How to Make a Mesh Faraday Cage
Faraday cages or screen rooms have three purposes. They are used to protect people and equipment in areas with high voltage. They isolate sensitive equipment from external electro-magnetic interference or radio frequency interference. In some cases, they are used to contain internal RF fields, such as when tuning a transmitter attached to a dummy load. Radio frequency energy and static discharge pulses travel over the outside surface of a Faraday cage by a phenomenon known as skin effect.
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Things You'll Need
- Aluminum screen or mesh
- Conduit
- Sheet metal screws
- Grounding rod
- Copper wire
Instructions
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Select a screen or mesh with openings smaller than the wavelength of the highest frequency you must block. Some commercial screen rooms use solid metal walls to block all frequencies. You can calculate the frequency that will penetrate the room by measuring the largest opening. Divide the speed of light in meters per second by the size of the opening (in meters) to obtain the frequency. For example, a screen with a mesh measuring 12mm would block all frequencies below 25 GHz.
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Construct the enclosure to ensure it is electrically conductive. This is true regardless of its size. The top, bottom and sides must be covered. Attach the screen to existing walls with brads or staples, but be sure to run conduit along the top and bottom. Fasten the screen to the conduit with sheet metal screws.
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Cover the door with screening. In commercial screen rooms, the door is fitted with a metallic gasket similar to a weatherstrip that acts like a spring. It contacts the door frame and floor to provide conductivity. If you cannot locate a metal door sweep, add a piece of chain lengthwise along the bottom of the door.
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Ground the screen room with a commercial grounding rod, if possible. Locate the rod close to the room, but not inside it, and connect the mesh to the rod with a piece of solid copper wire. A metal water pipe is an alternative to a grounding rod. Do not ground to a gas pipe.
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References
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