To Luis' point....ye ol' HP-8640 is a FLL sig gen. You can hear the "wobble" or shifts in freq/phase if you press the lock button and listen to the output on a good VHF or UHF receiver. Much better to use un-locked for non-timenut RF work! :-)
-Brian, WA1ZMS --- On Tue, 5/3/11, Luis Cupido <cup...@mail.ua.pt> wrote: > From: Luis Cupido <cup...@mail.ua.pt> > Subject: Re: [time-nuts] Darn you people.... > To: "Discussion of precise time and frequency measurement" > <time-nuts@febo.com> > Date: Tuesday, May 3, 2011, 1:14 PM > 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 -- 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.