Hello Tom,
What are the conditions for your charts? Are the Tbolts in locked condition or
holdover? If locked what settings do you have for time constant and damping? Is
it any other setting that is important?
For the frequency chart I see excursions up to +-3E-11 so not so far from the
values that Bert gives and as I understand his TBolt might have a default
setting of 100 seconds.
Lars
Från: Tom Van Baak<mailto:[email protected]>
Skickat: den 1 september 2016 21:12
Hi Bert,
> because the frequency is constantly changed to correct time.
A simple answer: you may have a bad TBolt. Was it part of the TAPR group buy,
or did you buy it from eBay/China? If TAPR, you get a free replacement. Contact
me off-list.
> Tbolt is an excellent time device but not good for frequency reference past
> 1E-10.
No, again it sounds like you have a bad TBolt. Or something is wrong (antenna?
reception? time constant? environment? China resoldered parts?). I appreciate
that Juerg did lots of testing -- do you happen to have his ADEV plot?
I'm willing to help you debug this.
(1) Attached is the ADEV of 8 random TBolts that I tested recently. How does
this compare to yours? You can see mine are all under 2e-12 at 1 s and under
4e-12 at 100 s. On a bad day during holdover it might climb to 1e-11 at 1000 s
but when locked GPS disciplining takes over and keeps it down to 2 or 3e-12.
(2) For locked vs. unlocked TBolt ADEV, see
http://www.leapsecond.com/pages/gpsdo/
(3) Also attached is a frequency plot showing the typical noise and wander,
down at the 1e-11 level. How does this compare with yours?
Your claim of 1e-10 is order(s) of magnitude worse than the TBolts that I see.
Something is wrong.
/tvb
----- Original Message -----
From: "Bert Kehren via time-nuts" <[email protected]>
To: <[email protected]>
Sent: Thursday, September 01, 2016 9:54 AM
Subject: [time-nuts] Tbolt issues
> We have been following the Tbolt power discussions but what I am missing is
> the main problem with Tbolts. All the power work will not improve the
> frequency performance of the unit because the frequency is constantly changed
> to correct time. Tbolt is an excellent time device but not good for
> frequency reference past 1E-10. I noticed it when I bought it and compared
> it with
> my Tracor 527E on the needle and ever since used an Austron 2110 with a
> digital 100 sec. loop for clean up. My Swiss partner Juerg has relied on an
> OSA F3 for Tbolt clean up but continuous bad results on our work resulted in
> a detailed analysis using a HP53132A counter and M100, FTS44060, two
> OSA8600's and one of the best FE405's. The rsult is that the OSA F3 does not
> clean up the Tbolt and we see +-4E-11 changes and old data shows even some
> +-8
> E-11 excursions. With the popularity of the Tbolt an analog or digital
> clean up loop would make sense. We are working on both, the analog because I
> saw similar behavior on the FE5680 and FE5650, we did a GPSDO but do not plan
> on using those Rb's but focus on M100 and FRK.
> The collective expertise of time nuts could make a significant contribution
> For power in critical applications we use the excellent work from Bern Kaa
> a friend for the last twenty years and well known because of his published
> work in the European HAM community
> Bert Kehren
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