G9A09 - What standing wave ratio results from connecting a 50-ohm feed line to a 200-ohm resistive load?

Question

What standing wave ratio results from connecting a 50-ohm feed line to a 200-ohm resistive load?

Answer Options

  • A) 4:1
  • B) 1:4
  • C) 2:1
  • D) 1:2

Correct Answer: A


Explanation

The Standing Wave Ratio (SWR) is the ratio of the maximum impedance (Z_{\text{max}}) to the minimum impedance (Z_{\text{min}}) along a transmission line. For a purely resistive load, SWR is calculated as the ratio of the load resistance (R_L) to the characteristic impedance of the feed line (Z_0), or the inverse, always resulting in a ratio \geq 1:1.

Since the load impedance (200 \text{ ohms}) is greater than the feed line impedance (50 \text{ ohms}), the SWR is calculated as 200/50 = 4. Therefore, connecting a 50 \text{ ohm} line to a 200 \text{ ohm} load results in an SWR of 4:1. This formula is SWR = Z_{\text{larger}} / Z_{\text{smaller}}.


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