wjm@lcuxc.UUCP (B. Mitchell) (01/03/85)
<gulpo> Yes, you can achieve RF shielding through the use use of a ground mat, which is a large sheet of conductive material. However, this is only part of the shielding system. Usually each equipment cabinet is bonded to this mat via ONE large conductor (a heavy piece of wire), as in the Sperry Univac computer systems described in your publication. The key idea is: put all sensitive equipment in a grounded enclosure that surrounds it with conducting material. Sometimes, this is done by constructing a room out of conducting materials, like copper sheets, or by putting the equipment in metal cabinets. Note tht all openings, like windows, must be covered with conduct- ive screens for this to work properly. This is called a "Faraday cage". Another important point is to avoid ground (or common mode current) loops. These allow currents created (induced) in the shielding system to circulate among components, creating more interference. To prevent this, only ONE conductor must be used between each equipment cabinet and the ground mat. References: The Radio Amateur's Handbook can provide some general grounding and shielding principles, while a good college physics text can explain why these shields are effective. You might look at Halladay & Resnick or the Berkeley physics series. 73's Bill Mitchell, WB2IAU (ihnp4!lcuxc!wjm)