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I want to take a non demodulate audio signal from webSDR portals (http://www.websdr.org/). In order to try to feed these in DREAM DRM Radio software or GNURADIO.

Could be cool almost try it for educational purposes.

A Youtube video very informational about I/Q could be see at: https://www.youtube.com/watch?v=h_7d-m1ehoY&t=150s

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Any radio in upper-sideband (USB) mode is effectively a frequency down-converter, WebSDR included. That is, USB simply shifts frequencies down, not changing the modulation other than the frequency shift. This is why digital modes such as PSK31, JT9, WSPR, etc can be implemented by an audio connection to an ordinary USB radio.

So simply tune in the frequency of interest in USB mode, and feed the resulting audio into GNU Radio. If you want it in IQ form you can use either the Hilbert transform block, or use "float to complex" and simply ignore or filter out all the negative frequencies, which will be a mirror of the positive frequencies.

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  • $\begingroup$ Does USB here mean the usb everyone knows, or Upper Side Band? $\endgroup$
    – NoBugs
    Jan 31 '20 at 1:30
  • $\begingroup$ Yes. (Extra words to meet minimum comment length.) $\endgroup$ Jan 31 '20 at 4:10
  • $\begingroup$ Yes upper side band or usb plug in sdr? $\endgroup$
    – NoBugs
    Jan 31 '20 at 4:42
  • $\begingroup$ Awesome Phil I will try to decode ft8 first and then will try with DRM. I will report in the future over here the results. Thanks so much. $\endgroup$
    – Hender
    Jan 31 '20 at 15:59
  • $\begingroup$ One thing that initially confused me when processing WebSDR audio in GNU Radio was the SDR's AGC causing unexpected amplitude variations. For some applications, you might need to turn off the AGC but then you need to decide on a specific gain setting. Choose too high and it overloads the WebSDR's audio. Choose too low, and you miss more signals. $\endgroup$
    – Bezewy
    Dec 4 at 21:07

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