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Re: [perseus_SDR] RE: ADC Output Randomizer

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  • Johan Letterstål
    Ok, Well this is not my turf anyhow... :-) I assume you ve seen Nicos YT video on the subject regarding the data scrambling feature of the LTC2206.
    Message 1 of 9 , Sep 6, 2013
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      Ok,
      Well this is not my turf anyhow... :-)
      I assume you've seen Nicos YT video on the subject regarding the data scrambling feature of the LTC2206.
      73 Johan SWE
       
      ----- Original Message -----
      Sent: Friday, September 06, 2013 7:56 PM
      Subject: [perseus_SDR] RE: ADC Output Randomizer

       

      Hi Johan,

       

      The Output Randomizer line on the LTC2206/2207 family  (RAND, Pin 46) is separate from the Dither line (DITH, Pin 17). I am hoping either that RAND is always on, or that there is a software "trick" to toggle it. I would be grateful if Nico could throw some light on this.

       

      73, Adam VA7OJ/AB4OJ



      --- In perseus_sdr@yahoogroups.com, <johan.letterstal@...> wrote:

      
      Hi,
      Is'nt this the "Dither" function (button)?
      I maybe completely wrong....
      /Johan
       
      ----- Original Message -----
      Sent: Friday, September 06, 2013 11:20 AM
      Subject: [perseus_SDR] ADC Output Randomizer

       

      Hi Nico,

       

      Is the Output Randomizer in the LTC2206-14 ADC on at all times? Is there a way of turning it on and off? I would very much like to run some measurements with the Randomiser activated and deactivated (if possible).

       

      73, Adam VA7OJ/AB4OJ

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    • dl4raj
      Hi Johann, in this Video Nico is showing how randomizing works: He is intentionally increasing the coupling from one of the digital output lines to the ADC
      Message 2 of 9 , Sep 7, 2013
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        Hi Johann,

        in this Video Nico is showing how randomizing works:
        He is intentionally increasing the coupling from one of the
        digital output lines to the ADC Input.
        Despite the increased coupling no IMD tones are generated
        at the expense of increasing the noise floor by the randomizing
        process of the ADC.

        73
        Clemens
        DL4RAJ

        --- In perseus_SDR@yahoogroups.com, Johan Letterstål <johan.letterstal@...> wrote:
        >
        > Ok,
        > Well this is not my turf anyhow... :-)
        > I assume you've seen Nicos YT video on the subject regarding the data scrambling feature of the LTC2206.
        > http://www.youtube.com/watch?v=OeJQ-YynENI
        > 73 Johan SWE
      • dl4raj
        Hi Adam, good to hear from you. For sure randomizing is always on because the undesirable effects with rand. off, i.e.more IMD products, would vastly outweigh
        Message 3 of 9 , Sep 7, 2013
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          Hi Adam,

          good to hear from you.
          For sure randomizing is always on because the undesirable
          effects with rand. off, i.e.more IMD products,
          would vastly outweigh the advantage of a slightly lower
          noise floor.
          Obviously the GUI of Perseus SW does not provide a toogle switch
          for rand. off/on.
          So only a "secret" command line prompt seems
          possible if any.

          73
          Clemens
          DL4RAJ


          >Hi Johan,
          >The Output Randomizer line on the LTC2206/2207 family (RAND, Pin 46) >is separate from the Dither line (DITH, Pin 17). I am hoping either >that RAND is always on, or that there is a software "trick" to toggle >it. I would be grateful if Nico could throw some light on this.
          >73, Adam VA7OJ/AB4OJ
        • va7oj
          Hi Clemens, Nice to hear from you as well. I was not sure, because the Apache ANAN-100 has a switch for randomizing off/on. I recently ran a test suite on the
          Message 4 of 9 , Sep 7, 2013
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            Hi Clemens,

             

            Nice to hear from you as well. I was not sure, because the Apache ANAN-100 has a switch for randomizing off/on. I recently ran a test suite on the ANAN, and found that whilst randomizing does not affect NPR or DR3, activating it increases DR2 by 14 dB.

             

            My ANAN test report is on my website, with a link on the Perseus page.

             

            I have found an interesting phenomenon during DR3 testing of direct-sampling SDR's using the classical 2-tone method at 500 Hz channel bandwidth; there is a definite "sweet spot" for DR3 vs. input power. DR3 degrades with input power above and below this level. NPR does not do this, as the noise loading is set just below ADC clip level.

             

            73, Adam VA7OJ/AB4OJ



            --- In perseus_sdr@yahoogroups.com, <cpaul@...> wrote:

            Hi Adam,

            good to hear from you.
            For sure randomizing is always on because the undesirable
            effects with rand. off, i.e.more IMD products,
            would vastly outweigh the advantage of a slightly lower
            noise floor.
            Obviously the GUI of Perseus SW does not provide a toogle switch
            for rand. off/on.
            So only a "secret" command line prompt seems
            possible if any.

            73
            Clemens
            DL4RAJ


            >Hi Johan,
            >The Output Randomizer line on the LTC2206/2207 family (RAND, Pin 46) >is separate from the Dither line (DITH, Pin 17). I am hoping either >that RAND is always on, or that there is a software "trick" to toggle >it. I would be grateful if Nico could throw some light on this.
            >73, Adam VA7OJ/AB4OJ
          • Strathmore
            Antony Long shot time. Have you tried this with another BC signal? It may be that one of your computers is producing a sprog on the same frequency as th BC
            Message 5 of 9 , Sep 8, 2013
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              Antony

              Long shot time.

              Have you tried this with another BC signal? It may be that one of your computers is producing a 'sprog'
              on the same frequency as th BC signal, either radiated into the Perseus antenna or conducted via the USB lead into the Perseus
              Regards

              Al.
            • Strathmore
              Sorry my last post should have been posted in the re CPU vs Performance thread! Al.
              Message 6 of 9 , Sep 8, 2013
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                Sorry my last post should have been posted in the 're CPU vs Performance' thread!

                Al.
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