Advanced Qualification · A-005 Transmitters, modulation and processing · A-005-006-008
The characteristic difference between a phase modulator and a frequency modulator is:
- A the centre frequency
- B de-emphasis
- C frequency inversion
- D pre-emphasis
Correct answer: D — pre-emphasis. From the official ISED question bank, verified word for word.
Why
Pre-emphasis boosts higher audio frequencies before transmission to improve signal clarity, and this specific processing step is the key feature that distinguishes how phase modulators are often set up compared to standard frequency modulators in exam contexts. 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.