationwide and international calling. Note that in many cases, digital cable telephone service is separate from cable modem service being offered by many cable companies and does not rely on IP traffic or the Internet.
Beginning in 2004 in the United States, the traditional cable television providers and traditional telecommunication companies increasingly compete in providing voice, video and data services to residences. The combination of TV, telephone and Internet access is commonly called triple play regardless of whether CATV or telcos offer it.
[edit] Consumer issues
The cable industry spends millions of dollars annually on government relationships.[9][10][11][12] Regularly this industry employs the spouses, sons and daughters of influential mayors, councilmen, commissioners, and other officials to assure its continued local monopoly and preferred market allocations, many of which have been questioned as unethical.[13]
The monopoly on cable television has historically been enforced by local governments. Cable maintains thousands of such de facto monopolies. In order to provide service to individual homes, a cable provider must place its cable wiring along and across local streets or other rights-of-way. To do so, the provider must get permission from the local government(s) that own those streets via rights-of-way permits.
The neutrality of this section is disputed.
Please see the discussion on the talk page. (December 2007)
Please do not remove this message until the dispute is resolved.
Operational permission comes in the form of a document called a local franchise agreement. Most of local government(s) chose to grant permission to only one company, however, recently states have developed broader franchising laws to drive more investment and competition. Changes in the federal law in 1992 had forced local governments to grant permission to other companies to provide service, however the U.S. Government found in 2006 that only 2% of U.S. households had a competitive choice. In some cases Comcast, with municipal government approval, had entered into market allocation schemes. By agreeing to not compete head to head, consumers thus are perpetually locked into a single monopoly cable provider with annual price escalations reaching 93% in the past decade.[14][15][16]
A recent third party survey of citizens found approximately 62% of the respondents were very dissatisfied (along with another 25% who were dissatisfied) with the cost of cable television service. A majority of the respondents were satisfied with the friendliness and courtesy of customer service personnel, however, approximately 30% of the respondents rated the cable company's performance as poor. With regard to open-ended comments, respondents felt that the cost of the cable service was too high, a need for cable competition existed and the desire for a basic cable package offering was desired. Although respondents cited these critical issues, the local monopoly structure preserves the status quo of poor customer service, limited product choices, no direct competition and uncontrollable annual cable TV price increases. Relief for consumers is being created by state level a multi jurisdictional franchise and service process that will spur investment and competition; thus driving economic development sought by state and local government leaders.[17]
The industry strongly lobbies against federal "family tier" and "a la carte cable television" bills that would give consumers the option to purchase individual channels rather than a broad tier of programming. These anti-consumer issues continue to garner attention from state governments, Congress and FCC Chairman Martin.[10]
Index
Broadcasting
Television history
Digital TV
General
Digital TV system in use in USA
Digital TV in Europe
RF technology used in digital TV
TV channel frequencies
Cable TV
Traditional cable TV networks
Cable TV technology
Cable TV standards and regulations
Bidirectional cable TV
Digital cable TV
Wireless cable
Satellite TV
Video protection systems
Satellite protection
VCR copy protection
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Video broadcasting technology page
Broadcasting
Nowadays, television broadcasting is an essential access point to information, culture and entertainment. Broadcast stations use a powerful antenna to transmit radio waves to the surrounding area. Viewers can pick up the signal with a much smaller antenna. The main limitation of broadcast television is range.
The radio signals used to broadcast television shoot out from the broadcast antenna in a straight line. In order to receive these signals, you have to be in the direct "line of sight" of the antenna, or pretty close to it. Small obstacles like trees or small buildings aren't a problem; but a big obstacle, such as the Earth, will reflect these radio waves. To get a perfectly clear signal like you find on cable, you have to be pretty close to the broadcast antenna without too many obstacles in the way.
Television transmissions normally occupy frequencies from about 50 Mhz to over 800 MHz. Television broadcasts do not use this whole frequency range (there are also FM radio, some radio communication and some cellaular communciation on that frequency range on their own bands).
Practically all analogue TV broadcasting system use interlacedscanning to save video bandwidth. In broadcasting, the most important one is usually bandwidth, meaning that a change to non-interlaced scanning ("progressive") would mean halving either theframe rate or the number of lines.
Practically all analogue TV broadcasting systems use a modulation called vestigial sideband (VSB). Vestigial sideband is an AM signal with most of one sideband filteredout to save bandwidth (all you need is the carrier and one sideband to recover the video). This is how broadcasters do this. Simple TV modulation devices usually just use simple AM modulation (it is easier to leave a "Vestige" of the other sideband to prevent extra cost and possible phase shift from needs to be cheap filter affecting the signal quality).
Here are many different TV transmission systems for terrestrial TVbroadcasts in use. The three main broadcasting standards are:
NTSC: This is what is used in USA
PAL: This is used in Europe
SECAM: This is used in France and some Eastern European countries
Plase note that those mentioned standarda re video signal standard. They define the video signal itself, but does not define things like broadcasting frequencies and such. There are several variations those general broadcasting standard in use. Many countries used to have years ago have some slight country specific modifications to the systems for various reasons (technical compatibility with some existing system, protectionism, marginal technical improvement etc.).
For example PAL has no direct connection with broadcastfrequencies (channels) world-wide. Any given hand-held TV receiver you buy locally may or may not receive both picture and sound in the various countriesyou intend to visit because, PAL or not, the local stations may broadcast onfrequencies your receiver cannot receive... and with sound mixed with picture inways your receiver cannot decode. Note that there are about half a dozen variations on "PAL", mostly being differences in things like sound carrier frequency. Do not assume that a PAL tuner/receiver will work correctly everywhere. The receivers designed for different variations have somewhat differently designed electronics in them.
Although nothing is impossible, modifying a table-top VCR tuner (and the associated demodulating circuitry) to handle different signal standards (PAL,SECAM, NTSC) and different channel assignments (frequencies) and different audio modulation schemes is not going to be easy. There are some multi-standard devices though on market that can be set to work with more than one broadcasting standard. If you want to go from broadcasting standard to another, you generally need to demodulate the video signal, the convert it and modulate it with a new standard modulator. There are standards-converting boxes (PAL-SECAM-NTSC) out there that can do video standard conversion (do your web search and you will find converter products/manufacturers).
The first color TV broadcast system was implemented in the United States in 1953. This was based on the NTSC (National Television System Committee) standard. NTSC is used by many countries on the American continent as well as many Asian countries including Japan. NTSC runs on 525 lines/frame. For example NTSC TV transmissions in USA use 6 MHz channel bandwidth. The analog RF is 4.2MHz vestigial sideband + 25KHz FM aural carrier for a channel of 6 MHz.
The PAL (Phase Alternating Line) standard was introduced in the early 1960's and implemented in most European countries except for France. The PAL standard utilises a wider channel bandwidth than NTSC which allows for better picture quality. PAL runs on 625 lines/frame.There are several commonly used PAL versions in use:
PAL System B/G: This is used in most Western European countries, 4,43 MHz color subcarrier, 5,5 MHz audio subcarrier, 7 MHz channels spacing in VHF and 8 MHz channel spacing un UHF
PAL System I: This is used in Great Britain, 4,43 MHz color subcarrier, 5,5996 MHz audio subcarrier, 8 MHz channel spacing in UHF
PAL System N: This is used in Argentina, 3,57 MHz color subcarrier, 4,5 MHz audio subcarrier, 6 MHz channel spacing
PAL System M: This is used Brazil, 3,57 MHz color subcarrier, 4,5 MHz audio subcarrier
The SECAM (Sequential Couleur Avec Memoire or Sequential Colour with Memory) standard was introduced in the early 1960's and implemented in France. SECAM uses the same bandwidth as PAL but transmits the colour information sequentially. SECAM runs on 625 lines/frame.
All RF-TV channels have a designated 6MHz bandwidth containing the separate video and audio RF carriers. The video carrier is amplitude modulated (AM) by the composite video signal using negative sync modulation. This means the sync tips produce maximum carrier amplitude (0% modulation) and the white peaks produce minimum carrier amplitude (87.5% modulation) (those modulation figures apply to NTSC signals). The video modulation is AM vestigial sideband. Full sideband modulation produces sideband frequencies above and below the RF carrier frequency ranging from 0-4.2MHz (this applies to NTSC, somewhat more for PAL signal). The upper and lower sidebands would equally contain the full 4.2MHz luminance and chroma signal information covering over 8 MHz bandwidth. Vestigial sideband operation limits the lower sideband to approximately .75MHz below the carrier frequency and permits the full 4.2MHz above the carrier frequency.
The audio carrier is frequency modulated (FM) by the composite audio signal, which may include multi-television sound signals (MTS). The RF carrier is deviated from its resting frequency by +/- 25 kHz producing sidebands ranging from approximately 0-200 kHz above and below the carrier. In NTSC system the RF channel the video carrier is positioned 1.25MHz above the lower edge of the channel. The color subcarrier is positioned 3.58 MHz above the video carrier. The FM modulated audio carrier is positioned 4.5 MHz above the video carrier. PAL broadcasts use the same idea, but somewhat different subcarrier frequencies (4.43 Mhz for color, usually 5.5 MHz for sound etc.).
Real life example in NTSC world: TV or cable channel 3 has a 6 MHz bandwidth from 60-66 MHz. The video carrier is positioned at 61.25 MHz with lower sidebands limited to ?1.25MHz and upper sidebands extending +4.2 MHz above the carrier (65.45MHz). The color subcarrier is positioned +3.58MHz from the video carrier (64.83MHz). The I color sidebands extend 1.3 MHz below the color subcarrier frequency and the I and Q color sidebands extend +.5 MHz above this frequency. The audio carrier is positioned +4.5MHz above the video carrier or at 65.75MHz.
TV transmitters needs lots of transmitting power to be able to transmit enough signal to the large coverage area. Analogue TV signal is wide bandwith signal that can easily pick up noise interference, so the actual TV signal that the antenna picks from air needs to be pretty strong to be able to be recevied without too much visible noise on it (when broadcast signal gets weaker as you move more away from transmitterm, you see more noise and less actual picture). For analog signals, the recommended level at the receiver input is more than 1 mV (+60 dBuV, -49 dBm). A typical common antenna systems in Europe aim to provide signal in +60-80dBuV (1-10mV) signal level to the receiver.
The typical TV transmitter has power of tens of kilowatts or more. The cost of electricity is significant cost in the operation of the transmitter. The published transmitter rating is ERP (effective radiated power), which is the power that the station would have to run to produce the same signal strength using a non-directional transmitting antenna. Because of antenna gain (transmitting a focused beam), the actual transmitter power is much less than the ERP. At UHF, it can be on the order of 1/20 the ERP or even less. This is offset somewhat by the fact that the transmitter is not 100% efficient, and there is some loss in the transmission line. But a 100KW ERP UHF station is typically running around 10KW transmitter power. It's cheaper to buy a big antenna once than pay the power company each month. Many low power and medium power TV transmitters are air-cooled with blowers. VHF TV transmitters are generally air-cooled (even up to 50kw). Very high power transmitters require water cooling and a lot more acreage for heat exchangers, a radiator and huge electrical power supply. Klystrons are special cavity vacuum tube transmitting devices used in high pewer radio and TV transmitters. Klystrons commonly used in Television work today typically have 4 to 5 cavities. Each cavity is individually tuned, and electromagnets are placed between cavities for focusing purposes.
Measuring the power for complex waveforms such as analog or digital TV is quite complicated. For analog systems with negative video modulation, the peak (rated) power is at the synch pulse, while the active video part is well below this and thus the average power with live program is quite a few dB below the rated power.
About TV and FM Antennas - TV and FM Antenna Tips, FAQ, Reception Help, Interference and Amplifier Guide, etc. Rate this link
Blockdiagram of a TUNER - This is a very simple blockdiagram over a TV tuner. Rate this link
Broadcast Net -broadcast industry home page Rate this link
Doug Lung's R.F. Technology Page - Focusing on TV RF Broadcast Technology Rate this link
FCC Interference Handbook - electronic version of FCC Interference to Home Electronic Entertainment Equipment Handbook Rate this link
HOT Buttons for Surfing thru Close-Up - lots of video links Rate this link
How Television Works Rate this link
Online Systems Integration Services - On-line interactive sutomized selection of TV/radio broadcasting and production sets Rate this link
Radio and Television Transmitters Site - different FM and TV conditions reflects the situation we have in southern Finland Rate this link
Society of Broadcast Engineers - serving the interests of Broadcast Engineers. Rate this link
Television Antenna Frequently Asked Question List Rate this link
The Transmitter Mast Gallery - This page has links to broadcast transmitter sites in the UK. Rate this link
TV Channel and CATV Frequencies - Here is a list of TV frequencies. In the US, a TV channel is a 6 MHz wide chunk of bandspace. The bottom edge of the over-the-air channel 2 is 54 MHz and the upper edge is 60 MHz. Within this 6 MHz space is a video carrier, a color carrier, and an audio carrier. Rate this link
TV Channel Frequencies (Mhz) - list in en end appendix of the document Rate this link
TV technical information for DXers: World TV systems - A summary of channel frequencies and related data for various countries. Rate this link
Video Signal Eavesdropping Threat Tutorial - some views of video signal through spectrum analyzer Rate this link
World Broadcast Systems Chart Rate this link
www.100000watts.com - US radio and TV directory Rate this link
Television history
At 1928 Baird transmits from London to New York, using his mechanical system.with 30 vertical lines. By 1930 it was clear that mechanical television systems could never produce the picture quality required for commercial success. For this reason mechanical system was rapidly succeeded by the electronic TV systems. The first all-electronic American systems in 1932 used only 120 scanning lines at 24 frames per second Since the mid-1930s picture repetition frequency (field rate or frame rate) has been the same as the mains frequency, either 50 or 60Hz according to the frequency used in each country. This is for two very good reasons. Studio lighting generally uses alternating current lamps and if these were not synchronised with the field frequency, an unwelcome strobe effect could appear on TV pictures. Secondly, in days gone by, the smoothing of power supply circuits in TV receivers was not as good as it is today and ripple superimposed on the DC could cause visual interference. If the picture was locked to the mains frequency, this interference would at least be static on the screen and thus less obtrusive.To determine what electronic system to use, the BBC sponsored trial broadcasts by two systems, one by Baird, with 240 lines, and one by EMI with 405 lines. Scheduled electronic television broadcasting began in England in 1936 using 405-line system (lasted until the 1980s in the UK). Germany made their forst TV broadcasts at 1936 olympics using 180-line TV system. Germany also made their TV broadcasts by the fall of 1937 using a 441-line system. Also fFrance tested TV (455 line system). RCA introduced electronic television to the U. S. at the 1939 World's Fair,and began regularly scheduled broadcasting at the same time (525 line system).In 1940 the USA established its 525-line standard. At year 1941 the 525-line standard, still in use today in USA, was adopted.Russia also produced TV sets before the war (240 and 343 line systems).World War Two interrupted the development of television. Immediately after World War Two production of TV sets started in the U.S-In USA there was TV broadcasts and few throusand receivers at 1945. In the early 1950s, two competing color TV systems emerged: CBS sequential color (used color wheel) and RCA dot sequential system. At 1953 color broadcasting officially arrives in the U.S. on Dec. 17, when FCC approves modified version of an RCA system.It calls this new RCA color system "NTSC" color. The first NTSC color TVs were on the marker at 1954.In Europe the TV broadcasts started to use experiment using 625 line system 1950s. This standard is used nowadays throughout Europe. France also tried 819 line system at the same time (this system was in use to 1980s). The rest of Europe opted for 625 lines, a system devised in 1946 by two German engineers, M??ller and Urtel (it appears that the Russians came up independently with a very similar system). The use of PAL color standard started at around 1967 and is still in use. The SECAM color system (used in France) testing started also at 1967. The TV broadcasting history has not ended. The newst thign is digital television. It is expected that terrestrial television will open up billion-dollar opportunities for those companies and organisations best prepared to embrace this new broadcasting era. At 1996 small digital satellite dishes hit the market. They become the biggest selling electronic item in history next to the VCR.
405 Alive - The emphasis is on British 405-line television but not to the exclusion of other countries? television lore and additional interesting features. Rate this link
A Chronological history of Television and Video Technologies Rate this link
Colour TV Subcarrier Offsets for World Colour TV Systems and History of Line Scanning Standards for World TV Systems Rate this link
History of Early Color Television - the web site for the history of early color television Rate this link
Mechanical TV Sets of the 20s and 30s Rate this link
Postwar European TV History Rate this link
Public Broadcasting PolicyBase - Key documents about the history, purpose, policy and structure of public broadcasting in the U.S. Rate this link
Television History - The First 75 Years Rate this link
The Dawn of Modern, Electronic Television Rate this link
The History of Film & Television Rate this link
Digital TV
Digital television is a hot topic now.If you have looked at television sets at any of the big electronics retailers lately, you know that Digital TV, or DTV, is a BIG deal right now in the U.S. In Europe Digital TV is also a hot topic, because many countries have started terrestrial digital TV broadcasts and plan to end analogue broadcasts after some years (will take 5-10 years). Satellite TV broadcasts have also shifted very much to digital broadcasts.The main advantage if digital broadcasts are that it does not havethe picture quality problems of analogue TVs (it had it's own videoproblems caused by video compression), it allowes putting more TV channels to same medium (TV channel frequencies and satellites) and it allows new services (like HDTV and interactive multimedia). The digital brodcasts are generally designed to use such modulation that the digital data stream (typically around 20-30 Mbit/s) is modulated to the same bandwidth (around 6 MHz) as the analogue TV broadcasts. The used modulation vary between different media, which means thatdifferent modulation techniques are used in terrestrial transmissions, cable TV and satellite. Different modulations are used because of the different characteristics of those transmission medias. There is not on "digital TV", but several different variations of it in use.The basic technology of digital TV, known as MPEG 2 video compressionand MPEG 2 transmission stream format, is same around the world, butis is used somewhat differently in different standards used in differentcountries.
USA uses ACTS Digital Televisio Standard, which standardizes NTSC format transmissions, HDTV transmission, sound formats and data signal modulation in use. The ATSC MPEG-2 formats for DTV, including HDTV, uses 4:2:0 samling for video signal. The US system uses a fixed power and a fixed maximum bitrate, at which some bits are always transmitted. That rate is typically 19.3 Mb/sec.
Europe uses DVB (Digital Video Broadcasting) standard. This standardallows basically normal PAL resolution transmisssion (vasically HDTVcould be added later but is not yet standardized) with several audio formats, digital data rates and digital signal modulation. There are several different variations fo DVB standard for different media:
DVB-T for terrestrial broadcasts
DVB-S for satellite
DVB-C for cable TV
Those different DVB versions varyon the data signal modulation methods, error correction and frequency bands used. DVB and option for some interactive extra services, but thestandardization of this is not ready here yet(there are fire different incompatible interactive servicessystems in use in different countries and by different broadcasters).
The process of transmitting digital TV signal is the following: Analog video/audio - digitisation - MPEG compression - Multiplexing ( youcan now call it digital) - Preparation for transmisson - modulation toanalog carrier.Reception process is the following: Demodulation of analogue carrier - Error correction - Demultiplexing - MPEG decompression - DA conversion to get analogue signal (unless you use digital display). The analoguie video signal that gets digitized can be practically from any video source, for example produced with old analogue video production equipment and distributed with a video tape. In high-end system the information is analogue only in the image sensor on the video camera, and from this on the signal gets digitally processed. In many real-life TV production systems the reality is something between those two extremes.
At least in Europe, the signal level requirements for DVB-T are well below the analog requirements, so the transmitter power is much less than on the analog side. In the NorDig recommendation the minimum received signal level for 64QAM, 7/8 code rate with a Rayleigh fading path and 8 dB receiver noise figure would be -64 dBm. With other code rates, modulations and fading mechanisms, the requirement is lower. Many receivers can perform much better at conditions where there is no fading (a quasi error free less than one uncorrected error/hour signal even at 27 dBuV (-82 dBm) with 64QAM and 8 MHz channel width). For analog signals, the recommended level is more than 1 mV (+60 dBuV, -49 dBm). While the ERP can be at least 10 dB lower than analog, the question of power consumption is more complicated, since COFDM with 64QAM carriers require a quite good linearity, which may affect the efficiency and hence power consumption.
General
Demystifying Digital Formats - There are many systems and formats for transporting digital information from one location to another. This article explains the fundamentals of digital data transmission and the myriad formats created in the pursuit of a robust yet compact data-handling scheme. Rate this link
Development of Satellite and Terrestrial Digital Broadcasting Systems and Services and Implications for Education and Training Rate this link
Digital TV (Part 1): A Multi-part Series Rate this link
Digital TV (Part 2): Anatomy of a New Television Standard Rate this link
Digital TV (Part 3): Datacasting Rate this link
Digital TV (Part 4): Converting to Digital Television Rate this link
How Digital Television Works Rate this link
How HDTV Works Rate this link
PC DTV - The PC DTV Promoters Group is an ad hoc assembly of companies interested in promoting the reception of rich DTV and/or data delivered by broadband broadcast signals from terrestrial broadcast, satellite or cable TV services. Each of these companies offers technology or services that enable PC users to receive digitally broadcast signals from terrestrial stations, cable services or satellite providers. Rate this link
Spatial Oversampling: Why HD0 Broadcasting Makes Sense - People seem to think that high definition television needs lots of lines, but it's a myth. Cameras and displays need a lot of lines to overcome aperture effects and to render the raster invisible, but the transmission medium between doesn't. In the early days of television, the capture, transmission, and display formats had to be identical for simplicity, but that's no longer true or desirable. Rate this link
Technology: HDTV - many articles Rate this link
Digital TV system in use in USA
The FCC mandate to change our broadcast standards from NTSC analog to ATSC digital broadcasting (DTV) is big bold move, requiring changes in everything from the way the studios shoot video, the format that's transmitted, to the equipment we use to receive and watch broadcastsDTV (digital TV) applies to digital broadcasts in general and to the U.S. ATSC standard in specific. The ATSC standard includes both standard-definition (SD) and high-definition (HD) digital formats. The notation H/DTV is often used to specifically refer to high-definition digital TV. The federal mandate grants the public airwaves to the broadcasters to transmit digital TV in exchange for return of the current analog NTSC spectrum, allowing for a transition period in the interim. At the end of this period scheduled for 2006, broadcasters must be fully converted to the 8VSB broadcast standard. Digital Television ("DTV") is a new broadcast technology that will transform television. The technology of DTV will allows TV broadcasts with movie-quality picture and CD- quality sound and a variety of other enhancements (for example data delivery). With digital television, broadcasters will be able to offer free television of higher resolution and better picture quality than now exists under the current mode of TV transmission. If broadcasters so choose, they can offer what has been called "high definition television" or HDTV, television with theater-quality pictures and CD-quality sound. . Alternatively, a broadcaster can offer several different TV programs at the same time, with pictures and sound quality better than is generally available today. HDTV (high-definition TV) encompasses both analog and digital televisions that have a 16:9 aspect ratio and approximately 5 times the resolution of standard TV (double vertical, double horizontal, wider aspect). High definition is generally defined as any video signal that is at least twice the quality of the current 480i (interlaced) analog broadcast signal. There are 18 approved formats for digital TV broadcasts, but only two (720p/1080i) are proper definition of the term HDTV. The advent of high definition has allowed monitors to read images differently, either in standard interlaced format or progressively. Sets that do not have any decoding capabilities but can display the high-resolution image is often labeled as "HD-Ready" a term that describes 80% or more of the Digital TVs on the market. HDTV displays support digital connections such as HDMI (DVI) and IEEE 1394/FireWire, although standardization is not finished. HDTV in the US is part of the ATSC DTV format. The resolution and frame rates of DTV in the US generally correspond to the ATSC recommendations for SD (640x480 and 704x480 at 24p, 30p, 60p, 60i) and HD (1280x720 at 24p, 20p, and 60p; 1920x1080 at 24p, 30p and 60i). In addition, a broadcaster will be able to simultaneously transmit a variety of other information through a data bitstream to both enhance its TV programs and to provide entirely new services. The technical specifications of USA DTV system is defined in ACTS Digital Television Standards.
Loop Bandwidth Optimization and Jitter Measurement Techniques for Serial HDTV Systems - This paper describes a system level optimization of a studio serial digital interface for uncompressed High Definition Television (HDTV). The HDTV data rate is 5.5 times that of Standard Definition Television (SDTV) which allows little design margin for jitter. Rate this link
ACTS Digital Television Standards - digital HDTV standard proposal for USA in pdf format Rate this link
ATSC Press Releases Rate this link
Digital Television Frequently Asked Questions Rate this link
Digital Television Radio Frequency Emission Safety Guidelines - On June 2, 2000, the Commission and the Local and State Government Advisory Committee jointly issued a Local Government Official's Guide to Transmitting Antenna RF Emission Safety. The guide is designed to provide local communities with a greater understanding of RF emission issues and comprehensive information and guidance in devising efficient procedures for assuring that local antenna facilities comply with the Commission's limits for human exposure to RF electromagnetic fields. Rate this link
Digital Television: The Site - professional information about digital television as well as discussions about different aspects of digital television Rate this link
DISTRIBUTION of digital television signals Rate this link
DTV Digital TV Basics Rate this link
DTV Signals Analysis Rate this link
Evolving to Digital and High-Definition TV - HDTV FAQ Introduction to Digital and HDTV Rate this link
FCC's Digital Television Website Rate this link
HDTV FAQ - Introduction to Digital and HDTV - The FCC mandate to change broadcast standards from NTSC analog to ATSC digital broadcasting is big bold move, requiring changes in everything from the way the studios shoot video, the format that's transmitted, to the equipment we use to watch. Rate this link
Loop-bandwidth-optimization and jitter-measurement techniques for serial-HDTV systems - Using commercially available general-purpose test units and some custom-built boards, you can easily measure some of the important jitter parameters associated with serial HDTV. Rate this link
The Difference Between HDTV, EDTV, and SDTV - The consumer electronics industry has done a spectacular job spreading mass confusion about video. Time was when there was just TV. Now we've got SDTV, EDTV, HDTV, 480i, 480p, 525p, 720p, 1080i, progressive scan, component, composite, blah blah blah. Enough to make you feel like you need an engineering degree to buy a projector or TV Rate this link
What exactly is 8-VSB anyway? - information on digital TV modulation in use in USA Rate this link
What exactly is 8-VSB anyway? - information on digital TV modulation in use in USA Rate this link
8VSB is the Tranmission method for HDTV and means 8-level vestigial sideband modulation - 8-VSB is the 8-level Trellis coded Vestigial SideBand Modulation developed by Zenith and adopted for FCC and ATSC(Advanced Television Systems Committee) standard of DTV (Digital TeleVision) in the USA. HDTV uses this for terrestrial broadcast transmission. Rate this link
Digital TV in Europe
Digital TV brodacasting in Europe is done according to DVB standards. DVB technology has become an integral part of global broadcasting, setting the global standard for satellite, cable and terrestrial transmissions and equipment. There are three versions of DVB in use: DVB-S, DVB-C and DVB-T.DVB-T is a flexible system allowing terrestrial broadcastersto choose from a variety of options to suit their various service environments. This allows the choice between fixed roof-top antenna, portableand even mobile reception of DVB-T services. Broadly speaking the trade-off in one of service bit-rate versus signal robustness.
DVB-T network is very flexible. Having many transmitters all on the same frequency is not a problem for the used COFDM based system. COFDM has been chosen and designed to minimise the effects of multipath in obstructed reception areas. In fact multipath signals can significantly improve the overall received signal with no adverse effects. These properties are particularly valuable for radio cameras and mobile links. DVB-T because of its unique design which allows single frequency networks (SFN). This means that many transmitters along the planned routes can transmit on the same frequency. It is also possible to use simple gap fillers that amplify and retransmit the signal. In-air digital TV broadcasts in Europe use DVB-T. 8 MHz of bandwidth may be used to provide a 24 Mbps digital transmission path using Coded Orthogonal Frequency Division Multiplexing (COFDM) modulation (theoretical maximum 31.67 Mbits for 8 MHz bandwidth). In cases where less bandwidth is available (6 or 7 MHz), the data rate is somewhat lower (around 20 Mbit/s).
DVB-C does the same function as DVB-T, but the modulation used in this system is optimized to operate well in cable TV networks. The modulation used in DVB-C is QAM. Systems from 16-QAM up to 256-QAM can be used, but the system centres on 64-QAM, in which an 8MHz channel can accommodate a physical payload of about 38 Mbit/s. Digital cable TV in Europe uses DVB-C. The DVB standard for the cable return path has been developed jointly with DAVIC, the Digital Audio Visual Council. The specification uses Quadrature Phase Shift Keying (QPSK) modulation in a 200kHz, 1MHz or 2MHz channel to provide a return path for interactive services (from the user to the service provider) of up to about 3Mbit/s. The path to the user may be either in-band (embedded in the MPEG-2 Transport Stream in the DVB-C channel) or out-of-band (on a separate 1 or 2MHz frequency band).
DVB-S is the satellite version of DVB. Satellite transmission has lead the way in delivering digital TV to viewers. Established in 1995, the satellite standard DVB-S is the oldest DVB standard, used on all six major continents. QPSK modulation system is used, with channel coding optimised to the error characteristics of the channel. A typical satellite channel has 36 MHz bandwidth, which may support transmission at up to 38 Mbps (assuming delivery to a 0.5m receiving antenna) using Quadrature Phase Shift Keying (QPSK) modulation. 16 bytes of Reed Solomon (RS) coding are added to each 188 byte transport packet to provide Forward Error Correction (FEC) using a RS(204,188,8) code. For the satellite transmission, the resultant bit stream is then interleaved and convolutional coding is applied.
The core of the DVB digital data stream isthe standard MPEG-2 "data container",which holds the broadcast and service information.This flexible "carry-all" can containanything that can be digitised, includingmultimedia data. The MPEG-2 standards define how to format the various component parts of a multimedia programme (which may consist of: MPEG-2 compressed video, compressed audio, control data and/or user data). It also defines how these components are combined into a single synchronous transmission bit stream. The process of combining the steams is known as multiplexing. The multiplexed stream may be transmitted over a variety of links, standards / products.Each MPEG-2 MPTS multiplex carries a number of streams which in combination deliver the required services. A typical data rate of such multiplex is around 24 Mbps for terrestrial brodcasts.
European DVB systems currently transmit only standard definition TV signals and set top boxes also handle only normal TV resolution. It would be possible to transmit HDTV signals on DVB data stream, but those broadcasts have not yet started in any wide scale. There is one satellite broadcater that broadcasts HDTV DVB signals in Europe (some cable TV operators carry that signal on their cable).
Many DVB-T integrated TV sets, and some set top boxes, in the Europe come with a Common Interface slot - which is pretty much the same form-factor as a PC Card (aka PCMCIA) used in PC laptops. This CI slot accepts a Conditional Access Module, in the same way that DVB-S receivers do, which implements at least one (some can do more than one) decryption algorithm. This CAM may also, itself, have a smart card slot to accept a consumer subscription card to authorise decryption - you plug your smartcard into your CAM and your CAM into the CI slot in your receiver/IDTV. Some DVB receivers have an integrated CAM (in the case of some receivers this is implemented purely in software, with no extra hardware required) rather than a CI slot to plug in a 3rd party device. With these type of receivers you just plug in the smart card and don't have to worry about CI slots and buying CAMs. So there is an interface standard for DVB - but different broadcasters can chose different encryption schemes, requiring different CAMs for decryption.
Here is a list of several DVB standards and related specifications:
EN 300 744: Digital Video Broadcasting (DVB); Framing structure, channel coding and modulation for digital terrestrial television.
TS 101 191: Digital Video Broadcasting (DVB); Mega-frame for Single Frequency Network (SFN) synchronization.
N 50083-9: Cable distribution systems for television sound and interactive services; Part 9: Interfaces for CATV/SMATV headends and similar professional equipment for DVB/MPEG-2 transport streams.
ETR 290: Digital Video Broadcasting (DVB); Measurement guidelines for DVB systems.
TR 101 190: Digital Video Broadcasting (DVB); Implementation guidelines for DVB terrestrial services; Transmission aspects.
ISO/IEC 13818-1: Information technology ? Generic coding of moving pictures and associated audio information: Systems.
DVB Standards and related documents are published by the European Telecommunications Standards Institute (ETSI). These include a large number of standards and technical notes to complement the MPEG-2 standards defined by the ISO.
There are few different standard how interactive TV functionaly is implemented in DVB-systems in use in differenct countries. DVB-MHP is one gaining some acceptance. Multimedia Home Platform (MHP) is the open middleware system designed by the DVB Project (www.dvb.org).
Digital Video Broadcasting (DVB) home site - Rate this link
Digital Video Broadcast (DVB-T) Technical Papers Rate this link
digitv.fi - Information on digital TV broadcasts on Finland Rate this link
DVB-RCT - A Wireless Return Channel system in the VHF/UHF Bands for Interactive Terrestrial TV incorporating Multiple Access OFDM. Promises to provide a wireless interaction channel for Interactive Digital Terrestrial Television. Rate this link
Future TV - link list on digital TV development issues Rate this link
NorDig - NorDig is specifying a common platform for digital-TV within the Nordic region (Denmark, Finland, Island, Norway and Sweden), you can download all released NorDig specifications, reports and documents Rate this link
NorDig information central - NorDig is specifying a common platform for Digital Television to be used within the Nordic region (Denmark, Finland, Iceland, Norway and Sweden). On this site you can download Documents, Reports and Specifications released by NorDig. Rate this link
Tutotial De Televisio Digital - Digital Television Tutorial wich takes care of all aspects of digital television but interactive TV. It's written in catalan. Rate this link
RF technology used in digital TV
Digital Video Microwave Links Rate this link
DTV Signals Mask Radiated Emissions - digital TV broadcast signals add yet another ambient signal to the mix Rate this link
Measure DTV Transmissions from Start to Finish - digital TV measurements cover everything from packet jitter to RF emissions Rate this link
TV channel frequencies
Kanavataulukko - TV channel frequencies in use in Finland, Eastern Europe and some other countries, texts in Finnish Rate this link
Cable TV
Cable TV network is a system designed to deliver broadcast television signals efficiently to subscribers' homes. To ensure that consumers could obtain cable service with the same TV sets they use to receive over-the-air broadcast TV signals, cable operators recreate a portion of the over-the-air radio frequency (RF) spectrum within a sealed coaxial cable line. CATV is comprised of multiple TV channels (and usually radio channels also) transmitted over a single cable, with each channel occupying a different frequency range. Several vide channels (thens of them) may be carried over a single cable. Cable TV is a transmission system can be viewed as abroadband cabling system that supports transmission of multiple services over a single cable by dividing the bandwidth into separate frequencies, with each frequency assigned to a different service. Each TV channel (or other service) uses a different frequency range. Cable TV signals occupy the freqs that are used for public service(police and fire, etc.) and for this reason the cable TV companies arerequired by law to maintain their cables to prevent leakage, so they doregular checks. If they find that the cable TV signal is gettingoutside the cable, they will take necessary action to stop it. If they find that your equipment/wiring is causing it, they will really take action, which means disconnecting you and possibly subjecting you to other action (possibly legal consequences that can get expensive).
Traditional cable TV networks
Traditional coaxial cable systems typically operate with 330 MHz or 450 MHz of capacity, whereas modern hybrid fiber/coax (HFC) systems are expanded to 750 MHz or more. Logically, downstream video programming signals begin around 50 MHz and uses the frequencies up from that. Each standard television channel occupies around 6 MHz of RF spectrum, just like in normal TV broadcasts. Thus a traditional cable system with 400 MHz of downstream bandwidth can carry theoretically the equivalent of 60 analog TV channels and a modern HFC system with 700 MHz of downstream bandwidth has the capacity for some 110 channels. In practical applications the number of usable channels is somewhat less than that. The cable television (CATV) industry has come a long way since it began using community antennas to receive broadcast signals and distribute them to homes on twin-lead wire (later coaxial cable). The earliest cable systems were, in effect, strategically placed antennas with very long cables connecting them to subscribers' television sets. Because the signal from the antenna became weaker as it traveled through the length of cable and it was split to many receiver, cable providers have to insert amplifiers at regular intervals to boost the strength of the signal and make it acceptable for viewing.For the first 40 years, the vast majority of technological advancements in the CATV industry were driven by engineering requirements to improve signal quality, expand systems to cover larger geographical areas and deliver more channels. Today CATV industry competition focuses on making CATV the primary carrier of digital sound and video plus voice and data communications to homes and offices.
General cable TV information links
Advanced Return-Path Cable TV Access Technologies Rate this link
Broadband Bob's CATV CyberLab - news, information and links Rate this link
Cable Signal Leakage - Signal leakage occurs when the signals within a cable system are not properly contained within the cable facility. Cable facility leakage may be caused by loose connectors, cracked or unterminated cables, and damage caused by accidents, such as cars knocking over poles supporting cable wires. Cable signal leakage can interfere with any of the radio services that happen to be using the same frequencies as the cable operator within the vicinity of the cable system. Rate this link
Catv Channel/Frequency Chart - Here is a list of TV frequencies. In the US, a TV channel is a 6 MHz wide. The bottom edge of the over-the-air channel 2 is 54 MHz and the upper edge is 60 MHz. Within this 6 MHz space is a video carrier, a color carrier, and an audio carrier. Rate this link
How Cable Television Works Rate this link
Society of Cable Telecommunications Engineering Rate this link
The History of Cable Television - short description of cable TV history Rate this link
Cable Television in the United States: An Overview - This document is published by Cable Television Laboratories, Inc. ("CableLabs") to inform the industry. This paper is intended to provide a technical briefing on cable television in the United States. It is organized into three sections. Section 1 gives a casual review of cable technology and the cable business in the U.S. Section 2 is a more detailed look, and the third section provides data and specifications. The reader can use the three sections independently depending on his background and needs. Rate this link
Cable TV technology
CATV systems typically utilise the 54 - some upper frequency region(330, 550, 750, 850 MHz), without breaks, to distribute TV channels. The frequency range used in modern bidirectional cable TV networks can cover frequencies from 5 MHz to 1000 MHz.
In a perfect world, the video quality you perceve on your TV is the same quality as the video signal source. In the real world, this is not usually the case. The video signal is usually degraded by a factor of dB from the source to the TV. The type and length of cable used, the number of splitters, the type of video amplifiers, the quality of the incomming video signal, all influence picture quality and dB differently. The key to good picture quality is to evenly amplify the video signal to all video devices without exeeding the 15.5dBmV maximum allowed by the FCC and not going below 1 mV signal level. The typical receivers are designed to work well in this signal level range. Lower signal levels cause easily noisy picture and higher signal levels can cause signal distortion problems. In Europe the signal levels are usually described in different units dBuV. For example regulations in Finland ask for 60-80 dBuV (=0-20 dBmV) to be available on the subscriber antenna outlet. When designing a video distribution system or adding a new component to an existing system, one must try to take into consideration all factors that influence dB.
There are many different components used in cable TV system:
The video amplifier is one of the most important components for producing a good quality picture. This device amplifies the video signal on the cable. Amplification is needed because cable and signal splitters attenuate the video signal on the cable. The amplifier is used to compensate those losses. Amplification needs to be done where signal is strong enough, because no amplifier can help the signal when it is buried below the cable noise. Amount of noise in signal plays an important part in the quality of cable TV a video signal. Cable amplifies their hardline coax trunk and feeder lines at intervals varying from every 600 feet out to every 1,200 feet - amplifiers are placed as a function of cumulative cable losses, signal splits along the trunk or feeder after an amplifier, and "tap" or "directional coupler loading". Cable TV amplifiers require power and every couple of miles of plant there is usually a pole mounted / ground mounted humoungous looking power supply. It takes 117/240VAC and turns it into 30, 60, or 90 VAC (DC to coax installed outside is no-no) which is then diplexed onto the coaxial cable to run throughout the plant to be a power source for the solid state amplifiers. The amplifiers generally operate internally at 30V DC or less. The cable TV amplifiers at the end user premises typically use the household power (230V AC or 120V AC). Many cable TV equipment components are powered through a mains power supply that supplies 24V DC power to the amplifiers. Some equipment have built-in mains power supply.
Coaxial cable is the medium which carries the video RF signal. Cable TV systems are built using 75 ohm coaxial cable. A typical RG6 Coax Cable attenuates the cable TV signal 4-6 decibels per too feet (30 meters) of cable. In some applications also RG-59 cable is used (it is more lossy than RG-6).
A splitter is a small device that has one input (the 75 ohm load) and 2 or more outputs, each driving a separate 75 ohm load. Essentially they are transformers that split the power in the input signal to multiple outputs, while maintaining the 75 ohm impedance. Every time you split an RF signal with a splitter, you drastically decrease the signal's strength. Splitters are used when cable TV video signal needs to be split to multiple viewers. A typical 1x2 Way Splitter splits the input signal to two output, maintains 75 ohm impedance on all connections and attenuates the video signal typically 4-6 decibels. 1x4 Way Spitter works in the same way but has four outputs and attenuates the signal 7-9 decibels.
A combiner is simply a splitter hooked up backwards. It combines the channels on two or more separate cables or signal source onto one cable. The only drawback to this piece of magic, is that the signal on the cables being combined cannot have any channels in common with each other (if they contain signal at same channels/frequencies the resulting signal on that channel would be trashed).
Taps are similar to splitters, but are "wound crooked" so that the outputs are not equal in signal strength. The "through" output of a tap may only reduce the signal level by a very small amount, while the "tap" output is a small fraction of the signal level. Taps are primarily used in complex commercial distribution installations. A typical applicaton for taps are to take out individual outputs from a strong signal main distribution line that goes through many taps. Other uses for taps are measurement applications where you can have a suitable high attenuation (high attenuation to tap out, very low on the signal going through) tap where you connect our measuting instrument to that tap output. Connecting and disconnecting he measuring equipment to that output does not affect considerably the main line operation, and the tap can be kept on the line all the time (the pass-through attenuation is neglegtable). When looking at measurement reasults you just multiply the reading you get with the tap attenuation and you know the signal strength on main line.
A Terminator is a small cap that screws on the end of an open coax connector. It contains a small 75 ohm resistor. A Terminator is used to prevent video signal bounceback and ghosting. All connections in your system should be terminated either by a video device or a terminator. An
Attenuators are simple "one in, one out" devices that reduce the signal strength. Attenuator pad reduces signal level (usually expressed in decibels). This component is usually necessary to equalize video signals with different signal levels before they are combined to the same cable. Attenuation pads are sometimes needed also when some signals are too strong to some sensitive devices. Attenuators come in various sizes and are useful when tuning up the video distribution system. Typical attenuator pad values are -3dB, -6dB, -10dB, and -20dB. There are also adjustable attenuation pads with typical attenuation range of 1-20 dB.
Antenna outlet is the connector on your wall. In the simplest case it can be just a coaxial connector terminating the cable coming from the main antenna line tap. The antenna outlets in USA have typically F connectors, while the coaxial IEC/DIN 45325 connectors (9.5 mm diameter) is the most commonly used antenna outlet connector in Europe. The antenna outlets in most European countries have two output connectors, one male IEC/DIN 45325 connector for TV signals and one female IEC/DIN 45325 connector for radio signals. A modern antenna outlet has typically attenuating directional coupler (1-12 dB attenuation) and filters to filter different frequencies to different outputs.
A Tilt Compensator attenuates lower frequency video signals, to compensate the fact that typical cables attenuate higher frequencies more than lower frequencies. Also video signal amplifiers sometimes amplify lower frequency signals much more than higher frequency signals. A Tilt Compensator is usually needed for every 250ft run of RG6 coax cable. This kind of compensator typically attenuated the low frequencies around 12 decibels compared to the highest frequencies. Nowadays tilt compensators when used are usully built into amplifiers designed for cable TV signals.
Modulators are devices that convert composite video signal and audio signals to to RF signal similar to TV broadcasts. The operation of RF modulator is similar to TV broadcast transmitter, the only main difference is that the output power of the typical RF modulator is very low (typically in milliwatts level). The signal from a RF modulator is typically suitable to be fed to a TV receiver or cable TV amplifier input. The modulators could be built to work on specified channel frequency or their channel can be altered with modulator controls. A tpyical use in cable TV head-end is that a set of modulator takes in the audio and video signals from different program sources (signal from local studios, signal from playbac VCRs, signals from satellite receivers etc.). A typical cable TV broadcasting head-end has many RF modulators transmitting ant different frequencies, and signals from them are combined together to form the cable TV channels that you see. Sometimes modulators are used also used at residential premises. The concept of "in-house" channel generation, together with the new cheaper and more reliable digital modulators, is opening up many new possibilities in residential video distribution. Also digital TV broadcasts used modulators, in this case those modulators take in digital video data stream and convert it to RF signal.
Channel converters are devices that take in the signal from TV receving antenna, receive one channel and give out RF signal at other frequency out. Channel converters are used to receiver on-the-air broadcasts and convert them to different channel frequency used for them in the cable TV (there are good reasons to use different freuqencies on cable and on-air broadcasts). A typical channel converter takes in one TV channel information, mixes it with a local oscillator to form intermediate frequency (IF) signal, filters that IF signal and then modulates that signal with another local oscillator to form the RF signal at wanted frequency. Typically the input and output frequencies, as well as the signal amplification, are are adjustable on modern equipment. A typical cable TV head-end has one channel converter per on-air channel that is converted to cable. The outputs from the channel converters are combined toghether with the signal from the RF modulators to form the channels on the cable TV system.
Fiber converters are devices that are used to convert the cable TV broadcast signal to light signal that can be transported through a fiber optic link. Many modern cable TV systems use fiber optic links to carry the cable TV signals long distances (for example from head-end on down-town to cable TV distribution amplifier rack somewhere on the suburb may kilometers away). The fiber optic transmitter consists of a powerful infrared laser transmitter and a high speed analogue modulator that can modulate the whole cable TV RF signal to the light signal on the fiber (the signal is amplitude-modulated to light signal). The receiver on the other end of the fiber consists basically just from a very high speed photodiode followed by cable TV amplifier. The cable TV fiber transmitter part is very expensive special device that must be carefully tuned to work well (the modulator must operate at "linear operation area" to avoid signal distortion). The fiber optic receiver can be a quite simple device and is much less expensive than the transmitter part. Fiber optic transmission systems can carry analog and digital signals in the form of light waves.
The whole cable TV system must be well impedance matched system. It must also be designed in such way that different devices connected to different cable TV outlets do not interfere with each other. The terminal isolation provided to each subscriber terminal shall not be less than 18 decibels (the exact decibers vary somewhat from country to country, usually in 18-22 dB range) and shall be sufficient to prevent reflections caused by open-circuited or shortcircuited subscriber terminals from producing visible picture impairments at any other subscriber terminal. The isolation is provided by correct design of the cable TV system. The antenna outlet usually has a considerable part in to guarantee the isolation between different outputs. Modern antenna outlets include typically directional coupler, some attenuation and filters. For example typical European antenna outlets have output connectors are according to IEC standard. One outlet supplies all TV frequencies and othet outlet has the radio frequencies (the outlet has needed filters built into it). Some outlets have nowadays a separate data outlet (passes wideband signals out, passes return channel data signals from cable modem also well).
The cable TV system needs to be continuoisly maintained to guarantee that it does not have excess signal leakage out of the system. FCC requirements say radiation must not exceed a few microvolts per metre at a distance of ten metres from the lines, equipment. Leaks are concern being potential interference to air and safety communications.This maintaining process can contain continumous measurement drive-outs, measurement flyoves, monitoring of reverse band monitoring of cable data services signal quality. One system to test this is is to have test equipment modulate a carrier (such as at 108 or 133 MHz) with an (FM) warble. The carrier is carried throughout the system and the service trucks have a mobile receiver tuned to that frequency. If they hear their inside-of-cable plant "warble" they know they have a leak. Radiation is very easily traced - a handheld or smaller battery operated TV set, an FM radio with "TV audio" frequency coverage and a whip antenna (or rubber duckie) and look for the TV-FM signals sent to cable. Radiation occurs because one (or more) of three conditions exist: there is a break/crack in the line, a connector is loose or there is a resonant line section someplace. The crack acts like a "slot antenna" and RF energy, resonant with the crack, literally leaks or radiates away from the line (most cracked line radiation occurs above 100 MHz). A loose connector typically radiates low band signals, seldom at frequencies above 200 MHz. A resonant line section can be very difficult to pinpoint. In practical world it is very hard to keep all the leakage out, because is practically not possible to install coax cabling system in the house with shielding better than 65 dB (the individual components are typically designed for 80-90 dB shielding).
The inner conductor of the coaxial cable consists generally of a solid, drawn copper wire. A speciality is the so-called copperwelded conductor, a copperclad steel wire, which is applied in small drop cable types for its high tensile strength. Due to the skin effect the thin copper cladding is decisive for attenuation with high frequencies.High qualtity polyethylene (PE) is is used as the insulating material in CATV coax cables. This material guarantees low dielectric loss with high frequencies. Maintaining the samelevel of transmission properties the outer diameter of the cable can be reduced considerably with the use of a compound dielectric of PE and air (foam PE). There are two versions: physical foam material, i.e. the socalledcellular PE insulation, and the chamber construction with PE discs and a PEtube, the so called Bamboo insulation. The outer conductor consists of pure copper in best cables. In outdoor installations exclusively outer conductors of copper are applied, i.e. as welded tube. However, for certain applications, it is recommendable as outer conductor for its low cost: i.e. for drop cables installed in buildings aluminium laminated plastic foils combined with a tinned copper braid are used. The quality of the electromagnetic screening is determined by the outer conductor of the cable. Real conductors with a finite conductivity radiate up to some 100 kHz of electromagnetic energy in the lower frequency range, with higher frequencies there is, however, a sufficient screening for all practical applications.
Generally the screening efficiency values used in CATV cables achieve approx. 80 dB for cables with low optical coverage (aluminium laminated plastic foils combined with a 35% optical coverage tinned copper braid) and 90 dB or more for cables with high optical coverage (aluminium laminated foils and copper braid with optical coverage of 80 %). There are some cabling shielding proposals: the screening classes A with 85 dB and B with 75 dB of the european andinternational standard proposals. The outdoor cables in line and distribution networks are generally provided with an UV-stabilized polyethylene sheath allowing direct burial or use as aerial cable. Indoor cables are generally provided with a PVC or FRNC sheath. because the needed flame resistance. Cables with FRNC sheath are preferably used for indoor installations, since their flameresistance is considerably higher than that of PVC and they are non-corrosive. The cables are usually identified by sheath materials in different colours and a sheath marking. This marking can be applied on the outer sheath by means of embossing, inkjet or sintering.
Essential properties of CATV coaxial cables are their characteristic impedance and its regularity, their attenuation as well as their behaviour concerning the electrical separation of cable and environment, i.e. their screening efficiency. Another important factor is the D.C. resistance, because the supply voltage for repeaters and other active components in a distribution network is partially transmitted via the coaxial cables.
Cable television companies provide broadcast and video programming to subscribers. In recent years, many companies have upgraded their systems to provide new cable services such as digital television, Internet access through a cable modem, and telephony. Upgraded systems typically use fiber optic cable based long distance signal transmission because optic fibers have large capacity, are reliable and and transmissions over them are not susceptible to interference by outside signals. Fiber optic transmission systems nowadays carry both analog and digital signals in the form of light waves. One fiber can carry on best cases many different signals on different wavelengths. The cable TV networks that use both fiber optics and coaxial wiring are called Hybrid Fiber Coaxial systems. The cable TV distribution network is constructed following a tree and branch structure. The cable TV signal from a main hub is first brought to an optical node through a glass optical fiber where the cable TV signal is Amplitude Modulated (AM) to an optical carrier frequency. After demodulation using Optical-Electronic (O/E) devices in the optical node, the cable TV signal is carried over a few branches of coaxial cable network to every subscriber. The root of each tree and branch distribution network is at the optical node. The main branch of the distribution network consists of distribution coaxial cables (usually cable types 500-F and 625-F). The distribution cable is connected to subscribers through a device called a Tap and drop coaxial cables. The common drop cable types are RG-6 and RG-59. Drop cables are also used for in-house TV signal wiring.
Proper in-house cabling is the last part of cable TV network. In a new construction, coaxial cables are connected from a central location near the TV signal source, be it a cable TV or a satellite dish, to every room where an in-house TV wiring connection should be available. This configuration forms a star topology. A multiport splitter is located at the center of the star. Depending upon the number of rooms to be served, some times an amplifier is inserted between the video source and the multiport splitter to raise the signal level, compensating signal losses caused by branch splitting. Assuming that signal separation loss is 15 dB between two output ports of every splitter stage, the minimal signal separation loss is 15 dB between coaxial cable outlets. Enough signal separation is needed to avoid the possibility of a problem in one outlet (broken cable, noise generating recevier etc.) would cause the signal on other outlets to become unuseable.
For in-house wiring installed by cable TV companies on existing homes, splitters are usually randomly installed at the cable TV entrance point and some other convenient splitting points. This configuration forms a star daisy-chain topology where splitter is used at every cable branch point.
Technology articles and links
Noise and intermodulation in cable distribution networks Rate this link
Attack on Pay-TV Access Control Systems - slide set by Rate this link
Avoiding a point of no return - Activating the return path on a hybrid fiber/coax network is the first step toward offering advanced services, but maintaining a healthy path back to the headend and .future-proofing. the network for higher take-rates presents a challenge to technicians. Rate this link
Cable TV Frequency Allocations in the United States Rate this link
Cable TV Leakage - some comments about signal leakage from cable TV systems Rate this link
CATV/Video, (Signal Balancing) - This article outlines an overview for video signal balancing for CATV/Video. Rate this link
Defining Shorts & Opens - dealing with CATV distribution equipment and power supplies, we are constantly confronted with shorted and open components and circuits Rate this link
Mechanics Of Aerial CATV Plant - understanding the mechnaics of aerial cable installation application note from Rate this link
Simplibying CATV Cabling with UTP - One of the largest untapped markets for structured cabling is community antenna television or cable television (CATV). This document outles CATV operation and how to adapt UTP to transfer CATV signals. Rate this link
Understanding Modulators - This article explains in simple terms, the basics of modulation as well as the different types of Modulators along with block diagrams and technical details of each Modulator topology. Rate this link
Understanding Power Splitters - how they work, what parameters are critical, and how to select the best value for your application Rate this link
Understanding & Measuring Video TV-RF Signals Part III - Measuring TV-RF Signal Levels dBmV Rate this link
Understanding & Measuring Video TV-RF Signals Part II - RF-TV Channel Frequencies and Channel Plans Rate this link
Understanding & Measuring Video TV-RF Signals Part I - NTSC video basics Rate this link
Home Networking: Understanding Coaxial Cable - Walter Chen provides some background on the cable TV distribution network and explains the components, capabilities, and limitations of coaxial cable. Rate this link
An Introduction to Basic CATV - From An Overview of Cable Television in the United States Rate this link
CATV installation basics - It is important for installers to maintain proper clearances above ground level anywhere a drop cable must be run across a public right of way. That means 18 feet from an alley or street surface, 15 feet over a commercial driveway and 13 feet over a residential driveway. On a telephone pole, the drop cable must be no less than 40 inches from the power drop and 12 inches from the telephone drop wire if one is in place. The mid-span clearance from any power drop is 30 inches, while the side-of-home clearance is 12 inches. At the side of the home, any telephone drop must be at least four inches from the coaxial cable drop. Underground drops are buried 36 inches deep when crossing a street or alley, 24 inches deep when crossing sidewalks and driveways, and at least 12 inches deep when crossing under lawns on the property. It is necessary to control signal leakage into and out of the network. Rate this link
Cable TV standards and regulations
There are some standards on European cable TV systems.
EN 50083-1:1993 Cabled distribution systems for television, sound and interactive multimedia signals -- Part 1: Safety requirements
EN 50083-3:1998 Cable networks for television signals, sound signals and interactive services -- Part 3: Active wideband equipment for coaxial cable networks
EN 50083-4:1998 Cable networks for television signals, sound signals and interactive services -- Part 4: Passive wideband equipment for coaxial cable networks
EN 50083-5:1994 Cable networks for television signals, sound signals and interactive services -- Part 5: Headend equipment
EN 50083-6:1997 Cable networks for television signals, sound signals and interactive services -- Part 6: Optical equipment
In USA FCC standardizes the operation of cable TV networks.
Cable TV Channel Frequencies Rate this link
Cable TV Frequency Allocations in the United States - This document is a presentation slide set. It describes dfrequency allocations and some signal leakage regulations. Rate this link
FCC's Cable TV Technical Standards Rate this link
Kaapelitelevisio- ja yhteisantennij??rjestelmien rakentaminen ja yll??pito - information on cable TV system building and operationstandards in use in Finland, text in Finnish Rate this link
TV Channel and CATV Frequencies - Here is a list of TV frequencies. In the US, a TV channel is a 6 MHz wide chunk of bandspace. The bottom edge of the over-the-air channel 2 is 54 MHz and the upper edge is 60 MHz. Within this 6 MHz space is a video carrier, a color carrier, and an audio carrier. The frequency of the video carrier is 1.25 MHz above the lower edge, so for channel 2 the video is at 55.25 MHz. The color carrier is approx. 3.58 MHz above the _video_ carrier (N.B. not the lower edge), so for ch 2 it is 58.83 MHz. The audio carrier is 4.5 MHz above the _video_ carrier, so for ch 2 it is 59.75 MHz. Rate this link
Bidirectional cable TV
To fullfill the data communication needs the cable TV network needs to be bidirections. While CATV is moving toward adequate downstream bandwidth to get signals to the customer, one of the remaining problems is the upstream bandwidth to carry signals from the customer to the cable system headend or interconnect with other networks for telephone, data, and interactive services. The available bandwidth for these upstream signals is small, ranging from 5 MHz to 42 MHz, and it is sensitive to the ingress of other frequencies. To deliver data services, like cable modem service, over a cable network, typically one television channel (in the 50 - 750 MHz range) is typically allocated for downstream traffic to homes and another channel (in the 5 - 42 MHz band) is used to carry upstream signals. A single downstream 6 MHz television channel may support up to 27 Mbps of downstream and upstream channels may deliver 500 Kbps to 10 Mbps. Some European cable TV systems use a larger bandwidth for upstream signals. For example using frequencies from 5 MHz to 65 MHz for upstream traffic gives much more bandwidth to this direction. The downside of this approach is that some of the lowest frequency TV channels cannot be used anymore in the cable TV network.
Cable modem links - A collection of links to information on two way data transmission using cable modems and similar devices. Rate this link
Connecting Homes to the Internet: An Engineering Cost Model of Cable vs. ISDN Rate this link
Measuring Cable Television Network Downstream Signal Amplitudes - Many of today's signal level meters, spectrum analyzers, and quadrature amplitude modulation (QAM) analyzers support the measurement of both analog TV channels and 64- and 256-QAM digitally modulated carriers. When configuring, maintaining, or troubleshooting a DOCSIS cable modem termination system (CMTS), one important task is to make certain that the 64- or 256-QAM digitally modulated carrier's average power is correct. Rate this link
Obtain Power Measurements of a DOCSIS Downstream Signal Using a Spectrum Analyzer - Spectrum analyzers provide a convenient way to measure the amplitude of digitally modulated carriers. If you are not careful about what you are doing, however, it is very easy to make mistakes. This document provides step-by-step instructions to accurately measure the amplitude of digitally modulated carriers. Rate this link
Digital cable TV
The TV brodcasting in cable TV networks is becoming nowdays also digital. This is usually called "digital cable". To understand this, let's comparethe analogue and digital cable first.In an analog cable you have the picture data encoded as analog voltagedifferences (relative) to a reference and a reference level. It is onseparate frequency carriers to separate signals. In a digital cable youhave the separate frequency carriers, but the data in encoded as pulsecodes which must be interpreted into values.Usually one carrier carries lots of data, enough to carry more than oneTV channel and accessory services. Generally few TV channels(typically 3-5) and some extra data are multipexed to this one carrier. In this way one carrier (which takes about same bandwidth as oneanalogue channel) can transfer more than one TV channel. Basically the digital cable system will work with the same cable TV insfrastructure (same cable, amplifiers, signal splitters etc.) as the analogue cable TV. Generally when cable TVs start offering digital cable service, they just send those signals to their existing cable TV network just to some unused channel freuquencies in the cable TV. So the cable TV network will carry at the same time both analogueand digital cable TV signals at the same time. The process of transmitting digital cable signal is the following:Analog video/audio - digitisation - MPEG compression - Multiplexing ( youcan now call it digital) - Preparation for transmisson - modulation toanalog carrier.Reception process is the following:Demodulation of analogue carrier - Error correction - Demultiplexing - MPEG decompression - DA conversion to get analogue signal (unless you use digital display).
Wireless cable
Wireless Cable is a broadband service that delivers addressable multichannel television programming, Internet access, data transfer services, and other interactive services over a terrestrial microwave platform. Multipoint Multichannel Distribution Service (MMDS) is often used as a synonym for "Wireless Cable." Multichannel Multipoint Distribution System, or MMDS, spectrum, has been in use for analog TV since the 1960s. The original idea was that educational institutions would use these frequencies for long-distance learning. But this part of the spectrum, with the capacity for roughly 30 analog TV stations, was later deployed by private companies planning to compete with cable franchises.
How Does Wireless Cable Work? - Wireless Cable is a broadband service that delivers addressable multichannel television programming, Internet access, data transfer services, and other interactive services over a terrestrial microwave platform. Multipoint Multichannel Distribution Service (MMDS) is often used as a synonym for "Wireless Cable." Rate this link
Wireless cable makes a surprise comeback - Wireless cable is an odd business that's been suffering a slow death for the better part of the 1990s. The wireless-cable industry, based on the Multichannel Multipoint Distribution System, or MMDS, spectrum, has been in use for analog TV since the 1960s. The industry looked promising in the early '90s and launched some of the hottest public offerings in pre-Internet times. Nowadays the wireless-cable spectrum is useful because it is wide enough to carry high-bandwidth data applications, including video-over-data and voice-over-data. Rate this link
Wireless Cable TV FAQ - Wireless cable is a name given to a service that is called Multichannel Multipoint Distribution Service (or MMDS). Wireless cable uses Super High Frequency ("SHF") channels to transmit satellite cable programming over-the-air instead of through overhead or underground wires. Rate this link
Satellite TV
Conceptually, satellite television is a lot like broadcast television. It's a wireless system for delivering television programming directly to a viewer's house. Both broadcast television and satellite stations transmit programming via a radio signal. Satellite television broadcast signals from satellites orbiting the Earth. Satellite television systems transmit and receive radio signals using specialized antennas called satellite dishes. The television satellites are all in geosynchronous orbit, meaning that they stay in one place in the sky relative to the Earth. Each satellite is launched into space at about 7,000 mph (11,000 kph), reaching approximately 22,200 miles (35,700 km) above the Earth. Those satellites are put to such orbit that that they stay always in the same direction when you look at them from the ground, so the people who want to receive signals from the just aim their satellite dish to the satellite they want and they can keep the aiming same all the time.
Today most satellite TV customers get their programming through a direct broadcast satellite (DBS) provider or other digital satallite broadcasting provider. . The provider selects programs and broadcasts them to subscribers as a set package. Basically, the provider's goal is to bring dozens or even hundreds of channels to your television in a form that approximates the competition, cable TV. Modern satellite provider's broadcast is completely digital, which means it has a goof picture and sound quality. The two major providers in the United States use the MPEG-2 compressed video format. Also European digital satellite broadcasters use MPEG-2 technology. TV signals are transmitted at many different frequency bands. Early satellite television was broadcast in C-band radio -- radio in the 3.4-gigahertz (GHz) to 7-GHz frequency range. Digital broadcast satellite transmits programming in the Ku frequency range (12 GHz to 14 GHz ).
The basic idea on the receiving side is simple: The viewer's dish picks up the signal from the satellite (or multiple satellites in the same part of the sky) and passes it on to the receiver in the viewer's house. The receiver processes the signal and passes it on to a standard television.
A satellite dish is just a special kind of antenna designed to focus on a specific broadcast source. The standard dish consists of a parabolic (bowl-shaped) surface and a central feed horn. The satellite dish is a very direction antenna that needs to be carefully adjusted to point exactly to the satellite. To be able to make the right adjustment, you need to first know to what satellite you want to point your dish to (know the direction and height). Then you need certain tools to make the adjustment. Usually a compass is a good tool to know the right direction to point to. For height there is often some kind of scale in the satellite dish mounting hardware. First you point your satellite dish to approximately to right direction, and then use a satellite signal strength meter to find the exact direction that gives the strongest signal. This signal strength meter is a simple meter (can have analogue or digital display or just audio signal) that is used to maximize a satellite signal between the LNB amplifier and the receiver. It just measures the signal strenght at 950MHz - 2,050MHz frequency range, -25 to -75 dBm signal amplitude and is typically powered by satellite receiver (same 18-18V power as used by LNB).
The central element in the feed horn is the low noise blockdown converter, or LNB. The LNB amplifies the radio signal bouncing off the dish, filters out the noise (radio signals not carrying programming) and converts the signal to frequency range that can be tranported practically through normal coaxial cable (converts many GHz frequency to below 2 GHz frequencies). The LNB passes the amplified, converted and filtered signal to the satellite receiver inside the viewer's house. The reception heads, the LNBs, have made enormous progress, with average noise factors in the range of 1.5 to 1.8 dB in 1990 and 0.8 to 1.1 dB in 1998, compared to 3 to 5 dB in 1977. This ensures the same service area with much smaller transmission power (50 to 100W instead of 200W at satellite) at identical or smaller antenna dimensions. Different satellite systems can use different signal polarisations. Circular polarisation is nowadays preferred over the linear polarisation in digital direct broadcasting satellite system in USA. This is because, for circular polarisation, the orientation of the reception head (LNB) around the propogation axis is unimportant, and therefore does not require any precise adjustment. This point is especially important for motorised antennae which, with linear polarisation, require a polarisation adjustment for each different satellite. Linear polarisation is traditionally used by telecommunication satellites and also used by some satellite TV systems (allows more channels for smae frequency band because there are choises for vertical and horizontal polarisation). There are different LNBs for different satellite bands. In many satellite TV applcations nowadays so called "Universal LNB" devices are used in Europe. Here are general specifications of such devices (from SHP catalogue 2004 page 472):
Freuqency in: 10.7-11.70 and 11.7-12.75 GHz
Frequency out: 950-1950 and 1100-2150 MHz
Local oscillator: 9.75 and 10.60 GHz
Amplification: 58 dB
Phase noise: less than -75 dBc (@10kHz)
X-polarization: greater than 23 dB
Switching voltage for vertical polarisation: 11.5-14.0 V
Switching voltage for horizontal polarisation: 16.0-19.0 V
Tone switching: Lo=0kHz, Hi=20kHz
DC current: typically 140 mA, max. 200 mA
Mounting: 40 mm diameter
Prices of this kind of devices typically vary from 10 Euros to over 100 Euros depending on the features (for example LNBs with outputs for multiple satellite receivers are more expensive than single output models).
The signal traveling through the cable from the satellite dish to the receiver is very deferent then a standard TV signal used by the cable companies or what you would receive with a roof top antenna. The signal from the dish to the receiver is typically in 1-2 GHz frequency range (where normal TV broadcasts and cable TV are all blow 1 GHz frequency). It takes a good quality cable to transfer this kind of hifh frequency signals well. Practically every manufacture calls for RG-6 cable to be used during the installation of satellite system. This is a very good cable to use, although not the only option. Not all RG-59 can be used for a satellite dish installation, but there is good RG-59 that can be used just fine and really low quality RG-59 cable that should not be used. Besides the cable signals from the dish, this coaxial cable generally also carries the power (typically 14-18V DC) to the LNB.
The end component in the entire satellite TV system is the receiver. The receiver has four essential jobs: extracts the data stream from incoming satellite signal, extracts the individual channels from the larger satellite data stream, de-scrambles the encrypted signal (you need to have deryption keys generally supplied in smartcard by the satellite provider), takes the digital MPEG-2 signal and converts it into an analog format that a standard television can recognize. Some receivers also keep track of pay-per-view programs and periodically phones a computer at the provider's headquarters to communicate billing information. In addition to the receiving functions the satellite receiver unit also sends the power to LNB (typically 14-18V DC) and possibly some control signals (DISEQ standard to control LNB switchers etc.).
General
AnalogueSat - A small web site dedicated to free tv transmissions visible across Europe on old analogue satellite receivers. Rate this link
Digital Broadcast Satellites FAQ Rate this link
Dish Network Vs Direct TV - This guide will help you decide between the two Satellite TV Services: Direct TV and Dish Network Rate this link
European Commission sets out right to use a satellite dish in the Internal Market - The European Commission has adopted a Communication in which it states that private individuals should be free to use satellite dishes without undue technical, administrative, urban planning or tax obstacles. Rate this link
How Satellite TV Works Rate this link
J-Track 3-D - Java applet which shows the orbits of many satellites Rate this link
Lyngemark Satellite Chart - service intends to cover all relevant technical data for all satellite TV & radio channels in the world in the Ku and C bands Rate this link
Lyngemark Satellite Chart: Europe, Africa & Middle East - direct link to satellistes list Rate this link
Masan Satelliittisivut - information on satellite reception in Finnish Rate this link
Satellite TV Frequently Asked Questions List (FAQ) Rate this link
SATCO DX Satellite Chart - intends to cover all radio & TV channels on satellites around the world in the Ku, C and S bands Rate this link
Satellite TV Free - Web-based dish dealers and providers are reviewed in this site. Searching for the best free satellite TV equipment (dishes and receivers) deals out there? This site is here to help you determine which of the free satellite TV companies offer the greatest deal. Rate this link
Satellite TV links Rate this link
Small Dish Installation Guide Rate this link
Tips and solutions to solve the most common satellite system problems Rate this link
Direct-to-home tv Enjoy more channels with better quality! - The recently approved direct-to-home (DTH) TV obviates the requirement of cable-wallahs and enables viewers to access error-free programmes with better picture- and audio-quality. Rate this link
Satellites
SES Astra Rate this link
Eutelsat Rate this link
Channels
SATCO DX Satellite Chart - covers all radio & TV channels on satellites around the world in the Ku, C and S bands Rate this link
Lyngsat satellite channel list Rate this link
Technology
Adjustable LNB Power Supply Is DiSEqC Compatible - This circuit provides a digitally switchable 13V or 17V for the low-noise block (LNB) typically found in satellite receivers at the antenna feedhorn. This variation of supply voltage "tells" the remotely located LNB electronics whether it should set the antenna polarization clockwise or counterclockwise, which thereby eliminates the need for an interface and cable connection to the antenna. The circuit shown also supports an emerging and more sophisticated communications bus called the DiSEqC standard (for Digital Satellite Equipment Control). Rate this link
Direct Broadcasting Service - lots of links Rate this link
Direct Satellite Broadcast brings downlink directly to your set-top box - tehnology article Rate this link
Error Recovery for MPEG-2 Satellite Receivers - article from Rate this link
SMW - links to satellites, standards and encryption Rate this link
SMW link software - necessary calculations for you about how to align your dish and what picture quality you can expect Rate this link
Satellite receving equipment technology
The conventional LNB known as the "Marconi (polarisation) Switching LNB" responds to the supply voltage to change the polarisation. If the supply voltage going up the dish cable is less than 15 volts, the LNB will "see" only vertically polarised transmissions. If the voltage is more than 15 volts, it will "see" only horizontally polarised transmissions. The "Universal" LNB switches polarisation with voltage but it also switches its internal oscillator for "High Band" when it "hears" a 22kHz tone. Specificallly, the oscillator changes from 9.75 GHz to 10.6 GHz. An alternative use for the 22kHz tone is to control an external switching box whichfeeds signals from one of a pair of LNBs into the receiver. When the box "hears" a 22kHz tone it swaps to the other LNB. ToneBurst is a method for controlling the simplest DiSEqC switches. The satellite tuner sends special 22 kHz signal to the antenna cable. When the switch destects this signal, it changes the switch position (no signal means one position, 22 kHz bursts present mean another position). Now this swithing is becomign digital. DiSEqC is an open standard that stands for Digital Satellite Equipment Control. DiSEqC messages are sent as sequences of short bursts of 22KHz tone modulated on the LNB power supply carried by the coax cable from the LNB input on the receiver (the master). Messages comprise a number of digital bytes of eight bits each. DiSEqC system has been designed primarily to meet the problem of two-satellite, two-band systems with ease. It has dedicated outputs to select polarity, satellite position and frequency band. In DiSEqC 1.0 system the satellite tuner sends digitally modulated 22 kHz audio tone to the antenna cable. This modulated signal then controls DiSEqC 1.0 compatible devices like antenn signal switchers. The newer DiSEqC specification (1.1, 1.2, 2x) have extra functionality to the system.
DiSEqC Specifications - Full specifications and associated documentation for the DiSEqC (Digital Satellite Equipment Control) system, which is a communication bus between satellite receivers and peripheral equipment using only the existing coaxial cable. DiSEqC can be integrated into consumer satellite installations to replace all conventional analogue switching, providing a standardised digital system with non-proprietary commands and enabling switching in multi-satellite installations. Rate this link
What is DiSEqC? - DiSEqC is an open standard that stands for Digital Satellite Equipment Control. Rate this link
Diseqc 1.2 to standard 36 V DC Motor interface - A Diseqc 1.2 compatible positioner for old 24/36V DC Motor positioner. Rate this link
Protection
Defiant Eurosat - lots of satellite cracking information Rate this link
Video protection systems
Cable and satellite TV protection is designed to protect the broadcaster's program material so that only the people who pay for viewing those protected channels can view them. Owning and/or using your own video protection decoding circuit is illegal in many countries. Just building your own cable decoder box is also not a generally good idea, beachus there are tens of different cable decoding box systems and many different protections schemes in use, so every cable decoder plan works only on a very limited number of cable TV networks and it is hard to get to know which cable TV decoder works in which network unless you build and test. And there is no guarantee that any of the circuits below has worked well in any cable TV network. Basically those following circuit have only informational value to electronics hackers who are interrested in cable TV decoding electronics.
General
Hackwatch - news and FAQ on Pay Television decoding/hacking Rate this link
Lakiotteita - legal information related to cable TV scrambling systems in Finland, text in Finnish Rate this link
Overview of protection methods in existing TV and storage devices Rate this link
Scrambling News magazine - insider information on the current TV video scrambling and de-scrambling Rate this link
Cable TV
Many cable TV operators use their cable to send both normal unencrypted TV channels (basic cable TV service) and encrypted channels (extra pay channels) to the customer usin same cable. Those pay channels are encrypted so that they can be viewed with only a proper decrypting device (you usually get it from the cable operato when you subscribe to the pay channel service). Those pay channels are usually encrypted using quite simple analogue encryption techniques. Those encryptions prevent normal viewers to view those channels. There are many ways and means of scrambling a video signal. Unfortunately, very few methods survive the combined requirements of being able to pass through non-linear transmission media, prevent TV's from holding lock, and deceive the human eye into not recognising scenes even though they are grossly distorted and corrupted. It is also desirable to remain compatible with all video equipment and be tolerant of other devices that can (and do) distort the signal. You might have heard of decrypting boxes which allow which allow you to view pay channels for free (without paying to cable TV operator). Such devices really exist, but is another thing to make such box to work. First using such box is a fraud, steal of a service you are not paying for (more or less illegal in most countries). If you think that you want to be a criminal and steal the service, the thigns do not get easy here. The problem of getting or building a right type of cable decrypting box that works for you is problematic. There are mor than half dozen different major encryption systems widely used. And there are many variations of the different encryption systems. When the cable TV operator does not tell you what encryption you use and most cable TV decoder plans are poorly documented what system they work with, so it is usually not a good idea to try to build such thign unless you know very well what you are doing and you are prepared to take the risks (like that the circuit might not work and you could get gaught of stealign cable service which can get you to problems). Due to different scrambling systems, you might find it hard to determine what kind of cable decoder you can use with your cable TV connection (if you plan to do this).
Build your own pay tv box decoder - Very simple cable TV deciver plan for some very ancient cable TV protection systems. Rate this link
Cable Descrambler - Here is a scanned article from the May 1990 issue of Radio and Electronics that describes how to build a cable descrambler. Remember, this circuit is for educational purposes only and may not apply to many of the digital systems in use today. Rate this link
FAQ - Decoding pay TV Rate this link
Suppressed Sync and Active Video Inversion (SSAVI) - document is in English and Finnish Rate this link
SSAVI Salausj??rjestelm??n FAQ - information on SSAVI video protection system in Finnish Rate this link
SSAVI Scrambling System FAQ Rate this link
Satellite protection
FAQ - European Scrambling Systems Rate this link
VCR copy protection
VCR copy protection systems are designed to prevent consumers to copy video material to their own VCR. The most commonly used and best known video protection system for this is called Macrovision. Macrovision is an analogue copy protection of Videotapes, DVD movies and pay-per-view television (Analogue signal). Its purpose is to make it harder to record such signals with a VCR. Generally the protection must be disabled or removed, before recording by a VCR is possible. Macrovision is the most commonly used antitaping process for VHS video tapes and digital video systems.Around 95% if VCRs on the market do not record Macrovision protected signal with any usable quality. If you try to copy a Macrovision-protected tape, the copy becomes crappy and not worth seeing, the picture changes brightness with time and the color is distorted. Not all TV's work very well with this form of protection e.g. the top of picture is distorted and it might look like the tape is damaged. Macrovision is based on using a hyper-brightsync pulse (to confuse the AGC of a VCR) and also does things to the chromato further confuse such. Macrovision works due to the differences in theway VCRs and TVs operate. The automatic gain control circuits within a TV are designed to respond slowly to change. Those for a VCR are designed to respond quickly to change. The Macrovision technique attempts to take advantage of this by modifying the video signal so that a TV will still display it but the VCR will not record a viewable picture. CGMS is Copy Guard Management system for NTSC systems. A method of preventing copies or controlling the number of sequential copies allowed. CGMS is transmitted on line 20 for odd fields and line 283 for even fields for NTSC. For digital formats it is added to the digital signal conforming to IEEE 1394.
How does copy protection on a video tape work? Rate this link
Implementation of Macrovision remover Rate this link
Macrovision - the company which created the most popular VCR copy protection system Rate this link
Macrovision Decoder - circuit to remove macrovision Rate this link
Macrovision video copy protection system removing circuit Rate this link
Video Stabilizer - unit designed to remove the copy-protection from prerecorded video tapes, to allow them to be played through older televisions or making backup copies of tapes which you own, designed for PAL format Rate this link
Circuits
