A broadcast relay station, relay transmitter, broadcast translator (U.S.), rebroadcaster (Canada), or repeater (two-way radio) is a broadcast transmitter which relays or repeats the signal of another radio station or television station, usually to an area not covered by the signal of the originating station. They may serve, for example, to expand the broadcast range of a television or radio station beyond the primary signal's coverage area, or to improve service in a part of the main coverage area which receives a poor signal due to geographic constraints. They may (but are not usually) used to create a single-frequency network.

Less commonly, a rebroadcaster may be owned by a community group rather than the owner of the primary station.

Types

Some fully-licensed stations simply simulcast another station. These are relay stations only in name, and are generally licensed the same as any other major station. This is not regulated in the U.S., and it is also widely allowed in Canada, which otherwise regulates radio formats to ensure a diverse variety of programming.

Boosters

Relays which broadcast within or very near the parent station's coverage area (a "fill-in") on the same channel or frequency are called booster stations in the U.S. However, this can be tricky because it is possible to have both stations interfering with each other unless they are carefully designed. Radio interference can be avoided by using exact atomic time obtained from GPS satellites to perfectly synchronise co-channel stations, as in a single-frequency network (SFN).

Analog TV stations cannot have same-channel boosters unless opposite (perpendicular) polarisation is used, due to video synchronization issues such as ghosting. In the US, no new on-channel UHF signal boosters have been authorized since July 11, 1975. Digital TV stations are technically capable of sharing a channel, however this is more difficult with the 8VSB modulation and invariable guard interval used in the ATSC standard than with COFDM used in the European and Australian DVB-T standard. US AM broadcasting stations do not have translators or boosters; though an SFN is actually easier to create in their frequency band, it is largely unnecessary as the longer wavelengths of these signals are more able to provide adequate coverage over longer distances despite a lack of line-of-sight transmission conditions.

Distributed transmission

Distributed transmission (DTx) is the use of several medium-power stations (usually digital) to cover a broadcast area, rather than one high-power and several low-power stations. Experiments have shown that this can be done even with ATSC if A-VSB is used. The use of virtual channels is another alternative, though this may cause the same channel to appear multiple times on a receiver (once for each relay station), and requires the user to tune manually to the best one (which changes due to radio propagation conditions like weather). Use of boosters or DTx instead causes all relay stations to ideally appear as a single signal, but requires significant broadcast engineering to work properly and not cause destructive interference to each other's signals.

Semi-satellites

A television rebroadcaster often sells local or regional advertising for broadcast only on the local transmitter, and may also air a very limited amount of distinct programming from their parent station. Some such "semi-satellites" broadcast their own local newscasts, or separate news segments during part of the newscast. For example, CHEX-TV-2 in Oshawa, Ontario airs separate daily late afternoon-early evening news and community broadcasts from its parent station, CHEX-TV in Peterborough, Ontario. The U.S. FCC prohibits this on FM translator stations, only allowing it on different fully-licensed stations.

National networks

Most broadcasters outside of North America maintain a national network and use several relay transmitters to provide the same service to a region or entire nation. In comparison to the other types of relays explained above, the transmitter network is often created and maintained by an independent authority, often paid for using license fees, and major broadcasters use the same transmitters.

Relay transmitters by country

Canada

In Canada, rebroadcaster or rebroadcasting transmitter are the terms most commonly used by the Canadian Radio-television and Telecommunications Commission.

Television

A television rebroadcaster may be permitted to sell local or regional advertising for broadcast only on the local transmitter. On rarer occasions, they may also air a very limited amount of distinct programming from their parent station. Some such "semi-satellites" broadcast their own local newscasts, or separate news segments during part of the newscast.

There is no strict rule for the call sign of a television rebroadcaster. Some transmitters have distinct call signs from the parent station (for example, CFGC in Sudbury is a rebroadcaster of CIII), while others use the call sign of the originating station followed by a number (e.g., CBLFT-17 in Sarnia). Officially, the latter type includes the television station's TV suffix between the call sign and the number, although in media directories this is often left out for convenience.

In the latter case, the numbers are usually applied sequentially, starting from one and denoting the chronological order in which the station's rebroadcast transmitters began operation. Some broadcasters may, at their discretion, use a system in which the number denotes the actual broadcast channel of the transmitter (e.g., CJOH-47 in Pembroke). A broadcaster cannot, however, mix the two numbering systems under a single call sign — the transmitters are either all numbered sequentially or all numbered by their analogue channel position. On the rare occasion that the sequential numbering reaches 99 (e.g., TVOntario's broadcast transmitters), rather than being numbered as 100 the next transmitter is assigned a new call sign and numbered as one. Translators which share the same frequency (such as CBLT's repeaters CBLET, CBLHT, CBLAT-2 and CH4113, all on channel 12) are also given distinct call signs.

Low-power rebroadcasters may also have a call sign which consists of the letters CH followed by four numbers. For example, CH2649 in Valemount is a rebroadcaster of Vancouver's CHAN. Rebroadcasters of this type are numbered strictly sequentially to the order in which they were licensed by the CRTC, and their call signs have no inherent relationship to those of the parent stations or of other rebroadcasters. Although the next number in the sequence, CH2650 in Anzac, is also a rebroadcaster of CHAN, this is simply because CH2649 and CH2650 happened to be licensed simultaneously — the following number, CH2651, is a rebroadcaster (also in Anzac) of Edmonton's CITV. A single station's rebroadcasters are not necessarily all named in the same manner. CBLT, for example, has some retransmitters which have their own call signs, some which use CBLT followed by a number and some transmitters with CH numbers.

Radio

As in television, a radio rebroadcaster may have either a distinct call sign or the call sign of the originating station followed by a numeric suffix. In the case of radio, however, the numeric suffix is always sequential.

For a rebroadcaster of an FM station, the numeric suffix is appended to the FM suffix. For example, rebroadcasters of CJBC-FM in Toronto are numbered CJBC-FM-1, CJBC-FM-2, etc. Where an AM station has a rebroadcaster operating on the FM band, the numeric suffix instead falls between the four-letter call sign and the FM suffix — for example, CKSB-1-FM is an FM rebroadcaster of the AM station CKSB, while CKSB-FM-1 would be a rebroadcaster of CKSB-FM.

Low-power radio rebroadcasters may also have a call sign which consists of the letters VF followed by four numbers. Some stations licenced under the CRTC's experimental broadcasting guidelines, a special class of short-term licence (similar to special temporary authority) sometimes granted to newer campus and community radio operations, may have another distinct class of call sign which consists of three letters from anywhere within Canada's ITU prefix range followed by three digits — e.g. CFU758 or VEK565. Some other stations within this license class, however, have been assigned conventional Cxxx call signs.

Occasionally, former rebroadcasters have been converted to originating stations in their own right, but have retained their former call sign instead of being reassigned a new one of their own. Such stations include CITE-FM-1 in Sherbrooke, CBF-FM-8 in Trois-Rivières and CBAF-FM-15 in Charlottetown.

As of October 2008 the largest radio translator system in the US belongs to KUER-FM, the non-commercial radio outlet of the University of Utah, with 33 translator stations ranging from Idaho to New Mexico and Arizona.

Mexico

In Mexico, all translator and booster stations are given the callsign of the parent station plus a sequential number, such as XHABC and XHABC1, XHABC2.

United States

Radio

As of August 2007, the basic FCC regulations on translators are:

• No station may be translated to another band (i.e. from AM to FM) with an exception given if the translator is to be located in a "white area" where no full power AM or FM stations exist. However, the FCC is considering a rules change to allow more AMs to own and operate FM translators.
• No translator or booster may transmit anything other than the live simulcast of its licensed parent station, except for emergency warnings (such as EAS), and 30 seconds per hour of fundraising.
• The parent station must identify all of its translators and boosters between 7 and 9 a.m., between 12:55 and 1:05 p.m., and between 4 and 6 p.m. each broadcast day; or each must be equipped with its own automated device (audio or FSK) for hourly identification.
• Maximum power is 250 watts ERP for a translator, and 20% of the parent station's power for a booster.
• A translator or booster must go off the air if the parent station's signal is lost. (This helps prevent unauthorized retransmission of other stations).

Commercial stations may not own their translators (except for boosters), or be translated outside of the parent station's area (they can only fill in where terrain blocks the signal). Thus, they operate by picking-up the signal of the main station off the air with a directional antenna and sensitive receiver, and directly retransmitting the signal. They also may not transmit in the FM "reserved band" from 88 to 92 MHz, where only noncommercial stations are allowed. Noncommercial stations may broadcast in the commercial band, however. Unlike commercial stations, they can also relay programming to translators via satellite, so long as those translators are in the reserved band. All stations may use any means to feed boosters.

All U.S. translator and booster stations are low-power and have a class D license, making them secondary to other stations (including the parent). They must accept any interference from full-power (100-watt or more on FM) stations, while not causing any of their own. Boosters must not interfere with the parent station within the community of license. Licenses are automatically renewed with that of the parent station and do not require separate applications, though each may still be challenged with a petition to deny.

FM booster stations are given the full callsign (always including an -FM suffix, even if there is none assigned) of the parent station, plus a serial number, such as WXYZ-FM1, WXYZ-FM2, etc.

Television

Unlike FM, LPTV stations may operate as either translators or originate their own programming.

Translator stations in the U.S. are given callsigns which begin with a W or K (respectively east or west of the Mississippi River, as with regular stations), followed by a channel number, and two serial letters for each channel. (The first stations on that channel are AA, AB, AC, and so on.) Television channels are always two-digit, from 02 to 83; while FM radio channels are from 200 (87.9 MHz) to 300 (107.9 MHz), one every 0.2 MHz. (Examples: W42BD, K263AF.) The presence of an X after the number in these callsigns does not indicate an experimental broadcasting license as it may in other services, as all 26 letters are included in the sequence. The highest pair of letters used, as of July 2008, is ZD, in K13ZD.

Numbered translator stations (a format such as "W70ZZ") are typically low-power repeaters, often 100 watts or less on FM, and 1000 or less on TV. The former "translator band", UHF TV channels 70 through 83, was originally occupied primarily by these low-powered translators. The combination of low power and high frequencies provided a very limited range for these broadcasts. This band was reallocated to cellular telephone services in the 1980s, with the handful of remaining transmitters from these channels moved to lower frequencies.

Full-power repeaters (such as WPBS-TV's identical twin transmitter WNPI-TV) are normally assigned -TV callsigns like those of any other full-power station. They do not bear numbered callsigns and must operate in the same manner as other full-power broadcasters. This simulcasting is generally not regulated by the FCC.

LPTV stations may also choose a regular four-letter callsign with an -LP suffix (shared with LPFM) for analog or -LD for digital, generally done only if the station originates programming. Class A television stations get -CA and -CD instead. Digital stations which use numerals get a -D suffix (as in W42BD-D). All of these are despite the fact the full-power digital TV stations had their -DT (originally -HD) suffixes dropped by the FCC before -D and -LD were implemented. Digital LPTV stations have their digital RF channel numbers as part of their digital callsigns, which means it may be different from the virtual channel (the analog number).

Numbered broadcast translators which are moved permanently to another frequency are normally issued new callsigns to reflect the updated channel assignments. The same is not true of displaced translators using another frequency temporarily under special technical authority, For instance, K55KD could retain its callsign while displaced temporarily to channel 57 to resolve interference to MediaFLO users, while W81AA would have received new calls when channel 81 was deleted from the bandplan. On the rare occasion a station moves back to it original channel, it is given its old callsign, as they are not reused by other stations like regular callsigns can be.

Digital transition

LPTV operations are not required to simulcast a digital signal, nor to shutdown analog operation in February 2009 when full-power US TV operators must do so. As of June 2008, no current or future DTV mandates have been forced on LPTV stations, however Congress has passed legislation to provide immediate funding so these low-power stations can switch to digital on February 18, or shortly thereafter.

Most digital TV sets include analog and digital tuners, however, most DTV set-top boxes fail to display analog stations, or even to include analog passthrough for RF from the TV antenna (the way a VCR does). This is an issue primarily with coupon-eligible converter boxes and cause for grave concern among LPTV operators; the Community Broadcasters Association has filed a lawsuit claiming it violated the All-Channel Receiver Act, the law on which the FCC based its digital mandate.

Controversy

Critics of the FCC's licensing procedures (such as LPFM promoters and some critics of dominionism) have charged that certain noncommercial broadcasters have taken unfair advantage of FM repeater regulations in regard to nonprofit repeater licensing, by allowing satellite-delivered programming hundreds or even thousands of miles outside the parent station's coverage area. Some religious outlets — such as Calvary Chapel's KAWZ-Twin Falls, Idaho or Family Radio's KEAR-FM-Sacramento – are relayed by hundreds of FM "translator" stations across the U.S. As these parent stations are owned by non-profit organizations, they are not required to have their translators receive their signal over the air, as would be required for a commercial broadcaster – a loophole that only exists for noncommercial broadcasters; this particular loophole has been used by a number of religious broadcasters to set up large satellite-based networks composed almost entirely of "distant translators" – translators outside of the market area (generally a 50-mile radius surrounding the transmitter).

Prominent in this regard are endeavors linked to Calvary Chapel (including Radio Assist Ministries, Horizon Broadcasting, and (formerly) Edgewater Broadcasting and REACH Media) and American Family Radio owned by the American Family Association. Educational Media Foundation, owners of the K-Love contemporary Christian music radio network, have also been cited as applying for distant translators en masse. The multiple networks associated with Calvary Chapel have been a particular focus in regard to translator-based networks. due to the extremely high volume of licenses applied for (a partial list is available at RECnet) At least four separate radio stations operated by Calvary Chapel churches and relaying Calvary Satellite Network programming have been identified as "home stations" for distant translators and there are many home churches in addition to the main "national" Calvary Chapel concerns applying for licenses (see RECnet link above).

An FCC licensing window for new translator applications in 2003 resulted in over 13,000 applications being filed, most of them coming from religious broadcasters; this has become known to LPFM advocates as the Great Translator Invasion. In many cases, multiple applications were submitted by different companies linked to Calvary Chapel in particular for the same channel.

This has posed difficulties for non-translator station operators, in particular LPFM license applicants. LPFM licenses often cannot get stations on the air due to translators eliminating any available channels in an area and (in the case of American Family Radio in particular) there are indications that this is a deliberate strategy by the religious broadcasters in question to crowd out rebroadcasters of National Public Radio stations. There are also cases where translator stations owned by "sat-casting" networks have threatened licenses of existing LPFM licensees. Other LPFM stations have been similarly threatened REC Networks has filed a petition with the FCC that would, among other things, require the FCC to give higher priority to LPFM stations.

Eventually, the problem with "application spam" from "religiocasting" distant translator networks became sufficiently severe that the FCC issued an emergency hold order on new translator applications until the present batch can be sorted through; this came after considerable criticism from LPFM lobbyist groups such as Prometheus Radio. There is at least one proposed rulemaking that would revise the procedures by which nonprofit groups may apply for translators (thus closing the "distant translator" loophole); in addition, the FCC has modified channel requirements for LPFM broadcasters to open up channel space.

In the meantime, though, there are still areas (including major metro areas) with no available FM spectrum for LPFM due to large distant translator networks (for example, Chicago IL and list of issued licenses which contain several Calvary Chapel and Educational Media Foundation stations; Atlanta, GA and list of issued licenses which contain Way-FM (associated with K-Love and Salem Communications) and Edgewater Broadcasting stations; Dallas, TX and list of issued licenses which show Calvary Satellite Network and American Family Radio; even Louisville, KY and Knoxville, TN; both small market areas, have a complete lack of LPFM channels due to distant translator invasion by Calvary Chapel and Way-FM translators in particular).

Australia

Radio

Australia's national radio networks (Radio National, ABC NewsRadio, Triple J, ABC Classic FM and SBS Radio) each have relay transmitters which allow each service to broadcast as wide as possible. In order to provide this, the ABC and SBS both allow community-based relay transmitters to rebroadcast radio or television in areas which would otherwise have no service. Commercial radio broadcasters normally have relay transmitters only if the local geography (such as mountainous terrain) prevents them from broadcasting to their entire market.

Television

Since market aggregation in the early 1990s, each television broadcaster transmits its service using multiple relays in order provide the same service throughout Australia's large market areas. While each market is often divided into submarkets due to the legacy of previous commercial broadcasts (for example, Southern Cross Ten maintains two separate stations in the single Victoria market, GLV and BCV), the only difference between these submarkets in practice is limited to news services or local advertising. Except in major cities, all major television broadcasters use the same network of transmitters, which may have dozens of relay stations in each market. As a result, some areas have had trouble starting digital or HD services due to problems with certain regional transmitters.

Europe

Because most radio and television systems in Europe are national networks, the entire radio or television system in some countries can be considered a collection of relay stations, in which each broadcaster uses a transmitter network (either developed by the public broadcaster or maintained through a government-funded authority) to provide broadcast services to the entire nation.

References