Meteor LRPT Decoding Troubleshooting

[Pavel]

Short answer: Troubleshoot Meteor LRPT in four stages: correct pass and frequency, complete baseband capture, demodulator synchronization, then image processing. Save the raw recording because image settings cannot repair clipped I/Q, wrong sample rate or missing signal.

Before you start​

• Choose one satellite and one supported downlink before building the entire station. Confirm pass time, maximum elevation, center frequency and required bandwidth.
• Keep antenna geometry and orientation documented; a V-dipole, QFH and dish solve different bands and polarization problems.

Step-by-step method​

1. Step 1: Verify the active Meteor satellite and current downlink configuration from a reliable current source before the pass. Do not assume an old frequency or operational status remains valid.
2. Step 2: Capture the entire signal with correct sample-rate metadata, moderate nonclipping gain and expected Doppler. Check that I and Q are not swapped unless the source requires it.
3. Step 3: In SatDump choose the exact Meteor LRPT pipeline and input level, then enter the recording's true sample rate and format. Watch synchronization and error indicators before image output.
4. Step 4: If lock is intermittent, compare higher passes and inspect SNR, frequency offset and dropped samples. Change one decoder option at a time using the same file.

Concrete example​

A file recorded at 2.4 MSPS but processed as 2.0 MSPS will have incorrect timing and frequency scaling even if the signal is visible. Correct metadata should be fixed before experimenting with image correction.

How to judge the result​

A healthy chain shows expected Doppler, sustained demodulator lock and image lines whose missing sections correspond to real fades rather than repeated configuration errors.

What to record​

• Record the complete pass as baseband when storage permits so tuning, Doppler and pipeline settings can be tested again offline.
• Judge a pass by lock duration, error rate and usable image lines rather than the brightest instant on the waterfall.
• Compare passes with similar elevation because a low horizon pass and an overhead pass are not equivalent antenna tests.

Common mistakes​

• Changing several hardware, software or RF variables at once, which removes the controlled comparison needed to identify the cause.
• Treating one autoscaled screenshot or one unusually good result as proof without recording the settings and repeating the test.
• Running many live decoder changes during one pass removes the stable RF recording needed to determine whether reception or processing failed.

Final check​

Process the saved baseband again with the recorded pipeline and metadata, then compare a similar pass. A satellite fix is confirmed by repeatable lock and decoded output, not one unusually strong pass.