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SESK: Stuff Everyone Should Know · sesk.info/ham-erratic-swr

What can cause erratic changes in SWR?

A loose antenna or feed-line connection can make SWR jump around.

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  1. A loose antenna or feed-line connection ✔
  2. Over-modulation
  3. A strong local station

Why: A loose connection changes the electrical path unpredictably. That changes the impedance seen by the transmitter, so the SWR reading can vary.

Huh, didn't know that: A stable mechanical connection is part of a stable RF connection.

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The SWR reading wandered because the connector was feeling loose.
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References

Answer: A loose antenna or feed-line connection. A loose connection changes the electrical path unpredictably. That changes the impedance seen by the transmitter, so the SWR reading can vary.

  1. NCVEC 2026-2030 Technician Question Pool www.ncvec.org/downloads/2026-2030%20Technician%20Pool%20and%20Syllabus%20Public%20Release%20Feb%2019%202026.pdf
    B. Loose connection in the antenna or feed line
    Checked 2026-10-09.

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