Deep Dive: T2B13
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.
Why Other Answers 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.
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 Example
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.
Source & Coverage
Question Pool: 2022-2026 Question Pool
Subelement: T2B
Reference: FCC Part 97.3
Key Concepts
Verified Content
Question from the official FCC Technician Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the T2B topic.