How to read and store minimum value displayed on the frequency sink in GNU Radio - Python code

Question

I am trying to read and store the gain value of the received signal using the QT GUI Frequency Sink block in GNU Radio. Is there any block that I can use to store this value?

Here is the graph that shows the gain of the signal:

The stored value in this case should be around -19.8 dB:

Answer 1

No, there isn't. A visualization is a visualization!

You want to programmatically calculate a spectrum estimate, find the maximum value, and safe that to a "File Sink" directly. That's easy:

• source
• -> stream to vector (vector length: desired FFT length)
• -> FFT (length: desired fft length)
• -> complex to mag² (vector length: fft length)
• -> Max (vector length: fft length)
• -> log10 (n=10)
• -> File sink

In case this seems like a challenge, you'll want to read the official tutorials on https://tutorials.gnuradio.org; and, I generally recommend reading the block documentation (linked from the "Documentation" tab in the block properties dialog), especially on the File Sink.