[time-nuts] Neutrinos not so fast? (defectove connector)

Azelio Boriani azelio.boriani at screen.it
Thu Feb 23 14:45:22 UTC 2012


I recommend the differential pair: here the trigger have to sense the
crossing of the two signals and this crossing is well definite.

On Thu, Feb 23, 2012 at 3:36 PM, Jim Lux <jimlux at earthlink.net> wrote:

> On 2/23/12 6:24 AM, Alberto di Bene wrote:
>
>>    On 2/23/2012 1:04 AM, Poul-Henning Kamp wrote:
>>
>> I simply don't buy the story that tightening the connector makes
>> a consistent 60 nanoseconds difference on a signal.
>>
>>    I spoke with a physicist of Cern, friend of the leader of the team that
>>    performed the Opera experiment.
>>    He told me that the badly seated connector caused the amplitude of the
>>    signal to be lower, and for this reason the trigger point, which was
>>    set at a specific level, was reached 60ns later.
>>    73  Alberto  I2PHD
>>
>
>
>
> Darn those finite rise times<grin>
> I've been bitten more than once by this very phenomenon (which I admit
> doesn't say a lot for me.. being bitten once is ok, but since I've had
> multiple bites...)
>
> But this brings up an interesting time-nut problem for the hive mind..
>
> If you had to design some scheme for interconnecting "boxes" and wanted to
> transmit an accurate time sync, what should it look like, so that you're
> insensitive to things like rise time.
>
> (maybe this harkens back to the discussion about 10 MHz, why sine vs
> square wave distribution)
>
> It has to be a single signal (maybe a differential pair), because
> otherwise, don't you have potential for skew between the multiple signals.
>
> Zerocrossing sort of works, if you take only one direction, but does
> asymmetry of the waveform screw you up?  (e.g. what's "zero".. is it half
> way between peak values + and -?)
>
>
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