Hardware · Cabling
EMI
Also known as: Electromagnetic Interference, RFI, Radio Frequency Interference
EMI (Electromagnetic Interference) is interference from electromagnetic radiation that disrupts electronic devices and communications — caused by motors, radios, power lines, and other radiating sources nearby.
EMI is the broader category that encompasses electrical noise from conducted interference (noise on cables) and radiated interference (electromagnetic waves through the air). Both can disrupt data communications and electronic equipment.
Sources of EMI in IT environments:
Radio transmitters — nearby cellular, radio, or radar equipment can interfere with Wi-Fi and other wireless systems operating at similar frequencies.
Industrial equipment — motors, welders, and variable frequency drives emit broadband EMI.
Power infrastructure — transformers, UPSes, and generators generate low-frequency EMI from their magnetic fields.
Fluorescent lighting — particularly near end-of-life, ballasts generate significant RF noise.
Mitigations:
Physical separation — more distance from noise sources is the simplest fix. Cable runs should be kept as far as practical from power infrastructure.
Shielded cable — STP or armored cable for copper runs in high-EMI environments.
Fiber optic — immune to EMI entirely, since it carries light rather than electrical signals.
Metal conduit — provides shielding for cable runs through high-interference zones.
EMI compliance (FCC Part 15 in the US, CE marking in Europe) requires electronic equipment to both limit its own emissions and demonstrate tolerance to typical EMI environments.