Hi Keep in mind that when you do 1800 samples at 1 second, that data will only meet the 100 sample requirement out to tau = 18 seconds. Past that you are in the “under 100 samples region”.
Bob > On Jan 12, 2017, at 2:32 PM, Bob Stewart <b...@evoria.net> wrote: > > Hi Bob, > OK, thanks for explaining. When you and others use highly technical terms > like "small number of samples" it's not always clear to me what you mean. =) > Ten samples? That's not enough for anything. Normally I run at least 1800 > samples; at least if I plan to share them with someone. > > Bob ----------------------------------------------------------------- > AE6RV.com > > GFS GPSDO list: > groups.yahoo.com/neo/groups/GFS-GPSDOs/info > > From: Bob Camp <kb...@n1k.org> > To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency > measurement <time-nuts@febo.com> > Sent: Thursday, January 12, 2017 1:03 PM > Subject: Re: [time-nuts] General questions about making measurements with > time interval counter. > > Hi > > It varies from 5370 to 5370. You see a lot of plots that run out to 10 > samples or less. Anything below 100 samples > is risky in some senses. > > Bob > >> On Jan 12, 2017, at 12:25 PM, Bob Stewart <b...@evoria.net> wrote: >> >> Hi Bob, >> OK, what's a small number of data points? Attached is a screencap of >> captures for 25, 50, 75, 100, and 150 seconds. Yeah, at 25 seconds, the 1S >> tau is up at 4.56E-11, but it falls pretty quickly. I will mention that >> this particular 5370 is much better than my other one. So, maybe this one >> is an exceptional example? >> >> Just for grins, I also included a screencap of the phase points. >> >> Bob ----------------------------------------------------------------- >> AE6RV.com >> >> GFS GPSDO list: >> groups.yahoo.com/neo/groups/GFS-GPSDOs/info >> >> From: Bob Camp <kb...@n1k.org> >> To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency >> measurement <time-nuts@febo.com> >> Sent: Thursday, January 12, 2017 11:04 AM >> Subject: Re: [time-nuts] General questions about making measurements with >> time interval counter. >> >> Hi >> >> There is a big difference between RMS and single shot. Single shot, the 5370 >> is a very different beast. >> That’s not a big deal when you have a few thousand readings and it all >> averages down. Unfortunately >> we all love to do runs with a very small number of points and then draw >> conclusions from them. As the >> sample size goes down, you no longer have a 2 to 4 x 10^-11 beast, it’s more >> like 5X that. >> >> Bob >> >> >>> On Jan 12, 2017, at 11:31 AM, Bob Stewart <b...@evoria.net> wrote: >>> >>> Hi Bob, >>> Normally I see somewhere between 2E-11 and 4E-11 at 1S tau on my 5370A, as >>> in the blue trace on the attached plot. Am I misunderstanding your >>> meaning? Granted, I am clocking the 5370A with a GPSDO, but I believe I >>> see about the same thing with the HP10811. This test was 1PPS vs 1PPS on >>> two different units. >>> The plot also has a test run by Tom, in orange, using his H Maser and a >>> Timepod to show how poor the 5370 is compared to the Timepod below about >>> 60S tau. These are essentially apples vs apples tests. >>> >>> Bob >>> >>> >>> >>> >>> From: Bob Camp <kb...@n1k.org> >>> To: Discussion of precise time and frequency measurement >>> <time-nuts@febo.com> >>> Sent: Thursday, January 12, 2017 8:27 AM >>> Subject: Re: [time-nuts] General questions about making measurements with >>> time interval counter. >>> >>> Hi >>> >>> There are a number of ways to improve the resolution (and accuracy) of your >>> data without spending >>> big piles of cash. They have been discussed here on the list many times >>> over the last few years. >>> What I’m suggesting is that you dig into that ahead of taking data. You >>> will dive into it eventually as you >>> look more and more at devices that are locked to some sort of stable >>> reference internally. >>> >>> Ideally you would like a device with a floor 5X to 10X better than what you >>> are measuring. For ADEV style >>> data, the 5370 is a 1x10^-10 sort of device single shot (so 1x10^-9 is the >>> limit at 10:1). With a lot of averaging >>> (which is not something you do with ADEV) you can get about 5X better than >>> that as a floor. In either case, it is getting in the way of any >>> readings that are much below 1x10^-9 at one second. A low cost XO can hit >>> that level of performance. >>> >>> Bob >>> >>> >>> <ADEV.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. >> >> >> <ADEVs.png><Phase.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. _______________________________________________ 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.