The cell phone wifi signal jammers used in the college entrance examination are used to block the signals of cell phones and base stations.Signal jammers can interfere in two ways.
One is to do it on the way that the mobile phone transmits the signal, so that the base station cannot receive the signal;
The other is to do it 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 way, signal shielding within a certain range can be achieved.But the two have different effects.Uplink interference affects the reception of all nearby mobile phone signals by the base station.
Downlink interference only affects the use of mobile phones within a certain range.
Therefore, improper use of jammers will affect nearby users.
Therefore, when jammers first appeared, they were controversial, even resisted and stigmatized.
How does the jammer interfere?
When using a wifi signal jammer, you only need to scan the radio waves in a certain frequency band, and when there is a signal transmission, it will emit an identical electromagnetic wave in this frequency band.
It uses high-intensity power to amplify the meaningless interference signal it sends out, to cover it, suppress it, and make the mobile phone and base station unable to recognize the signal, so as to achieve blocking and interference.
It can be seen that the so-called shielding does not mean that there is no signal, but that the signal is interfered and cannot be identified.
According to this principle, if the signal is to be anti-shielded, it is also simple. It only needs to transmit and receive the signal to a higher power than the shielder.
But the mobile phone and power are far from being comparable to the jammer signal, and the base station is too far away to compare with the jammer at the exam site.
In addition, if the frequency used by the new generation of communication technology exceeds the frequency band that the shielding device can scan, then the shielding device is powerless to work hard.
For example, with the shielding device in the 3G era, it is impossible to block the mobile phone in the 5G era, and the blind spot is too large.
