Question
What is the stage in a VHF FM transmitter that generates a harmonic of a lower frequency signal to reach the desired operating frequency?
Answer Options
- A) Mixer
- B) Reactance modulator
- C) Balanced converter
- D) Multiplier
Correct Answer: D
Explanation
Many older VHF and UHF Frequency Modulation (FM) transmitters used a crystal oscillator at a lower frequency to ensure high stability, as it is difficult to build highly stable oscillators that operate directly at high frequencies. The signal is then processed to reach the final operating frequency.
The stage that increases the signal frequency by generating a harmonic (an integer multiple) of the input frequency is called a multiplier. For example, a 48.54 \text{ MHz} crystal oscillator signal might be fed into a tripler circuit (a multiplier of 3) to reach a final output frequency of 145.62 \text{ MHz}.
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