Many people nowadays are installing aftermarket HID and/or LED conversion kits in their headlights and fog lights. These new conversion kits use an external power booster, called a Ballast for HID setups and a Driver for LED setups. Both of these external power supplies do similar functions, but technically they are quite different. Also, both of these products create RFI (Radio Frequency Interference); in fact every electronic device ever made creates RFI, but there are different types of this electrical interference. Sometimes when installing an LED conversion kit or an HID conversion kit in your vehicle the result can be better, brighter light, but also a side effect of AM or FM radio interference. This is characterized by where you once were able to pick up a radio station, with the new lights installed and turned on, now that same radio station is just white noise.
The solution for your problem might be what is called a ferrite coil, also known as a ferrite bead, a ferrite choke, or an RFI choke. All of these names mean the same thing. Ferrite beads prevent interference in two directions: from a device or to a device. A conductive cable such as the input power for the HID or LED headlight bulbs acts as an antenna – if the device produces radio frequency energy, this can be transmitted through the cable, which acts as an unintentional radiator. In this case the bead may be required to reduce RFI. Conversely, if there are other sources of RFI, such as an ignition module or battery charging alternator, the bead prevents the cable from acting as an antenna and receiving interference from these other devices.
Ferrite coils are already used in everyday household uses. You can find them on USB cables, power cords for your television or home stereo, and even on input power cables on your automotive satellite radio:
LED Conversion Kits Small Ferrite Coil:
For an LED Headlight conversion kit you can use a large ferrite coil and wind the input power wires around it, or you can use a small ferrite coil, and just clamp it over the power cable:
LED Conversion Kits Large Ferrite Coil:
HID Conversion Kits Small Ferrite Coil:
For the HID conversion kits you can put a smaller ferrite choke around the power input cable of the ballast like this:
HID Conversion Kits Large Ferrite Coil:
For the HID conversion kits you can put a larger ferrite choke around the power input cable where the small wires are exposed. This allows you to wrap the wiring around the choke for a better result. This is how to install the larger ferrite coil:
Sources for Ferrite coils:
Large style designed for looping wires around coil: RND-6 ( Wurtz number 7427151 ) snap on chokes
The inside hole size is 0.57″ (over 1/2″, 14.5 mm)
Small style designed snap onto power input cable: RCT2 RFI Radio Frequency Interference Ferrite Chokes – Black
measures approximately 1.25 x .75 x 75 inches