📡 TetraEar - Professional TETRA Decoder

February 12, 2026 · View on GitHub

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🎯 A modern, professional TETRA (Terrestrial Trunked Radio) decoder and analyzer for RTL-SDR with real-time voice decoding, encryption support, and an intuitive GUI.

✨ Features

🖥️ Modern GUI

  • Professional Dark Theme: shadcn/ui inspired interface
  • Real-time Waterfall: High-performance spectrum display (~60 FPS)
  • Intuitive Controls: Click-to-tune, zoom, and frequency tracking (AFC)
  • Live Status: Real-time signal strength, sync rate, and CRC validation

🔊 Voice Decoding

  • ACELP Codec: Uses ETSI reference codec (cdecoder.exe + sdecoder.exe) for voice decoding
  • Real-time Audio: Monitor decoded voice in real-time
  • Quality Validation: Automatic amplitude check (configurable)
  • Recording: Save decoded audio to WAV files

🔐 Encryption Support

  • Auto-Detection: Identifies TEA1/TEA2/TEA3/TEA4 encryption
  • Smart Decryption: Automatic bruteforce with common/weak keys
  • Key Management: Load custom keys from file
  • Validation: CRC checking and plaintext verification

📊 Data Analysis

  • SDS Decoding: Short Data Service text message extraction
  • Multi-frame Assembly: Automatic reassembly of fragmented messages
  • Call Metadata: Talkgroup ID, SSI (subscriber), call type tracking
  • Advanced Filtering: Dropdown-based filters for Calls, Groups, Users, and Message Types
  • Real-time Statistics: Frame counts, sync rate, encryption stats

🎛️ Spectrum Analyzer

  • Waterfall Display: Real-time frequency visualization
  • AFC (Auto Frequency Control): Automatically centers on signal peak
  • Click-to-Tune: Ctrl+Click to tune to peak frequency
  • Zoom Controls: Top, bottom, and threshold adjustments
  • Auto Sliders: Dynamic zoom/threshold calibration for optimal visibility
  • Denoising: Built-in noise reduction (configurable)

🛠️ Developer-Friendly

  • CLI Mode: Run without GUI using --no-gui flag
  • Rich Logging: Color-coded console output
  • Debugging: Logs/recordings live in the user data directory (override with TETRAEAR_DATA_DIR)
  • API: Modular design for easy integration

📋 Requirements

  • Python: 3.8 or higher
  • RTL-SDR: Compatible USB dongle with drivers installed
  • Operating System: Windows or Linux
  • Optional: TETRA speech codec binaries (cdecoder.exe + sdecoder.exe) for voice decoding

🚀 Installation

1️⃣ Clone the Repository

git clone https://github.com/syrex1013/TetraEar.git
cd TetraEar

2️⃣ Install Dependencies

pip install -r requirements.txt

3️⃣ (Optional) Install TETRA Codec

Place cdecoder.exe and sdecoder.exe in tetraear/tetra_codec/bin/ directory, or run:

python -m tetraear.tools.install_tetra_codec

4️⃣ Verify Installation

python -m tetraear.tools.verify_codec

🎮 Usage

python -m tetraear

CLI Mode

python -m tetraear --no-gui -f 392.225 --auto-start

Command-Line Options

-h, --help              Show help message
-f, --frequency         Frequency in MHz (default: 390.865)
-g, --gain              RF gain in dB (default: 50.0)
-s, --sample-rate       Sample rate in MHz (default: 2.4)
--auto-start            Automatically start capture on launch
-m, --monitor-audio     Enable audio monitoring
--scan START STOP       Scan frequency range first
--auto-decrypt          Enable auto-decryption (default: enabled)
-v, --verbose           Enable verbose logging
--no-gui                Run in CLI mode without GUI

Examples

# Launch GUI with specific frequency
python -m tetraear -f 392.225

# Auto-start capture with audio monitoring
python -m tetraear -f 392.225 --auto-start -m

# Run in CLI mode
python -m tetraear --no-gui -f 392.225 -g 35

# Scan frequency range then launch GUI
python -m tetraear --scan 390 392

⚙️ Configuration

Settings Menu (GUI)

Click the ⚙️ Settings button to access:

  • Audio Device: Select output device for monitoring
  • Delete Silent Files: Auto-remove recordings with zero amplitude
  • Max Recordings: Limit number of saved audio files
  • Log Level: Adjust logging verbosity

Frequency Presets

  • Save Frequencies: Click 📍 Save Freq to save current frequency with label
  • Load Presets: Select from saved frequencies in dropdown
  • Export/Import: Manage presets in settings.json

Key Management

  1. Click 🔑 Load Keys button
  2. Create keys.txt with format: 
    # TEA1 Keys (80-bit, 10 bytes)
00:11:22:33:44:55:66:77:88:99

# TEA2 Keys (128-bit, 16 bytes)
00:11:22:33:44:55:66:77:88:99:AA:BB:CC:DD:EE:FF

📊 Tabs Overview

📜 Decoded Frames

  • View all decoded TETRA frames
  • Filter by type (MAC-RESOURCE, MAC-FRAG, MAC-BROADCAST, etc.)
  • Decrypted/Text Only: Show only successfully decrypted or clear text messages
  • Real-time frame updates with encryption status

📞 Calls

  • Active and historical call list
  • Filter by group or client SSI
  • Call duration and status tracking

👥 Groups

  • Talkgroup activity monitoring
  • Filter groups by name
  • Member count and call statistics

👤 Users

  • Subscriber (SSI) tracking
  • Filter by group membership
  • Activity history per user

📝 Log

  • Real-time application logs
  • Color-coded by severity
  • Filter by log level
  • Exports to the user data directory (override with TETRAEAR_DATA_DIR)

📈 Statistics

  • Total frames decoded
  • Sync rate and CRC success rate
  • Encryption statistics (per algorithm)
  • Voice frame count
  • SDS message count

🔍 Tips & Tricks

🎯 Finding TETRA Signals

  1. Use SCAN mode to sweep frequency range
  2. Look for strong, consistent spikes in waterfall (~25 kHz wide)
  3. TETRA signals typically appear as 4 carriers (4x6.25 kHz slots)
  4. Enable Auto-Follow Spike (AFC) to auto-track signal

🔊 Voice Decoding

  • Ensure cdecoder.exe and sdecoder.exe are in tetraear/tetra_codec/bin/
  • Check Monitor Audio to hear decoded voice
  • Adjust gain (45-50 dB recommended)
  • Voice frames appear with 🔊 icon in Decoded Frames tab

🔐 Decryption

  • Auto-Decrypt tries common keys automatically
  • Load custom keys using Load Keys button
  • Successfully decrypted frames show ✅ in Status column
  • Use Decrypted/Text Only filter to view plaintext only

📡 Optimal Settings

  • Frequency: 390-395 MHz (varies by region)
  • Gain: 45-50 dB (adjust based on signal strength)
  • Sample Rate: 2.0-2.4 MHz (higher for better quality)
  • Bandwidth: 25000 Hz (standard TETRA channel)

🛠️ Troubleshooting

❌ No Signal Detected

  • Check Frequency: Verify TETRA frequency for your region
  • Adjust Gain: Try 45-50 dB
  • Check Antenna: Ensure proper connection and positioning
  • Sample Rate: Use 2.0-2.4 MHz

❌ Low Sync Rate (< 80%)

  • Increase Gain: Weak signal requires higher gain
  • Adjust Threshold: Lower threshold in Spectrum Display
  • Check Antenna: Improve signal reception
  • Frequency Drift: Enable AFC (Follow Frequency)

❌ CRC Failures (0%)

  • Wrong Frequency: Not a valid TETRA signal
  • Low Signal: Increase gain or improve antenna
  • Interference: Try different location or frequency

❌ No Voice Audio (Amplitude 0.0)

  • Codec Missing: Verify cdecoder.exe and sdecoder.exe exist
  • Encrypted Voice: Load decryption keys
  • Wrong Frame Type: Verify it's a Traffic/Voice frame

❌ Encrypted Frames Not Decrypting

  • No Keys Loaded: Load keys using Load Keys button
  • Wrong Algorithm: Check detected encryption type (TEA1/2/3/4)
  • Unknown Key: Signal uses unique/proprietary key

📁 Project Structure

Tetra/
├── tetraear/               # Application package root
│   ├── assets/             # Icons, banner, UI resources
│   ├── bin/                # Runtime DLLs
│   ├── tetra_codec/        # TETRA ACELP codec binaries
│   │   └── bin/
│   ├── tools/              # Build + packaging tools
│   ├── core/
│   ├── signal/
│   ├── audio/
│   └── ui/
├── tests/                  # Unit + integration tests
├── requirements.txt
└── README.md

🤝 Contributing

Contributions are welcome! Please:

  1. Fork the repository
  2. Create a feature branch (git checkout -b feature/amazing-feature)
  3. Commit your changes (git commit -m 'Add amazing feature')
  4. Push to the branch (git push origin feature/amazing-feature)
  5. Open a Pull Request

📜 License

This project is licensed under the MIT License. See LICENSE file for details.

IMPORTANT: This software is intended for educational and research purposes only.

  • ⚠️ Know Your Laws: Intercepting radio communications may be illegal in your jurisdiction
  • 🔒 Respect Privacy: Do not decode or disseminate private communications
  • 📜 Compliance: Ensure you have proper authorization before monitoring any radio system
  • ⚖️ Responsibility: Users are solely responsible for compliance with local laws and regulations

The authors and contributors assume no liability for misuse of this software.

🙏 Acknowledgments

  • TETRA Standard: ETSI EN 300 392 series
  • RTL-SDR Project: For making SDR accessible
  • OpenEar Project: Inspiration for encryption handling
  • telive: Reference TETRA decoder implementation
  • Community: Thanks to all contributors and testers
  • @Mrscanner2008: Special thanks for providing real TETRA signals and recordings to better understand the protocol and fix a lot of bugs!

📞 Contact & Support

🔗 Resources

Made with ❤️ by the TETRA community