How Do I Build a Faraday Cage?

Eldartford has it right from a physics point of view.

Practically speaking, we also used to use metal window screen material (stands up better & you can see through it). Then just run a wire to ground (if you use a water pipe, have to make sure that there is no plastic splice to break ground...for experimental purposes, we used to bury a piece of foil/screen about 1 foot deep & soak the ground with water).

good luck,

Three posts here speak of the Faraday cage needing to be earth grounded. I searched and searched the net a few months back to prove the case that the cage had to be grounded to reject RFI. The only thing I could find was that it did not... Example, CDP, DVD players, TVs, and radios. Two wire cord and plug no equipment earth ground. CDP and DVD players just a floating metal enclosure, a Faraday cage.
Jim

Jea48 is right - no grounding needed. We do it in the lab all the time. All you need is a sheet of copper that encloses the unit. If you ever visit radio telescopes, you will see that they line the entire data room with copper foil. Also, bust open a cell phone and you will find the same.

Also, many new switching circuits have a sheet of ferrite polymer that simply sticks down on the surface of the PCB. Ferrite works better than copper at lower frequencies actually (e.g. 60Hz line frequency and multiples thereof) but both sandwiched together gets you even better supression (copper on the outside).

Arthur

As Bgrazman points out the cage does not need to be a solid sheet of conductive material. A wire mesh with quite wide wire spacing works fine. Indeed, your metal car provides good protection from lightning strikes even though it has large openings for windows.

Also, as Jea48 points out, grounding is not necessary, although it might be a good idea if only for safety reasons. When I installed shielded 300 ohm twinlead wire from a roodtop FM antenna I was surprised to find that the shield, for which I had paid extra $, was left unconnected at both ends. Seemed like a waste, but it worked great for eliminating interference from passing auto trafic.

Try going to Office Depot and look for the new style "mesh" office products (letterholders, wastecans, etc).. You may find what you need to cover whatever it is that you need to set up a field around your equipment. Stopping extranious waves is a matter of stopping whatever wavelength(s) is causing the interference. You may need to eventually try some copper shielding postioned or vectored within the wavepaths.
Remember, WL (wavelengths) are not only absorded, they also bounce. what you may stop, may richocette and enter from another angle.

Good Luck,
Tubby