For all practical purposes the SE of commonly used metals is infinite except at audio frequencies where skin depth becomes a problem. The intrinsic SE of the material is always dominated by seams and apertures that are inherent in any enclosure design. If you think that steel is less conductive than Cu or Al and therefore should give lower SE, consider that almost all shield rooms are made of steel and depending on construction meet SE requirements of 100 dB or better. Steel actually gives better magnetic performance at low frequencies, again because of skin depth considerations. The absolute best doors for SE are not CU or brass knife edge into Cu or brass fingerstock but rather the sliding steel doors in a pocket with internal bladders which force the sides of the door against the inside of the pocket much like the brake cylinder forces drum brakes against the brake housing. This is steel on steel with tin flashing to provide a soft, deformable mating surface.
---------- From: "John Harrington" <[email protected]> To: <[email protected]> Subject: Shielding Effectivness List-Post: [email protected] Date: Fri, Sep 28, 2001, 3:11 PM Would somebody please be kind enough to point me in the direction of some information on the shielding effectiveness of such metals as copper, aluminium and steel. Thank you John Harrington RF Group Manager Nemko Canada [email protected] <mailto:[email protected]> Tel: +(1) 613 737 9680 ext 229 Fax: +(1) 613 737 9691
