In the Lake Mille Lacs area, 100 miles from the transmitters, computer (and monitor) generated interference is VERY obvious. The fundamental frequencies such as clock frequency are not the only problem. The harmonics are way up in the spectrum but are also the most easily shielded. The Fourier transform of a square wave digital pulse includes many sine wave components of many multiples of the fundamental frequency. -----Original Message----- From: Thomas T. Veldhouse [SMTP:veldy at veldy.net] Sent: Monday, January 14, 2002 1:38 PM To: tclug-list at mn-linux.org Subject: Re: [TCLUG] Static electricity (and an offer to buy) While I can not dismiss your claims about short wave interference, I can say I have run many computers without a case for extended periods of time and not run into any such interference. No AM or FM interference (although I don't listen to much AM -- occasional WCCO 830AM). No interference that I note. On the contrary, I can often here my cell phone negotiating with the tower on my FM Stereo in my car (and it is a new and quality system). Nobody has shown up at my door. There is a HAM guy in my [old] neighborhood that has a tower up behind his garage. No word from him either. Yes, I agree, use a steel case and put a nice plastic or wood case around it. Tom Veldhouse veldy at veldy.net ----- Original Message ----- From: "Steve Grobe" <steveg at transition.com> To: <tclug-list at mn-linux.org> Sent: Monday, January 14, 2002 11:36 AM Subject: RE: [TCLUG] Static electricity (and an offer to buy) > Tom, > > I gotta disagree with you. If what you said were true every PC manufacturer > would ship their product in a plastic case without any shielding. Take your > average home PC and remove it's case and it will fail FCC Class B (required > for domestic use) by at least 20dB. This is not just a problem at the main > clock frequency either, consider all the data buses with sub 10nS rise and > fall times and what you end up with a really nice broadband noise generator. > Most PCs do not meet FCC requirements with the case on. (Over the last ten > years I have tested enough of them to know.) > > The amount of interference will depend on how close you are to the radio/TV > station you are trying to monitor and their broadcast strength. It may not > bother you in the same room trying to listen to KQRS, but your neighbor down > the street trying to pick up shortwave transmissions will probably go nuts. > If you start interfering with air traffic or police/fire frequencies the FCC > can and sometimes will show up and make you shutdown your "transmitter". > > A wood/plastic case will not solve the ESD/safety problems either, the steel > in a typical computer case also serves as an earth ground for safety > reasons, a shield from ESD, and most importantly if something fails and gets > really hot steel does not easily burn. > > I'd find a small steel case and build something that looks nice around it. > > Blah, blah, blah........ > > > > -----Original Message----- > From: Thomas T. Veldhouse [mailto:veldy at veldy.net] > Sent: Monday, January 14, 2002 10:11 AM > To: tclug-list at mn-linux.org > Subject: Re: [TCLUG] Static electricity (and an offer to buy) > > > You are spending too much time in Physics class. In theory this is correct, > but the output is extremely low and should not interfere much with anything, > as per FCC regulations. It would be easier to bring in your FM to your > receiver using Coax (by nature a RF sealed system, again in theory -- or you > wouldn't need shielded cable) than it would to wrap your PC in a Faraday > cage. Not to mention, there is software out there to allow you to trasmit > AM broadcasts using your monitor -- so you need to wrap it as well. > > :) > > Tom Veldhouse > veldy at veldy.net > > ----- Original Message ----- > From: "Jared Burns" <jared-linux at mn.rr.com> > To: <tclug-list at mn-linux.org> > Sent: Monday, January 14, 2002 8:05 AM > Subject: Re: [TCLUG] Static electricity (and an offer to buy) > > > > You machine will emit RF (radio frequency) radiation at the frequency of > your > > machine's clock frequency (100kHz, 133kHz, etc.). > > > > Make sure you have the components inclosed in a Faraday cage or you and > your > > neighbors will have a hard time picking up radio signals (at least around > the > > frequency of your clock) while your machine is running. :) > > > > - Jared > > > > On Sunday 13 January 2002 02:53 pm, you wrote: > > > I'm looking at building my own PC, but in a literal sense, > > > including making a case (why not? to answer your obvious > > > question. Actually so that I don't have to have an obvious > > > computer case if I want it in the living room.) One option > > > is to house it in a plastic storage tub, but it suddenly > > > occured to me that ths may be a static electricity problem > > > waiting to happen. Any thoughts from the engineering types? > > > > > > As part of building the box, if anyone has a Socket A chip > > > of any speed they want to get rid of (i.e. if you're > > > upgrading) I'm in the market. > > > > > > Cheers, Paul > > > > > > > > > _______________________________________________ > > > Twin Cities Linux Users Group Mailing List - Minneapolis/St. Paul, > > > Minnesota http://www.mn-linux.org > > > tclug-list at mn-linux.org > > > https://mailman.mn-linux.org/mailman/listinfo/tclug-list > > _______________________________________________ > > Twin Cities Linux Users Group Mailing List - Minneapolis/St. Paul, > Minnesota > > http://www.mn-linux.org > > tclug-list at mn-linux.org > > https://mailman.mn-linux.org/mailman/listinfo/tclug-list > > > > _______________________________________________ > Twin Cities Linux Users Group Mailing List - Minneapolis/St. Paul, Minnesota > http://www.mn-linux.org > tclug-list at mn-linux.org > https://mailman.mn-linux.org/mailman/listinfo/tclug-list > _______________________________________________ > Twin Cities Linux Users Group Mailing List - Minneapolis/St. Paul, Minnesota > http://www.mn-linux.org > tclug-list at mn-linux.org > https://mailman.mn-linux.org/mailman/listinfo/tclug-list > _______________________________________________ Twin Cities Linux Users Group Mailing List - Minneapolis/St. Paul, Minnesota http://www.mn-linux.org tclug-list at mn-linux.org https://mailman.mn-linux.org/mailman/listinfo/tclug-list