Electronic – Suggestion to electrically disable a Faraday Cage


My plan is to ultimately develop an Autonomous Faraday Cage. The project seems very straight forward; however, I am unsure on how to effectively control the cage (turn on and off).

I have constructed a prototype Faraday Cage at home. From my research on these cages, my first theory was that an un-grounded cage with no external charge should not block the electromagnetic waves emitting from a cell phone. However, placing the phone in the cage, I observed that the cell phone still lost its network capabilities.

Google has provided no suggestions on how to disable the qualities of a Faraday Cage electrically. Obviously, I could arrange a method where the cage opens, allowing the phone to reconnect to the network and Bluetooth. I don't see this as ideal however since my design would involve moving parts (a final design I plan on completing thousands of iterations).

Are there suggestions on how to electrically disable the Faraday Cage?

Extra Note: As I wrote this, I just thought about grounding the inside and outside of the Cage. From my understanding, a Faraday Cage works by creating its own electromagnetic field which cancels external and internal Electromagnetic waves.
My reasoning on grounding the inside and outside is that if there is no charge to create the electromagnetic field, then the electromagnetic waves could escape the cage. Is this a reasonable theory?

TL;DR: How may I electrically disable a Faraday Cage?

Best Answer

The following is just a guess. I could be completely wrong.

You can't disable a cage, but you might be able to make a switchable "leak" in the cage.

Imagine this, you have a cage with two antennas. One antenna on the inside, one on the outside. The two antennas are connected with a wire. Where the wire goes through the wall of the cage you place a switch (or relay, or whatever). If the hole in the cage is smaller than 1/4th wavelength, and the switch effectively prevents the signal from penetrating the cage, then you might just have something.

You might need to do some fancy shielding around the hole and switch, to prevent leakage when the switch is off. You might also consider connecting one or both antennas to the wall of the cage when the switch is "off".

It probably won't ever be perfect, but it might do what you want. Unless you are a forigen spy, intent on disabling our security in sensitive military complexes. Then it won't work. For that you need to know the secret combination, which is 1234 by the way.