SESK: Stuff Everyone Should Know · sesk.info/hame-spurious-43db
For a transmitter installed after January 1, 2003, below 30 MHz, how far below the fundamental must spurious emissions be?
At least 43 dB below the mean power of the fundamental.
- At least 43 dB below ✔
- At least 20 dB below
- At least 60 dB below
Why: Rule 97.307(d) requires spurious emissions from newer HF transmitters to be at least 43 dB below the mean power of the fundamental. The 60 dB figure belongs to 30 to 225 MHz.
Huh, didn't know that: Transmitters built before April 15, 1977, or first marketed before January 1, 1978, are exempt from this spurious emission rule.
What did Johnny's mother do when she caught him zapping the other children with static electricity? She grounded him.
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References
Answer: At least 43 dB below. Rule 97.307(d) requires spurious emissions from newer HF transmitters to be at least 43 dB below the mean power of the fundamental. The 60 dB figure belongs to 30 to 225 MHz.
- 47 CFR 97.307 Emission standards (Cornell LII mirror of eCFR) www.law.cornell.edu/cfr/text/47/97.307
must be at least 43 dB below the mean power
Checked 2026-10-11. - 47 CFR 97.307 Emission standards (Cornell LII mirror of eCFR) www.law.cornell.edu/cfr/text/47/97.307
between 30-225 MHz must be at least 60 dB below
Checked 2026-10-11. - 47 CFR 97.307 Emission standards (Cornell LII mirror of eCFR) www.law.cornell.edu/cfr/text/47/97.307
A transmitter built before April 15, 1977
Checked 2026-10-11.
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