Loading ...
Sorry, an error occurred while loading the content.

Re: [SpectrumLabUsers] LTA trace ver 2.76,2.77 and ver 2.78

Expand Messages
  • kd7ts
    ... Hi Wolf, peak_f(550,650) peak_f(#LTA1,550,650) Using the two expressions above return different values. Looking at the spectrogram the two peaks are
    Message 1 of 5 , Jan 8, 2013
    • 0 Attachment
      On Tue, 08 Jan 2013 09:45:24 -0800, wolf_dl4yhf <dl4yhf@...> wrote:

      > You mean the entries in the header line(s) of the file, generated when
      > saving the long-term average spectrum to disk ?
      > Why does the frequency need to be corrected at all, is this due to an
      > error in the soundcard's sampling rate, or a slight offset in the VFO
      > setting of an externa radio ?
      > Cheers,
      > Wolf .


      Hi Wolf,

      peak_f(550,650)

      peak_f(#LTA1,550,650)

      Using the two expressions above return different values. Looking at the
      spectrogram the two peaks are visibly offset.

      This does not appear until the sound card correction is applied. Prior to
      correction they are both wrong, then after correction only the LTA is
      wrong.

      "Correction is not applied to the LTA trace. The FFT is corrected, but
      not the LTA trace, it remains at the original frequency."

      The difference of the two is the amount of correction applied to the FFT.

      The radios are GPS referenced via 10 MHz and appear to be capable of less
      than 1 Hz resolution. We would like, very much, to get this to the 40
      millihertz resolution. The error is abut 400 millihertz.

      An image of the screen is here:

      http://home.comcast.net/~kd7ts/html/SL/34.gif

      Mike KD7TS
    • wolf_dl4yhf
      Ok thanks - this makes it much easier to reproduce the effect. I normally use an SDR-IQ or Perseus on HF, which don t need an extra frequency calibration so I
      Message 2 of 5 , Jan 8, 2013
      • 0 Attachment
        Ok thanks - this makes it much easier to reproduce the effect.
        I normally use an SDR-IQ or Perseus on HF, which don't need an extra
        frequency calibration so I didn't notice this effect so far.

        More details when time permits, maybe tomorrow.

        Cheers,
        Wolf .

        Am 08.01.2013 22:35, schrieb kd7ts:
        > On Tue, 08 Jan 2013 09:45:24 -0800, wolf_dl4yhf <dl4yhf@...> wrote:
        >
        >> You mean the entries in the header line(s) of the file, generated when
        >> saving the long-term average spectrum to disk ?
        >> Why does the frequency need to be corrected at all, is this due to an
        >> error in the soundcard's sampling rate, or a slight offset in the VFO
        >> setting of an externa radio ?
        >> Cheers,
        >> Wolf .
        >
        > Hi Wolf,
        >
        > peak_f(550,650)
        >
        > peak_f(#LTA1,550,650)
        >
        > Using the two expressions above return different values. Looking at the
        > spectrogram the two peaks are visibly offset.
        >
        > This does not appear until the sound card correction is applied. Prior to
        > correction they are both wrong, then after correction only the LTA is
        > wrong.
        >
        > "Correction is not applied to the LTA trace. The FFT is corrected, but
        > not the LTA trace, it remains at the original frequency."
        >
        > The difference of the two is the amount of correction applied to the FFT.
        >
        > The radios are GPS referenced via 10 MHz and appear to be capable of less
        > than 1 Hz resolution. We would like, very much, to get this to the 40
        > millihertz resolution. The error is abut 400 millihertz.
        >
        > An image of the screen is here:
        >
        > http://home.comcast.net/~kd7ts/html/SL/34.gif
        >
        > Mike KD7TS
        >
        >
        >
        >
        >
        > ------------------------------------
        >
        > Yahoo! Groups Links
        >
        >
        >
        >
        >
      Your message has been successfully submitted and would be delivered to recipients shortly.