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QSD sampling question (again)

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  • Gary Winblad
    I am having trouble with my V6.2lite 8.83Mhz (Kenwood IF) receiver. In trying to troubleshoot a low sensitivity problem I have run into a question I can t
    Message 1 of 6 , Sep 27, 2007
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      I am having trouble with my V6.2lite 8.83Mhz (Kenwood IF) receiver.
      In trying to troubleshoot a low sensitivity problem I have run into
      a question I can't resolve.
      I have figured out my SR has very good sensitivity at the 2nd harmonic
      (5.9MHz) of the sampling frequency (2.9MHz). It DOES receive at the
      8.8MHz 3/4 subharmonic but its not nearly as strong as it receives at
      5.9MHz. It is NOT the input filter (I programmed up my DDS-60 as a
      sweep generator, man is that slick!! I was so impressed, I ordered
      another one).
      All my searching of the archives seems to say that the 2nd harmonic
      should "cancel out".. what could be wrong with my receiver (everything
      I look at seems perfect).. Does this need to be cancelled in software?

      Thanks,
      Gary
    • Tony Parks
      Hi Gary, I have recently found that the best configuration for the oscillator on the 8.83 MHz SoftRock Lite is to omit C4, have C3 at 180pF and to include R6
      Message 2 of 6 , Sep 27, 2007
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        Hi Gary,
         
        I have recently found that the best configuration for the oscillator on the 8.83 MHz SoftRock Lite is to omit C4, have C3 at 180pF and to include R6 on the board at 22.1k (20k or so should be fine). 
         
        Signals at 2x the clock frequency should be much lower in amplitude if the QSD circuit is working properly.  Please check to make sure the quadrature clock signals are getting to pins 2 and 14 of U4.
         
        73,
        Tony KB9YIG
         
        ----- Original Message -----
        Sent: Thursday, September 27, 2007 10:45 PM
        Subject: [softrock40] QSD sampling question (again)

        I am having trouble with my V6.2lite 8.83Mhz (Kenwood IF) receiver.
        In trying to troubleshoot a low sensitivity problem I have run into
        a question I can't resolve.
        I have figured out my SR has very good sensitivity at the 2nd harmonic
        (5.9MHz) of the sampling frequency (2.9MHz). It DOES receive at the
        8.8MHz 3/4 subharmonic but its not nearly as strong as it receives at
        5.9MHz. It is NOT the input filter (I programmed up my DDS-60 as a
        sweep generator, man is that slick!! I was so impressed, I ordered
        another one).
        All my searching of the archives seems to say that the 2nd harmonic
        should "cancel out".. what could be wrong with my receiver (everything
        I look at seems perfect).. Does this need to be cancelled in software?

        Thanks,
        Gary

      • Gary Winblad
        Thanks Tony, That confirms I should still keep working on it.. I did know about the R6 change.. I had to make it something like 8.5K (10K and 6K didn t do it)
        Message 3 of 6 , Sep 28, 2007
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          Thanks Tony,
          That confirms I should still keep working on it..
          I did know about the R6 change.. I had to make it something like
          8.5K (10K and 6K didn't do it) but its fine now.
          The clocks look fine though I haven't checked the exact phasing,
          holding two probes is too much for me! I do see the 2x clock going
          into the last FF though..
          Question: Could it be that the 2x response is canceled in the audio?
          What I am doing is sweeping RF into the ANT and scoping ONE audio
          channel only (either one looks the same, but are they 180deg out??).
          BUT, I found that there was a problem when I hooked the SR to an
          antenna and found nothing but AM shortwave broadcast that I found was
          the 5.9MHz band.
          I am wondering if one of the switches could be bad..?
          Gary

          --- In softrock40@yahoogroups.com, "Tony Parks" <raparks@...> wrote:
          >
          > Hi Gary,
          >
          > I have recently found that the best configuration for the oscillator
          on the 8.83 MHz SoftRock Lite is to omit C4, have C3 at 180pF and to
          include R6 on the board at 22.1k (20k or so should be fine).
          >
          > Signals at 2x the clock frequency should be much lower in amplitude
          if the QSD circuit is working properly. Please check to make sure the
          quadrature clock signals are getting to pins 2 and 14 of U4.
          >
          > 73,
          > Tony KB9YIG
          >

          >
        • Gary Winblad
          It s fixed. My bifilar secondary windings WEREN T somehow, rewound it. I works good now, no more 5.9MHz broadcast stations and at least good 8.8MHz reception.
          Message 4 of 6 , Sep 29, 2007
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            It's fixed.
            My bifilar secondary windings WEREN'T somehow, rewound it.
            I works good now, no more 5.9MHz broadcast stations and at least
            good 8.8MHz reception.
            Thanks again Tony!
            Gary
            --- In softrock40@yahoogroups.com, "Gary Winblad" <garywinblad@...> wrote:
            >
            > Thanks Tony,
            > That confirms I should still keep working on it..
            > I did know about the R6 change.. I had to make it something like
            > 8.5K (10K and 6K didn't do it) but its fine now.
            > The clocks look fine though I haven't checked the exact phasing,
            > holding two probes is too much for me! I do see the 2x clock going
            > into the last FF though..
            > Question: Could it be that the 2x response is canceled in the audio?
            > What I am doing is sweeping RF into the ANT and scoping ONE audio
            > channel only (either one looks the same, but are they 180deg out??).
            > BUT, I found that there was a problem when I hooked the SR to an
            > antenna and found nothing but AM shortwave broadcast that I found was
            > the 5.9MHz band.
            > I am wondering if one of the switches could be bad..?
            > Gary
            >
            > --- In softrock40@yahoogroups.com, "Tony Parks" <raparks@> wrote:
            > >
            > > Hi Gary,
            > >
            > > I have recently found that the best configuration for the oscillator
            > on the 8.83 MHz SoftRock Lite is to omit C4, have C3 at 180pF and to
            > include R6 on the board at 22.1k (20k or so should be fine).
            > >
            > > Signals at 2x the clock frequency should be much lower in amplitude
            > if the QSD circuit is working properly. Please check to make sure the
            > quadrature clock signals are getting to pins 2 and 14 of U4.
            > >
            > > 73,
            > > Tony KB9YIG
            > >
            >
            > >
            >
          • efkrome
            Gary: would you be kind enough to share the input filter design for your 8.8MHz unit? I haven t figured out what makes those filters tick yet. Thanks much, Ed
            Message 5 of 6 , Oct 4, 2007
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              Gary: would you be kind enough to share the input filter design for
              your 8.8MHz unit? I haven't figured out what makes those filters
              tick yet. Thanks much, Ed Krome K9EK Columbus, IN

              --- In softrock40@yahoogroups.com, "Gary Winblad" <garywinblad@...>
              wrote:
              >
              > It's fixed.
              > My bifilar secondary windings WEREN'T somehow, rewound it.
              > I works good now, no more 5.9MHz broadcast stations and at least
              > good 8.8MHz reception.
              > Thanks again Tony!
              > Gary
              > --- In softrock40@yahoogroups.com, "Gary Winblad" <garywinblad@>
              wrote:
              > >
              > > Thanks Tony,
              > > That confirms I should still keep working on it..
              > > I did know about the R6 change.. I had to make it something like
              > > 8.5K (10K and 6K didn't do it) but its fine now.
              > > The clocks look fine though I haven't checked the exact phasing,
              > > holding two probes is too much for me! I do see the 2x clock
              going
              > > into the last FF though..
              > > Question: Could it be that the 2x response is canceled in the
              audio?
              > > What I am doing is sweeping RF into the ANT and scoping ONE audio
              > > channel only (either one looks the same, but are they 180deg
              out??).
              > > BUT, I found that there was a problem when I hooked the SR to an
              > > antenna and found nothing but AM shortwave broadcast that I
              found was
              > > the 5.9MHz band.
              > > I am wondering if one of the switches could be bad..?
              > > Gary
              > >
              > > --- In softrock40@yahoogroups.com, "Tony Parks" <raparks@> wrote:
              > > >
              > > > Hi Gary,
              > > >
              > > > I have recently found that the best configuration for the
              oscillator
              > > on the 8.83 MHz SoftRock Lite is to omit C4, have C3 at 180pF
              and to
              > > include R6 on the board at 22.1k (20k or so should be fine).
              > > >
              > > > Signals at 2x the clock frequency should be much lower in
              amplitude
              > > if the QSD circuit is working properly. Please check to make
              sure the
              > > quadrature clock signals are getting to pins 2 and 14 of U4.
              > > >
              > > > 73,
              > > > Tony KB9YIG
              > > >
              > >
              > > >
              > >
              >
            • Gary Winblad
              Sure Ed, Well, I am just getting started with these filters too! I got a good free program at www.aade.com to model Tony s designs. Later I programmed my
              Message 6 of 6 , Oct 4, 2007
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                Sure Ed,

                Well, I am just getting started with these filters too!

                I got a good free program at www.aade.com to model Tony's
                designs. Later I programmed my DDS-60 to sweep the SR input
                while I scoped the output of the filter. It looks pretty good.
                With the aade software, I think I could even design my own filter
                now if I wanted to get to another band. Try it, is actually pretty
                fun to use. AADE sells some good looking equipment on his web site
                too, check it out. The DDS-60 is a great $40 RF generator too.

                BTW, I am using Tony's input filter from his kit as he designed
                it. I did a boo-boo in my winding of the secondary bifilar winding
                but after I fixed it the kit works perfectly. It now receives 8.8MHz
                and not 5.9MHz as it did originally.

                I posted my analysis and results in a .doc file in Folder:
                "8.8MHz Input Filter (V6.2lite)"

                Gary
                WB6OGD

                --- In softrock40@yahoogroups.com, "efkrome" <efkrome@...> wrote:
                >
                > Gary: would you be kind enough to share the input filter design for
                > your 8.8MHz unit? I haven't figured out what makes those filters
                > tick yet. Thanks much, Ed Krome K9EK Columbus, IN
                >

                > >
                >
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