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S-meter question

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  • Ingemar Lekteus
    I have been using Afedri Net-SDR and SDR Console v.2 and v.3 since a long time. With pleasure! I would like to get correct S-meter values according to IARU
    Message 1 of 7 , 16 Oct
      I have been using Afedri Net-SDR and SDR Console v.2 and v.3 since a long time. With pleasure!

      I would like to get correct S-meter values according to IARU Region 1 Technical Recommendations. This means that the software must implement the recommendations but also that I have to use correct RF gain setting, as S-meter values depend on that. 

      Do you know if SDR Console implements the IARU recommendations? If not, could you recommend some other software? And what is the RF gain setting that should be used for correct S-meter readings?

      73,
      Ingemar, SM0ECF


       



    • alex4z5lv
      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
      Message 2 of 7 , 16 Oct
        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 
      • Ingemar Lekteus
         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
        Message 3 of 7 , 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 



          Virusfritt. www.avast.com
        • alex4z5lv
          Ingemar, If S-meter reading (in dBm) in SDR Console does not change with RF Gain - I suppose it is correct behavior - because signal power does not depends
          Message 4 of 7 , 16 Oct
            Ingemar,
            If "S-meter reading (in dBm) in SDR Console does not change" with RF Gain - I suppose it is correct behavior - because signal power does not depends on RF Gain.

             I suppose Simon make correct compensation for "RF gain", still may be there is need to insert / change some constant offset.

            The only changes that we should see it is - background S-meter level increasing (lower S-meter limit) when user decrease the  "RF gain".

            So please check it again :-)

            Alex
          • Ingemar Lekteus
             Alex, After looking further into this I realize that the S-meter scaling must be correct. Although S units and dBm are not shown at the same time it seems
            Message 5 of 7 , 16 Oct
               Alex,

              After looking further into this I realize that the S-meter scaling must be correct. Although S units and dBm are not shown at the same time it seems that S1 is around -121 dBm and S9 around - 73 dBm. (You can change back and forth and compare with elements outside the spectrum window.)

              My remark that the S-meter change was not the same as the RF gain change was unfortunately based on signals that were too variable. I have now studied more stable signals and think that I was wrong. So, obviously Simon does not compensate for different RF gain settings.

              So a reasonable guess would be that the signal level is the SDR Console reading - RF gain. (Conversion needed if I want S units.)

              Thank you for pointing me in the right direction!

              73,
              Ingemar






              Den måndag, 16 oktober 2017 19:39 skrev "alex@... [afedrisdr]" <afedrisdr@...>:


               
              Ingemar,
              If "S-meter reading (in dBm) in SDR Console does not change" with RF Gain - I suppose it is correct behavior - because signal power does not depends on RF Gain.

               I suppose Simon make correct compensation for "RF gain", still may be there is need to insert / change some constant offset.

              The only changes that we should see it is - background S-meter level increasing (lower S-meter limit) when user decrease the  "RF gain".

              So please check it again :-)

              Alex


            • Anthony Casorso
              SDR Console V3 allows you to set up a gain offset for the receiver so that you can compensate for the actual receiver gain and still have an accurate S-meter.
              Message 6 of 7 , 16 Oct

                SDR Console V3 allows you to set up a gain offset for the receiver so that you can compensate for the actual receiver gain and still have an accurate S-meter. The setting is well hidden however. To adjust it you need to go to the radio definition window, select the AFEDRI, and select EDIT. There you will find a "gain" adjustment. There is an issue though. The gain setting only applies to live listening, not recordings. This is unfortunate.


                I use the AFEDRI gain setting to adjust for best dynamic range and then use the SDR Console gain calibration to make the S-meter correct.


                Tony

                ad0vc




                From: afedrisdr@... <afedrisdr@...> on behalf of alex@... [afedrisdr] <afedrisdr@...>
                Sent: Monday, October 16, 2017 11:39 AM
                To: afedrisdr@...
                Subject: Re:: SV: [afedrisdr] Re:: S-meter question
                 
                 

                Ingemar,

                If "S-meter reading (in dBm) in SDR Console does not change" with RF Gain - I suppose it is correct behavior - because signal power does not depends on RF Gain.

                 I suppose Simon make correct compensation for "RF gain", still may be there is need to insert / change some constant offset.

                The only changes that we should see it is - background S-meter level increasing (lower S-meter limit) when user decrease the  "RF gain".

                So please check it again :-)

                Alex

              • Ingemar Lekteus
                 Interesting. Did not know about that setting. 73,Ingemar, SM0ECF Den måndag, 16 oktober 2017 22:35 skrev Anthony Casorso canthony15@msn.com [afedrisdr]
                Message 7 of 7 , 17 Oct
                   Interesting. Did not know about that setting.

                  73,
                  Ingemar, SM0ECF


                  Den måndag, 16 oktober 2017 22:35 skrev "Anthony Casorso canthony15@... [afedrisdr]" <afedrisdr@...>:


                   
                  SDR Console V3 allows you to set up a gain offset for the receiver so that you can compensate for the actual receiver gain and still have an accurate S-meter. The setting is well hidden however. To adjust it you need to go to the radio definition window, select the AFEDRI, and select EDIT. There you will find a "gain" adjustment. There is an issue though. The gain setting only applies to live listening, not recordings. This is unfortunate.

                  I use the AFEDRI gain setting to adjust for best dynamic range and then use the SDR Console gain calibration to make the S-meter correct.

                  Tony
                  ad0vc



                  From: afedrisdr@... <afedrisdr@...> on behalf of alex@... [afedrisdr] <afedrisdr@...>
                  Sent: Monday, October 16, 2017 11:39 AM
                  To: afedrisdr@...
                  Subject: Re:: SV: [afedrisdr] Re:: S-meter question
                   
                   
                  Ingemar,
                  If "S-meter reading (in dBm) in SDR Console does not change" with RF Gain - I suppose it is correct behavior - because signal power does not depends on RF Gain.

                   I suppose Simon make correct compensation for "RF gain", still may be there is need to insert / change some constant offset.

                  The only changes that we should see it is - background S-meter level increasing (lower S-meter limit) when user decrease the  "RF gain".

                  So please check it again :-)

                  Alex


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