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SESK: Stuff Everyone Should Know · sesk.info/hame-repeater-duplexer-cavity

Which filter type is used in a 2-meter repeater duplexer?

A cavity filter does the job in a 2-meter duplexer.

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  1. Cavity filter ✔
  2. Crystal filter
  3. DSP filter

Why: A duplexer lets the transmitter and receiver share one antenna. Cavity filters handle the power and have very sharp, high-Q response at VHF.

Huh, didn't know that: Helical filters are frequently used as band-pass or notch filters in VHF and UHF transceivers (E7C08).

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References

Answer: Cavity filter. A duplexer lets the transmitter and receiver share one antenna. Cavity filters handle the power and have very sharp, high-Q response at VHF.

  1. NCVEC 2024-2028 Amateur Extra Question Pool, E7C10 (4th errata, Feb. 4, 2026) www.ncvec.org/downloads/2024-2028%20Extra%20Class%20Question%20Pool%20and%20Syllabus%20Public%20Release%20with%204th%20Errata%20Feb%204%202026.pdf
    B. A cavity filter
    Checked 2026-10-11.
  2. NCVEC 2024-2028 Amateur Extra Question Pool, E7C08 (4th errata, Feb. 4, 2026) www.ncvec.org/downloads/2024-2028%20Extra%20Class%20Question%20Pool%20and%20Syllabus%20Public%20Release%20with%204th%20Errata%20Feb%204%202026.pdf
    B. A helical filter
    Checked 2026-10-11.

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