Extra exam question E4D14
Subelement E4, AMATEUR PRACTICES· Group E4D
What power level does a receiver minimum discernible signal of -100 dBm represent?
- A.100 microwatts
- B.0.1 microwatt
- C.0.001 microwatts
- D.0.1 picowatts (correct answer)
WhyA receiver minimum discernible signal of -100 dBm represents a power level of 0.1 picowatts. Converting -100 dBm to watts: 0 dBm equals 1 milliwatt, and -100 dB below that is a factor of 10^-10, so -100 dBm works out to 1 mW times 10^-10, or 1 times 10^-13 watts, which is 0.1 picowatts (since 1 picowatt is 10^-12 watts), answer D. The other listed figures, expressed in microwatts, are off by several orders of magnitude from the actual power this signal level represents.
Published 2026-08-28 · Last updated 2026-08-28 · Question text is verbatim from the 2024-2028 NCVEC Element 4 pool (public domain); the explanation above is original writing, see our methodology.
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