In 1893, he enrolled in a three-year course of studies at Yale University's Sheffield Scientific School in New Haven, Connecticut, on a $300 per year scholarship that had been established for relatives of David de Forest.

Convinced that he was destined to become a famous—and rich—inventor, and perpetually short of funds, he sought to interest companies with a series of devices and puzzles he created, and expectantly submitted essays in prize competitions, all with little success.

He then completed his studies at Yale's Sloane Physics Laboratory, earning a Doctorate in 1899 with a dissertation on the "Reflection of Hertzian Waves from the Ends of Parallel Wires", supervised by theoretical physicist Willard Gibbs.

In the late 1800s he became convinced there was a great future in radiotelegraphic communication (then known as "wireless telegraphy"), but Italian Guglielmo Marconi, who received his first patent in 1896, was already making impressive progress in both Europe and the United States.

A series of short-term positions followed, including three unproductive months with Professor Warren S. Johnson's American Wireless Telegraph Company in Milwaukee, Wisconsin, and work as an assistant editor of the Western Electrician in Chicago.

Although an attempt was made to have the three systems avoid conflicts by rotating operations over five-minute intervals, the agreement broke down, resulting in chaos as the simultaneous transmissions clashed with each other.

Meanwhile, White set in motion a series of highly visible promotions for American DeForest: "Wireless Auto No.1" was positioned on Wall Street to "send stock quotes" using an unmuffled spark transmitter to loudly draw the attention of potential investors, in early 1904 two stations were established at Wei-hai-Wei on the Chinese mainland and aboard the Chinese steamer SS Haimun, which allowed war correspondent Captain Lionel James of The Times of London to report on the brewing Russo-Japanese War,[12] and later that year a tower, with "DEFOREST" arrayed in lights, was erected on the grounds of the Louisiana Purchase Exposition in Saint Louis, Missouri, where the company won a gold medal for its radiotelegraph demonstrations.

[13] The company's most important early contract was the construction, in 1905–1906, of five high-powered radiotelegraph stations for the U.S. Navy, located in Panama, Pensacola and Key West, Florida, Guantanamo, Cuba, and Puerto Rico.

His main complaint was the limited support he got for conducting research, while company officials were upset with de Forest's inability to develop a practical receiver free of patent infringement.

[14] On November 28, 1906, in exchange for $1000 (half of which was claimed by an attorney) and the rights to some early Audion detector patents, de Forest turned in his stock and resigned from the company that bore his name.

American DeForest was then reorganized as the United Wireless Telegraph Company, and would be the dominant U.S. radio communications firm, albeit propped up by massive stock fraud, until its bankruptcy in 1912.

Using his "sparkless" arc transmitter, de Forest first transmitted audio across a lab room on December 31, 1906, and by February was making experimental transmissions, including music produced by Thaddeus Cahill's telharmonium, that were heard throughout the city.

[15] De Forest also interested the U.S. Navy in his radiotelephone, which placed a rush order to have 26 arc sets installed for its Great White Fleet around-the-world voyage that began in late 1907.

Eugenia Farrar sang "I Love You Truly" in an unpublicized test from his laboratory in 1907, and in 1908, on de Forest's Paris honeymoon, musical selections were broadcast from the Eiffel Tower as a part of demonstrations of the arc-transmitter.

In early 1909, in what may have been the first public speech by radio, de Forest's mother-in-law, Harriot Stanton Blatch, made a broadcast supporting women's suffrage.

After determining that an open flame was too susceptible to ambient air currents, de Forest investigated whether ionized gases, heated and enclosed in a partially evacuated glass tube, could be used instead.

However, to many observers it appeared that de Forest had done nothing more than add the grid electrode to an existing detector configuration, the Fleming valve, which also consisted of a filament and plate enclosed in an evacuated glass tube.

In 1908, John V. L. Hogan reported that "The Audion is capable of being developed into a really efficient detector, but in its present forms is quite unreliable and entirely too complex to be properly handled by the usual wireless operator.

De Forest moved to San Francisco, California, and in early 1911 took a research job at the Federal Telegraph Company, which produced long-range radiotelegraph systems using high-powered Poulsen arcs.

One of de Forest's areas of research at Federal Telegraph was improving the reception of signals, and he came up with the idea of strengthening the audio frequency output from a grid Audion by feeding it into a second tube for additional amplification.

[32] Beginning in 1913 Armstrong prepared papers and gave demonstrations that comprehensively documented how to employ three-element vacuum tubes in circuits that amplified signals to stronger levels than previously thought possible, and that could also generate high-power oscillations usable for radio transmission.

Based on a notebook entry recorded at the time, de Forest asserted that, while working on the cascade amplifier, he had stumbled on August 6, 1912, across the feedback principle, which was then used in the spring of 1913 to operate a low-powered transmitter for heterodyne reception of Federal Telegraph arc transmissions.

However, much of the engineering community continued to consider Armstrong to be the actual developer, with de Forest viewed as someone who skillfully used the patent system to get credit for an invention to which he had barely contributed.

From October 1921 to September 1922, de Forest lived in Berlin, Germany, meeting the Tri-Ergon developers (German inventors Josef Engl (1893–1942), Hans Vogt (1890–1979), and Joseph Massolle (1889–1957)) and investigating other European sound film systems.

After recording stage performances (such as in vaudeville), speeches, and musical acts, on April 15, 1923, de Forest premiered 18 Phonofilm short films at the independent Rivoli Theater in New York City.

That camera was used by Case and his colleague Earl Sponable to record Calvin Coolidge on August 11, 1924, which was one of the films shown by de Forest and claimed by him to be the product of his inventions.

Meanwhile, theater chain owner Isadore Schlesinger purchased the UK rights to Phonofilm and released short films of British music hall performers from September 1926 to May 1929.

That same year, de Forest and early TV engineer Ulises Armand Sanabria presented the concept of a primitive unmanned combat air vehicle using a television camera and a jam-resistant radio control in a Popular Mechanics issue.

[58] The grid Audion, which de Forest called "my greatest invention", and the vacuum tubes developed from it, dominated the field of electronics for forty years, making possible long-distance telephone service, radio broadcasting, television, and many other applications.

In 1952, he wrote to the newly elected Vice President Richard Nixon, urging him to "prosecute with renewed vigor your valiant fight to put out Communism from every branch of our government".