What is Scrambling: An Overview of Radio Scrambling Techniques

Discover the world of scrambling in walkie-talkies and learn about the techniques that ensure secure communication in various scenarios.
set of radio waves, analog and digital line waveforms

Walkie-talkies are simple and convenient. But, because users share the same channel, occasionally, someone could listen in on your conversation. Thus, it’s not advisable to use walkie-talkies for private messages. 

But, organizations, businesses, and government agencies share confidential information. However, the vulnerability of analog walkie-talkies makes it hard to do so. That’s where scrambling techniques come in. 

Scrambling techniques make it possible to use walkie-talkies for private transmission. They add an extra layer of protection to voice messages. Hence, users can pass sensitive information without the fear of interception by eavesdroppers.

Scrambling Function Explained 

Scrambling is simply a way of mixing or hiding the content of a voice transmission. Hence, eavesdroppers will be unable to understand the conversation. Three techniques are available to walkie-talkie users: 

Types of Scrambling Techniques 

There are three primary scrambling techniques used in walkie-talkies. Each of them offers varying levels of security and compatibility with walkie-talkie systems. They are: 

  • Voice inversion
  • Frequency hopping
  • Digital encryption

Voice Inversion

Voice inversion scrambling is a simple method of securing information that only works with analog two-way radios. As the name implies, the feature inverts voice data, making it unintelligible to casual eavesdroppers. 

Voice inversion is a weak form of security. As said earlier, it is primary. Hence, experienced eavesdroppers can find ways to descramble the information. 

So, only those with basic security needs should use this method of scrambling. For example, casual users can use it when sending sensitive information. 

How Voice Inversion Works 

Voice inversion inverts the frequency spectrum of the transmitting radio. Two main steps are involved: 

  • Frequency conversion: Voice inversion modifies the original signal with a carrier frequency. The carrier frequency is usually within the range of 2.5kHz to 4.5kHz. When altered, it creates a new signal. The new voice data usually has higher and lower frequency parts, known as side bands. 
  • Frequency Inversion:  Next, it swaps the higher and lower sidebands, resulting in an inversion. Thus, when the transmitting radio sends the inverted signal to the receiving radio, only those with a compatible receiver and correct setup can intercept or listen to it. Others will hear inverted voice data.

Voice Inversion In Practice 

Without the voice inversion descrambler, you can’t decode the message. Hence, the receiver’s walkie-talkie must have a voice-inversion descrambler. What the descrambler does is reverse the inverted signal. It changes it back to its original state. Then, the message will be intelligible.  

Walkie-talkies with voice inversion scrambling have a designated channel or setting to enable or disable it.

Pros and Cons of Voice Inversion Scrambling


  • Simple and Easy to Use: Voice inversion is a simple scrambling technique. It’s easy to use and set up. You can use it without any advanced technical knowledge.
  • Affordable: Voice inversion is less expensive when compared to other scrambling options. 


  • Limited Security: The disadvantages of the simple inversion method are security concerns. Knowledgeable eavesdroppers can still decipher your message. They can intercept signals with specialized equipment or even software programs. Thus, the inversion method is not suitable for higher privacy needs. 
  • Analog-only: You can only use it on analog walkie-talkies. Hence, digital users can’t communicate with analog walkie-talkies with the voice inversion function. It also means digital users can’t use it, limiting its use. 
  • Potential Distortion: You may experience minor audio distortion sometimes. Thus, it may cause unclear communication between users. 

How to Set Up Voice Inversion Scrambling 

To set up voice inversion on your walkie-talkie, follow these steps: 

  1. Check if your walkie-talkie supports voice inversion. Some models already have a built-in voice inversion scrambler. If it doesn’t, then get an external scrambler device. 
  2. If there’s a built-in voice inversion, activate it through the menu or setting. If not, install the external scrambler according to the manufacturer’s instructions. 
  3. Set the scrambling code or inversion frequency on the walkie-talkies. Ensure you set it on all walkie-talkies in your group. 
  4. Test the walkie-talkies to ensure the scrambler is working correctly. 

Frequency Hopping

Frequency hopping scrambling is also called frequency hopping spread spectrum (FHSS). FHSS provides more security than the voice inversion technique. 

Frequency hopping involves quickly switching the carrier frequency within a narrow bandwidth. Hence, it becomes difficult for eavesdroppers to follow the conversation. Both analog and digital walkie-talkies can use this method. 

In simpler words, the signal hops between programmed frequencies, rapidly changing its carrier. Usually, it changes carrier frequency more than once in a second. 

How Frequency Hopping Works 

If your walkie-talkie uses the frequency hopping method, your voice signals rapidly hop from one frequency to another. Usually, the change occurs at predetermined intervals after a short burst of data. 

A pseudorandom sequence guides the process. The arrangement determines the order of frequency changes within the bandwidth. Frequency hopping is unique because it doesn’t scramble the message. 

Instead, it hides the message so eavesdroppers cannot intercept it. They can only do so if they can predict the frequency sequence. 

Also, frequency hopping protects you from intentional jamming and interference. Signals change their carrier frequency almost immediately. Hence, jamming and interference only happens for a short time. 

Frequency Hopping In Practice 

The first step is to check if the walkie-talkies can use the frequency hopping technique. If yes, you must program them with the same sequence. 

You can create your pattern on some walkie-talkies brands. But this is not always the case because some have a pre-set pattern. 

Also, frequency hopping needs extra licensing. You must also comply with the local regulations on its use. The main reason is that it uses many frequencies. Hence, you must consult local rules to know how to use it. 

Pros and Cons of Frequency Hopping Scrambling


  • Enhanced Security: Frequency hopping is more secure than voice inversion. Hence, it is more difficult for eavesdroppers to intercept and follow the conversation. 
  • Resistance to Interference and Jamming: The carrier frequency changes fast. Hence, interference and jamming only last for a short time. 
  • Analog and Digital Compatibility: Both analog and digital walkie-talkies can use frequency hopping. Thus, it allows broader compatibility and use. 


  • More Complex: Using this technique is tougher than voice inversion. You will need more technical knowledge to do so. It also requires that you synchronize the devices. 
  • Licensing and Regulatory Compliance: Users may need to get extra licenses. They must also follow local regulations to use frequency hopping legally.
  • Reduced Battery Life: Rapid frequency changes means more workload for your walkie-talkie. Hence, it may increase power consumption and reduce battery life. 

How to Set Up Frequency Hopping Scrambling

If you want to use frequency hopping, follow these steps: 

  1. Check if your walkie-talkies support frequency hopping. 
  2. Go to the menu or setting and activate the frequency hopping function. 
  3. Set the necessary parameters, like the number of hops per second and the frequencies you want to use for the sequence. 
  4. Test the walkie-talkies to know if the frequency-hopping scrambler is working correctly.

Digital Encryption

Digital encryption scrambling uses a mathematical algorithm to encrypt voice messages, which is only available on digital walkie-talkies. When it encrypts a message, no one can understand it without the correct key. 

This key is called the decryption key. So, once you send a message, only walkie-talkies with the same decryption key can decipher and understand you. 

The method adopted makes it almost impossible for eavesdroppers to intercept your conversation. Thus, it is the most secure form of walkie-talkie encryption. 

How Digital Encryption Works

Digital encryption uses cryptographic algorithms to protect your conversation. There are two types of digital encryption:

  • Symmetric Encryption: Symmetric encryption uses only one key to encrypt and decrypt voice signals. It means it’s the same key used in encrypting that you use in decrypting information. The main symmetric encryption is Data Encryption Standard (DES), triple DES, and Advanced Encryption Standard (AES).
  • Asymmetric Key Encryption: Asymmetric encryption uses two separate keys for encryption and decryption. Hence, it is more complex than symmetric encryption. Standard asymmetric keys are RSA and Public key infrastructure (PKI).

Digital walkie-talkies may use both symmetric and asymmetric encryption techniques. They may also have other security features like authentication and digital signatures.

Digital Encryption In Practice 

Both walkie-talkies must be compatible with the algorithm to use digital encryption. You may also need to set the encryption to fit your specific security needs. Such settings are the key length and algorithm selection. 

When you send an encrypted signal to another user, eavesdroppers can’t hear you. If they intercept your message, Your message will become unintelligible and sound like garble. Hence, only the intended recipient with the same decryption key can listen to your message. 

Pros and Cons of Digital Encryption Scrambling


  • Strong Security: Digital encryption makes it hard for eavesdroppers to decipher your message. Hence, it provides the highest level of confidentiality. 
  • Enhanced Privacy:  Your conversations are safe because it protects you from eavesdroppers. Thus, you can use digital encryption without anyone invading your privacy.


  • Very Complex: Digital encryption is more complex than other scrambling techniques. Generally, you will need specialized knowledge and equipment to use and maintain it.
  • Cost: Walkie-talkies with digital encryption functions are more expensive. They generally cost more than walkie-talkies with more straightforward scrambling techniques. 
  • May Affect Performance: Digital encryption may cause latency. It also uses more processing resources. All of these may even affect the performance of the walkie-talkie. 

How to Set Up Digital Encryption Scrambling

To set up digital encryption on your walkie-talkies, do this: 

  1. Ensure your walkie-talkies are digital and support digital encryption. 
  2. Go to settings or the menu to activate the digital encryption feature. 
  3. Choose the encryption algorithm (e.g., AES, DES) and the key length. 
  4. Input the encryption key in each walkie-talkie. If you use asymmetric key encryption, share the public key with all users in your group. 
  5. Ensure all the walkie-talkies have the same encryption setting. 
  6. Test the walkie-talkies to know if the digital encryption is working correctly.

Scrambling and Regulatory Compliance

If you intend to use any scrambling technique, check to see if it complies with your local regulations. Communication regulatory bodies differ from place to place. But, the Federal Communications Commission (FCC) is the regulatory body in the US. And Ofcom is the regulatory body in the UK. 

The regulatory body in your region gives rules on the use of scrambling. Hence, ensure you comply with the regulations. For instance, the FCC permits using digital encryption on all channels. But you can’t use it on the two nationwide interoperability calling channels.

Legal Considerations for Scrambled Communication 

In some areas, there may be restrictions to the use of scrambling techniques. Hence, scrambled communication can cause legal concerns like wiretapping and eavesdropping laws. 

Or, rather, you may need special licensing to use them. Hence, you must be aware of local and international regulations guiding the usage of scramblers. 

security using walkie talkie earphone to talk in vox mode

Choosing the Right Scrambling Technique for Your Needs 

There are several factors to consider when choosing a suitable scrambling technique: 

  • Desired Level of Security: When choosing a method, you should decide based on the level of confidentiality you need. You should use digital encryption or frequency hopping for sensitive information. But, if you have basic security needs, opt for the voice inversion method. 
  • Budget: You should also consider your budget. Ensure you don’t end up spending more than you should.
  • Compatibility: Not all techniques are compatible with the different walkie-talkies. So, check to see if yours is consistent with the method you intend to use.

Also, some encryption methods require specific hardware or software. Hence, you should ensure it is compatible with your walkie-talkie.


Scrambling techniques solve a significant problem for walkie-talkie users: eavesdropping. Users can protect their conversations from eavesdroppers, hence, enhancing privacy. You can pass on sensitive information over the walkie-talkie knowing they will remain confidential. 

The types of scrambling are voice inversion scrambling, frequency hopping, and digital encryption. Some scrambling techniques provide robust security. But the voice inversion technique can only protect your information from casual eavesdroppers. 

Hence, when buying walkie-talkies with scrambling features, consider the level of security needed. Also, consider your budget and its compatibility with your devices. 

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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