[time-nuts] Darn you people....

Brian Justin wa1zms at att.net
Tue May 3 17:28:53 UTC 2011


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 <cupido at mail.ua.pt> wrote:

> From: Luis Cupido <cupido at mail.ua.pt>
> Subject: Re: [time-nuts] Darn you people....
> To: "Discussion of precise time and frequency measurement" <time-nuts at 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 at 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 at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
> 



More information about the time-nuts mailing list