In a design review, a vendor claims 20 dBm equals 50 mW. Using the…

Question

In a design review, a vendor claims 20 dBm equals 50 mW. Using the rules of 10 and 3, what quick sanity check should the municipal RF lead apply?

Accepted Answer

0 dBm ≈ 1 mW, so +10 dB → 10 mW and another +10 dB → 100 mW at 20 dBm; 50 mW is incorrect for 20 dBm. — Remember the coffee-napkin rule: 0 dBm is about 1 mW, each +10 dB is ×10, so 20 dBm is 100 mW — not 50. Catching that in review saves a bad BoM. dBm isn't a mW lookalike, and +3 dB is ×2, not ×10.

Answer

20 dBm always equals 20 mW because dBm and mW share the same numeric scale.

Answer

Rules of 10 and 3 only apply to antenna gain in dBi, never to conducted power.

Answer

50 mW is correct because every +3 dB multiplies power by ten.

In a design review, a vendor claims 20 dBm equals 50 mW. Using the rules of 10 and 3, what quick sanity check should the municipal RF lead apply?

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