On Sat, Mar 10, 2012 at 5:07 AM, Filip Ozimek <me_su...@o2.pl> 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. THe references you got were good. But if you are looking for the big picture, it's simple. There are many methods but they are all much alike if you step back and look at what's really going on. What you need is a digital signal line that goes high on the leading edge ofht e PPS and then goes low on the next leading edge of the VCXO. Then you build a controller to keep the time signal is high at a constant. You can use a time to voltage converter and be 100% analog or you can go digital. The first thing you need is a divider. 20MHz is kind of fast. you might even go for a divide by 20. then your controller sees a more manageable 1Mhz. If the vxco is not ultra stable it is best to divide it down quite a bit. I assume this project is just for education and entertainment. If you really need a GPSDO in your llab it is cheaper and simpler to buy a Thunder both from eBay. You can buy one for many $120 and they are hard to build at that price. Chris Albertson Redondo Beach, California _______________________________________________ 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.