[time-nuts] Time nut newbie

Mark Spencer mspencer12345 at yahoo.ca
Wed May 1 13:27:53 EDT 2013

Hi, Tim:

For what it is worth I've been down a similar road using various crystal controlled lab frequency standards to drive internet time servers.   (I'm more of a plug and play person these days.)    Some of these lab standards feature external DC power inputs and have a fairly low power drain.    After running for a month my time server that uses an old (and probably very well aged) HP105B crystal standard as a reference is off by approx 1/100 of a second (it's hard to tell when looking at it via the internet.)   At first I synchronized the time server with a 1pps signal from a GPS receiver, then I removed the 1pps signal and the let the time server free run using the HP105B as the time base.
If you want to focus on building the clock vs building the reference some of the old crystal standards might be worth looking at and using a 1pps source from a GPS to initially sync your clock may be worth looking at as well.   I'd be curious to hear what your longer term results are.
You might also want to take a look at the 
http://tapr.org/kits_t2-mini.html  for ways of converting the output of an OCXO to a 1pps pulse and syncing the pulses to an external source.
Best regardsMark S
Message: 7
Date: Wed, 1 May 2013 09:45:06 +0200
From: Attila Kinali <attila at kinali.ch>
To: Discussion of precise time and frequency measurement
    <time-nuts at febo.com>
Subject: Re: [time-nuts] Time nut newbie
Message-ID: <20130501094506.966146722efbbaf9c80e5aca at kinali.ch>
Content-Type: text/plain; charset=UTF-8

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
The people on 4chan are like brilliant psychologists
who also happen to be insane and gross.
        -- unknown

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