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

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  • 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 1 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 2 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@...


        ____________________________________________________________________________________
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      • 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 3 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 4 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 5 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 6 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 7 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 8 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 9 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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