What Are Electromagnetic Interference (EMI) and Radio Frequency Interference (RFI)?
If you are old enough to remember when AM radios were standard equipment on new cars, you may recall the problem of ignition noise. It sounded like the putt putting of an outboard motor emanating from the speaker in the dashboard. The pitch and volume increased with engine RPMs. That was RFI. That signal emanating from the spark plug wiring entered those old AM radios through the antenna as well as through the power wiring that acted as an antenna for those RFI signals. When FM radios became standard equipment, RFI became less of a problem. Today, EMI is the problem that we need to be concerned with. The unvarnished truth is that EMI is just our old archenemy RFI with a new name, both are forms of unwanted electromagnetic waves that propagate from the spark plug wiring. These spurious signals are problem today because they send false signals to all the electronic control modules (ECMs) that manage engines, drive lines, and other vital systems on our cars. Those signals need to be suppr
