At that time, the signal input of TV was very single, usually RF and video AV input. Radio frequency (RF) is the cable TV line or the port connected to the outdoor antenna that we often used a long time ago (of course, the outdoor antenna at that time was different from that without amplifier, not the satellite pot you see now).
In order to cope with many old TV users, many VCRs, VCDs and DVDs all had RF output. This RF output is simply the electromagnetic frequency that can radiate into space, that is, the RF current. He has different frequencies, which is why we have to search for signals on TV series. The tuner is responsible for the main search signal on the TV set, which is used to search the RF signals of video recorders and VCD players to meet the viewing needs.
Many domestic devices, on the one hand, are not so fine in frequency band, on the other hand, they like practical high-power output, and can make the frequency band very wide to facilitate the audience's search. What's more, we are playing the edge ball on the frequencies of cable TV and wireless TV, and the set frequencies are relatively close, which is also for the convenience of search.
In this way, when someone is using, especially using some machines that focus on super-entanglement, super-reception and super-search, nearby neighbors will see images, which is actually interference. This range is only a dozen meters in space, but at that time, everyone's living environment was still relatively close, and the neighbors' upstairs and downstairs were only a dozen meters. It's not surprising to see it. This problem mainly appears in the VCD and DVD era, and the video recorder era is relatively rare, mainly because China has been unable to manufacture video recorders, which are all imported, and the imported equipment is still very strict in radio management such as radio frequency radiation.
Unless there was a unit on each floor at that time, everyone agreed to watch the video, made their own RF amplifier and flat feeder, peeled them off one by one, and threw them downstairs from the upstairs, so that everyone could watch it against the basic window, that is, they could watch it.
At present, the radio frequency management of electronic equipment is very strict, and the factory inspection of equipment is also very strict. There are many household appliances, and the influence of electromagnetic radiation should also be prevented.
Stop talking about VCD. In those days, in order to connect the old TV conveniently, Wang Ba Jr. had a special one with a wireless signal antenna, which could also interfere with the TV. I remember that my neighbors came to our house and said that they were watching TV, which was the shadow of your playing games.
At one time, many rich people installed a black spider wireless phone in their home phones. When he was on the phone, the whole TV screen upstairs was crooked, and voices could be heard from time to time.
In the simulator stage of mobile phone, TV and radio can know in advance when talking.
I have a deep understanding of this. I live in a small house with poor quality, not only without sound insulation, but also without signal. A single man in his fifties lives next door. It is said that his heart disease is quite serious. This product is often played on DVD. When I open my house, the image will ripple, and then I can see what he put on it when I search.
This product will be pornographic almost every day, and sometimes the details will be enlarged. When I was young, I sometimes followed suit. My wife scolded me when she saw it, and then knocked on the wall [covering her face].
One day, I watched him play the disc again, so I subconsciously searched it. The child was just talking and watching TV. As a result, people and animals, naked women and pigs came out, and the son blurted out the big pig. I quickly turned off the TV and the child suddenly cried to see the pig [I want to be quiet]. This is embarrassing.
Later, the neighbor had a heart attack within a few years. I guess every day is too exciting.
In the past, neighbors used VCD to play CDs, and our TV can also receive the same signal. What is the principle? I'll answer!
The truth of this problem is actually very simple, starting with the development history of TV sets and VCD players respectively.
television
The full name of TV is TV receiver. Its birth is the inevitable product of the development of radio technology. After people have solved the problem of wireless transmission of sound, it is urgent to realize wireless transmission of images. 1926, Baird, one of the inventors of television, successfully demonstrated video signal broadcasting and television reception in Britain. Television broadcasting began continuously from 65438 to 0927, which should be the earliest commercial television broadcasting in the world.
In 1980s, China began to popularize black-and-white TV, and the early black-and-white TV could only receive RF signals. With the increasing demand for vision, color TV became popular in the early 1990s. Besides watching TV programs, video recorders and DVD players are also used to watch movies.
VCD player
The full name of VCD is DVD player, and VCD refers to the optical disc that stores video materials. What is used to play VCD discs is commonly known as VCD. China made the world's first VCD DVD player and was listed in world record association as the world's first VCD DVD player. The price of VCD discs is very low, the quality of audio and video is much higher than that of tape recorders, and the storage capacity is very large. Therefore, VCD discs quickly spread throughout the country and entered thousands of households, gradually replacing the old tape recorders. In fact, it can also be regarded as a major iterative version of the old tape video player, because both of them are only because the medium for accessing video data has changed from tape to laser disk.
Most of the audio and video signal outputs of old video recorders are AV interfaces. In order to occupy the market quickly, the video output port of the iterative VCD player is also compatible with the AV standard audio and video output interface. However, in the early 1990s, although a large number of color TV sets supported AV ports appeared, a considerable number of TV sets still did not support AV ports and could not be directly connected with VCD players through two wires.
AV converter
In order to make these stock black-and-white TV sets that don't support AV interface also enjoy the visual pleasure brought by VCD, clever China people creatively invented a device-AV converter. The main function of this adapter is to convert the audio and video signals output by AV interface into RF signals that can be received by TV through radio modulation. In terms of physical connection, one end is connected to the VCD player through the AV cable, and the other end is connected to the TV set through the RF coaxial cable or wireless transmission. Simply put, it is a wireless transmitter of a mini TV station, which transmits on the same frequency as the TV station, but the power is far less than the high-power transmitter of the TV station.
I have the answer.
Although the power of the converter is very small, the signal will still radiate to a small range. If your TV is close enough to this converter, you are blessed. When your neighbors play CDs with VCD, your TV can receive their signals or be disturbed by their home. If the quality of your neighbor's AV converter is slightly worse and the power is slightly higher than the standard, then your neighbors are blessed!
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Early TV sets didn't have AV interface, so there was only one way for early TV sets to receive signals, the RF interface of the antenna.
In order to be compatible with early TV sets, VCD must have both AV and RF interfaces.
Radio frequency interface is an interface with antenna, which can receive signals as far as the wireless TV transmission tower, so of course it can receive the signals of VCD, a neighbor separated by a wall. Of course, the RF signal in VCD is theoretically a cable signal connected to TV, so the manufacturer will attenuate and shield the RF signal when making VCD, but it is inevitable that the antenna will receive the neighboring VCD because it is too close to the neighbor.
To put it bluntly, just like your current WIFI is definitely not for your neighbors, but your neighbors will definitely receive your WIFI signal, and the RF signal at that time was not encrypted. The TV will be fine if it finds that frequency!
I believe many users who have used VCD players have encountered similar situations. When a VCD movie is played on its own VCD player, the neighbor's TV can actually receive it. This happens because of the RF interface.
Early DVD players all had an RF interface, but they didn't need it at ordinary times, because DVD players and TVs were connected together, and they were both AV and audio ports. So as long as the DVD player at home works, there will be radio frequency signals released. Under normal circumstances, RF signals can cover the range of 20 meters in Fiona Fang.
Therefore, after the DVD player works, TV users within ten meters of Fiona Fang can watch other people's DVD players without connecting wires as long as they search the frequency band of RF signals. Of course, if you don't search each frequency band manually, the TV can't receive the content played by the shadow spy machine.
In fact, many DVD players that can play VCD or DVD do not meet the requirements, which will interfere with the neighbor's TV. And as long as the DVD player plays the content, neighbors can receive it directly, because the RF chip of the DVD player is not up to standard.
In addition to DVD players, bully learning machines and other products also have RF chips, which will also interfere with TV at work. As long as the neighbor's TV is tuned to the corresponding frequency band, you can also receive the content of the bully learning machine. Therefore, neighbors can receive the contents played by DVD players, which are all caused by RF ports.
I did this a long time ago. At 1998, I bought a BBK SVCD. My living room is a newly bought color TV. In my bedroom, I bought an old black and white TV set a few years ago. In order to watch movies while lying down, I use an aluminum coil to connect it to the RF output line of BBK·SVCD. Color TV is still connected with frequency-division signal, so that both color TV and black-and-white TV can watch it. Adjust the receiving antenna of the black-and-white TV again. The bedroom door is as clear as when it is opened, but it is almost ultramicro when it is closed. If there is no aluminum coil, only the radio frequency line is extended, there will be snowflakes, but you can see them, which is very unclear. If the RF cable is unplugged, only the RF terminal is left, and there is no signal, that is, the signal is too weak. In fact, the principle is very simple, which is equivalent to the transmission tower of a TV station, except that the output power of the RF line is too low. So you can receive the vcd signal from your neighbor's house because the distance is very close, which is also related to the neighbor's air quality and transmission power. If your receiving antenna amplifier is very powerful, you can receive and watch. Assuming that your receiving antenna amplifier is strong enough, you can also receive RF signals from other countries, provided that the RF line of that country is open to radiation, which depends on the length and quality of the RF transmission line of that country.
At that time, the TV signal input was very simple, that is, radio frequency and AV input. Radio frequency (RF) is an ordinary cable TV line or a long-term connection port with an outdoor antenna (of course, there was a difference between an outdoor antenna and an amplifier at that time, not the satellite antenna you see now).
In order to deal with many old TV users, many VCDs, VCDs and DVDs are equipped with RF output. This RF output, in short, is the electromagnetic frequency that can be radiated into space, that is, RF current. It has different frequencies, which is why we need to search the signals of TV series. The main search signal on TV is tuner, which is used to search VCD and VCD RF signals to meet the viewing needs.
Many domestic devices, on the one hand, are not so fine in frequency band, on the other hand, they like practical high-power output, which can broaden the frequency band and facilitate audience search. More importantly, it is playing the edge ball of cable TV and wireless TV frequencies. The frequency setting is relatively close, also for the convenience of search.
In this way, when someone uses it, especially when using some machines that mainly engage in super-entanglement, super-reception and super-search, the neighboring neighbors will see the image, which is actually interference. In terms of space, this area is only about 10 meter, but people's living environment was relatively close at that time, and the distance between the upstairs and downstairs of neighbors was only about 10 meter. It's not surprising to see this. This problem mainly occurs in the VCD and DVD era, and it is relatively rare in the VCR era. The main reason is that China is unable to produce video recorders, and all of them are imported. However, imported equipment is still very strict in RF radiation management.
Unless there is a building that is a unit, everyone will make an appointment to watch the video. Someone skillfully made a RF amplifier and a flat feeder, and peeled them off one by one. From upstairs to downstairs, you can basically see the windows, that is to say, you can see them.
At present, the radio frequency management of electronic equipment is very strict, and the factory inspection of equipment is also very strict. More household appliances should also be protected from the influence of electromagnetic radiation.
Stop talking about VCD. When using the red and white machine, in order to facilitate the connection of the old TV, the bully has a wireless signal antenna specially, which will also interfere with the TV. I remember my neighbor came to my house and said he was watching TV. Are the shadows of your game.
On another occasion, many rich people installed black spider wireless phones in their mobile phones. When he was on the phone, the whole TV picture upstairs was crooked, and these words could be heard from time to time.
In the mobile phone simulator stage, when you make a phone call, TV and radio can know in advance.
Neighbors play vcd, others receive TV. It was normal ten years ago. The scene at that time is still vivid, and it really conforms to the national conditions at that time. Usually, ordinary people have a vcd with a miscellaneous brand, and the radio frequency is 1 1, and the radio frequency is 10. Set the black and white TV to 10 or 165438. The picture is clear, the sound is pleasant, and you can watch it happily for a long time. Because it is a wireless signal, neighbors within a dozen meters will benefit. What my family sees, his family can see. Thanks to the RF converter in vcd, Av signals can be converted into high frequency signals.
If someone plays a VCD near your home, you can receive the signal, which is estimated to be many years ago. At that time, many antennas were used to receive signals.
This antenna has two functions, one is receiving and the other is transmitting. The wireless electromagnetic signal we receive is actually the electromagnetic signal that our film and television signals are edited into different frequency bands. Then, the electromagnetic wave propagates in space through the transmitting antenna. After our receiving antenna captures this electromagnetic signal, it is introduced into our TV set and converted into audio and video signals through the circuit.
Then, when your neighbor plays VCD, make sure that his outdoor antenna is connected to the TV. At this time, the VCD signal propagates to the outdoor antenna through the antenna interface of the TV set, and then is emitted through the antenna. At this time, your neighbor's outdoor receiving antenna actually becomes a transmitting antenna. So your neighbor's VCD signal is transmitted and can be received within the range of electromagnetic wave radiation. At this time, your outdoor receiving antenna receives the VCD film and television electromagnetic wave sent by the neighbor antenna, and then you can receive the same program through the conversion of the TV circuit.
If your neighbor disconnects his outdoor antenna and TV interface when playing VCD, you will not receive the signal at this time, because the signal of VCD cannot be transmitted through his outdoor antenna.