[time-nuts] DPLL for 10MHz

[EWKehren at aol.com]

I am patiently waiting for the code to drive the DAC.
Bert Kehren
 
 
In a message dated 5/7/2012 12:54:54 P.M. Eastern Daylight Time,  
attila at kinali.ch writes:

On Mon,  7 May 2012 10:30:56 -0500
Bill Dailey <docdailey at gmail.com>  wrote:

> Does anyone have any knowledge of a simple (just soldering  a
> few connections and maybe programming a hz/volt rate) PCB  for
> synchronizing a precision OCXO to a GPSDO?  I am trying to  improve
> short term stability with a high stability OCXO and dont want  to
> "cut into" my fury and replace the OCXO.  I cando it manually  but
> this seems like it would be nice and desirable for many yet I  can't
> find anything.  I presume it would have to be digital  because of the
> long time constant.

What speaks against a simple  design as used in the GPSDO by James 
Miller[1]?
Or if you want a better PLL  than just an XOR gate, use a 74x4046.
They are still available in DIL, so  building a complete PLL is possible
on a veroboard. This should be enough  if you want to improve the short
term stability below 0.1s, where the fury  rises above it's long term humb.

If you want to flatten down the humb  the fury has (the one between a tau
of 1s and x*1000s), then you need a  very stable OXCO to begin with.
Also, then i think the best approach would  be to scale down both
signals to 1kHz and use a PICTIC II to measure the  phase difference
between them. Then you can implement the control loop in  the PIC of
the PICTIC II and drive an _external_ DAC with it.

Attila Kinali


[1]  http://www.jrmiller.demon.co.uk/projects/ministd/manual.pdf
-- 
Why does  it take years to find the answers to
the questions one should have asked  long ago?

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