Can One Faraday Cage Block All ISM Band Frequencies?

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Discussion Overview

The discussion revolves around the feasibility of designing a Faraday cage that can block all frequencies within the ISM band, which ranges from approximately 6 kHz to 246 GHz. Participants explore various design concepts, including nesting multiple cages and the implications of different mesh sizes, while considering the effectiveness of such designs in practical applications.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether a design consisting of nested Faraday cages, each with different mesh sizes, could effectively block multiple ISM bands.
  • Another participant suggests that a gridded or holed Faraday shield acts as a highpass filter, potentially allowing higher frequencies to pass while blocking lower ones.
  • It is noted that a microwave oven's design demonstrates how certain frequencies can be contained while others may leak through gaps, indicating the importance of sealing techniques for effective RF containment.
  • Some participants emphasize the need for clarity on the specific goals of the design to provide more accurate advice.
  • One participant asserts that a single Faraday cage can suffice if designed properly, specifically mentioning that holes must be smaller than one tenth of a wavelength at the highest frequency of interest.

Areas of Agreement / Disagreement

Participants express differing views on whether multiple nested cages are necessary or if a single cage can achieve the desired outcome. There is no consensus on the best approach, and the discussion remains unresolved regarding the effectiveness of various designs.

Contextual Notes

Participants highlight limitations in understanding the specific requirements for the design, such as the intended application and the frequencies of interest, which may affect the effectiveness of the proposed solutions.

bigplanet401
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The ISM band is a set of frequency bands from about 6 kHz to 246 GHz; see http://en.wikipedia.org/wiki/ISM_band#ISM_bands.

Is there a design that will block all of these bands? A guess is in the attached file: each box is solid metal or wire mesh, and the boxes nest in a Matryoshka-doll fashion.
 

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If one of your 2.4 GHz devices is being interfered with, you may want to check out these ways of resolving interference.
 
My question's a little bit broader than that. I'd like to block as much of the ISM band as possible and would like to know if the design shown in the drawing (which is like King Tut's tomb; see below) is a reasonable approach. Will nesting, say, 4 Faraday cages each with different mesh sizes block four separate bands of frequencies?
 

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bigplanet401 said:
Will nesting, say, 4 Faraday cages each with different mesh sizes block four separate bands of frequencies?

Its more likely to block everything
a gridded/holed Faraday shield, like a waveguide is basically a highpass filter

Consider the holed grid of a microwave oven, it blocks everything up to and a little beyond ~ 2.5 GHz
everything higher in freq above that goes through up to light and beyond

so if there is something inside the box that you want to be able to receive say 450MHz
that signal will be filtered out

I think you need to explain in much more depth what you are trying to achieve

regards
Dave
 
"King Tut's tomb design", Lolo0)
 
Building a cage that blocks the high frequencies will block all below it. As davenn said,
"Its more likely to block everything a gridded/holed Faraday shield, like a waveguide is basically a highpass filter"
 
A microwave oven is designed to contain it's working frequency via a 1/4 shunt constructed along the periphery of the door. Thus wide bands below and above the design frequency will leak through the gap around the door. To get wide-band performance, the door would need a conductive seal all around.
To seal RF in / out, totally constructive chambers are constructed with conductive spring fingers all around the doors. Absorbent materials are usually included along the walls to suppress resonances.
 
To seal RF in / out, totally constructive chambers are constructed with conductive spring fingers all around the doors. Absorbent materials are usually included along the walls to suppress resonances.

Sorry, but what is a "constructive chamber"? I couldn't find it on Google.
 
You still haven't told us what you are trying to achieve

doing so will help you get better answers, at the moment we are all just guessing
 
  • #10
One faraday cage will solve the problem. You do not need to nest multiple faraday cages.
Make sure that any holes are smaller than about one tenth of a wavelength at your highest frequency.
 

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