By John Schneider, W9FGH


Copyright 2018 -
John F. Schneider & Associates, LLC

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 (Click on photos to enlarge)

Edwin Howard Armstrong


Major Edwin Armstrong, the inventor of wideband FM radio, demonstrates his FM receiver to executives at General Electric, 1939.

W2XMN Aerial View

W2XMN Building

A winter view of Armstrong's W2XMN building at Alpine, NJ.  The tower and building are still in use as a radio transmitting facility today.   (Columbia University Library image)

John Shepard III
John Shepard III, the owner of WNAC and the Yankee Network in Boston, was one of FM’s biggest proponents.  He built two of the first FM stations, at Paxton, Massachusetts, and Mt. Washington, New Hampshire.  

 At left are the 50 and 25 watt exciters, speech modulator and 1 kW amplifier.  At the right is the station's turnstile antenna, constructed from truck springs to withstand the mountain's fierce winter icing.  April, 1941.

Armstrong at WTMJ-FM

Major Armstrong, the inventor of wideband FM, is seen visiting W9XAO during its opening celebration in 1940. 

WTMJ's FM site

WTMJ in Milwaukee built this transmitter site for its station W55M in 1942.  The 200 ft. tower was situated on Richfield Hill, 21 miles NW of Milwaukee with an elevation of 450 ft.   The building included living quarters for the engineer/operators. 

WTMJ Truck


WTMJ-FM transmitter

When W55M moved up to the new FM band and became WTMJ-FM in 1948, it installed this RCA BTF-50A transmitter.  With 50 kW transmitter power, and 349 kW Effective Radiated Power (E.R.P.) it was one of the most powerful FM stations in the United States.  But when FM failed to attract an audience, WTMJ-FM was shut down  in 1950.

Yankee Network FM links

General Electric station W57A

This was the transmitter site for General Electric's  FM station W2XOY (later renamed W57A).  It was situated on the edge of a cliff overlooking the target coverage area of Schenectady and Albany, NY.  December, 1940.

General Electric's relay station

GE FM transmitter manufacturing

KNBC-FM's first antenna

KNBC-FM site 1949

In 1949, a year after the above image was taken, NBC completed this transmission facility on Mt. San Bruno, just South of San Francisco.  The building housed the transmitters and engineer’s living quarters for both KNBC-FM and the Chronicle Publishing Company’s KRON-TV.  KNBC-FM operated on 99.7 MHz with 45 kW.

KNBC-FM transmitter

This was the RCA FM transmitter that NBC installed at KNBC-FM in San Francisco in 1949.  In the days before transmitter remote control was allowed, an engineer was required to be on duty at the transmitter during all hours of operation. 

KNBC-FM antenna



 In the early and mid-1930s, radio communication was confined to the Low Waves (100-500 kHz), Medium Waves (500-1500 kHz), and the Short Waves (1,500 to 30,000 kHz).  The frequencies above that, referred to as the “ultra-high frequencies”, were truly the “Wild West” of radio.  It was a place for experimentation and a possible home to future radio services.  Commercial broadcasting to the public took place entirely on the standard broadcast band (540-1600 kHz), but it was affected by a number of defects that annoyed the public – natural and man-made static, local and skip interference, atmospheric fading, and limited fidelity.  Starting about 1932, a number of brave and daring broadcasters sought permission from the FCC to conduct experiments in the Ultra-Short Waves in an attempt to find solutions to these problems.  In particular, these experimental stations wanted to transmit wideband, high fidelity audio.  Amplitude modulation, the only known method of transmitting audio at the time, was the method utilized on these so-called “Apex” stations.  Experimental licenses were being issued for up to 1,000 watts on frequencies at 25-26 MHz and 42 MHz.  By 1939, these Apex stations were operating in 34 U.S. cities in 22 states   They suffered less skip interference than standard AM stations, but static was still a problem.

 At the same time that these Apex broadcasters were gaining a foothold in the upper frontiers of the radio spectrum, an entirely new type of radio service was also being demonstrated - one that was destined to cause Apex AM to become obsolete.  That service was called Frequency Modulation, or FM.


 Contrary to popular belief, Major Edwin Howard Armstrong did not invent FM.  The first patent for frequency modulation had been filed as far back as 1902.  In the 1920’s, RCA had experimented with FM, and found it lacking.  However, all of this work had been done using narrowband deviation.  In 1922,  Bell Labs engineer John R. Carson published a mathematical study that indicated FM was less frequency efficient than AM, and subject to heavy distortion.  In his 1922 paper to the Institute of Radio Engineers (I.R.E.), Carson wrote:  “This type of modulation inherently distorts, without any compensating advantages whatsoever.”  This and other “expert” papers effectively closed the book on further investigation of FM for a number of years. 

Meanwhile, in his research at Columbia University, Armstrong had long been searching for a cure for the problem of radio static, but he had come up empty-handed.  Once he finally concluded that it was impossible to separate intelligence from static with conventional amplitude modulation, he took another look at frequency modulation.  His truly revolutionary breakthrough was his discovery of “Wideband FM”.  Up until that time, all radio research had the goal of narrowing the bandwidth – trying to squeeze more intelligence into a smaller space.  Armstrong took the opposite approach - he discovered that the very wide deviation of the frequency delivered vastly superior audio performance -- high fidelity audio and a high signal to noise ratio.  Also, by spreading the intelligence over a larger frequency range, less transmitter power was required to achieve the desired range.  Furthermore, FM signals were much more immune to interference than AM due to its “capture effect” – an interfering signal needed to be more than 50% the strength of the desired signal to cause audible interference, compared to 5% or less with AM.  This characteristic would considerably reduce the required separation between stations occupying the same channel and allow more channel re-use, which compensated for its greater occupied bandwidth.  And most importantly, because all natural and man-made static is amplitude modulated, FM proved to be amazingly noise-free.  Armstrong improved its resistance to noise still further by incorporating a new receiver component – a limiter that stripped off the amplitude variations in the received signal before it reached the detector.  He had finally solved the problem of static interference that had confounded radio experts since the beginnings of the art.

It would been impossible to use Armstrong’s wideband FM system in the commercially active radio spectrum at that time (200 kHz to 30 MHz) – one 200 kHz wide FM channel alone occupied the space of twenty channels in the standard AM broadcast band.  But the “ultra-high” spectrum above 40 MHz was virgin frontier, and it had plenty of room to accommodate spectrum-hungry services like FM radio and television.

 Major Armstrong first demonstrated his revolutionary technology privately to David Sarnoff and the engineers of RCA in 1933 and 1934.  Then, when RCA failed to show an interest in licensing his technology, he gave his first public demonstration to the I.R.E. On November 5, 1935, its members heard amateur station W2AG operating in FM at a distance of 17 miles from the meeting location.  The following May, the IRE publishes Armstrong’s technical paper "A Method of Reducing Disturbances in Radio Signaling by a System of Frequency Modulation".

 All who heard FM for the first time were astonished at its clarity and robustness.  Nonetheless, while clearly superior to AM in all regards, the industry’s response to FM was mixed.  Although light years beyond the capabilities of standard AM broadcasting, it was not adaptable to the current structure of broadcast radio.  FM’s implementation would require a complete new infrastructure of broadcasting stations and millions of new consumer receivers.  FM could also potentially make obsolete more than 600 AM broadcasting facilities in the United States, destroying huge investments the major players had made in the broadcasting industry.  After surviving its financially challenging beginnings, radio broadcasting of the thirties was proving to be extremely lucrative, and the dominant big broadcasting corporations were not interested in seeing FM upend their business plans.  As a result, even as they gave positive lip service to FM, the powerful radio interests, led principally by David Sarnoff and RCA, quietly aligned their strategies to suppress the deployment of Armstrong’s FM technology. 


In 1934, RCA had permitted Armstrong to conduct FM tests from its facility atop the Empire State Building, but in 1936 he was asked to vacate to make room for television tests.  Undeterred, he requested permission from the FCC to construct his own high power FM station, and, although initially rebuffed by Commission staffers, he was finally granted permission to build a 40 kW experimental station in June of 1936.  The construction of this station was a multi-year project, which included building a giant 400 ft. tower on the Palisades at Alpine, New Jersey, near the George Washington bridge.

 Finally, on January 11, 1939, Armstrong’s station was ready to demonstrate FM’s capabilities to the world.  He invited FCC engineers to monitor the station at Sayville, New Jersey, 50 miles away from the transmitter site, operating on 42.8 MHz with 20 kW. They also listened to amateur station W2AG in Yonkers, operating on 110 MHz with 500 watts.  The following month, Broadcasting Magazine quoted the FCC’s enthusiastic praise of FM –it had demonstrated “a material gain in effectiveness of reception through static, especially the type of static resulting from nearby thunderstorms and from some types of man-made electrical disturbances.”   The FCC was sold on FM – so much so that they began to authorize other experimental FM stations while halting any further permits for Apex AM stations.  The FCC wanted to expedite FM testing before the Apex AM broadcasters could become too well entrenched.


 Among the broadcasters, Armstrong had found numerous supporters of his technology.  These were mostly well-heeled medium-market broadcasters that had been successful in their communities, but who had been shut out of the big leagues by the bigger operators and major networks.  The adoption of FM could allow them to completely bypass the existing broadcast hierarchy and stake an early footing in the next big radio frontier.  The first broadcaster to establish an experimental FM station was WDRC in Hartford, who converted their Apex station W1XPW in Meriden, Connecticut, to FM on May 13, 1939.  They were followed on July 18 by Armstrong’s Alpine station, W2XMN, which began regular broadcasts on 42.8 MHz using a modified RCA transmitter followed by an REL (Radio Electronic Laboratories) 40 kW amplifier.  W2XMN broadcast a daily schedule of music from high fidelity transcriptions and relays of programs from WQXR in New York.

 The next station to debut, on July 24, was W1XOJ in Paxton, Massachusetts.  Its operator was one of Armstrong’s biggest proponents - John Shepard III, the owner of WNAC in Boston and New England’s Yankee Network.  From the summit of Mt. Asnebumskit, W1XOJ broadcast sixteen hours a day with 2 kW on 43.0 MHz (this was upgraded to 30 kW in February, 1940).  After its provisional antenna was destroyed in an ice storm that winter, W1XOJ installed a ten element turnstile antenna on 250 ft. tower. 

 Broadcasters and the public alike were amazed at the coverage and fidelity of both the Alpine and Paxton stations, as they delivered studio-quality audio signals at distances that rivalled the biggest 50 kW AM stations.

 Shepard was passionate about FM, and he spared no expense to make his Paxton station a first-class operation.  W1XOJ was on the air from 8 AM to midnight daily, with programs selected from Yankee, Colonial, NBC Blue and Mutual Networks.  Because the standard broadcast-grade network phone lines just passed audio frequencies below 5 kHz, Shepard ordered a special 8 kHz “hi fi” network line between New York and Boston.  He also broadcast four hours of local studio programming daily to provide full 15 kHz fidelity.  And instead of using broadcast phone lines to link the Boston studios to the Paxton transmitter, 43 miles distant, he installed a second FM transmitter at the studio, operating with 250 watts on 133.03 MHz – one of the first wireless studio-transmitter links. 

 These three pioneer FM stations were facing one very substantial obstacle – there were only 25 FM receivers in the entire world at that time – all hand-built to Armstrong’s specifications.  Receiver manufacturers would not commit to making FM radios until the FCC made FM an officially-sanctioned technology.

 The Commission conducted a series of hearings about FM during March and April of 1940.  The often contentious proceedings pitted the proponents of Armstrong’s wideband FM system against RCA and other interests that favored a narrowband FM approach -- leaving more spectrum for the development of television.  Finally, on May 20, 1940, the FCC officially authorized commercial FM broadcasting.  To the shock of RCA and other television proponents, the commission reassigned TV Channel 1 – 42 to 50 MHz - creating 40 exclusive channels for FM radio.  All experimental Apex AM licenses were terminated, and those broadcasters were encouraged to apply for new FM licenses.  The Commission even chose FM as the modulation method to be used for television sound.  It was a complete victory for the Armstrong interests and a major setback for RCA and the television proponents.

Shortly thereafter (June 22), the commission released the new regulations governing FM broadcasting.  .  Of the 40 new channels, seven (43.1 to 44.3) were reserved for large cities; and six (48.9 to 49.9) for small communities.  Multiplexing and facsimile were permitted.  The stations were required to transmit a minimum 6 hours per day except Sundays, and this was to include a minimum of one daytime and one evening hour of non-duplicated full fidelity programs.


 A wave of FM excitement immediately swept over the broadcast industry, and the FCC was deluged with more than 150 applications for new FM stations.  On March 1, 1941, the Commission issued its first commercial FM license to W47NV Nashville (WSM).  Meanwhile, the Apex stations began shutting down or converting to FM in droves.  The first to convert was WTMJ in Milwaukee, whose experimental FM station W9XAO debuted five days before the FCC’s decision.  When the new regulations went into effect, it became W55M on 45.5 MHz with 10,000 watts, programmed entirely separate from WTMJ-AM. W55M operated from a new site constructed 21 miles northwest of Milwaukee, with a high fidelity phone line connecting it back to the company’s new half million dollar studio facility.   The FM building included living quarters for on-site engineers (unattended remote control of transmitters was not yet permitted).  The Journal’s vice president of broadcasting, Walter J. Damm, was one of FM’s most enthusiastic supporters, and in 1942 was elected president of the FM Broadcasters, Inc., a trade association of FM broadcasters that was later absorbed into the NAB.

 Over in Michigan, the Detroit News shut down its Apex station W8XWJ after four years of operation and applied for a new FM license on 44.5 MHz.  The station, W45D, broadcast from an antenna atop the Penobscot Building, the highest structure in Detroit, and was programmed separately from its sister AM station WWJ from studios in the Penobscot building.   (W45D can be directly traced to today’s WXYT-FM in Detroit.)  

Another early adopter was the General Electric Company, which built its high-powered FM station W2XOY (later W57A), in the Helderberg Mountains, twelve miles south of Schenectady.  GE simultaneously announced plans to manufacture both FM transmitters and receivers.  And there was the experimental station W2XOR, operated by WOR in New York, which later became W71NY.  It broadcast from 8:00 AM to 11:30 PM daily with a 10 kW transmitter from 42nd floor of 444 Madison Avenue.  Its programming was a mix of WOR and Mutual programs, with 65% of its time dedicated to separate W71NY programs or high fidelity transcriptions.  It was connected by land line to the WOR studios, just 4,000 feet away, although the station even experimented with a light beam link between the two locations.  

 The FCC had devised a unique call sign system for these commercial FM stations.  It was a combination of numbers that indicated the frequency, and letters identifying the city.  For example, W55M was on 45.5 MHz in Milwaukee; W47NV broadcast on on 44.7 MHz in Nashville; and K45LA was on 44.5 MHz in Los Angeles.  The dials of most receivers indicated channel numbers instead of the frequency – tuning from channels 21 to 99.

 Most of the early adopters were AM stations that were protecting their interests in case FM should supplant AM.  Their only investment, in most cases, was the purchase of an FM transmitter and antenna, and some studio upgrades to accommodate the higher fidelity needed by FM.  This was a boon for the equipment manufacturers – principally REL, G.E. and Western Electric.  Many of these FM stations just duplicated the programming of AM sister stations except for the required two of separate programming daily.  This was mostly fulfilled with live studio broadcasts or high fidelity transcriptions.

 The receiver manufacturers were early supporters of FM, and models were available from GE, Stromberg-Carlson, Philco, Meissner and Pilot at prices ranging from $50 to $200.  These were mostly combination AM/FM/SW sets, both tabletop and console models, and there were a few FM-to-AM tuner converters. The FM tuners in these early sets suffered from poor sensitivity, difficult tuning, and a tendency to drift off frequency.  RCA also entered the FM receiver market, but they refused to pay license fees to Armstrong, declaring that their proprietary “ratio detector” design was based on different technology (it was later found to violate two Armstrong patents).


 One of the most promising facets of FM broadcasting was its ability to create wireless regional networks by relaying the programs captured off air from other FM stations.  Because of FM’s superb audio quality, a program could be passed between stations in multiple hops and still have a quality that was vastly superior to the big AM networks.  In January, 1940, a program was relayed in six hops from Yonkers to Alpine, to Meriden and on to Worchester, through Paxton and Mount Washington and finally it was broadcast by a Boston AM station.  This prospect was another confidence-shaker for the big time broadcasters, who were paying huge sums to AT&T for their network lines.  These high distribution cost, plus the limited availability of these lines, gave the national networks a semi-monopoly by restricting the entry of others into the network business.  But now, groups of modestly-financed FM stations could form an alliance to create regional and even national networks having much better audio quality at a substantially lower cost!  This possibility represented a colossal threat to the big AM networks as well as to AT&T.

 Special relay receive sites with high-gain directional antennas were usually required for best performance of these FM program relays.  For its needs, General Electric built a separate mountaintop receive site 200 ft. higher and 1-1/2 miles south of its W57A transmitter site in Schenectady, which reduced potential interference from its own transmitter.  With this arrangement, GE regularly rebroadcast programs from Major Armstrong’s Alpine station, 129 miles distant.  In turn, GE’s rebroadcasts of these programs were being passed on for rebroadcast by another six stations.

 In Boston, John Shepard was busy establishing a New England FM Network.  He built an additional 5 kW FM station, W1XER (later W39B) located atop Mt. Washington in New Hampshire  At 6,288 ft. above sea level, it sat atop the highest peak on Atlantic coast.   Debuting on December 18, 1940, W1XER repeated programs received off-air from Paxton, and it was said to lay down a good signal from Maine to Boston.   The facility was designed to survive the extreme weather conditions at Mount Washington – it used a two-element turnstile antenna whose dipole elements were constructed from truck springs to withstand the heavy rime icing.


 1941 saw remarkable growth in FM broadcasting.  By March, there were 22 commercial stations on the air, with 70-more under construction or awaiting FCC authorization.  (Most in this latter group were just waiting for equipment deliveries, which were proceeding at a snail’s pace – only GE and REL were shipping FM transmitters.)  It was predicted that, by end of 1940, more than 60% of the U.S. population would be within range of at least one FM station.

Many of the big AM broadcasters around the country were now jumping on the FM bandwagon.  They included WTIC in Hartford (W53H), WGN in Chicago (W59C), WBZ in Boston (W1KX Boston and W1XSN Springfield), both NBC and CBS in New York (W51NY and W67NY), WHAM in Rochester (W8XVB, owned by Stromberg-Carlson), WFIL in Philadelphia (W53PH), and KHJ in Los Angeles (K45LA).  

In Chicago, the Zenith Corporation opened the city’s first FM station, W9XZN (later W51C and then WEFM).  The company had been out of the broadcast business since the Federal Radio Commission deleted its Chicago station WJAZ back in 1931, but it now saw good business potential in the FM receiver market.  It debuted in 1939 with a custom-made water-cooled 50,000 watt transmitter, broadcasting from the 45th floor of the Field Building at 135 S. LaSalle St.  W51C broadcast sixteen hours a day on 45.1 MHz, playing “only good music” from specialized high-fidelity transcription disks, ranging from classical to Latin music, to Gilbert and Sullivan.   There was no advertising except for one announcement each hour promoting Zenith products.  Program guides were sold to the public on a subscription basis.  

Growth on the receiver side was equally encouraging – the number of units in consumers’ hands grew from 15,000 at the end of 1940 to 180,000 by the following December.  By now, 29 different manufacturers were offering more than 100 models of receivers.  

Clearly, FM had gained major ground in 1940 and 41, and all indicators pointed to it being the future direction for radio.  There were predictions that many AM stations would move over to the FM band.  It was also attracting a good number of would-be broadcasters that had been shut out of the field by a lack of available AM channels in their communities.  Because the FCC was proposing to open every other channel for usage in the same community, the number of possible stations could exceed market demand in many areas of the country.

This possibility of explosive FM growth alarmed the radio establishment.  But by mid-1941 the tide was beginning to turn on several fronts.  It was already becoming clear the 42-50 MHz FM band was too small to meet the perceived demand for FM stations.  By February of 1941, the FCC had already received ten applications for the remaining four available channels in New York City, and it foresaw similar difficulties in other major cities.  Additionally, the FCC was becoming concerned with the concentration of media ownership in the hands of a few, and so it stopped accepting radio applications submitted by newspaper interests.  This caused a number of planned FM operations to halt in their tracks.  If these issues weren’t enough to slow FM’s growth, there was that pesky war over in Europe …


 Even before Pearl Harbor, US manufacturers were increasingly being drawn into producing arms for the European allies and some raw materials and essential electronic components were becoming scarce.  Then, after December 7, all manufacturing of broadcast equipment ended, as the electronics industry geared up for wartime production.  Thirty manufacturers of radio sets ceased all civilian production.   The FCC institutes a freeze on new licenses or changes of operations because of wartime material shortages.  Those broadcasters who had already received permits were allowed to continue building their stations, but in most cases the needed materials were simply not available.  Additionally, there were staffing shortages as many experienced announcers, musicians and engineers headed off to war.

In February, 1942, there were 31 FM stations on the air: 

Baton Rouge – W45BR (WJBO)

Mt. Washington – W39B (Yankee Net)

Boston – W43B (Yankee Network)
               W67B (WBZ)  

Nashville – W47NV (WSM)

Chicago –W51C (Zenith)
                W59C (WGN)
                W67C (CBS)
                W75C (Moody Bible)

New York– W47NY (Muzak)
                    W2XMN (Armstrong)
                    W51NY (NBC)
                    W59NY (WQXR)
                    W67NY (CBS)
                    W71NY (WOR)

Columbus, OH – W45CM (WBNS)

Philadelphia – W53PH (WFIL)
                     W69PH (WCAU)

Detroit – W45D (WWJ)
               W49D (WJLB)

Pittsburgh – W47P (Walker-Downing corp.)
                     W75P (Westinghouse, KDKA)

Evansville, IN – W45V (WEOA)

Rochester –W51R (Stromberg-Carlson)

Hartford – W53H (WTIC)
                 W65H (WDRC)

Schenectady – W47A (Capitol Broadcasting)
                       W57A (General Electric Co.)

Los Angeles – K45LA (KHJ)

Springfield, MA  W81SP (WBZA)

Milwaukee – W55M (WTMJ)


They all committed to maintaining their operations and programming schedules, but the further development of FM essentially stopped during the war.

In 1943, the FCC’s FM call letter system was found to be difficult to administer and confusing to listeners.  The system was abandoned, and all stations were reassigned standard four-letter call signs.  FM stations owned by AM broadcasters were allowed to affix “–FM” to end of the AM station’s call sign.

 At the war’s end, there were 46 FM stations on the air nationwide.   Another 430 applications were on hold, waiting for the FCC to end the freeze and renew the growth of the service.  But people and their attitudes had changed at the FCC during the war -- it was no longer the FM-friendly agency of four years earlier.

 Even as the war was being fought, RCA and other interests were continuing the development of television.  Once the end of the war was in sight, it was obvious that post-war TV was going to have tremendous consumer appeal, and its promoters felt FM’s spectrum allocation was robbing essential frequencies that would be needed for television.  In the war’s final year, big industry, led principally by RCA, was working quietly behind the scenes to undermine FM’s position.  During the war, manufacturers and government had worked closely together to equip the armed forces with electronics systems that helped win the war, and so the relationship between industry and government was very tight.  Over at the FCC, a steady stream of lobbyists made its way to its offices, and the industry-friendly commissioners were all too happy to receive them.  The interests aligned against FM were concealing a strong poker hand, and they planned to play their cards as soon as the war ended.


 In 1945, the FCC began a series of hearings into the post-war use of the high frequency spectrum.  On January 15, 1945, the FCC announced its proposal to move FM band to 88 to 108 MHz so it could reassign the pre-war FM band to television.   A bitter battle ensued, with the FM interests fighting the television interests, and with the FCC apparently entrenched in the TV camp.  Then a new issue was raised by the FCC.  Pre-war FM had operated during a sunspot minimum, and the next maximum was to occur in 1947.  The FCC was worried that sunspot disturbances could cause propagation interference in old FM band.  To investigate the issue, the FCC hired a War Department engineer named Kenneth Alva Norton.  Based entirely on mathematic calculations, and unsupported by any field tests, Norton proclaimed that the 42-50 MHz band would suffer between 830 and 2,410 hours of tropospheric and Sporadic E propagation interference per year because of sunspot disturbances.  He supported the FCC’s plan to move FM upward in the spectrum where it could enjoy a relatively interference-free service.  There were fundamental errors in Norton’s calculations, and Armstrong and other FM proponents pointed them out.  The FCC then scheduled engineering hearings where the testimony of Norton could be challenged by Armstrong and his supporters.  But the hearings were held in secret - no outside observers were allowed, and no transcripts of the hearings were made.  In the end, politics won out over engineering, and the FM band was moved “upstairs” to make more room for television. In two more years, when the 1947 sunspot peak proved that Norton’s calculations had been wrong, the move had already taken place and the issue was past history.

 The new 88-108 MHz band did not enjoy the long-range propagation of the old 42-50 MHz band, and three times the transmitter power was required for the same coverage.  In addition to this setback, the FCC further hindered FM by accepting a CBS proposal to reduce allowable transmitter powers, limiting coverage to single markets instead of entire regions (conveniently hampering the possibility for regional off-air networks.)  It also allowed combined AM/FM operations to fully duplicate AM their programming on FM.  This had the result of eliminating most separate FM programming – and took away a major incentive for the public to purchase FM sets.  These three moves by the FCC combined to deal a serious setback to FM – one that it would take 20 years to recover from.

 Some of the existing FM broadcasters transitioned to the new band, while others just left the air.  A few broadcasters chose to operate simultaneously on both bands until the FCC shut down the old band completely in 1949.  Because of the time needed for the electronics industry to retool for peacetime, transmitters and receivers for the new FM band did not become available until 1947. Once the backlog of FM applications began to be approved by the Commission on the new band, the number of FM stations began to slowly climb, up to 140 stations by the end of 1947. 

 One of the few positive aspects of the FCC’s band change was its reservation of 88-92 MHz for educational broadcasting.  After years of being generally shut out of broadcasting, colleges and universities were happy to take advantage of this new opening, and the educational stations they built would enjoy the most success during FM’s next 15 years.  The range of 92 to 106 MHz was assigned to commercial FM station, and 106-108 MHz was reserved for radio facsimile, but this last segment was later reassigned to FM radio when facsimile failed to gain popular acceptance.

 Still, FM had suffered a major setback which affected both broadcasters and listeners.  46 transmitters and 400,000 pre-war FM receivers had been rendered obsolete.  Although some converters were sold that allowed low-band FM sets to receive the new frequencies, they were complicated to install and often more expensive than a new set.


 By the end of 1949, over 600 FM stations were on the air, but they were discovering that the listeners were not there.  Post-war consumers were spending their money on television sets, and the sales of both AM and FM radios stagnated, as shown by these figures: 





























In competition with the public’s enthusiasm for television, FM was simply unable to recover from the wartime freeze and change in frequencies.  The number of stations would reach a peak of 700 in 1952, and then begin to slowly decline because of negative economics.  210 FM stations were deleted in 1949 alone, and 25 more in the first three months of 1950.  WTMJ in Milwaukee, one of the medium’s biggest early proponents, threw in the towel in 1950, closing its FM station WTMJ-FM, and sister station WSAU-FM.   The company notified the FCC of the stations’ closings in a letter, citing a lack of FM receivers as the principal cause.  “FM,” they said, “has not lived up to its bright promise of ten years ago.  Failure of the public to buy the anticipated number of receivers convinced the owners that continued operation would not be a worthwhile undertaking.”  With there being almost no marked for used FM transmitters, many of the closing stations donated their equipment to colleges and took a tax write-off.  In Seattle, Fisher Broadcasting closed its station KOMO-FM, and donated all equipment to the University of Washington, giving birth to the educational station KUOW.

 The nadir of FM radio’s existence was reached between 1953 and 1956, with numerous stations leaving the air and public interest being almost non-existent.   These were also dark years for FM’s inventor, Major Edwin Armstrong -- most of his FM patents had expired in 1950, and his licensing income was dwindling because of the downturn.  Further, RCA had steadfastly refused to pay him any licensing fees, despite the fact that they were manufacturing both FM transmitters and receivers.  Years of never-ending litigation against RCA and the corresponding legal fees drove him close to bankruptcy.  Finally, on February 1, 1954, at the age of 63, he took his own life, jumping out the window of his 13th floor Manhattan apartment.  RCA eventually settled and paid off Armstrong’s widow.

 The FM stations that did not succumb to the FM downturn found ways to survive as best they could.  Many were sister stations to profitable AM broadcasters who paid the bills.  Others survived by distributing background music to stores and offices, transmitted on multiplexed subcarrier channels.  Programming in the 1950’s was mostly “good music” and classical, with only occasional commercials. As previously mentioned, educational and school stations were the most successful FM operators, filling a demand for educational radio that had been mostly denied them on the AM band.  In 1951, schools and colleges were operating 100 FM stations in 34 states.   


 1957 was first year that number of stations on air increased over prior year.  This improvement was being driven by multiplexed subcarrier services, better FM receivers (now incorporating an AFC circuit), and increased interference on an increasingly overcrowded AM band.  Another factor that gave FM an important boost was the upsurge in the public’s interest in high fidelity audio in the late 1950’s.  There was growing public interest in stereo or “binaural” audio recordings, and combination AM/FM broadcasters were able to tap into this trend by broadcasting one channel on the FM band and the other on the AM band.  A few manufacturers even produced specialized AM/FM receivers to pick up these programs.  Finally, on April 24, 1961, the FCC authorized the multiplex stereo that had been created by Zenith, which greatly increased the public’s interest in FM.  Three years later, the FCC gave FM another shot in the arm by requiring AM/FM broadcasters in cities over 100,000 population to transmit separate programming half of the day. This generated a greater variety of programming for FM listeners.  To minimize costs, many AM stations hired young novice announcers to run their FM stations and gave them free rein on programming.  The free-form music formats they created, often based on longer album cuts instead of hits, appealed to a younger audience by offering music that could not be heard on the Top 40 AM stations.  This young audience developed a preference FM over AM, and as they matured into adulthood over the next twenty years, they never lost their FM radio habits.  In the 1970’s, FM was finally competitive with AM, and by the 1980’s it was the dominant radio medium.  In 1982, FM commanded 70% of the total U.S. audience and 84% among the 12- to 24-year-old demographic.  When the program duplication rule was repealed in 1986; it was the AM stations that needed help to stay competitive.


 In the end, the superior capabilities of Major Armstrong’s system of frequency modulation triumphed over the entrenched interests that had tried to suppress it.  Even though they successfully set back FM’s growth for twenty years, in the end its tremendous technical and sonic advantages could not be denied.

 One wonders what would have happened if FM had been allowed to continued its trajectory on the original 42-50 MHz band.  On one hand, the pioneer stations enjoyed greater coverage than today, as that band was less subject to line-of-sight limitations.  On the other hand, we know that the old band would have probably suffered more ducting and E-layer skip interference.  Anyone who is familiar with the amateur radio 6-meter band at 50 MHz knows that there would have been significant interference whenever skip was “in”.  

 FM broadcasting is also better off today because the band change increased FM’s available spectrum almost threefold, giving us 100 channels instead of the original 40.  As was already being detected in the early 1940’s, FM’s growth would have eventually been stifled by a lack of frequencies.  Assigned to a spectrum sandwiched between military frequencies and the low VHF TV channels, there would have been no room for FM broadcasting to expand to meet the eventual demand.  Today, as the standard AM band becomes increasingly neglected and handicapped in our high-noise digital world, even the present 88-108 MHz band is being stretched beyond its capacity in many parts of the country.

 The future course of radio broadcasting is uncertain today.  The public now has many more options for aural information and entertainment than it did twenty years ago.  We now have our choice between analog and digital AM/FM radio, satellite radio, and streaming Internet music fed through our phones and smart speakers – all of which serves to fractionalize the audience into smaller and smaller parts.  Nonetheless, it seems likely that FM radio broadcasting will still be a major source of entertainment and information for at least one more generation of listeners.



 Man of High Fidelity:  Edwin Howard Armstrong, by Lawrence Lessing, Lippencott Company, 1956

Empire of the Air by Tom Lewis, Burlingame Books, 1991

Proceedings of the Institute of Radio Engineers, May 1936 (Vol. 24, no. 5):  “A Method of Reducing Disturbances in Radio Signaling by a System of Frequency Modulation”, by Edwin H. Armstrong.

FM Magazine:

  • “FCC Rules Governing High Frequency Broadcast Stations”,  Nov. 1940
  •   “Description of Yankee Network’s W1XOJ at Paxton”, Nov. 1940
  •   “Planning an FM station”. Feb. 1941
  •   “What Broadcasters Have to Say:  Walter J. Damm”, Feb. 1941
  •   “FM Featured in $500,000 Plant”, Feb. 1941
  •   “More FM Service in New England”, April 1941
  •   “Status of FM Broadcasting”, April 1941
  •  “What the Broadcasters Have to Say:  W45D Detroit”, July 1941
  •   “What the Broadcasters Have to Say:  W71NY New York”, June 1941
  •   “W71NY is Model Installation”, Dec. 1941
  •   “GE Backs Broadcasting”, March 1942
  •   “War Revises Radio Industry”, April 1942
  •   “FM Broadcast Stations On The Air”, February 1947
  •   “US Educational Stations” March 1951
  •   “TV, AM, FM Set Production” various issues

 Broadcasting Magazine:

  •   “Armstrong soon to start staticless radio”, 2-1-39
  •   “Traffic jam confronts FCC in allocating FM facilities”, 2-17-41
  •   “FCC newspaper ownership freeze”, 3-24-41
  •   W9XAO becomes W55M, 4/21/41
  •   “FCC authorization for 53 commercial outlets given”, 8-18-41
  •   “No Curtailment Planned by W55M”, 10/26/42
  •   “FM Broadcasters Pledge Action”  8/9/43
  •   Testimonies to FCC re proposed band change, 2/26/45
  •   “FCC announces FM and TV reallocation plan”, 1-16-45
  •   “FCC allocates 88-106 band to FM”, 7-2-45
  •   “Second FM Shift”, 8/6/45
  •   “WTMJ Drops FM”, 4/30/50

 “Amendment of Section 73.242 Rules Regarding Program Duplication”, FCC Report and Order 4-4-1986

 “The Milwaukee Journal” 12/28/41:  “It Looks Like a Happy New Year in FM Field”.

 “FM Broadcasting Chronology” by Jeff Miller, http://jeff560.tripod.com/chronofm.html

 “WTMJ-FM:  A Case Study in the Development of FM Broadcasting”, by Christopher H. Sterling

 Wikipedia   https://en.wikipedia.org/wiki/FM_broadcasting_in_the_United_States


 NOTE:  This article appeared in the Spectrum Monitor Magazine, December, 2018


John F. Schneider & Associates, LLC
Copyright, 2018