Luis, You said: <<Furthermore the frequency counting resolution is 16 seconds, so the ZAZ gpsdo won't lock better than 0.0625Hz.>>
On my GPSDO design, a single 16-second frequency sample does have a resolution of 0.0625Hz. But the FLL firmware does averaging over as many samples as you want before adjusting the OCXO. So I don't agree with your statement that the ZAZ gpsdo won't lock better than 0.0625Hz. In fact, I have never seen my design go worse than 1x10E-9. It usually sit below 5x10E-10. This concurs with the many reports I got from other users. Please elaborate. Thanks, Bert, VE2ZAZ Message: 3 >Date: Tue, 03 May 2011 18:14:30 +0100 >From: Luis Cupido <[email protected]> >To: Discussion of precise time and frequency measurement > <[email protected]> >Subject: Re: [time-nuts] Darn you people.... >Message-ID: <[email protected]> >Content-Type: text/plain; charset=ISO-8859-1; format=flowed > >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. > > _______________________________________________ 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.
