Advanced Qualification · A-005 Transmitters, modulation and processing · A-005-006-005
What type of circuit varies the tuning of an amplifier tank circuit to produce FM signals?
- A A balanced modulator
- B A double balanced mixer
- C An audio modulator
- D A phase modulator
Correct answer: D — A phase modulator. From the official ISED question bank, verified word for word.
Why
A phase modulator creates frequency modulation by shifting the phase of the carrier wave in step with the audio signal, which effectively changes the frequency over time. The full explanation — and one for every question — is in Pro.
Practise this section
Transmitters, modulation and processing: AM, FM, SSB, keying, speech processing, and the numbers behind occupied bandwidth.