1888, German scientist heinrich hertz discovered the existence of radio waves.
1895, Soviet physicist Alexander Stepanovich Popov claimed that he successfully sent and received radio signals in two places 600 yards apart.
Later in the same year, Guglielmo Marconi, the son of a wealthy Italian businessman who was only 2 1 year-old, successfully launched his first launch on his father's manor land by radio waves.
1897 popov successfully communicated with the land platform on the naval cruiser with its own wireless communication equipment.
Marconi sent radio waves to the other side of the Atlantic in 190 1 year.
1906, the Canadian inventor Fessenden made the first sound, and the radio broadcast began.
In the same year, American Reed forest invented the vacuum tube, which was the ancestor of vacuum tube radio.
Since then, improved transistor radios (atomic particle radios) and transistor radios have appeared.
In fact, there is controversy about the inventor of the radio; Some say it's popov, others say it's Marconi. Alexander stepanov Yiqi popov (1859 1906), a Russian physicist, was born in Russia in 1859, and is the son of a priest. Since 1885, I have devoted myself to studying radio communication, following in the footsteps of my predecessors Maxwell and Hertz. In a speech on May 7th, 1895, he disclosed his research results of successfully transmitting and receiving radio signals after Rocky improved the receiver. 190 1, professor of physics at St. Petersburg university; Some people think that he is the real inventor of radio, but perhaps because he is a scholar and is too focused on academic research, the invention of radio has not been widely known by the world; Perhaps it is because popov's invention was regarded as a great weapon in the military by the Soviet Navy and classified as confidential. On the contrary, Marconi is very business-minded. It is said that he established the first radio factory in the world and obtained the patent right. However, some people criticized that the radio he made only combined other people's inventions-Hertz coil antenna, Lodge's tuner and receiver, and Nikolai Terca's spark device. However, he has made great contributions to the practical application of radio equipment!
Secondly, how the invention of the radio was recorded in history is controversial about the inventor of the radio.
Some say it's popov, others say it's Marconi. Popov, Russian physicist, 1859 was born in Russia, the son of a priest; He devoted himself to the research of radio communication from 1885, followed in the footsteps of Maxwell and Hertz, and in a speech on May 7, 1995, he announced his research results of successfully transmitting and receiving radio signals after improving Lodge's receiver.
190 1, professor of physics at St. Petersburg university; Some people think that he is the real inventor of radio, but perhaps because he is a scholar and is too focused on academic research, the invention of radio has not been widely known by the world; Perhaps it is because popov's invention is regarded as a great weapon in the military by the Russian navy and classified as confidential. On the contrary, Marconi is very business-minded. It is said that he established the first radio factory in the world and obtained the patent right. However, some people criticized that his radio only combined other people's inventions-Hertz coil antenna, Lodge's tuner and receiver, and Nicholas? Tesla's spark device.
There is no denying that he has made outstanding contributions to the practical application of radio equipment. Today, we are used to calling those radios which have no power supply and only one semiconductor element in the circuit "crystal receivers".
Crystal receiver refers to passive radio without amplification circuit, which consists of antenna, ground wire, basic tuning circuit and minerals as detectors. It is the simplest radio receiving equipment, mainly used to receive medium wave public radio broadcasting. 19 10, American scientists Dunwoodie and piccard used minerals as detectors, hence the name.
Because the crystal receiver does not need power supply and has a simple structure, it is very popular with radio enthusiasts. So far many enthusiasts still like DIY and research. But only one person can listen to it, and the receiving performance is poor, which of course objectively restricts the popularization and development of broadcasting.
1923 65438+1On October 23rd, Americans set up China Radio Company to broadcast radio programs and sell radios. The United States produces the most radios, one of which is a crystal receiver and the other is an electron tube radio. 1904, the world's first electron tube was born under the British physicist Fleming.
The birth of the first electron tube marked that the world entered the electronic age. Electron tube is an electronic device that generates current conduction in a closed container (usually a glass tube) and uses the effect of electric field on electron flow in vacuum to obtain signal amplification or oscillation.
Electron tube is the originator of the electronic age. After the invention of the electron tube, the circuit and receiving performance of the radio have made revolutionary progress and improvement. Before 1930, almost all electron tube radios used two sets of DC power supply, one set of filament power supply and one set of anode power supply, which consumed a lot of electricity, and the batteries needed to be replaced in a short time, so the radio was expensive to use.
Around 1930, radios using AC power were successfully developed, and electron tube radios entered people's homes on a large scale. However, due to the shortcomings of large volume, high power consumption, serious heating, short life, low efficiency of electric energy utilization, fragile structure and the need for high-voltage power supply, most of its applications have been basically replaced by solid-state device transistors.
1958 12 in September, kilby developed the world's first integrated circuit. Since then, integrated circuits have gradually replaced transistors, making it possible for microprocessors to appear, laying the foundation for modern microelectronics technology and modern information technology, creating a new era in the history of electronic technology, and making all electronic products that we are used to now possible.
On a tiny semiconductor wafer of several square millimeters, thousands of transistors, resistors and capacitors, including connecting wires, are made into an electronic component with a certain circuit function, which is called an "integrated circuit". The integrated circuit has the advantages of small volume, light weight, few leads and solder joints, long service life, high reliability, good performance and low cost, and is convenient for mass production.
Integrated circuit is the most advanced transistor in essence, which makes electronic components take a big step towards miniaturization, low power consumption and high reliability. Using integrated circuits to assemble electronic equipment, the assembly density can be several tens to several thousand times higher than that of transistors, and the stable working time of the equipment can also be greatly improved.
Three. The history of the development of radio crystal receivers Today, we are used to calling those radios which have no power supply and only one semiconductor element in the circuit "crystal receivers".
Crystal receiver refers to passive radio without amplification circuit, which consists of antenna, ground wire, basic tuning circuit and minerals as detectors. It is the simplest radio receiving equipment, mainly used to receive medium wave public radio broadcasting. 19 10, American scientists Dunwoodie and Pikard used minerals as geophones, hence the name.
Because the crystal receiver does not need power supply and has a simple structure, it is very popular with radio enthusiasts. So far many enthusiasts still like DIY and research. However, only one person could listen to it, and the receiving performance was poor, which objectively restricted the popularization and development of radio broadcasting at that time.
Electron tube radio 1904, the world's first electron tube was born under the British physicist Fleming. The birth of the first electron tube marked that the world entered the electronic age.
Electron tube is an electronic device that generates current conduction in a closed container (usually a glass tube) and uses the effect of electric field on electron flow in vacuum to obtain signal amplification or oscillation. Electron tube is the originator of the electronic age. After the invention of the electron tube, the circuit and receiving performance of the radio have made revolutionary progress and improvement.
Before 1930, almost all electron tube radios used two sets of DC power supply, one set of filament power supply and one set of anode power supply, which consumed a lot of electricity, and the batteries needed to be replaced in a short time, so the radio was expensive to use. Around 1930, radios using AC power were successfully developed, and electron tube radios entered people's homes on a large scale.
However, due to the shortcomings of large volume, high power consumption, serious heating, short life, low efficiency of electric energy utilization, fragile structure and high voltage power supply, most of its applications have been basically replaced by solid-state device transistors. Transistor radio transistor is a solid semiconductor device, which can be used for detection, rectification, amplification, switching, voltage stabilization, signal modulation and other functions (gold, silver, copper, iron and other metals with good conductivity are called conductors.
Wood, glass, ceramics, mica, etc. It is not easy to conduct electricity and is called an insulator. A substance whose conductivity is between conductor and insulator is called a semiconductor.
Transistors are made of semiconductor materials, most commonly germanium and silicon. 1947 12.23. The first transistor was born in Bell Laboratories, which was an important invention in the 20th century and a forerunner of the microelectronics revolution. Since then, mankind has entered the rapidly developing electronic age.
Transistor radio is a small radio based on transistor. 1954 10 081October18th, the world's first transistor radio was put into the market, which only contained four germanium transistors.
Only after the transistor appeared did the radio really become popular. In the late 1950s, China also began to develop transistor radios, which were produced in the 1970s.
Germany's Gende, Japan's Sony, the Netherlands' Philip, and China's famous brands of old radios such as Red Light, Peony and Panda all bear witness to this period of history. 1958, the first domestic transistor radio was successfully developed in China.
Transistor radio has won people's love for its advantages of low power consumption, no need of AC power supply, small size and convenient use, and has gradually occupied a dominant position in the market, becoming the most popular and cheapest electronic product. Transistor is one of the greatest inventions in modern history. After the invention of transistor, electronics has made rapid progress.
In particular, the appearance of PN junction transistor has opened up a new era of electronic devices and caused a revolution in electronic technology. Integrated Circuit Radio1958 September 12, American jack kilby developed the world's first integrated circuit.
Since then, integrated circuits have gradually replaced transistors, making it possible for microprocessors to appear, laying the foundation for modern microelectronics technology and modern information technology, creating a new era in the history of electronic technology, and making all electronic products that we are used to possible. On a tiny semiconductor wafer of several square millimeters, thousands of transistors, resistors, capacitors and connecting wires are made together and used as devices with certain circuit functions, which are called "integrated circuits".
Integrated circuits have the advantages of small volume, light weight, less lead-out wires and solder joints, long service life, high reliability, good performance, and low cost, which is convenient for mass production. Integrated circuit is the most advanced transistor in essence, which makes electronic components take a big step towards miniaturization, low power consumption and high reliability.
Using integrated circuits to assemble electronic equipment, the assembly density can be several tens to several thousand times higher than that of transistors, and the stable working time of the equipment can also be greatly improved. In China, 1982, the integrated circuit radio appeared.
DSP Radio DSP technology Radio is a new type of radio, which receives radio analog signals through an antenna, amplifies them in the same chip, then converts them into digital signals, then processes them, and then restores them to analog audio signals for output. The essence of DSP technology is to replace "hardware radio" with "software radio", which greatly lowers the threshold of radio manufacturing.
192365438+1On October 23rd, American Osborne and China Zeng Jun founded China Broadcasting Corporation, which broadcasted radio programs in Shanghai for the first time and sold radios at the same time. There are more than 500 radios in the city, which are the earliest radios in Shanghai.
Later, with the continuous establishment of radio stations, radios gradually appeared in Shanghai, all of which were imported, with the most produced in the United States. One of them is a crystal receiver, and the other is a tube radio. People like to use crystal receivers. 1In August, 924, the Ministry of Communications of Beiyang Government promulgated the Interim Provisions on the Installation of Radio Receivers, allowing citizens to install radios.
There are more and more people installing radios, and the method is mostly to connect them with regenerative wires. In August of the same year, Yan Jingyang of Shanghai Jiande Savings Office successfully installed a radio by superheterodyne line connection.
In June, 5438+the following year 10, the crystal receiver and tube radio assembled by Yamei Radio Co., Ltd. in Songjiang Library were successful, receiving not only the radio waves of Shanghai Radio Station, but also the radio waves of Japan.
4. What are the historical waves on the radio? How does it spread? Like the "unfair treatment" suffered by alternating current in the early days, radio was once considered useless for a long time after it was discovered more than 100 years ago, and this situation lasted until 190 1 year due to the epoch-making experiment of Italian scientist Marconi.
For this experiment, he camped in Signal Mountain (located in the southeast corner of Canada) and finally received transatlantic radio signals from Britain. This experiment proves to the world that radio is no longer a novelty confined to the laboratory, but a practical media.
Introduction of direct amplifier and superheterodyne radio unit circuit-antenna and input loop public broadcasting has been carried out in all countries since it came out. The radio circuit has been simplified and simplified. Because of the different use environment and objects, its index parameters are not comparable to those of special communication equipment, but it is still a complete radio receiving equipment, and its working principle and mode are the same. The difference is that the latter has special requirements for anti-interference ability and high sensitivity. Here we introduce some independent unit circuits of the radio, including input circuit, detection circuit, temperature compensation and secondary automatic gain control circuit, frequency fine-tuning circuit, duplex circuit and sliding class A audio power amplifier circuit specially designed to save the number of semiconductors used in the early days of the radio. These circuits are also the basic components of any communication system.
Analysis and comparison of several regenerative multiplexing unit circuits: diode radio has low sensitivity and can only receive broadcasts from nearby high-power radio stations. In order to solve this problem, the method is to add a high-frequency amplifier stage in front of the detector to amplify the weak signal received by the antenna first.
This transistor radio is suitable for large and medium-sized cities and rural areas near radio stations. If it is used in areas far away from radio stations, it is often necessary to connect outdoor antennas to obtain satisfactory listening effects.
The working principle of superheterodyne radio Compared with simple radio, superheterodyne radio is far superior to simple radio in sensitivity, selectivity, volume and sound quality, although the circuit is more complicated and more transistors and components are used, so the cost is more expensive. It is different from a simple radio, it adds two parts: frequency conversion stage and intermediate frequency amplification stage.
Introduction of unit circuits of direct amplifier and superheterodyne radio —— Other unit circuits This paper mainly introduces the representative design circuits of post-stage audio amplification in the period of expensive transistors —— frequency conversion stage, automatic gain control circuit of intermediate frequency amplification, temperature compensation circuit and sliding class A power amplifier, and their working principles and specific circuit analysis. The winding method of magnetic antenna and common components of radio If you plan to know more about it and make transistor radios yourself, it is necessary to have a general understanding of common components.
In addition to resistance-capacitance components and transistors, generally speaking, commonly used components refer to: bar antenna, intermediate frequency transformer and oscillating coil, speaker and earphone. The method of assembling and adjusting superheterodyne radio with discrete components is easy to manufacture, but it is not a simple matter to manufacture good performance.
The superheterodyne radio has a set of debugging methods, which are proved to be feasible by theory and practice. This method can also be extended to the design, assembly and debugging of other similar radio equipment. At the beginning of this century, people invented the wireless telegraph to transmit code information, and then invented the wireless telephone to transmit voice.
So people think: since radio can transmit sound, it can also transmit music; Moreover, radio signals can be received by many people at the same time, so they can be broadcast to the public as radio stations. 1906, in a radio communication experiment, Professor Fessenden of the United States used modulated radio waves to send music and voice for the first time in the world, and many radio communication stations nearby received Professor Fessenden's signal.
However, it is impossible for the general public to own a radio. In order to realize radio broadcasting, it is necessary to have a radio receiver, that is, a radio, which is specially used for listening to sound signals.
Crystal receiver is a simple receiver in the early days of radio broadcasting. It was invented by American scientists Dunwoodie and piccard. 19 10 years, with the rise of radio broadcasting, Dunwoodie and piccard began to study radio receivers. They experimented with some mineral crystals and found that galena has detection function. If you connect them with several simple components, you can receive the broadcast programs played by the radio station.
The crystal receiver receives radio waves through an antenna, and the machine is equipped with a simple tuning circuit. The received radio waves can be selected according to the required wavelength and sent to the ore detector, and the current recording audio signal is detected from the radio waves, and then the current is converted into sound through headphones. The crystal receiver does not need a battery and has a simple structure. Almost all radio enthusiasts can assemble it by themselves.
But only one person can listen, and the reception performance is poor. At the beginning of this century, great progress has been made in the research of radio propagation technology, and various radio components such as diodes with detection function and triodes with amplification and voltage stabilization functions have been invented one after another, which solved some problems in long-distance radio transmission and reception and provided technical and material conditions for the development of home radios.
19 12 years, Fessenden invented the heterodyne circuit in the research of improving the original receiver. The circuit works through the interaction of the received signal and the local oscillation generated by the receiving point. The combination of these two converter signals forms the beat of the audio, that is, the difference frequency of the two waves. Its invention laid the foundation for superheterodyne and sideband reception in the future.
19 13, American radio engineer Armstrong invented the superheterodyne circuit, which can effectively prevent two signals with similar frequencies from interfering with each other in the receiver, ensure that signals with different frequencies can be distinguished, and enable the receiver to receive signals with different frequencies respectively. In the same year, French Lv Xian and Levy made a radio using superheterodyne circuit and applied for a patent, thus ending the situation that many knobs and keys needed to be installed in the past.