From: Clint Wolff (VAX collector) <vaxman(a)qwest.net> First a faraday cage to run a vax is foolish. The FCC notice refered to is basically a hint about whose reponseability it is to fix RFI problems should they occur. Often it's not a problem save for at point blank range. RE: galvanized screening vs fine copper screening. If you cant do it right dont bother. As the holes get larger and the resistivity increases the attenuation decreases. Also as the holes get bigger the frequency at which the screen becomes RF transparent also gets lower. So to get an effective faraday screen fine copper screening with well bonded (often soldered) joints and a door that has RF tight joints are used. Also any wires that enter or leave have to be bypassed to avoid it becomming a leakage path in either direction. I participated in building one and it's a lot of work and after testing to find RF leaks. At the other extreme a cage of .500 galvanized will have effect but the effect is far more limited. to prove it take a roll and make a mini cage large anough to hold a battery AM/FM radio and see what I can hear and try it with the same radio. You will also find it very difficult to solder or otherwise effectively bond the joints of a galvanized wire cage. Last item: The average system (even a PDP-8) will be much better in the RFI derby if all the covers are on and the correct cables are used. The later smaller one box systems are fairly decent if the case is metal and all the screws/hardware are in place. The killer items for RFI are SCSI cables, external disks that used any unshielded cables (BC05s come to mind) or monitors that used shielded cables but are incorrectly terminated. RS232 wires that do not use an external shield can be a path to propagate noise out of and otherwise tolerable box as well. Worst offender awards: TRS80 with EI... ghastly both radiating and affected by nearby transmitters. (1w 144mhz ht at 4ft would crash the average TRS80). Some of the Apple][s Early S100s with non-stripline and unterminated busses (altair!!!!). SBCs, no case at all most often. Many of the early all plastic cased (no internal conductive spray coat) with no internal shielding systems. Many (most) CRTs that are not metal boxed internally are noisy. Allison