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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>All,<o:p></o:p></p><p class=MsoNormal>I’m no expert on these things but I want to share my experiences for what it is worth. The setup for me uses the same GPDSO for the HP 8656B synthesizer and the Excalibur in my Atlas based system, PSDR V2.2(11/17/12) RX2 as the software, the “Phase” screen selected and set to 50 points from the Display menu, and uses either the CWU or the Spec modes. I should add that my setup is arranged so the 122 MHz LVDS output from Pennylane is coupled to the LVDS input on Mercury and the 10 MHz clock in Mercury is disabled. One 122 MHz clock and one 10 MHz clock with is locked to the GPDSO via the Excalibur interface. <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>When measuring frequency calibration, the points in the phase display circle are essentially stationary at any common frequency I select and display for both the synthesizer and Mercury in either of these two modes. Incrementing the receive frequency either up or down 1 Hz causes the Phase circle points to rotate in a direction appropriate to the frequency change.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I agree that it is possible, but tedious, to “improve” the frequency calibration within limits by manually altering the Calibration settings in the Setup menu. The phase circle points in my setup are not quite perfectly stationary at the common frequency, but rotates very slowly in the direction consistent with a low indicated frequency in my Mercury set up. The offset is 1 Hz for 60 seconds or so, 1/60 of a Hz, 16 mHz, which is about the same offset I have measured previously of PSDR BFO frequency accuracy. Too many moving parts for me to really understand what is going on.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Wish I knew how to explain the differences we are seeing: A difference in software versions, differences in measuring techniques, something to do with multiple 122 MHz and 10 MHz clocks ?<o:p></o:p></p><p class=MsoNormal>Regards,<o:p></o:p></p><p class=MsoNormal>John Petrich, W7FU<o:p></o:p></p></div></body></html>