Which instrument can be used to determine SWR?

Which instrument can be used to determine SWR?

• A. A power meter
• B. A directional wattmeter
• C. An oscilloscope
• D. A signal generator

Answer: (B)

The correct answer involves the use of a directional wattmeter to determine the standing wave ratio (SWR) in a radio frequency (RF) transmission line. A directional wattmeter measures both forward and reflected power in the transmission line. By comparing these two measurements, you can calculate the SWR, which indicates how efficiently power is being transferred from the transmitter through the antenna system. When the forward power is significantly higher than the reflected power, it indicates a low SWR, suggesting that the antenna system is well-matched to the transmitter. Conversely, if a large amount of reflected power is detected, it indicates a high SWR, suggesting that there may be a mismatch, which can cause inefficient transmission and potential damage to the transmitter. Other instruments mentioned, like a power meter, can measure power levels but typically do not provide the capability to separate forward and reflected power necessary for calculating SWR directly. An oscilloscope is primarily used for analyzing waveforms and signal shapes, not for direct measurement of power in the context needed for SWR determination. A signal generator produces signals and doesn’t measure reflections or forward power, so it cannot provide the SWR directly either. Thus, the directional wattmeter is the instrument specifically designed for this purpose.

The correct answer involves the use of a directional wattmeter to determine the standing wave ratio (SWR) in a radio frequency (RF) transmission line. A directional wattmeter measures both forward and reflected power in the transmission line. By comparing these two measurements, you can calculate the SWR, which indicates how efficiently power is being transferred from the transmitter through the antenna system.

When the forward power is significantly higher than the reflected power, it indicates a low SWR, suggesting that the antenna system is well-matched to the transmitter. Conversely, if a large amount of reflected power is detected, it indicates a high SWR, suggesting that there may be a mismatch, which can cause inefficient transmission and potential damage to the transmitter.

Other instruments mentioned, like a power meter, can measure power levels but typically do not provide the capability to separate forward and reflected power necessary for calculating SWR directly. An oscilloscope is primarily used for analyzing waveforms and signal shapes, not for direct measurement of power in the context needed for SWR determination. A signal generator produces signals and doesn’t measure reflections or forward power, so it cannot provide the SWR directly either. Thus, the directional wattmeter is the instrument specifically designed for this purpose.