Extra exam question E4B10
Subelement E4, AMATEUR PRACTICES· Group E4B
Which of the following methods measures intermodulation distortion in an SSB transmitter?
- A.Modulate the transmitter using two RF signals having non-harmonically related frequencies and observe the RF output with a spectrum analyzer
- B.Modulate the transmitter using two AF signals having non-harmonically related frequencies and observe the RF output with a spectrum analyzer (correct answer)
- C.Modulate the transmitter using two AF signals having harmonically related frequencies and observe the RF output with a peak reading wattmeter
- D.Modulate the transmitter using two RF signals having harmonically related frequencies and observe the RF output with a logic analyzer
WhyIntermodulation distortion in an SSB transmitter is measured by modulating it with two non-harmonically related audio tones and observing the RF output on a spectrum analyzer. Intermodulation distortion in an SSB transmitter is measured by modulating it with two audio-frequency tones that aren't harmonically related, then examining the RF output on a spectrum analyzer for the extra intermodulation products those two tones generate when they mix inside the transmitter's nonlinear stages, answer B. Modulating with RF signals instead of audio tones doesn't test the transmitter the way it's actually used, and a peak-reading wattmeter or logic analyzer can't reveal the frequency-domain detail a spectrum analyzer shows.
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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