What signals can a jammer block

Issues related to signal jammers (also known as signal blockers) are quite common. Understanding their working principles, shielding ranges, and legal regulations can help us gain a correct understanding of these devices.

Their core working principle is to emit extremely high-intensity interference noise in specific frequency bands. This noise "drowns out" normal communication signals, preventing devices such as mobile phones and routers from establishing stable connections with base stations or signal sources, thus achieving signal shielding effects.

The signals that a signal jammer can block are entirely determined by its design objectives and power level. Specifically, they can be divided into the following two categories:

I. Commonly blocked signals (primary targets of civilian-grade jammers)

The design intention of civilian-grade jammers is primarily targeted at public communication and wireless networks that are frequently used in daily life, mainly including the following types of signals:

1. Public mobile networks (2G, 3G, 4G, 5G)

This is the core shielding target of the jammer, capable of covering all commonly used communication frequency bands of mobile phones. After shielding, the phone will display a "No Service" or "Emergency Calls Only" status, making it impossible to make phone calls, send text messages, or use mobile data to access the internet. Since different communication standards (such as GSM, CDMA, WCDMA, LTE, NR) correspond to different frequency bands, a full-band civilian jammer will cover all frequency bands of these standards to ensure comprehensive blockage of mobile phone signals.

2. Wi-Fi signals (2.4GHz, 5GHz, 6GHz)

The jammer will interfere with all the commonly used Wi-Fi frequency bands. No matter which frequency band the device tries to connect to the Wi-Fi router, it will fail to connect successfully due to signal interference, ultimately leading to wireless network interruption and inability to perform network operations such as web browsing and file transfer.

3. Bluetooth signal (2.4GHz)

Bluetooth devices (such as Bluetooth headphones, Bluetooth keyboards, Bluetooth mice, Bluetooth speakers, etc.) all use the 2.4GHz frequency band for communication. Interference from a jammer on this frequency band will directly interrupt all Bluetooth connections, resulting in inability to pair devices properly and transmit data.

4. Satellite positioning signals (GPS, Beidou, GLONASS)

This type of signal jamming primarily targets the positioning function of devices. After jamming, devices relying on satellite positioning, such as mobile phones, in-vehicle navigation systems, and drones, will be unable to obtain accurate location information and cannot perform functions like navigation and location tracking. It is important to note that jamming GPS and other satellite positioning signals is a serious illegal act in most countries and regions worldwide, and should not be attempted.

II. Signals that may be blocked by special or high-power jammers

In addition to civilian-grade jammers, some more powerful and targeted jammers (mostly for military or specific law enforcement agencies) can also block the following special signals:

1. Radio interphone signals (such as UHF/VHF bands)

This type of jammer can interfere with the commonly used UHF (Ultra High Frequency) and VHF (Very High Frequency) bands of walkie-talkies, blocking voice communication between walkie-talkies. It is commonly used in scenarios where stringent communication control is required.

2. Remote control signals (such as drone remote controls, specific remote control devices)

It can jam the specific frequency bands used by drone remote controls, some remote-controlled bomb devices, etc., preventing the remote control devices from sending commands to their targets. It is mainly used in special fields such as security prevention and control, anti-terrorism, etc.

3. RFID/NFC signals

It can block RFID (Radio Frequency Identification) and NFC (Near Field Communication) signals, which are commonly used in devices such as access cards, payment cards, and electronic tags on goods. After blocking, it can prevent cheating through micro RFID/NFC devices, and is widely used in examination rooms, confidential meetings, and other occasions that require strict control.

⚠️ Important reminder: Legal and usage restrictions

In the vast majority of countries and regions worldwide, it is strictly illegal to privately own, sell, or use any form of signal jammer. China has even clearer and stricter legal provisions on this matter:

According to the Regulations of the People's Republic of China on Radio Management, no unit or individual is allowed to install or use radio jamming equipment (including signal jammers) without authorization. Those who possess or use signal jammers without approval from relevant departments will face administrative penalties such as equipment confiscation and heavy fines; if the act constitutes a crime, criminal responsibility will be investigated according to law.

Currently, only a very small number of specific departments, such as public security, prisons, and confidentiality departments, are authorized to use signal jammers in specific legal settings (such as college entrance examination venues, national-level confidentiality meetings, and prison supervision areas) after going through strict approval procedures. The use of these devices must strictly comply with relevant regulations to avoid unnecessary impacts on public communication.

There are two main reasons for the strict control of signal jammers:

Public safety risks: Signal jammers cannot achieve targeted and precise interference, and will indiscriminately block the signals of all surrounding devices. If used maliciously by individuals, they may prevent others from making emergency calls such as 110, 120, and 119 in case of emergencies, potentially leading to serious safety accidents.

Disrupting radio order: The radio spectrum is a scarce public resource of the country, strictly protected by law. Illegal use of signal jammers can severely interfere with the normal operations of communication operators, undermine the public's freedom of communication, and affect the stability of social communication order.

❓ Common Misconceptions and Answers

Misconception 1: Can a jammer block all radio signals?

Answer: No. Any jammer can only block signals within its designed frequency range and cannot cover all radio frequency bands. For example, a cheap civilian jammer that only targets mobile phone signals may not be effective in jamming signals from walkie-talkies or military-specific frequency bands.

Misconception 2: After turning on the jammer, I can still see the Wi-Fi icon or phone signal bars. Does this mean the jammer is not working?

Answer: Not exactly. The Wi-Fi icon or phone signal bars displayed on the device only indicate that the device can detect the weak signal emitted by the base station or router, but it does not mean that communication is normal. Since the interference noise emitted by the jammer is much stronger than the normal signal, the device cannot effectively exchange data with the base station or router and is actually still in a state of unable to communicate.

Misconception 3: What should I do if I suspect there are illegally used signal blockers around me?

Answer: If you find that your phone suddenly loses service in legally controlled areas such as examination rooms and conference rooms, and the signal recovers after leaving, it is highly likely that the relevant department has legally activated a jammer, which is a normal control behavior and requires no intervention. If there is a widespread signal interruption in public places such as shopping malls and residential areas without any reason, it is suspected that there is an illegal jammer. You should promptly report to the local radio management department or communication operators (such as China Mobile, China Unicom, China Telecom) for professional intervention, verification, and handling.