Question
What is the effect of transmission line loss on SWR measured at the input to the line?
Answer Options
- A) Higher loss reduces SWR measured at the input to the line
- B) Higher loss increases SWR measured at the input to the line
- C) Higher loss increases the accuracy of SWR measured at the input to the line
- D) Transmission line loss does not affect the SWR measurement
Correct Answer: A
Explanation
When an SWR measurement is taken at the transmitter end (input) of a long, lossy transmission line, the measurement will be inaccurate because the line loss attenuates both the forward power and the reflected power. However, the reflected power is attenuated twice—once on the way to the antenna and once on the way back to the transmitter.
Because the reflected power is disproportionately reduced due to the losses in the line, the Standing Wave Ratio appears lower at the transmitter end than it actually is at the antenna feed point. Therefore, higher loss reduces SWR measured at the input to the line, creating a deceptively low reading that hides the true antenna mismatch.
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