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> "Wrap it in tin foil" is perhaps the most common advice [...] Unfortunately the results were extremely inconsistent [...] 90 dB attenuation in one test would produce only 50 dB the next time [...] You would have no way to tell whether you've managed to fold and seal it adequately well On the other hand, aluminium foil is incredibly commonly available, if not in a kitchen draw, it will be at the nearest shop. Although unreliable, the _potentially_ high attenuation the author shared is pretty good (we don't know his worst reading), better than all other improvised solutions tested, and similar to commercial products. I wonder if a more reliable construction method could be found. I'm not sure what movie scene scenario I'm envisioning, but in the case you needed a Faraday cage and don't constantly carry one around, perhaps simply taking an entire kitchen roll of foil and wrapping the device into a giant unsightly ball of it would be a reliable enough process for an "emergency" (if not pocket sized). i.e rather than trying to make a neatly folded minimal version, just resort to sheer number of layers of material - unless RF doesn't care and even 1000 layers with tiny gaps is no good? [edit] Similarly, I wonder how well (or poorly) common household appliances work as a Faraday cage, e.g a fridge, microwave-oven - From what the author described, it seems they would all have too many gaps, however they are also constructed from higher gauge metals... i'm particularly interested in a microwave-oven which is specifically designed to reflect and retain microwave frequency fields. |
You can test this: put your phone in the microwave and try to call it. Over the years I have had about a 75% success rate.
Other household appliances tend to be even worse; any gaps in metallic seals effectively turn into slot antennas and let signals through. You need a conductive mesh gasket to stop this, and I generally don't see mesh gaskets on consumer appliances.
Your "make an al-foil ball" strategy is what I would resort to in a pinch (I have some nice Anritsu shield boxes, but those are cheating). Quantity is a quality of its own. My only addition would be making sure that the gaps tend to not line up. You want to make it difficult for the "slot antennas" modeling the gaps in each layer to couple to each other.