Question
What causes reflected power at an antenna’s feed point?
Answer Options
- A) Operating an antenna at its resonant frequency
- B) Using more transmitter power than the antenna can handle
- C) A difference between feed line impedance and antenna feed point impedance
- D) Feeding the antenna with unbalanced feed line
Correct Answer: C
Explanation
Reflected power is the electrical energy sent back toward the transmitter from the antenna. This occurs when the antenna system cannot absorb all of the power sent down the transmission line.
The cause of this inability to absorb the power is a difference between feed line impedance and antenna feed point impedance. When the impedance of the transmission line (Z_0) does not match the impedance of the load (Z_L, which is the antenna feed point), the mismatch forces some power to be reflected, resulting in a Standing Wave Ratio (SWR) greater than 1:1.
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