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The United States’ confidence in the Iraq war is largely based on high-tech military equipment. Guided bombs such as JDAM can theoretically carry out precise “surgical” strikes against hostile parties. The Iraqis used low-cost signal jammers in an attempt to jam the mythical Global Positioning System (GPS) weapons guidance signals.  signal jammer
This kind of GPS jammer is only the size of a mobile phone and can be purchased in the market for a few hundred dollars. The Iraqis regard it as a magic weapon to “defeat foreign artillery” – it is said that it can interfere with the GPS signal, thereby allowing the Americans to accurately The weapon was “hitting crookedly.” It is said that the US military has found and destroyed 6 such jammers in Iraq.

The US military’s “Global Positioning Satellite System” is a signal network composed of 27 satellites. It can not only position and control weapons, but also provide navigation for troops and aircraft accurate to meters. If the GPS signal can be interfered with for a long time, it will cause the entire logistics system of the US military to malfunction.

Before the war began, U.S. military experts warned that the Iraqis’ GPS jammers might disable U.S. guided bombs. Douglas Lowero, the person in charge of the GPS system program in the United States, believes that this is nonsense. There is no instrument on the market that can effectively interfere with GPS signals.

How powerful is this gadget?

A Russian company makes such a cheap GPS jammer. Theoretically, this jammer can interfere with satellite signals within a radius of 200 kilometers. The signal sent by U.S. navigation satellites to the GPS receiving antenna is very weak, and its strength is only about one billionth of the signal received by a general TV antenna. Therefore, satellite navigation systems commonly used in automobile transportation, navigation and adventure travel are very susceptible to interference from such GPS jammers. However, navigation equipment used for military purposes is relatively “robust” and less susceptible to interference.

The “C/A” code of the GPS system is used for civil purposes, and its positioning accuracy can reach about 5 meters. The military uses the “P” code, which has a positioning accuracy of up to one meter.

Not only is the military’s “P” code more precise, it’s also encrypted and therefore less susceptible to interference. Douglas Lowero believes that military GPS codes are thousands of times more resistant to interference than civilian codes. He said that GPS jammers are only effective within a radius of a few kilometers. At most, they can only interfere with GPS-guided weapons within this range, and it is impossible to make guided weapons stray.

In addition to satellite positioning systems, the U.S. military’s precision weapons are also equipped with another navigation mechanism-the Inert Navigation System (TNS). The TNS system will not be interfered by external signals. Its working principle is to use the inertia of the high-speed rotating gyro system for positioning. Before the precision bomb is launched, the TNS system is input with a set of parameters that define its starting position; after the bomb is launched, the gyro system interprets each trajectory change relative to the starting position as a steady-state disturbance, thereby performing a new position calculation. describe.

The positioning error of a GPS-guided bomb is about 3.5 meters, while the positioning error of TNS is about 20 meters. If used to attack military installations, this positioning error of TNS can be ignored. However, if it is used to attack military targets in residential areas, the possible consequences of this error cannot be underestimated.

The mobile phone signal jammers purchased by the school in previous years did not have the function of interfering with 5G signals because 5G had not been launched when they were originally purchased. In the current use of signal shielding in examination rooms, they can no longer shield 5G signals. This leaves school examination room users faced with the problem of how to upgrade or replace the original mobile phone signal jammer. So how should you choose a 5G signal jammer during school exams? signal jammer
School examinations require the use of 5G signal jammers for examination room management to ensure that candidates will not be affected by wireless signals from the outside world. Therefore, it is recommended to consider the following points when choosing a 5G signal jammer for school exams:

1. First, make sure that the selected 5G signal jammer can block the signal in the 5G frequency band. Generally speaking, the frequency bands of 5G signals are divided into mobile 5G (2515MHz-2675MHz, 4800-4900MHz), China Unicom 5G (3500MHz-3600MHz), China Telecom 5G (3400MHz-3500MHz), radio and television 5G (703MHz-733MHz, 758MHz-788MHz, 4900MHz -5000MHz), so you should purchase a jammer that supports these frequency bands.

2. Choose a brand or model with good shielding effect. You can refer to some well-known domestic and foreign brands or models with a certain reputation in this field for comparison. Of course, you should also choose a signal jammer model with appropriate power based on your own usage scenario and environment to purchase a 5G signal that suits your needs. jammer.

3. Consider purchasing a multi-functional model that has other functions besides shielding, such as shielding GPS, Bluetooth, WIFI and other wireless signals, in order to adapt to the shielding requirements of different types of communication equipment in exam scenarios.

4. Finally, the price of the signal jammer must be considered. After all, the budget cost of some school examination rooms is limited, so it is necessary to choose signal jammer products with high cost performance. Of course, in addition to considering the price, the quality and performance of the 5G signal jammer should be given priority. Choosing a high-quality and high-performance 5G signal jammer can provide better protection and security for the exam process.

How to block your child’s cell phone signal? Many children have been exposed to various electronic products since birth, which is actually harmful to the growth and development of children, so we all need to keep children away from mobile phones in a timely manner.

Especially from last year to this year, due to the impact of the new coronavirus epidemic, many children have become accustomed to playing mobile phones at home and using computers to play games online. Having a signal jammer can help children slowly quit the habit of surfing the Internet and have better control. The amount of time children spend online. At the same time, adults can also spend less time using mobile phones and interact more with their children and their families. Helps improve family happiness index.

signal jammer

So how to block children’s mobile phone signals and control the time when children use the Internet?

Method/Step 1: Restrict children’s mobile phone access to the Internet in the router
Currently, all types of routers can filter the MAC address of mobile phones in the security settings. In this way, children’s mobile phones can be prohibited from accessing the Internet.

If you are more flexible, you can use the router to limit the time period for children to access the Internet, as well as the Internet speed, etc. Most current routers have this feature. By limiting the Internet speed, children can only check information when using mobile phones, but cannot play games.

Method/Step 2: Turn off mobile data service
Using the previous method, you can restrict the child’s mobile phone from connecting to the home Wi-Fi to access the Internet, but what should you do if the child can still access the Internet using data traffic? At this time, contact the operator and turn off the data service function of the child’s mobile phone, so that the child’s mobile phone can only make calls. Phone calls and text messages are now available, and the service is free.

If the child needs to access the Internet, we can turn on the hotspot on the mobile phone for the child to use temporarily, and then turn off the hotspot after use.

Method/Step 3: Use a signal jammer
Wireless networks make it easier for people to access the Internet, but the problems caused by them cannot be ignored. It’s not just a matter of access to the network, it’s also a matter of network security. In order to maintain a good network environment, signal jammers are installed in many places to prevent excessive network usage. This equipment has been widely used in countries and regions around the world. Schools, prisons, libraries, reading rooms and gas stations are typical examples.

Vehicle-mounted signal jammer equipment is an interference device installed on a vehicle. It is mainly used to shield or interfere with the signals of wireless communication equipment, such as mobile phone signals and remote control signals. During use, its interference effect is directly related to whether the task can be successfully completed, so it places very strict requirements on the vehicle-mounted signal jammer equipment itself. The factors that affect the interference effect of the vehicle-mounted signal jammer include the following aspects.    signal jammer

1. Signal strength at the use site: The signal interference range of the vehicle-mounted signal jammer equipment is affected by the signal strength at the site. The on-site signal strength is mainly determined by the distance of the base station and is closely related to the strength of the mobile phone signal. However, different mobile phone operators also have different strategies for signal distribution, making signal quality difficult to predict. Therefore, when setting up a vehicle-mounted signal jammer device, the spectrum distribution and signal strength can be measured to select specific modules to maximize the interference range, or contact the operator to reduce the signal strength on site. For other remote control signals, the interference effect depends on the distance between the signal source and the suspected explosive, which is difficult to predict. Therefore, the focus should be on shielding the remote control signal so that the interference remote control signal module of the vehicle-mounted signal jammer device can interfere seamlessly.

2. The transmit power of the radio frequency module: The interference effect of the vehicle-mounted signal jammer device is also related to the transmit power of the radio frequency module. The greater the transmission power, the greater the interference range. However, if the bandwidth of the signal transmitted by a single module is too wide, the interference effect will also be affected. In order to achieve the best interference effect, high-power radio frequency modules should first be selected, and secondly, the frequency bandwidth of the signal transmitted by a single module should be reasonably allocated to maximize the interference range.

3. Adaptability of vehicle-mounted signal jammer equipment: The types and frequencies of wireless signals interfered by vehicle-mounted signal jammer equipment vary, so the adaptability of vehicle-mounted signal jammer equipment is particularly important. Vehicle-mounted signal jammer equipment should have interference adaptation capabilities for various wireless signal types and frequencies, so that it can exert the maximum interference effect in various environments and ensure the safety and stability of the equipment.

4. Interference from the vehicle itself: The vehicle-mounted signal jammer device itself will also produce a certain amount of electromagnetic wave interference, which may have an impact on other electronic equipment. Therefore, additional shielding or isolation measures are sometimes necessary to reduce the effects of internal interference in vehicle-mounted signal jammer devices.

Cell phone signal jammers are not the latest scientific invention, but the high demand in the US market has driven dealers to stock up on them. Users of mobile phone signal jammers include coffee shop and barber shop owners, restaurateurs, theater operators, bus drivers and daily commuters who use public transportation to and from get off work.

signal jammer

This device is only as big as a cigarette box and is very convenient to hide. Users only need to press a button, and the device will emit a radio interference signal, blocking the communication between all mobile phones and signal towers within a radius of 4.5 meters to 9 meters. Cell phone users experiencing signal interference will immediately see the words “No Network Available” on their screen. Cell phone jammers range in price, from $50 to several hundred dollars, and the radio signal they emit varies in strength. The more expensive the mobile phone signal jammer, the wider the range it can affect.

However, U.S. law prohibits private blocking of signals and imposes fines of up to $11,000 on first-time violators. According to the New York Times, relevant U.S. departments have investigated many companies that manufacture such devices and have also held many users accountable.

The U.S. Wireless Industry Association submitted an opinion to the Federal Communications Commission on November 3, requesting that the regulations “prohibiting private signal blocking” be retained. Not long ago, two American companies proposed to the Federal Communications Commission that signals should be blocked in relevant places, such as prisons. But network companies from the Wireless Industry Association believe that lifting the regulations may allow criminals to abuse signal jammers, making it impossible for cell phone users to make calls for help in emergencies. Supporters of retaining the regulations also argue that blockers “punish” not just those who make noise, but also harm callers who deliberately speak quietly.

FCC spokesman Clyde Enslin declined to comment on the controversy or last year’s findings in Maryland. Jeffrey Nelson, a spokesman for Verizon Communications, which spends $6.5 billion a year on network system maintenance, commented: “This is a counter-intuitive approach: when mobile phone user demand increases due to better wireless network signal coverage, When it went up, those businessmen who made jammers also saw a market.”

With the continuous development of technology, mobile phones have become an indispensable part of our lives, but at the same time, the use of mobile phones has also brought some problems. On some occasions, people may need to block mobile phone signals to ensure information security, maintain order or other purposes. Cell phone signal jammers are widely used for this reason. However, it’s also crucial to know how to properly use and care for your cell phone jammer to ensure its long-term, stable operation and performance.

1. Use of mobile phone signal jammer
a. Reasonable circumstances
Before using a mobile phone signal jammer, you must first clarify the occasion where it will be used. Reasonable occasions include but are not limited to military areas, government agencies, prisons and other places where mobile phone signals need to be blocked. Make sure the use of jammers in these locations is legal and compliant.

b. Pay attention to the signal range
When using a mobile phone signal jammer, pay attention to its signal range and its impact on the surrounding environment. Make sure that the signal coverage of the jammer does not exceed the area that needs to be shielded, and try to minimize interference with normal communication equipment around you.

c. Comply with laws and regulations
When using a cell phone signal jammer, local laws and regulations must be strictly followed. Using the jammer without authorization or in illegal situations may violate relevant laws, resulting in legal liability and penalties.

d. Ensure safety
When using a cell phone signal jammer, make sure it is safe. Choose a regular and reliable jammer and operate it strictly in accordance with the instructions to avoid causing safety hazards or damaging the equipment.

2. Maintenance of mobile phone signal jammer
a. Regular cleaning
The mobile phone signal jammer may accumulate dust and debris during use, affecting its normal operation. Therefore, it is very important to clean the shield regularly. You can use a soft cloth to gently wipe the surface of the shield and make sure its vents are clean and clear.

b. Avoid getting wet
Cell phone signal jammers are usually made of electronic components, so try to avoid letting them get wet. Using or storing the shield in a humid environment may cause damage or reduced performance.

c. Pay attention to temperature and humidity
The working environment of the mobile phone signal jammer should be under suitable temperature and humidity conditions. Excessively high or low temperature and excessive humidity may affect the normal operation of the shield and even cause equipment damage.

① The higher the power, the better

1. The host frequency output is inaccurate, frequency drifts, the bandwidth is too wide, power is wasted, and interferes with the base station;

2. The simple frequency sweep power suppression method has low shielding efficiency and large radiation;

3. The power is falsely marked and exaggerated, and the nominal power loses its reference value;

4. Power is the foundation, technology is shutdown. Finding good methods and techniques is not as good as trying to gain power;

signal jammer

② Use directional antennas to avoid interference

1. There is a certain transmit signal strength outside the directional angle of the directional antenna, but it is much lower than the main lobe and is not completely directional;

2. Reflections from buildings will still cause external interference.

3. The host frequency drift seriously affects the base station and causes external interference;

4. TD full-time shielding interference must exist.

③ High-power equipment has large radiation, while low-power equipment has small radiation.

1. High-power uses an outdoor antenna, with long operating distance, large shielding coverage, uniform shielding signal but minimal radiation;

2. If low-power equipment does not use multiple antennas to provide long-distance shielding, but is centrally arranged or 5 antennas work together, its radiation power will be greater than 10 microwatts/square centimeter, and close-range radiation must seriously exceed the standard.

Wireless signal jammers can be divided into three levels according to the power size, and different application environments can use different power levels of shielding. One is the low-power type, that is, the transmitting power of each shield module is below 2-3W. The second is the medium power type, the transmission power is 10-20W. The third is the high-power type, that is, the transmitting power of the shielding module reaches 50W or even 100W.   signal jammer

High-power wireless signal jammers are typically used in outdoor open areas and larger open areas, while low-power types are used in indoor environments. In most cases, when the low-power network shield is installed outdoors, its effective shielding range is only 2-5 meters, after all, its transmission power is relatively low.

Power Strength: The power strength of the jammer is one of the key factors that affects the shielding range. Typically, the greater the power, the wider the shielding range. High-power jammers can cover a larger area and have a stronger impact on the target signal.
Frequency range: The frequency range of the interference signal emitted by the jammer also affects its shielding effect. If the jammer’s frequency range closely matches the frequency of the target signal, its shielding effect will usually be better.
Antenna Design: A jammer’s antenna design also affects its shielding range. A quality antenna design can improve signal transmission efficiency and coverage, thus extending the jammer’s shielding range.
Environmental factors: Surrounding environmental factors, such as buildings, topography, weather conditions, etc., will also affect the shielding range of the jammer. For example, dense buildings may impede the propagation of signals, limiting the jammer’s shielding range.
Target signal characteristics: The shielding effect of the jammer also depends on the characteristics of the target signal, including its power, frequency, modulation method, etc. Different types of target signals may respond differently to the jamming effects of the jammer.
Electromagnetic interference environment: In some cases, the surrounding electromagnetic interference environment may also affect the shielding range of the jammer. If there are other interference sources, it may interfere with the normal operation of the jammer, thereby reducing its shielding effect.

Common mobile phone signal jammers on the market have operating frequencies of: 869~894MHz; 825~960MHz; 1805~1880MHz and 1900~1990MHz, etc. The applicable frequency bands are CDMA800, GSM900, DCS1800, and PCS1900. It can control a range of about 40 meters in diameter, using a DC-DC converter input voltage and 5V output voltage. After turning on the signal jammer, garbled interference is formed in the message signal received by the mobile phone. The mobile phone cannot detect the normal data sent from the base station, so that the mobile phone cannot establish a connection with the base station. Mobile phones show symptoms such as searching the network, no signal, and no service system. The signal sending and receiving functions of mobile phones within the specified range are invalid, and outgoing and incoming calls cannot be made, thus achieving the purpose of mandatory ban.

signal jammer

Principles of mobile communication
The working principle of mobile phones is as follows: within a certain frequency range, mobile phones and base stations are connected through radio waves, and data and sound transmission are completed with a certain baud rate and modulation method.

Principle of mobile phone signal jammer (shielding device)
According to the communication principle, the jammer scans from the low-end frequency of the forward channel to the high-end at a certain speed during operation. This scanning speed can cause garbled interference in the message signals received by the mobile phone. The mobile phone cannot detect normal data sent from the base station, making it impossible for the mobile phone to establish a connection with the base station. Mobile phones show symptoms such as searching the network, no signal, and no service system.

Basic functions of signal jammer
1. After the slow start function is powered on, the working power supply rises from zero to stable within 4 seconds.

2. After the shielding function is activated, mobile phones within the range will be blocked within 35 seconds.

Application scope of signal jammer
Various examination rooms, conference rooms, gas stations, oil depots, churches, hospitals, courts, military sites, libraries, theaters and other places.

Mobile phone detection technology mainly detects when the electromagnetic wave signal emitted by the mobile phone when it is working causes the electromagnetic power in the area where the mobile phone is to increase to a set value, thereby determining that a mobile phone is working. This technology sounds very advanced at first, but in fact it is just a very superficial understanding. When this technology was proposed, the following issues were not considered:

signal jammer

1. Uncertainty of mobile phone transmit power

The specific base station through which a mobile phone enters the network when working is determined by the traffic volume and dynamic deployment of surrounding base stations. When the mobile phone is logged in and used, if the nearby base station is busy, it will log in to the idle base station farther away. The transmit power of the mobile phone will be adjusted accordingly according to the link loss of the mobile phone to the base station radio wave. Usually, the mobile phone receives the signal from the base station. The stronger the signal, the weaker the transmit power.

2. The distance between the mobile phone and the detector (link loss) is uncertain

The distance between the mobile phone and the detector and whether there are any obstacles in the middle will affect the strength of the signal received by the detector.

3. The intensity of space electromagnetic interference is uncertain

Common lightning, fluorescent lamps, electronic equipment, etc. are all sources of interference. At the same time, when mobile phones are working, there is a lot of out-of-band stray noise. Although the surface acoustic filter used in the detector is used on mobile phones, the filter has insufficient out-of-band suppression and is prone to cross-frequency phenomena. When used for detection, it cannot effectively filter out other interference signals, causing the detection system to be in chaos.

4. Detector setting sensitivity is uncertain

Generally, the sensitivity setting of a detector does not have a specific quantitative value. During debugging, adjust the sensitivity by constantly adjusting the position and dialing the mobile phone to observe whether the detector detects it.