[time-nuts] Rubidium Oscillators and Racal 1992
Ulrich Bangert
df6jb at ulrich-bangert.de
Wed Mar 12 06:46:14 UTC 2008
This one "110 ?C" should read "110 degree C"
Ulrich Bangert
> -----Ursprungliche Nachricht-----
> Von: time-nuts-bounces at febo.com
> [mailto:time-nuts-bounces at febo.com] Im Auftrag von Ulrich Bangert
> Gesendet: Mittwoch, 12. Marz 2008 07:21
> An: 'Discussion of precise time and frequency measurement'
> Betreff: Re: [time-nuts] Rubidium Oscillators and Racal 1992
>
>
> Gentlemen,
>
> I would like to place emphasis to the fact that the so called
> "lamp voltage" is just the operating point of a regulation
> loop in which the lamp's health is ONE of the involved
> parameters, exactly as Antonio's experiments verify.
>
> Within the lamp a plasma ignition is excited by means of an
> external electromagnetic field. The field's frequency as well
> as the lamp's temperature (which is in the near of 110 ?C)
> are important parameters for the quality of the plasma
> ignition and for where the operation point of the loop is.
>
> When Antonio was "Adjusting the capacitive trimmer solid with
> the lamp assembly (and) the lamp-V ranged from 1.5 to 6.5 V"
> he demonstrated the dependance of the operation point from
> the exciting field's frequency. Not sure whether the LPRO
> also has, but the FRK-Ls have trimmers for the temperature
> setpoint of the lamp's temperature controller. Would he have
> changed that he would have observed a similar dependance. And
> when "the lamp-V oscillates within 10 milliVolt basicly
> according to ambient temperature" this is simply the effect
> of the temperature controller's inability to control the
> lamp's temperature perfectly despite of ambient temperature changes.
>
> So a better phrase would be that the lamps voltage is an
> indicator of the lamp's health IF and ONLY IF everything else
> is sane. Don't blame the lamp before you have checked the
> temperature and the exciting field's frequency.
>
> I am stressing this a bit because exchanging the lamp is not
> exactly easy! While it is a snap to remove the lamp toghether
> with the lamp holder (a small metallic part that makes the
> whole thing look like an ordinary bulb) the lamp itself
> (which is ONLY the glas compartment) is glued (?) to the lamp
> holder and in order to exchange the lamp I guess you will
> need to destroy the current one and the glue in the new one.
>
> Has anyone of you already performed that action or can give
> an clue which adhesive is suited for that purpose???
>
> Best regards
> Ulrich Bangert, DF6JB
>
> > -----Ursprungliche Nachricht-----
> > Von: time-nuts-bounces at febo.com
> > [mailto:time-nuts-bounces at febo.com] Im Auftrag von iovane at inwind.it
> > Gesendet: Dienstag, 11. Marz 2008 15:31
> > An: time-nuts
> > Betreff: Re: [time-nuts] Rubidium Oscillators and Racal 1992
> >
> >
> > I purchased on ebay four rubidium LPRO and I'm quite
> > satisfied with them. The lamp-Volt parameter (which is an
> > indication of the lamp's health) was
> > respectively 8.4, 7.95, 6.8 and 5.1 Volt.
> > When an LPRO leaves the factory its lamp-V is around 12V. A
> > drop of up to 3 V
> > would be expected in the first year of operation, but after
> > that the voltage
> > decay rate slows down dramatically.
> > According to the manufacturer, when the lamp-volt drops down
> > to 3 V (this is
> > expected in not less than 10 years) the unit needs
> > maintenance. I've used the worst unit (5.1V) to make some
> > tests in order to get more
> > familiar with them. Adjusting the capacitive trimmer solid
> > with the lamp assembly
> > the lamp-V ranged from 1.5 to 6.5 V. It remained locked even
> > when the lamp-V was 1.5V. All of the units showed a VCXO
> > steering voltage in the middle of the usable
> > range.
> > The unit with 7.95 lamp-V is running continuously since 40
> > days. I'm monitoring and recording every 15 seconds the
> > lamp-V, the VCXO V and the temperature of
> > the heatsink at the baseplate (you should provide a
> > heatsink). After a few days
> > of stabilization (in wich the lamp-V showed a tendence to
> > increase, may be following
> > a long period of no operation) the lamp-V oscillates within
> > 10 milliVolt basicly
> > according to ambient temperature, and I've not yet noticed
> > any decay in the averaged data. This is a simptom of good
> > health from which one could expect some 10 more
> > years of continuous operation.
> > I'm measuring and recording at the same time its frequency as
> > read by a
> > Racal 1992 with option 04E (OCXO). Of course the observable
> > drifts would came
> > from the Racal oscillator.
> > Well, I would spend a few words on the Racal too.
> > I'm making the measurement at a resolution of 1 part in
> > 10e-10 (gate time 10 seconds, good ADEV for both units) and
> > often I' can't appreciate any drift at this level on
> > a daily basis. In averaged data, the drift is something like
> > 2*10e-11 per day
> > (Racal specs less than 5*10e-10 per day).
> > By the way, speaking of the Racal 1992, I have to say that
> > mine is the military
> > version 02M. I have two of them, and a friend of mine another
> > one. None of the
> > three units showed the problem with pushbuttons. May be the
> > military version used different materials? Anybody knows?
> > The unconvenience with the 02M version is that it uses a
> > military GPIB language (MATE/CIIL), and I had to get familiar
> > with it. Antonio I8IOV
> >
> > > On Mon, Mar 10, 2008 at 10:12:46PM -0500, Brian Kirby wrote:
> > > > For maximum stability, the rubidium should be run continuous.
> > > >
> > > > I lost a lamp in a FRK-L last summer. The unit had been
> > running for
> > > > 9
> > > > years continuous - and I was the second owner. It was
> > used at a LORAN
> > > > site previous, I am sure they probably ran it continuous,
> > for the same
> > > > reasons.
> > >
> > > According to various spec docs I have seen, many of the telecom
> > > oriented rubidiums (such as the LPRO and FE series) are
> > designed for
> > > between 15-20 years lamp life continuously on... so running
> > one that
> > > way is not likely to use up available life quickly unless
> > the unit already
> > > has lots and lots and lots of hours on it. And they
> > aren't absurdly
> > > expensive on Ebay these days - bet a new bulb (if even
> > available) is
> > > almost as much as a used but working rb off Ebay.
> >
> >
> >
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> >
>
>
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