[time-nuts] TICC / TimeLab fun

[John Ackermann N8UR]

Hi Chris --

Two possibilities:

1.  Make sure you have TimeLab set for the correct mode (timestamp vs
time interval), for two channels, and for the right scaling factor (for
timestamps, scale by 1).  Any of those can cause 1e0-type results.

2.  If the two channels have timestamps that are within a few
nanoseconds, there can be a crossover where the channel sequence doesn't
maintain strict "ABABABABAB" order.  TimeLab expects that order and if
you get something like "ABBA" apart from bad '80s music you also get bad
readings.

The easiest way to avoid the problem is to split the TICC output stream
into the two channels and then feed them into TimeLab separately.  It is
possible to do that and still get real time readings by using the "Read
Streaming ASCII file" TimeLab acquire option, but it takes a little
finagling to do it.

[ BTW -- this is not really a "bug" in either the TICC or in TimeLab,
it's just the way things work.  I've spent much time thinking about
addressing it in the TICC code, but there's no sure-fire fix that works
across all possible operating scenarios. ]

Hope this helps.

John
----
On 4/29/20 1:12 PM, Chris Burford wrote:
> I'm trying to characterize a pair of GPSDO units using the TICC / TimeLab.
> The issue I'm having is when both GPSDO units are wired simultaneously to
> the TICC the resulting ADEV plot looks a little strange, beginning at
> 3.74E-1. Both GPSDO units are referenced against my PRS-10 Rb for the clock
> source.
> 
> If the GPSDO units are wired individually to chA then all seems fine and the
> plot begins with a more anticipated value of about 1.4E-8. I'm at a loss as
> to where to proceed from here to get both units characterized
> simultaneously.
> 
> Thanks for the assistance.
> 
> Chris
> 
> 
> 
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