Deep Dive: E4B10
The correct answer is B: Modulate the transmitter using two AF signals having non-harmonically related frequencies and observe the RF output with a spectrum analyzer. Which of the following methods measures intermodulation distortion in an SSB transmitter is to modulate with two AF signals having non-harmonically related frequencies and observe RF output with spectrum analyzer. Two-tone test measures IMD. For amateur radio operators, this is important for transmitter testing. Understanding this helps when testing transmitters.
Why Other Answers Are Wrong
Option A: Incorrect. Two RF signals isn't correct - two AF (audio) signals are used for IMD testing. RF signals isn't the method. Option C: Incorrect. Harmonically related frequencies isn't correct - non-harmonically related frequencies are needed. Harmonically related isn't correct. Option D: Incorrect. Logic analyzer isn't used - spectrum analyzer is used to observe IMD products. Logic analyzer isn't used.
Exam Tip
Measure IMD in SSB transmitter = modulate with two AF signals (non-harmonically related), observe RF output with spectrum analyzer. Think 'I'MD = 'T'wo-'T'one 'T'est. Two-tone test measures IMD. Not RF signals, not harmonically related, not logic analyzer - just two AF signals and spectrum analyzer.
Memory Aid
Measure IMD in SSB transmitter = modulate with two AF signals (non-harmonically related), observe RF output with spectrum analyzer. Think 'I'MD = 'T'wo-'T'one test. Two-tone test measures IMD. Important for transmitter testing.
Real-World Example
Measuring intermodulation distortion in an SSB transmitter: Modulate the transmitter using two AF (audio) signals having non-harmonically related frequencies (e.g., 1 kHz and 2.5 kHz), and observe the RF output with a spectrum analyzer. The spectrum analyzer will show IMD products. This is the method - two AF tones and spectrum analyzer.
Source & Coverage
Question Pool: 2024-2028 Question Pool
Subelement: E4B
Reference: 2024-2028 Question Pool · E4 - Amateur Practices
Key Concepts
Verified Content
Question from the official FCC Extra Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the E4B topic.