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

Todd Eddy vr at vrillusions.com
Tue Dec 11 23:19:07 EST 2007

Bruce Griffiths wrote:
> 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.

It was the inverting gate that was throwing me off as I've never come
across it before. After doing a lot more searching and realizing what
exactly that inverting gate does the circuit makes a lot more sense now.

> 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.

My thought was using the ntp servers for that, since that will get the
signal withing a couple msecs of the time, then use the pps output to
get it even more accurate from there.  Kinda like one of the ways to
interface with the gps receiver that it only gets the PPS signal and not
the time.  Kinda ugly, but you got to start somewhere.  I'll probably
end up getting a gps receiver since there's lots of documentation on
that and I can mess with it at home, or maybe convince work to let me
drill a hole in the roof :)  Thanks the much simpler diagram though.

> 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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