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

On July 20, 1937, Galilmo Marconi, known as the father of radio communications, died in Rome. Tens of thousands of Romans held a state funeral for him, and the British Post and Telecommunications Office's wireless telegraphy and telephone services were interrupted for two minutes to express their reverence and condolences for the pioneer of radio communications.

Since Maxwell theoretically confirmed the existence of radio waves in 1864, it took nearly half a century for mankind to realize the value of radio waves. Among the many scientists who study radio waves, the most outstanding one is Marconi, who pioneered the development of radio communication technology for mankind and contributed his whole life to the practical application of radio waves.

Born in Bologna, Italy, on April 25, 1874, Marconi studied physics under the guidance of several prestigious teachers.

In 1894, Marconi came across an article about the experiment of Hertz electromagnetic wave, which touched him deeply and had a premonition of the potential practical value of electromagnetic wave. "when I started my first experiments with Hertz waves, I couldn't imagine why some famous scientists ignored to use this theory," he said. " From then on, Marconi began his life of radio communication research.

In 1895, Marconi used spark discharges, induction coils and keys to make a radio transmitter, modified a metal geophone and added an antenna to make a receiver. He installed the transceiver on the roof of his building and completed a 30-meter communication for the first time. He was greatly encouraged by this success. "I seem to have an intuition that in the near future, radio waves will provide a newer and more powerful means of communication for human beings," he said. " He decided to try it in a larger space.

The following summer, he completed a radio communication of 1.7 kilometers from the top floor of his home to the distant hills.

This success gave him more confidence and determined to expand the experiment to the practical use of communications, so he wrote to the Italian Minister of posts and Telecommunications for financial assistance. After being rejected, Marconi resolutely took his transceiver to England.

Fortunately, he not only applied for a patent in the UK, but also received enthusiastic support from William Price, chief engineer of the Post Office. With his help, Marconi performed several radio signal transmissions, from 300 meters apart between the Post Office Building and the Bank Building to two miles and five miles apart. Even 10 miles (16.09 kilometers) of experiments have been successful.

On May 18, 1897, Marconi did another experiment between a cliff lighthouse in Dover, England, and Wimereau, France, 45 kilometers apart. This time he completed the radio communication across the Bristol Channel, and this success shocked the whole of Europe and attracted a lot of attention.

Marconi took a picture with the transceiver he invented when he won his first radio patent, when he was only 22 years old. After the successful communication in the Bristol Strait, the Italian government began to be impressed with the young man and decided to build a transmission station for him in Spezia so that he could communicate with warships 20 kilometers at sea by radio. As the communication distance grew farther and farther, Marconi was ambitious to realize the commercial value of radio communications, so he formed a wireless Telegraph and signalling company, which was later changed to Marconi Wireless Telegraph Co., Ltd.

In 1898, Britain held a yacht race, which ended 32 kilometers from the coast. "Dublin KuaiBao" specially invited Marconi to send messages by radio signals. As soon as the yacht reached the finish line, radio signals were sent from the sea, and the audience on land was ecstatic. The yacht race made the world realize the practical value of radio waves. After this success, Marconi improved the equipment and found a way to control the oscillation frequency. He raised the antenna and increased the transmission distance.

On March 28, 1899, Marconi's radio communication crossed the English Channel.

Two years later, Marconi plans to experiment with radio communications on a larger scale. This experiment can be called a miracle and left a brilliant stroke in the history of world science and technology.

Marconi plans to achieve transatlantic radio communications from Newfoundland in Canada to Kunvor in the United Kingdom. The experiment will challenge unimaginable long distances and has attracted worldwide attention.

The experiment began as scheduled on December 12, 1901. Unfortunately, on the day of the experiment, Newfoundland was hit by a severe storm. The pre-hoisted antenna balloon was blown away by high winds, and Marconi had to temporarily use a kite to pull up the antenna. He stood in the ice and snow, waiting for a signal from Britain 3500 kilometers apart. Suddenly the signal came, and they were very weak. It was an intermittent Morse code signal of three points "S". It was not easy for them to get, and Marconi spent six years preparing for the faint signal of the three points and spent $200000.

Under the technical conditions at that time, it was indeed not easy or almost impossible to transmit radio signals 3500 kilometers apart. Atmospheric disturbance, unknown ionospheric interference, storm noise, the iron fan signal receiver used is very crude and simple, it is difficult to identify this weak radio signal in a large noise background. In addition, there is no way to repeat the experiment, nor can it give independent proof, so it is difficult to trust others with facts.

For this period of history, Canadian radio engineer John Belroth (John Belrose) has done a detailed study. In 1995, he published his research report entitled "differences in transatlantic (radio) transmission technologies between Fessenden and Marconi in the first 10 years of this century." it was published in the journal of the 100th anniversary conference of the International Radio Society held from September 5 to 7 of that year.

According to the report, Marconi not only made arduous efforts for this experiment, but also encountered unimaginable difficulties.

First, he built a signal transmitter on a towering cliff at a remote location called Poldhu on the south coast of Queenwall, England. The transmitting antenna consists of 20 masts, each 60 meters high, and when they are set up along a circle of 61 meters in diameter, the antennas are arranged between the masts.

Unfortunately, shortly after the completion of the antenna system, on September 17, 1901, three months before the test, a strong wind suddenly blew down all these masts, and it was too late to rebuild, so Marconi had to quickly put up two masts. Between the two masts, 54 antennas were laid, from which the test signals were transmitted.

The radio signal of Bodu station is sent out by the spark discharge of the capacitor. In order to enhance the signal, the transmitter uses a two-stage circuit, the first-stage circuit emits low-voltage sparks and the capacitors of the second-stage circuit emit high-voltage sparks.

The secondary radio transmitter used at that time was successfully designed by Marconi himself. according to the design at that time, the voltage of the secondary spark could reach 150 kV, and the energy of the capacitor was supplied by a generator located in Bodu. The design is so clever that it can be discharged every 7.5 to 12 seconds. Because of the long interval between signals, it is easy to identify.

In Newfoundland, Marconi chose signal Hill as the receiving station, and the receiving equipment was placed in the site of an abandoned military hospital on signal Hill. It was agreed that a radio signal would be sent from approximately 12:00 to 3 noon on December 12, 1901.

Due to the strong wind that day, the prepared 155m balloon blew away. Marconi borrowed a kite to pull the 152.4-meter-long cable into the air and used several cables to form a net in the air to temporarily secure the kite.

Although Marconi was well prepared for the experiment, some people suspected that Marconi had misled the world and mistook the noise of the atmosphere for the Morse code "S".

To clarify the matter, when Marconi returned to England in February 1902, he found a more sophisticated shipborne antenna receiver and redid the experiment.

The results show that the radio signal of 1120 km can be clearly received during the day and 2500 km at night. Today, Marconi's experiments are repeated with instruments at that time, and the frequency of 850 kilohertz at that time is also used to prove that the signal can indeed travel across the Atlantic and even further.

Under the technical conditions of 1901, both the doubts of a small number of scientists at that time and Marconi's insistence on experiments showed a spirit of respect for science, which was the primary driving force for the development of science.

The success of this transatlantic communication made Marconi a world celebrity overnight. Local newspapers published articles with big headlines, saying that he "transmitted the news by radio in an instant, which created a new era."

But at that time, it was also criticized by some people, claiming that radio waves would penetrate their bodies, destroy their nerves and damage their hearts. At that time, the scientific community was skeptical of his experiment, insisting that radio waves spread in a straight line and could not follow the curved surface of the earth, but in the face of the test results, Marconi had no choice but to admit that Marconi was successful.

The success of this experiment has promoted the rapid development of radio communication technology, a large number of radio transceivers have emerged, and governments and departments have begun to use radio waves to communicate. The success of radio wave transatlantic communication indicates that radio wave communication has entered a practical stage.

Marconi devoted all his life to the research of radio communication, and he obtained various patents such as wireless telegraphy, overhead antenna, magnetic detector, horizontal directional antenna and timing spark system transmitter. He used radio waves to quickly connect people far apart, thus bringing mankind to a new era of radio communication.

In recognition of his pioneering contributions to radio communication technology, Marconi won the Nobel Prize in Physics in 1909.

Wen Yuan: 365 days in the History of Science, slightly deleted

Author: Wei Fengwen and Wu Yi

Editor: Zhang Runxin

This article is from the official account of Wechat: Origin Reading (ID:tupydread), author: 365 days in the History of Science

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