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Hello Time-Nuts, I have an HP 5061A (relatively new chassis) with a very old Cs tube installed (working) and I’m trying to wrap my head around the set up and calibration of this unit, and just hoping for some help. As a little background, HP changed the Zeeman modulation frequency, C-field intensity, and A1 synthesizer frequency at serial number prefix 1336A. This is detailed in CHANGE 20 (pages 7-9 and 7-10) Model 5061A Manual Changes in the 5061A Manual, and covered in much more detail in HP Service Note 5061A-9 (document 05061-9061 6/80-02). OLD NEW Zeeman frequency 42.82kHz 53.53kHz C-field 61 milligauss 76 milligauss Synth. Frequency 12,631,771.6 Hz 12,631,772.5 Hz I can put the tube on frequency at the new synthesizer frequency by changing the C-field current (closer to the old C-field value, by changing A15R19). 1. The Zeeman modulation frequency is a complete mystery to me. Is it related to the value of the C-field that you are running? 2. If you are comparing the unit to GPS to calibrate it do you really care what the Zeeman frequency is? Adjust the C-field to put it on frequency and call it a day? I’m not sure if there was a physical change in the Cs tube as well. But HP mentions that the new values should have better stability. 3. Would I be better off changing the synthesizer frequency back to the old value and adjusting the C-field (I would think lower) to put the unit on frequency? My first thought is to leave well enough alone. Thanks for any insight. Skip Withrow

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Skip, There is a great deal of expertise as you know here. So several comments to get the ball rolling. The zeeman frequency allows you to establish the optimal beam current main peak by changing the magnetic field. What this is really doing is optimizing the state of the cesium atoms. Its physically separating them further apart so that when the beam hits the B magnet the bad cesiums head off to the getter. Thus the best signal to noise possible. I believe it also enhances focus of the beams. Less dispersion. Now there is no doubt you can use GPS to set frequency and optimize the beam current. But that particular point might not be the best signal to noise possible. That is the way I have always set Frankenstein since beam is impossible to see. Your last question is the hardest. Just use GPS and be done. I am really interested in the groups answer to that. All corrections to my lack of knowledge are greatly appreciated. Regards Paul WB8TSL On Fri, Mar 17, 2017 at 11:37 AM, Skip Withrow <skip.withrow@gmail.com> wrote: > Hello Time-Nuts, > > > > I have an HP 5061A (relatively new chassis) with a very old Cs tube > installed (working) and I’m trying to wrap my head around the set up and > calibration of this unit, and just hoping for some help. > > > > As a little background, HP changed the Zeeman modulation frequency, C-field > intensity, and A1 synthesizer frequency at serial number prefix 1336A. > This > is detailed in CHANGE 20 (pages 7-9 and 7-10) Model 5061A Manual Changes in > the 5061A Manual, and covered in much more detail in HP Service Note > 5061A-9 (document 05061-9061 6/80-02). > > > > OLD NEW > > Zeeman frequency 42.82kHz 53.53kHz > > C-field 61 milligauss 76 > milligauss > > Synth. Frequency 12,631,771.6 Hz 12,631,772.5 Hz > > > > I can put the tube on frequency at the new synthesizer frequency by > changing the C-field current (closer to the old C-field value, by changing > A15R19). > > > 1. The Zeeman modulation frequency is a complete mystery to me. Is it > related to the value of the C-field that you are running? > > > > 2. If you are comparing the unit to GPS to calibrate it do you really care > what the Zeeman frequency is? Adjust the C-field to put it on frequency > and call it a day? > > > > I’m not sure if there was a physical change in the Cs tube as well. But HP > mentions that the new values should have better stability. > > > 3. Would I be better off changing the synthesizer frequency back to the old > value and adjusting the C-field (I would think lower) to put the unit on > frequency? My first thought is to leave well enough alone. > > > > Thanks for any insight. > > Skip Withrow > _______________________________________________ > 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. >