[time-nuts] Performance verification for time counters

Magnus Danielson magnus at rubidium.dyndns.org
Sun Dec 3 10:07:31 EST 2017


On 12/02/2017 11:05 AM, Attila Kinali wrote:
> On Fri, 1 Dec 2017 21:10:55 +0000
> Leo Bodnar <leo at leobodnar.com> wrote:
>> As promised, I started setting up dual asynchronous sources experiment
>> and performed a quick sanity check.  What I have [unsurprisingly] found
>> is that at this level controlled environment is a problem in itself.
>> For example, undoing input signal SMA connector by one turn shifted my
>> results by around 3.5ps - close to expected figure but still inconvenient.
>> I'll have to plan the setup before I build and validate it, otherwise the
>> results are not trustworthy.
> 3.5ps is pretty much what I'd expect in additional delay, when undoing an
> SMA connector by one turn. One turn is about 0.7mm, assuming a VF of 0.6
> you get to ~3.5ps.

There is a reason that one should use SMA momentum keys for repeatability.

> I am quite impressed that you could measure it this accurately.

A VNA should not have a problem measuring that at RF frequencies.


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