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Re: [softrock40] Re: SoftRock40 Lite ... a bit deaf

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  • Chris Albertson
    ... 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
    Message 1 of 9 , May 1, 2007
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      --- 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@...

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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 2 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 3 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 4 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 5 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 6 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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