[time-nuts] Hanging bridge question

[EWKehren at aol.com]

The lowest cost solution is a DS chip in combination with a PIC. How ever  
has any one thought about a fix by going to the source of the problem. The 
TCXO.  Use a DDS with internal multiplier like the AD9851 or AD 9913 and use 
the  sawtooth message from the GRS receiver and change the frequency. An 
other  alternative would be to use the sawtooth word to fine tune a TCXO or any 
VCXO  for that matter.
Bert Kehren
 
 
In a message dated 3/25/2014 7:28:11 A.M. Eastern Daylight Time,  
phk at phk.freebsd.dk writes:

In  message <6B362A4D-834A-4733-BED8-FCFEC0CCBA6C at rtty.us>, Bob Camp  
writes:

I should add here, that you _can_ do a little bit better than  the
sawtooth correction.

We know, or at least assume, that the GPS's  internal clock is step-less
and slowly changing, so if you put a predictive  filter on this stuff,
it can actually do a reasonable job at estimating  which way the rounding
of the sawtooth correction went (since it is  integral ns).

This reduces the random rounding error on the sawtooth  correction
from +/- 0.5 ns to something like +/- 0.3 ns.

Totally not  worth it, but a cool and educational project :-)

-- 
Poul-Henning  Kamp       | UNIX since Zilog Zeus  3.20
phk at FreeBSD.ORG         | TCP/IP since RFC  956
FreeBSD committer       | BSD since 4.3-tahoe   
Never attribute to malice what can adequately be explained by  incompetence.
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