The NOAA weather satellites broadcast analogue images near 137 MHz, continuously. If you can hear them, you can draw your own cloud map. This is the record of one attempt.

Gear

  • A 137 MHz QFH antenna
  • An RTL-SDR
  • A laptop that can run satdump

Procedure

  1. Look up the pass time: only the ten minutes overhead are worth recording.
  2. Record baseband around 137.1 MHz — 48 kHz of sample rate is plenty.
  3. Decode to an image, then overlay a georeference.

Lessons

  • Antenna height matters far more than antenna price.
  • Miscalculate the pass once and you wait another twelve hours.
  • 137 MHz is noisier in a city than you expect; a filter is close to mandatory.

Next step: make it permanent on a Raspberry Pi, scheduling passes automatically and uploading results.