This article is about class A/class I protected AM stations. For stations owned by the company formerly named Clear Channel, see iHeartMedia.
A clear-channel station is a North American AMradio station that has the highest level of protection from interference from other stations, particularly from nighttime skywave signals. This classification exists to ensure the viability of cross-country or cross-continent radio service enforced through a series of treaties and statutory laws. Known as Class A stations since the 1983 adoption of the Regional Agreement for the Medium Frequency Broadcasting Service in Region 2 (Rio Agreement), they are occasionally still referred to by their former classifications of Class I-A (the highest classification), Class I-B (the next highest class), or Class I-N (for stations in Alaska too far away to cause interference to the primary clear-channel stations in the lower 48 states). The term "clear-channel" is used most often in the context of North America and the Caribbean, where the concept originated.
Since 1941, these stations have been required to maintain a transmitter power output of at least 10,000 watts to retain their status. Nearly all such stations in the United States, Canada and The Bahamas broadcast with 50,000 watts, with several clear-channel stations in Mexico going as high as 150,000 watts, and XEW in Mexico City having formerly operated with 250,000 watts for over 80 years before moving the transmitter and reducing to 100,000 watts in 2016. Cuba was originally included in the plan and had several stations given clear-channel status, but stopped participating after the Cuban Revolution of 1959.
Description
Sixty medium wave frequencies were set aside in 1941 under the North American Regional Broadcasting Agreement (NARBA) for use by usually only one, although in some cases two or three, AM stations, covering a wide nighttime area via skywavepropagation. These frequencies were known as the "clear channels", and the stations on them are thus clear-channel stations. NARBA set aside 37 Class I-A frequencies and 27 Class I-B frequencies. The Class I-N stations in Alaska shared those same frequencies. Where only one station was assigned to a clear channel, the treaty provides that it must operate with a nominal power of 50 kilowatts or more. These were for the most part Class I-A. Stations on the other clear channels, with two or more stations, must use between 10kW and 50kW, and most often use a directional antenna so as not to interfere with each other. In addition to the frequencies, the treaty also specified the specific locations where stations on Class I-B channels could be built.
Some of the original NARBA signatories, including the United States, Canada and Mexico, have implemented bilateral agreements that supersede NARBA's terms, eliminating among other things the distinction between the two kinds of clear channel: the original "I-A" and "I-B" classes, and the newer, U.S.-only "I-N" class, which are now all included in class A. Classes "I-A" and "I-B" still mandate a minimum efficiency of 362.10 mV/m/kW at 1km, whereas Class "I-N" is permitted to use the lower Class B minimum efficiency of 281.63 mV/m/kW at 1km. There exist exceptions, where a former Class B station was elevated to Class A, yet it maintained its previous antenna system, or made only minor changes thereto.
Clear-channel stations, unlike other AM stations in North America, have protection from interference to their nighttime skywave secondary service area. Other stations are entitled, at most, to protection from nighttime interference in their primary service area—that which is covered by their groundwave signal.
Many stations beyond those listed in the treaty have been assigned to operate on a clear channel (and some had been long before NARBA came into effect in 1941). In most cases, those stations operate during the daytime only, so as not to interfere with the primary stations on those channels. Since the early 1980s, many such stations have been permitted to operate at night with such low power as to be deemed not to interfere; these stations are still considered "daytimers" and are not entitled to any protection from interference with their nighttime signals. Another group of stations, formerly known as class II stations, were licensed to operate on the former "I-B" clear channels with significant power at night, provided that they use directional antenna systems to minimize radiation towards the primary stations.[citation needed]
Daytimers
Daytimers (also known as daytime-only stations) are AM radio stations that are limited to broadcasting during the daytime only, as their signals would interfere with clear-channel and other radio stations at night, when solar radiation is reduced, and medium wave radio signals can propagate much farther. Such stations are allowed three manners of operation after sunset; to sign off the air completely until sunrise, reduce power (sometimes dramatically, to only a few watts), or switch to a nighttime-only frequency (such as the Detroit area's WNZK, which broadcasts on 690 during the day, and on 680 at night). Their broadcast class is Class D. A great number of these stations use FM translators to continue their broadcasts overnight, and some also broadcast on the internet and have separate streams that air when the station's over-the-air signal has signed off.
Daytime-only stations first originated in the late 1920s shortly after General Order 40 was imposed. One of the first to do so was WKEN in Kenmore, New York (now WUFO). WKEN proposed the concept to avoid the then-common practice of having to share one frequency between multiple stations; under General Order 40, WKEN would have had to share its frequency with WKBW, and the daytime-only proposal allowed both stations their own frequency.[1] WUFO remains a daytime-only station to the present day, albeit with a 24/7 FM translator introduced in mid-2017.
As of 2013, daytimers exist only in the United States and Mexico. The last Canadian daytime station, CKOT, signed off on February 17 of that year after converting to the FM band. There were 61 daytimers in Mexico in 2015.[2]
List of clear-channel stations
The following two tables show all of the class-A stations in North America.
First is the Canada, Mexico, and contiguous United States table, for the former class I-A and class I-B stations. General Order 40 allocations are in bold.
Second is the Alaska table, for the former class I-N stations.
Under the most recent treaty, Mexican Class A stations that previously operated with 50kW or less (but a minimum of 10kW nights) may increase power to 100kW days while retaining their 10kW night operation. This created some anomalies where stations licensed for 10kW during all hours could increase power to 100kW days and 10kW nights, unless a directional antenna system was installed for nights, in which case the maximum night power was 50kW. Additionally, one Class B station that had been operating non-directionally with 100kW days and 50kW nights was required to reduce power to 50kW during all hours.
↑ 690 kHz at Montreal was originally assigned under NARBA to CBF (that station migrated to FM in 1998), and was later reused by CINF; after CINF closed in January 2010, CKGM applied for and was granted the frequency, and moved from 990 kHz to 690 kHz in September 2012.
↑ 740 kHz was used by CBC Radio One's CBL in Toronto until 2000 when the station moved to 99.1 FM. CFZM, known at the time as CHWO, acquired 740 in 2001.
↑ 940 kHz at Montreal was originally assigned under NARBA to CBM (that station migrated to FM in 1998), and was later reused by CINW, which ceased operations in 2010. Despite leaving the air, it remained notified to the U.S. as a class-A allotment. A new license has since been granted to Tietolman-Tétrault-Pancholy Media (TTP) to broadcast a French news-talk format at 940 AM by the CRTC. After numerous delays, the station began broadcasting a series of test tones intermittently on October 26, 2016. Official testing began on November 16, 2016, with music and recorded announcements with a phone number to report signal interference. Although the station was given a deadline of November 21, 2016, by the CRTC to launch its French news-talk format, the station has yet to do so.
↑ 1550 kHz was originally CBE (AM), which shut down the AM station after moving to 97.5 CBEW-FM in 2011. On November 1, 2012, CBEF, traditionally on 540 kHz, also started broadcasting on the same AM transmitter and frequency that CBE had used.
↑ KNZR is the only U.S. class-A station licensed to operate with less than 50 kilowatts full-time.
↑ WFME is currently operating with 1,000 watts under a special temporary authority after airing on a new transmitter site in West Orange, New Jersey. It is currently unknown if the station will return as a Clear-channel station.
↑ 1580 kHz was originally used by CBJ in Chicoutimi, Quebec. After that station moved to FM in 1999, CHUC applied for and was granted 1580 kHz in Cobourg, Ontario, with 10 kW, but chose instead to move to FM itself (despite being notified to the U.S. as an existing station on 1580). CKDO moved from 1350 to 1580 kHz on August 13, 2006, and became that day a class A station using 10 kW. U.S. FCC record is at
Migrated to FM as XHTQ-FM in 2013. At its height XETQ was authorized for 100kW day/50kW night. In the 1990s it lowered its power to 10kW day/1kW night.
Downgraded to class B in 1998 by reducing night power to 9.8 kilowatts with a three tower directional antenna; Inner City Broadcasting purchased WOWO so that its station in New York, WLIB, could remain on air 24 hours a day. WOWO was later purchased by Pathfinder Communications, the current owners.
A bad permit renewal, made in 2005, required this station to shut down in June 2016. When the university applied to resume operation on AM, it was denied, and the station moved to FM and launched XHRUV-FM on a frequency of 90.5MHz on June 1, 2016.
In the early days of radio, regulators had difficulty reducing interference between stations. There were two major limitations: a lack of good frequency control during the 1920s, resulting in heterodyne tones that were encountered far beyond the range of understandable audio, and no directional antennas or skywave-suppressing vertical antennas until the early 1930s. The problem was much more severe at night, when skywave signals expanded station signal coverage to hundreds of kilometers. However, with most stations located at urban locations, quality skywave service was considered to be important for providing nighttime reception to the extensive rural regions.
For the U.S., a form of clear channels first appeared in 1923 when the Commerce Department started moving stations which had previously shared three[6] (initially two)[7] frequencies (two for entertainment stations, one for "weather and crop reports") onto a band of frequencies from 550 to 1350 kHz,[8] which was later extended to 1500 kHz, with 550 to 1070 kHz reserved for higher powered "Class B" stations. Many of the Class B frequencies were assigned to a single station, although a few were used on both the East and West coasts, which were considered far enough apart to limit interference.[9] Class B stations with transmitters located in population centers were limited to 1,000 watts,[10] although stations that operated transmitters at remote sites were permitted to use up to 5,000 watts.
Problems intensified in the summer of 1926, when a successful challenge was made to the government's authority, under the Radio Act of 1912, to assign station transmitting frequencies and powers.[11] This led to unrestricted expansion of the number of stations to 732, and increased the number of stations operating on same frequency. Moreover, previously stations had been assigned to transmitting frequencies of multiples of 10 kHz, which largely eliminated heterodynes from adjacent frequencies. However, during the lapse in regulation, some stations relocated to non-standard "split frequencies", increasing heterodyne interference.[12]
The Federal Radio Commission (FRC) was formed in March 1927, and one of its key tasks was to reorganize the chaotic broadcast band. A May 1927 reallocation began the process, in part by eliminating "split frequency" operations.[13] A December 1, 1927 report on the FRC's ongoing work reviewed operations on 600 to 1000 kHz, which divided these frequencies into ones that were considered "clear" and "unclear".[14] Its 1928 implementation of General Order 32 was only partially successful in reducing the number of stations. On November 11, 1928, the FRC implemented General Order 40, which classified AM band frequencies as Local, Regional or Clear. Under restrictions imposed by the Davis Amendment, eight clear channels were assigned to each of five U.S. regions. This classification also reserved a small number of frequencies for use by Canada. The maximum power for clear channel stations was gradually increased to 50,000 watts: additionally there were some short-lived experiments with 250–500 kilowatt "super-power" operations, most prominently by WLW in Cincinnati, Ohio
The Federal Radio Commission was replaced by the Federal Communications Commission (FCC) in 1934. There was debate in Washington, D.C., and in the U.S. broadcasting industry, over whether continuation of the clear-channel system was justifiable. The licensees of clear-channel stations argued that, without their special status, many rural areas would receive no radio service at all. Rural broadcasters pointed out that most of the clear-channel stations were licensed to serve large cities on the two coasts, which made little sense for a service that was meant to provide radio to the vast rural areas in the middle of the country. On June 13, 1938, the U.S. Senate adopted resolution 294, sponsored by Burton K. Wheeler (D-Montana), which stated that it was the "sense of the Senate... that the Federal Communications Commission should not adopt or promulgate rules to permit or otherwise allow any station operating on a frequency in the standard broadcast band (550 to 1600 kilocycles) to operate on a regular or other basis with power in excess of 50 kilowatts".[15] However, the clear-channel licensees argued that a 50,000 watt limit in the U.S. should be lifted. They pointed to successful experiments made by WLW in Cincinnati before World War II, and in later years successful implementation by state broadcasters in Europe and the Middle East, as evidence that this would work and improve the service received by most Americans. Other broadcasters, particularly in the western states, argued to the contrary; that if the special status of the clear-channel stations was eliminated, they would be able to build facilities to provide local service to those rural "dark areas".
The clear channel standards were continued by the March 1941 adoption of the North American Regional Broadcasting Agreement, during which most stations shifted frequencies, in order to increase the number of Canadian clear channel assignments, as well as provide clear channels to Mexico and the Bahamas. Because FM and TV stations did not yet exist, the FCC's main intent for the clear-channel assignments was to provide reliable radio service to the thousands of Americans who lived in the vast rural areas of the United States.[16] As a result, these stations usually reached large portions of North America at night. Radio fans (and staff at those stations) often affectionately call such stations "flamethrowers" or "blowtorches" because of their high power, and boast about their reach by a combined state and provincial count of their coverage area. One of the most outspoken of the small-town broadcasters, Ed Craney of KGIR in Butte, Montana, went so far as to apply to move his station, then on the 1370kHz regional channel, to a class I-A signal on 660kHz, asking the FCC to downgrade the NBC New York flagship, WEAF, to make way for the Butte station.[17] The FCC denied Craney's petition.
After 1941, several clear-channel stations applied for power increases to between 500 and 750kW;[18][19] with dissemination of national defense information cited as one reason this would be in the public interest. In October 1941 the FCC's engineering department presented a report on a complete reorganization of the clear-channel service; the report considered the possibility of "some 25 superpower stations of 500,000 watts or more, strategically located to provide maximum service" (as Broadcasting described it), and suggested that stations would have to be relocated away from the east and west coasts in such a scenario, as coastal stations waste energy over the oceans. One complication the FCC considered was the 1938 Wheeler resolution suggestion that stations be limited to 50kW.[20]
One station, KOB in Albuquerque, New Mexico, fought a long legal battle against the FCC and New York's WABC for the right to move from a regional channel to a clear channel, 770kHz, arguing that the New York signal was so weak in the mountain west that it served no one there. KOB eventually won the argument in the late 1960s; it and several other western stations were allowed to move to eastern clear channels. (Western clear channels, such as 680 in San Francisco, had been "duplicated" in the eastern states for many years.) These new Class II-A assignments (in places like Boise, Idaho; Las Vegas and Reno, Nevada; Lexington, Nebraska; Casper, Wyoming; Kalispell, Montana; and others) began what would later be called "the breakdown of the clear channels". The class I-A station owners' proposal to increase power fifteen-fold was not immediately quashed, but the new II-A stations would make it effectively impossible for stations on the duplicated channels to do so, and the owners eventually lost interest. That proposal was finally taken off the FCC's docket in the late 1970s.[citation needed]
On May 29, 1980, the FCC voted to limit the protection for all clear-channel stations to a 750-mile (1,207km) radius around the transmitter. Stations on those frequencies outside the area of protection were no longer required to sign off or power down after sundown.[21]
In 1987 the FCC changed its rules to prohibit applications for new "class-D" stations. (Class-D stations have night power between zero and 250 watts, and frequently operate on clear channels.) However, any existing station could voluntarily relinquish nighttime authority, thereby becoming a class-D, and several have done so since the rule change.
Medium wave (MW) is a part of the medium frequency (MF) radio band used mainly for AM radio broadcasting. The spectrum provides about 120 channels with more limited sound quality than FM stations on the FM broadcast band. During the daytime, reception is usually limited to more local stations, though this is dependent on the signal conditions and quality of radio receiver used. Improved signal propagation at night allows the reception of much longer distance signals. This can cause increased interference because on most channels multiple transmitters operate simultaneously worldwide. In addition, amplitude modulation (AM) is often more prone to interference by various electronic devices, especially power supplies and computers. Strong transmitters cover larger areas than on the FM broadcast band but require more energy and longer antennas. Digital modes are possible but have not reached momentum yet.
Co-channel interference or CCI is crosstalk from two different radio transmitters using the same channel. Co-channel interference can be caused by many factors from weather conditions to administrative and design issues. Co-channel interference may be controlled by various radio resource management schemes.
KKOB is a commercial AM radio station, licensed to Albuquerque, New Mexico and owned by Cumulus Media. Its news/talk format is branded as "96.3 Newsradio KKOB", reflecting a simulcast with co-owned KKOB-FM 96.3 MHz. Studios and offices are located in Downtown Albuquerque. KKOB is the oldest station in New Mexico and is the state's primary entry point for the Emergency Alert System.
KFAB is a commercial AM radio station in Omaha, Nebraska, with studios and offices on Underwood Avenue in Omaha. It broadcasts a news/talk format and is owned by iHeartMedia, Inc.
CKLQ-FM is a commercial FM radio station in Brandon, Manitoba, Canada. In addition to its FM signal, it has a nested rebroadcaster at 880 kHz, CKLQ. The two stations simulcast a country format. They are owned and operated by Pattison Media Ltd. CKLQ-AM-FM, along with sister station CKLF-FM, have their radio studios and offices at 624 14th Street East, on Brandon's east end.
KNCO is a commercial AM radio station in Grass Valley, California. It is owned by Nevada County Broadcasters and airs a talk radio format. The studios and offices for KNCO and KNCO-FM are on East Main Street in Grass Valley. The station streams its programming on the iHeartRadio platform and app.
The North American Regional Broadcasting Agreement refers to a series of international treaties that defined technical standards for AM band (mediumwave) radio stations. These agreements also addressed how frequency assignments were distributed among the signatories, with a special emphasis on high-powered clear channel allocations.
KGNC is an AM radio broadcast station in Amarillo, Texas, United States with a news/talk format. The station is owned by Alpha Media LLC. Studios for KGNC and its partners are located in southwest Amarillo near the former Western Plaza shopping center. KGNC's programming is also broadcast on 97.5 FM by translator K248DE in Amarillo.
KFQD is a commercial radio station in Anchorage, Alaska branded as "News Talk 750 and 103.7 KFQD". It broadcasts a news/talk format and is owned by Alpha Media LLC. The studios and offices are on Arctic Slope Avenue in Anchorage.
WCRT is a Class B AM radio station licensed to the community of Donelson, Tennessee, near Nashville. Broadcasting a format of evangelical preaching and talk shows, WCRT is owned by Bott Communications, a Christian broadcaster, which bought the station, formerly WAMB, from longtime Nashville broadcaster Bill Barry.
KWPN is a commercial AM radio station licensed to Moore, Oklahoma, and serving the Oklahoma City metropolitan area. It is owned by Cumulus Media and airs a sports format. While Cumulus owns three sports stations in Oklahoma City, WWLS-FM and WKY have mostly local shows on weekdays, while KWPN carries mostly syndicated programming from ESPN Radio. The studios and offices are on NW 64th Street in Northwest Oklahoma City.
KHFX is a commercial AM radio station licensed to Cleburne, Texas, and serving the Dallas/Fort Worth Metroplex. It carries a Spanish language Christian radio format and is owned by the Siga Broadcasting Corporation. It calls itself "Radio Pentecostes Cristo Vive 1140" or "Radio Pentecostal Christ Lives."
KGNW is a commercial AM radio station licensed to Burien, Washington, and serving the Seattle metropolitan area. It airs a Christian talk and teaching radio format and is owned by the Salem Media Group. The radio studios and offices are on 5th Avenue South in downtown Seattle.
WEEU is a commercial radio station in Reading, Pennsylvania. It has a sports radio format and is owned by Treese Media Group, LLC, led by John and Kristine Treese.
WVUS is a Catholic Religious formatted broadcast radio station licensed to Grafton, West Virginia, serving Grafton and Taylor County, West Virginia. WVUS is owned and operated by Light of Life Community, Inc.
WZSK was a News/Talk formatted broadcast radio station licensed to Everett, Pennsylvania, serving Bedford, Somerset, and Altoona in Pennsylvania and Cumberland in Maryland. WZSK was last owned and operated by New Millennium Communications Group, Inc.
WKOK is a commercial radio station in Sunbury, Pennsylvania. It is owned by Sunbury Broadcasting Corporation and it broadcasts a combination News, Talk and Sports radio format. The radio studios and transmitter are on County Line Road in Selinsgrove.
KRHW is a radio station broadcasting a classic country radio format. Licensed to Sikeston, Missouri, the station serves the Missouri Bootheel region of Southeast Missouri, and operates on 1520 kHz in the AM radio band. KRHW is owned by Withers Broadcasting Company of Southeast Missouri, LLC.
WVLN is a radio station broadcasting a sports talk format. Licensed to Olney, Illinois, United States, the station is owned by Forcht Broadcasting and features programming from the Infinity Sports Network. 740 AM is a Canadian clear-channel frequency, on which CFZM in Toronto, Ontario is the dominant Class A station; WVLN must reduce nighttime power to protect the skywave signal of CFZM.
↑ "Federal Regulation of Radio Broadcasting" (July 8, 1926) by Acting Attorney General William J. Donovan, Official Opinions of the Attorneys General of the United States, Volume 35, 1929, pages 126-132.
↑ Rural Radio Magazine, Vol. 1 No. 1, Clear Channel Group (November 1938), p. 2
↑ "KGIR, Butte, Requests 50 kw. On WEAF Clear Channel". Broadcasting and Broadcast Advertising. 21 (9). Washington, D.C.: Broadcasting Publications, Inc.: 16 September 1, 1941.
↑ "WHAS Superpower". Broadcasting and Broadcast Advertising. 21 (17). Washington, D.C.: Broadcasting Publications, Inc.: 52 October 27, 1941. A half-dozen other applications ranging from 500,000 to 750,000 watts now are pending
↑ "WSB Revives Its 500-kw. Application, Seventh Stations Seeking Superpower". Broadcasting and Broadcast Advertising. 21 (18): 57. November 3, 1941. Already pending before the Commission were the applications of WLW, Cincinnati, for 650,000 watts, WOAI, San Antonio, seeking 750,000 watts, KSL, Salt Lake City, for 500,000 watts, and WSM, Nashville asking 500,000-watt operation. Similarly the application of WHO, Des Moines, for an increase to 500,000 watts is reported to be about ready for filing.
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