Ed, if there is a grand prize to be awarded here for the most amusing account ... you've got it hands down with this one... and your closing statement, is a gem !
george > -----Original Message----- > From: [email protected] [SMTP:[email protected]] > Sent: Thursday, March 11, 1999 11:59 AM > To: EMC-PSTC > Subject: Re: Awards for Worst EMC/PS qualities > > > > Subject: Awards for Worst EMC/PS qualities > > Author: <[email protected]> (Bailin Ma) at Internet > > Date: 03/08/1999 8:03 AM > > Hi Group, > > > > We have already seen awards for the most misleading ads, worst > attire, > > worst films, ..... > > Why not awards for worst EMC and PS qualities? > > > > Barry Ma > > Morgan Hill, CA 95037 > > OK, I'll submit just one more entry, even though this will need a new > category (which I'll call Stupid Construction). > > > Many years ago, a very large defense contractor decided that a black > program needed multiple shielded enclosures within their SCIF so as to > keep their classified data from leaking out and running down the > hillside. So, the Program Manager talked to the Facilities Engineer, > and together they said "We can build our own TEMPEST shielded room. We > will even do it cheaper and faster than any of these dumb quotes we > have." > > So it came to be that they ordered much chicken wire, and beryllium > copper fingerstock, and lumber, and drywall panels, and oh yes, very > very many 2" long drywall screws. And a three phase powerline filter. > And the facilities laborers then labored mightily for what may have > been months; no one really knows. But finally, it was completed. It > was painted, and carpeted, and even had plywood veneer paneling on the > walls. It also had fluorescent lights in each room. And telephones in > each room (but alas, no telephone line filters). And the program > occupied the area, setting up their computers and test equipment and > their "other stuff". > > After a while, the more troublesome technicians began to wonder why > their pagers had no problem functioning within the rooms, and that > workers could enjoy FM broadcast radio at their workstations. Wasn't > this supposed to be an RF shielded facility? > > I arrived on site, with spectrum analyzer and trusty loop antenna > (three turns of the extended coax center conductor formed into a > loop). I'd find those leaks and plug 'em fast. > > The first thing I noticed was that the room doors were ordinary steel > office doors, with painted frames. The fingerstock had been screwed > over the painted surfaces. Many of the fingers were broken, bent or > missing. And the steel door frame was mounted to the drywall. > > The RF shield consisted of "chicken wire", a wide-mesh, twisted steel > wire construction. The name should tell you what it was good for. The > average chicken cannot be forced through a chicken wire barrier (at > least without significant distortion). AM broadcast radio uses a > wavelength long enough that the barrier yields a certain amount of > shielding. But FM broadcast slips through like a mosquito. > > So I started to probe one of the rooms. I just tuned the SA to one of > the many convenient signals around 100 MHz, and started to sweep the > room. Not only did the mesh screen leak like crazy, but it also turned > out that most of those many thousands of drywall screws went right > through the wall without touching the mesh. So EACH of these little > conductive rods acted as a path for RF in and out of the screen > barrier. There were no leaky points; it was like playing laser tag in > an infinite hall of mirrors. > > And, just to show that none of the basics of proper shielding > technique had been followed, I found that the powerline filter was > located about 75 feet away from the shielded rooms. The filtered power > was run to the room in PVC conduit, and the filter was grounded by a > six foot long #00 pigtail. > > After wandering the facility for about two hours, I was approached by > the Program Manager, who inquired about my corrective actions. I told > him something to the effect that I hadn't been able to find any > shielded rooms, but that if we stripped this area clear to the > concrete, we could build some right here. I went on to detail that I > had seen just about every shielding mistake you could make, all > concentrated in one place. This site could qualify only as a museum of > inverse shielding. > > Bad report, bad career action. I went back to testing noisy gadgets > that smelled vaguely of ozone. The customer wouldn't let them use the > rooms for classified work. A year later, the PM became a VP. > > > -------------------------- > Ed Price > [email protected] > Electromagnetic Compatibility Lab > Cubic Defense Systems > San Diego, CA. USA > 619-505-2780 > Date: 03/11/1999 > Time: 08:59:26 > -------------------------- > > > > --------- > This message is coming from the emc-pstc discussion list. > To cancel your subscription, send mail to [email protected] > with the single line: "unsubscribe emc-pstc" (without the > quotes). For help, send mail to [email protected], > [email protected], [email protected], or > [email protected] (the list administrators). --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
