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Edward Armstrong was born in 1890. During his youth in Yonkers, NY he was fascinated with the early radio broadcasts and

tinkered with receiving equipment and antennas trying to improve the quality of his reception. After high school he went to

Columbia to study for a degree in electrical engineering.

While still a student at Columbia, Armstrong studied the Audion and developed it to its full potential when he discovered

feedback and how to control it. He noticed that if a small portion of the amplified signal was fed back to the grid (feedback), it

would pass through the grid again and again, and each time it would be amplified further. He was able to boost weak signals

over 20,000 times, to the point where stations could be easily heard. People no longer had to use earphones because radioscould be built with loudspeakers. He called his revolutionary design the regenerative circuit.

Through further experiments, Armstrong boosted the feedback signal to the point where the circuit would begin oscillating

rapidly, and that generated strong electromagnetic waves. Now the Audion could be used as a radio transmitter as well as an

amplifier in a receiver.

During World War I, Armstrong accepted a commission in the Army and was sent to France to develop devices that would

detect enemy radio signals. He invented an 8-stage amplifier he called the superheterodyne circuit, that could reliably tune in

very weak signals. After the war, he sold the rights to two of his inventions for $335,000 to Westinghouse and another amplifier

design to RCA for a large amount of RCA stock.

Lee de Forest

Armstrong was riding high, and then everything took a turn for the worse. Though he had received a patent for his regenerative

circuit in 1914, de Forest had the audacity to apply for a patent on the same concept in 1915.

Lee de Forest wasnt much of a scientist or a businessman, but he was an opportunist. He never really understood how his

Audion worked. His colleagues described his "research" as putting things together in different combinations and immediately

applying for patents in the hope that he would somehow come up with something of value. De Forest was embarrassed that a

young guy like Armstrong had figured the Audion out and made such important discoveries with it. He finally convinced himself

that it was really he who had discovered feedback and that Armstrong had stolen the idea from him. He decided to claim the

honor and profits he thought were due him, and filed a patent infringement lawsuit against Armstrong.

De Forest soon sold his patent to AT&T, who despite ample evidence to the contrary, cynically chose to believe his story that he

invented the regenerative circuit first so that they could pursue the lawsuit. This battle over who invented the technology

behind radio then turned into a war over which corporation was going to use the law to stifle their competition. On one side

was de Forest and AT&T, and on the other, there was Armstrong backed by RCA. What Armstrong didnt realize was that RCAwasnt really backing him. Everyone but Armstrong was already making fantastic profits from his inventions and stood to gain

10 more years on the patents they already owned if de Forest won.

The patent battle lasted from 1922 to 1934. Armstrong won the first case, lost on appeal and then lost again in the Supreme

Court. The scientific community believed that Armstrong should have won the battle and has always refused to recognize de

Forest as the discoverer of feedback, but de Forest won where it mattered, and reaped the rewards for it.

While the patent battle raged, Armstrong continued his research. There was one more major problem with radio that needed

to be solvedstaticthe background noise that is not normally audible unless it is amplified. Atmospheric conditions and

especially electrical storms can make static problems much worse. Newspapers would print the weather reports next to the

radio schedule so that people would know if a broadcast might be affected by the weather.

Sound was being encoded in a radio transmission by a method called amplitude modulation (AM). This meant generating a

signal at a fixed frequency and modulating (varying) the amplitude (strength). The problem with AM, is that when the sound ispicked up and amplified by the receiver, any noise that was received would be amplified along with the desired signal.

Armstrong Develops FM Radio

Armstrong tried to design AM circuits that would filter out the noise, but after many unsuccessful attempts, he decided to try

an entirely new concept. In 1933, he found a solution when he decided to keep the amplitude constant and vary the frequency

of the signal instead. Using frequency modulation (FM), the reception was clear and the overall quality of the sound was much

better. Another advantage to FM was that more stations could be contained in a smaller range of frequencies without

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interfering with each other.

FM was superior to AM in every way, but there was one problem that Armstrong needed to solve before he could cash in on his

idea. Switching everyone to FM would require that the millions of radios that had already been sold and the transmitters that

broadcast to them would be rendered worthless. Companies like RCA didnt have any interest in changing things because they

were making plenty of money already and they had already paid for the technology that they were using.

RCA and the rest of the industry that had evolved around AM radio began to conspire to keep FM off of the market. ThoughArmstrong had a close relationship with RCA prior to this, once RCA decided that FM was a threat to their current business

model they quit cooperating with him. RCA and the other companies used their political influence with politicians and Federal

Communications Commission (FCC) bureaucrats to get regulations passed that effectively prevented Armstrong from

demonstrating FM to the general public in any meaningful way.

FM radio

It is amazing that while Armstrong was fighting his endless legal battles with De Forest, he had the energy to be working at the

same time on another ideaFM radio. This was the result of a long study with Pupin: to combat the problem of static in AM

radio, the established technique at the time.

AM, or amplitude modulation, is the technique of varying the amplitude, or strength, of a radio signal in accordance to thevoice or music being transmitted. A radio receiving this signal is sensitive to such amplitude variations but is also sensitive to

other disturbances related to amplitude, notably static due to thunderstorms, electrical machinery, and so on. The technical

wisdom of the time held that nothing could be done about this. Static, like the poor, will always be with us, a well-known

engineer had pronounced. But Armstrong was unfazed. He believed that if, instead, one varied not the amplitude but the

frequency of the signal being transmitted, the receiver could be designed so that it would respond to frequency changes rather

than to amplitude changesand would thus be oblivious to static. This is FM, or frequency modulation.

Others had considered FM before Armstrong, but the verdict was that it offered no advantages over AM. When a mathematical

analysis by AT&T scientist John Carson was quoted as conclusive proof of this, the technical community committed the kind of

logical error that, unfortunately, continues to be quite common. Someone proves a statement based on certain assumptions;

others forget those assumptions and remember only the conclusions. People then tend to apply such conclusions to all cases,

even ones that do not satisfy the original assumptions. This is what had happened here, and it was tantamount to a prejudice

against FM.

The assumption under which FM has no advantages over AM is that its spectrum would occupy a narrow band of frequencies, a

property considered at the time to be desirable for keeping noise low. Armstrong, in a brilliant moment of lateral thinking,

decided to challenge that wisdom, and set out to find out what would happen if he used instead a wide band of frequencies for

his FM signal. After years of painstaking experiments, with equipment spread over several tables in Philosophy Hall and

involving as many as a hundred electron tubes, he was able to prove that wideband FM made possible a drastic reduction of

noise and static (a hundredfold, or even more). Since everyone else had followed the common wisdom that wideband is bad,

Armstrong was free to pursue FM by himself. By 1934, he had filed a series of patents relating to his latest brainchild.

Now a full professor, Armstrong was ready for a demonstration. During an IRE conference in 1935, he described FM radio and

then turned on his receiver in front of the audience. An FM transmission from a friends house in Yonkers came in totally free of

static and, thanks to the wide audio spectrum being used, with a fidelity never heard before. A stunned audience listened to a

live music performance transmitted with remarkable clarity and to a series of sounds, such as a glass of water being poured or apiece of paper being tornwhich would have been unrecognizable over AM radio.

The results of the demonstration were the opposite of what one would expect. As David Sarnoffput it, he was expecting an

evolution in the AM system that would reduce static; instead, Armstrong came up with a revolution. FM radio was so much

better than AM that the whole established order of things was threatened. Thousands of AM transmitters and millions of AM

radios could become obsolete. The established broadcasting networks, their investments, and their markets, were in jeopardy.

In addition, FM could interfere with the industrys up-and-coming big new sensation: television broadcasting, at the time being

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readied for the market by RCA under Sarnoffs leadership. Thus, ten days after Armstrongs demonstration of FM, the public

was reading RCAs extensive public releases concerning the upcoming marvel of televisionwith no word about FM.

Not even De Forests legal battles had prepared Armstrong for what was coming. This time he was up against too much and too

many. To him, things were clear: since FM was proved beyond doubt to be immensely superior to AM, the public had the right

to its benefits. He bet everything on this logic and decided to go it alone against corporate interests and lobbying efforts.

Sarnoff asked him to remove his equipment from the top of the Empire State Building, to which he had given him access initiallyfor his FM experiments. Various reports on the state of the art in communications ignored FM completely, including the Federal

Communications Commissions annual report to Congress. The view was propagated that the public is not interested in high

fidelity and would not pay for it. But Armstrong was convinced that FM radio would succeed. The only thing that could

temporarily slow it down was, in his words, those intangible forces so frequently set in motion by men, and the origin of which

lies in vested interests, habits, customs, and legislation.

But Armstrong would not give up. With the help of a few sympathetic senators, he carried the fight into Congress. In 1948

Armstrong charged RCA and NBC with infringement. An army of lawyers began pre-court proceedings, which were to last for

several years. Armstrong was interrogated endlessly during these proceedings about irrelevant details, from his income tax and

the size of the rooms in which he gave speeches to why he used Columbia letterhead for some of his communications and

whether he had a formal agreement with the University. It took years to get these pre-court proceedings to the point that

Sarnoff was called in as a witness.

Corporate Conniving

Because Armstrong had no desire to become a manufacturer or broadcaster, he approached David Sarnoff, head of

the Radio Corporation of America (RCA). As the owner of the top manufacturer of radio sets and the top radio broadcasting

network, Sarnoff was interested in all advances of radio technology. Armstrong first demonstrated FM radio broadcasting for

Sarnoff in December, 1933. This was followed by visits from RCA engineers, who were sufficiently impressed to recommend to

Sarnoff that the company conduct field tests of the Armstrong system.

In 1934, Armstrong, with the cooperation of RCA, set up a test transmitter at the top of the Empire State Building, sharing

facilities with the experimental RCA television transmitter. From 1934 through 1935, tests were conducted using the Empire

State facility, to mixed reactions of RCAs best engineers. AM radio broadcasting already had a performance record of nearly

two decades. The engineers wondered if this new technology could replace something that had worked so well.

This less-than-enthusiastic evaluation fueled the skepticism of RCA lawyers and salespeople. RCA had too much invested

in the AM system, both as a leading manufacturer and as the dominant owner of the major radio network of the time, the

National Broadcasting Company (NBC). Sarnoff was in no rush to adopt FM. To change systems would risk the millions of dollarsRCA was making as America emerged from the Great Depression.

In 1935, Sarnoff advised Armstrong that RCA would cease any further research and development activity in FM radio

broadcasting. (Still, engineers at RCA laboratories continued to work on FM to protect the corporate patent position.) Sarnoff

declared to the press that his company would push the frontiers of broadcasting by concentrating on research and

development of radio with pictures, that is, television. As a tangible sign, Sarnoff ordered that Armstrongs FM radio

broadcasting tower be removed from the top of the Empire State Building.

Armstrong was outraged. By the mid-1930s, the development of FM radio broadcasting had become a mission for Armstrong.

For the remainder of his life, Armstrong devoted his considerable talents to the promotion of FM radio broadcasting.

Quadraphonic FM

In 1969 Louis Dorren invented the Quadraplex system of single station, discrete, compatible four-channel FM broadcasting.

There are two additional subcarriers in the Quadraplex system, supplementing the single one used in standard stereo FM. The

baseband layout is as follows:

There were several variations on this system submitted by GE, Zenith, RCA, and Denon for testing and consideration during the

National Quadraphonic Radio Committee field trials for the FCC. The original Dorren Quadraplex System outperformed all the

others and was chosen as the national standard for Quadraphonic FM broadcasting in the United States. The first commercial

FM station to broadcast quadraphonic program content was WIQB (now called WWWW-FM) in Ann Arbor/Saline, Michigan

under the guidance of Chief Engineer Brian Brown.