Re: SNR meter, bandwidth and gain adjustment for transverters


Simon Brown
 

I have answered this before, also I cannot answer all questions as soon as they are asked, I do have my own priorities and a life away from coding.

 

  • The dB value comes directly from the FFT, for a RX signal it's the peak value of FFT bins inside the filter.
    • FFT bins are affected by Windowing and selected FFT resolution, so different windowing / resolution will affect noise.
  • SNR is peak as above, noise is the average of the lowest 10% (I think) of FFT bins displayed in the main window.
  • When there's no visible signal there will still be a peak as you observe and noise is not uniform.

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

-----Original Message-----
From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Conrad, PA5Y
Sent: 03 July 2021 09:02
To: main@SDR-Radio.groups.io
Subject: [SDR-Radio] SNR meter, bandwidth and gain adjustment for transverters

 

Hello Simon.

 

I asked about the main dB scale in the receiver window and how it relates to bandwidth, you did not reply. I see that the question has been asked before, What exactly does it display? Also, the SNR reading does not change with filter BW, surely it should. How does the SNR meter work? For instance, it shows a positive SNR where there is no signal present in the filter passband so perhaps it is finding the max a signal in a wide passband? It would be better if it only looked inside the filter BW.

 

Finally, as a feature request would it be possible to have some manual gain adjustment to compensate for transverters and LNAs?

 

Many thanks

 

Conrad PA5Y

 

 

 

 

 

 

 

 


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