Airspy R2 fails to lock on 600 bps Aero channels (while RTL-SDR v4 and EGC work fine)

[yasnieltc]

Hi Sarah,

I wanted to report a specific decoding behavior I am observing with the Airspy R2 in InmarScope regarding the 600 bps Aero channels.

The Problem:
When using the Airspy R2, I get a very strong signal level (excellent Eb/N0) on the 600 bps Aero channels, but the constellation remains unstable/spinning, and the demodulator never achieves a solid lock.

My Testing & Hardware Comparisons:

Hardware swap: If I switch to an RTL-SDR v4 using the exact same setup, InmarScope locks onto the 600 bps channels instantly and decodes perfectly.

Protocol swap: The Airspy R2 works flawlessly within InmarScope for EGC (1200 bps) and the 10500 bps Aero channels, achieving a rock-solid lock and decoding without any packet drops.

Could the timing recovery/decimation process for the 600 bps demodulator be reviewed or optimized for high-sample-rate SDRs like the Airspy R2?

Thanks for your time and the amazing work on this software!

[yasnieltc]

Hi Sarah,
​Thanks for the reply!
​To clarify: I haven't experienced any full software freezes/app lock-ups with the Airspy R2 on my side. The application runs stably, and other channels (EGC at 1200 bps and Aero at 10500 bps) decode smoothly without issues.
​My issue is strictly with the demodulator lock on the 600 bps Aero channels. The signal strength and Eb/N0 levels are great, but the constellation remains spinning/unstable and the demodulator just can't get a solid lock on those specific 600 bps streams.
​If you need a screen capture video of the software running, just let me know!

[yasnieltc]

Hi Sarah, ​Thanks for the reply! ​To clarify: I haven't experienced any full software freezes/app lock-ups with the Airspy R2 on my side. The application runs stably, and other channels (EGC at 1200 bps and Aero at 10500 bps) decode smoothly without issues. ​My issue is strictly with the demodulator lock on the 600 bps Aero channels. The signal strength and Eb/N0 levels are great, but the constellation remains spinning/unstable and the demodulator just can't get a solid lock on those specific 600 bps streams. ​If you need a screen capture video of the software running, just let me know! El vie, 24 jul 2026, 12:14 a. m., Sarah Rose ***@***.***> escribió:

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