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Re: SoftRock40 Lite ... a bit deaf

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  • natsystems
    Thanks Chris ... I m a great believer in home-brew gear. The kk5na website design looks intersting and I ll probably look into that one as I build up my
    Message 1 of 9 , May 1, 2007
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      Thanks Chris ... I'm a great believer in home-brew gear. The kk5na
      website design looks intersting and I'll probably look into that one
      as I build up my amateur radio test gear again after a very long break
      away.

      All the best ... Tom GM4DOZ

      --- In softrock40@yahoogroups.com, Chris Albertson
      <chrisalbertson90278@...> wrote:
      >
      >
      > --- natsystems <tom@...> wrote:
      >
      > > Hi Tony ... thanks for your reply.
      > >
      > > I'm afraid I don't have equipment that would allow me to measure the
      > > receiver sensitivity, all I have is a good multimeter and an old'ish
      > > oscilloscope.
      >
      > I also have an old scope too that is worthless as a measurement device.
      > Calibration is off by more than 10X. and all the traces run down hill.
      >
      > You can build an RF voltmeter for about a buck.
      > http://www.io.com/~n5fc/rfprobe1.htm
      > The trouble is the diode detector is not linear. The one
      > below uses a matched diode to compensate for the detector.
      > http://www.kk5na.com/kk5na_files/AccupManual.htm
      >
      >
      >
      > Chris Albertson
      > Home: 310-376-1029 chrisalbertson90278@...
      > Office: 310-336-5189 Christopher.J.Albertson@...
      >
      > __________________________________________________
      > Do You Yahoo!?
      > Tired of spam? Yahoo! Mail has the best spam protection around
      > http://mail.yahoo.com
      >
    • Len Warner
      ... Tell us what sort of pulse signal you were expecting and we may be able to tell you whether you should (or more likely, should not) be seeing it.
      Message 2 of 9 , May 2, 2007
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        At 09:20 07/05/02, [softrock40] Digest Number 1723 wrote:
        > Posted by: "natsystems" tom@... natsystems
        > Date: Tue May 1, 2007 9:52 am ((PDT))
        >[snip]
        >
        >I then measured the input side of U5 on pins 2 & 6 and these are
        >sitting at 2.5v DC. I would have thought I should have seen some form
        >of pulse signal on these pins?

        Tell us what sort of "pulse signal" you were expecting and we may
        be able to tell you whether you should (or more likely, should not)
        be seeing it.

        Otherwise, it is difficult to fathom what your reasoning might be.

        The SoftRock is a version of the Tayloe QSD, which is very well
        documented elsewhere, and does not (unless it is demodulating
        a pulsed signal) have a significant pulse waveform output.

        Also, you are measuring at an op-amp virtual ground, so you would
        be very lucky to see much baseband signal at all. If you really want
        to see that signal before the op-amp, you should view it on the
        source side of the input resistor, i.e. across C11 or C13, which
        conveniently provide low-impedance and RF-decoupled test points.

        [And please trim your quotes - it shouldn't be necessary to quote
        your query and all its replies - just the immediately relevant bits.]


        Regards, LenW
        --
        From Yahoo! Groups Help: ... trim all the irrelevant quoted text
        out of your message (as a courtesy to the other members of
        the group to make the digest easier to read).
      • natsystems
        Hello Len .. see below ... ... I had expected to be able to see some form of quadrature output signal from U4, but given my lack of experience, perhaps my
        Message 3 of 9 , May 2, 2007
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          Hello Len .. see below ...

          > Tell us what sort of "pulse signal" you were expecting and we may
          > be able to tell you whether you should (or more likely, should not)
          > be seeing it.

          I had expected to be able to see some form of quadrature output
          signal from U4, but given my lack of experience, perhaps my question
          should have been: "what should I expect to see on the OP Amp input
          pins?"

          > The SoftRock is a version of the Tayloe QSD, which is very well
          > documented elsewhere, and does not (unless it is demodulating
          > a pulsed signal) have a significant pulse waveform output.

          I'll look to see what I can find on the net about the Tayloe QSD and
          hopefully in future be able to sound more clued-up when required.

          > [And please trim your quotes -

          And I do apologise to all for not sticking to etiquette with my
          replies.

          In any case Len, your advice on an approach for actually locating the
          problem would be greatly appreciated. 'At this time' I am much more
          intersted in just getting the unit to work, rather than having to
          understand in detail how it works.

          Cheers .. Tom.
        • w7qjq
          ... on me! ... quite ... one ... been ... errors (snip...) Tom, since you are receiving faint transmissions , I am thinking that U4 and U5 are ok and there is
          Message 4 of 9 , May 2, 2007
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            --- In softrock40@yahoogroups.com, "natsystems" <tom@...> wrote:
            >
            > Hello All ...
            >
            > I'm new to this group and everything SDR so I know you'll go easy
            on me!
            >
            > I've built an SR40 Lite kit and it is definitely receiving but
            quite
            > deaf. I can say that it's deaf because I've compared it to another
            one
            > that a friend of mine built, and there's a bit output difference
            > between them.
            >
            > Since I can hear faint transmissions, and due to the board having
            been
            > checked out in detail by myself and someone else for potential
            errors

            (snip...)


            Tom, since you are receiving "faint transmissions", I am thinking
            that U4 and U5 are ok and there is a problem with T1. I am an
            experienced builder and I had some difficulty "decoding" the
            instructions for the winding and insertion arrangement. I thought
            about it awhile and finally soldered it in. Fortunately, it worked
            straight-away (MDS about -120 dBm) but I could just as easily have
            chosen the wrong arrangement. (Old age may have caused much of my
            confusion...)

            my $.02 73

            Sid W7QJQ
            Oklahoma
          • natsystems
            ... Hi Sid ... I appreciate your $.02 worth :) I too was suspicious of T1 and I went as far as re-winding a new one and very carefully following the
            Message 5 of 9 , May 2, 2007
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              > Tom, since you are receiving "faint transmissions", I am thinking
              > that U4 and U5 are ok and there is a problem with T1. I am an
              > experienced builder and I had some difficulty "decoding" the
              > instructions for the winding and insertion arrangement. I thought
              > about it awhile and finally soldered it in. Fortunately, it worked
              > straight-away (MDS about -120 dBm) but I could just as easily have
              > chosen the wrong arrangement. (Old age may have caused much of my
              > confusion...)
              >
              > my $.02 73
              >
              > Sid W7QJQ
              > Oklahoma
              >
              Hi Sid ... I appreciate your $.02 worth :)

              I too was suspicious of T1 and I went as far as re-winding a new one
              and very carefully following the instructions - and may I add, under
              guidance from a friend who also checked it out! I have to say
              that "as far as I can be sure," I think that T1 is okay now. The
              other thing I'm dealing with here is that I've now lost any ability
              to receive even faint transmissions, so it would appear that the
              fault has crept in gradually. Despite what's been said previously, I
              can see a signal on the input pins of the OP Amp (2&6) on a good
              working unit, but I can't see any hint of a signal on the faulty
              unit. I'm forced now to think that I need to take the plunge and
              replace either U4 or U5.

              As I said Sid, thanks for the donation!

              73's ... Tom GM4DOZ
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