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Re: Ensemble RXTX Rx I / Q

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  • g8voip
    Hi Joel, I think the intention of the check with listening on a FM receiver is only tell you the Si570 is oscillating, certainly no way of determining the
    Message 1 of 13 , Apr 2, 2011
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      Hi Joel,

      I think the intention of the check with listening on a FM receiver is only tell you the Si570 is oscillating, certainly no way of determining the frequency with any accuracy within a few 10's of kHz due to the width of the BC receivers filters.

      We can only work on the information given and you seemed to be pointing to a problem with resolving upper or lower sideband hence the focus by me and others on the I/Q settings. Simply having an error in the frequency calibration would not affect the signal you were trying to tune, only the absolute dial frequency.

      Frequency calibration is a completely separate process.

      Guess sometimes it is not possible to describe the problem or symptoms accurately enough to enable the correct solution to be given.

      Anyway, glad you managed to resolve your problem via a roundabout route.

      73, Bob G8VOI


      --- In softrock40@yahoogroups.com, Joel Black <w4jbb@...> wrote:
      >
      > Bob, et al,
      >
      > My problem was actually an LO that was not properly calibrated. Tony
      > pointed me to that.
      >
      > I had followed the instructions at the build site by Robby, WB5RVZ, and
      > they are great. I'm not complaining. However, the Si570 is a tad
      > broader than I expected. So yes, I had "calibrated" it, but it wasn't
      > even close... I'm getting to that.
      >
      > When I got to that step, I didn't use a freq counter as I should have, I
      > used a local FM broadcast station. When I tuned the Si570 to 98.1MHz, I
      > got full quieting on the FM radio (later, I tried this on 10MHz and got
      > the same result). Problem is, the LO was 1.1kHz high. So, everything
      > appeared to be LSB (1.5kHz below the carrier). No amount of me crossing
      > and uncrossing the I and Q jumpers or moving soundcard inputs was going
      > to solve that.
      >
      > Tony told me to go back and tune to WWV and re-calibrate. I did that
      > and it all worked out. It has been stable since.
      >
      > 73,
      > Joel - W4JBB
      >
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