[time-nuts] Measuring ADEV using TBolt-Tic tester

Azelio Boriani azelio.boriani at screen.it
Fri Oct 14 20:42:27 UTC 2011

Oh my, you're absolutely right... I've totally missed out those few lines!
Now I understand. I apologize and go immediately to search for a Tbolt. A
similar design is the ConnorWinfield/NavSync FTS125 but instead of
disciplining an OCXO they use a 20MHz fixed OCXO (without EFC) to drive the
GPS engine and then phaselock a 10MHz OCXO with a standard PLL (LMX2306 or
something like that). The PPS isn't derived from the disciplined OCXO but
from the GPS engine itself and has the typical jitter (better, because of
the ovenized 20MHz, but some jitter is present). By means of an NCO a 10MHz
is derived from the GPS engine to clock the PLL to phaselock the 10MHz OCXO.
The heart of the FTS125 is the CW25 GPS receiver.

On Fri, Oct 14, 2011 at 10:02 PM, <bg at lysator.liu.se> wrote:

> Azelio,
> > Oh, yes, you're right. 100pS is the noise. Very interesting in this case:
> > how this high resolution is obtained (excluding averaging, the real
> > hardware
> > resolution)? Analog interpolators? Wave union TDC? Vernier delay lines? I
> > haven't found any reference in the internet...
> There is no TIC, read page 1-1 in the Tbolt manual, on how the Tbolt is
> different from most GPSDO.
> http://trl.trimble.com/dscgi/ds.py/Get/File-10001/ThunderBoltBook2003.pdf
> --
>    Björn
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