I wasn't aware of the phase of the 1pps vs the 10mhz, I was just shocked to find the two were indicating as locked yet drifting apart to the tune of 6hz/minute. I'd be happy if the two were within 0.0625 hz. As I think I said, the ZAZ gpsdo unlocked shortly thereafter. Mine seems to have a hard time keeping the FLL locked and I suspect an issue with the 10881.
Was surprised to see the phase difference between the 10Mhz outputs of the ZAZ controller however. Bob On Tue, May 3, 2011 at 1:14 PM, Luis Cupido <[email protected]> wrote: > Bob, > > You must be aware that the VE2ZAZ GPSDO does not lock the 10MHz phase to the > phase of the 1pps. It is a frequency counter which uses the frequency error > to correct the 10MHz VCXO. So it is a frequency locked loop FLL. > > By definition on a PLL you will have the phase error being used to > compensate the 10MHz VCXO > On a FLL a frequency error is required to compensate the 10MHzVCXO > > While having a permanent very very slow OCXO trend (drift or aging) > a PLL(order 2) will exhibit a constant phase error while the frequency is > right. With an FLL it will have a constant frequency error. > > Furthermore the frequency counting resolution is 16 seconds, so > the ZAZ gpsdo won't lock better than 0.0625Hz. > A PLL scheme, thunderbolt, the old Brook Shera's, the 10KHz James Miller's, > or my reflock (I or II) will get you always on the ballpark. > > > This PLL/FLL aspect is a subtle difference that has absolutely no expression > whatsoever for radio-ham applications both TX and RX on HF to microwaves > etc. application to which it was targeted and serve very well. > > > But you will surely start to see these small aspects when you step into the > next level of timenutness !!! > Apparently you have both feet there... looking at sub Hz you're infected > that's a fact ;-) > > > Luis Cupido. > ct1dmk. > > > > > > Bob Bownes wrote: >> >> First it was building a VE2ZAZ GPSDO with an 10881 I happened across. >> Next came the TICII's followed closely by the 5370B. Then the >> thunderbolt. Now it's time to break down and get 10Mhz/5Mhz >> distributed to all the instruments in the lab. (Still looking for a >> distribution amp) >> >> Now the ZAZ GPSDO and the thunderbolt are side by side on the bench. >> Both said they were locked last night. But they were about 0.10hz >> apart. Now the GPSDO voltage adjust is all the way to the bottom rail. >> >> I have no idea what time it is! >> >> Grrr. :) >> >> I suspect the 10881. :( >> >> _______________________________________________ >> 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. > _______________________________________________ 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.
