Hi If you convert the data to +/- 50 ns, you will have a problem at the edges. Much easier to deal with unwrapped data. The same CSV approach works for taking the pps data from a module, logging the sawtooth info and combining them. There’s no practical way to get the “real” RMS of the module without doing that.
Bob > On May 3, 2017, at 11:56 AM, Bob Stewart <b...@evoria.net> wrote: > > Hi Bob, > > Won't I have a problem with the phase wrap unless I convert the data to a > range of +50ns to -50ns? Or am I still looking at this incorrectly? > Bob > > ----------------------------------------------------------------- > AE6RV.com > > GFS GPSDO list: > groups.yahoo.com/neo/groups/GFS-GPSDOs/info > > > From: Bob kb8tq <kb...@n1k.org> > To: Bob Stewart <b...@evoria.net> > Cc: Discussion of precise time and frequency measurement <time-nuts@febo.com> > Sent: Wednesday, May 3, 2017 10:48 AM > Subject: Re: [time-nuts] Three-cornered hat on timelab? > > Hi > > Dump it to a csv file and do it in Excel would be one way. You want to be able > to control the process a bit so that would give you the ability to tweak the > measurement. > > Bob > >> On May 3, 2017, at 11:01 AM, Bob Stewart <b...@evoria.net >> <mailto:b...@evoria.net>> wrote: >> >> Hi Bob, >> >> What I should have asked is this: "how do I get that from a Timelab >> dataset?" >> >> Bob >> >> >> From: Bob kb8tq <kb...@n1k.org <mailto:kb...@n1k.org>> >> To: Bob Stewart <b...@evoria.net <mailto:b...@evoria.net>>; Discussion of >> precise time and frequency measurement <time-nuts@febo.com >> <mailto:time-nuts@febo.com>> >> Cc: Tom Van Baak <t...@leapsecond.com <mailto:t...@leapsecond.com>> >> Sent: Wednesday, May 3, 2017 7:20 AM >> Subject: Re: [time-nuts] Three-cornered hat on timelab? >> >> Hi >> >> RMS: >> >> https://en.wikipedia.org/wiki/Root_mean_square >> <https://en.wikipedia.org/wiki/Root_mean_square> >> >> When we talk about things like “6 sigma” in QA, the sigma is the RMS. >> >> Bob >> >>> On May 3, 2017, at 1:44 AM, Bob Stewart <b...@evoria.net >>> <mailto:b...@evoria.net>> wrote: >>> >>> Hi Tom, >>> Could you clarify the term RMS? Is there some sort of calculation I need >>> to do on the raw data to get the RMS value? >>> I'm going to begin by doing a fresh 8 hour test of GPSDO Unit 1 vs GPSDO >>> Unit 2, with the same conditions as the tests involving the PRS. IOW, the >>> 5370 is being clocked by GPSDO Unit 2, and the trigger for the EXT input to >>> the 5370 is from GPSDO Unit 2. START is from GSPDO Unit 1 and STOP is from >>> GPSDO Unit 2. The ones I have on hand show about 4E-11 at 1s tau. >>> >>> After that, I'll run an 8 hour test of raw 1PPS from a LEA-6T against the >>> PRS. Since I don't really trust the PRS, I'll use GPSDO Unit 2 to clock >>> the 5370. If you really don't want the GSPDO to clock the 5370, I'll run >>> the same test using the internal 10811 as the clock, to compare the >>> difference. >>> >>> I also ran into an old test of the 5370 where START (10MHz) was fed by a >>> GPSDO and STOP (10MHz) was fed by the same GPSDO but with (I think) a 20 ft >>> cable from START to STOP. I'll probably want to rerun that, as well, but >>> it was an almost straight line from 2E-11 at 1s tau in that dataset. >>> Still, that test will verify that the 5370 hasn't degraded. Bob >>> >>> From: Tom Van Baak <t...@leapsecond.com <mailto:t...@leapsecond.com>> >>> To: Discussion of precise time and frequency measurement >>> <time-nuts@febo.com <mailto:time-nuts@febo.com>> >>> Sent: Wednesday, May 3, 2017 12:02 AM >>> Subject: Re: [time-nuts] Three-cornered hat on timelab? >>> >>> Hi BobS, >>> >>>> I've also made the timelab file (compressed by 7z) available here: >>>> http://evoria.net/AE6RV/Timelab/GFSvsCS.4.22.17.7z >>>> <http://evoria.net/AE6RV/Timelab/GFSvsCS.4.22.17.7z> >>> >>> Thanks for sharing that. To follow-up on recent emails... >>> >>> When you start to push the limits of your own test equipment it's good to >>> employ tricks such as 3-corner hat in order to get a few dB better >>> measurement. But there's a limit to that. And you probably don't want me to >>> suggest that you run 3 GPSDO, 3 counters and 3 cesiums all simultaneously. >>> >>> I've attached two plots showing 4+ days of your GPSDO data and 4+ days of a >>> TBolt (factory defaults, *untuned*) >>> >>> bob-gpsdo-3.gif -- Notice how much your GPSDO (blue trace) wanders all over >>> the place. >>> >>> bob-gpsdo-5.gif -- ADEV comparison. See below for comments. >>> >>> 1) >>> When I look at the ADEV for your data set it's pretty clear that the >>> limiting factor on the left (short tau) is the resolution of your 5370A >>> counter. That's why the TBolt looks better. Don't worry about that. >>> >>> 2) >>> In the middle of the ADEV plot it would appear that both your 5370A counter >>> and your PRS-45A cesium reference are sufficiently good to properly measure >>> your GPSDO. That's good. The TBolt looks bad in the middle but that's >>> simply because it was using a way-too-short default time constant. With >>> proper tuning the red trace would be mostly flat out to 1000 seconds. >>> >>> 3) >>> From the look of the phase plot and the ADEV plot it almost seems to me >>> like your PRS-45A is the limiting factor on the right (long tau). If so, it >>> would explain the lack of diurnal and sidereal effects in your data. If you >>> look at: >>> http://leapsecond.com/pages/tbolt-8d/sigma1.gif >>> <http://leapsecond.com/pages/tbolt-8d/sigma1.gif> from >>> http://www.leapsecond.com/pages/tbolt-8d/ >>> <http://www.leapsecond.com/pages/tbolt-8d/> >>> you'll note the sidereal "blip" is below 4e-14. Your ADEV doesn't get near >>> that level. >>> >>> >>> I say this because a rule-of-thumb is that a good M12+T timing receiver >>> should get you down to 3 ns per day RMS. And a good ublox-6T can get you to >>> 3 or 2 ns per day RMS. Your data shows something more like 5 ns -- which >>> for a GPSDO is worse than no GPSDO at all. So something's wrong. What set >>> of experiments can you perform to locate the problem? Or, what experiments >>> can you perform that don't require buying expensive gear? >>> >>> My first suggestion is for you run a standalone GPS timing receiver like a >>> M12+T or ublox-6. Put all your GPSDO away. Just use that OEM board, and >>> your TIC, and your PRS-45A. Collect sawtooth data too. You should get down >>> to 2 or 3 ns RMS. >>> >>> /tvb >>> >>> ----- Original Message ----- >>> From: "Bob Stewart" <b...@evoria.net <mailto:b...@evoria.net>> >>> To: "Discussion of Precise Time and Frequency Measurement" >>> <time-nuts@febo.com <mailto:time-nuts@febo.com>>; "Magnus Danielson" >>> <mag...@rubidium.se <mailto:mag...@rubidium.se>> >>> Sent: Thursday, April 27, 2017 9:48 AM >>> Subject: Re: [time-nuts] Three-cornered hat on timelab? >>> >>> >>> Hi Magnus, >>> Try as I might, the weather and the local power company had other ideas >>> about my long term capture. I'm running everything but the 5370 from a UPS. >>> I guess I'm going to have to get batteries for my other UPS and run the >>> 5370 from that. A one second power loss was all it took to stop the test. >>> >>> Anyway, I did manage to get 376,238 points of data. The data is captured on >>> a 5370A. The external clock input and the STOP channel are fed by the 10MHz >>> from my PRS-45A. The START channel is fed by the 10MHz from one of my >>> GPSDOs. The EXT channel is fed by the 1PPS from another of my GPSDO units. >>> "EXT ARM" is enabled. So, essentially, at every 1PPS pulse, the phase >>> difference between the two 10MHz feeds is captured. >>> >>> I've attached a screenshot of the phase plot which can also be found >>> here:http://evoria.net/AE6RV/Timelab/Screenshot.png >>> <http://evoria.net/AE6RV/Timelab/Screenshot.png> >>> I've also made the timelab file (compressed by 7z) available here: >>> http://evoria.net/AE6RV/Timelab/GFSvsCS.4.22.17.7z >>> <http://evoria.net/AE6RV/Timelab/GFSvsCS.4.22.17.7z> >>> >>> So, back to my question: Where are the large ionospheric phase moves? This >>> question has been causing me doubt since I started on this project. Or >>> don't I still have enough data collected for this to happen? >>> >>> Bob >>> >>> ----------------------------------------------------------------- >>> AE6RV.com <http://ae6rv.com/> >>> >>> GFS GPSDO list: >>> groups.yahoo.com/neo/groups/GFS-GPSDOs/info >>> >>> From: Magnus Danielson <mag...@rubidium.dyndns.org> >>> To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency >>> measurement <time-nuts@febo.com> >>> Cc: mag...@rubidium.se >>> Sent: Tuesday, April 18, 2017 1:09 AM >>> Subject: Re: [time-nuts] Three-cornered hat on timelab? >>> >>> Hi Bob, >>> >>> That is a good solution indeed. Good luck with that measurement run! >>> >>> One of the fun stuff with Timelab is that you can walk by and check the >>> developments. I've found that very useful for long measurements (as in >>> hours and days). >>> >>> I prepared a cesium for one vendor, and initially they did not care so >>> much, but then they saw more deviations between the receivers, so they >>> wanted to sort it out, but discovered that they could not cancel out the >>> common mode of GPS signals (and its shifts), so then firing up that >>> cesium was the right thing. I remember writing support emails while >>> waiting for the airplane in Madrid airport, happy that they was doing a >>> first run for the right measurement reason. :) >>> >>> Cheers, >>> Magnus >>> >>> On 04/18/2017 04:25 AM, Bob Stewart wrote: >>>> Hi Magnus, >>>> Today I started a long run against my PRS-45A. Maybe this time I won't >>>> have a power outage. I'll see what it tells me in a few days. >>>> Bob_______________________________________________ >>> 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.
