First Transatlantic Telegraphic Radio Transmission Summary

  • Last updated on November 10, 2022

Guglielmo Marconi received the first transatlantic telegraph signal sent without a cable, demonstrating that long-distance electronic communication through open space was possible.

Summary of Event

On December 12, 1901, Guglielmo Marconi was in St. John’s, Newfoundland, Canada, to receive a Morse code signal to be transmitted to him from Poldhu, Cornwall, England, a distance of 3,440 kilometers (2,137.5 miles) across the Atlantic Ocean. Humankind was about to enter the era of worldwide electronic communication. Radio;telegraphic Communications;radio Inventions;radio [kw]First Transatlantic Telegraphic Radio Transmission (Dec. 12, 1901) [kw]Transatlantic Telegraphic Radio Transmission, First (Dec. 12, 1901) [kw]Telegraphic Radio Transmission, First Transatlantic (Dec. 12, 1901) [kw]Radio Transmission, First Transatlantic Telegraphic (Dec. 12, 1901) Radio;telegraphic Communications;radio Inventions;radio [g]Canada;Dec. 12, 1901: First Transatlantic Telegraphic Radio Transmission[00230] [g]England;Dec. 12, 1901: First Transatlantic Telegraphic Radio Transmission[00230] [c]Science and technology;Dec. 12, 1901: First Transatlantic Telegraphic Radio Transmission[00230] [c]Inventions;Dec. 12, 1901: First Transatlantic Telegraphic Radio Transmission[00230] [c]Communications and media;Dec. 12, 1901: First Transatlantic Telegraphic Radio Transmission[00230] [c]Radio and television;Dec. 12, 1901: First Transatlantic Telegraphic Radio Transmission[00230] Marconi, Guglielmo Maxwell, James Clerk Morse, Samuel F. B. Henry, Joseph Hertz, Heinrich

The principles of electric telegraphy had been discovered in the nineteenth century, and for years individuals had worked to send the electric signal further and further through various wire conductors. According to David A. Hounshell of the Smithsonian Institution’s National Museum of History and Technology: “The word telegraph originally identified a visual, manually operated signaling system, or semaphore, used to communicate information rapidly over a large distance.” In the nineteenth century, however, as research into electricity progressed, the term was associated with signals sent and received over wires and then without wires.

Samuel F. B. Morse was an American artist and inventor who had sailed to Europe in 1832 to study art. On the return voyage, a fellow passenger and American, the chemist Charles T. Jackson, introduced Morse to the principles of electromagnetism, the basis for the telegraph. Telegraphy In 1835, Morse created a transmission device and a code, now known as Morse code Morse code (a series of dots and dashes representing agreed-upon alphanumeric symbols), to be transmitted as an electric signal through a wire and received at a distant location. On May 25, 1844, Morse demonstrated the principles of telegraphy by transmitting and receiving over an electric telegraph line that was 64 kilometers (39.8 miles) long, between Washington, D.C., and Baltimore, Maryland. From Washington, D.C., Morse transmitted this message in code: “What hath God wrought?”

Morse was not alone in his work in telegraphy; he borrowed ideas from another American, the physicist and inventor Joseph Henry, who, in 1835, had invented an electrical relay that was the forerunner of Morse’s telegraph. Unfortunately, Henry did not patent his electrical relay, and Morse’s name is the one commonly heard today in association with the telegraph.

The application of telegraphic principles proceeded on both sides of the Atlantic. In 1837, the Great Western Railway in England used an early telegraphic signal (with wires strung adjacent to railroad lines) to indicate train speeds. In 1852, Germany and France reached an agreement that allowed telegraph wires to cross their borders to carry messages.

Morse and Henry as well as the Scottish mathematician and physicist James Clerk Maxwell and the German physicist Heinrich Hertz all made contributions to the achievement of Marconi. No researcher works in a vacuum; each builds on and borrows from the work of earlier researchers and contemporaries. Maxwell pointed out that electricity and magnetism are really an instance of a single form of electromagnetic radiation, and he demonstrated that what is called “light” results from electromagnetic vibrations of a certain wavelength. What followed from this mid-nineteenth century discovery was the further discovery that electromagnetic waves other than light waves could be propagated or transmitted through space. (In 1968, the International Astronomical Union adopted the figure of 299,792.5 kilometers per second as the speed of light.)

As electric energy is transmitted through a wire, it does not travel at the speed of light; rather, it travels at speeds determined by the properties of the conducting medium and associated equipment. Materials such as copper and silver make excellent conductors, but resistance to the transmission of the electric energy is still present, as dictated by the laws of physics. If signals could be transmitted through space, without wires, they would be sent at the speed of light; this is what Marconi accomplished across the Atlantic Ocean on December 12, 1901.

After the initial successes of telegraphy by wire, individuals began to conceive of connecting networks of wires all around the globe. In 1850, a well-insulated copper wire was laid between France and England in the English Channel to carry telegraphic signals, and in 1854 individuals began to consider laying a wire cable across the Atlantic Ocean. According to James R. Chiles, “The first Atlantic cable, which took three attempts in 1857 and 1858 to lay, consumed 367,000 miles [590,503 kilometers] of iron wire and 300,000 miles [482,700 kilometers] of tarred hemp.” On August 13, 1858, President James Buchanan of the United States and Queen Victoria of England exchanged telegraphic messages via this first Atlantic cable. Queen Victoria’s ninety-word message took 16.5 hours to cross the Atlantic. The cable of 1858, however, worked for only one month, and in the 1860’s two additional cables were laid across the Atlantic Ocean. In 1866, two functioning cables connected North America and England, and by the end of the nineteenth century more than ninety million telegrams were being transmitted across the Atlantic Ocean each year. In 1894, Marconi became familiar with Hertz’s work on generating electromagnetic waves through space by using a transmitter. Marconi conceived of the idea of using these waves through space as a transmission signal or a form of wireless telegraphy: The signals would go through space at the speed of light and not be impeded by the resistance of any wire conductor. While in Italy, Marconi worked on his transmitting and receiving equipment. After he received little support to continue his work on wireless telegraphy in Italy, he was persuaded to go to England to pursue his work. Marconi thought that the transmission of signals through space to be received by ships at sea would be of importance to a maritime nation. He went to England because that nation was the world’s greatest maritime power, and on June 2, 1896, he applied for and received the first patent for wireless telegraphy in the world.

From 1896 to 1901, Marconi continued to experiment with transmitting and receiving wireless telegraph signals over greater distances, utilizing the code developed by Morse. In 1894, Marconi had succeeded in sending and receiving a wireless telegraph transmission 2.4 kilometers (1.5 miles). He gradually perfected his techniques and was soon sending and receiving wireless signals over distances of 6.4 kilometers (almost 4 miles), 14.5 kilometers (9 miles), 19 kilometers (11.8 miles), 50 kilometers (31.1 miles), 121 kilometers (75.2 miles), and finally, in January, 1901, on the south coast of England, he sent and received a signal over a distance of 299 kilometers (185.8 miles).

Individuals expressed great interest in the ability to convey messages even greater distances, and Marconi attempted his transatlantic transmission at the end of 1901. Success was not guaranteed, and many thought he was trying to do the impossible. At the transmission site in England, Marconi erected a transmission antenna 48 meters (52.5 yards) tall, consisting of fifty copper wires suspended between two towers standing 60 meters (65.6 yards) apart. In Canada, during a winter gale, Marconi sent aloft a kite that had a trailing antenna that was 152 meters (166.2 yards) in length. He received the letter S on December 12, 1901, when the signal was sent from Poldhu to St. John’s, a distance of 3,440 kilometers.


When Marconi received the letter S, the world was forever changed, because the transmission of information was no longer limited to a distinct physical medium; information could now be transmitted through space at the speed of light. Even though Marconi was successful on December 12, 1901, he was challenged immediately by individuals and corporations who claimed that he could not possibly have achieved a wireless transmission from Poldhu to Newfoundland.

In February, 1902, Marconi replicated his earlier test by conducting a series of transmission-reception tests between the origination station in Poldhu and the S.S. Philadelphia, which was 3,232 kilometers (2008.3 miles) away in the Atlantic Ocean, but still some people did not think highly of his achievements. One of Marconi’s daughters wrote in 1989 that her father’s “scientific work has not been without criticism” and that the point his critics seemed to have in common was that “Marconi, rather than an inventor of new devices, achieved his major successes by incorporating components already invented by others.”

Critics and disbelievers notwithstanding, Marconi continued with his experimentations and transmissions, and by the end of 1902 the first official messages, not test transmissions, were being sent across the Atlantic Ocean. By the early part of 1903, newspaper stories from New York City were being sent for publication in The Times of London by means of Marconi’s telegraphy, which was undeniably built on the work of Henry, Morse, Maxwell, Hertz, and other individuals.

A Nobel Prize, however, is not given to a committee, and in 1909, Marconi and Karl Ferdinand Braun shared the Nobel Prize in Physics. Nobel Prize recipients;Guglielmo Marconi[Marconi] (Braun was honored for his work on the first cathode-ray tube, which he had introduced in 1897.) As Marconi stated in his 1909 Nobel lecture in physics:

The results obtained from these tests, which at the time constituted a record distance, seemed to indicate that electric waves produced in the manner I had adopted would most probably be able to make their way around the curvature of the Earth, and that therefore even at great distances, such as those dividing America from Europe, the factor of the Earth’s curvature would not constitute an insurmountable barrier to the extension of telegraphy through space.

Marconi’s telegraphic achievements coincided with other achievements occurring in electromagnetics. Sir John Ambrose Fleming became a scientific adviser to the company that Marconi founded, and in 1904 Fleming developed a “valve” that could control the flow of electrons in a tube. In 1906, Reginald Aubrey Fessenden Fessenden, Reginald Aubrey invented a system to modulate electromagnetic radio waves that could be transmitted as a form of wireless telegraphy, and radio was thus invented. In 1908, the journal Nature published a brief letter by Alan A. Campbell Swinton Swinton, Alan A. Campbell titled “Distant Electric Vision,” and television as a form of “wireless telegraphy” eventually came about. The first public demonstrations of television occurred in England in 1926 and in the United States in 1927.

Marconi’s contribution evolved into a global telecommunications system that allows virtually instant access to people anywhere in the world, providing they have the appropriate technology. Fiber optics now substitute for copper wires, and signals are transmitted through space at the speed of light to geosynchronous communications satellites orbiting the earth some 36,000 kilometers (22,369.4 miles) above the equator. Although the world has not diminished in size since Marconi’s time, it definitely has “shrunk” through the advances that have been made in the ways in which information can be exchanged and shared since that first transatlantic telegraphic transmission on December 12, 1901. Radio;telegraphic Communications;radio Inventions;radio

Further Reading
  • citation-type="booksimple"

    xlink:type="simple">Baker, W. J. A History of the Marconi Company. New York: St. Martin’s Press, 1971. An excellent book about Marconi and the company he created; it also places telecommunications activities into the context of the times, from the beginning of the twentieth century to the 1960’s.
  • citation-type="booksimple"

    xlink:type="simple">Braga, Gioia Marconi. “Marconi and Instant Global Satellite Communications.” In Space Thirty: A Thirty Year Overview of Space Applications and Explorations, edited by Joseph N. Pelton. Alexandria, Va.: Society of Satellite Professionals, 1989. A short summary of Marconi by his younger daughter in a volume that looks at global communications.
  • citation-type="booksimple"

    xlink:type="simple">Chiles, James R. “The Cable Under the Sea.” American Heritage of Invention and Technology 15 (Fall, 1987): 34-41. This article (in an excellent journal on invention and technology) about the copper cables of the nineteenth century concludes with information on contemporary fiber-optic cables across the Atlantic Ocean.
  • citation-type="booksimple"

    xlink:type="simple">Dunlap, Orrin E., Jr. Communications in Space: From Marconi to Man on the Moon. New York: Harper & Row, 1970. This easy-to-read volume, by an individual who built his first wireless station in 1912, provides an excellent overview of progress in communications from the time of Marconi to space exploration.
  • citation-type="booksimple"

    xlink:type="simple">Franco, Gaston Lionel, ed. World Communications: New Horizons/New Power/New Hope. Navara, Italy: Franco, 1983. This coffee-table-style trilingual publication (English, French, and Spanish) provides an outstanding visual presentation of worldwide communications, with information on basic scientific discoveries that have contributed to telecommunications activities. Also provides information on contemporary organizations that regulate worldwide telecommunications policies.
  • citation-type="booksimple"

    xlink:type="simple">Hong, Sungook. Wireless: From Marconi’s Black-Box to the Audion. Cambridge, Mass.: MIT Press, 2001. Draws on previously untapped archival evidence and recent work in the history of technology to provide a new perspective on the early days of wireless communication. Offers new insights into the relationship between Marconi and his scientific adviser, Fleming. Concludes with a discussion of Lee de Forest’s audion and the shift from wireless telegraphy to radio.
  • citation-type="booksimple"

    xlink:type="simple">Hounshell, David A. Telegraph, Telephone, Radio, and Television. Washington, D.C.: Smithsonian Institution Press, 1977. This booklet provides just a small indication of the tremendous amount of information available from the institution that has been affectionately called “the nation’s attic.” In May of 1990, the National Museum of American History (part of the Smithsonian Institution) opened a new permanent exhibit titled “The Information Age” that covers the times from the work of Morse to twentieth century computers.
  • citation-type="booksimple"

    xlink:type="simple">Marconi, Degna. My Father, Marconi. New York: McGraw-Hill, 1962. For a warm and personal view of Marconi, this book by his older daughter cannot be surpassed. She points out that on the occasion of Marconi’s funeral in 1937, international wireless operators throughout the world halted their transmissions for two minutes in her father’s honor.
  • citation-type="booksimple"

    xlink:type="simple">Shiers, George, ed. The Development of Wireless to 1920. New York: Arno Press, 1977. Twenty articles are reprinted in this excellent volume, including the 1909 Nobel lectures in physics by Marconi and Braun. Contains papers from Fleming and Fessenden. The introductory essay on the “prehistory” period of 1876 to 1920 provides a very good overview of the technical aspects of broadcasting history.
  • citation-type="booksimple"

    xlink:type="simple">Weightman, Gavin. Signor Marconi’s Magic Box: The Most Remarkable Invention of the Nineteenth Century and the Amateur Inventor Whose Genius Sparked a Revolution. Cambridge, Mass.: Da Capo Press, 2003. In addition to describing Marconi’s experiments, this book focuses in large part on the competition that existed among the various inventors who were pursuing the goal of wireless communications at the same time as Marconi. Includes photographs.

Fessenden Pioneers Radio Broadcasting

First Demonstration of Transatlantic Radiotelephony

Principles of Shortwave Radio Communication Are Discovered

Radio Develops as a Mass Broadcast Medium

Radio Broadcasting Begins

National Broadcasting Company Is Founded

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