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.