[time-nuts] Time nut newbie

Attila Kinali attila at kinali.ch
Wed May 1 03:45:06 EDT 2013


On Tue, 30 Apr 2013 13:49:43 -0400
"Tim Bastian"<n714x at yahoo.com> wrote:


> I'm a time nut newbie. My obsession started with the search for an accurate chronometer to carry on my boat for celestial navigation. Yes there still are a few of us left that practice the art.
> 
> My current project is a quartz chronometer using a DS32Khz tcxo oscillator and two 74HC4060s (+ or- 10 seconds / year).  
> 
> For my next project I'm looking at an Abricon Part Number AOCJY2-10.000MHZ  ocxo 5 ppb running through a pic and using the algorithm posted on http://www.romanblack.com/one_sec.htm. I'm shooting for + or - 1 seconds / year.  
> 
>  Is there an archive of old posts that might be helpful in answering some of my questions and for getting ideas. 

You want to read Vig's Quartz Crystal Tutorial. That explains a lot about
where the instabilities of a crystal oscillator come from. You can find
them (and a lot more) on http://www.ko4bb.com/ in the Manuals section.
Have a look at different versions, as some interesting things were left
out in the newer versions.

An idea how to get to the stability you want without wasting too much
power might be an MCXO. [1] gives a pretty decent overview of the way how
they work including a schematic for an oscillator. [2] has some ideas how
to simplify the circuit and get lower power.

In your case, i guess it would be an idea to leave out the second stage
frequency generation (the VCO or DDS) and generate a PPS directly from
the microcontroller.

			Attila Kinali


[1] "A microcomputer compensated crystal oscillator using a
dual-mode resonator", by Benjaminson and Stallings, 1989

[2] "An Improved Method of MCXO", by Zhou, Liu, Wang, 2000
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