[time-nuts] TCVCXO Adjustment

[Bob kb8tq]

Hi

If you have a GPS on your local lan, just use it for the calibration. There’s no need for NTP
to get involved.

If you are running NTP over a normal home setup going to the internet, then you will be doing
very well to get low ms with NTP. 

Going back to the original post, the request is for a method to calibrate a newly assembled board. 
Since we are talking about a generalized calibration procedure, simply saying “use NTP” without 
mentioning setting up a LAN / GPS NTP empire seems to be a bit misleading. That is a very 
unique system that the vast majority of the world would not be using. 

Bob

> On Apr 13, 2018, at 2:18 PM, David J Taylor via time-nuts <time-nuts at febo.com> wrote:
> 
> Hi
> 
> NTP will give you “millisecond" level accuracy / stability. If you want to set an
> oscillator to 0.1 ppm, you will need to run for over 10,000 seconds. It is not
> uncommon to have things out in the 10 ms range. That would put you at
> 100,000 seconds. In more common units, a couple of hours to > 1 day
> would be needed.
> 
> Keep in mind, this is for a single observation. If you need to make three or four
> tweaks to get things set, the numbers would go up a bit.
> 
> The earlier mentioned GPS approach with a $10 USB dongle would do it a *lot*
> faster. More or less, you could expect a bit better than a 1000:1 speed
> improvement.
> 
> Bob
> ==================================
> 
> With respect, NTP using a GPS/PPS clock can give tens of microseconds or better, even on a Raspberry Pi.  For example:
> 
> http://www.satsignal.eu/mrtg/raspi1_ntp.html
> 
> (The slight downward slope back over time is an artefact of MRTG with small integers.)
> 
> Cheers,
> Davis
> -- 
> SatSignal Software - Quality software written to your requirements
> Web: http://www.satsignal.eu
> Email: david-taylor at blueyonder.co.uk
> Twitter: @gm8arv 
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