Satellite subcarrier audio
Encyclopedia
Satellite subcarrier audio is audio transmitted by way of satellite
that utilizes a separate analog
or digital
signal carried on a main radio transmission (usually video
) on a specific satellite transponder
. More technically, it is an already-modulated signal, which is then modulated into another signal of higher frequency and bandwidth. In a more general sense, satellite subcarrier audio is an early form of satellite radio
not intended for the consumer market but was initially unencrypted
, thus receivable to satellite hobbyists.
Original analog video only has one channel per transponder, with subcarrier
s 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 the satellite, rather than paying for a whole transponder, or using landline
s to send it to an earth station
for multiplexing with other stations.
"big dish" satellite receivers. The audio ranged in frequency from 5.0 to 8.5 MHz
for both left and right audio channels. Fine tuning options included monaural and discrete stereo tuning with three bandwidth modes: narrow (130 kHz), normal (280 kHz) and wide (500 kHz).
and bandwidth. Most often, this is used on broadcast satellites to indicate that radio stations are not multiplexed
as subcarrier
s onto a single video
carrier
, but instead independently share a transponder
. It may also be used on other communications satellite
s, or occasionally on non-satellite transmission
s. In an SCPC system, satellite bandwidth is dedicated to a single source.
Analog SCPC subcarrier audio is received using dedicated satellite receivers. SCPC audio receivers tune a frequency range of 50 to 90 MHz with both wide and narrow bandwidth options. Receivers in the hobbyist price range included the Heil SC-One and the Universal Electronics SCPC-100 and SCPC-200.
FM Squared is a method of transmitting analog satellite audio where video would normally be transmitted on a satellite transponder. FM Squared was once used to distribute Muzak and similar "business" music (sometimes referred to as elevator music
) to retailers. FM Squared audio receivers tune a frequency range of 100 kHz to 9 MHz. Receivers that fell within the hobbyist price range included the Universal Electronics SC-50.
deployed a digital audio transmission system linking their broadcast center to their remote transmitters. This technology wasn't applied to satellite communications, however, until the early 1980s.
, ABC Radio Networks and NBC
. The DATS system transmitted 15 KHz-wide audio subcarriers at a date rate of 1.544 Mbps using BPSK digital modulation.
DATS was later superseded by the Spectrum Efficient Digital Audio Transmission (SEDAT) satellite audio distribution system. SEDAT allows more audio channels to be carried in the same frequency range as DATS. SEDAT, also developed by Scientific Atlanta, was primarily used by ABC Radio Networks. SEDAT transmissions ended in 2001.
technology in 1986 and was further supplanted by leased space on DBS systems such as DirecTV
and Dish Network
. The two de facto methods for digital satellite audio transmission are digital single channel per carrier
and multiple channel per carrier multiplexing
.
In digital radio systems, several variable bit-rate data streams are multiplexed together to a fixed bitrate transport stream by means of statistical multiplexing. This makes it possible to transfer several video and audio channels simultaneously over the same frequency channel, together with various services. On communications satellites which carry broadcast television networks and radio networks, this is known as multiple channel per carrier or MCPC. Where multiplexing is not practical (such as where there are different sources using a single transponder), single channel per carrier mode (SCPC) is used. Digital SCPC differs from the older analog SCPC transmission method in that a digital SCPC signal carries more than just a single audio channel (two are used) but also coding and decoding information, ancillary and control data, and network identification data. Digital SCPC and MCPC subcarrier transmissions use satellite broadcast standards such as DVB-S
and its successor DVB-S2
along with MPEG-2
and MPEG-4
compression formats, respectively. BPSK modulation has been replaced with newer modulation schemes such as QPSK
(quadrature phase-shift keying).
s (LAN) using 10/100Base-T
Ethernet
connections.
, Premiere Radio Networks
(now a Clear Channel subsidiary) and Citadel Broadcasting
(who also owns the former ABC Radio Networks).
Communications satellite
A communications satellite is an artificial satellite stationed in space for the purpose of telecommunications...
that utilizes a separate analog
Analog signal
An analog or analogue signal is any continuous signal for which the time varying feature of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. It differs from a digital signal in terms of small fluctuations in the signal which are...
or digital
Digital
A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...
signal carried on a main radio transmission (usually video
Video
Video is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.- History :...
) on a specific satellite transponder
Transponder (Satellite communications)
A communications satellite’s transponder, is the series of interconnected units which form a communications channel between the receiving and the transmitting antennas .A transponder is typically composed of:...
. More technically, it is an already-modulated signal, which is then modulated into another signal of higher frequency and bandwidth. In a more general sense, satellite subcarrier audio is an early form of satellite radio
Satellite radio
Satellite radio is an analogue or digital radio signal that is relayed through one or more satellites and thus can be received in a much wider geographical area than terrestrial FM radio stations...
not intended for the consumer market but was initially unencrypted
Encryption
In cryptography, encryption is the process of transforming information using an algorithm to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. The result of the process is encrypted information...
, thus receivable to satellite hobbyists.
Original analog video only has one channel per transponder, with subcarrier
Subcarrier
A subcarrier is a separate analog or digital signal carried on a main radio transmission, which carries extra information such as voice or data. More technically, it is an already-modulated signal, which is then modulated into another signal of higher frequency and bandwidth...
s for audio and automatic transmission identification service ATIS
Automatic Transmitter Identification System
The Automatic Transmitter Identification System is a communications protocol used for the station identification of television channels carried on satellite TV....
. Non-multiplexed radio stations can also travel in single channel per carrier
Single channel per carrier
Single channel per carrier refers to using a single signal at a given frequency and bandwidth. Most often, this is used on broadcast satellites to indicate that radio stations are not multiplexed as subcarriers onto a single video carrier, but instead independently share a transponder...
(SCPC) mode, with multiple carriers (analog or digital) per transponder. This allows each station to transmit directly to the satellite, rather than paying for a whole transponder, or using landline
Landline
A landline was originally an overland telegraph wire, as opposed to an undersea cable. Currently, landline refers to a telephone line which travels through a solid medium, either metal wire or optical fibre, as distinguished from a mobile cellular line, where transmission is via radio waves...
s to send it to an earth station
Earth station
A ground station, earth station, or earth terminal is a terrestrial terminal station designed for extraplanetary telecommunication with spacecraft, and/or reception of radio waves from an astronomical radio source. Ground stations are located either on the surface of the Earth, or within Earth's...
for multiplexing with other stations.
Analog subcarriers
Satellite subcarrier audio was initially transmitted in analog form. This method of audio transmission was first employed by Fujitsu in 1973 as part of a data line between the United States and Spain. By the early 1980s, the use of analog subcarriers for radio network distribution had become well-established.Standard subcarrier audio
Initially, satellite subcarrier audio was tuned using commercial receivers or consumer-grade TVROTelevision receive-only
Television receive-only, TVRO, or Big ugly dish , is a term used in North America to refer to the reception of satellite television from FSS-type satellites, generally on C-band analog; free-to-air and unconnected to a commercial DBS provider...
"big dish" satellite receivers. The audio ranged in frequency from 5.0 to 8.5 MHz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
for both left and right audio channels. Fine tuning options included monaural and discrete stereo tuning with three bandwidth modes: narrow (130 kHz), normal (280 kHz) and wide (500 kHz).
Single channel per carrier (analog SCPC)
Single channel per carrier (SCPC) refers to using a single signal at a given frequencyFrequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
and bandwidth. Most often, this is used on broadcast satellites to indicate that radio stations are not multiplexed
Multiplexing
The multiplexed signal is transmitted over a communication channel, which may be a physical transmission medium. The multiplexing divides the capacity of the low-level communication channel into several higher-level logical channels, one for each message signal or data stream to be transferred...
as subcarrier
Subcarrier
A subcarrier is a separate analog or digital signal carried on a main radio transmission, which carries extra information such as voice or data. More technically, it is an already-modulated signal, which is then modulated into another signal of higher frequency and bandwidth...
s onto a single video
Video
Video is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.- History :...
carrier
Carrier wave
In telecommunications, a carrier wave or carrier is a waveform that is modulated with an input signal for the purpose of conveying information. This carrier wave is usually a much higher frequency than the input signal...
, but instead independently share a transponder
Transponder
In telecommunication, the term transponder has the following meanings:...
. It may also be used on other communications satellite
Communications satellite
A communications satellite is an artificial satellite stationed in space for the purpose of telecommunications...
s, or occasionally on non-satellite transmission
Transmission (telecommunications)
Transmission, in telecommunications, is the process of sending, propagating and receiving an analogue or digital information signal over a physical point-to-point or point-to-multipoint transmission medium, either wired, optical fiber or wireless...
s. In an SCPC system, satellite bandwidth is dedicated to a single source.
Analog SCPC subcarrier audio is received using dedicated satellite receivers. SCPC audio receivers tune a frequency range of 50 to 90 MHz with both wide and narrow bandwidth options. Receivers in the hobbyist price range included the Heil SC-One and the Universal Electronics SCPC-100 and SCPC-200.
FM Squared (FM²)
The FM Squared satellite audio format was developed in 1986 by Wegener Communications and Subcarrier Systems (later SpaceCom Systems, Inc.).FM Squared is a method of transmitting analog satellite audio where video would normally be transmitted on a satellite transponder. FM Squared was once used to distribute Muzak and similar "business" music (sometimes referred to as elevator music
Elevator music
Elevator music refers to instrumental arrangements of popular music designed for playing in shopping malls, grocery stores, department stores, telephone systems , cruise ships, airports, doctors' and dentists' offices, and elevators...
) to retailers. FM Squared audio receivers tune a frequency range of 100 kHz to 9 MHz. Receivers that fell within the hobbyist price range included the Universal Electronics SC-50.
Digital subcarriers
Although not widely used until the early 2000s, digital subcarrier audio has existed almost as long as its analog technology counterpart. In 1972, the BBCBBC
The British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...
deployed a digital audio transmission system linking their broadcast center to their remote transmitters. This technology wasn't applied to satellite communications, however, until the early 1980s.
DATS and SEDAT
The first widespread digital satellite audio distribution system was Digital Audio Transmission System (DATS). DATS was developed in 1982 by Scientific Atlanta. The DATS distribution system was first used by the largest U.S. radio networks such as Westwood OneWestwood One
Westwood One was an American radio network and was based in New York City. At one time, it was managed by CBS Radio, the radio arm of CBS Corporation, and Viacom and was later purchased by the private equity firm The Gores Group...
, ABC Radio Networks and NBC
NBC
The National Broadcasting Company is an American commercial broadcasting television network and former radio network headquartered in the GE Building in New York City's Rockefeller Center with additional major offices near Los Angeles and in Chicago...
. The DATS system transmitted 15 KHz-wide audio subcarriers at a date rate of 1.544 Mbps using BPSK digital modulation.
DATS was later superseded by the Spectrum Efficient Digital Audio Transmission (SEDAT) satellite audio distribution system. SEDAT allows more audio channels to be carried in the same frequency range as DATS. SEDAT, also developed by Scientific Atlanta, was primarily used by ABC Radio Networks. SEDAT transmissions ended in 2001.
Digital SCPC and MCPC
As digital subcarrier audio encoding and modulation methods have matured, less-expensive "standard" systems of satellite audio distribution have developed. This trend started with the emergence of VSATVery small aperture terminal
A very-small-aperture terminal , is a two-way satellite ground station or a stabilized maritime Vsat antenna with a dish antenna that is smaller than 3 meters. The majority of VSAT antennas range from 75 cm to 1.2 m. Data rates typically range from 56 kbps up to 4 Mbps...
technology in 1986 and was further supplanted by leased space on DBS systems such as DirecTV
DirecTV
DirecTV is an American direct broadcast satellite service provider and broadcaster based in El Segundo, California. Its satellite service, launched on June 17, 1994, transmits digital satellite television and audio to households in the United States, Latin America, and the Anglophone Caribbean. ...
and Dish Network
Dish Network
Dish Network Corporation is the second largest pay TV provider in the United States, providing direct broadcast satellite service—including satellite television, audio programming, and interactive television services—to 14.337 million commercial and residential customers in the United States. Dish...
. The two de facto methods for digital satellite audio transmission are digital single channel per carrier
Single channel per carrier
Single channel per carrier refers to using a single signal at a given frequency and bandwidth. Most often, this is used on broadcast satellites to indicate that radio stations are not multiplexed as subcarriers onto a single video carrier, but instead independently share a transponder...
and multiple channel per carrier multiplexing
Multiplexing
The multiplexed signal is transmitted over a communication channel, which may be a physical transmission medium. The multiplexing divides the capacity of the low-level communication channel into several higher-level logical channels, one for each message signal or data stream to be transferred...
.
In digital radio systems, several variable bit-rate data streams are multiplexed together to a fixed bitrate transport stream by means of statistical multiplexing. This makes it possible to transfer several video and audio channels simultaneously over the same frequency channel, together with various services. On communications satellites which carry broadcast television networks and radio networks, this is known as multiple channel per carrier or MCPC. Where multiplexing is not practical (such as where there are different sources using a single transponder), single channel per carrier mode (SCPC) is used. Digital SCPC differs from the older analog SCPC transmission method in that a digital SCPC signal carries more than just a single audio channel (two are used) but also coding and decoding information, ancillary and control data, and network identification data. Digital SCPC and MCPC subcarrier transmissions use satellite broadcast standards such as DVB-S
DVB-S
DVB-S is an abbreviation for Digital Video Broadcasting — Satellite; it is the original Digital Video Broadcasting forward error coding and demodulation standard for satellite television and dates from 1994, in its first release, while development lasted from 1993 to 1997...
and its successor DVB-S2
DVB-S2
Digital Video Broadcasting - Satellite - Second Generation is a digital television broadcast standard that has been designed as a successor for the popular DVB-S system. It was developed in 2003 by the , an international industry consortium, and ratified by ETSI in March 2005...
along with MPEG-2
MPEG-2
MPEG-2 is a standard for "the generic coding of moving pictures and associated audio information". It describes a combination of lossy video compression and lossy audio data compression methods which permit storage and transmission of movies using currently available storage media and transmission...
and MPEG-4
MPEG-4
MPEG-4 is a method of defining compression of audio and visual digital data. It was introduced in late 1998 and designated a standard for a group of audio and video coding formats and related technology agreed upon by the ISO/IEC Moving Picture Experts Group under the formal standard ISO/IEC...
compression formats, respectively. BPSK modulation has been replaced with newer modulation schemes such as QPSK
Phase-shift keying
Phase-shift keying is a digital modulation scheme that conveys data by changing, or modulating, the phase of a reference signal ....
(quadrature phase-shift keying).
StarGuide
StarGuide was the second-generation system of digital audio distribution via satellite. Many of the largest U.S. radio networks upgraded from or supplanted DATS/SEDAT audio feeds with StarGuide II and III audio receivers. The StarGuide platform is a proprietary MCPC digital audio distribution system that uses proprietary MX3 multiplexing technology. The StarGuide II receiver handles data rates from 512 kbps to 6.144 Mbps (in MX3 mode) and up to 8.192 Mbps in normal mode. The StarGuide III receiver can handle data rates up to 25 Mbps and is capable of a larger number of data and code rates than its predecessor. Both the StarGuide II and III receivers can utilize proprietary StarGuide Service Module expansion cards, including the ability to interface with local area networkLocal area network
A local area network is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building...
s (LAN) using 10/100Base-T
Ethernet physical layer
The Ethernet physical layer is the physical layer component of the Ethernet family of computer network standards.The Ethernet physical layer evolved over a considerable time span and encompasses quite a few physical media interfaces and several magnitudes of speed...
Ethernet
Ethernet
Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
connections.
X-Digital (XDS) format
The X-Digital Systems format is (as of 2011) the newest generation of digital satellite subcarrier audio technology used by the large radio networks in the United States. In 2007, X-Digital Systems acquired specific assets and patent licensing of StarGuide Digital Networks technology from DG FastChannel, Inc. The X-Digital Systems platform has been deployed by Clear Channel CommunicationsClear Channel Communications
Clear Channel Communications, Inc. is an American media conglomerate company headquartered in San Antonio, Texas. It was founded in 1972 by Lowry Mays and Red McCombs, and was taken private by Bain Capital LLC and Thomas H. Lee Partners LP in a leveraged buyout in 2008...
, Premiere Radio Networks
Premiere Radio Networks
Premiere Networks is an American radio network. It is the largest syndication company in the United States based on popularity of programming...
(now a Clear Channel subsidiary) and Citadel Broadcasting
Citadel Broadcasting
Citadel Broadcasting Corporation was a Las Vegas, Nevada-based broadcast holding company. Citadel owned 243 radio stations across the United States and was the third-largest radio station owner in the country...
(who also owns the former ABC Radio Networks).