Ryan Malloy
77ddec149c
fetch_apollo_audio.py downloads Apollo 11 audio highlights from Archive.org and extracts clips using ffmpeg (48 kHz mono WAV). Supports --list, --clip, --all with idempotent downloads and progress reporting. real_signal_demo.py auto-discovers downloaded clips and runs them through the full USB downlink TX/RX chain (PCM telemetry + FM voice), saving recovered audio for comparison. Falls back to the bundled demo clip if no downloads exist. Also adds .gitignore to keep large audio files out of the repo while preserving the small apollo11_crew.wav demo clip.
gr-apollo
GNU Radio 3.10+ out-of-tree module for decoding Apollo Unified S-Band (USB) telecommunications signals.
Overview
The Apollo Unified S-Band system was the primary communication link between the spacecraft and Earth during the Apollo missions (1967-1972). This module implements GNU Radio blocks to decode these signals, enabling:
- Reception of Apollo-era recordings
- Integration with the Virtual AGC emulator
- Educational exploration of 1960s space communications
Signal Specifications
| Parameter | Value |
|---|---|
| Downlink Frequency | 2287.5 MHz |
| Uplink Frequency | 2106.40625 MHz |
| Coherent Ratio | 240/221 |
| PM Peak Deviation | 0.133 rad (7.6°) |
| PCM Subcarrier | 1.024 MHz BPSK |
| PCM Bit Rate | 51.2 kbps (high) / 1.6 kbps (low) |
| Voice Subcarrier | 1.25 MHz FM |
| Frame Length | 128 words × 8 bits @ 50 fps |
Installation
# Using uv (recommended)
uv pip install -e .
# Install GRC blocks
cp grc/*.yml ~/.local/share/gnuradio/grc/blocks/
Signal Chain
RF 2287.5 MHz
│
▼
┌─────────────┐
│ Carrier PLL │ ◄── 240/221 coherent recovery
└─────────────┘
│
▼
┌─────────────┐
│ PM Demod │ ◄── 0.133 rad peak deviation
└─────────────┘
│
├────────────────────┬──────────────────┐
▼ ▼ ▼
┌──────────┐ ┌──────────┐ ┌──────────┐
│ 1.024MHz │ │ 1.25 MHz │ │ Ranging │
│ BPSK │ │ FM │ │ PRN │
└──────────┘ └──────────┘ └──────────┘
│ │
▼ ▼
┌──────────┐ ┌──────────┐
│ PCM Sync │ │ Voice │
│ 51.2kbps │ │ 300-3kHz │
└──────────┘ └──────────┘
│
▼
┌──────────┐
│ 128-word │
│ Demux │
└──────────┘
│
▼
Telemetry
References
- Virtual AGC Project
- NASA Technical Reports
- NAA Course A-624: Telecommunication Systems Study Guide (1965)
License
MIT