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Wireless & Mobility · Intermediate

Impedance

The opposition to alternating current flow, measured in ohms; Wi-Fi RF systems use 50 ohms.

Definition

Impedance must match across radio, cable, connectors, and antenna to avoid reflections. Most Wi-Fi and cellular RF components are designed for 50 ohms, while video systems use 75 ohms. Mismatches cause VSWR and return loss.

Exam tip

Mixing 75-ohm video cable into a 50-ohm Wi-Fi system causes VSWR.

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