What is the purpose of a bridge or reflectometer in RF instrumentation?

• A. To amplify signals.
• B. To measure transmission line parameters including impedance, VSWR, and line losses.
• C. To demodulate digital data.
• D. To generate RF.

Answer: (B)

A bridge or reflectometer is a measurement tool that characterizes how a transmission line or device reflects RF energy by comparing the unknown impedance to a known reference. By adjusting the reference impedance until the reflected signal is nulled, you determine the unknown impedance. From that impedance you can compute the standing-wave ratio (VSWR) and assess line losses, since these parameters describe how well the line matches and how much signal is lost along the path. This type of instrument is inherently a diagnostic device, not a signal amplifier, a demodulator, or a signal generator.