Celebrating 100 Years of Edwin Armstrong's "Regenerative Circuit" (Sept 22, 1912)

“Great Amplification Obtained at Once!”

Edwin Armstrong,  Journal entry  September 22, 1912

This Saturday marks the 100 year anniversary of Edwin Howard Armstrong’s first successful use of “feedback” to electrically amplify sound.  This breakthrough innovation would become known as Armstrong’s regenerative circuit, an essential component of most all subsequent radios. Armstrong filed his patent for the “regenerative circuit"  while still a student at Columbia.

He received Patent #1,113,149 a year later.

As Wikipedia currently describes it:

Because of the large amplification possible with regeneration, regenerative receivers often use only a single amplifying element (tube or transistor). In a regenerative receiver the output of the tube or transistor is connected to its input through a feedback loop with a tuned circuit (LC circuit) as a filter in it. The tuned circuit allows positive feedback only at its resonant frequency. The tuned circuit is also connected to the antenna and serves to select the radio frequency to be received, and is adjustable to tune in different stations.

Armstrong’s regenerative circuit or "autodyne” helped transform radio from a tinkerer’s domain into the dominant mass medium. Entire empires were built by the commercialization of radio. Visionaries recognized that this technology could become an indispensable appliance in the home.  And so, much like today’s Internet, early radio went from a domain of technical experts and hobbyists into a billion-dollar industry in only a few decades.

Like the much more famous inventor Nikola Tesla, Armstrong’s disruptive genius had a way of earning him powerful enemies. Though once its largest shareholder, Armstrong would deplete a vast personal fortune in a winner-take-all war with the corporation most dependent upon his work, The Radio Corporation of America. (RCA)  Armstrong not only lost all of his money fighting RCA, he eventually lost his life.

What happened to this man?

The man who created the first true amplifier,  the regenerative circuit, also went on to develop many other essential technologies for radio. (e.g. the superheterodyne or “superhet” receiver)  These initial inventions made him a very wealthy man. But when he set about to solve a problem that vexed radio from its inception, he started a chain of events that would lead the man jumping from his 13th floor apartment to his death.

High Fidelity

In Armstrong’s day, all radio was -AM- radio.  Even after a century, Amplitude Modulation radio exists. And it’s still a weak, low fidelity audio carrier. It sucked then. It sucks now.  Fixing AM’s inherent problems vexed the industry. One exasperated engineer, John Carson, famously declared the problem technically insurmountable.  He even went so far as to prophesy, “Static, like the poor, will always be with us.”

Such surrenders by lesser engineers never dissuaded Armstrong.  In fact, those declarations were the stuff of breakthroughs.  As Edwin Armstrong once said:

I could never accept findings based almost exclusively on mathematics. It ain’t ignorance that causes all the trouble in this world. It’s the things people know that ain’t so.”

The company who stood to gain the most from a better radio was the Google of it’s day.  It was the Radio Corporation of America (RCA) and it knew Armstrong quite well.  His regenerative circuit patents were essential for foundational for RCA and through them Armstrong had become their largest individual shareholder. RCA’s President David Sarnoff had implored Armstrong to use his genius to solve the problem of static.  But the President of one of the most powerful corporations in the world never imagined just what Armstrong would do to kill off all the noisy ghosts in RCA’s little machines.

“This is Not an Ordinary Invention-This is a Revolution!”

In the winter of 1933, Armstrong after a decade of toil, had something to show Sarnoff.  He called RCA’s President and asked him to come see him. Armstrong had done the impossible. As told by Daniel Stashower in “the Boy Genius and The Mogul”

With the confidence of youth, Armstrong initially expected a quick solution. In fact, more than ten years would pass before his labors brought results. In December of 1933, Armstrong once again summoned David Sarnoff to see his latest miracle. Sarnoff, now the president of RCA, appeared at Armstrong’s laboratory, in the basement of Philosophy Hall at Columbia University, expecting to see some new gadget or tube that would filter out bothersome background noise from radio carrier waves. Instead, Armstrong had found a way to alter the waves themselves, creating a fundamentally new form of radio communication. Instead of modulating the amplitude, or intensity, of a radio carrier wave, Armstrong had developed a means of modifying its frequency, or interval. If one imagined radio signals as ocean waves, Armstrong had found a way to control the rate at which they washed up on the beach–changing the frequency, rather than the size. In time, this form of transmission would be known as frequency modulation, or FM.

The implications of Armstrong’s breakthrough were stunning. “This is not an ordinary invention,” Sarnoff declared. “This is a revolution.” Determined to claim this latest innovation for RCA, Sarnoff immediately placed the company’s new experimental laboratories atop the Empire State Building at Armstrong’s disposal–in effect putting Armstrong at the peak of the world’s tallest broadcasting mast. To all outward appearances, it seemed that Armstrong had scored another technical triumph.

Despite the seeming victory, crappy, tinny radio was RCA’s cash cow. Recognizing the inevitability of FM Radio, Sarnoff was given the choice to license it (and thereby greatly enrich Armstrong) or to attack him.  But as RCA’s power had become almost absolute, the company’s disposition towards individual inventors took on a more disturbingly absolute tones.

Sarnoff summed it up the corporation’s philosophy by saying “RCA doesn’t pay patent royalties, we collect them.”  And rather than enrich Armstrong again, as has been documented ably by others,  Sarnoff crowded full sail into war with Armstrong.

When it was clear RCA would not partner with Armstrong, the inventor set out to develop his own broadcasting system.  It would be known as “Armstrong FM."  He licensed the technology to broadcasting stations and radio makers like Zenith.  The  FCC allotted valuable spectrum to Armstrong and his partners across the 42-50 MHz range. 

The End

Armstrong started the FM revolution without RCA.   But time and money were not on Armstrong’s side. Much like Nikola Tesla’s losing battle in the War of the Currents, this clash found a brilliant inventor up squaring off against an unbelievably powerful and entrenched monopoly.  RCA had a lot to lose if FM Radio took off.  And it was not accustomed to losing.

Using the virtually unlimited money and influence at RCA’s disposal, Sarnoff:

  • Successfully lobbied the FCC to change the FM Spectrum range from 42-50 Mhz. to 88-108 Mhz. which rendered all Armstrong radios useless.
  • Commercialized "new spectrum” FM Radios without licensing Armstrong’s Patents
  • Tied Armstrong up in patent litigation until the inventor’s considerable fortunes were drained

Armstrong fought to the last.  He burned through every dollar and then, against his wife’s wishes, declared he would use their personal nest egg to continue his fight.  When she protested, Armstrong desperately struck her on the arm with a fireplace poker.  She then left him in terror at his desperation and moved in with her sister in Connecticut. Before succumbing completely to his wounds, Armstrong asked RCA if they would settle with him for $2,000,000.  They offered him a tenth of it.

Not long thereafter, Edwin Armstrong reached the end of himself.  After writing his wife a brief note and, wearing his coat and hat, jumped from his 13th story window to his death.  His suicide note included these lines.

    I am heartbroken because I cannot see you once again. I deeply regret what has happened between us. I cannot understand how I could hurt the dearest thing in the whole world to me. I would give my life to turn back to the time when we were so happy and free. God keep you and may the Lord have mercy on my soul.

That year RCA almost achieved one billion dollars in profit and drove one of the world’s greatest living inventors to his death over $2,000,000.