Faraday cage made of a real conductor

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Discussion Overview

The discussion revolves around the effectiveness of Faraday cages constructed from real conductors, such as copper, in blocking electromagnetic (EM) radiation. Participants explore the limitations of these cages at various frequencies and propose potential improvements to their design, including considerations for grounding and sealing techniques.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants note that a Faraday cage made of a perfect conductor would theoretically have a zero electric field inside, but question the performance of real conductors like copper in blocking all EM radiation, particularly at very high or low frequencies.
  • One participant highlights that the effectiveness of shielded enclosures can be compromised by seams and access points, suggesting that conductive gasketing is essential for sealing doors and ports to maintain shielding integrity.
  • Another participant mentions that the ability of a Faraday cage to block EM radiation depends on frequency and conductivity, referencing that this is a common topic in textbooks.
  • There is a suggestion to investigate concepts such as skin effect and waveguide beyond cutoff to understand the limitations of shielding effectiveness further.

Areas of Agreement / Disagreement

Participants express uncertainty about the performance of real conductors in Faraday cages, indicating that multiple competing views exist regarding their effectiveness at different frequencies and the best design practices to enhance performance.

Contextual Notes

Limitations include the dependence on specific frequency ranges and the material properties of the conductor used, as well as unresolved details regarding the design and implementation of effective shielding techniques.

cuallito
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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?
 
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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

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cuallito said:
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.
 
cuallito said:
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.
 
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