On 02 Apr 2013 14:01, Zooz Engineer wrote:
> Dear All, > > I am having an issue with my 3 USRP-N200 synch. I use external synch sources for Ref/PPS. The LED's for Ref signal are green and the PPS test is successful for the three boards. However, when I input a sinusoidal signal split and fed into the RF input of the three board and I use a UHD source block for the three boards setting the time and clock as "external", the signals appear still unsynchronized as show in the attached image. > > Any insights on this? Is there anything I need to check? > > Best regards, > Zo Two (or more) issues to consider: o The scope sink has, in the past, had issues with displaying signals that are phase aligned, and showing them not aligned o Frac-N synthesizers, as one would find on your daughtercard, won't all have zero relative phase offset when they're tuned. o Your splitter isn't necessarily perfectly coherent across all ports o Relative phase will drift with temperature due to temperature effects on your cabling and your splitter If you use SBX daughtercards, you can use the timed-command feature to allow for phase-aligned frequency setting, using a special feature of the synthesizer chip. Not sure how you get at that from a .grc flow-graph, however.
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