| name | selcal-codec |
| description | Encode and decode SELCAL (Selective Calling) aviation HF radio signals in audio WAV format. SELCAL alerts specific aircraft crews on oceanic HF routes using sequential dual-tone bursts from 16 ICAO-standard frequencies (312.6-2122.5 Hz). Use this skill whenever the user mentions SELCAL, selective calling, aviation HF, HF radio alert, aircraft selective call, cockpit alert tones, ICAO SELCAL, oceanic HF, SELCAL decoder, or wants to create/analyze SELCAL audio WAV files. Covers encoding (SELCAL codes to WAV) and decoding (WAV to SELCAL codes).
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SELCAL Codec
Overview
SELCAL (Selective Calling) codec for aviation HF radio. Encode and decode SELCAL alerting signals used to alert specific aircraft crews on oceanic and remote HF routes.
SELCAL is the selective calling system used on HF aviation radio to notify pilots of incoming radio calls without requiring continuous audio monitoring. Ground stations transmit a SELCAL code (unique to each aircraft) which triggers an alert in the cockpit. This codec allows aviation enthusiasts and SDR hobbyists to monitor, encode, and decode SELCAL signals.
Features
- SELCAL Encoding: Generate SELCAL audio signals from 4-letter aircraft codes
- SELCAL Decoding: Detect and identify SELCAL codes from audio recordings using the Goertzel algorithm
- Code Validation: Verify SELCAL codes against ICAO standards
- ITU/ICAO Frequencies: Uses all 16 standard SELCAL tone frequencies (312.6–2122.5 Hz)
- HF-Ready: Designed for real-world HF audio recordings with noise and fading
Usage
Encoding
python3 scripts/selcal_encode.py ABCD output.wav
Decoding
python3 scripts/selcal_decode.py input.wav
SELCAL Basics
- 4-letter code: Each aircraft has a unique SELCAL code (e.g., "ABCD", "DGHK")
- Two bursts: Each code is transmitted as two dual-tone bursts
- Tone duration: ~1.0 second per burst, 0.2 second gap between bursts
- Total duration: ~2.2 seconds per SELCAL transmission
- Frequencies: 16 standard tones spaced ~1/6 octave apart (A–S, skipping I, N, O)
Use Cases
- Aviation HF monitoring and transcription
- SELCAL decoder for SDR enthusiasts
- Real-world HF radio signal analysis
- Aircraft alert systems research
- Oceanic and remote route communications study
Skill Triggers
SELCAL, selective calling, aviation HF, HF radio alert, aircraft selective call, cockpit alert tones, ICAO SELCAL, oceanic HF, pilot alerting, aviation dual-tone, SELCAL decoder, HF aviation frequencies
