[time-nuts] Rubidium Oscillators and Racal 1992

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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