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In software-defined radio, what is the phase difference between the I and Q signals?

90 degrees.

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  1. 90 degrees ✔
  2. Zero
  3. 180 degrees

Why: The I and Q signals are offset by 90 degrees. With that pair, an SDR can create all types of modulation using the right processing.

Huh, didn't know that: In a software-defined radio, filtering, detection and modulation can all be done in software.

The dad joke
Q is always 90 degrees behind I, but never behind schedule.
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References

Answer: 90 degrees. The I and Q signals are offset by 90 degrees. With that pair, an SDR can create all types of modulation using the right processing.

  1. NCVEC 2023-2027 General Class Pool and Syllabus (6th Errata, Feb 4 2026) ncvec.org/downloads/General%20Class%20Pool%20and%20Syllabus%202023-2027%20Public%20Release%20with%206th%20Errata%20Feb%204%202026.pdf
    90 degrees
    Checked 2026-10-11.

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