How much do you know about the “family history” of mobile phone signal blockers?



Mobile phone signal blockers are known by thousands of households because of the college entrance examination, but their birth is not because of the college entrance examination.

1. What is a mobile phone signal?
The game around the field of radio signals is also like the rivers and lakes, with two forces of good and evil, and the higher the Tao, the higher the devil. Where there is technological development, there are black loopholes. Signals and signal shielding are just like two contradictory things, confronting each other and running in a spiral. To understand the symbiotic relationship between the two, let’s start with their essence: What exactly is a signal? In this world, there are things we see, such as light, water, and everything within reach. There are also things that we can’t see, but they actually exist, such as air, heat energy, and waves. cell phone jammer

They are beyond the range of human vision, but they are inseparable from humans. In the science fiction movie “Lucy”, Scarlett Johansson plays a girl who has special abilities due to the misuse of drugs. She can see things that we can’t see. For example, when people make phone calls, she can see the scene of each mobile phone connecting to radio waves. Of course, this is science fiction. If you are interested, you can go and have a look.

In fact, these things do exist. Its essence is electromagnetic waves. In 1864, German physicist Hertz proved the existence of electromagnetic waves, and the speed of propagation is the same as the speed of light. Later, people used the name Hertz as a unit to indicate the frequency of waves. 1 Hz means that this wave vibrates once in 1 second. 10,000 Hz means that it vibrates 10,000 times in 1 second. The wifi we use is often marked with 2.4 GHz. It means that in 1 second, the radio waves it emits can vibrate 2.4G times.


Look carefully at the band logo, all with MHz, indicating that the frequency of the radio waves it uses is how many megahertz it vibrates in 1 second. The more times it vibrates, the stronger the ability of the wave to penetrate walls and obstacles, but it will weaken rapidly after penetration, so the transmission distance is short.

In essence, the radio waves used for mobile phones are the same as the principles of radios, microwave ovens, and hospital ultrasound instruments. They all use radio waves of a certain frequency band to work.

2. How do radio waves transmit sound and pictures?
Waves can be big or small, and the amplitude of vibration can be high or low. If the first wave is high and then low, these are two different signals. This is similar to the digital signal in the bit era. Digital signals are the binary world of 0 and 1. The high and low waves can be completely matched with the 0011 of a certain digital signal. However, this requires a translation – converting 0011 into corresponding waves on this side, and converting the waves into 0011 on the other side.


We call this translation device a modem. It has two functions: conversion to waves is called modulation, and conversion back to digital signals is called demodulation. In addition, it vibrates at a frequency of trillions or hundreds of millions of times per second. It is conceivable that there are many sounds, images, and movies that cannot be transmitted to us within 1 second? Modems are good things. Their English name is Modem, which is the “cat” we need to surf the Internet. Electromagnetic waves are common, but modems have only appeared for a few decades. Therefore, our communication technology is also constantly improving with the evolution and upgrading of modulation and demodulation technology.

3. The family history of mobile phone signals
Mobile phone communication technology has been updated five generations in 30 years, from the big brothers in the 1990s to the current 5G, namely 1G, 2G, 3G, 4G, and 5G. The G here is not the unit of quantity mentioned above, but the abbreviation of the English word Generation. 1G is the 1st Generation Mobile Communication System.

Translated, it is the first generation of mobile communication system. 1G signal is the perfect realization of radio wave carrying sound signal. Two big brothers can realize long-distance calls through signal transfer, amplification, and transmission. This was an amazing high-tech at the time, and only big bosses could afford it. However, it can only make calls, not even send text messages.


In the late 1990s, 2G appeared, Motorola could send text messages, and 2G became the era of text + sound. 3G, 4G, and 5G have developed into sound + text + image + video mode. During this period, the things carried by radio waves have become more and more, larger and faster. The reason is that in different eras, the way radio waves carry signals is different. But the principle remains the same, signal + radio wave = mobile phone signal.

There are thousands of mobile phones and thousands of radio waves. The three major operators share it, and the government departments stamp it, and each company has its own fixed frequency band. And each band has many different frequencies and channels, and each channel is not occupied by a mobile phone 24 hours a day. Therefore, countless mobile phones in an area can be used calmly without interfering with each other. The only problem is the attenuation of transmission signals. In the meantime, some base stations need to be built to relay signals. If you buy a house in the suburbs and encounter poor signals, it is because it is far from the base station, the signal is attenuated, and the community has no amplifier installed.

4. How does the signal jammer interfere?
Back to the topic, the mobile phone signal jammer used in the college entrance examination is used to block the signals of mobile phones and base stations. Signal jammers can interfere in two ways. One is to interfere on the way the mobile phone transmits the signal so that the base station cannot receive the signal; the other is to interfere on the way back from the base station so that the mobile phone cannot receive the signal. The former is called the uplink frequency band, and the latter is called the downlink frequency band. Either one can achieve signal shielding within a certain range. But the two have different effects. Uplink interference affects the base station’s reception of all nearby mobile phone signals. Downlink interference only affects the use of mobile phones within a certain range. Therefore, improper use of the jammer will affect nearby users. Therefore, when the jammer first appeared, it was controversial, even boycotted and stigmatized.


How does the jammer interfere?
When using a jammer, you only need to scan the radio waves in a certain frequency band. When a signal is transmitted, it will emit an identical electromagnetic wave in this band. It uses high-intensity power to amplify the meaningless interference signal it emits to cover it and suppress it, so that the mobile phone and base station cannot recognize the signal, thereby achieving blocking and interference. It can be seen that the so-called shielding is not the absence of a signal, but the signal is interfered and cannot be recognized. According to this principle, it is also simple to counter-shield the signal. It only needs to make the power of the receiving and transmitting signal greater than the power of the shielder. But the mobile phone and power are far from comparable to the jammer signal, and the base station is too far away, and it cannot be compared with the jammer at the examination site.

In addition, if the frequency used by the new generation of communication technology exceeds the frequency band that the jammer can scan, then no matter how hard the jammer works, it will be powerless.

5. The jammer was first used in the college entrance examination
It’s a long story. This signal jammer was not originally used in the examination room, but in the 2G era, it was used for prison confidentiality. To this day, the prison system is still the place where the jammer is used the most and most strictly. And it is written in the documents of the Ministry of Justice. Mobile phone signal shielding in my country emerged around 2000, when it was the 2G era. This spear and shield was very controversial at the time. Some people said that it was too powerful and would affect human health, just like when microwave ovens were introduced to the market, “scandals” arose. In fact, the key is that its appearance affected the service effect of operators and caused resistance. Later, some lawless elements used this to do bad things.

標籤: signal jammer