steel or aluminum case...which will sheild RF better?

[surlyjoe]

I am building a rig for a guy to do studio music on, he's concerned about RF sheilding, and wants to know which is gonna be better, steel or Alu? TIA!!

[JigPu]

I honestly don't know, though the case that conducts electricity better should. Also, I think you will need the case itself grounded to make a sheild. My guess... Aluminum. But of course I could just be saying it cuz it looks so cool!

Jigpu

[The Spyder]

Ya know ive built with both for people working in studio music..... and you could not tell the diff- but at the time steel is what was "cheaper" because these were already $4400 computers :-) -

[Áedán]

As far as RF sheilding is concerned, it makes no difference if you use steel or aluminium. What does make a difference is if there are any holes in the case, and if there are RF sealing gaskets around any joins in the metal.

An RF sealing gasket will be a) two very very close metal surfaces running in parallel, with a very good connection between the two to earth; b) A fine metal mesh (woven from strands of around 0.02inch); c) a woven mesh filled with an elastomer (allows for compression joints)

In terms of holes, any opening over 0.6mm will leak RF. This means any ventilation slots will need to have holes of less than 0.6mm! Any joins between the motherboard shielding and the case need to be in good contact, preferably with RF sealing gasket, rather than just in contact.

In terms of construction, the preference is welding, brazing, soldering then riveting. (In order from most effective to least effective)

Most RF sealed boxes are also coated internally with nickel, which provides most of the RF sealing abilities.

RF sealing is a pretty serious bit of work, and I don't know of any cases that would meet proper RF sealing.

Note: the 0.6mm is for attenuation of up to 10GHz signals. These would be easily generated as 10th order harmonics from a device running at 1GHz. Scary!

AidanII

[Pinky]

[lifts jaw back into place]

Amazed once again Aidan

[surlyjoe]

thanks man!! :-D

[Orbit]

(hand goes over head)

Man, AidanII, how do you know this stuff? They teach this in some school? ~whew~

[JigPu]

I forgot most of that stuff... Though now that you say it, I remember it again! Thanks!

Although I wouldn't think a 10th order harmonic would be that strong.... But hey, I did forget this stuff

JigPu

[Áedán]

Originally posted by JigPu
Although I wouldn't think a 10th order harmonic would be that strong...

It shouldn't be that strong, but with faster and faster CPUs coming up, 10GHz not really going to be 10th order much longer. With a 3GHz CPU, we're coming close to a 3rd order harmonic instead!

Orbit - One of the companies I worked for decided to do EMC testing of their own products. We had a RF quiet room, and all the analyser tools to do the compliance testing. Although I wasn't directly involved in the EMC testing, I knew the guys quite well and discovered lots...

Like how hard it is to prevent a steel room from resonating..

AidanII