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Re: [softrock40] Re: SoftRock V6 with AD9951

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  • John Melton
    The 50 ohm termination does help somewhat and, yes, it is before the 47pf cap. There are still frequencies where there are many spurs across the 48/96 KHz
    Message 1 of 14 , Jul 4, 2006
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      The 50 ohm termination does help somewhat and, yes, it is before the
      47pf cap. There are still frequencies where there are many spurs across
      the 48/96 KHz bandwidth but you can easily offset the DDS-60 to a
      frequency that has none or minimal spurs and use the software to tune
      the required frequency.

      I have been experimenting with some code for a version of my Java GUI
      for DttSP that is similar to the spur reduction code in PowerSDR but
      modified for the AD9951. I plan on making that code part of the release
      for DttSP2.

      John

      n3hkn wrote On 07/04/06 14:41,:

      > John,
      > You seem to have a lot of experience with the DDS60 as a VFO driving
      > the SoftRock series. My experience has been with the V5 where I found
      > the amount of spurs in the bandpass to be high (amount) enough to set
      > the DDS60 aside as a VFO. Do you find the number and amplitude of the
      > spurs excessive (used as a VFO) in your experience?
      >
      > The one thing I did not do was to put 50ohms across the DDS60. I would
      > guess that the resistor should be placed before the 47pf cap??
      >
      > Dick N3HKN
      >
      > --- In softrock40@yahoogroups.com
      > <mailto:softrock40%40yahoogroups.com>, John Melton <john.melton@...>
      > wrote:
      > >
      > > Hi Ben,
      > >
      > > In all cases I have not populated Xtal/2n3904 oscillator circuit and I
      > > have also put a 50 ohm termination across the input from the DDS-60.
      > >
      > > V4 - DDS-60 input to C8.
      > > V5 - DDS-60 input to pin 4 of J1 on QSD board with 47pF cap in series.
      > > V6 - DDS-60 input to C7
      > > V7 - DDS-60 input to C6
      > >
      > > Hope that helps,
      > >
      > > Regards,
      > >
      > > John g0orx/n6lyt
      > >
      > > Ben Hall wrote On 07/03/06 23:12,:
      > >
      > > > Hi John,
      > > >
      > > > How/where do you connect the DDS-60 to your various versions of the
      > > > softrock?
      > > >
      > > > thanks and 73,
      > > > ben, KD5BYB
      > > >
      > > > John Melton wrote:
      > > > > I have a DDS-60 from AMQRP
      > > > http://www.amqrp.org/kits/dds60/index.html
      > <http://www.amqrp.org/kits/dds60/index.html>
      > > > <http://www.amqrp.org/kits/dds60/index.html
      > <http://www.amqrp.org/kits/dds60/index.html>>
      > > > > <http://www.amqrp.org/kits/dds60/index.html
      > <http://www.amqrp.org/kits/dds60/index.html>
      > > > <http://www.amqrp.org/kits/dds60/index.html
      > <http://www.amqrp.org/kits/dds60/index.html>>>
      > > > > that I use with several different versions of the SoftRock.
      > Apart from
      > > > > some spurs, which can be avoided, it works well. Just make sure that
      > > > > you have a good 50 ohm termination.
      > > > >
      > > > > Regards,
      > > > >
      > > > > John g0orx/n6lyt
      > > >
      > > >
      > >
      > >
      > > --
      > > --
      > > John Melton
      > > Sun IT CTO
      > > Office: +44 1252 421708 (ext 21708)
      > > Mobile: +44 7714 708861
      > >
      >
      >


      --
      --
      John Melton
      Sun IT CTO
      Office: +44 1252 421708 (ext 21708)
      Mobile: +44 7714 708861
    • datosa2001
      John, I have idea to design I/Q generator with 2 AD9951 or AD9954 to avoid the X4 factor, I have some doubt about the internal AD9954 comparator, did you
      Message 2 of 14 , Jul 4, 2006
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        John,
        I have idea to design I/Q generator with 2 AD9951 or AD9954 to avoid
        the X4 factor, I have some doubt about the internal AD9954
        comparator, did you already try that one? any advantage?

        Davide

        --- In softrock40@yahoogroups.com, John Melton <john.melton@...>
        wrote:
        >
        > The 50 ohm termination does help somewhat and, yes, it is before
        the
        > 47pf cap. There are still frequencies where there are many spurs
        across
        > the 48/96 KHz bandwidth but you can easily offset the DDS-60 to a
        > frequency that has none or minimal spurs and use the software to
        tune
        > the required frequency.
        >
        > I have been experimenting with some code for a version of my Java
        GUI
        > for DttSP that is similar to the spur reduction code in PowerSDR
        but
        > modified for the AD9951. I plan on making that code part of the
        release
        > for DttSP2.
        >
        > John
        >
        > n3hkn wrote On 07/04/06 14:41,:
        >
        > > John,
        > > You seem to have a lot of experience with the DDS60 as a VFO
        driving
        > > the SoftRock series. My experience has been with the V5 where I
        found
        > > the amount of spurs in the bandpass to be high (amount) enough to
        set
        > > the DDS60 aside as a VFO. Do you find the number and amplitude of
        the
        > > spurs excessive (used as a VFO) in your experience?
        > >
        > > The one thing I did not do was to put 50ohms across the DDS60. I
        would
        > > guess that the resistor should be placed before the 47pf cap??
        > >
        > > Dick N3HKN
        > >
        > > --- In softrock40@yahoogroups.com
        > > <mailto:softrock40%40yahoogroups.com>, John Melton <john.melton@>
        > > wrote:
        > > >
        > > > Hi Ben,
        > > >
        > > > In all cases I have not populated Xtal/2n3904 oscillator
        circuit and I
        > > > have also put a 50 ohm termination across the input from the
        DDS-60.
        > > >
        > > > V4 - DDS-60 input to C8.
        > > > V5 - DDS-60 input to pin 4 of J1 on QSD board with 47pF cap in
        series.
        > > > V6 - DDS-60 input to C7
        > > > V7 - DDS-60 input to C6
        > > >
        > > > Hope that helps,
        > > >
        > > > Regards,
        > > >
        > > > John g0orx/n6lyt
        > > >
        > > > Ben Hall wrote On 07/03/06 23:12,:
        > > >
        > > > > Hi John,
        > > > >
        > > > > How/where do you connect the DDS-60 to your various versions
        of the
        > > > > softrock?
        > > > >
        > > > > thanks and 73,
        > > > > ben, KD5BYB
        > > > >
        > > > > John Melton wrote:
        > > > > > I have a DDS-60 from AMQRP
        > > > > http://www.amqrp.org/kits/dds60/index.html
        > > <http://www.amqrp.org/kits/dds60/index.html>
        > > > > <http://www.amqrp.org/kits/dds60/index.html
        > > <http://www.amqrp.org/kits/dds60/index.html>>
        > > > > > <http://www.amqrp.org/kits/dds60/index.html
        > > <http://www.amqrp.org/kits/dds60/index.html>
        > > > > <http://www.amqrp.org/kits/dds60/index.html
        > > <http://www.amqrp.org/kits/dds60/index.html>>>
        > > > > > that I use with several different versions of the SoftRock.
        > > Apart from
        > > > > > some spurs, which can be avoided, it works well. Just make
        sure that
        > > > > > you have a good 50 ohm termination.
        > > > > >
        > > > > > Regards,
        > > > > >
        > > > > > John g0orx/n6lyt
        > > > >
        > > > >
        > > >
        > > >
        > > > --
        > > > --
        > > > John Melton
        > > > Sun IT CTO
        > > > Office: +44 1252 421708 (ext 21708)
        > > > Mobile: +44 7714 708861
        > > >
        > >
        > >
        >
        >
        > --
        > --
        > John Melton
        > Sun IT CTO
        > Office: +44 1252 421708 (ext 21708)
        > Mobile: +44 7714 708861
        >
      • n3hkn
        The first low value resistor I came across was 42 ohms so installed that across the DDS60 output. The spur population is now much less. I do not think that you
        Message 3 of 14 , Jul 5, 2006
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          The first low value resistor I came across was 42 ohms so installed
          that across the DDS60 output. The spur population is now much less.
          I do not think that you could ever simply set your SDR at a place in
          the 48/96khz bandwidth and simply tune the DD60 as you would
          a "normal" VFO. While the spurs are less numerous, such tuning
          produces constant low level audible birdies that could be signals
          (perhaps CW).

          However, as John noted, you can select a region of a band (48 or
          96khz) and tune the DDS to produce minimum/acceptable spurs. Then
          tune as you would if the SDR was xtal controlled. As an example if
          you were interested in PSK you can easily find a setting with spur
          free operation in the 14.070 area. The same for CW (more 48/96khz
          segments) or SSB (many more 48khz/96khz segments). However, for SSB
          some software has notch filtering which allows more general tuning
          with good results even if a spur is setting within the selected
          passband.

          Dick N3HKN



          --- In softrock40@yahoogroups.com, John Melton <john.melton@...>
          wrote:
          >
          > The 50 ohm termination does help somewhat and, yes, it is before
          the
          > 47pf cap. There are still frequencies where there are many spurs
          across
          > the 48/96 KHz bandwidth but you can easily offset the DDS-60 to a
          > frequency that has none or minimal spurs and use the software to
          tune
          > the required frequency.
          >
          > I have been experimenting with some code for a version of my Java
          GUI
          > for DttSP that is similar to the spur reduction code in PowerSDR
          but
          > modified for the AD9951. I plan on making that code part of the
          release
          > for DttSP2.
          >
          > John
          >
          > n3hkn wrote On 07/04/06 14:41,:
          >
          > > John,
          > > You seem to have a lot of experience with the DDS60 as a VFO
          driving
          > > the SoftRock series. My experience has been with the V5 where I
          found
          > > the amount of spurs in the bandpass to be high (amount) enough
          to set
          > > the DDS60 aside as a VFO. Do you find the number and amplitude
          of the
          > > spurs excessive (used as a VFO) in your experience?
          > >
          > > The one thing I did not do was to put 50ohms across the DDS60. I
          would
          > > guess that the resistor should be placed before the 47pf cap??
          > >
          > > Dick N3HKN
          > >
          > > --- In softrock40@yahoogroups.com
          > > <mailto:softrock40%40yahoogroups.com>, John Melton
          <john.melton@>
          > > wrote:
          > > >
          > > > Hi Ben,
          > > >
          > > > In all cases I have not populated Xtal/2n3904 oscillator
          circuit and I
          > > > have also put a 50 ohm termination across the input from the
          DDS-60.
          > > >
          > > > V4 - DDS-60 input to C8.
          > > > V5 - DDS-60 input to pin 4 of J1 on QSD board with 47pF cap in
          series.
          > > > V6 - DDS-60 input to C7
          > > > V7 - DDS-60 input to C6
          > > >
          > > > Hope that helps,
          > > >
          > > > Regards,
          > > >
          > > > John g0orx/n6lyt
          > > >
          > > > Ben Hall wrote On 07/03/06 23:12,:
          > > >
          > > > > Hi John,
          > > > >
          > > > > How/where do you connect the DDS-60 to your various versions
          of the
          > > > > softrock?
          > > > >
          > > > > thanks and 73,
          > > > > ben, KD5BYB
          > > > >
          > > > > John Melton wrote:
          > > > > > I have a DDS-60 from AMQRP
          > > > > http://www.amqrp.org/kits/dds60/index.html
          > > <http://www.amqrp.org/kits/dds60/index.html>
          > > > > <http://www.amqrp.org/kits/dds60/index.html
          > > <http://www.amqrp.org/kits/dds60/index.html>>
          > > > > > <http://www.amqrp.org/kits/dds60/index.html
          > > <http://www.amqrp.org/kits/dds60/index.html>
          > > > > <http://www.amqrp.org/kits/dds60/index.html
          > > <http://www.amqrp.org/kits/dds60/index.html>>>
          > > > > > that I use with several different versions of the SoftRock.
          > > Apart from
          > > > > > some spurs, which can be avoided, it works well. Just make
          sure that
          > > > > > you have a good 50 ohm termination.
          > > > > >
          > > > > > Regards,
          > > > > >
          > > > > > John g0orx/n6lyt
          > > > >
          > > > >
          > > >
          > > >
          > > > --
          > > > --
          > > > John Melton
          > > > Sun IT CTO
          > > > Office: +44 1252 421708 (ext 21708)
          > > > Mobile: +44 7714 708861
          > > >
          > >
          > >
          >
          >
          > --
          > --
          > John Melton
          > Sun IT CTO
          > Office: +44 1252 421708 (ext 21708)
          > Mobile: +44 7714 708861
          >
        • gack.brkkarter
          Hi all, A quick update for the new users with V6.2 RX/TX: Depopulate the Xtal/2n3904 oscillator circuit and interface the DDS-60 input to C45, use the
          Message 4 of 14 , Dec 15, 2007
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            Hi all,

            A quick update for the new users with V6.2 RX/TX:

            Depopulate the Xtal/2n3904 oscillator circuit and interface the DDS-60
            input to C45, use the unpopulated emitter solder point for Q13.

            Todd
            KV1M

            --- In softrock40@yahoogroups.com, John Melton <john.melton@...> wrote:
            >
            > Hi Ben,
            >
            > In all cases I have not populated Xtal/2n3904 oscillator circuit and I
            > have also put a 50 ohm termination across the input from the DDS-60.
            >
            > V4 - DDS-60 input to C8.
            > V5 - DDS-60 input to pin 4 of J1 on QSD board with 47pF cap in series.
            > V6 - DDS-60 input to C7
            > V7 - DDS-60 input to C6
            >
            > Hope that helps,
            >
            > Regards,
            >
            > John g0orx/n6lyt
            >
            > Ben Hall wrote On 07/03/06 23:12,:
            >
            > > Hi John,
            > >
            > > How/where do you connect the DDS-60 to your various versions of the
            > > softrock?
            > >
            > > thanks and 73,
            > > ben, KD5BYB
            > >
            > > John Melton wrote:
            > > > I have a DDS-60 from AMQRP
            > > http://www.amqrp.org/kits/dds60/index.html
            > > <http://www.amqrp.org/kits/dds60/index.html>
            > > > <http://www.amqrp.org/kits/dds60/index.html
            > > <http://www.amqrp.org/kits/dds60/index.html>>
            > > > that I use with several different versions of the SoftRock.
            Apart from
            > > > some spurs, which can be avoided, it works well. Just make sure that
            > > > you have a good 50 ohm termination.
            > > >
            > > > Regards,
            > > >
            > > > John g0orx/n6lyt
            > >
            > >
            >
            >
            > --
            > --
            > John Melton
            > Sun IT CTO
            > Office: +44 1252 421708 (ext 21708)
            > Mobile: +44 7714 708861
            >
          • Alan
            ... From: gack.brkkarter ... What I have done is remove JP2 and JP1. Then a DDS60 (or whatever) can be connected to the centre pin of JP1. Quick and simple
            Message 5 of 14 , Dec 16, 2007
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              ----- Original Message -----
              From: "gack.brkkarter"
              >
              > Depopulate the Xtal/2n3904 oscillator circuit and interface the DDS-60
              > input to C45, use the unpopulated emitter solder point for Q13.

              What I have done is remove JP2 and JP1.
              Then a DDS60 (or whatever) can be connected to the centre pin of JP1.
              Quick and simple to revert to the crystals.

              73 Alan G4ZFQ
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