SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/hamg-secondary-allocation

What must hams do when the amateur service is a secondary user on a band?

Do not interfere with primary users, and accept interference from them.

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  1. Operate only during emergencies
  2. Operate only during certain hours of the day
  3. Avoid interfering with primary users and accept their interference ✔

Why: Secondary means the other service has first claim. Hams may use the band, but must not cause harmful interference to primary users and must tolerate interference from them.

Huh, didn't know that: On 30 meters, US hams are secondary and must accept interference from other nations' fixed stations.

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References

Answer: Avoid interfering with primary users and accept their interference. Secondary means the other service has first claim. Hams may use the band, but must not cause harmful interference to primary users and must tolerate interference from them.

  1. NCVEC 2023-2027 General Class Pool and Syllabus (6th Errata, Feb 4 2026) ncvec.org/downloads/General%20Class%20Pool%20and%20Syllabus%202023-2027%20Public%20Release%20with%206th%20Errata%20Feb%204%202026.pdf
    must not cause harmful interference to primary users
    Checked 2026-10-11.
  2. 47 CFR 97.303 (Cornell LII mirror of eCFR) www.law.cornell.edu/cfr/text/47/97.303
    must accept interference from, stations by other nations in the fixed service
    Checked 2026-10-11.

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