[time-nuts] Housing LPRO and Thunderbolt together

Javier Herrero jherrero at hvsistemas.es
Sat Apr 23 07:22:14 UTC 2011


I like the Schroff ones, in aluminium or steel:

http://es.farnell.com/jsp/search/browse.jsp?N=500001+1000845&Ntk=gensearch_001&Ntt=schroff+1u&Ntx=mode+matchallpartial
http://es.farnell.com/jsp/search/browse.jsp?N=500001+1006552&Ntk=gensearch_001&Ntt=schroff+1u&Ntx=mode+matchallpartial

They are available in US through Newark

Regards,

Javier

El 23/04/2011 02:42, brent evers escribió:
> Somewhat related to this, someone posted a link for 1U chassis a while
> back.  I thought I saved the link, but can't find it, and since the
> text of posts can't be searched from the archives, can't find mention
> of it that way either.  If anyone has a decent source for 1U chassis
> that I could mount a pair of tbolts in, I would appreciate it.  These
> were generic 1U rackmount chassis - not 'server' chassis with a bunch
> of preplanned holes.
>
> Brent
>
> On Fri, Apr 22, 2011 at 5:37 PM, WB6BNQ<wb6bnq at cox.net>  wrote:
>> Hi Pete,
>>
>> As Bob, K6RTM, pointed out the Thunderbolt and the Rubidium are two different
>> animals all together.
>>
>> True, you can treat a Rubidium like it was a normal crystal oscillator, but it is
>> not the same.  The Rubidium has a definite life span, the more you run it the less
>> the life.  A high quality crystal oscillator, on the other hand, just gets better
>> the longer you leave it on.  Aside from nominal electrical component failures, the
>> crystal blank in a properly designed circuit has no short term failure mechanism and
>> will last for decades with constant applied power.  The Rubidium’s life span is, at
>> best, 10 years.  The question is how long was it running before you got it ?
>>
>> A high quality crystal oscillator has excellent short term specs but does have drift
>> and aging functions that severely limit its use for long term purposes.  Long term
>> meaning more than a few hours for the best.  That is where the Rubidium oscillator
>> takes over as its drift function is measured in days to a month or more.
>>
>> For high quality measurements, the crystal excels for measurement times of less than
>> 10 seconds, as the Rubidium is noisier in that time frame.  That is, for taking
>> readings on a one second to second basis, such as with a high resolution time
>> interval counter, the crystal excels.  However, if the period of the measurement is
>> longer, then the Rubidium would be a better choice.  For portable purposes the
>> Rubidium also excels as its retrace is much better than a crystal oscillator.  You
>> also do not need to wait the thirty to sixty days for the crystal to stabilize.  The
>> Rubidium will be very close to its original set point in about 20 minutes.
>>
>> Adding GPS to mix has its own issues.  First, you need to know the coordinates
>> precisely or spend a couple of days getting a damn good fix.  The GPS is quite noisy
>> in the short term and the oscillator that is steered by the GPS has that noise show
>> up in its output.  That is mitigated by having a high quality crystal oscillator
>> where the GPS control loop seldom makes corrections; perhaps once an hour or more.
>> That is how the Thunderbolt works and depending upon its internal crystal
>> oscillator, it may possibly be tweaked to perform better then the standard factory
>> settings.
>>
>> As for use, it all depends upon what and how you’re making measurements.  With a
>> nominal 8 or 9 digit counter, for example, you may not notice all of the above
>> issues because they are typically beyond the resolution of the equipment in most
>> cases.  In other measurement processes it may be of major concern.
>>
>> As for your project boxes, I would use the rack mounted box to house the
>> Thunderbolt, distribution amps and perhaps a couple of other oscillators (like the
>> hp 10811) along with quality power sources.  Because crystal oscillators like a
>> constant operating condition, do consider battery power for the lab to handle those
>> occasional mains power drops.
>>
>> I would use the portable box for the Rubidium oscillator and include a battery
>> option depending upon your intent.  The emphasis should be to have very quiet and
>> stable power supplies for both projects.  Even batteries have a fair amount of noise
>> so make the mains power (and battery) voltage high enough to allow for running a
>> quality regulation circuit.
>>
>> My two cents !
>>
>> 73....Bill....WB6BNQ
>>
>>
>> g4gjl at btopenworld.com wrote:
>>
>>> I have a dilemma and wish to access the collective wisdom of the group to advise
>>> a solution.
>>>
>>> I am building a clock generator based on a Thunderbolt. I have an LPRO and would
>>> also locate this in the same enclosure. I will also add a distribution amp and a
>>> divide chain in due course.
>>>
>>> The ultimate purpose of the set up is to provide a self contained clock
>>> generator set for my other test equipment, and also an experimental workstation
>>> for Rubidium and GPS disciplined experiments.
>>>
>>> Most of my other equipment is for 19-inch rack mounting.
>>>
>>> I have two potential solutions for housing the timing kit:
>>>
>>> 1. An old dismantled HP 4U scope chassis which will fit in with my other
>>> equipment physically, and can be racked if necessary. The PSU would have to be
>>> built into the same enclosure.
>>>
>>> 2. A pair of Anritsu instrument cases which once house a bit error test set. The
>>> two units clip together beautifully, and are free standing. As there are two
>>> units, this solution would allow me to build the PSUs in one case and the more
>>> sensitive timing electronics in the other. These units cannot be racked on
>>> account of their form factors.
>>>
>>> Both solutions will require me to do some bespoke metalwork, but that is no
>>> problem for me and amounts to about the same amount of work for either solution.
>>>
>>> So what does the group advise? Is it vitally important to keep PSU components
>>> isolated from the timing electronics? I want to create the least noisy clock
>>> source given the components I have.
>>>
>>> Looking forward to hearing some opinions...
>>>
>>> Pete
>>> G4GJL
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>>> and follow the instructions there.
>>
>>
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-- 
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Javier Herrero                            EMAIL: jherrero at hvsistemas.com
Chief Technology Officer
HV Sistemas S.L.                          PHONE:         +34 949 336 806
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