Maybe if they covered the walls too? https://www.amazon.com/Reducing-Wallpaper-Faraday-Copper-Radiation-Shielding/dp/B09BW3CYQB
On Sat, Nov 11, 2023 at 7:51 PM Steve Thompson <ste...@wkyr.net> wrote: > Many years ago at Hagerstown MD, they had a computer (I think it > was an NCR3 or 3000, it's just been too long ago) that at odd > points would just fail. My father was an RF tech working on > radios, and had a contract for the Police Department... so I will > make this short. It turns out that a few stories below this > computer room was the door out of the garage where the police > cars were parked. And so upon exiting the parking garage and > entering the alley to the street, officers would key their mics > to verify their radio was working and that would cause the > computer system to lock up (machine check?). > > This was discovered by an NCR CE that had an Oscilloscope doing > tracing trying to find what was causing this problem and just > happened to be standing at the window looking down when a police > car came out and the machine froze..... the police mobile radios > were a harmonic of the system clock!! And were 100 Watts IRC. > > A sign was put at the exit of the garage informing anyone who > keyed their mic for their radio before getting out of the alley, > upon being discovered who they were, their pay check would be the > last one to be passed out at the end of the month. This problem > had been invariably happening during payroll runs and they had to > be restarted from the beginning. > > Problem stopped. > > Steve Thompson > > Oh, and the windows did have a metal grid over them in an attempt > to prevent things like this. > > On 11/11/2023 5:07 PM, Tom Brennan wrote: > > Just before I worked with mainframes I drew maps on a computer > > that had a big display, a small drawing pad and pen, and a > > large light table with a "puck" for tracing existing maps into > > the computer. Both the puck and pen worked by receiving a > > magnetic signal from the pad or table in order to determine its > > location. About once a week someone would complain that their > > pen was throwing the cursor all over the screen, so a new pen > > was ordered at maybe $500. > > > > The light table had bunch of fluorescent bulbs inside, and you > > could dim them with a knob if needed. One day I noticed that > > when the light was either full on or full off, there was no > > problem with my pen. But if the dimmer was in the middle, the > > pen had issues. Those dimmers used triacs which work by > > holding back each AC wave a bit and then sharply rising. The > > sharp rise generates all sorts of EMF and that's what was > > messing with the coil in the pen. > > > > On 11/11/2023 12:55 PM, Wayne Bickerdike wrote: > >> On the subject of RF interference. Years ago we came back from > >> living in > >> California to Australia. We had a 110V coffee espresso > >> machine. It worked > >> well and we ran it from a voltage changer plugged into the > >> socket. Early > >> rise time, my wife would go into the kitchen and make a coffee. > >> > >> I'm in the habit of reading my email and surfing at that time > >> (like now in > >> Australia). > >> > >> For weeks and months my internet would go off and come back a few > >> minutes later. I eventually tied it back to the coffee > >> machine/voltage > >> reducer. We stopped using it and all good. The wireless router > >> runs on > >> 2.4Ghz and is located in my study, maybe 30 feet from the > >> kitchen and there > >> is a double brick wall in the way. > >> > >> As an adjunct to this. I switch off my router at midnight and > >> I get much > >> better sleep. > >> > >> On Sun, Nov 12, 2023 at 6:11 AM Joel C. Ewing > >> <jce.ebe...@cox.net> wrote: > >> > >>> I think shielding of the PC itself is unlikely the problem, > >>> unless the > >>> case is not properly closed. All PCs I have ever seen have > >>> metal cases, > >>> which if properly seated and grounded act as a RF shield, > >>> inbound and > >>> outbound. > >>> > >>> Any electric motor could be producing power transients at > >>> power on/off > >>> and possible RF interference from contact arcing (which can > >>> increase > >>> with motor age), which might travel over the house wiring, or > >>> via air > >>> and get picked up by other cables in the room which are > >>> connected to the > >>> PC. Any magnetic effects of a motor should be minor by > >>> comparison. > >>> > >>> If it's a large enough motor, start up may produce a > >>> temporary dip in > >>> voltage big enough to be a problem for a computer that is not > >>> powered > >>> through an Uninterruptible Power Supply (UPS). If you notice > >>> any lights > >>> flicker when the shredder powers up, that definitely could be > >>> an issue. > >>> If you are not already using a UPS for your PC, you probably > >>> should be, > >>> for other reasons as well. The shredder definitely should not > >>> be plugged > >>> into the same outlet as your computer, and it would be best > >>> if it were > >>> on a different house circuit as well. > >>> > >>> If the problem only started occurring after adding RAM, maybe > >>> the PC > >>> power supply is now working harder making it more sensitive > >>> to power > >>> dips than before. It's also possible the computer may be > >>> getting old > >>> enough that the power supply is getting less effective at > >>> filtering out RF. > >>> > >>> If for some reason the shredder motor is broadcasting more RF > >>> interference than in the past, keeping it further away from > >>> any cables > >>> connecting devices to the PC may help. There are also some > >>> relatively > >>> inexpensive ferrite beads that can be clipped onto cables > >>> near the > >>> computer to block RFI from entering via that route. > >>> > >>> Assuming you are in a house, the simplest experiment is to > >>> try moving > >>> the shredder to another room far away from the PC where it > >>> can be > >>> powered from a different house circuit. If that eliminates > >>> the problem > >>> and having the shredder in a different room is acceptable, > >>> moving the > >>> shredder away from the PC may be the simplest short-term > >>> solution. > >>> Otherwise you can either try using a UPS for the PC and/or > >>> adding > >>> ferrite RF filters on PC device cables that don't already > >>> include a > >>> filter, especially if there are any cables that are routed > >>> close to the > >>> shredder. > >>> > >>> JC Ewing > >>> > >>> > >>> On 11/11/23 06:34, Bob Bridges wrote: > >>>> Hah! A few years ago I had my hardware-geek son build my > >>>> latest tower > >>> PC. It's pretty good - not water-cooled like the one he made > >>> for himself, > >>> but a nice big monitor and I finally gave him permission to > >>> load me up on > >>> RAM. But ... > >>>> > >>>> Do normal commercial PCs have Faraday cage around them, or > >>>> something? I > >>> can't use my old paper shredder any more, because when it > >>> fires up within > >>> the same room, the PC suddenly dies and has to be rebooted. > >>> A minor EMP, I > >>> take it. > >>>> > >>>> --- > >>>> Bob Bridges, robhbrid...@gmail.com, cell 336 382-7313 > >>>> > >>>> /* The will to win is not nearly as important as the will to > >>>> prepare to > >>> win. -R.M. Knight */ > >>>> > >>>> -----Original Message----- > >>>> From: IBM Mainframe Discussion List > >>>> <IBM-MAIN@LISTSERV.UA.EDU> On > >>> Behalf Of Leonard D Woren > >>>> Sent: Saturday, November 11, 2023 02:12 > >>>> > >>>> Long ago I was told why my shop didn't carpet the tape > >>>> storage area. > >>> Apparently some shop that did had a problem with unreadable > >>> tapes. > >>> Eventually they figured out that all the unreadable tapes > >>> were on the > >>> bottom row of the tape storage. And the outside cleaning > >>> people used a > >>> vacuum cleaner... > >>>> > >>>> --- Bob Bridges wrote on 11/8/2023 6:56 AM: > >>>>> /* The more sophisticated the technology, the more > >>>>> vulnerable it is to > >>>>> primitive attack. People often overlook the obvious. -Dr > >>>>> Who, 1978 */ > >>>> > >>> -- > >>> Joel C. Ewing > >>> > >>> ---------------------------------------------------------------------- > >>> > >>> For IBM-MAIN subscribe / signoff / archive access instructions, > >>> send email to lists...@listserv.ua.edu with the message: INFO > >>> IBM-MAIN > >>> > >> > >> > > > > ---------------------------------------------------------------------- > > > > For IBM-MAIN subscribe / signoff / archive access instructions, > > send email to lists...@listserv.ua.edu with the message: INFO > > IBM-MAIN > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN > -- Mike A Schwab, Springfield IL USA Where do Forest Rangers go to get away from it all? ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
