The shielding effectiveness of a wifi jammer depends not only on the structure of the shield. The shielding body should meet the basic principles of electromagnetic shielding. There are two basic principles of electromagnetic shielding:
Generally, except for low-frequency magnetic fields, most metal materials can provide shielding effectiveness of more than 100dB. But in actual work, it is very difficult to achieve a shielding efficiency of more than 80dB. This is because:
1) Conductive continuity of the shield:
This means that the entire shield must be a complete, continuous electrical conductor. This is very difficult to achieve. Because a completely closed shield has no use value. A practical case will have a lot of holes and slits for shielding: vents, display ports, openings for mounting various levers, joints between different parts, etc. Due to the existence of these factors that lead to discontinuous conduction, if the designer does not consider how to deal with it in the design, the shielding effectiveness of the wifi signal jammer is often very low, or even no shielding effectiveness.
2) There can be no conductors that pass directly through the shield:
A wifi jammer device with high shielding efficiency will lose more than 99.9% (60dB) of shielding efficiency once a wire directly passes through the shielded case. However, there will always be cables going out (in) to the chassis, at least one power cable, and if these cables are not properly handled (shielded or filtered), these cables can seriously damage the shield. Proper handling of these cables is an important part of shielding design.
(Conductors passing through the shield are sometimes more harmful than apertures)
The electromagnetic shield has nothing to do with grounding: for electrostatic field shielding, the shield must be grounded. But for electromagnetic shielding, the shielding effectiveness of the shielding body has nothing to do with whether the shielding body is grounded or not, which the designer must be clear about. In many cases, grounding the shield does change the electromagnetic state, but this is for some other reason than the grounding changes the shielding effectiveness of the shield.
