[time-nuts] time-nuts equipment verification from scratch (was: WTB: GPSDO)

Bob Stewart bob at evoria.net
Mon Mar 20 15:27:19 EDT 2017

I would say that the price for a home-built time-nuts quality GPSDO is going to be significantly greater than $200.  Yes, if you are making them for sale, eventually the unit cost will get down there.  But to build one single good GPSDO, you're going to throw away a lot of prototypes on the way to the one that works well enough to stand up to the scrutiny of this group.  The costs of those prototypes add up, and then there's your time engineering, building and testing.  It adds up to a lot.


      From: Attila Kinali <attila at kinali.ch>
 To: Discussion of precise time and frequency measurement <time-nuts at febo.com> 
 Sent: Monday, March 20, 2017 2:01 PM
 Subject: [time-nuts] time-nuts equipment verification from scratch (was: WTB: GPSDO)
On Thu, 16 Mar 2017 00:06:49 -0700
Chris Albertson <albertson.chris at gmail.com> wrote:

> I actually did use your method.  I have a Rb and Thunderbolt, a pair
> of freq. counters and so on.    But still I wanted to see if I could
> build from scratch and verify proper operation and keep the budget
> under say $50 for everything from antenna to power cord.    I think
> it can be done but one can only verify longer term stability.

Hmm.. doing verification of self-built (or aquired) equipment from
scratch is a different game altogether. If you want to build things
yourself, you first have to form a model of what disturbs your system,
measure these parameters and verify the model against your measurements.
Then you start building systems that exhibit different distortions,
model these, measure and verify them. After you have built enough
systems with different environmental characteristics, you verify
them against eachother to make sure that your models faithully
model reality and contain all parameters up to the error bound of the model.

After a couple of decades of building and verification, you can be 
reasonably sure your GPSDO works correctly ;-)

> (Yes you were correct a GOOD oversized XO is not sensitive to the
> environment.  But notice the above budget.)

50$ for a complete GPSDO, batteries included, is quite a low price limit.
A decent OCXO already costs 20-30$ on ebay. 100-200$ is a more realistic
limit for a homebrew GPSDO with time-nuts like performance.
A non-ovenized XO will not come close to time-nuts standards ;-)

                Attila Kinali
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
                -- Miss Matheson, The Diamond Age, Neil Stephenson
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