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<[email protected]> 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
[email protected] 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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--
------------------------------------------------------------------------
Javier Herrero EMAIL: [email protected]
Chief Technology Officer
HV Sistemas S.L. PHONE: +34 949 336 806
Los Charcones, 17 FAX: +34 949 336 792
19170 El Casar - Guadalajara - Spain WEB: http://www.hvsistemas.com
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