Igor, These were commercial cages used in the consumer products design business. Things like radios, TVs, 900MHz cordless phones etc...do I know for a fact that two or three layers of fine mesh copper ( BTW about an inch apart ) were necessary? No. I just took the word of the guys who had been doing the stuff for years. It wouldn't surprise me if the commercial cages were overkill. Neither would I be surprised if anything less leaked significantly. RFI is not an easy subject area. Find a commercial cage vendor and talk to an apps eng. Lacking an actual test facility, I suppose a really basic test would be to use a hand-held AM radio tuned to a space between stations and try out your PC with and without a chicken-wire cage. Sometimes a particular piece of SW will have a pattern that you can recognize, maybe following a keypress. I've been able to differentiate between button scan, watchdog, servos, processor etc... It's a relatively cheap, quick experiment. Try different frequencies and orientations of the ferrite loop antenna. For higher frequencies ( CPU clocks + other harmonics ) you'll need other methods. I've been meaning to take a look at a standard PC keyboard. Someday soon...if I do I'll let you know what I find. As for looks - tough - a PC generates lots of RFI, a partially functional cage is probably worse than none at all because of the false sense of security. Trying to shield the computer and the monitor is an entirely different can of worms. Probably an order of magnitude harder than making a good cage. Regards, Mike In real life even the easy things are not easy. Igor Chudov @ home wrote:
Michael Motyka wrote:
Now... Just curious, if I simply make my study into a faraday cage via use of fine (< 1/2 inch) chicken wire, and insulate my power system from the computer emenations, would that be enough? Chicken wire is not that expensive, and I think that I could make it look nice on walls.
The cages I've used were framed in wood and had several layers of copper screening. The mesh was like standard window screen, <.125". There were two, I think sometimes three, layers. The corners/joints were copper
Michael,
Was the amount of work involved really necessary? What do three layers accomplish compared to just one?
sheet. The screen was soldered to the corners. The doors were stepped or beveled and had several sets of fingers - indside edge, outside edge, perhaps one intermediate. Screen makes ventilation easier. Power should be brought in through a separate, partitioned, shielded box with filtering in each partition. Phone lines, same thing. You trust your apps, os and TCP/IP stack to not rat you out? If not, work off-line always.
Right.
Al foil if it were thick enough would be OK but how do you reliably join edges?
Glue? Perhaps some weak glue that would not destroy the underlying paint.
Converting your study is non-trivial. The door would look like crap. You would need the euivalent of a door over the window.
My window has a mesh on it. Is that not enough?
I wouldn't trust 1/2" galvanized chicken wire for containing anything but chickens or other non-gnawing furry woodland creatures.
Is that confirmed by evidence?
The reason for my question, I think that I somewhat value TEMPEST protection, but not enough as to cover my whole room with expensive and ugly looking copper or three layers of mesh and ferrite. I don't want all of it to be too conspicious.
- Igor.