This is the General History Section of
The Broadcast Archive

Maintained by:
Barry Mishkind - The Eclectic Engineer

Behind the Clear-Channel Matter
by Mark Durenberger
Minneapolis, Minnesota

This is the first in a series of 6 articles about the history of clear-channel AM radio stations.

The year was 1980. The FCC was about to dramatically alter the face of U.S. broadcasting by issuing two rule makings. Docket 80-90 would soon transform the FM band, but the issue with the longest history and heaviest baggage was the AM clear-channel proceeding.

This series of articles will describe how early radio regulations stimulated the development of high-power AM broadcasting, by protecting the signals of certain stations from interference across the United States. This protection was designed to allow these high-power stations to deliver radio to under-served rural areas. The mixed success of the plan and the opposition it generated from the "have-not" broadcasters stimulated a 50-year regulatory brouhaha that was finally settled by a 1980 Report and Order that would change the AM dial forever.

The break up of the United States 1-A clear channels makes interesting reading. The "clear channels" were the bedrock of what was called the "Standard Broadcast Band." The stations given clear-channel protection were incentivized by this protection to provide full-service programming across their service areas, and they invested in the resources to carry out that obligation. So it's not surprising that they were very concerned about protecting and growing their investment. A look behind the curtain, where the lobbying and maneuvering was going on, demonstrates the determination and resolve of the players involved.

And what a conflict! On one side were the clear-channel broadcasters, fighting to protect their wide service areas from encroachment by other signals. To better serve those regions some were also pushing for AM "super power", in the order of a half-million watts. On the other side of the table were the rest of the broadcasters, the "have-nots" and others who felt such a powerful concentration of media influence was not in the public interest. What makes this story so remarkable is that many of the pivotal issues in the battle would be irrelevant in today's radio world.

The dilemma

As far back as the late 1920s, industry regulators were concerned with providing reliable nighttime radio to the under-served "white areas" of the country. While a number of channels were set aside for wide-area coverage from a single site, it turned out the stations on these "clear" channels could not provide solid coverage of the vast under-served areas, even with 50,000 watts.

Given the physics of the situation, there seemed to be only two ways to solve the problem: add additional stations on the clears, or grant massive power increases to the existing solo operators. These alternatives would define the clear channel issue for more than a half-century.

In researching this matter, we looked at thousands of pages of pleadings and arguments, in public records and private libraries. We owe a debt of gratitude to WCCO Radio for providing a review of its technical files, and we thank WSM in Nashville for making available its own records and those of the Clear-Channel Broadcasting Service (CCBS).
CCBS would play a key role in promoting the welfare of the clear channels and advocating AM "super power."

In this regard we also want to recognize Ward Quall, one of radio's great statesmen. He was a key force behind CCBS, and his input into this report was invaluable. We also owe a "thank you" to Thomas White for his excellent work on the formation of the broadcast band. Learn more at

What is a 'Clear'?

Section 73.231 of current FCC Rules defines a "clear channel" as "one on which stations are assigned to serve wide areas." There was a time when that was an understatement. Until the early 1960s, "clear channel" meant just that: there was only one domestic assignment on each of a couple of dozen AM frequencies from 640 to 1210 kHz. These solo signals were not only protected within the United States but, because of the way international radio agreements were written, neighboring countries had to limit co-channel interference contours to no closer than several hundred miles from their borders with the United States.

The current rules also specify that the "clear channels" will provide wide-area service through a combination of daytime ground wave and nighttime sky-wave energy. As we know, nighttime sky wave can extend the service area of some AM stations far beyond the reach of tall-tower FMs. Sky-wave coverage was one reason for the early success of full-service clear channel stations, but it was this same sky wave that would become a major factor in the ultimate reconfiguration of the AM broadcast band.

Early days

To better understand the fate of the clear channels, it's useful to review how the initial "clear" assignments were made. In 1922 Secretary of Commerce Herbert Hoover convened the first of four "Radio Conferences" dealing with broadcasting in the United States. Out of that conference came the first standard classifications of stations, by power and type of service. (Of interest to our report was the so-called "Class B Radiotelephony Broadcasting Station," the grandfather of the high-power clear-channel operations.)

Because so many early stations were clustered around three general frequencies - "wavelengths" in the parlance of the day - it wasn't long before there weren't enough "wavelengths" to handle the demand. So in 1923, Hoover convened the Second Radio Conference, to deal with rising interference issues, as more and more stations came on the air with little regard for precise wavelength tolerance.

To satisfy the demand for licenses, the 1923 conference expanded the AM broadcast band from 550 to 1350 "kilocycles" ("kc"), setting aside channels from 550 kc to 1000 kc for "territorial" coverage, in 10 kc steps. (It would be more than a quarter-century before "kilocycles" (kc) would become "kilohertz.") The 1923 conference also began to label operating channels by frequency rather than wavelength. Forty of these frequencies (550-800 kc and 870-1000 kc) were reserved for high-power wide-area "Class B" operation. (Shortly thereafter, four more channels were added and the "B" group extended to 1040 kc.) The country was divided into five radio zones, with the "B" assignments spread more or less evenly across the five zones. The conference thereby set the table for extensive protection of stations providing high-power, wide-area service.

Déjà vu too

In 1924, the Third Conference extended the upper limit of the band to 1500 kc, grouped the high-power Class B stations from 550 to 1070 kc and recognized Canada's right to six of the channels. In the notes of the 1924 conference are concerns about the efficacy of expanding the band to 1500, "since few radios would tune that high." (This same concern would surface 60 years later, during the Expanded-Band proceedings.)

As the spectrum filled, regulators searched for new ways to provide more capacity. One group suggested narrowing the spacing to 8 kHz. Fortunately this idea was put to sleep quickly. But this same sort of silliness would resurface in the late 1970s when the NTIA, wishing to provide more channels "in the name of opportunity and diversity," tried to convert the Western Hemisphere to 9 kHz spacing.

Broadcast bedlam

While the broadcast industry was growing, radio receivers were undergoing design improvements that made them far more sensitive. Better receivers pulled in distant stations, which clashed with local signals. Listeners now heard interference "whistles" of varying beat notes generated by frequency drift in the equipment. (In broadcasting's infancy, the technical performance of frequency-control equipment left a lot to be desired, and the beat would change pitch, as tubes warmed up or as stations played with transmitter tuning).

In spite of the Radio Conferences, by the mid-1920s it was clear that radio's expansion was outstripping the government's ability to regulate the industry. Existing rules weren't adequate to govern operation on the crowded band. New technical guidelines were being announced, but there was little enforcement. It wasn't unusual for stations to change operating wavelengths and power levels arbitrarily, to find the "clearest dial spot." (In the earliest days, station frequency was set by aligning a knob pointer with a pencil mark on the transmitter's "wavelength" control dial - a pencil mark left behind by the last Radio Inspector.)

During what became known as the "Chaos of 1926," the Commerce Department's authority was gutted by a federal district court, on a ruling overriding Hoover's denial of a license to an unqualified applicant. Hoover and Commerce threw up their collective hands and began to authorize everyone who applied. Immediately some 200 new stations took to the air with abandon and with little regard for the rules, and the result almost destroyed U.S. radio. It quickly became obvious that, unless RF anarchy was to be the norm, a "sheriff of the airwaves" was needed. A massive groundswell of interference complaints finally stimulated Congress to enact the Radio Act of 1927, and to create the Federal Radio Commission to administer this new act.

The FRC's charter was two-fold: first, to establish "avenues through the sky," radio channels freed of interference to the extent they could provide reliable service over great distances; second, to "preclude obscenities into the home", by enforcing rules of decorum on the licensees. Through a set of "General Orders," the FRC confirmed 550 kc to 1500 kc as the U.S. "Standard Broadcast Band." To provide "avenues through the sky," they reaffirmed the set-aside of frequencies for wide-area coverage and proposed that only one station be allowed to operate at night on each of these 40 channels.

The "clear" channels and their occupants, as of October 1928, are listed below.

Many of these assignments would change over the next dozen years, and only KFI and WMAQ would remain where they started with their original call letters. Of interest to our story is that the Federal Radio Commission suggested the maximum authorized power on these 40 channels might be "several hundred kilowatts." This may have been the first official suggestion that "super power" stations in excess of 50,000 watts might one day be authorized.

Certainly the signals being sent by the FRC gave hope to early investors that their commitment to the growth of radio might be rewarded.

Moving ahead, we'll meet the "FCC" and watch as broadcasters built toward 50,000 watts and beyond.

Copyright 2000 by Mark Durenberger

The 40 clear-channel assignments as of October 1928

Frequency (kHz)/ Dominant Station

640 KFI
650 WSM
660 WEAF
670 WMAQ
680 KPO
700 WLW
710 WOR
740 WSB
750 WJR
760 WJZ
790 KGO
810 WCCO
820 WHAS
830 KOA
850 WWL
980 KDKA
990 WBZ
1000 KYW (Chicago)
1020 WHAS
1060 WBAL
1080 WBT
1090 KMOX
1110 WRVA
1140 WAPI
1150 WHAM
1160 WOWO
1170 WCAU
1180 KEX/KOB
1190 WOAI

Source: The October 1928 "Radio Index" Tuning Book