Do Faraday cage need to be grounded to block RF?

Faraday cages do not require grounding to block RF waves because the principle that makes them effective relies on the redistribution of charges on the surface of the conductive material, not on the discharge of these charges to the ground. When an RF wave strikes the surface of a Faraday cage, the conductive material responds by redistributing its electrons in a way that creates an opposing electric field. This opposing field cancels out the incoming RF wave, effectively neutralizing the electromagnetic field inside the cage. The cage itself contains the induced charges on its surface, preventing them from penetrating the exterior, which is what blocks the RF waves.

For blocking RF waves, grounding is unnecessary because the cage’s effectiveness is based on its ability to redistribute charges and cancel out the electromagnetic field within the enclosure. This means that even a Faraday cage that is not grounded will still effectively block RF waves, if the conductive material is continuous and the design is proper for the frequencies being shielded.