Tom, Don't confuse everybody with facts, we had a good thread going :)
The PicPet is holding its own very well in that application. I am surprised at the effect of the laptop supply. I would have certainly expected effect on phase noise (smaller taus), but not that close to the carrier. Do you know if it is a power factor corrected supply or not? Didier KO4BB Tom Van Baak <[email protected]> wrote: >Magnus, > >I'm going to push back a bit on your mains sampling claim. Mostly, I'd >like to see the results of the professional I-Q demodulated gear that >you mentioned. Can you post raw data, or a sample plot? > >I agree that looking at power line voltage with 16- or 24-bits at 1 >Msps is going to reveal interesting amplitude and phase noise >information. But see how well a $1 PIC can do. > >Attached is a plot made using TimeLab + picPET just now. The picPET is >fast enough to capture the zero-crossing of every 60 Hz cycle with 400 >ns resolution; the TimeLab plots have tau0 of 16.67 ms. > >-- The blue trace was simply plugging a 9 VAC wall-wart into the picPET >though a 10k resistor. >-- The pink trace was adding a 10 nF cap across the input. >-- The green trace was unplugging my laptop switching power supply from >the same outlet! >-- The red trace is replacing the mains wall-wart with a hp 33120A set >to 9VAC at 60 Hz, a tentative noise floor measurement of the picPET >when used this way. > >My conclusions are that at least here in the US, or at least at my >house, the short-term stability of mains hits about 5e-6, at about tau >0.2 seconds. The attached short-term plot is also not-inconsistent with >the long-term plot at http://leapsecond.com/pages/mains/ > >My other conclusion is that the picPET (a simple PIC-based >time-stamping counter) is doing a pretty good job measuring this. Note, >no software or data filtering was used. This is just raw serial/USB >data going into TimeLab. > >/tvb > > >------------------------------------------------------------------------ > >_______________________________________________ >time-nuts mailing list -- [email protected] >To unsubscribe, go to >https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. -- Sent from my Motorola Droid Razr 4G LTE wireless tracker while I do other things. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
