Question
What emission is produced by a reactance modulator connected to a transmitter RF amplifier stage?
Answer Options
- A) Multiplex modulation
- B) Phase modulation
- C) Amplitude modulation
- D) Pulse modulation
Correct Answer: B
Explanation
A reactance modulator is a circuit that electronically varies its own reactance (capacitance or inductance) in response to an applied audio signal. When this circuit is connected to an oscillator stage (often part of an RF amplifier), the oscillator’s output frequency is varied, effectively creating frequency modulation (FM).
However, a common method used is to apply the modulating signal to the oscillator, causing a change in frequency proportional to the change in voltage. This method is often technically phase modulation (PM). For amateur regulations, PM is considered equivalent to FM, but in the context of crystal-controlled or VFO-driven circuits using a reactance modulator, the signal is primarily a PM emission.
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