A clear-channel station is a North American AM radio 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

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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 skywave propagation. 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 10 kW 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 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 1 km, whereas Class "I-N" is permitted to use the lower Class B minimum efficiency of 281.63 mV/m/kW at 1 km. 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

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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

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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 50 kW or less (but a minimum of 10 kW nights) may increase power to 100 kW days while retaining their 10 kW night operation. This created some anomalies where stations licensed for 10 kW during all hours could increase power to 100 kW days and 10 kW nights, unless a directional antenna system was installed for nights, in which case the maximum night power was 50 kW. Additionally, one Class B station that had been operating non-directionally with 100 kW days and 50 kW nights was required to reduce power to 50 kW during all hours.

Class A (former I-A/I-B) stations
kHz Call
sign
City of license State / province Coun-
try
kW[3] Transmitter coordinates
540 CBK Watrous Saskatchewan   50 51°40′48″N 105°26′48″W / 51.68°N 105.446667°W / 51.68; -105.446667 (CBK 540 - 50 kW)
540 XEWA San Luis Potosí San Luis Potosí   150 22°09′29″N 100°55′35″W / 22.157944°N 100.92625°W / 22.157944; -100.92625 (XEWA 540 - 150 kW)
640 CBN St. John's Newfoundland and Labrador   10 47°34′08″N 52°48′45″W / 47.568889°N 52.8125°W / 47.568889; -52.8125 (CBN 640 - 10 kW)
640 KFI Los Angeles California   50 33°52′47″N 118°00′47″W / 33.879722°N 118.013056°W / 33.879722; -118.013056 (KFI 640 - 50 kW)
650 WSM Nashville Tennessee   50 35°59′53″N 86°47′27″W / 35.998194°N 86.790833°W / 35.998194; -86.790833 (WSM 650 - 50 kW)
660 WFAN New York City New York   50 40°51′35″N 73°47′07″W / 40.859722°N 73.785278°W / 40.859722; -73.785278 (WFAN 660 - 50 kW)
670 WSCR Chicago Illinois   50 41°56′03″N 88°04′24″W / 41.934167°N 88.073333°W / 41.934167; -88.073333 (WSCR 670 - 50 kW)
680 KNBR San Francisco California   50 37°32′50″N 122°14′00″W / 37.547222°N 122.233333°W / 37.547222; -122.233333 (KNBR 680 - 50 kW)
690 CKGM[a] Montreal Quebec   50 45°17′43″N 73°43′18″W / 45.2953°N 73.7217°W / 45.2953; -73.7217 (CKGM 690 - 50 kW)
690 XEWW Tijuana Baja California   77.5 / 50 32°17′52″N 117°01′48″W / 32.297778°N 117.03°W / 32.297778; -117.03 (XEWW 690 - 77.5 / 50 kW)
700 WLW Cincinnati Ohio   50 39°21′11″N 84°19′30″W / 39.353056°N 84.325°W / 39.353056; -84.325 (WLW 700 - 50 kW)
710 KIRO Seattle Washington   50 47°23′55″N 122°26′00″W / 47.398611°N 122.433333°W / 47.398611; -122.433333 (KIRO 710 - 50 kW)
710 WOR New York City New York   50 40°47′51″N 74°05′24″W / 40.7975°N 74.09°W / 40.7975; -74.09 (WOR 710 - 50 kW)
720 WGN Chicago Illinois   50 42°00′42″N 88°02′07″W / 42.011667°N 88.035278°W / 42.011667; -88.035278 (WGN 720 - 50 kW)
730 CKAC Montreal Quebec   50 45°30′50″N 73°58′24″W / 45.5139°N 73.9733°W / 45.5139; -73.9733 (CKAC 730 - 50 kW)
730 XEX Mexico City Mexico City   60 / 100 19°21′54″N 98°57′28″W / 19.36505°N 98.957703°W / 19.36505; -98.957703 (XEX 730 - 60 / 100 kW)
740 CFZM[b] Toronto Ontario   50 43°34′30″N 79°49′02″W / 43.575°N 79.817222°W / 43.575; -79.817222 (CFZM 740 - 50 kW)
750 WSB Atlanta Georgia   50 33°50′38″N 84°15′12″W / 33.843889°N 84.253333°W / 33.843889; -84.253333 (WSB 750 - 50 kW)
760 WJR Detroit Michigan   50 42°10′05″N 83°12′54″W / 42.168056°N 83.215°W / 42.168056; -83.215 (WJR 760 - 50 kW)
770 WABC New York City New York   50 40°52′50″N 74°04′10″W / 40.880556°N 74.069444°W / 40.880556; -74.069444 (WABC 770 - 50 kW)
780 WBBM Chicago Illinois   35 / 42 41°59′26″N 88°01′40″W / 41.990556°N 88.027778°W / 41.990556; -88.027778 (WBBM 780 - 50 kW)
800 XEROK Ciudad Juárez Chihuahua   50 31°41′44″N 106°23′01″W / 31.695556°N 106.383611°W / 31.695556; -106.383611 (XEROK 800 - 50 kW)
810 KGO San Francisco California   50 37°31′35″N 122°06′02″W / 37.526389°N 122.100556°W / 37.526389; -122.100556 (KGO 810 - 50 kW)
810 WGY Schenectady New York   50 42°47′32″N 74°00′43″W / 42.792336°N 74.011937°W / 42.792336; -74.011937 (WGY 810 - 50 kW)
820 WBAP Fort Worth Texas   50 32°36′38″N 97°10′04″W / 32.610556°N 97.167778°W / 32.610556; -97.167778 (WBAP 820 - 50 kW)
830 WCCO Minneapolis Minnesota   50 45°10′44″N 93°20′59″W / 45.178889°N 93.349722°W / 45.178889; -93.349722 (WCCO 830 - 50 kW)
840 WHAS Louisville Kentucky   50 38°15′40″N 85°25′43″W / 38.261111°N 85.428611°W / 38.261111; -85.428611 (WHAS 840 - 50 kW)
850 KOA Denver Colorado   50 39°30′22″N 104°45′57″W / 39.506111°N 104.765833°W / 39.506111; -104.765833 (KOA 850 - 50 kW)
860 CJBC Toronto Ontario   50 43°34′30″N 79°49′03″W / 43.575°N 79.8175°W / 43.575; -79.8175 (CJBC 860 - 50 kW)
870 WWL New Orleans Louisiana   50 29°50′14″N 90°07′55″W / 29.837222°N 90.131944°W / 29.837222; -90.131944 (WWL 870 - 50 kW)
880 WHSQ New York City New York   50 40°51′35″N 73°47′08″W / 40.859806°N 73.785444°W / 40.859806; -73.785444 (WHSQ 880 - 50 kW)
890 WLS Chicago Illinois   50 41°33′21″N 87°50′54″W / 41.555833°N 87.848333°W / 41.555833; -87.848333 (WLS 890 - 50 kW)
900 CKBI Prince Albert Saskatchewan   10 53°12′03″N 105°45′14″W / 53.2008°N 105.7538°W / 53.2008; -105.7538 (CKBI 900 - 10 kW)
900 XEW Mexico City Mexico City   100 19°21′54″N 98°57′28″W / 19.36505°N 98.957703°W / 19.36505; -98.957703 (XEW 900 - 100 kW)
940 CFNV[c] Montreal Quebec   50 45°23′34″N 73°41′53″W / 45.3928°N 73.6981°W / 45.3928; -73.6981 (CFNV 940 - 50 kW)
940 XEQ Mexico City Mexico City   30 19°21′37″N 98°59′32″W / 19.360217°N 98.992194°W / 19.360217; -98.992194 (XEQ 940 - 30 kW)
990 CBW Winnipeg Manitoba   50 / 46 49°50′10″N 97°30′46″W / 49.836111°N 97.512778°W / 49.836111; -97.512778 (CBW 990 - 50 / 46 kW)
990 CBY Corner Brook Newfoundland and Labrador   10 48°55′58″N 57°54′22″W / 48.9328°N 57.9061°W / 48.9328; -57.9061 (CBY 990 - 10 kW)
1000 KNWN Seattle Washington   50 47°27′49″N 122°26′27″W / 47.463611°N 122.440833°W / 47.463611; -122.440833 (KNWN 1000 - 50 kW)
1000 WMVP Chicago Illinois   50 41°49′05″N 87°59′18″W / 41.818056°N 87.988333°W / 41.818056; -87.988333 (WMVP 1000 - 50 kW)
1000 XEOY Mexico City Mexico City   50 / 10 19°23′18″N 99°07′29″W / 19.3883°N 99.1247°W / 19.3883; -99.1247 (XEOY 1000 - 50 / 10 kW)
1010 CBR Calgary Alberta   50 50°56′17″N 113°57′42″W / 50.9380°N 113.9616°W / 50.9380; -113.9616 (CBR 1010 - 50 kW)
1010 CFRB Toronto Ontario   50 43°30′40″N 79°37′48″W / 43.5110°N 79.6300°W / 43.5110; -79.6300 (CFRB 1010 - 50 kW)
1020 KDKA Pittsburgh Pennsylvania   50 40°33′34″N 79°57′09″W / 40.55948°N 79.9526°W / 40.55948; -79.9526 (KDKA 1020 - 50 kW)
1030 WBZ Boston Massachusetts   50 42°16′44″N 70°52′34″W / 42.2788°N 70.8761°W / 42.2788; -70.8761 (WBZ 1030 - 50 kW)
1040 WHO Des Moines Iowa   50 41°39′10″N 93°21′01″W / 41.652778°N 93.350278°W / 41.652778; -93.350278 (WHO 1040 - 50 kW)
1050 XEG Monterrey Nuevo León   150 25°41′53″N 100°10′30″W / 25.698056°N 100.175°W / 25.698056; -100.175 (XEG 1050 - 150 kW)
1060 KYW Philadelphia Pennsylvania   50 40°06′12″N 75°14′56″W / 40.103333°N 75.248889°W / 40.103333; -75.248889 (KYW 1060 - 50 kW)
1060 XECPAE Mexico City Mexico City   100 / 20 19°21′50″N 99°01′38″W / 19.363972°N 99.027194°W / 19.363972; -99.027194 (XEEP 1060 - 100 / 20 kW)
1070 KNX Los Angeles California   50 33°51′35″N 118°20′59″W / 33.859722°N 118.349722°W / 33.859722; -118.349722 (KNX 1070 - 50 kW)
1080 KRLD Dallas Texas   50 32°53′25″N 96°38′44″W / 32.890281°N 96.645561°W / 32.890281; -96.645561 (KRLD 1080 - 50 kW)
1080 WTIC Hartford Connecticut   50 41°46′39″N 72°48′19″W / 41.7775°N 72.805278°W / 41.7775; -72.805278 (WTIC 1080 - 50 kW)
1090 KAAY Little Rock Arkansas   50 34°36′00″N 92°13′30″W / 34.6°N 92.225°W / 34.6; -92.225 (KAAY 1090 - 50 kW)
1090 WBAL Baltimore Maryland   50 39°22′33″N 76°46′21″W / 39.375833°N 76.7725°W / 39.375833; -76.7725 (WBAL 1090 - 50 kW)
1090 XEPRS Rancho del Mar, Rosarito Baja California   50 32°24′08″N 117°05′12″W / 32.402278°N 117.086722°W / 32.402278; -117.086722 (XEPRS 1090 - 50 kW)
1100 WTAM Cleveland Ohio   50 41°16′50″N 81°37′22″W / 41.280556°N 81.622778°W / 41.280556; -81.622778 (WTAM 1100 - 50 kW)
1110 KFAB Omaha Nebraska   50 41°07′11″N 96°00′06″W / 41.119722°N 96.001667°W / 41.119722; -96.001667 (KFAB 1110 - 50 kW)
1110 WBT Charlotte North Carolina   50 35°07′56″N 80°53′23″W / 35.132222°N 80.889722°W / 35.132222; -80.889722 (WBT 1110 - 50 kW)
1120 KMOX St. Louis Missouri   50 38°43′22″N 90°03′19″W / 38.722778°N 90.055278°W / 38.722778; -90.055278 (KMOX 1120 - 50 kW)
1130 CKWX Vancouver British Columbia   50 49°09′27″N 123°04′01″W / 49.157601°N 123.067024°W / 49.157601; -123.067024 (CKWX 1130 - 50 kW)
1130 KWKH Shreveport Louisiana   50 32°42′18″N 93°52′55″W / 32.705°N 93.881944°W / 32.705; -93.881944 (KWKH 1130 - 50 kW)
1130 WBBR New York City New York   50 40°48′39″N 74°02′24″W / 40.810833°N 74.04°W / 40.810833; -74.04 (WBBR 1130 - 50 kW)
1140 WRVA Richmond Virginia   50 37°24′13″N 77°18′59″W / 37.403611°N 77.316389°W / 37.403611; -77.316389 (WRVA 1140 - 50 kW)
1140 XEMR Monterrey Nuevo León   50 25°45′52″N 100°15′11″W / 25.764444°N 100.253056°W / 25.764444; -100.253056 (XEMR 1140 - 50 kW)
1160 KSL Salt Lake City Utah   50 40°46′48″N 112°05′51″W / 40.78°N 112.0975°W / 40.78; -112.0975 (KSL 1160 - 50 kW)
1170 KOTV Tulsa Oklahoma   50 36°08′49″N 95°48′27″W / 36.146944°N 95.8075°W / 36.146944; -95.8075 (KOTV 1170 - 50 kW)
1170 WWVA Wheeling West Virginia   50 40°06′07″N 80°52′02″W / 40.101944°N 80.867222°W / 40.101944; -80.867222 (WWVA 1170 - 50 kW)
1180 WHAM Rochester New York   50 43°04′55″N 77°43′30″W / 43.081944°N 77.725°W / 43.081944; -77.725 (WHAM 1180 - 50 kW)
1190 KEX Portland Oregon   50 45°25′20″N 122°33′57″W / 45.422222°N 122.565833°W / 45.422222; -122.565833 (KEX 1190 - 50 kW)
1190 XEWK Guadalajara Jalisco   50 / 10 20°44′11″N 103°20′52″W / 20.736389°N 103.347778°W / 20.736389; -103.347778 (XEWK 1190 - 50 / 10 kW)
1200 WOAI San Antonio Texas   50 29°30′08″N 98°07′44″W / 29.502111°N 98.128806°W / 29.502111; -98.128806 (WOAI 1200 - 50 kW)
1210 WPHT Philadelphia Pennsylvania   50 39°58′46″N 74°59′13″W / 39.979444°N 74.986944°W / 39.979444; -74.986944 (WPHT 1210 - 50 kW)
1220 XEB Mexico City Mexico City   100 19°18′31″N 99°03′32″W / 19.308611°N 99.058889°W / 19.308611; -99.058889 (XEB 1220 - 100 kW)
1500 KSTP Saint Paul Minnesota   50 45°01′32″N 93°03′06″W / 45.025556°N 93.051667°W / 45.025556; -93.051667 (KSTP 1500 - 50 kW)[4]
1500 WFED Washington, D.C. Washington, D.C.   50 39°02′31″N 77°02′47″W / 39.041944°N 77.046389°W / 39.041944; -77.046389 (WFED 1500 - 50 kW)
1510 WLAC Nashville Tennessee   50 36°16′19″N 86°45′28″W / 36.271944°N 86.757778°W / 36.271944; -86.757778 (WLAC 1510 - 50 kW)
1520 KOKC Oklahoma City Oklahoma   50 35°20′00″N 97°30′16″W / 35.333333°N 97.504444°W / 35.333333; -97.504444 (KOKC 1520 - 50 kW)
1520 WWKB Buffalo New York   50 42°46′10″N 78°50′34″W / 42.769444°N 78.842778°W / 42.769444; -78.842778 (WWKB 1520 - 50 kW)
1530 KFBK Sacramento California   50 38°50′54″N 121°28′58″W / 38.848333°N 121.482778°W / 38.848333; -121.482778 (KFBK 1530 - 50 kW)
1530 WCKY Cincinnati Ohio   50 39°03′55″N 84°36′27″W / 39.065278°N 84.6075°W / 39.065278; -84.6075 (WCKY 1530 - 50 kW)
1540 KXEL Waterloo Iowa   50 42°10′48″N 92°18′38″W / 42.18°N 92.310556°W / 42.18; -92.310556 (KXEL 1540 - 50 kW)
1540 ZNS-1 Nassau New Providence   50 25°00′14″N 77°21′01″W / 25.003917°N 77.350333°W / 25.003917; -77.350333 (ZNS-1 1540 - 50 kW)
1550 CBEF[d] Windsor Ontario   10 42°12′56″N 82°55′15″W / 42.2156°N 82.9208°W / 42.2156; -82.9208 (CBEF 1550 - 10 kW)
1560 KNZR[e] Bakersfield California   25 / 10 35°18′30″N 119°02′46″W / 35.308333°N 119.046111°W / 35.308333; -119.046111 (KNZR 1560 - 25 / 10 kW)
1560 WFME[f] New York City New York   50 40°43′00″N 73°55′04″W / 40.716667°N 73.917778°W / 40.716667; -73.917778 (WFME 1560 - 50 kW)
1570 XERF Ciudad Acuña Coahuila   100 29°21′00″N 101°02′00″W / 29.35°N 101.033333°W / 29.35; -101.033333 (XERF 1570 - 100 kW)
1580 CKDO[g] Oshawa Ontario   10 43°52′19″N 78°45′53″W / 43.871944°N 78.764722°W / 43.871944; -78.764722 (CKDO 1580 - 10 kW)
Alaskan class A (former class I-N) stations
kHz Call
sign
City of license Nat-
ion
kW[3] Transmitter coordinates
640 KYUK Bethel   10 60°46′54″N 161°53′08″W / 60.78175°N 161.885639°W / 60.78175; -161.885639 (KYUK 640 - 10 kW)
650 KENI Anchorage   50 61°09′58″N 149°49′34″W / 61.166111°N 149.826111°W / 61.166111; -149.826111 (KENI 650 - 50 kW)
660 KFAR Fairbanks   10 64°48′29″N 147°29′34″W / 64.808056°N 147.492778°W / 64.808056; -147.492778 (KFAR 660 - 10 kW)
670 KDLG Dillingham   10 59°02′43″N 158°27′07″W / 59.045278°N 158.451944°W / 59.045278; -158.451944 (KDLG 670 - 10 kW)
680 KBRW Barrow   10 71°15′24″N 156°31′32″W / 71.256667°N 156.525556°W / 71.256667; -156.525556 (KBRW 680 - 10 kW)
700 KBYR Anchorage   10 61°12′25″N 149°55′20″W / 61.206944°N 149.922222°W / 61.206944; -149.922222 (KBYR 700 - 10 kW)
720 KOTZ Kotzebue   10 66°50′22″N 162°34′05″W / 66.839444°N 162.568056°W / 66.839444; -162.568056 (KOTZ 720 - 10 kW)
750 KFQD Anchorage   50 61°20′18″N 150°02′03″W / 61.338333°N 150.034167°W / 61.338333; -150.034167 (KFQD 750 - 10 kW)
770 KCHU Valdez   9.7 61°06′40″N 146°15′39″W / 61.111111°N 146.260833°W / 61.111111; -146.260833 (KCHU 770 - 9.7 kW)
780 KNOM Nome   25 / 14 64°29′16″N 165°17′58″W / 64.487778°N 165.299444°W / 64.487778; -165.299444 (KNOM 780 - 25 / 14 kW)
820 KCBF Fairbanks   10 64°52′44″N 147°40′06″W / 64.878889°N 147.668333°W / 64.878889; -147.668333 (KCBF 820 - 10 kW)
850 KICY Nome   50 64°29′15″N 165°18′53″W / 64.4875°N 165.314722°W / 64.4875; -165.314722 (KICY 850 - 50 kW)
890 KBBI Homer   10 59°40′14″N 151°26′38″W / 59.670556°N 151.443889°W / 59.670556; -151.443889 (KBBI 890 - 10 kW)
1020 KVNT Eagle River   10 61°29′02″N 149°45′44″W / 61.483889°N 149.762222°W / 61.483889; -149.762222 (KVNT 1020 - 10 kW)
1080 KOAN Anchorage   10 61°07′12″N 149°53′43″W / 61.12°N 149.895278°W / 61.12; -149.895278 (KOAN 1080 - 10 kW)
1170 KJNP North Pole   50 / 21 64°45′34″N 147°19′26″W / 64.759444°N 147.323889°W / 64.759444; -147.323889 (KJNP 1170 - 50 / 21 kW)

Notes

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  1. ^ 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.
  2. ^ 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.
  3. ^ 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.
  4. ^ 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.
  5. ^ KNZR is the only U.S. class-A station licensed to operate with less than 50 kilowatts full-time.
  6. ^ 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.
  7. ^ 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 [1]

List of former clear-channel stations

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Freq.
(kHz)
Call sign City of license State / province Country Fate
540 CBT Grand Falls-Windsor Newfoundland   Moved to FM on December 31, 2022.
850 XETQ-AM Ixhuatlancillo Veracruz   Migrated to FM as XHTQ-FM in 2013. At its height XETQ was authorized for 100 kW day/50 kW night. In the 1990s it lowered its power to 10 kW day/1 kW night.
1070 CBA Moncton New Brunswick   Moved to FM in April 2008. Canada has not withdrawn the international notification for CBA.
1190 WOWO Fort Wayne Indiana   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.
1510 KGA Spokane Washington   Downgraded to class B in 2011 to make room for co-channel sister station KSFN, Piedmont, California, reducing night power to 15 kW[5]
1550 XERUV-AM Xalapa Veracruz   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 90.5 MHz on June 1, 2016.

History

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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 1370 kHz regional channel, to a class I-A signal on 660 kHz, 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 750 kW;[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 50 kW.[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, 770 kHz, 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 (1,207 km) 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.

See also

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References

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  1. ^ Fybush, Scott (February 26, 2010). "Remembering Buffalo's BBC". Tower Site of the Week. Retrieved March 13, 2018.
  2. ^ Instituto Federal de Telecomunicaciones. Infraestructura de Estaciones de Radio AM. Last modified 2018-05-16. Retrieved 2015-12-15. Technical information from the IFT Coverage Viewer.
  3. ^ a b When two figures are listed, the first is daytime power, the second is nighttime.
  4. ^ Nighttime site.
  5. ^ FCC license BL-20100527AGH
  6. ^ "Amendments to Regulations: Regulation 57", Radio Service Bulletin, September 1, 1922, pages 10-11.
  7. ^ "Amendments to Regulations", Radio Service Bulletin, January 3, 1922, page 10.
  8. ^ "Radio Conference Recommendations: New Wave Lengths", Radio Age, May 1923, page 11.
  9. ^ "Broadcasting stations of the United States by wave lengths", Radio Service Bulletin, March 2, 1925, pages 12-13.
  10. ^ "U.S. Radio Power Scale Announced", Washington Star, October 29, 1924, page 18.
  11. ^ "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.
  12. ^ "Broadcasting stations, alphabetically by call signals", Radio Service Bulletin, December 31, 1926, pages 9-21.
  13. ^ "List of broadcasting stations issued temporary permits", Radio Service Bulletin, April 30, 1927, pages 6-14.
  14. ^ "Broadcasting stations by frequency, showing clear channels (600 to 1,000 kilocycles band), effective December 1, 1927, and subsequently" and "Broadcasting stations, by frequencies, showing uncleared channels (600 to 1,000 kilocycles), effective December 1 and subsequently", Jurisdiction of Radio Commission: Statement of Hon. Eugene O. Sykes, Acting Chairman Federal Radio Commission, pages 10-17.
  15. ^ "Limitation of Power of Radio Broadcast Stations" (Senate Resolution 294), Journal of the Senate of the United States of America (Seventy-Fifth Congress, Third Session), June 9, 1938, page 507.
  16. ^ Rural Radio Magazine, Vol. 1 No. 1, Clear Channel Group (November 1938), p. 2
  17. ^ "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.
  18. ^ "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
  19. ^ "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.
  20. ^ "Superpower, Clear Channels Slated for Early FCC Probe". Broadcasting and Broadcast Advertising. 21 (16): 12. October 20, 1941.
  21. ^ Facts on File 1980 Yearbook, p. 519
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