FAQ: EMI / RF Interference
EMI (Electronomagnetic Interference) is emitted by all computers no matter the type. RF (radio frequency) interference can be synonymous with EMI and in the computer environment is caused by oscillating clock cycles at a certain frequency (your front side bus). The reason the interference occurs is not important though as we are just looking at how to stop it.
RF interference will cause problems with AM/FM signal, GPS signal or stock or aftermarket alarm remotes. If once your computer is turned on, your AM/FM radio signal or alarm remote signal degrades then your computer is causing RF interference
I personally had a problem with my computer degrading the signal of the FM band, GPS and my alarm keyfob. Below I will list what I did to correct my problem.
To correct my interference problem I scrapped my computers old wood and fiberglass case and switched to a basic (custom made) aluminum box with mounts for my M10000, Opus and a 2.5" HD. The case has several holes on it for cables to go through but the more sealed the case is the better. The case will also shield better the thicker it is. I then mounted the case directly against the body of my car so all of the metal was in contact; this was done in the trunk area next to the spare tire. Mounting flat against the body of the car will create a good ground plane. Locating the computer further down in the trunk area also distanced it more from the radio and GPS antenna.
These simple steps completely eliminated my problems.
Further measures to eliminate RF interference include using cables that are well shielded and with ferrite ends. You can also relocate the computer even farther from any antennas; the more distance the better. Computer and electronic stores also sell EMI tape which supposedly will help stop EMI but I have personally not tried it
As well as your computer, your LCD or any other electronic device may be radiating interference. If you have an RF interference problem and are unsure of the source, eliminate the source possibilities by powering one thing at a time.