Since the question was: > Doesn't it take a greate amount > of RF power to excite cold Rb?
one should mention that it is NOT cold Rb that is excited. Instead, the whole of the resonator is heated up to give the lamp housing a temperature of 113+/-2 degree centigrade (FRK-L maintainance manual). This in conjunction with the RF power excites the plasma, not the RF alone. The plasma excitation process is quite sensible to the temperature as well as to the excitation frequency. I had bought a FRK-L from Lehman Scientific some years ago. When the so called 'lamp voltage' had slowly dropped down to 7 Volts over months of use the circuitry tended to unlock from time to time until a point when it would not lock at all anymore. First i thought that the physics package had reached the end of its life and that i had to throw away this 500 US$ beauty (Lehman Scientific price some years ago). Just because i thought that i could do nothing wrong in that situation i started to re-adjust the heater and the RF oscillator according to the maintainance manual. I was very surprised to see the 'lamp voltage" rise up some 100 mV and the whole unit to work again 'as new'. The lamp's temperature had only been off abt 8 degree centigrade. Because neither the heater control circuits nor the plasma exciting oscillator design are what we would call 'precision circuits' today, i expect a lot of old Rbs to suffer from misalignments of that kind. Cheers Ulrich Bangert, DF6JB > -----Ursprüngliche Nachricht----- > Von: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Im Auftrag von Magnus Danielson > Gesendet: Sonntag, 10. Dezember 2006 23:20 > An: time-nuts@febo.com; [EMAIL PROTECTED] > Betreff: Re: [time-nuts] Surplus Guidelines, was: Rubidium Standard > > > From: Robert_Deliën <[EMAIL PROTECTED]> > Subject: Re: [time-nuts] Surplus Guidelines, was: Rubidium Standard > Date: Sun, 10 Dec 2006 22:12:51 +0100 > Message-ID: > <[EMAIL PROTECTED]> > > > > > Isn't it deposited metal from the filament that blackens the > > > > glass? > > > > > > No. > > > > > > Therei is no filament. The Rubidium lamps are excited with a UHF > > > field which is external to the bulb. > > > > I didn't know that: How interesting! Doesn't it take a > greate amount > > of RF power to excite cold Rb? > > No. For instance, on my R&S XSRM it is a fairly basic 100 MHz > resonance setup with a single transistor in the core. It is > setup such that the RF coil is also part of the resonator in > a LC based oscillator. It is something like 1 W, which is > also what the literature say. > > Cheers, > Magnus > > _______________________________________________ > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-> bin/mailman/listinfo/time-nuts > _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
