Attila, > An ADEV plot would be much more informative on the stability.
I have found an old publication from former PTB researcher Dr. Peter Hetzel. This publication holds a diagram which (while not being exactly an ADEV plot) holds some interesting information on the topic: It shows the STANDARD DEVIATION of timing measurements made on DCF77's signal abt. 273 km away from the transmitter location as a function of the averaging time of the measurements. So no ADEV but coming close... The diagram starts at abt. 8E-8 std dev for 1 s avaraging time and is basically a straight line with a slope of abt. -0.8. that extends to 7E-14 for averaging times of 100 days. I list a few values: 8E-8 @ 1 s 1E-9 @ 10 s 2E-10 @ 100 s 5E-11 @ 1000 s 2E-12 @ 1 d 3E-13 @ 10 d 7E-14 @ 100 d The diagram has no log sub scale so the readings are my estimate. The diagram hold a lot of individual points between 10 and 100 days averaging time indicating that a lot of measurements with that averaging times have really been done. Best regards Ulrich Bangert > -----Ursprungliche Nachricht----- > Von: [email protected] > [mailto:[email protected]] Im Auftrag von Attila Kinali > Gesendet: Donnerstag, 14. Juni 2012 07:56 > An: Discussion of precise time and frequency measurement > Betreff: Re: [time-nuts] Paper about DCF77 performance > > > Hoi Dani! > > I see you've found the time-nuts as well :-) > > On Wed, 13 Jun 2012 21:46:56 +0200 > Daniel Engeler <[email protected]> wrote: > > > This is my first post to this mailing list. I wrote a paper > about the > > German longwave time transmitter DCF77 which you may find > interesting. > > Here is the link, unfortunately I am not allowed to post > the full PDF: > > There is an easy way to get around that: Prepare a second > paper with more data in it (all that stuff that IEEE tends to > get rid of during the publication process) and put that onto > your website. > > > > http://ieeexplore.ieee.org/xpl/articleDetails.jsp?tp=&arnumber=6202411 > > > > "Performance Analysis and Receiver Architectures of DCF77 > > Radio-Controlled Clocks", by Daniel Engeler IEEE Transactions on > > Ultrasonics, Ferroelectrics and Frequency Control (May 2012) > > Nice paper. I haven't had time to read it yet, but a few > comments after i skimmed it: > * you have a lot of simulation and measurments on BER vs SNR. > For time-nutty needs that's not so relevant. An ADEV plot > would be much more informative on the stability. > * Also some data on the absolute timing variations vs time > would be nice to have. > * Fig 23 shows a very complex board. Given that you only have > a relatively simple analog stage and an FPGA i wonder what > the rest is for. > * You use an LTC1562 8th order bandpass: Do you compensate > for it's frequency dependend delay and its variation? Or is > negligible compared to the antenna? > * Do you do any temperature stabilization? > * What kind of reference oscillator do you use? > * You talk about 20 to 50ppm variations for XO's, are you > aware that these are maximum variation including production > variabiltiy and that the stability of an good XO is usually > in the range of a few ppm in office conditions (i've measured > an XO in a PC that showed a long term (months) stability in > the ppb range) > * Why did you use an FPGA and not a simple DSP or one of the > more powerfull uC's like an Cortex-M3/4? The algorigthms > don't look computationally intensive. And that would simplify > the development considerably. > * Where did you do your measurements? In Schlieren? > * What is the application you had in mind while developing this? > > > Attila Kinali > -- > Why does it take years to find the answers to > the questions one should have asked long ago? > > _______________________________________________ > 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. _______________________________________________ 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.
