How to Make a Digital Walkie-Talkie

[ilianaboone]

Walkie-talkies, known for their ability to communicate without the need for network support and without incurring phone bills, have made our lives much more convenient. Typically, a walkie-talkie consists of an antenna, main unit, battery, and charging dock. There are three main types of walkie-talkies: analog, digital, and IP-based. But how can we make our own digital walkie-talkie?

The EWM201 series module from ebyte offers an easy and quick way to build a digital walkie-talkie. By simply connecting a microphone (MIC), audio amplifier, speaker, antenna, and power supply, you can quickly DIY your own walkie-talkie with a communication range of up to 5 kilometers.

Preparation

To complete this DIY project, you should have some basic electronics knowledge and prepare the following:

Materials:

• Ebyte EWM201-470A30S module
• Microphone (MIC), speaker, passive components (resistors, capacitors, etc.)

Tools:

• Soldering iron, solder wire, tweezers, etc.

Documents:

• EWM201-470A30S module user manual, recommended circuit diagram

Software:

• EDA software (such as KiCad)

Design the Circuit Diagram

Based on the pin functions of the EWM201-470A30S module, design the surrounding circuitry to match, including the microphone amplification circuit, speaker drive circuit, power supply circuit, control button circuit, antenna output, etc. You can refer to the recommended circuit diagrams provided on EBYTE's official website for guidance.

For example:

• Microphone Circuit: Amplify the analog audio signal collected by the microphone and feed it into the audio input pin of the EWM201-470A30S module.

• Speaker Circuit: Use an audio amplifier IC to amplify the audio signal output from the EWM201-470A30S module, driving the speaker to produce sufficiently loud sound. The volume and sound quality are affected by the quality of the speaker you choose.

• Ensure the parameters and values of the components, such as capacitors, resistors, and inductors, are determined based on the chip datasheet and previous design experience.

PCB Design and Soldering

Using professional PCB design software, such as KiCad or Lichuang EDA, create the PCB layout based on your circuit diagram and proceed with the soldering process.

Debugging and Testing

Once the circuit is assembled, connect the power supply and use instruments like oscilloscopes to observe the waveforms at key points, such as the power supply voltage and audio input/output signals, to ensure they meet design specifications.

Test the microphone and speaker functionality by speaking and listening to the audio to check if the signal is being correctly captured and played. If the audio is too quiet or distorted, check the audio amplification circuit and ensure all components are correctly placed and soldered.

At this point, you can start using your DIY walkie-talkie.

Optimization and Fine-Tuning

To achieve the best performance, use tools like a spectrum analyzer to test the transmission and reception frequency, output power, and sensitivity of the EWM201-470A30S module. If there is significant frequency deviation, adjust the components (e.g., inductors, capacitors) to bring the module to its optimal working state.

Ready-to-Use Test Kits

The EWT201-470A20S/30S test kits are available to help you test a basic digital walkie-talkie. These kits come with modules that provide a transmit power of 20 dBm or 30 dBm, helping you conduct tests for voice communication over distances of more than 3.5 kilometers or 5 kilometers.

By using the EWT201-470A20S/30S test kits, you can connect the antenna, power it with a power bank, press the PTT (Push-to-Talk) button, and toggle between transmit and receive modes on both devices to initiate communication. Optionally, you can add an enclosure to make the device more aesthetically pleasing.

Transmission Modes

The walkie-talkie supports three transmission modes: unicast, multicast, and broadcast. To configure these modes:

• Unicast: Set the DESTID to a non-zero value to specify the communication target.
• Multicast/Group Communication: Set the PANID to the same value on all devices within the group.
• Broadcast: Used for communication with all devices in the network.

To isolate communication physically, configure the transmission frequency point for the devices.

Communication Modes

In addition to the three transmission modes, the walkie-talkie also supports half-duplex and full-duplex communication:

• Half-Duplex Mode: Only one walkie-talkie can transmit at a time within the same network.

• Full-Duplex Mode: One walkie-talkie must act as the master, while the other is the slave. Both can transmit audio simultaneously in full-duplex mode.

With these features, you can explore various applications, such as traditional walkie-talkies, building intercom systems, or even wireless audio broadcasting systems.