Re: SNR meter, bandwidth and gain adjustment for transverters


jdow
 

So if you have a signal that features multiple peaks all about the same amplitude how big is the S-Meter error? Take an NFM signal modulated by a sine wave. Run up the modulation from zero until there are three spikes showing within the NFM bandwidth that are all the same level. What is the correct measurement? One of the peaks or the proper sum of all three? Now continue running up the amplitude of modulation into the BFM realms with the signal spread out over 200 kHz bandwidth. What is the correct S-Meter reading? Does that reading change when the announcer pauses for breath? Should it? Mark, I think you went off the cliff on that one.

{^_^}

On 20210705 07:43:04, oldjackbob@... wrote:
Per the info on Simon's page explaining the operation of the S-meter, "[The signal level] is the peak spectrum FFT bin (output value) which is within the current filter."

That page is found here: https://www.sdr-radio.com/s-meter

Simon explains it clearly. There is no correlation of peak FFT bin value to filter bandwidth (or AGC level, or any other consideration), nor should there be. Any modern SDR-based S-meter that changes its reading based on filter bandwidth is doing it wrong.

I've said it before: Simon got it right, many others are getting it wrong.

Mark


 


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