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69-635: Sky Multichannels was a package of analogue television services offered by BSkyB on the Astra satellites at 19.2° east from 1 September 1993 to 27 September 2001, which started off with 15 channels before expanding to over 40. The service started on 1 September 1993, based on the idea from chief executive officer Sam Chisholm and Rupert Murdoch of converting the company's business strategy to an entirely fee-based concept. The new package included four channels formerly available free-to-air on Astra's satellites, as well as introducing new channels. Some of

138-427: A bandwidth of tens of megahertz. Most transponders operate on a bent pipe (i.e., u-bend ) principle, sending back to Earth what goes into the conduit with only amplification and a shift from uplink to downlink frequency. However, some modern satellites use on-board processing, where the signal is demodulated, decoded, re-encoded and modulated aboard the satellite. This type, called a "regenerative" transponder,

207-414: A digital television (DTV) signal remains good until the signal level drops below a threshold where reception is no longer possible or becomes intermittent. Analog television may be wireless ( terrestrial television and satellite television ) or can be distributed over a cable network as cable television . All broadcast television systems used analog signals before the arrival of DTV. Motivated by

276-627: A given bandwidth. This is because sophisticated comb filters in receivers are more effective with NTSC's 4 color frame sequence compared to PAL's 8-field sequence. However, in the end, the larger channel width of most PAL systems in Europe still gives PAL systems the edge in transmitting more picture detail. In the SECAM television system, U and V are transmitted on alternate lines, using simple frequency modulation of two different color subcarriers. In some analog color CRT displays, starting in 1956,

345-527: A given signal completely, it is necessary to quote the color system plus the broadcast standard as a capital letter. For example, the United States, Canada, Mexico and South Korea used (or use) NTSC-M , Japan used NTSC-J , the UK used PAL-I , France used SECAM-L , much of Western Europe and Australia used (or use) PAL-B / G , most of Eastern Europe uses SECAM-D / K or PAL-D/K and so on. Not all of

414-503: A means of television channel selection. Analog broadcast television systems come in a variety of frame rates and resolutions. Further differences exist in the frequency and modulation of the audio carrier. The monochrome combinations still existing in the 1950s were standardized by the International Telecommunication Union (ITU) as capital letters A through N. When color television was introduced,

483-399: A number of different broadcast television systems are in use worldwide, the same principles of operation apply. A cathode-ray tube (CRT) television displays an image by scanning a beam of electrons across the screen in a pattern of horizontal lines known as a raster . At the end of each line, the beam returns to the start of the next line; at the end of the last line, the beam returns to

552-478: A number of false claims involving some of the channels which were due to be part of the package, as well as further complaints about the commercials failing to state that a one-year contract had to be taken out to take advantage of any special introductory offer. In conjunction with the launch of the Multichannels package, all Sky networks adopted a cohesive graphical and music appearance as idents featured

621-399: A second demodulator, the Z demodulator, also extracts an additive combination of U plus V, but in a different ratio. The X and Z color difference signals are further matrixed into three color difference signals, (R-Y), (B-Y), and (G-Y). The combinations of usually two, but sometimes three demodulators were: In the end, further matrixing of the above color-difference signals c through f yielded

690-462: A signal would not be compatible with monochrome receivers, an important consideration when color broadcasting was first introduced. It would also occupy three times the bandwidth of existing television, requiring a decrease in the number of television channels available. Instead, the RGB signals are converted into YUV form, where the Y signal represents the luminance of the colors in the image. Because

759-410: A television image is composed of scan lines drawn on the screen. The lines are of varying brightness; the whole set of lines is drawn quickly enough that the human eye perceives it as one image. The process repeats and the next sequential frame is displayed, allowing the depiction of motion. The analog television signal contains timing and synchronization information so that the receiver can reconstruct

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828-438: A two-dimensional moving image from a one-dimensional time-varying signal. The first commercial television systems were black-and-white ; the beginning of color television was in the 1950s. A practical television system needs to take luminance , chrominance (in a color system), synchronization (horizontal and vertical), and audio signals , and broadcast them over a radio transmission. The transmission system must include

897-523: A variant with the signature of Gari's pre-existing "Great News" package in 1989, which had been used since launch and received a slight update with the new look). The full package was used in promotional spots for what was termed as "the brand new Sky" and during periods where BSkyB channels were off the air. To promote the Sky Multichannels package on the Astra satellites, a selection of channels

966-480: A volt. At this point the IF signal consists of a video carrier signal at one frequency and the sound carrier at a fixed offset in frequency. A demodulator recovers the video signal. Also at the output of the same demodulator is a new frequency modulated sound carrier at the offset frequency. In some sets made before 1948, this was filtered out, and the sound IF of about 22 MHz was sent to an FM demodulator to recover

1035-508: Is Sound-in-Syncs . The luminance component of a composite video signal varies between 0 V and approximately 0.7 V above the black level. In the NTSC system, there is a blanking signal level used during the front porch and back porch, and a black signal level 75 mV above it; in PAL and SECAM these are identical. In a monochrome receiver, the luminance signal is amplified to drive

1104-411: Is a brief (about 1.5 microsecond ) period inserted between the end of each transmitted line of picture and the leading edge of the next line's sync pulse . Its purpose was to allow voltage levels to stabilise in older televisions, preventing interference between picture lines. The front porch is the first component of the horizontal blanking interval which also contains the horizontal sync pulse and

1173-506: Is easier to tune the picture without losing the sound. So the FM sound carrier is then demodulated, amplified, and used to drive a loudspeaker. Until the advent of the NICAM and MTS systems, television sound transmissions were monophonic. The video carrier is demodulated to give a composite video signal containing luminance, chrominance and synchronization signals. The result is identical to

1242-752: Is more complex, but has many advantages, such as improving the signal to noise ratio as the signal is regenerated from the digital domain, and also permits selective processing of the data in the digital domain. With data compression and multiplexing , several video (including digital video ) and audio channels may travel through a single transponder on a single wideband carrier . Original analog video only had one channel per transponder, with subcarriers for audio and automatic transmission-identification service ATIS . Non-multiplexed radio stations can also travel in single channel per carrier (SCPC) mode, with multiple carriers (analog or digital) per transponder. This allows each station to transmit directly to

1311-468: Is that the U and V signals are zero when the picture has no color content. Since the human eye is more sensitive to detail in luminance than in color, the U and V signals can be transmitted with reduced bandwidth with acceptable results. In the receiver, a single demodulator can extract an additive combination of U plus V. An example is the X demodulator used in the X/Z demodulation system. In that same system,

1380-405: Is the difference between the B signal and the Y signal, also known as B minus Y (B-Y), and the V signal is the difference between the R signal and the Y signal, also known as R minus Y (R-Y). The U signal then represents how purplish-blue or its complementary color, yellowish-green, the color is, and the V signal how purplish-red or its complementary, greenish-cyan, it is. The advantage of this scheme

1449-500: Is the original television technology that uses analog signals to transmit video and audio. In an analog television broadcast, the brightness, colors and sound are represented by amplitude , phase and frequency of an analog signal. Analog signals vary over a continuous range of possible values which means that electronic noise and interference may be introduced. Thus with analog, a moderately weak signal becomes snowy and subject to interference. In contrast, picture quality from

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1518-566: Is the same as the original U signal at the corresponding time. In effect, these pulses are discrete-time analog samples of the U signal. The pulses are then low-pass filtered so that the original analog continuous-time U signal is recovered. For V, a 90-degree shifted subcarrier briefly gates the chroma signal every 280 nanoseconds, and the rest of the process is identical to that used for the U signal. Gating at any other time than those times mentioned above will yield an additive mixture of any two of U, V, -U, or -V. One of these off-axis (that is, of

1587-542: Is transmitted. Therefore, the receiver must reconstitute the subcarrier. For this purpose, a short burst of the subcarrier, known as the colorburst, is transmitted during the back porch (re-trace blanking period) of each scan line. A subcarrier oscillator in the receiver locks onto this signal (see phase-locked loop ) to achieve a phase reference, resulting in the oscillator producing the reconstituted subcarrier. NTSC uses this process unmodified. Unfortunately, this often results in poor color reproduction due to phase errors in

1656-475: Is used to build the image. This process doubles the apparent number of video frames per second and further reduces flicker and other defects in transmission. The television system for each country will specify a number of television channels within the UHF or VHF frequency ranges. A channel actually consists of two signals: the picture information is transmitted using amplitude modulation on one carrier frequency, and

1725-413: Is used to reduce the channel spacing, which would be nearly twice the video bandwidth if pure AM was used. Signal reception is invariably done via a superheterodyne receiver : the first stage is a tuner which selects a television channel and frequency-shifts it to a fixed intermediate frequency (IF). The signal amplifier performs amplification to the IF stages from the microvolt range to fractions of

1794-492: The ITU in 1961 as: A, B, C, D, E, F, G, H, I, K, K1, L, M and N. These systems determine the number of scan lines, frame rate, channel width, video bandwidth, video-audio separation, and so on. A color encoding scheme ( NTSC , PAL , or SECAM ) could be added to the base monochrome signal. Using RF modulation the signal is then modulated onto a very high frequency (VHF) or ultra high frequency (UHF) carrier wave . Each frame of

1863-430: The back porch . The back porch is the portion of each scan line between the end (rising edge) of the horizontal sync pulse and the start of active video. It is used to restore the black level (300 mV) reference in analog video. In signal processing terms, it compensates for the fall time and settling time following the sync pulse. In color television systems such as PAL and NTSC, this period also includes

1932-465: The colorburst signal. In the SECAM system, it contains the reference subcarrier for each consecutive color difference signal in order to set the zero-color reference. In some professional systems, particularly satellite links between locations, the digital audio is embedded within the line sync pulses of the video signal, to save the cost of renting a second channel. The name for this proprietary system

2001-534: The control grid in the electron gun of the CRT. This changes the intensity of the electron beam and therefore the brightness of the spot being scanned. Brightness and contrast controls determine the DC shift and amplification, respectively. A color signal conveys picture information for each of the red, green, and blue components of an image. However, these are not simply transmitted as three separate signals, because: such

2070-532: The Doppler shift and thus infer range and speed from a communication signal without allocating power to a separate ranging signal. A transponder equivalent ( TPE ) is a normalized way to refer to transponder bandwidth. It simply means how many transponders would be used if the same total bandwidths used only 36 MHz transponders. So, for example, the ARSAT-1 has 24 IEEE K u band transponders: 12 with

2139-408: The NTSC and PAL color systems, U and V are transmitted by using quadrature amplitude modulation of a subcarrier. This kind of modulation applies two independent signals to one subcarrier, with the idea that both signals will be recovered independently at the receiving end. For NTSC, the subcarrier is at 3.58 MHz. For the PAL system it is at 4.43 MHz. The subcarrier itself is not included in

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2208-411: The NTSC system. PAL's color encoding is similar to the NTSC systems. SECAM, though, uses a different modulation approach than PAL or NTSC. PAL had a late evolution called PALplus , allowing widescreen broadcasts while remaining fully compatible with existing PAL equipment. In principle, all three color encoding systems can be used with any scan line/frame rate combination. Therefore, in order to describe

2277-405: The U and V axis) gating methods is called I/Q demodulation. Another much more popular off-axis scheme was the X/Z demodulation system. Further matrixing recovered the original U and V signals. This scheme was actually the most popular demodulator scheme throughout the 1960s. The above process uses the subcarrier. But as previously mentioned, it was deleted before transmission, and only the chroma

2346-407: The Y signal) represents the approximate saturation of a color, and the chrominance phase against the subcarrier reference approximately represents the hue of the color. For particular test colors found in the test color bar pattern, exact amplitudes and phases are sometimes defined for test and troubleshooting purposes only. Due to the nature of the quadrature amplitude modulation process that created

2415-435: The basic sound signal. In newer sets, this new carrier at the offset frequency was allowed to remain as intercarrier sound , and it was sent to an FM demodulator to recover the basic sound signal. One particular advantage of intercarrier sound is that when the front panel fine tuning knob is adjusted, the sound carrier frequency does not change with the tuning, but stays at the above-mentioned offset frequency. Consequently, it

2484-423: The beginning of the first line at the top of the screen. As it passes each point, the intensity of the beam is varied, varying the luminance of that point. A color television system is similar except there are three beams that scan together and an additional signal known as chrominance controls the color of the spot. When analog television was developed, no affordable technology for storing video signals existed;

2553-419: The brightness control signal ( luminance ) is fed to the cathode connections of the electron guns, and the color difference signals ( chrominance signals) are fed to the control grids connections. This simple CRT matrix mixing technique was replaced in later solid state designs of signal processing with the original matrixing method used in the 1954 and 1955 color TV receivers. Synchronizing pulses added to

2622-504: The channels for £3.99 a month until the start of 1994. Additional packages including the multiple channels alongside one or more of Sky's premium channels were available from £11.99 to £19.99. The channels were encrypted using NDS Group 's VideoCrypt system, and viewing them required a monthly subscription payment, a decoder and a valid viewing card. In 1995, the number of Sky customers exceeded five million. Sky Sports 2 , Sky Soap and Sky Travel which launched on 3 October 1994 joined

2691-415: The channels had been broadcast either in the clear or soft encrypted (i.e. a VideoCrypt decoder was required, but without a subscription card) prior to their addition to the Multichannels package. Within two months of the launch, Sky gained 400,000 new subscribers with the majority taking at least one premium channel, which helped BSkyB reach 3.5 million households by mid-1994. The service continued until

2760-480: The channels on Astra 1D had been discontinued. On 9 May 2001, it was announced that due to the possibility of lost revenue from the 242,000 analogue subscribers, the closure of the remaining analogue channels would be delayed from June to September. BSkyB closed down the last service in the Multichannels package - Sky One - on 27 September of that year. The subscription cost was £ 6.99 a month at launch, although those who signed up before 1 September 1993 could get

2829-578: The chrominance information was added to the monochrome signals in a way that black and white televisions ignore. In this way backward compatibility was achieved. There are three standards for the way the additional color information can be encoded and transmitted. The first was the American NTSC system. The European and Australian PAL and the French and former Soviet Union SECAM standards were developed later and attempt to cure certain defects of

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2898-436: The chrominance signal, at certain times, the signal represents only the U signal, and 70 nanoseconds (NTSC) later, it represents only the V signal. About 70 nanoseconds later still, -U, and another 70 nanoseconds, -V. So to extract U, a synchronous demodulator is utilized, which uses the subcarrier to briefly gate the chroma every 280 nanoseconds, so that the output is only a train of discrete pulses, each having an amplitude that

2967-409: The closure of BSkyB's analogue platform on 27 September 2001, due to the expansion of Sky Digital after its launch three years earlier. Channels added later include QVC (1 October 1993) and VH1 (1 October 1994). When VH1's German version started on 10 March 1995, VideoCrypt decoders would blank out the service to British viewers and prevent them from watching the channel for free. Nick at Nite

3036-425: The combining process, the low-resolution portion of the Y signals cancel out, leaving R, G, and B signals able to render a low-resolution image in full color. However, the higher resolution portions of the Y signals do not cancel out, and so are equally present in R, G, and B, producing the higher-resolution image detail in monochrome, although it appears to the human eye as a full-color and full-resolution picture. In

3105-486: The composite video format used by analog video devices such as VCRs or CCTV cameras . To ensure good linearity and thus fidelity, consistent with affordable manufacturing costs of transmitters and receivers, the video carrier is never modulated to the extent that it is shut off altogether. When intercarrier sound was introduced later in 1948, not completely shutting off the carrier had the side effect of allowing intercarrier sound to be economically implemented. Each line of

3174-634: The development of the cathode-ray tube (CRT), which uses a focused electron beam to trace lines across a phosphor coated surface. The electron beam could be swept across the screen much faster than any mechanical disc system, allowing for more closely spaced scan lines and much higher image resolution. Also, far less maintenance was required of an all-electronic system compared to a mechanical spinning disc system. All-electronic systems became popular with households after World War II . Broadcasters of analog television encode their signal using different systems. The official systems of transmission were defined by

3243-503: The disc to scan an image. A similar disk reconstructed the image at the receiver. Synchronization of the receiver disc rotation was handled through sync pulses broadcast with the image information. Camera systems used similar spinning discs and required intensely bright illumination of the subject for the light detector to work. The reproduced images from these mechanical systems were dim, very low resolution and flickered severely. Analog television did not begin in earnest as an industry until

3312-417: The displayed image is transmitted using a signal as shown above. The same basic format (with minor differences mainly related to timing and the encoding of color) is used for PAL, NTSC , and SECAM television systems. A monochrome signal is identical to a color one, with the exception that the elements shown in color in the diagram (the colorburst , and the chrominance signal) are not present. The front porch

3381-515: The launch of Sky 2 and a selection of channels operated in conjunction with Granada. The launch of Astra 1D allowed Sky to further expand the Multichannels package, including the pay-per-view Box Office channels on 1 December 1997. BSkyB ran television advertisements prior to the new service launching. However, in 1993, the Independent Television Commission ruled against BSkyB after ten complaints regarding

3450-505: The launch of Sky Sports 2 on 19 August 1994. Due to the growth of digital television and the Sky platform, alongside greater choice and the reduced need for channels to timeshare due to bandwidth constraints, BSkyB announced that its analogue service would cease transmission with all channels in this package closing by 2001. The first to be ceased was TV Travel Shop which became exclusive to digital in late 1999, and by February 2000 many of

3519-540: The logo's newly-added "ring" forming out of swirling energy streaks while the text formed out of glass copies. The graphics were produced by American graphical firm Novocom, the look for Sky News resembling their earlier work for the CBS Evening News from 1991. A new music package from composer Frank Gari dubbed the Sky Symphony was also used, with differing arrangements per channel (Sky News utilized

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3588-579: The lower bandwidth requirements of compressed digital signals , beginning just after the year 2000, a digital television transition is proceeding in most countries of the world, with different deadlines for the cessation of analog broadcasts. Several countries have made the switch already, with the remaining countries still in progress mostly in Africa, Asia, and South America. The earliest systems of analog television were mechanical television systems that used spinning disks with patterns of holes punched into

3657-401: The luminance signal had to be generated and transmitted at the same time at which it is displayed on the CRT. It was therefore essential to keep the raster scanning in the camera (or other device for producing the signal) in exact synchronization with the scanning in the television. The physics of the CRT require that a finite time interval be allowed for the spot to move back to the start of

3726-435: The modulated signal ( suppressed carrier ), it is the subcarrier sidebands that carry the U and V information. The usual reason for using suppressed carrier is that it saves on transmitter power. In this application a more important advantage is that the color signal disappears entirely in black and white scenes. The subcarrier is within the bandwidth of the main luminance signal and consequently can cause undesirable artifacts on

3795-410: The negative side-effect of causing image smearing and blurring when there is rapid on-screen motion occurring. The maximum frame rate depends on the bandwidth of the electronics and the transmission system, and the number of horizontal scan lines in the image. A frame rate of 25 or 30 hertz is a satisfactory compromise, while the process of interlacing two video fields of the picture per frame

3864-451: The next line ( horizontal retrace ) or the start of the screen ( vertical retrace ). The timing of the luminance signal must allow for this. The human eye has a characteristic called phi phenomenon . Quickly displaying successive scan images creates the illusion of smooth motion. Flickering of the image can be partially solved using a long persistence phosphor coating on the CRT so that successive images fade slowly. However, slow phosphor has

3933-1065: The package. By October and November 1995, the launch of Astra 1D allowed Sky to expand the Multichannels package further with the Sci-Fi Channel , Paramount Channel , Sky Sports Gold and History Channel , as well as the Disney Channel , Christian Channel Europe , European Business News , Television X and Playboy TV which were added to Astra 1C . QVC, which launched as part of the Multichannels package, switched to free-to-view broadcasting in this year. Channel 11 notes (up until October 1995): In 1996, Sky reached six million subscribers. New channels included Sky Sports 3 (replacing Sky Sports Gold), along with Sky 2 , Computer Channel , Granada Sky Broadcasting (with Plus , Men & Motors , Good Life and Talk TV ), Weather Channel UK , HSN Direct , Fox Kids , Sky Scottish and Trouble (from early 1997). During 1997, but same as above: Analog television Analog television

4002-452: The phase of the signal on each successive line, and averaging the results over pairs of lines. This process is achieved by the use of a 1H (where H = horizontal scan frequency) duration delay line. Phase shift errors between successive lines are therefore canceled out and the wanted signal amplitude is increased when the two in-phase ( coincident ) signals are re-combined. NTSC is more spectrum efficient than PAL, giving more picture detail for

4071-488: The picture, all the more noticeable in black and white receivers. A small sample of the subcarrier, the colorburst , is included in the horizontal blanking portion, which is not visible on the screen. This is necessary to give the receiver a phase reference for the modulated signal. Under quadrature amplitude modulation the modulated chrominance signal changes phase as compared to its subcarrier and also changes amplitude. The chrominance amplitude (when considered together with

4140-739: The possible combinations exist. NTSC is only used with system M, even though there were experiments with NTSC-A ( 405 line ) in the UK and NTSC-N (625 line) in part of South America. PAL is used with a variety of 625-line standards (B, G, D, K, I, N) but also with the North American 525-line standard, accordingly named PAL-M . Likewise, SECAM is used with a variety of 625-line standards. For this reason, many people refer to any 625/25 type signal as PAL and to any 525/30 signal as NTSC , even when referring to digital signals; for example, on DVD-Video , which does not contain any analog color encoding, and thus no PAL or NTSC signals at all. Although

4209-468: The received signal, caused sometimes by multipath, but mostly by poor implementation at the studio end. With the advent of solid-state receivers, cable TV, and digital studio equipment for conversion to an over-the-air analog signal, these NTSC problems have been largely fixed, leaving operator error at the studio end as the sole color rendition weakness of the NTSC system. In any case, the PAL D (delay) system mostly corrects these kinds of errors by reversing

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4278-432: The rendering of colors in this way is the goal of both monochrome film and television systems, the Y signal is ideal for transmission as the luminance signal. This ensures a monochrome receiver will display a correct picture in black and white, where a given color is reproduced by a shade of gray that correctly reflects how light or dark the original color is. The U and V signals are color difference signals. The U signal

4347-463: The satellite, rather than paying for a whole transponder or using landlines to send it to an Earth station for multiplexing with other stations. NASA distinguishes between a " transceiver " and "transponder". A transceiver has an independent transmitter and receiver packaged in the same unit. In a transponder the transmit carrier frequency is derived from the received signal. The frequency linkage allows an interrogating ground station to recover

4416-415: The sound is transmitted with frequency modulation at a frequency at a fixed offset (typically 4.5 to 6 MHz) from the picture signal. The channel frequencies chosen represent a compromise between allowing enough bandwidth for video (and hence satisfactory picture resolution), and allowing enough channels to be packed into the available frequency band. In practice a technique called vestigial sideband

4485-434: The three color-difference signals, (R-Y), (B-Y), and (G-Y). The R, G, and B signals in the receiver needed for the display device (CRT, Plasma display, or LCD display) are electronically derived by matrixing as follows: R is the additive combination of (R-Y) with Y, G is the additive combination of (G-Y) with Y, and B is the additive combination of (B-Y) with Y. All of this is accomplished electronically. It can be seen that in

4554-432: The video signal at the end of every scan line and video frame ensure that the sweep oscillators in the receiver remain locked in step with the transmitted signal so that the image can be reconstructed on the receiver screen. Transponder (satellite communications) A transponder is typically composed of: Most communication satellites are radio relay stations in orbit and carry dozens of transponders, each with

4623-555: Was originally going to be part of the Multichannels plan but ultimately the channel did not launch. Channels which joined the package were paid a fee of 15 pence per subscriber per month. A European Multichannels package run by BSkyB – also using the VideoCrypt encryption system – was planned to be launched soon afterwards but did not come to fruition. A package of channels called MultiChoice Kaleidoscope launched on 1 November 1993 using VideoCrypt 2 encryption. The MultiChoice service

4692-440: Was placed on Sky's preview service on transponder 47 of Astra 1C in the clear This showed promotional material in the centre of the screen and 12 channels around the edge, including some English services which were not part of the package. During football matches on Sky One , services which were also part of the Multichannels package were made available free-to-view, allowing sports subscribers to sample them. This continued until

4761-521: Was run by South Africa-based Network Holdings, separate from BSkyB, and initially included Filmnet and The Adult Channel as premium channels, and The Children's Channel (in Benelux only), Discovery , MTV , Country Music Television and QVC as basic channels. Sky Soap and Sky Travel launched, and were added to the package, on 3 October 1994 , but Sky News remained free-to-air. QVC was switched to free-to-view broadcasting on 7 March 1995. 1996 saw

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