Anyone build a Faraday cage before?

D

DatHak512

Gawd
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Jan 8, 2004
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Calling all physics majors.

So i like computers, and i also like amateur radio. I just recently built a caseless computer (lookie here if you're interested) but the problem is that it's really nosiy in the RF spectrum, especially when it's thinking hard. Which it is 24 hours a day because of Folding@Home. So i was going to build a Faraday cage so it would (1) keep its noise to itself, and (2) be protected from people trying to set things down on top of the open computer.
But then i got to thinking. Maybe i'll just build a Faraday cage around the whole amateur radio transceiver, that way i'm not just negating the RFI caused by the nearby computer, but from the whole house. Has anyone done something like this before? What do you think might make a good cage material and/or is wire mesh sold or would i have to make it? Basically i'm just looking for a little bit of direction. I'd have to allow for holes in the cage for a 12v DC power cable, two antenna co-axial cables, and a mic cable, and then a few hoes for the controls. Would these holes negate the advantages of having a RF cage in the first place? Any suggestions or comments welcome!

The radio i link to isn't the one i currently have. Right now i have the Yaesu FT-817, but i hope to upgrade to the 857 in the next year or so. My 817 is only slightly smaller than the 857, so i can build a cage that will work for the 857 and have it work for both radios.

Thanks,
_nick
 
a few of my office mates are amateur radio people, so I ran this by them.

-they suggest that it is your antenna picking up the noise, not the transceiver. The transceiver should be shielded (as well as the mic cables/etc)
-they say its not unusual for them to pick up noise from household appliances, even from car alternators starting

summary: case that computer, yo
 
I tend to agree, just put the computer in a case. Or your transceiver. Or both. The case when properly grounded, normally through the wall outlet IS a faraday cage.

But if you insist, farraday cages need to be made of materails with high iron content so they absorb the radio power and dissipate it as induction currents. According to wiki any conductive material will work but copper is expensive these days.

The screen "hole" size should be 1/2 or less of the wavelenth of the highest signal you want to block (othewise the wave can pass through the screen).

Some nice stiff hardware screen if you can find some fine enough and that a magnet will stick to it would do the trick. It should be grounded.

I wonder if you have a solid proper earth ground ? Find the ground rod for your homes electrical system and ground the chassis of both the pc and the radio directly to that with some number 14awg or larger wire.

http://en.wikipedia.org/wiki/Faraday_cage
 
Yeah, i was really confused about the whole shielded thing; it seemed like it was really poor design not to make sure that a ham radio wouldn't be properly shielded. And you're exactly right; the antenna is right in the same (college dorm) room as myself, the radio, and the computer: i just didn't even think about the antenna for some reason and jumped straight to the conclusion that it must be the radio itself that's picking up the RFI :rolleyes:. But of course it's the antenna!

Well, i'll just deal with it for now, and we'll see what happens when i move into a more permanant location; if it's still a problem then i'll look more into building a cage for the computer. (No sense in building a Faraday cage around the antenna! ;))
Maybe i'll try to properly ground the radio as much as possible in my current housing setup; i can't really ground the computer any more than it already is becuase of the way i have all the components just sitting out on my desk. In fact, it's a pretty weak grounding setup i've got; only the PSU is grounded, and all the componenets are more or less daisy-chained to that. Level groundplane... yeah right.
Sweet, i'm glad to hear that there's a thick hardware screen than i can use; that's exactly what i was hoping would exist so i could just cut and bend it, then solder the edges together and i'd be good to go.

Thanks for the replies.
 
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