[time-nuts] Newbie question about thunderbolts

Paul Berger phb.hfx at gmail.com
Wed Feb 27 19:35:55 EST 2013


I did peek inside the E not long after I got it and I do remember that 
the OXCO looks very different, it is much smaller than the one on my 
Nortel unit.  If it is the OXCO I can always source a potentially better 
OXCO and then I can have more fun playing with it.  Being a technician I 
really enjoy fixing things and seeing them work again.  One other big 
difference in the E model is it takes a single 24VDC power input and has 
a little switcher module in it to generate the voltage the GPSDO 
actually uses, this is similar to the setup on the Nortel unit, however 
it did not look to be built nearly as good.  I will give it a little 
more time and if it does not improve I will pull it out of its box and 
start to poke around inside.

Paul.

On 2/27/13 8:23 PM, John Miles wrote:
> 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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