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: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Im Auftrag von [EMAIL PROTECTED] > 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. > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-> bin/mailman/listinfo/time-nuts > and > follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
