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39251Re: [softrock40] Re: LO Question

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  • Alan
    Jan 2, 2010
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      ----- Original Message -----
      From: "g8voip"
      Subject: [softrock40] Re: LO Question


      > Hi Tom,
      >
      > Those LO frequencies seem to be pretty close to the programmed values. The
      > differences are due to the tolerance of the Si570 master oscillator.
      >

      The PIC software should compensate for the Si570's startup frequency but
      only if it is 56.32MHz. There is no simple way to rectify this so Bob's
      remedy will have to be used. (Reprogramming the PIC is possible.)

      >
      > It sounds like you have not optimised the image rejection, hence seeing
      > images each side of the centre frequency.

      If images are very obvious, if both sides are symmetrical then it is likely
      you have a fault. You seem to say the Softrock is not very sensitive? If so,
      then maybe the input transformer is wired wrongly.

      In a subsequent post you say the calibration is greyed out. This is probably
      only relevant with USB control, you cannot adjust the frequency of the Si570
      without reprogramming the PIC. Is it a 56.32? it looks as if reprogramming
      will be necessary to get the centre frequencies correct. You will have to
      enter the true frequencies in Rocky's ini file.

      73 Alan G4ZFQ
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