What is NB/ANL on a CB Radio?

Whether you’re a long-haul trucker navigating the open road or a hobbyist connecting with fellow enthusiasts, CB radios have been the trusted companions of communicators for decades.

However, amid the array of buttons and knobs that adorn these compact communication hubs, two switches often leave users puzzled: the NB (Noise Blanker) and ANL (Automatic Noise Limiter) switches.

NB/ANL switch on a CB Radio

What exactly do these switches do, and how can they enhance your radio experience? In this article, we delve into the CB radio world to demystify the NB and ANL switches, shedding light on their functions and the benefits they bring to your communication journey.

Whether you’re a seasoned CB enthusiast or a newcomer to the world of CB radios, understanding these switches can make a significant difference in the clarity and quality of your conversations. So, let’s dive in and unravel the mystery NB and ANL on a CB radio.

Dealing with Unwanted Noise

Common Sources of Background Noise and Interference

When using a CB radio, especially in a mobile or base station setup, dealing with unwanted noise and interference is a common challenge.

Some of the common sources of background noise and interference include:

  1. Engine Noise: The rumble of your vehicle’s engine can often bleed into your CB radio’s audio. This is particularly problematic in mobile setups where the CB radio is installed in a vehicle.
  2. Unwanted Ignition Noise: Ignition systems in vehicles can generate electrical interference that manifests as a buzzing or popping sound on your CB radio’s speaker. This noise can be more pronounced in older vehicles or those with poorly maintained ignition systems.
  3. Electrical Noise from Power Lines: If you’re using a CB in a building, electrical noise from nearby power lines and electronic devices can seep into your transmissions, causing unwanted background noise.

Understanding the Impact of Interference on CB Radio Communication

Unwanted noise and interference can significantly hinder your CB radio communication. Here’s how it affects your communication:

  • Reduced Clarity: Interference can make incoming messages garbled and difficult to understand. Likewise, your transmissions may be distorted, making it challenging for others to comprehend your messages.
  • Decreased Range: Noise can mask weaker signals, reducing the effective range of CB radios. This can limit your ability to communicate with others, especially if they are at a distance or in areas with a lot of interference.
  • Frustration: Constant background noise and interference can be frustrating and distracting.

The Importance of Effective Noise Filters and Suppression Methods

To mitigate the impact of unwanted noise and interference on your CB, it’s essential to employ effective noise filters and suppression methods. This is where the NB (Noise Blanker) and ANL (Automatic Noise Limiter) switches come into play:

What is the Noise Blanker (NB)

The Noise Blanker (NB) is a crucial feature in a CB (Citizens Band) radio system designed to combat unwanted static and interference during transmissions. It acts as a digital shield against various sources of noise that can degrade communication quality.

How NB Works to Eliminate Unwanted Static and Strong Signals

The Noise Blanker operates by detecting abrupt changes in the radio signal’s amplitude, typically associated with static or interference. When these disruptions are detected, the NB kicks in and momentarily mutes or reduces the volume of the audio output, effectively eliminating the unwanted noise. This process happens in real-time and is so rapid that it’s imperceptible to the human ear.

Practical Benefits of Using NB for Clearer Reception

Using the Noise Blanker provides several practical benefits for CB radio users. Firstly, it significantly improves audio clarity by eliminating static and interference, allowing for more comprehensible conversations. Secondly, it enhances the overall user experience by reducing listener fatigue caused by prolonged exposure to noisy signals. Ultimately, the Noise Blanker helps users maintain effective communication in challenging radio environments.

What is the Automatic Noise Limiter (ANL)

ANL is another essential feature in CB radios designed to enhance audio quality. Unlike the Noise Blanker, which focuses on sudden amplitude changes, the ANL specifically targets constant background noise and interference that may persist throughout a transmission.

How ANL Reduces Audio Interference and Background Noise

The ANL works by continuously monitoring the incoming audio signal for constant noise sources such as engine ignition systems, power lines, and other electronic devices. When it detects this type of noise, the ANL applies a dynamic filter that reduces or suppresses the unwanted background interference. This results in clearer and more intelligible audio output for both incoming and outgoing transmissions.


In summary, the main difference between the Noise Blanker (NB) and the Automatic Noise Limiter (ANL) lies in their respective functions and targets. The Noise Blanker primarily addresses sudden amplitude changes or static in radio signals, ensuring a more pleasant listening experience and improved clarity during transmissions.

On the other hand, ANL focuses on continuous background noise and interference, effectively enhancing audio quality by filtering out persistent sources of disruption.

While both features contribute to better reception, their specific roles make them complementary tools for maintaining clear and interference-free conversations.

Other Controls That Help With Noise Reduction

In addition to the Noise Blanker (NB) and Automatic Noise Limiter (ANL), there are two other essential controls that play a role in reducing noise in CB radio communication: RF Gain and Squelch.

While these controls will be explored more extensively in a separate article, here’s a brief overview of their functions:

  1. RF Gain: Short for Radio Frequency Gain it allows users to adjust the sensitivity of their radio’s receiver. By reducing the RF Gain, you can decrease the sensitivity to weaker signals, which can help minimize background noise and interference. Conversely, increasing RF Gain can enhance reception of weaker signals when needed. I go into more detail in the article, What is RF Gain?
  2. Squelch: Squelch is a control that helps eliminate the annoying background noise when no transmission is occurring. It mutes the audio output until a signal of a certain strength is received, effectively silencing the noise when the channel is quiet. Squelch can be adjusted to the desired threshold level, preventing continuous hissing or static from disrupting your listening experience. I have a more detailed article that explains, How to Use Squelch on Your CB Radio.

These two controls, when used in conjunction with the Noise Blanker and Automatic Noise Limiter, provide you with a comprehensive toolkit for effectively managing and reducing unwanted noise.

Should the NB/ANL Switch Be Left On?

In general, it is recommended to leave the Noise Blanker (NB) and Automatic Noise Limiter (ANL) switch in the “ON” position on your CB radio, especially when you are operating in areas with potential sources of interference and noise.

However, there may be specific situations where you might want to consider turning these features off temporarily:

  • Extremely Weak Signals: If you are trying to receive a very weak signal and the NB and ANL are overly aggressive in reducing noise, you can try turning them off to allow for better signal reception.
  • Testing or Adjusting: When troubleshooting or adjusting your CB radio settings, you may need to turn off the NB and ANL temporarily to isolate issues or fine-tune your audio.

Which CB Radios Have NB and ANL?

  1. Cobra 29 LX MAX: This CB radio offers both NB and ANL features, along with an array of advanced functions for improved communication.
  2. Uniden Bearcat 980 SSB: Known for its SSB capabilities, this radio includes NB and ANL features to enhance audio quality.
  3. President McKinley USA: This radio provides NB and ANL features, along with multiple power output options and other advanced settings.
  4. Galaxy DX-959B: A high-performance CB radio with NB and ANL, known for its excellent audio clarity.

Featured Image credit: Uniden

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