What is the name of a circuit that generates a signal at a specific frequency?
The correct answer is Oscillator. An oscillator is a circuit that generates a signal at a specific frequency. Oscillators produce periodic waveforms (sine waves, square waves, etc.) at a predetermined frequency, which is essential for many radio functions. For amateur radio operators, oscillators are found throughout equipment - as local oscillators in receivers (for frequency conversion), as carrier generators in transmitters, as clock sources in digital circuits, and as reference frequencies. The frequency is typically determined by a crystal, LC circuit, or phase-locked loop. Understanding oscillators is fundamental to understanding how radios generate and process signals.
Exam Tip
Oscillator = generates signals. Think 'O'scillator = 'O'scillates (generates) signals at specific frequencies. Modulators modify signals, filters remove frequencies - none generate signals.
Memory Aid
"Oscillator = Oscillates (generates) signals. Think 'O'scillator = 'O'scillates at a specific frequency. Creates periodic waveforms at predetermined frequencies."
Real-World Application
In your receiver, a local oscillator generates a signal at a specific frequency (e.g., 135.52 MHz) that's mixed with incoming RF signals to convert them to an intermediate frequency. This oscillator must be stable and accurate - if it drifts, your receiver tunes to the wrong frequency. Oscillators are the 'heartbeat' of radio equipment, providing the timing and frequency references needed for operation.
Key Concepts
Why Other Options Are Wrong
Option A (Reactance modulator): Incorrect. A reactance modulator varies the reactance of a circuit to create frequency or phase modulation. It modulates an existing signal, it doesn't generate a signal at a specific frequency.
Option B (Phase modulator): Incorrect. A phase modulator varies the phase of a signal to create phase modulation. It modulates an existing signal, it doesn't generate a signal.
Option C (Low-pass filter): Incorrect. A low-pass filter passes low frequencies and blocks high frequencies. It filters signals, it doesn't generate them.
题目解析
The correct answer is Oscillator. An oscillator is a circuit that generates a signal at a specific frequency. Oscillators produce periodic waveforms (sine waves, square waves, etc.) at a predetermined frequency, which is essential for many radio functions. For amateur radio operators, oscillators are found throughout equipment - as local oscillators in receivers (for frequency conversion), as carrier generators in transmitters, as clock sources in digital circuits, and as reference frequencies. The frequency is typically determined by a crystal, LC circuit, or phase-locked loop. Understanding oscillators is fundamental to understanding how radios generate and process signals.
考试技巧
Oscillator = generates signals. Think 'O'scillator = 'O'scillates (generates) signals at specific frequencies. Modulators modify signals, filters remove frequencies - none generate signals.
记忆口诀
Oscillator = Oscillates (generates) signals. Think 'O'scillator = 'O'scillates at a specific frequency. Creates periodic waveforms at predetermined frequencies.
实际应用示例
In your receiver, a local oscillator generates a signal at a specific frequency (e.g., 135.52 MHz) that's mixed with incoming RF signals to convert them to an intermediate frequency. This oscillator must be stable and accurate - if it drifts, your receiver tunes to the wrong frequency. Oscillators are the 'heartbeat' of radio equipment, providing the timing and frequency references needed for operation.
错误选项分析
Option A (Reactance modulator): Incorrect. A reactance modulator varies the reactance of a circuit to create frequency or phase modulation. It modulates an existing signal, it doesn't generate a signal at a specific frequency. Option B (Phase modulator): Incorrect. A phase modulator varies the phase of a signal to create phase modulation. It modulates an existing signal, it doesn't generate a signal. Option C (Low-pass filter): Incorrect. A low-pass filter passes low frequencies and blocks high frequencies. It filters signals, it doesn't generate them.
知识点
Oscillators, Signal generation, Frequency generation, Local oscillators
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.