Shulou(Shulou.com)11/24 Report--

This article comes from the official account of Wechat: back to Park (ID:fanpu2019), by Yang Weifeng and Wang Feng

After setbacks and hardships, Field finally succeeded (see the previous article, "A cable connects Europe and the United States, and the history of human communications has changed"). Under the admiration of people, he also freely hoped that if the current did not pass through the submarine cable, it would be nice to send messages directly across the ocean. This new great idea doesn't belong to him alone. But thinking and doing are two different things, and achieving and understanding are two different things. The story about this new conformation is even more wonderful.

Written by Yang Weifeng (radio management practitioner), Wang Feng (associate professor of Hebei normal University of Science and Technology)

With the advent of the era of radio communication, the German physicist Heinrich Rudolf Hertz confirmed the existence of electromagnetic waves by experiments between 1886 and 1889. He oscillated the discharge with an induction coil, generated sparks through the metal coil, and found the induced spark in the gap between another similar metal device in the room. Hertz's discovery ignited the dream of an Italian youth who fought for it all his life. He is Guglielmo Marconi.

In 1894, Marconi began to experiment in the attic of his home, using radio waves to send and receive telegrams, and gradually expanded the distance between them. In February 1896, he came to London with his mother to develop. The following year, with the help of the family, Marconi Radio Telegraph and signals, Britain's first company specializing in radio equipment, was set up.

In 1900, two companies named after Marconi, made up of international capital, were in business: one was Marconi Radio Telegraph and signal, and the other was Marconi International Shipping. At that time, a burgeoning industrial system had been established, and Marconi and Marconi attracted customers interested in high technology and were able to generate revenue to keep the wireless network running. One of the biggest orders came from the Royal Navy, where Marconi installed radio equipment for 28 warships and four land communication stations.

Marconi's business is blooming in all directions and seems to be growing rapidly, but the company is still not profitable on a large scale. The reason for the popularity is mainly due to the operating environment of the communications industry at that time. Although the initial radio communication experiments were carried out on land, the commercial operation of radio technology began at sea. The demand for instant communication between shore and ship gives the emerging radio technology the opportunity to display its talents. This does not mean that the communication on the land does not need radio, but because the wired Telegraph service occupied the license of the communication operation on the land at that time, and wireless was not allowed to grab the jobs of the cable.

The business volume of maritime communications is not enough to support Marconi's high site construction and daily operating expenses. Marconi, who is in a dilemma, must seek greater opportunities to maintain the development and operation of the company.

Another great idea across the Atlantic Marconi planned an earth-shattering event for the company's profitability and growth. Starting in 1901, Marconi was determined to devote almost all his energy and almost all the money available to the company (four times the total revenue from royalties in the first four years of its establishment) to radio waves for transatlantic communications. What a big gamble!

He worked on the board and hired John Ambrose Fleming (John Ambrose Fleming), a renowned professor of electrical engineering at the University of London, as a scientific adviser at an annual salary of £500. he built a communications station next to the Poldhu hotel in Cornwall, in south-west England, where equipment to transmit transatlantic signals was designed and tested. Makeni also promised to transfer 500 shares of Marconi Radio Telegraph to Fleming in addition to the company's fixed annual salary if the signal succeeds in crossing the Atlantic. The condition is: "if you succeed in crossing the Atlantic, the main honor will and must always belong to Marconi."

Marconi believed that radio waves could cross the Atlantic, but he didn't know how to do it in engineering. Fleming could find a way to implement it. Marconi is the company's biggest asset and the company's trademark. Only an organization like Marconi can support such risk-taking. Historians agree that it was a success and that Fleming played a decisive technical supporting role, but the main honor is always Marconi's.

Setbacks and challenges are inevitable. Fleming designed a transmitter with a 25 kilowatt alternator, a 20,000 volt transformer and a high voltage capacitor, which can produce sparks about 2.5 centimeters long and wrist thickness, which is already quite strong. The power of the generator set and transmitter should be the highest in the world at that time, and the emission index of this equipment far exceeds that of other equipment.

The antenna of the Poldu communication station was blown down by the wind. (Archive of Marconi Corporation, PLC.) on September 17, 1901, the Poldu communication station was hit by a severe storm, and 20 61-meter-high masts were almost destroyed, causing serious damage to the antenna of the transmission system. In order not to affect the implementation of the plan, Marconi decided to temporarily erect two 49-meter-high masts to support the antenna.

A makeshift antenna built after the Poldu communication station was damaged. (Archive of Marconi Corporation, PLC.) in Newfoundland on the other side of the Atlantic, after several surveys and comprehensive considerations, Marconi decided not to build a formal station at Cape Rees for the time being (the station was only built in 1904, mainly because the Telegraph company that previously installed Atlantic Telegraph cables enjoyed the monopoly privilege of Telegraph communications in Newfoundland from 1854 to 1904). Instead, use kites or balloons instead of fixed masts to temporarily build a receiving device. Just testing, not commercial operation, will not violate local laws and regulations.

On November 22, Marconi gave instructions to the Poldu communication station to transmit the signal: after receiving a telegram from the company's London office, it continued to send a simple Morse code "S" from 3 p.m. to 6 p.m. GMT every day. Perform the same procedure every day except Sunday until you are notified to stop.

On November 26, 1901, Marconi, with his loyal assistant George George Kemp and another assistant, P.W.Paget, along with two tons of iron tuning equipment and tanks of sulfuric acid, sailed from Liverpool to St. John's Port in Newfoundland on Allan's Carthaginian.

Imprisonment: it doesn't make sense. Marconi was nervous on this voyage across the North Atlantic. At that time, most physicists thought that it was impossible to transmit radio signals across the Atlantic. It is believed that radio waves radiate outward in a straight line like light and do not travel around the curvature of the earth. No matter how strong the signal is, the electromagnetic waves emitted will become tangents to the earth and will not fall thousands of meters away into the universe.

Technical experts always focus on the practical function of scientific discoveries, while scientists focus on the natural mysteries themselves. Even Hertz himself thought that it was of no practical use after completing the famous electromagnetic wave verification experiment. In a letter to Hertz at the end of 1889, Huber, a German electrical technologist and engineer, mentioned the idea of using electromagnetic waves (then called "Hertz waves") for communication. But Hertz's reply disappointed him. Hertz thought that if electromagnetic waves were to be used for long-distance communication, there would have to be at least a giant concave mirror the size of the European continent, and they would have to be hung high. This answer actually negates Hobble's idea. Hertz's answer was calculated, and the large mirror was designed to take care of the wavelengths of electromagnetic waves that could be generated by man at that time.

Marconi has more entrepreneurial thinking than scientist thinking, which makes him willing to believe that electromagnetic waves will propagate around the curvature of the earth and go his own way in the crazy experiment of transatlantic radio communication, which is of great commercial value after all. Perhaps Marconi's real teacher is Field, an American entrepreneur who has experienced setbacks in laying transatlantic Telegraph cables.

Radio waves across the Atlantic if scientific and technological progress has a clear direction, it must be guided by people's wishes. People's wishes often have to be realized by people who can integrate more resources.

A group photo of Marconi (center), Kemp (left) and Pegget on St. Johns signal Hill, Newfoundland. The large hexagonal kite behind the three is a "Baden-Powell-Levitt" kite (Baden Powell Levitor Kite) brought from England. It carries an antenna to lift off more than 150 meters, making efforts to receive transatlantic radio signals. Photo: James Wei (James Vey) (from the Library and Archives of Canada) on the afternoon of December 12, 1901, Marconi and his assistant picked up a radio signal from Ireland through a 155m antenna raised by a kite. When they heard the Morse code in the strong wind, "drip, drip." At that time, while excited and joyful, I could not easily believe that it was true: the radio waves from Poldu traveled steadily around the curvature of the earth for 3218.7 kilometers, across the Atlantic Ocean to the signal mountain of St. John's in Newfoundland! The distance of this signal transmission is nearly 10 times that of previous communication records, confirming Marconi's belief that "no matter how far away, radio communication is unlimited."

The verification signals they receive are only three consecutive short "", which is really too simple. The cold northwest wind is mixed with the noise of the equipment, and after a long period of intense monitoring, they will wonder whether they really heard the sound of the signal or their own hallucinations. Therefore, they also planned to listen to the clearer signal the next day before releasing the news, but the next day because the weather became worse, they did not receive any more signals. We know today that it is more advantageous to receive transatlantic radio signals at night than during the day because of solar radiation. It is disadvantageous for Marconi to choose to experiment in the afternoon.

Marconi did not rashly disclose the news to the outside world, because the explosive news is bound to affect the company's stock price. As early as 1898, the news of Marconi's successful cross-sea wireless communication experiment caused the share price of Transatlantic Cable and Telegraph Company to plummet. However, when Marconi was able to report to the company's headquarters as far away as London before the news was released, the company had the opportunity to inject more stock chips before the news was released, which was legal in Britain at the time.

On December 17, 1901, after the successful transatlantic radio communication experiment, the scene was "reproduced" by the media (the first on the left is Marconi, and two people other than three are local employees). This photo of the pose was widely circulated. Photo: James Wei (James Vey) (from the Library and Archives of Canada) Marconi announced the news to the press and the Italian government on December 14 after communicating with the company's headquarters in London. The whole of St. Johns was immersed in great excitement, followed by the frenzy of the news media, and newspapers around the world echoed the New York Times's remark that "Marconi announced the most surprising development of information science in modern times." On Sunday, December 15, the New York Times published the news of Marconi's transatlantic signal on its front page and published a biography of Marconi. To make the story more complete, the New York Times asked Martin (Thomas Commerford Martin) to conclude. Martin, then editor of Electrical World and an authority on electrical and media fields, was able to talk about Marconi's achievements in a larger context.

Martin co-founded the American Institute of Electrical Engineers (AIEE, one of the forerunners of the now world-famous Institute of Electrical and Electronic Engineers (IEEE) in 1884) and served as president of the Institute from 1887 to 1888. Martin eagerly praised Marconi as a new young technological genius and said he was surprised and pleased with Marconi's success in crossing the Atlantic.

Pundits came forward to support the fact that academia and the industry were skeptical about Marconi's experiment. when they received the signal, they did not invite other professionals to be present, let alone the media to watch it on the spot. Apart from him and his assistant Camp, there was no third person outside the company to testify at the scene.

At this time, there were professionals who supported Marconi, such as Michael Pupin, a famous Columbia University professor of electromechanics and authoritative physicist Michael Pupin, who publicly praised Marconi's feat.

But the person Marconi should be most grateful for is Martin. Because Martin decided that Marconi was a trustworthy figure. To this end, Martin made the young Italian a guest of honor at the annual dinner of the American Society of Electrical Engineers (AIEE) on January 13, 1902. Martin, a former president of AIEE and host of many events, easily persuaded the leaders of the society to give Marconi the honor. However, because not everyone believed Marconi's statement, Martin found it difficult to get engineers to attend the dinner, so he had to turn to Elihu Thomson (founder of Thomson Houston, which merged with Edison's company into General Electric in 1892) to support the campaign. It was only after word spread that Thomson approved Makeni that Martin was able to fill the 300-seat Astor Promenade of Waldorf Hotel Astoria.

Still, Marconi wants to find more evidence for himself. In February 1902, he traveled from England to the United States on the passenger ship Philadelphia, which was equipped with a wireless Telegraph system. During the transoceanic voyage, Marconi periodically listened to the Morse code message from Poldu and invited the captain and first mate to listen. He also recorded the time and place of the news on a chart. This chart, with witnesses on board the Philadelphia, is a stronger example of how radio waves can travel across the Atlantic. Repeated experiments and communication over longer distances later confirmed that Marconi was not lying.

Note: Marconi did not disclose the specific frequency of the first transatlantic radio wave to the media at that time. It was not that he deliberately avoided the technical specifications of the Poldu transmission system, mainly because it was difficult to accurately determine the radio frequency at that time. In 1903, Fleming said in a speech that the wavelength was estimated to be more than 1000 feet. In 1904, Fleming invented a device for measuring emission frequency (or wavelength). In 1908, Marconi said in a speech at the Royal Society that the wavelength should be 1200 feet, corresponding to a frequency of 820 kHz.

The success of transatlantic radio communication has brought great benefits and development opportunities for Marconi, but the significance of this experiment goes far beyond commercial value. From the point of view of human understanding of nature, its scientific enlightening value is more precious. It not only enabled Marconi and German physicist Karl Ferdinand Braun to win the 1909 Nobel Prize in Physics for their invention and improvement of the radio message, but also broadened the horizons of science. The thinking and confirmation around the scientific doubts of transatlantic wireless communications and the improvement of communication quality are like toppling dominoes and giving birth to a series of major scientific gains.

Harvest 1: human beings dare not think, dare not do, or even believe that this is true when they know the existence of the ionosphere, because at that time, people did not know that the high altitude outside the earth was still wrapped in a layer of ionosphere, and the ionosphere would reflect electromagnetic waves. It can act as a giant spherical mirror, so that electromagnetic waves are reflected many times between the ground and the ionosphere, thus allowing electromagnetic waves to travel around the curvature of the earth.

In 1902, Oliver Oliver Heaviside and American engineer Arthur Arthur Kennelly proved theoretically that radio waves spread around the world at the same time because they bounced off a layer of charged gas particles in the ionosphere. This ionosphere was later known as the "Conolli-Hewitzai layer". Hewitzer is a British self-taught mathematical genius and physicist. He has no formal higher education, but has made many original achievements in mathematics and engineering. He founded vector analysis, simplified the Maxwell equations to the form used today, and made a great contribution to the development of electromagnetism.

In 1924, British scientist Edward Victor Appleton, with the help of Miles Barnett (Miles Barnett), carried out experiments to detect the height of the ionosphere with continuous waves. They used electromagnetic waves with frequency conversion to receive echoes from the ionosphere, which directly confirmed the existence of the ionosphere for the first time. Their experiments confirm the existence of a conductive layer in the upper atmosphere that reflects radio waves beyond the earth's curve, and suggests that sometimes the reflection may come from a second layer, the higher conductive layer. Their preliminary findings were published in the journal Nature in 1925. Apton won the Nobel Prize in Physics in 1947 for confirming the existence of the ionosphere through the study of the physical properties of the upper atmosphere. As a result, it has triggered an in-depth study and new exploration of the earth's atmosphere.

Harvest two: ushering in the Age of Radio Astronomy in 1927, a college graduate named Karl Guthe Jansky joined the two-year-old Bell Labs as a radio engineer. At that time, there was still background noise in the transatlantic radio communication system, and he was ordered to investigate the source of the background noise and eliminate radio interference that might affect the transmission of the signal.

Jansky has set up a set of large rotating antennas to receive radio waves at a frequency of 20.5MHz (wavelength 14.6m). After months of recording and analysis, he classified the background noise into three types: nearby thunderstorms, distant thunderstorms and faint hisses of unknown origin. He spent more than a year investigating the third type of background noise and found that its intensity fluctuated once a day.

Jansky initially speculated that the noise came from solar radiation. A few months later, however, the strongest noise source began to move away from the sun. He determined that the repetition period of the signal was 23 hours and 56 minutes, which happened to be the rotation time of the earth relative to the universe (sidereal day), rather than solar day (24 hours). Jansky thinks it comes from the center of the Milky way, and the signal source in the direction of Sagittarius is the strongest.

His findings were widely publicized and published in the New York Times on May 5, 1933. He published a classic paper, "the obvious Source of Electronic interference in Outer Space". His discovery marked the birth of radio astronomy, ended the history that people could only observe the universe through visible light, broadened the horizons of human understanding of the universe, and opened a new era of astronomical observation. The four important astronomical discoveries in the middle of the 20th century-interstellar molecules, quasars, microwave background radiation and pulsars-were all made by means and methods of radio astronomy.

At this point, two stories about transatlantic communications have come to an end, but communications science and engineering for the well-being of mankind continue to develop. These two separate and interrelated stories have led to a series of major scientific events and achievements, these legends are sad, and the spirit of great scientists and entrepreneurs is worth remembering.

Main references

[1] W.BernardCarlson.Tesla:Inventor of the Electric age [M] .New Jersey:Princeton University Press,2013:331-352

[2] Marc Raboy. Marconi:the Man Who Networked the World [M]. New York:Oxford University Press,2016:34-192

[3] Sungook Hong.Wireless: From Marconi's Black-Box to the Audion [M]. Cambridge, MA: MIT Press, 2010 MIT Press 20-32

[4] Bruce J. Hunt.Oliver Heaviside A first-rate oddity [J] Phys. Today 65 (11), 48 (2012); doi: 10.1063/PT.3.1788 View online: http://dx.doi.org/10.1063/PT.3.1788

View Table of Contents:

Http://www.physicstoday.org/resource/1/PHTOAD/v65/i11

[5] Qian Changyan. The experimental method and process of Hertz's discovery of electromagnetic waves [J]. Physics experiment, 2005 (7): vol.25

[6] One family:generations of discovery see:

Https://www.otago.ac.nz/otagobulletin/news/otago740666.html

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