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</o:shapelayout></xml><![endif]--></head><body lang=DE link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Right Brian! The quality of the sampling oscillator determines the SFDR of the ADC besides resolution etc. Phase noise is some kind of jitter. The 122,88 Mhz oscillator acts as VCXO and the possible reduction of its native phase noise by means of the loop reference is very limited. The easier way to improve the system (if even necessary) is to run the VCXO on twice frequency and divide down by factor 2. So you gain 6 dB less phase noise.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>73, Helmut, DC6NY<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'><p class=MsoNormal style='margin-left:35.4pt'><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>Von:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> Brian Lloyd [mailto:brian@lloyd.com] <br><b>Gesendet:</b> Freitag, 13. Dezember 2013 19:07<br><b>An:</b> Helmut, DC6NY<br><b>Cc:</b> Kjell Karlsen; hpsdr@lists.openhpsdr.org<br><b>Betreff:</b> Re: [hpsdr] New clock oscillator for OpenHPSDR?<o:p></o:p></span></p></div><p class=MsoNormal style='margin-left:35.4pt'><o:p> </o:p></p><div><div><div><p class=MsoNormal style='margin-left:35.4pt'>On Fri, Dec 13, 2013 at 10:52 AM, Helmut, DC6NY <<a href="mailto:dc6ny@gmx.de" target="_blank">dc6ny@gmx.de</a>> wrote:<o:p></o:p></p><div><p class=MsoNormal style='mso-margin-top-alt:0cm;margin-right:0cm;margin-bottom:12.0pt;margin-left:35.4pt'>***** High Performance Software Defined Radio Discussion List *****<o:p></o:p></p></div><p class=MsoNormal style='margin-left:35.4pt'>Hi Kjell.<br><br>Thanks for information, but I see no direct chance for any substitution in<br>this 5V sine wave application. On the 10 MHz level phase noise hasn't been<br>an issue and concerning to the sampling frequency 122,88 Mhz I'm not sure<br>that the approx. 10 dB better phase noise can improve SFDR dramatically. But<br>it's interesting that a lot of suppliers meanwhile discover phase noise a<br>determining factor of total system's performance.<o:p></o:p></p><div><p class=MsoNormal style='margin-left:35.4pt'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:35.4pt'>Please correct me if I am wrong, but the loop filter at the output of the phase comparator prior to the control input at the 122.88MHz master oscillator effectively attenuates the phase noise from the 10MHz reference thus preventing it from affecting system performance. I would expect the native phase noise of the 122.88MHz master oscillator to dominate the phase noise performance of the system. This would mean that a low-phase-noise reference (GPSDO or Rb) is not that necessary.<o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:35.4pt'><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-left:35.4pt'>Am I correct?<o:p></o:p></p></div><div><p class=MsoNormal style='margin-left:35.4pt'><o:p> </o:p></p></div></div><p class=MsoNormal style='margin-left:35.4pt'>-- <o:p></o:p></p><div><p class=MsoNormal style='margin-left:35.4pt'><span lang=EN-US>Brian Lloyd, WB6RQN/J79BPL </span><img border=0 id="_x0000_i1025" src="http://www.catb.org/hacker-emblem/glider.png"><span lang=EN-US><br>706 Flightline Drive<br>Spring Branch, TX 78070<br></span><a href="mailto:brian@lloyd.com" target="_blank"><span lang=EN-US>brian@lloyd.com</span></a><span lang=EN-US><br><span class=gc-cs-link>+1.916.877.5067</span><o:p></o:p></span></p></div></div></div></div></body></html>