Workflow as below:

enter image description here When file_source after file_sink,center frequency is not recorded and replay in gui_sink.

enter image description here

How to record and replay the center frequency when file_sink?

  • $\begingroup$ The file sink actually has nothing to do with this. You get the exact same problem if you just wire the USRP source directly to the GUI sink. It's because you didn't set the center frequency on the GUI sink $\endgroup$
    – user253751
    Oct 5, 2021 at 13:03
  • $\begingroup$ Even you set the center frequency,file sink doesn't record it.That's the key problem. $\endgroup$
    – kittygirl
    Oct 5, 2021 at 13:18
  • $\begingroup$ Type in the same center frequency when you load the file? $\endgroup$
    – user253751
    Oct 5, 2021 at 13:24
  • $\begingroup$ @user253751,I will not ask this question if I can remember hundreds frequencies per hour. $\endgroup$
    – kittygirl
    Oct 5, 2021 at 13:28
  • $\begingroup$ You've got a fundamental misunderstanding what the file sink or source do. They just deal with the raw time samples. "Frequency" is not among the things they save. As @user253751 says, this isn't special about these sinks either: sample flows are just that, samples. There's no "interpretation" like "this is at frequency XYZ" inherent to these sample flows. $\endgroup$ Oct 5, 2021 at 13:59

1 Answer 1


Not at all. The file sink, as any sample-processing block in GNU Radio, is not aware of RF properties – all it sees are the baseband samples. So, the representation of things being centered around 0 Hz is correct; that's all the information there is in the signal.

You will need some other mechanism to save such information. SigMF is one option, filenames another, or a metadata file sink combined with adding the necessary tags yourself.


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