Questions about dc_block and dc removal or avoidance about satdump HOT 2 CLOSED

1. The DC Block option is available in the UI here as shown below. It's also available under the "processing" section of the recording screen.

   Note: DC removal is not reflected in the Recorder FFT/Waterfall display, but it is happening to the samples before being processed.

   

2. To offset the frequency to avoid the DC spike, I find it easier to manually tune to an offset frequency, then use the "Frequency Shift" option in SatDump UI (or --freq_shift from the CLI) to tell SatDump where the target signal is in the baseband when decoding. So, in your example, record at 1544.250 MHz, and set the frequency shift setting to 250e3 when decoding to "target" 1544.5 MHz. However, if you don't want to manually set the offset frequency at record time, you can use LO for record, then Frequency Shift for decode.

   

3. Similar to your first question, DC Blocking is only taken into effect when decoding, not recording. As such, DC block is SDR-agnostic and works on recorded basebands as well.

   Subsidiary answer: run satdump sdr_probe to get the source_id for your SDR

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Thanks a lot for spending your precious time to answer my novice questions.
And TKS for my memory backup about sdr_probe. Now it is written on my notebook.

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