How is squelch adjusted so that a weak FM signal can be heard?
The correct answer is A: Set the squelch threshold so that receiver output audio is on all the time. To hear a weak FM signal, you need to set the squelch threshold so that receiver output audio is on all the time (squelch fully open or turned all the way down). This allows you to hear signals that are below the normal squelch threshold.
Squelch mutes the receiver when no signal is present. If squelch is set too high (tight), it won't open for weak signals. To hear weak signals, you need to open the squelch completely (turn it all the way down) so the receiver audio is always on. You'll hear background noise, but you'll also hear weak signals that would otherwise be squelched out. This is the standard technique for weak-signal work on FM.
Exam Tip
Weak FM signal = Open squelch. Remember: To hear weak FM signals, set the squelch threshold so receiver audio is on all the time (squelch fully open). This allows weak signals to be heard.
Memory Aid
"**W**eak **F**M = **W**ide **O**pen **S**quelch (think 'WF = WOS' = Wide Open Squelch)"
Real-World Application
You're trying to copy a weak FM signal on 2 meters. The signal is too weak to open your squelch, so you can't hear it. You turn the squelch control all the way down (counter-clockwise), which opens the squelch completely. Now the receiver audio is always on - you hear background noise, but you can also hear the weak signal that was previously squelched out. This is how you work weak FM signals.
FCC Part 97.3Key Concepts
Why Other Options Are Wrong
Option B: Incorrect. Turning up audio level doesn't overcome squelch. Squelch is a threshold control, not a volume control. You need to adjust the squelch threshold itself.
Option C: Incorrect. There's no 'anti-squelch function' on standard transceivers. You simply open the squelch by turning it down.
Option D: Incorrect. 'Squelch enhancement' isn't a standard function. You open squelch by lowering the threshold.
题目解析
The correct answer is A: Set the squelch threshold so that receiver output audio is on all the time. To hear a weak FM signal, you need to set the squelch threshold so that receiver output audio is on all the time (squelch fully open or turned all the way down). This allows you to hear signals that are below the normal squelch threshold. Squelch mutes the receiver when no signal is present. If squelch is set too high (tight), it won't open for weak signals. To hear weak signals, you need to open the squelch completely (turn it all the way down) so the receiver audio is always on. You'll hear background noise, but you'll also hear weak signals that would otherwise be squelched out. This is the standard technique for weak-signal work on FM.
考试技巧
Weak FM signal = Open squelch. Remember: To hear weak FM signals, set the squelch threshold so receiver audio is on all the time (squelch fully open). This allows weak signals to be heard.
记忆口诀
**W**eak **F**M = **W**ide **O**pen **S**quelch (think 'WF = WOS' = Wide Open Squelch)
实际应用示例
You're trying to copy a weak FM signal on 2 meters. The signal is too weak to open your squelch, so you can't hear it. You turn the squelch control all the way down (counter-clockwise), which opens the squelch completely. Now the receiver audio is always on - you hear background noise, but you can also hear the weak signal that was previously squelched out. This is how you work weak FM signals.
错误选项分析
Option B: Incorrect. Turning up audio level doesn't overcome squelch. Squelch is a threshold control, not a volume control. You need to adjust the squelch threshold itself. Option C: Incorrect. There's no 'anti-squelch function' on standard transceivers. You simply open the squelch by turning it down. Option D: Incorrect. 'Squelch enhancement' isn't a standard function. You open squelch by lowering the threshold.
知识点
Squelch, Weak signals, FM reception, Squelch threshold
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.