[hpsdr] Frequency offset using Excalibur

[John Petrich]

All,

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.  

 

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.

 

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.

 

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 ?

Regards,

John Petrich, W7FU

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openhpsdr.org/pipermail/hpsdr-openhpsdr.org/attachments/20121209/b32871d0/attachment-0004.htm>