Ah, yes, now I see: you suggest to keep track of the FOM and DOP from message #21 and move the oscillator to minimize them. Interesting and doable.
Interesting, as usual, the references by Attila: I'm searching for the book by Roland E. Best. On Sat, Mar 10, 2012 at 3:59 PM, Attila Kinali <[email protected]> wrote: > On Sat, 10 Mar 2012 14:07:33 +0100 > Filip Ozimek <[email protected]> wrote: > > > could you recommend me a good project of GPS-DO? I've got a GPS module > > with 1PPS output and a 20 MHz VCXO. > > As I understand to do a phaselock to 1 PPS signal one must build some > > kind of digital PLL. But I'm not sure > > how to calculate a correction signal to the VCXO and how to test such > > a disciplined oscillator. > > Start with reading the following documents: > > [1]: > James Miller's GPSDO based on a 10kHz output of an Jupiter GPS unit. > It is by far the most simple system i've seen sofar. It's mostly analog > (beside the dividers) and uses a XOR based PLL for the FEC generation. > > [2]: > A GPSDO around a PIC16C73 from Brooks Shera. It is basically what you > want to do. > > [3]: > A GPSDO that is based on an FLL (frequency locked loop) by Betrand Zauhar. > Similar to the one above, but because it's using an FLL instead of an > PLL it has a slight frequency offset (instead of a slight phase offset) > > You also want to read: > "Phase-Locked Loops" by Best. > The best book on PLL's i've found. Explains everything you need to know. > > [4]: > The PICTIC as an example how to build a time interval counter that is > good to <1ns (see [5] for information on PICTIC performance). > > Depending on the stability and accuracy you want to accheive, it might > also be possible to use one of the modern uCs that run with >100MHz > clocks and use its internal timer as TIC. It will give you an measuremnt > accuracy better than 10ns, which is in the range of the width of a good > timing GPS receiver (see [6]), this would simplify your circuitry > quite considerably. > > Over the past years, there have been numerous discussions on GPSDOs > on this mailing list. I suggest you walk trough the archives and > read some of them. > > > HTH > > Attila Kinali > > [1] http://www.jrmiller.demon.co.uk/projects/ministd/manual.pdf > [2] http://www.rt66.com/~shera/QST_GPS.pdf > [3] > http://ve2zaz.net/GPS_Std/Downloads/VE2ZAZ_GPS_Derived_Std_QEX_09_10_2006.pdf > [4] http://www.ko4bb.com/dokuwiki/doku.php?id=precision_timing:pictic > [5] http://www.ke5fx.com/pictic.htm > [6] > http://www.u-blox.com/images/downloads/Product_Docs/Timing_AppNote_(GPS.G6-X-11007).pdf > > > -- > 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.
