Hi I think that if you switch to an averaging of a few seconds from "per pixel" the plot of frequency difference will look a bit different. The phase perturbations from DDS will still be there, and they are an issue. They just many not be as dramatic as that plot implies.
Bob On Jun 3, 2012, at 8:14 PM, ewkeh...@aol.com wrote: > The FEI 5680A we recently discussed uses the DDS to generate part of the > excitation to the filter. Fine stepping the excitation frequency. The > output is taken off the 60 MHz and divided by 6. I noticed the changes when > doing my aging tests but some disagreed. The attached I think it is from > John > Miles shows it very clearly and what is needed is a clean up loop with some > thing like a MV89. I think the source is the control loop which most > likely is digital. FRS and FRK are analog but will also improve with an > external > OCXO. > Bert Kehren >>> The FEI-5680A Rubidium that we discussed here some time ago has a much >>> worse phase noise plot of course, because the 10MHz is generated > digitally >>> through a DDS, not a 10MHz crystal oscillator.. >>> >> There is a version that generates 10MHz directly through DDS, but the > particular version we recently discussed a lot about generates the 10MHz > signal from a 60MHz oscillator, and the DDS is used for generating the > ~5.3125MHz signal for mixing with the 114th harmonic of the 60MHz to obtain > the Rb > resonance frequency. >> >> I don't remember if someone did a comparison in PN performance between > the two FE-5680A flavours. >> >> Regards, >> >> Javier > <freqdiff.png>_______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
