[time-nuts] Thunderbolt GPSDO

John Miles jmiles at pop.net
Wed Feb 14 01:28:14 EST 2007

To answer the original question, a Thunderbolt or similar GPS standard is
MORE than capable of telling you if it is working properly.  There is no
reason to use more than one of them at a single location.  The Trimble
software will tell you how many nanoseconds the 1-PPS output is off, and how
many parts per billion the 10-MHz output is off, compared to what GPS says
they should be.  And there are numerous diagnostic alarms that are monitored

It is a plug-and-forget device, except that you do want to set the saved
location and environment (trees, fixed/mobile, etc.) properties when you
install it.

-- john, KE5FX

> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
> Behalf Of Didier Juges
> Sent: Tuesday, February 13, 2007 10:12 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Thunderbolt GPSDO
> Well, some of us who have been on this list much longer than me can tell
> you that when you only have one clock, it's pretty hard to tell if it's
> working right, or how accurate it is. If you have two clocks, they
> probably won't agree perfectly, and you have no way to tell which is
> right, if any, so you are not much better off.
> So, if you have three clocks (more being better of course), you can
> compare them 2 by 2 and draw some conclusions, with any luck, about
> which one is the best, and how bad are the others. This will still not
> tell you how good the best one is, but you are getting closer.
> You compare clocks using a statistical tool called Allan Deviation...

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