What is the purpose of a squelch function?
The correct answer is B: Mute the receiver audio when a signal is not present. The squelch function on a radio receiver mutes the audio output when no signal is present or when the received signal is below a certain threshold. This prevents you from hearing constant background noise and static when no one is transmitting.
When squelch is properly adjusted, you only hear audio when there's an actual signal present. This makes monitoring much more pleasant and allows you to leave your radio on without being bothered by constant noise. The squelch threshold can usually be adjusted - set it too high and you might miss weak signals; set it too low and you'll hear noise.
Exam Tip
Squelch = Mute when no signal. Remember: Squelch mutes receiver audio when no signal is present, so you don't have to listen to constant noise and static.
Memory Aid
"**S**quelch = **S**ilence **Q**uiet (think 'S = SQ' = Silence Quiet, mutes when no signal)"
Real-World Application
You're monitoring a repeater with squelch enabled. When no one is transmitting, your radio is silent - no noise, no static. When a signal appears, the squelch opens and you hear the audio. This is much more pleasant than listening to constant background noise. You can adjust the squelch threshold to determine how strong a signal needs to be before the squelch opens.
FCC Part 97.3Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. Squelch doesn't reduce CW key clicks. Key clicks are a transmitter issue, not a receiver function.
Option C: Incorrect. Squelch doesn't eliminate parasitic oscillations. That's a transmitter problem requiring different solutions.
Option D: Incorrect. While squelch reduces noise, it doesn't specifically target impulse noise. It mutes all audio when no signal is present.
题目解析
The correct answer is B: Mute the receiver audio when a signal is not present. The squelch function on a radio receiver mutes the audio output when no signal is present or when the received signal is below a certain threshold. This prevents you from hearing constant background noise and static when no one is transmitting. When squelch is properly adjusted, you only hear audio when there's an actual signal present. This makes monitoring much more pleasant and allows you to leave your radio on without being bothered by constant noise. The squelch threshold can usually be adjusted - set it too high and you might miss weak signals; set it too low and you'll hear noise.
考试技巧
Squelch = Mute when no signal. Remember: Squelch mutes receiver audio when no signal is present, so you don't have to listen to constant noise and static.
记忆口诀
**S**quelch = **S**ilence **Q**uiet (think 'S = SQ' = Silence Quiet, mutes when no signal)
实际应用示例
You're monitoring a repeater with squelch enabled. When no one is transmitting, your radio is silent - no noise, no static. When a signal appears, the squelch opens and you hear the audio. This is much more pleasant than listening to constant background noise. You can adjust the squelch threshold to determine how strong a signal needs to be before the squelch opens.
错误选项分析
Option A: Incorrect. Squelch doesn't reduce CW key clicks. Key clicks are a transmitter issue, not a receiver function. Option C: Incorrect. Squelch doesn't eliminate parasitic oscillations. That's a transmitter problem requiring different solutions. Option D: Incorrect. While squelch reduces noise, it doesn't specifically target impulse noise. It mutes all audio when no signal is present.
知识点
Squelch, Receiver function, Audio muting, Noise suppression
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.