[time-nuts] Thunderbolt Hardware Versions & Perfomance Differerences - UPDATED

TheInfamousFlavio at hotmail.com TheInfamousFlavio at hotmail.com
Thu Feb 15 18:06:34 EST 2007


I meant to start a new thread with previous email regarding Thunderbolt 
hardware versions and performance.  So I'll repost again as new thread with 
some additional comments.

There are different hardware variations of the Thunderbolt out there.  There 
is the commercially available Thunderbolt which available from Trimble that 
everyone is familiar with, and then there are the industrial versions that 
are made for the telecoms.  The Andrews E-911 version, unfortunately,  looks 
to be regular commercial version from what I can see from the board layout 
and the form factor.

I'm lucky enough to own a couple of Thunderbolts as well as some of the 
different telecom versions and they DO NOT have the same performance.  The 
commercially available Thunderbolt (the one comes in the little red box) has 
the least favorable performance when compared to the industrial versions.

I've found that the industrial Thunderbolts, with their better hardware and 
much nicer oscillators, have a stability that is comparable to the Z3801A 
(if not exceeding it).   My commercial Thunderbolts have more jitter and 
don't stabilize as quickly as the higher end boards.  I don't have a cesium 
or hm to give hard Allan Variance numbers but I do use a counter that in 
it's nulling mode will show differences as small as 1.9e-9Hz ( 0.0000000019 
Hz ).   Using a 10sec gate I'll watch how often the lower differences are 
displayed.  So if I see a number displayed >1.0e-3Hz show up a lot, I'll 
know that the oscillator has more jitter than an oscillator that 
consistently displays <1.0e-3Hz.  But when I have an oscillator that is very 
stable I will see a lot of differences in the 1e-6Hz and 1e-9Hz range. I 
notice that commercial Thunderbolts display readings that have greater 
variance than the industrial boards when referenced against one of my 
favorite HP Z3801A's.  The industrial boards have a much tighter variance 
will show a lot of differences in the 1e-6Hz and 1e-9Hz range much more 
often.

Hardware wise:  The industrial versions seem to have better power supplies 
with more filtering (since they are not limited by space I guess).   They 
also have to seem more components that support the cpu (possibly for added 
functionality or to support different algorithms).   And of course, the 
oscillators.  The single oven in the commercial Thunderbolt does seem to 
even come close to the industrial boards.  The industrial boards I have are 
the Z3801A clone with a double oven oscillator and a couple of boards with 
high-end Vectrons.

On Trimble's Thunderbolt web page, there is a link for a Thunderbolt 
Performance with a Double Oven Oscillator. I think people might be mislead 
to believe that is the performance of the commercial Thunderbolt that they 
are selling, but it's not.  What the are showing is the performance of what 
I believe to be one  of the industrial boards with an older high-end Vectron 
double-oven (the  model 330Y4472) which was available in the Z3801A clone 
made for Nortel.   The commercial version doesn't even come close to that.

I think the "holy grail" of Thunderbolt boards is the Nortel boards.  The 
are still in service and have their firmware updated by Trimble unlike (the 
commercial version which Trimble doesn't give any info about firmware 
upgrading).    Unfortunately, the Thunderbolt everyone want to buy from this 
seller who has "hundreds" of them, is (and I say this with 99.94% certainty) 
a regular, commercial Thunderbolt in a different housing.  I certainly won't 
pay $250 for one.  And if this guy has 'hundreds', he will discover there is 
no market for them at $250.  I'll pick one up when it dips below $100.  The 
other Thunderbolt board on eBay now, with the 5 10mhz outputs is a steal at 
$225 if you can get one of the "last four".

Additional Comments:  Didier wrote that Trimble says the older Thunderbolts 
allowed for parameter changes to the OCXO disciplining parameters to allow 
for oscillator upgrading.  I didn't even realize that there was a new 
version that took away those parameters because I've only dealt with the 
older version (older is better).  Which basically means if these "hundreds" 
of Thunderbolts everyone is signing up for doesn't have these tweaking 
parameters, the fun factor has dropped significantly and so has the price 
I'm willing to pay for one.  All the industrial versions of the board that 
I've come across, even the newer ones, all allow for modifying the 
disciplining characteristics so you can upgrade the oscillator which is 
where the fun is for me. 




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