Advanced Qualification · A-005 Transmitters, modulation and processing · A-005-005-011
Quelle excursion de fréquence doit-on imposer sur un oscillateur tournant à 12,21 MHz dans un émetteur FM dont la sortie est de 146,52 MHz avec +/- 5 kHz d'excursion?
- A+/- 12 kHz
- B+/- 5 kHz
- C+/- 41,67 Hz
- D+/- 416,7 Hz
Correct answer: D — +/- 416,7 Hz. Question tirée de la banque officielle d'ISDE.
Why
The oscillator runs at 12.21 MHz while the final transmitter operates at 146.52 MHz, meaning the signal is multiplied by a factor of twelve to reach the target frequency. The full explanation — and one for every question — is in Pro.
Practise this section
Transmitters, modulation and processing is section A-005 of the Advanced exam: Transmitters, modulation and processing: AM, FM, SSB, keying, speech processing, and the numbers behind occupied bandwidth.
Drill A-005 — free, no account