[time-nuts] Newbie question about thunderbolts

EWKehren at aol.com EWKehren at aol.com
Wed Feb 27 20:10:39 EST 2013


I did get one bad one leak or pin hole aging so much that it would have run 
 out of tuning range in a month
Bert Kehren
 
 
In a message dated 2/27/2013 7:24:25 P.M. Eastern Standard Time,  
jmiles at pop.net writes:

Sounds  like a bad OCXO.  The crystal frequency jumps slightly, and  the
disciplining loop then has to compensate by steering the DAC   voltage
through the loop filter.  If that's the problem it may get  better if you
leave it running for a few more weeks.

The smoking gun  is the attack/decay characteristic of the DAC adjustment.
At least in  theory, no issues on the GPS side of the loop should result in 
a
fast  leading edge at the DAC. 

I haven't seen any Thunderbolts with  genuinely bad OCXOs yet, although some
of them are definitely better than  others.  The Thunderbolt-E, however, is 
a
very different model than  the ones that are normally found on eBay.  Almost
everything you hear  about a "Thunderbolt" refers to the older non-E 
version.


I've heard  (but can't exactly cite) that the Thunderbolt E models were a
reduced-cost,  higher-volume product.  If that's true, you can assume that
they don't  use the same OCXOs, because those OCXOs were much better -- and
would have  been more expensive -- than they had to be.  

(The Thunderbolt E  should not be confused with the more common Thunderbolts
running 'E'-level  firmware.)

-- john, KE5FX

> Hi, Paul. Glad to see you made it  here. For the time-nuts; Paul and I
> have spoken about these issues,  and I have had similar experience. The
> only thing I would add is the  the spikes to seem to occur less
> frequently with a better antenna  placement, but when they start to
> cluster, they fire off one every two  or three seconds, sometimes
> faster.
> 
> JimT
>  
> On Wed, Feb 27, 2013 at 2:08 PM, Paul Berger  <phb.hfx at gmail.com> wrote:
> >
> > Hello all:
>  >
> > I am an electronic technician with 30+ years experience  fixing
> > computers.   In my spare time I like to play  with old computers and
> > electronics.  Recently I got bit by  the precision timing bug, partially
> > after running across the  wonderful leapsecond.com site, which lead me
> > here.    First I got  a FE-5680A, then after reading some of the 
archives
>  > here I bought a Nortel / Trimble 45000   GPSDO and still later  a used
> >  Thunderbolt-E...

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