Most rubidiums have two tuning adjustments, one for the cavity frequency and one for the lamp RF frequency. I'd start by tuning those properly and see how your frequency offset changes.
Somewhere on the servo you'll find a test point for observing the second harmonic of the modulation. Clip that to your oscilloscope and adjust the cavity tuning for maximum response. Somewhere else, you should find a DC light level monitor, tune up the lamp frequency for maximum light. One or the other (or both) of these adjustments may move the frequency back towards the midpoint of the C-field adjustment. If you get them optimized it'll also improve the temperature sensitivity and long-term drift. -RL Please note that I am now automatically deleting all Email originating from "comcast.net" due to the large amount of spam originating from their servers. Please register your complaints with ComCast, since they have been ignoring mine. ------------------------------------------------------------ Robert Lutwak, Senior Scientist Symmetricom - Technology Realization Center 34 Tozer Rd. Beverly, MA 01915 (978) 232-1461 Voice [EMAIL PROTECTED] (Business) (978) 927-4099 FAX [EMAIL PROTECTED] (Personal) (339) 927-7896 Mobile ----- Original Message ----- From: "Christopher Hoover" <[EMAIL PROTECTED]> To: <time-nuts@febo.com>; <[EMAIL PROTECTED]> Sent: Thursday, April 20, 2006 5:31 AM Subject: Re: [time-nuts] How Rubidiums make their frequency (was RE:time-nuts Digest, Vol 21, Issue 22) > Tom Clark wrote: > >> Christopher Hoover asked: > >>> one issue remains: i have to crank the magnetic field setting almost >>> to >>> its high limit (9.91/10.00) to get 5 MHz out; lower settings give a >>> frequency that is too low. i presume this is unusual. > >>> i have a rudimentary understanding of the rubidium oscillator physics, >>> but i do not understand what would cause this. can i buy a clue? > >> I don't know the Tracor, but I imagine it is like most of the other >> Rubidiums in it's innards. > > Hi Tom, > > That's a good explanation, thank you. I got that much already. (While > it > took some time for my phyiscs, chemistry and semiconductor physics studies > to kick back in, it all clicked last week.) The Tracor, indeed, seems > fairly ordinary compared to the other Rb's I have, going by the test > points > and the various labels inside. There is the typical synthesizer section, > audio demodulation section for the photocell, etc. > > So what I'm really wondering is this: is there a wear mechanism or > failure > mode in the physics package that might explain why I have to crank the mag > field almost to its high limit to get 5 MHz? (This question presumes the > mag field control is working properly, and I cannot say for sure that it > is.) > > Thanks, > -- Christopher. > > > _______________________________________________ > 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