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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