I Faraday cage made of a real conductor

[cuallito]

A faraday cage made of a perfect conductor would theoretically have a zero E field inside.

However, are there cases where a faraday cage made of a real conductor like copper wouldn't block out all EM radiation, like very high or low frequencies? How can the design be improved to make a real faraday cage work more closely to an ideal one? Grounding?

 

[berkeman]

Depending on the application (size, frequencies involved, etc.), the biggest issue with shielded enclosures is seams (like along doorway edges) and entries for cables (like power, Ethernet data, etc.). Welding up a shielded box is not that hard, but putting doors and access ports on it can be challenging.

One of the things you do with doors and similar access ports is to use conductive gasketing to seal the door to the frame. Such gasketing must have many points of contact between the surfaces, and have high contact pressure at those contact points to prevent corrosion.

More info about typical shielded enclosures and rooms here:

https://www.ets-lindgren.com/products/shielding?page=Products-Landing-Page

https://www.ets-lindgren.com/support/articles-whitepapers?page=Articles-WhitePapers-Page

 

[hutchphd]

However, are there cases where a faraday cage made of a real conductor like copper wouldn't block out all EM radiation, like very high or low frequencies?

It will depend upon frequency and conductivity. This is in most textbooks.

 

[DaveE]

A faraday cage made of a perfect conductor would theoretically have a zero E field inside.

However, are there cases where a faraday cage made of a real conductor like copper wouldn't block out all EM radiation, like very high or low frequencies? How can the design be improved to make a real faraday cage work more closely to an ideal one? Grounding?

There's lots of stuff on the web about this. It's a big issue for the EMC requirements of electronic equipment.

Here are a couple of things you can look into to learn more about shielding effectiveness:

- Skin effect; the effect of limited conductivity of the shield material.
- "Waveguide beyond cutoff"; the effect of openings and seams in the enclosure.