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<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=984013508-21042007>Hi
Frank, All,</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=984013508-21042007></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=984013508-21042007>Being
basically an analog guy too and not at all an expert on this, I can point
you only to the Nyquist Theorem or Sampling Theorem, e.g. </SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=984013508-21042007></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=984013508-21042007><A
href="http://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem">http://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem</A></SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=984013508-21042007></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=984013508-21042007>A lot
of mathematic's!</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=984013508-21042007></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=984013508-21042007>What
this all comes down to, as I understand it, is that this guy (and others) proved
mathematically that EVEN WITH ONLY TWO samples per period of the
signal to be be digitized, it can be reconstructed correctly from these two
samples!</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=984013508-21042007></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=984013508-21042007>So for
10 meters / 30 MHz you would need a minimum of two samples per one single period
of 30 MHz.</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=984013508-21042007>So
your minimum sampling frequency would be 2 X 30 MHz = 60
MHz.</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=984013508-21042007></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=984013508-21042007>This
is why you always see the sampling frequency of e.g. an ADC is divided by 2
to get the highest possible signal frequency that can be digitized
correctly.</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=984013508-21042007></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=984013508-21042007>Confusing can be the fact that within SDR's we have
QSD's with I and Q signals, each coming from their own ADC. (e.g. as is the
case in a PC with a stereo sound card)</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=984013508-21042007>In
that case you have 2 channels and thus 2 samples each moment you sample, so in
fact doubling the sample rate/frequency.</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=984013508-21042007>Then
you have a maximum signal frequency of the signal that can be digitized
correctly equal to the full sampling frequency of a single channel, so no
division by 2.</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=984013508-21042007></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=984013508-21042007>Hope
this helps; Guru's, please correct me if I am telling this not correctly......
;-)</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=984013508-21042007></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=984013508-21042007>73's,</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=984013508-21042007></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=984013508-21042007>Henry.</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=984013508-21042007></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=984013508-21042007></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=984013508-21042007></SPAN></FONT> </DIV>
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style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #0000ff 2px solid; MARGIN-RIGHT: 0px">
<DIV></DIV>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left><FONT
face=Tahoma size=2>-----Original Message-----<BR><B>From:</B>
hpsdr-bounces@hpsdr.org [mailto:hpsdr-bounces@hpsdr.org] <B>On Behalf Of
</B>FRANCIS CARCIA<BR><B>Sent:</B> zaterdag 21 april 2007 2:23<BR><B>To:</B>
hpsdr@hpsdr.org<BR><B>Subject:</B> [hpsdr] A/D<BR><BR></FONT></DIV>
<DIV>Correct me if I am wrong but how well can we expect a 130 Ms
A/D to work at 10 meters?</DIV>
<DIV>4 samples per cycle sounds a bit lean. I'm sure it will really kick butt
at 455 KHz.</DIV>
<DIV>an analog guy trying to fit
in.....frank </DIV></BLOCKQUOTE></BODY></HTML>