Question
What is the relationship between high standing wave ratio (SWR) and transmission line loss?
Answer Options
- A) There is no relationship between transmission line loss and SWR
- B) High SWR increases loss in a lossy transmission line
- C) High SWR makes it difficult to measure transmission line loss
- D) High SWR reduces the relative effect of transmission line loss
Correct Answer: B
Explanation
Transmission line loss is the power dissipated as heat in the feed line conductors and dielectric material. This loss is always present. However, Standing Wave Ratio (SWR) is a measure of the mismatch between the load and the characteristic impedance. When SWR is high, the voltage and current along the line are not uniform, creating points of high current maxima.
At these high current points, the I^2 R loss in the conductors is maximized, which means high SWR increases loss in a lossy transmission line. This is particularly true for long runs of high-loss coaxial cable (like RG-58), making a low SWR critical for maximizing power transfer to the antenna.
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