Gentlemen, i have to correct myself: The pre-filter's time constant is 1/6 of the pll time constant and not 1/3 as i stated before. Sorry for that!
Best regards Ulrich Bangert > -----Ursprungliche Nachricht----- > Von: time-nuts-boun...@febo.com > [mailto:time-nuts-boun...@febo.com] Im Auftrag von Ulrich Bangert > Gesendet: Samstag, 31. Marz 2012 14:49 > An: 'Discussion of precise time and frequency measurement' > Betreff: Re: [time-nuts] CW12-TIM vs M12M and the world > > > Bert, > > sometimes a manual can be a true treasure chest! Just > download the PRS-10 manual at > > http://www.thinksrs.com/downloads/PDFs/Manuals/PRS10m.pdf > > and find starting on page 13 the complete instructions on how > to build your own GPSDO. A basic knowledge of math, > programming and control theory is needed to understand the > manual but then: It works. I have constructed my mown DIY > GPSDO on the base of the information that I have found there, > including the pre-filter. > > Best regards > Ulrich > > > -----Ursprungliche Nachricht----- > > Von: time-nuts-boun...@febo.com > > [mailto:time-nuts-boun...@febo.com] Im Auftrag von ewkeh...@aol.com > > Gesendet: Samstag, 31. Marz 2012 13:46 > > An: time-nuts@febo.com > > Betreff: Re: [time-nuts] CW12-TIM vs M12M and the world > > > > > > Ulrich > > can you tell us more about your pre filter? > > Thank you > > Bert Kehren > > > > > > In a message dated 3/31/2012 6:23:49 A.M. Eastern Daylight Time, > > df...@ulrich-bangert.de writes: > > > > Thomas, > > > > > Has anyone compared the M12M to the M12+? > > > > I have done some measurements on the M12+ with typical > > results as shown in > > > > http://www.ulrich-bangert.de/M12Performance.jpg > > > > The red line is the raw phase data of the M12's PPS against > > a PPS derived from a local FRK-L rubidium. Note that you do > > not observe an overall difference frequency (and a resulting > > drift in phase) because the FRK-L is disciplined by the GPS. > > The blue line is the sawtooth corrected phase data and it > > becomes immediatly clear HOW IMPORTANT applying the > > correction is. The yellow line show you what happens if the > > sawtooth corrected phase data is sent through a pre-filter > > (lowpass with 1/3 the time constant of the > > main > > pll loop) before entering the loop itself. That is something > > that I learned from the PRS-10 manual. You may decide on > > your own which data you would > > like > > to work on in a GPSDO. > > > > Best regards > > Ulrich Bangert > > > > > -----Ursprungliche Nachricht----- > > > Von: time-nuts-boun...@febo.com > [mailto:time-nuts-boun...@febo.com] > > > Im Auftrag von Tom Knox > > > Gesendet: Freitag, 30. Marz 2012 22:19 > > > An: Time-Nuts > > > Betreff: Re: [time-nuts] CW12-TIM vs M12M and the world > > > > > > > > > > > > Has anyone compared the M12M to the M12+? > > > Thanks for all the input, it is really appreciated. > > > best wishes; > > > Thomas Knox > > > > > > > > > > > > > CC: time-nuts@febo.com > > > > From: saidj...@aol.com > > > > Date: Fri, 30 Mar 2012 09:53:17 -0700 > > > > To: time-nuts@febo.com > > > > Subject: Re: [time-nuts] CW12-TIM vs M12M and the world > > > > > > > > Hello Ed, Azelio, > > > > > > > > We should also compare the same parameters. Sawtooth error > > > of the m12+ > > > > of +/-25ns is not its standard deviation, it's max/min. > > > Compare that > > > > number to your 30ns max/min measurement on the 5372a. > > > > > > > > Standard deviation of the m12+ is around 2ns with > > correction. That > > > > needs to be compared to the 5ns you measure on the 5372a > > as that is > > > > the best performance you will get from the CW12. Yes the > > > uncorrected > > > > 1pps of the m12 is worse, but it is designed to be used with > > > > correction. So in the end the m12m still performs better > > than the > > > > CW12. > > > > > > > > Bye, > > > > Said > > > > > > > > Sent From iPhone > > > > > > > > On Mar 29, 2012, at 1:56, Azelio Boriani > > <azelio.bori...@screen.it> > > > > wrote: > > > > > > > > > We (that is my company) use the CW12-TIM (NMEA version) and > > > its PPS > > > > > wonders as usual, nothing different from a uBlox LEA-5T > > > or the M12M. > > > > > > > > > > On Thu, Mar 29, 2012 at 9:32 AM, Hal Murray > > > > > <hmur...@megapathdsl.net> wrote: > > > > > > > > > >> > > > > >>>> The sawtooth error on the Motorola M12+ is about +/- > > > 25ns, while > > > > >>>> the CW12-TIM has a sawtooth error of +/- 2 ns, so > > > correcting for > > > > >>>> the sawtooth error is not as critical with the CW12-TIM. > > > > >> > > > > >>> The first claim > > > > >>>> The sawtooth error on the Motorola M12+ is about +/- 25ns > > > > >>> is correct but are you absolutely sure that the > > second claim is > > > > >>> correct too????? > > > > >> > > > > >>> It would mean a factor >10 improvement of the CW12-TIM > > > against the > > > > >>> M12 > > > > >> which > > > > >>> is hardly believeable. > > > > >> > > > > >> The 25 ns probably comes from period of the the free > > > running clock > > > > >> they are using. It doesn't seem unreasonable to me > > to get 10x > > > > >> better if they use a GPSDO for the local clock so they > > > can get the > > > > >> PPS edge right where they want it. > > > > >> > > > > >> > > > > >> > > > > >> -- > > > > >> These are my opinions, not necessarily my employer's. I > > > hate spam. > > > > >> > > > > >> > > > > >> > > > > >> > > > > >> _______________________________________________ > > > > >> 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. > > > > > > _______________________________________________ > > > 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. > > > _______________________________________________ > 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.