Hi The typical answer to this issue is to first try to clean up the supply to the DAC. If that does not fix the issue, you likely need a better DAC. Unless the TCXO has a crazy large tune range, rational parts should be able to do the job. If the TCXO has a crazy large range then maybe a different TCXO is the answer.
You can measure this or that to confirm / deny that the problem exists here or there in the circuit. An audio analyzer that gets down to a bit under 1 Hz should be able to tell you what’s what. Various sound card based approaches likely would be “good enough” ( yes, ground loops will be fun to take care of ….) Bob > On May 20, 2022, at 9:26 AM, Erik Kaashoek via time-nuts > <time-nuts@lists.febo.com> wrote: > > During testing a TCXO using a correct Vtune for 10MHz output, the ADEV at > tau=1 second was measured at 1.08E-10 (see attached plot[1], trace > DAC=normal) > When the DAC controlling the Vtune was forced to zero volt output the ADEV at > tau=1 s reduced to 5.43E-11 (see plot, trace DAC=0) > This clearly hinted at some noise present on the DAC output. > Adding substantial filtering between the DAC and the Vtune input of the TCXO > and setting to 10MHz resulted in an ADEV at tau=1 s of 7.28E-11 (see plot, > trace DAC filtered) > All measurements where done with the controller for the Vtune disabled. > The plot contains error bars. > > The extra filtering required for the reduction creates a lag of about 10 > seconds in controlling the TCXO and the controller without the filtering was > nicely able to correct fairly quickly random walks so I'm a bit worried about > the problems this 10 seconds extra lag may create in tuning the controller > loop. > > Is a reduction of the ADEV of a 10MHz reference output with 25% (or at most > 50%) for low tau in practice of any relevance if this may cause an increase > in ADEV for larger tau as the controller may have more difficulty to > correctly adjust Vtune to correct random walks? > > [1] Plot: > http://athome.kaashoek.com/time-nuts/DAC_Filtering.png<DAC_Filtering.png>_______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-le...@lists.febo.com _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
