Hi A good OCXO run continuously should get down to < 0.1 ppb / week. Doing a tweak every Saturday is likely enough to keep it in that range. The *big* advantage is that you have the ADEV of the OCXO without any scruffy stuff from the control loop getting in the way. If your objective is to run something like a frequency counter, you probably are better off with the trimmed OCXO.
Bob > On Mar 20, 2017, at 5:26 PM, Mark Spencer <m...@alignedsolutions.com> wrote: > > Hi: > > Bob's comment about adjusting an oscillator from time to time aligns well > with my limited experience in the time nuts hobby. Once I realized that in > practice my better OCXO's were typically more than stable enough for my > intended uses things became much simpler. I also realized that I could > utilize my collection of time interval counters to compare my chosen > reference to other references (including a GPSDO) while also comparing the > chosen reference to the "Device Under Test." I realize this isn't likely an > approach that a commercial lab would use but for my hobby use it seems to > work ok for me. > > I've more or less shelved my plans to discipline one of my high end OCXO's > via a home brew GPSDO scheme. > > Mark Spencer > > >> On Mar 14, 2017, at 5:24 PM, Bob Camp <kb...@n1k.org> wrote: >> >> Hi >> >> >>> On Mar 14, 2017, at 6:33 PM, Tim Lister <lister...@gmail.com> wrote: >>> >>> On Fri, Mar 10, 2017 at 2:35 PM, Chris Albertson >>> <albertson.ch...@gmail.com> wrote: >>>> A GPSDO is not hard to make. All you need is some way to compare the >>>> phase of two signals, an XOR gate can do that. Then a small $2 >>>> process moves the control voltage on the crystal. I tried one to >>>> build the simplest GPSDO that could still work. Got the parts count >>>> down to about four or five and the cost well under $10 plus the OXO >>>> which was about $20. The simplest dumb one I could make keeps about >>>> e-10. Not great but enough for many uses. I compared to my >>>> Thunderbolt and I could see the phase advance and retreat. Just a >>>> little most sophistication and I likely could do much better but my >>>> goal was to prove to myself that a GPSDO could be build VERY simply >>>> with cheap parts >>> >>> Hi Chris, that's good news that a GPSDO is that easy to make (at least >>> a basic one) as that is exactly my medium term plan ! >> >> Actually it’s much easier. Just put a DVM on the XOR once a week and >> adjust your oscillator with a screwdriver. It saves *lots* of time and money. >> >> Bob >> >> >>> The issue of >>> course is having something to test the newly built GPSDO against... I >>> got one of the rehoused Trimble UCCM-based GPSDOs off ebay a while ago >>> but haven't been super happy with it. It's quite a bit less sensitive >>> than more modern GPS receivers and it often struggles to get even 1 >>> satellite with the indoor patch antenna. At one point both red alarm >>> LEDs came on and stayed on despite power cycles - I eventually fixed >>> that by taking it apart and finding and hitting a reset button on the >>> board. Currently although I can talk to the unit over serial and it >>> seems to respond, Lady Heather is not seeing any output from it. >>> >>> Combined these things don't give me a great deal of confidence that >>> this unit will act as a stable master reference. I was wondering if a >>> second GPSDO like Russ linked to would work better (I have a ublox >>> LEA-6T GPS already which I plan to use as the basis of the homebuilt >>> GPSDO and it consistently sees many more satellites than the UCCM >>> with a similar indoor antenna) or put the money to getting an outdoor >>> antenna mounted (don't feel happy drilling holes in the house myself) >>> by someone. Do 2 GPSDOs tell you much more or just that each is >>> different and you need a third to adjudicate ? (I can see a slippery >>> slope looming from here...) >>> >>> Cheers, >>> Tim >>> _______________________________________________ >>> 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.