An antenna radiates a primary signal of 500 watts output. If there is a 2nd harmonic output of 0.5 watt, what attenuation of the 2nd harmonic has occurred?
• Decibel (dB) attenuation for power uses a logarithmic scale • For power ratios, the basic formula is dB = 10 × log10(P2 / P1) • You first need the ratio of harmonic power to fundamental power before converting to dB
• What is the ratio of the 2nd harmonic power (0.5 W) to the main signal power (500 W)? Simplify that fraction first. • Once you have the power ratio, how do you apply 10 × log10(ratio) to find attenuation in dB? • Is attenuation usually expressed as a positive or negative number, and how is that reflected in the multiple-choice answers?
• Be sure you are using the power ratio (not voltage ratio) in the dB formula. • Confirm your ratio is less than 1, since the harmonic is much weaker than the main signal. • After calculating the dB value, check which option most closely matches the magnitude of attenuation you found.
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