Dave Tweed <pic@DTWEED.CounterSpam.COM> wrote;
>j galt <galt_57@HOTMAIL.Take.This.Out.COM> wrote:
> > Yes there will be jitter but you don't improve things by adding
> > even coarser amounts of jitter.
>
>Have you ever heard of the concept called dithering? It doesn't
>harm things, and it often improves the statistics of the signal
>considerably...

Do you know of a reference which suggests dithering the input of a PLL? I
think I just misunderstood the approach that this design used. The 1PPS
signal does not go to the PIC interrupt. The output of the HCT4046 phase
detector goes to the PIC interrupt input, which makes much more sense.

> > And how do Brooks and others determine whether their GPSDO's > are
>working properly? Who has NIST class reference sources...
>
>Anyone with a shortwave receiver. Even though the signals from WWV et al
>have lots of short-term jitter and wander, and even an unknown constant
>time offset, the long-term frequency accuracy is directly traceable to
>NIST.

Sounds interesting but the QST article dismisses this method. How about the
NTSC color burst? Does anyone remember that being suggested as a calibration
source?

>And of course, you can always compare your disciplined clock with the raw 1
>pps pulses from the GPS receiver.

From my reading of the article you can look to see if the curve of the
correction voltage matches that which would be expected to correct crystal
aging.

Now what I would like to know is what are the most common and most
interesting applications for such a precision frequency reference?


_________________________________________________________________
The new MSN 8: advanced junk mail protection and 2 months FREE*
http://join.msn.com/?page=features/junkmail

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics