[time-nuts] Datum GPSDO up and running

Chris Albertson albertson.chris at gmail.com
Wed Jan 4 12:19:45 EST 2017

How to know if your 10MHz reference is accurate?    If you happen you
have a "known-good" 10MHz reference you compare your new one to the
old one.    But lacking and "old one" and any other sophisticated time
interval counters you can get a two channel oscilloscope and put your
10MHz signal on channel A and the a 1 pulse per second chanel on B and
observer the phase.  (where in the 10Mhz sine wave does the leading
edge of the 1PPS cut.    Watch his for some time, maybe for hours and
see the the phase is constant.   It is easy to "eyeball" a 45 degree

If the phase remains constant for 1 second the frequency is "good" to
one part in 10 million.  If it stays in phase for 100 seconds the the
frequency is 100x better and so on.

There might be better ways but this is easy to understand and do and
gives a level on confidence because "you see it with your own eyes".

But how do you know the 1PPS is accurate.   Ether just rust the GPS
that what it says "locked" is it locked or spend $15 and buy a second

On Tue, Jan 3, 2017 at 8:35 PM, J <info at epdac.com> wrote:
> Hello fellow time-nuts, newbie here with a couple of questions.......
> I hooked it up to a Datum Starloc II today. After a short delay I see this
> under DSP Mon:
>  My objective is to get an accurate 10MHz reference to drive a frequency
> counter, Spectrum Analyzer etc.
> Lady Heather is less cooperative, sometimes the GUI is mostly black ,
> while other times I get the following screen, however the clock is not
> updating
> My first question is how do I know when the GPSDO is actually disciplined,
> i.e. when can I trust the 10MHz output?
> There is a fair bit of displayd data on the above screens, some of it self
> explanatory and some of it not, I have not had a chance to read the LH
> manual yet, any obvious tips for getting it up and running with a Starloc
> II?
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Chris Albertson
Redondo Beach, California

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