Signal jammers, I believe students in the past few years know what they are, the most common radio interference equipment in the examination room. Mainly to interfere with the mobile phone signal in the nearby area, so that the mobile phone signal loses connection with the base station.
The principle of interference
In a certain frequency range, the mobile phone and the base station are connected by radio waves to complete the transmission of data and sound with a certain baud rate and modulation method. According to the above communication principle, the wifi signal jammer scans from the low-end frequency of the forward channel to the high-end frequency at a certain speed during the working process. The scanning speed can cause garbled interference in the message signal received by the mobile phone, and 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. The mobile phone manifests as the phenomenon of searching the network, no signal, no service system, etc.
How to Avoid Signal Interference
Method 1: Due to the rapid development of wireless network, it has now developed to 4G network, and many test rooms use older model wifi signal blockers, which can only block 2G networks such as PHS, China Mobile, China Unicom, etc., but not for 3G networks. Even the current 4G network is helpless, the cracking method: use a 3G or 4G card.
Method 2: Band cracking method. Because the working principle of the school's blocker is to block the mobile phone by interfering with the mobile phone signal in the specified band, as long as the receiving and transmitting frequency of the mobile phone is modified, it can be prevented from being blocked. The blocker only blocks the mobile phone signal of 900-1800MHZ, while the mobile phone's receiving and transmitting The frequency is 850-1900MHZ, which is much larger than the shielding range of the jammer, so as long as the receiving and transmitting frequency of the mobile phone is adjusted to the maximum in the mobile phone settings, the mobile phone signal can be received normally.
Method 3: WIFI cracking method. This method has relatively high requirements on the environment, and the premise is that there must be an available wireless network around. Some cell phone signal blockers cannot block WIFI signals and can communicate with the outside world.
Method 4: Bluetooth cracking method. It is suitable for short-distance communication in the shielded area. Some shields may ignore the transmission function of Bluetooth without shielding, so we only need to install the Bluetooth messaging software on the mobile phone to communicate normally in a small range.
Finally, with the rapid development of the network, the mobile phone signal blocker is also being updated, and the cost is very low. It only needs to add the frequency band of the known network to the interference ranks, and all radios can be blocked.
