On 10/25/2018 04:16 AM, Christopher Willuweit via USRP-users wrote:
Hi all,
I want to use a single X310 w/ two UBX-160-Daughterboards for a simple
transmission setup. You can find the GRC-Flowgraph and a screenshot of
the result attached in this mail. I'm experiencing an LO-Offset of
~12Hz and just wanted to know if this is normal. As far as i can tell
from schematics, the PLLs in the daughterboard have reference clocks
generated by a clock distribution chip in the X310. Since the wires
are of matched length i would assume that they can be used frequency
and phase synchronized. Did i get something wrong with my settings? On
the ettus website i can only find information for phase coherent
setups using multiple USRPs. For a start a frequency synchronized
setup would be sufficient for my application, phase does not matter.
Currently i'm using UHD version 3.14.0.HEAD-31-g98057752
kind regards and thanks!
Christopher Willuweit
I have to admit, this is a bit odd.
Does the frequency error change over time?
With both UBX getting the same clock, and the same programming, the
residual mutual frequency error should be zero. The absolute frequency
error, of course, could be much larger, but it will (should) be the
same for both UBX -- same PLLs, same refclock, same programming.
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