[time-nuts] Tbolt Damping setting

Peter Vince pvince at theiet.org
Tue Dec 15 20:01:52 UTC 2009


Thank you for your explanation.  Your Lady Heather plot prompts a
couple of questions though:

1) Presumably you created the 40ns phase step by changing the output
timing offset?

2) Presumably, again, the plotted data is from the self reported data
from the Thunderbolt?

I have been running a series of tests myself this year, but on looking
at the results, it became clear - and I should have twigged this
earlier - that all the Thunderbolt can do is report the differences
between itself and the noisy GPS signal.  Whereas what I really wanted
was a comparison to a stable external standard.  Sadly I don't have
TVB's Maser or 5071s, but I suspect that such a comparison would give
a rather different plot.  Tom has talked about these factors on his
page at http://www.LeapSecond.com/pages/tbolt-tc/  just showing MDEV
plots.

Tom: would you have the time to replicate Warren's experiment, but
show the phase and frequency plots with respect to your Maser or 5071?

As an aside, at the beginning of the year when the TAPR offer was on,
it was suggested on here that the time constant be set to that where
the ADEV plot reaches a minimum whilst on holdover.  A couple of days
after turning on, mine was about 700 seconds.  Now, nine months
continuous operation later, and with the Thunderbolt in the
recommended cardboard box to protect from drafts, the plot now reaches
a minimum at about 2500 seconds!

Peter



More information about the time-nuts mailing list