Trying to demodulate ADSB

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Hi, I am trying to demodulate and decode ADSB frames to be able to see the data printed in the gnu radio terminal. I am receiving ADSB frames (confirmed both with the Kraken SDR waterfall at 1090 MHz, and the time sink in GNU Radio, I include a picture of the latter), but I do not understand why when enabling the block chain from the threshold block till the end, errors pop up with “Failed to put IQ Samples into the Queue”. If anyone was able to achieved the above mentioned, please, I would highly appreciate any help.

Regards,
John

Screenshot 2026-03-18 124038
Screenshot 2026-03-18 1240381920×1032 119 KB

Screenshot 2026-03-18 124138
Screenshot 2026-03-18 1241381920×1128 43.9 KB

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Note:

  • Before the error it executes for some seconds.

  • Before the error this comment appears on terminal: thread_body_wrapper :error: ERROR thread[thread-per-block[5]: <block ADS-B Framer(7)>]: ValueError: can’t convert <class ‘numpy.float32’> type to pmt (19.32751)

    At:
    C:\Users\TRJCAT\AppData\Local\radioconda\Lib\site-packages\pmt\pmt_to_python.py(144): python_to_pmt
    C:\Users\TRJCAT\AppData\Local\radioconda\Lib\site-packages\pmt\pmt_to_python.py(28): pmt_from_tuple
    C:\Users\TRJCAT\AppData\Local\radioconda\Lib\site-packages\pmt\pmt_to_python.py(143): python_to_pmt
    C:\Users\TRJCAT\AppData\Local\radioconda\Lib\site-packages\gnuradio\adsb\framer.py(172): work
    C:\Users\TRJCAT\AppData\Local\radioconda\Lib\site-packages\gnuradio\gr\gateway.py(199): handle_general_work

  • The kraken is sampling at 2.4M, and the resampler leaves it at 2M.

  • The QT GUI Range if for the Time Sink to trigger.

  • The QT GUI Entry is for the ADS-B Framer to trigger.

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Are you running heimdall_daq_fw in the background, and did you set it to use 1 channel only? Heimdall might not function correctly with only 1 channel as it was designed for making 2+ channels coherent.

If you’re just using it as a 1 channel device, it would be much better to simply use a standard RTL-SDR source block, as the Kraken will present itself as individual RTL-SDR units.

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Hi Carl, thank you for the response. I am executing heimdall_only_start.sh, but I will try with a standard STL-SDR source block and see if it gets better.

John