The tower crane hook is talking
A burst of electric arcs on the ground carried the announcer’s well-spoken news broadcast and the accompanying music of the radio program. This scene happened at a construction site in Xi’an in 2012.
It is understood that the workers discovered this strange phenomenon while resting. At that time, the end of the hook of the tower crane was suspended in the air about 1.5 meters above the ground. The workers hung a wire on the hook when they were resting. . At this time, several workers resting nearby heard the intermittent sound of the radio program, but they could not find the source of the sound. Several people searched in a big circle, and finally found that the sound was made when the wire was scratched on the ground.
According to the instructions of the workers, the reporter tried to draw the end of the wire hanging on the hook of the tower crane on the ground, and a strong electric arc appeared between the end of the wire and the ground, accompanied by the broadcasting sound and music of the host of the radio station Voice. However, if the wire is drawn across the ground alone, there will be no arc and no sound. From this point of view, the reason for this phenomenon is that the wire connects the hook (and even the entire tower crane) to the ground. The entire tower crane is like a huge radio.
The sound of a radio program came out of my head?
These sounds come from the teeth
In 2022, at a construction site in Barcelona, Spain, workers discovered that the hook of the tower crane would generate continuous arcs and sparks when it touched the steel plate placed on the ground, and the sound of radio programs was heard from time to time during the process.
In fact, there are even more amazing examples in history. One night in 1942, American comedian Lucy was driving home when she heard music suddenly. She bent down to turn off the car radio, but found it was already off. It wasn’t until the music got louder that she realized it was coming from her head, more precisely from her mouth. She recalled: “At that time, my teeth kept ringing, and drumbeats kept coming out of my mouth. I almost thought I saw a ghost…” It didn’t take long for the voice in my mouth to gradually subside, and finally it never appeared again.
Some scientists speculate that the lead used in Lucy’s previous dental fillings may have formed a working radio circuit. In addition, in 1960, a man in Chicago, USA, who had undergone dental surgery and had a metal sleeve implanted said that he could often hear music from the radio station coming out of his mouth. A few years later, the man removed the metal sleeve and the phenomenon disappeared.
plasma speaker
What is the reason?
How do tower cranes and human mouths become radios? To answer this question, you first need to know how a radio converts radio signals into sound signals. To receive radio signals from radio stations, the radio must meet at least the following basic conditions: there are radio signals from radio stations nearby; there is a circuit for receiving radio signals; there is a detector that can demodulate voice signals in the radio; there are speakers to play sound.
In the example of a tower crane, the earth, the main body of the crane, the crane arm, the steel cable, the hook and the copper wire on the hook form an approximately closed large-section conductor frame, that is, a receiving circuit. When the nearby high-frequency radio waves encounter this conductor frame, induced voltage and current will be generated in the frame, which will continuously charge and discharge the conductor frame. When the hook or the wire on the hook of the tower crane touches the ground, a tip discharge phenomenon will occur and an arc will be generated. The arc acts as both a geophone and a speaker. Why does an arc make a sound? In fact, this is called a plasma speaker, and its sound principle is that the plasma oscillates the air to produce sound.
Dental fillings may have acted as detectors
So, is it possible for metal fillings in teeth to become “radio sets”? Some scientists believe that tooth filling radios are invented after experiments. But some scientists questioned that because the experimenter’s method was to pull out a false tooth from the mouth of a deceased person, drill holes in it and add metal fillings, but the real oral environment is far more complicated than the experiment. In fact, the radio receiving circuit is not complicated, and the mouth and metal fillings may indeed constitute such a circuit. In Lucy’s case, the strange teeth chatter only occurred when the car was driving into a certain area, possibly because she was driving in the vicinity of a radio transmitter. The human body is conductive and can be used as a conductor. The metal fillings in the teeth and saliva can act as detectors (semiconductors) under certain circumstances. The speaker can be any object that can vibrate in Lucy’s mouth, such as some loose fillings. things. While the odds of this happening are extremely low, it’s not entirely impossible.
The principle of radio is not complicated
The discovery of radio has epoch-making significance to human civilization. In 1888, German scientist Hertz discovered and confirmed the existence of electromagnetic waves. In 1906, the world’s first radio station was established, and mankind has entered the radio era since then.
All objects emit electromagnetic waves, for example, the human body emits infrared rays all the time. Infrared rays, radio waves, and microwaves are all electromagnetic waves, just like the visible light we can see. It’s just that the wavelength of visible light is shorter, and it will rapidly attenuate after passing through most obstacles (such as walls and our bodies), and cannot continue to propagate; while the penetration ability of radio with longer wavelength is much higher than that of visible light, and can The cost of small attenuation passes through the human body and buildings of a certain thickness, so it is very suitable for transmitting broadcast signals.
After the radio signal sent by the radio station is received by the radio, an induced current will be formed inside the radio circuit. The change in the strength of the induced current can be demodulated into a sound signal, which is the basic principle of the radio. The earliest radio made by humans was a device that did not require batteries. This radio was soon replaced by a tube radio, but because of its simplicity, many radio enthusiasts are still enthusiastic about it. This device is a mineral radio.
The structure of the ore radio is very simple: a metal antenna, a crystal ore, a thin metal needle and an earphone. Among them, a spider-web-shaped metal antenna receives radio signals, and a crystal mineral (most commonly galena) acts as a detector. The station modulates the sound signal into a radio signal, and the detector demodulates the radio signal into a sound signal. By adjusting the position and pressure of the metal needle touching the ore, and patiently trying a few more times, if the radio signal is successfully demodulated, you can hear the clear sound of the radio program from the earphones.
Open the information age
Communication has been a need of human beings since ancient times. The smoke from the beacon towers (beacon towers) erected on the Dunhuang Gobi in the Western Han Dynasty was an attempt by the ancients to communicate quickly over long distances. Among some tribes in Africa, the sound of drums is often used as a calling signal. During the period when the European colonists launched the heinous black slave trade in Africa, some tribes in Africa set up drum stations at intervals, and relayed the information of the colonists’ invasion to the tribes quickly by means of drum relay.
Beacon (beacon tower)
The frequency band of FM radio stations is mostly around 100 MHz. The electromagnetic waves in this band are characterized by weak ability to pass through obstacles, but they can propagate far without obstacles, which is the so-called “line-of-sight propagation”. Therefore, when the transmitting antenna is high enough, its coverage Large, a city only needs a few base stations to achieve full coverage of the signal. In the early years, microwave broadcasting TV required the construction of tall TV transmission towers. The development of radio transmission technology has entered the 5G era, that is, the fifth generation of mobile communication technology. The 5G network uses two frequency bands of 450 MHz to 6 GHz and 24.25 GHz to 52.6 GHz. Although the transmission bandwidth is very large, the signal transmission distance is short and the ability to cross obstacles is not strong. In order to fully cover 5G signals, it needs the support of a sufficiently dense 5G base station network.
China’s “Eye of the Sky” explores the universe by means of electromagnetic waves in the radio frequency band
City after radio visualization
In 1901, the Italian Marconi successfully carried out the first radio communication. Today, just over 100 years later, the world has realized high-speed wireless communication. The Earth today is surrounded by an “ocean” of radio in which we live. In addition to the radio we are familiar with, mobile phones, walkie-talkies, WiFi, bus cards, access cards and ID cards also use radio frequency identification or near-field communication technology based on radio principles. When we take the subway, we complete a radio communication every time we swipe the subway card . Not only that, even aircraft, high-speed rail, ocean-going ships and even spacecraft are inseparable from radio communication. Through radio communication, we can even remotely control Mars rovers. The “China Sky Eye” located in Qiannan Buyi and Miao Autonomous Prefecture, Guizhou Province is a radio astronomy telescope with a diameter of 500 meters, which receives radio signals from deep space.
Radio not only realizes the dream of being close to each other, but also helps human beings explore the universe.
Aircraft positioning and communication are inseparable from radio
The Origin of the Modem Name
The “cat” we need to use to surf the Internet has a Chinese name of “modem”. Using the radio only needs to download the signal, so the radio only has the demodulation function; while surfing the Internet needs to download and upload data at the same time, so both modulation and demodulation are required.
