Radio Frequency Interference (RFI) and ElectroMagnetic Interference (EMI) noise suppression is accomplished primarily through circuitry internal to the radio receivers. These internal suppression devices are only serviced as part of the radio receiver.External suppression devices that are used on this vehicle to control RFI or EMI noise include the following:Radio antenna base groundRadio receiver chassis ground wireEngine-to-body ground strapResistor-type spark plugsRadio suppression-type secondary ignition wiring.