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What impedance does a quarter-wavelength transmission line present to the generator when shorted at the far end?

Very high impedance.

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  1. Very low impedance
  2. Very high impedance ✔
  3. The line's characteristic impedance

Why: A quarter-wave line turns impedance upside down. A short at the far end looks like an open circuit at the input, so a shorted stub can act like an insulator.

Huh, didn't know that: A half-wave line shorted at the far end presents a very low impedance (E9F04).

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References

Answer: Very high impedance. A quarter-wave line turns impedance upside down. A short at the far end looks like an open circuit at the input, so a shorted stub can act like an insulator.

  1. NCVEC 2024-2028 Amateur Extra Question Pool, 4th Errata (Feb 4, 2026) ncvec.org/downloads/2024-2028%20Extra%20Class%20Question%20Pool%20and%20Syllabus%20Public%20Release%20with%204th%20Errata%20Feb%204%202026.pdf
    A. Very high impedance
    Checked 2026-10-11.

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