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Date: Mon, 03 Mar 2014 19:45:49 +0100
From: wolf_dl4yhf <dl4yhf@freenet.de>
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Subject: Re: LF: Would slower QRSS help?
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Hi Markus,

Since I also "suffer" from insufficient bandwidth for a link to my 
remote receiving site:

What about converting the signal down to 'easily managable audio 
frequency' (low enough for yet another narrow-band FM link), using a 
32.768 kHz 'clock' crystal for the mixer ? With reasonable pre-filtering 
the image frequency won't hurt much, and even a Gilbert cell mixer 
(NE/SA612) may get the job done quickly. Not sure if the frequency 
stability will be good enough for uHz resolution, but considering that 
in the days of IBM PC XT / AT the system time drift was low (and very 
predictable), it may work.


73,
   Wolf DL4YHF .


Am 03.03.2014 18:51, schrieb Markus Vester:
> Bob,
> nothing at all in Nuernberg last night. There seemed to be no diurnal 
> change in the background noise level, showing that my receiving setup 
> is not sensitive enough yet. Apparently the current LF-VLF diplexer 
> arrangement is too lossy for direct connection to the soundcard, and 
> in addition the ADC noisefloor is a bit higher above 24 kHz 
> (Sigma-Delta noise shaping?). Will try to redesign 
> the circuit and insert a simple preamp tonight.
> I have also slowed the grabber window to 424uHz bins, hoping for more 
> long carrier transmissions tonight.
> Best 73,
> Markus (DF6NM)
>


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    <div class="moz-cite-prefix">Hi Markus,<br>
      <br>
      Since I also "suffer" from insufficient bandwidth for a link to my
      remote receiving site:<br>
      <br>
      What about converting the signal down to 'easily managable audio
      frequency' (low enough for yet another narrow-band FM link), using
      a 32.768 kHz 'clock' crystal for the mixer ? With reasonable
      pre-filtering the image frequency won't hurt much, and even a
      Gilbert cell mixer (NE/SA612) may get the job done quickly. Not
      sure if the frequency stability will be good enough for uHz
      resolution, but considering that in the days of IBM PC XT / AT the
      system time drift was low (and very predictable), it may work.<br>
      <br>
      <br>
      73,<br>
        Wolf DL4YHF .<br>
      <br>
      <br>
      Am 03.03.2014 18:51, schrieb Markus Vester:<br>
    </div>
    <blockquote
      cite="mid:8D10520560462B7-434-1D66F@webmail-d276.sysops.aol.com"
      type="cite">
      <div style="FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt"><span
          style="DISPLAY: inline-block" contenteditable="false"></span>Bob,</div>
      <div style="FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt"> </div>
      <div style="FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt">nothing
        at all in Nuernberg last night. There seemed to be no diurnal
        change in the background noise level, showing that my receiving
        setup is not sensitive enough yet. Apparently the current LF-VLF
        diplexer arrangement is too lossy for direct connection to the
        soundcard, and in addition the ADC noisefloor is a bit higher
        above 24 kHz (Sigma-Delta noise shaping?). Will try to redesign
        the circuit and insert a simple preamp tonight.</div>
      <div style="FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt"> </div>
      <div style="FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt">I
        have also slowed the grabber window to 424uHz bins, hoping for
        more long carrier transmissions tonight.</div>
      <div style="FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt"> </div>
      <div style="FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt">Best
        73,</div>
      <div style="FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt">Markus
        (DF6NM)<br>
      </div>
      <div><br>
      </div>
    </blockquote>
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