EMI Problems – Bothering your Neighbors

EMI works both ways. All of the problems that EMI can cause for you and your computer can also be caused by your computer and it can affect your neighbors. Not only is it necessary to keep unwanted EMI out of your computer it is also necessary to keep your computer from radiating unwanted noise to other appliances and electronic devices. The same precautions that you take to prevent EMI from entering your computer also help prevent EMI from leaving your computer and affecting other devices.

FCC Device Designation

One important issue of which you need to be aware is the FCC class assigned to your computer. Make sure all of the components you purchase are listed as FCC Class B devices. Devices that have been listed as Class B by the FCC are suitable for use in a home, home office, or a regular office environment, and they radiate less EMI than devices listed as Class A. Class A devices are designated for a “business” environment; the devices are allowed to radiate more EMI than Class B devices. The FCC objective is to keep the home electronic environment as free as possible from EMI.

If you purchase a Class A device it will be much more likely to interfere with the operation of your neighbor’s TV, home theater system, telephone, computer Internet connection, fax and other devices. If this occurs, the FCC will come to your house and make you fix the problem. The vendor of the device is not responsible for this, nor is your neighbor responsible for sheilding his or her devices from the EMI caused by your “dirty” device. The cost of fixing this is your responsibility, too, and you will be restricted from using the device until the problem is fixed. Problems like this can be caused by Class B devices, too, but they are much less frequent because of the additional preventative measure designed into this class of device.

Home Brew

Many computer geeks, myself included, like to build our own computers. This is a really kool thing to do and it saves money because we can get exactly the computer we want without having to also pay for that trash that Microsoft calls an operating system.

If you do this, be aware that the computer you build is not approved by the FCC. No vendor is responsible for testing the completed unit for FCC compliance and to determine to which class of devices it belongs. The same caveats apply to devices you build yourself as to any other device should it be “dirty” and interfere with your neighbors electromagnetic environment. You will be responsible for the cost and effort required to clean up the problem.

In order to minimize problems, be sure to purchase a high quality case and power supply. Follow the recommendations I outline in the article, How to Minimize EMI Problems, and you should be in reasonably good compliance with FCC class B requirements.

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