Advanced Qualification · A-005 Transmitters, modulation and processing · A-005-005-002
What is the modulation index of an FM phone transmitter producing an instantaneous carrier deviation of 6 kHz when modulated with a 2 kHz modulating frequency?
- A 3
- B 0.333
- C 2000
- D 6000
Correct answer: A — 3. From the official ISED question bank, verified word for word.
Why
The modulation index equals the frequency deviation divided by the modulating frequency, so dividing the 6 kHz deviation by the 2 kHz tone gives exactly 3. 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.