If you have a small canned VCXO, thermal performance will not be as good as an OCXO like the HP10811, so the optimum time constant of the filter will not be very long, and the analog solution is more practical.
You may want to look at the James Miller design. He uses a Jupiter GPS receiver which has a 10kHz output, and a good quality OCXO, but if you add the necessary dividers to change the comparison frequency to 1Hz, and resize the filter accordingly, it will still be the simplest design around. Using a VCXO instead of an OCXO will give you only modest performance, but it will be an interesting test bed for experimentation. You may be tempted to put the VCXO in a home made oven, but that is unlikely to work very well because the VCXO has probably been designed to have minimum temperature sensitivity around 25 degrees, so running it at a higher temperature may not give you all the improvement you expect, unless the oven is very very good. That by itself is also quite a project. Didier KO4BB ------Original Message------ From: Filip Ozimek Sender: time-nuts-boun...@febo.com To: Time-Nuts ReplyTo: Time-Nuts Subject: [time-nuts] DIY GPS-DO Sent: Mar 10, 2012 7:07 AM Hello, 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. Filip. _______________________________________________ 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. Sent from my BlackBerry Wireless thingy while I do other things... _______________________________________________ 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.
