Ham Radio General Class Practice Test

In amateur radio, what does SWR stand for?

1. Static Wave Ratio

2. Standing Wave Ratio

3. Standard Wave Ratio

4. Single Wave Ratio

The correct answer is: Standing Wave Ratio

In amateur radio, SWR stands for Standing Wave Ratio. This term describes the relationship between the forward and reflected power in a transmission line. When an antenna is properly matched to the transmission line and the transmitter, most of the power sent from the transmitter is radiated by the antenna. However, if there is a mismatch—such as an impedance mismatch between the antenna and the line—some of the power will be reflected back toward the transmitter. The Standing Wave Ratio is calculated using the formula SWR = (1 + |Γ|) / (1 - |Γ|), where |Γ| represents the voltage reflection coefficient. A lower SWR value (close to 1:1) indicates a better match and more efficient power transfer, while a higher SWR indicates more reflected power and less efficient operation, which can potentially damage the transmitter if the SWR is too high. Each of the other options improperly defines SWR, as none accurately convey the principles of wave propagation and impedance matching in radio frequency systems, distinguishing the associated efficiency of the transmission setup.