js07@GTE.COM (Jack Shaio) (09/01/89)
A while ago I posted an article asking about whether it was possible to use a Class A PC at home (an ALR 25Mhz). Class A's produce higher levels of radio frequency interference (RFI) than Class B's and are only licensed for use in commercial environments. Most people answered to go ahead, it doesn't matter. Well... I tried an ALR at home, and it interfered heavily with TV channels 9-13. A 25 Mhz machine has a 50 Mhz circuit, which also emits RFI at multiples of 50 Mhz. Channel 9 is around 100 Mhz. There turned out to be a simple way of solving this. Most RFI comes from the PC to monitor cable. You can get ferrite chokes from an electronics supply store. Wrap the pc to monitor cable 3 times around the cores, and done. High quality cores will absorb only a selected range of frequencies; hence you should get low quality ones. They can also be gotten from a burned out TV. After this, it was possible to use a portable TV within a few feet of the pc with no interference. thought someone would like to know. =========================================================================== js07@GTE.COM - this email address will self-destruct in 7 days. ===========================================================================
mosley@peyote.cactus.org (Bob Mosley III) (09/03/89)
In article <7491@bunny.GTE.COM>, js07@GTE.COM (Jack Shaio) writes: > A while ago I posted an article asking about whether it was possible to use > a Class A PC at home (an ALR 25Mhz). Class A's produce higher levels of > radio frequency interference (RFI) than Class B's and are only licensed for > use in commercial environments. Most people answered to go ahead, it doesn't > matter. Well... ...listen to what the others have told you. Thanks to the efforts of the Ford and Carter administrations, the US Courts system, and the CB craze of the 70's, the FCC effectively showed that it could not manage itself worth a damn. This led to their being temporarily stripped of the power to collect licensing fees (except for commercial broadcast radio & TV), which in turn virtually neutered Unca Charlie to the point of total ineffectiveness. ...or, to look at it another way, the FCC doesn't have time to come hunt you down if you're running a computer that's causing RFI/TVI. Besides, odds are against it affecting any TV or radio that's outside of your house if you take a little care in where you place it. Same goes for an apartment. ...the Class A & B guidelines were concocted not just to protect your neighbor when he/she/it is trying to watch "Three's Stupidity" reruns, but to protect you as well - especially if you're an unelightened type that doesn't fully understand the concepts of RFI/TVI. If you choose to ignore the FCC "rules" concerning Class A within the confines of your own home, no problem. Uncle can't even get a search warrant these days to come bust you for "running a PC with a 1000kw Linear". He can, however, cause some hassle if you're in fact sending herringbones over on top of Mrs. Finklewhacker's attempts to watch "All My Children". ...but again, as stated above, a little common sense will keep the most ineffectual Federal agency off your back for virtually the rest of eternity. (If you have any further questions about RFI/TVI, I suggest you pop over to rec.ham-radio, and ask some of the net-OM's over there about suggestions on curing the problem if it's affecting your neighbors. Otherwise, again, take that system home, and don't sweat it.) OM [btw: as a side note, the Fords slammed the FCC in early '76 for busting one of Betty's nephews-in-law for running out of band with a CB radio, and added a little salt to the wounds by getting the ball rolling on making CB licenses free of charge. The Carters gave their full support to this when Billy was busted for the 3rd or 4th time for running illegal power amplifiers in CB frequencies, and for running a 2-meter ham rig without a license. Overnight, the FCC found their budget cut to a tenth of what it was at the start of FY '75, and they had to let most of their field ops go. Like I said, neutered. Remember, only Batman can fight crime singlehandedly, and Unca Charlie is no Batman.]