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This question already has an answer here:

Good day,

I have created a faraday cage with metal sheet of .5 mm thickness with aluminum foil wrapped outside and inside of the cage. I was happy at first to notice that the cellphone signal goes from one bar to nothing at all but the signal goes inside the cage intermittently and most of time stays at full strenght signal. I tried changing places and found dead zones but still frequencies go inside. Wifi signal though still cannot be attenuated. I was planning to create a topological shielding with 10x sheet of 1 mm and layer them together to deplete the frequency but i cant afford to do it if i plan to stay inside longer because of temperature issues. The reason I am doing this is because of electronic harrasment. I researched that devices can be hacked through emf emissions of devices and i need to protect my devices from these attacks.

My question is,

  1. is there by any chance that the signals inside can be cancelled consistently?

  2. Do i need to consider the thickness of metal sheet or do i need to just layer tin foils to be enough to reflect or absorb frequencies.

  3. Do i need to make earth stakes to transfer the electrons on the metal to earth to regain it's absorption and reflection?

  4. Do i need to create topological shielding to deplete the frequecy from GHz to MHz brcause i researched that cellhpone signals are on a MHz frequency?.

I found out as well that apperture/ appertures should be smaller than the wave.

I need your help thank you.

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marked as duplicate by Rob Jeffries, user36790, Jon Custer, John Rennie, honeste_vivere Oct 14 '16 at 14:32

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • $\begingroup$ How well was your cell enclosed in aluminum foil? Were there any gaps or regions of overlap with no good electrical contact? I wonder how you could still see the signal strength when you had a complete enclosure with aluminum foil. $\endgroup$ – freecharly Oct 13 '16 at 14:55
  • $\begingroup$ Full wrap of one layer outside of metal sheet and one full wrap inside too. I didn't ground it because i read that grounding is for static interferences only and it does not help with shielding emf. I left a little bit of apperture for ventilation inside and i dont know if this is the reason for it. $\endgroup$ – Kiko Bautista Oct 13 '16 at 15:05
  • $\begingroup$ Do I understand you correctly that you want a Faraday cage large enough so that you yourself can be inside with the cell phone? I am surprised that you still get a signal when the aluminum foil is completely enclosing the space. Do not forget to include the floor in this metallic enclosure. The electromagnetic waves could easily penetrate via the floor. $\endgroup$ – freecharly Oct 13 '16 at 15:13
  • $\begingroup$ A single sheet of (unearthed) standard aluminium foil easily blocks a mobile phone signal - as can be readily checked. $\endgroup$ – Rob Jeffries Oct 13 '16 at 15:21
  • $\begingroup$ Does dents on the metal sheet and rivets affect the performance of the shielding because of the distributions of electrons? Thanks $\endgroup$ – Kiko Bautista Oct 13 '16 at 16:13
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The primary principle of the faraday cage is electrostatic shielding. So it is important that it is a electrically static system (which in reality isn't but just a near approximation). So, the thickness doesn't matter, neither does the size and shape of the cage (provided static conditions). For MHz applications, typically relatively (to silver) poor conductors (like aluminum) are more suited primarily because of lesser cost, but don't worry about anything if you have GHz capable conductive covering already, it will just work the same (maybe better to handle variations towards higher frequencies - GHz for WiFi). Further, what I can conclude is that there might be some capacitive effect (due to layering design and a charged environment or polarising environment) or the wifi signals occasionally "slipping" in due to their high frequencies and your ventilation hole is also one of the culprits. Happy to help ;)

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Your conductive sheet needs to be continuous. Because aluminum surface easily oxidizes, you may have poor continuity where the sheet wraps onto itself. Usually RF cages are made from copper (soldered at the joins), and great care must be taken to install RF gaskets at the seams (e.g. the door). For "real" RF cages (like the ones used in MRI systems) you need a specialist. See also this datasheet for a lot of useful information on shielding principles and specifications, and this link for a possible source of copper tape (helpful to ensure continuity across seams - better than rivets).

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  • $\begingroup$ Because of budget i cannot create a faraday cage with metal sheet welded on a iron steel angle bars and instead i used rivets and i reckon that this will have an impact on redistribution of it to all sides. $\endgroup$ – Kiko Bautista Oct 14 '16 at 10:21
  • $\begingroup$ Consider purchasing conductive copper tape to tape over the seams. The slot formed by the seam, regardless how narrow, can act as an antenna. Don't forget the floor and ceiling! Cell phones (and towers) will increase their power depending on path loss - so if they ever "hear" each other they will keep trying to scream to get through the wall... $\endgroup$ – Floris Oct 14 '16 at 11:48

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