> 3) To look at several different noise *slopes*, looking for specific cases > where filtering or integration might cause the instruments to respond > differently depending on the spectral characteristics of the noise in a > given tau region. > > Bruce's concern is largely that of (3)...
One other point that might not be clear: the 5062C does exhibit a wide variety of noise types, but not at short timescales near that of either Warren's RC time constant or my low-pass decimation filter. As this PN plot shows, the 10811 is transitioning from 1/f^2 to 1/f noise (i.e., white frequency to flicker phase) by the 100-150 Hz offset where Warren's RC integrator is doing its thing, and the 5062C is, too, since its disciplining loop BW is somewhat lower: http://www.thegleam.com/ke5fx/pn_slopes.gif The medium-term ADEV measurement with the 5062C tells us that there are probably no time-variant effects that would jeopardize measurements at longer timescales regardless of their slope, but -- since the 5062C's noise statistics are so similar to the 10811's at 100 Hz -- it *doesn't* tell us as much about the quality of the integration or filtering as I may have suggested. As Warren says, at short timescales the technique's accuracy depends on oversampling, which I tend to agree has an effect similar to higher-quality integration. To put this assertion to a real-world test, one might use the tight PLL to observe both an oscillator which is still in 1/f^3 territory at t=0.01s, and one which is already well into its white-phase noise region by that point. -- john, KE5FX _______________________________________________ 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.