Question
If the SWR on an antenna feed line is 5:1, and a matching network at the transmitter end of the feed line is adjusted to present a 1:1 SWR to the transmitter, what is the resulting SWR on the feed line?
Answer Options
- A) 1:1
- B) 5:1
- C) Between 1:1 and 5:1 depending on the characteristic impedance of the line
- D) Between 1:1 and 5:1 depending on the reflected power at the transmitter
Correct Answer: B
Explanation
An antenna matching network (tuner) placed at the transmitter end of the feed line only transforms the impedance seen by the transmitter. It converts the complex impedance of the line into the pure 50 \text{ ohm} resistive load that the transmitter requires, allowing the transmitter to operate efficiently.
However, the tuner does absolutely nothing to fix the mismatch that exists at the antenna end of the feed line. The Standing Wave Ratio (SWR) on the feed line between the tuner and the antenna remains unchanged at 5:1. The power reflected by the antenna still exists on the line, but the tuner manages the effect of that reflected power at the transmitter.
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