[time-nuts] Frequency reference

[Didier Juges]

> Attila Kinali <attila at kinali.ch>, on Sun 20 Apr 2008 
> 05:50:21 AM PDT:
> 
> > On Thu, 17 Apr 2008 08:47:48 -0700 (GMT-07:00) "Richard W. Solomon" 
> > <w1ksz at earthlink.net> wrote:
> >
> >> You can build a very good GPSDO for about $100 in parts.
> >
> > Stupid question, but if one builds his on frequency 
> reference, how can 
> > you be sure it's acurate and precise?
> 

If you track the correction voltage of a GPSDO over time and compare it to
that of a comparable GPSDO (there is plenty of data to compare to on Tom Van
Baak's web site leapsecond.com), you gain some confidence that your unit is
performing comparably. Since GPS is referenced to UTC (maybe not from a
metrology standpoint, but good enough for most other applications), it is a
standard by and of itself.

For very basic frequency standard, other reference frequency signals are
available over the air (WWV, DCF, Loran and other), but of those, only Loran
would qualify as a time standard, the others are at best frequency standards
because of the variation in propagation that are difficult or impossible to
compensate for HF/LF signals.

Now, this is time-nuts, so monitoring this mailing list for a while will
show you that there is much more than meet the eyes.

Didier

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