NOAA Satellite Reception
End-to-end APT signal acquisition, decoding, calibration, and georeferencing from polar-orbiting weather satellites
NOAA / Meteor APT Constellation
The Automatic Picture Transmission (APT) system broadcasts continuous analog imagery on VHF frequencies near 137 MHz. Three NOAA POES satellites and the Russian Meteor-M2 currently transmit APT-compatible signals receivable with inexpensive hardware.
| Satellite | Frequency (MHz) | Status | Launch |
|---|---|---|---|
| NOAA 15 | 137.620 | Degraded | 1998 |
| NOAA 18 | 137.9125 | Active | 2005 |
| NOAA 19 | 137.100 | Active | 2009 |
| Meteor-M2 | 137.100 | Active (LRPT) | 2014 |
NOAA 19 Orbital Specifications
NOAA 19 occupies a sun-synchronous orbit (SSO) designed to maintain consistent solar illumination on every descending pass, crossing the equator near 13:30 local solar time.
APT Line Structure
Each APT scan line consists of 2080 pixels transmitted at 4160 samples/sec (two samples per pixel), yielding a line rate of exactly 2 lines per second. The line is divided into two frames (A and B), each containing synchronisation, space, image, and telemetry segments.
Receiver Hardware
RTL-SDR v3/v4
USB software-defined radio dongle based on the RTL2832U + R820T2 chipset.
- Frequency range: 24 – 1766 MHz
- Sample rate: up to 2.4 MSPS (8-bit I/Q)
- Noise figure: ~3.5 dB (without LNA)
- Cost: ~$25 USD
QFH / Turnstile Antenna
Circularly polarised antenna optimised for overhead satellite passes.
- Quadrifilar Helix (QFH): best gain pattern
- Turnstile + reflector: simpler build
- V-dipole: easiest, adequate for strong passes
- RHCP polarisation matches NOAA downlink
SDR# / SatDump Software
Software for signal capture, demodulation, and APT/LRPT decoding.
- SDR# (Windows): WFM demod + APT plugin
- SatDump: cross-platform, all-in-one decoder
- GQRX (Linux): GNU Radio-based SDR receiver
- Record baseband IQ for offline processing
LNA Upgrade
A filtered low-noise amplifier dramatically improves reception quality.
- Place at antenna feed before coax run
- SAW filter rejects pager/FM interference
- Typical gain: 20 dB, NF < 1 dB
- Nooelec SAWbird+ NOAA: popular choice (~$35)