“RFI” speaks to the radiated energy coming from
the engine’s ignition systems (spark plugs etc),
or equipment fitted with high frequency power invert
ers (used with colour graphics displays), and
high speed data leads (commonly found in the wiring of GPS and AHRS units). This type of
“radiated” noise is “induced” into the wiring, and is picked up by the radio.
A defense against this type of noise is the use
of ferrite core suppression. These devices are
fitted over wiring harnesses to “attenuate”
the RF noise signals passing along the wires.