Which of the following is characteristic of a direct digital synthesizer (DDS)?
The correct answer is D: Variable output frequency with the stability of a crystal oscillator. A characteristic of a direct digital synthesizer (DDS) is variable output frequency with the stability of a crystal oscillator. DDS generates frequencies digitally while maintaining crystal oscillator stability. For amateur radio operators, this provides precise, stable frequency generation. Understanding this helps when using modern transceivers.
Exam Tip
DDS characteristic = variable frequency with crystal stability. Think 'D'DS = 'D'igital 'D'irect 'S'ynthesizer = 'V'ariable 'F'requency with 'S'tability. DDS generates frequencies digitally while maintaining crystal oscillator stability. Not narrow range, not high power, not pure sine - just variable frequency with stability.
Memory Aid
"DDS characteristic = variable frequency with crystal stability. Think 'D'DS = 'V'ariable 'F'requency with 'S'tability. DDS generates frequencies digitally while maintaining crystal oscillator stability. Key DDS advantage."
Real-World Application
A DDS in a modern transceiver: You can tune across a wide frequency range (e.g., entire HF band), and the frequency is as stable as a crystal oscillator. DDS generates frequencies digitally (variable) while maintaining crystal stability. This is a key advantage of DDS - variable frequency with crystal stability.
Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. DDS doesn't have extremely narrow tuning range - DDS can tune over wide ranges. Narrow range isn't a characteristic.
Option B: Incorrect. DDS doesn't have relatively high-power output - DDS generates low-level signals that need amplification. High power isn't a characteristic.
Option C: Incorrect. DDS doesn't necessarily produce pure sine wave output - DDS can have spurious signals. Pure sine wave isn't guaranteed.
题目解析
The correct answer is D: Variable output frequency with the stability of a crystal oscillator. A characteristic of a direct digital synthesizer (DDS) is variable output frequency with the stability of a crystal oscillator. DDS generates frequencies digitally while maintaining crystal oscillator stability. For amateur radio operators, this provides precise, stable frequency generation. Understanding this helps when using modern transceivers.
考试技巧
DDS characteristic = variable frequency with crystal stability. Think 'D'DS = 'D'igital 'D'irect 'S'ynthesizer = 'V'ariable 'F'requency with 'S'tability. DDS generates frequencies digitally while maintaining crystal oscillator stability. Not narrow range, not high power, not pure sine - just variable frequency with stability.
记忆口诀
DDS characteristic = variable frequency with crystal stability. Think 'D'DS = 'V'ariable 'F'requency with 'S'tability. DDS generates frequencies digitally while maintaining crystal oscillator stability. Key DDS advantage.
实际应用示例
A DDS in a modern transceiver: You can tune across a wide frequency range (e.g., entire HF band), and the frequency is as stable as a crystal oscillator. DDS generates frequencies digitally (variable) while maintaining crystal stability. This is a key advantage of DDS - variable frequency with crystal stability.
错误选项分析
Option A: Incorrect. DDS doesn't have extremely narrow tuning range - DDS can tune over wide ranges. Narrow range isn't a characteristic. Option B: Incorrect. DDS doesn't have relatively high-power output - DDS generates low-level signals that need amplification. High power isn't a characteristic. Option C: Incorrect. DDS doesn't necessarily produce pure sine wave output - DDS can have spurious signals. Pure sine wave isn't guaranteed.
知识点
Direct digital synthesizer, DDS, Variable frequency, Crystal stability
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.