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SESK: Stuff Everyone Should Know · sesk.info/hame-terminated-long-wire

What is the effect of adding a terminating resistor to a rhombic or long-wire antenna?

It makes the pattern unidirectional.

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  1. Pattern changes from bidirectional to unidirectional ✔
  2. Standing waves reflect back to the transmitter
  3. Polarization changes from horizontal to vertical

Why: The resistor absorbs the energy that would reflect back from the far end. With no reflected wave, the antenna radiates mainly in one direction.

Huh, didn't know that: As an unterminated long wire gets longer, additional lobes form and line up closer to the wire axis (E9C04).

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What does an RF amplifier do after a careless crew leaves its output open? Sues for wrongful termination.
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References

Answer: Pattern changes from bidirectional to unidirectional. The resistor absorbs the energy that would reflect back from the far end. With no reflected wave, the antenna radiates mainly in one direction.

  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
    B. It changes the radiation pattern from bidirectional to unidirectional
    Checked 2026-10-11.

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