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Re: Fw: Fw: Re: [softrock40] Got my 5.0....Now what do I need?

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  • John H. Fisher
    Very Nice Work, and very nice pictures :-) Thanks for sharing. I bet one of these guys around here will have some answers for you :-) ... -- Regards, John
    Message 1 of 27 , Dec 30, 2005
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      Very Nice Work, and very nice pictures :-) Thanks for sharing. I bet one
      of these guys around here will have some answers for you :-)

      qrper723 wrote:

      > Kees,
      >
      > I added the photo of my experimenting SRv5.
      >
      > http://www.geocities.jp/qrper72/srv5spurious.html
      >
      > Sorry but I have no Spectrum Analyzer and I connect the DDS-60 into
      > a U2 #PIN2 of SRv5 directly...no LPF exists but only the DDS-60's
      > LPF will do.
      >
      > But I don't understand that the spurious occures or not as I change
      > the frequency of DDS. The spurious should occur constantly?
      >
      > 73...hidehiko ja9mat
      >
      --
      Regards,
      John

      =========================================================
      email: k5jhf@...
      photos: http://photos.yahoo.com/k5jhf@...
      files: http://briefcase.yahoo.com/k5jhf@...
      web page: http://www.geocities.com/k5jhf@...
      call sign: K5JHF
      =========================================================
    • qrper723
      John, Thanks for your help. Waiting for suggestions from you and your friends... hidehiko ja9mat ... one
      Message 2 of 27 , Dec 30, 2005
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        John,

        Thanks for your help.
        Waiting for suggestions from you and your friends...

        hidehiko ja9mat


        --- In softrock40@yahoogroups.com, "John H. Fisher" <k5jhf@s...> wrote:
        >
        > Very Nice Work, and very nice pictures :-) Thanks for sharing. I bet
        one
        > of these guys around here will have some answers for you :-)
      • qrper723
        Bill, Thanks for information. I feel good now and I can understand why the spurious occurs. It s the characteristics of DDS isn t it? I will measure the DDS
        Message 3 of 27 , Dec 30, 2005
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          Bill,

          Thanks for information.
          I feel good now and I can understand why the spurious occurs.
          It's the characteristics of DDS isn't it?

          I will measure the DDS spectrum using SRv4 when its frequency set
          to the fundamental (ex;7040KHz).
          The same spectrum occurs,it is not the problem of SRv5.

          BTW...

          You are right.
          I'm enjoying SRv5 this morning where a fewer spurious frequency.
          It's easy to tune to the less spurious area in an each band.
          So it is not a fatal problem for me.

          Great tiny radio both SRv4 and SRv5!

          73, hidehiko ja9mat

          --- In softrock40@yahoogroups.com, Bill Tracey <kd5tfd@a...> wrote:
          >
          > I think what you are seeing is normal and is a fact of life with
          DDS's --
          > they will generate spurs, and they will be dependent on the
          frequency the
          > DDS is set to. I don't claim to understand all the details of the
          > mathematics behind it, but I believe the root cause of the spurs
          are
          > essentially round off errors in the DAC in the DDS generating the
          sin
          > wave. As the DDS produces the sin wave it only has so many bits
          (10? in
          > the case of a 9851) to represent the current value of the sin wav.
          The
          > round off error on these bits is the root cause of the spurs.
          There are
          > frequencies you can tune the DDS to where the round off error is
          less than
          > others, and you will get fewer spurs.
          >
          > This is not fatal for an SDR - we've got 30-40 khz of DDS tuning
          > flexibility with an SDR, one just needs to find a spot where the
          DDS spurs
          > are minimal and then tune appropriately in software. The current
          SDR 1000
          > code has a spur reduction tuning algorithm that tunes to a minimal
          spur DDS
          > point within about +/- 3khz of the desired DDS frequency and then
          varies
          > the software tuning to compensate. This is based on some work Bob
          McGweir
          > (N4HY) did to figure out where the minimal spur points for the SDR
          1000's
          > DDS are (a 9854 I believe). More aggressive> spur dodging is
          possible by
          > mapping out where the spurs actually are and use that data to pick
          DDS
          > frequencies.

          > Cheers,
          >
          > Bill (kd5tfd)
          >
          > At 10:42 PM 12/30/2005, qrper723 wrote:
          >
          > >But I don't understand that the spurious occures or not as I change
          > >the frequency of DDS. The spurious should occur constantly?
          > >
          > >73...hidehiko ja9mat
          >
        • qrper723
          The result is as follows; http://www.geocities.jp/qrper72/srv5spurious.html No suprious has been seen at the 7040KHz with using Softrock40 + DDS 30/60.
          Message 4 of 27 , Dec 30, 2005
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            The result is as follows;

            http://www.geocities.jp/qrper72/srv5spurious.html

            No suprious has been seen at the 7040KHz with using Softrock40 +
            DDS 30/60.

            Suprious only occurs with Softrock V5 + DDS30/60 @ 7040KHz.

            I don't know whether the DDS or SRv5 has a problem...hi

            Hidehiko ja9mat

            > I will measure the DDS spectrum using SRv4 when its frequency set
            > to the fundamental (ex;7040KHz).
            > The same spectrum occurs,it is not the problem of SRv5.
          • Bill Tracey
            When running with the V4 is the DDS running at 4x the freq tuned? If so you d not see the same spurs with a V5 since the DDS would be set to 1x the freq
            Message 5 of 27 , Dec 30, 2005
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              When running with the V4 is the DDS running at 4x the freq tuned? If
              so you'd not see the same spurs with a V5 since the DDS would be set to 1x
              the freq of interest. Or am I missing something about you v4 vs v5
              comparison?

              Cheers,

              Bill (kd5tfd)

              At 12:40 AM 12/31/2005, qrper723 wrote:

              >The result is as follows;
              >
              ><http://www.geocities.jp/qrper72/srv5spurious.html>http://www.geocities.jp/qrper72/srv5spurious.html
              >
              >No suprious has been seen at the 7040KHz with using Softrock40 +
              >DDS 30/60.
              >
              >Suprious only occurs with Softrock V5 + DDS30/60 @ 7040KHz.
              >
              >I don't know whether the DDS or SRv5 has a problem...hi
              >
              >Hidehiko ja9mat
              >
              > > I will measure the DDS spectrum using SRv4 when its frequency set
              > > to the fundamental (ex;7040KHz).
              > > The same spectrum occurs,it is not the problem of SRv5.
            • qrper723
              Bill, Exactly I tuned the DDS at 1x7040KHz with Softrock-40(SRv4) not x4 freq. I expect that the same spurious occurs as the SRv5@7040KHz, but I did not see
              Message 6 of 27 , Dec 30, 2005
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                Bill,

                Exactly I tuned the DDS at 1x7040KHz with Softrock-40(SRv4) not
                x4 freq.

                I expect that the same spurious occurs as the SRv5@7040KHz,
                but I did not see that.

                SRv4's spectrum is clear! Hi...

                Hidehiko ja9mat

                --- In softrock40@yahoogroups.com, Bill Tracey <kd5tfd@a...> wrote:
                >
                > When running with the V4 is the DDS running at 4x the freq
                tuned? If
                > so you'd not see the same spurs with a V5 since the DDS would be
                set to 1x
                > the freq of interest. Or am I missing something about you v4 vs v5
                > comparison?
                >
                > Cheers,
                >
                > Bill (kd5tfd)
                >
                > At 12:40 AM 12/31/2005, qrper723 wrote:
                >
                > >The result is as follows;
                > >
                >
                ><http://www.geocities.jp/qrper72/srv5spurious.html>http://www.geociti
                es.jp/qrper72/srv5spurious.html
                > >
                > >No suprious has been seen at the 7040KHz with using Softrock40 +
                > >DDS 30/60.
                > >
                > >Suprious only occurs with Softrock V5 + DDS30/60 @ 7040KHz.
                > >
                > >I don't know whether the DDS or SRv5 has a problem...hi
                > >
                > >Hidehiko ja9mat
                > >
                > > > I will measure the DDS spectrum using SRv4 when its frequency
                set
                > > > to the fundamental (ex;7040KHz).
                > > > The same spectrum occurs,it is not the problem of SRv5.
                >
              • Leon Heller
                ... From: qrper723 To: Sent: Saturday, December 31, 2005 6:40 AM Subject: [softrock40] Re: DDS spurs, was
                Message 7 of 27 , Dec 31, 2005
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                  ----- Original Message -----
                  From: "qrper723" <qrper72@...>
                  To: <softrock40@yahoogroups.com>
                  Sent: Saturday, December 31, 2005 6:40 AM
                  Subject: [softrock40] Re: DDS spurs, was Got my 5.0....Now what do I need?


                  >
                  > The result is as follows;
                  >
                  > http://www.geocities.jp/qrper72/srv5spurious.html
                  >
                  > No suprious has been seen at the 7040KHz with using Softrock40 +
                  > DDS 30/60.
                  >
                  > Suprious only occurs with Softrock V5 + DDS30/60 @ 7040KHz.
                  >
                  > I don't know whether the DDS or SRv5 has a problem...hi

                  Could be the DDS. Spurs are the main problem when using them; they depend on
                  the output frequency and the clock frequency. ADI has an application that
                  enables them to be predicted, so that designers can avoid them by selecting
                  the clock frequency to suit the frequency range they are used on. It might
                  be worth using it, to see if that is the cause of the problem. You could
                  also try changing the DDS clock frequency.

                  73, Leon
                • Tony Parks
                  Hi Hidehiko, Very nice work you are doing to interface a DDS to several versions of the SoftRock. One thing that would be good to check is to actually look at
                  Message 8 of 27 , Dec 31, 2005
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                    Hi Hidehiko,

                    Very nice work you are doing to interface a DDS to several versions of the
                    SoftRock. One thing that would be good to check is to actually look at the
                    voltage comparitor output waveforms with a scope to see if there is a lot of
                    jitter on the switching edges at certain DDS frequency settings. Also with
                    the v5.0 SoftRock with the DDS set to 7.040 MHz, what is the actual
                    frequency the QSD cloking frequency?

                    I am enjoying following the experiments people are doing with the little
                    SoftRock receivers.

                    73,
                    Tony KB9YIG

                    ----- Original Message -----
                    From: "qrper723" <qrper72@...>
                    To: <softrock40@yahoogroups.com>
                    Sent: Saturday, December 31, 2005 1:40 AM
                    Subject: [softrock40] Re: DDS spurs, was Got my 5.0....Now what do I need?


                    >
                    > The result is as follows;
                    >
                    > http://www.geocities.jp/qrper72/srv5spurious.html
                    >
                    > No suprious has been seen at the 7040KHz with using Softrock40 +
                    > DDS 30/60.
                    >
                    > Suprious only occurs with Softrock V5 + DDS30/60 @ 7040KHz.
                    >
                    > I don't know whether the DDS or SRv5 has a problem...hi
                    >
                    > Hidehiko ja9mat
                    >
                    >> I will measure the DDS spectrum using SRv4 when its frequency set
                    >> to the fundamental (ex;7040KHz).
                    >> The same spectrum occurs,it is not the problem of SRv5.
                    >
                    >
                    >
                    >
                    >
                    >
                    >
                    >
                    > Yahoo! Groups Links
                    >
                    >
                    >
                    >
                    >
                    >
                  • qrper723
                    Tony, Hi, Thanks for your interest. How can I measure the jitter of DDS? Maybe PIN #7 of U2 and U3 with scope or not? Hidehiko ja9mat ... of the ... look at
                    Message 9 of 27 , Dec 31, 2005
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                      Tony,

                      Hi,
                      Thanks for your interest.

                      How can I measure the jitter of DDS?
                      Maybe PIN #7 of U2 and U3 with scope or not?

                      Hidehiko ja9mat


                      --- In softrock40@yahoogroups.com, "Tony Parks" <raparks@c...> wrote:
                      >
                      > Hi Hidehiko,
                      >
                      > Very nice work you are doing to interface a DDS to several versions
                      of the
                      > SoftRock. One thing that would be good to check is to actually
                      look at the
                      > voltage comparitor output waveforms with a scope to see if there is
                      a lot of
                      > jitter on the switching edges at certain DDS frequency settings.
                      Also with
                      > the v5.0 SoftRock with the DDS set to 7.040 MHz, what is the actual
                      > frequency the QSD cloking frequency?
                      >
                      > I am enjoying following the experiments people are doing with the
                      little
                      > SoftRock receivers.
                      >
                      > 73,
                      > Tony KB9YIG
                      >
                      > ----- Original Message -----
                      > From: "qrper723" <qrper72@y...>
                      > To: <softrock40@yahoogroups.com>
                      > Sent: Saturday, December 31, 2005 1:40 AM
                      > Subject: [softrock40] Re: DDS spurs, was Got my 5.0....Now what do
                      I need?
                      >
                      >
                      > >
                      > > The result is as follows;
                      > >
                      > > http://www.geocities.jp/qrper72/srv5spurious.html
                      > >
                      > > No suprious has been seen at the 7040KHz with using Softrock40 +
                      > > DDS 30/60.
                      > >
                      > > Suprious only occurs with Softrock V5 + DDS30/60 @ 7040KHz.
                      > >
                      > > I don't know whether the DDS or SRv5 has a problem...hi
                      > >
                      > > Hidehiko ja9mat
                      > >
                      > >> I will measure the DDS spectrum using SRv4 when its frequency
                      set
                      > >> to the fundamental (ex;7040KHz).
                      > >> The same spectrum occurs,it is not the problem of SRv5.
                      > >
                      > >
                      > >
                      > >
                      > >
                      > >
                      > >
                      > >
                      > > Yahoo! Groups Links
                      > >
                      > >
                      > >
                      > >
                      > >
                      > >
                      >
                    • Tony Parks
                      Pin 7 of U2 and U3 would be right. Those pins connect to the header at pins 5 and 8. Use the U2 output as the scope trigger signal and observe the edges of
                      Message 10 of 27 , Dec 31, 2005
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                        Pin 7 of U2 and U3 would be right. Those pins connect to the header at pins
                        5 and 8. Use the U2 output as the scope trigger signal and observe the
                        edges of the U2 and U3 outputs. Please let us know what you see.

                        Thanks,
                        Tony KB9YIG

                        ----- Original Message -----
                        From: "qrper723" <qrper72@...>
                        To: <softrock40@yahoogroups.com>
                        Sent: Saturday, December 31, 2005 5:22 AM
                        Subject: [softrock40] Re: DDS spurs, was Got my 5.0....Now what do I need?


                        > Tony,
                        >
                        > Hi,
                        > Thanks for your interest.
                        >
                        > How can I measure the jitter of DDS?
                        > Maybe PIN #7 of U2 and U3 with scope or not?
                        >
                        > Hidehiko ja9mat
                        >
                        >
                        > --- In softrock40@yahoogroups.com, "Tony Parks" <raparks@c...> wrote:
                        >>
                        >> Hi Hidehiko,
                        >>
                        >> Very nice work you are doing to interface a DDS to several versions
                        > of the
                        >> SoftRock. One thing that would be good to check is to actually
                        > look at the
                        >> voltage comparitor output waveforms with a scope to see if there is
                        > a lot of
                        >> jitter on the switching edges at certain DDS frequency settings.
                        > Also with
                        >> the v5.0 SoftRock with the DDS set to 7.040 MHz, what is the actual
                        >> frequency the QSD cloking frequency?
                        >>
                        >> I am enjoying following the experiments people are doing with the
                        > little
                        >> SoftRock receivers.
                        >>
                        >> 73,
                        >> Tony KB9YIG
                        >>
                        >> ----- Original Message -----
                        >> From: "qrper723" <qrper72@y...>
                        >> To: <softrock40@yahoogroups.com>
                        >> Sent: Saturday, December 31, 2005 1:40 AM
                        >> Subject: [softrock40] Re: DDS spurs, was Got my 5.0....Now what do
                        > I need?
                        >>
                        >>
                        >> >
                        >> > The result is as follows;
                        >> >
                        >> > http://www.geocities.jp/qrper72/srv5spurious.html
                        >> >
                        >> > No suprious has been seen at the 7040KHz with using Softrock40 +
                        >> > DDS 30/60.
                        >> >
                        >> > Suprious only occurs with Softrock V5 + DDS30/60 @ 7040KHz.
                        >> >
                        >> > I don't know whether the DDS or SRv5 has a problem...hi
                        >> >
                        >> > Hidehiko ja9mat
                        >> >
                        >> >> I will measure the DDS spectrum using SRv4 when its frequency
                        > set
                        >> >> to the fundamental (ex;7040KHz).
                        >> >> The same spectrum occurs,it is not the problem of SRv5.
                        >> >
                        >> >
                        >> >
                        >> >
                        >> >
                        >> >
                        >> >
                        >> >
                        >> > Yahoo! Groups Links
                        >> >
                        >> >
                        >> >
                        >> >
                        >> >
                        >> >
                        >>
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        > Yahoo! Groups Links
                        >
                        >
                        >
                        >
                        >
                        >
                      • qrper723
                        Tony, Thanks for help. I will see that and some photos will be upload to my website later. Have a nice new year! hidehiko ja9mat ... at pins ... the
                        Message 11 of 27 , Dec 31, 2005
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                          Tony,

                          Thanks for help.
                          I will see that and some photos will be upload to my website later.

                          Have a nice new year!

                          hidehiko ja9mat

                          > Pin 7 of U2 and U3 would be right. Those pins connect to the header
                          at pins
                          > 5 and 8. Use the U2 output as the scope trigger signal and observe
                          the
                          > edges of the U2 and U3 outputs. Please let us know what you see.
                        • John H. Fisher
                          I m a little confused here. I thought the SRv4 had to be clocked at 4 times the desired receive frequency. The SRv5 is clocked at the desired receive
                          Message 12 of 27 , Dec 31, 2005
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                            I'm a little confused here. I thought the SRv4 had to be clocked at 4
                            times the desired receive frequency. The SRv5 is clocked at the desired
                            receive frequency. So to compare spurs at the same desired receive
                            frequency, I would think the SRv4 DDS must be set at 28160 KHz to
                            receive 7040 KHz. For the SRv5 the DDS must be set at 7040 KHz to
                            receive 7040 KHz. Correct me if I am wrong :-)

                            Also I see this as another plus for the SRv4 design. It moves the spurs
                            way up in frequency and I like the 3db gain of using 4 capacitors for
                            differential quadrature sampling :-) Being a pure digital man, I plan on
                            using the SRv4 approach. That's my extra 2 cents :-)

                            Have a Great Day and Happy New Year,

                            Regards,
                            John

                            PS Thanks to Bill Tracey for his rounding error discussion of spurs :-)

                            qrper723 wrote:

                            > Bill,
                            >
                            > Exactly I tuned the DDS at 1x7040KHz with Softrock-40(SRv4) not
                            > x4 freq.
                            >
                            > I expect that the same spurious occurs as the SRv5@7040KHz,
                            > but I did not see that.
                            >
                            > SRv4's spectrum is clear! Hi...
                            >
                            > Hidehiko ja9mat
                            >
                            -
                            Regards,
                            John

                            =========================================================
                            email: k5jhf@...
                            photos: http://photos.yahoo.com/k5jhf@...
                            files: http://briefcase.yahoo.com/k5jhf@...
                            web page: http://www.geocities.com/k5jhf@...
                            call sign: K5JHF
                            =========================================================
                          • dmcmicro
                            There is an interesting post in the Spectrum Analyizer group regarding DDS spurs. This may go beyond what you are looking for but thought I d bring it up. In
                            Message 13 of 27 , Dec 31, 2005
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                              There is an interesting post in the Spectrum Analyizer group regarding
                              DDS spurs. This may go beyond what you are looking for but thought I'd
                              bring it up. In particular, Brian Davis commented on some work he did
                              with repsect to the DDS that is used in the Spectrum Analyizer being
                              build in that group. I'm not sure of how wide the distribution of the
                              document is, but Brian has a real interesting write up on spurs. The
                              message of interest is:

                              http://groups.yahoo.com/group/spectrumanalyzer/message/1027

                              You may have to join the group to view this topic.

                              Dave
                            • Alberto I2PHD
                              An interesting comparison between the spurs produced by DDSs of the 98xx family against those of the 99xx family can be found here :
                              Message 14 of 27 , Dec 31, 2005
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                                An interesting comparison between the spurs produced by DDSs of the 98xx family
                                against those of the 99xx family can be found here :
                                http://www.radioamatore.it/i0cg/add9951.html

                                I have bought that DDS board and plan to use it in the future for my SDR.
                                It even has a function that optionally displays a frequency value one fourth
                                of what actually is generated, to take into account a possible use of
                                a Johnson counter for I/Q generation.

                                73 Alberto I2PHD
                                -------------------------------------

                                dmcmicro wrote:
                                > There is an interesting post in the Spectrum Analyizer group regarding
                                > DDS spurs.
                                > [snip]
                              • S. Cash Olsen
                                Bill and group, A fellow named Brian Davis has put together a very interesting document on spur pile-up in the DDS. If your interested in some of the dirty
                                Message 15 of 27 , Jan 1, 2006
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                                  Bill and group,

                                  A fellow named Brian Davis has put together a very interesting document
                                  on spur pile-up in the DDS. If your interested in some of the dirty
                                  details of the DDS you might be interested in the following reference:

                                  http://members.aol.com/fpgastuff/dds_oddities.pdf


                                  Cash Olsen, KD5SSJ

                                  Kits to build Scotty's Spectrum Analyzer http://www.zianet.com/erg
                                  Scotty's Spectrum Analyzer website http://users4.ev1.net/%7Ewsprowls/
                                  Yahoo Builders Group http://groups.yahoo.com/group/spectrumanalyzer/

                                  -----Original Message-----
                                  From: softrock40@yahoogroups.com [mailto:softrock40@yahoogroups.com] On
                                  Behalf Of Bill Tracey
                                  Sent: Friday, December 30, 2005 10:14 PM
                                  To: softrock40@yahoogroups.com
                                  Subject: [softrock40] DDS spurs, was Got my 5.0....Now what do I need?


                                  I think what you are seeing is normal and is a fact of life with DDS's
                                  --
                                  they will generate spurs, and they will be dependent on the frequency
                                  the
                                  DDS is set to. I don't claim to understand all the details of the
                                  mathematics behind it, but I believe the root cause of the spurs are
                                  essentially round off errors in the DAC in the DDS generating the sin
                                  wave. As the DDS produces the sin wave it only has so many bits (10? in

                                  the case of a 9851) to represent the current value of the sin wav. The
                                  round off error on these bits is the root cause of the spurs. There are

                                  frequencies you can tune the DDS to where the round off error is less
                                  than
                                  others, and you will get fewer spurs.

                                  This is not fatal for an SDR - we've got 30-40 khz of DDS tuning
                                  flexibility with an SDR, one just needs to find a spot where the DDS
                                  spurs
                                  are minimal and then tune appropriately in software. The current SDR
                                  1000
                                  code has a spur reduction tuning algorithm that tunes to a minimal spur
                                  DDS
                                  point within about +/- 3khz of the desired DDS frequency and then varies

                                  the software tuning to compensate. This is based on some work Bob
                                  McGweir
                                  (N4HY) did to figure out where the minimal spur points for the SDR
                                  1000's
                                  DDS are (a 9854 I believe). More aggressive spur dodging is possible
                                  by
                                  mapping out where the spurs actually are and use that data to pick DDS
                                  frequencies.

                                  Cheers,

                                  Bill (kd5tfd)

                                  At 10:42 PM 12/30/2005, qrper723 wrote:

                                  >But I don't understand that the spurious occures or not as I change the

                                  >frequency of DDS. The spurious should occur constantly?
                                  >
                                  >73...hidehiko ja9mat






                                  Yahoo! Groups Links
                                • qrper723
                                  Cash, Thanks for your info. I find that the DDS is not clean. I will study more in this new year holidays. I wish to express my gratitude for introducing
                                  Message 16 of 27 , Jan 1, 2006
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                                    Cash,

                                    Thanks for your info.
                                    I find that the DDS is not clean.
                                    I will study more in this new year holidays.

                                    I wish to express my gratitude for introducing literary treasures.

                                    hidehiko ja9mat

                                    > Bill and group,
                                    >
                                    > A fellow named Brian Davis has put together a very interesting
                                    document
                                    > on spur pile-up in the DDS. If your interested in some of the dirty
                                    > details of the DDS you might be interested in the following reference:
                                    >
                                    > http://members.aol.com/fpgastuff/dds_oddities.pdf
                                    >
                                    >
                                    > Cash Olsen, KD5SSJ
                                  • Bill Dumke
                                    Thanks, Cash, for the link. That looks so bad, I feel like going back to a Tuned Radio Frequency receiver. Bill WB5TCO
                                    Message 17 of 27 , Jan 1, 2006
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                                      Thanks, Cash, for the link.

                                      That looks so bad, I feel like going back to a Tuned Radio Frequency
                                      receiver.

                                      Bill WB5TCO

                                      S. Cash Olsen wrote:

                                      > Bill and group,
                                      >
                                      > A fellow named Brian Davis has put together a very interesting document
                                      > on spur pile-up in the DDS. If your interested in some of the dirty
                                      > details of the DDS you might be interested in the following reference:
                                      >
                                      > http://members.aol.com/fpgastuff/dds_oddities.pdf
                                      >
                                      >
                                      > Cash Olsen, KD5SSJ
                                      >
                                      > Kits to build Scotty's Spectrum Analyzer http://www.zianet.com/erg
                                      > Scotty's Spectrum Analyzer website http://users4.ev1.net/%7Ewsprowls/
                                      > Yahoo Builders Group http://groups.yahoo.com/group/spectrumanalyzer/
                                      >
                                      > -----Original Message-----
                                      > From: softrock40@yahoogroups.com [mailto:softrock40@yahoogroups.com] On
                                      > Behalf Of Bill Tracey
                                      > Sent: Friday, December 30, 2005 10:14 PM
                                      > To: softrock40@yahoogroups.com
                                      > Subject: [softrock40] DDS spurs, was Got my 5.0....Now what do I need?
                                      >
                                      >
                                      > I think what you are seeing is normal and is a fact of life with DDS's
                                      > --
                                      > they will generate spurs, and they will be dependent on the frequency
                                      > the
                                      > DDS is set to. I don't claim to understand all the details of the
                                      > mathematics behind it, but I believe the root cause of the spurs are
                                      > essentially round off errors in the DAC in the DDS generating the sin
                                      > wave. As the DDS produces the sin wave it only has so many bits (10? in
                                      >
                                      > the case of a 9851) to represent the current value of the sin wav. The
                                      > round off error on these bits is the root cause of the spurs. There are
                                      >
                                      > frequencies you can tune the DDS to where the round off error is less
                                      > than
                                      > others, and you will get fewer spurs.
                                      >
                                      > This is not fatal for an SDR - we've got 30-40 khz of DDS tuning
                                      > flexibility with an SDR, one just needs to find a spot where the DDS
                                      > spurs
                                      > are minimal and then tune appropriately in software. The current SDR
                                      > 1000
                                      > code has a spur reduction tuning algorithm that tunes to a minimal spur
                                      > DDS
                                      > point within about +/- 3khz of the desired DDS frequency and then varies
                                      >
                                      > the software tuning to compensate. This is based on some work Bob
                                      > McGweir
                                      > (N4HY) did to figure out where the minimal spur points for the SDR
                                      > 1000's
                                      > DDS are (a 9854 I believe). More aggressive spur dodging is possible
                                      > by
                                      > mapping out where the spurs actually are and use that data to pick DDS
                                      > frequencies.
                                      >
                                      > Cheers,
                                      >
                                      > Bill (kd5tfd)
                                      >
                                      > At 10:42 PM 12/30/2005, qrper723 wrote:
                                      >
                                      > >But I don't understand that the spurious occures or not as I change the
                                      >
                                      > >frequency of DDS. The spurious should occur constantly?
                                      > >
                                      > >73...hidehiko ja9mat
                                      >
                                      >
                                      >
                                      >
                                      >
                                      >
                                      > Yahoo! Groups Links
                                      >
                                      >
                                      >
                                      >
                                      >
                                      >
                                      >
                                      >
                                      >
                                      >
                                      >
                                      > SPONSORED LINKS
                                      > Shortwave receivers
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                                      > Ham radio
                                      > <http://groups.yahoo.com/gads?t=ms&k=Ham+radio&w1=Shortwave+receivers&w2=Ham+radio&c=2&s=40&.sig=XNtLoznpXE_hqNE4dvfaHA>
                                      >
                                      >
                                      >
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                                      >
                                    • Bill Dumke
                                      Alberto, Where did you buy the AD9951 board? Bill WB5TCO
                                      Message 18 of 27 , Jan 1, 2006
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                                        Alberto,

                                        Where did you buy the AD9951 board?

                                        Bill WB5TCO

                                        Alberto I2PHD wrote:

                                        > An interesting comparison between the spurs produced by DDSs of the
                                        > 98xx family
                                        > against those of the 99xx family can be found here :
                                        > http://www.radioamatore.it/i0cg/add9951.html
                                        >
                                        > I have bought that DDS board and plan to use it in the future for my SDR.
                                        > It even has a function that optionally displays a frequency value one
                                        > fourth
                                        > of what actually is generated, to take into account a possible use of
                                        > a Johnson counter for I/Q generation.
                                        >
                                        > 73 Alberto I2PHD
                                        > -------------------------------------
                                        >
                                        > dmcmicro wrote:
                                        > > There is an interesting post in the Spectrum Analyizer group regarding
                                        > > DDS spurs.
                                        > > [snip]
                                        >
                                        >
                                        > ------------------------------------------------------------------------
                                        > YAHOO! GROUPS LINKS
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                                        >
                                      • Alberto I2PHD
                                        ... Bill, if you go to the page I referred to in my message, that is: http://www.radioamatore.it/i0cg/add9951.html at the end of the page you will find this
                                        Message 19 of 27 , Jan 2, 2006
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                                          Bill Dumke wrote:
                                          > Alberto,
                                          >
                                          > Where did you buy the AD9951 board?
                                          >
                                          > Bill WB5TCO

                                          Bill, if you go to the page I referred to in my message, that is:
                                          http://www.radioamatore.it/i0cg/add9951.html

                                          at the end of the page you will find this sentence:

                                          If intersted to this project please write to giulianori@...

                                          Just do that. Ask for the PDF with the price list. You can buy the kit
                                          in various forms, PCB only, mechanical or optical encoder, cased or not
                                          cased, etc. etc.
                                          I bought it assembled, cased and tested, and received it in a couple of
                                          weeks. Now I have to find a way to discipline its clock with a GPS...

                                          73 Alberto I2PHD
                                        • Bill Dumke
                                          Alberto, I already did that, but haven t heard a response back. I will be patient. Bill WB5TCO
                                          Message 20 of 27 , Jan 2, 2006
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                                            Alberto,

                                            I already did that, but haven't heard a response back. I will be patient.

                                            Bill WB5TCO

                                            Alberto I2PHD wrote:

                                            >Bill Dumke wrote:
                                            >
                                            >
                                            >>Alberto,
                                            >>
                                            >>Where did you buy the AD9951 board?
                                            >>
                                            >>Bill WB5TCO
                                            >>
                                            >>
                                            >
                                            > Bill, if you go to the page I referred to in my message, that is:
                                            >http://www.radioamatore.it/i0cg/add9951.html
                                            >
                                            >at the end of the page you will find this sentence:
                                            >
                                            > If intersted to this project please write to giulianori@...
                                            >
                                            >Just do that. Ask for the PDF with the price list. You can buy the kit
                                            >in various forms, PCB only, mechanical or optical encoder, cased or not
                                            >cased, etc. etc.
                                            >I bought it assembled, cased and tested, and received it in a couple of
                                            >weeks. Now I have to find a way to discipline its clock with a GPS...
                                            >
                                            >73 Alberto I2PHD
                                            >
                                            >
                                            >
                                            >
                                            >Yahoo! Groups Links
                                            >
                                            >
                                            >
                                            >
                                            >
                                            >
                                            >
                                            >
                                            >
                                            >
                                            >
                                          • Alberto I2PHD
                                            ... Maybe he hasn t received your email. Try again. In the meantime I will send you in a private message the price list PDF that I received when buying the
                                            Message 21 of 27 , Jan 2, 2006
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                                              Bill Dumke wrote:
                                              > Alberto,
                                              >
                                              > I already did that, but haven't heard a response back. I will be patient.
                                              >
                                              > Bill WB5TCO
                                              >

                                              Maybe he hasn't received your email. Try again. In the meantime I will send you
                                              in a private message the price list PDF that I received when buying the kit.

                                              73 Alberto I2PHD
                                            • Duncan Munro
                                              ... Alberto, I also sent a request for prices - would you be good enough to mail me too? -- Duncan Munro http://www.m0kgk.co.uk/
                                              Message 22 of 27 , Jan 2, 2006
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                                                Alberto I2PHD wrote:
                                                > Bill Dumke wrote:
                                                >
                                                >>Alberto,
                                                >>
                                                >>I already did that, but haven't heard a response back. I will be patient.
                                                >>
                                                >>Bill WB5TCO
                                                >>
                                                >
                                                >
                                                > Maybe he hasn't received your email. Try again. In the meantime I will send you
                                                > in a private message the price list PDF that I received when buying the kit.

                                                Alberto, I also sent a request for prices - would you be good enough to
                                                mail me too?

                                                --
                                                Duncan Munro
                                                http://www.m0kgk.co.uk/
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