Broadcast relay station
A broadcast relay station, also known as a satellite station, relay transmitter, broadcast translator, re-broadcaster, repeater or complementary station, is a broadcast transmitter which repeats the signal of a radio or television station to an area not covered by the originating station.
These expand the broadcast range of a television or radio station beyond the primary signal's original coverage or improves service in the original coverage area. The stations may be used to create a single-frequency network. They may also be used by an AM or FM radio station to establish a presence on the other band.
Relay stations are most commonly established and operated by the same organizations responsible for the originating stations they repeat. Depending on technical and regulatory restrictions, relays may also be set up by unrelated organizations.
Types
Translators
In its simplest form, a broadcast translator is a facility created to receive a terrestrial broadcast over the air on one frequency and rebroadcast the same signal on another frequency. These stations are used in television and radio to cover areas which are not adequately covered by a station's main signal. They can also be used to expand market coverage by duplicating programming on another band.Boosters and distributed transmitters
Relays which broadcast within the parent station's coverage area on the same channel are known in the U.S. as booster stations. Signals from the stations may interfere with each other without careful antenna design. Radio interference can be avoided by using atomic time, obtained from GPS satellites, to synchronize co-channel stations in a single-frequency network.Analog television stations cannot have same-channel boosters unless opposite polarization is used, due to video synchronization issues such as ghosting. In the U.S., no new on-channel UHF signal boosters have been authorized since July 11, 1975.
A distributed transmission system uses several medium-power stations on the same frequency to cover a broadcast area, rather than one high-power station with repeaters on a different frequency. Although digital television stations are technically capable of sharing a channel, this is more difficult with the 8VSB modulation and unvariable guard interval used in ATSC standards than with the orthogonal frequency-division multiplexing used in the European and Australian DVB-T standard. A distributed transmission system would have stringent synchronization requirements, requiring each transmitter to receive its signal from a central source for broadcast at a GPS-synchronized time. A DTS does not use broadcast repeaters in the conventional sense, since they cannot receive a signal from a main terrestrial broadcast transmitter for rebroadcast; to do so would introduce a re-transmission delay destroying the required synchronization, causing interference between transmitters.
The use of virtual channels is another alternative, although this may cause the same channel to appear several times in a receiver – once for each relay station – and require the user to tune to the best one. Although boosters or DTS cause all relay stations to appear as one signal, they require careful engineering to avoid interference.
Satellite stations
Some licensed stations simulcast another station. Relay stations in name only, they are generally licensed like any other station. Although this is unregulated in the U.S. and widely permitted in Canada, the U.S. Federal Communications Commission regulates radio formats to ensure diversity in programming.U.S. satellite stations may request an FCC exemption from requirements for a properly staffed broadcast studio in the city of license. The stations often cover large, sparsely populated regions or operate as statewide non-commercial educational radio and television systems.
Semi-satellites
A television re-broadcaster often sells local advertising for broadcast only on the local transmitter, and may air a limited amount of programming distinct from its parent station. Some "semi-satellites" broadcast local news or separate news segments during part of the newscast. CHEX-TV-2 in Oshawa, Ontario, aired daily late-afternoon and early-evening news and community programs separate from its parent station, CHEX-TV in Peterborough, Ontario. The FCC prohibits this on U.S. FM translator stations, only permitting it on fully licensed stations.In some cases, a semi-satellite is a formerly autonomous full-service station which is programmed remotely through centralcasting or broadcast automation to avoid the cost of a local staff. CBLFT, an owned-and-operated station of the French-language network Ici Radio-Canada Télé in Toronto, is a de facto semi-satellite of its stronger Ottawa sibling CBOFT; its programming has long been identical or differed only in local news and advertising. A financially weak privately owned broadcaster in a small market can become a de facto semi-satellite by gradually curtailing local production and relying on a commonly owned station in a larger city for programming; WWTI in Watertown, New York, relies on WSYR-TV in this manner. Broadcast automation allows the substitution of syndicated programming or digital subchannel content which the broadcaster was unable to obtain for both cities.
Some defunct full-service stations have become full satellite stations and originate nothing. If programming from the parent station must be removed or substituted due to local sports blackouts, the modified signal is that of a semi-satellite station.
National networks
Most broadcasters outside North America, portions of South America, and Japan maintain a national network, and use relay transmitters to provide service to a region. Compared with other types of relays, the transmitter network is often created and maintained by an independent authority ; several major broadcasters use the same transmitters.In North America, a similar pattern of regional network broadcasting is sometimes used by state- or province-wide educational television networks. A state or province establishes an educational station and extends it with several full-power transmitters to cover the entire jurisdiction, with no capability for local-programming origination. In the U.S., such regional networks are member stations of the national Public Broadcasting Service.
By country
Canada
In Canada, "re-broadcaster" or "re-broadcasting transmitter" are the terms most commonly used by the Canadian Radio-television and Telecommunications Commission.Television
A television re-broadcaster may sell local or regional advertising for broadcast only on the local transmitter. Rarely, they may air limited programming distinct from their parent station. Some "semi-satellites" broadcast local newscasts or separate news segments in part of a newscast.There is no strict rule for the call sign of a television re-broadcaster. Some transmitters have call signs different from the parent station, and others use the call sign of the originating station followed by a number. The latter type officially includes the television station's -TV suffix between the call sign and the number, although it is often omitted from media directories.
The numbers are usually applied sequentially, beginning with "1", and denote the chronological order in which the station's rebroadcast transmitters began operation. Some broadcasters may use a system in which the number is the transmitter's broadcast channel, such as CJOH-TV-47 in Pembroke, Ontario. A broadcaster cannot mix the numbering systems under a single call sign; the transmitters are numbered sequentially or by their analog channel. If sequential numbering reaches 99, the next transmitter is assigned a new call sign and numbered "1". Translators which share a frequency are given distinct call signs.
Digital re-broadcasters may be numbered by the TV channel number of the analog signal they replaced. TVOntario's CICO-DT-53 is an example; the station was converted in 2011 to vacate an out-of-core analog channel, and retains CICO-TV-53's former analog UHF television call-sign numbering as a surviving TVO repeater.
Low-power re-broadcasters may have a call sign consisting of the letters CH followed by four numbers; for example, CH2649 in Valemount, British Columbia, is a re-broadcaster of Vancouver's CHAN. Re-broadcasters of this type are numbered sequentially in the order they were licensed by the CRTC, and their call signs are unrelated to the parent station or other re-broadcasters. Although the next number in the sequence is a re-broadcaster of CHAN, this is because CH2649 and CH2650 were licensed simultaneously; the following number, CH2651, is a re-broadcaster of Edmonton's CITV. A station's re-broadcasters are not necessarily named in the same manner; CBLT had re-transmitters with their own call signs.
CBC and Radio-Canada owned-and-operated re-transmitters were shut down on August 1, 2012, along with most TVOntario transmitters and some Aboriginal Peoples Television Network transmitters in the far north. Private commercial broadcasters operate full-power re-broadcasters to obtain "must carry" status on cable television systems.
Transmitters in small markets with one originating stations were, in most cases, not required to convert to digital even if operating at full power. Transmitters broadcasting on UHF channels 52–69 were required to vacate the channels by August 31, 2011; some went digital as part of a move to a lower frequency but do not provide high-definition television, digital subchannels or any functions beyond that of the original analog site.
Radio
Like a TV station, a radio re-broadcaster may have a distinct call sign or use the call sign of the originating station followed by a numeric suffix. The numeric suffix is always sequential.For a re-broadcaster of an FM station, the numeric suffix is appended to the FM suffix; re-broadcasters of CJBC-FM in Toronto are numbered CJBC-FM-1, CJBC-FM-2, etc. If an AM station has a re-broadcaster on the FM band, the numeric suffix falls between the four-letter call sign and the FM suffix; CKSB-1-FM is an FM re-broadcaster of the AM station CKSB, and CKSB-FM-1 would be a re-broadcaster of CKSB-FM.
A broadcaster is limited to two stations on one band in a market, but a possible means to obtain a third FM signal in-market is to use a re-broadcaster of the AM station to move the signal to low-power FM. In Sarnia, Blackburn Radio owns CFGX-FM and CHKS-FM ; its third Sarnia station, CHOK, uses an FM repeater for city coverage as Country 103.9 FM.
Low-power radio re-broadcasters may have a call sign consisting of VF followed by four numbers; a call sign of this type may also denote a low-power station which originates its own programming. Some stations licensed under the CRTC's experimental-broadcasting guidelines, a special class of short-term license sometimes granted to newer campus and community radio operations, may have a call sign consisting of three letters from anywhere in Canada's ITU-prefix range followed by three digits. Other stations in this license class have been assigned conventional Cxxx call signs. Former re-broadcasters have occasionally been converted to originating stations, retaining their former call sign; examples include CITE-FM-1 in Sherbrooke, CBF-FM-8 in Trois-Rivières and CBAF-FM-15 in Charlottetown.