*Question G8B04:
What is the stage in a VHF FM transmitter that generates a harmonic of a lower frequency signal to reach the desired operating frequency?*  

*Correct Answer is  D: Multiplier*  

### AI Response: (may contain errors)  

In a VHF FM transmitter, the stage that generates a harmonic of a lower frequency signal to reach the desired operating frequency is the **Multiplier**.

### Explanation:

1. **Why the correct answer is correct (Multiplier):**
   - A **Multiplier** is a circuit that takes an input signal and produces an output signal at a harmonic frequency, which is a multiple of the input frequency. This is useful in VHF FM transmitters to increase the frequency of a lower frequency signal to the desired operating frequency. For example, if you have a signal at 50 MHz and you need to reach 150 MHz, a tripler (a type of multiplier) can be used to achieve this by multiplying the frequency by 3.

2. **Why the other choices are incorrect:**
   - **Mixer (A):** A mixer combines two frequencies to produce sum and difference frequencies. It is not primarily used to generate harmonics but rather to shift frequencies up or down in a process called heterodyning.
   - **Reactance Modulator (B):** This is used to vary the frequency of an oscillator in response to a modulating signal, typically for frequency modulation (FM). It does not generate harmonics.
   - **Balanced Converter (C):** This is another type of mixer that suppresses the carrier frequency and is used for frequency conversion, not for generating harmonics.

### Useful Concepts:

- **Harmonics:** These are integer multiples of a fundamental frequency. If the fundamental frequency is $f$, the harmonics are $2f$, $3f$, $4f$, etc.
- **Frequency Multiplication:** A multiplier circuit can be used to achieve frequency multiplication, which is essential in reaching higher frequency bands like VHF.

Understanding the role of each component in a transmitter helps in identifying the correct stage for specific functions like frequency multiplication.