What is Electro-Magnetic Interference?
E.M.I. is noise and interference from electrical appliances and nearby transmitters. EMI from VHF/UHF radios, Cellular phones, SSB marine or ham radio transmitters effect mobile equipment and degrade performance.
The RF voltage levels present at equipment terminals varies over a wide range depending upon frequency, proximity and power output of the interfering device. Installations cause even more variability. The length of power supply wires and cables often determines whether the fault is a 'minor annoyance' or a major cause for failure within the equipment. If the wire becomes 'resonant' at the operating frequency it can absorb significant amounts of power from the transmitter and present very high voltages at the equipment power terminals.
STO-P Power Fault Protectors incorporate passive filters to suppress EMI to levels that do not threaten damage to equipment. Typical suppression levels are 15 to 20 db (100 times reduction in power levels) over a broad band of frequencies.