dgt@myrias.UUCP (David Tang) (01/07/86)
>> From: Art Altman <altman> >> Finally got my IBM AT hooked up in the attic office where I study. >> When I turn it on, every FM radio in the house has static!! >> Anyone know why this happens and how I can eliminate the problem? >> Hints: >> [some deleted hints] >> - Moving the antenna affects the static dramatically. Sometimes I can >> move the antenna such that the static is quiet, but it never goes away. >> Arrrrrgh! Art, should I assume that you have a multiple element antenna in your attic from which you feed all the FM receivers in your house? In this case this would suggest that the problem is primarily one of radiated interference. Try operating a portable (battery-powered) radio next to your PC. If the 'static' increases in intensity the closer you get then this confirms my suspicions. This would necessitate separating the PC from your antenna even further. > From: prk@charm.UUCP (Paul Kolodner) > My poor friend, the reason your PC can run without a nuclear reactor to > power it is that is contains a very efficient "switching" power supply. > These are notorious for producing bursts of radio-frequency interference > ("rfi") at a carrier frequency of about 30 kHz. This noise, I believe, > is in the 1 to 10 MHz range - it is propagated very easily down power > lines, but, typically, the radiated component is not as strong as the > conducted component. That's good, because it means that you have a > good hope of curing your problem merely by installing an emi filter > on the power line, as close as possible to your PC. The above comment does not hold up given Art's statement that moving the antenna helps dramatically. Computer circuitry operates at a much higher frequency than switching regulators, thus the radiated harmonics in the FM band are still at quite a high intensity. I suspect that I'm closer to the truth, but I could be wrong. > Build a copper box the size of your desk, put your PC in it, and move > in there. The above is a possible (although drastic) solution, if the attic is the only place for your office.