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1045Re: [SpectrumLabUsers] SPECTRUMLAB and sampling oscilloscope as input device

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  • wolf_dl4yhf
    Nov 5, 2012
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      Hello Eduardo,

      Not that I heard of. I have a digital storage scope which can deliver blocks of -I think- 256 samples with 8 bit each, but the big problem is that blocks are not contiguous (coherent). So taking a 512-point FFT from two subsequent blocks read out of the oscilloscope (or whatever) is pointless, because of the gap in between.

      Spectrum Lab only operates on non-interrupted streams, i.e. without any gap in between. This is the main difficulty with most high-speed acquisition systems : They only deliver small snapshots (depending on their sample memory size) but only very few are capable of delivering a truly gapless output.

      The best, or at least the most simple and cost-effective method to acquire samples from a 21.4 MHz signal would be one of those direct sampling software defined radios. For example, I use the FiFi-SDR for comparison with an SDR-IQ and a Perseus, and imo for 130 Euros the FiFi-SDR does a good job, and can be tuned from LF to the upper end of the HF spectrum. A few notes about that radio from the SL manual:

      http://www.qsl.net/dl4yhf/speclab/settings.htm#FiFi_SDR

      The digital downconversion process (which takes place in the FiFi-SDRs internal soundcard) is not trivial, and a general purpose PIC will definitely not be up to the job. You will need at least a DSPIC for this, or an external DDC (digital downconverter) but you may end up re-inventing the wheel (wheel = SDR-IQ, but they use an ARM CPU to control the DDC chip).



      All the best,
        Wolf .


      Am 05.11.2012 18:42, schrieb ea3ghs:
       


      Hello dear friends,

      I would like to do a 10Hz/bin 512 point FFT over a 21.4 MHz signal
      with a microcontroller.

      As a prototiping tool, I am evaluating the posibility of use a
      sampling scope (TEK,HP,..) as a sampling device, and to use the
      digital downconversion capabilities of SPECTRUMLAB.

      - Has anyone done something similar?
      - Maybe there are available a linking script between oscilloscope with
      HPIB/ethernet and SpectrumLab.

      Please, write me directly too.
      I only read ocasionally this maillist.
      73 eduardo
      ea3ghs
      at gmail dot com


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