# Building a Faraday cage for mobile networks that is transparent for optical wavelenghts

A friend of mine is working on an architectonic project, where she designs a Faraday cage type of open space built in parks or other public places. The initial thought is to build it from some sort of metallic mesh (not metallic plates or foils), so the whole structure would be transparent for visible light, so the visitors would have some sort of feeling being outside, however without any mobile connection to the networks.

I have found the excellent answer by Rob Jeffries of the thickness needed for shielding the field by metallic shields, however I cannot find if the modulus of impedance $\eta$ would remain the same for metallic mesh (say hexagonal) made from the same material.

This problem raises several questions, such as how would one proceed with choosing the right materials and designing the structure? Would it be better to use one layer of mesh made from thicker wires or rather several layers of thin wire mesh? Typically at what orders of energy transmission cease the cellphones operate? Is the assumption, that sufficient diameter of the holes in the mesh is circa 1 cm, since it is safely smaller than $\lambda / 2$ for 3G networks (on the other hand the shielding in microwave ovens which utilize similar wavelengths seems to have holes cca 3 mm in diameter and is rather poor in terms of transparency / visibility).

Thank you for any helpful information!

• Coming from the experiment side of things, why not get some copper wire, weave a small mesh and put your phone inside and see what happens (ground the mesh). – user56903 Oct 24 '14 at 12:38
• You're right, I maintain the same opinion that the experiment is what ultimately settles the truth (Zombie Feynman xkcd :) I have been asked about this only this afternoon, takes some time to weave a wire mesh :) On the other hand, as our calculus teacher puts it: "The most practical thing in the world is a good theory." – Jan Hirschner Oct 24 '14 at 12:47
• I have once witnessed a small experiment where a cell phone was put in a biscuit tin and then dialed. It still started ringing. The only unshielded part would probably be the imperfect contact between the lid and the body of the tin. The people who performed the experiment thought that surface modes got excited in turn producing radiation inside the tin. – Urgje Oct 24 '14 at 15:35