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4577SV: [afedrisdr] Re:: S-meter question

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  • Ingemar Lekteus
    16 Oct
       Hello Alex,

      Thank you very much for your very informative answer!

       Unfortunately I have not got the right equipment to test this myself, so I will ask Simon. I have actually got the impression that the S-meter reading (in dBm) in SDR Console does not change with the same amount when I change the RF gain. This is a bit fishy!

      73,
      Ingemar, SM0ECF


      Den måndag, 16 oktober 2017 17:31 skrev "alex@... [afedrisdr]" <afedrisdr@...>:


       
      Hello Ingemar,

      1. I cannot give you the  answer relatively to SDR-Console, I simply do not know, suppose Simone knows it.
       
      2. To get correct signal level measurements SDR application should use in calculations the  "RF gain" settings, when measured in dB - it  is simple adding /subtracting "RF Gain" from the measured (calculated) signal level.
      I do not know how it is implemented inside SDR-Radio (SDR-Console), when "RF gain" is taken in account by software the S-meter will show correct results independently to Gain seeting, excluding the situation when RF gain is too low

      The usage of predefined "RF Gain" setting for the precision S-metering has some reason for SDR application that takes not in account "RF Gain" (for example HDSDR) , in the same time it will not solve the problem for full scale - it will create situation when you cannot measure signals  lower than S5 (due to sensitivity limit with specific gain = 11dB)...

      AFEDRI has relatively big gain steps - 3dB, so you cannot set it precisely.
       If I remember correctly "RF gain" level = +11dB  should give the result close to correct  (with S5 lower level limit) , it is hard to give you exact number - it is SDR application specific... so

      By the way  - You can find / check the most correct (for S-meter) "RF gain" settings by direct measurements using some reference signal.

      73!
      Alex 



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