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Re: [softrock40] Re: softrock with dds -tell me more

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  • RAY
    I have read several postings in he group about the DDS and I would like to know more about what the DDS is and how to build one. There seems to be a mixed
    Message 1 of 10 , May 31 9:50 PM
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      I have read several postings in he group about the DDS and I would like to
      know more about what the DDS is and how to build one. There seems to be a
      mixed signal as to whether the DDS kit is still availble. In any case can
      someone that has first hand knowledge try to make me a little smarter -
      right know I don't where to start.

      73, Ray, N0FY

      ----- Original Message -----
      From: wb8lga
      To: softrock40@yahoogroups.com
      Sent: Sunday, May 06, 2007 9:30 AM
      Subject: [softrock40] Re: softrock with dds



      I just tried this on my RxTx v6.2 board. I took and removed the
      hot side of the primary wind of T4 and connected it to my antenna.
      I took my DDS-60 and set the Osc. at 57 Mhz. The 20Meter band came in
      on Rx OK. The board work right along with the signals that I was
      receiving on my FT-757GX rig. Weak signal to weak signal they was around
      the same. It looks like I'll have to build a band filter that will be
      controled by my Pic processor.That will do a band filer changes as I
      change the DDS freq.
    • gandalfg8@aol.com
      In a message dated 01/06/2007 06:48:59 GMT Daylight Time, WA2HVI@Comcast.net writes: I have read several postings in he group about the DDS and I would like
      Message 2 of 10 , Jun 1, 2007
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        In a message dated 01/06/2007 06:48:59 GMT Daylight Time, WA2HVI@... writes:

        I have read several postings in he group about the DDS and I would like to
        know more about what the DDS is and how to build one. There seems to be a
        mixed signal as to whether the DDS kit is still availble. In any case can
        someone that has first hand knowledge try to make me a little smarter -
        right know I don't where to start.

        73, Ray, N0FY

        -----------------------------
         
        Hi Ray
         
        I think this is probably the kit you're thinking of.....
         
         
        I just checked the site and it says they're in stock but an email should soon confirm..
         
        A lot of the discussion here has been about the improvements to be obtained by usiing later DDS ICs but this still looks to be a very good introduction at a good price.
         
        No doubt I'll know better when I finally get around to constructing mine:-)
         
        regards
         
        Nigel
        GM8PZR
      • Chris Albertson
        ... Just in case you missed it, you will need a micro-controller to make use of the above. It is programmed by sending data over on of the header pins so you
        Message 3 of 10 , Jun 2, 2007
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          > I think this is probably the kit you're thinking of.....
          >
          > _http://www.amqrp.org/kits/dds60/_ (http://www.amqrp.org/kits/dds60/)

          Just in case you missed it, you will need a micro-controller to make
          use of the above.
          It is programmed by sending data over on of the header pins so you need
          a way to
          take input from a human and convert it to a serial data stream. An
          example would
          be (1) A PIC that reads a rotational encoder an sends data to the
          DDS-60 or
          (2) A program on a PC that puts up a little dialog box and sends data
          out an
          interface to the DDS-60.


          I think the DDS-60 is over kill. The SR40 wants only a square wave LO
          signal.
          You can do this with TTL. Simple use a fast clock that drives a
          counter and
          a magnitude comparitor that resets the counter. Use the reset line as
          the LO.
          Costa about $5 to make but you'd need to set the freq. with dip
          switches or
          again use a PIC as a fancy dip switch.



          Chris Albertson
          Home: 310-376-1029 chrisalbertson90278@...
          Office: 310-336-5189 Christopher.J.Albertson@...


          ____________________________________________________________________________________
          Shape Yahoo! in your own image. Join our Network Research Panel today! http://surveylink.yahoo.com/gmrs/yahoo_panel_invite.asp?a=7
        • k5nwa
          ... Just out of curiosity, have you actually tried this? Usually Fractional N Synthesizers start off with GHz clocks to get the resolution and that is not
          Message 4 of 10 , Jun 2, 2007
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            At 08:27 PM 6/2/2007, you wrote:


            >I think the DDS-60 is over kill. The SR40 wants only a square wave LO
            >signal.
            >You can do this with TTL. Simple use a fast clock that drives a
            >counter and
            >a magnitude comparitor that resets the counter. Use the reset line as
            >the LO.
            >Costa about $5 to make but you'd need to set the freq. with dip
            >switches or
            >again use a PIC as a fancy dip switch.
            >
            >Chris Albertson
            >Home: 310-376-1029
            ><mailto:chrisalbertson90278%40yahoo.com>chrisalbertson90278@...
            >Office: 310-336-5189
            ><mailto:Christopher.J.Albertson%40aero.org>Christopher.J.Albertson@...

            Just out of curiosity, have you actually tried this? Usually
            Fractional N Synthesizers start off with GHz clocks to get the
            resolution and that is not cheap compared to a DDS.

            You want to listen to 7.050MHz at the center of the pass-band that
            requires a clock of 28.200MHz(35.5 ns period), but then you want to
            listen to 7.220MHz that requires a clock of around 28.880MHz(34.5 ns period).

            So how fast is the main clock that you count down with enough
            resolution to be able to put out these and other in between frequencies?





            Cecil
            K5NWA
            www.softrockradio.org www.qrpradio.com www.hpsdr.com

            "Blessed are the cracked, for they shall let in the light."
          • RAY
            I guess I was doing a little day-dreaming here - It looks like the XTAL is still the most cost effective way to go. So I will just switch in what I want when
            Message 5 of 10 , Jun 2, 2007
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              I guess I was doing a little day-dreaming here - It looks like the XTAL is
              still the most cost effective way to go. So I will just switch in what I
              want when I need it - the DDS is nice but I agree it may be a little
              overkill and is frequency limited. I just thought it would be nice to use
              the SOFROCK as tuneable radio.

              73, Ray, N0FY


              ----- Original Message -----
              From: k5nwa
              To: softrock40@yahoogroups.com
              Sent: Saturday, June 02, 2007 10:27 PM
              Subject: Re: [softrock40] Re: softrock with dds -tell me more


              At 08:27 PM 6/2/2007, you wrote:

              >I think the DDS-60 is over kill. The SR40 wants only a square wave LO
              >signal.
              >You can do this with TTL. Simple use a fast clock that drives a
              >counter and
              >a magnitude comparitor that resets the counter. Use the reset line as
              >the LO.
              >Costa about $5 to make but you'd need to set the freq. with dip
              >switches or
              >again use a PIC as a fancy dip switch.
              >
              >Chris Albertson
              >Home: 310-376-1029
              ><mailto:chrisalbertson90278%40yahoo.com>chrisalbertson90278@...
              >Office: 310-336-5189
              ><mailto:Christopher.J.Albertson%40aero.org>Christopher.J.Albertson@...

              Just out of curiosity, have you actually tried this? Usually
              Fractional N Synthesizers start off with GHz clocks to get the
              resolution and that is not cheap compared to a DDS.

              You want to listen to 7.050MHz at the center of the pass-band that
              requires a clock of 28.200MHz(35.5 ns period), but then you want to
              listen to 7.220MHz that requires a clock of around 28.880MHz(34.5 ns
              period).

              So how fast is the main clock that you count down with enough
              resolution to be able to put out these and other in between frequencies?

              Cecil
              K5NWA
            • k5nwa
              ... Crystals offer top performance and are inexpensive but there is a lack of mobility. A DDS is still not a bad way to go but it s more expensive, and prone
              Message 6 of 10 , Jun 2, 2007
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                At 10:41 PM 6/2/2007, you wrote:

                >I guess I was doing a little day-dreaming here - It looks like the XTAL is
                >still the most cost effective way to go. So I will just switch in what I
                >want when I need it - the DDS is nice but I agree it may be a little
                >overkill and is frequency limited. I just thought it would be nice to use
                >the SOFROCK as tuneable radio.
                >
                >73, Ray, N0FY

                Crystals offer top performance and are inexpensive but there is a
                lack of mobility. A DDS is still not a bad way to go but it's more
                expensive, and prone to having spurs. The newer DDS families that run
                at 400MHz to 1 GHz clocks are pretty clean but the support circuitry
                is expensive. There are other alternatives available if you want mobility.

                If you want mobility within a ham band, then a PTO oscillator with a
                Huff and Puff stabilizer is not a bad way to have both purity and
                stability. But if you want a larger range then a DDS is the way to go.

                There are some inexpensive variable frequency chips that are cheap
                but suffer from excessive jitter, one way is to use one of those
                chips with a PLL to clean up the jitter, but you will have to
                experiment a bit to get the PLL set just right.

                I recently purchased a VNA, it uses a AD9951 running at 400MHz for
                it's LO, it besides being a VNA can be used a somewhat clean source
                of RF from about 100KHz to 180Mhz. It will be used in experimenting
                with the SoftRocks among other items.


                Cecil
                K5NWA
                www.softrockradio.org www.qrpradio.com www.hpsdr.com

                "Blessed are the cracked, for they shall let in the light."
              • RAY
                50 years as a ham and engineer I am still learning and reading about things that I never heard of (Huff and Puff, Hmmmm) - thanks for the input N0FY, Ray ...
                Message 7 of 10 , Jun 3, 2007
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                  50 years as a ham and engineer I am still learning and reading about things
                  that I never heard of (Huff and Puff, Hmmmm) - thanks for the input N0FY,
                  Ray
                  ----- Original Message -----
                  From: k5nwa
                  To: softrock40@yahoogroups.com
                  Sent: Sunday, June 03, 2007 12:35 AM
                  Subject: Re: [softrock40] Re: softrock with dds -tell me more


                  At 10:41 PM 6/2/2007, you wrote:

                  >I guess I was doing a little day-dreaming here - It looks like the XTAL is
                  >still the most cost effective way to go. So I will just switch in what I
                  >want when I need it - the DDS is nice but I agree it may be a little
                  >overkill and is frequency limited. I just thought it would be nice to use
                  >the SOFROCK as tuneable radio.
                  >
                  >73, Ray, N0FY

                  Crystals offer top performance and are inexpensive but there is a
                  lack of mobility. A DDS is still not a bad way to go but it's more
                  expensive, and prone to having spurs. The newer DDS families that run
                  at 400MHz to 1 GHz clocks are pretty clean but the support circuitry
                  is expensive. There are other alternatives available if you want mobility.

                  If you want mobility within a ham band, then a PTO oscillator with a
                  Huff and Puff stabilizer is not a bad way to have both purity and
                  stability. But if you want a larger range then a DDS is the way to go.

                  There are some inexpensive variable frequency chips that are cheap
                  but suffer from excessive jitter, one way is to use one of those
                  chips with a PLL to clean up the jitter, but you will have to
                  experiment a bit to get the PLL set just right.

                  I recently purchased a VNA, it uses a AD9951 running at 400MHz for
                  it's LO, it besides being a VNA can be used a somewhat clean source
                  of RF from about 100KHz to 180Mhz. It will be used in experimenting
                  with the SoftRocks among other items.

                  Cecil
                  K5NWA
                  www.softrockradio.org www.qrpradio.com www.hpsdr.com

                  "
                • Chris Albertson
                  I d just done something like it for another application. But you are right a counter based system here would require a very fast clock. Way to fast for us
                  Message 8 of 10 , Jun 3, 2007
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                    I'd just done something like it for another application. But you are
                    right a counter based system here would require a very fast clock.
                    Way to fast for us normal people to build. It's the small ~40Khz
                    tuning step size that makes it hard.

                    So even if the AD DDS chips are more then we need they have some
                    advantages. (1) AD will give them away as "samples". (2) Two of the
                    AD chips can be programed to run with a 90 degree offset.
                    They can share a crystal and actually take up no more space then the
                    FFs they'd replace. So if you do go the DDS route you can skip the 4X
                    LO and the divide by 4 FFs and the DDSes work even on 6 meters.
                    THe ability to skip the 4X clock is worth it.

                    But I'm thinking now that maybe multiple conversion is better.
                    Do the basic tuning by the "normal" method and end at an IF
                    that an SR40 can operate well at.


                    --- k5nwa <k5nwa@...> wrote:

                    > At 08:27 PM 6/2/2007, you wrote:
                    >
                    >
                    > >I think the DDS-60 is over kill. The SR40 wants only a square wave
                    > LO
                    > >signal.
                    > >You can do this with TTL. Simple use a fast clock that drives a
                    > >counter and
                    > >a magnitude comparitor that resets the counter. Use the reset line
                    > as
                    > >the LO.
                    > >Costa about $5 to make but you'd need to set the freq. with dip
                    > >switches or
                    > >again use a PIC as a fancy dip switch.
                    > >
                    > >Chris Albertson
                    > >Home: 310-376-1029
                    >
                    ><mailto:chrisalbertson90278%40yahoo.com>chrisalbertson90278@...
                    > >Office: 310-336-5189
                    >
                    ><mailto:Christopher.J.Albertson%40aero.org>Christopher.J.Albertson@...
                    >
                    > Just out of curiosity, have you actually tried this? Usually
                    > Fractional N Synthesizers start off with GHz clocks to get the
                    > resolution and that is not cheap compared to a DDS.
                    >
                    > You want to listen to 7.050MHz at the center of the pass-band that
                    > requires a clock of 28.200MHz(35.5 ns period), but then you want to
                    > listen to 7.220MHz that requires a clock of around 28.880MHz(34.5 ns
                    > period).
                    >
                    > So how fast is the main clock that you count down with enough
                    > resolution to be able to put out these and other in between
                    > frequencies?
                    >
                    >
                    >
                    >
                    >
                    > Cecil
                    > K5NWA
                    > www.softrockradio.org www.qrpradio.com www.hpsdr.com
                    >
                    > "Blessed are the cracked, for they shall let in the light."
                    >
                    >



                    Chris Albertson
                    Home: 310-376-1029 chrisalbertson90278@...
                    Office: 310-336-5189 Christopher.J.Albertson@...


                    ____________________________________________________________________________________
                    Fussy? Opinionated? Impossible to please? Perfect. Join Yahoo!'s user panel and lay it on us. http://surveylink.yahoo.com/gmrs/yahoo_panel_invite.asp?a=7
                  • Lawrence
                    ... From: RAY Subject: Re: [softrock40] Re: softrock with dds -tell me more ... It has been a relatively simple method for stabilising a conventional VFO
                    Message 9 of 10 , Jun 3, 2007
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                      ----- Original Message -----
                      From: "RAY"
                      Subject: Re: [softrock40] Re: softrock with dds -tell me
                      more


                      > 50 years as a ham and engineer I am still learning and
                      > reading about things
                      > that I never heard of (Huff and Puff, Hmmmm) - thanks for
                      > the input N0FY,
                      > Ray

                      It has been a relatively simple method for stabilising a
                      conventional VFO since about 1973. It does not have the
                      complexity of a synthesizer and can be added to an existing
                      analogue VFO.

                      http://home.wanadoo.nl/cmulder/ksbstabi.htm
                      http://www.holmea.demon.co.uk/Stab/Stab.htm

                      73, Lawrence GJ3RAX
                    • Dan
                      This sounds similar to the idea of using the Softrock to demodulate the IF from another radio, like at 10.7 MHz. (I always liked the idea of doing that, ever
                      Message 10 of 10 , Jun 3, 2007
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                        This sounds similar to the idea of using the Softrock to demodulate
                        the IF from another radio, like at 10.7 MHz. (I always liked the idea
                        of doing that, ever since I picked up a spectrum display unit years
                        ago for my IC-R7000 receiver that used the 10.7 MHz IF output.) If the
                        Softrock (or other SDR) is used that way, you can have a very robust
                        front-end and tuner, and all the bells and whistles of having the
                        computer do the demodulation/spectrum display/etc for you.

                        On 6/3/07, Chris Albertson <chrisalbertson90278@...> wrote:
                        >
                        > ...But I'm thinking now that maybe multiple conversion is better.
                        > Do the basic tuning by the "normal" method and end at an IF
                        > that an SR40 can operate well at.
                        >
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