What is Squelch On A Radio: An Ultimate Guide

Discover the world of squelch – the vital walkie-talkie feature that ensures clear communication and enhances your overall experience.
knobs that control volume and squelch on a cb radio

Noise can be unbearable, especially when it’s making it difficult for us to communicate. But unfortunately, it is one of the oldest challenges of radio communication. Early two-way radios could pick up background noises, and they get mixed up with transmissions. Hence, it was tough to differentiate noise from voice messages.  

For any walkie-talkie user, noise is a nuisance. It not only increases fatigue but also reduces communication quality. Hence, it had to be fixed, and that’s where squelch comes in. It was one of the earliest methods of filtering background noises. Rightly named so, squelch “silences” noise and reduces interference from other users. 

What is Squelch

Squelch is an electronic circuit that acts as a noise gate for a walkie-talkie speaker. The gate shuts out the noise and only opens when there’s a valid voice signal. 

In other words, the squelch circuit in walkie-talkies suppresses background noise and interference when there’s no signal. It mutes the speaker when there’s no detected transmission and only unmutes the user when it detects a signal frequency above the squelch level.   

How Squelch Works

Signal Detection

The squelch circuit first detects signal strength. It monitors the power of incoming signals and compares them to a predefined threshold. If the signal’s strength exceeds the threshold, it can pass through to the speaker. If not, the squelch circuit mutes the sound. 

Most walkie-talkies have an adjustable squelch control to set the squelch level. That is, how strong the audio should be before the walkie-talkie unmutes. A higher squelch level will only open the gate (unmute you) when there’s a strong signal. 

But, if you set your radio squelch level moderately, you can also pick up weak signals. Ideally, you should set the squelch level just high enough to block out background noise without blocking weak signals.

Noise Filtering

Once you set the threshold level just above background noise (static and hissing), your walkie-talkie will filter out the noise. Thus, since the noise is below the threshold, the squelch won’t unmute your speaker when it picks it up. As a result, you get clearer audio and can better understand relevant signals.  

Development of the Squelch Concept

In the early days of radio communication, users faced noise and interference issues. It was not only annoying but also affected audio clarity. Hence, it was difficult to distinguish between meaningful transmission and random noise. And this led to hearing fatigue and reduced productivity. 

Therefore, there was a need for a solution to this problem, and that’s how squelch came about. Engineers developed a system that automatically mutes the radio’s speaker when there’s no signal. Squelch was designed to suppress noise and reduce interference, thus enhancing audio clarity. 

They introduced the first squelch circuits in the 1930s. And ever since its implementation in radio devices, squelch has transformed communication for casual and professional users.  

Technological Advancements in Squelch Systems

Earlier squelch systems were basic. Most of them had knobs as squelch controls. The knobs were difficult to use because it was hard to determine the suitable squelch level.  

But over the years, squelch technology has evolved, keeping pace with the growing demands of modern communication. Engineers have developed more sophisticated squelch systems to improve performance, versatility, and ease of use. 

Types of Squelch

There are several types of squelch used in two-way radios: 

Carrier Squelch

Carrier squelch or standard squelch is the simplest squelch form. It functions strictly on the power of the signal. So, when it detects a signal on a frequency above the squelch threshold, it unmutes the speaker. 

Carrier squelch can either have a preset or adjustable control. It’s commonly used in basic walkie-talkies and is effective in most situations. But it may be susceptible to interference from other radio signals.  

Noise Squelch

Noise squelch provides better filtering than carrier squelch. It has an extra filter that distinguishes between meaningful transmissions and random noise. Noise squelch uses signal processing techniques to analyze the content of a signal. Hence, it ensures that only intelligible signals pass through to the speaker.

Tone Squelch

Tone squelch or Continuous Tone-Coded Squelch System (CTCSS) is a more advanced form of squelch. It is a form of selective calling that adds a low-frequency tone to transmissions. Hence, the squelch circuit only unmutes the speaker when it detects a signal with the same tone.

So, in this case, your walkie-talkie speaker won’t receive just any intelligible signal. It will only receive transmissions with the same tone as yours. But tone squelch is not foolproof. Sometimes, your speaker can pick up a false signal.  

Digital Squelch

Digital squelch or Digital-Coded Squelch (DCS) is similar to tone squelch. But it’s more advanced because it uses a digital method to filter noise and interference. DCS adds a digital code to a transmission. When sent, the receiving radio must recognize the code before it unmutes you. 

Hence, your two-way radio only receives signals with the same code as yours. Digital squelch provides better signal selectivity and protection from interference. It is ideal for congested radio environments or where secure communication is essential. 

Squelch Terminologies Explained

There are some terms related to squelch you should know. They include: 

1. Squelch Tail

The squelch tail is a brief burst of sound heard after a transmission ends. It happens when the radio circuit doesn’t mute the radio fast enough. In other words, it is the natural presence of noise between when the transmission ends and when the squelch function turns on.  

2. Squelch Tail Elimination

Squelch Tail Elimination (STE), also called reverse burst, is one of the systems used to eliminate squelch tails. The STE sends a brief low-frequency tone right before a transmission ends. The squelch will have turned on before the sub-audible tone ends. Hence, there will be no squelch tail. 

3.  Squelch Hysteresis

Squelch hysteresis prevents weak signals from rapidly toggling the squelch between mute and unmute states. This feature ensures that audio remains consistent even when the signal is weak or fluctuating.  

4.  Squelch Control

Squelch control is an adjustable setting that allows users to set the squelch threshold level. Adjusting the controls enables users to change the threshold level based on their environment.  

4. Squelch Threshold

The squelch threshold determines the level of audio strength needed to open the squelch. Level 0 means there’s no squelch. But the highest squelch level (the number will depend on your walkie-talkie brand) will only open your speaker when it picks up the strongest signal. As earlier said, the best threshold is just above the noise level. 

Importance of Squelch in Walkie-Talkie Communication

Blocking Out Background Noise and Interference

The squelch circuit filters out background noise and interference that can significantly decrease the quality of communication. Also, users won’t have hearing fatigue since they no longer struggle to discern meaningful transmissions.  

Enhancing Audio Clarity

Filtering out background noise and interference ensures that you only receive clear signals. Thus, it makes it easier for you to understand and respond to meaningful transmissions.  

Conserving Battery Life

Squelch mutes your speaker when there’s no signal. Hence, it reduces the active time of the speaker, which in turn conserves battery life. This is most beneficial for people who use their radio throughout the day without access to charging.  

Improving Overall User Experience

Noise and interference can be very annoying. By eliminating them, squelch improves audio clarity and conserves battery life. Hence, it significantly enhances the overall user experience. 

Setting Up and Adjusting Squelch on Walkie-Talkies

Some radios come with an automatic squelch control. Hence, the control automatically adjusts the squelch level based on the real-time signal condition.  

But other walkie-talkies have manual squelch control, so you must adjust it yourself. Manually changing the squelch setting allows you to customize your output. It also allows you to adjust the threshold based on your present environment. Here are a few tips for setting your walkie-talkie squelch level:  

  • During long-distance communication, the signal may become weaker. Hence, you should set the squelch level lower. 
  • For a shorter distance, the incoming signal becomes stronger. Thus, set the threshold higher.    
  • In poor signal areas, reduce the squelch level.  

In typical environments, turn the control to the lowest setting. Then you slowly increase it until you can no longer hear background noises. But ensure it is at a level where you can still hear weak signals.  


The squelch function in walkie-talkies offers a solution to background noise and interference. The squelch circuit mutes the speaker and only opens it when it detects a valid signal. Hence, it filters out background noise and interference that can affect the quality and clarity of transmissions. 

There are several types of squelch, with deferring levels of effectiveness. But they all help to improve audio clarity, filter noise, reduce interference, and reduce battery usage.  

About The Arthur
Picture of Kenny Zhang
I've been running a factory that manufactures two-way radios & their accessories. We want to share some knowledge and news about Walkie-Talkie from the sight of the supplier.

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