Ham Amateur Radio Technician Practice Exam

Which of the following can be measured with an antenna analyzer?

1. Voltage drop across a circuit

2. Impedance of coaxial cable

3. Current through a resistor

4. Frequency of a signal

The correct answer is: Impedance of coaxial cable

An antenna analyzer is specifically designed to measure the impedance of antennas and transmission lines, such as coaxial cables. Impedance is a critical parameter because it affects how efficiently RF power is transferred from the transmitter to the antenna. When the impedance of the antenna matches that of the transmission line (which is often 50 ohms for many systems), maximum power transfer occurs, minimizing signal loss and avoiding damage to the transmitter from high SWR (Standing Wave Ratio) conditions. The ability to measure impedance allows the operator to determine whether the antenna system is properly matched to the transmission line and to make adjustments as necessary, such as tuning the antenna or adjusting the feedline. While an antenna analyzer can provide additional data related to the antenna's performance—such as SWR and resonant frequency—its primary function revolves around measuring impedance specifically. While voltage drop across a circuit, current through a resistor, and frequency of a signal are important aspects of circuit analysis and operation, they fall outside the primary functions of an antenna analyzer, which focuses on antenna impedance characteristics.