[time-nuts] Using a Vectron OCXO 5mhz oscilator with ntpd

[Bruce Griffiths]

Todd Eddy wrote:
> I'm still pretty new to the whole time keeping thing.  Currently I just
> run an ntp server for the ntp pool.  I've been looking at some ways to
> get direct reference but without being expensive.  Only thing I've seen
> within my budget so far is the garmin gps receivers that people like.
> Problem is the server is in a high security colo center and I doubt they
> would let me drill a hole in the roof to put a gps receiver.  I have
> started to see this 5mhz frequency quartz oscilators that are really
> inexpensive (see
> http://www.alltronics.com/cgi-bin/category.cgi?item=04P010 ).  My
> question, how would you get this to work with ntpd?  Seems like it work
> great for my situation where I can just put inside the rack behind the
> server, use some ntp servers to get the time to within 1 msec usually
> and then use this to get into the nanosecond accuracy.
>
> Only information I've looked at so far in using direct reference is
> looking at the gps receivers.  I did find information about using a
> "clock shaper" to convert the oscillator to a digital pps signal (see
> http://www.ko4bb.com/Timing/ClockShaper.html ) but that first one just
> looks really cryptic to me with knowing very little in the way of
> electronics.  Has anyone made one of these and made a more "dumbed down"
> writeup on how to set it up?
>
> I've tried scanning a few months back in the archives and only really
> came accross the above mentioned site.  Anyone have any other resources
> I can look into?  Thanks.
>   
Todd

The first clock shaper is about the simplest reasonably high performance
clock shaper that can be devised.
However your application doesnt actually require a particularly high
performance clock shaper, you could use an inverting gate with a
resistor connected between its input and output plus a capacitor to
couple the sinewave into its input as illustrated in the attached
schematic. Its difficult to get much simpler than this.

By itself, even dividing down a 5MHz crystal to produce a PPS output
(which could be used to sync an ntp) isnt a great deal of use without a
means of syncing the generated PPS output to UTC.
You could use the 5MHz signal together with a small synthesizer board to
replace the crystal on the PC motherboard, however all this does is
improve the stability of the PC  timebase. You still have the
synchronisation problem.

If you are really new to electronics then it would be better to buy an
already debugged  system, there are no shortcuts  to learning sufficient
about electronics, you have to read the books and build /debug real
circuits.

Bruce
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