According to Appendix 2 of "Regulations on the Allocation of Radio Frequencies of the People's Republic of China," Section 2.2, "Maximum Spurious Radiation Power Limit Requirements for Business or Equipment," as specified.
We can see that for shortwave amateur radio stations, the requirements are 43 + lg10 PEP or 50 dBc (whichever is lower).
The following two points are noted below.
My question is: Why doesn't the dBc value here have a negative sign?
Personal calculation approach: According to the majority of information I have reviewed, dBc refers to "the ratio of harmonic or spurious power to carrier power in decibels (dB)" (a smaller value indicates a stricter requirement and lower dispersion). The formula is:
dBc = 10 * log10(Psideband / Pcarrier)
If I have a QRP device with Pcarrier = 5W, impedance = 50Ω, then PEP = 0.5, and the required spurious emission level is -50 dBc.
Therefore, when working backward, Psideband/Pcarrier = 105
This means that the power spectral density is significantly higher than the carrier frequency, which seems impossible.
https://wap.miit.gov.cn/cms_files/filemanager/1226211233/attach/20236/9086700eed45430bafe236efd1096fd3.pdf
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