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Re: New guy looking at sound card 'calibration'

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  • sm5le
    RRR Tnx Wolf /Sven
    Message 1 of 13 , Jun 20, 2013
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      RRR
      Tnx Wolf

      /Sven

      --- In SpectrumLabUsers@yahoogroups.com, wolf_dl4yhf <dl4yhf@...> wrote:
      >
      > Hi Sven,
      >
      > During all tests, the external soundcard was always better - MUCH better
      > - last not least because its temperature-dependent oscillator drift was
      > alway very predictable (decay function). All of the internal devices
      > suffer from rapid temperature changes when the PC's internal fan goes
      > on/off. Unless you have a fan-less PC, or a netbook which hardly ever
      > turns on one of the internal fans (but when doing number crunching they
      > usually have to turn on the fan sooner or later, even a netbook with an
      > Atom CPU was no exception).
      >
      > All the best,
      > Wolf .
      >
      >
      > Am 18.06.2013 16:39, schrieb Werner Karn:
      > > Sven,
      > > from my experience, that will depend on where you can best control
      > > temperature stability.
      > > BR
      > > Werner
      > >
      > >
      > > 2013/6/18 sm5le <sm5le@... <mailto:sm5le@...>>
      > >
      > > Hello Wolf
      > > Is it better to use internal soundcard "SoundMAX Digital Audio"
      > > insted of external "E-MU 0202" for best freq. accuracies and drift ?
      > > tnx /Sven
      > >
      > > --- In SpectrumLabUsers@yahoogroups.com
      > > <mailto:SpectrumLabUsers%40yahoogroups.com>, wolf_dl4yhf
      > > <dl4yhf@> wrote:
      > > >
      > > > Hello Bill,
      > > >
      > > > Without a means to monitor ("calibrate") the soundcard's
      > > sampling rate
      > > > against a reference signal,
      > > > you can expect accuracies in the range of a few ppm (parts per
      > > million).
      > > > Of course this requires measuring the soundcard's sampling rate
      > > *once*,
      > > > which can be done easily with an off-air standard like an audio
      > > tone
      > > > received in AM (not SSB!).
      > > >
      > > > After that, the accuracy depends largely on the soundcard (no big
      > > > surprise..).
      > > > The manual contains two examples of a 'good' and a 'poor'
      > > soundcard,
      > > > concering the stability of the clock source:
      > > >
      > > >
      > > http://www.qsl.net/dl4yhf/speclab/frqcalib.htm#soundcard_clock_drift_measurements
      > > >
      > > > As you can see, with the E-MU 0202 (used for the 2nd, "good"
      > > example)
      > > > the sampling rate settles to less then 0.1 ppm after > 1 hour of
      > > > warm-up. Thus, with a sufficiently large FFT (i.e. sufficient
      > > > *resolution* of the measurement), a 1 kHz audio signal can be
      > > measured
      > > > with an accuracy 0.1 milliHertz.
      > > >
      > > > Thus the accuracy of the entire system (with HF receiver /
      > > VFO+BFO +
      > > > Soundcard) is limited by the stability of the radio, not by the
      > > soundcard.
      > > >
      > > > All the best,
      > > > Wolf .
      > > >
      > > > Am 16.06.2013 15:39, schrieb Bill Cromwell:
      > > > >
      > > > > Hi,
      > > > >
      > > > > I'm a Ham radio licensee (I know not everybody here is). I
      > > have Spectrum
      > > > > Lab, Spectran, fldigi, and some other digital mode, sound card
      > > packages.
      > > > > Spectran does some of the same tricks that Spectrum Lab does
      > > (not a
      > > > > comparison) but not nearly as many. Ergo, Spectran has a smaller
      > > > > learning curve and is dramatically quicker to get into action.
      > > Spectran
      > > > > can do more for me when I get it "mastered".
      > > > >
      > > > > I have been working my way into the goodies in Spectrum Lab
      > > and I am
      > > > > ready to try calibration for general "frequency measurements".
      > > I have
      > > > > used my dual loop PLL receiver to apply signals from WWV in AM
      > > mode (no
      > > > > BFO to consider and VFO only needs to be 'close enough') to
      > > several of
      > > > > my sound card programs and they all show me that the standard
      > > tones are
      > > > > within just about 100 millihertz on the displays. I do NOT
      > > have my sound
      > > > > card or computer timebase synced to anything like a rubidium
      > > or gps
      > > > > "standard".
      > > > >
      > > > > I can look at the manuals myself to see how Spec Lab wants me
      > > to adjust
      > > > > for the sound card clock error (and the other packages, too).
      > > What kind
      > > > > of overall accuracy can I expect from Spectrum Lab under the
      > > conditions
      > > > > I have outlined? I intend to use the information I can get
      > > from Spectrum
      > > > > Lab and Spectran to correct the alignment of my duall loop PLL
      > > and BFOs
      > > > > in that (and other receivers). For the most part, being within 100
      > > > > milliHertz is overkill in most ham radio operation (never mind
      > > about
      > > > > WSPR for now). But it's always good to know the limitations.
      > > > >
      > > > > Incidentally, when I bring in the BFO the actuall PLL "VFO"
      > > frequency
      > > > > and the BFO come into play and it's definitely "out of whack".
      > > Starting
      > > > > point is sound card calibration.
      > > > >
      > > > > 73,
      > > > >
      > > > > Bill KU8H
      > > > >
      > > > >
      > > >
      > >
      > >
      > >
      >
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