Re: Building a Faraday's cage ?

On Mon, 26 Jun 2006 08:40:55 -0700, John Larkin
<jjlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

On Mon, 26 Jun 2006 15:08:58 +0200, "CS" <address@xxxxxxxxxx> wrote:

Hi :)

I have a small bedroom recording studio full of electromagnetic fields
(mainly 50hz+harmonics up to ~3,5khz from power cables in walls).

Here is how it looks on Adobe Audition's spectrum analyzer:
http://img158.imageshack.us/img158/4522/dirtysilence7th.jpg

I'm planning to build a 2m x 2m Faraday's cage/booth to protect active
electric guitar pickups from external electrostatic and electromagnetic
noise 20hz-96khz

Please suggest best material (copper ? aluminium ? iron ? or maybe a
combination of different metals), how thick should it be and how to get rid
of the current in a situation where no true ground is available.

How many dBs of attenuation should i expect ?

Thanks in advance.

ps. If this is not the right newsgroup to ask this question please suggest
the best one.


The three field types are magnetic, electrostatic, and
electromagnetic.

Forget magnetic shielding. Enough iron to give any useful shielding to
a room would collapse the structure of a house.

Electromagnetic shielding, aka RFI screen room, is difficult and only
keeps out high-frequency fields. Google "emi screen room" or somesuch.

You achieve good electrostatic shielding (block capacitively-induced
hum) with any conductive coating on the walls: foil, screen wire,
metal sheets. Just connect and ground them all. Some modest
electromagnetic shielding will result, too. A water pipe is a good
low-frequency ground.

But none of this should be necessary if cabling and grounding are
right.

John
Assuming the noise is coming from the wiring in the walls, could the
noise come from fluorescent fixtures, or other noise generating
devices, connected to the same circuit but in another room? I know
little about electronics so this question is because of curiosity.
Also, do the guitar strings act as antennas and transfer whatever they
receive to the guitar pickup?
Thanks,
Eric
.