1928 жылғы АҚШ радиоаппаратурасы жиіліктерінің қайта ұйымдастырылуы

1928 American reorganization of radio broadcasting frequencies
The Federal Radio Commission's (FRC) General Order 40, dated August 30, 1928, described the standards for a sweeping reorganization of radio broadcasting in the United States. This order grouped the AM radio band transmitting frequencies into three main categories, which became known as Clear Channel, Regional, and Local. It also included provisions for coordination with Canadian station assignments. The majority of the reassignments resulting from the plan's implementation went into effect on November 11, 1928.

Radio transmissions in the United States were originally regulated by the Department of Commerce, as authorized by the Radio Act of 1912. The first formal regulations governing broadcasts intended for the general public were adopted effective December 1, 1921. This initially established just two transmitting wavelengths — 360 meters (833 kHz) for "entertainment" broadcasts, and 485 meters (619 kHz) for "market news and weather reports". The number of broadcasting stations grew dramatically in 1922, reaching over 500 by the end of the year, and the government began making available additional frequencies. By November 1924 a band of frequencies, from 550 to 1500 kHz, had been established, with higher powered stations, known as "Class B", assigned to the frequencies from 550 to 1070, while lower powered "Class A" stations were assigned to 1080 to 1500. In 1926, the government's regulatory authority under the 1912 Radio Act was successfully challenged, and, for a chaotic period that lasted until early 1927, radio stations were free to use any frequency and power they chose, while the number of stations increased to 732. The Radio Act of 1927 was passed to regain control of the situation. The Act established a Federal Radio Commission, which reduced the number of stations, primarily through its General Order 32, in addition to eliminating "temporary" and "portable" stations. The Commission also reallocated frequency assignments to reduce interference and provide better service to smaller communities and underserved rural areas. A constraint was the Davis Amendment, which specified that the station assignments had to be equitably made throughout the country. Two technical issues limited the number of stations that could operate without interfering with each other. These issues were especially important at night, when a change in the ionosphere meant that radio signals traveled much greater distances. Most transmitters at this time were unable to precisely control their output frequencies, thus, signals from two stations operating on the same nominal frequency would combine to make a high pitched "heterodyne" tone that interfered with the reception of both stations. Secondly, directional antennas would not be developed until the early 1930s, so there was no effective method for limiting signals in a given direction.

On August 30, 1928, the Commission issued General Order 40, which set new standards for radio broadcasting. A "broadcast band" was defined, consisting of 96 frequencies, spaced every 10 kilohertz, from 550 to 1500 kHz. Six of them—690, 730, 840, 910, 960, and 1030—were restricted for use only by Canadian stations, leaving 90 available for US assignment. The country was further divided into five zones, to coordinate the Davis Amendment directive of an equitable assignment of stations.

Forty four frequencies, later known as "Regional", were designated to be used concurrently by stations in multiple zones. Forty of these frequencies had power limits of 1,000 watts, while the remaining four, 1460 1490, referred to as "Super Regional", had 5,000 watt limits. In numerous cases up to four stations in a given location were assigned the same frequency, requiring them to establish time sharing agreements.

The remaining six frequencies—1200, 1210, 1310, 1370, 1420 and 1500—later known as "Local", were issued to stations in all five zones, with a power limit of 100 watts.

The reorganization greatly reduced interference caused by the chaos that resulted from the earlier collapse of regulation. There was some controversy that the assignments had created groups of "have" and "have not" stations—with the Clear Channel stations receiving a major economic boost, while many remaining stations, often with limited hours due to time sharing, had constricted futures. Also, although the reorganization accounted for Canada, it did not include other nearby countries, most notably Mexico. Twelve years later this omission was addressed by the North American Regional Broadcasting Agreement (NARBA), which took effect March 29, 1941.

General Order 40's implementation took effect at 3 a. m. Eastern time on November 11, 1928, and required most U. S. radio stations to move to a new broadcast frequency. A survey conducted by Radio Retailing magazine concluded that, despite some continuing issues, the changes meant that "on the whole, the broadcasting situation has been much improved". The table below presents a general outline of the allocations made under the order. For "Clear" frequencies, the zone of that frequency's principal station is listed, followed by the principal station's call letters and location, then the frequency that had been previously used by the principal station, and any additional stations assigned to that frequency. Bolded stations' call signs are the original primary assignments, while call signs shown in parentheses were owned by the same licensee as the principal station. The additional stations on a frequency were: 1) shared allocations, 2) daytimers, or 3) secondary stations which eventually achieved full time status, but at lower power or using a directional antenna that protected the primary station's coverage. Freq. (kHz) Used for Max. Power(watts) Zone Principal station(s) Other stations sharingfrequency (zone) Calls, City Prev. freq. 550 Regional 1,000   — — — 7 U. S. stations 560  Regional 1,000   — — — 10 U. S. stations 570  Regional 1,000   — — — 11 U. S. stations 580 Regional 1,000   — — — 6 U. S. stations8 Canadian stations 590  Regional 1,000   — — — 5 U. S. stations 600 Regional 1,000   — — — 7 U. S. stations3 Canadian stations 610  Regional 1,000   — — — 5 U. S. stations 620 Regional 1,000   — — — 6 U. S. stations 630 Regional 1,000   — — — 4 U. S stations3 Canadian stations 640  Clear TBD 5 KFI, Los Angeles, California 640  WOI, Ames, Iowa (4)WAIU, Columbus, Ohio (2) 650 Clear TBD 3 WSM, Nashville, Tennessee 890  KPCB, Seattle, Washington (5) 660 Clear TBD 1 WEAF, New York, New York 610  WAAW, Omaha, Nebraska (4) 670 Clear TBD 4 WMAQ, Chicago, Illinois 670  none 680 Clear TBD 5 KPO, San Francisco, California 710  KFEQ, Saint Joseph, Missouri (4)WPTF, Raleigh, North Carolina (3) 690 Clear Canada CJCJ, Calgary, AlbertaNAA, Arlington, Virginia (2) 700 Clear TBD 2 WLW, Cincinnati, Ohio 700  none 710 Clear TBD 1 WOR, New York, New York (Newark, New Jersey) 710  KMPC, Los Angeles, California (5) 720 Clear TBD 4 WGN/(WLIB), Chicago, Illinois 720  none 730 Clear Canada CKAC, Montreal, Quebec CKWX, Vancouver, British Columbia 740 Clear TBD 3 WSB, Atlanta, Georgia 630  KMMJ, Clay Center, Nebraska (4) 750 Clear TBD 2 WJR, Detroit, Michigan 680  none 760 Clear TBD 1 WJZ, New York, New York (Newark, New Jersey) 660  WEW, Saint Louis, Missouri (4)KVI, Tacoma, Washington (5) 770  Clear TBD 4 WBBM/(WJBT), Chicago, Illinois 770  none KFAB, Lincoln, Nebraska 940  780 Regional 1,000   — — — 6 U. S. stations3 Canadian stations 790 Clear TBD 5 KGO, San Francisco, California (Oakland) 790  WGY, Schenectady, New York (1) 800  Clear TBD 3 WFAA, Dallas, Texas 550  none WBAP, Fort Worth, Texas 600  810 Clear TBD 4 WCCO, Minneapolis, Minnesota 740  WPCH, New York, New York (1) 820 Clear TBD 2 WHAS, Louisville, Kentucky 930  none 830 Clear TBD 5 KOA, Denver, Colorado 920  WRUF, Gainesville, Florida (3)WHDH, Boston, Massachusetts (1) 840 Clear Canada CFCA/CNRT, Toronto, Ontario 850  Clear TBD 3 WWL, New Orleans, Louisiana 1220  none KWKH, Shreveport, Louisiana 760  860 Clear TBD 1 WABC/(WBOQ), New York, New York 970  WHB, Kansas City, Missouri (4)KMO, Tacoma, Washington (5) 870  Clear TBD 4 WLS, Chicago, Illinois 870  none WENR/(WBCN), Chicago, Illinois 1040  880 Regional 1,000   — — — 7 U. S. stations7 Canadian stations 890 Regional 1,000   — — —9 U. S. stations 900  Regional 1,000   — — —7 U. S. stations 910 Clear Canada CFCF/CHYC, Montreal, Quebec CKY, Winnipeg, Manitoba CJAT, Trail, British Columbia 920 Regional 1,000   — — —6 U. S. stations 930 Regional 1,000   — — — 8 U. S. stations5 Canadian stations 940 Regional 1,000   — — —6 U. S. stations 950 Regional 1,000   — — —4 U. S. stations 960 Clear Canada CFRB/CKGW, Toronto, Ontario CFRN, Edmonton, Alberta 970 Clear TBD 5 KJR, Seattle, Washington 970  WCFL, Chicago, Illinois (4) 980 Clear TBD 2 KDKA, Pittsburgh, Pennsylvania 960  none 990 Clear TBD 1 WBZ, Springfield, Massachusetts / WBZA, Boston 910  none 1000  Clear TBD 4 WHO, Des Moines 560  KFVD, Los Angeles, California (5) WOC, Davenport, Iowa 800  1010 Regional 1,000   — — — 7 U. S. stations2 Canadian stations 1020 Clear TBD 2 KYW/(KFKX), Chicago, Illinois (4) 570  WRAX, Philadelphia, Pennsylvania (2) 1030 Clear Canada CFCF, Montreal, Quebec CNRV, Vancouver, British Columbia 1040 Clear TBD 3KRLD, Dallas, Texas 650 KTHS, Hot Springs, Arkansas (3)WKAR, East Lansing, Michigan (2) 1470 WKEN, Kenmore, New York (1) 1050 Clear TBD 5 KNX, Los Angeles, California 890  KFKB, Milford, Kansas (4) 1060  Clear TBD 1 WTIC, Hartford, Connecticut 560  WJAG, Norfolk, Nebraska (3)KWJJ, Portland, Oregon (5) WBAL, Baltimore, Maryland 1050  1070 Clear TBD 2 WTAM/(WEAR), Cleveland, Ohio 750  KJBS, San Francisco, California (5)WCAZ, Carthage, Illinois/ WDZ, Tuscola, Illinois (4) 1080 Clear TBD 3 WBT, Charlotte, North Carolina 1160  WMBI / WCBD, Chicago, Illinois (4) 1090 Clear TBD 4 KMOX, Saint Louis, Missouri 1000  none 1100  Clear TBD 1 WLWL, New York, New York 810  KGDM, Stockton, California (5) WPG, Atlantic City, New Jersey 1100  1110 Clear TBD 2 WRVA, Richmond, Virginia 1180  KSOO, Sioux Falls, South Dakota (4) 1120 Regional 1,000   — — — 10 U. S. stations4 Canadian stations 1130 Clear TBD 5 KSL, Salt Lake City, Utah 990  WJJD, Chicago, Illinois (4)WOV, New York, New York (1)WMAK, Buffalo, New York 1140  Clear TBD 3 WAPI, Birmingham, Alabama 880  none KVOO, Tulsa, Oklahoma 860  1150 Clear TBD 1 WHAM, Rochester, New York 1070  none 1160  Clear TBD 4 WOWO, Fort Wayne, Indiana 1310  none WWVA, Wheeling, West Virginia (2) 580  1170 Clear TBD 2 WCAU, Philadelphia, Pennsylvania 1150  KTNT, Muscatine, Iowa (4) 1180  Clear TBD 5 KEX, Portland, Oregon 1080  WDGY/WHDI, Minneapolis, Minnesota (4) KOB, Albuquerque, New Mexico 760  1190 Clear TBD 3 WOAI, San Antonio, Texas 1070  WICC, Bridgeport, Connecticut (1) 1200 Local 100   — — — 48 U. S. stations 1210 Local 100   — — — 44 U. S. stations5 Canadian stations 1220 Regional 1,000   — — —6 U. S. stations 1230 Regional 1,000   — — —8 U. S. stations 1240 Regional 1.000   — — —3 U. S. stations 1250 Regional 1,000   — — —12 U. S. stations 1260 Regional 1,000   — — —6 U. S. stations 1270 Regional 1,000   — — —10 U. S. stations 1280 Regional 1,000   — — —6 U. S. stations 1290 Regional 1,000   — — —7 U. S. stations 1300 Regional 1,000   — — —12 U. S. stations 1310 Local 100   — — —53 U. S. stations 1320 Regional 1,000   — — —6 U. S. stations 1330 Regional 1,000   — — —5 U. S. stations 1340 Regional 1,000   — — —4 U. S. stations 1350 Regional 1,000   — — —5 U. S. stations 1360 Regional 1,000   — — —8 U. S. stations 1370 Local 100   — — —42 U. S. stations 1380 Regional 1,000   — — —4 U. S. stations 1390 Regional 1,000   — — —4 U. S. stations 1400 Regional 1,000   — — —9 U. S. stations 1410 Regional 1,000   — — —11 U. S. stations 1420 Local 100   — — —38 U. S. stations 1430 Regional 1,000   — — —7 U. S. stations 1440 Regional 1,000   — — —9 U. S. stations 1450 Regional 1,000   — — —9 U. S. stations 1460  SuperRegional 5,000   2 WJSV, Washington, D. C. 1480 none 4 KSTP, Saint Paul, Minnesota 1360 1470  SuperRegional 5,000   3 WLAC/WTNT, Nashville, Tennessee 1330 none 5 KGA, Spokane, Washington 1150 1480  SuperRegional 5,000   1 WKBW, Buffalo, New York 1380 none  3 KFJF, Oklahoma City, Oklahoma 1100 1490  SuperRegional 5,000   1 WFBL, Syracuse, New York 1160 none 2 WCKY, Cincinnati, Ohio (Covington, Kentucky) none 4 WHT/WORD/WJAZ, Chicago, Illinois var. 1500 Local 100   — — — 31 U. S. stations