RF signal suppressors - are they available?

Hi!!! A good friend of mine has a 486DX2/66 that has a rather *** habit of interfering with the TV reception and hence has his parents whining quite a bit when he is using it. I was wondering if there was a device you could buy that would suppress the RF (or whatever they are) signals emanating from the computer and stop affecting the television reception? Thanks in advance, Cameron.. -- _________ ___ ___ / / / / / | BAYERISCHE MOTOREN WERKE - /__/__/__/ /__/|__/|__| ** THE ULTIMATE DRIVING MACHINE **

(Cameron Ing) says: Isn't that called FCC ? (or better: FCC approval ?)

>A good friend of mine has a 486DX2/66 that has a rather *** habit of >interfering with the TV reception and hence has his parents whining quite >a bit when he is using it. If it was bought from a dealer as a system, then check with your government's equivilant to the US Federal Communications Commission as the system should not interfere with the TV in usual situations. Here are some tips: 1. If the TV uses unshielded twin-lead, try converting to coax (and watch out for unshielded coax to twin-lead converters. If you are using cable, make sure it is completely shielded and not a cheap slip-on-slip-off type or one with a few flemsey ground strands (if it bends easy and looks nice, then it probably isn't any good). If the TV doesn't have a coax input, then you can try to construct a shield using solderable metal or copper tape. 2. If the computer is near the TV (i.e. on the other side of a wall or connected through the same AC) or is near the antenna/cable, try to relocate it as far away as possible. 3. Minimize the cables running from the computer and/or try to rearrange them to minimize the interference. Wiggle them a bit while looking at the TV to see if it makes any difference. If they aren't completely screwed-down, then tighten them. You can also buy clip-on ferrites for the cables. You can also buy shielded cables... I would suggest trying to borrow some just to see if they actually help. 4. If the computer's case isn't shut, then of course shut it. If it is shut, then try using copper tape to seal up all the long gaps like you would use weather spripping for your home... BUT DON'T SEAL UP THE AIR HOLES. Basically, you are looking for long gaps and slots rather than small round holes (don't worry about slots around the power supply right now). Also, if you put any tape near the circuit board or exposed connector, make certain that it doesn't short anything out. 5. If still a problem, try using metal screen taped with copper tape over the air holes on the case (including over the power-supply). Make sure the screen is of medium size to minimize the affect on the air circulation (not too small to impede the air nor to large to be ineffective). To be effective, it must be taped down all around. to observe the effects and minimize your waste of copper tape, you can try just holding it firmly against the metal chasis and observe the TV. 6. You might try to also use an AM or shortwave radio (even better might be a handheld TV) and see if you can use it near the computer to pin-point the leakage. One problem that you will find is that once you seal up one hole, it will start leaking out another. This is especially true if you are using a board which was not approved for home use and thus has very strong RF output. Unless you are a certified computer technician, it is unwise to attempt to add any suppression circuits to the boards. Tom -- url: [link lost in import: /.***ia.edu/~tdb8q/] [updated 28 Nov 94]

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>>A good friend of mine has a 486DX2/66 that has a rather *** habit of >>interfering with the TV reception and hence has his parents whining quite >>a bit when he is using it. >If it was bought from a dealer as a system, then check with your >government's equivilant to the US Federal Communications Commission as >the system should not interfere with the TV in usual situations. >Here are some tips: > [Lots of good tips snipped]

Before trying the complex "seal up your PC with copper tape/foil" stuff suggested, it would be a good idea to try to isolate where the problem is. One cheap PC I owned generated a lot of RF from the screen. Does the TV interference vary depending on what's on the screen? On the video mode? Try turning off the screen to see if the problem goes away. If it doesn't then try this: "Dad, the short wavelength of the screen is interfering with your TV. What I need is a 20 inch monitor (50% more wavelength), otherwise you'll never see BH90210 again. It'd make a great Xmas present too." :-) Frank.

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| 4. If the computer's case isn't shut, then of course shut it. If it is | shut, then try using copper tape to seal up all the long gaps like you | would use weather spripping for your home... BUT DON'T SEAL UP THE AIR | HOLES. Basically, you are looking for long gaps and slots rather than | small round holes (don't worry about slots around the power supply | right now). Also, if you put any tape near the circuit board or | exposed connector, make certain that it doesn't short anything out.

Also, you might make sure that the screws holding your case together are making good contact with the metal, so that that parts are grounded together well. You might even scrape a little paint from underneath the screws. -- Ed Haymore | AA6EJ

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| 4. If the computer's case isn't shut, then of course shut it. If it is | shut, then try using copper tape to seal up all the long gaps like you | would use weather spripping for your home... BUT DON'T SEAL UP THE AIR | HOLES. Basically, you are looking for long gaps and slots rather than | small round holes (don't worry about slots around the power supply | right now). Also, if you put any tape near the circuit board or | exposed connector, make certain that it doesn't short anything out. |

But before you try these steps you should first eliminate the cables from being the cause. Simply observe whatever device is being interfered with while you unplug each cable.

You could also trying putting snap-on, RF chokes on some of tha cables leading into your computer (eg. keyboard cable, mouse cable, telephone cable to an internal modem, etc.) The power cable, parallel printer cable and video cables should already be well shielded so you shouldn't have to bother with them. When putting these RF chokes on the cables, locate them as near the computer as possible, that is, at the connector end of the cable. These chokes are available at Radio Shack the last time I checked. Good luck and Seasons Greetings. John -- JOHN RUMBALL