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In the Bahamas, Canada, Mexico, and the United States, a clear-channel station is an AM radio station which is given extraordinary protection from interference to its nighttime signal. Clear-channel stations are sometimes known colloquially as blowtorches.

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Description

Certain mediumwave frequencies were set aside under the North American Radio Broadcasting Agreement (NARBA for short) for nighttime use by only one or two specific AM stations, covering a wide area via skywave propagation; these frequencies were known as the clear channels, and the stations on them are thus clear-channel stations. 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; stations on the other clear channels, with two or more stations, must use between 10 and 50 kW, 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 this second kind of channel (known as class I-B) could be built.

Some of the original NARBA signatories, including the United States, Canada, and Mexico, have implemented bilateral agreements that supersede its terms, eliminating among other things the distinction between the two kinds of clear channel: the original "I-A", "I-B", and "I-N" station classes are now all included in class A.

Clear-channel stations, unlike all other AM stations in North America, have a secondary service area—that is, they are entitled to protection from interference to their nighttime skywave signals. 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 to 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.

Clear Channel Communications, a San Antonio, Texas-based company which owns over 900 U.S. radio stations, was originally formed to purchase one clear-channel station, WOAI. The company now owns more than a dozen such stations.

History

For the U.S., clear channels first appeared in 1922 when the Commerce Department moved stations which had all used three (initially two) frequencies (two for entertainment stations, one for "weather and crop reports") onto 52 frequencies. Two were used for all low-power stations and the large stations each got their own frequency. A few frequencies were used on both the East and West coasts, which were considered far enough apart to limit interference. At this time large stations were limited to 1000 watts and some licences were revoked. Later in 1928, the AM band was reorganized with local, regional and clear channels (and a few reserved for Canada) by the new Federal Radio Commission's General Order 40. Gradually maximum power was increased to 50,000 watts (with some short lived experiments with 250–500 kilowatt "super-power" operation). This system was continued in the 1941 NARBA system although almost all stations shifted broadcast frequencies.

As early as the 1950s, debate raged 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. They requested that the power limit on the "I-A" channels in the U.S. be increased from 50 kW to 750 kW, pointing to WLW's successful experiments before the war, 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 were eliminated, they would be able to build new stations to provide local service to those rural "dark areas".

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, 770 kHz, arguing that the New York signal was so weak in the mountain west that it served no one. 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, like 680 in San Francisco, California, 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 fifteenfold 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.

On May 29, 1980, the FCC voted to limit the protection for the twenty-five clear channel stations to a 750 mile radius around the transmitter. Those stations outside the area of protection were no longer required to sign off or power down after sundown.[1]

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.

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Daytimers

Daytimers 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 radio signals can radiate much farther. Such stations are usually supposed to do one of three things: sign off, reduce power (sometimes dramatically, to only a few watts), or switch to another (typically near-by) frequency. Their broadcast class is Class D.

List of all clear-channel stations

The following two tables show all of the class-A stations in North America. Stations in Alaska (the former class I-Ns) are shown separately.

Frequency
(kHz)
Callsign City of license
540 CBK Watrous, Saskatchewan
540 CBT Grand Falls, Newfoundland and Labrador
540 XEWA San Luis Potosí, San Luis Potosí
640 CBN St. John's, Newfoundland and Labrador
640 KFI Los Angeles, California
650 WSM Nashville, Tennessee
660 WFAN New York, New York
670 WSCR Chicago, Illinois
680 KNBR San Francisco, California
690 CINF Montreal, Quebec
690 XEWW Tijuana, Baja California
700 WLW Cincinnati, Ohio
710 KIRO Seattle, Washington
710 WOR New York, New York
720 WGN Chicago, Illinois
730 CKAC Montreal, Quebec
730 XEX Mexico City, D.F.
740 CFZM[2] Toronto, Ontario
750 WSB Atlanta, Georgia
760 WJR Detroit, Michigan
770 WABC New York, New York
780 WBBM Chicago, Illinois
800 XEROK Ciudad Juárez, Chihuahua
810 KGO San Francisco, California
810 WGY Schenectady, New York
820 WBAP Fort Worth, Texas
830 WCCO Minneapolis, Minnesota
840 WHAS Louisville, Kentucky
850 KOA Denver, Colorado
860 CJBC Toronto, Ontario
870 WWL New Orleans, Louisiana
880 WCBS New York, New York
890 WLS Chicago, Illinois
900 XEW Mexico City, D.F.
940 CINW Montreal, Quebec
940 XEQ Mexico City, D.F.
990 CBW Winnipeg, Manitoba
990 CBY Corner Brook, Newfoundland and Labrador
1000 KOMO Seattle, Washington
1000 WMVP Chicago, Illinois
1010 CBR Calgary, Alberta
1010 CFRB Toronto, Ontario
1020 KDKA Pittsburgh, Pennsylvania
1030 WBZ Boston, Massachusetts
1040 WHO Des Moines, Iowa
1050 XEG Monterrey, Nuevo León
1060 KYW Philadelphia, Pennsylvania
1060 XEEP Mexico City, D.F.
1070 CBA[3] Moncton, New Brunswick
1070 KNX Los Angeles, California
1080 WTIC Hartford, Connecticut
1080 KRLD Dallas, Texas
1090 KAAY Little Rock, Arkansas
1090 WBAL Baltimore, Maryland
1100 WTAM Cleveland, Ohio
1110 KFAB Omaha, Nebraska
1110 WBT Charlotte, North Carolina
1120 KMOX St. Louis, Missouri
1130 CKWX Vancouver, British Columbia
1130 KWKH Shreveport, Louisiana
1130 WBBR New York, New York
1140 WRVA Richmond, Virginia
1140 XEMR Monterrey, Nuevo León
1160 KSL Salt Lake City, Utah
1170 KFAQ Tulsa, Oklahoma
1170 WWVA Wheeling, West Virginia
1180 WHAM Rochester, New York
1190 KEX Portland, Oregon
1190 WOWO[4] Fort Wayne, Indiana
1190 XEWK Guadalajara, Jalisco
1200 WOAI San Antonio, Texas
1210 WPHT Philadelphia, Pennsylvania
1220 XEB Mexico City, D.F.
1500 KSTP Saint Paul, Minnesota
1500 WFED Washington, D.C.
1510 KGA[5] Spokane, Washington
1510 WLAC Nashville, Tennessee
1520 KOKC Oklahoma City, Oklahoma
1520 WWKB Buffalo, New York
1530 KFBK Sacramento, California
1530 WCKY Cincinnati, Ohio
1540 KXEL Waterloo, Iowa
1540 ZNS-1 Nassau, Bahamas
1550 CBE Windsor, Ontario
1550 XERUV Xalapa, Veracruz
1560 KNZR[6] Bakersfield, California
1560 WQEW New York, New York
1570 XERF Ciudad Acuña, Coahuila
1580 CKDO[7] Oshawa, Ontario

Class A (former class I-N) stations in Alaska:

Frequency
(kHz)
Callsign City of license
640 KYUK Bethel
650 KENI Anchorage
660 KFAR Fairbanks
670 KDLG Dillingham
680 KBRW Barrow
700 KBYR Anchorage
720 KOTZ Kotzebue
750 KFQD Anchorage
770 KCHU Valdez
780 KNOM Nome
820 KCBF Fairbanks
850 KICY Nome
890 KBBI Homer
1020 KAXX Eagle River
1080 KUDO Anchorage
1170 KJNP North Pole

Notes

  1. ^ Facts on File 1980 Yearbook, p519
  2. ^ The 740 frequency was allocated to 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.
  3. ^ This frequency was formerly assigned to CBA, which moved to FM in April, 2008. Canada has not withdrawn the international notification for CBA, thus reserving the right to license a new class-A station on 1070 in the future.
  4. ^ WOWO was previously a class-A station and is called out in the treaties as such. However, in the 1990s WOWO was downgraded to a class B allotment by reducing its night power to 9.8 kW, and thus no longer has a secondary service area.
  5. ^ KGA, in 2007, was seeking authorization from the FCC to downgrade its nighttime power to 15 kW, with a directional signal, to allow for an upgrade to the nighttime signal of KPIG, broadcasting on the same AM 1510 frequency in the larger San Francisco market. If approved (as is expected), KGA would no longer have a secondary service area. [1]
  6. ^ KNZR is the only U.S. class-A station licensed to operate with less than 50 kilowatts full-time; KNZR is licensed for 25 kW during the day and 10 kW at night.
  7. ^ The 1580 kHz frequency was originally allocated to 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. [2]

See also

External links


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