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Re: [softrock40] Re: Big signal at 0 Hz even with SR40 is off

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  • Sam Morgan
    ... just curious, how new is your motherboard? I guess if u told me what cpu it s running that might also help. I m thinking everything I have it to old, I
    Message 1 of 21 , Oct 1, 2006
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      n3hkn wrote:
      > I switched off the spread pectrum BIOS option in my "home made" PC
      > and the width of the noise spike is now vey narrow. Looks like almost
      > a single frequency carrier.
      >
      just curious, how new is your motherboard? I guess if u told me what cpu it's
      running that might also help. I'm thinking everything I have it to old, I don't
      remember seeing anything like that in the settings on any of them.

      --
      GB & 73's
      KA5OAI
      Sam Morgan
    • Alberto I2PHD
      Marco IK1ODO wrote: There would be also a peak at 0Hz due to DC imbalance of the ADC inputs, but the ADCs used in 24bit souncards have an internal high pass
      Message 2 of 21 , Oct 1, 2006
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        Marco IK1ODO wrote:
        There would be also a peak at 0Hz due to DC 
        imbalance of the ADC inputs, but the ADCs used in 
        24bit souncards have an internal high pass filter 
        cutting under 1 or 2Hz, suppressing that.
          
        Marco is quite right, as demonstrated by these two screen captures. The first is the digitizing process carried on by Adobe Audition, using the onboard AC'97 chipset, with the card input left open. As you can easily see, there is a substantial DC offset produced by the ADC.



        The same chipset produced this strong zero frequency peak, entirely caused by the DC offset :


        73  Alberto  I2PHD

      • John
        I am playing with mine also. Maybe those of us with Cheap sound cards fine this, I do. Two things: If just a single frec it is most likely the math finding a
        Message 3 of 21 , Oct 1, 2006
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          I am playing with mine also.

          Maybe those of us with “Cheap” sound cards fine this, I do.

           

          Two things:

            If just a single frec it is most likely the math finding a 0 hrz tone.

            If two peaks close together it may be 60 hz pickup in the audio cord.&nbs

          (Message over 64 KB, truncated)

        • Cecil Bayona
          ... The picture of the single stand alone spike is what one of PC s has, the other four have the typical spike with noise going out quite a ways slowly and
          Message 4 of 21 , Oct 1, 2006
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            Alberto I2PHD wrote:
            > Marco IK1ODO wrote:
            >> There would be also a peak at 0Hz due to DC
            >> imbalance of the ADC inputs, but the ADCs used in
            >> 24bit souncards have an internal high pass filter
            >> cutting under 1 or 2Hz, suppressing that.
            >>
            > Marco is quite right, as demonstrated by these two screen captures. The
            > first is the digitizing process carried on by Adobe Audition, using the
            > onboard AC'97 chipset, with the card input left open. As you can easily
            > see, there is a substantial DC offset produced by the ADC.
            >
            >
            >
            > The same chipset produced this strong zero frequency peak, entirely
            > caused by the DC offset :
            >
            >
            > 73 Alberto I2PHD
            >
            >
            The picture of the single stand alone spike is what one of PC's has, the
            other four have the typical spike with noise going out quite a ways
            slowly and meeting the noise floor about 2-3 KHz away.

            On most PC's that is a rare item most people don't have that kind of
            response.

            --

            Cecil
            KD5NWA
            www.qrpradio.com www.hpsdr.com

            "Sacred Cows make the best Hamburger!" Don Seglio Batuna
          • n3hkn
            Spread Spectrum... CPU=AMD 2600 ECS is motherboadr mfg. KT-600 Dick N3HKN It is about 2 years old--- In softrock40@yahoogroups.com, Sam Morgan ... PC ...
            Message 5 of 21 , Oct 2, 2006
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              Spread Spectrum...

              CPU=AMD 2600
              ECS is motherboadr mfg. KT-600

              Dick N3HKN


              It is about 2 years old--- In softrock40@yahoogroups.com, Sam Morgan
              <ka5oai@...> wrote:
              >
              > n3hkn wrote:
              > > I switched off the spread pectrum BIOS option in my "home made"
              PC
              > > and the width of the noise spike is now vey narrow. Looks like
              almost
              > > a single frequency carrier.
              > >
              > just curious, how new is your motherboard? I guess if u told me
              what cpu it's
              > running that might also help. I'm thinking everything I have it to
              old, I don't
              > remember seeing anything like that in the settings on any of them.
              >
              > --
              > GB & 73's
              > KA5OAI
              > Sam Morgan
              >
            • Sparkes, John
              Yep, same here. Big peak at 0 with no inputs to D44. Totally goes away when 9V battery powered SR40V6 on-line. John JX________________________________From:
              Message 6 of 21 , Oct 2, 2006
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                Yep, same here. Big peak at 0 with no inputs to D44. Totally goes away when 9V battery powered SR40V6 on-line.
                 
                John JX


                From: softrock40@yahoogroups.com [mailto:softrock40@yahoogroups.com] On Behalf Of Mike
                Sent: Sunday, 1 October 2006 00:41
                To: softrock40@yahoogroups.com
                Subject: [softrock40] Re: Big signal at 0 Hz even with SR40 is off

                The big signal is 60 Hz pickup. The solution is isolation transformer
                (s), in the audio lines and/or at the antenna connection. Running on
                battery can help to, or a non-grounded power cube. These will help to
                reduce the mountain at the center but may not eliminate it entirely.

                73 - Mike WA8BXN

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