What is the most common method of reducing key clicks?
The correct answer is A: Increase keying waveform rise and fall times. The most common method of reducing key clicks is to increase the keying waveform rise and fall times. Longer rise/fall times create smoother transitions that don't generate wide-bandwidth noise.
Key clicks are caused by sharp transitions (short rise/fall times) that create high-frequency components. By increasing the rise and fall times, the transitions become smoother (more gradual), eliminating the high-frequency components that cause key clicks. This is typically done with a keying waveform shaper circuit that slows down the transitions. Most modern transceivers have adjustable keying speed or built-in keying filters that increase rise/fall times to prevent key clicks.
Exam Tip
Reduce key clicks = Increase rise/fall times. Remember: The most common method to reduce key clicks is to increase the keying waveform rise and fall times. Longer transitions eliminate the high-frequency components that cause key clicks.
Memory Aid
"**R**educe **K**ey **C**licks = **I**ncrease **R**ise/**F**all (think 'RKC = IRF')"
Real-World Application
Your CW transmitter is generating key clicks. You adjust the keying waveform shaper to increase the rise and fall times from 1 millisecond to 5 milliseconds. The transitions are now smoother, and the key clicks disappear. The longer rise/fall times eliminate the sharp transitions that were creating wide-bandwidth noise.
FCC Part 97.3Key Concepts
Why Other Options Are Wrong
Option B: Incorrect. Low-pass filters at the transmitter output can help reduce key clicks, but increasing rise/fall times is the most common and effective method. Filters are a secondary solution.
Option C: Incorrect. Reducing rise/fall times would make key clicks worse, not better. You need longer (increased) rise/fall times.
Option D: Incorrect. High-pass filters would remove low frequencies, not the high frequencies that cause key clicks. Low-pass filters might help, but increasing rise/fall times is the primary method.
题目解析
The correct answer is A: Increase keying waveform rise and fall times. The most common method of reducing key clicks is to increase the keying waveform rise and fall times. Longer rise/fall times create smoother transitions that don't generate wide-bandwidth noise. Key clicks are caused by sharp transitions (short rise/fall times) that create high-frequency components. By increasing the rise and fall times, the transitions become smoother (more gradual), eliminating the high-frequency components that cause key clicks. This is typically done with a keying waveform shaper circuit that slows down the transitions. Most modern transceivers have adjustable keying speed or built-in keying filters that increase rise/fall times to prevent key clicks.
考试技巧
Reduce key clicks = Increase rise/fall times. Remember: The most common method to reduce key clicks is to increase the keying waveform rise and fall times. Longer transitions eliminate the high-frequency components that cause key clicks.
记忆口诀
**R**educe **K**ey **C**licks = **I**ncrease **R**ise/**F**all (think 'RKC = IRF')
实际应用示例
Your CW transmitter is generating key clicks. You adjust the keying waveform shaper to increase the rise and fall times from 1 millisecond to 5 milliseconds. The transitions are now smoother, and the key clicks disappear. The longer rise/fall times eliminate the sharp transitions that were creating wide-bandwidth noise.
错误选项分析
Option B: Incorrect. Low-pass filters at the transmitter output can help reduce key clicks, but increasing rise/fall times is the most common and effective method. Filters are a secondary solution. Option C: Incorrect. Reducing rise/fall times would make key clicks worse, not better. You need longer (increased) rise/fall times. Option D: Incorrect. High-pass filters would remove low frequencies, not the high frequencies that cause key clicks. Low-pass filters might help, but increasing rise/fall times is the primary method.
知识点
Key clicks, Rise and fall time, Keying waveform, CW keying
Verified Content
Question from official FCC Extra Class question pool. Explanation reviewed by licensed amateur radio operators.