[time-nuts] Different Thunderbolt versions

Sylvain RICHARD sr75pro at free.fr
Sat Feb 21 15:44:37 UTC 2009

Markus Kern wrote:
> Hello everyone,
> I am new to the list and currently looking for a timing standard for a
> VLBI application. After some searching I have decided to use two
> thunderbolts for a first attempt and now have some questions regarding
> the different available versions.
> There seem to be two types of Thunderbolts available on eBay right now.
> One is the "flat" board mount version without PSU and which requires
> a (+12V, -12V, +5V) power supply. The other is the "boxed" version
> with integrated PSU and which requires 24V. These are all old
> Thunderbolts with 8 channel GPS. The new Thunderbolt E with 12
> channels obviously doesn't show up on eBay yet. (See [1] for
> comparison)
> My first question concerns the power supply. [2] shows that the output
> phase noise is significantly dependent on the PSU. How does the
> integrated PSU of the boxed version compare to the PSUs tested in [2]?
> Is it worth getting the boxed (somewhat more expensive on eBay) version
> just for the PSU?
I believe that the blue trace (#3) on the last figure from John Miles' 
page [3] is with the integrated 24 to -12, +12, +5 V PSU. So you are 
better off buying a cheap barebones Thunderbolt and a cheap linear PSU.
> My second question is about the Thunderbolt's OCXO. [3] shows how to
> replace the built in OCXO with a more stable one and suggest that not
> all Thunderbolts have the same OCXOs. The bad OCXO in [3] appears to
> be from PIEZO and has S/N 1384. The better Thunderbolts apparently
> have "10811-class" OCXOs (like the replacement). Neither,
> unfortunately, match the labeling of the OCXOs seen on eBay (e.g. [4]).
> Is there an easy way to distinguish these different Thunderbolts?
> Thanks,
> Markus
> [1] http://www.febo.com/pipermail/time-nuts/2008-May/031370.html
> [2] http://www.leapsecond.com/pages/tbolt/noise.htm
> [3] http://www.thegleam.com/ke5fx/tbolt.htm
> [4] http://cgi.ebay.de/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=170300146215
Good luck,


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