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

Bob Camp lists at rtty.us
Thu Feb 23 17:52:32 UTC 2012


Back in the long ago, processing was expensive. Much of what we do goes back
to that era and paradigm. 

A bidirectional loop with smarts on both ends would make a lot of sense
today. Spend $5 on each end and you can be sure of what's going on. Yell to
higher authority if something didn't look right. If it's "your" connection
(as it is for most simple timing links) send lots of data and average to
improve the SNR. The added cost is nearly zero...


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Jim Lux
Sent: Thursday, February 23, 2012 9:37 AM
To: time-nuts at febo.com
Subject: Re: [time-nuts] Neutrinos not so fast? (defectove connector)

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
>     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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